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LECTURES

COMPARATIVE ANATOMY AND PHYSIOLOGY

OF TUB

INVERTEBRATE ANIMALS,

DELIVERED AT THE ROYAL COLLEGE OF SURGEONS.

BY RICHARD OWEN, F.R.S/^toOs^- /.

HUNTERIAN PROFESSOR TO THE COLLEGE.

'^^.

L I L? R A R Y

/

SECOND EDITION.

IX.I.USTRATSD BY I7UMEROXTS IVOOBCUTS.

LONDON:

LONGMAN, BROWN, GREEN, AND LONGMANS.

1855.

London:

A- and G. A. Spottiswoode,

New-Street-Square.

TO

WILLIAM COOKE, M.D. M.K.C.S.

FOUNDER AXD TREASURER

OF

THE HUNTERIAN SOCIETY OF LONDON,

tlTfji^ Walximt

OF

HUNTERIAN LECTUKES ON THE INVEBTEBKATE ANIMALS
IS DEDICATED

BY A SINCERE ADMIRER OF HIS VIRTUES
AND TALENTS.

ADVERTISEMENT.

The present Volume is not a reprint of that on the same
subject, published in 1843. The difference between them
is in some measure indicative of the progress of the anatomy
and physiology of the Invertebrate Animals, during the ten
years which intervened between my first and last course of
Lectures on that subject.

My friend and former pupil, Mr. W. White Cooper, having
published his notes of the Lectures of 1843, in numbers, as
they were delivered, time was not allowed to add references to
the original authorities for many of the facts and opinions
quoted in those Lectures : in the present Work, I have
endeavoured to supply that omission according to the plan
adopted in the volume on the Anatomy of Fishes : and some
additions have been made of contributions to Invertebrate
Anatomy and Physiology up to the date of publication.

Royal College of Surgeons, London,
May, 1855.

CONTENTS.

INTRODUCTORY LECTURE.

CUARACTERS AND CLASSIFICATION OF AnIMALS

Page
1

Polygastria

LECTURE II.

- 16

ROTIFERA

LECTURE III.

39

Entozoa

LECTURE IV.

57

Entozoa

LECTURE V.

- 80

Polypi

LECTURE VI.

- 93

LECTURE VII.
Polypi, IIydrozoa and Anthozoa -

119

Bryozoa

LECTURE VIII.

144

ACALEPHTE

LECTURE IX.

- 157

ECHINODERMATA

LECTURE X.

190

Annulata

LECTURE XL

- 225

3129G

VIU CONTENTS.

LECTURE XII.

Page

Annulata. -------- 248

LECTURE XIII.
Epizoa and Cirripedia _----- 266

LECTURE XIV.
Crustacea -------- 296

LECTURE XV.
Crustacea -------- 314

LECTURE XVI.
Insecta -------- 344

LECTURE XVIL
Insecta .------- 372

LECTURE XVIII.
Generation of Insects - - - - - - 387

LECTURE XIX.
Arachnida -------- 442

LECTURE XX.
TuNiCATA, Brachiopoda - - - - - - 469

LECTURE XXL
Lamellibranchiata ------- 503

LECTURE XXII.
Pteropoda and Gastropoda - - - - _ 535

LECTURE XXIII.
Cephalopoda ------- 575

LECTURE XXIV.
Cephalopoda ------- 603

Works reperred to by Roman Numerals in the Present Volume 653
Glossary - - - -- - - - 667

Index --------- 682

HUNTERIAN LECTURES

1852.

INTKODUCTORY LECTURE.

CHARACTERS AND CLASSIFICATION OF ANIMALS.

In entering upon a description of the Animal Kingdom, the natu-
ralist's first and greatest difficulty is to determine its bounds. The
same difficulty meets the anatomist, and must meet whoever under-
takes to write on any particular quality of animals in general.

LiNN^us, the great framer of precise and definite ideas of natural
objects and terse teacher of the briefest and clearest expressions
of their differences and diagnoses, divided them into three kingdoms,
and characterised them as follows : —

"Lapides, corpora congesta, nee viva^ nee sentientia.

" Vegetabilia corpora organisata et viva^ non sentientia.

" Animalia, corpora organisata et viva et sentientia^ sponteque
se moventia." *
In other words — minerals are unorganised ; vegetables are or-
ganised and live ; animals are organised, live, feel, and move
spontaneously.

By organisation is meant such an internal cellular or cellulo-yas-
cular structure as relates to the reception of fluid matter with the
power of altering that matter and adding it to the alterative structure,
the fluid being on that account called '"nutritive," and the actions it
is subjected to, "assimilation" and "intussusception." As these acts

* I. tom.i. p. 11.
B

d INTRODUCTORY LECTURE.

are not explicable on any known chemical or mechanical principles,
they are called "vital" acts, and so long as they are continued the
plant or animal is said to " live." A mineral or unorganised body can
undergo no change save by the operation of mechanical or chemical
forces ; and any increase of its bulk is due to the addition of like
particles to its exterior: it augments not by "growth" but by
" accretion."

Organised beings differ so much more from the unorganised than
they do from each other, that the co-equality of the three Linnaean
kingdoms of nature is no longer admitted, and the primary division
of natural bodies is into " organic" and " inorganic," the former being
collectively designated " organisms." For the distinction of these into
two kingdoms, moreover, the Linnasan diagnosis no longer suffices.
Nothing seems easier than to distinguish a plant from an animal, and
in common practice as regards the more obvious members of both king-
doms no distinction is easier; yet as the knowledge of their nature has
advanced the difficulty of defining them has increased, and seems now
to be insuperable. Not that the lack of such power of definition is
any loss to the Naturalist, if he has gained, instead, a truer conception
of the fundamental unity of all organic nature.

Any circumscription of the Animal Kingdom must, therefore, be
arbitrary, as will, I think, be evident from the following consider-
ations.

Linnosus was not aware that many movements in unquestionable
animals, that seem to be " spontaneous," are not so. Experiment had
not proved that all those of Hartley's first class * depending on
nervous influence, " which is detached down the motory fibres before
reaching the brain," are unaccompanied by sensation, and inde-
pendent of volition. f It has, indeed, been remarked Avith regard to
this difficulty, that " if we always possessed the means of determining
where consciousness and spontaneity do and do not exist, we should
have comparatively little difficulty in drawing a definite line of demar-
cation between " plants and animals." J Yet, in point of fact, we should
then have merely a psychical character, which, in reference to other
characters purely physiological, anatomical, and chemical, might
prove after all to be an artificial one, drawing the boundary-line as
arbitrarily as would be done by any other single character. But
taking the power of self-motion, irrespective of its cause in living

* n. Vol.i. p. 97.

f III. p. 190, where the author, after detailing certain experiments, concludes
from them, '* that thei'c is a property of the sentient and motory system of nerves,
which is independent of sensation and volition."

X IV. p. 182.

CLASSIFICATION OF ANIMALS. 3

beings, if Linniisus meant "locomotion," this truly is as striking a
characteristic of a large proportion of the Animal Kingdom as the
fixed or rooted state is of a still larger proportion of the Vegetable
Kingdom : but the vegetative fixity of the individual is a character
which advances pretty far into the animal series. Not only are most
polypes and a few echinoderms adherent to the place of their growth,
but the whole class of cirripedes and some genera both of articulate
and molluscous animals, e. g. Serpula and Ostrea, are cemented by
their shells as immoveably to the rock on which they grow as are the
sea-weeds that float beside them from their adherent base. On the
other hand, many microscopic single-celled plants, as well as the cili-
ated zoospores or embryos of the Vaucheria* and other algae, and of the
sponges, have a more rapid locomotion than some of the polygastric
animalcules enjoy ; although in neither case, probably, does it arise
from a distinct act of volition. The movements of the oscillatoriae,
and the more partial shrinkings of the sensitive-plant from the touch,
show that "motion" merely, whether of the whole or of the parts
of a living organism, will not determine to which kingdom it belongs.
Blumenbach, who appreciated the insufliciency of the psychical cha-
racter from "spontaneous motion," adopted an anatomical one: —
" Plants absorb their nutriment by means of numerous fibres placed at
the lower end of their bodies : animals have a simple opening at their
upper or anterior extremity, leading to a capacious bag, into which
they introduce their food: "f Boerhaavelj: had long before said that
the food of plants was absorbed by external roots, and that of ani-
mals by internal roots ; and Hunter's favourite anatomical character
for animals was the "mouth and stomach." But the free parasitic
genus Gregarina §, with its contractile cell-wall, which is soluble in
acetic acid, and many of the freely moving infusoria, have no mouth
nor alimentary canal ; and there is nothing that can be properly
called "stomach" in the cestoidea. The cellular parenchyme of tape-
worms is traversed by canals more analogous in character to those
which take the place of the digestive cavity in 'sponges. The sap-
vessels, and the whole system of intercellular spaces, with their outlets
in the stomata, of plants, exhibit an analogous arrangement. Carbonic
acid, the nutritive material in plants, passes through the pores of
the elongated canals of the intercellular spaces and is taken into
the surrounding cells as formative material ; just as albumen and
the hydrates of carbon are introduced by the stomata of the tape-
worm into the longitudinal canals, and pass through their pores
into the surrounding vacuolse or cells : the same materials, in a

* V. t VI. p. 4. X CL. p. 64. § VII. p. 10.

B 2

4 INTRODUCTORY LECTURE.

coarser form, passing by the more obvious mouth into the wider
digestive sac of the higher animals. There is no essential or well-
defined distinction of assimilative structure here : the difference is at
most one of form and proportion of the internal cavities and of their
external openings : they are the same as to function in plants and
animals. The more free and locomotive the organism, the more
capacious the internal receptacle for the matters to be assimilated,
the characteristic differences of form fading away in the passage from
the pendant parasites and the polypes to the astomatous polygastria,
the sponges, and plants proper. So that if the presence of absorbent
pores and assimilative cells, instead of a mouth and stomach, be
deemed a Vegetable characteristic, then this, like the rooted character,
mounts up a certain way into the Animal Kingdom.

When the chemist entered upon his valued investigations into the
changes which living organisms wrought upon surrounding media
and those media upon them, he found that plants and animals
differed in their behaviour in these respects. Plants exhaled oxygen,
animals carbonic acid : the gas which was food to plants was poison
to animals ; animals inspired the oxygen which plants exhaled.
Thus the balance of the gases in the atmosphere was beneficially
maintained by the antagonistic actions of the two kingdoms. And
in a general way this is true, but the chemical antagonism fails as a
boundary line where we most require it, as we approach, viz., the
confines of the two kingdoms. Wohler * has shown that some of the
free and locomotive Polygastria, e. g., Chlamidomonas pulvisculus,
Euglena viridis, Frustidia salina, eliminate pure oxygen, as the
ultimate metamorphosis of their tissues : and on the other hand,
Drs. Schlossberger and Dopping | have proved that mushrooms and
sponges exhale carbonic acid. The green-coloured matter called
" chlorophyll " which is common in most plants, exists in the Poly-
gastria, in the green Planariie, and the fresh-water polype.

As regards the conversion of the surrounding elements into their
own matter, animals combine carbon, hydrogen, oxygen, and nitrogen
to form the proximate principles of most of their tissues, which are
thus " quaternary " compounds ; whilst the tissues of plants are in
general " ternary " compounds of carbon, hydrogen, and oxygen, and
sometimes, as, e. g., the cellulose substance, only " binary " ones of
carbon and hydrogen. But if the presence of nitrogen in the
organic tissues be taken as an animal characteristic, then we find it
descending pretty far into the vegetable series, the element being

* VIII. 1843. p. 206. ] lb. bd. Hi. p. 119.

CLASSIBICATION OF ANIMALS. 5

present in the alga3, the fungi, and almost all cryptogamia. On
the other hand, it has been shown by Schmidt * that some animal
tissues are binary compounds, as e, g., the mantle of the Frustidice and
the thick cellular tunic of the Ascidice.

Thus whilst it may be affirmed in a general way that plants decom-
pose and animals recompose carbonic acid, the one fixing the carbon
and yielding the oxygen, the other freeing the carbon in combination
with oxygen taken from the atmosphere ; that the plant exhales
less water, and the animal more water, than it imbibes ; that
whilst the plant Jixes ammonia and uses its elements for the produc-
tion of organic compounds, the animal sets free azotised substances
which speedily resolve themselves into ammoniacal compounds; — the
beneficial antagonism can only be predicated in a general way of the
more complex or typical members of each kingdom respectively, and
will not serve as a rigorous basis of definition in the lower approxi-
mated forms where the aid of the chemist has been most wanted for
that purpose.

The physiologist has asserted that plants alone can subsist on
inorganic matter, and that animals depend upon plants for combining
the elements into binary and ternary compounds essential to animal
support, f And this also is in some degree true : the lichen that
first clothed the granite rock must have converted the inorganic
elements into cellular tissue. Animals, as a general rule, subsist on
vegetable or on animal matter, or on both. But no proof has been
given that the Frustidice and other astomous polygastria, which
separate oxygen in excess, do not effect this by reducing the carbonic
acid of the atmosphere, and fixing the carbon, in order to produce
their fats and hydrates of carbon : or that they do not, in like
manner, assimilate their ammonia either directly, or by taking the
nitrogen of the atmosphere into the required combination ; and so by
its subsequent combination with the elements of the fats and hydro-
carbonates, produce their proteine compounds and albuminates. Still
less proof or probability have we that the typical or higher organised
forms of vegetation could flourish without the support of decaying
organised tissues, superadded to the air and water.

Ehrenberg \ seems to have rested from his analysis of the distinc-
tion between plants and animals, on arriving at considerations offered
by the generative function, and accordingly refers the "• Desmidice,''^
" DiatomacecB^'' and " Closterice " to the animal kingdom, which he
characterizes by "the power of increase by voluntary division," super-

* IX. p. 34. t ^' ^^^' i- P- 2- X XI. p. 88.

B 3

6 INTRODUCTORY LECTURE.

added to self-motion. But growth by elongation and bisection of tli6
cells is very frequent if not universal in the more simple algae ;
whilst propagation by spontaneous fission is the common mode of
increase of the single-celled plants which constitute yeast {Torula
cerevisii) and the colouring matter of red snow {Protococcus ?iivalis).

All living organs are continually receiving additions to their sub-
stances ; and so long as these exceed in quantity the parts removed,
they are said " to grow." Plants seem to grow as long as they live ; but
if the tree and other compound kinds be rightly regarded as organic
associations of individual phytons,then these, when fully developed into
the form of the leaf, the sepal, the petal, or the pistil, abide, like the
polype of the compound coral, without further growth, until the period
of their decay or fall. And if this philosophic interpretation of the
" tree " be rejected and the common notion of its individuality be held
to be the truer one, it will as little assist in differentiating the plant and
the animal by the character of growth : for the compound zoophyte must
then be regarded as a many-mouthed individual, and any climacteric
cessation of its growth can be as little predicated of it, as of the com-
pound individual plant. But in regard to both trees and zoophytes
it is plain that there is a certain term of growth, even for the com-
pound whole ; for most species have a characteristic maximum of
size, otherwise we should not see the Elm of 50 years surpassing the
Yew of 500 years : and no term of life would bring the Elm or the
Yew to an equality of size with the mighty Boabdad {Adansonia).

The creatures that appear least equivocally to enjoy growth during
the whole term of their existence are the Trout^ the Pike, the Ana-
conda, the Testudo elephantopus, and the like cold-blooded vertebrate
individuals : although as the rate of growth, which is always slow,
becomes slower as age advances, they seem, during the few years
that a naturalist can watch an aged individual of these long-lived
species, to be stationary in regard to their growth. The records of
unusually large specimens of such cold-blooded animals always asso-
ciate such uncommon size with far advanced age, and imply that there
is no definite period arresting their growth as in the warm-blooded
vertebrates. Still, however, as in trees and zoophytes, the recog-
nised average size characteristic of different species of fishes and
reptiles, which all start from a germ-cell of nearly the same minute-
ness, shows plainly that there is a specific limit of growth for each.
And this at least is certain, that the " continually receiving additions
during the term of existence",* however understood, helps us no way
towards the discrimination betvveen plants and animals.

* V. p. 182.

CLASSIFICATION OF ANIMALS. 7

Thus, after reviewing the different characters by which it has been
attempted to distinguish the special subjects of the botanist and
zoologist, we find that neither sensation and motion, the internal
assimilating cavity, the respiratory products, the chemical constitu-
tion of the tissues, nor the source of nutriment, absolutely and un-
equivocally define the boundary between the animal and vegetable
kingdoms. We can only recognise the plant or animal when a cer-
tain number of their supposed characteristics are combined together.

A rooted organism, exhaling oxygen, with tissues chiefly com-
posed of cellulose or of binary or ternary compounds, is, without
question, to be called a "plant." An irritable or locomotive orga-
nism, with a mouth and stomach, with gelatinous or albuminous
tissues, or chiefly composed of quaternary compounds, exhaling car-
bonic acid, is as certainly an "animal." But such "plants" and
"animals" are specially defined members of one and the same great
family of organised beings.

An internal assimilative cavity, whether in the form of cells, canals,
or bags, is essential to all. The movement of a part, when stimulated,
is a property continued from the higher organised forms far down
into those that manifest the combined characteristics of the vegetable
kingdom, as, e. g. in the Mimosa pudica and the Dionma muscipula,
as to which the statement that such movements were destined solely
for the furtherance of formative operations, would be purely gra-
tuitous. Locomotion also crosses the supposed line, and is an en-
dowment of the embryos or spores of the sea-weeds. On the other
hand, the rooting or fixation of the organism is continued upwards
from the vegetable kingdom into the Radiate, the Articulate, and
the Molluscous divisions of the animal kingdom. The cellular and
cellulo-vascular forms of the assimilative cavity, common to plants
and sponges, is repeated in the cestoid entozoa, the astomous poly-
gastria, the rhizopoda, and in the early embryos of all higher animals.
Tissues of binary compounds are found in polygastria and ascidise,
and the chitinous coverings of insects and crustaceans have a much
closer resemblance to ligneous fibre than to proper animal tissues.
The presence of starch is of itself quite inadequate as a ground of
distinction, even were it proved to form part of the proper cell-
walls. And, on the other hand, nitrogen combines with carbon and
hydrogen to constitute the chief tissues of the sponges, algae, and
fungi. These exhale carbonic acid like well-organised animals, and
the polygastria exhale oxygen like typical plants.

Thus the groups of characters that are essential to the true defini-
tion of a plant and an animal interdigitate, so to speak, in that low
department of the organic world from which the two great branches

B 4

8 INTRODUCTORY LECTURE.

rise and diverge. Every naturalist or physiologist is at liberty, of
course, to adopt any one of the characters that have been supposed
to divide the two kingdoms ; but the boundary, so defined, will be
artificial, and each different character will bisect the debateable ground
in a different latitude of the organic world.

Animals and plants, then, are not two natural divisions, but are
specialised members, of one and the same great group of organised
beings. When a certain number of characters concur in the same
organism, its title to be regarded as a ''plant" or an "animal"
may be readily and indubitably recognised ; but there are very nu-
merous living beings, especially those that retain the form of nucleated
cells, which manifest the common organic characters, but without
the distinctive superadditions of either kingdom. Such organisms
are the Diatomacece, Desmidice, Protococci , VolvocincB, Vibriones,
Astasicece, Thalassicolce, and SpongicE ; all of which retain the cha-
racter of the organised fundamental nucleated cell, with comparatively
little change or superaddition.

In a work treating expressly of the animal organisation I am un-
willing to include more than the zoologist may fairly lay claim to, and
I therefore look for certain combinations of characters as qualifications
for admission, although occasional illustrations of organic functions
will be derived from the indeterminate organisms above mentioned.

Thus if irritability of parts or locomotion of the w^hole be not
accompanied with mouth and stomach, it must be manifested by
proximate tissues of quaternary compounds, and the cell-w^alls and
fibres must consist of albuminous or gelatinous matter, or be soluble
in acetic acid.

If some of the tissues of an organism are binary compounds, yet
if they include a stomach with a mouth, and are also associated either
with irritable parts or a power of locomotion, such organism will be
referred to the animal kingdom.

When to a mouth and alimentary canal are superadded definite
muscular and nervous filaments, a heart, a breathing apparatus, and
generative organs, no doubt of the animality of the organism can
be entertained.

Having thus laid down the grounds on which I have marked out
that higher division of organised bodies which is the proper subject
of the studies of the zootomist, I proceed next to offer a ^^"^ remarks
on the leading varieties and grades of structure in the animal king-
dom, in so far as tbey are guides to its classification.

Little useful progress can be made in Comparative Anatomy
witliout some knowledge of Zoology. Zoology is the key to the na-
ture and habits of the animals of which Zootomy unfolds the struc-

CLASSIFICATION OF ANIMALS. 9

ture. Some knowledge of natural history and of the principles of
classification, therefore, is essential to the comprehension of the con-
nection between structure and habits, on which the utility of Anatomy
in the advancement of Physiology mainly depends.

The classification of animals is not now what it was in the time of
Linnaeus. I do not mean merely to say that animals are differently
arranged, but the objects and principles of that arrangement are very
different.

Linnaeus in his Systema Naturce wished to give, as it were, a
Dictionary of the Animal Kingdom, by reference to which you might
as readily ascertain the place of the animal in his system as that of a
word in a lexicon by merely knowing its first and second letters.
To this end, LiniiEeus selected a few of the most obvious characters
for the establishment of his groups.

Taking, for example, a certain number of incisor teeth and the
pectoral position of the mammje, as the characters of his first order of
animals, he thereby associated man with the monkeys and the bats.
But, independently of the psychical endowments which place the
human species far above the lower creation, it may readily be con-
ceived that great differences of organisation must exist in animals
which enjoy the erect position on two feet, in those which climb by
having four hands, and in those which fly by having their anterior
members in the form of wings.

External and arbitrary characters, selected merely for the con-
venience of their appreciation, thus tend to the association of very
differently organised species, and as often separate into very re-
mote groups of an artificial system two animals which may have
very similar anatomical structures. Of this we have several ex-
amples in the Linnaean subdivisions of the class of fishes, the orders
of which are characterised by the easily recognisable position of the
fins. Linnaeus's attention was particularly directed to the very vari-
able position of the ventral pair of fins, which are the homologues
of the hinder limbs in land animals. In some fishes, as the pike and
many other fresh-water species, the ventral fins are at some distance
behind the pectoral fins, or in their usual place — these formed the
order Abdominales : in others, as the perch, the ventral fins are
attached beneath the tliorax — these constitute the Thoracic order:
in others, as the cod, you find the ventral fins in advance of the
pectorals, or under the throat — such species formed the Pisces jugu-
lares of Linnaeus : lastly, those species in which the ventral fins are
altogether wanting, as the eel, formed the Apodal order.

Such a sywStem has the advantage of enabling the collector to refer
with great facility any firih to its artificial order: but you can scarcely

10 INTRODUCTORY LECTURE.

express any general proposition in comparative anatomy in reference
to such groups. There are two sword-fishes, for example, having the
same anatomical structure, and not easily distinguishable externally
save by the height of the dorsal and the difference in the position of
the ventral fins : but in the Systema Naturce of the Swedish Na-
turalist, the Xiphias is placed in one order and the Istiophoriis in
another ; the variable and little influential fins prevailing over all
the rest of the organisation in the artificial ichthyology of Linnaeus.
Amongst the lower animals, we find the slug, placed in one class,
viz. the F<?rme5 mo//i^5ca, and the snail in a different class, viz. Vermes
testacea^ in the Systema Naturce; whilst in their whole anatomy
these two mollusks most closely resemble each other, the rudimental
state of the shell being the main difference in the Limax as com-
pared with the Helix. Similar instances of the violation of natural
affinities might be multiplied, and are, indeed, inevitable in an artifi-
cial system.

I confess that if the classifications of zoology of the present day
continued to be of the same character as that to which I have just
referred, which however, let it be remembered, was the best that could
be made in the time of Linnoeus, and a necessary transitional step to
improved views on this subject, I should not have been justified in
occupying so much of the time of my auditors in this theatre of
anatomy and physiology, by the details of such artificial helps to the
recoo^nition of the outward characters of the members of the animal
kingdom. But the principle on which animals are now grouped to-
gether are of a different and much higher kind : they are the fruits
of the best results of the researches of all the great comparative
anatomists since the time of Linneeus. The characters of the classes
of animals have been rendered by the immortal Cuvier*, the highest
expressions of the facts ascertained in the animal organisation. I
know not any thing more calculated to impress the stranger to
anatomical science with the immensity of the labour that has been
gone through, and with the vast number of careful and minute dis-
sections that have been made, than the propositions which now form
the definitions of the primary groups of the animal kingdom.

The whole organisation of one species has been compared with that
of another, and this with a third, and so on, in order to ascertain in
what organ, or system of organs, the greatest number of animals
would be found to present the same condition : so that they might
not be arbitrarily but naturally associated together. In the terms of
logic, the characters common to all animals having been ascertained,

* XII.

CLASSIFICATION OF ANIMALS. 11

the anatomist, in the next place, has sought to discover the difference
which, added to the definition of animal^ would form the most ex-
tended species of that genus.

Ai'istotle thought he had found this primary differential character
in the blood, recognising as blood only the circulating fluid which
was red coloured. He accordingly divided the Zoa into Enaima
and Anaima, or the sanguineous and exsanguineous animals. For
a long time no advance was made beyond this early step in the
primary division of animals. It was at length discovered that many
of the exsanguineous animals of Aristotle did actually possess blood,
though differing in colour from that of the so-called sanguineous
species. This led, however, only to a nominal improvement in the
classification ; the Enaima were called " red-blooded," the Anaima
"white-blooded" animals. It was reserved for Cuvier* to discover?
in the course of his minute dissections of the lower animals, that an
extensive class of worms had red blood circulating in a closed system
of arteries and veins ; and this discovery first materially affected the
value of the character applied by Aristotle to the primary groups of
the animal kingdom.

The Annelides, or red-blooded worms, could not, however, be com-
bined with birds, beasts, and fishes, in a natural system, since they
differed from them widely in almost every other particular of their
organisation.

Some other character was therefore sought for, since it became
obvious that the colour of the blood led to an artificial combination of
species. Lamarck | thought he had discovered the desired character
in the vertebral column, this structure being present in all the Enaima
of Aristotle, and absent in all his Anaima. Lamarck proposed,
therefore, the name of Vertebrata for the one class, and Invertebrata
for the other. Now it will be observed that the Invertebrata are
grouped together by a negative character ; and I know not any in-
stance where such a character has been employed in zoology, in which
very differently organised species have not been associated together.
What indeed can be predicated in common of the snail, the bee, and
the polype, than that they are animals, have no red blood, no vertebral
column, and the like negations ? It was obvious also that the Verte-
brata and the Inverte])rata were not coequal groups, and the idea of
equivalency or proportion, as well as that of likeness, ought always
to govern the labours of the classifier.

In the attempt to remedy this defect, the discovery was made that
the vertebral column was subordinately related to a condition of a
much more important system in the animal body than the skeleton,

* XII. t. ii. p. 515. t Xin.

12

INTRODUCTORY LECTURE.

viz. the nervous system. Cuvier* thereupon applied himself with
indefatigable industry to ascertain the arrangement of the nerves in
the Invertebrata, and after a long series of minute and elaborate
dissections, he discovered three modifications of that system, each of
equal importance with that which governed the vertebral character
of the red-blooded animals of Aristotle. Cuvier, accordingly, pro-
posed to divide the animal kingdom into four primary groups or
sub-kingdoms, viz. Vertebrata, Mollusca, Articulata, and
Radiata.\

It is due to Hunter J to state that the general results of
his dissections of the nervous system are expressed in the
definitions of the same leading types as those of Cuvier ;
but he made the minor differences which he had detected
in the Vertebrate series equal to those primary types of the
nervous system which now characterise the Mollusca and
Articulata of Cuvier, — a view which would have led to
erroneous results if applied to the classification of the pri-
mary groups of animals.

The sub-kingdom Vertebrata, or Myelencephala, is cha-
racterised by the disposition of the principal mass of the
nervous system in a median axis, consisting of the brain
and spinal chord {Jiy. 1.), situated along the dorsal aspect
of the body, behind the heart and digestive system ; and
inclosed in a bony or cartilaginous case, constituting a verte-
bral column. The organs of the five senses, sight, hearing,
smell, taste, and touch, are almost always present.

The respiratory organs communicate with the pharynx,
or anterior part of the alimentary canal.
The mouth is provided with two jaws, placed one above or in front
of the other.

The blood is red.

The heart is a compact muscular organ,
having never fewer than two cavities, an
auricle and ventricle, propelling the blood
through a closed system of arteries and veins.
The muscles surround the bony or gristly
levers on which they act.

Tlie locomotive members never exceed two
pairs.

The sexes are distinct and no species is
parthenogenetic.

In the sub-kingdom Mollusca, or Hetero-

XIV.

t XV.

X X, Vol. iii, p. 10.

CLASSIFICATION OF ANIMALS.

13

gangliatay the principal centre of the nervous system bears the form
of a ring, surrounding the gullet, from which the nerves
radiate, often unsymmetrically, to different parts of the
body {Jig. 2.) : the brain is represented by ganglions
above («) or at the side {b) and below the gullet ; other
ganglions {c d) are developed in other parts of the body.
The form of the body corresponds with the disposition of
the nervous system, and is commonly unsymmetrical. In
a single order (Cephalopods) the muscles originate from
an internal rudimental cartilaginous skeleton : in the rest
they are attached only to the skin, which forms a soft
envelope in which there are developed in many species
one or two, rarely more, calcareous plates, called shells.

The blood is colourless, or not red ; the lieart compact,
muscular, and propelling the blood througb a closed sys-
tem of arteries and veins, or venous sinuses. *

The respiratory organ is never absent ; and, with the
exception of one family {Ascidians), the cavity containing
it receives, or opens near, the anus.

The Mollusca are dioecious or hermaphrodite : some of
the lowest organised species are parthenogenetic.

The third primary division of the animal kingdom, viz.
the Articulata, has the brain in the form of a ring, em-
bracing the gullet : a double ganglion above the tube
supplies the chief organs of sense : from the sub-oesopha-
geal ganglions two chords are extended along the ventral
surface of the abdomen, and are, in most species, united
at certain distances by double ganglions, which give origin
''^ to the nerves of the body-segments and their appendages

{fig. 3.). From the symmetrical disposition of the nervous
centres, I have called this sub-kingdom Homogayigliata. The body
presents a corresponding symmetrical form. The skeleton is external,
and consists of articulated segments, of frequently an annular form :
the articulated limbs in those species which possess them have a similar
condition of the hard parts, in the form of a sheath, which encloses the
muscles.

The respiratory organs commonly open upon the sides of the body ;
rarely near the anus, and never communicate with the mouth.

* The latter phrase is added, in the p esent edition, because the term " closed
system " has been supposed to imply a particular fonn of the veins, viz. the tubular :
and has been objected to by the supporters of the hypothesis that the blood in many
Mollusks is difiused in interspaces or lacuna of the viscera (XVI. p. 292.). I have
shown, however, that these supposed lacuna? are sinuses closed or formed by the
proper tunic of the veins. See XVI. p. 315. pi. 4,, and pi. 1. of the present volume.

^k

^^

14

INTRODUCTORY LECTURE.

The jaws, when present, are lateral, and move from side to side.
The heart is situated in the back, is often vasiform ; and the veins
are frequently in the form of large, irregular sinuses * ; there is always
a circulation, and the blood is red in one class (A??ellides).

Most Articulata are dioecious : a few are hermaphrodites : still
fewer are parthenogenetic.

The Radiata, or fourth primary division of animals in the system
of Cuvier, is so called because most of the species comprising it have
their parts arranged around an axis, on one or several radii, or on
one or several lines extending from one pole to the other. The
nervous system, when traces of it have been visible, is also arranged

in radii {Jig* 4.). It does not
present the homogangliate or
heterogangliate type. In one
family only {Holothuriadce) is
there a distinct respiratory sys-
tem : the other characters as-
signed by Cuvier are negative
ones.

I have already observed, that
there is no instance in which
animals, grouped together by
negative characters, have formed
a natural assemblage ; nor is the
sub-kingdom Radiata of Cuvier
an exception to this rule.
The truth is simply that the anatomy of this immense assemblage
of low-organised animals is not yet sufficiently understood ; and, con-
sequently, general propositions, and at the same time positive ones,
like those which define the Vertebrate, Molluscous, and Articulate
sub-kingdoms, cannot be enunciated.

Much has unquestionably been done in this field of Natural
History since the time of Cuvier, and attempts have been made, with
various degrees of success, to subdivide the Radiata according to
positive characters.

The binary division, which I proposed in 1835 f, was founded on
the following considerations. The Radiata of Cuvier, in w^hich the
nervous system could be most unequivocally traced in a filamentary
form, present an alimentary canal as a distinct tube, with a mouth

* Eirst demonstrated by Hunter, in the Crustaceans and Insects. See " Treatise
on the Blood," p. 174., and X. vol. ii. p. 138. plxvii.

t Syllabus of the Lectures on Comparative Anatomy, given at the Medical
School of St. Bartholomew's. 8vo.

CLASSIFICATION OF ANIMALS. 15

and anus, suspended in a distinct abdominal cavity : the well-defined
nerves govern a corresponding development of the muscular system.
Generation is by impregnated ova, rarely by spontaneous fission or
gemmation. The Echinodermata, Rotifera^ Ccelehnmtha, and Bryo-
zoa, are the classes of Cuvier's zoophytes, which were grouped
together by positive characters, under the title Nematoneura.

But a filamentous condition of the nervous system is not to be de-
nied in the rest of the zoophytes ; each day brings with it testimony
of its presence in animalcules, where it had not before been detected.
Nevertheless, in those classes in which the condition of the nervous
system is most obscure, we find that the digestive cavity is generally
excavated in the common parenchyma of the body, is devoid of free
parietes, and seldom has an anal outlet : particular organs are often
indefinitely multiplied, as the digestive cavities in the Polygastria,
the generative organs in the Tcenice, the prehensile mouth in the
Polypi. Parthenogenesis by gemmation and spontaneous fission is
the rule in this lowest division of the animal kingdom, to which I
applied the name Acrita, and of which the Hydrozoa, Sterelmintha,
and Polygastria are examples.

The groups called Acalephce and Anthozoa stand in an inter-
mediate position between the Acrita and Nematoneura ; and most
of the classes in the lowest division of the Radiata lead by
more or less gentle gradations into those of the higher one. Nor
is this surprising : the radiated animals are closely analogous
to the embryo forms of the higher classes ; and as the earlier changes
of such embryos succeed each other more rapidly than the later ones,
so also each class of the Acrita more closely approximates some class
of the Nematoneura than is observed in the classes of the higher
groups, and the characters of the lowest or acrite classes are the
least definite and fixed.

Moreover, the positive characters assigned to the Nematoneura do
not link together groups in other respects so naturally allied as those
which are united together by the molluscous and articulate characters.
The Rotifera^ e. g., are more nearly related to the lower Crustacea
than they are to the Echinodermata ; and the Codelmintha are more
nearly allied to the Epizoa and Anellata than to any nematoneurous
group. Where Nature, therefore, seems not to have intrenched herself
within recognisable bounds, it is vain to attempt to impose them upon
her : and I shall, therefore, content myself with indicating, in the
subjoined Table of the Provinces and Classes of the Animal King-
dom, the subordinate groups of Cuvier's Zoophytes*, which appear
to be best defined by the light of embryonal development.

* XII. torn. iv. (1817).

16 LECTURE II.

Kingdom ANIMALIA.
Province Vertehrata,
Class Mammalia.
Ayes.
Reptilia.
Pisces.
Province Articulata. Province MoUusca.

Class Arachnida. Class Cephalopoda.

Insecta. Gasteropoda.

Crustacea. Pteropoda.

Epizoa Lamellibranchiata.

Anellata. Brachiopoda.

cirripedia. tumcata.

Subprovince Radiaria.

Echinodermata, Bryozoa, Anthozoa, Acaleph^, Hydrozoa.

Subprovince Entozoa.

Ccelelmintha, Turbellaria, Sterelmintha.

Subprovince Infusoria.

ROTIFERA, RhIZOPODA, PoLYGA STRIA.*

LECTURE II.

POLYGASTRIA.

I PROPOSE first to invite your attention to a class of animals, the most
minute, and apparently the most insignificant of created beings. It
might almost seem needful to apologise for the design of trespassing
on your time and patience during one or two lectures with the Ana-
tomy and Physiology of creatures which are wholly invisible to the
naked eye. But we are too apt to let our judgments of the impor-
tance of objects be unduly influenced by first impressions, especially
by those of magnitude or the contrary, which deeper insight into
their true nature and value rectifies.

The active atoms about to be described, for the knowledge of
whose very existence we are indebted to the microscope, are by no
means the least complex of organised beings ; those which will be the
subject of the present lecture belong to the higher division of organic
nature, and most of them manifest the distinctive properties of animals
in a striking and unequivocal manner.

* A Glossan' and explanation of the scientific terms will be added to the con-
cluding Lecture.

POLYGASTRIA. 17

Leeuwenlioek was little aware how large a prospect of organic life
he was opening to our view, when, in the year 1675, he communi-
cated to his scientific friends his discovery of the little bell-shaped
animalcule {Jig. o.), now known as one species of an immense class,
and called the Vorticella convallaria. His observations were pub-
lished in one of the early numbers of the " Philosophical Transac-
tions": * much discussion on the subject ensued, and called forth the
wit of the philosophers of the day. However, the records multiplied,
and now we have obtained a view of the Infusoria, which shows
them to be the most widely diffused and by far the most numerous
of all the forms of organised life. Wherever Ehrenberg went in his
travels with Humboldt, he there detected with his microscope some of
the manifold forms of these animalcules ; and wherever his pupils have
repeated his observations, the same phenomena have been presented.
Not only in fresh water, but almost over the w^hole ocean, species of
Infusoria abound ; if you catch a drop of water from the spray that
rises from the paddle of the steam-boat, in it you will hardly fail,
with an adequate magnifying power, to detect some specimens of this
class. When Sir James Ross and his companions, in accordance with
their directions, took up the film from the surface of the Antarctic
Sea, that film, in its dried remains, was found to consist of siliceous
cases of the Infusoria ; in the mud brought up from the depths of
the ocean, at the highest southern latitudes sounded by the deep-sea
line, they were found ; and they have also been detected in the sand
adhering to specimens dredged up at Melville Island, by Captain
Parry ; so that from north to south poles, and in all intervening
latitudes, these animalcules are diffused, and extend the reign of
animal life beyond that of the vegetable kingdom.

You may obtain specimens of Infusoria almost at will. If you
skim a small portion of the green matter, which in summer time
mantles the surface of a stagnant pool, place a drop of this in
the object- holder of a microscope, and examine it with a glass of a
quarter of inch focus, you will find it teeming with animal life ; you
will see numerous little objects, of one or other of the forms depicted
in these diagrams {figs. 5, 6, 7.), leisurely coursing or darting with
rapidity across the field of view, or rolling over, or gyrating on their
axes. If you examine in like manner a drop of water in which has
been infused any vegetable or animal substance, and which contains
the particles of such substances in a state of decay or decomposition,
you will find such infusions similarly tenanted with these active ani-

* XVII. p.821.

c

18

LECTURE IT.

malcules ; they have been termed from this easy and common mode
of procuring them, the animals of infusion, or Infusoria.

The earlier microscopi-
5 cal observers confounded

all the minute living ob-
jects which they thus met
with under that term ;
but the progressively in-
creasing powers of defini-
tion at the command of
later observers have led to
the removal of the single-
celled locomotive plants
{Jig. 7.), together with
the embryos of polypes,
worms, and insects, from
this motley and heteroge-
neous group, and have re-
stricted it to those ani-
mals which, in their fully
developed state, mani-
fest a form of body more
or less amorphous, devoid
of radiated prehensile arms, without definite locomotive members,

commonly moving by means
of minute superficial vibra-
tile cilia more or less dif-
fused over the surface of
the body, or aggregated in
circular groups near the
head, where they produce
by their successive oblique
action the appearance of
rapidly rotating wheels.
Only the largest species of
Infusoria are provided with
the last specified arrange-
ment of vibratile cilia, and
these " wheel-animacules,"
as they are termed, being
endowed with a higher
type of organisation, more
especially of the digestive system, constitute a distinct class of Infu-

Vorticella nebulifera.

I, 2. Spirostomum vircns ; 3—8. Glaucoma scintillans

POLYGASTRIA. 19

serial animalcules, of a higher grade of organisation than the
more diffusely ciliated group {figs, 5. & 6.), which is the subject of the

present lecture.

The species of this group
are essentially nucleated
cells, with a superadded
organisation for locomotion,
digestion, and, in some spe-
cies, for circulation and ge-
neration. The cell-wall in-
closes a colourless and trans-
parent gelatinous plasma,
with numerous minute and

1-3. Vibrio .ubtilis ; 4, 5. Vibrio ru^ula ; 6, 7. Closterium. ^^^^^ COlourcd COrpUSClcS.

Particles of food wlien
taken in are seen to occupy subspherical and subequal spaces in the
same plasma, and the spaces so occupied being regarded by Ehrenberg
as stomachs, he has thence proposed for this class the name of Poly'
gastria, which may well be retained, although the idea of these
assimilative cavities having distinct walls and intercommunicating
canals be abandoned.

The most minute forms, as the species called Monas crepusculus,
Ehr., have been estimated at the 2^^^^ ^ of a line in diameter.* Of
such Infusoria a single drop of water may contain five hundred mil-
lions of individuals, — a number equalling that of the whole human
species now existing upon the surface of the earth. But the varie-
ties in the size of these invisible animalcules are not less than that
which prevails in almost every other natural class of animals : from
the minutest ilTowttc? to the larger species oi Loxodes or Amphileptus,
which are one sixth or one fourth of a line in diameter, the difference
of size is greater than between a mouse and an elephant. Within
such narrow bounds might our ideas of the range of size in animals
be limited, if the sphere of our observation was not augmented by
artificial aids !

Many of the polygastric animalcules are naked, covered only by an
elastic, transparent integument, which, in some {Euglena^ Amoeba\
is smooth ; in most is more or less ciliated. Others are protected by
a shell, which consists of pure, colourless, and transparent silex.
This shell may present the form of a simple shield, indicating by its
position the back of the animal, as in Eiiplcpci Charon ; others have

* A line is the twelfth of an inch,
c 2

20

LECTURE II,

Navicula.

Dictyocha.

Actinocyclus, bivalve.

their flinty armour resem-
bling a minute bivalve shell:
in some, as the Navicula, it
has the form of an elongated
case, or flattened cylinder,
open at both extremities {fig. 8.) : it is sometimes straight, some-
times bent, like the Australian boomerang ; it may present the form
of a reticulated cone {fig. 9.), or a discoid case
{fig. 10.) : in short, the
varieties of the siliceous
shells of the Infusoria
are as numerous as those
of the calcareous shells
of the Mollusca. But
whatever their form, the
superficies of these delicate microscopic objects is generally sculptured
with a beautiful, well defined, and more or less complicated pattern,
which makes it easy to recognise the species, and distinguish them
from one another.

Most of these animated minims are locomotive and free ; a few, as
the VorticellcB, are attached to foreign bodies by a long and highly
irritable and contractile pedicle ; others, as the Gomphonema, are
appended to the extremities of the branches of a dichotomously di-
vided stem.

In Loxodes Bursaria (fig. 18.) the parietes of the body, which
equal about one-sixth of its transverse diameter, consist of an outer,
firm, colourless substance supporting the cilia, and of an inner, softer
matter, in which green globules are imbedded. The outer layer is
marked by numerous close-set, fine grooves, extending obliquely or
spirally, and in opposite directions, over the w^iole outer surface,
giving it an "engine-turned" or reticulate character. The cilia are
attached to the eminences defined by the decussating grooves, and are
of considerable length, when seen in the quiescent, dying, or decom-
posing animacule.*

The green corpuscles imbedded in the deeper layer are spherical
nucleated cells, corresponding in their chemical characters with the
chlorophyll-corpuscles of Vaucheria and other Algce ; the similar cor-
puscles which float in the fluid contents of the body are seen in cir-
culation close to the inner surface of the parietes, in the direction
indicated by the arrows in fig. 18.

The locomotive Polygastria propel themselves through the water
by the action of their vibratile cilia, which are sometimes generally
* XVIII. t, xxxiv. fig. vii. Bursaria i^eruah's.

POLYGASTRIA. 21

diffused, as in Leucophrys {fig. 13.), Loxodes {fig. 1 8), Bursaria, Nas'
sula; sometimes aggregated in longitudinal rows, as in Amphileptus ;
or in transverse circles along narrow bands, as in Trichodina ; or they
are limited to the region of the mouth, as in the VorticellcB, {Jig. 5.), in-
dicating the passage to the higher or Rotiferous group. The body in
Peridinium is girt with an oblique hoop of long cilia. In most Poljgas-
tria the cilia are longer than they are commonly represented, and the
marginal cilia of the flat body in Stylonychia, and the ventral ones in
Oxytricha and Euplotes, are of such relative size as to give the species
a mjriapodous character, and are used, like little feet, to creep along
the stems of the chara, and other minute vegetable plants. In some
Polygastria cilia are supported on one {Amblyophis) or two ( Chlorogo-
niuni) tentacular processes, which wave to and fro and create currents
> in the water ; in Peridinium tripos there are three such prolonga-
tions ; but true jointed locomotive members are never developed in
any of this minute and primitive race of animated beings. They retain,
throughout life, those simple vibratile organs which produce the ro-
tatory movements in the ova of MoUusca whilst imprisoned in their
nidus, which are the agents of analogous movements of the Mamma-
lian ovum in the fallopian tube, and which are probably common to
the embryos of all classes of animals at that early period which the
Polygastric Infusoria seem permanently to represent.

These cilia, the outward instruments of locomotion in Infusoria,
and which are retained on a greater or less proportion of the mucous
surfaces of all animals, most probably vibrate by virtue of the con-
tractility of their tissue. Ehrenberg, however, directs attention to
their expanded base in some Polygastria, and especially to a radiated
structure there which he conceives to indicate the disposition of the
muscular fibres moving such cilia.

In observing the motions of the Polygastric Infusoria, one per-
ceives that they avoid obstacles to their progress ; rarely jostle one
another ; yet it is difficult to detect any definite cause or object of
their movements. Some species, it is true, prey upon animalcules of
their own class, and will gorge an individual of nearly their own
size, which they attract by the currents in the water caused by the
oral vibratile cilia, or entangle and inclose by those organs.* But
the greater number of the class subsist on the minute atoms of the
decomposing animal and vegetable substances of the fluids or in-
fusions in which they exist, — particles which do not require a
definite pursuit, since they are inert and generally diffused through-
out the infusion.

* XIX. p. 202.
C 3

22

LECTURE II.

The motions of the Polygastria have appeared to me, long watching
them for indications of volition, to be in general of the nature of
respiratory acts, not attempts to obtain food or avoid danger. Very
seldom can they be construed as voluntary, but seem rather to be
automatic ; governed by the influence of stimuli, within or without
the body, not felt, but reflected upon the contractile fibre ; and
therefore are motions which never tire. We may thus explain the
fact which Ehrenberg relates — not without an expression of surprise
— namely, that at whatever period of the night he examined the
living Infusoria, he invariably found them moving as actively as
in the day-time ; in short, to him it seemed that these little beings
never slept. Nor did this appear to be merely the result of the
stimulus of the light required to render them and their movements
visible ; since when they were observed upon the sudden application
of light without any other cause of disturbance, they were detected
coursing along at their ordinary speed, and not starting off from a
quiescent or sleeping state.

Evidence of muscular action in the Polygastria is afforded by the
contraction and change of form of the entire body. These changes
are so rapid, extensive and various in certain species that it is impos-
sible to refer their bodies to any definite shape : such form the genus
Proteus of Miiller, and the family Amoebcea of Ehrenberg. No defi-
nite arrangement of nervous matter has yet been detected in the
Polygastric Infusoria ; but its presence is indicated by the coloured
eye-speck in certain genera : and nervous conductors of impressions

are no less requisite for reflex
than for voluntary motions.

The eye-speck {Jig. 11. c), as
the bright pink spot has been
interpreted by Ehrenberg, is
usually single, e. g. Amblyophis,
Euglena, Chlorogonium ; but is
double in Distigma : it is absent
in the AstasicBce, which have
other close relations to the single-
celled plants.

In many Polygastric animal-
cules, e. g. Vorticella, Loxodes,
there is a permanent cavity
{fig. 18. a.) in the interior of the
cell-like body, which opens ex-
ternally. This aperture, which
may be termed the mouth, is sometimes sessile, sometimes placed upon

Monad of Volvox.

I'OLYGASTKIA. 23

a long extensile neck, as in Lacrijmaria ; in some monads, if Ehren -
berg have rightly interpreted its presence and position, it is pro-
vided with a long tentacle or a pair of tentacles {p'g. 11. a.) ; it has a
conspicuous fringe of cilia in some Polygastria {Jig- 13. «.) ; in other
species it is unequivocally armed with a curious dental apparatus,
consisting of a series of long, slender and sharp teeth, arranged side
by side, in the form of a cylinder, as in Chilodon and Nassula
{Jig. 14. a, a).

Later Microscopists have failed to detect the mouth or the canals
converging towards it from the green globules, which canals Ehren-
berg has described and figured in the constituent monad of the
Volvox glohator{fig. 11).* Sieboldf refers, indeed, the Volvoci7icB to
the same group of the Vegetable Kingdom as the Closterince and
BacillaricB ; and he cites the unusually large species of the genus .
Opalina (0. Ranarum), parasitic in the intestines of the Frog, as
affording indubitable evidence of the absence of any mouth, and
of the power of these astomatous Infusoria to absorb fluid nourish-
ment by generally diffused surface-pores, as shown by the bile-
stained contents of their body. In certain Astomata, with long
cilia or filaments, e. g. Actinophrys Sol, when a prey is brought
within their reach the filaments incline towards and bend over it,
intercrossing each other and pressing the prey to the surface of the
animalcule. That part of the surfiice yields ; the prey, whether it be
a smaller animalcule or plant-sporule, sinks into the substance of the
body, which closes over the prey without leaving any trace of its pas-
sage : functionally such passage performs the office of a mouth ; just
as the vacuolae in the central plasma, which receive the nutriment so
taken in, perform the office of stomachs : but neither such mouths nor
stomachs have proper parietes or a permanent existence J: and the same
may be said of any part of the external parietes of the animalcule
through which insoluble or indigestible parts of the food are extruded.
In the higher forms of the Polygastria provided with a determinate
mouth armed with teeth, the larger objects of food are seized and
bruised by them: the dental cylinder first expands in front to
receive the morsel, and, as this passes along, the cylinder contracts in
front and dilates behind, so as to push the food into the digestive cavity.
If such larger animalcules with unequivocal mouths be removed from
their native infusion to a drop of clear water, and after they have fasted
a few hours, a drop of the solution of pure indigo or carmine be added,
the fine particles of these colours will be greedily swallowed, and will
soon be seen to fill successively a number of pyriform or spherical

* XL, tab. iv. fig. 1. 13. t X. p. 7. % XIX. p. 198, pi. xvii.

c 4

24

LECTURE II.

cavities (y?^. 13. b.) in the interior of the animal. In some species
these cavities have been so shown to be very numerous; and if, with
Ehrenberg, we call them stomachs, they afford a very interesting ex-
ample, in these early forms of animal life, of the irrelative repetition
of this most essential and characteristic organ of the animal.
Ehrenberg has described and figured certain definite arrangements of
these digestive cavities, as well as of the alimentary canal, to which
he states that they are appended. In the Monads, and many other
of the more minute species of the Polygastria, he affirms the stomachs
to arise by separate tubular pedicles from a common mouth, as shown
mjig. 11., copied from his great work. Such species have no intes-
tine, no anus, and are said to be anenterous. In others, he believes
the so-called stomachs to be appended to an alimentary canal {Poly-
gastria eiiterodela Ehr.) : which canal may be bent into a loop, and
describe a circle, with the anus opening near the mouth, as in Vor-
ticella {Jig. 12.) ; or it may pass in a straight line through the axis
of the body, as in Enchelis ; or form several flexuous curves in its
passage from the mouth to the opposite extremity of the body, as in
Leiicophrys {Jig. 13.). But sometimes, as in the Kolpoda, neither
the mouth nor anus is terminal in position.

Vorticella.

It has been objected to this interpretation given by Ehrenberg of
the nature of the vacuola3 which receive and assimilate the nutrient
molecules, that certain species, as the Enchelis pupa, will swallow
another animacule nearly equal to itself in bulk, and thereby undergo
a total change in the form of its body ; but this may only imply great
dilatability of the oesophagus or common canal, such as we observe in
the boa constrictor, which becomes in like manner deformed after

POLYGASTRIA. 25

gorging a goat or other animal much thicker than the snake itself ;
for doubtless the little cavities successively receive and digest, like
the stomach of the boa, the dissolved parts of the swallowed prey.
But it has been further objected that the cavities are not fixed in
definite positions, but are seen constantly, though slowly, moving,
and apparently rotating through the general cavity of the animal.
This phenomenon, first observed by Focke in 1835*, led him to dis-
sent from Ehrenberg's account of the alimentary canal, at least in re-
gard to the Loxodes Bursaria, in which not only the balls of coloured
food, but the green corpuscles, which are constant elements in the
organisation of the animalcule, are subject to a regular circulating
movement, like the granules of chlorophyll in the leaf-cells of the
Valisneria spiralis : both food and granules being carried along by
the corresponding motion of the gelatinous fluid or plasma in which
they are suspended.

Analogous phenomena observed by Rymer Jones f, MeyenJ, Erdl§,
and Siebold||, have accumulated a body of evidence against Ehren-
berg's determinations which the sub-circular arrangement of the
food-filled spaces in Vorticella, and their subspiral disposition in
Leucophrys, are inadequate to repel. The only expressly organised
internal digestive apparatus in the stomatode Pohjgastria is a simple
wide and very dilatable cavity {Jig. 18. «.), extending into the middle
of the body from the mouth'; having a ciliated inner surface in Loxodes^
and probably other species. The spaces in the surrounding soft
tissue into which the digesting parts of an engulphed prey, or the
particles of carmine and indigo, pass, are usually filled with a clear
fluid, and they have no constant and specially organised canals of
communication with the common digestive cavity. In some species
this cavity has a second opening or anal outlet {Nassula eleyans) :
in most species the same opening serves both as mouth and vent.

Although a vascular system v/ith proper parietes has not been
detected in any Polygastrian, all the species which possess a mouth
and digestive cavity also manifest one or more pulsating vesicles,
varying as to shape and position in the diflerent species. During the
diastole the vesicle is filled by a clear colourless fluid ; in the systole
it disappears. The fluid is the product of the digestive process, and
answers to both chyle and blood in the higher animals ; by the action
of the pulsatile cells it is driven through the soft parenchyme and its
stagnation there is prevented. In the genera Vorticella, Epistylis,
Loxodes, in Amceha diffluens, Paramceciiim Kolpoda, Stylonychia

* XX. p. 785. t X^l- P- 121. X XXII.

§ XXIII. II XXIV. p. 16.

26 LECTURE II.

mytilus, and Euplotes patella, the pulsating sac is single and sub-
circular, and situated at one side of the body. In Actinophrys,
Sursaria and Trichod'ma there are two pulsating sacs : in Loxodes
Bursaria one of them is situated in the anterior third, tlie other in
the middle third part of the body {fig' 18. v, v.). In Arcella vulgaris
from three to four pulsating sacs have been observed. In Nassula
elegans four round hearts follow one another along the dorsal region
of the body ; in Trachelius Meleagris there is a row of from eight
to twelve such hearts. The contractile sac presents the form of a
long pulsating vessel in Spirostomum ambiguum and in Opalina
Planariarum. In Paramcecium Aurelia canals extend from the
circular sac in the form of rays. The Cryptomonas ovata and Opalina
Planariarum are the only species of the Astomatous Infusoria in
which the contractile sac has been observed.*

By the analogy of the gills of the acephalous Mollusks we may
regard the mechanism for renewing the surrounding oxygenised
medium upon the respiratory surface, to be the superficial vibratile
cilia, the action of which upon the water is necessarily attended in
the free Infusoria with a reaction which rolls the little animalcule
through its native element and produces the semblance of a definite
voluntary movement.

In the saline springs at Konigsborner and Rodenberg, Wohlerf ob-
served that the green mantle, formed of innumerable individuals of
Frustalia salina, Chlamydomonas pulvisculus and Euglena viridis,
was raised from the surface, here and there^ by bubbles of gas. He
collected the gas, and found it to be almost pure oxygen. This in-
teresting discovery clearly indicated a respiratory process like that of
plants. The minute green corpuscles, partly fixed in the inner layer
of the integument, partly circulating in the contained fluid of the
Polygastria, and regarded by Ehrenberg as ova, correspond in their
nature with the chlorophyll corpuscles of AlgcE, and most probably
perform an analogous function, fixing the carbon of the atmosphere
in the hydro-carbonates, and evolving oxygen.

Perhaps the most marvellous part of the organisation and economy
of the Polygastric Infusoria is that which relates to the function of
generation : the only one which does not necessarily require a special
organ for its performance — a proposition which will be quite intelli-
gible when the essential nature of the generative process is understood.

The part which Ehrenberg describes as the " testis " is the usually
large sub-spherical corpuscle (Jig. 17. n.\ situated at or near the
middle of the body in the Polygastria. It presents an extremely

* XXIV. p. 20. t VIII- 1843, p. 206.

POLYGASTRIA. 27

fine granular appearance, and is much firmer than the loose tissue in
which it is embedded. Its colour is commonly a dull yellow by
transmitted light ; and in the more minute species it is highly re-
fractive : upon the whole it presents the nearest resemblance to the
matter of the spermatozoa, which are themselves modifications of a
cell-nucleus; and from the close analogy which the so-called "testis"
presents to the " nucleus " in both the animal and vegetable cell, it
has now generally received the latter name. It is commonly single,
and presents the spherical or oval form in Chlamydomonas {fig. 17.
n n.\ Euglena, Actinophrys, Arcella, Amceba, JBursaria, ParamcB-
cium, Glaucoma^ Nassula, Chilodon, Loxodes {fig' 18. w.), &c. There
are usually two nuclei, one behind the other, in Amphileptus Anser,
Trachelius Meleagris, and Oxytricha Pellionella : four nuclei have
been observed in Stylonychia mytilus. More numerous nuclei, partly
united, like a row of beads, have been seen in Stentor polymorphus,
Spirostomum ambiguum, and Trachelius moniliger. The nucleus
assumes the elongated form in Vorticella convallaria, Epistylis leucoa,
and Bursaria truncatella, in which it is slightly bent : in Euplotes
Patella it is horse-shoe shaped, and in Stentor Roeselii is spirally
twisted.*

The nucleus performs an essential part in, and seems to govern, the
act of propagation by spontaneous fission, which is the most common
mode in the Polygastria. In Tab. xxxvi. of Ehrenberg's great work -f,
fig. vii. 13. shows, in Chilodon cucullulus, the nucleus divided in the
direction of the long axis of the body : in fig. 14. the division of the
whole body in the same direction has commenced: in fig. 15. it is
nearly completed. Figure 16. shows the preliminary division of the
nucleus transversely, and the succeeding figures illustrate the trans-
verse fission which follows. In most well-fed Polygastria, after the
preliminary division of the nucleus, which may be obscured from
view by the coloured contents of the body, the first sign of the
approaching fission is usually a clear line which may be discerned
stretching itself transversely across the middle of the body and indi-
cating a separation of the contents into two distinct parts. The
containing integument next begins to contract along this line, and
the creature to assume the form of an hour-glass {fig. 6, 7. and Jig. 14.) :
this, though an uncontrollable, seems to be a spontaneous action, and
the struggle of each division to separate itself from its fellow indicates
an impulse in each to assume its individual and independent character;
the which they no sooner effect than they dart off in opposite direc-
tions, and rapidly acquire the normal size and figure. In the Vorti-

* XXIV. p. 24. t XI.

28

LECTURE II.

Nassula.

cella and some other species, we have examples of spontaneous divi-
sion in the longitudinal
direction, which com-
mences at the mouth {Jig.
5. b.), and extends {ib.
c, d.), to the irritable and
contractile stem, from
which one or both of the
new-formed individuals
detach themselves (ib. e,
/.). Both the longitudinal
and transverse mode of
fission may take place in the same species (as in the Glaucoma,
figured in Jiff. 6, 3 — 8.), and as in the Chilodon cuculluliis above
cited. Cohn* observed, in Loxodes Bursaria, that the two indivi-
duals produced by longitudinal fission had almost the same size and
shape as the previous single individual ; whilst the two resulting
from transverse fission seemed longer to remain as mere halves or
mutilated individuals. Sometimes one of the individuals or halves
from the longitudinal bisection will set up another act of fission be-
fore it has quite separated from its fellow. The circulation of the
green globules is arrested during the process of spontaneous fission. |
In some species this spontaneous fission, which corresj)onds in so
interesting a manner with the earliest phenomenon in the develop-
ment of the ovum in the higher animals f , is arrested before its com-
15 pletion, but the partially separated individuals
continue in organic connection and form
compound animals, sometimes in the form of
long chains, sometimes branched, sometimes
expanding to form a spherical bag, as in the
well-known Volvox globator, which was long
deemed a single individual of a peculiar
species. New spherical groups of Volvoces

* XVIII.

f Beccaria, who first saAV a Polygastrian in the act of dividing, supposed it to be
two in copulation. Saussure, in 1765, first recognised its real character.

J This analogy I pointed ont in ilhistration of the cleavage -process of the ova
of the Mednsa in my "Lectures on Generation," delivered in 1840. It is alhided
to in the following passage in Dr. ISI. Barry's " Memoir on the Nucleus of the Animal
and Vegetable Cell," 8vo. 1847. "Between the appearances presented by the
mammiferous germ during the passage of the ovum through the oviduct, and cer-
tain infusoria, including the Volvox globator as figured by Ehrenberg, the resem-
blance first mentior^ed by Professor Owen is so remarkable that we cannot avoid
the beUef, that the same process operates in both."

rOLYGASTRIA.

29

are thrown oli' into the interior of the parent monadiary, which is
rent open to allow them to escape, as in,fiy. 15.

Another mode of generation is by gemmation or the development
of buds, which in some species, as Cheroma, grow out of the fore
part of the body, and in others, as Vorticella, from the hind part,
near the stem, or from tlie stem itself, from which the young animal
soon detaches itself. In most Vorticellidce, as in Carchesium and
Epistylis, the small liberated end of the body opposite the mouth is
provided with a circle of vibratile cilia, so long as the individual swims
freely : but these disappear when the pedicle is developed.

In the Zygnema, a freshwater confervoid Alga, the filaments of
which it is composed are developed, separately, by a linear multipli-
cation of cells ; the filaments then approximate, protuberances are
formed from corresponding cells of each, and these meet and adhere :
the co-adapted parts of the cell-walls disappear after a time, and the
contents of the confluent cells freely intermingle. This mode of de-
velopment is called " conjugation," and appears to be common to the
Algae generally. According to Stein*, the Gregarince conjugate, and
so form motionless spherical sacs, in which are developed a vast
number of minute bodies resembling Naviculce in shape, whence they
are called " navicella-sacs." But of these minute parasitic monads
more will be said in the Lecture on " Entozoa." In the ciliated
Polygastria conjugation has been observed to take place in the genus
Acti7iophrys^, i. e., two individuals of A.
Sol, have been observed to unite, coalesce, and
become one. The same has been recorded
of species of Epistylis and of Vorticella.

With regard to the more common fissi-
parous mode of multiplication, Ehrenberg
has figured gradations of this spontaneous
division of the organised contents of the
integument in the Go7iium {Jig. 16.) and
Chamydomonas {fig. 17.), which may be
compared with the earliest stages of the development of the germ,

as figured by Siebold in the
Strongylus and Medusa, by Baer
in the frog, and by Barry in the
rabbit; who, in 1841, remarked:
" On examining the figures given
by Ehrenberg of successive genera-
tions of the Chlamydomonas {fig.

Gonium.

Chlamydomonas.

XXY

p. 182.

t XIX. p. 207.

30 LECTURE n.

17.), I see a resemblance to the two, four, eight, &c. groups of cells
in the mammiferous ovum too striking not to suggest that the
process of formation must be the same in both : the essential part of
this process consisting in the division of the pellucid nucleus."* Ehren-
berg, who, as we have seen, calls this nucleus of the Poljgastria
the " testicle," views its division simply in the relation of the ne-
cessity of each individual resulting from the general fission having
such an organ : meaning that each monad, developed by spontaneous
fission, is perfected, as regards its so-called testis, by the spon-
taneous division of the previous testis, and not by the formation
of a new one. But this is not the mode in which the eye, or the
circle of teeth, or the pulsating sac, is gained by the second indivi-
dual from the fission : the division usually takes place so as to in-
clude the original organ in one or in the other moiety ; and that in
which it may be wanting gets the organ by a special and independent
development of it. The constancy of the preliminary fission of the
nucleus would therefore show that it related rather to the totality of
the act itself than to the partial completion of the individual in
respect of its being provided with a particular male organ of genera-
tion. How then, we may inquire, does the division of the nucleus
relate to the performance of the general act of spontaneous fission ?
Our hope of any insight into this mysterious relationship would be
from some light to be derived by analogous pheenomena. But with
what phsenomena is the one in question analogous ? Obviously most
closely with those which have been observed in the successive fissions
of the impregnated germ- cell of those ova, such e.g, as the ova of
the Ascaris {figs. 48-59.), best adapted to give a view of the fission
analogous to those which the perseverance of Ehrenberg enabled him
to trace in the spontaneous fission of the monad.

If this spontaneous fission of the nucleus and germ-cell preliminary
to the division of the germ-yelk has not been seen in the ova of other
animals, it is because hitherto only the coarser phaenomena of such
division of the yelk in the ova of Medusas, Mollusca, Fishes, Frogs,
&c. have been noticed. In Dr. Barry's observations however on the
development of the germ-mass in the pellucid ova of the rabbit f,
phaenomena were noted closely analogous to those described by Sie-
bold and BaggeJ in the ovum of the entozoon.

In reflecting on the cleavage phaenomena in the monad and the ovum
— that a central something is first established, and the consequence
thereof — I have been led to draw the same conclusion with respect to
both, and to regard the establishment of the special centre as the cause

* XXVI. p. 24. t XXVII. p. 320-324. + XXVIII.

rOLYGASTRlA. 31

of the confluence of the parts around it, and to call it " a centre of
attractive and assimilative force." * Since the pellucid centre of the
germinal body has not divided from the necessity of endowing the
moiety to be separated by the subsequent fission with a particular
organ required for its individual completeness, I infer that the same
preliminary act in the monad was not solely for the purpose of pro-
viding its separated moieties with their respective testes, but that it
had a higher significance.

As the pellucid centre in the ovum is the result of impregnation or
the reception of the matter of the spermatozoon, so it may be con-
cluded that the nucleus of the monad is of a nature similar to, if
not identical with, that of the spermatozoon. It was doubtless a
gross view of its nature and analogies to regard it as the homologue
of the whole preparatory organ of the spermatic fluid, such as is re-
quired in the higher animals ; because as the germ-cells exist in the
body of the Polygastria without the organ called ovarium, so we
ought to expect that the essential matter of the sperm would likewise
exist without a special testicular envelope.

The objection, however, to Ehrenberg's determination of the
nucleus as the " testis," that it has never been observed to produce
spermatozoa, is akin to that which has been opposed to his determin-
ation of the ova, viz. that the young have never been seen to quit
them and leave the shell behind. Neither of these objections will
apply to the view of the nucleus as the essential matter of the
sperm, and of the germ-cells as the essential elements of ova and
embryo.

A spermatozoon is doubtless a very general form of the essential
matter of the sperm : but in tracing the modifications of the sper-
matozoa from mammalia down the scale of animal life, we find them
gradually reduced to the head or nuclear part, and discern in the
vibratile caudal appendage an accessory relating to the passage of the
fertilising principle to the germ-cell, rather than to its essential opera-
tions when arrived there.

The best microscopical examinations of the spermatozoa show that
they consist of a homogeneous or minutely granular substance, which
exhibits a yellow amber-like glitter. The nucleus of the Polygas-
trian oiFers the closest resemblance to this character of tissue. And
it is not uninteresting to notice the close analogy of the modification
of form which the nucleus of some of the larger Polygastria, Stentor

* XXTX. p. 203. XXX. p. 60.

32 LECTURE II.

Roeselii e. g., presents to the spirally disposed elongated head of the
spermatozoon in the Torpedo, Pelobates, and the Passerine birds.

Besides the more frequent and commonly observed mode of propa-
gation by spontaneous fission, the Polygastria generate in the more
normal and perfect way. This, indeed, has been rarely seen, and has
been denied by some.* No doubt the term 'ova' has been applied to
many of the minute granules and nucleated cells in the soft paren-
chyme of the Polygastria, without that evidence which is requisite
to produce conviction of the accuracy of such determination. The
green-coloured nucleated cells, for example, which circulate in
LoxodeSy like the chlorophyll-particles in the leaf-cells of Valisneria,
are more probably concerned in fixing carbon and eliminating
oxygen, like their answerable parts in plants. But the essential
part of the ovum, e. g. the germ -cell, must exist to set on foot those
processes of development which lead to the formation of the embryo
in the viviparous species of Polygastria. And I may here cite the
remark of a distinguished chemist in support of the partial accuracy
at least of Ehrenberg's ascription of ova to the Infusoria. In the
simplest animals in which the ova or ovarium can be distinguished
with certainty, it is the only organ in which oil or fat is accumulated.
The yellowish masses which Ehrenberg discovered, by the aid of a
high magnifying power, on each side of the siliceous carapace in the
gelatinous envelope of the Friistulia salina, when chemically tested,
yield abundance of fat : tl.ey disappear, e.g. when treated with aether,
and the latter then contains a brownish fat in solution. This result
of Schmidt's minute analysis leads that accurate observer to regard
Ehrenberg's determination of those yellowish masses, as ovaria, to be
well founded.! The formation of locomotive germs in, and their
escape from, the interior of a Polygastrian, appears to have been
seen by Dr. Arlidge \ in the Trichodina pediculus, in which he de-
scribes the phenomena as a kind of internal gemmation. The best
description of the viviparous generation of a Polygastrian is that given
by Focke § and Colin || in Loxodes Bursaria. In this species, at the
latter end of autumn and in winter, there may be seen within the
body one or more large globules, which, when from six to eight in
number, present, by mutual pressure, a parenchymatous structure
(Jig. 19.). They are of different sizes, from -y^'" to -[^"' in dia-
meter, well-defined, almost colourless, filled with fine granules and
one or more hyaline nuclei {h) ; and they are inclosed by tw^o
contractile cysts, defining the individual life in each. These germs

* XXIV. p. 23. t IX- P- 36. X XXXI.

§ XXXII. II XVIII.

POLYGASTRIA.

33

lie free in a clearly defined cavity of the body, which opens by a
narrow canal through a projecting portion of integument, upon
an infundibular orifice with a labiated border. Cohn saw these
germs escape by this canal and orifice, the canal expanding, and
the germ yielding to the pressure and becoming a narrower and
longer body in transitu {fig. 18, e). The parturition lasted twenty
minutes, giving ample time to observe and delineate a germ half
in and half out of the mother. As soon as one end of the germ
enters the surrounding water, it begins to ciliate and create a cur-
rent, which accelerates the birth : this completed, the young rests
awhile beside the mother, then separates itself and moves freely
through the water. It is cylindrical, thrice as long as broad, obtuse
at both ends : but the embryos vary in size from -j^'" to -^-^"' in
length. They are colourless, sometimes present little tubercles at one
end, have no mouth, are beset by fine and long cilia, and differ so
much from the parent that their relationship could not be recog-
nised without observation of the birth. They have accordingly been
referred to a distinct genus, viz. Cyclidium, by Ehrenberg. * As soon

as one germ is born,
out follows another ; and
■.'''''/'/'. ^ Cohn thinks that when
; only one or two are
I, seen in a Loxodes, the
rest have already es-
'% caped ; and that many
J. are developed as a rule.
^ The position of the
^ outlet varies ; and Cohn
once saw two embryos
escaping by two distinct
apertures, which indi-
cates that the 'vulva' like the 'anus' may be casual and temporary.
The pulsatile vesicles of the parent are not disturbed in their actions
during the parturition. The rotation of the chlorophyl-cells is arrested
so long as a germ is inclosed in the body : but it is resumed, and goes
on more rapidly, as soon as the parent is relieved of her burden. One
of the moieties of a longitudinally splitting Loxodes may sometimes
be seen to contain germs, and these also to be excluded even before
the other moiety has become separated : thus the two distinct gene-
rative processes may go on simultaneously.

Cyclidium margaritaceum, XL p. 387., pi. xxii.

34 LECTURE n.

The Vorticella microstoma secretes, and surrounds itself by, a
smooth cyst, in which all its previous organisation is resolved into
a minutely granular fluid, save the pulsatile sac, which ceases to beat,
and the elongated bent nucleus. Two processes of development start
from this partial dissolution and passive pupal condition. In the one
(acinetiform) process the nucleus contracts itself into a shorter and
thicker shape; two pulsatile sacs are developed ; and a new integu-
ment is formed, from which radiate groups of long vibratile filaments.
The creature thus starts afresh into locomotive life as an Actiiio-
phrys ; and then developes a hollow stem, and becomes the Acineta
mystacina of Ehrenberg.* In this the nucleus expands, attracts
and assimilates the surrounding granular fluid, and becomes deve-
loped into a pyriform monad with a circular band of vibratile cilia : the
embryo escapes from the Acineta, swims off, and lays the foundation
of a new colony of Vorticellce. In the second (monadiform) process
of development the nucleus of the encysted pupa elongates and
divides by spontaneous fission into many nucleoli : each of these
exercises its attractive, assimilative, and modifying properties upon
the contiguous granular fluid : as many minute simple locomotive
monads are the result, which escape from a rent in the cyst, and
swim abroad, doubtless to undergo further changes, completing the
metagenetic cycle. \

By virtue of these diversified modes of multiplication, the powers
of propagation of the most diminutive of organised creatures may be
truly said to be i?nmense. Malthusian principles, or what are vulgarly
so called, have no place in the economy of this department of orga-
nised nature. To the first great law imposed on created beings,
"increase and multiply," none pay more active obedience than the
Infusorial animalcules.

Attempts have been made to calculate approximatively their rate of
increase.

On the 14th of November, Ehrenberg divided a Pa r«?72<Ecmm aurelia,
a polygastric animalcule measuring one twelfth of a line in length, into
four parts ; which he placed in four separate glasses.

On the 17th of November, the glasses numbered 1 and 4, each con-
tained an isolated Paramascium, swimming actively about. The
pieces in numbers 2 and 3 had disappeared.

On the 18th there was no change.

On the 19th each animalcule presented a constriction across the
middle of the body.

On the 20th No. 1. had propagated five individuals by transverse

* XL, tab. XX., fig. X. t XXV* pp. 478—485, XVIII., fig. 1 — 13.

POLYGASTRIA. 35

spontaneous division : in No. 4. eight individuals had in like manner
been generated.

On the 21st no change had taken place.

On the 22nd there were six nearly equal-sized individuals in No. 1.,
and eighteen individuals in No. 4.

On the 23rd, the individuals were too numerous to be counted.

Thus it was demonstrated that this species of Poljgastrian would
continue for six days without any diminution of reproductive force,
and that on one day a single individual twice divided, and one of its
divisions effected a third fission.

A similar experiment on a Stylonychia Mytilus, an animalcule one
tenth of a line in length, was attended with nearly the same results ;
it was well supplied with the green nutrient matter, consisting of the
Mo7ias pulvisculus, and on the fifth day the individuals generated by
successive divisions were too numerous to be counted.

The conditions of this parthenogenetic mode of propagation appear
to be the close conformity of the entire Polygastrian to the condi-
tion of the nucleated cell, the attractive and assimilative force of the
nucleus, and the large proportion of unchanged secondary cells in its
organisation.

Cells predominate in the tissues of the vegetable kingdom, the
lower members of which consist exclusively of them, and have been
thence called ' planta3 cellulares : ' the lowest of all consist of a single
nucleated cell.

The animal kingdom starts from the same elementary beginning :
a cell-wall forms the smooth elastic and contractile integument of
the Gregarina — a genus of microscopic parasites which infest gre-
gariously the internal cavities and canals of insects and worms — in
which a fluid with granules, and a firm nucleus with sometimes a
nucleolus, are the sole representatives of organs or viscera. Yet
the power of the Gregarince to live and grow independently by assi-
milating foreign nutriment, the vital contractility of their tegu-
mentary tunic, their chemical composition and their definite forms,
with such well-marked specific characters, in a few instances, as
the Greg, brevirostris and Greg. Sieboldii present, render their in-
terpretation by Kolliker as a low and primitive form of parasitic
animal, the most accordant with actual physiological and zoological
knowledge.*

The Gregarina is a single-celled animal, which differs from the
single-celled plant by the vital contractility of its tissue, and the solu-
bility of its cell-wall in acetic acid. Devoid of mouth, stomach, or

VII. p. 10.

D 2

Ob LEOTUKE U.

any other organ properly so called, it reduces our definition of an
animal to the difference indicated in the preceding comparison.

The Rhizopoda are but little better organised, although they are
locomotive, and provided with long slender branched filamentary feet,
and have their simple contractile tissue protected, in most species, by
chambered foraminiferous shells.

The ciliated Polygastria exhibit the next step in the progress
of individualising a higher independent embodiment of animal life.
A firm central nucleus in which, as in Gregarina and Amceba, resides
the mysterious property of spontaneous division, indicates, however,
their essential character as animated cells, and recalls to mind the bold
figure in which Oken long since indulged, when he aflBrraed that the
higher animals, and even Man himself, were aggregates of Infusoria.
The very step, however, which the Infusoria take beyond the primi-
tive astomatous cell-stage of their existence, invests them with a spe-
cific character, as independent and distinct in its nature as that of the
highest and most complicated organisms. No mere organic cell,
destined for ulterior changes in a living body, has a mouth armed
with teeth, cavities for digestion, pulsatile cells for circulating a clear
plasmatic fluid, an irritable and contractile integument beset with
vibratile cilia, or prolonged into tentacnla.

And now you may be disposed to ask : To what end is this discourse
on the anatomy of beings too minute for ordinary vision, and of
whose very existence we should be ignorant unless it were revealed
to us by a powerful microscope ? What part in nature can such
apparently insignificant animalcules play, that can in any way interest
us in their organisation, or repay us for the pains of acquiring a know-
ledge of it ? I shall endeavour briefly to answer these questions.
The polygastric Infusoria, notwithstanding their extreme minuteness,
take a great share in imj)ortant offices of the economy of nature, on
which our own well-being more or less immediately depends.

Consider their incredible numbers, their universal distribution,
their insatiable voracity ; and that it is the particles of decaying
vegetable and animal bodies which they are appointed to devour and
assimilate.

Surely we must in some degree be indebted to these ever active
scavengers for the salubrity of our atmosphere. Nor is this all :
they perform a still more important office, in preventing the pro-
gressive diminution of the present amount of organised matter upon
the earth. For when this matter is dissolved or suspended in water,
in that state of comminution and decay which immediately precedes
its final decomposition into the elementary gases, and its consequent
return from the organic to the inorganic world, these wakeful

POLYGASTRIA. 37

members of nature's invisible police are every where ready to arrest
the fugitive organised particles, and turn them back into the ascending
stream of animal life. Having converted the dead and decomposing
particles into their own living tissues, they themselves become the
food of larger Infusoria, as e. g. the Botifei^a, and of numerous other
small animals, which in their turn are devoured by larger animals, as
e. g. fishes ; and thus a pabulum, fit for the nourishment of the highest
organised beings, is brought back by a short route, from the extremity
of the realms of organic nature.

There is no primordial and self-subsistent organic matter, as Buffon
taught : the inorganic elements into which the particles of organic
matter pass by their final decomposition are organically recomposed,
and fitted for the sustenance of animals, through the operations of
the vegetable kingdom. No animal can subsist on inorganic matter.
The vegetable kingdom thus stands, as it w^ere, in the breach between
animal matter and its ultimate destruction ; but in this great office
plants must derive most important assistance from the polygastric
Infusoria. These invisible animalcules may be compared, in the
great organic world, to the minute capillaries in the microcosm of the
animal body, receiving organic matter in its state of minutest sub-
division and when in full career to escape from the organic system,
and returning it by new channels towards the central and highest
point of that system. Like true beneficence, they work their good
unobtrusively and unseen.

But besides the important functions which the Polygastria per-
form in relation to the conservation of organic matter and of the
purity of the atmosphere, they likewise take their share in modi-
fying the crust of the earth. It has been shown that some Poly-
gastria are naked, others loricated or defended by silicious shells, of
definite and easily recognisable forms and patterns in difi'erent
species. Professor Ehrenberg had not long made these observations
before he discovered that a certain kind of silicious stone, called
Tripoli or Polierschiefer, was entirely composed of such cases —
was, in fact, the debris of Polygastric animalcules, chiefly of an
extinct species, called Gaillonella distans. The substance alluded
to has long been known in the arts, being used in the form of
powder for polishing stones and metals. At Bilin, in Bohemia, there
is a single stratum of this substance, not less than fourteen feet thick,
forming the upper layer of a Tripoli hill, in every cubic inch of which
layer Ehrenberg estimates that there are forty-one thousand millions
of individuals of the Gaillonella distans. It likewise contains the
shells of NaviculcE, Bacillaria, Actinocyclus, and other silicious ani-
malcules. The lower part of the stratum consists of the skeletons of

D 3

38 LECTURE II.

these animalcules, united together without any visible cement ; in the
upper and more compact masses the infusory shells are cemented
together, and filled by amorphous silicious matter, formed out of dis-
solved cases. Corresponding deposits of the silicious cases of these
animalcules have since been discovered in many other parts of the world,
some including fresh water species, others marine species of Infusoria.
At Egea, in Bohemia, there is a stratum of two miles length, and
averaging twenty-eight feet in thickness, of which the uppermost ten
feet are composed wholly of Infusoria, including the beautiful shells
of Campylodiscus : the remaining eighteen feet consist of the silicious
cases of Infusoria mixed with a substance like pollen. The town of
Richmond, in Virginia, is built on barren silicious strata, twenty feet
in thickness, composed chiefly of Infusorial shells, including the well-
marked Actinocyclus and Coscinodiscus. A quantity of a pulverulent
matter is deposited upon the shores of the lake near Uranea in
Sweden, and which, from its extreme fineness, resembles flour. This
has long been known to the poorer inhabitants under the name of
Serg mehl, or mountain meal, and is used by them mixed up with
flour as an article of food : it consists almost entirely of the silicious
shells of pulverised Poli/gastria, and of closely allied single-celled
locomotive plants.

Most of the Infusorial formations, as the polishing slates of Cassel,
Planitz, and Bilin, are, in fact, extraordinary monuments, which have
handed down to us the record of the existence of polygastric Infu-
soria at remote periods of the history of this planet. Their minute
size, elementary structure, tenacity of life, and marvellous powers of
reproduction, have enabled them to survive, as species, those destroying
causes which have exterminated all the contemporaneous higher forms
of animals. Several species, for example, still exist, which were in
being at the period of the deposition of the chalk, and which contri-
buted their silicious remains to the flinty masses that are always
more or less intermixed with cretaceous matter. Existing species of
Polygastria have even been detected as low down as the Oolite. Be-
fore this discovery no remains of higher organised animals at present
in existence had been detected, with the same degree of certainty,
even in the cretaceous formation. A fe,w existing zoophytes and
testacea first make their appearance in the tertiary beds immediately
above the chalk ; hence called Eocene, from eoc, the dawn, as indi-
cating the first dawn of the creation of existing species. The num-
ber of existing species of shells increases in the ' Miocene,' and is still
greater in the ' Pliocene ' tertiary strata ; but the higher animals, as
the Anojjlotherla, Palmotlieria^ Mastodons, Mammoths, and other
mammalian contemporaries of the Eocene, Miocene, or Pliocene tes-

ROTIFERA. 39

tacea, have utterly perished. The discovery, therefore, by Ehrenberg,
of several, at least twenty, species, of silicious-shelled Infusoria, fossil,
in the chalk and chalk marls, which are perfectly identical with those
now living in the sands of the Baltic and North Sea, is a most interest-
ing addition to the obscure history of the introduction of the successive
species of animals on this planet, and must add greatly to the interest
of the Infusorial class in the eyes of the naturalist and geologist.
"For these animalcules/' says Ehrenberg, "constitute a chain, which,
though in the individual it be microscopic, yet in the mass is a
mighty one, connecting the organic life of distant ages of the earth,
and proving that the dawn of the organic nature co-existent with us
reaches further back in the history of the earth than had hitherto
been suspected."

The still existing species are by no means rare or isolated, but fill
in incalculable numbers the seas of Northern Europe, and are not
wanting on the tropical coasts of the globe. With reference to the
operations of the invisible Polygastria at the present day on these
and other coasts, I have only time to refer you to a paper by the
indefatigable Berlin Professor, entitled " Observations upon the im-
portant Part which Microscopic Organisms play in the choking up
of the Harbours of Wisraar and Pillau ; also, in the Formation of the
Mud which is deposited in the Bed of the Elbe, at Cuxhaven, and
upon the agency of similar Phenomena in the Formation of the Bed
of the Nile, at Dongolar in Nubia and in the Delta of Egypt."
" Truly, indeed," says Ehrenberg, " the microscopic organisms are
very inferior in individual energy to lions and elephants, but in their
united influences they are far more important than all these animals."*

LECTUKE TIL

ROTIFERA.

The animal kingdom may be likened to a cone, the species of which
it is constituted diminishing in number as they ascend in the scale of
complexity. Rising from different parts of the basal circumference,
the different groups reciprocally approximate, interweaving their
mutual affinities within a progressively closer reticulation, until they
finally culminate in the apex, which is crowned by Man.

* XXXII. p. 386.
D 4

40

LECTURE m.

The interest with which you listened to the anatomical details of
those minute creatures, which, by their low grade of structure, their
extensive distribution and incalculable myriads, form the base of the
animal pyramid, encourages me again to invite you to condescend
from the high sphere of your habitual studies and duties to this most
remote and lowly region of animal life.

Low though the Infusoria be, and remote from man in the scale of
organisation — literally at an invisible distance from us — yet, by
the aid of the optician's science and skill, analogies may be discerned
in them to the human structure, which ought to enlist your sympa-
thies with the discoveries that have been made in their Microscopical
Anatomy.

Time was, and not many years ago, in this country, when that
term. Microscopical Anatomy, was almost regarded as synonymous
with the anatomy of the imagination : but the numerous and highly
important discoveries which have been made and confirmed by
observers in almost every European state, by means of the greatly
improved microscopes at their command, have placed the value, the
indispensability, of that instrument to the anatomist, beyond the
necessity of vindication.

Some scepticism may be natural and pardonable, when the anatomy
of an animalcule xoVo" ^^ ^ ^^^^^ ^^ diameter is attempted to be
demonstrated : but trace it to its source, and you will find such
incredulity to be essentially based, not merely on distrust in our
means of observation, but in the difficulty of adequately conceiving
the relations of size. Just ideas of these relations are essential to the
acceptance and full appreciation of the discoveries which have extended
for us the bounds of space ; and I will ask permission to quote the
words of one of our old philosophers, which bear directly on this
subject, and, expressing a noble confidence in intellectual progress,
shed a prophetic gleam upon the present improved powers of pene-
trating space.

" In consistency, I suppose some bodies to be harder, others softer,
through all the several degrees of tenacity. In magnitude, some to
be greater, others less, and many unspeakably little. For we must
remember that, by the understanding, quantity is divisible into
divisibles perpetually. And, therefore, if a man could do as much
with his hands as he can with his understanding, he w^ould be able to
take from any given magnitude a part which should be less than any
other magnitude given. But the omnipotent Creator of the world can
actually from a part of any thing take another part, as far as we by
our understanding can conceive the same to be divisible. Wherefore
there is no impossible smallness of bodies. And what hinders but

ROTIFER A. 41

that we may think this likely ? For we know there are some living
creatures so small that we can scarce see their whole bodies. Yet
even these have their young ones ; their little veins and other vessels,
and their eyes so small as that no microscope can make them visible.
So that we cannot suppose any magnitude so little, but that our very
supposition is actually exceeded by nature.

"Besides, there are now" (the book was published in 1655) "such
microscopes commonly made, that the things we see with them appear
a thousand times bigger than they would do if we looked upon them
with our bare eyes. Nor is there any doubt but that, by augmenting
the power of these microscopes (for it may be augmented as lono- as
neither matter nor the hands of workmen are wanting), every one of
those thousandth parts might yet appear a thousand times greater
than they did before. Neither is the smallness of some bodies to be
more admired than the vast greatness of others. For it belongs to
the same Infinite Power as well to augment infinitely as infinitely to
diminish. To make the great orb, namely, that whose radius
reacheth to the sun, but as a point in respect of the distance between
the sun and the fixed stars ; and, on the contrary, to make a body so
little, as to be in the same proportion less than any other visible body,
proceed equally from one and the same Author of Nature. But this
of the immense distance of the fixed stars, which for a long time was
accounted an incredible thing, is now believed by almost all the
learned. Why then should not that other, of the smallness of some
bodies, become credible at some time or other ? For the majesty of
God appears no less in small things than in great ; and as it exceedeth
human sense in the immense greatness of the universe, so also it doth
in the smallness of the parts thereof. Nor are the first elements of
compositions, nor the first beginnings of actions, nor the first
moments of time more credible, than that which is now believed of
the vast distance of the fixed stars."*

I have said, that in the diminutive Polygastria, there might be
discerned structures analogous to our own. Vibratile cilia — their
sole organs of locomotion — are the first actively moving parts with
which the mammiferous ovum is endowed, with which, therefore, we

* XXXni. vol. i. p. 445. A similar idea had occurred to a much older philo-
sopher : —

" Tertia pars nulla ut possit ratione videri.
Horum intestiimm quodvis quale esse putandum 'st ?
Quid cordis globus aut oculi ? quid membra ? quid artes ?
Quantula sunt ? quid prseterea primordia quaeque,
Unde anima, arque animi constet natura, necessum est ? "

Lncret. lib. iv.

42 LECTURE ni.

ourselves commence life. They are retained throughout life as an
essential part of the organisation of a very extensive tract of our in-
ternal mucous membranes ; and these most minute and incalculably
numerous vibrating filaments, like their homologues in the Poly-
gastria, know no repose. It might almost have been anticipated that
this earliest possessed, and most extensively diifused, organical dynamic
in every member of the animal kingdom, should be the most conspi-
cuous, if not the sole, moving power in the first-born of Fauna.

Is man liberated from one narrow spot in space, and enabled to
move to and fro on the surface of his little world, by virtue of an
internal receptacle of nutriment ? So, likewise, is the Infusorial ani-
malcule. Even some of the superadded complications of the digestive
sac are present ; the Polygastrian seizes food with prehensile organs,
reduces it by the action of a score of dental spines, arranged, as we
have seen, like the teeth of the circular trephine : it is the very type
of the digestive function : assimilating and re-organising the decom-
posing particles of animal and vegetable matter with a hundred-
stomach power. That low delight, the bliss supreme of the civilised
gourmand, is given most liberally where it ought to be, to the crea-
tures at the lowest grade of animality.

Nor is the procreative function so abundantly or so variously en-
joyed by any other animal as in the Polygastria : they are fissipar-
ous, gemmiparous, oviparous, and viviparous. In creatures whose
most obvious and common mode of propagation is by spontaneous
fission, a power so actively exercised, as, according to Ehrenberg's
experiments, to be productive of an incalculably rapid rate of mul-
tiplication, it may be demanded : To what end were special organs
of generation developed ? Yet the essential elements of these existed
in the Loxodes and Vorticella, and laid the foundation of the ciliated
embryos which those species brought forth. If Ehrenberg be cor-
rect in his ascription of ova to any of the Polygastria, it is reasonable
to suppose that the fissiparous reproduction has reference principally
to increasing the numbers of individuals in the infusions, or recep-
tacles of decayed organisms, in which they at that time exist ; whilst
the development of fertile ova, like the germs in the multiparous
pupae of Vorticella, which long retain their latent life in the en-
cysted state, have relation to future and different localities or collec-
tions of such infusions, into which the ova or germs may be
conveyed more easily than the entire animals, and so lay the
foundation of new generations of Infusoria. In the heats of sum-
mer, for example, many of the pools and stagnant collections
of water in which Infusoria abound are dried up. Now, it is true,
that certain Infusoria have the power of retaining their vitality

ROTIFEEA, 43

for a long time in a state of desiccated torpidity. I sliall presently
have to allude to the experiments of Spalanzani and others on the
wheel-animalcules, in illustration of this curious property. Some
who have repeated his experiments have not succeeded in reviving
the subjects after so long a period of inanimation as four years*;
nevertheless, great tenacity of life is unquestionably, notwithstanding
the delicate tissues of the Infusoria, a property of creatures of their
grade of organisation ; and what holds good of the parent, in regard to
this property of latent life, must, a fortiori, be allowed to the ovum
and encysted pupa.

The supposed act of oviparous generation, that of sending forth
countless germs through the fatal laceration or dissolution of the
parent's body, is most commonly observed in the well-fed Polygastria,
which crowd together as their little ocean evaporates; and thus
each leaves, by the last act of its life, the means of perpetuating
and diffusing its species by thousands. When the once thickly ten-
anted pool is dried up, and its bottom converted into a layer of dust,
these inconceivably minute and light germs will be raised with the
dust by the first puff of wind, diffused through the atmosphere, and
may there remain long suspended ; forming, perhaps, their share of
the particles which we see flickering in the sunbeam, ready to fall
into any collection of water, beaten down by every summer shower
into the streams or pools which receive or may be formed by such
showers, and, by virtue of their tenacity of life, ready to develope
themselves wherever they may find the requisite conditions for their
existence.

The possibility that such is the design of the alleged oviparous
and of the observed encysted multiparous generation of the Infu-
soria, and such the common mode of the diffusion of their germs,
renders the hypothesis of spontaneous generation, which has been
so frequently invoked to explain their origin in new formed natural
or artificial infusions, quite gratuitous. If generative organs might,
at first sight, seem superfluous in creatures propagating their
kind by gemmation and spontaneous fission, equivocal generation
is surely still less required to explain the origin of beings so
richly provided with the ordinary and recognised modes of multipli-
cation. Many experiments have, however, been detailed, in which
adequate precautions appeared to have been taken to prevent the
possibility of the entry of fertile germs into the fluid experimented
on, after means had been taken to destroy all that it might contain.
From these experiments, the mere access of atmospheric air, light,

* CXXXV. vol. ii. p. 127.

44 LECTURE m.

and heat to the infusions has been deemed to include all the condi-
tions required for the primary formation of the lower animal or of
vegetable organisms. The results in favour of such a view are,
however, explicable by supposing that due precautions had not been
adopted at the beginning of the experiment to exclude every animal
or germ capable of development in the infusion, or to gain satisfactory
assurance that the air subsequently admitted contained nothing of the
kind. The only experiment in which these difficulties appear to have
been fully overcome, is that in which the requisite apparatus was
conceived by Professor Schulze of Berlin. He filled a glass flask
half full of distilled water, in which were mixed various animal and
vegetable substances : he then closed it with a good cork, through
which were passed two glass tubes, bent at right angles, the whole
being air-tight : it was next placed in a sand-bath, and heated until
the water boiled violently. While the watery vapour was escaping
by the glass tubes, the Professor fastened at each end an apparatus
which chemists employ for collecting carbonic acid : that at the one
end was filled with concentrated sulphuric acid, and the other with a
solution of potash. By means of the boiling heat, it is to be pre-
sumed that every thing living and all germs in the flask or in the
tubes were destroyed ; whilst all access was cut off by the sulphuric
acid on the one side, and by the potash on the other. The apparatus
was then exposed to the influence of summer light and heat ; at the
same time there was placed near it an open vessel, with the same
substances that had been introduced into the flask, and also after
having subjected them to a boiling temperature. In order to renew
constantly the air within the flask, the experimentor sucked with his
mouth several times a day the open end of the apparatus, filled with
the solution of potash, by which process the air entered his mouth
from the flask after passing through the caustic liquid, and the atmos-
pheric air from without entered the flask through the sulphuric acid.
The air was of course not at all altered in its composition by passing
through the sulphuric acid in the flask ; but all the portions of living
matter, or of matter capable of becoming animated, were taken up by
the sulphuric acid and destroyed. From the 28th of May until the
beginning of August, Professor Schulze continued uninterruptedly
the renewal of the air in the flask, without being able, by the aid of
the microscope, to discover any living animal or vegetable substance ;
although, during the whole of the time, observations were made
almost daily on the edge of the liquid ; and when, at last, the Pro-
fessor separated the different parts of the apparatus, he could not
find in the whole liquid the slightest trace of Infusoria or Confervas,
or of mould ; but all three presented themselves in great abundance

KOTIFERA. 45

a few days after lie had left the flask standing open. The vessel
which he placed near the apparatus contained on the following day
Vibriones and Monads, to which were soon added larger polygastric
Infusoria, and afterwards Rotifera.* To the organisation of this
higher form of Infusoria, which are always the last to appear in
infusions,, I now proceed.

The Rotifera are so called on account of the aggregation of their
cilia into circular or semicircular groups upon lobes or processes of
the head, which resemble rudiments of the ciliated tentacles of the
higher or Ciliobrachiate Polypes. ] By the vibration of these cilia,
which occasions the appearance of little wheels in rapid motion,
strong currents are produced in the surrounding water, and they thus
serve as the instruments for locomotion and the prehension of food.
The body in the Rotifera is more or less elongated or vermiform. It
is provided, at its posterior extremity, with a pair of slender and
pointed claspers, protected by a sheath, into which they can be re-
tracted when not in use. These appendages are longer than the body
in some species, as the Notommata Tigris : their sheath is much elon-
gated and slightly annulated in the Brachioni : it is telescopiform in
Scaridium : both claspers and sheath are wanting only in the AnurcBUS.
The integument of the body is smooth, and never ciliated : although
the parasitic jointed fibres of Hygrocrocis, which attach themselves
sometimes to the integument of the larger species, as Notommata
centrtira, give it that appearance. In Chcetojiotus and Philodina
aculeata the integument is beset with stiff bristles. The Polyarthrce
have long jointed filaments, like the rays of a fish's fin, attached to
the sides of the body ; indicating the first rudiments of lateral
members.

Not any of the species are known to secrete a silicious shell ; but
many of them are provided with a transparent gelatinous case, into
which they can contract their bodies ; thus offering another analogy
to the Ciliobrachiate Polypes, and also to the bivalve-sheathed Ento-
mostraca. The principal loricate genera are Noteus, A?iurcBa, Bra-

* XXXIV. vol. xxiii. p. 165. PL 1. fig. 2. gives a representation of the simple
and effectual apparatus devised by Prof. Schulze. In a glass of water containing
decaying SpirogyrcB Colin first observed Pararncecium Aurelia, which was followed
in qu.ick succession by Baker's Proteus, Lacrimaria Proteus or Trachelocerca Olon
Chilodon cucullatus, species of Colpoda, Euplotes of large size with green globules
inside, and the colourless Euplotes Charon. All these succeeded each other in the
course of three weeks. Then came the Rotifers.

f Ehrenberg remarks that the Rotifera are " Bryozoa without the i>ower of pro-
pagating by gemmation."— XI. p. 384.

46

LECTURE 111.

chionus, and Pterodina. In all the species tlie shell is a cylinder or
case (testiila), not a mere shield (scutellum). Horn-like processes
project from the front margin of the firm shell in some species of
Brachionus, and from both front and back margins in other species.
In some Notei and AtiurcBCB the shell is ornamented by large pen-
tagonal or hexagonal groups of granules.

The cephalic cilia are aggregated into from two to five groups, upon
lobes (Jiff' 20, a), or pedunculate discs, which in some species are
developed into short tentacular processes, with a verticillate arrange-
ment of cilia, as in Floscularia and Stephanoceros {Jiff' 22.). These
lobes or processes Ehrenberg regards as muscular. The movements

of the ciliated quasi-wheels are
under the control of the will. They
can be instantly arrested, the whole
apparatus drawn out of sight,
again protruded, and as instantly
set in motion. The muscles which
protrude and retract the ciliated
lobes, which bend and modify the
form of the body, and which throw
out, attach, or heave in the anal
anchors, are developed in the form
of distinct narrow fibrous bands,
which are transversely striated.
The long and narrow longitudinal
muscles which retract the head and
shorten the whole body are some-
times in two pairs, one lateral and
the other dorsal (6,^^.20.). There
are other mere filamentary longitudinal muscles, which are usually
forked at their insertions. Very fine muscular threads are attached
to the principal viscera, and keep them in their places. The antagonist
transverse bands which diminish the breadth of the body and restore
its length, are shown at c c, fig. 20. All these muscles are attached
to an inner layer of the skin separable from the outer one.

With this advanced condition of the muscular system the parts of
the nervous system now likewise become distinctly visible. Ehren-
berg delineates a large cerebral ganglion, which in some species is of
a trilobate form, in others {fig. 22, b) is double, and which is always
in close connection with the coloured, generally red, ocellus or eye-
speck {fig. 20, e, fig. 22, a). Some of the nervous filaments ex-
tend from this ganglion forwards to the muscular lobes supporting

Notommata.

KOTIFERA. 47

and moving the wheel-like cilia ; other filaments of greater length
stretch backwards into the cavity of the body, apparently attached to
the ventral integument, on the outer side of the principal longitudinal
retractor muscles. In Notommata clavulata Ehrenberg describes two
radiated ganglions in the neck {Jig. 20, d, d), superadded to the prin-
cipal cerebral ganglion connected with the rotatory muscle, and other
gangliforra bodies on each side, developed upon the long abdominal
nervous filaments. Besides these, other small enlargements are
figured as ganglions upon the transverse bands or " vascular circles " of
Ehrenberg, making altogether eight pairs of ganglions in this little
animalcule, which measures one-eighth of a line in length. With
regard to the ganglions on the so-called transverse vessels, both these
and the vessels bear a striking analogy to those transverse muscles
with a middle swelling, which Dr. Arthur Farre* has described and
figured in his Ciliobrachiate Polypes. The most satisfactory indica-
tion of the nervous system in a Rotifer appears to be that given by
Leydig in the Lacinularia socialis. It consists of two groups of four
spindle-shaped nucleated cells, the extremities of which are attenuated
and produced into fine (nervous) filaments. One group is situated
between the pharynx and ingluvies ; the other and more conspicuous
group is placed in the base of the tail. |

The movements of the Rotifera are of a more varied character than
those in the Polygastria ; they sometimes dart swiftly forwards, at
others glide leisurely along, or, anchoring themselves by their little
terminal claspers, employ their ciliated paddle-wheels to create the
currents which prove so fatal to the minuter race of Infusories. The
Philodina creeps, like a leech, by the aid of a sucker at the mouth,
and another at the end of the tail. When the Rotifer has attached
itself to some fixed body by its hinder claspers, the vortices which it
occasions in the water are so directed as to draw the smaller Infusoria
and other particles of food towards the orifice of the infundibular
mouth. In some species this cavity is so large as to allow of a con-
siderable accumulation of food, as e.g., in the Stephatioceros {Jig.
22, c). In Lacinularia a pair of bifid salivary glands open into it.

Having seized their prey, it is exposed in a second cavity or pharynx
to the destructive action of a complicated dental apparatus {Jg. 21, f).
This consists of two horny jaws, acting horizontally upon a median
piece, or anvil. The hard maxillae are each bent upon themselves at
a right, or, rather, acute angle ; the transverse or dental part, w^hich
beats upon the surface of the anvil, being divided into two or more
sharp spines. The muscles which work these dental hammers are

* XXXV. p. 394., pl.xxi., fig. 13. f CLVIL, p. 452. t. xvii.

48

LECTURE III.

21

disposed in four masses, and inserted into the longitudinal or poste-
rior portion, which may be regarded as the rudimental jaw. The
efficacy of these instruments in tearing to fragments the objects swal-
lowed up may be easily discerned in the living animal through its
transparent parietes.

The condition of the alimentary organs differs in the two sexes of
the Rotifera. In the minute males there is a simple digestive sac,
without intestine or anus ; and those parts are absent, according to
Gosse, in the female also of his Asplanchyia priodonta* In the
females of all the species previously observed the alimentary canal is
a more or less simple tube {fig. 20, f,g, h), commonly extending lon-
gitudinally through the well-developed abdominal cavity, to terminate
by a cloacal outlet (h) at the hinder end of the body, generally above
the base of the sheath of the claspers. In the loricate Tubicolaria
and Melicerta the intestine is bent and the anus opens far forwards.
The canal is sometimes wider, sometimes narrower, sometimes with
(EuchlaniSf l^racliionus) and sometimes without {PhilodincC) a
constriction indicative of the stomach : this cavity is
usually well marked in Notommata {Jig. 20, g) : in
Rotifer {Jig. 21.) and Ptyura there is a distinct ter-
minal dilation or rectum : sometimes the intestine is
complicated with many ceeca, as in Diglena and Mega-
lotrocha. The lining membrane of the alimentary
canal is beset with vibratile cilia, and the parietes con-
sist of cells, with a colourless nucleus, and with a
brown or green finely granular contents, which may
elaborate a fluid analogous to bile. Most of the Roti-
fers (certain species oi Ichthydina being exceptions)
have, just behind the pharynx, or continued from the
stomach, two large oval glandular sacs, rarely cylin-
drical or bifurcated, to which sometimes filamentary
CJfica are appended, as in Enteroplea. These secerning
sacs {Jig. 20, i) are also lined by a ciliated epithelium,
Ai. canal. Rotifer, and, from the colourlcss nature of their contents, are
probably of the nature of pancreatic glands.

Ehrenberg recognises a vascular system in the parallel transverse
slender bands Vy'hich surround the body ; these are in close connec-
tion with the integument, and are more probably muscular.

In most Rotifers there extends down each side of the body a
narrow band or tjeniiform organ, containing a motionless vasiform
canal. At the anterior part of the bands many short lateral vessels

* XXXVL p. 20.

ROTIFERA. 49

appear in some Rotifers to be in connection with the longitudinal
canals : in Lacinularia these terminate here in a small convoluted knot.
Rapidly vibrating or undulating ciliated tags are attached to dif-
ferent parts of the vasiform bands. The number of the vibratory
tags varies not only in different species, but even in individuals of the
same species. In general there are from two to three on each side,
sometimes from five to eight, as in Notommata copeus and N. syrinx ;
and in the rare instance of Notommata claviculata as many as from
thirty-six to forty-eight have been seen on each lateral band.

At the anal end of the abdomen the two lateral bands converge,
and their longitudinal canals anastomose and open into a common
contractile bladder, which expels its watery contents into the cloacal
outlet. An aperture, sometimes supported on a special process at the
fore-part of the trunk, probably admits the water into the abdomen,
where it may be received into the freely suspended lateral canals,
and expelled by the contractile bladder. This apparatus is viewed by
Siebold with much probability, as subserving respiration. Enter oplea,
Hydatina, and Diglena, have a simple anterior branchial aperture.
Rotifer, Philodina, Brachionus, and some species of Notommata,
have a branchial tube : Tubicolaria and Melicerta have a double
branchial tube.

Groups and rows of minute granules may be observed in rapid
molecular motion, immediately beneath the integument ; and these
are sometimes hurried along in currents, indicative of a circulatory
movement.

The gelatinous cell or tube protecting the body in some Rotifera
must be cited as one of the secretions in that class : the gland is
situated at the base of the tail in Lacinularia, and its duct traverses
that extensile part to terminate at its extremity. Many individuals
of Conochilus and Lacinularia may be found in a conglomerate of
such gelatinous shells, diverging from their fundus as from a centre.
The individuals of Tubicularia, Floscularia, and Stephanoceros are
protected in more elongated tube-shaped cells, which are commonly
insulated. In 3Ielicerta the protective tube is composed of multan-
gular brown corpuscles, expelled from the cloacal opening, and com-
pacted together.*

The Rotifera are of distinct sex ; the females being larger than
the males, and almost exclusively the subjects of scrutiny by the
eminent micrographers to whom we are indebted for a knowledge of
the anatomy of the class. Any other than female organs in these
larger individuals has been ascri^d to them only on the supposition

* XXIV. p. 183.
E

50

LECTURE in.

StephaiKiceros Kichonm.

that part of the respiratory
or aquigerous apparatus was
the male organ. Most of the
Rotifera are oviparous, the
ova being large and few in
number {fig. 22, «.) : the
Philodince are commonly vi-
viparous. No species has
yet been found to be par-
thenogenetic, either by way
of spontaneous fission or
gemmation.

The egg-forming organ
consists of a simple wide
sac, single in Notommaia
{fig. 20, /.), but more com-
monly divided into two cor-
nua, the body terminating
by a short contracted cervix,
which communicates with the
cloaca. The two other longer
and more slender canals con-
nected with the cloaca by
the medium of the pulsa-
tile sac, which are supposed
by Ehrenberg to be the
testes and seminal vesicle,
are the parts already de-
scribed as the respiratory
system. In the first place
Siebold has shown, that
in the development of the
Rotifera, the long and slender
tubes appear and increase in
the ratio of the growth of the
intestinal organs and before
the ovaria ; secondly, they
contain nothing but clear
liquid ; thirdly, the true
nature of the pulsatile sac
beinof determined in the Po-
lygastria, we may infer that
it has to do with the circulat-
ing and respiratory process

ROTIFERA. 51

in the Rotifera ; and lastly, neither the pulsatile sac nor the slender la-
teral canals ever contain spermatozoa. The conclusion to which Siebold
arrived, viz., that only female organs could be determined in the large
and complex Rotifera, which had been examined by him and others,
appeared, therefore, to be well-founded. At this stage of know-
ledge of the nature of the generation of Rotifera, the following ob-
servations were very timely and acceptable. Mr. Brightwell, who
has paid much attention to the Infusoria, and has published a work
on those found in the county of Norfolk, met with some small
individuals of a species of Notommata, so different in character to the
ordinary large female ones, to which they were often attached, as to
give him the impression that they were the male individuals*; and
in a letter which I have received from him he says : " I have lately
repeatedly seen the male in connexion with the female ; and it re-
mains so for about seventy seconds." In these small individuals
Mr. Dalrymple has discovered organs with abundant spermatozoa ;
but the rest of their structure is much more simple than that of the
female : e. g. they have neither intestine nor anus. This may seem
at first opposed to all ordinary analogies ; but inferiority, not of size
only, but in grade of organization, is no uncommon characteristic of
the male in the invertebrate series. Nordmann discovered the male
of the Lernaea to be a minute parasite upon the vulva of the female.
Darwin has detected an analogous condition of the impregnating
individual in certain Cirripedes ; and the worm which Cuvier de-
scribed under the name of the Hectocolylus, as the parasite of the
Argonaut, appears from the observations of the accurate Kolliker, to
be actually the male of that species.

In the Notommata Syrinx the male is about half the size of the
female : it has a large round sperm-sac, or testis, at the lower end of
its body, communicating by a short duct with a short penis or sperm-
tube. The spermatozoa may be seen in active motion within the sperm-
sac. On the 15th of June Mr. Brightwell f placed one of these males
and six females in a small glass trough, and on the following day saw
it attach itself to a female by his sperm-tube, remaining so attached
twenty or thirty seconds : it afterwards repeated the act with four
other females : the whole occupying a period of about fifteen minutes.
Mr. Gosse % has subsequently recognised similar males in the genus
Asplaiichna ; and Dr. Leydig has described from one to four indi-
viduals in each colony of LacinularicB §, which exclusively develope
spermatozoa : but he recognises in these the ovarium also, and believes
them to be hermaphrodites, whilst the rest are females. There can

* XXXVII. p. 153. fXXXVII. p. 17. J XXXVI. p. 22. § XXXV*. p. 47 L

F -2

52

LECTURE III.

be no doubt about the functions of the conspicuous ovarium in the
latter, for the structure of the ovum can be discerned through its
transparent walls {Jig. 22. //): in the Rotifer vulgaris, the young
may be seen to escape from the eggs in the uterus, and leave the
empty shells behind them : they issue from the parent after intervals
of from five minutes to an hour. The unimpregnated eggs are oval,
with a firm colourless coat, containing a minutely granular, usually
colourless, yolk, with a conspicuous germinal vesicle. In Philodina
roseola and Brachionus ruhens the yolk is of a reddish colour. In
the tubicular Rotifera the eggs are generally deposited within the
tube. In Triarthra and Polyarthra they remain attached to the
cloacal opening. In some species two kinds of eggs are laid, one
having two shells, and a later period of hatching, carrying the latent
life of the germ through the winter, after the death of the parent.

In the Hydatina senta Ehrenberg has carefully traced the forma-
tion of the ova. They are first manifested as clear spots or vesicles
filled apparently with albumen. In two or three hours a dark speck
is seen in the middle of the clear vesicle, which he compares with the
yolk. In five or six hours the yolk fills the clear space and pushes it
to one side, and in this state the ova are fecundated and excluded
from the cloaca.

The change in the position of the clear spot is important, from its
interesting analogy with the change in the position of the germinal
vesicle in relation to the yolk of the rabbit's ovum, and with the
altered position of the entire ovum in relation to the ovisac, pre-
paratory to impregnation ; both being, to use Ehrenberg's expression,
*' pushed to one side ;" to that side, viz., which approximates the
important vesicle whence all subsequent development radiates, to
the surface which admits the fertilising principle. The result of
this admission is seen in the commencement of the series of successive
divisions of the yolk, the whole of which is acted upon by the pre-
viously dividing central hyaline nucleus, and is so converted into a
'germ-mass.' This process of 'total cleavage' of the impregnated
egg-material has been described by KoUiker * in 3Iegalotrocha, and
by Leydig in Lacinularia^, where the progression is 1, 2, 3, 4, 5, 6,
7, 8, &c., instead of 2, 4, 8, 16, 32, 64, as in the usual formation of
the germ-mass. The further development of the Rotifera has been
very well followed by Ehrenberg. He states, that in the ovum
of the Hydatina, three hours after its exclusion, the clear spot (ger-
minal vesicle) has disappeared, and the egg is occupied by the yolk,
which is granular at one end and clear at the other. A dark spot

XXXYIII. t XXXY* p. 473. tf. xvii. f. 4.

ROTIFERA. 5JJ

then appeared in the middle of the ovum, which, six hours after
excluwsion, could be distinguished as the head, with the rudimental
dental apparatus of the embryo. At the eleventh hour the wheel-
like ciliated organs began to plaj, and the foetus to move in the Qgg.
At the tivelfth hour the body was completely formed, and bent some-
what spirally, the bifurcated anal appendage being doubled backwards
towards the head. The revolutions of the young Rotifer are now so
powerful as to threaten every instant to burst the egg-shell, but they
often continue two hours.

The average period of development of a young Hydatina under
favourable circumstances is twenty-four hours ; twelve within and
twelve without the parent's body. When it proceeds more slowly?
Ehrenberg recommends the liberal supply of the green monads,
( Chlamydomonas pulvisculus, and Euglena viridis).

Ova deposited in the cold early days of winter remain undeveloped
until spring, and are protected by their dense double shell. Ehren-
berg watched during eighteen days successively an individual
Hydatina senta, which was full-grown when singled out, and did not
die of old age, which proves this species to live more than twenty
days. Such an individual is capable of a four-fold propagation every
twenty-four or thirty hours, bringing forth in this time four ova,
which grow from the embryo to maturity, and exclude theii* fertile
ova in the same period. The same individual, producing in ten days
forty eggs, developed with the rapidity above cited, — this rate, raised
to the tenth power, gives one million of individuals from one parent,
on the eleventh day four millions, and on the twelfth day sixteen
millions, and so on.

Although this rate of production from fertile ova is the greatest
hitherto observed, far exceeding that in the class of insects, it is
much inferior to the propagative power in the Polygastria. We saw
that in the Paramcecium aurelia, which lives several days, a trans-
verse fission took place, the individual becoming two, every twenty-
four hours. It is affirmed also to propagate by ova, which are
excluded, not singly, but in masses ; which ova rapidly develope and
repeat the acts of propagation ; so that the possible increase in forty-
eight hours is quite incalculable. Who can wonder that infusions
should, with the brood of two or three days only, swarm with these
animalcules.

All the ordinary Infusoria live through the winter beneath the ice.
After having been once completely frozen, Ehrenberg found them
dead when thawed. They, however, manifested considerable powers
of resistance to this effect of extreme cold. Ehrenberg endeavoured

E 3

54 LECTURE III.

to freeze some Infusoria in a watch-glass, and examined the clear ice
in a cold room : he observed that those which appeared to be frozen
and imbedded in the mass were actually inclosed in very minute
vesicles in the ice. He conceives that they may remain torpid in this
state through the winter, and revive when their little ice-houses have
been melted away in spring.

Infusoria are destroyed generally by expanding and bursting, after
a few minutes* subjection to the heat of boiling water.

In water subjected to a galvanic current strong enough to cause
decomposition, the contained Infusoria are killed. When subjected to
a weaker current, those only which came into its course were affected :
some Rotifera were observed to be stunned only, and afterwards
recovered ; others were killed.

Tenacity of life is a very striking physiological character of the
Infusoria.

The famous phenomena of the revival of Rotifera, after having
been completely dried and apparently killed, certainly when reduced
to the state of the most complete torpidity, were first observed by
Leeuwenhoek in the year 1701.* The father of microscopical anatomy
had been engaged in examining some specimens of Rotifer vulgaris
with Euglena sanguinea, and had left the water in which they were
contained, to evaporate. Two days afterwards, having added some
rain-water, which he had previously boiled, within half an hour he
saw a hundred of the Rotifera revived and moving about. A similar
experiment was followed with the same result after a period of five
months, during which period the Rotifera had remained in a state of
complete desiccation and torpidity. These observations were repeated
by Hill f and Baker.^ You will find all the experiments that were
recorded before the time of Haller accurately quoted in his great
" Physiologia Corporis Humani," vol. viii. p. 111. Fontana § kept
Rotifera two years and a half in dry sand, exposed to all the power
of an Italian summer's sun : yet in two hours after the application of
rain-water they recovered life and motion. Goze, Corti, and Miiller
recorded similar experiments : but those performed by the celebrated
Abbe Spallanzani are perhaps most generally known. He succeeded
in reviving his Rotifers after four years' torpidity : he alternately
dried and moistened the same animalcules twelve times with similar
results, except that the number of the revivers was successively
smaller ; after the sixteenth moistening he failed to restore any of
them to life. |'|

* XXXIX. p. 386. t XL. p. 11.

X XLI. Chapters iv. and vi. § XLII. toin. i. p. 87.

II XLIII. vol. ii. p. 127.

ROTIFERA. 55

One of the essential conditions of the revival of the Rotifers ap-
peared to Spallanzani to be their burial in sand : the access of air
seems prejudicial to their retention of vitality. MUUer *, the famous
Danish observer of Infusoria, only succeeded in reviving them when
they were surrounded by foreign particles, and defended from the air.
Both Oken and Rudolphi f deny the revival of desiccated animals ;
but later observers have succeeded in reproducing the wonderful phe-
nomena described by Spallanzani, especially Professor Schultze ; and
I myself witnessed at Freiburg, in 1838, the revival of the arachnidal
Arctiscon which had been preserved in dry sand by the Professor
upwards of four years.

Summary of the Classes, Orders, and Families of the " Infusoria "
of Cuvier and Ehrenberg.

Class POLYGASTRIA.

Form, more or less that of a cell. Shell, when present, siliceous or
calcareous.

Motion, a few pedunculate, most are free and move by more or less
generally diffused superficial vibratile cilia.

Digestion, by cavities in a soft parenchyme, without proper walls ;
the food taken either by superficial absorption or breach into the
parenchyme, or by a mouth into a ciliated dilatable cavity.

Circulation, by one or more pulsating sacs.

Respiration, by rotating chlorophyl and by ciliated integument

Generation, by spermatic nucleus governing partial or total fis-
sion of body, by gemmation, and by germ-cells, excluded as such (?),
or developed within the body. No distinction of sex.

Order ASTOMA. Shell, when present, siliceous.
Families Monadina. Genera Monas, Microglena, Chilomonas,

Bodo, Gregarina.
AsTAsiiNA. Amhlyophys, Euglena, Chlorogo-

nium.
Peridinina. Peridinium, Glenodinium.

Opalinina. Opalina.

AcTiNOPHBYNA. Actinophrys.

Order STOMATODA. Shell, when present, siliceous.
Families Vorticellina. Genera Stentor, Trichodina, Vorticella,

JEpistylis, Carchesium.
Ophrydina. Vaginicola, Cathurnia.

Enchelia. Leucophrys, Prorodon.

* XLIV. p. 98. t XLV. Bd. I. p. 285.

£ 4

.56

LLCTURE in.

Trachelina.

KOLPODINA.

OXY

TRICHINA.

EUPLOTINA.

Glaucoma, Spiiostomum, Trache-
litis, Loxodes, Chilodon, Phia-
li?ia, Bursaria, Nassula.

Kolpoda, ParamcEcium, Amphi-
leptus.

Oxytricha, Stylonychia, Uro-
styla.

Euplotes, Himantophorus, Chla-
midodo7i.

Order EHIZOPODA.
Shell, calcareous, camerated.
Locomotion, by branched, retractile processes.

Tribe Monosomatia.
Genus Amceba.

Genera Arcella, Difflugia, Gromia,
Euglypha, Trinema.

Family Amcebina.
Family Arcellina.

Miliola,

Form
jointed.

Tribe Polysomatia.
Genera Vorticialis, Geoponus, Nonionina.

Class ROTIFERA. (Wheel-animalcules).
Body oblong, with a tail or post-abdomen more or less
Shell, when present, gelatinous.
Locomotion, by peculiar aggregates of vibratile cilia on the head.
Digestion, by an alimentary sac or canal, in an abdominal cavity.
Circulation, by a pulsatile sac, vessels, and sinuses.
Respiration, by an aquigerous apparatus with peculiar vibratile
organs.

Generation, oviparous or ovoviviparous. Sexes distinct.
Family Monotrocha. (Single-wheeled). Qte\^ev2i Ptygura, Ichthy-

dium, ChcBtonotus, (Ecistes, Conochilus.
(Notch -wheeled). Genera Megalotrocha,
Tuhicolaria, Stephanoceros, Lacinularia,
Melicerta, Floscularia.
(Many-wheeled). Genera Enteroplea, Hyda-
tino, Noiommata, Polyarthra, Triarthra,
Euchla7iis, Scdpina.
(Double-wheeled). Genera Rotifer, Acti-
7iurus, Noteus, Philodina, Anurma,
Brachionus.*

Family Schizotroch.

Family Polytrocha.

Family Zygotrocha.

* In this summary adopted, with slight modiiication, from Siebold (XXIV.),
only those families and genera are cited which best serAe as types of the organisation
of the rc:?pective groups.

ENTOZOA. 57

LECTURE IV.

ENTOZOA.

The ancient philosophers styled man the microcosm, fancifully con-
ceiving him to resemble in miniature the macrocosm or great world.

Man's body is unquestionably a little world to many animals of
much smaller size and lower grade of organisation, which are
developed upon and within it, and exist altogether at the expense of
its fluids and solids.

Not fewer than eighteen kinds of parasitic animals have been
found to infest the internal cavities and tissues of the human body ;
and of these, at least fourteen are good and well established species of
Entozoa.

Hippocrates and Aristotle had distinguished the human intestinal
worms by the names of " Helminthes stronguloi " and " Helminthes
plateiai ; " but the study of these parasites in general has been re-
served for recent times. Since Linnaeus the stimulus which that
great master gave to every branch of Natural History has been in no
department more potent than in encouraging researches into the
before neglected field of the Internal Animal Parasites.

To the labours of Goeze* Zederf, Bremser J, and, above all, to
those of Rudolphi §, we are indebted for our knowledge of these
animals as an extensive class, which Rudolphi has characterised,
under the name o^ Entozoa, as white-blooded worms without respira-
tory organs, and (but less accurately) without nerves.

The number of these parasites may be conceived when it is stated
that almost every known animal has its peculiar species, and generally
more than one, sometimes as many as, or even more kinds than, infest
the human body.

There are few common and positive organic characters which can
be attributed to this very extensive and singular group of animals ;
they have generally a soft, absorbent, colourless integument, which in
a few species is armed with spines. That the integument should be
uniformly white or whitish might, a priori, have been expected of
animals which are developed and exist in the dark recesses of other
animal bodies. The mature ova are almost the only parts which
naturally acquire a distinct colour ; and the subtransparent body some-
times derives other tints from the accidental colour of the food. Ex-
cluded also by the nature of their abode from the immediate influence

* XLVIII. t XLIX. t L. and LI. § XL VI. and XLVII.

58 LECTURE IV.

of the atmosphere, no distinct respiratory organ could be expected to
be developed in the Entozoa; but this negative character is common
to them with most of the other " Zoophytes " of Cuvier. In animals
surrounded by and having every part of their absorbent surface in con-
tact with the secreted and vitalised juices of higher animals, one might
likewise have anticipated little complexity and less variety of organ-
isation. Yet the workmanship of the Divine Artificer is sufficiently
complicated and marvellous in these outcasts, as they may be termed,
of the Animal kingdom, to exhaust the utmost skill and patience of
the anatomist in unravelling their structure, and the greatest acumen
and judgment of the physiologist in determining the functions and
analogies of the structures so discovered. What also is very re-
markable, the gradations of organisation that are traceable in the in-
ternal parasites reach extremes as remote, and connect those animals
by links as diversified, as in any of the other groups of Zoophytes,
although these play their parts in the open and diversified field of
Nature.

Beginning with the lowest link of the Entozoal chain, we have to
commence with a condition of organisation more simple than is
presented by the lowest Infusory or Polype. We end with a grade
of organisation, which, whether it is to be referred to the radiated or
articulated types, zoologists and anatomists are not yet unanimous.

Amongst the vermiform animals with colourless integument, colour-
less circulating juices and without respiratory organs, two leading dif-
ferences of the digestive system have been recognised : in the one it
is a tube with two apertures contained in a distinct abdominal cavity ;
in the other it is excavated or imbedded in the common parenchyme
of the body, and has no anal outlet. The first condition characterises
the Vers Intestinaux Cavitaires of Cuvier ; the second the Vers In-
testinaux Parenchymateux of the same naturalist.*

I have rendered the Cuvierian definitions of the two leading
classes or groups of the Entozoa by the single-worded names "Coelel-
mintha," and " Sterelmintha."

The Coelelmintha include the Linguatulce with the Gordiacea or
* hair-worms', and the cylindrical Entozoa or 'round worms' which
form the order Nematoidea of Rudolphi.

This great entozoologist, who devoted the leisure of a long life
to the successful study of the present uninviting class, divided the
parenchymatous Entozoa, here associated in the class Sterelmintha^
into four orders. The Acanthocephala, in which the head has a
retractile proboscis armed with recurved spines, the body round and

* XII. torn. iv. p. 38.

ENTOZOA.

59

elongated, and the sexes in distinct individuals. The Trematoda, in
which the head is unarmed and has a suctorious foramen, the body
rounded or flattened, and generally one or more suctorious cavities
for adhesion, and in which the organs of both sexes are in the same
individual. The Cestoidea, in which the body is elongated, flattened,
and generally articulated : the head, variously organised, generally
provided with suctorious cavities, sometimes armed with a coronet of
hooks, sometimes with four unarmed or uncinated tentacles: both
kinds of generative organs are combined in the same individual.
Lastly, the order of Cystica^ in which the body is rounded or flattened,
and terminates posteriorly in a cyst, which is sometimes common to
many individuals : the head is provided with suctorious cavities,
and with a circle of booklets, or with four unarmed or uncinated ten-
tacles. No distinct generative organs are developed in the cystic
Entozoa, and there is good evidence that most, if not all, are larvae of
a higher order.

The anatomy of the Entozoa is so distinct in each of these orders
that I shall describe it successively in a few typical species, selecting
more especially for demonstration those which infest the human body ;
and which chiefly concern the medical practitioner.

In this category the common pathological product called hydatid, and
" Acephalocyst" by Laennec, is by many received, and ought not, per-
haps, in this place to be omitted. The acephalocyst {Jig. 23, b.) consists

of a sub-globular or oval vesicle filled
with fluid. Sometimes suspended freely
in the fluid of a cyst of the surrounding
condensed cellular tissue («) ; some-
times attached to such a cyst; deve-
loping smaller acephalocysts (c), which
are discharged from the outer or the
inner surface of the parent cyst.
These acephalocysts vary from the
size of a pea to that of a child's head. In the larger ones the wall of
the cyst has a distinctly laminated texture. They are of a pearly
whiteness, without fibrous structure, elastic, spurting out their fluid
when punctured. Their tissue is composed chiefly of a substance
closely analogous to albumen, but differing by its solubility in hydro-
chloric acid; and also of another peculiar substance analogous to
mucus.* The fluid of the acephalocyst contains a small quantity of
albumen with some salts, including muriate of soda, and a large pro-
portion of gelatin.

The tunic of the acephalocyst is usually studded with more or less

* Ln,

Acephalocyst.

60 LECTURE IV.

numerous and minute globules of a clear substance (c), analogous to
the " hyaline," whose remarkable properties in reproductive cells, Dr.
Barry has demonstrated*, and from which the young acephalocysts
are developed. No contractile property, save that of ordinary elas-
ticity, has been observed in the coats of the acephalocyst ; no other
organisation than that above described ; no other function than that
of assimilation of the surrounding fluid by the general surface, and
the development of new cells from the nuclei of hyaline. It stands
on a still lower step in the series of organic structure than the Pro-
tococci of the vegetable kingdom ; for spontaneous fission has not been
observed in any acephalocyst ; and it ought, therefore, to be regarded
rather as an abnormal organic cell, than as a species of animal, even
of the simplest kind.

Yet these productions have not escaped the ingenuity and dis-
criminative powders of the classifier. Of the numerous species,
nominal or real, which are to be found in the works of naturalists
and pathologists, I shall notice only a few: — 1st, the Acephalocystis
endogena of Kuhn, likewise called socialis, vel prolifera, by Cru-
veilhier: the "Pill-box Hydatid" of Hunter. It is the kind most
commonly developed in the human subject, and in which the fissi-
parous process takes place usually from the internal surface of the
parent cyst, the progeny being sometimes successively included :
and, 2dly, the Acephalocystis exogena of Kuhn, eremita vel sterilis,
of Cruveilhier, which developes its progeny generally from the ex-
ternal surface, and is found in the ox and other domestic animals.

Mr. H. Goodsir, who has particularly studied the development of
the acephalocysts f, has described three species of the genus, the
specific characters being derived from the structure of the membrane
from which they originate, and from the mode of growth and structure
of the young.

In Acephalocystis simplex the membranes appear to be more or
less inseparable, transparent, and the young vesicles are very few in
number.

In A. Monroi the ^'germinal membrane" is divided by means of a
fibrous tissue, into numerous compartments, each of which is occupied
by a delicate transparent vesicle filled with cellular substance, of
which the cells or division are very large. Each of these vesicles
contains one or more small dark bodies — the young hydatids.

In A. armatus the young arise from the germinal membrane of the
parent as very distinct small separate vesicles, which at first are quite
transparent, but soon become opaque from the addition of young
within them.

* XXIX. t Lllh P- 563.

ENTOZOA. 6 1

A small transparent vesicle jutting out from the surface of the
germinal membrane is the first vestige of a young hydatid, which
speedily becomes opaque in consequence of young cells growing
within it. This vesicle very soon separates, and then becomes what
Mr. Goodsir terms a secondary hydatid. The young cells which were
seen growing within it before its separation now also increase iu size,
and soon become parent cells, but do not separate from the germinal
membrane of their parent until she escapes from the primitive
hydatid. Thus there are four generations, the primitive hydatid
still containing the three generations to which she had given birth.

If the primitive hydatid is buried so deeply in the tissues of the
infested being as to prevent the escape of the secondary hydatids,
with their two inclosed series of young, decomposition ensues, upon
which they speedily disappear.

And now some may naturally be tempted to ask, having heard this
description of a free and independent being, whose tissues are chemi-
cally proved to be of an animal nature, imbibing nourishment without
vascular connexion with the cavity containing it, and reproducing its
kind. How is an animal to be defined, if this be not one ? The
answer that the acephalocyst has no mouth, would not be regarded as
satisfactory, after the recognition of the animality of the astomatous
Polygastria : these, however, are locomotive and can propagate by
spontaneous fission. But, definitions apart, our business is to discover
to what organic thing the acephalocyst is most similar.

Almost all the animal tissues result from transformations of free
cells, which grow by imbibition, and which develope their like
from their nucleus of hyaline. It is to these primitive or fun-
damental forms of tissue that the acephalocyst bears the closest
analogies in physical, chemical, and vital properties. When the
infusorial monads are compared to such cells, and man's frame is
said, by a figure of speech, to be made up of monads, the ana-
logy is overstrained, because no mere organic cell has its cilia, its
stomachs, its pulsatile sac, &c. So also it appears to me that the
analogy has been equally overstrained, w^hich makes the acephalocyst
a kind of monad, or analogous species of animal. We may, with some
truth, say that the human body is primarily composed or built up
of hydatids ; microscopical, indeed, and which, under natural and
healthy conditions, are metamorphosed into cartilage, bone, nerve,
muscular fibre, &c. When, instead of such change, the organic cells
grow to dimensions which make them recognisable to the naked eye,
such development of acephalocysts, as they are then called, is com-
monly connected in the human subject with an enfeeblement of the
controlling plastic force, which, at some of the weaker points of the

62 LECTURE IV.

frame, seems unable to direct the metamorphosis of the primitive cells
along the right road to the tissues they were destined to form, but
causes them to retain, as it were, their embryo condition, and to
grow by the imbibition of the surrounding fluid, and thus become the
means of injuriously affecting or destroying the tissues which they
should have supported and repaired. I regard the different acepha-
locysts, therefore, as merely so many forms or species of morbid or
dropsical cells.

The conclusion to which' the known phenomena of the parasitic
gregarinse lead is a different one ; and to this much-mooted question
I next pass.

In 1826, M. Leon Dufour* described and figured some minute
entozooids, of very simple form and structure, which he discovered in
the alimentary canal of several species of Coleoptera.

Subsequently, detecting them in great abundance in the chylific
stomach of the earwig in the month of August, the same distinguished
entomologist communicated a particular description of them to the
'Annales des Sciences Naturelles," 1828 f^ proposing the name
Gregarina for the genus ; and he gives three figures of the species,
under the name of Gregarina oralis. It is half a line in length.
One individual is characterised as having a spherical anterior seg-
ment. In a second this appears to have been lost, and is said to be
replaced by a sort of skull-cap (calotte). The third, besides the
constriction defining the anterior sphere, shows another constriction
equally bisecting the trunk. Of this latter specimen Dufour re-
marks : — " Deux individus fixes bout a bout ou tete a queue, peut-
etre accouples:" — but either in the act of conjugation or of sponta-
neous fission. M. Dufour could detect nothing in the interior of
these parasites except " des corpuscules arrondies." They were ob-
served to vomit these " corpuscles " by the anterior end (probably
after the fission).

Siebold, in 1837, not succeeding in observing any signs of volun-
tary movement in the Gregarina, rejected them at first from the
kingdom of completely-formed animals, and supposed them to be eggs
of insects. \ Returning to the investigation, he soon, however, re-
nounced his first opinion, and retained the genus, as unique and
exceptional in its nature amongst the Entozoa. He observed, in
some, a feeble contraction of the body, producing a vermiform figure.
They consist of a very firm, smooth, completely-closed skin, which is
highly elastic, and includes a milk-white, minutely granular mass,
imbedded in which there is a clear cell, including smaller cells.

* LTV. p. 44. t XIII. p. 366. % LV. p. 56.

ENTOZOA. 63

Usually only two individuals were seen to be attached to one another.
" Auch sah ich gewohnlieh nur zwei individuen aneinander kleben.*

Dufour had conjectured, that the genus Gregarina might belong
to the Trematoda. Siebold, with better judgment, refers the genus
to the order Cystica. He describes several species ; and figures
some in the state of either conjugation or of spontaneous transverse
fission ; he describes this as two complete individuals sticking toge-
ther. Each shows the central multinucleate cell. Schleiden f has
viewed these Gregarinag as essentially a single organic cell, and
would refer them to the lowest group of plants. And here, indeed,
we have a good instance of the essential unity of the organic division
of matter. It is only the power of self-contraction of tissue, and its
solubility in acetic acid, which turn the scale in favour of the ani-
raality of the Gregarinae; they have no mouth and no stomach, which
have commonly been deemed the most constant organic characteristics
of an animal.

Henle J and others have questioned the title of the Gregarina to
be regarded as an organic species or individual at all, or as any
thing more than a monstrous cell : thus applying to it my idea
propounded in 1843 of the true nature of the acephalocyst.

In 1848 Kolliker§ published an elaborate memoir on the genus,
in which good and sufficient grounds are given for concluding
that the Gregarina not merely resembles, but actually is an ani-
mated being ; it stands on the lowest step of the animal series,
parallel with that of the single-celled species of the vegetable king-
dom. The Gregarina consists, as Schleiden and others have well
shown, of a cell-membrane, of the fluid and granular contents of the
cell, and of the nucleus with (occasional) nucleoli. The nucleus is
the hardest part, resisting pressure longest, like that of the Polygas-
trian. It divides, and its division is followed by spontaneous fis-
sion. Sometimes the establishment of the two centres of assimila-
tive force separates the cell-contents into two groups, without the
concomitant division of the cell-wall ; but an inner partition-wall is
developed. Stein believes that this is the result of the conjugation of
two individuals. However this may be, another mode of propagation
is then set up ; the granules of the divided cell-contents, as if im-
pregnated, develope cells, divide and subdivide, and are ultimately
resolved into embryos having the form of Navicellae ; but without the
siliceous shell. KoUiker is of opinion, from the frequent co-existence
of these pseudo-navicellar capsules with the ordinary Gregarinae and
the identity of structure of the capsules, prior to the development

* LV. p. 57. t LVI. p. 97. X LVn.p.369. § VH.

64 LECTURE IV.

of the pseudo-navicellae, that this is one mode of propagation of the
Gregarinae, but the progress of the Navicella to the Gregarina has
not been seen.

The firm nucleus of the Gregarina answers to that of the Polygas-
trian ; the cell-membrane to the ciliated integument, and the granular
contents to the more-specialised cells which surround the nucleus.
The Gregarina may be regarded as a parasitic Monad, and the most
simple of the animal kingdom. It differs from the single-celled plant
by the contractility of its tissue, and the solubility of its cell-wall by
acetic acid.

I next proceed to consider the internal parasites, which present the
characters assigned by Rudolphi to his Cystic Entozoa.

The name Echinococcus has been given to a cyst resembling the
acephalocyst, in the absence of any external organised appendage,
but differing in the structure of the innermost layer or "membrana
propria," which is very thin and contains many minute clear calca-
reous corpuscles, which on the application of a weak acid, liberate
bubbles of gas and disappear. The other tissues of this, which
should be called the " echinococcocyst," consist, as in the acephalo-
cyst, of coagulated albumen, the product probably of the adventi-
tious cyst of the organ in which the echinococcocyst is imbedded.
From the innermost or proper tissue of the echinococcocyst small
pyriform buds protrude, in which are developed one or more minute
vesicular organisms, having a head armed with a circle of more or
less bent spines {Jig. 24. a.) and in some species also four suckers (ib. b.).
These properly represent the genus Echinococcus. As their de-
velopment advances, their nursing-cysts become pedunculate, and
finally burst or break off, liberating the organisms which then float, or
freely swim, in the sero-albuminous fluid of the parent-cyst.* The
tissue of the little echinocoeci is highly contractile, and the uncinated
head can be retracted within the cavity of the body.

In the Echinococcus Veterinorum, the species which infests the
common domestic animals, the oral spines, so retracted, offer a resem-
blance to the cylinder of teeth, which characterises the Nassula
{Jig. 14.) and many other Polygastria. The tissue of the body pre-
sents a number of clear oval cells or spaces. On examining the fluid
of an echinococcocyst from the abdomen of a recently-killed sow, I
saw the young echinocoeci moving freely about in it : the anterior end
of the body presented a trilobate depression produced by the retraction
of the uncinated head, and at the opposite end there was, in some, a
small orifice, " from which a granular and glairy substance was

♦ LVIII., LIX., LX., LXI.

ENTOZOA. 65

occasionally discharged."* The echinococci from a small musk-
deer ( Tragulus) closely resemble those of the hog. Each tooth or
spine presents an elongated triangular form, a small process extending
from the middle of its outer margin, probably for the attachment of the
protractor fibres.

The Echinococci of the human subject {Jig. 24.), which have been
accurately described by Professor MuUer in a case where
they were developed in the urinary bladder, and which
9i'iy ^^'^^ h^Qn carefully figured by Mr. Quekett in a case ob-
EcTiinococcus scrvcd by Mr. Curling, where they were developed in the

^g"n!* liver, present well developed suctorious cavities {b), external
to the circle of teeth («), and thus closely resembling the head of a
Taenia, appended to a small cyst.

The hydatid developed in the substance of the brain of sheep and
rabbits, called Ccenurus cerebralis, consists of a large cyst, with which
many heads, like those of the Taeniae, are in organic connection.
These can be retracted within, or protruded without, the common
cyst.

Our present knowledge of the generation of the Ccenurus is limited
to one of the alternating modes, viz., the gemmation of the armed and
suctorious vermiculi. The common or parent cyst is composed of two
layers of substance, — the external one fibrous, or striated, in different
directions ; the internal of a delicate pulpy texture, locally thickened,
and studded with minute clear cells. The gemmation of the vermiculi
is not a process of continuous growth from the tunics of the parent cyst,
but commences from an independent cell, situated between the layers,
like the commencement of the bud from the hydra. Mr. Goodsirf has
figured the progressive multiplication of cells from the primary one,
closely analogous to the mode of establishment of the germ-mass from
the primary-impregnatedgerm-cell in the ovum, until the cellular basis of
the vermicule is established : it then pushes out before it the external
fibrous layer of the mother-sac ; and the organisation of the head is
completed by the metamorphosis of the pre-developed cells. At this
point, however, the generation by gemmation is arrested ; the young
individual is not cast off* like the young Echinococcus or Hydra ; its
base continues in organic connection with the parent stock, and thus
a compound animal, or aggregate of vermiculi results, analogous to the
compound polypes, or as regards the general form of the community,
to the Volvox globator.

* LX. p. 118. Mr. Erasmus Wilson has noticed a similar fact in the Echinococcus
hominis. LXI. p. 36. pi. 1. fig. 8. " Some of the granular contents of the animal
expelled through the aperture left by the torn peduncle."

t LIII. p. 565, pi. xvi.

P

66 LECTURE IV.

The genus Cysticercus is characterised by having only a single
25 uncinated and suctorial head, connected by a neck or body,
sometimes annulated, and of greater or less length, with the
terminal cyst. Of this genus one species, Cysticercus cellu-
losce {Jig. 25.), is occasionally developed in the human sub-
ject. It has been met with in the eye, the brain, the sub-
stance of the heart, and the voluntary muscles of the body.

Cysticercus ^ •' "^

ceiiuiosae. The pcculiar inflammation which it excites leads to the form-
ation of a condensed bag of cellular tissue around it, which, in the
muscular tissue, lengthens in the direction of the fibres, and so im-
presses an oval form upon the Cysticercus : but this form does not
characterise the specimens developed in the softer tissue of the brain
or liver. The Cysticercus cellulosce is generally about half an inch
in length.

The most common hydatid in the ox and other ruminants, is a
large species of the present genus, called Cysticercus tenuicollis,
which has been found weighing 25 drachms and containing 3 oz.
of fluid. In these much-expanded Cysticerci muscular fibres are
developed in different directions in the substance of the cyst, and
produce lively contractions. The clear calcareous corpuscles which
in Ccenurus and Echinococcus are scattered through the walls of the
cyst immediately under the skin, in the Cysticercus are exclusively
aggregated in the undistended part of the animal called the " neck."
In the progress of the accumulation of the fluid in the main body,
shreds of the tissue get occasionally detached from the inner surface
of the dropsical cyst, and are occasionally seen hanging from the
base of the neck and floating in the fluid.* In the oral circle of
spines, these are arranged in a double row alternately long and short,
and from twenty to thirty in number. The four suckers are im-
perforate. This well-armed head may serve to irritate the interior
of the adventitious cyst and excite the secretion on which the pa-
rasite subsists.! All the Cysticerci manifest their affinity with the

Cestoidea by the organisation of their head, and this is more strikingly
illustrated by the length and segmentation of the body, with the
comparatively small size of the cysts, in the Cysticercus fasciolaris,
which is commonly found encysted in the liver of the rat and mouse.
The question of the larval relation of all the above- described cystic
entozoa to the Cestoidea will be entered upon after a description of
the latter, to which I shall next proceed : limiting myself chiefly, in
regard to the organisation of the Tapeworms, to the two species
which infest the human intestines ; namely, the Tcenia solium and

* LXII. p. 205. f LXI. p. 183.

ENTOZOA.

67

the Bothriocephalus lati/s, and which may be regarded as the types
of the two leading genera of the order Cesloidea.

The Tcenia solium is that which is most likely to fall
under the notice of the British medical practitioner. It
is the common species of tapeworm developed in the in-
testines of the natives of Great Britain ; and it is almost
equally peculiar to the Dutch and Germans. The Swiss
and Russians are as exclusively infested by the Bothrio^
cephalus latus. In the city of Dantzig, it has been re-
marked, that only the Tcenia solium occurs; while at
Konigsberg, which borders upon Russia, the Bothrio-
cephalus latus prevails. The inhabitants of the French
provinces adjoining Switzerland are occasionally infested
with both kinds of tapeworm. The natives of north Abys-
sinia are very subject to the Tcenia solium^ as are also the
Hottentots of South Africa. Such facts as to the prevalent
species of tapeworm in different parts of the world, if
duly collected by medical travellers, would form a body of
evidence not only of elminthological but of ethnological
interest. In the Bothriocephalus latus of some parts of
central Europe and of Switzerland we may perceive an
indication of the course of those north-eastern hordes which

Head and contributed to the subversion of the Roman Empire ; and

n 8CK , 1 ^n i a.

solium. the TcEnia solium affords perhaps analogous evidence of
the stream of population from the sources of the Nile southward
to the Cape.

The Tcenia solium attains the length of ten feet and upwards : it
has been observed to extend from the pylorus to within seven inches
of the anus. Its breadth varies from one fourth of a line at its an-
terior part {fig. 26.), to three or four lines towards the
posterior part of the body, which then again diminishes.
The head is small, and generally hemispherical, broader
than long. It commences by a central rostellum, which
is surrounded by a double circle of small recurved
hooks {fiy^ 27, a), occasionally shed in old individuals.
Behind these are four suctorious cavities {fig. 27, b),
by which the head is firmly attached to the intestinal
membrane. The anterior segments are feebly repre-
sented by transverse rugae ; the succeeding ones are
subquadrate, and as broad as long. They then become
sensibly longer, narrower anteriorly, thicker and broader at the pos-
terior margin, which slightly overlaps the succeeding joint. The
last series of segments are sometimes twice or three times as long

F 2

27

Taenia solium.

68 LECTURE IV.

as they are broad, proportions which are never observed in the
Russian tapeworm. But the chief distinction between
the Bothriocephalus latus and the Tcenia solium is
in the position of the generative orifices, which, in the
Tcenia solium^ are placed near the middle of one of
the margins of each joint, and are generally alternate
{fig. 28, «, a).

The integument of the Taenia is soft, like a mucous
membrane ; beneath it is a layer of delicate transverse
muscular fibres, and a more easily recognisable stratum
of longitudinal fibres. There must also be special muscles
for the movements and retraction of the uncinated

Taenia solium. proboScis.

The condition of the nervous system is a matter of analogical con-
jecture. Its principal part most probably exists in, or near, the
well-organised head, whence, as in the Trematoda, it may send back-
wards two delicate filaments.

The correspondence of the digestive system with that of many
Distomata is more certainly known, since it consists of long and
slender canals continued lengthwise, with transverse connecting
channels in most species, through the soft parenchyme. The mode
of commencement of this system of canals appears to have been best
seen by Siebold*, who describes and figures it in the larva of a
tapeworm {fig. 33.), as commencing by a circular canal around the
opening of the fossa in which the uncinated proboscis is retracted.
Four longitudinal vessels are continued from this circle, which bi-
furcate on arriving at each of the four suckers and re -unite below
them, to be continued downwards as the main longitudinal vessels
of the body {fig. 32, /, /). These contain a clear colourless liquid,
and are readily seen in recent Ta3nia3 subjected to moderate pressure.
This mode of investigation is better than that by injection, the na-
tural extent of which cannot be defined by distinct walls of the spaces
into which it may be driven. The transverse canals which connect
the longitudinal ones in the Tcenia solium are situated near the pos-
terior margin of each segment. No other system of vessels can be
detected in recent Taenise scrutinised in the way recommended. The
longitudinal nutrient canals have no communication with the marginal
pores : they equally exist in those Cestoidea which liave no marginal
pores, and the nutriment may be received by cutaneous absorption,
the head being organised to serve chiefly as a hold-fast.

The tissue of the Taeniae in which the alimentary canals are im-

* LXIII. p. 20G. 1)1. xiv.

ENTOZOA. by

bedded is beset with numerous minute nucleated cells. These, doubt-
less, take an important share, by their assimilative and reproductive
powers, in the general nutrition of the body. The subcutaneous
tissue is also characterised by the minute, clear and colourless cal-
careous bodies which are common in the cystic entozoa. There are
also globules of oil.

The TaeniaB are androgynous, and each joint contains a compli-
cated male and female apparatus equal to the production of thousands
of impregnated ova. The ova are developed in a large, branched
ovarium {fig. 28, c\ occupying almost the whole space included by
the nutrient canals, at least in the posterior segments, where it is
very conspicuous from the amber colour of the more mature ova.
The oviduct is continued from near the middle of the dendritic ovary
to the marginal papilla, where it terminates by a small orifice, some-
times produced into a vulva, posterior to the pore of the male organs.
The parts of the male apparatus which have at present been recog-
nised consist of a small pyriform vesicle {fig- 28, h\ situated near
the middle of the posterior margin of the segment ; this, however, is
most probably only a seminal vesicle, and not the testis. The vas
deferens is continued from the vesicle with slight undulations, to the
middle of the segment, where it bends upon itself at a right angle,
and terminates at the generative pore {^fig- 28, a), from which the
lemniscus, or rudimental penis, projects. The ova may be fecundated
by intromission of the lemniscus into the vulva before they escape.

The segments containing the mature ova are most commonly
detached and separately expelled. The development and metamor-
phoses of the embryo Tjeniag have not yet been completely traced out.
But much has recently been done, especially by the sharp-sighted
and clear-minded Siebold, to whose most valuable observations on
this subject we shall return, after the description of the generative
organs in the Bothriocephalus latus.

For a knowledge of the minute anatomy of this species of human
tapeworm {figs. 29, and 30), we are indebted to the admirable skill
and patience of Professor Eschricht, of Copenhagen, whose work*
on the subject has received the prize of the Academy of Sciences,
at Berlin. His observations were made on a specimen of the worm
which, after various remedies, was dislodged from one of his patients.f

* LXIV.

f In Denmark, as in Holland, the Tcenia solium is the common tapeworm ; but
the case in question occurred in a female aged twenty-three, born at St. Petersburg,
of Russian parents, Avho had spent almost all her childhood and youth at Copen-
hagen, with, however, occasional sojourns of three or four months' duration in
Russia. The usual symptoms of tapeworm, with occasional ejection of fragments

F 3

70

LECTURE IV.

The head and neck of this specimen are represented of the natural
29 size in fig. 29. and magnified in fig. 30. Instead of the
i coronet of hooks and circle of suckers which charac-
terise the head of the Tcenia solium, it forms a simple?
elongated, sub-compressed enlargement, with an anterior
obtuse prominence, fig. 29, a, and two lateral sub-trans-
parent parts separated by a middle opake tract. Accord-
ing to Bremser, the margins are slightly depressed, form-
ing what are termed the bothria or pits, ib. b, b, whence
the generic name of this tapeworm. There is no trace
of joints for a short distance from the head : these are at
first feebly marked ; then the segments expand posteriorly,
and slightly overlap the succeeding ones : their length
nearly equals their breadth. At sixteen inches from the
head a slight prominence at the middle line, the anterior
part of the ventral surface of the segment, indicates the
genital apertures. These become conspicuous in the pos-
terior segments, and are two in number, situated on the
same prominence (fig- 30.).

The tegumentary and muscular systems appear to re-
semble closely those in the Tcenia solium. Dr. Eschricht
could not discern any trace of nerves. Of the nutrient
system, he obtained evidence only of the submarginal
longitudinal canals : by placing the recent segments in
dilute acetic acid, he coagulated the contents of these

Head and neck, , . , i • r« i i •

Bothr. latus. cauals, wliicli wcrc then manifest by their opacity and
whiteness. How the nutritious fluid is absorbed by the Bothrio-
cephalus Eschricht was unable to discern : he supposes, analogi-

occuiTed in 1 834. She had also distorted spine and other indications of a weakly
constitution. Thrice, in that year, oil of turpentine with castor oil, and once some
strong drastic pills and pomegranate rind, were administered ; and, with the excep-
tion of the last medicine, which produced no effect, each time from twelve to twenty
feet of the wonn were expelled, but Avithout the head. In the spring of 1835 she
was induced to try a remedy called " Schmidt's cure," which consists of strong
coffee, and salt hen'ing ; and it was followed by the expulsion of a piece of the
worm measuring ten yards, still without the head. She then paid a \asit to Peters-
burg, and there parted with four or five pieces of the tapeworm measuring from two
to four feet in length. She returned to Copenhagen in the winter of 1835, still
suffering from her pertinacious parasite. Castor oil and turpentine were again ad-
ministered on the 3rd of December, and procured the ejection of two pieces of the
tapeworm, measuring together twelve feet in length, but without the head. Eighteen
days afterwards, Nouffer's remedy, which consists of a preparation of fern seed, was
resorted to, whereupon the remaining part of the worm, twenty feet in length, with
the neck and head, came aAvay, and all the symptoms of the malady disappeared,
and had not returned in 1838, when this instructive case was recorded.

ENTOZOA.

cally, by an anterior suctorious mouth, leading to a gullet,
30 bifurcates m the neck to form the two lon-

cc gitudinal canals. Eschricht could not detect the

transverse anastomosing canals. We shall be
justified, perhaps, by the analogy of a species
of Bothriocephalus from the Python*, in which
I succeeded in injecting with quicksilver both
the longitudinal and transverse canals, in con-
cluding that the anastomosing channels are pre-
sent at the posterior margins of the segments in
the Bothriocephalus of the human species. Sie- laiSL'
bold states that the annular vessel by which the nutrient
canals commence in the rostellated TcBJiice, is not present
in the genus Bothriocephalus, nor in the unarmed Tccnia
rostellata and Caryophyllceus mutahilis : in these tape-
worms four longitudinal vessels when they approach the
head begin to ramify and form there a rich network. This
arrangement is more favourable to the idea of nutrition
by cutaneous absorption, than by a hypothetical mouth
and bifurcating gullet.

Innumerable and very minute nucleated cells are apparently disse-
minated through the tissue of the Bothriocephalus. Eschricht
points out their analogy to the blood-cells in the lower animals, but
could not perceive any ramified system of blood-vessels, superadded
to the longitudinal canals.

At the deepest part of each segment there is a stratum of whitish
granules or glands {fig. 32^ «, a), composed of a cluster of minute

Bothr. latus.

32

blind sacculi, filled with opake fluid,
each group or gland being sus-
pended in a separate cell, the pedicle
of which is, without doubt, the duct
of the sacculated gland which
Eschricht regards as a testis, and
estimates at 400 in number at each
Bothr. latus. joiut. Their ducts unite to form a

network, having the capsules of the gland in the interspaces. The
vas deferens {fig. 32, b), is best seen on the dorsal aspect of the joint,
along the middle of which it runs in close transverse folds, pro-
gressively increasing in breadth, until it terminates in a pyriform
seminal receptacle or " bursa penis" {fig. 32, c). From this bursa a
small lemniscus is protruded through the anterior of the two

Prep. No. 846. A.
F 4

72 LECTURE IV.

generative pores, situated upon the eminence near the middle of the
anterior part of the ventral surface of the segment.

The ovaria {Jig. 32, d) are situated near the posterior margin of
the segment. They consist of two large transversely oblong lobes,
and a smaller median annular portion. They are composed of tubes
in which the small germinal and vitelline rudiments of the ova are
arranged in rows. The oviducts terminate in a long tubular uterus
{Jig. 32, e\ which is considerably wider than the vas deferens, and
advances forwards, making many transverse convolutions, the two
last being wider than the rest, and extending on each side of the
bursa penis. The ducts of a very complicated series of glands commu-
nicate with the uterus before its final termination at the vulva or pore,
which is behind the male opening. The glands just alluded to form
a stratum next beneath the skin at the sides of the joints. Eschricht
calculates that there are 1200 of these glands in each joint. In the
joints furthest from the head, containing the mature ova, these glands
become filled with a thick yellow matter which they pour into a
system of ramified ducts, which unite to discharge themselves in the
dilated part of the uterus. Their office seems to be to cement together
the ova in hard cylindrical masses by forming a crust around them, in
which state they are found in the detached joints. This is the first
example we have yet seen of nidamental glands, which we shall sub-
sequently find to be a conspicuous part of the generative organs in
many oviparous Invertebrata.

From this description it will be seen that the proportions and
almost the forms of the ovarium and testis, are reversed in the Bo-
thriocephalus and Tcenia : the positions of the sexual outlets are
unquestionably very different in the two genera. Both, however,
agree in presenting the most extensive development and preponder-
ance of the generative system that is known in the Animal Kingdom.
In fact there is scarcely space left in the hinder joints of the tape-
worms for the organs of any of the other systems.

The natural rate of life of a tapeworm, the consequences to the
remaining adherent part of the repeated detachment of the ovigerous
segments, the extent to which they are detached and subsequently
renewed, have not yet been, nor are likely ever to be, the subjects
of direct observation in these internal parasites of man.

Some highly interesting facts have, however, been made known by
the same professor, to whom v/e are indebted for a knowledge of the
anatomy of the Bothriocephalus latus, in the economy of another
species of Bothriocephalus (B. pwictatus) which is extremely
common in the small sea-fish called Cottus scorpius.

During midsummer these tapeworms are fully developed, and their

ENTOZOA. 75

segments are laden with ova. They adhere by the fore part of the
head to the mucous surfaces of the appendices pyloric^e, and cast off
the ovigerous segments, sometimes in their whole length ; so that
headless tapeworms are found in the lower part of the intestine,
whilst a number of heads without bodies may be observed adhering
to the pyloric appendages between other tapeworms of very diflferent
lengths. The heads thus left behind generate a new series of perfect
joints in the following way: the joint next the head is divided by a
transverse fissure into two, each of which repeats the same process
as soon as it is somewhat grown. Whilst the joints multiply in this
way, they continue to increase in size, and so become removed from
the head ; but at a certain distance from the head, this mode of sub-
dividing ceases, and the whole nutritive power is applied to the de-
velopment of the organs of generation. During winter the Bothrio-
cephalus piinctatuSy still adhering firmly to the mucous surface of the
pyloric appendages, grows to its full length, the segments with
the generative organs being formed ; but no ova can be seen.
These begin to appear at the commencement of spring in the
posterior joints, and by degrees fill the uteri of all the joints, until
they occupy those which are close to the head, when the separation
from the head before described ensues, and this last-named member
is left to repeat the important process. No single joint of a tape-
worm can develope a head, and so form a new nutrient individual ;
the transverse fission relates only to the dissemination of the fertile
ova. But the joints, so separated, may be regarded as "generative
individuals," and those of the Tcenia solium live and move about,
and closely resemble Distomata, They may be seen in all grades
of development, some as infants, others adolescent, and the terminal
ones fully formed and pregnant.

The eggs of some Cestoidea have a single shell or tunic, which
is colourless in Tcenia literata, T. Scolecina^ as well as in the genera
CaryophyllcEUS and Tricenoplioriis ; but is of a brown colour in
many species of Bothriocephalus. The round eggs of Tcenia
amphitricha, T. serrata, and T. bifaria, and the elliptic eggs of T. an-
gulata and T. villosa, have two colourless tunics. In Bothriocephalus
proboscideus and Tcenia porosa, the eggs have three colourless
tunics. In Tcenia solium, the innermost of the three tunics is thick
and becomes a yellowish brown in the ripe eggs. In Tcenia in-
fundibuliformis and T. planiceps, the outer tunic has two long
pointed processes on each side : in T. cyathiformis it is provided
with two round vesicular appendages. In Tcenia injiata, the inner-
most of the three tunics is transversely elliptical, the middle tunic is
produced into two long diverticula, and the outer tunic has two long

74 LECTtTRE IV.

lateral appendages. The eggs of T. cucumerina and T, crateri-
formis are collected in groups of from ten to twenty, in a common
gelatinous nidamental capsule. In the eggs with a single brown shell
the young are liberated by the fall of a kind of lid from one end.*
In the other eggs the tunics dehisce irregularly to liberate the larva.

Wide and interesting questions on animal development are con-
cerned in the solution of the narrower, but not less interesting
ones, as to how and where the young of the impregnated ova of tape-
worms are developed ? In no instance have they been observed to
be excluded in the intestines of the animal in which they were
formed. The eggs are cast out with the excrement into the waters
or on the surface of the earth.

Development of the cestoid embryo begins, however, as soon as the
proper tunics of the ovum are formed, and it is commonly far
advanced before the generative joints of the parent are expelled.
The process has been studied by Siebold in the Bothriocephalus pro-
boscideus, B. crassicollis and B. infwidibuliformis; in Tcenia solium,
and in a score of other species of Tcenia. In each case the embryo,
presenting a rounded or oval shape, according to the shape of the
Qg%^ is characterised by having six spines or booklets, retracted into
the interior of the body : one middle pair lying in the axis of the
body, the other two lateral pairs diverging and directed outwards.
The embryos were found so armed even in the Cestoidea, which,
when mature, are devoid of hooks and form the Tcenice. inermes of
Rudolphi. In the T. cyathiformis, the two middle hooks are the
largest and most bent. In Tcenia porosa, one of the oblique lateral
hooks is very thick, the other very slender. The young of the
Bothriocephalus proboscideus present an ovate subdepressed form ;
and when they are two-thirds of a line in length, the bothria may be
discerned at the larger end. The embryo of Tcenia ocellata, when
half a line in length, shows plainly, under the compressor, the four
suckers, f

This discovery was soon confirmed by Dujardin, who gave a
figure of the embryo of Tcenia cucumerina, observed by him in the
ova of the fully developed generative joints of that tapeworm from
the intestines of a dog J: and he has described the contractions of
the body of the larva and the movements of the booklets.

The earlier phases of development have been well traced by
KoUiker, in both Tcenia and Bothriocephalus.^ Development is
first indicated by a clear place in the centre of the egg, which becomes
more and more clear, larger, and nearer the surface of the yolk, where

* LX. p. 201., and XXIV. p. 148. t LX. p. 202.

X LXV. p. 29. pi. i. tig. 10. § LXVI. p. 91.

ENTOZOA. 75

it is seen to be a nucleated cell. In this are developed two cells,
which are liberated, and, repeating the process, form four* cells ;
this cluster of germ-cells divides the more opaque yolk mechanically
into two parts. The germ-cells become progressively smaller and more
numerous, and the yolk becomes in the same ratio acted upon and
diminished, until it is wholly absorbed and assimilated by the germ-
cells, and the egg finally contains only the germ-mass so constituted ;
that is, consisting of the progeny of the primary germ-cell, de-
veloped and multiplied at the expense of the yolk, which is,
therefore, exclusively a " germ-yolk " in the Tcenice. The embryo
above described is the result of the metamorphoses of certain cells of
the germ-mass into its different tissues ; viz. the skin, the proboscis,
the six booklets, and the suckers ; the contained parenchyme consists
of the remnant of the germ-mass comparatively little changed.

The next step in development has been observed by Siebold in
the larvae of TcBnicB, which have become parasitic in
animals of quite distinct species from those in which
the ova and ovigerous segments were formed.

In a species of slug {Ario7i empiricorum), e. g., Sie-
bold observed minute white cysts projecting from the
inner surface of the pulmonary sac. Each cyst con-
tained a vermicule, with an uncinated and suctorial
head retracted within the body. By regulated pres-
sure the head was everted, and also the opposite end
of the body, which had previously been intussuscepted,
and the animalcule then presented the form given in
Jig. 33. Instead of six hooks, these were now ar-

Larva of Tania ^^^S®^ ^^ ^ doublc roW of ten in each. The con-
magnified. ' tractile parenchyme of the unjointed body shows
the vascular system above described, together with numerous minute
cells and the clear calcareous corpuscles, but no trace of genera-
tive organs. These sexless larval cestoids are probably excluded
from the ova of the taeniae of some species of bird, voided with
the excrement. Being hatched, they creep upon the body of the
first slug that may crawl near them, and entering the open orifice of
the pulmonary sac excite a certain inflammation by their hooks,
become surrounded by an adventitious cyst, and attain that grade of
development, as manifested by the number of the hooks, the suckers,
and the length of the body, by which they differ from the larvae as
first formed in the egg of the tape-worm.* They have never been

* With regard to the change from the six-uncinated embryo to the larvas with
the double crown of hooks, Stein states that the latter are a new formation which
supersedes the embryonal armature of the proboscis. LXVII. p. 69.

76 LECTURE IV.

found in a higher grade of development, or with sexual organs, in
the intestines or other parts of the slug. Siebold therefore concludes
that they may be restored to their native locality — the intestinal
canal of a warm-blooded animal — by the slug being devoured by some
mammal or bird, and that there they undergo Iheir further and com-
plete development ; quitting their cysts, and forming their segments
with the generative organs, which are detached by spontaneous
fission.

This seems a bold hypothesis, and it would be a hazardous one if
it rested on the mere facts of the resemblance of the vermicule (yfig.
33.) in the pulmonic cysts of the slug to the embryo in the ovum of
the Cestoidea. But the modifications of the hooks and suckers in
some other vermicules, having the general character of cestoid
larvas, correspond so closely with peculiarities of the same parts in
the tapeworms of animals feeding on those in which such larvae are
found encysted, as to add greatly to the probability of the migratory
hypothesis. Siebold discovered vermicules, having the general cha-
34 racter of cestoid larva3, in cysts in the coats of the

^r'v^g^^l intestine, and free in the cavity of the intestine, of a
j^ ---^^^ ") cuttle fish {Eledone moschatd). These vermicules had
^-^ _ ,^ ^ a large quadrangular head, divided by a slight con-
striction from the body, and bearing on its anterior
flattened surface nine suckers, arranged as VLifiQ' 35.,
the largest in the middle, the rest in four pairs, with
the inner one largest in each. The parenchyme of
the body of this vermicule presented the clear calcareous corpuscles
characteristic of the cestoid tissue, together with the
four longitudinal canals, as in Jig. 33, I; with which
evidence of its cestoid character, the next step was
to examine what known species of mature or sexual
cestoid presented the nearest resemblance to the pecu-
liar cephalic organisation of the presumed larva. This Siebold
found in the Bothriocephalus auriculatus, in which the four angles
of the head are produced into distinct lobes, each bearing on its
flattened anterior surface a pair of suckers corresponding in their
inequality of size and relative position with those in the larvas from
the cuttle-fish ; the large central sucker having disappeared in the
course of the modification of the central interspace through the
progressive development of the lobes {Jig. 34.). That such change
takes place in the condition of the peculiar head of the B. auriculatus
is made probable by further changes observed in different individuals
of that species. The suckers, for example, are seen in the younger
specimens, and gradually disappear in the older ones. The animal

ENTOZOA. 77

infested by the B. auriculatus is a carnivorous fish {Musteliis vul-
garis), inhabiting the same sea as the Eledone inoschata, and prone
to devour that and other kinds of cuttle-fishes. The fertile ova of
the B. auriculatus are discharged by thousands from the molluski-
vorous fish, and thousands of the larvae doubtless perish. Some,
however, gain an entry into the interior of the lower organised
marine animals suited to their further development and encysted
life ; still fewer complete their vital career when the, to them, lucky
accident occurs of the devouring of the moUusk containing them by
the fish whose intestines form a suitable nidus for their ultimate
transformation, and for the development and propagation by spon-
taneous fission of the generative segments.

Another cestoid larva found in cuttle-fishes and other marine
invertebrata is characterised by its four lateral elliptical suckers, the
tumid borders of which are facetted, or divided by many incisions.
The Bothriocephalus coronatus, " bothriis tumidulis transversira
costatis," of Rudolphi, presents the like peculiarities of its suckers,
and it is found in the intestines of fishes that feed upon the inverte-
brates and smaller fishes in which the larva in question {Scolex
pohpnorphus, Auct.*) is found.

To take a final instance, indicative of the migration of the cestoid
larvae, from land animals. The common tapeworm of the cat,
TcBuia crassicollis, is remarkable for the disproportionate size of the
head, the short and thick neck, the position of the four suckers, and
the shape and number of the booklets of the uncinated proboscis : all
these peculiarities are repeated in the larval form of tape-worm
which is commonly developed in cysts of the liver of the mouse and
rat, and which has already been described as the Cysticercus fascio-
laris. The warm blood and "high organisation of the small mammal
in which that larva is developed may well be regarded as favouring
a further advance of that development than takes place in the en-
cysted cestoid larvae found in the cold-blooded invertebrates ; and
accordingly we find, not only the uncinated proboscis and suckers of
the tapeworm established, but also a lengthening and segmentation
of the body, in the so-called Cysticercus of the rat, without, how-
ever, the development of the generative organs, and with a tendency
to a dropsical accumulation of nutrient fluid in a few of the terminal
joints.

All cestoid larvce which find their early entrance into the soft tissues

* LL t. xi. fig. 10. The cestoid larvse, in their various grades of development,
have served as the grounds of many nominal genera of entozoa ; e. g. Anthoce-
phalus, Balanophorus, Bothriocephalus bicolor, Dibothriorhynchus, Floriceps, Gymno-
rhynchus, Hepatoxyhn, Rhynchohotlirium, Scolex, Tentacularia, and Tetrarhynchus.

78 LECTURE IV.

of mammalia seem to be subject to that accumulation. It is shown in
a slight degree in the so-called Cysticercus pisiformis of the liver of
the hare, which probably finds its full development as the Tcenia
serrata of the dog. But in many instances the dropsical enlargement
of the encysted cestoid larva proceeds to such an extent as to make
it highly improbable that they can carry out the future phases of
their proper life-cycle.

This we may conclude to be the case with the Cysticercus cellulosce
of the human subject, from the number of the adventitious cysts of
that parasite which are found to contain the dead hydatids ; these,
moreover, have sometimes undergone a decomposition into an adipo-
ceral and cretaceous mass, like a tubercle, but the true nature of which
can frequently be demonstrated by the recognizable remains of the
head, or of the booklets of the abortive parasite.

In the encysted, probably cestoid, larvse of the ruminants
( Cysticercus tenuicollis, Auct.) the accumulation of the fluid proceeds
to a greater extent ; and in that to which the name Echiriococcus has
been given, it seems to be carried so far as to obliterate entirely both
head and neck of the original larval form. The Echinococcus how-
ever, like the Ccenurus, retains so much of the original spermatic force
in the germ-cells that remain unmetamorphosed in its parietes, as to
set up a multiplication of its kind by gemmation. But the product
never goes beyond the sexless vermicule with the uncinated and suc-
torial head, like that which is developed in the egg of the tapeworm.
In the Ccenurus, these larvae are retained, as we have seen, in
organic connection with their parent-cyst, and bud out from her
outer surface. In the Ecldnococcus they proceed from the inner
surface of the cyst, and become free, reminding us of the development
and accumulation of the navicellar larvae, within the cyst-like body of
the parent Gregarina.

The parthenogenetic mode of generation being the only one that
the hydatid-like sexless progeny of the Cestoidea are able to manifest,
the life-period of these dropsical larvas, when not liberated, 'seems to
be determined by the progressive accumulation of their parenchymal
calcareous corpuscles, which have been absurdly described as their
ova. The right recognition of the nature of the cystic entozoa of
Rudolphi shows the futility of looking for normal organs of genera-
tion in any part of their structure.

The hypothesis of equivocal generation has been deemed to apply
more strongly to the appearance of internal parasites in animal bodies
than to the origin of animalcules in infusions. But if a tapeworm
might be organised from a fortuitous concourse of organic particles,
or by the metamorphoses of an organic cell in the animal it infests,

ENTOZOA. 79

why that immense complication and extent of the organs for the pro-
duction of normal fertile ova ?

" The division of the body into joints is intended," Professor
Eschricht observes, " to produce a corresponding number of bunches
of ova, just as the repeated ramification of plants is destined to
provide space for the production of new bunches of seeds." The head
of the tapeworm is fixed to the mucous surface, and thence it may
derive the nutritive juices required for the whole organism, in a
degree analogous to that in which the root procures the nourishment
of the plant from the soil ; and the analogy of the extent to which a
plant is nourished by its leaf-pores may also be carried out by the
extent to which the tapeworm is supplied by the absorbent action of
its mucous integument. The ova having reached maturity, the joints
rupture to liberate them; or the whole joint will be thrown off in
the same way as the seeds of plants are freed, sometimes one by one,
sometimes in masses, according to the particular manner of life
assigned to every species of plant. " And is there any one," asks
Dr. Eschricht, " who, upon the contemplation of this wonderful
apparatus, and the extraordinary results of its agency, can for a
moment imagine that it is without an object or an end?"

The geographical distribution of the human Cestoidea is, likewise,
opposed to the doctrine of their spontaneous origin. The organic
particles, or alimentary mucus of a Swiss and Dutchman, are not so
distinct in their nature as to account for the difference in their
tapeworms. Yet no Swiss that never left his native mountains ever
had a TcBiiia solium, and no Dutchman, the constant resident of his
swamps, ever had a Bothriocephalus latus. But a native of either of
these countries may be infested by the tapeworm peculiar to another
region, if he sojourn there, just as the English sailor may be attacked
by the Guinea-worm, if he visits the tropical regions where that
entozoon is common.

The great anatomist Soemmering suffered from a Bothriocephalus
latus. Now he was a German ; but it was ascertained that he paid
occasional visits to a friend in Switzerland. There, doubtless, the
larvae of the parasitic worm was introduced into his body. The
countless ova of the tsenige, with their hard crusts or shells, and
tenacity of latent life, are, doubtless, widely dispersed ; the larvae are
early provided with express organs for attaching themselves to the
animals and tissues suitable for their first phase of existence, and
these nursing animals serve as food for the higher species destined, in
their turn, to subserve the complete development of the migratory
parasites.

80 LECTOPvE V.

LECTURE V.

ENTOZOA.

The essential anatomical character of the third order of Entozoa in
the classification of Rudolphi may be represented by combining the
head of an unarmed Taenia, with one of its joints, containing the fully
developed androgynous organs. The digestive system being repre-
sented by simple canals, imbedded in the soft cellular parenchyme,
and without anal outlet.

The Trematoda may be characterised as having a soft, flattened,
rarely rounded, body, with an indistinct head, an unarmed mouth,
and generally one or more suckers for adhesion in different parts of
the body : the organs of both sexes are in the same individual.

Rudolphi was a pupil and ardent admirer of Linnaeus, and adopted
external and easily recognisable characters for the generic sub-
divisions of the Trematode order, the species of which he distributed
according to the number and positions of the suctorious orifices and
cavities. When there is a single one, it constitutes the genus Mono-
stoma : when there are two, which are terminal or at opposite ends of
the body, you have the character of the genus Amphistoma : when
the posterior of the two suckers is not terminal, but on the inferior
surface of the body, this constitutes the genus Distoma : three suc-
torious cavities characterise the genus Tristoma ; five, the genus
Pentastoma ; and a greater number that called Poli/stoma. Subse-
quent anatomical investigations have led to the formation of other
genera of Trematoda, and have likewise shown that those species
which were grouped together by the external and artificial characters
of the Rudolphian system, manifest differences of organisation,
indicating, at least, the generic distinction of such species : nay,
most of the Pentastomata of Rudolphi appertain to the Coelelminthic
class of Entozoa.

tr

My illustrations of the anatomy of this order will
be chiefly derived from the two species which infest
the human subject ; these are the Distoma hepaticum
{Jig. 36.), and the Distoma lanceolatum {Jig. 37.).
Both are peculiar to the biliary ducts and gall bladder,
but may pass thence into the intestine. Both, like-
wise, are more commonly found in the ordinary
domestic animals, as the sheep and ox, than in the

Dist. hepaticum, human SubjCCt,

A full-grown Distoma hepaticum is of a flattened,
ovate, or oblong-ovate form, broader and rounded anteriorly, attenu-

ENTOZOA. 81

ated posteriorly ; from ten to sixteen lines in length, from four to
seven in width : the broad end sends forward a sort of conical neck
or head, convex above, flat below ; one of the suckers (a) is at
the extremity of this process, a little turned downwards, and is the
true mouth ; the other (b) is at the under part of the base of the
neck, is imperforate, and serves, merely as an organ of adhesion.
Between these is a small depression (d) in which the genital pores
are placed : not unfrequently the curved or spiral penis may be
observed projecting from the anterior of these pores.

The body is of a whitish yellow colour, variegated near the margins
by the yellow ova, and on the dorsal aspect by the brown colour
of the double ramified alimentary tube. The integument is soft :
traces of muscular fibres can hardly be discerned, except around the
larger subventral sucker.

Dr. Mehlis*, who has given the best anatomical account of the
human Trematoday describes and figures the nervous system of the
Distoma hepaticum as a delicate oesophageal filamentary ring, with a
slight ganglionic enlargement on each side, from v/liich minute fibres
pass into the oral sphincter ; and two large filaments pass backwards,
one on each side, as far as the ventral sucker.

I have tested this description by a dissection of the largest known
species of Distoma, the Dist. clavatum, whose anatomy I have de-
scribed in the Zoological Transactions. You may distinctly perceive
in this preparation t the oesophageal nervous circle, the small cephalic
filaments, and the two widely separated nervous chords of the trunk.
In this specimen also, you will see the integument raised as a distinct
membrane from the outer transverse muscular fibres, and a portion
of these is reflected from the inner longitudinal stratum. Feeble
analogues of these parts of the muscular system are doubtless pre-
sent in the smdM^r Distomata of the human subject. Pigment-specks,
called " eye-specks," are present in the Pohjstoma of the urinary
bladder of the toad and frog, as in the locomotive cihated larva of
most Trematoda. In the Pohjstoma six long muscles diverge from
the hinder part of the body to have an expanded insertion into the
convex sides of the six suckers.

The sole aperture of the alimentary system is that of the anterior
pore, which is surrounded by the fibres of the suctorial organ.
The alimentary canal in the Distoma hepaticum is continued from
this pore for a very short distance as a single tube, and then bifur-»
cates ; the divisions {Jig. 36. c, c) diverge to enclose the bursa penis
and the ventral sucker, again approximate, and afterwards run

* LXVIII. p. 22. fig. 13.

82 LECTURE V.

parallel with each other, with a narrow interspace, along the middle
of the body to the caudal extremity. At their first bend, each tube
gives off three or four branches from its outer, but none from its
inner side. The parallel tubes send off a few short and simple
branches from the inner side, and many larger ramified branches
from their outer sides, which terminate in blind extremities near the
margin of the body.

These canals seem, at first sight, to be simply excavated in the sub^
stance of the body ; but, attentively examined, they present a delicate
proper tissue. They are usually tilled with a brownish chyme, which
appears to be mucus stained with cholesterine.

A more minute system of ramified tubes, which by some have been
regarded as the nutrient vessels, commences or terminates by a small
foramen at the caudal extremity of the body. The trunk of this
system runs forwards with a slightly serpentine course, along the
interspace of the forked alimentary canal, to the anterior part of the
body, where it bifurcates, and terminates in many finely ramified
branches : similar branches come off in pairs from, or terminate in,
the main canal. These vessels seem to be an excretory rather than a
nutrient system. They are beautifully figured by the ingenious ana-
tomist Blanchard, who has succeeded in injecting them independently
of the digestive canals.*

The vascular system of Diplostoma volvens, so beautifully illus-
trated by Nordmann f, is the equivalent of the system of capillaries,
described by Mehlis in the Distoma hepaticum ; and the median
trunk {Jig. 38, 6), which is compared by Nordmann to the dorsal
aorta in the Anellides, must be the principal excretory conduit : it
passes directly backwards to the terminal pore {ib. h), distinctly
recognised by Nordmann in the Diplostonia as an excretory outlet ;
and he does not positively deny, what his figures indicate, its con-
tinuity with the straight duct terminating at that pore. In the Dist.
clavatum I have shown that the excretory system is complicated by a
large terminal receptacle or bladder, of which the hinder pore is the
outlet. %

The male organs of the Distoma hepaticum consist of the secern-
ing seminal tubes, a vesicula seminalis, a penis, and its bursa: the
convoluted tubuli testis equal the smallest branches of the alimentary
canal in size ; they occupy a great extent of the middle part of the
body, are inextricably interwoven, are recognisable by their opake

* LXIX. pi. 36. and LXX. (1820), p. 305. taf. ix. The idea of the natiu-e and
function of these vessels, given in my former edition, p. 57, has been adopted by the
experienced Siebold, XXIV. p. 136. " So gh\ube ich gehort das Gefassnetz
welches Bojanus aus Distomum hepaticum beschreibt jeuem Excretionsorgans an."

t LXXI. p. 37. taf. iv. fig. 6. J LXXH. p. 41. fig. 18. g.

ENTOZOA.

83

37

white colour, and terminate bj two trunks in a common canal, which
ends at the base of the receptaculum penis. This appendage is
spirally disposed when flaccid, is tubular, and distinctly perforated at
the apex.

The ovaria occupy the whole margin of the body for a line in
breadth : they consist of minute, branched tubes, in which the ova
are developed, as in acini. The oviducts are close to the ventral
integument, and terminate in a single large uterine canal, which is
disposed in many convolutions between the subventral acetabulum
and the bursa penis: it terminates by a vulva, or distinct pore,
immediately behind the male bursa. The ovarian ova are colourless
and pellucid, but become opaque as they approach the oviduct :
having entered this tube they acquire a white glistening tunic, and
afterw^ards a yellow colour, which becomes deeper as they approach
the vulva.

The Distoma lanceolatum {fig. 37.) has been regarded as the young
of the Distoma hepaticum ; but it is of a dilFerent
form, has a different anatomical structure, particularly
as regards the alimentary canal, and its title to rank
as a distinct species is sufficiently vindicated by its
power of developing fertile ova without changing its
characteristic shape or increasing in size. It rarely
equals five lines in length, but is more commonly three
lines long ; flat, lanceolate, more attenuated anteriorly,
and with an obtuse caudal apex.

The suctorial pores are relatively larger than in the
D. hepaticum. The anterior sucker («) looks down-
wards, and is perforated in the centre by the mouth :
the genital pores are half way between this and the
hinder sucker (Z>). The transparency of the integu-
ment allows the internal parts to be readily discerned.
The alimentary canal, commencing by a kind of
pharynx, is continued as a very slender tube (c) to
the bursa penis, where it bifurcates, each division (c?)
being continued without further ramification along the
right and left sides of the body to the tail, where it
ends in a blind extremity. The minuter excretory
system of vessels has not been discerned in this small Distoma. The
simplicity of its digestive apparatus makes the analogy very close
between the D. lanceolatum and the Tcenice.

In the interspace of the two digestive tubes four opake whitish
spots are visible, of which the three anterior or larger ones {e) form
the testes. Each transmits from its anterior margin a very minute

G 2

i

Dist. lanceolatum,
magiiihed.

84

LECTURE V.

duct, which, advancing forwards, unite in a common vas deferens,
terminating in a small vesicle at the base of the penis, which is pro-
vided with its proper bursa. The ovaria (/,/) are two in number,
of a milk-white colour, situated at the margins of the middle third of
the body, exterior to the alimentary tube. They present a dendritic
form, small branches being given off chiefly from their outer side.
The oviducts run transversely to the middle line, and form there, by
their convolutions, a fourth white opake body behind the testes.
From this subspherical body the common uterine tube (g) is continued.
This is a simple and ample canal, very long and tortuous, occupying
all the posterior part of the interspace of the alimentary forks, thence
continued forwards with decreasing convolutions, and terminating
at the vulva.

The digestive system in the species of Diplostoma, a genus which
has two ventral suckers {Jig. 38, b, c\ is as simple as in the Dist.

lanceolatum ; but the blind extre-
mities {f,f,) of the two divisions of
the alimentary cavity {e, e) are each
^lodged in a sac, i, which, from the
milky character of its contents, has
been termed the chyle-receptacle.
It is supposed that the nutritious
contents of the alimentary tubes
exude through the parietes of their
coecal extremities into these recep-
tacles. Two delicate vessels, k, k,
are continued from the anterior and
outer angle of each chyle-receptacle,
which extend forwards to the ante-
rior third of the body, and are there
brought into communication by a
transverse vessel, I, which extends
across the dorsal aspect of the body.
From the point of union of the
transverse with the external lateral
vessels, a single trunk is continued
forwards on each side to the anterior
angles of the body, m, m, where they
bend inwards and unite in the middle line to form a median
trunk, w, 7^, which is continued to the posterior extremity of the body,
distributing or receiving branches on each side throughout its
entire length, and apparently terminating at the posterior excretory
pore, h. Through the connections of this system of vessels with the
chyle-receptacles, the terminal pore might be regarded as an anal

ENTOZOA. 85

outlet to the digestive system, and the capillary vessels, extending
from the chyle-receptacles to that pore, as a ramified form of intes-
tine, fulfilling at the same time the office of lacteals, lymphatics,
arteries, and veins ; but an excretory function is doubtless the chief
one of this ramified system of vessels.

In Monostoma mutahile the two digestive canals bend towards,
and anastomose with, each other at the hinder end of the body. In
Aspidogaster the digestive canal is continued backwards, without
dividing, and ends by a cul-de-sac. A similar simple blind tube is
continued from the mouth of Gasterostoma, which, as that name
implies, is situated at the middle of the abdomen. In Distoma chi-
lostoma and other species from the abdomen of Neuropterous insects,
two short blind tubes diverge right and left from the gullet. The
ramified type of the alimentary canal, exhibited by Dist. hepaticum,
is repeated in Octobothrium pahnatum^ 0. Merlangi, Poly stoma
appendiculatimi, Tristoma elongatum, and in the genus Diporpa*^
which, in the state of conjugation "j", represents that apparently most
extraordinary form of the present order, called by Nordmann, its
discoverer, Diplozoon paradoxum. In this Trematode, as well as
in some others, e. g. Distoma echinatum, Aspidogaster conchicola,
certain parts of the vessels show a ciliated inner surface, or special
ciliated processes extending therefrom, which actively vibrate, and
may relate to a respiratory process.

The posterior contractile sac, already referred to in the Distoma
clavatum, is present under certain modifications in many Trematoda.
It is simple in Monostoma Faha, Distoma cirrigerum and Gastero-
stoma Jimbriatum ; is bifurcate in Distoma clavigerum, D. tereticolle,
D. variegatum, and in many Monostomata^ in which the two blind ends
of the sac reach almost to the head. If I have been right in regarding
the so-called "vascular system" of Dist. hepaticum as homologous
with this sac and its prolongations, we have, then, in that species, a
third (ramified) form of the excretory organ. An intermediate mo-
dification is presented in the Amphistoma conicum. The contents
of the excretory sac consist usually of a colourless fluid containing
many granules and vesicles : but sometimes it is filled by clear cal-
careous corpuscles like those found in the parenchyme of thecestoid
worms and their cystic larvae. These substances are excreted by the
terminal pore. In the above-cited lower' organised Sterelmintha
the lime-corpuscles remain aggregated beneath the skin.

The genus Planaria of Milller is now known to include many
generic types of fresh-water vermiform animals, not internal parasites,
yet closely allied, by their organisation, to the order Trematoda,

* LXXIII. p. 316. pi. 8. f. c. 200. t LXXTV. p. 63.

G 3

86 LECTURE V.

They differ, in fact, chiefly by their ciliated external surface : and
they form the order Turbellaria of Ehrenberg. Their soft paren-
chyme shows, in many species, immediately under the ciliated integu-
ment, peculiar corpuscles resembling the "thread-cells" of the
Hydrozoa and AcalephcB : some of these cells contain six, eight or
more spiculje. The whole parenchyme is remarkably contractile,
and they creep or swim by movements of the whole body, as well as
by the action of the vibratile cilia : where muscular fibres are obvious
in the larger Plajiarice, they are smooth. The chief part of the
nervous system consists of a pair of ganglions, sometimes confluent,
near the head, from which many filaments diverge, the largest and
longest pair being continued backwards. More or fewer of the
smaller anterior nerves terminate in minute bulbs beneath the co-
loured eye- specks, which are clustered in one or more groups on the
upper surface of the forepart of the body. Exploratory organs or
processes are sent off from the anterior border of the Planaria ten-
taculata.

The mouth is placed either at the anterior end of the body, or
beneath that end, or under the middle of the body, and these differ-
ences of position serve as generic characters. In certain Planarice
the digestive canal is continued from the muscular pharynx to the
hinder end of the body, where it terminates in a blind end : this
simple type characterises the family Wiahdocceli. In the rest of the
order the pharynx can be everted, like a proboscis ; it leads to a
wide, more or less elongated, canal, from which numerous branched
blind tubes radiate into the surrounding parenchyme: this type of
the digestive apparatus characterises the DendroccelL In the latter
PlanaricB there are two lateral vascular trunks which anastomose
together at both ends of the body. In the Rhabdocceli there are one
or two pairs of vessels, which form loops at the extremities of the
body, and do not send out branches. These vessels contain a clear
colourless fluid in both families, and have ciliated lobes or surfaces
at certain parts.

The male and female organs are so combined in the same individual
in the larger Planarice, that self-impregnation may be possible ; but
reciprocal impregnation seems to be the rule : and the twofold
connection of two hermaphroditical individuals has been witnessed
by Von Baer, Duges, and other observers of these non-parasitic
Sterelmintha. The two ovaria are diffusedly branched through the
parenchyme of the body, and terminate in a capacious oviduct or
"bursa copulatrix." A double testis transmits the sperm with
moving capillary spermatozoa through two convoluted sperm-ducts
into a sperm-sac, with which an erectile organ is connected. A
common generative outlet, close behind the mouth, serves for both

ENTOZOA.

87

39

the eversion of the intromittent organ and the exclusion of the eggs.
Two accessory vesicles communicate with the common generative
passage, one of which is probably a sperm-reservoir, the other a
nidamental sac ; the ova of some species are attached by short
filaments, the secretion of such a sac, to the stems of aquatic plants.
The chief modifications of the generative organ in the parasitic
Trematoda will be understood by reference to the de^scription of
them already given in the two species infesting the human subject.
A third modification may be briefly noticed as it exists in the
Distoma perlatiun, discovered by Nordmann in the intestines of the

Tench. It is illustrated in the sub-
joined cut from the magnified figure,
given in that excellent observer's beauti-
ful work. * In^^. 39. i, is the vagina
expanding into k, the glandular uterus,
or nidamental'organ ; /, m, are the two
testes, beset internally with small spines;
n, the prominent tube, by which the
ova are excluded; o is the termination
of the oviduct in the cavity of the tes-
tis 711 ; p^ p, are the convolutions of the
oviduct, laden with ova, received by r,
the short tubes leading from the ova-
ria q^ q, which are widely extended
through the parenchyma of the sides of
the body.

As to the development of the Tre-
matoda. When the Entozoologist
contemplated the Tcenia fixed to the
intestine, with its uncinated and suc-
torious head buried in the mucous
membrane, rooted to the spot, and im-
bibing nourishment like a plant ; —
when he saw the sluggish Distoma adher-
ing by its sucker to the serous membrane of a closed internal cavity ;

he naturally asked himself how they got there ? And finding

no obvious solution to the difiiculty of the transit on the part of such
animals, he was driven to the hypothesis of spontaneous generation
to solve the difficulty. It is no wonder that Rudolphi and Bremser,
who studied the Entozoa rather as Naturalists than Physiologists,
should have been led to apply to them the easy explanation which
Aristotle had given for the coming into being of all kinds of Vermes,

Distoma perlatum.

* LXXII. p.91.t. ix. fig. 4.
G 4

88 LECTURE V.

viz., that they were spontaneously generated. No other explanation
in the then state of the knowledge of development of the Entozoa
appeared to be adequate to account for the fact of their getting into
the interior cavities and tissues of higher animals. Subsequent
researches have, however, shown that the tapeworm quits the
ovum as a minute locomotive Echinococcus, and exchanges its
6-uncinated character for a head like that of the Tcenice. armatce, in
an encysted pupal state, within the body of some animal which
is the natural food of that higher species, in which the ultimate
development of the tapeworm is to be effected. The chances
against the introduction of such a minute ovum or embryo are, of
course, great, but these impediments are met by the incredible
numbers that are developed in a single individual of the Tcenia or
Bothriocephaliis. The mode of introduction of the Entozoa of the
order Trematoda becomes in like manner more intelligible as the
phenomena of their development are better understood. Certain
fresh-water snails are infested by this order, as the Limncea
stagnalis, e. g. by the Distoma tarda. The ova, or products of the
ova, of this species are found in early summer, adhering in vast
numbers to the inner surface of the respiratory cavity, and to the
exterior of the lobes of the liver and generative organs of the snail ;
where they increase in size, and detach themselves as free animal-
cules, having a twisting vermicular motion, and assuming a bright
yellow colour, whence they were Ccilled by Bojanus " konigsgelben
Wurmern." If one of these be microscopically examined, none of
the lineaments of the organs of the future Distoma can be discerned ;
they resemble in structure rather the Gregarinae, consisting, in fact,
of little else than the cell-progeny of the primary germ- vesicle. Few
of the cells have perished as such, or have been metamorphosed, save
those that have gone to form the outer contractile skin, whilst still
fewer have been liquefied and absorbed into a larger subcentral cell.
As the growth of this Gregariniform parasite proceeds, a progeny
is seen to rise in its interior by the development of several of the
contained germ-cells into embryos ; these gradually acquire a ce-
phalic spiculum and a caudal appendage ; they escape from the
parent cyst and from the snail, and disperse themselves as free
swimming ciliated cercariform animalcules in the water. After a
brief enjoyment of this free and active state of existence, they shrink
in size, the vibratile tail is cast off, and they attach themselves to
the skin of the snail. Here they become buried, form for themselves
a pupa-case out of the condensed mucus, and are metamorphosed
into true Dist07nata, which gain their parasitic habitat by piercing
the soft integument of the water-snail. Thus we have a Trematode
entozoon, successively assuming the form of a Gregarina^2^ Cercaria,

ENTOZOA. 89

and a Distoma ; many individuals under the two latter forms being
developed out of one impregnated ovum.*

Professor Sieboldl has traced the metamorphoses of another species
of Trematoda up to a certain point, the rest being made intelligible
by the analogy of those of the snail. He found that certain water-
fowl were, at particular seasons, infested with a small kind of fluke-
worm, the Monostoma mutabile. Rudolphi and others had described
them in the alimentary canal ; Siebold likewise found them in the
air-cells of the abdomen. He discovered this species to be viviparous,
and observed the act of bringing forth, when the Monostoma was
placed in cold or luke-warm water. The ova and embryo are de-
veloped as in the t^nia. The first germ-cell appears in the midst of
a thick granular germ-yolk ; it multiplies, and its progeny, as they
become smaller and more numerous, break through or divide the
yolk, and finally consume it. The embryos escape from the vulva,
close to the penis, and swim briskly, while the egg-shells fall to the
bottom. Sometimes an gq^ was excluded, containing the embryo,
which soon escaped. It is l-9th of a line in length, of a long oval
shape, with a truncated head and a rounded tail-end. On the upper
part of the head are a pair of square dark pigment-spots, which re-
minded Siebold of the eyes of the cercaria. In the terms of the
" alternate generation " theory the gregariniform being is the grand-
nurse " gross-amme ; " the ciliated monadiform larva is the great-
grand-nurse. This is an exposition of the main facts in figurative
language, but is not an explanation of them. What we require are
the conditions of structure, which give or admit of the power of pro-
creation without the coitus or act of impregnation in the procreating
animal. They appear to be these ; and they are revealed by examin-
ing the structure of the entozoon in question in the several stages of
its genetic cycle, comparing them with each other and with the
changes operated in the ovum by the reception therein of the sper-
matic principle.

In the development of the monadiform larva of the monostoma or
distoma, either the vitelline membrane is metamorphosed into the
ciliated skin of the larva, or this is formed by the metamorphosis and
coalescence of the peripheral layer of the germ-mass. But, admitting
■4;he latter process, no other parts of that impregnated germ-mass are
changed excepting those which form the external contractile and
ciliated integument ; there is no mouth, no stomach or other internal
organs, and no members ; the only change which has taken place in
the impregnated germ-cells is rather a kind of change of the relative
position of the essential spermatic or clear nuclear matter, which has

* XCIII. p. 52. t XCIV. p. 321.

90 LECTURE V.

become aggregated in the centre of the locomotive larva, which may
be compared to the locomotive germ or zoospore of an alga or sponge.
It is, in fact, a single-celled animal with a ciliated as well as a con-
tractile cell-wall.

In a short time after it has escaped from the ovum the ciliated
integument ruptures and its contents disappear, with the exception
of the concentrated nuclear matter, which is left clear and distinct,
and of a definite form. A spontaneous movement is observed in this
body: it grows, and now a granular structure may be seen in it
under a high magnifying power. Before its escape it seems to be a
compact structureless mass ; but afterwards numerous points or
centres of independent force begin to operate, and give rise to multi-
tudinous minute granules or nuclei, and it takes on a structure com-
parable to that of the Gregarina. Now, what is the condition of this
second phase or form in the metagenetic progress of the entozoon ?

It will be observed that the embryo of the monostoma, when it
quits the ovum, is not like the chick ; the primary germ-cells have
not been converted into numerous and diversified tissues and organs ;
the great majority of them remain unchanged, and without exhaustion
of the spermatic force. This force would seem to be concentrated in
the clear nucleus, which expands to constitute the smooth-skinned
Gregariniform worm. In this, as in the pseudo-navicellar capsules,
numerous unchanged germ-cells or nuclei set up as many centres of
development, from each of which a cercariform embryo results. In
this process many of the germ- cells and nuclei are metamorphosed
into organs, and a corresponding proportion of the spermatic force is
exhausted. What remains serves to govern the subsequent develop-
ments, which result in the change of the individual Cercaria into a
Monostoma or a Distoma ; this is a " metamorphosis ; " but the ante-
cedent phases should rather be called a " metagenesis," * and the con-
ditions essential to that act are the retention of a due proportion of
the primitive germ-mass unchanged, and with its primarily received
spermatic force unexhausted.

Some of the Trematode Entozoa are remarkable on account of the
places they are found in ; as, for instance, the Diplostoma volvens,
which infests the interior of the eye of the perch and other fishes.
The pupa of this species has been found in the eye of the perch,,
coiled up, adhering to the inner side of the cornea, and then there
has been observed an oblique line, or trace in the cornea, which shows
how the cercariform larva bored its way through to get there. But
frequently it does not get so far, and one finds such pup^e in cases like
a watch-glass adhering to the skin or conjunctiva outside the eye. It is
probable that different stages of the Diplos to ?na volve?is have been de-

* XXX.

ENTOZOA. 91

scribed as distinct species, and that the Holostoma cuticolay Nordmann,
is the pupa, and Diplostoina clavatum, the larva of the same species.

In the PlanaricB the ordinary development is by ova; and it
is remarkable to watch the instinct of these animals during ovi-
position ; although they have no limbs, they take the ova as they
are excluded, but covered with a gelatinous fluid, which they draw
out into threads, and thus fix the ova to the stems of little aquatic
plants. All this is done by the flexible and extensile mouth
and neck. The ova are large, and contain numerous germ-masses,
which manifest remarkable peristaltic movements of the cell-mem-
brane surrounding them. After a time these movements cease, and
the germ-masses conjugate? two or more losing their defining mem-
brane and blending their albuminous and granular contents together.
The embryo is developed from these larger, conjugated germ-masses,
and acquires its ciliated skin and a mouth by which it imbibes the
surrounding yolk-matter before exclusion. Several embryos are
thus developed in a single ovum, but not in a constant number. When
there are few, the embryos are large ; when many, they are small, at
the time of hatching. The species that propagate by spontaneous
fission are the smaller RhabdoccBli, which show no trace of generative
organs, and which are, perhaps, larvae of some larger Planarise.

Of the order Acanthocephala which includes the most noxious of
the internal parasites, no species is known to infest the human body.
They resemble the nematoid Entozoa in outward form, and in the
distinction of the sexes, but in their digestive system they still mani-
fest the sterelminthic type.

The species of this order constitute but one genus, EchinorJiynchus^
characterised by a more or less elongated, round, subelastic body, the
head having a retractile proboscis armed with recurved spines.
Similar spines beset the whole outer surface in the Echinorhynchus
hystrix. The Echinorhynchi abound in the lower animals, and are,
some cylindrical, and others sacciform. The largest known species
{Echinorhynchus gigas) infests the intestines of the hog. As regards
the tegumentary and muscular system, it resembles the nematoid
worms, as well as in its dioecious generation ; but its digestive system
is very diiferent, and somewhat obscurely developed. The proboscis
is provided with a sheath, which projects freely into the abdominal
cavity ; two long and slender muscles are detached from the inner
surface of the general muscular investment and are inserted into the
base of the sheath, and two muscles pass from the most anterior part
of the body backwards to the sides of the sheath, for its extrusion.

At the base of the proboscis there is a group of ganglion-corpuscles,
from which a number of nervous filaments radiate, and perforate the

92 LECTURE V.

muscular investment.* The mouth is a minute pore, situated on the
extremity of the uncinated proboscis : it leads to two long cylindrical
canals excavated in the soft parenchyme adherent to the muscular
tunic, and are continued to the posterior extremity of the body, send-
ing oiF throughout their course a number of fine transverse vessels
which anastomose together. Two short, slender, cylindrical, or flat-
tened bodies, are continued backwards from the sheath of the pro-
boscis, and are freely suspended in the anterior part of the general
cavity : they are called lemnisci. These bodies contain a fine gra-
nular parenchyme, and are richly supplied by a reticulate system of
vessels, which communicate with those of the lateral canals, where
the pedicles of the lemnisci are attached to the sheath of the proboscis.
This apparatus, which in its form resembles a vascular system*]*, is the
only part of the organisation that appears to relate to the nutrition of
the worm. Hunter has left some remarkable instances of the boring
powers of the Echinorhynchi : in No. 289, he shows the Echino-
rhynchus porrigens, attached to a portion of the intestine of the Piked
Whale {Balcena Boops, Linn.). The worm has perforated the intes-
tine, and has formed in its parietes a tortuous passage ; the head
having penetrated the mucous and muscular coats^ and returned again
through the latter, into the intervening cellular coat. The sides of
the canal are composed of thickened and condensed cellular mem-
brane, and in the enlarged cavity which contains the head there is a
quantity of curdled matter, which appears to be lymph thrown out in
consequence of the irritation. The main body of the parasite con-
tinued to float in the chyle and mucus of the intestine, which may
be received into the fine vascular network of the skin by cutaneous
absorption : the uncinated proboscis serving chiefly as an anchor or
hold-fast. Hunter has placed this preparation in his series of " Parts
analogous to Teeth in Invertebrate Animals^

The male organs consist of two fusiform testes, attached to each
other and to the proboscis by a suspensory band; two varicose vasa
deferentia, which unite together to terminate in a single vesicula
seminalis ; and a long intromittent organ provided with a bursa occu-
pying the posterior extremity of the body, and having a special mus-
cular apparatus for the retraction and extrusion of the contained
organ. Beneath the testes there are from one {Ech. claviceps) to six
pyriform bodies, which secrete a minutely granular matter, and whose
ducts, in the latter member, which is most common, unite into two
tubes that terminate in the bursa penis. The secretion of the proper
the size of the female. The generative organs in this sex consist of
two ovaries and one oviduct. The ovaries are long and wide cylin-

* XXIV. p. 125.

•[ LXXVII. tab. 2. f. 10., tab. 3. figs. 10. 12. 21. LXXIX. figs. 1. 8.

ENTOZOA. 93

drical bodies, which of themselves occupy almost the whole cavity of
testes is characterised by the numerous actively moving capillary
spermatozoa. The yellowish wax-like cement which is often found
sticking round the vulva of the female is probably the secretion of the
accessory pyriform bodies. The male echinorhyncus is generally half
the body, extending from the proboscis to the tail, and appearing to
float freely in the fluid of the general cavity: they contain a granulo-
cellular mass in which the ova are developed. When ripe, the ovaria
dehisce and the ova fall into the cavity of the body. The oviduct is
supported by a suspensory ligament answering to that in the male,
and opens freely, like the fallopian tube, by a bell-shaped mouth, into
the cavity. The ova are taken up by it, and conveyed to a short mus-
cular uterus, and are excluded by a vulva at the liinder end of the
body. When first liberated, the ova have a single tunic, and consist
of the vitellus in a minutely granular, and sometimes vesicular mass,
but without a trace of germinal vesicle. In the uterus the ova have
acquired two additional coats.

LECTUEE YI.

ENTOZOA.

The four orders of the class Entozoa which have already been
described, are less natural than the order Nematoiclea, w^hich will
chiefly occupy our attention in the present lecture. The Cystica,
Cestoidea, Trematoda, and Acanthocephala, are far from being re-
spectively equivalent to the order Netnatoidea, either as regards
grade, difference, or circumscription of organic characters. The
transition from the cystic to the ta^nioid Entozoa was so obvious and
close, by the Cysticercus fasciolaris, for example, that they were
combined in the snme order '•'■ Tceinoidea^'' in the " Regne Animal."
Cuvier, however, did not abolish the order Cestoidea, but separated
the jointless Ligidce^ in wliich the head has neither suckers, bothria,
nor uncinated proboscis, from the other Taanioids, in order to form it.
It is hardly possible, however, to separate from the Tsenioids of
Cuvier, the intestinal Ligidm of water-fowl, in which traces of both
bothria and generative organs begin to manifest themselves. And
Rudolphi's hypothesis that such Ligulce might be the more simple
Ligulce of fishes that had been transferred to the warmer intestines of
the birds preying upon such fishes, there to undergo their final meta-
morphoses, has been established by later observations, which have
also shown that the Cystica of Rudolphi are for the most part, if not
all, larval forms, in a normal or abnormal state, of the Cestoidea.
With respect to the higher organised Cestoidea of Rudolphi, it has

94

LECTURE VI.

been already observed that they very closely resemble a composite
form of Trematoda. The extensive and natural group formed by
the two androgynous orders of " Sterelmintha " form, therefore, the
equivalent of the Nematoidea. The Acanthocephala constitute a
more limited, yet natural order ; and the Linguatidce {Pentastoma of
Rudolphi) are the type of an analogous circumscribed group ( Oncho-
phora) with a higher type of organisation, which entitles them to
rank in the class Ccelelmintha. This class includes all the cavitary
intestinal worms of Cuvier, with the exception of the " Vers ridi-
o-ules " of Lamarck, or Epizoa, which are proved by their metamor-
phoses to belong to the siphonostomous Crustaceans.

The order Nematoidea, which forms the chief part of the class
Ccelelmintha, must chiefly interest the physician, since it includes the
principal internal parasites of the human sub-
ject : viz. Trichina spiralis, Filaria medinensis,
Filaria oculi, Filaria bronchialis, Trichocephaliis
dispar, Spiroptera hominis, Strongylus gigas,
Ascaris liimhricoides, and Ascaris or Oxyurus
vermicularis. To the order Nematoidea, repeated
examinations, since my first observation of the
minute Trichina spiralis *, induce me to refer
that singular microscopic parasite (^^. 40.). I have
satisfied myself of the accuracy of Dr. Farre'sf
and Dr. Henle's \ description of the distinct canal
in the cavity of the body. In a specimen of
Trichina now under the microscope, a loop of this
Cysts of Trichina, in situ, caual may be sccu protruding through a rupture
Nat. size. of the abdominal Wall. The vermicule is always

contained in a cyst. The occurrence of these cysts in vast numbers
in the muscular tissue was first made known in an interesting case pub-
lished by Mr. Hilton § : and many others have since been recorded.

The cysts are very readily detected by gently com-
pressing a thin slice of the infected muscle between two
pieces of glass and applying a magnifying power of an inch
focus. They are of an elliptical figure, with the extremi-
ties more or less attenuated, often unequally elongated, and
always more opake than the body or intermediate part of
the cyst, which is, in general, sufficiently transparent to
show that it contains a minute coiled-up worm {Jig. 41.).
The usual size of tlie cyst is -y^t\i of an inch in the long
spiralis, and diameter, and y^ oth of an inch across their middle part,
magn. ' Thc cysts are arranged with their long axis parallel to
the course of the muscular fibres {Jig. 40.), which probably results
* LXXX. vol.i. p. 315. t LXXX* J LXXXI. p. 528. § LXXXII,

Tricliiiia

ENTOZOA.

42

from their yielding 'to the pressure of the contained worm, and be-
coming elongated at the two points where the separation of the mus-
cular fasciculi most readily takes place, and offers least resistance.

The innermost layer of the cyst can sometimes be detached entire,
like a distinct cyst, from the outer portion, and its contour is generally
well marked when seen by transmitted light. By cutting off the
extremity of the cyst, which may be done with a cataract needle or
fine knife, and gently pressing on the opposite extremity, the Tri •
china and the granular secretion with which it is surrounded, will
escape ; and it frequently starts out as soon as the cyst is opened.

AYhen first extracted, the Trichina is usually disposed in two or
two and a half spiral coils ; when straightened out it measures ^^^tli
of an inch in length and -^^0*^ ^^ ^^ i^^^ i^ diameter, and now
requires for its satisf\ictory examination a magnifying power of at
least 200 linear admeasurement.

The worm {fig. 42.) is cylindrical and
filiform, minutely annulated, terminating
obtusely at both extremities, which are of
unequal sizes ; tapering towards one end
for about one-fourth part of its length,
but continuing of uniform diameter from
that point to the opposite extremity which
is trilabiate.

The free canal, Avhich commences or is
attached by a capillary tube or filament, at
the small end {fig. 42. «.), rapidly widens
and presents a saccular form through one
half of its course : it is then continued of
a more slender and equable form to the
great end. At the junction of the saccular
with the slender part, 6, of the canal
there are, according to Luschka*, two
small coeca. Near these is the blind end,
of a second canal which contains the small
cluster of minute dark granules |, and is
continued to the trilabiate end of the body;
Luschka:]: believes both tubes to terminate
here in a blind end.

The worm has no organic connection
'^"'^'"' '.agmfied. ^-^j^ ^j^^ ^^^^ . gomctimes two TrichincEf

rarely three, occur in the same cyst.

* LXXXIII. p. 77. taf. iii. fig. 5. c c. f LXXXIV. p. 63., and LXXXV.

X This author seems only to have read LXXX., and to have been unacquainted
with the additional observations on the " Anatomy of the Trichma," in LXXXIV,

^'

96 LECTURE VI.

The Medina or Guinea-worm (Filaria medinensis, Gmel.) is de-
veloped in the subcutaneous cellular texture, generally in the lower
extremities, especially the feet, sometimes in the scrotum, and also,
but very rarely, beneath the tunica conjunctiva of the eye. It
appears to be endemic in the tropical regions of Asia and Africa.

The length of this worm varies from six inches to two, eight, or
twelve feet ; its thickness is from half to two-thirds of a line ; it is of
a whitish colour in general, but sometimes of a dark brown hue. The
body is round and sub-equal, a little attenuated towards the anterior
extremity. In a recent specimen of small size, we have observed
that the orbicular mouth was surrounded by three slightly raised
swellings, which were continued a little way along the body and
gradually lost ; the body is traversed by two longitudinal lines
corresponding to the intervals of the two well-marked fasciculi of
longitudinal muscular fibres. The caudal extremity of the male is
obtuse, and emits a single spiculum ; in the female it is acute, and
suddenly inflected.

The Filaria inedmeiisis, as has just been observed, is occasionally
located in the close vicinity of the organ of vision ; but another much
smaller species of the same genus of Nematoidea, infests the cavity of
the eye-ball itself.

The Filaria oculi humatii was detected by Nordmann in the liquor
Morgagni of the capsule of a crystalline lens of a man who had under-
gone the operation of extraction for cataract under the hands of the
Baron von Grafe. In this instance the capsule of the lens had been
extracted entire, and upon a careful examination half an hour after
extraction there were observed in the fluid abore mentioned two
minute and delicate FilaricB coiled up in the form of ring. One of
these worms, when observed microscopically, presented a rupture in
the middle of its body, probably occasioned by the extracting needle,
from which rupture the intestinal canal was protruding ; the other
was entire, and measured three-fourths of a line in length ; it pre-
sented a simple mouth without any apparent papillae, such as are
observed to characterise the large Filaria which infests the eye of
the horse, and through the transparent integument could be seen a
straight intestinal canal, surrounded by convolutions of the oviducts,
and terminating at an incurved anal extremity.

The third species oi Filaria enumerated among the Entozoa hominis
is the Filaria hronchialis ; it is described by Treutler * as occurring in
the enlarged bronchial glands of a man : tlie length of this worm is
about an inch ; it is slender, subattenuated anteriorly, and emitting
the male spiculum from an incurved obtuse anal extremity.

* LXXXVI, p. 10.

ENTOZOA. 97

The next human entozoon of the Nematoid order belongs to the
genus Trichocephalus, which, like Filaria, is characterised by an orbi-
cular mouth, but differs from it in the capillary tenuity of the anterior
part of the body, and in the form of the sheath or preputial covering
of the male spiculum. The species in question, the Trichocephalus
disparRud. (Jig. 43.) is of small size, and the male is rather less than
^ — >v^ 43 the female. It occurs most commonly in the csecum

%£/ ^"-^S^ and colon, more rarely in the small intestines. Occa-
" sionally it is found loose in the abdominal cavity,

Trichocephalus , p,. . rn

dispar. Nat. size, havmg perforated the coats of the intestine. The
capillary portion of this species makes about two-thirds of its entire
length ; it is transversely striated, and contains a straight intestinal
canal ; the head («) is acute, with a small simple terminal mouth.
The thick part of the body is spirally convoluted on the same plane,
and exhibits more plainly the dilated intestine ; it terminates in an
obtuse anal extremity, from the inner side of which project the
intromittent spiculum and its sheath.

The species called Spiroptera Hominis was founded by Rudolphi
on some small nematoid worms expelled, with many larger elongated
bodies of a solid texture, and with granular corpuscles, from the
urinary bladder of a woman, whose case has been described by Mr.
Lawrence in the Medico-chirurgical Transactions.* The Spiroptera
varies from eight to ten lines in length ; the head is truncate, the
mouth orbicular, with one or two papilla, the body is attenuated at
both extremities ; the tail in the female, thicker, and with a short
obtuse apex ; that of the male more slender, and emitting a small
tubulus ; a dermal aliform production near the same extremity
determined the worms in question to belong to the genus Spiro-
ptera. I

The most formidable, but, happily, the rarest of the nematoid
parasites of man, the Strongylus gigas, also infests the urinary
system, but is developed in the kidney, where it hns attained the
length of three feet, with a diameter of half an inch ; occasioning sup-
puration and destructive absorption of that important glandular organ.

The male ijig' 44.) of this species is less than the female, and is
slightly attenuated at both extremities. The head («) is obtuse, the
mouth orbicular, and surrounded by six hemispherical papillae ; the
body is slightly marked with circular striae, and with two longi-
tudinal impressions ; the tail is incurved in the male, and terminated
by a dilated pouch or bursa, from the base of which the single intro-
mittent spiculum {g) projects. In the female the caudal extremity

* Vol. ii. p. 385. t XL VII. r- 251.

98

LECTURE VI.

lii

is less attenuated and straighter, with the anus a little below the apex ;
the vulva is situated at a short distance from the anterior extremity.
The Strongylus gigas is not confined to the human subject, but
more frequently infests the kidney of the dog, wolf,
otter, racoon, glutton, horse, and ox. It is generally
of a dark blood-colour, which seems to be owing to
the nature of its food, which is derived from the
vessels of the kidney; as, where suppuration has taken
place, the worm has been found of a whitish hue.

The round-worm (Ascaris lumbricoides Linn.)
{Jig. 46.) is perhaps the most anciently known* and
common of the human Entozoa, and is that which has
been subjected to the most repeated, minute, and
successful anatomical examinations. It is found in
the intestines of man, the hog, and the ox. In the
human subject the round worms are much more
common in children than in adults, and are extremely
rare in aged persons. They are most obnoxious to
individuals of the lymphatic temperament, and such
as use gross and indigestible food, or who inhabit low
and damp localities. They generally occur in the
small intestines.

The body is round, elastic, with a smooth shining
surface, of a whitish or yellowish colour ; attenuated
towards both extremities, but chiefly towards the
anterior one {fig- 46, a), which commences abruptly
by three tubercles, which surround the mouth, and
characterise the genus. The posterior extremity {d)
terminates in an obtuse end, at the apex of which a
small black point may frequently be observed. In
the female this extremity is straighter and thicker
than in the male, in which it is terminated more
acutely and abruptly and is curved towards the ventral
side of the body. The anus is situated in both sexes
close to the extremity of the tail, in form like a trans-
verse fissure. In the female the body generally
presents a constriction at the junction of the anterior
with the middle third, in which the vulva (e) is
situated.

The body of the Ascaris lumbricoides is trans-
versely furrowed with numerous very fine stride, and is marked

strongylus gigas
Nat. size.

* It is the eXfiivs arpoyyvKos of Hippocrates.

ENTOZOA.

99

with four longitudinal equidistant lines extending from the head
to the tail. These lines are independent of the exterior envelope,
which simply covers them; two are lateral, and are larger
than the others, which are dorsal and ventral. The lateral lines
commence on each side of the mouth, but, from their extreme fine-
ness, can with difficulty be perceived ; they slightly enlarge as they
pass downwards to about one-third of a line in diameter in large
specimens, and then gradually diminish to the sides of the caudal
extremity. They are occasionally of a red colour, and denote the
situation of the principal vessels of the body. The dorsal and ab-
dominal longitudinal lines are less marked than the preceding, and
by no means widen in the same proportion at the middle of the body.
They correspond to the two nervous chords, hereafter to be de-
scribed.

The last species of human Entozoon which remains to be noticed
is the Ascaris vermicularis {Jig. 47.), a small worm, also noticed
by Hippocrates under the name of arrKcipig, and claiming the
attention of all physicians since his time as one of the most trou-
blesome parasites of children, and occasionally of adults, in both
of whom it infests the larger intestines, especially the rectum. The
size of the male Ascaris vermicularis is two or three lines ; that of
the female is five lines.

The integument in the nematoid parasites of the human subject,
and in almost all the order, is more or less smooth : it consists
of a thin compact epidermis, and of a fibrous corium firmly attached
to the outer transverse muscular fibres. The epiderm is homo-
geneous ; i. e. it does not show the nucleated cellular structure. It
is impressed by minute, close-set, transverse indentations, which, in
some of the Nematoidea of the lower animals ( Strongylus annulatus^
e. g.) are so deep as to give an annulate character to the integument ;
and in the Ascaris nigrovenosa the sides of the body appear thereby
to be fringed. Lobes, or aliform processes of the integument, charac-
terise certain genera and species ; e. g. the alas of Spiroptera^ the
finely-striated " moustaches " on the head of the Ascaris mystax, the
serrated membrane supported on tubercles near the tail of the same
worm. The corium consists of decussating fibres. The entire
integument is highly absorbent ; and, after death, endosmose will go
on to such an extent as sometimes to cause the parietes of the body,
if immersed in fluid, to burst. The epiderm is developed in the
Strongylus horridus of the water hen, into four longitudinal rows
of reflected booklets ; and similar spines are arranged in circular
groups upon the anterior part of the Gnathostoma spinigerum.

M. Cloquet, in his elaborate monograph on the Ascaris lumhri'

*^ LECTURE VI.

coides, correctly states that the exterior layers of muscular fibres are
transverse, and the internal longitudinal ; the latter are arranged in
most Ascarides in four groups. In this large specimen of the Stron-
gyliis gigas, which I have dissected for the muscular system, you will
perceive that a very thin layer of transverse fibres adheres strongly
to the integument, the fibres being embedded in delicate furrows on
the internal surface of the skin. Within this layer, and adhering to it,
but less firmly than the transverse fibres do to the integument, there
IS a thick layer of longitudinal fasciculi, which are a little separated
from one another, and distributed, not in eight distinct series, but
pretty equally over the whole internal circumference of the body.
Each fasciculus is seen, under a high magnifying power, to be com-
posed of many very fine fibres ; but these do not present the trans-
verse stri^ which are visible by the same power in the voluntary
muscular fibres of the higher animals. They anastomose in many
parts. The inner surface of the stratum of longitudinal fibres is
covered vdth a soft tissue composed of small obtuse processes, filled
with a pulpy substance, and containing innumerable pellucid globules.

In the muscles of the oral booklets of the Linguatula tcenioides,
the fibres show the transverse striae.

Coincident with this higher development of the muscular system
in the coelelminthic Entozoa is the more obvious elimination of the
nervous filaments, which, in the Lingtiatula, radiate from a distinct
suboesophageal ganglion. Amongst the Nematoidea the great Sfron-
gylus is a favourable subject for the demonstration of the nervous
system : a slender nervous ring surrounds the beginning of the
gullet * ; and a single chord is continued from its inferior part, and
extends in a straight line along the middle of the ventral aspect to
the opposite extremity of the body, where a slight swelling is formed
immediately anterior to the anus, w^hich is surrounded by a loop
analogous to that with which the nervous chord commenced, f The
abdominal nerve is situated internal to the longitudinal muscular
fibres, and is easily distinguishable from them with the naked eye by
its whiter colour, and the slender branches which it sends off on each
side. These transverse twigs are given off at pretty regular intervals
of about half a line, and may be traced round to nearly the opposite
side of the body. The entire nervous chord in the female of the
Strongijlus gigas passes to the left side of the vulva, and does not
divide to give passage to the termination of the vagina, as Cloquet
describes the corresponding ventral chord to do in the Ascaris lum-
bricoides. In the latter species, a dorsal nervous chord has been
described as being continued from the oesophageal ring, down the

* LX. p. 130. fig. 79. a. f lb, e.

ENTOZOA.

101

middle line of that aspect of the body corresponding to the ventral
^^ chord on the opposite aspect.*

^ In the, Linguatula tcenioides {^fig. 45.), a propor-

tionally large ganglion {g) is situated immediately
behind the mouth, and below the cesophagus, which
is turned forward in the figure at o : small nerves
(h, i, k) radiate from this centre to supply the mus-
cular apparatus of the mouth and contiguous pre-
hensile booklets ; and two large cords (/, I) pass
backwards, and extend along the sides of the ab-
dominal aspect of the body to near the posterior
extremity, where they expand and are lost in the
muscular tissue, f There is also a stomato-gastric
system, represented by four small but distinct gan-
glions situated on the under part of the oesophagus,
from which minute filaments extend along the ali-
mentary canal. J I have already alluded to the evi-
dences of the nervous system afforded by the ocelli
in the young of some species of Trematoda, and in
the full-grown Polystoma of the urinary bladder of
the toad and frog. We have as yet no evidence
that any species of Coelelmintha possesses rudimental
organs of vision at any stage of existence.

The digestive organs are very simple, and are
subject to little variety in the Nematoid worms ;
an ample alimentary canal, suspended to the pa-
rietes of an abdominal cavity, extends in nearly a
straight line from the mouth to the anus, which are
at opposite extremities of the body.

In the Filaria the mouth is a simple circular pore,
sometimes surrounded by a circle of radiated papillee ;
a short and slender oesophagus suddenly dilates into
the stomach, which is fusiform, and indicates the be-
ginning of the intestine by its posterior contraction.

The mouth of the Trichocephalus dispar is small
and orbicular ; the oesophagus is narrow and short ;
the intestinal tube is narrow and sacculated where
it occupies the filiform division of the body, dilated

a

Nervous System and
female organs of ge-
neration.

Linguatula,
magnified.

* This arrangement is denied by Siebold, who confirms only that above de-
scribed in the Strangylus ; and he does not hesitate to declare : — " Die Abbildung
eines doppelten Nervenfaden, welcher sich nach Grant (Outlines of Comp. Anat.,
p. 186. fig. 82. A.), durch den Leib von Ascaris hinziehen soil, ist wol nwr eine
ideale Zeichnung." XXIV. p. 126.

t LXXXVIL p. 328. pi. 41. figs. 12, 13. } XCII.

H 3

102

LECTURE VI.

and simple in the thicker division of the body, at the posterior ex-
tremity of which it terminates in a contracted straight tube, which
may be called the rectum : the anus is transverse and bilabiate.

In the Strongylus gigas the mouth is surrounded by six papillae.
The oesophagus {b,Jig. 44) is round, slightly bent, and suddenly
dilates at the distance of about an inch from the mouth into
the intestinal canal (c) ; there is no gastric portion marked off in
this canal by an inferior constriction, but it is continued of uniform
structure, slightly enlarging in diameter to the anus {d). The chief
^g peculiarity of the intestine in this species is that it is a
four-sided and not a cylindrical tube, and the mesenteric
M processes pass from the four longitudinal and nearly equi-

distant angles of the intestine to the abdominal parietes.
These processes, when viewed by a high magnifying
power, are partly composed of fibres, and partly of strings
of clear globules, which appear like moniliform vessels
turning around the fibres. The whole inner surface of
the abdominal cavity is beset with soft, short, obtuse,
puljjy processes, which probably imbibe the nutriment
exuded from the intestine into the general cavity of the
body and carry it to the four longitudinal vessels, which
traverse at equal distances the muscular parietes.

The analogous processes are more highly developed in
the Ascaris liwihricoides, in which species I shall de-
scribe the digestive and nutritive apparatus more in detail.
The mouth {Jig. 46, a) is surrounded by three tubercles,
of which one is superior, the others inferior; they are
rounded externally, triangular within, and slightly granu-
lated on the opposed surfaces, which form the boundaries
of the oral aperture^ The longitudinal muscles of the
body are attached to these tubercles ; the dorsal fasciculus
converges to a point to be inserted into the superior one ;
the ventral fasciculus contracts, and then divides, to be
inserted into the two which are situated below. By
^ means of these attachments the longitudinal muscles serve
^bHcoides""" t^ produce the divarication of the tubercles and the open-
Haif nat. size, jj^g ^f ^j-^g mouth : the tubercles are approximated by the
action of a sphincter muscle.

The oesophagus {Jig. 46, b) is muscular, and four or five lines in
length, narrow, slightly dilated posteriorly, and attached to the mus-
cular parietes by radiated filaments. Its cavity is occupied by three
longitudinal ridges, which meet in the centre of the canal. It is
separated by a well-marked constriction from the second part of the
alimentary tube (c, c), which extends to the terminal outlet (^) with-

ENTOZOA. 103

out presenting any natural division into stomach and intestine. The
lower third of the tube is the widest. Numerous long pyriform villi
project from the mucous lining of the alimentary canal. Many
minute filaments pass from the intestine to the soft obtuse papillse
which project from the walls of the abdomen into that cavity, and
which are called "the nutritious appendages" by Cloquet.* The
nutriment which these processes or appendages are presumed to
imbibe, is collected, according to the same author, into two canals,
situated each in a narrow tract of opaque substance, which extends
along the sides of the body, and has sometimes been mistaken for a
nerve, and which Vallisnieri believed to be a trachea. Morren has
lately described and figured the nutritive appendages as hollow ve-
sicles : he calls them " Vesicules aeriennes,^^ because, he says, " they
evidently subserve respiration by furnishing air to the blood." Few
physiologists are likely to acquiesce in this view, which makes the
respiratory apparatus of an animal having no other atmosphere than
the mephitic gases of the intestinal tube, the largest and most ex-
tensively developed organ in the whole body.

With reference to the organisation of the nematoid Entozoa, not
parasites of the human subject, I shall limit my remarks to those
structures which offer interesting approximations and analogies to
the organisation of higher vermiform animals, and of the existence of
which we must have remained ignorant if our attention had been
wholly confined to the human Entozoa.

The entry to the mouth is beset by a circle of horny teeth in the
Strongylus armatiis, Sfr. dentatus^ and Str. tetr acanthus^ for the
movements of which special muscles are provided. In Spiroptera
strongylina the whole inner surface of the elongated mouth is pro-
vided with a spirally disposed horny ridge. The horny apparatus by
which the mouth in Cucullanus is opened and closed is very com-
plex.f The pharynx is unusually long in some nematoids, e. g. the
Trichocephali : and in Trichosoma Falconum it is divided into many
successive segments : it has sometimes a horny scabrous lining.

I may next refer to a secreting apparatus, consisting of four slender
blind tubes, each about two lines in length, which are placed at equal
distances around the commencement of the alimentary canal in the
Gnathostoma spinigerum, a small nematoid worm closely allied to
Strongylus^ which I discovered in the tunics of the stomach of a
tiger.J The mouth of this Entozoon is a vertical fissure, bounded on
each side by a jaw -like lip, the anterior margin of which is produced
in the form of three straight horny points. The secerning tubes
terminate at the mouth by their smaller extremities, and there pour

* LXXVIIL t XXIV. p. 131. X LXXXVIII.

H 4

104 LECTURE ■v^.

out a semi-pellucid secretion. They are as simple as the so-called
salivary caeca in the Holothuria ; and their coexistence with a struc-
ture of the mouth, better adapted for trituration than any that
seems hitherto to have been detected in the Entozoa, is conformable
with the laws which regulate the coexistence of the salivary ap-
paratus in higher animals. Cloquet supposes that the thickened
glandular parietes of the oesophagus in the Ascaris lumhricoides may
provide a secretion analogous to that of salivary organs. Diesing*
has described four caecal tubes analogous to those in Gnathostoma in
species of his genus Cheir acanthus, in which he considers them,
erroneously according to Siebold, to be analogous to the ambulacral
vesicles in the Echinoderms. Mehlisf has also figured, in the
Strongyhis hypostomus, two white organs with blind extremities,
which are extended into the abdominal cavity on each side the
intestine, and which appeared to him to terminate in the animal's
mouth. These glands Mehlis supposed to pour out an irritating
liquor, which excited an increase of the secretion of the mucous
membrane, to which the parasite was attached. Dr. BaggeJ, has
more recently described a pair of blind secerning tubes in the
Strongyhis auricularis and in theAscaris acuminata, which unite
and terminate by a common transverse fissure on the exterior of the
animal, at a short distance behind the mouth, and to which he assigns
the same irritating office as that attributed by Mehlis to the glands
in the Strongylus hypostomus.

The alimentary tube in a species of Ascaris infesting the stomach
of the Dugong is complicated by a single elongated caecum, arising at
a distance of half an inch from the mouth, and continued upward, so
that its blind extremity is close to the mouth. From the position
where the secretion of this caecum enters the alimentary canal, it may
be regarded as a primitive rudiment of the liver.

The generative organs of the Coelelmintha are more simple than in
the androgynous Sterelmintha, or even than in the dioecious Echino-
rhynchi ; yet they are adapted for the production of a surprising
number of fertile ova. In the Linguatula the organs of both sexes, and
especially of the female, are more complex than in the Nematoidea :
I shall, however, briefly notice them before proceeding to demonstrate
the parts of generation in the human coelelminthic parasites.

The male Linguatula, as in other dioecious Entozoa, is much
smaller than the female : the generative apparatus consists of two
winding seminal tubes or testes, and a single vas deferens, which
carries the semen from the testes by a very narrow tube, and after-
wards grows wider. It communicates anteriorly with two capillary

* LXXXIX. -f XC. p. 81. taf. 2. fig. 6. % LXXXV.

ENTOZOA. 105

processes, or penes, which are connected together at tlieir origin by a
cordiform glandular body, representing a prostate or vesicula semi-
nalis. The external orifices of the male apparatus, according to
Miram, are two in number^ and are situated on the dorsal aspect of
the body just behind the head. Diesing, however, describes the male
Pentastoma as having only a single penis, which protrudes just
behind or below the oral aperture.

The female generative organs of the Linguatula tcenioides present
a structure in some respects analogous to that of the Distotna per-
latum : the ovary {^fig. 45. ii) is a part distinct from the tubular ovi-
duct, and is attached to the integument or parietes of the body, extend-
ing down the middle of the dorsal aspect. It consists of a thin stratum
of minute granules, clustered in a ramified form to minute white
tubes, which converge and ultimately unite to form two oviducts.
These (o, 6) proceed from the anterior extremity of the ovary, diverge,
pass on each side of the alimentary canal, and unite beneath the
origins of the nerves of the body, so as to surround the oesophagus and
these nerves as in a loop. The single tube (jo) formed by the union
of the two oviducts above described, descends, winding round the ali-
mentary canal in numerous coils, and terminates at the anal extremity
of the body. But, besides receiving the ova from the two tubes, the
single canal communicates at its commencement with two elongated
pyriform sacs (m, m), which receive from the male, in coitu, the semen,
and convey it into the oviduct, with the addition of a mucous secretion.

The male organs in the Nematoidea consist of a single and simple,
slender, elongated tube {^fig. 44, e, e', /), or testis under its most
elementary form of a sperm-duct, which is merely a contracted con-
tinuation of the tubular testis of a seminal reservoir, which is a wider
part of the same tube, and of a single or double intromittent spicu-
lum with its prepuce, or bursa.

The spiculum is simple in the genus Filaria. According to the
observations of Dr. Leblond*, the male-duct in the Filaria papillosa
terminates at the anterior extremity of the body, close to the mouth.
From this aperture the slender duct, after a slight contortion, is
continued straight down the body to a dilated elongated sac, which
represents the testis. In the Filaria attenuata the blind end or
beginning of the testis is bifurcate.

In the Trichocephalus dispar the testis, a single tortuous tubule,
commences by a blind extremity near the rectum, passes forwards to
a dilated seminal receptacle at the anterior part of the thick portion
of the body, from which it bends backwards nearly the whole length
of the thick part, constricted at irregular intervals, and terminating

* LXXXIP. p. 20. pi. 3. f. 1.

106 LECTURE VI.

in a narrow straight canal, which is continued into the inverted
pyramidal appendage, or bursa, attached to the hinder extremity of
the body, from which the single spiculum projects.

In the Strongylus gigas the blind beginning of the testis is usually
found in the anterior half of the body, as at e {fig. 44.), the tube
descends into the posterior half, and is disposed in a number of long
coils, reaching from near the head, e\ to the tail. One part of the
canal is wider than the rest, and forms a kind of seminal reservoir.
The terminal portion, y, is slender. The bursa or sheath of the penis
forms the posterior extremity of the body, and is a cutaneous produc-
tion of a round, expanded form, d, with the spiculum e, projecting from
its centre. In other species of Strongylus, as e. g. Strong, injlexus,
the bursa penis is bifid, and the intromittent organ is double : both
divisions are of great length in the Strongylus paradoxus : in the
Strongylus armatus the bursa is quadrifid. The Spiropterce are dis-
tinguished by the aliform membranous caudal appendage in the male.

In the Ascaris lumhricoides the penis projects from the anterior
part of the anus in the form of a slender, conical, slightly curved
process, at the extremity of which a minute pore may be observed
with the aid of the microscope. The base of the penis communicates
with a seminal reservoir, and is attached to several muscular fibres,
destined for its retraction and protrusion : the reservoir is about
an inch in length, and gradually enlarges as it advances forwards : the
testis, or seminal tube, extends to the anterior third of the body,
forming numerous convolutions or loops about the intestine : its
attenuated caecal extremity adheres closely to the dorsal wall of the
abdomen. The total length of the seminal tube is about three feet.
In the Ascaris mystax the basal half of each long and slender penis
is tuberculate for the attachment of its protractor and retractor
muscles : the apical half, which alone is protruded, is a slender
transversely striated horny spiculum. Accessory parts to aid mecha-
nically in the coitus are added to some of these limbless vermiform
parasites. In the Ascaris mystax, e. g., there is on either side of the
concavity of the caudal end of the body a tubercular ridge supporting
a membrane which is finely serrated, and gives a secure hold when
the tail of the male is wound round that part of the female's body
where the vulva is situated.

The first steps in the development of the spermatozoa of the Nema-
toidea have been well observed by Siebold * in the Ascaris paucipara,
a species favourable for this kind of research, on account of the large
size of the sperm-cells. The blind end of the tubular testis is occupied
by cell-nuclei (zellenkerne) with their nucleoli (kernkorperchen). A

* XXrV. p. 153.

ENTOZOA. 107

little further on a quantity of very fine granular matter is added, and
the cell-nuclei become severally enclosed (eingehiillt) by the fine
granular matter, as by a yolk ; around which envelope a cell-membrane
is formed. This cell-wall gradually expands ; its inner surface being
lined by a layer of granules, whilst in the cavity of the cell the granules
have liquified and disappeared. As these changes take place the
cell-nucleus becomes developed into an elongate, sharply defined
solid corpuscle, which is the spermatozoon.

The observations recently communicated to the Royal Society by
Dr. Nelson * on the development of the spermatozoa in the Ascaris
mystax, correspond in the main with Siebold's description. Dr. N.
finds the blind end of the testis composed of a thick membrane,
which becomes resolved at its inner surface into very minute granules,
which, when liberated, swell out into nucleated cells. A little further
on these cells are obscured by an immense number of fine granules,
which form envelopes for the cells. These cells, which are described
to have a very transparent cell-wall and a nucleus attached to one
side, answer to the " zellenkerne " of Siebold. According to Dr.
Nelson no further development of the spermatozoon goes on in any
part of the testis, but is reserved for the transmission of the semen
into the uterine tube of the female. Here he describes the sperm-cells
as being deprived of their granular envelope and becoming enlarged,
forming transparent spheres, with a discoid nucleus which now con-
tains a nucleolus. The granular substance of the nucleus increases
and projects towards the centre of the cell, and its external layer is
converted into a distinct tunic, where it is in contact with the cell-
wall, which, as the nuclear matter increases, sometimes pushes out the
cell-wall. This, however, does not form the tail-part of the sperma-
tozoon in Asc. mystax : the change of the conical to the cylindrical
form of the progressively elongating nuclear matter takes place within
the sperm-cell, close to its wall. The nucleolus remains in the en-
larged or clavate end of the bent cylinder, but the granules disappear,
and the nucleus is transformed into a flask-shaped cjecal tubule, which
is liberated, as the spermatozoon, by the liquefaction of the surround-
ing cell-wall. The nucleolus at the open clavate end of the sperma-
tozoon afterwards disappears.

From the examples which have been adduced of different genera of
the Nematoidea, we may perceive that although there are many
varieties of structure in the copulative part of the male generative
apparatus, the essential or secerning portion uniformly consists of a
single tube. A like uniformity of structure does not obtain in the
essential parts of the female organs : in a few instances the ovary is

* XCI.

108 LECTURE VI.

single, corresponding to the testis in the male, but in the greater
number of the nematoid worms it consists of two filamentary tubes.

The Strongylus giyas is an example of the more simple structure
above alluded to.* The single ovary commences by an obtuse blind
extremity close to the anal extremity of the body, and is firmly
attached to the termination of the intestine; it passes first in a straight
line towards the anterior extremity of the body, and, when arrived
to within a short distance from the vulva, is again attached to the
parietes of the body, and makes a sudden turn backwards ; it then
forms two long loops about the middle of the body, and returns again
forwards, suddenly dilating into an uterus, which is three inches in
length, and from the anterior extremity of which a slender cylindrical
tube or vagina, about an inch in length, is continued, which, after
forming a small convolution, terminates in the vulva, at the distance
of two inches from the anterior extremity of the body.

In the Trichocephalus dispar the ovarium and uterus are conti-
nuations of one and the same single tube, which by its folds more or
less conceals the intestines ; the vulva is situated nearly at the junction
of the filamentous with the thick part of the body. The female ge-
nerative tube is, also, single in Trichosoma, in Sphcerularia, in
Filaria rigida^ and in Ascaris paucipara.

The theory which had suggested itself to Rudolphi, of the correla-
tion of a simple oviduct in the female with the spiculum simplex of
the male, and of the double oviduct with a spiculum duplex, is dis-
proved by the circumstance of the uteri and oviducts being double
in the Strongylus armatus and in the Ascaris lumbricoides, in the
males of which the penis is a single spiculum. In the Stro7igylus
injlexus, which infests the bronchial tubes and pulmonary vessels of
the porpoise, each of the two female tubular organs may be divided
into ovary, oviduct, and uterus ; the ovary is one inch in length,
commences by a point opposite the middle of the body, and, after
slightly enlarging, abruptly contracts into a capillary duct about two
lines in length, which may be termed the oviduct or Fallopian tube,
and this opens into a dilated moniliform uterus three inches in length.
Both tubes are remarkably short, presenting none of the convolutions
characteristic of the oviducts of Ascaris and Filaria, but extend in
a straight line (with the axception of the short-twisted capillary
communication between the ovaria and uteri) to the vulva, which
forms a slight projection below the curved anal extremity of the
body. The reason of this situation of the vulva seems to be the
fixed condition of the head of this species of Strongylus. In both

* LX. p. 141. fig. 95.

ENTOZOA.

109

sexes, it is commonly imbedded so tightly in a condensed portion of
the periphery of the lung, as to be with difficulty extracted ; the anal
extremity, on the contrary, hangs freely in the larger branches of
the bronchi, where the coitus, in consequence of the above disposition
of the female organs, may readily take place.

In the Strongylus armatus, the two oviducts
terminate in a single dilated uterus, and the vulva
is situated at the anterior extremity of the body,
close to the mouth.

I find a similar situation of the vulva in a species
of Filaria, about thirty inches in length, which
infests the abdominal cavity of the Rhea, or Ameri-
can ostrich. The single portion of the genital
tube continued from the vulva, is one inch and
a quarter in length ; it then divides, and the two
oviducts, after forming several interlaced convolu-
tions in the middle third of the body, separate ;
one extends to the anal, the other to the oral ex-
tremities of the body, where the capillary portions
of the oviducts respectively commence.

In the Ascaris vermicularis^ the vulva i^fig-
47, e) is situated about one fourth of the length of
the body from the head. One division or horn
of the uterus, with its capillary ovarium, passes
towards the forepart of the body ; the other di-
vision towards the opposite end.

In the Ascaris lumbricoides the female organs
{Jig. 46.) consist of a vulva, a vagina, and a uterus,
which divides into two long tortuous oviducts,
gradually diminishing to capillary tubes, which
form the ovaria. Both divisions extend back-
wards from the point of bifurcation. All these
parts are remarkable in the recent animal for
their extreme whiteness. The vulva is situated
on the ventral surface of the body, at the junction
of the anterior and middle thirds of the body,
which is generally marked at that part by a slight
constriction. The vagina is a slightly wavy canal
five or six lines in length, which passes beneath
the intestine, and dilates into the uterus. This
manifests strong peristaltic motions in the living
worm. The division of the uterus soon takes place, and the cornua
extend with an irregularly wavy course to near the posterior extremity

d

Ascaris vermicularis
(magnified).

110 LECTURE VI.

of the body, gradually diminishing in size; they are then reflected
forwards, as the ovaria, and form numerous, and apparently inextri-
cable coils about the two posterior thirds of the intestine. The vagina,
like the uterus, is lined by flat nucleated epithelial cells.

In Cucullanus elegans and C. microcephalus the uterus is bifid,
but only one of the divisions is prolonged into the capillary ovarium :
the other horn terminates abruptly in a blind end. In Ascaris micro-
cephala Siebold found the uterus to divide into three horns, each
of which was produced into an ovarium: and in Filaria labiata
Nathusius saw the uterus divided into five tubes.*

In the Nematoidea the male individual is always smaller, and
sometimes disproportionately so, than the female. At the season of
reproduction, the anal extremity of the male is usually bent round
the part of the body where opens the vulva of the female, to which it
attaches itself by the intromission of the single or double spiculum, and
by the adhesion of the surrounding tumid labia, or of accessory dermal
appendages. As the vulva of the female is generally situated at a
distance from either extremity of her body, the male so attached has
sometimes the appearance of a branch or young individual sent off
by gemmation at an acute angle to the body of the female.

The evidence of the fertility of the compound cestoid Entozoa was
sufficiently marvellous. That which I have now to adduce, from a
calculation made by Dr. Eschricht in reference to the Ascaris lum-
bricoides, the commonest intestinal parasite of the human species, is
scarcely less surprising. The ova are arranged in the ovarian tubes
like the flowers of the plantago, around a central stem or rachis.
There are fifty in each circle ; that is to say, you might count fifty
ova in every transverse section of the tube. Now the thickness of
each ovum is 1*500 of a line, so that in the length of one line there
are 500 wreaths of fifty eggs each, or 25,000 eggs ! The length of
each ovarian tube is sixteen feet, or 2,304 lines, which, for the two
tubes, gives a length of 4,608 lines. The eggs, however, gradually
increase in size so as to attain the thickness of -^-^ of a line ; we
therefore have, at the lower end of the tube, sixty wreaths of ova, or
3,000 ova in the extent of one line. The average number, through
the whole of the extraordinary extent of the tube, may be given at
14,000 ova in each line, which gives sixty-four millions of ova in the
mature female Ascaris lumbricoides I

The embryo is not developed within the body in this species : the
ova may be discharged by millions ; and most of them must, in large
cities, be carried into streams of water. An extremely small pro-

*XXIV. p. 151.

ENTOZOA. Ill

portion is ever likely to be again introduced into the alimentary canal
of that species of animal which can afford it an appropriate habitat.
The remainder of the germs doubtless serve as food to numerous
minute inhabitants of the water ; and the prolific Entozoa may thus
serve these little creatures in the same relation as the fruitful Cerealia
in the vegetable kingdom stand to higher animals, ministering less to
the perpetuation of their own species than to the sustenance of man.

The nematoid Entozoa present, perhaps, the most favourable sub-
jects for studying, with the requisite attention, the successive steps of
impregnation, and of the processes by which the germinal vesicle and
yolk become finally transmuted into the young and active worm.

I described and showed diagrams of some of these changes in the
ova of the Srongylus inflexus in my lectures on Generation in 1840.
The subject has been carefully prosecuted by Professors Siebold *
and Kollikerf, from observations made upon the ova of the Stron-
gylus auricularis and the Ascaris acuminata, both of them viviparous
species of Nematoidea, and subsequently by Dr. Nelson with great
care and ability, in the oviparous Ascaris mystax.\

The blind end of the tubular ovarium detaches from its inner
surface, and contains, minute round cells, which, as they proceed
along the tube, enlarge, become nucleated, and surrounded by a
finely- granular yolk matter, in which the cell floats as the 'ger-
minal vesicle ' with its nucleus. In the more advanced part of the
ovarium, these ova are discoid, of an irregular form, and disposed
either in simple rows, one behind another, or are grouped round a
stem or rachis in the centre of the tube, according to the species.
In the oviduct, the ova acquire a colourless chorion, the secretion of
that tube. A short diverticulum proceeds from each pole of the
^^^g in Trichosoma and Trichocephalus.

In the fundus, or beginning of the uterus, much seminal matter is
accumulated in the impregnated females. § Dr. Eschricht describes
fifty ova as forming a single whorl or wreath in the Ascaris lumhri-
coides ; but in the Ascaris mystax Dr. Nelson found but four flat-
tened ova in the same plane, filling the transverse section of the
ovarian tube. They assume, by mutual pressure, a triangular form
with the rounded base next the walls of the tube. In the contracted
part of the canal, answering to that which I have called "oviduct"
in the Strongylus injiexiis ||, the ova in the A. mystax become
separated, and pass in single file to the uterus, altering their form
during the passage, in which they first meet the spermatozoa ; but

* LXXXV. t LXVI. \ XCI.

§ XXIV. p. 151. II LXXXIV. p. 74.

112 LECTURE VI.

whether these be present in the oviduct or not, the following changes
take place. The ovum becomes spheroidal and acquires a chorion ;
the vitelline granules become smaller; the germinal vesicle disappears ;
and a number of large, transparent, oil-like globules appear, probably
the combined result of the condensation of the yolk granules and
the diffused contents of the germinal vesicle. The oil-like globules
approach the circumference of the ovum, and disappear ; the con-
densed yolk-mass assumes a spherical form in the centre of the egg ;
and the membrana vitelli is now recognised surrounding it, divided
by a clear fluid from the chorion. If impregnation have not pre-
viously taken place, the chorion is granulated, and such ova perish
without undergoing further developmental change. *

When impregnation has taken place, the narrow oviduct is filled
by the flask' shaped spermatozoa, and the ovum, as it passes singly
into it from the ovarium, becomes surrounded by them. They indent
the previously well-defined surface of the tenacious granular yolk,
bury themselves in it, and partially break it up in the process.
Sometimes only one spermatozoon is thus seen embedded ; but more
commonly several spermatozoa penetrate the same ovum. The ger-
minal vesicle can be faintly recognised in some of these so penetrated
ova. As the ova proceed along the impregnated oviduct, the chorion
begins to be formed, as in the unimpregnated one. It appears at
first upon the smooth unperforated parts of the ovum, and afterwards
covers the ruptures themselves, and incloses the spermatozoa with
the yolk and its germinal vesicle. The inclosed spermatozoa now
lose their characteristic form, and swell into irregular masses having
a distinct outline, and, being highly refractive, give a mottled
appearance to the contents of the egg. They are then gradually
resolved into a transparent fluid, diffused, and effect changes, by
partial solution, on the yolk granules themselves, these changes pro-
ceeding from the surface towards the centre. The germinal vesicle
remains for a while in the centre of the ovum, more or less sur-
rounded by the undissolved yolk granules, whilst the egg acquires
one or two additional layers of the chorion secreted by the oviduct.
The germinal vesicle then ruptures or disappears ; but its nucleus,
with a now visible nucleolus, remains. The rupture of the germinal
vesicle is followed by a change in the character of the remaining yolk
granules, which become larger, less opaque, and float more loosely in
the fluid. The nucleus begins to swell out into a transparent cell — the
"primary germ-cell"! — of which the former nucleolus is now the

* XCI.

f Fii'st defined under that name, and so distinguished from its predecessor the
" germinal vesicle," in XXX. pp. 4, 5.

ENTOZOA.

113

nucleus ; and the surrounding granules are aggregated about it by
the formation of a yolk membrane, which compresses them into a
spherical mass, the clear fluid being, as it were, filtered through, as
the membrane contracts, into the interspace between the germ-mass
and the chorion. In this state the egg quits the parent in the Asc.
mystax.

The subsequent changes observed by Dr. Nelson in this species
accord with those which have been described by Barry, in the mam-
miferous ovum *, and by Sieboldf, Kolliker|, and other observers, in
the impregnated ova of the Entozoa and other invertebrate animals.
The nucleus of the primary germ-cell {Jig. 48, a) first divides. Its
division {Jig. 49.) is followed by that of the germ-cell itself (^^r. 50.) ;
and the two " secondary germ-cells" {Jig. 51, h^ b) thus established,
4\) 50 51 52 5i

Development of Ascnris acuminala. LXXXV.

recede to opposite ends of the germ-yolk. Dr. Nelson has observed
that these germ-cells revolve in circles, each appearing to mould its
portion of the germ-yolk into a spherical form ; and he considers the
subsequent division of the germ-yolk to be a mechanical effect. § By
its division, two germ-yolks, each with its nucleated germ-cell, result
{Jig. 52.). The division of the germ- cell takes from five to ten
hours ; the r.ubsequent one, of the yolk, not more than half an hour,
in the Asc. mystax. By the repetition of this process, as mjgs. 53,
54, 55, the number of derivative germ-cells increases in the geome-
trical ratio of 4, 8, 16, 64, 128, 256, &c., until the whole egg appears
to be filled by opaque spherical granules {Jg. 56.\ each, however,
having its share of the original impregnated germ-cell. A membrane
is then formed around the germ-mass.

In the ova of Nematoidea, many of which are viviparous, the
embryo is developed by two different modifications of the diffusive
process by multiplication of germ-cells from the primary central one :

XXVII. p. 307.

t LXXXV.

I

i LXVL

§ xci.

114 LECTURE VI.

in the one process the successive division of the germ-cells goes on
without a corresponding cleavage of the yolk, but this is penetrated
by the multiplying germ-cells, is absorbed, assimilated, and converted
into the matter of such germ-cells : in the other process the attractive
force of the germ-nuclei seems to be greater ; the whole yolk is divided
by the first bipartition of the original germ-cell, and is afterwards
assembled around these divisions, as they successively arise, as in Jigs.
52 — 56. The subdivisions of the yolk decrease in size as they aug-
ment in number, and the vitelline matter is at length, by the reiterated
processes of developement, liquefaction, and assimilation of nucleated
cells, sufficiently subdivided and refined, and each subdivision or cell,
by the concomitant partition of the clear spermatic nucleus or hya-
line, has become adequately vitalised or fertilised, so as to be ca-
pable of its further metamorphosis into the appropriate tissues of the
embryo worm.

So far the process is essentially the same with that in all other ova
up to the mammal, and without doubt in man. The materials for the
future being are accumulated in a duly subdivided state, like the
bricks or hewn stones collected for the builder to operate on under
the guidance of the architect. With regard to the rough material for
formation of the Ascaris, a depression first appears on one side of the
minutely subdivided germ-mass, which, as this deepens, assumes the
form first of a cup, and then of a ring : the space so formed between the
germ-mass and the chorion becomes filled by a clear fluid. The ring
next presents a constriction at one point, which divides and transforms
it into a cylinder with two equal obtuse ends in apposition {Jig. 57.).
By the lengthening and attenuation of the cylindrical mass, the ends
overlap and the ring assumes the character of a coil {Jig. 58.) ; and
now something like an integument, containing a fine granular tissue,
may be discerned. Further elongation and attenuation produce one or
two spiral coils, and a greater clearness of the tissues of the embryo
worm makes its character plainly manifest {Jig. 59.). In the Ascaris
at this period the characteristic three-lobed mouth may be discerned ;
and soon after the alimentary canal can be distinguished from the
integument, both having been formed by the subdivision and meta-
morphosis of the primitive cells. The young animal, thus built up,
now begins to move briskly within the egg-membrane, assimilates the
remaining vitelline mass, and is soon strong enough to burst its prison,
and commence its independent career of existence.

The Entozoa are hardly less remarkable for their tenacity of life
and revival from a state of apparent death than the Infusoria, and the
knowledge of this property is indispensable to a fair estimation of the
chances of the re-introduction of the ova of Entozoa into the bodies

ENTOZOA. 115

of living animals. In no class of animals has the origin from equi-
vocal generation been more strenuously contended for than in regard
to the Entozoa. The great entozoologists Rudolphi and Bremser were
advocates of this doctrine ; and Bremser did not scruple to charge the
Berlin Professor with a physiological heresy, when he ventured to
account for the high organisation of certain Ligulee infesting pisci-
vorous birds, by the hypothesis that they had been developed from
the lower grade which they previously exhibited in the cold-blooded
fishes swallowed by the birds, through the stimulus of the heat and
nutritious secretions of the more comfortable intestinal domicile into
which they had thus been accidentally introduced.

The advocates for the equivocal generation of the Entozoa adduce
the fact, that herbivorous mammals are not less subject to Entozoa
than carnivorous ones ; and how, they inquire, could the ova of
Entozoa be preserved in the water that serves as the drink of such
animals ? Or how, having become dried in the air, could such ova
afterwards resume the requisite vitality for embryonic development ?
We may admit that the ova of Entozoa could not, like the much more
minute germs of Polygastria, remain suspended in the atmosphere,
since they are specifically heavier than water ; but, with respect to
their powers of retaining dormant life, we have sufficient analogical
evidence to reject the assumption that they soon fall into decomposi-
tion. Dr. Nelson* found that he could best observe the develop-
ment of the ova of the Ascaris mystax by placing the females entire in
spirit of turpentine for two or three weeks, at the end of which the
ovaries were found distended with ova containing young worms, not
only fully developed but alive, and endeavouring to rupture the
chorion by tightening the coils of their spiral and suddenly reversing
them.

Mr. Bauer has recorded many experiments on the Vibrio tritici,
or parasite of wheat, a minute worm possessing the essential organi-
sation of the Nematoidea, not less remarkable in their results than
those of Spalanzani on the Rotifer ; the Vibriones were dried, and
when re-moistened, after the lapse of four to seven years, they
resumed their living and active state. De Blainville states that the
Filaria papulosa revives from a similar state of torpidity produced
by desiccation.

It has been proved that the mature Entozoa will resist the effects of
destructive agents, as extremes of heat and cold, to a degree beyond
the known powers of endurance of the Rotifera, and which would
be truly surprising were not the simplicity of the organisation of the

* XCI.
I 2

116 LECTURE VI.

Entozoa taken into account. A nematoid worm has been seen to
exhibit strong contortions — evident vital motions — after having
been subjected above an hour to the temperature of boiling water,
with a codfish which it infested ; and, on the other hand, Rudolphi
relates that the Entozoa of the genus Capsularia, which infest the
herrings that are annually sent to Berlin, hard frozen and packed
in ice, do, when thawed, manifest unequivocal signs of restored
vitality. If, then, the fully developed and mature Entozoa can
resist such powerful extraneous causes of destruction, how much
more must the ova possess the power of enduring such without losing
their latent life !

Burdach, who has summed up the evidence at great length in
favour of the equivocal generation of the Entozoa, adduces the
example of the oviparous species as involving the limitation of the
offspring to the lifetime of the individual which they themselves
infest ; but on this point Dr. Eschricht has well observed that the
transmission of the living young of the Strongylus ijiflexus from one
porpoise to another is readily explicable. This species of Strongylus
lives in the bronchial tubes, with its head immersed in the substance
of the lungs, and its tail extended into the larger branches of the
trachea. The living young must naturally escape into the mouth,
and, as porpoises are gregarious, the young worms would, by a short
passage through the water, readily be introduced into the mouth of
another porpoise, and so reach the trachea.

The young of most Entozoa are subject to metamorphoses. I have
already alluded to those of the Cestoidea, in which the embryo assumes
the form of an echinococcus, the head being provided with six hooks.
So armed it is enabled to attach itself to the species of animal in which
it becomes encysted and undergoes its next transformation : and such
species, being the food of the higher organised animal in which the
ultimate metamorphosis of the taenia takes place, the pupal tape-worm
is in that way introduced into its final abode. So far as observations
have yet gone, two different animals, having the mutual relation of
prey and devourer, are subordinated, so to speak, to the well-being of
each species of tape- worm. The metamorphoses of the Trematoda are
still more astonishing, and the locomotive condition of the earlier phases
of the Distoma evidently relate to the securing their entry into the
animal's body, which they are destined either temporarily in a larval
state, or permanently, to infest. Siebold has noticed the difference
of form between the j^oung of the Echinorhynchi and their viviparous
parents ; and this difference was so great in regard to the viviparous
Filaria medinensis, that Dr. Jacobson was led to suppose its multitu-
dinous progeny to be parasites of the parasite. Dr. Eschricht has

ENTOZOA. " 117

observed, that the flesh of fishes in summer is often studded with
small worms, which, in one instance, he ascertained to be Echino-
rhynchi; and he suggests whether it may not be the breeding-place of
such species, and whether the Trichina spiralis may not belong to
the same category. But how these embryos (if they be embryos) are
diffused through the intermuscular cellular tissue, can only be known
after long and laborious investigations ; and nothing is more true than
that a particular inquiry will be required for each particular species.

Summary of the Classes, Orders, and Families of the Entozoa of
Rudolphi : —

Class STERELMINTHA.
The nutrient canals or cavities excavated in the parenchyme of
the body.

Order T^nioidea.
The head provided with two, four, or six acetabula, and usually
with spines, either sessile or placed on a proboscis, or on tentacula.

Family Cystica.
No organs of generation ; body terminated by a bladder filled with
fluid. (All are, probably, tsenioid larvae.)

Genera : Echinococcus, Ccenurus, Cysticercus.

Family Scolecibm,

Body short, or moderately long ; sometimes partially vesiculated,
usually encysted ; no generative organs. (All are, probably, larvae.)

Genera : Anthocephalus^ DibothriorhynchuSy Floriceps, Gymno-
rhynchus^ Hepatoxylon, Rhynchobothriuniy Scolex, Tentacularia,
Tetrarhynchus (many species).

Family Ligvlibm.
Acetabula and spines obsolete ; body solid, depressed, long, with a
longitudinal furrow, not jointed, but finely striated transversely.
Genus ; Ligula. (Those of fishes are, probably, larvae.)

Family Cestoidea.

Body long, depressed, jointed, with male and female organs com-
bined in each of the mature segments.

Genera : Tetrarhynchus (certain species), Bothriocephalus, Tcenia,
Caryophyllceus.

Order Trejiatoda.
Body generally depressed, not jointed, with one or more acetabula ;
mouth an unarmed pore, from which a bifurcate or branched alimen-

I 3

118 LECTURE VI.

tary canal is continued, rarely provided with a vent. Male and
female organs in the same individual ; impregnation by reciprocal
coitus.

Sub-order Pendularia.

Integument not ciliated and no spontaneous fission in the mature
worms.

Genera : 3Ionostoma, Amphistoma, Distoma, Diporpa (in conju-
gation Diplozoon), Gasterostoma, Holostoma, Tristomay Polysioma.
(^Gyrodactylus, Axine, Octohothrium, Aspidocotylus, Aspidogaster,
are all, probably, larvae.)

Sub-order Turbellaria.
Integument ciliated in the mature worms.

Family Rhabdoccela, with a simple cylindrical alimentary cavity.

Genera: Vortex, Derostomum, Gyratrix, Strongylostomum, Me-
sostomum, 3Iacrostomum, Microstomum. (Some of these are, pro-
bably, larvae.)

Family Dendroccela, with a ramified alimentary cavity.
Genera : Polycelis, 3Ionocelis, Planaria, Leptoplana, Eurylepta,
Planocera, Thysanozoon.

Order Acanthocephala.

Body saccular, cylindrical, or subdepressed ; head provided with
,an uncinated proboscis. A ramified vascular nutritive system.
Sexes distinct.

Genus : Echinorhynchus.

Class CCELELMINTHA.

An alimentary canal suspended in an abdominal cavity. The
sexes distinct.

Order Gordiacea.

Body filamentary and cylindrical ; alimentary canal without anus.
Genera : Gordius, 3Ier?nis, ( Trichina, probably a larva).

Order Nematoidea.

Body elongated, cylindrical. Alimentary canal with both mouth
and vent.

Genera : Filaria, Trichosoma, Trichocephalus, Spiroptera, Stron-
gylus, Ascaris, Oxyurus, Cucullanus, Hedrurus, Ancyracanthus,
Gnathostoma, Cheiracanthus, Lecanocephalus, Liorhynchus, Physa-
loptera, Sphcerularia, Anguillula.

POLYPI, 119

Order Onchophora.

Body depressed, subarticulate. Mouth provided with hooks. Anus
distinct.

Genus : Linguatula.

LECTURE VII.

POLYPI.

Hydrozoa and Anthozoa.

The two great divisions of Cuvier's Zoophytes, viz. the Infusoria
and Entozoa, which have hitherto engaged our attention, approxi-
mate to the vermiform type ; and each ascends by rapid steps to the
confines of the articulate province. The remaining classes of the
Zoophytes are constructed on the radiated type ; and some of them,
as the Bryozoa and Acalephce, conduct to the molluscous series.

To-day I have to request your attention to the history of a race
of animals almost as widely diffused, almost as numerous, and some
of them hardly less minute than the Infusoria, with which we com-
menced the survey of the vermiform zoophytes. Our present sub-
jects form at least three classes of radiated zoophytes, which have
been grouped together under the common name o£ Polypi, on account
of their external resemblance to the many-armed cuttle-fishes, which
were so denominated by the ancient Greek naturalists. But the
knowledge of the organised beings now called Polypi, as members
of the Animal Kingdom, is of comparatively recent introduction : it
cannot be dated further back than the time of Imperato* and
Peyssonel. f Amongst those naturalists who have subsequently
contributed to improve and extend the history of the Polypes, our
countryman Ellis J will always take a high rank.

A polype generally presents a soft cylindrical oval or oblong body,
with an aperture at one of its extremities, which is surrounded by a
coronet of long tentacula. In most of the class, this aperture leads
to a simple digestive cavity, consisting of a stomach without intestine.
In the highest organised group, the digestive sac is prolonged into
an intestinal canal, which is bent upon itself, and terminates by a
distinct anus opening upon the external surface. The organisation
of the polypes is in general simple ; their faculties are limited ;
and the vital phenomena, save those of irritability and contractility,
are inconspicuous. Nevertheless the influence of the combined

* XCV. (1599). t XCVI. (1723 and 1727). t XCVII and XCVIII.

I 4

120

LECTURE VII.

powers of some of the species, in modifying the crust of the earth, is
neither slight nor of limited extent.

This great division of the radiated animals is divided into three
groups or classes, according to the modifications of the alimentary
canal. In the first and lowest organised class, which I have called
Hydrozoa*, digestion is performed by the secretion of a simple sac,
excavated in the gelatinous and granular parenchyme of the body.
In the second class, called Anthozoa, the digestive sac, which, like
the first, throws out the rejectamenta by the same aperture as

that which receives the
nutriment, is suspended
by a series of vertical
folds of membrane, in
a distinct abdominal ca-
vity, to the outer parietes
of the body. In the
) third and highest class,
called Bryozottf the ali-
mentary canal, which is
suspended loosely in an
abdominal cavity, is pro-
vided, as has been already
stated, with a distinct
mouth and anus.

It is remarkable that
the most locomotive of the
Polype tribe is at the
same time the type of the
lowest organised group.
The Hydra\, or common
fresh-water Polype {fig.
60.) consists, when mag-
nified even with a mode-
rately high power, appa-
rently of a granular sub-
stance of a greenish or
reddish hue, the granules or cells being loosely connected by a semi-
fluid matter. The external cells are condensed, and elongated in the

Hydra fusca.

* Nat. size.

* LXXXIV. p. 82. Dimorphoea of Ehrenberg ; Sertulariens of Miliie Edwards ;
Nudihrachiata of Fan'e ; Hydroida of Johnston ; Hydraidce and Sertulariadce of
E. Eorbes.

f "In Africa et Arabia Hydras studiose fnistra qu£esivi," CXVIL, p. 292.

POLYPI. 121

axis of tlie body, so as to form two tegumentary layers : the internal
cells are elongated transversely to the axis of the body, and form a
stratum of villi, projecting into the abdominal cavity : the thick
intermediate mass of nucleated cells seems to fulfil the ordinary
functions of muscular or contractile tissue.

The hydra commonly adheres by a small prehensile disc or rudi-
mentary foot {^fig. 60, d\ situated at the extremity of the stem or
body opposite to the mouth. When the little animal would change
its position it slowly bends its body, and, fixing one or more of its
tentacula to the supporting surface, detaches the foot, approximates
it to the head, and advances by a succession of these leech-like
motions. The hydra can make progress in water, as well as on a
solid plane ; when it would swim it suspends itself to the surface of
the water by its terminal foot, which it expands, and exposes to the
air : the disc soon dies, and in this state, repelling the surrounding
water, it serves as a float, from which the hydra hangs with its
mouth downwards, and can row itself along by means of its tentacula.
Its ordinary position is one of rest, adhering to an aquatic plant by
its foot, with the dependent oral tentacula spread abroad in quest
of prey : these are of great length and tenuity in the Hydra fusca.

Should a small nais or entromostracan, or any of the larger infu-
sories, come within the reach of the little carnivorous polype, they are
immediately seized, pulled towards the mouth {fig. 60, h\ and swal-
lowed. The rapidity of the digestive process is manifested by the
diffusion of any characteristic colour of the animalcules swallowed
through the gelatinous parenchyme of the devourer ; and when this
process is completed, the indigestible debris of the prey are rejected
by the same aperture which had just gorged it. The inner surface
of the digestive bag is lined by a ciliated epithelium, and has many
peculiar cells containing a clear fluid with brown pigment granules :
these are very conspicuous in the Hydra viridis ; the contents are
probably discharged into the stomach by the bursting of the cells,
which have been conjectured to perform a function akin to that of a
liver. A careful investigator, Corda *, afiirms the existence of an
anal outlet {fig. 60, c), and figures it of small size, close to the hind
sucker or foot ; and Baker f several times saw " the dung of the po-
lype in little round pellets discharged at this outlet or anus." Mr.
Hancock J, also, observing a Hydra viridis in a highly contracted
state and about to discharge an egg, saw a narrow channel passing
from the digestive cavity through the substance of the foot, appa-
rently about its centre. From this channel issued a long, linear

* XCIX. t C. p. 27. X CIV. p. 288.

122 LECTURE VII.

mass of excrementitious matter composed of a tenacious mucus im-
bedding a granular substance resembling both in colour and texture
that which lined the digestive cavity. Such pore may give passage
to certain excretions of the lining membrane of the cavity, but the
coarser indigestible parts of the prey are habitually regurgitated by
the mouth.

Each tentaculum in the Hydra grisea, according to Trembley, is
a tube, which communicates with the common digestive cavity. The
food which is rotated in that cavity is driven up some way into the
tentacles, and sent back again.* Cordaf found the walls of the tenta-
cular cavities to contain a fluid albuminous substance mixed with oil-
like particles. This substance swells out at certain definite places
into denser nodules, which are arranged in a spiral line {fig. 60, a, a).
Each nodule is furnished with tactile filaments, and a singularly con-
structed organ for catching and wounding the prey. The parts re-
garded by Corda as organs of touch consist of a fine sac, inclosing
another with thicker parietes, and within this there is a small cavity :
from the point where the two sacs coalesce above, there projects a
long and very slender filament, which is non-retractile. The wounding
or seizing organ consists of an obovate transparent sac, immersed in
the nodule with a small aperture. At the bottom of the sac, and
within it, there is a solid corpuscle, which gives origin to a clear
calcareous sharp dart or spine, that can be pushed out at pleasure, or
withdrawn until its point is brought within the sac. When the
hydra wishes to seize an animal, the darts are protruded, by which
means the surface of the tentacula is roughened, and the prey more
easily retained: Corda believes that a poison is at the same time
ejected. The nodules of the tentacula are connected together by
means of four muscular bands, which run up, forming lozenge-shaped
spaces by their intersections : these are joined together by transverse
bands. % The lip of the mouth is armed with darts similar to those
of the tentacula ; and they have been found in the skin of the body
and of the foot.

That the tentacula have the power of communicating some be-
numbing or noxious influence to the living animals which constitute
the food of the Hydra, is evident from the effect produced, for
example, upon an entomostracan, which may have been touched, but
not seized, by one of these organs. The little active crustacean is
arrested in the midst of its rapid, darting motion, and sinks, appa-
rently lifeless, for some distance ; then slowly recovers itself, and

* CI. torn. i. p. 260., torn ii. p. 228. f XCIX.

X CIV. p. 35.

POLYPI.

123

resumes its ordinary movements. Siebold states that when a nais,
a daphnia, or the larva of a Cheironomus have been wounded by the
darts, but not seized, they do not recover, but die.* These and other
active inhabitants of fresh waters, whose powers should be equivalent
to rend asunder the delicate gelatinous arms of their low-organised
captor, seem paralysed almost immediately after they have been
seized, and so countenance the opinion of Corda that the secretion
of a poison enters the wounds.

The most extraordinary properties of the Hydra are, however,
those which best accord, and might be expected to be associated,
with its low and simple grade of organisation ; although they excited
the greatest astonishment in the physiological world when first
announced by their discoverer, Trembleyf, and are often still called
wonderful.

If a polype be partially bisected, each portion forms a perfect
polype : RoeselJ devotes three plates to figures of monstrous Hydrae,
the results of such incisions. If a Hydra be transversely bisected,
both halves survive ; the cephalic one developing a terminal sucker,
the caudal one shooting forth a crown of tentacula ; each moiety
thus acquiring the characters of the perfect individual. But in
a healthy and well-fed Hydra, the same phenomena will take
place if it be divided into ten pieces. The Hydra, notwith-
standing the want of a nervous centre thus indicated, and the
absence of any hitherto recognised nervous filaments, manifests an
obvious predilection for light, and, when confined to a glass, always
moves itself to the brightest side. Trembley succeeded in inverting
these delicate animalcules, and retaining them inverted until they
accommodated themselves to this singular change in their condition.
The pigment or hepatic cells of the gastric membrane, now external,
are cast off* : the orifices, by which the cavities of the tentacula
communicate with the stomach, are exposed a little below the rim
of the mouth ; these orifices are soon obliterated, and new ones are
formed in communication with the new digestive sac. The ciliated
epithelium and hepatic-cells must be developed on what was the
outer surface : and the dart-cells in what before was the gastric
surface. At least Trembley assures us, and gives corroborative
evidence, that digestion was eff*ected as actively by the surface
which before was external, as by that which had been the digestive
surface ; whilst this as readily assumed the ordinary gemmiparous
function of the skin.§

* XXIV. p. 30. t CI. t CV. (Tab. Ixxx., Lxxxi., and Ixxxii.)

§ J'ai retourne un nombre considerable de Polypes de la seconde espece

124 LECTURE VII.

The Hydras are not less remarkable for their power of generation
than for that of regenerating mutilated parts. They have been
observed to multiply by spontaneous fission, dividing themselves
transversely. Roesel* figures a specimen in the act of transverse
fission ; but there may have been some previous injury at the part.
The most ordinary process of generation is by the development of
young polypi, like buds, from the external surface of the old one.
This property depends on the small amount of change which the
germ-mass has undergone in the development of the body.

In the freshwater polype, the progeny of the primary impregnated
germ-cell retained unaltered in that body, may set up, under favour-
able stimuli of light, heat, and nutriment, the same actions as those
to which they owed their own origin ; certain of the nucleated cells
do set up such actions, those, e. g. in the Hydra fusca, which are
aggregated near the adhering pedicle or foot ; and the result of their
increase by assimilation and multiplication is, to push out the con-
tiguous integument in the form of a bud, which becomes the seat of
the subsequent processes of growth and development; a clear cavity or
centre of assimilation is first formed, which soon opens into the
stomach of the parent ; but the communication is afterwards closed,
and the young hydra is ultimately cast off from the surface of the
parent. This mode of propagation is termed " gemmation." It differs
from the development of the hydra ab ovo, inasmuch as the im-
pregnated germ-cell, which set on foot the process, is derivative and
included in the body of the adult, instead of being primary and
included in a free ovum. But the germ-cell is the essential part of
the ovum, and the chorion an accessory and non-essential part.f

According to my observations, buds are not developed indifferently
from any part of the polype. I have never seen one growing from a
tentacle, nor does a wound of this part lead to the development of a
young hydra, like a wound of the base of the body. I conceive that
the greater amount of metamorphosis which the germ-cells and nuclei
have undergone in the formation of the complex organs of the
tentacula is the condition of this inferior power of generation and
regeneration.

The very small size in relation to the entire body, and the super-
ficial position of the secondary germ- cell which takes on the pro-

(^Hydra grisea), " qui sont restes retournes et qui ont longtemps vecu. lis ont
mange, cru et multiplie." CI. t. ii. p. 224.

* CV. tab. Lxxxiii. fig. 3.

f IMr. Goodsir gives the name of o\nile to the germ-cell which sets on foot the
analogous process of bud-formation in the Coenurus (LIIE. p. 570).

POLYPI. 125

cesses of development in the Hydra, appear to be the chief conditions
influencing that modification of the generative process by which a
small portion only of the Hydra is taken into the system of the new
individual, instead of one-half of the body, as in the case of the
Monad. So insignificant is the distinction between gemmation and
spontaneous fission ; the essential condition of both being, as in the
development of the ova, the presence of the pellucid nucleus of a
secondary impregnated germ-cell, as the centre from which all the
processes in the formation of the new individual radiate.

The Hydra propagates by ova as well -as by buds. It even
presents a periodical development of sexual organs of two kinds; one,
at the anterior or oral extremity of the body, consists of small nodules
or sacs, which Ehrenberg discovered to contain moving filaments, or
seminal animalcules ; another series of cells, developed in the pos-
terior part of the stem, contain ova. Sometimes one individual
Hydra developes only the male cysts, or sperm-vesicles ; sometimes
only the female ones, or ovisacs ; but the rule is generally to have
both kinds.

The ova are spherical, with a bristled chorion, which is of a deep
brown colour in the Hydra fusca. In the formation of the ova, certain
of the retained germ-cells multiply themselves, and coalesce to form a
larger central cell, surrounded by others of smaller size, with nuclei,
the exterior of which cells are metamorphosed into a chorion. Certain
other germ-cells are converted into sperm-cells, and develope sperma-
tozoa. The ova are extruded and fertilized by these, and they
develope a hydra, retaining, however, a large proportion of un-
changed cells in its composition. Accordingly, this hydra may
propagate by buds, and the hydra so developed may propagate again
by ova, and these two kinds of generation may alternate indefinitely :
but it usually happens that the same Hydra, after having exhausted
its power of forming buds, then developes the eggs.

The seas which wash our own shores are tenanted by numerous
forms of minute Polypi, having essentially the same simple organisa-
tion as the Hydra ; but which are protected from the dense briny
element by an external horny integument. Now these likewise
develope new polypes by gemmation ; but, as the external crust
grows with the growth of the soft digestive sac, the young polype
adheres to the body of the parent, and, by successive gemmations, a
compound animal is produced. Yet the pattern according to which
the new polypes and branches of polypes are developed is fixed and
determinate in each species ; and there consequently results a par-
ticular form of the whole compound animal or individual by wliich
the species can be readily recognised {Jig. 61.). This compound

126

LECTURE VII.

Campanularia dicliotoma, magnified.

hydriform polype-animal, or association of polypes, resembles a minia-
ture tree ; but consists essentially of
a ramified tube of irritable animal
matter, f^ defended by an external,
flexible, and frequently jointed, borny
skeleton, a ; and is fed by tbe activity
of the tentacula, c?, and by the diges-
tive powers of the alimentary sacs, g^
of a hundred polypi, the common pro-
duce of which circulates through the
tubular cavities for the benefit of the
whole community. These currents of
the nutrient fluid have been observed
and described by Cavolini*, and more
recently by Mr. Lister.j* The genera
Sertularia, Campanularia, Tuhu-
laria, he, which form the principal
subjects of Ellis's beautiful and clas-
sical work on Corallines, compose the
present division of the compound Hi/-
drozoa, or hydriform polypes. The soft integument of the nutrient
polypes {^g. 61, d, e, g) is characterised by peculiar cells, like the
"dart-cells" of the Hydras, which have a transparent firm cell-wall,
containing a clear fluid, and extremely delicate, sometimes spi-
rally disposed, filaments. These are protruded when the skin is
irritated, and give the tentacles the appearance of being beset by
bristled prominences. The digestive sac of each polype is lined by a
ciliated epithelium, and by hepatic cells, as in the Hydra : but its
base is perforated by the hole which communicates with the tube, /,
passing along the branch supporting the polype, to the general cavity
of the stem. But this outlet allows only the fluid contents of the
stomach to pass : the coarser rejectamenta are cast out by the mouth.
It appears that sea-water may have entry to these canals and cir-
culate with the chyle, and so contribute some share to the respir-
atory process of the corallines. It is certain that sea-water is admitted
to the corresponding cavities in the Anthozoa. Both Lister and
Lowen have observed an alternate imbibition and expulsion of water
in the polypes of Sertularice and TubularicE. The chylaqueous fluid,
as it may be termed, which circulates in the general ramified cavity
of the coralline is colourless, and contains only some minute round
corpuscles. This fluid is sent into the cavities of the prehensile arms,

CVI.

t CVII. p. 299.

POLYPI. 127

and returns back into the digestive cavity. The movements of the
fluid appear to depend on a delicate ciliated epithelium Avhich lines
the cavities of the tentacles, as well as the tubular cavities of the
stem and branches of the compound polypes.*

The peculiar external horny defence prevents, as I have just ob-
served, the exercise of the gemmiparous faculty from effecting any
other change than that of adding to the general size, and to the
number of prehensile mouths and digestive sacs, of the compound
coralline. It is equally a bar to propagation by spontaneous fission ;
so that the ordinary phenomena of generation by ova or germ-masses
are more conspicuous in the composite than in the simple Hydrozoa.
At certain points of these ramified polypes, which points are constant
in, and characteristic of, each species, there are developed little
elegant vase-shaped or pod-shaped sacs, which are called the ovige-
rous vesicles or "' ovicapsules." These are sometimes appended to the
branches, sometimes to the axillce, as at h, i, k,Jig. 61, of the ramified
coralline : they are at first soft, and have a still softer lining mem-
brane, which is thicker and more condensed at the bottom of the
vesicle: it is at this part that the ova or germs are developed, h,
and for some time these are maintained in connection with the vital
tissue of the polype by a kind of umbilical cord, k, I. In all the com-
pound Hydrozoa, the ovicapsules are deciduous, and having performed
their functions in relation to the development of the new progeny,
drop off like the seed-capsules of plants. This phenomenon afforded
to the early botanists an additional argument in favour of the relation
of these ramified and rooted animals to the Vegetable Kingdom.

The species of the marine Hydrozoa which is most nearly akin to
the fresh-water Hydra, is the Tubularia indivisa, beautifully figured
in his fine work on the "Remarkable Animals of Scotland," by Sir
John G. Dalyellf, who devoted thirty years to the careful examination
of the animals of the Frith of Forth. In this species each individual
is distinct, like the Hydra ; it propagates its kind by gemmation, and
has, also, great powers of reparation, reproducing its polype head and
double crown of tentacles many times in succession. It also propagates
by ova. These are formed in ovicapsules, aggregated in groups which
proceed from the space between the long and the short tentacula ; and,
in proportion as the ovicapsules are developed, the tentacula begin to
decay, and the whole flower-like head falls. When cast off, the head
does not lose its vitality, but moves, for a few days, perhaps, and
crawls off with the ovicapsules to some distance from the parent.
A locomotive polype, which is called by Sir J. G. Dalyell a "hydra,"

* CVIII. p. 107, t CIX. pis. 1, 2, and 3.

128

LECTURE VII.

escapes from each ovicapsule, crawls off, becomes attached, and
developes its elongated stem and other characters of the Tubularia.
The process of development has been well observed by M. Van
Beneden* in another species of Tubularia {T. coronata Abildg.).
There are numerous clusters of ovicapsules in the same position as in
the T. indivisa. The capsules in each cluster are developed from
the sides of a short stem, and become more pedunculate as they are
situated nearer its extremity. The common nutrient cavity is con-
tinued into the stem, and sends off branches to enter the bases or
pedicles of the capsules. The germ-cell makes its appearance be-
tween the end of this canal and the summit of the capsule, as shown
^^ ^5 ^^. 62., which represents a young sessile ovicapsule detached
from the ovarian stem, showing the portion of the nutrient canal con-
tinued into it and the germ-cell below. The nutrient and respiratory
g2 currents are continued from

the general cavity of the
body through the ovarian ca-
nal and its diverticula which
enter the ovicapsules. The
germ-cell is thus supplied
with matter for its growth,
which proceeds rapidly by
the ordinary mode of multi-
plication of secondary germ-
cells by spontaneous fission.
As growth proceeds the ovi-
capsule expands, and the end
of the nutrient diverticulum
becomes surrounded by the
germ-mass, into the middle
of which the diverticulum
seems now to dip, as shown

Development of Tubularia coronata. -j^ g, fg. 62. The nCXt

change is the development of a series of lobes which push aside the
diverticulum, as in 3 : the lobes elongate into rudimentary tentacles,
and the base of the inner series of tentacles begins to appear, as at
b, 4 : this stage is better seen when the ovisac is viewed under pres-
sure as at 5. Where development has advanced thus far, the parietes
of the ovicapsule rupture and the embryo escapes, as a young polype,
with one series of tentacles, 6. It then becomes fixed, and begins
to develope its tubular body and its inner series of tentacles as in 7,
Jig. G2.

* CXI. p. 37. pi. i.

POLYPI. 129

In a third species of Tubularia {T. Dumortieri) the embryo
assumes the form of a transparent, gelatinous, longitudinally ribbed
Beroe, before it escapes : and afterwards moves like a INledusa by-
alternate contraction and expansion of the body. The change of
this medusoid larva into the Tubularia was not seen.

In the Hydraetinia rosea V. Beneden found several ova, with
the germinal vesicle and nucleus, developed in each ovicapsule.

The modification in the growth of the coralline to form the ovi-
capsule, has been compared by Professor E. Forbes* with that '-me-
tamorphosis in flowering plants in which the floral bud is constituted
through the contraction of the axis and the whorling of the indivi-
duals borne on that axis, and by their transformation into the several
parts of the flower." Many elegant varieties are observable in the
form of the ovicapsules. Sometimes they are crossed by transverse
bars ; sometimes shaped like a vase, and provided with a little lid or
cover; usually traversed along the middle by a continuation of the soft
tissue of the polype, from which the ova or germs proceed, and which
may be compared to an umbilical cord, and is termed the " placenta-
rium." According to the botanical analogy, they may be either
essentially " single individuals, ideally metamorphosed into repro-
ductive organs comparable to the monocarpous germens of plants,"
or a "series of individuals joined together and merged into each
other so as to present the appearance of an organic body in which
the ova are reproduced comparable to the syncarpous germens" of
plants ; the pod-like ovicapsule of most Plumularice well illustrates
the latter view.f

Ehrenberg \ regarded the ovicapsule as a modified individual, viz.,
a female generative polype, differing from the nutrient and sexless
polype, in having the tentacula rudimentary or abortive. The
contractile power of the ovicapsules in Pennaria and in Syncoryne
ramosa, together with Loven's description of the deciduous nursing-
polypes developed from the ovicapsule in the Campamdaria geni~
culata, gave apparent support to this view, which, however, later
facts as to the nature of the progeny developed in the ovicapsule
have induced most zoophytologists to abandon.

Sperm-capsules, similar in situation and form to the ovicapsules, are
developed in certain individuals of the marine Hydrozoa. In Pennaria
Cavolini the spermatozoa are developed in the interspace between the
inner wall of the sperm-capsule and an axial cord of the soft tissue
answering to the placentarium of the ovicapsule. § In the Tubularia

* ex. t XCVII. pi. 11. B. {Plumularia fakata.)

X CXVII. § CXVI. p. 197.

K

130 LECTURE vn.

indivisa, also, the sperm-capsules repeat the grape-like arrangement
and situation of the ovicapsules. In Eudendrium racemosum the
sperm-capsules are raoniliform, and are supported on particular stems;
the outermost capsules, which first appear, contain the best developed
spermatozoa. These sperm-capsules were distinguished by Cavolini,
as " nova a corimbo," * from the ovicapsules, which he called " uova
a racemo."! The distinguished Neapolitan zoophytologist also re-
marks that each kind of capsules occur in different individuals ; and
Krohn, to whom science is indebted for a determination of the true
nature of the " uova a corimbo," found as a general rule that the
sperm-capsules were developed in the Eudendrium racemosum, the
Plnmularia cristata, and Sertularia misenensis, on particular indi-
viduals or compound groups of individuals, the ovicapsules being
developed on other such individuals.

The true ovum of the Hydrozoa has its germinal vesicle and spot,
and after impregnation the germ-mass is formed by spontaneous
fission of the germ-cells and cleavage of the granular yolk, as in the
ova of the Ascaris (p. 113.).

In the Hydra this process goes on before the ovum quits the
parent, and before it has acquired its bristled chorion. In the marine
species the young may escape from the ovicapsule in the condition
of ciliated locomotive bodies, called "planulce" by Daly ell J; or the
planula3 may be hatched in the interior of a polype-individual de-
veloped from the summit of the ovicapsule, and which, after liberating
them, may wither and fall like the flower of a plant § ; or a generated
individual of a particular form, such as e. g., the Medusa octocilia and
31. duodocilia of Dalyell ||, developed from Eudendrium ramosum, and
the Tintinnabidum or Bell-medusa observed by the same author as
the progeny of the Campanidaria dicliotoma, may be developed in
and escape from the ovicapsule, and, by its own power of locomotion,
carry the contained ova to a distance from the composite and fixed
group of nutritive individuals. The ova may be developed within
the bell-shaped Acalephoid prior to its detachment, as in the Coryne
vulgaris, observed by Wagner, or not until it has become detached
and acquired the full characters of a bare-eyed Medusa.

The phenomenon of the development of a polype-like larva in the
vesicles did not escape the keen eye of Ellis. He says, " I first per-

* CVI. tab. vi. fig. 14. t CVI. tab. ri. fig. 6.

X CIX. p. 150. pi. xxiv. {Sertularia abietina), p. 162. pi. xxix. (Sertularia
halecina^.

§ CXII. p. 259. tab. vi. fig. 13. (Campanularia geniculata).
II CIX. pi. xi. figs. 9 and 11.

POLYPI. 131

ceived tlie polypes alive in the vesicles of the denticulated class of
corallines, and particularly in this" — now the Sertularia pumila :
— " these animals are of a much larger size in the vesicles than
those in the denticles."* In another species {C amp anul aria di-
chotoma) he figures "the young polypes coming out of the vesi-
cles, but still adhering to the umbilical chord." Dr. A. Farre has
seen the development of the germ-masses, which are included in
a delicate membrane and extend along the axis of the germ-vesi-
cle, in the same Campanularia : the germs are covered by a cili-
ated epithelium ; they then become bell-shaped medusae, with mar-
ginal tentacles, and escape swimming freely. Mr. Lister's figures
b 5 and b 6jf show the little medusoids escaping from the germ-
vesicles of the Ca^npanidaria dicJiotoma ; but they are represented,
as Ellis described them, as polypes. Abundant evidence has been
afforded, especially by Dalyell, that Ellis did not, as Dr. Grant has
stated J, commit the error of mistaking mere ciliated locomotive
gemmules or ova for young polypes. In many Sertulari<B, as Dalyell
has shown, the young quit the germ-vesicles as locomotive ciliated
animalcules, like Planarioe, which move not only by the cilia^ but by
a general contraction of the tissue. This kind of larva, which he
calls " planula," crawls rather than swims, and in twenty-four hours
presents the appearance of a disc with a series of peripheral rays ; it
then settles, expands, and a stem shoots up, developes a polype, and
thus a new hydrozoal individual is generated. This metamorphosis,
first observed and described by Cavolini § in the Sertularia racemosay
has been illustrated with accurate and minute details by Loven. ||

The more remarkable phenomenon of the medusoid form of larva
is best shown in the claviform Corallines, and has been especially
described by Loven^, in an excellent Memoir on the Syncoryne
ramosa of Sars, and by Steenstrup in the Coryne Fritillaria.'^^ This
species originally developes a many-armed nutritive polype, or
individual; but retaining many unchanged germ-cells, these, by the
stimulus of the excess of nutriment, begin to repeat the process, and
push out buds in an analogous position to that in the Hydra fusca,
viz., around the base of the stomach of the first, or parent animal ;
but the buds, instead of repeating the form and condition of that
animal, take on a higher form, resembling that of a bell-shaped
Medusa ; they become detached and swim off to a distance^ forming

* XCVII. p. 10. pi. V. A. also p. 21. and 23. pi. xxx%-iii. fig. 3. b.
t CVII. pi. X. X CXIX. p. 54.

§ CVI p. 261. tab. \i. II CXII. tab. vi. figs. U— 1 7.

t CXII. ** XCIII.

K 2

132 LECTURE vn.

and discharging tlie ova, wliicL, as Steenstrup conjectures, in tlieir
turn develope the fixed polype-shaped Coryne. This stage of the
cycle has not yet been the subject of observation ; but, by the
analogy of the larger Medusce, is the more probable process than
that direct metamorphosis of the medusiform individual into the pe-
dunculate polypoid individual, which V. Beneden has described by
the aid of a conjectural figure in the Tuhulai^ia.*

In the Eudendrium racemosum Sir J. G. Dalyell observed the germ-
vesicles containing the young medusoid animal to be developed from
many parts of the parent stem. A very active movement of the
inclosed animal may be seen near the mouth of the ovicapsule. It
then opens ; a small white bud protrudes, then some tentacula, in
active struggling motion ; and at last a little free-swimming medusoid
animal appears, in the shape of a small bell. It courts the light, and
manifests all the characteristics of the Acalephse.

The medusiform ovigerous locomotive or distributive individual of
the Coryne Fritillaria, and Campanularia dichotoma is obviously
homologous with the polype-shaped ovigerous individual which seems
to nurse, as it were, the ova into planulre in the Cam-panularia
genicidata ; and the nutritive gemmiparous individuals in all the
compound Iljdrozoa would seem rather to manifest the typical form
of the species, as the leaf is a more typical form of the plant than the
parts of the flower. Superadd, however, distinct nutritive and
circulating organs to the free-moving ovigerous individual, and
prolong its existence, and it would then cease to have the sub-
ordinate character of a nurse to the ova of the fixed individuals^ and
wonld assume that of the perfected form of the species ; and such, in
fact, is the case wntli the larger gelatinous Radiaries called 'Mediispe.*

When the ovicapsule is the seat of development of a medusoid
oviparous individual, as observed by Dalyell, the phenomena attend-
ing the escape of these are remarkable. Great exertions are made to
force the orifice, until the animal finds its way out. The vessel of
sea water iu which specimens of Eudendrium ramosum have been
kept is sometimes found crowded with the medusoid animalcules :
this phenomenon much surprised the venerable Scottish Naturalist
until he became aware of the origin of the little larvce. His observa-
tions have been confirmed by Sars and others on the Podocoryne
earned and the Coryne nutans. In the same month in which Sars
observed the development of Medusoid animalcules from the Podo-
coryne carnea, he found other specimens of Podocoryne developing
clear capsules containing ova. Steenstrup, who was more successful

* CXI. pi. 2. fig. 5.

POLYPI. 133

than Sars in preserving the life of the meclusoid individuals, appears
to have traced the phenomena of the development of the ova in them,
and arrived at the conclusion that they are not directly transformed
into the polype as Van Beneden believed to occur in the Tubularia
Dumortieri. The ova so developed would give origin to " planulge,"
and these, by the metamorphosis so well described by Dalyell, %vould
produce the rooted zoophyte, from which a compound ramified group
might result by successive incomplete gemmations. So that with
regard to the generation of the marine Hydrozoa, we find these modi-
fications : — either the ovicapsules are developed as buds on the
nutrient polype which is cast off, and the young polype is afterwards
developed in and escapes from the ovicapsule ( Tubularia indivisa) ;
or the ovicapsules are transformed polypes or pinnje on different
and determinate parts of the compound Ilydrozoon, give issue to
ciliated planulee, and are cast off (most Sertularia) ; or bell-shaped
Medusse are developed in similarly formed ovicapsules, and escape
{Eudendrium ramosum) ; or a small nursing polype is developed
from the summit of the ovicapsule which incubates the ova, and
falls like a flower {Campamdaria geniculata)\ or Medusoids may
be directly produced by gemmation, as in Syncoryne, and these,
becoming detached, continue to move for some time (fifteen or
eighteen days) before they fully develope the ova, which produce the
planulce, which are metamorphosed into the compound zoophyte.

The medusoid brood, which V. Beneden saw to be the produce of
the fixed and composite Campanularia gelatinosa, closely resemble
those minute acaleph^ which Sars* has described as the Cytaeis
octopunctata, and Willf as Cytaeis polystala. With regard to the
special capsule in which certain Hydrozoa produce locomotive larvee
of the acalephoid character, although it is called " ovicapsule," from
its analogy to those that give issue to planulae, it does not contain
a proper " ovum" with its germinal vesicle, vitellus, and chorion,
requiring the distinct act of impregnation before development of the
medusoid embryo can begin. The development of such forms of
embryo in the ovicapsules of the Eudeyidrium ramosum and Cam-
panularia dichotoma seems to be the result rather of the last remnant
of the old spermatic force in the slightly modified cell-tissues of the
parent, and to be a modification of the same gemmiparous faculty as
that to which the previous multiplication of the nutrient form of
polype and the compound character of the whole was due.

The development of the true ova and the reproduction of the

* CXIII. p. 28. tab. vi. f. 14. t CXIV. p. 68. tab. ii. f. 5.

e: 3

134 LECTURE VII.

spermatic force in the ordinary form of spermatozoa seem to be the
last act of the free medusoid individuals which are liberated from the
Coryne^ Syncoryne, and certain species of Campcmidaria and Tubu-
Icma; and the hydriform polype which results from the development
of such ovum, together with the organically connected colony of
such, developed by successive gemmation, and bearing the name of
Coryne, Campanularia, &c., are larval forms, procreating partheno-
genetically, and answer to the larval vesicles developing the cer-
carioids which ultimately change into the generative forms of tre-
matode entozoa. With regard to those numerous species of Sertularia
(e. g. S. Polyzonias, abietina, rosacea, pumila, halecina, Beanii,
uber, Dal., argentea, antennina, ramosa, thuia) and of Plumularia
(e. g. PL falcata*, innnata\ in which the ovicr.psules give issue to
planulee, subsequently transformed into sertularian polypes, their
genetic cycle is of a more simple character ; the germinal basis of
the planula must be viewed as an ovum impregnated by the
spermatozoon developed in the sperm-capsules of the males above
described.

The Anthozoa {Jigs. 63-67.), or polypes of the second great class,
characterised by a distinct abdominal cavity in which their simple di-
gestive sac is suspended, constitute the most numerous and important
part of the whole race, and include the largest individuals. They
are principally the inhabitants of the warmer or tropical seas.

They are subdivided chiefly according to the number and structure
of their oral tentacula. Most of the species have only eight of these
radiated prehensile organs : the rest have a greater number. To this
latter group belong the soft-bodied and solitary species called Sea-
Anemonies, or ActinicE, which are common upon our own coasts.

In the Actinia here dissected {Jig. 63.), you will see that the skin
of the body, a, is thick and opaque : in the living Actinia, it is lubri-
cated by a mucous secretion : it is lined by a thick stratum of mus-
cular fibres, the disposition of which is indicated by the superficial
striae, and may be shown, in the larger Actiniffi^, to be in antagonising
longitudinal, and transverse or circular, fasciculi. In the middle of
the circle of the tentacles, c,c, is situated the contractile and dilatable
mouth, d, from which a short oesophagus leads to a large gastric
cavity, e, the parietes of which are connected by a great number
of membranous vertical folds, g, g, with the external wall of the body.
The tentacula are beset with numerous dart-cells : they are tubular,

* The ciliated cliaracter of the embryo, and its locomotive power, settlement and
metamorphosis into the Plumularia were first discovered, and are beautifiilly de-
scribed by Dr. Grant, in CXI*., who calls the embryo " ovum."

POLYPI.

135

Actinia, dissected.

are perforated at their free extremity, and communicate with the

interspaces, h, of the meso-
gastric lamellaa, g. They ab-
sorb the sea-water into these
spaces, and are elongated by
the injection of that water
into their interior. The ex-
tended surface of the abdo"
minal cavity is beset with
innumerable minute cilia,
through the action of which
it is bathed by a constant
current of the admitted me-
dium of respiration, the sea-
water, mixed with the chyle
from the stomach. These re-
spiratory streams pass from
one compartment to another
by the orifices marked g\ g' : the arrows show their direction in the
opened tentacule, h.

The ova are formed within the mesogastric folds : beneath which
are situated an equal number of bodies composed of convoluted tubes
which contain sperm-cells and spermatozoa, demonstrating the an-
drogynous nature of the Actinia. Tiie impregnated ova are developed
into ciliated gemmules in the abdominal reservoir of sea-water : they
sometimes enter and distend the hollow tentacles ; then make their
way by the small inferior aperture of the stomach into that cavity,
and finally escape by the mouth of the parent.

Many of the large actiniform polypes of the tropical seas com-
bine with a structure which is essentially similar to our. own sea-
anemonies*, an internal calcareous axis or skeleton, which, pene-
trating the interior of the mesogastric fokls, presents the lamellated
and radiated structure recognisable in the enduring support
of the large Fungice and in the polype-cells of the skeletons of the
CaryophyllecE, 3[adreporcey &c. This skeleton consists of carbonate
of lime, which in the Madre'porincB is in the condition of organised
corpuscles compacted into a closely reticulated mass, on a basis of
gelatinous matter. This animal constituent exists in such a propor-
tion in some CaryophyllecB (C. smuosa, e. g.) as to preserve the form
and in some degree the foliated character of the skeleton after solu-
tion of the earthy part in acid.f

The species of polypes which take the most important share in the

* CXXII. p. 176. pl.viii.

K 4

I Sec Prep. No. 82. c.

136

LECTURE Vn.

Corallium
rubrum.

fabrication of the coral islands and reefs belong to the present group,
and have essentially the organisation of the sea-anemony, which has
just been described; but those of the genera 3Iaclrepora proper,
Asti^cBci, and Oculina have not more than twelve tentacles.

To the eight-armed division of the anthozoic Polypes belong those
species which have an internal ramified calcareous, or flexi-
ble, or jointed axis, e. g. as the red coral, (fig^ 64, c), the
gorgonia, and the isis. To this division likewise belongs
our common Lohularia digitata. or " dead-man's-toes," in
^tS^ which the hard axis is wanting ; and the phosphorescent
'^nM* Sea-pens, the Verefillum, and other Pen?iafulidcB, in which
it is in detached pieces. In all this division the polypes, «,
are retracted into the soft enveloping tissue, b, not into
calcareous cells.

These examples of the compound Anthozoa differ from
the compound Hydrozoa in having an internal instead of an external

skeleton. The body of each polype
(Jfg. 65.) is relatively longer than
in the ActinicE ; the prehensile ten-
tacles {a, a) are broad and pinnate,
or with scolloped margins.. At the
centre of their base is situated the
mouth (h), which leads to a straight
membranous alimentary cavity, fixed
by vertical septa (d, d), called meso-
gastric folds, to the external inte-
gument: w^hich septa are continued
down the general visceral cavity.
The digestive canal communicates
with this cavity by a small orifice (c),
at its inferior part. Sea-water passes,
probably with chyle, through this
aperture, to circulate over the ex-
tended ciliated surface of the abdo-
minal cavity and the interior of the
tentacles. The hepatic cells of the gastric parietes present a yel-
lowish colour in Alcyonium, and a brown colour in Veretillum.

The contractile power of both the Polypes and of their common
fleshy base in the softer compound kinds is considerable. In the
Alcyonidium the lower half of the polypary is of a firm coriaceous
texture, the upper half is softer and divided into branches, the sum-
mits of which are crowned with polypes of the structure shown in
%. 65. These polypes, when touched, not only shrink into their

Polype of the Alcyonydium elegans,
dissected and magnified.

POLYPI. 137

flesliv fossae, but the whole of the soft part of the poljpary is con-
tracted and withdrawn into the harder basal portion.* Mr. Darwin
relates of the Virgularia — a long and slender kind of sea-pen, which
he saw in vast numbers projecting like stubble above the surface of
the muddy sand — that when touched or pulled they suddenly drew
themselves in with force, so as nearly or quite to disappear. The
slender calcareous axis supporting the fleshy beds of the polypes of
this sea-pen becomes softer and bent toAvards its base, and the elasticity
of this part contributes, with the expansion of the irritable tissue, to
enable the Virffularia to rise again through the mud.|

Ovaria and sometimes tortuous filamentary secreting organs (/)
analogous to the testes in the Actinia, are developed from the meso-
gastric folds in the chylaqueous cavity. In the anthozoic polypes
of the red coral most of the individuals are androgynous, and present
both the ova and the spermatozoa ; but a few instances occur in
which some polypes develope only the one kind of generative pro-
duct, and others the other kind. In those singular forms of com-
pound polypes, called Pennatulce, or sea-pens, the ova are found in
the pinnge or branches of the common stem or axis of the polypes.
But groups of individuals have been found in which only the sperm-
sacs are developed.! In the Veretillum a delicate network of vessels
conveys the nutrient fluid prepared by each polype to the common
connecting parenchyme of the entire compound animal.

In the Gorgonia verrucosa Cavolini states § that the ova, which
are developed in an ovarium situated at the base of each polype^
doubtless in the mesogastric folds, are discharged by eight small pores
which open between the bases of the eight tentacles. The ova escape
as ciliated '^planulse" of an ovoid form, which emerge from the
ovarian pore with their small end foremost, then turn and swim with
the great end foremost. In the month of June a Gorgonia, six inches
in height, discharged ninety such larvte in the space of an hour.
They first rose spirally towards the surface of the water, then swam
horizontally. They have the same property as the ciliated planula3
of the marine Hydrozoa of changing their form by contraction of
their tissue, a property which the ciliated zoospores of sponges and
algoe do not possess. When the larvae of the Gorgonias rested they
attached themselves to the vessel containing them by their larger
end. The ciliated embryos of the Caryophijllia calycularis are also
discharged by small apertures at the basal interspaces of the tentacles
of each polype. || They are of a deeper red colour than those of the
Gorgonia^ have the same locomotive power, and show the same

* CXXIV. p. 2. t CXXIX. p. 99. X CXV. p. 101.

§ CVL pp. 47. 50. tab. iv. figs. 7—10. aud 13—15. || CVI. p. 56.

138

LECTURE Vn.

homogeneous granular texture when broken up under the microscope.
In the Pennatula phosphorea the ova, of the size and form of poppy-
seeds and of a yellow colour, are found at the back part of the pinnse.
In Virgularia mirabiUs the small, round white ova are seen in spring,
ranged in a double transverse row under each of the lateral fleshy
expansions, forming external projections ; but as the embryo acquires
its ciliated superficies and yellow colour, it advances slowly into the
body of the polype beneath which it was developed, and begins to
manifest contractions of its tissue and revolving movements, by which
it escapes from the mouth of the polype and swims slowly away.*
This locomotive faculty is much abridged, if not wholly lost, when
the animal has acquired its mature form and begins to propagate by
continuous gemmation. The Pennatulse do not swim, as has been
supposed, by the movements of the pinna?, but move languidly ; most
of the family remain at the bottom ; and the Vii^gularice and Pavo-
naricB have one end stuck deeply in the sand or mud, into which they
can retract themselves. In the Lohidaria the ova are formed and
matured in the longitudinal mesogastric folds of the polypes, f Ellis J
has well represented them, in groups of from five to eight in each of
the canals below the polypes, and also the larvae in their passage
through the transparent bodies of the polypes. When the larvae have
acquired their ciliated surface and red colour they become detached
from the mesogastric folds, and work their way slowly through the
polypes when the bodies of these are expanded and distended with
water. Certain individuals, or groups of individuals, of the Lobularia
digitata have been found to develop only sperm-sacs and spermatozoa. §
The fleshy substance of the ActhiicCf Lohularice and Alcyonia is
strengthened by numerous minute calcareous spiculse. Analogous spi-

culee, but of varying and cha-
racteristic forms, strengthen
likewise the fleshy crust of
the red corals, jointed corals,
and GorgoniiE ; but to these
spiculse is superadded the in-
ternal branched axis, which,
according to its composition
and structure, characterises
the different genera of this
group. The spiculae of the
cortical part consist princi-
Lobophyiia anguiosa. p^^jj^ ^f carbouatc of lime, like

the denser skeletons of the 3IadreporidcE, fig. Q6, with which they

m

I

* CXVIII. p. 350.
% CXX. pi. XX.

t CXIX. p. 104.

§ cxv. p. 101.

POLYPI. 1 39

are homologous ; but the axis jig. 64, c, consists of a substance
analogous to horn, hardened by phosphate of lime with only a slight
trace of carbonate of lime. In one genus of Anthozoa, the external
position of the skeleton which characterises the hydriform compound
polypes is repeated, viz. in the Tubipora ; but the organisation of the

polypes, protected by the crimson
pipes of this beautiful coral, Jig. 67,
is essentially the same as in the Ah
cyonium, Gorgonia^ and Pe7inatula.

The most important productions of
the apparently insignificant race of
Polypi are the accumulations of the
calcareous skeletons of the Anthozoa,
which form the coral islands and
reefs ; — the dread of the navigator,

Tubipora musica. ,-, t.,. p,, , „,

— the admiration ot the lover of the
picturesque, — the subjects of the closest and most interesting specu-
lation to the naturalist and geologist.

That masses of rock many leagues in extent should be founded in
the depths of the ocean, and built up to the height of hundreds of
feet, by minute, frail, gelatinous animalcules, is indeed a phenomenon
calculated to stagger the unversed in zoological science, and which
has demanded the repeated observation of the most accomplished
naturalists and enlightened voyagers to render intelligible.

These zoophytic productions are classified under three heads :
" atolls," " barrier reefs," and " fringing reefs." The term " atoll " is
the name given to the coral-islands, or lagoon-islands by their
inhabitants in the Indian ocean. An atoll consists of a wall or
mound of coral rock i^Jig. 70. r"^ r''), rising in the ocean from a con-
siderable depth, and returning into itself so as to form a ring, with a
lagoon, or sheet of still water (??), in the interior. The wall is gene-
rally breached in one or more places, and when the breach is deep
enough to admit a ship, the atoll affords it a convenient and safe
harbour. The outer side of the reef usually sinks to a depth of from
two to three hundred fathoms, at an angle of forty-five degrees or
more : the internal side shelves gradually towards the centre of the
lagoon, forming a saucer-shaped cavity, the depth of which varies
from one fathom to fifty. The summit of the exterior margin of the
reef or wall is usually composed of living species of Porites and
3Iillepora. The Porites form irregularly rounded masses of from
four to eight feet broad, and of nearly equal thickness ; other parts of
the reef are composed of thick vertical plates of the Millepora com-
planata intersecting each other at various angles, and forming an
exceedingly strong honeycombed mass. The dead parts of these

140 LECTURE VII.

calcareous skeletons are often cemented over with a layer of the
marine vegetable called Nullipora, which can better bear exposure
to the air.

This strong barrier is well fitted to receive the first shock of the
heavy waves of the fathomless ocean without ; and, what at first
appears surprising, instead of wearing away at its outer edge, it is
here only that the solid reef increases. The coral animals thrive
best in the surf occasioned by the breakers. Through this agitation
an ever-changing and aerated body of sea water washes over their
surface, and their imperfect respiration is maintained at the highest
state of activity. Abundant animalcules, and the like objects of
food, are thus constantly brought within the sphere of the tentacula
of the hungry polypes. Their reproductive gemmules are rapidly
and extensively dispersed amongst the crevices of the calcareous mass.

By the force of unusual storms this outer reef is occasionally
breached, and huge masses are torn off and driven towards the lagoon,
where they form an inner barrier or reef. The broken surface be-
comes the seat of attachment of the young of the neighbouring corals,
the successive generations of which, by the rapid growth and de-
velopment of their calcareous skeletons, soon repair the damage of
the storm. The masses of broken coral thus driven inward towards
the lagoon, accumulate in time to the height of some feet above high
water. These fragments are mixed with sand and shells, and form a
favourable soil for the development and growth of vegetables, as
cocoa palms, the large nuts of which may be borne hither by currents
of the ocean, from Sumatra or Java, 600 miles distant. Turtles like-
wise float to the nascent island, browse on the sea weeds which grow
in the lagoon, and breed there. Numerous species of fish and shell-
fish flourish in the same still water, which abounds with animal life.
Man comes at last and takes possession of the island ; and the cocoa-
nut, the turtle, and the fish afford him abundant and wholesome food.
But you will ask how he supplies himself with that necessary of
life, fresh water ? This is obtained in a very simple and unexpected
manner from shallow wells, dug in the calcareous sand, which ebb
and flow with the tides, yet are almost wholly free from the saline
particles of the ocean. Some have supposed that the sea water lost
its peculiar salts by infiltration through the calcareous mass. Mr.
Darwin thinks that it is derived from the rain water, wdiich, being
specifically lighter than the salt, keeps floating on its surface, and is
subject to the same movements : howsoever this may be, the fact is
certain. A fit and convenient abode for the human species is fabri-
cated by the action of the feeble, gelatinous polypes, and a wild and
almost boundless waste of waters is enlivened by oases which navi-
gators have described as earthly paradises.

POLYPI. 141

A barrier reef {fig* 69. r', r') is essentially similar to the atoll or
coral-island. It runs parallel with the shores of some larger island or
continent ; separated, however, from the laud, by a broad and deep
lagoon channel (??, n), and having the outer side as deep and steep as
in the Lagoon Islands. Here likewise the skeletons of the Zoophytes,
of which the reef is composed, are found on the outer precipitous wall
as deep as sounding line can reach.

The third class of coral productions which Mr. Darwin terras
" fringing reefs" {fig. 68. r, r), differ from the barrier reefs in having
a comj)aratively small depth of water on the outer side, and a nar-
rower and shallower lagoon channel between them and the main land.

These differences in the characters of the wonderful fabrications of
the coral animalcules are explicable by the following facts in their
physiology. The animals of the Porites and Milleporce cannot exist
at a greater depth than twenty or thirty fathoms ; beyond this the
stimuli of light and heat derived from the solar beams become too
feeble to excite and maintain their vital powers. On the other hand,
their tissues are so delicate, that a brief direct exposure to the sun's
rays kills them ; and unless they are constantly immersed in water or
beaten by the surf, they cannot live. Thus, in whatever position
the calcareous skeleton of a Madrepore or Millepore may be found, it
is certain that it must have been developed within thirty fathoms of
the surface of the ocean. If it coats the summit of the lofty moun-
tains of Tahiti *, it must have been lifted above the sea by the eleva-
tion of the rock on which it was originally deposited. If it is brought
up from the depth of 200 or 300 fathoms, as at Cardoo Atoll or
Keeling Atoll, it must have been dragged down to that depth by a
gradual subsidence of the foundation on which the living madrepore
once flourished. It is by these movements of upheaval and sub-
sidence of the earth's crust, that Mr. Darwin explains the different
forms which characterise the extraordinary productions of the coral
animals. Atolls, according to this author, rest on land which has
subsided, ai'd part of which was once dry. Barrier reefs indicate
the islands or continents, which they encircle, to be the remains of
land now partly submerged, and perhaps in progress towards final
disappearance. Fringing reefs, on the contrary, indicate either that
the shores are stationary, or that they are now rising, as in most of
the Sandwich Islands, where former reefs have been raised many
yards above the sea.

Elizabeth Island, which is eighty feet in height, is entirely com-
posed of coral-rock. The coral animals, thus progressively lifted

* Mr. Stutchbuiy here found a regular stratum of semifossil coral at 5000 and
7000 feet above the level of the sea.

142

LECTURE VII.

above their element, are compelled to carry on their operations more
and more remote from the former theatres of their constructive
energies, but cannot extend deeper than their allotted thirty fathoms ;
the direction of their submarine masonry is centrifugal and descend-
ing. Where the land that supports them is, on the contrary, in
progress of submergence, they are compelled to build their edifices
progressively higher and in a narrower circuit ; in other words, the
direction of their growth is centripetal and ascending. The terms
ascending and descending, of course, only here apply to the relation
of the coral-builders to the unstable land, not to the level of the un-
changing sea.

The formation of an atoll by the upward growth of the corals
during a gradual sinking of the land forming their supporting base is

illustrated by these dia-
grams from Mr. Dar-
win's work.* Figure 68.
represents the section of

Fringing Reef. ^^^ -g^.^^^j ^^^ ^^^ g^^,.

rounded by a fringing reef, r, rising to the surface of the sea, s. 1.
As the land sinks down, the living coral, bathed by the surf on the
margin of the reef, builds upwards to regain the surface. But the
island becomes lower and smaller, and the space between the edge of
the reef, r, and the beach proportionately broader. A section of the
reef and island, after a subsidence of several hundred feet, is given in

figure 69. The former
living margin of the reef,
r, is now dead coral,
dragged down to depths
at which the polypes
cease to exist ; but their progeny continue in active life at r', now the
margin of a barrier reef, separated by the lagoon channel n, from the
remnant of the land b. Let the island go on subsiding, and the
coral reef will continue growing up on its own foundation, whilst the
water gains on the land, until the highest point is covered, and there

remains a perfect atoll,
of which figure 70. re-
presents a vertical sec-
tion. In this diagram
r'' is the living and
^*°"- growing outer margin of

the encircling reef, and the lagoon channel is now converted into the
calm central lake n, of the atoll. Thus by the process of subsidence

/•'

■" X

n

.- 65 ..

b#

\W^

"^"-^snui^Q

""^-^^^-^

Barrier Reef.

* CXXXII.

POLYPI. 143

the fringing reef (^figs 68.) is converted into the barrier reef {^fig. 69.),
and this into the atoll (^^. 70.).

If the movement of the land should now be reversed, and the level
of the sea be again brought back by elevation of the island, to the
line (s. \'fig. 70.), an island apparently composed exclusively of coral
rock, like Elizabeth Island, would be the result.

The prodigious extent of the combined and unintermitting labours
of these little world-architects must be witnessed in order to be
adequately conceived. They have built up a barrier-reef along
the shores of New Caledonia for a length of 400 miles, and
another which runs along the north-east coast of Australia 1000 miles
in extent. To take a small example, a single atoll may be 50 miles
in length by 20 in breadth; so that if the ledge of coral rock forming
the ring were extended in one line it would be 120 miles in length.
Assuming it to be a quarter of a mile in breadth, and 150 feet deep,
here is a mound, compared with which the walls of Babylon, the
great wall of China, or the pyramids of Egypt, are but children's
toys ; and built too amidst the waves of the ocean and in defiance of
its storms, which sweep away the most solid works of man.

The geologist, in contemplating these stupendous operations,
appreciates the conditions and powers by which were deposited in
ancient times, and under other atmospheric influences than now
characterise our climate, those downs of chalk which give fertility to
the south coast and many other parts of our native island. The
remains of the corals in these masses, though similar in their general
nature, are specifically distinct from the living polypes which are
now actively engaged in forming similar fertile deposits on the
undulating and half submerged crust of the earth, washed by the
Indian and Pacific oceans.* Again, those masses of limestone rocks
which form a large part of the older secondary formations, give
evidence, by their organic remains, that they too are due to the
secretions of gelatinous polypes, the species of which perished before
those that formed the cretaceous strata were created. As the polypes
of the secondary epochs have been superseded by the Porites,
MilleporcB, 3Iadreporce, and other genera of calcareous Anthozoa of
the present day, so these, in all probability, are destined to give way
in their turn to new forms of essentially analogous Zoophytes, to
which, in time to come, the same great ofiice will be assigned, to
clothe with fertile lime-stone future rising continents.

* See the admirable description of the corals of the chalk by ^Ix. Lonsdale, in
CXXI. pp. 237—324.

144 LECTURE VIII.

LECTURE VIII.

BEYOZOA.*

If a deeper and truer insight into the structure and vital properties
of the low-organised, ramified, composite, hydriform polypes, which,
like little trees adorned with polypetalous flowers and supporting
their annual crop of deciduous fruit or seed-capsules, deceived such
clear-sighted observes as Tournefort and Ray as to their real nature,
and were classed by them with vegetables ; if organised beings, so
obviously like plants in external form and in some of their most con-
spicuous changes, can be proved by the anatomist to belong unequi-
vocally to the Animal Kingdom, without the determination being
vitiated or obscured by any real or essential vegetable character ; —
if the calcareous masses of Madrepores and Millepores, classed by
Boccone and Guison as species of minerals, and which once were the
subjects of curious speculations on the growth of stones, have been
proved by the recognition of the more complicated organisation of
the polypes which they support, to be the products of the vital actions
of such polypes, and as essentially a part of those animals as the
skeleton of a man is a part of his body ; — still more does the ana-
tomical structure of the third division of polypes prove how in-
adequate is a superficial survey of an organised being to lead to true
notions of its nature and affinities. The Bryozoa, which coat, as
with a delicate moss, fuci, shells, or other marine productions, or
which rise in dendritic forms, like the hydrozoic corallines, with
which they were associated by Ellis|, with which they would equally
have passed for plants with Ray, are, perhaps, the most striking
examples of how complicated an animal structure may be masked by
mere outward form.

A locomotive organised being must possess an internal digestive
store-room ; but the converse of the proposition does not hold good,
— a digestive cavity does not imply the powers of locomotion.

The Bryozoon has not merely a digestive cavity, like the Hydra
and the Actinia ; it has not merely the characteristic mouth and
radiated prehensile organs for the capture of living prey ; but it has

* Ehrcnberg, CXXXIII. (1827), PoJyzoa, Thompson, CXXIII. p. 92. (1830.)
Ciliobrachiata, Farrc, XXXV

f This accurate obsen'cr, however, places many of the Bryozoa in a family, as
*' cellifcrous corallines," dietinct from the " vesiculated " and "tubular" corallines,
XCVII. p. 33.

BRYOZOA. 145

also an oesophagus for deglutition, an intestine for tlie separation
of the nutrient chyle, and a distinct external outlet for the indi-
gestible refuse of the food : it may possess a stomach with strong
muscular walls and a dentated lining for trituration, and a second
stomach with glandular walls for digestive solution or chymification,
and thus present an alimentary canal as complicated and as highly
elaborated as in the bird. Yet the microscopic polypes which
manifest this high condition of the digestive apparatus are fettered
to the spot, where, as ciliated gemmules, they finally rested after
their brief early locomotive stage : the complex digestive apparatus is
developed for the service of an organised being as immovable as the
plant which is rooted in the soil. But we shall, hereafter, meet with
animals of higher grade of organisation than the Bryozoic polypes, as
e. g. the Barnacle, the Oyster, and the Spondylus, which are equally
fettered to the spot on which they grow, and which more strikingly
demonstrate how secondary a character of animal life is mere
locomotion.

The complicated and characteristic condition of the alimentary
canal in the Bryozoa was discovered independently and nearly about
the same time, by Ehrenberg*, by Audouin and Edwardsf, and by
Dr. V. Thompson.J The ciliated structure of the arms was observed
by Steinbuch § and Dr. Fleming. || The ciliated larvss, and their
place of development, have been well described in the Flustra
carbesia by Dr. Grant.^ All these observations have received a
welcome confirmation, and many highly interesting facts in the
organisation and properties of the Bryozoa have been added by Dr.
A. Farre ; a careful perusal of whose admirable Memoir in the
Philosophical Transactions for 1837**, will amply repay the reader.

Most of the Bryozoa are microscopic ; but, being composite or
aggregated animals, they sometimes form sufficiently conspicuous
masses. The most familiar and common species constitute the
substance called sea-mat (^Flustra), which incrusts, by its little
hexagonal cells, as by a delicate mosaic pavement, sea-weed, shells,
and other marine bodies. The calcareous sea-mat is called Eschara,
Some species {Halodactylus) rise from their surface of attachment
and form amorphous masses, like sponge ; others ( Vesicularia^
Valkeria, Serialaria, Cellularia) are regularly and delicately rami-
fied, like the little hydriform corallines.

* CXXXni. Bryozoa " ore anoque distinctis tubo cibario perfecto."
t CXXIV. p. 13. X CXXIII.

§ CXXV. p. 89. II CXXVL p. 488. pi. xv. fig. 1. c.

\ CVIII. p. 116. ** XXXV. p. 387. plates xx. to xxvli.

L

146

LECTURE Tin.

Each polype presents an oblong depressed, or elongated and

cylindrical figure, and is protected by
a dense integument in the form of a
cell or case i^fiQ' 71, a, a), to the mouth
of which is attached a sac (^, h') com-
posed of very delicate and flexible
membrane. This constitutes the upper
or anterior integument of the polype
when it is protruded, and is reflected,
like the inverted finger of a glove, into
the firmer portion of the cell when the
polype is retracted, as at B. In general
the integument forming the firm cell is
of a horny texture ; but in the Escharce
it is hardened by the deposition of par-
ticles of carbonate of lime in the orga-
nised animal basis ; so that the external
skeletons of the Bryozoa offer analogous
conditions to the cartilaginous and bony
states of the internal skeletons of fishes.
The mouths of the cells in Eschara and
Cellepora are provided with a moveable
lid with a pair of muscles for closing
it, when the polype is retracted.* In
the Tendra zostericola there is instead

Polypes ofaBryozoon, magnified, x 80. of a SOlid OpcrCulum a large flat flcshy

I'ing, fixed to the walls of the cell by four muscular fasciculi : four
other bundles attach the opercular ring to the border of the opening
of the cell: the movements of this muscular mechanism are both
curious and beautiful when the little polype protrudes from or draws
back into its ceU.

In the cylindrical Bryozoa, as the Boiverhankia, the flexible part
of the integument consists of two portions ; the lower half being a
simple continuation of the cell ; the upper one consisting of a cylin-
drical series of setce {h'), connected together by an extremely delicate
and elastic membrane, permitting a certain extension of the cylinder,
which, at the same time, supports and allows free motion to the upper
part of the body in its expanded state. The mouth of the polype is
situated at this extremity of the body, and is surrounded by a
radiated series of slender, ciliated tentacula (c), eight, ten, twelve, or
more in number, according to the genus.

The muscular system is developed in the present highly organised

* CXXVII. p. 25. pi. i. fig. 1. e and

BliYOZOA.

147

class of polypes, in the form of distinct groups of fibres. Their
arrangement, and the actions by which they effect the protrusion and
retraction of the polype, are minutely and clearly described by Dr.
Farre.* The retractor muscles form two series, one acting upon the
alimentary canal, and the other upon the flexible part of the cell.
One series rises from the bottom of the cell, and is inserted about the
base of the stomach {d) ; the other {e, B) arises from the opposite
side of the bottom of the cell, and passes upwards to be inserted near
the base of the tentacula. The muscles which retract the flexible
integument and the setose operculum arise near the upper margin of
the cell (between e and a, B), and are disposed in six fasciculi, three
of which act upon the membrane, and the other three upon the
bundle of seta3 by which it is crowned. When the animal is re-
tracted, the setag, which are drawn in after the tentacula, converge
and form a kind of defensive operculum. The a3sophagus and in-
testine are bent into folds : their parietes are contractile.

The protrusion of the animal is effected, partly by the action of
short transverse muscular filaments (e), which tend to compress the

inclosed viscera, and partly
by the action of the ali-
mentary canal itself. The
bundle of setee {Jig. 72., 1.,
a, b, c) first rises out of the
apex of the cell (c), and is
followed by the rest of the
flexible integument (ib. 2.) :
the tentacula next pass up
between the setse (c?), and
separate them ; the folds of
the oesophagus and intestine
are straightened, and when
the act of protrusion is completed, the crown of tentacles expands
and their cilia commence vibrating {Jig. 71. c).

The advantage to Physiology of the researches of the comparative
anatomist in the minute forms of animal life, is often very great, in
consequence of the favourable conditions which the transparency of
the integument, and the distinctness of the contained parts of such
animalcules, afford for the direct observation of some of the most
recondite and important vital actions. As regards the Bryozoa, the
muscles are, as it were, naturally dissected or separated into their
component filaments. Each filament generally presents a small knot

Unfolding of the operculum and upper part of the
body, in four stages. Bowefbaiihui.

* XXXV. pp. 394—398.
Jb 2

148 LECTURE VIII.

upon its middle part : this is most apparent, being tliickened when
the filament contracts, at which time the whole filament is obviously
thicker. When the action ceases and the filament is relaxed, the
distance between its fixed points being diminished, as happens to the
longitudinal fibres when the polype is retracted into its cell, such
fibre falls into undulations. The thickening of the muscular fibre in
the act of contraction, and its folded state when it relaxes, before the
antagonising muscles have restored the extremities of the contracted
fibre to their ordinary distance, has been observed in other low
organised animals, as small Filariae.* The higher organised subjects
selected by MM. Prevost and Dumas, were less favourable for this
delicate experiment, and they consequently mistook the zig-zag re-
laxation of the muscular fibre for its act of contraction. In Notamia
and Anguinaria a faint striation has been observed on the ultimate
fibre. Minute appendages called "pedicellarite" are fixed to the cells
in most Bryozoa. Ellis, who has figured them in the Cellularia avi^
cularis^ compares them to " a bird's head with a crooked beak, opening
very wide : " f they consist of a fixed and a moveable nipper, like a
crab's claw, the latter being worked by muscles arising from the in-
terior of the fixed portion. In the Retepora celluJosa the pedicellarias
resemble a pair of pincers : in the Telegraphina they are simple one-
jointed spines. The entire pedicellariic, in many Bryozoa, have oscil-
latory movements, more or less rapid and regular, in different species.
The removal of the polype from the cell to which they may be attached
does not afiect these movements : and if a chelate pedicellaria be cut
off, its moveable nipper continues for some time to open and close.J

Dumortier describes two nervous ganglions near the mouth of the
Plumatella cristata, and Nordmann similar ganglions in Plum,
campanulata and Tendra zostericola, V. Beneden believes that he
has traced an oesophageal nervous collar in the Alcyonella § ; but
Dr. Farre was unable to satisfy himself as to any definite trace of a
nervous system in the marine Bryozoa^ which he has so ably ana-
tomised. The reaction of stimuli upon the contractile fibre was,
however, a striking phenomenon in these. The animal retires into
its cell on the slightest alarm, and refuses to expose itself to water
which has become in the least degree deteriorated. Dr. Farre has
observed the creeping of a very small animalcule over the top of one
of the closed cells to be followed instantly by the shrinking of the
soft parts beneath. But the nervous system is indicated in these
little polypes by something more than reflex phenomena : they seem

'> CXXVm. p. 261. t XCVII. p. 36. pi. XX. A.

X CXXIX. p. 201. § Cited in XXIV. p. 34.

BRYOZOA. 149

to exercise a certain caution before emerging from their cells. One
or more of the tentacles have been seen to be protruded and turned
over the side of the cell, as if to ascertain the presence or absence of
an enemy.*

I must now proceed to describe these tentacula (c, c), which are
the means whereby the Brijozoa obtain their food. They differ
considerably from the corresponding tentacula in the Hydrozoa and
Antliozoa, in being stifFer and provided with vibratile cilia. These
cilia are arranged on opposite sides of the tentacle, along which sides
they occasion, by their active vibration, opposite currents of the
surrounding water : they vibrate, not in the plane of the arms, but at
right angles with it, and bend obliquely in the form of a hook.f In
some species a few fine hair-like processes, which are motionless,
project from the back of the tentacula. The action of the tentacular
cilia appears to be under the control of the animal, and they are
sometimes seen completely at rest. The arms are tubular throughout,
and have an aperture at each extremity. The ring upon which they
are set forms a projecting edge around the mouth. The particles of
food are carried down the inner surface of each arm, and the mouth
and pharynx expand to receive such as are appropriate, as if by an
act of selection. The rejected particles pass out between the bases of
the tentacula, or are driven off by the centrifugal currents.

In the fresh-water Alcyonellce and CristatellcB the mouth is pro-
vided with a tongue- shaped process covered with vibratile cilia.
Nordmann describes each of the eight ciliated tentacles in the Tendra
zostericola as being traversed by two longitudinal canals.J

The pharynx in all Bryozoa is less dilatable than is the mouth
of the Hydra or Actinia. The constriction of the pharynx, by
which the food is driven into the oesophagus, is a very well-marked
action. The parietes of the gullet consist of three layers of which
the two outer ones seem to be muscular, and are thick in Tendra :
the inner layer is a thin epithelium over which a network of de-
licate canals in a polygonal pattern is spread. The cardiac orifice
{Jig. 71, g) seems to project into the oesophagus upon a valvular pro-
minence ; it opens into a small globular cavity (Ji\ which has the
construction of a gizzard : the interior of this cavity is lined by a
strong epithelium, the cells of which project into the cavity like
pointed teeth, and the food is subject to comminution in this cavity.
With the gizzard is associated, as in birds, a distinct glandular com-
partment of the stomach {i) ; but this is situated betw^een the gizzard
and intestine, not between the gizzard and oesophagus : its walls are

* XXXV. p. 414. t XXXV. p. 411. X CXX. p. 187.

L 3

150 LECTURE YIU.

Studded with cells or follicles filled with a deep brown secretion,
which may be regarded as hepatic follicles. The intestine is con-
tinued from a distinct pyloric orifice (A), which is situated at the
upper part of the glandular stomach near the gizzard. This orifice
is surrounded by vibratile cilia. The food is frequently regurgitated
into the gizzard, and, after having undergone additional comminution,
is returned to the stomach. Here it is kept in constant agitation,
and the particles pass by a rotatory action from the pylorus into the
intestine. The indigestible particles are there formed into little
pellets, which are carried rapidly upwards to the anal orifice (/), and
after being expelled, are immediately whirled away in the current
produced by the ciliated tentacula. The intestine in Cristatella is
short as compared with that in Jig. 71., and in Vesicularia. The
action of the sphincter may be seen when the faeces are expelled.

A small filament, conjectured to be tubular, which passed from the
base of the glandular stomach to the common stem {in) supporting the
cell of the polype, is the only trace of the nutrient or vascular system
which Dr. Farre could detect. When the common stem of a ramified
Bryozoon is cut across, it seems to be nearly homogeneous, and does
not present that obvious distinction between hard and soft parts, nor
the canal with circulating particles, which are observed in the stems
of the compound Hydrozoa. Yet it can scarcely be doubted but that
nutrient currents must traverse the common connecting organic
medium or stem of the Bryozoa, both for its own support and growth,
and for the supply of the means of growth to the young animals ( C)
which are developed from it by the process of gemmation.

The function of respiration must be referred to those parts of the
body which are provided with the means of efiecting a constant re-
newal of the surrounding oxygenized medium upon its surface. In
the ciliated tentacula, whose currents, Dr. Farre observes, seem much
beyond what is necessary to afibrd a sufiicient supply of food, we
most probably perceive the principal respiratory as well as prehensile
organs. There is a regular and uninterrupted stream of fluid in a
given direction in the abdominal cavity : whence it extends into the
canals of the tentacula. Siebold regards this movement as being
due to the ciliated epithelium which he detected lining the abdo-
minal cavity of Cristatella mirabilis and Alcyonella stagnorum.
Van Beneden indicates a series of pores at the bases of the tentacula
in the Alcyonella, which he calls " bouches aquiferes," conceiving
that by them water is admitted into the abdominal cavity.*

The individuals of the Bryozoa are multiplied by two processes of

* CXXXIV. p. 222.

BUYOZOA. lol

generation ; the one by gemma3 or buds from the common stem or
polypary, which appears to be uninfluenced by season, and which in-
creases the size of the aggregate mass of the Bryozoon ; the other by
the liberation of the young, usually in the form of locomotive ciliated
larvae, which takes place at certain seasons, generally in spring.

In the Flustra the gemmae are developed from the cells of the
pre-formed individuals ; but in those Bryozoa which have connecting
stems the buds arise from the stem. They are at first homogeneous ;
then a distinction may be observed between the cell {fig- 71, C, a)
and the visceral contents (b) ; afterwards the tentacles may be dis-
cerned, which are at first short and stumpy ; finally, the cavity, walls,
and divisions of the alimentary canal become distinguishable.

In regard to the generation by locomotive larv£e, these are, doubt-
less, originally developed from fertile ova.

Certain phenomena have been observed in the Bryozoa which
justify the belief that the individual polypes are male and female.
Dr. Farre has figured a specimen of the Valkeria cuscuta* ; in which
he observed a very remarkable agitation of particles in the visceral
cavity, caused by a multitude of minute cerearioids swimming about
with the greatest activity in the fluid with which that cavity is filled :
they consisted simply of a long slender filament with a rounded ex-
tremity, by which they occasionally fixed themselves. Similar moving
filaments were not unfrequently observed in other species. On one
occasion Dr. Farre observed them in a specimen of Halodactylus,
drifting rapidly to the upper part of the visceral cavity, and issuing
from the centre of the tentacula, indicating an external communica-
tion with the cavity of the body. Dr. Soulby, of Dover, informs me
that he distinctly saw a stream of spermatozoa escaping, like smoke,
from the terminal orifice of each tentaculum of a Halodactylus. The
analogy of these cerearioids with the spermatozoa discovered by
Wagner in the tortuous generative tubes of the Actinia, indicates
their real nature and importance in the generative economy of the
Bryozoa. Van Beneden has since communicated his discovery of
male and female polypes on the same polypary of the Alcyo7iella ;
the males are fewer than the females, and are recognizable by
the conspicuous spermatozoa, formed by a testis, which holds a
similar position in the male polype to that of the ovary in the female,
viz. behind the stomach.f

To the same able observer w^e are indebted for illustrations of the
development of the impregnated ova in another genus of Bryozoon,
viz., Pedicellina. The ova are pyriforra, and are aggregated like

* XXXV. pi. xxiii. fig. 5. t CXXXIV. p. 222.

L 4

152

LECTURE VIII.

grapes in clusters by tlie pellucid (chorionic ?) membrane in which
they are enclosed {Ji(/. 73., 1.) ; tlie yolk is a "germ-yolk," and has a
;o vitelline membrane separated

by a whitish fluid from the
chorion. The fission of the
germ-cell is followed by
total cleavage of the yolk, as
in 2 ; it next subdivides into
four, as in 3 ; after which the
formation of the germ-mass,
4, proceeds rapidly. Its sur-
face becomes smooth, large
cilia are developed from one
end, which becomes marked
oif by a constriction from the
Development of Pediceiiina. other, as at 5. The larva

escapes from the chorion under the form 6, and swims freely abroad.
The ciliated margin expands, and renders that end of the larva
funnel-shaped. Tubercles bud forth from the funnel, and a pedicle
is developed from the opposite end, as at 7 ; by this the larva attaches
itself, and in the course of the subsequent metamorphosis the linea-
ments of the parent Bryozoon soon begins to be traceable, as at 8.

The development and vital phenomena of the reproductive gem-
mules have been studied by Dr. Farre with much care and success in
the sponge-like Halodactylus (^Alcyo7iium gelatinosunij of Pallas).
They appear in spring as minute whitish points just below the surface.
If one of these points be carefully turned out with a needle, it is
74 found to consist of a transparent sac, containing

generally from four to six of the larvas. These
are of a semi-oval form, with the margin of their
plain surface developed into tubercles support-
ing groups of vibratile cilia {fig. 74.).* The
body presents a simple granular structure ; the
gemmule swims about actively by the vibration
of its cilia, the motion of which seems to be
under its control. They generally swim with

Larva of Halodactylus, from ^, n t . i

above; the cilia as when slowly the couvcx part lorwards ; somctimcs tliev

acting round the margin in • , , . .

waves. Simply rotate upon their axis, or execute a

series of summersets ; or, selecting a fixed point, they whirl round

* The movements of the cilia, which give the appearance of a succession of
Avaves, have been closely analysed in XXXV. pp. 410, 41 1.

BRYOZOA. 153

it in rapid circles, carrying every loose particle after them; or
they creep along the bottom of the watch glass upon one end with
a waddling gait: but at the expiration of forty-eight hours they
attach themselves to the surface of the glass, and the rudiments
of the cell may be observed.

In the Flustra carbesia the ova are developed between the cell and
the body of the polype, which yields to, and is destroyed by, them as
they are developed. They produce ovate, yellow, ciliated larvce,
which, by virtue of the contractility of their tissue and the active
vibration of their cilia, escape with their small end foremost from
the opening of the cell. They then, after a short term of locomotive
life, settle and subside, the outline of the cell being first formed, and
the polype with its tentacula, muscles, and alimentary canal being
afterwards developed in a distinct small closed sac* The embryo
acquires its ciliated surface and power of contraction before it
ruptures the chorion ; it afterwards escapes from the parent cell.
These ciliated larvce are called " ova" in cviii. and other writings
of the same Author. Nordmann found in a Flustra of the species
called Tendra zostericola, that spermatozoa were developed in the
polypes of certain cells and ova in those of others, and that the
male cell communicated by an opening with a contiguous female
cell : this latter is distinguished externally by the trellis-work
pattern of its upper surface, that in the male being smooth. The
formation of the spermatozoa is ascribed to eight vermiform organs,
which are wanting in the female polypes ; but are attached near
the base of the tentacula in the males.

There are a few genera of fresh -water polypes, e. g. Alcyonella,
Plumatella, and Cristatella, which have the ciliated tentacula in the
form of crescentic or horse-shoe lobes. The generative organ is a
membranous band extending from the bend of the stomach to the
bottom of the alimentary sac, in which are developed, according
to the sex, either ova or spermatozoa : the latter in sperm-cells which
succeed each other in a beaded series. The ova are usually few in
number : the germinal vesicle disappears, as in the ova of the Ascaris,
before the chorion is formed. This membrane is coriaceous, smooth,
and brown-coloured in the elliptic compressed eggs of Alcyonella,
The CristateUa has been observed to produce ova of a flattened
discoid form, with their outer surface singularly beset with long
bifurcated hooks like the infusorial Xanthidia. Tlie young Crista-
teUa undergoes its metamorphosis from the ciliated gemmule-state to
the mature form of the polype in the ovum, from which it escapes by

* CVIII. pp. 116-118.

154 LECTUPtE YIII.

splitting it into two parts. Sometimes a second polype is developed
by gemmation before this takes place ; and others bud out before the
colony becomes fixed : and in this free state it forms the Cristatella
mucedo of Cuvier.

In thus tracing upwards the organisation of the animals which
present the common external character of a circle of radiated oral
tentacula, we have met with modifications of anatomical structure
which clearly indicate three classes, and conduct us from a grade of
organisation as low as that of the monad, to one as high as that of
the wheel-animalcule. We have already seen that certain forms of
the Rotifera, as the StephanoceroSy combine the external character-
istics of the Bryozoa, e. g. the cell and ciliated tentacula, with an
equally complicated type of internal organisation ; but no rotiferous
animal developes buds ; the Bryozoa still retain this common cha-
racteristic of the whole race of polypi.

The Bryozoa make a still closer approximation to the compound
Ascidians, which form the lowest step of the molluscous series : but
in these w^e find the ciliated tentacles reduced to mere rudiments at
the entrance of the alimentary canal ; whilst the pharynx, or first
division, is disproportionately enlarged, and, being highly vascular,
and beset with vibratile cilia, performs the chief part of the respira-
tory function. No compound Ascidian, moreover, quits 'the ovum,
as a gemmule swimming by means of cilia either generally diffused,
or aggregated on special lobes after the type of the rotifer ; and no
Bryozoon quits the ovum, in the guise of a cercarian, to swim abroad
by the alternate inflections of a caudal appendage.

The metamorphoses which the Bryozoa undergo are essentially of
the same type as those of the lower Polypi : the embryo developed
from the ovum is an oval, discoid, or subdepressed body, with a
general or partial ciliated surface, by which it enjoys a brief locomo-
tive life after its liberation from the parent : the exceptions to this
rule being few, and confined to some fresh-water forms, e. g. AlcyO'
nella, w^hich, thereby, depart further from the known course of
development in the AscidijB, and resemble rather the fresh-water
Hydrce, if M. Laurent be correct in representing the young of the
H. grisea as emerging, under the mature polype-form, from the
ovum. *

The Anthozoa appear, without exception, to pass from the state of
the ovum to that»of the ciliated locomotive " gemmule " as the larva
has been termed : most of them quit the parent in that guise : but in
the large Actinice they appear occasionally to undergo their trans-

* CXXXI.pl.ii.figs.il, 12, 13.

BRYOZOA. 155

formation into the polype-form before they escape from the mouth of
the parent.*

In the marine Hydrozoa the offspring developed in the ovicapsules
are, as a general rule, the ciliated larvse called '' planulas : " the
Plumularia coronata offering an exception analogous to the Alcyo-
nella in the highest, and the Hydra in the lowest, class of polypes ;
whilst other Plumularice^ the CorynidcB, and certain species of Cam-
pamdaria deviate in a still more remarkable manner by the develop-
ment and liberation of the locomotive offspring in the guise of a
minute Medusa.

We should be thus led fj-om the Hydrozoa to the AcalephEe if we
were guided solely by the phenomena of development ; but more
comprehensive views of the relations of the polype-shaped zoophytes
have conducted to higher types than that from which the Acalephae
seem to diverge, and, in the necessarily consecutive course of de-
scription, we now find ourselves, as at the conclusion of the discourses
on the Entozoa and Infusoria, compelled to retrace our steps and start
afresh from a lower level of the broad basis of the animal pyramid.

Summary of the Classes, Orders, and Families of the Polypi of
Cuvier.

Class HYDROZOA.
Tentacles hollow, muricated with dart-cells or thread-cells. Sto-
mach without intestine, fixed in the parenchyme of the polype.
Polypary, when present, flexible, external.

A. Naked, free, and solitary. Genus Hydra.

B. Naked, or sheathed in a thin membrane, fixed and compound :
, tentacles claviform. Family Corynidje. Genera, Coryne, Syn-

coryne, Hydractinia, Corymorpha, Eleuthera. (These, like the
Hydra tuba of Daly ell, may be regarded as the procreating larvae
of Acalephae.)

C. Protected by horny tubes, from the ends of which the polypes
emerge. Family Tubulariid.e. Genera, Tubularia, Eudendrium,
Pennaria.

D. Protected by cells, developed according to regular patterns, from
a rooted and ramified horny tubular polypary. Spermatozoa and
locomotive progeny developed in external vesicles (sperm capsules
or ovicapsules), larger than the polype-cells. Family SertU'
LARiiDM. Genera, Sertularia, Plumularia, Campamdariaj &c.

* CIX. vol.ii. p. 209.

156 LECTURE vm.

Class ANTHOZOA.
Tentacles hollow, with thread-cells, and, in most, with pectinated
margins. Stomach suspended by radiating mesogastric folds in an
abdominal cavity : no intestine. Pohjpary, when present, usually
internal.

A. Free and solitary, without polypary. a. Tentacles simple, rarely
branched or clavate, more than twelve, often in more than one row.
Family Actiniid.^. Genera, Actinia, Acti?iodendro7i, Eumenides,
Edvardsia. b. Tentacles clavate and aggregated in tufts on the
corners of the angular disc. Genus, Lucernaria.

B. Fixed, compound, without polypary. a. With many simple ten-
tacles. Family Zoanthid.^. Genera, Zoantlius, ManuniUfera.
b. With eight pinnate tentacles. Family Xeniid.^. Genera,
Xenia, Ajithelia.

C. Fixed, compound, polypes with eight pinnate tentacles, retractile
in cells of an amorphous fleshy substance, strengthened by de-
tached calcareous spiculce. Genera, Alcyonium, Lobidaria, Alcyo-
nidium, Ammot/tea, Nephthya, Sympodiiim.

D. Free, compound, polypes with eight pinnate tentacles, retractile
in cells of a fleshy substance, strengthened by calcareous spiculce,
supported by, and sometimes arranged more or less symmetrically
on a stem with a horny or calcareous axis. Family Pennatulidm.
Genera, Penjiatula, Virffularia, Benilla, Vcretil/um, Pavonaria.

E. Fixed, compound, polypes with eight pinnate tentacles, retractile
in calcareous tubes. Family Tubiporibje. Genera, Tubipora,
Catenipora.

F. Fixed, compound, polypes retractile in calcareous cells on the sur-
face of a calcareous axis, which they cover with their common con-
necting tissue, a. With numerous and simple tentacles. Genera,
Fimgia, Agaricia, 3Ieandrina, Pavonia, Explanaria. b. With
more than twelve tentacles. Genera, Turbinolia, Lobophyllia^
CaryophylUa. c. With not more than twelve pinnate tentacles.
Genera, 3Iadrepora, Oculina, Astrcea. d. With the tentacles
obsolete. Genera, 3IiUepora.

G. Fixed, compound polypes, with eight pinnate tentacles, retractile
in cells of a fleshy substance, strengthened by calcareous spiculce,
and supported on a branched, calcareous, firm or flexible axis.
Genera, Gorgonia, Corallium, Isis, Melitcea,

Class BEYOZOA.
Tentacles hollow, with ciliated margins. Alimentary canal with
stomach, intestine, and anus. Polypary , when present, external,
horny or calcareous.

ACALEPH^. 157

Family VesiculabiiDj^ -, genera, Vesicularia, Serialaria, Valkeria,
Bowerbankia, Family Crisiid^^ ; genera, Crisia, Notamia, An-
gmnaria. Family Tubuliporid.e ; genera, Tubulipora, Disco-
pora. Family Celliporid^ ; genera, Cellepora^ Lepralia, 3Iem-
hranipora. Family Escharibje ; genera, Flustra, Tendra,
Cellularia, Retepora, Eschara. Family Alcyonidid^ ; genera,
Alcyonidium, Halodactijlus. Family Alcyonellid^ ; genera,
Alcyonella, Cristatella, Plumatella,

LECTUEE IX.

ACALEPH^.

In the preceding lecture we saw that, whilst the new individuals pro-
pagated by gemmation were, for the most part, like the parent, those
that came from the ova were in very few instances like the parent,
but underwent a considerable metamorphosis. They quitted the egg-
state either as a ciliated planula under the guise of a leucophrys, or
were partially ciliated on special lobes, like a rotifer ; or, what was
more extraordinary, they came forth under the form of an animal
which is usually ranked as a member of a higher class of Radiata,
viz., a free-swimming, bell-shaped, or discoid medusa. The laro-er
marine animals, so called, are commonly regarded as the typical
forms of the class Acalephce,

This class, the anatomy of which we have now to consider, compre-
hends creatures which are amongst the most singular of the whole
animal kingdom ; and each additional contribution to our knowledge
of their economy adds to the interest, and indeed astonishment, with
which the physiologist reflects upon it.

The Acalephm are remarkable on account of the peculiar nature of
their tissues, which are often as transparent as the purest crystal, and
seem more like the vitreous humour than any other in the higher
classes : they are not less interesting for the elegance of their forms,
the beauty of their colours, and for the peculiar property which many
of them possess of stinging and inflaming the hand that touches them,
whence the name of " Acalei^hae " applied to them by the ancient
Greek naturalists, and " sea-nettles " by our own fishermen and
sailors. These qualities, being presented by animals which are
almost the sole visible representatives of living nature in the wild

158 LECTURE IX.

wastes of waters most remote from land, have always attacted the
attention of the navigator, who sometimes finds the surface of the
sea studded with these gelatinous gems, glistening by day with all
the brilliant hues of the rainbow, and betraying their course during
the night-season by the lambent phosphorescent light which they
dilFuse.* The Acalephcs are represented on our own coast by nume-
rous discoid and spheroid species, varying in size from an almost
invisible speck to a yard in diameter, and which, besides the ver-
nacular name above cited, are known as "sea-blubber," "jelly-fish,"
or by the Linntean generic term " medusa."

The form of many of the species is most typical of the great group
'^ Radiata " as characterised in the " Regne Animal," and they were
called by Lamarck f, on account of their tissue, "Radiaires Mollasses,"
or soft Radiaries, in contradistinction to the hard-skinned " Radiaires
Echinodermes." Cuvier retained for them their ancient name of Aca-
lephcB, and he characterises the class as free-swimming gelatinous
animals, having a vascular system superadded to the digestive one,
although he admits that the former may be only a continuation of the
intestinal tubes ramified through the parenchyma of the body. J He
acknowledges, also, that the vascular system has not been demon-
strated in every species of the class ; and that those species in which
it cannot be shown to exist, can hardly be distinguished from the
Polypi.

The division of this class has been founded on their mode of loco-
motion. There are some singular forms which float by means of
air-bladders, and in which the place of a stomach is supplied by
many hollow tentacles : the Acalephes of this order are called " Phy-
sogrades," and have sometimes been denominated Siphonophora. In
a second group locomotion is efiected by longitudinal series of
cilia, whence the name " Ciliogrades ; " these have a single central
mouth and a digestive cavity ; they have also been called Ctenophora.
The third order have also a central, but sometimes ramified, nutritive
sac ; and they swim by means of the rhythmical contractions of a
musculo-membranous disc, whence they have been called " Pulmo-
grades " and " DiscophoraP The species of the last order are those
that are most constantly met with in the seas washing our own coasts.
But some of the tropical forms of the other orders are occasionally
stranded on the south-western shores of England. I have picked up on
those of Cornwall the little Velella, which had been wafted thither, un-

* The Mammaria scintillans has, perhaps, the greatest share in producing the
luminosity of the ocean.
. t CXXXVI. torn. ii. p. 450. _ t ^H. torn. iii. p. 274.

ACALEPH^E. 159

able to strike its characteristic latteen-sail ; and there also I have seen
wrecked a fleet of the "Portuguese men-of-war" (Pht/salia), which
had been buojed up by their air-bladders to that iron-bound coast.

Extremely diversified are both the forms and powers of the free-
swimming radiated animals which have been grouped together by the
character of their gelatinous tissue and their independent movements.
And, in testing the title of this group to be regarded a natural one,
the zoologist has first to remark_, that the animals so associated are
characterised as they manifest themselves at one stage only of their
existence ; and has next to consider the question, what is the relation
of this stage to the true or typical form of the species ?

Zoological ideas of the typical form of a species appear to have been
governed by different rules : as, e. g., according to the length of time
during which a species may exist under a given form ; or, according
to the form mQst commonly presented to observation, and with which
we are accordingly best acquainted; or, according to the superior
number of the individuals of a species which present a given form,
especially where such individuals are produced by gemmation, or
otherwise parthenogenetically ; or, lastly, according to the form
finally assumed by the individuals developing the ova or spermatozoa.
The three former circumstances have plainly influenced the best
modern naturalists in the classification of such genera as Campanu-
laria and Coryne, which have been placed amongst the Hydrozoa,
with the distinctive character of " Progeny medusiform."

What may be the fate of this progeny, which swarm at certain
periods, is not yet quite determined. M. Van Beneden's notion of
their metamorphosis into the base of a compound parent, although
seemingly natural, is hypothetical. Sars and Steenstrup*s observa-
tions of what they believed to be generative organs* or ovaria, de-
veloped in the medusiform off"spring of Coryne, more probably point
to the right direction of the function and signification of such
offspring. The fact that such medusiform progeny do engender ova
seems to repose on good evidence, and is important, so far as it goes^
and the processes by which the genetic cycle is completed will be
indicated with much probability by the phenomena of that cycle
which may be determined in the larger medusiform radiaries.

If these generate ova and spermatozoa, what then, it may be next
asked, do their impregnated ova produce ? If planulas and polypes,
then there will be strong ground for concluding the same with respect
to the ova of the medusiform progeny of Ccimpanularia and Coryne.
That these compound, rooted, hydriform polypes do produce free-

. * XCIII. p. 29.

160 LECTURE IX.

moving meduslform individuals, is most clearly determined ; and the
phenomena are most important and suggestive. No one who wit-
nesses these changes in the form of different individuals, representing
one and the same species, but must feel that, by prosecuting these re-
searches, we shall arrive nearer and nearer to the possibility of solving
those questions, the difficulty of which has been eluded by the gra-
tuitous hypothesis of the transmutation of species, and which may lie
at the bottom of the mystery of the progressive introduction of new
specific forms of animal life upon this planet.

" The natural system of classification," says Cuvier, " must be
based upon a consideration of the totality of the organisation, and a
comparison of such in different beings, directed by the principle of
the subordination of characters." Granted. But suj^pose that
organisation to materially change at different periods of the life of
the individual of one and the same species, and these periodical
characteristics to be propagable by parthenogenesis ; which of these
periods, it may be asked, is to be deemed to manifest the typical
form, or that in which the whole organisation is to be studied and
compared ?

The philosophic botanist sees in the tree the same condition of
an aggregate of essentially distinct individuals as the philosophic
zoologist sees in the compound polype or the compound monad. No
anatomist could look upon the polype of the Bryozoon, with its rich
organisation and independent generative system, as a mere part or
organ of a compound individual whole. No microscopical anatomist
now regards the Volvox as any other than a spherical group of dis-
tinct and essentially independent monads. The polypes of the
Anthozoa and of the Hydrozoa manifest the two lower grades of or-
ganisation in their sub-province ; but are as essentially distinct
individuals, as the polype of the Lagenella. The gemmiparous
leaf of the Bryophyllum is the vegetable equivalent of the animal
polype, and is equally a distinct individual plant ; and, according
to the present botanical philosophy, it is a more typical individual
than the leaf which has been metamorphosed into the stamen, the
pistil, or any other element of the flower.

By this analogy and course of reasoning, therefore, the naturalist
would seem to adhere closest to Nature, and to interpret her best who
should classify his subjects according to the typical character pre-
sented by the individual, whatever might be the phase of its develop-
ment in reference to the genetic cycle ; and the zoophytologists are
justified on this principle who include the Campanularia and the
Coryne amongst the Hydrozoa, notwithstanding their medusiform

ACALEPH^. 161

progeny. But, to be consistent, the rule should be extended to other
medusiform progeny of liydriform polypes, and so to many of the
larger acalephie.

Such a modification, amounting virtually to a suppression, of the
class Acalephcc, however consistent with the reasoning based upon
the principles which have been just laid down, would be opposed to
the practice of naturalists in almost every instance, except the Cam-
pa?iidaria and Coryne^ and a few analogous cases of compound
polypes with medusiform oviparous individuals.

The cockchaffer lives laboriously three dark years under ground,
eroding the roots of plants, before it emerges into light, and disports
a few merry weeks in the bright summer sunshine, in its winged
state. The vermiform larva, in giving birth to the winged insect,
has exhausted most of its substance, and all its vital energies as such,
and leaves nothing but its emjDty skin behind.

The ephemeron, after a year's obscure existence as a water-worm,
creeps out of the vermiform case, and uses its newly-acquired aerial
locomotive organs, and its procreative powers, for a brief day or
hour.

We do not, however, class the cockchaffer and the may-fly with
the Vermes, as we ought to do according to the analogy of the Cam-
j)anularia and Coryne. So vast a proportion of the parent worm has
supplied the material to the plastic force, which has operated in the
re-arrangement of parts for the completion of the winged insect, that
we say the worm has been converted into the insect.

The larval aphides, however, unequivocally propagate, and so
frequently, as quite to parallel the condition of the procreant larva3
of the medusa-producing polypes ; and the analogy is both true and
close of the winged male and oviparous female aphides to the loco-
motive male and female medusie and to the male and female modified
leaf-individuals of plants. Yet, notwithstanding these analogies,
another rule guides the zoologist in the majority of such cases, which
is this : to regard as the t^'pical phase of the species that most perfect
form which parallels the winged state of the insect, the medusa state
of the polype, and the seed-producing and pollen-bearing flower-parts
of the plant. And the zoologist accordingly classes the batrachian
and the butterfly, the chaffer and the ephemeron, the beroe and the
medusa, according to the structure of the last phase of their de-
velopment.

Few naturalists will be found to object to this : but, to be consistent,
they ought not to place in separate classes the Campanularia and the
Cyancea.

The bell-shaped medusoid which Dalyell saw struggling to escape

M

162 LECTURE IX.

from the ovicapsule of the Campanularia is the equivalent, or homo-
logue, of the ciliated planula which, in like manner, escapes from the
ovicapsule of the Sertularia ; and the difficulty or inconsistency
cannot be eluded by affirming the bell-shaped medusoid to be a
" locomotive ovarium," a mere organ of the compound polype that
produced it.

In the pulmograde Acaleph^e the' body is chiefly composed of the
"disc/' which is circular, almost flat in some, e.g. ^quorea, but
rising in others by degrees to a hemispheric form, and becoming
nearly cylindrical, as, e.g. in Turris. It is usually smooth, rarely
pilose. Around its margin there is, in many species, a projecting
ledge of membrane called the " velum," and the margin itself is usually
provided with more or less numerous tentacles, and with the " cys-
ticles " and pigment specks. From the centre of the under surface
of the disc there depends a simple or complex, long or short, process,
called the "proboscis," including more or less of the digestive cavity.

The most characteristic features recognisable by the naked eye, in
' the organisation of the Acalephag, may be exemplified by the anatomy
of the larger MedusoB of our own seas.

The first thing which astonishes us in commencing the dissection
of these creatures is the apparent homogeneity of their frail gela-
tinous tissue ; secondly, the very large proportion of the body which
seems to consist of sea water ; for let this fluid part of a large
Medusa, which may weigh two pounds when recently removed from
the sea, drain from the solid parts of the body, and these, when
dried, will be represented by a thin film of membrane, not ex-
ceeding thirty grains in weight. The anatomist is baffled by the
very simplicity, as it seems, of his subject, instead of, as in other
cases, by the inability to pursue and unravel all the obvious in-
tricate combinations of the created mechanism. Peron and Lesueur,
two experienced French naturalists, who, during the circumnavi-
gatory voyage to which they were attached, paid great attention
to the floating Acalephte, have thus summed up the results of
their experience in regard to their organisation. " The substance
of a Medusa is wholly resolved, by a kind of instantaneous fusion,
into a fluid analogous to sea water ; and yet the most important
functions of life are effected in bodies that seem to be nothing more
than, as it were, coagulated water. The multiplication of these
animals is prodigious ; and we know nothing certain respecting their
mode of generation. They may acquire dimensions of many feet
diameter, and weigh occasionally from fifty to sixty pounds ; and
their system of nutrition escapes us. They execute the most rapid
and continued motions ; and the details of their muscular system are
unknown. Their secretions seem to be extremely abundant ; but we

ACALEPHiE.

163

perceive nothing satisfactory as to tlieir origin. They have a kind of
very active respiration ; its real seat is a mystery. They seem
extremely feeble, but fishes of large size are daily their prey. One
would imagine tlieir stomachs incapable of any kind of action on
these latter animals : in a few moments they are digested. Many of
them contain internally considerable quantities of air ; but whether
they imbibe it from the atmosphere, extract it from the ocean, or
secrete it from within their bodies, we are equally ignorant. A great
number of these Medusa are phosphorescent, and glare amidst the
gloom of night like globes of fire ; yet the nature, the principle, and
the agents of this wonderful property remain to be discovered. Some
sting and inflame the hand that touches them ; but the cause of this
power is equally unknown." *

In this series of lively paradoxes the more obvious characters of
the Acalephse are strikingly exemplified ; but I have quoted them
rather to contrast with the actual knowledge which has since been
gained on these points, and as showing how little the best and most
abundant opportunities of observing the Acalephas will avail, if the
higher powers of the microscope be not brought in aid of the inves-
tigation. Before, however, entering upon these results of later re-
searches, let us see what Hunter was able, by the ordinary anatomical
procedures, to demonstrate and leave for our instruction. In these
specimens f, which belong to the genus Rhizostoma, he has inserted
his skilful injecting apparatus into the central cavity of the body

{.fiO' *^^^-> ^-^\ plunged, so to speak,
"in medias res," and made con-
spicuous by his coloured injec-
tion, both the extraordinary route
by which the nutriment reaches
that cavity, and also the channels
by which it is distributed for the
support of the general system.
The prolongation of the common
cavity a into the base of the
proboscis {li) there divides into
four canals (c), which enter the
base of the four branches (/>, p),
into which the proboscis divides.
These branches again divide and
subdivide along their plicated bor-
ders ; the nutrient canals follow
tliese ramifications, and terminate in numerous fringed pores ((/, tZ),

* CXXXVII. p. 219. f Nos. 847. 982, 983.

M 2

Khizostoma.

164 LECTURE IX.

upon tlie ultimate ramifications at the margins and clavate ends of
the proboscis. These pores are, in truth, the commencement of the
nutritive system ; they are, in this respect, analogous to the numerous
polype-mouths of the compound coral zoophyte* ; but in the Rhizo-
stome a common central sac is interposed between the ingestive
conduits and the vascular or chylaqueous system of the body. Minute
animalcules, or the juices of a decomposing and dissolving larger
animal, are absorbed by these pores, and are conveyed, more or less
digested "in transitu," by the successively uniting canals to the
central cavity. Digestion being completed, the chyle passes at once
into the vascular system, which is in fact a continuation and rami-
fication of the digestive cavity. The nutrient fluid, with sea-water,
passes by vessels (e), which radiate from that cavity, to a beautiful
net- work (f,/) of large capillaries, which is spread upon the under
surface of the margin of the disc. The elegance and precision with
which the injections of Hunter have demonstrated this network in
his pre|)arations cannot be surpassed ; but it is to Cuvier that we owe
the first description of the very remarkable and interesting system of
nutrition in the Rhizostome.f

The rich development and reticular disposition of this part of the
vascular system, in which the circulating fluids are exposed to the
surrounding medium in a state of minute subdivision, upon that
surface of the body which rests upon the water, indicate that the
respiratory interchange of the gases, and the absorption of the oxygen
from the air contained in the sea water, take place principally at this
vascular surface of the gelatinous disc ; and that Hunter is correct in
placing it amongst the series of respiratory organs. It stands, indeed,
at the lowest step of that series, since the organ is not specially
eliminated; but only indicated or sketched out, as it were, by a modi-
fication of part of the common integuments.

The CyancBa aurita, another species of our coasts, exemplifies

* LXXXIV. (1843.) p. 104. Mr. Huxley, who describes the oral pores in
Mhizostoma as oiJening obliquely in a channel fonned by two irritable marginal
membranes, states that in Cephcea the membranes unite in front of and behind
each pore " so as to fonn a distinct polype-like cell." The outer membrane and
the richly-ciliated lining membrane of the digestive canals unite at the f/ee edge of
the fold, and are there produced into tentacles. Belie"\ing the business of diges-
tion to be perfoiTned in the minute dilatations of the beginning of the canals col-
lected upon the edges and extremities of the ramuscules of the proboscis, he
carries out the analogy suggested in the text, and observes "that the Rhizostomida;,
quoad their digestive system, have the same relation to the monostome Medusae, as
the Sertularian Polypes have to the Hydra?, or the coralline Polypes to the Actinite,"
Phil. Trans. 1849., p. 414.

t CXXXVIII. p. 436.

ACALEPH.E.

165

another (monostome) type of the digestive system. The homologue
of the central cavity in Khizostoma, and wliicli in CyancEa must be
the digestive sac, consists of four cavities, from which as many short
oesophageal tubes are continued to their commencement, upon the
under surface of the body, by a single quadrangular mouth (y?^/. 76, a)

with the angles prolonged
into four tentacles which
consist of a solid hyaline
axis, with two fimbriated
membranes along their
under surface. Sixtee^i
canals radiate from the
central cavities, eight of
which (5, b) form, by their
ramifications, the systems
of nutrient and respiratory
capillaries and terminate in
a circular canal near the
margin of the disc ; whilst
the alternate eight termi-

'''''l;i!l">lllllll"i' ^'^^ nate without dividing, each

Cyansea. by a minute excretory ori-

fice (c) at the margin of the disc.

We must suppose the mouths of these excretory vessels to be
endowed with an irritability of a different kind from that of the
nutrient canals, like the mouths of the different cavities of a ruminat-
ing stomach. For, as the orifices of the third and fourth stomachs
contract upon the coarse unmasticated food, whilst those of the first
and second open to receive it, and close when it is presented to them
in its remasticated state, so the nutrient diverticula of the stomach of
the Cyansea receive the digested and exclude the excrementitious
part of the food, which passes along the efferent canals and is thus
rejected from the system.

The discovery of this condition of the nutrient apparatus in the
Cyancea aurita is due to the ingenuity and perseverance of Prof.
Ehrenberg, who induced the living animals to swallow indigo with
their food. He has represented the canals so injected^, in the ela-
borate plates of his memoir on the anatomy of this species.* Prof.
"Wagner f saw the currents of the nutrient fluid in the vascular
system of the Oceania : they were produced, not by peristaltic con-
traction of the canals, but by the vibration of the cilia lining them.
In the "bare-eyed" Medusee digestion is chiefly if not exclusively

* CXL. p. 189. taf. i. micl iv. fig. 2., z.

M 3

t CXLII.

166 LECTURE IX.

performed in the cavity of the proboscis. At the fundus of this
cavity Will saw in Geryonia pellucida four small obtuse prominences,
each of which presented a small aperture leading to the system of
the ciliated chylaqueous canals. In Thaumantias leucostylus he
found a distinct ciliated cavity separated from the stomach at its base
and from which the chylaqueous vessels sprang. Prof. E. Forbes also
found either a well-defined cavity at the base of the stomach or
an indication of such a cavity, from which the chylaqueous vessels
were continued.* This cavity and system of vessels is homologous
with that to which I have given the name "chylaqueous" in the
Anthozoic and Sertularian polypes.

A progressive simplification of the appendages of the mouth may
be traced from the Cyangea downwards in the small bare-eyed^ and
probably larval forms of Medusse : in Geryonia and Oceania the
lips are produced into fimbriated lobes ; in Circe and many species of
Thaumantias into simple lobes ; in Sarsia the lip is a thickened ring
round the orifice of the tubular digestive cavity.f

In all Pulmogrades the inner or lining membrane of the digestive
and nutritive cavities and canals is soft and cellular, and lined by a
ciliated epithelium : it is applied either to the gelatinous basis of the
disc, or directly to the integument, or to the walls of the generative
cavities (e e,jfig. 76.). The gelatinous basis of the disc in Rliizostoma
consists of " an apparently homogeneous substance containing a mul-
titude of delicate fibres interlacing in every direction, in the meshes of
which lie scattered nucleiform bodies :" \ its upper surface is covered
by a tessellated epithelium of polygonal nucleated cells ; on the lower
surface the epithelium " is replaced by a layer of parallel muscular
fibres."§ The integument contains many cells analogous to the
thread-cells in the Hydrozoa and Anthozoa, and to which Prof.
Wagner has ascribed the function of urticating, calling them " nettle-
cells" (nessel-organe). || These cells are usually of an oval form and
contain a long filament, which when retracted is spirally disposed,
but darts out, often to considerable length, when the skin is touched.
They are very numerous in the strongly urticating Pelagia noctiluca :
in the feebly urticating Oceania they are principally located in the
marginal tentacles ; and Ehrenberg, who detected them in the
stinging tentacles of the Cyancea capillata ^, could not find them in

* CXLVIL p. 4. t CXLVIL p. 8 % CXLV. p. 415.

§ CXLV. p. 416. II CXLin. p. 38.

^ Prof. E. Porbes states that only a small minority of the medusae of our seas
are stingers, and amongst these the Cyanaa capillata is a formidable one, and " the
terror of tender-skinned bathers. With his broad tawny, festooned, and scalloped
disc, often a full foot or more across, it flaps its way through the yielding waters

ACALEPHiE. 167

the disc of that species. Will * could discover them only in the
generative tentacles of the Cephea, and in the marginal tentacles of
the Polyxenia. When in action the capsule of the thread-cell is first
protruded from the skin and the filament afterwards.

Some superaddition to the thread-cell would seem, however, to be
essential to the urticating faculty, since those cells are present in
species and parts that do not sting.

Another kind of cell, analogous to the "dart-cells" of the Hydra,
is also present in the Acalephas, and consists of an oval capsule from
which a stiff* bristle-like spine protrudes : these do not urticate :
they lie in groups in the skin of the disc of the non-urticating
species, and are very abundant in the marginal, oral, and generative
tentacles of such species.

The oral tentacles, those, viz. which are continued from the fringed
margins of the oral pores in Rhizostoma and Cephea, are productions
of the outer membrane or integument, and are solid, as are also the
marginal tentacles in the same genera. The short tentacles produced
from the membrane depending from the mouth in Mesonema contain
"a central axis made up of large transparent cells, and extending
beyond the base of the tentacle into the substance of the membrane."
The marginal tentacles in Mesonema, Oceania^ and Cyancea {fg. 76.)
are hollow, and lined by a continuation of the ciliated epithelium of
the marginal canal. The large interbrachial tentacles of Cephea are
processes of the branched proboscides and have the same structure,
consisting of a thick transparent outer substance and an inner mem-
brane inclosing a tubular canal : but at the extremity they are
thickened, and the outer wall is raised into a number of small pyri-
form processes. The central canal branches into a kind of plexus which
occupies the interior of the enlarged end of the tentacle. In the
smaller tentacles which depend from the concavity of the pro
boscidian base the central canal terminates in a simple blind end.f

and drags after it a long train of riband-hke arms, and seemingly interminable
tails, marking its com'se when the body is far away fi'om us. Once tangled in its
trailing " hair," the unfortunate, who has recklessly ventured across the graceful
monster's path, too soon ^vi-ithes in prickly torture. Every struggle but binds the
poisonous threads more finnly round his body, and then there is no escape : for,
when the winder of the fatal net finds his course impeded by the terrified Human
wrestling in its coils, he, seeking no combat with the mightier biped, casts loose
liis envenomed anus, and swmis away. The amputated weapons, severed from
their parent body, vent vengeance on the cause of theu- destruction, and sting as
fiercely as if their original proprietor itself gave the word of attack." CXLVII.
p. 10.

* CXIV. p. 62. t CXLV. pp. 418-420.

M 4

168 LECTURE IX.

The tentacula in the British species of bfire-eyed Medusae are
simple, usually filiform, and highly contractile. "Each of these
organs," writes Prof. E. Forbes, " may be extended or contracted
singly, or in concert with its fellows, evidently obeying promptly the
will of the animal of which they form part. They guide the Medusa
through the sea, and can anchor it. I have seen a Geryonia anchor
itself by means of its lips, clasping a coralline with them, and remain-
ing tranquil so fixed for a considerable time." *

The Medusae swim by the contractions of the margin of their disc ;
and Hunter has put up a corrugated portion of the under surface of
this part of a Rhizostoma f which he considered as indicative of the
arrangement of muscular fibres in that part. Subsequent microscopic
observations have confirmed the accuracy of his views of this etnic-
ture.

The fibres run parallel with each other, with occasional interrup-
tions in their coursej, and their component fibrillce, like those in
Oceania and Pelagia noctiluca^, present the transverse striated
character of voluntary muscle. Prof. E, Forbes states that he has
paralysed one side of a Rhizostoma, whose disc measured more than
a foot across, by removing wath a scalpel the subdiscal fibrous bands
of that half, whilst the other side contracted and expanded as usual,
though with more rapidity, as if the animal was alarmed or suf-
fering. ||

The evidence of distinct nerves and ganglions in the pulmograde
Acalephce rests, at present, on the interpretation which Ehrenberg has
given of certain appearances in connection with the eight brown
marginal "cysticles" {d, d,Jig. 76.), which in the Cyancea aurita are
made conspicuous by a speck of red pigment on their upper or dorsal
side. He describes a glandular, bi-crural ganglion at the base of
each of these cysticles, interprets the cysticles as " eyes," and the two
crura of the ganglion as optic nerves. Ehrenberg also describes a
smaller ganglion, shaped like the above, between each pair of the
marginal tentacles.^ Mr. Huxley is disposed, from the analogy of
what he has observed in Rhizostoma and Phacellophora, to regard
the so-called "optic nerves" as merely the thickness of two superim-
posed membranes, '*' and a very similar explanation may be given of
the intertentacular ganglia, which appear to be nothing more than
the optical expression of the thickened walls of the circular canal."**

With regard to the part, which, from its characteristic constancy

* CXLVII. p. 4. t Prep. No. 55. % CXLY. p. 424. § CXI.H

II CXLVn. p. 3. ^ CXLI. p. 572. ** CXLV. p. 418.

ACALEPH.^. 169

under a certain range of modifications in tlie Acalephaa, I have
proposed the definite term of " cjsticle " *, I may remark that Gaede
first described, in Medusa aurita, eight of these bodies in the margin
of the disc, Avhich to the naked eye appear as white points, but under
the microscope are seen to be hollow bodies containing at their
free end minute corpuscles f, the uppermost of -which are grayish,
the undermost brownish, and all of them more or less hexan-
gular. Ehrenberg compares these corpuscles with the crystals of
quartz, but found them, contrary to Rosenthal's statement, soluble
and effervescent in sulphuric acid. Observing a little cell filled with
red pigment granules above each cysticle in the CyancBci auricula,
the same eminent micrographer suggested that they might be organs
of vision analogous to the ocelli or coloured specks in Rotifera and
Entomostraca.\

In all the larger Medusos which are characterised by a much rami-
fied and anastomosing series cf chylaqueous vessels the cysticles are
protected by more or less complicated membranous hoods or lobed
coverings : in the smaller Medusee which possess a more simple
chylaqueous system, the radiating canals of which are either
unbranched, or if ramified, not anastomosing, the cysticles are
unprotected, exposed, and often obsolete. Prof. E. Forbes, adopting
Ehrenberg's idea of their function, proposes to divide the Pul-
mogrades into the Steganopthalraata and Gymnopthalmata. In the
latter or bare-eyed family the pigment-cells associated with the
cysticles vary much in colour, being purple, orange, yellow, black

* Hohlen KiJrper mit Kdrperchen, Gaede. Rand Korpern und Auge, Ehrenberg.
Tubercules vesiculaires, Edwards. Geho/blaschen, Will. Gehorwerkzeuge, Siebold.
In the excellent monograph, CXLV., they are called, in paragrajjh 21, "marginal
corpnscles," in the next paragraph " marginal vesicles ; " in par. 22 " the cor-
puscle " simply. In the description of the plates, " fig. 8. is a portion of the
marginal canal, with a tentacle, and two marginal corpuscles. Fig. 9. portion of
the marginal canal, with a young tentacle, and a marginal vesicle, containing iwo
corpuscles." (p. 431), the same name being sometimes applied to the contents, and
sometimes to the thing containing, or to the whole organ. One so zealous for the
right understanding of the structures of the marine invertebrata, as the clear-
sighted author of CXLV., will be the first to excuse the attempt to remove a
source of ambiguity in any detail of their descriptive anatomy. I have proposed
for the constant and remarkable organ in question, the term " cysticle" (from ci/sti-
cula), instead of cysticule, agreeably with the analogy of " tentacle," and " pe-
duncle," applied to other parts of the Acalephce. This single-worded name has
also the advantage of suggesting no hypothetical view of function.

t " Unter dem mikroskop aber wird mann einen hohlen Korper gewahr, der an
dem einen freien Ende viele kleine Korperchen tragt." CXXXIX. p. 1 8.

; CXLI. p. 574, 575.

170 LECTURE IX.

and even variegated, in diiFerent species. Yellow with a red dot is
a common condition and is well defined in Oceania.*

In some Acalephre the cysticles are not complicated with pigment-
cells. In the uEquorea violacea the marghial tentacular interspaces
are divided by a mammillary process^, on each side of which are two
cysticles, of an oval or spherical form, containing each two or three
spherical corpuscles.f In Geryonia, Thaumantias, Oceaiiia and
PoJyxenia the cysticles are sessile upon the circular vessel, and
placed between its inner and outer membranes : in Phacellophora as
in Cyancea^ each cysticle is placed at the extremity of a short double-
walled tubular pedicle projecting downwards, the under margin of
the fissure in which it is lodged being prolonged into two overlapping
fringes, whilst the pedicle is a prolongation of the marginal system
of canals. In Cepliea and Rliizostoma the cysticle is placed in a notch
between two lobe-like processes of the margin of the disc and looks
upwards. On the upper surface a semilunar fold extends from one
lobe to the other and covers the cysticle. :j: The cysticles are below
the marginal tentacles in Thaumardias, but alternate with them in
the nearly allied Geryonia.\ The cysticles are yellow in Pelagia
noctiluca, but colourless in Cassiopcea and Aurelia, and the colourless
pedunculate marginal cysticles of Polyxeiiia leucostyla contain each a
single round corpuscle, whilst the cysticles of Cytaeis polysfyla con-
tain a cluster of yellowish calcareous corpuscles. || Will and Siebold
regard these contained corpuscles as homologous with the otolites of
higher animals and the cysticle as an organ of hearing^ ; its cavity is
lined by vibratile cilia in Oceania **, which impress a vibratile move-
ment upon the contents, like that which characterises the otolitic
corpuscles in the Mollusca. As the pigment-cell, when present, is
distinct from the cysticle it may do the ofiice of a light-appreciating
organ, and tlie cysticle that of a simple organ of hearing. We may
with much reason regard as organs of touch the labial and marginal
tentacles.

The ciliograde Acaleph^e are beautifully represented in seas that
wash our coasts by the little semi-transparent, delicately-tinted, sphe-
roidal animals {Jig- "11.) called Bero'e by Miiller, and now the types
of many genera, which have this in common, that their chief or-
gans of motion consist of unusually large vibratile cilia, aggregated
in lamelliform groups ( ib. c, c), Avhich seeming plates are arranged

* CXLVn. p. 9. t CXLVI. p. 19G. pi. 1. fig. Ic,

% CXLV. p. 416. § CXLVIL p. 8.

11 CXIV. pp. 64. 68. ^ XXIV. p. 6L

** Observed by Kolliker, quoted in CXLVIL p. 9.

ACALEPHyE.

171

Cydippe.

like the paddles of a propelling wheel, along eight equidistant convex

bands, extending from near
one end or pole of the body-
to near the other, like the me-
ridians of an artificial globe.
The organs by which the Beroe
can attach itself to, or poise
its body on, a solid surface,
are two very long tentacles,
which are fringed on one side
with cirri. These cirrated ten-
tacles {d; d, Jig. 77.), which
can be stretched out in some
species to more than twenty times the length of the body, can be
instantaneously retracted into the two cavities or sheaths which
extend along each side of the slender intestine ; the marginal cirri
in this act being as instantaneously coiled up in a series of close
spirals, and the whole complex tentacles compacted within the limits
of a pin's head.

" Like a planet round its sun, or, more exactly, like the comet with
its magic tail, our little animal moves in its element as those larger
bodies revolve in space ; but, unlike them, and to our admiration, it
moves freely in all directions, and nothing can be more attractive
than to watch such a little living comet, as it darts with its tail in
undetermined ways and revolves upon itself, unfolding and bending
its appendages with equal ease and elegance ; at times allowing them
to float for their whole length, at times shortening them in quick
contractions, and causing them to disappear suddenly, then dropping
them, as it were, from its surface, so that they seem to fall entirely
away, till, lengthened to the utmost, they again follow the direction
of the body to which they are attached, and with which the connec-
tion that regulates their movements seems as mysterious as the
changes are extraordinary and unexpected. For hours and hours I
have sat before them and watched their movements, and have never
been tired of admiring their graceful undulations. And although I
have found contractile fibres in these thin threads, showing that these
movements are of a muscular nature, it is still a unique fact in the
organisation of animal bodies, that by means of muscular action parts
may be elongated and contracted to such extraordinary and extensive
limits. At one moment the threads, when contracted, seem nodose ;
next, the spiral, elongating, assumes the appearance of a straight or
waving line. But it is especially in the successive appearances of
the lateral fringes, arising from the main thread, that the most

172 LECTURE IX.

extraordinary diversity is displayed. Not only arc tliey stretched
under all possible angles from the main stem, at times seeming per-
pendicular to it, or bent more or less in the same direction, and again
as if combed into one mass ; but a moment afterwards every thread
seems to be curled or waving, the main thread being straight or
undulating, then the shorter threads will be stretched straight for
some distance, and then suddenly bent at various angles upon them-
selves, and perhajDS repeat such zigzags several times, or they will be
stretched in one direction, then they will be coiled up from the tip,
and remain hanging like pearls, suspended by a delicate thread to
the main stem, or, like a broken whip, be bent in an acute angle
upon themselves, with as stiff an appearance as if the whole were
made up of wires ; and, to complete the wonder, a part of the length
of the main thread will assume one appearance, and another part
another, and pass from one into the other in the quickest possible
succession, so that I can truly say I have not known in the animal
kingdom an organism exhibiting more sudden changes, and present*
ing more diversified and beautiful images, the action, meanwhile,
being produced in such a way as hardly to be understood. For,
when expanded, these threads resemble rather a delicate fabric spun
with the finest spider's thread, at times brought close together,
combed in one direction without entangling, next stretched apart,
and preserving in this evolution the most perfect parallelism among
themselves, and at no time, and under no circumstances, confusing
the fringes of the two threads. They may cross each other, they
may be apparently entangled throughout their length, but let the
animal suddenly contract, and all these innumerable interwoven
fringes unfold, contract, and disappear, reduced, as it were, to one
little drop of most elastic India rubber." *

If we regard with Agassiz the halves of the body of the Beroe,
which might be divided by a plane passing through the split of the
oblong mouth, as " right " and " left," the tentacles are there placed
one on the right, and the other on the left, side of the animal.

The transverse mouth, situated in Cydippe at the extremity marked
o,Jig. 77., is bounded in most ciliogrades by lobes, and the buccal
membrane in some species is produced into minute and highly con-
tractile tentacles. Below these the alimentary canal expands into a
moderately wide stomach extending about half-way towards the
opposite pole. The form of the cavity varies according to its state of
contraction, from circular to oblong or angular. Towards the fundus

* This beautiful description is given by Agassiz, in his valuable and elaborate
monograph, CXLVUI. pp. 314, 315.

ACALEPELE.

173

the walls of the stomach present four folds, which are lined by brown
cells, like those in the Hydra, and probably fulfilling an hepatic func-
tion. The ciliated epithelium is best developed at the bottom of the
stomach. This part of the digestive sac communicates with a cili-
ated chylaqueous (nutritive and respiratory) cavity, comparable to that
in Actinia (^jig. 63. g, g' ), by two small apertures, each guarded by
a sphincter. The chylaqueous cavity surrounds the stomach, beyond
which its narrower end extends vertically as a cloacal canal to the
pole opposite the mouth, where it terminates by two small excretory
outlets. Between and below the sheaths of the tentacles {g, g,Jig. 78.)
the chylaqueous cavity sends out transversely two w^ide canals in

opposite directions, which bifurcate at
acute angles, each branch again bifur-
cating at similar angles (somewhat as
shown in the transverse section of the
Ci/dippe,Jig. 78., but varying according
to the point of view), thus sending off
eight radiating horizontal canals, which
send off as many vertical canals along
the whole extent of the eight rows of
vibratile fringes ; branches are also
sent to supply the tentacular sheaths,
and two tubes extend vertically along the flat surface of the stomach
to the margin of the mouth. At the oral end of the spheroid the
longitudinal canals communicate with a circular one, and a similar
circular vessel surrounds the anal disc, in Bero'e Forskalii*

Willf has given a good description and figure of the infundibular
chylaqueous cavity, and the canals sent off to the stomach, to the
long and short rows of cilia, to the tentacles and the body-lobes, in
the Eucharis multicornis, a lobed Beroe, belonging to the same family
as the Lesueuria of Edwards and the Bolina of Agassiz, who confirms,
in the main, this account, in his elaborate description of the chyla-
queous system of a North American Beroe {Pleurobrachia rhodo-
dactyla, Ag4). In this species M. Agassiz observed that, besides
the movement of the chylaqueous fluid due to the ciliated epithelium
lining the system containing it, the parietes of the central cavity of
the main trunks, as well as those of the vessels to the ciliated bands,
contracted and dilated ; and that the dilatation of the vessels of one
side of the body alternated with the dilatation of those of the other

Cydippe.

* See tlie beautiful figure of the system of ciliated chylaqueous canals, injected
in CXLVI. pi. 6. fig. 1., a. ^^<^'n

t CXIV. p. 31. tab. i. fig. iii. ^rri i .

X CXLVIII. pp. 332—339. pi. iii. and iv.

174 LECTURE IX.

side. Chyle, or reduced chymous particles of the food, with sea-water,
circulates freely through the cavity and canals of the system above-
described, and eifete particles are sent out with the fluid by the
excretory pores, which are homologous with those of the correspond-
ing system of canals in the Cyancea {jig. 76. c, c), and only remotely
analogous to the anal outlet of the true intestinal canal in the Brijozoa
and higher forms of animals. In Cytaeis, Geryonia., and Thaii-
mantias four canals are continued from the digestive chylaqueous
cavity to the marginal circular canal ; whilst in JEquorea not fewer
than seventy-four canals radiate from the stomach to the marginal
canal.

Agassiz has described the longitudinal muscular fasciculi beneath
the superficial rows of vibratile fringes, and the pinnate bundles of
fibres attached to the sides of those rows, and which penetrate into
the substance of the gelatinous mass. By means of these muscles,
the fringes, although they usually move together, yet sometimes act
independently, and even particular cilia in each lamelliform fringe
may move whilst the others are at rest. The same acute and inde-
fatigable observer has figured the radiating fibres of the muscles
which dilate the mouth, and the circular fibres which close it, and
the diverging fibres of the main vertical fasciculi, which form a kind
of sphincter around the tube leading into the tentacular sheath.*

The evidence of the nervous system in the Ciliogrades is doubtful
and conflicting.

Dr. Grant "f has described and figured a double filamentous chord
connecting a chain of eight ganglions around that extremity of the
Bero'e ( Cydlppe) pileiis {Jig. 77, b\ from near which the two long
cirrigerous tentacula {d d) are protruded, and where he supposed the
mouth to be placed. Whatever analogy such nervous system may
bear to that of the Echinoderms in the circular disposition of the
central filaments, and the radiation of nerves from that centre, it has
none in regard to its situation, for the mouth of the Beroe is at the
opposite end of the body. \

Milne Edwards § and Will || both reject the above described
nervous system. A single cysticle appears to be present in all
BeroidfB at the anal pole of the body, in a depression, protected by
lobes of the integument; and beneath the cysticle is a yellowish
mass of a ganglionic appearance, which both the above-cited ob-
servers refer to the nervous system. The cysticle contains some
clear fluid with an aggregate of crystalline corpuscles of a white

* CXLVIII. pp.332— 339. pi. 2. v, o, p. f CXLIX. p. 10. pi. 2. f. 1.

X CXLVII. p. 20G. pi. 4. § CXLVI. p. 207. 1| CXIV. p. 44.

ACALEPHiE. 17

colour, in Cydippe and Eucharis, of a reddish tinge in Beroe. These
corpuscles vibrate by the action of the cilia of the lining epithelium
of the cysticle. Some superimposed dark-coloured pigment-cells
render its situation conspicuous. By some anatomists the combined
cysticle and pigment-cells have been regarded as a simple organ of
vision, by others as a simple organ of hearing ; both would probably
be right if they would limit the one sense to the pigment spot, the
other to the cysticle. The remarks by ISL Agassiz on the nervous
system of the Beroidce appear to me so just, and accord so well with
the conclusions to which my own observations have led, that I cannot
better conclude my notice of this part of the ciliograde structure than
by quoting them : —

" As for the nerves which are said to arise from the ganglion con-
nected with this black speck, I have been unable to make them out.
I have seen numerous muscular or contractile fibres connected with
the lower extremity of the chymiferous funnel ; I have seen these
fibres diverging from above the so-called ganglion, but have never
been able to trace any one of them beyond the length which con-
tractile fibres have ; again, I have repeatedly seen these fibres in a
state of contraction or relaxation, presenting so little regularity
in their distribution, that for the present I think it were rather
assuming to decide upon the disposition of the nervous system of
Beroid Medusoe. I am even satisfied, from the descriptions published,
that the eight converging narrow tubes, of which I find no mention
in former authors, must have been probably mistaken for nervous
threads by some ; and when Professor Grant states that Beroe has
eight nervous threads, I suppose he alludes to the eight narrow
chymiferous tubes, the connection of which with the ambulacral
tubes is so easily traced, though their central connection with the
vertical funnel still remains doubtful. I do not, however, deny that
this centre" (the cysticle), "is a point where we have to look for at least
one part of the nervous system, and the gelatinous lobes about the
mouth for the other part, if there be really a distinct nervous system
in Beroid, as in Discoid Medusee. But, for my own part, I have
failed in tracing it out ; though, I may add, that I am sufiiciently
acquainted with the structure of the region where it is said to have
been observed, to doubt the accuracy of the statements which have
been made about it, especially in the precision and distinctness with
which it is mentioned. And I express these doubts notwithstanding
the doubts I have myself respecting the real nature of some organs
around the central black speck, for the very reason that, after finding
there more than has been seen and described, and various things

176

LECTURE IX.

whicirmay answer the vague description given, I do not in reality
find what has been said to exist in that part of the animal." *

The most conspicuous, if not the most typical, member of the

physograde order
of Acalephas is the
Physalia {fig- 79.),
in which all that
part answering to
the disc in the "pul-
mograde" order, is
expanded into a bag,
the major part of
which is occupied
by an air-bladder,
•whilst the digestive
cavity is subdivided
amongst a series of
appendages attached
to one part of the
under surface of the
bag. This part con-
sists of an outer thin
and dense mem-
brane, of an inner
thicker membrane
beset with long cilia,
and of an air-bladder,
which at one point, a, is attached to the above membranes, where
there is a small constricted aperture, at least in the outer membrane.
This membrane is developed into a kind of crest along its upper part.
It is provided with many fine muscular fibres, and the whole bag
contracts into a small irregular mass when punctured and the air
evacuated ; but it seems that the Physalia has no power of voluntarily
emptying its air-bag.

The appendages are of three kinds, — urticating, digestive, and
(probably) generative. The urticating tentacles are the longest;
they are hollow, and are provided with muscular fibres, of which the
most conspicuous are longitudinal, and serve to retract them ; they
contain many corpuscles of a reniform shape, and are richly provided
with thread-cells, whose filaments are of the spiral kind. The gastric
appendages are shorter and wider, and are provided with stomata,

Physali

* CXLYIII. p. 348.

ACALEPH^. 177

which are applied to the prey seized and benumbed by the tentacles
If the prey be small, it is sucked bodily into the gastric sac ; if large
the sac becomes distended with its juices and dissolved parts, the
gastric secretion being a very rapid and powerful solvent. The
mouth of each sac is wide, with a broad eve'rted lip, armed with a
series of "nettle-cells." The whole gastrio appendage is highly
contractile and in constant motion in the living animal. Tlie ap-
pendages of the third class are cyathiform ; the development of gene-
rative parts has not yet been followed out in these. The question of
the genetic cycle of the Physalia is one of the most interesting that
remains open to the observations of the naturalist who may traverse
the tropical seas where they most abound.

The Physophora differs from the Physalia in having, besides the
principal or axial air-bladder, a number of smaller ones appended to
it, placed one below the other, and forming by their aggregation
prisms or cylinders : the tentacles, as in Physalia, are of three kinds :
some are filiform, beset with thread-cells and cirri, susceptible of
much elongation ; the others form a racemose cluster at their lower
extremity, e. g. in the Physophora hydrostatica : some form groups
of pyriform or spherical vesicles ; a third kind are short and conical,
and perform the office of digestion. The sac or body is defended by
substances of cartilaginous hardness. Only the external membrane
of the air-bladder appears to be perforated in the Physophora. For
the description of a compound form of physograde Acalephe, formino-
the genus Stephanomia, I may refer to the excellent paper CXLVI.
p. 217.

The genus Diphyes presents a long, conical, subangular bodv of a
cartilaginous firmness, closed and pointed anteriorly, with two wide
apertures at its base : the upper of these is the outlet of the cavity
containing the air-vesicle, and is called the natatorial cavity ; the lower
orifice is that of the nuclear cavity, from which issues a tubular ten-
tacle, with polypoid organs seated upon it. Within this cavity is
usually sheathed a second conical capsule, traversed by the common
tube or " chapelet," and having also its air-bladder : in this the ovary
or testis is developed. As it enjoys independent movement when
separated from the former, it was regarded by Cuvier as a distinct
individual, developed by gemmation ; and it is homologous with the
medusoid individuals similarly developed, and appropriated to the
generative function, by ova, in the Coryne. The canal into which
the stomach opens terminates in a long rounded cavity, lined by a
ciliated epithelium.

Two genera of physograde AcalephaB have an elliptic or circular
discoid body, supported by an internal cartilaginous or subcalcareous

N

178 LECTURE IX.

plate. In the circular form called Porpita the plate consists of two
lamellas, including a great number of air-canals, the parietes of which
are slightly calcified: the prehensile organs are chiefly developed
from the margin of the^ float. In the elliptical Velella the horizontal
disc consists of four pieces united together by oblique sutures : from
the upper surface of the body-disc there rises a second thin semi-
elliptic plate, which is set at the same angle to the disc or deck as
the lateen sail of the Malay boat. By means of this plate the little
Velella is wafted along by the action of the wind, and has probably been
often mistaken by navigators for the fabled cephalopodic Paper-sailor
{Argonautd). Prehensile and digestive tentacula depend from the
imder surface of the disc, in the centre of which, both in Porpita and
Velella, is a short tube, with an orifice that probably relates to the
excretory and respiratory functions.

The Acalephse propagate by spontaneous fission, by gemmation,
and by impregnated ova; the parthenogenetic modes are chiefly
limited to the young or larval state. In some species the gem-
mation is incomplete, and a chain of organically-connected individuals
results, as, e. g. in the Diphyes campanulifera and the Stephanomia
prolifera. Both these and the PhysophoridcB are also oviparous.
In the DiphyidcB the generative individual commences as a bud or
process of the common tube, and, after great changes in its form,
becomes provided, like the parent individual, with a natatory organ
and with a sac composed of two membranes suspended from its
centre. The ova, or the spermatozoa, according to the sex, are
developed between the two membranes of the sac ; the individual
then becomes detached, and swims freely about.

In the Norwegian seas there are little Medusae, very similar to
those called by Eschcholtz Cytais, in which Sars observed that gem-
mation took place from the sides of the pendant stomach ; this organ
has four sides, and from each of these proceeds a little bud, and these
buds are observed in difl'erent grades of development : they are
successively detached as they attain the form of the parent in mi-
niature, and soon acquire their full size.* In May, 1837, Sars ob-
served a similar gemmation in the Thaiimantias multicirrata, a
(probably larval) Acalephe, one inch in diameter.f In the Sarsia
prolifera Forbes found the buds produced at the bases of the four mar-
ginal tentacles, and hanging from them in bunches. The degree of
development is not equal in all the four bunches, and in each case buds
are seen in very various stages of development, from embryo wart-like
sproutings to miniature medusa?. \ Will states, that in the Beroe
{Eucharis) multicoimis he saw the tubercles and lobes occasionally

* CLI. p. 10. pi. IV. 7-13. t 1^- X CXLVII. p. 17.

ACALEPH^. 179

detached, and assuming signs of independent life * ; swimming freely,
and acquiring, with a slight growth, a certain radiated form : but the
acquisition of the form of the parent by these buds has not been wit-
nessed. Martens observed small portions of the body of the Cestum
veneris detached, which moved independently for some time.f

The most common mode of generation in the completed, forms of
AcalephcB is by the development of ova impregnated by sperma-
tozoa. In certain ciliogrades, e. g. Eucharis multicornis, the ova are
developed in the common cavity of the body along one side of each
longitudinal rib or ridge, and the testes on the other side ; so that
there are eight rows of ova and eight of testes. An efferent canal
extends from each row towards the mouth. This androgynous con-
dition, with the distinct stomach and chylaqueous cavity, indicates the
affinity of the Beroidge with the Actiniae. The pulmogrades are highly
prolific, and propagate in the ordinary manner by impregnated ova ;
the germs of which are developed in one set of individuals, whilst the
spermatozoa are developed in organs peculiar to other individuals, the
Acalephje of this order being male and female. Gaede first pointed
out the ovaria, and described and figured the ova in the medusae. If
Ehrenberg confirmed and added to Gaede's observations of the fe-
males ; but he thought the spermatozoa of the male medusas parasitic
cercariee, the testes and ovaria having the same form and colour in
the younger medusae § : but they are different in structure, and the
males have never the marsupial sacs on the arms.

In Geryonia and Thaumantias the generative sacs are situated in
some part of the canals traversing the disc ; in Aurelia they are formed
by pushing in the wall of the Stomach; in Rhyzostoma and Cephea they
are attached to the under vv^all of the stomach ; in Cyancea the organs
of generation are situated, in both sexes, in four cavities {fig. 71, e, e,)
which push in the walls of the stomach and open on the under-part
of the disc, near the mouth. The females of Cyancea aurita are
distinguished, at the advanced stage of the breeding season, by the
numerous small flask-shaped marsupial sacs ^vhich are attached to
the under surface of the oral tentacles.

Male medusae do not differ, in respect of size, from the females.
Siebold || finds that, when the Cyancea aurita is but 1^ in. to 1^ in.
long, the males may be distinguished by the sperm-sacs in the tjenii-
form testis, and the females by the germ-vesicle and spot in the
similarly shaped ovaria ; but the band-like genital organ is small, and
instead of folds, shows only risings and depressions. When the

* CXIV. p. 42. I CLIII. p. 494. tf. i. fig. 2—4.

X CXXXIX. taf. i. fig. 1. § CXL. || LV. p. 6.

180 LECTURE IX.

medusae are still younger, the organ is only a flat band, without in-
equalities. Each testis consists of a band with many folds ; the whole
bent in a bow, with the convexity attached to the concave wall wdiich
divides the generative cavity from the stomach.

If a probe be inserted into the generative cavity, it immediately
touches the under or outer surftice of the testis; if it be passed into the
digestive cavities, it touches the upper or inner surface of the testis,
but not immediately, the epithelium of the digestive cavity covering
this surface of the testis. The testis is much longer than the cavity
containing it, but is adapted thereto by its numerous folds. Its con-
cave side gives off a numerous series of highly irritable coloured
tentacles, having the same structure as those on the arms : they are
richly ciliated, and contain many hyaline rounded corpuscles and
thread-cells immediately beneath the surface. The spermatic ten-
tacles are capable of only moderate extension : at the breeding time
they project from the mouth of the generative cavity, leaving only
a small passage in their centre. By their powerful ciliary apparatus
they keep up a strong current of sea-water in the cavity, and thus
aid in the expulsion of the semen. No ciliary movement is observable
upon the delicate epithelium covering the lower surface of the testis.
The parenchyma of the testis consists of a transparent granular sub-
stance in which are imbedded innumerable pyriform sacs, having their
basis turned towards the upper surface of the testis, and their apical
orifices opening upon the under-surface of the testis, which they
make uneven by their tumid margins. The spermatozoa are developed
in these sacs, which permanently represent the earliest rudiments
of the extremely elongated seminal tubes in higher animals The
parietes of the seminal sacs are pretty thick, and, perhaps, contractile.

In young males the sperm-sacs contain numerous cells with many
nuclei, from each of which nuclei a spermatozoon is developed ; and
as this development proceeds, the sperm-cell presents a striated cha-
racter, and, lastly, a fasciculus of spermatozoa. These have an enlarged
end, or body, and a filiform appendage, so fine as scarcely to be seen
save by its undulatory movements. The fasciculus of spermatozoa
does not exhibit these parts in the same degree of development in each
sperm-sac : those nearest- the cervix of the sac are the most perfect.
The tails of the spermatozoa are always directed towards the opening
of the sperm-sac. The bundles of these filaments follow each other,
and often the apical tails of one bundle are infixed in the central
interspace of the bodies of the preceding bundle, and a chain or string
of bundles are thus formed which are easily seen by a moderate
microscopic power. These spermatozoa are very lively in sea-water.
In order to observe the actual ejaculatio se?ni?iis, cut off a piece of the

ACALEPHiE. 181

testis from a fresh male medusa, place it on a watch-glass with the
under surface, on which the sperm-sacs open, uppermost, when if
the Acalephe is in the rut, the escape or emission of the spermatozoa
may be seen. The development of the sperm-cells is not always
according to the size of the animal; they have been found, fully
formed^ in medusae one inch and three-quarters to three inches broad,
and even a specimen of one inch in diameter had active spermatozoa
in the testes.

The coloured frill in the generative cavities forms in the female, as
in the male, the essential generative apparatus. The ovarium, like
the testis, consists of a band, with many folds, attached to the septum
dividing the generative from the digestive cavities ; it has a proper
peristaltic motion ; its concave border is beset with similar tentacles,
which are extensile and flexible in all directions, are armed with
many urticating cells and are beset with vibratile cilia. The thin
epithelium on the under surface of the ovarium is here and there
slightly ciliated, which has not been observed in the testis. The
tissue of the ovarium is looser than that of the testis, and the band
has more the appearance of a flattened tube ; but the ovarium is not
a simple folded sac, witli an oviducal opening, as Ehrenberg supposed.
The minutest germs of the ova are nearest that surface of the
ovarium which is attached to the membranous septum : as the
germinal vesicles acquire their vitelline investment they approach the
opposite or free surface, from which the mature ova protrude, covered
only by a very thin membrane, and giving a coarse granular character
to that part of the ovarium. The germinal vesicle has its spot, or
nucleus; tlie surrounding yolk, as it accumulates, becomes violet
coloured. It is covered by an extremely delicate membrane with
a smooth surface. In this state the ova are transferred from the
ovarium to the marsupial sacs ; but how they get there is not known ;
they are doubtless impregnated in transitu. In the marsupial ova
one can no longer discern the germinal vesicle ; it has combined
with the matter of the spermatozoa and become diffused through
the yolk. The primary germ-cell, developed most probably as in the
Ascaris, from the impregnated nucleus of the germinal vesicle, at-
tracts the whole germ-yolk about it, and divides it progressively
with its own divisions. The first division of the yolk resembles the
spontaneous fission of some infusorial monads, inasmuch as it begins,
not at every part of the circumference, but on one side (Jig. 80.), and
proceeds across to complete the bipartition {Jiff> 81.). Subsequent
subdivisions, corresponding with those of the ova of the Ascaris
(p. 113.) are described and figured by Siebold, from whose menioir*

* LV. tab. 1.
N '}

182

LECTURE IX.

I have selected the successive two-fold {fig. 81.), four-fold {fig.
82.), and eight-fold {fig. 83.) generation of germ-cells. As the fis-
sures become more numerous^ they take a diverging or radiating

80 81

3

CyaiiEea aurita.

course, until the whole surface of the ovum presents a granulated cha-
racter. And now the ovum loses its violet colour and transparency
and becomes a dark yellow ; it is covered by an epithelium, with
traces of cilia ; these increase, and at length cover the whole surface,
and the new being passes from tlie condition of an ovum to that of
the embryo and obeys the involuntary moving powers. A cavity next
begins to be developed in the centre of the germ-cells, which, by
continued and reiterated division, take on the form of truncated
pyramids, converging towards that centre {fig. 84.).

The deep yellow ciliated embryo of the Medusa, which has now a
diameter of one eighth of a line, exchanges its rounded for an oval
form. It gradually elongates, and takes on a leucophrys-like form,
being half a line to one-third of a line in length. At the upper end is a
fossa, which does not, however, communicate with the central cavity,
and is not a mouth. This stage of development occupies two or three
days, when the ciliated monadiform embryo {fig. 85.), quits the
maternal pouch, and swims forth : the arrows indicate the direction of
the ciliary currents. The liberated and locomotive larvoe sometimes
re-enter the generative cavity and get entangled between the folds and
tentacles of the ovarium, which led Ehrenberg to describe them as
ovarian ova ; but Siebold observes, that if they were produced there as
gemmules with the power of swimming, the marsupial sacs, in which
they actually acquire that development, might have been dispensed with.

The great or cephalic end next becomes shortened and thickened,
and a depression is observed in its centre, which is the commencement
of a digestive cavity; then the margin of this cavity expands, and is
developed into four processes, riclily furnished with vibratile cilia
{fig. 86.). A small cavity or disc for adhesion is formed at the
opposite extremity of the body, and thus the metamorphosis from the
polygastric to the rotiferous form is effected.

The young Medusa, having swam through its infusorial stages,
attaches itself to some firm body, preparatory to its next metamor-
phosis ; during which the yellow colour disappears ; and the body
becomes subtransparent ; it also manifests a much more general irri-

ACALEPH^.

183

Larval Cyansea.

tability, the larva sometimes elongating, sometimes contracting itself.
Four other tubercles bud out in the interspaces of the first four, and
all increase in length. These eight arms have the power of remark-
ably shortening and lengthening themselves, as exemplified by the two
outlines of the same polypoid larva, at a a and b b, Jig. 83. Their

superficial cilia create vor-
tices in the surrounding water,
which carry the nutritive
molecules to the mouth of the
larva, now metamorphosed
into an eight-armed naked and
solitary polype. By the sub-
sequent development of new
arms from the interspaces of
the old ones, a many-armed
polype results, and the type of
the hydra is exchanged for that
of the actinia. The tentacula
are very like those of the ovaria
and testis in the adult Medusce; they are ciliated, but not in two regular
rows, as in Flustra and Alcyonella. They contain clear corpuscles,
or thread-cells, arranged in regular bracelets, like the tentacles on the
margin of the disc of fully developed medusae. The mouth of the po-
lypoid larvce is very contractile and expansible : they feed on infusoria
and on their infusory-like younger brethren, one-half of the body of
one of which may often be seen hanging out of the devourer's mouth.
If nourishment be abundant the larval polype propagates by gemma-
tion {fig. 88.).

Still more remarkable to Siebold was the production in a few of
these larvae of lateral branches from the body, of a great lengthy —
in one case three such stolones were developed. These branches have
continuations of the digestive cavity in them, and contract and elongate
like ordinary arms. If these were irregularities, and the ordinary
metamorphoses were delayed, it was, he conceived, through the in-
fluence of captivity. Siebold also thought that the larval medusas, which
in autumn, in open sea, thus change to fixed polypes, hardly would con-
tinue in that state through the winter, but about the beginning of the
stormy period would change to free-swimming medusa, and settle
down to tranquil depths of ocean. Sir J. G. Dalyell, however, has
determined the period of the duration of the polype form of the larval
medusae to be much longer than Siebold conjectured, and he even
succeeded in keeping a colony of these larva3, which he called " hydrce
tubae," for six years.

N 4

184

LECTURE IX.

With regard to the marsupial sacs on the arms of CycmcBa aurita,
these are attached to the fringed processes on each side of the oral

3. Gemmation of

Hydra tuba.

89. Scyphistoma.

92

Spontaneous fission of Strobila.

Ephyra.

arms. They are developed before the ova quit the ovaria; are
largest on the upper and middle part of the arms, while at the under-
most part only small and usually empty sacs are found. Do they
disappear after the progeny is developed and the breeding season
past, or does the parent perish with them when her maternal and
nutricial functions have been performed ? The membrane from which
the sacs are developed is beset on its free edge, both in males and
females, with numerous tentacles, similar to those found in the gene-
rative or respiratory cavities. Siebold thinks they are more numerous
in the male than the female.

The subsequent metamorphoses, or rather metageneses, of the
larval medusae are equally extraordinary with those above described,
which the observations of Siebold have mainly contributed to explain.
The cycle of these changes is so remarkable, that I feel bound to
submit the whole body of evidence, from different and independent
witnesses, by which the phenomena have been established and linked
together.

It is now sixty years since Otho Fred. Miiller first described and
fif^ured* a marine Polype, which, from its general resemblance to the
fresh- water kind, he called Hydra gelatinosa : it is the Hydra tuba,
of Daly ell, or a larval Medusa at the same polypoid stage.

Eschcholtz, in 1829 f, first described a small medusoid animal
which he called Ephyra ; this now turns out to be the penultimate
^tage of Cyancea aurita.

* CLIV. vol. iii. p. 25. t. xcv.

t CLV.

ACALEPH^. 185

Sars, in 1833, discovered a gelatinous Polype differing from the
Hydra gelatinosa hy its thicker body, slightly marked by transverse
rings ; believing it to be a new genus of Polype, he described
it under the name of Scyphistoma (Jig. 89.). In the same year
Sars also described a gelatinous polypoid animal, differing from the
above in the deeper annulation of its thicker body, the rings of which
developed bifid processes {Jig. 90.) ; and he called this very sinijular
creature Strobila, from its resemblance to an artichoke. He finally
saw the rings or segments separate from one another {Jig. 91.) and
swim off as little medusas {Jig. 92.).*

At the meeting of the British Association, at Edinburgh, in 1834,
Sir J. G. Dalyell communicated his observations on a marine Hydra,
which he had called Hydra tuba, or the trumpet-polypus ; he
described it as about five lines long, and with about thirty tentacula,
stated that it was very predacious, would gorge young actiniae, and
discharge the rejectamenta again by the mouth. It was very sensitive
to light, contracting and retreating from it. It was not very locomo-
tive, and propagated by complete gemmation, the young not removing
themselves very far from the parent.

In his later workj, published in 1847, Sir J. Dalyell remarks,
" Hence it is natural to assume that a germ, or deposition of elemen-
tary matter, subsists somewhere in the flesh," and that " generated
within as a compact substance, its Avay is made, by a regular process,
to the exterior, where it becomes visible as a rising prominence."
And at page 89. he asks, " Whether the budding results from a germ
come of an earlier principle," which shows how nearly the ingenious
author had arrived, by independent thought, at the true condition of
parthenogenesis. J

Upon the whole, Dalyell has given us the best history of this
polype stage of the Medusa, of its longevity, of its powers of propaga-
tion by gemmation, and also its powers of repairing injury. To give
an idea of the reproducing force in the Hydra tuba : on April 23rd
an adult was detached from its site and insulated; in four days a spur
or bud had issued from one side of the base, and a large protuberance
with a row of papillae, an originating embryo, was rising from the other.
On the 2nd of May these papillae had elongated into perfect tentacuJa,
like those of the adults. Another protuberance on the opposite side
of the parent was now visible, which gradually matured into a young
hydra, and began to feed on the 17th. On the 30th of May separa-
tion had taken place ; four individuals were to be observed, and one

* CLVI. t CIX. vol. 1. p. 82.

X First pointed out in LXXXIV. (1843), pp. 234. 36G.

186 LECTURE IX.

was in the progress of developing two others. Dalyell obtained from
these a colony of eight larval " hydrae tubae." These were extremely
voracious ; they were fed with the flesh of mussels ; and in proportion
as they were fed was their power of converting their food into crea-
tures like themselves. By July 21st fifteen hydrae were propagated,
and ultimately a colony of eighty-three were obtained from the
individual insulated on the 23rd of April. It would seem that con-
finement tended to check the metamorphosis into the " oviparous
form," and favoured the gemmation of the polype individuals, or the
" typical form." At length, however, in the spring of a subsequent
year he observed the phenomena which he thus describes, in the
" Edinburgh Philosophical Journal" for 1836 : —

*'Ikept a colony of these animals and their descendants during six
years ; numbers attained maturity ; they fed rapaciously ; grew and
bred, succeeding at all seasons of the year. But, in February and
March, the face or disc of some hydras is invested by a pendulous
flexible prolongation of an inverted conical form^ obliterating the
tentacula entirely. The apex being connected with the disc, this
pendulous mass extends two or three lines in the course of time, and
is gradually developed in twenty or thirty successive strata, gradually
broadering outwards. Wlien more mature, the vehement clasping of
extending arms at the extremity denotes that each stratum is an
animated being, which, after excessive struggling, is liberated, to
swim at large in the water. This also maybe associated with the
medusarige. It is considerably larger than the preceding, two lines in
diameter : of a whitish colour, tending to transparence. The body
resembles a flattened watch glass ; the margin dilating into from
five to twelve horizontal, broad, flattened lobes, each cleft half way
down the middle, and with a black glandular-looking speck in the
centre of the fork. A crest, resembling a quadrangular clustered
column, rises from the convex surface of the body, and four organs
may sometimes be observed on the same surface near its base.
Motion is accomplished in jerks or leaps, somewhat as by the Medusae
proper, from percussion of the lobes on the water, the crest being
downwards. Whether the pendulous mass or its individual parts be
contained in one common involucrum, or in many specific integu-
ments, is uncertain ; but each of the animals composing it comes
successively to maturity and departs. As the pendulous prominence
disappears, the vigour of the hydra is restored, and the tentacula,
liberated of the encumbrance, effecting temporary obliteration, resume
their natural form and functions. Weeks elapse in the course of this
process, and during survivance of the animals." So that here the
observations by Sars, of his Scyphistoma (1833), illustrated by

ACALEPHiE. " 187

those of Dalyell (1836), established a series of metamorphoses carried
on from the Hydra gelatinosa or Hydra tuba, to the medusa state.
Our next question, at that date, would have been; — What does this
Hydra tuba come from ? For this part of the history of the Medusa,
we are indebted to Prof. Siebold (1838), who traces the development
of the ova of the Medusa ( Cyancea aurita) to the Hydra tuba, as has
been already detailed ; during which, as in Campanularia, a ciliated
monadiform planula precedes the polype stage ; and thus the two
detached series of links are united into one harmonious metagenetic
cycle.

Confirmation by different observers is not wanting. The accurate
Sars, pursuing his researches, followed out, independently, the whole
series of changes of the ova of the Medusa, from the infusorial to the
polype-type, thence to the scyphistoma and strobila ; finally to the
budding forth of the flattened segments, and the splitting up into a
pile of Medusa3. The details, with figures, were published in 1841.*
But Dalyell has shown us that the polype larva may have propagated
hundreds of hydrse, before it issues into the pile of Medusae. The
sea which washes our coasts is sometimes covered by millions of
these little Medusae. Dalyell narrates, in his beautiful work, that
one summer having selected a specimen of a Medusa of the genus
Chrysaora, he kept it alive in a capacious jar of sea-water for a few
days. On removing it from the jar in which it had been placed, he
found that a quantity of brownish matter, like dust, remained at the
bottom. Subjected to the microscope this proved to be a host of
animated creatures in quick and varied motion ; each was of an oval
form, ciliated, actively moving, like the planulae. Some of these,
after a period of ten or twelve days, become developed into stationary
hydr^e.f

Such is the nature of the full and satisfactory evidence on which
the main facts of the generation of the Medusae are established. In
comparing different stages of the very interesting development of
the Cyancea aurita to Infusories and Polypes, it must be under-
stood that such comparisons are warranted only by a similarity of
outward form and of the instruments of locomotion and prehension.
The essential internal organisation of the persistent lower forms of
the Zoophyta is wanting in the transitory states of the higher ones.
A progress through the inferior groups is sketched out, but no
actual transmutation of species is effected. The young Medusa,
before it attains its destined condition of maturity, successively re-

* CLIL t CIX. vol. i. r- 103.

188

LECTURE IX.

sembles, but never becomes, a Polygastrian, a Rotifer, a Hydrozoon
and an Anthozoon.

The Cyancea aurita is, however, but the representative of one
of the three leading divisions of the remarkable animals grouped
together under the name of Acalephce. With regard to the develop-
ment of the ciliograde and physograde species, scarcely anything
connected or precise is at present known. The Medical Officer
who may be destined for foreign service, and to whom the study
of Nature offers any charm, could hardly contribute observations
more valuable to natural history than such as he might be able to
make on the generation and development of the Pelagic Acalephse.

Summary of the Orders and Families of the

Class ACALEPH^.
Free swimming marine animals of a gelatinous or membranous
tissue with thread-cells. Digestive cavities or canals adherent
to the surrounding tissues, and communicating with a more or less
ramified chylaqueous system. Most are dioecious, and pass by
metagenesis through the forms of the monad and the polype, before
acquiring the sexual acalephoid character.

Order PULMOGRADA. (Medusse.)
Body discoid, with a marginal velum, and a central inferior
mouth, usually prolonged into a more or less complex proboscis.
Locomotion by rythmical contractions of the disc. Sexes distinct.
Suborder Gtmnophthal:mata. (Bare-eyed Medusae.)
Cysticles unprotected : Chylaqueous canals simple, or, if ramified,
not anastomotic. Gemmiparous. (Some are probably larvce.)

Families Sarsiidje. Chylaqueous canals simple, four : ovaries

in the substance of the proboscis.
Genera: Sarsia, Euphysay Steen-
strupia.

Geryoniid^. Chylaqueous canals simple, four: ovaries

beneath the disc. Genera Geryonia,
Thaumantias, Slabberia.

CiRCEiBJE. Chylaqueous canals simple, eight:

ovaries eight, beneath the disc.
Genus Circe.

^avoREiDJE. Chylaqueous canals simple, eight or

more : ovaries linear on the course
of the canals beneath the disc.
Genera Polyxenia, Stomotrachium,
j^quoria^ Phorciinia.

ACALEPH^.

1S9

Families Oceanidje. Chylaqueous canals simple : ovaries

convoluted, and lining the peduncu-
lated stomach. Genera Oceanea,
Saphenia, Turris, Cytaeis.
WiLLsiiBM. Chylaqueous canals branched. Genus

Willsia *, Berenix, Orythia.
Sub-order Steganophthalmata. (Clothed-eyed Medusas.)
Cy slides protected by complicated coverings: Chylaqueous catials
canals branched and anastomotic. No gemmation.
Families Bhizostomatid.^. Mouths numerous on the branches and

borders of a ramified proboscis. Chy-
laqueous canals without outlets. Ge-
nera Bhizosfoma, Cephea, Cassio-
pcea.
3IoNOSTOMATiDm. Mouth single : Chylaqueous canals, (in
some) with distinct outlets. Genera
Phacellophora, Cyancea, Pelagia,
Chrysaoro, Aurelia.

Order CILIOGRADA.
Body spheroidal, oblong, or lobated, rarely lamelliform. Locomo-
tion by longitudinal bands of cilia. Sexes, in some, combined.
Families Behoibje. Genera Beroe, Lesueuria, Medea, Cy-

dippe, Pleurobrachia.
Genera Mnemia, Eucharis, Janira,

Alcinoe, Bolena.
Genera Callianira.
Genera Ocyroe, Cestum.

Mnemeidje.

Callianiridm.
Cestid^,

Order PHYSOGRADA.

Body, floated by air-cells. Locomotion by parts exposed to and
acted upon by the winds. Nutrition by numerous suctorial tubes.
Families Diphyidm. Genera Diphyes, Ersma.

pHYsopHORii)^. Genera Physophora, Stephanomia.

Physalid.e. Genera Physalia.

Velellidje. Genera Velella, Bataria, Porpita,

* CXL VII. p. 1 7.

190 LECTURE X.

LECTUEE X.

ECHINODERMATA.*

The soft and gelatinous Radiaries have often baffled the anatomist
by the seeming simplicity and uniformity of their texture ; the
harder, spine-clad, or Echinodermal species, perplex the most patient
and persevering dissector by the extreme complexity and diversity of
their constituent parts.

This class of animals, the organisation of which will be explained
in the present Lecture, includes species in which the form is most
strictly or typically radiate : in it, also, the Zoophyta of Cuvier
attain their highest conditions of organisation. With a radiated
filamentary system of nerves is combined not only a distinct ab-
dominal cavity with an alimentary canal suspended therein by a
vascular mesentery, and having a distinct anal outlet, but there are
distinct vascular and chylaqueous systems together with a large
and well-defined respiratory organ. This organ, however, may
be regarded as the exceptional condition of the radiated type of
structure, and is found only in the highest and aberrant forms of the
present class, which indicate the transition from the Echinoderms
to the Annelides. At the opposite extreme of the class, the digestive
sac {fig- 93, a), though suspended freely in an abdominal cavity, has
yet but one aperture common to the reception of food and the
ejection of excrement. These anenterous Echinoderms (^Ophiuridce,
Luidea^ Asterias proper, Astropecten,) belong to the order Asteroidea\y
in which the radiated form is most complete and general, whence the
species have received the common appellation of *^ star-fishes," and
" sea-stars."

The almost extinct order Crmoidea, in which the radiated body is
supported on a jointed and rooted stem, is connected with the order
Asteroidea by the genus Comatida, wliich in its last stage becomes
free.

In certain starfishes {Asteroidea) we trace a shortening, flattening,
and expansion of the rays, until the body assumes a pentangular
discoid form.

In the next order {Echinoidca), the angles disappear, and the disc
expands until a spheroid or globular form is obtained, which charac-

* ex^'os a hedge-hog, Icpjia skin.

f See the " Sumraaiy " at the conchision of the Lecture, for the characters of this
and other orders of the class.

ECUINODERMATA.

191

terises the Echinoderms commonly called " Sea-urchins," and Eckinoi
by the Greeks.

The Echinoderms of the order Holothurioidea may be described as
being constituted by a softening of the calcareous skin of the spheroidal
species, and by the reduction of the earthy matter to a greater or
less number of reticulate calcareous corpuscles, the globe being then
drawn out by the two opposite poles into an elongated cylindrical
form. These vermiform Echinoderms seem to lead, by the concluding
order Sipunculoidea^ to the true worms, which stand on the lowest
step of the Articulate division of the Animal Kingdom.

The name Echinodermata has been applied to these diversified
forms of the higher organised Zoophytes of Cuvier, because in many
of the species the integument is defended by spines : they, however,
possess, and are associated together by, another and more general
tegumentary character ; the skin is perforated in most of the species
by minute foramina, through which a multitude of small tubes or
hollow suctorial tentacles ("^ tube-feet') can be protruded and retracted,
and these constitute the common organs of adhesion and locomotion
in the Echinoderms.

192 LECTURE X.

In the aberrant Sipimculoidea the tube-feet are wanting, together
with the calcareous corpuscles, the worm-like form and annulation
of the integument are more decided, but the chylaqueous fluid con-
tinues to be agitated in the abdominal cavity by the cilia of the lining
membrane.

Before commencing the demonstration of the anatomy of the
Asferoidea, I may point out the chief characters of the allied order
Crinoidea, in which the radiated disc is fixed by a long jointed
calcareous stem to some foreign body, as they are shown in the
existing species, called Pentacrinus Caput- Mediisce, the type of a
very numerous assemblage of analogous pedunculated star-fishes,
which existed in countless myriads during some of the ancient
(secondary) periods of geology. Those species in which the stem is
cirri^erous and pentagonal, as in the recent form, are called "Penta-
crinites:" those in which it is rounded, and seems to have been
devoid of cirri, are called " Encrinites." Both kinds have received
the common name of " stone-lilies." Their remains sometimes con-
stitute extensive tracts of marble-limestone. The Melocrines are
more especially the crinoid prototypes of the StelleridcB.

The stem of a stone-lily is composed of numerous joints or segments
having a central aperture, which, when separated, are called " wheel-
stones," or " entrochi : " casts of their cavity remaining after the
calcareous wall have been dissolved away constitute the " screw-
stones " of the Derbyshire chert, and other transition limestones.
The jointed column supports at its summit a series of plates forming
a cup-like body, containing the viscera, and from the margin of the
cup proceed five jointed arms, which radiate and divide into delicate
tentacula. The upper side of the arms support numerous short
jointed cirri or pinnules. Groups of five long and slender cirri
radiate at nearly equidistant points from the stem of the recent
species of Pentacrinus. Both the arms and pinnules are grooved
along their ventral side, which groove is bridged over by a membrane
called "perisome."

The form of star-fish to which the radiated capital of the crinoideal
column bears most resemblance is that which is presented by the
species of Comatula, the ova of which have been discovered by Dr.
V. Thompson* to pass through a pedunculated pentacrinite state,
before their final metamorphosis into a free star-fish. In the con-
dition of their digestive system the Pentacrinites and Comatula3
correspond with the fettered Bryozoa among the polypes. The free
Comatula is a step in advance, and manifests its afiinity to the

* CLVIII. p. 295.

ECHINODERMATA.

193

Section of ray of Asterias rubcns, showing arrangement of
calcareous pieces.

gelatinous Radiaria by its mode of swimming : the movements of
its pinnate arms exactly resemble the alternating stroke given by the
Medusa to the liquid element, and with the same effect of raising the
animal from the bottom, and propelling it back foremost.

The rays of the ordinary star-fishes are not cirrigerous or bifur-
cated : their soft ex-
ternal integument is
supported by a tough
coriaceous membrane,
strengthened by calca-
reous matter {Jig' 94. )>
disposed in a coarsely
reticulate form upon the
dorsal and lateral as-
pects of the radiated
body, and arranged in
series of more compact and regularly-formed transverse pieces, a, by
which bound each side of a longitudinal furrow, extending along the
under surface of each ray from its attached to its free extremity.
The sides of this groove are perforated by alternating rows of minute
fissures, and external to these are situated the largest and most
numerous spines.

The tube-feet are protruded, in two {Ast. aurantiacd) or four {Ast.
rubens,Jig. 95 c, c) rows, through the marginal pores of the furrows,
which are termed " ambulacra." These tube-feet have muscular pa-
rietes, and they communicate with internal vesicles, d, c?, full of fluid,
which form, in fact, the bases of the feet. By the contraction of the
parietes of the vesicle the fluid is injected into the tube-foot, c, c, and
protrudes and extends it : when the muscular parietes of the tube-foot
contract, the fluid is returned into the sac, and the tube-foot is short-
ened and retracted. The basal vesicles are in communication with,
and are supplied by, a system of vessels, i, small brown sacs, m, and
larger pendent pyriform sacculi, which are lodged in the central disc
or body of the star-fish, and surround the oral aperture, a.

There are other kinds of soft contractile appendages to the integu-
ment, some tufted, others of simple form ; but the tube-feet just de-
scribed are the most important organs for prehension and locomotion.
The tegumentary processes called " pedicellariae," which resemble
miniature pincers, will be more particularly described in connection
with the skeleton of the Echinus. In the star- fishes they are of the
kind called Pedicellarice forcipatcB and Pedicellarice valvulatcp.

Various are the forms of the calcareous parts which strengthen and
defend the skin of the star- fishes ; but in all the echinoderms in w^hich

o

194 LECTURE X.

the hardening earth is present, its ultimate arrangement is a fine
network, the microscopic meshes or areolce being more or less
circular.

In the genera Oreaster and Culcita the whole surface is beset with
tubercles and granules. In Asteropecten and Stellaster there are
moveable flat spines and marginal plates. In Solaster and Chcetaster
there are innumerable spines, the summits of which are beset with
Betas. The sides of the arms in Ophiocoma and Ophiomastix are
defended by smooth spines ; in Ophiothrix by bristled spines. In
Opliionyx there are moveable double hooks beneath the bristled spines.

The ultimate muscular fibres in the Asteroids are smooth. The
joints of the arms and pinnules of the Crinoids and Comatules are
moved by a pair of small muscles on their ventral aspect, antagonised
by elastic bands. The spaces between the joints of the skeleton of
the Asteroids are occupied by muscular fibres, which are antagonised
by the general elasticity of the integument. In the Crinoids the
margins of the ventral grooves extending from the mouth along the
soft perisome are beset with very delicate cylindrical muscular feet,
and the surface of each foot is beset with small clavate tentacules.
In the OphiuridcB at the sides of the arms there are poriferous plates,
out of which protrude cylindrical obtuse feet, covered by a quantity of
wart-like protuberances. In this family the rays are extremely
attenuated and elongated, and have no ambulacral grooves : nor is
the complicated mechanism of the ambulacral feet in the ordinary
star-fishes here needed, for the flexile and spinous rays can twine
round and seize other objects so as to perform directly the offices of
prehension and locomotion. The facility with which an Ophiura or
Luidia casts off a ray which may be touched, and even all the rays,
leaving only its central disc, when it is seized, is very surprising ; it is
consequently very difficult to preserve specimens of these genera
entire. To do this it is recommended to plunge them suddenly
into fresh water, when they instantly die in a state of the most rigid
extension.

According to Miiller there extends along the tentacular groove of
the perisome on the ventral side of the body of the Crinoids a nervous
chord, which forms a slight enlargement at the base of each pinnule, to
which a filament is sent. In the OphiuridcB the nervous chords are
lodged in a canal protected by the ventral plates of the arms. The
soft labial membranes, tentacles, and tubular feet seem adapted to a
delicate reception of impressions ; and so far as these may be felt by
the individual, and cause voluntary movements, such parts may be
regarded as organs of touch. The nervous system of the Asterias
(p. 14.,^^. 4.) consists of a slender white chord surrounding the

ECnTNODER:\rATA.

195

mouth {g) immediately exterior to the circukr chylaqueous vessel :
from this nervous riiioj three delicate filaments are sent off opposite

Section of Asteracanthion rubens, showing the tubular feet.

the base of each raj : the lateral filaments enter the discoid body :
the middle one is continued along the ambulacral groove, and swells,
according to Ehrenberg, into a small terminal ganglion, immediately
behind that bright-coloured speck at the extremity of the ray which
the same acute observer regards as a rudimental organ of vision (b).

This pigmental organ manifests itself at the earliest appearance of
the arms, when they form five marginal lobes of the discoid body of
the young star-fish, and give it the pentagonal form which is retained
throughout life in the A. discoidea.*

It is objected by the laborious Siebold that no dioptric apparatus
(keine deutliche lichtbrechende Korper) is connected with the pig-
ment-speck ; nor has any better reason been given for the visual
function of that speck than its relation to a subjacent mass of nervous
matter, the analogy of the accumulation of pigmental matter in the
choroid of true eyes, the position of the pigment-specks at the fore-
part of the body in Rotifers, Planarioe, Borlasiae, Leeches, &c., and the
obvious proof that such simple pigment-speck must absorb those rays

* CLXIV. p. 172.
o 2

196 LECTURE X.

of light, at least, on wliich its peculiar colour depends. The terminal
pigment-speck in most star-fishes is defended by a circle of moveable
spines, which on the visual hypothesis of the speck have been called
" eyelids." But, without regarding the subjoined facetious descrip-
tion by a witty contemporary, either " as giving additional weight to
their asserted claims to be regarded as true visual organs,"* or as
meriting the grave refutation with which it has been honoured by a
worthy matter-of-fact German anatomist +, we quote it simply as
indicative of the prevalent notion amongst sound naturalists of the
function of these problematical parts. Prof. E. Forbes, often baffled
by the suicidal powers of the star-fishes, liad taken special precau-
tions to obviate the consequences in regard to a rare " brittle-star ; "
and had provided a bucket of fresh water to receive and kill instan-
taneously any specimen that might be brought up by the dredge.
"As I expected, a Luidia came up — a most gorgeous specimen. As
it does not generally break up before it is raised above the surface of
the sea, cautiously and anxiously I sank my bucket to a level with
the dredge's mouth, and proceeded, in the most gentle manner, to
introduce Luidia to the purer element. Whether the cold element
was too much for him, or the sight of the bucket too terrific, I know
not, but in a moment he proceeded to dissolve his corporation, and at
every mesh of the dredge his fragments were seen escaping. In
despair I grasped at the largest, and brought up the extremity of an
arm, with its terminating eye, the spinous eyelid of which opened and
closed with something exceedingly like a wink of derision."

The mouth in the star-fishes is situated at the middle of the under
surface of the body : it is edentulous, and leads by a short wide
gullet into a large stomach {fig. 93, a), which, in the StelleridcB,
sends off a pair of sacculated ccecal appendages {bb) into each of the
rays, but is without intestine or anus in Ast. aurantiaca {Astero-
pecten). The small terminal pouches of these appendages appear to
secrete a substance subservient to chylification : two or more small
glandular sacs (cc) of a yellowish colour open into the bottom of the
stomach, and have been regarded as a rudimental form of liver. In
Asteracanthion, Asterogoiiiwn and Solaster, there is a short intestine
with an anal opening, opposite to the mouth ; and in these there are
inter-radial caeca, which in Asteracanthion rubens contain a brownish
fluid, in which uric acid has been detected. Each long sacculated

* CLXV. p. 253.

•j- " Die von Forbes (History of Star-fishes, p. 139.) mitgetheilte Erzalilung, wie
Luidia fragilissima cliireh freiwilliges Abtrennen der Arnie, mit spottisch blinzelnden
Augen ihren Verfolger anblickend, sich der Gefangenscliaft zu entziehen -Riisste, ist
recht anziehend zu lesen, kann aber natiirlich nichts iiber das Dasein von Augen
bei den Seesternen entschieden." XXIV. p. 88.

ECPIINODERMATA. 197

Caecum is suspended from the dorsal wall of the ray by a pair of
peritoneal folds {fig. 95, w, n\ which include a space communicating
with the central part of the body, at the root of the cceca : the csecal
area and appendages are shown in transverse section at g, g,fig. 95.*

The alimentary canal is lined by a ciliated epithelium. The
Crinoids use the delicate tentacles of their pinnules and arms to seize
their prey and bring it to the mouth ; the Asteroids use their
prehensile rays, or the ray-like prolongations of the body with the
suctorious feet, and also their pedicellari^, for the same purpose. As
the star-fishes feed on decaying portions of animal substance, they may
be gifted with the sense of smell. The lip in Comatula is simple ; in
Asterias it is beset with hard papillae, which extend along the angles
of the mouth ; in Ophiura the entering angles of the mouth are beset
with calcareous teeth, and there are soft tentacles in the intervening
chinks. The mouth in Ophiura is divided from the stomach by a cir-
cular sphincter : the sides of the stomach bulge out into, usually ten,
c£eca, which in Aster opliyto7i are subdivided into sacculi : but cnecal
appendages are not continued from the central stomach into the rays
of the Ophiura, which seem to be rather appendages to, than divisions
of, the body. In the Comatula the alimentary canal presents a higher
type of structure : there is a slightly convoluted intestinal canal
which terminates by a distinct tubular anus opening on the ventral
side of the disc, near the mouth.

Professor Tiedemann, in his celebrated monograph on the Echino-
derma'\, has successfully demonstrated a vascular system in all the
leading forms of that class. In the Asteracanthion rubens the vessels
which absorb the chyle from the digestive sac terminate, after a
series of reticulate anastomoses, in a circular trunk, which likewise
receives branches from the radiated c^ca. The venous circle com-
municates by means of a dilated tube {fig. 91, h), regarded as a
rudimental form of heart, with an arterial circle surrounding the
gullet, which lies internal to, and is distinct from, the chylaqueous
circular tube. The arterial circle sends off branches which diverge
to the rays and other parts of the body. The cardiac tube ascends
from the depression in the madreporic plate, and accompanies the
sand-canal, h, which opens into the chylaqueous ring. From this
annular vessel five chylaqueous canals diverge, and extend along the
ambulacral spaces, and supply the tubular feet. I have not been able
to trace any direct communication between the true vascular system
of the Asteinas and the system of chylaqueous canals, which, by their
connection with contractile pyriform diverticula, govern the supply of

* CLX. p. 36. t CLIX.

o 3

198 LECTURE X.

fluid to the vesicles at the base of the hollow tentacles protruded
through the ambulacral pores. Tiedemann and Sharpey * also agree
in rejecting the continuation of the chylaqueous or erectile system of
the feet from the intestinal vascular system. In the Crinoids a cordi-
form sac lies at the bottom of the cup-shaped body, from which vessels
diverge along the axial canal of the arms, pinnules, and cirri, and a
vessel descends into the spongious axis of the body-cavity and stem.
A chylaqueous canal, which runs immediately beneath the tentacular
furrow, conveys the fluid to the hollow feet : in the Comatula the
canal is divided by a medi-vertical septum. In the Ophiurid(E two
or four broad respiratory lamellce project from each of the five
inter-radial angles into the visceral interspace.

In some star-fishes there is a small membranous tube, filled with
calcareous particles, called by Tiedemann the sand-canal : its position
is indicated by the circular multiperforate prominence or nucleus
{Jig^ 95, z), on the dorsal aspect of the disc of the Asterias, near the
angle between two of the rays, which prominence resembles a minia-
ture brain- stone madrepore. In other Stelleridce a jointed calcareous
column {fig. 95, s\ is continued from the nucleus into the interior of
the body, and consists of minute hexagonal plates, which are united
into larger joints. The precise function of these appendages to the
nucleus is not yet understood. From the analogy of one of its modi-
fications with the jointed column of the crinoid star-fishes, it has
been suggested that it may be the analogue or remnant of that
column ; but, according to the observations of M. Sars, the Asterise
are not fixed animals in the young state. Dr. Sharpey has con-
jectured that it may serve as a filter in the admission of sea-water to
the tubular system of the ambulacral feet : and it unquestionably
relates to the chylaqueous system, of which it is a part distinguished
by the calcareous deposits superadded to the canal. The sand-canal
is adherent to the parietes of the body in the OphiuridcB and
EchinidcB as well in the Stelleridce : but the spot to which it adheres
in the Ophiuridce is imperforate. In the Holothuriadce it hangs
loose in the abdominal cavity. In the Asterophyton the madreporoid
nucleus is situated on the ventral aspect of the disc.

As the sea-water is freely admitted into the general cavity of the
body, and bathes all the viscera, their vascular surfaces thus stand
in the relation of a respiratory organ to the aerated medium, and they
are every where provided with vibratile cilia, which maintain the
currents of oxygenated fluid. f But with the sea-water is mingled a
kind of chyle-corpuscles, long since recognised by Erdl J, the forms of
which in difierent Echinoderms have been lately described by

* CLX. p. 35. t CLXT. X CLXII. p. 58.

ECHLNODERMATA. 199

Dr. Williams.* The water of the chylaqueous cavity of the abdomen
is introduced by the numerous contractile slender tubes which project
from the dorsal aspect of the body, and are perforated at their free
end : these tubes are covered both within and without by a ciliated
epithelium.

In the true star-fishes the organs of generation consist of groups
of ramified tubes (yfig. 93, d\ arranged in pairs in each ray, and
opening upon the calcareous circle which surrounds the mouth. In
the males these sacculi {^fig. 95, o, o,) are distended with a white
fluid abounding in spermatozoa : in the females they are laden with
ova of a bright yellow or orange colour, which distend the rays
during the breeding season. They are discharged by groups at dis-
tinct intervals of time, and are found in very different stages of de-
velopment in the same ovarium.

The generative products in the ventless star-fishes (e. g. Astero-
pecten) dehisce into the chylaqueous cavity and escape by the re-
spiratory tubes ; but in some of the species with a vent {Astera-
canthion rubens and Solasier papposus) there are two so-called
" laminae cribros^e " at each angle of the inter-radial space, where the
excretory ducts of the ovaria or testes open and expel their contents.
The five pairs of generative organs are restricted to the central disc
in the OphiuridcB, which part in the breeding season is distended
with the milky fluid of the testis in the male, and with the round
yellow eggs in the female. They are discharged by orifices on the
ventral surface. In the Ophiothrix fragilis each testis or ovarium
is coiled like a ram's horn, and is deeply cleft into many lobes. In
the ComatulcB and Pe7itacrini, the seminal or ovarian receptacles are
much more numerous, and are of smaller size : they occupy the inner
side of each of the pinnules, are covered by the soft perisome, and
discharge their contents by dehiscence.

Echinoidea. — The calcareous pieces entering into the composition
of the complex skeleton of the Echinus are those of the shell, of the
buccal apparatus called the " lantern," of the ambulacral tubes, and
of the pedicellarias.

All the Echini are admirable for the regular and beautiful pattern
in which, as in a tesselated pavement, the numerous calcareous pieces
composing their globular crust are arranged ; many of the species
are formidable from the size and form of the spines with which the
shell is beset. The component plates of the shell are divided into
several series, called oral, anal, genital, ocular, ambulacral, and inter-
ambulacral plates. The proper shell, one half of which is exposed
by removal of the spines y^fig- 96, is built up of the two latter kinds,

* CLXIII.
o 4

200 LECTURE X.

which constitute a hollow spheroid, having a large aperture at each
wy/i ,1^///. pole, where the first four kinds of

^,v^vj <ru:^^<j^// plates are situated, ihe ambula-

cral plates (a) are perforated for
the passage of the tubular feet, the
parallel rows of which intercept
and overshadow spaces compared
by Linnjeus to avenues or ambula-
cra ; these plates likewise support
spines. The interambulacral plates,
{i) which support a greater num-
^^^"""^' ber of the spines, are characterised

by more numerous tubercles, and are not perforated. Both kinds of
plates are of a pentagonal form, and are arranged each kind in five
alternate pairs of vertical rows. The plates of each pair are united
together by a zigzag suture, and increase in size as they approach
the equator of their living globe. These twenty series of ambulacra!
and interambulacral plates constitute the chief part of the spheroidal
skeleton of the Echinus. The large oral aperture is partly occupied
by the small irregular oral plates, which have no tubercles or spines,
and are suspended in the oral integument, from the middle of which
project the points of the five teeth. At the opposite aperture, imme-
diately surrounding the vent, are the small anal plates ; external to
these are the five genital or oviducal plates, so called because each
is perforated by the duct of an ovarium or testis ; the ocular plates
are wedged into the external interspaces of the genital plates, and
are pierced near the apex by a very minute pore, which lodges the
ocellus and its little nerve.

One of the genital plates is larger than the rest, and bears a
tubercle corresponding with the nucleus or madreporiform tubercle on
the back of the star-fish. M. Agassiz, assuming this plate to be at
the back part of the Echinus, showed that the other four genital
plates were in symmetrical pairs, and thus discovered the right and
left sides of the animal.

The calcareous constituent of the shell of the Echinus lividus has
the following chemical composition, according to the analysis of Pro-
fessor Brunner, quoted by Professor Valentin.*

Carbonate of lime - - 96-27

Sulphate of lime - - 1 '53

Carbonate of maofnesia - 0-93

100-00
* CLXVII.

ECniNODERMATA. " 201 .

The small anal plates are united together like the oral ones by an
extensile and contractile membrane. Both the internal and external
surface of the rest of the complicated shell is covered by a similar
organised membrane, which likewise extends through all the numer-
ous sutures of the shell. With this explanation of the general
structure of the crust of the Echinus we are in a condition to under-
stand the manner of its growth, which otherwise would be a difficult
physiological problem.

The Echinus maintains nearly the same spheroidal figure from its
earliest formation to full maturity ; and, notwithstanding that its soft
parts are almost entirely confined by a fragile and inflexible globular
crust, this is never shed and reproduced, like the shells of the crab
and lobster. At the same time the calcareous plates possess not more
power of inherent growth than do the crusts of the Crustacea. By the
subdivision of the hollow globe into many pieces, and the apposition
of a formative membrane to all their margins, addition is made to
the circumference of each component plate, and by the plan of their
arrangement the spheroidal shell gradually expands, with little change
in its figure and relative proportions.

The amount of change in the form of the shell, which difi'ers in
different species, depends upon the addition of new plates to the
ambulacral and interambulacral series. These are developed near
the oral and anal poles, but chiefly near the latter, where, in the
young Cidaris, for example, the plates are more loosely connected
together, and support incomplete spines. In the membrane con-
necting such plates may be seen small irregular pieces, without tu-
bercles or spines, w^hich grow by accretion to their margins, and then
have the tubercles developed upon their outer surface. The spines
are at first immoveable, and stand out like processes from the tuber-
cle ; the joint is not developed until after they have acquired a certain
size. The growth of the globe in the direction of its poles is chiefly
by the development of the new plates ; its expansion at the equator
is by the addition to the sutural margins of the old plates. In full
grown and aged specimens, especially of Scutella and Clypeaster, the
sutures become obliterated.

The spines of the Echini vary in form and relative size in different
genera ; in each the proximal extremity is adapted, by an excavation,
to one of the tubercles on the outer surface of the plate, to which it
is attached by a capsular ligament, and upon which it can be rotated
by muscular fibres external to the capsule. In the species of Cidaris,
where the spines are unusually large, an internal ligament extends
from a little pit upon the centre of the tubercle to the centre of the
articular cavity of the spine, analogous to the round ligament in the

202 LECTURE X.

hip joint. The spines grow by successive additions, through calcifi-
cation of that part of the common organised membranous covering
of the shell of the Echinus, which is attached to their base. The
varied areolar organisation of the spines affords beautiful microsco-
pical objects when viewed in thin transverse slices.

In the typical genera. Echinus and Cidaris, e. g. the ambulacral
pores extend from pole to pole ; but in Scutella and Rotula they are
confined to the dorsal aspect of the more flattened spheroid, where
they form a five-leaved rosette.

The tube-feet that issue from the ambulacral pores can be extended
beyond the longest spines in the Echinus Sphcera of our own coasts ;
they terminate in suckers, which appear to be highly sensitive, and
by which the Sea-urchin attaches itself to foreign bodies, and moves
along them with a rotatory course, with its mouth downwards, the
spines serving to balance and direct the progress of the animal. The
bases of the tube-feet communicate with the cavities of the internal
vesicles or branchiae (Jig. 98, g); their outward surface is ciliated.
The terminal sucker of the tube-foot is supported by a circle of five
or, sometimes, four reticulate calcareous plates, which intercept a
central foramen, and by a single delicate reticulated perforate plate on
the proximal side of the preceding group. The centre of the suctorial
disc is perforated by an aperture conducting to the interior of the
ambulacral tube-foot.

I have reserved the notice of another class of appendages to the
integument, not only of the Echini, but of the Asteriae, for this part
of my discourse, because they are most developed, most varied in
structure, and have been most minutely investigated in the species of
the globular family of Echinoderms. The appendages to which I
allude are called " pedicellarise," and consist of a dilated end or head,
usually prehensile, supported by a slender stem or pedicel. They
present different forms, which hold constant and determinate positions
in the crust of the Echinus : they seem at no season to be absent, and
must therefore form part of the integral organisation of the Echino-
derm. They have, however, been conjectured by some naturalists to
be parasitic animals ; by others to be the young of the Echini, to
which they are attached.

In the Ech. lividus, Professor Valentin, to whom we owe the most
minute descriptions of these bodies, divides them into gemmiform,
tridactyle, and snake-headed pedicellarise. They are all composed of
an internal calcareous axis, and a soft external tissue.

The gemmiform pedicellariae* are placed around the tubercles,

* PedicellaricE globifera, Muller.

ECHINODERMATA. 203

especially the largest ones : their pedicel is long and slender ; their
capital resembles the bud of a flower, defended by three sepals, the
apex of each of which is produced inwards in the form of two pairs
of long and slender teeth. The quadridentate sepaloid plates can be
divaricated and approximated, and constitute a very effective pre-
hensile instrument : they are highly irritable ; a needle introduced
into their grasp is instantly seized. The ciliated gemmule of any
parasitic coralline, which might settle about the base of a spine, and
there commence its growth, would be liable to be seized and uprooted
by the prehensile gemmiform pedicellariae, which are of microscopic
minuteness.

The tridactyle pedicellariae {Jig. 97, a) are of
larger size, are visible to the naked eye, and fit to
grapple with and dislodge young sedentary pa-
rasites of larger species, as Cirripeds and Con-
chifers. They are found more particularly around
the large tubercles of the interambulacral plates
which support the largest spines. Their capital
is longer, narrower, and more pointed than in
the gemmiform kind ; and the three pieces are
PediceiiariJE dcntated and close upon each other, like the blades

of pincers.
The "pedicellariae ophicephalas" are aggregated principally upon
the buccal membrane.

The pedicellarige of the star-fishes are diffused generally over the
surface, and form dense groups round the spines : they consist of a
slender contractile stem ; but the head resembles a forceps with two
blades (^fig. 97, b) : they are continually in motion, opening and
shutting their blades. They would wage as effective and serviceable
a war in defence of the integument of the Asterias against the
attacks of the host of parasites which the sea engenders as their
tridactyle analogues in the Echini may do. In some species of
Goniaster the pedicellarije resemble the vane of an arrow, and are so
numerous as to give a villous appearance to the integuments.

The muscular system of the Echinus, into the details of which the
limits of the present lecture forbid me to enter, includes the muscles
of the spines, those of the jaws or lantern, of the buccal membrane,
of the anus, of the ambulacral tubes, of the internal branchiae, and of
the pedicellariae. The muscles of the lantern and spines have their
ultimate filaments collected into primitive fibres or fascicles, which
are marked by transverse striae at regular distances as in the muscles
of insects.*

* CLXVIL p. 101.

204

LECTURE X.

Alim. canal of Echinus.

The digestive apparatus of the Echinus {Jig. 98.) consists of a

mouth armed with teeth, surrounded
by a muscular labial membrane, and
five pairs of pinnate tubular ten-
tacula, of an oesophagus and sto-
mach, and of an intestine suspended
by a mesentery to the interior of
the shell, and which, after perform-
ing one or two circumgyrations,
terminates by a distinct outlet op-
posite to the mouth. The outer
margin of the lip is fringed by a
circle of the ophicephalous pedi-
cellariae, visible to the naked eye.

The teeth (a) are five in number ;
they are calcareous, three sided
prisms, dense at the working apex,
(f, fig. 99.), with the inner edge
sharp and fit for cutting, and becoming softer at the root, ^, which
rises above the base of the socket, is bent inwards and downwards,
and is inclosed in a membrane. Each tooth is implanted in a larger
triangular pyramid (6, and /?., fig. 99.), two sides of which are
in close apposition with opposite sides of the adjoining pyramids,
and are transversely grooved like a file (/<, fig. 99.), so as to
operate upon the alimentary matters which have been divided by
the incisor plates, and which are thus minutely comminuted before
they pass into the membranous oesophagus. The adjacent sockets
are connected together by short muscular fibres (/^, fig. 99.). Ten
additional pieces contribute to form this apparatus, which has been
called " Aristotle's lantern." Five of these (z, fig. 99.) are placed

horizontally on the upper surface
of the lantern, occupying the basal
intervals of the pyramids h ; the
other live pieces, k, are placed
directly over the first, and are
longer and more slender, and bent
with the convexity upwards.

The secretion of some simple
salivary follicles assists in com-
pleting the mastication of the
food. These singular representa-
tives of molar and incisor teeth
and the entire pyramidal mass can be

Two sockets with teeth ; B. Single socket viewed
on the outside.

Echinus esculentus.

are moved upon each other

ECIIINODERMATA. 205

protruded and retracted by certain muscles, which have their fixed
points of attachment in five calcareous ridges and arches which project
from the inner surface of the plates near the margin of the oral vacancy
of the shell. These processes are short in Clypeaster, and obsolete in
Spatangus. For the particular description of these masticatory muscles,
which are classed under the following heads — 1. Musculi interarcuales,
s. comminutores ciborum, 2. Musculi arcuales, s. dilatores orificii den-
tium, 3. Musculi interpyramidales (sphincter oris), 4. Musculi trans-
versi, — I must refer to the Legons d^Anatomie Comparee of Cuvier
(CLXVIL), the Article by Professor Sharpey (CLX. j9. 38,/^. 17.),
and the monograph of Professor Valentin, already cited.

The pharynx occupies the cavity of the lantern, and is divided by five
longitudinal folds, most prominent at their commencement ; the small
salivary caeca are placed close to its continuation with the ossophagus,
from which it is separated by a marked constriction. A slender oesopha-
gus (c, Jig. 98.), conducts to the gastric or caecal portion of the
intestine {d) ; and that canal twice performs the circuit of the abdo-
minal cavity before its final termination. The vent, its membrane,
and the anal plates, have appropriate muscles for constriction and
dilatation. The intestine is generally found more or less loaded with
fine sand ; its surface and that of its mesentery is covered with a
rich vascular network, which conveys the nutrient fluid eliminated
from the organic particles swallowed with the sand, to a large vessel
or vein, which accompanies the intestine from the anus to the mouth,
where it terminates in the vascular circle around the oesophagus,
from which the arteries are given off for the supply of the whole
body.

In the Spatangus a moderately long csecum is developed from the
first coil of the intestine. In the Clypeaster there are several shorter
lateral caeca ; and both these and the convolutions of the heavily-laden
alimentary canal are supported by peritoneal lamellae from the inner
surface of the shell.

The sea-water is admitted into the peritoneal cavity, and its con-
stant renovation over the surface of the vascular membranes of the
Echinus is provided for by the same mechanism of vibratile cilia as
in the Asterias.

There are external as well as internal organs of respiration in the
Echinoids : the former are the short, pyramidal, branched or pinnate
hollow processes, attached by pairs to the oral extremities of the inter-
ambulacral areae, and consequently ten in number : their outer surface
is highly vibratile. The internal branchiae are the transversely ex-
tended hollow bases of the tube-feet, which are covered with so rich a
network of vessels that Valentin compares them with the lungs of

206 LECTURE X.

the salamander. The cliief office of these sacs, according to Tiede-
raann, is to protrude, by contracting upon their fluid contents, the
tube-feet, continued from them through the ambulacral pores ; but
as the terminal sucker of these feet is unquestionably perforated,
Valentin* rejects this explanation: he thinks the tube-feet imbibe
the sea-water by their terminal pore, and convey it to the internal
basal sac, for the oxygenation of the blood, circulating over its
parietes. The sea-water can be admitted into the interior of the
visceral cavity through the interspaces of the teeth : if it be actually
introduced by the tube-feet it must pass by exosmose through the
pores of the basal sacculi, which is contrary to analogy.

The external branchise are a more complicated form of respiratory
sac everted and extended ; they float in the external respiratory me-
dium, while the internal sacs receive it into their interior.

Cuvier, Tiedemann, and Delia Chiaje have given more or less ac-
curate descriptions, but conflicting explanations, of the vascular
system of the Echinus. There is no doubt that the fusiform dilated
contractile vesicle, situated near the oesophagus, and surrounded by a
double fold of the mesentery, is the central organ or heart. Its
cavity is subdivided by muscular walls. From its oral end a trunk
proceeds, which forms a circle around the oesophagus at the base of
the lantern, from which the vessels of that part proceed. A second
trunk is continued from the opposite end of the heart, in the opposite
direction, and forms a cerresponding circle around the anus. A
vessel called the intestinal artery runs along the concave margin of
the intestine ; another trunk called the intestinal vein accompanies
the outer or convex contour of the intestine, and receives many
branches from the membrane of the shell. The vascular circle round
the anus {^fig- 98, /), receiving the veins of the ovaria, sends off
five trunks which run in the interspaces of the bases of the tubular
feet, or internal branchise ; the capillaries of these branchiae return
into five other trunks, accompanying the preceding five along the
median interspace. One set must fulfil the ofiice of branchial
arteries, the other that of branchial veins. The blood is of a deep '
yellow colour ; the blood-cells are granular and irregular, but gene-
rally manifest a nucleus.

Prof. Valentin, after a minute and searching scrutiny into the
anatomy of the vascular system of the Echinus, is unable to deduce
from that alone the course of the circulation. The ascertained facts
will permit of two explanations. In the first and most probable mode

CLXVII. p. 85.

ECniNODERMATA. 207

the heart transmits arterial blood to the artery proceeding to the
lantern, and from its arterial ring to its soft parts, to the pharynx
and to the buccal membrane. From these parts the blood returns
into the venous ring of the lantern, and thence into the intestinal
vein, where, mingling with the venous blood from the intestine, it is
conveyed to the annular vessel of the rectum, which also receives the
venous blood of the ovaria. The blood thence passes into the five
trunks which represent the branchial arteries. These distribute the
blood over the internal gills, or bases of the tube-feet, where it
acquires the arterial character. Thus changed, the blood returns by
the branchial vein into the arterial ring of the anus, whence it is dis-
tributed in part to the ovaria, and the remainder by the intestinal
artery to regain the heart. In this view the vessel called by Tiede-
mann the intestinal artery performs the office of a vein.

According to the second explanation, the heart transmits the
arterial blood by the intestinal artery to the oesophagus, intestine,
and rectum, and then supplies the ovaria, and perhaps also the
membrane of the shell. The venous blood collected into the in-
testinal vein is poured into the anal venous ring, which receives the
ovarian veins, and distributes the blood through the five branchial
veins : these will disperse it over the branchial sacs, where it will be
oxidized. Thus changed, the. blood returns by the branchial vessels
towards the auricles, and would be continued by their apertures
into the vessel of the internal oblique ligament, w^ould then pass
along the pharynx, gain the arterial circle of the lantern, and re-enter
the heart by the vessel w^hich passes from the lantern to it.

The circular vessel of the chylaqueous system surrounds the gullet
at the base of the lantern external to the arterial circle, between it
and the nervous ring. With the chylaqueous ring are connected the
Polian vesicles and the sand-canal — here a membranous tube.
From the circular canal five vessels extend along the ambulacral
spaces to supply the system of tube-feet. The chylaqueous has no
connection with the proper vascular system.

The nervous system consists in the Echinidce^ as in the Asterias,
chiefly of a delicate chord surrounding the pharynx, immediately
external to the chylaqueous ring, and of five trunks extending along
the ambulacral interspaces. The pharyngeal ring is an equilateral
pentagon in the Echinus, and an oblong pentagon in the Spatangus.
In the Echinus the ambulacral nervous trunks are flattened, and may
be distinguished from the vessels by the connection of the latter with
the internal branchiae. Smaller nervous branches are sent ofi" from
each arch of the pentagon to the inter- pyramidal muscles and the
oesophagus. The ambulacral or branchial nerves diminish in size as

208 LECTURE X.

they proceed, supplying the internal branchice and the ambulacral
tube-feet ; they finally terminate by penetrating the pore of the ocular
plate to gain the base of the red ocellus.

The generative apparatus of the Echinus consists of five mem-
branous sacs {fig. 98. h^ h), the efferent ducts of which perforate
five plates, surrounding the anal plates, and thence called genital or
ovarian plates. This structure is common to both sexes, which are
in distinct individuals in the Echinoids, as in the Star-fishes. The
ovaria, when distended with the mature ova, which generally present
a bright orange colour, fill a great part of the cavity of the shell, and
resemble the ovaria or roe of fishes. They have at all periods con-
stituted a favourite article of food with the inhabitants of the
Mediterranean shores.

The ova consist of a vitelline membrane, a vitellus, the transparent
germinal vesicle, and its solid nucleus.

The spermatic corpuscles are elongated, oval, rounded anteriorly,
pointed behind. They abound in the opake milky fluid, distending
the five secerning sacculi at the breeding season.

In the multiplicity of the pieces of which the shell of the Echinus
is formed, we may discern, by the contrast wdiich it presents with the
bivalve and univalve characters of the shells of the MoUusca, the
same low vegetative condition of an external skeleton which is ex-
emplified by the frequent repetition of similar parts in the multiplied
mouths of the Polypi, the multiplied stomachs of the Polygastria, the
multiplied ovaria in the Tseniee, and the multiplied marsupia in the
Medusas. If we view the articulated moveable spines and the ex-
tensile and prehensile tubes in the light of primitive forms of
locomotive extremities, we shall see in their great numbers and
irrelative repetition an illustration of the same law.

Holothurioidea. The Holothuria, which is the highest organised
of the Echinoderms, may be compared, as has been already observed,
to an Echinus deprived of its spines, wdth its shell softened and
elongated by divarication of its poles. The coriaceous integument is
strengthened by scattered areolar calcareous concretions, and con-
tinues to be perforated by innumerable apertures, which give passage
to tubular feet of precisely the same structure as those in the sea-
urchins and star-fishes. These tube-feet are likewise in some species
of Holothurice disposed in five longitudinal ambulacral series ; in a
few species {Psolus Oken) they are confined to a sort of ventral
disc: in other species they are generally difi'used over the integu-
ment. The chief calcareous substances in this coriaceous integument
consist of a circle of osseous pieces, usually ten in number, and
homologous with the parts of the ^'lantern" in Echinus^ which

ECHINODERMATA.

209

partlj defends the nervous ring, and affords a firm attachment
to the branched retractile tentacles which surround the mouth.
These tentacles may be likened to a more complicated form of the
ordinary tube-feet of the body, each being connected at its base with
a long hollow sacculus, and being distended and protruded by the
injection of the fluid therein contained. In Synapta the oral circle
includes twelve plates, five of which are perforated for the passage
of the chylaqueous canals. The integument in this genus is beset
with small anchor-shaped spiculte, which are articulated to reticulate
calcareous plates in the skin.*

The alimentary canal of the Holothuria is closely analogous to
that of the Echinus; but its disposition is accommodated to the
vermiform character of the softer-skinned species : its anal termina-
tion dilates into a cloaca, from which two long ramified C£eca are
continued ; but these admit only sea-water from the cloaca. In the
Sjnapta {Holothuria digitata, Montagu) the stomachal portion of the
alimentary canal is defined by its strong muscular parietes : there
are distinct layers of muscular fibres in certain parts of the
mesentery, which also has many peculiar slipper-shaped ciliary
organs -j^jjth of a line in length, its general surface not being
ciliated.

The alimentary canal in the Sipunculus\ differs from that in
the Holothuria in being reflected from the posterior extremity of
the body to terminate near the anterior end, without dilating into
a cloaca, and without the development of any anal caeca. The
intestine is longer and more convoluted in its course. The Sipun-
culus is a marine vermiform animal which burrows in sand, and,
although it has no tegumentary tube-feet nor organs of respira-
tion, is most closely allied to the Holothuria, and is therefore
retained in the class Echinoderma, in which it makes the nearest
approach to the true Vermes. The oral tentacula are replaced by a
kind of proboscis provided with a circular fimbriated lip, and two
contractile vesicles appear to be connected with the erection of the
fimbrige. The anterior position of the vent in the Sipunculus pre-
cludes the necessity of the worm quitting its retreat to evacuate : and
its safety seems to demand such a modification on account of its in-
tegument being less thick and coriaceous than in the Holothuria.

The rich vascular system of the Holothuria is most conspicuous
upon the intestine and mesentery, and has been beautifully illustrated
by the injections and drawings of Hunter. J Here, however, we
find the intestinal vessels carrying the nutrient fluid to those cloacal

* CLXVIII. Hefl. ii. p. 12. CLXIX. p. 35. f ^^^^V- No. 438. A.

X See Preps. Nos. 437, 438. 984., and X. pis. 3. and 49.

r

210

LECTURE X.

caeca which are transformed into a distinct respiratory organ, and
which presents the form of two long and beautiful arborescent tubes.
The complex circulating system in the Ilolothuria is in great part
represented in this diagram (^^. 100.) in connection with the equally
extensive system of chylaqueous sinuses and canals which regulate

the protrusion and
retraction of the nu-
merous tubular feet.
The most important
part of the circu-
lating system is the
trunk (e), which runs
along the free border
of the intestine, and
which is character-
ised by the short
and wide vessel (di-
vided at y^/) homo-
logous with the heart
in the Echinus, and
which connects the
corresponding ves-
sels of the two prin-
cipal folds of the
intestine. The in-
testinal capillaries
reunite, performing
at the same time the
office of absorbents
and conveying the
chyle to the great
intestinal vein (^),
from which proceed
the singular and
beautiful respiratory
plexuses (A, h),
w^hich are submit-
ted to the influence
of the sea water by
contact with the
branchial trees (w, 72).

Holothuria. (CLXVIT.) x Jii j

The aerated blood
is conveyed to a great mesenteric trunk (i, i), or branchial vein, from

i

ECIIINODERMATA. 211

which it is transmitted to the parietes of the body, and returns by
the cloaca to form the intestinal artery.

The ampulla Poliana {fig. 100. a\ which is double in some species,
is the homologue of the blind sacculi, which supply the circular chyla-
queous canal sending off the vessels to the bases of the feet in the
Asterias. It transmits its fluid principally to an annular reservoir
round the pharynx {h\ whence proceed the canals of the oral ten-
tacula (c) and those supplying the tubular tentacles or feet which
perforate the coriaceous integument. The latter canals {d, d) run
down in the interspaces of the pairs of muscles, and distribute trans-
verse branches to the bases of the tubes as they proceed.

Hunter * has figured certain glandular sacs opening into the stem
of the hollow branchi^ (?^, ^^), which may be regarded as a rudi-
mental form of an excretory or renal system.

The chief divisions of the nervous system consist of the pharyngeal
ring, which is closely applied against the inner side of the circle of
calcareous plates, and of the flattened chords which proceed, external
to the chylaqueous canals, along the groove or middle interspace in
each of the pairs of longitudinal muscles. These muscles are
attached anteriorly to the calcareous plates, are arranged in five
pairs in most Holothuriae, and traverse the interior of the integument
of the animal through its entire length. The integument is also
acted upon by transverse fibres which run external to the longitu-
dinal bands ; and such is the irritability of this muscular system,
that when the Holothuria is disturbed or captured it will sometimes
eject its sand-laden intestine and most of the other viscera by the
cloacal aperture, and very effectually unfit itself for anatomical in-
vestigations. The longitudinal muscular bands are more numerous
in the Sipunculus, and the stratum of circular fibres is more dis-
tinctly developed. The disposition of the nervous system accom-
panies this progress towards the annulose type, and only a single
ventral chord is sent off from the pharyngeal collar. f

The generative organs of the Holothurias constitute, as in other
Echinoderms, a very considerable part of the abdominal viscera in
the breeding season ; but they present a more complicated form :
they consist of a branched system of long and slender ccecal
tubes {fig' 100. r), opening externally by a single common canal,
whose orifice is near the mouth. The generative organ of the male
Holothuria resembles that of the female in structure ; but the sexes
may be readily recognised at the breeding season by the different
character of the contents of the tubes, which are white or colourless
in the male, whilst the ova present a reddish or yellowish hue.

* X. Vol. i. pi. 3. t Prep. No. 1292.

P 2

212 LECTURE X.

The generative organs of the Sipunculus are two straight, slender,
unbranched, blind tubes, symmetrically disposed, and terminating
each by a distinct orifice at the anterior third of the body.

With respect to the generation of the Echinodermata there seems
to be no instances of the mode by gemmation, and very few of
that by spontaneous fission. This, however, has been noticed by
Montagu in the Holothuria (Si/napta) digitatd, which separates
itself without violence into an indefinite number of pieces, apparently
by muscular constriction ; and he deems it probable that it thus
multiplies itself by natural division. He discovered this Echinoderm
on the coast of Devonshire.* In another species of Synapta ( S. Du-
verrKBo) M. Quatrefages states, that it, also, is in the habit of casting
off segments from the extremity of the body, and that the segments
so cast off begin to move, and ultimately acquire the form of the
parent animal. \ Professor Miiller has observed that, in Synapta
digitata, the head once separated, the fragments of the body, however
long they may be, do not break up again, but remain living and
moving for a day or more : but the piece with the head redivides as
often as it is irritated, and it is only by longitudinally bisecting the
head that this process can be finally stopped. | Whoever has ex-
amined the Holothuriae in a state of nature must have been struck
with their proneness to spontaneously eject the interior organs : Sir J.
G. Dalyell, after witnessing this phenomenon, found that they had the
power of reproducing the alimentary canal, and he observed another
process, in which the parts of the entire body were separated by
spontaneous fission. § The brittle-stars {Ophioco7yia) are remarkable
for the promptness with which they break themselves up into pieces
when laid hold of ; and equally so for the power they possess of re-
producing their arms. If a portion of the disc remain attached to a
separated arm, the entire individual may be reproduced. But this is
an exceptional mode of increase in the Echinoderms.

The ordinary mode is by the formation of ova and sperm, followed
by impregnation. As a general rule, these reproductive elements
are respectively developed in distinct individuals. But the genus
Synapta offers an exception : here the organs of generation are yellow
cords suspended from the pharynx and floating freely in the abdo-
minal cavity, where they exhibit vermicular movements. They are
covered with a ciliated epithelium : the thick walls of their cavity
consist externally of a muscular layer, next of a glandular layer in
which the sperm-cells and spermatozoa are developed, and the inner-
most layer has a cellulo-glandular structure in which the ova are

* CLXXX. p. 22. t CLXIX. p. 63. % CLXX. p. 24. § CIX. vol. ii.

KCHIXODERMATA. 213

developed ; and thus is arranged the combination of male with female
parts, which w^e shall find not uncommon in the hermaphrodite
mollusks. In all other known Echinoderms, the male organs are
peculiar to one individual, and the female organs to another ; but the
organs are very much alike in both sexes, and, with the modifications
which have already been described, are, upon the whole, simple in
their structure.

With regard to the development of the typical star-fishes, we are
indebted for our first and chief information to Sars.* This con-
scientious observer found, in the month of March, great numbers of
a small kind of star-fish crouching under the rocks at low water, of
different forms, but generally with their disc forming a prominent
dome above them. The ova, as they become matured in this species,
assume a comparatively large size, break out of the ovisacs, and
escape by the genital apertures near the mouth. The ova are of a
bright red colour, and are received and incubated, as it were, in the
hollow of the dome-shaped disc ; and in them Sars traced almost
every stage in the development of the species. He commenced his
observations in the month of February, 1840, at Floroe, in Nor-
way, on the species called Echinaster sanguinolentus. This has ten
ovaria, usually whitish, then reddish, as the ova are matured. In
these the chorion is strong and elastic, the yolk finely granular;
there is no white or albumen. The nucleated germinal vesicle is
large and distinct, and usually escapes entire when the q^% is burst
under compression. The ovaria are grape-like bunches of pyriform
sacs, with ova of different sizes : they being progressively developed.
In each ovarium two or three eggs were as large as all the rest put
together. The thin, colourless chorion immediately invests the yolk,
which is blood-red and opaque in the big eggs : in the small ones it
is lighter coloured and clear, permitting the germinal vesicle and
nucleus to be seen. In March he found seven or eight large eggs in
each ovarium.

How they escape was not seen ; the genital pores were too small
to be clearly discerned. Tiedemann thinks the eggs escape by the
pores above the five dentated processes of the mouth, and Sars thinks
so likewise ; because he once, by pressure on the body of the star-
fish, saw a red slimy filament, like the yolk of squashed eggs, come
out of a little hole near the angle of each ray, above the mouth, and
because the ripe eggs are always at the upper or free end of the
ovarium, and not likely to traverse the stem or radius of the oviduct
which he deems a tendinous band. Most likely they fall into the

* CLXIV. and CLL p. 47., pi. 8.
!• 3

214 LECTURE X.

cavity of the body, and so reach the genital pores on the ventral
surface. The Echinaster cannot have these pores on the dorsal
surface (as Miiller describes in the Aster acanthion rubens and Solas-
ter papposus), because the ova would fall into the sea, and not into
the ventral concavity, into which they are received, as into a mar-
supium, and are hatched there. On the 17th March, Sars found the
star-fish strongly contracted, and the disc raised into a dome shape,
the mouth and its surrounding parts forming the pouch, in which the
ova are hatched, and the young remain some time. Some embryos
were one and a half line, others three-fourths of a line, in size : the
ova and the monadiform young are loose in the concavity ; but the
further developed young are attached by a special pedicle to the
walls of this improvised marsupium.

The impregnated eggs have the chorion separated from the yolk
or germ-mass by a clear fluid. In the excluded ova the germinal
vesicle had disappeared, and the yolk was seen in different stages of
division. On the 7tli March, at 9 a.m., the yolk was seen in two
hemispherical, not quite distinct parts. In the evening each of
these were similarly divided, forming four lobes. At ten the next
morning, each lobe had again divided, and thus eight spheroids were
seen. In the evening of the 8th all the surface of the germ-mass
resembled a mulberry. On the 17th March the ciliated embryos
were seen, oval, blood-red, swimming about the marsupial chamber.
They first develop two tubercles, then four tubercles, which are
ciliated, and they swim, rotifer-like, with these forwards. After-
wards the body becomes depressed. The next, which may be called
the pentacrinal or polype, stage, was noticed on the 3rd April, when
the embryo star-fishes presented an organ of adhesion or pedicle, well
developed ; it is short, cylindrical, with thick round ends ; four
shorter processes then bud out, and a fifth much smaller tubercle.

The smooth dorsal surface, and the ventral surface of the flattened
body, may be now recognised, with five double rows of small, clear
tubercles, radiating from the centre : these become the ambulacral
tentacles. The young attach themselves, like crinoids, by their
quadrifid pedicle to the side of the glass vessel into which they may
be put. When detached, they still can swim round the bottom of
the glass by the cilia covering the pedicle and body, with the pedicle
foremost, and the belly upwards. When turned with the back
upwards they lay still. The whole yolk is here converted into the
germ-mass, and then into the embryo.

On the 15th April, five corners began to grow out of the periphery
of the depressed body. Ambulacral tentacles protrude from the
tubercles. At the under surface and outer end of each of the arms

ECHINODERMATA.

215

or rays one sees a small, round tubercle, which is persistent, and,
from its constancy and early manifestation, important : it becomes
the so-called eye. The back is now convex, and raised clear from
the arms. The quadrifid attaching pedicle still remains in the inter-
space between two of the arms, more towards the ventral than the
dorsal surface.

On the 23rd of April the five arms were very distinct, the ambu-
lacral tentacles were longer, and now the young creeps by means of
them, and alters its position when turned on its back. The attaching
pedicle contracts, and becomes softer and more contractile. On May
the 1st it was reduced to two tubercles, and was more on the dorsal side,
at the angle between the two arms ; and the hitherto bilateral asteroid
now becomes the completely radiated animal ; the five arms lengthen,
their small spines grow, the ciliograde powers are lost, and the young
star-fishes creep away, and slowly acquire the mature dimensions.

In the larva of another species of star-fish, to which larva Miiller *
gave the name of Bipinnaria, the long oblique fissure lodging the
mouth is bordered by a ciliated fringe, and there is a distinct circular
band of cilia above, and in front of the oral fissure, the anterior
boundary of which is formed by the hind part of that band. The
intestine is short and straight. The anus opens on the ventral surface
of the body. The Bipinnaria grows to the length of an inch or
more, chiefly by the increase of the anterior part of the body, long
processes being developed from the ciliated fringe and band, which
form two fin-like expansions one above the other.

The next series of metamorphoses w^hich claim our attention are
those which Miiller has traced out in the genus Ophiura. In 1835,
this eminent physiologist and naturalist visited the coast at Heligoland,
accompanied by some of his pupils, and they occupied themselves in
investigating the minute forms of marine animal life. They met
with some singular forms, and the results of their researches were
communicated to the Academy of Sciences at Berlin. | Three minute
animals, about 1-4 or 1-2 line in diameter, were referred respectively
to the genera Mesotrocha, Vexillaria, and Pluteus. The first of these
afterwards proved to be the larva of a Nereis, the second of an
Ascidian, and the third of the Echinoderm in question.

The Pluteus is compared, in form, to an easel ; it is better adapted
than the larvas of the Asterias for observation, because it is more
transparent. It resembles the larvae of the ordinary star-fishes in
having an elongated form, traversed by a straight intestine with the
mouth at one extremity and the anus near the other, and in being
girt by a ciliated fringe ; but the fringe passes above the mouth and

* CLXXIII. p. 29. taf. vii., fig. 5—8. f CLXXI.

p 4

216 LECTURE X.

before tlie anus, completely encircling the body obliquely, and is con-
tinued upon the processes, all of which are developed in one direction,
in which they are divergent, and the creature is more plainly bilateral ;
the processes are also longer, and have no relation to fixation. The
body is conical and pointed behind, and branches into eight processes
in front ; these contain calcareous rods and spiculae, which also occur,
interlacing, on the upper part of the body ; the lateral processes are
the longest, and each process is provided with two ciliated borders,
which are prolongations or continuations of the encircling fringe.
The obtuse points of the body, and the ends of the processes, are
orange-coloured : the other parts are colourless and transparent.
These Plutei occur in great numbers in August and September, when
they are from one to two lines long : they swim freely, with the pro-
cesses turned forwards. One part of their truncated side is prolonged
into a single flat and wide process, which carries the mouth and
gullet : on the side of the hemispheric portion opposite to this is the
circular anus. The mouth and stomach are ciliated. A little con-
tractile movement of mouth and pharynx may be noticed ; but the
streams of nutriment are seen, by means of indigo, to be directed by
ciliary action towards the mouth. Two small ganglions are situated
below the mouth, from which nerve-filaments diverge. These larvae
are not luminous by night.

The first indication of the production of an Ophiura, within the
Pluteus, is the appearance at the sides of the stomach and pharynx,
or the granular germ-mass, of certain caecal winding tubes, with a
double contour: they soon surround the so-called stomach like a circle ;
they next project from the surface, like tubercles ; then the whole
takes on the form of a disc, with five short processes. The em-
bryonal ciliated arms, or rods, take no share in the formation of this
disc. Calcareous spiculfe begin to take a new arrangement on the
nascent disc and arms. The mouth of the Ophiura is a new forma-
tion ; it is at first round, and quite distinct from that of the Pluteus,
which disappears. Before the processes of the Pluteus disappear,
the tentacula of the arms of the Ophiura are developed. Short
processes, or pinnje, next shoot out on each side the base of the
elongating rays, or arms, and these processes move violently. The
remnant, or case, of the ciliograde Pluteus is absorbed or cast off,
and the young Ophiura is plainly manifested. The transparent gela-
tinous larval animal, from its general resemblance to the Bero'idce^
might be classed with the ciliograde acalephag, but for the appearance
of certain opaque lines of calcareous matter.

In regard to the next order, the Echinoidea, the observations of
Prof. Miiller are more full and remarkable. His attention was

ECHINODERMATA. 217

attracted by the circumstance of some of the minute Plutei differing
from others in certain proportions, in having three processes with cal-
careous rods developed from the hinder convexity of the larva, and
by the development of particular tubercles, richly beset with cilia.

y. Baer, who led the way in experimenting and observing the
artificially impregnated eggs of the Sea-urchins (Echinus), found
them to be first developed into a ciliated monadiform animalcule, like
that of the Medusa aurita. In the course of four days this had be
come metamorphosed into a minute transparent acalephoid creature
which he compares to a Beroe. Here his observations ceased, the
animals having perished on the fifth day.

In the autumn of 1845 Professor Miiller discovered in the sea at
Heligoland the transparent acalephoid animalcules which have been
mentioned, referable by this mode of motion to the "ciliograde"
order, one of which, from its singular form, somewhat resembling a
painter's easel, he described under the name of Pluteus paradoxus.
Returning in the following year to the same field of observation,
he pursued with admirable detail the change of this species, as
above described, into an Opiiiura (Brittle star-fish), and that of the
other kind of Pluteus into an Echinus.

The larva of the Echinus^ like that of the Ophiura, has a quadri-
lateral pyramidal body, of a colourless, transparent, or hyaline sub-
stance, dome-shaped behind, expanded and slightly excavated in
front, the corners of which are prolonged into straight slender legs,
strengthened by filiform rods of calcareous matter, reaching to the
summit of the dome : the mouth is prolonged from the middle of the
concave base into a four-sided proboscis, the angles of which are also
produced into slender processes shorter than the four outer legs.
Were the creature to stand upon these it would resemble a table-clock
case, and the proboscidiform mouth and appendages might swino- to
and fro like the pendulum. The larva is, however, a free-swimmino-
animalcule, and propels itself, with the base and processes forwards,
chiefly by means of strong cilia, grouped on two tubercles at the
sides of the dome, which are compared to epaulets : but it is also
provided with a fringe of cilia, girting the dome and continued upon
all the columns, up one side and down the other. The mouth is sur-
rounded by a distinct band of cilia : it is triangular and bounded
inferiorly by an oblique projecting lip. In the centre of the dome-
shaped body is a subspherical granular mass, apparently the remnant
of the primordial germ-mass, which Professor Miiller calls the
stomach, and which doubtless surrounds the cavity to which the
mouth and pharynx conduct.

The first evidence of the change to the Echinus is the formation

218 LECTURE X.

of a circular disc, like a clock-face, on one side of the granular mass :
five double lines, like pointers, radiate from the centre of this disc,
and their extremities expand into circles with a double outline.
These circles form the bases of as many hollow tentacles, like those
that traverse the ambulacral pores of the adult Echinus, but which
are here single, not in pairs. Opposite this disc there appear upon the
dome, on each side, two triradiate pedicellaria, which exhibit spon-
taneous motion, the arms of the pincers opening and shutting. The
disc progressively expands, extending over the cellular mass to which
it owes its origin, and developes tubercles, which push through the
transparent dome of the Pluteiis, and are transformed into spines and
tentacles, both of which, together with the pedicellariae, manifest
their characteristic motions and combine these seemingly voluntary
actions with the automatic continued vibrations of the ciliated
epaulets of the larva ; so that it can now both swim and creep : the
mouth of the larva still remains in its first position and, like the oeso-
phagus, is in full action. By the time the disc has grown over half
the granular sphere little of the larva remains, except some of the
slender calcareous rods, and the mouth is obliterated : the perforated
oviducal plates are formed round the pentagonal space, as yet imper-
forate, in the centre of the original disc, determining the anal pole of
the developing spiny globe, close to which the cicatrix of the ruptured
pharynx of thePluteus is completed by the so-called "madreporiform
plate. The mouth of the Echinus is quite distinct and remote from
that of the Pluteus : it is first indicated in the centre of the naked
or unspined moiety of the granular sphere by the formation of the
hard summits of the five characteristic dental masses of the Echinus,
The spines, which soon acquire a considerable length, contain a cal-
careous framework. When the latter is perfectly developed, it forms
a hexagonal prism placed within tlie cylindrical skin of the spine,
which consists of a regular calcareous lattice-work, terminating at
the extremity in minute teeth. The horizontal arrangement of the
axial network of the spine is radiate. Before the framev/ork of the
spine is thus far developed, when it first appears, it has exactly the
form of a candelabrum. The basis of the framework of the spine is
thus a star with six rays, from the centre of which there arises a
simple axis, which immediately subdivides into other branches which
subsequently re-unite. The segments of the delicate nascent shell of
the Echinus growing into tentacles and spines cannot be considered
as the subsequent plates of the shell, but as the foundations of the ten-
tacles and spines. The outer skeleton is at length completed by the
progressive extension of the " ambulacral " and " interambulacral,"
or spine-bearing plates, and by the less regular " oral " plates.

i

ECHINODERMATA. 2 1 9

Thus the Echinus is completed, and becomes either a male by the
development of testes, or a female by that of ovaria. The ova are
impregnated, and develope the monadiform embryo : this is probably
metamorphosed into the beroiform Pluteus, which produces, by
" metagenesis," rather than by " metamorphosis," the young Echinus^
which completes the cycle by growing into the oviparous adult.*

In so defining the nature of this process in the work above cited,
I wished to express the fact, subsequently recognised by an able com-
mentator on Miiller's original and admirable observations f, viz., that
the new or echinoid structure throws off a large part of the pluteal
larva in and from which it was developed.

In the metamorphoses of the Holothurice the nascent mature form
unites with the larval one, no part of the latter being thrown off.
The larva of the Holothurice is bean-shaped, convex dorsad, concave
ventrad. An irregular transverse fissure answers to the hilum of the
bean, and in this the mouth is placed. The margins of the fissure
are edged by a ciliated fringe exactly similar to that of the Pluteus.
The anus opens on the ventral surface of the larva, behind the fringe,
which forms a continuous circle, the anterior part of which is bent
back to form the anterior margin of the fissure in which the mouth
lies. In the course of its growth the margins of the larva and the
corresponding parts of the fringe are thrown into numerous lateral
processes, which give it a scolloped appearance. A portion of the
dorsal integument of the larva is inverted towards the stomach, as a
tube terminated by an enlarged globular extremity, whose cavity
communicates with the exterior and is ciliated internally. The
vesicle, which terminates this tube, now sends forth processes, form-
ing a "rosette," which lies close upon the stomach. The rosette
becomes the circular canal of the chylaqueous system, from which
caeca are given oiF anteriorly to form the tentacles, posteriorly to form
the chylaqueous canals. The former mouth of the larva is obliterated,
and a new and permanent one is formed in the centre of the circular
canal and its tentacular appendages. In the meanwhile the
Polian vesicles are developed from the circular canal, and a deposit
of calcareous matter takes place round a portion of the tubular canal,
from whose globular extremity the chylaqueous system has been
formed. That portion of the tubular canal which lies between the
dorsal parietes and the calcareous deposit dies away, and the re-
mainder hangs freely from the circular canal as the "sand canal."

The rose-coloured ova of the Sipunculus niidus are found in vast
numbers in the breeding season floating in the chylaqueous fluid of

* XXX. p. 22. t CLXXVII. p. 9.

220 LECTURE X.

the abdominal cavity. The males show in the same fluid a like
abundance of subdepressed roundish heaps of aggregated vesicles or
cells full of granular matter. These are the formative cells of the
spermatozoa : they continue in this undeveloped state all the winter,
but in the early spring the surface of the granular masses begins
to be beset with minute filaments, and in the middle of April the
liberated spermatozoa abound in the chylaqueous fluid.

The chorion of the mature ova is uneven, and its surface is beset
with oblong nucleated cells: the yolk is inclosed by a firm mem-
brana vitelli, with a facetted surface, like the cornea of insects : it is
divided by some limpid fluid from the chorion. The yolk is minutely
granular, and contains a clear germinal vesicle with a solid nucleus.
The embryo, when developed, carries out with it part of the peculiarly
facetted vitelline membrane, of which it afterwards disembarrasses
itself. The broad semicircular head of the larva supports a pair of
pigment- or eye-specks, behind which it is encircled by a ciliated band.
The alimentary canal floats in an abdominal cavity : the pharynx is
divided by a constriction from the capacious stomach : a short and
narrow intestine is twice bent, its last fold returning to terminate on
the dorsal surface of the body, and thus early indicating the charac-
teristic position of the vent in the adult. The two blind sacs are
short and wide, and open on the sides of the ventral surface of the
abdomen. There is a pair of small spherical glands beneath the
pharynx, with a common duct which opens just in advance of the
ciliated band. A pair of retractor muscles proceed from both the
dorsal and ventral aspects, to be inserted into the band for its re-
traction, and five or six more feebly developed transverse bands for
the constriction and elongation of the body may be discerned.*

Thus it appears that, diversified as are the mature forms of the
Echinodermata, each begins its free and locomotive existence as an
oval ciliated larva, like a polygastric animalcule: the variations in
the subsequent metamorphoses are thus summed up by Professor
Miiller : —

" i; — The change of the bilateral larva into the Echinoderm takes
place when the larva yet remains an embryo, and is wholly covered
by cilia, without a ciliated fringe. A part of the body of the larva
takes on the form of the echinoderm : the rest is absorbed by the
latter. (A part of the StelleridcB, e. g., Eclibiaster, Asteracanthion,)

" 2. — The change of the bilateral larva into the Echinoderm takes
place when the larva is perfectly organised ; that is, possesses
digestive organs and a ciliated fringe. The Echinoderm is con-

* CLXVIII.

ECHINODERMATA. 221

structed within the Pluteus, like a picture upon its canvas, or a
piece of embroidery in its frame, and then takes up into itself the
digestive organs of the larva. Hereupon the rest of the larva dis-
appears {Ophiuray Echinus), or is thrown off (Sipinn aria),

" 3. — The larva changes twice. The first time it passes out of the
bilateral type with the lateral ciliated fringe into the radial type, and
receives, instead of the previous ciliated fringe, new locomotive larval
organs, the ciliated rings. Out of this pupa condition the echinoderm
is developed without any part being cast olF. (Holothuria and some
Sielleridce)."*

Prof. Mliller, whilst prosecuting his researches into the develop-
ment of the soft vermiform species of Echinodermata, at Trieste, in
August, 1851, was further rewarded by the discovery of a very
singular phenomenon. In upwards of seventy instances he found in
the Synapta digitata a tube, one half green, the other half yellow,
and in more than twenty instances this tube was organically con-
nected by both ends with the Synapta, — viz. to the head by its
yellow half, where the tube opens externally, and to the intestine by
its green half, which contains an intus-suscepted portion like the in-
verted finger of a glove. The vessel which runs along the free side
of the intestine gives off a branch which surrounds the open end of
the intus-susception. Where the sac is embraced by the vessel it is
enlarged into a sort of knob, from the middle of which the involuted
portion passes into the interior of the sac. The place of attachment is
a short way behind the muscular stomach. Sometimes there are two
or three such tubes so attached one behind the other : their outer sur-
face is not ciliated, like the ordinary branched ovarian tubes of the
Synapta : they exhibit slow vermicular motions executed by a
muscular coat consisting of transverse and longitudinal fibres ; the
inner surface, save at the green portion^ presents a lively ciliary
motion, and in this ciliated part the sperm-sacs and ovarium lie free.
The ovarium is a closed tubular capsule, ciliated upon its whole outer
surface : it contains orange-coloured ova, attached to short branches
from a central stem : each ovum consists of a yolk, and a germinal
vesicle ^^th of a line in diameter : when fully developed the ovarian
tubule is rent, and the ova escape into the common tube. The sperm
sacs are from eight to eighteen in number, and lie free in a rather
wide portion of the common tube : they are lined by a layer of cells,
and are filled with Spermatozoa. These are liberated by solution of
their formative sacs, and impregnate the similarly free ova. The
progressive geometric fission of the yolk follows : a ciliated embryo

* CLXXIV. p. 33.

222 LECTURE X.

is developed, which afterwards acquires a shell, about y\3th of a line
in diameter, and effervescing with acids : a discoid foot, like that of
a gastropod, is formed, which supports an operculum ; and a respira-
tory cavity is established like that of aPectinibranchian : in short, an
unmistakeable young univalve mollusk is the result of the develop-
ment of the impregnated ova in the tubular sac — hence called
"moUuskigerous" — which Prof. Miiller discovered in so many
specimens of the Synapta.

In two cases the moUuskigerous sac was found in specimens which
also possessed the ordinary generative organs of the Synapta, and this
coincidence might have been more common had not the specimens
brought for examination consisted only of those fragments of the
body which result from the usual spontaneous transverse fission which
follows the capture of this Holothurioid. The shell of the embryo so
developed bears most resemblance to that of the Natica, and it re-
mains to be determined, therefore, how the Mediterranean species of
that genus propagate and are developed.

The analogies that offer the most probable explanation of the occur-
rence of a moUuskigerous sac in an Echinoderm also possessing the
ordinary generative organs of its class, are such instances of parasi-
tism, for the purposes of development, as occur in the lymneus in-
fested by the cercarial larvse of a distoma, in the bee which hatches
the strepsipterous larv£B, and in the living caterpillar which is made
the similar nursery of the ichneumons.

We have here, therefore, probably a generic phenomenon, which
relates more immediately to the Gasteropoda than to the Eclimo-
derinata, and I shall return to the latter with a few concluding words
on the singular metamorphosis of the Comatulce. The ovicapsules
of this genus, which are developed in each of the pinnse of the long
and branched rays, at least as far as the fifteenth or twentieth pair,
become distended with ova about the month of July, when they escape
by a round aperture, but adhere together for a while, in a cluster of
about one hundred. They have been next observed dispersed, and
attached in the form of flattened oval discs to corallines and sea weed;
they then develope an obscurely jointed stem, ending in a clavate
head, which soon shows traces of the arms and mouth with its
tentacula. When the column presents a distinct division into twenty-
four joints, its expanded capital bears five bifurcating arms, which
are at first simple, but afterwards acquire the pinnte, and subsequently
the dorsal cirri. They further resemble small Comatulce, in having a
median mouth and a distinct lateral prominent vent, as well as in
their sulphur-coloured arms. These small Pentacrines attain the
height of about three-fourths of an inch, and were originally de-

ECHINODERMATA. 223

scribed by their discoverer*, to whom also we owe the subsequently
acquired knowledge of their metamorphoses, as a new species of
Pentacrmus (P. EuropcBus). These small Pentacrines entirely dis-
appear in September, at which season the young Comatulse make
their appearance : but the actual metamorphosis of the Pentacrine
into the Comatule has not yet been seen. The latter we know
enters life as an active ciliated larva; it next selects a suitable
situation for its sedentary pentacrinite stage of existence ; and
analogy plainly indicates that the crinoid capital, dropping from the
stalk by an act of transverse fission, becomes the Comatula, which
thus a second time assumes a free condition of existence under its
mature form. Nor are these metamorphoses a whit more extra-
ordinary than those of the gelatinous Medusae : nay, the parallel
would be extremly close, since we saw that the Cyancea entered life
as a ciliated locomotive infusory, then became a sedentary polype,
supported on a central stem, which finally resolved itself into freely
swimming aclephans by several transverse fissions. Other highly
interesting considerations arise out of the predominance of the
Crinoid forms over the Asteroids, and of the Cystideoids over the
Echinoids in the secondary and palaeozoic formations respectively ;
for the Crinoids would seem to be not the only representatives of the
larvae of actual species, if the bold conjecture of Prof. Ed. Forbes be
true, that the pectinated rhombs of the more ancient Cystideae answer
to the ciliated ''epaulettes" of the Pluteus\\ for in that case the
pedunculated Cystideee would, as old permanent forms of Echinus-
larvas, represent the Crinoids in the family Echinidae.

As we advance in our survey of the organization and metamor-
phoses of animals, we shall meet with many examples, in which the
embryonic forms and conditions of structure of existing species have
at former periods been persistent and common, and represented by
mature and procreative species, sometimes upon a gigantic scale.:):

Summary of the Orders and Families of the

Class ECHINODERMATA.

Marine, commonly free, repent animals, with the integument, in
most, perforated by erectile tubular tentacles, hardened by a reticulate
deposit of calcareous salts, and, in many, armed with spines. A vas-

* CLVIII. t CLXXEX. vol. ii. p. 184.

\ LXXXIV. (1843), p. 129. V. Baer rightly characterised the course of de-
velopment of an individual animal as " a passage from a more general to a more
special type." But, in substituting this mode of expressing the idea broached in
the text, the modifier of the phraseology seems scarcely justified in claiming that
idea as " particularly his own." See IV. (1851), p. viii.

224 LECTURE X.

cular system distinct from the chylaqueous and digestive systems ;
the latter in a distinct abdominal cavity ; in some a distinct respi-
ratory organ.

Order Crinoidea.
Body with ramified rays, supported temporarily or permanently on
a jointed calcareous stem. Alimentary canal with mouth and vent.
Sexual organs very numerous and distinct.

Family EncbinidjE. Body persistent on stem.

Genera Encrinus, Pentacrinus (most of the
species are extinct).
CoMATULiDM. Body liberated from stem in the adults.
Genera Comatula,

Order Asteroidea (Star-fishes).

Body radiate ; integument hardened by calcareous pieces, and
more or less armed with spines. No dental apparatus. Alimentary
canal symmetrical, and in some without a vent.

Family Ofhivribje. Genera, Astrophyton^ Ophionyx, Ophio-
thryx, Ophiomastyx^ Ophiocoma, Ophio-
lepis, Ophioderma.
Stelleridm. Genera, Luidia, Astropecten, Cteiiodisciis,
Archaster, Stellaster, Astrogonium, Ore-
asteVf Pteraster, Asterisciis^ Culcita,
Ophidiaster, Chcetaster, Solastery Echin-
astevy Aster acanthion.

Order Cystoidea.

Body spheroid, incased in a crust of inflexibly joined calcareous
pieces; and supported on a jointed stem.
(All the species are extinct.)

Order Echinoidea (Urchins).

Body spheroid or discoid, incased in a crust of inflexibly joined
calcareous plates, and armed with spines. Dental system complex,
forming a part called 'lantern.' Intestine convoluted, with a distinct
vent.

Family Clypeasterid^. Genera Clypeaster, Scutella, Ericope,

Botula, Lobophora, Echinocyamus^
Mellita, Echinanthus.
EcHiNiDM. Genera Echinus, Cidaris.

Spatangidje. Genus Spatangus.

ANNULATA. 225

Order Holothurioidea (Sea-cucumbers).

Bodi/ vermiform ; integument flexible, with scattered reticulate

calcareous corpuscles, and a rudimental " lantern." Intestinal canal

convoluted, vent terminal Respiratory organ, an anal ramified tube.

Tstmilj IIoLOTHUEiiD^. Genera Holothuria, Pentactes, Bohad-

schia, Cladolabes.
Synaptid^. Genera S7/?iapta, Chirodota.

Order Sipunculoipea.

Body vermiform; integument without calcareous corpuscles, and not
perforated by tubular tentacles. Intestinal canal convoluted, vent at
the fore part of the body. No respiratory organ.

Family Sipunculibm. Genera Sipunculus, Phascolosoma.
EcmuRiBM, Genera Echiurus. Thalassema.

LECTURE XL

ANNULATA.

In both the infusorial and entozoic classes the body assumes a more
perfect linear and bilateral form as the species advance in the scale
of organisation ; and we hare seen in the subjects of the preceding
discourse, that even the typical radiated class of the zoophytic
province conducts by the holothurian and sipuncular families to the
vermiform class of the articulated province, in which the vegetative
principle of development, by the frequent repetition of similar parts,
is still conspicuously manifested, but exercises its energies in a linear
direction, and forms successive segments from before backwards.
We find, in fact, at the lowest step of the great homogangliate series
of the Animal Kingdom an extensive group of vermiform animals,
some of which very closely resemble the trematode, and others the
nematoid, Entozoa, and all are devoid of jointed limbs : but they
possess a distinct circulating system of arteries and veins, and in
almost all the species the blood is red.* They have therefore been

* The first notice of this colour of the blood in an anellid I believe to be due
to Pallas : —

" Ibi trans cutem distincte apparet stria albicans — quam vena tequalis, rubra,
maximam partem sinisterior comitatur."

" Intestiuo prune longitudinahter exterius adnascitur ductus crassus, subflexuosus,

226

LECTURE XI.

called " red-blooded worms," " vers a sang rouge," and " anellides,"
by the French naturalists ; in Latin Aiinulata, from annulus, a little
ring, because the entire body of these worms is made up of a suc-
cession of segments like little rings.

The mind is not easily liberated from the sway of opinions that
have long been held as authoritative : although Cuvier recognised
the exaggerated importance of the zoological character derived by
Aristotle from the colour of the blood, yet the judgment of the great
modern reformer of zoology continued to be so far biassed by that cha-
racter, that, in his latest edition of the " Regne Animal," he continued
to place the anellids, on account of the colour of their circulating
fluid, at the head of the articulate series, above the crustaceans,
above the arachnidans, and above the insects, whose transitory larval
condition these apodal worms seem permanently to represent.

The body of an anellid is always long, soft, and subdivided into a
number of segments, for the most part closely resembling or identical
with each other. In many species the first segment is so slightly
modified as scarcely to deserve the name of head ; in others it is the
seat of higher senses and more varied functions, and is at once recog-
nisable as the cephalic segment.

In the lowest forms of the Annulata the locomotive instruments
are suctorial discs, and the alimentary canal adheres to the integument,
as in the Trematode worms ; but the suckers are always two in
number, and are terminal in position. The species next in order
have the alimentary canal less extensively attached, and have stiff"

hairs or minute hooks projecting from
each segment. In the higher Anellides
the alimentary canal is freely suspended
in an abdominal cavity, and most of
the species have on each side of the
body a long row of tufts of bristles, sup-
ported upon fleshy tubercles, which in-
dicate the rudiments of lateral and
symmetrical locomotive members (Jiff'
101 .) There are often two such organs,
Aphrodita. placed ouc («) abovc the other (b),

on each side of the segments of the
body. In some species the two setigerous tubercles are confluent,

ruberrimo liquore pleuus, qui mihi cordis sui trunci systematis yasculosi vice fungi
videtiu'."

" Vas rubrwn intestinalem tractum concomitans in hac Nereide (iV. conchilegd)
seque ac cylindraria inveni."

Anatome Nereidis Belgicse, in "Miscellanea Zoologica," v. pp. 128, 129. (1766.)

ANNULATA. 227

and in almost all there exists at the base of each a long soft cylin-
drical appendage (c). The bristles in the setigerous anellids are
their chief organs of locomotion, and at the same time their weapons
of attack and defence. They are generally sharp, or barbed, and
hard enough to readily penetrate the soft bodies which they strike.

The nervous system of the anellids presents a marked advance
beyond its condition in the white-blooded parasitic worms ; it consists
of a double median central chord or chain of small ganglions, ex-
tending from one end of the body to the other ; the two chords diverge
anteriorly to allow the passage of the oisophagus, and again unite
above that tube to form a distinct, though small, bilobed cephalic
ganglion or "brain."

Most of the anellids are provided with pigment- or eye-specks,
'* ocelli ; " and in many of them the head supports soft cylindrical
tentacles, which are obviously organs of touch, but differ from the
antennjB of insects in the absence of joints. In the first appearance
of these not yet well understood organs of sensation, which form so
remarkable and conspicuous a character and so important an endow-
ment of the higher articulate classes, we have again an interesting
illustration of the principle of vegetative repetition ; for every seti-
gerous tubercle in the anellids with cephalic feelers has a similar
organ of sensation : the distinction is merely local and nominal ; the
feelers on the first segment being called "antenna;" those on the
other segments " cirri."

The mouth is at the lower surface of the head, or at the anterior
extremity of the body in the acephalous anellids ; in some species it
is provided with a protractile proboscis and with lateral jaws in the
form of curved dentated horny plates: the alimentary canal is gene-
rally straight ; in some species simple, in others sacculated, or pro-
vided with a greater or less number of lateral ceecums : the anus is
situated above, or at, the posterior extremity of the body.

The degree of redness of the circulating fluid varies considerably; in
some species it is very pale; in one or two the fluid even presents a
greenish hue : it circulates in a closed and very complicated system
of vessels, of which the chief dorsal one is distinguished by its
undulatory pulsations ; and in some species the circulation is further
aided by contractile sinuses, called hearts.

All anellids have organs of respiration, adapted in a few species
for extracting oxygen directly from the atmosphere, and in the rest
of the class through the medium of water : in these the gills are
usually external, vary considerably in form and position, and form
the only part of the external surface which retains the ciliated
epithelium.

Q 2

228 LECTURE XI.

Such are the general anatomical characters of the class Annulata,
and such the progress each system of organs has made in the transit
from the Nematoneurous to the Homogangliate types. The anellids
are distributed into orders, according to obvious and easily recog-
nisable modifications of the locomotive and respiratory organs; vs^hich
characters fortunately coincide with the general conditions and
grades of their organisation, and are therefore natural ones. Dr.
Milne Edwards, the pupil of Cuvier who has devoted most attention
to the Vermes thus grouped together by his great master, divides
them into four orders.

The first is the Annulata suctoria^ and comprises the leeches,
which are provided with a suctorial disc at each extremity of the
body, and have neither bristles nor tuberculate feet.

The second order is the A?inulata terricola, which includes the
earth-worms ; these have neither tubercular feet, nor external gills,
nor suckers, but are provided with short stiff bristles fulfilling the
function of feet, and which, in fact, are the rudiments of such.

The third order is the Annulata tubicola, and includes all those
which are provided with setigerous feet and have the respiratory
organs at the anterior extremity of the body, whence they have also
been called Cephalo-brancJiiata. The anellids of this and the two
preceding orders can scarcely be said to have a distinct head.

The highest organised Annulata are also the most locomotive :
they have been called errantia by Dr. Edwards. In them, the re-
spiratory organs are most developed, and from their position,
Cuvier, who first defined the order, has denominated it Dorsi-
branchiata, the gills being attached to the sides of the body on the
dorsal aspect, along the middle part, or through the whole length of
the body. They are provided with setigerous processes for loco-
motion, and have always a distinct head. They are commonly known
by the name of Sea-centipedes, Sea-mice, or Nereids, from the
LinnjBan generic name Nereis, which is almost equivalent to the
present ordinal term.

The tubular sheaths and protractile bundles of bristles which
constitute the organs of locomotion in this order have been already
noticed in the general characters of the class. The integument is
naked, soft, vascular, and highly susceptible of impressions in all the
anellids. It consists of a delicate non-ciliating epidermis, and of a
moderately firm corium composed of obhquely crossing filaments.
In some earth-worms the skin is red, from the colour of its contained
or subjacent circulating fluids ; in leeches it is variegated by a layer
of pigment-cells ; in most anellids the epidermis reflects iridescent
tints, and in such it is readily detached from the cutis ; but it closely

ANNULATA. 229

adheres thereto in the Suctoria. In many Errantia the cutis deve-
lopes filiform and lamelliform processes, and the latter, in some
species {Aphroditce), are so large and numerous as to overlap one
another like scales. The hairs and bristles, already mentioned, are
also developed, in some species, e. g. Aphrodita aculeata, so abun-
dantly as to give it the mammalian character of a hairy investment,
whence it has been called by our fishermen the " sea-mouse." The
hairs of this beautiful anellid reflect brilliant iridescent hues.

In the tubicolar order the habitations are commonly formed of
foreign substances, as particles of sand or shells agglutinated together
by the mucous secretions of the worm, which is sometimes done with
a considerable degree of neatness and apparent skill, as in the Pecti-
narice and Terehellce. The Serpula secretes a calcareous tubular
shell, consisting of carbonate of lime and animal matter, like the
shells of Mollusks ; but differing in being quite external to the inte-
gument, and not organically attached to the animal, which can quit
and return to its tube. Most species of Serpulce^ as the Serp, con-
tortuplicatay which coats the shells of oysters and other bivalves with
its characteristic dwelling, have a pedunculated operculum for closing
the entry of the tube.

The organisation of the integument has been studied chiefly in
the naked Anellids. It consists, in the leech, of a strong, smooth,
whitish epiderm, and of a fibro-cellular corium divided into short
segments, and having many pigmental cells of a brown or greenish
colour, except in the intervals of the rings. The muscular fibres
liave a tendinous lustre : those of the outer layer are transverse ;
those of the next layer cross each other diagonally, and form a fine
regular reticulation : beneath these are the longitudinal fasciculi,
which form the most conspicuous stratum. There are also other
smaller muscular fasciculi in the under surface of the body, besides
those which specially regulate the action of the terminal suckers and
the dentated jaws i^fig. 102. H). The anterior
border of the mouth is produced on the dorsal
aspect, in the medicinal and some other leeches,
so as to form a kind of upper lip, which com-
bines with the rest of the muscular and verru-
cose border to form a sucker. In some sea-
leeches {Pojitobdella, Piscicola)t]ie oral sucker
is divided by a constriction or neck from the
Lggj,h. body. In Branchiobdella the pharynx is pro-

vided with a horny upper and under jaw. In
the genus Clepsine a protractile flexible tube, like a proboscis, can
be protruded from the bottom of the mouth. The mouth of the

Q 3

230

LECTURE XI.

104

Jaw and teeth.
Leech.

medicinal leech {Sanguisuga) {fig. 102.), and of Hcemopis, is tri-
angular, and is armed with three crescentic jaws
(a, a, a), presenting their sharp convex margin to-
wards the oral cavity, which margin is beset with
sixty small teeth {fig. 103.). It is by the action of
these little saws upon the tense in-
tegument seized by the labial sucker,
that the characteristic triradiate bite of
the leech is made.

The oesophagus {fig. 104. b) is short,
and terminates in a singularly compli-
cated stomach, divided by deep con-
strictions into eleven compartments,
the sides of which are produced into
C£ecal processes {c, c'), progressively,
though slightly, increasing in length to the tenth, and
disproportionately elongated in the eleventh compart-
ment. The first gastric chamber is the smallest. In
the eight postei'ior compartments the anterior part of
frf'^ each slightly expands to form a pair of small acces-

■■"^ - sory cceca. The middle part of the eleventh division

extends backwards, in the form of a small funnel-
shaped process, and opens into the commencement of
the slender intestinal canal {d, d) ; this is situated be-
tween the two last and longest gastric caeca (c^) ; it
terminates by a small anus (e) above the terminal
sucker.* This is the position of the vent in most
Suctoria ; but some sea-leeches {Piscicola) offer an
exception in the ventral position of the outlet upon the
last segment.

The modifications of the alimentary canal itself in
other genera are considerable. In Nephelis it is a
simple tube, gradually expanding towards the vent ; in
Branchiobdella the canal presents many circular con-
in Pontohdella it gives off a single pair of caeca near its
hinder third ; Hcemopis and Clepsi?ie present the same multiccecal
type of the canal as that which has been described and figured in
Scmguisvga.

There is a stratum of round whitish glandular corpuscles, beneath
the coats of the pharynx and cesophagus of the medicinal leech, which
represents the salivary system. A peculiar brown tissue extends

L^ech.

strictions

* See Preps. Nos. 442. 46C, 467, 468. 569. 595. A,

ANNULATA. 231

along the alimentary canal between the nervous chord and the mucous
glands, and also upon the dorsal aspect of the anterior part of the
cavity. It is composed of a congeries of elongated, convoluted, and
irregularly constricted follicles, which are united in groups by the
confluence of their ducts into a single slender excretory tube. These
tubes unite with those of other groups of the follicles, and pour a
secretion, analogous to bile, into the posterior divisions of the stomach
and into the intestine. The confluence of the hepatic ducts is very
remarkable and conspicuous when they lie upon the testes.*

The walls of the sacculated alimentary canal are connected with
the integument by a vascular tissue, like the corpus spongiosum,
mixed with many pigment cells. The chylaqueous fluid transuded
into this tissue is there taken up into the largely developed vascular
system.

Terricola. — The mouth is furnished in the earth-worm with a
short proboscis, but is without teeth : a long lobulated salivary glan-
dular mass surrounds the pharynx. The decaying parts of animals
and vegetables are swallowed with the soil, and conveyed by a short
and wide oesophagus to a muscular compartment of the digestive
canal, analogous to a gizzard. The oesophagus is sometimes dilated,
like a crop, above this part. The long and wide intestine is con-
tinued straight to the terminal vent, and is constricted in its course
by the transverse septa of the common cavity of the body ; but the
sacculi are not produced into creca.^f Morren % describes a long and
slender blind tube, which he calls the " typhlosole," as being attached
to one side of the inner surface of the gut, in which tube he supposes
the chyle to be strained off" from the coarse contents of the wider sur-
rounding canal. A muscular compartment of the alimentary canal
maybe distinguished in Nais proboscidea, but not in Lumbriculus or
EnchytrcBus. The latter worm has four pairs of clear vesicles, which
pour their secretion into the gullet.

Errantia. — In this order the pharynx is developed into a loose
and muscular cylinder, forming a kind of proboscis, provided with
special muscles for its protrusion and retraction, eversion and inver-
sion. It is short in Nereis, Eunice, and Peripatus ; longer in Gly-
cera, Phyllodoce^ and Polyno'e. In Arenicola, Chcetopferus, Aricia,
Phyllodoce, and Amphi7iome, the proboscis is unarmed : its everted
extremity is encircled by small papilla?. In Nereis, Lycastis, and
Peripatus, it is provided with a pair of strong, curved, horny jaws ;
and in other Errantia they are present in greater number : in Eunice,

♦ CLXXXV. Bd. ii. p. 260. f Prep. No. 595. B. % CCXII.

Q 4

232 LECTURE XI.

e. g., there are four on one side and three on the other side of the
protractile pharynx : in Lumhrinereis there are eight jaws, and in
Aglaura nine. These jaws are sharp-pointed and dentated on their
inner border, and, when the pharynx is everted, they project exter-
nally, and can be used as prehensile organs. The Tubicola are
edentulous.

The obliquity of the constrictions of the alimentary canal in the
Sahella pavoiiina* give it the appearance of being a long and narrow
tube disposed in a series of close spiral coils ; but it is merely saccu-
lated. In most other tubicolar anellids the intestine is less constricted
than in the Sabella ; and in Amphitrite it is uniform, irregularly con-
voluted, and loosely suspended in the abdominal cavity.

In the TerebellcB nebulosa and conchilega the wide and long oeso-
phagus is coated by a yellow glandular mass, and is separated from
the slightly sacculated yellow gastro-intestinal tube by an elongated
colourless gizzard. In the Hermella there is a short oval dilatation
or stomach between the oesophagus and intestine.

In the sand- or \ug-wovxn.(^Arenicold)ihQ gastro-intestinal canal {Jig»
106.) commences at the termination of the oesophagus (^)by a sudden
dilatation, into which two csecal glandular pouches (c) pour their
secretion : the rest of the canal is simple in its outward form ; but
its walls are thickened by a stratum of minute secerning cells (d),
which prepare a greenish-yellow fluid. The oesophagus can be
everted and protruded ; the sand is seized and swallowed as the worm
bores its way ; the organic particles are assimilated as the earthy
medium traverses the digestive canal, and it is finally rejected in the
form of the sand coils, which betray the retreats of the " lugs " on
the sea-strand.

In most of the Errantia there is no distinction between stomach
and intestine ; this runs straight to the terminal vent in Eunice and
Amphi7io7ne, as in Arenicola : in Cirratulus it takes a spiral course ;
and it is irregularly convoluted in Ammotrypane. In some Nereids
the canal is provided with lateral pouches, a pair of which, in Nereis
proper, open into the compartment of the canal which answers to the
stomach. The intestinal canal is lined by a ciliated epithelium in all
anellids. In the AphrodUa aculeata the part homologous with the
projectile proboscis of the Nereids is converted into a kind of gizzard,
by the thickening of the muscular coat. The alimentary canal, con-
tinued from its posterior extremity, bends forward at first for half
the length of the gizzard, a disposition which indicates the occasional
protrusion of this part. The canal then bends backwards, and is

* No. 441.

ANNULATA. 233

continued straight to the anus. Through the whole length of the
intestine, cjBcal processes are sent off on each side, to the number of
about twenty pairs. They commence of a slender diameter, but gra-
dually enlarge, send off many short branches, which subdivide, and
terminate in fusiform pouches. These productions of the intestinal
canal are homologous with the gastric C2eca of the leech ; but they
are more isolated from the common canal, and more distinct in their
functions. It is thought that the chyme passes into them, and that
the chyle is separated from it by a secretion of the terminal casca
analogous to bile. Hunter has placed a preparation* of them at the
commencement of his series of hepatic organs, as one of the early
forms of that system.

The more unequivocal form of hepatic organ is that yellowish
or brownish glandular mass which surrounds almost the whole
intestinal canal in most Anellides, and which consists of aggregated
follicles, opening either singly or by a duct common to several, upon
the inner surface. These follicles give a villous character to the
outer surface of the gut in Enchytrceus ; their homologues form the
part called " chloragogena " by Morren in the Liunbricus. In Atn-
phitrite the follicles are of a bright yellow colour.

The abdominal cavity is obliterated in the suctorial Anellids by
the spongy vascular tissue uniting the sacculated alimentary canal
to the skin : in the Terricola it is divided into numerous small com-
partments by the septa, which closely connect the intestine with the
skin : it is also more or less subdivided by the incomplete septa and
the muscles of the setigerous sheaths in the higher Anellides ; but
all the recesses and ramifications of the abdominal cavity intercom-
municate freely with each other. In this complex space there is a
colourless fluid containing organic corpuscles, which is kept in
constant motion by the varying contractions and dilata4;ions of the
surrounding segments, a ciliated epithelium being rarely present, as
e. g. in Aphrodita acuhafa ; or only partially developed upon the
peritonaeum, as, e. g. in the part lining the tubular feet of the Her-
mellae"!*, and the hollow branchiae of the Glycera. This fluid answers
to the chylaqueous fluid of the Radiata.l In the Errantia it performs
one of the functions of an internal skeleton, acting as the fulcrum or
base of resistance to the cutaneous muscles, the power of voluntary
motion being lost when the fluid is let out ; the vermicular motions
of the intestine are aided or determined by its resistance and support ;

* No. 782. t CXC. p. 36.

X lb. pp. 170 — 173., -where different forms of the chylaqueous corpuscles are
described.

234 LECTURE XI.

it favours circulation by obviating the pressure upon the blood-
vessels, which would follow the contact of the intestine with the
integument, and is, perhaps, the source, or one of the sources, of the
blood itself. Besides the organic and definitely shaped corpuscles, it
contains albumen, fibrine, and also crystalline products identical
with those obtained by evaporation of pure sea-water, and, therefore,
merits, as in the Polypes and Echinoderms, the name of the chyl-
aqueous fluid. Dr. Williams believes that " sea-water is vitalised
with wonderful facility by the solid organic elements contained in
the chylo-peritoneal fluid." *

In the majority of the Anellids the blood is red; in some of a
brilliant red, as in Are7iicola, Nereis, Glycera, Nephtys. In Aphro-
dita and Polynoe, the blood is of a pale yellow colour ; in a species
of Sahella it is olive green ; so that, as Milne Edwards well observes,
the colour of the blood is far from being a character of such phy-
siological importance as to justify the location of the Anellides at the
head of the articulate sub-kingdom. Dr. Williams denies that the
blood of the Anellides contains any coloured or other corpuscles.
It circulates in a closed system of arteries and veins, the modifi-
cations of which are considerable when examined in the different
genera of the class.

A large vessel which runs beneath the dorsal integument is the
seat of undulating contractions, by which the blood is propelled from
behind forwards ; it fulfils the functions of the heart, and is the
homologue of the dorsal vasiform heart in insects. A corresponding
venous trunk conveys the blood in an opposite direction from the head
to the tail, along the under or ventral surface of the abdominal cavity.
These are united at each segment by transverse vessels, which
convey the fluid from the ventral vein to the dorsal artery: the
latter or annular circulation is often aided by the contractile walls of
partial dilatations of certain of the vessels, and by the actions of the
gills themselves in the higher anellids.

In the leech the vascular system consists principally of four great
trunkSj none of which present any local dilatations meriting the
name of heart ; one of these trunks is situated on each side, a third
above, and a fourth below, the alimentary canal. They are shown
in transverse section, as connected together in two of the middle
segments of the leech in the diagram {Jig. 105.), from Brandt's Mo-
nograph.f The lateral trunks (c, c) are the largest ; they are widest
in the posterior third of the body; their anterior end terminates in
branches to the head ; the posterior end unites with that of its fellow

* CXC. p. 173. t CLXXXV.

ANNUL AT A.

235

more conspicuously than at the anterior part, and supplies the ter-
minal sucker. Branches
are given off at each
ring, which almost im-
mediately divide into a
dorsal {d) and ventral
(e) ramulus ; the six pos-
terior dorsal branches
unite with those of the
opposite side, and the
six arches thus formed
are joined together by
near the middle line of

Leech.

two nearly parallel longitudinal vessels
the back.

The dorsal vessel {Jig. 105. a), in which the blood moves from behind
forwards, is formed by the union of the dorso-intestinal vein and of
the dorso-dermal vessel, which run parallel with each other along
the posterior third of the body. The trunk is thence continued
forwards, sending outwards a pair of transverse branches at each
ring, and bifurcating behind the mouth to enclose the oesophagus.
From the under part of the oesophageal ring the great ventral vein
{Jig. 105. b) begins, which is continued along the nervous ganglionic
chord, and swells at each ganglion, forming a sinus around it ; the
nervous matter being thus, as it were, bathed in the nutrient fluid.*
From each of these swellings a transverse branch is sent off to either
side {f,f\ and from the seventh to the fifteenth ganglionic sinus a
second pair of transverse vessels of smaller size is given off, just
behind the ganglionic sinus.

The respiratory function would seem to devolve partly upon the
tegumentary capillaries, and partly upon those capillaries which
spread upon the mucous sacculi. These latter capillaries are not,
however, more numerous than those of the other organs of the body.
The more important office of the sacculi would seem to be as the
recipients of the secretion of peculiar loop-shaped glands, which they
receive by a very short and slender duct. There are seventeen pairs
of these mucous glands {Jigs. 104, 105. g^ g), the five posterior of which
lie on each side the long terminal gastric sacculi, and the rest in the
interspaces of the shorter cceca. Each gland pours its secretion into
a circular sac {Jigs. 104, 105. h, h), which opens externally {fg. 104.
i, i) upon the skin. These dermal pouches have commonly been
described as the respiratory organs ; and from their relative position

* CLXXXIV. p. 114.

236 LECTURE XI.

they may be deemed homologous with the tracheal respiratory organs
of the higher Articulata ; but in fanction they seem to be reduced to
supplying the skin with its abundant mucous secretion, and the ova
with their cocoon-like coverings at the season of generation.*

Morren has minutely described the circulating system of the earth-
worm ; in a species of which (^Lumbricus variegatus) Bonnet f saw
the red blood propelled forward by the systole and diastole of the
dorsal vessel towards the head, and noticed its accelerated course
near that part.

In the tubicolar anellids, according to Dr. M. Edwards J, the
dorsal contractile artery is unusually short. In the Terebella it re-
ceives numerous veins from the intestine, and a large accession of
the circulating fluid from two wide transverse venous trunks, which
encircle the commencement of the intestine, and which receive recur-
rent veins from the oesophagus, also a small vein from the integu-
ments of the back. This short dorsal vessel is, in fact, the general
receptacle of the venous system, and, by its function, it represents a
pulmonic heart. It transmits the venous blood almost exclusively to
the cephalic branchiae by three pairs of branchial arteries, which
arise from its anterior extremity. The oxygenated blood is returned
by the branchial veins to a large ventral trunk, situated immediately
above the orano^lionic nervous chord. This vessel, which has the
function of a systemic heart or aorta, supplies a pair of transverse
branches to each ring of the body, which distribute filaments to the
integuments and the feet, and then ascends to supply the intestine,
where, with the absorbent veins of that canal, it returns again into
the dorsal vessel. In some other species of Terebella, as the Ter,
conchilega, the lateral branches of the ventral trunk do not ascend in

* Dr. Williams (CXC. p. 257.) affirms that " spermatozoa can always be dis-
covered in the interior of these sacs ;" and states that they are " true vesiculae
seminales." I have never been so fortunate as to detect spermatozoa in the mucus-
sacs of young leeches, in which those parts have been relatively as fully developed
as in the fuU-grown leeches fit for copulation. The looped glands (^) are described
by the same MTiter to be ovai'ia, " ovarian utricles," the glandular granular par-
ticles, enclosed in their waUs, which are figured and described by Brandt and
Katzeburg (CLXXXV. *' Dnisensubstanz," p. 251, tab. xxix. A. fig. 8), having
apparently been mistaken for ova. Dr. Williams further describes a minute duct
as extending outwards, crossing beneath the longitudinal sperm-duct, and " be-
coming united to the base of the ovarian utricle," p. 254 (looped mucus-gland, ^r).
Although my dissections have enabled me to distinguish the small blood-vessels
uniting the testes to a neighbouring mucus-duci, I have failed to make out the
sperm-duct so described.

t Observations sur les Vers, CEuatcs, i. p. 193., 1779.

% Sur la Circulation dans les AneUidcs, Annales des Sciences, Nat. X. p. 121.

ANNULATA. 237

loops upon the upper surface of the intestine, but terminate almost
exclusively in a vascular network situated on each side of the abdo-
minal cavity near the base of the feet. The principal organs of im-
pulsion of the circulating fluid in the tubicolar anellids seem to be
the contractile branchiae, which thus combine, as it were, the functions
of both heart and lungs.

Cuvier has noticed the alternate expansion of the branchiae of the
Arenicola when they are coloured by the bright red blood, and their
contraction, when, by expelling the blood to the internal vessels, they
become of a pale grey colour.

In the Eunice sanguinea * there is, as in the Terebella, a large and
short dorsal vessel, which rests upon the pharyngeal part of the ali-
mentary tube, and which communicates, by its posterior extremity,
with a vascular ring surrounding the commencement of the intestine.
This ring receives two vessels, which run parallel and close together
along the dorsal aspect of the intestinal canal, and correspond with
the single vessel in the Terebella. The dorso-pharyngeal contractile
trunk receives other branches from the parietes of the digestive tube,
and a small medio-dorsal cutaneous vessel. It gives off by its an-
terior extremity several branches to the head, and others which sur-
round the pliarynx, and anastomose with the ventral vessel. From
this vessel a pair of lateral branches is given off at each ring of the
body. These branches immediately dilate, and are bent upon them-
selves in a strong sigmoidal curve, appearing at first sight to be simple
oval vesicles. They send an ascending branch to the digestive tube,
form a small plexus at the base of each of the feet, and penetrate the
branchial filaments. The blood is returned from these respiratory
organs by transverse veins, which terminate on each side in the dorso-
intestinal vessel of that side. Here, therefore, the respiratory circu-
lation is removed further from the dorso-pharyngeal heart, which
consequently receives a greater quantity of blood in its arterial or
oxygenated state. The principal dynamical organs are, however, the
curved dilated sinuses at the bases of the branchiae, which pulsate
with strong contractions, and propel the blood at once to the
branchiae, the feet, the skin, and the intestine. If we call these
pulsatile reservoirs by the name which their functions would claim
for them, there will be several hundred hearts in one of these gigantic
Nereids. In the Nephthys Hombergi the dorsal vessel is double
throughout the greater part of its extent.

In the Amphinome capillata, which Hunter has here f dissected for
the vascular system, this is chiefly remarkable for the size and com-
plexity of the branchial plexuses.

* Edwards, loc. cit. p. 204. f Preps. Nos. 875, 889, and x. pi. xiv. fig. 10.

238

LECTURE XI.

T/As

In the Arenicola {Jig. 106.) there is, on each side the base of the
oesophagus, an ovoid contractile sac (jT), which
sends off a large and short vascular trunk
106 downwards and backwards to the medio-ven-
tral line, where, uniting with its fellow trunk,
a ventral vessel (e), analogous to that in the
Eunice and Terebella, is formed. This me-
dian vessel furnishes a pair of transverse
branches to each ring, which at the seventh
segment begin to penetrate the ramified bran-
chia, attached to the sides of that and suc-
ceeding middle segments of the body. The
pulsations of the two oesophageal sinuses, or
ventricles, propel the blood into the ventral
vessel from before backward through these
vessels (m, m) to the gills, where it receives
a new impulse by the contractions of these
organs, and, after having been oxygenised, it
is returned, partly by cutaneous vessels, which
form many anastomoses, and chiefly by a di-
rect and continuous lateral vessel {k, A), to
the medio-dorsal intestinal artery (g). This
' E/m%^F-ii i-M?^r ai'teiy extends from one end of the body to
lUMl^SflfiMJ ^'^ the other. At its middle part it receives
many transverse branches from the digestive
tube, and through them anastomoses with
the inferior intestinal vein (k). The vascular
network thus formed around the intestine,
gives origin anteriorly to two lateral veins
(^), which terminate in the dorsal vessel im-
mediately behind the oesophageal ventricles.
The blood from the inferior intestinal vein is
conveyed to the same point or sinus. After
the communication of this common sinus
with the two hearts, a slender median vessel
(g'), a continuation of the dorsal one, extends forwards towards the
head, and terminates by forming two vascular rings around the base
of the proboscis, from the lower part of which the ventral vessel
arises, which vessel (e), passing backwards, receives the great accession
of blood from the two contractile hearts, and thus the circulation is
completed.

This has much analogy with the circulation of the blood in the
earth-worm, in which the blood travels from behind forwards in the
dorsal vessel, and descends in great part towards the ventral vascular

Arenicola.

ANNULATA, 239

system through the pairs of anterior beaded contractile sinuses or
hearts *, which differ only from the two ventricles in the Arenicola
by their greater number. In the lateral vascular canal, which extends
along the anterior part of the body, at the base of the feet in the
Arenicola, and which is formed by the anastomoses of one of the
branches of the cutaneous arteries, we have the horaologues of the
lateral vessels in the leech tribe, which are wanting in most of the
higher Anellides. The dorsal and ventral trunks are common to all,
and in most there are four longitudinal vessels attached to the intes-
tinal tube.

The most striking physiological character of the circulation in the
Anellides as a class, is the continuity of their capillary system, and
the difficulty of determining which is the arterial, and which the
venous trunk of any one of the organs or parts of the body, excepting
the branchice. There alone, we find that the blood received from the
distinct artery is sent back by as distinct a vein, which returns along
the same route as the artery, as it does in the limbs of the higher
animals. By the rapid division and general system of anastomoses of
the arteries and veins, it follows that almost all the parts of the body
are supplied by a mixture of arterial and venous blood.

The position and general relations of the branchial organs have
already been incidentally pointed out ; and it seems only necessary
here to allude to their different forms. In the leech and earth-worm,
a series of pores or stigmata on each side of the body lead to as
many simple sacculi (Jig. 104. h, h\ formed by an inward folding of
the integument. Carry the duplicature further in, divide and sub-
divide it, and ramifications of air tubes, like the tracheal respiratory
system of insects, would be produced. "We may perceive in the
lateral sacs of the leech and earth-worm, the first step, morphologi-
cally, in the development of the very peculiar air-breathing organs of
the higher Articulata ; but, in their actual rudimentary form, their
respiratory functions are reduced to the lowest state, and they serve
chiefly the office of excretory organs, preparing and discharging
mucus. In Branchiobdella a pair of looped canals open at the begin-
ning of the middle third-part of the body, and a second pair at the
hinder end of the body, both at the median line of the under surface.
Close behind the orifice each of these four canals expands into a
round yellow-coloured sac, from which many convoluted tubes pro-
ceed. They are lined by a ciliated epithelium. A greater number
of such pairs of organs are found in other leeches at the second third-
part of the body, one behind another as far as the posterior extremity i

* See Preps. 876, 877, 878.

240 LECTDRE XI.

those in Nephelis are not ciliated. In the earth-worm there are on
each side of the commencement of the intestine many looped tubes
which open externally by a small orifice on the under surface on one
side of the middle line, and have their inner surface beset with
festooned ciliated ridges. They are dilated near the orifice, and con-
tain a clear fluid, kept in movement by the action of the cilia;
which fluid the worms may obtain from the moist earth. These
" water-canals " are surrounded in Lumhricus by a remarkable plexus
of vessels, to which numerous pedunculated blood-receptacles are
appended, giving the whole system a racemose character. Similar
blood-sacs are appended to the same system of vessels in Nephelis
vulgaris ; but such sacs are simple reservoirs, and have no pulsation.

The respiratory organs of the tubicolar anellids are in the form
of long, flattened, and sometimes tortuous, filaments* which radiate
from the head, generally in two lateral fasciculi, disposed in a funnel-
shaped or spiral form. When not coloured by the red circulating
fluid, they are often barred and variegated by bright purple, green,
and yellow tints, forming a rich and gorgeous ornamental crown.
Each filament, in Serpula, Sabella, and Amphitrite^ is fringed by a
row of actively vibrating cilia, which effect the requisite change of
the respiratory medium in contact with the vascular surface. In
Amphitrite they are semipinnate. In Terebella the branchial fila-
ments are florid blood-vessels, inclosed in a delicate non-ciliated
integument. The cephalic tentacles, which are hollow, and are pene-
trated by the chylaqueous fluid, expose an extensive surface to the
surrounding medium, which must react on the contained fluid, and
thus aid in respiration.

The branchiae of the Amiulata errantia are usually in the form of
shorter tufts than the cephalic ones of the Tubicola, and they are
attached to the upper parts of the sides of a greater number of seg-
ments. The following descriptions of some of their chief modifica-
tions are from the excellent "Report on the Anellida" above cited.
" Respiration is performed in Arenicola Piscatorum by means of
naked blood-vessels, projecting at the root of the setiferous process
upwards and outwards one-fourth of an inch in the adult worm from
the surface of the body. They are limited in number and distribu-
tion to the fourteen or sixteen middle annuli of the body. They are
commonly described as forming an arborescent tuft ; the division of
vessels is however regulated by a fixed principle. When fully in-
jected with blood, the vessels of each branchia form a single plane,
rising obliquely above and across the body, and immediately behind

* Prep. No. 990.

ANNULATA. 24 1

each brush of setje. In the adult animal each gill is composed of
from twelve to sixteen primary branches, proceeding from a single
trunk, which arises from the great dorsal vessel ; the vessels in the
branchial tuft describe zigzag outlines ; the secondary branches pro-
ject from the salient point, or the outside of each angle of the zig-
zags ; and the tertiary from similar points on the secondary branches.
This mode of division, occurring in one plane, and in all the smaller
branches, results in a plexus of vessels of extreme beauty of design.
Each branchial tuft and each individual vessel possess an inde-
pendent power of contraction ; in the contracted state the tuft almost
entirely disappears, so completely effected is the emptying of the
vessels. The contraction, or systole, in any given tuft occurs at fre-
quent but irregular intervals ; this movement does not take place
simultaneously in all the branchiae, but at different periods in differ-
ent tufts. As there is no heart-like dilatation in the afferent vessels
of the branchiae, the contractile power with which the exposed
branches are endowed, becomes an important means of reinforcing
the branchial circulation. The vessels appear quite naked, and if
examined in the living state, each ramuscule seems to consist only of
a single trunklet ; if this were really the case, it would of course re-
solve itself into a tube ending in a cul-de-sac, and the blood move-
ment would be a flux and reflux ; but by injection it is easy to show
that the finest division of the branchial arbuscle contains a double
vessel, enveloped in a common muscular, although extremely diapha-
nous sheath. That these vascular sheaths, which are only fine pro-
ductions of the integuments, are furnished with voluntary muscular
fibres, is proved by the rapid and simultaneous retraction of all the
branchiae into the interior of the body, which follows when the animal
is touched.

" The genus Eunice presents another and different type of bran-
chial vessels. Arranged in a prominent row of bright vessels, stand-
ing erect as minute combs at the dorsal base of each foot in the body,
the branchiae impart to all the species of this genus a graceful and
characteristic appearance. In every species the branchial vessels
divide on a uniform plan peculiar to this genus. The primary trunk
rises vertically along the inner side of the branchia, and sends off
from its outer side, at intervals, straight vessels, which gradually
decrease in size from below upwards ; each branch forms a straight
undividing vessel, curving gently upwards and towards the median
line : these branches become in their number characteristic and dis-
tinctive of species. In some of the smaller species inhabiting the
British coasts, the branchiae are composed only of a single vessel ;

242 LECTURE XI.

this is the case also with the young of the larger species ; in others
they vary from the single vessel to the number of six or eight.

" In the genus Lycidice the branchia consists of a flat lanceolate
process, more or less developed, surrounded marginally by a blood-
vessel, the mid-space between the lines of the advancing and return-
ing vessels being composed of large-celled tissue, lacunose, into
which the peritoneal fluid penetrates by a flux and reflux move-
ment. The branchiae in L. Ninetta are situated dorsally, and are
supplied at their bases with single rows of vibratile cilia. Those of
Aglaura fulgida are similarly constructed, although they differ
slightly from those of the former genus in size and figure. In
(Enone maculata they occur under a more developed form, consti-
tuting flattened, pointed, trowel-shaped processes, the plane of which
is vertical with reference to that of the body. A blood-vessel, as in
the former cases, trends along the borders, immediately beneath the
cuticle. The course of these vessels is followed by a row of large
and prominent vibratile cilia.

" In the branchial system of the genus Nereis (Cuv.), Lycoris
(Savigny), the anatomist encounters a structure strikingly different
from anything hitherto described. Whether round or laminated, the
true branchias in this genus are always penetrated by the fluid of the
visceral cavity, and the blood-vessels assume a peculiar disposition.
When the branchial process is conical in shape, its base is embraced
by a reticulated plexus of true blood-vessels, which is situated quite
superficially and immediately beneath the epidermis. These vessels
are most prominently developed on the dorsalmost process, which,
therefore, may be called the branchial ; but they extend more or less
over all the cirri. A better characteristic of the branchiae, both the
conical and the foliaceous, in the Nereids^ is that of their being pene-
trated by the peritoneal fluid. In those species in which the bran-
chial process is round, the interior of the base is hollow, and filled
with the fluid of the visceral chamber. Floating in this fluid may
be seen, when viewed transparently, coils of naked blood-vessels : in
those in which they are laminated or foliaceous, as in Nereis renalis,
the step of the exterior surfiice does not extend beyond the limits of
the base ; the flat portion, however, is tunnelled by straight spacious
canals, which radiate with great regularity from the base to the ex-
panded circumference of the process. In these canals the corpuscles
of the peritoneal fluid may be seen rolling to and fro, advancing and
returning in the same channel. These movements are regulated by
those of the great current in the chamber of the peritoneum. This
type of structure prevails in Nereis renalis, N. longissima, and in a
slightly modified form, in consequence of the less flattened shape of

AXNULATA.

243

the branchiae, in JV. viridis. The round variety of branchial processes
obtains in N. margaritacea, N. Dumerillii, N. fucata, N. pelagica,
and N. brevimanus. It is a fact difficult to explain that the branchial
organs in the Nereids should be destitute in every species of vibratile
cilia.

" The laminated or foliaceous type attains the point of its maxi-
mum development, in the branchial appendages of the genus Phyllo-
doce. Rich leaf-like projections, it was difficult to assign any other
than a respiratory use to these parts in these beautiful worms. The
branchiae in Phyllodoce viridis are prominent dorsal appendages : in
this worm the blood-system can be traced only by a few scanty
vessels distributed over the roots of these processes ; nor are the
canals very spacious and distinct, they are more like lacunae in a
spongy tissue. In P. hilineata and P. lamelligera, the radiating
passages, distinct from each other and communicating only indirectly
through cells, are extremely obvious under the microscope. They
carry the fluid of the peritoneal cavity, the corpuscles of which may
be seen flowing and ebbing in the same channeh Nothing can, how-
ever, more conclusively prove the true branchial character of these
laminae than the presence of cilia, the vibrations of which can be ob-
served only at the edges of the respiratory laminae. These are best
seen in P. lameUigera. This is a striking point of distinction be-
tween the Phyllodoce and the Nereids, in which vibratile cilia on the
branchiae have no existence. The peritoneal fluid, then, may be
affirmed as that, in the economy of the Phyllodoce, which is the
subject exclusively of the respiratory function, the true blood receiv-
ing its supply of oxygen from this fluid, afterwards to convey it to
the solid structures of the body.

" In the genus Glycera the blood-proper is entirely excluded from
the organs of respiration. This office devolves exclusively on the
chyle-aqueous fluid, which in nearly all the species of this genus is
profusely supplied with red corpuscles. The gills consist of hollow
cylindrical appendages, emanating from the base of each dorsal foot
at its superior aspect, filled in the interior with the fluid of the vis-
ceral cavity ; but what is remarkable in the structure of these organs
and quite peculiar to this genus, is that the interior parietes of the
cylindrical hollow of the branchiae is lined with vibratile cilia ; these
motive organules cause the corpuscles of the fluid by which the bran-
chise are penetrated, to move with great rapidity in a definite direc-
tion, viz. peripheradly on one side and centradly along the other,
each corpuscle whirling on its own axis as it proceeds. Ciliary
vibration cannot be detected on the outside of the branchial appen-

dage.

K 2

244

LECTURE XT.

" In the SyllidtB the branchial organs are penetrated by the peri-
toneal fluid; but it can be detected in motion only in the bases of the
feet, and these parts only are furnished with vibratile cilia, which are
large and active. The long filiform and, in some species, moniliform
appendages, which are described commonly as the branchiae of these
worms, have no central hollow ; they are filled with large-celled tissues,
through which the fluid parts of the contents of the visceral cavity
slowly penetrate. In the Syllidan family, which excels all others in
grace and beauty, the proper blood-system is almost indetectible, in
consequence of the colourlessness of the contents. It may be stated
with confidence, that blood-vessels do not enter into the structure of
the branchial processes. The respiration therefore devolves exclu-
sively on the chyle-aqueous fluid.

" Amongst the family Ariciadce several other varieties in the con-
figuration of the breathing organs occur. In the genera Leucodore,
Nerine, and Aricia, the branchial appendages affect a dorsal situation.
In every species they are traversed from base to apex by a single
blood-vessel returning upon itself. This vessel, however, is sup-
ported by a lobule of spongy tissue, into the cells of which the fluid
of the visceral chamber penetrates. The ofiice of respiration in this
family is therefore discharged in part by the blood and in part by the
chyle-aqueous fluid. In very species of this family the branchice are
supplied by vibratile cilia having a distinct disposition in each. Leu-
codore ciliatus, on the dorsal aspect and over the posterior two-
thirds of the body, is covered on each side with a row of flattened
conical branchial processes, blood-red in colour and richly ciliated.
They are largest anteriorly, and smallest near the tail. The cilia are
disposed in a spiral line, from the attached to the extreme end.
Viewed with a high magnifying power, and transparently, a camerated
axis, composed of exquisitely fine hyaline cartilage, may be dis-
covered, fulfilling on the branchiae of this elegant little boring Anne-
lid the ofiice of mechanical suj^port, as a similar structure was for-
merly shown to do in those of the Sabellce.

" In the genus Nerine the respiratory organs occur under forms of
the highest beauty. They constitute flat, membranous, penknife-
shaped appendages, curving gracefully over the back with the curve
of the " ring " of the body by which they are supported, and crossing
over the dorsal median line, and alternating with the corresponding
process of the other side. The plane of each process is vertical in
relation to the longitudinal axis of the body ; they lie, therefore, one
over the other in an imbricate manner. They are less flat and close
in N. vulgaris than in N. coiiiocephala. They are largest in size
towards the middle of the body, smallest anteriorly and posteriorly.

ANXULATA. 245

The blood-vessels, the afferent and efferent, run close to and parallel
with the inferior border of the process ; the upper part of each is
composed of a membranous lobular addition to the inferior and vas-
cular portion. Into the cells of this lobule the chyle-aqueous fluid
slowly finds its way, and participates obviously in the office of re-
spiration. In JV. coniocephala it is remarkable that the cilia should
be limited in their distribution to the margin, along which the true
blood-vessel runs. This fact is less manifest in N. vulgaris, in conse-
quence of the smallness of the membranous lobule. In Aricia Cu-
vieri the branchial appendages are more conical in figure, more
vertical in position, and developed only at the posterior four-fifths of
the body. They are covered with large vibratile cilia, which likewise
extend over that segment of the dorsum which separates the bases of
the branchiae. Like those of the preceding genera, they are supplied
with spongy tissue for the exposure of the peritoneal fluid.

" It may have been remarked, that in all the members of the pre-
ceding family the real branchial organ has consisted of an evolved or
exaggerated develoj)ment of the superior element of the dorsal foot.
In the genus Nephthys, which comes now under review, it is the in-
ferior element of the dorsal foot which becomes the subject of this
evolution. Nephthijs Hombergii of our coasts is a remarkably vigor-
ous and active worm, and yet its organ of breathing consists only of a
comparatively small curved ciliated process, situated under cover of
the dorsal foot, and carrying only a single-looped vessel. It may be
mentioned, as an interesting proof of the real appropriation of this
process in Nephthys to the function of breathing, that the same
process, although similarly shaped, on the ventral or inferior foot, is
7iot provided with cilia, nor is it penetrated by any blood-vessel.

^' The genus Cirrhatulus of Lamarck, and the allied group consti-
tuted by Savigny under the name of Ophelia, introduce to the phy-
siologist another modification of the branchial organs within the
limits of the dorsibranchiate order. As in the preceding families,
they are in these latter only ' developments ' of the dorsal cirri. In
Cirrhatulus Lamarckii, a linear series of yellowish and blood-red
threads, remarkably irritable and contactile, project to a considerable
distance, from each side of the body, thoughout its whole length; at
the occiput, however, they are arranged in a crown-like form. These
beautiful filaments, which are obviously designed to fulfil the twofold
office of touch and respiration, appear under the microscope to con-
sist only of a single blood-vessel inclosed in a delicate sheath of inte-
gument. Closer analysis, however, discovers two vessels in each of
these filaments, and traces of longitudinal and circular muscular fibres
in the investing sheath. By the contraction of this sheath, the iu-

K 3

246 LECTURE XT.

closed vessels may be completely emptied of their blood from one end
of the filament to the other. This contraction does not take place
simultaneously in every part, but undulatorily, the wave motion be-
ginning at the extreme fore-end. It is especially to be noted, that,
in this variety of appendage, in which the respiratory is only an inci-
dental function, there exist no vibratile cilia. These organs in
Ophelia coarctata exhibit analogous characters, while they are less
numerous and much shorter.

" The AphroditacecB constitute a group of Annelids to which the
term ' dorsibranchiate ' by no means correctly applies ; that is, in the
majority of the species embraced in this order, no branchial appen-
dages exist, either on the dorsum or any other part of the body. Re-
spiration is performed on a novel principle, of which no illustration
occurs in any other family of worms. In all Aphroditacece the blood
is colourless. The blood-system is in abeyance, while that of the
chyle-aqueous is exaggerated. Although less charged with organic
elements than that of other orders, the fluid of the peritoneal cavity
in this family is unquestionably the exclusive medium through which
oxygen is absorbed. The true Aphrodite type of respiration occurs
in Aphrodita aculeata. In this species the tale of the real uses of
the ' elytra,' or scales, is plainly told. Supplied with a complex ap-
paratus of muscles, they exhibit periodical movements of elevation
and depression. Overspread by a coating of felt readily permeable to
the water, the space beneath the scales during their elevation becomes
filled with a large volume q{ filtered water, which during the descent
of the scales is forcibly emitted at the posterior end of the body. It
is important to remark, that the current thus established laves only
the exterior of the dorsal region of the body. It nowhere enters the
internal cavities ; the latter are everywhere shut out by a mem-
branous partition from that spacious exterior inclosure bounded above
by the felt and the elytra. In this species the peritoneal chamber is
very capacious, and filled by a fluid which only in a slight degree
contains organised particles. The complex and labyrinthic appen-
dages of the stomach lie floating in this fluid, and in the chambers
which divide the roots of the feet. From this relation of contact be-
tween the peritoneal fluid and the digestive ca^ca, which are always
filled by a dark rjreen chyle, it is impossible to resist the conclusion
that the contained fluid is really a reservoir wherein the oxygen of
the external respiratory current, already described, becomes accumu-
lated. From the peritoneal fluid the aerating element extends in the
direction of the caeca, and imparts to their contents a higher character
of organisation. These contents, thus prepared by a sojourn in the
C£Eca of the stomach, become the direct pabulum for replenishing the

ANNULATA. 247

irue blood which is distributed ia vessels over the parietes of these
chylous repositories."

The rythmical elevation and depression of the respiratory scales of
the Aphrodite are interesting facts, and we shall afterwards see their
homologues taking an important share in the locomotive functions of
the higher organised forms of Articulata.

Most Annelids exude a tenaceous mucus from the skin ; the excre-
tory follicles are arranged in curved rows on both the dorsal and
ventral aspects of the rings in the leeches and larger earthworms.

The precise locality of the secretion of the horny or leathery tubes
of certain Annelids is not yet understood ; but the tumid ridge around
the first segment of the SerpidcB, seems to be the formative organ of
tlie calcigerous cells in tlie production of the shelly sheath. Four
yellowish glands, terminating by a common orifice on the first body-
segment of the Amphitrite, most probably prepare the mucous cement,
by which the particles of sand and shells are attached together to
form their neat artificial tubes. The long and delicate cephalic ten-
tacles of the Terehellce take an important share, hardly to be suspected
at the first glance, in the nidification of these humble sea-worms.
" They consist," writes Dr. Williams, " in T. nebulosa, of hollow flat-
tened tubular filaments, furnished with strong muscular parietes. The
band may be rolled longitudinally into a cylindrical form, so as to in-
close a hollow cylindrical space, if the two edges of the band meet ; or
a semi-cylindrical space, if they only imperfectly meet. This inimi-
table mechanism enables each filament to take up and firmly grasp, at
any point of its length, a molecule of sand ; or, if placed in a linear
series, a roiv of molecules. But so perfect is the disposition of the
muscular fibres at the extreme free end of each filament, that it is
gifted with the twofold power of acting on the sucking and on the
muscular principle. When the tentacle is about to seize an object,
the extremity is drawn in, in consequence of the sudden reflux of
fluid in the hollow interior; by this movement a cup-shaped cavity is
formed, in which the object is securely held by atmospheric pressure;
this power is, however, immediately aided by the contraction of the
circular muscular fibres. Such, then, are the marvellous instruments
by which these peaceful worms construct their habitation, and pro-
bably sweep their vicinity for food."*

* CXC. p. 194.

R 4

248

LECTUEE XII.

JO'>rT

'j^<p\-a

m

LECTURE XII.

ANNULATA.

Hitherto the highest condition of the nervous system which we have
observed, has been that of detached unganglionic fila-
ments diverging from a single sub-oesophageal gang-
lion or from a simple oesophageal ring, continued un-
connectedly along the abdomen, or diverging in rays
down equidistant tracts of the common parietes of
the body. If we have met with ganglionic masses
in connection with coloured ocelli, these have been,
as, e. g., in the Acalephge, either so situated as to
give no indication of a head, or so multiplied as to
lose all significance as a common cerebral centre of
sensation.

In the class Annulata, the nervous system has
reached a higher type and more constant plan of
arrangement. It always commences by a symme-
trical bilobed ganglion, meriting, both by its- situation
above the mouth and by the parts which it supplies,
the name of brain, which it has commonly received.
The sub-oesophageal ganglion is, however, the ana-
logue, if not the homologue, of the medulla oblongata,
and should be included in the encephalic division of
the nervous system in both the Articulate and Mol-
luscous animals.

In the medicinal leech there are sent off from the
super-oesophageal ganglion {fig. 107, a) ten distinct
optic nerves (b b), besides many smaller filaments to
the integument and other parts of the head ; each
optic nerve or filament terminates by expanding
upon the base of a black eye-speck or ocellus, ten of which you will
easily distinguish by the aid of a moderate magnifying power, dotting
at equal distances the upper margin of the expanded suctorial lip.

The principal nervous productions of the brain of the leech are
what may be termed its crura, which diverge as they descend to
embrace the oesophagus, and are called the oesophageal chords ; they
then converge and reunite to join the large cordiform sub-oesophageal
ganglion (c). From this ganglion the muscles of the three serrated

\^

Leech.

ANNULATA. 249

jaws, as well as the principal muscles of the oral sucker, derive their
nervous influence. Those who have watched the vigorous workings
of this part in a hungry leech beginning its parasitic feast, will not
be surprised at the great development of the nervous centre of the
suctorial and maxillary mechanism. Two chords, in such close appo-
sition as to seem a single nervous band, are continued from the sub-
cesophageal ganglion along the middle of the under part of the
abdomen, attached to the ventral integument, and inclosed, as it were,
by the great ventral vein. Twenty-one equidistant rhomboidal
ganglions are developed upon these chords, which distribute their
filaments to the adjoining segments by two powerful diverging trunks
on each side. The segments indicated by the external circular in-
dentations of the integument, are much more numerous than the
ganglions. Dr. Brandt has detected a simple nervous filament
continued from the oesophageal ganglion along the dorsal aspect of
the alimentary canal. This is an interesting structure, as being an
early trace of a distinct system of nerves, usually called the stomato-
gastric in Entomology, and to which our great sympathetic and nervus
vagus seem answerable.

The structure of the abdominal ganglion in the Articulata was
first illustrated by the microscope and pencil of Ehrenberg as it
exists in the leech* ; in the centre of the ganglion are several clavate
corpuscles, the enlarged end of each being formed by a nucleated cell,
the tapering extremity is continued into the diverging nervous chords :
the clavate cells are arranged in eight groups, two groups being
continued into each of the four diverging chords of the ganglion ; a
few filaments pass lengthwise through the ganglion, and are in more
immediate communication with the cerebral one.f

In the earth-worm the super-oesophageal ganglion consists of two
lateral lobes, which send off small nerves to the proboscis and the
two large chords to the sub-oesophageal ganglion ; some small fila-
ments are derived from the oesophageal collar. The two ventral
nervous trunks are more distinct from each other than in the leech ;
but the ganglions are relatively smaller and more numerous, corre-
sponding in number with the segments of the body. Two pairs

* Poggendorfs Annalen, 1833, and CLXXXVL p. 665, tab. vi. fig. 6. (1834.)
t The homologues of these are pointed out by ^Mr. Newport in the Lobster
(CXCn. 1834, p. 406). Dr. Carpenter, in CXXXVIII. (1839), cites Dr. M. Hall
as having " suggested that the ganglionic portion of the chord ministers to the reflex
actions of the respective segments, whilst the white tract (continuous filaments in
connection with the brain) conveys the motor influence of the cephalic gangha "
(p. 62). He adds, that it may also " convey sensory impressions to those
ganglia " (ib.).

250 LECTURE XII.

of nerve's are given off from each ganglion, and a third pair comes off
from the intermediate chords. The terminal or anal ganglion distri-
butes a plexus of nerves to that termination of the body.

In the Nereis the abdominal ganglions are more distinctly bilobed
than in the earth-worm, and the super-oesophageal ganglion is rela-
tively larger, having to furnish nerves to both antennee and ocelli ; the
latter projects as a black spot from the base of each of the two chief
cephalic tentacles. The pairs of ganglions developed upon the ventral
chord, correspond with the segments of the body in number, and are
very close together. In the Eunice gigantea there are upwards of
1000 ganglia ; but this complicated condition of the nervous system
is more apparent than real, and, like the multiplication of the pul-
satile sinuses of the vascular system in the same animal, depends
upon the vegetative repetition of like parts, without any mutual sub-
ordination in reference to the performance of a special office.

In the Aphrodita the body is broader and thicker than in other
Anellids, and begins to exhibit that concentration which characterises
its form in the higher Articulata. But the segmental nervous ganglions,
though more closely approximated, are yet not confluent at any central
part. The brain is heart-shaped, having its bilobed base turned back-
wards, and connected in the usual manner by large oesophageal columns
with the inferior ganglion. The antennal nerves are continued from
the apex. The visceral nerves are given off from the oesophageal
circle, and pass to the upper surface of the intestine, and there swell
into a small ganglion. The sub-oesophageal ganglion is of large size,
and bifurcates anteriorly : the second ganglion is situated close by
the first, and gives off two pairs of nerves: the third to the fifteenth
ganglions send off respectively three pairs of nerves, the first of
which corresponds with the interganglionic nerve in the earth-worm,
and supplies the branchial organs ; the second pair is distributed to
the ventral muscles ; the third, to the lateral and dorsal muscles. The
abdominal ganglions, which succeed the fifteenth, send off each two
pairs of nerves, and gradually diminish and approximate at the pos-
terior extremity of the body. In this highly organised anellid the
nerves may be distributed into those of special sense (antennal), the
sentio-volitional, the excito-motory, the sympathetic or stomato-
gastric, and the respiratory. The leech is very susceptible of meteoric
changes ; and instruments have been constructed, of which a very
ingenious one was shown in the '* Great Exhibition of 1851," in order
to make the characteristic movements of these Anellids subservient
to the purposes of a barometer.

" Those who have watched the habits of the Nereids will scarcely
doubt that they are gifted with the power of discriminating external

ANNULATA. 251

objects, of making towards some point, and of avoiding others. In
the absence of such an optical arrangement as may be fitted to collect
the rays of light, the physiologist, however, can form no conception
of the mechanism of sight in these animals, if this endowment really
is conferred upon them, under the conditions and in conformity with
the laws which atfect these organs in all the higher animals. It were,
however, by no means irreconcileable with the views entertained at
present as probable by many philosophers with reference to the pro-
perties of light, to suppose that this subtile agent may be rendered
perceptible to the sensorium of the humblest animals, by means of a
mechanism very different from that which anatomists and opticians
recognise in the apparatus of an eye. It is not essential to the practical
purposes of the lowest forms of life, that the objects of the external
world should be seen, that pictures of them should be painted upon
the retina ; it were enough that the mere presence or absence of an
objective body should become evident to the sensations of the animal
by the positiveness or ncgativeness of the impressions received. A
refinedly exalted sense of touch, tactile sensibility, would suffice to
accomplish this object. It is not easy for those who have never enjoyed
the spectacle of the ' feat of touch,' performed by the tentaculated
worms, to estimate adequately the extreme acuteness of the sensi-
bility which resides at the extremities of the living threads with
which the head and sides of the body are garnished. They select,
reject, move towards and recede from minute external objects with
all the precision of microscopic animals gifted with the surest eagle-
sight. The necessity, therefore, of ordinary organs of sight, in the
present state of physical and physiological science, it is by no means
essential to admit, while acknowledging that under the agency and
stimulus of light the humblest beings, though unendowed with normal
visual organs, may yet steer themselves harmlessly, readily, and un-
erringly through the thickly tangled labyrinth of mud and stone, and
gravel and weed, amid the twilight of which the habitat of many of
them may have been cast.

"It is a remarkable fact in the history of the AneUids, that scarcely
any species, however organised, whether furnished or not with exter-
nal locomotive organs, in its numerous and varied muscular evolutions
ever moves directly backivards. The movements consist always of
serpentiform pranks, or those of elaborate coiling. It is by the head,
however, that the movement is invariably initiated. The tail is
always in the rear, never in the van." *

On the first appearance of the embryo anellid, it usually consists of a
single segment, which is chiefly occupied by a large mass of unmeta-

* CXC. p. 268.

252 LECTURE xir.

morphosed germ-cells. And these are not used up. as in higher animals,
in developing the tissues and organs of an undivided or individual
whole ; but, after a comparatively slight growth and change of the pri-
mary segment, proceed, in the typical orders, to form a second segment
of somewhat simpler structure^ and then repeat such formations, in a
linear series, perhaps more than a hundred times. So that we may have
a seeming individual anellid consisting of many hundred segments, in
which a single segment would give all the characteristic organisation of
such individual, except some slight additions or modifications character-
ising the first and last of the series. Thus the anellids are more simple
in their structure than they appear at first sight, especially before
arriving at full maturity, when in certain species, as the leech, nais,
and earth-worm, particular segments are distinguished by the deve-
lopment therein of the special male and female generative organs.
With this characteristic mode of growth by repetition of segments,
we should be prepared to expect in these creatures great powers of
repair after injuries and mutilations — powers w^hich have been made
the subject of many and ingenious experiments. In the works of
Spalanzani and Bonnet more particularly are recorded the most
striking results of such experiments. A worm cut in two was found
to reproduce the tail at the cut extremity of the cephalic half, and to
form a head upon the caudal moiety. Bonnet * progressively in-
creased the number of sections in healthy individuals of a small
worm or nais, which he calls the Lumbricus variegatus ; and when
one of these had been so divided into twenty-six parts, almost all of
them reproduced the head and tail, and became so many distinct indi-
viduals. Sir John G. Dalyell has succeeded in artificially propagating
a SabeUa in the same way. The small fresh-water naids show great
powers of repair and reproduction ; these little worms have a paler
colour of the blood than in most Annulata ; but through the trans-
parent skin you may clearly see its circulation. There are some
species found in sand or mud, such as those that stain of a red
colour extensive tracts of the Thames mud at low water, which, when
submerged, habitually protrude the anterior half of their body, which
is remarkable for its regular oscillating movement. Bonnet cut off
the head of one of the naids of this genus, which was soon repro-
duced ; and, when perfect, he repeated the act ; and again as often
as the head was reproduced. After the eighth decapitation the un-
happy subject was released by death ; the execution took effect, the
reproductive virtue had been worn out. This series of experiments
occupied the Genevese philosopher two summer months. Since many

* CLXXXII. pp. 117.245.

ANNULATA. 253

of the smaller kinds of naids frequently expose a part of their body,
the rest being buried in the earth, both they and their enemies profit
by the power of restoration of the parts which may be bitten ojQT.

With this power of reproduction of lost extremities is associated
that of spontaneous propagation by developing and detaching new
series of segments.

Spontaneous fission has now been observed to take place in almost
every order of Annulata ; and in all it takes place at nearly the same
part, near the beginning of the posterior third part of the body ; but,
the formation of the new anellid is due to a process of gemmation
of new segments, which proceeds from the last or penultimate joint.
It is most common, or has been oftenest witnessed, in the little abran-
chial fresh water naids. But Otho Frederic Miiller has represented
a young Syllis (his Nereis prolifera) in the act, in his great work,
the '^ Zoologia Danica." Gruithuisen has described the process in a
Chmtogaster ; Oersted, in an Eosoloma ; M. Edwards, in a Myrianes
(Nereis) ; and Schmidt in a tubicular anellid, called Filograna
Schleideni*

The place where the process of forming the new segments is to be
carried on, is soon indicated by a slight swelling and increased vascular
action. If the head or anterior segment of the species be charac-
terised by eye-specks, antennoe, a proboscis, or branchiae, these are
developed in a certain and always recognisable degree, before the
final separation takes place. In the Myrianes, the coloured eyes in-
dicate the young fry. In the cephalobranchiate anellid, the gills
are shown, in the stage of fission represented by Professor Schmidt,
as four pairs of articulated filamentary vascular processes. In the
Nais proboscidia, the characteristic proboscis shoots out from the
nascent head of the young worm, which is thus duly armed before it
is cast off to provide its own nutriment. The last joint of the young
naid is specially ciliated, like that of the mother ; and the corre-
sponding portion of the alimentary canal has thick walls, with
numerous filamentary or vascular appendages. This gemmiparous
segment resumes its procreative function in the parent as soon as the
lineaments of the head of the first young nais are established ; and a
second young nais, with a rudimental proboscis, intervenes between
the first and the original parent ; sometimes even a third nais is indi-
cated by the elongation, swelling, and active vascularity of the last
joint ; and thus four generations of naids may be seen organically

* The ill success of a later experimenter does not justify the contemptuous tone
in which the results of his, perhaps more skilful and careful, predecessors, are
rejected. See CXC. passim.

254

LECTURE XII.

108

connected and constituting one individual. Such individual is due
to the succession of incomplete gemmations ; the reproductive process
is comj^leted, and the compound animal is resolved into the single
individuals, by spontaneous fission. The nucleated cells that are
aggregated in the penultimate or proligerous segment, form a signi-
ficant feature in its organisation. As long as the anellids propagate
by this primitive mode, they manifest no ovaria or testes. These are
developed in those individuals which are propagated by gemmation
and spontaneous fission, when the proper season for ovij^arous gene-
ration has arrived. M. Edwards observed, that a nereis allied to
Myrianes generated in succession six young from the same posterior
segment, each of which developed the true generative organs, without
the parent itself showing any trace of them. M. Quatrefages has
noticed the same fact in a species of Syllis,

In many of the Anellids, therefore, the phenomena of partheno-
genesis are manifested in the immature state ; and, since the indi-
viduals so propagated alone acquire the generative organs, an alter-
nation of generations may here be affirmed of such species : the
oviparous individuals producing eggs from which the
gemmiparous individuals come, and these, in their turn,
reproducing the oviparous individuals.

I next proceed to point out the chief modifications of
the generative organs properly so called. And first, as
to the generative organs of the leech. In the medicinal
species {Hirudo or Sanguisuga inedicinalis) may be seen
a number of pairs of little gray rounded bodies, usually
nine pairs, which are the testes, Jig. 108., a a ; these
are round whitish sacs, containing a milky fluid, abound-
ing in spherical sperm-cells. A little duct proceeds from
'^O y^ each to a common longitudinal vas deferens {b), near
r^ the anterior fourth of the leech, which forms a saccu-

l/Q OK lated vesicula seminalis (c c), each of which sends its
duct to a common small pyriform prostatic gland (e), from
which is prolonged a filiform intromittent organ (/*), which
projects from the ventral surface of the twenty-fourth
ring. But the leech is androgynous, and the female
organs are situated behind this prostate and penis, be-
tween the seventh and eiorhth abdominal j^an^lia ; they
consist of two subspherical ovaria (a), two short oviducts
(h\ which unite to form a single oviduct (c) that expands into a
pyriform muscular uterus {d).

Brandt and Ratzeburg * found in the bodies which they, with

d

04

s.

* CLXXXV.

ANNULATA. 255

preceding anatomists, call the ovaries, roundish corpuscles with a
reticulate surface, presenting in that structure an unmistakable resem-
blance to the parts regarded by Weber as the ova of the medicinal
leech, and by Wagner as those of the H. vulgaris.

The uterus, d, has a glandular lining membrane, a muscular tunic
of longitudinal and transverse fibres, and a cellular
outer coat. It opens by a short duct, or vagina, on
the twenty-ninth ring. It contains a collection of
eggs, with chorion. Brandt remarked, in a much
distended uterus, although the major part of its con-
tents had been already evacuated, a delicate mem-
brane like the chorion of an ovum, in which were
many small yellowish corpuscles, very like the above
described ova, which led him to suppose that that
Leech. dclicate membrane was the already developed inner-

most cocoon-skin.
In the naids the orifices of the male and female organs are in two
pairs, situated about the anterior third of the body. In the Neds
proboscidia the ovarium is included by the substance of the testis.
Two caeca extend inwards, at the breeding season, from' the two
anterior generative pores, which are then found filled with sperma-
tozoa grouped into fasciculi, and probably received from another
individual i7i co'itu. The ova are carried out by long convoluted
oviducts.

In the earth-worm the external characters of the generative organs
may be clearly seen in Hunter's dissections. We perceive here, that
the generative apparatus is more concentrated in the earth-worm than
in the leech, and more individualised than in any other animal of the
anellidous class. The three pairs of small opaque organs, which
Hunter regarded as testes, may possibly be only " spermathecie,"
like the anterior pair in the naids. They are laden with sperm atoza
during the breeding-time. The germinal vesicles and developing ova
are found in the larger gray-coloured caeca ; each of which sends out
a distinct short oviduct, and these combine into a common oviduct on
each side, opening behind the orifices leading from the testes or sper-
mathecas. If a section of one of these ovarian sacs is made, it is
found filled with a spongy matter in the centre, and the ova are
situated in this. The common oviduct from each lateral series of
ovaria terminates in the fissure upon the sixteenth segment, about
one-third from the head. It is interesting to note here, that the con-
dition and function of the oviduct in the earth-worm is analogous to
the arrangement of the generative parts in plants. In plants, the
part answering to the oviduct is a distinct canal, communicating with

256 LECTURE XII.

the pistil, and serving to convey the pollen to the ova ; but the ova
afterwards escape by rupture of the ovarium, or by what the botanist
calls dehiscence of the seed-capsule. It is exactly so with the earth-
worm ; the so-called oviducts serve to convey the impregnating prin«
ciple to the ova, which escape into the abdominal cavity of the earth-
worm, by bursting through the ovarian sacs. In these sacs, however,
there is always found a quantity of spermatozoa in different stages of
development; and accordingly the generative organs of the earth-
worm are open to two interpretations. The anterior organs may be
regarded, as by Hunter and Cuvier, as the testes, or they may answer
only to the spermatheca in insects ; and, in that case, the true male
organ may be that external spongy part which surrounds the proper
ovarium ; and this would not be a solitary instance of such an
arrangement of the essential organs of generation in the animal king-
dom, but one which is very common in the androgynous gasteropods.
However, there is much room for research and experiment to clear
up this difficult moot-point.

Both the leech and the earth-worm enjoy a double or reciprocal
coitus ; the leech has a true perforated intromittent organ ; the earth-
worm has not. During the breeding season, however, two imperforate
appendages are developed from about the thirty-second ring ; their
base adheres intimately to the cellular tissue ; they have no commu-
nication with the genital apertures ; are developed only at the breed-
ing season ; and are deciduous. The second accessory organ is that
thickened part of an earth-worm which is situated between the thir-
tieth and the fortieth segments ; it is called the *' clitellum," and,
when two earth-worms are disturbed in co'itu, the adhering clitella
are the last parts to give Avay.

With regard to the dorsibranchiate and tubicolar Anellides, many
of these are dioecious. The sperm-sacs or testes are situated on the
ventral aspect, between the layers of the ventral muscles. The deve-
lopment of the ova is more clear and obvious ; because they are com-
monly remarkable for the bright colour of their vitelline mass ; and
the number of ova is so great, that the ordinary colour of the anellid
is changed at the breeding season. Thus, in the Aphrodite cirrata,
Sars found that, in February, the three posterior fourths of the body
were of a brilliant red colour, on account of the great number of ova
there accumulated. Neither testes nor ovaria have external ducts ;
the products of both are discharged by dehiscence, into the abdomi-
nal cavity, and are excluded by pores situated near the base of the
setigerous feet. In the Aphrodite, the ova pass between the dorsal
scales, and there development takes place. There is but one known
genus of anellid that exhibits external sexual characters, viz., the

ANNULATA.

2.5:

Sperm-celis and spermatozoa, Lumbricus.

Exogone or Cijstonereis. In the females the middle segments exhibit
pyrifbrm sacs, attached to their ventral surface, which receive the
ova after they are impregnated ; the male is without these and is
smaller. The genus Eunice is viviparous, and the young escape from
the ruptured skin of the hinder segments.

Finally there remains to be considered the development of the ge-
nerative products. As to
the spermatozoa, these are
formed in a number of cells
connected together by a
spherical mass, and stud-
ding its surface. {Fig.W^^
A.) Each ceU is the seat
of development of a sepa-
rate spermatozoon, and this
in its growth pushes the
cell-wall outward : the fila-
mentary extremities di-
verge from the common
basis of the sperm-cells
(c) ; then, by mutual attraction, they become amassed together (d) ;
and the bundle is finally resolved into the individual spermatozoa (b).
Dr. A. Farre has communicated to me the following phenomena
which he witnessed during microscopical observations of the sperma-
tozoa of the earthworm. He placed the contents of the testis between
two slips of glass. " In about ten minutes the whole mass is seen to
lieave and writhe with astonishing energy, the form of the movement
being that of the peristaltic action of the intestines. Everything in
contact with the spermatozoa becomes ciliated by them, one end of the
filaments fixing itself w^iilst the other vibrates free. The result is,
that if the body to which the spermatozoa attach themselves is fixed,
such as the glass, on the margin of a mass of granules, a line of cilia
is formed, Avhose action creates a strong current, and everything
moveable is drawn into the vortex, and is seen drifting rapidly ah)ng.
But if the body to which they attach themselves is mo\ cable, such as
the globular bodies found in the Testis itself, or those which occur in
every part of the ovary, and which, being extracted from the latter,
are placed, for the sake of experiment, amongst the spermatozoa from
the testis, then the globular bodies soon become clothed with sperma-
tozoa, whose free ends, moving rapidly, cause the whole body to rotate.
A most remarkable object is thus formed, which continues for a con-
siderable time in motion, clearing for itself a free area, and in this it
revolves, whilst its revolutions are apparently assisted by the action

s

258 LECTURE XII.

of other spermatozoa, which, having attached themselves to the peri-
phery of the cleared space, keep up a complete vortex, in which the
centre body is partly a passive and partly an active agent. This re-
markable property of spermatozoa, in performing the office of cilia,
is, as far as I am aware, a new fact, and one which may serve to
explain possibly the transference of the sperm fluid, or even of ova,
of various animals, along surfaces or tubes not naturally ciliated."*

In regard to the development of the ova and embryo in the earth-
worm, the ova, when they are impregnated, are discharged from the
ovarium, pass into the abdominal cavity, and are pressed on to a re-
ceptacle near the anal end of the worm. Dr. A. Farre has traced the
development in some instances, which is so far analogous to that of
the Ascaris, that the embryo acquires the worm-like form before it
leaves the egg. It appears that some earth-worms are developed
before they are excluded, but this is not always the case. The
whole of the process, however, is complicated and obscured by a con-
siderable number of parasites, eggs of gregarinae and pseudo-navicellar
capsules, so that it is one of the most perplexing fields of microscopic
observation.

The generative phenomena of the leech are less dubious. Mr.
Quekett and others have found that the spermatozoa are developed in
the testes, a, Jig. 108., in the same manner as in the earth-worm and
other Anellids. The ova of the leech are spherical, and exhibit,
when found in the ovaria, a, fig. 109., and oviducts, the usual con-
stituents of ova. There is a germ-yolk with a germinal vesicle and
spot, and a delicate vitelline membrane. When the ova are received
into the uterus, the germinal spot has disappeared, intimating that
impregnation has taken place, and a delicate reticulate chorion is
acquired.

The medicinal leech is oviparous ; the fertile ova are successively
discharged in groups of from six to fourteen, enveloped in a nidus
or cocoon of mucus. The cocoon is ovate, two-thirds of an inch
in length, and half an inch in diameter. It has a flocculent outer
surface, but is smooth and slightly tuberculate within ; a more con-
spicuous, though minute albuminous plug, projects inwards from
each pole of the cocoon. In the month of August, conical exca-
vations may be observed in the slime at the sides of the reservoir, in
each of which there is a cocoon. The formation of the cocoon is the
result of a curious mana^uvre. In the Hiriido vulgaris, when
the cocoon is about to be formed, the body is observed to be greatly
contracted, both above and below the uterus; the included part

* CXCVI.

ANNULATA. 259

swells, then becomes milky white, from the formation of a film, into
which the animal, having attached itself by its anal sucker, forces,
after some effort, the whole contents of the uterus. This being done,
the leech elongates the anterior part of its body, and, thus loosening
the enveloping membrane, withdraws its head as from a collar. It
sometimes bends back its head, and, drawing the collar forwards,
gently aids in its removal. The process usually occupies about twenty
minutes. The cocoon is at first very elastic, and has no determinate
figure. After the leech has attached to it some adjoining substance,
it fashions it with its mouth into an oval form. The points of the
cocoon from which the leech withdrew its head are weaker than the
rest, and from these the young escape.

Mr. Brightwell, who has carefully observed this common species of
our freshwater pools, states: — "On the 2nd of June, H. vulgaris
deposited one capsule containing ova ; on the 5th, another ; on the
10th, another; and on the 15th, two more ; each of them containing
from seven to ten eggs. On the 22nd, the young appeared in the
capsule deposited on the 2nd ; and on the 13th of July they emerged
from the capsule, and in six weeks were fully developed, and left the
capsule. Examining the young of tliis species with a power of about
sixty linear, we detected a Cypris and four specimens of a common
rotiferous animalcule in its stomach, one of the Rotifera being still
alive."*

Both Weber t and Filippi J have figured ova of the leech-tribe in
certain stages of cleavage ; but the primary and subsequent steps of
this important process in anellidous ova were first noticed by Kolliker §
in a small Nereis (^Exogone Orstedii), with the impregnated ova con-
tained in marsupial sacculi arranged in two rows along the ventral
side of the body ; each sacculus held a single ovum, and was sus-
pended, a pair to each segment from the tenth to the twenty-third
inclusive, by a short stem to the ventral integument. These sacculi
are probably formed by albuminous mucus, exuded and hardened by
sea-water. Kolliker figures the single central germ-cell ; the double
germ-cell, followed by the total fission of the yolk with the secondary
germ-cell in each ; these cells again divided, and the consequent
quadrifid division of the yolk ; folloAved by successive subdivisions,
as in the Ascaris.

In the e^g of CIepsine\\, after the disappearance of the germinal
vesicle a whitisli discoid mass of molecular corpuscles appears at one
end of the yolk. Assuming this to mark the pole, the first line of
cleavage is a meridional one, Avhich bisects the disk unequally :

* CXCVII. t CXCV. t CXCVIII. § CC. II ccV.

s 2

260 LECTURE XII

a second, third, and fourth meridional cleft succeed each other, and
then the yolk is further subdivided by an equatorial cleft into nine
yolklets, the ninth occupying the opposite pole ; the process continues
until the yolk is well subdivided : when the germ-rudiment appears
at the germinal pole, it consists of parietal granules, spread out into
a layer which progressively expands to cover the germ-cells. The
influence of the primary germ-cells operates more partially or locally
upon the yolk-mass than in the Nereids; and, although the spontaneous
fission of the germ-cells is accompanied by total cleavage of the yolk
in all Anellids, that process is less regular in the aberrant Suctoria
than the typical orders of the class.

The best account of the development of the medicinal leech is
given by Dr. E. H. Weber*, whose illustrations are copied by
Brandt and Ratzeburg.f The egg-mass in the uterus is cylindrical,
brownish, and subtransparent : it is extruded with difficulty, and can
hardly be taken from the cavity uninjured. When the mass has been
four hours in water, it assumes a longish oval form. Some of the
stages of the cleavage of the yolk have been observed in eggs in the
cocoon ; two of these appear to be figured by Weber. J When the
yolk has undergone its subdivision, and its peripheral stratum has been
metamorphosed into the primitive germ- layer, a large clear space or cell
appears in the centre, from which an infundibular canal extends to, and
opens upon, a part of the periphery, covered by a ciliated epithelium ;
the sucker, which afterwards forms the mouth, is here developed, and is
the first recognisable part of the future leech. The mouth, when the
embryo is little more than a line in length, dilates and contracts, and
some fine lines radiating from it already indicate the muscles sub-
servient to the act of nutrition, which consists in the embryo's
swallowing the surrounding albumen. The integument extends in
a straight line from the mouth, along a narrow median tract of the
ventral surface of the germ-mass^ to about one-third from the opposite
end ; and when the embryo is three lines in length, if it be placed in
alcohol, and afterwards in water to restore the translucency of the
gelatinous parts, the ganglionic chain may be traced along tlie median
line of this part of the integument. Wiien the ganglions are visible
without chemical preparation, the mucous loops begin to appear as
whitish transverse streaks. Next, the anal sucker is developed, and
the cephalic end of the embryo begins to stretch forth from the yolk
or germ-mass. The testes, with their common sperm-duct on each
side, and the ovaria and uterus, are now discernible ; but they are

* CXCV. pp. 127—197. t CLXXXVII. taf. xxx. .

% Op. cit. t, X. figs. 2 and 3.

ANNULA.TA. 26 1

l^roportionally, especially the testes, more minute than the mucous
loops and round mucous sacs, whose development keeps pace witli
that of the general integument. The circulation can be discerned
before tlie pigment-cells are formed in the skin ; and the large lateral
veins are early conspicuous. The superficial cilia disappear; and the
embryo, which hitherto, by its vibratile surface and single opening of
the digestive cavity, lias resembled a planaria, now acquires an anus.
The yolk-mass is progressively pushed by the growth of the integu-
ment to the dorsal and anal parts of the body, the last remnant
appearing as a conical papilla above the anal sucker. The internal
yolk-mass is divided by the growing septa or constrictions of the
stomach, the intervening dilatations of which are afterwards developed
into sacculi, and of these the last pair is already the largest ; the
remainder of the yolk is inclosed by the intestine, whose outlet
surrounds the external projecting part. The alimentary canal con-
tracts and expands on the contained yolk -material. This course of
development extends over six weeks. Weber traced it from the 6th
of July to near the end of August. At this time, the young move
about in the cocoon, which may contain from five to fifteen ; the
comparative paucity of the young, even when a vigorous leech suc-
cessively forms and fills as many as six cocoons, agreeing with the
small size and number of the ovaria. They escape by perforating
one end of the cocoon, and are subtransparent, but show as many
rings as the parent. But little growth takes place up to the month
of December : the young get sustenance by sucking the mucus of the
parents, but w^ill grow, if isolated, by assimilating the remnant of the
yolk-mass in the stomach. The period of acquiring the full growth
and power of propagation depends much on the opportunities tlie
young leech may have of sucking the blood of other animals. John-
son believes that five years elapse before the medicinal leech is
full-grown, and speaks of one which he kept alive twenty years. De
Blainville found two-year-old leeches only three inches long. Audouin
could not succeed in keeping them beyond from eight to twelve years,
when they were allowed to propagate. The Naides and ArejiicoIcB,
according to the author of the " Report,"* are annuals. " They are
born during the latter months of one summer, and survive the winter,
attain to the maturity of growth, reproduce the species, and die by
the spontaneous subdivision of the body into fragments on the arrival
of the same season of the succeeding year."

Kochf found a specimen of Eu?2ice, probably E. sangiiinea, witli
developed embryos in most of the joints ; some of the hindmost seg-

* CXC. t CCVII.

262 LECTURE XII.

nients seemed to have been spontaneously cast off, and the embryos
escaped from the ruptured surface. Those at the lowest observed
staGje of development presented a roundish or oblong form with
feeble lateral indentations indicating two or three segments, a wide
alimentary canal filled with the yolk-mass, and no trace of antennas,
feet, eye-specks, or jaws. When the embryo has attained one line
in length, the segments are defined and increased in number to
twenty or thirty ; on the anterior half of these, commencing with
the third segment, the conical bases of the setigerous feet are de-
veloped; the segments appear to be increased in number by suc-
cessive divisions of the second; a pair of eye-specks and jaws are
next developed ; and the segments, being multiplied and provided
with single-bristled feet, the young Eunice presents the characters
of a Lumbrinereis of Audouin and Edwards.

In most branchiated anellids the embryo is excluded as a ciliated
spheroidal animalcule. It lengthens, partially casts its cilia, retaining
them arranged either in a cincture round the middle of the body, or
in two bands one about each extremity. At the anterior end the eyes
or eye-specks appear ; the segments are indicated on the rest of the
body, and the tubular feet and their bristles sprout forth ; the little
anellid afterwards taking on the modifications which distinguish its
family, its genus, and, finally, its species.

In the development of the typical Anellids, there is something, there-
fore, which merits the name of a metamorphosis. Professor Loven,
for example, captured, in August, on the shores of the Baltic Sea, a
discoid animalcule {Jig. Ill), which rapidly moved by means of two
rows of vibratile cilia : the principal row being situated upon a pro-
jecting ring {b\ at the margin of the disk. This ciliated body dif-
fered from the gemmules of the Polypi, in being provided with a
mouth (e) and an anus (c), the latter occupying the
apex of the cone. The course of the alimentary
canal, which extended from one to the other
aperture, was detected by feeding the little animal
with indigo. In a short time the cone began to
elongate and to be divided into segments, which
were developed in four parts, the two principal
pieces forming half-rings, one upon the ujjper, the
other upon the lower surface, which were united by
two shorter side-pieces. Coincident with the elon-
rt''''^SS<r gation and segmentation of the body, was the de-

\, velopment of the head from the discoid surface (a\

tmbryo ol Nereis. ^ \ y

upon which first the black ocelli, and then two
pointed filaments, or antennae (/), made their appearance. The

ANNULATA. 263

length of the body, and the number of segments, continued to in-
crease, the disk with its vibrating cilia (6) still existing. This disk
is afterwards reduced to an appendage on each side of the head, and
finally disappears. The new rings are added in front of, and not
behind, the older ones, agreeably with the order of development of
the segments in the Bothriocephalic described in a former lecture.
Each ring originally consists of an upper (^) and an under half-
ring (Ji), analogous to the tergum and sternum in the external
skeletons of insects. The tubular and setigerous feet are lastly
developed from the small lateral pieces. These observations beau-
tifully exemplify the repetition of structures and phenomena, charac-
teristic of mature animals widely separated in the natural scale, in
the immature states of an intermediate species.

With regard to the genus Aphrodite, Sars * took a small species,
in the month of February, on the Norwegian coast, which produced
richly-coloured ova, and he traced the successive development of
these. He found that the ova escaped from small pores, and w^ere
received into a kind of pouch beneath the dorsal scales, and there
underwent their development and escaped. He observed the geo-
metrical division of the rose-coloured yolk, and the clear spot in the
centre of each successive division. The embryo is an active loco-
motive oval mass, with a little group of cilia, and an indication of an
eye-speck to guide its course ; after swimming freely for twenty-four
hours the development of segments commenced. In the Cystonereisy
in which the ova are incubated in marsupial sacs, the development of
the animal appears, as in Koch's Eunice, to take place without that
amount of metamorphosis which has been observed in other Errantia,
First, there are two short tentacula, then three ; then the animal
elongates, and before it quits the marsupium, it presents a recog-
nizable miniature of the parent.

Observations have been made on the development of the tubicolar
anellids by Milne Edwards. f He found a group of ferruginous yellow
ova, aggregated in a gelatinous mass, at the entry of the tube of the
Terehello, nehulosci. The embryo, when excluded, is raonadiform,
and swims by the vigorous vibrations of its superficial cilia; it
leogthens, and the cilia, which at first were generally diffused,
become confined to a cincture behind the head, a transverse ventral
band near the tail, and a small circle round that part. The head is
distinguished by two red eye-specks ; new segments are successively
added, one behind the other, and always in front of the anal one ;
but as yet the embryo is apodal. The tubercles and setas are next

* ecu. t CCVI.

s4

264 LECTURE XII.

developed in the same order^ and a free-moving or " errant " anellid
ensues. Finally, the cilia of the buccal rings are lost, the young
Terebella reposes,' and envelopes itself in a mucous tube. It is now
half an inch in length, and the circulation may be seen in the dorsal
vessel, the branchial filaments, and the cephalic antennae.

Thus, in the class Annulata^ the observations on development, so
far as they have extended, show that its progress varies in different
orders, and in a minor degree in different families. The embryo of the
leech, as soon as it is individualised, or made distinct from the germ-
mass, presents the characteristic forms and locomotive organs of tlie
parent: it indicates, only in a very transient way, during the develop-
ment of this form, some characteristics of the Tiirbellaria. In the
earth-worm the ultimate form is obtained by a successive develop-
ment of segments, without any previous free locomotion of the embryo
as a ciliated monad. The embryos in some viviparous Errantia, e.g.
Eunice and Cystonereis, are at first acephalous, apodal, and abranchial,
but do not manifest a rotifer-like stage. The young of other dorsi-
branchiate and of some eephalobranchiate anellids, on the contrary,
start into free locomotive life under a form, and with instruments
and modes of locomotion, quite distinct from those that characterise
the adult. '\\q may hence deduce the necessity for caution in
generalising as to the metamorphosis or non-metamorphosis of a par-
ticular class. A very interesting phenomenon in the development of
some of the Errantia is that which has been noticed in the young
of certain species when it has acquired the form of the parent : its
manifestation, viz., of a power of parthenogenetic propagation by
virtue of the retention of unchanged germ-cells or nuclei in the
penultimate and last segments of the body : it would seem, moreover,
that it did not develope male or female organs in its own person, but
that these are formed in the offspring propagated by gemmation and
spontaneous fission. Should these observations receive confirmation
and extension, they will show that such Annulata are subject to
what has been called " alternate generation," although somewhat
modified as compared with th at which has been noticed in the
Entozoa and AcalephcB.

Class ANNULATA.

Body soft, symmetrical, verniiform;, annulated ; with suckers, seta3
or setigerous tube-feet. Alimcntnry canal with two apertures and
proper parietes. A vascular sys tini cirtulating, in most, red bleed :
respiratory organs. Ganglionic double nervous chord.

ANNULATA. 265

Order Suctoria (Leeches).

Bodu, terminated by a sucker at each extremity, without sette or
tubular feet. Alimentary canal adherent to the integument. An-
drogynous and ametabolian.

Genera Branchiobdella, Piscicola, Clepsiiie, JVephelis, Hoemopis,
Sanguisuga^ Pontobdella. (This aberrant order leads, by the Ne-
mertine worms, to the Turhellaria.)

Order Terricola (Earthworms, Naiads).

Body, long, cylindrical, the rings provided with setre. Alimentary
canal closely attached by numerous bands to the abdominal walls.
Androgynous.

Genera Chcetogaster, Enchytrceus, Nais, Lumhriculus^ Eiiaxes,
Scemiris, Lumbricus, Sternaspis.

Order Eerantia (Nereids, Sea-centipedes, Lug-worms,
and Sea-mice).

Body-rings with tubular setigerous feet ; external gills on the
greater number. Alimentary canal loosely attached to the ab-
dominal walls. Dioecious. Metabolian.

Genera Arenicola, Ammotrypane. Chcetopterus, Aricia, Aricinella^
Cirratulus, Ophelia^ Peripatus, Glycera, Nephthys, Alciopa, Syllis,
P/iyl/odoce, Hesioiie, Lycastris, Nereis, Oenone, Aglaura, Lumbri-
jiereis, Eunice, Amphinome, Sigalion, Polynoe, Aphrodite.

Order Tubicola (Animal-flowers).

Body-rings with tubular setigerous feet ; gills attached to or near
the head. Alimentary canal loosely connected with the abdominal
walls. Dioecious. Metabolian.* Inhabiting natural or artificial
tubes.

Genera Serpula, Sabella, Amphilriie, Terebella, Amphicora,
ChlorcEma.

* The SabeUina brachjcera, Dujardin (Annates des Sciences Nat. t. xi. 1839, p.
291, pi. 7. f. 6.), and the Anisomeleus liiteus, Templeton (Trans. Zool. Soc. t. ii.
pi. V. figs. 9 — 14.), are probably larvae of Tubicolar aneUids.

266 LECTURE XIII.

LECTURE Xm.

EPIZOA AND CIRRIPEDIA.

The phenomena of the generation and development of the animal
kingdom, so far as we have traced them, must, already, have impressed
us with the inadequacy of the knowledge of the nature of an animal
in its final and complete stage of existence only, for the determination
of its affinities and proper place in the natural system. This we have
learnt from a study of most of the previous classes of animals ; it is
more plainly demonstrated by the subjects of this day's discourse. I
may also here observe, that whilst it is essential to trace the meta-
morphoses of each species in order to rightly comprehend its true
nature, the study of the generative organs shows that we cannot rely
on them alone for a system of classification. We saw^, for example,
that some of the anellids combined both male and female organs in
the same individual, while others had those organs separate and
peculiar to distinct individuals ; one order was androgynous, another
dioecious. In the earth-worm we had evidence of a certain concen-
tration of the generative system within a few segments ; in the leech,
of a sub-division and more extended placing of the male organs :
but this vegetative character was most remarkable in the dioecious
anellids, in which almost every joint presented either its pair of testes
or of ovaria, according to the sex of the individual. Then, in refer-
ence to the progress of development of these worms, some transitorily
manifested the form and character of one class, inferior to them in the
animal scale, and others those of another lower class ; thus the
embryo leech represents the planaria, whilst most of the higher
anellids quit the ovum in the infusorial form. The further progress
of development was interesting, since it reminded us of that singular
propagation of certain Acalepha), in which the larva produced other
larvae like itself, before it was metamorphosed into the final form of a
medusa. For the. ordinary mode of growth of the Anellid, by the
development of joint after joint, one precisely similar to the other,
throughout a series of, perhaps, hundreds of joints, with only the first
and the last segments distinguished by any peculiar characteristics, —
all this process of growth looked very like an incomplete partheno-
genesis ; but this mode of production is fully manifested by the suc-
cessive casting off of groups of segments, with the characteristic head
and tail, as in the instances cited in the preceding Lecture ; the young
anellid from the ovum propagating at first by gemmation and spon-

EPIZOA AND CIRRIPEDIA. 267

taiieous fission ; and the individuals so produced developing the
ordinary organs of generation.

The low organised articulated classes, which succeed the Anellids
in the rising progress, undergo such extraordinary metamorphoses
before attaining their mature state, as to mask their true relations,
not only to the class, but to the primary division of animals to which
they belong. This is especially the case with the creatures whose
organisation and development will form the subject of the present
Lecture.

This elongated, cylindrical, unarticulated Lerna^a {fig. 112), whose
smooth soft body seems devoid of any other appendages than the two

^^ 113

112 .^fe'^

Peniculus fistula. a

Balanus sulcatus.

long slender ovisacs (/), might be regarded, on the fall of these de-
ciduous appendages, as one of the entozoa of the fish to which it is
attached, and on the nutrient juices of which it subsists.

This Ballanid {fig. 113), imprisoned in its conical calcareous shell,
and cemented to the stone on which it grew, might seem as naturally
to belong, like its neighbour the limpet, to the testaceous Mollusca.

How minute and accurate must have been the investigation of the
forms and structures of these animals, at every stage of their exist-
ence, before the truth began to dawn, that they were more nearly
allied to one another than to any other class of animals ! The most
vivid imagination of the boldest generaliser or sjieculator upon the
unity of organisation in the Animal Kingdom could never have di-
vined that the Lernjca and the Cirriped were at one period of their
lives locomotive animals, swimming about under very similar forms,
and by almost identical natatory instruments, — not under the com-
mon ciliated infusorial form, in which the Polype, Acalephe, Echino-
derm and certain Entozoa, Anellids, and Mollusks, first enter into
active life, — but with symmetrical pairs of jointed setigerous legs like
those of the full-grown errant Anellids and the lower organised
Crustaceans, to which the Epizoa and Cirripedia are, in fact, essen-
tially and most closely allied, although they end their career as

268

LECTURE XIII.

sedentary animals under such different, such diversified, and, often,
such grotesque forms.

These metamorphoses, moreover, lead to very different results, as
respects the powers of their subjects, from those of the Medusa and
Comatula. The Epizoa and Cirripeds acquire increase of bulk and
organs of generation ; but, in every other respect, the varied course of
their development ends in a retrograde movement.* Their develop-
ment would seem to have been at first, as it were, hurried forward at
too rapid a pace, and the young parasite, starting briskly into life,
ranging to and fro by the highest developed natatory organs we have
yet met with, and guiding its course by visual organs, must lose its
eyes and limbs before it can fulfil the destined
purpose of its creation.

The Epizoa, by which name we recognise the
singular class of animals which infest the skin, the
eyes, and the gills of fishes and other marine ani-
mals,— these external parasites, which are as nu-
merous as, and perhaps more numerous than, the
whole class of fishes, — are distinguished in their
mature state by a body of a more or less elongated
or sub-cylindrical form, defended by a smooth, semi-
transparent, parchment-like integument, having a
more or less distinct head, and generally a pair of
long cylindrical ovisacsf {Jigs. 112, 114,/), depen-
dent from the opposite extremity of the body.

In this low organised class of Articulate animals,
as in the classes which commence all other great pri-
mary groups, there is an extensive gradation of
forms by which we pass from species slightly ele-
vated above the cavitary Entozoa to the true Crus-
taceans.

The lowest and most simple Epizoa adhere by a
suctorious mouth {Jig. 114, a), and traces of ex-

* LXXXIV. p. 155.(1843.) " ]1 faiit done distinguer
avec soiu les formes zoologiques qui peuvent etre assimilees a
celles qui produirait \m arret de developpement chez d'autrcs
animaux de la meme serie, et cclles qui resultent d'un de-
veloppement recurrent." — Milne Edwards, "Aunales des
Sciences." Feb. 1844, p. 77.

f By these appendages the Epizoa are distinguished from
those highly-organized Entozoa — the Linguatul(s, e.g., —
which by the inferior size of the male, the complex structure
of the female, the two pairs of articulated and iincinated limbs of
the larva, and the grade of development of the nervous system,
seem to make the nearest approach to the present group.

EPizoA. 269

tremities exist only in the form of a few minute pairs of obtuse inar-
ticulate processes (b). In the higher organised species, the adhesion
is effected by suctorial (/tg- 116, ?n) or prehensile limbs, or by jointed
mandibles, with terminal hooks or forceps (Jig. 1 1 5, b). The head,
in most of the species, is found, when closely examined, to present a
pair of jointed antennae (Jigs. 115, f, 117, c), which, contemplated by
the experienced naturalist, cognisant of the value of such characters,
might excite the suspicion that relations to higher Articulata than
the Anellids were hidden under the bloated form which indolent
and gluttonous habits had superinduced upon the pendent parasite.
Observation of it during its early and locomotive state has proved
this to be actually the case to an extent which could not have been
anticipated.

The Epizoa are of distinct sexes: the male (Jig. 117) appears
always to retain his freedom, and is, perhaps on that account, singu-
larly smaller than the female, generally not more than a fifth part of
her size ; consequently, for a long time, the males escaped recognition.
They adhere to the vulva of the other sex with one antenna usually
inserted therein. The female individuals, distinguished throughout
a great part of the year by their pendant ovisacs, are the examples
usually seen of this curious class ; and in these I shall proceed to
describe the anatomical characters of the Epizoa.

The body, independently of the ovisacs, is generally divided into
two segments : the anterior and smaller division sometimes supports
a distinct head, but more commonly corresponds with the cephalo-
thorax of the Crustacea: the larger segment is called the abdomen,
and in it the ovaria are developed. You will not unfrequently find
adhering to the eye of the sprat an Epizoon or Lernsea *, which is a
nearly allied species of the same genus (Peniculus) as the specimen
figured and described by Nordmann (Jig. 112)t, which infests the
boar-fish (Zeus aper). In the Peniculus Jistula, the head (Jig' 114,
A), is oval and notched anteriorly, each division being armed with an
inwardly bent hook, or rudimental jaw (c). The mouth (a) is imme-
diately beneath these, in the form of a circular orifice, supported by a
short cartilaginous tube. At the posterior contracted part of the
head are two pairs of short, oval, flattened processes (b) : a constric-
tion or neck separates' them from the thorax, at the commencement
of which there is a third pair of similar rudiments of locomotive
appendages. The thorax (t) is round, and separated by a constriction
from the abdomen (a b), a fourth pair of appendages (b) being de-
veloped from the interspace. The basis of the smooth parchment-
like integument is chitine. The alimentary canal (d) is much

* CCVIII. t LXXI. Heft. ii.

270 LECTURE Xlll.

contracted in the neck and thorax, but expands in the abdomen
into a moderately wide and uniform intestine, which again
slightly contracts to terminate by a distinct anus at the hinder
extremity. The alimentary canal has the same simple straight
course in other species of Epizoa. One cannot be surprised at this
correspondence with its general condition in the cavitary Entozoa,
when the similarity of their easily assimilable nutriment is remem-
bered. The intestine is, however, complicated in the Epizoa with a
conglomerate or minutely-lobed adipose mass, which surrounds, like
a net-work, nearly the whole extent of the abdominal tract of the
intestine in Lerncea, Lerneocera^ and Lamproglena, and which
Nordmann supposed, from its gland-like character, might fulfil the
function of a liver.

In some species which attach themselves to the gills and the like
favourable positions for an abundant supply of the most nutritious
fluid, the body is frequently deformed, as it were, by excessive
growth, and ccecal productions from the simple straight intestine are
continued into the prolongations of the thoracic or abdominal walls.
The Nicothoe, a small parasite of the gills of the lobster, is an ex-
ample of this condition of the digestive organ. The first segment of
the body is produced into two lateral symmetrical wing -shaped lobes,
each four times the length of the segment to which they are attached,
and they contain corresponding csecal prolongations of the straight
intestine.*

In the Peniculus Jistula, the abdomen contains, in addition to the
alimentary canal, two slender tubes, the ovaria and oviducts (o, o),
commencing by blind extremities near the anterior part of the dilated
intestine, and continuing with a slightly wavy course to terminate at
the two apertures, to which the ovisacs are attached. These ovisacs
(f) singularly resemble the seed-capsules of certain plants, the Cassia
fistula.) e. g., being divided into a series of cells or chambers by
transverse septa, placed at regular distances. Each cell contains an
elliptical or lenticular ovum.

Two slender white filaments (^ g) running almost parallel v.'ith,
but at a distance from, each other, through the whole length of the
under surface of the abdomen, nearer the margins than the middle
line, form the chief and most conspicuous part of the nervous system.

The Epizoa differ from one another in their mode of adhering to
the fish they infest : some stick fast by a suctorial mouth ; others by
processes that grow from the head ; but the most common mechanism
of adhesion in this singular class is a circular sucker, ^^. 116, m,

* CCIX.

EFIZOA.

271

developed upon the confluent extremities of a pair of obscurely jointed
tubular feet — the third thoracic limbs of the larva (Z, /), — as in the
Lerneopoda of the shark*, the Achtheres of the perch, ^^. 116, and
the Tracheliastes of the chub. In the last-named parasite, which
may be found adhering to the fins of the Leuciscus cephalus in the
months of October and November, the head and thorax are confluent,
unless the segment to which the bases of the before-mentioned
feet are attached be held to represent the thorax. The abdomen
is, as usual, the largest segment. The mouth, ^^. 115, a, is a cir-
cular aperture, fringed with minute
short bristles ; on each side there is a
maxilla ( e, e), dentated at the inner
margin, and terminated by a bifid hook.
The antennce (/), are represented by
two short lancet-shaped processes, ter-
minated at the apex by a few extremely
short bristles. The most conspicuous
appendages of the head are, however,
a pair of mandibles {b, b), which con-
sist of two obscure joints, the second
iUtH ^^ which has a bifid extremity ; the
III' ' outer division (c), is armed by a strong

Tracheliastes. CUrVCd SpinC, whicll is OppOSCd tO tWO

short straight spines ; the inner division (d), is tipped with four small
spines. Immediately behind the large tubular prehensile process is
a short rudimental extremity, supporting a moveable hook, which
is opposed, as in the mandibles, by tw^o short spines. The muscular
system is sufiiciently conspicuous in the head of this Epizoon in the
form of distinct fasciculi of fine fibres (g).

In the P€7ieUa-\, the head resembles a cauliflower, swelling out into
a globose group of slightly branched and obtuse wart-like processes,
which must have grown after the head had become imbedded in the
flesh of the fish to which it is attached. Two long tubular processes
or extremities are developed at the junction of the thorax with the
abdomen ; but their extremities are free, simple, slightly attenuated,
and obtuse. On the under surface of the body, in the interspaces of
these appendages, there are four pairs of simple, small, oval, flattened
feet ; their pointed extremities extend only half w^ay to the sides of the
part of the body to which they are attached. The body is prolonged
beyond the ovisacs in the form of a tail, which is provided on each side
with a series of sixteen slender cylindrical appendages, close set in an

* Prep. No. 286. A.

t Prep. No. 286.

272

LECTURE XIII.

oblique position, like the barbs of a feather, or the vane of an arrow,
whence the specific name Sagitta, given to this parasite. The caudal
lamellae of the higher Crustacea would seem to be here sketched out.
The anatomy of the Epizoa has been most elaborately traced out
by Nordmann* in the parasite of the common perch, called Achtheres.
In this species two lateral teeth project from the circular mouth, the
labial margin of which is fringed with bristles. Here, also, we have
mandibles (6), and maxillse, the latter provided with palpi ; and, be-
sides these, a pair of jointed antennae (c), each terminated by three
setae. Now, this is a very important external character ; it is the first
instance of true jointed antennae that we have met with in our ascend-
ing survey of the animal kingdom, and the acute zoologist might be

led to surmise, from their presence, that
relations of higher affinity were masked
beneath the general character of the ver-
miform body of the parasite, and we shall
be able to raise the mask as we trace the
metamorphoses of the species. The ali-
mentary canal is, as usual, straight, and
terminated by a bituberculate vent {v), at
the opposite extremity to the head. The
abdominal intestine {d\ is fusiform, and
divided by a series of slight constrictions
into sacculi. It is maintained in its posi-
tion by a transverse muscle {h). The he-
patic organ (e) is more concentrated than
in the Peniculus, and surrounds the ante-
rior part of the canal. The walls of the
abdomen are distinctly provided with lon-
gitudinal (i) and transverse {k\ fasciculi
of muscular fibres. The nervous system
consists of a single cephalic ganglion, from
which are continued two principal chords
{g\ extending along the under surface of
the body.

The circulating fluid consists of a clear
plasma, with granular corpuscles of diffe-
rent forms and sizes. The pulsatile vasi-
form heart may be seen at the middle line
of the cephalo-thorax propelling the blood
forwards by rythmical contractions. Two canals {ii\ pass from it
into the hollow prehensile feet. The rest of the blood is distri-

* LXXI. Heft. ii.

Achtheres, female, magnified.

EPizoA. 273

buted to the head, and along each side of the commeneement of the
alimentary canal to the under part of the body, where it passes back-
wards in the vessel which accompanies the intestine.

The ovaria at first appear in the form of a slightly flexuous, long,
blind tube, sacculated along one side {o,Jig. 116). As the ova are
developed, the ovarium takes on the form of a bunch of grapes, and
occupies the whole cavity of the abdomen external to the intes-
tine 6' : each ovarium terminates by a triangular, and somewhat pro-
minent orifice, to which the external ovisac (/) is appended.

The Epizoa are remarkable for the disproportionate size of the
117 ^^ sexes. In the minute male {Jig- 117), the testes are

indicated by four dark coloured and finely granulated
bodies {d d) situated in the posterior segment or
abdomen. He appears like a mere parasite of the
female to which he adheres, near the vulva, and
having usually one antenna inserted into that aper-
ture.

The first remarkable circumstance in the natural
Achtheres, male. history of the aquatic Epizoa is the constancy with
Magnified. ^vhich particular species infest particular fishes or

Crustacea. And how, it may be asked, can creatures so devoid of
means of transport, nay, in most instances, of the power of detaching
themselves from the animals whence, like foetuses, they derive their
means of growth, originally reach the precise species of animal and
organ to which they are habitually attached ?

Are certain of the ova accidentally retained near the parent after
the rupture of the ovisac ; and do they there grow, like seeds of plants
fallen in a favourable soil ? Or, do some of the liberated ova, by a
happy fortuity, arrive at the appropriate organ of the appropriate
species ; and are they there accidentally retained until the prehensile
instruments are developed ? Such_hypotheses may be permitted in
reference to the ova of an Entozoon, which are developed by millions,
and need only gain an entry into the animal they may infest, or
which may be the common food of the species in whose intestine they
are adapted to exist ; but the ova are too few in the Epizoa, and the
parts to which they are attached are too exposed, to allow of the
supposition that their parasitic growth is dependent on such acci-
dental circumstances.

MM. Audouin and Edwards appear to have been the first to
suggest that the sedentary Lern^an Epizoa might enjoy at a previous
period of existence locomotive powers, and the hypothesis was sup-
ported by the discovery, made by Dr. Surriray*, of the embryo of a

* CCXL p. 401.

T

274 LECTURE XIII.

LerntBocera, still in the ovum, which, instead of resembling the
parent, presented the characters of a locomotive Entomostracous
monoculous Crustacean.

The singular metamorphosis thus indicated has been traced out and
generalised by the careful observations of Dr. Nordmann. The
following is the course of development of the Lernaean parasite of the
Perch.

The female Achtheres is devoid of ovigerous appendages in the
months of December, January, and February. In March they are
developed by the eversion of a membrane prepared in the ovarian
sac. Each sac hangs by a short tubular peduncle which is in direct
communication with the short oviduct. The outer membrane of the
ovum or chorion is moderately thick and transparent ; the inner mem-
brane is thinner, and includes both the vitelline mass and albumen.
The yolk forms the largest proportion of the contents of the ovum,
and is finely granular. One of the first parts of the embryo discerned
by Nordmann was the dark ocellus {fig. 118, e,). A pair
of cylindrical processes shoot out from each side of the
fore part of the embryonic or vitelline mass ; and a
pencil of hairs is developed from the extremity of each
process. The body (d) slightly elongates, the exterior
Achtheres. Egg albumiuous fluid (c) increases, the inner membrane {b)
and Embryo. Q^pands, and the outer one {a) bursts and is shed. The
movements of the imprisoned embryo increase in force until it bursts
the remaining obstacle, and escapes from the ovigerous sac. It then
119 ,^s^^^ presents the form represented in figure
119. The digestive sac {Ji) isnow discerni-
ble, together with a peculiar tortuous tube
{g'\ which is continued from the mouth.
The locomotive organs are in two pairs,
and consist of tubular processes of the
Achtheres: first stage. intcgument, including a fasciculus of

bristles ; they now present the type of those of the Anellids. And
since we were led from the Infusoria to the Polypi, because the cili-
ated larvae of these resembled the monads, and from the Polypi to
the Acaleph^, because these in their larval state were polypes, so we
have now the same indication, from a transitory step in development,
of the right track in passing from the Annulata to the Epizoa ; and
the succeeding steps will lead us to place these parasites on a higher
grade of articulate structure ; and not with the Entozoa, where
Cuvier and Lamarck left them.

In the course of half an hour the young Achtheres undergoes its
second stage : the first integument (e) is loosened by the formation of

EPizoA. 275

a second beneath it, which now incloses a body, altered in its shape
and in the number and nature of its appendages {Jig. 120.).

The process of moulting lasts from eight to ten
minutes. A great proportion of the original germ-
mass remains unaltered, surrounding the simple in-
testine, and extending into the bases of the tubular
feet of the larva. The nisus formativus proceeds to
120 "*in.'!^ operate on this material, but on a modified plan. The
second body, which is formed inside the husk of the
first now cast off, is divided into an anterior and a
posterior segment, the latter consisting of four joints.
A pair of four-articulate setigerous antennse diverge
from the anterior part of the body. Betv\reen the
Achtheres : second antemioi is thc large single median eye, as in the mo-
stage, nocular Entomostracous Crustacea. The little Epi-

zoon is now provided with five pairs of feet ; the first three pairs ter-
minate by a simple hook; the last two pairs are bifurcated, one
division being hooked and prehensile, the other tubular and emitting
tufts of bristles ; these natatory feet strike the water together, and
propel the body forward with a jerk ; they are aided by the last seg-
ment, which is terminated by four setigerous tubercles.

The antennae probably serve to indicate to the young parasite its
appropriate object, to which it then proceeds to attach itself. The
first pair of feet is approximated towards the mouth, and forms the
uncinated mandibles. The second pair of feet increases in size, and
the terminal hook enlarges ; they serve to seize and hold on to the
surface of the fish selected. The feet of the third pair lengthen
and unite together to form a cartilaginous circular sucker, and per-
manently anchor the parasite to its prey.

The two sexes are alike in their young and locomotive state: the
male at its final metamorphosis retains the first pair of feet as mandi-
bles, very similar in form to those of the female : the second pair is
shorter and thicker : the legs of the third pair always remain sepa-
rate from each other, and consist usually each of two large joints,
the last one terminated by a claw. The posterior natatory feet dis-
appear in both sexes ; and, with the loss of these instruments of loco-
motion, the eyes, also, are blinded and absorbed.

Before proceeding to the Cirripedia, I would offer a few remarks
on the -nature of the changes just described. They are commonly
spoken of under the same name as that given to the changes
of insects, and perhaps they differ only in degree. The metamor-
phosis in all insects is attended with the casting off of a certain
proportion of the precedent individual, called the " moult," or the

T 2

276 LECTURE xni.

new animal may be said to creep out of the old, from which the pro-
cess is called the "ecdysis." With regard to the so-called metamor-
phosis which issues in the succession of a fixed, blind, sessile, multi-
valve barnacle to a free-swimming crustacean with pedunculated eyes,
or in the succession of a rooted vermiform parasite to a natatory
animal with articulated setigerous limbs, — when these phenomena
are closely traced, they are seen to depend in a greater degree upon
the action and coalescence of retained cells, than upon a change of
form of pre-existing tissues. If the development of the ovum in the
pedunculate ovarian sac of the low crustaceous external parasite of a
fish be closely traced, the peripheral cells of the germ-mass are seen
to combine and coalesce to form the smooth transparent skin of the
embryo Lernaea, from which also tubular processes extend in two
(^Achtheres) or three {Lernceocera') pairs, including setee v/hich pro-
ject from their extremities.

In the LerncBocera the anterior pair is directed forward like an-
tennae, but they are unjointed ; and the head is further indicated by
a coloured eye-speck. Another layer of germ-cells have perished,
as such, in order to form the parietes of a straight and simple
intestine, with a mouth and anus. Thus the anellidous type is first
manifested.

But a large proportion of the minute germ-cells remain in the wide
abdominal interspace, amassed around the alimentary tube, and ag-
gregated in groups at the base of the tubular and setigerous feet.
With respect to the latter, we might say that the same provision is
made for the reproduction of the limbs as is retained throughout life
in regard to those of the lobster. In the larval Lerntea, however,
those reserve-cells commence the formation of new limbs irrespective
of any injury to the old ones. The whole peripheral stratum of the
retained germ-mass, in contact with the primary integument, is trans-
formed into a new integument. These germ-cells have increased
and propagated at the expense of the aliment assimilated by the
alimentary canal. The formation of the new integument and of the
new feet proceeds connectedly and contemporaneously ; but the new
parts are not moulded upon the inner surface of the old ones. The
plastic force has changed its course of operation. A hinder segment
of the body is added to the front one, which answers to the whole of
the body of the first larva. If antennre did not before exist, a joined
pair is now developed. Instead of two pairs of tubular setigerous
limbs, three pairs of uncinated prehensile limbs are developed from
the anterior or cephalothoracic segment, and as many pairs of arti-
culated setigerous limbs from the abdominal segment. New muscles,
new nerves, and new vessels are formed for the support and exercise

CIRRIPEDIA.

277

of these various instruments. The outer case, and all that gave form
and character to the precedent individual, perish and are cast oft';
they are not changed into the corresponding parts of the new indi-
vidual. These are due to a new and distinct developmental process ;
rendered possible through the retention of a certain proportion of the
unchanged germ-cells. The process is essentially the same as that
which developes the cercariform larva of the Distoma within the
gregariniform one, or the external bud from the Hydra, or the in-
ternal bud from the Aphis. It is a slightly modified parthenogenesis ;
and the phases by which the locomotive anellidous larva of the Lerntea
passes through the entomostracous stage before retrograding to the
final condition of the oviparous, limbless, bloated, and rooted parasite,
are much more those of a metagenesis than a metamorphosis.

I now proceed to the second class of Articulated animals which are
associated in the present Lecture with the Epizoa.

Many of the Cirripedia* are parasitic animals, like the Epizoa, but
are dependent upon the organised bodies to ^vhich they are attached
for their place of residence, not for their food ; those Cirripeds which
do not infest other animals are attached to sea-weed, floating timber,
^21 or rocks. The Cirripeds are

symmetrical animals, with a
soft, obscurely articulated body
enveloped in a membrane (^JiQ'
121, c c) ; they are provided
with six pairs of thoracic feet
(ib. A), divided into three
joints, and terminated each by
a pair of long and slender,
many-jointed, ciliated tentacles, curled towards the mouth, whence
the name of the class. They are androgynous, and in some species
there are also small males parasitic on the bisexual individuals.f
The mouth (ib. ci) is prominent, and, in most species, provided
with a broad upper lip, with two palps or feelers (ib. h\ and three
pairs of dentated and ciliated jaws. The opposite extremity of
the body is prolonged into a slender, many-jointed, ciliated caudal
appendage {fg. 123, g), which is traversed by the generative
canal. The mouth is situated near the anterior extremity of the
body, which is modified to form the organ of attachment of the
animal. It is sometimes produced to a considerable extent, and is of
contracted diameter, forming a long and flexible peduncle ; sometimes

1 a d
Lepas anatifera.

* Lat. cirrus, a curl, pes, a foot.

t CCXXIIL pp. 189. 248.

T 3

278

LECTURE XIII.

it expands at once into a broad disc or basis of adhesion ; in both
cases the immediate attaching substance is a peculiar cement pro-
ceeding from a modified portion of the ovaria.* The typical Cirripeds
are divided according to these modes of attachment into two primary
groups, viz., the pedunculated, or Lepadoids, and the sessile, or Bala-
noids. The first are commonly known by the name of Barnacles ; the
second by that of Crown-shells or Acorn-shells. Such are the
characters of the typical members of the class. The aberrant bur-
rowing genus Alcippe, and the naked, ventless Proteolepas, para-
sitic on other Cirripeds, form, according to Darwin, types of two
orders, equivalent respectively to that including all the ordinary
Cirripeds.

Most of these Cirripeds have their visceral cavity protected by a
calcareous shell composed of many pieces ; but in some, as, e.g. Alepas,
Ibla, the membranous investment of the viscera is enveloped by
a smooth elastic sheath, continued from the outer chitinous covering
of the peduncle. In Otio7i two small calcareous bodies {scuta), de-
veloped in the substance of the outer envelope, just above the brachial
fissure, are usually the sole rudiments of a shell, and the chitinous
covering is produced at its free extremity into two cylindrical plicated
ear-like appendages. In the earless Otions ( Cmeras), the external
tunic is strengthened by five calcareous bars, two at the fissure {scuta),
giving outlet to the arms, two along the terminal
I"> margin of the tunic {terga), and one along the

dorsal aspect {carina). In the common Barnacle
{Lepas anatifera), the calcareous matter extends
from five homologous centres, so as to protect the
whole of the visceral or thoracic-abdominal ca-
vity or body. In Jig. 122, c is the "scutum," d
the " tergum " and e the " carina ;" the first two
•^ are in pairs, the last is single, and was compared
by Cuvier to the symmetrical dorsal valve of
the Pholas ; but the relation is one of analogy
only.

Ail the valves, however, are strongly marked
with lines of growth, formed by successive ad-
Lepas anatifera. ditions to their margins, as in the shells of
Mollusca. In the genera Pollicipes and Scalpellum, there are other
smaller calcareous plates arranged round the junction of the body
with the peduncle. l^Jig- 122, a and & are the peduncle, which is a
development of the head including the aborted eyes and antenna3 of

122

* CCXXIII. p. 33.

CIRRIPEDIA. 279

the larva ; g is the caudal end of the body ; / the ventral surface,
with the aperture of the shell from which the cirrigerous feet pro-
trude : e is the dorsal surface. The relative position of the retracted
soft parts to the multi valve shell is shown in jig. 121.

All the sessile Cirripeds are strongly defended by a multivalve
conical shell, closed by a four-valved operculum {fig. 113). The base
of the shell is usually formed by a calcareous plate, and the walls are
apparently divided into twelve conical compartments, six of which
(««), called "arese prominentes" and "parietes," rise from the margin
of the base^ and terminate in a point at the free margin of the shell ;
whilst the other six {hh\ in the form of inverted cones, called "areae
depressse" and " radii," occupy the interspaces of the preceding series.
This calcareous citadel is divided into from four to eight pieces by
fine sutures. The piece at the part of the shell nearest which the
cirri (c) are protruded is called the " carina ; " the opposite piece is
the "rostrum." The symmetry or bilaterality of the shell is deter-
mined by these pieces, which have two lateral appendages, called
" al«." Three pieces are, in Octomeris, interposed, on each side, be-
tween the carina and rostrum. They are called " carino-lateral,"
"lateral," and "rostro-lateral." The two first have a radius on the
carinal side, and an ala on the rostral side ; the third piece has a
radius on each side. Our common Acorn-shells {Balanus, fig. 113)
have two pieces on each side, the " carino-lateral " and " rostro-
lateral." Each piece consists of an outer and inner plate, united
by longitudinal plates. The whole shell has a cellular and or-
ganised texture, and its gradual expansion is provided for by the
successive growth and calcification of processes of the mantle which
penetrate the uniting sutures. The cone is lengthened and widened
below by successive additions to its base, and is widened superiorly
by the gradual increase in breadth of the wedge-shaped pieces of the
second or inverted series. In the Tuhicinella *, a parasitic balanid
of the whale, the compound shell is a long subcylindrical tube, re-
minding us of that of an amphitrite ; but the animal, in both sessile
and pedunculate Cirripeds, is fixed to the bottom of the shell with
the head downwards, and the head is, therefore, superior in the ordi-
nary pendent position of the barnacles {Lepas^fig. 121).

The external integument consists of chitinef , which also forms the
animal basis of the shell % 5 the calcareous part of the latter consists
of 99'3 of carbonate of lime, with 0*7 of phosphate of lime§. The
chitine is lined by a soft vascular corium, the formative organ of both

* Prep. No. 279. f IX.

X lu Lepas and PoUicipes, CCXXIII. p. 30. § IX

T 4

280 LECTURE XIII.

the calcified and uncalcified cliitine. In the growth of the body the
membrane between the valves splits periodically, and a new strip of
membrane is formed beneath, connected on each side with a fresh
lajer of shell, the old strips disintegrating and disappearing*, but the
valves are not shed. The integument of the peduncle consists, in
Lepas, of corium, covered by smooth layers of chitine {Jig. 121, A);
but in Scalpellum and Pollicipes its outer surface is roughened by
small calcified scales. If the peduncle be very carefully removed
from the surface of attachment, the larval antennee can always be
found quite close to the end, but not at the actual apex.f

The movements of the peduncle in such species are effected by a
strong muscular tunic, consisting of three layers of non-striated fibres,
longitudinal, transverse, and oblique (ib. b). In Otio7i they extend
half-way down the sheath of the body J ; and in Alepas they line the
whole of the body-sheath. The action of these muscles is antagonised
by the elasticity of the chitinous tunic. The common Barnacle
approximates its scuta by a strong transverse adductor muscle ; its
body or visceral mass is moved towards the aperture of the shell,
which is thereby at the same time widened, by longitudinal muscular
fibres, and is retracted by shorter fibres attached to its base. In
Lithotrya there are two fan-like transverse muscles extending from
the basal points of the terga to a central line on the under side of
the carina. § The cirrigerous arms in all the Cirripeds have powerful
muscles for their actions, which are of the utmost importance to the
animal, inasmuch as the food is obtained by the currents which they
123 produce, and almost incessantly maintain, in

■ " the surrounding water. The sessile Barna-

cles are provided with a series of muscles
attached to the margin of the conical shell,
which act on the opercular calcareous pieces,
and close the opening of the shell.

The nervous system {Jig> 123), first de-
scribed and figured by Cuvier in the Lepas
anatifera^ presents the homogangliate type.
The oesophagus is surrounded by a wide
oral ring, closed above by a pair of super-
oesophageal ganglions, which send off nerves
to the peduncle, the ovaria, and to the
aborted and confluent eyes. Mr. Darwin
^ \J/ lias detected a small ganglion on each op-

tic nerve in the Lepas fascicular is. ^

* CCXXIII. p. 30. t lb. p. 33. % Prep. Nos. 62, 68, 69.

§ CCXXIII. p. 33, II lb. p. 49.

%

Nervous System. Lepas.

CIRRIPEDIA. 281

The ring is completed below by tbe large suboesophageal ganglion,
which gives off the nerves to the trophi, the first pair of cirri-
gerous feet, and the adjacent muscles. The second thoracic gan-
glion supplies the second pair of feet ; the third ganglion supplies the
third pair of feet ; the fourth and fifth pairs of ganglions are approxi-
mated to each other ; and the tubular extensile tail or penis receives
the two last pairs of nerves. Two branches from the oesophageal
ring pass to a small ganglion on either side of the stomach, from
which the alimentary canal is supplied. The nervous system is that
part of the organisation of the mature animal which most unequivo-
cally indicates the province of the Animal Kingdom to which the
class Cirripedia belongs ; and it indicates their superiority to the
Anellids, and their closer affinity to the crustaceous type by the
large size of the confluent ganglions on the abdominal chords. In
the degree of approximation of the two chords to each other, the
Lepades most resemble the lower isopodous Crustacea, for example,
the Talitrus. The neurilemma is stained by a dark brown pigment
in the Lepas fascicularis. In Pollicipes 31ifella, the fourth and
fifth thoracic ganglia are confluent. In the Balanus thitinnahulum
and Coronula diadema all the nerves, save those connected with
the brain, radiate from a single great suboesophageal ganglion.*

The acoustic organs are situated just beneath the basal articulation
of the first pair of cirri. Each consists of a sac-like cavity, which
incloses the true acoustic vesicle. The orifice of the vesicle is
closed by a delicate lid, formed by the expansion of a large nerve,
which here abruptly terminates.f Mr. Darwin, to whom we owe
the knowledge of this structure, has not found any otolites in the
acoustic vesicle, but only groups of yellowish nucleated cells in
the pulpy fluid. The same excellent observer is of opinion that
the pouches situated in the confluent segments beneath the free
part of the outer maxillae are " olfactory ; " their orifices are
produced or tubular in many Barnacles, but not in the sessile
Cirripeds.

Although the eyes of the Cirripeds are more or less aborted in
their mature state, they retain sufficient susceptibility of light to
excite, in the pedunculated species, when a shadow passes over
them, retraction of the cirri, and, in the sessile species, a sudden
shutting of their opercules ; the same act is caused by the sound or
vibration of an approaching footstep ; it indicates that they appre-
ciate the atmospheric movements produced by the approximation of
the hand, even, according to Dr. Coldstream, when it is not brought
nearer the shells than twelve or fourteen inches.J

* CCXXIV. p. 88. t lb. p. 95. X CCXVI. p. 688.

282

LECTURE XIII.

The marine animalcules brought to the mouth {^fig. 124, a\ by the
currents of the cirrigerous feet (6), and seized by the lateral jaws, are

124

Lepas.

conveyed by a short oesophagus, having a bell-shaped expansion of the
lining membrane, to a dilated stomach (<?), which is of unusual length
in Tubicinella, From six to eight c^eca are developed from the upper
part of the stomach, in several species of Balanus, and are branched
in Bal. 'perforatus. They are not developed in Tuhicinella. The
intestine {d) is bent upon the stomach, and tapers with a slightly
sinuous course to terminate at {d'\ the base of the caudal appendage {e).
The intestinal canal is lined by a chitinous epithelial tube, which is
continued above into the cseca. Darwin has observed it to be ex-
pelled entire, with the excrement, in a living Balanus ; it has been
deemed analogous to the typhlosole in the earth-worm's intestine.*

The stomach is coated by small, opaque, pulpy, branched glands,
probably subserving a hepatic function : these are arranged in longi-
tudinal lines in most Barnacles.

Poll states that he saw a heart pulsating a little above the anus,
and Dr. Coldstream, who quotes the remark, says that there is a
"central canal situated on the dorsal aspect of the body;"f but the
exact condition of the circulating system of the Cirripeds has yet to
be determined, and by the examination of living specimens. Much
of it — probably all the venous part — appears to be in the condition
of diffused channels or sinuses, defined only by the extremely delicate
tunica propria of the veins. There is one main channel along the
ventral surface of the thorax, dividing and surrounding the mouth,
and giving out branches which enter the inner of the two channels
in each thoracic leg ; there are also two canals in the penis. " There

CCXV. p. 26.

t CCXVI. p. 689.

CIRRIPEDIA. 283

are two dorso-lateral channels in the prosoma, which are in direct
connection with the great main channel, running down the ventral
side of the peduncle. This latter main channel branches out in the
lower part, and transmits the blood through the ovarian tubes, whence,
I believe, it flows upwards and round the sac, re-entering the body
near the sides of the adductor scutorum muscle. The main ventral
channel, in the uppermost part of the peduncle, has a depending
curtain, which, I think, must act as a valve, so as to prevent the
circulating fluid regurgitating into the animal's body during the
contractions of the peduncle." *

In the pedunculated Cirripeds slender appendages, which from
their position and connections are homologous with the branchiae of
the higher Crustacea, are attached to, or near to, the bases of a
greater or less number of the thoracic feet, and extend in an opposite
direction, outside the visceral sac. In the common Barnacle {Lepas
anatifera) there are two pairs of such branchiae; the first {d, fig, 121),
is attached to the side of the prosoma, anterior to the first cirrigerous
foot, and seems to answer to the gill developed from the last
maxillary foot in the lobster ; the second appendage {d) springs from
the dorsal surface of the swelling {g) at the basal joint of the first
thoracic foot. In the Ley as fascicular is I find one gill attached to
the prosoma, and three others radiating from the base of the first
thoracic leg.f In the Otion there are two gills from the side of the
prosoma, and five from the bases of the first five thoracic legs ; seven
pairs in all, most of which are unusually long and tapering. With
respect to the function of these appendages, I concur with Mr. Darwin
in deeming them of very secondary importance in respiration, having,
like him, always found them occupied by lobes of the testis. The
extensive vascular surfaces of the corium and of the body-sac, ex-
posed to the sea-water, with the active cirri themselves, most probably
sufiSice for the aeration of the blood ; and the additional expansion of
surface, afforded by the plicated tubular appendages to the body of
the Otion, concurs to effect the same end. The homologues of the
branchial appendages of the Barnacles are not present in the Balanids ;
the respiratory function is here especially aided by the production of
plicated folds of the body-sac, which are very numerous and complex
in the Coronula diadema.\

The Cirripedia are hermaphrodite : there are no known exceptions
to this rule in the sessile order : in the pedunculated one a ^^w ex-
ceptions have been discovered by Darwin, e. g. Ibla Cummingii
and Scalpellum ornatum, in which the large attached individuals

* CCXXIII. p. 46. t i*rep. No. 994. ; Prep. No. 997,

284 LECTURE XIII.

develope ova only, the spermatozoa being formed in distinct and
much smaller parasitic males. The same excellent observer has detected
similar parasitic individuals, mouthless and stomachless, containing
abundant spermatozoa, attached to the larger individuals, possessing
both male and female organs, of Ibla quadrivalvis, Scalpellum
vulgare, Sc. rutilum, Sc. rostratum, Sc. Peronii, and Sc. villosu?n,
such supplemental males having specific characters as distinct as
those of the hermaphrodite individuals to which they are attached,
and in which the vesiculas seminales are unusually small.

The ordinary hermaphrodite combination of generative organs
prevails so far as is hitherto known in all the species of Lepas, Pceci-
lasma, Oxyiiaspis, Anelasma, Pollicipes, Lithotrya, Otion, and Cineras.
The male organs consist of two testes, two sperm-bladders with their
sperm-ducts, and the penis. The testes consist of minute compressed
seminiferous lobes, forming usually a leaden-coloured pyriform digi-
tate or dendritic mass : they coat the stomach, enter the pedicels and
basal joints of the cirri, in some genera occupy certain swellings on
the thorax and prosoma, and in others penetrate the filamentary
appendages. They are confined to the thorax and prosoma in the
sessile Cirripeds. The sperm-bladders are, in most species, very
large : in the Lepadoids they lie along, and, save in some species of
Scalpellum, penetrate the prosoma, where their broad ends are often
reflexed : here the branched ducts from the testes enter. The coats
of the bladder are formed of circular fibres, which Darwin concludes
are muscular, having seen the spermatozoa expelled with force from
the cut end of a living specimen. The sperm-bladders, as they extend
backwards, gradually contract to canals w^hich unite in a single
sperm-duct at the base of the penis, or, in Otio7i, half-way along it.
In the bell-barnacles {Balanus) the sperm-reservoirs are very long
and tortuous : they lie within the thorax and prosoma, and unite at
the base of the proboscidiform penis. This organ is of great length,
except in certain species of Scalpellum, and can move freely in all
directions ; it is supported on a straight unarticulated base, short in
most, but in Ihla qiiadrivalvis of great length*: the rest of the
extent is more or less distinctly articulated ; short hairs project from
the intervals of the rings, and more abundantly from the end of the
penis.

In the Balanoids the ovaria consist of glandular bodies^ of un-
branched or main tubes, and of branching tubes and ca3ca. The
ovarian glands are situated near the basal edge of the labrum : the
branched tubes lie between the calcareous or membranous basis and

* CCXXIII. p. 5G. pi. iv. fig. 9 a.

CIRRIPEDIA. 285

the inner basal lining of the sac extending a certain way upwards
around the sac. There are no true oviducts. In the Lepadoids the
ovaria have a more complex form and extended place : they consist,
on each side, of a thoracic and peduncular portion connected by a long
unbranched canal. The thoracic ovaria {fig, 124, o), mistaken by Cuvier
for salivary glands, correspond in position with the entire ovaria in the
Balanoids : they are of an orange colour, and present the form of two
parallel, gut-shaped masses, having, in Otion, a great flexure, and
generally dividing at the end near the mouth into a few blunt
branches. Mr. Darwin, who has given the best account of the female
organs in the pedunculated Cirripeds, writes, " The state of these two
masses varied much ; sometimes they were hollow, with only their
walls spotted with a few cellular little masses ; at other times they
contained, or rather were formed of, more or less globular or finger-
shaped aggregations of pulpy matter ; and, lastly, the whole consisted
of separate pointed little balls, each with a large inner cell, and this
again with two or three included granules. These so closely re-
sembled, in general appearance and size, the ovigerms with their
germinal vesicles and spots which I have often seen at the first com-
mencement of the formation of the ova in the ovarian tubes in the
peduncle, that I cannot doubt that such is their nature."* The
connecting canals diverge at the bases of the first pair of limbs, bend
along each flank of the prosoma, under the superficial muscles, and
converge to penetrate the peduncle, along the ventral side of which
they run close together, and, when half-way towards the end, begin
to branch out in all directions ; the ova being developed within the
stems of the branches as well as at their ends. " A minute point
first branches out from one of the tubes, its head enlarges like the
bud of a tulip on a footstalk ; becomes globular, shows traces of
dividing, and at last splits into three, four, or five egg-shaped ballsj
which finally separate as perfect ova"t {fig. 121, ^).

According to the same author, the ova, immediately before one of
the periods of exuviation, burst forth from the ovarian tubes in the
peduncle, and round the sack of the animal, and, moving " along the
open circulatory channels, are collected (by means unknown to me)
beneath the chitine tunic of the sack, in the corium, which is at this
period remarkably spongy and full of cavities." The corium forms or
"resolves itself into the very delicate membrane separately enveloping
each ovum, and uniting them together into two lamellae : the corium
having thus far retreated, then forms, under the lamellae, the chitine
tunic of the sac, which will of course be of larger size than the last-

* CCXXIII. p. 57. t CCXXIII. p. 57.

286 LECTURE XIII.

formed one, now immediately to be moulted with the other integuments
of the body. As soon as this exuviation is effected, the tender ova,
united into two lamellae, and adhering as yet to the bottom of the sac,
are exposed ; as the membranes harden, the lamellae become detached
from the bottom of the sac, but are prevented from being washed out
by becoming united to semicircular folds of skin continued from each
side of the point of attachment of the body to the sac. These folds,
or " fraena," usually large, but in Ihla minute, are formed of chitine
with underlying corium, and their free border is beset with minute
pedunculate or clavate glandular bodies, secreting an adhesive sub-
stance serving to unite the ovigerous lamellae to the fraena. In some
species of Pollicipes the frasnal folds are destitute of the glands, and
do not subserve the function allotted to them in other Lepadoids.

Mr. Darwin, to whom we owe the above details, is of opinion that
the lamelliform gills of the Balanoids are the homologues of the
fraena. " The ova are impregnated (as I infer from the state of the
vesicular seminales) when first brought into the sac ; and whilst the
membrane of the lamellae is very tender the long proboscidiform penis
seems well adapted for this end. In the male of Ihla Cummingii, which
has not a probosciformed penis, the whole flexible body, probably,
performs the function of the penis : in Scalpellum ornatitm^ however,
the spermatozoa must be brought in by the action of the cirri, or of the
currents produced by them. That cross impregnation may, and some-
times does take place, I infer from the singular case of an individual
in a group of Balarii, in which the penis had been cut off, and had
healed without any perforation ; notwithstanding which fact, larvce
were included in the ova."

Mr. Darwin has shown that the organ, by the secretion of which
the Cirripeds attach themselves to foreign bodies, is a modified part
of the ovarian tube. In the Lepadoids there are two cement-glands,
situated high up in the midst of the ovarian cceca, with one cement-
duct proceeding from each ; the cement issues from the prehensile
antennae, and in some cases, at a later period, it escapes through
apertures in the peduncle. In the Balanoids, at each period of
growth a pair of new cement-glands is developed, larger than those
last formed, and making, w-ith the older glands, a chain connected
together by the cement-trunk. They all adhere to the basal mem-
brane or the basal shelly plate.

The supplemental male of the Scalpellum vulgar e {fg> 125) is
found attached over the fold in the occludent margin of the scutum
of the large hermaphrodite individual ; and is sometimes imbedded
more than half its length in the spinigerous chitine. It is an ovate,
compressed, flask-like body, having a fimbriated orifice (a) at one

CIRRIPEDIA. 287

end : a little behind this are four obtuse bristly processes {h) ; and
125 behind them are four little calcareous nodules, or rudi-
mental valves. The cavity of the body contains a
brownish pear-shaped bag, containing, in some indivi-
duals, a mass of spermatozoa. With this testis are con-
nected small vesiculae seminales, and Mr. Darwin be-
lieves he has distinguished an orifice at the end of the
'\^^^y abdomen. After the most careful dissection of very many
Supplemental specimens, he can positively affirm that there is no vestige
lum vuigare. of moutli or masticatoiy organs, stomach, or intestine.*

When we reflect on the uniformity of distribution of the Cirripeds,
particular species being attached to particular objects, and these not
always stationary and extended bodies, but often living animals, and
sometimes animals with quick powers of locomotion; when we further
call to mind that they adhere, not by prehensile jaws or feet, but by
the growth of a pedunculated root, or by the gradual application of a
layer of cement forming the base of their shell ; Vv-e must be con-
vinced that the organisation and properties of the fettered animal
are wholly inadequate to afford an insight into the process by
which it acquired its resting-place ; and that a knowledge of the
previous career from the time of quitting the egg is not less essential
to an explanation of the subsequent attachment of the Cirripedia,
than it was for the elucidation of corresponding phenomena in the
Ejnzoa,

No fortuitous dispersion of ova giving origin at once to a pedun-
culated or sessile multivalve can account for the invariable attachment
of the Coronula to the skin of the whale, and of the Otion to the
shell of the parasitic Coronula ; of the Chelonobia to the carapace of
the turtle, of the Cineras to the tail of the sea-serpent, or of the im-
bedding of the Acasta in the substance of a sponge. Tiiese remark-
able phenomena have been explicable only since the discovery of the
singular metamorphoses which the Cirripeds undergo, and of the
power which they possess, at one period of their existence, of attain-
ing and selecting their peculiar and appropriate place of permanent
abode. Nor were the real nature and affinities of this singular shell-
covered class of animals less problematical and doubtful before the
phenomena of their development had been traced out.

Mr. V. Thompson, whose minute and careful researches into the
natural history of marine animalcules have thrown much light on the
structure and development of radiated animals, was also rewarded by
the discovery of the metamorphosis of the Cirripeds.f On the 28th of

* CCXXIII. pp. 234, 235. f CCXXV. Memoir iv.

288

LECTURE XIIT.

April, 1823, he captured, with a small muslin towing net, a number
of translucent animalcules, about the tenth of an inch in length, of a
subelliptic form, slightly compressed, and of a brownish tint ; the
body of each was defended by a shell composed of two valves, joined
by a hinge along the back, and opening along the opposite margin for
the protrusion of a large and strong anterior pair of limbs (Jig.l26, «),
126 provided with an adhesive sucker

and hooks, and of six pairs of
posterior jointed members (b),
terminated by a pencil of bris-
tles. These natatory limbs acted
^ in concert, so as to cause the

animal to swim by a succession
upa a anus. ^£ j^^Q^^^jg ^].g ^j^g water flcas

(Daphnia). The body was terminated by a short tail (e), composed
of two setigerous joints. A pair of pedunculated compound eyes {d)
was attached to the anterior and lateral part of the body. Other
specimens of this little seeming crustaceous animal were taken on the
1st of May, and preserved alive in a glass vessel of sea-water. On
the night of the eighth two of them had thrown off their outer skin,
and were firmly adhering to the bottom of the vessel, where they ra-
pidly assumed the form of the young of the sessile Barnacle called
Balanus pusillus. The sutures between the valves of the shell and of

the operculum were visible, and
the arms, though not yet per-
fectly developed, were seen mov-
ing within. The eyes also were
still perceptible, although the
principal part of the black co-
louring matter appeared to have
been thrown off with the exu-
vium. On the 10th of May
another individual was seen in
the act of throwing off its exu-
vium, and attaching itself to the
bottom of the glass. As the cal-
cification of the shell proceeds,
the eyes gradually disappear,
and the visual ray is extinguished
for the remainder of the animal's
life. The arms at the same time
acquire their usual ciliated
structure.

Larval Lepas.

CIRRIPEDIA. 289

In a subsequent memoir*, Mr. Thompson described and figured
larvae of the Lepas and Cineras. The young Lepas, at the stage at
which it was observed, somewhat resembles the entomostracous genus
Cyclops {^fig. 127). It has a single median sessile eye-speck, three
pairs of members, the most anterior of which are simple, the others
bifid. The back of the animal is covered, like the Argulus armiger,
by an ample shield, terminating anteriorly in two extended horns, and
posteriorly in a simple elongated spinous process.

The discoveries of Mr. Thompson have been abundantly con-
firmed by Audouinf, Wagner J, Burmeister§, Goodsir||, Bates ^[, and
Darwin.*''"

In a ^ew Cirripeds, e. g., the species of Cryptophialus^ the changes
from the <ig^ to the pupa take place within the sack of the parent.

Fig. 127 illustrates the form of the " larva," or first stage, in both
pedunculated and sessile Cirripeds, at least after the second moult.
Before the moult, the horns, including the second antennie and the
caudal appendages c, are less developed ; and are always shorter in
Balanus than in Lepas. The general form of the larva is a de-
pressed oval, the body inarticulate, with a carapace covering the
dorsal surface. The eye (of) often appears to be due to a confluence
of two eyes. Behind the eye there arise a minute pair of horns, or
sheaths containing the rudimental antennae of the first pair. The
large lateral horns (^, e) contain the second pair of antennae ; they are
amongst the earliest developed organs, as in the larvae of the Crus-
tacea. The mouth is more or less proboscidiform, and is situated
between the first or second pairs of natatory legs ; the oesophagus
extends from it anteriorly, as in Limidus. The first pair of natatory
legs has a simple terminal joint ; the second and third pairs have
bifid terminal joints, or are biramous, in all the genera, as in Lepas
(yfig. 127). Darwin regards the natatory limbs as answering to the
second, third, and fourth thoracic limbs in the Crustacea. Behind
these limbs the trunk is produced, and terminates in a horny forked
appendage, which becomes much elongated, as in fig. 127, after the
first moult. In some larvae a second, and even a third fork, then
appears, indicative of an articulated abdomen.

In the second stage of the larva the carapace is much changed : the
second or great antennse become prehensile organs ; the first pair
disappears ; the eye has become double ; but the mouth is still simply
suctorial, although advanced in position. The three pairs of thoracic
limbs retain their larval character.

* CCXXVI t CCXXVIT. p. 31. t CCXXIX. p.467.

§ CCXIV. II CCXXX. pi. iii. and iv.

% CCXXVTIL pi. 6, 7, and 8. ** CCXXIII. and CCXXIV. p. 102.

u

290 LECTURE XIII.

In the third or pupal stage^, the anterior natatory legs become, like
the others, bifid or biramous : and three posterior pairs of legs are
superadded ; the small abdomen becomes defined from the thorax.
The prehensile antennre are freed from their cases ; the two eyes
stand further apart. The carapace consists of two portions, like tlie
valves of a bivalve shell, which fold over and include the thorax and
abdomen and their appendages, permitting also the prehensile an-
tennas {^fig. 126, a) to be bent back within the lower edge. The tw^o
valves of the shell are drawn together by an adductor muscle, which
crosses anterior to the basal margin of the mouth. Darwin has
observed the pupa of the Lepas australis to " swim very rapidly, and
often on one side, in a circle ; it could walk by the aid of its antennas,
but it often fell over." The antennce are the organs by which the
young Cirriped finally anchors itself to the spot where its future
adult existence is to be spent. The cement-ducts may be traced as
far as the third or disc-segment of the antennoe. There the cement
seems to transude, and to fasten down the disc : soon both antenna3
are surrounded by a common border of cement, which gradually
increases in extent after the metamorphosis. In the Lepas faseicu-
laris, the cement is poured out in sufficient quantities to form, itself,
the substance to which the peduncle of the adult barnacle adheres,
and, for a cluster of which barnacles it constitutes a central vesicular
float, as may be seen in the preparations, Nos. 275 and 276, Nat.
Hist. Series, Hunterian Museum.

The three terminal segments of the antennae, into which the
cement-ducts are prolonged, are retained in an otherwise functionless
condition, in the young Cirriped. The mouth is formed under that
of the pupa, with a new oesophagus round the old oesophagus, leading
into the same alimentary canal. The twenty-four extreme tips of
the six pairs of biramous cirri of the young Cirriped are formed
within the twenty- four extremities of the six pairs of biramous
natatory legs of the pupa. " Consequently," writes Darwin, " in
the Cirripede and pupa, thus far, part corresponds with part, not-
withstanding that new eyes are formed posteriorly to the old eyes,
and new acoustic organs in a quite different position from the old
ones ; but now we come to a most important diversity in the meta-
morphosis, or rather, to follow Professor Owen *, in the metagenesis,
of the young Cirripede. Although, as just stated, the extremities of
the cirri are formed within the legs of the pupa, yet, from the great
length of the cirri, they occupy more than the whole of the thorax of the
pupa : so that the thorax of the young Cirripede is not formed within

* Parthenogenesis, pp. 13 and 26.

CIRPvTPEDIA. 291

the pre-existing thorax of the pupa, but within that part of the pupa
(homologically a portion of the first three cephalic segments) which
lies anterior to the thorax. As a consequence of this, the pedicels
and lower portions of the cirri, the segments of the thorax and its
dorsal surface, all come to occupy a position at nearly right angles
to that of the corresponding parts in the pupa. And, as a further
consequence (and this is a more important point), the sack, which both
in the young Cirripede and pupa is formed by the overhanging
and produced portion of the carapace, and which is internally lined
by a reduplication of the membrane of the thorax, is necessarily,
owing to the changed position of the thorax, altered in extent and
carried much further ; namely, from extending merely parallel to the
longitudinal axis of the pupa, it is now, in the young Cirripede, in
addition, carried almost quite across the inside of the animal. Hence
it comes that the young Cirripede is internally almost intersected ;
and its body remains attached only by a small space to the sternal
or ventral inner surface of the carapace, — the carapace being modified
either into the capitulum and peduncle, or into the shell with its
operculum and basis. As a still further consequence of this change
of position of the body of the young Cirripede within the body of
the pupa, the alimentary canal becomes shortened to fully half its
former length. At the same time, the interspace between the mouth
and first pair of legs of the pupa (consisting of the seventh and
eighth segments of the archetype) is quite lost in the Cirripede by
coalescence. The first cause of the thorax of the young Cirripede
not being developed within the thorax of the pupa, probably is, that
the cirri may be formed of considerable length, so as to be immediately
able to seize prey; and that the thorax, which supports the cirri
(and this probably is even more important), should be as free as
possible within the sack, so as to aid the captorial action of the
cirri." *

When the due time for the act of metamorphosis has arrived, the
pupal carapace splits along the dorsal ridge, and is cast oflP together
with the acoustic sacks, the basal segments of the two antennae, and
the great black compound eyes. " Besides the split along the dorsal
ridge, the carapace separates all round the orifice from the delicate
tunic" lining the sack and investing the thorax and natatory legs of the
pupa ; for those membranes are not moulted for some considerable
time afterwards. Hence all these inner parts retain for a period the
appearance and structure of the natatory pupa, whilst the exterior
resembles in every respect a fixed and perfect cirripede." f

* CCXXIV. p. 123. t lb. p. 126,

u 2

292

LECTURE Xlll.

Of this most singular form of Articulate animal, the same acute
Observer from whom the above passages are quoted has determined
analytically the common pattern on which the cirripedial modifications
have been superinduced. The archetype consists of seventeen seg-
ments, the first fourteen of which, as in the Crustacea, constitute the
cephalo-thorax ; the other three are abdominal segments. The two
pairs of antennae and the eyes determine the first three segments of
the head ; the three pairs of jaws mark the next three segments ; and
the seventh cephalic differs from the succeeding seven thoracic seg-
ments. In all the common cirripeds two segments disappear : these
Mr. Darwin believes to be the last cephalic and the first thoracic ;
and the six pairs of cirri belong therefore to the six last thoracic
segments.

The general analogy of the pedunculated cirriped to the typical
Crustacea, and the true nature of the peduncle, will be best understood
by the diagram reduced mjig. 128, from Mr. Darwin's monograph.

A. Leucifer.

B. Lepas.

The upper figure is of a stomapod crustacean : the abdomen, which
in cirripeds is rudimentary, is given in outline. The lower figure is
a mature Lepas, with the outer antennae {a) and eyes (e), which are
actually present in the larva, retained and figured of proportionate
size. All that we see externally of a cirriped, whether pedunculated
or sessile, is the three anterior segments of the head of a crustacean,
with its anterior end permanently cemented to a surface of attachment,
and with its posterior end projecting vertically from it.

The capitulum, or shell, answers to the carapace in higher crusta-
ceans, which is a backward production of the tergal elements of the
third segment. It is divided into {s) the scutum, (t) the tergum, and
the dorsal line of splitting is defended by the narrow carinal piece c ;
b is the basis of the capitulum, compound carapace or shell ; m,
the position of the mouth ; p, the termination of the intromittent

CIRRIPEDIA. 293

organ, developed from the vertical surface of the apex of the abdomen,
but not, according to Darwin, the modified homologue of the ab-
domen.

Class EPIZOA.

Body, chitinous, vermiform, subarticulated, not always symmetrical;
with antennae and articulated limbs terminated either by suckers,
hooks, or bristles. Vascular system diffused: white blood. No re-
spiratory organs. Dioecious. Males small or rudimentary : females
with external pendent ovisacs. Metagenesis resulting in a usually
permanent parasitic attachment on the bodies of fishes.

The class is subdivided according to the mode of that attachment.

Order I. Cephaluna.*

Attachment by cephalic processes, sometimes numerous and com-
plex.

Genera Peniculus, Lerncea, Chondr acanthus ^ LerncBocera^ Penella.

Order II. Brachiuna.

Attachment by a suctorial disc at the confluent extremities of the
last pair of thoracic limbs.

Genera Achtheres, Tracheliastes, Brachiella, LerncBopoda, Ancho-
rella.

Order III. Onchuna.

Attachment by hooks at the free extremities of the first pair of
thoracic limbs.

Genera Dichelestium, Lamproglenay Ergasilus, Nicothoe.

Class CIRRIPEDIA.t

Body, chitinous or chitino-testaceous, subarticulated, mostly sym-
metrical, with aborted antennse and eyes. Mouth, prominent, com-
posed of a labrum, palpi, two mandibles, and two pairs of maxillse.
Thorax, attached to the sternal internal surface of the carapace, with
six pairs of multiarticulate, biramous, setigerous limbs. Abdomen,
rudimentary ; vascular system diffused : white blood. Branchiae,
when present, attached to the inferior lateral part of the surface.
Most are hermaphrodite ; a few have minute rudimentary male indi-
viduals parasitically attached to the females. Penis, proboscidiform,

* K€(pa\ri, the head, and ew-rj, a bed or last resting-place, in the plural
" anchors."

t In the characters and subdivision of this class I have followed Darwin.

u 3

294 LECTURE XIII.

multiarticulate, attached to the hinder end of the abdomen. No
oviducts. Metamorphosis and metagenesis resulting in a permanent
parasitic attachment of tlie fully developed female or hermaphrodite
individual.

Order I. Thoracica.

Carapace, either a capitulum on a pedicle, or an operculated shell
with a basis. Body, formed of six thoracic segments, generally
furnished with six pairs of cirri ; abdomen rudimentary, but often
bearing caudal appendages ; mouth with labrum not capable of inde-
pendent movements ; larva, first one-eyed, with three pairs of legs ;
lastly two-eyed, with six pairs of legs.

Sub-order Balanid^e. (Acorn-shells.)
Sessile, or without a peduncle : scuta and terga' provided with
depressor muscles : the rest of the valves immoveably united
together.

Family BalanincB.

Shell, with the rostrum having radii, but without alae ; lateral
compartments all having alae on the one side and radii on the other
side. Mouth, with the labrum notched in the middle, not tumid ;
palpi large, almost touching each other ; mandibles generally with
the lower teeth laterally double; third pair of cirri with their segments
resembling those of the second pair.

A. Scutum and tergum articulated together, or overlapping each
other ; each branchia composed of a single plicated fold.

Genera Balanus, Acasta, Elmijiius, Tetraclita, Pyrgoma, Creu-
sia, Chelonohia.

B. Scutum and tergum (when both are present) not overlapping
each other ; basis membranous ; parietes often deeply folded, with
the outer lamina, towards the basis, generally imperfect; each
branchia composed of two plicated folds ; shell attached to living
vertebrata.

Genera Coronula, Platylepas, Tubicinella, Xenobalanus.

Family Ctham,alinoB,

Shell, with the rostrum having alee, but without radii, rostro-lateral
compartments without alae on either side ; parietes not porose.
Mouth, with the labrum bullate ; palpi hardly touching each other :
third pair of cirri with the segments resembling those of the fourth
pair.

Genera Cthamalus, Chamcesipho, Pachylasma, Octomeris, Cato-
phragmifs.

CIRRIPEDIA. 295

Sub-order Verrucid^.

Sessile. Shell, asymmetrical, with the rostrum and carina united
on one side with scuta and terga, which are moveable on the other
side of the shell, but not furnished with a depressor muscle.

Genus Verruca.

Sub-order Lepadid^. (Barnacles.)
Pedunculated. Peduncle, flexible, provided with muscles: scuta

and terga, when present, not furnished with depressor muscles : other

valves, when present, not united into one immoveable ring.

Genera Lepas, Pcecilasma, Dichelaspis, Oxynaspis, Conchoderma

{Otion and Ci7ieras), Alepas, Anelasma, Alcippe, Ibla, Scalpellum,

PolUcipes Lithotrya.

Order II. Abdominalia.

Carapace, flask-shaped ; body formed of one cephalic, seven
thoracic, and three abdominal segments, the latter bearing three pairs
of cirri : the thoracic segments without limbs. Mouth, with the
labrum greatly produced, and capable of independent movements :
oesophagus armed with teeth at its lower end. Larva, firstly egg-
like, without external limbs or an eye ; lastly binocular, without
thoracic legs, but with abdominal appendages.

Genus Cryptophialus. (This singular genus appears to be allied to
the Alcippe, like which it is a burrower.)

Order III. Apoda.

Carapace, reduced to two separate threads, serving for attachment.
Body, consisting of one cephalic, seven thoracic, and three abdominal
segments, all destitute of cirri. Mouth suctorial, with the mandibles
and raaxillee placed back to back, enclosed in a hood formed by the
union of the labrum and palpi.

Genus Proteolepas. (This aberrant genus is parasitic on Alepas
cornuta : it makes the nearest approach,
among the Cirripedia, to the Suctorial
Epizoa )

tJ 4

296 LECTURE XIV

LECTURE XIV.

CRUSTACEA.

The class of invertebratecl animals which forms our present subject
may be regarded, from one point of view, as having been entered upon
in the preceding Lecture ; for, were we cognisant of the Lernoeans
and Cirripeds in no other than their locomotive state, we might be
led, with those naturalists who judge of an animal from one of its
vital stages only, to classify them with the Crustacea, and the pupal
barnacles more especially with the bivalve Entomostracans. All
Crustacea, however, differ from the Epizoa in being branchiferous ;
and from the Cirripedia in being dioecious, with well-developed males.
And the subjects of the preceding Lecture must have sufficiently
impressed us with the necessity of careful investigation of problematic
species at every stage of their development, in order to determine
their affinities and position in the scale of nature.

In tracing the progressive march of structural complications in the
animal kingdom, we see that the organs of vegetative life much more
rapidly acquire their full development than those of animal life ;
and, in reference to the latter, we find a more regular gradation of
perfection as the classes ascend in the scale. Take the Articulate
sub-kingdom for example. The Entozoa may show a complete alimen-
tary canal, with mouth and vent, and with salivary and biliary coeca:
they may have the sexes separate, and the male and female organs
marvellously developed; yet be devoid of every trace of a locomotive
organ, and have a smooth, soft, continuous, lubricous integument.
In the Annulata we found the integument firmer, but alternately
harder and softer, so as to be divided into segments with flexible
articulations; and in the higher forms of this class, each of the joints
was provided with distinct limbs, although these presented the lowest
form of such, e. g., as simple tubes including protractile setae. In the
larval Epizoa we saw the limbs presenting a true jointed structure,
but lost or becoming more or less abortive in the fixed adults ; whilst
in the Cirripedia several pairs of jointed limbs are retained in the
adult state, but their rapid actions are subservient to the acquisition
of food, not to locomotion.

We make the easiest and most natural transition from the lower
forins of Articuhitu to the Crustaceous class., by passing to it iVom

CRUSTACEA. 297

the larval state, — which I have argued to be the typical one*, — of
the Epizoa and Cirripedia ; in which view we may regard the
Crustacea as representing those larvae on a gigantic scale, and so
retaining the typical character with the faculty of locomotion.

We thus arrive at a class of articulated animals in which some or
all of the annular segments of the skeleton of the body are constantly
provided with articulated limbs or appendages, in which all the species
are free and locomotive, and are provided with distinct respiratory
organs. These animals are still, however, aquatic ; only a part of the
class can support themselves and move with their jointed limbs on
dry land ; the highest act of locomotion is that of climbing reeds or
trees, w^hich a few species of the present class are enabled to effect
by long prehensile claws. But the breathing organs in all the species
are organised for aquatic respiration ; in other words, are branchiee ;
and it is the combination of branchiae with jointed limbs and distinct
sexes which constitutes the essential character of the class Crustacea.

The name of this class refers to the modification of the external
tegument by which it acquires due hardness for protecting the rock-
dwelling marine species from the concussion of the surrounding
elements and from the attacks of enemies, and for forming the levers
and points of resistance in the act of supporting the body and moving
along the firm ground. The animal basis of this external skeleton is
the same peculiar tissue as in the two foregoing classes, viz., chitine,
which is insoluble in caustic potash, and is charred, not consumed, by
fire. In the crab and lobster tribes the integument is hardened by
the addition of earthy particles, consisting of the carbonate with a
small and varying proportion of the phosphate of lime. This crust is
coloured by a pigmental substance, diffused more or less irregularly
through its outer surface : its basis being a vascular organised mem-
brane, or corium. The crust exhibits a minutely tubular structure f,
is covered by a thin chitinous layer composed of hexagonal cells J,
and it is lined by a thin fibrous membran'e, which plays an important
part in the moulting process. The tubercles and bristles which beset
many parts of the shell are prolongations of it, or its basis — chitine.
In the smaller Crustacea the tegument retains a flexible pergameneous
character, and is usually so transparent as to allow the internal
coloured parts to appear through it.

Whatever be the consistence of the external integument or skeleton,
it is always disposed in a series of segments, either actually separate
and moveable on each other, or confluent in a variable extent and

* A character indicative of type is not to be confounded with the sum of cha-
racters determinative of class.

t XXIV. p. 420. X CCXXXI. vol. ii. p. 333.

298

LECTURE XIV.

degree, so as more or less to obliterate the traces of their primitive
distinctness. The segments are variously proportioned and combined,
so as commonly to permit the entire body to be divided into three
parts, viz., the head, the thorax, and the abdomen ; and most of the
Crustacea manifest their peculiarly distinctiv^e forms by different
combinations and proportions of the same number of primary rings
or segments. Each ring, again, consists of certain elementary parts,
which, by varying their proportions, contribute to the peculiar form
of the region of the body into the formation of which they enter.

There may be distinguished in the annular segment of a Crus-
tacean, a dorsal arch and a sternal arch, each consisting of a median
and two lateral elements: the lateral elements in the upper arch
are called " epimeral," and in the lower one " episternal," pieces ;
the middle element above, or " tergum," consists of two pieces united
in the middle line, and that below, or the " sternum " has the same
structure. In a great proportion of the class the body consists of
twenty-one of these rings, of which seven are more or less blended
together to form the head {Jig* 129, c), seven more obviously enter
into the formation of the thorax {g, ^), and the
remaining seven constitute the abdomen or tail
(a hY

The Crustacea, with seven thoracic and seven
abdominal segments, form the sub-class Malacos-
traca\\ but a few large species and a very great
proportion of the smallest members of the class
have the thorax and the abdomen composed re-
spectively of a greater or a less number of consti-
tuent segments than seven : these Crustacea form
the sub-class Entomostraca. The best-marked
group, that including the largest species of this sub-
class, is named Xiphosura, because the last seg-
ment of the body forms a long three-edged sharp-pointed weapon : it
is typified by the Limulus, or Molucca crab, in which the head and
thorax are more completely blended together than in the true crabs,
which they resemble in the general form of the body ; but they are
peculiarly distinguished from all other Crustacea by having the office

Cyraothoa.

* CCXXXII.

f In the larger species of Crustacea, where the chitine is combined with such
a proportion of carbonate and phosphate of lime as to be firm and brittle, it is,
as Aristotle has observed, less hard and less brittle than the shell of the mollusks,
whence that philosopher called those Testacea Ostracoderma, but gave to the
Crustacea the name of Malacusti aca, which name is still retained for that division
of the class which alone was known to the Greek naturahst.

CRUSTACEA, 299

of jaws performed by the basilar joint of the six pairs of thoracic legs,
which surround the mouth, the internal branch of those legs forming
an ambulatory and prehensile member. The large cephalo-thoracic
segment is protected above and laterally by an expanded crescentic
shield, obscurely divided by two longitudinal impressions into three
lobes, supporting the organs of vision on their highest part. The
tergal parts of the segments of the second division of the body are
also blended into one trilobate clypeiform piece, their original separa-
tion being indicated by the branchial fissures, and the number of the
segments by that of the lamelliform appendages attached to their
inferior surface. The termination of the intestine beneath the last
segment of the second division of the body of the Limulus proves that
division to answer to the abdomen in the Malacostraca : but admitting
the sessile eyes to indicate a distinct segment, not more than sixteen
segments can be determined by the appendages to enter into the
composition of the entire crust of the Limulus, including the sword-
shaped appendage, which is analogous to the last or post-anal segment
of the higher Crustacea, and consists of a single modified segment.

In the small Entomostraca, the number of the thoracic and ab-
dominal segments generally exceeds that in the Malacostraca. The
Branchipus stagiialis, for example, has eleven thoracic segments, and
nine abdominal or caudal rings, besides a distinct head protected by
a cephalic shield. In the Isaura, in which this shield is developed,
as in the Cypris, Daphnia^ and other Entomostraca, to the extent,
and in the form, of a bivalve shell, enveloping the whole body, the
number of thoracic and abdominal segments exceeds twenty-four.

The distinction between the Entomostraca and Malacostraca in the
number of the segments of the body is of the first importance in deter-
mining the affinities of the ancient extinct Crustacea, called Trilobites.
These remarkable animals were almost the sole representatives of the
present class in the periods which intervened between the deposition
of the earliest fossiliferous strata to the end of the coal formation.*
Neither antennae nor feet appear to have been found in their remains :
the structure of the tergal part only of their body-segments is yet
known ; but these are grouped togetlier to form a distinct head, thorax,
and abdomen or tail. The head is formed by a large semicircular or
crescent-shaped shield ; the thorax consists of from six (^Ampyx,
CryptoUthus), seven {Ogygia\ eleven {Phacops), thirteen {Caly-
mene\ to fifteen segments : and the abdomen or tail includes at least
eight segments in this Calymene^, in which it is bent under the
thorax, as in the crab : the abdomen, post-abdomen, or tail, as the

* Buc'kland, Bridgwater Treatise, i. p. 390. f No. 208.

300 LECTURE XIV.

third segment is variously termed, contains fifteen fettered segments
in the Asaphus caudatus : the segments of both thorax and abdo-
men are very similar to each other, and gradually decrease in size.
They are divided by two longitudinal furrows into three lobes. The
head usually supports a pair of large compound eyes situated near the
sides, like the larger ou'ter pair of eyes in the Limulus^ which they
resemble in form and structure.

The Malacostraca are divided into two groups, according to the
attachment of the eyes : those with immoveable sessile eyes form the
Edriophthalmay those with moveable pedunculated eyes the Podoph-
thalma.

The lower organised or edriophthalmous forms of malacostracous
Crustacea resemble the Trilobites in the non-confluence and uniformity
of the segments of the thorax, and abdomen. Certain genera, as aS'^-
rolis and Bopyrus, have the tergal arcs of the segments trilobed j but
they exceed not the characteristic number in the Malacostraca, and
the seven rings of the thorax are clearly indicated in each by the
seven pairs of articulated feet which they support, although these are
very small in the parasitic Bopyrus. In the Cymothoa {fig. 129) the
seven thoracic and seven abdominal segments are more distinctly
characterised.

The seven segments of the head are rather indicated by the ap-
pendages of that part than demonstrable in any of the Crustacea.
The Stomapoda afford, in the genus Squilla, the most favourable ex-
amples for studying the conformation of the head. The first segment
supports the pedunculated eyes : the second the smaller antennas :
the third and fourth segments are confluent, but indicated by the
larger pair of antennas and a pair of mandibles ; the tergal part of
these confluent segments is greatly 130

developed, and extends over the rest
of the head and part of the thorax.
Three other pairs of jaws indicate
the rest of the seven cephalic seg-
ments ; and these are succeeded by
the seven thoracic rings and their
articulated appendages {fig. 128, a).
Of these the first two pairs, which
are organised for locomotion in the
isopods and amphipods, are now mo-
dified to serve as jaws ; and the re-
maining five pairs (ib. 3 — 7) are

reserved for locomotion in all the sternal arcs of thorax, Astacus.

podophthalmous Crustacea. In the Decapoda (Crabs, Lobsters,

CRUSTACEA. 301

Prawns), the first of these five ambulatory thoracic legs is commonly
the largest, and diilactyle {Jig. 130, 3). They all consist of six
joints, called, as they recede from the trunk, coxa, trochanter, femur,
tibia, tarsus, metatarsus : the latter is often prolonged into a sharp
stiif claw ; but, in the swimming crabs, it is flattened and expanded
in certain legs : when modified as pincers, the tarsus is expanded and
prolonged into a finger-shaped process, against which the last seg-
ment can be applied like a thumb. Each leg has usually two append-
ages attached to its base, called the palp and fiagellum : analogous
appendages are attached to most of the thoracic and cephalic articu-
lated appendages, which subserve as jaws.

The tergal arc of the blended third and fourth cephalic segments
extends over all the thoracic segments in the macrourous and brachy-
urous Crustacea, and constitutes the broad carapace in the crab. In
most Macroura the thoracic shield is formed of the lateral or epimeral
elements of the fourth cephalic ring, which meet along the back, and
give way preparatory to the moult. The tergal elements of the tho-
racic rings are not developed in either crabs or lobsters ; when these
rings are exposed by lifting up the cephalo-thoracic shield, the epi-
meral parts alone are seen converging obliquely towards one another,
but not joined at their apices. The thoracic legs, besides serving for
mastication, prehension, and locomotion, usually support more or
less of the branchial apparatus, and certain pairs are perforated
by the generative ducts, except in the crabs, in which the broad
sternal arc supports the generative outlets.

The sternal arcs of the thoracic segments (Jig. 130) send inwards
certain processes, called apodemata, which include spaces for protect-
ing the abdominal nervous chords and the branchiae, and which give
origin to the muscles of the legs.

The seven abdominal segments are always united by flexible
joints, and have no apodemata. In those Crustacea in which the
thorax and its cephalic shield are small, the abdomen is long, as in
the squillae (Jg. 128, a, 1 — 7, in outline), lobsters, and shrimps, and
it characterises the great tribe of Podophthalma called Macroura ; in
those in which the thorax and its shield are greatly expanded, the
abdomen is very short, as in the crabs, and it characterises the tribe
hence called Brachyura. This alternating excess and arrest of
development of the opposite divisions of the trunk well illustrate the
law of organic equivalents.

In a small intermediate group, called Anomoura, including the
PaguridcB, or Hermit-crabs, and the Galatheidce, the abdomen
presents intermediate proportions, and in some an anomalous struc-
ture : the fifth pair of ambulatory legs, e.g., is attached to the first

302 LECTURE XIV.

abdominal ring, and is usually folded upon the back : it performs
the office of sweeping the gills, the flabellae, which have that function
in the Brachyura and Macroura, being absent from the branchial
chamber.

The appendages of the abdominal segments {Jig. 128, l — 7) are de-
veloped, like those of the thoracic ones, from the inferior arcs : they
are usually broad, flat, ciliated plates, which may sometimes aid in re-
spiration, are more commonly organs for swimming, form a temporary
place of attachment and protection to the ova, and are restricted to
this use in the females of the Brachyura, in which the abdomen or
tail is concealed by being bent forwards upon the sternum. In the
hermit-crabs, which present an anomalous softness of their abdominal
segments, the last pair of appendages form the claspers by which the
parasite holds fast by the columella of the shell it may have selected
for its abode.

The calcified integument of the Crustacea being inelastic, inex-
tensile, and not endowed with inherent powers of growth ; being
likewise so disposed in the Podophthalma as to inclose and protect
the greater part of the body by annular or large shield-like pieces
like back- and breast-plates, must needs be thrown off to allow of the
growth of the animal. This moult of the external integument has
been observed in a few species of Crustacea, in the full-grown
specimens of which it appears to take place annually ; and a like
ecdysis is probably common to all the class. Reaumur gave the first
good account of the process in the craw-fish (Astacus fluviatilis).
It takes place generally in the month of August. The animal pre-
viously retires to some place of concealment, is quiet and fasts for a
few days, during which time the old crust is loosened from the lining
membrane beneath, which becomes thickened, vascular, and like velvet.
As this begins to harden, the animal takes measures to rid itself of its
old crust ; it rubs its legs against each other, throws itself upon its back,
contracts and swells out the body, with alternate violent inflections
and intervals of rest. The carapace is thus separated from the abdominal
segments, is pushed upwards, and the animal liberates its head with
the eyes and antennaj, which are provided with new sheaths : then
the more difficult operation of freeing its extremities takes place :
finally, the craw-fish creeps out of the remainder of its old shell by
withdrawing the abdominal segments ; when the parts of the cast-off
shell frequently return so nearly to their old positions as to represent
the outward form of the animal with all its appendages, even the
hairs and lining of the stomach. In one or two days the calcification
of the new crust is completed, and the animal is restored to health
and activity. During this period two very remarkable accumu-

CRUSTACEA. 303

lations of calcareous matter, situated at the sides of the stomach,
and known in the old pharmaceutical works as " Oculi Cancrorum,"
have disappeared: it would seem that the hardening material had been
previously accumulated in readiness for the rapid calcification of the
new crust, in order to reduce to the shortest period the defenceless
state of the craw-fish after its moult.

The chief difficulty in accepting this account of the moult has
been with regard to the possibility of the soft parts filling the ex-
panded segments of the pincer-claws of the crab or lobster being
withdrawn through the narrow apertures of those segments where
they are joined together. But the whole muscular system of the
moulting Crustacean is subject at that period to active absorption,
which reduces it to about a third of what the cavity is capable of
containing. A quantity of sea-water is introduced between the
shrunken soft parts and the old hard shell. This interposed fluid
stretches every part of the yielding walls of the joints, and facilitates
the passage of the reduced muscular structure through the contracted
apertures. The limbs are subject, in the act of extrication, to
spasmodic twitchings ; but, when a small portion of the soft claw
has been thus withdrawn from the orifice, the rest follows almost
without an effort.

In shedding the main part of the shell or carapace, the line of
union round the sides and front, which passes between the eyes and
mouth, and terminates on each side near the insertion of the hinder
legs, is dissolved by absorption. The lining membrane of the old
shell, which is the basis of the formation of the new, is reflected
into each hard compartment lodging the muscular masses, and into
the chambers for the stomach and other soft parts : by the changes
it undergoes in the preparation for calcification it cuts off the former
close connection of the included parts with the apodemata and
manifold processes of the old complex shell. In the act of sepa-
ration the crab has sometimes been seen to throw itself on its
back, working the branchiae with unusual force, and making the
utmost effort to disengage the internal processes. It escapes at the
fissure where the tail is connected with the carapace. Sometimes the
crab hitches one of its claws into some crack or fissure, and from this
point of resistance gains more power in emerging and withdrawing
itself from between the carapace and tail. The parts of the old crust
once evacuated, fall by the elasticity of their joints into their natural
relative position : even the line around the carapace does not appear
separated unless minutely examined ; while the antennae, palpi,
eyes, complicated organs of the mouth, branchi^, internal tendons,
inner membrane of the stomach, with the gastric teeth, the double
%

304 LECTURE XIV.

crustaceous body at the pyloric orifice, the two levers that proceed
internally from the jaws to further triturate the food after it has
undergone the maxillary mastication, together with the whole of the
internal chambers of the crust, are left as entire as if dissected by a
skilful anatomist.

When the common crab has thus emerged from its old shell, its
first feeble effort is to creep to the friendly shelter of the nearest
crevice. Its general appearance is that of a lump of dough, inclosed
in a coloured membrane. Its growth, however, at this period is
remarkably rapid. *

The elementary fibre of the voluntary muscles, in the Crustacea, is
pale, semitransparent, but is transversely striated : the flat tendon -like
body into which the strong peninform muscle of the lobster's claw is
inserted is an internal process of the shell, and has a chitinous basis :
all the seeming tendons are in like manner " apodemata," or internal
processes, appertaining to the exoskeletal, not to the muscular, system.
The muscles of the trunk-segments are usually rectilinear flattened
masses : they are accumulated in great force in the long post-ab-
domen, or tail, of the lobster and other Macroura : here the flexors
are on the ventral, the extensors on the dorsal surface, the former
being the largest and most powerful. They usually pass from one-
segment to the next ; mostly with a longitudinal course, a few being
oblique and decussating. In the little Cypris, some muscular fibres
arising from the back of the animal act like adductor muscles on the
bivalve shell.

The Crustaceous Homogangliata are not less remarkable for
the different conditions of their nervous system, arising out of the
progressive concentration of its central masses, than for the diver-
sity of their outward forms. Even in the higher, or Malacostracous
division, a very extensive series of modifications are presented,
which lead from the Anellidous to the Brachyurous type, or that of
the crab.

In the lowest worm-like, equal-footed, and equal-ringed Crus-
tacea, the dermal skeleton has become suflficiently firm and resisting
to enable the trunk to be raised by the articulated members above
the ground. The muscular system attains a proportionate increase
of volume and force : so that when we contrast the conditions of the
sensitive integument and of the motor system in these Crustacea
with those of the same systems in the Anellids, we obtain most
instructive tests of the worth of that hypothesis which ascribes sen-
sation exclusively to the ganglions, and the motive energy to the

* CCXXXIII. p. 8.

CRUSTACEA. 305

non-ganglionic nervous columns of the Articulata. The same
hypothesis will be more severely tried by the comparative anatomy
of the nervous system in the higher species of the Crustacea, on
account of the varying conditions as to sensation and motion which
different parts of their more diversified forms of body present.

We find in the lowest Isopoda, as the woodlouse (0?iiscus) and
the sandhopper {Talitriis), that the supposed sensitive organs, the
ganglions of the abdominal chords, are more developed than in the
highest Anellides : they are likewise more distinctly bilobed ; each
lateral chord presenting its own ganglionic enlargements, which are
in juxtaposition, but not confluent, so that there is a distinct pair of
•■ganglia for each segment. If these ganglions be microscopically
examined, they present, as their essential structure, large round or
pyriform cells with a large nucleolated nucleus ; and three orders of
nervous filaments may be perceived in them. The first is longi-
tudinal, and extends over the dorsal aspect of the ganglia; the
second is also longitudinal, and originates from, or terminates in,
the ganglia ; the third is transverse : these fibres pass round the
ganglionic cells, and emerge laterally : they, in Talitrus, connect the
two ganglions of each pair with each other, and in all Crustacea
form the transverse or peripheral nerves. Talitrus presents ten
pairs of nearly equidistant sub-abdominal ganglions, the two first
and the two last being most approximated. In Cymotlioa {Jig. 129.),
a species in which the tapering terminal segments of the body have
begun to be concentrated by longitudinal approximation, the corre-
sponding nervous ganglions at the posterior part of the abdominal
chord present a corresponding change, advancing forwards like
the caudal part of the spinal column in the metamorphosed larva of
the frog.

In the higher Crustacea, with a thorax covered by the cephalic
shield, and supporting disproportionately large and preliensile anterior
extremities, the thoracic ganglia exhibit proportionate increase of size,
with a tendency to unite, or with actual confluence. The gan-
glions of each lateral abdominal chord have now more completely
coalesced by transverse approximation. In Squilla mantis, the
super-oesophageal ganglion or brain sends off five nerves on each side,
those to the long antennae being recurrent in their course. Stomato-
gastric nerves arise from the oesophageal chords, which unite below
into a long sub-oesophageal ganglion, apparently formed by a con-
fluence of three originally distinct pairs. This is succeeded by three
other ganglions in the thorax, supplying three pairs of thoracic legs ;
and there are six ganglions in the muscular taih The oesophageal
chords are unusually long and slender in the transparent Phyllosoma.

X

306 LECTURE XIV.

The neurology of the Crustacea has been most completely illus-
trated in those species which are covered by a dense insensible crust.
Succow, in 1818, and Brandt, in 1833, published excellent descrip-
tions of the nervous system of Astaciis fluviatilis {Jig. 3. p. 13.).
The cephalic ganglion sends branches to the eyes, to the large and
small antenuEe, to the antennal sheaths, and to the organs of hearing.
A nearly straight chord is continued from this ganglion, on each side
of the oesophagus, to the first of the sub-abdominal series. An
azygous nerve arises from the middle of the posterior surface of the
cephalic ganglion, and passes backwards to the stomachy where it
communicates with two nerves given off one from each of the oeso-
phageal chords to supply the stomach. The sub-oesophageal ganglion
distributes nerves to the masticatory organs and to the pharynx, just
as the medulla oblongata sends off the fifth pair and glosso-pharyn-
geal in the vertebrate animals. The second to the sixth thoracic
ganglia inclusive supply the feet and gills with nervous influence ;
the generative organs receive long filaments from the fourth, the
fifth, and the sixth thoracic ganglions. The ventral or sternal artery,
descending from the heart, passes between the nervous columns at
the interspace between the fourth and fifth ganglions. Six ganglions
are developed on the abdominal chords, which are continued along
the muscular tail : the last^ which is above the anus, is the largest,
and radiates the nerves to the terminal swimming plates of the tail.
This is probably a coalescence of the originally distinct ganglions of
the sixth and seventh segments of the abdomen or tail.

The nervous system of the lobster is well displayed in dissections
by John Hunter*, and has been beautifully illustrated by Mr. Swan.f
The nerves of the lobster closely correspond with those of the fresh-
water species, or craw-fish. The non-ganglionic tracts are shown in
a dissection of the lobster by Mr. Newport J ; but the distinctions of
the origins of the nerves from the dorsal and the ventral tracts are,
as Mr. Swan remarks, by no means clear. The oesophageal columns
are united in both species of Astacus by a transverse commissural
chord.

In the prawn {Palemoii) and rock-lobster {Palbmrus)^ the thoracic
ganglia coalesce to form a long, elliptical, perforated nervous mass.
In the hermit-crab {Pagurus)\^ the cephalic ganglion presents
a transversely quadrate form, and sends off the usual nerves to the
eyes, the ears, and the antennas. The lateral oesophageal chords,

* Preps. Nos. 1301, 1302, 1303, described in X. vol. iii. p, 15.
t CCXXXIV. Part I. pi. 3. and 4. X Prep. No. 1302, A.

§ Prep. No. 1 303. B.

CRUSTACEA. 307

after supplying the digestive system with the stomato-gastric nerves,
unite below to form the ganglion which distributes nerves to the
maxillary apparatus and pharynx. This is succeeded by a large
oblong ganglion, situated at the base of the great nippers, and of the
second pair of feet, both of which pairs it supplies. The lateral
chords diverge for the passage of the artery, re-unite to form a third
thoracic ganglion, smaller than the second, supplying the third pair
of thoracic legs, and sending oif three pairs of nerves posteriorly. Of
these the lateral pair goes to the fourth diminutive pair of feet ; the
median pair supplies the fifth pair of feet ; the two remaining dorsal
nerves, which are of minute size, form the continuations of the ab-
dominal chords, and pass along the under or concave side of the soft,
membranous, and liighly sensitive abdomen to the anus, anterior to
which the last small ganglion is situated : this su[>plies the nerves to
the muscles of the caudal plates, here converted into claspers, and
enabling the animal to adhere to the columella of the univalve shell,
which it may have selected to protect that portion of its body which
nature has left undefended by the usual dense and insensible crusta-
ceous covering.

Experiments have been made, and repeated, in order to determine
whether the ganglionic portions of the abdominal chords of the
Articulata have the same restricted function which the posterior
roots of the spinal nerves in the Vertehrata have been proved to
possess. With respect to the anatomical grounds which were first
adduced in proof of this correspondence of function, they are in-
validated by the fact that the presence of ganglions in the sensitive
roots of the spinal nerves is not their constant character.

The results of the experiments alluded to, though somewhat con-
tradictory, are, upon the whole, as might have been anticipated,
hostile to the conclusions founded upon a partial anatomical analogy.
A more extended investigation of the Comparative Anatomy of the
Nervous System has remedied the imperfection of the experimental
inquiry, has supplied the answers which were in vain attempted to be
gained by mutilating the living Crustacea, and has brought the hypo-
thesis in question to the test of deductions which may be legitimately
drawn from those surer experiments which Nature herself has left
for our instruction in the modification of the crustaceous type of struc-
ture. We have here* two opposite conditions of a large and important
part of the trunk of two nearly allied Crustacea. In the lobster {Ag-
tacus) the abdomen or tail is encased in a series of calcareous rings,
forming a hard and insensible chain armour : but in the same degree

* Pteps. No. 1301. and 1303. B.
X 2

308 LECTURE XIV.

as sensibility is iost, motility is acquired ; a great proportion of the
muscular system of the animal is concentrated in the tail, which
forms its most powerful and almost exclusive organ of swimming.
In the hermit-crab {Pagurus), on the other hand, the muscular system
is almost abrogated in the long abdomen ; for this, in fact, takes no
share in the locomotive functions of the body : it is occupied by part
of the alimentary canal, and by glandular organs : the sensibility of
the external integument is not impaired or destroyed by the deposi-
tion of calcareous particles in its tissue ; but it retains the necessary
faculty of testing the smooth and unirritating condition of the inner
surface of the deserted shell, which the animal chooses for its abode :
minute acetabula are develoj^ed in groups upon this sensitive in-
tegument*, to which, also, delicate ciliated processes are attached.
The muscular system is reduced to a few minute fasciculi of fibres
regulating the action of the small terminal claspers. Now, if, as has
been conjectured, the ganglionic enlargements of the abdominal
chords monopolize the sensorial functions, and the non-ganglionic
tracts the motor powers, we ought to find the nerves, which supply
the muscles of a tail constructed almost exclusively for locomotion, to
be derived from non-ganglionic columns ; whilst in the tail, which is
almost as exclusively sensitive, the ganglions ought to have been large
and numerous, for the supply of nerves to the integument. The
contrary, however, is the fact ; six well developed ganglions dis-
tribute nerves to the muscular fibres of the lobster's tail ; non-gan-
glionic columns supply the sensitive tail of the hermit-crab. One
ganglion, indeed, is present in the Pagurus, but both its situation
and office alike militate against the hypothesis of its special subser-
viency to sensation : it is developed upon the end of the smooth ab-
dominal chords, and seems to have been called into existence solely
to regulate the actions of the muscles of the terminal claspers by
w^iicli the hermit keeps firm hold of the central pillar of his bor-
rowed cell.

The general progress of the development of the nervous system in
the Crustacea has been, as we have seen, attended with increased
size, and diminished numbers of its central or ganglionic masses.
The divisions of each pair of ganglia first coalesce by transverse
approximation : distinct pairs of ganglia approximate longitudinally,
conjoining as usual from behind forwards : confluent groups of
ganp^lia are next found in definite parts of the body, as on the thorax
of those species which have special developments and uses for par-
ticular legs. In the crab, in which the general form of the body

* Broderip, Zool. Journ. vol. iv. p. 200.

CRUSTACEA.

309

attains most compactness {^fig. 131.), the ventral nervous trunks
are concentrated into one large oval ganglion (^), from which the
nerves radiate to all parts of the trunk, the legs, and the short tail.

131

This condition of the nervous system has been described by Cuvier
in the common crab, and is illustrated by Mr. Swan's dissections,
from which his beautiful plates have been taken.* The correspond-
ing structure of the nervous system is also well displayed by Audouin
and Edwards in Maia. An analogous concentration, but not a
homologous one, obtains in Limuhis. Here the nervous substance is
chiefly massed round the oesophagus, the fore part of the ring
expanding into a pair of ganglions from which the nerves are sent oif
to the small median and large lateral eyes : the nerves to the latter
are of great length, wind round the anterior apodemata, and bend
back to their termination, breaking up into a fasciculus of minute
filaments before penetrating the large compound eye. Two stomato-
gastric nerves arise from the upper and fore part of the ring. From
the under surface of the fore part of the ring, a small pair of nerves
pass to the first short pair of forcipated jaw-feet: five large nerves
proceed from each side of the ring to the five succeeding jaw-feet.
A pair of slender nerves pass to the spiny-edged lamelliform appen-
dage. The posterior part of the nervous ring is prolonged backwards
in the form of a chord, having four ganglionic enlargements on its
ventral surface, and terminates opposite the penultimate postabdo-
minal plate in a fifth slight ganglionic enlargement which bifurcates :
each division sends off a few nerves as it proceeds to the caudal

CCXXXIV. Part I. pi. 1. and 2.
X 3

310 LECTURE XIV.

appendage, on entering which, it is resolved into a plexus or kind of
** Cauda equina." Besides the principal nerves above mentioned, many-
smaller nerves are given off to other parts of the body. The sides
of the great oesophageal ring are united by two transverse com-
missural bands : but the most remarkable feature of the nervous
axis of this Crustacean is its envelopment by an arterial trunk. A
pair of aortge from the fore part of the heart arch over each side of
the stomach, and seem to terminate by intimately blending with
the sides of the cesophageal nervous ring. They, in fact, expand upon,
and seem to form its neurilemma ; a fine injection thrown into them
coats the whole central mass of the nervous system with its red colour.
Such is the condition of this governing part of the organisation in
the most gigantic form of the Entomostracous tribe, and probably the
only existing genus from which we may derive an insight into the
structure of the extinct Trilobitic Crustaceans.

Three principal divisions of the nervous system of the Crustacea
may be defined according to their probable functions. Thus, ad-
mitting, from analogy, that the super-oesophageal ganglionic centre
{figs. 129. and 131. c) is that in which true sensation and volition
reside, then those nervous filaments which are exclusively connected
therewith, and some of which would seem to extend the whole length
of the animal along the dorsal aspect of the ganglionic columns, will
form with their ganglionic centre the true sensori-volitional system ;
whilst any other ganglions superadded to the abdominal columns,
with the nervous filaments terminating in or originating from them,
will constitute the system for the automatic reception and reflection
of stimuli. The stomato-gastric nerves, connected partly with the
brain and partly with the oesophageal columns, will form a third
system analoo^ous to the great sympathetic or organic nerves of the
Vertebrata. In these views I coincide with the accomplished phy-
siologist. Dr. Carpenter, believing that their accuracy and soundness
have received confirmation from the facts of Comparative Anatomy,
described in the previous pages, and which, in the Hunterian
Lectures of 1842, were for the first time brought to bear upon this
interesting problem.

The sense of touch can be but very feebly exercised by the com-
mon integument of the Crustacea, can hardly, indeed, exist except in
those parts of the surface of the body which remain soft and un-
defended by the liard crust, such as the joints of the under part of
the body, and the surface of the soft tail in the hermit crabs. The
fine hairs which project from many parts of the integument may
compensate for its low endowment of the tactile sense : the two pairs
of jointed antenna: {fo^- ^28. 131. a) are instruments fitted for the

CRUSTACEA. 3 1 1

most delicate exploration; and the smaller but similar organs at-
tached to the jaws, and called palpi, may also receive some impressions
analogous to those of savour or smell. The Crustacea have no true
tongue, but the sensations of the membrane lining the interior of
the mouth and the oesophagus may guide them in the selection
which they make of objects of food.

The sense of smell is referred to a shallow excavation in the basal
joint of the first or median antenna, which opens by a fissure fringed
by fine hairs on the upper surface of the joint : this cavity is lined
by a soft membrane, supplied by a branch of the internal antennal
nerve. The organ is well described and figured in CCXXXV.,
pi. 9. and 10., in which memoir the author calls attention to the
presence of minute grains of sand ; and these, although they must
enter accidentally into the cavity, he suggests may act as otolites,
surmising the cavities in the small antennae to be acoustic organs.

The sense of hearing is referred by most authors to a conical pro-
cess containing a cavity with a round orifice closed by a membrane,
proceeding from the first joint of the second (external and larger)
pair of antennae, in the lobster and other Macroura. Behind the
process there is continued from its cavity a large sac filled with a
clear liquor : a nerve arising in common with the external antennal
nerve is spread upon the delicate walls of the supposed acoustic sac.
In most of the Brachyura the membrane is stated by Dr. Edwards to
be replaced by a small moveable calcareous disc, which is pierced
with a small oval opening, over which there is stretched a thin and
elastic membrane. The external opening of the ear is closed by this
bony disc. A second small plate is so situated as to regulate the
tension of the auditory membrane, whilst the rigid stem of the
antennae, in which the whole organ is situated, is well adapted to
render the auditory vibrations more distinctly perceptible. These
vibrations are conveyed through the medium of a vesicle filled with
fluid to a branch of the antennal nerve which expands in the vesicle.

In both the lobster and crab a tube, filled by a greenish substance,
is concealed in the lower portion of the shell, and communicates, or
is in close contact with, the membranous sac. This structure, and
the absence of otolites, has led Farre to suggest that the organ may
be olfactory : but the chief parts of the structure bear a close cor-
respondence vvith an auditive vesicle and a tympanitic membrane.

With respect to the organ of vision, we find in the class Crustacea
a most extensive and interesting series of gradations, leading from
the simple sessile median eye-speck to two distinct eyes, provided
with all the essential optical apparatus and placed upon moveable
peduncles. Ocelli or stemmata are combined with compound eyes

X 4

312 LECTURE XIV.

in the same species in certain Entomostracans, as Apus and Limulus.
A transparent speck of the integument forms the cornea of the
ocellus, immediately behind which there is a spherical crystalline
body in contact with a gelatinous or vitreous humour, upon which
the extremity of the optic nerve expands : a layer of dark pigmentum
covers all these parts with the exception of the cornea. In the com-
pound eyes of Daphnia, the smooth undivided cornea protects and
transmits the rays of light to an aggregation of small ocelli, each of
which is lodged in a pigmental cell : the similarly constructed com-
pound eye of the active little Branchipus is supported on a short
moveable peduncle.

The large lateral compound eyes of the Limulus are sessile : the
cornea is divided into a considerable number of small circular facets,
each of which corresponds to an ocellus ; and the optic nerve, after
its long course as a simple chord, divides near the eye into a pencil of
fine filaments, which severally receive the impressions from their
respective ocelli, of the aggregate of which the large lateral eye is
composed. The two small simple median eyes, which are almost in
contact, command the space before the head, which is out of the range
of the large compound eyes : each simple eye receives its distinct
nerve from the anterior apex of the corresponding cerebral lobe.

In some of the Trilobites, the cornea presents the same subdivided
surface as in the Limulus ; and the position of the two eyes agrees
with that of the corresponding compound pair in the large existing
Entomostracan. The eyes are more elevated in some of the Trilobites,
as Phacops. In Asaphus caudatus the cornea is divided into at
least 400 compartments, each supporting a circular prominence : its
general form is that of the frustum of a cone incomplete towards the
middle line of the head, but commanding so much of the horizon in
other directions, that where the distinct vision of one eye ceases, that
of the other begins.

In certain Phyllopoda and Amphipoda a common cornea covers
numerous closely aggregated simple eyes, consisting each of a py-
riform lens, the apex of which is sunk in a black or brown pigment.
The optic nerve, before reaching the pigment, divides into as many
branches as there are lenses. In the sessile eyes of other Edrioph-
thalma, as, for example, in Serolis, the inner layer of the cornea
is divided into hexagonal facets, corresponding with the number of
the conical crystalline lenses of the aggregate eyes. In Amphithoe
this has been regarded as a second distinct cornea.

In the mandibulate Crustaceans, distinguished by having their
compound eyes supported on moveable peduncles, the form of the
corneal facets varies ; they are square in the lobster and river craw-

CRUSTACKA.. 313

fish, hexagonal in the hermit and common crabs. There is a conical
crystalline lens behind each facet imbedded in a small vitreous
humour, upon which the optic filament expands, and each ocellus is
lodged in a pigmental cell, which likewise covers the bulb of the
optic nerve ; the cavity containing the compound eye is closed behind
by a membrane continuous with the inner layer of epiderm, and
pierced for the passage of the optic nerve {fig' 131. e). In the
podophthalmous Crustacea there is generally a spacious furrow or
cavity, in which the eye and its peduncle can be lodged and protected,
and it is termed the orbit. In one or two species, e. g. Gelasirnus
telescopicus, the eye-stalks project beyond the margins of the
carapace.*

One of the most valuable and interesting results of the study of
the comparative anatomy of the eye in the Crustacea is the insight
which the fossilised remains of similarly constructed organs of vision
in the extinct Crustacea have given into the state of the world
at the time when they existed ; and I cannot better conclude the
present discourse than in the eloquent language of the geologist who
first taught the value of the evidence in question. The eyes of the
Trilobites of the transition rocks, and those of their nearest congeners,
the fossil Limuli from the Carboniferous series, "give information,"
says Dr. Buckland, "regarding the condition of the ancient sea and
ancient atmosphere, and the relations of both these media to light, at
the remote period when the earliest marine animals were furnished
with instruments of vision in which the minute optical adaptations
were the same that impart the perception of light to Crustaceans now
living at the bottom of the sea.

"With respect to the waters wherein the Trilobites maintained
their existence throughout the entire period of the transition formation,
we conclude that they could not have been that imaginary turbid and
compound chaotic fluid, from the precipitates of which some geologists
have supposed the materials of the surface of the earth to be derived;
because the structure of the eyes of these animals is such, that any
kind of fluid in which they could have been sufiicient at the bottom,
must have been pure and transparent enough to allow the passage of
light to organs of vision, the nature of which is so fully disclosed by
the state of perfection in which they are preserved. With regard to
the atmosphere, also, we infer that had it difiered materially from its
actual condition, it might have so far affected the rays of light, that
a corresponding difference from the eyes of existing Crustaceans
would have been found in the organs on which the impressions of
such rays were then received.

* CCXXXVL, p. 78., pi. xxiv. fig. 1.

314 LECTURE XV.

"Regarding light itself, also, we learn, from the resemblance of
these most ancient organisations to existing eyes, that the mutual
relations of light to the eye, and of the eye to light, were the same
at the time when Crustaceans, endowed with the faculty of vision,
were first placed at the bottom of the primeval seas, as at the present
moment.

" Thus we find among the earliest organic remains, an optical in-
strument of most curious construction, adapted to produce vision of a
peculiar kind, in the then existing representatives of one great class
in the articulated division of the Animal Kingdom. We do not find
this instrument passing onwards, as it were, through a series of ex-
perimental changes from more simple into more complex forms; it
was created at the very first, in the fulness of perfect adaptation to
the uses and condition of the class of creatures to which this kind of
eye has ever been, and is still, appropriate."

LECTURE XV.

CRUSTACEA.

The Limuli, which form the only genus of large Crustaceans repre-
sented by species which co-existed with the Trilobites, difier from all
other living Crustacea in their organs of mastication, which are the
modified basal joints of the five posterior pairs of legs : the first
small pair serve to bring the objects of food to the mouth ; they are
supported on a rudimental labrum, and have their basal joint sub-
trenchant, if working from before backward. The basal joints of
the four following pairs are beset with spines, and act as " carders : "
that of the sixth pair is hard, subtrenchant, and works from behind
forward: a pair of subquadrate compressed plates, with spiny bor-
ders, working in the same direction and closing the mouth below,
may represent a rudimental seventh pair of limbs, or a divided
labium. In Asaphus plati/cep/ialus Mv. Stokes* discovered a dis-
tinct subquadrate labrum deeply emarginate anteriorly ; the nearest
approach to this, the only known part of the trophi of the Trilobites,
seems to be made by the entomostracous genus Apiis, in which, how-
ever, the labrum is truncated. A few of tlie lowest organised Crus-
tacea, as Caligus, Ni/mp/wn, and Pycnoyonon, obtain their aliment,
like the Epizoa, by suction.

* Geol. Trans. N. S. vol. i. pi. 27.

CRUSTACEA. 315

In the malacostracons Crustacea the mouth is closed by a small
and simple membranous labrura above, by a bifid labium below, and
by a pair of mandibles and maxilles at the sides; the mandibles
are the legs or jointed appendages of the fourth cephalic segment ;
the maxilles are the same appendages of the fifth. The mandibles
are worked by large muscles arising from the cephalo-thorax : their
internal border is hard and often toothed ; they support palpi. The
maxilles are weaker, softer, and without palpi. In the common
crab you will observe behind and exterior to the maxilles a third
pair of jaws, which have their principal part terminated by a cutting
edge, and are without palpi : the two following pairs of jaws are dis-
tinguished by their articulated feeler or palp and by their flabelliform
appendages, which penetrate into the interior of the branchial cavity;
the maxillary plate is armed with teeth ; the sixth and last pair of
jaws has the maxillary plate so much expanded as to cover and
protect the whole oral apparatus : it has likewise a palp and flagellum
articulated to its base. All the foregoing maxillary organs are
modifications of entire limbs, which are thereby translated from the
locomotive series : the jointed legs so metamorphosed belong to the
last four cephalic, and the first two thoracic, segments.

The alimentary canal is most simple in the suctorial Crustacea, in
which it presents no noticeable difference from that in the Epizoa ;
the hepatic appendages are however more localised and better de-
veloped.

In the Limulus the mouth is situated nearly in the centre of the
inferior surface of the great cephalo-thoracic segment ; the oesophagus
is continued from it in a very unusual course forwards, and expands
into a stomach, which is situated at the anterior part of the head.
This organ is abruptly bent upon itself upwards and backwards,
and is continued by a gradual diminution of diameter, as appears
upon an external view, into the intestine, which passes backwards
with a slight vertical bend to the base of the penultimate abdominal
segment. When w^e examine the interior of the alimentary tract, the
distinction between the stomach and intestine is effected, as Yan der
Hoeven has shown, by a conical valvular pylorus, which projects
into the commencement of the intestine. The stomach is lined by
a very dense and corrugated horny membrane. The hepatic mass,
composed of contorted slender c^eca, which, with the generative
glands, fills the greater part of the cephalo-thoracic cavity and also
extends into the abdomen, pours its secretion into the commencement
of the intestine by two ducts on each side.*

Amongst the smaller Entomostraca Lipiceus departs most from

* Prep. No. 477. A.

316

LECTUEE XV.

the common simple type of the intestine in Crustacea, by having that
canal disposed in one or two spiral coils. In the Stomapods or
SquilljB the stomach bends forwards in advance of the cardiac orifice ;
a bi-articulate plate extends from that orifice backwards tlirough the
pylorus into the intestine, and regulates the passage of the alimentary
substances into that tube ; they are previously subjected to the action
of four lateral dentated pyloric processes.

In the higher Crustacea the stomach {fig, 132, c) is of a globular

132

Cancer pagurus.

form, more capacious than in the Limidus, and its walls are connected
.with a calcareous frame-work supporting dense tubercles, whiclv
project into the interior of the stomach around the pylorus, and are
so situated and moved with relation to each other as to divide and
bruise the alimentary matters before they pass into the intestine. In
the common lobster these gastric teeth are three in number, the middle
one serving as a kind of anvil upon which the two larger lateral pieces
work.* This complex kind of gizzard is sometimes found to be everted
and protruded from the mouth, the gastric teeth being then external,
like those of the anterior muscular segment or proboscis of the alimen-
tary canal in the Anellides. The inner tunic of the stomach is com-
posed of chitine, and is beset with groups of hair-like processes in most
Decapoda.

The intestine in almost all Crustacea is continued to the vent with-
out convolutions ; a terminal portion, or rectum, is sometimes, as in
the lobster, indicated by a slight circular valve ; the vent is situated

Preps. Nos. 407, 408.

CRUSTACEA. ' 317

beneath the terminal segment of the abdomen, anterior to its appended
swimming plates in the Macroura, which would indicate that the long
sword-shaped appendage of the Xiphosura was not the homologue of
the post-abdomen, but of its last joint in the Macroura.

The liver is a considerable organ in all the Crustacea ; it makes its
appearance in the inferior specie- as so many ccecal prolongations of
the intestine, continued from many points, according to the primitive
form which it presents in the Apbrodita. The biliary caeca extend
even into the limbs in the Nymphons. In the Stomapods the biliary
cseca, continued ten or eleven in number at equidistant points from
each side of the intestine, are more ramified, and are confined to the
thoracic-abdominal cavity, where they penetrate the interspaces of
the muscles.*

In the Decapod Crustacea the liver (^fig. 132, I) consists of two
symmetrical halves, communicating by distinct ducts with the in-
testine ; each half consists of numerous lobes, which, in the larger
Macroura and Brachyura, are leaf-shaped, and composed of straight
tubular c^eca, arranged obliquely to a median canal, which forms, as it
were, the leaf-stalk. In some species one or two pairs of long slender
and simple tubuli likewise communicate with the intestine. The bile
is acid in the Crawfish {Astacus Jliiviatilis).

In many Crustacea the digestive canal is surrounded by cells filled
by an oily or fatty matter of a yellow or blue colour : they may be
compared to an omentum, and probably serve as a store of nutriment,
to be drawn upon during the moult, or when food is scarce.

Xo other vessels are yet known to convey the chyle or nutrient
fluid to the circulating system than the irregular venous receptacles
which are in contact with the parietes of the intestine. Almost the
whole venous system presents the form of wide flattened sinuses, and
offers an intermediate condition between that in the Nereids and the
generally diffused state of the venous blood through all the cellular
interspaces of the body in the class of insects. Through these
siiiuses, however, the blood flows in a constant and definite course.

The numerous experiments of Audouin and Milne Edwards | on
the circulation of the Crustacea, and the apparently favourable cir-
cumstances under which they were made, have very generally been
regarded as conclusive of the accuracy of their explanation of that
important function in the present class. According to these physio-
logists no other than the two great branchial veins terminate in the
heart, and, consequently, only pure aerated or arterial blood is pro-
pelled by it over the general system : the circulation is the same as

* Duvernoy, Annales des Sciences, vi, p, 243.
t Hist. Nat. des Crustaces. 1829.

318

LECTURE XV.

in the Gasteropodous Mollusca : the ventricle is exclusively systemic,
and is provided with only two venous apertures. Four such apertures
are described and figured by Dr. Lund on the dorsal surface of the
heart, but these are regarded by Audouin and Edwards as depres-
sions merely between the muscular fasciculi, having no communica-
tion with the ventricular cavity.

I have tested the conflicting evidence of these observers by dissec-
tion of the heart in the lobster ; and you will perceive by this prepa-
ration* that it is more complicated than even the Danish Naturalist
supposed, and fully bears out the opinion of Hunter in regard to the
mixed nature of the circulation in the Crustacea.

Fig. 133. shows the heart laid open on the ventral aspect; by ex-
posing its cavity from this side, it was
readily determined whether the exterior
depression on the dorsal surface did or did
not lead into the cavity. On either side of
the anterior depression from which the
ophthalmic (/) and the antennal {g) arte-
ries arise, there is a large oblique fissure,
guarded by a pair of semilunar valves. The
vein, which terminates by each of these
orifices, is an extended, irregular, and ex-
tremely flattened sinus, lying above the
heart, and between it and the lining mem-
brane of the shell, communicating anteriorly
with a similar broad irregular flattened sinus, which occupies a simi-
lar situation above the stomach, and receiving posteriorly the blood
from a series of flat and expanded sinuses which correspond to each
segment of the tail. There are two similar openings at the sides of the
ventricle, posterior to the preceding, which conduct the blood from la-
teral sinuses into the heart : these orifices, indicated by the bristles
(c, c), have each a pair of semilunar valves. The arterial blood, re-
turned from the branchiie, enters the heart by the large orifices on the
sides of the ventral aspect (<?, c?), regurgitation being likewise prevented
by two semilunar valves at each orifice. The muscular fasciculi of the
ventricle are so arranged as to leave tolerably distinct chambers for
each series of arterial orifices. The strongest bands or columns are
transverse, and dorsad of the branchial apertures : anterior to these is
a chamber receiving the carbonized blood from the two anterior dorsal
apertures; it is partially divided, the upper chamber giving off (/)the
ophthalmic, and {g) the antennal arteries. The lower chamber sends

Astacus marinus.

* No. 898. A.

CRUSTACEA. 319

off (k, k) the hepatic arteries. The larger posterior chamber receives
the two lateral venous apertures, and gives off (Jt) the superior caudal
artery, and {i) the sternal artery, which is the chief vessel, and the
only one which has a pair of semilunar valves at its origin.

A portion only of the ordinary venous blood is returned directly
by the four valvular orifices just described. The blood is returned
from the maxillie and legs to a series of inferior lateral sinuses at the
bases of the branchice ; from these sinuses it passes, by vessels per-
forming the office of branchial arteries, along the outer margin of the
gill, and after being distributed over the branchial lamellee, is collected
into the vein along the inner margin of the gill, and by the union of
the branchial veins into one trunk, on each side, is poured into the
ventricle by the two orifices on its under surface (f/, d).

We may trace in the heart of the Crustacea a gradational series of
forms, from the elongated median dorsal vessel of the Limulus, to the
short, broad, and compact muscular ventricle in the lobster and the
crab {fig. 132,/). In all the Crustacea, as in all the other articulate
animal?, the heart is situated immediately beneath the skin of the
back, above the intestinal tube, and is retained in situ by lateral
pyramidal muscles {fig. 133, a, a). In the Entomostraca, and in the
lower, elongated, slender, many-jointed species of the Edriophthalmous
Crustacea, the heart presents its vasiform character : it is broadest
and most compact in the crab.

In this series we may trace a general correspondence in the pro-
gressive development of the vascular as of the nervous system, con-
comitant with the concentration of the external segments, and the
progressive compactness in the form of the entire body. But there
is a remarkable exception to this concomitant progress in the Limulus,
indicative, with the general condition of the instruments of locomo-
tion and respiration, of the essentially inferior grade of organisation
of that genus, which, as has already been observed, seems to be the
last remnant of the once extensive group of Trilobitic Crustacea,
which swarmed in the seas of the ancient secondary periods of the
earth's history.

We have seen in the compact and broad existing representative of
those extinct gigantic Entomostracans, that the nervous system ex-
hibits a concentration of its principal central mass around the mouth,
but with a ganglionic double cord continuing from it. The heart,
however, is far from presenting a corresponding degree of concentra-
tion ; it remains an elongated fusiform tube, extending parallel with
the intestine from the pylorus to the rectum, like that of the SquillcB :
in Limulus, it is contained in a pericardium with thin membranous
walls, formed by the central sinus of the venous system, and it receives

320 LECTURE XV.

the blood from that sinus and from the branchial veins by a series of
from seven to ten lateral vertical slits, defended by valves as in the
higher Crustacea.* An aortic trunk proceeds from each extremity
of this heart. The anterior aorta is the largest, and immediately
divides into three branches. The middle and smallest branch passes
forwards to the anterior edge of the cephalic shield, following the
curve of its middle line, and supplying the small median ocelli in its
course. The two larger lateral branches form arches which curve
down the side of the stomach and the oesophagus, giving branches to
both those parts and to the intestine, and becoming intimately united
with the neurilemma of the oesophageal nervous collar. They unite
at the posterior part of that collar, and form a single vessel, which
accompanies the abdominal nervous ganglionic chord to its posterior
bifurcation, where the vessel again divides. Throughout all this course
the arterial is so closely connected with the nervous system as to be
scarcely separable or distinguishable from it. The branches of the
arterial and nervous trunks which accompany each other may be
defined and studied apart. The posterior aorta is chiefly destined
for the supply of the sword-like tail of the Limulus : the first part of
its course is wavy, to adapt it to the strong inflections of that appen-
dage. The aerated is mixed with the venous blood in the heart, and
is propelled in that mixed condition throughout the body in the
Limulus, as in the lobster.

The respiratory organs in the Crustacea are essentially appendages
to the basal articulations of a certain number of the feet, and are
originally developed from the flabelliform appendage, although they
ultimately become entirely distinct from the extremities in the higher
Crustacea.

The Branchiopods are so called because their fins or feet present
the form of simple plates or flattened vesicles, which float in the
surrounding fluid, and expose the blood to the oxygen which the
water contains. The branchia are appended to the thoracic limbs,
in the form of membranous plates, in the Ampldpoda ; and to the
abdominal limbs, as subdivided lamellae, in the Isopoda : the
branchial plates expand into vesicles attached to the thoracic feet
in the LcBjnodipoda. In the Stomapoda, the respiratory plates are
also external, and are appendages of distinct locomotive organs, and
each plate is divided into a series of small filaments or tubes ; so as
to resemble a broad feather : their position is abdominal. Similarly
formed external gills are appended to the thoracic segments in the
Thysanopoda.

* Van der Hoevon, loc. cit. pi. 2. fig. 9.

CRUSTACEA. 321

In Limulus the two outer thirds of the posterior surface of the
basilar joint of the abdominal prolegs are occupied by a great gill
formed of a number (130 — 150) of folds of skin, disposed transversely
and piled on one another like the leaves of a book : they adhere
throughout the length of their base or anterior border, are elsewhere
free, are semicircular or triangular, with curved borders, and
increase in size from the upper end of the branchia to its base, so as
to give this last the form of a pyramid. The free edge of each leaf
is rounded, and furnished with a horny band destined to sustain it,
and fringed with cilia : elsewhere the gill is membranous.

In the lobster and crab tribes the branchiae are protected by the
carapace, and are lodged in lateral recesses {Jig. 132, K) formed by
the apoderaata of the thoracic segments. These branchial recesses
are parts of a common cavity, lined by an internal fold of the
tegumentary membrane, and having two apertures of communication
with the surrounding medium. The posterior aperture lets in the
water, which, traversing the branchial cavity, escapes by the one in
front. In the crabs the entry is a cleft in front of the base of the
chela3 or forceps-claw, and is so placed in reference to the prolonged
base of that limb as to be closed or opened at the will of the animal.
In the lobster and other Macroura, the entry to the branchial
chamber is an extended fissure. The efferent passage from the
branchial cavity passes over the lateral portions of the palate or
prelabial area. In the Leucosia group it passes over the median
portion of the palate.

The dynamical part of the respiratory functions is performed by
the lamelliform appendages of the second pair of jaws, w^hich are so
situated in regard to the outlets of the branchial chambers as to drive
out a certain quantity of the water which has been admitted into the
chamber.* The loss of the foul water necessitates the entry of fresh
water by the inferent orifices ; the respiratory cavity being neither
capable of expansion nor contraction. The mode of breathino- in
the crypto-branchiate or decapod Crustacea is thus the reverse of
that in the Batrachia, in which the dynamical mechanism serves
only to draw in the respiratory medium in successive quantities.
In the higher vertebrata the thorax is so constructed as to execute
acts both of inspiration and expiration.

The branchiae in the decapod Crustacea {Jig. 132, g, 71) are in the
form of long and slender quadrangular pyramids, and consist of either
numerous thin plates, or minute cylinders closely arranged perpen-
dicular to the axis of the pyramid. There are nine branchial

* Milne Edwards, Annales des Sciences Nat. torn. xi.

y

322 LECTURE XV.

pyramids on each side in the crabs, two being rudimental and seven
forming the exterior of the pyramid in Cancroids and Maioids ; but
the number is more variable, and usually greater, in the Macroura,
amounting to twenty-two in the lobster. In both Brachyura and
Macroura slender appendages called "flabellae" (^^. 132, w?,) are
adapted to sweep over the surface of the branchiae and free them
from foreign particles : in the hermit-crabs and other Anomoura,
this office is performed by the fifth pair of legs, which can be
inserted for that purpose into the branchial chamber, the carapace
being raised to admit them. By this elevation of the carapace a
large quantity of water can be admitted to the branchiai ; a membrane
connecting the carapace with the inner walls of the branchial
chamber and extending along the anterior edge of the first abdominal
ring, precludes the admission of water into the cavity occupied by
the thoracic viscera.

So far as the gills are attached to the bases of the ambulatory or
natatory legs, they must be influenced by their movements; and the
more active the progress of the Crustacean, the more briskly will it
breathe ; and, since the muscular energy directly depends upon the
amount of respiration, the two functions are brought into direct
relation with each other by this simple connection of their respective
instruments.

The land-crabs have their branchiae always supported by water
through special modifications of the apertures of the branchial
cavities, which enable them the better to retain fluid, and also by
numerous folds or by a spongy structure of the lining membrane of
the respiratory cavity by which the quantity of the contained fluid
may be augmented. The moisture contained in the branchial
chambers of the land-crabs (^Gecarcinus) and tree-crabs (^Birgus) is
doubtless much more highly aerated than the water which bathes the
branchiae of the strictly aquatic species, and thus may explain the
fact that the Crustacea which habitually live out of water are
drowned by being long immersed in that fluid.

No other trace of distinct excretory organs has hitherto been
detected in the present class than the simple, unbranched, long, and
slender tubes which open into the intestinal canal of some of the
liigher Crustacea. Swammerdam* figures one such tube opening
at the hinder end of the intestine in Paguriis. In 3Iaia there
are three such tubes ; two inserted on each side of the pylorus, and
a third a little further behind. These may be uriniferous tubes, like
the corresponding parts in certain insects and spiders.

* CCXXXIII. p. 87. t. xi. fig. 3.

CRUSTACEA. 323

Tenaclt}'- of life in the Crustacea appears not to be enjoyed in any
unusual degree : but some species, as the Artemia salina, can exist
in hot and strong brine, which would quickly destroy most other
animals. This shrimp abounds in the brine-pans of the Lymington
salt-works.

Like other Articulata subject to periodical ecdysis, the Crustacea
have the power of reproducing lost extremities. If a leg be frac-
tured across one of its segments, it is cast off by a violent muscu-
lar effort : if the Crustacean have not the power of thus ridding
itself of the wounded member, it usually dies from the haemorrhage ;
otherwise this is immediately arrested by the contraction of the
lacerated part of the joint where the limb is cast off with least dif-
ficulty and pain. The pre-arranged place of easiest and safest sepa-
ration is close to the basal end of the first joint, along a transverse
ciliated groove. This joint is filled by a mass of nucleated cells,
surrounded by a vascular band. The vessels of the band pass half an
inch beyond it, and return upon themselves forming loops. The
reproductive cells multiply after the loss of the limb, and form five
masses, which are the rudiments of the five joints of the future
limb: this, in the crab, is folded at the first joint, but is extended in
the lobster : in both it is enveloped in a sac or dilated cicatrix, which
the young limb, as it grows, bursts ; and it then resembles in minia-
ture the limb which it is destined to replace : its growth is slow until
the j)eriod of the moult, when, if the animal be in vigorous health,
the ne-w member rapidly acquires its normal size.

Generation of the Crustacea. — With regard to some of the smaller
Entomostraca, only the females have hitherto been discovered ; and
some naturalists have endeavoured, as in the case of the Aphides, to
solve the phenomena of parthenogenesis in such Entomostraca by-
alleged gynandrism. Thus, in the genus Apus, the lamelliform
respiratory sacs which, after death, get distended with blood, as
Siebold has shown *, were described by Berthold to be the testes co-
existing with ovaria, which are large and conspicuous. Again, in
the "genus Cypris, Straus-Durkheim t points out, in addition to the
ovaria, a pair of sacculi at the fore-part of the stomach ; but, with his
usual philosophic caution, doubtfully alludes to their nature as either
testes or salivary glands : they appear to me to be homologous with
the caBca in the Daphnia, which most comparative anatomists have
agreed in determining to be the liver ; there is no other part that
could be mistaken for a male organ.

In the genus Daphnia the males are well known ; they are

* XXIV. p. 484. t CCXXXIV. p. 384.

Y 2

324

LECTURE Xy,

always smaller than the female, but have longer and larger antennae.
Miiller deemed these antennoe to be themselves the male organs ;
thej are, however, only accessories, like the claspers in the sharks,
being provided with a hooked claw for holding on. Strauss points
out a modification of the lateral borders of the shell, and suggests
that thereby the valves of the female's shell are divaricated, and the
sperm ejected into their inter- space. The ovaria are simple coecal
tubes, coiled subspirally, one on each side the hinder half of the
abdomen. Several groups of ova are successively hatched within the
bivalve shell, and the young are excluded during the spring and
summer ; these young ones propagating in a similar way, without
fresh impregnation : the males do not appear until the autumn, and
the ova which are then impregnated are retained in peculiar recep-
tacles throughout the winter months, and are hatched in the following
spring.

In autumn an opake layer is developed on the inner surface of the
common incubating cavity, which hardens in two pieces like a small
bivalve-shell, with their concave opposed inner surfaces forming a
special cavity when the valves are closed; this is called the "ephip-
pium," or saddle, being placed on the dorsal surface of the Daphnia,
but beneath the common shell. Between the valves of the ephip-
pium is formed a similar but smaller apparatus, attached only to the
dorsal symphysis or hinge of the carapace, which also affects the form
of a small bivalve shell: this is the "internal ephippium ;" it in-
cludes, also, two bivalve capsules, in each of which an egg is lodged,
which remains in the passive state through the winter.

If the mother have strength to undergo a moult after tlio formation
of the winter nest, this is cast off with her outer skin, which remains
with the ephippial apparatus, protecting the eggs during the winter.
They are hatched by the early warmth of spring, and produce only
females, which, after moulting three times, exclude a batch of ova.
Now, if these be insulated, a successive production of fertile females
may be observed to the sixth generation. But the germ-cells
retained unchanged in the developing Daphnia acquire the superad-
ded yelk and chorion of an ovum, from which the young are ex-
cluded. The males are a later production, and the winter eggs are
always the products of impregnation.

In the male Cyclops the right antenna is peculiarly thickened and
jointed a little beyond its middle, so as to permit it to be bent upon
itself. With this organ the male seizes the female, and then grasps
the base of her tail by the great hook of his hindmost pair of feet.
After a slight resistance, she is quiet, and both gradually sink to the
bottom. A cylindrical tube, filled with sperm, escapes from the

CRUbTACEA. 325

orifice of the male organ, and he seizes the tube as soon as it has
escaped, and glues it to the abdomen of the female above the vulva.
No female has this tube prior to the coitus, and none is without it
afterwards. A male fit for coitus always has this tube or spermato-
phore in the lower dilated half of his seminal canal, and after the
coitus it is no longer there. Professor Siebold* has found the sperm-
tube attached to the rounded end of the last pair of feet of the
male, indicating the instrument of fixation. The females so pro-
vided are not, therefore, disdained by other males, — three, four, or
even six sperm-tubes may be found attached to the same female.
The sperm-tube consists of three different kinds of substance, sper-
matic matter, expulsatory cells, and agglutinating fluid. The
action of the cells, in expanding, is to push out the spermatozoa,
which, as the sac is suspended to the ventral surface of the first
caudal segment, thus escape close to the vulva.

The Cyclops has a single testis, which is a pyriform sac concealed
in the dorsal region, beneath or behind the heart. A long and wide
sperm-duct descends to the inferior half of the body ; then rises
abruptly, and again descends by a sudden curve, to arrive at the
sexual opening, which is simple, and at the middle of the base of the
tail. In the pyriform testis are sperm-cells and also spermatozoa. In
the descending part of the sperm-duct is the spermatophore, which is
homotypal with the ovicapsule.

How they become occupied with their proper threefold contents
has not been observed, but it does take place gradually as the sper-
matophore descends towards the spermatic outlet. There is no
proper coitus, i.e., the male does not intromit directly ; but he appends
or attaches the spermatophore to the female. Each spermatophore
contains, besides spermatozoa, two other substances ; one expulsatory,
which swells in water, and expels the spermatozoa ; the other coagu-
lates in the water, and serves for the attachment of the spermatophore.
The contemplation of the complex machinery requisite for this
curious mode of impregnation, whilst it exemplifies the necessity of
direct contact of tlie spermatozoa with the ova, must fill the mind
with admiration at the unusual interdependent arrangement, or,
humanly speaking, contrivance, which is manifested in subserviency
to the propagation of an animal so minute and seemingly so insig-
nificant.

In the genus Cypris the ovaria consists of two long cagcums,
curved, and applied to the sides of the hinder half of body, but

* LV. p. 36. ; also the excellent supplementary remarks by Mr. Lubbock,

cccxxv.

Y 3

326 LECTURE XV.

covered by the shell, and opening exteriorly, one by the side of
the other, at the fore-part of the extremity of the abdomen,
where they communicate with the canal formed by the incurved tail.
The first two-thirds of the ovarium lies free in a capsule, formed
by the membrane which lines the valves. The ova are minute at
the blind beginning, but progressively augment in size as they
approach the outlet, or the fixed vertical and terminal part of the
oviduct. These little Entomostraca oviposit on some fixed foreign
body, agglutinating their ova in a mass of some hundreds derived
from several individuals, by a substance of a greenish filamentary
structure like moss. Thus, like the ostrich, many females con-
tribute to one nest. In four days and a half the eggs are hatched ;
the young come out in form like the parent ; there is no metamor-
phosis, only the valves are of a slightly different form, and of a red
colour. As the pools dry, they bury themselves in the sand or mud
at the bottom ; if that remains moist, the old animals survive ; if it
becomes dry, they perish, but their eggs retain their latent life, and
are hatched on the return of rain. This explains the seemingly
marvellous phenomenon sometimes observed in a shallow pool, which
has been dried up in the summer, and may have long remained so,
but which, in a day or two after it has been refilled with water, is
found swarming withjittle Entomostraca.

In the Branchipus stagnalis we have another example of the
rapidity of the appearance of swarms of individuals in recent pools
through a similar economy of latent vitality of the ova. The Bran-
chipus is characterised by the great number of its segments ; the
males are distinguished by their antennse having long antler-like
terminal joints or processes, which serve to retain the female ; and at
the termination of the sperm-ducts aretwointromittent plates. There
are two sperm-sacs and two testes in the form of long and straight
caeca, which extend the whole length of the tail ; and from the
anterior dilated end the csperm-duct proceeds inwards and back-
wards. Both sperm-ducts soon after their origin dilate into a sperm-
sac; and then proceed to a swelling at the base of the tail, where
they open near a spine-bearing peduncle. The ova, when they are
impregnated, are received into an external capsule. When the pools
are dry, the ova have the power of retaining life for two or three
years.

The generative organs attain an enormous extent in Limuhis :
they are packed closely, interblending with the ramified cfeca of
the liver, in both male and female, throughout the body. In the
female the ovarian tubes present the dendritic or ramified dispo-
sition. We distinguish the sexes by the external character of

CRUSTACEA. 327

the first pair of thoracic limbs, which are short, swollen, and hooked
in the males, while in the females they are long, straight, and
pointed. On the first of the abdominal respiratory limbs there
is a prominent tubular appendage, on which the sperm-duct ter-
minates ; in the female there is a simple perforation at the corres-
ponding part.

No instance of parthenogenesis has been determined in the higher
sub-class of Crustacea, called Malacostraca ; but, like other Arti-
culata subject to periodical ecdysis, they have the power of re-
producing lost extremities, as has been already explained. There
is no propagation by spontaneous fission or gemmation: every
species is developed from ova formed by organs peculiar to one
series of individuals, and impregnated by the fertilising product
of organs as peculiar to another series. But, although the male
and female organs are never naturally combined in the same indi-
vidual, accidental or monstrous hermaphrodites occasionally occur,
in which the male organ is developed on one side, and the female
organ on the other side of the same animal. This dimidiate her-
maphroditism has been most commonly observed in the lobster,
and is indicated by external characters. The generative orifices
open on the last thoracic leg on the male side, in which the ab-
dominal plates are smaller and more simple ; Avhilst on the oppo-
site side they are broader and more ciliated, and the generative
aperture is situated on the middle or third ambulatory leg. This
singular kind of malformation seems to depend upon the very
slight connection, or want of connection, between the right and left
generative organs of the same individual, whether male or female.
The external apertures are always distinct on each side ; and when
a combination of the right and left generative organs does occur, it
is by a partial union of the two testes, or of the two ovaria.

In the male Cymothoa both the essential and efferent portions of
the male apparatus are distinct on each side: the testis is here much
simplified, and consists of three elongated pyriform vesicles forming
a common tube by the union of the short vasa deferentia, which
arise respectively from the great end of each vesicle. In this and
some other of the Isopoda, the disproportion between the male and
female is still retained ; and is almost as extreme in the parasitic
Bopyrus as in the LernoBans.

In Squilla, the testes are ramified glandular lobes, from which
the sperm-ducts pass off laterally to terminate each in a hollow
evertible penis at the base of the last thoracic leg.

In Astacus fluviatilis the testes are blended together at the

Y 4

28 LECTURE XV.

middle line along the posterior half of their extent, anterior to
which they are separated and symmetrical : they consist of packets of
minute contorted capillary secerning tubes. The vasa deferentia quit
the gland at tlie junction of its three apparent lobes ; they form
many convolutions at the sides of the hinder part of the thoracic
segment, where they may be distinguished by their opake white
colour. They dilate into sperm -receptacles in the last portion of
their course, and terminate at the small prominent orifice at the
basal joints of the last pair of thoracic legs.

In the Maia the testis consists of an elongated and convoluted mass
of extremely minute vermicular tubuli, which mass is united by a
slender transverse commissural process with the testis of the opposite
side. The vas deferens is formed by the gradual enlargement of the
tubuli, and is disposed in a number of close convolutions, and some-
what suddenly dilates into a spiral seminal receptacle, which termi-
nates, as in the Astaciis, on the basilar piece of the last pair of legs.
In many crabs, how^ever, as in the Grapsus and Oci/poda, the
external opening of the male organ is found on ths sternal part of
the last thoracic ring. The testes in the common crab {fig. 132, /)
consist of a net-work of very small seminiferous tubes, occupying the
lateral portions of the cephalothorax, which gradually increase in
size until they form the long sperm-ducts : these (ib. d) form
numerous convolutions on each side of the stomach, and dilate into
large ejaculatory ducts before opening upon the plastron. The ter-
minal part of the duct can be everted by a kind of erection to form a
temporary organ of intromission ; and the Crustacea are singularly
analogous to serpents in the double number as well as the structure
of this part. Certain appendages of the first and second abdominal
rings in the male crabs are probably connected as exciting organs
with the sexual function.

The spermatic fluid is white and sometimes opalescent : the sperm-
cells present varied and remarkable forms. In the Cyclops they are
oval corpuscles ; in Cypris they are large, filiform, and flexuous. In
the Isopods and Amphipods they are long filaments pointed at both
ends^ or with a slight thickening at one end : they are motionless.
134 In the Decapoda the nucleus

of the sperm-cell developes
one or more filiform pro-
cesses, which project from
the cell itself. In fig. 134,

Spermatozoa of Crustacea, highly magnified. ^ shoWS the form of the Spcr-

matozoa in the Grapsus marmoratus ; b and c, that in Pagurus
oculatus ; and d, that in Pisa tetraodoii.

CRUSTACEA.

329

The female organs present, like the male, a progressive com-
plication of structure as the species ascend in the class. Most of
the small Entomostraca carry the impregnated ova in appended
ovisacs, like those of the Lernege. These sacs are not developed in
the Limulus, which also differs from the smaller Entomostraca
inasmuch as the ovarian mass interblends its lobes and processes
with those of the liver ; the oviducts form more frequent com-
munication with each other than in the higher Crustacea, but ulti-
mately terminate, like the vasa deferentia, by two distinct but
contiguous orifices on the back part of the first abdominal lamelli-
form appendage.

The ovaria in the lobster are of great length on each side ; the
oviduct comes off from the outer part of nearly the middle of the
gland, and descends to terminate at the basal joint of the third pair
of ambulatory feet.

In crabs the female apparatus reaches its highest state of compli-
cation, and consists of an ovary, oviduct, and a copulatory pouch, or
spermatheca, on each side. The ovaria are elongated cylindrical

sacs in the Maia {Jig. 135), and
are divided into an anterior («)
and a posterior part {h), the short
oviduct {d) being continued from
the union of the two : the anterior
parts of the ovaria are united
together by a short transverse
canal {a') ; the posterior divisions
are intimately united through half
their extent ; the spermatheca (c)
is developed a little above the ter-
mination of each oviduct ; and the
spermatophora and spermatozoa
in this receptacle afford favour-
able subjects for microscopic obser-
vation.

The species of a genus of Mac-
roura {3Ii/sis) are called " Opossum shrimps " from carrying their
ova during the process of development in abdominal recesses, an-
alogous to the marsupial pouch ; but this superadded complexity
in the reproductive economy is common, under various modifi-
cations, to all the Crustacea.

The wider our survey of living nature extends — the greater the
number of facts in the history of animals with which we become
acquainted — the more do the points of correspondence between the

Female organs, Maia Squinndo.

330 LECTURE XV.

different species increase, and the clearer becomes our conception of
the unity of the general plan which pervades their organisation.
This is especially the case with regard to the phenomena which we
recognise in tracing the development of particular animals. But,
before entering on the stages of the development of the individual
Crustacean, I may premise a few remarks on the phases which the
class itself has passed through from the period when we first re-
cognise its representatives among the animals that have heretofore
peopled our planet.

To render my remarks on the paleontology of the Crustacea more
intelligible, I may repeat that the class is naturally divisible into
two great groups ; but not, as Leach and Macleay believed, according
to the sessile or pedunculate character of the eyes, for you find eye-
stalks in Entomostracans — to use the language of Leach, "podoph-
thalmatous " species may be found amongst the lowest Phyllopoda,
e. g. in the genus Brancliipus, as well as in the highest members
of the class. We had to seek, therefore, for some more constant and
important character for the primary division of the Crustacea, and
this character we found in the constancy of the number of the seg-
ments composing the body in certain members, and the variability of
the number of segments in the rest of the class. In the majority of
the existing species, including the typical members of the class, the
thorax includes seven segments, the abdomen seven segments, and
seven are likewise indicated by the appendages in the head, twenty-
one being the archetypal number of the segments in the division of
the Crustacea, called " Malacostraca ; " at all events, the number
seven is constant with regard to the thoracic segments, and is never
exceeded in the abdominal segments in this sub-class. In the
lower sub-class, the number of segments varies, being often more
and sometimes less than seven.

The Malacostraca, again, were divided according to the relative
length of the thorax and abdomen, or according as they have " long "
or "short" tails, as the latter part is commonly called ; in accordance
with which, the technical names of these subdivisions, or orders,
have been devised. The lobster is the type of the Macroura, or
long-tailed order, and the crab of the Brachyiira, or short-tailed
Crustaceans. But Nature never moves per saltum, and there is a
little group which has an intermediate proportion of the abdomen,
and it has been called '^ Ajio?)ioitra."

All the three orders are represented in the tertiary formations and
in their pliocene, miocene, and eocene divisions ; but no species of
crab, or brachyurous Crustacean, has hitherto been met with in

CRUSTACEA. 33 1

Strata more ancient than the eocene. In the chalk formation, the
highest form of Crustacean would be classed with the Anomoura ;
but the Macroura are the prevalent forms. Lobsters, crawfish,
shrimps, and other Macroura^ but all of species now extinct, are met
with fossilised in the secondary strata, from the chalk to the coal
formation ; but below the ciialk, there are no higher forms of Crus-
tacean than the Macroura. When we come to the coal-measures, the
Malacostraca disappear ; but we then find the gigantic Entomostracan
called the King-Crab {Limiilus) ; thence down to the lowest strata in
Avhich any trace of animal life has been found, the Crustaceous class
is exclusively represented by Entomostracous species, and more
particularly by a peculiar form of Entomostraca, which became
extinct before the coal-measures were deposited. Almost endless,
however, are the varieties under which this form was manifested in
the Palaeozoic periods : the term " trilobite " is given to the funda-
mental type or form, on account of the segments of the body being
divided into three lobes.

Our countryman Lhwyd, or Lloyd, first discovered this fossil in
1699, and he save it the name of Trinucleus. At that time zoo-
logical science was not sufliciently advanced to afford a definite
binomial sign for the extinct animal ; and Lloyd's name rather indi-
cated the petrifaction as such, than a species of the animal kingdom.
The idea of the place of the Trilobite in that kingdom began first to
be mooted about the time of Linnaeus, by whom it w^as consigned to
the class of insects, with the name of Entomolithus paradoxus. Knorr
next studied it, and gave it the name of " Trilobite," believing it to
be allied to the molluscous Chitons, which opinion prevailed to the
time of the Entomologist Latreille, and died with him. The better
preserved fossils, in fact, gave evidence of distinct organs of vision,
large compound eyes, with a cornea divided into numerous segments,
thus proving that the Mollusca could not be the primary division of
animals to which the Trilobites belonged ; and since that time all
naturalists have agreed in referring these fossils to the Crustacea.

With regard to their nearer affinities, all who had studied the
Trilobites up to 1843, were of opinion that they were allied to the
hio-her, or Malacostracous, division of the Crustacea ; and Mr.
Macleay, in his valuable appendix to "' Murchison on the Silurian
Strata," places the Trilobites in a distinct order between the Isopoda
and Aspidophora. He based his views on the trilobed character of
the segments in Serolis and Bopyrus^ and showed that the eves v/ere
large, sessile, and compound in Cijmothoa, as in Trilobites. The
Cymothoa and other Isopods roll themselves up into balls, as we

332 LECTURE XV.

find many of the Trilobites to have done before they perished. But
we find these characteristics also in Limulus : the segments of the
hinder division of its body are divided into three elevations, or lobes ;
the large, sessile, compound eyes of Limulus are more like those of
the Trilobite than the eyes of any Isopods are ; and the larval Limuli
roll themselves into a ball. Moreover, the excess in the number of the
segments of the thorax or abdomen, over and above the number
seven which governs them in the Malacostraca, proves the particulars
of resemblance to the sessile-eyed members of that sub- class, which
Mr. Macleay indicates, to be no characters of immediate affinity to
the Cymothoidce or to the Epicarides, although some of these^ like
SphcBroma^ may present a large, convex, semicircular anal segment,
such as we see in the Trilobitic genus Bwnastus of the Silurian
strata.

In a lecture on the Crustacea, delivered at the Royal College of
Surgeons, April 27, 1843, and published in the following month, I
introduced the Trilobites with the following remark: — " The dis-
tinction between the Entomostraca and Malacostraca, in the numerical
character of the segments of the body, is of the first importance in
determining the affinities of those ancient extinct Crustacea, called
'Trilobites.'"* And I pointed out how Bopyrus and Cymothoa
differed by their normal number of thoracic and abdominal segments,
viz., 7 — 7. M. Burmeister, in the same year (1843), with equally
original views of the importance of this numerical character, also
availed himself of it, in determining the position of these extinct
animals in the Systema Naturae, and showed how it invalidated the
marks of resemblance which had been noticed between certain Isopods
and Trilobites. But he errs, I believe, in thinking Limulus to be
still more widely removed from the Trilobites than the Isopods are,
not apparently knowing the King-crab in its larval state. Professor
Emmerich, in a memoir in Bronn's Neuer Jahrbuch, 1845, regards
the Trilobites as a peculiar order, connecting the Malacostraca with
the Entomostraca, but more nearly related to the latter. He thinks
them allied to the Malacostraca by their crust-like shell, and by their
not possessing simple eyes together with compound ones ; but this
combination is rare even in the Entomostraca. He deems the
Xiphosura and the Phyllopoda to be the two orders of Entomostraca
to which the Trilobites are united by the nearest characters of affinity.
They correspond with both as regards the form and size of the
clypeoid head or cephalo-thorax. The soft texture of the under side
of the body of the Trilobites, and the circumstance that no one has

* LXXXIV. p. 165.

CKUSTACEA. 333

yet succeeded in detecting unequivocal vestiges of legs, are in favour
of the supposition that they must have corresponded, in the perisli-
able structure of their feet, with the Apus and Branchipus.

But, to what end, it may be asked, tends all this discussion con-
cerning the affinities of animals that have long since ceased to exist ?
How are we concerned w^ith it, in considerations relative to the
generation and development of the actual Crustacea ? To this I
have to answer, that it is only by a knowledge of the transitional
larval forms of these, that we come rightly to comprehend the nature
and affinities of the extinct Trilobites ; and that our knowledge of
the most interesting relations of actual InrvjB requires a previous
knowledge of the forms of their class that have heretofore existed
in this planet. In no mature stage of any existing Crustacean do we
find the trilobites so closely resembled, as they are by the larval
stages of the Limulus, and of some of the smaller Entomostraca.
The metamorphoses of these are such that different stages are
figured as distinct species in the well-known work " On Ento-
mostraca," by 0. r. Mliller.* In the larval Cyclops^ wliich is his
genus Naiiplius, the body is rounded and without the tail; it has
only two pairs of limbs : the eyes are distinct ; but, in the course of
the first and second moult they approximate, and finally unite to-
gether. The body of the larval Branchipus consists at first of two
oval divisions, like the spiders : that which represents the thorax
and abdomen united has no legs ; but two pairs of natatory seti-
gerous legs, and two antennae, are developed from the head, which
has a single median eye. The form of the head is also different
from that of the parent. After the first moult the head has three
eyes, a pair being added to the first median one ; but all are ses-
sile. The abdomen elongates, and divides into rings, and is now
provided with rudimentary tubular feet. At the secondary moult,
the first pair of foliaceous feet appear, and are succeeded by seven
pairs of rudimentary ones. In succeeding moults the lateral eyes
become pedunculated, and the median eye disappears ; the ab-
domen grows longer, and its limbs are perfected. The Apus
quits the Qg% with fewer segments than it afterwards acquires. The
larval Sao has but three thoracic segments, but the number of these
increases with each successive moult, until the adult form is acquired ;
the new segments being developed between the thorax and abdomen.
Similar metamorphoses have been evinced by fossil specimens of the
tribolitic genus Ogygia, in which the additional segments were
developed at the hinder part of the abdomen.

* ccxxxv.

334 LECTURE XV.

One cannot witness the earlier stages of Branchipus and Apus
without being struck by their resemblance to certain forms of Tri-
lobites. And so likewise with the larva of Limulus. The argu-
ment against the affinity of this genus to the Trilobite which had
most weight with Burmeister, was the peculiar bayonet-shaped
weapon proceeding from the post-abdominal division of the body in
the fully-developed King-crab. Now, when it quits the ovum, this
weapon is not developed ; the cephalo-thorax is relatively smaller ;
the abdomen longer, and more trilobed, and altogether the larva is
much more like the Trilobite than the later stages. The cephalo-
thoracic shield is enormous in the larval Sao^ but becomes reduced
to comparatively small dimensions in the adult animal. Some of
the forms of the smaller Trilobites, which figure as distinct genera,
e. g. Battus and Agnosfus, may also be larval forms of other genera ;
for, like the existing Entomostraca, the Trilobites underwent their
metamorphoses, which, as in the case of Ogygia, were, also, of a
similar nature. Therefore, by these facts in the development of the
lower Crustacea — few indeed, I admit, when compared with the great
number of known Entomostraca that now exist — a clearer light is
thrown on the real nature of those ancient Trilobites than could have
been expected in regard to extinct creatures, the affinities of which
were so long and so lately considered problematical.

The ova, after extrusion from the oviducts, are retained and pro-
tected in Cymotlioa and other sessile-eyed Malacostraca by means
of the flabelliform appendages of the thoracic extremities, wdiich ap-
pendages are unusually expanded, and overlap each other, so as to
form a marsupial cavity or temporary receptacle, in which the incu-
bation of the ova is completed. In the Podophthalma, the lamelli-
form ciliated appendages of the abdominal segments include similar
marsupial or incubatory recesses for the ova. The female lobster
and other Macroura are distinguished from the male by the greater
development of these appendages ; and in the Brachyura the shorter
abdomen or tail is so much more expanded in the females as to cover
nearly the whole sternum, and render the sex distinguishable at a
glance.

With regard to the higher group of Crustacea, up to a late period
naturalists had believed that they differed from insects, as well as
from Entomostraca, in undergoing no metamorphosis ; but they offer
differences in this respect in different species. The phenomena of
development common to all are the following : — The primary germ-
vesicle, after impregnation of the ovum, propagates its progeny not at
the expense of the whole germ-yolk, but only of a small portion of
it ; so that the process of yolk-fission is a partial, not a total one.

CRUSTACEA. 335

All Crustacea show the same direction of development, — i.e., they
obey the law of the Articulate type by the commencement of the
embryo at its ventral surface, — it is literally built up from below ;
and consequently the umbilicus, or the last cicatrix closing in the
yolk-sac, is on the back ; the body is completed by the finishing of
the segments or rings at the dorsal surface of the body. In regard to
the Malacostraca, there are many modifications of the secondary or
subsequent phenomena of development. As long ago as 1778, a
Dutch naturalist, Slabber*, described and figured a minute swimming
Crustacean of the genus called Zoea by modern naturalists ; it was
provided with a pair of large and distinct eyes ; its carapace was
armed with a long frontal and a dorsal spine ; and its abdomen was
terminated by a forked tail. He preserved this little animal alive in
sea water, which was daily renewed, and on the fourth day he found
that the animal had moulted and changed its form; the feet, eyes, and
antenna were more developed, the frontal spine had become compara-
tively small, the dorsal one had disappeared, and the tail had changed
from the bifurcate to the spatulate shape, and was fringed by a row
of short spines. Many years elapsed ere this observation was re-
peated, and it seems to have been forgotten, when Dr. Leach, the
most accomplished Crustaceologist of his day, founded the principal
character of the class Crustacea on the absence of metamorphosis.

During the spring of 1822, Mr. V. Thompson f, to whom we
are indebted for the discovery of the metamorphoses of the Cirripeds,
captured an abundance of the singular Zoeas in the harbour of Cove ;
the largest of them was daily supplied with fresh sea-water from
May 14th until the loth of June, when it died in the act of changing
its skin. The disengaged members, invested with the new integu-
raents, were changed both in number and form, and corresponded
with those of the decapod Crustracea, the anterior pair being
furnished with large pincers. Here, therefore, was a strong indica-
tion that, under the form of a Zoea, was masked that of some one or
other of the higher Crustacea ; and, probably, one of the common
species of the Irish coast. To the development of these, therefore.
Dr. Thompson next turned his attention, and he succeeded in
hatching the ova of the common crab during the month of June, and
found that the young were excluded under the form of the Zoea
Taurus, with the addition of lateral spines to the thorax ; where-
upon he concluded that the decapod Crustacea indisputably under-
went a metamorphosis.

These observations were, however, called in question, after the

* CCXXXVI. t CCXXV. No. 1. 1828.

336 LECTURE XV.

appearance of the elaborate monograph by Rathke, on the develop-
ment of a freshwater species.

In the year 1829, Dr. Rathke published his "Researches on the
River Craw-fish {Astacus Jiuviatilis).* In this species the ovum
first appears in the shape of a minute transparent vesicle, which
afterwards becomes surrounded by a second, forming the membrana
vitelli : the nature of the processes effecting this stage appears not to
have been observed. The yolk increases in quantity, and is rendered
opaque by the presence of numerous granules, or nucleated cells,
which are at first angular, and change from the lenticular to
the spherical figure ; then the internal minute transparent germinal
vesicle quits the centre, and comes into contact with one part of the
parietes of the ovum. The colour of the yolk successively changes
to yellow, orange, and brown ; the spermatozoa, enveloped in their
spermatophore, when they are received into the oviduct, escape
therefrom, and ascend the duct to the ovarium, and after coming into
contact with the ovum, the clear vesicle disappears, and the produc-
tion of the embryo commences. Rathke failed to ascertain vrhat
became of the vesicle. The formation of the ovum in the ovary
continues half a year. In the month of November, the vesicle was
visible ; in the ensuing March it had disappeared.

The ovum escapes into the oviduct by bursting the inner lining of
the ovary. It is surrounded by a layer of albuminous matter, and is
enclosed within a coriaceous chorion, and an irregularly doposited
nidamental tunic, by which the ovum, after exclusion, becomes
attached to the ciliated plates beneath the tail of the mother.

The first appearance of development is as a whitish cloud of
indeterminate form, spreading over the vitellus, and assuming, as it
extends, a reticulated appearance. It seems as if the germ-cells had
propagated themselves over the superficies of the yolk-mass. A
discoid portion of the opake layer is defined from the rest, and
increases in thickness at its middle part : its longest diameter is

136^ -^^ about half the radius of the egg. A depression

appears in the centre of this, which passes more
and more deeply into the vitellus, and the em-
bryonic spot expands at its margins The patch
next grows heart-shaped, and the antennee, the
labrum, mandibles, and abdomen become simul-
taneously recognizable (Jig. 136). The first
^ . .,. appearance is a minute median prominence,

Astacus fluviatilis. '■ ^ r ?

which becomes the labrum e ; that part of the
mouth which we find most constantly in the Crustacea. Then the

* CCXXXVIL

CRUSTACEA. 337

other parts appear in pairs; the antennge {b, c), at first short and
simple processes, increase in length, and their extremities become
notched ; the mandibles (d) also lengthen and enlarge, particularly
in their basal portion ; the labrum recedes from between the anterior
antennae, and takes its station between the posterior : the eyes (a)
now make their appearance. All these parts are, at first, slight
elevations above the surface of the germ. A cavity is formed behind
the labrum, which communicates with the commencement of the oeso-
phagus ; the tail or abdomen (^j elongates, and the depression in its
surface is converted into the anus ; the rest of the alimentary canal
is a simple wide sac, which, by the extension of the mucous layer of
the germinal membrane, now includes the vitelline mass.

The three anterior pairs of maxillse begin to show themselves at a
little distance behind the mandibles, and afterwards the fourth and
fifth pairs ; the last (Jig» 137, g 5) increasing in size more rapidly
than the rest. Thus, including the
eyes (a) and the two antennae {b, c), nine
pairs of appendages may now be recog-
nized, of which the two last belong to
the thorax : the five posterior pairs of
thoracic members, which are not, like
the first two, developed into jaws, are
produced in regular succession from be-
fore backwards from that portion of the
body which is turned upwards, or the
epimeral elements of the rudimental
segments. Each pair of legs at its first ^''^'''' ^"''''"''•

appearance is exactly similar to the hindermost maxillse ; these, there-
fore, are retained in the service of manducation by an arrest of develop-
ment. The ambulatory legs increase inversely with respect to the
maxillae, the anterior {Jig. 137, A 1) soon acquiring four times the size
of the posterior {h 5). The rudiments of the future branchige next
appear as small processes from the base of each leg. The seven seg-
ments of the third division of the body may now be distinguished by
six transverse furrows, and by the rudiments of foliaceous appen-
dages. Part of the cephalic segment (m) above the antennae is the
basis of the great shield Avliich afterwards covers the whole cephalo-
thorax ; it grows upwards and backwards until it meets its fellow
along the median line of the dorsal aspect, and so completes the
carapace.

The heart (s) appears at first in the shape of a small compressed
vesicle, or "punctum saliens," situated near the junction of the

338 LECTURE XV.

anterior and posterior divisions of the body: blood-vessels seem
to be prolonged from it, and its pulsation speedily becomes dis-
tinguishable. The nervous system consists at first of two parallel
lines, on each of which are eleven minute white spots : from the
anterior of these a short and broad process passes forwards on either
side of the oesophagus. The above described stages of development
are in progress from the beginning of April to the middle of May.
The whole of the organs continue to approach more nearly to their
mature form. The brain, liver {v\ and salivary glands next make
their appearance. The outer integument of the body is developed
from the ventral to the dorsal aspect, and the yolk-laden intestine is
finally, with the heart, Availed in by the confluence of the lateral
lobes of the integument along the middle line of the back.

The integument is very soft when the animal quits the shell:
the young craw- fish subsists, at first, on the remaining portion of
the yolk, during which time its coat becomes sufficiently hardened
to admit of its moving about in quest of food with more safety.
The different appendages increase in length, and more especially
the branchiae, the growth of which is now remarkably rapid.
The changes of the interior parts of the animal, with the exception
of the development of the sexual organs, consist in a gradual
adaptation of parts already formed to their proper functions. The
relative positions of embryo and vitellus are the same in the
craw-fish as in the Daphnia pulex and Branchipus stagyialis. The
maxillae present at an early period a considerable resemblance to
those of the Apus ; the legs, at the period when they are devoid of
branchial appendages, typify the persistent condition of the Bran-
chiopoda; after the branchiae are developed, and before they are
enclosed in the branchial chamber, the characteristic persistent con-
dition of the respiratory system of the Edriophthalma and Stomapoda
is sketched out.

M. M. Audouin and Milne Edwards have shown that the successive
changes of development of the nervous system of the craw-fish cor-
respond in like manner with distinct types of formation observed by
them in its permanent condition in lower species of the class ; thus
the two series of ganglions, which first indicate the suboesophageal
central part of the nervous system in the embryo craw-fish, are ana-
logous to the permanent state of the nervous system in the mature
Talitrus. At a more advanced period, the two series of ganglions
in the foetal craw-fish approach the median line and become united
together as in the abdominal ganglionic chain in the adult Cymothoa.
We have seen, that in the brachyurous Crustacea a further con-
centration takes place by the longitudinal blending together of the

CRUSTACEA. 339

whole series of the suboesophageal ganglia, which clearly indicates
that the brachyurous Crustacea are more highly developed than the
macrourous species; contrary, how^ever, to the opinion of Rathke.
The eyes are at first sessile in all Crustacea.

It is certain that the moult of the young craw-fish is not at any
period accompanied by a marked change in the form of the body, or
in the structure and functions of the locomotive members ; this
Crustacean, in short, undergoes no sudden metamorphosis. The
progress of development is not interrupted by arrested phases.

A series of less complete observations on the ova of a species of
land-crab ( Gecarcinus\ more recently published by Westwood*, lead
to the same inference in respect of that species ; although the ma-
crourous proportions of the abdomen, and the exposed position of the
gills at the base of the thoracic legs, obviously unfitted the larva for
land life, and demonstrated the necessity for the parent's migration
to the sea. Nevertheless, this accomplished entomologist coincides
with Rathke in the general conclusion, that the Crustacea undergo
no metamorphosis, and that the contrary evidence adduced by
Slabber and Mr. Thompson must depend on some erroneous ob-
servation.

The opposite conclusions of both parties from the phenomena
afibrded them by the solitary species examined, may be compared
with analogous premature generalizations which might have been
drawn, in reference to the class of Insects, by the observer of the
development of a cockroach on the one hand, and by the observer of
the metamorphoses of a butterfly on the other. As reasonably might
the one, after detailing the progressive development of the orthop-
terous insect, broach the inference that insects underwent no other
metamorphosis than the gradual acquisition of wings ; and, with
equal reason, might the other observer of the wonderful changes of
the lepidopterous insect affirm them to be characteristic of all insects.
It needs only that each theorist should question the reality of the
other's observation to make the parallel complete. The failure of
both to arrive by so short and easy a route at the entire truth incul-
cates the necessity of acquiring a sufficient foundation, by careful and
extensive induction of facts, before proceeding to erect the super-
structure of general theory.

With regard to the metamorphosis of the common crab, valuable
testimony in confirmation of Mr. Thompson's discovery has been
contributed by Capt. Du Cane, R. N.f This gentleman obtained
crabs with ova under their tails in the month of December, from

* CCXXXVII. p. 311. t CCXXXVIII. p. -138.

z 2

340

LECTURE XV.

which the larvae were produced in the months of March and April.

The form under which they first appear is represented in^^. J38. :

138

%

139

Larva of Crab. Second stage.
Larva of Crab. First stage.

they are then about half a line in length. Soon after exclusion this
larva casts off its envelope and assumes the appearance represented
in Jig. 139., which closely corresponds with that zoeaeiform Crustacean
whose further changes were witnessed by Thompson, and which he
had assured himself was an early or larval state of a common crab.
The last form which immediately precedes the assumption of the
mature characters corresponds, according to Thompson, with that of
the genus Megalopa.

The additional evidence adduced, in 1839, by Capt.Du Cane in proof
of the actual metamorphosis of the Crustacean in question, was most
acceptable. He affirms a corresponding metamorphosis to occur in the
ditch-prawn {Palemon variabilis) and common shrimp {Crangon vul-
garis). Dr. Thompson has witnessed similar metamorphoses in the
genera Palinurus, Squilla, Pagurus, Porcellana, Galatea, and the
marine species of Asfacus, as well as in Palemon and Crangon.

Mr. Couch, a medical gentleman residing on the coast of Cornwall,
contributed further conformation in a paper to the Cornish Natural
History Society in 1843*, in which he described, with much care and
detail, the metamorphoses of the common crab. The nervous system
first appears on the ventral aspect of the embryo ; at this period it
agrees in its arrangement with that which is persistent in the
edriophthalma, and the eyes of the larval crab are likewise now
sessile. A second metamorphosis takes place, when the eyes become
supported on long and thick peduncles. None of the phenomena are
more remarkable than that of the nervous system, where ten pairs of
ganglia are consolidated into one great central ganglion in the crab.

* CCXXXIX. p. 28.

CRUSTACEA, 341

With respect to the Maia, or spider-crab, also, there is a very com-
plete metamorphosis. According to Couch, in both kinds of crab the
larva quits the ovum in a form more strictly aquatic than the adult ;
and this gives us an insight into the curious law of the periodical
migrations of the land-crabs ( Gecarcinus) of the West Indies to the
sea.

Brown, in his "History of Jamaica," gives a graphic account of
these migrations. About the month of February or March they
may be seen in crowds on their way to the sea-side, impelled thereto
in order to deposit their ova in the sea. These ova have been ex-
cluded from the oviduct, and are attached, by the nidamental gluten,
to the ciliated sub- caudal appendages ; and Brown's idea was, that it
required the sea to wash them off. But now, as we know that the
larval land-crabs are natatory and more especially fitted for sea life,
we see the necessity for the migration of the parent-crab to that
element for oviposition.

Finally, the metamorphoses of another species of shrimp ( Caridina
Desmarestii) have been described with all the requisite care and
detail by M. Joly, in the " Annales des Sciences Naturelles" for
January, 1843. The development of the ovum, up to the period of
exclusion and attachment to the maternal ciliated plates, closely
corresponds with that described by Rathke in the Astacus fiuviatilis.
The first stages in the formation of the rudimental extremities, —
the first steps in the definition of the alimentary canal and circu-
lating system, were likewise the same ; the heart was observed to
beat thirty-five times in a minute in the embryo Caridina. But the
formation of the abdomen is anterior to that of the antennae, the
labrum, and the maxillae ; and the ambulatory thoracic legs precede
the masticatory pairs in their formation. The young Caridina,
moreover, is born with only three pairs of jaws, and the represen-
tatives of the ambulatory feet are bifid, like those of the 3Iysis, and
are at first likewise only in three pairs. The abdominal segments
are without any vestige of lamelliform limbs.

The bifid feet of the larva are metamorphosed into auxiliary jaws,
and the later bifid thoracic limbs are metamorphosed into the ordi-
nary ambulatory legs. With respect to the branchiae, they are not
at all developed when the young Caridina quits the ovum. The
first moult takes place three days after exclusion from the egg ; the
subsequent ecdyses are numerous, and take place at long intervals.
It is unquestionable that the Caridina, unlike the Craw-fish, is ex-
cluded neither under the form, nor with all the parts which it pos-
sesses in its mature shape. It wants, for example, the branchiae, a
certain number of maxillae, the ambulatory thoracic, and the lamelli-

z 3

342 LECTURE XV.

form abdominal feet ; it possesses neither the squamous tail nor the
complex stomach of the mature creature.

The cumulative evidence of the metamorphoses of Crustacea can
no longer be rejected ; but their modifications in different genera,
and the number of the exceptions to the law, like that presented by
the Astacus Jluviatilis, are yet to be determined. Here, therefore,
is an ample field open to the researches of the original observer ; a
field which must be diligently and extensively cultivated before it can
yield the fruits of true generalisations as to the extent, the nature,
and varieties of the metamorphoses in the class of articulate animals
which support their bodies on jointed limbs and breathe by gills.

Sufficient has been observed to show, that if certain stages of the
development of a higher Crustacean were arrested, and growth alone
proceeded with, an animal would result having the characters of the
Crustacea of an inferior order. The Crab is "anomourous" before
it becomes brachyurous ; at an earlier period it is " macrourous," and
it is "edriophthalmous" before it becomes " podophthalmous ;" all
which stages typify the successive forms of the Crustacea, as they
were introduced into this planet. The entomostracous characters
were never overpassed by the Crustacea anterior to the coal measures,
and the type of the Macroura did not begin to be departed from
until the period of the deposition of the chalk. All the decapod
Crustacea are, at first, macrourous, or manifest the Oolitic type ; and
all Brachyura pass through the anomourous or cretaceous type
before the proper brachyurous or tertiary character is finally ac-
quired. But these resemblances are general, and by no means exact in
specific details. No extinct species could be reproduced by arresting
the development of any known existing species of Crustacea; and
every species of every period was created most perfect in relation
to the circumstances and sphere in which it was destined to exist.

Class CRUSTACEA.
Body articulated, with articulated limbs : head with antennae :
branchial respiratory organs. Sexes distinct. Metamorphosis in
most ; in none resulting in fixed individuals.

Subclass ENTOMOSTRACA.

Body with more or fewer segments than fourteen ; integument
chitinous. Eyes sessile.

Order Trilobites.
Abdominal segments trilobed : limbs rudimentary, lamelliform,
probably branchial : sessile compound eyes in most.

CRUSTACEA. 343

Genera Asaphus, Calymene, Bumastus, Trinucleus, Ogygia, &c.
(all extinct).

Order Xiphoshra.

Abdominal segments trilobed : limbs forcipated and lamelliform :
branchiae lamelliform and abdominal; a sword-shaped caudal ap-
pendage.

Genus Limulus.

Order Phyllopoda.

Body divided into numerous segments, with lamelliform branchial
limbs. Eyes sometimes confluent, sometimes distinct and subpedun-
culate.

Genera Branchipus, Apus, Limnadia, Artemia.

Order Cladocera.

Body articulated, defended by a bivalve carapace, and with mem-
branous lamelliform branchial limbs. Eyes, in most, confluent.
Genera Daphnia, Evadne.

Order Ostrapoda.

Body obscurely articulated, defended by a bivalve carapace, with
natatory limbs. Eyes confluent.
Genera Cypris, Lynceus.

Order Copepoda.

Body distinctly articulated, with many pairs of natatory limbs ;
females with external pendent ovisacs.

Genera Cyclops, Cyclopsina, Anomalocera, Calayius.

Sub-class MALACOSTRACA.

Body divided into thorax and abdomen, with seven segments in
each.

Division EDRIOPHTHALMA (with sessile eyes : no carapace).
Order L^modipoda.

Abdomen rudimentary ; palp of thoracic limbs vesicular and
branchial.

Genera Cyamns, Caprella, Leptomera, Aegina.

Order Isopoda.
Abdomen normal, with branchial limbs : thoracic limbs subequal,
uncinated, with basal marsupial plates in the female.

Genera Cymothoa, Sphceroma, Idotea, Asellus, Oniscus, Bopyrus,

z 4

344 LECTURE XVI.

Order AMrniPODA.

Abdomen terminated by saltatorj or natatory appendages : thoracic
limbs unequal, with basal vesicular branchial appendages.

Genera Amphitho'e^ Talitrus, Gammarus^ Hyperittj Phronima,
Vibilia.

Division PODOPHTHALMA (with eye-stalks, and a cephalo-
thoracic carapace).

Order Stomapoda.

BranchicB exposed, usually tufted, attached to the abdominal and
(in some) to a few of the thoracic limbs : rarely abortive.

Genera Phyllosotna, Amphion^ Mysis, Lucifer, Cynthia, Alinia,
Squilla.

Order Decapoda.

BrancMcB in cavities at the sides of the thorax : first two thoracic
limbs serving as jaws : the other five chelate, uncinate, with the last
pair sometimes lamellate. Crust commonly calcified.

Tribe Macroura. (Abdomen long, with lamelliform limbs, and
terminated by a natatory appendage. An-
tennae long.)
Genera Penceus, Alpheus, Caridina, Hippolife, Palcemon, Gebia,
Callianassa, Crangon, Nephrops, Astacus, Homarus, Palinurus,
Scyllarus, Galathea.

Tribe Aiiomoura. (Abdomen moderately long, not a natatory organ.

Antennae long.)
Genera Pagurus, Birgus, Porcellana, Remipes, Ranina, Homola,
Lithodes, Dromia, Dorippe.

Tribe Brachyura. (Abdomen short, bent beneath the thorax.

Antennae short.)
Genera A. Matuta, Calappa, Leucosia ; B. Pinnotheres, Grapsus,
Gelasimus, Ocypoda, Gecarcimis, Thelphusa ; C. Portunus, Cancer;
T). 3Iaia, Inachus.

LECTURE XVI.

INSECTA.

Although spontaneous locomotion is the peculiar attribute of the
Animal Kingdom, we have seen that the lowest members, the Zoophy-
tes as they were termed, were, for the most part, fixed and rooted
like plants : we have seen that the first manifestations of locomotion

INSECTA. 345

were of the feeblest and simplest character, a rowing of the body
through an element of equal density with itself, or a trailing of the
body along the ground, which supported it at every point. As we
advanced to the survey of the Articulate series of animals, we saw
the integument progressively hardened ; divided into segments which
were united by flexible joints ; at length supported upon moveable
jointed limbs, consisting of hollow columns of integument compacted
into a dense exterior crust, capable of serving the office of levers and
fulcra, whereby the animal could raise its belly from the dust, and
swiftly traverse the surface of the ground.

We now come to a class of Articulata in which the highest problem
of animal mechanics is solved, and the entire body and its appendages
can be lifted from the ground and be propelled through the air. The
species which enjoy this swiftest mode of traversing space breathe
the air directly : but their organs of respiration are peculiarly modi-
fied in relation to their powers of locomotion ; they consist of innu-
merable tracheee commencing from lateral pores called stigmata, or
by anal tubes, which are ramified through and over every tissue and
organ of the body. The nervous system is homogangliate ; the organs
of sense include two jointed antennse and two compound eyes ; the
skeleton is principally external, and cut deeply into segments, whence
the name of the class Insecta.

Not every Insect, however, has the power of flight, nor any Insect
save in its last and most perfect state ; many undergo most remark-
able transformations before they acquire their wings, and although
some Insects, which ultimately are so endowed, undergo a less amount
of change, yet the metamorphoses are always least remarkable in the
apterous species.

Of these lowest members of the class of Insects^ many have more
than three pairs of legs, have sometimes indeed eighty pairs and
upwards in their mature state : metamorphic development exhausts
itself, as in the Anellides, in the successive acquisition of new seg'
ments * and legs in addition to those which previously or originally
existed ; these Insects are therefore termed Myriapoda.

True orHexapod Insects have thirteen rings ; one for the head, three
for the thorax, and nine for the abdomen. Certain flying Insects
in their early or larval state present several pairs of rudimental feet,
in addition to those attached to the first three segments succeedino-
the head ; but no true Insect in its mature state has more than the
three pairs of articulated limbs just indicated.

* Always, as De Geer, Savi, and Newport have shown, developed between the
penultimate and anal segments.

346 LECTURE XVI.

The common or typical number of articulated legs, therefore, in
this class, is six ; disposed in three pairs developed exclusively from
the thorax. In the Crustacea we saw that the number was greater,
and that the limbs were developed from the abdominal as well as
from the thoracic segments of the trunk. Such is the case also with
the Myriapodous Insects ; but these breathe the air directly by means
of tracheae, not by gills, and they have only one pair of antennae :
they likewise manifest, as we shall find, the typical Hexapod character
in their larval state, — a period during which, as in the Cirripeds,
Epizoa, and Acalephae, the Myriapod shows more of its true nature
and is more in accordance with the common type than during its final
and oviparous stage.

Taking, however, a survey of the tracheal air-breathing Articulata
under their mature condition, they present more important characters
in common than any which indicate an affinity to the gill-bearing
classes ; and we find them offering the same ground for a primary
division as the Crustacea did, viz., in the number of the segments of
the body.

This number is constant and definite in the higher and typical
members of the group, in which it is neither more nor less than
thirteen : in the rest it exceeds thirteen, and is variable.

There is no distinction between thorax and abdomen in the indefi-
nitely-jointed division ; and all the segments, save the first and last,
support jointed limbs. The Myriapoda I regard as a group equiva-
lent in the tracheal Articulata to the Entomostraca in the branchial
Articulata ; and, like them, they are the lowest organised, and the
least numerous and varied of the two divisions of their primary group.
The Myriapodous sub-class is divided, according to modifications of
the mouth, into Chilognatha and Chilopoda, answering to the genera
lulus and Scolopendra of Linnaeus, who first detected these natural
divisions.

The Hexapod Insects may be classified, —

1st. According to the phenomena of their development ;

2nd. According to the structure of their mouth ; or

3rd. According to the nature of their wings.

Agreeably with the first character they would be divided into, —

Ametabola, or those that undergo no metamorphosis ;

Hemimetabola, or those that undergo a partial metamorphosis; and

Metahola, or those that undergo a complete metamorphosis.

According to the modifications of the trophi, instrumenta cibaria,
or oral organs, the Hexapod Insects are divisible, like the Myriapods,
into two groups, viz., the Haustellata or suckers, and the Mandibu-
lata^ or chewers and biters.

INSECTA. 347

But this binary division is insufficient for the general propositions
which the comparative anatomist has to enunciate ; and I take,
therefore, the third kind of characters, the value of which was first
fully discerned by Linnaeus, viz., that founded upon the organs of
flight. Those Hexapod Insects which are devoid of wings are called
Aptera ; those with two wings only are the Diptera. All the rest
have four wings. The Lepidoptera have four scaly wings ; the
Hijme7ioptera have four veined wings, crossing each other when at
rest ; the Hemiptera have one pair of wings partially thickened, and
called hemelytra ; the Orthoptera have one pair of wings wholly
thickened, the other folded lengthwise ; the Coleoptera have one pair
wholly and much thickened, called elytra, and the other pair folded
crosswise ; the Neuroptera have four reticulated wrings ; the Stre-
psiptera have one pair of wings rudimental and curled up. In the
Aphaniptera both pairs are rudimental and functionless as wings.
Of these orders the first five are " haustellate ; " the next four
are " mandibulate." The Aptera are ametabolian ; the Hemiptera
and Orthoptera are hemimetabolian ; the remaining orders are " me-
tabolian." These characters, therefore, briefly and succinctly express
the highest generalisations, as yet reached, relative to the Hexapod
Insecta.

Although, typically, the Hexapods have thirteen segments, in
the last stage of the metabolian orders, one, two, or three segments
may become blended together; and although we reckon the head
as a single segment, the number of jointed appendages which it
supports, under the name of antennae, mandibul^, maxillae, palpi, &c.,
indicates that here, as in the Crustacea, it consists essentially of
several coalesced segments.

With regard to the orders of the Myriapoda, the Chilognatha have
two biarticulate mandibles, without palpi, armed with imbricated
teeth planted in a cavity at the upper extremity of the mandible ;
they have also a kind of lip situated immediately beneath, and
covering the mandibles, notched into four divisions, and answering
to the two pairs of maxillae of the Crustacea ; whence the name from
the Greek, signifying, " feeding by jaws." The lulus, or Gally-
worm (Jig. 140), is a tjpe of this order. The Chilopoda have the
mouth composed of two mandibles, with a small palp ; a quadrifid
lip, also the homologue of the crustaceous maxillae confluent ; two
labial palpi, hooked at the tip; and a second pair of jaws, or foot
jaws, — the obvious homotypes of feet, — terminated by a strong
hook, moveable, and pierced beneath the extremity by a poison-
duct. The Centipede {Scolopendra) is the type of this order of
Myriapods, which "feed by feet."

348

LECTURE XVI.

Every Insect has a distinct head {Jig. 140, 141, a\ provided with one
pair of antennae (c), and every true or Hexapod Insect has its trunk
divided into two regions, called thorax {d^J /,) and abdomen {ah).

140

^"'^^ 141

lulus.

Locusta.

The thorax is interposed between the head and the abdomen, and
so far is analogous to that part in human anatomy ; but it has
neither the same relation to the contained viscera nor to the locomo-
tive extremities which characterises the thorax in the vertebrate
animals. To the Insect's thorax are attached all the locomotive
members ; both the first pair, which may be compared with the pec-
toral extremities of the vertebrate animal, and the last pair, which
are analogous to the pelvic members, as well as the middle pair, to
which there is no correlative in the vertebrate series. This centre of
the locomotive powers is divided into three segments, which corre-
spond with the three pairs of legs : the first segment is termed the
" pro-thorax " {d\ the second the " meso-thorax " (/), and the third
the " meta-thorax " {%). Each of these segments has a dorsal and a
sternal piece : the dorsal half-rings are called respectively " prono-
tum," " mesonotum," and *' metanotum ; " the ventral or sternal arcs
bear the corresponding terms, " prosternum," '' mesosternum," and
" metasternum." From the inferior arches of the segments, the legs
(e, A, k) are developed, or with them they are principally articulated,

INSECTA. 349

like tbe legs of the Crustacea and the ventral oars or setigerous
prolegs of the Anellides. In the flying Insects there are developed
from the dorsal arches of the middle and third segments, locomotive
appendages which constitute the wings {g j).

It must not be supposed that the parts of the thorax which have
just been described are naturally or uniformly separate, and moveably
connected with one another ; they are more commonly confluent, but
in different degrees in different families, so as more or less to ob-
scure the primitive traces of their original distinctness, which can
only be demonstrated, as has been done by Macleay, Audouin, Bur-
meister, and others, by an extended comparison of the thorax in the
whole class of Insects, or by tracing its development and modifications
during the various stages of the metamorphoses. When the compo-
sition of the thorax of an Insect is thus studied, it is found to be
made up of not less than fifty-two pieces, which have for the most
part received, and necessarily, distinct names in Entomology, and
many of them, very unnecessarily, more names than one.

The abdomen is usually formed of a greater number of segments,
always nine in the larva, which retain a greater degree of mobility
upon each other ; but it supports no locomotive appendages in the
Hexapod Insects.

The tissue of the external skeleton is of a dense, resisting, but
light material ; it looks and feels like horn, but it has for its base a
peculiar substance called " chitine," which, like the " cellulose " of
plants, is insoluble in caustic potash, and retains its form like charcoal
when submitted to a red heat ; but it contains nitrogen. The articu-
lated appendages consist, like the segments of the trunk, of hollow
cases or tubes of the same firm and slightly flexible substance ;
which tubes contain the muscles, nerves, and other soft parts in
their interior. The integument is softer and more yielding in larvse,
flies, and most parasitic insects : it is thickest and hardest in the
burrowing beetle tribe, in which the flexible property is limited to
the joints of the segments and their appendages. Uncalcified chitine
is always more or less elastic, and no tissue could be better adapted to
enable a light flying animal to resist external violence than that
which constitutes the seeming horny case of Insects. It consists of
three layers, epidermal, pigmental, and dermal ; the derm and epiderm
more closely resemble each other in physical properties than in other
animals : they are separated and cemented together by sometimes
two distinct coloured layers of rete mucosum ; but the pigmental
matter is often combined with the dense chitine. The hairs, spines,
and scales are processes of the epiderm, which often include a
coloured substance: the bulbs of the hairs are imbedded in the

350 LECTURE XVI.

corium. The primitive cellular basis of the chitlne is usually de-
monstrable in the thin integument of larvae, and of the smaller
parasitic insects, when it presents under the microscope a hexagonal
structure * : sometimes the cells show nuclei, as in the larva of Hy-
drous piceus. "j" In some insects the hairs are beset with smaller
hairs ; such barbed hairs, in the processionary moths e. g.^ are easily
rubbed off, and, if they penetrate the skin, occasion intolerable
itching.

With regard to the jointed and aliform appendages of the skeleton,
the first pair inserted into the front or upper part of the head, are the
antennae, which present a vast variety of shapes and sizes in different
Insects, but seem in all to have most intimate relation to the senses of
touch and hearing. Their precise function has not, however, yet been
well defined. The entomologist avails himself of their various con-
formation to obtain characters for the distinction of families, of ge-
nera, or of species of Insects ; and a considerable section of the gloss-
ology of this extensive department of Natural History is devoted
to the technical terms required to express the antennal characters.
To the head likewise belong more or less complicated oral instru-
ments, called " trophi," or " instrumenta cibaria," modified in some
insects to serve for suction, in others, for mastication : they properly
fall under the demonstration of the digestive system..

The jointed legs attached, as before stated, to the three thoracic seg-
ments, consist each of a hip, a thigh (Jig. HI, k), a leg (/), and a foot
(m), commonly called the tarsus ; but which are not to be taken as
answerable to the parts so termed in Human Anatomy. The hip, for
example, consists of two joints, called " coxa " and " trochanter," usu-
ally the shortest of the whole leg : the foot or "tarsus" includes from
two to five joints, and is usually terminated by a pair of diverging
hooks or claws : a third hook is found in the chaffer (Jig. 142, g) and
stagbeetle: the legs of the larvae of the darkling beetles {Meloidce) have
three lanceolate hooks. The peculiar powers of moving upon land
or in water depend upon the modifications of the forms or proportions
of these extremities. In water Insects the tarsi are usually flattened,
fringed with hair, and stretched out in the same plane with the trunk,
like oars. In leaping Insects, the hinder limbs present as dispropor-
tionate a development as the legs of the kangaroo. In burrowing
Insects, the anterior limbs are distinguished by short, broad, and
massive proportions, with a strong and flattened hand like that of
the mole, as in this best of Insect burrowers J, which has been called
the mole- cricket. Most Insects are able to crawl up vertical walls,

* XXIV. p. t CCXXXI p. 387. t Pj-ep. No. 463, A.

INSECTA.

351

and some along glass and the ceilings of rooms, against gravity :
the house-fly achieves this by virtue of the development of discs
upon the under surface of certain expanded joints of the tarsus,
which some have supposed to act as suckers, and others contend
to be pads exuding an adhesive mucus from the hair follicles of the
cushions ; which accordingly require the act of frequent friction
or cleansing, as may be seen when a fly rubs its feet against one
another.

The muscular system is, as may be supposed, developed in relation
to the several kinds and powers of locomotion indicated by the modi-
fications of the extremities. As a necessary corollary of the cylin-
drical form and external position of the principal parts of the ske-
leton, the joints are for the most part ginglymoid, and restricted to
movements in one plane : the muscles of those segments of the limb
are consequently simply flexors and extensors. The coxa has three
flexors and one extensor ; the trochanter has three extensors {Jig.
14-2, a, 6, c), one flexor {d\ l U2

and one abductor (e). The
femur has one long penniform
flexor (^) and a similar ex-
tensor (y). The tibia has one
flexor (2), inserted into a long
slender process like a tendon,
which traverses the joints of
the tarsus to be attached to
the inferior margin of the claw:
the extensor (A) occupies the
inferior portion of the tibia :
its tendonlike attachment is
fixed to the upper margin of
the claw. Besides these mus-
cles, which are common to the
joints of the tarsus, there are
two others belonging to the
trifid claw of the last joint :
the extensor (m) is short, the
flexor {n) is a longer penni-
form muscle, and is attached,

like the long flexor of the Muscles of leg of a chaffer (Mc/o/ow^/ia).

tarsus, to the inferior part of the claw -joint. The cox£e have a round
head inserted into a cup of the mesosternal arc, and the movements
of the hip-joint are rotatory ; the head is usually connected with the
thorax by a similar joint, which, from the greater freedom of the

352 LECTURE Ji.Vl.

movements, may be termed arthrodial. In Insects of flight, the
cavity of the thorax is almost entirely occupied by the muscles of the
wings. There are two extensor and several small pairs of flexor
muscles, which arise from the meso- and meta-thorax, and are in-
serted into a process at the base of each wing. The muscles of
the legs have similar fulcral processes, but longer, like tendons;
they are, however, chitinous apodemata of the external skeleton.
The muscular fibre is transversely striated, and is also charac-
terised by a second series of transverse indentations at regular but
wider intervals.

The wings of Insects are essentially flattened vesicles, sustained by
slender but firm hollow tubes called "nervures," along which branches
of the tracheae, and channels of the circulation, are continued. The
wings never exceed two pairs, which are developed from the meso-
notum and metanotum. Sometimes one or other of these pairs is
wanting. The wings present many varieties in their shape, their
consistence, and their teguments. When they subserve flight, they
are thin and transparent ; or, if opake, are rendered so by an imbri-
cated clothing of most delicate scales, which, when detached, resemble
the pollen of flowers. In certain insects, especially those that bur-
row, the first pair of wings become thick, hard, and opake, forming a
kind of shield to the back ; they are called " elytra," and cover the
posterior pair of membranous wings when these are not expanded
for flight. Sometimes the anterior wings are membranous at their
extremities, hard and opake at their base, when they are called
" hemelytra," When the hinder pair of wings is wanting, it is re-
placed by a pair of rudimental appendages called balancers : other
modifications of, or appendages to, the wings have been called "alulaa"
and "patagia."

The Orders of Insects being, as before remarked, founded upon
the modifications of the wings, the chief of these are best exemplified
by recapitulating the ordinal characters. Those Insects in which the
first pair of wings are hard, infiexible, and serve as sheaths (elytra),
and the second alone are used for flight, and are folded transversely
when at rest, constitute the order Coleoptera : these insects undergo
complete metamorphosis, and are subdivided according to the number
of joints of the tarsi. Beetles and most burrowing Insects belong to
this order.

Those Insects in which the anterior pair of wings are converted
into elytra, of less density than in the Coleoptera, and in which the
posterior wings are folded longitudinally when at rest, constitute the
order Orthoptera : they are said to undergo a semi-metamorphosis,
the chief chaiige being the acquisition of wings. This order in-

INSECTA. 353

eludes the most voracious and destructive insects, as the Locust,
Cockroach, &c.

Those insects which have both pairs of wings membranous, trans-
parent, strengthened by numerous nervures, and finely reticulated,
form the order Neuroptera^ which includes the highest organised
insects, as the predatory dragon-flies.

The insects which have four membranous wings simply veined, and
crossing each other horizontally when at rest, form the order Hyme-
iioptera : they undergo a complete metamorphosis, and include the
most useful of insects, e. g.^ the bee.

The insects with four wings, more or less clothed with minute
scales, are called Lepidoptera : they 1^3

undergo complete metamorphosis,
and include the most beautiful spe-
cies of the class, as the butterflies :
in one family of this order the wings

are divided lengthwise intoanum- ^'^^9iWi§^^'^

ber of feathered pieces, which ra-
diate from the body like the stems pterophora.
of a fan {fig, 143).

The insects which have the anterior pair of wings in the condition
of the hemelytra, form the order Hemiptera ; but certain genera
have the dense part of the anterior wings reduced to so small a strip,
that they are scarcely distinguishable, except by size, from the pos-
terior pair, and these insects constitute a section of the order termed
Homoptera.

A few remarkable genera of insects have the anterior pair of
wings reduced to small or rudimental elytra, and the posterior pair
unusually large, and folded longitudinally, like a fan when at rest.
The anterior wings being reduced to minute appendages twisted
spirally, the Order has been hence termed Strepsiptera. The spe-
cies, in their larval state, are parasitic on the bee tribe.

The order Diptera is characterised by the development of the an-
terior pair of wings into organs of flight, and the retention of the
hinder pair in the condition of minute clavate appendages, usually
called the " balancers." The prothorax and metathorax are rudi-
mental whilst the mesothorax is disproportionately large to form the
required space for the powerful muscles, which execute, through the
two anterior wnngs, the function of flight.

In almost every Order of Insects there are species, or there are
individuals, as the females of particular species, w^hich are apterous ;
but since the time of Aristotle, who divided insects primarily into the
" winged," Ptilota, and the " wingless," Aptera, most of the hexapod

A A

354 LECTURE XVI.

insects devoid of wings have been artificially grouped together. Cu-
vier and Latreille divide the Apterous Insects into three tribes, the
Suctoria (fleas), the Parasita (lice, including the Pedlculus capitis
and Pthirus inguinalis of the human species), and the Thysanoura,
including tlie Lepisma and Podura or skip-tails.

The grand and characteristic endowment of an insect is its wings ;
every part of the organisation is modified in subserviency to the full
fruition of these instruments of motion. In no other part of the
Animal Kingdom is the mechanism for flight so perfect, so apt to
that end, as in the class of insects. The swallow cannot match the
dragon-fly in its aerial course ; this insect has been seen to outstrip
and elude its swift pursuer of the feathered class : nay, it can do
more in the air than any bird, — it can fly backwards and sidelong, to
right or left, as well as forwards, and alter its course on the instant
without turning.

Now what are these " limber fans," that give the little articulate
animals such command over aerial space ? I do not mean their struc-
ture or composition ; the anatomical question has been already
answered. I do not ask for their analogy ; that is rightly expressed
by their common name ; they have the same relation to the insect as
instruments of motion, which the feathered wing bears to the bird.
But what is their essential nature, or with what are the wings of the
insect homologous ? Are they modified anterior limbs> like the wings
of bats and birds and flying-fishes ? Not so, for they co-exist with
and are superadded to the jointed anterior pair of legs. Are they
such expansions as form the parachute of the little dragon {Draco
volans) ? These do, indeed, co-exist with arms and legs, but they
consist of a fold of integument stretched out upon elongated and
straightened ribs, which are appendages of a vertebral column.
But an insect has no vertebral column, no true internal skeleton.
The strong and numerous nervures which sustain the thin alar mem-
branes of the Libellula are articulated processes of the external chi-
tinous tegument.

A circulation can be traced through these membranes, at least in
their early and softer state ; air-vessels are abundantly spread over
the supporting frame-work : the wings of the Lepidoptera appear
after the third moult, as tegumentary flattened vesicles, soft, and
permeated by trachea?, and when fully expanded in the imago, they
must still take their share in the business of respiration. Nay, it has
been found that the rudimental wings of the pupae of certain water
insects are the gills of such ; they perform the same function as the
very similar membranous and vascular tegumentary expansions in
certain Anellides (see fig. 101,) ; which expansions are developed,

INSECTA. 355

as in the larvte of the Ephemera, from the tergal arch of the segment,
and co-exist with rudimental legs from the ventral arch of the same
segment.

Well, therefore, has the deep-thinking Oken * called the wings of
insects "aerial gills ;" they are, in fact, the homologues of the tergal
branchi^ of the vermiform Articulata, raised to a higher function in
correlation with a generally transmuted state of the rest of the orga-
nisation, which is advanced to the utmost perfection of which the
Articulate type of structure is susceptible. And have we not already
seen the membranous aliform branchiee of the beetle protected, like
the gills of the lobster, by an elytral carapace developed from a more
advanced segment ? Have we not likewise found the metamorphosed
branchial wings of the Pterophora subdivided lengthwise like the
tufted tergal gills of the Nereis ?

The air-breathing articulated animals with jointed legs offer a
close correspondence with those that respire by gills in the progres-
sive steps of complication of the nervous system and the order in
which those steps succeed each other. The lowest insects, like the
lowest Crustaceans, resemble the worms, in the great length and
slenderness of their body, and in the uniform size, shape, and number
of the constituent segments. In the lulus {fig' 140.), whose very
short and numerous rings support each two pairs of rudimental legs,
the corresponding ganglions of the abdominal chords are much less
conspicuous than in the earth-worms, and the whole central axis of
the nervous system, continued from the brain, is almost as devoid of
partial swellings as the spinal chord of the apodal vertebrate. It
lies, however, as in other Articulata, on the opposite side of the
body to that in which the brain is situated.

The cephalic ganglion (^fig. 144, a) of the lulus is transversely
elongated, and obscurely divided by a slight median indentation into
two side-lobes : its upper and latter extremities are prolonged out-
wards into the short and thick optic nerves (c, c), which resolve
themselves half way towards the compound eye into a plexus of fila-
ments for its several divisions. Two separate antennal nerves, con-
jectured by Straus to be motory and sensory (^, d\ are sent off on
each side below and in front of the optic nerves to the short seven-
jointed antennae. On each side also, but below the antennal nerves,
arise the two nerves {h) united together by an anastomosing branch
which supply the palpless mandibles.

The thick oesophageal chords (^) are continued from the posterior
and inferior angles of the brain ; and, though apparently simple,

* Natur. Philosophie, 2d Ed. p. 418.
A A 2

356

LECTURE XVI.

consist essentially of two chords, which become separate at the lower
part of the pharynx : the anterior chord girts the pharynx by a trans-

lulus.

versely oval ring, formed by its confluence with its fellow ; the pos-
terior and normal columns converge at an acute angle backwards,
blend together, and expand into the commencement of the abdominal
nervous trunk ; thus inclosing the oesophagus by a second and looser
collar. The closer anastomotic ring is homologous with that formed by
the transverse commissural band of the oesophageal chords in the
lobster and limulus ; and probably also to the anterior nervous ring
discovered by Lyonnet in the Cossus ligniperda. The stomato-gastric
nerves which arise from the posterior part of the brain imme-
diately form a third slender ring (e), about the oesophagus, from the
middle of the upper part of which the trunk of the stomato-gastric
system (f) is continued a short way back upon the stomach, when it
divides ; the two divisions diverge at an angle of 45°, bend abruptly
backwards, and run parallel with each other along the dorso-lateral
parts of the wide and straight alimentary canal.

Two large nerves (A) are sent forwards from the beginning of the
thick suboesophageal or ventral chord (i, i), to supply the confluent
maxillfe, which form the under lip : the nerves of the two single
pairs of feet, belonging to the thoracic segments, next arise, and

INSECTA.

357

afterwards the more numerous minute nerves to the little feet, which,
by their articulation to the segments in double pairs, indicate such
segments to be severally a confluence of two. The simplicity of the
abdominal chords corresponds with the close approximation and
great numbers of the organs from which they receive impressions
and to which they transmit stimuli. The analogy of this exceptional
condition of the abdominal chord or nervous axis in the lulus to the
dorsal spinal chord of the Vertebrata, is as instructive as is that of
the equally exceptional ganglionic condition of the spinal chord in
the Tetrodon amongst fishes to the normal abdominal knotted chords
in the Articulata, in tracing their mutual relations to each other.

The segments of the Polydesmus are relatively fewer and larger
than in the lulus, and their lateral margins are produced: each,
however, with the exception of the first three, which answer to the
thorax in hexapod insects, supports two pairs of legs : but these are
longer than in the lulus. Accordingly we find the sub -abdominal
nervous chords {fig. 145, z), which show as little trace of their median
separation as in the luli, swelling into two slight enlargements (^, ^)
opposite each of the abdominal segments : two nerves are sent off
from either side of each enlargement, and the anterior of these four
pairs of nerves is directed at an acute angle forwards and outwards
to the stigmata: the remaining pairs supply the muscles 145
of the segment and the legs, and are of equal size.

In the Centipede, a series of equal and equidistant \
ganglia is developed upon the ventral surface of the two \
abdominal chords. Only in the first and last of the ab-
dominal ganglions can any modification of size be de- ^^^
tected. The anterior, or sub- oesophageal ganglion, for ;^
example, is larger than the rest, having to supply the ^
modified legs which perform the function of jaws and
undePlip ; the chords, diverging as they escape on each ;;

side of the oesophagus, enclose it by uniting with the .
large bilobed ganglion, or brain above. The nerves from \,
this part supply the large antennae and the aggregated
ocelli. In the structure of the abdominal columns a tract
less closely connected with the ganglionic nerves may
be traced along their dorsal aspect. This was first pointed
out by Mr. Newport, who attributes to it the motor
function. A large, vascular trunk, connected also with
the dorsal aspect of the nervous system, has been regarded as part
of the nervous system ; by some as a motor, by others as a respiratory
column : its true nature was detected by Mr. Lord.* AYith regard to

^

Polydesmus.

* Med. Gazette, March 3d, 1838.

A A 3

358 LECTURE XVI.

the ganglionic and nonganglionic portions of the true nervous axi^,
the same physiological reasonings Avill apply as have led to the conclu-
sions ah'eady given respecting their office in the crustaceous animals.

Of the four nerves which come off from the sides of the ganglionic
portions of tlie columns, the second, which is principally distributed
to the muscles of the corresponding pair of legs, arises in a great pro-
portion from the ganglion itself. The first and third nerves, which
are smaller than the second, supply the muscles and integuments of
the segment. The fourth pair of nerves passes to the breathing
pore and to the integument. This, therefore, must be regarded as the
respiratory nerve. The stomato-gastric nerve is a distinct system
connected with the anterior ring or brain.

Thus in the Myriapodous insects we find that although the prin-
ciple of irrelative repetition prevails in the nervous system as in the
skeleton and locomotive instruments, yet it does not prevent the
recognition of the leading physiological divisions of that system. We
have, for example, the super-oesophageal or cephalic portion, which is
subservient to the functions of the special organs of the senses, and is
the centre whence voluntary impulse may be directed along the non-
ganglionic tracts of the nervous axis, and to which ordinary sensa-
tion may be transferred by similarly uninterrupted nervous filaments.
We have, secondly, a large sub-oesophageal mass, which, originating
the nerves analogous to the fifth pair, for the masticating organs and
other parts of the head, may be regarded as analogous to the medulla
oblongata. In the abdominal chords and ganglions we have the re-
quisite machinery for the automatic reception and reflexion of stimuli,
independently of sensation and the will ; and to these are superadded
internuntiate and uninterrupted chords, for bringing the body under
the dominion of the will, and for producing harmony and consent of
action throughout its extent. The special nerves to the respiratory
system, and the stomato-gastric nerves, complete this already compli-
cated nervous system.

In the hexapod insects the nervous system differs chiefly from that
in the Myriapods in having its primary divisions more definitely de-
veloped, and in manifesting degrees of concentration corresponding
with the increase of bulk and strength in particular parts of the trunk,
and in the locomotive organs appended thereto. Most insects, how-
ever, commence their career as worms ; the high form which they are
ultimately destined to attain in the articulate series is at first masked by
the guise of an Anellid or Entozoon. Some insects retain their larval
or vermiform state much longer than others ; and after passing a great
proportion of their lives under this form, fall into the state of the pupa,
or chrysalis, — relapsing, as it were, a second time into the condition of

INSECTA. 359

an ovum, — there and then undergoing that part of their development
which before was left incomplete : finally they emerge in their perfect
state to enjoy for a brief period the highest faculties, animal and
organic, which they are destined to acquire ; fluttering in the air, it
may be, for a single day, procreating their kind, and perishing. Now
the development of the nervous system, like that of the muscular,
digestive, and other systems, being completed at distinct and some-
times remote periods, requires to be studied in the first and last of the
active states of the insect, and also in the intermediate period, when,
owino; to the rapidity and extent of the changes which it undergoes,
the nervous system offers to the comparative anatomist and physiologist
phenomena of the highest interest.

The apodal entozoiform larvie, in which the segments of the body
are obscurely defined, as those of most Diptera, Hymenoptera, and
of some Coleoptera with very rudimental feet, have a simple ventral
nervous chord, almost as devoid of ganglionic enlargements as in
the Nematoidea and lulidge: it is, however, usually relatively shorter,
failing to reach the posterior extremity of the body, and the fine nerves
pass off on each side and radiate from the extremity.

In the larva of Stratiomys chamceleon the ventral chord is divided
by a series of constrictions into eleven consecutive and contiguous
ganglia.

The larvae, which present, like the Centipede, larger and more
definite segments, most of which are provided with legs or prolegs,
have a ganglionic centre for each segment, and intermediate chords.

This anellidous and chilopodiform type of the nervous system has
been best described and figured by Lyonnet.* The subject which this
inimitable dissector and artist selected for his patient investigations
was the caterpillar of the Cossus ligniperda. The nervous axis
consists of thirteen ganglions, arranged along the median line of the
body, and connected by two chords or columns. The first and largest
ganglion, situated in the head above the mouth, and of a bilobed form,
Lyonnet calls the brain ; the remaining twelve ganglions (as in Jig.
159, 1 to 12.) are situated below the alimentary canal; the eleventh
and twelfth are so close together that their distinction might readily be
overlooked ; but it was pointed out by Lyonnet. The sub-abdominal
ganglions and inter-communicating chords were called by Lyonnet
the spinal marrow. Some anatomists who have applied the analogy
of the ganglionic and non-ganglionic roots of the spinal nerves in the
higher Vertebrata to the explanation of the functions of the ganglionic
and non-ganglionic parts of the nervous axis in Insects, have thought

* CCXL.

A A 4

360

LECTURE XVI.

that they found in the works of Lyonnet corroboration of this incon-
clusive physiological view, Lyonnet, however, expressly denies that
the parts which he called brain and spinal marrow in the insect were
similar in anatomical structure to those in the higher animals.

" The spinal marrow of the ca- 146

ter pillar, if one may say that it
possesses such," observes Lyon-
net, "sensibly differs from that
of man. It is slender ; it bifur-
cates at intervals, and enlarges
from distance to distance to form
its masses, which I have named
ganglions." The intervening
chords Lyonnet terms "conduits
de la Moelle epiniere." He par-
ticularly points out the difference
in relative position, and in the
means of protection assigned to
the ganglionic columns in insects,
and to the spinal chord in the
higher animals. As to any views
of distinct physiological proper-
ties in the ganglions or the non-
ganglionic nervous tracts^ none
such appear in the works of
Lyonnet ; nor, indeed, did they
form part of the domain of phy-
siology at that period; and it
was a great advantage to Zootomy
that Lyonnet looked at his sub-
ject with the eye of truth, and
not through the prism of any pre-formed physiological notions.

The super-oesophageal ganglion gives off ten nerves ; eight in pairs,
and two solitary or azygos nerves ; one of these latter is the anterior
oesophageal ring (^fig. 146, e). Its extremities are connected with
the cephalic ganglion immediately anterior to the attachment of the
principal columns which form the posterior oesophageal ring. The
second solitary nerve (c) is sent off from the middle of the posterior
side of the cerebral ganglion, and proceeds backwards to the oeso-
phagus. The cephalic nerves, sent off in pairs (b, b), supply the
antennae, the ocelli, the muscular and integumentary parts of the
head, and communicate with branches of the maxillary nerves. The
most remarkable pair, however, is that which arises anterior to the

Vanessa urticae.

INSECTA. 361

annular or oesophageal nerve, and which constitutes the cephalic
roots, or connections of the stomato-gastric system. Each of these
nerves passes forwards and divides : the external tract joins one of
the maxilhirj nerves of the sub-cesophageal ganglion ; the internal
one converges towards its fellow, and terminates with it in the first
of the median cephalic series of ganglions (e), which Lyonnet terms
frontal gangHons. The longest nerve in the whole body of the
caterpillar is given off from these ganglions as it passes along the
oesophagus to the stomach and intestines : it was called by Swam-
merdam the recurrent nerve. There are two other small ganglions
situate in the head of the caterpillar on each side of the large bilobed
or cephalic ganglion («, a). The largest nervous columns connected
with the super-cesophageal ganglion, are those which enclose the
oesophagus by uniting with the first of the lower series of ganglions (i).
From this ganglion nerves are distributed to the mandibles, the max-
illae, the lips, and their special organs of sensation or palpi. Two
distinct columns connect the first with the second ventral ganglion
(2) ; and this is connected by more diverging columns with the
third (3). The inter-communicating chords of the remaining ganglions
appear single at their anterior part, and bifurcate as they are con-
nected with the next ganglion in succession. They are of a greyish
blue but transparent colour, and are very elastic. From each side
of the abdominal ganglions are given ofi* two principal branches ; the
anterior to the muscles chiefly, the posterior chiefly to the integu-
ments, but communicating with the muscular branch of the succeed-
ing ganglion. From the beginning of the separation of the bifurcated
inter-ganglionic columns, or conduits, Lyonnet says, "there descends
a nerve, the extremity of which is enlarged a little above the suc-
ceeding ganglion, which sends off from the enlargement a transverse
nerve to the right and to the left, to which I give the name of spinal
rein (bride epiniere, o, o). Of these transverse nerves there are ten
pairs ; they terminate chiefly in the stigmata and tracheae, but send
off" small branches to the skin, and to the dorsal vessel. These are
the respiratory ganglia and nerves, and have been erroneously con-
sidered as the motor column and nerves.

The nervous system in perfect insects approaches to its larval con-
dition according as the segments of the body and their locomotive
appendages are less concentrated and developed ; thus, in the darkling
beetle {Melde) the abdominal nervous columns still manifest eight
distinct ganglions, of which the last, perhaps including three ganglions
of the larva, is now the largest, and radiates its branches to the
generative organs. The sub-ossophageal ganglion sends forward four
median branches to the under parts of the mouth, and is connected

362 LECTURE XVI.

with the super-oesophageal ganglion by the two lateral chords forming
the post-oesophageal collar. The usual nerves are given off from the
brain ; those to the eyes having acquired an increase of bulk, cor-
responding with the great change in the size and complexity of the
organs of vision. The stomato-gastric nerves arise close to the an-
tennal branches, and form a median frontal ganglion, and are con-
nected with a pair of lateral ganglions : from these the usual recurrent
nerve is given off. In the thorax we distinguish the second ventral
ganglion, which, as it distributes branches to the first pair of legs,
I have called the brachial ganglion. The third ventral ganglion,
supplying, amongst other parts, the elytra, may be termed the elytral
ganglion. The fourth ventral ganglion is distinct in the present
species, and, supplying the nerves to the second or true wings, may
be termed the alar ganglion. The fifth, sixth, and seventh, or first
three ganglions in the abdomen, distribute nerves to as many large
and moveable segments of that division of the trunk : the last
ganglion is the largest, and its size is conformable with the bulk of
the generative apparatus, upon which, on the rectum, and the modified
terminal segments of the abdomen, its branches are expended.

In insects having the organs of flight better developed, the elytral
and alar ganglia present a greater proportional size ; but different
degrees of concentration in the centres of the nervous system are
met with in these higher forms of insects. In the Blattae, for example,
there are as many as ten distinct ventral or inferior ganglions. The
super-cEsophageal nervous centre or brain is a transversely oblong
bilobed mass, sending its upper and largest pair of nerves to the eyes.
Anterior and below, the antennal nerves arise from small mamillary
processes of the brain, reminding us of olfactive lobes. The stomato-
gastric nerves are seen a little in advance of those in the deflected
part of the head. The oesophageal chords are short, uniting in a maxil-
lary ganglion, or first of the ventral series, which is situated in the
head ; the inter-communicating chords, which pass from this to the
brachial ganglion, are long, straight, parallel, and juxta-posed. The
brachial ganglion sends off two large and two small pairs of nerves ;
the anterior ones are distributed to the muscles of the arm, which are
lodged within the anterior portion of the thoracic shield ; the second
nerve is continued to the terminal segment of the anterior extremities
like the second nerve from the ganglions of the centipede. The
elytral ganglion, or the third of the ventral series, is larger than the
preceding one. Viewed from the dorsal aspect, it is seen to distribute
three small nerves to the muscles of the wing-cover ; the posterior
branch, anastomosing with the nerve sent from the succeeding gan-
glion to the wing, thus serves to combine these organs of flight in

INSECTA. 363

action in the Ortliopterous insects. In the Coleoptera, whose elytra
do not move in flight, this anastomosis of the nerves does not take
place. Four pairs of nerves come into view when the elytral ganglion
of the cockroach is exposed from below. The anterior of these runs
forward at an acute angle to the muscles of the first and second pairs
of legs. The next two anastomose with an alar branch. The third
pair enters the second pair of legs, and is distributed to their terminal
segments. The posterior nerve passes to the alar plexus. The sub-
stance of the bilobed elytral ganglion seems to be superadded to the
under or ventral part of the nervous chord. The alar ganglion, formed
by a confluence of the fourth and fifth of the larval ganglions, is
situated at the same distance from the elytral as this is from the
brachial ganglion. It is not quite so broad as the elytral ganglion,
the wings which it supplies being shorter than their covers. The
anterior nerve enters into communication with the elytral branches,
as does also the second nerve, with the addition of branches to the
muscles of the legs. The third nerve is distributed to the third
pair of legs ; the fourth to the muscles of the wing. The remaining
six ganglions of the ventral series are contained in the abdomen:
they are smaller than the preceding, the distance between them pro-
gressively increasing after the third. The last, formed by the conflu-
ence of the eleventh and twelfth ventral ganglions of the larva, is of a
triangular form, and the largest of the series. It sends ofi" a pair of
conspicuous nerves to the cercae or anal antenuis. The two inter-
ganglionic columns are in contact lengthwise from the head to the
anal ganglion. In the Meloe they are smaller, and separated by a
marked interspace. The respiratory nerves may be seen on the
dorsal aspect above the second, third, and fourth ventral ganglion.
If the nervous system of the Blatta be compared with the stages of
development of that system in an insect presenting a more con-
centrated type in the perfect state, as in the species of butterfly
described by Herold*, it will be found to correspond with the sixth
stage figured by this author in the pupa of the Papilio hrassicce.

In the predatory leaf-insect {Mantis) the progress of coalescence
has reduced the number of abdominal ganglia to four, the three
thoracic ganglions continuing distinct, so that the nervous system
corresponds with the eighth stage figured by Herold in the Lepidop-
terous insect just mentioned. The super-cesophageal mass consists
of two triangular lobes having their bases rounded and anterior, and
their apex prolonged into the oesophageal chords. Two small nerves
are sent off" from the anterior part to the ocelli, where they swell into

* CCXLL

364 LECTURE XVI.

a slight enlargement. Two short and thick optic nerves pass from
the sides of the brain to form the ganglions supplying the large com-
pound eyes. The stomato-gastric nerves arise, one on each side, near
the optic nerves. The oesophageal columns are short, and directly
converge to the inferior cerebral ganglion, which gives two large and
several small nerves to the jaws: it is situated in the head. Two
long and parallel columns extend to the first thoracic ganglion, which
transmits long and large nerves to the formidable prehensile anterior
pair of legs. The second thoracic or elytral ganglion is at a great
distance from the first, and much nearer the third or alar ganglion.
Anastomosing branches connect the nerves which these ganglions
respectively distribute to the elytra and wings. The Mantis is
chiefly remarkable for the great length of the ventral chords con-
necting the brachial with the elytral ganglia, and which renders
them favourable for minute analysis of their structure. Anterior
and posterior columns, or divisions analogous to those in the spinal
marrow of higher animals, cannot be distinguished. The so-called
sensorial tract is confined to accumulations of nervous matter at the
origin of the nerves to the locomotive organs.

Experiments in which the body of the living Mantis has been so
divided that a segment with one of these ganglionic enlargements
and the locomotive organs it supplies has been detached from the
rest, illustrate the functions of the aggregated centres of nervous
matter in relation to their power of receiving and transmitting im-
pressions, so as to maintain the order of action of such detached
organs upon the application of a stimulus, for a considerable period
after the mutilation.

The jaws of the separated head of a Mantis bite forcibly the stick
which is held to them. The formidably armed prehensile legs in
like manner wound the finger that touches them, when the segment
of the body supporting them is separated from the head and the rest
of the trunk. And if decapitation or amputation of the prothorax be
neatly performed on the living insect, while in its natural and
ordinary position, perched by its middle and hinder pairs of legs
upon a twig, the rest of the trunk does not fall to the ground, but is
maintained for a certain period in that posture, which it even
recovers by actions of the wings, when the balance is slightly and
purposely disturbed.

The super-cesophageal or cerebral mass in insects obtains its largest
development in the dragon-fly (Libellula), which from the size and
perfection of its organs of vision^, its great and enduring powers of
flight and predatory habits, may be regarded as the eagle of insects.
From the side of each of the superior lobes of the brain, the optic

INSECTA. 365

nerve is continued of equal breadth, so as to seem rather as a lobe of
the brain. It expands, and, like the stalk of a mushroom, forms the
stem of a very large reniform ganglion, the convexity of which is
turned forwards and outwards, and the free concave projecting
margin developed at the under part. Thousands of branches to the
divisions of the compound eye are given off from the convex surface
of this ganglion. The brain presents a single median inferior lobe ;
the oesophageal chords sent downwards to the maxillary ganglion are
short and thick. This ganglion is succeeded by three large equi-
distant thoracic ganglia, of which the last two, corresponding with
the elytral and alar ganglions of the preceding insect, are, as might be
expected, from the development of the muscles of the wings (both of
which are alike organised for flight), considerably the largest. Of
the ganglia of the abdomen, the terminal one resulting from the con-
fluence of two, and which supplies the organs of generation, is
remarkable for its large size.

In the white butterfly (Papilio brassicce) the brain is a thick trans-
verse rounded mass, indented by a longitudinal furrow along the
median line. From its sides proceed the large optic nerve, now greatly
surpassing the other cerebral nerves in size. The oesophageal collar
is triangular, leaving a very small interval for the passage of the
alimentary gullet. The maxillary ganglion is relatively much smaller
than in the dragon-fly, the blatta, and other mandibulate insects.
The first two thoracic ganglions are blended into one, and the third
thoracic and first abdominal ganglions have coalesced to form a
similar mass in the thorax, connected with the preceding by short
chords, separated by an interval to allow the passage between them
of certain processes of the thorax giving attachment to the muscles of
the legs. The ganglions of the thorax have been observed in some
species (as the Bombyx Neustria) to present a reddish tint. They are
succeeded in the Lepidoptera by four other ganglions in the abdomen,
of which the last, as usual, is the largest.

The nervous system of the chaffer {Meloloiithd) has been dissected
and delineated by Strauss* with a minuteness and accuracy second
only to those of Lyonnet. In his beautiful plates are shown the
bilobed brain with its auxiliary ganglia for the eyes and antennae ;
the stomato-gastric nerves and their small lateral cephalic ganglia
are also clearly exhibited. The sub-oesophageal or maxillary ganglion
is of an oblong form ; the brachial ganglion is triangular ; the elytral
ganglion is of a circular, and the alar ganglion of a pyriform, figure ;
these two latter being concentrated into almost a single mass, and

* CCXLII.

366

LECTURE XVI.

radiating the nerves to the abdomen, like the termination of the spinal
marrow called cauda equina. The two median nerves of this series
chiefly supply the organs of generation.

The three thoracic ganglia are blended together into one mass in
the Diptera ; and only two ganglions are developed on the abdominal
portion of the ventral chords.

The greatest degree of concentration of the nervous system is pre-
sented in the insects of the Strepsipterous and Hemipterous orders.
In the Nepa or water-scorpion, for example, only three ganglions are
present in its nervous system. The first, or brain, consists of two
pyriform lobes in contact by their base. The maxillary ganglion is
square-shaped, receiving the oesophageal chords at its anterior angles,
and sending back their continuations from its posterior angles ; these
continue parallel with each other to the thorax, there expanding
into a large rounded ganglion, much more voluminous than the brain,
and from which radiate the nerves supplying all the rest of the body.
In the water-bug {Ilanatra linearis) a like concentrated condition of
the nervous centres prevails : the super-cesophageal mass resembles
that in Nepa; the sub-oesophageal ganglion {Jig. 147, a) is rounded ;
two long and slender columns connect it with a large 147

4-lobed ganglion (b) situated at the end of the thorax. w.
From each side of this ganglion are given off three nerves
which diverge as they proceed to the brachial hemelytral
and alar muscles ; from the lower part of the ganglion,
which is subfusiform in shape, are sent off two bundles
of delicate nerves (c), which pass down into the lengthened
abdomen to supply the parts there situated.

In certain Coleoptera, Hymenoptera, and Diptera, the
principal changes which the nervous system undergoes
in the progress to the imago state are the acquisition of
ganglions not present in the larva.

The progressive changes which the nervous system
of the Lepidopterous insect undergoes in its metamor-
phoses from the larval into the perfect state, have been
beautifully and accurately illustrated by Herold * in the
cabbage butterfly, and by Newport f in a species of
sphynx; but Lyonnet had anticipated both these ob-
servers, in recognising as well the principle as the de-
tails of these changes, which he briefly describes at the
termination of the monograph already quoted.^ Ranatra linearis

The twelve ventral ganglions of the larva (Jig. 159) are sub-equal,

* CCXLI.

t CCXLIII.

t CCXL.

INSECTA. 367

and, except the two last, at regular distances ; in the pupa the inter-
ganglionic columns are shorter, but the body, becoming still more
abbreviated and concentrated, throws those columns into curved
lines {Jig. 146.). The eleventh and twelfth ganglions coalesce ; the
sixth and seventh disappear {ih. between the 5*^ and 8*^ ganglions in
the third subject) ; the fifth blends with the fourth, and the third with
the second ; thus leaving four ganglions in the abdomen and two in
the thorax {fig. 159). Corresponding changes take place in the
cerebral portion of the nervous system. The maxillary ganglion de-
creases with the diminution and change in the maxillary apparatus.
The oesophageal collar contracts, as does the canal which it surrounds.
The brain enlarges, having to supply organs of sense, especially those
of sight, which are perfected to correspond with the acquisition of
new and improved locomotive forces. (Compare the third with the
first subject in fig. 146).

Analogous changes we may naturally conclude to take place in
other orders of insects ; and we find, indeed, in some of these that
the nervous system continues stationary at stages of development
which are progressive and transitory in the Lepidoptera, and that
further concentration is discovered to have taken place in the Melo-
lontha, Cicada, Ranatra, &c., than that \vhich constitutes the highest
stage observed by Herold and Newport in the Lepidoptera. The
marvel is, that these changes, due in part apparently to mere me-
chanical influences, should be so regular, so orderly, so admirably
adapted in their final results to the general condition and exigencies
of the perfect insect : one might have supposed that the particles of
the soft and semi-fluid nervous matter, squeezed by the pressure of
the surrounding parts, when the body seems to be, as it were, con-
tracted by an universal spasm, would be irregularly dislocated or
aggregated into one or more masses ; but, on the contrary, we perceive
the nervous particles and ganglionic cells moving forwards and re-
arranging themselves in orderly groups, definite in their forms, in
their proportions, and in their relative positions ; these being appa-
rently regulated by a law of prospective arrangement and collocated
precisely in those situations where the greatest supply of nervous
energy is required to radiate from them in the active and perfect
insect.

An idea of the situation and degree in which the sense of touch is
exercised in insects may be formed by observing the modifications of
the different parts of the integument, the papillfe, or folds upon its
surface, the hairs, plumes, or soft jointed organs developed from par-
ticular parts of the body. The soft balls on the feet of grasshoppers,
the pulvIUi and adhesive discs on those of flies, the extremity of the

368 LECTURE XVI.

snout in suctorial insects, the long and slender ovipositors of insects
which place their eggs in holes of various depths, the soft, setaceous,
or plumed antennce, and above all, the palpi, often provided with a
terminal vesicle, present the requisite physiological conditions of the
organ of touch. Although another sense, and most probably that of
hearing, may reside in the antennce, yet no one can witness the use of
these organs by bees and ants, the exploratory actions of those of the
ichneumon and of many other insects, without recognising in them
instruments of the tactile faculty.

All Mandibulate insects have a process from the labium, within
the mouth, so analogous to a tongue as to have received that name.
It is particularly well developed in the wasps ( VespidcB), the dragon-
flies {Libelliilidce), the grasshoppers {Locustidcp), and certain beetles
( CarahidcB\ in which its soft, finely ridged, upper surface receives a
rich supply of nerves. Tt is not present in the suctorial insects,
which, as Burmeister well observes, always subsist upon one and the
same food, generally inhabit what they feed on, and consequently
less require the sense of taste.

Although a few physiologists have suspected that some part or
appendage of the head, and others that the membranous lining of
the spiracles were the organs of smell, the precise seat of that sense,
which unquestionably exists in insects, has not yet been experi-
mentally determined. The application by the common house-fly of
the sheath of its proboscis to particles of solid or liquid food before it
imbibes them, is an action closely analogous to the scenting of food
by the nose in higher animals : and as it is by the odorous qualities
much more than by the form of the surface, that we judge of the
fitness of substances for food, it is more reasonable to conclude that
in this well-known action of our commonest insect, it is scenting,
not feeling, the drop of milk or grain of sugar. But no one ever saw
an insect present its spiracles to a nutritive substance before feeding.

The signs of attention and hearing are plainer in insects than
those of smelling ; yet the precise organ has not yet been more defi-
nitely recognised, unless the structure indicated by J. Miiller* in the
fore-leg of the Gryllus hieroglyphus, and more definitely described
by Sieboldl in other Orthoptera, be the true seat of the auditory
sense. Between the pro- and meso-thorax of the grasshopper and
cricket is a double pair of stigmata; one of each pair is conspicuous
by its large oval unlabiate aperture, which leads to an infundibular
trachea ; close to this large aperture is the second stigma of the
ordinary size and shape ; the tracheae from this stigma ramify in the

* CCXLIV. p. 439. t CCXLV. p. 56—72, tab. I.

INSECTA. 369

prothorax and head ; but the infundibuliform trachea sends off no
branches in its course through the prothorax. Pursuing this trachea
from the infundibular beginning backwards to the coxa of the an-
terior feet, we see that here it sends off various larger and smaller
branches, but enters the limb without material diminution of calibre.
In traversing the slender knee, the trachea is obliged to contract ;
but it soon again expands, and forms at the part of the tibia of the
first pair of legs, where the two folds and apertures are seen, a long
vesicular dilatation of a peculiar form. This vesicle is in con-
nection, externally, with a tympanic membrane closing an orifice in
the leg, and internally with a peculiar part of the nervous system.
Two nerves, both derived from the first thoracic ganglion, and
both unusually large, accompany the trachea down the leg : the lesser
nerve attaches itself to the vesicular dilatation, and there expands
into a flattened ganglion, on which is situated a row of transparent
vesicles containing a collection of cuneiform, statt-like bodies, with
very finely pointed extremities, which are surrounded by ganglion-
cells. An undulated prolongation of the ganglion is thence con-
tinued, and is lodged in a depression on one side of the vesicle. The
aperture in the leg is compared to an external ear ; the membrane
closing it and the chamber behind, to the tympanic cavity and drum ;
the nerve and ganglion to the acoustic nerve ; and the thoracic aper-
ture to the Eustachian tube. It is strange, however, that the organ
under so well marked a form should not exist in the tree-hoppers
(Cicadce), which attract their females by peculiar notes. In these
Homoptera the soft capsular membrane of the joint of the antenna,
which in son^e movements may be rendered tense, has been alluded
to by Burmeister as a structural indication of the organ of hearing
in the peculiar appendages in which he supposes, with many other
entomologists, that the sense resides. Two, at least, and often more
numerous, nervous filaments from a slight ganglionic enlargement
penetrate the antennae in insects ; and these may subserve the distinct
offices of the appreciation of the vibrations of sound, of the characters
of surface, and of the regulation of the movements of the antennae.

Of all the organs of the special senses not only is that of sight
manifest without ambiguity, but it is more complicated and relatively
larger in insects than in any other class of animals.

What would be thought of a quadruped, whose head, with the ex-
ception of the mouth and the place of juncture with the neck, was
covered by two enormous convex masses of eyes, numbering upwards
of 12,000 in each mass ? Yet such is the condition of the organs of
vision in the dragon-fly, which, besides the two great compound eyes,

B B

370 J.ECTURE XVI.

supports, in the narrow interspace on tlie vertex of the head, three
simple eyes, called ocelli and stemmata.

In all insects the eyes are sessile, or, if supported, as in a few rare
instances {Diopsis, e. g.), on prolongations of the head, such peduncles
are not moveable like those which support the compound eyes of the
higher Crustacea. The eyes are either "simple" or "compound:"
the first are found in the larva, the second in the imago of hexapod
insects ; in some of the latter both kinds occur. The blind exceptions
in the class are few ; such are certain species of Ptiliurn that live
under the bark of trees, the Claviger, which dwells in ants' nests, and
the Anophthalmus, peculiar to dark caverns. The larvae of Hyme-
noptera and Diptera, and most of the apodal larvae of Coleoptera,
are blind.

A simple eye (ocellus, stemma) is composed of a cornea, behind
which is a spherical or cylindrical lens, lodged in a kind of calyx
formed by an expansion of the optic nerve, and which is surrounded
by a layer of diversely coloured pigment.

There is only one ocellus on each side of the head in the lice
(PediculidcB, Nirmidce), cochineal insect (Coccidce), and the larvee of
the Phryganidce. The ocelli are in groups of four to eight in the
skiptails {Poduridce)^ the hexapod larvae of the Strepsiptera and
Coleoptera, the larvae of Lepidoptera, Hemerohidce, MyrmelionidcB,
and RaphididcB.

The Centipede has many simple eyes, arranged in a cluster on
each side of the head, and requiring only a little closer approximation
to form a compound eye. The required approximation takes place in
the lulus, but the optic nerve, instead of swelling into a ganglionic
mass, separates into a pencil of nerves at the base of the cluster, one
for each ocellus. The transition to the large compound eye of the
hexapod is made by the lulus and Scutigera ; but the interval is very
wide between the Myriapods and Anellids in regard to both the
number and structure of the organs of vision.

The lateral compound eyes of winged insects are generally cir-
cular, sometimes oval, or reniform ; they occupy the sides of the head,
and sometimes encroach upon the upper part so as to meet there.
In some Capricorn beetles, as Tetraopes, the antennae project from
the middle of the ovate eyes and divide them into an upper and lower
half: the compound eyes of certain beetles of the genera Ateuchus
and Geotriipes are almost or quite divided into two on each side by
the encroachment of the canthus ; some Ephemercc and the Gyrimdce
have two pairs of compound eyes : in the latter they are situated one
on the upper, the other on the lower surface of the head, and must

INSECTA. 371

serve the aquatic whirligigs to discern at the same time objects be-
neath them in the water, and above them in the air.

The integument of the head, which passes uninterruptedly over
the compound eye, there becomes transparent^ and is subdivided into
a number of hexagonal corneules, varying in number from 50 in the
ant, to 4,000 in the house-fly, to above 17,000 in the butterfly, and
to more than 25,000 in the Mordella beetle. The size of these facets '
is not uniform even in the same eye, for sometimes those above or
those in the centre are the larger ; e. g. Libellula, Lagria, Tahanus,
In general each corneule is thicker than it is broad, and thicker at
its middle than at its circumference ; a layer of pigment here in-
sinuates itself into the interspaces between the corneules. In bees
and flies fine hairs project from these interspaces, which must defend
the eye or warn the insect against the approach of foreign bodies.
Each division of the compound eye has its lens, which combines the
characters of both crystalline and vitreous humours : it is always of
a more or less elongated conical form, having its base applied to the
corneule, and its apex to the optic nerve. The base is not imme-
diately in contact with the cornea, but is separated by a minute
aqueous chamber into which a process of the pigmental membrane
penetrates, leaving a small pupil opposite the middle of the base of
the lens. The pigment is continued along the crystalline vitreous
cone to its apex, forming a sheath around it, and enveloping also the
adhering filament of the optic nerve ; at once separating and con-
necting together the component ocelli of the compound eye. Fine
tracheal ramifications have been traced upon the pigment, which
displays very various, and often brilliant or metallic, hues in its
outer layer.

The larvae of the Coleoptera, Lepiclopfera, Neuroptera^ some Hy-
menoptera, and Diptera, have merely simple eyes. Two or three of
the larval ocelli are retained, with the superadded compound eyes, in
most of the winged orders save Coleoptera, in which only compound
eyes are present in the perfect state.

The high degree in which the power of discerning distant objects
is enjoyed by the flying insects corresponds with their great power of
traversing space. The few exceptional cases of blind insects are all
apterous, and often peculiar to the female sex, as in the glow-worm,
cochineal insect, and parasitic Stylops.

B 2

372 LECTURE XVIT.

LECTURE XVII.

INSECTA.

The extraordinary powers of locomotion possessed by insects, the
variety of elements which they can traverse, their aptitude to gain
access to every situation where organised matter may be obtained,
prepare us to expect that they should manifest all the modifications
of the digestive system which may be required for the assimilation
of the different kinds and conditions of the solids and fluids of plants
and animals.

One insect preys upon another ; pursues and attacks, like the
falcon, on the wing ; but, with better mastery over the air-element,
it can tear to pieces and devour its prey without alighting : another
insect, sedentary and inactive, imbibes the juices of a plant : a third
eats its way into the hard wood : a fourth burrows in the earth for
roots or worms.

Some traverse the surface of the earth with a succession of steps
too swift for definition ; some by leaps so extraordinary, as to have
excited the powers of the dynamical calculator from the earliest
periods. The waters, also, have their insect population ; some
swiftly cleaving the clear element, some gyrating on the surface,
whilst others creep along the bottom. Nor are the activities of the
aquatic insect confined to that lower sphere. Nepa and Dytiscus
possess organs of natation, of reptation, of burrowing, and of flight.
Like Milton's fiend, each is qualified for different elements, and

" Through strait, rough, dense, or rare,
With head, hands, wings, or feet, pursues its way,
And swims, or sinks, or wades, or creeps, or flies."

With such diversified powers of attaining food are associated, in
Insects, as varied structures for imbibing, seizings masticating, and
digesting nutritious substances. The patience of the anatomist is
taxed to the utmost to unfold these delicate complexities ; but his
admiration is chiefly excited by the discovery that they are clearly
referable to a common type.

The most marked modifications of the digestive organs relate
rather to the physical condition than the chemical constitution of the
food ; depend more upon its being solid or fluid, than upon its being
of a vegetable or animal nature. Some entomologists have separated
all the insects which suck the juices of plants and animals from those

INSECTA. 373

which operate upon the solids, and have made the Haustellata and
Mandihulata the primary divisions of the class.

The composite parts of the proboscis or siphon are however fun-
damentally the same as those that form the strongest or most
formidable apparatus for mastication ; but as they are most con-
spicuous and most uniformly developed for the latter office, I shall
commence the demonstration of those complex parts of the mouth, —
the trophi or cibarial instruments, — as they exist in a Mandibulate
insect, {fig. 148.)

Man has two jaws only, and no Vertebrate animal has more ; they
work up and down, or in the direction of the axis of the body.
Insects have also their upper and lower jaws — horny edentulous
plates, serving in many for little else than to close the mouth, and
hence called lips ; the upper one {^fig. 148, a) is the " labrum," the
lower one (c?) the "labium:" but they have like- 148
wise four more complex jaws, acting upon each
other in pairs, from side to side, or transversely
to the axis of the body. The upper pair of jaws
{h) are called the " mandibles," the lower pair (c)
the "maxillae."* The three lower instruments,
viz. the two maxillae and the labium, arc pro-
vided with the jointed instruments of sensation,
called " palpi ;" the maxillse, in some insects, sup-
porting each a pair of these appendages, which,
besides their sensitive and selective offices, serve Trophi of a Mandibulate
also to seize and hold steady the alimentary sub-
stances whilst these are divided by the mandibles and maxillae, and
represent, in fact, a third pair of lateral jaws. The lower lip has a
basal joint {mentiim), supporting a more flexible part (ligula, or
labium proper), near to the base of which the palpi are articulated.
The upper, or inner integument of the ligula, is usually developed
into a kind of tongue, which is a distinct part {lingua) in the lo-
custs and Libellulae. The labrum, or upper lip, is generally a simple
transverse flattened plate.

The mandibles are subject to most variety in relation to the habits
and kind of food of the insect. In texture they vary from the hardest
chitine to soft membrane. In the predatory tiger- beetles they ter-
minate in sharp hooked points, like canine teeth, and are hard enough
to pierce the firm integument of other insects. In the dragon-fly the

* In vertebrate anatomy the upper or anterior jaw is called maxilla, the lower
or hinder jaw mandibida. It had been well if the analogy had governed the
entomological nomenclature.

BBS

374

LECTURE XVII.

inner margin of the mandibles is armed witli three or four sharp
laniariform processes. In some insects the upper dentations of the
mandibles have a trenchant edge, like canine teeth ; while the lower
ones are broad and framed for bruising, like molar teeth, as in the
cockchaffer or the locust. The maxillse usually correspond with the
mandibles in their general characters; but the teeth, which may be
developed from their inner edge, are more uniform and delicate :
their terminal piercing hook in the tiger-beetles is moveable. The
maxilljB are often clothed with short hairs.

The mandibles of the bee-tribe are simple, but strong and tren-
chant ; they are most important instruments in the economy of the
different species, and are modified accordingly. They model the
waxen cells in the honey-bee, and form the nest in the wild-bees. In
Anthophora retusa, the species whose trophi are figured in 149, the

149 / 1

Mouth and head of a wild bee.

mandibles (/) are notched at the apex. The maxillge {g) and
labium are lengthened out to form the proboscis, but especially the
labial palpi (It) and the lingual appendage or ligula (*), which has
also two feelers, called " paraglossae " (**), developed from its base,
and has its upper surface and sides beset with hairs. In the under
view of the honey-sucking and pollen-sweeping apparatus of the bee,
added io fig. 149, m is the submentum, 1 the cardo of the maxilla, 2
the stipes, g the lacinia or blade of the maxilla, h the maxillary palp.

INSECT A,

375

/ the mentum, i the labium, k the labial palp, * the lingua or ligula^
** the paraglosscB. This definition and nomenclature of the bee's
trophi are indispensable for conveying the results of such comparisons
as those which enabled the venerable Kirby to enrich Entomology
with so valuable an accession of knowledge as is contained in his
" Monographia Apum Angliag," a work which the young Entomolo-
gist may take as a model.

In the Hemiptera both the mandibulee and maxillas are alike
attenuated, and prolonged into stiff needle- or lancet-shaped organs,
which are protected by a sheath formed by the equally elongated
labium, the upper groove of which at the same time serves to conduct
the liquid food into the mouth : the maxillary and labial palpi have
disappeared ; the latter may have coalesced with, and transferred
their properties to, the labial sheath. With such an instrument
the Cicada perforates the bark of the trees on which it lives, and
exhausts their sap ; and with a similar modification of the trophi, the
bug and flea pierce the skin and suck the juices of animals.

In the blood-thirsty Diptera, as the gnat and forest fly, the labrum,
as well as the two lateral pairs of jaws, are prolonged into lancet-
shaped organs, and are sheathed in a thickened lower lip, which is
terminated by two fleshy suckers : the maxillary palpi are attached
to the base of the maxillae.

The singular spiral "antlia" of the butterfly and other Lepido-
ptera is formed by the elongated slender maxillae, still characterised
by the minute palpi at their base. The inner margins of the max-
illae are concave, and the edges of the channels are in close contact,
or are confluent, so as to form a canal along which the juices of
flowers can be pumped up into the mouth. Each maxilla is likewise
hollow, and it is uncoiled or coiled by the varying tension of this
canal. The labial palpi are of large size, and defend the antlia when
it is retracted and coiled up. The labrum is a small triangular
piece, which bends down towards the mouth, and the rudimental,
conical, slightly bent mandibles are hidden by the labial palpi.

The large curved piercing jaws of the Centipede are hollow, and
traversed by the duct of a poison-gland. The anterior pair of legs
are modified to come in aid of the jaws in some predatory insects,
notably in the Mantis, Nepa, and Ranatra, where they serve to
seize and hold the food to the mouth.

The alimentary canal is most simple in the larvae of insects, in
which, as in worms, it usually extends, without convolutions, from
one end of the body to the other ; in a few larvae, as that of the bee,
it has only the anterior opening or mouth, and the opposite or anal
orifice is not developed until the pupa-state. In all mature insects

B B 4

376 LECTURE xvir.

the alimentary tract presents the two distinct apertures : it is simplest
in the carnivorous larviform Myriapods ; presents more numerous
and distinct constrictions and divisions in the Hexapods, and increases
in complexity and length, as the food requires most preparation in
order t3 its conversion into the animal nutrient fluid or chyle.

The oesophagus of the Centipede is long, and dilated posteriorly,
where it communicates with the stomach ; this is a small muscular
cavity, bent upon itself, and lined by a longitudinally plicated horny
membrane. The intestine is long, straight, and wide, slightly saccu-
lated transversely ; it contracts, and is longitudinally folded near its
termination. In the lulus a short and wide oesophagus expands into
a shorter and wider muscular stomach. This is succeeded by a long
and wide chylific stomach, with longitudinal folds, separated by a
circular linear constriction, in the posterior third of the body, from
the intestine : this, again, is divided by a second constriction into two
equal partS; the first longitudinally folded like the stomach, the last
puckered into short transverse sacculi, until within a little distance
of the anus, which is protected by a pair of horny valves.

In the Polydesmus the oesophagus gradually expands into the long
chylific stomach, which is separated by a short contracted pyloric
tube from the intestine. This suddenly swells out to equal width
with the stomach, is puckered up in its posterior half by short trans-
verse plicae, where it first gradually, and then suddenly, contracts to
terminate at the anus.

The accessory glands of the digestive tract are slender tubes in the
Myriapod as in the Hexapod tracheary Insects. In the Polydesmus
and lulus there are two such salivary glands at the sides of the oeso-
phagus, converging anteriorly to open into the pharynx. The more
compact and similarly situated poison glands, which terminate in the
large perforated hooked mandibles, in the Centipede, are superadded
to the simpler salivary glands of the Chilognatha.

Slender biliary tubes creep upon the intestinal tunics in the Cen-
tipede, and pour their secretion into the canal close to the gizzard.
Excretory, probably urinary, tubes open into the terminal division
of the intestine ; and these are present in the Iulid?e.

The alimentary tract in Hexapod Insects is divided into pharynx,
oesophagus, ingluvies or crop, gizzard, chylific stomach, small intes-
tine, caecum, and rectum. Ail these parts rarely co-exist in the same
insect. The oesophagus is directly continued from the sucking ap-
paratus in Haustellate Insects without a pharyngeal dilatation.

In the carnivorous Dragon-fly* the alimentary tract is short and

* Prep. No. 589.

IXSECTA.

377

straight : there is neither crop nor gizzard, the chylific stomach is
long, cylindrical, and is divided from the oesophagus by a slight con-
striction ; the short intestine which succeeds is dilated at its com-
mencement, and plicated longitudinally as far as the contracted
rectum. In other insects a duodenal and iliac tract of intestine may
be distinctly recognised. In the tiger-beetle {Cicendela, Jig. 150)
and the carnivorous CarabidcB,
there is a small gizzard (h),
preceded by the usual ingluvial
dilatation of the cesophagus (a)
and followed by a long chylific
stomach, the external surface of
which is beset with secerning
follicles (c). The small intes-
tine (e) makes a slight bend
before terminating in the di-
lated colon (/).

The alimentary canal of the
browsing cockchafer is consi-
derably longer, and is disposed
in three or four coils. But in
the Orthopterous vegetable-
feeding insects^, the canal is
characterised by its superior
width rather than by its length ;
and in them the complications
requisite for animalizing the
food are chiefly manifested by
the gastric division. The ceso-
phagus dilates into a wide glandular crop in the cockroaches* and
locusts |, and has a similar receptacle appended to it in the mole-
cricket.:|: The gizzard has a strong muscular coat and a callous
epithelium, the inner surface of which is beset with projecting teeth
or hooks, as in the cockroach, or with scale-like plates, as in the
cricket, generally disposed in longitudinal rows. The tunics of the
chylific stomach are produced at its commencement into csecal ap-
pendages, which augment and complicate its cavity. There are two
such caica in the common and mole-crickets, four in Locusta ser-
rata, six in the migratory locust, and eight in the cockroach. In the
coleopterous Buprestidce the stomach is prolonged into two ctecal ap-

Cicendela campestris.

* Preps. Nos. 607, 608, 609.

t Nos. 443. 610.

X No. 611.

378 LECTURE XVII.

pendages, themselves beset bj smaller creca. In the water-beetles a
longish cjBCum extends forward from the rectum.

The gizzard always coexists with the crop, but not always the
crop with the gizzard, in insects. All the suctorial species have a
crop, either appended to the oesophagus, or forming a preliminary
dilatation to the chylific stomach. It is of small size in the bug
( Cimex lectiilarius), and almost obsolete in other Hemiptera. In the
bee {Jig. 151)*, the oesophagus (a), having traversed the thorax as
a slender tube, dilates in the abdomen into the
large honey-bag {b). The valvular funnel-
shaped orifice of the chylific stomach (c) pro-
jects into the side of the ingluvial reservoir,
and must be withdrawn by a special action, in
order to receive any portion of the nectar for
the nourishment of the bee itself: it then re-
turns by an antiperistaltic motion, and forms a
kind of intussusception in the crop, converting
it into the convenient, closed receptacle for the ^(^

collected sweets until the bee reaches its hive; Alimentary canal. Bee.

when the honey, having undergone a slight
change, which renders it less susceptible of the acetous fermentation,
is regurgitated into the waxen cell, and the crop collapses into lon-
gitudinal folds. The chylific stomach {d) is long, gradually widened
to its termination, and transversely plicated. The ileum (e) is short
and slender: the colon or rectum (/), wide and capable of great
distension. The bees on which Hunter experimented f endured a
long confinement, but could not be compelled to foul their hive ; as
soon as liberated, they rose in the air and disburthened their over-
laden cloaca.

In the Lepidoptera {fig. 160.), the ingluvies projects, like a bag,
from the side of the oesophagus {j) ; and in the Zygcence it is divided,
as in the pigeon, into two equal parts. The chylific stomach is very
small, but is sacculated, and, according to Meckel, is shaggy in the
death's-head moth. The small intestine (Z) is longer and more con-
voluted than in the bee ; the large gut (m) is short and wide.

In the Diptera the crop J, though situated upon the stomach in
the abdomen, is appended by a long and slender neck to the be-
ginning of the narrow oesophagus. The lower end of the oesophagus
expands into the chylific stomach, the cardia being sometimes marked
by a callous ring, which is the remnant of a small bladder existing there
in the larva. The small intestine is convoluted ; the rectum short

* Nos. 476, 477. f CCXLVI. p. 176. % Prep. No. 596,

INSECTA. 379

and dilated, and provided with t^Yo lateral conical glandular bodies.*
Hunter made experiments to determine the function of the appen-
diculated crop. " I kept a fly," he says, " for twelve hours without
food, and then gave it milk and killed it, and found no milk in the
crop, but it had got through almost the whole tract of intestines :
here the animal had immediate occasion for food, therefore the milk
did not go into the crop. This experiment at the same time shows
that every part of the intestine digests." Another time Hunter killed
his flies after they had drunk their fill, and found the crop full, as
well as the stomach and intestines : he suspects, therefore, that the
crop serves as a reservoir, and " that when there is more food than
what is immediately necessary, then it is thrown into the crop to be
used in future."!

The result of Hunter's first experiment, and the absence of the
crop in the flea and some other suctorial insects, negative the idea of
Burmeister that the crop in Hijmenoptera, Lepidoptera, and Diptera
promotes the suction of food by a voluntary power of self-expansion,
if even the structure of the part justified the idea; but, on the con-
trary, they prove it to be a receptacle of nutriment.

In the Cicadidse the chylific stomach is of great length, intestini-
form, looped, and its termination is connected, penetrating in Cicada
beneath the muscular tunic of the first stomach, but it does not
communicate therewith : the chymified fluids pass at once from its
termination into the intestine.

The entire alimentary canal consists of three tunics, — an external,
fine, membranous, or peritoneal layer ; a compact muscular coat com-
posed of a layer of longitudinal and a layer of circular fibres^ most
developed at the two extremes of the canal ; and an internal mucous
coat, the chitinous epithelium of which is thickest at the pharynx
and the rectum. Between the muscular and epithelial coats, in the
intestinal division, there is a white spongy layer of tissue, composed
of aggregated cells, compared by Ramdohr to transuded chyle, and
which is sometimes the seat of gastric glands.

The several divisions and convolutions of the alimentary canal are
supported and attached to the adjoining parts by the air-vessels:
there is no mesentery.

At least three kinds of glands add their secretions to those of the
coeca and follicles of the alimentary canal. The first kind open in or
near the commencement of the canal, and are regarded as salivary
glands. They are classified by Professor Burmeister as follows: —

* Prep. No. 2123.

t Physiol. Catalogue of Hunterian Collection, vol. i. p. 189.

380 LECTURE XVII.

A. Salivary vessels which open into the mouth, generally beneath
the tongue, sometimes at the base of the mandibles. They take the
following forms : —

1. As simple, long, undivided, twisted tubes ; thus in the majority
of insects, viz. all butterflies, many beetles, and flies.

2. As a narrow vessel which empties itself into one or two
bladders, whence the salivary duct originates (^Nepa, Ci?nex, Sarco-
phagd).

3. As a ramose vessel with blind branches {Blaps).

4. As two long cylindrical pipes, which unite into one excretory
duct {Reduvius).

5. As four small, round bladders, each pair of which has a common
duct {Pulex, Li/gccus, Cimex).

6. As a multitude of such vesicles (JVepa).

7. As capitate tubes, in the free ends of which many very fine
vessels empty themselves ( Tahanus).

8. As tubes which at intervals are surrounded by spiral coeca
( Cicada).

9. As granulated glands, which on each side unite into a salivary
duct, both of which join into a single excretory duct. Miiller has
observed this high form of conglomerate salivary glands in Phasma ;
Treviranus in Apis ; and Burmeister in Locusta, Gryllus, and
Termes.

Some Entomologists ascribe a hepatic function to the closely ag-
gregated cells forming the internal tunic of the chylific stomach, and,
with more reason perhaps, to similar cells in the ceecal appendages
of the stomach, when these are present. A pancreatic function is
assigned to certain glandular appendages to the ilium, as e. g. to the
two or four rows of follicles in that of some hugsi^Pentatomidce)^
and to the ramified appendages below the gastric (hepatic ?) cseca in
the mole-cricket (Gryllotalpa). There are, however, secerning
organs, in the condition of long, slender, cylindrical tubes, such as
Cuvier, who seems not to have been aware of the conglomerate
structure of certain salivary and seminal glands, describes as the
character of all the secrethig organs in insects, which tubes have a
degree of constancy more befitting the important excretory and
accessory digestive functions of a liver, than the exceptional cha-
racter of the parts above cited.

These tubes are called " ]\Ialpighian," after their discoverer.* In
a few instances, as Coccus, Chermes, and Aphis, they are wanting : in
almost all insects they are four in number, never fewer ; sometimes
they are six or eight in number : in a few instances, as the mole-

* CCCXXII.

INSECTA. 381

cricket and cockroach, they are very numerous. Burmeister has
generalised the observations of different anatomists on the Mal-
pighian tubes, as follows : —

1. Four.

a. Free at the end ; most Diptera, and the families Termi-
Una, Psocina, and Mallophaga.

b. Anastomosing ; many Coleoptera, Hemiptera, and Diptera.

2. Six tubes.

a. Anastomosing ; many Coleoptera ; for example, Ceram-
hycina and Chrysomelina.

b. Free at the end ; Lepidoptera.

3. Eight free tubes ; Neuroptera.

4. Many tubes ; Hymenoptera, Orthoptera, and the Dicfyoptera
subulicornia.

Those Malpighian tubes are longest which are fewest in number :
they lie in folds by the side of the stomach and intestine, an it ter-
minate in a circle at the commencement of the small intestine. In
Lyyceus apterus they terminate in a dilatation on one side of the
gut.

Uric acid has been detected* in these tubes : they have no proper
epithelial lining, but are filled with cells, disposed in rows : these
cells contain mucus and numerous fine granules, which impart
a yellowish or greenish colour to the tubes. The granular
contents pass by rupture of the discharged cells into the intestine,
and may be found accumulated in the colon or ceecum : they are
ultimately evacuated with the faeces. If no biliary principle be
eliminated together with the uric acid from the Malpighian tubes,
they are, nevertheless, by the character of their connections, relative
position, and place of development from the alimentary canal, the
horaologues of the hepatic organs. The glands, which by the same
morphological characters are more strictly urinary, are usually in the
form of long and delicate tubes, but sometimes present the structure
of groups of round vesicles, as in the Carabus, in which the common
duct terminates in a small dilatation : the urinary bladder is likewise
present in the water-beetles. The excretion is poured into the ter-
mination of the intestine, or evacuated contiguous to the anus.

No absorbent vessels have been detected in insects : the chyle,
which is a clear or greenish fluid, with round or oval corpuscles, is
supposed to transude through the tunics of the intestine into the
free cavity of the abdomen : it passes, in reality, into the wide and
irregular sinuses which seem to constitute the cavity of the abdomen,
but which communicate with similarly ilhdefined venous receptacles

* CCXLVII. A. p. 629., B. p. 213. CCXLII. p. 251.

382

LECTURE XVII.

152

extending into other parts of the body and its appendages, resembling
the general interspaces of the cellular tissue, and constituting the
venous system, through which the blood moves in a definite and
regular course to the heart. This organ i^fig. 160, s) is an elongated
muscular and valvular tube, situated along the middle of the back,
and usually called the dorsal vessel : it is largest in the abdomen, and
so diminishes anteriorly, that its continuation in the thorax may, in
most insects, be regarded as the aorta.
It is retained in its position by flat-
tened triangular bands of muscular
fibres. This character, its distinct
transverse linear muscular fasciculi,
its slight constriction at regular in-
tervals, and the peculiar valvular
loops at these constrictions, charac-
terize the long and slender vasiform
dorsal heart in the lulus and Scolo-
pendra, and indicate a corresponding
advance with the rest of the articulate
structure beyond the condition of the
pulsating dorsal sanguiferous tube in
the Anellids.

In the perfect Hexapod Insect, the
heart {Jig. 152) has the appearance of
a series of slightly conical segments
(rt), partially sheathed one upon the
other: lateral apertures (c, 6) exist
at the sides of the intus-susceptions,
where, in fact, valvular folds (c, d)
of the inner tunic do project into the
interior of the heart, and, with the
semilunar valves (c), partially divide
its cavity into so many separate cham-
bers. The whole of this part of the
heart is included in a saccular venous
sinus (a, c), from which the blood
passes into the interior of the heart,
and, by the disposition of the valves, y?^M>

it is at once prevented from returning -' r^>

into the sinus, or passing in any other Dorsal heart ot stag-ueetie.

direction in the heart than towards the head, or into the next chamber
in advance of that by which the fluid was admitted. The number of
venous orifices varies in different insects:— in most species there are

INSECTA. 383

eight pairs of apertures ; in the stag-beetle {fig. 152) there are six
pairs ; in the humble-bee five pairs ; in the phasma there is, according
to Miiller, only a single pair at the posterior chamber of the heart,
by which, in fact, in all Insects, the chief currents of the blood
appear to enter the organ. As far as the head the blood is propelled
from the heart along a tubular aorta of the usual form ; but the
branches from this (b) would appear soon to lose themselves in the
generally diffused sinuses. In the Myriapoda, however, the blood is
continued in a vessel along the dorsal aspect of the ventral nervous
chord ; but the traces of the true tubular vascular system are scanty
and obscure.

The blood of Insects is usually a colourless fluid, sometimes
greenish or straw-coloured, rarely, as in the larvie of Chironomus,
approaching to a red colour : it contains flattened oat-shaped par-
ticles, which are sometimes tuberculated.

Cuvier, misled by the anomalous diffused condition of the venous
system, supposed that there was no circulation of the blood in Insects ;
yet the dorsal vessel was too conspicuous a structure to be overlooked.
Such, however, was the authority of the great anatomist, that the
nature of the heart began to be doubted, and the strangest functions
to be attributed to it. Hunter, however, who was prepared to ap-
preciate the true state of the circulating system in insects, by his
discovery of the approximatively diffused and irregular structure of
the veins in the Crustacea, has described in his Work on the Blood *
all the leading characters of the circulation in Insects as it is recog-
nised by Comparative Physiologists of the present day. He says,
that, "As the lungs of the flying Insect are placed through the whole
body, the heart is more diffused, extending through the whole length
of the animal;" that "where the veins near the heart are large, there
is no auricle, as in the lobster and generally in insects ; " that " in
the winged Insects, which have but one heart, as, also, but one cir-
culation, there is this heart answering both purposes" (viz. the cor-
poreal and pulmonary circulations); and again, "with respect to its
use, it is, in the most simple kind of heart, to propel the blood through
the body, immediately from the veins^ which blood is to receive its
purification in this passage, when the lungs are disposed throughout
the body, as in the flying Insect." In the note at p. 221. he alludes
to the animals in which the veins are entirely cellular ; and expresses
his idea more definitely in the following passage from his manuscript
Observations on Insects : — " Of the veins. The veins of the Insect
would appear to be simply the cellular membrane ; but they are

* CCXLVIII. p. 220. et seq.

384 LECTURE XVII.

regularly formed canals, although not so distinctly cylindrical canals
as in the quadruped, &c., nor branching with that regularity. They
would appear to be, or to fill up, the interstices of the flakes of fat,
air-cells, muscles, &c., and therefore might be called in some measure
the cellular membrane of the parts."*

The chief merit of the rediscovery of the circulation of the blood
in insects is due to Carusf; its phenomena have been witnessed in
the appendages of insects by other observers, as Ehrenberg, Wagner,
Burmeister, Bowerbank, and Tyrrell. Hunter counted thirty-four
pulsations in a minute in the heart of a silkworm. Herhold counted
from thirty to forty pulsations of the heart in a minute in a full-
grown caterpillar : Suckow observed thirty per minute in a full-
grown caterpillar of the pine moth, and only eighteen in its pupa
state. The action of the heart is accelerated in insects, as in other
animals, by muscular exertion and excitement ; and Newport has
counted as many as 142 pulsations in a minute, in a species of wild
bee so excited.

Although the anatomist searches in vain for that profusion of
arterial and venous vessels which pervade the body of most animals,
the insects are not without their systems of capillary tubes, which
ramify as richly over all the organs and through every tissue, and
which connect together the different parts of the body. These ves-
sels, however, carry air instead of blood: the relations between the
sanguiferous and respiratory systems are reversed, and the air is dis-
tributed by a vascular system over the reservoirs of blood, instead of
the blood being distributed by a capillary net-work over reservoirs of
air. The aeriferous tubes in insects are called " trachece," having
their parietes strengthened by an elastic cartilaginous filament, not
indeed disposed in a series of distinct rings, but in a continuous close
spiral coil. By this structure the most delicate and invisible ramifi-
cations of the air-tubes may be easily recognised under the micro-
scope. The spiral filament is situated between the external cellular
and an internal delicate epithelial lining.

The tracheae commence either from lateral apertures, called spi-
racles and stigmata (7?^. 153,/), or from pneumatic tubes (z), gene-
rally continued from the anal segment ; these latter are peculiar to
insects which live in water, as the Nepa and Ranatra ; and usually
co-exist with stigmata.

The air is conducted by the spiracles or the pneumatic tubes, or, as

* Vol. ii. p. 31. Mr. Bowerbank (CCXLIX. p. 239), accurately observed that
the blood was inclosed in distinct parietes, and did not flow in the common
abdominal cavity, as Cams and Wagner believed.

t CCL.

IXSECTA.

385

U^l^cJ^^^X^

in Nepa, by both, Into a large longitudinal tracheal trunk (g\ which
runs near each side from one end of the body to the other ; they are
connected together by transverse
tubes, which run across the pos- j ^^
terior margin of each abdominal
segment, and distribute an in-
finitude of smaller tracheal ra-
mifications. Some of these
branches dilate into air recep-
tacles (//), the number and size
of which, like the air-cells in
birds, are in direct relation with
the powers of flight. In the
Nepa these reservoirs of air
are confined to the thorax : in
other insects, as the grasshop-
per, they are frequently deve-
loped also upon the transverse
abdominal trachece: they are
very capacious in the abdomen
of the bee.

The spiracles are narrow
two-lipped orifices, situated at
various points on the external
surface of the body, and differ-
ing in number and size in diffe-
rent insects. In the Coleoptera
there is a spiracle at the inter-
space between every two segments :
spiracles ; they are reduced to two, e.
domen in the CEstrus larvae. In some insects the orifice is situated
upon an entire oval horny ring. In many insects, especially those that
burrow, the margins of the spiracles are defended by a fringe of hairs,
which prevent the entry of extraneous particles. In the larv^ of the
lamellicorn beetles, the orifice is closed by a sieve-like membrane,
admitting the air by the marginal pores. In the mole-cricket, the
thickened margin of the spiracle is strengthened by two horny
half rings, and can be closed by the action of a small sphincter
muscle.

Most of the aquatic larvae breathe by temporary gills {hranchice
tracheales) ; these consist of membranous cylinders or laminas contain-
ing tracheal tubes. In the Phryganeae they are filiform, united in groups
of from two to five, developed from each side of the upper part of each

c c

Respiratory system, Nepa.

the Diptera have the fewest
g., at the extremity of the ab-

386 LECTUKE XVIT.

abdominal segment, and projecting towards the back; in the Semhlidce
plumose branchiae are similarly situated. In SialidcB the branchiae are
four or five-jointed, and are said to aid in swimming. In the larval
Mayflies {EphemeridcB) each of the anterior abdominal rings has a pair
of branchiae, sometimes ramified, sometimes of two kinds, one fasci-
culate, the other lamelliform, and performing oscillatory movements.
Certain larval dragon-flies (Agrion, Calopteryx) have three long
lamelliform branchiae standing vertically on the hinder part of the
abdomen : others {^JEsthna, Libellula) have numerous epithelial folds,
including many fine branches of tracheae, projecting into the large
rectum, the outlet of which is provided with valves to regulate
the entry and escape of the water required for respiration. Rosel *
has beautifully figured the branchiae of the Gyrinus, or whirligig
water-beetle. In a large N. American neuropterous insect {Piero-
narcys regalis) the branchiae, developed from the lower or sternal
arcs, are persistent, and co-exist with the modified branchiae from
the upper arcs, which form the wings. They consist of eight pairs
of sacs, supporting numerous long setose filaments, which form a
thick tuft from the exterior of each sac ; and are situated over the
stigmata at the infero-lateral parts of the thorax and anterior seg-
ments of abdomen; each filament is traversed by a tracheal vessel.
The branchi-tracheal system is more simple in the larvae of Tipu-
Ud(B, in which the tracheae that transfer the air from the water are
subcutaneous. In all the modifications, the tunics of the branchial
tracheae efiect that transference by actions analogous to endosmose
and exosmose.f

The amount of respiration is directly as the degree of the activity
of the insect ; and its temperature is increased in an approximate
ratio. The extraordinary development of the breathing organs de-
monstrate their essential relations to the energies of the muscular
system; and, by a minor modification, they are made subservient to
the diminution of the weight of the insect. In the Apterous insects,
and especially the Myriapods, there is no trace of air vesicles, but
both in the Centipede and lulus the minute tracheae ramify throughout
the body.

The powerful and often disagreeable odour emitted by certain
insects in their larval or winged state, is secreted in most by subcuta-
neous follicles, and excreted at particular parts of the body. The
larvae of the CoccinelJidcE and TentliredinidcB exude such fluid
secretion from pores diffused over the surface of the skin. In the
water-beetle {Dytiscus) a nauseous fluid escapes from the cephalo-
thoracic joint ; in many Melo'idce and Chrysomelidce, it escapes from

CV. Th. ii. tf. 23. f XXIV. p. G13.

IXSECTA. 387

the knee-joints ; in the bug it is tl.e product of a single pyriform
gland, situated in the centre of the metathorax, and opening between
the hind-legs. Other insects have anal glands, in the usual form of
tubes, which, in the GyrinidcE, e. g., emit a very fetid iiuid. In the
mole-cricket the anal glands consist of small lobular bodies, opening
into a reservoir for their secretion. In the Carabidce and Staphy-
linidcB the anal glands are ramified, or are vesicular, and have long
excretory ducts opening into muscular reservoirs, which expel, or, in
the Brachinus, explode the excretion, which, in the latter Bombar-
dier-beetles, immediately becomes gaseous on its ejection.*

The wax of bees is formed in little scales between the hind-pair of
legs. The saccharine secretion of the Aphides^ much sought after by
certain ants, exudes from teat-like processes near the vent. The
pungent caustic acid (formic) of the true ants, is elaborated by a
glandular apparatus in the anal region. The termites have not this
excretion, and the great ant-eater refused to feed on the British
species of Formicidce presented to it during its captivity at the
London Zoological Gardens, probably on account of their peculiar
acid. The phosphorescent organs of the glow-worms {Lampyridce)
and fire-flies (^Elateridce) consist of a mass of spherical cells, filled
with a finely granular substance, and surrounded by numerous
tracheal ramifications. This substance, which by day-light fills, in
the glow-worms, a portion of the abdominal cavity, shines through
the thin integument of the ventral arcs of the last abdominal
segments. In the fire-flies, the luminous substance shines through
two transparent spots on the dorsal arc of the prothorax. The lio-ht
brightens and dims synchronously with the acts of inspiration and
expiration ; it appears to be due to a slow species of combustion kept
up by the oxygen of the surrounding tracheae.f

LECTURE XVIIL

GENERATION OF INSECTS.

I:^ the generative organs of insects, as in those of plants. Nature
seems to have been prodigal in her power of producing endless
varieties of forms out of one common type of organ ; these varieties
being subservient all the while to one common end or ofluice. The ana-
logy of the reproductive parts of the insect to the reproductive flower
is the more striking, from the brilliant colours which the essential

* CCLI. t XXIV. p. G32.

c c 2

388 LECTURE XVIII.

parts of generation assume in some species of insects. But all insects
are dioecious, or of distinct sex : and there are not only " males " and
"females;" but in certain families there are other kinds of indivi-
duals, which are essential to the successful propagation of the species.
In the social Bees and Ants, for example, there is a third form or con-
dition of the individual, commonly called "neuter," and sometimes
labourer or nurse : these, however, are essentially female, having the
female organs, but imperfectly developed and passive. The working
bee, at least, exercises the function of only one part of those organs,
an accessory part, which is metamorphosed into a special poison
organ, but which is the homologue of the ovipositor in fertile female
insects. This working bee, or " non-breeder/' as Hunter called her,
relieves the parturient queen of her ova, places them in the appro-
priate nest-cell, and feeds the larva when it is hatched : it thus acts
the part of midwife as well as nurse, and is an indispensable adjunct
to the nmltiplication of the species. There is, again, in insects^ a
fourth modification of the individual, in relation to the sexual func-
tion. I allude to that remarkable state of the Aphis, which, like the
working bee, is an arrested stage of the female, constituting the larvi-
parous individual, but which propagates by a kind of internal gem-
mation, without sexual concourse in her own person. She possesses,
however, the female organs ; but, contrariwise to the working bee,
the external and accessory parts of the apparatus are wanting,
whilst the more essential organs are extremely active. Thus, at the
outset of our survey of the generative system and function in
hexapod insects, we encounter four different kinds of individuals in
relation to that function — males, nubile females, sterile females, and
procreant virgins.

Certain modifications of the generative functions have served as a
basis for the classification of the hexapod insects, some of which, as
e. g. Aptera, are said to undergo no metamorphosis, and have been
called "ametabola." Others, as e.g., the Myriapoda, Hemiptera,
and Ortlioptertty are described in entomological treatises as undergoing
only a partial metamorphosis, and are called, " hemimetabola." The
metamorphosis being more patent and conspicuous in the rest of
the class, is admitted, said to be perfect or complete, and made the
characteristic of the "metabola." The divisions so founded and de-
fined are insufficient, however, for the generalizations of the compara-
tive anatomist, and, by that very defect, are evidently less natural
than the orders in the Linnaean system, from the characters of the
wings.

The external characters which distinguish the sexes of insects
are least conspicuous in the Myriapoda: the external outlets of

GENERATION OF INSECTS. 389

the generative organs of the male are, however, in the Chilognatha,
as in many Crustacea, situated on a segment posterior to that which
is perforated by the generative organs in the female.

In the male Gally-worm {lulus terrestris\ the testis consists of
minute ceeca appended, for the most part alternately, to the sides of a
long efferent tube : there are two of these on each side, which, com-
mencing in the posterior fourth of the body, advance forwards, and
unite on each side so as to form a pair of tubes ; the coecal glands
continue to be developed, but in smaller number, and from one side
principally of each of the common tubes. These tubes then ap-
proximate, communicate together by three or more transverse canals,
and, after a slight bend or convolution, extend straight forward to
the sternal arc of the seventh segment of the trunk, where they ter-
minate by distinct orifices, on short conical protuberances^ behind the
seventh pair of legs.

The structure of the spermatic cseca is so similar to that of the
longitudinal tubes, that the secerning function is doubtless exer-
cised by both parts ; tliey consist of a thick mucous coat, with an
external muscular tunic ; they are situated beneath, or ventrad of,
the alimentary canal, and between the two large salivary vessels.
In the Crustacea the testes are dorsad of the alimentary canal, and
their ducts external to the glandular appendages of that canal.

The transverse anastomosing canals, between the right and left
testes, remind one of the single transverse communication between
the two testes in the lobster and in the crawfish ; but this character
is so multiplied — Newport * having found more than twenty such
transverse canals in one species of lulus — that the testes offer no
unapt resemblance to a ladder. In a large species the same la-
borious entomotomist discovered that the semicorneous intromittent
organ was defended by an uncinated valve, serving as a holder or
clasper.

The contents of the testes are a clear fluid at the hinder beginning
of the organs, but it becomes thick and more opaque as the outlets
are approached. The change is due to the appearance of numerous
sperm cells, 1 •450th of a line in diameter, with a highly refracting
nucleus I'ToOth of a line in diameter, lying close to the cell-wall. In
the progress of development the nucleus enlarges and becomes conical,
the apex protruding from the surface of the cell, which finally dis-
solves and leaves the nucleus free. This is the spermatozoon : its
breadth always exceeds its height or length. In the lulus fabulosus
the cell- wall becomes enlarged at the part opposite to the nucleus,

* ecu. p. 101.
c c 3

390 LECTURE XVIII.

and produces there a siiinlar nuclear body : tlie whole thus appears
like two of the spermatozoa of the lulus terrestris, with their broad
bases turned towards and touching each other.

In the Chilopoda the generative organs terminate at the anal seg-
ment of the body, not, as in the Chilognatha, near the fore part of
the body.

In the Centipede { Scolopendrd) the male organs are more complex,
and resemble those of insects. The testes of the Scolopendra morsi-
tans are seven in number, and closely packed in parallel lines ; each
testis is composed of two parts, fusiform, and precisely similar to
each other in mutual contact, but easily separable. From each ex-
tremity of the fusiform testis arises a narrow duct, so that there are
fourteen pairs of ducts arising from the fourteen secreting organs.
Each of the testicular bodies is hollow internally. The ducts ul-
timately end in a common tube, w^hich soon becomes enlarged and
tortuous, terminating by a simple aperture near the anus. Just prior
to its termination, the enlarged canal receives five accessory glands,
four of which are intimately united, until unravelled, while the fifth
is a simple caecum of considerable length. The sexual outlet is
situate near the anus.

There is great diversity in the structure of the male organs in the
different genera of Myriapoda. In the Scutigera^ according to Leon
Dufour *, the testes are two fusiform organs, with a duct continued
from each extremity ; those from the upper end anastomose together,
and a long and slender canal is continued from the middle of the arch,
which, after a certain course, becomes disposed in a scries of progres-
sively increasing transverse folds, and finally divides into two terminal
slender pyriform sacs : these are the accessory vesicles. The sperm-
ducts continued from the lower ends of the fusiform testes bend up-
ward upon themselves, and dilate into reservoirs called " sperma-
thecae," similar in size and shape to the testes themselves, and each
of these terminates separately upon the anal segment. The fusiform
testes have many small pouches, or diverticula, produced from their
outer side.

In the genus Lithobius], the testes are fusiform, but free at their
upper pointed ends, and they are everywhere beset with numerous
subspherical or graniform secerning follicles. Three long blind
tubes — accessory glands — communicate with the proper sperm-
ducts ; the common opening being, as in other Chilopoda, at the ter-
minal segment. Treviranus speaks of a small fleshy corneous penis
in the Lithobius.

» CCLIII. p. 97. pi. V. fig, 5. t CCLIII. p 87. pi. v. figs. 2, 3.

GENERATION OF INSECTS. 391

With regard to the female organs of the Myriapoda. In the lulus
terrestris the ovarium is a simple elongated sac, with the exterior
surface nodulated by sacculi ; the larger ones, of uniform size, being
arranged in a double series. The ova are developed and completed
ill these sacculi, one in each ; the germinal vesicle here is surrounded
by the yolk and vitelline membrane ; upon this is laid the thin layer
of albumen and the corion before it passes into the common oviduct.
The ova in the earlier phase of development form small projections
at the interspaces of the larger and more regularly-sized ovisacs con-
taining the more mature ova. The common elongated sac extends
from the anal segment forward to near the fourth segment, where it
divides, and the two vulvae are situated on two scale-like bodies on
the under surface of that apodal segment, behind the second pair of
L'gs. A short reservoir for the male semen (spermathecci) commu-
nicates with each oviduct. The ovarian tube is situated beneath the
alimentary canal ; not above it, as in the Crustacea. If the male
apertures on the seventh segment indicate, by the analogy of the
Crustacea, the hinder boundaries of the thorax, w^e see that the more
advanced position of the female apertures keeps up that analogy.
Another interesting analogy presents itself in the double aperture of
the generative outlets and the double intromittent or clasping organs
in the male lulidcB. I allude to the serpent tribe, which these Articu-
l;rta resemble in their length, slenderness, and tortuous movements ;
for the serpents alone, amongst Vertebrata, present the double termi-
nation of the generative ducts and the double unciform claspers.

In the Lithobius forficatus the ovarium, a single elongated blind
sac, extends from the anal segment to near the middle of the body,
and is supported by the tracheal capillaries. It is beset by numerous
subpedunculate unilocular bursas, each containing a white globular
ovum. These give a granular aspect to the exterior of the ovarian
tube ; w^hich tube Leon Dufour suspects to be naturally divided by
a median longitudinal septum.* On each side of the termination of
the ovarian tube is a racemose colleterium, consisting each of two
rows of granular utricules : a common duct and reservoir communi-
cates with the oviduct.

The generative function offers so many distinctive peculiarities in
the present aberrant subclass, that I shall conclude my account of it
before entering upon the same subject in the typical hexapod insects.

Some important facts were early recorded relative to the meta-
morphoses of the lulidae by Degeerf and Savi |, and their generation
has been very ably and minutely worked out by Newport. §

* CCLIII. t CX'LIV. X CLV § CCLII.

c c 4

392 LECTURE XVIII.

The lulus terrestris hibernates from October to I\Iarch ; the female
is probably impregnated prior to hybernation, for her first act after
a,wakening from the long winter sleep is to prepare to disembarrass
herself of the load of impregnated ova : the act of oviposition is
generally over by the month of May. She previously excavates a
special nidamental cavity in the soil, and is careful to place the eggs
where no access of light, and only a certain degree of moisture, can
affect them. In this process she bores the soil about an inch in depth,
just wide enough to admit her own body, and then excavates a circu-
lar cavity by removing the soil, pellet by pellet, the earth being made
up into a little pill by mixture with her saliva ; she withdraws herself
backwards from her hole, bringing up the pellet, which is held between
her bent-down head and the first pair of legs : it is then passed back-
w\ards to the second pair, which transfers it to the next in succession,
and so onwards, until it is removed quite out of the way. When, by
the repetition of this manoeuvre, the egg-chamber is completed, ovi-
position takes place, and the entry to the chamber is carefully closed
by earth thoroughly moistened, so as to form a thick paste, which she
gently presses into the entrance, and fills up nearly to a level with
the surface of the soil ; thus protecting the eggs from enemies that
would devour them, or from the atmosphere and light which might
decompose them. In this operation we may perceive that the large
salivary glands have a function analogous to that of the silk glands'of
the Bombyx mori.

In the fresh-laid e^^ the chorion is transparent, but it becomes
opaque, soon dries and shrivels when exposed to the air. The first
period of development occupies about twenty-five days, when the
chorion is ruptured, the egg previously augmenting in size and
becoming reniform. The embryo may be recognised about the
twelfth day, but presents no trace of segments or limbs; it is bent
upon itself. On the thirteenth or fourteenth day there is an indica-
tion of segments on the ventral aspect. On the eighteenth day the
shell bursts along the dorsal surface, and on the twenty-fifth day the
embryo protrudes, by the elastic quality of its body overcoming the
compression to which its growth has subjected it ; but the embryo is
passive and motionless, and is still connected by a n flection of an
amniotic covering upon the inner surface of the merabrana vitelli,
which connection Newport calls the " umbilicus." There is now a
head and seven segments, and the antennce may be seen budding from
the sides of the head. The internal structure of the embryo is
wholly cellular, with a cavity resulting from the coalescence and
liquefaction of certain central cells. On the third day after exclusion
the embryo {Jig. 154.) is passive, motionless, and still attached to the

GENEKATION OF INSECTS.

393

154

I

shell (/) by the funis-like duplicature {d) of the amniotic covering
(c), and it is protected by the two halves of the
egg-shell, suggestive of an analogy to the ento-
mostracous Cypris. The head, antennss, and seg-
ments of the body are better marked ; transverse
depressions appear on the dorsal surface of the
segments, the beginning of their division into the
double ones of the mature insect : but the embryo
is still apodal, though rudiments, or buds of tho-
racic limbs, now begin to be discernible. Some of
the peripheral cells become pushed into these
buds of limbs, making them obtuse prior to elongation. On the
ninth day the funis is ruptured, and the alimentary canal com-
pleted ; but other internal parts consist of cells of different sizes.
On the tenth day the dorsal vessel betrays itself by its pulsations ;
it drives the colourless blood to the head, which now becomes
corneous ; the antennse become clubbed, and now a simple ocellus
may be distinctly seen on each side. On the seventeenth day the
embryo leaves the debris of its shell : it presents definite segments,
articulated antenna, and three pairs of jointed legs ; it is, in short, a
hexapod larva. But at the next stage of progress it quits the high
road of insect development to enter a by-path of its own : new seg-
ments are form.ed from the penultimate or germinal segment ; a rem-
nant of the funis is converted into a rudimental anal spine; the
amniotic covering and the rest of the funis are moulted.

The first spontaneous movements of the embryo are to burst and
slip off the amnion with the first integument ; after which exertion
the larva reposes, with slight occasional movements of the antennae.
We may now distinguish {^fig. 155.) eight primary segments (1 — 8)
besides the anal one (9). Six new segments 155

have also been formed at the germinal space
(7/), but these are short, and collectively are
only equal to one of the original segments. The
new segments are not formed by a division of
the old, but by gemmation from the penulti-
mate segment at the germinal space. Tlie
primary three pairs of legs {b a) are developed
from the second, third, and fifth primary seg-
ments. New pairs of limbs bud out from the
sixth and seventh segments. The female aper-
tures are perforated in the fourth segment ; the male outlet is estab-
lished at the seventh segment, at a period when this is near the
posterior end of the body of tlie larva. It is then marked by a patch

394

LECTURE XVllI.

156

of a darker tint than the rest of the body (jo), and retains this cha-
racter, which is of use in determining the now numerous and rapidly
produced segments behind it.

The antennse first begin to move, then the legs, and the first
instinct of the locomotive larva is to shun the light. In this pro-
gression the anal segment expands, and attaches itself to the firm
surface ; then the body is carried forwards, the motion being pro-
pagated from segment to segment. On the twenty-sixth day the
young lulus casts off the covering in which it had hitherto been
enfolded and enters the fourth period of development ; having now
seven pairs of legs and fifteen segments to its body {Jig. 156.). The
antennae are elongated and exhibit six
joints; the eye is a single ocellus, but
is surrounded by pigment preparatory
to subdivision ; the new legs {h, c) are
as long as the old ones, but not so strong ;
the transverse markings of the primary
segments are more distinct; the patch
on the seventh (p) is darker. The first
of the new segments (8) is almost equal
to the seventh primary one ; the penul-
timate (14) and anal (15) primary seg-
ments have not much enlarged. In the
progress of growth new segments are
successively added at the germinal space
(g), being always produced beneath the common integument, wdiich
is afterwards moulted. These segments are added in a certain
numerical ratio, six at a time, between the antepenultimate and the
penultimate segments. Movements of the larva are always observed
to be fettered by the approach of the ecdysis. All the limbs super-
added to the primary three pairs are bifid; and these double legs
are homologous with the prolegs of caterpillars. The further course
of growth is attended with a more distinct definition of the segments,
and by transverse indents of the primary segments. The limbs also
become more straightened. Tlie whole period of development oc-
cupies four or five weeks, and then development is superseded by the
mere act of growth.

With regard to the Centipedes, we still need a series of researches
to make us properly acquainted with their development. In the month
of May, the larva of Lithobius — a modified centipede, consisting of
seventeen segments, and having fifteen pairs of extremities — presents
but ten joints and seven pairs of legs with two simple ocelli on each

GENERATION OF INSECTS. 3.95

side of the head. Early in June, it has acquired twelve segments,
and eight pairs of legs, and the head presents three ocelli on each
side. Later, in the same month, the segments have increased to
fifteen, and the legs to fifteen pairs, and the number of ocelli is eight ;
finally, two more segments are added, and the cluster of ocelli
includes twenty on each side. The chief distinction between the
Lithobius and lulus appears to be, that the successive joints are not
developed, as in the lulidcB, at the posterior part of the body, from
one particular germinal space, but at the interspaces of the pre-
existing segments.

With regard to the affinities of the Myriapoda as they are il-
lustrated by the known phenomena of their development, we discover
in the peculiarly localised power of superadding the additional joints
in the lulidse, a marked analogy to the anellids ; yet the appendages
of the segments being distinctly jointed limbs, we have in these a
well-marked character of the superiority of the Chilognatha. Then,
in reference to the Crustacea, which the Myriapoda more resemble
in their jointed antennae and hmbs, we perceive also an interesting
additional resemblance in the Chilognatha, in the circumstance of the
organs of the generative apparatus not terminating in the homolo-
gous segments in the male and in the female ; whilst in both they
are situated nearer the anterior part of the body. But this crus-
taceous character disappears in the Chilopoda. And when we per-
ceive that the first form of the articulated animal with jointed limbs,
which the Myriapoda assume, is that of the hexapod insect, and
further, that in departing from this type, the pair of limbs succes-
sively added in the lulus are, like the temporary ones in caterpillars,
of a different character from the primary six, — we cannot but derive
from these facts a well-founded confidence in the importance of that
character of the respiratory system which associates the Myriapoda
v.'ith the Insecta rather than the Crustacea.

I proceed now to demonstrate the structure and modifications of
the organs or instruments subservient to the formation, retention,
nourishment, defence, and transmission of the sperm-cells and germ-
cells, and their products or developments, in the true or hexapod
Insects.

In entering upon a review of the structure of the male organs of
insects generally, we found their simplest type in the lowest or-
ganised members of the class, viz., the chilognathic myriapods.
The testes and their ducts, with short and simple intromittent
organs, alone existed ; there were no accessory glands, no me-
chanical adjuncts in relation to the coitus. The sexual apertures,

396 LECTURE XVIII.

on the fourth and seventh primary segments, though, in the male,
they be near the anal end of the body in the nine-jointed larva,
become advanced much nearer the head in the fully developed
lulus, by reason of the vast superaddition of joints, through the
successive sextuple gemmation of segments between the penulti-
mate and antepenultimate primary segments of the larva. In the
chilopoda, the ordinary insect-type of the generative apparatus vi^as
more nearly approached, by not only the more definite boundary
between testis and vas deferens, but by the termination of the
sperm-ducts at the anal segment, and, likewise, by the presence of
accessory glandular organs.

Testes with distinct sperm-ducts and superadded glands are
present in all hexapod insects ; and in all, with a few exceptions, the
sperm-ducts open at the base of an intromittent organ, developed
from the anal segment.

The testes are remarkable for the endless diversity of their forms,
and often for the bright or brilliant-coloured pigment which besets
the tunica vaginalis ; in both characters reminding us of the flowers
of plants. They appear to form a single organ in most Lepidoptera,
but are actually two confluent testes, and were originally distinct in
the larva of all that beautiful order ; that distinction being indicated
by a circular groove, and still more significantly by the two distinct
sperm-ducts.

In most insects the testes form a distinct pair of glands ; but their
ca3cal structure, and the gradational development of the secerning
follicles, at length produce a seeming multiplication of testes, and it
is difficult to avoid giving this definition to the six clusters of sperm-
atic casca, with their six ducts, on each side in the dung-beetle,
Scarabmis^ or to the twelve flattened circular glands, with as many
ducts, which represent the testis on each side in the rose-beetle, Cetonia.
In all these cases, however, the ducts from the divisions or distinct
lobes of the testis rapidly unite to form the beginning of a single vas
deferens on each side ; and the essentially dual character of the
testes is manifested by the pair of vasa deferentia, whether the cha-
racter be masked in the gland itself by confluence, as in the butter-
flies, or by multifid division, as in the beetles.

In the Aptera, Treviranus* has given a good description and
figure of the male organs of the Lepisma. The testes are repre-
sented, on each side, by four or five elliptical glands, the slender
ducts of which, after some irregular ramifications, communicate with
a common vas deferens, which, after a long fold, descends and dilates

* CCLVI. ii. p. 15. taf. iv. fijr. 2.

GENERATION OF INSECTS. 397

into a sperm-reservoir. The accessory prostatic glands are bent
upon themselves, like a common magnet ; one end of each opens into
the ductus ejaculatorius.

In the order Diptera the testes always present themselves as two
simple glands, either pyriform, oval, or elongated and twisted, the
outer capsule of which is of a brown or yellow colour ; in the
Asilus, when this outer coat is removed, the surface of the testis is
nodulated by the prominent ends of the component caeca ; two
slender sperm-ducts terminate in a small sperm receptacle, which
also receives two long filamentary prostatic glands ; a long ductus
communis is then continued to the base of a trifid penis.*

In many of the Lepidoptera the testis is clothed with bright pig-
ment, crimson in the common white butterfly {Pontia hrassiccB\
and green in the Sphinx. In most of the species the two glands
approximate, and become confluent in the progress of the meta-
morphosis \\ but in certain moths, as, e. g., the Tinea, the originally
distinct condition of the testes is retained in the imago state ; the
testes also remain distinct in the Yponomeuta. % In most Lepidoptera
the vasa deferentia, or sperm-ducts, after a short course, receive two
capillary prostates, and then a long and convoluted ductus ejacula-
torius. What is remarkable in some butterflies {Pontia, e. g.\ is not
only the great length of the prostatic gland, but also the extreme
length and winding convolutions of the common terminal duct.
The structure of the introraittent organ in the Lepidoptera is such
as to preclude the repetition of the act, and they consequently live in
a state of compulsory monogamy. The bifid hooks on the terminal
segment of the dorsal valve of the penis, whilst they serve to retain
the female, prevent the entire extraction of the virile organ.

With respect td the order Hymenoptera, Hunter has left some
good dissections of the male organs in the bee.§ The testes
are of a simple oblong form ; but, when we dissect away the cap-
sule or " tunica albuginea," we expose many long ca^cal tubes,
which, as they uncoil and float in the liquid, give a bushy cha-
racter to the gland. The sperm-duct rises from near the middle
of each testis, and soon swells into a large cellular reservoir common
to it, with the openings of two pyriform prostatic glands, whence a
common ductus ejaculatorius is continued to the base of the intro-
mittent organ. Newport has given a good description and figures of
the male organs in a wild bee {Athalia centifolia,Jig. 157.)} in which

* CCLVIII p. 250. CCLVIII. p. 9. taf. 1—3.

t CCXLI. tf. iv. xxxii. X CCLIX. Bd. 10. f. 10.

§ X. vol. iv. pp. 34—41, Preps. Nos. 2332—2344.

398

LECTURE XVIII.

Male organs,
Athalia centifolia.

we have the same characteristics; the testes (a, a) are two in num-
ber, but lobulated ; the sperm-ducts {b) slightly ^^ ^^^
expand, and are convoluted into a kind of epi-
didymis (c), answering to the reservoir in the
hive-bee ; from this part the duct (d) extends
to the neck of the prostatic sac (e), which re-
peats the bent form. The short ductus ejacula-
torius (/) terminates at the base of a virile or-
gan {h) covered by two pointed plates (m) beset
with soft hairs. Above these are two other
irregular double jointed plates (l), folded some-
what fan-wise, and furnished with horny hooks.
Between these are two muscular parts, which
immediately enclose the intromittent organ.

As an example of the male apparatus in the
order Hemiptera, we may take that of the
Aphis. The male insect is winged, and is com-
monly smaller than the winged female. Tlie internal organs of the
male consist of six oval testes, two larger and four smaller, so closely
impacted together as to resemble a single sexlocular organ. Ti:e
two gently convoluted sperm-ducts proceed close together from the
testes and open externaUy, in common with the ducts of two long,
colourless, C£ecal appendages, upon a soft, unarmed penis. These
appendages never contain spermatozoa ; they are a simple form oi
accessory prostate. The spermatozoa are found in various degrees
of development in the testes ; when fully developed, they form oval
bundles of very fine filaments, which separate in w^ater, at one end
expanding like a bunch of flowers. The intromittent organ is not
broken away in coitu, and the male aphis may, therefore, enjoy a
frequent repetition of the act.

The tree-bugs {PentatomidcB) have two simple pyriform testes,
often of a beautiful red colour : the ground-bugs ( GeocoriscB) have
seven long testicular tubes united in a fan-like manner. The testes
are numerous, and similarly fasciculate, in the CicadidcB, Kotonecta
has two pairs of long spiral tubular testes : Nepa and Ranatra have
five flexuous testes on each side. The prostatic glands are largely
developed in most Hemiptera.

Amongst the Neuroptera the testes of the May-flies (Ephemeridce)
and Dragon -flies {LihellulidcB) consist of a multitude of round fol-
licles, disposed botryoidally around a long dilated portion of each of
the sperm-ducts : the prostates are absent. In Panorpa the testes
are simple and ovoid : in the Ant-lion {Myrtneleo) they consist
of tufts of round follicles surrounded by a capsule ; the sperm-

GENERATION OF INSECTS. 399

ducts : re short, and receive the secretion of two long prostatic fol-
licles.

In the order Orthoptera, we find the locusts with testes composed
of numerous blind tubes, in most species enclosed in a common
capsule ; and in some, e. g. the cockroaches {Blatta\ the testicular
follicles are collected into a common mass in the middle of the
abdomen. The prostatic glands also consist of fasciculi of tubes, and
remind us of the condition of the prostate in some rodentia. Their
secretion is moulded into spermatophora.

The order Coleoptera offers the greatest diversity in the form
and structure of the male organs. In Dytiscus each testis is a
filiform tube, much longer than the abdomen, but convoluted into
a round ball. In Hydrophilus the gland is represented by a series
of short blind processes given off from one side of a common
sperm-duct. In Buprestis a fasciculus of longer caecal tubes radiate
from the end of the sperm-duct. Sometimes the extremities of
similar radiating tubes are dilated into sacculated flattened glands, as
in the rose-beetle {Cetonia), and numerous more composite forms have
been detected ; all, however, are referrible to modifications of the
primitive blind secerning sac. Their analogy to the sexual parts of
plants has already been alluded to, and entomologists have found it
requisite or advantageous to borrow the neat and descriptive terms,
with which Linnaeus has enriched botanical science, in order to in-
dicate the diversified forms of the male apparatus in the subjects of
their favourite class. The intromittent organ is a long horny tube ;
usually retracted within the abdomen, but not capable of retraction
after complete intromission, which usually terminates by rupture of
the organ. Hence the Coleoptera, like the Lepidoptera, are mono-
gamous. The terminal portion of the ejaculatory duct is continued
into the penis, and, in Carahus clathratiis, opens upon the centre
of a soft glandiform termination of the intromittent organ.

Much unity of plan may be traced throughout the varied modifi-
cations of this organ in insects. In general terms, the intromittent
organ may be defined as a modification of the last, or two last, seg-
ments of the abdomen. It consists of a large exterior sheath and a
delicate membranous tube ; the sheath commonly consists of two
lateral valves. It is usually retracted out of sight. Accessory pre-
hensile organs are developed in some insects, of which the most re-
markable are those which are attached to the base of the abdomen
in the male Libellula. In this remarkable insect, the sperm-ducts
terminate, as usual, on the anal segment; but the vesicula seminalis
is situated at the base of the abdomen. The semen is transferred
thither by a strong inflection of the caudal end of tlie abdomen, prior

400 LECTURE XYIII.

to the coitus, and passes from the sperm reservoir into the vulva of
the female, which is retained in contact with the base of the male's
abdomen by the claspers attached to that part.

The spermatozoa in all hexapod insects are filiform, and often re-
markable for their extreme length ; the anterior extremity is usually
thickened for a considerable extent.

The sperm-cells usually contain many " spermatoa," or vesicles of
development ; these spermatoa are at first transparent, then granular,
and lastly, the spermatozoon is developed, one in each. This makes
the spermatoon change its form : it is stretched by the uncoiling
of the spermatozoon, bursts and allows it to escape. Thus let
free in the common sperm-cell, the spermatozoa group themselves
into regular bundles. Sometimes these fasciculi resolve them-
selves, and the spermatozoa disperse as soon as the sperm-cell gives
way ; but usually a part of the sperm-cell remains as a partial
sheath to the bundle, and when the spermatozoa remain in this way
closely packed together, the whole bundle might be taken for a gigan-
tic spermatozoon. The bundle is very long, and appears convoluted
in a knot in Staphylinus, but is resolvable into its constituent sper-
matozoa, which become separated as they advance along the sperm-
duct. But here frequently, by the addition of the prostatic secre-
tion, they are again collected into fresh bundles, and packed up
into " spermatophora." These secondary aggregates present an
elegant arrangement in the Locustin(E, being delicately barbed like
a feather, and the spermatophora, with their fertilising contents,
are finally conveyed in coitu to the proper " vesicula seminalis," or
" spermatheca," which, as in most other hexapod insects, belongs to
the female.

As a general rule, the life of an insect soon ends after the great
act of impregnation has been fulfilled. The change of form prior to
the acquisition of the procreating power is usually extreme, and
rapidly undergone ; the ordinary every-day life of the insect, spent in
acquiring and consuming its daily food, forms a far larger proportion
of its existence, and is passed under a very different and a very in-
ferior form ; which, if in comparison to the last stage, we should
regard as the more typical form of the animal, we shall not probably
err. The cockchafFer passes three years as a subterranean worm,
but lives hardly as many weeks in its winged state. An ordinary
observer sees and knows the May-fly only in that last joyous stage of
its existence, and deems its life concentrated in one winged nuptial
holiday ; but this so-called Ephemera has previously passed three
hundred and more working days as an aquatic larva.

In no class of animals are the parts of generation so complex as in

GENERATION OF INSECTS. 401

insects. The internal female sexual organs consist of the ovaries, the
oviducts, the uterus, the sperraatheca, the bursa copulatrix, the mucous
glands or coHeteria, the scent-glands, and the vagina ; but these are
not all present in all insects. The external organs are the vulva,
the sting, the holders, and ovipositor ; some of which are likewise
peculiar to particular species.

The most constant and essential parts of generation of the fe-
male insect, viz., the ovaria, are subject to almost as many varieties
as the testes in the male ; their forms may be arranged into almost as
many genera and species, which are very often analogous to those of
the essential glands in the opposite sex. The ovaria in the Lepido-
ptera do not, hoAvever, coalesce into a single mass, like the testes in
the male ; they are either digitate or verticillate ; that is to say, they
consist either of a few egg-tubes suspended to the end of the oviduct,
becoming attenuated as they recede from it ; or they consist of nu-
merous very long egg-tubes, proceeding from a very short oviduct,
and terminating in filiform extremities, when they are usually disposed
in spiral coils bending at the two sides in opposite directions, as in the
Noctica BrassiccB (Jig. 154, a, a). In the forest-fly each ovarium
consists of two egg-tubes ; in the flesh-fly it consists of a single tube,
which is of great length, and twisted spirally. In the mantis a single
series of short egg -tubes are attached to one side of a common duct.
In the gnats, crickets, and locusts, the numerous egg-tubes, which are
somewhat compressed, lie upon one another like scales, or the tiles
upon a roof. In the Ephemera and Stratiomys the ovaries have the
primitive form of simple elongated bags, in which the eggs are
contained linked together by delicate filaments. In almost all cases
the caecal terminations of the ovaries are attached by a delicate thread
to the thorax : the tubes themselves being connected together by a
complex tracheal network.

Swammerdam* has given an accurate description, with excellent
figures of the female organs of the louse, the discovery of which
helped him to an excellent argument, requisite in his day, against the
spontaneous generation of that parasite from the filth of the abject
members of our species which it commonly infests. Five egg-tubes
converge and coalesce into a single short oviduct on each side ; the
two unite into a common tube, with which a pair of branched or
varicose accessory follicles communicate. The vulva is surrounded
by four mammillary eminences ; the spermatheca and bursa copulatrix
are wanting.

* CCXXXm. p. 37, pi. 2.

D D

402

LECTURE XVIII.

In most Diptera the ovaria consist of numerous short egg-tubes,
each divided into three or four compartments : the egg-tubes are va-
riously disposed, combined, and associated in the different species :
in Ephydra and Tachina they are long enough to contain about
twenty egg-chambers. The sperm-reservoir is present ; it is gene-
rally trifid, rarely bifid, as e. g. in the Stomoxis, still more rarely
simple, as in Pulex. The colleteria consist of two simple, rarely, as
in the TipulidcB, ramose tubes ; which, in the latter, furnish a con-
siderable quantity of albuminous matter, binding the eggs together
in filamentary forms, when they are committed to the waters.

There is no bursa copiilatrix ; but beneath the sperm reservoir,
in the common fly, the vagina swells out into a cordiform cavity,
which receives the impregnated ova, and in which they are developed
in the larviparous genera, e. g., 3Iusca, Anthomyia, Sarcophaga,
Sachina, and Dexia.

In the forest-fly (Ilippobosca), the ovaria are each a small simple
cjEcum, opening into a short common oviduct, which swells out
a little above the communication. A pair of small sperm-reser-
voirs next open into the oviduct, and afterwards the ducts of two
voluminous ramified colleteria ; the part answering to vagina, swells
out below this into a uterus, in which the ova are developed, and the
larva metamorphosed, in this pupiparous insect.

In most Lepidoptera, the ovaria consist of four pairs of egg-tubes,
disposed as I have already described. The sperm-reservoir {Jig> 158,
b) is pyriform, and generally provided
with a long spiral ductus seminalis,
in whose basis a sometimes simple,
sometimes bifurcate glandular csecum
opens. The colleteria {e) are situated
below, and consist of a pair of convo-
luted casca, swelling out into pyriform
receptacles at the vagina, where they
open by a common duct.

In some butterflies, two small
branched glandular organs are super-
added, called the " scent-glands" (c) ;
they secrete the peculiar odorous particles that attract the males ;
and of which property the entomologist sometimes avails himself in
catching the finest specimens of that sex.

The bursa copulatrix (/) finally presents a remarkable develop-
ment, being a capacious pyriform, sometimes hour-glass-shaped,
reservoir, which is furnished with a peculiar, intussusceptive canal

158

Noctua Brassicae.

GENERATION OF INSECTS. 403

opening outwardly beneath the vulva (g). This latter canal gives
off, by the way, a narrow convoluted lateral canal, wliicli opens into
the vagina near the orifice of the spermatheca, and thus effects the
communication between the copulative sac and that reservoir.

Experiment has proved the office of the spermatheca to be that
which its name implies. By the application of the fluid contained
in it to the eggs of an unimpregnated female, Hunter * made them
fruitful : he also found that the intromittent organ penetrated its
canal, — an observation which has since been confirmed by Audouin
and other observers.

In the Hymenoptera the ovaria present great diversity as to the
number of the egg-tubes, which varies from 3 or 4 in the humble-
bee, to 6 in the wasp, to 10 in Pimpla^ up to more than 100 in the
queen-bee. f To the short canal of the sperm-reservoir there are
always attached tubular and glandular appendages, which usually
bifurcate and open into the duct of the reservoir. There is no bursa
copulatrix in the Hymenoptera. The colleterium is metamorphosed
into the poison-bag and glands ; unless, indeed, we may view the
appendages to the sperm-reservoir as homologues, and not merely as
analogues, of the coUeteria in other insects.

With regard to the hemipterous modifications of the female organs,
I shall first refer, as in the case of the male organs, to the Aphis.
The two kinds of fertile females of this remarkable genus present
two modifications of the female organs.

The viviparous females have two ovaria ; from each of these, four
multilocular oviducts are continued. The vagina is devoid of all
appendages. The eight oviducts are similar in size, and the embryo
is contained in the lowest or hindmost chamber.

The oviparous females have, also, two ovaria with eight oviducts,
divided into two chambers each. The oviducts are seen in the most
different stages of development, so that usually not one of the eight
resembles another. In the fullest developed tube, the last chamber
is capacious, large, and oval ; the upper one small and conical. In
the undeveloped state, the whole tube forms only a simple pyriform
swelling of the oviduct, from which the upper conical compartment
is by degrees established. The lower chamber contains a finely
granular mass, which is gradually transformed into an oval egg ; the
upper chamber is full of cells, containing smaller nucleated cells. If
we regard these nucleated cells as germ-cells, we may conclude that

* X. vol. iv. p. 113—116. CCXLVII. p. 175.

t X, vol. iv. p. 117—119; Preps. 2609—2638.

D D 2

404 LECTURE XVIII.

more than eight eggs are laid. Near the outlet of the vagina are
two short caeca with thick walls, which contain a colourless, oil-like
mass. A little before these the spermatheca opens ; it is a colour-
less piriform appendix to the vagina, and is of so delicate a struc-
ture as to be readily overlooked when it is empty, but it is filled
with the spermatozoa after the coitus. The spermatheca is not so
crowded as in many other insects with the spermatozoa, and hence
their marvellous vibratory and undulatory movements may be wit-
nessed.

The ova are fertilised during their passage along the vagina by
the spermatozoa, and are smeared with the viscous secretion of the
" colleteria," called glandes sebifiques by Leon Dufour. From the
different organisation of the internal generative organs of the ovi-
parous and viviparous female Aphides, it follows that the first cannot
ever bring forth living young ; and that when once this oviparous
generation is produced, no external circumstances, e. g,, warmth,
can convert the individuals of such generation into viviparous
iiemales.

The males are frequently seen in coitu with the oviparous females,
and the embrace is so close, that when seized by his wings the female
is raised along with him. The males seem to be much fewer in num-
ber than the oviparous females ; yet Siebold * detected in all that he
examined spermatozoa in the spermatheca, and thence concludes that
the Aphides are polygamous ; to which the structure of the male
organs offers no physical impediment, as in Lepidoptera and Cole-
optera.

In the Cicada the oviducts divide into several branches, on the ex-
tremity of each of which is a tuft of ovarian tubes. The spermatheca
consists of two small caeca. In the GeocoriscB the spermatheca is a
single long and flexuous caecum : in the Pentatoma it is pyriform,
and sometimes dilates into a second vesicle.

In all Neuroptera the ovaries consist of multilocular tubes. In
the Ant-lion the spermatheca is a long, pedunculated sac : it is com-
plicated in the Phryganidce with a long tortuous tube ; and at the
base of the canal of communication there is a second flexuous tube,
and a short pedunculated *' bursa copulatrix."

The proportion of the genital organs to the rest of the body in the
female Termites (Prep. No. 3147) is analogous to that in the male
LerncBa.

In the Orthoptera, the ovarian tubes are commonly numerous and

* CCLX. p. 308.

GENERATION OF INSECTS. 405

multilocular. The sperm-reservoir communicates with the vagina
by a short neck in Locusta, and by a longer canal in Acheta. There
is no "bursa copulatrix;" and the colleteria are likewise wanting in
Forficula, Phasma, and the Acrididce, but they exist in the genus
Locusta, and are complex and ramified in the cockroach, where they
have to provide the materials for the complex egg-case.

The ovarium presents two types of structure in the Coleoptera, the
flagelliform and the sacciform ; in the former type, there may be
either three or six egg-tubes in each ovarium, according to the
species. The sacciform type is presented in the darkling beetles
{3Ieloe\ and the ovarium is remarkable for the imbricated ar-
rangement of its countless egg-capsules. The sperm-reservoir is
claviform in Scarabc^iis, or is bent upon itself, with a long neck, com-
municating with the vagina, or with the copulative pouch. Usually
a simple, sometimes a bifid, rarely a ramified, accessory mucous
gland opens into the base of the sperm-reservoir. There are no true
colleteria ; and I may remark that these organs are likewise ab-
sent in the neuropterous May-flies (^Ephemera) and Dragon-flies
(^Libelluld),

The vulva is a complex aperture in most insects, and is defended
by an upper and two lateral valves or plates ; it is usually accom-
panied by other modifications or appendages of the terminal segments
for grasping the penis and for oviposition.

Certain social Hymenoptera, which, as John Hunter quaintly
observes, "have property to defend,"* possess a peculiar poison-
apparatus, which is essentially a modication of those accessory parts
of the female organs, which are the only parts that acquire a func-
tional activity in the neuters of the bee and wasp. The poison is
secreted by two long and slender ducts — the homologues of the
" colleteria," which unite together and empty their secretion into an
oblong bag, which discharges itself by a narrow duct between the
valves of the sting. This is a long, slender, and sharp process, with
a serrated edge, which generally prevents its retraction when thrust
into the skin ; it is the homologue of the " ovipositor :" the protecting
valves are developments of the last abdominal segment.

The corresponding parts are variously modified in other insects to
insure a proper deposition of the eggs. In some Orthoptera, e. g.
the Locusta viridissima, the bivalve ovipositor is longer than the
body, and, by means of it, the ova are conveyed to the proper depth
in the soil, the act of oviposition being precisely analogous to that of

* CCXLVI.

D D 3

406 LECTURE xviri.

setting seeds in the earth. In the saw-flies ( Tenthredo), the main
part of the ovipositor is long, slender, and serrated^ like the sting in
the bees. With this instrument the female saw-fly saws into the
substance of leaves, and there insinuates her eggs. The Ichneu-
mons have a similar apparatus, but extremely elongated and slender,
by means of which they introduce their ova beneath the skin of
other insects.

Insects, like crustaceans, are occasionally subject to one-sided or
dimidiate hermaphroditism. Numerous instances of this kind are
given by Ochsenheimer.* In fourteen of the instances which he
cites, the right side was male and the left female ; in nine instances
it was the reverse. Occasionally hermaphrodites are found, where
the characters of one sex, instead of extending over one-half, are
limited to particular parts of the body, which agrees in the main with
the other sex. Thus an individual of the Gastrophaga Qiiercus has
been observed, in which the body, the antennae, and the left wings
were those of the female, the right wings those of the male. The
external sexual characters are very striking and various in the class
of insects, and readily lead to the detection of the hermaphroditical
condition of the internal organs.

So far as regards the organic machinery for propagation, that
mechanism has reached its highest grade of complexity in the
class of insects. In the male individuals we have found " testes,"
"epididymys," "vasa deferentia," "vesiculas seminales," "prostates,"
" penis," and " claspers :" with a hundred-fold variety in the forms
and proportions of the several parts. In the female individual we
have seen, besides the ovaria and oviducts, special enlargements of
the latter, to which the name of " uterus " might be applied,
seeing that in certain insects the embryo was developed therein ;
and the vagina was complicated with a spermatheca, bursa copulatrix,
coUeteria, vulva, ovipositor, and copula. As might be expected from
the very common form of the ovaria, as long and slender tubes, they
offer peculiar facilities for observing the development of the ovum.
Professor Wagner f has ably availed himself of this peculiarity in
tracing out the progressive steps in its formation, and has given
good descriptions of the process, illustrated by figures of the parts,
in the female dragon-fly {Agrion virgo). The germs of the ova first
appear in the capillary beginning of the ovarian tube as a single file
of minute elliptical granules or nuclei : as the tube expands the cell-
wall appears surrounding the first part, and the ovum is now in the

* CCLXI. t CCLXIL, p. 554, tf. 2.

GENERATION OF INSECTS. 407

condition of a minute pellucid vesicle, having a central nucleus.
Such nuclei and nucleated cells make their appearance in the capil-
lary beginnings of the ovarian tubes, where they are drawn out to
microscopic tenuity. From these extremities the ova successively
pass into the wider part of the tubes, and in this course increase in
size by the expansion of the nucleus, and by the multiplication of
vitelline granules around the primitive cell ; at first the ova are sepa-
rated from each other by an amorphous granular substance of equal
size, which is called a placentula, but lower down by mere constric-
tions of the ovarian tube. Here the ova acquire a distinct vitelline
membrane, and then, continuing to increase in bulk by the addition
of vitelline matter, they reach the converging end of the ovarian
tubes, and enter the shorter and wider oviduct. In this tube they
receive additions to their external surface from the secretions of the
colleterial organs, and admit into their interior the mysterious
principle of the male fluid, which would seem to be assimilated into
their substance, more especially into that of the central nucleated
germ-cell.

The eggs of the Lepidoptera, Diptera, Hymenoptera, and some
Coleoptera {CicendelidcB, Creabidce, e. g.) are formed on a different
type. The rudimental ova, or vitelline masses, are separated by
groups of large vitelline cells, whose contents are blended with the
subjacent ovum. The chorion is formed by a layer of vitelline cells,
and gradually extends over the vitelline mass, closing at the upper
portion of that mass. The eggs have reached maturity at the end of
the pupa state, in the Lepidoptera, so that they are ready for im-
pregnation and oviposition as soon as those insects have cast off the
pupal envelope. But in the Agrion and Libellula they are not
matured until a later period.

It is essential to the development of the embryo, that the germ-cell
receive the matter of the spermatozoon ; the ovum is then said to be
impregnated. The phenomena that thence ensue are essentially the
same up to a certain point in all animals, and consist in the propaga-
tion on the part of the impregnated germ-cell, by a series of reite-
rated spontaneous divisions, of a numerous offspring. A right com-
prehension of the purpose of this process, or the object effected by
it, is essential to the elucidation of the nature and relations of the
subsequent modifications and varieties in the course of development.
The progeny of the primary impregnated germ-cell are the "secondary
or derivative germ-cells," and the whole is the " germ-mass."

This progeny resembles the parent-cell in all respects, save that they
show a diminution of size. When they cease to exist as germ-cells,

D D 4

408 LECTURE XVIIT.

either by coalescing with others or by h'qaefaction, they do not lose
their vitality ; as individuals, indeed, they may be said to die, but by
their death they minister to the life of a being higher than themselves ;
they combine to construct its tissues, or dissolve and impart properties
to its fluids ; these metamorphoses being mysteriously governed by
a plastic nature or mode of force operating unconsciously upon
the matter, but according to a law of order and harmony, and
directed to a fore-ordained and definite end, resulting in a distinct
and specific form of animal, adapted by its organisation for a par-
ticular sphere of existence, and forming a more or less valuable^ but
not, as once was thought, an essential link in the great chain of
organic life.

It is important, hovrever, to bear in mind, that not all the progeny
of the primary impregnated germ -cell are required for the formation
of the body in all animals : certain of the secondary germ-cells, or
their nuclei, may remain unchanged, and become included in that
body which has been composed of their metamorphosed and diversely
combined or confluent brethren. So included, any such cell, or its
nucleus, may commence and repeat the same processes of growth by
imbibition, and of propagation by spontaneous fission, as those to
which itself owed its origin ; followed by metamorphoses and com-
binations of the cells so produced, which concur to the development
of another individual ; and this may be, or may not be, like that in
which the secondary germ-cell was included.

In the previous Lectures we have seen that, in proportion as the
subjects of anatomical investigation descend in the scale of animal
life, the number of the derivative nucleated cells which retain their
individuality and spermatic power is greater, and the number of
those that are metamorphosed into tissues and organs less (p. 35).

A large proportion of such impregnated cells is retained un-
changed in the compound hydriform Polypes and in the parenchy-
matous Entozoa : a smaller proportion in the Acaleph^ and cavitary
Entozoa. We fiad derivative germ-cells and masses of nuclei, like
those resulting from the final subdivision of germ-cells, retained
unchanged at the filamentary extremities of the flabelliform uterus,
and forming the ovaria of the larval Aphides. By the observation
of this phenomenon in the newly hatched larval Aphis from the
ovum deposited by the oviparous species, and by reflection on the
relation of the observed germ-masses to the successive spontaneous
fissions of the primary impregnated germ-cell, and to the effect of
such spontaneous fissions in the subdivision and diffusion of the
spermatic force, I arrived, some years ago, at what I felt to be a clear

GENERATION OF INSECTS. 409

insight into the circumstances which rendered the successive genera-
tions from virgin Aphides possible and conceivable ; and I have the
greater confidence in the truth of that insight from having found it
equally explanatory of the analogous phenomena of " Lucina sine
concubitu " in other animals.

It is now more than a century since Bonnet, in his " Traite d'ln-
sectologie," 8vo., 1745, first attracted the attention of physiologists
and naturalists to this mode of generation in the Aphides, or plant-
lice. And because it was the first of a large class of phenomena, till
then utterly unknown and unsuspected, it was received with consider-
able doubt, or met by total incredulity.

The facts are briefly these : —

The impregnated ova of the Aphis are deposited, at the close of
summer, in the axils of the leaves of the plant infested by the
species, and the ova, retaining their latent life through the winter,
are hatched by the returning warmth of spring : a wingless hexapod
larva is the result of the development. This larva, if circumstances,
such as warmth and food, be favourable, will produce a brood, and,
indeed, a succession of broods, of eight larvce like itself, without any
connection with the male. In fact, no Avinged males, at this season,
have appeared. If the virgin progeny be also kept from any access to
the male, each will again produce a brood of the same number of
aphides ; and carefully prosecuted experiments have shown that this
procreation from a virgin mother may continue to the seventh, the
ninth, or even the eleventh generation before the spermatic virtue of
the ancestral coitus has been exhausted.

When it is so exhausted, a greater proportion of cells in the
germ-masses developed from the remnant retained by the last pro-
creant larvae are used up : individual growth and development proceed
further than in the parent ; some members of the last larval brood
are metamorphosed into winged males, others into oviparous females ;
the ova are impregnated and oviposited, and thus provision is made
for disseminating the individuals and for continuing the existence of
the species over the severe famine-months of winter.

These phenomena, first observed, as I have said, by Bonnet, in the
genus Aphis, were the first to which the thoughts of physiologists
were bent to explain. But, being viewed in the light of an anoma-
lous exception, and at a period when the phenomena of embryonic
development were not known, the earliest steps more especially,
success could not be expected.

Reamur eluded the difficulty of the fact which Bonnet had dis-
covered, by affirming the Aphides to be androgynous. The vagina

410 LECTURE XVIII.

in the perfect oviparous females has appendages called spermatheca
and colleterium ; and Reaumur might have even appealed to the
microscope in support of his idea, for he might have detected, by its
aid, spermatozoa in the spermatheca. But this would not have proved
the hermaphroditic structure ; for the spermatheca receives the intro-
raittent organ of the male, and retains the semen in store for the suc-
cessive impregnation of the ova as they pass out ; the ova at the same
time being coated by the adhesive and protective matter of the collete-
rium. These appendages of the vagina are found in most oviparous
insects ; and the true male Aphis is as well known now as that of any
other species of insect. Moreover, it is found that the viviparous virgin
larvae of the Aphides have not got a trace of those appendages of the
vagina, which Reaumur supposed to be male organs. They were not
required in her mode of generation, and are not developed. The germ-
cell already exists in her, with sufficient spermatic and plastic force for
its development ; no semen, therefore, was required to be retained,
and there is no spermatheca : the embryonic development is completed
in utero, and no secretion for the protective covering of ova was
needed. The structures, therefore, which Reaumur, under a miscon-
ception of their nature, cited in order to solve the problem of the
alleged virgin procreation, are present only in that perfect form of
Aphis where no such phenomena are manifested.

Leon Dufour,* whose extent of research and comparison of the
generative organs of insects led him to a true appreciation of the
nature and function of the appendages to the female organs of the
oviparous Aphides, referred the phenomena of the generation of
the larviparous Aphides to " spontaneous or equivocal generation."
Now, if we consider what we actually learn from these words, — that
the larvse produced by the virgin Aphides are produced by " spon-
taneous" or equivocal generation, — it will seem to be little more
than another mode of stating the fact. The condition or mode of
the fact, the phenomena rendering it possible, are not explained by
them ; M. Leon Dufour, however, meant to record his belief in a
hypothetical mode of generation, in which, as he expresses it, " the
act of impregnation was in no degree concerned." Having detected
the male Aphis, and well scrutinised the structure of its organs,
having witnessed the coitus with the winged female, and carefully
excluded the male in repeating the observations and experiments of
Bonnet, M. Dufour satisfied himself, and affirmed, that impregnation
had no share whatever in the phenomena of the development of the
larval aphis in the body of another virgin larval aphis.

* CCLVII.

GENERATION OF INSECTS. 411

With regard to the hypothesis of spontaneous generation, the
reasons which have led me to concur with most physiologists of the
present day in rejecting it were fully given in a former Course of
Lectures on the subject of Generation, and every exact observation
and experiment subsequently recorded serve to render that hypo-
thesis less tenable and more gratuitous.

Professor Morren, a comparatively recent and very exact observer
of the anatomy and generative economy of the Aphides, retaining
the hypothesis of spontaneous generation as it has been applied to
the Entozoa, propounded, though not without reserve, a theory that
the larval aphides were developed in the body of the virgin parent,
like Entozoa, "by the individualisation of a previously organised
tissue." Now here also is a phrase which, w^hen the meaning of it
is analysed, does little more than express the old facts in a new way.
When a larval aphis is developed, a new individual exists ; in other
words, it has been "individualised;" and, as nothing can come out
of nothing, it must have been by the individualisation of a previously
existing something. The question to be solved is, what is that
something, and w^hat has happened to that something to make its
individualisation under the form of a larval aphis possible and con-
ceivable by us according to the known analogies of other embryonic
developments or individualisations ? That would be the explana-
tion of which we are in quest, — an explanation going as far as that
which we are able to give, for example, of the development of an
ordinarily impregnated ovum ; and, by the proved analogy of the
essential condition of the development in the virgin aphis with
that condition in the impregnated ovum, capable of having every
advance of knowledge of the operation of such essential condition
applied to it.

When, however, M. Morren affirms " que la generation se fait ici,
comme chez quelques Entozoaires, par I'individualisation d'un tissu
precedemment organise*," the objection immediately arises, that no
one has ever seen a portion of mucous membrane, muscular fibre,
or other organised tissue detach and transform itself into an ento-
zoon : such a process is as gratuitously assumed, and as little in ac-
cordance with observed phenomena, as "spontaneous generation" in
the abstract. In a former Course I objected, that "the fissipa-
rous nucleated cells of the ovum, once metamorphosed into a tissue,
can produce nothing higher, and nothing else save by their decay,
which products are excreted ; but the cells which retain their

* Annales des Sciences Nat. t. v. 1836, p. 90.

412 LECTURE xvin.

primitive state amidst the various tissues which the rest have con-
stituted in building up the bodj of the new animal may, by virtue
of their assimilative and fissiparous forces, lay the foundation of a
new organism."*

The learned and ingenious authors of the deservedly popular
*' Introduction to Entomology" admit it to be "an incontestible fact
that female Apliides have the faculty of giving birth to young ones
without having had any intercourse with the other sex," and they
suppose "that one conjunction of the sexes suffices for the impreg-
nation of all the females that in a succession of generations spring
from that union." They adduce, in order to show that such a sup-
position is not contradictory to the general course of nature in the
production of animals, the case of the hive-bee, " in which a single
intercourse with the male fertilises all the eggs that are laid for the
space of two years ; " and the case of a common spider, showing
*' that the sperm preserves its vivifying powers unimpaired for a
long period, indeed a longer period than is requisite for the impreg-
nation of all the broods that a female Aphis can produce." But
these instances do not touch the question how one of such a brood,
insulated from all connection, should give birth to others. Admit-
ting that this phenomenon may depend on the inheritance of the
impregnating principle transmitted from generation to generation,
the problem for the natural philosopher to explain is, how this is
brought about. The superaddition of the "spermatheca" to the
vagina of the queen-bee, as of other oviparous insects, plainly ac-
counts for the fact in the economy of that insect which Messrs.
Kirby and Spence quote, according to the function of the part
determined by the well-devised experiments of Hunter on the silk-
moth.f To say that one conjunction of the sexes suffices to impreg-
nate the females of the successive generations of Aphides spring-
ing from that union, is little more than a statement of the fact ;
and it seems to have been so felt by the able entomologists cited,
who conclude their remarks by confessing — "It is, however, one
of the mysteries of the Creator that human intellect cannot fully
penetrate." J

The completion of an embryonic or larval form by the develop-
ment of an ovarian germ-cell, as in the Aphis, without the immediate
reception of fresh spermatic force, has never been known to occur in
any vertebrate animaL

* LXXXIV. p. 234. t CCXLVII. p. 175.

t CCLI. vol. iv. p. 161.

GENERATION OF INSECTS. 413

The condition which renders this seemingly strange and mysterious
generation of an embryo without precedent coitus possible, is the
retention of a portion of the cells of the germ-mass unchanged. One
sees such portion of the germ-mass taken into the semi-transparent
body of the embryo Aphis, like the remnant of the yelk in the chick.
I at first thought that it was about to be enclosed within the alimen-
tary canal ; but it is not so. As the embryo grows it assumes the
position of the ovarium, and becomes connected with, or aids in
forming the filamentary extremities of the eight oviducts. Individual
development is checked and arrested at the apterous larval condition.
It is plain, therefore, that the essential condition of the development
of another embryo in this larva is the retention of part of the progeny
of the primary impregnated germ-cell. All gemmation, external or
internal, is essentially the same process ; but we should learn nothino"
by being told that the virgin procreation of the Aphis was a process
of internal gemmation *, unless it were shown how that was connected
with the primitive mode of diffusion of the fertilising force through
the germ-mass ; in other words, unless the signification of the
"cleavage-process" of the impregnated egg had first been appre-
ciated, and the resemblance of its product to the basis of the bud
been duly recognised.

The production of a larval Aphis may be repeated from seven to
eleven times in as many successive virgin generations, without any
more accession to the primary spermatic virtue of the retained cells
than in the case of the successive development of polypes in the
compound zoophyte, or the successive budding of the individual
leaves in the equally compound plant.

At length, however, the last apterous or larval Aphis, so developed,
proceeds to be " metamorphosed," as it is termed, either into a winged
individual, in which only the fertilising filaments are formed, as in
the case of the stamens of the plant ; or, it perfects the female
generative organs, and developes the ovules, as in the case of the
pistil. Thus there become " male and female individuals," pre-
ceded by procreative individuals of a lower or arrested grade of
organisation, analogous to the gemmiparous polypes of the zoophyte
and the leaves of the plant.

The process has been described for its better intelligibility in the
Aphides as one of a simple succession of single individuals, but it is
much more marvellous in nature. The first-formed larva of early
spring procreates not one but eight larvie like itself in successive

* Very good observations are, nevertheless, contained in CCLXVIII.

414

LECTURE XYIII.

broods, and each of these larvas repeats the process ; and it may be
again repeated in the same geometrical ratio until a number which
figures only can indicate and language almost fails to express is the
result. The Aphides generated from virgin-parents, by this process
of internal gemmation, are as countless as the leaves of a tree, to
which they are in some respects analogous.

But why, it may be asked, should there be this strange combination
of viviparous generation at one season and of oviparous generation
at another in the same insect ? The viviparous or larviparous gene-
ration effects a multiplication of the plant-lice adequate to keep
pace with the rapid growth and increase of the vegetable kingdom
in the spring and summer. No sooner is the weather mild enough
to effect the hatching of the ovum which may have retained its vi-
tality through the winter, than the larva, without having to wait for
the acquisition of its mature and winged form, as in other insects,
forthwith begins to produce a brood, as hungry and insatiable, and as
fertile as itself. The rate of increase may be conceived by the fol-
lowing calculation : —

The Aphis lanigera produces each year ten viviparous broods, and
one which is oviparous, and each generation averages 100 indi-
viduals.

1st generation

1 aphis produces

2d

100

hundred.

3d

10,000

ten thousand.

4th

1,000,000

one million.

5th

100,000,000

hundred millions.

6th

10,000,000,000

ten billions.

7th

1,000,000,000,000

one trillion.

8th

100,000,000,000,000

hundred trillions.

9th

10,000,000,000,000,000

ten quatrillions.

[0th

1,000,000,000,000,000,000

one quintillion.

If the oviparous generation be added to this you will have a thirty
times greater result.

It generally happens that the metamorphosis sometimes occurring
after the seventh or eleventh larviparous generation takes place
much earlier in the case of some of the thousands of individuals so
propagated : just as a leaf-bud near the root may develope a leaf-
stem, a flower and seed-capsule, with much fewer antecedent genera-
tions of leaves from buds than have preceded the formation of the
flower at the summit of the plant ; or just as one of the lower and
earlier formed digestive polypes may push out a bud to be trans-

GENERATION OF INSECTS. 4J5

formed into an ovarian sac and a generative medusa. The analogy
is beautifully and closely maintained throughout.

The wingless larval aphides are not very locomotive ; they might
have been attached to one another by continuity of integument, and
each have been fixed to suck the juices from the part of the plant
where it was brought forth. The stem of the rose might have been
incrusted with a chain of such connected larvae as we see the stem of
a fucus incrusted with a chain of connected polypes, and only the last
developed winged males and oviparous females might have been set
free. The connecting medium might even have permitted a common
current of nutriment contributed to by each individual to circulate
through the whole compound body. But how little of anything
essential to the animal would be effected by cutting through this
hypothetical connecting and vascular integument and setting each
individual free ! If we perform this operation on the compound zoo-
phyte, the detached polype may live and continue its gemmiparous
reproduction. This is more certainly and constantly the result in
detaching one of the monadiform individuals which assists in com-
posing the seeming individual whole called "vol vox globator;" and
so, likewise, with the leaf-bud. And this liberation Nature has
actually performed for us in the case of the Aphis, and she thereby
plainly teaches us the true value or signification in morphology of
the connecting links that remain to attach together the different
gemmiparous individuals of the volvox, the zoophyte, and the
plant.*

The phenomena of parthenogenesis have not been manifested in
any articulate animal of higher organisation than insects : they cease
at a lower grade of the parallel series of the molluscous invertebrata.
In some lepidopterous insects, which have been supposed to have the
faculty of producing fertile eggs without sexual intercourse, closer
observation has shown the mistake to have arisen from the unusual
circumstances under which the act of impregnation takes place. This
is the case with the moths of the genus" Ps7/che, which the German
entomologists call "sac-trager" from the remarkable cases or sacs
which the larvae inhabit. The true state of the case has been ex-
plained by the observations of Yon Scheven and Siebold.f The
females of these moths never acquire wings, but develope their ova
under a grade of metamorphosis very little beyond that of the larval
state. The larvae which become females fjibricate an entirely different
cocoon from that of the larvae which become males, and the sexes of

* XXX. t CCLXIIL p. 93.

416 LECTURE XVITI.

such larvae are readily distinguishable by such cocoons. Von Scheven
secluded one of these virgin female larvae of the Psyche vestila, and
found that she laid only barren eggs.

The female larv^ of certain species of Pysche live quite separate
from the males on peculiar feeding localities. When about to become
pupas, most of the cocoon-bearers leave those localities, and attach the
mouth of the cocoon to branches of trees, to stones, or rocks. Before
becoming pupae, the grub turns itself in the cocoon, and brings its head
opposite the hinder or lower free opening of the cocoon. The female
pupae manifest very little motion, but remain passive at the upper
end of the sac, by which it is suspended ; whilst the active male
pupae protrude their thorax from the lower opening of the cocoon
shortly before emerging as the perfect moth. The almost apodal
maggot-shaped females cast their pupa-skin without quitting the
cocoon ; they wait, in the hinder or lower free end of the cocoon,
the approach of the male, which accomplishes the act without ever
seeing the female of his choice.

The male Psyche has not the penis of any remarkable length, but
he is able to elongate considerably the abdomen ; the skin of that part
is soft and extensible ; he inserts the abdomen into the hinder open-
ing of the female cocoon, and brings the external genitals into con-
nexion with the copulatory canal of the female. After the coitus,
the female, which has no ovipositor, pushes herself back again into
the cast pupa-skin, and there oviposits. Also, if such a female,
awaiting the male, be disturbed at the closed end of the cocoon, she
returns and betakes herself wholly within her old shed pupa-skin.
In the allied genus Talcsporia, the larviform females emerge from
the hinder aperture of their short cocoon, and creep, by means of
their well-developed legs, to the under side of the cocoon ; the gene-
rative act being performed in open day. These females have a long
ovipositor, and by means of it they fill their old pupa-skin with the
impregnated ova. The procreant female of Psyche is maggot-shaped,
has no fully-developed legs, no articulate antennae, nor distinct eyes ;
neither has she a trace of an ovipositor ; the last abdominal segment
consists only of a short fleshy cylinder, on which a short oviduct
opens. The colleterium is a double pyriform glandular sac, with a
short common duct. A sperraatheca communicates, by a short con-
voluted duct, with the common vagina, which has two lateral fleshy
folds, and is connected with a round bursa copulatrix, with thin and
delicate walls.

Such accessories to the flabelliform ovaria and short oviducts of
the Psyche are of themselves sufficient to show that her ova are

GKNERA.TION OF INSECTS. 41 7

destined to be impregnated. The ideca that the females of this genus
of moth were parthenogenetic would, however, naturally arise from
observation of insulated facts in the singular series of her generative
processes. Our science ever presents a picture of truth evolving
itself by slow degrees from the misapprehensions of observers. An
entomologist collecting the female Psyche in her unusually early
arrested stage of metamorphoses, and without cognisance of the
singular mode of impregnation, would at first conclude, from the
analogy of other moths, that she was a virgin pupa ; and, keeping
her carefully insulated, would be astounded by her abundant pro-
duction of fertile ova. Or, if ignorant of the peculiar place of her
natural oviposition, he might well mistake the shed pupa-case, filled
M'ith fertile eggs, for an actual pupa in which such eggs had been
developed.

There are many striking and beautiful manifestations of instinctive
prescience in the modes of oviposition, and in the location and
attachment of the ova. Observe the actions of the common white
butterfly. Her food is the nectar of flowers ; but, after impregna-
tion, she flits about with a purpose quite distinct from anything
connected with the act of supplying herself with nutriment : if the
plant suitable to the food of the larvae to be developed from her eggs
happen to be within the range of her flight, it will soon be seen what
her object is. The larvce of most Lepidoptera infest, and can only
be nourished properly by, the leaves of particular plants : thus, the
mulberry is suitable to the silk-worm, and the cabbage to the Pieris
brassicce; when that commonest of our butterflies has found the cab-
bage, she has attained the end of her quest, and proceeds to the work
of oviposition.

But a more striking illustration is found in the ichneumon-fly,
which is remarkable for the great length of the anal appendages.
Her food, also, is nectar ; but her chief occupation' in crossing over
the leaves of trees and plants, after being impregnated, is to discover
the larva that may be lurking in the bend of the folded leaf, pre-
paratory to its change into the pupa-state. The ichneumon, by
means of her peculiarly long, sharp, and slender ovipositor, pierces
the skin of the larva, and in spite of its writhing and the ejection
of an acrid fluid, she succeeds in introducing the instrument, and,
by divaricating the two parts of the sheath, makes a little canal by
which the ova are transmitted and lodged under the skin : sli^
then flies off to seek another. Sometimes the female ichneumon,
when she has found a larva, seems to take no notice of it ; and, in
that case, it has been found that another ichneumon has previously
oviposited there, and, by some peculiar sense, she ascertains that

418 LECTURE XVIII.

there is no room for more ova, or not food enough for such when
hatched. After the ichneumon has deposited the ova, she plasters
over the wound with the colleterial secretion.

In the insects of the genus Cynips, which are nearly allied to the
ichneumons, the female has an ovipositor very similarly modified ; their
place for oviposition is the leaves of trees ; and the ova excite an
action in the cellular tissue of the leaf, which results in the formation
of a warm and nutritious bed for the larvae. The products called
" nut-galls " result from such a procedure of the Cynips Querci.
In an insect allied to Aphis, the Chermes, or Psylla ahietis, the last
act of the oviparous female, at the close of summer, is to deposit her
ova in the rudimentary leaves of the fir-tree ; when these leaves,
instead of growing to the length of the others, become thickened, and
are converted, by the irritation of the ova of the Chermes, into a
series of cells of a compact structure. In the Hunterian preparation
(No. 2972) a section has been removed, showing the cavities con-
taining the larva3. In another preparation (No. 2975) is a specimen
of the article in the old Materia Medica, called " Bedeguar." It is a
twig of the common wild rose, from the end of which a tuft of mossy
fibres has shot out, in consequence of the irritation induced by the
presence of the ova and larvae of the Cynips Roscb. Hunter has
made a section of this monstrous growth, exposing several of the
nidamental cavities and their small white larvae.

In the gad-fly {(Estrus bovis) the ovipositor is like a telescope,
terminated by boring instruments ; by means of these the integument
of the ox is perforated, and the egg is then deposited underneath the
skin ; a peculiar kind of inflammation is set up, followed by hyper-
trophy and condensation of the cellular tissue, and in the nidus thus
produced the larvae are developed. In the Bot-oestrus ( Gasterophi-
lus equi) the ova are destined to be incubated in the alimentary canal
of the horse ; and one might wonder how tlieir passage could
be insured into such a locality. The instinct of the female impels
her to attach the ova to the hair of those parts of the body which is
most readily reached by the horse's lips or tongue ; the irritation
of the attached ova excites the action, and so they are picked or
licked oiF and swallowed.

Many insects deposit their eggs in the earth, and the females of
such are provided with instruments for digging. In the preparations
of the Locust (No. 3166 & 3168), they are seen to consist of two hard
elongated valves ; these, in close juxtaposition, are thrust into the
earth, like the gardener's dibble ; the valves are then separated by
muscles, and the eggs are protruded along the interspace and depo-
sited like seeds in the ground. The analogous part in the bee is that

GENERATION OF INSECTS. 419

which forms the sting, and this, as the defensive instrument of the
nursing female, has a certain relation to the well-being of the young.
Many insects not only provide the germ with the nutritive vitelline
mass, or the material for the first development of the embryo, (if,
indeed, the parent can be said to be concerned in that supply which
is the result rather of a series of spontaneous fissions with an inherent
power of assimilation of the primitive germ-cell itself,) but, in some
cases, the parent having selected a fit place for the deposition of her
precious burthen, continues the maternal ofiice by placing near the
ovum the kind of food which the larva will necessarily require in
order to complete its growth.

Some insects, as bees and ants, feed the larvae ; supply them with
the required food from time to time, as nurses satisfy the cravings of
a child ; but these cares seldom devolve upon the mother in the insect
class : they are performed by a distinct race of individuals, of the
feminine sex, but incapable themselves of exercising the procreative
faculty.

The mother ear-wig, however, attends to and broods over her eggs
during the whole period of larval development, turning them and re-
moving them from place to place, according as the locality may
happen to be of the required warmth or moisture.

The forms of the eggs of insects are very variable : often beautiful
and regular, like the seeds of plants ; sometimes very singular ;
always perfectly adapted to the required conditions for the develop-
ment of the future insect. The eggs are cylindrical in Bomhyx
everia ; conical, with tuberculate ribs, in Pontia napi ; hemispherical
in Bomhyx diimeti ; lenticular in Noctua psi ; cup-shaped in Orgyia
antiqua; flask-shaped in Culex pipiens ; petiolate in Hemerobius
perla ; provided with diverging processes like ears in Scatophaga
putris, to prevent their sinking too deep in the soft dung ; provided
with a special adaptation for floating in some aquatic insects ; with
numerous other modifications.

When impregnation has taken place, the germ yolk becomes con-
densed, as in the Ascaris, receding a little from the vitelline mem-
brane at its poles. The impregnated germ-cell propagates itself at
the expense of part of the yolk, forming an oblong germ-mass, of a
hyaline character, and corresponding to the ventral side of the future
embryo. From the peripheral part of this, the cell-progeny extends
until the whole of the vitelline mass becomes invested by a stratum
of minute and nucleated cells. The first phases of development have
been well observed by Herold* and Kolliker : the latter gives the
following account of the process in the Chironomus tricinctusA The
* CCXLI. t CCLXIV.

E E 2

420 LECTURE XVIII.

primordial cells, at first round, and provided with one nucleolus,
become afterwards elliptical, and generally two nucleoli can be dis-
cerned in them ; afterwards two cells exist, of smaller size than the
parent cell. He concludes, that this fissiparous generation of cells,
which accords with that observed by Siebold and Bagge in the
Ascaris, is the general mode of their multiplication : — " Hsec omnia,
etsi nunquam cellulas in aliis inclusas offendi, ne ad sententiam
adducunt, posteriores a prioribus gigni, ita semper binte in unaque
cellula matre oriantur.

The vitelline mass becomes elongated and vermiform, and, by
further subdivision and coalescence of the peripheric stratum of the
derivative germ-cells (" cambium " of Herold), a transparent integu-
ment is formed, like that in the Entozoon, first along the ventral
aspect, then ascending up the sides to the dorsal aspect, which is
likewise closed in by the reciprocally approximating folds which
cover first the cephalic and then the caudal segments. The portion
of the germ-mass remains long unchanged in the anal segment of the
larva of the bee. No part of the yolk can be properly said to enter
or be taken into the body of an insect. It never was out of the
body : it is a " germ-yolk ;" and forms the basis of the future body :
there is no appended or superadded vitellus, as in the shark or bird.
The division of the integument into the thirteen segments commences
at the ventral aspect, which is convex, the vermiform body of the
embryo being, at first, bent backwards.

Li the capitate larvje the entozoal type is quickly left by the
cervical constriction, and the development of a distinct head, which
commences by the formation of the part afterwards retained as the
labrum. The mandibulaa and antennas next appear behind the
labrum as convex lobes ; and the part of the head in the lower inter-
space of the mandibles forms the labium : the maxillce then bud forth
between the labium and the mandibles. The median fissure, thus
surrounded by the rudimental trophi, sinks deeper into the substance
of the head, and, meeting a slender anterior production of the in-
ternal vitelline sac or cavity, establishes the mouth and oesophagus.
TV hilst these stages are in progress, the peripheral series of included
vitelline cells have undergone a series of spontaneous fissions ;
whereby the remaining mass becomes included Avithin a second
stratum or cambium, which, by coalescence and further metamor-
phoses of the cells, is transformed into the tunics of the alimentary
canal, the interspace between which and the outer integument forms
the abdominal cavity. A certain proportion of the vitellus, not in-
cluded in the ellipsoid alimentary canal, has undergone transforma-
tions, by which the foundations of the muscular system, the ventral

GENERATION OF INSECTS. 421

nervous chord, and the dorsal vessel, are laid. An attenuated pos-
terior prolongation of the ellipsoid vitelline or alimentary sac forms
the rectum, and opens upon the thirteenth segment.

In such a condition, but without the cephalic and trophal develop-
ments, the entozoiform larva of the flesh-fly is born or excluded from
the parent : in a similar condition the larva of the bee and of the
parasitic Hymenoptera quits the vermiform ovum, but without the
external communication with the digestive or vitelline sac having
been established at the posterior extremity.

In some Coleoptera development proceeds to the formation of the
appendages of the head, as above described, and a capitate but
apodal larva is excluded, as in the nut-weevil.

In other Coleoptera, as the Donacim, the ventral arcs of the
second, third, and fourth segments send out bulbous rudiments of
the thoracic legs, before the tergal or notal elements of the segments
are completed ; the abdomen is clos(^d above, whilst the development
of the extremities has proceeded to the formation of obscure joints
and terminal hooks. The rudiraental palpi begin to bud from the
maxillae and labium ; the mandibles acquire their hard terminal
hooks, and closely resemble the thoracic feet. In this state the larva
is excluded.

At an earlier period the simple bulbous antennae, mandibles, and
maxillae, indicate three cephalic segments, equal in size and dis-
tinctness to those of the thorax. The maxillary palpi, the labrum
and labium, might perhaps be regarded as indicative of three other
abortive segments ; and if, according to the analogy of the Crustacea,
the eyes are to be regarded as appendages of a proper segment,
then seven cephalic segments may be reckoned, although three only
can be defined by observation of the early development of the insect.
The malpighian and other tubular glands result from juxtaposition in
a linear series of derivative nucleated germ-cells, which coalesce by
liquefaction of the parts of the cell-wall in contact with each other,
the nuclei remaining longer and indicating the primitive separation
of the cells. The ovarian tubes have appeared to me, in the larva
of the silkworm, to retain the primitive series of nuclei of the germ-
cells at their capillary beginnings ; wdiilst coalescence of the germ-
cells themselves, has taken place to form the lower part of the tube :
such persistent, primitive, nuclei, or granules, seem to form the basis
for the formation of the subsequent ova.

The further progress in the development of the Insect cannot be
better entered upon than in the words of our celebrated entomolo^
gists, Kirby and Spence, to whom we owe the most useful and popular
introduction to their delightful science. They say : —

E E 3

422 LECTL'RE xvin.

" Were a naturalist to announce to the world the discovery of an
animal, which for the first five years of its life, existed in the form
of a serpent ; which then, penetrating into the earth, and weaving a
shroud of pure silk of the finest texture, contracted itself within
this covering into a body, without external mouth or limbs, and re-
sembling, more than anything else, an Egyptian mummy ; and which,
lastly, after remaining in this state without food and without motion
for three years longer, should, at the end of that period, burst its
silken cerements, struggle through its earthly covering, and start
into day a winged bird, — what think you would be the sensation
excited by this strange piece of intelligence ? After the first doubts
of its truth were dispelled, what astonishment would succeed I
Amongst the learned, what surmises ! what investigations ! Amongst
the vulgar, what eager curiosity and amazement ! All would be in-
terested in the history of such an unheard-of phenomenon ; even the
most torpid would flock to the sight of such a prodigy." *

Now a marvel of this kind, in all its essential features, is mani-
fested in this country under a thousand modifications. You will
witness it, if you trace the life of the common beetle from the egg, or
watch the same course of changes in the silk-worm.

The first form under which insects appear after quitting the ovum,
is called the larva, a name devised by Linnaeus, to signify, that
beneath this worm-like or snake-like guise there was masked a
higher form. The second stage is the pupa or chrysalis ; and the
third and last stage is the imago, as being the image to which all the
former stages tended.

Linnaeus gave, also, precise terms to the difi'erent conditions of the
pupa- state of the insect ; and these terms have been applied by some
entomologists to characterize metamorphoses generally. When the
last larval skin or sheath of the pupa shows no signs whatever of the
limbs or appendages of the creature within it, Linnaeus called it a
" coarctate pupa." When the pupa-case shows, as if by a kind of
sculpture in relief, the character of the organs beneath it, the pupa
is " obtected." When the pupa case forms a special sheath for all
the projecting parts and appendages, the pupa is " incomplete*"

In all insects the development of the embryo proceeds, with a few
secondary and unimportant modifications, in the order which has just
been described. The subsequent changes of the insect consist in the
growth of all the parts, which takes place chiefly during the period
of the moult ; and in the gradual acquisition of the wings, which are
developed, either when the insect has reverted to the passive state
analogous to that of the ovum, as in the kinds of pupa above defined ;
* CCLI. vol. i. Letter iii. p. 59.

GENERATION OF INSECTS. 423

or without their development being attended with any loss of activity
or diminution of voracity, as, e. g. in the Hemiptera and Orthoptera.

The successive states of an apodal worm, of a worm with feet, and
of one with feet and wings, being accompanied likewise with the ac-
quisition and perfection of the antennal and visual organs of sense,
and of the internal and external organs of generation, and often with
great changes in the digestive, muscular, and nervous systems, in the
development of one and the same insect, have been emphatically
termed the *' metamorphoses." And entomologists availing them-
selves of the neat definitions of the pupae by Linna3us, have defined
various kinds of metamorphoses under special heads, as the " coarc-
tate," " obtected," " incomplete," " semi-complete," and " complete "
metamorphoses.

The progress of the insect through these several stages being in
many species interrupted, and active life enjoyed for a longer or
shorter period under one or other of the immature forms, these have
been sooner and more prominently brought nnder the notice of the
naturalist, than if they had been to be sought for, as in the bird or
mammal, in the early periods of the development of the minute
embryo. They have consequently had assigned to them a character
of singularity and exception which they do not intrinsically
deserve. The difierent stages of development have been likewise,
for the most part, studied only in the instances in which they are
manifested by insects after exclusion from the Qgg, and thus their
minor modifications and difierences have attracted more attention
than their essential resemblances and relations to one and the same
type and course of development. As soon as the young insect
breaks through the egg-shell it is, in modern Entomology, a larva,
whatever grade of development it may have attained in ovo : during
the period when it acquires the wings, and until their complete
acquisition, it is a pupa.

From the importance which has been assigned, in some estimable
entomological treatises and classifications, to the developmental
changes of insects, and the special denominations that have been
multiplied to express them, you might suppose the " complete," the
"semi-complete," the "incomplete," the "obtected," and "coarctate"
metamorphoses, to be difierent degrees, if not distinct kinds of trans-
formations. But the insects which are said to be subject to the
semi-complete and incomplete metamorphosis pass through the same
kind and amount of change as those characterised by the obtected or
coarctate pupa. The difierences resolve themselves essentially into
the place where, and the time in which, they assume and quit the
vermiform state.

E E 4

424 LECTUKE XVIII. '

The Orthopterous and Hemipterous insects, characterised in
entomology by a semi-complete metamorphosis, are, at one stage of
their development, apodal and acephalous larvae, like the maggot of
the fly ; but instead of quitting the egg in this stage, they are
quickly transformed into another, in which the head and rudimental
thoracic feet are developed, to the degree^ which characterises the
liexapod larvse of the Carabi and Petalocera ; the thorax is next
defined, and the parts or appendages of the head are formed, at
which stage of development the young Orthopteran corresponds with
the hexapod antenniferous larva of the 3Ieloe ; but it differs from
all Coleopterous larvae in being inactive and continuing in the Qgg
almost until all the proportions and characters of the mature insect
are acquired, save the wings.

Oddly enough that development is called " a complete metamor-
phosis," which is permanently arrested at the stage in which the
orthopterous insect enters life, and the only hexapod insects, as the
apterous Cimex and Pediculus, in which the metamorphosis is never
completed, are those in which it is said to be " complete." Bur-
meister, however, seems to be the only entomologist who has pointed
out the inaccuracy of the Fabrician definitions ; but he failed to free
himself from the thraldom of words when he supposed that, in the
development of any insects, there was, "properly speaking, no change
of form, but merely a repeated casting off of the exterior skin." *

With regard to the terms incomplete, obtected, and coarctate, they
indicate, in fact, comparatively unimportant modifications of the
last moulted skin of the larva of those insects which are torpid or
quiescent at the period of the development of the wings. In the bee
and beetle, and all Hymenoptera and Coleoptera, the legs, wings, and
antenna3 bud out and carry with them processes of the last larval
integument, which thus forms in the pupa special sheaths for each
growing organ of sense or locomotion in the perfect insect, and
which organs are therefore comparatively free, although the pupa
be quiescent. Lamark called such pupas " Mumiae."

In the obtected Lepidoptera the growing wings, antlia, antennse,
and thoracic legs are only partially covered by the pupal integument,
being lodged in recesses on its inner surface, which make corre-
sponding projections on its exterior, where their form and position
may thus be recognised.

In the coarctate metamorphosis of the Diptera, the larva sheds its
last skin before the growing legs and wings have impressed their
forms upon it, and the exuvium constitutes an egg-shaped horny case,

* CCLXV.

GENERATION OF INSECTS. 425

iqDon wliich there is not the least indication of the parts of the per-
fect insect.

Under whatever form the insect be excluded from the egg, if we
trace its development further back, we shall find that the tendency
of the mysterious multiplication, coalescence, arrangement, and trans-
formation of the hyaline nucleus and germ-cells is vermiform. In all
insects the embryo first manifests itself as an apodal smooth Ento-
zoon ; next as an Annellide of thirteen rings : in all insects the first
segment is quickly modified, and the mouth established ; and in this
state the larva is excluded in some insects, as the bee and fly, without
any appendages being developed ; and in the bee before the com-
pletion of the intestinal canal.

The maggots of the order Dlptera and Hymejioptera typify the
Entozoa ; they have no distinct scaly head, and no thoracic legs ;
lience they have been termed " vermilarves." Those of the Diptera
and of the Ichnemnonidce represent the parasitic worms, not only in
structure, but in habits ; the larvaa of the Gastorophili called " bots,"
pass that stage of their existence in the alimentary canal of higher
animals. The larvas of the Anthorugia canicularis may be, in like
manner, considered as entozoa of the human subject. There is a
breeze-fly ( CEstrus honmiis), which deposits its egg beneath the inte-
gument of the living body, and its larva there grows and flourishes
like the Filaria in the cellular tissue. The larva of a species of
Cuterebra occasionally finds its way into the human frontal sinus.
Other vermilarves, as those of (Estrus Bovis and (Est. Tarandi, are
developed beneath the integument or in the nasal sinuses of the Ru-
minants indicated by their specific names. I know not to what other
modes of animal life than that of the parasitic Entozoa we can com-
pare the habits of the voracious maggots of the flesh-fly, the essential
condition of whose existence is the putrid fiesh of higher organised
beings. Here, however, the development of helminthoid larva has
been beneficially ordained in order to neutralise the noxious efifects of
the otherwise inevitable processes by which dead animal matter
reverts to its primitive elements. Insignificant, indeed, do these
larvie seem to be in the scale of nature, yet Linnaeus used no' exag-
geration when he averred that three flesh-flies would devour the
carcase of a horse as quickly as would a lion. The assimilative
power is so great in the meat-maggot, that it will increase its own
weight two hundred times in twenty-four hours.

But the developmental energies are not exhausted by the rapid
growth of the larva ; some remain to be exercised in the formation
of the new and peculiar organs which entirely change the form and
properties of the creature. For this exercise they usually require

426 LECTURE XVIII.

the suspension of all the ordinary actions of life. The larval skin is
thrust off by the new integument of the new organs, and is converted
into an opaque brown case ; the enclosed insect shrinks partly by the
loss of exhaled fluids, partly by the condensation of its former soft
tissues into the new and firm substances constituting the legs and
wings. A large and distinct head is now developed, with eyes, an-
tennae, and instrumenta cibaria ; all which processes are carried on
in the quiescent concealment of the opaque and dark exuvium, like
the analogous processes in the egg of the oviparous, and within
the womb of the pupiparous, insect. The active carnivorous ver-
milarve returns, in fact, a second time to the state of an ovum,
when it becomes the coarctate pupe ; and the perfect insect, split-
ting its cerement, issues forth as by a second birth.

The larvae of the gnats ( Culex) and crane-flies ( Tipulce) have a
distinct corneous head with jaws ; the former have a plumose anal
coronet, by which they sustain themselves at the surface of the
water ; the orifices of the tracheae are placed in the middle of this
coronet. A pair of tracheal tubes extend through the long, slender,
and extensile anal canal of the aquatic grub of the Musca {Eristalis)
tenax. By this mechanism, which is analogous to the tube of the
diving-bell, the rat-tailed larva can derive its requisite supply of air
from the surface while groping for food in the mud at the bottom of
the pool.

Insects differ much in their dependence on the stimulus of heat
for different generative processes, the Diptera being the hardiest.
Some gnats come forth during the depth of winter and a continuance
of frost, if merely the sun's rays for a while produce a slight rise of
temperature. And amongst the Perlidce the Canadian Capina ver-
nalis comes forth at the end of winter, when the thick ice begins to
crack, and changes from nymph to imago in the crevices, leaving its
slough there, even when the temperature of the air has again sunk
to freezing. Brachyptera glacialis even pairs in the crevices of the
decaying ice.

The economy of the Hymenoptera^ and the various circumstances
attending the development of the apodal larvje, form the subjects of a
long chapter in the History of Insects.

I must be governed in the unavoidably limited selection from this
rich storehouse of interesting facts by the specimens which Hunter
has left for our instruction. In No. 3104, we have a portion of the
nest of a- social hymenopterous insect of the wasp tribe {Polistes
major), showing the larvae and their cells in every stage of growth ;
the smallest larvae and the shallowest cells are at the lower margins
of the pendent nest ; and observe how, in these beginnings of cells.

GENERATION OF INSECTS. 427

the part of the incomplete circumference forms two, three, or more
sides of a complete hexagon, demonstrating that this is the form of
cell originally and expressly made by the insect, and not the acci-
dental and inevitable result of the reciprocal pressure of originally
cylindrical cells, moulded upon the bodies of their simultaneously-
working fabricators. The parent wasp of this colony began her
labours in spring. A solitary mother and independent builder of the
required shelter for her offspring, she herself nursed and fed her first
brood, which, being non-breeding labourers, soon aided their parent
in building the cells and rearing her larvas. You will observe that
the full-grown grubs, which require no more food, and are about to
fall into the pupa state, are shut in by a transparent convex pellicle,
wliich covers the mouth of the cell.

In the common wasp, the larva is hatched eight days after ovi-
position ; it grows to its full size in twelve to fourteen days, then
spins its delicate hood, casts its integument, which has grown with
its growth from the time of quitting the egg, and after a passive
pupa state of ten days, emerges a perfect insect. The males and
perfect females are reared at the beginning of autumn ; the abundance
of food yielded by the ripe fruit at that season may influence the
higher development of the larva, which are fed by the regurgitated
contents of the crop of the nurses.

The fertile females share with the non-breeders or neuters of the
rapidly increasing community the labour of rearing the young broods;
the males, or drones, perform no kind of work. At the close of au-
tumn, when provender is scanty and hardly to be got, the neuters,
by a strange, and, as it would seem, perverted instinct, save the later
brood of grubs from the pangs of famine by killing and casting them
out of the nest. The young females are impregnated previous to the
setting in of winter ; the males soon after die ; the females then dis-
perse, seeking winter quarters in sheltered situations ; and those
which survive the rigours of the frosty season commence, at the
return of spring, the foundation of a new colony.

The higher instincts of the honey-bee {Apis mellifica) teach it to
lay up a winter store of food, upon which, the males having been de-
stroyed on the performance of their sole office, the queens, with a
family of neuters, subsist till spring. The neuters alone now recom-
mence their labours of housing, in waxen cells, the eggs of the fertile
female, and feeding the larvee. New colonies so raised successively
emigrate from the parent hive or "swarm;" they consist of a queen
or fertile female, some males or drones, and perhaps a thousand
attendant neuters. Thus the association, which is annually dis-
solved and recommenced by the wasp, is permanent in the honey-

428 LKCTURE XVIII.

bee, and the fertile female, or queen, never shares with the neuters
the labours of the hive.

The development of the bee is more speedy than that of the wasp ;
the larva is hatched in three days after the exclusion of the egg ; it
feeds and grows five or six days ; is then shut up by the workers,
spins itself a cocoon in thirty-six hours, remaining a passive pupa
eight or nine days_, when it breaks through the lid and emerges in
its perfect state. Thus the whole period of development from the
exclusion of the ovum is from eighteen to twenty days; this, how-
ever, relates to the neuter. The male larva spends only twenty-
four hours in spinning its cocoon, and emerges on the sixteenth
day after its deposition as an egg. A young queen is perfected on
the twenty-fourth day. It is remarkable that the larva of the bee
and of the parasitic Hymenoptera have no anal outlet : no fasces
are passed until the larva has acquired full growth, and has ceased
to feed, preparatory to the pupa-state : thus the fluids of insects
infested by the parasitic larvae are not contaminated by the excre-
ments of their parasites ; and the bee-cells are kept sweet and clean
during the active life of the larva.

In the preparations Nos. 3117 to 3123 inclusive, are shown the
irregular subelliptical cells with the larvae and perfect insects of the
humble bees {Bombi terrestris and lapidarius). The societies of
this genus, which consist of from sixty to a hundred and more
individuals, continue, as in the wasp-tribe, only until the beginning
of winter, and the few impregnated females which survive the frosts
found fresh colonies at the commencement of the following spring.
The fertile female shares in the labours of the community which she
has originated, and she is provided, like the neuters, with the dense
fringe of hair surrounding the pollen plate of the hind legs, which
the queen of the hive-bee does not possess. The first progeny of the
humble-bee are neuters ; the males are not developed until autumn,
and they are the produce of a smaller kind of fertile female. The
w^hole economy of the humble-bee was very completely observed by
Hunter, whose MS. notes on this subject have been published in the
Catalogue of his Physiological Collection.*

The neuropterous tropical Termites, commonly known as " white
ants," are social, like the above-described Hymenoptera ; and the
societies include different kinds of individuals.! The " workers "
(Prep. No. 3150, A) are wingless, with a larger head than the winged
females ; and, usually labouring in the dark, their eyes are more
feebly developed. Another kind of apterous non-breeder (Prep.
No. 3150, B) has the head still larger and stronger, with the man-
* X. vol. V. pp. 38—48. t CCLXVTI.

GENERATION OF INSECTS. 429

dibles elongated, sliarp-edged and pointed, and crossing each other
like the blades of a pair of curved scissors : these live near the outer
border^ and guard the entries to the nest, and their eyes are well
developed : they are less numerous than the purblind workers, and,
their duty being to defend the fortress, they are called " soldiers."
A third kind of individuals are those in progress of transformation ;
they show rudiments of wings, and are called " demi-nymphs." All
these Termites are associated in colonies of incalculable numbers,
and live concealed beneath the surface of the earth, in trees, and
other wooden matters, such as the rafters, beams, furniture, shelves,
&c. of houses, in which they form galleries, with routes conducting
to the centre of their nest : so that these objects, of which the outer
surface is, with curious instinct, left uninjured, fall to pieces on the
slightest touch. The nests of the African Termes bellicosus are some-
times elevated to such a height above the surface, as to appear, at a
distance, like a small village or kraal of the natives.

"When arrived at the perfect state the male (Prep. No. 3145, A)
and female Termites quit their habitation, fly abroad during the
night, in great numbers, and perform the nuptial rites : they lose
their wings before morning, and, falling to the earth, become the prey
of insectivorous lizards, birds, and mammals. Such impregnated
. females as escape this fate, are carried off by the larvae, and the
foundation of a new nest and colony is laid by building around the
rescued queen a royal chamber : here she acquires an enormous size
through the expansion of the abdomen by the myriads of ova there
developed (Preps. Nos. 3146 — 3151). Around the royal chamber
are successively built the cells for the eggs and for the stores of
provision. Thus one species of insect may be represented by six
forms of individuals — the perfect winged female, the same impreg-
nated and apterous, the perfect male, the demi-nymph, the soldier,
and the worker.

The true ants (FormicidcB) of the Hymenopterous order have a
similar economy, with many interesting modifications ; but, perhaps
the most singular peculiarity is presented by the species, thence
called " Amazon ants," whose nest and society include individuals
of distinct species. The neuters of the Formica amazonica seize
by violence those of the Formica fusca; they march in close
column to the nests of that black species and carry off the larvae
and pupse to their own nest, where they are tended by other neuter
slave ants of the same species which have been previously stolen ;
and these, with the slaves they rear, take charge of the young of the

Latreille, XII. torn. v. p. 310.

430 LECTUEE xvni.

The larvjB of the Coleoptera are active, although some, as the
nut-weevil, are apodal, like the larvse of the bee. In most of the
herbivorous species the thoracic legs are represented by fleshy
tubercles ; but the larvae of the carnivorous beetles have the thoracic
legs more completely developed before quitting the ovum. The head
is horny, and the trophi are well developed in all : the jaws frequently
resemble those of the perfect insect, as in the CarabidcE, the larvae
of which likewise have antennae.

The circumstance of most physiological interest in the develop-
ment of the Coleopterous order of insects is the great length of time
during which the species actively exist in the vermiform or larval
stage of their development. The larvae of the cockchafer typify the
earth-worm in their habits, and continue for three years burrowing
in the soil and devouring the roots of grass and other vegetables.
The larva of the stag-beetle bores its way into the trunk of a tree,
generally a willow or oak, and remains there six years. It is fur-
nished with two powerful jaws, with which it gnaws the wood. It
forms a cocoon of the minute chips or tan, to which it reduces the
wood, and passes a considerable period in the pupa state ; during
which, the large horns of the male are folded upon the breast and
abdomen, protecting the antennae and legs.

The anatomy of an insect in its different stages of development,
and the changes of both the external and internal parts in the
progress from the larva to the imago state, have been most accurately
and closely examined in Lepidopterous insects. Many of these
changes are shown by Hunter, in his extensive series of preparations
of the silkworm moth (Preps. 2976 — 3037). They were investigated
by Lyonnet in the Cossus ligniperda. They have been described
and illustrated with much accuracy and detail by Herold in the Papilio
brassicce, and by our own indefatigable entomologist, Newport,
in the Sphinx ligustri, and other insects. Ilie larvae of the Lepi-
doptera quit the Q^,g with a scaly head {fig- 159, h) and jaws, wuth

Sphinx Ligustri. Larva.

three pairs of thoracic legs, short, and with claws (o, p^ q), and
usually four pairs of tubercular prologs (r, r), supported by the sixth,
seventh, eighth, and ninth segments ; sometimes there is also a fifth

GENERATION OF INSECTS. 431

pair upon tlie anal segment. The prolegs, which entirely disappear
in the pupa, are, however, less constant than the thoracic legs. The
larvse of the Lepidoptera are commonly herbivorous, and devour
considerable quantities of vegetable matter. The coarsely masticated.
leaves are conveyed, by a short and wide oesophagus (d), to a much
longer and wider chylific stomach (A.) Six pairs of capillary malpi-
ghian tubes indicate, by their insertion, the commencement of the
intestine (m), w^hich terminates by a wide, short, and longitudinally
plicated rectum, upon the last segment (/«).

In its perfect state, the butterfly, or sphinx, subsists only on the
fluids of vegetables : its maxillary apparatus is converted, by the
abrogation of the horny mandibles and the extreme prolongation of
the maxillae, into a long suctorial tube, called " antlia" {Jig. 160, i).
A long and slender oeso- leo
phagus {j) conveys the
fluids to the chylific sto- ^
mach, and to a wide crop,
which during the pupa »^
state has been gradually
expanded from one side of

Sphinx Ligustri. Imago.

the end of the gullet. 1 he

chylific stomach (^k) has shrunk into a comparatively short fusiform
cavity, which is still characterized by the transverse sacculi and
constrictions. The small intestine (/) has diminished in width, but
increased in length, and now lies in several convolutions between
the chylific stomach and colon, the upper part of which has also been
produced into a caecum, (m) The malpighian vessels are diminished
in length, but still communicate, by a short common duct on each
side, with the commencement of the small intestine.

In the bee the metamorphosis of the digestive organs is still more
striking than in the butterfly, inasmuch as the alimentary cavity con-
sists, beyond the short and wide oesophagus, exclusively of a large
transversely plicated chylific stomach without intestine or vent.
The larvse of the parasitic Hymenoptera are in the same condition,
so that the fluids of the insect they may infest are not contaminated
by the faeces of the parasite. The larvae of bees and wasps have
from four to six malpighian vessels, which shrink in diameter and
contract in length during the pupa state.

The gizzard is never present in the vermiform larv^ of the
Coleoptera, although usually possessed by the perfect insect. In
those of the Scarabcei, MelolonthcB, and most herbivorous Coleop-
tera, the chylific stomach is shorter than in the imago ; but it is
furnished at both ends with caecal appendages, which disappear

432 LECTURE XVIII.

during the metamorphosis, except in the genus Hister, in which some
traces remain in the perfect insect.

The salivary vessels of the caterpillars of the Lepidoptera are of
two kinds : one pair is short and broad, sometimes vesicular, as in
the Cossus ligniperda ; and their ducts terminate at the base of the
maxilla?. Those of the second pair are very long and slender, occupy-
ing, with their longitudinal coils, the sides of the abdomen, and sending
their slender ducts forward to unite together and terminate upon
a peculiar prominence upon the under lip, which is called the spinneret.
(Prep., Nos. 2985 to 2988.) These tubular glands, though classed
with the salivary apparatus, are peculiar, in their full development,
to the larvae, and are called " sericteria," or silk-tubes, because they
prepare the glutinous material, or silk, which the larva spins to form
its cocoon. In the perfect insect the remains of the salivary appara-
tus are limited to the thorax, and the common duct opens beneath the
tongue.

The epithelial lining of the alimentary canal of the larva is shed at
each moult ; that of the closed stomach in the bee-maggot is evacuated
in the pupa state through the new-formed anus.

The superabundant nutriment prepared by the voracious larva is
stored up in the condition of masses of fat, which surround the viscera
and occupy their interspaces.

The parasitic Ichneumons introduce their ova beneath the skin of
the larvae of Lepidoptera. When hatched, the Ichneumon larvoa
subsist upon the fat of the caterpillars which they infest. They avoid
penetrating the alimentary canal, but evidently destroy many of the
minute branches of the trachea which ramify in the adipose tissue.
Such wounded tracheae probably permit the escape of sufficient air
for the respiration of the parasitic larvae ; for though the caterpillars
80 infested survive and go into the pupa state, they are uneasy, and
evidently diseased ; the loss of the adipose store of nutriment pre-
vents the completion of the metamorphosis, they perish, and in-
stead of a butterfly, a swarm of small Ichneumons emerge from the
cocoon.

With respect to the outward form and integuments of the vermi-
form larvae, these are contracted lengthwise, and partially dilated
during the pupa state. The longitudinal muscles contract, and are
permanently shortened by interstitial absorption: they shorten the
body by sheathing the segments one within the other, the intus-
suscepted portions being afterwards modified or removed.

The dorsal vessel {Jig. 159, s) which is developed above the intes-
tine, and begins to pulsate before the larva quits the Qgg, undergoes
a corresponding change with the common integument in i\\Q pupa

GENERATION OF INSECTS. 433

state. It seems to be contracted by a series of intus-susceptions ;
the abdominal part is slightly expanded, more definitely divided into
chambers, and better provided with valves ; the thoracic portion is
simplified, shrunk in diameter, and is more distinctly defined as an
aorta sent off from the heart. {Fig. 160.)

The respiratory system undergoes still more remarkable modifica-
tions. The branchiae of the aquatic larvae either disappear or are
developed into wings : the long pneumatic tubes of those which,
living in water, breath air, shrink and disappear. The partial dilata-
tions of certain tracheae, to form reservoirs of air for diminishing the
specific gravity of the body, begin to be formed in the pupa state of
the flying insect.

Herold has shown that germs of the generative organs exist in the
larvae of the Lepidoptera; the testes appear on each side as four
nucleated cells in a longitudinal series, which, by progressive coales-
cence longitudinally, by approximating transversely, and ultimately
uniting at the middle line, first form an eight-chambered, and after-
wards a spherical gland {Jig. 160, s). The ovaria, retaining their
primitive separate state, increase in length and assume the spiral dis-
position in the pupa state.

The progressive changes which the nervous system of the Lepido-
pterous insect undergoes, in its metamorphoses from the larval into the
perfect state, have already been described (p. 366); and I need only now
remark that the general principle of those changes is like that which
governs the modifications of the muscular system, viz., a localisation
of special masses at particular parts for special purposes ; the result
of which is the departure from a common to a particular type of
arrangement.

One of the most obvious and remarkable phenomena in the larval
life of an insect is the successive sheddings of the skin. The number
and frequency of the ecdyses vary in different species and relate to
two circumstances, viz., the rapidity of the growth of the body, and
the susceptibility or otherwise of the skin to be distended or to grow
with the increase of the body.

The soft-skinned maggots of many flies, which acquire a vast in-
crease of size during their brief larval state, never moult until they
change into pupae, when the exuvium forms the pupa-case. In like
manner^ the soft -skinned apodal larvae of the Hymenoptera do not
moult until they have acquired their full size. The caterpillars of
the Lepidoptera moult at least three times, and some more frequently;
the Bomhyx villica, for example, from five to eight times, and the
tiger-moth {Arctia caja) ten times.

With regard to the nature of the mutations and moults which

F F

434 " LECTURE XVIII.

culminate in the perfect insect, I should hardly have felt justified,
after what has been already detailed respecting the development of
the larva in the egg, in referring to the hypothesis of Swammerdam,
— that the imago was actually included in the larva, and that all new-
skins pre-existed beneath the old one, — if such opinion had not been
adopted to explain the metamorphosis of insects in the admirable
work, already cited, of Kirby and Spence, and maintained by Cuvier
in the second and posthumous edition of his celebrated "Lemons
d' Anatomic Comparee," where, in the eighth volume, p. 2. (1846), he
writes, "des I'instant ou les corps vivants existent, quelque petits
qu'ils soient encore, ils ont toutes leurs parties : ce n'est point par
I'addition de nouvelles couches qu'ils croissent, mais par le developpe-
ment de parties toutes pre-existantes a tout accroissement sensible."
The accurate observations of Herold on the changes and development
of the organs, during the pupa state, show these to be, like the
original processes of the development of the larva itself, the results
of a transmutation, increase, and coalescence of primitive elements of
the different tissues, — elements which consist of nucleated cells or
nuclei, like those that result from the spontaneous fissions of the
primary impregnated germ-cell, — elements which may be viewed as
parts of the original germ-mass, retained to be successively meta-
morphosed into the successive larval-skins, pupa-skin, and imago.

The few instances of the reproduction of mutilated parts in insects
have been observed to take place only at the period of the moult, and
are never manifested by the imago. A young Blatta, in which both
the antennae had been cut off, moulted a fortnight after the operation,
and then acquired two new but shorter antennae : the legs and pro-
legs of caterpillars are said to be produced in like manner after one
or two moultings.

The passive and, as it were, embryonic condition to which most
insects (Coleoptera, Lepidoptera, Hymenoptera, Diptera, many Neu-
roptera) return when, after an active larval life, the organising
energies again superinduce the processes of development upon those
of mere growth, is called the pupa-state. The chief modifications of
the pupa have already been explained in relation to the terms
coarctate, obtected, incomplete, by which they are designated by
Linnseus.

Some pupae are protected only by the exuvial skin of the preceding
stage, and have been termed " naked ; " others repose in cases or
" cocoons," artificially prepared by the larva. The valuable silken
cocoons of the larva of Bomhyx mori, called, par excellence, the
"silkworm," are familiar examples of pupal chambers. In the
cocoon shown in No. 3073, of a larger lepidopterous insect ( Oiketicus

GENERATION OF INSECTS. 435

Kirbyi), the larva, by one of those marvellous and seemingly
prescient instincts which give so much interest to entomological
inquiries, covers the close and thick web of fine and soft silk which
it has prepared for its pupal repose, with a stronger outer defence of
portions of twigs irregularly bound together by silken filaments ;
thus suspended to a branch of the tree, it deceives, and escapes the
attacks of, predatory insectivorous birds. Some spin a thread, let
themselves down from their birth-tree by their silken cord, and bury
themselves in the earth, there to undergo their pupal sleep, as in a
grave, and to rise, gloriously transformed and winged, as at a resur-
rection. The pupae whose cocoon remains partially open, as in
Saturnia and Phrygmiea are usually called " guarded," {piipcB custO'
diatce).

All pupae which are placed in dark situations are colourless, or of a
yellowish white, and become darker when exposed to the light. The
pupse of most butterflies, which are suspended in open day, are of a
green or yellowish brown colour ; some are speckled with glittering
spots of golden hue, either natural, or produced by the attacks of
parasitic insects ; and such pupae have obtained the name of " chry-
salis " and " aurelia."

The active pupae of Orthoptera and Hemiptera are called "nymphs."
These insects, which are also said to have semi-complete pupae, and
to undergo an imperfect metamorphosis, are subjected, as I trust I
have already proved, to the same law of repetition or analogy which
is expressed so conspicuously in insects to which alone a perfect
metamorphosis has usually been attributed; for, although moulting
be no metamorphosis, even when accompanied, as it usually is in
insects, with a certain change in the form of the body, yet the course
of the development of those insects which, after exclusion from the
egg, are subject only to ecdysis and growth of wings during an
active nymph-hood, manifests, prior to exclusion, the same analogies,
which Oken expresses in the following words : — " Every fly creeps
as a worm out of the Qg%\ then, by changing into the pupa, it
becomes a crab ; and lastly a perfect fly." *

It is not, indeed, true that every flying insect creeps, as a worm,
out of the Q^^^ ; all the Orthoptera and Hemiptera are excluded
under the type of the crab, i.e., with perfectly developed jointed legs,
eyes, antennae, and maxillary organs. The metamorphoses which
the locust undergoes in its progress from the potential germ to the
actual winged and procreative imago are nevertheless as numerous
and extreme as those of the butterfly. The differences are relative,

* CCLXVI. p. 577.

F F 2

436 LECTURE xvin.

not essential ; they relate to the place in, and the time during, which
the metamorphoses occur, and to the powers associated with particular
transitory forms of the insect. The legs of the worm-like embryo-
locust were once unarticulated buds, like the prolegs of the caterpillar ;
but the creature was passive, and development was not superseded for
a moment by mere growth ; these organizing processes go on simul-
taneously ; or rather, change of form is more conspicuous than increase
of bulk. The six rudimental feet are put to no use, but constitute
mere stages in the rapid formation of the normal segments, which
attain their mature proportions, and their armature of claws and
spines, before the egg is left. The first segment of the original apodal
and acephalous larva is as rapidly and uninterruptedly metamorphosed
into the mandibulate and antennate head, with large compound eyes.

Thus developed, the young Orthopteran or Hemipteran issues forth
into active life. Instead of further individual improvement or de-
velopment, it may at once begin the great business of its existence
by parthenogenetic propagation of its kind, as in the Aphis, and feed
and die without further change of form ; but, generally, the active,
crab-like larvas are subject to three moults. After the first the larva
has merely increased in size ; but the rudiments of the wings begin
to bud forth beneath the second skin ; and, after the second ecdysis,
they present themselves externally as small leaves, which cover the
sides of the first abdominal segment. When this active pupa or
nymph again moults, the insect attains its perfect condition; the, at
first, short, soft, and thick wings rapidly expand to their full size,
then dry in the air ; the circulation of the blood along the nervures
is arrested, and the metamorphosis of the individual is complete.
Here, then, we see that the pupa stage, which, in the butterfly, was
passive and embryonic, in the locust is active and voracious ; whilst
their respective conditions in the larval state are reversed. The
whole period of the life of the Orthopterous insect, from exclusion to
flight, may, if its organization during that period be contrasted with
that of the Lepidopterous or Coleopterous insects, be called an active
nymph-hood.

Entomologists, overlooking that stage of the Orthopterous and
Hemipterous insects, in which they are masked by the vermiform or
true larval condition, have arbitrarily applied the term " larva " to
the more advanced stage in which these insects, with certain Neurop-
tera, quit the egg. Mr. Westwood seeing that at this stage they are
nearly similar in form to the perfect insect, though wingless, has
proposed to call them " homomorphous," or " monomorphous ; " and
those insects in which the larva is generally worm-like, &c., hetero-
morphous. It needs only an acquaintance with the embryonic changes

GENERATION OF INSECTS. 437

of a cockroach or cricket to feel how inapplicable is the term mono-
morphous or uniform to such an insect or its development.

The chief business of an insect, for good or for evil, is performed
in its larval state. The moth, which destroys our clothes, does it
not in its complete, but its larval, stage. The cockchafer, which
makes the young wheat-blade wither and fall, is a mere grub- Me-
tropolitan duties shut out much of the field of nature ; but still she
may be found and studied everywhere. I first learned to appreciate
the true nature and relations of the nominally various and distinct
metamorphoses of insects, by watching and pondering over the de-
velopment of a cockroach, which quits the egg as a crustacean. I
saw that it passed through stages answering to those at which
other insects were arrested : there was a period when its jointed
legs were simple, short, unarticulated buds, — when its thirteen seg-
ments were distinct and equal, — when it was apodal, — when it was
acephalous.

Now, the differences of the larvae which are distinguished by the
entomological terms, Heteromorphous, Homomorphous, Capitate, &c.,
essentially depend upon their quitting the egg to enter into active
life at different periods of development, arrested at different grades.
And it is most interesting to observe, that these several grades are
analogous to, or are typified by, the complete forms of the different
recognised classes of the great articulate sub-kingdom.

These phenomena of insect-development are most important in
zoological classification. They establish satisfactorily our ideas of the
natural character of a true natural group, as also the natural progres-
sion of the affinities of its several grades.

When we see the entozoiform acephalous type assumed by an insect
in the first transformations of the germ-mass, we feel an assurance
nothing else could give, that we are in accordance with Nature in
commencing the ascending series of articulate animals, which are
to culminate in the winged insect, from the entozoa.

When we find that the annulose w^orm, with a modified segment
for a head, and tubular feet, is the next form assumed, according to
the type of the anellides, we are thereby confirmed in our departure,
in this instance, from the authority of the great Cuvier, who, through
assigning undue value to a single character, the colour of the blood,
placed the anellides at the head, instead of near the foot, of the
articulate series.

When the next step is seen to be the acquisition of articulate
limbs and jointed antennee, we conclude that the articulated animals
arrested at this grade of outward form ought to be the next in posi-
tion in the series, notwithstanding that certain higher members of

438 LECTURE XVIII.

the Crustacea manifest a concentrated character of heart, as the
anellides showed a high character in the red colour of the blood.

Other larvae, by the successive development of simple feet (pro-
legs) upon numerous segments, with aggregated ocelli on the head,
typify the myriapodous order, and then pass on to the simultaneous
acquisition of jointed legs and wings, and thus indicate the close and
essential affinity of the myriapods to the hexapod insects. Thus do
insects in their metamorphoses diversely typify a Divine archetypal
pattern.

In the Coleoptera and Lepidoptera the general articulate type is
longer retained, and the particular one later acquired. In the He-
miptera and Orthoptera the morphological and histological changes
more rapidly and uninterruptedly effect the ascent from the common
to the special form. Professor Burmeister, in his richly-stored
Manual of Entomology, translated by Mr. Schuckard, states that
" In insects with an imperfect metamorphosis there cannot con-
sequently be a passage through the earlier forms and grades of the
animal kingdom." (Shuckard's Translation, p. 423.) The conse-
quence here referred to appears to be, as far as I can understand the
author, a hypothetical necessity in Nature for a difference among
insects with respect to their metamorphosis ; but no insect, however
metamorphosed, passes through the forms and grades of the radiate
province. Commencing as a Hydatid, it quits the acrite sub-king-
dom by the analogy of the Entozoa, and its subsequent grades are
through the forms of the Articulata exclusively. No insect ever
is or resembles the ciliated Infusory, the Polype, or the Acalephe.
The insects with a so-called imperfect metamorphosis, contrary to
the statement of Burmeister, do pass through the earlier forms of
the articulate sub-kingdom, but more rapidly and uninterruptedly
than those in which the metamorphosis has been deemed more com-
plete. In these the worm-like insect or larva is active, and the crab-
like insect or pupa passive ; in those the larva is passive, and the
pupa active.

If the different stages in the development of man were not hidden
in the dark recesses of the womb, but were manifested, as in insects,
by premature birth and the enjoyment of active life, with a limita-
tion of the developmental force to mere growth ; if the progress of
development w^as thus interrupted and completed at brief and remote
periods, with great rapidity, and during a partial suspension of active
life ; his metamorphoses would be scarcely less striking and extreme,
as they are not less real than those of the butterfly.

As the insect must pass through the earlier forms of the Articulate,
so must man through those of the Vertebrate, sub-kingdom. The

GENERATION OF INSECTS. 439

human embryo is first apodal and vermiform ; not, however, at any-
period an articulated worm. The metamorphoses of the germ-cells
in the spherical monadiform ovum have laid down the foundation of
the nervous system coeval with the first assumption of a definite
animal form ; and, by placing it along the back as a myelon or spinal
chord, supported by a gelatinous notochord, have stamped the vermi-
form human embryo with the characters of the apodal fish. When
the four undivided compressed extremities bud out, the form of the
abdominal-finned fish, or of the Enaliosaur, is indicated. The de-
velopment of the heart, of the vascular arches, of the generative
organs with their cloacal communication with the rectum, typify the
oviparous reptile. But these stages are rapidly passed, and the
special character acquired.

Let us suppose that man, or any mammiferous animal, quitted the
ovum and the parent in the guise of the fish, passed a certain period
in water, retaining the branchial structure, the undivided extremities
and the cloaca, and acquired only increase of bulk under that guise ;
let us suppose that then such larva, seeking some safe hiding-place,
returned to embryonic passivity and unconsciousness, and was rapidly
transformed into the perfect state. Under this hypothetical modifi-
cation of the course of human development, the changes of form
would be plainly recognisable, and in the accessory circumstances,
as well as the essentials, the mammalian metamorphoses w^ould re-
semble those of the insect.

If, on the other hand, every insect had been developed like the
Diptera pupipara, and the changes from e,gg to larva and from larva
to pupa had been hidden in the oviduct of the mother, a long period
might have elapsed before the recognition of these metamorphoses,
and they could only at length have been discovered by a series of
embryotomies, like those that have brought to light the corre-
sponding metamorphoses of man and the mammalia generally.

By a premature exclusion and activity of the embryo, and by
alternate periods of growth and development, one small group of
vertebrate animals, the anourous Batrachia, do actually manifest the
correspondence with the metamorphoses of insects, which I have il-
lustrated by an instance of hypothetical possibility in man. Nay, do
not the Marsupial mammalia offer an example of the premature ex-
clusion? It needed only that the young kangaroo, with its equal and
rudimental limbs, should possess, like the tadpole or caterpillar, the
power of self-subsistence, and have gone on feeding and growing,
whilst the further and final changes of form were reserved for, and
concentrated in, a future brief period of torpidity, to render the
parallel almost complete. The creeping or swimming larva of the

F F 4

440 LECTURE XVIII.

Mammal would then have gained its instruments for leaping, as the
caterpillar acquires its organs of flight, and the concomitant de-
velopment and metamorphoses of the organs of sense, of digestion,
and of generation, would have been closely analogous in both
animals.

Class INSECTA.
Body chitinous, articulated, with articulated and uncinated limbs :
head provided with jointed antennae : respiratory system tracheal.

Sub-class Mtriapoda.
Metamorphosis, proceeding from the hexapod type to the acquisition
of a greater number of limbs.

Order Chilognatha. (Gaily worms.)

Two mandibles without palps, divided into two portions, with im-
bricated teeth ; covered by a lower lip composed of the confluent
maxillae. Genera Glomeris, Platyulus, Polydesmus, Julus.

Order Chilopoda. (Centipedes.)

Two mandibles with small palps ; a quadrifld lip, followed by two
pairs of foot-jaws ; the second dilated, terminated by a strong hook,
perforated for the discharge of a poisonous liquid. Genera Geophilus,
Scolopendra, Lithobius, Scutigera.

Sub-class Hexapoda.

Metamorphosis attended with the reduction of a greater number of
legs to six, or not leading to the acquisition of a greater number than
six, and usually with the superaddition of wings.

Mouth suctorial.

Order Aptera. No wings. .(Lice, Fleas.)

A. Thysanoura. Abdomen furnished at the sides with move-

able pieces, or terminated by appendages
fitted for leaping. Genera Lepisma, 3Ia-
chilis, Podura.

B. Anoplura. Abdomen without appendages. Mouth com-

posed of a retractile sucker, or bilabiate
with two hooked mandibles. Genera Pe-
diculus. Nirmus, Ricinus.

C. Aphaniftera. Thorax with scales representing rudimentary

wings. Mouth composed of two lancet-

GENERATION OF INSECTS. 441

shaped mandibles, two scale-shaped max-
illae with antenna-like palpi, a slender
setiform tongue with lamelliform palpi,
and a labium. Genus Pulex.

Order Diptera. (Flies, Gnats.)

Two (mesothoracic) wings : the metathoracic pair rudimentary, and
called "halteres" or balancers. Larvae apodal. Labium elongated,
forming a sheath for the attenuated mandibles and maxillae.

Families MuscidcB, HippoboscidcE, (EstridcB, SyrphidcB, Cercopidce,
Stomoxid<B, BombylidfB, AnthracidcB, Leptidce, Henopidce^ Asilidce,
Stratiomydce, TahanidcB, TipKlidce, Culicidce.

Order Lepidoptera. (Butterflies, Moths.)

Four wings, covered by small coloured scales. Larvae myriapodal.
Maxillae very long and confluent, forming a tube spirally folded
between two palpi : mandibles rudimentary.

Families TineidcB, PyralidcB, Geornetridce, Noctuidm, Bombycidce,
HepiolidcBj ZygcenidcB, SphingidcB, PapilionidcB,

Order Hymenoptera. (Bees, Ants.)

Four wings, membranous, veined with nervures : larvae, in most;,
apodal : tongue and labium elongated : maxillae long and slender :
mandibles short and strong.

A. Securifera. Ovipositor like a saw. Families TenthredinidcBy

SiricidcB.

B. PupivoRA. Ovipositor a long and slender perforator. Fami-

lies Ichneumonidce, CynipidcE, ChrysididcB.

C. AcuLEATA. Ovipositor modified to form a sting. Families

Formicid(E, ScoliadcBj Mutilidce^ Pompilldce,
BembecidcB, Crabronidce, Vespidce, An-
drenidce, ApidcB.

Order Hemiptera. (Bugs, Plant-lice.)

Four wings, the first pair wholly or partially coriaceous. Larvae
with a thorax and six well-developed legs. Mandibles and maxillae
long, filiform, protected by a long sheath-shaped tongue.

Families Pentatomidce, CoreidcB, NepidcB, Naucoridce, Cercopidce,
CicadidcB, Psyllidce, AphididcB, Coccidce.

Mouth mandibulate.

Order Strepsiptera. (Screw-wings.)
Two (metathoracic) wings, the mesothoracic pair rudimentary and
twisted. Larvae apodal. Genera Xenos, Stylops.

442 LECTURE XIX.

Order Neuroptera. (May-flies, Dragon-flies.)

Four wings, membranous, veined with numerous reticulate ner-
vures. Larvae hexapod, unlike imago ; in many aquatic.

Families PhryganidcB, SialidcB, HemerobidcB, Myrmeleonid<B, Tev
mitidce, Raphidiadce, Panorpidce, MantispidcBf EphemeridcBj Libel-
lulidcB,

Order Orthoptera. (Crickets, Cockroaches.)

Four wings ; the first pair coriaceous, nerved ; second pair folded
fan-wise, longitudinally. Larvee like imago, save in wanting wings.

Families Forficulidce, PsocidcBy AcrididcE, Achetidce, PhasmidcB^
Mantidce, Blattidce,

Order Coleoptera. (Beetles.)

Four wings ; the first pair elytra, or hard covers to the under
wings, which are folded transversely when so protected. Larvse ver-
miform, hexapod in most.

A. Pentamera. Five joints in all the tarsi. Families Cicinde-

lidcBf Carabidce^ Hydrocariihari, Brach-
elytra, Buprestidce, Elateridce, Clavicornes,
HydrophilidcB, Lamellicornes.

B. Heteromera. Five joints in the four anterior tarsi, four joints

in the last tarsi. Families Blapsidce^ Tene-
hrionidcB, Taxicornes^ CistelidcB, Meloidcs.

C. Tetramera. Four distinct joints in all the tarsi. Families

BhyncophoridcE, Curculionidce, Xylophagi,
CerambycidcB, Chrysornelidce, CoccinellidcE,
PselaphidcB.

LECTURE XIX.

arachnid A.

There remains one class of articulate animals to be considered in
our present ascending survey of the animal kingdom, and which,
therefore, you will conclude to be the highest organised of the
homogangliate Invertebrata. Yet the species which are grouped
together under the name Arachnida never acquire wings : some are
parasitic, many terrestrial, and a few aquatic : there are species,
however, that, notwithstanding their apterous condition, can rise and
float through the air, which they effect in a manner analogous to
our aeronauts, by manufacturing, and suspending themselves to, a
foreign substance light enough to be buoyed up and wafted along by
the atmospheric currents. The animals to which I allude, and whose

ARACHNIDA. 443

anatomy and physiology I propose to make the subject of the present
lecture, are those commonly known under the name of mites, scor-
pions, and spiders.

You will be disposed to ask why these Articulata are held superior
to insects ? They present not only, as in the Crustacea, a more
concentrated form of the nervous system and of the heart ; but the
larger species, likewise, show a higher condition of the respiratory
system, which is less diiFused than in insects, and in some consists
only of air-sacs or lungs. A more essential mark of the superiority
of the Arachnids is, perhaps, indicated by the course of their develop-
ment. The spider undergoes no metamorphoses comparable with
those of insects. It is at no period of its development an apodal
worm. The mature form is sketched out from the beginning, the
divisions of the body characteristic of the perfect animal are
established before the vitelline mass is included by the tegument ;
and long before the characteristic palpi and legs are completed, the
equally characteristic ocelli are developed upon the head. K you
should still be disposed to think that the more complex eyes and
the wings of insects are essential signs of a higher organisation,
by parity of reasoning, you must be prepared to place birds above
mammals. The Arachnids, however, form, in fact, a short special
branch of the great Articulate tree, beginning very low down, with
species hardly higher than the Entozoa or Rotifera, and ascending
through the anellid-like Demodex, and the rotifer-like Macrobiotus
to the mites, scorpions and spiders.

The Arachnids, like insects, are organised to live in air ; but they
are distinguished at first sight by the general form of the body and
the number of their legs, and by some important modifications of
their internal structure. The head is always confounded with the
thorax, and is deprived of antennae, or at least of such parts ex-
clusively employed in sensation ; the homologues of the antennae in
insects being metamorphosed into organs of prehension, or weapons
of offence. They have four pairs of legs. Some of the species re-
spire by pulmonary sacs only, in others these are associated with
ramified tracheae, and the smaller Arachnids breathe, like insects,
by tracheae exclusively. The dorsal vessel and a circulating system
exist in all : the heart presents a more compact and muscular form
in the pulmonary Arachnids.

The integument is chitinous, as in insects, but presents the same
variations in density, in different species, as in the winged Articulata.
In the scorpions it is as dense and inextensible as in the Coleoptera r
in the spiders and mites it is generally softer than in insects, espe-
cially that of the abdomen, which is extremely extensible.

444

LECTURE XIX.

The body is divided into two principal parts, of which the anterior
is called the " cephalothorax," because it answers to the two first
segments of insects in a confluent state : the second and larger divi-
sion is called the abdomen ; it is generally larger and wider than
the first, from which it is divided by a deep constriction ; but in
scorpions it forms, as in Crustaceans, a slender continuation of the
thorax, a kind of caudal appendage divided into many joints. The
organs of locomotion are all attached to the cephalothorax, and con-
sist of eight legs, presenting different grades of development in the
different forms of the class, but, in most, being very similar to those
of insects, and almost alwaj^s terminated by two hooks.

The microscopic parasite of the sebaceous sacs and hair-follicles of
the human skin, {Demodex folliculorum^ Jig. 162)*, represents the
lowest organised form of the class Arachiiida, and, like the parasitic
Cymotlioe and Bopyrus of the Crustaceous class, makes a transition
from the Anellids to the higher Articukta. In length, it ranges
from ^oth to xw*^ ^^ ^^ inch. Fig. 161 gives a magnified view of
the human hair-follicle (a), containing the bulb of the hair (b), the
appended sebaceous sac (c), and the duct (d) containing the parasitic
Arachnidan in question (e). That this parasite ranks with the

162 6

161

II

Demodex folliculorum in situ. Demodex folliculorum magnified.

Arachnids, and not with the red-blooded or any of the lower or-
ganised worms, is evident from the division of the body into thorax
and abdomen, from the structure of the head and mouth, which are
confluent with the thorax, and from the undivided abdomen. The
thoracic appendages {Jig. 162, c, c), eight in number, as in the
Arachnids, are however of the simplest and most rudimental kind,

* CCCLXXXI.p. 218. pl.xi.

ARACnNIDA.. 445

and are terminated bv tliree short set« ; the anellidous type of the
locomotive appendages being still retained. The integument of the
abdomen is very minutely annulated. The mouth is a suctorial one,
or proboscidiform, consisting of two small spine-shaped maxillae (6),
and an extensile labium, capable of being elongated and retracted ; it
is provided on each side with a short and thick maxillary palp
(rz, a), consisting of two joints, and with a narrow triangular labrum
above. Although the structure of the mouth, as described and
figured by Dr. Simon, has much analogy with that of the Acari, like
which, also, the follicular parasite in one of its stages of develop-
ment is a hexapod, yet it differs from the Acari, and from all other
Holeterce of Duges, in the articulations of the thorax'; whilst it
equally differs from the Pseudo-scorpionidce, and the PycnogonidcB,
which have the thorax articulated, in the rudimental form of the
feet, and the structure of the trophi.

It can hardly be supposed that the changes of form indicated by
the figures 8, 1, and 2 of Dr. Simon's Memoir can be acquired with-
out ecdysis ; but such a metamorphosis, with the natural divisions of
the body and the structure of the oral and thoracic appendages, in-
dubitably raise the parasite of the hair-follicle above the Entozoa, to
which class Prof. Erichson, in Dr. Simon's Memoir, has correctly
stated that the present parasite cannot belong. For the reasons
above given, the Arachnid in question cannot be generically asso-
ciated with the Acarid(B, and it has been referred to a genus
called Demodex, from Bt/juoc, lard, and Zr]^, the name of a bori no-
worm, indicative of the habitat and vermiform figure of this parasitic
Arachnid, which insinuates itself into the hair-follicles and the seba-
ceous o-lands that communicate therewith.*

* LXXXIV. p. 252. This generic name, and the position of the genus in the
class Arachnida, have been accepted by the judicious and experienced naturalist
Siebold (xxiv. p. 507.)- The Demodex is not confined to man, as the following
paragraph shows : — "A communication from A. Tulk, Esq., upon certain para-
sites in the dog, was read. These parasites were found by Mr. Topping, on ex-
amining, microscopically, the contents of the pustules in a mangy dog. They
belong to the genus Demodex (Owen), founded upon parasites, described by
Dr. Simon, of Berlin, as inhabiting the sebaceous sacs and hair-follicles of the
human skin. The insects now described as existing in the dog, were found in
such abundance, that thirty or forty were frequently seen in a single drop of pus.
They differ very slightly from the human parasites before referred to; but
analogy would lead to the conclusion, that they are of a different species. The
discovery of this parasite may throw some light on the cause of the disease called
mange, a disease by no means confined to one class of animals, while at the same
time it is far from being certain whether this insect is the exciting cause, or is
merely developed during the progress of the disorder." — Proceedings of the
Microscopical Society, 20th December, 1843.

446 LECTURE XIX.

Before entering npon the anatomy of the typical forms of the
Arachnida, a few remarks may be premised on another low-organised
member of the class, which, on account of its remarkable power of
retaining life, and reviving after some years' complete desiccation, has
received the generic name of Macrohiotus. This minute and peculiarly
shaped mite, in which the hinder rudimental legs come off from the
abdomen, was discovered by Eichhorn in 1767 *, and was described by
him under the name of " water-bear" (wasser-baer), Corti, in 1774^,
recounted its power of returning to life after being dried. It is not
uncommonly found in the gutters of the roofs of continental houses ;
it crawls along the sediment like a tortoise, and was grouped by
SpahmzaniJ with the Rotifers, under the name of "tardigrade."
Otho Fred. Miiller§ first detected its true relationship with the mites.
It is subject to many moults and oviposits in its exuviae, which, as
the integument is chitinous, is long preserved from decay. The
transparency of the skin is such, in the living animal, as to show a
complicated muscular system beneath, the ultimate fibre of which is
smooth. The nervous system consists of four ganglia, corresponding
with the four segments of the body ; there is no superoesophageal
ganglion. The mouth is suctorial, situated at the end of a retractile
proboscis, on each side of which are two tooth-like styles, — the rudi-
ments of lateral jaws. The stomach is oblong, occupying a large
portion of the body, and is divided by numerous constrictions into
irregularly disposed ca3ca ; their walls are provided with hepatic
cells. Near the mouth are two large lobulated 163
glands, that seem to be salivary. No traces of
respiratory organs have yet been found ; and the
respiration in Macrohiotus^ as in Demodex,
must be cutaneous.

In some of the small and parasitic tracheary
Arachnids or mites, certain pairs of legs are
terminated by adhesive suckers, and others are
occasionally terminated by setae, as in the itch-
mite {Sarcoptes Galei^Jig. 163.).

The mouth, in all Arachnids, is situated on
the anterior segment, and is provided with in-
struments adapted either for suction or masti- sarcoptes Gaiei, or itch-

,. T ^1- -x* 'L ^1 -y , o insect, magnified.

cation. In the parasitic mites the rudiments of

the jaws are more or less enveloped in a sheath formed by the lower

lip : the maxillary palpi are usually the only parts which have free

* CCLXXXII. t CCLXXXIII.

X XLIII. § XLIV.

ARACHNIDA.

447

and independent movements, and their extremity is commonly armed
either with a hook or with a pair of small nippers.

In spiders the parts called mandibles {^fig. 172, cl) are situated at
the front of the head and are terminated by a moveable and very
sharp hook, which is pierced at its extremity by a small fissure,
serving to give issue to the poison secreted by a gland lodged in the
preceding joint. The maxillse (ib. h, h) are two in number, and the
labium (ib. e) situated between these organs is composed of a
single piece. The maxillary palpi (ib. c), compared with those of
insects, are of great length and size, and resemble the thoracic feet,
which, in the Mygale, they nearly equal in length. In female spiders
they are terminated by a single moveable claw : in the males the last
joint (ib. d) is dilated, and presents a more complicated structure.
In the scorpion the mandibles {fig. 164, a) are short, and terminate in
a pair of strong pincers : the
maxillary palpi (ib. 6) are
proportionally more deve-
loped than in the spiders, and,
like the mandibles, they ter-
minate by pincers, which are
so strong and large in the
great scorpion {Biithus Afri-
canus), as to resemble the
chelae of the Crustacea, and
more especially as they are
succeeded by four pairs of
simple and smaller thoracic
legs.

In the genus Galeodes the
mandibles are chelate, but
much longer and larger than
in the scorpions. The maxil-
lary palpi resemble small
slender feet, but without the
terminal hooks ; and the
succeeding pair of append-
ages being similarly modi-
fied, only six ambulatory
feet of the ordinary structure
remain. Two rudiments of
antennae have been noticed
attached to the mandibles in
certain species of this genus.

The head is likewise more distinct

448 LECTURE XIX.

from the thorax, and it supports the first of the four pairs of legs
usually ascribed to the Arachnids. These modifications, with the
union of the ocelli into two groups, indicate the Galeodes to form the
passage to the Hexapod insects.

The modification and the connections of the pair of appendages
which succeeds the maxillary palpi in the Galeodes demonstrate
that they are the homologues of the labial palpi in Hexapod insects.
In most spiders they are explorers, and are carried forwards ex-
tended, while the other legs are used in progression. The position
of the rudimental antennae in the same interesting genus confirms the
indication afforded by the nervous system in spiders and scorpions,
that the antennae are confluent with the so called mandibles, if these
be not altogether modified antennae. They are not the homologues
of the mandibles of insects.

In the composition of the cephalothorax of spiders the tergal
elements of the coalesced segments are wanting, and the back of
the thorax is protected by the elongation, convergence, and central
confluence of the epimeral pieces ; the sternal elements have coalesced
into the broad plate {fig. 172, K) in the centre of the origins of the
ambulatory legs, from which it is separated by the episternal
elements. The traces of the original separation of the four epimeral
pieces may be easily distinguished in some spiders, as in Pholcus
jivulatus. The non-development of the tergal elements explains the
absence of wings, which we have seen, in the Articulata, to be the
appendages of those elements, and to be very frequently restricted to
the branchial function. The tergal parts of the thoracic segments
are equally absent in the decapod Crustacea ; but, in them, the back
of that division of the body is protected by the carapace, continued
backwards from certain cephalic segments : when this is raised, the
epimeral pieces are seen converging, as in spiders, but not meeting
and coalescing.

The soft and flexible integument of the abdomen in mites and
spiders gives no indication of the segments or their component parts,
but it is favourable for the study of its intimate organisation. Beneath
the epiderm and pigmental layer may be distinguished a thin chorion,
the fibres of which, probably contractile, surround the abdomen in
various directions. To the epiderm belong the hairy and spinous
appendages : the large bird-spiders {Mygale) are clothed with a thick
coat of hair : some of the smaller species, as Aranea domestica^
have complex hairs, like the down of birds, implanted by a stem. In
other spiders, similarly implanted stems support scales, analogous to
those of the Lepidoptera ; the bright colours of the SalticcB and
Oxyopes are due to these scales.

ARACHX]DA. 449

The dense cbitinous covering of the cephalothorax in the great
tropical spiders {My gale), and of a larger proportion of the skeleton
in the African scorpion, consists of a series of layers of a brown
colour; the superficial are darker than the rest: the layers are
traversed, in the scorpions, by minute tubes.*

The legs, answering to the six in hexapod insects, consist each of
a coxa, a short trochanter, a longer bi\W femur, a tibia, divided by an
articulation into two unequal parts, and a tarsus composed of a long
and short joint; the latter is commonly armed by two claws. In
some spiders these have a pectinated appendage on their convex side.
Tiiere is a spine on the end of the tarsus of each hind leg opposed to
the terminal hooks. In the aquatic Hydrachuce the legs are thickly
set with hairs on one side.

The muscular system is principally aggregated in the cephalo-
thorax for working the organs of mastication and locomotion : some
small muscular bands are attached to a median ventral raphe of
the abdomen in certain spiders. There are better developed muscles
in the slender jointed abdomen of the scorpions for its inflection and
extension, and more especially for the purpose of wielding the
poisonous weapon with which it is terminated. The elementary
muscular fibres are transversely striated.

A well-marked gradation of structure may be traced in the nervous
system of the Arachnids. The brainless condition of Macrobiotus
has already been alluded to. In the Pycnogonidce the first of the
four ventral ganglions is connected by a slender oesophageal collar
with an ovoid cerebral ganglion ; this is divided in the FhalangidcB.

The principal masses or ganglions of the nervous system are con-
centrated around the cesophagus in the cephalothorax of the scorpion.
From the small superoesophageal or cephalic bilobed mass are sent
upwards the optic filaments, forwards the nerves of the forcipated
mandibles or " chelicera," and, backwards, the stomato-gastric nerves ;
the sub-oesophageal ganglionic columns distribute nerves to the
great maxillary chelif'orm palpi, and to the four pairs of thoracic
legs : two slender continuations of the median columns are continued
along the jointed abdomen or tail, and seven small ganglions are
developed upon them, from which and from the interganglionic
chords nervous filaments are distributed to the surrounding parts.

The ventral continuation of the anterior aorta, which lies loosely
upon the dorsal aspect of the ganglionic chords, must be injected in
order that its branches, which accompany the nervous filaments, may
be distinguished from them. The vessel itself has been mistaken for

* CCXXXr. p. 405.

V, G

450

LECTUIIE XIX.

a nerve, and lias been regarded by some as the motor, by others as
the respiratory tract.

In spiders the central masses of the nervous system are wholly, or
in great part, concentrated in the cephalothorax. The brain {Jig- \^Qoy
and 166, c) is a bilobed ganglion, sending forwards and upwards the
optic nerves (o) from its anterior angles, and below these, the two
large nerves (m) to the les
mandibles {m') : a short
and thick collar encloses
the narrow gullet, and
expands into a second
very considerable stel-
late or radiated gan-
glion (5), situated below
the stomach upon the

plastron: it sends off Nervous system, Mygale.

five principal nerves on each side ; the first {p) to the pediform
maxillary palpi ; the second (Z) to the more pediform labial palpi,
which are usually longer than the rest of the legs and used by
many spiders rather as instruments of exploration than of locomotion :
the three posterior nerves (/, /, /) supply the remaining legs, which
answer to the thoracic legs of Hexapod insects. The nervous axis is
prolonged beyond this great ganglion, as two distinct chords, into the
beginning of the abdomen, where, in the Epeira diadema, it divides
into a kind of cauda equina ; but in the Mygale a third ganglion of
very small size is formed, from which the nerves diverge to supply
the teguments of the abdomen and its contents. The origin of the
mandibular nerves close to the optic ones from the superoesophageal
ganglion strongly indicates the antennal relations of the mandibles,
whilst the homologues of the maxillary and labial palpi receive, as in
insects, their nerves from the subcesophageal mass. The stomato-
gastric nerves are sent off from the posterior and lateral parts of the
brain, and form on each side a reticulate ganglion, which distributes
filaments to the stomach.

Many of the lower parasitic species of arachnids are blind : not
any of this class have compound eyes, but Galeodes and Pholcus
have their ocelli arranged in two lateral groups. The scorpions
have eight ocelli, two of which are situated near the middle line,
and three on each side near the anterior angles of the cephalothorax.

In the spiders the ocelli are generally arranged in a group, upon an
eminence at the middle of the anterior part of the cephalothorax ;
they are generally eight, never less than six in number. The posi-
tion of the four median ones is the most constant; they generally

ARACnNIDA. 45 1

indicate a square or a trapezium, and may be compared with the
median ocelli in hexapod insects. The two, or the two pairs of
lateral ocelli may be compared with the compound eyes of insects ;
the anterior of these has usually a downward aspect, whilst the pos-
terior looks backwards ; the variety in the arrangement of the ocelli
of spiders always bears a constant relation to the general conformation
and habits of the species. Dujes has observed that those spiders
which hide in tubes, or lurk in obscure retreats, either under-ground
or in the holes and fissures of walls and rocks from which they only
emerge to seize a passing prey, have their eyes aggregated in a close
group in the middle of the forehead, as in the bird-spider {fig. 165),
the clothos, &c. The spiders which inhabit short tubes, terminated
by a large web exposed to the open air, have the eyes separated, and
more spread upon the front of the cephalothorax. Tliose spiders
which rest in the centre of a free web, and along which they fre-
quently traverse, have the eyes supported on slight prominences
which permit a greater divergence of their axes ; this structure is
well marked in the genus Thomisa, the species of which lie in am-
buscade in flowers. Lastly, the spiders called Errantes, or wanderers,
have their eyes still more scattered, the lateral ones being placed at
the margins of the cephalothorax. The structure of these simple
eyes resembles that which has been so well described by Miiller in
the scorpion ; Lyonnet had recognised the crystalline lens. The iris,
or process of pigment which advances in front of the lens, is green,
red, or brown in the diurnal spiders, and black at the back part of
the eye. The nocturnal species, as Mygale and Tarantula^ have a
brilliant tapetum, but no dark pigment.

In the scorpion the transparent prominence which indicates each
ocellus is a thick dermal cornea, not divided into facets ; it is deeply
.excavated at the middle of its inner surface for the lodgment of the
spherical lens : the back part of this body rests upon, without sinking
into, the anterior surface of a hemispherical vitreous body. The
interspace between this body and the lens forms a circular channel
tilled with aqueous humour and receiving a circular process of the
thick pigmental chorion which defines the pupil and confines the lens
to the anterior chamber. The pigment coats the retina and covers
part of the optic nerve.

Spiders have the sense of hearing, but neither the organ nor its
situation are known. The same may be said of the sense of smell.
The membrane lining the mouth and pharynx may have the faculty
of taste, and influence the Arachnids in their choice of food. The
soft and often hairy integument must be to a certain degree sen-
sitive, but touch would appear to be exercised principally by the

G G 2

452 LECTUP.E XIX.

leg-like instruments into which the maxillary and labial palpi are
convert*^.

The Saltatores have the terminal joint of the palpi abundantly
beset with hairs, and use them to brush off dust or other extraneous
matters from the anterior eyes : requiring distinctness of vision to
make their sudden springs available in seizing their prey.

The alimentary canal is short and straight in most Arachnids : a
slight convolution of the intestine takes place in some spiders : that
of mites is straight and wide, but the stomach, in some which have
the anus near the middle of the abdomen {Erythreus\ is produced
into lateral sacculi ; these are bifurcated in Ixodes. In the Pycno-
gonidce the long and slender gastric cjBca penetrate the chelicera, and
the eight long and slender legs, as far as the end of the tibia. In
scorpions, the alimentary canal extends, without any gastric dila-
tation or intestinal convolution, from the mouth to the anus. Five
short and straight diverticula are seiit off at equal distances from
each side of the thoracic portion, and are lost in the granular and
seemingly adipose masses, which hav^ been regarded as a kind of
epiploon by some, by others as an hepatic organ. Two delicate
capillary renal tubes unite on each side, close to the intestine, and
open into that part of the canal which is in the anterior part of the
tail-like abdomen.

Tlie spiders are remarkable for the minuteness of the pharynx and
oesophageal canal. Savigny believed that in some species there
existed three pharyngeal apertures, through which the juices, ex-
pressed from the captured insect by the action of the maxillary plates
i^fig' 16.5, 7i) were filtered, as it were, into the narrow cesophagus.
In the jVIygale, however, there is certainly but one aperture : this is
defended above by a liorny plate, or rudimental labrum ; below by
the labium, which is solder<^d to the plastron in the l^Iygale, but
jointed and movable in most of the smaller spiders.

The pharyngeal fissure {^fig. 16.5, h) ascends between an anterior
convex plate or palate and a posterior concave plate, both of which
are shed and renewed at each moult. The slender oesophagus passes
backwards at a right angle to the pharynx, perforates the nervous
ring, and expands into the stomach (ib. d). In the house-spider
{Tegenaria domesticd)^ the gastric cavity is produced into four sacs,
which are susceptible of great distension when a large prey is cap-
tured. In another species of spider {Pholcus rividatus)^ the oesophagus
(^Jig- 166, «), having passed under the brain (c), suddenly expands
into a stomach, almost as broad as the sternum, which sends off a
long clavate c^ecal process into the base of the maxillary palpi (e),
and of each thoracic leg (e'). A shorter diverticulum (c?) is continued

AlvACIlNIDA.

453

from the upper part of the stomach. The intestiue is contracted
where it passes through the pedicle o-f the abdo- 166
men ; it sliglitly expands in its straight course (/)
along the anterior part of that cavity, then con-
tracts and forms two short convolutions {g), and
communicates with a large globular caecum (A),
from which the short rectum passes to the vent.
In some mites, e. g. Ixodes, the salivary glands
consist of masses of vesicles situated on the sides
of the fore part of the body ; and pour tlie secre-
tion by branched canals into the mouth at the base
of the labium. In the spiders a slit in the upper
lip leads into a cavity at the base of which is a
transparent glandular mass, the secretion of which
flows through the slit, and moistens the substances
from which the nutriment is being extracted. Four
biliary ducts {i, i) open into each side of the -^^^"^^"^K/S'^.'' ^^'''^"''
straight portion of the intestine. Two longer and
more slender urinary tubes (A, h) communicate with the beginning
of the caecum, which seems to stand to them in the relation of an
urinary bladder. Large masses of adipose epiploon occupy, in well-
fed spiders, the sides of the abdomen, and cover and conceal tlie gra-
nular brownish ciecal terminations of the voluminous hepatic organ.

The gastric ca^ca and the stores of fat may botli contribute to the
power of endurance of the prolonged fasts for which spiders are
remarkable. Mr. Blackwall kept a young Theridion '^•punctutum
alive without food from the loth October, 1829, to the 30th April, 1831.
It had alvine evacuations at distant intervals and in small quantities
to the end of its existence. It also spun several snares, which were
successively removed by the experimenter.

Tlie chyle is received immediately by the veins, and conveyed to
the dorsal vasiform heart. Tiie heart is situated in all Arachnids,
as in the other Articulata, beneath the dorsal integument and above
the alimentary canal. In the Phalangldce it is three-chambered * :
in the scorpions it is confined to the six dilated anterior segments of
the abdomen, where it is of uniform diameter, except at its two
attenuated extremities : it receives the venous blood from the surround-
ing pericardial sinus by ten or eleven pairs of apertures, each guarded
by a pair of valves. From the anterior and larger extremity the anterior
aorta is continued, which is short, and soon divides into three branches :
a longer and more slender vessel is continued along the terminal
segments of the abdomen from the narrower posterior end of the heart.

CCLXV. p. 154.

454

LECTURE XIX.

In the spiders the heart {^fig. 167, a) extends, as in flying insects,
along nearly the whole of the abdomen, but is wider than in the
scorpion or in insects. It is fusiform, with thick walls, composed
chiefly of transverse muscular fibres, slightly decussating on the
inner surface : a narrow strip of longitudi-
nal fibres extends along the middle of the
dorsal surface.

The blood is returned to the heart either
by from four to six pulmonic vessels (i, h) on le:
each side, or by the great sinus that sur-
rounds it like a pericardium, or by both ways.
It is propelled forwards by the contraction
of the muscular walls, which action can fre-
quently be discerned through the thin inte-
gument of the smaller spiders. M. Duges *,
who succeeded in throwing a solution of car-
mine into the heart from behind forwards,
affirms that it flowed readily by the lateral
pulmonic vessels (6, h) to the base of the pul-
monary lamellaB, and that these productions
of the breathing sacs were coloured rose-red
by the injection of their capillaries. Hence he
concluded that those vessels were pulmonic
arteries. M. Blanchardf, who has equally
succeeded in injecting them, deems them to
be veins, and the sole channels by which the blood returns to the heart.
The disposition of the venous pericardial sinus inclines me, how-
ever, to believe that the heart serves the purposes of both pul-
monic and systemic circulations, as Hunter discovered to be its
function in the flying insect. An artery is continued from both
extremities of the heart ; the anterior aorta (c) gives ofi" two trans-
verse branches {d\ the posterior vessel soon divides into the genital
arteries (e). It sends off" an inferior branch to the intestine, and,
having penetrated the thorax, it gives two branches, which divide to
supply the gastric cjeca. It then divides into two branches, which
run forward nearly parallel to the brain and ej'es ; supply the chelicers
and the poison-organ of that part; and bend down to become inti-
mately blended with the suboesophageal nervous mass. The arteries
have few ramifications, are usually short, and soon lose themselves in
the diffused venous sinuses. The venous apertures are bivalvular,
as in the heart of the scorpion. The blood contains colourless round
corpuscles, which have been seen to circulate in the limbs of young

* CCLXXIII. t CCLXXVIII.

Heart of Spider. Pholcus.

ARACHNIDA.

455

spiders ; returning by a less regular channel than the arterial one :
the veins of the great cavities of the body are irregular and wide
sinuses.

All true Arachnids breathe the air directly : the tracheary respi-
ratory apparatus of the mites commences by a few, usually two,
orifices, sometimes concealed between the anterior feet ( Trombi-
diuni)\ sometimes very apparent above the third pair of legs ( (r«-
masus) ; sometimes behind the last pair of legs. In Deniodex, the
Tardigrada, and P?/cnogo7iidcB, notraces of respiratory organs have yet
been found. In the species, parasitic on the hedgehog (Ixodes Erina-
cei), there are three stigmata; two near the sides, and one below, at
the middle of the abdomen : the latter is described by Audouin as a
spherical tubercle, pierced by a number of minute holes, by which
the air penetrates the tracheae. They usually arise by a simple
tuft from the two stigmata : in Gamasus, there are given off from
the tufts two unbranched tracheae, which course along the sides of the
cephalothorax, and terminate in c£eca at the base of the mouth.
The tracheas are very delicate, and their spiral filament discernible
only in the larger kinds of mite. Those of the w^ater spiders {Hy-
drachnd) doubtless act, like the branchi-trachejs of aquatic insect
larvae, in extracting the air from the water.

The spiders of the genera Segestria and Dysdera have four stig-
mata, situated on the under and anterior part of the abdomen : the
anterior one on each side {Jig- 168, a)
is the aperture of the pulmonary sac (6);
the lower orifice (c) leads to a short and
wide cylinder, from which radiate nume-
rous tracheae (c?) having the usual shining
surface. These tubes are united together
in bundles, and diverge to the surround-
ing parts by dissociation, not by true
ramification, like the tracheae of mites
and insects. One bundle is dispersed
throughout the abdomen ; another enters
the cephalothorax and resolves itself
into groups corresponding in number
with the limbs to the extremity of Avhich
the fine silvery tracheae can be traced.
In Epeira and some other spiders there
is a transverse fissure in front of the spin-
nerets, from which a short tracheal trunk
proceeds : this sends off four simple flat-
tened tracheae, devoid of the spiral filament, which extend, gradually

G G 4

168

Respiratory organs, Stgestria

456

LECTURE XIX.

attenuating to the base of the abdomen.* The pulnaonary sac ^figs.
168, 170, h\ which receives the air by the anterior respiratory ori-
fice, is of an elliptical form ; the vascular surface is augmented by a
number of broad and close-set lamellae which project into its interior.

In the scorpion {^fig. 164), the stigmata or pulmonary orifices are
eight in number, four on each side of the under surface of the an-
terior broad segments of the abdomen (1, 2, 3, 4). They have
the form of oblique fissures, surrounded by a thickened margin, to
which tlie name of" peritrema" has been given. The vascular lining
membrane of the cavity adheres to this margin, and is at first
simple, but afterwards gives attachment to a series of twenty
broad and close-set lamellag, arranged, as in the spiders, like the
leaves of a book. The genus Phrynus has only two pairs of pulmo-
nary sacs ; but each sac has eighty lamellae.

The peculiar organs of secretion in the class Arachnida are those
which prepare the material of the web, which is analogous to silk, and
those which secrete the venomous liquid. The former are proper
to spiders ; the latter common to both spiders and scorpions. The
modification of the abdominal segment of scorpions, by which its
hinder half is converted into a slender, jointed, flexible, tail-like ap-
pendage, seems to have special reference to the wielding of the
envenomed sting. The glands which supply this weapon with its
poisonous fluid are lodged in that well-known pyriform dilatation
formed by the last joint of the tail, and which is terminated by the
slender, sharp, recurved sting.*]' A minute slit
may be observed near the point, which is the
common outlet of two slender ducts, that gra-
dually dilate into two secreting sacs, lodged in
the cavity of the expanded part of the joint,
and separated from each other by a double ver-
tical partition. Their chief tunic is formed by
a layer of smooth muscular fibres, external to
which is a stratum of cylindrical cells.

The poison-apparatus of spiders is placed at
the opposite extremity of the body. The perfo-
rated sting or fang forms the second joint of the
mandible or modified antenna, upon which it
has a gynglymoid movement, and lies concealed
and protected, when not in use, in a furrow with
dentated margins upon the basal joint {fig.
165, mf). The poison gland {fig. 169, a) is an elongated ovoid vesicle,
the exterior of which is characterised by spiral folds produced by the

169

Mygale.

* XXIV. p. 535.

t Prep. No. 2161.

ARACHNIDA.

4o7

arrangement of the fibres of the contractile tunic. The duct (b) tra-
verses the basal joint of the mandible and the cavity of the fang (c),
and terminates in a fissure on its convex surface near the point. In
the true Aranece, the Clubiones, and the Lycozw, the poison glands
extend into the cephalothorax ; but in the bird-spiders {Mygale)
they are limited to the mandibles. It is probable, therefore, that
the effects of a Avound occasioned by these gigantic spiders may be
exaggerated : those species of our native spiders, which are most for-
midably armed, cause little or no inflammation in piercing the human
skin ; but their poison seems to take fatal effect upon insects. The
mechanical laceration, and the sucking out their juices, must, how-
ever, be taken into the account of the lethal powers of the spiders"as
exercised upon their entrapped prey. Litmus paper pierced by the
mandibular hooks of irritated spiders becomes red as far as the
emitted fluid spreads, showing tiie poison to be acid.

The organs which secrete the material of the web are lodged in
the posterior part of the abdomen, and in Epeira fasciata, whicli
is remarkable for the large size of its web, they occupy, when in full
activity, about one fourth of the abdominal cavity. They present
the form either of slender and more or less branched tubes, or of di-
lated sacs, the excretory ducts of which terminate upon projecting
jointed organs at the posterior extremity of the abdomen, called
spinnerets {Jig. 172, ii).

In the Clubiona atrox the glands consist of four larger and nume-
rous smaller tubes : two of the larger branched 1 "0
tubes are twice the size of the other pair.
In the genus Pholcus (Jig. 170) the organ is
reduced to a more simple condition ; it con-
sists of six vesicles of different shapes and
sizes ; two {q) are large and elongated ; they
occupy the middle of the under part of the
abdomen, and their slender ducts are con-
tinued in a tortuous course to the spinnerets ;
two others (r) are also elongated, but are
smaller than the preceding ; the remaining
two are spherical {s). Tlie duct of each of (
these glands terminates upon its appropriate
spinneret, and there are consequently six of
these organs.

Mygale avicularia has only four spinnerets,
and in Mygale cementaria tw^o of them are
imperforate. Clubiona atrox and some species of Drassns have eight
spinnerets ; the two accessory ones being situated in advance of the

Pholcus.

458 LECTURE XIX.

rest, and connected, in Calamisfrum, with a kind of comb attached
to the metatarsus of the hind legs. Six, however, is the ordinary
number of spinnerets in the spiders, two of which are longer than
the others. The secretion does not issue by a simple outlet, but by
a multitude of microscopic pores (Jig. 171), ^^^

which, in the shorter pairs of spinnerets, are
prolonged from the terminal surface upon minute
processes. If you throw a little dust upon the
web of any of the orbitele spiders, of the Epeira
diadema for example, you may observe that it
adheres to the spiral, but not to the radiated,
threads ; for the spiral thread is beset with minute
viscid globules. Lyonnet supposed that the ad- uppeT s^T^ret.

hesive threads issued from the tubular, and the egenauaavt is.

others from the sessile orifices. The secretion is a glutinous fluid,
insoluble in water, and quickly drying in air ; some species, as Ar-
gyroneta aquatica^ spread their nets habitually under water.

The decree and mode in which spiders exercise this singular
secreting faculty varies considerably in the different species. Some,
as the Cluhiones^ line with silk a conical or cylindrical retreat,
formed, perhaps, of a coiled-up leaf, and having an outlet at both
extremities, from one of which may issue threads, to entrap their
prey. Others, as the SegestricB, fabricate a silken burrow of five or
six inches in length, in the cleft of an old wall. The Mygale cemen-
taria lines a subterraneous burrow with the same substance, and
manufactures a close-fitting trap-door of cemented earth lined with
silk, and so attached to the entry of the burrow as to fall down and
cover it by its own weight, and which the inmate can keep close shut
by means of strong attached threads.

The arrangement of spiders by M. Walcknaer* into families, cha-
racterised by their habits, places the principal varieties of their
webs in a very concise point of view.

The Cursores^ Saltatores, and LaterigradcB, make no webs ; the
first catch their prey by swift pursuit, the second spring upon their
prey by insidious and agile leaps ; the third run, crab-like, sideways
or backwards, and occasionally throw out adhesive threads to entrap
their prey. The LatebricolcB hide in burrows and fissures, which
they line with a web. The Tubicolce inclose themselves in a silken
tube, strengthened externally by leaves or other foreign substances.
The NiditelcB w^eave a nest, whence issue threads to entrap their
prey. The FUitelcB are remarkable for the long threads of silk which
they spread about in the places where they prowl in quest of prey.
* Histoire des A.raneides.

ARACHNIDA. 459

The TapitelcB spin great webs of a close texture like hammocks, and
wait for the insects that may be entangled therein. The OrhitelcB
spread abroad webs of a regular and open texture, either circular or
spiral^ and remain in the middle, or on one side, in readiness to
spring upon an entangled insect. The Retitelm spin webs of an
open mesh-work, and of an irregular form, and remain in the middle
or on one side, to seize their prey. Lastly, the AquitelcB spread
their silken filaments under water to entrap aquatic insects.

The silken secretion of spiders is not applied only to the formation
of a warm and comfortable dwelling for themselves, or of a trap for
their prey; it is often employed to master the struggles of a re-
sisting insect, which is bound round by an extemporary filament,
spun for the occasion, as by a strong cord. It forms the aeronautic
filament of the young migratory brood. It serves to attach the
moulting Hydrachna to an aquatic plant by the anterior part of the
body, when it struggles to withdraw itself from its exuvium. Lastly,
a softer and more silken kind of web is prepared for the purpose of
receiving the eggs, and to serve as a nest for the young.

The lower forms of the Arachnids, e. g. Macrobiotus and AcaridcF,
are remarkable for their great longevity and their power of retaining
latent life. Some spiders live only twelve months ; others, e. g.
Segesti^ia senoculata, do not reach maturity until two years old.

The Macrobiotus is androgynous, and the only known arachnid
that is so. The testes are two long fusiform sacs, situated one on
each side of the single ovarium and of the intestine ; they com-
municate with a median dorsal vesicula seminalis, in which Doyere
and Dujardin have detected actively moving spermatozoa. The
ovarium is a large sac, with loose and dilatable tunics, situated
dorsad of the intestine and advancing, when gravid with ova,
as far forwards as the first segment of the trunk. A short
oviduct opens at the fore part of the cloaca, which is on the ventral
aspect of the penultimate segment. The ovarian sac is sustained
by two suspensory ligaments or muscles, which diverge to be
attached, above the gastric division of the alimentary canal, to the
internal dorsal muscle of the second segment. The ova, which are
usually five or six, rarely more than ten in number, are simul-
taneously developed, and of large proportional size. The clear ger-
minal vesicle is imbedded in a coloured yolk, enclosed in a membrana
vitelli. When oviposition and moulting go on together, and the cast
skin receives the eggs, the chorion is smooth : at other times the
chorion is beset with points or tubercles. The germ-mass is trans-
formed at once into the Macrobiotus ; the young animal moves on
the twentieth day, and is excluded on the twenty-fourth, unless it

460 LECTbRE XIX.

happens to become dried, when the young becomes torpid like the
parent, and both revive when they are re-moistened. It is about one-
fourth the size of the parent.

All the Arachnids of the mite family are remarkable for their
power of resisting lethal influences, and for the retention of their
vitality when torpid and apparently dead. The ova of such are, with
still greater difficulty, deprived of their latent life. As all the mites
have been endowed with well-developed, if not complex, generative
organs, the requisite proof must be satisfactorily afforded of the
impossibility of the existence of the eggs of mites in, or of the access
of such to, fluids traversed by galvanic currents, before credence can
be reasonably given to the statements that acari have been developed
by such agency, without any pre-existing eg^, i. e, by way of the
" generatio spontanea sen equivocal

In the genus Trombidium, tlie species are, as in other true mites,
represented by distinct males and females ; the testes form one com-
pact mass, consisting of a group of red-coloured sperm sacs, attached
by a short stem to an annular vas deferens, which opens between the
hindmost pair of legs, but receives before its termination the ducts
of two vesiculse seminales. In the female the ovarium is large and
apparently single, but from it there proceed two oviducts. Mites
are oviparous ; the eggs of the Acarus or Sarcoptes Galei, have
been detected beneath the epiderm, in itch-patients. The females of
the Pi/cnogonidce are known by their filiform jointed ovicapsules,
situated in front of the first pair of legs.

In the true spiders [Araneidre) the males are characterised by their
smaller size, their longer limbs, and brighter colours, as compared
with the females; but more decisively by the tumid and unarmed
termination of the long maxillary palpi ; the parts analogous to
'* vesiculse seminales " being lodged here. The essential and the
accessory generative organs of this sex are quite distinct and remote
from each other : the principle of such separation, which is exem-
plified in the relation of the Fallopian tube to the ovarium in Mam-
malia, is carried to an extreme in regard to the vesicula seminalis
and testis in the spiders. If the analogy of the female parts be here,
as in other animals, a guide in the determination of the essential
organs of the male, the testes ought to be the two long vermicular
tubes, applied to the under wall of the abdomen, which commence
posteriorly, either by a simple sac, as in the Mj'gale, or by an oblong
vesicle, as in the genus P/ioIcus, the ducts of both of which terminate
anteriorly by two approximate orifices, or else by a common opening,
as in Tegenaria {fig. 172, k), situated between the two pulmonary
stigmata (ib. i, i). These abdominal testicular sacculi are, in fact, laden

ARACITNTDA.

461

.it the breeding season ^Yith sperm-cells and their characteristic nuclei
or "spermatoa," from which the spermatozoa are afterwards developed.
The second or copulatory part of the generative organs is confined
to the tvro last joints of the maxillary palp (ib. c, d); the dilatation
of these joints is chiefly formed by a spoon-shaped membranous tube
or sac, commencing at the penultimate and reaching its greatest ex-
pansion at the last joint (c?): this tube appears to line a cavity in the
ordinary state ; but it can be distended, everted, and erected, when it
is seen to be terminated by a horny appendage. In this sac the
spermatozoa are found both free, and in the interior of the sperm-

172

Tpgenaria domestica.

Kpeira (liadema. Female organs.

cells, having escapcd'from the spermatoa into the cavity of the parent
sperm-cell.

In the female spider the ovarium sometimes presents the form of a
simple elongated fusiform vesicle {fig. 170, o), closed at one ex-
tremity and communicating with a slender oviduct (p) at the other,
which duct, after more or fewer convolutions, terminates at the cor-
responding angle of the simple transverse vulva. It is situated, like
the outlets of the vasa deferentia, between the pulmonary stig-
mata {h, b). Each ovarium {Jig. 173, c) is divided in the Epeira, or
diadem-spider, by a median septum, and the eggs are laid at two
distinct periods. The ducts {b) are short, and terminate each by a
distinct orifice {a) within the transverse vulva. In the common
house spider the ovisacs are developed, like grapes, from a central
stem-like ligament, to which they are appended by slender peduncles,
the whole being inclosed in the common capsule. The short vagina
or vulva receives the ducts of two sperm-reservoirs ; they are of
a brown colour and horny texture, and are attached to the skin.

462 LECTURE XIX.

Their ducts are sometimes long and intertwined ; e. g. Salticiis,
Thomisus*

The most careful observations, repeated by the most attentive and
experienced entomologists, have led to the conviction that the ova
are fertilised by the alternate introduction into the vulva of the
appendages of the two palpi of the male. Treviranus's supposition
that these acts are merely preliminary stimuli, has received no con-
firmation, and is rejected by Duges, Westwood, and Blackball ; and
with good reason, as the detection of the spermatozoa in the palpal
vesicles has shown. At the same time, the most minute and careful
research has failed to detect any continuation of the vas deferens
into the terminal erectile sac of the palp, or any other termination
than the abdominal opening above described. Duges offers the very
probable suggestion that the male himself may apply the dilated
cavities of the palpi to the abdominal aperture, and receive from the
vasa deferentia the fertilising fluid, preparatory to the union ; and
the discovery of the spermatozoa at an earlier stage of development
in the abdominal testes, which development is completed after the
transference of the semen to the vesiculre, equally demonstrates the
respective shares which the two widely separated parts of the male
apparatus perform in these remarkable Articulate animals. The
analogy of the separate location of the testes and vesicular seminales
in the dragon-fly will no doubt present itself to the mind. Certain
it is that an explanation of this singular condition of the male ap-
paratus, in which the intromittent organ is transferred to the remote
and outstretched palp, is afforded by the insatiable proneness to slay
and devour in the females of these most predacious of articulated
animals.

The young and inexperienced male, always the smallest and
vv^eakest of the sexes, has been known to fall a victim, and pay the
forfeit of his life for his too rash proposals. The more practised
suitor advances with many precautions, carefully feels about with his
long legs, his outstretched palpi being much agitated ; he announces
his approach by vibrating the outer border of the web of the female,
who answers the signal, and indicates acquiescence by raising her
fore-feet from the web, when the male rapidly approaches ; his palpi
are extended to their utmost, and a drop of clear liquid exudes from
the tip of each clavate end, where it remains attached, the tips them-
selves immediately coming in contact with a transverse fleshy kind of
teat or tubercle protruded by the female from the base of the under
side of the abdomen. After consummation, the male is sometimes

* XXIV. p. 547.

ARACHNIDA. 463

obliged to save himself by a precipitate retreat : for the ordinary
savage instincts of the female, " etiam in amoribus saeva," are apt to
return, and she has been known to sacrifice and devour her too long
tarrying or dallying spouse.

There is a redeeming feature, however, in the psychical character
of the female spider^ in the devotion with which she fulfils all the
duties of the mother. But before proceeding with the examples of
the maternal instinct, I shall first point out the anatomical character
of the generative organs in the scorpion.

The palpi of the scorpion take no share in the formation of the
generative system in either sex ; both male and female are provided
with a pair of peculiar comb-like appendages i^fig. 164, d\ attached
directly behind the genital aperture (ib. c\ which is situated at the
middle line of the under and posterior part of the abdomen. Miiller
has observed, that the teeth in the comb of the male scorpion {Buthus
Africanus) are much more numerous and smaller than those in the
female ; but the sexes are not otherwise distinguishable outwardly.
The males appear to be fewer in number than the females.

Each testis of the scorpion is a long and slender tubulus, which
divides, and the divisions anastomose together to form three loops or
meshes enveloping the substance of the liver, and connected with its
fellow by two transverse canals. A short blind sac (vesiculd) and a
longer accessory glandular tube communicate with the termination of
the short sperm-duct. The common duct terminates in an oblong
receptacle, the outlet of which is situated close to the corresponding
one on the opposite side of the body, at the middle of the under part
of the last segment of the thorax. A small crenate papilliform penis
projects from the genital orifice.

The tubular oviduct of the female scorpion divides and unites with
its fellow through the medium of a third short middle canal, forming
three meshes on each side, and a seventh longer anterior loop by the
terminal union of the oviducts before they open upon the bivalvular
vulva : anterior to their union each oviduct dilates into a sperm-
reservoir.

The ovaria consist of lateral appendages going off at right angles
from the longitudinal canals, and expanding into elliptical sacculi
before communicating with the canals ; the ova are developed in the
slender blind free extremities or beginnings of the ovaria, and the
embryo is developed in the sacculus, the scorpion being viviparous.
The course of its development, which would be a subject of great
interest, has not yet been traced. In the separate outlets of the
sperm-ducts in the male, and of the oviducts in the female, the
higher Arachnida manifest an analogy with the Crustacea.

464 LECTURE XIX.

All spiders are oviparous. The mother prepares a soft and warm
nest for the eggs, which she guards with great care. If kept from
the male the female will lay infertile eggs, and take the same care of
them. The Lycosa vagabunda carries her cocoon about with her ;
if it be removed, and a ball of cotton substituted, she has been known
to bestow upon it the same care ; but when the cocoon was offered
together with the cotton ball, she seldom failed to select her own fa-
brication. The Saltica selects an empty snail-shell for her cocoon,
and spins a silken operculum across the mouth. The Epeira fasciata
encloses her eggs, which are as big as millet-seeds, in a papyraceous
cell, surrounded by a cottony covering, which she then suspends by a
dozen threads or pillars to a larger chamber of silk. The whole is
attached to a branch of a high tree, and is guarded by the mother,
who quits it only in extreme danger, and returns when this is past.

Bonnet, finding in his garden the pit-fall of the larva of the ant-
lion, took a spider with her cocoon, and threw them in ; the spider
crawled up the side of the pit, but before she could escape the ant-lion
seized the cocoon and tore it from the female ; she returned and
seized it, and a battle of some minutes ensued. The ant-lion, how-
ever, succeeded in mastering the spider and retaining the cocoon.
Bonnet then rescued the mother, and placed her at the margin of the
pit ; but she refused to abandon her offspring, and remained there,
passive, as if she had lost everything that was worth living for.

The eggs of most spiders are spheroidal. Prior to impregnation
the ovum consists of a yolk and delicate yolk-membi^ane, containing
a large germinal vesicle, whose nucleus shows several nucleoli, and,
besides tliis, a peculiar firm corpuscle, discovered by Siebold * and
Von Wittich f, usually consisting of fine concentric layers, more
seldom granulated, and disappearing in the fully developed ova.

After one intercourse with the male the Tegenaria civilis has been
observed to produce several sets of eggs, intervals of ten months oc-
curring between each act of oviposition, and two years elapsing before
all the eggs were deposited.

The impregnated ovum of the spider, at its exclusion, consists of a
large and finely granular vitellus, invested by the membrana vitelli,
which is separated from the chorion by a very thin structure of
colourless liquid, analogous to the albumen or the white of the hen's
Qg^. The yolk is generally of a yellow colour ; but in some species
of spider is grey, white, or yellowish brown. The germinal vesicle
has disappeared. An opaque, white, elliptical spot indicates, at this
period, the metamorphosed and impregnated centre from ^vhich sub-
sequent development radiates. The previous changes which have

* XXIV. p. 543. t CCXC.

ARACHNIDA.

465

led to this condition of the excluded ovum, have been ascertained to
be due to the attraction and assimilation by the primary germ-cell
and its progeny of a small proportion of the yolk, which is thus seen
to consist of a germ-yolk and a food-yolk. The subsequent processes,
up to the complete formation of the young spider, have been de-
scribed and figured by the accurate and industrious Herold.*

The germ-mass consists of derivative germ-cells, like minute
opaque whitish granules of smaller diameter than those of the vitellus ;
in some species Herold observed what he believed to be several
germ-spots on different parts of the saperficies of the yolk, which
rapidly coalesced into one body. Development commences by expan-
sion of the circumference of the germ -mass, which, as it expands,
covers the yolk with a semi-transparent thin layer, the basis of the
future integument. Herold next describes the granules of the germ-
mass as being decomposed into almost imperceptible molecules, in
which we may recognise the ordinary result of the fissiparous pro-
perty of its constituent nucleated cells : their powers of assimilation
are at the same time manifested by the changes which they effect in
the albumen, at the expense of which they seem, in the first instance,
to increase their numbers, and diffuse themselves over the surface
of the vitellus. This covering of the yolk Herold calls " coliqua-
mentum." He observes, that the original position of the germ-spot
is indicated by a clear, transparent point (hyaline ?) ; that this point
becomes thickened, pearly, and opaque, so as to conceal the subjacent
vitelline cells. He calls this the nucleus of the germ or the cambium
{fig. 174, «). A similar change progressively extends over the col-
liquamentum ; and, when one-fourth of the circumference of the yolk
is thus covered, the opaque layer has taken on a definite form,
174 175 176 a h

Development of Spider.

resembling the figure 8 {fig- 175), the small and anterior division {a)
being the base of the future head, the posterior and larger one (6),
of the thorax. A fissure is next observed to divide the cephalic
{fig. 176, a) from the thoracic portion {h\ the two parts being
distinct at this period, and determining the essential nature of the

* CCXLI.

De generatione Aranearum in Ovo, 1824.
H H

466 LECTURE XIX.

first great segment of the body in tlie mature spicier. The margins
of the thorax are next seen to be subdivided on each side by three
parallel fissures into four segments (1, 2, 3, 4.) ; these are the basis
of the epimeral pieces. The part of the opaque
integument which connects the two series below
is the rudimental sternum. A second constric-
tion begins to divide the thorax from the abdo-
men; the mandibles or antennae {^fig. 177, h b)
begin to bud forth as two convex processes
from the anterior part of the head ; the part
intervening between these and the epimeral
pieces forms the rudiment of the maxilla (c).

The intermediate labium also begins to be de- EmbrTTider

fined from the sternum. The opaque peripheral
layer (e), extending from the thorax to the opposite end of the ovum,
lays the foundation of the ventral integument of the abdomen. Upon
the opaque integument, which is extending backwards over the dorsal
part of the head, the characteristic group of simple eyes {d) begins
at this time to be distinctly developed, and the rudiments of the
maxillary palps and of the four pairs of thoracic legs become recog-
nizable, raised in relief upon the epimeral segments ; now, also, the
dorsal vessel {f) appears along the upper curvature of the abdomen ;
and thus all the chief characteristics of the future spider are mani-
fested, whilst the great mass of the vitellus remains still visible
through the transparent and incomplete lateral and dorsal parts of
the integument.

The constriction between the two divisions of the body increases ;
the legs and palpi next present slight traces of articulations ; as they
increase in length they cross the middle line of the sternum and
interlock with those of the opposite side. The mouth, the vent, and
the wide alimentary canal are formed ; the integument is completed,
as in other Articulata, by a dorsal cicatrix, and in this state the
young spider breaks through the attenuated chorion. The jaw-
shaped antennae, the cephalothorax, and abdomen, are first extricated,
and afterwards, but with more difficulty, the palpi and legs are with-
drawn. A similar process has soon to be repeated in the casting off
the foetal integument, which becomes too small for the rapid growth
of the young spider. This first moult always takes place in the
silken nest of the parent ; the young spider then issues forth, and is
subject to repeated moults before acquiring the mature size. We
perceive, therefore, that throughout the whole process of the de-
velopment of a spider, there is nothing worthy to be called a meta-
morphosis. The highest of the Articulata never acquires the condition

ARACHNIDA. 467

of the apodal and acephalous worm ; the rudiments of the head, with
its eye-specks, and of the limbs, are manifested before the vitelline
mass is included by the abdominal walls or intestinal membrane:
the tripartite character of the insect — head, thorax, and abdomen —
is faintly and briefly indicated ; but, with the first indications of the
ocelli, trophi, and legs, the special arachnidal form is acquired.

In certain aquatic Arachnida, Nymphon, Pycnogonum, e. g., there
is such a change of proportions of the body and limbs as might
deserve to be called a metamorphosis ; but even these first acquire the
Arachnidal type before retrograding to a lower parasitic form. Most
mites have only six legs when hatched, but they otherwise resemble the
adults, and after the ecdysis acquire the fourth pair of legs. The
young of Hydrachna are likewise at first hexapod, and they have
also a long and large snout, like a distinct head. With this they
pierce the bodies of water-insects, and pass their first stage in a
parasitic state, in which they have been called AchlysicB*

The regeneration of the legs of the spider follows precisely the
same law as that which regulates their reproduction in the Crustacea.
If the limb be injured at the tarsus, tibia, or femur, it must first be
cast off at the coxo-femoral joint, before the process of reproduction
can commence, and this must be preceded by a moulting of the in-
tegument ; the new leg being at first of small size, but with all its
joints and appendages, and acquiring the full proportions at the
second moult. The palp, with the accessory generative organ, has
been reproduced in the male, and has proved to be efficient.

Class ARACHNIDA.

Head usually confluent with thorax, and provided with modified,
commonly mandibuliform, antennee : no wings ; four pairs of legs.

Respiratory system, when present, tracheal, or pulmonary, or
both.

Order Dermophysa.

No distinct respiratory organs: respiration performed by the
common integument. Cephalothorax multiarticulate.

Tarbigrada. Legs rudimentary ; abdomen wanting : herma-
phrodite.
Genera Macrohiotus, Emydium, Mihiesium.
NuLLiGRADA. Lcgs rudimentary ; abdomen long and slender :
hermaphrodite.
Genus Demodex.

* CCXCI. p. 138. taf. 1.
H H 2

468

LECTURE XIX.

Levigrada.

Legs much developed ; abdomen rudimentary :

bisexual.
Genera Pycnogonum, Nymphon, Ammothea, Pal-

lene, Phoxichilus.

Order Trachearia.

Cephalothorax one or

Respiratory organs consisting of tracheae.
two articulated. Bisexual.

A. AcARiNA. Abdomen unarticulated and fused with the cepha-

lothorax. Palpi simple.
AcARiD^. Genera Sarcoptes, Glycyphagus, Tyroglyphus,

MelichareSy Acarus, Pteroptus.
Genera Limnochares^ Arrenurus, Diplodontus,

Hydrachna, Atax.
Genera Hoplophora, Oribates, Pelops, Damceiis.
Genera Dermanyssus, Uropoda, GamasuSy Argus.
Genus Ixodes.
Genera Bdella, Molgus.
Genera Erythrceus^ Trombidium, Smaridia, Te-

tranychus, Rhyncholophus, PeiUhaleus.
Abdomen articulated, but indistinctly separated

from the cephalothorax. Palpi simple.
Genera Phalangium, Gonyleptes^ Eusarcus.

C. PsEUDOSCORPn. Abdomen articulated, but indistinctly separated

from the cephalothorax. Palpi forficulate.
Genera Obism?n, Chelife7\

D. SoLPUGii. Abdomen articulated, distinctly separated from

the cephalothorax. Palpi simple.
Genus Galeodes.

Hydra chnidje.
Oribatibm.

GAMASIDm.

ixobibje.

Bdelbibm.

Trombibibm.

B. Opilionixa.

Order Pulmotracheaeia.
Respiratory organs consisting of tracheae and pulmonary sacs. Ab-
domen and cephalothorax unarticulated, distinct from each other.

Nat ANTES.
Sedentes.

Errantes.

VaG ANTES,

VeN ANTES.

Genus Argyroneta.

Genera Theridion, Episina, Linyphia, Zosis, Ulo-

borus, Tetragiiatha, Epeha, JVyssus, Agelena,

Lachesis, Tegenaria.
Genera Artema, Pholcus, Latrodictus, Clotho,

Brassus, Clubio?ia.
Genera Clastes, Sparassus, Philodromus, Eripus,

Seleiiops, Tho??iisns, Delejia.
Genera Attus, 3Iyrmecia, Dolophenes^ Sphasus,

Ctenus, Dolomedes, Lycosa^ Omosites, Seges-

TUNIC AT A. 469

tria, Uptiotes, Dysdera, Sphodros, Filistata,
Oletera, Mygale.

Order Pulmonaria.

Respiratory organs consisting only of pulmonary lamelligerous sacs.
Cephalothorax unarticulated ; abdomen articulated.

Phrynid^. Abdomen distinct from cephalothorax. Chelicers

unguiculate
Genera Phrynus, Theliphonus.
ScoRPiONiDM. Abdomen indistinctly separated from the cepha-
lothorax. Chelicers forficulate.
Genera Scorpio, Buthus, Androctonus.

LECTURE XX.

TUNICATA, BRACHIOPODA.

The Articulate series of animals leads the investigator of the ascend-
ing course of organic development from the Entozoa to the higher
organised worms which circulate red blood, and through the strange
and changeable forms of Epizoa and Cirripedia to the Crustacea, the
Insecta, and the Arachnida, in which three highest classes of articu-
lated animals with jointed limbs, as many diverging branches from
the common vermiform root seem respectively to terminate.

Yet having attained these several summits of the articulate branch
of organisation, the inquirer still finds himself at a great distance
from any of the Vertebrate forms of animal life. How vast the
hiatus which separates the worm from the lamprey, the crab from the
tortoise, and the beetle from the bird or bat ! He soon attains the
conviction that there is no regular and uninterrupted ascent in the
scale of organisation, as Bonnet fancied ; no single progressive series
of beings ; no necessitated connection of such, as the Poet believed,
who sang, —

" From Nature's chain whatever link we strike,
Tenth or ten thousandth breaks the chain alike."— Pope.

How strikingly illustrative of the subsequent progress of the
science of animal life is this evidence of the creed of the bard of
Twickenham, in which he has recorded in imperishable verse the
convictions of the most cultivated minds of his day !

Not even the insight which we now command into the living forms

H H 3

470 LECTURE XX.

that peopled this planet during past and remote epochs of its history,
can supply all the actual hiatuses, and connect together in a linear
series the existing and extinct members of the Animal Kingdom.
But we can discern that many connecting links in partial series have
perished ; and we know that the broken hypothetical chain of Nature
nevertheless continues to flourish and to adequately fulfil its ap-
pointed office in maintaining the balance of the conflicting influences
of increase and decay, and the general well-being and progress of
organic life upon the present surface of the earth.

If we would make a closer approach to the vertebrate type of
organisation, we must retrace our steps, and, again returning to the
Kadiata, ascend by another and very different series of animals from
those which have occupied our attention in the preceding Lectures.

In the Articulata the advance is most conspicuous in the organs
peculiar to animal life, and was manifested in the powers of locomo-
tion, and in the instincts, which are so various and wonderful in the
insect class.

In the Mollusca the developmental energies seem to have been ex-
pended chiefly in the perfection of the vegetal series of organs, or
those concerned in the immediate preservation of the individual and
the species.

The Mollusca are so called on account of the soft unjointed nature
of their external integument. The scattered centres of the nervous
system, disposed according to the Heterogangliate type of that domi-
nant system of organs, is often accompanied with an unsymmetrical
form of the entire body; which, in compensation for the low condition
of the perceptive energies, is protected in most of the species by one
or more dense calcareous plates, called shells.

All Mollusca have a complete alimentary canal, with mouth,
stomach, intestine, and vent ; and they are provided with circulating
and respiratory organs.

The nervous system, as has been explained in the introductory
lecture, consists of a medullary collar, surrounding the oesophagus,
and communicating with more or fewer ganglions near the oesophagus,
or dispersed, usually below the alimentary canal, in other parts of the
body.

In a large proportion of the lower organised Mollusca there is no
head and no brain ; no nervous centre being needed above the gullet
for the reception of the impressions received by special organs of
sense. The inlet for the food is simply a pharynx or beginning of
the oesophagus, without jaws, tongue, or mouth properly so called.
All other Mollusca are provided with a head, which generally sup-
ports feelers or soft tentacula, eyes, and a mouth armed with jaws.

TUNICATA. 471

The Molluscous province may thus be primarily divided into Acephala
and Encephala.

The acephalous Mollusca are all aquatic, and are divided into classes
according to the modifications of their integument or of their gills.

The Tunicata are those which are inclosed by an elastic gelatinous
uncalcified integument ; they breathe either by a vascular pharyngeal
sac, or by a riband-shaped gill stretched across the common visceral
cavity.

Hunter, who had anatomised the typical forms of this class, and had
recognised the homology of their flexible case to the shells of the
bivalves, to which molliisks he saw that Banks's " Dagyza " and the
"Squirters"of our own shores were most nearly allied, grouped to-
gether the SalpcB and AscidicB, as they are now called, into a natural
family, which he termed "soft-shelled;"* this familyjs the same as
that afterwards defined and called " shell-less Acephala " by Cuvier,
and Tunicata by Lamarck. All the other Acephala have a shell.

The Brachiopoda are defended by a bivalve shell, have two long
spiral arms developed from the sides of the mouth, and respire by
means of their vascular integument or mantle. One valve of the
shell is applied to the back, the other to the belly of the animal,
which is attached by its shell or a pedicle to some foreign body.

The LamellibrancJiia are bivalve conchiferous Mollusca, which
respire by gills in the form of vascular plates of membrane attached
to the mantle. One valve is applied to the right side, the other to
the left side, of the animal. The common oyster and mussel are
examples of this best known class of Acephalous Mollusca.

The Encephalous Mollusca are divided into classes according to
the modifications of the locomotive organs.

The Pteropoda swim by two wing-like muscular expansions ex-
tended outwards from the sides of the head.

The Gasteropoda creep by means of a muscular disc attached to a
greater or less extent of the under part of the body.

The Cephalopoda have all or part of their locomotive organs
attached to the head, generally in the form of muscular arms or
tentacula.

In the last class only do we find, in the present series of animals,
an internal skeleton, combined, in some, with a shell. In the rest of
the Mollusca the hard parts, when present, are external ; but the
integument is sometimes uncalcified and flexible, as in the low organ-
ised class which will occupy our attention to-day, and which in this
condition of their exo-skeleton afford the parallel to the cartilaginous
state of the endo-skeleton in some of the lowest of the vertebrate series.

* X. vol. i. p. 266.

H H 4

472 LECTURE XX.

To connect the Tunicata with any of the classes of animals which
we have previously considered, it is necessary to revert to the Polypi,
for it is in this group of the Radiata that we shall find the animals
which have the closest natural alliance with the present class of
Mollusca.

Suppose a Bryozoon to have its ciliated oral tentacula reduced to
mere rudiments, and to have the pharynx enormously expanded, with
its vascular internal surface richly beset with vibratile cilia ; it would
then be converted into an Ascidian, and the transition from the
Radiated to the Molluscous series would be effected ; — so easily, as it
w^ould seem, and at the expense of so slight a change of any essential
structure, that some, according to the importance they may attach to
the Zoologist's definitions, groupings, and divisions, might be dis-
posed to blame the present entry upon the molluscous type of organ-
isation by the class in w4iich the respiratory organ is distinctly
developed and the polype-form abandoned. It is chiefly by reason of
the external character of the crown of radiating tentacles that the
Bryozoa have been placed in the radiated sub-kingdom. Their
minute size, fixed position, composite aggregation, and gemmiparous
propagation added, doubtless, to the belief in their being Polypi.
But relations of size have no value in classification ; the mouse is as
good a mammal as the elephant. The choice of their position mainly
depends upon the importance assigned to certain phenomena of de-
velopment (p. 153). According as the Naturalist calls the Flustra a
polype or a mollusk, he exemplifies his mode of interpreting the sig-
nification of the difl'erence between the ciliated gemmule of the
Flustra and the cercariforra larva of the Polyclinum, of the resem-
blance of the bristled coriaceous ovum of the fresh-water Alcyonella
to that of the fresh-water Hydra, and of the difference of both from
the ovum of any known compound Ascidian. If these significant
indications of the fundamental affinity of the Polypes, with the re-
tention of the polype-form, and the absence of a respiratory organ in
the highest of that class should beget a doubt as to the propriety
of calling a Bryozoon a Mollusk, and thereby losing the advantage of
the latter term as a definite and intelligible sign of a certain advance
of organisation, the comparative anatomist, whilst admitting the full
amount of the affinity of the Bryozoa with the Tunicata, and thereby
illustrating his view of the Molluscous series as constituting a great
parallel branch of the animal kingdom with the articulate series*,
may anticipate a verdict in favour of his judgment, in the necessarily
artificial mode of successively treating of the different types and
grades of organisation, if he should select the compound Ascidians as

* LXXXIV. p. 269.

TUNICATA.

473

the point at which, for his needs of description and generalization, he
severs an unequivocally natural series of animals from the wide-
spread root or base from which it springs.

The Brjozoa and many Tunicata, after their severally distinct
modes of larval locomotive life, become rooted, like plants : some
Tunicata^ moreover, form groups of individuals united together by
a common organised external integument ; the present order of
the class consists, in fact, of compound and simple Ascidians. I
shall first demonstrate the organisation of this group by the larger
examples of the simple or solitary Ascidians *, which do not essen-
tially differ in anatomical structure from the compound species,
whose small size renders this a subject for microscopic investigation.

TUNICATA.

The exterior tunic of the solitary Ascidian {fig. 178.) is a thick
gelatinous or coriaceous elastic substance, adhering by its base or by
a long flexible peduncle to some foreign
body, and perforated at the opposite end
or at the side by two apertures (a and h).
The exterior of this tunic is sometimes
rough and warty, the inner surface always
smooth and lubricous. Microscopically
examined, it consists chiefly of a conglo-
merate of non-nucleated cells like the pa-
renchyma of Cacti ; chemically analysed,
100 parts of the tissue, free from ash and
water, gives of carbon 45*38, Hydrogen
6*47 ; being the same composition as the
" cellulose " of plants.f This non-azotised
tissue is traversed by large blood-vessels,
and towards its inner surface crystals and
nuclei are abundant in the clear homo-
geneous basis. The lining membrane is
composed of a layer of polygonal, nucle-
ated, epithelial cells.

The second tunic is muscular; it ad-
heres to the outer tunic at the circumfe-
rence of the two orifices, and is connected
to it by blood-vessels at a few other points ; elsewhere it is quite free,
and the opposed surfaces of the intervening space between the mus-
cular and elastic tunics has the aspect of a serous cavity. Its fine
fasciculi of fibres are remarkably distinct, and are arranged in two

Ascidia mammillata.

* Preps. Nos. 614, 615, 616. 785, 898 b. 998. 1303 c.
t IX. p. 34. 4

474

LECTURE XX.

layers, — the external circular, the internal longitudinal. The fibres
or fasciculi of the outer layer are smaller than those of the inner one,
and less regularly disposed. They describe regular circles around the
processes leading to the orifices of the shell. Other fibres of the outer
layer pass transversely from one tube to the other. The longitudinal
fasciculi radiate from the two orifices, and decussate each other,
winding round the bottom of the sac. Deeper, again, than this layer
there is a sphincter surrounding the base of each tube, or orifice, from
which a third more delicate layer of longitudinal fibres is given off".

Of the two more or less protuberant and stellate apertures in the
outer tunic, one (b) leads directly into the muscular sac, the other (a)
into a wide vascular branchial sac contained in the muscular one.
The entry to the branchial sac is defended by a circle of short ten-
tacles (Jig.l79,f). The sac is dissected away in this figure. The inner
surface of the sac is marked by parallel
and equidistant transverse lines, the
interspaces of which are divided into a
series of narrow vertical, perforated,
and richly ciliated compartments ; two
opposite narrow longitudinal tracts are
entire (fgs. 180, 184,/,/). A groove
along that which traverses the larger
curvature of the sac leads to the
mouth — an orifice {Jig. 179, a) at fhe
bottom of the branchial sac, which
conducts, by a short oesophageal canal,
to the stomach [b) ; this is an oblong
cavity, with longitudinal folds. The
intestine is disposed in a sigmoid
flexure, adheres to the outside of the
branchial and the inside of the mus-
cular sac, and terminates by a fim-
briated anal aperture (c) near the base
of the second orifice of the tunic (d).

The liver consists of blind follicles, Cynthia canopus.

produced into tubes which anastomose, surrounding more or less of
the intestine, as by a net-work, and ultimately, at least in Cynthia
tuberculata, communicating with the stomach by a single aperture,
from which a groove is continued towards the cardia.

The heart (Ji) is a simple, elongated, vasiform muscle, inclosed in
a pericardium, attached to the branchial sac ; continued at either end
into a vessel ; the ramifications of one being expended chiefly upon
the respiratory organ ; those of the other upon the tunics of the body,
or speedily expanding into sinuses surrounding the viscera. Ac-

TUNIC ATA. 475

cording to the direction of the circulating currents the one trunk-
vessel will be an artery, the other a vein, and the circulation itself
will be pulmonic or systemic.

The nervous system must be first sought for in the interspace
between the two openings of the muscular tunic ; there you will find
a ganglion {g), from which it is not difiicult to trace filaments
diverging to each aperture of the sac where the circular disposition
of the muscular fibres prevails ; other branches accompany the
longitudinal fibres, and supply the respiratory sac ; two contiguous
filaments are continued to the oesophageal orifice.

Eight pigment- or eye-specks have been detected at the entrance
of the respiratory tube ; and six, of a deep yellow colour, at the
entrance of the anal tube.

In the animal manifesting this organisation, which is much richer
unquestionably than the amorphous and rugged exterior would seem
to promise, the only vital actions obvious to ordinary vision are an
occasional ejection of water from the orifices of the tunic by a sudden
contraction, succeeded by a slow and gradual expansion. Such con-
tractions and expansions, aided by the ciliary currents, and the
peristaltic movements of the alimentary, circulating, and secerning
tubes, are all the actions which the organic machinery has to perform
in the living ascidian.

The respiratory currents of sea water with the nutrient molecules
in suspension are introduced by the ciliary action through the
branchial orifice {e, fig. 179) into the pharyngeal respiratory sac,
from which the oesophagus (a) selects the appropriate food. The
alimentary excretions and the generative products are expelled
through the anal outlet (c) by the contraction of the muscular tunic.

In consequence of the space between this and the outer tunic being
closed, that tunic accompanies the muscular tunic in its contraction,
through the influence of the surrounding pressure ; when the muscle
ceases to act, the elasticity of the outer coat begins to restore the
fibrous sac to its former capacity, and the surrounding water flows
into its cavity, either directly or by distending the branchial sac.
We shall find other instances of the economising of muscular force
by the substitution of elasticity as we ascend in the survey of the
molluscous organisation.

In the small compound Ascidians the organisation is essentially
like that of the solitary species, but the viscera are somewhat dif-
ferently disposed : the cavity of the body is longer and narrower, the
entire animal viewed singly being more vermiform. In their natural
organic association they are arranged in different modes, and under
different forms ; some, as the beautiful Diazona, diverging like the

476

LECTURE XX.

petals of a compound flower from a common base ; others, as the
Botryllus, being arranged in circles round a common central aper-
ture, beneath which the anal extremity of the intestine of each
individual terminates; whilst many of these circles of individuals
are aggregated together, and enveloped in a common cellulose tunic.
The substance of this is. in some species, e. g. Leptodi7ium, crowded
with calcareous granules ; m oih^vs^'Q. ^. Botryllus, it exhibits dis-
tinct fibres.

In fig. 180., from Milne Edwards' elaborate memoir*, the anatomy
of one of the individuals of the species which he has igo ^^^
called Amaroucium proliferum, extracted from the
common investing tunic, is displayed, a is the proper
or muscular tunic, in which most of the fibres are
longitudinal ; it is much more feeble than in the so-
litary Ascidians : c is the oral or branchial orifice ;
e,f, the branchial sac ; e, the anal or cloacal outlet ; it
is protected by the overhanging valve 'i, which is re-
quired by the compound Ascidians on account of the
excretory outlet in the muscular tunic communicating
with a common cloacal cavity in the external tunic,
around which the individuals of the composite series
are grouped : j is the ganglion of the nervous system ;
k, the short and wide oesophagus ; /, the stomach, the
exterior of which is rendered shaggy by the appended
biliary follicles ; m, is the intestine ; n, the anus ;
o is the heart, which, by its remoteness from the
branchial sac, diff"ers more in relative position from
its homologue in the simple Ascidians than any other
viscus ; it is provided with a pericardium 6 : p is,
the ovarium; p" an ovum about to escape through the
cloacal outlet, with the embryo ripe for exclusion.
The most important structural difference between the
aggregate and solitary Ascidians is the combination in
the former of a male apparatus with the ovarium. In ^'"P"""
fig. 180, g is the testis, and r, the vas deferens, which terminates at
r\ in the common cavity of the muscular tunic. In Botryllus the
branchial sac resembles, in its relative size and position to the intes-
tine, that of most solitary Ascidians.

Some of the compound Ascidians are ramified, and their tunics so
transparent as to permit the movements of the internal organs to be
studied in the living animal. A very singular condition of the circu-
lating system has thus been detected.f The blood actually moves

* CCXCIV. t CVII. p. 379.

TUNICATA. 477

backwards and forwards, to and from the heart in the same vessels,
as it was supposed to ebb and flow in the human veins before Harvey's
great discovery. The oscillation of the currents is not constant and
regular ; the blood is received from the vessel at one end of the heart,
and propelled by a contractile wave into the vessel at the opposite
end : after a true circulation has gone on in this course for a cer-
tain period, a change is observed in the course of the peristaltic
contractions of the heart ; the blood for an instant stagnates in the
sinuses and vessels, and then the wave travels in the opposite direction ;
the heart drives the blood into the vessel from which it had before
received it, and the course of the circulation is reversed. In the
compound Ascidians the vascular systems of the different individuals
anastomose freely with each other. The veins are in the condition
of large lacunar sinuses. The heart and vessels circulate blood, not
water: if the vessels, as some contend, had no proper tunics (and
their transparency in the living Ascidians renders them, in most of
the sinuses, invisible), the sea-water which freely passes from the
branchial to the muscular cavities would flow into the so-called inter-
visceral lacunge, were they merely such as they seem.

At first sight it is difficult to conceive how the fixed and compound
Ascidians can multiply their race in situations at a distance from
that which they themselves occupy. This difficulty has been re-
moved by MM. Audouin and Milne Edwards, who observed that
the young of the compound Ascidians were not only at their origin
solitary and free, but possessed the power of swimming rapidly by
the aid of the undulatory movements of a long tail. They were seen
occasionally to attach themselves to the side of the vessel of sea-
water containing them, and then to recommence their course, as if to
seek a more suitable point of attachment. After two days of free
and locomotive life, they finally fixed themselves; and, when de-
tached, remained motionless.

These phenomena are now known to be common to the embryo of
many of the lower sedentary animals. In regard to the Ascidians, it
has been confirmed by Sars in the BotrylU of the coast of Nor-
way * ; by Sir John Graham Dalyell, in a solitary Ascidian of the
Frith of Forth ; and the embryogeny of the Cynthia ampulla has been
well followed out by Prof. Van Beneden.f The solitary Ascidiee are
of distinct sex. In the male a generative gland (Jig. 179, ^), generally
dendritic in shape, occupies the concavity of the intestinal fold, and
sends a short and simple duct to terminate near the anus. In the
female of the Cynthia tuberculata there are two ramified ovaria ;
the ovisacs being appended to the branches of a central stem, passing

* CCXCVl. t CCXCVII.

478 LECTURE XX.

up by the side of the rectum, and extending over one side of the
branchial sac.

In these the ova in different stages of development may be seen.
In Jig. 180., a shows the unimpregnated ovum with the germinal

Development of Cynthia ampulla.

vessel and nucleus. In b, the impregnated germ-cell is multiplying
itself at the expense of the yolk, and inclosing that by a series of
secondary cells. As this process goes on, the yolk, so subdivided and
assimilated, takes on a granular surface, as at c, each granule or
tubercle having its hyaline nucleus. By the coalescence of the peri-
pheral layer of these cells, an external membrane is formed, as d, on
the exterior of which are oil-like globules. An albuminous fluid is
now interposed between the chorion of the egg and the germ-mass.
A filamentary body next begins to be formed from a part of the ex-
terior germ-cells forming the basis of the test ; which body bends
over the visceral mass, e. This body or process progressively elon-
gates, then uncoils itself, liberating the rest of the test with the
visceral mass, and becoming a freely vibrating locomotive caudal
appendage. In the larva, as it may now be called, f, a shows the
anterior part of the body, b what is deemed a rudimental eye, c is
the integument. In the farther advanced cercariform larva, g, the
inner substance of the caudal prolongation is absorbed, leaving the
cellulose sheath empty: the anterior process, «, is produced, and
some traces of a definition of visceral parts may be detected. In h
the caudal appendage is lost ; the stomach and intestine are recog-
nisable. In I the young Ascidian may be recognised as such : a is
the branchial orifice with tentacles ; b is the anal orifice ; c is the eye-
speck still visible, though fading ; d, the oesophageal nervous collar ;
€y the position of a pulsating sinus ;/^/, ciliated circles, which are
rudiments of the respiratory bag ; g, g, are muscular bands.

In the genera PolycUnum and Amaroucium, amongst the com-
pound Ascidians, Milne Edwards has observed that the ovum, whilst

TUNIOATA.

479

still included in the ovarian mass, consists of the small central
germinal vesicle, of a granular vitellus, and a vitelline membrane.
In the progress of the ovum to the cloacal cavity, the yolk acquires
a deep yellow colour, the germinal vesicle disappears, and in its
place there is a nebulous speck upon the surface of the yolk. This
is doubtless the modified germinal vesicle, which has come to the
surface of the yolk to meet the impregnating influence, and has
undergone the changes by fissiparous multiplication, to which I have
so often had occasion to allude. Edwards has observed the contact
of the spermatic animalculse with the ova in the cloaca.

The next stage which he records Is the granular or mulberry
structure of the vitellus. The subdivided mass through which the
properties of the hyaline and fertilising principle have been diffused,
is next covered by what appears to be the expansion of the germ-
spot, or a propagation from that centre of nucleated cells, closely
pressed together into hexagonal forms, constituting what Herold
calls the " cambium " in the spider's ovum, and forming the basis of
the integument. A process of this integument then begins to extend
from a particular point, and, rapidly elongating, wraps itself like a
cord about the vitellus. This body, with its integument, next be-
comes condensed, and separates from the chord, which, retaining
only its basal attachment to the pellucid integument, forms the cau-
dal appendage. The integument {fig. 181, a) increases in thickness.
The extremity of the yolk opposite the caudal attach-
ment developes a series of cylindrical productions.
Three of them have expanded extremities {l)\ h")
which increase in length ; whilst the other processes di-
minish, and finally disappear. A spiral filament is con-
tinued from the membrane of the vitellus down the
centre of the tail.

In this state the embryo escapes from the ovum, gene-
rally while in the cloaca of the parent, but sometimes
after the ^%% has been expelled from the common central
outlet. The young animal immediately unfolds its tail,
and begins to swim like the tadpole of the frog, which
it so much resembles in form. The three clavate cephalic
processes are the organs by which Edwards believes it
effects its final adhesion and settlement. When this has
taken place, the tail shrinks, and is usually detached by
progressively increasing contraction at its base ; — a
kind of spontaneous fission.

The sessile and adherent trunk now becomes the seat of an active
development : the integument is thickened ; the germ-mass becomes
elongated and divided by a circular constriction into two unequal parts,

Larva of
Amarouciuni
prolilVrum.

480 LECTURE XX.

which severally open a passage constituting, the one an oral, the other
an anal, orifice. The subdivided germ-mass, which now begins to
be rapidly metamorphosed into the special tissues, also acquires a
distinct tunic, which soon separates itself from the thick and gela-
tinous external integument. The quadrifid orifice of the branchial
sac is first formed upon the internal tunic. The contour of the great
respiratory pharynx can next be discerned, and the constriction of the
sac opposite to the mouth, which indicates the o^sopbagus. About
the same time may be seen the outline of the anal orifice upon the
internal integument ; then the opaque yellow tunics of the dilated
stomach, and the reflected intestine appear ; and below these parts
the pulsations of the large transparent vasiform heart render that
organ conspicuous. Around each external orifice some mammilloid
processes bud out, which first lengthen, then become lost in the thick-
ening integument. The eye-speck continues for some little time, and
is situated in the middle of the nervous collar. At the base of the
abdomen the opalic concretionary body appears, to which the heart is
subsequently attached, and which is provided with vibratile cilia.

The whole of the viscera included by the smooth integument have
been observed to rotate in the cavity formed by the thick gelatinous
tunic, to which the visceral mass again becomes attached by the ad-
hesion of the muscular tunic at the branchial and anal orifices, and
by the establishment of corresponding orifices in the integument.

Savigny was of opinion, that the ovum of the compound Ascidian
contained the germs of all the individuals composing the characteristic
groups in the mature aggregate animal, and that their development
was simultaneous. In one sense, doubtless, the ovum contains the
germs of all the future individuals developed by gemmation, in so far
as a portion of the germ-mass is retained unchanged in the body of
the first developed individual ; but the cell-progeny of the primary
germ-cell constituting that germ-mass, are not simultaneously deve-
loped : nor does any development begin until the first individual is
completed, fixed, and nourished by the actions of its proper digestive
apparatus. Thus stimulated and strengthened, the second mode of
reproduction, namely, that by gemmation, is superinduced upon the
young Ascidian, after the foregoing development from the impreg-
nated ovum, which offers an interesting analogy to the phenomena
presented by the polype-larva of the Medusa. The individuals
formed by the gemmation of the primary bud of the young Ascidian,
instead of being detached, are retained ; the process of gemmation
being regulated so as to produce the characteristic pattern in
which the diffej'ent individuals are grouped in the mature compound
animal.

TUNICATA. 481

Eysenhardt* has observed the act of gemmation in a simple As-
cidian. In this, as in the compound kinds, gemmation commences
by the development of a small tubercle from the abdominal portion of
the internal tunic of the young Ascidian. This is prolonged, retain-
ing an active circulation in its interior, and is accompanied by a cor-
responding growth of the outer gelatinous integument, which becomes
clavate. The process then bifurcates ; the divisions, in like manner,
becoming elongated, expanded, and bifurcated at their extremities.
Soon the outline of an Ascidian is sketched in each of these extremi-
ties. The primitive connection with the parent is obliterated ; but
the young individuals remain united together by their common
peduncle, according to the law which determines their mode of
grouping into systems. By the progressive increase of their outer
gelatinous integument they coalesce and form the compound mass.

The procreative force of the germ-mass finally exhausts itself in
the formation of the male and female organs ; in which that force is,
again, mysteriously renewed, under its two forms of the sperma-
tozoon and the germinal vesicle, by the combination of which the
reproductive cycle again begins its course. On comparing this course
of development with that in the Bryozoa, p. 151, I may again request
attention to the genetic difference, in addition to the absence of the crown
of radiating tentacles and the presence of the vascular respiratory sac,
which distinguishes the compound Ascidians from the Bryozoa, and
which seems to have been overlooked by those who w^ould call the
latter MoUusks. No compound Ascidian quits the ovum as a ciliated
gemmule, swimming by means of groups of those vibratile organs
aggregated in lobes, after the type of the Rotifera ; and no Bryo-
zoon, so far as I know, quits the ovum in the guise of a tadpole or
cercarian, swimming by the alternate inflections of a caudal ap-
pendage.

If the term Appendicularia should not prove to have been applied
to a caudate larve of some fixed species, that genus will permanently
represent the transitional locomotive stage of the rest of the Asci-
dians. Its organisation does not, however, lead to the next division
of the class.

A connecting link between the Ascidians and Salpians is
afforded by certain compound floating gelatinous Tunicata, e. cj.
the phosphorescent Pyrosoma, the individuals of which are per-
manently aggregated into a compound organic whole having a
definite form, like a flattened cylinder. The common tegumentnry

♦ CCXCVIII. p. 263. t. 30. fig.
I I

482

LECTURE XX.

mass, of which a portion, including three individuals, is shown at A
fig. 183, is toughish and semi-
transparent. The tubercles with
which its exterior is covered,
consist each of one end of an
individual member of the living
group {d d) ; the opposite end
of the individuals b), opens into
the cavity of the cylinder. Be-
sides the common envelope, each
individual has a distinct tunic
or mantle attached at the oral or
branchial orifice (tit, b), at the
anal orifice (6), and also to the
two rounded bodies {h) at the
upper part of the branchiae.
These {f f) are two in number,
oval in form, with their dorsal
borders in contact and attached
to the mantle, and their ventral
borders separated by a large
sinus {i) ; their numerous ves-
sels anastomose at right angles,
and the covering tissue is beset
with vibratile cilia, which per-
form vortex -like movements
with beautiful harmony and
rapidity. The oesophagus is curved, and of a bright red colour : the
stomach {d) is subglobular, yellowish, and opake : the intestine is
short, bent abruptly on itself; the anus {b) directed backwards
towards the posterior orifice. The liver (e) is a globular gland, with
converging segments : it is attached to the intestinal loop. These
viscera are situated posterior to the branchial sac, leaving a free
passage to the water which traverses that cavity. The nerve-gang-
lion (J) lies upon the anterior end of the branchial sac. The heart
is placed at the posterior part of the body, below the visceral mass.
In Jig. c, k represents an ovum, and the part marked g in b, was
supposed by Savigny to be an oviduct : but the precise condition of the
generative organs in the Pyrosoma, is at present not clearly made out.

The second order of the Timicata includes the Salpians, which
float in the sea, and are characterised by their transparent elastic
outer tunic, which is elongated, compressed, and open at both

Pyrosoma giganteum.

TUNICATA. 483^

184

Salpa maxima.

extremities. The efferent orifice {^fig. 184, hi) is simple and tu-
bular : it can be closed by a
sphincter when the outer tu-
nic expands, the water then
flowing in by the opposite
orifice: this is in the form of
a transverse slit, having an
upper lip («) and a lower one
(^) : the latter forms a semi-
lunar valve, allowing the entry
and preventing the exit of water. The muscular fibres of the mantle,
or membrane lining the cartilaginous tunic, are arranged in flattened,
often subannular bands ; their elementary fibre is plicated. The
mouth and stomach, the liver and the heart, are aggregated in a small
mass or ' nucleus' (c), near the anterior aperture of the tunic ; the intes-
tine extends towards the opposite aperture, and terminates freely in the
common cavity of the mantle. The intestine in Salpa gihbosa has
two caeca which project into the centre of the loop. In Salpa zoiiaria,
the liver envelopes nearly all the intestinal canal, and consists of
a mass of caecal tubes, with a few small appendages near their
free ends.* The group of small yellowish ganglia is situated just
above the posterior attachment of the branchia : near it is often
observed a pigment-speck or ocellus (/). A single narrow plicated
ribband-shaped branchia {d) extends obliquely lengthwise across the
pallial cavity. The heart (e) is elongated, and in some species slightly
curved and sacculated ; it communicates with a large vessel at each
extremity, one of which is ramified principally upon the visceral
mass ; the other upon the branchia and the muscular tunics. The
blood passes into extensive venous sinuses before returning to the
heart : its course is oscillatory, as in the Ascidians.

The sexes are distinct in the Salpians, as in the solitary Ascidians.
The testis is described by Krohn as of an oblong form, single, lodged
in the centre of the nucleus in Salpa maxima^ in which it consists of
numerous delicate seminiferous tubes, filled with a white fluid, and
opening by a short canal into the common cavity of the body. The
two oblong bodies, sometimes of a violet colour, attached to the mantle
at the dorsal aspect of the test, have been regarded as ovaria. Sars,
however, affirms that the solitary individuals of the Salpee are sex-
less. The germinative tube, in which the chain of young salpas {Jig.
185.) is contained, winds round the visceral nucleus, hanging freely
by one end in the cavity of the mantle, and being attached by the
other end to the back of the nucleus.

* CCXCIX.
I I 2

484

LECTURE XX.

185

The only conspicuous vital action in the Salpians is the rhythmical
contraction and expansion of the mantle ; in which the elasticity of
the outer tunic antagonises the muscular contraction of the inner one.
During expansion, the sea-water enters by the aperture (a), and is ex-
pelled, in contraction, by the opposite one (6), its exit by the first aper-
ture being prevented by the valve. The re-action of the jet, which
is commonly forced out of a contracted tube, occasions a retrograde
movement of the animal. The currents which successively traverse
the interior of the animal renew the oxygenated medium upon the
surface of the respiratory organ, bring the nutrient molecules within
the reach of the prehensile subspiral labial membrane of the mouth,
and expel the excrements and the generative products. Thus, a single
act of muscular contraction is made subservient, by the admirable co-
adjustment of the different organs, to the performance of the func-
tions of locomotion, nutrition, respiration, excretion, and generation.
The aggregate Salpians quit their gemmiparous parent asso-
ciated together in long chains. In Jig. 185, a^ h indicates part of

the first set of young Salp^e :
c, c?is the second set : e,f\s the
third set: ^is the stem with its
germs: h shows the anterior ori-
fices: 2 2 are the visceral masses;
j j, the ganglia ; k k, the pos-
terior orifice; /, the vessels ; and
m, the muscular band of the
branchial sacs. After floating
for a certain time, each indi-
vidual, as Dr. Chamisso first
discovered, propagates a young
one like itself. The solitary
Salpa propagated by each in-
dividual of the chain, is the
product of an impregnated ovum, and is, for a time, suspended by a pe-
duncle from the dorsal wall of the visceral cavity of the parent. In the
Salpa zonaria, however, as many as three of such pedunculated young
have been found in one parent. When liberated, the solitary Salpa
grows to the size of the grand-parent, and then brings forth a social chain
of young Salpoe, which, by the exercise of their uniparous generation,
again give origin to the solitary and multiparous individuals. Thus, ob-
serves Chamisso, only the alternate generations resemble each other.
The case is strictly analogous to the generation of the compound
Ascidians, of which the solitary young gives origin, by gemmation, to
a connected group, each individual of which again procreates, by
impregnated ova, free individuals.

Aggregated young of Salpa zonaria.

BRACHIOrODA.

48o

BRACHIOPODA.

The Brachiopods, like the Ascidians, are deprived of the power of
locomotion, and are attached by their shell or by a peduncle to
foreign bodies. Their muscular tunic or mantle is, as it were, slit
open, and consists of two broad membranous expansions, called " pal-
lial" lobes, which are covered by, and closely adhere to, two cal-
careous plates, adapted to enclose and defend all the soft parts of the
animal. The branchial sac may be supposed to be equally cleft and
adherent to the muscular one, so as to form the internal vascular
layer of the pallial lobe.

The Brachiopods have left their testaceous remains in the most
ancient deposits known to contain evidence of animal life : they flou-
rished during the palaeozoic and secondary periods, and are most
abundant, and exemplified by the most varied forms, in the fossil
state. They are now, of all MoUusks, the most widely diffused over
the earth's surface, and they can exist at greater depths than most
other bivalves : they are thus amongst the oldest of existing forms of
animal life, and their range in time is as extensive as in space.

Of the few existing genera of this singular and beautiful order of
shell-fish, the Lingula is characterised by its long peduncle, and by
the equality of the valves of its shell, neither of which are perforated :
the Orbicula {Disci?ia, Lam.) is sessile, and adheres by one end of a
short transverse muscle, which perforates the ventral valve of the
shell, which is the flatter valve. The Terebratula {figs. 186 and 187)
is attached by a short peduncle (6), which projects through a hole in
a beak-shaped prolongation of the ventral valve (v), which is the more
convex one. To the dorsal valve (d) is attached the internal cal-
careous process, usually in the form of an elastic loop, and called the

apophysary system (a, h, c, d.fig.
187). The subdivision of the
genus Terebratula*, the most cha-
racteristic of the Brachiopods, and
the type of the most extensive
family of the order, is based chiefly
on modifications of the internal
processes. The foramen in the
ventral valve is usually more or
less formedbyasmall detached part
called the " deltidium." The valves are articulated by two curved

* Dim. of terehratus, perforated.
113

Terebratula flavescens.

486 LECTURE XX.

teeth, developed from the margin of the ventral valve, and received
by sockets in the other: the joint permits only a very slight divari-
cation of the valves.

The viscera are situated at the part of the shell next the hinge or
peduncle, and are confined to a very small space in the Terehratula.
The rest of the interspace of the lobes of the mantle is almost entirely
occupied by two long fringed arms, continued from the sides of the
mouth, and disposed in folds and spiral curves {m). The bases of
the arms are confluent, and form a transverse fringed band above
the mouth : a narrow parallel fold of membrane passes below the
mouth (7^), which opens upon or towards the mantle-lobe attached to
the perforated valve.

In the Terehratula australis each arm extends outwards, advances
forwards, curves slightly inwards, and bends abruptly back upon
itself, the two parts of the bend being connected together; then the
stem again curves forward, and becomes united to the corresponding
bend of the opposite arm, the conjoined extremities describing spiral
convolutions ; the bent portions of the fringed arms are supported by
the slender and elastic calcareous loop {b,Jig. 187), which is bent
back upon itself (c). In the Ter. dorsata the advancing crura of
the loop, beside their basal origins, are attached by two slender
transverse bars to a median ridge of the valve. In Ter, caput
serpentis the crura are united by a slender arch, half way between
their bases and the loop, which is short and not reflected. In The-
cidiiim the calcareous loop is folded into two or more lobes, lying in
hollows of the dorsal valve. In Rhynchonella the apophysary system
is reduced to two short flattened and grooved lamella3 attached to the
inner side of the beak of the dorsal valve. Remains of more com-
plicated internal calcareous appendages are presented by certain
extinct Brachiopods, as the Spirifer. In some species of existing
Terebrattdce, as Ter. (^Rhyncho7iella) psittacea, the arms are wholly
disposed in a series of spiral folds, supported by only the short and
simple calcareous processes at their base. The spiral arms of the
OrbicidcB and Lingulce have no internal calcareous support. In all the
Brachiopods, the stem which supports the brachial fringe is hollow,
and the canal is a closed cavity in each arm. In the Terehratulce and
Orhiculce the spiral terminations of the arms have the canal sur-
rounded by muscular fibres ; the canal is filled with fluid, and, by the
contraction of these fibres, the extremities are extended by the pres-
sure of the contained fluid which is injected into them.

In most TerebratuUdcB the [shell is traversed by minute canals
from one surface to the other nearly vertically and at regular dis-
tances; their external orifices are slightly expanded. The adhesion

BRACHIOPODA.

487

187

of the mantle to the shell is due to the penetration of these pores by-
minute tubular processes of the external layer of the mantle *, which
are covered externally by the epidermis. The free borders of the
mantle-lobes are usually fringed by fine bristles, setigerous in Tere-
hratula\^ jointed in Lingula.\

The muscular system is very complex. Taking the ventral or
perforated valve, to which the peduncle is directly attached, as the
more fixed point, the adductorcs longi {Jig. 187, e,f) arise from a

single pyriform area at the middle of
that valve, a little behind a line trans-
versely bisecting it ; the fibres soon
become tendinous, converge, and
group tliemselves into two lateral
muscles forming a pair ; each of these
muscles, as it approaches the oppositti
valve, expands and subdivides into an
anterior and posterior portion; glides
between the stomach and the crus of

Teiebratula flavescens. tllC CalcarCOUS loop of itS OWn sidc (i),

and is attached by the double expanded insertion into the dorsal or
perforated valve (d), the anterior division {f) is the " adductor longus
anticus," the posterior one (e), "adductor longus posticus;" but
both of the so-divided adductors, by reason of their ventral confluent
attachment, may be regarded as constituting one quadricipital muscle.
The action of this complex muscle is directly to close or adduct the
valves, in which action it will slightly compress the hepatic lobes
and stomach. The adductor brevis (g) forms a symmetrical pair,
having their expanded disc of attachment to the ventral valve ex-
tended somewhat in advance of the confluent origin of the preceding
muscles : the fibres of each pass obliquely backwards, and converge
to a small round shining tendon, the tendons passing on each side
the intestine to be inserted close together into the cardinal process
of the dorsal valve (d). Their action will be to adduct the valves ;
but with a more oblique movement bearing upon the ventral valve

* Carpenter, Report on the Microscopic Structure of Shells, Part II., Trans.
Brit. Association, 1847, p. 93. " In these tubes, as will hereafter be shown,
certain coecal appendages of animal membrane are situated." — Quekett, " Histo-
logical Catalogue," vol. i. 1850, p. 270. In the same work it is shown that
•' each perforation has a series of radiating lines or tubes on its outer margin "
(p. 270). The corresponding part of the membranous tubes would resemble a
terminal brush of vibratile cilia.

t CCCL pi. 23. fig. 13. X CCCVIII. taf i. fig. 13.

II 4

488 LECTURE XX.

(v), which they, as it were, help to suspend from the hinge/as from a
fixed point.

A third pair of carneo-aponeurotic muscles (h), which pass from
valve to valve, have both extremities nearer the hinge, and, by com-
pressing the sides of the base of the peduncle, may aid in protruding
that part after it has been forcibly retracted : these " musculi cardi-
nales,'^ or hinge-muscles, are attached by their smaller and most
tendinous extremity to the linear ridge between the hinge-teeth
cavities and hinge plate in the imperforate valve. They arise by
their larger and more fleshy ends from the imperforate valve, close
together, behind the common attachment of the adductores longi, the
rectum alone intervening ; some of their fibres appear to be lost upon
the sides of the sheath of the peduncle. The proper muscles of the
peduncle consist of two pairs, for its retraction and attachment to the
valves ; and of some circular or transverse fibres of the sheath,
which, though for the most part of an aponeurotic character, appear
to be arranged so as to act as compressors and elongators, or pro-
trusors, of the peduncle.

The name retractor inferior (^) is given to a pair of muscles which
arise from the ventral valve by a thick carneous end, exterior to the
"adductores longi " and '^brevis:" the fibres pass obliquely back-
wards, and rapidly diminish to a tendon which penetrates the upper
and lateral part of the sheath of the peduncle, and the terminal fibres
of which appear to constitute part of the peduncle itself. This pair
of muscles serves to suspend the Terebratula by means of the perfo-
rated valve to the peduncle, and forms the most direct retractor of
that part, and consequently the chief agent in such limited move-
ments, as the fettered state of the shell will allow.

The name '^^ retractor superior ^^ (i) is applied to a pair of muscles
which have a broad subtriangular carneous origin from the hinge-
plate, and a strong aponeurosis extending therefrom to the crus of
the calcareous loop {a) ; the fibres curve over the sides of the swollen
part of the capsule of the peduncle (/), penetrate the capsule, interlace
with the inserted fibres of the inferior retractor, and terminate for
the most part in the peduncle.

Some not very clearly defined, partly carneous, chiefly tendinous?
fibres, which interlace, running mostly in the transverse direction
upon and in the capsule of the peduncle, and make up, in fact, a chief
part of its substance, have a transversely oblong surface of attach-
ment or strong adhesion to the lower part of the bent conical pro-
longation of the ventral valve lodging the peduncle : this surface
appears in the exterior of the soft parts of the Terebratula, behind

BRACHIOPODA. 489

the origins of the cardinales muscles. I have proposed the name of
^^ capsidaris,'' for the sum of the carneo-tendinous fibres which have
the attachment in question.* In conjunction with the completely
encircling fibres of the peduncular capsule, they must compress and
elongate the peduncle.

In addition to the muscles arranged in the more or less definite
masses above described, there must be enumerated the fibres
which are lodged in the walls of the canal {Jig, 186, m) travers-
ing the stems of the fringed arms ; and the muscular fibres of the
pallial lobes, which latter are extremely feebly developed, and recog-
nisable only near the periphery. Thus, to recapitulate the designa-
tions of the several muscles in the Terebratula, as demonstrated by
dissections of the Ter. chilensis, Ter, psittacea, and Ter. jiavescens^
there may be enumerated the —

Adductor longus cmticiis,

Adductor longus posticus,

Addtictor brevis,

Cardinalis,

Retractor superior.

Retractor inferior,

Capsularis,

Brachial muscles,

Pallial muscles.
The first seven muscles leave more or less recognisable impres-
sions on the interior of the valves; the marginal muscles of the
mantle are too feebly developed to mark the shell, as it is impressed
in the Lamellibranchiate bivalves.

In the Lingula the homologue of the adductor brevis is situated at
the peduncular end of the shell ; it is very short and thick, and
passes from one valve to the other. The adductor longus posticus
arises from by a common origin on one side and by two origins on
the other side of the visceral mass, behind the middle of the sliell.
They pass obliquely to the opposite valve, the single muscle gliding
between the fasciculi of the divided one.'f Each adductor longus
anticus arises single from the ventral valve, near the fore part of the
visceral mass, and divides as it passes obliquely to the dorsal valve,
the divisions decussating, but being inserted close together. The
arrangements of these powerful adductors are such as to effect sliding
movements of the valves on each other, besides closing the shell, and
to compress and variously affect the interposed viscera and visceral
lacunae with their contained sinuses. The long pedicle of the Lin-

* CCCIII. t CCC. pi. vi. fig. 13.

490 LECTURE XX.

gula has a stratum of muscular fibres. For the modifications of the
muscular system in Orbimda, I may refer to my monograph on its
anatomy.* The four adductor muscles are distinct at both ends in
that genus and in Crania.

In Terebratula the fringed portions of the spiral arms are not
immediately supported by the loop ; this serves only for the attach-
ment of the thin but firm aponeurotic membrane which forms the
true basis of support of the beautiful and peculiar organs in ques-
tion.

The aponeurotic fold supporting the basis of the arms is perforated
by the oesophagus, the mouth opening downwards into the pallial
cavity below the beginning of the spiral fold : the alimentary canal
bends backwards over the basal fold, after perforating it ; the fold
thus intervening between the oesophagus and intestine. The fila-
ments given off from the beginning of the arms, supported by the
basal fold are shorter than the rest. The aponeurosis, reflected from
the lateral to the spiral folds, forms the fore-part of the small visceral
cavity ; the pallial membrane is continued from the union of the
lateral with the basal folds, is stretched over the visceral inter-
space between the advancing crura, and is then continued backwards
towards the hinge, protecting the hearts and sinuses behind the trans-
verse fold. The lateral folds decrease in breadth as they advance
forwards : the spiral fold, which, at its beginning, is broader than the
broadest part of the lateral folds, gradually becomes narrower as it
approaches the termination of the spire. The lamellae of the several
above-defined parts of the aponeurotic supporting and connecting
brachial folds, separate when they reach the calcareous plate, and the
hollow muscular stems of the fringed arms closely surround and
adhere to these stems, being continued thence upon the border formed
by the roots of the fringe-filaments, where the aponeurotic character
is exchanged for that of a delicate membrane, which is finally lost
upon the filaments themselves.

The fibres of the muscular walls of the brachial canal {Jig. 186, m)
are arranged in a decussating double spiral, evidently adapted for
compressing the contained fluid, and thereby reacting upon the arm
of which the muscular canal forms the base. In the Terebratulidce,
like Rhynchojiella psittacea, with free multispiral brachia, the fluid of
the canal being acted upon by the spirally-disposed muscles compos-
ing its parietes, is forcibly injected towards the extremity of the arm,
which is thus unfolded and protruded outwards. In the species
resembling Ter. flavescens, the spiral portion may also be, in like

* CCCI. vol. i. p. 149.

BRACIIIOPODA. 491

manner, so far unfolded as to react upon the closed valves of the
shell.

What power the animal may possess of further unfolding and pro-
truding the free extremity of the united spiral portions of the arms,
can only be determined after careful observation of the living Tere-
hratulce in their native localities. The structure of the parts in
question led me to note, in 1833, the important difference between
Lingula and those species of Terehratula which resemble Ter. chi-
lensis in the structure of the arms, "since, from their attachments,
they are fixed and cannot be unfolded outwards as in Lingula.''*

The muscular stem, by means of its attachment to the calcareous
loop (Jig- 187, a, b, c), has the power of acting upon that part to the
extent its elasticity admits of, which is sufficient to produce such a
degree of convexity in the reflected part of the loop, as to cause it to
press upon the perforated valve, and separate it slightly from the
opposite one. Observations on ''living Mollusks are, however, essen-
tial to the formation of adequate and exact ideas of the uses of parts
of the several muscular parts of their organisation.

The fringe-filaments of the produced and reflected portions of the.
brachia are in a single series ; they are compressed, very narrow,
close set, with their f]at sides to^vards each other, very gradually
tapering to the extremity which is slightly bent, the rest of the fila-
ment being usually straight : those(^^. 186, m)of the spirally-disposed
portion are split at the end, and the split is deeper as the filaments
are situated nearer the end of the spire, where they appear thereby
to be arranged in a double row. In most specimens the filaments of
the spire incline towards each other, and meet at their extremities,
inclosing a triangular space or channel. The curve of the spire is
towards the dorsal valve at its commencement ; and this, with the
dorsal aspect of the transverse base of the arms, serves to determine
the dorsal valve in Orbicula and Lingula. By Cuvier"|* the spiral
arms of the Brachiopods are compared with the tentacles of the
Cephalopods : by Siebold to those of Bryozoa (AlcyonellaX) ; perhaps
the true homology lies midway : the closer connection of the soft un-
calcified base of the arms to the mouth, in Lingula, seems transitional
to the long labial tentacles of Anomia.

The nervous system of the Terebratula consists of three principal
parts, the " pallial," " brachial," and " visceral." The roots or origins
of these three systems centre in the oesophageal ring.§

This annular centre is situated in and defended by the basal fold

* CCCI. vol. i. p. 149. t CCC. Mem. sur la Lingule, p. 4.

X XXIV. p. 260. This idea is reproduced in CCCIX. p. 117.
^ CCCIII. C, pl- ii. fig- 1.

492 LECTURE XX.

of the brachial aponeurosis, surrounding the aperture by which the
CEsopbagus penetrates the visceral chamber. A few very delicate
filaments pass off from the part of the ring which is turned towards
the aperture of the shell, and which part, from the downward bend
of the mouth, is made anterior, instead of being, as in the normal
position of the mouth, " dorsal." These filaments are lost in the be-
ginning of the spiral connecting fold, the brachial arms thus receiving
some of their nerves from the same part of the oesophageal ring, as
the antennse do in insects, and the cephalic tentacula in the higher
Mollusks. The two chief nerve-trunks from the ring come off from
its lower and lateral angles ; a very slight swelling, hardly to be
called a ganglion, occurring at their origin. Each of these trunks
quickly divides, one division going to the mantle, the other pene-
trating the base of the fringed arm of its own side. The pallial
trunk is the largest ; it soon divides to supply the upper and lower
mantle-lobes of its own side : the course of that distributed upon the
dorsal lobe is shown in Plate IL Jig- 2 of CCCIII.

The dorso-pallial nerve extends a short way upon it, and then
expands into what appears to be an oblong narrow ganglion ; but
which is a loop formed by the slight divarication and reunion of the
fibres of the trunk. From this loop most of the pallial filaments
diverge. In their course towards the margin of the lobe they cross
obliquely the great pallial sinus, and give off branches, most of
which correspond with the branches of the sinus, these branches
subdividing, and their ramifications appearing to unite in a common
circurapallial nerve which runs along the inserted bases of the mar-
ginal cilia. The brachial nerves may be traced some way along the
muscular canal of the fringed arms. Two delicate filaments which
traverse part of the visceral chamber come off from the lower part of
the oesophageal circle near the origins of the great pallio-brachial
trunks ; they probably supply the muscles which traverse the visceral
chamber, as well as the hearts and alimentary canal. In Lingula
the visceral nerves are more developed. Tliey are shown i^./jg- 3,
PI. II., CCCIII. Filaments to the muscles are also more distinct : a
pair, which come off from the suboesophageal ganglion, diverge as they
pass backwards along the visceral chamber, then converge to their
insertion in the anterior muscles ; a second pair, also from the sub-
oesophageal ganglions, run more parallel as they pass along the
ventral aspect of the anterior muscles to go to the posterior muscles.
Lingula has also the pallial and brachial systems of nerves as well
developed as in Terehratula. I have not been able to detect any
traces of special sen?e-organs in the Braohiopods.

BRACHIOPODA. 493

The mouth {fig. 186, ?0 ^^ ^^ Terebratula is situated in the middle
line, about one-third of the length of the shell from the hinge ; it
opens downwards, towards the ventral valve, at the base or beginning
of the passage formed by the spiral brachial fold and the converg-
ing fringes of the brachial spire;, it has a tumid and sub-bilobed
upper or anterior lip, and a thinner and broader lower or posterior
lip, which is attached to the basal portion of the fringed arms
uniting the central portions. The swollen margins of the mouth
are formed by both muscular fibres and secerning cells : there are
no rudiments of a maxillary or dental apparatus. The organic
molecules subserving the nutrition of the Brachiopods are brought
by ciliary action within reach of the mouth, are there seized and
swallowed. In Orhicula the mouth is opposite the centre of the
perforated valve ; in Lingula it is nearer the fore part of the
sheU. The oesophagus in Terebratula is short, of uniform diameter,
has a delicate membranous outer tunic, a muscular coat, and a thicker
epithelial lining than that of the rest of the alimentary canal. It
inclines slightly forward as it ascends, between the anterior portions
of the liver, to terminate in the stomach, where it is slightly con-
stricted. The stomach (o) is a curved oblong cavity, swelling out
slightly at the cardiac end, where it receives the biliary secretion,
continuing thence for some way of the same diameter, which is rather
more than half its length ; and gradually contracting to the pylorus.
Its tunics consist of an outer membranous, a muscular, and a smootli
inner mucous coat, the epithelium of which is more delicate than in
the cesophagus. The whole cavity is bent down at an acute angle
with the oesophagus, and the cardiac half is buried in the large
granular liver (ib. q). There is no valvular structure at the pylorus :
but in some specimens it presented a slight circular constriction.
The intestine is short, straight, and is continued downwards and a
little backwards, in a line with the pyloric part of the stomach to the
interspace between the attachments of the adductores longi and car-
dinales to the ventral valve, where the minute vent opens into the
pallial cavity. It does not perforate the capsule of the pedicle. The
faeces are carried out by the pallial and brachial currents.* The
intestine is enveloped to within a very short distance of the vent by
an extremely delicate venous sinus, the outer wall of which is con-
nected with the plicated auricles (ib. r) situated on each side of the
gut, a little above its middle. The muscular tunic of the intestine

* Mr. Huxley (CCCIX. p. 108) has been unable to find this vent, and describes
the anal end of the intestine as imperforate. There may be blindness somewhere,
but I think not at the termination of the intestine of Terebratula, any more than
in Orhicula and Lingula.

494 LECTURE XX.

presents the same uniform thickness as that of the stomach. The
muco-epithelial lining membranes are disposed in very delicate
transverse plaits. In Orhicula the intestinal canal is somewhat
longer, bends to the right side, where the vent opens into the pallial
cavity near the right anterior adductor. In Lingula the intestine
is still longer, forms two bends before it extends forwards to ter-
minate at the right side, in the pallial cavity.

The liver {q) is about three times the bulk of the stomach, and
forms the most conspicuous of the chylopoietic viscera, when the
abdominal cavity is exposed. It consists of very numerous ramified
follicles, the terminal ones of which are of equal tize, and their round
closed ends give the apparently granular exterior surface to the
gland : the intimate structure of the hepatic follicles in Ter.flaves-
cens agrees with that described in my earlier Memoir*, in Ter.
psittacea and Ter. chilensis. There is no natural division into lobes ;
a slight pressure suffices to displace groups of follicles, which then
assume the lobular character. The ducts form the common stems of
the manifold ramifications, and they are usually two in number, com-
municating, each by a distinct aperture, with the cardiac end of the
stomach.

The vascular system of the Brachiopods is peculiarly well adapted
to demonstrate that remarkable condition of the veins in the Mollus-
cous class which, w^hen first and somewhat imperfectly observed, gave
rise to the idea of the blood being extravasated into the lacunse of the
viscera and the interstices of other soft parts and tissues.

Such is the condition of the major part of the vascular system in
the Terebratulce. The hearts are two in number, and distinct ; they
consist, as in other Brachiopods, each of an auricle f and a ventricle,

* CCCI.

f This organ was first described in my Lectures of 1843 (Lecture XX., deli-
vered May 11., published June (No. IX.) of that year), as '• a small transversely
plicated membranous process, continued from each side of the beginning of the
intestine." In the same year, 1843, M. Vogt communicated a memoir on the
Anatomy of the Lingula anatina to the " Allgemeinen Schweizerischen Gesell-
schaft," at Neuchatel, in which he described the homologous part as follows : —
" Upon each heart lies a peculiar sac, unseen by Cuvier and Owen, but plainly
visible in my specimens. This sac lies with its under concave smooth border
upon the upper convex surface of the heart, and its free upper border is folded
like a shirt-frill. The sac is depressed and hollow : at the connecting line of the
folds, where this rises teat-wise (zitzenartig), there is a fissure, which leads to an
extremely delicate canal, whose further continuations I could not follow; but
it seemed to me that it opened externally between the two lobes of the mantle,"

No other relation of this sac to the heart is recognized, save its contiguity or
contact with that organ : respecting the heart itself, M. Vogt repeats the descrip-
tion by Cuvier, viz. that there are two, and he expressly states that they are

BRACHIOPODA. 495

and are situated In the Ter. flavescens, at the back part of the
visceral cavity, on the dorsal aspect of the intestine, one on each
side of its upper or anterior half. If the dorsal valve and corre-
sponding lobe of the mantle be removed, and the " musculi retractores
superiores" be gently divaricated, or the mesial fasciculi carefully
removed, the delicate membrane of the venous sinuses, continued
from the margin of the basaV aperture of each auricle, is immediately
exposed, and is so transparent as to permit the plicated structure of
those cavities to be clearly seen.* If the viscera be exposed by a
side view, as m Jig. 186, the heart (r, s) of the side exposed will be
seen behind the beginning of the intestine.

The ventricle in each heart is a smooth, feebly- muscular cavity,
from which are continued what have appeared to me to be arteries |;
the largest ramified on the two halves of the mantle lobes nearest
the ventricle, the smaller one proceeding to the viscera and muscles.

The auricular cavity consists at the half next the ventricle of a
plicated muscular coat, in addition to the membranous one ; but
at the other half, next the venous sinuses, of venous membrane
only : the latter might be termed the auricular sinus, the former
the auricle proper. The proper auricle presents the form of an

" simple, thin-coated, pyriform sacs." " Es sind einfacke dunnhautige, birn-
formige Sacke." Vogt subsequently (" Zoologische Bi-iefe," 1851, yoI. i. p. 285)
recognised the auricular character of the part, in Lingula, which is so described
in Terebratula (CCQll. 1845, p. •>92).

Mr. Huxley, who erroneously, as he afterwards acknowledged, ascribed this
discovery to Vogt, specifies it as " the true complex structure of the heart."
(CCCIX. p. Hi.)

* CCCIII. pi. iii. 1,1.

f The best demonstration I have been able to make of the vascular system is
that shown in the injected preparations 998 A and B (X. vol. ii. p. 74), and more
particularly described in CCC I. (1835), p. 154. "In one of the specimens (of
Orbicula) I succeeded in injecting the vessels of one lobe of the mantle from one
of the ventricles ; in this injected preparation there evidently appeared a small
uninjected line {n' fig. 13), as in the Terebratulce, accompanying each of the larger
branchial veins, running along the centre of every trunk ; and these lines I con-
clude to be branchial arteries ; if they were retractile muscles of the mantle, tht-y
might be expected to have a straighter course."

If it be true that Mr. Hancock has " arrived at the conclusion that no such
arteries exist" (CCCIX. p. 112) in the sense that the ramified filaments above
described have no existence, I feel no doubt that renewed examination by that
excellent observer will convince him of the accuracy of my descriptions and
figures (CCCL pi. 22, fig. 11, pi. 23, fig. 11.) The interpretation of the nature
of the parts is another matter. Vogt adopts my original idea. He figures the
homologous part (CCCVIII. tab. ii. fig. 14. b) as a ' blutgefass.' In all my me-
moirs I have called attention to the relation of the generative parts to the pallial
vessels, and I have figured the ovaria as being developed from the so-called
arteries, in CCCIII. pi. 2, fig. 2, 11.

496 LECTURE XX.

oblong depressed cone, attached by its apex to the ventricle, the
apex being perforated by the auriculo-ventricular aperture, and
adherent by its base to the auricular sinus, which might be said to
conduct into the common peritoneal cavity, since the delicate tunics
of the visceral sinuses appear to take the place of a peritoneum.
The auricular walls are disposed in small plaits or folds, radiating
from the apex : and the longitudinal or radiating folds are puckered
by transverse folds. The figures ii and iii, pi. 3, of CCCIII., which are
magnified to the same degree, exemplify two of the different states
in which the plicated auricles are found in different individuals, and
so far exemplify the extent of dilatation and contraction of which
these complex cavities are susceptible ; but they have presented
more extreme diff'erences of size in other specimens, and they must
possess considerable powers of altering their capacity. It is, there-
fore, probable, that, when the circulating fluid is accumulated in
unusual quantity in the pallial and visceral sinuses, the longitudinal
auricular fibres evert and expand the margins of the basal aperture
to which the delicate tunic of the sinuses is attached, that the fluid is
drawn by a kind of vermicular movement or peristaltic suction into
the auricles, and thence propelled by successive contraction of tlie
circular fibres into the ventricles. From the ventricles the blood
may be driven through the ramifications of the pallial and visceral
vessels into the more or less irregular and capacious sinuses, and so ,
returns slowly back to the heart. The auricles are relatively smaller
in Lingula than in Terebratiila.

The part of the vascular system wliich most conspicuously presents
the usual ramified form, is that which is on the inner layer of the
mantle. In Terebratula and Orbicula the branches are given off
from four trunks on one pallial lobe, and two trunks on the other lobe :
they terminate at the periphery in a cicumpallial vessel. In Lingula,
there are two trunks on each lobe, which are longer and their branches
are more regular and parallel, and some of them terminate in blin<l
ends. The primary external parallel branches in Lingula Andehardi
give off" a series of short loops or caeca.* In all a more slender body f
accompanies the larger vessels throughout their ramifications : in all
the generative cells (testes or ovaria) are developed within the pallial
vessels and apparently from the more slender ramified body.J

Wherever the blood is exposed in its delicate vessels and sinuses
to the sea-water, a respiratory action must go on ; most actively at
the part where the blood is most subdivided, viz., at the ciliated

* CCCI. pi. 23. fig. 16.

t CCCI pi. 22. fig. 11. pi. 23. fig. 11. CCCVIII. tab. ii. fig. 14 h.

X CCCI. pi. 22. fig. 1 6.

BUACIIIOrODA. 49?

border of the mantle. The larger pallial vessels, and especially
those that terminate by closed ends in Lingula, may be regarded as
generative rather than branchial vessels, i. e., as being chiefly con-
cerned in nourishing and affording pabulum to the generative
cells. In Lingula and Orbiciila, the pallial trunk is continued
from the ventricle. The visceral chamber, in all Brachiopods, is
occupied by larger and less regular venous sinuses, which seem to
form a complex peritoneal cavity. The sinus which surrounds the
intestinal canal, is figured in CCCIII. pi. \',Jigs. 5 & 6, 8 {Lingula),^\.
Z, figs. 1, %, (^Terebratula) : the communication of this and other
visceral sinuses with the plicated auricle in Terebratula is accurately
represented in pi. Z^fig. \, of the same monograph.

The course of the circulation can only be determined by observa-
tion of the living Brachiopod : it may be subject to oscillations, as in
the Tunicata. Whatever its course, there is no actual extravasation :
I find, after the most patient scrutiny, no evidence of an escape of
the blood into mere lacunce or interspaces excavated in the tissues of
other and surrounding systems ; but the result of such scrutiny has
been, invariably, the detection of the continuation and expansioix of
the proper tunic of the veins into such seeming lacunae or interspaces.
And although, in the wide clefts between the viscera and muscles in
the abdominal chamber, the tunic of the sinuses is disposed like a
peritoneum, seems to perform, also, the function of a peritoneum, and
the contained fluid, that of peritoneal serum, in addition to their own
more proper and important offices, and although an anatomist might
be permitted, by such similarity of function, to call the cavities of
the sinuses " intervisceral lacunse," and the walls of the sinuses "pe-
ritoneum,"— yet, if he were guided in his nomenclature by con-
siderations of homology instead of analogy, he would more correctly
term them " abdominal venous sinuses" and " venous tunic" respec-
tively. In either case, as a matter of fact, there is no real or essen-
tial departure from a circulation in a closed system of vessels ; but
only a morphological departure from the typical character of the
organs of circulation, — an extreme one, it is true, but little likely to
lead astray the zootomist who had been prepared for such formal
modifications of the vascular system by the discoveries of Hunter, as
they are manifested in his preparations, and by the descriptions and
figures of such preparations, of the venous system in the classes
of Insects and Crustaceans.

The absorbent system, as Cuvier truly states*, is wanting in
molluscs. In the comparatively low organised order under consider-

* CCCXXI. p. 300.

K K

498 LECTURE XX.

ation the clijle or product of digestion must transude through the
intestinal tunics into the intestinal sinus*: all the fluid answering to
lymph, from other parts of the organisation, will be received into the
intervisceral, intermuscular, and pallial sinuses, which will perform
the double but closely allied functions of veins and absorbents.

The streams of sea-water excited and maintained by the complex
ciliated structure of the mantle f, will effect the requisite respiratory
changes as they course over the delicately coated, branched vessels
of the pallial lobes ; these, therefore, form the chief seat of the
breathing function ; but, wherever similar currents come in contact
with the vascular system, to that extent the respiratory operations
will be diffused. In CCCIII. I suggested that the minute caecal pro-
cesses continued from the mantle into the shell-tubes " might perform
an excretory function and be associated in that action with the de-
purative respiratory office of the mantle, the probable condition of
their development being the low grade of the proper branchial organi-
sation." (p. 4.) Dr. Carpenter, believing that certain corpuscles which
he has observed in the caecal processes are blood-corpuscles, deems it
not improbable " that the apparatus in question is branchial in its
nature." J

The generative organs present the same form in the Terebratulce^
OrhiculcB, and Lingulce, and correspond with that of the pallial
sinuses in which they seem to be situated. The figures 15 & 16 r, r,
pi. 22, CCCL, and fg. 2, pi. 2, CCCIIL, represent the general
form and disposition of these organs in Terebratula, I have
observed, however, a manifest difference of texture and colour in
the generative organs of different individuals of Ter. fiavescens
collected at the same period. In some specimens the organs are
better defined, more compact, and of a paler colour : in others
the organs are broader or more diffused, and of a deeper yellow
colour. On a microscopic examination of the first kind, they
are found to consist of an aggregate of minute cells, closely
resembling those in the half mature testes of the common oyster.
I conclude, therefore, that they are the male generative organ in the
Terebratul(Bi and that the individuals of this genus are dioecious,
not, as I formerly supposed, simple hermaphrodites. § The true ova are
very plainly manifested in the broader and deeper-coloured dendritic
organs. They are developed, like the sperm -cells, between the mantle
and the delicate tunic of the venous sinus, apparently form the accom-
panying branched organ, and protrude into the sinus, pushing its

* CCCIir. pi. 1. 2. 8. t CCCI. pi. 23. fig. 13. CCCVIII. tab. 1. fig. 13.
X CCCX. p. 36. § CCCI.

BRACnioroDA. 499

lining membrane inwards. The generative organs, in the male, as
in the female, developed in the ventral lobe of the mantle, commence
— if we may term the part next the hinge of the shell their beginning
— by a loop on each side of that lobe, situated at the point of bi-
furcation of the two sinuses ; these loops are shown in CCCIII.,^^. 1,
pi. 3, the inner layer of the mantle, with the adherent tunic of the
sinus, being reflected to show the looped portions of the ovaria (12, 12).
In the dorsal lobe the generative organ commences at about the same
distance from the hinge, by a simple obtuse extremity, and follows,
as it advances, the ramifications of the sinus in which it is lodged.
There are thus four distinct ovaria or testes, two in each mantle lobe ;
those of the ventral lobe being doubled, or bent upon themselves,
near the cardinal-attached border of the lobe. It may be presumed
that the embryos developed under the influence of their suspension in
the aerated and nutrient fluids of the pallial sinuses, escape, at a certain
stage of that development, by dehiscence, at or near the free ciliated
border of the pallial lobes. The course and phenomena of this de-
velopment would form a most interesting and acceptable subject to
a competent microscopical observer favourably situated for pursuing
it throughout the breeding season of the Terehratulce. I have ob-
served the following stages in ova taken from the ramified pallial
ovarium of a Lingula, preserved in spirits. CCCIII, pi. l^Jig 7, «,
shows an impregnated ovum, in which the germinal vesicle or vesicles
have disappeared, and the germ-mass has been formed, occupying the
entire ovum, which has assumed an oblong form : a peripheral stratum
of the derivative germ-cells was more compact and of a somewhat
lighter colour than the central mass. lb. 5, shows the formation of
a smooth membrane, probably covered by ciliated epithelium, around
the germ-mass : lb. c is a transverse section of such an ovum, show-
ing its triedral figure : lb. d is an ovum further advanced, with the
rudiment of a peduncle : lb. e, an embryo with the peduncle more
produced. I could distinguish no organs in these embryos of the
Lingula : there was no trace of shell. Thus the LingulcB are pro-
vided with a peduncle before they quit the parent.

On comparing together the existing genera of Brachiopods we
may perceive that the modifications which are traceable in their
respective organisations bear relation to the different situations
which they occupy in the sea.

The Lingula, living usually near the surface, and sometimes where
it would be left exposed by the retreating tide, if it were not buried
in the sand of the shore, must meet Avith a greater variety and
abundance of animal nutriment than can be found in the deeper
waters, where the Terebratula usually resides. Hence its powers of

K K 2

500 LECTURE XX.

prehension are greater ; and Cuvier suspects tliat it may even enjoy
a species of locomotion from the superior length of its peduncle. The
organisation of its mouth and stomach indicates the molecular
character of its food ; but its convoluted intestine shows a capacity of
extracting a quantity of nutriment proportioned to its superior
activity and to the greater extent of its soft parts. The more ex-
tended pallial respiratory apparatus is in exact harmony with the
above conditions of structure and habits.

With regard to the Orhicula, and more especially the deep sea
species of Terebratula, both the respiration and nutrition of such
animals which exist beneath a pressure of from sixty to ninety
fathoms of sea-water, are subjects suggestive of interesting reflec-
tions, and lead one to contemplate with less surprise the great
strength and complexity of some of the minutest parts of the frame of
these diminutive creatures. In the unbroken stillness which may
pervade those abysses, their existence must depend upon their power
of exciting a perpetual current around them, in order to dissipate tlie
water already laden with their effete particles, and to bring within
the reach of their prehensile organs the animalcules adapted for their
sustenance. The actions of the Terebratula and Orbicula, {rom their
attachment to foreign bodies, are confined to the movements of their
brachial and branchial fringe cilia, and to a slight divarication and
sliding motion of their protecting valves ; the simplicity of their
digestive apparatus, the still greater simplicity of their branchiae,
and the diminished proportion of their soft to their hard parts, are in
harmony with such limited powers. The soft parts, in both genera,
are, however, remarkable for the strong and unyielding manner in
which they are connected together. The muscular system is much
more complex than in ordinary bivalves, and is remarkable for the
compactness of its fibre and the density of the glistening tendons.
Here is obviously an apparatus of sufficient power to effect the
requisite motions of the valves at the depth of which they may be
destined to live. The TerebratulidcB and SpiriferidcE have an internal
.skeleton superadded to the bivalve defensive covering, by means of
which additional support is afforded to the shell, a stronger defence
to the viscera, and a firmer basis of attachment to the spiral arms.

Class TUNICATA.

Body unsymmetrical, with an uncalcified tegument in form of a
tunic, having two openings, and lined by the mantle ; oral tentacles
rudimentary or absent ; no foot.

Generation by gemmation alternating with impregnated ova.

BRACIIIOPODA. 501

Order Saccobranchiata.

Mantle united to the tunic at the two orifices ; elsewhere com-
monly more or less detached. Branchia, a dilated vascular sac, with
a tentacular orifice.

Family Botryllidce.

Body fixed : tunics of many individuals fused together into a mass,
in which the individuals are grouped into systems.

Genera Sigillina, Polyclinum, ApUdiiun, Amaroucium, Diazona,
Didemnum, Leptoclinum, Botryllus.

Family Clavellince.

Body fixed; individuals connected by repent tubular prolongations
of their common fused tunics.
Genera Clavellbia^ Perophora.

Family AscidladcB.

Body fixed : individuals gregarious or isolated.

Sessile Genera. Ascidia, Cyathia, Dendrodoa. Chelyosoma.

Pedunculated Genera. Boltenia, Cystinyia^ Bipapillaria,

Family PelonaiadcB.

Mantle adhering extensively to tunic, which is usually buried in
mud.

Genus Pelonaia.

Family Pyrosomidce,

Body floating : tunics of many individuals fused into a cylindrical
mass, in which they have a verticillate arrangement with two ori-
fices, one £t't the extremity next the outside, the other at that next
the inside, of the common cylinder.

Genus Pyrosoma.

Order TiEXiOBRANcniATA.

Mantle adhering throughout to the tunic. Orifices without ten-
tacles. Branchia ribband-shaped. Individuals connected, chain-
wise, in one generation, solitary in the next : free and floating.

Genus Salpa.

Class BRACHIOPOBA.
Body symmetrical, with a dorso-ventral bivalve shell, lined by a

K K 3

502 LECTURE XX.

closely adherent mantle of two widely separated lobes. Oral tentacles
two, long, fringed, usually more or less spirally disposed.

Family Terehratulidce.

Ventral valve with a prominent notched or perforated beak, and
two curved hinge-teeth : dorsal valve with a depressed umbo, a
cardinal process between the dental sockets, and an internal calca-
reous, usually, looped brachial appendage. Animal attached by a
short pedicle or by a ventral valve.

Genera Terehratula^ Terebratulma, Waldheimia, Terebratella,
3Iagas, Bouchardia, Morrisia, Kraussia, Argiope, Thecidium,
Stringocephalus.

Family Spiriferidce,

Ventral valve with prominent hinge-teeth, and slightly produced
and notched beak, Dorsal valve with a small cardinal process, a
divided hinge-plate, and a pair of internal slender calcareous brachial
appendages disposed in numerous close spiral coils, nearly filling the
shelL

Genera Spiinfer, Athyris, Retzia, Uncites.

Family RhynchonellidcB.

Ventral valve with a prominent notched beak ; giving passage to a
peduncle ; hinge-teeth supported by dental plates. Dorsal valve
with a deeply divided hinge-plate; and two short, rarely spiral,
internal brachial processes.

Genera Rhynchonella, Pentamerus, Atrijpa.

Family Orihidce.

Both valves with short subequal beaks ; a straight and wide hinge-
plate, notched in the middle. Ventral valve with prominent teeth:
dorsal valve with a tooth-like cardinal process, between two curved
brachial processes.

Genera OrtJiis, Stropho7iema, Leptcena, Koninckia, Davidsonia,
Calceola.

Family ProductidcB.

Ventral valve convex, with a slightly notched hinge line : dorsal
valve concave, with a prominent cardinal process and subcentral
short brachial processes.

Genera Producta^ Strophalosia, Chonetes.

LAMELLIBKANCIIIATA. 503

Family Craniadce.
Shell hinge-less, attached by the umbo or whole breadth of the
ventral valve : a short median brachial process.
Genera Crania.

Family Orbiculidce.
Valves not articulated. Ventral valve perforated for the passage
of the pedicle.

Genera Orbicula {Discina, Lam.), Orbiculoidea, Siphonotreta.

Family Lingididce.
Shell hinge-less, subeqnivalve, attached by a longish pedicle
passing out between the cardinal end of the valves. Generative
sinuses prominent and parallel on the inner surface of the mantle-
lobes.

Genera Lingula, Oboliis.

LECTURE XXL

LAMELLIBRiLNCHIATA.

The relation of the contained soft parts to the bivalve shell of the
Brachiopoda is such that one valve is ventral, the other is dorsal
in position. In the Lamellibranchiata one valve is applied to the
rijrht and the other to the left side of the animal. In the common
oyster and the Anomia, which are as fixed and motionless as the
Brachiopods, the two lobes of the mantle are as little united with
each other, and there is as little evidence of any locomotive organ
or foot. The muscles of the shell retain a certain complexity in
Anomia^ but in Ostrea are reduced to a single adductor.* The
spiral brachia are replaced by two shorter and more simple processes,
and the inferior labial fold is produced on each side to the same
length, so that there is a pair of labial processes on each side of the
mouth. These appendages, like the arms in Orbicula and Lingula,
have no internal calcareous support, which, by being bent, could
open the valves ; but they are long enough, in some species of Ano-
mia, to be protruded from the shell. Li other Lamellibranchs the
labial processes {Jig. 188, d) are short, and are more glandular than
muscular. Most of the present acephalous class are free and loco-
motive. The instrument by which they move from place to place is

* Preps. Nos. 65.

K K 4

504

LECTUKE XXI.

188

Tellina.

a single symmetilcal muscular organ (ib. b) developed from the
ventral surface of the visceral mass. The body and protecting
shell {ib. a) is longer in proportion to its depth
in these locomotive bivalves; and there are two
muscles provided for closing the valves.* The
superadded one {ib. c) is anterior to the mouth ;
the homologue of that which exists in the oyster
being the posterior adductor {ib.f). In all the
present class the divarication of the valves is
provided for by the insertion of an elastic sub-
stance at their hinge | ; and the valves are drawn '
together and closed by the contraction of the ad-
ductors. The bivalves with one adductor muscle
are termed *' monomyaries ;" those with two ad-
ductors "dirayaries." The dimyary bivalves have
always a foot {Jig. 188, b) : in its least developed
condition it is subservient to the function of
a gland which secretes a glutinous material ana-
logous to silk, the filaments of which serve to at-
tach certain bivalve?, as the Pinna and the common mussel, to rocks ;
these filaments are termed the " byssus {Jig. 191, ?/, o)." The visceral
mass occupies about half the cavity of the shell next the hinge. The
rest of the interspace of the pallial lobes is almost wholly occupied by
the branchial laminre (Jig.lSS, e, e\ which are usually four in number,
of a crescentic figure, placed two on each side of the visceral mass.
This is the characteristic condition of the respiratory organs in the pre-
sent class of Acephalous MoUusca, and from which it derives its name.
In the oyster the mouth opens beneath a hood-shaped fold of the
mantle, at the middle of the base of the labial processes : the canal
is continued by a short oesophagus to an expanded stomach, from
which numerous ramified hepatic follicles are developed. The in-
testine, after describing a few convolutions, is continued along the
branchial interspace towards the extremities of the branchiae Avhich
are furthest from the mouth, where it opens into the pallial cavity.
The ovarium or the testis surrounds the intestinal convolutions, and
forms with the liver the chief part of the visceral mass.

The veins of the oyster terminate in a single auricle, which
transmits the blood to a pyriform ventricle ; the two divisions of the
heart being contained in a distinct pericardium, situated between the
visceral mass and the concave margin of the adductor muscle.

The principal centre of the nervous system lies upon the opposite
convex margin of tlie same muscle, supplies it with nervous influence,

• Preps. Nos. 51 and 52. f Preps. G6, 67, X. vol. i. p. 16.

LAME LLIBRANCIII ATA- 505

distributes branches to the mantle, to the gills, and sends forwards
two long filaments, parallel with each other, one on each side of the
visceral mass, to the sides of the mouth, where they form a pair of
small ganglions, communicating with each other L^ a transverse
branch above the mouth, supplying the labial processes, and forming
a second feeble communicating arch beneath the mouth, from which
the gastric nerves are continued.

After a few examinations, guided by the foregoing sketch, of the
anatomy of the most simple bivalve, the student will be prepared to
comprehend and avail himself of the further details of the modifica-
tions of the Lamellibranchiate type of organisation.

In most dimyary bivalves the foot is an organ of locomotion. To
some which rise to the surface of the water, it acts, by its expansion,
as a float ; to others it serves, by its bent form, as an instrument to
drag them along the sands ; to a third family it is a burrowing organ ;
to many it aids in the execution of short leaps. In the piddocks
{Pholas) two strong muscles are sent from the foot to be attached to
the rough spatulate terminations of the bent processes under the beaks
of the valves ; these serve as fulcra in the excavating actions of the foot.

We may generally observe in relation with the greater develop-
ment and more active functions of the foot, a corresponding com-
plexity of the respiratory system. This is effected by the super-
addition of accessory organs in the form of tubular prolongations
of certain parts of the margin of the mantle, which are provided
with a special development of muscular fibres : these are called
"siphons" {ib.g,h), and have for their retraction special muscles
attached to the valves of the shell : in the Pholas crispata there is a
third small accessory gill on each side.

In the Mediterranean bivalve called CytJierea chione (Jig. 189) we
have an example of one of these highest organised of tlie acephalous
MoUusca, in which the characters of its grade of structure are in-
structively impressed upon the valves of the shelh The muscular
fibres («, a) which retract the margins of the mantle have their fixed
point within the margin of the shell, and leave there a linear im-
pression at a a : the closing shell-muscles leave deeper im-
pressions ; b is the anterior adductor, and b' its corresponding
impression ; c is the posterior adductor, and c its impression ; d
is the retractor of the siphons, and d' its impression : e shows
the transverse fibres of the foot, which, by their contraction,
lengthen the organ, and cause it to protrude : y marks the longi-
tudinal fibres or retractors of the foot : their origin leaves a small
roundish impression near the back part of the hinge of the shell.
When the siphons are present, they are always two in number, cor-

506

LECTURE XXI.

responding with the oral and anal apertures in the tunic of the As-
cidian : in fig. 189, g is the inhalent, and g' the exhalent, siphon.

Citherea chione.

The labial processes are shown at h : the stomach at i. A remark-
a-ble elongated amber-coloured body, called the crystalline style, is
indicated at k : it is contained in a special cyst, surrounded by cir-
cular fibres, with its free extremity protruding into the stomach.
Its homologue exists in a rudimentary state " as a detached piece of
cartilage" in the stomach of the Oyster ; its office, as conjectured by
its discoverer, being "to assist in the trituration of the food."* In
the Pholas it has the form of a folded plate. To pound and mix the
alimentary molecules with the gastro-hepatic secretions seems more
obviously to be its function in the Bivalves, in which the style is
fully developed and projects into the stomach like a pestle in a
mortar.f

The intestine {l\ after a few convolutions amongst the lobes of the
liver and genital gland, forms the rectum {m\ which perforates the
ventricle of the heart (w), and passes dorsad of the posterior adductor
to terminate by the anal opening, at the base of the siphon g' . The

* CCCXI. p. 17. t X, torn. i. p. 137 ; preps. Nos. 404 a. 487, h.

LAMKLLlBRANCniATA. 507

blood is received from the veins of the gills (/>) in this, as in all other
dimjary bivalves, by two auricles (o, o), which transmit their con-
tents to the single fusiform ventricle, perforated in the remarkable
manner just shown. In the genus Area, which is remarkable for its
great breadth^ the ventricle itself is divided into two cavities,
having the rectum in the interspace. An artery is continued from
each Extremity of the ventricle, which distributes the oxygenated
blood over the viscera, the muscular system, and the mantle. The
efferent vessels speedily lose the cylindrical form and expand or open
into large sinuses conformable with the lacunae of the viscera and
other organs.

The gills are essentially internal highly vascular folds of the pallial
membrane, and are strengthened by series of delicate jointed fila-
ments which support several rows of curved vibratile cilia. The
respiratory currents are occasioned by the ceaseless action of these
cilia, and are not dependent upon any opening or closing of the
valves of the shell. The ciliary action is that likewise which brings
the nutrient molecules to the mouth, chiefly along the marginal
grooves of the branchial plates, where the molecules are mixed with
mucus and moulded into small filamentary masses.

In Lucina and Corbis there is only a single gill on each side : as a
general rule there are two. Each gill consists of two membranous
plates, continued into each other at the free margin of the gill {Jig.
193, b) ; the contiguous plates of the two gills are continuous at the
base or bottom of the branchial interspace, where they are fixed : the
basal border of the plate forming the opposite side of the gill is free
where it extends along the base of the foot, and is continued into the
base of the inner gill of the opposite side, behind the foot, in the
fresh-water muscles, as at e. The two plates of each gill are united
together at pretty regular intervals in the direction of their breadth
by transverse septa or bars {Jigs. 190, z, 193, c) so as to include
canals running transversely to the gill-plates. According to the
course of the current of water through these interlaminar canals they
commence by the small slits or pores along (e) the groove on the free
margin, in the branchial chamber, and terminate by the wider
openings at the fixed margin of the gill in the anal chamber.

Fig. 190 shows a magnified section of the free margin of the two
gill-plates and their sustfiiiiing laminae, showing the terminal cilia
on the prominent border of each, the processes {a, a) by which con-
tiguous bars of the same plate are joined together, and the slips or
septa {i) uniting the bars of the opposite plates. The way in which
the contiguous bars are united is shown at d. In the more highly
magnified section, /shows the thick border, and h the thin border of

508

LECTURE XXI.

the bar ; i the septum, and g the interlaminnr canal. Each blade-
shaped bar supports three rows of cilia on each side of its base.

iM

%

m

190

-V^-r

■ " Branchial bar and cilia magnified. Mijtilns cdulis.

Tlie minute particles suspended in the branchial currents are carried
by the ciliary actions towards the mouth ; and the water is filtered
through the interlaminar canals before it escapes. The walls of the
interlaminar tubes support a regular network of blood vessels, longi-
tudinal and transverse, the latter being most prominent : the meshes
are parallelograms, and form open spaces, fringed internally by a
narrow ciliated membrane. The cilia compel the requisite move-
ments of the water in the branchial chamber, when the bivalve
remains suspended in the air, as happens to a mussel attached to a
rock above low-water mark. Even when the animal is in such a
position as to be immersed only for about two hours in seventy-five
days out of the year, it can live and grow : the retained water de-
riving oxygen from the atmosphere, and the animalcular food propa-
gating therein. The life of the "tree-oysters" {Ostrea polymorpha)
suspended to the mangrove branches is similarly explained through
the wonderful mechanism of the ever active microscopic cilia.

The two gills of one side are usually connected with those of the
opposite side by their hind ends only ; but somesimes the union is
more extensive. In a few genera, as Anatiria and Pliolodomya the
two gills of the same side are so united as to appear like a single
gill. In the Pholadomya this forms a thick oblong mass, finely
plicated transversely, attenuated at both extremities, slightly bifid at
the posterior one. A line traverses longitudinally the middle of the
external surface, which has no other trace of division. The branchia;

LAMELLTBRANCIIIATA. 509

on each side adhere to the mantle by the whole of their dorsal
margin, and are united together where they extend beyond the
visceral mass, being separated, by the interposition of that mass,
along their anterior two-thirds. A narrow groove extends along the
free anterior margins of each gill. When the inner side of this ap-
parently simple gill is examined it is seen to be divided into three
longitudinal channels, by two plates, containing the vascular trunks
and nerves of the gills. A style passed from the excretory siphon,
behind the conjoined extremities of the branchiae, enters the dorsal
channel, from which the excretory respiratory currents are discharged ;
the middle channel is characterised by an orifice which conducts into
the cavity of the gill, where the ova are hatched : the third channel
forms the inner or mesial surface of the gill, which is not otherwise
divided.

Although the microscopic cilia form the ordinary and constant
dynamical part of respiration, the function is occasionally influenced
by the muscles of the shell, as when the water is squirted out of the
siphons by a sudden shutting of the valves. The quiet and ordi-
nary respiratory current enters, in Anomia, at the anterior base of
the shell, and escapes posteriorly near the termination of the branchia3.
In Modiola vulgaris the current enters by the cirrigerous border of
mantle, and between that part and the foot : it escapes by the
posterior produced part of the mantle. In Mactra and Tellina, when
the conjoined siphons are extended and the hyaline valve is exserted
from the anal siphon, the current flows in at the " inhalent " branchial,
or ventral siphon {JiQ' 188, h), and rushes out by the "exhalent/'
dorsal, or anal siphon {ih. (J) : there is no current at the pedial aperture.
The branchial siphon is often much dilated, so that its diameter greatly
exceeds the anal one, e.g.^ in Pholas. The siphonal apertures, espe-
cially the inhalent one, are provided with a circle of tentacles, to
prevent the ingress of noxious particles.

There is a remarkable plexus at the base of the gills, near the pe-
ricardium, which surrounds a distinct glandular organ in the higher
bivalves. It is double : each sac is elongated with glandular walls,
and communicates with the pallial cavity by a small prominent ori-
fice, usually close to the genital pores. The secretion of this body
abounds with calcareous particles, and it was called by Poll the secre-
ting organ of the shell: it is shown at^^. 189, r. Modern analysis
has detected a large proportion of uric acid in these sacs, and has
thus determined them to be the renal organ.

An orifice at the extremity of the foot of Solen, at the middle of
the foot of Cardium, and the tube situated above the pedunculate
anus of Pinna, admit the sea-water into a reticulate system of

510

LECTURE XXr.

channels in the substance of the foot, thence extending into the
lobes of the mantle, and into a part of the visceral mass : by this
provision for the admission of water the foot can be swollen out, like
a sponge, and made to exceed the capacity of the shell. The rela-
tions of this aquiferous system to the sanguiferous one, are not
satisfactorily determined. The fine jets of water expelled from the
foot, and the border of the mantle, when a Solen is suddenly removed
from the water, are from the aquiferous canals.

The nervous system advances in a regularly proportional degree
with the complexity of the general organisation, and especially with
,the muscular system : the ganglion upon the posterior adductor,
which is most conspicuous in the oyster, is the largest and most
constant in all other bivalves :
it supplies the branchia3 with
their nerves, and when these
are approximated on each side,
it is single ; when they are
wider apart, it is double {b).
It is called, therefore, the
branchial ganglion, but it dis-
tributes an equal share of
nerves to the posterior and
dorsal parts of the mantle.
In the common muscle (^ff-
191) the labial ganglions (/)
may be distinguished by their
yellow colour at the base of
the labial processes. They
are connected by a short trans-
verse nervous chord (c), pass-
ing above or in front of the
mouth. From each of the
ganglions two principal nerves
are given off, one (a) passing
forwards to the anterior ad-
ductor, the other (d) back-
wards along the base of the foot and the visceral mass to the poste-
rior adductor, where it joins the branchial ganglion (b). At a short
distance from the labial ganglion this latter nervous chord sends
off a branch (e), which communicates with its fellow by means of a
bilobed ganglion, situated at the anterior part of the base of the
foot. This pedial ganglion (p) and the labial and branchial ganglions
constitute the principal centres of the nervous system in the Mi/tilus

Mytilus edulis.

LA^fELLICRANCniATA. 511

edulis. The pedial ganglion distributes nerves in one direction to
the retractors, in another to the substance of the foot, and it sends
the nerve to the acoustic sac (5). The branchial ganglions {b) send
off nerves (/), which diverge as they pass to the base of their re-
spective gills : then each gives off a large nerve {g) which passes over
the adductor muscle to the hinder part of the pallial lobe, along
which it curves, and is continued forwards near the border of the
mantle until it meets and anastomoses with the corresponding nerve
(a) which is continued over the anterior adductor from the labial
ganglion. These circumpallial nerves {y, a) send off branches which
form loops at the base of the tentacles from the posterior border of
the mantle, and, along the rest of the free border,form a circumpallial
plexus {h, //), which is, also, continued along the anterior and cardinal
borders of the mantle, unconformably with the circumpallial nerve.*
The nerves of this and other bivalves present the soft and pellucid
structure which is so common in the aquatic invertebrata. The mo-
dification of the nervous system, in other bivalve mollusca, have been
ably compared and homologised by Mr. Garner.f In the oyster the
suboesophageal loop is slender and contracted, and unconnected with
any other ganglion excepting the labial ones in the pedate bivalves ;
the suboesophageal loop is more or less lengthened, having the form
of a Roman arch in the Pecten, and that of the Gothic or pointed
arch in the Cardium and Mya ; it has for its keystone, if we may
pursue this analogy, the pedial ganglion. In some species this
ganglion is more distinctly bilobed than in others ; sometimes, as in
the Pholas, it is situated more superficially near the tip of the foot ;
in all it seems to be the centre from which the viscera derive their
nerves. The largest and most constant ganglions are those situated
upon the posterior adductor muscle, following this muscle in all its
varieties of position, and manifesting likewise differences in relation
to the branchiae, but always brought into direct communication with
the oral or labial ganglions. In these bivalves, as Ostrea, Cardium^
Unioy Atiomia, Venus, Pholas, Teredo, Solen, Mya, and Mactra, in
whicli the gills of one side are united to those of theopposite, the
branchial ganglia are conjoined. But in those, as MjjtUus, Modiola,
Pecten, in which the branchia are separate, and a ta distance from
one another, the two ganglia are distinct, and joined by a transverse
chord of greater or less extent. A small siphonic ganglion is deve-
loped at the point of confluence of the muscular respiratory tubes
in the bivalves which possess those accessory organs of respiration.
Dr. Siebold J discovered the organ of hearing in tlie Cyclas Naia^

* See the beautiful dissections by Mr. Goadby, Nos. 613—619.
t CCCXIV. X CCCXIII. p. 49.

512 LECTURE XXI.

and certain Pyrolidce: it consists of a small sacculus, with thick
transparent walls, attached to the anterior part of the pedial ganglion,
and containing a cretaceous nucleus of a crystalline structure, reso-
luble into four prismatic pieces, and performing remarkable oscil-
latory movements : this sac he regards, with much probability, as a
rudimental organ of hearing. It is shown 2X fig. 191, in Mytilus.

The Pecten has a number of small sub-pedunculated ocelli arranged
around the inner margin of the mantle ; they were recognised as
rudimental organs of vision, by Poll*, who, thereupon, called the
Pecten Argus. But the name is equally merited by many other
bivalves. As many as sixty ocelli have been counted on the convex
side of the mantle, and ninety on the plane side, in Spondylus gceder-
opus. The Pinna has about forty brownish yellow tubercles, at the
anterior part of each lobe of the mantle, near the adductor muscle.
In the burrowing bivalves, with long siphons, the ocelli are aggregated,
as might be anticipated, on the tentacular orifices of the breathing -
tubes, usually the only parts of the animal which are exposed. In
the cockles {Cardiuin) each of the numerous protractile tentacles of
the short siphons bears an eye of sparkling brilliancy. The Anomia
lias about forty pallial eyes hidden amongst the marginal tentacles.
In the oyster they are more numerous, of a yellowish brown colour,
and situated between every second tentacle along about one-third of
the mantle border. f

In the Pecten and Spondylus, the retinal expansion of the branch
of the circumpallial nerve incloses a vitreous body composed of non-
nucleated cells, in front of which is a flattened crystalline lens : the
pigmental coat consists at the back part of staff-shaped corpuscles,
and in front terminates by a circular pupil. In most other bivalves
the simple elements for exalting touch to a sense of light, viz., a
nerve-mass and pigment mass, are alone found, without any dioptric
adjuncts for the recognition of an image. Carlisle J first showed
that oysters were sensible of light ; having observed that they closed
their valves when the shadow of an approaching boat was thrown
forward, so as to cover them before any undulation of the water
could have reached them.

The labial palps seem well adapted, both by structure and position,
to exercise the sense of smell ; but of the existence of this sense, or
of taste, in the acephalous mollusks, we have no proof. In Nucula
the palps are rigid. The mantle is highly susceptible of impressions
by contact at its free border ; and the soft, often highly coloured,
ciliated processes from that and other parts of the unattached surface

* CCCXII ii. p. 153. t. xxii , fig. 1, 4.

\ XXIV. p. 261. cccxvj. X cccxr.

LAMELLIBRANCHIATA. 513

of the skin, especially about the inhalent and exhalent orifices, are
very irritable.

Between the freely open state of the mantle in the oyster and
similar monomyary bivalves (^Ostracea\ and its condition in the
dimyary bivalve (^Cytherea), selected for the demonstration of the
general organisation of the Lamellibranchs, there are intermediate
modifications. The common mussel is the type of a family (^Mytilacea)
in which the mantle is widely open anteriorly, the margins of the
lobes being united together posteriorly, except for a small space
forming an inlet for the respiratory currents and an outlet for the
excrements. In the Chamacea the margins of the pallial lobes
coalesce, leaving a small anterior aperture for the foot, a second
smaller one for inhaling the respiratory and nutrient currents, and a
third posterior orifice for excretion. The families typified by the
Venus and Mactra have the two latter orifices produced into a
siphonic tube, and the anterior or pedial aperture corresponds in
width with the superior size of the foot. In the TellimdcE {Jig. 187.),
the siphons are separate and can be much elongated. The modifi-
cations of the mantle are essentially the same in the family called
Inclusa ; but the narrower and longer figure of the body occasions a
greater proportion of the confluent margins of the mantle between
the anterior pedial and the posterior siphonic apertures, whereby the
moUusk, especially when the foot is small, becomes inclosed in a
membranous tube or sheath. The siphons are short and united in
the razor-shell ( /S^o/e;^ siliqua) ; they are longer and partly separate in
the shorter-bodied solens. In the Panopcea the long common siphonic
tube is covered by a thick rough epiderm and is not wholly retractile.
The still longer siphon of the shipborer {Teredo), which forms a
very great proportion of that vermiform moUusk, is unprotected by
the bivalve-shell. A well-marked modification of the mantle is pre-
sented by the Pholadomya, which has, besides the pedial and two
siphonic apertures, a fourth orifice at the under part of the base
of the siphon, leading by a valvular protuberance into the anterior
of the pallial cavity. This additional aperture co-exists with a
second small muscular process or foot^ which is bifurcate at the
extremity.

The bivalve shell of the Lamellibranchs offers, as might be ex-
pected, many modifications corresponding in general with those of
the mantle ; but otherwise related, in a few species, with borin:^
habits and a peculiar locality, other calcareous parts in a tubular or
other form being then usually superadded. The shell consists es-
sentially of an organised extravascular combination of gelatinous
membrane and calcareous earth, chiefly carbonate of lime, arranged

L L

514 LECTURE XXI.

in successive layers, the innermost being tlie largest and latest
formed ; and each layer presenting a cellular lamellar or prismatic
texture, which presents characteristic variations in different families.
Each valve of the normal shell is a cone, showing every grade of
depth, from the flat plate of the Placuna^ to the produced and spiral
cavity of Isocardia and Diceras ; it is commonly shallow, with the
apex or umbo turned more or less to one side and directed forwards.
If you place a bivalve shell in the position of the Mactra {Jig. 192.),
b is the umbo, and de-
termines e as the ante-
rior border ; g, there-
fore, is the posterior
one, a the upper or
dorsal, and /* the lower
or ventral border. The
length of the shell is
taken from e io g \ its g\
breadth, at right angles,
from the dorsal to the
ventral border, /; its
thickness is measured
across the closed valves,
at the most prominent
part, from the right to

the left side of the animal. Transfer yourself, in imagination, within
the shell {fig- 192.), with your head towards e, and your back
towards a and b, and you will recognise the valve figured, as the
right valve. Anterior to the umbo b, there is usually an oval de-
pression, forming a concavity in the outline of the valve ; it is called
the lunula c. The hinge-ligament is sometimes between the umbones,
never anterior to them. If the shell be divided by a line dropping
from the umbo into an anterior (e/*) and posterior {f g^ part,
it is never equally divided ; in other words, it is inequilateral.
Pectunculus is least so : in Ghjcymeris and Solemya the anterior
moiety is longer than the posterior one ; in almost all other bivalves
it is shorter, as in fig. 192., and commonly much shorter. Most
Lamellibranchs are equivalve, that is, the right and left valves are of
the same size and shape. The exceptions occur in the stationary
and often fixed species, which lie on one side, when the lower valve is
deeper and more capacious than the upper one: this lower valve in the
oyster. Pandora, and Lyonsia is the left valve, the smaller and flatter
upper valve is the right one : in Chomostrea and Corbula, the left is
the smallest valve. Tiie Placume, Pectenes, Spondyli, and Aviculidce

LAMELLIBTIANCHIATA. 515

rest on the right valve : the A?iomicB are attached by degenerated
muscular fibres passing through a hole or notch in that valve. All
these shells are called iuequivalve. The bivalve is called close when
the valves fit accurately ; it is gaping if part of the borders do not
come into contact when the shell is shut: in Gastroclicena this per-
manent opening is anterior, and serves for the passage of the foot ;
in Mya it is posterior, and serves for the passage of the siphons ; in
Byssoarca it is at the ventral border, and serves for the passage of
the byssus ; in Soleii and Glycymeris the shell gapes at both ends.

The outer surface of the shell is usually coated by an uncalcified
layer of albumen called the periostracum or epiderm, continuous with
the mantle. This surface is variously ornamented in many species ;
sometimes with ridges or "ribs," which may be either concentric and
conformable with the layers of growth, or radiating from the um-
bones to the free margins of the valves ; and the ribs may be
direct, bent, oblique, or wavy. In Tellina fabula the sculpturing
is confined to the right valve. In many species of Pholas, Teredo,
and Cardiumy the surface is divided into two areas by a dorso-
ventral furrow, or by a change in the direction of the ribs. The
thorny oysters {Spondylus), are so called on account of the spines
which project from the rib-lines ; they are longest and in greatest
number upon the non-adhering valve. In some conditions of the
shell the spines expand into foliaceous forms.

The part where the two valves are joined together is called the
hinge. The cardinal or hinge-line is short in Vulsella, long and
straight in Avicula and Area, of moderate length and curved in
most genera. The locomotive bivalves have, generally, the strongest
hinges : however, a very well-developed example of the hinge
mechanism may be studied in the Spondylus. Certain projections
or teeth of one valve interlock into cavities in the opposite valve.
The central teeth, usually beneath the umbo, are called cardinal
teeth ; those on each side are lateral teeth. In Alasmodon and Kellia
only lateral teeth, in many bivalves only cardinal teeth, are present :
the teeth are apt to become thickened and even obliterated by age,
through irregular growth or by the encroachment of the hinge-line.
Many of the fixed and boring shells are edentulous.

The soft mechanism of the hinge consists of the ligament and
spring. The ligament is a tough thickened portion of albuminous
matter, like that of the periostracum, and is usually attached to
ridges on the outer (dorsal) part of the hinge-margin, behind the
umbones ; it is consequently stretched by the closing of the valves.
The spring, sometimes called " internal ligament," and (though im-

LL 2

516 LECTURE XXI.

properly) the " cartilage," is lodged in the furrows between the
ligamental plates, or in pits along the hinge-line ; it is composed of
elastic fibres placed perpendicularly to the surfaces of attachment, so
as to be compressed by the shutting of the shell, which they con-
sequently tend to open as soon as the action of the adductors ceases.
The two parts are very distinct in the bivalves thence called
Amphidesma (double ligament) ; but coexist in most genera, with
alternate proportions, the ligament being small in Mactra which has
a large spring, and large in Anodon which has a small spring. Tlie
Pholades have the spring, but have not the ligament: this is replaced
by the homologue of the anterior adductor, which is so situated as
to act as an opener of the shell, and is called the " umbonal muscle."
The functions of the shell in this boring bivalve are too active
and too frequently in exercise to be performed by the passive elastic
antagonist of the muscular closing powers which sufl3.ces for or-
dinary bivalves.

The formation and repair of the shell are due to the development,
change of form, and calcification of cells from the mantle, its whole
outer surface being the matrix of the nacreous layer, its thick and
periodically glandular margin that of the opake outer portion.

The microscopic structure of bivalve and univalve shells has been
well illustrated by Profs. Carpenter* and Quekettf. The primitive
nucleated condition of the cell is sometimes retained after calci-
fication.J The dissolved lime-salts, after endosmotic penetration of
the organic walls of the modelling cell, obey so far the general
crystallising force as to polarise light. The forms of the constituent
lime-particles of the shell, so moulded by combined vital and polar-
ising forces, are manifold in the various genera of bivalves. The
shell of the Pinna, save a thin internal layer, is composed of vertical,
slender, usually hexagonal prisms. A thin outer layer of the shell
of the oyster also presents the prismatic cellular tissue ; but in a
great proportion of this shell nearly all trace of development from
cells is lost : the gelatinous basis is lamelliform, and this variety is
called the subnacreous shell-substance.

Fine tubes, analogous to those of dentine, permeate the thickness
of this substance in many shells ; radiating vertically between the
ribs in Area ; vertical and scattered in the inner layer, and reticulate
in the outer foliaceous spines, of the shell of Chama, which has an
intermediate layer of ill-defined vertical prisms. The prismatic
structure is rarely found, and then only in a small proportion, in
the bivalves which have the mantle lobes in any degree united.

* CCCX. t CCXXXL X lb. p. 270., fig. 157.

LAMELLIBR.VJ7CHIATA. 517

The distinction between the internal or nacreous layers, and tlie
external or fibrous layers, has long been recognised, and has been
forced, as it were, upon the notice of the palaeontologist by the cir-
cumstance of the two being often separated from each other in fossil
shells, and sometimes from one having perished whilst the other
remained. As the nacreous layer alone forms the characteristic
hinge uniting the two valves of the shell, and alone receives the im-
pressions of the soft parts, the true characters of fossil shells, as those
of the AviculidcB and Radiolites, which, in consequence of their
position in porous chalky beds, have lost all the nacreous layer, cease
to be determinable, save when a natural mould of the interior has
been formed before the pearly lining of the shell was dissolved.
When the inner layer is preserved, its impressions reveal the organ-
isation of the ancient fabricator of the shell as clearly as do the forms
and processes of fossil bones that of the extinct vetebrate animal.
The layers of the thick subnacreous inner substance of the shell of
the Spondylus have frequently wide interspaces, called from their
contents " water chambers : " this " camerated " structure is well
shown in the right or lower valve of Sp. varius.*

The siphon in some of the elongated Inclusa cannot be retracted
into the shell ; they are consequently exposed, as in Pholadomya
and Pholas : such species derive extrinsic shelter by burrowing in
sand or stone. The Pholades have supplemental calcareous pieces in
the hinge of the shell. Two small plates protect the umbonal
muscles, and a long narrow plate fills up the dorsal interspace of the
valves. The Clavagellce and Aspergilla line their burrows with a
calcareous layer, which forms in the latter a distinct tube, closed at
the larger extremity by a perforated calcareous plate. One of the
valves of the normal shell adheres to the tube in the Clavagella, and
both are cemented to its inner surface in the Aspergillum. In the
Teredo navalis the valves are reduced to mere appendages of the
foot, at one extremity of the animal, and are almost restricted in
their function to the operation of boring. As the ship-worm ad-
vances in the wood it lines its burrow with a thin layer of calcareous
matter. The length of the body is chiefly due to the prolongation
of the respiratory tubes, each of which is provided with a small
elongated calcareous triangular paddle-shaped plate. In the Teredo
gigantea the tube, which sometimes surpasses six feet in length, has
parietes of from four to six lines in thickness, the texture of which
is crystalline or spathose. Two tubes are developed within its
siphonal end. In Teredo norvegica the tube is divided longitu-

* CCCXVIII. p. 407.

L L 3

olS LECTURE XXI.

dinally, and also transversely, into compartments by irregularly
placed, incomplete, concave septa.

The valuable pearls of commerce are a more compact and finer
kind of nacre, often developed in the substance of the mantle, or
around a particle of sand or other foreign body which has gained
admission to the pallial cavity. The Meleagrina or Avicula mar-
cjaritifera of the Indian seas is most famous for these productions.
Those developed in the gills or inner layer of the mantle are small
and numerous ; those of the outer layer are the largest, but least
regular, and attached to the shell.

The " external " pearls consist of concentric layers of minute
vertical prisms, the " internal " pearls of concentric layers of wavy
calcified membrane. The iridescent nacreous lining of the pearl-
oysters (Avicida), and many other shells, consists of tlie same wavy
lamelliform tissue : the pearly lustre is due to the diffraction of the
rays of light by the out-cropping edges of the laminae, and, in some
cases, to the minute plication of a single lamina.

If the shell of a living pearl-oyster be perforated, and a minute
particle of sand introduced, it becomes a nucleus round which a pearl
is developed. Linntcus was knighted on making known to his
sovereign this practical application of his science ; but the artificial
production of pearls had long been known to the Chinese, who
obtain them of definite forms by introducing substances of the re-
quired shape into the sheU.

The U?iio margaritifera, or pearl-mussel of British lakes and rivers,
is fished up for the ornamental excretions to which it is subject. It is
probable that the pearls from this source, collected by the ancient
Britons, may have given rise to the statement by Tacitus in his Life
of Agricola, of " pearls not very orient, but pale and wan," being
among the indigenous products of the conquered island.*

The peculiar shape and development of the foot in the Solen and
other " burrowing " bivalves might have led to its recognition as the
excavating agent, if even it had not been seen to effect the purpose in
the living mollusk. Direct observation of the " boring " bivalves in
the act of perforation has been rarely enjoyed, and the instruments
have been guessed at or judged of from the structure of the animal.

The peculiar shape, great strength, and restricted size of the con-
centrically ridged valves in the Teredo navalis, the disproportionate
size and strength and the red colour of their adductor muscle, with
the curved umbonal processes for its advantageous leverage, could
not fail to attract the attention of the unbiassed observer to their

* CCCXIX. p. 164.

LAMELLIBRANCHIATA. 519

adaptation for the fanction of excavating wood. It indicates a mind
unfitted for physiological discovery to deny this adaptation, because
the exterior of the valves be sometimes coated by a dried layer of
the abundant mucus which is exuded from the pedial aperture
during the active movements of the borer. The rasp-like exterior of
the shell of the Pliolas crispata, with the modifications of the ad-
ductors and their fulcral apophyses, in like manner, suggests the
rasping rotatory action by which the valves may produce or aid in
producing the burrows in the rocks in which the piddocks conceal
themselves. To deny this use of the Pholas-shell, because the shell
of some other rock-boring bivalves is smooth, is a another sign of a
narrow mind. There are, doubtless, other modes of boring besides
the shell-action ; but the recognition of any such need not involve a
negation of every mode but the one so recognised.

Mr. Osier* has advocated the hypothesis of a chemical solvent as
the boring agent ; but such solvent has not been demonstrated ; and
the necessity of its being applied in currents of water to such cal-
careous rocks on which it could alone operate, with the liability of
the shell of the animal secreting the solvent to be affected thereby,
have been insuperable obstacles to the acceptance of the hypothesis.
Mr. Garner f has called attention to the ciliary currents generated
by the extensive surface of ciliated epithelium in the lamellibranchs
as probable aids to the rasping action of the valves : and since this
demonstrated and constantly acting dynamic causes as unceasing a
current of water in the holes of the borers, the non-extension of such
current between the shell and the rock, where they may be in close
contact, is no argument against the influence of the current in the
rest of the hole, and especially at the line where it is opposed by such
contact. The ingenious idea of the ciliary action as an accessory
power in boring may, therefore, be accepted, from its universal ap-
plicability, and is certainly worthy of notice.

More than twenty years ago I suggested the same kind of instru-
ment as applied to boring in rock, which had been recognised as the
one used for burrowing in sand. The anatomy of the ClavagellaJ
offered many points highly suggestive of the inadequacy of the hypo-
theses of the burrowing-agents promulgated at the time when I first
had the opportunity of dissecting that lithodomous bivalve ; and its
structure indicated a power that had not been previously suspected
in rock-borers. In the first place, it was evident that the valves
could not act, as they do in Teredo and Pholas; for the terminal

* CCCXVII. p. 270. t CCCXIV. X CCCXX. p. 269.

L L 4

520

LECTURE XXI.

expansion of tlie chamber had an irregular elliptical form in trans-
verse section ; and^ moreover, one valve was fixed, so as to form the
lining -plate of its side of the chamber. The animal I dissected
{Clavagella lata) had formed its chamber in a rock of calcareous
grit ; but a nearly allied species {Clav. australis) had bored its way
into siliceous grit ; whilst specimens of Clav. melitensis were en-
sconced in argillaceous tufa. A special solvent for each species
greatly complicates the chemical hypothesis. The mantle of the
Clavagella presented, however, a peculiar modification, being ex-
panded into a thick convex cushion where it was applied to the
bottom of the chamber, through the development in its substance of
a mass of interlaced muscular fibres. The last-excavated part of the
chamber was, as it were, moulded to the surface of the cushion,
which was perforated by a minute slit for the occasional passage of
a filamentary foot. I suggested, therefore, this muscular develop-
ment of the mantle as being ^' one of the principal instruments in the
work of excavation."* But, viewing its attachment to the moveable
valve, and the strength of the adductor muscles, I supposed that that
valve might be applied, not only to eiFect the forcible expulsion of
the fluid from the pallial cavity, but also, " probably, to assist in the
excavation of the abode." Mr. Hancock f has recalled attention to
the excavating agency of soft and muscular masses in other boring
bivalves, analogous to that in Clavagella, as, e.g., the thickened
portion of the mantle in Saxicava and Gastrochcena, and the foot in
Pholas and Teredo.

If siliceous particles be actually secreted in the superficies of any
of the burrowing discs, they must add to their efficiency : and it is
certain that the perpetual renewal of a softer surface will render it
capable of wearing away a harder one, subject to the friction of such
softer surface, and not, like it, susceptible of being repaired.

The admission of the wearing and boring power of muscular discs
need not, however, involve the rejection of the allied action of shelly
valves and ciliary currents. The diversity of the organisation of the
boring mollusks plainly speaks against any one single and uniform
boring-agent in all.

The action of the foot and thickened border of the pedial aperture,
may be inferior to that of the valves in Teredo, as it certainly is
in Pholas. A valued correspondent, Mr. Robertson, of Brighton,
writes, " Between thirty and forty Pholades have been at work in
lumps of chalk, in a finger-glass and a pan of sea- water at my window
for the last three months. The Pholas dactylus makes its hole by

* CCCXX. p. 271. t CCCXXII.

LAMELLIBRANCHIATA. 521

grating the chalk with its rasp-like valves, licking it np when pul-
verised with its foot, forcing it through its principal siphon, and
squirting it out in oblong nodulos. They turn from side to side,
never going more than half-round, in their hole, and cease to work as
soon as the hole is deep enough to shelter them." The Pholades
attain their largest size in soft yielding stone ; whilst in hard, and
especially gritty rocks, they are dwarfed in size, and the rough
surface of their shell is worn away. M. Caillaud has shown that the
valves are quite equal to the work of boring in limestone, by imitating
the natural conditions as nearly as possible, and making such a hole
with them.*

In Lithodomus, Saxicava, and Ungulina, the valves are smooth,
and retain the periostracum ; yet they bore into the hardest marble,
and still harder shells : their holes, like that of Clavagella, are not
cylindrical, and are doubtless formed, as in that genus, by the agency
of the thickened muscular borders of the pedial aperture.

Teredo navalis bores in the direction of the grain, unless it
meets another Teredo, or a knot in the timber : they are probably
warned by their organ of hearing of such contiguity. The rasp-dust
is introduced by the foot into the pallial cavity, and is swallowed :
the long intestine of the ship-worm is usually laden with this debris.
The piles of the dikes in Holland received so much damage from the
ravages of the Teredo, in 1731-2, as to occasion serious alarm of a
destructive inundation of the country, as the consequence of the ope-
rations of this seemingly feeble vermiform mollusk.

Generation of Lam ellibranchs. — So far as actual experience ex-
tends, parthenogenesis is arrested in the molluscous province at the
Tunicated class. The Lamellibranchs propagate exclusively by im-
pregnated ova; the individuals from which, after undergoing more
or less metamorphosis, exhaust the remnant of their developmental
force by completing the male or the female organs. Here, therefore,
there is no alternation of generative modes, save in so far as the
sexless state of the twin glochidium {Jig. 194., c) intervenes between
the impregnated ovum and the perfect male or female bivalves.

The sexual organs of the higher Acephala, although as a general
rule developed separately on distinct individuals, present a very
simple and low character. Enormous in bulk, they ramify over the
mantle in some footless Lamellibranchs {Aiiomia, e. g.), as in the
Brachiopods, whilst the sperm-cells or the ova are aggregated at the
base and interior of the foot in those bivalves which have that
appendage.

* CCCVII. p. 327.

522 LECTURE XXI. " •

The latest and best observations of naturalists and physiologists
on the sexual characters and generation of the Lamellibranchs have
established the correctness of Leuwenhoek's original conclusion * that
these moUusks are of distinct sexes, some individuals being male and
others female. In the small species of Anomia parasitic upon fuci
on the south coast of England, I have found the males and females
nearly equal in number, the males being distinguished by their
opaque white testis abounding in spermatozoa, the females by their
yellow or orange-coloured ovarium.

Milne Edwards f has pointed out two substances, of diflferent
colours, occupying the abdominal mass in the Pecten. The part to
which he restricts the term ovarium occupies the inferior and poste-
rior region of the mass ; and sends a duct w4iich traverses a portion
of the different-coloured body situated above, and ascends to termi-
nate between the bases of the labial tentacles, the summit of the ab-
domen, and the anterior ends of the gills. To the opaque whitish
mass occupying the upper and larger half of the abdominal mass he
gives the name of testis : it is composed of small vesicles grouped in
bunches ; its duct is continued into the foot, and terminates by two
small orifices opening upon the inferior fissure of that organ. J These
Siebold suspects may be the orifices of the secreting glands of the
byssus, and Edwards has perhaps mistaken the gland and duct of the
byssus, with part of the undeveloped ovary, for the testis. He did
not apply the only true test of the nature of the uncoloured part,
viz. the microscopical examination of its contents.

Krohn§ has dissected a so proved hermaphrodite Clavagella : he
found the testis beneath the liver, while the ovary surrounded it and
the stomach : this appears to be an exceptional condition in the class,
though perhaps constant in that peculiarly domiciled genus.

In the male Lamellibranchs the testes are double, and have a
somewhat more circumscribed form than the ovaria, but sometimes
appear to be blended together at the median line. In the oyster
they are situated on each side of the liver, and extend in the form of
a triangular process between the adductor muscle and the gills. The
testes extend at the breeding season in certain genera, as Anomia,
Hiatella, Mytilus, and Modiola, into the substance of the lobes of the
mantle ; but in those bivalves which have a large foot, the testes are
confined to the base of that organ. The ultimate texture of the testes
is a congeries of vesicles containing a milky fluid, which seems to

* XXXIX. p. 16. t CCCXXV. pi. 10. fig. 1. p.

X XXIV. p. 289. § CCCXXIII. p. 52.

322.

LAMELLIBRANCHIATA. 523

consist almost wholly of spermatozoa in the breeding season.
The vasa deferentia are short and wide, and they open behind the
mouth in the oyster, and terminate upon papillae at the posterior
part of the foot in most dimyary moUusks, as Cardium, Pholas,
Verms, &c.

The ovaria have a similar form and position in the female bivalves,
but are usually more extensively ramified. The short oviduct and
sperm-duct are both strongly ciliated, and open on each side at the
base of the foot or visceral mass, by a narrow fissure with tumid
borders, either very close to the opening of the kidneys into the
mantle-cavity or in the urinary sac itself. At all seasons of the year
some ova may be discerned in the ovarian cells, characterised by the
germinal vesicle and spot. Towards the breeding season they are
developed in immense numbers ; and the addition of the coloured
vitellus to the essential part of the ovum gives the characteristic
colour to the ovaria. They are generally distended with the ova in
the winter months. It is by virtue of the currents produced by the
action of the vibratile cilia of the mantle and gills that impregnation
is effected in the separate sexes of bivalves, and especially of those
that, like the oyster, are fettered, male as well as female, to the rocks ;
just as the pollen of the rooted male of the dioecious palm is wafted
by currents of air to the moist stigma of the equally fixed and rooted
female tree. The fertilising filaments retain their influence after
being discharged from the males, are drawn in with the respiratory
currents, and at the breeding season the ovaries and oviducts contain
a milky fluid abounding with the moving filaments. The ova then
escape by the short oviducts, which terminate in positions analogous
to those of the vasa deferentia.

The ova have usually a spherical, rarely a pyriform or elliptical,
figure : the yolk {Jig. 194, a b), when mature, varies from a yellow
to a reddish hue ; it is inclosed by a smooth vitelline membrane, and
this by a thin chorion. The (often overlooked) germinal vesicle (a)
has usually two co-attached nuclei. The small amount of albumen
(c) which lies between the yolk -membrane and the chorion becomes
more conspicuous after impregnation.

The ova do not escape when excluded from the oviduct, because
during that act the shell is kept forcibly closed ; and so they slip
back into the gill-channels. In the Naiadm the two external gills are
developed into uteri or marsupial pouches for the ova, which cleave
loosely together in the compartments of those gills ; and in the fresh-
water genus Unio they are excluded by the anal fissure, near to
which they form oval discoid masses, in which may be recognized the

524

LECTURE XXI.

Anodon.

form of the brancliial compartments. In

Jig. 193. is shown a transverse section of

the right lobe of the mantle {a) and of

the right pair of gills in a fresh-water

muscle {Anodon\ at the period when the

external gill is performing its marsupial

function, and is laden with the ova : h is

the inner gill, c the outer gill, showing

the basal canal and the free margins of

the partitions of the branchial cells in

which the ova are incubated.

One feels surprised at first that the ova

should pass into the outer gills, when the

inner ones are nearer the two sexual ori-
fices, V. Baer pointed out the roundabout way in which the ova

glide along the basis of the inner gill as far as the cloaca, and from

thence through a particular canal of the mantle into the compartments

of the external gill : and the same acute observer has explained how,
in like manner, in Tellina, the semen ejected from the anal tube
enters bj the ventral respiratory tube into the branchial chamber of
the female, and passes thence into the receptacles for the ova formed
by the gills.

The external gills swell out to such a size in the fresh-water
mussel, Aiiodon, as to require a particular space in the shell
for their lodgment, and the valves of the female are consequently
more convex than those of the male. The same sexual character of
the shells is observable in the genus Uiiio^ and the whole family
of the NaiadcB, as Kirtland and Lea have remarked in their beau-
tiful monographs on the North American species of these fresh-
water bivalves.*

The actual penetration of the ovum by the spermatozoon, first ob-
served by the keen-eyed and accurate Martin Barry, who demon-
strated the capital fact to me in the year 1843, has, amongst other
confirmations, received satisfiictory ones from Keber's and Webb's
observations of the mode of impregnation of the ova of the river-
mussel {Anodon) ; and from those by Loven on Cardium pyg-
m(Eum.\ A tubular orifice, analogous to the micropyle in the
vegetable ovum, is formed in or from the chorion : the sperma-
tozoa penetrate by this temporary orifice, which then closes, and is
indicated by a clear spot with a corrugated border. The sperma-
tozoon penetrates the yolk, and there, according to Barry, divides
into many parts.J

* CCCXXVI.

t CCCXXIV.

1 CCCXXIV. a.

LAMELLIBEANCHIATA. 525

In all the bivalves hitlierto observed the yolk is a germ-yolk only,
and is divided concurrently with each spontaneous fission of the
contained impregnated germ-cell. Two superficial cells, alone, seem
not to participate in this process, but, after the formation of the germ-
mass, are changed into triangular discs, the rudiments of shells : the
rest of the surface developes a ciliated epithelium, by which the
embryo rotates in the ovum. In ^lytilidce a swimming disc is next
developed, fringed with long cilia, and an exploratory filament is deve-
loped in association with the increased locomotive power.

In Anodo?i the embryonic mass soon divides itself, but not quite com-
pletely, into two halves*, each half being supported by its own valve.
It looks like an attempt at spontaneous fission, — some lingering mani-
festations of parthenogenetic force. In fact, each of these embry-
onal moieties has its own mouth, which is situated near the hinge,
beset with cilia, and its own intestine : on the inner sides of the cleft,
at the angle which the two embryonal moieties form at the future
hinge of the shell, there rises, on each side of the adductor-muscle,
a hollow byssiphorous organ, from which two transparent byssus-
filaments proceed. The inner surface of each moiety is also beset
with three tentacle-like stiff" points, with their base surrounded by a
thick border. Near the hinge there passes the broad adductor-
muscle above mentioned from one embryonal half to the other, which,
after the young bivalve has quitted the egg, manifests its contractile
force by closing the valves ; these have now become slightly concave,
but continue triangular in shape. Each embryonal moiety has, like-
wise, at first, its own distinct though simple heart ; and it is by the
approximation and ultimate fusion of the two ventricles that the
common rectum of the originally distinct intestines is intercepted.
The rest of the canal blends with its fellow as the visceral mass grows
up from the bottom of the cleft, chiefly by the progressive increase
of the testis or ovarium "f ; and thus two sexless individuals combine
to form one with sexual organs.

M. de Blainville:]: denied the passage of the ova of the Lamel-
libranchs into the gills, and maintained their direct exclusion from
the shell ; on the faith of which assertion Jacobson § was led to
suppose the odd-shaped embryos in the branchial marsupium to
be parasites, as the elder Rathke || had long previously described
them to be. But, whilst many true and singular parasites have
been detected and described in the Lamellibranchs, the real na-
ture of the Glochidium of Rathke has been well traced out : the

* CC(;XXX1II. t CCCXXXIV. p. 312.

X CCCXXVJI. p. 137. § CCCXXIX. p. 22.

II CCCXXVIII. p. 166. t. X. fig. 3.

526 LECTLTIE XXT.

young Anodons, so denominated, quit their marsupium usually late
in September, after an intrabranchial development of two
or three months. The young animal, when excluded,
uses the prehensile or adhesive filament, to anchor itself
to the shell of the parent or to some foreign body.

Prof. Carus* has ably traced out the course of deve-
lopment of Unio litoralis. Fig. 194, a, shows the unimpreg-
nated ovarian ovum. Before the ovum has reached the
branchial marsupium, the germ-mass has been formed,
and some pentagonal and hexagonal cells are developed at
its periphery, supporting vibratile cilia. The quantity of
albumen has increased. At first movements may be ob-
served in that part of the albumen, which is contiguous to
those superficial ciliated cells. As these extend over the
germ-mass the currents of albumen increase in strength,
and, finally, the yolk itself begins to revolve in the surrounding fluid
in the direction marked by the arrow in b. This singular pheno-
menon was first observed by Leuwenhoek in 1695. The embryos
have now penetrated the gill. Two parallel fissures next make their
appearance, which, sinking deeper into the germ-mass, divide that
part into two, and mark out at the bottom the rudiment of the vis-
ceral mass, which is subsequently to rise between the lobes of the
mantle. Calcification commences on the outer surface of these lobes,
and the first layer of the future shell forms a small triangular valve
on each side.

When the rotation of the embryo is most active, seven or eight
revolutions may be observed in the minute. The gills make their
appearance as ciliated wavy folds from the inner surface of the mantle,
near the angle between the pallial lobes and the visceral mass. The
development of the adductor muscle, single at the beginning and near
the hinge, is indicated by feeble attempts at opening and closing the
valves. The albumen during this development is absorbed and as-
similated, and the embryo now distends the chorion. In the young
Anodon {Jig. 194-, c), long filamentary processes twisted together like
a byssus, are developed from the visceral mass : the thick short fleshy
foot is subsequently developed in place of the byssiform filaments.
Both the young Uniones and Anodontes escape from the chorion
before they quit the marsupium, and may be observed swimming
freely about in the cavity of the external gill. They are so different
in form from their parent, and so singularly located, as readily to
suggest the venial error of Rathke respecting their nature and rela-
tions. The hooked apex and the spines, with which the shell of the

* CCCXXX, p. 43. tab. "

LAMELLTBKANCmATA. 527

young Anodon, when first excluded, is armed, may serve to defend it
against some small persecutor or other.

In the genus Cyclas Mr. Garner* has observed from ten to twenty
of the young fry, situated in the internal branchiae, where each has
its special compartment : they are discharged one by one when they
attain about the sixth of an incb in diameter. The oviducts in the
Cyclas open over these internal branchiae, and are only accessible to
the water from behind, as are the external branchiae of the U7iio.
The young Cy eludes are sometimes found adhering by a byssus to
different parts of the body of the parent. The young of the genus
Naias have been observed to anchor themselves, after exclusion from
the parent, by a byssus, which is usually wanting in the large and
full-grown animals.

This temporary means of attachment must prevent many of the
young and feeble bivalves from being carried away by the stream at
a period when their shell has not attained sufficient hardness to pro-
tect them from the numerous predatory aquatic animals to w^iose
attacks they would be exposed ; and we may thus discern, in the de-
ciduous byssus, an evidence of prospective design for the well-being
of the weak and defenceless.

Prof. Edward Forbes, in an interesting paper published in tlie
" Edinburgh New Philosophical Journal," has cited some facts of the
periodical cessation of development of bivalves in certain shell-banks,
and has alluded to the knowledge of such phenomena as being familiar
to fishermen, who express it as being a " shifting "of shell-beds, which
they erroneously attribute to the moving away and swimming off of
a whole body of shell-fish, such as mussels and oysters. But even
the Pectens, though much better endowed with locomotive power
than the cemented oysters or byssus- bound mussels, have very little
power of progressing to any distance when fully developed. With
respect, however, to Prof. Forbes' opinion, that "the shiftino- or
migration is accomplished by the young animals when in a larva
state," this cannot be accepted as one of general application. The
facts, at least, that have been ascertained in regard to the develop-
ment of fresh-water bivalves are directly opposed to such migratory
powders in the "larvse;" for these are distinguished by organs of at-
tachment which are peculiar to the immature state of the bivalve,
and fetter them to their birthplace until, in the progress of o-rowth,
they attain freedom with maturity. I confess that I entertain great
doubts whether the so-called " shifting " of shell-beds be the result
of a migration en masse of the mussels or oysters, either in their
larval or mature states ; but deem it more probable that the disap-

* CCCXIV. p. 97.

528 LECTURE XXI.

pearance of the bed of living individuals is due to tlieir dying out
through influences, which Prof. Forbes himself recognises and ex-
plains, as unfitting the ground for further sustenance and increase of
the tribe ; and that the appearance of a colony in another position is
due to the progressive increase from a few individuals, and not to the
migration of the whole colony.

So far as observations have been made on the development of
bivalves, although it is true that, as yet, they have been, with
few exceptions, limited to the fresh-water kinds, the young Lamelli-
branch, however free the parent, is attached at the beginning
by a byssiform peduncle : it has no lamelliform gills, but respires by
the vascular and ciliated surface of the mantle-lobes, and it has two
distinct hearts.

In all these characters we perceive the manifestation, though it be
transitory, of some peculiarities of the Brachiopodous order ; and
hence we derive an additional argument for concluding that the Bra-
chiopods are on a lower step of molluscous organisation than the
Lamellibranchs : and this is congruous also with the earlier appear-
ance and multiplication of the Brachiopods in the primeval seas of
this planet.

The contemplation of the phenomena of the development of
Anodon also makes us comprehend better the cause of some of the
peculiarities of the structure of the Lamellibranchiate mollusks.
There seems to be in that development a tendency, at the begin-
ning, to form two individuals out of one germ-mass, — to develope
two univalves in the place of one bivalve : and some of the differences
of structure characteristic of different bivalves evidently relate to
the arrest of development at given stages of the progressive confluence
by which the two primary individuals are ultimately fused into one.
Thus we may regard the two separate hearts of the Brachiopods as
a retention of that distinctness or doubleness of the organ which it
manifests at its first appearance in the embryo Lamellibranch, when
not only the auricles, but the ventricles, are on separate halves of the
almost divided body. In Area, the ventricles have approximated
but hot coalesced. In Anodon the two ventricles have coalesced,
but not the two auricles, which continue permanently separate, and
impart the seemingly complex condition of the reptilian tripartite
heart to this inferior form of mollusk. It has been long shown, how-
ever *, how the function of the two auricles of the bivalve being the
same, that very doubleness or repetition of the part became a mark
rather of inferiority, as compared with the more compact form of the
single-auricled heart of the univalve mollusk ; and we now see that

* X. vol. ii. p. 33.

LAMELLIBRANCHIATA. 529

the circumstances under which the tripartite heart of the Anodon is
developed, confirms that inference. In the Oyster the progress of
union of the two individuals has proceeded to the confluence of both
the two ventricles into one, and of the two auricles into one, and a
bipartite heart is the result : unless, indeed, in this and in other in-
equivalves, one individual or moiety of the divided and embryonal
mass be developed at the expense of the other, which may undergo
partial absorption.

The ordinary course of confluence, by which, in the growth of the
13arenchyme from the line of union of the divided moieties of the
embryo, the two intestines become one, commences, as regards the
intestinal tube, from the anus ; and, being followed or accompanied
by the progressive co-approximation, co-adaptation, and ultimate
confluence of the two ventricles, these, through the relative position
of the rectum of each individual moiety, along the inner or mesial
side of the originally distinct ventricles, come to be included between
those co-adapting ventricles, and, ultimately, the single rectum becomes
included by the single ventricle, each resulting from the fusion of a
primitive pair ; and hence we are able to comprehend the cause of
that most singular anatomical fact which, hitherto, has been, without
any intelligible explanation, a mere empirical one, viz., the passage
of the rectum through the centre of the ventricle of the heart in most
Lamellibranchs.

"We may discern in that well-marked and peculiar feature of the
Lamellibranchian development, viz., the almost complete fission of
the embryonal mass, with the establishment, in Anodon, of digestive
and circulating systems in each, an indication of the last remnant of
the parthenogenetic force, which, in its complete manifestation, ceases
with the Tunicata in the molluscous series. Nature, however, does
nothing abruptly, and a transitional character to higher kinds of
development of a single individual from a single ovum is indicated by
this attempt, as it appears to be, to form two individuals out of one
germ-mass. Their respective completion, however, as such, is checked ;
and development proceeds to form one (more complex) bivalve out of
two (less complex) univalve individuals.

I may further remark, that the period and mode of the develop-
ment of the two valves of the incipient bivalve are subversive of
Oken's conjecture*, that the operculum of the operculated univalve

* Defining the univalve moUusks, Oken says, " ^'on den beiden Muschel-
schalen wird eine rohrenforniig, umschliesst das ganze Thier allein, und die
andere bleibt als blosser Deckel iibrig, der die Kohrenmundung schliesst." —
Lehrbuch der Philosophie, Th. iii. p. 259. 8vo. 1811.

" Of the two mussel (bivalve mollusks) shells " (which he treats of in the
preceding section), " one becomes excavated, tube-shaped, and alone incloses the

M M

530 LECTURE XXI.

is a stunted homologue of one of the valves of the bivalve, and espe-
cially of the smaller and flatter valve in the inequivalve bivalves.

Both valves are simultaneously and equally developed in the oyster,
as in the mussel, and form the peripheral layer of the germ-mass,
prior to the formation of any muscular organ : the recognisable basis
of each valve is prior, indeed, to the fission of the germ-mass, which
is preliminary to the formation of the digestive and circulating
systems of the two primarily incomplete individuals. The oper-
culum, in the operculated univalves, is the subject of a much later
growth ; it does not appear simultaneously with the proper univalve
shell, nor is it ever equal to that shell in size or similar in shape.
Both the external temporary locomotive organs, I mean the vibra-
tile cilia, and certain internal organs, are developed before there is
a rudiment of the operculum in the univalve : even the permanent
locomotive organ, the foot, is plainly established, before the oper-
culum makes its appearance ; and when it does so, it is not as a
metamorphosis and coalescence of certain of the peripheral cells of
the germ-yolk, but as a thickened epithelial layer upon the back part
of the previously formed foot.

And whilst upon the subject of Oken's ideas of the homology of
the operculum, we may as well test, by the light of molluscous em-
bryology, some others which he has propounded relative to the nature
of the bivalve shell.

" In the mussel," says Oken, " a structure originates for the first
time which can be compared with a thoracic cavity. What covers
the branchi^ must stand in the signification of the thorax. The
pallium or mantle of the mussels is pleura. Their shells are branchial
opercula (as in fishes). They are secretions from the mantle, and
everywhere accompany the branchiae. The hinge of the shell-valves
corresponds to the rachis or spina dorsi. The shells of bivalve
mollusks are a calcareo-thoracic box, open in front, inverted behind,
and moveable like ribs." *

Each valve in the Bivalve pre-exists, as we see, to any trace of
gill : the first organs which it pi-otects are the stomach, the liver,
and the whole length of the intestine ; it does not defend a thoracic
or pectoral cavity, but an abdominal one. If the two valves are
comparable to opercula they are ventral, not thoracic or pectoral ;
and the pallium, or layer of germ-mass lining the valves, in which

whole body ; the other remains as the mere opercukim, which shuts the opening
of the tube." And in the edition of the same work, translated by the " Ray
Society," Oken says, " With the one-sided evolution of the mantle, one shell also
is only developed, while the other is stunted or placed under arrest. The snail's
shell is one of the bivalve mollusk's shells, its operculum is the other. This last
is stony, horny, and finally is entirely wanting."
* lb. Th. iii. p. 254. 8vo. 1811.*

LAMELLIBRANCHIATA. 531

the above-cited organs are formed, is peritoneum rather than pleura.
The hinge of the valves is the unseparated, but modified, remnant of
the germ-mass, which connects together the two individuals resulting
from its incomplete fission : it is much more like the common pedicle
or base of the compound Ascidian, than the " spina dorsi " of a verte-
brate animal.

Thus we learn how valuable are the facts derived from the study
of the progressive building up of the animal frame. In the case of
the chiss which has this day occupied our attention, a knowledge of
their development, partial and imperfect as it must be confessed to
be, has nevertheless thrown new light on the peculiar organisation
of the mature animal, has rectified misconception of the nature and
homologues of their parts, and may have suggested truer theories of
some of their more remarkable living habits.

Class LAMELLIBRANCHIATA.

Body with a dextro-sinistral bivalve shell, lined by a commonly
more or less closed mantle. Oral tentacles four ; branchiaj lamelli-
form, usually in two pairs.

A. MoNOMYARiA. With one (the posterior) adductor.
Family Ostreadce.

Lobes of the mantle widely separated ; foot small, byssiferous, or
absent. Shell inequivalve, slightly inequilateral ; hinge usually eden-
tulous.

Genera Ostrea, Anoinia, Placu7ia, Pecten, Lima, Spondylus,
Pedum, Plicatula.

B. DiMYAEiA. With two adductors.

Family AviculidcB.

Lobes of the mantle widely separated; foot small, byssiferous;
anterior adductor very small, leaving its impression within the umbo.

Genera Avicula, Meleagrina, Malleus, Vulsella, Gervillia, Perna,
Crenatula, Inoceramus, Pinna.

Family Mytilidce.

Mantle-lobes united between the branchial and anal slits or orifices;
foot cylindrical, byssiferous. Shell equivalve ; hinge edentulous.

Genera Mytilus, Myalina, Modiola, Lithodomus, Crenella, Dreis-
sena.

MM 2

532 LECTURE XXI.

Family Arcadce,

Mantle-lobes separated ; foot large, bent, and deeply grooved.
Shell equivalve ; hinge long, with many denticles.
Genera Area, Cucullcea, Pectunculus, Limopsis, Nucula, Isoarca.

Family Solenellidce.

Mantle-lobes united behind, with a single siphonal orifice, or with
two short united siphons. Shell equivalve ; hinge edentulous, or with
fine sharp teeth.

Genera Solemya, Solenella, Yoldia, Leda.

Family Trigoniadce.

Mantle-lobes separated ; foot long, pointed, sharply bent. Shell
equivalve, trigonal ; hinge-teeth few, diverging.
Genera Trigonia, Myophoria, Axinus, Lyrodesma.

Family UnionidcB.

Mantle-lobes united between the siphonal orifices and, rarely, in
front of the branchial opening ; foot very large, tongue-shaped, com-
pressed, byssiferous in the fry. Shell usually equivalve ; anterior
hinge-teeth thick and striated, posterior laminar, sometimes wanting.

Genera Unio, Castalia, Anodon, Iridina, jEtheria, 3Iulleri(B.

C. DiMYARiA SiPHOJ^iFERA. With rcspiratory siphons.

a. Siphons short, pallial line simple.

Family ChamidcB.

Pedal and siphonal orifices small, subequal ; foot very small. Shell
inequivalve ; hinge-teeth 2-1, or two in one valve, one in the other.
Genera Chama, Monopleura, Diceras.

Family Hippuritidce. {Rudistes, Lam. ; extinct.)

Shell inequivalve, unsymmetrical, thick, attached by the right
umbo; umbones frequently camerated ; hinge-teeth 1-2. Adductor
impressions two, large ; three of the left valve on prominences.

Genera HippuriteSy Radiolites, Capri?iella, Caprotina.

Family Tridacnidce.

Pedal orifice large ; siphonal orifices surrounded by a thickened
pallial border, the anal one with a tubular valve ; foot small^ cylin-
drical, byssiferous. Shell equivalve, open ; muscular impressions
sub-central and blended.

Genera Tridacna, Hippopus.

LAMELLIBRA.NCHIATA. 533

Family Cardiadcp.

Pedal orifice large ; siphons usually short ; foot large, sickle-
shaped. Shell equivalve, cordiform ; cardinal teeth 2, lateral teeth
1, 1, in each valve.

Genera Cardium, Hemicardium^ Lithocardiiim, Serripes, Adacna^
Conocardium.

Family Lucinidce.

Mantle usually widely open below, with one or two siphonal aper-
tures ; foot long, cylindrical, or ligulate, sometimes byssiferous. Shell
orbicular, closed; hinge-teeth 1 or 2, lateral teeth 1-1, or obsolete.

Genera Lucina^ Cryptodon, Corbis, Ungulina, Kellia, Montacuta,
Lepton, Galeomma.

Family Cycladidm.

Mantle open in front; siphons more or less united; foot large,
tongue-shaped. Shell suborbicular, closed ; hinge with cardinal and
lateral teeth.

Genera Cyclas, Cyrena, Pisidium.

Family Cyprinidce.

Mantle-lobes united behind by a curtain pierced with two siphonal
orifices ; foot thick or compressed, tongue-shaped. Shell equivalve,
closed ; cardinal teeth 1-3, and usually a lateral tooth in each valve.

Genera Cyprina, Ciree^ Astarte, Crassdtella, Isocardia, Cypri-
cardia, Megalodon, Cardinia, Cardita.

b. Siphons long ; pallial line sinuated.

Family VeneridtB.

Mantle with a rather large anterior opening ; siphons unequal,
more or less united ; foot tongue-shaped, compressed, sometimes
grooved and byssiferous. Shell regular, closed ; hinge with usually
three diverging teeth in each valve.

Genera Venus^ Cytherea, Artemis^ Lucinopsis, Venerupis, Petri-
cola, Glaucomya.

Family Mactridce.

Mantle more or less open in front ; siphons united with fringed
orifices ; foot compressed. Shell equivalve, trigonal ; hinge with two
diverging cardinal teeth, and usually with lateral teeth.

Genera Mactra, Gnathodon^ Lutraria, Anatinella.

Family TellinidcB.
Mantle widely open in front ; foot tongue-shaped, compressed ;
siphons separate, long and slender. Shell usually equivalve and

M M 3

534 LECTURE XXI.

closed ; cardinal teeth not exceeding two, laterals 1-1, sometimes
wanting.

Genera Tellina^ Psammobia, Sanguinolaria, Syndosniya^ Scrohi-
cularia, MesodesmUy Doiiax.

c. Mantle sheath-shaped, closed, save at the pedal and siphonal
apertures.

Family Solenidce.

Siphons short and united (in the long-shelled genera), long and
partly separate (in the shorter and more compressed genera) ; gills
prolonged into the branchial siphon ; foot large, subcylindrical. Shell
gaping at both ends.

Genera Solen, Cultellus, Machcera, Solecurtus.

Family Myacidce.

Siphons united ; foot small. Shell gaping behind.
Genera Mya, Corbula, NecBra, Thetis^ PanopcBa, Sdxicava, Gly-
cimeris.

Family AnatinidcB,

Siphons long, more or less united ; foot very small. Shell often
inequivalve.

Genera Anatina, Thracia, Pholadomyay Lyonsia, Pandora, Myo-
chama, Chamostrea.

Family GastrochcenidcB.

Siphons long, united to near the extremities ; foot finger-shaped,
sometimes grooved and byssiferous ; mantle with a boring disc in
front. Shell regular, wedge-shaped, gaping in front, in some more
or less cemented to a superadded calcareous tube.

Genera Gastrochcena^ Clavagella, Aspergillum.

Family Pholadidce.

Animal clavate or vermiform ; siphons large, long, united nearly
to their ends ; foot short and truncate. Shell gaping at both ends ;
hingeless, with sometimes accessory valves, or a supplementary tube
and palettes.

Genera Pholas^ Xylophaga, Teredo, Teredina.

PTEROPODA AND GASTKOPODA. 535

LECTURE XXII.

PTEROPODA AND GASTROPODA,

Although the Acephalous MoUusea are for the most part deprived
of the power of locomotion, or have it granted to them in a very low
degree, yet some species of Lamellibranchs can swim, and the pectens,
from their lively movements in the water, and the vigorous flappings
of their brightly tinted valves, have obtained the name of sea-butter-
flies. Amongst the Mollusca provided with a distinct head locomo-
tion is the rule. Lithedaphiis, indeed, is fettered by its calcareous
operculum to the rock on which it grows, and Magilus becomes im-
moveably sunk in its coral bed ; but these are rare exceptions.
Amongst the numerous free and locomotive Encephala, some creep,
some climb, some swim ; a few combine these different powers ;
whilst certain small species have no other mode of progression than
by floating or swimming on the surface of the ocean. These are pro-
vided with two fin-like muscular expansions, attached to the sides of
the neck, which, from their resemblance to wings, suggested to
Cuvier * the name Pteropoda for this small but well marked group
of MoUusks with heads.

Some Pteropods are provided with a light and delicate semitrans-
parent shell. In the Hyalcea, it resembles a bivalve shell, of which
the two valves had been cemented together at the hinge, leaving a
narrow fissure in front and at the sides. In the Cleodora, the two
plates of the shell are united together along the sides as weU as at the
base, leaving an opening only in front. The shell of the Limacina
is a cone twisted spirally in one turn and a half. The shell of the
Cymbulia is symmetrical, like a boat or slipper, but is cartilaginous.
The Clio and Pneumodermon are naked, or without shells.

All the species of Pteropoda are of small size ; they float in the
open sea, often at great distances from any shore, and serve, with the
Acalephae, to people the remote tracts of the ocean. In the latitudes
suitable to their well-being, the little Pteropoda swarm in incredible
numbers, so as to discolour the surface of the sea for leagues ; and
the Clio and Limacina constitute, in the northern seas, the principal
article of food of the great whales.

Those Pteropoda which have symmetrical shells composed of two
plates have one applied to the dorsal, and the other to the ventral,

* CCCXXI.

M M 4

536

LECTURE XXII.

195

surface of the body, as in the Brachiopods. The shell is bivalve in
form, but the two valve-shaped plates are confluent at the part
representing the hinge («, b, c), and their free borders do not correspond.

In Jiff. 195, No. 1 shows the
ventral surface of the Hi/-
alcBa, with the head w, and
its wing-like muscular ex-
pansions I, m. The hinder
or abdominal division of the
body is protected by the
shell, which terminates be-
hind in three points, a,
b, c. The ventral plate d
is the shortest and most
convex : the dorsal plate,
2, is nearly flat and oblong.
The lateral borders of the
two plates, c e, bf^ are sepa-
rated by a long and narrow fissure, through which the extensile borders
or appendages of the mantle can be protruded. The head and its fins
project from the wider anterior opening. The fins /, m, are supported

on a short and thick neck or
pedicle (3, c) : in the living
animal they are of a bright yel-
low colour with a deep violet
spot near their base, which, with
their flapping movements, gives
them a resemblance to the wings
of a butterfly. Between the fins
are two small labiate folds, in-
cluding the mouth and the outlet
of the penis.

A cylindrical muscle {fig- 196,
u) arises from the middle point
{a) of the shell, and traverses the
visceral mass to be inserted into
the neck ; it divides for that
purpose into four short fasciculi,
which diverge in the substance
of the fins : other strata of mus-
cular fibres decussate the pre-
ceding obliquely in those loco-
motive expansions. The nervous

196

PTEROPODA AND GASTROPODA.

537

Hyalaea.

system in this blind and non-tentaculate pteropod partakes of
the simplicity of that in the bivalves ; inasmuch as there is no
ganglionic enlargement of the upper part of the oesophageal loop.
The chief centre (_Jig* 197, r) consists of a large flat subquadrate

suboesophageal mass, from the an-
197 terior angles of v\'^hich proceed

the chords encircling the gullet,
and some nerves to the fins : the
other nerves to the fins and those
to the rest of the body are given
off from the posterior angles of
the great ganglion.* The acous-
tic vesicles are in contact with the
fore part of this ganglion ; they
are large, and have otolites, kept
in motion by the vibratile cilia
of the inner surface of the vesicle.
The lingual teeth are arranged
in transverse rows of three in
each ; they are long and recurved.
The oesophagus {v,Jigs. 196, 197)
overlies the penis ; it dilates into
a kind of crop {Jig. 197, w), which conducts to a cylindrical gizzard
{x) : both these have their inner surface produced into longitudinal
folds (9), those of the crop {w) being more numerous than
those of the gizzard (x). The intestine {Jig. 197, y) is a narrow
tube of uniform diameter, which describes two convolutions, bending
towards the ventral surface, in the substance of the liver (^Jig. 196,
6, a?, and 197, z^ z). The anus is on the right side of the neck,
beneath the right fin. In Sagitta the hepatic substance appears to
be blended with the intestinal walls. In Pneumodermon the stomach
is lined by a layer of small hepatic follicles. If the dissection of
Ilyalcea be made from the dorsal aspect, as in Jig. 196, 6, the heart,
which consists of an auricle and a ventricle, is seen on the left side
upon the inner border of that end of the gill, s. This branchial
organ is a long narrow body subdivided into small transverse
ciliated lamellge, and describing a curve which runs almost parallel
with the border of the shell-cavity, p, q, s^Jig. 196, 6, and^^. 19o, 4.
A contractile renal organ opens into the branchial cavity.

The male and female organs are combined in the same individual
in all Pteropods. The ovario-testis {Jig. 196, 6, iv), presenting a

* Cuvier, owing to his opinion as to the dorsal and ventral aspects of the
Hyalaea, describes this ganglion as the brain, CCCXXI.

538

LECTURE XXII.

Structure like that in the snail (p. 561),* is a large oblong body
placed in the middle of the visceral mass. A long and slender vas
deferens, with which communicates a csecal tube, communicates with
the duct of a large albuminiparous gland or uterus {fig. 196, 5, y)
occupying the left side of the abdomen : the common canal terminates
by an orifice anterior to the mouth. From this orifice the exciting
organ (^fig. 197, 8) can be protruded.

Of the naked Pteropods, fig. 198, shows the Clio borealis, of the
198 natural size: 1 from the

ventral aspect, with the
cephalic lobes contracted :
2 and 3 the same, with
those lobes expanded,
showing the conical ce-
phalic appendages s, the
two tentacles 4 the eyes
o, the rudimental foot o,
and its posterior lobe k' ;
the fins a, a ; the gene-
rative pouch g ; and the
protruded intromittent
organ h, along the con-
cave side of which runs
the generative duct d. 4
shows the animal from
the dorsal aspect, with
the cephalic lobes con-
tracted. 5 and 6 show
the animal, as seen from
the right side with the
fins cut off, so as to ex-
pose e the long orifice of
the accessory generative
pouch ; i the proper generative pore, and t, the anus : p is the " con-
strictor cervicis " muscle ; o the rudimental foot. Each lateral lobe
of the head supports three of the retracted processes, which, when
fully expanded, form a radiated crown about the mouth. Each of
the six processes is perforated by numerous cavities, recognisable to
the naked eye as red points, but which consist each of a transparent
sheath inclosing a central body composed of a stem terminated by a
tuft of about twenty microscopic pedunculated discs, the total number
of which in the head of the Clio, Eschrieht, their discoverer f,

* CCCXXX. t CCCXXIX.

Clio borealis.

PTEROPODA AND GASTROPODA. o39

estimates at 360,000 ! The head of the Pneumodermon, also a
naked Pteropod, is provided with ocular tentacles ; the mouth is
covered by a large hood supporting two small simple tentacles, and
two large processes beset with numerous pedicellate suckers. There
is a small oval foot, with a pointed posterior lobe, beneath the neck,
and a rudimental shell protecting the small branchial processes at
the bottom of the visceral cavity.

The cervical aliform expansions of the Clio are muscular, like those
of the HyalcEa, subserving locomotion, not respiration, as Cuvier
believed. In swimming, the Clio flaps the ends of the wings in
contact, first above, then below. The true branchial ciliated and
vascular surface is developed in all Pteropods upon the inner surface
of the mantle.

There are two slender and simple tentacula (^fig. 198, 3, k k\
which seem to exercise only the tactile faculty. Two superoeso-
phageal ganglia are developed upon the upper part of the nervous
collar which incloses the beginning of the alimentary canal ; the two
pedial and the two branchial ganglia are closely approximated and
connected with the inferior and lateral parts of the nervous collar.
From these centres the nerves are distributed to all the viscera and
parts of the body. The acoustic vesicles receive their nerves from
the suboesophageal ganglion, or the anterior pair, where the mass
is subdivided, as in Clio. Hyalcea seems to be blind : most other
Pteropods have eyes, and even the Sagitta has a pair of ocelli,
forming two prominences on the top of the head, and resting directly
on the ganglionic enlargement of the optic nerve.

The male and female sexual organs are combined in the same in-
dividual Clio : the duct of the voluminous ovario-testis communicates
with a spherical albuminiparous sac, and is then continued to the
base of the intromittent organ, which projects from an orifice on the
right side of the head ; it is almost as long as the body, and indicates
that impregnation takes place by reciprocal coitus, as in many of the
androgynous Gastropods. The sperm-reservoir is a pyriform vesicle
with a short peduncle.

The development of the ova of the Pteropoda has not yet been
observed ; but the larvse of some species have been detected ; that of
Pneumodermon has the end of the body encircled by two ciliated
bands. Vogt affirms that two deciduous ciliated cephalic " vela " like
those of the larvce of most marine Gastropods precedes the develop-
ment of the aliform fins.

540 LECTURE XXII.

Class Gastropoda.

The transition from the Pteropoda to the present class appears to
be made by the Philliroe. the Glaucus, the Carinaria, and the Firola^
all floating pelagic genera remarkable for the delicacy of their tissues,
and the rudimental character of their gastric foot. These aberrant
Gastropods manifest the same affinity to the preceding group by the
presence, in some, of lateral, symmetrical, more or less aliform ex-
pansions, and, in others, of a shell characterised by its elegant sym-
metry, lightness, and transparency ; that of the Carinaria much re-
sembles the shell of the Cymhulia in form, but is of a calcareous
texture.

The typical Gastropods, characterised by the greater development,
especially the breadth of their ventral muscular locomotive disc, con-
stitute a very extensive and widely distributed class of Molluscous
animals, many of which appear to have superseded the extinct in-
habitants of the chambered shells in the organic economy of the ex-
isting shores. Most of the species are marine ; many inhabit fresh
waters ; a few are terrestrial. They offer corresponding conditions
of the respiratory organs in relation to these media, with minor mo-
difications, of which systematic naturalists have availed themselves
in distributing the numerous and diversified members of the class
into orders.

In certain small shell-less marine genera, e. g. Rhodope, Tergipes,
Eolidina, no distinct respiratory organs have been detected ; these
form the order Apneusta.

Where those organs are present they are, in the lower forms of the
class, exposed. The genera which support them on the back, or the
sides of the back, as the Glaucus^ Scyllcp.a, Tritonia, form the order
Nudihranchiata, in which all the species are without shells in the
mature state. Those genera which carry the gills at the lower part of
the sides of the body, between the foot and mantle, as the Phyllidia,
constitute the order Inferohranchiata ; they are likewise naked when
mature. The genera in which the gills have a similar position, but
extend around the body, as in Patella and Chiton, form the order
Cyclobranchiata : they are defended by a conical shell composed of
one or many pieces.

In the rest of the class the respiratory organs are concealed. Those
genera, as the Aplysia and Bulla, which have the gills protected by
a fold of the mantle containing a rudimental shell, or by a reflected
process of the foot, form the order Tectibranchiata. Those genera,
as Limax or Helix, which have a vascular air-sac or lung, protected

PTEROPODA AND GASTROPODA. 541

by a rudimental, or fully developed shell, form the order Pulmonata.
In all the foregoing orders of Gastropods the male and female organs
of generation are associated in the same individual. In the re-
mainder of the class the sexes are distinct. A small order of marine
Gastropods, including the Fissurella and Haliotis^ which have their
pectinated branchiae protected by a wide shield- shaped shell, is
called Scutibranchiata. Another small group in which similar
branchiae are protected, with the entire body, by a tubular shell, is
called Tuhulihranchiata. In the last and highest organised order,
called Pecti?iibranchiata, from the comb-shaped gills which have a
special cavity at the fore part of the back, the males are provided with
an intromittent organ.

The soft parts of the Gastropods are immediately invested by a
soft inarticulated lubricous integument, forming, in most, a sub-
circular fold {Jig. 199, c) about the neck, behind which it is dilated

into a sac (ib. d) containing a portion
of the viscera, which fold and sac are
called the "mantle." In the skin
may be recognised an epidermal, a
pigmental, and a dermal layer, the
latter being of a musculo-cellular
structure and highly contractile.
'^^^^^- The epiderm is ciliated over

nearly the whole body in the aquatic Gastropods, but only in certain
spots in the terrestrial species. The white striae at the sides of the
neck and foot of Helix are composed of short, thickly-set, calcareous
needles: the entire skin of Polycera and some other Nudibranchiates
is studded with analogous ramified spiculae.

The shell results from the metamorphosis and calcification of cells
deposited in layers beneath the epidermis, in the situation of the
rete-mucosum in the human integument. In Limax and Clausilia
the first trace of the rudimental shell is in the form of crystals of
carbonate of lime in the substance of the mantle.* Its formation in
the univalve Gastropods commences in the embryo, and the first-
formed part is called the nucleus of the shell ; the succeeding layers
are not, however, formed around this, but are added to the inner
surface of the circumference of the previously formed parts ; and the
proportions in which the new-formed layers extend beyond their
predecessors determine the figure of the future shell. In some
Gastropods, at certain seasons, the margin of the mantle, in which
the shell-forming process is most active, extends outwards at an

* CCCXLI. p. 372.

542

LECTURE XXII.

200

obtuse or right angle to the last-formed margin of the shell, and after
having formed a calcareous plate in this position, the mantle extends
in the ordinary direction, increasing the length of the shell, and is
again similarly extended at a right angle with the last-formed part ;
it is to this periodical growth of the mantle and plethoric condition
of the calcifying vessels that the ridges on the exterior of the shell
in the wentletrap {Scalaria pretiosa, Jig. 200) are due. Should the
margin of the mantle, instead of being uni-
formly extended, send outwards a number of
detached tentaculiform calcifying processes,
these will form a row of spines corresponding
in length and thickness to the soft parts on
which they are moulded; and, as the calcification
of the processes proceeds, the spines, which
were at first hollow, become solidified, and
finally soldered to the margin of the shell.
This development of pallial calcifying processes
or filaments, and of the resulting spines, likewise
alternates with periods of the ordinary increase
of the shell ; and thus its exterior surface
may become bristled with rows of spines, as
in the Murex crassispina. The periodical ex-
cretion of the excess of calcareous matter in the
blood is greatest in the carnivorous univalves.

The most simple form of univalve shell is the cone, which may be
much depressed, as in the genus Umbrella, or extremely elevated and
contracted, as in Dentallum, or of more ordinary proportions, as in
the Limpets (^Patella). The apex of the cone is always oblique and
excentric ; directed in the Limpets towards the head, but in other
Gastropods towards the opposite extremity of the body. The
conical univalve shell is generally spirally convoluted, sometimes in
the same plane, e.g. Planorbis, but more usually in an oblique
direction. The apex of the shell (a) is formed by the nucleus, or
part developed in the egg : it is maramillated in Fiisus mitiquus.
The spiral turns of the shell {h h) are called "whirls," the last
(6, d\ being the ^' body-whirl."

As a general rule the spiral univalve, if viewed in the position in
which its inhabitant would carry it if it were moving forwards from
the observer, is twisted from the apex downwards from left to right,
the spire being directed obliquely towards the right ; but in a few
genera, e. g. Clausilia, Physa, the shell is twisted in the opposite
direction, when it is called "reverse" or "sinistral." Some individuals
of BiiUnus, Par tula, and Pupa, and of a few marine species, as Fusus

Scalaria pretiosa.

PTEROPODA AND GASTROPODA. 543

sinistrorsus, are sinistral. The part around which the spiral cone is
wound is termed the " columella : " this is sometimes simple, some-
times grooved, sometimes plicated ; in some shells it is solid, in
some hollow; in the latter case its aperture is termed the "umbilicus *'
( Solarium).

The aperture which forms the base of the spiral univalve is bounded
by an "outer lip" {d\ and an "inner lip;" the latter offers a
smooth convex surface, over which the foot of the Gastropod glides
to reach the ground. In many univalves the aperture of the shell is
entire ; in others, the left side is formed only by the " body-whorl ; "
or the peristome (as the margin is called) may be broken by a notch,
or perforated by one or more holes, or a portion of it be produced
into a canal or siphon. These modifications are important on
account of the constancy of their relation to certain conditions of
the respiratory organs. Thus all the pectinibranchiate Gastropods,
in which the water is conducted to the shell by a muscular tube or
siphon, have the margin of the aperture of the shell either notched or
produced into a canaL Sometimes there is a posterior channel
which is anal in its function {Strombidce) : it is represented by a
slit in ScissureUa, a tube in Typhis, a perforation in Fissurella, and
a series of holes in Haliotis.

The Gastropods which first appear in the palaeozoic strata have
entire mouths ; the siphonated species are not found lower than the
lias, and they go on increasing in numbers in and from the tertiary
series to the actual sea shores.

In some of the Gastropods the shell consists of one piece, when it
is termed an " inopercular univalve ; " but the aperture of the shell
is in the majority of the species closed by a plate, attached to the
back of the foot, and called the " operculum " {Jig. 208, b). This is
sometimes calcareous, forming a second shelly plate ; but it more
frequently consists of albuminous membrane only, or is horny ;
thus presenting the condition which the shell itself manifests in
certain genera, as Limax and Aplysia. Some opercula increase by
the addition of matter to their entire circumference, and these are
either concentric, as in Paludina, or excentric, as in Ampullaria
and most of the Pectinibranchs. Other opercula grow by the
addition of matter to part of their circumference, and these are
either spiral or imbricated ; in the latter the layers of growth
succeed each other in a linear series. No operculum presents an
annular form. Deshayes figures the operculum of Solarium patulum
as composed of many distinct and spirally disposed lamellce. Mr.
E. Layard has discovered a similarly complex operculum in the
Cataulus Austeiiianus, a little univalve of Ceylon. As the oper-

544 J.ECTURE XXII.

culum sometimes varies in structure in the same genus, being horny
in some species, and shelly in others of AmpuUaria and Natica, — as
it is present in some volutes, cones, mitres, and olives, and absent in
other species of those genera, — and as some genera in a natural
family, e.g. HarpcB and Dolium among the Buccinoids, are without an
operculum, whilst the other genera of the same family possess that
appendage, — it obviously affords characters of secondary importance
in classification. In Lithedaphus ( CaiyptrcEd) equestris the whole
base of the foot secretes a calcareous plate which is cemented to the
rock, and the shell appears to consist of two valves. In the Chiton
the shell is divided into eight symmetrical pieces arranged like scales
upon the back : the first of these is the smallest, the last the longest
and most approaching the circular form.

In the interior of the shell the muscular impression is usually
crescentic, with the horns turned towards the head of the animal.

Most univalve shells are composed of three strata, which differ
in the arrangement of the calcareous particles : the innermost layer
is nacreous in the fucivorous univales, e. g. Patella, Haliotis, and
resembles enamel in the marine species. In Cassis rvfa each
layer is composed of many laminse, which are perpendicular to the
plane of the main layer ; and each lamina consists of a series of
prismatic cells, adherent by their long sides : the laminae of the
outer and inner sides are parallel to the lines of growth, while those
of the middle layer are at right angles to them. In the Cowries
(^CyprcBce), there is an additional layer, which is nacreous, and formed
by the over-lapping mantle-lobes when the animal has attained its
full growth. Such shells are called " Cameo-shells," those ornaments
being formed by the removal of one layer, and the carving of the
next. Hunter* discovered that the molluscous inhabitant of a shell
had the power of absorbing part of its dwelling. This property,
which is now generally recognised, is well illustrated by the thinning
of the parietes of the internal whorls of the Cones and Olives, from
which two out of the three layers of which they were originally
composed may be observed to have been removed. The absorption
of shell is also illustrated by the removal or smoothing down of the
spines of the 3Iurices, as the growing whorl expands and overlaps its
predecessor ; by the flattening of the inner lip of the mouth of the
PurpurcB ; by the widening of the f^cal aperture of the Fissurellce ;
and it gives rise to various other modifications in the form and
structure of shell in the progress of growth. Another change of
form is due to the physical decomposition or destruction of a part of

* Phitos. Trans. 1785, p. 343,

PTEROPODA AND GASTROPODA. 545

a shell during the lifetime of the inhabitant. This occurs to the
apex of certain univalves after the shell has been evacuated by the
original occupant in the widening and lengthening the shell to
accommodate it to an increase of bulk : such shells are said to be
" decollated," as, for example, the Bulinus decollatus.

The inhabitants of univalve shells dispose in different ways of that
part of their calcareous abode which they evacuate in the progress of
growth ; in the decollated shells the vacated spire is portioned off,
prior to its abrasion, by the formation of a thin nacreous plate. In
the Vermetus gigas the vacated portions of the tube are retained, and
successively portioned off, a series of concave plates or septa being
thus developed. In the Magilus antiquus the posterior part of
the shell, as the soft parts move forwards, is progressively tilled up
with a dense, solid, subtransparent, crystalline deposit of carbonate
of lime.

Univalves which inhabit rocks upon which surf-waves are ever
breaking, have stronger and denser shells than those that live in
calmer seas, or in sandy and muddy bottoms. The shells of air-
breathing mollusks exhibit analogous effects of external influences ;
those of the burrowing Bulini, e. g., are colourless and subtrans-
parent ; but the shell is vividly coloured in the species inhabiting
plains with scanty vegetation and much exposed to solar light : the
shells are largest and thickest in the arboreal Bulini of tropical
forests, which live amongst an abundance of decaying vegetable
matter.

The part of the mantle which invests the viscera in the conchifer-
ous Gastropods is smooth, thin, and sub-transparent, resembling the
sac of a hernia, which, with the viscera themselves, appears to have
escaped from the common muscular integument of the body. This
visceral mass, as it is termed, is lodged in the upper part of the cone
of the shell, the spiral turns of which it follows. The head and foot
of the animal can be protruded from the mouth of the shell, and be
retracted within its last whorl, by the action of a muscle, which has
its fixed point in the columella of the shell. This retractor, to which
the operculum when present is attached, answers to the posterior
retractor of the foot in bivalves. The form and size of the shell-
aperture correspond with, and indicate the size of, the foot. In the
pectinibranchiate Mollusks, which are the chief fabricators of the
beautiful turbinated shells of the conch ological cabinet, the foot is
attached to the anterior part of the body by a narrow base ; whence
they have been termed by Lamarck Trachelipods.

The primitive muscular fibre is smooth in all Gastropods : the pri-
mitive fasciculi have often numerous nuclei scattered through them.

N N

546 LECTURE XXIT,

The cutaneous muscular layer consists of oblique, longitudinal^
and transverse fibres, intimately united with the corium. Upon the
ventral surface it becomes very thick, and forms a long disc called
the " foot." The fibres of this part contract successively, so as to
form -wrinkles or transverse waves following each other from behind
forwards ; whereby the disc glides over solid bodies or the surface of
water. The circular foot of the limpet is used as an adhesive sucker.
In some species it expands to a great breadth; in many it is ex-
tended lengthwise, and more or less cleft transversely; so that in
some species three divisions may be indicated : the anterior of these
is distinct in Natica ; the middle division forms the chief creeping
disc ; the posterior one supports the operculum, when this is deve-
loped. The posterior lobe of the foot in the inoperculate Harpa is
said to separate spontaneously when the animal is irritated. In
Atalanta it is compressed, but supports the operculum : it seems
also to form the tail in the beautiful Carinaria, in which the
middle part of the foot is reduced to a small suctorial disc, sup-
ported by a part the form of a fin.* This mollusk and its allies,
hence called Heteropoda^ swim on their back with their locomotive
foot upwards. The tentacles, buccal mass, and penis, have their
special retractor muscles in most Gastropods.

In the living Cyprcea and Ovula the mantle-lobes are observed to
be in almost constant tremulous motion : but the most^ vigorous
muscular efforts in Gastropods are those of the foot combined with
the retractor shell-muscle. The Strombs and Scorpion-shells thereby
progress by successive jumps ; the active Olives can turn over when
laid on their back, and bury themselves in the sand as the tide
retires ; the periwinkle advances alternately the sides of its longi-
tudinally indented foot ; Buccinum arcularia defends itself by its
dentated operculum.

At the grade of the Molluscous organisation which the Gastropods
have reached, their capabilities and spheres of action become more
extended and diversified than in the Pteropods and Acephala ; some
are terrestrial, some arboreal, whilst the more numerous aquatic
species are endowed with power to attain, subdue, and devour organ-
ised matter, dead and living. The nervous system of the Gastro-
pods is accordingly not only more complex and concentrated, not
only subordinated to better developed masses in connection with
organs of special sense and exploration, but it offers greater variety
in its general arrangement, and especially in the position of its gan-
glions, than in the Lamellibranchiate class, and with these modi-
fications considerable differences in the outward configuration of the
body are associated.

* CCCVII. p. 198.

PTEROPODA AND GASTROPODA. 547

A few Gastropods, for example, are symmetrical, more or less flat,
or depressed; others are compressed; the majority are contorted and
lose their symmetrical form in an oblique twist : there are other di-
versities of organic structure which more immediately affect the con-
dition of the nervous system, for some species possess both eyes and
tentacles, whilst others are blind and akerous.

The nervous system has a distinct fibrous neurilemma, often
charged with pigmental cells. The ganglion-cells are often pedun-
culated, and have usually a very large nucleus composed of obscure
granules, in the midst of which are usually two to four transparent
nuclei. The central part of the system surrounds the oesophagus,
and consists of different parts, of which that which is above the tube,
and which usually includes two contiguous ganglia, is called the
brain.

In the limpet (Patella), and bubble-shell (Bulla), we find that the
cerebral ganglions, as in the bivalves, are still distant from each
other, and situated at the sides of the oesophagus, connected together
by a nervous chord or commissure which arches over that tube :
from these ganglions two filaments proceed backward on either side ;
the median and superior pair passes along the sides of the oesophagus,
converges and meets below to form a pair of ganglions in close
contact with one another which supply the foot and viscera : these
are evidently homologous with the bilobed pedial ganglion of the
Mytilus. The lateral and inferior filaments pass downwards to join two
widely separated branchial ganglions, homologous with those situated
on the posterior adductor in the Mytilus. We observe, however, a
considerable difference in the relative positions of the pedial and
branchial ganglions in the limpet ; the latter have advanced into
close contiguity with the pedial ganglions, and are connected with
them by the same transverse chords, which in Pecten and Mytilus
serve merely to bring the branchial ganglions themselves into mutual
communication.

We thus observe in the lowest and least locomotive Gastropods a
tendency in the nervous system to be aggregated at the fore-part of
the body, the cerebral ganglions rising more to the upper surface of
the now well-developed head, and the branchial and pedial ganglions
beginning to concentrate themselves about the mouth. But this
march of development does not prevent the homologies of the different
ganglia from being satisfactorily traced. In the limpet there is a dis-
tinct head and mouth, with organs of special sense ; and besides the
large antennal and small ophthalmic branches given off from the
cephalic ganglia, we find also superadded (infero-pharyngeal) ganglia,
having evident relation to the muscular mouth and pharynx and to

N N 2

548 LECTURE XXIL

the complex tongue, which are so many accessory parts appended io
the simple opening of the gullet, with which the alimentary canal
commences in the bivalves. The additional ganglia in question are
placed below the pharynx, and are brought into communication with
the sentient centres by a filament continued downwards and forwards
from each of these ganglia : they also inter-communicate by a loop
which forms a third azygos rudimentary ganglion beneath the
oesophagus completing an anterior ring corresponding to that which
is formed by means of pedial ganglion posteriorly.

The ganglions corresponding to the pedial pair in the BullcBa ap-
pear not to be joined together by a transverse band, but to be con-
nected only with the branchial ganglion, and through them with the
cerebral ones. The three are placed so close together, that Cuvier
describes them as forming one mass. There are two pharyngeal
ganglia formed upon filaments descending from the cerebral ganglions.
The labial ganglions, which are developed in addition to the pedial
ganglions, originate from the latter in the JBulla lignaria and are
connected, through them, with the cerebral ring.

In the HaliotiSy the superior or oesophageal part of the oesophageal
circle is still a simple commissural chord. The sides of the circle are
formed by a double chord, which unite below in a single branchio-
pedial ganglion ; from which the visceral, as well as the branchial and
muscular, nerves radiate. The cerebral ganglia are distinct and
connected by a commissure in Janthina^ Turbo, Lymneus, and
Planorbis. The sub-oesophageal mass in the Limnceus stagnalis is
of an orange-colour, and consists of seven ganglions united together
by a loose cellular tissue.

In the Doris and Onchidium the cerebral, pedial, and branchial
ganglions have coalesced into one annular mass, which, however, is
chiefly super-oesophageal in its position, united below^ by a slender
chord passing across the under parts of the oesophagus. Two small
nerves are given off, which descend and form two small pharyngeal
ganglia, which, according to Cuvier, are united together. In the
Doris Solea the quadripartite character of this large mass is however
obvious. The olfactory ganglia are sessile in front of the cerebrals.
This is the general character of the nervous centres in other Nudi-
branchiate and Apneustal Gastropods. The optic ganglia are at the
back part of the cerebral, on which the acoustic capsules are sessile.
The pharyngeal ganglia complete a small ring about the beginning
of the oesophagus, and the pedial, or chief sub-oesophageal masses,
with their intervening commissure, form the second and chief ring.
The branchial ganglia are behind the cerebral ; they supply the
skin of the back and the gills : beneath and sessile on their front

PTEROPODA AND GASTROPODA.

549

border is the single visceral ganglion, from which proceed the nerves
forming the plexuses about the viscera, which are in communication
with the pharyngeal or anterior ganglia of this stomatogastric system
of nerves.*

In the Paludina vivipara the super-oesophageal ganglions (y%r. 204.
w, ti) are distinct, and connected together by a transverse commis-
sural filament. The sub-oesophageal mass sends its principal branches
to the foot ; but one nerve comes off from the right side, crosses the
oesophagus, and expands into a small ganglion :c, which distributes
its filaments to the retractor muscle that attaches the animal to its
shell.

In the slug and snail (j^g, 201.) the principal centres of the ner-
vous system are a super-oesopha- 20 1
geal (/) and a sub-oesophageal {m)
mass ; but the complex character
of the latter and larger mass is
indicated by the triple nervous
chord, which completes on each
side the collar round the alimen-
tary tube. From the inferior mass
the nerves radiate to the muscular
foot, the soft and susceptible in-
tegument, and the circulating and
respiratory organs. The upper
ganglion receives the large nerves
of the tentacles (ef) and ocelli
(w) ; it also communicates on each
side by two minute filaments, pro-
ceeding from its posterior and
outer angles, with a small pair of
stomatogastric ganglions situated on the side of the oesophagus.

In the Aplysia the sub-oesophageal ganglionic mass is divided into
two parts, which are joined together by a transverse chord, and
brought into communication with the cerebral ganglions by ascend-
ing and converging chords. The cerebral ganglions are blended
together above the oesophagus, and assume the position of a true
brain. They supply nerves to the tentacles, and give off anteriorly
two chords, which turn forwards to join below the mouth, where
they form a second oesophageal collar upon which the pharyngeal
ganglions are developed. The branchial ganglion is situated towards
the posterior part of the body ; the connecting chords of this ganglion

structure of the tentacles in the Garden- Snail;
{Helix ne7)ioralis).

* CCCXLVI.

N N 3

550 LECTURE XXII.

join those of the pedial ganglia, but may be traced directly to the
brain.

The position of the cerebral ganglions varies according to the
degree of extensibility of the mouth and oesophagus. Thus, in the
Helix., they are placed above the mouth ; in Carocolla^ at the com-
mencement of the oesophagus ; in the Buccinum or Whelk, near the
end of the tube ; in the Purpura^ beyond the stomach.

As a general rule, we find that the superior ganglions give off
tentacular, ocular, and oral nerves, whilst the inferior masses are the
centres of the muscular, respiratory, and visceral internuntiate chords.
The latter have, in addition to the infero-pharyngeal centres, also a
posterior splanchnic ganglion, or pair of ganglions, from which a
plexus of nerves proceeds, in many Gastropods ( Carinaria, Doridiumf
Pleurobranchus). They are situated beneath the folds of the intes-
tine, communicate with the sub -oesophageal ring and the branchial
ganglion, and supply the intestinal canal, liver, and genital glands.
In the spiral pectinibranchiate univalves, where the branchiae and
their nerves are twisted to the left side, it is the left branchia which
is atrophied, while the right one is of large size. The nerves are
similarly affected, the left one being filamentary ; whilst the right is
a large chord, and has the accessory branchial ganglion developed
upon it. The principal oesophageal ganglionic circle is surrounded
by a thick membrane, which, in the large Tritons, assumes almost a
cartilaginous hardness. A coloured pigment is not unfrequently
found occupying a position analogous to that of the arachnoid, be-
tween the dense outer membrane and the ganglions. In the Limnceus
and in the Planorbis this pigment gives to the ganglions their orange
or roseate hue.

Amongst all this diversity in the number, size, and position of the
nervous masses, certain ganglia are obviously homologous with those
which have received determinate names in the lamellibranchiate
Mollusks.* The branchial ganglions receive impressions from, and
transmit them to, the gills : they communicate also with the brain,
and through that centre associate the gills with all other parts of the
body. The pedial ganglion is more commonly divided than in the
bivalves, and the two divisions are wider apart, in consequence of
the great breadth of the foot. In those Gastropods which possess a
naked muscular mantle, we find a pallial ganglion associated with a
pedial one, as in the Ajjlt/sia. The cephalic ganglions assume the
character of optic lobes concurrently with the constancy and better
development of the eyes ; even when the organs of vision are more

* CCCLVL p. 488.

PTEROPODA AND GASTROPODA. . 551

than usually minute or wanting, these ganglions are always larger
than in the Acephala, and more decidedly superior in position ; they
supply the acoustic vesicles in many Gastropods. When separate,
they are united by a thicker communicating chord, and are larger in
proportion to the nerves given off from them. With the cephalic
ganglions, likewise, we find connected the labial and pharyngeal
ganglions. The anterior of the aggregated ganglions, which form
the sub-cesophageal mass in most Gastropods, are in immediate con-
nection with the acoustic vesicles in Pleurobranchcea and Paludina,
as in Clio and some other Pteropods. The functions of the other
ganglions of the body seem to be limited to the automatic reception
and reflection of stimuli.

Soft, lubricated, and irritable as is the skin of the naked
MoUusks, there are not wanting reasons for supposing it to be
possessed of a very low degree of true sensibility. Baron Ferussac,
for example, states that he has seen the terrestrial Gastropods, or
slugs, allow their skins to be eaten by others, and, in spite of large
wounds thus produced, show no sign of pain.

The vascular inferior surface of the foot may, perhaps, take cog-
nisance of the character of the surface over which it glides ; but the
special organs of the tactile sense are the tentacula or horns which
project from the lateral and upper parts of the head. These are
wanting in a few Gastropods, hence called Akera : they are some-
times two, and never exceed four, in number in the present class.
In the snails and slugs they can be retracted by an act of inversion.
The mechanism by which this is effected will be understood by re-
ferring to^^. 201., which exhibits the tentacles in different states of
protrusion. Each tentacle (b, c, d,) is here seen to be a hollow tube,
the walls of which are composed of circular bands of muscle, and
capable of being inverted like the finger of a glove. From the
common retractor muscles of the foot four long muscular slips are
detached, one {g) for each horn ; these run in company with the
nerve (/) to each tentacle, passing within its tube, when protruded,
quite to the extremity. The contraction of this muscle dragging the
apex of the organ inwards, as seen at c, inverts it, whilst its pro-
trusion is effected by the alternate contractions of the circular bands
of muscle of which the walls of each tentacle are composed. There
is, however, another peculiarity rendered necessary by this singular
mechanism, by which the nerves supplying the sense of touch may
be enabled to accommodate themselves to such sudden and extensive
changes of position ; for this purpose the nerves supplying these
organs are of great length, reaching with facility to the end of the
tubes when protruded, and in their retracted state the nerves are

N N 4

552 LECTURE xxn.

seen folded up within the body. In the figure, a a indicates the
origins of the retractor muscles of the foot from the columella ; b, the
right superior tentacle fully protruded ; c, the left superior tentacle
partially retracted ; d, the left inferior tentacle extended, and o, the
right inferior tentacle fully retracted and concealed within the body ;
f, the nerve supplying the superior tentacle elongated by its exten-
sion ; g, the retractor muscle of the same tentacle arising from the
common retractor muscle of the foot, and inserted into the extremity
of the tube ; h, the nerve of the opposite side thrown into folds ; i,
the retractor muscle of the same tentacle contracted ; k, the aperture
through which the nerve and retractor muscle enter the tentacle d ;
Z, the brain ; m, the sub-oesophageal ganglion ; ?^, the eye. In the
CyclostomidcE the tentacles are contractile, but not invertible.

The anterior is the normal or constant pair of tentacles ; the pos-
terior pair, which supports the eyes in the snail, is reduced to two
short processes, which extend from behind the basis of the anterior
tentacula in the Turbo, and which form slight projections from the
outer side of the base of those tentacula themselves in the Paludina
{Jig. 204.), and in most Pectinibranchiata. In the Aplysia, however,
which has four tentacula, the ocelli are sessile, and situated in ad-
vance of the bases of the posterior pair.

The eyes never exceed two in number in the Gastropods : they
are always very small in comparison with the bulk of the body ; they
present their largest relative size in the Pectinibranchiata. In the
preparation * from a large species of Murex, there may be readily
discerned the sclerotic tunic with its anterior orifice, the expansion
of the optic nerve posteriorly between the fibrous and the pigmental
tunic, and the large spherical crystalline lens, covered anteriorly by
the transparent corneal integument; between which and the lens
there is a very small interspace for the aqueous humour and the
pupillary circular opening left by the pigmental layer or choroid.
M. Lespes has summed up the results of an extensive series of
researches on the eyes of the Gastropods, by the following definitions
of the leading types of their structure : — a lenticular crystalline lens;
the vitreous humour fluid, non-adherent {Helix) : a lenticular crys-
talline body ; the vitreous humour thick and united to the lens : the
crystalline lens thick and slightly convex ; the vitreous humour
viscous and slightly adhering thereto.

The existence of the sense of hearing in the Gastropods was
inferred by Dr. Grant, long before the organ was detected : he justly
concluded that the sounds emitted by the Tritonia arborescens under

* No. 1628.

PTEROPODA AND GASTROPODA. 553

water, were doubtless intended to be heard by others of the same
species. The very general existence of an acoustic apparatus under
its most simple conditions, in the lower MoUusks, has been established
by the discoveries of Siebold. It consists of two round vesicles,
containing fluid and crystalline or elliptical calcareous particles, or
otolites, remarkable for their oscillatory action in the living or
recently killed animals. In the Limnceus {Jig» 202.), the acoustic
cells adhere to the posterior part of the 202

anterior ganglions of the great sub-oeso-
phageal mass {a a): e is the capsule ; f
the otolites. They hold a similar position
in the snail and slug, in which the num-
ber of otolites ranges from eighty to above
a hundred. The acoustic sacs are easily
recognised by submitting the head of the
smaller species of Gastropod, or of the
young of the larger species, to a gentle
compression under the microscope. The ^^""^^"^ ''^^''^^''^

movements of the otolites, due to the action of vibratile cilia, is
truly, as Siebold remarks, " a wonderful spectacle."

From the analogy of the soft mucous skin of the Gastropods to
the pituitary membrane of the nose, Cuvier was led to conjecture
that it might be the seat of the sense of smell ; but the analogy seems
to be too vague to render so general a diffusion of the nerves of a
special sense very probable. That the sense is possessed by these
Mollusca, is determined by the evidence which snails afford of scent-
ing their food : the structure which best suggests the olfactory
function is that which the two conical tentacles present in Doris,
Tritonia, and Scyllcea. The confluent tentacles forming the cephalic
lobe in the Bullidce may have the same function.* It is remarkable
that the laminated dorsal tentacles of the Nudibranchs, which seem
never to be used as organs of touch, are supplied with nerves from
the fore part of the super-oesophageal ganglions.

The tongue is, in almost all the Gastropods, a mechanical organ
for the attrition of the food : its complex horny unciuated armature
seems to unfit it for the delicate office of appreciating the sapid
qualities of nutritive substances ; but some sense of taste may be
exercised by the soft membranes of the pharynx.

The Gastropods are organised to subsist on a great variety of
food : they select both animal and vegetable matter in both their
living and decomposing states. The damage which the common slug

* CCCXLIX. p. 189.

554 LECTURE xxn.

and snail do, by devouring the produce of the garden, is too well
known: the whelk preys upon its congeners, nor do their strong
shells defend them from its attacks.

The mouth is always anterior, and is bounded by fleshy contractile
lips. These are developed, in Haliotis, into a pair of labial processes :
it is likewise generally armed with horny plates, trenchant or spiny,
disposed either as jaws, or covering the tongue. The upper lip in
the snail is armed with a crescentic dentated horny jaw, which is
opposed by the bifid soft lip below. In the Tritonia, a curved
trenchant horny plate works vertically upon another of similar form,
and with these, as with a pair of curved scissors, this molluscous
animal crops the tough sea-weed which constitutes its food. Certain
fresh-water Gastropods, as Limnceus and Planorbis^ combine two
lateral horny jaws with a superior dentated labial plate. The Limpet
rasps marine plants with a narrow horny plate or ribband beset with
numerous (160) rows of minute recurved hooks (supported by the
tongue, Jig. 203. a)*, which armature extends beyond the mouth, and
is longer than the entire body. 203

The apparatus is supported /p'"''^^'^^cl las a

by two firm parts (5, b\ from ^<^v ^^^^^K?^

which arise the muscles {a, a) yi /"^I^^^:^:^^^^^^^^^^^)

that work the rasp. A mag- y^ f.ff^ ^^^^^=^

nified view of the arrange- ff ^^^\ -^ a

ment of the lingual teeth is ^^^^ >) fi^SJ

given at b. These teeth are ^^^I^^ ^^^^S

amber-coloured, transparent, a b

^ ^ ^ • • j i • i Tongue of Patella.

insoluble in acid : plainly

silicious in the limpet and most other Gastropods. It is only at
the fore part of the tongue {d) that these teeth have the requisite
hardness : when worn down the part supporting them goes, and the
waste is supplied by the progressive * growth, with concomitant
hardening, of the lingual plate (c) behind. The soft reserve portion
of the spiny tongue is found folded sub-spirally beneath the viscera
of the Limpet.

The whelk is provided with a more complicated instrument in the
shape of a proboscis, susceptible of considerable elongation, or of
being entirely concealed within the interior of the body. Its ex-
tremity is vertically cleft, the divisions or lips having their inner
surface beset with recurved spines. In the interior of the muscular
cylinder, there is a tongue armed by an uncinated ribband, as in the
Limpets, but of much less length : it is stretched upon two elongated

* CCCXXXVIII.

PTEROPODA AND GASTROPODA. 555

cartilages, which can recede from or approximate each other, or be
moved together to and fro, by special muscles : by these movements
the spines can be made to scrape with force, the action being
like that of a convex saw against any opposed surface ; and it is by
the repetition of such movements, aided, perhaps, as Cuvier conjec-
tures, by a solvent property of the saliva, that the whelk effects
the perforations in the hard shells of other mollusca, upon the soft
parts of which it preys. In many other Pectinibranchs the mouth
has the form of a retractile proboscis {Cyprcea, Murex, Valuta,
Paludina, Jig. 204. p). In Doris, and most other Nudibranchs, the
tongue is beset with the siliceous spines. Excellent descriptions
and figures of the lingual dentition in the present class will be
found in CCCLVni. and CCCLIX.

The salivary glands present different forms and degrees of develop-
ment in different Gastropods, bearing the ordinary relations to the
construction of the mouth and the nature of the food. They are
usually two in number : their ducts, which are lined by a ciliated
epithelium, open into the oral cavity on each side of the tongue. In
the Calyptrcea I found the salivary glands represented by two simple
elongated secreting tubes : they also present the tubular form in
Aplysia, Thetys, and many Nudibranchs. In the whelk they present
a conglomerate structure, are situated on each side of the oesophagus,
at the base of the proboscis, along which they transmit their slender
ducts to terminate on each side the anterior spines of the tongue. In
the Paludina vivipara {fig^ 204.) the salivary glands are shown at
v. their structure consists of ramose caeca. In the vegetable-
feeding slugs and snails, the salivary glands are largely developed
{^fig, 207 a.) : they expand upon the sides of the stomach, partially
blend with each other and encompass that cavity, sending their long
ducts, «, forwards to the mouth, and are readily distinguishable by
their whitish colour. In many proboscidian pectinibranchs the sali-
vary glands are placed in the abdomen, and have long and tortuous
ducts, adapted to follow the movements of the dentated proboscis,
near the anterior end of which they terminate. In a few Gastropods,
e. g., Janthina, Actceon, Atalanfa, there are two pairs of salivary
glands.

A common type of the divisions and disposition of the digestive
canal in the Gastropods is exhibited in the common river-snail {Palu-
dina vivipara, fig. 204.) The oesophagus q is long and slightly convo-
luted ; q' is the last bend which the tube makes before expanding into
the stomach, r : s, s' show the folds of the intestine in the substance
of the liver and ovary ; it penetrates the branchial chamber at s", in
which the rectum, ^,is seen passing along the base of the pectinated gills,

556 LECTURE xxn.

g, to terminate at i, close to the margin of the'mantle/, which forms
the branchial aperture. The letter a indicates the foot in its state of
contraction, when its inferior or ambulatory surface is bent trans-

204

Paludina vivipara.

versely upon itself : b shows the operculum attached to the posterior
part of the foot : c are the tentacula with the attached ocelli : d is
the small siphon which projects below the right tentacle : 9i is the
heart, which consists, as in almost all Gastropods, of a single auricle
and ventricle : h is the long and wide oviduct, which performs the
office of the uterus in this ovoviviparous species : I is the duct of a
mucous or renal organ attached to the walls of the branchial cavity.*

The disposition of the viscera of other Gastropods offers few im*
portant deviations from that in the Paludina vivipara ; but some of
the peculiarities in the structure of certain organs deserve special
mention.

The oesophagus is comparatively short in Helix {Jig. 207. e.), and
shorter in Thetis and HoJiotis,

In a few Gastropods, the pond-snails {LyynncBa^ Planorbis), for
example, the oesophagus presents a small ingluvial dilatation : in the
whelk {Buccinum) a crop-like caecum is developed from the cardiac
end of the stomach. The gastric crop is wider in Aplysia, in which the

* CCCXXI.

PTEROPODA AND GASTROPODA.

557

Stomach of Aplysia.

coat3 of the second stomach, or'gizzard {fig. 205.), are thickened, and
the interior callous lining is beset with firm horny processes, some in
the form of hooks or canine teeth, others in that of rhomboidal plates
or molar teeth. These complexi- 2^2

ties relate to the low organised cha-
racter of the food of the Aplysice :
the sea-weed on which these Mol-
lusks subsist, after coarse masti-
cation and commixture with the
salivary secretions, is macerated in
the crop, conveyed to the stomach,
there pierced by the gastric spines,
percolated by the solvent juices,
and pounded by the horny plates.
The chyme is then mixed in the
duodenum (a) with the hepatic
secretion, and with the fluid, pro-
bably analogous to pancreatic
juice, which is secreted by a single long blind glandular sac {b\
communicating with the beginning of the intestine. A similar simple
form of pancreas is present in some species of Doris, and other fuci-
vorous genera of Gastropods, as Tritonia and Scyllcea, which like-
wise have horny gastric teeth. In the BullcBa aperta *, in which
the tongue is not armed with teeth, the stomach is surrounded with
three large horny plates, concave externally and convex towards the
cavity. In the Bulla lignaria^ the gastric triturating plates are
calcareous : two of these plates present an irregular triangular form,
with the angles rounded off, slightly concave externally, and convex
towards the gastric cavity : they are united together by strong trans-
verse muscular fibres attached to their circumference, except at the
upper part of the gizzard, where a third valve of an oblong form is
interposed between the two lateral ones. The imposition of the
name Gioenia upon the large gastric plates of the Bulla, as the
valves of a new bivalve shell, which was sold, whilst the deception
lasted, at fabulous prices, will not soon be forgotten by conchologists.
In regard to the number of cavities, the most complex stomachs
in the Gastropoda are those of Oncliidium, which has three longi-
tudinally plicated gastric compartments, and of Pleurobranchus, in
which they resemble those in the Ruminants. The first stomach
(fig. 206. a), which is membranous, receives the bile by a large orifice
(6) placed near its communication with the second digestive cavity

Preps. Nos. 493. 494.

t Prep. No. 492.

558

LECTURE XXII.

(c), which IS smaller and more muscular ; to this succeeds a third {d),

the sides of which are gathered into broad longitudinal 206

lamellae, precisely similar to those of a ruminant ; and

to render the analogy still more perfect, a groove is

found running along the walls of the second cavity

from one orifice to the other, apparently subservient

to rumination. The fourth stomach (e) is thin, and

its walls smooth. This animal feeds on Alcyonia and

small Zoophytes.*

The' intestine, after performing a few convolutions
in the substance of the liver and generative gland,
always more numerous, and of greater width in the
herbivorous than in the carnivorous Gastropods, ter-
minates, with a few exceptions, at or near the entry
of the respiratory cavity on the right side of the
body. The anus has a median position in the Doris
and Testacella, and terminates on the left side of the
body in the Planorbis.

In the Apneusta the alimentary canal departs so
widely from the ordinary gastropodous type, as to
have led some anatomists to regard it as a ground for
their separation from the class.f Caecal appendages
extend from the stomach, which, in most, are ramified, Pieurobranchus.
and in some {Eolis, Tergipes, Zephyrina) are continued into the dorsal
appendages.;]: But in all there is a rectum, terminating by a vent,
which usually opens on the right side of the fore part of the body.
The biliary secreting cells, in these little Gastropods, are developed
in the walls of the gastric caeca, most abundantly at their blind

ends.§

In the other orders of Gastropods the liver is a distinct and
usually bulky gland, subdivided into numerous lobules of a yellowish-
brown or brownish-green colour ; so disposed as more or less to en-
velope the intestinal convolutions {Jigs. 204. 207. h, h). Its secretion
is derived from arterial blood, and is usually poured by one or two
ducts into the commencement of the intestine. It is carried, how-
ever, into the stomach, near the pyloric orifice in Limax, Helix,
Testacella, Doridium ; and even into the oesophagus, in Oncliidium,
by two of its ducts, the third opening into the first stomach. The
Haliotis not only resembles the Palliobranchiata in the perforation of

* CCCXXI.

+ Under the term Phkbenteres, e. g. by Quatrefages, CCCLXII.
i CCCXLIII. § CCCLVI.

PTEROPODA AND GASTROPODA. 559

the stomach by the bile-ducts, but likewise in the perforation of the
ventricle of the heart by the rectum, and in the division of the
auricle into two cavities.

The blood of the Gastropods is often opalescent, with a few colour-
less corpuscles or cells, having an indistinct granular nucleus.

The auricle is divided in Fissurella and Chiton as in Haliotis.
Both auricles, however, equally receive the oxygenated blood from
the respiratory organ, as does the single auricle {fig' 207., o) in all
the other Gastropods. The ventricle (ib. p) propels the blood to
the viscera and muscular system of the body, and the heart is thus
systemic, co-ordinately with the condition of the muscular system
and the general endowments of the animal.* The heart is situated on
the right side of the back in the Pulmonata, most Tectibranchiata,
and the dextral Pectinibranchiata : it is on the opposite side in
Ancylus, Haliotis, and the sinistral Gastropods : it is to the left of the
dorsal median line in Carinaria ; and near the hinder end of the
body in Firola and Atlanta, The heart has a distinct pericardium
in all Gastropods save the Aptieiista, where it is not clearly defined.
The aorta, continued from tbe apex of the ventricle, divides into
two principal branches in most of the Gastropods. The auriculo-
ventricular aperture is usually defended by two semilunar folds.
The aorta, at its commencement, is frequently strengthened and en-
larged by a muscular layer, similar to the bulbus arteriosus in fishes,
and which, in the Aplysia, is continued beyond the origins of the
primary branches of the aorta. The ramifications of the aorta, as in
Crustaceans and Insects, are sooner or later lost in veins which
expand to form sinuses, occupying the lacunae of the viscera and other
organs of the body.f The anterior aorta terminates, e. g.y in Patella,
Triton, Haliotis, in a large lacunar sinus containing the brain, the
salivary glands, the oesophagus and retracted tongue. The resump-
tion of the normal vascular character by the venous system is more
or less sudden : and is best exemplified near the respiratory organ
upon which such venous trunk ramifies, like an artery, without any
interposed branchial or pulmonic heart. The large vence cavoe of the
Aplysia, e.g., are perforated by minute apertures, communicating
with the great sinus that lines the cavity of the abdomen ; and the
exterior of those veins is provided with decussating muscular fibres,
which probably regulate the diameter of such communications. The
diff'used condition of the vascular system most prevails in those Gas-
tropods in which the respiratory organs are least developed, e.g.,
the Apneusta. In the rest of the class the general modifications of

* LXXXIV., p, 7. t CCCXLL, CCCXLVII.

560 LECTURE xxn.

the respiratory organs are indicated by the characters of the orders
already defined. In the terrestrial Gastropods the breathing organ
has the form of the simple undivided vascular sac {fig' 207. m ii) like
the lung in the lowest air-breathing Vertebrate animals : its orifice
m, is on the right side near the head. The forms of the aquatic
breathing organ are as various as is its position.

In most of the Nudibranchiate species the gills are tufted and rami-
fied, as in the higher Anellides; they are penniform in the Haliotis, and
pectinated in all the dioecious Gastropods {fig. 204. g), as the name
of their order indicates : in these they never exceed two in number,
which are of unequal size, and the branchial chamber is usually pro-
longed into a siphon. In a few genera of amphibious Gastropods a
pulmonary sac is combined with branchial organs. The branchial
surface is ciliated in all the Gastropods, as is also the exterior surface
of the body in the small fresh-water species.

As a compensation for the absence of gills, some Apneusta {Actaeon,
e. g.), have an aquiferous system, consisting of a reservoir, filled with
water, behind the heart, from which branched canals pass ofi" in all
directions, one of which, according to Vogt, opens on the right side
behind the vent. Conspicuous aquiferous pores are situated at the
centre of the foot, in CyprcEa, Conns, and Ancillaria, and at its mar-
gin in HaliotiSy Doris, and Aplysia. Delia Chiaje * has described
a similar system in many of the higher organised Gastropods.

Besides the large and well developed hepatic and 'salivary glands
which are associated with the alimentary canal, we have seen that cer-
tain fucivorous Gastropods present the simplest rudimental condition
of the pancreas. The situation of the follicular urinary gland and of
its excretory duct has already been pointed out in the Paludina
vivipara: in some species the duct dilates to form a small recep-
tacle-t A group of follicular glands, sometimes imbedded in a distinct
glandular sac, is present in many species for the elimination of some
peculiar and characteristic colour ; the yellow liquid of the BuHcb,
and the famous purple secretion of the Purpura, are products of
saccular modifications of this follicular gland, which is situated
between the heart and liver. Numerous simple and scattered folli-
cular glands lubricate the mantle with its characteristic mucus in all
the Gastropods. In several terrestrial species, the median line of the
foot is occupied by a straight canal, lined with ciliated epithelium,
which ends in a large orifice beneath the mouth. On each side of
this canal are rows of follicles which secret a granular mucus.J A
follicle excreting a similar mucus opens on the extremity of each

* CCCLXXIII. t CCCLX, p. 13. and CCCLXI. J XXIV. p. 343.

PTEROPODA AND GASTROPODA. 561

dorsal or lateral lobe in the Apneusta with those appendages. Some
peculiar scent-follicles must exist in the garlick snail {Helix aUiaria)-
A species of slug, called plwsphorax, is slightly luminous.

Gastropods have the power of repairing injuries and of reproducing
lost parts to a considerable extent. New tentacula soon grow to
replace those which may have been amputated. When they support
eyes, as in the snail, the organs of vision are also reproduced : the
mouth, with the horny jaw, has grown again in this Gastropod; and
when the snail has been decapitated, but with the oesophageal gang-
lions left behind, the head has been restored.

The general conditions of the sexual system have been already
briefly defined. The complexity and bulk of the combined organs in
the common slug and snail are truly extraordinary. The essential
organs, testis and ovarium, are associated together in the form of a
small, compact gland {fig. 207, q)*, composed of many parallel caeca,
imbedded in tlie substance of the liver, and occupying, in the snail,
the apex of the shell. Each ca3cum consists of an external layer,
producing ova, and an internal sac, folded in the first, producing
semen.f The walls of these invaginated sacs are usually in contact,
but become separated at the points, where the ova push the ovarian
sac outwards, and the sperm-cells the testicular one inwards. The
common ducts from these series of combined sacs are also invaginated,
the oviduct being external, the sperm- duct internal, and usually un-
dulated. The testicular C£eca and sperm-duct are lined with ciliated
eiDithelium : this is not present in the ovarian sacs.

Both invaginated tubes (r) enter the albuminiparous sac {s\ and
separate where they quit that part : there is a dilatation or sperm-
reservoir, where the sperm-duct quits the base of the albuminiparous
sac, and this latter may be regarded as a more special dilatation of the
oviduct, with follicular walls. The sperm-duct, enlarged and with
more glandular walls {t\ now proceeds with many short folds parallel
with the uterus to the base of the penis. This is a long and slender
organ (v), usually retracted and concealed within the visceral cavity,
but, like the finger of a glove, capable of being everted and protruded
externally. The so-called " uterus " {u) is a long canal, with trans-
versely plicated glandular walls, terminated by a vagina opening into
the common genital vestibule, the external orifice of which is near
the mouth of the respiratory sac, on the right side of the head.
With the vagina there communicates the duct {z') of a small pyriform
vesicle {z), which is a sperm-reservoir, for the fecundating element of
another individual received in coitu. A small caecum is developed

* CCCXIII. p. 370. t CCCLXIV. p. 378.

o o

562

Helix pomatia, dissected.

from the duct in Helix pomatia, and a very long one in Hdix ai-bus-
torum: the duct is short and simple in the slug (Limax). The
genital vestibule receives the terminal outlets of two groups of
brrnched ceeca (x, x), or "multifid vesicles," the function of which is
unknown. But the complexity of th^ generative apparatus does not
end here : the snail is provided with a pyriform muscular sac (y), the
aperture of which terminates close to the generative outlet. The
expanded base or head of a slender conical calcareous style or dart
(6, in the detached figure) is attached to the fundus of the sac (a) j
its sharp apex (c) extends close to the orifice, and by the contraction
of the sac it can be protruded outwards. With it the snails pierce
each other's skin, and the function of this curious organ would seem
to be to cause a preliminary excitement to the reciprocal union of the
two androgynous individuals.

PTEROPODA AND GASTROPODA.

563

The modifications of the parts of the complex combined organs of
the androgynous Gastropods are manifold. In regard to their ulti-
mate terminations or outlets, a common genital orifice is found in
Doris, Tritonia, Thetis, Bulimiis, Clausilia, and Limax, as in the
above described Helix. In Planorhis and Physa the male and female
orifices are situated side by side ; the male in front, on the left side
of the neck, behind the tentacle. In Bulla, Bullcea, and Aplysia,
the male orifice is under the right tentacle, the female one much
further back. In Boridimn the male orifice is beneath the left ten-
tacle ; the female one on the same side, but near the opposite end of
the body. In Onchidiii7n the female orifice is situated close to the
anus at the posterior end of the body ; the male orifice is beneath the
right tentacle. In all cases where the male and female organs are
separate, a furrow may be traced from one to the other : the penis,
when everted, projects from the male orifice.

The dioecious Gastropods form two sections, in one of which the
copulatory organs are wanting, in the other highly developed. The
non-copulants include the Cyclobranchiata and Scutibranchiata ;
the other section comprises the operculated jPulmonata, the Hetero-
poda, and the Pectinibranchiata. In these the intromittent organ is
usually of extraordinary length : it is grooved in most, perforated in
a few ; capable of retraction in the Paludina, but doubled back upon
the outside of the mantle when drawn into the shell by the Buccinum
and Strombus. In the Carinaria it is bifid.

The internal organs of the male whelk, represented in the annexed
figure, consist simply of a testis
and sperm-duct. The testis («) is
of considerable size, sharing with
the liver the smaller convolutions
of the shell ; from this arises the
vas deferens, which forms by its
convolutions a kind of epididymis
{b), and then increasing in dia-
meter enters the root of the penis,
through which it passes by a tor-
tuous course (d) to the tubercle at
the extremity of this organ, where
it opens externally. The penis is
composed of strong transverse fas-
ciculi of muscle, with lacunar sinu-
ses, which together cause the erec-
tion of this organ : the muscles will at the same time lengthen it, and

o o 2

208

Male organs of Buccinum.

564 LECTURE XXII.

Straighten the zig-zag turns into which the vas deferens is thrown in
its usual relaxed state.

In the female the position of the testicle is occupied by the ovary,
while the vas deferens is represented by a thick and glandular
oviduct. There is no rudiment of exciting organ (clitoris) : the ge-
nerative aperture is situated a little within the edge of the branchial
cavity, and is a simple hole leading to the oviduct.*

In Murcx the penis is proportionally smaller ; and, instead of a
complete vas deferens, penetrating to its extremity, there is merely a
groove along its surface, along which the semen flows. In Voluta
the exterior groove only runs to the base of the penis, and in
Strombus the male organ is a mere tubercle.

In the Pulmonalia operculata the organs of both sexes are in every
respect similar to those of the Pectinibranchiate order. In Paludina
{Helix vivipara, Lin.) the penis is closely united to the right tentacle,
and, like it, is retractile. The ovarium, in the female, is shown in
Jig. 204. by its lighter colour, combined with the liver and intestine^
with which it is lodged within the upper whirls of the shell. The
oviduct (A) is susceptible of considerable dilatation at the breeding
season, the young being developed therein : it terminates just within
the branchial chamber.

In the male Limpet the testis is situated beneath the liver ; its
duct passes forwards and terminates near the vent on the right side.
The ovarium and oviduct have the same disposition in the female.
The Haliotis differs merely in having the genital orifice on the left
side. The spermatozoa in these non-copulant Gastropods have a long
body with a still longer filamentary tail : in Paludina the body has a
spiral form, as is the case, likewise, with the shorter body of the
spermatozoa of the Helix and Limax. In the sperm of Paludina
there have also been observed long cylindrical bodies, from one of
the extremities of which project many delicate filaments having lively
motions. The ovarian ova present a round and sometimes elliptical
form, and consist of a finely granular and variously coloured yolk,
containing the germinal vesicle and nucleus, and inclosed in a thin
smooth membrane. Upon this is laid the secretion of the albumini-
parous gland, as the ova traverse that cavity in the Pulmonata ; and
they are coated and often connected together by analogous secretions
in other orders of Gastropods ; fecundation having previously taken
place in the oviduct or uterus.

The ova of the marine Gastropods are enveloped, before exclusion,
in mucous capsules, prepared by a special gland situated near the

* CCCXXL

PTEROPODA AND GASTROPODA. 565

termination of the oviduct. The secretion in some species is soft,
flexible, and transparent ; in most it hardens by contact with the sea-
water, and assumes various definite and characteristic forms : the
nidus is sometimes simple, sometimes compound, but each compart-
ment contains many ova ; and the development of the embryo pro-
ceeds in the nidamental chamber until its own little defensive shell is
acquired.*

In the terrestrial Gastropods the ova are usually spherical and
opake, and separately extruded. Snails and slugs oviposit in the
earth. The tropical Bulmi^ cement leaves of trees together to form
an artificial nest for their large eggs.

The ova of the sea-slug ( Tritonia) are expelled together in the
form of a long thread, and are arranged in a spiral manner in the
tenacious transparent covering of the thread. In the Doris muricata
the ova are aggregated in a flattened spirally disposed albuminous
band when excluded from the oviduct. The harder albuminous cap-
sules which defend the ova of other marine Gastropods ofier a great
variety of forms, some of which are remarkable for their complexity,
others for their symmetry and beauty. Here are displayed the nida-
mental sacs of the frail Jantliina\\ they are of a flattened pyriform
shape, composed of a delicate reticulate film of albumen, and are at-
tached by one extremity to a float, formed likewise by a secretion of
albuminous matter, dilated into a group of cells filled with air. To
this float the parent Jatithina commits her little progeny, and having
securely fastened their several cradles or nursery cells, she detaches
the float, which bears the ova to the surface, and sustains them where
they may best receive the full influence of solar light and heat. The
nidamental capsules of the Pyriila rapa^ are attached in regular
linear series to portions of decayed wood ; they are of a flattened
sub-conical figure, adhere by their apex, and have their base emar-
ginate. The nidamental capsules of the whelk || are common objects
on our sea-shore ; they are aggregated in large irregular masses,
often attached to portions of oyster-shell ; each capsule presents a
depressed ovoid figure, with one side convex, the other flat or concave.
The small nidamental cells of the Cowry (^Cypred) are aggregated
in a flattened group. In the Tmhinella the cells are of a flattened
sub-pentagonal form, and adhere together, superimposed one upon
the other, forming what is termed a camerated nidus. Each chamber
contains between twenty and thirty embryos. In the preparation
No. 2950, it may be observed that the rudimental shell is completely

* CCCLXV. p. 84. pi. vi. t Prep. 2943. B.

X See Preps. 2945, 2946. § See Prep. 2947. A. || Preps. 2948. 2949.

o o 3

566 LECTURE XXTI.

calcified and fitted to defend the little Gastropod before it emerges
from the temporary shelter provided for it by the parent. Numerous
other modifications of these secreted nests of the Gastropodous
Mollusca might be enumerated.

The development of the Gastropods has hitherto been traced in a
few apneustal, nudibranchiate, tectibranchiate, pulmonate, and pecti-
nibranchiate species ; and the results show considerable modifications
in its course and phenomena. Most Gastropods are oviparous ; some
species of Litorina are ovo-viviparous : Paludina and Clausilia
ventricosa are viviparous.

With the singular exception observed in Buccinum*, in which the
segmentar or granular germ-mass from which the embryo is deve-
loped results from a confluence of numerous, perhaps fifty, previously
distinct minute germ-masses f in the nidamental capsule, that germ-
mass is due to progressive segmentation of the yolk, the result of the
usual multiplication of germ-cells which clothe themselves with the
so-subdivided, but coherent, yolk substance. One cell in Pulmonata
and Aplysia, indeed, is from the beginning conspicuously larger than
the rest, and has been called the directive cell (richtungs blaschen.
Jig. 210, a). In all Gastropods the germ-mass takes the form of a
long round embryo, one end of which becomes indented and clothed
by ciliated epithelium, by which it rotates on its axis in the albumen
of the egg. Sars J, who noted the oviposition of the Tritonia Ascaiiii
on the 1st February, 1840, traced the segmentation of tjie yolk to the
8-fold division on the 4th day, and the completion of the germ-mass
on the 8th day. The indentation producing the bilobed end of the
embryo took place on the 15th day; after which the ciliated lobes
extended outwards, and assumed the form of wings or " vela." Dr.
Grant § had long before discovered the corresponding ciliated vela in
the embryos of Purpura^ TrocJius, Nerita, Doris, and jEoUs.

On the 20th day the rudiment of the foot appeared beneath the
bases of the vela, and on the 22nd a transparent shell was developed
which covered all the body save the ciliated vela and foot. " I could
scarce believe my eyes," writes Sars, " when I made this discovery."
As the body and shell enlarge and elongate, the cilia become stronger
on the lobes, and the active movements of the embryos, crossing each
other like midges in the clear albumen of the nidamental band, offer
a most singular spectacle : the vela now move by muscular contrac-

* CCCLII.

f Called " ova " by the Authors of CCCLII., whose observations were,
however, made on " ova " in the nidamental capsule, not in the oviduct of the
female whelk, where the first effects of impregnation are to be traced.

X CCCLXVII. § CCCLXXIV. p. 121.

PTEROPODA AND GASTROPODA. 567

tion alternately approximating and stretching outwards. On the
hinder part of the foot is an operculum, which closes the mouth of
the shell when the embryo retracts itself. Among the internal
organs the acoustic capsules appear first, then the eyes. The ten-
tacles next protrude, and the border of the mantle appears. The
mouth is established between the vela. On the 36th day the stomach
and a looped portion of intestine come into view out of the germ-
mass, the remnant of which is chiefly changed in the hepatic and
genital glands. A longitudinal muscle for retracting the body into
the shell also now appears.

During this course of development the nidamental band has become,
by endosmose of sea-water, three times as thick as before. The al-
buminous substance is absorbed by the embryos : they respire by the
reaction of their ciliated surface on the imbibed water ; as they grow
they, with difficulty, find room for their evolutions, and, between the
32nd and 38th ^days, rupture the delicate membrane of their nest,
and struggle out. They are now about one-eighth of a line in
length, and swim by ciliary action, the vela being kept stiffly out-
stretched. They survived in the vessels of daily renewed sea-water
two weeks, then died, their embryo shells floating on the surface.

The ova of the Aplysia are excluded in a long string, enveloped
by a transparent flexible mucus, in the centre of which they are
aggregated in several irregular series. When examined at this
period, the yolk has apparently divided itself into six, seven, or more
numerous globules ; or, in other words, as many germinal vesicles
included in the same mass of albumen and in a common chorionic
coat, have given origin to as many aggregations of vitelline cells ;
these, therefore, may be regarded as so many independent yollvs, in
each of which the same progressive fissiparous multiplications have
been observed, as in the single vitellus of the ovum of the Planorbis,
and of animals in general. Fig, 209. exhibits one
of these yolkleis prior to the commencement of the
fissiparous action, by which subdivision of the
mass is produced. Fig. 210. shows the quadrifid

Aplysia.

product of that action and of the assimilative

powers of the resulting divisions. The directive cell is indicated by

Van Beneden at a*

In Jig. 211. the multiplication of the globules has increased, and
two of them, of larger size than the rest, indicate, one, the seat of the
future branchial organs, the other that of the muscular mass.

The ciliated epithelium, with which the vitellus is now almost

* CCCLXVIII. pi. 123. p. I.
o o 4

568 LECTURE XXII.

entirely covered, occasions tlie usual rotations of that body. The
211 212 progress of transformation of this monad-like

\ embryo to the Gastropodous form, resembles
closely that which has been described in
Tritonia. The remains of the vitelline mass
{Jig. 212, a), not yet metamorphosed into
special organs, indicates the expanded alimen-
tary sac ; b is the apex of the rudimental foot, and c the velum with its
strongly ciliated border. These parts protrude from a rudimental,
thin, pellucid, and flexible shell, which covers all the rest of the sur-
face of the body. The arrows indicate the direction of the rotatory
movements of the embryo, which now likewise describes its elliptical
revolutions in the chorionic cavity. As development proceeds and
the embryo increases in size, the shell acquires a more distinctly tur-
binated form, and is slightly bent out of its vertical plane {fig. 213).
An operculum (e) is formed upon the pro-
— truded surface of the foot : the course of in-

ternal development accords with that in
Tritonia. The ciliated branchial surface (c)
begins to be withdrawn more into the inte-
^ rior ; and, in this state, protected completely
by an external shell, the young Aplysia is
launched into the ocean.
■^P^^'^'^* Truly may the subsequent growth, which

effects an entirely internal position of the shell, with such a mutation
of its form that the primitive nucleus can scarcely be detected upon
the almost flattened plate now destined to protect the equally internal
respiratory organs of the mature animal^ justify us in applying to it
the term metamorphosis. This term is still more applicable to the
developmental phenomena in the Tritonia and Doris ; since these
Gastropods, which are not only naked, like the Aplysia, are devoid of
any internal rudiment of a shell, and yet are provided w^ith a delicate
little operculated nautiloid horny external shell in their young state.
The same general course of development, in which the embryo or
larval mollusk is provided with the ciliated lobes and operculated
shell, has been traced by Loven in jEoUs, Bulla, Cerithium* ; by
Nordmannf in Tergipes ; by AllmanJ and Vogt§ in ActcBon ; by
Lund II in Murex and Natica ; by Carus^ in Paludina, and by
Siebold in Vermetus** Rudiments of the vela are retained in Ter-
gipes, JEolis, Doris, Tritonia, and Aplysias ; and in Thetys they

* CCCLXIX. t CCCXL. X CCCLXX. § CCCLXXI.

II CCCLXV. If CCCLXXII. ** XXIV. p. 360.

PTEROPODA AND GASTROPODA. 569

continue in almost their primitive form and proportions, unless the
broad lobes of the adult be substituted for the embryonal vela, as is
the case with the fins of the Pteropods ; otherwise the little Cymbulia
with its delicate symmetrical shell would represent a persistent em-
bryo form of the higher Gastropodous Encephala, Prof. Muller*
has detected ova and embryos of a Gastropod, which he believes to
belong to a species of Natica, within the body of the Synapta digi-
tata : they were contained in elongated sacs, firmly attached or fused
at one end to the head, at the other end to the gut of the Synapta.
The upper portion of the sac contains both spermatozoa (like those
of Natica) and ova ; the lower portion of the sac was intus-suscepted
with a blind end, and this contained the ova with developed embryos,
according to the velated type. This remarkable discovery indicates
some singular parasitic habit in the generative economy of the
moUusk (ante, p. 221.).

The development of the pulmonated Gastropods proceeds without
any such metamorphosis as that above described. In the testaceous
species its course has been ably traced by Prevost and Dumortierf
in Limjiceus, by Pfeiffer J in Helix, and by Jacquemin and Quatre-
fages in Planorbis. §

The transparency of the albuminous capsules of the ova, and of the
ova themselves in the fresh-water Pulmonata, renders them beautiful
and favourable objects for such researches.

In the Physa, the nidamental mass is short and ovate: in the
Limnceus it is oblong, and not striated, as in the Planorbis. The
double movement of the embryo is more conspicuous in the LimncBus
than in the Planorbis. The first movement of the yolk is one of
rotation upon its axis ; but, as development proceeds and the ciliary
vibrations are strengthened, the embryo begins to travel in an ellip-
tical course around the interior of the Qgg ; its two movements (to
compare small things with great) resembling those of the planets in
the solar system.

In the Planorbis the single centre of the ovum, or the germinal
vesicle with its nucleus, is very evident in the ovarian ovum. The
processes which lead to the disappearance of the vesicle, take place
in the oviducal pouch called the " matrix." The transparent nida-
mentum in which the ova are excluded is shield-shaped and striated ;
it is not attached to any foreign body but falls to the bottom. After
the usual subdivisions of the yolk, a group of less opake cells makes
its appearance in a particular part of the periphery of the granular
mass ; and an epithelial membrane begins to spread over its surface,

* CLXX. t CCCLXVI. X CCCLXXV. § CCCLXXVI.

570 LECTURE xxn.

from which cilia are soon developed. Their action begins about the
third day to affect the surrounding albumen, and afterwards to rotate
the embryo itself. The embryo now elongates : its hinder end assumes
a spiral form. The aggregation of stronger and more numerous cilia
on a particular part of the surface of the yolk indicates the seat of
the development of the respiratory organs. Two groups of extremely
minute and compact cells, covered by a thicker epithelium, project
from two other parts of the surface, and constitute the rudiments of
the head and foot. The centre of the yolk presents the form of
larger and less regular globules, which indicate the position of the
wide digestive sac. The rudiments of the head and foot are suffi-
ciently obvious on the fifth or sixth day ; the acoustic capsules ap-
pear : the respiratory organs are formed on the sixth or eighth day,
according to the warmth of the weather. On the eighth day the
characteristic tentacles begin to sprout from the rudimental head. On
the tenth day all that spirally disposed part of the embryo which is
not occupied by the head, the foot, and the breathing organ, is covered
T)y a thin and transparent pellicle, which is the rudiment of the shell.
On the eleventh day one of the large central globules of the yolk
begins to distinguish itself from the alimentary mass by feeble con-
tractions and dilatations, of which about sixty may be counted in a
minute : this is the heart. The mouth can now be discerned, and
the small eyespecks appear like black granules at the base of the ten-
tacula. On the twelfth day the embryo moves by its own contractions
independently of the rotation produced by the cilia. On the thirteenth
day acts of deglutition are discernible ; the embryo swallows the re-
maining albumen, the anus is completed, and the genital organs begin
to be formed. On the fourteenth day the young Planorhis ruptures
by more violent contractions the chorion, and escapes into the water,
protected by its own flexible shell.

The course of development is different in the naked Pulmonata.
In the month of February Van Beneden and Windischmann* found
ova of a slug (Limax agrestis) buried in groups. They are laid in
autumn and remain until spring, resisting the cold that kills the
adults. At the beginning of spring the germ and embryo may be
found in all stages of development. The Qg^, when laid, has an ex-
ternal lamellated nidamental membrane ; a thin chorion inclosing the
albumen; a vitelline membrane with a twisted filamentary appendage;
and the vitellus, which is small as compared to the albumen.

Two clear germ-cells rise from the centre of the vitellus and pass
to its periphery : their existence is followed by the first fission of

* CCCLIV.

PTEROPODA AND GASTROPODA. 571

yolk ; successive cleavage reduces it to the mulberry state ; and the
subdivision proceeds to such a degree of minuteness, that the yolk
seems to have returned to its primitive condition : it is now the
germ-mass.

These divisions and subdivisions take place rapidly under the eyes
of the observer. By compression the hyaline centres escape from the
yolk-segments or germ-cells. A vibratory movement of the germ-mass
gives the first intimation of the ciliated epithelium, which, as it is per-
fected, effects a rotation of that body : this movement is increased by
warmth and checked by cold. There next is seen a thickening of
the integument, with a development of two tubercles ; one of these
enlarges and remains above the germ-mass, representing the mantle
and visceral cavity ; the other elongates, represents the foot or basis
of the embryo, grows quickly, and soon acquires a cavity with fluid :
then a bud grows from its hinder part, which also becomes a vesicle.
This " caudal vesicle " grows to one-third the size of the rest of the
embryo, and contracts so as to drive its contents into the cavity of
the embryo, which, in turn contracting, sends the fluid back to the
caudal vesicle. Sometimes the caudal vesicle contracts twice before
the embryo-sac reciprocates. The liquid so oscillating contains
spherical vesicles like blood-discs. " Trabeculse " next appear in the
caudal vesicle, which seems a mere appendix to the embryo. The
cilia upon the caudal vesicle and tentacles are very small compared
with those of the Aplysia.

With the caudal appendage appears the fissure indicative of the
anterior border of the foot ; and in advance of this, a lobe which soon
becomes bifid, and forms two tentacles. Above the foot the sub-
cesophageal ganglion is developed. A crystal of carbonate of lime
is the first rudiment of the shell, and is deposited in the substance
of the skin, above the visceral cavity. The cephalic lobe proceeds to
divide into the upper or ocular pair, the second pair of tentacles, and
a lower pair of processes forming the sides of the mouth.

The embryo-sac now becomes pyriform, and is pressed between the
advancing head and the shield ; it next elongates and enters the
body ; the intestine begins to appear, and the germ-cells may be
distinctly seen to pass to and fro into it, by a movement like that
which took place between the embryo-sac and the caudal vesicle.

The third period of development is marked by the appearance of
the heart, by the disappearance of the caudal vesicle, by the com-
pletion of the digestive canal, and by the total intus-susception of
the unconverted germ-mass.

The rudimentary shell or shield is pushed backwards : the heart is
plainly indicated by its pulsations under the shield, before its contour

572 LECTURE XXII.

can be clearly seen. Next, the auricle and ventricle are formed by a
constriction of the pulsating tube ; afterwards the pericardium and
two vessels are visible. The globules in the fluid sent into the body
by the caudal vesicle go towards the heart. The embryo slug has
now an extensile proboscis, which is formed by the lobes below the
tentacles, and which afterwards disappears. A peculiar glandular
body attached to the parietes of the embryo-sac is compared to the
transitory kidney, or Wolffian body in the vertebrate embryo. At a
short distance from the anus there projects a caecum, which after-
wards becomes the urinary sac. The nervous system is at first a
tubular ring containing fluid ; it then swells out into the super- and
sub-oesophageal masses, and gets neurine in the interior of the sheath.
The acoustic vesicles appear above the suboesophageal mass.

The ocular tentacles appear for a long; time as rounded and later-
ally compressed fins, by the side of the vitelline sac ; they may be
the homologues of the vela of the pectinibranchiate embryos.

The caudal vesicle disappears before the young is excluded from
the egg ; its contractions go on after those of the heart have begun ;
and thus there are two currents, one of blood in vessels through the
viscera, and the other of fluid outside of and bathing the viscera.

The pulmonary sac is formed by a simple depression at first, which
deepens as the heart and vessels become developed, and the vascular
network spreads over its inner surface. The generative organs are
formed after exclusion.

Class PTEROPODA.

Encephalous mollusks, with wing-like fins from the sides of the
head or neck.

Order Thecosomata.
With an external shell : head indistinct.
Family Hyaleid<B. Shell symmetrical.

Genera Hyalea, Cleodora, Cuviericiy Euryhia^ Cymbalia, Tiede-
mannia.

Family Limacimd(B. Shell spiral.

Genera Limacina, Spiricdis^ Cheletropis,

Order Gyjinosomata.

Without a shell : head distinct : fins attached to the neck.

Family CliidcB.

Genera Clio, PneumodermoHf Pelagian Cymodocea. '

PTEROPODA AND GASTROPODA. 573

Class GASTROPODA.

Enceplialous mollusks, with a locomotive ventral disc, or foot.

A. MON(ECIA.

Order Apneusta.

No distinct respiratory organs : no shell.

Genera Actceon, Rhodope, Zephyrina, Tergipes, Eolidma, jEolis.

Order Nudibranchiata.

Branchiae extending more or less freely from various 'parts of the
body.

Genera Scyllcea, Tritonia, Doris, Thetis, Polycera.

Order Inferobranchiata.

Branchiae at the lower part of the sides of the body, between the
foot and mantle.

Genera Phyllidia, Diphyllidia, Ancylus.

Order Tectibranchiata.

Branchise covered by the shell or mantle : a shell in most. An-
drogynous.

Genera Tornatella, Bidla, Bullcea, Doridium, Gastropteron,
Aplysia, Dolabello, Notarchus, Icarus, Lobiger, Pleu-
rohranchus. Umbrella.

Order Pulmonata.

Part of the mantle- cavity forming a vascular air-sac or lung.

Family Helicidce. Shell external, usually well developed, closed
by an epiphragm during hybernation.

Genera Helix, Vitriiia, Succinea, Bulinus, Achatina, Pupa,
Clausilia.

Family LimacidcB. Shell rudimental, internal.

Genera Limax, Arion, Parmacella, Testacella.
Family Oncidiadce. No shell.

Genera Oncidium, Vaginulus,

Family Limneidce. Shell thin, horn-like, well developed.
Genera Limnea, Physa, Ancylus, Planorbis.

Family AuricuUdce. Shell with a horny epidermis.
Genera Auricida, Co7iovulus, Carychium.

574 LECTURE XXII.

Family Cyclostomidce. Shell with an operculum.
Genera Cyclostoma, Pupina^ Helicina,

Family Aciculidce. Shell elongated, cylindrical, with a subspiral
operculum.

Genera Acicula^ Geomelania.

B. DIOECIA,

Order Nucleobraxchiata.

Branchia3, when distinct, packed in small compass with the heart
in a dorsal mantle cavity, or in a small symmetrical shell ; sometimes
wanting together with the shell. Foot rudimental.

Family Firolidce. A small branchial shell, or none.
Genera Firola, Carinaria^ Cardiapoda.

Family Atlantidw. A body-shell.

Genera Atlanta, Porcellia, Bellerophon, Cyrtolites.

Order Tubulibranchiata.
Animals inclosed, with their branchiae, in long, curved, or flexuous
shelly tubes.

Genera Vermetus, Dentalium, Magilus.

Order Cyclobranchiata.

Branchias usually a series of lamellge surrounding the body between
the foot and mantle.

Family PatellidcB, Shell with the apex turned forwards.
Genera Patella, AcmcBa, Gadinia.

Family ChitonidcB. Shell subdivided into eight pieces.
Genera Chiton, Chitonellus, Acanthopleura,

Order Scutibranchlata.
Branchise protected by a simple or shield-shaped shell.
Family Halyotidce. Shell with the outer lip notched or per-
forated.

Genera Haliotis, Scissurella, Pleurotomaria.

Family Fissurellidce. Shell limpet-shaped, perforated at the apex,
or notched anteriorly.

Genera Fissurella, Emarginula, Parmophorus.

Order Pectinibranchiata.

Branchiae pectinated or comb-shaped ; in a special cavity at the
fore part of the back. Sexes distinct.

PTEROPODA AND GASTROPODA. 575

A. Holostomata, Margin of the shell-aperture entire.
Family CupuloidcE. Shell limpet-shaped, with the apex sub-
spiral.

Genera Pileopsis, Ilipponyx^ Crepidula, CalyptrcBa, Lithedaphus.

Family TurhinidcB. In the following families the shell is spiral
and pyramidal, or turbinated.

Genera Turbo, Phasianella, Trochus, Monodonta, Delpliiimla,
Euomphalus, Stomatella, J3roderipia.
Family NeritidcB.

Genera Nerita, Pileolus, Neriti?ia, Navicella.
Family Paludinidce.

Genera Paludina, Ampullariaf Valvata, Janthina.

Family Litorinidce.

Genera Litorina, Solarium, Litiopa, Rissoa.

Family TurritellidcE,

Genera Turritellay Vermetua, Scalaria.
Family MelaniadcB.

Genera Melania, Paludomus, Melanopsis.

Family CerithiadcE.

Genera Cerithium, PotamideSy Nerin^a, Struthiolaria,

Family Pyramidellidce.

Genera Pyramidella, StylinOy Macrocheilus.

Family Naticidce.

Genera Naticay Sigaretus, Velatina,

B. Siphonostomata, Margin of the shell-aperture notched or
produced into a canal.
Family Cyprceidce.

Genera, Cyprcea, Erato, Ovulum.

Family VolutidcB.

Genera Voluta, Oliva, Cymba, Mitra, Valvaria, Maryinella.

Family Conidce.

Genera Conus. Pleurofoma.

Family BuccinidcB,

Genera Buccinumy Harpa, Cassis, Piirpura, Eburneay Terebra,
Nassay Monoceros, Dolium.

Family Muricidce.

Genera Murex, Ranella, Tritoiiy FasciolariUy Turbinellay Can-
cellariay Pyrulay Fusus.

Family Strombidce.

Genera StrombuSy Pteroceras, Rostellaria.

576 LECTURE XXIII.

LECTURE XXIII.

CEPHALOPODA.

We trace the progressive diminution of the existing species of Gas-
tropodous Mollusca by their fossil shells through the descending
strata of the tertiary periods of geology, beyond which such indi-
cations become very doubtful and obscure.* In the oldest tertiary
deposits, not more than 3J per cent, of the remains of any class of
Mollusca have been identified with species now living. From this
fact, which indicates the dawn of the existing state of the testaceous
fauna, the term " eocene " is applied to these strata : in the superim-
posed or " miocene " tertiary beds there are about 17 per cent, of fossil
shells, identical with recent species ; in the deposits of a third or
" pliocene " era from 35 to 40 per cent. ; and, in still more modern
" pleistocene " formations, the older tertiary shells have almost dis-
appeared, and the number of species identical with those now living
is from 90 to 95 per cent.

Amongst the shells which characterise the eocene strata, there
are four or five of symmetrical figure, divided into chambers, which
are perforated by a tube or siphon, like the existing large Nautilus
and the little Spirula ; but they belong to species which are unknown
in modern seas. In the secondary formations, which succeed the
eocene in depth and order of antiquity, the chambered siphoniferous
shells become more numerous and diversified ; they depart further
from the two remaining recent types, and manifest a rich variety of
form and structure. From these modifications of the shells we not
only infer corresponding differences in the habits of their extinct
occupants, but we can trace, in some instances, the nature of the
associated differences in the organisation of the soft parts.

The vast number of the complex shells known by the names of
Ammonites, Orthoceratites, Hamites, Baculites, Turrilites, Belem-
nites, &c., and the constancy which particular genera and species
manifest in their relations to particular strata, indicate that the
functions which their molluscous fabricators performed ix^ the organic
economy of the ancient world must have been equal and closely
analogous to those which have since been assigned to the Pectini-
branchiate Gastropods that have superseded them in the seas of the
tertiary and existing epochs.

* The supposed recent species of Trochus observed by Defrance in chalk, and
the Paludina and Cyclas, described by Dr. Fitton from the Wealden, are not con-
sidered to be identical with existing species by Deshayes and Lyell.

CEPHALOPODA. 577

What, then, were the nature and affinities of the extinct con-
structors of those ancient chambered siphoniferous shells ? Earnestly
and repeatedly had this question been pressed upon the attention of
zoologists and comparative anatomists, and long was it before any
satisfactory reply could be returned. The Nautilus Pompilius and
Spirula australis, the representatives in the existing seas of that
vast assemblage of siphoniferous Mollusks which peopled the ocean
during the secondary epochs, could alone yield the requisite data for
its determination, and for a long period comparative anatomists were
disappointed In their demands for these most rare and coveted sub-
jects. In fact, until the year 1832, geologists could be supplied only
with conclusions based upon more or less probable analogies and
conjectures. Before this period, only one account of the Nautilus
Pompilius was extant, in the work of Rumphius *, a Dutch naturalist
of the 17th century, whose figure of the animal was pronounced by
Cuvierf, the profoundest malacologlst of his age, to be unintelligible
(' indechiffrable '). The little light that it might have thrown
upon the interesting question of the affinities of the Nautilus was ob-
scured by the grotesque, and, as they have since proved to be, ficti-
tious figures of the animal, subsequently published by De Montfortf
and Dr. Shaw §, and the evidence of Rumphius seems to have been
rejected by the naturalists of the French circumnavlgatory expedition
under Captain Freycinet, who, on their return in 1831, published a
description and figures of part of an unknown molluscous animal,
presumed to be that of the Nautilus Pompilius^ ; and which, had
their conjecture been verified, would have indicated the chambered
shell of the Nautilus to have been an appendage to some hu<^e
heteropod, allied to the Carlnaria.

If the claims of the Ammonite and its extinct congeners to take
rank in a higher class of Mollusca, had appeared to some zoologists
to be established by the figure of the animal of the Spirula, pub-
lished by Peron% it might, at the period to which I allude, have
been objected that this evidence, likewise, had been invalidated by
Fremenville's assertion to Brongniart, cited by De Blanville**, that
the animal of the Spirula was wholly different from Peron's descrip-
tion of it.

If an appeal had been made from the unsatisfactory and conflictino-
evidence derivable from the existing chambered siphoniferous shells
to the simple univalve of the Argonauta, which resembles them in its

* CCCLXXXII. t XTL torn. iii. p. 18. t CCCLXXXIII.

§ CCCLXXXIV. II CCCLXXXV. ^ CCCLXXXVI

** CCCXXVII. t. i. p. 381., 8vo. 1825. Nouvelles Annales du Museum, t. iii.
p. 20. 4to. 1834.

P P

578 LECTURE XXIII.

symmetrical figure, it might, on the one hand, have been objected that
the correspondence of outward form alone, without the camerated and
siphonated structure, was insufficient to support the conclusion of the
cephalopodic nature of the Nautilus or Spirula, since the shell of the
Carinaria might have been adduced as much more closely resembling
that of the Argonauta ; and, on the other hand, the scepticism of the
majority of conchologists at that period, as to the Argonaut shell
being actually fabricated by the Cephalopod usually found in it,
might have been adduced to show how little value could be attached
to the superficial resemblance between the Argonaut shell and that
of the Nautilus, in the determination of the Cephalopodic character
of the constructor of the latter ; and, by inference, of those of the
allied extinct chambered shells. Most acceptable, therefore, at this
conjuncture, was the arrival of the molluscous inhabitant of the
Nautilus Pompilius.

The long-sought-for animal was captured in the South Seas by
Mr. George Bennett, a member of the Royal College of Surgeons,
and by him presented to the museum of the college : it was entrusted
to me to be anatomised, and my description with illustrations was
liberally published by the Council.*

The dissection of this unique specimen established the claims of the
Nautilus Pompilius to rank in the highest class of Mollusca, and at
the same time brought to light so many important modifications in
the cephalopodic type of structure as to necessitate the establishment
of a new order for its reception. The present Lecture will be devoted
to the demonstration of the principal organic characters of this order,
which is called Tetrabranchiata, and to a brief review of the extinct
chambered siphoniferous shells, and of their relations to the existing
Cephalopods.

The soft parts of the pearly Nautilus {Jig. 214.) form an oblong
mass divided by an irregular transverse constriction into two nearly
equal segments ; the posterior is smoothly rounded, soft, and membra-
nous, containing the viscera, and adapted to the last chamber of the
shell ; the anterior is densely muscular, and includes the organs of
sense and locomotion.

The mantle is very thin upon the posterior part of the body ; it is
continued backwards in the form of a slender tube, which penetrates
the calcareous siphon (c), in the septum closing the occupied chamber
behind, and is thence continued, as the membranous siphon {d)
through all the other divisions of the shell to the central nucleus. As
the mantle advances towards the anterior part of the abdomen, it in-

* CCCLXXXVII.

CEPHALOPODA.
214

579

Nautilus Pompilius.

creases in thickness, becomes more muscular, and extends freely out-
wards, forming a wide concave fold on the dorsal aspect (e), which is
reflected over the black-stained involuted convexity of the shell. The
margin or collar of the mantle is continued downwards and forwards
on each side with a sinuous outline, and is perforated below for the
passage of the muscular expiratory and excretory tube called the
funnel (i). Besides the muscularity of the free border of the mantle,
which indicates its power of extension and contraction, its surface is
studded with the orifices of many minute glandular crypts ; and it is
the organ by which the growth of the shell is principally effected.
The nidamental glands form, in the female, two circular convexities
on the ventral surface of the abdomen, behind which the mantle is
encircled by a thin layer of brown matter, like the periostracum,
which band is very narrow above and below, but expands on each
side into a broad plate, corresponding in size and form with the
surfaces of attachment of the two great muscles for adhesion to the
shell.

The anterior or muscular division of the Nautilus, which may be
termed the head, forms a strong and wide sheath, containing the
mouth and its more immediate appendages ; its inner surface is for
the most part smooth, the outer one divided and extended into many
parts or processes. The chief of these forms a broad triangular mus-
cular plate or hood (/), covering the upper part of the head, and
presenting a middle and two lateral superficies ; the former being

580 LECTURE XXITI.

traversed by a median longitudinal furrow, indicating the place of
confluence of tlie two large hollow tentaculiferous processes of which it
is composed. The back part of the hood is excavated for the lodg-
ment of the involuted convexity of the shell, and the above-described
fold of the mantle covering it. Each side of the head supports a
group of perforated processes or digitations, the largest of which is
next the hood, and the rest decrease in size as they descend in posi-
tion. Exclusive of the short subocular, perforated process*, the digi-
tations are eighteen in number on each side disposed irregularly, but
all directed forwards, some not reaching as far as the anterior margin
of the head, others projecting a few lines beyond it. They are of a
conical, subtriedral form : the large one next the confluent pair which
forms the hood, has, like that part, a papillose outer surface. Each
process contains a long and finely annulated tentacle (<7), of a sub-
triedral form, with the inner surface incised, as it were, by deeper and
fewer cuts {^fig. 216, e), so as to present the appearance of a number of
close-set transverse plates, slightly indented by a median longitudinal
impression (ib. /). This modification must increase the prehen-
sile and sentient properties of the inner surface of the tentacle, and it
is on the corresponding part of the larger and fewer tentacles of the
dibranchiate cephalopods that the acetabula are developed. The
angle between the two outer finely annulated surfaces subsides near
the end of the tentacle, which thus becomes flattened.

To the nineteen tentacula which are supported by the confluent
and free digitations on each side of the head, two others must be
added, which project from very short sheaths, one before, the other
behind, the eye ; the lateral transverse incisions are deeper in these
than in the digital tentacles. The eyes are about the size of hazel
nuts, and are attached each by a short peduncle to the side of the
head, behind the digitations, and a little below the margin of the
hood. The inferior surface of the oral sheath is excavated for the
lodgment of the infundibulum.

The mouth is armed with two mandibles, shaped, as in other
cephalopods, like the beak of a parrot reversed, the lower mandible
(^^. 214, I) overlapping and curving upwards beyond the upper
one Qi). Both mandibles are horny, with their tips encased by dense
calcareous matter, and their base implanted in the thick muscular
parietes of the mouth.

They are immediately surrounded by a circular fleshy lip with a
plicated anterior border, external to which there are four broad flat-

* Particularly described and shown not to be tentaculiferous by M. Valenciennes,
CCCLXXXVIII.

CEPHALOPODA. 581

tened processes called " labial," continued forwards from the inner
surface of the oral sheath, two of which are superior, posterior, and
external, the other two (k) are inferior, anterior, and more imme-
diately embracing the mouth : the latter are connected together along
their inferior margins by a middle lobe, the inner surface of which
supports a series of longitudinal lamellae. On the inner surface of
the oral sheath beneath these processes there are two clusters of soft
conical papillas, and on each side of these a group of lamellae. Each
of the four labial processes is pierced by twelve canals, the orifices of
which project in the form of short tubes from the anterior margin,
and each canal contains a tentacle similar to, but smaller than, those
of the digitations. Thus the number of tentacles with which the
pearly Nautilus is provided, amounts to not less than ninety, of which
thirty-eight may be termed digital, four ophthalmic, and forty-eight
labial. In the second specimen of this rare molluscous animal,
presented to the college by Captain Sir Edward Belcher*, there was
a slight difference in number in the digital tentacula of the two sides,
nineteen being on the right, and seventeen on the left side. The
labial processes in the specimen of Nautilus described by M. Valen-
ciennes contained thirteen tentacles instead of twelve ; and some
variation is not surprising in the number of prehensile organs deve-
loped in such unwonted profusion in the Nautilus. A more marked
modification of the labial processes has been found in a male spe-
cimenf , which is probably sexual, and will be subsequently described.
The skeleton of the Nautilus consists of two parts, equally distinct
in their position, texture, and organic properties : the one is the
external chambered shell ; the other is a rudimental cartilaginous
cranium, which sends out processes for the attachment of the prin-
cipal muscular masses. The shell of the Nautilus consists of an
elongated sub-compressed cone, convoluted in close spiral whorls,
upon the same plane, so as to be perfectly symmetrical. In the full
grown mollusk, three-fourths of the shell from the commencement no
longer serve to lodge the animal, but have been partitioned off*, as
they have been progressively evacuated, into a number of chambers
(Jig. 214, b, b), increasing regularly and gradually in size from the
first to the last, or to the last but one. The open chamber (a, «),
which contains the animal, is much larger than the rest, slightly
curved, concave behind and on the ventral aspect, and divided into
two concavities on the dorsal aspect, by the projecting involuted
spire. At the sides are two slight impressions of the large lateral
muscles, and that of the connecting narrow cincture, and, posteriorly,

* CCCLXXXIX, t CCCXC.

r p 3

582 LECTURE XXIII.

the infundibular aperture of the calcareous siphon is seen at the
middle of the last septum. This calcareous tube extends about one
fourth of the way towards the succeeding septum, which, with all the
others, is similarly perforated and prolonged backwards near their
middle part. The septa, about thirty-five in number, are concave
towards the aperture of the shell, except below, where they are
convex transversely ; for their circumference does not follow precisely
the transverse section of the spiral cone, but describes a slightly sinuous
outline. The shell consists of two substances ; the outer one opake,
white, or stained with the characteristic red-brown stripes ; the
internal layer is twice as thick as the former, and of a nacreous
structure and lustre : the external surface of the shell is naturally
covered with a reddish brown or greenish epiderm or periostracum ;
and upon the involuted convexity of the shell, the dorsal fold of the
mantle deposits a thin plate of a nacreous texture, stained externally
of a deep black colour, which can be traced as an extremely thin ad-
ditional layer along the interior whorls of the shell. In the Nautilus
Pompilius the hole or umbilicus, at the extremities of the imaginary
axis round which the involutions of the shell have been made, is
filled up by the deposition of semi-nacreous material : but in the
species or variety termed Nautilus umbilicatus, the margins of the
dorsal fold of the mantle are not developed to the same extent, and
the umbilicus continues open. The septa consist exclusively of the
nacreous substance : they are thinnest at their margins, which, from
their oblique applications to the wall of the shell, increase its thick-
ness at the line of contact. The chambers are lined by a thin mem-
branous pellicle, thrown off by the mantle when the animal was in the
act of advancing forwards to enlarge its shell and form a new septum.

The internal cartilaginous skeleton of the Nautilus is confined to
the inferior surface of the head : no part of it extends above the
oesophagus. Viewed sideways, it presents a triangular form ; a por-
tion of the annular brain is protected by a groove on the upper sur-
face of the cartilage : two strong processes are continued from its
anterior and superior angles into the crura of the infundibulum,
giving origin to the chief muscles of that part. Two other thinner
processes are continued backwards, and curve inwards and down-
wards ; they give origin to the two great muscles which pass from
the internal to the external skeleton, or, in other words, attach the
animal to the shell.

The muscular fibres of the head or oral sheath arise from the
whole of the anterior or outer part of the internal skeleton. The
muscular structure of the funnel presents a much greater develop-
ment than in the naked Cephalopods ; and, from its relation to those

CEPHALOPODA. 583

masses which, on the one hand, attach the soft parts to the shell, and,
on the other, connect the head to the body, we may conclude that
the funnel is the principal organ of natation, and that the Nautilus is
propelled, like the Octopus, by a succession of jerks occasioned by
the reaction of the respiratory currents upon the surrounding water.
The orifice of the funnel is guarded by a valve {fig. 214, i!).

The retraction of the tentacula is done by longitudinal fibres, the
elongation by transverse ones. These are not, however, disposed in
circular or spiral series, so as to attenuate and lengthen the tentacle
by a general compression, but present a more complex disposition
by which they diminish the transverse diameter without com-
pressing the central nerve. The transverse fibres {fig. 216, a) arise
in numerous and distinct fasciculi from the dense cellular tissue
{h\ surrounding the nerve in the centre of the tentacle {d\ and
radiate at equal distances to the circumference ; they divide and sub-
divide as they diverge, and also send off lateral fibres, which form a
delicate network in the interspaces of the rays, especially at the
angles : the meshes include the longitudinal fasciculi, the cut ends of
which are shown at c.

The mechanical arrangement of the contractile fibres is very
similar to that of the complex muscles described by Cuvier in the
proboscis of tlie elephant. The attenuation and elongation of this
brobdignagian tentacle must be effected without compressing the
central breathing tubes, and transverse fibres accordingly radiate
from the dense ligamentous tissue which surrounds them : the same
prospective contrivance is manifested to prevent the compression of
the nerves and vessels in the muscular system of the ninety probos-
cides of the Nautilus.

For the special account of the myology of the Nautilus, which in-
cludes the muscles of the oral sheath and its digitations, of the labial
processes and mouth, and of the infundibulum, those for adhesion to
the shell, those of the mantle, those of the tongue, the fibres of the
tunic inclosing the liver and stomach, and the muscles of the organic
system, I must refer to the published monographs on the anatomy of
this animal.*

The principal masses of the nervous system of the Pearly Nautilus
{fig. 215.) are concentrated in the head. The super-oesophageal
part, or brain (a), presents the form of a short, thick, transverse,
round chord or commissure, connected at each extremity with three
ganglionic masses. The middle and superior of these (6) supplies the
eye and the inferior hollow tentaculiform organ : the anterior and

* CCCLXXXVII. & CCCLXXXVllI.
r r 4

584

LECTURE XXIII.

inferior ganglion (c) meets its fellow 215
below the oesophagus : the posterior
ganglion (c?), in like manner, joins
that of the opposite side and forms
a second and posterior (Dcsophageal
ring. The nerves given off imme-
diately from the super-oesophageal
mass supply the muscular and other
parts of the mouth, and have small
pharyngeal ganglions developed upon
them. The anterior cesophageal ring
gives off principally the nerves to the
tentacula {f,f\ and the two median
ones {g) are connected with a gan-
glion {h\ which supplies the tenta-
cula of the inferior labial processes
and the lamellated organs on that
part of the oral sheath. The ten-
tacular nerves are continued, like
those of the arms in the hio^her
Cephalopods, along the middle of the
tentacle, attached by loose cellular
tissue to the vessels of the part. The
posterior collar gives off numerous
nerves {m) of a flattened form, which
supply the muscles of the shell. The
respiratory nerves form a small ganglion {q) at the base of each pair of
gills, from which branches are sent to those organs, to the heart, and
to the appendages of the veins. A plexus of more delicate visceral
nerves (r) is continued backward along the interspace of the branchial
nerves, and the chief branches are connected with a small ganglion
situated between the cardiac and pyloric orifices of the stomach. The
posterior suboesophageal nervous mass combines the homologues of
both the branchial and pedial ganglions in the inferior Mollusca : the
anterior ring answers to the ganglia in the higher Cephalopods,
called " pes anseriaus " by Cuvier : the ophthalmic tentacula, which
derive their nerves (?^, 7i) close to the origin of the optic ganglion,
may be considered as homologous to the four tentacula in the Aplysia.
The hollow plicated process beneath the eye, which Valenciennes
regards as the olfactory organ, likewise receives its nerves from the
extremity of the super-oesophageal chord. Three small nervous fila-
ments, described by the same author as passing from the extremity
of the super-ocsophngeal chord to the adjoining part of the cephalic

Nervous System. Nautilus.

CEPHALOPODA. 585

cartilage, he considers as acoustic nerves ; but these nerves are given off
from the sub-oesophageal ganglion in the higher Cephalopods, and in
all the Gastropods, in which the organ of hearing has been observed.

The eyes, as before stated, are attached each by a short pedicle to
the side of the head, over-arched by the projecting margin of the hood.
The form of the ball is sub-hemispherical, being flattened anteriorly
along its inferior border, there is a slightly elevated ridge, from
which a smaller ridge is continued to the middle of the anterior sur-
face of the eye, which is perforated by a round pupillary aperture,
about a line in diameter. The sclerotic tunic, which is a tough,
ligamentous membrane, is thickest posteriorly, and becomes gradually
thinner to the margin of the pupil. The optic filaments form a
pulpy mass at the floor of the eye, from which the retinal expansion
is continued as far forwards as the semidiameter of the globe : it is
lined, like the rest of the interior of the eye, by a thick black pig-
ment, which is doubtless perforated by the retinal papillae, or other-
wise a perception of light must take place in a manner incompatible
with our knowledge of the ordinary mode in which the retina is
effected by luminous rays. The crystalline lens was not present in
the specimen dissected by me, and M. Valenciennes states that he was
unable to observe any of the humours of the eye.* In the Nautilus
umbilicatus, Mr. Macdonald found " a mere viscous matter protecting
the retina from the sea-water."

The cavity in the cephalic cartilage, apparently that described in
my Memoir f as containing a sinus of the cephalic veins, but which
M. Valenciennes regards as the organ of hearing, is defective in the
structures which the uniform analogy of that organ in the molluscous
subkingdom leads us to conclude are essential to it : there were no
traces, for example, of otolithes.J In the Naut. umbilicatus there are
"two spheroidal acoustic capsules placed one on each side, at the
union of the supra- and sub-oesophageal ganglia, and measuring each
about -j^^th of an inch in diameter. Each capsule rests internally
against the nervous mass, and is received on its outer side into a little
depression in the cephalic cartilage. It is enveloped in a kind of
fibrous tissue^ and filled with a cretaceous pulp, consisting of minute
otoconial particles, varying much in size, and sometimes combined in
stellate cruciform or other figures." §

With respect to the organ of smell, the structure and position of
the soft close-set membranous lamellae at the lower and inner part of

* Loc. cit. p. 289. t CCCLXXXVII. p. 16.

% " Elle ctait remplie d'une pulpe homogene " (coagulated blood ?), " et ne con-
tenait aucune sorte de concretions." — Loc. cit. p. 291. Siebold suggests (xxiv.
p. 384.), that the otolithes may have been originally uncalcified, as in Eledone, and
have become dissolved, § CCCCVII. p. 312.

586

LECTURE XXIII.

the oral sheath immediately in front of the mouth, appeared to me
to manifest the conditions of the olfactory organ more obviously than
do those short hollow internally lamellated processes which project
from the outside of the head beneath the eyes. If, however, the
cavity with tumid margins, opening near the eye of the higher Ce-
phalopods, be actually, as KoUiker conjectures*, the olfactory organ,
Valenciennes' idea of the sub-ocular hollow processes may be the
true one.

The complex and well developed tongue of the pearly Nautilus
exhibits in the papillae of its anterior lobes and in the soft ridges of
its root, the requisite structure for the exercise of some degree of taste.

The papillae upon the exterior surface of the two large confluent
digital processes forming the hood and of the two digitations next in
size immediately beneath them, form a remarkable character in the
Nautilus, on account of their obvious similarity to tactile papillae ;
but the sense of touch must be

216

specially exercised by the nu-
merous cephalic tentacles, which
from their softness of texture, and
especially their laminated inner
surface {fig. 216, e, /), are to be
regarded as organs of exploration \
not less than as instruments of
prehension.

The calcareous extremity of the
upper mandible is sharp-pointed
and solid to the extent of five lines,
with a thinner layer of the hard white substance, which forms a den-
tated margin. The fossils termed " rhyncholites," are the homologues
of these calcareous extremities of the beak in cognate extinct cepha-
lopods. The muscular subspherical mass, which supports and moves
the mandibles, is provided wdth four retractors, and can be protruded
by a strong semicircular muscle, which is continued from the margin
of one of the inferior labial processes over the mandibles and their
retractor muscles to the labial process of the opposite side.

The tongue is supported by a horny, slightly curved, and trans-
versely striated plate. The fleshy substance of the tongue forms
three distinct papillose caruncles anterioi'ly, into which the retractor
muscles are inserted. The dorsum of the tongue is incased by a thin
layer of horny matter, supporting four longitudinal rows of recurved
spines ; behind which the surface is again soft and papillose. Two
broad duplicatures of mucous membrane project forwards from the

* CCCXCI. p. 107.

Section of tentacle. Nautilus.

The lower mandible is sheathed

CEPHALOPODA. 587

sides of the pharynx ; they each include a simple layer of salivary
follicles, the secretion of which escapes by a single perforation in the
middle of the process.

The lining membrane of the pharynx is disposed in numerous longi-
tudinal folds, where it begins to contract into the cesophagus. This
tube, having passed through the nervous collar, dilates into a capacious
crop, from the bottom of which a contracted canal, half an inch in
length, is continued to an oval gizzard. The intestine commences
near the cardiac orifice, and soon communicates with a small round
laminated pouch, through which the biliary secretion passes to the
intestine. This canal forms two abrupt inflections, and terminates in
the branchial cavity near the base of the funnel close to the probos-
cidian end of the oviduct.

The epithelium of the oesophagus and ingluvies is developed into a
thick cuticular membrane with minute ridges in the gizzard. In the
specimen dissected by me the crop and gizzard were laden with the
fragments of a small crab, the pieces being more comminuted in the
gizzard.

The liver is a bulky gland, extending on each side of the crop as
low down as the gizzard; it is divided into four lobes, connected
posteriorly by a fifth transverse portion : the lobes are subdivided
into numerous lobules of an angular form. The secretion of the bile
is derived, as in other mollusks, from arterial blood ; it is conveyed
from the liver by two main trunks, which unite into one duct, about
two lines from the laminated sac. The bile, having entered the sac,
is diverted by a peculiar development and disposition of one of the
laminae from flowing towards the gizzard. The follicular structure of
this and the other folds of membrane indicate their glandular character;
and the entire laminated pouch may be considered as a more developed
form of pancreas than the simple caecum which represents that gland
in some of the Gastropods. No other foreign secretion enters the
alimentary canal, as there is not any ink-gland in the Pearly Nautilus.

The heart and large vessels, with their follicular appendages, are
contained in a large cavity, subdivided into several compartments,
which I have termed pericardium ; it is separated from the branchial
cavity by a strong membranous partition, in which the following ori-
fices are observable. In the middle the termination of the rectum,
to the left of this the orifice of the oviduct, and on each side at the
roots of the anterior branchiae there is a small mamillary eminence
with a transverse slit, which conducts from the branchial cavity to
one of the compartments of the pericardium containing two clusters
of venous glands. There are also two similar, but smaller, slits con-
tiguous to one another, near the root of the posterior branchia on

588

LECTURE XXIII.

each side, which lead to, and may admit sea-water into, the compart-
ments containing the posterior clusters of the venous follicles.

The venous branches, from the labial and digital tentacles, and
adjacent parts of the head and mouth, terminate, with those from the
funnel, in the sinus, partly excavated in the body of the cartilaginous
skeleton, and in part continued round the oesophagus. From this
sinus, the great vena cava {Jig. 217, «) is continued, running in the
interspace of the shell-muscles on the ventral aspect of the abdominal
217

Nautilus Pompilius.

cavity, and terminating within the pericardium by a slight dilatation
(c), which receives by two veins {d) the blood from the different
viscera. The vena cava is separated by a layer of decussating mus-
cular fibres from the abdominal cavity, which closely adheres to the
parietes of the vein. There are several small intervals left between
the muscular fibres and corresponding round apertures {h) in the
membrane of the vein and peritoneum. This communication with
the diffused sinuses occupying the general abdominal cavity, is similar
to that already noticed in the Aplysia * : M. Valenciennes detected
the same structure in the specimen of the Nautilus dissected by him.j
The branchial circulation may be considered to commence, when
the blood again begins to move from trunks to branches, four of
which trunks are continued from the terminal venous sinus to con-
vey the carbonised blood to the four gills, of which there is a larger
and a smaller one on each side. Each pair of gills is connected by
a common peduncle to the inner surface of the mantle ; the larger

r. 559.

t Luc, cit. p. 287.

CEPHALOPODA. 589

branchia consists of a central stem supporting forty-eight vascular
plicated lamellae on each side : the smaller branchia has thirty-six
similar lamellae on each side.

The four vessels (/,/} continued from the venous sinus have at-
tached to them, in their course to the gills, clusters of glandular
follicles {g, g) of a simple pyriform figure : each vessel has three
clusters of such glands contained in the membranous receptacles
above mentioned. The walls of these receptacles exhibit in some
parts a fibrous texture, apparently for the purpose of compressing
the follicles, and discharging the contents of the membranous recep-
tacles into the branchial cavity, by the apertures above mentioned at
the base of the gills. Doubtless, therefore, the glands are emunc-
tories, and eliminate from the venous blood an excretion, most pro-
bably urine. Their homologues exist in the higher Cephalopod, in
which they are considered to act as kidneys by Mayer ; and it is
more probable that the organs of so important an excretion should
be present in all the class, than that they should be represented by
the ink-gland and bag, which are peculiar to one order.

The veins (f,f) extend beyond the follicles each to the root of its
respective gill, where it receives a small vein. At this part there is
a valve (A) which opposes the retrogression of the blood ; the vessel,
which may now be termed branchial artery, penetrates the root of
the gill (i), and dilates into a wider canal, which is continued through
the soft white substance forming the branchial stem. A double
series of branches are sent off from the lateral lamellaj^ which ramify
and subdivide to form the capillary plexus, from which the returning
vessels terminate in the branchial vein. These veins (/, I) quit the
roots of the gills, and return to terminate at the four corners of a
subquadrate transversely elongated ventricle (m). From this ven-
tricle two arteries arise, one superior and small (n), the other in-
ferior (r), and strengthened by a muscular bulb (q) to the extent of
nearly half an inch. An elongated pyriform sac (o) is attached by
a contracted origin near the root of the large aorta, and dilates to a
width of two lines ; then, again contracting, becomes connected by
its other extremity, to the venous sinus : it contained a firm coagu-
lated substance.* The anterior aorta supplies the nidamental
gland, and adjoining part of the mantle, and the rectum ; then bends
back to form the small artery (p), continued along the membranous
siphon (5). The large aorta supplies the gizzard and ovary, winds
round the bottom of the abdominal sac, sends off large branches to
the liver, and regains the dorsal aspect of the crop, along which it

* CCCLXXXVII. p. 35. pi. 5. 18.

590 LECTURE XXIII.

passes to the oesophagus, distributing branches on either side to the
great shell-muscles. It bifurcates near the beginning of the ceso-
phagus, and terminates by furnishing branches to the mouth, the
surrounding parts of the head and funnel.

In the male Nautilus, at the part of the branchial cavity where
the vulva opens in the female, there is a short conic penis, somewhat
bent at the basis towards the ventral side, having an obtuse and per-
forated apex ; a very narrow canal extends from this aperture to the
base, and there expands into a pouch, of a firm parchment-like
texture. This pouch contained a conglobate tube of a brown colour,
of little more than a line in diameter : the walls of the tube consisted
of an external transparent membrane, and an internal thicker tunic
of circular fibres. In the interior of the tube was a narrow band
disposed in close spiral convolutions. Between the spiral band and
tube were several free oblong or navicular microscopic corpuscles.
For so much knowledge of the male organs of the Nautilus — all that
science hitherto possesses — we are indebted to Van der Hoeven.*

The female organs of the Nautilus consist of an ovary, an oviduct,
and, as in the Pectinibranchiate Gastropods, of an accessory gland-
ular nidamental apparatus. The ovary {fig, 214, ii) is situated at.
the bottom of the sac on the right side of the gizzard in a peritoneal
cavity peculiar to itself. It is an oblong compressed body, one inch
and a half in length, and an inch in breadth ; convex towards the
lateral aspect, and on the opposite side having two surfaces sloping
away from a middle longitudinal elevation. At the anterior and
dorsal angle there is an orifice about three lines in diameter, with a
puckered margin, which conducts into the interior of the ovary. It
is filled with numerous oval ovisacs of diff'erent sizes, which are
attached by one extremity to the ovarian capsule, but are free and
perforated at the opposite end ; are smooth exteriorly, but rugose
and apparently granular on the inner surface, owing to numerous
minute wavy plicae adhering thereto. The largest of the ovisacs
were four or five lines in length ; they were principally attached
along the line of the exterior ridge, at which part the nutrient vessels
penetrated the ovary.

The oviduct (^fig. 2 1 4, i;) is a flattened tube of about an inch in length,
and from four to five lines in breadth ; it extends forward by the side
of the intestine, and terminates at the base of the funnel close to the
anus. It becomes enlarged towards the extremity, and is deeply
furrowed in the transverse direction both within and without ; the
parietes are also here thick and pulpy, and apparently glandular. It

* CCCXC.

CEPHALOPODA. 591

is probable, however, that the ova derive an additional exterior co-
vering and connecting substance from the secretion of a large glan-
dular apparatus, which is situate immediately below the terminal
orifice of the oviduct. This apparatus is attached to the mantle, and
gives rise to the two rounded convexities observable on the ventral
aspect of the body behind the funnel. It is a transversely oblong
mass, composed of numerous close-set pectinated membranous la-
minge, which are about a quarter of an inch in depth, and are dis-
posed in three groups; those of the larger group extend transversely
across the mesial line of the body, and are unprotected by a mem-
brane ; but the two smaller divisions are symmetrically disposed, and
have the unattached edges of the laminae covered by a thin membrane,
which is reflected over them from the anterior margin of the glandular
body. These divisions form the sides and anterior part of the gland ;
and as the secreted matter must pass backwards to escape from be-
neath the margin of the protecting membrane, this membrane may
serve both to conduct the secretion nearer the orifice of the oviduct,
and also to prevent its being drawn within the respiratory currents of
water, and so washed away as soon as formed.

In contrasting the organisation of the Nautilus with that of the in-
ferior Mollusca treated of in the two preceding Lectures, we find the
main advance to have been made in the organs of animal life.

A true internal skeleton is established in the Nautilus, and thus the
lowest Cephalopod offers an approximation to the Vertebrate type,
which not even the highest of the Articulate series had attained.
Perfect symmetry now reigns throughout the animal and vital organs.
The muscular system forms a larger proportion of the body, with va-
rious arrangements and complications unknown in the lower Ence-
phalous mollusks. The respiratory tube, though still completed by
the overlapping, not by the coalescence, of its side-walls, has re-
ceived an enormous development as contrasted with the siphonated
Trachelipods ; and, by its powerful muscles and their firm cartila-
ginous basis of attachment, it is evidently endowed with a new func-
tion, in relation to propelling the . Cephalopod with its testaceous
dwelling through the sea.

The nervous centres concentrated in the head have received a
marked increase of bulk, which, nevertheless, is still manifested more
strongly in the inferior masses, and especially the anterior suboeso-
phageal ring than in the superior or cerebral part. Here, however,
we find for the first time in the Molluscous series, especial ganglions
subordinated to the greatly enlarged organs of vision.

The organs of reptation, which had progressively advanced (as
Lamarck's denomination of the higher Gastropods indicates) towards

592 LECTURE XXIIT.

the head, are exclusively attached to that part in the Nautilus, and
project from before the eyes and mouth. The mouth, besides its jaws
and spiny tongue, is now served by organs of prehension ; and it is
most interesting to observe that these cephalic preliensile tentacula,
at their first appearance, manifest the vegetative character in their
multiplied repetition and comparative simplicity, compared with
their homologues in the superior Cephalopods.

Some of the Gastropods have a pair of jaws working upon each
other, but in the horizontal plane, as in insects : in the Nautilus they
are opposed to each other vertically, as in the Vertebrate series, and they
present a form which is repeated amongst fishes by the Scari, amongst
reptiles in the Chelonia, a,nd almost universally in the class of Birds.
The resemblance to the latter class which the Nautilus offers in the
modifications of the alimentary canal is also remarkable.

In the very few conchiferous Gastropods that are able to swim, the
shell is of diminutive size, of a simple form and structure, and of an
extremely light and delicate texture. The strong and muscular oc-
cupant of the Pearly Nautilus-shell would not have been able, not-
withstanding its higher organisation, to have risen and swam on the
surface of the ocean unless it had been relieved from the impediment of
its large and dense abode by the introduction of some special mo-
dification in the testaceous structure.

This is effected by the adoption, in the Nautilus, on a more definite
plan and larger scale, of the second mode of dealing with the part of
the shell successively vacated during the rapid growth of the animal,
which has been defined in the general account of the structure and
formation of univalve shells given in the foregoing Lecture.* The
abdominal part of the mantle of the Nautilus is attached to the
inner surface of the shell by the intervention of a horny or epithelial
cincture, the expanded lateral portions of which serve as the medium
of insertion of the adherent muscles of the shell : the cavity of the
shell posterior to this attachment is thus hermetically closed. A
third point of attachment is to the bottom of the shell by the pos-
terior extremity of the mantle,, which probably presents a conical
form in the embryo Nautilus. The line of attachment of both the
muscles and the cincture progressively advances with the growth of
the animal. A certain portion of the fundus of the shell thus becomes
vacated, and the Nautilus commences the formation of a new plate
for the support of the part of the body which has been withdrawn
from the vacated shell. The formation of the plate proceeds from
the circumference to the centre, and there meeting the conical pro-

* P. 545.

CEPHALOPODA. 593

cess of the mantle, wliicli retains its primitive attachment, the calcifi-
cation is continued backwards for a short distance around that pro-
cess, which now forms the commencement of the membranous siphon,
and acquires the partial protection of the calcareous tube. An air-
tight chamber is thus formed, traversed by the siphon, which per-
forates its anterior wall or septum ; by a repetition of the same
processes, a second chamber is formed, included within two perforated
septa ; and similar, but wider partitions continue to be added, con-
currently with the formation of the new layers which extend and
expand the mouth of the shell, until the animal acquires its full growth,
which is indicated by the body having receded for a less distance
from the penultimate septum before the formation of the last septum
is begun.

The periodical formation of these septa in the progress of growth
is analogous to that of the projecting external plates in the Wen-
dletrap, and of the rows of spines in the Murex ; but these ex-
ternal processes consist of the opake calcareous layer of the shell,
whilst the internal processes in the Nautilus consist of the nacreous
layer like the septa in the Turritella. Thus the embryo Nautilus
at first inhabits a simple shell like that of most univalve Mollusca,
and manifests, according to the usual law, the general type at the
early stage of its existence ; although it soon begins, and apparently
before having quitted the ovum, to take on the special form.

In acquiring the camerated structure of the shell the Nautilus
gains the power of rising from the bottom and the requisite condition
for swimming ; by the exhalation of some light gas into the deserted
chambers it attaches to its otherwise too .heavy body a contrivance
for ascending in its atmosphere, as we ascend in ours by the aid of
a balloon. But the Nautilus, superior to the human aeronaut,
combines with the power of elevating and suspending itself in the
aqueous medium, that of opposing its currents and propelling itself
at will in any direction. It possesses the latter essential adjunct
to the utility of the balloon as a locomotive organ, by virtue of the
muscular funnel, through which it ejects into the surrounding water,
doubtless with considerable force, the respiratory currents.

It appears that the proportion of the air-chambers to the dwelling
chamber of the Nautilus and its contents, is such, as to render
it of nearly the same specific gravity as the surrounding water.
The siphon, which traverses the air-chambers, communicates with
the pericardium, and is most probably filled with fluid from that
aquiferous cavity.

Dr. Buckland* conjectures that the Nautilus may possess the power

* CCCXCII. p. 328.
Q Q

594 LECTURE XXIII.

of ejecting such fluid into the siphon, and thereby of compressing the
gas of the chambers and increasing the specific gravity of the shell.
Such, indeed, were the siphon dilatable, would be the natural effect
of the contraction of the animal within its shell. The consequent
pressure of the dense anterior muscular segment upon the soft
and yielding visceral cavity, resisted at the same time by the
unyielding posterior plate at every point, save that from which the
siphon was continued, would propel into that tube as much fluid as it
might be capable of receiving. These consequences would follow
the instinctive retraction of the animal when alarmed ; and if they
should take place while it was floating on the surface, it would im-
mediately begin to descend. If, desiring to rise again from the
bottom, the Nautilus should protrude its body from the mouth of the
shell, extend the folds of its mantle, and spread abroad its tentacula,
it would withdraw the pressure from the abdomen, and, by the act of
advancing, create a tendency to a vacuum in the posterior part of
the shell. The fluid in the siphon would then, if that tube were con-
tractile, return into the pericardial cavity, the gas in the chambers
would expand, and the specific gravity of the animal be sufficiently
diminished to cause the commencement of its ascent, which would
doubtless be accelerated by the reaction of the respiratory currents
upon the water below.

Neither the contents nor the vital properties of the siphon are
however yet known : an artery and vein are assigned for its life and
nutrition, and to extend a low degree of the same influence to the
surrounding shell : but the structure of the membranous siphon,
in the specimens from which I have had the opportunity of exa-
mining it in a recent state, presents, beyond the first chamber, an
inextensible and almost friable texture, apparently unsusceptible of
dilatation and contraction : it is also coated beyond the extremity of
the short testaceous siphon with a thin calcareous deposit. A graver
objection to the hydrostatic action of the siphon is founded upon its
structure in certain extinct species of Nautilus, as the JV. Sipho, in
which it is provided through its whole extent with an inflexible outer
calcareous tube, rendering it physically impossible that the gas of the
chambers could be affected by any difference in the quantity of fluid
contained in the siphon. In the Nautilus striatiis, also, the calcareous
siphon is a continous tube, slightly dilated in each chamber.

From these facts I incline to the conclusion, that the sole function
of the air-chambers is that of the balloon, and that the power which
the animal enjoys of altering at will its specific gravity, must be
analogous to that possessed by the fresh-water testaceous Gastropods,
and that it depends chiefly upon changes in the extent of the surface

CEPHALOPODA. 59o

which the soft parts expose to the water, according as they may be
expanded to the utmost and spread abroad beyond the aperture of
the shell, or be contracted into a dense mass within its cavity. The
Nautilus would likewise possess the additional advantage of pro-
ducing a slight vacuum in the posterior parts of the chamber of
occupation which is shut out by the horny cincture, and muscles of
adhesion from the rest of that cavity.

Whatever additional advantage the existing Nautilus might derive,
by the continuation of a vascular organised membranous siphon
through the air-chambers*, in relation to the maintenance of vital
harmony between the soft and testaceous parts, such likewise must
have been enjoyed by the numerous extinct species of the tetra-
branchiate Cephalopods Avhich, like the Nautilus, were lodged in
chambered and siphoniferous shells.

If the Nautilus extended itself in a straight line during its growth,
instead of revolving round an imaginary axis, a straight conical shell
would be produced, with the chambered part divided by simple septa
concave next the outlet. Such are the more obvious characters of
the fossil shells called Ortlioceratites. The siphon is usually central,
but sometimes marginal ; it is testaceous throughout, and sometimes
moniliform or dilated at each chamber ; this structure. Dr. Buckland
remarks, would admit of the distension of a membraneous siphon. f
Mr. Stokes if has discovered in a species of Orthoceratite {Actiiio-
cei^as) from Lake Huron, a second slender calcareous tube included
within the moniliform siphon, which shows no corresponding partial
dilatations, but is connected to the external siphon by successive
series of radiating plates ; the inner siphon was probably produced
by a calcification of the membranous siphon, and of processes con-
tinued from it at regular intervals. The complex siphons of these
OrthocercB are of great relative capacity. In Ormoceras the siphun-
cular beads are constricted in the middle. In Gomphoceras the
shell is fusiform or globular, tapering towards the aperture of the
last chamber, which is much contracted, so as to suggest that the
soft parts could not have been wholly retractible into that chamber.
The chevron-shaped coloured bands preserved on Orthoceras an-
gulifcrum show that the shell, like that of Nautilus, was external.
The Ortlioceratites are abundantly and widely diffused through the
pala30zoic rocks : specimens of the Orthoceras giganteum, of the
length of six feet, have been discovered in the carboniferous lime-

* LXXXIV. p. 331. (1843). According to Vrolik (CCCXCIII.),the gas with
which the chambers are filled consists chiefly of nitrogen, without a trace of
carbonic acid.

t CCCXCII. p 364. X CCCXCV. p. 705.

QQ 2

596 LECTURE XXIII.

Stone in Dumfriesshire : they indicate a high temperature of the
then existing climate of that northern latitude.

I have already alluded to the slightly undulating contour of the
margins of the septa in the Nautilus, which makes the surface next
the aperture of the shell convex at one part and concave at another.
In an extensive genus of extinct chambered shells called " Am-
monites," no example of which has been discovered in strata more
recent than the chalk, but which were exemplified under a rich di-
versity of forms before their final disappearance, the sinuosity of the
margins of the septa is much greater, and most of the surface next
the outlet is convex ; the siphon perforates the septa at their centre
in extremely few species, and in the rest is situated at that margin
which is next the outer or ventral curve of the shell.* Certain
chambered shells thus characterised are straight, like the Orthocera-
tites, but generally compressed, with their numerous septa joining the
outer shell by foliated dentations : they are termed BacuUtes, In
the true Ammonites the shell is discoid and coiled upon itself as in
the Nautilus ; but it is strengthened by arched ribs and dome-shaped
elevations on the convex surface, and by the tortuous windings of the
foliated margin of the transverse partitions. Separate casts of the
interior of the chambers are not unfrequently obtained, which have
become detached by the solution of the calcareous walls and septa of
the shell, or are held together by the interlocking of the dove-tailed
lobes of the margins of the chambers. The last chamber of the Am-
monite was of large size, as in the Nautilus, and doubtless contained
all the soft parts of the animal save the small proportion which was
prolonged into the siphon. The aperture of the inhabited chamber
was closed by an operculum. Certain species, described by Mr.
Pratt fj from the Oxford clay, were characterised by the production
of a long and narrow process from each side of the mouth of the
shell, indicating a corresponding modification in the lobes of the
mantle, analogous to that which produces the auricular appendages of
the mouth of the shell in certain Argonauts. The same gentleman
has likewise recently shown me a small Ammonite, in which the
mouth of the shell is arched over transversely by a convex plate of
calcareous matter continued from the lateral margins of the outlet,
and dividing this into two apertures, one corresponding with that
above the hood of the Nautilus, which gives passage to the dorsal
fold of the mantle ; the other with that below the hood, whence issue
the tentacles, mouth, and funnel : such a modification, we may
presume, could not take place before the termination of the growth

* The dissection of the Nautilus proved that what had been called the ventral
part of the ammonite was the dorsal.
t Annals of Nat. Hist., November, 1841.

CEPHALOPODA. 597

of the individual. This structure reminds one of Gomphoceras ; to
which illustration may now be added the more remarkable instance of
the Rhizochilus, a siphonated univalve, in which both the outer and
inner lip of the shell-aperture is extended, so as to cement the shell
to the axis of a coral {A?i tip at lies ericoides), or to another shell, and
at length to reduce the aperture to the slender tube of the anterior
siphon of the mantle, — the sole medium of entry and exit of the re-
spiratory currents, and of the nutritive and excretory particles.

The Turrilite is essentially an Ammonite disposed in spiral coils.
The Samite and . Scap kite are other modifications of the outward
form of similarly constructed chambered shells : in the former the
small extremity of the shell is curved, the rest being straight ; in the
latter both ends are curved towards each other like those of a canoe.

With none of these species has there ever been found a trace
of the ink-bag ; a part, indeed, of so delicate a texture that some
surprise may be naturally felt that any evidence of its existence could
be expected to be met with in a fossil state.

I shall, however, conclude this Lecture by bringing before you ex-
amples in which not only the ink-bag, but the muscular mantle, the
fins, the eyes, and the tentacles and their horny hooks, of extinct
Cephalopods have been preserved from the remote periods of the
oolitic deposits to the present time. Independently of these and
many other examples of the durability of the inky secretion of the
gland which is peculiar to the naked Cephalopods, the absence of
the organ in the shell-clad Nautilus, too well protected to need such
means of temporary concealment, would lead to the inference that the
ink-bag must have been absent in the other low-organised Cepha-
lopods covered by chambered siphoniferous shells.

A more complicated fossil shell than any of the preceding, but
allied to them by the camerated and siphoniferous structure of one
of its constituent parts, once occasioned much perplexity amongst
palaeontologists ; the evidence of its nature has however for some
years been in the main sufficient to determine its affinities, about
which there now appears to be no difference of opinion. The shell
to which I allude is that called the '• Belemnite," which is associated
with the more obvious congeners of the Nautilus through a consider-
able range of the secondary rocks. It makes its first appearance,
with Teudopsis and Celceno, in the Lias, as the precursors of the
Calamaries and Cuttles.

The chambered part of the shell of this extinct Cephalopod has
the form of a straight cone {Jig. 218, b)^ the septa being numerous,
with a slight and equable concavity directed towards the outlet or
base of the cone. The intervening chambers are so shallow that

Q Q 3

598

LECTURE XXIII.

the septa have been compared to a pile of
watch-glasses. They are traversed by a
marginal siphuncle. The septa are chiefly
composed of nacreous substance, with a thin
layer of opake and friable calcareous matter
on both surfaces, and the entire cone is en-
veloped in a sheath of opake calcareous mat-
ter lined vi^ith nacreous substance, and having
on the outer surface, or there degenerating ^^^
into, a pellicle or thin layer of a horny sub-
stance. This essential characteristic of the
Belemnitic shell is called the "phragmocone."
Its horny or albuminous tissue is continued
forwards beyond its base, and forms the
parietes of a cavity («) containing some
of the viscera of the animal. In some spe-
cimens, two blade-shaped processes of al-
bumino-nacreous matter are prolonged for-
wards from the dorsal side of the phragmo-
cone. This chambered part, with its sheath,
is lodged in a conical cavity or alveolus*
excavated in the base of a conical or fusi-
form, sometimes compressed, usually long and
spathose body (c), resembling the head of a
dart or javelin, whence the name '^Belem-
nite," applied to this genus of extinct Cepha-

lopods. This sheath or " guard " of the chambered cone is most
commonly found detached from the rest of the shell, with its thin
aveolar portion fractured, especially if fusiform, as in the younger
Belemnites, when it is pointed at both ends. In this state it has
been mistaken for the spine of an Echinoderra.

In the typical Belemnites with a spathose guard, this consists of
successive layers, of which the exterior ones run parallel with the
outer surface, and progressively increase in length as they approach
it, thus forming the conical cavity for the lodgment of the chambered
cone. The innermost or first-formed layers of the guard are not
parallel with the outer ones, but recede from them at their upper
extremity, where they form a point, and sometimes a dilated nucleus,
in contact with the apex of the chambered cone. The interspace
thus left between the early and the later strata of the guard is occu-
pied by the coarse calcareous matter continued from the sheath of the

Belemnite restored.

* The term alveolus has been given improperly to the contents of the socket,
iz., to the " phragmocone."

CEPHALOPODA. 599

chambered cone, and a filamentary process of apparently the same
matter is continued down the centre of the guard to its apex.

The structure of the spathose hiyers of the guard is fibrous ; the
fibres being directed at right angles to the plane of the strata : viewed
in thin sections by transmitted light it bears a close resemblance to
that of the teeth of Pycnodont fishes ; but certain proportions of the
transverse fibres are apt so to intercept the light as to cause the
appearance of elongated triangular dark specks, with their apices di-
rected on one surface of the section to the periphery, and on the other
surface to the centre of the guard.* The microscopic structure,
which resembles that of the Pinna, proves this aggregation of sub-
transparent calcareous matter to be the effect of original formation,
and notj as Walsh, Parkinson, and Lamarck supposed, of infiltration
of mineral substance into an originally light and porous texture. A
section of a Belemnite, in which the chambers of the cone have been
filled with crystalline matter infiltrated from the water of the stratum
in which the dead shell was imbedded, affords a favourable oppor-
tunity of contrasting the crystalline condition of the infiltrated matter
with the organised texture of the solid guard.

The exterior surface of this guard always exhibits, when entire,
traces of vascular impressions : it is sometimes granular, and presents
other modifications, which prove that it was covered by an organised
membrane in the living Cephalopod. I have occasionally seen the
remains of a more immediate investment by a thin friable layer of
calcareous matter analogous to that of the outer layer of the sheath of
the chambered cone, with which layer it becomes continuous. The
exterior of the spathose guard is generally impressed with a longitu-
dinal groove extending from the apex upwards, sometimes along the
ventral (Gastrocoeli), sometimes along the dorsal side {Notocceli). In
some of these the exterior of the guard is impressed with two oppo-
site longitudinal channels in addition to the dorsal groove : the un-
grooved Belemnites form the tribe called Acceli.

The septa of the chambered cone are perforated by a marginal
siphon, situated in most Belemnites on the side which is nearest the
dorsal line, or groove ; but in certain species of Belemnites, charac-
terised by the flattened form of the spathose guard, the siphon is on
the opposite side. These Belemnites, which at first sight look like
distorted or accidentally compressed specimens, are peculiar to certain
members of the greensand formation, called the " older Neocomian."

Specimens of Belemnites have been discovered in which the spa-
those guard has been fractured during the lifetime of the animal ;

* CCCXCVI. p. 67. pi. vii. fig. 2.
Q Q 4

600 LECTURE XXIII.

but the broken portions have been held together by the investing
organised integuments, and have been reunited by the deposition of
new layers of the fibrous structure peculiar to the guard.*

The existence of a camerated and siphoniferous structure on this
complex and remarkable shell, induced most zoologists to class it with
the Ammonites and other more simple chambered shells. Mr. Miller
having detected evidence of the internal position of the Belemnite in
the exterior characters of the guard, first ventured upon a conjectural
restoration of the entire animal f ; and as only the dibranchiate type
of Cephalopods vras then known, he placed it in the body of a Cala-
mary {Loligo), assigning to the terminal fins the office of clasping the
guard and retaining it in its proper position.

The first evidence that bore directly upon the position of the Be-
lemnite in the Cephalopodic class was detected by Drs. Buckland and
Agassiz in specimens of Belemnite from Lyme Regis, in which the
fossil ink-bag and duct was preserved in the basal chamber of the
phragmocone. We must connect with this fortunate discovery the im-
portant fact, that remains of an ink-bag have never been met with in
connection with any of the more simple or typical forms of chambered
shells : we know that the ink-bag does not exist in the recent Nautilus;
and it will be shown in the following Lecture that it is present in all
the existing Cephalopods which possess more or less rudimental in-
ternal shells. I may here anticipate a few remarks on the relations
of co-existence of the ink-bag with the organisation of the naked
Cephalopods. These highly organised species enjoy active powers
of locomotion, which would be incompatible with the incumbrance of
a large external protecting shell ; but, to compensate for the want of
this defence, nature has provided them with the power of secreting
an inky fluid, which, when alarmed, they eject into the surrounding
water, and are concealed by the obscurity which they thus occa-
sion. The branchial character of the naked Order of Cephalopods is
an essential condition of their muscular powers. The presence of an
ink-bladder, therefore, in the extinct Belemnites, would have implied
the internal position of the shell, even if other proof had been
wanting ; and, by the laws of correlation, it implies likewise the
presence of the muscular forces for rapid swimming, and the con-
comitant conditions of the respiratory, the vascular, and the nervous
systems. Connecting, therefore, all these considerations with the
detection of the ink-bag in the shell of the Belemnite, I could not
hesitate in referring the Belemnites, and likewise the Spirula, on
account of the ascertained internal position of its shell, to the Di-

* Duval- Jouve, Memoire sur les Belemnites. 4to. 1841. pi. x.
t Geological Transactions, N.S. vol. ii. p 45. pi. ix. 1823.

CEPHALOPODA. 601

branchiate order ; and I, therefore, separated tliese chambered and
siphoniferous shells from the Nautilus and the Ammonites in the
Classification of the Cephalopoda proposed in 1836.*

Leopold Von Buch, who believed that he could trace in certain
slabs containing Belemnites the impressions of the Cephalopods to
which they belonged, concluded " that the body of the animal enve-
loped the greater part of the shell, and exceeded its length by eight
or ten times." f Other considerations, taken from the shell itself,
prove, as has already been shown, that it was wholly internal.

M. Duval, the latest and most accurate author on fossil Belemnites,
reproduces the figure which M. D'Orbigny has published, and which
is essentially the same as that given by Dr. Buckland in his Bridge-
water Treatise ; and, like it, differs from Mr. Miller's restoration,
only in the position of the ink-bag and in the extended state of the
terminal fins. With respect to these parts, M. Duval, from his dis-
covery of the united fractures of the spathose guard, objects, with
much acumen, that, if the fins of the Belemnite had been placed at
the side of the guard, they must have been rendered useless by its
fracture, and the creature, thus deprived of its power of swimming,
would soon have fallen a prey to its numerous enemies, and would
not have survived to exemplify the reparative powers of those ancient
Cephalopods. It seemed vain to hope that the soundness of the
principles on which the classification of the Belemnites with the
dibranchiate Cephalopods had been definitely proposed, should ever
be vindicated by an example of parts apparently so perishable as the
mantle, the fleshy arms and fins of these Mollusca. I have, however,
been enabled to examine and describe a fossil specimen, in which
not only the ink-bag, but the muscular mantle, the head, and its crown
of arms, are all preserved in connection with the most essential cha-
racteristic of the Belemnitic shell, viz., the phragmocone. % It appears
to have been the peculiar property of the matrix, in which this and
many similar valuable and instructive specimens were entombed, to
favour the conversion of the muscular tissue into adipocire, and its
subsequent preservation to the present time. Yet this matrix is a
member of the Oxford-clay formation, belonging to the middle oolite
system ; older, therefore, than the Portland stone, the Wealden, and
the Cretaceous group. The Cephalopod, in which we may now study
the microscopic character of the muscular fibre §, must therefore have
existed at a period antecedent to the gradual deposition of these
enormous masses of the secondary strata, which themselves preceded
the formation of the entire tertiary series, and the overspreading un-

* CCCXCVII. t Oken's Isis. Bd. xxi. p. 438.

X CCCXCVI. pi. V. § lb. pi. vi. figs. 3 and 4.

602 LECTURE XXIII.

Stratified masses called diluvial. The attempt to conceive or calculate
the period of time which must have elapsed since the Belemnites were
thus embalmed, baffles and awes the imagination.

A second less complete, but highly instructive, specimen of the
same kind of Belemnite*, exhibited the funnel, a great proportion of
the muscular parts of the mantle, and the remains of two lateral fins,
the ink-bladder and duct, and a considerable portion of the chambered
cone. The two fins {fig. 218,//) present the form of flattened
transversely striated fibrous masses with their free border entire and
rounded. They are situated on each side of the visceral cavity, and
demonstrate the accuracy of M. Duval's objection to their position in
the previous conjectural restorations. A large tract of the grey
fibrous substance, running parallel with and on one side of the re-
mains of the head, indicates the position of the infundibulum, and is
terminated by a concave truncation. At the middle of the visceral
mass at the interval of the two lateral fins, there lies a compressed
body of a horny texture and somewhat bilobed form, on which may
be clearly distinguished striae passing outwards in opposite directions
from a middle line, and diverging from each other in their course,
which resembles that of the fibres of the digastric muscle in the
gizzards of the Cephalopods : this apparent remnant of the stomach
lies anterior to the ink-bladder. There is a strong negative evidence
that the Belemnite possessed horny mandibles like the other naked
Cephalopods, since no calcareous ones, called Rhyncholites, have been
discovered associated with these remains. The cephalic arms, which
are preserved in a third specimen with the contour of the large ses-
sile eyes, belong to the normal series, and were eight in number :
they were provided, not with simple acetabula, but with a double
alternate series of slender elongated horny hooks, as in the genus of
existing Calamaries, called Onychoteuthis. Each arm seems to have
been provided with from twelve to twenty pairs of these hooks. They
were doubtless developments of the horny hoop which encircles the
central process of the acetabulum, as in the modern Onychoteuthides ;
but in the position of the pallial fins, the Belemnite resembled the
Sepiola. The traces of the superadded pair of tentacula are some-
what doubtful.

The modern decapodous Cephalopod, which most nearly resembles
the Belemnite in the structure of its internal shell, is the Sepia, or

* CCCXCVI. pi. iii. For these apparently guardless species, first submitted to
me by Mr. C. Pearce, I suggested the subgeneric name of Bekmnoteuthis, which he
adopted. But the importance of the subsequently discovered specimens, with the
soft parts, for the elucidation of the nature of the Belemnitidce, is in no way
affected hy subgeneric nomenclature, so long as naturalists concur in regarding the
*' phragmocone " as the essential part of the Belemnitic shell.

CEPHALOPODA. 603

common cuttle-fi^h : the lateral fins of this species extend from the
apex to near the base of the mantle. The nucleus, or terminal spine
of the cuttlebone corresponds with the spathose guard of the Belem-
nite : the convex posterior broad layer of friable calcareous and
horny matter is homologous with the enveloping cone; but its
margins, instead of being approximated and soldered together, are
free and lateral in position : the successive plates, embedded in its
concavity, answer to the camerated cone of the Belemnite ; but, in-
stead of being perforated by one or many siphons, they are connected
with each other by a series of minute undulating lamellae.

Thus at length has been obtained the proof of the dibranchiate nature
of the Belemnite, and we learn from the same ocular evidence that it
combined characters at present divided between three distinct genera
of the order ; namely, first the calcareous internal chambered shell,
to which the Sepia offers the nearest approach ; secondly, the for-
midable hooks of the arms, which characterise the modern genus
Onychoteuthis ; and, thirdly, the limited attachment of the lateral
fins to a position a little in advance of the middle of the body, as in
the Sepiola.

The Belemnite, having the advantage of its dense but well-balanced
internal shell, must have exercised its power of swimming backwards
and forwards, which it possessed in common with the modern decapod
Dibranchiates, with greater vigour and precision. Its position was
probably more commonly vertical than in its recent congeners. It
would rise swiftly and stealthily to infix its claws iir the belly of a
supernatant fish, and then dart down and drag its prey to the bottom
and devour it. We cannot doubt at least but that, like the hooked
Calamaries of the present seas, the ancient Belemnites were the most
formidable and predacious of their class.

LECTURE XXIV.

CEPnALOPODA.

The deductions which were founded on the modifications of the
chambered siphoniferous shell and other enduring remains of the
very remarkable extinct genus which occupied our attention at the
close of the last lecture, obliged me frequently to refer to the type of
structure which characterises the Dibranchiate order of Cephalopods,
and which places these Mollusks not only at the head of that division

604

LECTURE XXIV,

219

of the Animal Kingdom, but, in respect of its closer proximity to the
Vertebrate type, unquestionably at the head of the whole Invertebrate
series.

The body of the Dibranchiate Cephalopod is divided, as in the Nau-
tilus, into two parts ; a head {fig. 220, A.), containing the organs of
sense, mastication, and deglutition, and supporting the prehensile
and principal organs of locomotion (c), and a trunk or abdomen (b),
consisting of a muscular sac or mantle, with a transverse anterior
aperture, and containing the respiratory, generative, and digestive
viscera. With the exception of the females of one genus (^Argonauta,
fig. 220.), the body is naked, includes a more or less rudimental shell,
and supports, in most of the species, a pair of fins. Compared with
the Nautilus, the cephalic appendages are much reduced in number,
the external ones, continued from the oral sheath, not exceeding eight
{fig. 219, c, c), to which, in most of the genera, is added a pair of
internal and much longer tentacula
(d, d). The arms are much in-
creased in size and of a more com-
plicated structure, supporting on
their internal surface numerous
suckers, and sometimes connected
together by a powerful muscular web.
The eyes are much larger and more
complex, are no longer peduncu-
lated, but lodged in orbits. The
mouth is armed with two piercing
and trenchant jaws, resembling in
shape and in their vertical move-
ments those of the Nautilus, but
wholly composed of horn. The
gills are two in number, each witli
a ventricle appropriated to the
branchial circulation ; the systemic
circulation having a single mus-
cular ventricle, as in the Nautilus.
The infundibulum {i) is a complete
muscular tube, shaped like an in-
verted funnel. The Dibranchiates
possess a gland and membranous re-
ceptacle for secreting and expelling
an inky fluid. The sexual organs are
in distinct individuals, as in the Te-
trabranchiate order. All the species of both orders of Cephalopods

Loligo vulgaris.

CEPHALOPODA.

605

are aquatic and marine, and they are mostly nocturnal and gregarious
in their habits.

The Dibranchiate order may be subdivided into two tribes ; the
one provided with the eight ordinary arms and the two longer ten-
tacles, hence c?d\ed Decopoda {fg. 219.) ; the other tribe without
the tentacles, and called Octopoda {Jig. 220).

220

Argonauta Argo, faem.

The various forms of the extinct BelemnitidcB (Jig. 218.) consti-
tuted one family in the Decapod tribe. The little Spirula, charac-
terised by a less complex, but internal, chambered shell {Jig- 221.), is
the type of a second family. The cuttle-fish, characterised by its
internal calcareous shell, which feebly represents that of the Belem-
nite, exemplifies a third family of Decapods called Sepiadce, The
common calamary {Loligo), in which the internal shell is reduced to
a horny quill-shaped plate, represents the fourth and most extensive
family of the present tribe, which I have called Teuthidce ; and in
which one genus ( Onychoteuthis) had the caruncle of more or fewer
of its acetabula produced into horny claws.* In all the Decapods the
mantle supports a pair of fins {Jig. 219, h, b\ and the funnel is gene-
rally provided with a valve.

In the tribe Octopoda fins are rarely developed from the mantle ;
but the eight ordinary arms are longer, thicker, and are united to-
gether by a broader web, which forms a powerful organ for swimming
in a retrograde direction. One family in this tribe (^Testacea) is
represented by the genus Argonauta, in which, in the female sex f,
the first or dorsal pair of arms {fig, 220, c, 1) are dilated at the ex-

* CCCXCVII.

t CCCXCVIII. p. 39.

606 " LECTURE XXIV.

tremity into a broad thin membrane, like the mantle in the testaceous
raollusks ; by means of these membranes, the animal, in fact, forms
for itself an extremely light, slightly flexible, and elastic, but calca-
reous, symmetrical shell, which is simple, and not divided into
chambers ; the vacated portion communicating with the rest, and
being used by the inhabitant as the receptacle for the eggs : it has
no muscular attachment to the body. * The siphon is without a
valve, but is articulated at its base on each side to the inner surface
of the mantle. The second family of the Octopods is termed Nuda^
the species not being provided with an external shell. The first pair
of arms is elongated, and contracts to a point : the funnel or siphon
is without an internal valve or external joints. The rudimental shell
is represented by two short styles, encysted in the substance of the
mantle. The typical genus of this family is termed Octopus, in which
the arms are provided with a double alternate series of sessile aceta-
bula. In a second genus Eledone, the arms are provided with a
single series of acetabula. The third family is the Pinnata, typified
by the Sciadephorus, which has a pair of filaments between each of
the suckers, and a pair of fins from the sides of the body.f

The shell or dermal skeleton, which has been progressively reduced
in the present highly organised class, attains its lowest or most rudi-
mental condition in the Octopus and Eledojie. The genus in which
the shell most nearly resembles that of the tetrabranchiate Cepha-
lopods, belongs to the Spirula. A few mutilated specimens had
demonstrated it to be an interjial shell, and the more perfect examples
of the animal, dissected by M. de Blainville J and myself §, proved it to
liave the characteristic organisation of the Dibranchiate order, and
to possess, as Peron had indicated, the eight short arms and the two
lono- tentacula of the Decapodous tribe. The shell of the Spirula
(fig. 221.) is perfectly symmetrical, convoluted in a vertical plane
221 with the whorls contiguous, but not touching. The

shell commences by a small oval cell, followed by a
series of chambers (6), which rapidly increase in size.
The septa («) are concave towards the outlet, and
are perforated by a siphon at the internal or concave
Spirula austraiis. niargiu of the shell. A small funnel-shaped tube
(r) is continued backwards from each perforation ; and its apex
penetrates the mouth of the succeeding tube. The circumference of
the siphonic aperture is impressed, as Mr. Stokes first observed, by a

* The honour of having experimentally determined the true relation of the
Argonaut shell to its cephalopodic tenant, and the true functions of the expanded
arms, is due to INIadame Jeanette Power, CCLXXIIt.

t CCCXCIX. & CCCC. X CCCCI. p. 396.

§ CCCCIL pi. iv.

CEPHALOPODA. 607

circle of minute pits. The shell seems to be exclusively composed of
a fine white nacreous substance ; it is imbedded in the posterior part
of the mantle, with a small part of its surface exposed on both the
upper and lower sides of the animal's body : the exposed parts of the
shell are invested by a granular straw-coloured epidermis. The
shelly siphon is traversed by a tubular membranous siphon.

The principal characters of the internal shell of tlie cuttle-fish have
already been pointed out in the illustration of its analogies with that
of the Belemnite. The preparations, Nos. 106, 107, 108. demonstrate
the great proportion of animal membrane which enters into the com-
position of this slight friable laminated shell. The laminae consist
of a subopake minutely granular substance, and are connected
together by thin wavy leaves of a transparent substance, the folds of
which resemble little pillars, and are marked by fine transverse strice,
like those on the prisms of tlie shell of the Pinna.

In the rest of the Decapoda the rudimental shell consists exclusively
of animal matter, of the consistency of horn, and presents either tlie
form of a pen, as in the common Calamary, or that of a straight
three-edged sword, as in the hooked squids.* This body was called
" xiphos " by Aristotle, and " gladius " by Pliny. In Sepioteuthis it is
as broad in proportion to its length as the cuttle-bone. In Onycho-
teuthis, Loligo, and Loligopsis, it is much narrower, but is as long as
the mantle. In Sepiola and Rossia the gladius, commencing at the
anterior margin of the mantle, ends before it has reached half-way
down the back. In the Octopus and Eledone, the last traces of a
shell exist in the form of two small am.ber-coloured styliform bodies,
contained loosely in capsules in the substance of the mantle. All
these bodies present a minutely laminated structure when trans-
versely bisected.^ The shell of the Argonaut presents a minutely
granular texture ; "it exhibits no trace of cellular or j^rismatic tissue." f

The skin of the naked Cephalopods is generally thin and lubricous,
and can be more easily detached from the subjacent muscles than
in the inferior Mollusks. In some of the smaller Cephalopods it is
semitransparent : it is densest in the Calamaries, in which the
epidermal system is most developed, as is exemplified in the horny
rings or hooks upon the acetabula. In the Octopods the epidermis is
reflected over the interior of the acetabula without being condensed
into horn. Upon the body the epiderm may generally be detached in
the form of a thick white elastic semitransparent layer. The second,
or pigmental layer of the skin, analogous to the rete mucosum, con-

* In some extinct Cephalopods from oolitic strata the shell was externally
calcareous, internally horny, e. g. Coccottuthis. See CCLXXII.
t CCXXXI.

608 LECTURE XXIY.

sists of numerous cells of a flattened oval or circular form, containing
coloured particles suspended in a fluid. The colour is rarely the
same in all the cells ; the most constant kind generally corresponds
more or less closely with the tint of the inky secretion. In the Sepia
there is a second series of vesicles containing a deep yellow or
browish pigment : in the Loligo vulgaris there are three kinds of
coloured vesicles, yellow, rose-red, and brown : in the Octopus vul-
garis there are four kinds of vesicles, red, yellow, blue, and black.
In the skin of the Argonauta all the colours which have been ob-
served in other Cephalopods are present, and contained in their ap-
propriate cells. These cells possess the power of rapid alternate
contractions and expansions, by which the pigment can be driven
into the deeper parts of the corium or brought into contact with
the semitransparent epiderm. If the skin of a living Octopus be
touched, the colour will be accumulated, gradually or rapidly, like a
cloud or a blush upon the irritated surface. If a portion of the skin
be removed from the body and placed in sea-water under the micro-
scope, the contractions of the vesicle may be watched for some time :
their margins are well defined, and they pass, during their dilatations
or contractions, over or under one another. The power which the
Cephalopods possess of changing their colour and of harmonising it
with that of the surface on which they rest, is at least as striking and
extensive as in the Chameleon, in which, it seems, from the latest
observations, to be produced by a similar property and arrangement
of pigmental cells. The external surface of the branchial membranes
in the Argonauta has many pigmental cells ; the internal surface has
very few ; it is covered by numerous reticulated lines, which become
prominent, and their interspaces deep, when the membranes contract.
The internal organised skeleton of the dibranchiate Cephalopod
is cartilaginous, as in the Nautilus, but consists of a greater number
of pieces, and enters into a larger proportion of the organisation of
the animal. The cranial cartilage is no longer limited in its position
to the under side of the oesophagus, but completely surrounds that
tube, which, together with the inferior salivary ducts and the cephalic
branches of the aorta, traverses a narrow canal in its centre. The
cartilage above forms the cavity containing the brain, while below it
is excavated to lodge the organ of hearing, and at the sides expands
into the broad and thick orbital cavities. There is also a thin and
long cartilage which supports the eyeball, and reminds one of the
ophthalmic peduncle of the Rays and Sharks. A process continued
from the anterior part of the cranial cartilage expands into a broad
transverse plate, and gives attachment to the muscles of the arms.
In Sepia and Loligo there is a thin semilunar cartilaginous plate,

CEPnALOPODA. 609

situated on the dorsal part of tlie mantle, near the anterior end of
the internal shell : in Loligo^ there is a second long rhomboid dorsal
cartilage. The infundibular cartilage, which is a process of the
cranial one in the Nautilus, is a distinct piece in the Dibraiichiata.
It is of a large size, and of a flattened triangular figure in the cuttle-
fish, in which it is situated above the base of the funnel. It consists
of three distinct portions in the Calamarj. On each side the base of
the funnel there is a smooth oblong articular cavity, formed by a
distinct piece of cartilage, which is articulated with a corresponding
cartilaginous prominence from the inner surface of the side of the
mantle. These cartilaginous joints of the funnel vary in shape in
the different genera : they are wanting in the Octopus. The lateral
fins of the Decapoda are each supported by a narrow flattened
elongated cartilaginous plate, which forms the medium of attachment
of the powerful muscles of those fins. These appear to be homologous
with the parial fins of fishes ; but as they are not fixed to a vertebral
column, their position is variable ; in the Rossia, for example, they are
situated near the anterior part of the body ; in the Loligo, they are
placed at the posterior extremity ; in the Sepia they extend, like the
great pectoral fins of the Rays, along the whole side of the body. In
the Octopods the mantle-fins and their cartilages are wanting, except
in the anomalous genus Sciadephorus in which they are attached to
the anterior part of the sides of the mantle.

The sole locomotive organs in the ordinary Octopods and the sole
prehensile organs in all the Dibranchiates are the appendages deve-
loped from the head, termed " arms," " feet," " tentacles," and " pro-
boscides." They have no true homology with the locomotive members
of the Vertebrata, but are analogous to them, inasmuch as they relate
to the locomotive and prehensile faculties of the animal.*

The eight arms of the Octopus commence by a hollow cone of
muscular fibres attached by a truncated apex to the anterior part of
the cephalic cartilage. The fibres are for the most part oblique, and
interlace with one another in a close and compact manner, as the cone
advances and expands to form the cavity containing the mandibulate
mouth, at the anterior extremity of which they are continued forward,
and separate into eight distinct portions which form the arms. The
development of the eight external arms bears an inverse proportion
to that of the body ; they are longest in the short round-bodied Octopi,
and shortest in the lengthened Calamaries and Cuttle-fishes, in which
the two elongated retractile tentacles are superadded by way of com-

* Geoffroy St. Hilaire regarded the cuttle-fish as a vertebrate animal bent double,
with the approximated arms and legs extending forwards : a similar comparison
may be found in Aristotle.

R R

610 LECTURE XXIV.

pensation. These latter organs are not continued from the muscular
cone which corresponds with the cephalic sheath in the Nautilus, but
arise, like the internal labial processes in that Cephalopod, close to-
gether from the cephalic cartilage, internal to the origins of the
ventral pair of arms. They proceed at first outwards to a large
membranous cavity situated anterior to the eyes, and emerge between
the third and fourth arms on either side.

In most Octopods the two dorsal arms are the longest : they are ten
times the length of the body in Oct. Aranea. But besides their su-
perior length, the dorsal arms present other peculiarities in this
family of Cephalopods. In the males of Tremoctopus and Argo?iaicta,
one of them is enlarged and excavated to receive part of the male
sexual apparatus*: in the female Argonaufa they are provided, as
before stated, with the expanded calcifying membranes (Jig- 220, c. 1),
which are usually spread over the exterior of the delicate shell («),
meeting and overlapping each other along its slender keel. The fabled
office of these membranes, as sails to waft the argonaut along the
surface of the ocean, and that of the attenuated arms as oars extend-
ing over the sides of the boat, have afforded subject for poetic
imagery and constructive analogy in all ages : and the little hypo-
thetical navigator of nature's ship has been the subject of the disquisi-
tion of the naturalist from Aristotle to Cuvier, and of the song of the
poet from Callimachus to Byron.

In Octojms velifer both the first and second pairs of arms support
broad and thin membranous appendages at their extremities. In the
common Poulp, Octopus vulgaris, the eight arras are connected to-
gether for some distance beyond the head by membranes and muscles,
which form a circular fin ; this constitutes its sole locomotive organ
when swimming, and, by its powerful contraction, aided, however, by
the ejection of the currents from the funnel, the animal is propelled
through the water by a quick retrograde motion. In Oct. semi-
palmatus the fin is extended along the basal interspaces of only the
four dorsal arms. In Sciadephorus it extends between all the arms,
and as far as their attenuated extremities. There are two layers of
transverse fibres in this web, the external of which arises from a
white line along the back part of the base of each arm, the internal from
the sides of the same arms between the attachments of the suckers.
They decussate one another as they pass from arm to arm in the middle
of the webs, and are included between two thin layers of radiating or
longitudinal fibres.f

The internal surface of the arms is that which is specially modified

* CCCCIX. & CCCCX. t Eschricht, CCCXCIX. p. 627.

CEPHALOPODA.

611

222

in the Dibrancliiate as in tlieTetrabrancliiate Ceplialopods for the pre-
hensile and tactile faculties ; but the structure is much more compli-
cated in the higher order. On this surface each arm supports a
single or double series or more numerous rows of acetabula or cir-
cular sucking cups : in the elongated pair of superadded tentacles of
the Decapods the suckers are limited to the expanded extremities,
where they are generally aggregated in more numerous and irre-
gular rows. These tentacles serve to seize a prey which may be
beyond the reach of the ordinary arms, and also act as anchors to
moor the Cephalopod in some safe harbour during the agitations of a
stormy sea.

Each muscular arm is perforated near the centre of its axis for the
lodgement of its nerve and artery {Jig. 222, «), which are surrounded
by a layer of cellular tissue (c) ; from
the dense outer sheath of this cellular
canal the transverse fibres of the arm
{d) radiate to the periphery, intercept-
ing spaces containing the longitudinal ^
fibres of the arm, the whole being sur-
rounded by two thin and distinct strata
of fibres, of which the external is
longitudinal, and the internal trans-
verse.

The mechanical structure of the
acetabulum may be favourably studied
iii the Octopus, in which those organs
are of large size, and sessile. The
circumference of the disc of the sucker
is raised by a tumid margin {h) ; a
series of slender folds of membrane {f)i
covering corresponding fasciculi of mus-
cular fibres, converge from the circum-
ference towards the centre of the sucker, where a circular aperture
{g) leads to a cavity which widens as it descends, and contains a soft
caruncle (/), rising from the bottom of the cavity like a piston of a
syringe. When the sucker is applied to any surface for the purpose
of adhesion, the piston, which previously filled the cavity, is retracted,
and a vacuum produced.

The complex irritable mechanism of all these suckers is under
the most complete control of the predatory Cephalopod. My friend
Mr. Broderip, F.R.S.*, informs me, that he has attempted, with a

Octopus.

* Author of valuable original Memoirs in the Transactions of the Zoological
Society ; of the admirable articles on zoology in the Penny CyclopBcdia ;

R R 2

612 LECTURE XXIV.

hand-net to catch an Octopus that was floating within sight, with its
long and flexible arms entwined round a fish which it was tearing
to pieces with its sharp hawk's bill ; the Cephalopod allowed the
net to approach within a short distance of it, before it relinquished
its prey, when in an instant it relaxed its thousand suckers, ex-
ploded its inky ammunition, and rapidly retreated under cover of the
cloud which it had occasioned, by quick and vigorous strokes of its
circular web.

The Cephalopods which frequent the more open seas, and which
have to contend with more agile and powerful fishes, have still more
complicated organs of prehension. In the Calamary the base of the
piston is enclosed in a horny hoop with a dentated margin. In the
Onychoteuthis the margin is produced into a long, curved, sharp-
pointed claw. These formidable weapons are sometimes clustered at
the expanded terminations of the tentacles, and in a few species are
arranged in a double alternate series along the whole internal surface
of the eight ordinary arms, as they were in the extinct Belemnite.

The peripheral fold of membrane of the sucker can be expanded
beyond the piston, so as to act on a hard surface like the unarmed
sucker of the Octopus : but, so applied to the mucous surface of a
fish, it might glide off : the better to hold on such slippery ground,
the horny dentacles and hooks are superadded ; the latter, in Onycho-
teuthis, are retractile, as in the cat's paw ; and it is interesting to find
this earliest appearance of the retractile claw illustrating numerically
the law of vegetative repetition.

In connection with the uncinated acetabula at the extremities of
the long tentacula of the Onychoteuthis, may be observed a cluster
of small simple unarmed suckers at the base of the expanded end.
When these parts in each tentacle are applied to one another, they
become locked together, and the united strength of both the peduncles
is thereby more efifectually brought to bear upon any resisting object
which may have been grappled by the terminal hooks. This is a very
striking mechanical contrivance : human art has remotely imitated
it in the fabrication of the obstetrical forceps, in which either blade
can be used separately, or, by the interlocking of a temporary joint, be
made to act in combination.*

In the diminished number, increased size, and progressive complica-
tion of the cephalic muscular appendages, and in their final modifica-
tion for combining with one another to produce a determinate action,
we trace the common order which regulates the development of other

of " Zoological Recreations," and other delightful contributions to our common
favourite science.

* CCCCIV. vol. i. p. 529.

CEPn.u.0P0DA. 613

parts of the animal organisation. In our past review of tlie Inverte-
brata, we have witnessed this order in the appearance of the more
essential organs, as the nervous centres, the eyes, the stomach, the
heart, the gills, the generative parts ; we find it equally regulating
the development of the peculiar prehensile instruments of the Cepha-
lopodic class.

At first very numerous, comparatively small and feeble, essen-
tially alike, the cephalic tentacles of the Nautilus strikingly illus-
trate the law of vegetative or irrelative repetition. Their primary
import is, however, plainly indicated by the direct derivation of their
central nerve from the anterior cephalic ganglion ; and they present
the same complex plan of arrangement of their muscular fibres which
characterises the arms and tentacles of the dibranchiate Ceplialopods.
The prehensile surface of the tentacula of the Nautilus {^Jig^ 214.) is
made adhesive after the type of the simple laminated sucker of the
Remora ; the median longitudinal impression which partially divides
the lamella may represent the complete interspace which separates
into two series, in the arms of most of the Dibranchiates, the more
complex suctorial appendages which are developed on their internal
surface : but at all events, the reduction of these arms in number,
their augmentation in size, and perfection as prehensile instruments
by the superadded complications, are phenomena which ordinarily
attend the march of development. The order of this progress
would be anomalously reversed if the tentacles of the Nautilus repre-
sented, as M. Valenciennes supposes, the caruncles of the acetabula,
and the hollow processes of the oral sheath the Cavities of those
appendages of the arms of the Dibranchiates. According to the
French Malacologist, the anterior circumference of the head or oral
sheath in the Nautilus represents four of the eight arms developed
therefrom in the Dibranchiates, and the two dorsal arms consist each
of two enormous acetabula, whose cavities are deepened into tubes,
and whose caruncles are produced into tentacula as highly organised
in regard to their nerves and muscles, as are the acetabuliferous
arms themselves in the higher orders. The four other arms of the
Octopus are represented, according to M. Valenciennes, by the four
groups of tentacula which are included within the oral sheath in the
Nautilus. Such is not, however, the place of origin of any of the
eight arms in the Dibranchiata ; nor is it conformable with the ge-
neral law of development, that a prehensile organ consisting of two
large and highly complicated acetabula in a low organised Cephalopod
should support two hundred smaller and more simple suckers in the
higher organised species.*

* CCCCIII.

R R 3

614 LECTURE xxiy.

The primitive fibres of the muscles of the Cephalopods are smooth :
they are more parallel than in the lower moUusks, and are bound
together, so as to form well-defined flat fasciculi.

The pallial sac is chiefly composed of a layer of circular fibres,
interrupted behind in Sepia, where the shell is lodged. A pair of
round longitudinal muscles pass from the ventral wall to the base of
the funnel : a second pair extend from the dorsal wall to the cephalic
cartilage and the back part of the base of the arms. Other smaller
fasciculi arise from the sides of the cephalic cartilage, and are in-
serted into the funnel.

Fasciculi of muscular fibres are continued from the ventral pair of
feet and the back part of the cranium to the muscular partition which
divides longitudinally the branchial cavity : other fibres descend to
join the muscular tunic enveloping the liver and oesophagus. In the
cuttle-fishes and calamaries the branchial septum is not developed.
The respiratory tube or funnel is a complete muscular cylinder,
formed by an external longitudinal, and an internal transverse, layer
of fibres, with which are blended the insertions of the accessory
retractor muscles.

The homologues of the great muscles which attach the Nautilus to
its shell may be traced in the different genera of Dibranchiates,
diminishing in size as the internal shell becomes more and more
rudimentary. They arise in conjunction with the fibres of the fleshy
tunic of the liver from the posterior part of the cephalic cartilage ;
but, soon quitting these fibres, they extend downwards and outwards,
being perforated in their course by the great lateral nerve, and are
inserted into the epidermic capsule of the internal shell.

The thin shell of the female Argonauta, which is external in regard
to the true mantle, but internal in relation to the branchial mem-
branes which formed it, is retained in its position chiefly by these
membranes ; and when they are, as they are capable of being,
retracted into the cavity of the shell, it adheres to the surface of the
body by the adhesion of contact only and its own elasticity, not by
its attachment to any muscular fibres : hence the animal commonly
drops out of the shell when dead.

The principal muscular fibres of the pallial fins extend, transversely to
the axis of the body, to the margins of the fins: they present the same
direction in the fossilised fins of the animal of the Belemnite. The
action of the powerful muscles in the terminal fins of the calamaries
must be aided in its effect upon the body by the elasticity of the in-
ternal pen or gladius. By these means they are enabled not only to
propel themselves forward in the sea, but they can strike the surface
of the water with such force as to raise themselves above it, and dart

CEPHALOPODA,

61o

like tlie flying fish for a short distance through the air. This is
the highest act of locomotion, the nearest approach to flight, which
any of the molluscous animals have presented.

We find associated with the varied and active powers of loco-
motion just described, visual organs of large size and singular com-
plexity of structure ; the whole surface of the body is highly
sensitive; and there is a concomitant development of the nervous
centres, which exhibit the highest conditions of this system in the
Invertebrate series of animals.*

The brain is lodged in a cartilaginous cranium, together with a
portion of the oesophagus, from which it is separated by the mem-
brane analogous to the dura mater : the same strong membrane
protects the brain where the cranium is open anteriorly. Between
that part of the fibrous membrane which lines the cerebral cavity and
the pia mater covering the brain,
there is an intervening space
filled with a gelatinous and oily
arachnoid tissue. In the cuttle-
fish, the super-oesophageal cere-
bral mass (^fig- 223, a) consists
principally of a cordiform body,
superficially divided into two
lateral lobes by a median longi-
tudinal furrow. From the lower
and lateral parts of this body
proceed the short and broad
optic nerves, which constitute
the peduncles of the large reni-
form optic ganglions {h\ and
upon each peduncle there is
placed a small spherical medul-
lary tubercle: these tubercles
exist also in the calamaries, but
appear not to be present in the
Octopods.

From the inferior and anterior
parts of the super-oesophageal
mass, a thick cord descends on
each side of the oesophagus,
unites with its fellow, and di-
lates below that tube to form
the anterior sub-oesophageal

Nervous system, Sepia officinalis.

* CCCXXL, CCCCIV., CLXXXV., Bd. ii. p. 317. t. 32., & CCLXXA^ir,

R R 4

616 LECTURE XXIV.

ganglion, from ^vliich the nerves of the feet and tentacles arise.
Two broader bands descend from the super-oesophageal mass behind
the preceding, and form, by a like enlargement and union, the
posterior oesophageal body, which blends laterally with the anterior
one, and forms with it a large mass with a central perforation. Four
short and slender chords, two of which (e) are continued from the
anterior apices of the optic lobes, and two from the anterior sub-
oesophageal lobes, converge forwards and unite to form a round
flattened ganglion {g\ which is closely applied to the back part of
the fleshy mass of the mouth above the pharynx, from which are sent
off" the nerves to the retractors of the mouth. Two filaments from
the pharyngeal ganglion descend to join a pair of ganglions below
the pharynx, homologous with the labial ganglions of the Nautilus,
and the buccal ganglions of Gastropods. The nerves of the arm
(f, f) proceed from the anterior sub-oesophageal ganglion, and
correspond in number to the organs which they supply, being eight
in the Octopoda, and ten in the Decapoda : the corresponding nerves
are much more numerous in the Nautilus. In the Loligo they have
a double origin, the anterior sub-oesophageal mass being divided into
an anterior and posterior portion, and each brachial nerve deriving a
root from both centres, which may have distinct functions, one
motory, the other sensory.* In the Octopus the brachial nerves
pass along the inner surface of the base of the arms before they
penetrate the axial canals. As soon as the acetabula begin to be
developed, a series of closely approximated ganglions are formed
upon the brachial nerves, of which some of the longitudinal fibres
pass over the ganglions. Before the ganglionic enlargements
commence, each brachial nerve in the Octopus gives off two large
branches, which traverse the fleshy substance of the base of the arms
to join the tw^o corresponding brunches of the contiguous nerves
which are thus associated together for consent of action by a
nervous circle.

The infundibular nerves arise behind the origin of the brachial
ones. Posterior to these the small acoustic nerves are given off from
the sub-oesophageal mass. The delicate motores oculi arise from the
upper part of tlie lateral connecting bands of the infra- and supra-oeso-
phageal masses, which may be compared with the crura cerebri, as the
nerves in question obviously answer to the third pair in the Vertebrata.
The nerves going to the cavities, supposed to be olfactory, arise close
to the optic nerves. The nerves which correspond to those of the
shell-muscles of the Nautilus, form a single large pair (w, in), which

* CCLXXVIir. p. 2.

CEPHALOPODA. 617

arise from the posterior and lateral angles of the sub-oesophageal
mass, extend outwards and backwards, perforate the shell-muscles,
and form the large stellate ganglions (n, n), from which the nerves
of the mantle are principally derived. In the Octopoda this may be
described as the termination of the nerve-trunk ; but in the Deca-
poda, in which lateral fins are superadded to the body, the great
nerve previously divides into two branches, of which the outer one
expands into the ganglion, whilst the inner branch, having been
joined by one of the rays of the ganglion (o, o), pierces the fleshy
substance of the mantle, and ends in a diverging series of twigs
appropriated to the muscles of the fin. In proportion as the trunk
of the Cephalopod is attenuated and elongated, the pallial nerves
become more parallel in their course, more dorsal in their position,
and more similar to a rudimental spinal chord of which the two la-
teral columns have retained their primitive embryonic separation.
The ganglions {n, n) are connected by a transverse commissural nerve
in Loligo*

The two large visceral nerves {p) arise from the interspace of the
origin of the pallial pair; after distributing filaments to the muscles of
the neck they descend parallel and close to one another behind the
vena cava, give off the small filaments which constitute the plexus
upon that vein and around the oesophagus, then diverge from each
other towards the root of each gill, where they divide into three prin-
cipal branches: one of these dilates into an elongated ganglion {q)
and penetrates the fleshy stem of the branchia ; the second descends
to the generative organs ; the third passes to the middle or systemic
heart. The oesophageal plexus unites into a ganglion (r), attached
to the parietes of the gizzard in the interspace between the pyloric
and cardiac orifices. Some filaments connect the ganglion with the
(esophageal nerve sent off from the buccal ganglion {s).\

With respect to the parts of the brain in the Vortebrata, which are
represented by the cephalic nervous masses in the Dibranchiate
Cephalopods, we may regard the cordiform superior mass (a), which
is principally in communication and coexists with the large and
complex eyes, as the homologue of the optic lobes ; it cannot be the
cerebellum, as Cuvier supposed, for that body never gives origin to
any nerve ; the cerebellum is also less constant than the optic lobes
of the Vertebrate brain, and is posterior to them in both position and
order of development. The smaller super-cesophageal mass, anterior
to the optic lobes in the Octopus and some other ceplialopods, may
represent an olfactory lobe, or the rudiment of a true cerebrum. I

* XXIV. & CCLXXVIII. p. 9, pi. 1. i. t Ih. p. 10.

618 LECTURE XXIV.

have already indicated the parts which seem to represent the crura
of the cerebrum ; they unite with that large sub-oesophageal nervous
mass, which, since it gives origin to the brachial nerves or the
homologue of the fifth pair, to the acoustic and respiratory nerves,
and to those two large moto-sensory columns which resemble in
their structure, position, and distribution, the spinal chord of the
Vertebrata, must be regarded as the representative of the medulla
oblono-ata : it is obviously the part of the nervous centre which is
most intimately connected with the vitality of the animal, and which
is therefore here, as in the higher animals, the deepest seated and
best protected part of the nervous system.

The disposition of this system determines the surfaces of the body
of the Cephalopod which correspond with those of the fish. The
nervous centre («, Jig. 223.), in which, from its comparative in-
dependence of, or indirect connection with, nerves, sensations are
most probably raised into ideas, denotes the dorsal aspect, to which,
as in the Vertebrata, the term " neural " would not be inapplicable,
regard being had to the value of the brain-mass marking the aspect,
and to the corresponding position of the chief nerve-trunks of the
body. Thus, in the Argonaut {Jig. 220.), b, e, a mark the dorsal
aspect, i the ventral one, d the anterior part, and c the posterior
part. The homology of the cerebrum («, Jig. 223.), with the
reduced super-oesophageal mass («, Jig. 215.), determines unequi-
vocally the true dorsal or neural aspect in that and all inferior forms
of mollusk. But the inconstancy of the position of the heart and
chief vascular developments for breathing, renders the terms " neural "
and " licemal," as now accepted for the Yertebrata, too arbitrary or
contradictory for the JMollusca.

The integument is remarkable in several of the naked Cephalopods
for its irregular surface, which seems designed to increase its natural
sensibility : in some, it is provided with flattened crenate processes ;
in others it is beset with branched papilliB ; in a third with simple
obtuse papillae ; in a fourth with pointed tubercles ; all which pro-
jections may serve to warn the animal of the nature of the surfaces
with which it may come into contact. The margins of the acetabula
and the attenuated flexile extremities of the arms which support
them doubtless possess a delicate sense of touch. The fringed
circular lip presents another example of the dermal covering modified
to be the seat of this sensation.

The tongue is as highly developed for the exercise of the sense of
taste in the Dibranchiate Cephalopods as in the Nautilus. In
Onijchoteuthis {Jig. 225.), the fleshy part of the tongue is " produced

CEPHALOPODA. 619

into three caruncles (^, f^ g), very soft in texture, and beset with
numerous papillje."*

Siebold and Kollikerf describe the olfactory organs of the Dibran-
chiates as situated in the neighbourhood of the eyes, and consisting
each of a cavity with tumid borders, or of a cutaneous fossa which
has an opening and, sometimes, at the bottom, a whitish papilla.
The nerves of this organ arise from the optic ganglion. They are
at first closely united with the optic nerves, enter the orbit with
them, and extend along its posterior wall to the olfactory papillce, to
which they are distributed in a radiated manner.^ The sense of
smell has been attributed to the Cephalopods by all naturalists who
have observed their habits from Aristotle to Cuvier. It appears that
the ancient Greek fishermen were in the habit of attaching strong-
scented herbs to their baits to deter the cuttle-fishes from coming to
devour them.

The organ of hearing consists of two vestibular cavities, excavated
in the thick and dense under part of the cartilaginous cranium wdiich
supports the sub-a3sophageal ganglions. § In Sepia and Loligo several
obtuse elastic processes project from the inner surface of the cavity,
which contains a delicate sacculus and otolite. A slender canal,
lined by a ciliated epithelium, forms part of the vestibule in the
embryos of Sepia ^ni!i Loligo. \ The acoustic nerve is -spread over
the sacculus, and is impressed by the movements of the otolites,
which respond to the sonorous vibrations that may be strong enough
to afi^ect the body generally. The sinuosities in the intervals of the
vestibular processes seem to be the first rudiments of those which in
Vertebrata are extended in the form of canals and spiral chambers,
within the substance of the dense nidus of the labyrinth. In the
Octopus the vestibules are nearly spherical with a smooth internal
surface ; the otolite is hemispherical ; in the Eledone it is shaped
like the shell of a limpet, with the apex rounded and curved back-
ward, and appears not be calcified : in other Cephalopods the otolites
contain carbonate of lime.

The orbit in the cuttle-fish is formed posteriorly by a thick car-
tilaginous cup {jig. 224, a a\ and is completed anteriorly by a dense
white fibrous dermal membrane {b), which becomes transparent at
the anterior part of the globe, and forms the cornea (c). The cornea
and the fibrous tunic are lined by a thin serous membrane, which is
reflected over the anterior part of the sclerotica {d), passes through its
anterior aperture (to which the cornea does not adhere), like the

* CCCCIV. p. 532., fig. 218. t XXIV. p. 381. % CCCXCI.

§ CCCLXXIX. p. 380. II CCCXCI. p. 105.

620

LECTURE XXIV.

224

Sepia officinalis.

membrane of tlie aqueous humour, and is finally continued into the
groove of the crystalline lens (j^).

The space between the eye-
ball and its capsule, thus cir-
cumscribed, is filled with an
aqueous humour, by which
the cornea is separated from
the eyeball, and kept tense.
The outer tunic of the proper 6
eyeball is a fibrous mem-
brane (d) covered by the ^
aponeurotic expansion of the
muscles of the eye, and with
an anterior aperture which is
closed by the crystalline lens.
Within the fibrous tunic there
is a thin cartilaginous coat (e)
perforated posteriorly by the
numerous fibrils from the optic ganglion (gg). The layer of fibrous
membrane (m) is continued from the anterior margin along with the
outer fibrous layer {i) to form the pupillary aperture {n), which is en-
croached upon by a bilobed process analogous to the curtain, which de-
pends from the iris of the ray. The cartilaginous sclerotic is lined by a
thick expansion of the nervous fibres given off* from the optic gan-
glion. These fibres are sent off" from the outer surface of the ganglion,
which presents a pulpy texture in its centre. They are grouped
into flattened bundles, which decussate each other before perforating
the cartilaginous sclerotica, and, after expanding into the retina (o o),
extend towards the groove of the crystalline lens, and, being joined
by a thin membrane from the anterior margin of the cartilaginous
sclerotic, it forms a ciliary plicated zone {p p), which penetrates the
groove of the crystalline lens.

The inner surface of the retina is covered by a layer of dark pig-
ment {q), which is penetrated by the papillae of the retina. The
vitreous humour has a distinct and strong hyaloid coat. The crys-
talline lens is of large size, and consists of two distinct parts ; the
anterior or smaller moiety being the segment of a larger sphere, and
the posterior that of a smaller sphere : they are separated by delicate
transparent membranes continued from the ciliary body. The lens
presents the same denticulated fibrous structure arranged in con-
centric laminas, as in the higher animals.

The large optic ganglion {f) is imbedded in a white lobular sub-
stance (/i), which defends it from the pressure of the muscles of the

CEPHALOPODA.

621

eye-ball. These consist of three straiglit muscles and one oblique,
wliich take their origin from the orbital cartilages, and expand upon
the sclerotic tunic of the eye-ball. The cornea of the cuttle-fish is
perforated by a minute hole near the inner or anterior margin. In
the Octopus the corresponding aperture is somewhat larger, and
situate more in the axis of vision. In the Calaraaries the corneal
aperture is still larger, of a vertically oblong form, and the capsule of
the crystalline lens, which projects through the sclerotic aperture, is
immediately exposed to the sea water.

The Dibranchiate Cephalopods are, without exception, predatory
and carnivorous animals. We have seen that they are endowed with
formidable organs for seizing and overcoming the struggles of a living-
prey, and their strong sharp hooked jaws are well adapted for de-
stroying and lacerating them when caught. The jaws {fig. 225, «, h ;
fig. 227, ^, /) are sheathed upon a firm fleshy substance (c), the fibres

225

Onyclioteathis.

of which are so attached to the base of the mandibles as to open
them ; their closure is effected by fasciculi of muscular fibres which
surround them externally.

The tongue is partially covered with a liorny plate (/), beset with

622

LECTURE XXIV.

recurved spines, which must assist in the further comminution and
deglutition of the food. The fauces are also provided with spinige-
rous folds {h, h) of membrane. In some of the Calamaries, in which
the suj^erior salivary glands (i) penetrate the folds, the ducts open
upon the inner surface, as in the Nautilus. In the Octopus the an-
terior or upper salivary glands are on the outside of the buccal mass.
In most of the Dibranchiates, including the Spirula, a second and
laro-er pair of salivary glands is situated on each side of the oeso-
phagus, at the commencement of the abdominal or hepatic cavity;
their ducts unite to terminate below the tongue in the concavity of
the lower mandible.

The peritoneal membrane is divided and disposed as in the Nau-
tilus, in order to form special receptacles for the different viscera.
The oesophagus, in all the Dibranchiates, is narrower than in the
Nautilus ; its inner surface is disposed in longitudinal plicae : in both
the Octopus and Argonaut it dilates, 226

soon after having passed through
the cranium, into a long ingluvies,
forming a large cul-de-sac at its
commencement; but in the Deca-
pods {fig. 226, a) it continues nar-
row and of uniform breadth to the
stomach. This cavity (c) is an
elongated sac, presenting, in the
dispositton of its muscular fibres, in
the proximity of the cardiac (d) and
pyloric (e) orifices, and in the thick-
ness of the epithelial lining, the usual
characters of the gizzard. The in-
testine, at a short distance from Ul
the pylorus (e), communicates with
a glandular and laminated sac (g),
analogous to that in Nautilus, and
presenting a similar globular form
in Rossia and Loligopsis ; it is
elongated in LoUgo vulgaris, and
spirally convoluted in Sepia and
Loligo sagittata (f). It receives
the biliary secretion between two
broad lamella, as in Nautilus. The
intestine is very short in all the
Dibranchiates. In Octopus it is
bent upon itself {fig. 227. r), as in ^"^'^'^ ^^^^"^^"

CEPHALOPODA.

623

227

Nautilus ; but in Sepia and Loligo {fig. 226, i) it is continued for-
wards in a straight line, from the stomach to the vent. Its internal
membrane is longitudinally folded, but is smooth at the short tract
beyond the entry of the duct of the ink-bag (Jt) ; its termination is
constricted eitlier by the muscular fibres of the branchial septum, or
by those which connect together the pillars of the funnel. In most
Decapods provided with fins for swimming forwards, the anus can
be closed by rhomboidal {Sepia) or triangular fleshy valves {Sepio-
teuthis) : in LoUgopsis these are modified into the form of antennal
filaments. There is no ciliated epithelium in the intestinal canal of
the Cephalopods. '

The liver {fig. 227, x) is of large size in the Dibranchiates, but of
more simple form than in Nautilus. It is usually of a reddish yellow
colour. In Sepia it is divided
into two lateral lobes, which are
notched at the upper extremity; in
Onyclioteuthis it is a simple, elon-
gated, compressed lobe with un-
divided extremities : in Octopus it
forms a single oval mass, flattened
anteriorly: in Eledone it is spherical,
corresponding with the ventricose
visceral sac. In the two latter
genera the ink-bag (d) is enclosed
within the capsule of the liv^er, and
was mistaken for the gall-bladder
by some of the early anatomists of
these MoUusks ; but in the Argo-
naut and the Decapods it manifests
its distinct function by its sepa-
rate position. The liver is sur-
rounded by a smooth capsule, and
into lobules, as in the Nautilus and lower MoUusca. The biliary
ducts in the Octopods are simple canals which unite and terminate
by a common orifice in the pancreatic sac. In the Decapods they
receive the ducts of numerous clusters of caecal appendages beyond
the smooth part of the liver, which may perform a function analogous
to the pancreas.*

The ink-bag consists of tough white fibrous texture, the outer sur-
face of which is coated by a thin silvery or nacreous layer ; its inner
surface presents a fine spongy glandular texture. It is usually of an

Octopus.

is not subdivided externally

* Prep. No. 775. X., vol. i. p. 229., & CCCLXXX. pi. 41, L.

624

LECTURE XXIV.

oblong pyriform shape, as in Octopus {fig. 227, d), Sepia, and Loligo
{fig. 226, /) ; but it presents at certain seasons a trilobate form in
the Sepiola, in -which Peters * has observed it to contract regularly.
It is a very active organ, and its inky secretion can be reproduced
with great activity. The tint of the secretion varies in different
species, as is exemplified, in its inspissated state, by the Italian pig-
ment called " sepia," and the Chinese one, called " Indian ink." It is
also very durable, as is shown by its frequent preservation in a fossil
state in both the extinct Calamaries and the Belemnites. It is affirmed
by some chemists to contain a peculiar animal principle, which Vizio
has termed "melanine."

Many of the Cephalopods possess the power of emitting a luminous
secretion. | All of them are nocturnal and social animals, and are
readily attracted by bright metallic substances.

Prior to the dissection of the Pearly Nautilus, the Cephalopods
were regarded as having three distinct hearts ; but two of these, which
are appropriated to the branchial circulation, are peculiar to the higher
order, and are perhaps
the main-spring of their
superior muscular ener-
gies.

In the Dibranchiates
the venous blood returns
from each arm along its
lateral and posterior parts
by two veins, which
severally unite at the
base of the arm with the
opposite vein of the ad-
joining arm, the whole
being ultimately con-
veyed to an irregular
circular sinus, which sur-
rounds the pharynx, and
is continued between the
anterior cava {fig. 228, a).
two semilunar valves at its commencement ; in Sepia witli a single
valve. At its entrance into the pericardium it usually receives two
lari^e visceral veins, returning the blood from some large irregular

Sepia officinalis.

head and the funnel into the great
In Octopus this vessel is provided with

* XXIV. p. 329.

f Linnffius quotes a passage from Bartholinus, illustrative of the luminous
surface of a species of Octopus which shone so hrightly, "ut totum palatium
ardere videretur." This phosphorescence might be post-mortem, and the result of
commencing decomposition.

CEPHALOPODA. 625

abdominal sinuses, and it divides into two branches {g, g), con-
tinued downwards and outwards to the branchial hearts at the base
of each lateral gill : previously to communicating with these it
dilates into a sinus, which receives the venous blood from the
sides of the mantle. The two divisions of the vena cava, and also
the visceral veins (b, b), after having entered the pericardium,
are furnished with clusters of glandular follicles, which open
into these veins by conspicuous foramina. The follicles vary
in form in diflferent genera; in Eledone they are elongated and
pyriform : in Argonauta and Octopus they are shorter, and arranged
in distinct clusters : in Loligo they are represented by a spongy
thickening of the tunics of the veins : in Sepia the secerning ap-
pendages are more elongated, but are very numerous, close-set, and
of an irregular form, giving a floccular character both to the great
divisions of the vena cava and to those parts of the visceral veins
which are contained in the pericardial or great venous cavity. The
special compartments, into which these glandular appendages to the
veins are lodged, communicate with the respiratory cavity by two
papillary orifices, situated near the base of the gills. Cuvier had
suggested that these appendages might serve to eliminate some prin-
ciple from the blood : and, as the kidneys derive their peculiar excre-
tion from venous blood in the lower Vertebrata, Mayer's supposition*
that the venous follicles of the Cephalopods were analogous organs,
was not an improbable one : it has since been confirmed by the dis-
covery in them of purpurate of ammonia, f They may serve in a
secondary degree as temporary reservoirs of the venous blood when
it is impeded in its course through the gills ', and, as the venous fol-
licles are endowed with a peristaltic motion, they may regulate the
quantity of blood transmitted to the gills.

The accessory hearts {fig. 228, h, h) are situated one at the base
of each gill. The regurgitation of the blood into the glandular veins
is provided against by the interposition of the two semilunar valves
at the entry of the ventricle, where it receives the blood from the
great vein. In the Decapods and in the Argonaut, each branchial
ventricle has a fleshy appendage {x) attached to its lowest surface.
Cuvier correctly observes that the ventricle itself is more cellular
than fleshy % : but its direct connection with the branchial inferent
vessel, and its valvular structure, incline me to regard it as more
properly belonging to the circulatory than the aquiferous system.

A single branchial vein which dilates into a small sinus (fig. 228, I)

* Analekten fur Vergleichenden Anatomie, 4to. 1835.
t XXIV. p. 400. X CCCXXI. p. 20. pL ii. fig. 3, 12.

S S

626 LECTURE XXTV.

returns the blood to a single median systemic heart, which is rounded
in the Octopods, lozenge-shaped in the Calamaries, and fusiform, but
bent upon itself, in the Sepia (ni) Sepioteuthis, and Sepiola. It
sends off two aortae, as in the Nautilus, the larger or posterior one
(r) being provided with a muscular bulb, and with two semicircular
valves at its origin. The distribution of the large aorta very closely
resembles that of the Nautilus. The vascular ring which encircles
the oesophagus typifies the branchial arches in the Vertebrate animal ;
but it supplies the head and all its complex radiating appendages.
Dilatations of the branchial arteries, like accessory hearts, have been
observed * in the substance of the arms of the great Calamary {Loligo
sagittata). Hugh Miller, in a vivisection of this species, saw " the
yellow tubular heart propelling into transparent tubular arteries
yellow blood," and he noticed lying detached from it " the two deeper-
coloured hearts." f The small aorta supplies the stomach, intestine,
branchiae, and genital organs.

The branchiae {fig. 227, t.fig. 228, i) are two in number, as the
name of the order indicates. They are concealed, as in the Nau-
tilus, by the mantle, /, which extends in front of the viscera to
form the branchial chamber : the muscular tube called the funnel
{fig. 227, i) projects from its outlet. The rectum opens into
the branchial chamber at the base of the funnel, manifesting the
same relation of the breathing organs to the termination of the
alimentary canal, which characterises the Mollusca generally. Each
gill consists, as in the Nautilus, of a number of triangular vascular
laminae, extending transversely from either side of the fleshy glandular
stem, and decreasing in size to the extremity of the gill : each plate
is composed of smaller transverse laminae, which are themselves simi-
larly subdivided, the entire gill presenting the tripinnate structure,
which affords an extensive, though close-packed, surface for the
minute subdivision of the blood-vessels. In Loligopsis each gill has
twenty-four pairs of plates : in Sepia, thirty-six pairs ; in Loligo
sagittata, sixty pairs. The stem of the gill is not only attached by
its base, but by a thin fibrous membrane through nearly its whole
length to the mantle ; the branchial artery extends along the attached
border or stem, the branchial vein along the free border : the circu-
lation through the artery is accelerated by the contraction of the
surrounding fibres of the stem.

The mechanical part of the respiratory act is performed by the
muscular actions of the mantle and funnel, the gills not being pro-
vided with vibratile cilia, as in many of the inferior Mollusks. The

* CCCCVI. t CCCXCIV. p. 447.

CEPHALOPODA. 627

water is admitted into the branchial cavity at the anterior aperture
of the mantle, outside the base of the funnel. Two large valvular
folds of fibrous membrane, which are concave towards the respiratory
cavity, prevent the currents from escaping by this entry : they are,
therefore, propelled by the whole force of the contraction of the
muscular mantle through the cavity of the funnel, the base of which
is articulated, in most of the Cephalopods, by lateral joints, with the
sides of the anterior aperture of the mantle.

Although the apertures which I first pointed out in the Nautilus,
near the base of the gills, are situated on prominences, which seem
intended rather to let excretions out than fluids in, they are regarded
by Siebold as being, together with some analogous apertures in the
Dibranchiates, parts of an '•' aquiferous system." This system is
described by that usually accurate and sound-judging anatomist* as
" occupying the entire trunk of the Cephalopods, and terminating by
two orifices, between which lies the duct of the ink-bag, and which
are often situated on a small tubular eminence of the peritoneum.
Each of these orifices leads to a spacious thin-walled cavity, near the
pericardium. It contains the two venas cavae, with their appendages,
and communicates by orifices and canals with other aquiferous cavities
surrounding the various viscera, as e. g. the stomach and csecum,
and the two so-called branchial hearts. There is another system of
aquiferous canals under the skin of the head and neck. It consists
of several large reservoirs, which extend somewhat deeply between
the organs of this portion of the body. These reservoirs commu-
nicate externally by orifices situated upon different points of the
head." The peritoneal and pericardial orifices in some cartilaginous
fishes, and the peritoneal orifices in the crocodile, are the last homo-
logous traces of the aquiferous system of the marine invertebrates :
but the valvular structure of the orifices is opposed to the idea of
their performing a similar function, viz., admitting water into the
peritoneal and pericardial cavities. And further research is needed
to determine what actually goes in or out of the openings between
the branchial and peritoneal cavities in the Cephalopods.

The Cephalopods are dioecious : the males are fewer, and generally
smaller, than the females ; and some species have more definite out-
ward sexual characters.

In a male Nautilus pompilius, V. der Hoeven f found, beneath and
external to the internal labial processes, a fold from which a dis-
memberment of the right external labial process, consisting of the
confiuent sheaths of four tentacles, projected. On the left side, in

* XXIV. p. 398. t CCCXC.

SS 2

628 LECTURE XXIV.

the place of the external labial process, there was a conoid process
2^ inches long, also formed of four tentacular sheaths, one of which
was shorter and terminated freely, the other three remained confluent
to the end of the process : it occupied much of the space included by
the external circle of tentacular sheaths.

The male Argonaut has an analogous modification of the tentacular
system, indicative of its sex. Not any of the cephalic arms are sail-
shaped, but one of them is longer and much thicker than the rest,
and its double series of suckers are longer and more numerous.* In
the female Argonaut (Jig. 220.), two of the arms develope the broad
and thin membranes, which form, repair, and usually overlap the
delicate nidamental shell t, which is peculiar to this sex. J In the
Calamary {Loligo vulgaris)^ the gladius of the male is one-fourth
shorter, but is broader than that of the female. The sepium of the
Cuttle ( Sepia) shows a similar, but not so much sexual, difference in
its proportions. In the pibranchiates the male organs consist of a
testis, a vas deferens, a vesicula seminalis, a prostate, the sac of the
spermatophora, and the penis.

The testis is situated in a particular compartment of the perito-
neum at the bottom of the visceral cavity ; that membrane being
reflected over it, from one point, to form its serous capsule : it is
simple, roundish or oblong, and consists of a fibro-membranous pouch
(fig. 229, a a\ to one part of the inner surface of which are attached
a number of slender branched tubuli (5), diverging, dichotomising,
and terminating in blind extremities: the tubuli swell at the breeding
season, burst, and discharge an opaque white fluid, crowded with
spermatozoa, into the cavity of the sac, whence it escapes by a con-
tracted orifice (c) into the slender and convoluted vas deferens (c?),
where the fluid is moulded, by the addition of a mucous secretion,
into a cylindrical coherent mass. In this state it is transmitted to a
wider glandular canal (e), having fibrous parietes and a cellular cavity
in Octopus, and being encroached upon, in Sepia, by a plicated produc-
tion of the lining membrane : this division of the efferent part of the
male apparatus answers to the glandular part of the oviduct in the
female : here the spermatozoa are enclosed in filamentary sheaths of
albuminous matter, of a definite form, according to the species of
Cephalopod. The anterior extremity of this contractile vesicula
communicates, in Octopus, with a wide, bent, csecal tube (prostate,/),
with thick glandular parietes, and having the form of a simple pouch
in Sepia, from which a short and wide duct leads to a longer and
larger pyriform pouch, " Bursa Needhamii," or spermatophorous sac

* CCCCIX. and CCCCX. f CCrOVIIT. % COCXCVlII.

CEPHALOPODA.

629

{g\ with thinner walls, containing the spermatophores, or moving
filaments of Needham* and from which pouch the short muscular

penis Ck) is continued. Tlie

229

prostate, in Sepiola, com-
municates by a long and
slender duct with the vesi-
cula seminalis. The moving
filaments {li) in the terminal
pouch are capsules of sper-
matozoa and sperm -fluid,
with a singular associated
mechanism. They form one
of the most remarkable pecu-
liarities of the Cephalopoda,
and have been regarded as
parasitic worms, under the
names of Echinorhynchus^
Scolex dibothrms, Need-
hamia expidsatoriay &c, ; but
were rightly recognised as
sperm-holders by Swam-
merdam.f

In Octopus {fig. 229, K)
they are from six to eight
lines in length, slightly en-
larged at one extremity.
Their outer tunic or capsule
is elastic and transparent : this contains an elongated sac, occupying
the larger extremity of the sheath, and filled with the minute clavate
spermatozoa. This sperm-sac communicates by a short narrow canal
or isthmus, with a second narrower, elongated sheath, inclosing a
highly-elastic piston, from which a spiral filament is continued to the
small extremity of the outer sheath. In the Cuttle-fish, the isthmus
connecting the sperm-sac with the ejaculatory sac is longer, and the
coils of the spiral membrane are closer and more numerous. The
spermatophores of the Calamary are remarkable for the superior size
and length of the internal sac containing the spermatozoa. Under
every modification, the analogy of the apparatus which forms the
receptacle of the essential particles of the fertilising fluid, with the
nidamental sacs containing the ova in the opposite sex, is very
obvious. The spermatophores in the bursa are regularly arranged

Male organs, Octopus.

* CCCLXXVIII.

t CCXXXIII.

s s 3

630 LECTURE XXIV.

in superimposed longitudinal layers: their anterior ends directed
forwards, their opposite ends often bound together by interlaced
filaments. The movements of the spermatophores, when liberated
from the sac, are truly remarkable : the smaller extremity of the
outer capsule, to which the spiral spring is attached, protrudes by a
kind of inversion, and the inner spermatic sac is drawn forwards;
the action is repeated until the ejaculatory sac is extended from the
sheath, when there is a slight cessation of movement. It then re-
commences ; the sperm-sac is compressed and protruded farther ; the
isthmus gives way, and the spermatozoa are violently expelled, both
outwards and into the cavity of the external sheath. The efficient
cause of the movements appears to be a combination of the contrac-
tility of the external sheath and sperm receptacle, with the elasticity
of the spiral membrane, and the very rapid endosmosis through the
highly hygroscopic capsule. The final intention of the superaddition
of protecting sheaths for the semen, like those for the ova, appears to
relate to the safe conveyance of the spermatozoa to the ova of the
female, there being apparently no true intromission in the Cephalo-
pods ; the peculiar mechanism of the sperm-receptacles insures their
rupture and the dispersion of their contents after their brief transit
through the sea-water. The spermatozoa in the Octopods have a
small button-shaped head: those of the Decapods have a longer
cylindrical head, and a very long and slender tail.

The spermatozoa in the receptacle of the modified cephalic arm
{Hectocotylus) of the male Argonaut present the same form as in the
Eledone.

The cumulative experience of numerous observers, since 1839, had
led to the conviction that the Argonauta, with the expanded arms
and shell, was the female form of the species.*

The discovery of the male has been attended with such difficulties
as we have seen to beset the like problem in some of the lower
invertebrata.

Delia Chiaje first (1828)t figured and described an organism
which he found attached to the female Argonaut, and which he
believed to be a parasite, describing it under the name of Trichoce-

* CCCXCVIII. " He had dissected every specimen of Argonaut in the present
collection, in which the absence of ova in the shell left the sex doubtful, and they
all proved to be females : this fact rendered it allowable to conjecture that the cal-
cifying brachial membranes, and consequently the shell, might be sexual characters
and peculiar to the female." " Should it be hereafter proved that the male Argo-
naut possessed neither a shell nor the organs for secreting it, this fact would not
render the hypothesis of the parasitism of the female, which does possess the calci-

fying membranes, at all the less tenable." p. 39.
t CCCLXXIII. vol. ii. p. 225. taf. 16. fig. 4.

CEPHALOPODA. 631

phalus acetabularis, on account of the number of suckers with which
it was beset. In the following year, Cuvier, having received a similar
organism which Laurillard had detected in a Cephalopod called Octo-
pus granulosus, also believed it to be a parasitic worm, for which he
proposed the name oi Hectocotylus Octopodis*, assigning the name
of Hectocotylus AigonautcB to the previously-observed species.

In 1842 Kollikerf, having detected the same organism, apparently
parasitic on the female Argonaut, carefully scrutinised its structure,
found that of the skin, with its complex pigment cells, and that of
the acetabula, identical with the same parts in the Argonaut : he de-
tected, moreover, in a dilated hollow part of the organism, a quantity
of spermatozoa, having the characteristic form of those of the Octopod
Eledone, and came to the bold conclusion that it was the long-sought-
for male of the Argonaut, arrested in its development, and subsisting
parasitically on the female, like the diminutive males of the Rotifera,
Epizoa, and Cirripedia. It may serve as a wholesome warning
against entering upon a scrutiny of parts whilst prepossessed by
a foregone conclusion, to remember that the acute and usually
accurate observer describes and figures the digestive, circulating and
respiratory organs of the same supposed independent individual
male animal.

Verany % first had the good fortune to discover the Hectocotylus,
or presumed parasitic male Argonaut, forming one of the arms, sin-
gularly modified and developed, of a little Octopod, which he figured
under the name of Octopus Carence. Miiller §, Ruppell, and others
were not slow in demonstrating that this, or a similarly modified
Octopod, was really the male of the Argonauta.

As in the spiders, which some Cephalopods so singularly resemble
in outward form, certain species of the Octopod family have the male
apparatus extended into one of the cephalic arms. In the Araneidis
the spermatic reservoir of the palp is quite isolated from the testis of
the abdomen : in the Octopus granulosus and Argonauta argo the
spermatic duct is continued from the testis, which occupies the usual
position in the abdomen, into the base of the sexual arm, and opens
into a dilated reservoir at the termination of that singularly modified
member. It is somewhat longer than the longest of the ordinary or
unmodified arms, and is much thicker. The acetabula are larger
and more numerous, but retain the arrangement in a double row.
The structure of these suckers, and of the skin, resembles that of the
homologous parts in the female Cephalopod, as KoUiker most acutely

* CCLXXVr. vol. xviii. pi. 11. t CCLXXVII.

t CCLXXV. § CCLXXIV.

s s 4

632 LECTURE XXIV.

made out : the other modifications of the arm relate exclusively to
the impregnating function assigned to it-
One presumes that, in the coitus, the arms of the two sexes being
mutually interlaced, as described by Aristotle, the expanded recepta-
cular end of the modified arm, with the spermatozoa, is introduced
into the funnel of the female : but with whatever part of her surface
the masculine arm comes into contact, it adheres thereto forcibly by
means of the double close-set row of large suckers. In the violent act
of termination of the embrace, whether through alarm or other cause,
the modified arm is snapped off" and left adhering to the female by the
suckers, where it long retains the power of motion. Such is the con-
clusion of the long-mooted questions of the Argonaut, its shell, the
jse of the brachial membranes or " sails," and the true sexual dis-
tinctions of the male and female.

The female organs consist in the Dibranchiate Cephalopods, as in
the Nautilus, of an ovarium, oviduct, and, usually, nidamental glands,
but with several modifications in the efferent part of the apparatus.
The ovary is always single, of a round or oblong form, longest and
narrowest in Loligo sagittata ; it is a sac with a serous and a firm
fibrous tunic : the ovisacs {Jig. 230, a, a), formed of a thin membrane
derived from the general sac, are usually of an elliptical form and
seem reticulate by the characteristic folding of the vitelline tunic of
the ovum appearing through the transparent membrane : they are
attached to one part of the ovarian cavity, as in the Nautilus. The
ova and ovisacs are proportionally larger in the Decapods than the
Octopods ; are largest in Sepiola, smallest in Argonauta. In the
Octopods there is a communication between the ovarian sac and
the aquiferous pericardial cavities which open into the branchial
chamber.

In Sepia, Sepiola, Rossia, and Loligo vxdgaris, there is a single
oviduct, with a glandular laminated outlet ; and there are two distinct
laminated nidamental glands on each side of its termination. In the
Octopods there are two oviducts, which in Argonauta and Trem-
octopus are simple ; but in Octopus and Eledone are each provided
with a special glandular enlargement about the middle of their
course : there are no detached nidamental glands. In Loligo sagit-
tata and Onychoteuthis there are two distinct convoluted oviducts,
and two separate nidamental glands. These glands in the Cuttle-
fish rest upon a soft parenchymatous body, of a bright orange colour :
the corresponding part is rose-coloured in Sepiola : it is double in
Rossia {Jig. 230, i, i), and the Calamaries : these bodies have no
ducts, and appear to be the homologues of the suprarenal bodies in
the vertebrate animals.

CEPHALOPODA.

633

2*^0

The subjoined illustration (y?^. 230) of the female organs in the
Cephalopoda is taken from the Rossia* The ovarian cavity is laid

open, showing the ovisacs
{a, a), which are fewer in
number, but relatively double
the size of those in Sepia ; one
{b) is in the act of shedding
the ovum (/) ; others {c, c),
having discharged their ovum,
were collapsed and in progress
of absorption. The oviduct

(d) commences by a round
aperture, and continues mem-
branous to the terminal gland

(e) allowing the ova (/,/) to
be seen through it. The gland
(e) consists of two semioval
groups of transverse glandular
lamellae. The oviduct termi-
nates, as in Sepia and Sepiola,
on the left side, behind the
orifices of the nidamental
glands (^, g). These bodies
are situated on the ventral
aspect of the abdomen, but are

attached, like their homologues in Nautilus and the Gastropods, to the
mantle. They are each composed of a double series of transverse,
parallel, close-set lamince, the straight margins of which are free and
turned towards each other, along the middle line of the gland. When
this is laid open, an impacted layer of soft albuminous substance is
found occupying the interspace of the two sets of laminae ; in which,
in Rossia, it is moulded into a filamentary form, whence it escapes by
the anterior orifice, as at hJi.Jig. 230. Each supplementary body,
2, i, is indented by a deep groove close to the aperture of the nida-
mental gland : it may assist in moulding the secretion, and applying
it to the ova as they pass out. The female organs of Spirula are
like those of Rossia; but I found the ova in the oviduct packed so as
to lie, three or four, in the same transverse line. In the Argonauta
the oviducts form several convolutions before they ascend to their
termination in the branchial chamber, where, as in Octopus, the
vulvae are wide apart : their lining membrane has an uniform thick

Rossia palpebrosa.

CCLXXL, and Prep. No. 2962 A.

634 LECTURE XXIV.

glandular character. In the Loligo sagittata the oviducts commence
about one-third of the length of the ovary from its anterior end ; and
after a short course are disposed in sixteen close, transverse folds,
after which they are continued straight to their terminal glandular
division.

With respect to the act of impregnation in the Cephalopods, Ari-
stotle, whose knowledge both zoological and zootomical of this class
was great, gives two accounts.* In the fifth book of the " Historia
Animalium," he states that the Octopus, Sepia and Loligo copulate
in the same manner; the male and female having their heads turned
towards each other, and their cephalic arms being so co-adapted as
to adhere by the mutual apposition of their suckers. In this act the
Poulps {Octopus) are said to seek the bottom, while the Cuttles and
Calamaries swim near the surface, the individual of one sex moving
forwards and the other backwards. It would seem, also, that the
modified arm of the male in certain Octopods had not escaped
notice, for he adds (eh. v. 1.), " Aiunt nonnulli marem habere non
nihil simile genitali in uno ex brachiis, quod duo maxima acetabula
continent : id protendi quasi nervosum usque in medium brachium
atque totum in infundibulum feeminse inseri."

From the position of the vulva or vulvas at or near the base of the
funnel, and from the inclination of the penis in the Cuttle to the
side corresponding to that where, in the female, the vulva opens, it
is most probable that the sexes do combine as above described ; but
actual intromission by the vulva seems physically impossible in the
Cephalopods. The males may, and probably do, introduce the sper-
matophores into the pallial cavity of the female : they have, in fact,
been seen attached to the internal surface of this cavity, near the
vulva. The male Argonaut leaves the modified spermatophorous
arm attached by its suckers to the interior of the funnel or branchial
chamber, whence arose the natural mistake as to its being a parasitic
worm. The spermatozoa, expelled from the spermatophora while in
the branchial chamber, may be conveyed either by the oviduct, or more
directly by the aquiferous canals, to the ovarium : and it is certain
that impregnation takes place before the ovum has passed into the
oviduct and has acquired its nidamental covering.

The ovarian ova consist of a deep yellow or rose-coloured vitellus,
enclosed in a delicate vitelline membrane, which is folded longitudi-
nally in the Octopods, and both lengthwise and transversely in the
Decapods, the folds penetrating the vitellus, and giving the ova a
reticulate exterior. After dehiscence, and when received in the

* CCCLXXVII. lib. iv. and v.

CEPHALOPODA.

635

231

membranous part of the oviduct, the vitellus expands, the folds dis-
appear, and the surface of the egg is smooth. There they acquire
the chorion and receive additional layers of a thick albuminous matter
from the gland of the oviduct, which may be compared to the shell-
secreting cavity in the oviduct of the fowl. The ova are connected
together in characteristic clusters by the secretion of the superadded
nidamental glands when these are present.

In the Argonaut the minute ova are appended by long filamentary

stalks to the cavity of the involuted
spire of the shell where they are
hatched. In the Tremoctopus the
chaplets of eggs are bound together
in the form of a staff, by a lamel-
lated and subgranular secretion, and
are so carried, according to Kolliker,
attached to one of the arms. The
ova of the Calamary are enclosed in
long transparent gelatinous cylindrical
sheaths, and offer a close analogy to
the spermatophora in the male. The
ova of the Sepioteuthis are likewise
enclosed in cylindrical sheaths ; but
these are shorter, and contain fewer
ova, than in the Loligo. The eggs
of the Cuttle-fish are of comparatively
large size, of an oval form, attenuated
at the extremities, and each enveloped
in a lamellated horny covering, which
is prolonged into a short cleft pedicle at one extremity, and attached
by it to some foreign body : numbers of these ova are generally found
clustered together, and they have commonly received the name of
sea-grapes {Jig. 231).

Of the many noble contributions to Embryology, which science
owes to German physiologists, none surpass in importance that *
from which the following remarks have been abridged.

At the beginning of the development of the egg, in Sepia officii
nalis, the germ-vesicle with its nucleus is surrounded by a small
quantity of colourless yolk, and all the parts of the egg grow, but
the germ-vesicle in a less ratio than the yolk. When the germ-
vesicle has reached its full size the yolk increases and acquires its
characteristic colour. The srerm-vesicle advances close to the vitel-

Ova of Sepia officinalis.

* CCCXCI.

636

LECTURE XXIV.

line membrane near the narrower end of the egg ; and, when the
folds of the vitelline membrane have been obliterated in the detached
egg, the germ-vesicle has disappeared or become obscured through
the effect of impregnation. The influence of the resulting impregnated
vesicle, or primary germ-cell, extends over only a small part of the
yolk, like the cicatricula of the bird's egg. The fission of that
germ-cell manifests itself by two slightly elevated prominences, as at
Jig. 232, A, a, in each of which is a secondary nucleated cell. The next

232

stage shows four prominences ( ib. b) ; these by their fission form
eight {ib. c), of a triangular form, becoming more acute, and the
apex of each showing the hyaline nucleus : and now spontaneous fis-
sion manifests itself in another direction, and the apices of each seg-
ment seem to be detached, each fission-sphere (ib. d, a) having, like
each fission-segment (5), its proper nucleus. This figure shows
the sixteenfold division, affecting the central cells (a) as well as the
segments (5). The progressive multiplication of sperm-force-centres
multiplies the peripheral segments, and fills the central space with
smaller and more numerous derivative germ-spherules.

The germ-mass thus formed may be divided into two layers, and
the outer surface becomes smooth. Its further increase by fission-
growth and confluence of germ-cells manifests itself by slight eleva-
tions from this " cambium " {^g. 233) ; the first of these is a median
rhomboid one, which is the basis of the 233

trunk or mantle-sac (a); two small bean-
shaped prominences (b) become the eyes ; a
linear elevation (d) on each side of the
mantle indicates the lateral halves of the
funnel. At this period the germ-mass is
two lines long and subcircular. Next
appear the cartilages of the funnel (e) ;
then the rudiments of the gills (c) ; afterwards the anterior (k) and
posterior (z) cephalic lobes and the arms, the latter beginning with
the ventral pairs (1, 2) ; and now there is evidence of ciliary action at
many parts of the embryonal surface, as, e. g., on the mantle, the

CEPHALOPODA.

63:

crura of the funnel, the cephalic lobes and eyes, but not in the gills.
The two crura of the funnel elongate ; the eyes become reniform.
Two other (dorsal) pairs (3, 4) of arms appear, and now the mouth {g)
is established as a median semilunar depression with a raised border.
The mantle (which is built up from below or behind) becomes larger
and more prominent, its free border begins to be detached along its
ventral side, and the germinal membrane expands upon the yolk.
The mouth liberates its anterior border and slides from the vitelline
mass. The crura of the funnel {Jig- 234, d) approximate ; the small
gills (ib. c) begin to get under the still-growing border of the
234 mantle (a), and a small pulsating

eminence (w), between the gills
indicates the systemic heart.
The two tentacles (2) now rise
near the posterior cephalic lobes,
and, from the beginning, are
more slender than the ordinary
arms (1, 3, 4, 5). The miniature
Sepia is recognisably sketched out : but all its parts, save the gills
and funnel-lobes, are ciliary. By this ciliary action the embryo
Loligo rotates in its chorion ; but the yolk of the Sepia is too big,
and the albumen yields to the microscopic dynamic and flows over the
embryonal disc. The crura of the funnel first coalesce at their dorsal
margin : the gills, not yet quite covered by the mantle, begin to show
their subdivisions : the eyes (ib. b) receive their pigment : the arms
converge towards the centre of the cephalic lobes, but they show no
trace of suckers : the yolk (p) is now almost quite surrounded by the
germinal membrane (/). The anterior or ventral divisions of the infun-
dibular crura lay with their free, arched, thick borders overlapping,
and finally coalesce, completing the dibranchiate tubular funnel, the
apex of which now reaches nearly to the base of the arms. The
sepium, or internal shell {Jig. 235,/), the digestive canal {b\ with its
appendages, and the ink-bag (e), are formed suc-
cessively : the basis of the nervous system was
probably coeval with the appearance of the
cephalic lobes and cartilage. In the course of
the investment of the yolk, and the concomitant
growth of the embryo, the vitelline sac becomes
constricted into an external (c) and an internal
{d) portion : the constricted portion is gradually
elongated, and becomes a narrow^ canal, extend-
ing from the head by the side of the mouth.
The external yolk progressively becomes in-
ternal as the latter is absorbed, and is finally

235

Embryo Sepia.

638 LECTURE XXIV.

subdivided and disappears, whilst the intestinal canal is completed.
The last remnant of the internal yolk-sac appears to be indicated in
the Octopus by the anterior csecal prolongation of the crop. At the
later periods of development the respiratory movements are vigorously
performed by the alternate dilatation and contraction of the mantle,
and by a corresponding erection and depression of the funnel : the
ink-bag (e) is now conspicuous by the colour of its contents, which
are sufficient to blacken a considerable quantity of water, and the
little Cephalopod is thus provided with the means of concealing itself
from any enemy that might be prepared to devour it upon its emerg-
ence from the defensive covering of the ovum. At the period of ex-
clusion five of the layers of the dorsal shell (/) of the young cuttle-
fish have been formed ; but, except the nucleus, which is calcified,
they are horny and transparent. The lateral fins are not merely
developed, but are broader than in the mature animal; and the ce-
phalic arms are furnished, not only with their suckers, but with a
basal web ; so that the young Sepia is enabled to swim either for-
wards or backwards, and its eyes have acquired the requisite deve-
lopment to warn it of an approaching enemy, or direct its course to
its appropriate food.

Thus in the class at the summit of the Molluscous, as in that which
crowned the Articulate, series, there is no metamorphosis. The ce-
phalopodic character is manifested long before the parts of the em-
bryo are completed : even the dibranchiate peculiarity of the infun-
dibular cartilages is recognisable when, as yet, only the visceral sac,
the funnel, the eyes, and the gills are sketched out. No phase or
form of Invertebrate existence below the Cephalopod is even transi-
torily manifested. Before the ciliary action is visible on the germ-
mass, the parts that exhibit it bear unequivocally the cephalopodous
stamp. Whilst the funnel remains ununited along the ventral aspect,
whilst the arms are without suckers, and the prominent eyes unpro-
vided with orbits, the characters of the lower order of the Cephalo-
poda are indeed temporarily exhibited, but the gills at no period show
the tetrabranchiate condition.

"Were growth superinduced at any arrested stage of Cephalopodic
development, no known inferior form of MoUusk would result. No
arrested stage of development of any higher animal would produce
any thing like a Cephalopod.

There is so small a part of the multifarious and diversified details
of the anatomy and physiology of the Invertebrata from which the
practical Surgeon can directly profit, they seem so remotely connected
with human physiology, the animals themselves are so different in

CEPHALOPODA. 639

form, in powers, in modes of life, from those which more obviously
attract the interest of the anatomical Teacher, that some apology may
seem necessary for the devotion of an entire course of Lectures, in
the theatre of a College of Surgeons, to the lowest and most minute
forms of animal life.

We learn, indeed, with little surprise, that the import of the dissec-
tions of the Invertebrate animals, by the busy care-worn practitioner
who, in the last century, prepared the most instructive illustrations
of these lectures, were not understood ; and that these occupations of
Hunter were regarded by some of his contemporaries as a kind of
laborious trifling. But the question of " cui bono ? " which might
then be pardonable, would be inexcusable at the present day, when
the relations of Surgery as a science to Physiology, and the depend-
ence of Physiology upon Comparative Anatomy are so much better
understood : and I trust that a brief retrospect of some of the deduc-
tions from the details of Invertebrate Anatomy will suffice to de-
monstrate their indispensable value to all who are interested in the
progress of physiological science.

The Invertebrated classes include the most numerous and diversi-
fied forms of the Animal Kingdom. At the very beginning of our
inquiries into their vital powers and acts we are impressed with their
important relations to the maintenance of life and organisation on
this planet, and their influence in purifying the sea and augmenting
and enriching the land — relations of which the physiologist con-
versant only with the Vertebrated animals must have remained
ignorant. At our first entrance, and by the lowest portal, into the
vast and intricate repositories of the animal mechanisms, we are at
once introduced to the phenomena of spontaneous fission and ciliary
motion, of the generality and importance of which in the animal
economy each day seems to bring fresh proof, but which are most
conspicuously manifested in the monads.

The physiologist must have remained in ignorance of the most
instructive modifications and combinations of the principal organs of
the animal frame, if the researches of the Comparative Anatomist
had been confined to the Vertebrated animals, or those which are
constructed on the same general type as ourselves. Without a much
deeper investigation, we never could have understood the relative
importance of the different organs, the order of their introduction
and progressive complication, their homological and analogical
relations.

Only in the Invertebrated classes do we find examples in which
the lungs, like the liver, are supplied by the ramifications of the
trunk of a vein without the interposition of a heart. Only in the

640 LECTURE XXIV.

lowest of the Invertebrate animals could we have found the office of
the lung performed by a vascular portion of the integument ; and the
Invertebrata alone could have furnished us with examples of the
progressive modifications of this portion of the vascular skin, by
which the breathing organ is at length definitely developed. But
why specially cite the respiratory system ? The earliest and most
instructive forms of almost every organ, as it is variously arrested
in its development and adapted to the exigencies of the mature
animal, must be sought for amongst the Invertebrata.

These animals alone furnish us examples of the oscillation through
the living tissues of a fluid which seems to differ but little from sea-
water, and of the direct communication of the chylaqueous system
with the external oceanic medium ; — of the co-existence of an aqui-
ferous with a sanguiferous system in the same animal, and the pro-
gressive development of a true vascular organisation by which the
aquiferous channels are at length superseded ; — of a circulation of
the blood without a heart, and of a circulation aided by the hundred-
fold repetition of the propelling'reservoir in the same individual; — of
the meandering of the circulating fluid back to the heart through
diffused venous lakes, instead of cylindrical canals. Only the low
organised Invertebrate animal could have revealed to us the actual
existence in nature of a condition of the blood's motion, once errone-
ously held to be universal, viz., its flux and reflux in the same
vessels, from trunks to branches and from branches to trunks, to and
from the heart*, as Aristotle conceived to be the nature of the blood's
movement in all animals, and which he illustrated by the analogy of
the tides of the Euripus !

In the Invertebrate series we can contemplate the most simple and
essential condition of the nervous system, — a ganglion with radiated
internuntiate chords, — a centre for the reception and transmission of
stimuli. In this series we see such centres multiplied and set apart
for different segments, or for different organs of the body. Of such
arrangements, the anatomist of the Vertebrata exclusively could
have formed no adequate conception. And not only are the con-
ditions for the performance of the most essential function of the ner-
vous system, — viz. the working of the muscular machinery agreeably
with impressions received from external objects, independently of
any consciousness of such changes, or of any choice and volition in
the mode of remedying or avoiding them, — most plainly set forth in
the Invertebrate types of the nervous system ; but they afford the
best subjects for illustrating that primary function by experiment.-]-

* Lecture XX. Tunicata, p. 469. f Lecture XVI. Insecta, p. 364.

CONCLUDING SUMMARY. 641

Tlie relation of the physical defence of an animal by shells or
crusts to the low condition of the sentient system is most strikingly
manifested in the Invertebrate series, and could be but feebly dis-
cerned in the higher animals, none of which exhibit the external or
dermal skeleton modified to encase the limbs and form the levers and
fulcra of the moving powers. The defence of the crab and oyster
by dense and impenetrable armour as a compensation for their lack
of intelligence and defective powers of action, reminds one of the
condition of the soldier in the early and ruder states of the art
of war.

If the structure and functions of the human mechanism had been
illustrated only by comparison with those of other Vertebrata, the
physiologist would have been acquainted with only one leading
modification of the generative system in the Animal Kingdom,
namely, the dicecious or bisexual. The analogy between animals and
plants in the modes of continuing the species is fully illustrated only
by the Invertebrata. Here the anatomist finds the self-sufficing
combination of fertilising and productive organs in the same indivi-
dual, as in most flowers. Other Invertebrata present the still more
remarkable combination of male and female parts arranged for reci-
procal union. The closer and more remarkable analogy with the
vegetable kingdom offered by that peculiar modification of the gene-
rative system, in which we found the oviduct and vulva exclusively
destined for the transmission of the moving particles of the fertilising
fluid, the fertilised ova escaping into the abdomen by dehiscence of
the ovarium, so that extra-uterine gestation was a natural and con-
stant phenomenon, was demonstrated by dissection of the earthworm.
The small transparent vermiform parasites have afforded the best
subjects for the demonstration of the entry of the fertilising principle
into the ovum, and of the first changes therein and thereby operated.

The diversified structures of the Invertebrate animals not only
teach us the most remarkable modes of action, and instructive modi-
fications and correlations of individual organs and systems, but they
lead to an insight into, and can alone furnish the demonstrations of,
the most important generalisations iii zootomical science.

Of that which I have termed " the law of vegetative or irrelative
repetition," by which is meant the multiplication of organs performing
the same function, and not related to each other by combination of
powers for the performance of a higher function, the Invertebrata
afford the most numerous and striking illustrations.

Almost every organ of the body illustrates tliis vegetative con-
dition at its first appearance in the Animal Kingdom. A stomach
or assimilative sac is the most general characteristic of an animal,

T T

642 LECTURE XXIV.

Such sacs are developed in great numbers in the body of the Poly-
gastrian, but each sac performs the same share of the digestive
function, irrespective of the rest. The case is very diiferent in the
ruminant animal, in which each of the four stomachs has its appro-
priate office, and all combine together to produce a more efficient
act of digestion.

The organs of generation, the next essential parts of the mere
animal, when first definitely introduced with their characteristic
complications in the low organised Entozoa, illustrate more forcibly
the law of irrelative repetition.

We trace the definite development of the heart and gills in the
Anellids, in some species of which both organs are irrelatively
repeated above a hundred times. And when these, like most of the
vesetative or<xans, assume a more concentrated form in the Mollus-
cous series, we perceive in the structure and relations of the two
auricles of the bivalve as compared with the single auricle of the
univalve, and of the four gills of the Nautilus as compared with the
two gills with their more perfect circulation in the Sepia, that plu-
rality is but a sign of inferiority of condition.

When locomotive and prehensile appendages first make their
appearance in free animals, they are simple, soft, and unjointed, but
they are developed by hundreds, as in the Asterias and Echinus :
they manifest the principle of vegetative repetition to a remarkable
extent when they are developed into symmetrical pairs of setigerous
tubercles in the Anellids, and even when they first appear as jointed
limbs in the Myriapods : but as they become progressively perfected,
varied, and specialised, they are reduced to ten in Crustaceans, to
eight in Arachnids, and to six in Insects. We have just seen that
the same law prevails in the introduction of the analogous cephalic
organs of locomotion and prehension in the Mollusks. It is beauti-
fully illustrated in the introduction of the organ of vision into the
Animal Kingdom.

The numerous ganglions, nerves, and muscles, called forth by the
vegetative succession of the segments of the body and their locomotive
appendages in the Articulates, have sometimes been adduced as
invalidating the claims of the Mammalia to be regarded as of higher
or more complex organisation*; but when the law of irrelative repe-

* Thus the acute philosopher Young writes : — " There are even Hving beings,
visible to the microscope, of which a million million would not make up the bulk
of a common grain of sand. But it is still more remarkable, that, as far as we can
discover, many of these animalcules are as complicated in their structure as an ele-
phant and a whale. It is true that the physiology of the various classes of animals
is somewhat more simple as they deviate more from the form of quadrupeds and
from that of the human species ; and some of the lower classes appear to approxi-

CONCLUDING SUMMARY. 643

tition is rightly understood, the multiplication of similar parts for the
repetition of the same actions is at once appreciated as essentially
the more simple, as well as the inferior, condition, compared with the
assemblage of less numerous parts in the same body with different
offices, and with prospective arrangements that enable them to
combine their different powers for definite ends.

The lowest Invertebrata resemble locomotive cells: they propagate
by spontaneous fission and grow by assimilation; sometimes they
exhibit their geometrically multiplied divisions to a certain extent
within a common capsule. The earliest phenomena in the develop-
ment of the mammiferous ovum most closely resemble the common
mode of multiplication of the Gonium and Volvox. Like phenomena
have been observed in the vitelline germ of the frog and the fish.
But the universality of the phenomena of spontaneous division, of
the fissiparous procreation of nucleated cells, and of their growth by
assimilation and coalescence round definite centres, as the properties
of the primordial germ in all animals which produce the most conspi-
cuous changes in the yolk, has been mainly established by collecting
the observations that have been made upon the development of
the embryo in the different classes of Invertebrata, and by the
comparison of these with the analogous phenomena observed in the
development of certain Vertebrata which we may conclude to cha-
racterise the first step in the formation of the human embryo.

And since later observations have established what I believe
'myself to have first observed, and suggested to be a general property
of the blood-cell, — viz. its power of spontaneous subdivision into
smaller centres prior to its solution*, it is highly probable that the
preliminary steps to its conversion are the same as those of the
nucleated cell which constitutes the germ of the entire animal ; and
the proposition that the phenomena of spontaneous fission, of which
the Monads offer the most conspicuous examples, are the most

mate very roucli to the nature of the vegetable world. But there are single
instances that seem Avholly to destroy this gradation. Lyonnet has discovered a
far greater variety of parts in the caterpillar of the willow-butterfly than we can
observe in many animals of the largest dimensions ; and amongst the microscopic
insects in particular, we see a prodigality of machinery, subservient to the various
purposes of the contracted life of the little animal, in the structure of which nature
appears to be ostentatious of her power of giving perfection to her minutest works."
— Young's Lectures oti Natural Philosophy, 4to., p. 608. My predecessor in the
Hunterian chair adopted the same view. " There arc 500 muscles attached to this
hard ring, which passes rovmd the body of the Willow- caterpillar, each muscle
having its nerve. Now, if 1 take this opportunity of making a comparison,
let me ask whether there be any part of man which presents a complication
equal to this? " — Sir Charles Bell, Hunteriaii Lectures, Lancet, 1833, p. 284.

* Medical Gazette, November 13. 1839. Dr. Martin Barry's Paper in Philos.
Transactions, 1840.

T T 2

644 LECTURE XXIV.

universal and important in the operations of the living animal, ceases
to wear the aspect of exaggeration.

It is, however, certain that the most extraordinary consequences of
the fissiparous property of the nucleated cell are unknown in the
Yertebrated classes, of which generation without fecundation of the
procreating individual is an example. This phenomenon, which at
first so much astonished and perplexed physiologists, as observed
only in the Aphides, becomes inteUigible and reducible to general
law, and is extensively manifested in the Invertebrate series of
animals.

The Monad divides itself before our eyes, constituting two, then
four, next eight individuals, and so on. The impregnated germinal
vesicle, which the Monad permanently represents in nature, propa-
gates, in like manner, by spontaneous fission and assimilation, a number
of impregnated cells like itself. Most of these cells are metamor-
phosed into the tissues of the growing embryo, but not necessarily all.
Certain nucleated cells, the progeny of the primordial one, and in-
heriting its powers, may become, without further stimulus, the centres
of development of processes like those which have built up the body
that contains them : they may bud forth from the stem of the Hydra,
and form new individuals by the process of gemmation ; they may bud
forth, in like manner, from the larval polype of the Medusa, which
thereby procreates in its immature, and, as it seems, virgin state, like
the wingless larvae of the summer Aphides ; they may enter the
unimpregnated oviducts of these insects, and be there developed in
the manner which has already been described.*

Did time permit, I might easily multiply the instances from the
Invertebrate organisations, which bear directly on the establishment of
the most important general laws in physiology. I shall conclude by
adverting to one which is alike interesting to the anatomist and natu-
ralist, and which has exercised the powers of the most active and
enquiring intellects of the present age. To the disquisitions and
discussions in which Goethe, Oken, Cuvier, and Geoff'roy have
taken part, the doctrines of Morphology and of Unity of Organisation
owe their existence.

Some of the medical acquaintances of John Hunter, who, we are
told, complacently apostrophised his pursuits in the language of pity,
when they found him dissecting a snail, a bee, or a worm, little
dreamt of the expanded views of the animal organisation at w^iicli he
w^as obtaining glimpses through those narrow casements. It would
seem that Hunter himself was oppressed with the vastness of the
prospect, w^th the grandeur of the generalisations which his investi-

* Lecture XVIEI. Inskcta, p. 387.

CONCLUDING SUMMARY. 645

gations of the lower animals, and of the embryonic forms of the
higher ones, were forcing upon his reflective mind, if we may judge
from his struggles to express ideas, at that period so novel, and to
which he could but give imperfect utterance. " If we were capable,"
he says, " of following the progress of increase of the number of the
parts of the most perfect animal, as they first formed in succession,
from the very first, to its state of fidl perfection, we should probably
be able to compare it with some one of the incomplete animals
themselves, of every order of animals in the creation, being at no
stage different from some of those inferior orders ; or, in other words,
if we were to take a series of animals from the more imperfect to the
perfect, "we should probably find an imperfect animal corresponding
with some stage of the most perfect." *

With the great accession of facts with which Comparative Anatomy
has since been enriched, particularly from monographs detailing dis-
sections of the Invertebrate animals, we may now attempt a more exact
enunciation of the resemblance which a higher organised animal pre-
sents to those of a lower order in its progress to maturity : and the
consequent extent to which the law of "Unity of Organisation " may
be justly, and without perversion of terms, be predicated of animal
structures. We shall see some grounds for the statement that the
more perfect animal is at no stage of its development different from
some of the inferior species ; but we shall obtain proof that such
correspondence does not extend to every order of animals in the
creation.f

The extent to which the resemblance, expressed by the term
"Unity of Organisation," may be traced between the higher and
lower organised animals, bears an inverse ratio to their approxima-
tion to maturity.

All animals resemble each other at the earliest period of their
development, which commences with the manifestation of the as-
similative and fissiparous properties of the polygastric animalcule :
the potential germ of the Mammal can be compared, in form and
vital actions, with the Monad alone; and, at this period, unity of
organisation may be predicated of the two extremes of the Animal
Kingdom. J The germ of the Polype acquires more conspicuously the
locomotive organs of the Monad, — the superficial vibratile cilia, —
before it takes on its special radiated type. The Acalephe passes

* Hunterian MS. quoted in my ' Physiological Catalogue,' X, vol. i. p. 4.

t This proposition is well supported and illustrated by Von Baer, CliXXXIX.
and CCLXX.

X V. Baer, not recognising this phase of germ-life, affirms that " the Verte-
brata cannot descend to the lowest grades of organisation," and that their
embryos pass through no permanent forms of animals whatsoever.

T T 3

646 LECTUKE XXIV.

through both the Infusorial and Polype stages, and propagates by
gemmation, as well as spontaneous fission, before it acquires its
mature form and sexual organs. The fulness of the unity of
organisation which prevails through the Polypes and larval Acale-
phes, is diminished as the latter approach maturity and assume their
s^oecial form.

The Bryozoa, after simulating the higher Infusoria by their
spheroid shape and active movements, due to well-developed zones
or lobes of conspicuous vibratile cilia, mask their low molluscous
character beneath the polype form. The Ascidian Mollusks typify
more feebly and transiently the polype state in passing from that of
the cercariform ciliated larva to the more special molluscous form. The
Univalves and Bivalves obey the law of unity of organisation in the
spontaneous fissions of their amorphous germ, and in its ciliated epi-
thelium, by which it gyrates in the ovum ; but they proceed at once
to assume the molluscous type without taking on that of the Polype ;
the Bivalve retaining the acephalous condition, the Univalve as-
cending in its development to the acquisition of its appropriate head,
jaws, and organs of sense.

Thus all mollusks are at one period like Monads, at another are
Acephalous; but few typify the Polypes, and none the Acalephes,
or Echinoderms. In the Encephalous division we meet with many
interesting examples of the prevalence of unity of organisation at
early periods, which is lost in the diversity of the special forms as
development proceeds. Thus the embryos of the various orders of
Gastropods are first abranchiate, next nudibranchiate, but only a
few retain that condition of the respiratory system through life ;
most of them move at first by aliform anterior lobes, like those which
characterise the mature Pteropods, but afterwards exchange the
swimming organs for the repent disc which marks their class. The
naked Gastropods are at first univalve Mollusks, like the great bulk
of the class at all periods. The testaceous Cephalopods first
construct an unilocular shell, which is the common persistent form in
Gastropods, the Polythalamia afterwards superadd the characteristic
chambers . and siphon. This simple fact would of itself have dis-
proved the theory of ^ evolution,' if other observations of the phe-
nomena of development had not long since rendered that once
favourite doctrine untenable.

Thus, as we trace the development of the Molluscous animal, we
find the application of the term unity of organisation progressively
narrowed as development advances : for whilst all Mollusks manifest,
at their earliest and most transitory period, a resemblance to the
lowest or monadiform zoophytes, only the lowest order of Mollusks in

CONCLUDING SUMMARY. 647

the next stage of development represents the polypes ; and all analogy
to the radiated type is afterwards lost, until we reach the summit of
the Molluscous series, when we find it interestingly, though illusively,
sketched by the crown of locomotive and prehensile organs upon the
head of the Cephalopods.*

In the great Articulated branch of the Animal Kingdom, there is
unity of organisation with the Molluscous series at the earliest periods
of development, in so far as the germ divides and subdivides and
multiplies itself; but the correspondence rarely extends to the ac-
quisition by the nascent articulate animal of the locomotive power by
superficial vibratile cilia: in the great majority of the province the
progeny of the fissiparous primitive germ-cell begin at once to
arrange themselves into the form of the Vibrio or apodal worm, while
those of the Molluscous germ diverge into the polype-form or into a
more special type.

Unity of organisation prevails through a very great proportion of
the Articulate series in reference to their primitive condition as
apodal worms. Only in the higher Arachnids, the nucleated cells
are aggregated under a form more nearly like that of the mature
animal, before they are metamorphosed into its several tissues. In
lower or more vermiform Condylopods, the rudimental conditions of
the locomotive appendages, which are retained in the Anellides and
the lower Crustaceans, are passed through in the progress of the
development of the complex-jointed limbs. In the great series of
air-breathing insects, we have seen that the diverging branch of the
Myriapods manifests at an early period the prevailing hexapod type,
and that all Insects are at first apterous, and acquire the jointed
legs before the wings are fully developed. An articulate animal
never passes through the form of the Polype, the Acalephe, the
Echinoderm, or the Molluskf : it is obedient to the law of unity of
organisation only in its monad stage : on quitting this, it manifests
the next widest relations of uniformity as a Vibrio or apodal worm ;
after which the exact expression of the law must be progressively
contracted in its application as the various Articulata progressively
diverge to their special types in the acquisition of their mature
forms.

* Von Baer believed that the head completely represented the radiate type, the
molluscous structure being seen only on the sac-like part of the body. He
remarks, " the Cephalopoda most frequently swim with their heads downwards ;
the radiate portion of the body therefore seems to hold and to move itself in
accordance with the mode of locomotion prevalent in its type, overcoming the
tendency of the molluscous body." — CLXXXIX. p. 760. I have always regarded
this supposed combination of the two types as illusory.

t CLXXXIX. p. 753.

T T 4

648 LECTUKE XXIV.

In the proper Radiated series itself we discern the same principle :
the radiated type culminates in the Echinoderms ; but the most typical
forms, called emphatically star-fishes, are pedunculated in the em-
bryo-state, at least in one family, and so far manifest conformity
of organisation with the Polypes and the vast and almost extinct
tribes of the Pentacriuites, before acquiring their free and locomotive
maturity.

It will be found when we enter upon the consideration of the
development of the Vertebrate embryo, that its unity of organisation
with the Invertebrata is restricted to as narrow and transitory a point
as that of the Articulate with the Molluscous series. Manifesting the
same monad-like properties of tlie germ, the fissiparous products
proceed to arrange and metamorphose themselves into a vermiform
apodal organism, distinguished from the corresponding stage of the
Insect by the Vertebrate characteristics of the nervous centres, — viz.
the spinal chord and its dorsal position ; whereby it is more justly
comparable to the apodal fish than to the worm.

Thus every animal in the course of its development represents
some of the permanent forms of animals inferior to itself ; but it does
not successively repeat them all, nor acquire the organisation of any
of the inferior forms which it transitorily typifies. Had the Animal
Kingdom constituted, as was once supposed, a single and continuous
chain of Being progressively ascending from the Monad to the Man,
unity of organisation might then have been demonstrated to the
extent in which the theory has been maintained by the disciples of
the school of Bonnet and Geoffroy St. Hilaire.

There is only one organic form which is either permanently or
transitorily represented throughout the Animal Kingdom : it is that
of the microscopic infusorial Monad, with the consideration of which
the present survey of the Invertebrate animals was commenced, and
which is to be regarded as the fundamental or primary form.

Other forms are represented less exclusively in the development
of the Animal Kingdom, and may be regarded as secondary forms.
These are, the Polype, the Worm, the Tunicary, and the Lamprey ;
they are secondary in relation to the Animal Kingdom at large, but
are primary in respect of the primary divisions or provinces.*

Thus the Radiata, after having passed through the monad-stage,

* Von Baer adopted Cuvier's view of four leading types — Radiate or *' peri-
pheral," Articulated or " longitudinal," Molluscous or *' massive," and Vertebrate :
but he superadded the idea that the Vertebrate type united in itself the three
others, " the head being an outline of the radiate type." CLXXXIX. p. 746.
Here, however, an unreal signification seems to be assigned to the " circulus
arteriosus " and its four vascular trunks.

CONCLUDING SUMilARY. 649

enter that of the polype ; many there find their final development ;
others proceed to be metamorphosed into the Acalephe or the Echi-
noderm.

The Articulata, at an early stage of their development, assume
the form or condition of the apodal and acephalous worm ; some
find their mature development at that stage, as the parasitic Eutozoa ;
others proceed to acquire annulations, ahead, rudimental feet, jointed
feet^ and finally wings : radiating in various directions and degrees
from the primary or fundamental form of their sub-kingdom.

The Mollusca pass from the condition of the ciliated Monad to that
of the shell-less Acephalan, and in like manner either remain to work
out the perfections of that stage, or diverge to achieve the develop-
ment of shells, of a head, of a pair of fins, of a ventral foot, or of
cephalic arms, with all the complexities of organisation which have
been demonstrated in the concluding Lectures of this Course.

The Vertehrated germ having manifested its monadiform relations
by the spontaneous fission, growth, and multiplication of the primor-
dial nucleated cells, next assumes, by their metamorphosis and primary
arrangement, the form and condition of the finless cartilaginous fish,
from which fundamental form development radiates in as many and
diversified directions and extents, and attains more extraordinary
heights of complication and perfection than any of the lower secondary
types appear to be susceptible of. The ultimate stages of these de-
velopments, the various permanent or mature structures of the Verte-
brated series, with their physiological and other relations, will form
the subjects of succeeding lectures.

650

Class CEPHALOPODA.

Enceplialous mollusks, with locomotive and prehensile organs
radiating from the head : dicecious and ametabolian.

Order TETRABRANCHIATA.

With four gills : no ink-bladder. Shell external, camerated and

siphonated.

Family NautilidcB. Shell discoid or spiral ; dwelling-chamber large ;
aperture simple ; sutures simple ; siphon simple, central, or
near the concavity of the shell-curve.

Genera Nautilus, Aiuria, Discites, TemnocheiluSj Cryptoceras,
Lituites, Trochoceras, Clymenia.

Family Orthoceratidce. Shell straight, curved, or discoidal ; dwell-
ing-chamber small ; aperture contracted ; siphon central,
wide, or complex.

Genera OrthoceraSy Cameroceras, Actinoceras, Ormoceras, Hu-
ronia, Endoceras, Gompfwceras, Onchoceras, Phrag-
moceras, Cyrtoceras, Gyroceras, Ascoceras.

Family AmmonitidcB. Shell discoidal, curved, spiral, or straight ;
dwelling-chamber elongated ; aperture guarded by processes
and closed by an operculum (called Trigonellates and
Aptychus) ; sutures angulated, or lobed and foliated ;
siphon peripheral, or at the convexity in the curved
shells.

Genera Goniatites, Ceratites, Amniojiites, Criocerasy Toxoceras,
Ancyloceras, Scaphites, Helicoceras^ Turrilites, Ha-
iuiteSf Ptychoceras, Baculites. ^

CEPHALOPODA.. 651

Order DIBRANCHIATA.

With two gills ; an ink-bladder. Shell commonly internal and
rudimentary.

Tribe Decapoda.
Family SpirulidcB. Shell chiefly internal, nacreous ; whorls sepa-
rate, chambered ; siphon near the concavity of the shell-
curve.

Genus Spirula.

Family Belemnitidm. Shell internal, consisting of a " phragmocone "
with a marginal siphon, lodged in a *' guard," sometimes
produced into a horny plate or " pen."
Genera Belemnites^ Belemnitella, Belemnoteuthis, Conoteuthis.

Family SepiadtE. Shell internal, consisting of a flattened " phrag-
mocone," lodged in an open " guard," prolonged behind into
a " mucro."
Genera Sepia, Beloptera, Belemnosis.

Family Teuthidce. Shell internal, simple, wholly or in great part

horny, called " gladius " or " pen."

Genera Coccoteuthis, Enoploteuthis, Onychoteuthis, Histioteuthis,

CheiroteuthiSj Loligo, Loligopsis, Cranchia, Rossia,

Sepiola, Sepioteuthis, LeptoteuthiSf Geoteuthis, Belo-

teiithis.

Tribe Octopoda.

Family Pinnata. Shell rudimental, internal, uncalcified : a pair of
pallial fins.
Genera SciadephoruSy Pinnoctopus,

Family Nuda. Shell rudimental, internal, uncalcified. No pallial
fins.
Genera Octopus, Tremoctopus, Eledone.

Family Testacea. Shell calcareous, simple, external, peculiar to the
female. No pallial fins.
Genus Argonauta,

653

WORKS

REFERRED TO BY ROMAN NUMERALS IN THE PRESENT
VOLUME.

I. LiNN^rs. Systema Natiiras. Ed. duodec. Holm. 1766.
IL Hartley. On Man, 1749. 8vo. Ed. 1801.

HL Hall, Marshall. On a peculiar Function of the Nervous System,
Proceedings of the Zoological Society of London, November 27th'
1832.
IV. Carpenter, W. Principles of Physiology, General and Compara-

tiA-e. 8vo. 1841.
V, Ungzr. Die Pflanze im Momente der Thierwerding. 1843.
VL Bllmenbach. Handbuch der Naturgeschichte. 8vo. 11th ed
1825.
VIL KoLLiKER. Ueber die Gattung Gregarina, Siebold's Zeitschrift f Ur

Wisscnschaftliche Zoologie. Band i. 1848.
VHL WoHLER and Liebig's Annalen. 1843,
IX. Schmidt, Carl. Contributions to the Comp. Physiology of the In-
vertebrate Animals, Taylor's Scientific Memoirs, vol. v.
X. Hunter, John. Manuscripts printed in the Catalogue of the Phy-
siological Series in the Museum of the Royal College of Sur-
geons. 4to. 5 vols. 1832 — 1840.
XI. Ehrenberg. Die Infusionsthierchen als Vollkommene Organismen

Fol. 1838.
XH. CuviER. Le Regne Animal distribue d'apres son Organisation.
8vo. 1817. 2d ed. 1829.
Xni. Lamarck. Systeme des Animaux sans Vertebres. 8vo. 1801.
XIV. CuviER. Decade philosophique des Memoires de la Societe d'His-
toire Naturelle de Paris. 1795.
XV. CuviER. Annales du Museum d'Histoire Naturelle, torn. xix. 1812.
XVI. Edwards, Milne. Observations et Experiences sur la Circulation
chez les Mollusques, Annales des Sciences Naturelles, torn iii
1845.
XVII. Leeuwenhoek. Observations concerning some little animals ob-
served in rain-, well-, sea-, and snow-water, &c. Philosophical
Transactions, xii. 1677.
XVni. CoiiN. Beitriige zur Entwickelungsgeschichte der Infusorien, Sie-
bold's Zeitschrift fiir Wisscnschaftliche Zoologie, Bd, iii. 1851.
XIX. KoLLiKER. Ueber das Sonnenthierchen, Siebold's Zeitschrift fiir
Wisscnschaftliche Zoologie. 1849.
XX. FocKE, in Amtlicher Bericht der Naturforscher zu Bremen. 1844.
XXI. Ry3ier Jones, in Taylor's Annals of Natural History. Oct. 1838.
XXIT. Meyen. Mailer's Archiv fiir Physiologic. 1839.

XXIII. Erdl. Muller's Archiv fiir Physiologic. 1841.

XXIV. Siebold. Lchrbuch der Vcrgleichenden Anatomic der Wirbellosen

Thiere. 8vo. 1848.

65\ WORKS REFERRED TO BY ROMAN NUMERALS.

XXV. Stein, Fr. Untersuchungen iiber die Natiir d. Gregarinen, Miil-
ler's Archiv fiir Physiologie. 1848.
XXV*. Stein, Fr. Neue Beitriige zur Kenntniss der Infusionsthiere, Sie-

bold's Zeitschrift fiir Wissens. Zoologie, Bd. iii. 1851.
XXVI. Barry, Martin, in Owen's Lectures on Invertebrate Animals. Ed.

1843.
XXVn. Barry, Martin. Researches in Embryology, 2d Series, Philoso-
phical Transactions. 1839.
XXVIII. Bagge. De evolutione Strongyli. 4to. 1841.
XXIX. Barry, Martin. On the Nucleus of the Animal and Vegetable

" Cell," Edinburgh New Philosophical Journal. Oct. 1847.
XXX. Owen, Richard. On Parthenogenesis. 8vo. 1849.
XXXI. Arlidge, Dr. On some Phases of Development of the Trickodina

pediculus, Annals and Magazine of Natural History. 1849.
XXXn. Ehrenberg in Edinburgh New Philosophical Journal, vol. xxxi.

XXXIII. HoBBES, Thomas. Elements of Philosophy, Molesworth's ed.

XXXIV. ScHULZE. Edinburgh New Philosophical Journal, vol. xxiii.
XXXV. Farre, Arthur, Observations on the Minute Structure of some of

the Higher Forms of Polypi.
XXXV*. Leydig. Philosophical Transactions for 1837.
XXXVI. GossE, P. H. Description of Asplanchna priodonta, an Animal of the
Class Rotifera, Annals and Magazine of Natural History. 1850.
XXXVII. Brightwell, T. Some Account of a dioecious Rotifer allied to the
genus Notommata, Annals and Magazine of Natural History.
1838.
XXXVin. KoLLiKER. Froriep's Neue Notizen, Bd. xxviii. 1843.
XXXIX. Leeuwenhoek. Continuatio Arcan. Naturae. 1702.
XL. Hill, J. History of Animals. 1752.
XLI. Baiver. Employment of the Microscope. 1753.
XLII. Fontana. Sur le Venin de la Vipere. 1781.

XLIII. Spallanzani, L. Opuscoli di Fisica Animale e Vegetabile. 1776.
XLIV. MuLLER, O. F. Animalcula Infusoria. 4to. 1786.
XLV. RcDOLPHi, C. A. Grundriss der Physiologie. 8vo. 1821-27.
XL VI. RuDOLPHi, C. A. Entozoorum Historia Naturalis, 8vo. 1808-10.
XLVIL RcDOLPHi, C. A. Entozoorum Synopsis. 8vo. 1819.
XL VIII. GoEZE. Versuch einer Naturgeschichte der Eingeweidewiirmer.
1782.
XLIX. Zeder. Erster Nachtrag zum vorhergehenden Werke. 1800.

L. Bremser. Ueber lebende Wiirmer in lebenden Menschen. 1819.
LI. Bremser. Icones Helminthum. Fol. 1824.
LII. Collard. Ai't. Acephalocystes, Diet, de Med. et de Chir.

prat.
Lin. GooDSiR, H.D.S. On the Development, Structure, and Economy of
the Acephalocysts of Authors, Transactions of the Royal Society
of Edinburgh 1844.
LIV. DuFODR. L. Recherches Anatomiques sur les Carabiques, &c.,
Annales des Sciences Nat., torn. viiL ( 1826.) and tom. xiii. (1828).
LV. SiEBOLD. Beitriige zur Naturgeschichte der Wirbellosen 'J'hiere. 4to.
1839. Ueber die zur Gattung Gregarina gehorigen Helminthen.
Entwickelungsgeschichte der Medusen.
LVI. ScHLEiDEN. Zeitschrift fiir Wissenschaftliche Botanik, Heft ii.

1840.
LVn. Henle. Miiller's Archiv fur Physiologie. 1845.
LVIIL MCller, J. Ai'chiv fiir Physiologie. 1836. p. evil.
LIX. Siebold. Burdach's Physiologie, Bd. ii. 1837.
LX. Owen, R. Art. Entozoa, Cyclopedia of Anatomv and Physiologv,

Vol. ii. 1837.
LXI. Wilson, E. On the Classification, &c. of the Echinococcus Hominis,

Medico-Chirurgical Transactions, vol. xxviii. 1845.
LXIL Rose. On the Anatomy and Physiology of the Cysticercus tenui-
collis; in Medical Gazette, 1833, and Medico-Chirurgical Trans-
actions, vol. xiii.

WORKS REFERRED TO BY ROMAN NUMERALS. 655

LXIII. SiEBOLD. Ueber den Generationswechsel der Cestoden nebst einer
Revision der Gattung Tetrarhynchus, Zeitschrift fiir Wissenschaft-
liche Zoologie, Bd. ii. 1850.
LXIV. EscHRiciiT, Prof. Anatomisch. Physiologische Untersuchungen

iiber die Bothryocephalen. 4to. 1840.
LXV. DuJARDiN, M. F. Observations sur les Taenias, Annales des Sciences

Naturelles, t. x. 1838.
LXVI. KoLLiKER. Beitriige zur Entwickelungsgeschichte Wirbellose Thiere,

MUUer's Archiv fiir Physiologie. 1843.
LXVII. Stein, in Leuckhart's Morphologie der Wirbellosen Thiere. 8vo.
1848.
LXVIII. Mehlis. De Distomate hepatico. Isis von Oken. 1831.
LXIX. Blanchard, Em. In Cuvier's Regne Animal, ed. avee Planches,
Atlas, Zoophytes, PI. 36.
LXX. BoJANUS, in Isis v. Oken. 1820.
LXXI. NoRDMANN. Micrographische Beitrage zur Naturgeschichte der

Wu-bellosen Thiere. 4to. 1832.
LXXII. Owen, R. On the Anatomy of Distoma clavatum, Transactions of

the Zoological Society, vol. i.
LXXITI. DujARDiN. Histone Naturelle des Helminthes. 1845.
LXXIV. SiEBOLD. Ueber die Conjugation des Diplozoon paradoxum,

Zeitschrift fiir Wissenschaftliche Zoologie, Bd. iii. 1851.
LXXV. DuGES. Recherches sur I'Organisation et les Moeurs des Planaires,

^_ Annales des Sciences Naturelles, t. xv. 1828.
LXXVI. Orsted. Entwurf einer systematischen Eintheilung und speciallen

Beschreibung der Plattwiirmer. 1844.
LXXVII. AVestrumb. J^e Helminthibus Acanthocephalis. Fol. 1821.
LXX VIII. Cloquet. Anatomie des Vers Intestinaux. 4to. 1824.
LXXIX. BuROW. Echinorhynchi Strumosi Anatome. 1836.
LXXX. Owen, R. Description of a microscopic Entozoon ( Trichina spiralis^
infesting the Muscles of the Human Body, Transactions of the
Zoological Society, vol. i. February, 1835.
LXXX*. Farre, Ur. A. On the Trichina spiralis, in Medical Gazette,

December, 1835.
LXXXI. Henle. Note to the Translation of LXXX, in Miiller's Archiv
fiir Physiologic. 1835.
LXXXII. Hilton. On a peculiar Appearance in Human Muscle, in Medical

Gazette, February, 1833.
LXXXII*. Le Blond. Quelques Materiaux pour servir a I'Histoire des Fihiires

et des Strongles. 1836.
LXXXIII. LuscHKA, Dr. H. Zur Naturgeschichte der Trichina spiralis, Sie-

bold's Zeitschrift fiir Wissenschaftliche Zoologie, Band iii. 1851.
LXXXIV. Owen, R. Lectures on the Comparative Anatomy and Physiology

of the Invertebrate Animals. 8vo. 1843.
LXXXV. Bagge. De Evolutione Strongyli auricularis, &c. 4to. 1841
LXXXVI. Treutler. Opuscula Pathologica et Anatomica. 1793.
LXXXVII. Owen, R, On the Anatomy of Linguatula Tcenioides, Transactions

of the Zoological Society, vol. i. 1835.
LXXXVIII. Owen, R. On the Genus Gnathostoma, Proceedings of the Zoo-
logical Society, November, 1836.
LXXXIX. DiEsiNG, in Annalen des Wiener Museums. Bd. ii. 1839.
XC. Mehlis, in Oken's " Isis." 1831.

XCL Nelson, Dr. The Reproduction of the Ascaris Mystax, Trans-
actions of the Royal Society." 1851.
XCII. Blanchard, Em. Recherches Zoologiques et Anatomiques sur I'Or-
ganisation des Vers, Compte Rendu de I'Acad. des Sciences,
June 14, 1847.
XCin. Steenstrup. On the Alternation of Generations, translation by the

Ray Society. 8vo. 1845.
XCIV. SiEBOLD. Helminthologische Beitrage, in Wiegmann's Archiv fiir

Naturgeschichte, for 1835, and for 1843.
XCV. Lmperato. Ilistoria Naturale. Fol, 1599.

656 WORKS REFERRED TO BY ROMAN NUMERALS.

XCVI. Peyssonel. Traite clu Corail, Phil. Trans. 1756; communicated to
the French Academy in 1727.
XCVn. Ellis, John. An Essay towards a Natural History of the Gorallines,

&c. 4to. 1755.
XCVIII. Ellis, John. The Natural History of many curious and uncommon
Zoophytes (Solander). 4to. 1786.
XCIX. CoRDA. Nova Acta Physico-Medica, &c. Bonn, vol. xviii. 18.36.
C. Baker, H. An Attempt towards a Natural History of the Polype.

8vo. 1 743.
CL Trembley, Abr. Memoires pour servir a I'Histoire d'un Genre de

Polypes d'eau douce. 12mo. 1744.
CII. Darwin, C. Structure and Distribution of Coral Reefs. Svo. 1842.
Cni. Pallas. Elenchus Zoophytorum. Svo. 1786.
CIV. Hancock, A. Notes on a Species of Hydra found in the Northum-
berland Lakes, Annals of Natural History, April, 1850.
CV. RoESEL, A. J. Historic der Polypen und anderer kleiner Wasser-
insecten, 4to., in Insecten Belustigungen. 1749.
CVI. Cavolinl Memorie per servire alia Storia dei Polipi marini. 1785.
CVII. Lister, J. Some Observations on the Structure and Functions
of tubular and cellular Polypi, Philosophical Transactions. 1834.
CVin. Grant, R. E. Observations on the Structure and Nature of Flustrre,
Edinburgh New Philosophical Journal, 1827.
CIX. Dalyell, Sir J. G. Rare and Remarkable Animals of Scotland.

4to. Vol. i. 1847 : vol. ii. 1848.
ex. Forbes, E. On the Morphology of the Reproductive System of the

Sertulariae, Annals of Natural History, vol. xiv. 1844.
CXL Van Beneden. Recherches sur I'Embryogenie des Tubulaires.
4to. 1844.
CXI*. Grant, R. E. Observations sur les Mouvemens spontanes des
CEiuk de plusieurs Zoophytes, AnnaleS des Sciences Naturelles,
tom. xiii. 1828.
CXII. Loven. Beitrag zur Kenntniss der Gattungen Campanula ria und

Synco7^yne, Weigmann's Archiv fiir Naturgeschichte. 1837.
CXIII. Sars. Beskrivelser og Jagtagelser, &c., levende Dyr af Polypcrnes,
Acalephernes, Radiaternes, Anuelidernes og Molluskernes Classer.
Bergen. 4to. 1835.
CXIV. Will. Horce Tergestince. 4to. 1844.
CXV. Erdl, in Froriep's Neue Notizen. 1839.
CXVI. Krohn. Einige Beobachtungen fiber die Geschlechtverhaltnisse bci

den Sertularinen, Miiller's Archiv fiir Physiologic. 1843.
CXVII. Ehrenberg. Beitriige zur Kenntniss der Corallenthiere des rothen
Meeres, Abhandlungen der Konigl. Akad. der Wisscnschaften
zu Berlin. 1832-34.
CXVIII. Grant, R. E. On the Generation of VirguJaria mirahilis, The
Edinburgh Journal of Science, vol. x. 1829.
CXIX. Grant, R. E. Observations on the Generation of the Lohularia digi^

tata, The Edinburgh Journal of Science, vol. viii. 1828.
CXX. Ellis, J. Of the Sea-pen or Pennatula phosphorea of Linnasus,
Philosophical Transactions, vol. liii.
CXXL Dixon, Fred. The Geology and Fossils of the Tertiary and Creta-
ceous Formations of Sussex. 4to. 1850.
CXXII. Le Sueur, in Transactions of the Academy of Sciences of Phila-
delphia, vol. i.
CXXin. Thompson, J. V. Zoological Researches. Part I. 8vo. 1830.
CXXIV. AuDouiN and Edwards, Milne. Resume des Recherches sur les
Animaux sans Vertebrcs, faites aux iles Chanssey, Annales des
Sciences Nat., tom. xv. 1828.
CXXV. Steintjuch. Analecten ncuer Beobaclitungen und Untersuchungen

fur die Naturkunde. 1802.
CXXVI. Fleming, Rev. J. Observations on the Sertuhr'ia cuscuta of Ellis,
Werncrian Transactions, vol. iv. 1823.

WORKS REFERRED TO BY ROMAN NUMERALS. 657

CXXVII. Edwards, Milne. Eeclierches Anatomiques, &c., sur les Polypes.

8vo. 1838.
CXXVni. Owen, E. Notes to Hunter's Animal Ecouomy. 8vo. 1837.
CXXLX. Darwin, Ch. Journal of Researches into the Natural History
and Geology of the Countries visited during the Voyage of the
Beagle, limo., 2nd Ed. 1845.
CXXX. NoRDMANN. Recherches JNIicroscopiques sur I'Anatomie et le
Developpement du Tendra Zostericola, Annales dcs Sciences
Naturelles, torn. xi. 1839.
CXXXI. Laurent. Zoophytologie, Voyage de la Bonite. Fol.
CXXXIL Darwin, Ch. Structure and Distribution of Coral Reefs. 8vo.

1845.
CXXXIH. Ehrenberg. Syrabolse Physicas, Fol. 182^1828.
CXXXIV. Van Beneden. Quelques Observations sur les Polypes d'Eau
douce, Annales des Sciences Naturelles, t. xiv. 1840.
1 CXXXV. ScHAFFER. Die Blumenpolypen der siisscn AVasser. 1755.
CXXXVI. Lamarck. Histoire Natm*elle des Animaux sans Vertebres. 8vo.
1816,
CXXXVn. Peron and Lesueur. Histoire Generale et Particuliere de tons les
Animaux qui composent la Famille des Meduses, Annales du
Museum, torn. xiv. 1809.
CXXXVni. Cuvier. Journal de Physique, torn. xlix. 1799.
CXXXVin*. Carpenter, W. Inaugural Dissertation on the Physiological In-
ferences to be deduced from the Nervous System in the
Invertebrata. 8vo. 1839.
CXXXIX. Gaede, H. M. Beitriige zur Anatomic und Physiologic der Medusen.
8vo. 1816.
CXL. Ehrenberg. Ueber die Acalephen des rothen Meeres und den
Organismus der Medusen der Ostsee, Abhandlungen der
Berlin Akad. der Wissensch. 1835.
CXLL Ehrenberg, in INlUller's Archiv fiir Physiologic. 1834.
CXLII. Wagner. Ueber den Bau der Pelagla noctiluca. Fol. 1841.
CXLIII. Wagner. Ueber Muthmassliche Nesselorgane der Medusen.

Weigmann's Archiv fiir Naturgeschichte. 1841.
CXLIV. Wagner, Icones Zootomicse. Fol. 1841.
CXLV. Huxley. On the Anatomy and Affinities of the Medusae, Philo-
sophical Transactions. 1849,
CXLVI. Edwards, Milne. Observations sur divers Acalephes, Annales

des Sciences, t. xvi. 1841.
CXL VII. Forbes, Ed. Monograph of the British Naked-eyed Medusse. 4to.

1848.
CXLVIII. Agassiz. Contributions to the Natural History of the Acalephge
of North America, Transactions of the Academy of Sciences of
Philadelphia. 1849,
CXLIX. Grant, R. On the Nervous System of Beroe pileus, Transactions
of the Zoological Society, vol. i, 1833.
CL. BoERHAAVE. lustitutioncs IMedicte in usus annuoe exercitationis
domesticos, 1740.
CLI. Sars. Fauna littoralis Norwegige. Fol, 1846.
CLII, Sars. Ueber die Entwickelung der Medusa aurita und Cyancca
capillata, Weigmann's Archiv fiir Naturgeschichte, Bd. i.
1841.
CLIII. Martens, in Memoires de I'Acad. de St. Petersbourg, tom. ii.
CLIV. MiJLLER, O. F. Zoologia Danica. Fol. 1788.
CLV. Eschcholtz. System der Acalephen, 1829.
CLVL Sars. Beytrage zur Natui'geschichte der Seethiere, Isis von
Oken, 1833.
CLVII. Letdig, F. Zur Anatomic und Entwickelungsgeschichte der
Laclnularia socialis.
CLVIIL Thompson, J. V. Memoir on the Genus Coraatula, demonstrative
of the Pentacrinus europceus being the young of our indigenous
species, Edinburgh New Philosophical Joui'nal, vol. xx. 1836.

u u

658 WORKS REFERRED TO BY LOMAN NUMERALS.

CLIX. TiEDEMAKN. Anatomie der Rohrenliolotlmrie, des pomeranzenfnr-

bigen Seestems und Steinseeigels. Fol. 1816.
CLX. Shakpet, W. Article Echixodermata, Cyclopiedia of Anatomy,
vol. ii. 1839.
CLXI. Sharpey, W. Article Cilia, Cyclopaedia of Anatomy, vol. i. 1836.
CLXII. Erdl. Ueber den Ban der Organe, welche an der ausseren Ober-
flache der Seeigel sichtbar siud, Weigmann's Archiv fiir
Naturgeschicbte. 1842.
CLXIII. "Williams, Dr., in Proceedings of the Eoyal Society. March, 1852.
CLXIV. Sars. Ueber die Entwickelnng der Seesterne, Weigmann's Archiv

fiir Naturgeschicbte. 1 844.
CLXV. Jones, Rymer. The Natural History of Animals. 8vo., vol. 1.

1845.
CLXVI. Agassiz, Monographies d'Echinodermes "vivans et fossiles. 4to.

1838-1842. ,

CLXVII. Valentin. L' Anatomie du genre Echinus, in the 4th Li\Taison of
Agassiz, Monographies d'Echinodermes. 1842.
CLXVII*. Cutier. Le9ons d' Anatomie Comparee. 8vo. Ed. 1835 — 46.

Avec Planches.
CLXVIII. EscHCHOLTZ. Zoologischer Atlas. 1829.
CLXIX. QuATREFAGES. Memoirc snr la Synapta Duvernma, Annales des

Sciences Naturelles. 1842.
CLXX. MtJLLER, J. Upon the Development of Mollusks in Holothizrice^
Annals of Natural History, January, 1852 ; or Ueber die
Erzeugung von Schnecken in Holotburien, Miiller's Archiv
fiir Physiologic. 1852.
CLXXI. MiJLLER, J. Ueber die Larven und die Metamorphose der
Ophiuren, Abhandlungen der Konigl. Akad. der Wissen-
chaften zu Berlin. 1846.
CLXXII. MuLLER, J. Ueber die Larven imd die Metamorphose der Echi-

nodermen. Ibid, 1848.
CLXXm. MtJLLER, J. Ueber die Lan^en und die Metamorphose der Holo-
tburien und Asterien. Ibid. 1849-50.
CLXXIV. MiJLLER, J. Berichtigung und Nacbtrag zu den anatomischen
Studien iiber die Echinodennen, Miiller's Archiv fur Phy-
siologic. 1 850.
CLXXV. MiJLLER, J, Fortsetzung der Untersuchungen iiber die Metamor-
phose der Echinodermen. Ibid. 1850. Heft v.
CLXXVI. MiJLLER, J. Ueber die Ophiuren-larven des Adriatischen
Meeres. Ibid. 1851. Heft i.
CLXXVII. Huxley, T. Eeport upon the Researches of Prof. Miiller into the
Anatomy and Development of the Echinoderms, Annals of
Natural History, 1851, p. 7.
CLXXVIII. Krohn, Dr. A. Ueber die Larve des Sipimculus nudus, Miiller's
Archiv fiir Physiologie. 1851.
CLXXIX. Forbes, E. On British Cystidese, Memoirs of the Geological

Survey of Great Britain, vol. ii. 1849.
CLXXX. Montagu, G. Descriptions of several new and rare Animals
discovered on the South Coast of Devonshire, Linngean
Transactions, vol. xi. 1807.
CLXXXI. Pallas. Miscellanea Zoologica. 1766.
CLXXXH Bonnet. Observations sur les Vers ; ffiuvres. 1779.
CLXXXIII. Savigny. Annclides, Description de I'Egypte, tom. xxi.

1826. Tab. vi. fig. vii.
CLXXXIV. Johnson. On the Medicinal Leech. 8vo. 1816.
CLXXXV. Brandt and Ratzeblrg. Medizinische Zoologie. 4to. 1829 —

1833—1843.
CLXXX VI. Ehrenberg, Beobachtung einer bisher unerkannten Struktur des
Seelenorganes des Menschen, Abhandlungen der Berliner
Akademie. 1843.
CLXXXVII. Edvtards, IMilne. Sur la Circulation dans les Annelides, Annales
des Sciences Naturelles, tom. x. 1838.

WORKS REFERRED TO BY ROMAN NUMERALS. 659

GLXXXVni. Carpenter, Prof. Inaugural Dissertation on the Physiological

Inferences from the Nervous System of Invertebrata. 8vo.

1839.

CLXXXIX. Baer, Von, K. E. Beitrage zur Kenntniss der niedern Thiere,

Nova Acta Acad. Nat. Cur. t. xiii. 1827.

CXC. Williams, Thomas, M.D. Report on the British Annelida, Trans.

Brit. Association, 8vo. 1852.
CXCI. Newport, G. On the Nervous System of the Sphinx Ligustri,

Philosophical Transactions, 1832.
CXCII. Nem^port, G. On the Nervous System of the Sphinx Ligustri,

Philosophical Transactions, 1834.
CXCIII. Leidt. Descriptions of some American Annelida abranchiata,

1850.
CXCIV. Johnstone, G. On the British Annelides, Annals of Nat. Hist.

iv.
CXCV. Weber, E. H. Ueber die Entwickelung des medicinscheii

Blutegels, Meckel's Archiv fiir Physiologic. 1823.
CXCVI. Farre, Dr. A. Observations on the Spermatozoa of the Earth-
worm, cited in Medical Gazette, vol. xx. 1849.
CXCVII. Brightwell. On ihe Development of Leeches, Annals of
Natural History. 1841.
CXCVIII. FiLippi. Sopra I'Anatomia e lo Sviluppo delle Clepsine. Pavia,
1839.
CXCIX. LovEN. Ueber die Entwickelung einer unbekannter, zu den
Nereiden gehorenden Annelide, Weigmanu's Archiv. 1842.
p. 302, pi. 7.
CC. KoLLiKER. Ueber die ersten Vorgange in befnichteten Ei,

Miiller's Archiv fiir Physiologic. 1843.
CCI. Oersted. Annulatorum danicorum Conspectus, fasc. i. 1843.
ecu. Sars. Zur Entwickelung der Anneliden, Weigmann's Archiv
fiir Naturgeschichte. 1845.
CCin. Menge, a. Zur Roth\viirmer Gattung Zuaxes, Weigmann's

Archiv fiir Naturgeschichte. 1845.
CCIV. Frei, in Gottinger gelehrte Anzeigen. 1845.
CCV. Grube. Untersuchungen iiber die Entwickelung der Clepsiuen.

1844.
CCVI. Edwards, Milne. Sur les Annellides, Annales des Sciences
Naturelles, t. iii. 1845.
CCVII. Koch. Einige Worte zm* Entwickelungsgeschichte von Eunice.

4to. 1846.

CCVin. Owen, R. Catalogue of the Invertebrata of the Zoological Series

in the Museum of the Royal College of Surgeons. 4to. 1830.

CCIX. KoLLAR. Beitrage zur Kenntniss der lernaeartigen Crustaceen,

in Annalen des Wiener Museums der Naturgeschichte, Bd. i.

1835.

CCX. AuDouiN and Edwards. Histoire Naturelle des Crustaces.

1834-40.
CCXI. Surrirat. Sur les GEufs de Calyge, Journal de Physique,

Ixxxix. 1819.
CCXII. MoRREN. De lumbrici terrestris Historia naturali. 4to. 1829.
CCXin. CuviER. Memoire sur les Animaux des Anatifes et des Balanes,

Memoires du Museum d'Histoire Naturelle, t. ii. p. 85. 1815.
CCXIV. Burmeister. Beitrage zur Naturgeschichte der Rankenfiisser.
4to. 1834.
CCXV. Martin St, Ange. Memoire sur I'Organisation des Cirripedes.

1835.
CCXVI. Coldstream. Art. Cirrhopoda, Cyclopedia of Anatomy,

vol. i. 1836.
CCXVII. LovEN. On the Alepas squalicoh, Ofversigt Konigl. Vetens.

1844.
CCXVIII. Leidt. Proceedings of the Academy of Sciences of Philadel-
phia, vol. iv. Jan 1848.
u u 2

660 WORKS REFERRED TO BY ROMAN NUMERALS.

CCXIX. Hancock, A. Alcippe Lampas, Annals of Natural Historj,

2d Series. Nov. 1849.
CCXX. GooDsiR. On the Larv» of Balanus in the first Staire of De-
velopment, Edinburgh New Philosophical Journal. July,
1843.
CCXXL Bate, C. Spence. On the Development of the Cirripedia, An-
nals of Natm-al History. Oct. 1851.
CCXXII. Reinhardt. Lithotrya Nicobarica, Copenhagen Journal of

Natural History.
CCXXni. Darwin, Ch. Monograph on the Sub-class Cirripedia {Lepa-

didce). 8vo. 1851.
CCXXIV. Darwin, Ch. Monograph on the Sub-class Balanida. 1854.
CCXXV. Thompson, J. V. Zoological Researches. 8vo. Cork. 1828 —

1834.
CCXXVI. Thoimpson, J. V. Account of the Larvse of Lepas and Cineras^
Philosophical Transactions.' 1835.
CCXXVn. AuDOuiN. Memoires relatifs aux Animaux sans Vertebres.
CCXXVHI. Bate, C. Spence. In Annals and Magazine of Natural History,
vol. viii. 2d series. 1851.
CCXXIX. Wagner. Ueber die Zeupungsorgane der CiiTipeden, &c.,
Miiller's Archiv fiir Physiologic. 1834.
CCXXX. GooDSiR, H. D. H. On the Sexes and Development of Cirri-

peds, Edinburgh New Philosophical Journal. 1843.
CCXXXI. Quekett, Prof. Lectures on Histology. 8vo. 1853-4.
CCXXXH. Savignv, J. Ces. Animaux Invertebres d'Egypte, in the

Description del'Egypt, xxii. and xxiii. 1827.
CCXXXin. SwAMMERDAM. Biblia Naturje. Eol. 1737-8.
CCXXXIH*. Couch, Jonathan. On the Process of Exuviation in Crabs and
Lobsters, Report of the Cornwall Polytechnic Society. 1843.
CCXXXIV. Swan, Jos. Illustrations of the Comparative Anatomy of the
Nervous System. 4to. 1835.
CCXXXIV*. Straus-Dijrckheim. Memoire sur les Daphnia, Mem. du
Mus.,tom.v. 1819.
CCXXXV. Farre, Arthur, M.D. On the Organ of Hearing in the Crus-
tacea, Philosophical Transactions. 1843.
CCXXXV*. MtJLLER, O. F. Entomostraca, &c. 4to. 1785.
CCXXXVI. Owen, R. Description of tlie Crustacea, Zoology of Capt.
Beechey's Voyage. 4to. 1830.
CCXXXVI*. Slabber, Mart. Natuurkundige Verlustigingen, behelzende
microscopische Waarnemingen van in- en uit-landische Water-
en Land-Dieren, Haarlem. 4to. 1769-78.
CCXXXVII. Rathke. Untersuchungen iiber die Bildung und Entwickelung

des Flusskrebses. Fol. 1829.
CCXXXVII*. Westwood, J. (). On the supposed Existence of Metamorphoses

in Crustacea, Philosophical Transactions, vol. cxxv. 1835.
CCXXX VIII. Du Cane, in Annals of Natural History, vol. iii. 1839.
CCXXXIX. Couch, J. On the Metamorphosis of the Decapod Crustaceans,
Report of the Cornwall Polytechnic Society. 1843.
^ CCXL. Ltonet. Traite Anatomique dc la Chenille que ronge le bois

de Saule. 4to. 1762.
CCXLI. Herold, Fr. Disquisitiones de Animaliura vertebris caren-
tium in Ovo formatione. 1835-38. Fol. Entwickelungs-
geschichte des Schmetterlings.
CCXLII. Straus-Durckheim. Considerations generales sur 1' Anatomic
Comparee des Animaux Articulees. 4to. 1828.
CCXLIII. Newport. On the Nervous System of the Sphinx Ligiistri, and
on the Changes which it undergoes during a Part of the
Metamorphoses of the Insect, Philosophical Transactions,
CXXII. & CXXIV.
CCXLIV. MiJ'LLER, Johan. Zur vergleichenden Physiologic des Ge-

sichtssinnes des INIenschen und der Thiere. 8vo. 1826.
CCXLV. SiEBOLD. Ueber das Stimm- und Gehororgan der Orthopteren,
Wiegmann's Archiv fiir Naturgeschichte. 1844.

WORKS REFERRED TO BY R03IAN NUMERALS. 66 i

CCXLVI. Hunter, John. Observations on Bees, in the Pliilosophical
Transactions, vol. Ixxvii. 1792.
CCXLVIL Bruqxatelli and Wurzer, in Meckel's Archiv fiir Physiologic,

Bd. ii. 1816, and Bd. iv. 1818.

CCXL VIII. HuxTER, John. On the Blood and Inflammation. 4to. 1794.

CCXLIX. BowERBANK, J. S., in Entomological Magazine, vol. i. 1833.

CCL. Carus, C. G. Entdeckung eines Blutkreislaufes in den Larven

netzfliiglicher Insecten. 4to. 1827.

CCLI. KiRBY and Spence. Introduction to Entomology 8vo. 1818-

1826.
CCLIL Newport. On the Organs of Reproduction, and the Develop-
ment of the Myriapoda, Philosophical Transactions, vol.
cxxxi. 1841.
CCLIII. DuFouR, Leon. Recherches Anatomiques et Physiologiques sur
divers Ordres des Insectes, in Memoires de I'Acad. Royale
des Sciences. Paris, tom. iv. vii. and xi.
CCLIV. De Geer. Abhandlungen zur Geschichte der Insekten. 4to.

1782.
CCLV. Savi. Osservazione per servire alia storia de una Specie de
Julns communissima, 1817.
CCLVI. Treviranus, G. R. & L. Vermischte Schriften. 1816-21.
CCLVIL DurouR, Leon, in Annales des Sciences Naturelles, vol. i.

1844.
CCLVIII. LoEW. Horge Anatomicse, i.
CCLIX. Sdccow, F. W. L. Ueber die Geschlechtsorgane der Insekten,

Heusinger's Zeitschrift, Bd. ii. 1828.
CCLX. SiEBOLD. Ueber die Inneren Geschlechtswerkzeuge der

Blattliiuse, Froriep's Neue Notizen. Bd. xii.
CCLXI. OcHSEXHEiMER, Fr. Die Schmetterlinge von Europa. 8vo.
1807-36.
CCLXII. Wagner, R. Beitriige zur Geschichte der Zeugung und
Entwickelung, Abhandlung Baier. Akad. Miinchen, Bd.
ii. 1837.
CCLXIII. SiEBOLD. Ueber der Fortpflanzung von Psyche, in Siebold und

KoUiker's Zeitschrift fiir Zoologie. 1848.
CCLXIV. KoLLiKER. Observationes de prima Insectorum Genesi. 4to.

1842.
CCLXV. BuRMEisTER. Haudbuch der Entomologle. 8vo. 1832.
CCLXV*. TuLK. On the Anatomy of the Phalangium Opilio, Annals of

Natural History, vol. xii. 1843.
CCLXVL Oken. Naturgeschichte fiir Schulen. 8vo. 1821.
CCLXVII. Smeathmax, H. On the Termites which are found in Afi-ica,

Philosophical Transactions, Ixxi. 1786.
CCLXVIII. Burnett, W. J. On the Generation of Aphides, American
Academy of Arts and Sciences. 1853.
CCLXrX. Reaujiur. Memoires pour servir a I'Histoire des Insectes.
1784.
CCLXX. Baer, Von, K. E. Ueber Entwickelungsgeschichte der Thicre.

4to. 1828
CCLXXI. Owen, R. Mollusca Cephalopoda. Description of Marine
Invertfbrate Animals, Appendix to Sir John Ross's Second
Arctic Voyage. 4to. 1835.
CCLXXH. Owen, R. Description of our extinct Genus of Cephalopod (Cocco-
teufhis), intermediate between Sepia and Loligo, Quarterly
Journal of the Geological Society, vol. xi. 1855.
CCLXXIII. Power, Mad. Jeanette. Osservazione fisiche sopra il polpo dell'
Argonauta Argo, della Socia Corrispondente Madame
Jeanette Power, Lette nella toruata del 26 Novembre, 1836.
Vol. xii. Atti Accademici Catania, 1838.

Ragguaglio delle Osservazione et Esperienze fatte sullo
Argonauta Argo (L.) da Madama Jeanette Power, del Pro-
fessore C. Maravigna. 8vo. Messina, 1836,
u u 3

662 WORKS REFERRED TO BY ROMAN NUMERALS.

Further Experiments and Observations on the Argonauta
Argo, by Mad. J. Power, communicated with remarks, by-
Prof. Owen, Trans. British Association. 1844.
CCLXXIV. MiJLLER, H. Ueber das Mannchen von Argonauta und der
Hectocotylen, Siebold's Zeitschrift fiir Zoologie. 1852.
CCLXXV. Verant. Mollusques Mediten-aneens. 4to. 1847-51- Ve-
rany and Vogt, Memoire sur les Hectocotyles et les Males de
quelques Cephalopodes, Annales des Sciences Nat. t. xvii.
1852.
CCLXXVI. CuviER. Memoire sur un Ver Parasite d'un nouveau Genre
(^Hectocotylus), Annales des Sciences Naturelles, vol. xviii.
1829.
CCLXXVn. KoLLiKEK, A. On the Male of the Argonaut, Transactions of
the Linnsean Society, vol. xx. 1843.
CCLXXVni. Hancock, A. On the Nervous System of the Ommastrephes
todarus. Annals of Natural History, vol. x. 1852.
CCLXXIX. Macdoxald, J. D. On the Anatomy of the Nautilus uvibili-
catus, Proceedings of the Royal Society. March, 1855.
CCLXXX. Bell, Th.P.L.S. History of British Crustacea. 8vo. 1840-52.
CCLXXXI. Si3iox, Dr. Ueber eine in den kranken und normallen Haar-
sacken des Menschen lebende Milbe, Miiller's Archiv fur
Physiologic. 1842.
CCLXXXn. EiCHHORN. Beytrage der Naturgeschichte der kleinsten TVas-

serthiere. 4to. 1781.
CCLXXXni. DuGES. Observations sur les Ai-aneides, Annales des Sciences

Nat. 1836.
CCLXXXrV. DoTERE. Memoire sur les Tardigrades, Annales des Sciences

Nat. t. xiv. 1840.
CCLXXXV. Kaufjiann. Ueber die Entwickelung der Tai'digrada, Sie-
bold's Zeitschrift fiir Naturgeschichte. 1851.
CCLXXXVI. ScHULTZE, C.A.S. 3Iacrobiotus Hufelandi, 8cc. 4to. 1834.
CCLXXXVn. Blackwall. Notice of several recent Discoveries in the
Structure and Economy of Spiders, Linnaan Transactions,
tom. xvi. 1833.
CCLXXXVIII. Blaxchard, Emile. De I'Appareil, Circulation, et des Organes
de la Respiration dans les Arachnides, Annales des Sciences,
Nat. 3°^e g^rie, tom. iii. 1849.
CCLXXXIX. Blackwall. A Catalogue of Spiders, with Remarks on their
Habits and Economy, Proceedings of Linna;an Society. 1848.
CCXC. WiTTiCH. Observationes qusedam de Aransearum ex ovo

evolutione. 1845.
CCXCI. BuRMEiSTER. Ucbcr die Gattung Achlisia, in Isis von
Oken. 1834.
CCXCn. DuFouR. Observations sur rAnatomie du Scorpion, Annals

des Sciences Nat. 1849.
CCXCni. MiJLLER, J. Beitrage zur Anatomic des Scorpions, Meckel's

Archiv fiir Physiologic. 1828.
CCXCrV. Edwards, Milne. Observations sur les Ascidiens composees,

M6mou-es de I'Acad. des Sciences, t. xviii. 1 840.
CCXCV. Satignt. Memoires sur les Animaux sans Vertebres. 8vo.

1816.
CCXCVL Sars, M. Zur Entwickelungsgeschichte der Mollusken und
Zooptiyten, Wiegmann's Archiv txir Naturgeschichte, 1837
and 1840.
CCXCVII. Van Beneden. Rechcrches sur I'Embryogenie, &c. des As-
cidies simples, Memoires de I'Acad. Roy. de Belgique.
1847.
CCXCVin. Etsenhardt, K. W. Ueber einige merkwiirdige Lebenser-
scheinungen an Ascidien, Nova Acta Acad. Nat. Cur. t. xi.
1823.
CCXCIX. EscHRiCHT. Anatomisk - physiologiske Undersogelser over
Salperne. 1841.

WORKS REFERRED TO BY ROMAN NUMERALS.

663

CCC. CuviER. Memoire sur les Lingules, Annales du Museum
d'Hist. Nat. torn, i, 1802
CCCL OwEX, R. On the Anatomy of the Brachiopoda of Cuvicr,

Ti*ansactions of the Zoological Society, vol, i. 1835.
CCCn. OwEx, E. Lettre sur I'Appareil de la Circulation chez les
Mollusques de la Classe des Brachiopodes, Annales des
Sciences Naturelles, torn. iii. 1845.
CCCIII. Owen, R. On the Anatomy of the Terebratula, Monographs

of the Palffiontographical Society. 4to. 1853.
CCCrV. Carpenter, W. Report on the Microscopic Structure of
Shells, Trans, of British xissociation. 1847.
CCCV. Davidson, Thos. Sketch of the Classification of the Recent
Brachiopoda, Annals of Natural Histoiy. 1852.
CCCVI. DA"vaDSON. Monograph on the Fossil Brachiopoda, Mono-
graphs of the Pala?ontographical Society. 1853-4.
CCCVII. Woodward, S. P. Rudimentary Treatise on Recent and Fcssil

Shells. 12mo. 1854.
CCCVm. VoGT. Anatomic der Lingula anatina, Neue Denkschriftcn
der Schweizerischen Gesellschaft fiir die gesammte Wissen-
schaften. Bd. vii. 1843.
CCCIX. Huxley, Th. Contributions to the Anatomy of the Brachio-
poda, Proceedings of the Royal Society, vol. vii. 1854.
CCCX. Carpenter, W. On a peculiar Arrangement of the sangui-
ferous System in Terebratula and certain other Brachiopoda^
Proceedings of the Royal Society, vol. vii. 1854.
CCCXI. Carlisle, Sir Anthony. Hunterian Oration. 1826.
CCCXII. Poll Testacea Utriusque Sicilise. Fol. 1791-95.
CCCXIII. SiEBOLD, C. Th. Ueber ein riithselhaftes Organ einiger Bi-

valven, Miiller's Archiv fiir Physiologic. 1838.
CCCXIV. Garner. On the Anatomy of the Lamellibranchiate Bivalves,

Zoological Transactions, vol. ii. 1835.
CCCXV. Alder and Hancock. On the Branchial Currents in Pholas

and Mya, Annals of Natural History. 1851.
CCCXVI. Will. Ueber die Augen der Bivalven und Ascidieu, Proriep's

Neue Notizen, No. 622. 1844.
CCCXVn. Osler, On burrowing and boring Marine Animals, Philoso-
phical Transactions. 1826.
CCCXVni. Owen, Richard. On the Stmcture of the Shell of the Water
Clam {Spondylus varius). Annals and Magazine of Natural
History, 2nd Series, vol. ii. 1838.
CCCXrX. Owen, Richard. Report on Animal Substances in the " Great
Exhibition" of 1851, chiefly used in Manufactures, as Imple-
ments or for Ornaments. 8vo. 1852.
CCCXX. Owen, Richard. On the Anatomy of Clavagella, Transactions

of the Zoological Society, vol. i. 1834.
CCCXXI. CuTiER. Memoires pour servir a THistoire et 1' Anatomic des

Mollusques. 4to. 1816.
CCCXXn. ]\L\LFiGHL Dissertatio epistolica de Bombyce. 4to. 1669.
CCCXXni. Krohn. Ueber die miinnlichen Zeugungsorgane der Ascidien

und Salpen, Froriep's Neue Notizen, No. 356. 1841.
CCCXXIV. Barry, Martin. Confirmation in two Quarters of the Penetra-
tion of a Spermatozoon into the Ovum of a Freshwater
Mussel, Monthly Journal of Medicine, January, 1855.
CCCXXV. Lubbock, J. On Calanidce, with Observations on the spermatic
Tubes ofPontella, Diaptomus, &c.. Annals of Natural Histoiy.
1853.
CCCXXVL Lea, Isaac. Observations on the Genus Unio and on the Naiades,

Trans. Amer. Phil. Societv, 2nd Series, vols. iii. iv.
CCCXXVn. De Blainville. Manuel de Malacologie. 8vo. 1 825.
CCCXXVHL Rathiu.', J. Om Dammuslmgen, Skrivter of Natiir-historie-
Selskabet, iv. Kjobenha^'^, 1797.
u u 4

664 WORKS REFERRED TO BY ROMAN NUMERALS.

CCCXXIX. Jacobson. Observations sur le Developpement pretendu des
CEiifs des Moulettes ou Unio et des Anodontes dans leurs
Branchies, Annales des Sciences Nat., t. xiv. 1828.
CCCXXX. Carus. Neue Untersuchungen iiber die Entwickelungsge-
schichte unserer Flussmuschel, Nova Acta Acad. Nat. Cur.,
torn. xvi. 1832.
CCCXXXI. ]Meckel, J. P. Beschreibung einer neuen Molluske, Arcliiv

fiir Physiologic, Bd. viii. 1823.
CCCXXXII. Hakcock, a. On the boring of the MoHusca into Rocks,

Annals of Natural History. 1848.
CCCXXXm. QuATREFAGES. Sur la Vie intrabranchiate des petites Ano-
dontes, Annales des Sciences Nat., t. iv. 1835, and t. v. 1836.
CCCXXXIV. LovEN. Ueber die Entwickclung der Mollusca acephala,

Wiegmann's Archiv fiir Naturgeschichte. 1849.
CCCXXXV. Edwards, Milne. Observations sur la Structure et les Fonc-
tions de quelques Mollusques, &c., Annales des Sciences
Nat., torn, xviii. 1842.
CCCXXXVI. Cha3iisso. De animalibus quibusdam e classe vermium Lin-

nteana. Fasc. i. De Salpis. 1819.
CCCXXXVn. BojANus. Ueber die Athem- und Kreislauf der zweischaligen
Muscheln. Isis, 1819.
CCCXXXVm. Forbes and Hanley. History of British Mollusca and their
Shells. 1853.
CCCXXXIX. EscHRicHT. Anatomische Untersuchungen iiber die Clio
Borealis. 4to. 1838.
CCCXL. NoRDMANN, A. Monographic des Tergipes Edwardsi, Bulletin
Phys, Acad, de Petersboui*g, t. iii. 1845.
CCCXLI. PoucHET, Prof. Recherches sur I'Anatomie et Physiologic des

Mollusques. 1842.
CCCXLH. QuATREFAGEs. Memoires sur les Gasteropodes Phlebenteres,
Annales des Sciences Nat. 1844.
CCCXLin. QuATREFAGEs. MeHioire sur I'Eolidine paradoxale, Annales

des Sciences Nat., t. xix. 1843.
CCCXLIV. Edwards, Milne. Observations sur les Mollusques Gastero-
podes designes sous le nom de Phlebenteres par M. de Qua-
trefages ; Comptes Rendus des Sciences, &c., t. xix. 1844.
CCCXL V. RoBix, Ch. Rapport sur les Communications de M. Souleyet
relatives a la question de Phlebenterisme. 8vo. 1851.
CCCXLVI. Hancock and Ejibleton. On the Anatomy of Eolis, Annals

of Natural History. 1845.
CCCXLVn. Edwards, Milne. Observations siu- la Circulation chez les
Mollusques, Annales des Sciences Naturelles, t. viii. 1847.
See xvi., p. 1.
CCCXLVIII. Alder and Hancock. Monographs of the British Nudibran-
chiate Mollusca (Ray Society).
CCCXLIX. Hancock, A. On the olfactory Apparatus of the BuUidee,
Annals of Natural History. 1852.
CCCL. Hancock, A. On the Anatomy of the Doris, Philosophical

Transactions. 1852.
CCCLI. Leidy. Terrestrial air-breathing Mollusks of the United

States, 1853.
CCCLH. KoREN and Danielssen. Bidrag til Pectinibranchiernes Ud-

viklingshistorie. 8vo. 1851. Supplement, 1852.
CCCLHI. Gegenbaur. Beitriige zur Entwickelungsgeschichte der Land-
gastropoden, Siebold's Zeitschrift fiir Naturgeschichte, Bd. iii.
1852.
CCCLIV. Van Beneden and "Windischman. Recherches sur I'Embiyo-
genie des Limaces, Miiller's Archiv fiir Physiologic. 1841.
CCCLV. Schmidt, Oscar. Ueber Entwickclung von Limax agrestis,

Miiller's Archiv fiir Physiologic. 1851.
CCCLVI. Garner, Robt. On the Nervous System of the Molluscous
Animals, Transactions of Linnaean Society, vol. xvii. 1837.

WORKS REFERRED TO BY ROMAN NUMERALS.

665

CCCLVII. Lespes. Recherches sur rCEil. 1851.
CCCLVIII. LovEN. De Dcntitione Molluscorum, Ofversigt af Kongl.
Vetenskaps-Akademiens Forhandlingar, June, 1857.
CCCLIX. Thompson, W. On the Dentition of British Pulmonifera, An-
nals of Natural History. 1851.
CCCLX. Meckel, H. Mikrographie eiiiiger Dmsenapparate der nie-
deren Thiere, Miiller's Archiv flir Physioiogie. 1846.
CCCLXI. Jacobsen. Ueber die Anwesenheit von Nieren in den Mol-

lusken, Meckel's Archiv f iir Physioiogie, Bd, vi. 1820.
CCCLXn. Wagner and Leuckardt. Article Semen in Cyclopaedia
of Anatomy, vol. iv. 1851.
CCCLXin. "Wagner, R,, in Wiegmann's Archiv f iii* Xaturgeschichte.

1836.
CCCLXI V. Meckel, H. Ueber den Geschlectsapparat einiger herraaphro-
ditischer Thiere, Miiller's Archiv fiir Physioiogie. 1844,
CCCLXV. Lund. Recherches sur les Enveloppes d'CEufs des Mollusquei
Gasteropodes, Aunales des Sciences Xat., 2d Series, vol. i.
1834.
CCCLXVL Dumortier. Sur les Evolutions de I'Embryon dans Ics Mol-
lusques Gasteropodes, Xouveaux Memoires de I'Academie
Royale de Bruxelles, torn. x. 1837.
CCCLXVII. Sars. Beitrag zur Entwickelungsgeschichte der Mollusken
und Zoophyten, Wiegmann's Archiv fiir Naturgeschichte.
1837 and 1840.
CCCLXVni Van Beneden. Recherches sur le Developpement des Aply-
sies, Annales des Sciences Nat., tom. xv. 1841.
CCCLXIX. LovEN, S. Bidi-ag till Kanedomen oni Utvecklingen af j\Iol-
lusca Acephala Lamellibranchiata, Kongl. Yetenskaps-Akad.
Handl. 1838.
CCCLXX. Allman. On the Anatomy of Actseon, Annals of Natural

History. 1845.
CCCLXXL VoGT. Recherches sur I'Embryogenie des Mollusques Gastero-
podes, Annales des Sciences Nat. 1846.
CCCLXXn. Carus, L. G. Neue Beobachtungen iiber das Drehen des Em-
bryo im Ei der Schnecken, Nova Acta Acad. Nat. Cur.
tom. xiii. 1827.
CCCLXXni. Della Chiaje. Memorie suUa Storia e Notomia degli Animali

senza Vertebre del Regno di Napoli, vol. iv.
CCCLXXIV. Grant, R. E. On the Existence and Uses of Cilia; in the
Young of the Gasteropodous Mollusca, Edinburgh Journal
of Science, vol. vii, 1827.
CCCLXXY. Pfeieeer, C. Naturgeschichte deutscher Land- und Suss-
Tvasser Mollusken. 4to. 1825.
CCCLXXVI. Jacquemin. Histoire du Developpement du Pkmorbis cornea,

Nova Acta Nat, Cur., tom. xviii. 1840.
CCCLXXYI*. QuATREFAGES. Memoire sur I'Embryogenie des Planorbes ct
des Limuees, Annales des Sciences Nat., 2ud Series, t. ii.
1841.
CCCLXX V 11. Aristoteles. De Animalibus Historiae Libri X. Ed. Schnei-
der. 8vo. 1811.
CCCLXXVDI. Needham, T. An Account of some Microscopical Discoveries
in the Calamaiy, and its wonderful Milt-vessels. 8vo. 1745,
CCCLXXIX. Hunter, John. Account of the Organ of Hearing in Fish,
Philosophical Transactions, vol. Ixxii.
CCCLXXX, Monro, A. The Structure and Physiology of Fishes, &c.

Fol. 1785.
CCCLXXXI, Rathke. Ueber Perothis, Memoires de I'Acad, Imp, de Pe-

tersbourg, tom, ii, 1833, '

CCCLXXXII. RuMPHius. D'Amboinische Raritat-kammcr. Fol. 1741.
CCCLXXXni Montport, D. Conchy liologie Systematique. 8vo. 1810. In
the Supplement of Sonnini's Edition of BufFon's Histoire
Naturclle.

666 WORKS REFERRED TO BY ROMAN NUMERALS.

CCCLXXXIV. Shaw, Dr. Naturalist's Miscellany, vol. xiv. 8vo. 1803.
CCCLXXXV. QuoY and Guimard. Description cl'un Fragment de Mollusqne
inconnu, presume etre celui du Nautiie flambe (A'autiius
Pompilius), Annales des Sciences Nat., t. xx. 1830.
CCCLXXXVI. Peron. Voyage de Decouverte aux Terres Australes. 4to.

1807—1816.
CCCLXXXVII. Owen, E. Memoir on the Pearly Nautilus (Nautilus Pompilius).
4to. 1832.
CCCLXXXVIIT. Valenciennes, Prof. Nouvelles Eecherches sur la Nautiie
flambe. Archives du Museum. 4to. 1839.
CCCLXXXIX. Owen, K. On a Specimen of the Pearly Nautilus obtained at
Amhoyna, Proceedings of the Zoological Society, October,
1842.
CCCXC. Van der Hoeven. Contributions to the Knowledge of the
Animal of JVautilus Pompilius, Zoological Transactions,
vol. iv. 1850.
CCCXCI. KoLLiKER, A. Entwickelungsgeschichte der Cephalopoden.
4to. 1844.
CCCXCII. BucKLAND, W. Bridgewatcr Treatise, Geology and Mine-
ralogy. 8vo. 1836.
CCCXCIII. Vrolik, Prof. On the Anatomy of the Pearly Nautilus, An-
nals of Natural History, vol. xii. 1843.
CCCXCI V. Miller, Hugh. My Schools and Schoolmasters. 8vo. 1854.
■ CCCXCV. Stokes, Charles. On some Species of Orthocerata, Geological
Transactions, 2nd Ser., vol, v. 1837.
CCCXCVI. Owen, R. Descriptions of certain Belemnites, preserved, with
a great proportion of their soft parts, &c., Philosophical
Transactions. 1844.
CCCXCVII. Owen, R. Description of some new and rare Cephalopoda,

Transactions of the Zoological Society, vol. ii. 1841.
CCCXCVin. Owen, R. On the Sex of the Argonauta Avith expanded arms
and shell, from an examination of specimens brought from
Sicily by Madame Power, Proceedings of the Zoological
Society, February 26th, 1839.
CCCXCIX. EscHRiCHT, Dr. Cirroteuthis Mulleri, eine neue Gattung der
Cephalopoden, Acta Acad. Ores. Nat Cm*., vol. xviii. 1836.
CCCC. Reinhardt and Prosch. Om Sciadephonis Miilleri. 4to. 1846.
CCCCI. Blainville, Prof. de. Sur I'Animal de la Spirule, Annales
Fran^. et Etrang. d' Anatomic et de Physiologic, t. i. 1837.
CCCCII. Owen, R. Descriptions of the Cephalopoda collected by
Capt. Sir E, Belcher, R.N., -svith an account of the xVnatomy
of the Spirula australis, Zoological Appendix to the "Voyage
of the Samarang." 4to. 1850.
CCCCni. Owen, R. On the Stnicture and Homologies of the Cephalic
Tentacles in the Pearly Nautilus, Annals of Natural History,
vol. xii. 1843.
CCCCIV. Owen, R. Article Cephalopoda, Cyclopaedia of Anatomy
and Physiology, vol. i. 1836.

667

GLOSSARY

OF ANATOMICAL AND OTHER SCIENTIFIC TERMS USED IN THESE

LECTURES.

Abdomeis. (Lat. ahdo, I conceal.) The posterior and principal cavity containing

the bowels and many other viscera of the animal. The abdomen is distinct from

the thorax in crustaceans, spiders, and insects.
Abdominales. (Lat. abdomen.) An order of fishes, so called from the attachment

of the ventral fins to the abdomen behind the pectorals.
Aberrant. (Lat. aberro, I wander from.) This term is applied to those species

Avhich deviate most from the type of their natural group.
Abranchiate. (Gr. cr, without ; bragchia, gills.) When an animal is devoid of

gills.
AcALEPHA. (Gr. akalephe, a nettle.) The class of radiated animals with soft

skins, which have the property of stinging like a nettle.
AcALEPHOiD. Like a Medusa or other common form of Acalepha.
AcANTHocEPHALA. (Gr. akanthos, a spine ; kephale, a head.) The order of intes •

tinal worms having the head armed with spines or hooks.
AcARUs. (Gr. akari, a mite.) The name of a genus of Arachnida, to which the

cheese-mite and allied species belong.
AcARiD^. The family of which the genus Acarns is the type.
AcASTA. (Gr. akaste.) A name arbitrarily applied to a genus of Barnacles, jiara-

sitic upon sponges.
Acephalous. (Gr. a, without ; ^ej9/w?e, head.) Headless. The animals in which

a distinct head is never developed.
AcEPHALOCTST. The parasitic hydatid, which consists of a cyst or bag without a

head.
AcErABiJLA. (Lat acetabulum, a shallow cup.) The fleshy sucking-cups with

Avhich many of the invertebrate animals are provided.
Acini. (Lat. acinum, a berry.) The secerning parts of glands, when they are

suspended like grains or small beiTies to a slender stem.
Acoustic. (Gr, akouo, I hear.) Appertaining to sound, or the organ of hearing.
AcRiTA. (Gr. akrifos, confused.) A term applied to the lowest animals, in which

the organs, and especially the nervous system, were supposed to be confusedly

blended with the other tissues.
Actinia. (Gr. aktin, a ray.) The genus of Polypes, which have many arms

radiating from around the mouth.
Actinoceros. (Gr. aktin, a ray ; keras, a horn.) A generic term, signifying the

radiated disposition of parts like horns.
Adipose. (Lat. adeps, fat.) Fatty.
Akera. (Gr. a, without ; keras, a horn.) The family of Mollusca, without horns

or feelers.
Alar. (Lat. ala, a wing.) Belonging to a wing.
Albuminiparous. a part, gland, or surface which secretes albumen.
Albuminous. (Lat. albumen, white of egg.) Consisting of albumen, or the sub-
stance which forms the white of an egg.
Aliform. Shaped like a wing.
Alternate generation. That modification of generation in which the young do

not resemble the parent, but the grand-parent j so that the successive series of in-

668 GLOSSARY.

dividuals seem to represent two species alternately reproduced, in which also
parthenogenesis alternates with the ordinary engendering by impregnation.

Alula. A little wing.

Ambdlacea. (Lat. ambulacrum, an avenue or place for walking.) The perforated

series of plates in the shell of the sea-star or sea-urchin.
Ambulatory. (Lat. ambulo, I walk.) An animal or a limb made for walking.
Ammonites. An extinct genus of Mollusca, allied to the Nautilus, which in-
habited a chambered shell, called Ammonite from its resemblance to the horns
on the statues of Jupiter Amnion.

Amorphous. (Gr. a, without ; morphe, form.) Bodies devoid of regular form.

Amrhipods. (Gr. amphi, on both sides ; pons, a foot.) The order of Crustacea,
which have feet for both walking and swimming.

Amphistoma. (Gr. amphi; stoma, a mouth.) The genus of suctorial parasitic
worms, which have pores like mouths at both ends of the body.

Ajipulla. (Lat. a bottle.) A membranous bag, shaped like a leathern bottle.

Anaima. (Gr. a, without ; aima, blood.) The name given by Aristotle to the
animals which have no red blood, and which he supposed to be without blood,

Analogue. A part or organ in one animal which has the same function as another
part or organ in a different animal. See Homologue.

Anastomose. (Gr. ana, through ; stojna, mouth.) When the mouths of two
vessels come into contact and blend together, or when two vessels unite as if
such kind of union had taken place.

Androgynous. (Gr. aner, a man ; gujie, a woman.) The combination of male
and female parts in the same individual.

Anellata. (Lat. annellus, a little ring.) The worms in which the body seems to
be composed of a succession of little rings, characterised by their red blood.

AnelliDe. The anglicised singular of Anellata.

Anenterous. (Gr. a, without ; enteron, a bowel.) Animals which have no in-
testinal canal.

Annulated. (Lat. annulus, a ring.) When an animal or part appears to be
composed of a succession of rings.

Anourous. (Gr. a, without ; oiira, a tail.) Tail-less.

Antenna. (From the Latin for yard-arm.) Applied to the jointed feelers or
horns upon the heads of insects and Crustacea, and sometimes to the analogous
parts, which are not jointed in worms and other animals.

Anthozoa. (Gr. anthos, a flower ; zoon, an animal.) The class of Polypes, in-
cluding the actinia and allied species, commonly called animal-flowers.

Antiperistaltic. (Gr. anti, against ; and peristaltic.') When the vermicular
contractions of a muscular tube follow each other in a direction the reverse of the
ordinary one.

Antlia, (From the Latin for pump.) Restrictively applied to the spiral instru-
ment of the mouth of butterflies and allied insects, by which they pump up the
juices of plants.

Aorta. (Gr. aorte, the wind-pipe ; and also the name of the great vessel spring-
ing from the heart, which is the trunk of the systemic arteries.) It is exclusively
applied in the latter sense in modern anatomy.

Aphidian. Belonging to the insect called aphis, or plant-louse.

Apical. (Lat. apex, the top of a cone.) Belonging to the pointed end of a cone-
shaped body.

Apodal. (Gr. a, Avithout ; poda, feet.) Footless ; without feet or locomotive
organs: fishes are so called which have no ventral fins.

Apterous. (Gr. a, without ; pteron, a wing.) Wingless species of Lisects or
Birds.

Arachnida. (Gr. arachne, a spider.) Spiders, and the animals allied to them in
structure.

Arborescent. (Lat. arbor, a tree.) Branched like a tree.

Arthrodial. (Gr. arthron, a joint.) It is restricted to that form of joint in
which a ball is received into a shallow cup.

Articulata. (Lat. articulus, a joint.) Animals with external jointed skeletons
or jointed limbs.

GLOSSARY. 669

AsciDiAN. (Gr. ashos, a bottle.) The shell-less acephalous Mollusks, which are

sliai:)ed like a leathern bottle.
Assimilation. (Lat. assimilatio.) The act by which organised bodies incorporate

foreign molecules and convert them into their own proper substance.
AsTOMATOus. (Gr. a, without ; stoma, a mouth.) Certain Infusoria Avhich have

no true or determinate mouth.
Atol. The name given by the Polynesians to certain forms of coral islands.
Automatic. (Gr. automatos, self-moving.) A movement in a living body without

the intervention or excitement of the will.
Axilla (from the Latin for armpit) ; and applied to other parts of the animal body

which form a similar angle.
AzYGOS. (Gr. a, without ; zugos, yoke.) Single, without fellow,

Baculite. An extinct genus of molluscous animals allied to the Nautilus, which

inhabited a straight-chambered shell, resembling a staff; whence the name of

the genus, from baculus, a staff.
Balanoids. (Gr. balanos, an acorn.) A family of sessile Cirripeds, the shells of

which are commonly called acorn-shells.
Basilar. (Lat. basis, a base.) Belonging to the base of the skull.
Batrachia. (Gr. batrachos, a frog.) The order of reptiles including the fi'og.
Belemnite. (Gr. belemnon, a dart.) An extinct genius of molluscous animals

allied to the sepia, and provided with a long, straight, chambered, conical shell in

the interior of the body.
Bifid. Cleft into two parts, or forked.
Bifurcate. Divided into two prongs or forks.
Bilateral. Having two symmetrical sides.
Bilobed. Divided into two lobes.
Bipartite. Divided into two parts.

BiRAMOUS. A limb which forks into two oar-like extremities.
Bituberculate. With two knobs or tubercles.
Bivalve. When a shell consists of two parts, closing like a double door. The

MoUusca, so protected, are commonly called bivalves.
Botiiriocephalds. (Gr. bothros, a pit; kephale, a head.) The genus of tape-worms

Avith depressions on the head.
BoTRYLLi. (Gr. botrus, a bunch of grapes.) A little cluster of berry-shaped

bodies.
Brachial. (Gr. brachion, the arm.) Belonging to the arm.
Brachiopoda. (Gr. brachion ; poda, feet.) A class of acephalous Mollusca, with

two long spiral fleshy ai'ms continued from the side of the mouth.
Brachyura. (Gr. brachus, short ; aura, tail.) The tribe of Crustacea with short

tails, as the crabs.
Brachydrous. Short tailed ; usually restricted to the Crustacea.
Braxchia. (Gr. bragchia, the gills of a fish.) The respiratory organs which

extract the oxygen from air contained in water.
Branchiopods. (Gr. bragchia, gills ; />o(/a, feet.) Crustacea in which the feet sup-
port the gills.
Bryozoa. (Gr. Srwow, moss ; 2:oon, animal.) A class of highly-organised Polypes,

most of the species of which incrust other animals or bodies like moss.
Buccal. (Lat. bucca, mouth or cheeks.) Belonging to the mouth.
Byssus (from the Greek word, signifying the silky filaments which project from the

bivalve called Pinna). Applied to the analogous parts in other Mollusks.

CuECUM and C^ca. (Lat. coecus, blind.) A blind tube, or productions of a tube

which terminate in closed ends.
Canthus. (Cty. (Jianthos.) The corner of the eye.
Capitate. (Lat. caput, head.) When a part is terminated by a knob like the

head of a pin.
Carapace. The upper shell of the crab or tortoise.
Cardia. (Gr. kardia, the heart or stomach.) The opening which admits the food

into the stomach ; also the region called the pit of the stomach.
Carnivorous. (Lat. caro, flesh; voro, I devour.) The animals which feed on flesh.

670 GLOSSARY.

Caruncle. (Lat. caruncula.) A soft wart-like eminence.

Caudal. (Lat. caitda, a tail.) Belonging to the tail.

Cauda Equina. The brush of nerves which terminates the spinal marrow in the

human subject, and the homologous part in the lower animals.
Cellular tissue. (Lat. cella, a cell.) The elastic connecting tissue of the dif-
ferent parts of the body, which every where forms cells or interspaces containing
fluid.
Centipede. (Lat. centum, a hundred ; pes, a foot.) A genus of insects with very

numerous feet.
Cephalo-thorax. (Gr. kephale, head ; thorax, chest.) The anterior division of
the body in spiders, scorpions, &c., which consists of the head and chest blended
together.
Ceppl\lic. (Gr. kephale, head.) Belonging to the head.
Cephalopoda. (Gr. kephale; poda, feet.) The class of molluscous animals in

which long prehensile processes or feet project from the head.
Cercari^. (Gr. kerkos, a tail.) The animalcules whose body is terminated by a

tail-like appendage.
Cercariform. Shaped like Cercariae.
Cerc^. (Gr. kerkos, a tail.) The feelers which project from the hind part of the

body in some insects.
Cerealia. {Ceres, the Goddess of corn.) The name of the natural family of plants

which produce corn, oats, rye, &c.
Cestoidea. (Gr. Aestos, a girdle.) The order of intestinal worms with long and

flat bodies like tape, usually called tape-worms.
Chelonia. (Gr. chelone, a turtle.) The order of reptiles including the tortoises

and turtles.
Chele. (Gr. chele, a claw.) Applied to the bifid claws of the Crustacea, scor-
pions, &c.
Chelicera. (Gr. chele, a claw; keras, a horn.) The prehensile claws of the

scorpion, which are the homologues of antennte.
Chilognatha. (Gr. cheilos, a lip ; gnathos, a jaw.) The order of many-footed in-
sects typified by the Gally-worm or lulus.
Chilopoda. (Gr. cheilos, a lip; poda, feet.) An order of many-footed insects

typified by the Centipede.
Chitine. (Gr. chiton, a coat.) The peculiar chemical principle wliich forms the

integument of insects.
Chlorophyll. (Gr. chloros, light green ; phyllos, a leaf.) The colouring matter

of the leaves and some other parts of plants.
Choledochus. (Gr. chole, bile ; d^che, receptacle.) The tube formed by the union

of the hepatic and cystic ducts.
Chorion, From the Greek word signifying the membrane which encloses the foetus

and applied generally to the outer covering of the ovum.
Chrysalids. (Gr. chrusos, gold.) The stage of the butterfly immediately preced-
ing its period of flight, when it is passive, and enclosed in a case which sometimes
glitters like gold .
Chyle. (Gr. chulos, juice.) The nutrient fluid extracted from the digested food

by the action of the bile.
Chyjie. (Gr. chumos, juice.) The digested food which passes from the stomach

into the intestines.
Cicatrix. From the Latin, signifying scar.

Cilia. (Lat. cilium, an eyelash.) 'I he microscopic hair-like bodies which cause,
by their vibratile action, ciu-rents in the contiguous fluid, or a motion of the body
to which they are attached.
Ciliated. Provided with vibratile cilia.

Ciliobrachiata. The class of Polypes in which the arms are pro-vided with vibra-
tile cilia.
CiLiOGRADES. (Lat. ciUum ; and gradior, I walk.) The order of AcalephiB which

swim by the action of cilia.
Circumgyrations. (Lat. circiim, around ; gyrus, a circle.) IMotions in a circle.
Cirri. (Lat. cirrus, a curl.) The curled filamentary appendages, as the feet of the
barnacles.

GLOSSARY. 671

CiRRiGEROUs. Supporting cirri.
CiiiRiGRADES. Moving by cirri.
CiERiPEDS or CiRRiPEDiA, (Lat. cirrus, a curl ; pes, a foot.) A class of articulate

animals having curled jointed feet. Sometimes written Cirrhipedia and Cirrho-

poda.
Clavate. (Lat. clavus, a club.) Club-shaped ; linear at the base, but growing

gradually thicker towards the end.
Cloaca. (Lat. cloaca, a sink.) The cavity common to the termination of the in-
testinal, urinary, and generative tubes.
Cltpeiform. (Lat. clypeus, a shield ; forma, shape.) Shield -shaped ; applied to

the large prothorax in beetles.
Coarctate, (Lat. coarcto, I compress.) The pupa of an insect, which is enve-
loped by a case, which gives no indication of the parts it covers.
Coelelminth A. (Gr. ^oz7os, hollow ; hehnins, an intestinal worm.) The intestinal

worms which are hollow, and contain an ahmentary tube in the cavity of the body.
CoLEOPTERA. (Gn koleos, a sheath ; pteron, a wing.) The order of insects in

which the first part of wings serves as a sheath to defend the second pair.
Columella. (From the Latin for a small column.) Used in Conchology to signify

the central pillar around which the spiral shell is wound.
CoioiissuRAL. (Lat. committo, I solder.) Belonging to a line or part by which

other parts are connected together.
CoNCHiFERS. (Lat. concha, a shell ; fero, I bear.) Shell-fish ; usually restricted

to those with bivalve shells.
CoNDYLOPODS. (Gr. kondulos, a joint ; pons, a foot.) The articulate animals with

jointed legs, as insects, crabs, and spiders.
CoRiACEOcs. (Lat. corium, hide.) When a part has the texture of tough skin.
CoRNDA. (Lat. cornu, a horn.) Horns or horn-like processes.
Cornea. (Lat. corneus, horny.) The transparent horny membrane in front of

the eye.
Corneous. Horny.
CoRNECLE. Diminutive of cornea ; applied to the minute transparent segments

which defend the compound eyes of insects.
Cretaceous (Lat. creta, chalk.) Belonging to chalk.
Crinoid. (Gr. krinon, a lily ; eidos, like.) Belonging to the Echinoderma which

resemble lilies ; the fossils called stone-lilies or encrinites are examples.
Crura. (Lat. cms, a leg.) The legs of an animal, or processes resembling legs.
Crustacea. (Lat. crusta, a crust.) The class of articulate animals with a hard

skin or cmst, which they cast pei-iodically.
Crtptobranchiate. (Gr. kruptos, hidden ; bragchia, giUs.) Those molluscous

and articulate animals, which have no conspicuous giUs.
Cryptogamic. (Gr. kruptos, concealed ; gamos, marriage.) The animals or plants

in which the organs of generation are concealed.
Cyclobranchiata. (Gr. kuklos, round ; bragchia, gills.) The molluscous animals

which have the gills disposed in a circle.

Decapoda. (Gr. deca, ten ; pons, a foot.) The crustaceous and molluscous ani-
mals which have ten feet.

Decollated. (Lat. decollo, to behead.) The univalve shells in which the apex or
head is worn off in the progress of growth.

Deciduous. Parts which are shed, or do not last the lifetime of the animal.

Dehiscence. (Lat. dehisco, to gape.) The splitting open of the bag containing
the eggs.

Deflected. Bent down.

Demodex. (Gr. demos, lard ; dex, a boring worm.) The worm-like parasite of
the human sebaceous follicles.

Dendritic. (Gr. dendron, a tree.) Branched like a tree.

Dermal. (Gr. derma, skin.) Belonging to the skin.

Diagnosis. (Gr. diagignosco, I distinguish.) The scientific distinction of one ani-
mal or part from another, or the definition of its essential characters.

Dibranchiata. (Gr. dis, twice; bragchia, gills.) The order of Cephalopods
having two gills.

672 GLOSSARY.

DicosLous. (Gr.dis; koihs, a cay'ity.) A heart with two cavities.

DiDACTTLE. (Gr. (lis ; and dactulos, a finger.) A limb terminated by two fingers.

Digitate. (Lat. digitus, a finger.) When a part sxippoits processes like fingers.

Dimidiate. (Lat. dimidium, half.) Divided into two halves.

Dioecious. (Gr. dis, twice, and oikos, a house.) The species which consist of

male and female individuals.
Dimtary. (Gr. dis ; muo7i, a muscle.) A bivalve whose shell is closed by two

muscles.
DiPTERA. (Gr. dis ; pteron, a wing.) The insects which have two wings.
Discoid. (Lat. discus, a quoit.) Quoit-shaped.

Distoma. ({j(\: dis ; stoma, month.') The intestinal worms with two pores.
Diverticulum. (From the Latin for a bye-road.) Applied to a bUnd tube

branching out from the course of a longer one.
Dorsad. (Lat. dorsum, the back.) Towards the back.
Dorsibranchiate. (Lat. dorsum ; and bragchia, gills.) The Mollusca with gills

attached to the back.
Dorso-intestinal. a part which is on the dorsal aspect of the intestine.
Ductus. A duct or tube which conveys away the secretion of a gland.
Duodenum. The first portion of the small intestine, which, in the human subject,

equals the breadth of twelve fingers.

Ecdtsis. (From the Greek, signifying the act of stripping.) Moulting of the

skin.
Eciiinoderms. (Gr. echinos, a hedgehog ; derma, skin.) The class of radiated

animals, most of which have spiny skins.
Edentulous. From the Latin word for toothless.
Edriophthalivia. (Gr. edraios, sitting or sessile ; and ophthalmos, an eye.) The

Crustacea with sessile eyes.
Elytra. (Gr. elutron, a sheath.) The wing sheaths formed by the modified an-
terior pair of M'ings of beetles.
Emarginate. (Lat. emargino, to remove an edge.) When an edge or margin

has, as it were, a part bitten out.
Emunctories. (Lat. emungo, to wipe the nose.) Parts which carry out of the

body useless or noxious particles.
Enaliosaur. (Gr. enalios, marine ; sauros, a lizard.) An extinct order of marine

gigantic reptiles allied to crocodiles and fishes.
Encephala. (Gr. en, in ; kephale, head.) The molluscous animals which have a

distinct head.
Entomology. (Gr. entoma, insects ; logos, a discourse.) The department of Na-
tural History which treats of insects.
Entomostraca. (Gr. entoma, insects ; ostracon, a shell.) The order of small

Crustaceans, many of which are enclosed in an integument, like a bivalve shell.
Entozoa. (Gr. entos, within ; zoon, animal.) The animals which exist within

other animals.
Eocene. (Gi\ eos, the dawn ; kainos, recent.) The tertiary period, in which the

extremely small proportion of living species indicates the first commencement or

dawn of the existing state of animate creation.
Epiderbial. (Gr. epidermis, the cuticle.) Belonging to the cuticle or scarf-skin.
Epimeral. (Gr. epi, upon; meron, a limb.) The part of the segment of an ar-
ticulate animal which is above the joint of the limb.
Epiploon. (From the Greek.) It is the fatty membrane which covers or occupies

the interspaces of the entrails in the abdomen.
Episternal. (Gr. epi, upon ; sternon, the breast-bone.) The piece of the segment

of an articulate animal which is immediately above the middle inferior piece or

sternum.
Epithelium. The thin membrane which covers the mucous membranes : it is

analogous to the epiderm of the skin.
Epizoa. (Gr. epi, upon ; zooii, animal.) The class of low organised parasitic

Crustaceans which live upon other animals,
Errantes. (Lat. erro, I wander.) An order of the class Annelida, remarkable

for their locomotive powers.
Excito-motory. The function of the 'nervous system by which an imp'-cssion is

GLOSSARY. 673

transmitted to a centre, and reflected so as to produce contraction of a muscle

without sensation or volition.
ExosMosE. (Gr. ex, out of; otheo, I expel.) The act in which a denser fluid is

expelled from a membranous sac by the entry of a lighter fluid from without.
ExcviUM. (From the Latin, signifying the skin of a serpent.) The skin which is

shed in moulting.
ExuviAL. Any part which is moulted.

Facet. (From the French.) A flat surface, with a definite boundary.

Fascicle. (From the IjHi'm fasciculus.) A small bundle.

Filiform, (hat. Jilum, a thread ; forma, a shape.) Thread-shaped.

FissiPAROUS. (Lat. findo, I cleave ; pario, I produce.) The multiplication of a
species by the self-cleavage of the individual into two parts.

Flabelliform. (LatJlabeUum, a fan.) Fan-shaped.

Flagellum. (From the Latin.) An appendage to the legs of the Crustacea re-
sembling a whip.

Flexors. (Lat. j^ecto, I bend.) The muscles employed in bending a limb.

Flexuous. a bending course.

Foliaceods. (Lat. folium, a leaf.) Shaped or arranged like leaves.

Follicle. (Lat. folUculus, a small bag.) Minute secreting bags which conmionly
open upon mucous membranes.

FossiLiFEROus. (Lat. fossHis, any thing dug out of the earth ; and f era, I bear.)
Applied to the strata which contain the remains of animals and plants, to which
remains Geologists now restrict the term Fossil.

FucivoRODS. (Lat. /?/cM5, sea-weed; and roro, I devour.) Animals which subsist
on sea-weed.

Fusiform. (Lat. /m5M5, a spindle; andybrnicr, a shape.) Spindle-shaped.

Ganglion. (Gr. gagglion, a knot.) A mass of nervous matter, forming a centre
from which nervous fibres radiate.

Gastropoda. (Gr. gaster, stomach ; pons, a foot.) That class of molluscous
animals which have the locomotive organ attached to the under part of the body.

Gemmiparous. (Lat. gemma, a bud; par/o, I bring forth.)' Propagation by the
growth of the young, like a bud from the parent.

Gemmule. (Dim. of gemma.) The embryos of the radiated animals at that stage
when they resemble ciliated monads.

Germen. In plants, the part answering to the ovarium in animals.

Germ-cell. The first nucleated cell that appears in the impregnated ovum, after
the reception of the spermatozoon and the disappearance of the germinal vesicle.
The germ-cell assimilates the surrounding yolk and propagates its kind by spon-
taneous fission, whence the first or parent-cell has been tci'med the " primary
germ-cell," and its progeny the " derivative germ-cells."

Germ-mass. The material prepared for the formation of the embryo, consisting
of the derivative germ-cells and the yolk which they have assimilated.

Germ-vesicle or Germinal vesicle. The nucleated cell which is the first formed
and most essential pai-t of the ovum ; it is surrounded by the yolk, and usually
passes to the periphery of that part prior to impregnation.

Germ-yolk. That portion of the primary yolk of the egg which is assimilated by
the germ-cells in the formation of the germ-mass. In some animals the whole
yolk is so assimilated, in others (sepia, e. g.) only a small portion, the remainder
being the " food-yolk," and absorbed by the future embryo or young animal.

Globose. (Lat. globus, a globe.) Globe-shaped.

Glossology. (Gr. glosse, the tongue ; Gr. logos, discourse.) The science of
scientific language.

Granules. (Dim. of granum, a grain.) Little grains.

Gynglymoid. (Gr. gigglumos, a hinge.) A joint formed for motion on one plane.

Haustellate. (Lat. haurio, I drink.) The structure of mouth adapted for
drinking or pumping up liquids ; also the insects which possess that kind of
mouth.

Helminthoid. (Gr. helmins, an intestinal worm.) AYorm-shaped.

X X

674 GLOSSARY.

HE3IELTTKA. (Gr. hemisu, half ; elytron^ a sheath.) A wing, of which one half is

opaque and firm like an elytrum.
Hemiptera. (Gr. hemisu, half ; ptero?i, a wing.) The order of insects in which

the anterior wings are heraelytra.
Hepatic. (Lat. hepar, liver.) Belonging to the liver.
Herbivorous. (Lat. herba, grass ; voro, I devour.) The animals which subsist

on grass.
Hersiapiirodite. {Hermes, Mercury ; Aphrodita, Venus.) An individual in

which male and female characteristics are combined.
Heterogaagliate. (Gr. Aete/-os, diverse ; gagglion.) The animals with the gan-
glionic ncrA'ous system, and the ganglions scattered, often unsymmetrically.
Heteromorphous. (Gr. heteros, another ; viorphe, form.) Of an irregular or

unusual form, applied to the larvae of certain insects which differ in form from

the imago, and applicable to the true larval state of all insects.
Hexapod. (Gr. hexa, six ; pons, a foot. ) The animals with six legs, such as true

insects.
Histological. (Gr. histos, a tissue ; logos, discourse.) The doctrine of the tissues

which enter into the formation of an animal and its different organs.
Homogangliate. (Gr. homos, like ; gagglion.) The animals with the ganglionic

nei'vous system and symmetrical arrangement of the ganglions.
Homologue. (Gv. homos ; /o^os, speech.) The same organ in different animals

under every variety of form and function.
HoMOMORPHOUS. (Gr. homos, like ; morphe, form.) Of similar form.
HoMOPTERA. (Gr. homos, like ; pteroji, a wing.) The insects in which the four

wings have a similar structure, but restricted, in its application, to a section of

Hemiptera.
Hyaline. (Gr. hualos, crystal.) The pellucid substance which determines the

spontaneous fission of cells.
Hydatid. (Gr. hudatis, a vesicle.) A bladder of albuminous membrane, con-
taining serous fluid ; generally detached ; sometimes with an organised head

and neck.
Hydra. (Gr. hudra, a water-serpent.) The modern generic name of certain

freshwater Polypes.
Hydrieorm. Similarly-formed Polypes to the Hydra.
Hydrozoa. (Gr. hudra; zoon, animal.) The class of Polvpi organised like the

Hydra.
Hymenoptera. (Gr. /iw/wen, a membrane ; pteron, awing.) The order of insects

including the bee, wasp, &c. which have four membranous wings.

Imbricated. (Lat. iinbricatus, tiled.) Scales which lie one upon another like
tiles.

Ingluvies. a crop or partial dilatation of the cesophagus.

Inopercttlar. Univalve shells Avhich have no operculum or lid.

Instrumenta Cibaria. (Lat. cibus, food.) The parts of the mouth in insects
concerned in the acquisition and preparation of the food.

Interambulacra. The imperforate plates which occupy the intervals of the per-
forated ones, or ambulacra, in the shells of the Echinoderms. See Ambulacra.

Interganglioxic. (Lat. inter, between ; and gagglion.) The nervous chords in
the intervals of the ganglions, which they connect together.

Interstitial. (Lat. interstitium.) Relating to the intervals between parts.

Intra-uterine. (Lat. m^z-cf, within ; w^erMS, the womb.) That whicli is, or takes
place, within the womb.

Intussusception. (Lat. intus, within ; suscipio, I take up.) The act of taking
foreign matter into a living being. Also the state of a part of a tube when it is
inverted within a contiguous part.

Invaginated. (Lat. in ; vagina, a sheath.) When a part is contained in another,
as in a sheath.

Intertebrata. (Lat. in, used in composition to signify not, like tin ; vertebra, a
bone of the back.) Animals without back -bones.

IsocYCLOus. (Gr. isos, equal ; kuklos, a ring.) An animal composed of a succes-
sion of equal rings.

GLOSSARY. 675

IsoPODA. (Gr. isos, equal ; pons, a foot.) An order of Crustaceans in which the
feet are alike, and equal.

Labium. Latin for a lip ; but applied only to the lower lip in Entomology.

Labrum. Latin for a lip ; but applied only to the upper lip in Entomology.

Lamellibraxchiata. (Lat. lamella, a plate ; bragchia, gills.) The class of ace-
phalous jNIollusks with gills in the form of membranous plates.

LA3IELL1FOKM. Shaped like a thin leaf or plate.

L-VNiARiFORM. (Lat. lanio, to cut or tear ; forma, shape.) Shaped like the canine
teeth of the Caruivora, which are called laniaries from their office.

Larva. (Lat. larva, a mask.) Applied to an insect in its first active state, which
is genei-ally ditferent from, and as it were masks the ultimate form. Larviform,
shaped like a larva.

Larviparous. (Lat. larva; pario, I produce.) The insects which produce their
young in the condition of larva.

Lemniscus. (TJie Latin for riband.) Applied to the minute riband-shaped ap-
pendages of the generative pores in Entozou.

Lepidoptera. (Gr. lepis, a scale ; pteron, a wing.) The order of insects in which
the wings are clothed with fine scales, as butterflies and moths.

Macroura. (Gy. mafiros, long ; owra, tail.) The tribe of decapod Crustacea wdiich
have long tails, as the lobster.

Malacology. (Gr. malakos, soft ; logos, discourse.) The histoiy of the soft-
bodied or molluscous animals, which Avere termed Malakia by Aristotle.

Malacostraca. (Gv. malakos ; ostrakon, a, &\\q\\.^ The name given by Aristotle
to the modern Crustacea, because their shells were softer than those of the Mol-
lusca, or ordinary shell-fisb.

Mamm^vlia. (Lat. mamma, a breast.) The class of animals which give suck to
their young.

Mandibulata. (Lat. mandibula, a jaw.) The insects which have mouths pro-
vided Avith jaws for mastication ; the term mandible is restricted in Entomology
to the upper and outer pair of jaws.

Mantle. The external soft contractile skin of the Mollusca, which covers the
viscera and a great part of the body like a cloak.

Marsupial. (Lat. marsupium, a purse.) The tegumentary pouch, in which the
embr3'o is received after birth, and protected during the completion of its de-
velopment.

Mastodon. (Gr. mastos, a teat; odon, a tooth.) A genus of extinct quadrupeds
allied to the ele])hant, but having the grinders covered Avith conical protuberances
like teats.

Maxilla. (From the Latin for a jaw.) In Entomology restricted to the inferior
pair of jaws.

Median. Having reference to the middle line of the body.

Medulla oblongata. The oblong medullary column at the base of the brain, from
Avhich the spinal chord or marrow is continued.

JMedus^. a genus or family of soft radiated animals or acalephes, so called because
their organs of motion and prehension are spread out like the snaky hair of the
fabulous Medusa.

Mesentery. (Gr. mesos, intermediate ; and enteros, entrail.) The membrane
Avhich foi'ms the medium of connection between the small intestines and the
abdomen.

Mesogastric. (Gr. mesos; and gaster, stomach.) The membrane Avhich forms
the medium of attachment of the stomach to the Avails of the abdomen.

Mesonotum. (Gr. mesos, middle ; notos, back.) The middle piece of that half of
segment Avhich covers the back.

Mesosternum. (Gr. mesos ; sternon, breast.) The middle part of that half of the
segment Avhich covers the breast.

ISIesothorax. (Gr. mesos, middle ; and thorax, the chest.) The intermediate of
the three segments Avhich form the thorax in insects.

Metabola. (Gr. metabole. change.) Those insects which undergo a metamor-
phosis.

X X 2

676 GLOSSARY.

Metagenesis. (Gr. meto, indicating change; gignomai,! jivodnce.) The changes
of form which the representative of a species of animal or phint undergoes in
passing by a series of successively generated individuals from the egg to the
mature or imago state. It is distinguished from " metamorphosis," in which
those changes are undergone in the same individual.

Metamorphosis. (Gr. tyieta, signifying change; and morphe, form.) The change
of form which the individual of certain species undergoes in passing from one
stage of existence to another.

Metatitorax (Gr. 7neta, after; thorax.) The hindmost of the three segments
which compose the thorax of an insect.

Miocene. (Gr. meiou, less; kainos, recent.) The tertiary epoch in which a
minority of fossil shells are of the recent species.

Molecules. (Dim. of moles, a mass.) Microscopic particles.

MoLLCscA. (Lat. mollis^ soft.) The primary division of the Animal Kingdom,
characterised at page 13.

Monad. (Gr. moiias, unity.) The genus of the most minute and simple micro-
scopic animalcules, shaped like spherical cells. Monadiform, like a monad.

Monadiary. The common envelope of many organically associated monads.

MoNiLiFORM. (Lat. monile, a necklace.) A structure like a necklace or string of
beads.

MoNocARPOus. (Gr. monos, single; carpos, fruit.) An animal or plant which
perishes when they have once borne fruit.

MoNOCULUS. (Gr. monos, single ; Lat. oculus, an eye.) The animals which have
but one eye.

Moncecious. (Gr. monos, single ; and oikos, house.) Organisms whose structure
is both male and female.

MoNOMYARY. (Gr. vionos, single; muon, a muscle.) A bivalve whose shell is
closed by one adductor muscle.

MoNOTHALAMOus. (Gr. monos ; thalamos, a chamber.) A shell forming a single
chamber, like that of the whelk.

Morphology. (Gr. mor^Ae, form; Zo^o5, discourse.) The history of the modifica-
tions of fonn which the same organ undergoes in the same or in different
organisms.

Motor Y. The nerves which excite and control motion.

MuLTivALVE. (Lat. multus, many; valvcE, folding-doors.) Shells composed of
many pieces or valves.

Myelencephala. (Gr. muelos, marrow; egkephalon, brain.) The primary divi-
sion of animals chai*acterised by a brain and spinal marrow.

Myriapoda. (Gr. mwios, ten thousand ; pons, foot.) The order of insects cha-
racterised by their numerous feet.

Nacreous. Pearly, like mother-of-pearl.

Natatory. An animal or part formed for swimming.

Nematoidea. (Gr. nema, a thread; eidos, like.) The intestinal worms, which

are long, slender, and cylindrical like threads.
Nematoneura. (Gr. nema, a thread; neuron, a nerve.) The animals in which

the nervous system is filamentary, as in the star-fish.
Nervures. (Lat. nervus, a sinew.) The delicate frame-work of the membranous

wings of insects.
Neurilemma. (Gr. neuron, a nerve ; lemma, a covering.) The membrane which

surrounds the nervous fibre.
Neurology. {Gv. 7ieuron, a nerye; Zo^os, a discourse. ) The science of the nervous

system.
Neuroptera. (Gr. neuron, a nerve ; pteron, a wing.) The order of insects with

four wings, characterised by their numerous nervures, like those of the dragon-

fly.

Nidamental. (Lat. nidus, a nest.) Relating to the protection of the egg and
young, especially applied to the organs that secrete the material of which many
animals construct their nests.

Nodule. (Dim. of jiodus, a knot.) A little knot-like eminence.

Normal. (Lat. norma, rule.) According to rule, ordinary or natural.

GLOSSARY. 677

NoTAL. (Gr. 7iotos, the back.) Belonging to the back.

Nucleated. Having a nucleus or central particle ; applied to the elementary
cells of animal tissues, the most important properties of Avhich reside in the nu-
cleus.

NuDiBRACHiATE. (Lat. nudus, naked ; brachia, arms.) The Polypes, whose arms
are not clothed with vibratile cilia.

NuDiBRANCHiATE, (Lat. nudus, naked; bragchla, gills.) An order of Gastro-
pods in which the gills are exposed.

OcTOPODA. (Gr. octo, eight ; pons, a foot.) Animals with eight feet. The name

of the tribe of Cephalopods with eight prehensile organs attached to the head.
CEsoPHAGDS. The gullet or tube leading from the mouth to the stomach.
Olfactory. (Lat. olf actus, the sense of smelling.) Relating to that sense.
Onychoteuthis. (Gr. onux, a hook ; teuthis, a calamary.) The genus of Cala-

maries armed with hooks or claws.
Oolite. (Gr. oon, egg ; lithos, stone.) An extensive group of secondary lime-
stones, some of which are composed of rounded particles, like the roe or eggs of a

fish.
Operculum. (From the Latin for lid. ) Applied to the horny or shelly plate

which closes certain univalve shells ; also to the covering of the gills in fish, and

to the lids of certain eggs.
Oral, (Lat. os, the month.) Belonging to the mouth or to speech.
Orthocera and Orthoceratite. ( Gr. orthos, straight ; keras, horn.) The extinct

Cephalopods which inhabited long conical chambered shells like a straight horn.
Ortiioptera. (Gr. orthos, straight ; pteron, a wing. ) The order of insects, with

elytra and longitudinally folded wings.
Osseous. (Lat os, a bone.) Bony.

Otolithes. (Gr. o?«, an ear ; lithos, a stone.) Tlie stony or chalky bodies be-
longing to the internal ear.
Ovarium. (Lat. ovum, an egg.) The organ in which the eggs or their elementary

and essential parts are formed.
OvicAPSULE. (Lat. ovum, an egg ; capsula, a bag.) An egg-bag formed by

some membrane or secretion of the animal.
OviGEROUs. (Lat. ovum, an egg ; gero, I bear.) Animals or parts containing or

supporting eggs.
Oviparous. (Lat. ovum; pario, I bring forth.) The animals which bring forth eggs.
Ovipositor. (Lat. ovum ; pom, I place.) The organ in insects, which is often

large and complicated, for the transmission of the eggs, during exclusion, to

their appropriate place.
OvoviviPAROUS. (Lat. ovum, egg ; vivus, alive ; pario, I produce.) The animals

which produce living young, hatched in the egg within the body of the parent,

without any connection with the womb.

Palaeontology. (Gr. palaios, ancient ; onta, beings ; logos, discourse.) The

history of ancient extinct organised beings.
Pallial. (Lat. pallium, a cloak.) Relating to the mantle or cloak of the Mol-

lusca.
Palliobranchiata. (Lat. pallium; bragchia, gills.) The class of acephalous

Mollusca in which the gills are developed from the mantle.
Palpi. (Lat.pa/po, I touch.) The organs of touch developed from the labium

and maxillffi of insects.
Papilla. (Lat. for nipple.) Minute soft prominences generally adapted for

delicate sensation.
Papyraceous. (Gr. papuros_, paper.) Of the consistency of paper.
Parenchyma. The soft tissue of organs; generally applied to that of glands. ^
Parietes. (Lat. paries, a wall.) The walls of the dirterent cavities of an animal

hody. . _

Parthenogenesis. (G\\ parthenos, a virgin; gignomai, to be born.) Propagation

by self-splitting or self-dividing, by budding from without or within, and by any

mode save by the act of impregnation; the parthcnogcnetic individuals being

sexless or virgin females.

X X 3

678 GLOSSAKY.

Pectinated. (Lat. pecten, a comb.) Toothed like a comb.

Pectinibranciiiata. (Lat. /lecten, a comb; bragchia, q'iWs.) The order of Gas-
tropods in which the gills are shaped like a comb.

Pediform. (LiVlL pes, afoot.) Shaped like a foot.

Peduncle. JFrom the Latin pedunculus, a stalk.

Pedunculated. Suspended or supported by a stalk.

Pelagic (Gr. pelagos, sea.) Belonging to the deep sea,

Pentacrinite. (Gr. penta, five ; krinos, hair.) A pedunculated star-fish with five
rays : they are, for the most part, fossil.

Pergameneous. (Lat. pergamen, parchment.) Of the texture of parchment.

Periostracum. (Gr. peri, around ; ostrakon, shell.) The membrane analogous to
scarf-skin, which covers shell.

Peristaltic. (Gr. peri; stello, to range.) The vermicular contractions and motions
of muscular canals, as the alimentary, the circulating, and generative tubes.

Peritoneal. (Gr. peritojiaios, the covering of the abdomen.) Restricted to the
lining membrane of that cavity.

Peritrema. (Gr. peri, around ; trema, hole.) The raised margin which sur-
rounds the breathing holes of scorpions.

Petiolate. (Lat. petiolus, a fruit stalk.) Ducts supported or suspended by a
slender stalk.

Pharynx. The dilated beginning of the gullet.

Pharyngeal. Belonging to the pharynx.

Phragmocone. (Gr. pliragma, a partition ; konos, a cone.) The chambered cone
of the shell of the Belemuite.

Piiysograde. (Gr. physis, air ; and gradior, I proceed.) The Acalephes that
swim by means of air-bladdeis.

Phytophagous. (Gr. phiiton, a plant ; phago, I eat.) Plant-eating animals.

Pigmental. (Lat. pigmentum, paint.) The cells which secrete the coloured par-
ticles of the skin and eye, and the membrane formed by such cells.

Pinnate. (Lat. pinna, a feather or fin.) Shaped like a feather, or provided with fins.

Planula. (Iu2it. planus, flat.) A name applied to the flat ciliated form of larva,
under which many polypes first quit the egg.

Plasma. (Gr. plasma, mouldable matter.) The fluid part of the blood, in which
the red corpuscles float : also called liquor sanguinis

Plastron. The under part of the shell of the crab and tortoise.

Plexus. (Gr. pleko, I twine.) A bundle of nerves or vessels interwoven or
twined together.

Pleiocene. (Gr. pleion, more ; kainos, recent.) The tertiary strata, -which are
more recent than the mioccne, and in which the major part of the fossil testacea
belong to recent species.

Pleistocene. (Gr. pleistos, most ; kainos, recent.) The newest of the tertiary
strata, which contains the largest proportion of living species of shells.

Plic.e. (Lat. plica, a fold.) Folds of membrane.

Plumos. (Lat. pluma, a feather. ) Feathery, or like a plume of feathers.

Pneumatic. (Gr. jmeuma, breath.) Belonging to the air and air-breathing organs.

Podophthalma. (Gr. pous, a foot ; ophthalmos, an eye.) The tribe of Crustacea
in which the eyes are supported upon stalks.

PoLYGASTRiA. (Gy. polus, many ; gasfer, a stomach.) The class of infusorial ani-
malcules which have many assimilative sacs or stomachs.

PoLYPL (Gr. polus ; pous, a foot.) The class of zoophytes with many prehensile
organs radiating from around the mouth.

Prolegs. The wart-like tubercles which represent legs on the hinder segment of
caterpillars.

Prothorax. (Gr. p7r>, before, and thorax.') The first of the three segments which
constitute the thorax in insects.

Psychical. (Gr. psuche, the soul.) Relating to the phenomena of the soul, and
to analogous phenomena in the lower animals.

Pteropoda. (Gr. pteron, a wing ; pous, a foot.) The class of MoUusca in which
the organs of motion arc shaped like wings.

Pulmograde. (Lat. pulmo, a lung ; gradior, I walk ) The tribe of Medusse
Avhich swim by contractions of the respiratory disc.

Pulmonata. (Lat pulmo.) The order of Gastropods that breathe by lungs.

GLOSSARY. 679

Pupa. (From the Latin for a doll or little image.) The passive state of an insect
immediately preceding the last.

PupiPAROus. (Lat. pupa; pario, I produce.) The insects that bring forth their
young in the pupa state.

Pylorus. From the Greek. The aperture which leads from the stomach to the in-
testines.

PrRiFORM. (Lat. pyrum, a pear.) Pear-shaped.

QuADRiFiD. Cleft in four pai-ts.

Quaternary. In chemistry, bodies composed of four elementary substances.

Radiata. (Lat. 7-adius, a ray.) The name of the lowest primary division of the

animal kingdom.
Ramose. (Lat. ramus, a branch.) Branched.
Keniform. (Lat. ren, a kidney.) Kidney-shaped.
Reptilia. (Lat. repto, I creep.) The class of Vertebrate animals with imperfect

respiration and cold blood.
Rete Mucosum. The cellular layer between the scarf-skin and true skin, which is

the seat of the peculiar colour.of the skin.
Rhyncholithes. (Gr. rliunchos, a beak ; lithos, a stone.) Beak-shaped fossils ; the

extremities of the mandibles of Cephalopods, allied to the Nautilus.
RoTiFERA. (Lat. rota, a wheel ; fero, I bear.) The name of the class of infusorial

animalcules, characterised by the vibratile and apparently rotating ciliary organs

upon the heads.

Salpians. (Gr. Salpe, a kind of fish.) The order of tunicated Mollusca which
float in the open sea.

Sarcophaga. (Gr. sarx, flesh ; phago, I eat.) Flesh-eating animals.

Sacciform. Shaped like a sac or bag.

ScuTiBRANCHiATA. (Lat. scutum, a shield ; hragcliia, gills.) The order of gas-
tropodous Mollusca, in which the gills are protected by a shield-shaped shell. .

Sebaceous. (Lat. sebum, tallow.) Like lard or tallow.

Segjientation. The act of dividing into segments.

Semilunar. Crescent-shaped, like a half-moon.

Semipinnate, Fringed on one side.

Sepal. The divisions of the calyx of a floAver.

Septa. Partitions.

Sericteria. (Gr. serikos, silky.) The glands which secrete the silk in the silk-
worm.

Serrated. (Lat. serra, a saw.) Toothed like a saw.

Sessile. Attached by a base.

Set.e. (From the Latin for a bristle.) Bristles, or similar parts.

Setigerous. Bristly.

Siliceous. (Lat. silex, flint.) Flinty.

Sinus. A dilated vein or receptacle of blood.

Siphonostomous. (Gr. siphon, a tube ; stoma, a mouth.) Animals furnished with
a suctorious mouth like a tube. The term is usually applied to Crustacea so
characterised.

Spatulate. (Lat. spatula.) Shaped like a spatula.

Spermatheca. (Gr. sperma, seed ; theke, sheath.) A receptacle attached to the
oviducts of insects.

Spermatoa. (Gr. sperma, and gov, an egg.) The nucleated cell in which the sper-
matozoon is developed.

Sperimatophora. {GiV. sperma; phero, I bear.) The cylindrical capsules or sheaths
which convey the sperm. In the Cephalopods are called the moving filaments
of Ncedham, after their discoverer.

Spermatozoa. (Gr. sperma ; zoon, an animal.) The peculiar microscopic moving
filaments and essential parts of the fertilizing fluid.

Sphincter. (Gr. sphigkter.) The circular muscles which contract or close natural
apertures.

SpicuLA. (Lat. spiculum, a point or dart.) Fine pointed bodies like needles.

X X 4

680 GLOSSARY.

Spinnaret. The articulated tubes with which spiders fabricate their webs.

Spiracles. (Lat. spiro, I breathe.) The breathing pores in insects.

Squamous. (Lat. squama, a scale.) Arranged like scales.

Stemmata. (Lat. stemma.) The simple and minute eyes of worms, and those which
are added to the large compound eyes.

SrERELMiNTHA. (Gr. steveos, solid ; helmins, an intestinal worm.) Intestinal
worms which have no true abdominal cavity, and which were called " parenchy-
matous" by Cuvier, as the tape-worms.

Sternal. The aspect of the body where the sternum or breast bone is situated.

Stigmata. (Gr, stigma, a mark.) The breathing pores of insects.

Stojiato-gastric. (Gr. stoma, a mouth ; gaster, a stomach.) The system of
nerves which are principally distributed upon the stomach and intestinal canal.

Strepsiptera. (Gr. strepho,! twist ; pf.eron,a, wing.) The singular order of in-
sects discovered by Mr. Kirby, in which the first pair of wings is represented by
twisted rudiments.

SuBMUSCULAR. Beneath muscles or muscular layers.

SuBCESOPHAGEAL. Beneath the gullet.

SucTORiA. (Lat. sugo, I suck.) The animals provided with mouths for sucking,
and the appendages of other parts organised for sucking or adhesion.

SUPERCESOPHAGEAL. AboVC the gullct.

SuTURAL. Appertaining to a suture.

Suture. (Lat. suo, I sew.) The immoveable janction of two parts by their
margins.

T^NioiD. (Gr. tainia, a riband; eidos, like.) Riband-shaped, like the Taenia or

tape-worm.
Tapetum. (Lat. tapetum, a carpet. ) The coloured layer of the choroid coat of the

eye.
Tarsus. (Gr. tarsos, a part of the foot.) Applied to the last segments of the

legs of insects.
Tectibranchiate. (Lat. tego, I cover ; bragchia, gills.) The order of Mollusca

in Avhich the gills are covered by the mantle.
Tergal. (Lat. tergum, the back.) Belonging to the back.
Tetrabranchiate. (Gr. tetra, four ; bragchia, gills.) The order of Cephalopods

with four gills.
TEUTHiDiE. (Gr. teuthls, a calamary.) The family of Cephalopods, of which the

calamary is the type.
Thoracic. Belonging to the thorax.
Thysanoura. (Gr. thusanoi, fringes; oiira, a tail.) A family of apterous insects

with fringed tails.
Tracheae. (Gr. tracheia, the rough arterj- or windpipe.) The breathing tubes of

insects.
Trachelipods. (Gr. trachelos, the neck ; pons, a foot.) The Mollusca which

have the locomotive disc or foot attached to the side of the neck.
Trematoda. (Gr. trema, a pore.) The order of Entozoa characterised by sucto-
rial pores.
Trenchant. Sharp edged, cutting.
TRIDACTTI.E. Three-fingered.
Trilobate. Divided into three lobes.
Trilobite. An extinct genus of Crustacea, the upper surface of whose body is

divided into three lobes.
Triradiate. Consisting of three spokes or rays.
Trophi. (Gr. trophos, a nourisher.) In insects, the parts of the mouth emjjloyed

in acquiring and preparing the food.
Tuberculate. "Warty, or covered with small rounded knobs.
TuNiCATA. (Lat. tunica, a cloak.) The class of acephalous Mollusca which are

enveloped in an elastic tunic not defended by a shell.

Uncinated. Beset with bent spines like hooks.

Univalve. (Lat. unus, onej valvce, doors.) A shell composed of one calcareous
piece.

GLOSSARY. 681

VASIFOR3I. (Lat, vas, a vessel.) Shaped like a bloodvessel or tube.

Ventral. Relating to the inferior surface of the body.

Ventricular. (Lat. ventriculus, a ventricle or small cavity, like those of the

heart or brain.) Belonging to a ventricle.
Vermes. (Lat. vermis, a worm.) Worm-like animals : applied in a very extensive

sense by Linnteus.
Vertebrata. (Lat. vertebra, a bone of the back ; from vertere, to turn.) The

highest division of the Animal Kingdom, characterised by having a back-bone.
Verticillate. (Lat. verticillus, a whirl.) An'anged like the rays of a wheel or

spindle.
Vermiform. Worm-shaped.

Vesicul^. (Lat. vesica, a bladder.) Receptacles like little bladders.
Villi. Small processes like the pile of velvet.
Vitelline. (Lat. vitellus, yolk.) Of or belonging to the yolk.
Viviparous. (Lat. vivus, alive; pario, I bring forth.) The animals which bring

forth their young alive.

Whorl. The spiral turn of a shell, and the like arrangement of a group of leaves

or polypes upon a stem.
Whorling. The act of disposing parts in a series of spiral cm-ves round an axis.

XiPHOSURA. (Gr. xiphns, a sword; oura, a tail.) A family of Crustacea with
sword-shaped tails, as the Limulus.

Zoophyte. (Gr. zoon, animal; phi/ton, plant.) The lowest primary division of
the Animal Kingdom, which includes many animals that are fixed to the ground
and have the form of plants.

Zoospore. (Gr. zoon, animal; spora, seed.) The reproductive bodies of sexless
water-plants, wliich enjoy the power of locomotion for a certain time.

682

INDEX.

Acalephw, 157. 188.
Acanthocephala, 58. 91. 118.
Acarus foUiculorum, 445.
Acepbalocyst, 59. 61.
Acephalous Mollusca, 471.
Acetabula of Cephalopods, 611.
Acrita, 15.
Adheres, 272 — 275.
Actinia, 134.
Actinocyclus, 20.
Akera, 551.
Alcyonidium, 136.
Alcyonium, 136.
Alimentary canal of

Annixlata, 230—233.

Arachnida, 452, 453.

Beroe, 72.

Brachiopoda, 493.

Bryozoa, 149.

Cephalopoda, 622,

Cin-ipedia, 282.

Crustacea, 315, 316.

Diplostoma, 84.

Distoma, 81 — 83.

Echinoderma, 196. 205, 209.

Epizoa, 272,

Gastropoda, 555 — 558.

Insecta, 375 — 379.

Lamellibranchiata, 504. 506.

Pteropoda, 537.

Tunicata, 474. 476. 482. 483.
Alternate generation (see Partheno-
genesis).
Amazon ants, 429.
Ametabola, 346.
Ammonites, 596.
Amphipoda, 344.
Anaima, 11.
Anatomical distinction between plants

and animals, 3.
Androgynous orgaris of

Annulata, 254—256.

Bothriocephalus, 7 1 .

Cin-ipedia, 283—286.

Distoma, 82, 84.

Gastropoda, 561—563.

Pteropoda, 537. 539.
Taniffi, 69.
Anellides, 11. 14. 225—265.
Animals, classes of, 16.
Animal Kingdom, tabular vicAV of, 16.
Primary division of, 12. Distinction
from Ycgetable, 2. 8.
Animal matter preserved from loss by

Polygastria, 36.
Annulata, 225. Orders of, 265.
Anodon, marsupial gills of, 52. Ova

of, 523.
Antennae of

Anellides, 227.
Cirripedia, 289.
Crustacea, 300.
Epizoa, 269.
Insects, 348. 368.
Anthozoa, 134. 156.
Ants, 429.

Aphaniptera, 347. 440.
Aphides, larval genei-ation of, 409. As-
tonishing fecundity of virgin females,
414. Ordinary generation of, 409. 414.
Aphrodita, 226. 232. 233. 246. 263.
Aplysia, 549. 657. 559. 567.
Aptera, 347. 353. 440.
Arachnida, 442. Comparison with in-
sects, 443.
Aranea, 448. 465.
Arenicola, 231, 232, 238. 240. 261.
Argonauta, 178. 605. 628. Male of, 630.
Arms of Cephalopods, 609—613.
Articulata, 13. 16. 225.
Arctiscon, 55. See Macrobiotus.
Ascaris acuminata, 113.

lumbricoidcs, 98. 102.
vermicularis, 99. 109.
Ascidians, 13. 471.473. Compound, 475.
Astacus fluviatilis, 302. 306. 327. 336.

marinus, 300. 306. 318.
Asterias, 14. 191. 193. 195. 213.
Asteroidea, 190. 224,
Athalia, 398.
Atoll, 139. 141. 142.
Avicula margaritifcra, 518.

INDEX.

683

Baculite, 596.

Balanoids, 267. 278. 294. Larva of, 288.

Barnacle, 278.

Barrier reef, 139. 141, 142.

Bee, stomach of, 378. Tongue of, 374.
Development of, 428.

Belemnite, 597. Its shell, 598. Mantle,
601. Fins, 602. Arms, 602. Ink-
bag, 601.

Bergmehl, 38.

Beroe, 171. 175.

Binary compounds, 7.

Boring bivalves, 518.

Bothriocephalus auriculatus, 76. Both,
latus, 69. 71. Both, punctatus, 72.
Development of, 73.

Botryllidffi, 501.

Botts, 425.

Brachiopoda, 471. 485. 501.

Branchiopods, 320.

Bryozoa, 144. 156.

Buccinum, 208. 566.

Bulla, its gastric shell, 557.

Byssus, 504.

Cameo shells, 544.

Cambium, 420. 465.

Campanularia, 126.

Cardinal teeth, 515.

Carinaria, 540. 546.

Cells, 35.

Cellulose, 4. 473.

Centipede, 347. 357. 390. 394.

Cephalopoda, 13. 474. 576. 649.

Cestoidea, 59. 67 — 79. 117.

Chambered shells, formation of, 592.

Chemical distinction between plants and

animals, 4.
Chilognatha, 347. 440.
Chilopoda, 347. 440.
Chitine, 279. 297. 349. 463. 469.
Chlamydomonas, 29.
Chlorophyll in animals, 4.
Chr^'salis, A 22.
Chylaqueous system, 135. 150. 197. 199.

207. 211. 233.
Cicendela, 377.
Ciliobraehiata, 144.
Ciliograda, 170. 180.
Circulation in

Anellids, 234.

Arachnids, 454.

Brachiopods, 496.

Cephalopods, 588—624.

Cirripeds, 582.

Crustacea, SI 8.

Echinoderms, 206.

Gastropods, 559.

Insects, 383

Lamellibranchs, 507.

Tunicaries, 476.

Cirripedia, 267. 277. 293.
Citherea, 506.

Cladocera, 343. Homology of, 292.
Classes of animals, 16.
Classification of

Acalephai, 188.

Annulata, 264.

Anthozoa, 156.

Arachnida, 467.

Brachiopoda, 501.

Bryozoa, 156.

Cephalopoda, 650.

Cirripedia, 293.

Crustacea, 342.

Echinodermata, 223.

Entozoa, 117.

Epizoa, 293.

Gastropoda, 573.

Hexapoda, 441.

Hydrozoa, 155.

Infusoria, 55.

Insecta, 440.

Lamellibranchiata, 531.

Myriapoda, 440.

Polvgastria, 55.

Polypi, 155.

Pteropoda, 572.

Rhizopoda, 56.

Eotifera, 56.

Sterelmintha, 117.

Tunicata, 500.
Classification, 9. 1 60,
Clavellinre, 501.
Coarctate metamorphosis, 422.
Cocoon, 258, 434,
Coelelmintha, 58. 94. Ii8.
Coleoptera, 347. 352. 442.
Colleterium, 402.
Comatula, 192. 224.
Compound

acalephes, 178.
ascidians, 475.
polypes, 125. 136, 145.
Conjugation, 29.
Copepoda, 343.
Coral Islands, 1 39
CoralHnes of Ellis, 126.
Corallium rubruni, 136.
Corvne, 131.
Crab, 301. 309. 316. 340.
Cranidae, 503.
Crinoida;, 224.
Crustacea, 296—342.
Cyauica, 16.5. 182. 184.
Cyclobranchiata, 574,
Cydippc, 171. 173.
Cymothoa, 298.
Cynthia, 478.
Cystica, 59. 64.
Cysticercus, 66.
Cvstoidca, 224.

684

INDEX.

Decapod crustaceans, 300. 344. Di-

branchiates, 605. 649.
Demodex folliculorum, 444.
Dermophysa, 467.
Development of

Acalephffi, 181.

Annulata, 260.

Anthozoa, 137.

Arachnida, 464.

Ascaris, 113,

Ascidia, 478.

Asterias, 213.

Bothriocephalus, 72.

Biyozoa, 151.

Cephalopoda, 635.

Cestoidea, 74.

CiiTipedia, 287.

Comatula, 222.

Crustacea, 333.

Echinoderais, 220.

Echinus, 217.

Epizoa, 273.

Gastropoda, 566.

Holothuria, 219.

Insecta, 419 — 440.

Lamellibranchiata, 524.

Medusa, 181.

Myriapoda, 392.

Ophiura, 251.

Polygastria, 32.

Polypi, 124. 129.

Eotifera, 52.

Salpa, 484.

Ti-ematoda, 87.

Tunicata, 478. 484.
Dibranchiate Cephalopods, 603.
Dictyocha, 20.
J)imyaries, 504. 531.
Dioccia, 574.
Diplostoma, 84.
Diplozoon paradoxum, 85.
Diporpa, 85.
Diptera, 347. 353. 441.
Distoma clavatum, 81.
hepaticum, 80.
lanceolatum, 83.
perlatum, 87.
Dragon-fly, 369.

Earthworm, 228. 231. 236. 249. 257.
Ecdysis, 276. See Moulting,
p^chinococcus, 65. 78.
Echinodemaata, 190—223.
Echinoidea, 190. 199. 225.
Echinorhyncus, 91.
Echinus, 200. 204.
Edriophthalma, 300. 343.
Elytra, 352.
Enaima, 11.

Encephalous Mollusca, 471.
Encrinites, 192. 924.

Entomostraca, 298. 342.
Entozoa, 57—118. Orders of, 58. Te-
nacity of life, 114. Human, 59. 65,
66. 67. 70, 80. 83. 94. 97, 98. 102. 109.
Entrochi, 192.
Eocene, 38. 576.
Epeira, 461.
Ephippium, 324.
Epizoa, 267.

Equivocal generation, 78. 116.
Errantia, 265.

Extinct chambered shells, 595.
Eye in Acalephje, 168. 170. 175.

Annulata, 227. 248.

Arachnida, 450.

Ascidia, 475. 478.

Asterias, 195.

Cirripedia, 280. 288.

Crustacea, 311.

Echinus, 200. 220.

Entozoa, 81. 86.

Epizoa, 274.

Gastropoda, 552.

Insecta, 369.

Lamellibranchiata, 512.

Nautilus, 585.

Polygastria, 22.

Tteropoda, 539.

Rotifera, 46.

Sepia, 619.

Trematoda, 81. 89.

Farre,Dr. A., 145. 257. 311.

Eeet, tubular, of Echinoderms, 193. 202.

208.
Filaria broncln'alis, 96. Medinensis, 96.

Oculi, 96.
Fission, spontaneous, 27. 34. 63. 124.

178. 185. 253.
Flustra, 145.
Foot of bivalves, 504, 505.

univalves, 546.
Fringing reefs, 139. 141. 142.

Gastropoda, 471. 540. Orders of, 573.
Gemmation, 15. 29. 64. 124. 157. 178.

254. 481.
GeneratiA-e organs in

Acalephte, 179.

Annulata, 254.

Arachnida, 459.

Brachiopoda, 498.

Cephalopoda, 590. 628.

Cirripedia, 284.

Crustacea, 326.

Echinoderma, 190. 208. 21 J.

Entozoa, 69. 82. 86. 92. 104.

Epizoa, 273.

Gastropoda, 561.

Insecta, 396.

Lamellibranchiata, 521.

INDEX

685

Myriapoda, 389.
Polygastria, 32.
Polypi, 125. 137. 151.
Pteropoda, 537.
Eotifera, 49.
Tunicata, 477. 483.
Generation, cqnivocal, 43. 78. 87. 115.
Eissiparous, 27. 34. 63. 124. 178. 185.
Larviparons, 402. Gemmiparous, 29.
64. 124. 157. 178. 254. 481. Pupi-
parons, 402. 426. Eapid rate of, in
Infusoria, 34. 53.
Gcrm-ccU, 65. 75. 113. 124. 152. 182.

259. 276. 478. 525. 566. 570. 636.
Germinal vesicle, 52. 112. 181. 213.

229. 464. 478. 523. 635.
Germ-mass, 113. 407.
Glaucoma scintillans, 18.
Gnathostoma, 99.
Gonium, 29.
Gordiacea, 58.
Gorgonia, 137.
Gregarina, 3. 29. 35. 62.
Guinea-worm, 96.
Gyninosomata, 512.

Hairs of Anellides,

of Spiders, 448.
Haliotis, 548. 559, 560.
Halodactylus, 151, 152.
Ilamitc, 597.
Haustellata, 346.
Hearing, organ of, in

Cephalopoda, 585. 619.

Cin-ipedia, 281.

Crustacea, 311.

Gastropoda, 553.

Insecta, 368.

Lamellibranchiata, 511.

Pteropoda, 537.
Heart, 6.

In Annulata, 234. 237.

Arachnida, 454.

Brachiopoda, 494.

Cephalopoda, 587. 624.

Cirripedia, 282.

Crustacea, 318.

Echinoderma, 197. 206. 210.

Epizoa, 272.

Gastropoda, 559.

Insecta, 382.

Lamellibranchiata, 504. 507.

Polygastria, 25.

Pteropoda, 537.

Rotifera, 49.

Tunicata, 474. 476. 483.
Helix, 541. 549. 562.
Hemimetabola, 347.
Hemiptera, 347.
Hermaphrodite, 13. 86. 327. 406.

Heterogangliata, 13. 470.

Hexapod insects, 345. 440.

Hinge of bivalve shells, 515.

Hive- bee, economy of, 427.

Holostomata, 575.

Holothurioidea, 208. 210. 225.

Homogangliata, 13. 225.

Humble bee, economy of, 428.

Hunter, John, 3. 12, 163. 168. 318.
His experiment on a fly, 379. On the
circulation in Insects, 383. His soft-
shelled mollusks, 471.

Hyalca, 536.

Hyaline, 32. 465.

Hydatina, generation of, 52.

Hydra, 120.

tuba, 183, 184.

Hydrozoa, 120. 155.

Hymenoptera, 347. 353. 441.

Iclmeumon, parasitic habits of, 417.

Inferobranchiata, 540, 573.

Infusoria, 16. Tenacity of life in, 42,

Siliceous deposits of, 37.
Ink of Cuttle-fish, 623.
Insect metamorphosis, 422. Analogy of

development of human embryo with,

438. Of Marsupialia with, 439. Of

Batrachia with, 439.
Insecta, 344. Orders of, 440. Wings

of, 347.
Instrumenta cibaria, 373.
Invertebrata, 11.
Isopoda, 305. 343.
lulus, 348. 356. 392, 393, 394.

Janthina, 565.

Lremodipoda, 343.
Lamellibranchiata, 471. 503. 531.
Land-crabs, 322. 341.
Larva, animals typified by in Insects,

definition of, 422.
Leech, 228. Stomachs of, 104. Suckers

of, 229. Teeth of, 230. Eyes of, 248.

Genitals of, 254.
Leeuwenhoek, 17. 54. 522.
Lepadoids, 278. 295.
Lepas, 277. Its shell, 278. Its nervous

system, 280. Its digestive system,

282. Its larva, 288.
Lepidoptera, 347. 353. 441.
Lerna^a, 267.
Leucophrys, 24.
Levigrada, 468.
Ligament, 515.
Limnceus, 553. 569.
Limulus, 298. 312. 343.
Linguatula, 101.
Lingulida;, 503.
Linnaeus, 1. 9.

686

INDEX.

Lithedaphus, 544.
Liveij in

Annulata, 231. 233.

Arachnida, 453.

Erachiopoda, 278.

Biyozoa, 150.

Cephalopoda, 587. 623.

Cirripedia, 282.

Crustacea, 317.

Echinoderma, 196.

Entozoa, 104.

Gastropoda, 558.

Insecta, 376.

Lamellibranchiata, 504, 506.

Pteropoda, 537.

Rotifera, 48.

Tunicata, 474. 476.482, 483.
Lobophylla, 138.
Lobster, 300. 318. 329.
Locomotion of Acalephse, 171.
Infusoria, 22. 47.
Polypi, 121. 131. 137. 152.
Locust, 348. 373. 418.
Loligo, 604. 622.
Loricate Infusoria, 19, 20. 45. 49.
Loxodes, 25. 33.
Lug-worm. See Arenicola.

Mactra, 514.
Macrobiotus, 446.
Maia, 329.

Malacostraca, 298. 330. 343.
Male of Rotifera, 51.
of Epizoa, 273.
of Cirripedia, 286.
of Argonauta, 628. 630.
Mandibulata, 346.
Mantis, 363, 364.
Marsupial sacs of

Acalepha;, 181.

Annulata, 259.

Cin-ipedia, 285.

Crustacea, 324. 326. 329.

Epizoa, 273.

Lamellibranchiata, 533.
Medusa^ 162. 165.
Mclanine, 624.
Metabola, 346.

Metagenesis, 90. 131. 183. 215. 253,
262. 275. 288. 290. 324. 409. 4^0, 484.
Metamorphosis of

Acaiephae, 182.

Annulata, 262.

Ascidians, 478.

Cin-ipedia, 288.

Comatula, 222.

Crustaceans, 116. 333 339,

Echinodermata, 215. 220

Entozoa, 74. 88. 90.

Epizoa, 274.

Gasti'opoda, 566.

Human embryo, 4 39.

Insecta, 422.

Lamellibranchiata, 525.

Polygastria, 34.

Polypi, 130. 137. 152.
Microscopical anatomy, 40.
Migration of bivalves, 527
Millepora, 139.
Minerals detiued, 1.
Miocene, 576.
Mites, 446. 460.
MoUusca, 13. 16. 470.
Molluskigerous sac in Synapta, 219.

221.
Monad, 19.
Monoecia, 573.
Monomyaria, 504. 531.
Moulting of

Arachnida, 466.

Cirripedia, 288.

Crustacea, 302.

Epizoa, 275.

Insecta, 422. 433.
Mussel, 504. 510. 525. 530.
Myelencephala, 12.
My gale, 450. 456.

Myriapoda, 345. 347. 356. 388. 440.
Mytilus, 508. 510.

Nacre, 517.

Nais, 231.252,253.

Nassula, 28.

Natural affinities, illustrated, 39.

Nautilus Pompilius, 578 — 595,

Navicula, 20,

Needham's moving filaments, 629.

Nematoidea, 58. 93. 118.

Nematonem-a, 15,

Nepa, 385.

Nereis, 262,

Nervous system,

Acalephae, 168. 174,

Annulata. 248.

Arachnida, 449.

Erachiopoda, 491.

Cephalopoda, 583. 615.

Cirripedia, 280.

Crustacea, 13. 304. 310.

Echinoderma, 14. 194. 207. 211.

Entozoa, 81. 86. 100.

Epizoa, 272.

Gastropoda, 546 — 551.

Insecta, 358 — 367.

Lamellibranchiata, 510.

^lyriapoda, 355.

Nautilus, 583.

Polygastria, 22.

Polypi, 148.

Pteropoda, 537.

Rotifera, 46.

Tunicata, 475, 476. 482, 483.

Vcrtebrata, 12.

IMetamorphoses of, in insects, 360.

IKDEX.

687

Neuroptera, 347. 353. 442.
Niclamental capsules, 418. 565.

glands, 564. 591. 632.
Noctua, 402.
Non-ganglionic chords, their function

in Articulata, 249. 307,
Notommata, 46.
Nucleobranchiata, 574.
Nudibranchiata, 540. 573.
Nulligrada, 467.
Nullipora, 140.

Obtected metamorphosis, 422. 424.
Octopod dibranchiates, 605.
Octopus, 611. 623. 629.
CEstrus Bovis, 425.

Hominis, 425.
Onchophora, 119.
Onychoteuthis, 603. 612. 621.
Operculum, 146. 229. 279. 458. 529.

543.
Ophiura, 190. 194. 197. 224.
Orbiculidffi, 503.
Organic matter, 36.

not self-subsistcnt, 37.
Organisation, defined, 1.
Orajanised beings, 2.
Orthidse, 502.
Orthoceratite, 595.
Orthoptera, 347. 352. 442.
Ostrapoda, 343.
Ova of Acalephse, 181.

Annulata, 258.

Arachnida, 459. 464.

Bothriocephala, 73.

Brachiopoda, 498.

Bryozoa, 152.

Cephalopoda, 633. 635.

Cirripedia, 285.

Crustacea, 336.

Echinus, 208.

Epizoa, 274.

Gastropoda, 564, 565. 567.

Insecta, 406. 419.

Lamellibranchiata, 523.

Polygastria, 32, 33.

Polypi, 125. 135. 137.

Eotifera, 52.

Taenia, 73.

Tunicata, 476. 478.
Oviparous generation, its final purpose
in Infusoria, 42.

Pagurus, nerves of, 308.
Paludina vivipara, 556.
Parthenogenesis, 15. 88. 133. 160.
Parthenogenetic animals, 13, 14. 78. 90.

124. 128. 131. 136. 151. 178. 184.

212. 253. 262. 324. 409. 480, 481.

484.
Patella, 554.

Pearl, 518.

artificial mode of producing, 518.

Pectinibranchiata, 441. 574.

Pedicellaria;, 193. 202.

Pedicellina, 152.

Pendularia, 118.

Penella, 271.

Peniculus, 267.

Pentacriuus, 192. 223.

Per-centage of Fossil shells in tertiaiy
strata, 576.

Pholcus, 453. 454. 457.

Phragmocone, 598.

Phyllopoda, 343.

Physalia, 176.

Physiological distinction between plants
and animals, 3. 5. 6.

Physograda, 176. 189.

Planaria, 85. 94.

Plants, distinction from animals, 2 — 8.

Pleistocene, 576.

Pleurobranchus, 558.

Pluteus, 215.

Poison-glands, 347. 405. 4 6.

Polierschiefer, 37.

Polygastria, 16. Conjugation of, 29.
Classification of, 55. Generation of,
26. Mouths of, 29. Nucleus, or testis
of, 27. Ovarium of, 33. Shells of,
19. Sleep, none in, 22. Stomachs
of, 23. Teeth of, 23, 42. Vascular
system of, 25.

Polypi, 119.

classification of, 155.

Productidae, 502.

Psyche, 416.

Pteropoda, 471. 585. 572.

Pulmogrades, 162. 188.

Pulmonaria, 469.

Pulmonata, 541. 573.

Pulmotrachearia, 468,

Pupa, definition of, 422.
kinds of, 422.

Pyrosoma, 482.

Pyrosomida3, 501.

Quaternary compounds, 4. 7.

Kadiaria, 16.

Radiata, 14.

Ranatra, 366.

Reparative power, 123. 272. 252. 323.

434. 467. 561.
Reproduction of parts, 73. 123.212.252.

302. 323. 434. 476. 561.
Respiratory organs in

Acalephae, 164.

Annulata, 239.

Arachnida, 455.

Brachiopoda, 498.

Bryozoa, 150.

Cephalopoda, 588. 626.

688

INDEX.

Cirripedia, 283. 286.
Crustacea, 320.
Echinoderma, 210.
Gastropoda, 540. 560.
lusecta, 384.
Lamellibranchiata, 507.
Pteropoda, 537.
Rotifera, 48.

Tunicata, 474. 476. 482, 483.
Rhizostoma, 163.
Rossia, 633.
Rotifer, 48.

Rotifera, 39. Alimentary canal in, 48.
Classification of, 56. Chylaqueous
system, 49. Cilia of, 46. Generation
of, 49. Locomotion in, 47. Males
of, 51. Muscular system, 46. Ner-
vous system in, 47. Shells of, 45.
Teeth of, 47. Vascular system, 48.
Wheels of, 46.
Rotation of embryo in ovo, 526. 566.

568. 636.
Rudistes, 532.
Rhynchonellidte, 502.

Saccobranchiata, 501.
Salivary glands in

Cephalopods, 586. 622.

Echinoderms, 204. 209.

Entozoa, 103.

Gastropods, 555.

Insects, 380.
Salpa, 471. 483.

metagenesis of, 484.
Sand- canal of Star-fish, 198.
Sarcoptcs Galci, 446.
Scalaria 542.
Scalpellum, male of, 287.
Scaphite, 597.
Scorpion, 447. 654.
Scutibranchiata, 574.
Scyphistoma, 184.
Sea-anemone, 134.
Sea-grai)es, 635.
Segestria, 455.
Sepia, 615. 624. 635.
Scrtularia, 126.
Shell of Annulata, 229.246.

Brachiopoda, 485, 486.

Cephalopoda, 576. 581. C92. 59.5.
605.

Cirripedia, 278.

Crustacea, 297. 302.

Echinoderma, 192. 199.

Gastropoda, 541.

Lamellibranchiata, 513.

Polygastria, 19.

Polypi, 125. 138.

Pteropoda, 535.

Rotifera, 45.

Tunicata, 473. 482.

Absorption of, 544.

Ship-borer, 517. 521.

Siliceous deposits of Infusoria, 37.

Single-celled Animals, 35.

Sinistral shells, 542.

Siphon of bivalves, 505. 513. 517.

of univalves, 543.

of Cephalopods, 593.
Siphonifera, 532.

Siphoniferous shell, formation of, 592.
Function of, 525. Structure of, 581.
595. 598. 606.
Siphonostomata, 575.
Sipunculus, 209, 225.
Skeleton, exteraal. See Shell.
Arachnida, 448.
Crustacea, 300.
Insecta, 348.

Internal, 136. 486. 582. 608.
Slug, 549. 565. 570.
Snail, 199. 207.

Spermathcca, 329. 401.461. 464.
SperraatoiDliora, 329. 400. 629.
Spermatozoa of

Acalephse, 180.

Annulata, 257.

Arachnida, 461.

Bryozoa, 151.

Cephalopoda, 630.

Crustacea, 32.5. 328.

Echinoderma, 208. 220.

Gastropoda, 564.

Insecta, 400.

Lamellibranchiata, 524.

Myriapoda, 389.

Nematoidea, 106.

Polypi, 125. 135.

Rotifera, 51.
Sphinx Ligustri, 430.
Spiders, loves of, 462. Webs of, 458.
Spines of Echinus, 201.
Spinnarets of spiders, 457.
Spiriferidfe, 502.
Spiroptera Hominis, 97.
Spirostomum, 18.
Spirula, 577. 606.

Spontaneous fission, 27.69.73. 125. 178.
186. 196. 212.
generation, 43. 78. 87. 115.
experiment on, 44.
Squilla, 300. 305.
Stag-beetle, 382.
Star-fish, 19 L
Stephanoceros, 50.
Sterelmintha, 58. 117.
Stomapoda, 300. 320. 344.
Stone-lilies, 192,
Strepsiptera, 347. 353. 441.
Strobila, 184.
Strongylus Gigas, 97.
Sub-kingdom of Animals, 12.
Suctoria, 265.
Swammerdam, 401. 434.

INDEX.

689

Tape-worms, fertility of, 72. Geogra-
phical distribution of, 79. Metamor-
phosis of, 74. Migrations of, 75 — 77.
Larva of, 75.
Tffiiiia Solium, 67.
Tseniobranchiata, 501.
Tardigracla, 446.467.
Tectibranchiata, 573.
Tegeiiaria, 458. 461.
Teeth of

Crustacea, 315, 316.

Echinus, 204.

Gastropods, 554.

Leech, 230.

Nereids, 231.

Polygastria, 23.

Eotifera, 47.

Of bivalye shells; 515.
Tellina, 504.
Tenacity of life in

Entozoa, 115.

Infusoria, 53, 54.
Terebratula, 485. 502.
Teredo, 518. 521.
Termites, 428.
Ternary compounds, 4. 7.
Terricola, 265.
Tetrabranchiata, 578. 649.
Thecosomata, 572.
Tongue of Bee, 374.

Cephalopods, 586. 618.621.

Limpet, 554.

Gastropods, 553.

Whelk, 554.
Torj^idity, 54. 392.
Touch, organs of,

Annulata, 227.

Arachuida, 451.

Bryozoa, 149.

Cephalopods, 586. 618.

Crustacea, 319.

Epizoa, 272.

Gastropods, 551.

Insecta, 367.

Lamellibranchia, 512.

Pteropoda, 539.

Tunicata, 474.
Trachearia, 468.
Tracheliastes, 271.
Trachelipods, 545.

Transition from Radiata to Mollusca,472.
Tree- crabs, 322.
Trematoda, 59. 80. 117.
Trichina spiralis, 94. 117.
Trichocephalus dispar, 97.
Trilobite, 299. 313. 331.
Trophi, 373.
Tubicola, 265.

Tubipora, 139.
Tubularia, 128.
Tubulibranchiata, 574.
Tunicata, 471. 473. 500.
Turrilite, 597.

Unio, 526.

Unity of organisation, defined, 644.

Unorganised, compared with organised

bodies, 2.
Urinary organs, 211. 317. 322. 381. 453.

509. 560. 689. 625.

Vanessa, 146.
Vascular system of

Acalepha?, 169. 173.

Anellides, 234 — 239.

Ai-achnida, 453.

Asterias, 197.

Brachiopoda, 495.

Bryozoa, 150.

Cirripedia, 282.

Crustacea, 317.

Echinus, 205.

Entozoa, 82.

Epizoa, 272.

Gastropoda, 559.

Holothuria, 269.

Insecta, 382.

Lamellibranchia, 507.

Nautilus, 587.

Polygasti-;a, 25.

Rotifcra, 48.

Sepia, 624.

Tunicata, 474.
Venous follicles of Cephalopods, 589.

625.
Vermes, 10.
Vertebrata, 11, 12. 16.
Vesiculie seminales, 69. 87. 105. ?54.
284. 328. 390. 397. 461. 539. 561. 629.
Vibrio rugula, 19.

subtilis, 19.

tritici, 115.
Volvocina?, 8.
Volvox, 22. 28.
Vorticella, 18. 24.

Webs of spiders, 458.
Wasp, procreative economy of, 426.
Wings of insects, 347. 352. Their ho-
mology, 355.
Whelk, 554. 563.

Xiphosura, 298. 343.

Zoa, 11.
Zoophytes, 15.

THE END.
Y Y

ERRATA.

Page 13, last line of Note*, for "pi. i. of the present volume," read "pi. iii. of ccciii.'
Page 51. line 24. after Cirripedes a full-stop, and dele to "species at line 27."

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0

7

0

3

6

3

6

3

6

3

6

28

0

A CATALOGUE

OF

NEW WOEKS m GENERAL LITERATUEE,

PUBLISHED BY

LONGMAN, BROWN, GREEN, and LONGMANS,

39, PATEEIS^OSTEE -ROW, LONDON.

CLASSIFIED INDEX.

Agriculture and Rural
Affairs.

Pages.

Bajldon On valuing Rents, &c. - 4

Caird's Letters on Agriculture - 5

Cecil's Stud Farm . - - 6

Loudon's Affriculture - - - 13

" Self-Instruction - - 13

Low's Elements of Agriculture - 13

" Domesticated Animals - 13

Arts, Manufactures, and
Architecture.

Bourne On the Screw Propeller - 4

Brande's Dictionary of Science, &c. 4

" Oreanic Chemistry- - 4

Chevreul on Colour - - - - 6

Cresy's Civil Engineering - - 6

Eastlake On OifPainting - - 7

Gwilt's Encyclo. of Architecture - 8

Jameson's Sacred & Legendary Art 10

" Commonplace Boc'k - 10

Konig's Pictoiial Life-of Luther - 8

Loudon's Rural Architecture - 13

Moseley's Engineering - - - 16

Richardson's Art of Horsemanship 18

Scrivener on the Iron Trade - - 19

SteamEngine,by the Artisan Club 4

Tate on Strength of Materials - 21

Ure's Dictionary of Arts, &c. - 23

Biography.

Arago's Autobiography

„ Lives of Scientific Men -
Bodenstedt and Wagner's Schamyl
Bright« ell's Memorials of Opie "-
Buckingham's (J. S.) Memoh-s
Bunsen's Hippolytus -
Chesterton's Autobiography -
Clinton's (FyTies) Autdbiography
Cockayne's >Iarshal Tureune
Dennistoun's Strange & Lumisden
Forster's De Foe and Churchill
Freeman's Life of Kirby
Haydon's Autobiography ,by Taylor
Hay ward's ( hesterfield and Selwyn
Holcroft's Memoirs
Holland's (Lord) Memoirs -
Lardner's Cabinet Cyclopaedia
Maunder's Biographical 'Treasury -
Mayne's Czar Nicholas L - -
Memoir of the Duke of "Wellington
Memoirsof James Montgomery -
Meriv ale's Memoirs of Cicero
Russell's Hemf.irs of Moore -

" Life of Lord Wm. Russell
Southey's Life of Wesley

" Life and Correspondence

Stephen's Ecclesiastical Biography
Sydney Smith's Memoirs
Taylor's Lovola - - - .
■" Wesley - - - -
Townsend's Eminent Judges
Waterton's Autobiography &Essays

Books of General Utility.

Acton's Cookery - - - - 3
Black's Treatise on Brewing - - 1
Cabinet Gazetteer - - - - 5
" Lawyer - - - - 5
Gust's Invalid's Own Book - 6

Gilbarfs Logic for the Million - S
Hints on Etiquette - - - 9

How to Nurse ^ick Children - - a
Hudson'sExecutor's Guide -

" On Making Wills
Lardner's Cabinet Cyclopsedia
Loudon's Self-Instruction

" Amateur Gardener
Maunder's Treasury of Knowledge
" Biographical 'Treasury

" Scientific Treasury

" Treasury of History

" Natural'HistOry -

riscator's Cookery of Fish
Pocket and the Stud -
Pycroft's English Reading -

Pages.

Recce's Medical Guide - - - 18

Rich's Comp. to Latin Dictionary 18

Richardsons Art of Horsemanship 18

Riddle's Latin Dictionaries - - IB

Roget's English Thesauius - - 18

Rowton'.^ Debater - - - - 18

Short Whist 19

Thomson's Interest Tables - - 21

Webster's Domestic Economy - 24

West on Children's Diseases- - 24

Wilhch's i opular Tables - - 24

Wilmot's Blackstone - - - 24

Botany and Gardening.

Conversations Oh Botany - - 6

Hooker's British Flora - - - 9

" Guide to Kew Gardens - 9

Lindley's Introduction to Botany 11

'' Theory of Horticulture - 11

Loudon's Hortus Britannicus - 13

" Amateur Gardener - 13

" Self-Instruction - - 13

■' Trees and Shrubs - - 13

" Gardening - - - 13

" Plants - - - 13

Pereira's Materia Medica - - 17

Rivera's Rose Amateur's Guide - 18

Wilson's British Mosses - ^ 24

Chronology.

Alcorn's Chronology - - - 3

Blair's Chronological Tables - 4

Bunsen's Ancient Egypt - - 5

Haydn's BeatsOn's Index - - 9
Johns and Nicholas's Calendar of

Victory ..... 10

Nicolas's Chronology of History - 12

Commerce and Mercantile
Affairs.

Atkinson's Shipping Laws - - 3

Francis On Life Assurance - - 8

Francis's Stock Exchange - - 8

Loch's Sailor's Guide - - - 11

Lorimer's Young Master Mariner 13
M'Culloch'sCom'merce & Navigation 14

Scrivenor on Iron Trade - - 19

Thomson's Interest Tables - - 21

Criticism, Histoi-y, and
Memoirs.

Austin's Germany - . - - 4

Balfour's Sketches of Literature - 4

Blair's Chron. and Histor. Tables - 4

Bunsen's Ancient Egypt - - 5

•' Hippolytus - - - 5

Burton's History of Scotland - 5
Chalybaeus's Modern Speculative

Philosophy - - - . 6
Conybeare and Howson's St. Paul 6
Eastlake's History of Oil Painting 7
Erskine's History of India - - 7
Francis's Annals of Life Assurance i
Gleig's Leipsic Campaign - - 23
Gurney's Historical Sketches . 8
Hamilton's Essays from the Edin-
burgh Review - - . . g
Havdon's Autobiographv,bv Taylor 8
Holland's (Lord) Whig'Party . 9
Jeffrey's (Lord) Contributions - 10
Johns and Nicholas's Calendar of

Victory - - - - 10

Kemble's Anglo-Saxons - 11

Lardner's Cabinet Cyclopsdia - 12

Macdulay's Crit. andKitt. FIssays 14

" History of Ecgland " - 13

" Speeches - - - 13

Mackintosh's Miscellaneous Wor'xs 14

" History of England - 14

M'Culloch'sGeographicalDictionarj 14

Martineau's Church History - -' 15

Maunder's Treasury of History - 15

Mayne's Czar Nicholas I. - 15

Memoir of tlie Duke of Wellington 23

Jleiivale's History of Rome - - 15

Merivale's Roman Republic-
Milner's Church History
Moore's (Thomas) Memoirs, &c. -
Mure's Greek Literature
Ranke's Ferdinand & Maximilian
Ricli's Comp. to Latin Dictionary
Riddle's Latin Dictonaries -
Rogers's EssiiysfromthfcEdin burgh

Review . - .
Roget's English Thesaurus -
Russell's (Lady Rachel) Letters -

" Life of Lord W. Russell
St. John's Indian Archipelago
Schmitz's History of Greece
Smith's Sacred Annals ...
Southey's Doctor - . . .
Stephen's Ecclesiastical Biographv
" Lectures on French History
Sydney Smith's Works - - -
" Select Works

" Lectures

" Memoirs

Taylor's Loyola . . . .

" "W^esley - - . -
Thirlwali 's History of Greece
Thirty Years of Foreign Policy -
Townsend's State Trials
Turkey and Christendom
Turner's Anglo-Saxons

" Middle Ages -

" Sacred Hist, of the World
Tehse's Austrian Court
Whitelocke's Swedish Embassy -

Geography and Atlases.

Arrowsmith's Geogr. Diet, of Bible 3

Butler's Geography and Atlases - 6

Cabinet Gazetteer - ... 5

Cornwall, its Mines, &c. - - 23

Dalton's British Guiana - - 7

Durrieu's Morocco - - - 23

Hughes's Australian Colonies - 23

Johnston's General Gazetteer - 11
M'Culloch's GeographicalDictionary 14

" Russia and Turkey - 23

Milner's Baltic Sea . . . ja

Murray's Encyclo. of Geography - 16

Sharp's British Gazetteer - - 19

Wheeler's Geography of Herodotus 24

Juvenile Books.

Amv Herbert - . . . jg

Earis Daughter (The) - - . 19

Experience of Life - -. - 19

Gertrude - - . - 19

Gilbarfs Logic for the Yorrhg - i 8

Howitt's Boy's Country Book - 9

(Mary) Children's Year - 9

Katharine Ashton ... 19

I.aneton Parsonage - - - 19

Mrs Marcet's Conversations - - 14

Margaret Percival - - . - I'J

Pycroft's English Reading - - 18

Medicine and Surgery.

Brodie's Psycholosical Inquiries - 5

Bull's Hints to Mothers - - . 5

" . Management of Children - r>

Copland's Dictionary of Medicine - 6

Cust's Invalids Own Book - - (i

Holland's Mental Physiology - <j

How to Nurse Sick Children - - 9

Latham On Diseases ol the Heart - 1 1
Moore On Health', !Jisease,&Remedy l.i

Pereira On Food and Diet - -" 17

Pereira's Materia Medica - - 17

Recce's Medical Guide - - - Ifs

West on Diseases of Infancy - - 21

Miscellaneous and General
Iiiterattzre.

Atkinson's Sheriff-Law
Austin's Sketches of German Life

Carlisle's Lsctiores and Addresses

•^

CLASSIFIED INDEX.

Pa^es
Chalybaeus's Modern Speculative

Philosophy - - . - (

Defence oi Eclipse of Faith . - 7
Eclipse of Faiih - - - ',

Greg's Essays on Political and

Social Science - - . - f
Hassail on Adulteration of Food - i
Haviln's Book of Dignities ■ - <
Hoiland'.s Mental Physiology
Hooker's Kew Guide
Howitt's Rural Life of England

11

9

9

Visitsto RemarkahlePlaces 9

10

Jameson's Commonplace Book

JettVev's (Lord) Contributions - 10

Last of the Old Squires ^ - 16

Macaulay's Cr;t.and Hist. Efsays U

" Speeches - - 13

Mackintosh's Miscellaneous Works U

Memoirs of a Maitre-d'Armes - 23

Maitland's Churchin the Catacombs 14

Pascal's Works, bv Pearce - - 17

Pycroft's English Reading - - 18

Rich's Comp. to Latin Dictionary 18

Riddle's Latin Dictionaries - - 18

Rowton's Debater - - 18
Seauard's Narrative of his Shipwreckl9

Sir Roger de Coverley - - - 20

Smith's (Rev. Sydney) Works - 20
Southey's Common -place Books -

" ■ The Doctor &c.
Souvestre's ^ttic Philosopher

" Confessions of a AVorkmg Man
Stephen's Essays - - - -
StoWs Training System
Thomson's Laws of Thought
Town>end's State Trials
Willich's Popular Tables
Yonge's English-Greek Lexicon -

" Latin Gi adus
Zumpt's Latin Grammar

Natural History in general.

Catlow's Popular Conchology - 6
Ephemeraand Young On the Salmon 7

Gosse's Nat. Hist, of Jamaica - 8

Kenip's Natural Hist, of Creation 23

Kirby and Spence's Entomologj - 11

Lee's Elements of Natural History 11

Maunder's Natural History - - 15

Turton's Shells oftheBritishlslands '^\i

Waterton's Essavs on Natural Hist. 23

Youatt's The Dog - - - - '^.3

" The Horse - - - 2i

1-Volume Encyclopsedia:
and Dictionaries.

Arrowsmith's Geogr. Diet, of Bible
Blaine'!) Rural Sports
Brande s Science, Literature,* Art
Copland 's Dictionary of Medicine -
Cresy's Civil Engineering
Gwilt's Architecture - - .
Johnston's Geographical Dictionary
Loudon's Agriculture

" Rural .Architecture

" Gardening

" Plants - - - .

" Trees and Shi ubs -
M'CuUoch'sGeographicul Dictionary
" Dictionary of Commerce

Murray's Encvclo. of Geography -
Sharp's British Gazetteer
Ure's Dictionary of Arts, &c. -
Webster's Domestic Economy

Religious & Moral W^orks.

Amy Herbert - - - - 19

Arro^smith's Geogr. Diet, of Bible a

Bloomfield's Greek Testament - 4

" Annotations on do. - 4

Calvert's Wife's Manual - - o

Conybeare's Essays - - - g

Conybeare and Howson's St. Paul 6

Dale's Domestic Liturgy - - 7

Defence o' Eclipse of Fniih - - 7

Disciiline 7

Earl';. Daughter (The) - - - 19

P:clirise of • aith - - - 7

Englishman's Greek Concordance 7

Englishman'sHeb&Chald. Concord. 7

Exoenence of Life(The) - 19

Gertrude - - - - - 19

Harrison's Light of the Forge - 8

Hook's Lectures on Passion Week 9

Home's Introduction to Scriptures 9

" Abridgment of ditto - 9

Jameson's Sacred Legends - - 10

" Monastic Legends - - lo

" Leasndsrf the Madonna 10

•' Sisteis of Charity - 10

Jeremy Taylor's Works- - - 10

Katharine Ashton - - - 19

Kippis's Hymns -

Kouig's Life of Luther •

Laneton Parsonage - - 19

Letters to My Unknown Friends - 11

" on Happiness - - - 11

Litton's Church of Christ - - 11

Maitland's Church in theCatacombs 14

Margaret Percival - - - - 19

Maitineaus Church History - - 15

Milner's Church of Christ - - 15

Montgomery's Original Hymns - 16

Moore On the Use of the Body - 16

" " Soul and Body - 16

" 's Man and his Motives - 15

Morn onism - - - - 23

Neale's Closing Scene - - - IG

" Resting Places of the Just 16

" Riches that Bring no

Sorrow 16

" Risen from the Ranks - 16

Newman's I J. H.) Discourses - 16

Ranke's Ferdinand & Maximilian 2^3

Readings for Lent - - - 19

" Confirmation - - 19

Robinson's Lexicon to the Greek

Testament 18

Saints our Example - - - 19

Self Denial - ... 19

Sermon in the Mount - - 19

Shortland's \ew Zealand Tradit. 19

Sinclair's Journey of Lile - - '.'0
Smith's (Svdney)'Moral Philosophy 20

" (G'.) Sacred Annals - 20

Southey's Life of Wesley - - 20

Stephen's Ecclesiastical Biography 20

Taylor's Lovola - - - 21

Wesley - - - - 21

Theologia Germanica - - - 21

Thomson on the Atonement - - 21

Thumb Bible (The) - - 21

Turner's S.icred History- - - 23

Wheeler's Popular Bible Harmony 'H

Wilberforce on Supremacy - - 24

Poetry and the Drama.

Arnold's Poems - ... 3

Aikin's (Dr.) British Poets - - 3

Baillie's (Joanna) Poetical Works i

Bode's Ballads from Herodotus - 4

Calvert's Wife's Manual - - 5

Goldsmith's Poems, illustrated - 9

Kippis's Hymns - - - - 11

L. E. L.'s Poetical Works - - 11

Linwood's Anthologia Oxoniensis- 11

Macaulay's Lays of Ancient Rome 14

Montgomery's Poetical Works - 16

" Original Hymns - 1 6

Moore's Poetical Works " - - 16

" Lalla Rookh - - - 13

" Irish Melodies - - - Iti

" Songs and Ballads - - 16

Roby's Remains - - - - is

Shakspeare, by Bowdler - - 19

" Sentiments & Similes lu

Southey's Poetical Works - - 20

«' British Poets - - - 20

Thomson's Seasons, illustrated - 21

Watts'sLyricsof the Heart - - 23

Political Economy and
Statistics.

Caird's Letters on Agriculture - a
Francis On Life Assurance - 8

Greg's Essays on Political and

Social Science - - - - 8

Laing's Notes of a Traveller - 11 & 23

M'CuUoch's Geog. Statist. &c. Diet. 14

" Dictionary of Commerce 14

" London - - - 23

" Statistics of Gt. Britain 14

Marcet's Political Economy - - 15

Tegoborski's Russian Statistics - 21

WflLch's Popular Tables - - 24

Tlie Sciences in General
and Mathematics.

.\rago's Meteorological Essays - 3

„ Popular Astronomy - - 3

Bourne On the Screw Propeller - 4

Brande's Dictionary of Science, &c. 4

" Lectures on Organic Chemistry 4

Cresy's Civil Engineering - - 6

DelaBeche'sGeology ofCornwall,&c. 7

" Geological Observer - 7

De la Rive's Electricity - . 7

Faraday's Non Metallic Elements 7

Herschel's Outlines of Astronomy 9

Holland's Mental Physiology - 9

Humboldt's Aspects of Nature - 10

" Cosmos - - - 10

Hunt On Light - - . ly

Lardner's Cabinet Cyclopjedia - 12

Pa^'^A- I Pagec.

I Marcet's (Mrs.) Conversations - 14

Moseley'sEngineering&Architecture 16

Owen's LecturesonCbmp Anatomy 17

Our Coal Fields and our Coal Pits 23

Pereira on Polarised Light - - 17

Peschel's Elements of Physics - 17

Phillips's Fossils of Cornwall, &c. 17

" Mineralogy - - 17

" Guide to Geology - - 17

Portlock's Geologv of Londonderrv 17

Powells Unity of' Worlds - '- 20

Smee's Electro- Metallurgy - - 20

Steam Engine (The) - - . 4

Tate On Strength of Materials - -1

Wilson's Electric Telegraph - - 23

Rural Sports.

Baker's Rifle and Hound in Ceylon
Berkeley's Reminiscences -
Blaine's Dictionary of Sports - 4
Cecil's Stable Practice - - -
" Records of the Chase -
" Stud Farm - - - - ■
The Cricket Field - - - - >
Davys Piscatorial Colloquies-
Ephemera On Angling - - - -

" Book of the Salmon

Hawker's Young Sportsman -
The Hunting Field

Idle's Hints on Shooting - - ■

Pocket and the stud . - -

Practical Horsemanship - . ^

Pulman'sFly Fishing - - - J8

Richardson's Horsemanship - - 18

St John's Sporting Rambles - 19

Stable Talk and Table Talk - - 8
Stonehenge On the Greyhound 21

The Stud, for Practical'Purposes - H

Veterinary Medicine, &:c.

Cecil's Stable Practice " " ^

•' Stud Farm - - . ''

Hunting Field (The) - - - -

Pocket and the Stud . - - -
Practical Horsemanship

Richaril son's Horsemanship - 1
Stable Talk and Table Talk -
Stud (The) ...--;

Youatt's The Dog - - - - 2i

" The Horse . . . zi

Voyages and Travels.

Baker's Rifle and Hound in Ceylon 4

Barrow's Continental Tour - - 2.'1

Burton's Medina - - - - 5

Carlisle's Turkey and Greece - 5

De Custine's Russia - - 23

Eothen ------ 23

Ferguson's Swiss Travels - - 23

Forester and Biddulph's Norway - 8

Gironifire's Philippines - - - 23

Gregorovius's Corsica - - - '..'3

Hill's Travrjs in Siberia - - 9

Hope's Brittany and the Bible - 24

" Chase in Brittany - - 24

Howitt's -Art-Student in Munich - 9

" (W.) Victoria - - - ;

Hue's Chinese Empire - - - :
Hue and Gabefs Tartary & Thibet
Hughes's .Australian Colonies
Humboldt's Aspects of Nature
Jameson's Canada - - - -
Jerrmann's St. Petersburg -
Laing's Norway . - - -

Notes of a Traveller 11 &
Macintosh s Turkey and Black Si
Marryat's California
Mayne s .Arctic Discovery - -
Mil'es's Rambles in Iceland -
Month before Sebastapol

Oldmixon's Piccadilly to Pera - 10

Osborne's North West Passage - 17

Paton's Bulgarian. &c. - - - 17

PleilTer's Voyage round the World 23

Power's New' Zealand Sketclies - IT

Richardson's .Arctic Boat Voyage If*

Seaward's Narrative - ' - 19

St. John's (H ) Indian Archipelago 19

" (Hon.F.)Hambles - )U

Sutherland's Arctic Voyage - - 21

Wathen's Victoria - "- - " "f

Werne's African Wanderings - 23

Works of Fiction.

Arnold's Oakfield - . - 5

Lady Willoughby's Diary - - 24

Macdonald's'Vilia Verocohio - U

Sir Roger de Coverley - - - -'■'■

Srathev's The nocto'r &c. - - '"

Trollope's Warden - - - V.

White's Charles Random - - '-■!

ALPHABETICAL CATALOGUE

OF

NEW WOEKS AND NEW EDITIONS

PUBLISHED BT

Messrs. Longman, Brown, Green, and Longmans,

PATERNOSTER ROW, LONDON.

Miss Acton's Modern Cookery-Book.—

Modern Cookery in all its Branches, reduced
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Alcorn.~A Compendium of Chronology.

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Member of the Institute, Perpetual Secretary
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W. H. S:j:tth, Foreign Secretary, R.S.,
Corresponding Member of the French
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Baden Powell, M.A., Y.P.R.S., Savihan
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22 IS-EW WOUKS and NEW EDITIONS

THE TRAYELLER'S LIBRAHY,

IN COUESE OP PUBLICATION- IN YOLUMES PEICE HALF-A-CE0W2h EACH :

Comprising books of valuable information and acknowledged merit, in a
form adapted for reading vrliile Travelling, and also of a character that
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List of 39 YoLUMES already {nihUshed.

Vol. 1. Mr. MACAULAY's ESSAYS on WARREN HASTINGS and LORD CLIVE .... 2/6

2. ESSAYS on PITT and CHATHAM, RANKE and GLADSTONE .... 2/fi

3. LAING's RESIDENCE in NORW^^Y 2/6

4. IDA PFEIFFER's LADY's VOYAGE ROUND the Vv^ORLD 2/6

5. EOTHENjOr TRACES of TRAVEL from the EAST 2/6

6. Mr. MACAULAY's ESSAYS on ADDISON, WALPOLE, and LORD BACON. . . . 2/6

7. HUC's TRAVELS in TARTARY, THIBET, and CHINA 2/6

S. THOMAS HOLCROFT's MEMOIRS 2/6

9. WERNE's AFRICAN WANDERINGS 2/6

10. MRS. JAIMESON's SKETCHES in CANADA 2/6

11. JERRMANN's PICTURES from ST. PETERSBURG 2/6

12. THE REV. G. R. GLEIG's LEIPSIC CAMPAIGN 2/6

13. HUGHES'S AUSTRALIAN COLONIES 2/6

14. SIR ED^VARD SEA WARD'S SHIPWRECK 2/6

i.>. ALEXANDRE DUMAS' MEMOIRS of a jMAITRE D'ARMES 2/6

16. OUR COAL FIELDS and OUR COAL PITS 2/6

17. M'CULLOCK's LONDON ; and GIRONIERE's PHILIPPINES . 2/6

13. SIR ROGER DE COVERLEY ; and SOUTHEY's LOVE STORY 2/6

(LORD CARLISLE'S LECTURES and ADDRESSES; and^

^^- \ JEFFREY'S ESSAYS on SWIFT and RICHARDSON j" ^-^^

20. HOPE'S BIBLE in BRITTANY, and CHASE in BRITTANY 2/'6

Ti. THE ELECTRIC TELEGRAPH ; and NATURAL HISTORY of CREATION .. 2/6

22. :\IEMOIR of the DUKE of WELLINGTON ; LIFE of MARSHAL TURENNE. . 2/6

23. TURKEY and CHRISTENDOM ; & RANKE's FERDINAND and MAXIMILIAN, 2/6
jBARROW^'s CONTINENTAL TOUR; and ]

-^- ( FERGUSON'S SWISS MEN and SWISS MOUNTAINS | ^'^^

^ JSOUVESTRE's ATTIC PHILOSOPHER in PARIS, and^j

""*• I ' WORKING MAN'S CONFESSIONS . . . . f "^'^

^^ r Ivlr. MACAULAY's ESSAYS on LORD BYRON and the COMIC DRAMATISTS ; 1

-^- 1^ and his SPEECHES on PARLIAMENTARY REFORM (1831-32) | ^^°

^_ rSHIRLEY BROOKS'S RUSSIANS cf the SOUTH; and 1

^■^ • I DR. KEMP'S INDICATIONS of INSTINCT j ' ''^

28. LANMAN's ADVENTURES in the WILDS of NORTH AMERICA 2/6

29. RUSSIA. By the MARQUIS DE CUSTINE 3/6

30. SELECTIONS from the I^ev. SYDNEY SMITH'S WRITINGS, Vol. 1 2/6

j BODENSTEDT and WAGNER'S SCHAMYL ; and ^

^^•(M'CULLOCH'S RUSSIA and TURKEY | -'^

32. LAING'S NOTES of a TRAVELLER, First Seiies 2/6

33. DURRIEU'S MOROCCO ; and an ESSAY on M0RM0NIS3I 2/6

34. RAMBLES in ICELAND, by PLINY' MILES 2/6

L5. SELECTIONS from the Rev. SYDNEY SMITH'S WRITINGS, Vol. II 2/6

,_ (HAYWARD's ESSAYS on CHESTERFIELD and SELWTN ; and]

"''• I MISS MAYNE'S ARCTIC VOYAGES and DISCOVERIES j ^

Zl. CORNWALL : its MINES, MINERS, and SCENERY ' 2, C

38. DE FOE and CHURCHILL. By JOHN FORSTER, Esq 2/6

39. GRSGOROVIUS'S CORSICA, transiated bv RUSSELL MARTINEAU. M.A. .. 3/6

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