FOEMS OF ANIMAL LIFE

ROLLESTON

MACMILLAN AND CO.

PUBLISHERS TO THE UNIVERSITY

FORMS OF ANIMAL LIFE

BEING

OUTLINES OF ZOOLOGICAL CLASSIFICATION
BASED UPON
ANATOMICAL INVESTIGATION

AND ILLUSTRATED

BY DESCRIPTIONS OF SPECIMENS AND OF FIGURES

BY

GEOEGE EOLLESTON, D.M., F.E.S.

LINACRB PROFESSOR OP ANATOMY AND PHYSIOLOGY
IN THE UNIVEBSIIX,OF OXFORD

AT THE CLARENDON PRESS

M.DCCC.LXX

[All rigUa rmrved']

Ato Set ju,^ bv(rx€pa[v€LV 'TratStKO)? ttji/ irepl t&v aTifioTepav (awv

€tt[<tk€^i.v. kv nacTL yup rots (jiva-iKois evca-rC rt davnaarov /cat

TTpos TTjV CriTr](rLV Trept kKaarov T&v ((oa)V irpocrUvaL h^l p}} bvcrui'uovp.evov
0)5 €v airaa-iv ovtos (pvatKov koL koXoC.— Ahistotle, De Part. Anim. i.5.

UavTos TTpoddeivai to eAAetTroy. — Aristotle, Ethic. Nicom. i. 7.

MUSEUM, OXFORD,
March 5, 1870.

CL*3«

sou

BA7B

»--[.i"f'

PREFACE.

LHIS book is intended to meet certain requirements
which, as the writer's experience has shown him, are
felt by students of Comparative Anatomy. It consists
of three parts ; the first is an introduction, giving a
Classification of the animal kingdom, with a Zooto-
mical account of its various Sub-kingdoms and their
subordinate Divisions and Classes; the second con-
sists of descriptions of certain readily procurable spe-
cimens which illustrate in the concrete a very large
number of the systematic descriptions contained in the
introduction; and the third contains descriptions of
figures supplementary to the descriptions of speci-
mens, and intended to aid them in furnishing that
groundwork of particular facts, without which it is
impossible to obtain any real knowledge or perma-
nent hold of general principles. The distinctive cha-
racter of the book consists in its attempting so to
combine the concrete facts of Zootomy with the out-
lines of systematic Classification as to enable the
student to put them for himself into their natural
relations of foundation and superstructure. The foun-
dation may be made wider, and the superstructure may

VI

PREFACE.

have its outlines not only filled up, but even considerably
altered by subsequent and more extensive labours ; but
the mutual relations of the one as foundation and of
the other as superstructure, which this book particularly
aims at illustrating, must always remain the same.

It is hoped that this work, though written with a
view chiefly to the needs of University students of
Comparative Anatomy, and with especial reference to
the apphcation of that branch of science as an engine
for education, may in some measure meet the require-
ments of the now not inconsiderable nmnber of persons
who are attracted to the study by seeing the important
bearings which it has upon questions not only of theo-
retical and philosophical but also of practical interest.

The amount of knowledge which is presupposed in
aU persons who may use this book, may be judged of
by the following account of the short preparatory
course through which it is the rule that persons
entering for the first time upon the study of Anatomy
in the Oxford Museum should pass. The first requi-
site for a commencing student in this department of
knowledge is that he should be taught how much there
is to be observed and described in a natm-al object,
and it has been found that such a person can have this
lesson impressed upon his mind in an excellent yet easy
way, by addressing himself with osteological specimens
actually before him to the task of verifying the state-
ments made relatively to them in some work specially
devoted to the description of them. The vertebral
column and the bones of the cranium are the specimens

PREFACE.

vii

selected, and recourse is taken to human rather than
to other osteologies, inasmuch as the descriptions they
contain are at once more intelligible to beginners, as
being couched in less technical language, and more full
and precise, and therefore more valuable for the purpose
in question, than most of the ordinarily accessible de-
scriptions of the bones of the lower animals.

Whilst the student is directed not to be dissatisfied
at any failure of his memory to retain, in the absence
of the natural object, the multitudinous details to which
a good descriptive work will have directed his attention
during his examination of it, he is warned that he must
not acquiesce in any failure of power to verify in such
an object, when present, the structural arrangements
which he is informed are to be seen in it.

When this portion of the preliminary course is com-
pleted, a similar study of the principal organs of animal
and vegetable life, such as the brain, the heart, the
digestive tract, the hepatic, and the renal organs, is
entered upon; preparations of these structures pre-
served so as to be accessible to manipulation, and also
microscopic specimens, being available for comparison
with such descriptions as the ordinary works on An-
thropotomy give in their chapters on Visceral Ana-
tomy.

It has been found that after this comparatively small
amount of previous preparation a student is competent
to follow such a description as is given in this work
at pp. 1-4 of a dissection of a mammal ; and it is re-
commended that in all cases the study of the described

viii PREFACE.

preparation or specimen should precede that of the
accounts in the introduction of the Class and Sub-
kingdom to Avhich it belongs, and that the study of
the Descriptions of the Plates should be taken up only
after the attainment of a considerable familiarity with
actual specimens by the practice of dissection.

A short statement of the method which has been
adopted in the preparation of each specimen has in
most cases been prefixed to the description of it ; and
thus persons who have not, as well as those who have,
access to the series in the University Museum, are en-
abled to reproduce for themselves the objects described.
The specimens themselves, it will be observed, ai'e in
the great majority of instances taken from animals
which may be found living in inland parts of this
country; and even when they have been taken from
an exclusively marine Class or Sub-kingdom, such as
the Tunicata or the Echinodermata, they are, Avith an
exception or two, readily procurable in places at a
distance from the sea-coast*.

Small print has been employed in the notes and in
other passages, which the student may do well to omit
when first reading this book.

In some cases, even the beginner will find it necessary

a A dissecting microscope will be required for the verification of the
Descriptions of many of the Preparations of the Invertebrata, and in
these cases the specimens should be affixed to a loaded cork or wax
tablet, and dissected under water or spirit. Some of these animals are
speedily killed by being placed in a glass-stoppered bottle with a few
drops of chloroform ; others by immersion in water several degrees
below 140° F.

PEEFACE.

ix

to consult some of the many works referred to in the
Descriptions of the Preparations and in the Descriptions
of the Plates ; but the bibliographical references have
been added with a view rather to the wants indicated
in the words ' Fur Akademische Vorlesungen und zum
Selbstudium; so often prefixed to German works on
science, than to those of the commencing student. A
local reason for giving development to the bibliographical
portion of this work lay in the fact, that through the
well-advised liberality of the Radcliffe Trustees, one of
the best of existing scientific Libraries had been trans-
ferred to the University Museum ; and much of what-
ever value this volume may possess is to be ascribed
to the happy arrangement in the way of concentration,
whereby that magnificent collection of books has been
placed under the same roof, with so much other scien-
tific apparatus of a non-literary kind.

Nine of the twelve plates described in the third part
of this book, were drawn from nature by Mr. George
Crozier, formerly draughtsman to the Radcliffe Library.

The fifty specimens described in the second part were
prepared by Charles Robertson, Esq., Demonstrator of
Anatomy in the University Museum ; and the greater
part of them were exhibited by him as a ' Zoological
Series with Dissections in Illustration,' in the Educa-
tional Department of the Exhibition of 1862. I have
to thank him for other assistance rendered in the course
of bringing this book to completion.

To the biological teachings of Professor Huxley I
owe a larger debt than even my numerous references

X

PREFACE.

to his works would indicate. I stand in a relation of
similar, though of less extensive, obligation to the
systematic works of Professor Gegenbaur of Jena, of
Professor V. Carus of Leipzig, of Professor Glaus of
Marburg, of Professor Bronn, and of Professor Kefer-
stein of Gottingen. I have also to make acknow-
ledgment to Professors Acland, Phillips, and West-
wood of Oxford, and to Albany Hancock, Esq., of
Newcastle-upon-Tyne, for suggestions requested and
valued by me. In most cases in which other authori-
ties have been consulted upon points of importance,
special references have been given, except in the
Introduction.

GEORGE ROLLESTON.

CONTENTS,

I. INTRODUCTION.

PAGE

(General Considerations suggested by a survey of the Subjects

- treated of ^^^"^^^

'Tabular Views of the system of Classification adopted in this

Work xxYi-xxx

(Characteristics of the Sub-kingdom Vertebrata • • • • • xxxi-xxxix

Divisions Anallantoidea and AUantoidea . xxxix-xl
Subdivisions Sauropsida and Ichthyopsida . xli xlii

'I Class Mammalia xlii-xlvii

Sub-classes Monodelphia, Didelphia, Orni-

thodelphia xlvii-xlviii

Class Aves xlix-lv

Orders, Katitae and Carinatae . -. . . Iv

'I Class Keptilia . Iv-lxi

„ Amphibia Ixi-lxviii

„ Pisces Ixviii-lxxxv

Six orders of Fishes Ixxxi-lxxxv

Characteristics of the Sub-kingdom MOLLUSCA Ixxxv-lxxxviii^^

Divisions Mollusca Proper and Molluscoidea Ixxxvii-lxxxviii

Class Cephalopoda Ixxxviii-xcii

„ Pteropoda xcii-xcv

„ Gasteropoda xcii-xciii

„ Lamellibranchiata xcv-xcviii

„ Brachiopoda xcviii-c

„ „ Tunicata c-ci

„ Polyzoa ci-ciii

Characteristics of the Sub-kingdom Arthropoda civ-cviu

„ Divisions Tracheata and Branchiata . . . cv-cvi

„ Relations of Arthropoda to Vermes . . . cvii-cviii

Class Insecta cviii-cxiii

„ Class Myriopoda cxiv-cxvi

„ „ Arachnida cxvi-cxviii

„ Crustacea cxviii-cxxii

CONTENTS.

Characteristics of the Sub-kingdom Veemes .... cxxii-cxxvii

» Class Annulata Proper cxxvii-cxxxi

" » Gephyrea cxxxi-cxxxiii

« „ Nematelminthes .... cxxxiii-cxxxvii

» y> Rotifera cxxxviii-cxl

» » Platyelmintlies cxl-cxliii

Characteristics of tte Sub-kingdom Echinodermata . cxliii-cxlvii

» Class Holothurioidea cxlvii-cl

'» 55 Echinoidea cl-cliii

»» » Asteroidea cliii-cliv

» » Crinoidea cliv-clvi

Characteristics of the Sub-kingdom Coelenterata . . clvi-clvii

» Class Ctenophorae clvii-clviii

" » Anthozoa clviii-clix

» Hydrozoa clix-clx

Characteristics of the Sub-kingdom Protozoa. , . . clx-clxi

Relations of the various classes of this sub-kingdom,

^^^^ ^« [ clxi-clxii

Means for distinguishing animal fi-om vegetable organisms clxii-clxiv

Characteristics of the Class Infusoria clxiv-clxv

" » Rhizopoda clxv-clxvi

„ Spongiadae clxvi-clxvii

„ Gregarinae clxvii-clxviii

II. DESCRIPTION OF PREPARATIONS.
From the Class Mammalia.
Prep. I. Dissection of Rat {Mm decumanus), showing its
craniospinal nei-vous axis, and portions of
most of the organs of vegetative life . . . l_4
Prep. 2. Skeleton of Common Rat {Ifus decumanus) . . 5-9
Prep. 3. Cervical, Dorsal, and Lumbar Vertebrae of Rabbit

{Lepus cuniculus) 10-12

From the Class Aves.
Prep. 4. Dissection of Common Pigeon {Columba lima),
showing neiwous, digestive, circulatory, and part

of respiratory and renal systems 12-16

Prep. 5. Skeleton of Common Pigeon ((7o^M7?j,6a Ziuia) . . 17-25
Prep. 6. Skull and Trunk-bones of Common Fowl {Galbis

gaUinaceus) 25-29

CONTENTS. xiii

PAGE

From the Class Reptilia.

Prep. 7. Dissection of Common Ringed Snake {Tropido-
notus natrix), showing the an-angement of the

various organs of vegetative life 29-33

Prep. 8. Vertebrae of Constricting Serpent (Sp. 1) . . . 33-35

From the Class Amphibia.

Pi'ep. 9. Dissection of Common Frog {Eana temporcma),
sliowing its nervous, circulatory, and respira-
tory systems, together with some of its repro-
ductive and digestive organs 35-37

Prep. 10. Skeleton of Common Frog {Rcma temporaria) . . 38-40

From the Class Pisces.
Prep. II. Dissection of Common Perch {Ferca Jluviatilis),
showing its circulatory, nervous, digestive, re-
spiratory, and reproductive systems in situ . 40-42
Prep. 12. Skeleton of Common Perch {Perca Jluviatilis) . 42-45
Prep. 13. Vertebrae of Common Cod {Gadus morrhua) . . 45, 46

From the Class G-asteropoda.

Prep. 14. Shell of Edible Snail (jSeZia; ^omafo'a) .... 47,48

Prep. 15. Dissection of Edible Snail (Helix pomatia),
showing its digestive and reproductive, together
with parts of its circulatory and respiratory,

systems 48-5 1

Prep. 16. Dissection of Edible Snail {Helix pomatia),
showing the position of the heart and of the

respiratory cavity 51-52

Prep. 17. Dissection of Edible Snail {Helix pomatia),

showing its nervous system 52-54

From the Class Lamellibranchiata.

Prep. 18. Shell of Fresh- water Mussel {Anodonta cygnea) . 54-57

Prep. 19. Dissection of Fresh-water Mussel {Anodonta c?/^-

nea), showing the course of its digestive tract . 57-60

Prep. 20. Dissection of Fresh-water Mussel {Anodonta

cygnea), showing its mantle 60-62

Prep. 21. Dissection of Fresh-water Mussel {Anodonta
cygnea), showing its nerve system, and the
route taken by the ova in passing from the

ovary to the interior of the external gill . . . 62-66

xiv CONTENTS.

PAGE

Prom tlie Class Tunicata.
Prep. 2 2. Dissection of Ascidian {Ascidia affinis), showing
the homological relations of its various systems
to those of the Lamellibranchiata 66-71

. rrom tlie Class Polyzoa.

Prep. 23. Specimens of Broad-leafed Hornwrack {Flustn-a

foliacea) 71, 72

Prep. 24. Specimen of Bugle Coralline [Salicornaria fa/rcv-

minoides) 73

From the Class Insecta.
Prep. 25. Specimen of Larva of Death's-head Moth (Ache-

rontia atropos) 73-76

Prep. 26. Specimen of Pupa of same species . ..... 76-78

Prep. 27. Specimen of perfect Insect of same species . . . 78, 79
Prep. 28. Dissection of Larva of Goat Moth (Cossus ligni-

perda), showing the organs of vegetative life . 79-82
Prep. 29. Dissection of Larva of Privet Hawk Moth (Sphinx

ligustri), showing the nervous system . . . 82-85
Prep. 30. Dissection of Common Cockroach {Periplcmeta
~ orientalis), showing its digestive, renal, nervous

and reproductive organs 86-90

Prom the Class Crustacea.

Prep. 31. Specimen of Common Crayfish (^siacMs^wvia^tYis) 90-98

Prep. 32. Dissection of Common Crayfish {Astacus fluvia-
tilis), showing the nervous, digestive, and circu-
latory organs in situ 98-100

Prep. 33. Dissection of Common Crayfish (Astacus fluvia-

tilis), showing the heai't and arteries .... 100-102

Prep. 34. Dissection of Common Crayfish (Astacus Jluvia-
tilis), showing its digestive, respiratory, and
reproductive organs in situ 102-105

Prep. 35. Dissection of Common Crayfish (Astacus fluvia-
tilis), showing its nerve system. Tables of
homologies of nerve-ganglia, and of appendages,
arc to be found at pp. 110, 116, 117 .... 106-119

From the Class Annulata Proper.
Prep. 36. Specimen of Common Earthworm (Lwnihricus

terrestris) 119-121

CONTENTS. XV

PAGE

Prep. 37. Dissection of Common Earthworm (Lumbricus

t&rrestris), showing its nervous system . . . 121-123

Prep. 38. Dissection of anterior segments of same animal,

showing its reproductive organs 124-126

Prep. 39. Specimen of Medicinal Leech {Hirudo medicinalis) 127-129

Prep. 40. Dissection of Medicinal Leech {Hirudo medicinalis),

showing nervous and digestive systems in situ . 129-131

Prep. 4 1 . Dissection of Medicinal Leech {Hirudo medicinalis),

showing nervous system 131-133

Prep. 42. Dissection of same animal, showing the reproduc-
tive and segmental organs in situ 133-136

From the Class Platyelminthes.
Prep . 43 . Specimen of Many-headed Bladder-worm {Caenurus

cuniculi) 136-140

From the Class Asteroidea.

Prep. 44. Specimen of Common Crossfish {Asterias ruhens) . 141-143
Prep. 45. Dissection of Common Crossfish {Asterias rubens),

showing digestive and motor systems . . . 143-145

From the Class Holothurioidea.
Prep. 46. Specimen of Angular Sea-Cucumber {Oucumaria

pentactes) 145-147

Prep. 47. Dissection of Angular Sea-Cucumber {Oucumaria
pentodes), showing motor, digestive, respira-
tory, and reproductive systems 148-158

(Eelations of Echinodermata to Coelenterata
and to Vermes severally at pp. 152-157 of the
Description of this Preparation.)

From the Class Anthozoa.
Prep. 48. Dissection of Sea-Anemone {Actinia crassicornis),
showing its various external and internal
organs 158—160

From the Class Hydrozoa.
Prep. 49. Specimen of Sea-Fir (^S'er^M^arm a6ie<ma) . . . 160-163

From the Class Spongiadae.

Prep. 50. Specimen of Fresh-water Sponge {Spongilla lacu-

stris) 163-1G6

xvi

CONTENTS.

III. DESCRIPTION OF PLATES.

PAGE

Plate I. Dissection of Mammal (J/ws cZecwmanws) . . 167-173

Plate II. Dissection of Bird {Golumba livia) 175-180

Plate III. Dissection of Amphibian ie??ipomrm) . 181-185

Plate IV. Dissection of Gasteropod (Zimax/avws) . . . 187-191

Plate V. Dissection of Lamellibranch {Anodonta cygnea) . 192-198

Plate VI. Dissection of Insect {Periplaneta orientalis) . . 199-204

Plate VII. Dissection of Crustacean (-4stociis /wuiaii^is) . 205-210

Plate VIII. Dissection of Annelid (XwrnftWcws ierresiris) . 211-216

Plate IX. Dissection of Annelid (^M-McZo mecZicmaZw) . . 217-222

Plate X. Dissection of Echinoderm (Asterias ruhens) . . 223-229

Plate XT. Fig. i. Diagram of Cephalopod 231

Fig. 2. Section of Bracbiopod {Rhytichonella

psittacea) 232-234

Fig. 3. Diagram of Ascidian 235, 236

Fig. 4. Diagram of Polyzoon 237, 238

Fig. 5. Fig\ire of Eotifer (£2/(iaima se?ito) . . 239,240
Fig. 6. Figure of Turbellarian Worm [Dendro-

coeh/m nausicaa) 240-243

Fig. 7. Figure of Gregarine {Stylorhynchus oli-

gacanthus) 243, 244

Plate XII. General account of first six figures 245, 246

Fig. I. Semi-diagrammatic figure of Strobile of

Taenia 246

Fig. 2. Immature segment of Strobile of Taenia 246-248

Fig. 3. Matui-e segment 249

Fig. 4. Segment intermediate in age .... 249, 250

Fig. 5. Proscolex of Taenia 250, 251

Fig. 6. Cystic stage of Cae?mn<^ cere6m?w . . 251,252

Fig. 7. Figure of Coelenteratum (iTyc^m t'incfis) 253-255

Fig. 8. Figure of Infusorium (P?wWo?i feres) . 255-257

Fig. 9. Figure of Rhizopod (uiwoe&a mc^iosa) . 257-259

Errata and Addenda

Index 261-268

INTRODUCTION.

jLN several different departments of research, and from many-
different points of view, we are brought to see that the study of
Comparative Anatomy, while raising- questions of the highest
theoretical importance, throws light at the same time upon pro-
blems of great practical interest. Of its twofold bearings, the con-
troversies carried on at the present moment as to the Origin of
Life and as to the Origin of Species, extending, as they do, on the
one side into the provinces of Hygiene and Therapeutics, and on
the other into yet higher regions than those, furnish two apposite
but not isolated illustrations. It is not within the scope of this
work to do more than thus glance ^ at such practical questions

^ It may be well here to give a few instances in which light has been thrown upon
complex questions of Hygiene and Pathology in the course of investigations ap-
parently wholly dissociated from such subjects. Dr. Charlton Bastian has, in the
Philosophical Transactions for 1866, vol. 156, pt. ii., pp. 583, 584, put upon record a
most instructive account of the production of a spasmodic and catarrhal affection not
altogether unlike hay fever, under circumstances, however, which appear to preclude
the possibility of any living organisms having been, as has recently been suggested,
the cause of it. This affection was invariably produced from the emanations inhaled
during the dissection of a particular Nematoid worm, the Ascaris megalocephala, from
the Horse, and this not only when the animal was fresh, but 'after it had been
preserved m methylated spirit for two years, and even then macerated in a solution
of chloride of lime for several hours lefore it was submitted to examination.' It would
seem certain that no morphological unit, nor even any cell-like or ' cytoid' body, can
have been at work under circumstances such as these. On the other hand, we have
no less an authority than Helmholtz for the coexistence of vibrios in the nasal
passages with the presence of hay fever (Virchow's Archiv. xlvi., p. loi, Feb. 1869),
and indeed for the causal relation of the former to the latter condition. Chauveau's
experiments, again (Revue des Cours Scientifiques, Jan. 1, 1870, p. 77), shew that in the

b

xviii

Introduction.

as those relating to the possible modes of origination, and to the
available methods for the combating of disease ; neither is it
advisable here to occupy space in pointing out at length or in
detail the various lines along which the results of Comparative
Anatomy come to bear upon the more purely speculative questions
alluded to. There are, however, certain considerations of greater or
less general interest, either as premises or as conclusions, which a

absence, if not of certain animal cells, still of certain animal ' cytoids' or 'leucocytes,'
the vaccine poison is inoperative. For the application of such investigations to actual
practice see Professor Lister's Introductory Lecture delivered in the University of
Edinburgh, Nov. 8, 1869 ; British MedicalJournal, Dec. 4, 1869. — The vexed question
of the method in which nerves influence nutritional processes receives considerable
elucidation from the facts that not only do certain Holothurioidea (Stichopus and Colo-
chirus) possess the power of shedding off the non-muscular elements of their in-
tegument as amorphous slimy matter upon irritation, but also that isolated fragments
even of their integument, in which it would appear nerve structures are contained,
possess the like power, and go through the process of self-dissolution more quickly or
more slowly in correspondence with more or less stimulation. (See Semper, Eeisen
im Archipel der PhUippinen, Theil. ii., Bd, i., pp. 72, 171, 172, 200.) The universally
acknowledged but often practically ignored influence of changes in the circum-
ambient medium are well illustrated by such observations as those of M. Claparfede
on the growth of Annelida (see Ann. and Mag. Nat. Hist. Ser. iii., vol. xx., p. 359,
1867), and those of Professor Wyville Thomson on the varying rate of development
of certain Echinoderm larvae (see Phil. Trans, vol.155, ii-> PP- 5i4> S^Sj 532)
under varying conditions of light, heat, and aeration. Dr. Charlton Bastian has
drawn attention (Linn. Soc. Trans, xxv., p. 84, 1865) to the quantity of large fat
globules often seen within the intestinal canal of free Nematodes as being ' remark-
able, and also interesting in a physiological point of view, as an exemplification of the
almost direct conversion of cellulose into fat and other products.' The facts of Com-
parative Anatomy and Physiology as distinct, though not dissociated, from those of
Comparative Pathology and Experiment, are appealed to by both sides in the ques-
tions ' Ueber die Fettbildung im Thierkorper,' and that of the relations of various
kinds of food to the various exigencies of the animal body. (See Donders, Nederl.
Arch, voor Genees. en Natuurkunde, Deel. i., Uti-echt, 1864 ; translated, Dublin
Quarterly Journal of Medical Science, 1866; Lawes and Gilbert, Phil. Mag., July
and December, 1866 ; Volt. Zeitschrift fiir Biologic, Bd. v., Hft. i., pp. I47-155,
1869.) For the way in which the intimate relations of the fifth nerve to the optic may
be illustrated by reference to Comparative Anatomy, see Mooren, Ueber S3Tnpa-
thische Gesichtstorungen, pp. 11 7-1 19, Berlin, 1869 ; and for numerous illustrations
of the fact that the organisms of the lower animals give answers in simple language
to what are difiicult problems in Anthropotomy, see Schroeder Van der Kolk, on the
Spinal Cord and Medulla Oblongata ; New Sydenham Society's Translation, passim,
and especially chapter vi., pp. 170-178, 1859. For other points of connection be-
tween Comparative Anatomy and Practical Medicine, see 'Medicine in Modern Times,
pp. 79-91, London, 1869.

General Considerations. xix

contemplation of the subjects here treated of with reference to
their bearings upon Classification, is calculated to impress upon
the mind ; and these it may be well to state in a few words.

After some study of the details of Comparative Anatomy we
begin to see that the animal kingdom is divisible into a certain
nimiber of Sub-kingdoms accordingly as the various structures or
organs su.bserving' the functions of animal and vegetable life re-
spectively are combined with, separated from, or otherwise arranged
relatively to, each other. It is, in the next place, easy to see that
whilst in the Sub-kingdom Vertebrata, motor, nervous, vascular,
visceral, and perivisceral systems all exist in specialized and differ-
entiated forms, no such ' division of labour' is recognisable in the
structural arrangements of the Sub-kingdom Protozoa ; and that,
by a farther and detailed reference to the principle just mentioned,
we are justified in speaking of the one as the highest and the others
as the lowest of the seven animal Sub-kingdoms. It is not easy,
however, to assign to the three Sub-kingdoms known as Mollusca,
Arthropoda, and Echinodermata their relative rank inter se ; and
the Sub-kingdom Vermes would appear to underlie each and all of
the three obliquely, rather than to be subordinated to any one of
them in particular. The Coelenterata, finally, are approximated to
the Protozoa by the low degree to which specialization has been
carried out in their organization ; but they form a more than
ordinarily well-circumscribed group, which we are in no way
justified in regarding as forming a transitional stage intermediate
between the Protozoa and the other Sub-kingdoms, from which
latter it lies far apart.

Within the limits of each Sub-kingdom the differentiation of
organs, by the assignment of them to the more or less exclusive
performance of particular functions, is very often carried out in the
different classes to such a different extent as to allow us to speak
without violence and without hesitation of such classes as being
higher or lower in the scale of existence. Elevation in the scale
of life is indirectly entailed in Sub-kingdoms which possess air-
breathing representatives, as aerial respiration renders possible a
greater activity of function than an organism differing in this,
though similarly constituted in all other particulars, can put forth ;
whilst the special habit of parasitism, which often renders not
merely single organs but even whole systems superfluous, and is

b %

XX

Introduction.

then found to be correlated with the complete or nearly complete
disappearance of such structures, must be regarded as entailing
a true morphological degradation.

Sharply circumscribed outlines are, in the second place, as com-
monly wanting in the classifications we have to deal with as are
precisely graduated scales of dignity. The boundaries of species, of
orders, of classes, and, in more than one instance, even of sub-king-
doms, may be closely apposed not only at many single points
but even along considerable lengths and depths, so that in not a
few cases it is a matter of difiiculty to decide whether a particular
organism or set of organisms shall be placed within the one or the
other of the thus complexly approximated groups.

The distances, thirdly, which intervene between the various sub-
kingdoms at their points of widest separation from each other are
exceedingly unequal. And in particular, it may be said that, in
spite of recent discoveries'', it would still appear that the Vertebrate
Sub-kingdom lies at a greater distance from the group made up by
all the other Sub-kingdoms than that by which any one of these is
separated from its nearest neighbour.

Groups, fourthly, which would be allowed on all hands to possess
the same morphological or qualitative rank are found to difier very
widely as to the numbers of the objects they severally include;
and if, by the aid of diagrams, we represent to ourselves the quan-
titative relations which the corresponding divisions in almost any
two of the animal sub-kingdoms hold to each other as wholes of
• extension' or of ' denotation,' we are at once struck by the great
inequality of size indicated by the figures thus constituted. A
similar result would ensue upon the application of a similar process
to many non-biological classifications ; the especial significance
which these difierences possess in organic classifications depends
upon two singular but suggestive facts, actual observation having
shown, firstly, that the poorer a species is numerically the more
aberrant is it ordinarily found to be from the type of the group
to which it is subordinated ; and secondly, that with a paucity
of individuals or of species, as the case may be, a similar paucity
of the localities on the earth's surface in which they are now to be

•> For a Bummary of these diBcoveries, see the Quarterly Journal of Microscopical
Science, January, 1870.

Gen ercd Cons icier ations.

xxi

found living is ordinarily correlated. The Ganoids among-st Pishes,
the Perennibranchiata amongst Amphibia, the Crinoids amongst
Echinodermata, and the Monotremata amongst Mammals, furnish
us with illustrations of these laws for the enimciation of which we
are indebted to Von Baer

A remark of the late Mr. W. S. Macleay, to the effect that no
character is natural until it has been proved to be so ^, has the merit
of at once expressing tersely the necessity of constant recourse to
verification when we make deductions from general principles, and
of drawing attention to the striking morphological fact of the
varying valne of class characters. In the face of statements as to
the eligibility of particular systems ® as bases of classification, which
are only less sweeping and general than they are mutually con-
tradictory, it is a satisfaction to be able to quote the following
words from the writings of another English naturalist, the late
Professor Edward Forbes, — ' no character, whether of structure or
form, preserves an equal value in every tribe, but varies in its im-
portance, in one group characteming a class, in another scarcely
determining a species;' whilst the words of Macleay should be

<= See Nova Acta, xiii., i, p. 742, 1826, or Professor Huxley's Translation in
♦Scientific Memoirs/ pp. 180, 181, 1853.

d See Linnaean Society's Transactions, xxiii., p. 75, i860.

e For the applicability of the nervous system as a basis of classification, see Cuvier,
The Animal Kingdom, English Translation, 1854, p. 31 j Lacaze Duthiers, Comptes
Bendus, 1865, torn, ii., p. 800; Blanchard, Ann. Sci. Nat., Ser. iii., tom. v., pp. 276,
376, 1846 ; Dana, Crustacea, pp. 46, 59 ; Waterbouse, Ann. and Mag, Nat. Hist.,
vol. xii., p. 399, 1843 ; Professor Owen, Linnaean Society's Proceedings, 1857. For
the applicability of the Reproductive, see Dana, I.e., p. 62 ; Professor Owen, cit.
Darwin, Origin of Species, chap, xiii., p. 490, 4th ed. t866 ; Fischer, Orthoptera,
p. 62 ; Stein, Vergleichende Anatomic und Physiologie des Insekten ; erste Mono-
graphic ; Die weibHchen Geschlechts-Organe der Kafer, 1847, passim. For the appli-
cability of the Respiratory, see Dana, I.e., p. 62. For the value of the changes gone
through in development, see Professor Wyville Thomson, Phil. Ti-ans., vol. 155,
pt. ii., pp. 514, 532, where attention is drawn to the power which circumstances of
light, warmth, aeration and nourishment have in modifying and hurrying over certain
stages of larval growth ; Oskar Schmidt, Sitzungsbericht, Nat. Wiss. Class. Kaia.
Akad. Wien. xix., p. 193, 1856 ; Darwin, Animals and Plants under Domestication,
vol. ii., pp. 366-368 ; Origin of Species, p. 494, ibique citata. For the value of the
motor system as a basis for classification, in the sub-kingdom Echinodermata, see
Brandt, Prodromus, 1835. For that of the Placental system in the class Mammalia,
Bee Zool. See. Trans., vol. v., pt. 4, p. 285, 1865 ; H. Milne Edwards et Alphonse
Milne Edwards, Recherches pour servir h. I'Histoire Naturelle des Mammif feres,
Livraison i., p. 18, seq^q., ihiqiie citata, 1868.

XXll

Introduction.

bome in mind with reference to certain otlier statements ^ of even
greater generality as to the applicability or inapplicability of phy-
siological differences as bases of zoological arrangements. Nothing
is easier than to say that by the nervous, or by the reproductive,
or by the respiratory systems, or by the history of the changes
gone through in development, ' characters of the widest bearing in
classification are furnished ;' but nothing is more certain, as a
veiification of statements referred to below will demonstrate, than
that what is true of one of these bases of classification within the
limits of one Sub-kingdom, or within the limits of one Class, or even
within the limits of yet smaller groups, will not be by any means
invariably found to be true within the limits of another similar
division. Our knowledge, again, of the power which organisms
have of adjusting themselves to their environment, may incline us
to think the motor and tegumentary systems to be bad bases for
classification, as it is through them that the animal comes mainly
and mostly into relation with external influences. Yet, if Seals
and Whales exhibit marks of their aflanities to the Carnivora and
the Artiodactyla respectively, even in such matters as the cha-
racter of theii- placentae, the number of the bronchi in their lungs,
and, in spite of the modifications which their motor and tegu-
mentary systems have undergone, it is nevertheless true that the
specialization of the same systems in Aves and Echinodermata
appears to have entailed corresponding variations throughout the
entirety of their respective organisms, and in organs of vegetable
as well as in organs of animal life.

The facts of the varying morphological value of zoological dif-
ferentiae ; of the unequal quantitative extent of di\dsions of equal
morphological rank ; and of the unequal distances separating such
divisions, go some way towards accounting for the arbitrary way
in which the same division has had very different morphological
rank assigned to it by different classificatory writers. A pro-
visional character however must always attach itself to a greater
or smaller part of all our classifications ; if they succeed in pre-

f See Erichson, Entomographien, p. i, 1840, 'Dies ist ein pliysiologischer, kein
• zoologischer Character,' Semper, Reisen in Archipel der Philippinen, Theil. ii., Bd. i.,
p 52 ■ Carpenter, Foraminifera, Ray Society, p. 14, 1862 ; Herbert Spencer, Pnn-
ciplea of Biology, vol. i, pp. 306. 307. 1864; D^^win, Origin of Species, 4th ed.,
p. 490.

General Consideixitions.

xxiii

senting to our minds the knowledge we possess at the passing
moment in a form which gives it compactness as to the past and
availability for use in the future, that is all which in the nature of
the ease they should be regarded as doing, or expected to do, for
us. An increase in our knowledge may confirm, but it may, on
the other hand, overthrow the most perfectly symmetrical of
systems °.

e It is not a little instnictive to note that Macleay, to whom Zoology is indebted
for the 'grand principle' referred to above, should yet have been the inventor of
the 'quiaary system,' with its independent but numerically identical groups arranged
in circular series. For the history and for iHustrations of the working of this iclolon
theatri, see Macleay, Horae Entomologicae, vol. i., pt. ii., p. 322, 1821 ; Swainson,
Geography and Classification of Animals, p. 202, et passim, 1835; Edward Forbes,
Starfi.shes, p. xvi. 1841 ; Milne Edward.s, Ann. Sci. Nat., Ser. iii., tom. i., p. 79,
1844 ; Agassiz, Essay on Classification, p. 344, 1859. Bacon's words are singularly
appropriate in relation to these arbitrary assumptions : — ' Intellectus humanus ex pro-
prietate sua facile supponit majorem ordinem et equalitatem in rebus quam invenit ;
et quum multa, sint in nature monodica, et plena imparitatis, tamen affingit parallela
et correspondentia et relativa quae non sunt. Hinc commenta ilia in coelestibus
omnia moveri per circulos perfectos.' Nov. Organ, slv. Neither are the words
of the modern poet quoted by Sir John Richardson (Introduction, Fishes, Museum
Natural History), in relation to a recent attempt to unite Fishes, Amphibia, and
EeptUes into one division, the Haematocrya, unworthy of being quoted here : —

' Our Uttle systems have their day,
They have their day and cease to be.
They are but broken lights of Thee,
And Thou, 0 Lord, art more than they.'

Tennyson, In Memoriam, vi.

Striking evidence is borne to the scientific fact of the great difference which exists
between the works which are and those which are not of man's creating, by the
singular circumstance that of all the many metaphors which have been used to
express the general or picturesque* effect produced on the mind by the study of a
system of biological classification, those only retain a strong hold upon the imagination
which are borrowed from natural objects ; whilst those which are borrowed from
works of art, or from productions of the arts, are at once felt to be inadequate even
when not untrue. In illustration of this, it is sufficient to lay specimens of the two
kinds of metaphor mentally alongside of each other. In the latter we have the
divisions of the organic world compared to the steps in upward-sloping stairs ; or to a
series of columns placed upon a flight of such stairs ; or to the meshes of a net ; or to
the artificial boundary-lines of neighbouring kingdoms ; the more modern and truer
comparisons we refer to are drawn from such objects as single stars, each surrounded
with its own proper atmosphere ; as aggregations of such stars in constellations ; as
trees with stems, branches, twigs and leaves ; as hiUs clothed with woods, and sepa-
rated by valleys dipping to various depths, and themselves bestudded with clumps

xxiv

Introduction.

■The above-quoted saying of Mr. Macleay's, by suggesting the
question,, * When is a character to be considered as proved to be
natural ? ' brings us face to face with the most distinctive pecu-
liarity of zoological classification. A character is a good basis for
classification in zoology, as in every other subject, when its presence
enables us to predict the presence of many, or at least of some
other characters besides those which its name implies etymolo-
gically ; but when we are concerned with species in zoology, these
other characters must relate not only to the entirety of the or-
ganism as such, but also to the main facts of its life history.
When we class two living organisms together in the same species,
we include always among the other facts which their common
specific name must connote, the particular fact that it is possible
for them both to have descended from one ancestor or ancestors,
which, either directly, or after certain stages in cyclical metamor-
phosisj they could reproduce. For cyclical self-repetition in the
way of parentage, being eminently the characteristic of living
organisms, as opposed to non-living objects, no classification of
such organisms would be either natural or valuable which did not
lay that particular part of their history in a compact and manage-
able form before the mind, whensoever evidence as to it was ob-
tainable. It is true that such evidence is by no means invariably
accessible ; and when it is not, we have only likeness to guide us
as to saying that it is more or less probable that between any two
organisms such prospective and retrospective community in parent-
age might or did exist. On the other hand, where this evidence is
forthcoming, the question of identity of species is instinctively
and at once settled in the affirmative ; even when the unlikeness
between the individuals compared may be as extreme as that
which exists between the well-known larvae of Batrachia and their
adult forms, or between the less familiar but even more strikingly
difiering larvae and adults of Cirripedia, of other Crustacea, of
the Platyelminthes, and of many Hydrozoa (see iiifra, pp. 162,
245, 252). The theory of evolution ^vith which Mr. Darwin's
name is connected, asks us to deal with species in their relation

of trees ; as systems of mountain-ranges, more or less connected by outliers ; or,
happiest metaphor of all — as the islands of an archipelago, sometimes all but conti-
nuous through the intermediation of connecting reefe, sometimes sharply separated
by unfathomable seas.

General Considerations.

XXV

to genera and still higher divisions, as we deal with individuals
in referring' them to particular sj)ecies, and to believe that the
'secret bond' which colligates species under larger groups, is
of the same genealogical character as that which we look for
always, and often find in the case of individuals. Many of the
peculiarities which attach to biological classifications would thus
receive a reasonable explanation ; but where verification is, ex h^/po-
thesi, impossible, such a theory cannot be held to be advanced out
of the region of probability. The acceptance or rejection of the
general theory will depend, as does the acceptance or rejection of
other views supported merely by probable evidence, upon the par-
ticular constitution of each individual mind to which it is presented.
But whether the general theory be accepted as a whole or not, it
must be allowed that in the face, on the one hand, of our know-
ledge of the greatness of the unlikeness, which may be compatible
with specific identity ; and, on the other, of our ignorance of the
entirety of the geological record, the value of the special ' Phylo-
genies,' or hypothetical genealogical pedigrees, reaching far out of
modern periods, are likely to remain in the very highest degree
arbitrary and problematical.

xxvi

Introduction.

Tabular View of the System of Classification adopted in this
work, shewing the various Sub-kingdoms in some of the
relations of mutual affinity and of rank which they have
been supposed to hold to each other. In the cases of several
names an oblique position would have been truer to nature
than the horizontal one which they occupy in the Table. The
lines abut upon the names of the Classes or Orders by which
the several Sub-kingdoms have been regarded as connected
with each other. (Arrangement of Sub -kingdoms after
Gegenbaur.)

VEKTEBBATA

(Pharjngobranchii)

ARTHROPODA

(Cmstacea)

ECHINODERMATA

(Crinoidea) (Holothurioidea)

MOIiliUSCA

(Polyzoa) (Tunicata)

VERMES I
(Annulata. Tubicolae) (Gephyrea) (Platyelminthes) (Eotifera)

COELENTERATA

PROTOZOA
(Spongiadae) (Infusoria)

Introduction.

xxvn

Tabular View of the System of Classification adopted in this
work^ giving the various Classes into which the seven Sub-
kingdoms are divided. The relative positions of the names of
the Classes indicate the relations of affinity and of rank which
each Class has been supposed to hold to the other Classes
in its own Sub-kingdom.

Mammalia

Aves
Reptilia

VEBTEBRATA

Amptibia
Pisces

Arachnida Myriopoda

ABTHROPODA

Crustacea

Insecta

Cephalopoda pt^^opoda

Gasteropoda
MOLLUSCA Lamellibranchiata
Tunicata
Brachiopoda
Polyzoa

Ctenophorae

COELENTEBATA

Anthozoa

Hydrozoa

Holothurioidea Echinoidea
ECHINODBKMATA

Crinoidea Asteroidea

Anntdata Gephyrea

VERMES ^ ^^^.^^^^

Nematelmintliea

Platyelminthes

Spongiadae Infusoria
PROTOZOA
Rhizopoda Gregarinae

XXVUl

Introduction.

Tabular View of the System of Classification adopted in this work, giving-
the pages at which the characteristics of the various Sub-kingdoms
and of the Provinces and Classes subordinated to them ; those at which
the Descriptions of the Specimens; and those at which the Descriptions
of the Figures in illustration, are to be found.

I. SUB-KINGDOM. VERTEBEATA, pp. xxxi-lxxxv.

Allantoidea, p. xl.

Subdivisions

DrwsiONs <

Mammalia = Class 1. Mammalia
pp. xlii-xUx. pp. xlii-xlix. pp. i-i 2
PI. i. pp. 167-173

Sauropsida
p. xli.

Anallantoidea, p. xli-xlii =

Subdivision'

Class 2. Aves

pp. xlix-lv. pp. 12-29
PI. ii. pp. 175-180

Class 3. ReptUia
L pp. Iv-lxi. pp. 29-35

Ichthyopsida
pp. xli-xlii.

"Class 4. Amphibia

pp. Ixi-lxviii. pp. 35-40
PI. iii. pp. 1 81-185

Class 5. Pisces

pp. Ixviii-lxxxv. pp. 40-46

II. SUB-KINGDOM. MOLLTJSCA, pp. Ixxxv-ciii.

Divisions -

Molluaca Proper, pp. Ixxxv-lxxxvii.

Subdivisions

Class 1. Cephalopoda
pp. Ixxxviii-xcii.
PI. xi. fig. I

Odontophora J Class 2. Pteropoda
p. Ixxxvii. ' pp. xciii-xcv.

Class 3. Gasteropoda
pp. xcii-xciii. pp. 47-54
PI. iv. pp. 187-191

. 1 , V fClass 4. Lamellibranchiata
Anodontophora ...

n VPV i PP- XCV-XCVIU. pp. 54-66

p. xcv.

Molluscoidea, pp. Ixxxvii-lxxxviii. . .

1^ PI. V. pp. 192-198

"Class 5. Brachioijoda
pp. xcviii-c.

PI. xi. fig. 2, pp. 232-234

Class 6. Tunicata
pp. c-ci. pp. 66-71

PI. xi. fig. 3, pp. 235, 236

Class 7. Polyzoa
pp. ci-ciii. pp. 71-73

PI. xi. fig. 4, pp. 237, 238

Introduction,

xxix

(Tabular View with Pages.)

Ill, SUB-KINGDOM. ABTHBOPODA, pp. civ-cxxii.

DDmsioNs

Tracheataj pp. cv-cvi.

Branchiata

Class 1. Insecta

pp. cviii-cxiii. pp. 73-go
PI. vi. pp. 199-204

■ Class 2. Myriopoda
pp. cxiv-cxvi.

Class 3. Arachnida
pp. cxvi-cxviii.

'Class 4. Crustacea

pp. cxviii-cxxli. pp. 90-119
PI. vii. pp. 205-210

IV. SUB-KINGDOM. VEBMES, pp. cxxii-cxliii.

[Divisions «

Annulata, pp. cxxi-cxxiii. . .

Annuloida, p. cxxiii.

Class 1. Annulata Proper
pp. cxxvii-cxxxi. pp. 119-136
PI. viii. ix. pp. 211-222

Class 2. Gephyrea

pp.cxxxi-cxxxiii. pp. 155-157

Class 3. Nematebnintlies
pp. cxxxiii-cxxxvii. p. 155

Class 4. Eotifera

pp. cxxxviii-cxl. p. 154
PI. xi. fig. 5, pp. 239, 240

Class 5. Platyelminthes
pp. cxl-cxliii. pp. 138, 139
PI. xi. fig. 6. pp. 240-243
PI. xii. figs. 1-6, 245-252

W. SUB-KINGDOM.

ECHINODEBMATA,

pp. cxliii-clvi.

'Class 1. Holothurioidea
pp. cxlvii-cl. pp. 145-158

Class 2. Echinoidea
pp. cl-cliii.

Class 3. Asteroidea

pp. cliii-cliv. pp. 141-145
PI. X. pp. 223-229

Class 4. Crinoidea
pp. cliv-clvi. p. 165

XXX

Introduction.

(Tabular View with Pages.)

VI. SUB-KINGDOM. COELENTEKATA, pp. clvi-clx.

Class 1. Ctenophorae
pp. clvii-clviii.

Class 2. Anthozoa

pp. clviii-clix. pp. 158-160

Class 3. Hydrozoa

pp. clix-cLs. pp. 160-163
PI. xii. fig. 7, pp. 253-255

VII. SUB-KINGDOM. PKOTOZOA, p. clx.

Class 1. Infusoria
pp. clxiv-clxv.

PI. xii. fig. 8, pp. 255-257

Class 2. Bliizopoda
pp. clxv-clxvi.

PI. xii. fig. 9, pp. 257, 258

Class 3. Spongiadae

pp. clxvi-clxvii. pp. 163-166

Class 4. Gregarinae
pp. clxvii-clxviii. pp. 243, 244.

CHAEACTERISTICS OF THE SUB-KINGDOM VEETEBRATA.

Sub-Kingdom, Vertebrata^.

Animals with bilaterally symmetrical bodies, divided internally
into two perfectly distinct cavities, one of which is placed dorsally
and contains the principal nerve-centres, whilst the other contains
the organs of vegetative life. The ventrally-placed cavity of the
Vertebrata must be considered to correspond to the entire in-
terior of the body of the Invertebrata, and their dorsally-placed
cavity, the cerebro-spinal canal, to be without any homologue in
the inferior Sub-kingdoms. The motor organs of Vertebrata are
directed towards their heart, and point away from their nervous
systems, both cerebro-spinal and sympathetic; whilst in Inverte-
brata the motor organs are developed upon the neural aspect of
their bodies. Thus the arrangement by which the heart of the
Invertebrate animal is dorsal and the nerve-system ventral in posi-

» In the account here given of the characteristics of each Sub-kingdom and Class,
a few general remarks are prefixed to a more detailed zootomical account of each
Division. In that account the various organs and systems are treated of very nearly
in the same order as that of the ' Physiological Series of Comparative Anatomy con-
tained in the Museum of the Royal CoUege of Surgeons in London,' vehich was fol-
lowed by Professor Acland in the arrangement of a large part of the Christ Church
Collection now contained in the University Museum. The inbegumentary and motor
organs are first treated of ; then the digestive, circulatory, respiratory and renal ; a
sketch of the nervous system is then interposed before the account of the reproductive
organs. Objection may be taken to this method of arrangement on the ground of the
separation it effects between the motor and the other organs of animal life ; but this
theoretical drawback is more than compensated for by many practical advantages.
A short notice of any peculiarities in the history of Development, which it may have
seemed expedient to add, comes next in order ; and in some cases an account of its
subordinate divisions is prefixed or appended to the description of a larger group.

xxxii

Introduction.

r

tion, is exactly reversed in the Vertebrate; and the former may
consequently be spoken as ' neuropodous/ and the latter as ' haema-
podous/ In both cases the digestive tube interposes itself for '
greater or smaller distances between the haemal and neural systems^
but the perforation of the nerve-system, by the anterior segments
of the digestive tube, which constitutes the nerve-collar of Inverte-
brata, finds no representation in the relations subsisting between
the principal or cerebro-spinal nerve-centres of Vertebrata and
their digestive tube, the anterior or oral opening of which is always
directed towards the ventral, and away from the neural surface
of their bodies. The perivisceral cavity of Vertebrata never com-
municates with the blood-vascular, though it has recently been
shown to communicate with the lymphatic system ; nor is it ever
prolonged into their limbs, which possess always an internal and
segmented skeleton either of cartilage or of bone. The limbs of
Vertebrata diflPer further from the limbs of Arthropoda in never ex-
ceeding the number of two pairs. Externally, the Vertebrata show
no appearance of segmentation, and the segmentation which they do
exhibit internally does not affect the organs of vegetative life, but
is exemplified only in theii* skeleton, nerves, and muscles. The
axial portion of the internal skeleton, which separates the body of
the Vertebrate animal into a neural and haemal cavity, is not
always divided by segmentation into the structures whence the
Sub-kingdom takes its name. In the Ampliioxus, the endo-skeleton
is represented simply by the rod-like aggregation of cells known as
the cliorda dorsalis ; by the sheath surrounding this structure ; and
by fibrous arches, which are developed above and below in con-
nection with these axial structui-es, and give attachment laterally
to the inter-muscular septa ; but it shows no other signs of segmen-
tation except by the possession of series of mesially-arranged carti-
laginous nodules, which correspond in position to the inter-spinous
bones and fin-rays of more highly organized fish. In all other
Vertebrata, the endo-skeleton becomes definitely segmented poste-
riorly to the head, either by the development of cartilaginous neural
arches alone, as in Petromi/zon, or by the development of axial, in
addition to neural indurations. By the more or less perfect fusion,
and, ordinarily, by the calcification of these elements, the structures
known as 'vertebrae' are formed.

In all Vertebrata, with the exception of Amjdioxus, which is

Characteristics of the Vertehrata. xxxiii

hence called ' Acranial/ the neural canal widens considerably in the
anterior region of the body, in correspondence with the increased
size of the neural axis it encloses, and with the organs of special
sense to which its walls give support. The superior and the central
elements of this portion of the axial skeleton make up the skull,
and are differentiated from those of the vertebral series, not only
by the greater size of the canal they form, but also by the fact that
they undergo no segmentation until the stage of ossification is
attained to. In the anterior portion, on the other hand, of the
lower of the two cavities of the body, segmentation of a character-
istic kind is established at an early period of the development of all
Vertehrata, by the formation of the vertical 'branchial fissures,^
which, in the absence of any anterior prolongations of the peri-
visceral cavity, lead directly from the exterior into the digestive
tract. The first, and in part the second of these fissures are repre-
sented permanently by the Eustachian tube, and the tympanic
cavity in all air-breathing Vertehrata possessed of these structures ;
the other fissures which are retained in relation with the gill-bearing
arches of Fish and Perennibranchiate Amphibia, are, in the higher
representatives of the Sub-kingdom, obliterated in the course of
their development.

The integumentary system of Vertehrata may develope either a
dermal or an epidermal skeleton, or both; and muscular fibres are
ordinarily interwoven in considerable abundance with its substance.
But these structures are never, as in Invertebrata, of primary loco-
motor importance, the more deeply-placed skeletal and muscular
systems being little less characteristic physiologically than morpho-
logically of this sub-kingdom. The jaws of Vertehrata are always
modifications of the cephalic parietes, and never, as in Invertebrata,
modifications of limbs. No vertebrate animal is aproctous; the
digestive tract has the shape of a distinct and independent tube,
except in the region of the cephalic parietes, to which, as also to
the branchial arches when present, its walls are adherent. In the
abdominal region, the digestive tube is suspended by membranous
lamellae, which are never fenestrated except as a consequence of
absorption in adult fish, but which do occasionally resemble the
membranes with similar functions in Invertebrata by possessing
muscular fibres. The digestive tract rarely takes a direct antero-
posterior course. Its absorbing and secreting surface is often

c

xxxiv

Introduction.

increased by the addition to it of coecal diverticula^ which may
be very numerous, and arranged in whorls in Fishes^ but are never
80 numerous, nor so arranged in higher Vertebrata. Oral salivary
glands are often wanting in aquatic Vertebrata, the pancreatic are
less frequently, and the hepatic is never absent. Microscopic ab-
sorptive, as well as secreting glands, exist in great abundance in
the walls of the digestive tube.

With the exception of AnqjJiioxus, all Vertebrata possess a
lymphatic as well as a blood-vascular system; and the ultimate
ramifications of the former of these systems have been recently
shown to be continuous with the perivisceral or pleuro -peritoneal
cavities. The blood-vascular system, on the other hand, never
communicates either with the perivisceral or with the inter-
muscular spaces, and the efferent arteries are all but invariably
connected with the efferent veins by means of capillaries, with
walls distinct from the tissues they pass through. With the
exception of Amphioxus, in which animal we find all the mam
vascular trunks endowed with contractility, all Vertebrata possess
a heart of saccular shape, consisting even when most simple of two
chambers, one of which receives the blood returned by the veins
from the system at large, whilst the other propels that blood into
the aerating organs. Thus the heart of the Vertebrata is a respi-
rator}'^, whilst that of the Invertebrate animal is a systemic heart.
The formation of retia mirabilia, by the breaking up of arteries
into plexuses, in the interstices of which no great amount of
interstitial matter is deposited, appears to be a peculiarly verte-
brate arrangement ; as is also the so-called ' portal system,' which
appears to be formed by the development of retia 7nirabilia, in the
course of the veins returning from the chylopoictic viscera, and the
intercalation of the elements of the hepatic glands in the interstices
of the plexuses thus formed.

The blood of all Vertebrata, except Amphioxus, is red; the
colouring matter being contained in corpuscles, which appear to
be developed from the white corpuscles which are always found in
company with them. The spleen and thymus glands are connected
like the lymphatic glands, and many other but smaller bodies of
somewhat similar histological character, found in the substance both
of mucous and serous membranes, with the process of haemato-
poiesis ; and appear to be structures peculiar to Vertebrata.

Characteristics of the Vertebrata. xxxv

Whether the respiration of Vertebrata be aquatic or aerial, the
apparatus by which it is effected is always connected with the
commencement, and never, as in some Invertebrata, with the outlet
of the digestive tract. The efferent ducts, on the other hand, of the
renal organs, are usually confluent and always in near relation with
the anal, and also with the generative outlets. In Plagiostomous
Fishes, and in all Vertebrata above the Amphibia, a primordial as
well as a secondary kidney is developed; and in all cases, ex-
cept those of the Cyclostomi and AmpMoxus, the renal are closely
connected either in their development, or throughout life, with
the generative glands. When a primordial kidney, the so-called
' Wolffian body,'' is replaced by a secondary and persistent kidney,
the provisional gland and its efferent ducts are in the male sex
partly converted into spermatic ducts, the so-called epididymis and
vasa deferentia, and partly remain as the rudimentary ' cyst of
Morgagni,"" and ' organ of Giraldes of the class Mammalia ; whilst
in the female sex the primordial kidney and a certain part of its
efferent apparatus become atrophied, and are known in Mammals
as the organ of Rosenmiiller or ''parovarium,'' and the ''canals
of Gaertner '' respectively ; and the remaining part of the efferent
apparatus, the so-called ' duct of Miiller,-' becomes the functional
oviduct. In the males of Amphibia, where no secondary kidney
is developed, the efferent testicular ducts pass through the anterior
part of the substance of their functional kidney, which in higher
animals becomes limited to the functions of an epididymis ; and
these ducts are, on the distal side of the uriaary gland, known as
'vasa tiro-sj)ermatica.' The posterior part of their functional
kidney is exclusively urinary in function, and its ducts may
coalesce more or less completely before joining the (Miillerian)
duct, into which the uro-spermatic vessels from the anterior part
of the gland open ; foreshadowing thus the more perfect dif-
ferentiation of these structures which we meet with in the air-
breathing Vertebrata. According to some authorities, however,
the duct of Miiller, the parovarium, and the epididymis are deve-
loped independently of the Wolffian bodies and their ducts. This
appears to be certainly the case in Mammals

In the Amphioxus, the brain can scarcely be said to exist at
all, being represented merely by the nervous tissue surrounding
the open ventricle, which is formed by a slight expansion of

c a

XXXVl

Introduction.

the central canal of their spinal cord, and has an aggregation
of pigment granules, the rudimentary eye, placed anteriorly to
it. The cerebro-spinal system of other Vertebrata resembles this
axial nervous cord of the AmpUoxus, in being developed from the
uppermost part of the three layers into which the germinal mem-
brane divides itself in the embryo, but differs from it in the great
size and complete differentiation which its anterior segments
attain to in the brain and organs of special sense. The brain
consists of three primary vesicles, the anterior one of which is
subsequently differentiated into a ^prosencephalon'' and ''dien-
cephalon/ the latter division corresponding to the parts sur-
rounding the 'third ventricle' of anthropotomy ; the middle one
of which, or ' mesencephalon,' remains undivided ; whilst the
posterior, like the anterior, is ultimately distinguishable into two
portions, an anterior corresponding to the cerebellum, and a pos-
terior corresponding to the parts bounding the posterior parts of
the ' fourth ventricle ' of anthropotomy, or to the single ventricle
of the Amphioxus already mentioned. As in the higher Mollusca,
the organs of smell, taste, sight, and hearing are always limited
to the head; and with the exce]3tions of the AmpJdoxus and
Cyclostomi, in which there is but a single nasal opening, and of
the asymmetrical Pleuronectidae, these organs always consist of
single bilaterally symmetrical pairs. The essential elements of
the peripherally-placed portions of the organs of special sense, are
mainly, though not exclusively, developed from the epidermic
portion of the same uppermost layer of the trifid germinal mem-
brane, whence the cerebro-spinal nerve-centres are themselves
developed. The so-called olfactory and optic ' nerves ' are direct
outgrowths of the anterior cerebral vesicle ; but in all other cases
the central and peripheral factors of the sensory organs are brought
into connection through the intermediation of nerves, strictly
so called, and developed in the middle one of the three layers of
the germinal membrane. In the peripheral apparatus also, certain
enveloping and protecting structures, such as the sclerotic coat of
the eye, and the skeletal elements in the auditory and olfactory
organs are also productions of this intermediate layer ; and in the
eye the cornea, and in part the lens, are also formed from it. The
peripheral apparatus retains its typical character as an involu-
tion of the integument in the olfactory, but loses it in the optic

Characteristics of the Ve^'tehrata. xxxvii

and, with the exception of the ElasmohrancMi, in the auditory
organs.

Tactile sensibility is possessed in a greater or less degree by
the entire cutaneous system. Special tactile organs are developed
in many Vertebrata around the region of the mouth, and in some
upon the extremities ; and we find in Fishes, and in the larvae of
Amphibia, an additional set of tactile organs in the structures
which constitute the system of the lateral line, and are distributed
over the walls of the head as well as along the sides of the trunk.
Taste may be localized either in the tongue, or in the throat, or
in both ; or is probably absent altogether, where the epithelium
covering this region becomes indurated or spinous. The nerves,
as opposed to the nerve-centres of Vertebrata, are developed in the
middle, and not in the uppermost layer of the embryo ; they are
divisible into dorsal, latero-motor, and splanchnic sets, accordingly
as they are distributed to the structures formed by the dorsal
laminae, by the ventral laminae, and by the visceral factor into
which that middle layer divides itself. The sympathetic nervous
system is not contained within the cranio-spinal canal, and its
branches are mainly, though not exclusively, distributed to the
viscera of organic life. It consists, firstly, of bilaterally symme-
trical chains of ganglia arranged on either side of the thoracico-
abdominal, of the cervical, and occasionally, as in osseous Fishes,
also of the caudal vertebrae : and, secondly, of certain great prae-
vertebral plexuses, partly lodged in the substance, but for the most
part placed upon the exterior of the viscera they supply. With
the first of these divisions are to be ranked four pairs of ganglia
developed in connection with branches of the fifth cranial nerve,
and in relation with the cephalic parietes. The entire sympathetic
system is developed out of the middle layer of the embryo, and the
greater part, if indeed not the whole of its first division, is a
dependency of the similarly'- developed cerebro-spinal nerves with
which it is connected functionally and anatomically in adult life,
and which must be taken into account when the nervous systems of
Vertebrata and Invertebrata are compared with each other. Certain
ganglia developed upon the posterior roots of these spinal nerves
in the intervertebral foramina, and upon the roots of certain
cranial nerves, in or close to certain cranial canals, resemble the
sympathetic ganglia in structure ; but from their very obvious and

xxxviii

Introduction.

permanent condition of dependency upon the cerebi'o-spinal nerves,
and also from their position, they are often ranked with these
latter nerves rather than with the sympathetic system.

Though the generative glands of all Vertebrata appear to be
hermaphrodite at certain periods of foetal life, they are, with
the exceptions of a few Fishes and Amphibians, differentiated as
either male or female organs, before the attainment of adult life.
In man}'- Fishes, in Amphibia, and in all higher Vertebrata, the ova
are impregnated by sexual congress ; parthenogenesis and meta-
genesis are entirely unknown in this Sub-kingdom, and metamor-
phosis has only been observed amongst Amphibia and in a few
lower Fishes. In all Vertebrata, except certain osseous Fishes, the
ova are set free by dehiscence into the perivisceral cavity, whence
they are ordinarily taken up by the infundibuliform orifices of
bilateral oviducts, or as in a few Fishes left to find their way into
the circumambient water, through an azygos orifice in the abdo-
minal walls known as the 'porus genitalis.'' On the other hand,
vasa deferentia, directly continuous with the capsular envelope of
the testes, are found in all Vertebrata except the AnqiMoxus, ^
the Ct/clostomi, the Ganoiclei, and the Eel.

The yolk of the impregnated ovum sometimes undergoes entire,
sometimes only partial segmentation. The germinal membrane
very early divides itself into three layers, from the uppermost of
which the cerebro-spinal nervous centres and the cuticular systems
are evolved ; from the lowermost the epithelial structures of the di-
gestive tube, and its glands with the exception of the parotid ; and
from the intermediate layer all the other structures of the body, the
cutis vera, the nerves, muscles, bones, and the various vegetative
organs with the exceptions given. The first indication of the forma-
tion of the embryo is seen in the appearance of the 'primitive groove
by the upgrowth of the walls of which, the cranio-spinal canal and
the cerebro-spinal nervous axis are both formed as demi-canals at
first, and as closed tubes ultimately, by the intermediate, and by the
upper layers of the germinal membrane severally. The chorda dorsalis
is developed along the infero-median line of these structures ; and
at a point corresponding to the level thus marked out, lamellar
prolongations are sent off" downwards, which form the walls of the
inferior cavity of the vertebrate body, and are known as the laminae
ventrales. The intestine in all Vertebrata except Amphioxus (and

Characteristics of the Vertebrata. xxxix

Cyclostomi and Amphibia ?) is formed by the junction to the third
layer, which has tlie shape of a groove open towards the yolk
cavity, of an outer fibrous covering, due to the splitting into two
portions of the ventral part of the middle layer ; and by the sub-
sequent conversion of the demi-canal, thus formed, into a tube at
its two ends. The space contained between the two layers into
which the downward prolongation of the middle layer divides
itself, corresponds with the future pleuro-peritoneal cavity of the
adult Vertebrate; and the orifice and canal of communication
betwen the yolk cavity and the tube which the demi-canal is thus
converted into, correspond with the more or less transitory om-
phalo-mesenteric duct, which connects the vertebrate intestine with
the umbilicus. In no Invertebrate animals are the walls of the
perivisceral cavity thus constituted ; and in none does the intestine
ever possess any umbilicus. In the Amphioxus, however, (as also
in Cyclostomi and Amphibia ?) the intestinal tract is said to be
formed, as it is in many Invertebrata, by a process of invagination
commencing at the future anus ; and the larvae of certain Asci-
dians have been stated to have their nerve-centre developed similarly
to the tubular cerebro-spinal centres of Vertebrata, and to possess
within the locomotor caudal appendage, with which they are fur-
nished in their larval condition, a structure closely similar to the
chorda dor sails of Vertebrata.

In all Vertebrata, with the exceptions just mentioned, a larger
or smaller ' umbilical vesicle' is formed by the separation of a distal
or extra-abdominal portion of the yolk-sac from an intra-abdominal
moiety, at the point where the ventral laminae close upon it in the
medio-ventral line, and form the umbilicus.' The 'umbilical ve-
sicle' is usually cast off when the embryo is set free from the egg ;
the part of the yolk sac which is intercepted within the abdominal
cavity, frequently persists for a considerable period after birth as
the ' omphalo-mesenteric duct.'

Divisions, Allantoidea and Anallantoidea.

Vertebrata are divided into Amniota and Anamniota, accordingly
as the dermal and cuticular elements of the ventral laminae are in

xl

Introduction.

development reflected upwards from the medio-ventral line^ so as to
meet along the medio-dorsal line^ and form thus the foetal envelope
known as the Amnion ; or as no such envelope is superadded to the
more or less complex ones, furnished by the maternal organism.
In the Vertebrata Amniota, a second foetal envelope, the Allantois, is
always developed^ originating from the anterior aspect of the poste-
rior extremity of the trunk as a body, which is at first bilobed and
solid^ but which subsequently becomes hollow internally, and covered
externally with vascular ramifications, whereby in Reptiles and
Birds the respiration, and in Mammals both the respiration and
the nutrition of the developing embryo are provided for. From
their possession of this structure, the Amniota are also known as
'Allantoidea and as gills are never developed upon their branchial
arches, they are also called ' Abranchiata,^ whilst the Anamniota
have in their turn the two additional names ^ Anallantoidea'' and
' Branchiata,'' as never develoj)ing an Allantois, at least beyond
the stage of a urinary bladder, into which its proximal portion is
converted in the higher Vertebrata, and as always developing
either deciduous or permanent gills.

Division, Allantoidea.

The Allantoidea comprise the three Classes, Mammalia, Aves, and
Reptilia, and possess the following characteristics distinguishing
them from the Anallantoidea, in addition to those which their several
names given above connote. The axis of their basi-cranial bones
always forms a considerable angle with the axis of their vertebral
column ; the parasphenoid, which is large in the Anallantoidea, is
in them rudimentary, whilst the basi -occipital and basi-sphenoid are
always well ossified ; and the former is never anchylosed with any
of the anterior vertebrae, of which more or fewer are always dis-
tinguishable as cervical, from a thoracic or thoracico-abdomiiial
series. Inferiorly-placcd ' stcrnar bones ordinarily complete the
costal arches. They never have a permanent muscular bulbus
arteriosus ; but they always have a trachea, and a secondary kidney.
They never have more than five branchial arclies ; and it is only in

Characteristics of the Vertehrata. xli

the three most anteriorly placed of these that cartilaginous supports
have been observed to be developed.

Sub-division, Sanropsida.

The two Classes Aves and Reptilia are united into a single
province^ that of the ' Sauropsida,' by the possession of the following
characteristics which distinguish them both from the other sub-
division of Allantoidea, the class Mammalia. Their integumentary
system always developes either feathers or scales ; their skull is
articulated by a single occipital condyle to the cervical vertebrae ;
they have their ankle-joint interposed between the proximal and
distal bones of the tarsus, and not between the distal extremity of
the lower leg and the proximal tarsal bones; they have also a
single auditory ossicle, the stapes ; the malleus of Mammals being
represented by their os quadratum, and the incus by their supra-
stapedial process. Their blood corpuscles are oval and nucleated.
They never have the single aorta turning over the left bronchus,
nor a perfect diaphragm, nor a corpus callosum, nor mammae, all
of which structural arrangements are found in all Mammals.

Division, Anallantoidea.

The Anallantoidea comprise the two Classes, Amphibia and Pisces,
and the province thus constituted is known as that of the ' Ichthy-
opsida,'' as well as by the names of ' Branchiata' and ' Auamniota,^
given above. They differ from the Abranchiate province in the
following particulars in addition to those which their various names
imply. Their integument never developes any epidermic skeleton,
except in a few Amphibia (see p. 35, infra), and in some Fishes the
bony structures of the cutis may cause the total or almost total
disappearance of the cuticle. The axis of the head and vertebral
column form one continuous line ; the basicranial bones are, except
in some fishes which have not an osseous skeleton, underlaid by a
large parasphenoid. The basi-occipital may be rudimentary or

i

xlii

Introduction.

cartilaginous, and may be connected by suture, and not by movable
articulation, with the first vertebra of the trunk. The apex of
the scapular arch, so far as it is constituted by true endo-skeletal
elements, corresponds at its first appearance to the interspace be-
tween the second and third vertebrae, marking off thus two cervical
vertebrae ; but a cervical region is not by any means invariably
recognisable in the adult condition of these animals ; when there
are two occipital condyles, they are constituted by the ex-occipitals
alone. They never possess a series of costal arches completed in-
feriorly by sternal bones ; and it is only rarely that (in Amphibia)
there is any sternum present at all. They always possess two
aortic arches at least, and nearly invariably an aortic bulb. They
are in many cases competent to the maturation of sexual products,
before they attain their full size ; and in the case of the Amphibian
Axolotl, before the gills characteristic of the larval or tadpole-stage
are discarded.

No Vertebrata are social, nor are any fixed to one spot. The
power of repairing injuries and mutilations is, with possibly a few
exceptions, confined to the cold-blooded Amphibia and Reptilia. As
in the two higher Sub-kingdoms of the Invertebrata, the Mollusca
and the Arthropoda, there are both air-breathing and water-breathing
representatives of this Sub-kingdom,

As in the Sub-kingdom Mollusca, so in that of Vertebrata, there
are very few animals of parasitic habit. All parasitic "Vertebrata
belong to the class Pisces, and amongst these we may mention the
Myxinoids, which are not only ecto-parasitic, but penetrate even
into the abdominal cavity of other Fishes, such as the Sturgeon.
A Siluroid fish has been found to inhabit the branchial cavity of
another fish {Platystonms) of the same family ; and the invertebrate
Asterias discoidea is infested by Oxyheles limbricoides, and certain
Holothurians by a Fierasfer. These latter cases, however, are
considered by Van Beneden to be instances of ' commensalism'
rather than of parasitism strictly so called. See Bulletins de
I'Academie Royale de Belgique, 2™^ serie, torn, xxviii., no. 12,
pp. 624-626, 642, 643, ibique citata.

Class, Mammalia.
Air-breathing, warm-blooded Vertebrata, in which the epidermis
developes hairs over a greater or lesser extent of the surface of the

f

Characteristics of the Vertehrata. xliii

body, either persistently or during foetal life only, as in most of
the true Cetacea ; which are always viviparous, and always nourish
their young- for longer or shorter periods after birth with the
secretion of lacteal glands. The anterior pair of limbs is never
wanting ; a perfect diaphragm always exists between the thoracic
and abdominal cavities ; the aorta is single, and bends over the left
bronchus ; the red-blood corpuscles are ' apyrenaematous,^ or ' non-
nucleated/ In all Mammalia, with the exception of the Cetacea
and Sirenia, the abdominal vertebrae are separated into a lumbar
and a sacral division, by the abutment of the iliac bones upon the
vertebrae immediately anterior to the caudal series. In the
Marsupial Perameles, however, there may be but one 'sacral'
vertebra, whilst in the Edentata, where the ischium as well as
the ilium abuts upon the vertebral column, there may be as many
as nine. The cervical vertebrae are, with a few exceptions, neither
more nor less than seven in number. Of these, the two first arti-
culate with each other and with the two occipital condyles by
synovial joints, whilst all the other vertebrae have their centra
articulated together by fibro-cartilaginous discs, in the axis of
which remnants of the chorda dorsalis are to be found. The
number of dorsal vertebrae is very frequently thirteen, but it may
vary from ten to twenty-four; that of the lumbar is very fre-
quently six or seven, but may vary from two to nine ; that of the
sacral, as already said, varies from one to nine ; whilst that of the
caudal varies from four, as in certain Simiadae, up to forty-six, as
in Manis Macmra. As in Sauropsida, the centres of the vertebrae
are always well ossified, but they differ from those of the cold-
blooded representatives of that division of the Vertebrate Sub-
kingdom, in being always anchylosed with the neural arch in adult
life j and from those of both Birds and Reptiles in being during
the period of growth provided with epiphyses. There are always
two occipital condyles, each of which is constituted by factors from
both basi- and ex-occipital. The lower jaw articulates directly vtdth
the squamosal element of the cranial walls, the homologue of the
OS quadratum of Sauropsida having been withdrawn into the
cavity of the middle ear, where it is known as the malleus. The
lower jaw itself consists always in adult life of a single bone on
each side, which in some Mammals does, and in others does not,
anchylose with its fellow of the opposite side at the mental

xliv

Introduction.

symphysis. It does not however appear to be always developed, as
usually stated^ from a single centre of ossification in the membrane
covering- the distal portion of the cartilage (Meckel'' s) of the first
branchial arch. In the human subject it has been observed to be
developed from as many as four centres of ossification, of which one
probably corresponds to the dentary bone of the Crocodile, and the
other to the splenial. In the terminal segment of the limbs, the
digits never consist of more than three phalanges each, except in
the true Cetacea, which order also forms an exception to the rule
that the terminal digital phalanges are always in Mammals pro-
tected by a nail, a claw, or a hoof.

In addition to, and together with the hairs so characteristic of
this class, and found even in some adult Cetacea upon the lips, we
find the integument developing structures as various as the vibrissae
on the snout of Carnivom ; the scales on the body and limbs of the
Pangolins, and on the tail of certain Eodents, and of Piilocercus
amongst Insectivora ; the spines on many members of the two
last-mentioned orders ; the horns as opposed to the horn-cores
of the hollow-horned Euminants ; and the horns of the Rhino-
ceros. The scutes of the Armadillo are exclusively dermal pro-
ductions. Glands of various kinds are found on very various parts
of the body. Some of them are known as sebaceous, sudoriparous,
lacteal and lacrymal, according to the character of their secretion ;
whilst others, which are usually modifications of the sebaceous
type, are, according to the locality in which they are situated,
known as anal, inguinal, interungular, and preputial. In all
Mammalia, with the exception of the Hare, Lepus timidus, a layer
of adipose tissue, the paimiculus adipos?is, sometimes of great thick-
ness, is interposed between the etdis vera and the subjacent muscles
or bones. The teeth, which are developments of the mucous mem-
brane continuous with the external integument, are normally limited
to the lower jaw below, and to the pre-maxillary and maxillary
bones above. They may be absent altogether or replaced by horny
plates, as in the Ornithorhynchis: Only a certain number of the
teeth, the so-called ' milk teeth,' are ever replaced in Mammalia
after being shed ; and in many Mammals no such replacement has
ever been observed. In the Marsupials, none of which are ever
edentulous, there is only a single ' dent de remplacement the one,
namely, which corresponds to the second human premolar. In

Characteristics of the Vertehrata. xlv

some Mammals, such as the true Cetacea, which have only a single
set of teeth, the pulp atrophies or undergoes calcification j and a
term is thus necessarily put to the duration of the teeth, and of the
life of the animal. In others, which are similarly ' Monophydont/
as the Sloths {Bradi/poda), amongst the Bruta, the pulp is persistent ;
as it is also in the ' Diphyodont ' Armadillos belonging to the same
order, and in the incisors of all, in the molars of some Rodents, and
in the permanent incisors, or ' tusks'' of the Elephant. It is only in
the Mammalian class that teeth have been observed to be implanted
by more than a single fang, and the dentinal tissue is ordinarily
free from anchylosis with the alveolus in which the tooth is lodged.
The digestive tract is always rich in interstitially-placed glands,
and of the larger glands appended to it by ducts, none are ever
wanting except the oral salivary glands in the true Cetacea, and
one pair of these glands, the parotid, in the Monotrematous
EcJndna. There is much variety from order to order, as to the
simplicity and complexity of the stomach, and as to the presence or
absence of intestinal coeca. It is only in the OrnitJwdelpJda, thence
called ' Monotremata,'' that the generative and renal ducts are
confluent for any great distance with the terminal segment of the
intestine, so as to form a true ' cloaca though in Marsupialia,
as also in certain Rodentia, in Centetes amongst the Insectivora,
and in certain Bruta, a common sphincter muscle may surround
the distal orifices both of urogenital and of the rectal tubes.

The red-blood corpuscles of Mammalia differ from those of all
other Vertebrata not only in being ' apyrenaematous,^ but also in
being, with the exception of those of the Camelidae, circular. Their
heart is always quadrilocular ; their aorta always single, and bent
over the left bronchus. The valves, which in other Vertebrata
guard the entrance of the great veins into the right auricle, are
either absent as usual, or rudimentary as in Bradypus, ElepJias,
Simiadae. Correlated with this structural arrangement is the
fact that in Mammals the ventricles are the first, the auricles
the second in point of time to contract in each systole. In many
Rodentia and Insectivora, and in all Marsupialia and Montremata,
there are two superior venae cavae. The lymphatic and lacteal
glands are always largely developed, as are also the tonsillar and
Peyerian aggregations of adenoid substance in the walls of the
digestive tube. The entrance to the larynx is always prdrtected

xlvi

Introduction.

by an epiglottis, and with the exception of Bradypus tridactylus,
the trachea always takes a direct antero-posterior course from the
lai'ynx to its bifurcation. The lungs are always freely suspended
in pleural cavities, and they are never prolonged into abdominal or
other air-sacs. A perfect diaphragm is always present. Portions
of this and of other muscles are always interposed between th.e
kidneys and the lower dorsal and upper lumbar vertebrae in the
region of which they lie ; and their external surfaces are, conse-
quently, not conformed, as in other Vertebrata, so as to fit into the
sinuosities of the osseous structures in their neighbourhood. The
kidneys are provided with a fibrous envelope, surrounded by a
panniculus adiposus, the venous system of which is in anastomotic
connection with that of the gland ; but this connection never
attains to the functional importance of a 'renal-portal' sj^stem.
Similar anastomoses, possessed similarly of merely morphological
importance, exist between the renal arteries, which bring to the
gland the blood upon which its secretion as well as its nutrition is
entirely dependent, and certain branches of the lumbar arteries.
The substance of the gland is always differentiated into an external
cortical secretory, and an internal medullary excretory stratum.
A urogenital canal, which is only occasionally found or rudi-
mentarily represented in other Vertebrata, is always found in
Mammals, except in the females of some Rodentia or Insectivora,
where the clitoris forms a closed tube for the urethra.

The cerebral hemispheres, as distinct from the corpora striata
and optic thalami which they overlie, attain a greater development
than in any other class of Vertebrata. Their external surfaces are
in many small, and in most large representatives of the Class,
convoluted, so as to allow of the ready access of blood to the sub-
stance of the hemispheres, at the same time that the amount of the
grey matter is greatly increased. The cerebral hemispheres are
always connected by a more or less extensive 'corpus callosum,'
and the mesencephalon is always represented by more or less
sharply separated ' corpora quadrigemina.' In a few of the true
Cetacea the olfactory bulbs are absent, and in certain burrowing
Rodentia and Inseciivora, the eyes may be absent or rudimentary,
but in all other Mammals the organs of special sense are all
present. Special organs of tactile sensibility are very ordinarily
developed upon the snout, as in the Carnivora and Solidungula.

Characteristics of the Vertehrata. xlvii

The malleus of Mammalia, though limited to auditory functions,
and placed within the cavity of the middle ear, corresponds to the
OS qnadrakm, which carries the lower jaw of Sauropsida, being-
developed out of the proximal elements of the first visceral arch,
whilst the stapes and incus hold a similar relation to the second,
and represent the columella of those animals and its supra-stapedial
appendage.

All Mammalia have a urogenital canal independent for a greater
or less length, or altogether, of the termination of the intestine ;
all male Mammalia have an intromittent organ ; in all female
Mammalia during the period of gestation, the blood-vessels of the
uterus come into intimate relation with those of the foetus, and
provide thus for its nutrition aud respiration during a longer or
a shorter portion of its developmental life.

The reproductive system has furnished a basis for the division of
the Class Mammalia into the three Sub-classes, OrnithodelpMa,
DidelpMa, and MonodelpMa.

Sub-class, Ornithodelpliia.

The Sub-class, Ornithodelphia, is represented by the single order
Monotremata, and the two genera, Ornithorhpichis and EcJddna. In
these animals, as the names Monotremata and Ornithodelpliia imply,
the urogenital and the rectal canals both open by a common cloaca!
outlet, and the oviduco-uterine ducts remain distinct up to then-
points of entry into the urogenital canal. In the males, however,
there is a perforated penis, which, though not continuous at its
base with the urogenital canal, can be brought into apposition
temporarily with the orifices of the vasa deferentia, so as to form a
functionally distinct sexual canal. The mammary glands have no
nipples ; in Echidna, the lacteal ducts open into a pouch-like invo-
lution of the integument ; in the Ornithorhynchus they open upon
a plane surface ; in both, the embryoes are extruded from the
uterine cavities whilst in an exceedingly immature state. In the
Monotremata, as in Sauropsida, the coracoid reaches the sternum ;
they possess an interclavicle ; and the so-called ' marsupial ' bones,
which are ossifications of cartilages segmented off from the pubic
elements of the pelvis, and which give insertion to a portion of the
tendon of the external oblique muscle. The Echidna is edentulous ;
the Ornithorhynchus has horny plates in the place of teeth.

xlviii

Introduction.

Sub-class, Didelphia.

The Didelpliia are represented- by the single order Marsu-
pialia, which resembles the Monotremata in the possession of
' marsupial ' bones, though in few other points besides those
common to all Mammalia. The urogenital canal is much more
distinct from the rectum than in the Monotremata^ but, as is
the case also in certain Monodelphia, the external orifices of both
canals are embraced by a common sphincter muscle. The testes
are never retained in the abdomen, as in the Ornithodelpliia and
in some MonodelpJda^ but are suspended in a scrotum placed an-
teriorly to the penis. The young are extruded from the uteri in
an imperfect condition of development, and whilst going through
the further stages necessary for enabling them to provide for
themselves, they are attached to a long mammary nipple, which is
ordinarily contained within a marsupial pouch. The coracoid never
reaches the sternum ; true teeth are never absent ; the angle of the
lower jaw is almost always inflected.

Sub-class, MonodelpMa.

The Monodelphia, which are also known as ' Placentalia/ differ
from the two other sub-classes in the following points : with a few
exceptions, such as the Hare amongst the Eodents, and Orycteropm,
amongst the Bmta, their female generative canals form an azygos
corpus uteri of greater or less length, which opens into an azygos
'va;gina; which, again, with the exception of Brady pis, opens
always by a single orifice into a urogenital canal. In all Mono-
delphia the vessels of the allantois come into relation with the
vessels of the uterus, and the two sets of vessels form a placenta,
which has not been observed in the other two sub-classes. Accord-
ingly as portions of the maternal structures come away with the
foetal elements of the placenta at birth or not, the Monodelphia
are divided into Becidmta and Non-deciduata^ the former of
these groups corresponding to the Unguiculata, with the exclusion
of Manis and probably also of Rhinoceros; and the latter to the
Ungulata and Mutica of Linnaeus. The scrotum is never prepenial
as in Marsupials ; the testes are, however, sometimes retained
within the abdomen as in Monotremata : and in Centetes, in which
this is the case, a tendency to develope an inflection at the angle

CJiaracteristics of the Vertehrata.

xlix

of the lower jaw is observable, so that in the organism of a single
Monodelphous animal are combined peculiarities of both the other
Sub-classes. Marsupial bones are never present in MonodeljoJda.

Class, Aves.

Air-breathing warm-blooded Vertebrata, which have epidermal
appendages of the structure of feathers, and which are always
oviparous. Their anterior pair of limbs have the shape of wings,
which are formed thus : the two digits of the ulnar side are aborted
together with theii? metacarpals the remaining three metacarpals,
and the os magnum of the carpus, are fused into a single bone,
upon which three digits are carried, and which abuts proximally
upon two free carpa,l bones. Of these digits the middle one,
corresponding to the index finger, and the carpo-metaearpal bone,
carry the ' primary ' quill feathers, whilst the ulna carries the
' secondaries,'' and the humerus the ' seapularies ' s. ' parapterum '
of pterylography. Most of the peculiarities which distinguish the
Avian from the Reptilian organism, are to be correlated more or
less directly with their power of flight. The necessity for the
possession of the power of exerting great muscular force entails
the possession of warm blood ; and the immobility of the dorsal,
the pliability of the cervical, and the great extent of the sacral
vertebral regions, are nearly as directly connected with the function
of flight as the great development of the sternum, whence the
muscles of flight take origin, or the conformation of the limbs upon
which they act. The warm-bloodedness or ' homoeothermal ' character
of Birds, might appear to connect them more closely with Mam-
mals than with Reptiles ; but it will be found to be correlated with
but few distinctively Mammalian characters, beyond those which
may be expressed by saying that in both these homoeothermal
classes, the venous and arterial systems are prevented from directly
intermingling their blood by the existence of a quadrilocular heart,
and of a single systemic aorta ; whilst the brain holds a more
favourable relation quantitatively to the body and to the spinal
cord ; and the spinal cord again is, with perhaps a few exceptions,
larger relatively to the body than is observed to be the case in cold-
blooded Vertehrata of any Class. On the other hand, the totality
of the Avian organization, with the exception of the epidermal

d

1.

Introduction.

system^ as observed in existing Birds, and the fossil remains of
sueli transitional forms as are preserved in Archaeopieryx on the
one side, and the Dinomuria on the other, show that their more
essential morphological affinities are distinctly Reptilian. The
aberrant integument of Birds, being, as it is, by virtue of its
polished surface, an imperfect radiator, and, by virtue of the layers
of air it entangles, an exceedingly bad conductor of beat, is a
powerful auxiliary in the economization of the heat generated by
the rapid rate at which their various functions are carried on. Both
Reptiles and Birds are favourably conditioned for the conser\'ation
of heat, by the semi-solid character of their excreta ; and at par-
ticular seasons, as has been observed in the case of the incubation
of the Python, Reptiles do appear to obtain the power of raising
their temperature considerably above that of the medium in which
they live. The skeleton of Birds contrasts with those of Reptiles
and Mammals generally, by its greater hardness and lightness,
and its greater readiness to form anchyloses. The cervical and
dorsal vertebrae have their centra articulated by sj'^novial joints, in
which cartilaginous menisci are to be found. The anterior surfaces
of these centra have the procoelous appearance when looked at
in situ and from in front; but when one of these vertebrae is
removed from apposition with the one next in front of it, the
anterior surface of its centrum is seen to be saddle-shaped or cylin-
droidal transversely, whilst the posterior surface, being conformed
so as to articulate with an anterior surface of that shape, is, in
its turn, convex transversely, but concave from before backwards.
On the other hand, the occipital condyle, at least of the more typical
Birds, is more perfectly spheroidal as retaining less trace of its
trifid composition out of the basi-occipital and the two ex-occipitals
than in most Reptiles. The neck vertebrae may vary in number
from nine to twenty-four, the dorsal from six to ten, of which the
four or five most anteriorly placed are ordinarily anchylosed with
each other, except where, as in the Ratiiae and some of the Cari-
' natae, as the Penguin, the power of flight is lost. The sacral
vertebrae vary in number from nine to twenty, the enormously
elongated ilia abutting directly upon them without the interposition
of any sacral ribs as in Reptiles, or the separate centres of ossifi-
cation which represent those ribs in Mammals. There are from
cio-ht to ten caudal vertebrae, the last of which forms an ' os en

«

Characteristics of the Vei'tehrata. li

chaiTue ' for the support of the ' rectrices ' feathers. The two
anterior ribs having often no sternal element^ the character of
' dorsal or ' cervical ' comes to depend upon the relation these
movahly articulated appendages hold to the subjacent lung. In
the Ratitae, the osseous system of which order shows many Rep-
tilian affinities^ the cervical ribs often remain unanchylosed. for
considerable periods of their adult life. ' Processus Uncinati ' are
attached by ligament or anchylosed to the dorsal ribs, with the
exception of the first and last.- The largely developed sternum
gives support to the strong coracoids anteriorly, and to the ossified
sternal elements of the costal arches laterally, but it is never pro-
longed outwards at its posterior angles into costal processes as in
Reptiles. The clavicles are occasionally absent, but ordinarily form
a furculum by fusion at their anterior extremities, with which, as
also vdth their upper ends, elements segmented ofi" from the cora-
coids are found to anchylose. The iliac bones extend so far forwards
as to overlap some of the ribs, so that no distinct lumbar region
exists. The ischiac and pubic bones are prolonged backwards, so
as to be approximately parallel with each other and with the long
axis of the body ; except in Rhea, the ischia never form any sym-
physis ; nor do the pubic bones, except in StnUhio Camelus. The
femur moves in the acetabulum in a direction parallel with that of
the long axis of the body. The fibula never reaches the ankle
joint, which is situated as in Reptiles between the proximal and
distal row of the tarsus. In adult Birds, the tibio-tarsus and the
tarso-metatarsus are each perfectly anchylosed into a single bone.
This is not the case in Reptiles. The external toe is never present
in Birds. The hallux is sometimes absent; when present, it is
carried upon a metatarsal articulated to the tarso-metatarsus near
its distal extremity, and consists of two phalanges. In the Ostrich,
both hallux and index are absent, as well as the fifth toe, and the
foot is reduced to the didactylous condition, though the tarso-
metatarsus retains a rudiment of the third distal articular trochlea.

©gntal jpapillaej with caps of dentine, have been observed in the
emb^oes^ of Psittaciclae ; in adult Birds, the digestive tract is
characterized by the absence of teeth, of lips, and of a velum
pendulum palati ; and by the presence of a horny beak, and of a
muscular gizzard placed posteriorly to a glandular proventriculus.
With the absence of comminuting organs anteriorly to the gizzard,

d %

lii

Introduction.

is correlated tlie width of the oesophagus, which often expands into
a crop. The liver ordinarily consists of two lohes, into the fis-
sure between which the apex of the heart is received. There are
always two, and sometimes three bile-duets in Birds : they open
separately into the intestine ; and on one of them a gall-bladder is
usually developed. A large and compact pancreas, with two or
three duets, is always to be found in a fold of the duodenum.
With few exceptions, two coeca are appended to the intestine at the
junction of the ileum to the colon ; and a third, representing the
omphalo-mesenteric duct of embryonic, and of early life subsequently
to hatching, is occasionally present at a point higher up in the
small intestine. The urinary and genital ducts ordinarily open
separately into the cloaca, but there may be a short m-ogenital
cavity distinct from the lower segment of the digestive tube, but
opening directly into it. The characters of the beak, tongue, crop,
gizzard, and circum-oral salivary glands, vary much, in correspond-
ence with the nature of the food.

The heart is quadrilocular, and the right auriculo-ventricular
valve_ muscular in all Birds. The fourth aortic arch of the right
side^ instead of that of the left, as in Mammals, forms the single
systemic aorta ; the fourth aortic arch of the left side is converted
into the subclavian artery instead of forming a second, or left, sys-
\ temic aorta as in Reptiles, though its homology with this latter vessel
is spoken to in many Birds, especially Acdjntres, by its retention of
a fibrous prolongation onwards to the functional aorta. The aorta
and pulmonary artery have each three semilunar valves. The aorta
divides after a very short course into three great trunks, by giving
off two subequal innominate arteries. In Birds of powerful flight,
these trunks are often of larger calibre than the continuation of the
aortic trunk itself. There are always two superior venae cavae, which
open separately from each other, and from the vena cava inferior,
the sinus venosus having disappeared by absorption into the right
auricle. The vena cava inferior is formed by the confluence of the
efferent renal veins, with which the veins from the lower extremities
are, as in Mammals, directly continuous; though, as in Reptiles,
the blood which these latter vessels carry can find its way also into
the kidney, forming thus a 'renal portal' system, as well as into
the liver by anastomosis with factors of the true portal system.
The trachea in Birds is always of considerable length ; it is often

Characteristics of the Vertehrata.

liii

tortuous, and dilated at intervals. Its cartilaginous supports form
usually perfect rings, and are not rarely ossified. In most Birds
with the exception of the Uatitae, a lower larynx is developed upon
the junction of the trachea with the two bronchi. The bronchi
lose their cartilaginous rings when they enter the lungs, where they
dilate into membranous canals which subsequently become smaller
by giving off branches, and finally end by opening into air sacs.
The lungs are deeply indented in correspondence with the ribs, but
are not otherwise lobed. There are nine air sacs, of which one is
placed asymmetrically between the furculum and the trachea, two
in the abdomen and pelvis, four in the posterior and lateral parts of
the thorax, and one on either side of the azygos interclavicular sac.
Processes are prolonged from the anterior and posterior of these
sacs into the bones. The bones of the skull are sometimes, as in
Mammals, the only pneumatic bones ; the vertebrae, humerus and
sternum come next in order as to the possession of air cavities ;
whilst in some Birds all the bones of the body are said to have been
obserred to be pneumatic. The bones of the fore-arm, on the other
hand, of the lower leg, of the manus and of the foot, are often found
to retain their medulla, and to be devoid of pneumatic cavities. ,

The kidneys are divided into three lobes, and have their outlines
conformed to the sinuosities of the pelvic bones. There is never
any urinary bladder ; the ureters open internally to the generative
ducts, either directly into a cloaca, or into a urogenital pouch of
small antero-posterior extent.

The brain is much larger relatively both to the entire body and
to the spinal cord than it is in Reptiles, and the spinal cord again
holds a more favourable relation to the entire body than in those
cold-blooded creatures. It occupies however a greater relative
length in the spinal canal than it does in Mammals, and in this
resembles the cord of the other Sauropsida. The cerebellum has
only rudimentary lateral lobes ; its grey matter however is con-
siderable in quantity, owing to its transverse lamination. It
projects forwards so as to come into relation with the prosen-
cephalon, and, as it were, to displace the bigeminal hollow optic or
mesencephalic lobes on to either side of its forward prolongation.
The cerebral hemispheres are represented by a thin shell of nervous
matter, which covers the large corpora striata, and incloses the
lateral ventricles. The corpus callosum is absent ; and the fornix

liv

Introduction.

can only be considered to be rudimentarily represented by a portion
of the inner wall of either lateral ventricle. The anterior com-
missure is not, the posterior is largely developed. The optic thalami
are smaller than the optic lobes. Tactile sensibility is limited to the
beak. Smell and taste are lowly developed. The cochlea of the
ear is a much simpler, the tympanum a much more extensive cavity
relatively than in Mammalia. The eyes are never absent, and,
though small in the Apieryx, are never rudimentary. The globe of
the eye consists of two segments, the anterior one of which is more or
less obtusely conical, whilst the posterior is spheroidal ; bony plates
inlaid in the anterior part of the sclerotica preserve the relative
conformation of the two portions. As in many lower Vertebrata,
a vascular process is prolonged from the choroid into the interior of
the bulb. This structure is known in Birds as the 'pecten,'' or,,
from its shape in Ratitae, as the ' marsupium and in many,
grallatorial and aquatic Birds it reaches to the lens. It is absent
in Apteryx. The yitreons humour is relatively smaller than in
Mammals. Except in Owls and aquatic Birds, the lens is flat.
The ciliary muscle upon which the bird's power of accommodating
the eye so as to obtain clear vision at very rapidly varying distances
depends, is, in correspondence with this need, composed of trans-
versely, striped muscular fibres. The muscular fibres of the iris are
of similar character. A special muscular apparatus and a special
(Harderian) gland are developed, in relation with the third eyelid
or memhmna nictitans.

As in the Sub-kingdom Arthropoda, the sexes differ much ex-
ternally; and in the case of the Accipitres, the females, as is so
commonly observable in that Sub-kingdom, are larger than the
males.

The testes are always retained within the abdomen anteriorly to
the kidneys; the left is occasionally the larger of the two. Tlie
vasa deferentia are often dilated towards their terminations, but in
neither sex are there ever any accessory glands, distinct from and
appended to the generative canals by ducts, as are the Cowperian,
the prostatic glands and the vesiculae scmiuales of many ISIammals.
The right ovary is usually atrophied, and when it is persistent, as
in some Accipitres, its ova do not come to maturity. In the upper
part of the oviduct the albumen, in the lower the calcareous shell of
the egg is formed. Many young Birds are, as are also the young

Characteristics of the Vertehrata, Iv

of Chelonia and OphicUa, provided with a hard knob on their upper
mandible^ for breaking through their shell when ready for hatching.
In some Birds the fodd-yolk is largo, and the young are ordinarily
more or less entirely competent to provide for themselves when
hatched. "V\'Tiere the yolk is relatively small, the young are in-
competent to locomotion when hatched, and require to be brooded
upon whilst going through further stages of development. Birds
which are possessed, immediately after hatching, of the faculty of
self-help have been called ' Autophagi/ in opposition to those which
require further maternal care, and are called ' Insessores/

Existing Birds are divided into two orders, the Raiiiae, in which
the sternum has no crest and the wings are rudimentary, and
the Carinatae, in which the sternum has a crest or keel, ossi-
fied from an independent median azygos centre, and which have
powerfid anterior limbs oi'dinarily organized for flight, though
sometimes not, as in the Penguins. The former order- includes only
the genera Strut/do, Bromaeus, Casuarim, AptevT/x, and is distin-
guished not only by many modifications curtailed hy the stunting
of their anterior limbs, but also by many morphological points of
aflinity to the cold-blooded Sauropsida, amongst which the cha-
racters of the osseous system are peculiarly striking. The Ratitae
have_ the barbs of their feathers disconnected, have no inferior
larynx, and no angle aF the junction of coracoid and scapula. A
more perfect diaphragm exists in them than in the 'Oarinatae.
This latter order comprises all other existing Birds. The fossil
ArcJiaeopteryx appears to have differed from existing Birds by
possessing a series of caudal vertebrae equalling the body in length,
and in having well- developed non-anchylosed metacarpals. A sepa-
rate order, that of Saururae, has been established for the reception
of this transitional form.

Class, Reptilia.

Air-breathing cold-blooded Vertebra ta, with epidermal struc-
tures of the character of scales, into which processes of the cutis
vera are prolonged, but which are not developed like feathers within
saccular involutions of the integument. Accordingly as bony
scutes are combined with these scales, and constitute an osseous
dermal skeleton or not, existing Keptiles are divided into the

Ivi Introduction.

two groups of Lor'icata and Scpiamata, tlie former containing
the two orders, Chelonia and Orocodilina ; and the latter the
Sauna and the OjMdia. The anterior limbs are sometimes en-
tirely absent, together with the scapular arch ; they are never
modified so as to form wings like those of Birds ; the caudal
vertebrae very frequently form a series equal in length to the
length of the rest of the body; the jaws are usually armed with
teeth, which are constantly reproduced during the life of the animal.
There__are two systemic aortae^ which either fase {Squamata) or
tmastflffiogg {Loricata) with each other in front of the dorsal verte-
brae; and in no Reptiles, except CrococUUna, is there a complete
separation of the ventricular part of the heart into two cavities.
And in Ch-ocodilina, the two systemic aortae arising from the two
distinct ventricles, communicate with each other at the base of the
heart by the foramen Panizzae j so that in all Reptiles the venous
and the arterial blood come to be more or less freely intermingled
without the interposition of capillaries, at, at least, two points of the
vascular system, Copulatory organs are always present, except^in
Hatteria ; for the peculiarities of which see Dr.__Griinther, JPhil,
1r^^i867^p. 5^5^
r^/u U ~TEe~skuTI isTess vaulted and less capacious than in Aves. Traces
^ of the entrance of the two exoccipitals into the formation of the

occipital condyle are usually persistent. The os quadratum is
sometimes movably, sometimes immovably [Loricata and HaUeria)
articulated to the cranial walls, a considerable part of the antero-
lateral elements of which remain in the condition of fibro- cartilage,
except in OjMdia,

\ r ^ \ ki Amphicoelian vertebrae are found in the existing Gechotidae
\j iL^AsV"^^^ and HaUeria, where they are connected, as in Mammals, by inter-
central cartilages, in the axis of which are persistent masses of
substance representing the chorda dorsalis. Vertebrae of similar
shape are found in the fossil Enaliosauria and Teleosauria. The
Vertebrae are ordinarily procoelian ; and, with the exception of
Crocodilina,_ in which a considerable quantity of intervertebral
substance remains between the centra of the vertebrae, they are
J. connected with each other simply by sj'uovial joints. In the
«\ ^S^**^^^^ / Chelonia, the vertebral centra vary very much in shape, especially
^ g \ ivi the neck and tail, where they may either be amphicoelous,
^, j biconvex, or procoelous. The neuro-central sutures disappear

Characteristics of the Vertehrata. Ivii

in Sqnamata, but are persistent in Loricata. The number of
the vertebrae may amount to several hundreds in the OjjJddia,
and in the Saurian Amplmhaenoidea may be as many as one
hundred and thirty. Though ordinarily the number is much
smaller in Reptiles provided with limbs, even in the non-serpenti-
form Monitor it may be no less than one hundred and forty. There
are two cervical vertebrae in Ophidia ; in Sauria their number may
amount to ten ; in the Loricata it is usually eight. The dorsal
vertebrae are movably articulated with each other^ except in
Chelonia ; the sacral vertebrae are seldom more than two in
existing Reptiles, though this number was often much exceeded in
extinct forms of the Class. Lumbar vertebrae do not exist in
OpJiidia ; they are present in Chelonia^ and in number from fom'
to five^ whilst in Sauria they are reduced to two, or even one.

The shoulder girdle is entirely absent only in OpJddia, but
present in a rudimentary condition in the serpentiform Sauria.
The clavicle is wanting in Loricata, CJiamaeleonoidea, and Sa^l-
ropterygia. The sternum is wanting in OpJddia, Chelonia, and in
some of the serpentiform Sauria. The ribs in the Chelonia form
by fusion with exoskeletal ossifications the expanded lateral or
'costal'' plates of the carapace. The sternum is absent, and the
ventral plates, constituting the 'plastron,'' are exclusively dermal
ossifications. In the Crocodilina, the ribs of the anterior thoracic
vertebrae, and, with the exception of those belonging to the atlas,
of the cervical also, articulate with their respective vertebrae by
two separate processes, the ' tuberculum,'' and the ' capitulum.''
The ribs of the Sauria have only a single articular facet, which,
however, may show a tendency to bifurcate. The ribs carry pro-
cessus 2mcinati in the Crocodiles and in Hatteria. Many Reptiles
have free abdominal ribs, which may be either true endoskeletal
elements, or ' parostotic ossifications of intermuscular fibrous septa,
or, as in Hatteria, of the subcutaneous fibrous mesh. In Ophidia,
the posterior pair of limbs is sometimes, represented by a pair of
small bones placed anteriorly to the anus ; and in the serpentiform
Sauria the pelvic girdle and its appendages are represented merely
by a single iliac bone, attached on either side to a single ' sacral '
vertebra. But in all other Reptiles the three pelvic bones are
present, forming pubic and ischiac arches by abutment upon the
ossa ilii, which do not extend forwards anteriorly to the acetabulum.

Iviii

Introduction,

The number of the phalanges increases in the digits of both extre-
mities from the innermost digit outwards, and reaches its maximum
in the fourth digit. In the foot of the Crocodilina this digit has
no claw on its terminal phalanx, and the fifth digit is altogether
lost.

Teeth are always present; except in Chelonia, where a homy
1^ sheath covers the jaws, as in the bills of Birds. The teeth are
limited in Crocodilina to the homologues of the bones which carry
teeth in Mammalia ; but in many Sauria they are carried upon the
pterygoid also ; and in Ophidia upon both palatine and pterygoid
bones, in addition to the mandibular, maxillary, and premaxillary
bones. Teeth are provided with sockets in Crocodilina, but in no
other existing Reptiles ; they are reproduced, as shed, during the
whole period of the life of these animals. The tongue may be
either spatula-shaped and immobile, as in Chelonia and Crocodilina,
and some Sauria, or bifid, elongated, and protrusible, as in other
Reptiles. The wide oesophagus, and the muscular stomach, are
ordinarily not unlike those of Birds ; and this resemblance is made
more striking in the Crocodilina, which, in addition to the muscular
^^^^j^|r^^^gazzard^^a^^ a special 93ortio p^ loric such, as is developed in many
"aJL/^ grallatorial and natatorial Birds. But the digestive tract of

' Reptiles, which are with few exceptions of carnivorous habits,

exhibits, in correlation with this uniformity of diet, fewer varia-
tions of arrangement than that of Birds. Labial and lingual
salivary glands are occasionally present. Of the former of these,
c\\iL£j^'^'*^® poison-gland of Ophidia is a modification. The liver and
, xr- pancreas have, as in Birds, two or more excretory ducts ; the latter

• ^^ B t of the two glands is ordinarily perforated by the hepato-enteric
ducts ; a gall-bladder is always present, but is sometimes developed
upon the biliary duct at a distance from the liver. This gland is
unilobed in Sqiiamata, bilobed in Loricata.

In the Squamate Reptiles and Chelonia, in which the heart has
not four distinct and separate cavities, the venous blood returned
from the system to the larger right auricle, is kept more or less
completely apart from the arterial, returned from the lungs or lung
to the left by the non-isochronism of the action of the anterior and
posterior parts of the ventricular cavity. The anterior or inferior
portion of the ventricular cavity is filled from the right auricle,
and empties itself into the pulmonary artery, and partly into the

Characteristics of the Vertebrata.

Hx

left aorta, before the posterior part of the ventricular cavity, into
which the blood from the left auricle is discharged, commences to
contract. When this part of the ventricular mass begins to con-
tract upon its arterialized contents^ access to the pulmonary artery
has been cut off by the closing up of the muscular demi-canal
leading to that outlet ; and the arterialized blood is consequently
thrown into the two systemic aortae. Of these, the one which C\yf^^
bends over the left bronchus, or, in Oplddia, to the left side of the ^ i
body, and which is consequently known ordinarily as the left aorta, ^Q^^'^^J
never gives any branches to the anterior parts of the body ; biit 5jl^,w(o/|L
either as in Smcria and OpJddia^ simply joins the right aorta without 1]
giving off any branches; or, as in Loricata, distributes itself to
the chylo-poietic viscera, and communicates with the right aorta
simply by a branch of anastomosis. In the Crocodilina this vessel
arises from the right auricle, together with the pulmonary artery,
and consequently never carries any arterialized blood. Its com-
munication, by the foramen Panizzae, with the right aorta, which
supplies the anterior parts of the body, may be held to foreshadow
the conversion which the fourth left aortic arch undergoes into a
left subclavian artery in Aves. The close proximity of the com-
mencement of the left aorta to that of the pulmonary artery, enables
it in all Reptiles alike to relieve the pulmonary circulation, when
respiration may be put into temporary abeyance. The arterial
outlets of Reptiles have only two semilunar- valves. In all Reptiles,
as in all Birds, there are two superior as well as one inferior vena
cava; but in Reptiles these three vessels open into a pulsatile
venous sinus, and have their contents poured through it by an
orifice guarded with eyelid-like valves into the ventricular cavity.
In all Reptiles there is a ' renal portal ' circulation, by which the
venous blood returning from parts placed posteriorly to the kidneys
finds its way into these organs, at the same time that by means of
anastomoses with factors of the true portal system, it may be
returned to the heart by way of the hepatic system. The supra-
renal bodies are, like the renal, possessed of a system of venous
inferent vessels. The lymphatic vessels, which often take the shape
of loose sheaths surrounding the large arteries, communicate with
the veins both anteriorly in the brachiocephalic, and posteriorly in
the caudal regions. Upon their junction with the veins of this
latter region, contractile sacs, the so-called ' lymphatic hearts,-" are

Ix

Introduction.

developed. Glands which in Birds are only scantily developed
upon the cervical lymphatics, are not represented as distinct
from lymphatic plexuses, except by a mesenteric gland in the
CrococliUna.

Tlie trachea of the Loricata has a more perfect larynx than that
of the Scfuamata, and in some cases it describes a couple of convo-
lutions before entering the lungs. These organs differ in the Lori-
cata from those of other Eeptiles in having, in correlation with
their non-transpirable integument, a much greater development of
internal parenchyma; and in not projecting freely into the general
cavity of the body, dissepimental processes of peritoneal membrane
separating them from it and foreshadowing thus, as also by their
possession of intrinsic muscular fibres, the diaphragm of warm-
blooded animals. In the Squamata the lungs may be prolonged
in air-sacs, with little or no reticulation of vessels developed upon
them_, and these prolongations may be numerous as in Chamae-
leonoidea, or simple as in OpJiidia. In some of the lower Lizards,
again, as Hatteria, the lungs may be nearly as simple as those of
the Amphibia. The kidneys are situated posteriorly in the trunk,
and, except in the OpJdclia, within the pelvic cavity, and close to
the cloaca. In the Crocodilina, indications of a separation of the
substance of the kidney into a cortical and medullary stratum are
not wanting. A urinary bladder is usually present in Sauria and
Chelonia, but is absent in Opjddia and Crocodilina. In the Che-
lonia, a simis urogenitalis is present. The kidneys are not con-
formed to the sinuosities of the bony structures as in Birds. The
cerebral hemispheres are smaller relatively to the rest of the
encephalon, and to the spinal chord, than in Aves. The cerebral
hemispheres, corpora bigemina, and cerebellum, are larger in the
Loricata than in the Sq^iamaia. A tympanic ca\dty is present
except in OpJddia, Anvpldshaenoidea, and Ilaiieria. This latter
animal has the commencement of a spiral turn indicated in its
cochlea, which in other Reptiles is, as in Birds, merely a flask-
shaped cavity; but it differs both from Birds and from other
Eeptiles in the absence of any intra-ocidar structure corresponding
with the avian ^ pecten,' or the 'processus falciformis' of other
Eeptiles.

Copulatory organs of two distinct types exist in the Loricata
and Sqmmata respectively; those of the former division being

Characteristics of the Vertehrata.

Ixi

developments of the anterior wall of the cloaca, whilst those of the
latter consist of two protrusible hollow conical bodies^ which open
into that cavity from behind. In the Chelonia, two peritoneal
canals are prolonged into the penis^ in the distal extremity of which
they terminate blindly ; two canals^ probably homologous with
them, and also with the similarly situated pores of the Selachian
and Ganoid Fishes, exist in the Grocodilina, but open at the base
of the intromittent organ. Tbe testes and ovaries are bilaterally
symmetrical, except in the Ophiclia, where the right gland is placed
anteriorly to the left, and in the females is the larger of the two.
The ova often undergo development whilst in the oviducal canals,
but the young are not set free from the foetal envelopes before
extrusion from the maternal organism. For liberating themselves
from these envelopes, the young of the really ovo-viviparous Viper,
as also of many other Reptiles, are provided with a temporary
premaxillary tooth. All Loricata are oviparous in the strict sense ;
and amongst the Squamata, nearly allied forms may vary as to
being ovo-viviparous or oviparous.

Some lowly organized Lizards, such as Hatteria, possess the
power of reproducing lost portions of the tail.

The sub-division Loricata, under which are comprised the two
orders of Crococlilina and Chelonia, differs from the sub-division
Squamata, comprehending the two orders Satma and Ophiclia, in
the following particulars besides those already enumerated. Their
anal cleft is longitudinal, there is usually some calcareous deposit in
the shells of their eggs, their ribs are double-headed in the anterior
regions of the body. Setting aside a few points which may be
correlated with their aquatic and less active habits, the Loricata
may be considered as more highly specialized, and possessed of
nearer affinities to the higher Vertehrata than the other sub-
division of this class.

Class, Amphibia.

Cold-blooded Vertehrata, which for longer or shorter periods, or
throughout the whole of their lives, are provided with gills for
aquatic, in addition to lungs for aerial respiration, and which even
when the gills are permanently retained go through some stages of
metamorphosis after being set free from the egg. Amongst these

m

Ixii Introduction.

stages of metamorpliosis, the development of limbs never exceeding
a pentadactyle division in their terminal segment, and possessing
the same segmentation as that seen in the higher Vertebrata, is to
be reckoned as an obvious external characteristic, which, together
with the absence of scales, differentiates them, with very few ex-
ceptions, from Pisces. They never have median fin-rays supported by
dermal spines ; and, in the absence of an ossified basi-occipital, they
always have two condyles formed by the exoccipitals, for articu-
lation with the atlas. The heart has always two auricles, perfectly
separated ordinarily, and communicating with a single ventricular
cavity.

Their integumentary system differs from that of Fishes in not
having either dermal ossifications or dermal scales developed in
the region of the trunk ; Cera6o^/iiys, however, and Brachjceplialus
amongst existing Amphibia, form exceptions to this rule, having
dermal ossifications developed in their dorsal region; and the
Caeciliae develope dermal scales. In the Salamandra unguiculata
again, and in the DactyletJira cajoensis, a development of nails has
been observed, contrary to the rule that in the branchiate Verte-
brata there is no epidermal skeleton. The cutaneous system of
Amphibia {Triton) has been observed to possess, during their larval
life, rudimentary^ structures, resembling the sensory organs deve-
lop ed^nl^, in connection with the /lateral line.' In adult Am-
phibia, the cutaneous glandular system often attains a great deve-
lopment as in the 'parotoids' and other glands of many Annra.

The suspensorium is immovably articulated to the skull, and is
continuous with the pterygo-palatine elements of the maxillary
apparatus anteriorly, whilst externally it has applied to it a mem-
^,5.,-^Vt(^7vV^brane bone, homologous probably with the praeoperculum of Tele-
tr^'^ ostean Fishes. No Amphibian, however, ever possesses in the cu-
' ' taneous opercular flap which it developes, any representatives of

the operculum, sub-operculum, inter-operculum, or branchiostegal
bones of Fish. The maxillary and praemaxillary bones are never
absent, and are ordinarily dentigerous. The vertebrae are very
numerous, and amphicoclian in the lower Amphibia; they are
few, and show, ordinarily, the procoelian, though, sometimes, the
opisthocoelian arrangement of the articular ends of their centra in
the hio-hcr orders. The neurocentral suture is usually absent.
Except*^ in the serpentiform apodal Caeciliae, the ribs are rudi-

Characteristics of the Vertehrata. Ixiii

mentary in this class. Thoug-li there is never any prolong-ation of
costal structures to the medio-ventral line, there is a true sternum
developed in relation with the coracoids in most Amphibia except
Caeciliae and Proteus. The ilium never abuts upon more than a
sing-le vertebra, but the ilium of one side has been observed to abut
upon one, whilst the ilium of the other abutted upon another ver-
tebra. No ^parostotic'' bones are ever developed in relation with
either limb-girdle.

In the highest order of Amphibia, the Amira, the tongue is
attached to the front of the mouth and is protrusible ; with the
exception of Pipa and Dactylethm, where the organ is altogether
absent. It is not protrusible in other Amphibia. Amphibia are
sometimes edentulous; but usually more or fewer of the bones
forming the walls of the mouth, and amongst these, the vomerine,
pterj'goid, and sphenoid as well as the lower jaw, the maxillary
and the praemaxillary bones, are dentigerous. In Proteus, the
digestive canal takes a direct antero-posterior course, without any
specialization of the stomach as a segment of larger calibre than
the intestine ; in other Amphibia a small and a large intestine are
ordinarily differentiated as well as a stomach. The small intestine,
of the larvae of the Anura, which, during that period, feed on vege-'
table food, is of great length and disposed in numerous coils. Ati
the conclusion of their metamorphoses, the digestive tract has as-\
sumed a comparatively simple character, though the calibre, direc-
tion, mucous and muscular coats of the stomach, small intestine,
and colon, severally, are most characteristically developed. A bilobed
liver and a compact pancreas are always present, but oral salivary
glands are represented only by small glandules impacted in the
mucous membrane of the mouth.

The heart consists of a sinus venosus, a right and left auricle, a
single ventricle, and an arterial bulb. Within this latter portion of
the organ, a longitudinal lamellar ridge is developed, which is
attached along the dorsal line of the bulb and projects freely into
its interior; being connected at either end with a semilunar valve,
and describing a curve like that of an italic s, in the interval be-
tween those points. This imperfect dissepiment may be held to
foreshadow the differentiation of the pulmonary and systemic ar-
terial trunks which we find in Eeptiles ; whilst physiologically, by
its relation to the orifices of the branches passing to the anterior

Ixiv.

Introduction.

and to the posterior parts of the body respectively and to the lungs,
it provides for the more or less perfect separation of the streams of
arterial and venous blood received from the two auricles. All Am-
phibia possess a renal:j20£tal system, the factors of which anastomose
freely with those of the true portal system. This latter system
always receives, by the intemxfidiation of the epigastric veins, an
important factor from the .allantoid bladder; by which' connection
the connection of ^ the umbilical and placental veins, as seen in
Mammals, is very olmQiislyLjQifishadpwed^^ The transpirable and
glandular character of the skin would appear to confer an aerating
function upon the vascular ramifications which it contains in great
abundance. The lymphatic vessels are greatly developed ia the
subcutaneous spaces ; and lymphatic hearts are present in the
Anura, both upon the anterior and upon the posterior junctions of
this system to the blood- vascular. In the Urodela, as in Reptiles,
the posterior hearts only exist. In the higher Amphibia, two sets
of gills are developed. One of these is the external set which
corresponds to the permanent gills of the Perennibranchiate Am-
phibia, and to the deciduous external giU filaments of the Plagio-
stomous Eishes, which latter it resembles in being shed early.
The other is the internal set which are developed subsequently to,
and retained in the Urodela and A7mra longer than the ciliated
external set. In certain Amphibia {Meiiopoma, AmpJiiuma, Crypto-
hranclms, thence called Derotrematd), a fissure remaius in the pha-
lyngeal walls after the shedding of the branchiae. This event does
not always take place at the same date in the life of the larva.

Cartilages representing a larynx are developed round the inlet
from the phaiynx into the air passages. There is a trachea of con-
siderable length in Menopoma, AmpUima, and the Caeciliae ; and
there are bronchi of considerable length in Pipa and Bactylethra ;
but ordinarily, these tubes are only rudimentarily represented in
Amphibia.

The Amphibia appear to have no secondary kidney developed;
and the products of the urinary and sexual glands are always dis-
charged into a cloaca by a single orifice, that of the duct of the
Wolffian body, on either side. In Proteus, the transversely running
ducts of the primary kidney remain distinct from each other, up to
their junctions with the antero-postcriorly running duct of the
primary kidney, the so-called ' Muller's duct.' In other Amphibia,

Characteristics of the Vertebrata.

Ixv

the ducts of the Wolffian body form by fusion with each other a
secondary duct, which opens into the primitive duct of MliUer
at its lower end, leaving the upper portion of that duct to serve
exclusively as a generative canal.

The cerebral hemispheres always contain a lateral ventricle, which
is prolonged into the interior of the sessile olfactory lobes. The
optic lobes are smaller relatively than in Fish, in correlation with
the smaller eyes ; the optic thalami are always differentiated from
them, and from the corpora striata in front. The membranes of
the brain and spinal cord have an abundance of pigment cells in
their visceral laminae, and upon the exterior of these membranes,
and especially upon their prolongations upon the spinal nerves, y f -1
deposits of crystalline carbonate of calcium are commonly observ-
able. As in many Fishes, the portio dura often fails to be entirely
differentiated from the fifth pair of nerves ; as in Lepidosiren, the
glossopharyngeal is represented by branches of the vagus, and the
hypoglossus by the first spinal nerve. The eye is small in com-
parison with that of Fish, but as in that Class the lens is sphe-
roidal, and the cornea, except in the Land Salamander, flat. There
is jLO__tympanic cavity except in_the _.^^^r^. and no cochlea except
in a ru.dimentary condition in the same order. In the aglossal
Anura {Pipa, Bactyletlira), there is a single median pharyngeal
orifice to the two Eustachian tubes. The two nasal cavities open
into the mouth by a canal passing between the bones of the roof
of the mouth in Anura, but between those bones and the lips in
Perennibranch lata .

Rudiments of an ovary have been observed to coexist with the
testes in the male Biifo variabilis and einereus. The sexes are very
frequently distinguishable by external differences of colour, size,
and conformation, but there are no external copulatory organs in
this Class. The ova and spermatozoa come into relation with each
other externally to the maternal organism, but by means of
congress between the two sexes in the Anura; they come into
relation with each either externally to, or within the maternal
organism in the Urodela, and probably also in the Perennibran-
chiata, but without, at least in the aquatic species, any sexual
congress. The Land Salamanders appear to be, under certain
circumstances, such as those of the Alpine species living at points
of great elevation in the mountains, ovo-viviparous or viviparous,

e

Ixvi

Introduction.

tlie larvae having in some cases shed their external branchiae
previously to birth. The ova are small, the yolk undergoes nearly
complete segmentation. With a few exceptions, the Amphibia are
oviparous. In every case, except possibly that of tbe Caecilia
compressicmula, the embryos very shortly after hatching develope
branchiae, or, as in the case of Notodelphi/s, structures equivalent
to them.

Existing Amphibia are divisible into three orders. In the most
highly organized of these, the swimming tail is discarded in the
course of metamorphosis as well as the gills, and they are thence
called Amira ; in the second order, thence called ' Urodela ' the tail
is retained, whilst the gills are, in the sub-orders, Salamandrina
and Derotremata, deciduous ; and in the FereiiJiibranchiata, retained
permanently. In these two orders limbs are developed, at least on
the pectoral arch ; but a third order, that of the Gymnopliiona,
represented by the single family, Caeciliae, is constituted by
Amphibia in which, though the gills are deciduous, no limbs
are developed, and the body remains serpentiform.

In development, the body cavity is not formed apart from and
around the yolk sac, but the intestine is formed, as in Amphioxm
and the Ci/clostomi, by a process of invagination, beginning from
without at a spot corresponding with the situation of the future
anus. The oral opening is not formed when the embryos are first
set free from the egg. The Anura and the Caducibranchiate
Urodela have two sets of gills, an external set of three pairs, which
is soon lost, and in the land Salamanders partly or wholly before
the end of intra-uterine life ; and an internal set. After the dis-
appearance of the external set an opercular fold, in which however
irn no Amphibia are bones ever developed, forms over the internal
gills,- and within the branchial cavity thus produced the anterior
extremities first bud forth. When in the course of metamor-
phosis the gills disappear, the continuity of the circulation is main-
tained, or, in other words, the primitive continuity of the proximal
or cardiac with the distal or dorsal elements of the aortic arches
is re-established, by the expansion in calibre of a branch of ana-
stomosis, which, whilst the branchiae were functionally active,
connected the efferent directly with the aflercnt branchial trunks,
but was itself at that time functionally insignificant. The oper-
cular structures close up the visceral fissures, except in the Dero-

Characteristics of the Vertebrata.

Ixvii

imnata, and more or fewer of the cartilaginous branchial arches
disappear after the disappearance of the branchiae they carried.

The Alpine Triton, one of the Caducibranchiate Amphibia, has
been observed to attain sexual maturity as indicated not only by
external characteristics, but by the maturation of ova and sperma-
tozoa, at a time when the branchiae were still in functional activity,
and when the characters of the bones in the roof of the mouth, and
the presence of a continuous non-constricted cylindriform chorda
dorsalis, showed the animal to be really in a larval state. The
Axolotl [Siredon pisciformis) has long" been known to be competent
to sexual functions, whilst organs, regarded as provisional in other
Amphibia, were still persistent; and it has consequently been
classed with the Terennihrancliiata until recently, when it was
discovered that its gills are really deciduous, though at varying
periods in the life of the animal. Similar instances of larval
Ichthyoids maturing sexual products are furnished to us by the
immature Lamprey, and the young male Salmon, known as the
' parr.' Some Amphibia possess a great power of repairing injuries,
and of reproducing destroyed or amputated organs. It has been
stated, however, that it is necessary for such reproduction that the
basal or some other portion of the mutilated organ or limb should
be left in situ; and it is not certain that the Urodela with well-
developed lungs, such as Salamandra terrestris, and the Anura
generally, possess this power in their adult state, at least to the
same extent as they do when larvae, or to the same extent as
other Amphibia in which the organs for aerial respiration are
less highly evolved.

The Amphibia are placed together with the class Pisces in a
single group, the Ichthyopdda, s. Anamniota. It is with the mote
generalized forms of that class, viz., the Ganoidei and the Dijmoi,
rather than with those which, as the Teleostei, combine in this
organization the largest number of specially piscine characteristics,
that the Amphibia are allied. The Dipnoi indeed have been ranked
as a separate order of Amphibia, under the title ' Ichthyobatrachia,'
though, if we have regard to the entirety of their organism, we
are compelled to regard them as true Fish. The Elasmobranchii
resemble certain of the Amphibia in developing external gills in
embryonic life, and they were spoken of by Linnaeus as Amphibia
nantia. The absence, however, in them of any save an occasional

e %

Ixviii

Introduction.

and rudimentary homologue of the pulmonary organs of the
Amphibia, appears to put this order of Fishes into a position much
farther removed from the higher Vertebrata with which they were
thus classed, than that which the Dipnoi, and even the Ganoidei
occupy.

Class, Pisces.

Branchiate Vertebrata with motor organs in the shape of fins,
supported by numerous internal rays, and placed along the medio-
dorsal and medio-ventral lines, or along these lines and bilaterally
also. The endo-skeleton of Fishes takes far more various forms than
that of any other vertebrate Class ; and their exoskeleton is simi-
larly distinguished with reference to all other classes except the
Mammalia.

The dermal exoskeleton may take the form of scales, as in the
great majority of Fishes ; of placoid or spiny dentinal formations,
as in Masmobranchii ; of enamelled scales or of bony plates, as in
Qanoidei ; and in Dipnoi, Ganoidei, and Teleostei, it extends into
the sub-cutaneous fibrous mesh, and along intermuscular aponeuroses
forming ' splint bones.^ There are no scales in Marsipohranchii,
and the Spahdaridae, a genus of Ganoidei, have an almost entirely
naked skin. There are no splint bones in the Elasmobranchii.
The cutaneous system is further distinguished by the possession of
the system of the 'lateral line,^ which has not been detected else-
where, except in certain Amphibian larvae, and which is supposed
to be sensory in function. The epidermis is ordinarily prolonged as
a continuous, even if thin layer, superficially to the various dermal
formations, except in the cases of some of the outgrowths deve-
loped in the Masmobranchii, and sometimes of the enamelled scales
of the Ganoidei.

However various the endoskeletal structures of Fish may be, they
all agree in the non-possession of a sternum, the absence of which is
connected with the peculiarities of their reproductive processes ;

* The low grade of organization to which the Phan/ngobranchii, as represented by
the Lancelet, have attained, makes it convenient to omit this Order from consideration,
whilst detailing the characteristics more or less universally found in the other five
Piscine Orders, viz. Marsipobranchii, Teleostei, Ganoidei, Elasmobranchii, and
Dipnoi.

Characteristics of the Vertehrata. Ixix

and in the presence of a lai'gely developed branchial apparatus,
which is similarly correlated with their aquatic life. In the Mar-
sipobranchii, vertebrae are indicated rather than differentiated by
the development of a few cartilaginous neural and haemal arches,
the sheath of the chorda dorsalis remaining unsegmented through-
out. Indications of the formation of vertebral centra are presented
to us in the calcified annuli developed in the sheath of the chorda
in Chimaerae. The characters of the axial elements of the endo-
skeleton vary much in Plagiostomi, attaining in some represen-
tatives of this sub-order to perfect differentiation and partial calci-
fication. Greater variety is observable in the same structures in
the now numerically much smaller order of Ganoidei, where the
centra may be represented by a cylindrical fibro-cartilaginous sheath
surrounding the cylindrical notochord, as in the Sturgeons ; or by
perfectly ossified opisthocoelian masses connected by anchylosis
with perfectly ossified neural arches, as in the Bony Pikes {Lepi-
dosteidae). In Teleostei, as the name implies, the vertebrae are
differentiated, and, in various degrees, calcified, the amount of lime
deposited rarely or never attaining the proportions it assumes in
other classes of Vertebrata. The neural arches are in Teleostei
ordinarily, but not always, anchylosed to the centra, without the
interposition of any neuro-central suture. The number of the ver-
tebrae may be as many as 365 in some Sharks ; in some Ganoids,
and in some of the Phi/sostomi amongst Teleostei, it may amount
to 200 ; in mo^i Phi/sostomi it is, about 80 ; it falls much lower in
Acanthopteri, and may be as low as 15 in the Plectognaihi. The
trunk is divisible into two main regions, the dorsal and the caudal ;
from the former of which a cervical region may be said to be marked
off, at least morphologically, inasmuch as the scapular arch makes its
first appearance opposite the interval between the second and third
vertebrae. The Elasmohranchii and most of the Ganoidei, have
their greater geological antiquity spoken to by their retention of
the more typical heterocercal form of the tail. This peculiar shape
is produced by a disproportionate development of the haemal caudal
arches, whereby the tail, which was in the early embryo equilobed,
and, as in Marsipohranchii and Dipnoi, a direct continuation of the
axis of the dorsal region, is bent upwards. An additional factor in
the production of the heterocercal tail, is brought into play in the
case of the Holostean Ganoidei, and the Physostomous Teleostei,

9

Ixx

Introduction.

which are nearly allied to them, by the stunting of the neural in
correspondence with the greater development of the haemal arches.
This form of tail may to a superficial examination appear quite
equilobed^ and it is ordinarily spoken of as ' homocercal.' It is,
however, morphologically ' heterocercal,'' as the haemal and neural
arches enter into its composition in very unequal proportions, the
chorda dorsalis being really prolonged to the upper angle of the
tail fin, and the ' hypural ' plates being all modified haemal arches,
and not half of them haemal, and half of them neural ossifications,
A true ' diphycercal ' tail is finally produced in the Acanthopteri,
by a reduction of the disproportionate size of the haemal, and by
a simultaneous stunting of the central elements of the terminal
vertebrae.

Tlie difierences in the structural arrangements of the skulls of
Fishes are very much greater than those observable in the skulls of
members of any other Vertebrate class, relating as the}^ do to points
of no less morphological and indeed physiological importance than
the absence or j)resence of cranial bones; of freely movable gill-
covers, and suspensoria; of maxillary and premaxillary, and of
mandibular bones. In the Masmohranchii and Marsijwhranchii,
there are no cranial bones ; and with regard to the praemaxillaiy
and maxillary bones, it can only be said, that the sites which those
membrane-bones occupy in other fishes may, perhaps, be considered
as marked out in these orders by the presence of certain labial
cartilages. The Chimaerae differ from the other Elasmoh-anchii,
the Sharks and Rays, in having a movable operculum and an
immovable suspensorium, and in this latter particular the non-
mandibulate Marsipohranchii more or less closely resemble them.
The Teleostei and Ganoidei differ from these Fishes by possessing
cranial, maxillary, praemaxillary and opercular bones. Their oper-
cula and suspensoria are always movable.

In the Elasmohranchii the skull is distinctly articulated to the
first trunk vertebra. In the Chondrosteal Ganoidei, the largely
developed parasphenoid reaches for a considei'able distance back-
wards underneath the anterior vertebrae ; whilst in the Holostean
Ganoidei and many Physostomous Teleostei, the first and some of
the following vertebrae may be suturally connected with the basi-
occipital. In other osseous Fish the basi-occipital presents a concave
conical cavity for apposition with the similar one upon the anterior

Characteristics of the Vertehrata. Ixxi

surface of the first vertebra ; and the biconical cavity thus formed
is filled with a structure formed by the development of the chorda
dorsalis, and of semi-g-elatiniform consistence.

Fish are very rarely edentulous. Teeth are ordinarily present,
and are very variable in number, shape, and situation. Most of the
bones of the oral and pharyngeal cavities may be dentigerous ; but
in Cyprinoids, there may be only a single tooth superiorly, carried
by the basi-occipital. The teeth are replaced as often as they are
shed, and in the family just mentioned, the inferior pharyngeal are
so shed and replaced periodically. It is only in Fish that the dental
series is continued in an unbroken row across the middle line,
without forming a diastema corresponding to either upper or lower
median raphe. Fish have no oral salivary glands, and the tongue
is only movable as a part of the hyoid apparatus upon which it is
carried. In the IlarsipohrancJdi , the branchial sacs open both in-
ternally and externally by the means of larger or smaller ducts,
which again may form a common duct before their inner or outer
termination respectively. In all other Fishes the branchial inlets
and outlets both have alike the form of fissures, the inlets leading
directly from the interior of the pharynx, and the outlets opening
either directly on to the external surface of the body, as in the
Sharks and Rays, or into a branchial cavity covered by the opercular
apparatus as in Chiniaerae, Dipnoi, Ganoidei, and Teleostei. The
oesophagus is ordinarily short ; and it is also, as the food is usually
swallowed with little or no comminution, of considerable width. In
the Marsipohrancliii, the digestive tract takes an antero-posterior
course, without any external diflTerentiation into stomach and in-
testine. In other Fishes the intestine is readily distinguishable from
the siphonal or coecal stomach ; and describes one or two convo-
lutions before terminating at the anus through the intermediation
of a short rectum, from which a colon can scarcely be said to be
differentiated. The length of the entire tract is shorter relatively
to that of the entire body than in the air-breathing Vertebrata gene-
rally ; it is however not inconsiderable in the species which support
themselves upon vegetable diet ; and the absorbing surface of the
canal is greatly increased in Dipnoi, Ganoidei, and Elasmohranchii,
by the development of internal folds of the mucous membrane into
a spiral valve, which appears to be rudimentarily represented in the
Marsipohranchii by a longitudinal ridge running along the internal

Ixxii

Introduction.

surface of the intestine. In the three more highly organized of the
four orders just mentioned, a duodenal segment is distinguishable
in the small intestine anteriorly to its valvular portion. This seg-
ment is known as the ' V^wtr^ Ejitiana' in Elasmobranchii^ where it
is of considerable size, and marked externally by the entrance of the
functional biliary and pancreatic, and the rudimentary omphalo-
mesenteric ducts. The rectum always opens anteriorly to the
urinary and genital ducts ; except when these tubes open upon its
dorsal surface near its termination, so as to constitute a cloaca.
The suspensory mesenteric laminae often become largely fenestrated,
or may disappear altogether in consequence of absorption, in adult
Fish. . A liver is always present ; it is ordinarily unilobar ; in some
Fish it is multilobar ; in the Cyprinoids it is trilobed, and interdi-
gitates with the convolutions of their intestine, much as the lobes of
the Hver do in many of the Gasteropoda. There may be several gall
ducts, and a gall bladder is very rarely wanting. Secretory coeca,
the so-called pyloric ajDpendages,^ are developed in many Fish
upon the commencement of the intestine. They are very variable
in number, and ordinarily simple and distinct, though sometimes
ramified and bound together more or less closely. A glandular
pancreas of smaller size but more compact structure, coexists some-
times with these pyloric appendages. The heart consists of a
branchial auricle and ventricle, to the former of which a sinus
venosus is superadded, and to the latter, except in Marsipohranchn,
an arterial bulb, which breaks up into branches corresponding in
number to the gill arches. In the Ganoidei and Elasmobranchii,
the arterial bulb has a layer of transversely striped muscular tissue
in its walls, and several rows of valves in its interior; whereby
it is enabled, as in Amphibia, to act as an accessory ventricle.
The muscular fibre of the arterial bulb of Teleostei is not of the
striped variety, and the bulb has only two valves internally. In the
Dipnoi a second auricle exists, which receives blood brought back
to the heart from the pulmonary air sacs. The systemic aorta is
formed, in the embryo, by the confluence of the aortic arches into
which the bulb divides ; and, after the develojiment of the gill
fringes, for the supply of which these arches resolve themselves
into efferent branches, by the confluence of the efllerent branchial
veins with which those afferent vessels are continuous through the
intermediation of the aerating capillary plexuses. In the Dipnoi,

Characteristics of the Vertebrata.

Ixxiii

as also in certain Muraenoid Teleostei, more or fewer of the
branchial arches fail to develope gills, and the direct connections
between the sub-branchiall}'- jDlaced bulb and the sub-vertebrally
placed aorta, which in other Fishes exist only in the foetal state,
persist here throughout life. From each of the posterior aortic
arches {Lepidosiren pamdoxa), or from each of the compound factors 1/
of the dorsal aorta, made up on each side {Uhinocryptis annectens), a
branch is given off to the cellular air sac ; and during the period in
which these animals live out of the water, the aeration of their
blood is dependent upon the ramifications thus formed there. The
vein which brings the blood from the pulmonary air sacs back to,
the heart, instead of opening into the portal or hepatic vein, as the
veins from the air-bladders of ordinary Fishes do, or into a vena
cava inferior, as does the vein from the air-bladder of the Ganoid
Tolypterus bichir, opens independently into the ventricular cavity
after dilating within the pericardium ; and thus, though diverging
but a very little from the arrangements common in (uni-auriculate)
Fishes, it constitutes a system analogous to and homologous with the
pulmonary veins and auricles of higher Vertebrata. Ordinarily in
Fish, the blood from the parts of the body posterior to the heart
exclusively of the chylopoietic viscera, is collected into the two
subvertebral venae cardinales, v\^hich meet the two venae jugulares
from the anterior parts of the body, and form with them the trans-
verse ductus Cuvieri which open into the sinus venosus. The hepatic
veins, which bring the blood of the chylopoietic viscera back to the
heart, very ordinarily end by opening into the sinus venosus, with-
out receiving any factors from any other than those organs. ^^,-%r»e~ v • '2- ,
vena cava inferior is constituted in some Fishes, as in the Perch c:- VSou^
amongst Teleostei, and in the Polyptenis amongst Ganoidei, by the +
fusion either of veins from the air-bladder with veins from the j( X ,
genital glands as in the former of the two Fishes named, or of a ' * '
vena cava sub-vertebralis impar with veins from the bifid air-bladder •^z c.*^ + "O- c
as in the latter. A renal-portal system is present, except in the ^^-b'-^t-^UAr. -IvJ-.

Marsipobranchii ; it is constituted either by caudal and dorsal veins
both or by the latter only ; and anastomoses, though not always,
with the hepatic portal system.

The Teleostei, Ganoidei, Dipnoi, and Chimaerae have free oper-
cular valves covering a more or less extensive branchial cavity.
The gills of Teleostei are ordinarily four, and are never more than

Ixxiv

Introduction.

four in number. They are usually found to form double comb-like
rows upon each branchial arch ; but the last of the branchial arches
very commonly fails to develope more than a single row of gill-
processes ; and not rarely is wholly gill-less.

This reduction may be accompamed by a similar reduction in the giU
arch immediately in front, and we find the third arch carrying a uniserial
gill in Malthea, whilst it is gill-less in the Cuchia (Amphipnous). The
fifth branchial ai'ch, which is dentigerous in most, and branchiferous in no
Teleostei, has a uniserial gill developed upon it in the Dijmoi and in
Hexanchus. All the Elasmohranchii, the Bijjnoi, and the Ganoidei, with
the exception of Polypterus and Planirostra, have a uniserial gill developed
upon the opercular arch anteriorly to the most anterior of the gill-laminae
developed in Teleostei. In the Sharks and Rays this anterior gill forms
the anterior fixed gill lamina of their anterior gill-pouch ; in the Chi-
maerae and Ganoidei, it forms the so-called ' opercular' gill. In the
Dipnoi, the development of the opercular gill appears to have prevented
that of the two biserial gills placed next posteriorly in typical fish ; in
the American species the gills of the third branchial arch appear to have
been lost also, whilst they persist in the African, as do those of the fourth
and fifth branchial arches in both species. Except in Hexanchus and
Heptanchus, there are only five gill-sacs in the Sharks and Rays, the last
of which contains only a single gill-lamina disposed upon its anterior
wall. This half-gill is homologous with the posterior row of the biserial
gill developed upon the fourth branchial arch of Teleostei, but it is not
represented in the Chimaerae. The pseudobranchia of osseous Fish is
homologous with the spiracular pseudobranchia of Ganoidei and Elasmo-
hranchii, and not with their anterior functional half-gill, nor with the
thyroid vaso-ganglion, which in many Fish underlies the anterior basi-
branchials. In osseous Fish, the pseudobranchia receives arterialized
blood from the first branchial efierent vein ; and it serves as a diver-
ticular rete mirahile for the eye within which the vessels proceeding from
it develope the so-called 'choroid gland.' In the Elfi^mohranchii, Ga-
noidei, and Dijynoi, it seiwes as a rete mirahile for the brain as well as for
the eye, but it has no ' choroid gland' developed in connection with it.
Accessory aerating organs which enable the fishes possessing them to
support respiration when out of the water, are developed in several
genera of I'eleostei {Anahas, SaccohranchtLS, Amphiimou^^, in relation
with the interior of their branchial cavity.

The morphological identity of the functionally pulmonary air-sacs of
the Dipnoi with the air-bladder of an ordinary Teleostean Fish, which

Characteristics of the Vertehrata.

Ixxv

is functionally all but exclusively hydrostatic, may be considered to be
established by a comparison of those lung-like air-sacs with the air-
bladder of the Ganoid Polypterus, which is somewhat similarly bifid,
and opens similarly into the pharynx by an air-duct entering it on its
ventral surface. From the air-bladder of the Polypterus to that of the
Lepidosteus, which however opens into the pharynx from its dorsal side,
and which, though divided internally into two longitudinal compartments,
is yet externally a single sac, the transition is not abrupt ; nor that from
such air-bladders as those of the Lepidosteus and the Physostomatous
Teleostei, to the ductless air-bladders of the Acanthopteri and other
bony Fish.

The swimming bladder is developed as an outgrowth from the
oesopliageal portion of the digestive tube, and its chictus pneuma-
tmis, when persistent, ordinarily communicates with this portion of
the tract. Both bladder and duct are absent in the Marsipo-
branchii, and, except as rudimentary structures in certain Sharks,
iu all MasmohrancJiii also. The duct is aborted in the majority of
Teleostei (the Acanthopteri, Pharpigognathi, Lopkohrmicliii^ Plec-
tognathi)^ but is present in the remainder of this order, nearly
corresponding to the Malacopterygii of Cuvier, and hence called
Phi/sostomi, as also in all Ganoidei and Dipnoi. With the presence
or absence of an air-duct to the air-bladder, the presence or ab-
sence of bone corpuscles appears to be nearly universally correlated.
The shapes which the air-bladder assumes are very various, es-
pecially when it is ductless. In many Acanthopteri it sends two
prolongations into relation with the caudal muscles, whilst in
many Phi/sostomi {Ci/jorinoideae, Siliiroideae , Clupeidae), its ante-
rior prolongation is brought into relation with the auditory ap-
paratus.

It is only in the Masmohranchii that a secondary kidney takes
the place of the primordial Wolffian body, which remains as the
functional renal organ in other orders of Fishes. This difference
is illustrated not only by the difference of form and of compactness
of the renal organs in the Elasmobrayichii, but also by the facts that
in the females of this order the oviducts open separately from the
ureters into the cloaca ; that in the males the vasa deferentia are in
some species {Muslelus laevis) bestudded with what is probably the
remnants of Wolffian bodies for nearly their entire length ; and
that the ureters are developed mainly along the internal, and not

Ixxvi

Introduction,

as in Amphibia along the outer edge, or as in many Teleostei,
along the anterior or inferior surface of the renal gl.nds. Uro-
genital canals are formed in Ganoidei of both sexes, and in the
males of Elasmobranchii. In the Teleostei, the ureters often
fuse into an azygos duct, which opens above, or behind, or to-
gether with the generative duct, but always posteriorly to the
anus. The urinary bladder may take the shape of a bilateral
dilatation, as in the Sharks and Kays; or that of a vesica bi-
cornis, as in some Ganoidei ; or of that an azygos sac, as in many
Teleostei.

The encephalon fiUs the brain-case in the embryonic Fish, but
subsequently, by the disproportionate growth of the cranial walls,
it comes to occupy a very small space in the cavity which they
inclose, the intervening space between it and the perichondrium or
periosteum, as the case may be, of the cranial vault being filled with
a mass of loosely compacted tissue, richly laden with fat. The
membranes, in relation with the external and internal surfaces of
the cerebro-spinal centres, develope pigment cells as in Amphibia.
The nerve-centres are smaller in relation to the body in this than in
any other vertebrate class; the relation of the encephalon to the
body is stated as being on an average as low as i to 3000 ; and
the spinal cord of a Sturgeon which weighed laolbs., has been
stated to have been no thicker than that of a Frog. The spinal
cord is ordinarily, but not always, devoid of any enlargements, and
of uniform diameter throughout its length, which is usually com-
mensurate with that of the spinal canal. The cerebellum is very
variable in size, but it sometimes, as in Sharks and in the Ttmny,
attains a greater size relatively to the rest of the brain in this than
in any other vertebrate class. It is never bilaterally bilobed, as the
divisions of the brain placed anteriorly to it are. The optic lobes
are frequently in osseous Fish larger than any other division of the
brain, a proportion which they never attain to in any other class.
The diencephalon, the homologue of the optic thalami, fails in some
Teleostei, as also* in the Dipnoi, to be differentiated from the
mesencephalon or optic lobes behind, and the prosencephalon in
front of it; but in many other Teleostei, in the Ganoidei, and
Elasmobranchii, this division of the brain is considerably elongated
antero-posteriorly, and bounds a ' third ventricle ' by its two halves.
In the Sharks and Rays, the prosencephalon attains the preponder-

Characteristics of the Vertehrata. Ixxvii

ance relatively to the other divisions of the brain, which it main-
tains in the hig-her Vertehrata, and developes lateral ventricles in
its two halves, which communicate with similar cavities in the
rhinencephalon. These two divisions of the brain are solid in
most Fishes, the rhinencephalic lobes appear to be attached laterally
and by peduncles to the prosencephalic in the Elasmobranchii j
they are pedunculate in many Teleostei, but sessile in the Ganoidei.
Besides developing in Silwus and Cyprinoids a supero-median
' lobus impar,' or ' nodulus,' the medulla oblongata presents in
various families certain lateral ganglionic enlargements, which^
from their connection with peripheral nerves, are known in Cypri-
noids as ' vagal/ as ' lobi nervi trigemini ' in the Sharks, and as
' electric lobes ' in the Torpedo.

In Dipnoi, and to some extent in MarsipohrancMi, the muscles of
the eye are supplied by the fifth nerve ; and in most Fishes the
nervous supply of the superficial structures in the maxillary, hyo-
mandibular, and palatine regions supplied in higher Vertehrata, with
the exception of the Anurous Amphibia, by the portio dura of the
seventh pair, is dependent partly upon factors from the fifth nerve,
as well as upon an independent stem. The nervus lateralis which
supplies the sensory organs of the lateral line, as well as the medio-
dorsal region of the trunk, anastomosing in its course with the
spinal nerves externally, much as the sympathetic chain anasto-
moses with them within the thoracico-abdominal cavity, is in
ElasmobrayicJtii, Ganoidei, and many Physostomous Teleostei, con-
stituted by the vagus. In some osseous Fish [Gadus), it is formed
chiefly by the fifth nerve. The glossopharyngeal is not always
difierentiated from the vagus, and in some Rays it interchanges
fibres with the auditory nerves. The spinal accessory nerve does
not exist in Fish, and the place of the hypoglossus is taken by the
first spinal nerve. The existence of the sympathetic has not been
demonstrated in MarsipohrancJiii ; in Teleostei the bilateral gang-
liated chain does, in Elasmobranchii it does not, extend into the
caudal region.

Organs of tactile sensibility are constituted in some Fishes by the
development of flexible rays upon their fins ; in some others, and
more commonly, by that of similar structures, in the shape of
barbules upon the snout ; but in most cases by the muco-nervous
organs developed upon the head, where they are supplied by the

Ixxviii

Introduction.

trigeminus, and upon the trunk along the lateral line. The ol-
factory organ is an azygos sac in the Marsijjohranchii, hence called
' Monorrhina;' it ends blindly in the sub-order Tetromyzoniidae,
which are hence called ' Hyperoartii,' but opens into the pharynx
in the Myxinoids, hence called ' Hyperotreti.' All higher Verte-
brata have paired nasal sacs, and have consequently been st}'led
' Amphirrhina.' In the Dipnoi, the nasal sacs have valvular poste-
rior openings, externally to the pterygo-palatine teeth ; in all other
amphirrhine Fishes they end blindly. The eyes are relatively large
in Fish, the cornea is flat, the lens spheroidal. The Elasmohranckii
possess eyelids, and sometimes a membrana nictitans. A peculiarly
piscine rete mirabile, the ' choroid gland,' exists in most Fishes,
except the Elasmobranchii and Ganoidei, between the layers of the
choroid, where it surrounds the entrance of the optic nerve. A
structure homologous with the ' pecten ' of Birds exists in many
Teleostei, where it is known as the ' processus faleiformis.' Certain
structures, consisting of pigment specks with lens-like bodies inlaid
in their substance, have been found regularly arranged between the
branehio-stegal rays, upon the head, and in two pairs of longitu-
dinal rows on the ventral surface of Chauliodes and Stomias, and
have been regarded as accessory eyes.

The auditory apparatus of the Marsipobrajic/ni consists of a
vestibule, with, in Myxinoids one, and in Tetromyzontidae two
semicircular canals, contained in cartilaginous capsules attached to
the skull laterally. In all higher Fishes there are three semicircular
canals. In the Sharks and Eays, and in the Dipnoi, the mem-
branous labyrinth is entirely surrounded by the cranial walls, but
in the Chimaerae, the Ganoidei, and the Teleostei, a median portion
is always to be found lying free in the cranial cavity. The air-
bladder of some Acanthopteri, and of many Physostomous Teleostei,
comes into relation with the membranous labyrinth, either directly
or through the intermediation of ossicula. In Elasmobranchii
canals exist, marking the line along which the integument was
invaginated, to form the 'internal ear.^ The electric organs of
Fishes are not represented in higher Vertebrata. They are most
largely developed in the Torpedo and Gymnotns, and in a lower
degree in Malapterurus and Mormyrus. They are found in various
parts of the body, but consist essentially of prismatic columns,
made up by the superposition of flat plates, to which nerves from

Characteristics of the Vertehrata. Ixxix

the fifth and eig-hth pairs, and from the spinal series, are distri-
buted. The nerves fuse with one surface of these plates, which is
electro-negative, whilst the other is electro-positive.

In several species of the genus Serramis, a testis has been ob-
served overlying the ovary, and a similar hermaphroditism has
been observed occasionally in Cyprinoids, and in some other Fishes.
On the other hand, asj^mmetry is often, as in the Perch, seen to be
produced by the stunting of one or other of the (tj^pically sym-
metrical) ovaries. The reproductive glands in the two sexes are
often so much alike externally, that an examination of their sub-
stance is necessary for deciding the sex to which they belong.
Sometimes, however, and especially at the breeding season, the
sexes may be distinguished by external differences. Fishes are
mostly oviparous, but are sometimes viviparous. Rudimentary in-
tromittent organs exist in the male Elasmobranchii, as the so-called
'^claspers.' Sexual congress or contact takes place in many ovi-
parous as well as in the viviparous Teleosfei.

The products of the generative glands sometimes find their way
into the water by extrusion, by an abdominal pore or pores, as in
Marsipohranchii, Anguilla, and the females of Salmonidae, from
the abdominal cavity into which they have been set free by dehis-
cence. But in most Teleostei, the walls of both the generative
glands are directly continuous with their ducts, so that neither ova
nor spermatozoa are ever set free into the peritoneal cavity. This
is the case also in Lejndosteus amongst the Ganoidei ; but in the
other members of that order, the sexual products of both kinds are
taken up after dehiscence by the open mouths of ' Fallopian tubes.'
In the Elasmohranchii, where the ovary is single, and the mouths
of the oviducts approximated, the lower parts of the oviduct are
specially modified to secrete the shell in the oviparous Scyllium
and in the Rays, and to serve as a uterus in the viviparous species
of Squalidae. In the males of MasmobrancMi, as of all higher
Vertehrata, the testis is continuous on each side, with an epididymis
and a vas deferens. The lower segment of the vas deferens is
expanded into a vesicula seminalis. The Elasmobranchii have
large yolked ova with partial segmentation, and in Miistelus laevis,
the vessels on the yolk sac come into such relation with the ma-
ternal vessels on the walls of the uterus^ as to form a sort of
placenta. In osseous Fishes, where the ova are very much

\

Ixxx

Introduction.

smaller, the segmentation of the yolk is more extensive than in
Elasm.ohranclm, but less so than in Mammals or Amphibia.

In Marsipohranchii, as in Amphibia and Amphioxus, the intes-
tinal canal is formed within the yolk sac, as the result of an
invagination commencing at the future anus, proceeding from
without inwards, and forming thus a tube without any umbilicus,
within a cavity which is at once yolk cavity and peritoneal sac.

Fishes, like Amphibia, are competent not rarely to sexual fime-
tions before they are mature in other particulars. Their power
of repairing injuries, and reproducing lost parts, is confined to the
fins. The capacity for growing as long as life lasts, which some
Fishes are said to possess, may be explained by the facts that their
bodies are, firstly, of very nearly the same specific gravity as the
water in which they Kve ; and, secondly, of a temperature which is
but a very little higher than that which they are there exposed
to. Thus the force which in other animals is expended in the
way of opposition to that of gravity, and in the way of producing
heat, is available for sustaining continuous growth.

The Class Pisces is divided into six orders — the Dipnoi, the Elas-
mobrancMi, the Ganoidei, the Teleostei, the Marsipobraiichii, and
the Pharyngohranchii. Of these the Dipnoi are to be considered
the highest, as presenting in their organization many points of
affinity to the Amphibia; the Elasmohranchii and the Ganoidei
have the oldest known geological history of any members of the
class ; they possess many characters in common with each other
and with the Dipnoi, such as the abdominal position of the posterior
pair of limbs ; the retention ordinarily of more or less of the axial
endoskeleton in a cartilaginous condition ; the possession of an
anterior functional uniserial gill, which is lost as such in osseous
Fishes; and the possession of a spiral intestinal valve. Though
coeval in geological time with the Ganoidei, the Elasmobmnchii are
a distinctly specialized, whilst the Ganoidei are a generalized type
of Vertebrata. The Teleostei, and amongst them the Physostomi
especially, are linked by many afiinities to the Ganoidei, The Mar-
sipohranchii may be looked upon as representing a very low grade of
development of the type upon which the Eksmohranchii are con-
structed ; the superaddition of specializations has however proceeded
so far as to leave few points of positive similarity beyond those which
an endoskeleton in great part or wholly cartilaginous ; a branchial

Characteristics of the Vertehrata.

Ixxxi

apparatus differing- iu its pouched arrangement and posterior po-
sition from those of Ganoidei and Teleostei ; the absence of maxillary
and intermaxillary cartilages ; and the presence of a raised ridge
along the intestine constitute. The sixth order, that of the Pha-
Tyngohranchii, are the lowest of Vertehrata; their claim to that
title resting indeed not upon the possession by them of a vertebral
column, but merely upon that of a chorda dorsalis, underlying a
membranous neural canal, and overlying a cavity containing the
organs of vegetative life. Its digestive tract appears to be formed
as in many Invertebrata by an invagination commencing on the
exterior of the germinal membrane, and it is to certain of the stages
of its metamorphosis that certain similarly transitory phases in the
life-history of certain sessile Ascidians have been stated to present
a strong resemblance unknown in other Invertebrata.

The Dipnoi are represented by the Mud-fishes, Lepidosiren and
Ehinocryptis, of the South American and West African rivers.
They possess, in addition to small external gills, seen elsewhere
amongst Fishes only in developing ElasmobrancUi, and to func-
tional internal gills covered by an operculum, a pulmonary auricle
into which blood is returned from two pulmonary sacs. These sacs
communicate with the digestive tract by a ventrally-placed opening
guarded by cartilage ; they receive blood in a venous, and return it
in an arterialized state. The Dipnoi differ further from the Ga-
noidei, the piscine order with which they are most nearly allied,
and resemble the Amphibia in the communication of their paired
nasal sacs with the mouth, in the possession of three external
branchiae, in the internal structm-e of their arterial bulb, and in the
microscopic characters of their chorda dorsalis. The totality of
their organism however shows them to belong to the Sub-kingdom
Pisces; the persistence of the structure last mentioned; the absence
of vertebral centra; the development of cycloid scales; and, more
distinctively, of the system of the lateral line ; the presence of
clavicular, of branchiostegal, of opercular bones, of dermal spines,
and of a spiral intestinal valve ; constituting a sum of characters
which justify us in referring them to that class. The order Dipnoi
differs from the orders ElasmobrancUi and Ganoidei, to which in
so many points it appears to be more or less closely allied in the non-
heterocercal character of the tail. In this particular it resembles
on the one hand the lowest of the Fishes; and on the other,

/

Ixxxii

Introduction.

the Urodelous and the larvae of the Anurous Amphibia; illus-
trating well what is meant by the phrase ' a generalized type/
The Dipnoi resemble the ElasmobrancUi and Ganoidei in having
the posterior pair of limbs placed near the anus, as in all Verte-
brata above the Teleosfcean Fishes in which a posterior pair of limbs
is developed.

The second order of Fishes, that of the Elasmohranchii, is repre-
sented by the Sharks, Rays, and Chimaerae. They differ from the
Dipnoi and Ganoidei in the following points besides those which
their name connotes. They never have an air-bladder, except occa-
sionally as a rudimentary structure; they have no cranial, nor
clavicular bones ; their exoskeleton has the form of ' placoid'
granules, not of scales; and in the males, accessory copulatory
organs are developed. They resemble the Ganoidei in the hetero-
cercal character of their tail; in the formation of their caudal
haemal arches by costal elements ; and in the possession of several
rows of valves within their arterial bulb ; of a coating of transversely
striped muscular fibre on the exterior of this structm-e ; and of an
optic chiasma.

The order Ganoidei is divisible into two sub-orders — the Chon-
drostei represented by the Sturgeons ; and the Holostei represented
by the Bony Pike, the Polypterus, and the Amia. They always
possess a freely moving operculum, supported by one, as in Stur-
geons, or by several bony plates, and an air-bladder pro^dded with
an air duct. With a few exceptions, {Polypierus, Amia, ScajjU-
rhyncJhUs,) they possess an opercular gill as well as a pseudobranchia ;
and a blowing cavity, the remains of the first visceral cleft, may
exist together with, or independently of one, or other, or both of
these structures. The angular or round enamelled scales, whence
their name is taken, are ordinarily but not always present, the skin
being sometimes naked and sometimes developing bony plates as
in the Sturgeons. The extent to which ossification proceeds in
their axial skeleton is, as the two subordinal names above given
indicate, very various. The Holostei and especially the genus
Amia, make a considerable approximation towards the Physo-
stomous division of the Teleostean Fishes, by the distinct speciali-
zation of maxillary and intermaxillary bones, and by failing to
develope either the enamel on the scales, the fulcra on the fins, or
the gill on the operculum, so characteristic of Ganoidei generally.

Characteristics of the Vertehrata. Ixxxiii

The Tehostei comprise an immense majority of existing- Fishes.
They may be subdivided into two great sub-orders : the Plhysostom%
which possess an air-bladder and an air-duct, and, with the ex-
ception of the Pike, bone corpuscles in their skeleton; and the
Physoklisti (Haeckel) in which the air-duct is always absent, the
air-bladder sometimes, and in which, with the exception of the
Tunny, bone-corpuscles are wanting. The vertebrae vary much in
number, and iu the extent to which calcificatory deposit takes place
in them; but they are always individualized, though the most
anteriorly placed of them may be suturally united with each other
and with the basi-occipital bone. The gill-fringes may vary in
number accordingly, as upon each of four branchial arches a biserial
or uniserial gill is developed ; but they never exceed the number
of four biserial gills, an opercular gill being never developed.
They have always more than a single bone in the opercular valve.
The cartilaginous cranium may either persist or disappear, but
cranial bones are always developed in addition to it. The scapular
arch has a clavicular element ; the anterior fins are rarely absent ;
the position of the posterior, which are much more commonly
absent than the anterior, varies from the 'abdominal' to the 'tho-
racic,' and from the ' thoracic' to the 'jugular' region. The aortic
bulb is not provided with more than two valves, nor has it a
covering of transversely striated muscular fibre. The optic nerves
decussate, but do not form a chiasma.

The fifth order of Fishes, the MarsipolrancUi, consists of the
two families of Myxinoidei and Petromyzontidae. Their sac-like
gills are supported on a cartilaginous framework, which is more
superficially placed than the analogous visceral skeleton of higher
Fish. They have a single nasal opening, and have been hence
called ' Monorrhina,' in contradistinction to all higher Vertebrata.
TTiey have no mandible, and higher Vertebrata have, in contra-
distinction to them, been on this account spoken of as ' Gnatho-
stoma.' They have no traces of air-bladder, of limbs, of limb-
gu-dles, of cranial bones, of scales, of spleen, or of pancreas. Their
tail retains the homocercal form characteristic of the early embryo
m other Fishes. They have no vertebral centra. The sympathetic
system is wanting, and the commencement of their aortic trunk has
neither striped nor smooth muscular fibres developed upon it. The
Myxinoids are less highly organized, being of parasitic habits, than

Ixxxiv

Introduction.

the Lampreys ; their single nasal sac eommunicates with the pha-
rynx, whence they are called 'Hyperotreti whilst in the Petromy-
zontidae, hence called ' Hyperoartii/ it ends blindly as in other
Fish. The embryos of Petromyzontidae go through a metamor-
phosis, being blind and edentulous when set free from the egg.
These larvae were formerly supposed to be a distinct species, and
were known under the name of Ammocoetes hrancJiialis. Like the
larvae of some other Fish and of some Amphibia, they may attain
sexual maturity whilst still in one of the stages preparatory to the
perfect adult condition. The evolution of the sexual organs appears
however to exhaust the powers of such larvae as attain to it, and
to be incompatible with the completion of the entire curriculum of
metamorphosis.

The sixth order of Fishes, the PliaryngobrancUi, are represented
by a single species, the Lancelet, Ampkioxus lanceolatus. These
animals are somewhat vermiform in outline, semi-transparent, of
small size, being only two inches in length even when adult,
without either cranium or brain strictly so called, or any differen-
tiation of the axial notochordal, or the primitive membranous neural
canal.

In this order we have pulsating vessels in the place of a saccular
heai-t, whence the name ' Leptocardia' has been given to it in con-
tradistinction to that of ^Pachycardia,' which expresses the condition
of the central organ of the circulating system of all other Verte-
brata. Another name, ' Acrania,' indicates the fact that in corre-
spondence with the absence of any other encephalic nervous centre
beyond a dilatation in which the myelon ends, and which may be
considered as homologous with the medulla oblongata, no cranial
cavity is developed upon the anterior prolongation of the notochord.
The mouth is surrounded by a cartilaginous ring, carrying ante-
riorly tentacular outgrowths, whence the name ' Cirrhostomi ' has
been given to this order. The digestive tract immediately pos-
teriorly to the mouth is constituted by a multiperforate branchial
skeleton, along the bars of which blood is propelled by contractile
branchial arteries, and through the fissures of which the inhaled
water finds an exit into a cavity homologous with a branchial
cavity, and opening by a single orifice on the medio-ventral line,
posteriorly to the middle point of the animal's length. The blood-
vessels, which pass from a sub-branchial vessel upwards along the

Characteristics of the Mollusca. Ixxxv

branchial bars, are collected into a dorsal aorta, which distributes
blood to the various organs of the body. A portal system is rudi-
mentarily represented by a vessel, which is formed by the veins of
the intestine, and sends ramifications to a coecal outgrowth of that
tube representing the liver. There is no lymphatic system, nor
have any renal organs been discovered in this small Fish. The
eye appears to be represented by an azygos pigment speck, sessile
upon the anterior prolongation of the nervous axis. No auditory
organ has been observed. The generative glands discharge their
products by simple dehiscence into the cavity surrounding the
branchial sac, whence they escape by the abdominal pore together
with the respired water. The ova undergo complete segmentation;
the ciliated embryo is set free before the primitive streak and
chorda dorsalis are differentiated, and goes through a peculiar
metamorphosis.

Sub-kingdom, MoUusca.

Invertebrata, in which the body is bilateraUy symmetrical, but
often not obviously so ; in which it never is segmented nor pro-
vided with articulated appendages ; and in which the length is
usually less in relation to the bulk than in either Vertebrata, Ar-
thropoda, or Vermes. The organs of animal life often attain but
an insignificant degree of evolution in this sub-kingdom; whilst
those of vegetative, which are ordinarily massed together in a
sacciform envelope, may attain a great predominance in point of
size, with which their precedence in order of development is to be
correlated. The tegumentary envelope of these latter organs is
almost always prolonged so as to form a mantle, which may itself
entirely surround the body, and which usually furnishes it with an
external shell, or shells, or test. A weU-developed digestive tract,
consistmg of oesophagus, stomach, and intestinal segments, and never
opening into the perivisceral cavity, though it is occasionally aproc-
tons, IS always present in Mollusca. It very rarely takes a direct
antero-postenor course, but has almost always its terminal segment
bent round so as to be approximated to the mouth, and when it is

Ixxxvi

Introduction.

proctuchous, tlie anal outlet is very usually in close relation to the
respiratory inlet. The hepatic organ is very various in shape, but
is usually, as in most water-breathing animals, largely developed. A
heart is usually but not always present; it is, when present, always
systemic, receiving blood, when afferent veins are present, from the
aerating and renal organs, or from the general lacunar system when
no such vessels exist, and propelling it by an aorta to the mam
organs of animal and vegetable life respectively. In many aquatic
MoUusca, the external water can find its way by variously situated
apertures, so as to become directly intermingled with the blood ; in
others, a multi-ramified water-vascular system appears to spread
itself throughout the body, without becoming directly continuous
with the blood-vessels. In some cases no specialized respiratory
organs are present ; in a few Mollusca aerial respiration is attained
to, in most it is aquatic. The renal organ may be represented by a
simple non-glandular sac, which communicates internally with the
lacunar blood-vascular system, and externally with tbe circum-
ambient medium. When its walls are clothed with glandular cells,
it receives an abundant supply of venous blood, some of whicb is
passed onwards to the aerating organs, and some sent directly to
the heart.

The nervous system may be reduced to a single ganglion, as m
Polyzoa and Tunicata, and in the former class organs of special
sense are wanting, except occasionally as rudiments.

Eeproduction may be either sexual or asexual ; and in the Po-
lyzoa polymorphic zooids are produced by gemmation. The ova
undergo entire segmentation, except in the Cephalopoda ; and with
the exception of that class, and a few Gasteropoda, of the pulmonale
order mostly, the embryos go thi'ough metamorphosis subsequently
to being set free from the egg.

The great majority of Mollusca are water-breathers, and marine
in habitat ; some however are fluviatile, or lacustrine and a few
are terrestrial and pulmonate. A few Mollusca are parasitic.
Enioconcha mirahilis inhabits the perivisceral cavity of a SjTiapta;
in the genus Eidima, which preys upon Holothurioidea, some species
are ento-, others ecto-parasitic. SiyUfer lives ecto- or pseudo-
parasitically attached to the soft tissues clothing the exterior of
Asteriae and Echinoidea and Holothurioidea, as also within their
digestive tract. Grenella infests Tunicata; and Vulsella, Gastro-

Characteristics of the Mollusca. Ixxxvii

cliaena, and Magilus infest certain Coelenterata ; but, like certain
Polyzoa^ such as Loxosoma and Pedicellina, which attach them-
selves to Vermes as to other marine objects, are not parasitic in a
strict sense.

The Sub-kingdom Mollusca contains two great divisions or pro-
vinces— ^the Mollusca proper, under which are comprehended as
classes the Cephalopoda, the Gasteropoda, the Pteropoda, and the
Lamellibranchiata ; and the Molluscoidea, under which are compre-
hended the Brachiopoda, the Tunicata, and the Poljzoa. The Mol-
lusca proper are distinguished firstly by the great development of
their organs of animal life. Their motor organs consist of a ' foot/
which may be of very various shapes, and is divisible morphologically,
and sometimes actually, into a ' propodium/ ' mesopodium/ and ' me-
tapodium;' and of an ' epipodium/ developed by the foot proper along
its line of junction with the visceral mass. The names of the three
classes. Cephalopoda, Gasteropoda, and Pteropoda, relate to the dif-
ferences observable in these motor organs. The nervous system in
all four Classes of Mollusca consists of three pairs of ganglia at least,
which are sensory, parieto-splanchnic, and motor respectively; and
which, being mutually connected by commissures, form a collar
round the commencement of the digestive tract. The organs of
vegetative life in the Mollusca contrast with those of the Mollus-
coidea in two chief points : firstly, their heart is all but invariably
provided with one or two auricles, in correlation with their more
perfectly developed and specialized respiratory apparatus, whence
they have been called ' Otocardia ; ' and secondly, their digestive
system is, also all but invariably, proctuchous. The three classes.
Cephalopoda, Gasteropoda, Pteropoda, are placed together in one
sub-division as 'odontophorous' Mollusca, in contradistinction to the
'bivalve' Lamellibranchiata, b;^virtue of their uniformly possessing
the peculiar dentigerous raspijj^ organ known as the tongue, and
of their never pQssessing a l/valved shell. With these differences
others are correlated, as will^ be detailed in the description of the
class Lamellibranchiata.

The Molluscoidea, as a sub-division, are distinguished from the
Mollusca proper by the followmg characteristics. They are not
only,^ like the Lamellibranchiata, destitute of any prehensile or
masticatory apparatus, and dependent therefore upon ciliary action
for the ingestion of alimentary matters, but they are, with the

Ixxxviii

Introduction.

exception of the Nectascidiae and a few Polyzoa, also devoid of organs
for motion from place to place^ at least in their adult state. The
entire sub-division is aquatic, and, with the exception of a part of
the Polyzoa, is marine. Most of its members are monoecious, and
many are social, which the Mollusca proper never are. They
always have a more or, less indm-ated external envelope, which in
two of the classes, the Tunicata and the Polyzoa, into which the
Molluscoidea are divided, is sacciform ; and in the third, the Bra-
chiopoda, takes the form of a bivalve shell. In this latter case the
nerve-system attains a higher development in certain species than
it ever does in either of the other two classes of Molluscoidea ; but
as no Molluscoid has a foot,^ pedal ganglia are never developed,
nor the three pairs of ganglia characteristic of the higher sub-
division of the sub-kingdom attained to.

Class, Cephalopoda.

Mollusca, in which the foot proper has its margins split up into
tentacles, or into acetabuliferous arms, which are arranged so as to
form a corona round the mouth. The epipodia, which in Pteropoda
are the principal, remain, in Cephalopoda, important locomotor
organs, forming as they do, by then- partial or perfect coalescence,
the 'fimnel,'' which is lodged in their capacious nem-ally-situated
mantle cavity, and which by the contraction of the muscular walls
of that cavity has water so projected into it as to effect the peculiar
backward swimming movement characteristic of the class. Move-
ment from place to place in the way of crawling is effected by the
multifid foot proper. By virtue of the high evolution of their
organs generally, and especially of those of animal life, such as the
eyes, the Cephalopoda are by common consent placed at the head
of the Molluscan Sub-kingdom; by the retention, however, of a
bilateral arrangement relatively to a median autero-posterior plane
in many organs, and especially in those of vegetable life, they show
indications of affinity to lower Mollusca, which are lost in the inter-
mediate classes of Gasteropoda and Pteropoda. Tlie Cephalopoda are
divided into two orders, according to the number of their gills ; the
Tetrahranchiata being the less, and the Dibranchhixi the more
highly organized of the two. All Cephalopoda possess an internal
cartilaginous framework which supports and protects their nerve-

»

Characteristics of Cephalopoda. Ixxxix

collar and their organs of special sense; the TetmlrancUaia, in
which the internal skeleton attains much less importance than it
does in the Dibranchiata, have an external shell; and the Bibran-
cUata ordinarily possess an internal calcareous shell, as in Sepia,
Belemiiitidae, and Spirula, or a rigid support of conchiolin, as in Lo-
liginidae. The Octo^mlidae, however, in which locomotion ordinarily
is of the crawling kind, are devoid, with the exception of Cirrhoteu-
tlds, of any internal shell distinct from their various internal car-
tHaginous supports. The external shell of the female Argonautidae
is secreted by the external surface of the expanded ends of their two
mesiaUy-placed dorsal arms; the body of the animal is not attached
to it by the insertion of any muscles, and it is not homologous
with the external sheU of the Nautilus, nor indeed with that of any
other MoUusc. The tegumentary system is distinguished, except in
the TetrabrancMata, by the absence of cHia, and by the presence of
chromatophores, and of certain more deeply-placed lameUar cells
upon which their well-known power of changing colour depends.
The organs of animal life being aU highly developed, those of
digestion, cii-culation, and respiration are so also in subservience
to them. The entrance to the digestive tract, besides being armed
with a rasping tongue, is frirther furnished with a powerful ex-
ternally-placed beak resembling that of a parrot, but having its
posterior segment the larger of the two.

Though the animals are exclusively carnivorous and marine, they
have always, with the exception of the TetrabrancJiiata, a very largely
developed salivary system. A crop, and also a spiral stomachal
coecum, are usually present ; as also glandular appendages, which,
as bemg distinct, at least to the naked eye, from the great mass of
the liver, have been regarded as pancreatic. The intestine proper
does not describe any complex convolutions in its course to the anus
which opens always in the middle line of the mantle cavity, and
contributes thus, with other arrangements, to give these animals
their very obvious appearance of bilateral symmetry.

The systemic heart consists of a single ventricle, the walls of
which, m the higher Cephalopoda at least, are composed of trans-
versely-striated muscular tissue. The branchial veins which return
the aerated blood to the heart have, in some species of those orders,
dilatations developed upon them representing auricles : and in addi-
tion to the systemic heart, we find in all the BibrancJdata accessory

xc

Introduction.

branchial hearts, developed upon the great afferent branchial veins.
In the BibrancMata the peripheral circulatory system appears to be
closed, consisting of arteries connected by capillaries, in many
organs at least, with the veins or great venous sinuses into which
the veins expand. In the TetrabrancUata the blood appears to be
more widely distributed throughout the various perivisceral cham-
bers than it is, according to Mr, Hancock, in the BibrancJdata ;
and as the external water finds in the former free access to the
various perivisceral cavities, it would appear that it may thus
come, as it does, according to some authorities, in the latter order
also, to mix directly with the blood. The gills are in the Dibran-
chiate order attached in their entire length to the interior of the
mantle cavity, upon the contraction of the muscular walls of which
they are, in the absence of any cilia upon their external surface,
dependent for fresh supplies of water and aeration. The giUs of the
Nmiiili differ from those of the BibmncUata not only in their
number, but also in being attached only at their bases. The renal
organs take the shape of bilaterally symmetrical spongy appendages
to the stems into which the vena cava divides, and which carry its
blood to the sunilarly bilateral gills. Certain orifices in the bran-
chial chamber exist, by means of which the secretion of these
organs can more or less directly find its way into the external
water.

The three typical pairs of excitomotor ganglia are readily recog-
nizable in the Cephalopoda as in aU other MoUusca proper, the
anterior position of the pedal ganglia and of their cerebro-pedal
commissure to the visceral or parieto-splanchnic ganglia, and their
cerebro-visceral commissure, being as readily demonstrable in these,
the highest, as in the Lamellibranchiata, the lowest of the Mollusca
proper. The accessory nerve-systems, however, which this latter
class does not possess, attain a high development in the paired
stomatogastric, parietal, and branchial ganglia, as also in the un-
paired stomachal and other visceral ganglia of Cephalopoda. An
olfactory organ appears to exist in Cephalopoda in addition to the
highly-developed eyes and the auditory organs.

The Cephalopoda are always dioecious. The reproductive glands
differ from most of their other organs in not being bilaterally
symmetrical, and they differ from those of all other Invertebrata,
except certain of the Vermes, in setting free their respective

Characteristics of Cephalopoda. xci

products into the cavity of a compartment of the perivisceral
space, whence they are taken up by the open mouth of the effe-
Tcnt generative duct, as the ova in most Vertebrata are taken up
by the Fallopian tubes. The oviducts are bilaterally symmetrical
in the sub-order Octopoda, and in the genus Ommastrephes ; but
both male and female efferent ducts are in all other Cephalopoda
unpaired like the glands with which they are in relation. The
male and female Cephalopoda are distinguishable from each other
by external differences, and most markedly by the modification of
one of the arms or tentacles of the males to serve as an intro-
mittent organ, the so-called ' Hectocotylus,' which in some species,
Argonauta argo, Octopus carena, Tremoctopus violaceus, and Tremoc-
topus Qiioi/anus, is set free from the male animal, and, probably,
reproduced after each act of sexual congress. The Cephalopoda
differ from other Invertebrata in the very large proportion of the
yolk which escapes segmentation ; and with the large size of the
nutritive yolk we may correlate the fact that the embryos do not
undergo any metamorphosis after leaving the egg.

The Tetrabranchiate differ from the Dibranchiate Cephalopoda in
the following particulars besides those which their name connotes.
They have an external shell, to which the body is attached by
strong muscles, but no ink-bag; their tentacles are much more
numerous, but are not armed with the suckers which gave the
mhmnchiata their name of ' Acetabulifera their internal cartila-
ginous skeleton is limited to the head, and does not there form a
perfect ring; the two halves of their 'funnel' are not anchylosed,
but project by two free edges into the mantle cavity, where they
form a tube by mutual apposition ; their blood- vascular system ap-
pears to be less sharply differentiated from their water- vascular or
perivisceral, and their eyes are pedunculate. The families Nantiliclae
and Ammonitidae make up the entire order Tetrahranchiata, and
are represented in the Silurian formations by numerous genera,
species, and individuals, whilst at the present time the order is
represented only by the rare Nautili, the living species of which
are variously stated to be two, four, or six. The more highly-
organized mhranchiata have attained their greatest development as
an order in the modern Period, but make their first appearance in
the Tnassic formation. They are divided into three sub-orders—
the Becapoda calciphora, to which the existing Spimlidae and

xcii

Introduction.

Sepiadae, and the extinct Belemnitidae are referred ; the Becapoda
cJiondrojohora, which do not possess a calcified shell, hut a horny
' pen' or ' gladius / and the Octopoda, which, with the exception of
Cirrhoteuthis, have no internal shell.

Class, Gasteropoda.

Mollusca, distinguished as a class from the Pteropoda and Cepha-
lopoda most obviously by the characters of their ' foot/ which is
ordinarily flat and sole-shaped, and adapted for crawling. Usually
the foot is not divisible into a propodium, mesopodium, and meta-
podium_, though the posterior part of the organ is nearly always
well developed^ and even when no division exists to denote its
typically trifid character^ the presence of an operculum frequently
enables us to differentiate its metapodial portion. In the Hetero-
poda however, and in the Stromhidae, the three divisions of the foot
are very clearly distinguishable; and the epipodium is occasionally
recognizable, as in Aplysia and Turbo. The foot proper may be
longitudinally divided for crawling, as in PJiasianella, or expanded
into lateral lobes for swimming, as in Gasteropteron and Bullidae ;
or it may be adapted for the purpose of swimming by being con-
verted anteriorly into a vertical fin, whOst it retains its ordinary
caudate shape posteriorly, as in the Reteropoda. Finally, the foot
may be merely rudimentary, as in Glaucus, lantJdna, and Termettis.

The Gasteropoda count among their number the only representa-
tives of the Sub-kingdom which have attained to aerial respiration,
and they form by far the most numerous of all IMolluscan, and, with
the exception of the Insecta, of all animal Classes.

Their digestive tract is almost invariably more or less convoluted,
and with the exception of the parasitic EntoconcJia mirabiUs, and
possibly a few Apneusta (see Baur, Nova iicta, 1864, p. 71), it is
always proctuchous. The mouth and anus are ordinarily near to
each other, but are never in the same median plane. In certain
Apneusta and NudibrancJiiata, the intestinal tract takes a straight
antero-posterior course, but is provided with lateral gastro-hepatic
diverticula, which give it much the appearance of the digestive
tract of one of the Dendrocoelous Planarian or Trematode Vermes.
The heart, which has been supposed to be absent in the Gasteropoda
just mentioned, does not seem to be so in any member of the class

Cliaracteristics of Ptero'poda.

xciii

except the MntoconcJia and Rhodope ; it is sometimes, as in Chiton,
Neritina, Haliotis, perforated by tlie rectum, as is the case in the
Lamellibvanchiata, to which some of these Gasteropoda furnish an
additional point of resemblance in possessing two auricles. In many,
though probably not in all Gasteropoda, the perivisceral cavity is in
dii-ect communication with the blood-vascular system. There may
be no specialized organ of respiration ; gills, however, are ordinarily
present, except in the Ptdmonata, where atmospheric air is inhaled
into a cavity formed by the mantle. The renal organ is single.

The Gasteropoda may be either dioecious or hermaphrodite. In
a few dioecious species which are, as Vermehis and Siliquaria, fixed
to one spot, there is no sexual congress, but the ova are fertilized
by the spermatozoa finding their way to them after being set free
into the water ; and in a few of the hermaphrodite species, such as
Tergipes JEclwardsi and Limnaea auricularis, heautandrous impreg-
nation has been observed to take place. Eut with these exceptions,
sexual congress always precedes impregnation, and indeed all re-
production, in Gasteropoda. The accessory reproductive apparatus
is greatly developed and complex in the hermaphrodite orders, Pul-
monata and NudibmncJdata, whilst in some of the dioecious orders,
CyclohrancUata and AspidohrancUata, even the intromittent organ
may be wanting, and microscopic examination may be necessary for
the distinguishing of the sexes. Gasteropoda are all but universally
oviparous, the yolk undergoing segmentation, and manifesting the
phaenomenon of rotation whilst within the egg. When the embryo
is set free from the egg, it ordinarily goes through a metamorphosis
which is marked by the possession of a provisional organ in the shape
of a bilobed ciliated locomotor velum. The embryos of the Pid-
mmata, in which order the ova may attain a very great size, may
possess from the first the form and organization of the adult animal,
but provisional organs have been observed in their development
{Limax) as in that of Branchiogasteropoda.

Class, Pteropoda.

Mollusca of small size varyhig from i'" to 3" in length, of pelagic
habitat, of nocturnal habits, with the head and eyes rudimentary,
and with the epipodia largely developed and constituting swimming
organs. The foot proper is ordinarily much reduced in size and

xciv

Introduction.

importance, but its various divisions, propodium, mesopodium, and
metapodium, may sometimes be all recognizable in the interspace
between the epipodial alae. The processes corresponding to the
propodium may be, like the arms of the Cephalopoda, armed with
suckers ; and these latter structures may be, as in Clione Borealis,
set in great numbers upon certain circumoral retractile upgrowths,
which may correspond both to the acetabuliferous arms, and to the
buccal membrane, (itself also sometimes, as in Loligo, acetabuliferous
in members) of that highest class of MoUusca. The Pteropoda may
fLirther resemble the Cephalopoda by having, as ia Cleodora, their
ordinarily large mantle cavity opening on the ventral or neural sur-
face. This cavity, however, may .open upon the dorsal surface, as ia
Gasteropoda, and it may be absent altogether, as in Clione. The
heai-t consists of a ventricle and auricle, and gives off an anterior
aorta which passes forwards through the nerve-collar to supply the
epipodial swimming organs. The small size of then- bodies enables
them to dispense in most cases with branchial organs, both ia the
femilies provided with a shell {Thecosomata), and in those destitute
of it {Gymnosomata). Their renal organ has the normal internal
communication with the pericardial blood-sinus, as well as an opemng
on to the exterior, but its walls may be either merely hyaline, or con-
tractile, without secretory tissue ; or thirdly, spongy and glandular,
as in the conchiferous families Eyalea and Cleodora. The eyes and,
usually, the sensory tentacles are more or less rudimentary. Auditory
vesicles are always present, and in relation with the pedal ganglia.

The Pteropoda are hermaphrodite. The embryos go through a
metamorphosis, berag provided, when set free fi-om the egg, with
a bilobed ciliated velum, which is replaced by the epipodia. The
Gymnosomatous Clionidae and Pneumodermidae go through a second
stage of metamorphosis, in which they have three zones of cilia.

Most of the points of degradation, or simplicity, observable in the
stractural arrangements of the Pteropoda, appear to be referrible
either to their nocturnal habits, which have entailed a stuntiag of
the cephalic organs, or to their minute size, which has rendered any
complex evolution of the circulatory and respiratoiy organs imneces-
sary. They have frequently been classed as an order of Gasteropoda,
but the general relations of their motor organs and their mantle
cavity appear to approximate them rather to the Cephalopoda, with-
out however justifying us in ranking them as an order of that class.

Characteristics of Lamellihranchiata. xcv

On the other hand, the Pteropoda are closely allied to the Denta-
Udae, the Solenoconchae of Lacaze Duthiers, or Prosopocephala of
Keferstein ; and this aberrant order, though possessed of a ' tongue,'
of cephalic tentacles, and of epipodial lobes, as well as a foot proper,
has nevertheless been separated from the Odontophora, on account
of the many points of affinity which subsist between it and the
Lamellihranchiata. The most important of these appear to be,
the bilateral character of the organ of Bojanus, and of the gene-
rative gland; the absence of any accessory reproductive organs,
either glandular or intromittent ; the absence of sexual congress
and the consequent extra-corporeal fertilization of the ova; and
the singleness of the larval velum. Each one of these points,
however, is reproduced either amongst the Cephalopoda or the
Gasteropoda, and the sum total of them therefore proves, not that
the Dentalidae ought to be dissociated from, but merely that the
Lamellibranchiata are rightly associated with the Odontophora,
as Mollusca proper, notwithstanding these points of degradation.
The organization of the Dentalidae is modified for their special habit
of living immersed, during the daylight at least, in the sand ; and
as many of the points of difference between them and the natatorial
Pteropoda may be explained by a reference to this peculiarity, whilst
such points of resemblance as the likeness of their larvae to those of
Pmmodermon and Glione are of purely morphological value, the two
sets of animals may, as suggested by Mr. Huxley, be placed together
in a class which would have very generalized affinities on the one
hand to the Cephalopoda, and on the other to the non-odontophorous
Mollusca s. Lamellibranchiata.

Class, Lamellibranehiata.

Mollusca, which, while agreeing with the other three classes of
the Sub-division of Mollusca proper in the properties distinguishing
it from the Sub-division of Molluscoidea, differ from them in having
a bivalve shell secreted by a medio-dorsally attached and bilaterally
symmetrical mantle, in the absence of odontophore, of salivary
glands, of stomato-gastric and sympathetic nerve-ganglia, in the
great size of the collars formed by the cerebro-pedal and cerebro-
visceral nerve-commissures, in the bilaterality of their reproductive
glands, and in the absence of any accessoiy reproductive organs.

Introduction.

In having their organs bilaterally symmetrical in relation to a
vei-tical antero-posterior plane^ the Lamellibranchiata diflFer from
the Gasteropoda and Pteropoda, but not from the Cephalopoda.
Their bivalve shells diflPer from those of the Braehiopoda in being
placed one on either side right and left of the antero-posterior axis
of the body ; in being scarcely ever equilateral ; in being very fre-
quently eqmvalve, except as regards the hinge ; and in having the
hinge opened by the action of an elastic ligament^ and closed by
that of one or two transversely-running adductor muscles. Their
foot is ordinarily compressed from side to side, so as to be hatchet-
or ploughshare-shaped. It may be rudimentary, and not rarely
secretes a ' byssus,' whereby the animal attaches itself to one spot.
It never developes an epipodium, nor presents the trifid division into
propodium, mesopodium, and metapodium. Movement is effected
ordinarily by means of the foot j but in some instances, as Pecten,
by the alternate opening and shutting of the valves. Two or more
pairs of retractor, and one pair of protractor muscles, may be present
to act upon the foot and visceral mass from bilateral points of
attachment to the valves of the shell. In the absence of any pre-
hensile or manducatory organs, the Lamellibranchiata are dependent
for the ingestion of food upon the currents set up by the ciha
covering not only all their external organs, except the outer surfaces
of their mantle, but also lining their alimentary canal. The mouth
is provided with labial tentacles^ which are homologous with the
arms of the Braehiopoda.

The digestive tract has its anterior segments closely and inse-
parably connected with the visceral mass made up by the hepatic,
and in some cases by the reproductive coeca, after disengaging itself
from which it, with some exceptions {Ostrea, Aiiomia, and Teredo),
passes through the ventricle of the heart, before passing over the
main adductor muscle of the two valves to end in a cloaeal
atrium. The ventricle of the heart is, with, the exception of
Area, single, whilst the auricles are, with the exception of
Anomia, bilaterally symmetrical relatively to a median vertical
plane, like the gills and the organs of Bojauus. Gills are uni-
versally present, and are in most cases two in number on each side.
They take ordinarily the shape of laterally-compressed multi-fene-
strated pouches, attached along the upper line of the mantle cavity,
much as the leaves of a book are attached to the interior of its

Characteristics of Lamellihi^anchiata. xcvii

covers ; but in some cases, as Pecten, Sponclylus^ Trigonia, owing' to
the absence of the antero-posterior elements of the lattice-work, the
gills may be reduced to rows of comb-like processes, as in a Pectini-
branchiate Gasteropod, or in an osseous Fish. Ordinarily, there are
two gills on each side; there may, however, be only one, as in
Lucina and Gorhis ; and in these cases it is always the external
pair which is absent. It is later to be developed, and very often
smaller, when present, than the inner gill ; and in some cases it
serves as a marsupial pouch, in which the ova are imj)regnated by
the spermatozoa brought to them by the inhaled water, and go
through certain stages of embryonic development (see p. 65, infra).
The renal organ is always bilaterally symmetrical ; it consists ordi-
narily of an excretory sac, which opens into the mantle cavity, and
of a secretory lamellar and glandular sac, which opens internally
into the pericardial blood-sinus ; but it may consist only of a single
sac on either side, which communicates with its fellow, but prob-
ably not with the pericardial cavity. The external orifice of the
organ of Bojanus may receive the duct of the generative gland of
its own side of the body, or that duct may open within the organ,
or independently of it, but at a short distance from its external
orifice.

The Lamellibranchiata never possess any stomato -gastric nor sym-
pathetic ganglia; but they may have accessory ganglia developed
for the innervation of certain of their organs of animal life when
these are largely developed, as in the cases of the siphons of some
of the siphonate families, and of the sensory organs developed along
the free edge of the mantle lobes.

The Lamellibranchiata are, with a few exceptions, such as 0*-
trea and Cyclas, dioecious. The generative glands are alwa3's
bilaterally symmetrical, and never possess any accessory glandular
or intromittent organs. There is no sexual congress in this class ;
the spermatozoa find their way to the ova either in the cir-
cumambient water, or in the cavity of the mantle ; or in that of
the outer gill; or in the cloacal space; or in the few viviparous
species, Kellia, Galeomma, Mofitacuta, within the ovary itself. The
embryos always go through a more or less complex metamorphosis,

a See Description of Preparations, pp. 54-66, infra ; and Description of Plate V.
PP- 193-198, ihique citata.

9

xcviii

Introduction.

in which they are provided with a unilobar ciliated velum. The
fresh-water species, as is often the case^ go through less complex
changes than the marine ; and in one instance, that of Cyclas Cor-
7iea, the foot, and not, as usual^ the mantle with its shell, has been
stated to have been the first organ which difierentiated itself in the
germinal membrane. The imilobar velum may be armed with a
flagellum, and in the marine species come to resemble the homo-
logous organ of the Dentalium.

The Lamellibranchiata are mostly marine. They may be either
fixed or free. They are never social in the sense of being organically
connected, but the peculiarities of their reproductive functions render
it necessary in their case_, as in those of many similarly conditioned
creatures, that they should be massed in considerable numbers upon
the same spot.

Class, Brachiopoda.

Molluscoidea with bivalve shells,, which admit of being opened,
though usually not widely, either by means of a hinge acted upon
by muscles, or by muscles alone, but which are not provided with
an elastic ligament as are those of the Lamellibranchiata, to which
the term ' bivalve' is sometimes exclusively applied. The shell of
the Brachiopoda differs from that of the Lamellibranchiata further
in being almost always equilateral, but not equivalve, and in
having its valves articulated across and not along the dorsal ridge.
They are in the adult state always fixed ; either, as ordinarily, by a
peduncle which is attached to the internal surface of a ' ventral '
shell, placed in the living animal superiorly to a shell called,
from its relation to the heart, ^dorsal,' or by the attachment of
the ventral shell, then placed inferiorly, to* some marine object.
Larval Brachiopoda have been observed to move from place to
place in two ways ; viz. either by means of the ciliated epithelium
covering their arms, which are then jirotruded as is the lophophore
of a Polyzoon, or by means of spines implanted in the ventral lobe
of the mantle. The Brachiopoda are ordinaril}'- said to be dioecious,
and in Thecidinm the sex can be predicated from an inspection of
the shell ; but observations exist to show that hermaphroditism also
exists in this class, as in some representatives of every molluscan
Class, except the Cephalopoda. They are never social, though, as is

Characteristics of Brachiopoda.

xcix

ordinarily the case with animals which are destitute of the power of
moving from place to place, and thus accomplishing sexual congress,
they are found frequently placed closely together. They are always
marine. They fall into two great Sub-classes, accordingly as they
possess, or as they are destitute of an anus. The proctuchous
Sub-class is represented hjLingulidae, Discinidae, and Craniadae; the
aproctous by Uhynchonellidae and TerehratuUdae. The proctuchous
Brachiopoda differ from the aproctous in having no hinge to their
shell, in having a vasiform instead of a globular heart ; in having a
convoluted intestine instead of one describing but a simple curve ;
in the much smaller evolution of their nervous system, the existence
of which has not, as yet, been fully demonstrated; and in the
limitation of their generative glands to their perivisceral chamber.
In the existing species of Brachiopoda provided with a hinge, a Q^^'H
calcareous process of greater or less length and of various shapes is • 'l-^""'
given off from it for the support of the arms. Some fossil arti-
culate Brachiopoda were destitute of these calcified supports, and
they are absent in all the hingeless Sub-class. The mouth opens as
a simple unarmed transverse slit between the two arms; and it is
by the action of the cilia covering their cirri that the ingestion of
food, as also the aeration of the blood, is effected. The mantle cavity,
a very large part of which is occupied in all Brachiopods, and
especially in the aproctous Sub-class, by the arms, is continuous
through the oviducts or ' pseudo-hearts,' with a multivamified sys-
tem of interviscerally-placed cavities and canals, which make up
the perivisceral system, and in TerehratuUdae are prolonged into
the arms. The ''pseudo-hearts,-' or oviducts, consist each of them of
two segments — the one which opens externally being tubular, and-
the one which brings the exterior communication with the peri-
visceral cavities being of wider calibre. They appear to correspond
witb-Jilie_orgaQs. of Boj^^^^ the Lamellibranchiata. They give
passage outwards to the products oTthe generative glands.

A nerve-system has been demonstrated in the hinged Brachiopoda,
and consists. of. five ganglia, connected so as to form a collar around
the commencement of the oesophagus. Three of these ganglia are
placed below the oesophagus, and the other two at the base of the
arms.

9 2

c

Introduction.

For a monograph upon the organization of the Brachiopoda, see

Hancock, Phil. Trans,^ 1 858 ; see also Lacaze Duthiers, Comptes

Rendus_, 1 86 5, ii., p. 800.
For a monograph of the species Thecidium Mediterraneum, see Lacaze

Duthiers, Ann. Sci. Nat.^ Ser. iv., tom. xv., i86t.
For the microscopic structure of the shelly see Carpenter, Palaeon-

tographical Society's Memoirs, ^853, pp. 23-40.
For an accoimt of a larval Brachiopod with figures, see Fritz Miiller,

Reichert und Du-Bois Eeymond's Archiv., i860, p. 72, Taf. i.,

figs. I and 2.

See also pi. xi, fig. %, and Description, pp. 233-234, infra.

Class, Tunicata.

Molluscoidea, which may be either solitary or social, either fixed
or free, but which are exclusively marine and are never aproctous.
The animals communicate with the exterior by two orifices, pierced
in a sacciform envelope, and here regarded as homologous with the
inhalant and exhalant siphons of the siphonate Lamellibranchiata.
As in those animals, the inhalant orifice brings into the organism
not only food and oxygen, but also spermatozoa, which find their
way to the ova by a route homologous to that described as taken
from the neural to the haemal surface of the gill, by the male
element in the Anodon (see pp. 64, 65, infra) ; and consequently
over and along a structure which is regarded as the homologue
not of a dilated pharynx, but of the gills of the bivalves. The
external envelope of the Tunicata, from the external form of which
the name ' Ascidiae' was given to the class by Savigny, is of very
various consistency, and of very various histological appearance ;
but it ah\iaja_s£C):stesjcellii^^ and is made in

the way of conversion, and not in that of excretion as is the case in
other members of the sub-kingdom. In Tunicata as in Lamelli-
branchiata, the anus and generative ducts open into a space lined
by the internal tunic, more or less separable from the muscular
mantle ; but in the cloacal space of the Tunicata there is no pos-
terior adductor nor any specialized organ of Bojanus, though there
is contained in it their single nerve ganglion, which supplies parts
homologous with those supplied by the parieto-splanchnic of the
Lamellibranchiata. The heart of the Tunicata is ordinarily elon-

Characteristics of Polyzoa.

ci

gated and vasiform, with one end directly connected with that side
of the branchial organ which is opposite to that nearest the rectum.
Its action is periodically reversed during life ; but this end of the
heart may be regarded as the homologue of the vessels which bring
blood to the heart, whilst the other end may be considered to
represent the systemic aorta of bivalves. The Tunicata are her-
maphrodite, but may multiply by gemmation as well as sexually.
With the exception of Salpa, they all go through a metamorphosis,
the larval form being caudate and active.

The larvae of certain sessile Ascidians, Phallusia mammillata, Phallusia
intestinalis, and Phallusia canina, have been recently described by Kowa-
lewsky and KupfFer a^^j^ossessing^ m_Jheir_jcau^^ appendage a structure
closely similar to the chorda dorsalis previously held to be a - distinctive
characteristic of Vertebrata ; as having their nerve-centres formed by the
fusion of lamellar upgrowths into tubes, in the manner which had
been similarly supposed to be peculiar to the higher Sub-kingdom,
thence spoken of as ' bicavitary ; ' and finally as having the caudal axis-
cylinder resembling the vertebrate chorda dorsalis either actually inter-
posed between one part of their nerve-centres, or, at least, so placed, that
if prolonged, it would come to be so interposed. ... It may be added
that Professor Gegenbaur, in the recently published second edition of his
'Grundziige der Vergleichenden Anatomic,' p. 158, 1870, has placed the
T^micata^in the Sub-kingdom_Yennes, assigning in justification of this
step the fact that the peculiar specialization of the anterior segment of
their digestive tract as a respiratory organ finds a parallel in the organ-
ization of a rare order (or Class) of worms, the Unteropneusti, represented
by two species, the Balcmoglossus clavigerus, and the Balanoglossus
minutus found on the Neapolitan coast. See Kowalewsky, Mem. Acad.
Imp. St. Petersburgh, Ser. vii., Tom, x. 3, 1866. Against this is to be
set the close correspondence in the way of homologies which may be \
shewn (see infra, pp. 66-69, 235, 2,36) to exist between at least the \
adult Tunicate and the Lamellibranchiate organism.

Class, Polyzoa.

Molluscoidea which are always social; and, with the excep-
tion of Cristatella and, perhaps, also Lophoptis and Selenariadae,
always fixed in their adult state, in a 'polyzoary^ or ' coenoe-
cium.' This structure, which is either erect or adnata, and, under

cu

Introduction.

either of these conditions, may be either dendritic or foliaceous,
is more or less flexible or rig-id, accordingly as the ectocyst of
each polypide is more or less hardened by calcareous or siliceous
deposit. The animals are never aproctous, but there is only a
single orifice in each cell for both mouth and anus, though, when
the polypide is protruded, a considerable interval intervenes be-
tween these two terminal apertures. The digestive tract is freely
suspended in a perivisceral cavity ; which, as these animals possess
neither heart nor generative ducts, serves as a receptacle for the
blood at all times, and for the products of the generative glands
at the periods at which they come to maturity. The mouth opens
always between the two lips of a lophophore ; both lips being also
always, with the exception of Pedicellina, beset with tentacles.
The lophophore itself may be circular, as in all marine species,
with the exception of the family just named, and of Rkabdopleura ;
or it may be prolonged into two arms, extending from the mouth
towards the neural or rectal aspect of the animal, as in all fresh-
water species, hence called ^ hippocrepia,n,'' except Paludicella
and Urnatella. In the freshwater species the tentacles are con-
nected at their bases by an infundibuliform membrane, known as
the ' calyx and the mouth is guarded by a valvular organ, the
* epistome,'' by virtue of their possession of which they have been
classified as ' Phylactolaematous,^ in contradistinction to the ' Gym-
nolaematous^ marine sub-orders. The lophophore, being attached
round the mouth, either by its entire circumference, as in the
marine Polyzoa, or by the base of its two arms, as in the hippo-
crepian representatives of the class, forms a roof to the perivisceral
space, with which cavity, the cavities of the lophophore, of the
entire series of tentacula which it carries, and of the epistome when
present, are freely continuous. The tentacles are not flexible in the
Polyzoa, with the exception of the Pedicellineae^ and probably some
allied forms. Both the external and the internal surfaces of the
lophophore and its tentacles are clothed with cilia, the action of
which subserves the functions of ingestion of food, and of aeration
of the blood. The interior of the perivisceral space is also similarly
clothed with cilia ; and the movements of the blood between the
mutually intercommunicating cavities of the lophophore with its
appendages and the general perivisceral system, are further carried
out by the contractions of the muscular fibres of the endocyst, and

Chai'acteristics of Polyzoa.

ciii

of the retractor and protractor muscles of the entire polypicle. The
nerve mass situated between rectum and oesophagus^ has been
figured and described as sending filaments to the lophophore, ten-
taclesj epistome, digestive tract, evaginable endocyst, and retractor
muscles, and as also throwing a collar round the oesophagus ; and
it may consequently be considered as representing both the parieto-
splanchnic and the cerebroid ganglia of higher Molluscs. Repro-
duction in the Polyzoa is both sexual and asexual. The asexual
takes place in the way of gemmation ; and in the case of the
Fresh- water Polyzoa by means of ' statoblasts^ or gemmae, in which
the developmental activity remains latent for a period. The Polyzoa
are hermaphrodite ; the testes being situated near the bottom, the
ovary beiag attached to the parietes of the upper part of the cell.
It is by gemmation that the polymorphic organisms known in
Polyzoa as ' ovicells,^ ' avicularia/ and ■' vibracula^ are produced ;
and in Serialaria, where the entire colony may have its individual
polypide brought into connection by a common nerve-system, we
find some cells modified for the discharge of purely passive functions,
as ' stem-'' cells and 'root-^ cells.

The Polyzoa have, like the Tunicata, been removed from the Sub-
kingdom MoUusca by Gegenbaur and Haeckel, and classed with the
Yermes. The_iuos.culant form Loxosoma described by Kowalewsky
(Mem. Acad. Imp. St. Petersburgh, Ser. vii., Tom. x. 2) has been sup-
posed to connect them with this latter Sub-kingdom. Against this view
we must set not merely the many structural homologies which can be
pointed out as existing between adult individuals of the undoubtedly
MoUuscoid Classes Brachiopoda and the Polyzoa ; (for which see p. 72,
infra, ibique citato), but also the striking similarity which the larval
form of a Brachiopod has been obsei'ved by Fritz Miiller to present to
the Polyzoa with orbicular lophophores such as all the marine sub-
orders with the exception of Pedicellinea. See Reichert und Du-Bois
Reymond's Archiv. fiir Anatomic und Physiologie, p. 79, i860.

For an account of the nervous system in Serialaria, see Fritz Miiller,
Archiv. fiir Naturgeschichte }S6o, p. 311, Taf. xiii.

civ

Introduction.

Sub-kingdom, Arthropoda.

Ajstimals consisting of a series of more or less heteronomous
segments, the ' Metameren ' or ' Folgestiicke ' of Haeekel, to which
jointed appendages are articulated ventrally in pairs, and, ordi-
narily, in very different proportions and grades of development in
the different regions of the body. These appendages are, in con-
tradistinction to those of Vermes, hollow, and have muscles pro-
longed into their interior. This external integument is rendered
more or less rigid by chitinous deposit, which may be made still
more resistent by calcification. Chitinization extends itself from
the exterior into the interior, and in many cases an endophragmal
skeleton is thus formed, which arches over the ventrally-placed
portion of the nervous system. Tubular prolongations of the cuti-
cular chitine extend inwards along the various duets and canals
opening on to the exterior, and are shed together with the inte-
gument in the moultings which these animals, so long as they
continue to grow, must necessarily go through.

The chitinous deposit at the commencement of the digestive canal
may take the shape of ' lips,' or even of non-segmented processes,
like the 'jaws" of certain Vermes, but the true functional jaws of
Arthropoda are always produced by the modification of the hollow
segmented appendages of more or fewer of the anterior segments
of the body. The organs of special sense are orduiarily confined to
the prae-oral segments, and, like the rest of the appendicular skeleton
with which they are, either actually or morphologically, connected,
contribute at least as much to the heteronomy of the external
appearance as the segments upon which they are carried.

The antennae, eyes, and auditory organs are all but invariably
limited to the prae-oral cephalic segments, and the muscles of the
chitinous elements of the segments are never found to form con-
tinuous antero-posterior layers, as in Vermes, corresponding wnth
the length and often with the circumference of the body. On the
other hand, the chief intemally-placed system of animal life, the
gangliated nerve-cord, presents a striking resemblance to the homo-
logous system in Vermes ; and the respirator}'- system of certain
Myriopoda appears to attain in its stigmata an approximation to

Characteristics of the A7'thropoda. cv

correspondence with the number of the seg-ments of the body, which
resembles that manifested by the multiple respiratory organs of
many Annulata. But the circulatory, depuratory, and reproductive
organs are never found to be thus multiplied, such segmentation
as they may exhibit being ordinarily limited to one, and that the
abdominal region of the body. The digestive tract takes ordinarily
a very direct antero-posterior course, rarely presenting any lateral
diverticula except in Arachnida, or any convolutions, except in
adult Insecta, and some Cladocera. This latter Crustacean family
has the anus placed dorsally, and some way anteriorly to the termi-
nation of the body segments, and furnishes an exception to the
general rule, that the intestine in Arthropoda ends in the last
segment of the body. Except in the larvae of Hymenoptera and
of Myrmeleon, the intestine is always proctuchous. But in the
suctorial Cirripedia, and ia the ' complementary males ' of the other
families of that order, as also in a suctorial Entomostracan, Mon-
strilla Banae, the digestive tract is wanting altogether, and the
mouth when, as in the last case, present, leads directly into the
general cavity of the body. A heart is very usually present,
underlying the dorsal elements of the abdominal segments, and
ending in an aorta in the thoracic region. It is usually vasiform
and segmented, lateral apertures at the anterior end of each seg-
ment serving as venous inlets for the blood filling the pericardial
sinus in which the heart is suspended by means of the elastic alae
cordis. The circulation is always more or less extensively lacunar ;
even arteries may be wanting.

Accordingly, as the respiration is aquatic or aerial, the Arthro-
poda are divisible into two great groups, one of which is con-'^
stituted by the Crustacea, iu which respiration is branchial, or in
the absence of branchiae, carried on in water by the general sur-
face of the body ; and the other by the other three classes, Ara-
chnida, Myriopoda, and Insecta, in which respiration is eflPected by
the admission of air into the interior of the body by tracheae,
or some modification of those organs. "The air-breathing Arthro-
poda agree with each other, and differ from the Crustacea in the
following points: — they ngyeEjiaye_tvro_^ii:s^^^ a^^ and,
with the exception of certain Ephemeridae, Strepsipiera, and Diptera
amongst Insecta, and certain Epeirae amongst Arachnida, their
eyes are never pedunculate ; their mandibles are not palpate ; one

cvi

Introduction.

or both pairs of maxillae are more or less completely fused mesially
so as to form a functional lower lip; and, \vith the exception of
the lower Myriopoda, their post-abdominal segments, when present,
rarely or never carry appendages with locomotor functions in the
adult state. The portion of the supra-oesophageal ganglionic mass
which corresponds with the eyes, is much larger relatively to that
which corresponds with the antennary organs than it is in Crus-
tacea; and in exact opposition to what we observe in this latter
class, we find the salivary and renal organs largely developed, and
the hepatic only represented rudimentarily. The digestive tract is
never aborted in air-breathing Arthropoda, nor aproctous in adult
individuals. Except in certain lower Crustacea and Arachnida,
where the supra-oesophageal nerve-mass is represented simply by
a fibrous conmaissure, the nerve-system consists of supra-oesophageal
and of ventrally-placed ganglia, connected with each other so as
to form a collar round the oesophagus, and connected with a
sympathetic system ordinarily consisting of a ' stomatogastric '
division and of ' nervi trans versi.'

All Arthropoda, with the exception of the Cirripedia and Tardi-
grada, are dioecious, and, with the exception of the Tetradecapodous
or Hedriophthalmatous Crustacea, and comuted Insecta, the males
are ordinarily smaller in size than the females. Reproduction is
ordinarily sexual, but both parthenogenesis and asexual genesis by
means of pseudovaria, if not also by internal metagenesis without
the intermediation of such structures, are known to occur in this
Sub-kingdom. The Arthropoda are ordinarily oviparous, but are
sometimes viviparous, and even pupiparous. Except in the cases
of certain of the lower Crustacea and Arachnida, the segmentation
of the yolk is always partial, and the first appearance of the embryo
takes the shape of a 'primitive streak.' Though the embryos of
Arthropoda very ordinarily go through more or less numerous stages
of metamorphosis, neither larvae nor adults ever possess cilia. In
the more usually observable forms of metamorphosis, the embryo
leaves the egg not only with its reproductive system, but also with
its motor and sensory organs in a less perfect condition than those
of the adult ; in the less ordinary, or retrogressive metamoqihosis,
observable in parasitic families, the animal organs of the larva are
more perfect than those of the adult. In both cases, change of
tegument accompanies metamorphosis.

CharacteHstics of the Arthropoda.

cvii

The most essential difference between the various Classes of the Sub-
kingdom Arthropoda, is that which tracheal and branchial breathing re-
spectively correspond to, and with this principle of classification in view,
we place the Crustacea, the earliest representatives of the Arthropodal
type in geological times, apart from the other three Classes.

Within the limits of any one of these four Classes, the greater or lesser
heteronomy of the several regions of the body, the greater or lesser
extent, that is, to which the specialization of segments, and, even more,
of appendages, has been carried out, constitutes the most important dif-
ference between one order and another, next to that which the actual
abortion of segments or appendages entails.

The two Classes, Crustacea and Arachnida, differ from the Myriopoda
and Insecta in comprehending much more varied forms ; the MjTiopoda
contrast with the other three Classes by their low degree, whilst the
Insecta are distinguished by their high degree of heteronomy.

The Crustacea and Arachnida are very closely approximated by such
forms as the Gyami(iae and the Pycnpgonidae. This latter family is re-
ferred to the Class Arachnida mainly on account of the lateral diverticula
which the digestive tract is furnished with, but there is reason to believe
that some of its species possess free and functional antennae, and it should
be considered therefore as Crustacean. If the parasitic Redriophthalmata,
such as the Cyamidae, connect the Crustacea with the Arachnida on
the one side, they connect them also with the Insecta through Pediculus
on the other. A more striking, though perhaps not more real, link be-
tween the Crustacea and the Insecta and Myriopoda, is presented' by the
air-breathing Isopoda, such as Oniscus, on the one side, and the apterous
Orthoptera and Glomeris on the other. The Arachnida approximate to
the Insecta very obviously by such forms as Galeodes ; and though their
marked heteronomy and the definite number of their body segments
cause them to differ very widely in external appearance from the Myrio-
poda, the peculiarities of their reproductive and respiratory systems
appear to speak to the existence of a real affinity between them and the
Chilognathous division of that class.

The Arthropoda have frequently been classed together with more or
fewer of the Vermes in one Sub-kingdom, that of the 'Annulosa;' and
whilst by such highly-organized forms as the Marine Polychaeta an
approximation appears to be made to certain of the less specialized of the
Crustacea ; or even of the Myriopoda, or the larvae of Insects, amongst
the air-breathing Arthropoda : the microscopic Kotifera connect the Vermes,
to which Sub-kingdom they are to be referred, very closely to the Crus-
tacea. The possession at one period, or, as usual throughout life, of

cviii

Introduction.

hollow ai'ticulated and segmented motor organs, into the interior of which
transversely striated muscles are prolonged, and the absence at all periods
of cilia, are points which distinguish all Ai'thropoda from all Vermes ;
and a third point of nearly equal generality is furnished by the early
appearance of a ' primitive streak ' and the partial segmentation of the
yolk in development. I'ourthly, whilst in Vermes it is only rarely
possible to differentiate the postcephalic segments into several regions,
this is always possible in Arthropoda ; the history of the development
and that of the relation of the internal organs to the external skeleton
rendering this possible even in the externally nearly perfectly homo-
nomous Myriopoda, and in the most degraded representatives of the
Crustacean Class as well as in such homonomous forms as certain of the
Isopoda, Fifthly, true metagenesis is unknown in Arthropoda. The
various organs and systems of the Crustacean, as being a water-breathing
Class, appear to attain a lower degree of evolution than those of the other
Arthropoda, and the Vermes may be supposed to approximate to them
more closely than to any of the air-breathing classes ; but the points just
specified will ahvays serve to differentiate the members of the two Sub-
kingdoms, howsoever closely they may at first sight resemble each other.
Still it must be said, that the two Sub-kingdoms have their boundaries
approximated at many points, if not along great lengths, in space ; and
for a concrete illustration of this principle, the student is referred to the
description of Echioioderes Dujardinii, an animal which, though classed
as a Crustacean, combines with many of the characters of Arthropoda
many also of those of such Vermes as the NematelmintJies and the Oli-
gocliaeta, and has been pointed out by Claparede, (Anatomie und Entwick-
elungsgeschichte Wirbelloser Thiere, i86, p. 92,) as constituting a link
between these two Sub-kingdoms.

Class, Insectsu

Air-breathing Arthropoda with well-marked lieteronomous divi-
sion of the adult body into three distinct regions, the head, thorax,
and abdomen. The middle region, or thorax, is composed of tliree
segments, the prothorax, mesothorax, and metathorax, each of which
has a pair of jointed appendages, the legs, articulated to it ventrally,
whilst each of the two posteriorly-placed segments has also, ordi-
narily, a pair of unsegmented appendages, the wings, or the wing-
covers, articulated to it dorsally.

A post-abdomen is never very obviously marked off from the

Characteristics of hisecta.

cix

abdomen, but there are not wanting more or less obscure indications
of the presence of three segments between the generative outlet and
the terminally-placed anus, which may be considered as representing
the post-abdomen. The abdomen proper never carries any articu-
lated appendages in adult insects, with the single exception of the
Coleopterous Sjoirachtha Bntymedusa, in which the third, fourth, and
fifth abdominal segments each carry a pair of biarticulated appen-
dages. The post-abdominal segments however may carry segmented
appendages both in the adult and in the larval condition, but
these organs, though they may attain a considerable development,
especially in Ortlioptera {Chloeon dimidiatum), do not appear to
possess locomotor fonctions in adult insects. The motor organs are
mainly localized in the thoracic, the vegetative in the post-thoracic
regions. None of the thoracic segments are ever, except in certain
Coccina, fused with the cephalic, nor are any thoracic appendages
ever modified so as to serve as manducatory organs. The greater
relative size of the eyes gives as distinctive a character to the head
in this Class of Arthropoda as its freedom from fusion with the
thorax. The mandible has never even a rudiment of a palp ; and
the second pair of maxillae are always more or less completely
soldered together so as to form a functional lower lip, the ' labium'
of entomologists. The digestive canal is never aproetous except in
the larvae of most Hpnenoptera, of the parasitic Diptera, and of
Myrmeleo. In these larvae the renal organs open into what is
subsequently by moulting brought into communication with the
blind end of the digestive tube, and so converted into a ' rectum;'
the entire apparatus previously to this change bearing a striking
resemblance to the so-called 'water-vascular' or excretory system
of certain Vermes. The digestive tract presents more numerous
and more distinctly distinguishable divisions than in other Arthro-
poda ; and it is often, at least in adult insects, arranged in convolu-
tions, and is thus longer relatively to the body than in other mem-
bers of the Sub-kingdom. The salivary glands may be large and
racemose as in OrtJioptera, or very small and tubular as in the adult
Lepidoptera. The liver appears to be represented by certain coeca
which are set round the commencement of the digestive tract in
varying numbers in the Ortlioptera and Hemiptera, the great
development of the respiratory tracheal system appearing to com-
pensate for this rudimentary or aborted condition of the hepatic

cx

Introduction.

org^n, as in the reverse way the great development of the h'ver in
Araehnida may be supposed to compensate for their less developed
aerating organs. The other set of depuratory organs, those, namely,
which are charged with the direct elimination of effete nitrogenous
substances, are always, with the exception of Aphis, Coccus, and
Ghermes, present in insects as the ' Malpighian vessels.' The tra-
cheae of insects inosculate or anastomose in various parts of their
course, but the capillary tracheae in which the spiral thickening of
the inner lining membrane may fail to be developed, end blindly in
the tissues to which they are distributed. The aquatic larva of one
insect, Chloeon dimicliatum, has no tracheae developed in the first
three stages of its larval life, but subsequently, like the larvae of
many other Orthoptera, Neuroptera, and Diptera, has tracheae
developed which are exposed to the action of the oxygen dissolved
in outgrowths known as ' tracheal gills.' These organs do not ordi-
narily possess any ' spiracle ' whereby to come directly into commu-
nication with the air of the atmosphere, and must therefore obtain
the oxygen they contain as gas from that which is dissolved in
the water they live in. They may be said therefore to present us
with an instance of an arrangement transitional in character
between aquatic and aerial respiration. In a single insect, Ptero-
narcys regalis, one of the Orthoptera Amphibiotica, which is of
lucifiigous habits, and inhabits damp localities, tracheal branchiae
are retained during adult life, but in other cases, when the insect
leaves the water, the external lappets into which the internal
tracheae send ramifications fall ofi", and the ordinary laterally-
placed spiracles are formed at the points of their separation.

The heart is a vasiform organ, consisting ordinarily of eight
segments, with as many pairs of venous inlets. It imderlies the
dorsal elements of the abdominal segments, is ordinarily closed
posteriorly, but ends anteriorly at the thorax in an aorta which
may be prolonged forwards as far as the cephalic ganglia.

In Insects there is never wanting a ventrally-placed ganglionic
mass in addition to the first sub-oesophageal centre, which by its
commissural junction to the cerebroid mass forms the nerve collar.
The first sub-oesophageal ganglia supplies the jaws, and thoiigh not
so closely apposed to the supra-oesophageal centres as is the case in
Araehnida, it is yet so close as often, but inconveniently, to have
been spoken of as part of the ' brain.' Tlie ganglionic centres

Characteristics of Insecta.

cxi

placed posteriorly to it may be represented by a single continuous
mass giving- off nerves laterally and posteriorly; or tbey may take
the shape of a chain of ganglia, which are never more than eleven,
three being thoracic and eight abdominal, though by fusion or
abortion they ordinarily fall below this number. The sympathetic
system, both in its stomato-gastric division, and in that part of
it which is in connection with the ventral ganglia and supplies the
tracheae, attains in insects a large development. The eyes are
always confined to the head; in a few instances, of which the
Chloeon dimidiatum, one of the Orthoptera Amphihiotica, already
mentioned, is one, as also in certain Dipterous, Strepsipterous, and
Hemipterous genera, the eyes are elevated upon peduncles or pillars,
which however are never movably articulated to the head. In
most orders of insects, but most frequently amongst Hymenoptera,
Diptera, and Orthoptera, the so-called ' simple eyes,' s. ' stemmata,'
s. ' ocelli,' coexist with the larger multifacetted eyes.

The males and females are ordinarily very different in insects ;
the males, except in the cornuted species, being slighter in make,
swifter, furnished with larger eyes and antennae, and more brightly
colom-ed. The difference may be so great, especially when the
females are apterous and the males winged, as to amoimt to a kind
of Dimorphism.

The generative organs of Insects are very varied in the details of
their arrangement. The reproductive glands are always double
and symmetrical, but the efferent ducts always fuse into a common
duct before opening. This they do posteriorly to the eighth abdo-
minal segment ; which is homologous with the third caudal segments
of Scorpionidae and Crustacea, and therefore posterior by eight seg-
ments to the genital segment of the Arachnida just named, and to
that of Limulus ; and by three to the hinder of the two genital
segments of the Decapodous Crustacea. The female generative
organs of insects have often a large number of accessory appendages ;
the most constant of these is the ' receptaculum seminis ;' but there
may be present also an ' accessory gland ^ appended to the ' recepta-
culum seminis;' secondly, a 'bursa copulatrix;' and thirdly, a num-
ber of ' colleterial' glands which secrete a glutinous material for
fixing the ova to various external objects. The male accessory organs
are of two kinds, one of which is considered as analogous to the pro-
static organ, and the other to the vesiculae seminales of Mammals.

cxii

Introduction.

The segments of the body posterior to the eighth abdominal may
be modified so as to serve in either sex as ' ovipositors' or as iatro-
mittent organs. There are no hermaphrodite insects, and sexual
reproduction is the rule in the class.

Several forms of agamogenesis have been observed amongst
Insects. In one of these^ females with a reproductive apparatus
provided with a receptaculum seminis produce (without any congress
with males), either embryos, as Lecanktm Jiesperidum, Chermes abietis,
amongst the Coccina ; or ova, as, amongst Lepidoptera, Psyche helix,
Solenobia lichenella, and Solenohia triquetrella-, and as, amongst
Hi/menoptera, Cpiips, apterous Queen bees, and normal winged
Queen bees before they leave the hive. In this class of cases sexual
may alternate with asexual genesis, and it is to be noted that the
male offspring of the Queen bees are only and exclusively due to
the agamogenetic process. In a second class of cases^ females with
a more or less imperfect reproductive apparatus produce either ova,
as is the case with the ' workers' amongst the social Hymenoptera,
Apis melUfica, Vespa^ Bomhus, in which the vagina as well as the
receptaculum seminis is rudimentary, and which, with, possibly, the
exception of the Vespidae, always produce males ; or embryos, as
is the case with Aphis, in which certain generations without sper-
mathecae or coUeterial glands are viviparous agamogeneticaUy,
whilst others with a perfect sexual apparatus are oviparous gamo-
genetically. This form of asexual genesis is called ' pseudopartheno-
genesis,' and the reproductive gland a ' pseudovarium.' Asexual
genesis was supposed to take place metagenetically, that is to say,
by a process of internal gemmation in a non-differentiated part of
the body, in the larvae of certain Diptera of the family of Ceci-
domyidae; but the discovery, by Leuckart, of specialized germ-
producing organs in these animals appears to show that the only
differences between this process and that observable in A^jhis consist
in its taking place in forms of a holometabolous order, which, as
being larvae, are very different in external appearance from the
perfect sexual insect, and in the ' pseudovaria ' being destitute of
any ' pseudoviduct.'

In the development of the ovum the yolk is surrounded by a
germinal membrane, in which the first traces of the head and the
ventral half of the embryo make their appearance as the so-called
i primitive streak.' Insects are ordinarily oviparous, but they may

Characteristics of Insecta.

cxiii

he viviparous, and the larva in one sub-order (the so-called Pupi-
parae), is so far developed, by means of the nutriment furnished
to it by a g'land opening* within the maternal oviducal canal, as
to be nearly ready to enter upon the stage of chrysalis or pupa
when set free from the mother's body. The form which an insect
has on leaving the egg always differs more or less from that which
it possesses when adult, and capable, as only full-grown insects ^-rej^
of reproducing its kind by sexual genesis. The larvae of apterous
insects, such as certain of the Orthoptera and Hemiptera, differ
fi-om the adult, irrespectively of the undeveloped state of the gene-
rative organs, only in such points as size, the number of joints in
the antennae, and the number of facets in the corneae. It is only
in the quantitative increase accruing to these two sets of organs
of special sense that the adult after the entire number of its moults
comes to differ from the larva in the way of heteronomy. A
greater degree of heteronomy is attained to in the families of the
two orders specified which are endowed with wings, by the super-
addition of those organs, and by the concomitant greater differentia-
tion, of the thoracic from the abdominal region of the body. Insects
which go through either of these two series of metamorphosis are
called 'iimetabolous.' A third kind of metamorphosis is that in
which the adult insect, whilst gaining certain organs which the
larva does not possess, such as wings, loses certain others, which
the larva does possess, such as the provisional structures making up
the ' mask' of the LihelluUdae. Such insects are called ' Hemimeta-
bolous,' and in them the tLeteronomy of the various regions of the
body is always well pronounced. Insects, finally, which when adult do
not only differ very markedly from their larval forms both by general
heteronomy and by the conformation of their particular organs, but
also attain to this condition after going through a period of quies-
cence known as the ' pupa' or ' chrysalis' stage, preparatory to their
final moult and the assumption of the adult condition, are called
' Holometabolous.' A period of quiescence as ' pupae,' in addition to
the period of quiescence as ova, gives the Holometabolous orders of
Insects an advantage as regards their distribution over the colder
regions of the earth, relatively to the orders the pupae of which are
active ; and, therefore though certain small Poduridae resist cold
well, it is amongst the Holometabola that we find a nearer approach
made to cosmopolitanism than is usual elsewhere amongst Insects.

h

cxiv

Introduction.

Class, Myriopoda.

Air-breathing Arthropoda in whicli the segments and their ap-
pendages make a nearer approach to homonomy than in either
^hsecta or Arachnida, and in which the post-cephalic locomotor
appendages, even when least numerous, and amounting to nine
gairsonly as in Pmoropus, are still more numerous than the similar
organsln either of the two other classes mentioned, except in the
larvae of certain Kymeno'ptem, Gimhex and Tenthredo, which possess
eight and seven pairs, respectively, of prolegs, besides the three pau-s
of true legs. In the homonomy and number of their segments
and appendages, the Myriopoda resemble certaiu of the Crustacea,
with which Class they have often been ranked, as also in having the
first, or the first two pairs of post-cephaHc appendages, subordinated
more or less completely to the manducatory organs, so as in one
order, CJdhpoda, to form 'foot-jaws/ and in another, CJdlognatJia,
to form 'labia^ by the partial fusion and other modifications of
their coxae, whilst m Pmiropus the anterior pair of legs is rudi-
mentary. There is however no fusion of segments in the [Myrio-
poda of the kind which produces a cephalo-thorax in Crustacea,,
It may be added here that an additional point of similarity to the
Crustacea is manifested by the Myriopoda in their mode of growth ;
as their larvae instead of leaving the egg, as insect larvae do, ^^^th
at least as many segments and legs as they ever afterwards possess,
leave the egg with a much smaller number of segments and legs
than by the periodical addition of segments at successive moultings,
they attain in the adult state. The Myriopoda however must be
classed with the air-breathing Arthropoda, not only on account of
their respiration being tracheal, except in the case of the diminutive
Pauropus, but also on account of the singleness of their antennae;
the sessile position of their eyes; their non-palpigerous mandibles;
the fusion of their maxillae into a labium ; the large development
of their salivary and renal, and the rudimentary condition of their
hepatic glands.

The Myriopoda appear to stand midway between the two other
classes of air-breathing Arthropoda, as to the mutually correlated
and mutual supplementing complexity and simplicity of the circu-
latory and respiratory apparatus. Their digestive and nervous
systems are closely similar to those of the larvae of Insects.

Characteristics of Myriopoda.

cxv

The Class Myriopoda is orclinainly divided into two orders — the Chilo-
poda and the Chilognatha or Diplojooda, from which the /Svphonizantia
and the genus Paitropus ought, it is probable, to be separated.

The Chilopoda are the most highly organized of the Myriopoda. They
are distinguishable externally by the flatness of their bodies ; the large
size of their antennae, which always possess fourteen joints at least ; by
the modification of the two anterior pairs of post-cephalic appendages
into foot-jaws, the hinder pair of which is armed with a sickle-shaped
unguis and poison-gland ; and by their locomotor legs being attached in
single pairs. With these external characters, the following points of
internal structure are correlated ; the stigmata for the admission of air
to the tracheae do not correspond with the number of segments, and are
situated on the sides of the body between the bases of the feet and the
dorsal shields ; the generative ducts open at the posterior extremity of
the body ; and there is no intromittent organ. It is amongst the Chilo-
poda only (in Scutigera) that we meet with compound facetted eyes. In
another Chilopodous family {Scolopendridae) we find the generative ducts
single, and the tracheae anastomosing as in Insects. The larval Chilo-
poda may have as many as six or eight pairs of locomotor appendages
when they leave the egg ; and the addition of fresh segments takes place
in the way of intercalation at each moult, in the intervals between each
pair of older segments.

In the Chilognatlia the body is sub-cylindriform, the antennae are
inconspicuous and do not possess more than seven joints ; the two
anterior pairs of post-cephalic appendages, or at least the first of
them, may be spoken of as ' foot-jaws,' or as forming ' labia,' inas-
much as they are directed forwards like the operculiform ' foot-jaws'
of Crustacea, and have their basal joints or coxae more or less enlarged,
apposed mesially, and anchylosed, though they are much less altered in
function and structure than their homologues in the Chilopoda; and
their legs are, after the first six, or, in the males, seven post-cephalic
segments, arranged in double pairs. Difiering thus externally from the
Chilopoda, they differ from them also in the following points of structure
and developmental history, and approximate more closely than they do
to the Arachnida and Crustacea, and less closely to the Insecta. The
stigmata leading into their tracheae correspond in number with their
segments, and are situated on the anterior border of the ventral plates,
under cover of the coxae of the legs, which are articulated to the pos-
terior border of these plates ; the tracheae do not anastomose ; the gene-
rative ducts are bilaterally symmetrical, having double openings in or
upon the borders of the third thoracic segment, which never carries legs,

h 2,

cxvi

Introduction.

and con-esponds precisely with the genital segment of the Scoqiion (see
p. 1 1 6, infra), and with that of the Poecilopodous Crustacea. The seventh
post-cephalic segment ordinarily carries a double penis, which may how-
ever, as in Glomeris, be removed to the posterior extremity of the body,
indicating hereby an approximation to the Chilopoda. The larvae of
Chilognatha, when they leave the egg, have ordinarily only three pairs
of appendages, which are carried upon three of the fom* first post-cephalic
segments ; and they contrast still further with the Chilojjoda, by at-
taining their additional segments at each moult by intercalation only in
that portion of germinal membrane which is interposed between the
penultimate and ante-penultimate segments.

Pauropus appears to resemble the Ghilognailia in having the generative
orifices situated anteriorly instead of posteriorly in the body, and its
larvae are hexapodal ; but it differs from them in many points of its
external anatomy. The shape of its body as a whole, its dorsal plates,
and elongated posterior legs, give it a resemblance to some Chilopoda.
As tracheae may be absent in the early developmental stages even of an
Insect, Ghloeon Dimidiatum, too much weight must not be laid upon
their absence in Pauropus ; and it may be safely said that for our present
purpose, that, namely, of showing the relationships which subsist between
the various classes of Arthropoda, the most important morphological
point in this genus (or order X) is its possession of bifid antennae, can-ying
multi-articulate flagella, by which peculiarity, as also by the others
specified above, a very distinct afl&nity is shown to exist between Myrio-
poda and Crustacea.

For tlie structure and affinities of the Myriopoda, see Sir Jolm
Lubbock, on Pauropus, a new type of Centipede; Linn. Soc.
Trans., xxvi., 1867, iUque citata ; and also Mr. Neuq^ort's
Papers on the Myriopoda, in the Transactions of the Royal
and Linnaean Societies.

Class, Araehnida.

Air-breathing Arthropoda, with well-marked heteronomy be-
tween the several divisions of the body, which are usually only
two, a cephalo-thorax to which the limbs are limited, and an
abdomen, usually marked off from it l)y a constriction, a post-
abdomen being developed only in the Scorpions. Their antennae
are modified so as to serve in the prehension of food ; and they

m Characteristics of Arachnida. cxvii

h^e four pairs of limbs, which correspond to the maxillary, and
to the labial palps, and to the two anterior pairs of legs in Insects.
The fiision of head and thorax approximates the Arachnida to the
Crustacea, and puts them into a position of contrast to the other
Arthropoda ; the Mpiopoda furnishing here, as frequently else-
where, an example of a transitional arrangement, by having the
two anterior pairs of thoracic appendages subordinated functionally
to the oral appendages, though the segments carrying them are
not in them actually fused with the head. As the history of the
development of the nervous system in the Scorpion appears to show
that the first post-oral, which is the cheliferous appendage, corre-
sponds to the mandible, and not, as is ordinarily stated, to the first
maxilla of other Arthropoda; we may add that the Arachnida
resemble the Crustacea in a second point of external anatomy,
that of possessing a palp on the mandible, a structure never seen in
the air-breathing Arthropoda except as a rudiment in some Chilo-
podous Myriopoda. The lesser development of the respiratory
apparatus is a point of internal anatomy which distinguishes the
Arachnida from the other Arthropoda ; and the large development
of the hepatic organ, which may be considered to compensate for
this comparative deficiency, is another point of resemblance to
Crustacea. As peculiarities which may possibly be correlated with
these, and which certainly point in the same direction, we may
mention the power of repeatedly moulting ; of reproducing at those
periods limbs which have been detached or mutilated ; and of
producing ofispring repeatedly in the adult state, which the Arach-
nida possess in common with Crustacea. The higher Arachnida
resemble the CMlognatha and the Crustacea, in the bilateral ter-
mination of their generative ducts on anteriorly-placed segments of
their body ; and they resemble the ChilognatJia in the non-anasto-
mosis of their tracheae. The digestive tract of the Arachnida differs
from that of all other Arthropoda in having in many cases lateral
coeca appended to it, and prolonged into the interior of the limbs
and mandibular palps. Their respiratory system consists either of
tracheae alone ; or of the so-called ' lungs,' which are sacciform
modifications of tracheae, alone ; or of both combined ; and in some
cases, such as those of certain parasitic families and orders, and of
the Tanligrada, a specialized air-breathing apparatus is wholly want-
ing. The tracheae when present have very ordinarily a fasciculate

cxviii

Introduction.

rather tlian an aborescent arrangement, and they not rarely differ
also from those seen in Insecta and Myriopoda, by not possessing
the internal spiral thickening, so characteristic of the respiratory
tubes in those two classes.

The limits within which the variations of the circulatory and ner-
vous systems may range, are very wide ; the arteries and veins may
attain, as in Scorpions, a very high grade of evolution and distinct-
ness, or both sets of vessels and the heart also may be absent, as in
such lower forms as the Acarina and Linffuatnlina, in which the
nerve-system is reduced to a single ganglionic mass perforated by
the oesophagus. The supra-oesophageal and the sub -oesophageal
ganglia are always closely approximated in Arachnida, in corre-
spondence with the assignment of the antennary to act in aid of
the manducatoiy organs, and with the more or less suctorial modi-
fication of their carnivorous habits, with which a small pharynx
and oesophagus are correlated.

The Arachnida, with the exception of the Tardi^rada, are dioecious ;
and with the exception of the order just named, and the Linguatu-
lina, the segmentation of the yolk is partial in the class. With the
exceptions of Scorpionidae and some Acarina, the Arachnida are
oviparous. Most Arachnida, when hatched, resemble the adult
animal ; amongst the Acarina, however,, we meet with hexapod
larvae, which attain their fourth pair of legs subsequently by moult-
ing, whilst the Linguatulina reverse this history in their develop-
ment, and undergo a retrograde metamorphosis from a larval form
provided with two pairs of biarticulate and unguiculate appendages
to a vermiform adult destitute of limbs.

Class, Crustacea.

Water-breathing Arthropoda, which may, in accordance with the
grade of specialization attained to by their segments and appendages,
be as markedly heteronomous as the Insecta, or as homonomous ex-
ternally as the Myriopoda. Normally, every segment in the Crus-
tacean body carries a pair of articulated appendages ; and two pairs
of antennae are all but invariably present, indicating the presence of
two cephalic segments between the jaws and the eyes. The append-
ages of one or more of the three segments immediately posterior to
the jaws, are always converted into auxiliary jaws, or ' maxdlipedes;

Characteristics of Crustacea.

cxix

and the subordination of these thoracic segments to the cephalic,
may he still forther manifested by a fusion of the segments them-
selves into a cephalo-thoraeie carapace. The post-thoracic segments
in Crustacea are more obviously divisible into an abdominal and
post-abdominal series, than they are in such other Artliropoda as
do possess a post-abdomen. The normal number of the abdominal
segments is five, and the appendages they carry are in the adult
state very ordinarily either alone, or in association with the post-
abdominal segments and appendages, the locomotor organs. Ac-
cordingly as only one of the three pairs of thoracic appendages, or 2^ t '*r r
as all three lose their primordial and typical locomotor functions
and become associated with the oral appendages, the higher Crus-
tacea are classified as ' Tetradecapoda' (Dana) (the five abdominal
segments furnishing ten, and the two posterior thoracic four limbs),
or as ' Deeapoda.' The normal number of the caudal or post-
abdominal segments is six, the appendages of the first four of
which may be modified so as to carry ova, or branchiae, but do not
attain the importance as locomotor limbs, which those of the five
abdominal segments do.

The appendages of the sixth segment, however, very ordinarily
attain considerable importance as locomotor organs, and they con-
stitute, together with a median azygos element, developed poste-
riorly to the sixth segment, the powerful ' swimmeret' of the Macru-
rous Lecajjocla. Their morphological importance is equally great, as
they correspond with the caudal feet of naupliiform larvae, and
together with the two pairs of antennae which they may resemble
by carrying, as in Mi/sis, organs of special sense, and the mandibles,
make up the entire sum of the appendages of the ' primitive body '
of Crustacea, as represented by those forms. The bilateral append-
ages which certain lower Crustacea carry at the posterior extremity
of their bodies, are not articulated ventrally as these caudal feet are,
and on this account, as also upon others, they cannot be considered
as homologous with them. There is much difference of opinion as
to whether the mesially-placed azygos element of the swinmaeret
ought to be counted as a seventh post-abdominal segment. (See
p. 113, infra.)

The mandible is ordinarily provided with a palp, which in a
Class with but few exceptions aquatic in habit, serves to direct j(u?£ jf-cv*
floating food towards the mouth. There are no salivary glands in ^ 1^-

cxx

hitroduciion.

Crustacea, the so-called antennary glands of Decapoda, the ' cement
glands' of Cirripedia, and the poison-glands of ^rg^.^^g^hough homo-
logous probably with each other, not being homologous with salivary
organs. The stomach consists very commonly of two portions, the
anterior one of which corresponds in fvmction and position to the
gizzard of Insecta, whilst the posterior receives the ducts of what when
multi-ramified is spoken of as a ' liver ;' what when simply coecal is
spoken of as 'hepatic coeca;' and, what is sometimes considered, as
in Argiblus, to be simply 'lateral diverticula,'' such as those often ob-
servable in Arachnida. The intestine, except in certain Cladocera,
takes a straight course to the anus. This orifice is usually situated
on the ventral aspect of the terminal segment, or the median
appendage of the terminal segment of the post-abdomen, except in
the Cladocera and Gopepoda. An azygos coecal sac may open into
the digestive tract dorsally on the line of demarcation between the
pyloric portion of the stomach and the duodenum; and three other [
coeca may similarly open on the dorsal surface of the duodenum at \
one or other part of its course. These latter coeca have been spoken
of as urinary organs ; they are, however, as being by no means con-
stantly present, probably homologous rather mth the midtiple
hepatic organs of the Scorpion than with its renal organs, or with
those of the other air-breathing classes. The heart is ordinarily
oIa'^^O^ present, and is either elongated and vasiform, as in the sessile-eyed
s and many of the lower Crustacea, or short and polygonal in the

7 Decapoda, where it gives origin to several arterial trunks ; or short

and semiglobular, as in Copepoda, where no arteries exist. In
every case blood finds its way into the interior of the organ through
venous inlets, which are dilated as in other Arthropoda, by the
recoil of the elastic alae cordis,
p , L- I I Respiration is sometimes effected by the general surface of the

/'^''^•''^'^"body, specialized branchial organs are however usually present, and
take the shape either of tree-like or of leaf-like hollow outgrowths
attached either to segments or to appendages, or to both. As
there are' no jciliajin Arthropoda, the aerating surfaces have fresh
supplies of water brought into relation with them either by the
movements of appendages specially modified for the pui'pose, or by
the movements of ordinary locomotion, or by both combined. The
gill-covers of certain air-breathing Isopoda contain multi-ramified
cavities, which have been supposed to constitute a rudimentary

CharaGterlstics of Crustacea.

cxxi

tracheal system, but which with more probability have been con-
sidered to have a glandular function, and to keep the gill-plates
lubricated and transpirable by their secretion.

The nerve-system resembles that of other Arthropoda in its ge- j]^'
neral arrangement^ but differs in the two following points : — The! ^
commissural cords connecting their prae-oral and post-oral ganglia^
are of so much greater length, that their 'brain' is never described'
as that of other Arthropoda sometimes is^ as consisting of an infra-
oesophageal as well as of a supra-oesophageal mass, the ganglia of
the jaw-bearing segments having receded so as to become apposed
to the first of the thoracic series, with one or all of which they are
always fused, whilst the ganglia of the two antennary segments
maintain their usual continuity with those of the eye-bearing seg-
ment. And, secondly, the paired^ and the azygos systems of stomato-
gastric nerves, except in the terrestrial Isopoda, take origin from
the commissural cords of the nerve collar, and from the prae-oral
ganglionic mass instead of from any distinct ganglia, such as the
lateral and frontal ganglia of other Arthropoda. The nervi transversi,
however, appear to be represented in Crustacea by a nervous stem,
passing off from each interganglionic segment of the cord, as is the
case in other Arthropoda, and indeed also in those Vermes which
possess a chain of ventral ganglia. The eyes may vary from the very
simplest up to the most complex form observed in the Sub-kingdom ;
two kinds may co-exist in the same individual, and in two genera,
M(,p7ia2isia and Thi/sanopocla, eyes may be, contrary to the otherwise
invariable i-ule in Arthropoda^ found elsewhere than upon the head.
An auditory organ has been observed in Decapoda in the basal joint
of the superior antennary organs; and in Mysis, in the lateral
appendages of the last post-abdominal segment, which, together
with the two pairs of antennary organs, were the only appendages
developed in the earliest period of its larval life. ^ ca*-^'

With the exception of the Cirripedia, all the Crustacea are dioe- ^^.y,^-*
cious. 'Complementary males' are found in the order Cirripedia, ^
and also amongst the parasitic Entomostraca, and in the former
order these 'pygmy' males are devoid of any digestive tract, and
even of any oral opening. The sessile-eyed Crustacea furnish an
exception to the rule, that in Arthropoda the females are larger in
size than the males. The generative organs have bilaterally sym-
metrical ducts^ opening a considerable distance anteriorly to the

cxxii

Introduction.

anus, except in Daphnidae ; but not always on numerically corre-
sponding teguments in the two sexes. Crustacea attain tlie power
of sexual reproduction before they attain their full size, and they
retain it, and repeatedly exercise it, in many cases at least, for an
indefinite period.

In development the yolk may undergo complete segmentation,
and a larva of the form known as NaupUus may be produced with-
out the formation of any primitive streak, as is the case with the
Cirripedia, Entomostraca, Penaeus amongst Decapoda, and most
BrancMopoda ; or, as in all the higher Crustacea, the yolk under-
goes a partial segmentation, and the embryo, when ready to be set
free from the egg, may either be of the larval form known as Zoea,
as in most Decapoda ; or may differ from the adult form only by
the possession of certain structures, which are subsequently aborted,
as is the case with the outer division of the abdominal limbs of the
common lobster, Romarus vulgaris ; or, finally, may, as is the case
with Astacus fluviatilis, from the time it is set free from the egg,
possess the same number and proportions of appendages as the
adult. Instances of retrograde metamorphosis are common in this
class, several of the orders of which possess pai-asitic families. Par-
thenogenesis occurs in the Gladocera, the summer eggs' oi Daphiia
being developed without sexual congress, and one genus, Cythere, of
the allied family, Ostracodea, is viviparous.

Sub-kingdom, Vermes.

Bilaterally symmetrical animals, very various in shape and other
external characters, but agreeing in the absence of heterouomy
from their post-cephalic regions, in not possessing hollow seg-
mented limbs, and in having their locomotor muscles closely con-
nected with their integumentary system, not only on the ventral,
but also on the dorsal and lateral aspects of their body walls.

The Sub-kingdom Vermes consists of two Divisions, the Aunulata
and the Annuloida. The first of these contains the multisegmental
Vermes, which, in Mr. Herbert Spencer's language, would be spoken
of as ' aggregates of the third order.' Their bodies are more or less

Characteristics of Vermes.

cxxiii

distinctly divided externally by annulation, and internally by the
development of dissepiments forming compartments. The nerve-
ganglia, the organs of motion, and, sometimes, even those of special
sense, exhibit a more or less closely corresponding multiplicity as do
also the organs of vegetative life. The Annulata are divisible into
two Classes, the Annulata proper s. Annelides and the Gephyrea.
The Annuloida are unisegmental Vermes or 'aggregates of the
second order.' Their nervous system consists (with, possibly, an
exception in the case of certain Turbellarians, see p. 155, infra) at
most of a simple oesophageal collar to which a few accessory nerve-
centres, but now a chain of ganglia may be appended; and their
water-vascular or depuratory system is (with an exception again in
the case of certain Turhellaria, the Nen/iertinea,, see description of the
class Platyelminthes given below, p. cxli.) the only vascular system
which they possess. The Division Annuloida contains three Classes,
the Nematelminthes, the Eotifera, and the Platyelminthes.

The integument may possess a perfectly smooth chitinous ex-
terior; or it may be covered with cilia; or it may develope nu-
merous chitinous outgrowths in the shape of spines, hooks, bristles
or hairs. These appendages often attain a very considerable degree
of hardness ; but the chitinized cuticular secretions of the body- wall
as opposed to these specialized developments which often pass
right through the thickness of the visceral envelope, are usually
much less resistent both to physical and to chemical agencies than
the similarly placed structures of the Arthropoda; they never
become indurated by calcificatory deposit, and have only rarely
(in Nematoidea and Hirudineae) been observed to be changed by
moulting as in that sub-kingdom. In some of the ento-parasitic
Vermes [Cestodes), which lie immersed in an atmosphere of more
or less perfectly digested and diflPusible albumen, and which by
virtue of their readily permeable integument can imbibe nutriment
at all points of their external surface, there is absolutely no digestive
system present. In the parasitic Nematoids, on the other hand, in
which the integument developes a much more considerable chitinous
cuticular deposit, a proctuchous digestive tract is always present.
The non-parasitic Vermes, with the exception of the male Eotifera,
always possess a digestive tract, which is usually proctuchous, except
in the case of the Dendrocoelous Turlellaria, which in this as in
other points resemble the parasitic order Trematodes.

cxxiv

Introduction.

The digestive canal in Vermes when present resembles their ex-
ternal teg-umentary system in being homonomous exce^Dt in its
anterior portion. In this part of the tract we often find a muscular
protrusible and dentigerous oesophagus; the stomach is by no
means always difierentiated from the intestine, and the segments
which intervene between the oesophagus and the short often upward
turning rectum, may be conveniently called ' gastro-ileal/ It may
take a simple antero-posterior course, or it may have lateral diver-
ticula of very various degrees of complexity developed upon it.
It is seldom convoluted. " The salivary glands are usually, and the
hepatic are always represented merely by layers of cells impacted in
the walls of the digestive tube.

Many Vermes possess an extensive vascular system, which,
however, as containing usually a coloured, but not a corpusculated
fluid, is called a ' pseudhaemal' system, and is to be considered respi-
ratory in function. The corpusculated nutritive true blood is con-
tained usually in the perivisceral cavity alone ; in a few instances
it has been found to penetrate into the so-called pseudhaemal
vessels. Specialized respiratory organs are rarely found in Vermes ;
the possession of a peculiar depuratoiy apparatus is characteristic
of the entire Sub-kingdom. This system appears to stand in a
complementary relation to the branchial ; being largely developed
where, as in the Oligochaeta and parasitic worms, that system
fails to be developed, on account of the medium in which those
animals live; and being reduced to comparative insignificance in
the marine Polychaeta, where the branchiae are so prominent a
feature in their organization as to have gained for them the name
of ' Branchiata.' In the non-segmented worms these organs are
known as the ' water- vascular' system; and they take the shape
of two bilaterally symmetrical tubes, opening by one or two orifices
on the external surface of the body, and ramifying abundantly in
its interior. In the segmented Vermes or Annulata, these organs
are known as ^segmental organs;' and may be repeated in nearly
eveiy segment of the body. In most Vermes the internal terniiual
segments of these tubes appear to be clothed with cilia ; the seg-
ments in more imraeTTiate connection with the exterior outlet are very
ordinarily possessed of much thicker, glandular, and contractile
walls. In the Annulata, with a few exceptions, tbe inward pro-
lono-ations open by infundibuliform orifices into the perivisceral

Characteristics of Vermes.

cxxv

cavity; and in certain segments these organs are modified, so as
to serve as efferent ducts for the generative products.

The existence of a nerve-system appears to be doubtful in cer-
tain of the Platyelminthes (Cestodes). In the parasitic Acantho-
cephali it is reduced to a single anteriorly-placed ganglion. In
certain both of the free and of the parasitic Platyelminthes^ it
consists of two ganglia placed one on either side of the pharynx
{Trematodes), or one on either side of the anterior extremity of the
body {Twrhellaria), and connected with each other by a transverse
commissure. The ordinary Nematoidea possess a complete circum-
oesophageal collar^ which again is represented in the microscopic
Rotifera by a single bilobed supra-oesophageal ganglion. The
Gephyrea have in addition to the nerve-collar of lower Vermes a
simple elongated band of nervous tissue, extending from the an-
terior to the posterior pole of the body along its medio- ventral line.
In the Annulata proper the ventral chain is distinctly bilaterally
symmetrical, and its two halves are sometimes widely divaricated.
In many Vermes the organs of special sense (optic and auditory) are
very well developed ; in many, they are entirely absent.

In the Annulata proper, with the exception of the DiscopJiora, the
ova and spermatozoa are set from the secretory glands, by dehiscence
into the abdominal cavity, and are conveyed thence to the exterior
by modified ' segmental organs.' In the other Vermes, with the
exception of the female Acanthocephali, the generative glands
have their walls prolonged into ducts ; and their products are thus
conveyed out of the body without falling into the perivisceral
cavity. Structures corresponding to the intromittent organs of
higher animals are found in representatives of every class of Vermes,
not even exclusively of the Rotifera; the Platyelminthes almost
invai-iably possess a complicated reproductive apparatus, in which,
besides other accessory organs, vitelligenous exist independently of
germigenous glands. The marine Annulata, on the other hand,
are distinguished by a great simplicity in their reproductive appa-
ratus, contrasting herein at once with the lowest Vermes, and with
the Discophorous and Ohgochaetous members of their own class.

Vermes may be either hermaphrodite or dioecious ; either vivi-
parous or oviparous ; they may reproduce their kind either sexually
or asexually, and their embryos may or may not go through a
metamorphosis. When reproduction takes place asexually, it may

cxxvi

Introduction.

take place either in the way of parthenogenesis, as in Rotifera and
Ascaris nigrovenosa in its ento -parasitic stage ; or in that of meta-
genesis from a part of a protozooid, which is not differentiated as a
sexual gland. Metagenesis is observable both in the highest and
in the lowest of the Vermes.

In some instances, at the time of the setting free of the deu-
terozooid produced by gemmation, both protozooid and deutero-
zooid may be in the asexual condition, as is ordinarily the case
with Nais and Chaetogaster amongst Annulata, and with Micro-
stomeae amongst Turhellaria, In the cases of certain other Tur-
hellaria {Strongylostoma and Catenula)^ no other than this simple
metagenetic form of reproduction has been, as yet, observed. When
this form of reproduction alternates as in the other Turhellaria, and
in the Annulata just mentioned, with sexual reproduction, we liave
a series of phaenomena before us which has been spoken of as
' Digenesis with Heterogony.'' In some cases, as occasionally in
Microstomeae, and in the Annelidan Syllidea and Protula, a sexual
protozooid has been observed to give origin by gemmation to a
sexual deuterozooid, furnishing thus an example of digenesis with
contemporaneous heterogony. In some rare cases, the sexual
organs of the protozooid have been observed to be of one, and those
of the deuterozooid of the other sex. In other cases, the protozooid
is always asexual, when it is known as a 'nurse;' whilst the
deuterozooids it gives origin to attain the sexual condition, either
whilst still attached to the parent organism, as in the Taeniadae
amongst Platyelminthes, and Autolytus amongst Annulata; or
subsequently to detachment from it, as in Trematodes. These forms
of reproduction may be spoken of as cases of ' digenesis with alter-
nation of generations,' inasmuch as the asexual forms or stages of
metamorphosis interposed between the products of sexual congress
and another set of sexually perfect individuals may be regarded
as sufficiently distinct and independent to merit the title of ' gene-
rations.'

The relations held to the adult forms by the provisional organs of
the larvae of certain Turbellarian worms {Pilidimi), and also of
certain Gephyrea (Aciinofrocha), bear a considerable resemblance to
those observable in the larvae of Echinoderms. The Oligochaetous
and the Discophorous Annulata do not go through any metamor-
phosis. In worms of parasitic habits, even where, as in Nematoids,

Characteristics of Annulata.

cxxvii

no alternation of generations is observablcj the history of the evolu-
tion of the embryo is much complicated by the fact that two 'hosts'
are necessarily required for its harbouring- and sustentation at dif-
ferent periods ; in one only of which, usually a vertebrate animal,
the sexual condition can be attained to. The enormous quantities
of ova which parasitic Vermes produce, stand in direct relation to
the very great difficulties which their peculiar mode of life opposes
to the continuation of the species.

Vermes of the same species in the higher orders of the sub-
kingdom appear to be competent to the maturation of sexual
products at very different ages. In thus assuming sexual functions
before attaining their full size, these Vermes resemble the Fishes
in the Vertebrate Sub -kingdom, but differ not only from the air-
breathing classes of Arthropoda, but also from the lower members of
their own Sub-kingdom.

It is sometimes said that the power of repairing injuries and
mutilations which distinguishes this sub-kingdom as a whole in
an eminent degree, is connected with the possession of the faculty
of metagenesis. The power of repair however is very great in the
terrestrial Oligochaeta s. Lumbricidae, in which metagenesis has
not been observed ; and though the two faculties are both alike
absent in the Nematoidea and in the Discophora, it is better to
explain this fact by a reference to the special habits of these animals,
which, as testified to by the imiversal presence in the one, and the
verj^ common presence in the other of caudal suckers, would appear
to be more or less incompatible with reproduction by gemmation.

Class, Annulata proper.

Vermes of elongated and almost always cylindrical shapes, made
up of a series of segments, which are homonomous except at either
extremity of the body. They are annulated externally, and inter-
nally their perivisceral cavity is divided by dissepiments into more
or less perfectly separated compartments and chambers. They all
possess a chain of ventral in addition to, and in commissural junc-
tion by a circum-oesophageal collar with a prae-oral cerebroid
mass ; the digestive tract is in all of them proctuchous, and, with
the exception of the Hirudineae, suspended in a large perivisceral
space. With a few exceptions they possess a closed system of

cxxviii

Introduction.

' pseudhaemal vessels/ and a series of depuratory organs, opening
internally into the perivisceral cavity, as well as externally on the
surface of the body. They are divided into two sub-classes, the
Chaetopliora s. Chaetopodes, and the Discopliora, accordingly as
their external locomotor organs are chitinous spines, or terminal
suckers. The Cliaetopliora again are divided into Polychaeta s.
Branchiata and Oligochaeta, according to the number of their
locomotor and the presence of branchial appendages. The Disco-
pliora, with the exception of Brancliellion, have no external append-
ages locomotor, branchial, or tactile ; in the absence of appendicular
organs of the two latter kinds, as also in being hermaphrodite,
the Oligochaeta resemble the Discophora, and differ from the
Polychaeta.

The Annulata may form tubes for the lodgment of their bodies
by the secretion either of calcareous matter (Serpula), or of organic
(chitinous?) substance (Onuphis), or by the agglutination of are-
naceous particles {Terehella), and their integument, which is always
ehitiuogenous, even in the Hirudineae, where it developes no ex-

^ ■ ternal appendages, may develope chitinous appendages of the most
varied forms. But these chitinized outgrowths are with the single
exception of the operculum of Serpula, never indm-ated by any
deposit of calcareous salts, as is the case in Echinodermata and
Crustacea. The integument is frequently, even in adult Annulata,
found to be beset with cilia, especially in the anterior regions of
the body. This is the case with many Naidina, with Polyoph-
thahnus, with Siphonostomum gelatinosum, and with Spio and
Tomopteris ; and in these two latter, as in many other genera, the
integument has been observed to contain tricho-cysts, or ' bacillar
corpuscles,' which have been compared with the acicular or urti-
cating organs of the Coelenterata, of certain Infusoria, of the
Apneustie Mollusca, of the Turbellarian Vermes, and, according
to M. A. de Quatrefages, of Synapia amongst the Echinoderms. y
All Annulata possess two layers of muscles in their body-walls^
an external consisting of circular, and an internal of longitudinal

tj(j>7 fibres. To these an additional layer may be superadded internally,
and enter into the formation of the dissepiments which divide the
perivisceral cavity into its transverse and longitudinal compart-
ments. The digestive tract takes, with the exception of Chloraema,
a direct antero-posterior course, without describing any convolu-

Characteristics of Annulata. cxxix

tions, but its absorbing" surface is very ordinarily largely increased
by the development of lateral sacculations. It is very often armed
with a protrusible, muscular and dentigerous, proboscis. The mouth
opens ventrally, and the anus dorsally or terminally. A perivisceral
cavity is present in all Annulata except certain Discophora, in
which it becomes obliterated in the course of the evolution of the
internal organs. In this cavity^ when present, the true corpus-
culated blood is ordinarily contained. In some Annulata which are
called 'anangian/ there is no 'pseudhaemaP vascular system deve-
loped, and in them the internal surface of the perivisceral cavity is
richly ciliated, and the circulation and aeration of the corpusculated
fluid it contains thus secured. But in most members of the class
we find a closed system of contractile vessels, which, as they contain
a fluid which, though ordinarily coloured, is not corpusculated, are
called ' pseudhaemal,'' and appear to be respiratory in function ;
and in these worms the perivisceral cavity shows no other ciliation
than that of the mouths of the segmental organs which open into
it. In a few Annelids again {Sylliclea armata, the Opheliae, the
Cirratulida, and the Staurocephali and BrancMobdella), the so-
called ' pseudhaemaF system contains corpusculated blood, and com-
municates with the perivisceral cavity so as to form a lacunar
circulation. Arborescent branchiae are not rarely developed in the
Polychaeta on the dorsal aspect of the parapodia ; and the tactile
cirri ordinarily present on the same, as also on the ventral aspect
of the locomotor outgrowth, must possess an aerating as well as a
sensory function. The branchiae are often ciliated, aud contain
afferent and efferent branches of the pseudhaemal system, which
run parallel and are connected with each other by a double series bf
vascular loops within the aerating lamina. Nearly all Annulata
possess certain organs, known as the ' segmental organs,-" which
open externally on the surface of the body, and internally into the
perivisceral cavity. The internal orifice is wanting in some Pohj-
chaeta [Capitellae) as also in some Discophora ; a part of the often
complexly convoluted canal which they consist of is glandular, and
as the movement set up by the cilia with which they are lined,
ordinarily sets outwards, they may be supposed to be depuratory
in function, except in those segments in which they are specialized,
as they are in all Annulata except the Discophora, to act as efferent
ducts for the generative products. In some cases, however, as in

cxxx

Introduction.

Tomopieris, the ciliary movement within these organs has been
observed to set inwards and to carry spermatozoa with it ; and this
must be the case whenever the ova are impregnated within the
maternal body. The nervous system consists of a ganglionic prae-
oral mass, and a veutral ganglionic chain, which by their com-
missural junction form the oesophageal collar. In the Polychaeta
accessory ganglia are developed . upon their muscular proboscis ;
in Oligochaeta upon the pharynx; and in Discophora in relation
with the jaws (in the GnathoideUeae), and also with the ventral
surface of the digestive tract. In some Annulata the cirri are
supplied with nerves, and would appear to be tactile organs. The
eyes are usually but not exclusively carried upon the praestomium ;
they may be repeated in each segment {Myxicola and Polyoph-
thalmus), or carried upon the branchiae (some Subellae and Tere-
bellae), or carried upon the caudal extremity {Amphicora). Bila-
terally symmetrical otolithic capsules have been found in a few
Annulata {Arenicola, Fahricia, Sabella), in the neighbourhood of
the oesophageal nerve-collar. In the Polychaeta, which with the
exceptions of Protula, Spirorlis, and Exogone pusilla, are dioecious,
the sexual glands develope themselves round branches of the pseud-
haemal vessels, and discharge their products, as in Oligochaeta but
not in Discophora, by dehiscence into the perivisceral cavity,
whence they are taken up by specially modified segmental organs.
In the Oligochaeta and Discophora, which are hermaphrodite, certain
accessory generative organs are present, which are not found, except,
possibly, as rudiments, in the Polychaeta ; and the Discophora differ
from all other Annulata, in that their generative products do not
find their way into the perivisceral cavity by dehiscence, but are
conveyed along closed ducts to azygos efferent canals, the terminal
segment of the male division of which is modified so as to serve
as an intromittent organ as in the Platyelminthes. In development
a ' primitive streak,-' out of which the various organs both of vege-
table and of animal life, with the exception of the digestive tract,
are evolved, has been observed to make its appearance ; it appears,
however, subsequently, and not, as in Arthropoda, anteriorly to the
formation of the primitive embryo. The embryos of the Oligo-
chaeta and Discophora undergo no metamorphoses after being set
free from the egg. Those of the Polychaeta are, with a few excep-
tions [Amphicora), when set free from the egg, furnished with

Characteristics of Gephyrea,

cxxxi

provisional organs, in the shape of terminal or biterminal (telo-
troehal) or mesially-placed (mesotroehal) zones of cilia ; and some-
times in that of long setae. In every case the cephalic and caudal
segments alone are present when the Polychaetous embryo leaves
the egg; and their full complement of segments is attained to
in the way of intercalation anteriorly to the terminal segment. A
few Folychaeta belonging to the genera Eunice, Nereis, Syllis,
have been observed to be viviparous. The Discophora differ from
the other Annulata, in never multiplying asexually ; and in pos-
sessing but little power of repairing injuries, and none of repro-
ducing lost organs. In these points the Discophora differ very
widely from the Platyelminthes, with which they have sometimes
been classed (see p. 138, infra), and resemble the Nematelminthes,
a Class to which also they are approximated by the possession of
a terminal sucker, though by few other properties beyond those
common to all members of the Sub-kingdom Vermes.

Class, Gephyrea.

Marine worms, which have been supposed, as their name denotes,
to furnish an example of a transitional form connecting two distinct
types, and which not only in habits of life and in external appear-
ance, but also in a few points of internal structm*e, do appear to be
allied to the apodal Holothurioidea, though the totality of their
organism causes us to class them amongst the Vermes, and to
consider them as most nearly related to the Annulata proper. They
are usually cylindriform in outline, their integumentary system is
indurated by chitinous, but never by calcareous deposit; in two
families [Sternaspidea and Echiuridea), it carries locomotor setae ;
and in one species at least [Anoplosomatim antUlense) of another
family [Friapwlaceae), it developes trichocysts. It ordinarily pos-
sesses numerous follicular glands. The Gephyrea never have their
bodies definitely segmented, but the integument is not rarely so
corrugated as to form more or less distinct zonular folds ; and in one
case {JPhascolosoma Cimaneme^), rudimentary dissepiments have
been observed in the large perivisceral cavity. The mouth is
surrounded in the SipuncuUdae with a coronet of ciliated tentacles,

Keferstein, Zeitschrift fiir WisR. Zoologie, xvii., 1867, p. 53.

i 2

cxxxii

Inti'oduction.

into which a circular vessel surrounding* the oesophagus, and fur-
nished with contractile ampullae, sends prolongations. Though
this vascular system has no locomotor feet, like those of the normal
Echinodermata, in connection with it, yet, as it is clothed with cilia
internally, and as it sends branches to the integument as well as to
the tentacles, it would be considered homologous as well as analo-
gous to the ambulacral system of the apodal Holothurioidea, were it
not observed to contain a corpuscidated fluid of the same characters
as the blood in the perivisceral cavity. Another point of resem-
blance to the Echinodermata is furnished to us by the respiratory
cloacal trees of the Echiuridea, which in Bonellia have been very
clearly shown to open by numerous infundibuliform orifices into the
perivisceral cavity. The cloacal respiratory trees or ' lungs ' are said
by Semper, to open similarly in the Holothurioidea ; and the resem-
blance between the two classes is made stronger by the fact that
where these respiratory trees are absent, or, as in Sipunculus, only
rudimentary, in both classes alike we find the intestinal mesentery
beset with certain ciliated infundibuliform organs, which are, prob-
ably, connected with a water- vascular system. The muscular sys-
tem consists, as in Holothurioidea and Chaetophorous Annulata,
of an external circular and an internal longitudinal stratum,
to which in the Sipunculidae special retractor muscles may be
superadded, as in the DendrocMrotae amongst the Holothurians.
The chitinous armature of the proboscis, upon which these muscles
act in the Sipunculidae, and the peculiar prolongation of the organ
seen in the Echiuridea, are points which do not find any parallel in
the Echinodermata. The digestive tract is usually complexly con-
voluted ; the anus opens always on the dorsal surface, often at a
point in the anterior third of the body's length, as in Sipunculidae.
It is clothed with cilia internall}^, and richly glandular in its middle
segments, from which an oesophagus and rectum are distinguish-
able. The Echiuridea and Sternaspidea appear to possess a pseud-
haemal system, which may be distinct from the vascular system
already spoken of in the Sipunculidae. The nervous system con-
sists of a ventral cord, and of a circum- oesophageal collar, in
which, however, a supra-oesophageal ganglionic mass is not always
present. The ventral cord, it would appear, does not ever deve-
lope ganglia, as it has been stated to do ; and it resembles, in
this absence of aggregations of nerve-cells, the band-like radial

Characteristics of Nematelminthes. cxxxiii

nerve-cords of the Echinodermata. There are no organs of special
sense in this Class, with the exceptions of the tentacles of the Si-
puncididae ; and of the eye-specks retained by some members of
that family from their free larval into their adult life, which they
spend immersed in mud or sand.

The Gephyrea are not hermaphrodite ; the organs formerly con-
sidered to be testes having been shown to be ducts for the gene-
rative products, and homologous with the segmental organs so
characteristic of the Annulata, The embryos go through more
or less complicated metamorphoses ; the provisional organs of the
larval form known as Actinotrocha, attaining proportions and rela-
tions to the future Sipunculus, which are similar to those of the
most characteristically developed Echinodermata ; whilst in other
cases the larval may differ from the adult form only by its possession
of locomotor ciliated zones, and of a relatively more prominent
nervous system.

For the anatomy and classification of the Gephyrea, see Lacaze
Duthiers, Ann. Sei. Nat., Ser. iii., tom. x., 1858; Claparede,
Anatomic und Entwickelungsgeschichte Wirbelloser Thiere,
1863, pp. 61, 83; Keferstein und Ehlers, Zoologische Beitrage,
1861 ; Ehlers, Zeitschrift fiir Wiss. Zoologie, xi. ; Keferstein,
ibid, xii., p. 35, 1 86a ; Semper, ibid, xiv., p. 420 ; Keferstein,
ibid. XV. and xvii., 1867.

Class, Nematelminthes.

Cylindriform non-segmented Vermes, in which the external layers
of the integument ordinarily attain considerable rigidity by chiti-
nization, and occasionally develope hooks and bristles, but in which
true locomotor more deeply implanted setae, and cilia are absent.
Three orders, the Chaetognatha, Nemaioidea, and Acanthocephali,
are contained in this class, of which the first consists of a very
few species which are always free ; the second comprises a very large
number of species which may be either free or parasitic ; and the
third is exclusively entoparasitic, and devoid of any digestive
tract.

Lateral and caudal fins, and suckers, as well as setiform spicula,
are often present in this Class ; and in the two orders, Chaetognatha

cxxxiv

Introduction.

and Nemaioidm, the muscular system does not possess the external
circular layer so universal in other Vermes, its presence being ren-
dered superfluous by the chitinization of the cuticular layer of the
body walls. This chitinous deposit is secreted by a suljcuticular
'granular layer/ and as in Arthropoda it is frequently changed
by moulting during growth and metamorphosis. In many cases
the muscular envelope is divided into four bands by the median and
lateral lines. In the Nematoids, bladder-like processes are some-
times ffiven off from the muscle-cells, in such abundance and pro-
portions as to fill up a large part of what in the entire class is
ordinarily a large perivisceral cavity ; and a second set of processes
given off from them make up the internal ' transverse muscles ' of
authors. In the Chaetognatha the muscular fibres are very defi-
nitely marked with transverse sti-iae. The digestive ti-act is
entirely absent in the Acanthocephali, and the short oesophagus
is said to open into the general cavity of the body in Gordius, and
into a simple coecal sac in Mermis. In the Nematoidea, whether
parasitic or free, a digestive tract is always present and always
proctuchous ; the anus being situated some distance anteriorly
to the caudal extremity in the free species, but terminally or sub-
terminally in the parasitic. The oral opening is always placed
terminally at the front of the body, a point of some consequence
in differentiating certain forms, such as Ichthydium and Chaeto-
notus, which have sometimes been referred to the Turhellaria,
and sometimes to the Rotifera, as well as to the Nematoidea. The
pharynx may be armed with horny plates or teeth, and the oeso-
phagus is often highly muscular, and the remainder of the digestive
tract simple, and of a uniform calibre. There is no blood- vascular
system as distinct from the perivisceral cavity, nor any respiratory
organs. The water- vascular depuratory system has, in compen-
sation for the absence of special respiratory structures, and, in the
parasitic Nematelminthes, in correlation also with their habits, a
very considerable development. In the Nematoidea it opens. exter-
nally by an azygos ventral pore, and in some cases by two sym-
metrically placed lateral pores, both of which orifices are situated
in the anterior portion of the body ; in the AcanthocepMi, the
homologous system appears to have no external orifice, though its
cutaneous ramifications are very extensive ; and it is possible, there-
fore, that this system may be in this order circulatory and nutri-

Characteristics of Nematelminthes. cxxxv

tional rather than depuratory, as the water-vascular system of the
Infusoria is supposed to be by some authors.

The nervous system in the Chaetognatha consists of a single
ventral and a single prae-oral ganglion, connected by commissures,
so as to form a collar round the oesophagus ; in the Nematoidea
we have a fibrous ring, with ganglion cells interspersed in its sub-
stance, surroundi ng the oesophagus, and connected posteriorly with
three main aggregations of ganglionic cells. Of these three ag-
gregations the first is placed medioventrally, and consists of two
symmetrical masses, one of which is on either §ide the middle line ;
the other two are placed on either side in the substance of the two
lateral bands j and the three ganglionic centres correspond thus
with the triradiate cephalic lobes of some famiHes, a,nd the tri-
quetrous division of the oesophagus of most Nematoids. In the
AcaniJiocephali there is only a single ganglion, placed at the base
of their proboscis, and resembling thus the structure which has
been stated to exist in the anterior extremity, the so-called 'head'
of the Tdeniadae. In the free Nematoids, certain aggregations
of pigment granules, situated on the dorsal surface of the oeso-
phagus, are spoken of as oceUi, but no nerve filaments have been
traced into continuity with them, as there have been in the case of
the similar organs in the Chaetognatha. The cephalic lobes when
present, as also certain papillae developed on the ventral surface in
many Nematoids, are considered to be tactile organs.

With the exceptions furnished by the order Chaetognatha, and
the Nematoid genus Telodytes (Schneider), all Nematelminthes are
dioecious. Their generative organs resemble those of the Platyel-
minthes and Discophora, in possessing an intromittent apparatus ;
and, with the exception of the female Acanthocephali, where the
ova escape by dehiscence into, and are taken up by an infundibuli-
form oviduct from the perivisceral cavity, the Nematelminthes
resemble the Eotifera, Discophora, and Platyelminthes, and differ
from the Annulata in having the walls of their generative ducts
continuous with the envelopes of their generative glands. The
ovaria are greatly developed, and the ova very small and numerous
in the parasitic Nematoids, the reverse being the case with the
free species. The spermatozoa of the parasitic Nematoids are
spherical or ovoidal cells, and move only by the protrusion of
pseudopodial protoplasmic processes; in the free genera they are

cxxxvi Introduction.

cylindriform, and possessed of the power of oscillatorial move-
ment.

The impregnated ova of the Chaetognatha are developed vsdthout
going through any metamorphosis, and without the formation of
any ciliated coat. The first stage of the embryonic life of the
Acanthocephali is constituted by a form armed anteriorly with
deciduous spiny hooks, and containing internally a mass of germ-
inal matter^ out of which the internal organs are developed after
the animal has found its way into the appropriate portion of the body
of its first host, and discarded its provisional organs. The sexual
condition is only attained in the body of a second host, which is a
Vertebrate, whilst the first is ordinarily (or always?) an Inverte-
brate animal. In the free Nematoids the development appears
to be direct ; but in the parasitic species it is complicated by the
fact that the embryo is not developed in the same medium as that
in which its mother lived, but migrates either into some other organ
of the same animal, or into the exterior water or damp earth,
whence it may find its way back into the body of the animal
whence it was extruded, either directly or after a migration into
some second host. A parasitic Nematoid may be undistinguishable
in its free stage from a true free Nematoid, being of the same
shape, and feeding-, growing and moulting in the same way. Ascaris
nigrovenosa, when set free from the body of the frog where it is
produced parthenogenetically, attains to sexual perfection in the
free state which they spend in moist earth. The development of
the Guinea-worm, Filaria Medinensis, within the subcutaneous
tissues of the human subject, would appear to be similarly partheno-
genetic, and probably alternative with a free stage, which, though
it has not been observed, may be supposed to be similar to that of
the Ascaris nigrovejiosa. Parthenogenesis has also been observed
in a Nematoid worm infesting L 'wiax cinereus ; and Sphaer7daria
hombi, if Schneider's explanation of Sir John Lubbock's account
of this animal be correct, must be considered as furnishing a fourth
instance of asexual reproduction in this class. No instances of
reproduction by gemmation or metagenesis have been observed in
the adult Nematelminthes ; the power of repairing injuries has, in
the free Nematoids, been found to be low, or absolutely none ;
and the breaking of the body of the Guinea-worm, Fihria Medi-
nensis, appears to entail its death even under the condition of its

Characteristics of Nematelminthes. cxxxvii

entoparasitic life in the human subject, which is so favourable in
this creature to the reproduction of the species. The tenacity of
life, as against desiccation, which has been supposed to characterize
many members of the class, is possessed in reality by only a few
land and fresh-water genera, Ti/lenchus, Cephalohus, Aphelenchus,
and Plectus; and in them is to be considered as partly, but, as
it would appear, not wholly, dependent upon the power which they
have of maintaining their tissues in a moist condition, and vsrhich
they owe to the absence from their integument of the pores so
characteristic of other free Nematoids.

The Chaetognatha, an order of marine worms of small size, represented
by the single gemis Sagitta, have been here ranked with the Nematoidea
and Acanthocephali as Nematelminthes, instead of being placed in a
separate Class. The diflferences which separate them from the free
Nematoids appear to be in no respect of more than ordinal importance,
consisting mainly in the facts of their hermaphroditism, and of their
possession of transversely-striped muscles. The peculiar armature of the
mouth, with two laterally and two dorsally-placed series of setae in the
Sagittae, is obviously homologous with the intra-oral armature so common
in Nematoidea ; and the production of the external layers of the integu-
ment into fins, supposed to be characteristic of the Sagittae, is often
observable both in the free and in the parasitic representatives of the
order with which we are comparing them. The same remarks apply to
the cuticular setiform spicula, and to the muscular structures of the
Sagittae. The interior of the digestive tract in Sagitta is lined with
ciliated epithelium, and Claparede has described a species, Sagitta Cepha-
loptera, which has a semilunar area in its nuchal region surrounded with
a band of cilia. Thus the Sagittae, and through them the entire class of
Nematelminthes, come to coincide with the rest of the Sub-kingdom
Vermes in the possession of ciliated epithelium.

The animal described by Claparede, Anatomie und Entwickelungs-
geschichte Wirbelloser Thiere, p. 88, Taf. xviii.. Figs. 2 and 3,
under the name of Chaetosoma ophiocephalum, would appear to
stand as a transitional form midway between Nematoidea
and Chaetognatha ; whilst Gordius, and possibly also Echino-
deres, described by Claparede, /. c, p. 92, and by Greef, Archiv.
fiir Naturgeschichte, 1869, connect the former of these two
orders with the somewhat aberrant Acanthocephali.

cxxxviii

Introduction.

Class, Rotifera.

Vermes with a retractile ciliated disk at the anterior extremity of
tlieir bodies, which are ordinarily microscopic in size, though they
may attain as large a size as -^th of an inch in length. They are
usually more or less plainly annulated externally, but they never
are divided internally into compartments by auy transverse septa.
In most Rotifera tbe entire body is divisible into a ' body ' proper,
and a tail or foot, anteriorly to which tbe digestive and reproductive
viscera with, their ducts and outlets are situated. The ' body ' can
often be seen, when chitinization has not advanced so far as to form
a carapace, not only to be distinctly annulated, but to possess both
circular and longitudinal muscles in its walls. Cilia are never found
on the external surface of the body, except upon the cephalic organ,
whence they take their name ; the chitinous surface of the integu-
ment may develope setiform outgrowths of various shapes, or the
animals may secrete or agglutinate a tube for the lodgment of their
body, or may clothe themselves, as Notommata centrura, with a
mucous envelope. The ' tail' is usually annulated when its integu-
ment is soft, or segmented when it is indurated ; it often carries
paired claw-like processes, or a suctorial disk terminally, and it may
be ciliated externally. Internally it contains muscles and a peculiar
glandular body. It has been considered to represent a fused pair of
arthropodal appendages, by those naturalists who would class the
Rotifera with Arthropoda ; it is more correct to compare it with
that portion of the body of a free Nematoid, anteriorly to which
the anus and generative ducts open; and though the anal outlet
is upon the ventral surface in the Nematoids, and upon the doi-sal
surface anteriorly to the foot in the Rotifers, it must be recollected
the anus is placed dorsally in a veiy great number of Vermes, as
well as in a few of the lower Crustacea with which the Rotifera
have been supposed to be allied. The opening, however, of the
genital organ on the dorsal surface, is a point in which the Rotifera
stand alone among Vermes, but in which they resemble not only
the Arthropoda in question, but also many Echinodermata.

The muscles of the Rotifera appear to be, in some cases at least,
transversely striated; but their ciliated ' rotary ' disk is in most the

Characteristics of Rotifera.

cxxxix

main organ of locomotion. The ingestion of food is dependent upon
the agency of the same organ, on the ventral aspect of which it
almost always lies ; though the anterior portion of the digestive
tract is protrusible in the Rotifera, as in the most typical Annulata.
In the male Rotifera the digestive tract is entirely absent, or repre-
sented only by a rudiment of an oesophagus. In the females of
certain orders, the digestive system consists merely of an oesophagus
and a eoecal stomach, as in Ascomorpha, JSfotommata, Asplanchna ;
whilst in others it possesses a proctuchous intestine which ends in a
cloaca, together with the outlets of the water- vascular and oviducal
apparatus. A gizzard armed with chitinous, often complex,
characteristic jaws is interposed in all female Rotifera between the
mouth and the stomach ; two or more coecal appendages are affixed
to the commencement of this latter organ, which, as also the in-
testine, is clothed internally with cilia.

The Rotifera have no heart; the perivisceral cavity contains a
corpusculated fluid. There are no specialized respiratory organs.
The water-vascular depuratory system has a great development,
taking the shape of symmetrical tubes, which open inferiorly into the
cloaca, and ordinarily, after entering an azygos contractile vesicle ;
and which have appended to them, peripherally at least, as many
as five ciliated infundibula opening into the perivisceral ctivity.

The nervous system consists of a bilobed ganglionic mass, which
is placed above the oesophagus, but does not throw a collar round
it. One or two eye-specks are sessile upon this ganglionic mass ;
and certain spots beset with non-mobile bristles, as well as a tubular
process, the so-called 'respiratory tube,^ are, inasmuch as they
receive nerves carrying ganglioniform intumescences, to be re-
garded as being probably sensory organs.

The Rotifera are dioecious. The males, besides possessing no
digestive tract, and living therefore but a short time, differ from
the females in their external appearance ; in their much smaller
size ; and in their much smaller numbers. The testis and ovary are
azygos glands, and have their external walls continuous with those
of the efferent ducts, opening at the posterior boundary of the body
proper, anteriorly to the ' foot ' or ' tail ' when present, and on the
dorsal surface. Reproduction takes place by means of two kinds of
ova, the ' summer ' and the ' winter ova.-* Of these, the former are
agamogenetic, like the summer ova of the Daphnidae and Cladocera

cxl

Introduction.

amongst the Crustacea ; whilst the winter ova are gamogenetic.
The embryos are developed from the entire yolk, without the
formation of any primitive streak ; and they do not ordinarily go
through any metamorphosis.

They may be either solitary or social. They are mostly inhabit-
ants of fresh water, but some are marine j a few are found living
as parasites upon animal and vegetable organisms. They possess
great powers of recovery after desiccation.

Class, Platyelminthes.

Vermes, with more or less completely flat, leaf-shaped, or tongue-
shaped bodies, devoid both of external annulation and of internal
perivisceral cavity. They are ordinarily aproctous, and, though
possessed of complex reproductive organs, hermaphrodite. Meta-
genesis, with ^alternation of generations/ is very common in this
class. They are divisible into three orders — the Turbellaria, the
Trematodes, and the Gestodes. Of these the two latter are para-
sitic in habit, as is indicated by their possession of organs of adhe-
sion in the shape of suckers or of hooks, or of both, and by their
non-possession of cilia in their adult parasitic life ; whilst the
Turbellaria have a ciliated integument, whence their name is taken,
and never possess either suckers or hooks. Even in the richly
ciliated Turbellaria, the muscular layers of their body-walls are
their active locomotor organs. There are three of these muscular
layers in most Platyelminthes, the innermost, however, is said to
be wanting in certain Turbellarians j like the outer layer it takes,
when present, a direction more or less completely at right angles to
the long axis of the body. Layers of granular glandular substance
are observable in the more deeply-lying of the cortical layers of the
integumentary system of all members of this class ; and crystals of
carbonate, and of phosphate of calcium are very commonly found in
the cortical, and more sparingly in the more centrally placed por-
tions of the body, especially of the Trematodes and Gestodes, and
occasionally also of Turbellaria. Chitinous hooks and spines are
very commonly present, but there is never any extensive induration
of the integument in this Class, either by chitinous or calcificatory
deposit.

The Gestodes, which are always entoparasitic in their sexual

Characteristics of Platyelminthes. cxli

state, never possess any di^^estive tract ; Am,pUptijches nrna, which
appears to be the connecting link between the Tremaiodes, to which
order it belongs, and the Cestodes, is also devoid of this system,
and dependent upon imbibition through the external integument
for nutriment. In the Tremaiodes, and Turhellaria, with the
exception of the Nemertinea in which there is a perivisceral cavity,
the walls of the digestive tract are not separable ordinarily as
distinct layers from the rest of the parenchyma, except so far as the
contents of the hepatic cells, which clothe the interior of the system,
may enable us to distinguish them. In the Trematodes, the
digestive tract consists either of a simple stomachal coecum, or
of two similar structures, appended to a short muscular pharjoix ;
and the two coeca may either each end blindly, or may anastomose,
or may give off great numbers of lateral ramifications. The Tre-
matodes qxq never proctuchous ; and in this those Turbellaria which,
from their possession of a multi-ramified digestive apparatus, are
called ' Dendrocoelous,^ resemble them. The ' Rhabdocoelous ' Tur-
lellnria may be either proctuchous or aproctous. The Nemertine
Turhellaria, which are called ' Rhynchocoelous,' from possessing
a proboscis armed with a calcareous style, and lodged in a tube
distinct from the digestive canal, are always proctuchous. Their
digestive tract takes a straight antero -posterior course, but is
provided with lateral sacculations. The Nemertinea difier further
from the other Platyelminthes in possessing a pseud-haemal vas-
cular system, which consists of a dorsal and two lateral vessels
connected with each other in the neighbourhood of their nerve-
ganglia. All Platyelminthes possess a water-vascular depuratory
system, which opens externally either by a single posteriorly placed
pulsatile vesicle, or by two symmetrical orifices more anteriorly
placed. Its walls are often of difierent characters in various parts,
being contractile towards their outlets, and possessed of vibratile
cilia in their peripheral ramifications, in which again the calcareous
concretions already spoken of are often observed to be contained.
The flatness of their bodies, which enables aeration to be so readily
and thoroughly efiected in the most of the free and in the ento-
parasitic representatives of this class ; and the multi-ramified
character of the digestive and depuratory systems, enable the
Platyelminthes to dispense with specialized respiratory and circu-
latory organs, the more or less cylindriform Nemertinea alone

cxlii

Introduction.

possessing any pseudhaemal respiratory vessels^ and in this as in
so many other points approximating to the Annulata.

The nerve-system consists, in the Trematodes and many Turhel-
laria, of a single pair of ganglia, placed in the anterior part of the
hody, and connected with each other by a transverse commissure.
(See, however, p. 155 infra.) In the Nemertinea it consists of a double
pair of ganglia,connected by two commissures, one passing above and
the other below the proboscis. From these ganglia two main nerve-
stems pass off down either side of the body. Certain Trematodes, in
the free locomotor stages of their larval life, may possess eyes, but
with this exception, it has only been amongst Turhdlaria that
either these organs or auditory capsules have been observed to be
present. In the Nemertine Turhellaria, two ciliated depressions
on the anterior part of the body, underlaid by certain solid organs,
are supposed to be sensory in function. It appears to be doubtful
whether the Cestodes really possess any nerve-system at all; a
structure similar and similarly placed to the single ganglion of the
Nematelminthous Acanthocephali has been described as such.

With the exception of the Nemertine Turhellaria and the proc-
tuchous Ehahdocoela, which are sometimes placed in the same
sub-order with them, all the Platyelminthes are hermaphrodite,
and provided with accessory intromittent male organs, and accessory
vitelligenous, uterine, and receptacular organs. The walls of the
efferent ducts are always continuous with the envelopes of the
sexual glands themselves, except in the Nemertinea, where the
generative glands are sessile upon the body-walls, and no ducts
exist as distinct from temporary, or permanent orifices in those
walls. All Platyelminthes are oviparous, except a few Nemertinea
and a few of the proctuchous Rhahdocoela amongst the Turhel-
laria. In a few fresh-water Trematodes, and Turhellaria with large
ova, the embryos undergo no metamorphoses after leaving the
egg ; but in all other cases the embryos of the Platyelminthes go
through more or less numerous stages of metamorphosis, which
furnish typical instances of what is known as ' digenesis with
heterogony/ and '^alternations of generations.' The histories of
these metamorphoses are complicated in the parasitic orders by the
fact that the different ' generations,' or, in other words, the sexual
and the asexual stages in the metamorphosis, require different
animals as ' hosts ' for their sustentation and lodgment ; and that

Characteristics of the Echinodermata. cxliii

in the Trematodes more than one asexual stage may interpose
itself between the stage of embryo and that of the perfect sexual
form. In the Cestodes, the sexual zooids are retained for con-
siderable lengths of time attached to the asexual zooid, in the suc-
cessive antero-posterior series in which they have been budded off
from its posterior extremity. Compound colonies are thus formed,
in which the setting free of the sexually perfect deuterozooid does
not entail the death of the ' nurse.' In the Trematodes the deutero-
zooids are contained within the body of the ' nurse/ and are only
set free by its disruption and death. Several of the forms of
reproduction observable in the Turhellaria, have been mentioned
above in the history of the Sub-kingdom Vermes.

The Turhellaria possess a great power of repairing injuries and
mutilations, and differ herein very markedly from the Discophorous
Annulata, which have sometimes been classed with them.

Sub-kingdom, Echinodermata.

Animals which may be spheroidal or vermiform, star- or disc-
shaped, but which, whatever their external form, combine with a
radial and, ordinarily, pentamerous arrangement, traces of a bilateral
symmetry always detectible in developmental, and usually also in
adult life. The Sub-kingdom is divided into four Classes, the
Holothurioidea, the Echinoidea, the Asteroidea, and the Crinoidea.
The Class Asteroidea is divisible into two Sub-classes, the Asteriae
and the OpMiiridae.

They possess a water- vascular system which surrounds the com-
mencement of their digestive tract, and, from the central ring
thus formed, sends out prolongations into the radii. Tubular pro-
cesses are developed upon these radial water-vascular stems in all
Echinodermata except the apodal Holothurioidea, and, except in
the Crinoidea, are used for the purpose of locomotion. The
water, with which this system is distended finds its way into it
through the usually calcareous ^madreporic' canal and 'tubercle,'
which are in all Echinodermata, except the Crinoids, appended to

cxliv

Introduction.

the water-vascular ring-, and admit fluid to filter into it, through
their pores, either from tbe exterior sea-water when they are part of
the external skeleton (Astei'oidea, Echinoidea), or from the peri-
visceral cavity when they are contained in it (Holothurioidea).
Other appendages^ either of the nature of accessory reservoirs^ the
' Polian vesicles,'' or of a glandular character, the ' racemose ap-
pendages/ are very ordinarily found in connection with the water-
vascular ring. The madreporic system may consist of a single, or
of multiple canals and tubercles. Triehocysts have been said to
exist in the integument of Synaptidae, but some doubt appears to
attach to this statement. (See Semper, Reisen nach Philippinen
Hffc. iv. 164.) Their integument never developes any chitinous
structures, but is always more or less indurated by calcareous
deposits, and more or less roughened by spinous out-growths.
The calcareous deposits may be almost, or quite microscopic ;
or they may form a continuously and immovably articulated
skeleton for the entire animal, or for its central disc ; the spinous
outgrowths are similarly various in size, as also in shape, and they
may be movably, or immovably articulated to the subjacent inte-
gumentary system. In any case they are normally covered with
an epidermal layer of sarcode, which is often richly cihated. Where
the calcareous skeleton forms a continuous capsule for the animal's
body, the muscular system is correspondingly reduced, and in
Echinoidea there are no specialized muscles except for the movable
spines, and for the pedicellariae homologous with them, and for
the manducatory organs. Where the calcareous skeleton, though
greatly developed, is yet made up of movably articulated pieces
the muscular system may be moderately developed, as in Aste-
roidea, where the water- vascular system is locomotor in function ;
or greatly developed, as in Crinoidea, where it is not. Where, as
ordinarily in Holothurioidea,. the calcareous deposits, botli external
and internal, are reduced to a minimum, the muscular system
attains a very high grade of evolution. There i<; always a large
perivisceral cavity in the Echinodermata, into which the sea-water
finds its way. The digestive tract never communicates with the
perivisceral cavity directly, and is only rarely aproctous. Though
it never possesses any specialized, salivary, or hepatic glands, by
its possession of extensive radial diverticula {Asteriae) or of lengthy
convolutions (Echinoidea and Holothurioidea), the digestive system

Characteristics of the Echinodermata. cxlv

comes to possess an absorbing surface which is by no means incon-
siderable in relation to the other organs of the body. Coeca are
appended to the anal segment of the digestive tract m AsUnae
and Holothurioidea. In the Holothurioidea these coeca take a
creat development, and are known as the ^ungs^ or « respiratory
trees/ and their terminal ramifications are supposed to be perforated,
and to admit the sea-water into the perivisceral space. Eespiration
is fui-ther provided for by the existence of perforations in the nite-
gument, through which tubular processes of the perivisceral spaces
which contain true blood as well as sea-water, project into, the
aerating medium. The very numerous but non-locomotor tubular
processes of the water-vascular system of the Crinoidea must be
supposed to exercise an aerating function, as must also the pro-
cesses of the same system known in certain Echinoidea as ' ambu-
lacral gills.' A system of 'pseudhaemal' vessels exists, in all
Echinodermata, in connection with a ring-shaped vessel or plexus
which surrounds the oesophagus between the nerve- and the water-
rings; and in Asteroidea and Echinoidea it is further connected
with 1 second and circum-anal ring. The branches of this system
are distributed to the viscera and pass into the radial divisions of
the body; when there are two rings present, they are connected by
a pulsatHe sac, the so-caUed heart. The pseudhaemal system has
been often supposed to communicate with the water-vascular and
the perivisceral systems; it differs from them both in not possess-
ing cilia on its internal surface; but this difference would not
disprove the possibility of the several systems being continuous.

The nerve-system .consists in all Echinodermata, so far as is at
present known, with perhaps an exception in the case of the
Crinoidea, of nerve-cords containing nerve-cells which run along
the axis of each ray externally to the pseudhaemal and water- vas-
cular radial stems, and have their proximal ends connected by com-
missures of less complex structure than themselves, so as to form
a more or less pentagonal collar in the peristomial region.

The Echinodermata are, with the exception of the Symptidae,
dioecious; there is no external difference between the sexes, nor
between the generative glands. The generative glands very ordi-
narily have a radiate arrangement ; the ova are usually very small,
and impregnated externally to the body of the female ; but in some
cases they are large, and several species of OpMuridae (Opholepis)

k

cxlvi

Introduction.

are viviparous. In probably every case, except perhaps the last-
mentioned, the impregnated ovum takes the shape of a bilaterally
symmetrical and ciliated larva, provided with more or fewer pro-
visional organs. Where the ova are few and large, and during
development, as in Pteraster, Echinaster, and some other Aste-
roidea, protected by a dorsally or ventrally formed maternal marsu-
pium, the provisional organs may be reduced to a minimum, and the
development becomes ahnost direct. But in most cases the Echi-
nodermata go through a very well-marked metamorphosis, which
often has more than one larval stage. The distinctive character
of the metamorphosis appears to be the possession by the larvae
of at least a mouth and pharynx, which, whether absorbed or cast
off, is never converted into the corresponding organs of the perfect
Echinoderm developed inside of the provisional organism. The
mass of more or less differentiated sarcode, of which the larva or
pseudembryo as opposed to the Echinoderm within it, is made up,
always carries upon its exterior certain bilaterally-arranged ciliated
bands, by the action of which the whole organism is moved from
place to place; and it may be strengthened by the superaddition to
it of a framework of calcareous rods. In the larval Asteriae known
as Bipiimariae, the provisional organism, when discarded, as it is, by
the young Echinoderm, has been observed to retain an independ-
ent vitality for some days ; but it has not been observed to give
rise to any second zooid ; and when we consider the greater tenacity
of life which isolated portions of these animals {Asteriae and Holo-
thurioidea) have often been observed to possess, the history of a
Bipinnaria might appear to be analogous rather to the ecdysis of a
Crustacean, or the metamorphosis of a Dipterous Insect, than to
true metagenesis.

The history, however, given by Professor Grube (Monatsbericht. Konigl
Akad. Wiss. zu Berlin, 12 Marz, 1868) of the discovery of an Echinoid,
AnocJianus sinensis, which, while possessing the external organs, such as
spines, pcdicellariae, and ambulacra, characteristic of adult Echiuodermata,
had neither genital glands nor orifices ; but in place of them an apically
situated sac containing several young Echinoidea in very various stages of
development ; will, if confirmed, cause us to demur to the view adopted
helow (pp. 147, 153), to the effect that in Eehinodcrmata metagenesis
with alternation of generations, as distinct from mctamoiiihosis, is not to
be found. At in-escnt, as hut a solitary specimen has been observed, it

Characteristics of Holothurioidea. cxlvii

n.ay be allowable to suggest that we bave in reality a case of intra-marsu-
piaf development, sucb as that known to occur in Pteraster ra.Ua...

The radial character of the future Echinoderm is first shown in
the formation of the ambulacral elements of the water-vascular
system, which first shows itself as a simple tubular depression, the
future ^madi-eporic' system, on the dorsal surface of the larva.
The Echinodermata are exclusively marme ; some of the Holothu-
rioidea, however, can live in brackish water, or, rather, m the sand
and mud of estuaries. They are never social ; and, with the
exception of Fentacfims, all the living representatives of this sub-
kingdom are free.

Class, Holothurioidea.

Echinodermata, varying in shape from being subcylindrical and
vermiform to being plano-convex like an ordinary snail, with an in-
tegument diiferent from that of other members of the sub-kingdona
with the exception of a single Echinus, in being, through default
of development of the calcareous skeleton, left supple and phab e.
Their mouth is surrounded by a circlet of tentacles which are modi-
fications of the ambulacral feet ; are frequently used as locomotor
organs ; and in certain Bynaptidae, as also in the developing stages
of other Holothurioidea, are provided with suckers. With a lew
exceptions {Byna^tidae and Molpadidae), the Holothurioidea have a
well-developed radial ambulacral system, in addition to their peri-
stomial ambulacral tentacles. If the ambulacra are arranged m five
functionally similar rows, the body of the animal obtams a somewhat
pentagonal outline ; if they are scattered over the entire surface so as
to leave no distinct inter-ambulacral areae, the body is vermiform m
general outline ; if the five rows are divided into a ventral locomotor
?rivium ; and a dorsal bivium, the ambulacral feet in which may have
no suckers, or be wholly absent ; the body comes to resemble that ot
a Gasteropodous Mollusc. In the Molpadidae the radial stems ot
the water-vascular system are present, as also certain tubular pro-
longations of them which pierce the skin, but they have no ieet
developed upon them; in the Synaptidae the water-vascular system
has no radial stems, and consists simply of the circum-oral ring
with its Polian and madreporic appendages, and its ampullae and
branches for the tentacles. In some cases the Polian, glandular,
and madreporic appendages of the water-vascular ring are very

k 2

cxlviii

Introduction.

numerous, and the madreporic canals may be branched as well
as multiple; but in all Holothurioidea the madreporic tubercle
or tubercles are contained withui the perivisceral cavity^ and it is
from thence consequently that the fluid for the ambulacral system
is drawn. The madreporic canal, when single, is always to be found
marking out the inter-radial space of the dorsal bivium by its
suspensory lamellar mesentery. The ambulacral feet of the pedate
Holothurioidea are very frequently strengthened, as in Echinoidea,
by the addition to them of calcareous discs ; they may, however, and
especially along the two rays of the dorsal bivium, as also when
scattered over the inter-ambulacral areae, be tuberculate and conical,
when they are called 'ambulacral papillae.-' All Holothurioidea
possess an internal skeleton iu the shape of a calcareous ring in
relation with the pharynx, and thus with the water-vascular ring,
the nerve-collar, and the annular pseudhaemal plexus. It consists
of five radial ossicles, which are either notched, or, as iu Synaptidae,
pierced for the passage of the water- vessels and nerves, and of a cor-
responding number of inter-radial pieces. The five radial ossicles are
the fixed points to which the five radial muscular bands which give
the body of all Holothurioidea a pentamerous character, are attached.
As the calcareous skeleton, except in a very few cases (Psolus and
Ocnus), is merely represented by spiculae scattered in the substance
of the corium, the muscular system is more largely developed than
in the other classes of this sub-kingdom, the externally-placed cir-
cular layer being especially and distinctively prominent. By means of
this highly-developed muscular system the Holothm-ioidea not only
obtain the power of moving in the same way as the Vermes, but,
so long as its connection with the nerve-system, and that of
the several radial factors of their nerve-system with each other are
uninjured, they possess also the singular faculty of ejecting their
viscera, and in the case of Synapta digitata of dividing their bodies
at various points when injured or alarmed.

The digestive tract is, with the exception of a few Synapiidae,
where it takes a straight antero-posterior course, arranged in convo-
lutions, as in the Echinoidea. It consists of a pharynx and an intes-
tine, between which a small and short muscidar stomach is distin-
guishable as interposed. When these animals discharge their ^^sce^a
upon irritation, the intestinal tract is always separated about the line
of junction of the pharynx and stomach, and immediately posteriorly

Characteristics of Holotliurioidea. cxlix

to the water- vascular ring. The first segment of the digestive tract
is suspended by a muscular mesentery along the middle line of the
dorsal bivium, which is thus made actually as well as morphologi-
cally a line for the bilateral division of the body. The terminal
segment has, as in so many Invertebrata, a respiratory function,
and, in the great majority of Holothurioidea, has certain multi-
ramified coeca, the so-called ' lungs,' or ' respiratory trees'* of the
' Pneumonophorous-' order, appended to it. Where these ' trees' are
absent, as in Byna'ptidae, certain ciliated ftmnel-shaped organs are
to be found bestudding the mesenter j ; and as these organs are in
the Gephyreau Worms similarly absent, or present, accordingly
as in them cloaeal respiratory trees are present (EcJduridae), or
absent {Sipunculidae), the two sets of organs may be supposed to
stand to each other in a supplementary relation. The apical termi-
nations of the respiratory trees are supposed to be perforated, and
thus to furnish a route whereby the sea-water can find its way
into the perivisceral cavity. As the cQiated infondibula are, accord-
ing to the figm-es of them given by Sars, Norges Echinodermer,
Tafs. XV. xvi. ; and Leydig, Lehrbuch der Histologic, p. 391, fig.
203; Miiller's Arch., 1852, p. 514; connected with a system of
vessels in the mesenteric membrane, it would appear that they may
discharge the same function.

To the respiratory trees or to the cloaca whence they arise,
the so-called ' Cuvierian organs ' are appended, which may have a
glandular function, but which are probably organs of defence, as
they are observed to be very readily discharged upon irritation.

The pseudhaemal system consists of two main stems, connected
the one with the dorsal, and the other with the ventral line of the
digestive tube ; and of a circular plexus representing the circular
pseudhaemal vessel surrounding the pharynx. These two vessels
are connected with each other by reticulations in the walls of the
intestine, and the 'rete mirabile' developed by the dorsal vessel is
brought in many cases [Aspidochirotae) into intimate connection
with the left respiratory tree.

The nervous system is said to differ from the nerve-systems of
other Echinodermata by having its circular commissural collar
thicker than the radial ' Ambulacral-gehirne.' It appears, however, to
be of less complex structure, and it must be recollected that in some
other Echinodermata the radial stems taper towards their proximal

cl

Introduction.

as also towards their distal ends. Organs of special sense, in the
shape of otolithic vesicles, have been observed in Bynaptidae ap-
pended to the radial nerve-cords just where they pass through the
foramina in the radial ossicles of the internal calcareous ring.

With the exception of the Synaptidae, the Holothurians are
always dioecious, resembling in this all other Echinodermata, but
differing from them in never having the radiate arrangement re-
tained in their generative glands. These organs take the shape of
longer or shorter, simple or branched coeca, which are attached to
one or both sides of the inter-:^adial dorsal mesentery, and discharge
their products by a single duct running in the same medio-dorsal
line to open either posteriorly to, or within the circle of oral tentacles.
In one case, Solothwia tremula, the development has been observed
to be nearly direct, the provisional organs being represented merely
by a rapidly-disappearing layer of ciliated sarcode ; but in most cases
there are two larval or pseudembryonic forms, the earUer of which,
Auricularia, possesses a mouth and alimentary canal, and special
bilaterally symmetrical natatory lobes, whilst the second, the
so-called ''pupa,-' is ban-el-shaped, devoid of mouth and of lateral
outgrowths, and girded with five zonular ciliated bands, which dis-
appear as the ambulacral system is developed.

Class, Eehinoidea.

Echinodermata varying in shape from that of a sphere to that of
a disc, with, in all living species but one, in which the skeleton has
been reported to be flexible, an immovably articulated external
shell, the so-called 'corona,' which, with its ambulacral and inter-
ambulacral spaces, occupies the entire exterior of the body, with the
exception of a small circum-oral and a small anti-ambulacral cir-
cum-anal area. When the mouth and anus are at opposite poles,
the Eehinoidea are called ' regular,' or ' endocyclica ;' when the anus
is placed excentrically, they are called * irregular,' or ' cxocyclica.'
The two types are mutually connected by transitional forms ; the
irregular shows bilateral symmetry very ob\aously ; the bivium,
however, and the trivium do not hold the same relations to the
dorsal and ventral surfaces as in Ilolothurioidea. The locomotor
feet are in many of the regular forms uniformly sucker-shaped, and
provided with a distal calcareous support ; but the dorsal feet, even
in some regular forms, may lose their sucker-shape ; and in the

Characteristics of Echinoidea. cli

irregular forms Spatangiclae and Clypeastridae, they take very-
various shapes, and amongst them that of the so-called ambulacral
gills, which form a rosette of petaloid ambulacra limited to the
apical half of the shell.

The madreporic plate is always to be found at or near the apical
pole of the body, and is usually fused with one or more of the
genital plates. Five eye-bearing plates alternate radially with the
inter-radially placed genital plates. The ambulacral plates lie ex-
ternally to the free radial water-vascular trunks, but there are
certain internal calcified processes, the so-called ' Auriculae/ which
may, as in the genus Clypeaster (Lam.), EcJiinanthus (Miiller), attain
a great development, homologous with the internally-placed ambu-
lacral ossicles of the Asteroidea. Both the ambulacral and the inter-
ambulacral plates are beset with very numerous movably-arti-
culated spines of the most varied forms, between which pedicellariae
are, as in Asteriae, interspersed. In Spatangidae certain areae, the
' semitae,' are occupied by bristle-like appendages, which have club-
shaped ends, are strengthened internally by calcareous deposit, and
are covered externally with cilia.

The tentacular corona of the Holothurioidea is represented in
Echinoidea by certain largely-developed ambulacral feet placed
radially on the innermost circle of the peristomial area, and imme-
diately therefore on the edge of the mouth. But in EcJiinidae and
Clypeastridae, a complex prehensile masticatory apparatus exists
as the so-called ' Lantern of Aristotle,' at the entrance of the diges-
tive tract. The teeth of this apparatus are lodged in inter-radially
placed, alveoli, composed of two main and two accessory pieces,
and alternating with radially-placed structures, each consisting
in Clypeastridae of one, and in Echinidae of three, ossicles. The
elements in the radially-placed portion which both families alike
possess, are known as the 'rotulae' or 'falces,' and as they, like
the radial elements of the calcareous ring of the Holothurioidea,
cover in the junctions of the radial water-vascular trunks to
the central water-vascular ring, and as they resemble them still
further in not belonging to the perisoma, but being true internal
calcifications, they would appear to be, as Miiller taught, homo-
logous with them.

An oesophagus, and sometimes, as in Echinus saxatilis and Spa-
tangus, a coecum, is distinguishable at the commencement of the

clii

Introduction.

digestive tract ; wliicli, in the rest of its course, is intestiniform and
attached by a fenestrated mesentery in festoons round the interior
of the shell. They are never aproetous.

The pseudhaemal system has a circular vessel developed both at
the oral and apical poles, the ring- at the oral pole Ipng inferiorly
to the water- vascular ring at the base of the dental apparatus. The
two rings are connected by a pulsatile sac, the so-called ' heart,' and
vessels are given off to the viscera, arid especially to the intestine.

Special respiratory organs are developed in many Ecliinidae in
the shape of arborescent outgrowths communicating with the peri-
visceral, but, according to most authorities, not with the water-
vascular system, and arranged in the peristomial area. They are
absent in the Echinoidea with petaloid ambulacra, the widely
expanded lamellar gills carried by which exercise an aerating
function.

The nerve-pentagon lies immediately below the oral peristoma, at
a much lower level than the pseudhaemal and water- vascular rings.
The nerve-stems, which are given off from it radially, are much
wider in the middle part of their course than at either distal or
proximal end.

It is of importance to note, that, though growth ordinarily takes
place in Echinoidea in the way of interpolating fresh plates at the
apical pole of the corona, similar additions may be made in Cidaris
at the oral pole to the movable plates which, in that genus, are
prolonged on to the peristomial area from the immovably arti-
culated corona.

The generative glands in the regular forms are five in number,
opening by five separate ducts in the five genital plates. In the
irregular forms, Spatangidae and Clypeastridae, there are only four
genital glands, ducts, and plates.

The larva is pluteiform, and strengthened by a calcareous frame-
work. The embryo appropriates no part of the larva except the
stomach and some formative blastema which is aggregated round it.

Professor Gnibe is rcpoi'ted by Dr. Semper, Eeisen im Archipel dor
Philippincn, p. 163, to have met with an Echinid with a perfectly soft
integumentary system. The structural diffei-ences between such an animal
and a Holothurian would be comparatively small — the resemblances vciy
numerous. Amongst them may be mentioned, as probably existing, the
possession of calcareous discs by the feet ; the presence of specially mo-

Characteristics of Asteroidea.

cliii

dified feet homologous with the Holothurian tentacles on the peristomial
area, and the peeiiliarities of the digestive tract. The ordinary represen-
tatives of these two classes resemble each other in the small size of their
auti-ambulacral area, and in the tendency they have to assume bilaterally
symmetrical forms. Their developmental history, however, is very
different.

Class, Asteroidea.

Echinodermata, with flat, star-shaped, or simply pentag-onal, bodies,
with a well-developed and functionally locomotor water-vascular
system, the amhvilacral surface in relation with which is developed
commensurately with the anti-ambulacral^ centrally or sub-centrally
in which the. anus, when present, opens.

The Asteroidea differ from the other Echinodermata in having a
well-developed ' internal skeleton/ externally to which their nerve -
cords and radial ambulacra! vessels lie. This system is represented
rudimentarily by the auriculae of Ecliinidae, and the similar but
more developed internal structures of Clypeaster ; but it is whoUy
wanting in the Crinoidea.

The Asteroidea are divided into two sub-classes^ the Asteriae and
the Ophiuridae ; in the former of which the arms^ firstly, are pro-
longations of the central disc ; and^ secondly^ contain within them
prolongations of the digestive tract, and portions, or the whole of
the reproductive organs j and thirdly, are furrowed on their medio-
ventral surface for the reception and protrusion of the ambulacra!
feet; whilst in the latter, the arms are difl^erentiated from the
central disc, not only by their mode of taking origin from it,
but also by not containing any portions of the viscera of or-
ganic life, and by not having any medio-ventral ambulacral
furrows, but in place of them, ordinarily, a row of dermal
scales, on either side of which the feet are protruded. The verte-
bral ossicles of the Ophiuridae resemble those of the Asteriae in
being composed of two symmetrical halves ; but these two halves
are articulated together immovably, except in the pair next the
mouth, whilst the entire series of mesial ambulacral ossicles is in
Asteriae composed of mesially and movably articulated bilateral
halves, for the adduction and divarication of which special muscles
are developed. The Ophiuridae have not the internal prolongations
of the branches of the radial vessel to the feet, which are known in
Asteriae and the other higher Echinodermata as ampullae; but

cliv

Introduction.

these branches are lodged in a separate canal, leading from the
central demi-canal, in which the nerve-cord and the radial water-
vessel are both lodged, outwards. The madreporie tubercle, instead
of being a prominent object on the dorsal surface as in Aster iae,
is situated on the ventral surface, where it is either distinct but
very small as in Astrophi/ton, or partially fused with, and concealed
by one of the oral plates, so as to communicate only by a very
small pore with the exterior. There are no pedicellariae in the
OpMuridae. The OpMuridae have a digestive system consisting of
a simple sac without diverticula or anus ; whilst, except in the thi-ee
genera Astropecten, Ctenodiscus, and Luidia, the digestive tract
of the Asteriae is always proctuchous, and is without any excep-
tion even in the case of the genus Brisinga, which is described
as being intermediate in character between the two Sub-classes,
is prolonged for a greater or less distance into the arms.

The feet of the OpMuridae differ from those of the Asteriae, with
the exception of the three genera just mentioned, in not possessing
terminal suckers. In some further points in which the OpMuridae
differ from the Asteriae they appear to resemble the Echinoidea.
Their feet sometimes show a tendency to eflBioresce into lateral
ampullae, and thus to approximate in character to the ambulacra!
giUs and tactile feet of certain Echinoidea ; they possess a calcified
peristomial apparatus which finds its homologue in parts of the
peculiar manducatory apparatus found in that class, but which is
not represented in Asteriae ; and their larvae, finally, are plutei-
form, whilst those of the Asteriae are vermiform, and never possess
a pseud-embryonic calcareous skeleton. It is mainly upon the
descriptions of such transitional or inter-connecting living forms
as Brisinga endecaencmos ; and of such fossil forms as Protaster
and Paleodiscus, that a justification of the placing the Asteriae
and OpMuridae together in one Class must rest.

Class, Crinoidea.

Echinodermata with arms radially appended to a central disc or
' calyx,^ which disc at one period of their lives, or permanently, is
attached by a segmented peduncle to marine objects. They pos-
sess a well-developed dermal skeleton, which is movably articu-
lated in the arms, but immovably in the region of the disc. The
water- vascular system gives off a great number of tentacular tubules

Characteristics of Crinoidea.

civ

along- the furrows, which radiating- from the mouth pass down
the medio-ventral surface of the arms, and of their laterally arti-
culated pinnulae. But the water-vascular system appears to be in
the Crinoidea wholly, as it is in other Echinodermata partly,
respiratory in function. The segmented arms can execute exceed-
ingly active movements by means of the muscles with which
they are provided; but these movements are mainly confined to
the action of closing the arms upon the oral surface of the disc,
and so protecting it from the contact of irritating matters. The
act of swimming from place to place however by the alternate
action of the arms, is by no means so habitual to the Crinoidea as
has been supposed. The Crinoidea are dependent mainly upon the
action of cilia lining their digestive tract, and partly upon that of
the similar structures upon the integument of their arms, for the
ingestion of alimentary matters. Their oral surface is, in the
natural condition, always turned upwards ; the digestive tract,
in the living genera, Antedon and Pentacrinus, possesses an anus
opening in one of the spaces between two of the water- vascular
furrows radiating from the mouth. The digestive system is confined
to the central disc ; but the perivisceral space has tubular prolong-
ations along the arms and their pinnules, whereby the nutritive
fluid is on the one hand itself aerated, and on the other brought into
relation with the powerful muscles whereby the movements of the
arms are executed. Their generative organs differ from those of
aU other Echinodermata in being lodged externally in the mem-
branous lamellae developed from the ventral surfaceof the pinnulae,
and in setting free their products' simply bydehiscence. TheT^va
or pseud-embryo gives rise within itsehf to a second form, which,
without taking up any part of the short digestive tract of the first,
developes a peduncle which is discarded in Antedon, but is per-
manently retained in Pentacrinus.

Jointed cirri project at intervals from this peduncle in Pentacrinus,
and in the non-pedunculate Antedon are attached to the aboral surface
of the calyx. The existence of these cirri would appear to show that
the true homologue of the 'arms' of the Crinoidea is to be found in
the ambulacral tentacles of the Holothurioidea, whilst they themselves
are homologous with the radial ambulacra of other Echinodermata.
It shows further that the Echinodermata are in Mr. Herbert Spencer's
language ' tertiary' rather than 'secondary aggregates,' a view to which

clvi

Introduction.

elsewhere in tlie sub-kingdom, evidence is only obscurely borne in the
mode of growth of the Echinoidea, and possibly also in the spontaneous
self-mutilation and division observable amongst the Holothurioidea.

See, for the development of Antedon Rosaceus, {Comatula Rosacea,)
Professor Wyville Thomson, Phil. Trans., 1865 ; Dr. Carpenter,
ibid., 1866.

Sub-kingdom, Coelenterata.

Radially-arranged or bilaterally-symmetrical animals, in which
the general cavity of the body and that of the digestive sac are
always continuous. They may be fixed or fi-ee, solitary or social ;
they are exclusively aquatic, and almost exclusively marine. The
walls of the body consist always of two layers, an ectoderm and an
endoderm; both, but especially the outer layer may become in-
dm-ated by interstitial deposit j and the outer layer may secrete a
more or less hard exterior cell. Both laj^ers, but especially the
exterior, are provided with ' thread-cells/ and both layers, but es-
pecially the interior, are, at one period or other, ciliated. The mouth
is the only outward opening of the digestive tract ; it is ordinarily
surrounded by a corona of tentacles, the hollow interior of which
is continuous with the general body cavity. This cavity may be
a simple and direct prolongation of the digestive sac ; or this sac
may, whUst suspended by its sides in the perigastric space, open at
its bottom into it. Tlie interior of the stomach and of the general
body cavity being ordinarily ciliated, circulation is maintained in
the alimentary fluids; but there is no tubular vascular system of
any kind, nor any specialized respiratory apparatus in these animals.

The Sub-kingdom is divisible into three Classes, the Cteuophorae
of which the Cesium Veneris^ the Ci/dippe, and the Beroe may be
taken as examples ; the Anthozoa ; and the Hydrozoa.

A nerve-system has been supposed to exist centrally in the Cte-
nophorae ; and peripherally, as special sense organs in the Medusae
in their marginal cysticles, but much doubt has been justifiably
raised as to the really nervous character of the structures in
question. (Sec Claus, Zeitschrift Wiss. Zool., xiv., 1864, pp. 385,
388). The Ctcnophorae are hermaphrodite ; the Anthozoa and Hy-

Characteristics of Ctenophorae.

clvii

drozoa are ordinarily dioecious. The generative prodyicts are always
developed between the two layers of the body walls ; and are dis-
charged by dehiscence, either into the external medium in which the
animal liveSj as in Hydrozoa ; or into the perigastric cavity, to be
thence discharged by the digestive tract, as in the two other Classes.
Reproduction may take place asexually by gemmation or by fission ;
and the power of repair and regeneration is very great. The sexual
method is very ordinarily accompanied by metamorphosis and meta-
genesis; and the variety of forms found in any one of the compound
specieSj is often increased by the specialization of certain zooids to
particular functions, so as to be pm-ely agamic and digestive, purely
motor as in Siphonophorae, or purely reproductive.

Class, Ctenophorae.

Bilateral Coelenterata, ordinarily oval, rarely cestoid in form;
the place of the corona of tentacles seen in the two other Classes
of Hydrozoa and Anthozoa, is taken ordinarily by a pair of long
highly contractile cord-like prehensile organs, the interior of which
communicates with that of the system of canals, representing the
body cavity, and the exterior of which is armed with thread-cells.
Their most distinctive characteristic, and the one whence they take
their name, is the possession of four pairs of motor organs, con-
sisting of parallel comb-like rows of plates, which work like paddle-
wheels in propelling the creatures. They are all marine, and
never microscopic in size, nor social, nor indurated by deposit of
any kind. They differ from the Anthozoa in having the inter-
mesenteric spaces of the body cavity reduced to a system of bilateral
canals by the increase of the gelatinous parenchyma ; and from the
Hydrozoa, in having the stomach surrounded by, and suspended,
though not freely, in a perigastric cavity ; and from both, not only
in their well-marked bilateral symmetry, but also in having a com-
munication between the external medium and the body cavity, not
only through the digestive tract and the mouth, but also by means
of a funnel-shaped, and ordinarily bifid canal at the opposite pole of
the body. A central nerve-system, consisting of a single or double
ganglionic mass, has been supposed to be demonstrable in these
creatures at the point where the funnel-shaped canal just mentioned
comes into communication with the system of perigastric canals,
and to send branches in correspondence with the rows of swimming

clviii

Introduction.

plates. An otolithic cysticle, sometimes called the ' ctenocyst/ is
situated at the point of junction indicated. (See, for the doubtM
character of the nerve-system, Claus, Zeitschrift fiir Wiss. Zoologie,
1864, p. 386.) The Ctenophora are hermaphi-odite, the testes and
ovaries being placed on either side of each of the eight canals, cor-
responding with the rows of swimming plates. The development
of the embryos, which are as in Anthozoa set free through the
mouth, is ordinarily simple; but they are in some instances fur-
nished with provisional ciliated and other organs.

Class, Anthozoa.

Coelenterata, of sub-columnar form, with their mouth surrounded
by a corona of tentacles, the number of which is either four or six, or
some multiple of fom- or six, contrasting herein, as in so many other
points, with the pentamerous Echinodermata. Their opposite imper-
forate extremity is ordinarily fixed ; and they are ordinarily social.
They are all marine, and may be no more than a line in length and
breadth. With the exception of Actmidae and Cerianthidae, all have
the external integumentary system more or less indurated by inor-
ganic deposits, which form ' the coral structures.' These structures
are ordinarily divided into two classes, accordingly as they have been
supposed to be cuticular formations or ' foot secretions,' when they
have been called ' sclerobasic / or to be due to deposition within
the tissues, when they have been called ^sclerodermic;' but doubt has
been thi'own on the soundness of this distinction by Kolliker (see
Icones Histiologicae, ii., pp. 1 17-170). The body cavity is not only
directly continuous with the cavity of the stomach by means of an
orifice at the bottom of this latter cavity, but it is also continued
upwards round the outside of the stomach, which is freely suspended
in it by means of lamellar mesenteries. These lamellae divide the
body cavity into a series of radially-ai-ranged chambers, which again
are prolonged upwards so as to be continuous \\iih. the interior of
the tentacles. The interior of the tentacles may communicate
directly with the exterior by perforations placed at their lips, as
may also the general cavity of the body by peripherally-placed aper-
tures called ' ciuclides.' In Cerianthus and Fcachia, the axis of the
foot may be perforate.

The Anthozoa are, with the exception of Cerianthus, dioecious.
The generative organs are developed in the mesenterial lamellae.

Characteristics of liydrozoa.

clix

The embryos are discharged by the mouth of the i^areut as free
ciHated larvae of smaller size and with fewer tentacula, or without
any, but in other points they are like their parents. Reproduction
may take place also in the asexual ways of gemmation and of fission,
and the entire animal may be regenerated from a separated frag-
ment ; but there are no ' Medusae' in this Class.

Class, Hydrozoa.
Coelenterata, which may be fixed or free, social or solitary, but
which are often of much smaller size, and invariably of a simpler
construction than either of the other two Classes in this Sub-
kingdom. The wall of the digestive cavity is continued directly
into that of the body cavity, or, in other words, the stomach is
never suspended freely in a perigastric cavity. The general body
cavity is prolonged, under the form of ' gastro-vascular canals,'
through the parenchyma of the body, and into the interior of the,
tentacles. The body wall is made up of two layers, an ectoderm,
which in early stages is ciliated, and in later is very richly provided
with thread-cells; and an endoderm, which is ordinarily ciliated, and
keeps up a circulation in the gastro-vascular fluids, and contains
also some, but fewer thread-cells than the ectoderm. The outer
layer of the ectoderm secretes a chitinous tubular polypary in the
fixed orders, with the exception of the Hydridae ; the deeper layers
of the body may attain in the free forms a greater or less amount
of induration, either in a disc-shaped (Medusae), or tube-shaped
[SipJionopJiorae) mass ; but it is only rarely that in the fixed orders
any calcareous deposit takes place, as in the Litliydrodea. (See,
however, Kolliker, Icones Histiologicae, ii., p. ii7)- No central
nerve-system has been demonstrated in these creatures j the mar-
ginally-placed cysticles of the Medusae may represent special sense
organs. The Hydrozoa are rarely hermaphrodite ; the generative
organs are developed in them as in all Coelenterata between the
two layers of the body walls, but owing to the absence of any
perigastric cavity, such as that of the Anthozoa and Ctenophora,
they come to be placed externally, and to be discharged into the
water not through the mouth, but simply by dehiscence of the
exterior layer. Reproduction may be asexual in the way of gem-
mation frequently, and of fission rarely ; development may be nearly
direct, as in Tuhularia and Coryne Van Benedenii, where the stage

clx

Introduction.

of a ciliated embryo, s. 'planula/ is wanting; or it may be aceom-
plished by metamorphosis, complicated with ' alternation of genera-
tions.' In this latter case the specialized generative zooid may be
either fixed to the asexual eoenoecium, or set free as a medusifbnn
zooid.^ The power of repair and of regeneration after injuries, and
from isolated portions of body substance, is very great.

Sub-kingdom, Protozoa.

Organisms, which, being ordinarily microscopic and unicellular,
rarely have their exterior outlines fixed in definite forms, or their
interior parenchyma distinguished by much histological difi-erentia-
tion. By the absence of a rigid external envelope the unicellular
Protozoon is distinguished from most forms of vegetable life, except
the Mycetozoa and the locomotor gonidia of certain Ciyptogamia ;
and by the absence of histological difierentiation in correspondence
with the difierent vital functions, it is distinguished from most or
all higher animal organisms. The greater part, or even the whole
of the body of a Protozoon, may consist simply of Protoplasm,
s. Cytoplasm, s. Sarcode, which may vary from being purely
hyaline to being markedly granular, and from being semifluid to
being exceedingly viscid and strongly coherent, but which, chemi-
cally, is nitrogenous, and physiologically, contractile. The exterior
or cortical layers of the body ordinarily difier more or less in con-
sistence from the interior ; they may secrete a calcareous, or agglu-
tinate an arenaceous shell; and the internal layers may, in their
turn, furnish themselves with a solid support in the shape of an
internal skeleton composed of inorganic, siliceous, or calcareous
particles, or of organic homy substance. In some cases an exter-
nal shell is secreted, of an organic substance resembling chitiue.
Movement may be accomplished by the contraction of the general
mass of the parenchyma, as in Gregarinae ; or the protoplasm may
develope cilia, as in Infusoria; or pseudopodia, as in other Pro-
tozoa. Nutriment is absorbed in some cases by the general paren-
chyma of the body which envelopes the alimentary matter wdthin
its own substance, as in Amoehina and Actinophryna; or the entire
animal may live immersed in an atmosphere of assimilable albumen,

Characteristics of the Protozoa.

clxi

as is the case with the parasitic Gregarinae, and absorb soluble
pabulum at all points of its exterior. In other cases the pseudo-
podia, in which a constant cyclosis of the granular cytoplasma may
be observed to be carried on between the central part of the animal's
body and its radial processes, act as suctorial and absorbing organs.
In one class only, the Infusoria, do we find both mouth and anus ;
but these two orifices are not connected with each other by any conti-
nuous tubular canal, the ingested aliment passing from the mouth and
oesophagus into the general parenchyma of the body, and the refuse
matter finding its way into the neighbourhood of the anus, whence
it is extruded by the contractile sarcodic substance surrounding it.
In many Protozoa the vacuolation of the contractile protoplasm
produces the structures known as ''contractile' or ''pulsatile vesi-
cles,' which have sometimes been regarded as a rudimentary circula-
tory apparatus, but which, as they have sometimes been observed
to open externally, may with more probability be considered to
be depuratory in function, and to correspond with the water-vas-
cular system of higher animals. No specialized respiratory nor
nervous system exists in this sub-kingdom, unless the red pigment-
specks of certain Infusoria may be considered to correspond to
eyes.

Reproduction is ordinarily asexual, taking place in tbe ways of
fission and gemmation, but in the Spongiadae and Infusoria we find
true sexual reproduction by means of ova and spermatozoa. Encys-
tation very frequently accompanies the agamogenetic, and conju-
gation the sexual process.

The Protozoa may be either solitary or social, and are found
either in sea or fresh water, or as Entozoa, but their respiration is
never aerial.

The Gregarinae would by most writers be considered, as they are here,
to be the lowest of the Protozoa. Their ento-parasitic habits, however,
which will account for much of the simplicity or degradation of their
organism, must not cause us to overlook their close affinity to certain
forms of Rhizopoda, especially the Amoehina; and it has been rather
from considerations of convenience, which, in the absence of any actual
demonstration of genetic affinity, have weight in classification, that they
have been here separated from that class. The Rhizopoda are by some
writers placed higher, by others lower, in the scale of life than the lufu-

l

clxii

Introduction.

soria ; but tlie ' polyinor])liismus' of tlieir more complex forms, amongst
wMdi the EadiolaHa are usually included, may be considered in some
sense to counterbalance tlie higlier gi-ade of specialization to wliicb the
Infusoria in virtue of tlieir digestive, reproductive, and motor organs,
must be allowed to have attained. The Spongiadae should, for the same
reason and in the same sense as the Ehizopoda, be placed in co-ordinate
rank with the Infusoria.

It is not rarely difficult to differentiate a unicellular organism as animal
or vegetable, unless we happen to be acquainted with its past or future
history. The gonidia of many Algae are locomotor, ciliated, possessed of
contractile vesicles, and devoid, whilst yet active, of that eminently vege-
table structure, an encapsulating envelope of cellulose. Whilst these
organisms imitate the movements, structure, and chemical composition
of the Infusorial Protozoa, the mycelium of certain Fungi, the Myxo-
gastres, s. Myxomycetes, which have hence been called * Mycetozoa,' is
similarly devoid of any cellulose envelope, and exhibits the pseudopodial
movement so characteristic of Rhizopoda ; while such forms of life as
Euglena Viridis and the Volvocineae must be held to belong to the
vegetable kingdom, not so much on account of the abundance of chloro-
phyll in their parenchyma, as because of the history of their develop-
ment, in which a period of quiescence and encapsulation in cellulose is
readily observable. ■

There are not a few organisms for the identification of which, as
belonging to the animal or vegetable kingdom, we have no other guide
than a consideration of their gradational affinities to other organisms, as
to the position of which in one or other of the two kingdoms there can
be no question. By the application of this test, it would seem that the
Monera of Professor Haeckel should be ranked as animals, as they are so
closely similar to certain of the Rhizopoda, as to the right of which Class
to be considered as animal few other naturalists would raise a doubt.
And as either from the point of view furnished by the facts of gi'adational
affinity, or from that into which we are put by the knowledge of the
history of development, probably all the other forms of life out of which
the naturalist just mentioned has formed a third Kingdom of life, the
Regnum Protisticum, can, without violence, be regarded as either animal
or vegetable, the necessity for accepting such a third Kingdom would
appear to be doubtful.

In dealing with the microscopic organisms, about the position of which
it is possible to raise a doubt, the most unambiguous criterion is that
which the formation of an external envelope of cellulose, when present,
furnishes. When this means of deciding is absent, the exhalation of

The Regnum Protisticum. clxiii

oxygen, aud the power of supporting life upon inorganic matters, are,
perhaps, the two points to which we should next look, though both of
them would fail us in the case of the Fungi. The presence of chlorophyll
in very great abundance in the parenchyma of an organism points, though
less certainly, than any of the three characters already specified, to the
vegetable character of an organism. Stentor, however, among Infusoria,
Hydra among Coelenterata, Vortex amongst the Turbellarian, and Bo-
nellia amongst Gephyi-ean Worms, are said, though not in all cases upon
the evidence of the spectroscope, to possess this chemical substance as an
essential ingredient of their parenchyma irrespective of any which may
be ingested with their aliment. An organism which should be seen to
envelope alimentary substances within its own parenchyma would be, in
almost any case, rightly considered an animal ; but this test would fail
with the ento-parasitic forms of either kingdom which live by the ab-
sorption of the soluble nutriment in which they live immersed at all"
points of their exterior ; and would further be held by most naturalists
to prejudge unfairly the allocation of organisms feeding by means of suc-
torial pseudopodia, in the face of the preponderating evidence in favour
of theii' animality which the totality of their history offers. It would
fail also, in the cases of the spermatozoa, which may be called the male
'gonidia' of most animals, and the male zooids, the ' complemental males,'
of a few animals, such as the Cirripedia.

Irritability, contractility, locomotion and the ' cyclosis,' or circulation
of absorbed and assimilated nutritive matters, are phaenomena universal
in the animal, and occasionally observable in the vegetable kingdom ;
whilst the secretion of chlorophyll, and of cellulose, and the power of
regenerating an entire compound organism from a more or less frag-
mentary portion, are properties nearly though not quite universal in
vegetables, and only occasionally noticeable among animals. It may be
anticipated that in the few cases in which it may at present be difficult to
decide with perfect certainty as to the animal or vegetable character of
an organism, an increase in our knowledge, if not of its very simple
structure, yet of its development, and if not of either its development or
its structure, yet of the development and structure of forms which by
gradual transitions connect it with undoubted animal or undoubted vege-
table forms, is likely at some time to enable us to place it in one or other
of these two kingdoms of life. But it must be said that there are organ-
isms which at one period of their life exhibit an aggregate of phaenomena
such as to justify us in speaking of them as animals, whilst at another
they appear to be as distinctly vegetable. A monad may at one period
be possessed not only of a nucleus and contractile vacuole, but of a cilium,

l2

clxiv

Introduction.

by the aid of which it swims about ; at another it may have lost its
cilium, and effect locomotion by the protrusion of pseudoiiodia, like an
Amoeba ; whilst in a third it may surround itself with an envelope of
- cellulose. If it should prove to be true that organisms as high in the
scale as the Amoebina and Aclinoplwyna, can have their development
traced back to the specialization of protoplasm within vegetable cells,
it Avould appear to be necessary to adopt a phraseology which should
speak of such creatm-es as being at one time plants, and at another
animals.

Class, Infusoria.

Protozoa^ which have the external layers of their bodies so far
indurated as to give them more definitely-fixed external outlines
than the other classes of the Sub-kingdom, and are provided, except
in the case of the adult Acinetina, with cilia as motor organs. They
may secrete a cuticular shell or carapace, distinct from their more or
less indurated external cortical cuticular envelope, but they never
form any shell or skeleton of inorganic substances. They always
possess a nucleus and nucleolus, which are in function ovary and
testis respectively, and a contractile vesicle ; and with the exception
of the order Acinetina, which is provided with suctorial tentacula,
and the parasitic genus Opalina, they have always a mouth and
anus. From the mouth a short oesophagus lined with a prolonga-
tion of the cuticle leads ordinarily, and opens by an oblique or
transverse aperture, into the central parenchyma of the body, which
is more loosely compacted than the cortical layers. In the inter-
trabecular or vacuolated spaces of this central parenchyma, the
ingested alimentary particles are circulated together with the water,
along with which they are drawn in by the ciliary currents ; and
from it the refuse particles are finally extruded by the anus, into
which there is only rarely a tubular process of the cuticle prolonged.
The cortical layers of the parenchyma are less difiluent than the
central, and in them we find the contractile vesicle, the generative
nucleus with its adherent or closely approximated nucleolus, the
trichocysts, and a certain amount of very fine pale granular matter.
By the use of reagents, it is easy to see that the cilia are in reality
processes not of the cuticular membrane, but of the outer layers of
the enclosed parenchyma ; and they must therefore when protruded
find their way through very fine orifices in the external envelope.

Characteristics of Rhizopoda. clxv

This membrane is not always demonstrable, and appears to be occa-
sionally wanting", as in Oxytrichina. The contractile vesicles may
be very numerous, as in Trachelius ovum, but ordinarily they are
not more than two in number. They are in some cases seen to give
off vessels into the body ; and they are said to communicate with
the exterior, and thus to become analogous to the water-vascular
rather than, as is often said, to the circulatory system of higher
animals. The so-called ' nucleus'' or ovary may vary in sbape from
that of a spheroid to that of a horse-shoe. The ' nucleolus^ or
testis is also very variable in sbape, but is usually closely apposed
to or immersed in tbe substance of the ovary, which is much larger
in size.

In sexual reproduction the ' nucleus^ breaks up into a number of
ova, which it is probable are directly transformed into embryos. It
is often seen to be preceded by conjugation, in which the spermatic
elements of the two individuals have been supposed to be inter-
changed.

Asexual reproduction takes place in the ways of gemmation,
when compound colonies may be formed, as in Episiylis and Car-
chesium; and of fission, which is ordinarily preceded by encystation.

Class, Rhizopoda.

Protozoa possessed of pseudopodia, by which, in the absence of
cilia, the functions of locomotion and of ingestion of aliment are
performed. Their bodies may consist of sareode alone without any
morphological element except fine granules, and without any cell
wall ; and in these cases a calcareous shell may be secreted, as in
the majority of the Foramini/era, or a test of organic cbitin-like
substance, as in Gromida ; or an external casing may be formed by
the agglutination of arenaceous particles, as in Lituolida; or the
sareode may show considerable difierences between its central and
peripheral layers, and may contain a nucleus and a contractile
vesicle, but be devoid of any external inorganic deposit of the
nature of a shell, as in Amoehina and Actinophryna ; or, finally,
the sareode may be divided into two portions by a central capsule,
and be further supported by a siliceous skeleton, in which case
both the extra-capsular and the intra-capsular sareode contains
many and various morphological elements, as in the multi- cellular

clxvi

Introduction.

Radiolaria. In all Rhizopoda^ except the Amoehina, the pseudo-
podia are very namerous, ramify minutely, inosculate by their
ramifications, and show in their interior a cyclosis or circulation
of granular sarcode ; and it is by their suctional agency that nutri-
tive matters are absorbed. In the Amoebina, which on this ac-
count have been sometimes, as by Kolliker and V. Carus, separated
from the Ehizo*poda and classed with the Infusoria, the pseudo-
podia are few and large, and neither anastomose nor show any
cyclosis of granular sarcode in their interior. The exterior layer of
the bodies is better defined than that of other Rhizopoda, and they
extract nutriment from their food by enveloping it, as indeed the
Adinophryna do also, in the substance of their parenchyma.

The differentiation of the outer layers or ' ectosarc-* of the Amoe-
Una, from the inner or ' endosarc,^ is carried so far in the direction
of increase of tenacity and consistence as to render it probable that
a definite spot must exist in their external periphery, which acts as
an oral inlet. No other Rhizopoda possess either a mouth or anus.

Reproduction appears to be effected in the simpler Rhizopoda by
fission of the protoplasmic mass, of which their bodies are exclusively
made up j but in the higher forms of the class, the Amoebina and
Actinophryna, it would appear that true sexual products may be
formed.

The Rhizopoda may be either solitary or social. They are mostly
marine, but some Ainoebina, Actinophryna, and Groviida are found
in fresh water.

Class, Spongiadae.

Social Protozoa, which form one or many aggregated colonies,
each one of which possesses on its exterior a single exhalant ' os-
culum,' and a great number of smaller inhalant ' pores whence
the Class has taken its name of ' Porifera.^ The cells which make
up each colony, are supj)orted upon an internal skeleton, which
may be siliceous or calcareous, horny or leathery in consistence ;
Halisorcina, which has been described as devoid of any skeleton,
and as being merely a colony of naked amoebiform bodies, having
been shown by Dr. Bowerbank to possess more or less of a siliceous
skeleton. The cells are of very various forms in each colony ; some
being ciliated, some amoebiform, whilst others may have their sar-
codic substance so fused together as to form continuous masses,

Characteristics of Gregarinae.

clxvii

which however do not lose the power of reappearing as separate
organisms. The ciliated cells line the interior of certain spheroidal
chambers in the suhstance of the Sponge ; and by their action water
is drawn in through the smaller ' pores/ and with it the alimentary
particles which the amoebiform cells appropriate. The larger ori-
fices or 'oscula' are exhalant in function. Both sets of orifices are
opened or closed at the will of the animal ; but the larger are
permanent^ whilst the smaller are intermittently formed and in-
termittently obliterated. A wide interspace intersected by irre-
gular trabeculae may be interposed between the exterior layer of
the Sponge in which these orifices are situated^ and the deeper
layers which make up the great mass of the organism. The spi-
cula have a cavity in their interior, which is occupied by sarcode,
and are thus to be considered as produced like ' external skeletons^
or ' tests'" by an outward excretion-process.

Reproduction may be sexual^ ova and spermatozoa being produced
by the specialization of cells in the general parenchyma ; or asexual,
in the way of fission, or in that of the production of gemmules.
The gemmules of the fresh-water Sponge are formed towards the
close of the warmer period of the year by means of the '^encys-
tation' of portions of the parenchyma, whilst the sexual process
takes place during the summer months ; so that the history of the
' winter'' and ^ summer^ ova of the Daphnidae and Rotifera is here
exactly reversed.

Class, Gregarinae.

Protozoa, with an external envelope only obscurely limited off
from the contained parenchyma, without either mouth or anus, of
parasitic habits, moving in some cases with considerable energy, not,
however, by the protrusion of pseudopodia, but by the contraction of
their ordinarily vermiform bodies in a direction from behind for-
wards. They are very ordinarily visible to the unassisted eye,
presenting, when circular in shape, the appearance of small white
specks, which may be as much as a millimetre in diameter, but
which attain sometimes a length of as much as half an inch, when,
as more usually, they are elongated and vermiform.

They may have the appearance of being divided {Dicystidea) into
two unicellular organisms : the septum, however, is stated by Kolli-
ker to be produced, not by an involution of their extenial cell- wall.

clxviii

Introduction.

but by the thickening of a part of the contained protoplasm, so that
they are truly unicellular organisms. This cell-wall is readily
permeable by water, which first separates it from the contained
parenchyma, and ultimately^ as in the case of many other Entozoa,
bursts it. The integument may be longitudinally striated or
costatCj and may carry delicate or strong bristles, or even vibratile
cilia, and more or fewer spines. The contents of the cell-wall are
of three kinds : the nucleus, the hyaline protoplasm, and the fatty
granules, which give the adult animals their milky appearance, but
which may be wanting in young specimens. The nucleus is placed
centrally in the Monocystidea, and in the anterior half of the
posterior half of the body in the JDicystidea. It contains a nucleolus,
or several small granules. The reproduction of the Gregarinae, so
far as it is known, appears to be accompanied by the successive
processes of encystation : of resolution of the nucleus and the paren-
chyma, firstly, into small round corpuscles a little larger than a
human red blood-cell ; and, secondly, into the organisms known as
'pseudo navicellae :' and, lastly, of the change of the amoebiform
contents of those bodies into Gregarinae by direct growth. The
resolving up, and the rearrangement of the contents of these uni-
cellular organisms, resemble the process known in the higher ani-
mals as the segmentation of the yolk ; and it is preceded, though
not always, by ^ conjugation,' which might, had it been an inva-
riable antecedent, been compared to sexual congress.

The Gregarinae have been regarded as merely Amoebae, which are
possessed of a better defined external envelope than other Rhizo-
poda in adjustment to their parasitic habits. They have again been
supposed to have, by virtue of the peculiarities of their reproductive
process, and of their first stages of development, to show much
affinity to certain fungi. And, finally, whilst the pseudo-navicular
cysts bear some resemblance to the ' psorospermiae' of Fishes, the
adult Gregarinae, as ordinarily, though not exclusively, found in the
digestive or perivisceral cavities of luvertebrata, are by no means
unlike the wormlike organisms found in the heart and the voluntary
muscles of many Mammals, and known as ' pseudentozoa.'

DESCRIPTIONS OF PREPARATIONS.

1. Common Eat {Mus Decumanus),

Dissected so as to show its craniospinal nervous axis in its entire length as well as
portions of most of the organs of vegetative life.

A RED injection has been thrown into the veins, and the left
halves of the walls of the craniospinal, thoracic, abdominal, and
pelvic cavities, as well as the greater part of the integument
in the facial region and the greater part of the left lung, have
been removed so as to show in situ the organs previously concealed
by these structures.

Of the encephalic nerve-centres we see most anteriorly the
olfactory lobes : next to them the cerebral, separated from each
other by the longitudinal fissure in which is lodged the longitu-
dinal sinus : next the cerebellum bounded off anteriorly from the
posterior border of the cerebral ovoids by the diverging lateral
sinuses, into which the longitudinal sinus divides. The presence of
the lateral sinuses prevents us from seeing the corpora quadri-
gemina which would otherwise be visible « in the middle line,
owing to the divergence there from each other of the cerebral
lobes. The medulla oblongata, which is, like the cerebellum, of
considerable width, comes into view between the two occipital
condyles, from which point down to the second dorsal vertebra,
recognizable by its long spine carrying an ossicle articulated to its
apex, the medulla spinalis is of much greater thickness than it
attains posteriorly. It is seen in the lumbar region to break up
into the cauda equina.

In the dorsal region, a black bristle has been passed under the
aorta where it underlies the bodies of the vertebrae, and this position

• For the relations held by the cerebrum and cerebellum to each other and to the
tentorium, see Turner, 'Proceedings Royal Society of Eidin burgh,' March 3, 1862.

2 Descri'ptions of Frejoarations.

relatively to the craniospinal canal superiorly, as also to the digestive
tract next inferiorly, and the heart most inferiorly, is held by the
aorta in all vertebrata. The singleness of the aortic trunk in the
adult state is characteristic of all warm-blooded animals ; but mam-
mals, as is seen here, diifer from birds in having the single trunk
arching from the heart over the left and not over the right lung's
root. Behind and to the right of this black bristle from before
backwards are to be seen, firstly, the fourth lobe of the right lung
in its pleural cavity resting on the diaphragm below, and in relation
above with the heart, and on the left with the phrenic nerve;
secondly, the oesophagus, a lowly vascular tube the small cahbre
of which is correlated with the working of the dental apparatus in
these creatures j thirdly, the third lobe of the right lung placed
far back and to the right, and, like the lungs of aU mammals, freely
suspended in its pleural cavity and bearing no impressions on its
exterior from the different bony constituents of the thoracic ca\dty ;
fourthly, the vena azygos ^ of the left side between the aorta and
the vertebral column, passing up to arch over the root of the left
lung, and join the vena cava descendens of that side; and fifthly,
the spinal cord. The complete diaphragm, forming a dome-shaped
floor, with the heart and lungs in relation with its convex, and the
liver, stomach, spleen, and kidney in relation with its concave
surface, and receiving a large nerve, the phrenic, from the cervical
region, is eminently characteristic of Mammalia. The upper part
of the pericardial sac has been removed, and the two ventricles
(less distinctly separated from each other than in many mam-
mals) and the left aui^lS^are brought into %dew. The anterior
surface of the heart is^'ore equally shared in by the two ven-
tricles than is the case in many mammals, in which the right
ventricle forms nearly the entire anterior aspect of the organ.
The left vena cava descendens, a trunk which is found in most
Rodents, except the Guinea Pi g^jnd. Agouti, is seen to pass in
front of the root of the" left lung in company with the phrenic
nerve round to the back of the heart to end in the right auricle.
The vena azygos of the left side is seen to join it just above the
root of the left lung, and at a point some way above this, the vein
from the fore-leg, which is in connection with the nerves going to

b For the various arrangements obser^■able in the system of the vena azygos, see
Milne-EdwArds, 'Le^-ons Rur la Physiologie/ vol. iii. p. 598. ibiq"e citnta.

Common Rat.

3

that limb, is seen passing* np to join another vein, which, from its
being placed superficially to the sterno mastoid muscle, we know to
be the homologue of the external jugular of anthropotomy. The ex-
ternal jugular is the main trunk by which the blood from the interior
of the skull returns to the heart in the Rodents and many of the
lower Mammalia, and by its confluence with the vein from the
anterior limb the vena cava descendens is constituted. Internally
to the external jugular, just above its confluence with the subclavian
vein, is seen a part of the hibernating" gland; externally to it
lies the submaxillary ; above this again we see the parotid with its
duct ; and above the pai'otid, the facial portion of the lacrymal gland
sending up a duct, under which a piece of blue paper is placed, to -
enter the orbit and join there with the duct of a second portion
of the lacrymal gland, which is placed within the orbit, and an-
teriorly to the duct of the extraorbitally-placed portion. Within
the orbit we see the Harderian gland. For a fuller description of
these glands, see Description of Plate I, which represents a dis-
section somewhat diflerent from that which we have of these
organs in this preparation.

In the middle line of the body inferiorly to the heart we see the
cut sm-faces of the six sternal bones, and in the angle intercepted
between the lowermost of these and the diaphragm, we see some
lobules of fatty tissue set in the process of serous membrane which
connects the apex of tte pericardium with the sternal bones and
with the diaphragm. From these structures a vein passes back
along the pericardium to end in the vena cava descendens of the
left side.

In the angle between the inferior surTatte of the diaphragm and
the lumbar muscles, the two psoas muscles and the quadratus
lumborum of the left side, we see the smooth-surfaced kidney,
which by this external character, as also by the internal one, of
the separation of its cortical or secretory from its medullary or
excretory parts, characterizes the class Mammalia. The spleen is
in relation with it on the right ; to the right of the spleen we have
the left end of the stomach, which is less vascular and" glandular
than the pyloric half, which is here concealed and overlapped by the

•= For the histology and literature of the Hibernating Gland, see Hirzel and Frey in
Siebold's and KoUiker'a ' Zeitschrift fiir Wissenachaftliche Zoologie,' Bd. xii. Hft. ii.
1862.

B 2

4

Descriptions of Preparations.

left lobe of the liver. Fi-om tlie inferior or convex margin of the
stomach the curtain-like omentum or ejjiploon, a process of perito-
neum found only in mammals, hang-s down over the left cornu
of the uterus, which is distended with emhryoes, and over portions
of the intestines. Immediately below the kidney and the spleen,
the left ovary and Fallopian tube and the upper end of the left cornu
uteri are situated. A fibrous band, under which a black bristle is
placed, and which is the remnant of the ligament d by which the
Wolffian body in the foetus was kept in relation \vith the dia-
phragm, attaches the ovary and tube to the peritoneal covering
of that muscle. Below the upper end of the left comu uteri is
seen the caecum, which is of less size and complexity than in
Rodents with rootless molars and less varied and nutritious food
than these omnivorous representatives of the order, or than those,
such as the Squirrels, which live on seeds and have, like the Murini,
rooted molars. It tapers off" superiorly into the large intestine,
which however in many Eodents is not, when compared with the
small intestine, as much inferior in length and larger in calibre
and thicker in its walls as its name and the homology of anthro-
potomy might lead us to expect. Below the caecum we see
the cut ends of the veins from the hind-limb, and lower still
we see a bristle passed underneath the ureter as it passes
forwards to enter the base of the conically contracted bladder.
The vagina, rectum, and bladder have, each of them, separate and
independent outlets e; into those from the two latter organs
black bristles have been passed. The flat nail on the rudimentary
thumb, the presence of tactile vibrissae above the eyes as well
as upon the snout, and of hairs of great coarseness along the
mesial dorsal region, the absence of hair from a small area, in which
are the orifices of the nostril, and which is called the ' muffle and
its presence between the annulate scales on the tail, are points
worthy of notice.

d For a figure and account of this ligament in the foetal state, see Kolliker's
' Entwickelungsgeschichte,' p. 4.^8, fig. 215.

c For an account of a similar arrangement in another Rodent, see ' Hunterian
Catalogue of the Physiological Series contained in the Royal College of Surgeons,'
vol. iv. p. 2745 ; for a similar an-angcment in an Insectivore and the Simiadae, see
loc. cit. 2810, 2811, 2812.

f For the various senses in wliich the word 'muffle' is used, see Waterhouse's
•Natural History of the Mammalia,' vol. i. p. 5° ; vol. ii. pp. 7. 8.

Skeleton of Coriimoii Rat.

5

2. Skeleton of Common Rat {Mus Decumaniis),

The skeletons of many of the lower Mammalia bear a general
resemblance to those of certain quadrupeds lower in the scale of life
in such points as the nearness of the level at which their trunk is
cai-ried by their limbs to that of the ground on which they move ;
and in the maintenance by the long axis of their head, of much the
same direction as that of the long axis of their entire trunk. But
they invariably present the following distinctive characters, which
are as peculiar to the Mammalian class as any of the points fur-
nished by the soft parts, such as the blood-cells, the hairy integu-
ment, or the mammary glands. In every Mammalian skeleton the
lower jaw will be found to be made up of a single mandibular bone
on each side, which articulates by a convex facet with the squamosal
element of the cranial wall ; and the vertebrae in the trunk always
differ from those of the different lower vertebrata in one or more or
all of the following points : either in the anchylosis of their several
elements, or in the size of their neural canal, or in the shape of
the articular ends of their centra, or in the means whereby in the
recent state these articular ends are brought into relation with each
other. In the vertebra of a young mammal the neural arch may
not have anchylosed with its centrum ; but in all such cases two
discoid epiphyses belonging to the articular ends of the centrum
would also remain unanchylosed, as they fuse with it at a later
period than the neural arch, and they furnish a mark as distinctive
of the Mammalian class as any other connected with the vertebrae.
Some mammals have an opisthocoelian ball and socket articulation
between the centre of their vertebrae ; and the crocodiles resemble
the mammals in having interarticular fibrocartilaginous discs to
connect their ball and socket centre-joints instead of synovial joints;
but in such cases the greater size of the neural canal or the absence
of neurocentral sutures, or the absence of sutures between the body
and the lateral processes, would enable us, without having recourse
to a microscopic examination of the bony tissue, to identify a ver-
tebra as having belonged to a mammal. In all mammals, except
the Cetacea, the maximum number of phalanges in any one digit
is limited to three ; in nearly all the number of cervical vertebrae is

6 Descrijotions of Prejxirations.

neither more nor less than seven ; and the number of the lumbar
vertebrae is never less than two. There are very rarely any verte-
brae with unanchylosed ribs anteriorly to the first dorsal vertebrae.
The jaws are ordinarily dentigerous^ but teeth ai'e never found
elsewhere than upon the mandibular, maxillary, and intermaxillary
bones; the grinding teeth very frequently have more than a
single root or fang, a method of implantation never observed in
any other class.

The most distinctive character of the Rodent order is the posses-
sion of the pairs of scalpriform incisors in the upper and lower jaws,
from the functions of which their class-name is taken. There is a
single pair of incisors in the upper jaw in all Rodents, except those
of the family Leporidae, in which there are two pau-s placed one
behind the other, the hinder pair being the smaller. In the lower
jaw there is a single j)air only in all Rodents, without exception.
The upper incisors form a larger segment of a smaller circle, the
lower a smaller segment of a larger circle. The peculiarities of
their growth, which goes on uninterruptedly during the life of the
creature from a persistent pulp, and of their functions, entail
changes of great importance in the general conformation of the
skull and of particular bones. The intermaxillaries, in relation
with which the upper incisors are first developed, and which form
a large part of the sockets in which they are permanently lodged,
are larger in relation to the rest of the skull and of the animal than
in perhaps any other mammals ; — they form the whole, or nearly the
whole, of the sides and under surface of the bony snout, and in all
Rodents they shut off the nasals from contact with the niaxil-
laries. The maxillary bone, besides fonning' part of the socket for
the lodgment of the teeth, furnishes in its malar process a point of
origin for a deeply-placed part of the masseter, which co-operates
very strongly with the temporal muscle in moving the lower jaw
m a vertical direction, and bringing its incisors into play upon those
of the upper jaw ; whence probably the inverse ratio which has
been observed to obtain between the temporal and the antorbital
fossae is to be accounted for. The masseter muscle arises from
nearly the whole length of the malar arch, which is made up ordi-
narily of the malar process of the maxillary, of the malar bone, and
of the malar process of the squamosal, and sometimes of the lacry-
mal also. It is by the contraction of those of its fibres which pass

Skeleton of Common Rat. 7

backwards on to the posterior edge of the lower jaw, aided by that
of the pterygoids, that the anteroposterior movement of the lower
jaw with its molar series upon that of the upper jaw is effected.
The glenoid cavity has, to allow of this movement, an anteropos-
terior dii-ection throughout the order, with the exception of the
Leporidae, and the unbroken molar series and the absence of canines
is characteristic of the order without even that exception. Though
the malar arch has a downward, rather than, as in Carnivora, an
outward curve, still the interzygomatic diameter is in all Rodents
the widest transverse cranial diameter. The temporal is never
separated from the orbital fossa; the cranial cavity is always much
compressed from side to side on a level with the optic foramina,
so as frequently to leave an interorbital fenestra by the fusion of
the two foramina into one, at a point a little behind that at which
the olfactory chamber succeeds the cerebral internally.

The length of the tail and the number of the caudal vertebrae
vary much within the limits of this order, just as the external
concha of the ear and the characters of the integumentary system
do. But, in spite of the very various special habits of the animals
belonging to this order, the two pairs of limbs almost invariably
present the same ratio of development inter se, the hind limbs being
the stronger and longer pair. The tibia and fibula are anchylosed,
as they are here, more frequently than the ulna and radius. There
is, however, little tendency to anchylosis in the skeleton of the
Rodents ; in this specimen the posterior pair of sacral vertebrae are
not anchylosed with the anterior, with which the ilia articulate,
and the mandibular bones never throughout the order become an-
chylosed with each other at the symphysis of the lower jaw, in spite
of the great afilux of blood which their permanently growing inci-
sors bring into them. In the trunk we observe that the spines of
the dorsal vertebrae, from the largely developed spine of the second
dorsal to that of the tenth inclusively, point backwards, whilst
those of the six lumbar vertebrae and of the two last, the thirteenth
and the twelfth dorsal, point forward towards the vertical spine of
the eleventh dorsal, which has been called in consequence the
* anticlinal ' vertebra. The anterior dorsal vertebrae diminish pro-
gressively in size as they are placed nearer to this vertebra, whilst
the vertebrae placed posteriorly to it, and markedly the transverse
processes of the lumbar vertebrae, increase in size as we pass

8 Descrijptions of FrejKtrations.

backwards from it towards the sacrum. Well-marked and distinct
anapopliyses and metapophyses are developed on the anticlinal
vertebra,, and are to be seen on the succeeding vertebrae nearly or
quite up to the sacrum. The direction of its spine relatively to those
of the other vertebrae in front of and behind it causes it to be the
point of greatest mobility in the trunk. Points of less striking
proportions, but more or less distinctive of, and universal in, the
order are presented in the skull by the presence of an interparietal
bone ; by a vacuity in the skull walls for the blood to pass out
from the lateral sinus, either as here by a conjugate foramen
between the squamosal and the periotic, or by a foramen in the
squamosal itself, the so-called ' canalis temporalis;'' by the develop-
ment of the post-auditory process of the squamosal into a lamina
of bone, which may reach as far back as the occipital, but serves
always to keep the tympano-periotic, with which it never anchy-
loses, in place ; and, finally, by the smallness of the angle formed by
a line drawn from the posterior edge of the supraoccij^ital on to the
basicranial line. The depth of the symphysis pubis, and the oblique
forward direction of the transverse processes in the lumbar region,
are points probably correlated functionally with the strength of the
hind limbs. The large size of the abdominal relatively to the
thoracic cavity may be connected with the multiparous character
of the order generally. The spine of the second dorsal vertebrae
has a small ossicle articulated to its apex, and pointing forward,
much as in the long-necked grazing mammals the ligamentum
nuchae is placed along the dorsal and cervical regions. The two first
cervical vertebrae are, as is usual in mammals, much the largest in
the series, and they contrast with the other cervical vertebrae, as
also with all the rest of the moveable vertebrae, in having, when
adult, the centre of the first fused with that of the second, and
in being connected with each other and the skull by cartilages
and synovial membranes without fibro-cartilaginous discs. The
first rib has its head articulated to the bodies, and its tubercle
to the transverse processes of both the last cervical and the first
dorsal vertebra. There are two lateral epist^rnal bones between
the first of the six sternal bones, the so-called manubrium' and the
clavicle, one on each side, but there is no central episternum.

In the carpus there are tlie same number of bones as in that of
man, for though the scaphoid and lunar arc fused into one bone, the

Skeleton of Common Rat.

9

scapho-lunar^ as they are also in Carnivora and Cliiroptera^ a howe,
the OS centmle, exists between it and the os trapezium, or trapezoides,
and OS magnum in the second row of carpals, which is not repre-
sented by a distinct bone in the human carpus, nor in those of
Ung-ulata, Cetacea, Chiroptera, Edentata, Marsupialia, and Mono-
tremata, but only in those of Rodentia, Insectivora, and Simiadae,
exclusively of the Chimpanzees. Asjn all mammals, though in no
re]Dtile_ iiQr jamphi^ a single bone, the os unciforme, supports
theJ}wq_outer metacarpals. In this enumeration the ulnar sesa-
moid bone, or ' os pisiforme,^ is not reckoned as a carpal bone, nor
any bone of similar function in connection with the tendons on the
volar side of the hand.

In Rodentia we find two more bones in the tarsus than we do in
the human subject, owing to the division of the os scaphoides, and
to the presence of an accessory bone on the inner side of the inner
OS cuneiforme.

For the general characteristics of Mammalian vertebrae, see Pro-
fessor Owen, Descriptive Catalogue of the Osteological Series
of the Royal College of Surgeons, vol. i. pp. 7, 8.

For the nomenclature of the several elements of a vertebra, ibid. p. xliv.

For the Osteology of the Rodentia, see Cuvier^s Ossemens Fossiles,
2nd ed., 1833, vol. v. pt. i. pp. 4, 14, 44; and GiebeFs Beitrage
zur Osteologie der Nagethiere, 1859.

For the Carpus and Tarsus and Shoulder-girdle, see Gegenbaur's
Untersuchungen zur Vergleichenden Anatomic, Hft. i. ii.
1864, 1865. Carpus and Tarsus, Hft. i. pp. 42 seqq., 53,
109 — III, et passim. Schultelgiirtel, Plft. ii. p. 21.

For the ' Canalis Temporalis,^ see Otto, Nova Acta, xiii. pt. i. p. 27,
and Kolliker^s Entwickelungsgeschichte, p. 422.

For the means whereby the vertebral centra are articulated in the
different classes of vertebrata, see Rathke, Entwickelungs-
geschichte der Wirbelthiere, mit eineni Vorwort von A. Kolliker,
1861, p. 130.

For the characters of the order Rodentia, see Waterhouse, Natural

History of the Mammalia, vol. ii. pp. i — 9.
For the Osteology of the Muridae, see Osteological Catalogue,

Royal College of Surgeons, vol. ii. Preparations 2223 — 2245.

10

Descriptions of Prejxirations.

3. Cervical, Dorsal, and Lumbar Vertebrae of
Rabbit {Lepus Cuniculus).

Geeat mobility is secured by the particular arrangements
observable in the region where the two upper cer'sdcal vertebrae
articulate with each other and with the skull^ and in the region of
the lower dorsal and upper lumbar vertebrae. On the other hand,
the transverse processes of the lower cervical vertebrae and the
imbricated neural spines of the upper dorsal vertebrae prevent the
possibility of any great range of movement between any two of
the constituent segments of those portions of the spinal column.

The cervical vertebrae are seven in number, as almost invariably
in the Mammalian class; the numbers of the dorsal and lumbar
series are variable, but twelve and seven, the numbers of the dorsal
and lumbar vertebrae respectively in the Rabbit, are verj'^ common
numbers for those series throughout the class. The number of the
caudal vertebrae is the most variable, that of the lumbar next, that
of the dorsal less than that of the lumbar, that of the cervical the
least variable of these four sets of vertebrae. As the number of
the cervical vertebrae is all but invariable, the variability of the
length of the cervical region depends upon variations in the length
of the bodies of the seven vertebrae. The first cervical vertebra
or ' atlas^ is the widest from side to side of all the neck vertebrae ;
it has a low but broad neural arch, and superadded to it in front
a smaller arch which is in the perfect condition of the parts made
into a ring for the reception of the 'odontoid process' of the next
vertebra by a transverse ligament. Its neural arch is overhung
by the spine of that vertebra, and it does not give any point of
attachment to the ligamenium nuchac. It contains two moi'e or less
separated canals for segments of the vertebral artery ; one of them
pierces the base of its broad 'transverse process' from behind
forwards, the other turns more or less horizontally from without,
inwards, behind and below the articular processes. This latter
canal may be represented merely by a groove in the Rat, and
ordinarily has this imperfect character in the human subject. The
former has generally a short horizontal canal leading forward from
it and opening on the anterior surface of the transverse process it is

Vertebrae of Rahhit. 11

however absent in the Leporidae, though present in the Rat and
many or most other Rodents. The second cervical or 'axis'
vertebra has its spine greatly developed, both auteroposteriorly
and vertically, giving attachment by it both to the muscles which
move, and the elastic Ugamentnm nuchae which supports the head.
It has no anterior articulating processes upon its neural arch in
mammals, but it comes into articular relation with the atlas
by means of two oblique zygapophysial surfaces developed on
either side of the base and a third on the front of its odontoid
process, which is the backward!}^ displaced and anchylosed centrum
of that vertebra. It is the deepest from above downwards, and
the longest from before backwards, but also the narrowest from
side to side of the cervical series. The first two cervical vertebrae
articulate with each other and with the occiput by means of
synovial joints as the neurapophysial processes are articulated to
each other throughout the rest of the trunk, where however the
centra are connected by interarticular fibrocartilaginous discs
containing in their central pulp remnants of the primitive chorda
dorsalis. The neural spines of the third and fourth cervical
vertebrae are low but long, corresponding with the long neural
roof which these two vertebrae possess ; the spines of the shorter
neural arches of the fifth, sixth, and seventh vertebrae have more
of the shape which their name implies. The lateral processes or
'cervical ribs' of these vertebrae are greatly developed; those of
the atlas more or less obliquely outwards, those of the axis back-
wards; those of the third, fourth, fifth, and sixth, both anteriorly
and posteriorly, and those of the seventh outwardly. The fourth,
fifth, sixth, and seventh have prominent upgrowths developed on
this process or rib which are homologous apparently with the
prominent tubercles of the ribs of these creatures, or, possibly, with
the metapophyses of the dorsal ribs. This process makes up by
itself almost the whole of the transverse process of the seventh
cervical vertebra, the inferior, anteroposteriorly-produced, process,
which is much larger in the preceding vertebrae and largest of all
in the one immediately preceding, being lost in this, the last of the
series. These inferior elements of the transverse processes, by
bending inwards form with the vertebral bodies furrows, in which
the long anterior neck muscles are lodged, a central slightly-raised
line marking the line of separation of these muscles and repre-

12 DescriiJtions of Preparations.

senting the homologously-plaeecl hypapoi3hyses of lower verteLrata.
The segment of bone which completes the ring of the atlas ante-
riorly is homologous with these hypapophysial downgrowths.
The last cervical vertebra in the Rabbit has not, as it has in the
Rat, any connection with the tubercle of the first dorsal rib.

Eight of the dorsal vertebrae, from the second to the ninth inclu-
sively, have, each, two half facets on their centra, the first has one
whole facet anteriorly and a half facet posteriorly, and the tenth,
eleventh, and twelfth have, each of them, single whole facets placed
on the anterior superior angle of the lateral aspect of their centra,
for articulation with the heads of the ribs. The neural spines of
the dorsal vertebrae are largely developed, their apices from the
second to the ninth showing a tendency to become bifid antero-
posteriorly. The tenth is the anticlinal vertebra, and upon it and
upon each succeeding vertebra down to the sacrum a lai-ge meta-
pophysis is developed. A small anapophysis is also seen to take
origin from the base of its neural arch, and to be possessed by each
succeeding vertebra up to the antepenultimate lumbar. Several of
the anterior, as also of the posterior dorsal vertebrae, have low
hypapophysial ridges developed subcentrally ; and longer ones pos-
sessing the character of spines are developed on the three anterior
lumbar vertebrae. The lumbar vertebrae, their metapophyses, and
their distally bifid transverse processes increase in size from before
backwards as far as the penultimate one ; the transverse processes
point obliquely forward, but form a more open angle with the long
axis of the column than they do in the Rat.

4. Common Pigeon (Colamha Livia),

Sho\ving nervous, digestive, circulatory, and parts of respiratory and renal systems.

The brain has been exposed in situ by the removal of the roof
of the cranium ; the integument has been removed from the right
side of the front of the cervical region, as have also most of
the feathers from the entire body ; an opening has been made into
the right side of the crop, which has been distended ; the larger
part of the right half of the body walls has been removed,
together witli the muscles and the limbs which it supported, and
a red injection has been thrown into and filled the venous system.

Common Pigeon.

13

The surface of the cerebral ovoids is smooth S ; the proportion
of the encephalic nervous mass to the intraspinal is much greater
than in the cold-blooded vertebrata. The backward projection
of the cerebellum is very considerable. The eyes are large. The
vertical third eyelid is drawn forward. The nostrils open externally
as long slits overhung by a tumid membrane ; the external audi-
tory meatus, which has no concha, has the feathers arranged round
it like a circlet of tentacles. The great pectoral h muscle, the
main depressor of the humerus and the wing, is seen in section
along its origin from the lower portion of the keel of the sternum,
and from the furculum, the outer and lateral portions of the sternum,
from which it also took origin, having been removed. Placed dor-
sally with reference to this muscle we see the second pectoral, the
main elevator of the humerus and the wing, arising from a larger
portion both of the keel and of the lateral parts of the sternum than
the pectoralis major, and passing internally to the coracoid to enter
its pulley-like canal, formed by the clavicle or furculum, the cora-
coid, and the scajpula. . ,

From this canal, its tendon, which is cut short, is seen issuing on the
further side of the glenoid socket for the head of the humerus. The
cut-short triangular end of the pectorahs major is seen to become
partially bifid towards its apex ; in the perfect condition of the parts
the smaller inferiorly-placed division of the muscle gave off two tendons,
one to the long and the other to the short extensor plicae alaris an-
terioris ; the larger division passed over a smooth facet on the humerus
and over the coracoid head of the biceps to be inserted into the great
triangular tuberosity of the humerus. Dorsally to the apex of the great
pectoral we see a thin stratum of muscle in relation internally with
the crop and homologous with the deltoid of anthropotomy. This muscle
was divided into three portions, of which the first and most internally-
placed joined the long extensor of the anterior fold of alar membrane ;
the second and mesially-placed portion joined the short extensor, whilst
the third was inserted into the outer aspect of the humerus from its

S For the nervous system of birds, see C, G. Carus, 'Tabulae Anat. Comp. Illus.'
pars vii. tab. v. fig, 7.

•> For the muscular system generally, see Cuvier, 'Le9ons d'Anatomie Compar^e,'
vol. i. For the muscles of the wing and shoulder, see Schoepss's Monograph in
'Meckel's Archiv,' 1829, and plate ii. with description in this work. For those of the ■
lower extremity, see Professor Haughton, ' Proceedings Royal Irish Academy,'
May 23, 1864 ; Professor Owen, 'Comp. Anat.' vol.ii. p. 107.

14

Descriptions of Preparations.

middle down to a nodule marking the commencement of its lower fourth
and of the origin of the long radial extensor of the metacarpus. Under-
neath the alar extensor portions of the deltoid are seen two thicker muscles
cut short. They seem to coiTcspond to the shoi'ter coracobrachiales
sometimes seen in the human subject'. The long tendon of the biceps may
be seen passing internally to those two muscles to be inserted into the
anterior and internal process of the coracoid. Immediately below the
origin of the humeral poi-tion of the deltoid, from the anterior internal
process of the scapula, is seen the origin of the long head of the triceps
from the upper surface of the anterior external process which supports its
glenoid facet.

On the lower poi'tion of the coracoid are seen the remnants of the
origins of the longer coracobi-achiales, the so-called coracobrachiales
' superior ' and ' inferior.' In the posterior tibiofibular region the peroneus
medius muscle has been exposed, together with parts of the flexors of
the toes, with the exception of the deeply -placed flexor perforans, and
of the gastrocnemius. A black bristle has been placed under the
tendon of the peroneus medius J*:, which a little below is seen to
bifurcate and send one of its divisions inwards to lose itself in the
fibrous tissues at the back of the tibiometatarsal joint, and the
other onwards to pass under the sole and become a flexor of the
middle toe. Superiorly between the under part of the origin of the
peroneus medius from the fibula, and that of the outer head of the
gastrocnemius from the femur, a muscle is interposed which bifurcates
about opposite the junction of "the upper with the second fourth of the
tibia. One of its divisions runs in close relation with the tendon of
the external gastrocnemius, and is finally distributed to the index digit,
whilst the other passes to the medius. This bifid muscle is known as the
flexor perforatus et perforans. In the interval formed by its bifurcation
we see parts of the flexor communis s. perforatus, which by one of its
divisions is connected with the tendon of the peroneus medius, and by
another with that of a muscle which, arising from the spine of the pubis,
passes along the inner .side of the thigh and crosses in front of the knee-
joint round to the flexor aspect of the lower leg. Most posteriorly we see
the external gastrocnemius, in the muscular belly of which an artificial
division has been made.

The crop forms a bilateral poucli with glandular walls, at the
lower end of the distended ocsophag-us. It rests on either side

' See Henle's ' Aiiatomie des Menschen. Muskellehrc,' pp. 172, 180.
^ See Curler, ' Le9on8,' pp. 542, 558.

Common Pigeon.

16

upon the furculum and the muscles arising from it. In the cavity
of the thorax a black bristle liae been passed between the proven-
triculus and the aorta as this vessel arches over from the left to
the right. The gizzard is concealed from view by the right lobe
of the liver and the posterior or xiphisternal end of the sternum
which supports and protects both these viscera. The distal segment
of the duodenal loop of intestine is held in relation with the under
surface of the right lobe of the liver^ which is excavated conformably
to it. In the concavity of the duodenal fold is seen the longitudi-
nally-fissured^ compact, elongated, largely-developed pancreas. An-
teriorly to this duodenal fold are seen the two other main folds of
smaller calibre which the lengthy small intestine of these birds
describes. The right side of the heart rests upon the right lobe of
the liver ^, from which the vena cava inferior is seen to pass up into
the right auricle, entering it at a point a little superiorly as well
as posteriorly placed to that at which the vena cava superior of the
right side opens into it. The veins from the upper extremity
and shoulder are cut short at their point of junction with the
jugular to form the veiia cava superior. The pneumogastric nerve is
seen in relation superiorly with the jugular vein ; superiorly again,
and internally to the nerve, we see the proventriculus ; and supe-
riorly again to it, the longi colli muscles arising from the vertebral
hypapophyses. Tracing the aorta backwards towards the heai't from
the point where it arched over the right bronchus, which, together
with the pulmonary artery placed before it and the pulmonary
vein placed behind it, has been removed in this dissection, we
see it pass behind the vena cava superior dextra, and give oW the
two arteriae innominatae, one for either side of the body, very close
to the base of the heart. The right arteria innominata is seen to
divide into its common carotid and subclavian trunks. This latter
vessel, after giving off a small branch homologous with the in-
ternal mammary artery of anthropotomy, divides into an axillaiy
tnmk, which passes into the wing together with the brachial
nerves, and into the much larger arteria thoracica externa which
supplies the gi'cat pectoral muscles. The lung, which occupies a
much smaller space in the dorso-sternal plane than in mammals,

' For the peculiarities of the circulatory system, see Cuvier and Duvenioy, 1. c.
tom. vi. p. iiji; Barkow, 'Meckel's Archiv,' 1829, p. 493; and for a figure of the
circuhitory system, 'Hunterian Catalogue,' Phys. Series, vol. ii. pi. xxv.

16

Descr ijJtions of Preparations.

reaches backwards so far as to interpose itself for some distance
between tbe anterior lobe of the kidney and the os ilii. It differs
from the Mammalian lung also in being lodged conformably to
the intercostal spaces, and being indented by the six unanchylosed
ribs, instead of being freely suspended, as is invariably the case
in mammals, and divided into lobes, as is very ordinarily the case
in those animals. Another and most important point of difference
is furnished by the prolongation of the lung, by means of its bron-
chial stem and branches, into air-cells ™ permeating a very large
part of the entire body. The largest of these receptacles are the
infrarenally -placed ' abdominal air sacs/ the right one of which,
presenting an appearance like that of the Mammalian omentum,
is seen extending from the posterior border of the lung above and
behind the liver, so as, firstly, to interpose itself between the inferior
surface of the kidney and the intestines, and, secondly, to stretch
beyond the region of the kidney into that of the rectum. The
kidney, like the lung, is indented by the bones it is in relation
with ; and it is divisible here into three lobes, increasing in size
from before backwards conformably with the iliac and pelvic fossa.
There are no specialized renal arteries in bii-ds as there are in
mammals, but we see some branches passing to the organ from
the ischiadic artery in the interval between the middle and posterior
lobe, whilst one of the chief factors of their short vena cava inferior
is seen in the interval between the middle and the anterior lobes.

In all birds, and in no other class of animals, will the same
description as that given here apply to the nerve-system, and the
relations of the muscles of the anterior limb, and to the relations
of the aorta to the right bronchus. The peculiarities of the pan-
creas and duodenum are probably nearly equally distinctive. Tlie
crop and the uropygial gland are peculiar to, though not universally
found in Birds.

m For an account of the air sacs, see Milne-Edwards, 'Lemons,' ii. 351, and for the
relations of the air sacs shown in this preparation, see Natalis Guillot, ' Ann. Sci.
Nat.' 1846, series iii. torn. v. p. 60 ; and for figure, C. G. Carus, 1. c. pars. vi.
tab. vii.

Skeleton of Common Pigeon.

17

5. Skeleton of Common Pigeon (Columba Livia).

The relations held by the hind limbs and the pelvic bones to the
rest of the body serve at once to distinguish the Bird from all other
classes of animals. The peculiarly distinctive character of its
skeleton as compared with that of the living and extinct animals
which it most essentially resembles, viz. Reptiles, depends in the
second place upon the relative proportions and the different degrees
of mobility of the cervical, dorsal, sacral, and caudal vertebrae re-
spectively ; upon the great development of the sternum relatively
to the entire body, of the ilium anteroposteriorly relatively to the
vertebral column, and of the tibia relatively to the bones of the
whole hind limb ; and, thirdly, upon the greater proportion of in-
organic elements, the greater tendency to anchylose with their
fellows, and the greater pneumaticity which the individual bones
ordinarily possess. Peculiarities less striking, but not less distinc-
tively and universally avian, are furnished us in the hand and foot.
Parts of the carpus and tarsus are in either extremity fused with
three of the bones of the segment, placed distally to them into
a single bone, which directly supports all, or, in the foot, all but
one, of the terminal digits. In the foot the fifth or outer digit is
never present ; in the hand neither fourth nor fifth, and in it the
outer, the homologue of the middle finger, is never arwed with
a claw. In very nearly all Birds, and in very few and in some cases
in no other animals, may the following peculiarities be noted : —
The articulations of the vertebrae when looked at from in front pre-
sent the procoelian appearance, the anterior articular surface being
concave from side to side, though convex, and therefore saddle-
shaped, from before backwards. The basitemporals form a second-
ary floor to the cranium, concealing the junction of the basisphenoid
to the basioccipital .

The caudal vertebrae vary little in number, are not numerous,
are mobile, and are terminated by a single bone compounded of
several fused segments and of a ploughshare shape. The ossa ilii
and ischii coalesce posteriorly to the acetabulum to form a foramen
more or less homologous with the sacroischiatic notch of anthropo-
tomy. Finally, in most birds most or all of the vertebrae, with the
exception of the atlas, and also sometimes of the caudal vertebrae,

o

18

Descri'ptions of Preparations.

are pneumatic (i.e. have air cells in tlie place of the fatty medulla
of other bones). In all birds, though not exclusively in them, at
least as regards some of the points to be heremth specified, the
following structural arrangements may be noted : — The lower jaw,
which is compounded originally of twelve distinct bones, swings
upon a moveably articulated os quadratum, which has ordinarily two
crura for articulation with the skull, and a largely-developed orbital
process. The upper jaw is mainly made up of the premaxillary bone,
the maxilla being lost or rudimentary, and its place being taken
by the prevomerine bones, which by their outer surface articulate
at once with the premaxillary bone and with the quadratojugal
rod, and bring thus the upper jaw into connection with the os
quadi'atum. A second chain, also consisting of two bones, viz. the
palatine and the pterygoid, serves the same purpose as the quadra-
tojugal in connecting the os quadratum with the upper jaw. The
squamous never reaches the jugal bone. The occipital always
articulates by a single head, which however may, like the occipi-
tal condyle in Reptiles, show traces of its primitive composition
out of three bones, by being bifid superiorly, with a more or less
perfect cup on the atlas. The sclerotic is strengthened by bony
plates. The scapular arch is completed inferiorly by the junction
of the coracoids to the sternum. The number of the carpals
existing in the adult bird as separate bones is, as a rule, two. The
tarsals always coalesce, the proximal ones with the tibia above, and
the distally-placed with the metatarsus below. The fibula never
articulates with the tarso-metatarsus. There are no limibar verte-
brae ; and respiration is mainly eflPected by the movement of the
sternum from above downwards, the vertebral and sterual ribs mov-
ing on each other, and on the sternum, all but exclusively in that
direction. The length of the cervical region is never less than the
height from the ground at which the body is carried by the legs,
nor than the length from the root of the neck to the terminal
ploughshare-shaped vertebrae which supports the uropygial gland.
It depends not, as in mammals, exclusively upon the greater or
less length of the bodies of its vertebrae, but also upon the in-
creased or diminished number of these vertebrae, which may vary
from eleven to twenty- four, being thus in birds the most, as it is
in mammals the least, variable number of any of the numbers of
the several vertebra series. The dorsal vertebrae, or vertebrae

Common Pigeon.

19

carrying iiiianchylosed ribs, are much fewer and less variable in
number than the cervical, their number varying- from six to ten ;
they contrast even more strongly with the cervical in their posses-
sion of scarcely any mobiHty, some of them being ordinarily fused
with each other, and one or more with the ilium and sacrum. The
sacral vertebrae vary in number from nine to twenty, the caudal
from five to nine ; they resemble the cervical in being mobile, but
differ from it, as also from the series homologous to themselves in
mammals, in being the least variable in number of any of the seg-
ments of the vertebral column.

The neck vertebrae of this, as of other birds, differ from those of
mammals in their greater number, in the conformation of the
articular surfaces of their centres, and in the soft tissues, cartilages,
and synovial capsules, with which those articular surfaces were clothed
in the fresh state; in the attachment of the ligamentum nuchae
to the bases and not to the apices of the neural spines, a condition
by which, as by those previously specified, greater mobility was
secured for this part of the column in the bird ; and, finally,
by the development of hypapophyses in the anterior and posterior,
and of a demi-canal in the middle portion of the region along and
beneath the bodies of the vertebrae. The second cervical vertebra
has articular processes developed upon its neural arch as well as
upon the odontoid process, a point in which the Bird and Reptile
coincide as in many others, and differ from the mammal, and
which throws hght upon the homological nature of the odontoid.
The neural arches of the cervical vertebrae posterior to the second
are considerably emarginated in the middle line, both before and
behind, so that a lozenge-shaped space crossed in the natural con-
dition of the part from before backwards by the ligamentum
nuchae is left uncovered by any bony roof in the middle line of the
roof of the neural canal. The neural spines, or ratlier the central
depi'essions at the base of the most elevated portions of each neural
arch, to which each segment of the ligamentum nuchae is attached,
being situated at about the central point from before backwards in
each neural arch, greater length and greater range of extensibility
and recoil is secured for the elastic ligament. In the Pigeon the
four anteriorly and the two posteriorly-placed cervical vei-tebrae
are provided with hypapophyses. The six centrally- placed, which
make the entire complement of twelve cervical vertebrae which this

20

Descriptions of Prejoarations.

bird possesses, have the place of the hypapophysis taken by the
carotid demi-canal. The ten posteriorly-placed cervical vertebrae
have by the anchylosis of the lateral process or cervical rib to the
body of the vertebrae a lateral and complete canal formed for the
deep portion of the sympathetic and the vertebral vessels. Between
the cervical vertebrae and a projection which is the homologue
of the ^ promontory^ of the sacrum in anthropotomy seven
dorsal vertebrae, or vertebrae carrying unanchylosed ribs, in-
tervene. Each rib is, as all but invariably in Birds, articulated to
the anterior portion of the body, and also by its tubercle to
the transverse process of its own vertebra. The two first ribs
have no sternal element superadded to them, and fail conse-
quently to reach the sternum ; the first, however, is in relation
with the lung, and the second forms an indentation on its surface.
Tlie four ribs which succeed them have ossified sternal ribs con-
nected directly with the sternum, and the fifth has its sternal rib
connected indirectly to it by means of that belonging to the ver-
tebra next in front of it. Each rib, with the exception of the first
and last, has an epipleural process, the so-called processus uncinalus,
developed from its posterior edge and overlapping the rib next
behind it ; the third, fourth, and fifth vertebrae have their spines,
neural arches, transverse processes, and hypapophyses anchjdosed, as
well as their centra, which are laterally compressed so as to pass
into the greatly-developed hypapophyses quite gradually. The
flexor muscles of the neck, seen in the preceding Preparation, take
their origin from these hypapophyses. The sixth dorsal vertebra is
not anchylosed either anteriorly or posteriorly; the seventh is
anchylosed to the sacral vertebrae posteriorly, but its rib remains
unanchylosed, and in the fresh state has the lower portion of the
lung in relation with, and indented by, itself. The sacral ver-
tebrae are thirteen in number ; their spines form a long, low, con-
tinuous ridge, which is not in this, as it is in some Columbidae and
in the Rasores, fused anteriorly with the ossa ilii; the foramina on
either side are much encroach e<l upon but not as yet closed up
by ossificatory ingrowth, the longest transverse process is on
a level with the anterior edge of the acetabulum, and divides the
cavity of the true pelvis internally and posteriorly into two fossae,
in which the middle and posterior lobes of the kidney are lodged
conformably to the irregularities in the surfaces of the bones. A

Common Pigeon.

21

much shorter but also stouter transverse process limits the iliac
fossae, into relation with which the superior lobe of the kidney
and the lower end of the lung come, from the Hrue pelvis/ The
iliac bones have their internal margins in apposition or anchylosed
with the outer ends of transvei-se processes of the sacral
vertebrae; they anchylose with ossa pubis and ischii to form
the acetabular annulus, and with the ossa ischii, as usual in Birds,
to form the sacroischiatie foramen which is homologous with the
sacroischiatic notch of anthropotomy. In the Pigeons the ossa
pubis do not ordinarily coalesce with the ossa ischii, so as to con-
vert the notch for the tendon of the obtusator internus, which
lies immediately below the sacroischiatic foramen, into a foramen
also. Neither do they coalesce with them, as they do in some
birds, posteriorly to this point, so as to form a « foramen ovale/
The iliopectineal spine, which is well developed in the Rasores,
is absent in the Columbidae. The caudal vertebrae, which are
not pneumatic, are seven in number, counting the compound os en
charrue which supports the uropygial gland and certain of the tail
feathers, the rectrices, as one. These vertebrae possess considerable
mobility, having no zygapophyses developed on their neural
arches, and being articulated simply by ball and shallow socket
joints on their centra and intercentral fibrocartilaginous discs.
The pelvis and coracoids are pneumatic, but the furculum and
scapulae are not, and it is only in adult birds, either of the Fowl
or the Pigeon tribes, that the coracoids become so. The humerus
is the only bone in either limb which is pneumatic. The coracoid
is exceedingly strong, and the keel of the sternum very deep, as
if to compensate for the feebly-developed furculum. The muscular
ridges for the origin of the second pectoral muscle, the chief
elevator of the humerus, are well marked both upon the keel
and upon the body of the sternum. The sternum has a wide
lateral emargination homologous with the exterior emargination
in the Rasorial sternum, but it presents only a small fontanelle
to correspond with the deeper and more internally-placed emar-
gination of those birds. The grooves for the reception of the
articular ends of the coracoids meet anteriorly, and there is no
downward prolongation of the episternum between those bones
as in the Rasores. On either side of the middle line of the epister-
num, a large pneumatic foramen is seen entering the bone ; other

22

Descriptions of Prejxiratioiis .

similar foramina are seen on the upper or visceral surface of the
bone^ as also in the interspaces of the bifid articular surfaces for the
sternal ribs. Short hyposternal processes project upwards from
the anterior end of the line on which these ribs abut^ but they do
not attain the proportions nor take the direction of the homolog-ous
processes in the common fowl. Neither has the furculum the
downward projecting- lamina developed at its symphysis, which
is characteristic of that bone in the Rasores. The scapula, a
broadsword-shaped bone, has a small bony outgrowth developed
on its lower edge, about one third of an inch from its articular
surface. The process is very well marked in the Dodo, and serves
in the Pigeon to give insertion to the tendon of the serratus
antic us minor. The processes of membrane which pass from the
episternum to the coracoids and furculum have been taken to
represent the episternum and epicoracoids of LacertiUa and Mono-
tremata. From the upper end of the coracoid two strong liga-
ments pass outwards to be attached, one in front of, the other
behind, the articular head of the humerus. Immediately posteriorly
to the insertion of the anterior ligament, a broad smooth facet
is seen, which, in the perfect condition of the parts, was played
upon by the tendon of the great pectoral muscle inferiorly and
superiorly by the coracoid head of the biceps, to the shorter or
humeral head of which latter muscle it gave origin by its posterior
concave border. Superiorly to this smooth facet we have the
great tuberosity of the humerus rising into a triangular process
for the reception of the insertion of the great pectoral tendon,
and nearer to the middle dorsal line we have a low ridge for the
insertion of the tendon of the second pectoral, the great elevator
muscle of the humerus. An irregularly-shaped bony process,
placed internally to and between the articular head and the
smooth facet of the humerus, and separated externally from this
latter surface by the furrow in which the anterior coracohumeral
ligament is inserted, forms with this smooth facetted process a
cup-shaped cavity perforated at its bottom by pneumatic foramina.
From the inner and outer lips of this cup, and from a considerable
portion of its internal surface, the triceps took an extensive and
bifid humeral origin ; whilst into the segment of its nm, which
is placed immediately inferiorly and posteriorly to the insertion
of the coracohumeral ligament, the large teres major s. infra-

Common Pigeon.

23

spinatus muscle was inserted. Into the anterior surface of the
irregularly-shaped process were inserted the eoracobrachialis in-
ferior and the conjoined tendons of the eoracobrachialis superior
and subscapularis muscles, for which see Plate II. u, v, and I, with
description. Into its upper surface the posterior coracohumeral
ligament and also scapulohumeral ligament are inserted. A
nodule on the outer or radial side of the humerus towards the
lower fourth of its length, marks the limit to which the insertion
of the deltoid reaches downwards, and itself gives origin to the
upper head of the extensor metacarpi radialis longior, which
upper head seems to represent the supinator radii longus of anthro-
potomy. The humerus is shorter than the antibrachium, and the
antibrachium than the hand-segment of the fore-limb. The three
metacarpals have fused with each other and with the os magnum
of the carpus into a single bone with a wide lacuna between its
elements, corresponding to the metacarpals of the index and middle
finger. Between the latter of these elements and the distal end of
the ulnar is wedged the ulnar carpal bone ; and between the former
and the distal end of the radius is wedged the radial carpal bone.
On the proximal arch and radial side of the compound metacarpal is
carried the pollex, consisting in the Pigeon of one phalanx ; on
the distal end and ulnar side of the same bone is carried the single
phalanx which, in this and all birds, makes up the whole of
the homologue of the middle digit. This single phalanx is in
close apposition with the lamellar portion of the strigil-shaped
first phalanx of the index digit, which is succeeded in the Pigeon
by one more which is somewhat similarly shaped; some birds,
however, possess three phalanges in this digit and two in the
pollex.

The same proportion prevails between the three segments of
which the lower limb is made up, as prevails between the humerus
antibrachium and manus in the fore-limb; the great length of
the middle toe compensating for the great length of the tibia
on the one side, and the comparative shortness of the tarso-
metatarsus on the other. The posterior extremity resembles the
anterior also in having a compound bone made out of elements
taken from parts homologous with the caxpus and metacarpus,
and supporting, like that bone, three digits. But it differs from
it in having no unanchylosed representatives of the carpal series.

24

Descmptions of Preparations.

whilst it has an unanchylosed metatarsal which is unrepresented
in the fore-limb^ and which carries a hallux consisting of two
phalanges, and in having a medius digit with four phalanges,
and a fourth or ' annularis ' digit with five, which latter is not
represented at all in the bird's fore-limb, butrcorresponds to the
similarly constituted ' annularis ' of the Lacertilia. In the tarso-
metatarsus two foramina are seen to pass through from before
backwards a little below its proximal double articular head, showing
its essentially triple composition. At the same end and on the
posterior aspect of the bone, a bony canal passes along the outside
of the base of the entocalcaneal process for the lodgment of the
tendon of the flexor perforans digitorum; and at the distal end
of the bone, a little above the external intertrochlear notch, we
see another bony canal for the tendon of the adductor annularis.
The posterior unanchylosed metatarsal bone has, in Pigeons as
ordinarily in perching birds, its distal articular facet at such a
level as to put the inferior or plantar sm-face of the inner or hind
toe on to a level with that of the other three.

For the points in which the skull of the Pigeon contrasts with that
of the gallinaceous birds, see Description of next Preparation ;
and for many other points in the comparative anatomy of
the Columbidae, the Rasores, and the extinct Dodo, see
Strickland and Melville, The Dodo and its Kindred, 1848,
pp. 44, 71, et passim. See also Alphonse Milne -Edwards,
Sur POsteologie du Dronte, Ann. Sci. Nat. Ser. v. tom. v.
1866, p. 355 J Professor Owen, Transactions of the Zoological
Society, vol. vi. pt. 2, 1867. A description of the tarso-meta-
tarsus and the posterior or inner metatarsus, with a specifica-
tion of the very slight differences which exist between them
and those of Columba Livia, is given by Professor INIelville in
the work on the Dodo just referred to, pp. 100-109.

For the Osteology of the Gallinaceous and Pigeon Tribes generally,
see the very valuable paper by W. K. Parker, Zoological
Transactions, v. pt. 3, 1864; the views put forth in which
have been adopted to a considerable extent in this descrip-
tion.

For the Osteology of the skull, see the paper by the same author,
Phil. Trans., 1866, and Professor Huxley's Lectures, pp.
69-129.

Skull and Bones of the Trmik of Common Fowl. 25

For the Tarsus and Carpus and Scapular Arch, see Professor
Gegenbaur's Monographs, Untersuchungen zur Vergleichenden
Anatomie der Wirbel thiere, 1864, 1865, Hft. i. pp. 38, 40,
51, 93; Hft. ii. p. 27, et passim.

For the Homologies of the digits of the fore-limb see Gegenbaur,
1. c. Hft. i. p. 41.

6. Skull and Bones of the Trunk of Common
Fowl (Gallus Gallinaceus).

The skull of the Common Fowl differs from that of the Common
Pigeon in being less ' pneumatic and polished ; and in being less
evenly globose in its fronto parietal and fronto nasal regions ; in
the shape of its nostrils ; in the much smaller obliquity of its quad-
ratojugal arch ; in its much smaller occipital angle, superethmoidal
and interorbital vacuities ; in its possession of a rudimentary vomer,
of a larger external angular process to the lower jaw ; in the abor-
tion of the posterior crus of its os quadratum or incus, the anterior
head retaining two facets, one for the prootic and the other for the
squamosal; in its differently-shaped palatines, pterygoids, squa-
mosals, and lacrymals, and in the absence of an azygos supra occi-
pital fontanelle, or venous canal. The basioccipital articular con-
dyles, however, of the Fowl and Pigeon, resemble each other in
being emarginated in the middle line superiorly, as though to
indicate, as the single occipital condyle does more plainly in the
Reptiles, its primitive composition out of three elements. The cup
of the atlas is alike in both families, imperfect and not typically
avian, and the two families resemble each other yet further in the
absence in both alike of the lateral vertebral canal in the axis and
atlas.

There are in the Common Fowl seven vertebrae which carry
unanchylosed ribs. One of these vertebrae, however, is itself an-
chylosed to the sacrum, and is sometimes reckoned as a sacral
vertebra ; but it may be better, perhaps, reckoned in the dorsal
series, as its rib is, besides being unanchylosed and articulated just
as the ribs placed anteriorly to it, in such relation in the fresh state
with the lower end of the lung as to form an indentation upon it.

26

Descriptions of Preparations.

The first and the second of the unanchylosed ribs have no sternal
rib articulated to them, and the first, besides failing thus to reach
the sternum, has less relation also than the six placed posteriorly
to it to the lung and the respiratory process ; and these two ribs
consequently are often reckoned as cervical ribs. But on account
of the absence of anchylosis, and the presence of 2l processus uncina-
tes on the second, which difiers very little in size from the first,
though the lung is indented by it, it may be better to speak of
them as dorsal, even though they do not become connected with
any sternal element inferiorly. Adopting then this nomenclature,
we may say that the Fowl has the same number of dorsal vertebrae
as the Pigeon, namely, seven ; but fourteen cervical as against
twelve in the latter bird ; fom-teen sacral as against thirteen ; and
six caudal as against seven. The congeneric subfamilies, under either
great family of the Rasores and Columbidae respectively, ai'e found
to maintain pretty regularly these numerical relations between
their several sets of vertebrae. The differences given may be
accounted for as follows : — The terminal bone of the colvmin, the
OS en charrue, appears in the Fowl to have coalesced vrith a verte-
bra which remains ordinarily free in the Pigeon j and a simple in-
spection of the sacral vertebrae from in front shows us that it is in
the more elongated anterior iliac fossa, or 'false pelvis,^ that the
Fowl possesses one more sacral vertebra than the Pigeon. In the
neck of the Fowl, the five anteriorly-placed vertebrae have hj^Dapo-
physes, the five in the middle have the carotid demi-canal, and the
four posterior have hypapophyses again, on the under sm-faces of
their centra, and it may be seen that it is from one of each of the
series provided with hypapophyses that the Pigeon has lost the two
vertebrae which place its cervical series in a numerical inferiority to
that of the Fowl. For the two vertebrae which come in the Fowl
after the axis and atlas are remarkable, as they are also in man}'^ other
Birds, and (as remarked in Description of Preparation III.) also in
the Rabbit, for the width and depth of the roof of then- neural arch,
which is less emarginated both before and behind in the middle line
than those of the vertebrae placed posteriorly to them, and is pro-
longed out laterally into alar processes connecting the anterior and
posterior zygapopbyses, and pierced by foramina only faintly indi-
cated in the mammal .specified. Now, as the Pigeon possesses only
one vertebra in this region which answers this description, one of

Shull and Bones of the Trunk of Common Fowl 27

its missing- cervical vertebrae may be said to correspoDcl to one of
the two which come third and fourth in order in the neck of the
Fowl. The other seems to correspond to one of the four vertebrae
bearing hjpapophyses which interpose themselves in the Fowl
between the first dorsal vertebra and the last cervical with a demi-
canal on its under surface^ as well because this portion of the neck
which corresponds to the lower portion of the italic S shaped curve
which this region describes in Birds is markedly shorter in the
Piffeon than in the Fowl, as for other reasons relating to number
and shape.

The neural spines are not greatly developed anywhere in the
cervical region, and least in its central portion, where the hypapo-
physes are also wanting, and their place taken by the carotid demi-
canal. In the dorsal region in the Fowl, the second, third,
fourth, and fifth vertebrae are anchylosed to each other by their
bodies, arches, and outgrowths, making thus a rigid central bar
with one free vertebra interposed, both anteriorly between itself
and the cervical series, and posteriorly between itself and the last
dorsal vertebra which is anchylosed to the sacral series. In the
Pigeon and many of its allies it is only the third, fourth, and fifth
vei-tebrae which have thus coalesced, the second remaining free. In
the Fowl the second, third, fourth, and fifth ribs carry each an epi-
pleural appendage, the processus uncinatus, as they do also in the
Pigeon, in which bird, however, the sixth also is similarly armed,
which is not the case in the Common Fowl. In both bii'ds alike,
four only of the seven ribs articulate by means of the sternal ribs
with the sternum. Each of these sternal ribs has its upper or cos-
tal articular surface elongated anteroposteriorly, and its lower or
sternal elongated transversely, and more or less distinctly bifacetted,
to correspond to the more or less distinctly bifacetted articular sur-
face of the costal border in the sternum. The last sternal rib artic-
ulates not with the sternum but with the sternal rib next in front
of it, and both of these haemapophysial elements, and especially the
more posteriorly-placed one, are at their upper end much broader
than any of the other ribs. The similarly-expanded, or ' pedate '
extremity of the external hyposternal process overlaps the pos-
terior sternal ribs, and shows, as does also the shape of the articu-
lations of the ribs, that little, if any, transverse dilation of the
thorax is possible in these creatures, and that the act of respiration

28

Descriptions of Preparations.

depends mainly upon the opening" and closing of the angles formed
by the sternal ribs with the vertebral ribs and with the sternum.
In the Fowl the fontanelle in the posterior part of the Pigeon's
breastbone is represented by a deep emargination, reaching from
the level of the xiphisternal portion of the sternum up nearly, or
quite in some specimens, to that of the last or fourth articular
facet for the fourth sternal rib. The hyposternal element of the
sternum is thus divided into two long distally pedate processes,
which, it may be remarked, are developed on each side from a
single centre of ossification, distinct and apart from the three
others from which the sternum is made up in Rasores. The hyo-
sternal processes are continued forward in the direction of the
articvdar costal border, instead of taking a direction at right angles
to it as in the Pigeon. The coracoid grooves are continued into
each other by means of a canal which pierces the base of a vertical
lamella prolonged downwards from the episternum into the ento-
sternal raphe. The episternum differs also from that of the Pigeon
in having no pneumatic foramina anteriorly at its base, though it
is sometimes perforated here by a canal opening on the upper or
visceral surface of the bone. Pneumatic foramina, it may be
added, are in the sternum of the Fowl, as in many or most other
parts of its osseous system, much more sparingly distributed than
in the Pigeon, as may be noted in the intervals of the costal artic-
ular facets, and superiorly, along the middle line, and internall}^ to
the costal processes on either side. The entosternal crista, which,
owing possibly to unequal pressure during incubation, is rarely
straight from before backwards, slopes up to its maximum height at
a point posterior to the level of the last costal facet, instead of rising
to it almost immediately from the episternal level as in the Pigeon.
It is much less deep relatively, and the space marked out upon it for
the great pectoral muscle is very little deeper absolutely than the
corresponding parts in the Pigeon. The xiphisternal portion of the
sternum is a little wider and more concave upwards than the euto-
sternum, and by virtue of its shape furnishes some protection to the
gizzard and other viscera it is in relation with during incubation.

The FowFs pelvis differs from that of the Pigeon in general
shape and texture much as its cranium does from that of the same
bird, being, as it is, more elongate and angular and less polished. As
minor points of difference, which arc nevertheless with certain ex-

Common Ringed Snake.

29

ceptions to be observed in the congeners of the subjects of com-
parison, are to be noted,— the anchylosis of the iliac bones with the
neural spines of the anterior sacral vertebrae, the vertical rather
than horizontal direction of the external iliac fossae, and the
presence of jn-aeacetabular spurs, of closed obturator tendinal fora-
mina, and of a more elongated sacro-ischiatic foramen. Internally,
the iliac fossae which are in relation with the upper lobe of the
kidney and the lower portion of the lung- have one more vertebra
entering- into their composition than the Pigeons ; and the middle
are less sharply limited off from the posterior renal fossae.

The caudal vertebrae contrast with the rest of the column, with
the exception of the atlas, in being non-pneumatic ; and with all
the rest in the absence of well- developed articular facets on their
neural arches, and the connection of their centra, as in Mammalia
and crocodiles, by interarticular fibrocartilages.

7. Common Einged Snake {Tropidonotus Natrix),

Injected and dissected so as to show the way in which its various organs are arranged
within its cylindriform body, and especially how by their subordination to the
functions of prehension and deglutition of a living prey, the digestive system
becomes the dominant system in the organization of these creatures. The dif-
ferent viscera have been exposed in situ by an incision carried along the middle
line of the ventral surface, and by the fastening out of the reflected integuments.

The following peculiarities, most of which are explicable by a
reference to the special habits and needs of the creature, may be
first noted in a description of this preparation. Both the liver and
the pulmonary organs are unilobar, the left lung being merely
represented by a rudimentary structure seen immediately to the
left of the apex of the heart ; the generative and the renal organs
are not arranged severally side by side, but each one of the right
side is placed more or less completely in front of its fellow of the left.
The oesophagus and stomach form together a highly distensible
tube running nearly directly from before backwards, whilst the
small intestine furnishes an example of a transversely folded di-
gestive tube arranged in short coils intimately connected with each
other. There is, however, no such approximation of the large

30

Descri2)tions of Preparations.

intestine to the stomach and commencement of the small intestine
as is usually found in vertebrate animals. The position of the
tong-ue in a sheath beneath the trachea which thus intei-poses itself
between that tactile organ and the oesophagus^ and also the re-
moval of the gall-bladder from immediate connection wnith the liver
down to a level where it is less liable to be injured by sudden
pressure, are probably to be regarded as modifications specially
subserving the special habits of Ophidia.

In this specimen, which is thirty inches long, the liver measures
about seven and the lung about twelve inches in length. But
the walls of the lung are but very lowly vascular after the first
three inches of its length. Its blind posterior non-vascular end is
seen just anteriorly to the right ovary; the anterior end of the
lung, represented by the development of a spongy layer on one side
of the trachea, is seen a little anteriorly to the base of the heart.
Just where the trachea begins to lose its distinctive character on
the surface of the lung, it gives off the rudimentary left lung, which
occupies the angle intercepted between the apex of the heart and the
vena cava inferior, as it passes up from the apex of the liver to enter
the heart. Midway between the apex of the heart and the apex of
the liver a black bristle has been passed between the dorsal aorta
which has been raised a little from its natural position some dis-
tance below the vertebral column, and the oesophagus, with which
it is in close relation below this point. The dorsal aorta is seen to be
constituted by the confluence of two trunks., a larger one which
gives off no branches, and which as it passes to the left on leaving
the heart is called the ' left aorta,^ and a smaller one which owes its
diminished calibre to the fact of its having given off the arteries of
the anterior parts of the body, and which, from the course it takes,
is known as the ' right aorta.^ The walls of the oesophagus are seen
to be thin and lowly, or not at all, muscular. The absence of con-
tractile power in this tube is compensated for by the working of
certain muscles homologous with the transversales abdominis of an-
thropotomy. A slip of blue paper has been passed under a fascicle
of one of these muscles immediately opposite the apex of the
liver on the left side, whilst on the right the muscle of that side
is seen to take origin from the internal aspect of the thoracico-
abdominal cavity along a line passing about midway between the
ventral apex and the vertebral abutment of each rib. Each muscle

Common Ringed Snake.

31

consists of two layers, and meeting-, as tliey do, by means of a median
aponeurosis, they must, in these animals which possess ribs of great
mobility, and no sternum, act to great advantage in propelling the
food which they swallow. Branches of the intercostal nerves are
seen passing over the homologue of the rectus abdominis along the
outer surface of the costal cartilages. Immediately above the line
occupied by this muscle are seen a series of muscular fasciculi
which arise from the tips of the ribs, and from the cartilages
at their junction with the ribs, and pass from behind and above,
forwards and downwards, to attach themselves to the lateral and
ventral rows of scales. More superiorly again we see a similar
row of muscles passing from an insertion on the ribs to an attach-
ment on the scales in such a direction as to decussate with that
of the first series.

By the removal of the front wall of the right auricle a view is
obtained of the eyelid-like valve which guards the entrance of
the great veins into the auricle. The left auricle is very much
smaller than the right. The left superior cava is seen winding
over it. Between the two superior cavae we see the thyi'oid gland.
Anteriorly again we see the hyoid apparatus which is not connected
with the larynx, and consists of two long delicate bars of cartilage
which are free posteriorly, but anteriorly are connected with each
other by a fibrous commissure about on the level of the angle
of the lower jaw. The hyoglossi muscles, which make up a con-
siderable part of the general mass of the tongue, are seen to take
origin from the posterior portion and inner aspect of each hyoid
bar, and to enter the dark-coloured sheath in which the tongue
is lodged in front of the trachea. A large salivary gland is seen
to lie along the outer surface of both upper and lower jaw ; each
gland discharges its secretion by numerous ducts, which open
externally to the rows of teeth in each jaw. In the angle between
the eye and the superior maxillary gland we see the lacrymal
gland, which, like the other two just mentioned, is large in non-
venomous Snakes.

Posteriorly to the liver a slip of blue paper has been placed
under tlie cystic duct just where it leaves the gallbladder and
passes down to join the hepatic duct. The ductus choledochus
communis thus formed comes into relation with the pancreas, and
receives its ducts as it passes to empty itself into the duodenum.

32

Descriptions of Py^eparations.

The pancreas is in relation, and, by means of bloodvessels and
fibroeellular tissue, in connection with the spleen anteriorly. The
small intestine describes two more or less open convolutions at
its commencement, but after this, is arranged, differently from the
intestinal tract of the other reptiles, in several elosely-apposed
festooulike coils which lie between the right ovary and the left
side of the body-cavity, and are enveloped in a sac of the perito-
neum which is continuous posteriorly with a mesentery, and, an-
teriorly, takes the shape of a membrane laden with deposits of fat.
By the fastening of this membrane out to the right of the animal,
we are enabled to see the upper end of the right oviduct, which is
prolonged much farther forward than the left onej secondly, the
upper end of the right ovarian sac ; and, thirdly, the lower end of
the lung ] in the interval between the duodenum and the right side
of the body. In that portion of the peritoneal membrane which
supports the lobules of fat, a large vessel is seen, the homologue
of the vena abdominalis anterior, which is usually more closely
united with the anterior muscular wall of the abdomen, just as
the dorsal aorta is usually more closely connected with its posterior
or vertebral wall, than is seen to be the case in Snakes. It passes
forward and joins the portal vein which is seen passing from the
right side of the gall-bladder to gain the inner aspect of the liver,
along which it distributes itself.

The lower half of the left ovary lies side by side with the upper
half of the right kidney. Below the lower end of this ovary, the
two oviducts are seen passing side by side down towards their
common termination in the cloaca, into which a black bristle
has been introduced. Posteriorly to the transversely directed
opening of the anus we see, the integument and muscles having
been removed, the two conically-shaped sacs which correspond
to the intromittent organ of the male.

For the muscular system of Ophidia, see D' Alton, Miiller's Archiv.
1834.

For the digestive system, see Duvcrnoy, Ann, Sci. Nat. torn. xxx.
1833 ; PI. xi. fig. 3, ibigue citata.

For the circulatory, see Jacquart, Ann. Sci. Nat. torn, i v. ser. iv.
1855. Jourdain, ibid. torn. xii. ser. iv. 1859; where the
Portal and Renal-Portal systems of the Common Ringed

Vertebrae of Constricting Serpent.

33

Snake are described at p. 178. Briickej Denkschrift. Kais.
Akad. Wiss. Wien. iii. p. 342, 1853.
For the reproductive, see Martin St. Ange, Etude de TAppareil
Reproducteur, 1854, pi. x. fig. 4.

8. Vertebrae of Constricting Serpent (FytJion Spl).

The vertebrae of Opbidia may be divided into three classes : the
first of which consists of the two anterior vertebrae corresponding
to the atlas and axis of anthropotomy ; the second of the trunk
vertebrae, which in these animals possessed of no functional limbs
nor limb-girdles nor sternum, all support moveable ribs, and corre-
spond with the posterior cervical, dorsal, lumbar, and sacral of other
Reptiles ; and the third of the caudal series which is placed pos-
teriorly to their anal outlet, and has the ribs anchylosed with the
other vertebral elements. The number of the first series is, probably,
constant in the Ophidia ; that of the trunk vertebrae may vary
from one hundred to three hundred; that of the caudal is the
most variable, being in some snakes as few as five, and in others
as many as three hundred. The neural arches of all the vertebrae,
except the atlas, are anchylosed with their centra in the squamate
Reptiles, whereas in the loricate a neurocentral suture is permanent.
The Ophidia differ from all other Reptiles in having the anchylosed
costal elements of the anterior caudal vertebrae bifid on each side
for the protection of their lymphatic hearts ; and in the non-
development in the same region of detached chevron bones for
the protection of their caudal bloodvessels, for which however the
bifid exogenous hypapophyses form a channel at least in part of
their course.

The special needs of these limbless animals are met by the ' ball
and socket^ articulation or ' enarthrosis ^ of the procoelian bodies
of their vertebrae ; and by the presence of a ' zygosphene ' on the
anterior, and of a ' zygantrum ' on the posterior aspect of the
opisthocoelian roof of their neural canal, internally and superiorly
to the ordinary zygapophyses. The ' balP in the enarthroses of
the trunk and tail vertebrae of the Ophidia forms a larger portion
of a sphere, and that sphere a more perfect one than in ordinary
Reptiles. The socket for its reception is proportionately deeper.

34

DescriiJtions of Preparations-

especially at the sides and above ; and the enarthrosis thus formed
between each pair of vertebrae being supplemented by the arthro-
dial joints developed above, mesially by the neurapophyses, and
laterally by the zygapophyses, great flexibility is conferred upon
the trunk as a whole, whilst great security against the dislocation of
individual vertebrae from their fellows is obtained at the same time.

In venomous snakes the hypapophyses are greatly developed and
present in all the trunk vertebrae ; in non-venomous snakes they
may be, as in the Python, aborted for the posterior two-thirds or
three-fourths of the length of the trunk. They are always present,
and mostly bifid in the caudal region.

There are no very important difierences between the two cervical
vertebrae of Ophidians and the atlas and axis of any other Reptiles.
The first of the two cervical vertebrae has no neural spine, con-
trasting herein with that of the Crocodilidae, but coinciding with
that of the rest of the class. Its neurapophyses neither anchylose
with each other above, nor with any other autogenous vertebral
element ; together with the anterior hypapophysis of the vertebra
and its centrum which is more or less confluent with that of the
' axis,^ the neurapophyses form the transversely elongated and
shallow articular cavity for the trefoil or heart-shaped occipital con-
dyle which is usual in Reptiles, and still retained in the less highly
specialized Birds ^. The centrum of the ' atlas,^ the so-called ' odon-
toid,^ comes into apposition and partial coalescence in the way of
amphiarthrosis with the concavity of a crescent-shaped surface on
the body of the second cervical vertebra. Its homology with the
centra of the succeeding vertebrae, which is proved by other con-
siderations, is illustrated by the presence on its upper surface of a
foramen on either side of the middle line just as in these vertebrae.
A second hypapophysis is articulated to its inferior surface and to
that of the ^axis^ where they come into amphiarthrosis. The axis
resembles the vertebrae placed posteriorly to it in having its
hypapophysis anchylosed with its centrum, and in having a well-
developed ball diflerentiated by a slight constriction both fi'om the
hypapophysis and from the posterior end of the centrum for
articulation with the socket in the anterior end of the vertebral
centrum next behind it.

' See Parker, Osteology of Gallinaceous Birds and Tinamous, Zool. Soc. Trans.
1862, p. 183.

Common Frog.

35

For a full description of the Ophidian Skeleton, see Professor Owen,
Monograph on the Fossil Reptilia, pt. iii. p. 53, 1850. Hun-
terian Osteological Catalogue, Prep. 603 et seqq., 1853. Orr's
Circle of the Sciences, Organic Nature, vol. i. p. 196, 1834.

For an account of the development of the two first cervical ver-
tebrae in Vertebrata Allantoidea, as discovered by Rathke, see
KoUiker, Entwickelungsgeschichte, p. 187, and H. Miiller,
cit. in loc. See also, Rathke, Entwickelungsgeschichte und
Korperban der Krokodile, p. 46, 1866.

9. Common Frog {Rana Temporaria), \^

Injected and dissected so as to show its nervous, circulatory, and respiratory systems,
together vdth some of its reproductive and digestive organs.

The roof of the cranium, and the body- walls in front and on the
left side, have been removed with the integument and muscles in
connection with them. The reproductive appears to be the domi-
nant system in the economy of this and of the other Amphibians,
the sudden evolution of the generative glands, especially in the
females at the breeding season, necessitating certain special coor-
dinations and correlations in all, or nearly all, the other organs of
the body. The absence of complete costal arches may be explained
by the fact that great room must of necessity be available for
the lodgment of the ova previous to extrusion, and the trans-
pirability of the skin compensates in some measure for the sus-
pension of the function of the lungs which the great distension
of the thoracico-abdominal cavity entails at those periods. The
transpirability of the skin again exercises an important influence
on the special habits of these animals as it is incompatible with
the sustentation of life except in media containing a certain pro-
portion of watery vapour. The physiological importance of the
skin as an aerating and depurating organ, in correlation at once
with the kidneys and liver as well as with the lungs, is well shown
by the distribution of vessels to it as illustrated in Plate III.
The skin of the true Reptiles is far inferior in' this point of view
to that of the Amphibia, which again is inferior to that of the
more highly organized classes in the all but universal absence of
scutes, scales and claws, and the universal absence of any of those

D 2

36

Descriptions of Preparations.

' parosteaF bones which are developed from the skin and the sub-
cutaneous and aponeurotic tracts underlying it, and form the
important bones known as 'clavicle'' and ' interclavicle/ This
preparation shows eminently well the loose connection and wide
interspaces which exist between the skin and the muscles of the
body-walls. In this interspace the bloodvessels and lymphvessels
take a considerable development, but, as in cold-blooded animals
usually, we observe an entire, or an almost entire, absence of
adipose tissue.

The heai-t is seen in the middle line in the notch between the
main lobes of the liver. In the main median fissure of this latter
organ the gall-bladder is lodged, but, like the posteriorly-placed
commissural bridge of hepatic tissue connecting the two lobes, is
concealed from view by their apposition. The epigastric, or anterior
abdominal vein, here, as in all cold-blooded air-breathing animals,
one of the main factors of the portal vein, passes into this fissure
to join the visceral factors of that vessel. The left division of the
liver, which is much the larger of the two, and is itself deeply
incised as though to indicate its moi-phological correspondence
with much more of the substance of the gland than is called by
the same name in Anthropotomy, overlies, superiorly, the lower
three-fourths of the distended left lung, and, inferiorly, the stomach
and duodenum. In the angle between the pylorus and the lower
end of the lung is seen the testis of that side in a state of tur-
gescence, with which the condition of the basal joint of the pollex
is to be noted as correlated. The epigastric vein is seen in the
region of the symphysis of the pelvic arch to receive factors from
the bifid allantoid bladder. On the dorsal surface of this organ is
seen the rectum round and behind which the first segment of the
intestine has passed, so as to abut upon the epigastric vein by the
convex aspect of a loop open towards the right. This first portion
of the intestine, it may be remarked, has its internal surface greatly
increased by the development upon it of mucous folds the larger
of which have the direction of the ' valvulae conuiventes,' and the
smaller of which have a longitudinal direction, so that the internal
surface of the bowel has a beautifully reticulated appearance. The
portion of intestine which follows upon the coil just described, lies
on the right side of the median line, and having formed one or
two more or less well-marked loops, ends in the large intestine

Common Frog.

37

at a point between the liver and the duodenum. The terminal
and proximal segments of the digestive tracts are thus brought,
as is usual in vertebrata, into close apposition". On the dorsal
surface, and immediately behind the tip of the coccygeal style,
is seen the anus. From the tip of the coccyx a slender muscle,
the pyriformis, passes outwards to be inserted into the femur,
and in_th_e ,angle between it and the coccyx anteriorly and in-
ternally, we see the posterior lymphatic heart.
"The cerebral ganglia form elongated ovoidal masses separated,
from each other by a median fissure, and by a slight constriction
from the olfactory lobes which are fused mesially with each other.,
The cerebral ovoids have their anterior extremities converging
and their posterior extremities diverging, whilst the anterior ex-
tremities of the somewhat similarly shaped but much smaUer
corpora bigemina, or ' optic lobes,' homologous with the corpora
quadrigemina of mammals, diverge, and the posterior are in mutual
apposition. An irregularly diamond-shaped space is thus marked
out between these two divisions of the encephalon ; and in it we
see the vascular pineal gland and the homologues of the 'optic
thalami.' Posteriorly to the optic lobes, and interposed between
them and the triangular 'fourth ventricle' formed by the diver-
gence of the strands of the spinal cord, we^efi_a thin transverse
lamina of nerve-substance, the homologue of the cerebellum.

Good figures and detailed descriptions of various organs and
systems in this creature will be found in Professor Ecker's
Icones Physiologicae. See, for the circulatory system, Taf. iv.,
for the lymphatic system, Taf. v., for a history of the develop-
ment, Taf. xxiii., and for the nervous system, Taf. xxiv. For
a detailed account of the venous system generally, see Gruby,
Ann. Sciences Naturelles, Ser. ii., tom. xvii., 1842; and for
one of the renal portal system, see M. Jourdain, Ann. Sci. Nat.
Ser. iv., tom. xii. 1859, whose very valuable paper appeared
subsequently to the third volume of M. Milne-Edwards' Legons
sur la Physiologic, but has had its conclusions endorsed by
that authority in his vol. vii. p. 349, 1862.

For the tegumentary system with its muco-nervous organs, see
Leydig, Nova Acta, 1868, p. 63.

o See Duveraoy in Cuvier's Le9ons d'Anatomie Compar^e, torn. iv. pt. ii. p. 657.

38

DescrijDtions of Preparations.

10. Skeleton of Common Frog {Rana Temporaria).

The following points relating to the skeleton are common to
the entire sub-kingdom Amphibia. Their vertebrae have no neuro-
'^^^<^^f.frj central suture. They have no sternal ribs, nor any representatives i
^^^^^lo^V^. of the clavicle and interclavicle of higher and lower vertebrata.\^\
Their cervical vertebrae do not exceed two, or at most three, in
number^ the supra-scapula making its appearance first opposite the
second vertebral intercentrum. Their first cervical vertebra differs
from that of all higher vertebrata, except a few Chelonia, in re-
taining as its centre what is known in them as the odontoid process
of the second vertebra ; and it differs from that of all vertebrata,
except Mammalia and a few Selachian fishes, in having two lateral
articular facets for articulation with the occipital bone, which latter
bone rarely possesses even a rudimentary centrum, and never any
spine. There is a common suspensorium, as in nearly all fishes but
in no higher vertebrata, for both the hyoidean and the mandibular
apparatus ; and there is no natural division between the suspen-
sorial and the palato- quadrate cartilages. The long bones and
some others may have epiphyses ; the terminal limb-segments are
never more than pentadactylous.

TheJbllQwing. points in the skeleton of Eana are common, prob-
ably, to the entire order Anura. The number of their free vertebrae
is small, being nine in the Raninae, and most members of the
order, but falling occasionally as low as seven ; the coccygeal style,
however, which is not reckoned in this numeration, represents at
least more than two fused primordial vertebrae. The vertebrae are
procoelian ; with the exception of the first, they all have long
diapophyses which carry cartilaginous rib -rudiments,; the diapo-
physis of the third vertebra expands distally and carries a hammer-
shaped cartilage behind which the anterior lymphatic heart lies on
the inner surface of the thoracico-abdominal cavity. In Anura
alone is the supra-scapula ossified both by ectostosis and endostosis.
The_os^pubis is of a triangular shape aud enters into the formation
of the acetabulum together with the ischium and ilium ; it may
be indurated by the deposition of calcareous salts, but it is-Jiever
converted into true bone. By apposition of each pubis and ischium
with its fellow of the opposite side, and with each other, a vertical

Skeleton of Common Frog. 39

symphysis is constituted instead of the more or less horizontal
one seen in other Amphibia. Anteriorly to the symphysis thus
formed the ilia form a second continuous with it by the apposition
of two processes homologous with the praeacetabular spurs of the
Gallinae, mentioned at p. a8.

A similar advantage in point of strength is conferred upon the
shoulder girdle of the Anura by the prolongation of the more
perfectly developed praecoracoids towards, or to the middle Ime,
and by the somewhat similarly more perfected structure of the
sternum posteriorly to the coracoid or epicoracoid symphysis.

The greater development of the limbs, together with the greater
strength of the arches supporting them, compensates for the ab-
sence of a swimming tail such as the Urodela possess. The bones
of both forearm and lower leg are anchylosed to each other. In
the lower limb the tarsal segment is greatly elongated. It consists
of two bones, the astragalus and calcaneum, which are connected to
each other at either end by epiphyses, but have a wide interval
between them for the greater part of their length.

The following points serve to distinguish the Frog's skeleton from
the Toad's. Its ossa ilii are relatively longer, as also the segments of
its lower limb ; it is not edentulous ; it has an azygos osseous^^ omo-
sternum' segmented off from its praecoracoids anteriorly in the
middle line; the ossification of the coracoid proper has encroached
upon the area occupied by the epicoracoid in the Toad, so that
scarcely any of this merely endosteally ossified bone appears in the
Frog in the line it occupies so prominently in the Toad from the
interspace between the mesial end of the coracoids and the mesial
end of the praecoracoids.

The male Fzog .differs from the female in having a large ridge
developed along the posterior aspect of the humerus from the inner
condyle upwards for two-thirds of the length of the bone, and in
the appearance at the breeding season of a supernumerary ossicle
near the thumb. The scapular arch is stronger in correspondence
with these structures than we find it in the female.
For an account of the skull of Amphibia, see Professor Huxley,

Elements of Comparative Anatomy, pp. 213-218.
For an account of the shoulder girdle, see Mr. Parker's work On
the Shoulder Girdle and Sternum, published by the Bay
Society, pp. 58-89.

40 Descriptions of Preparations.

For an account of the development of the vertebral column, see
Gegenbaur, Untersuchungen zur Vergleichenden Anatomie
der "Wirbelsaiile bei Amphibien und Reptilien^ i86a, pp. 30
and 40.

For the sexual peculiarities, see F. Pouchet, Comptes Rendus, 1 847,
pt. ii. p. 761.

11. Common Perch {Perca Fluviatilis),

Injected and dissected so as to show its circulatory, nervous, digestive, respiratory,

and reproductive systems in situ.

The part of the body posterior to the middle of the second dorsal
fin above and the anal fin below having been removed, an injection
was thrown into the dorsal aorta ; the walls of the body-cavity and
the opercular and branchiostegal apparatus were removed upon the
right side ; and the roof of the cranial cavity superiorly.

In the triangular space bounded by the four bipectinate gills
of the right side anteriorly, by the liver posteriorly, and by the
middle line of the body in front ; we see the heart with its auricle
above, its ventricle below, and the bulbus arteriosus anteriorly.
Posteriorly to the liver we see the large single ovary, the upper
three-fourths of the right half of which have been removed, but,
owing to its extreme distention, without showing the transversely
lamellar arrangement of its more or less annular ovigerous in-
volutions. The upper end of the turgescent gland has interposed
itself between the under surface of the liver to the right and the
stomach, and the commencement of the small intestine and the
pyloric appendages to the left. A loop of intestine, which is a little
less in length than the half-length of the abdominal cavity, and
which, passing downwards fi-om the commencement of the duo-
denum, contains the spleen in its concavity, is similarly concealed
from view by the distended ovary.

Owing to the same cause only one of the three pyloric caeca is
visible in this preparation, the two which arise from the posterior
or concave aspect of the commencement of the duodenum having
been displaced to the left. The gall-bladder has been displaced
upwards and to the right ; and may be seen occupying the apex
of an oval emargination in the free edge of the liver, which is

Common Perch.

41

homologous with the fossa ajstis felleae of anthropotomy, but with
which the gall-bladder of this fish does not come into relation
when the ovaiy is not in a state of turgescence.

The rectum, on the other hand, is seen commencing, as in so many
vertebrate animals, in close proximity to the commencement of the
small intestine, and passing with a straight course down the middle
line of the body to terminate, as in fishes only, in an anus placed an-
teriorly to the openings of the urinary and generative ducts. In the
peritoneal lamellae which connect the rectum with the ovary, and
also along the outer side of the air-bladder, are seen bands of yellow-
coloured pellets of fat in a condition of atrophy correlated with the
hypertrophy of the ovary. In the glistening walls of the air-
bladder may be _seenits_vaso-ganglia. Between the upper end of
this organ and the hindermost gill is seen a gland placed homo-
logously to the thymus of the Frog, and resembling the spleen
both in its naked eye, and in its microscopic appearances. The
upper end of the kidney is separated from this gland by a fibrous
partition, and its entire length, corresponding with that of the
abdominal cavity, is concealed by the air-bladder below it. Im-
mediately in front of the dorsal end of the first true gill is placed
the uniserial pseudobranchia.

The four divisions of the encephalon are in apposition with, but
do not overlap, each other in any case from before backwards;
they fall far short of filling the cranial cavity, whence much cellular
tissue, richly laden with oleaginous matter, has been removed. The
optic lobes are the largest of the four ganglionic centres; they
are, like the prosencephalon and rhinencephalon, paired, whilst the
sub-globular cerebellum is unpaired.

Tie large size of the eyes, and the bilateral pairing of the nasal
orifices, which do not communicate with the digestive tract, are
characteristically piscine peculiarities, though not universally found
in members of the class.

The membranous valve projecting backwards into the mouth
from the under surface of the upper jaw deserves notice.

A series of scales, perforated by mucous ducts supplied with
nerves, forms a 'lateral line' along the trunk, the contour of which
corresponds with that of the upper line of the back, beginning
with the bone called by Cuvier surscapulaire' (Hist. Nat. des
Poissons, i. 374), but recognized by him (1. c. p. 273.), as also by

0

42 Descriptions of Preparations.

Parker (Shoulder Girdle, p. i6.), as being merely a 'scale bone/
Similar mueo-nervous organs are to be seen upon several of the
dermal bones of the head, especially upon the scaleless praeoper-
cular and dentary bones.

As is the rule in Acanthopterygii with two dorsal fins, all the
rays of the anterior one are rigid and spinous. The first of the
thirteen fin-rays of the second dorsal is similarly rigid, as are two
of the anal, and one of the ventral. All the pectoral fin-rays are
soft and jointed.

For the general anatomy of fishes, with remarks as to its bearing
upon their zoological position, see Miiller, Vergleichende Ana-
tomic der Myxinoiden, 1838-1845; Eathke, Darmkanal und
Geschlechtstheils der Fische, 1824, especially p. 7 and p.
121 ; Cuvier et Valenciennes Hist. Nat. des Poissons, vol. i.
1838, p. 201 and p. 419.

For a detailed account of the anatomy of the perch, see Cuvier and
Valenciennes, vol. ii. pp. 38-30, pi. i.-viii., with plates.

For an account of the brain, see Gottsche, Miiller's Archiv., 1835.

For the Thymus, see Stannius, Handbuch der Zootomie, i. 356 ;
Ley dig, Handbuch der Histologic, p. 43 1 .

For the lateral line, see Macdonnell, Transact. Royal Irish Academy,
vol. xxiv. 1862;, p. 169, and F. Leydig, NoA'-a Acta, 1868.

For the terms employed in zoological description, see British Mu-
seum Catalogue of Acanthopterygian Fishes, by Dr. Giinther,
1859, "^ol- ^' P* ^11^ P- S^} YarrelFs British Fishes,
vol. i.

12. Skeleton of Common Perch {Perca Fluviatilis).

The perch, and indeed the entire Acanthoptorous order to which
it belongs, may be taken as illustrations of highly specialized, as
opposed to high types of organization ; as they accumulate in their
economy a large number of the peculiarities of their own class
rather than show any afiinity, as do the ganoids, to forms of life
higher in the scale than themselves.

One half of the moveable vertebrae are caudal, and by the
absence of ribs and transverse processes, and by the presence of
three vertical fins in this moiety of the animal's body, great power

Skeleton of Common Perch.

43

is o-iven to the organ of motion thus constituted. The imbrication
of the spinous first dorsal fin shows that the movements of the
vertebral column must be but limited in the vertical plane, and
whilst for rising and sinking leisurely, the expansion and con-
traction of the air-bladder may suffice, the animal is seen to be,
as experiments have shown it is, dependent upon its pectoral and
ventral fins for giving to the movement generated by the lateral
strokes of its tail an upward or downward direction. Besides thus
dii-ecting movement, the ventral fins serve by extension to maintain
the fish at any desired level in the water; and the pectorals, by
moving horizontally, are competent to move the animal, though
but feebly, in a forward or backward direction. The anterior dorsal
fin has a great vertical as well as anteroposterior development
which, besides subserving the purpose of defence for a fish with
a dentition ' en fin velours' serves to maintain the fish in a position
of stable equilibrium with which the large size at once of the
muscles along the upper dorsal region and of the air-bladder at
a lower level below them, would otherwise have been incompatible.
The tail-fin, having its upper and lower lobes equally developed,
does not retain any indication of the more generalized heterocercal
form of tail which many Malacopteri, such as the herring and
salmon, and some Acanthopteri show. The plane of greatest trans-
verse sectional area lies at a point about one-fourth the entire
length of the animal's body from the tip of its snout; the
narrowing from this plane forwards to the tip of the snout is, in
a well-fed fish, sudden and abrupt. The absence of both neck
and sacrum, which is otherwise expressed by saying that fish
possess only trunk and tail vertebrae, is as obviously correlated
with the peculiarities of these animals' locomotive, as the absence
of a sternum is with the peculiarities of their generative functions.

The suspensorium is articulated moveably to the outer and back
part of the cranium by a glenoid cavity which is formed for its
head by the squamosal, opisthotic, and prootic bones. Into the
composition of the suspensorium there enter four bones, viz. the
hyomandibular which forms the articular head just mentioned,
the symplectic, the quadrate, and the praeoperculum. The lower
end of the quadrate is received into the articular cavity formed by
the OS articulare of the lower jaw. On the inner surface of the
suspensorium the stylohyal comes into relation with the synchon-

44

Descriptions of Preparations.

drosis between the hyomandibular and the symplectic. The rect-
angular praeopereulum by opposing itself to the posterior and outer
edges of the hyomandibular, symplectie, and quadrate, at once
clamps them together into a coherent suspensorial pedicle, and
brings the entire apparatus into as direct a functional relation with
the true opercular bones posteriorly as that into which it is brought
anteriorly with the upper jaw through the meta- ento- and ecto-
pterygoids.

Riblike ossifications of the intermuscular aponeuroses are attached
to the neural arches of the two first trunk vertebrae and to the
true ribs of the succeeding twelve. The majority of these latter
structures are appended to the extremities of the parapophyses,
which again in the caudal region bend down and fuse at their
apices, to form a haemal canal.

The pectoral fin with the four brachials, scapula, and coracoid,
is supported on an arch consisting of three parostotic bones. The
uppermost of these, a forked bone, suspends the arch to the squa-
mosal and epiotic bones by its two branches ; it has been called the
' supra-scapula,'' but is not homologous with the structure properly
so named in placoids and sturgeons, being in reality the first
' lateral line^ scale bone, and perforated, as the insertion of a bristle
shows, for one of the mueo-nervous tubes of that system. It over-
laps the clavicle from the outside, and this latter bone, after giving
support to the true scapula and coracoid, comes into relation with
the apex of its fellow of the opposite side, in the middle line, with
the bones supporting the ventral fins, posteriorly, and \vith the
urohyal in front. The scapula has a sub-circular fenestra ; it gives
support directly to some of the upper rays of the pectoral fin, and
mediately by the two upper and smaller of the four brachials to a
larger number of these rays ; the lowest of the four brachials is
carried by the coracoid ; and a fourth finds a glenoid facet for itself
on the lower edge of the scapula, the upper edge of the coracoid,
and the line of suture between them. The clavicle overlaps a
postclavicular bar consisting of two bones, one squamiform and
placed superficially, the other styliform and placed beneath the
integuments in the fresh state.

A number of muco-dermal bones lie on the exterior of the
cranium and are connected with the system of the lateral line.

Six such, of which the most anteriorly-placed is the largest, form

Vertebrae of Common Cod.

45

the inverted suborbital arch, and three or four others, the ossa
supratemporalia, occupy the space beneath the bifurcation of the
post-temporal scale, the so-called ' supra-scapula/ A black bristle
introduced into a canal passing down the vertical limb of the
rectangular praeoperculum shows that it holds the same functional
relation to the muco-nervous ducts as the bones just mentioned.

For accounts of experimental investigations into the functions of
the vertical and of the paired fins of fish, see Sir Anthony
Carlisle, Phil. Trans., 1806, p. 4; J. Miiller, Vergleich. Ana-
tomic der Myxinoiden, 1845, p. 53; Monoyer, Ann. Sci. Nat.
Ser. V. torn, vi., 1866.

For the homologies and nomenclature of the shoulder girdle in
Fish, see W. K. Parker, on the Shoulder Girdle and Sternum
of the Vertebrata, pp. 4, 12, 50, 52, and fig. 6, D. p. 46.

For the microscopic characters of the skeleton of osseous fishes, see
KoUiker, Royal Society's Proceedings, 1859, ix. p. 656.

For those of the cartilaginous skeletons of this class, see Quekett,
' Histological Catalogue, Coll. of Surgeons, ii. pp. 5-37.

For those of the Chorda dorsalis, see Quekett 1. c. pp. 108, 109.

13. Vertebrae of Common Cod {Gadus Morrhua).

The anterior and posterior surfaces of the bodies of the vertebrae
are, as in the great majority of fishes, concave, and intercommu-
nicate with each other by a fine canal. These surfaces are marked
by concentric rings of striation, which are wider as we pass from
the centre of each terminal surface towards its periphery, and
indicate thus the rate at which the animal's growth progressed.
Deep wedge-shaped cavities are observable around the periphery of
each vertebral centrum, two of especial depth and significance lying
in many vertebrae at the base of the parapophysial outgrowths on
their under surface, and bounding a single similarly shaped, but
sometimes shallower cavity in the middle line of that aspect of
each bone. The cod's vertebra resembles those of the majority
of osseous fish,, but difl'ers from those of the common fluviatile
representatives of the class such as the Cyprinidae, Salmonidae,
and Esocidae, in having its various processes and arches anchylosed

46

Descriptions of Prej^arations.

with its centrum. About twelve of the trunk vertebrae have two
parapophyses, developed one in front of the other, from the lateral
surfaces of their centra, the more forwardly placed being the larger
of the two. These two outgrowths, besides serving as zygapo-
physes, as may be seen in the dried bone, gave in the liying
animal, protection to the air-bladder, which, though devoid of the
air-duct possessed by the three fresh-water orders just specified,
is yet largely developed in the Gadidae. There are two articular
facets, a larger looking outwards and a smaller one looking in-
wards, developed upon the anterior aspect of the base of each
neural arch, as it rises from the anterior edge, or close upon the
anterior edge of each centrum. An imperfect socket is thus
formed in some of the vertebrae for the posterior zygapophyses
of the vertebrae next in front, which zygapophyses are upgrowths
developed upon the centra, independently of the neural arch, and
have their single articular facets looking inwards. The parapo-
physes of the trunk vertebrae after the fifth, carry ribs, or rib-like
intermuscular ossifications, or both, and in the caudal region they
form perfect haemal arches.

The bones of fishes are the poorest in inorganic constituents of
all the five classes of vertebrata, and the bone cells, the microscopic
morphological essential of true bone, are wanting in both Plagio-
stomi and Cyclostomij in Acanthopteri, and most other fishes, with
the exception of the Physogtomi and Ganoids. In the small pro-
portion of inorganic matter in their bony or 'osteoid^ tissue fish
resemble the Amphibia ; but as the lowest of this latter class
possess true bone-tissue, it may seem that the absence of bone cells
is correlated more or less exactly with the absence of the air-duct
which is possessed by the two orders, Physostomi and Ganoidei,
which possess true bone. The low proportion of inorganic salts in
the bones both of Amphibia and of Pisces, may be correlated in
both alike with their aquatic habits.

For the absence or presence of bone cells in the skeleton of fish,
see Kolliker, Royal Society's Proceedings, ix. p. 656, 1 859 ;
Quekett, Histological Catalogue, ii. B. a. 132, p. 40.

Shell of Edible Snail.

47

14. Shell of Edible Snail {Helix Pomatia).

When the shell has its apex directed upwards, and its aperture
downwards, and towards the describer, its spire will be seen to
ascend obliquely towards the right, and this is the case in the
great majority of spiral Gasteropodous shells, which are in con-
sequence ordinarily called 'dextral/ In such molluscs the heart
is placed on the left, and the generative, respiratory, and anal
orifices on the right of the animaVs body. The columella is seen
in the angle formed by the left border of the peristome, and the
first whorl of the shell ; its umbilicus is partly, but not wholly,
as in the common garden snaU, Helicc Aspersa, concealed by the
reflection over it of the peristome, corresponding to which structure
in this situation, there was developed in the mantle of the living
animal, a process of the collar known as the ''columellar lobule.''
The smooth rounding off" of the peristome shows the animal to
have been adult. The shell is coarsely striated in a longitudinal
direction, that is to say, in a direction corresponding with the
lines of growth ; and more delicately in a spiral direction, that
is to say, in a direction at right angles to these lines, and parallel
to the five coloured bands with which it is marked. The ' apex'
or ' nucleus ' of the shell, which was the earliest developed or
embryonal shell-whorl, differs, as is so often the case, from the
rest of the shell, and in this instance, by possessing a smooth and
semi-porcellanous appearance. The way in which the injuries
which the shell had received during the life of the animal, have
been repaired, without any attempt at a restoration of the damaged
exterior layer, shows_ymt_jt is only along the peristomal margin
that such repair can be effected. Injuries received posteriorly to
the free rim of the shell, which is in relation with the collar of
the mantle, call forth the secretion of protecting layers, by the
thin and transparent portion of the mantle ; and these layers by
successive super-imposition from the mantle outwards, produce the
thickenings visible on the interior, in correspondence to the in-
juries on the exterior of the shell which is left unrepaired.

The thickness of the Gasteropodous shell diminishes from its
free rim upwards, and it is probable, consequently, that, except
under the stimulus of injury, little accession of growth takes place

48

Descriptions of Preparations.

in it posteriorly to the peristome. In this point, as also in that
of possessing a much smaller amount of organic matter, the Gaste-
ropodous contrasts with the Lamellibranchiate shell.

For the structure and mode of development of the shell, see Huxley,
Cyclopaedia of Anatomy and Physiology, Article 'Tegumentary
Organs,' pp. 489-492. For views somewhat different from
those put forth there, see Bronn und Keferstein, Klassen
und Ordnungen des Thierreichs, iii. 2, pp. 901, 902, 913,
920, 1 177, 1 18 1, and E/Ose, Abhandlung, Berhn, Akad. 1858,

PP- 94. 95-

For the terminology employed in describing shells, see English
Cyclopaedia, Article ' Gasteropoda,'' p. 925.

15. Edible Snail {Helix Pomatia).

Dissected so as to sliow its digestive and reproductive, together with portions of its

circulatory and respiratory, organs.

The shell has been detached from the body to which it adhered
mainly by means of the columellar muscles, and that part of the
general muscular envelope of the viscera, which was continuous
with their insertion. The greater part of this muscular envelope
and of the mantle has also been removed. The coils of the
liver, which were lodged in the uppermost whorls of the shell,
and which contain the hennaphrodite gland impacted in their
substance, have, together with the rest of the reproductive ap-
paratus, been arranged on the animal's right side ; the larger part
of the liver with the intestine, heart, and respiratory sac, occupies
the left of the preparation ; the nerve collar and digestive ap-
paratus down to the pylorus, are seen in the middle line; and
between them and the parts to the left, lies at a lower level the
sole-shaped locomotor disc known as the ' foot.' A black bristle
has been passed between the cephahc ganglia, or supra-oesophageal
portion of the nerve-collar and the buccal mass, which, together
with the horny crescent-shaped jaw, has been retracted somewhat
from its natural position. From the lower part of the buccal mass,
a small conical body, in whicli the back part of the so-called
Uongue' is lodged, projects posteriorly. Along the upper and

Edible Snail.

49

posterior border of the buccal mass^ we see mesially the entrance
into it of the oesophagus ; and on either side that of the duct
of either saHvary gland^ just above the stomatogastric ganglion.
Posteriorly to this^ the oesophagus expands gradually into the
stomachy which is embraced by the salivary glands, and has a
pyloric caecum developed upon it, just where it comes into relation
with the liver. The bile-duct, which is single at its termination,
opens at the pylorus, as__directly_into_ the- intestine as into the
stomach. The first segment of the intestine runs up towards the
heart, and, together with the oesophagus and stomach, makes up
a curve with its concavity towards the pedal ganglion ; as is the
case also in Cephalopoda, Pteropoda, and Lamellibranchiatap. Just
below the heart, and above the aorta, which is seen to be cut
across, the intestine msses on to the external surface of the liver,
to reappear again on tEe~left of the gireparation, whence it runs
with a straight course to the anus, into which a white bristle has
been introduced. To the right of the terminal segment of the
intestine we see the pulmonary sac, its vessels, and the heart ;
and between these structures and the buccal mass, the left parietal
nerve passes off to distribute itself in two divisions to the body
walls. At a little lower level, and a little posteriorly, a more
delicate nerve distributes itself to the muscular fibres, which retract
the posterior part of the foot, joining them just as they rise above
the level of the mass of the foot, to pass up to thej,r_ insertion on
the. columella. This portion of the columellar muscles lies, in this
preparation, immediately to the left of the buccal mass. It is
much feebler than the anterior retractor columellar muscles, as
may be seen from the fact that much of the posterior part of the
animaFs foot is still left unprotected, when during life it has
retracted itself as far as usual into the shell. The posterior
retractor fibres are continuous on either side with the general
muscular envelope of the viscera, and a deep furrow separates
them, as in life, from a portion of the mantle which is here left
in situ. Immediately above these structures we see three nerves,
which have been cut away from their peripheral distribution, but
remain attached to the centre whence they arise, viz. the upper

P See Huxley, Royal Society's Transactions, 1853, pp. 46, 57 ; English Cyclopaedia, •
Article 'Mollusca,' p. 858 ; but see also page 68, infra.

60 Descriptions of P^^eparations.

or parieto-s]janchiiic portion of the sub-oesophageal mass. Two
of these are the'parietal nerves of the right side ; and the third,
which is seen to be double at its termination, is the visceraj_ ne^e
in connection with the aorta. The hermaphrodite ^laad is lodged
in the concavity of tlie penultimate and ante-penultimate coils
of the hver7 which occupy the^Iowest part of the preparation on
the right hand. From the gland a convoluted hermaphrodite duct
passes up to a spleen-shaped body, the albuminiparg^ and
after this junction, the duct passes upwards again as a much
thicker tube consisting of two parts, one of which is much plicated,
whilst the other is a riband made up of granulations. These two
elements of the tube are not differentiated from each other till
just opposite the convex end of a cylindiical hollow muscular
organ, the dart-sac, where they separate and form, the one the
oviduct, an(nErother the vas deferens. The vas deferens loops
round the right tentacle, and joins the basis of the penis;:cylinder
at the point where the flagellum, or organ for secreting the sper-
matophore, also joins it. This latter organ is of great length,
en5ng~blindly at the lowest part of the preparation, and to the
right of it is placed the pedunculate jeceptaculum seminis of
commensui-ate, as obviously of correlated, length. The retractor
muscle of the penis is attached to it a little below the point of
junction to it of the vas deferens and flagellum. Below the penis
are seen the multifid vesicles, forming ultimately two main trunks.
These vesicles, ~the dart-sac and the flagellum, are peculiar to,
though not uniformly found in, Em-opean Helicidae. The flagellum
is never found in American species, and the dart-sac and the
multifid vesicles are much rarer in these representatives of the
family than in the European species. Some, however, of the
American Limacidae possess them, which is not the case with
the Old World slugs. Much variability, both as to size and as
to constancy, is, as is usually the case with structures specially
developed in particular families, and not generally possessed by
the entire order to which they belong, observable in these struc-
tures, as investigated in one species after another in the families
possessing them.

For the anatomy of the Pulmonate Gasteropoda, see Leidy, vol. i.
p. 198, in Binney's Terrestrial Air-breathing Molluscs of the

Edible Snail.

51

United States ; see also Semper, in Siebold and Kolliker's
Zeitschriffc fur Wiss. ZooL, viii. 1857, p. 340; and for the
points of difference between the reproductive apparatus of the
Old and New World Pulmonata, see Leidy, 1. c. p. 229.

Por a monograph of Helix Pomatia, see Cuvier, Memoires pour
servir h, FHistoire et k FAnatomie des Mollusques, 1817, or
Ann ales du Museum, torn, vii., 1806.

For the reproductive apparatus, see Owen, Comp. Anat. Inverte-
brata, p. 562; Baudelot, Ann. Sci. Nat. Ser. iv., torn, xix.,
p. 170, pi. ii. fig. 17, 1862. The identifications of the various
organs adopted by the two latter authors, differ from those
adopted by Cuvier and Leidy, but are doubtless more correct.

16. Edible Snail {Helix Pomatia),

Dissected so as to show the position of the heart, and the respiratory cavity.

The greater part of the shell has been removed, but a part of
the spire has been left in situ. An incision has been made trans-
versely through the roof of the pulmonary sac, and its cavity
has been exposed by turning forward the anterior fiap. The vessels
have been injected with a red-coloured fluid from the auricle. The
bilocular heart is seen, as in dextral molluscs, on the left side, and
posteriorly, and, in this preparation, inferiorly to it is seen the
tria^gular^ pale-coloured kidney. Along the front border of the
posterior section of the roof of the pulmonary sac, the pulmonary
vein is seen passing towards the apex of the pyramidal auricle.
Just before entering it is joined, as not rarely in mollusca, by
the e^ent renal veins. The right half of the roof of the re-
spiratory cavity is covered by vascular ramifications ; the anterior
part of the left half is destitute of them, the posterior corresponds
to the kidney, or is constituted by the ' pericardium. The non-
vascular floor of the respiratory cavity is seen to be formed by
muscular fibres, arranged somewhat after the fashion, and doubtless,
during life, performing some of the ftinctions of a diaphragm.
A more delicate muscular layer enters into the formation of the
roof of the sac, taking origin from a thickened band which runs

52

Descriptions of Preparations.

along the concavity of the visceral spire, and joins the free thick-
ened rim or ^ collar^ of the mantle, a little posteriorly and su-
periorly to the respu-atory orifice. One of the afferent pulmonary
veins is figured by Milne Edwards, Memoires de FInstitut, tom.
XX., 1849, pi. V. d., as taking a similar course. The musctdar floor
of the respiratory sac discharges a secondary function, in propelling
the animal downwards when it has been retracted into its shell,
as well as a more obvious and primary function in the act of
breathing. In the completion of the act of forcing the animal's
body out of the shell, the '^collar'' takes a share. And it is to
this thickened muscular and glandular border of the mantle that
the segj^etiaiLoXthe epidermisjif t^ and its increase of capa-
city is due in all shelled Gasteropoda, whilst the formation of the
epiphragm_i& also to be ascribed to it in the air-breathing repre-
sentatives of the class.

For the formation of the epiphragm, as observed in the Eelix
hortensis, see Binney, Terrestrial Air-breathing Molluscs of
the United States, vol. ii. p. 114; Keferstein, Klassen und
Ordnungen des Thierreichs, iii. ii. p. 11 86.

For figures of the pulmonary vessels in Helix Pomatia, see Milne
Edwards' Memoires de FInstitut, tom. xx. 1849, pi. iv., pi. v. ;
C. G. Carus, Tabulae Comp. Anat. iv. vii., a, 5.

17. Edible Snail {Helix Pomatia),

Dissected so as to show its nervous system.

The mantle has been separated from its attachment around the
base of the visceral mass, except for a short distance, corresponding
to the middle line of the foot posteriorly, and along from that
attachment, a short distance round on the animal's left side, where
a triangular lappet, the so-called ' columellar lobule,' is developed
upon it. It has been turned over to the left side, together with
the organs in connection with the roof of the cavity it developes,
viz. the heart and the pulmonary vessels, the rectum, and the
kidney with its duct. The integument covering the head and
neck has been divided in the middle line, and fastened out on

Edible Snail.

53

either side ; the muscular envelope which was continuous with
this part of the integument, and formed the floor of the mantle
cavity on the one hand, and a roof over many of the viscera not
already specified on the other, has been removed, as have also
all the viscera unconnected with the mantle, except the nerve
system and the buccal mass. A black bristle has been passed
through the nerve collar, between the supra-oesophageal cerebroid
ganglia and the commencement of the digestive tube ; and another
has been inserted between the stomato-gastric ganglion of the right
side, and the back part of the buccal mass. A stout nerve passes
from either side of the sujDra-oesophageal mass to the superior
or eye-bearing tentacle, indicating thus by its distribution the
sensory character of the nerve centre whence it arises. The in-
ferior tentacles are supplied from the same source, as are also the
rudimentary 'organs of Semper,^ and the upper lip. A long and
delicate commissural cord is seen to connect the cerebroid mass
with the stomj^Orgastric ganglion, which is placed in the re-entering
angle between the oesophagus and the retracted buccal mass. A
much stouter and double commissural cord is seen passing down-
wards, from the supra-oesophageal mass on the right side. By one
of its strands, the shorter and the more posteriorly placed of the
two, it connects the upper or parieto-splanchnic portion of the
sub-oesophageal mass with the supra-oesophageal of its own side ;
and by its longer and more anteriorly placed, it comes into a
similar relation with the lower or pedal portion of that part of
the nerve collar. From the upper part of the sub-oesophageal
mass, three nerves pass off to the parietes, as opposed to the foot,
two on the right side, and one on the left. Certain other nerves
which supply the columellar retractor muscles, as also the great
visceral nerve, which has been removed together with the aorta,
which it accompanied, had a similar origin. Immediately below
the origin of these nerves, the sma,ll otic vesicles may be seen
situated at the upper and posterior aspect of the pedal mass, which
is so closely connected with the parieto-splanchnic portion of the
sub-oesophageal mass in the Helicidae, as to be differentiated from
it mainly by the position of these vesicles externally, by the orifice
through which the cephalic aorta passes mesially, and by the
origin of the nerves passing off to the locomotor-disc or ' foot'
infer iorly.

54

Descriptions of Preparations.

For the nervous system of the Cephalous Mollusca, see Hancock'
and Embleton, Phil. Trans. 1852, p. 238; Huxley, Phil.
Trans. 1853, p. 53.

For figures of the nerve system of this and other Pulmonate Gas-
teropods, see Keferstein, Die Klassen und Ordnungen des
Thierreichs, iii. 2,, Taf. xcvi., and Walter, Microscopische
Studien, 1863, cit. in loc.

For a figure of the nerve collar with the otic vesicles and aorta in
situ, see Leidy in Binney^s Terrestrial Molluscs of the United
States, vol. i. pi. xvii. fig. iv., and vignette, p. 248.

For the distribution of the nerves, see Cuvier Ann. du Museum,
torn. vii. p. 172, 1806; or Memoires pour servir ^ FHistoire
et a I'' Anatomic des Mollusques.

%

18. Shell of Fresh-water Mussel {Anodonta Cygnea).

When the bivalve shell of the fresh-water mussel, or of any of
the British fresh-water species of Lamellibranchiata, is held with
its hinge-line upwards, its line of aperture downwards, and its
ligament and its umbones, the most convex portions of the valves,
placed, the one proximally, and the other distally to the observer,
he will then have the animaFs right valve at his right hand,
its* left valve at his left hand, the anterior portion of its body
placed distally, and the posterior proximally to himself. Such
Lamellibranchiata as have the power of moving from place to
place, by the protrusion of their distensible 'foot,^ do so in the
direction which the words 'anterior' and 'posterior,' as used here,
imply. The shell of the Anodon is, as in the immense majority
of Lamellibranchiata, nearly or quite equivalve, whilst, as in all, it
is inequilateral. By its size, which is in an inverse ratio to the
extent of junction of the lobes of the mantle which secretes it,
it surpasses all European fluviatile bivalves, and sections, or indeed
fragments of it, are consequently exceedingly instructive, as to the
structm-e of the various layers of which the shell is composed.
Nearly the whole of the inner surface of the shell possesses an iri-
descent appearance, due, probably, mainly to the light being dif-
fracted by the layers of delicate lamellae with irregularly overlapping
edges, which make up the nacre or inner layer of the shell, and are

Shell of Fresh-tuater Mussel.

55

themselves made up of polygonal masses of small size secreted by
the mantle exclusively of its margin. Very frequently, even in the
diy shell, it is possible to separate a thin white layer consisting
of a structureless membrane, laden with granular calcareous deposit
from the nacreous or ' mother of pearF internal layer of the shell,
which was formed by the successive super-impositions of such
membranes from within outwards. The free rim of the shell is
constituted by the coloured opaque epidermal layer, which forms a
flexible border of several lamellae, immediately internally to which,
in this, and in all still growing shells, on the inner surface of the
shell, a similarly dark-coloured but non-flexible strip intervenes
between the epidermal free border and the nacreous surface of the
shell. This portion of the shell which bounds the nacreous portion
like a fringing reef, is seen, when looked at with a simple lens,
to possess an appearance like that of shagreen, and this appearance
on examination under a higher power, is found to be due to its
being divided into minute polygonal spaces, over which the nacreous
layer has not yet extended. The inner of the two layers of which
this portion of the shell is made up, is known as the ' prismatic'
layer, and is formed by the deposition of calcareous matter in the
interior of vertical prismatic cavities, which are themselves formed
by the successive super-addition and coadaptation of fenestrated la-
minae secreted by the margin of the mantle. There is less difference
between the thicknesses of the two inner layers of the shell in
the Anodon than in most other Lamellibranchiata ; the middle
or prismatic layer is, as the fact of its being secreted by the margin
of the mantle would have led us to anticipate, thickest, both
absolutely and relatively, in those parts of the shell in which
peripheral growth is carried on at the most rapid rate ; and con-
sequently it is thicker at the free edges than along the dorsal
region, and in the posterior than in the anterior parts of the shell.
The relation held by the ' prismatic' layer of the shell to the parts
where growth is going on most rapidly ; its existence there inde-
pendently of the ' nacreous' layer ; and, thirdly, the fact that the
calcareous particles in its substance do not possess a crystalline
character, appear conclusive against the viewi which has been

' See H. Muller quoted by Hassling, 'Die Perlmuscheln und ihre Perlen,' p. 261,
Bronn and Keferstein, iii. 2, 913, and Rose, Berlin Akad. Abhand. 1858, p. 98.

56

Descrijptions of Pi'ejparations.

proposed, to the effect that the prismatic layer has been formed
by some such rearrangement of the particles deposited in the inner
nacreous layer, as takes place in certain calculi, after the primary
deposit of the solid substance of which they are made up in an
amorphous condition, or in the alteration of an amorphous glass into
the so-called ' Reaumur^s porcelain/ The ' ligament'' which connects
the two valves along the dorsal line, posteriorly to the beaks of
the umbones, consists of two layers — an outer corresponding to the
epidermal layer of the shell ; and an inner, the so-called ' cartilage,'
which combines by its two sets of striae, one rimning vertically
and the other horizontally, the laminate appearance characteristic
of 'nacre,"* with the ' columnar' characteristic of the prismatic layer
of shell, and illustrates thus the fundamental morphological and
developmental identity of these structures. The ligament in the
Anodon is said to be ' external it is, however, a Uttle overlapped
on either side for a short way by the superficial layers of the
valves which it connects, and divaricates when not antagonized
by the adductor muscles. Corresponding to the ligament, there is
on the inner surface of the shell a long low ridge, indented at its
posterior end ; a similar structure exists in the pearl mussel, Unio
Margaritifer ; and seems to be a rudimentary representative of the
elongated posterior lateral tooth, developed in the two other British
Naiades, Unio Pictorum and Unio Tumidtis. The cardinal teeth are
absent also in the Anodon, and the anterior laterals are wanting in
all the British Naiades. There are three principal muscular de-
pressions on the inner surface of each valve, two towards the upper
edge of the blunted anterior end, and one at about the same
distance from the dorsal or haemal edge of the valve, and about
midway between the posterior limit of the ligament and that of
the valve. Of the two anterior depressions, the larger marks the
place of attachment of the anterior adductor of the valves, and also
of the anterior retractor of the foot ; the smaller, which is close to
the posterior inferior aspect of the larger in the angle between it
and the pallial line, marks the place of attachment of the protractor
of the foot. The larger part of the posterior muscular depression
coi-responds to the insertion of the posterior adductor, the irregular
process into which its anterior and upper angle is prolonged into,
corresponds to the point of origin of the posterior and larger re-
tractor of the foot. An in-egularly denticulated line, which is

Shell of Fresh-'wate'r Mussel.

57

known as the ' pallial line/ and which corresponded in the living
animal to the line along which the muscular border of the mantle
was more or less loosely attached, just where it became confluent
with the central lobes of the organ, describes a curve, similar to
those of the concentrically arranged ribs on the outside of the
shell, between the two principal muscular depressions. Certain
smaller muscular depressions are visible just anteriorly to the apices
of the umbones, marking the points of origin of certain retractor
fibres. The thinner, lighter coloured, and less eroded of these two
shells came from shallow water; the thicker, darker, and more
eroded is an ordinary deep water form. That the amount of in-
organic salts wbich these as also other organisms take up, is by
no means dependent upon the amount present in the medium in
which they live, but upon the selective working of their tissues,
which may be intensified or diminished by other chemical and also
by non-chemical conditions, is seen from instances such as these,
as also from a comparison of the dense shell of the Pearl Mussel
from mountain streams, such as those of Westmoreland, with the
thin light shells of the Anodons from the Oxford waters so much
richer in salts of lime.

For an excellent disquisition upon the last-mentioned point, as well
as upon many others relating to the physiology of the Pearl
Mussel, Unio Margaritifer, a species allied to the Anodon,
see Voit in Siebold and Kolliker^s Zeitschrift fur Wissen-
schaftliche Zoologie, x., 1859, p. 470.

For a monograph of the former species, see T. von Hessling, Die
Perlmuscheln und ihre Perlen, Leipzig, 1859.

For accounts of the formation and structure of the shell, see Bronn,
Klassen und Ordnungen des Thierreichs, iii, i. p. 420; Voit,
1. c. p. 487 ; Huxley, Cyclopaedia of Anatomy and Physiology,
Article Tegumentary Organs/ Carpenter, British Assoc.
Reports, 1847, P^- ii^-^ figs. 8, 9, 10.

For a description of the animaFs muscles, the impressions of which
on the interior of the shell are mentioned above, see Poli
Testacea Utriusque Siciliae, tom. i. p. 36, tab. ix., fig. 2.

For the amorphous non-crystalline character of the calcareous de-
posit in the shell of Unio, see Hessling, 1. c. pp. 251, 261.
See also Rose, Berlin Abhandlungen for 1858, p. 98.

58

Descriptions of P^^eparations.

19. Fresh-watee- Mussel {Anodonta Cygnea),

Dissected so as to show its digestive tract, with a neural flexure formed by it at

its commencement.

The mantle and the lamellae of the gills have been removed from
the animaFs right side, together with so much of the body-walls
as it was necessary to remove so as to expose the coils of intestine,
and the stomach, m sikt, and in connection with the liver and
reproductive gland. The passage from the mouth to the stomach
is similarly laid open, and is seen to be lined with a smooth mem-
brane, lying upon the anterior adductor and the anterior retractor
muscles, and thrown by their contraction into corrugations. The
ingestion of alimentary matters depends, as no prehensile apparatus
exists in the Lamellibranchiata, upon the currents of water which
find entrance into the digestive tract, and have their passage along
it greatly promoted by the readiness with which the circumjacent
tissues become charged with, and also set free from the transuding
fluid; by the alternate opening and closing of the valves j and,
finally, by the ciliary movement of the microscopic epithelium
which clothes the interior of the digestive tube as well as tlie neural
surfaces of the mantle, gills, and labial tentacles. The bilamellate
oral tentacle of the left side is seen to become continuous with the
lining membrane of the mouth, to which, by its junction with its
fellow of the opposite side, removed in this preparation, it furnished
lips. Further down, the liver is seen supporting the lining mem-
brane of the stomach and sending ducts to open into its cavity.
The diverticulum for the 'crystalline style,' an organ somewhat
variable, but found in greatest size and constancy after the winter,
opens on the right side of the stomach ; whilst the pylorus leads
into the intestine from the left in the preparation. A black bristle
is passed along the first segment of the intestine which is seen to
form, when viewed in connection with the stomach, a curve with its
concavity towards the pedal ganglion. This, the primary flexure of
the intestine, is thus a ' neural' flexure ; the conca^^ties, however,
of the other loops which the intestine alone describes, look towards
the dorsal or 'haemal' surface. Considering the intestine exclu-
sively of the stomach, we may speak of it roughly, as describing
three concentric curves in intimate connection with the viscera, and

Fresh-watei' Mussel.

59

before it disengag-es itself from the mass they make up. Of these,
the one directly continuous with the stomach, is placed between
the other two, and two raised ridges are visible upon its inner
surface — one, the larger of the two, upon its neural, the other, the
more delicate, upon its haemal aspect. With this first loop, the
one placed most externally is continuous, and is seen bending
sharply back from, and closely round upon it along the posterior
free margin of the foot. Upon its surface there is no longitudinal
ridge developed, but a raphe with pliccs running from it at right
angles to the long axis of the intestine. It is in close relation
with the muscular strata of the ' foot.-* In ends in the third loop,
which at its beginning passes over the first so as to become quite
superficial in the middle of the right side of the visceral mass ;
and then takes a horizontal course, as seen in this preparation,
to the haemal border of the animaFs body, at a deeper level parallel
to and immediately posteriorly to the portion of intestine imme-
diately continuous with the pyloric end of the stomach. Where it
reaches this deeper level, a raised ridge is developed upon it, which
commences with a club-shaped end, and is prolonged on the neural
wall of the intestine as far as the anus. After thus completing its
third coil, by reaching the haemal edge of the visceral mass, the
intestine emerges from it, and turns at a right angle to its previous
direction to pass, as in the great majority of Lamellibranchiata,
through the heart, the cut edge of the ventricle of which is seen to
the left of the intestine. The pericardial space appears, in section,
as a triangular cavity, bounded by the heart and intestine to the
left, the retractor pedis posterior below, and the organ of Bojanus
to the right. The two cavities or sacs of which this organ is made
up, are well seen in section; though the walls of the superiorly
placed and non-glandular sac are more nearly in apposition than in
nature. The lamellate glandular sac is seen prolonging itself
around the tendon of the posterior retractor, and along the anterior
and inferior surface of the posterior adductor. Posteriorly again
to the posterior adductor, we see the attachment of the gill of the
left side to the mantle at a point corresponding to the junction
of the fimbriate with the non-fimbriate portion of the mantle.
The preparation is suspended by the apex of the muscular ^ foot;'
by the protrusion and implantation of which into the soft bottoms of
the ponds and streams in which these creatures live, they can move

60

Descriptions of Preparations.

themselves slowly along the furrow they thus form. The shape of
the ' foot' varies much within the limits of the class, from being
exceedingly small or rudimentary, up to the proportions we see
here, where the name ' pelecypoda' has been coined to express its
shape and proportions.

For a description of the digestive system of the Anodon, see
Langer, Denkschriffc. Akad. Wiss. Wien. viii., 1854, p. 19,
and TaflF. i. and ii. figs, i, 3, and 9, or V. Hessling, Die
Perlmuscheln, p. 266.

For that of Lamellibranchiata generally, see Huxley, English
Cyclopaedia, Article 'Mollusea,' p. 861.

For a description of the organ of Bojanus, see Lacaze Duthiers,
Ann. Sci. Nat. Ser. iv. tom. iv. 1855, with semi-diagrammatic
figure, pi. V. fig. 2, which is reproduced by V. Hessling, 1. c.
pi. V. fig. 6. Langer, Denkschrift. Akad. Wiss. Wien. B. xii.,
p. 39, 1856, tab. i., figs. 3 and 4.

20. Fresh-water Mussel (Anodonta Cygnea),

Prepared so as to show some of the functional as well as the anatomical relations

of the mantle.

A RED injection having been thrown into the auricles, has passed
not only into the gills, but also over the central portion of each
mantle lobe, from the line of attachment to it of the external gill,
down to the border where the central portion becomes continuous
with the free muscular rim of the mantle, and where it was at-
tached to the 'pallial line' in the shell. From the central portion
of the mantle, the injection has spread by anastomosis into the
vessels of the free muscular and tentaculate rim of the organ, and,
more freely, into the labial tentacles. Thus the functions of the
principal aerating organ, the gills, are seen to be more or less
supplemented by the subsidiary working of the structures specified.

The mantle lobes are not united below the plane of the inferior
or neural surface of the two adductor muscles, except indirectly
by the commissural junction of the branchiae posteriorly to the
foot. By this junction of the gill plates the mantle cavity is divided
into two chambers, an inferior or branchial chamber, the entrance

Fr'esh-ivater Mussel.

61

to which is guarded by the tentacidate postero-inferior portion of
the mantle, representing- the inhalant siphon of the siphonate
orders ; and a superiorj or anal chamber, into which a white bristle
is introduced in this preparation, and which corresponds to the
exhalant siphon of the other orders just named. The large mantle
lobes have been turned upwards, and fastened on to the haemal surface
of the animal on either side of the raphe, along the middle line of
that aspect of the animals body. Their thickened muscular border,
corresponding to the collar of the Gasteropoda, is well seen, the
radiating striae on its lateral surface marking its extent, which
corresponded in the living animal to the space between the free
edge of the shell and the ' pallial line.^ Two main lips run along its
free edge, inclosing however between them two somewhat smaller
ridges. To segments of this furrowed and ridged surface, portions
of the epidermal shell-layer which they secreted are still left ad-
hering. The prismatic layer appears to be deposited by the most
peripherally-placed strip of the external surface of the organ, just
where it becomes continuous with the downward-looking surface
just mentioned. The two halves of the dorsal raphe diverge from
each other in the genus Unionidae, and then re-unite immediately
anteriorly to the posterior adductor. The cirrhi, which guard the
entrance to the branchial compartment of the mantle cavity in the
natural condition of the animal, are developed from the inner of
the two lips of the mantle edge, beginning at a point corresponding
with the line of attachment to it of the outer gill lamina. The
inner gill lamina of each side fuses, as already said, with its fellow
of the opposite side so as to form a continuous floor, perforated only
by microscopic apertures, between the anal and branchial chambers.
But as the gills fail to become attached to the body for about the
posterior three-fifths of its length from before backwards, free
intercommunication exists between these two chambers for this
space. In this interval between the free gill-edge, along which
a large branchial vein is seen to run, and the visceral mass, the
glandular portion of the organ of Bojanus comes into view from
above. It is from the retia mirabilia of this organ that the branchial
inferent vessels take their origin, and pass upwards to distribute
themselves on the inner surface of the gill-laminae, whilst the
efferent branchial veins have their distribution, as seen by the
injection, on the outer or inferior surface of these ore-ans. As shown

62

Descriptions of Preparations.

by Dr. Sharpey,'" it is in the direction fi*om without inwards that
the currents of water pass through the gills under the influence
of ciliary action; and it will be seen therefore that the water
which comes into relation with the vessels returning blood to the
hearty has lost as little as possible of its aerating value, by contact
with other tissues of the animaFs body. It is well to add that the
surface of the mantle which looks towards the gills is like them
clothed with ciliated epithelium ; whilst its surface which looks
towards and secretes the two inner layers of the shell, is covered
with non-ciliated cylindrical cells.

For the structure of the gills, and the relations subsisting between
the vascular systems of the body generally, of the gills, and of
the organ of Bojanus in the Naiades, see Langer, Denkschriften
Akad. Wiss. Wien. viii., 1854, and xii. 1856, pp. 36, 37, 61
V. Hessling, Die Perlmuscheln, pp. a 16, 230, 245, 247 J
and the figures in V. Carus' Icones Zootomicae, xix., i, 6, 8,
9 and ] o, which are taken from the former of these two au-
thorities. See also Robin, Eapport h, la Societe de Biologic,
1852, p. lao.

21. Fresh-watee, Mussel (Anodonta Cygnea),

Dissected so as to show its nerve system, and tlie route along which the ova pass
from the generative gland into the interspaces of the external gUls, where, as in the
pouch of a marsupial mammal, they are lodged, and go through certain stages
of their development.

Paet of the muscular foot has been removed on the left side to
show the pedal ganglion in situ ; part also of the organ of Bojanus
has been cut away on the same side, and the commissure which
connected the two inner lamellae of the two inner gills posteriorly
to the posterior limit of the foot has been divided, so as to show the
nerve cord connecting the labial with the parieto-splanchnic ganglia
in its entire length. The labial ganglion, which is homologous
with the supra-oesophageal of the Odoutophorous molluscs, is seen
lying upon the tendon of the retractor pedis anterior, and just

' Cyclopaedia of Anatomy and Physiology, Article 'Cilia,' p. 621.

Fresh-ivater Mussel.

63

anteriorly to that of tlie protractor pedis. Three commissural cords^
under each of which a slip of blue paper has been placed, pass off
from it. The one which passes vertically downwards in the pre-
paration,, and passes vertically, or nearly so, upwards in the position
ordinarily maintained by the animal during life, brings the labial
ganglion into commissural junction with the parieto-splanchnic or
branchial ganglion, which is seen lying upon the posterior adductor.
A second cord passes obliquely forwards towards the foot, to join
the pedal ganglion, which is situated a little way within the in-
ferior periphery of the ' visceral mass,-* a division of the body which
in these molluscs is less sharply differentiated from the ' foot'
proper than in many other members of the class. The third cord,
which looks like a production of the second, from the ventral to
the haemal side of the plane of the labial ganglion, is in reality the
cord of commissure between this ganglion and its fellow of the
opposite side. This cord holds the same relation to the commence-
ment of the digestive tract as the commissure of the cephalic
ganglion holds in the Odontophora ; and the cord of commissure to
the pedal gangHon is, as in them, placed anteriorly to the cord
of commissure to the parieto-splanchnic. There are, however, no
stomato-gastric, nor any separate sympathetic ganglia in the La-
mellibranchiata. The absence of the former of these structures is
obviously correlated with the absence of any prehensile apparatus,
or any triturating 'buccal mass," whilst the absence of the second is
ordinarily to be noted in structures and in organisms, which are as
richly provided with cilia as are those of this class. Special siphonal
ganglia are however sometimes superadded to the three pairs of
ganglia here specified in the siphonate species ; and small ganglia
may be developed in this class along the free edge of the mantle,
m connection with the sensory plexuses which the anterior and
posterior pallial nerves, from the labial and parieto-splanchnic
ganglia respectively, make up by their ramifications along it. The
cord of commissure from the labial to the parieto-splanchnic ganglia
passes from before backwards; firstly, between the fibres of the
anterior retractor and those of the protractor pedis ; and, secondly,
after skirting the orifice of the reproductive gland, on its inferior
or inner edge, through the glandular portion of the organ of
Bojanus, externally to the tendon of the posterior retractor. Im-
mediately posteriorly to this tendon, and anteriorly to the large

64 Descriptions of Preparations.

parieto-splanchnic ganglion, the nerve of the right side, as well
as that of the left, has been brought into view, and a sHp of blue
paper has been passed under the two nerves just before they enter
the ganglion. This nerve-centre is well seen giving off sensory
branches to the mantle, and motor to the adductor muscle, and
visceral branches to the giUs. Its finer visceral branches given
to the organ of Bojanus, and to the anus, are not seen in this pre-
paration. Four or five delicate nerves may be seen to pass off from
the pedal ganglion into the muscular strata of the foot; to the
most posteriorly placed but one of these, the auditory vesicle may
be found appended, at a point corresponding pretty nearly with
the junction of the anterior two-thirds with the posterior third of
the foot, close to the line beyond which the viscera do not extend
downwards within theii' muscular envelope. The branches which
the labial ganglion gives to the anterior portion of the mantle, are
not seen in this preparation.

By the division of the transverse commissural floor which united
the inner lamellae of the two inner giUs across and below the
structures already described as being placed posteriorly to the
posterior edge of the foot, and by the tm-ning outwards of the flaps
thus formed, a view is obtained of the spaces bounded by the two
lamellae of each gill, and also of the line of junction of the outer
lameUa of the inner gill and the inner lamella of the outer gill,
on each side to the organ of Bojanus, which sends blood into the
lamellae of the gills along their internal surfaces.

Each gill is seen to be a hollow pouch or sac with its cavity
divided into innumerable partitions by strips of tissue which run
across from one lamella to another. But for some distance down-
wards from the attached or upper border of each gill, these tens-
verse bands fail to be developed, and passages are thus left along
this border of the gills along which the ova pass in their circuitous
course from the reproductive gland to the marsupial pouch which
the external gill is formed into for them. The portion of this canal
which the inner gill forms is divisible into three segments— an
anterior, a middle, and a posterior. The anterior segment is formed
permanently by the attachment of the inner gilVs inner lameUa to
the visceral mass; and it is just within the posterior portion of
this se-ment that in the Anodon the orifice of the generative
gland opens. The middle segment is formed temporarily into a

Fresh-tvate7' Mussel.

65

closed canal, by the apposition of the inner gill-lamella to the
visceral mass, when the ova are being extruded, and the foot and
visceral mass retracted and compressed by the contraction of the
animaFs various muscles. The third portion of this canal is con-
stituted, below, by the commissural floor passing between the two
inner gills, and, above, as in the two anterior segments, by the
posterior part of the organ of Bojanus. It is easy to see in this
preparation, how, by the contraction of the retractor pedis muscles,
the ova would be extruded, and the upper portion of the visceral
mass brought into close temporary apposition with that portion
of each inner gill, which, ordinarily, is separated from it by a slight
interspace. We can see also how under these circumstances a
closed canal for the transmission of the ova is formed from the
orifice of the generative gland up to the point at which the large
branchial nerves enter the gills, and beyond which the internal
gill passage and also the outer, open into a space which, as the anus
opens into it also, we may call the ' cloaca." This space being but
small in the Naiades relatively to their ovaries, is rapidly filled by
the large quantities of ova which are poured into it under pressure ;
and, the shell being closed, there is no other path left for the ova
to take but the one which leads into the cavity of the external gill.
As these animals are dioecious, and as spermatozoa are sometimes
found free in the interior of the gills, to which it is plain they
would find access more readily when inhaled with the water for
respiration than to the interior of the ovaries of the female, it is
probable that it is not till after they reach the external branchial
marsupium that the ova are fertilized. The ova may be found
in great abundance in the external gill cavity of the Anodon during
the autumn and winter months ; and whilst lodged there, they go
through several stages of their development.

For an account of the way in which the ova reach the external gill
cavity, see V. Baer, Meckel's Archiv. 1830, p. 313, Taf. vii.,
figs. I, 2, and 4.

For observations which V. Hessling thinlcs make it probable that
the ova of one mussel may find their way into the external
gill-cavity of another, see Zeitschrift fur Wissenschaflitche
Zoologic, i860, p. 358.

For a detailed account of the nervous system in the Lamclli-

66 Descriptions of Preparations.

brancliiata, and in the Anodon particularly, see Duvernoy,
Memoires de I'Institut, torn, xxiv., 1854, and pi. 7, fig. 2,
pi. 8 and 9, figs, i and 2, and pp. 87-96 for that of the
Naiades.

For a more general account, see English Cyclopaedia, Article
'Mollusca,' p. 869; Siebold's Comparative Anatomy, Ame-
rican Translation, p. 198 ; Gegenbaur's Vergleichende Ana-
tomic, p. 310, with excellent figures 77, A. B. C, pp. 315, 3 ^
Hancock and Embleton, Phil. Trans. 1852, p. 239.

22. AsciDiAN {Ascidia Affinis).

Dissected and prepared similarly to Preparation 19, and showing thus the homolo-
gical relations of the several structures of the Tunicata to those of the LameUi-
branchiata.

The animal has been suspended by what was, in its erect position
during life, its base of attachment; and its inhalant and exhalant
orifices point, consequently, downwards instead of upwards. Parts
of the test, of the two internal tunics, and of the upper part of the
brancHal sac, have been removed on the animal's right side, which
corresponds with the front of the preparation ; and so much also of
the walls of the stomach, and intestine, and of the vesicular substance,
and of the Uver in connection with them, has been similarly taken
away, as was necessary for exposing the interior of the digestive
tract from the mouth to the anus. A black bristle has been mtro-
duced through the inhalant orifice along the interior of the branchial
sac into the mouth and stomach, and a white one has been simi-
larly passed through the exhalant orifice into the rectum. In this
species the inhalant orifice is terminal, and the anal is lateral;
just as in many Lamellibranchiata the inhalant siphon, or the
tentaculate portion of the mantle which corresponds to it in the
non-siphonate orders, rea^ihes farther backwards than the anal
siphon, or the anal portion of the mantle. The mantle, which is
recognisable by its muscular fibrillation, has since the death of the
animal shrunk away from the external test, the homologue of the
bivalve shell. The rectum and the generative ducts are seen to open,
as in life, a little way within the periphery of the mantle, and into
a space which is homologous %vith that described, Preparation 21,

Ascidian.

67

p. 65, as the ' cloaca' in the Anodon, but which differs from it by-
being" much larg-er, by not possessing an organ of Bojanus, except in
a rudimentary condition, and by not being traversed by any muscle
such as the posterior adductor. A wide interspace thus exists here
between the branchial sac and the envelopes or tunics placed ex-
teriorly to it, to which, however, it is attached continuously along
the white band seen along the median ventral line, and known as
the ' endostyle along an encircling zone, placed immediately su-
periorly in this preparation to the circlet of tentacles just within the
inhalant orifice ; along a line passing from the other end of the
endostyle to the neighbourhood of the mouth ; and lastly at in-
tervals in all parts of its circumference except in the cloacal region,
by hollow tubular suspenders, which convey blood between its
vessels and the visceral and pallial sinuses. The line of the *■ endo-
style' is constituted by four folds, the two external being mem-
branous, and the two internal of a rigid yellowish substance ; and
in this, as also in the relation it holds to a large vessel, the
so-called ^thoracic sinus' of Milne-Edwards, passing along it
from the heart, and in the more general relations which it holds
to the other organs of the animal, it resembles the line of the
symphysis of the mantle of the Lamellibranchiata which have the
mantle lobes united inferiorly, or the free margin of the mantle
lobes of such bivalves as the Anodon (see Preparation 30, p. 61).
Along the opposite side of the branchial sac there runs the ' oral
lamina,' which in other species, such as AscicUa Intestinalis, may be
represented by a row of ' languettes.' It is connected with the line
of the 'endostyle' by the encircling zone already spoken of as lying
superiorly to the circlet of tentacles. In the interval between this
encii'cling zone and j}he coronet of tentacles, at the point where the
oral lamina becomes continuous with the former of these structures,
is seen the ' ciliated sac' or ' anterior tubercle.' Posteriorly to the
encircling zone, or ' anterior collar' of Hancock, in the immediate
neighbourhood of the anterior tubercle, is seen the single ganglion
of the Tunicata, supplying the mantle. This ganglion therefore
would seem to be homologous with the branchial or parieto-
splanchnic ganglion of the Lamellibranchiata; and the circlet of
tentacles will, by consequence, be seen to be homologous with the
tentaculate inhalant portion of the mantle in those animals.

The ' oral lamina' is seen to be underlaid by a large vessel, the

68

Descriptions of Preparations.

'branchiar or 'dorsal sinus' of Milne-Edwards, the 'branchial
vein' of Savigny. It is connected with the one already spoken
of as holding- a similar relation to the endostyle on the opposite
side of the branchial sac, firstly, by means of the numerous trans-
verse vessels encircling the branchial sac; secondly, by a vessel
takinff a similar course to these vessels around a zone in relation
with the 'anterior collar/ and thirdly, by a vessel holding a
similar relation to a chord uniting the upper end of the endostyle
to that of the oral lamina, and known as the ' posterior collar/
The 'dorsal sinus' receives factors from the pallial plexuses by
means of tubular ties similar to those which pass from these and
the visceral plexuses on the left side of the animal's body to the
other portions of the branchial network. Finally, it is seen to
receive a large vessel from the neighbourhood of the anus, and
by this vessel, which passes to it through the visceral mass from
the heart, it is brought into direct communication with the dorsal
end of that vasiform organ as the ' thoracic sinus' in relation with
the line of the endostyle is, even more directly, with its ventral
end. On either side blood-vessels are seen crossing the interval
between the test and the mantle to join one or other of the two
vascular trunks in connection with the dorsal and ventral end of
the heart respectively.

The mouth, in all Ascidians, occupies a point in the branchial sac
which is on the opposite side to the line of the ' endost^de,' and
to that of the 'thoracic sinus' of Milne-Edwards, the so-called
'branchial arteries' of Savigny, which are here regarded as more
closely homologous with ' branchio-cardiac veins.' In this species
the mouth is much nearer the upper or anterior extremity of the
sac than it is in Ascidia Mentula. The digestive tract is seen to
describe two cui-ves ; the first of these is made up by the stomach,
and the first segment of intestine which bends sharply back upon
it; whilst the second is made up by this first segment of intestine
and the rectum. The concavity of the first of these curves looks
anteriorly, or towards the base of attachment of this erect species
and away from the nerve ganglion; the concavity of the second
looks posteriorly, or towards its inhalant aperture. But if, as in
this description, the single ganglion of the Tunicata be regarded
as the homologue, not of the pedal but of the parieto-splanchnic
ganglia if their branchial sac be also regarded as homologous not

Ascidian.

69

with a dilated phaiyux, but witli the branchial cavity, and if their
inhalant aperture be taken to represent, not the mouth, but the
inhalant siphon of the LameUibranchiata, it will be seen that the
essential character of the curves described by the digestive tract
beg-inning with the orifice into which the upper end of the black
• bristle is introduced, is the same as that of those described in the
Anodon, Preparation 19, p. 58, and that the two classes cannot be
contra-distinguished as 'haemal' and ' neural' respectively. The
digestive tract of the Ascidian is seen to diifer from that of the
Anodon mainly in not possessing the two posterior of the three
concentric coils, described in that animal, whilst its first and most
important curve, and also that portion of it which is seen in the
cloaca, and in relation with the large blood-vessel passing from
the heart through the visceral mass to the '^branchiaF or 'dorsal
sinus ' of Milne-Edwards, corresponds very closely in all essential
particulars with the initial and the terminal segments respectively
of the digestive tract of the bivalve. The floor of the stomach is
occupied by a longitudinally folded eminence, which again is pro-
longed into and along the intestine, where it forms an elevated
ridge, dividing the tube into two demi-canals, and much increasing
its absorbing surface. The liver., which Mr. Hancock (Proc. Linn.
Soc, June 1867, p. 313), has, in opposition to Savigny, shown to
exist in the genus Asciclia, opens into the cavity of the stomach
by two ducts. The reproductive organs are seen in the concavity
of the second or intestinal cvirve of the digestive tract ; and their
excretory ducts open into the cloaca, together with the anus.

The view which has been taken in this description of the rela-
tionship subsisting between the Lamellibranchiata and the Tunicata,
was suggested by Cuvier in his memoir on the Ascidians (Memoires
du Museum, 1815, tom. ii., p. 34), and was adopted by V. Baer, in
his paper on the route taken by the ova of Unionidae in passing
from the ovary into the branchial marsupium, already referred to,
and published in Meckel's Archiv. for 1830, p. 341. This view
has been revived by Mr. Hancock (see Proceedings of Linnaean
Society, June 1867, p. 343), and illustrated by many new argu-
ments.

Professor Huxley's view, according to which the branchial sac of
the Ascidian is to be regarded as a dilated pharynx, will be found
expounded by him in the British Association Report for 1H52,

70

Descriptions of Preparations.

p. 77, as also in his article on ' Mollusca' in the English Cyclo-
paedia. See also Professor Allman, Fresh-water Polyzoa, 1856,
p. 44, seqq., and Mr. J. D. Macdonald, Transactions of the Eoyal
Society of Edinburgh, vol. xxiii. 1862, 1863, for general remarks
on the morphology of the Tunicata.

Much information as to the anatomy of the various orders of this
class will be found in the memoirs of Cuvier and Hancock,
already quoted ; in the second volume of Savigny's Memoires
sur les Animaux sans Vertebres ; in Milne-Edwards^ ' Obser-
vations sur les Ascidies Composees/ published in the Memoires
de PInstitut for 1839, and in Professor Huxley's Papers in the
Royal Society's Transactions for 1 85 1 .

For figures of Pyrosoma giganteum, a free social Ascidian, which
lend much probability to the view which has been here
adopted, as to the homological identity of the branchial sac
of the Ascidian with the gills of the Lamellibranchiata, see
Le Sueur, in the Bulletin des Sciences par la Societe Philo-
mathique, 18 15, pi. i. fig. 2,, or Journal de Physique, June
1 8 15; and Keferstein und Ehlers, Zoologische Beitrage, 1861,
Taf. xii., figs. iv. and v.

For the essential character and structm-e of the branchial sac, see
Milne-Edwards, 1. c. pp. 271-274 ; Hancock, 1. c. pp. 327~5S4..

For a description of the three tunics of the Ascidians, see JSIilne-
Edwards, 1. c. p. 270.

For an account of the circulation in this class, see Bronn, Klassen
und Ordnungen des Thierreichs, iii. i. pp. 172-176; Milne-
Edwards, 1. c. pp. 224-228; Hancock, 1. c. pp. 321-325.

Cuvier's and Savigny's figures of the various systems and organs of
Ascidians, as well as those given in V. Cams' Icones Zooto-
micae, tab. xviii., fi'om the most recent authorities, are well
worthy of being studied.

For an account of a new genus of Ascidian which possesses a
bivalve shell, see Lacaze Duthiers, Ann. Sci. Nat., Ser. v.
torn, iv., 1865, p. 293. Sur un genre nouveau d'Ascidien,
Lc Chrevreidius Callensis, Lac. Duth., where, at p. 307, the
difTercftces between the type of organization which the animal
named presents and that of the Lamellibranchiata are pointed
out.

Broad-leafed Hornwraclc.

71

The internal anatomy of the species here described resembles in
many points that of the Ascidian, Ascidia Phmca, figured by
Cuvier, Memoires du Museum^ torn, ii.^ 1815, pi. i., fig. 9,
and described by him, 1. c. pp. 39, 30 ; or Memoires pom- servir
h THistoire et a 1' Anatomic des MollusqueSj Memoire sur les
Ascidies, pp. %o, 21. The mouth is similarly situated at the
bottom of the branchial sac in Ascidia Scabra, which dififers
from this species, Ascidia AJifiis, in being smaller and rougher
externally.

23. Broad-leafed Hornwrack {Flustra Foliacea).

A Seaweed-like Polyzoon, very common and universal in Euro-
pean seas. The Polyzoary is flexible, of silk-like texture and ap-
pearance, ordinarily forming erect fronds but occasionally loosely
adnate to marine objects. The cells, which by their mutual appo-
sition in these social animals form the Polyzoary or Coenoecium,
are arranged multiserially in parallel longitudinal rows on both
sides of the frond they make up. The individual cells are ovoidal
in shape, and have from four to eight spines set round their larger
end, in which their mouth, which is crescentic and protected by
a lip, is placed subterminally. The avicularium and mandible are
semicircular and immersed. There are no vibracula. The polypide
itself is, when contained in its cell, bent several times upon itself.
Its tentacles are very long. It resembles the great majority of
fresh-water Polyzoa in the absence of a gizzard. The ovicell, a
sort of marsupial pouch, analogous, in respect of function, if not
homologous, with the cloaca of the Ascidians, and continuous with
the perivisceral space through a passage at the upper and back part
of each cell, is inconspicuous in this species, being deeply immersed.
The ova themselves are of a striking colour, and, as in other
Polyzoa, are set free by the death and disruption of the parent
polypide.

For excellent figures of the external and internal anatomy of this
animal, see Van Beneden, Recherches sur TAnatomie, la Phy-
siologie, et le Developpement des Bryozoaires qui habifcent la
cote d'Ostende, Mem. Acad. Royale de Bruxellcs, torn, xviii.,

72

Descriptions of Preparations.

1844, pp. 32-34, pi. iv., figs. 11-17, similar figures of

another marine Polyzoon, Acamarchis Avicularia Lmx. Bugula
Avicularia, Busk. Brit. Mus. Cat. p. 45 ; see Bronn-'s Klassen
und Ordnungen des Tliierreichsj iii. 1, Taf. v._, fig. 3, A.B.C.D.

For figures of the Hippocrepian fresh-water species, see Allman,
Fi'esh-water Polyzoa, pi. ii. et passim.

For an account of the zoological characteristics of the class, and
especially of the marine subdivision of it, see Busk, ' Fossil
Polyzoa of the Crag,^ Palaeontographical Society's Memoirs,
1859, part 12; and British Museum Catalogue of Marine
Polyzoa, J 852, where, at pp. 103—108, an account of the struc-
tures above mentioned under the names of ' vibracula' and
' avicularia,' will be found.

For the microscopic anatomy of the fresh-water Polyzoa, see
Nitsche, Reichert und Dubois B,eymond's Archiv., 1868,
p. 465 ; and for that of the nerve-system especially, see
Taf. xiii. fig. 23. For similar observations, see Alpheus Hyatt.,
Proceedings of Essex Institute, Salem, Mass., U. S. A., vol. iv.
No. v., 1 864-1 868.

For remarks as to the homologies and afiinities of the class to the
Brachiopoda, and also to other Molluscan classes, see Lister,
Phil. Trans. 1834, p. 385; Farre, Phil. Trans. 1837, p. 417;
Hancock, Phil. Trans. 1857, p. 849; Allman, 1. c. pp. 43-55;
and Quarterly Journal of Microscopical Science, January, 1869,
p. 62 ; Hyatt, 1. c. vol. v. No. v., pp. 150-157 ; Fritz Miiller,
Reichert und Dubois Reymond's Archiv. i860, p. 79, where
at Taf. i. fig. 2, a larval Brachiopod is represented with four
arms borne upon a retractile proboscis ending in an oval pro-
tuberance closely similar to the epistome of the Hippocrepian
Polyzoa.

For the identification of the Polyzoa, as belonging to the sub-
kingdom Mollusca, see Audouin and Milne-Edwards, Ann.
Sci. Nat. torn. xv. 1828 ; Milne-Edwards, ibid. torn, xi., p. 16,
1836; Recherches Anatomiques, Physiologiques et Zoologiques
sur les Polypiers de France, 1841 -1844, 8vo.

For the literary history of the nomenclature of the class, see Busk,
Ann. Nat. Hist, x., 1852.

Bugle Co7'aUme.

73

24. Bugle Coralline {Salicornaria Farciminoides).

The Polyzoary is plant-like^ erect, caleareouSj dividing dicho-
tomously, the internodes articulating by flexible cbitinous bands
instead of being- continvious as in the preceding specimen. It is
ordinarily about three inches high, and is attached by a fibrous
branching root-like base. The cells are arranged quincuneially
round an imaginary stem, and divide the surface of the internodes
which they make up, into more or less regularly rhomboidal or
hexagonal spaces bounded by the raised borders of the cells. The
mouth has a tooth on each side at its orifice within its lowest
border. The avicularia are distinct from and placed above the
cells, but not regularly. Their rostrum is immersed, and their
mandible semicircular. No vibracula are present in this species.
The ovicells, which are immersed as in the preceding specimen,
have here their position frequently identifiable by the presence of a
perforation above the mouth.

For specific characters, see Busk, British Museum Catalogue of
Marine Polyzoa, pp. 16-18, pi. Ixiv., fig. 3 ; Fossil Polyzoa of
the Crag, p. 23 ; Johnston's British Zoophytes, p. 355, 2nd ed.;
English Cyclopaedia, article ' Polyzoa,' p. 420, fig. 4 • Cam.
Heller. Verhand. Zool. Bot. Gesellschaft im Wien, bd. xvii.,
1867, p. 85.

25. Larva of Death's-head Moth
{Acherontia Atropos).

This and the following five preparations are intended to illustrate
the various points of external and internal anatomy, such as the
presence of prolegs, the absence of wings, the rudimentary con-
dition of the reproductive system, the shortness, large calibre and
straightness of the digestive tract, the great development of the
salivary glands and of the fat body, in which the larva or pupa,
or both difier from the perfect insect. The caterpillar of the
Death's-head Moth is the largest of all European species. The
greater or less homonomy of its segments from head to tail, and
the fact that the segmentation of its legs and antennae is not very

74

Descriptions of Preparations.

obvious to the unassisted eye, give the larva somewhat of a vermi-
form appearance ; and together with the absence of wings and of
the dense scaly covering clothing both wings and body in the adult
Lepidopterous insect, put it into sharp contrast with the imago.
Each of the three segments immediately posterior to the head carries
with them a pair of quinquearticulate legs. The fourth and fifth
post-cephalic segments have no appendages, but, like the first and
unlike the second and third, are pierced on each side by a re-
spiratory foramen known as a ^ spiracle' or ' stigma.' The sixth,
seventh, eighth, and ninth segments possess spiracles, and carry
sucker-shaped motor organs, armed with spines, which axe known
as 'pedes spurii' or ^prolegs.' The tenth and eleventh segments
are furnished with spiracles but have no prolegs ; the eleventh
carries on its dorsal surface a tuberculate horn characteristic of the
family SpJdngidae^ with the exception of a few species, one of
which is North American ; and representing the funis of the
embryo. Posteriorly to this horn and between it and the tri-
angular supra-anal valve are two half-ring-shaped ridges, reaching
from the level of the spiracle of one side over the dorsum to the
level of the spiracle of the other. They appear to be distinct from
the ventrally-placed half-ring which carries the posterior or fiifth
pair of prolegs, and it is possible therefore that the presence of
three segments may thus be indicated posteriorly to the eleventh,
whereby fom'teen, the typical number of post-cephalic segments in
Arthropoda, would be made up. The greater part of the covering
of the head is made up by two large scales, the 'parietal scales'
of Lyonet, the 'procephalic lobes' of Huxley;' the ' Scheitel-
platten' of the German authors referred to below, corresponding
to the ' epicranium' of the imago. Anteriorly a triangular plate,
the 'frontal scale' of Lyonet, the representative of the 'labrum'
and ' clypeus' of the perfect insect, is intei-posed between the pro-
cephalic lobes. These lobes or scales are each divided into two
nearly equal halves by a dark stripe, on the inferior termination of
which are to be found the six ocelli. Mesially to the lower part of
the area occupied by the ocelli, the parietal scales give articular
origin to the antennae, and more mesially again we have on either
side the articulation of the mandible. From the position thus held
by the antennae of the larva relatively to that of the organs of the
mouth on the one hand, and to that of the antennae of the imago

Larva of Deatlis-head Moth.

75

on tlie other, they have been supposed by Zaddach to correspond
to the inferior or posterior pair of antennary organs of the Crus-
taceans, the so-called ' antennae/ whilst the antennae of the imago
correspond with the superior or anterior antennary organs or ' an-
tennules' of the Crustaceans. The structures corresponding to the
maxillae and labium of such insects as the Coleoptera and Or-
thoptera, and to the two pairs of maxillae in Crustaceans, are here
more or less fused into a horizontal plate which forms a sort of
operculum to the mouth, and carries three segmented organs on its
free edge. Of these three organs, the one which is placed mesially
is the labium, modified so as to give exit to the common duct of the
two silk glands ; and the organs placed one on either side of this
' spinneret ' are the maxillae, modified so as to serve not only in the
prehension of food, but also, in many larvae, in the construction of the
cocoon. The two pairs of appendages which this compound organ
thus represents in the larva, retain more of their typical distinctness
in the imago, where they take the shape of a spiral proboscis, and a
largely developed and palpigerous labium. On the other hand, the
largely developed mandibles of the larva are represented by merely
rudimentary organs in the imago, reversing thus the history of the
posterior oral appendages. If the eyes be taken as indicating the
presence of one segment, the antennae of the larva a second, and
those of the imago a third segment, to which three other segments
would have to be added for the mandibles, maxillae and labium, the
head of the insect will be seen to consist, like that of the typical Ar-
thropod, of six segments indicated by as many pairs of appendages ;
and the six cephalic segments, together with the three thoracic and
eleven abdominal, will make up the entire number of all the seg-
ments of the body to twenty. In their possession of prolegs and
of bright colours upon the integument, the larvae of Lepidoptera
differ from those of Coleoptera and Hymenoptera Genuina, which
they resemble, as they do also those of the Diptera and Neuroptera,
in passing into a state of perfect quiescence as pupae.

For the typical number of segments in the Arthropoda, see Huxley,
* On the Agamic Reproduction and Morphology of Aphis/
Linn. Soc. Trans., vol. xxii., 1858, p. 225.

For the indication of a distinct cephalic segment which the pre-
sence of the eyes furnishes, see Zaddach, Die Entwickelung

76

Descriptions of Preparations.

und Bau der Gliederthiere, pp. 78^ 87^ 88 j Rathke, Mor-
phologies pp. 126-127.

For the antennae of the larvae in relation to those of the imago,
and the antennae and antennules of Crustacea^ see Zaddach,
1. c. pp. 13, 86, 89.

For a history of the metamorphoses of Lepidoptera, see Westwood,
Introduction to the Modern Classification of Insects, vol. ii.,
pp. 310-321.

For figures of the oral organs of the Larvae of Lepidoptera, see
Lyonet, Traite Anatomique de la Chenille qui ronge le bois
de Saule, pi. i. ii., and p. 59 for functions.

For those of the imago, Savigny, Memoires sur les Animaux sans
Vertebres, vol. i,, pi. i. ii. iii.

26. Pupa of Death's-head Moth
{Acherontia Atropos),

Showing the form of chrysaKs known as 'obtected,' or better, as ' larvate'

or ' signate.'

In this form the external organs of the future perfect insect are
more or less obscurely distinguishable beneath the hard elastic
membrane in which they are inclosed instead of being free as in the
so-called ^ exarate'' or 'liberae' pupae of Coleoptera and Hymen-
optera, and which is a product of the hardening of a secretion
instead of being merely the dried integument of the maggot, as
in the ' coarctate' pupa of many Diptera. The conical form of the
pupa case is characteristic of the Heterocerous Lepidoptera, in
contradistinction to the angular form of the Rhopalocerous. The
apical portion of the cone, the ' cremaster' of Kirby and Spence,
is made use of by the pupa when it works its way up from the
chamber, six inches or so deep in the ground, before entering
upon the imago-stage of its existence. In possessing thus a
power of motion in the last stages of their pupa-life, the Lepi-
doptera resemble the Phryganeodeae or ' caddis flies,' as they do
also in many other particulars, though the chrysalis of the family
just mentioned diflers from that of the Lepidoptera in being
'free' or 'exarate' like that of the beetles and bocs. Seven
spiracles are seen on cither side upon the abdominal segments;

Pupa of Death's-head Moth. 77

an eighth, which belongs to the most anteriorly placed of the
abdominal segments, is concealed by the wing-case on either side.
The ninth abdominal ring is marked by a depression on either side
of the middle ventral line, the lines limiting which extend into
the interspace between it and the eighth segment, and indicate
thus the normal position of the outlet of the generative glands.
Posteriorly to this symmetrical depression, and separated from it
by the entire breadth of the tenth segment, is seen an azygos
depression with an antero-posterior direction indicative of the true
position of the anus, which is in relation with the eleventh ab-
dominal segment and its appendages, one of which the apical horn
may be taken to represent. The dorsal part of the mesothorax or
'mesonotum' is largely developed; and the wing-cases are seen
to take origin along either side of it, as well as from the much
smaller ' metanotum,' which is represented by a dumb-bell-shaped
mass, constricted mesially and rugose on the surface. The ' pro-
notum' is much larger both relatively and absolutely than in the
perfect insect, and forms a transversely elongate oval mesially
carinate shield. The head-cover is divided by faintly marked
transverse lines into three portions; the most posterior of which
gives origin to the ^ ceratothecae,-' and appears to correspond to
the 'parietal scales' of the larva and the ' epicranium' of the imago,
whilst the two anterior portions correspond to the ' frontal scale'
of the larva, and the posterior and anterior ' clypeus' of the imago.
The middle division of the head cover is the largest, the anterior
is minute and the smallest of the three. In the middle line infe-
riorly between the ' ophthalmothecae ^ is seen the ' glossotheca'' in
which the ' spirignatha' or ' antlia' of the future imago is lodged ;
and externally to it on either side upwards, the ' podothecae,'
' ceratothecae,' and ' pterothecae,' lodging respectively the future
feet, antennae, and wings.

For the relations of the posterior segments of the abdomen to the
generative and anal outlets, see Lacaze Duthiers, Annales des
Sciences Nat., 1853, tom. xix., Ser. iii., p. 220; Huxley,
Linn. Soc. Trans., 1858, vol. xxii., p. 230.

For the nomenclature adopted by various writers for the various
parts of the external skeleton, see Newport, Cyclopaedia of
Anatomy and Physiology, Article 'Insecta,' pp. 885, 913 ; and

78

Descrijptions of Pre'parations.

for a fuller vocabulary, Burmeister's Manual of Entomology,
translated by W. E. Shuckard, chaps, ii. and iii.

27. Imago of Death's-head Moth
(Acherontia Atr 0200s).

The development of wings and tbe differentiation of the body
into three great heteronomous divisions, the head, the thorax, and
the abdomen, are the most prominent external points in which the
perfect insect differs from the imago. The scaly covering of the
body and wings, the great development of the eyes, the somewhat
smaller but still not inconsiderable relative increase of the size of
the antennae and of the legs, the replacement of the fused maxillae
and labium of the larva by a spiral sucking proboscis, and a labium
provided with large palpi, and the reduction of the actively
functional mandibles to purely rudimentary structures, are almost
equally obvious points of difference between the larva and the
imago of a Lepidopterous insect. The maxillary palps are, as in
many Hymenoptera, and unlike what we observe in Diptera, very
small as compared with the labial. The prothorax is much reduced
in size. When viewed from above, the dense covering of scales
having been removed, it has the appearance of a narrow ring,
whence its technical name of ' collar,' interposed between the head
in front and the largely developed mesothorax behind. Tbe
pronotum carries laterally a pair of vesicular scales covered with.
hairs, and known as 'patagia.' They are characteristic of the
order, and distinct from the 'tegulae' or wing-covers, with which
they have been sometimes confounded, and which are carried by
the meson otal praescutum, and though very largely developed in
the Lepidoptera, are not peculiar to them.

As points of more or less classificatory importance, mostly with
reference to the differences observable as existing between the
diurnal and nocturnal Lepidoptera, may be noted, firstly, the ter-
mination of the multi -articulate antennae in a filament, not in a
club ; secondly, the existence of a ' retinacular' apparatus, whereby
a spinous outgrowth on the under surface of the base of the hinder
wing connects it with an annular hgament similarly developed on
the under side of the anterior wings ; and thirdly, the two pairs
of spurs on the inner side of the posterior tibiae. The family

Imago of Death' s-head Moth.

79

Sphingidae have no ocelli, and the genus Acherontia has the spiral
proboscis much shorter than other genera belonging to the family.

In their possession, when larvae, of provisional organs, of which
no traces are left in the perfect insect, the Lepidoptera resemble the
Neui-optera and Hymenoptera Phyfcophaga, amongst the orders dis-
tinguished by quiescence in the pupa-stage, and said consequently
to have a ' perfect metamorphosis,'' as also the Orthoptera Am-
phibiotica amongst Ametobolous insects. The true Hymenoptera,
on the other hand, and the Coleoptera, with a few exceptions,
possess no provisional organs in this larval state, though they pass
into perfect quiescence as pti^pae. This latter condition therefore
should be taken as the essential characteristic of a ^ perfect meta-
morphosis.''

For the characteristics of perfect and imperfect metamorphosis, see
Gerstaecker, Klassen und Ordnungen des Thierreichs, bd. v.,
p. 189.

i

28. Larva of Goat Moth {Cossus Lignijperda),

Dissected so as to show the various internal organs of vegetable life, and the points
in which they differ frona those observable in the perfect insect.

Tke dorsal integuments have been divided down the middle line,
and turned outwards on either side, together with the muscles
which were in connection with them. The greater part of the body-
cavity is occupied by lobulated masses of adipose tissue, known
as the ' fat body,"" or ' rete,' which disappear almost completely
in the adult insect of the orders with a perfect metamorphosis.
In the middle line we see the digestive tract, which passes, without
forming any convolutions at right angles to the long axis of the
body, from the mouth to the anus. Its most anterior segment,
seen in this Preparation, is the transparent- walled oesophagus upon
which is seen the highly developed nervus recurrens. This nerve is
connected, anteriorly, with a series of three ganglia which are placed
one behind the other, and correspond with the single ganglion
frontale of some insects; and, posteriorly, at the junction of the
oesophagus and stomach, with a plexus into which the two lateral
stomato-gastric nerves enter. The stomato-gastric nerves undergo
less change in metamorphosis than perhaps any other system of

80

Descriptions of Preparations.

the larva. The stomach succeeds to the oesophagus, from which it
is readily distinguished by the opacity of its walls and the tracheae
which are distributed to it in great abundance. Bands of oblique
muscles are observable decussating superficially, and longitudinal
muscles lying at a deeper level in its walls. Th'e tubular renal
organs, the so-called ' Malpighian vessels/ are seen upon the pos-
terior half of the stomach, forming two loops on either side, the
mesially placed being shorter than the more externally placed
loops, and having its limb which passes towards the anal end of
the body bifurcated, whilst the returning limb of each outer loop
remains undivided. The two loops on each side thus form three
trunks which form an intricate interlacement in the posterior part
of the body-cavity, on either side of the intestine. The two stems
themselves fuse on either side into a single trunk, which opens
into the intestine a short way below the pylorus ; and as the
product of these tubules is uric acid, the portion of intestine below
their opening may be regarded as excretory, and that intercepted
between their opening and the pylorus, as corresponding func-
tionally with the small intestine. The point however at which
these vessels open into the digestive tract may vaiy, in different
orders, from the immediate vicinity of the pylorus to the immediate
vicinity of the anus. The looped portions of these organs are of
larger calibre than the more complexly convoluted posterior por-
tions ; from which they differ also in being smooth exteriorly, and
cylindriform, instead of having a moniliform appearance, from being
beaded over with sacculi. The rectum, which is considerabl}'^ longer
than the small intestine, has its external surface divided into six
longitudinal strips by as many muscular bands; and the spaces
thus marked out are again subdivided by a very much larger
number of very much smaller transversely running muscular bars.
The long convoluted white tubes, the coils of which are seen to
commence with a blind end on either side, about opposite the
junction of the stomach and intestine, are the silk glands, and they
pass to the under surface of the digestive tract, anteriorly, to end
in a common duct opening in the modified labium or ' spinneret.'
Underneath the coils of the silk gland of the left side, a large trans-
parent walled bladder is seen, from the posterior end of which a
tubular gland passes off to form the mass of convolutions called the
' queue du vaisseau cUssolvant ' by Lyonet in his elaborate mona-

Larva of Goat Moth.

81

graph of the anatomy of this larva, and bent round so as to lie
in apposition with the bladder into which it opens, and in the
interval between it and the stomach. The bladder, with the pos-
terior extremity of which this tubular gland is thus connected,
opens anteriorly by means of a wide duct into the mouth ; and the
organ thus made up of a duct, a bladder-like receptacle, and a
tubular gland, may be seen to correspond with the much smaller
salivary glands of the perfect insect. Neither upon the fasciculi of
tracheae which are seen passing inwards from the spiracles to dis-
tribute themselves to the viscera, nor upon the longitudinal canals
connecting the stem whence these fasciculi spring, which may be
seen here and there in the intervals left between the lobes of the
'fat body,'' are there any vesicular dilatations developed in the ,
larval state. This relatively inferior evolution of the respiratory
system may be explained upon purely mechanical grounds, when
we consider the comparatively sluggish movements of the larva,
whilst the physiological necessity which exists during periods of
growth and development for an active performance of the renal
functions, will account for the large development of the Malpighian
vessels here observable. And the all but complete absorption and
disappearance of the 'fat body^ at the end of the metamorphoses
of metabolous insects, is to be explained by the need they have,
especially during their period of existence, as pupae, for a large
supply of force and matter, for the carrying out of the complex
changes in, and the superadditions to, the larval organism which the
arrangements of the muscles and the evolution of the reproductive
organs in the imago may be taken as illustrating. Such dif-
ferences in the digestive apparatus of the larva as those already
spoken of (Prep. p. 75) in the appendages of the oral segments,
as the larger calibre and the lesser length of the digestive canal, as
the absence of convolutions, and of a crop, and as the much larger
size of the salivary glands, are obviously correlated with the dif-
ferences existing between its mode of sustenance and that of the
butterfly. The presence of a rectal eoecum in the perfect insect,
is to be noted as an additional point of contrast. The disappear-
ance of the silk-glands during the pupa-stage is readily explicable
by the fact, that all need for such organs ceases after the forma-
tion of the cocoon ; and the condition of semi-fluidity to which the
various organs of the pupa are reduced in the early stages of the

a

82

Descriptions of Preparations.

period of quiescence, makes the metliod of their disappearance
easily intelligible.

A monograph of great merit and detail has been written upon the
anatomy of the larva of the Goat Moth, by P. Lyonet, Traite
Anatomique de la Chenille qui ronge le bois de Saule, 1762,
in which excellent figures will be found of the digestive system
in pi. V. xiii. xviii., of the respiratory in pi. x. xi., of the mus-
cular in pi. vi. vii. viii., of the ganglia frontalia of the azygos
stomato-gastric system, pi. xviii., for which see also Brandt,
Ann. Sci. Nat., Ser. ii., tom. v., 1836, p. 99.

For the sources for the production of fat VTithin the animaFs body,
see Voit, Zeitschrifb fiir Biologic, Bd. v., Hft. i., p. 79, 1869.

For the development of the ^fat body' in Lepidoptera, see Hermann
Meyer, Zeitschrift fiir Wissenschaftliche Zoologie, i. 175.

For the absorption of it in the processes of growth and develop-
ment, especially of the reproductive organs, see Peters, Carus,
and Gerstaecker, Handbuch der Zoologie, p. lao, and Weis-
mann. Die Entwickelung der Dipteren, p. 178.

For the changes of consistence observable in the tissues and organs
of the Lepidopterous pupa, see Newport, Phil. Trans., 1832,
p. 390 j and for the much more extensive changes in the way
of histolysis which appear to furnish an instance of ' free cell-
formation' on the one hand, and on the other to approximate
the character of the metamorphosis of the coarctate dipterous
pupae to that of ' alternation of generations,' see Weismann,
1. c, pp. 135, 164, 176, 331, 232, 239.

For the respiration and temperature of insects, see Newport, Phil.
Trans., 1836, 1837.

29. Larva of Privet Hawk Moth {Sphinx Ligtistri),

Dissected so as to show its nervom system.

The dorsal integuments and the various organs of vegetative
life have been removed; a black bristle has been passed through
the nerve collar, and slips of blue paper placed under various parts
of the chain of ventral ganglia. In the nerve system as thus ex-

Larva of Privet Haivk Moth.

83-

posed and prepared, twelve main ganglionic masses are readily,
detectible with the naked eye. The first of these is placed above
the oesophagus, is divisible into two lobes by a shallow antero-
posterior depression, and from its relation to the eyes and antennae,
may be called the 'cerebroid' ganglion. The first sub-oesophageal
ganglion, by the commissural junction of which to the cerebroid,
the nerve collar is formed, is in closer proximity to the second than
this is to the third, or the third to the fourth, or the fourth to the
fifth. These five ganglia resemble each other in being more or less
heart-shaped, the nerves they give off being directed forwards;
the first of them supplies the organs of the mouth, and the other
fom- those of the thorax. The first of these ganglia is represented
in the developing Crustacean Astacus fluviatilis by three pairs of
ganglia corresponding severally to the mandibles, the anterior, and
the posterior maxillae, but, so far as is known, it is connate in the
developing insect from the earliest periods. The second, third^
fourth and fifth pairs of ganglia are distinct in development in
both these animals ; they are fused into a single ganglionic mass
in the adult forms of both; the single mass thus formed may
retain more or less distinct indications of its originally composite
character, but in the insect it does not, as in the Crustacean spe-
cified (see Prep. 34), fuse with the similarly fused mass supplying
the three true jaws. Thus the distinctness of the head of the
insect from its thorax is preserved and reproduced in its nervous
system, whilst the fusion of head and thorax in the Crustacean is
similarly reproduced also. The fact so far as relates to the class
Insecta is sometimes expressed by speaking of their brain as con-
sisting of a sub-oesophageal as well as of a supra-oesophageal
portion, or of a ' cerebellum^ as well as a ' cerebrum,^ the former of
which is in connexion with a chain of ventral ganglia. As however
the serial homology of the various ventrally -placed appendages of
the articulate Neuropods is universally recognised, this nomen-
clature is less to be recommended than one which by numbering
the segments of the nerve cord as is done here, enables us at once
to see where correspondence has or has not existed, or been re-
tained between the external and the internal organs. Though the
line of division between the head and thorax of the insect, both in
its larval and its perfect state, has thus a diastema in the ganglionic
chain corresponding to it internally, which is not preserved in the

G 1

94

Descriptions of Preparations.

3ephalo-tlioracic ganglion of the Crustacea; it is by no means
nvariably the case in other parts of the insect^s organism, that a
fusion or distinctness of external segments is reproduced internally
by a fusion or segmentation of the chain of nerve ganglia. The
sixth, seventh, eighth, ninth and tenth ganglia are more or less
spheroidal in form, the two first disappear, the three last are re-
tained in the adult insect. The eleventh ganglion is distinctly
divisible into two lobes by a bilaterally symmetrical construction,
representing thus, as also by the distribution of its nerves, the two
ganglia, by the fusion of which it is composed. In the larvae of
some insects, as, for example, P/talaena neustria, Dorcus paral-
lelej)i2Jediis, and Corethra plumicornis, these ganglia retain as much
or more of their typical distinctness, and even in the larvae of
Miiscidae, where the ventral cord is not itself segmented, eleven
pairs of nerves are given off from it exclusively of those in con-
nection with the jaws, indicating thus that the number of post-oral
ganglia is twelve. The tenth, and the bilobed eleventh ganglia,
appear to correspond to the six post-abdominal ganglia of Astacus
fluviatilis ; and the five ganglia from the fifth to the ninth, with
the five ganglia in relation with the five pair of ambulatory
limbs in the Crustacean. A slip of blue paper has been passed
underneath the two diverging cords of commissure of the third and
fourth post-oral ganglia, and we see in the intercepted space one
of the systems of ' respiratory,' ' accessory,' or ' transverse' nerves,
connecting itsehP with the larger ganglia of the ventral in much
the same way as the 'ganglion frontale' and the lateral nerve
ganglia' are connected with the cerebroid ganglia. The ' transverse
nerves' of each inter-ganglionic space are not only connected with
these larger ganglia, but also with each other, so as to form a
continuous chain overlying the ventral cord. From this chain,
nerves pass to the tracheae and spiracles, and also to the muscles
which act upon these organs and upon the wings. One of the
large longitudinal tracheae is seen on the right side of the future
thorax, in which part of the body the respiratory system attains
ultimately its greatest size and importance, and has the system
of transverse nerves similarly evolved in correlation with it. One
of the diagonal muscles is seen passing through the interval between
the cords connecting the second and third ventral ganglia. This
and the succeeding interspace are represented in the perfect insect

Larva of Privet Haivh Moth. 85

by a single oval foramen, the third post-oral ganglion having dis-
appeared, and the mass made up by the fusion of the fourth and
fifth, having closely approximated to that representing the second.

For a detailed account of the metamorphoses of the nervous system
in the Sphinx Ligustri, resulting in the replacement of the
eleven ventral ganglia of the larva by one sub-oesophageal,
two thoracic and four abdominal in the imago, see Newport,
Phil. Trans., 1832 and 1834; or. Cyclopaedia of Anatomy and
Physiology, Article ' Insecta,' p. 963 ; Herold, ' Entwickelungs-
geschichte der Schmetterlinge,^ pp. 58. 59 > ^nd description
of Tab. ii., where he speaks of the ventral ganglia of the larva
of Papilio Brassicae as being twelve in number ; the com-
missural cords bet^reen the eleventh and twelfth being absent.
For accounts of the first appearance of the nerve system, in the
developing embryo of various orders of insects, see Weismann,
' Entwickelung der Dipteren,' 1864, pp. 38, 83, 190, 19a j
Eathke, 'Zur Morphologic, Reisebemerkungen aus Taurien/
1837, pp. 123-127; Leon Dufour, Ann. Sci. Nat., Ser. ii.
tom. 18, pi. iv. and v. See also, for the relatively late period
at which the nerve system is developed and differentiated from
the structures which underlie it, Rathke, ' Bildung und Ent-
wickelung des Flusskrebses,' p. 85 ; Zaddach, ' Die Entwicke-
lung und den Bau der Gliederthiere/
For development of the first sub -oesophageal ganglion, see Metschni-
kow,, ' Embryologische Studien an Insecten,' p. 79^ '^^^^ ^^^'^
fig. 33 ; Zeitschrift fiir Wissenschaftliche Zoologie, Bd. xvi.
For the 'nervi transversi,' see Newport, 1. c. 1834, p. 401 ; Leydig,

Vergleich Anat. p. 205, Taf. vii. fig. i, Taf. ix. fig. 2.
For descriptions and figures of the systems of tracheae and of
muscles, see Lyonet, Traite Anatomique de la Chenille qui
ronge le bois de Saule, 1762; and Newport, Phil. Trans.
1836 J and for descriptions of the variations in the muscles of
the larva of Pygaera Bucephala, see Lubbock, Linn. Soc.
Trans., vol. xxii. pt. iii., 1857.
For the relations existing between the external and internal struc-
tures, see Burmeister's ' Manual of Entomology,' translated by
W. E. Shuckard, p. 281 ; Blanchard, Ann. Sci. Nat., Ser. iii.,
tom. v., 1846, p. 281.

86 Descriptions of Preparations.

30. Common Cockroach {Periplaneta Orientalis),

Female,

Dissected so as to show its digestive, renal, nervous, and reproductive systems.

The greater part of the dorsal integumental system has been
removed by incisions carried along either side ; the short elytron,
the only representative of the wings in the females of this species,
has been left in situ on the right side, where it is seen reaching
just far enough back to overlap a part of the metanotum ; the
greater part of the fat body which abounds in the interspaces
between the viscera, especially in the abdominal region of these
insects even in their adult state, has been removed, and the digestive
tract fastened out upon the left side of the body. The upper seg-
ment of the digestive canal, seen in this preparation, is the crop,
which is about three-fourths of the entire length of the body, and
-is distended with food. The entire length of the digestive tract
would be little more than twice that of the body, and this compara-
tive shortness may be considered as compensated for partly by the
-character of the food of this species, and partly by the large quan-
tities which, as seen in this preparation, they devour, A muscular
subcorneal gizzard, an organ which is not developed in the larvae
of insects with a perfect metamorphosis such as the Coleoptera, even
in species which have it when adult, but is developed in the larvae
of Orthoptera, including Libellulidae, follows after the crop. Eight
coeca are arranged in a whorl round the commencement of the 'chy-
lific stomach,"' and a very much larger number of very much longer
and more slender tubes are similarly arranged around its lower end.
The gizzard does not open directly into the chylific stomach, a
narrow neck of about the same length as the gizzard itself inter-
vening between the apex of the gizzard and the zone marked out
by the eight coeca just mentioned. These coeca appear, from the
facts that they often contain a yellowish fluid, and that they never
afford lodgment for particles of food even when the digestive tract
is distended, to be analogous to the liver of higher animals, whilst
the existence of uric acid in the other set of tubules already men-
tioned, the so-called ' Malpighian vessels/ would appear to justify

Commo7i Cockroach.

87

us in speaking of them as 'renaP organs. The colon, which is
Lent upon itself, and has its external surface beaded over with
granulation-like pouches by the action of its muscular coats, is
connected with the lower end of the chyMc stomach by a short
segment of small calibre, and of similar length to that which
connects the upper end of the chylific stomach with the larger
end of the gizzard. The colon ends in a rectum, which is divided
into six longitudinal areae by as many longitudinal muscular bands,
alternating with internally-placed lamelliform projections of the
inner coats of the intestine. A somewhat similar arrangement
has already been noted in the larva of the Goat-moth (p. 80) ; and
in the larvae of certain Libellulidae the supply of tracheae to the
ridged surface thus constituted, is so abundant as to convert it
into a respiratory organ. On either side of the junction of the
crop to the oesophagus is seen the bilobed salivary gland.

On the right side in this preparation is seen the salivary recep-
tacle, a pellucid bladder, reaching a little farther back than the
gland. The duct from this receptacle fuses with that of its fellow
of the opposite side, and into the common duct thus formed a second
duct, formed by the junction of the ducts of the two glands, is re-
ceived, so that all the four ducts find an outlet into the mouth by a
short common canal.

An azygos nerve, the nemis recurrens, from the 'ganglion impar'
or ' ganglion frontale' of the stomato-gastric system, is seen passing
from before backwards to join a triangular ganglion placed a little
way in front of the middle point of the dorsal median line of the
crop. Prom this ganglion a nerve passes off on either side to the
posterior extremity of the crop, and may be seen to have an elon-
gated thickening developed upon it at the lower third of its length.
A third nerve, not seen in this preparation, has been described as
passing off from the centrally-placed triangular ganglion to the
salivary glands. The ganglion impar, from which the nervus re-
currens takes origin, is not seen in this preparation, being situated
anteriorly to the cerebral ganglia, with which it is connected by
delicate filaments joining it just internally to the large antennary
nerves. The paired ganglia of the stomato-gastric system are
situated some way posteriorly to the cerebral ganglia; and the
short nerve seen on either side of the nervus recurrens, just where
the salivary gland abuts upon the crop, is given off by the posterior

Descriptions of Preparations.

of the two pairs of ganglia, of which the symmetrical portion of
the stomatogastric system consists, in this as in most other insects.
The paired ganglia are connected with each other, with the cere-
bral ganglia, and finally with the nervus recurrens, which struc-
ture, however, together with the ganglia in connection with it,
constitutes in these and most other insects by far the most im-
portant part of the stomato-gastric system.

In the abdominal region are seen six ganglia corresponding to
the six posterior ganglia of the Lepidopterous larva. The two
first of the six, which correspond to the two which become obsolete
in the butterfly, are more closely apposed to each other than are
any of the succeeding four. The last ganghon is more or less
cordiform, and larger than those which precede it, and gives off
nerves to the lower portions of the generative and digestive tubes.
The ovaries are of the kind called ^ verticillate by Miiller; and
consist of eight moniliform tubes on either side, which are connected
anteriorly with the dorsal element of the prothorax by means of a
suspensory ligament, made up of the fusion of filaments given off
from their apices ; and which inferiorly open upon the convex end
of a pear-shaped oviducal infundibulum, as ordinarily figured. The
infundibula of the two sides which may be seen, when imdistended,
to have the egg-tubes inserted laterally as in other Orthoptera, pass
beneath the terminal nerve structures and the ''oviscapt^ to form a
common vagina, which opens in the interval between the eighth and
ninth abdominal segments. Immediately posteriorly to the last
nerve ganglion, in the angle limited by its branches, we may see
with a lens the receptacula seminis, which take the shape of two
short contorted coeca, one of which is rather larger in calibre than
the other, and which open by means of a single short duct in the
sternum of the ninth segment. The 'colleterial'' or 'sebaceous^
glands, which consist of numerous delicate tubules of much gi-eater
length than the receptacula seminis, open by two ducts in an
orifice upon the sternum of the tenth segment. The sternum of
this segment developes the smaller and inner processes of the
* oviscapt/ whilst that of the ninth developes the elongated ex-
terior pieces of that apparatus; and as the lateral anal valves re-
present an eleventh segment, we have thus the typical number of
the segments of the Arthropodous abdomen made up. The recep-
taculum seminis is ordinarily in insects an azygos vesicle, and it is

Common Cockroach.

89

possible that the aberrant arrangement observable in the Blattinae
may foreshadow the more usual one in which a single receptaculum
seminis has a gland of a secretory character superadded to it. And,
as the number of the ' colleterial ' tubules is very considerable, they
may be taken, perhaps, to correspond not only to the colleterial
glands of other insects, but also to their so-called ^scent glands/ The
food, and to a considerable extent the habits, of the larvae and of
the adult insect being identical in this family, we find little differ-
ence existing between their internal structural arrangements beyond
that which a greater prominence in the evolution of the reproductive
apparatus constitutes. The retention of the ' fat body' is obviously
correlated with the absence of any period of quiescence and absti-
nence from food, such as that of the pupa stage of Metabolous
insects, and of the need for a supply of force which the changes
gone through by those classes entail. Externally the imperfect
insect in the class Orthoptera does not, with the exception of the
Orthoptera Amphibiotica, such as the Libellulidae and Ephemeridae,
differ from the adult by the possession of any provisional organs of
which the perfect insect is destitute, but contrasts with it almost
exclusively by inferiority of size, by the smaller number of facets in
its corneae, by the absence of wings, and in this family by a greater
lightness of colour. Great differences, however, exist as to this
latter particular between adult individuals of this species.

Eor a monograph of the order Orthoptera, see the Latin work,
'Orthoptera Europaea,' Auctore Leop. Henrico Eischer, Lip-
siae, 1853, where a general account of the external and internal
anatomy of the entire order will be found, pp. 5-32, and an
account of the anatomy of the family Blattinae will be found,
pp. 84-88. See also Leon Dufour, Kecherches Anatomiques et
Physiologiques sur les Orthopteres, 1834, Mem. Acad. Sci.,
tom. vii., des Savans fitrangers ; also in 4to, Paris, 1 841 . At
pi. v., figs. 44—47, good figures of the digestive and reproductive
systems are given. See also PI. vi. infra, with description.

For a monograph on the digestive and renal systems of this insect,
see S. Basch, Sitzungsberichte, Kaiser Alcad. Wiss. Wien,
vol. 33, 1858, p. 234, Math. Nat. Classe.

An account of the natural history, as well as of the anatomy of the
common Cockroach, may be found in a short monograph.

90

Descriptions of Preparations.

entitled ^Beitrage zur nahern Kenntniss von Periplaneta
(Blatta) Orientalis/ von C. Cornelius, Elberfeld, i^53-

For an account of the various glands superadded to tte essential
organs of the female reproductive apparatus, see Siebold, in
Miiller's Archiv. for 1837, p. 393 seqq., and for their arrange-
ment in Blatta (Periplaneta) Orientalis, p. 408. For figures of
a female reproductive apparatus essentially similar to that here
described, see Lespes' account of the Termes Lucifugum, Ann.
Sci. Nat. Ser. iv., Tom. v., PI. 6, fig. 24-27. For the orifices
of the various ducts in the reproductive apparatus, see Hux-
ley, Linn. Soc. Trans., vol. xxii. p. 231. For the 'suspensory
ligament' of the ovary, see Stein, ' Vergleichende Anatomic
imd Physiologic der Insecten,' pp. 36, 41-43; Miiller, Nova
Acta, xii., pt. ii., p. 578. For the composition of the 'oviscapt'
and the number of the abdominal somites, see Lacaze Duthiers,
Ann. Sci. Nat., Ser. iii., torn, xvii., 1852, p. 227 ; torn, xix., pp.
229-233, and Huxley, Linn. Soc. Trans., vol. xxii., 1858, p. 231.

For the development of the fat body independently of the yolk, see
Elias Metschnikow, ' Embryologische Studien an Insecten,'
p. 73, and for its connection with the production of phospho-
rescence in such insects as the Lampyris sjilendidula, see Leydig,
' Lehrbuch der Histologic/ p. 342.

For a description, with figures, of the stomatogastric nervous
system, see Brandt, Ann. Sci. Nat., Ser. ii., tom. v., 1836,
p. 103, pi. iv., figs. 4, 5.

For Bibliographical references, see Scudder, Smithsonian Institu-
tion's Catalogue of Orthoptera, Washington, 1868, pp. 17-63.

31. Common Crayfish (Astacus Fluviatilis),

Female.

This Crustacean's body consists of two great divisions, the
so-called ' cephalo-thorax,' covered dorsally and at the sides by
a carapace, and carrying fourteen pairs of articulated appendages,
and the post-abdomen consisting essentially of six definitely an-
nulate and calcified segments, to the posterior one of which a
powerful natatorial organ, the 'swimmeret,' is articulated. The

Common Crayfish.

91

ceplialo-thoracic carapace again is divisible into two regions^ an
anterior and a posterior, by the well-marked curved line with its
concavity looking forwards, which is known as the ' cervical su-
ture/ The anterior portion of the carapace is eailled the ' cephalo-
stegite ' and the posterior the ' omo-stegite inasmuch as an
examination of the relation of the inner aspect of the cervical
suture to the hindmost of the three pairs of jaws, that is to say,
to the most posterior of the cephalic appendages, shews that the
anterior portion of the carapace corresponds with the head, and the
posterior with the post-cephalic segments. The crayfish furnishes
an excellent example of the general law that every segment carries
an appendage in the Crustacean, the jG.rst post-abdominal segment
in this (female) specimen being the only segment in which a
distinct pair of appendages is not readily recognizable. The pe-
dunculate position of the eyes in the Decapodous Crustaceans
makes it easy to understand, even without a reference to the
history of development, or to instances of abnormal replacement of
the eyes by articulated appendages ^, how the eyes may be regarded
as homologous with articulated appendages ; and that the eyes and
antennae do not really belong to the tergal aspect of the anterior
cephalic segment, may be shewn not merely from the history
of the reflection upwards and backwards of the developing cephalic
blastoderm, but also from the direction and relations of these
three pairs of sensory appendages in such Crustaceans as the
Squillina. With the history of the relations of these organs in the
developing Astacus, or with that of their disposition in the family
just mentioned, before the mind, it is easy to see how the oph-
thalmic peduncle may be spoken of as the most anterior of the ap-
pendages, and as marking out the most anterior of the segments
of the body. Next in order to the ophthalmic peduncles come the
'antennules/ consisting, as usual in Crustacea, of three basal joints,
succeeded by a multi-articulate flagelliform element, which is here
double. The 'antennules' are said to correspond to the antennae

» See A. Milne-Edwards, Comptes Rendus, vol. Hx., p. 710, £, 1864. It may be
added that the pedunculate position of the two centrally-placed eyes in certain
Ephemeridae, for which see Westwood, Modem Classification of Insects, pp. 25, 31,
De Geer, Histoire des Insectes, viii., pi. 18, torn. 2, fig. 10; Kirby and Spence, pi.
XXVI, fig. 39, is, when we consider the many Crustacean affinities of the order Orthop-
tera, not without significance.

92

Descriptions of Preparations.

of perfect insects j in some Isopoda, however, which in many-
points approximate to insects, they are rudimentary. The inner
of the two antennulary flagella is the smaller, and correspond to
the structure described in other Crustacea as a ' secondary ap-
pendage/ Posteriorly, and a little externally to the antennules,
come the antennae, each of which consists of a single multi-
articulate flagellum cai*ried by a series of five basal joints, the
second one of which, if we count the sternal or proximal joint
as the first, carries the representative of the appendages which
are developed early upon this joint, but are subsequently aborted
in Carcinus maeiias, in the shape of two scales, one much the
larger, somewhat of the shape of a short wide knife-blade, the
other minute, prolonged into a spinous point externally, and ar-
ticulating internally with the fourth basal segment. A com-
parison of the five basal joints of the antenna with the five basal
joints of such a typical seven-jointed appendage as any one of the
four posterior ambulatory legs in the Astacus, wall leave no doubt
as to their correspondence ; and the multi-articulate flagellum will
thus come to be the homologue of the two terminal joints of those
appendages which are known as the *" propodite'' and ''dactylo-
podite,^ and are sometimes supposed to correspond to the ' tarsus'
of insects. The proximal joint of the antenna has a conical process
developed on its inferior surface, internally to the apex of which
there exists an orifice leading into the antennary gland. On the
triangular space between these two conical processes which is
known as the 'epistoma/ and is constituted by the sternum of
the antennary segment, are seen lying the anterior extremities
of the palpiform exopodites of the two anterior maxillipeds, which
correspond to the two anterior thoracic legs of insects. The pos-
terior pair of maxillipeds have been displaced a little backwards, so
as to give a better view of the two other pairs of foot-jaws, and of
the three pairs of jaws which they partly conceal ; though they
never form for them, either in Macrurous or Anomurous Decapods,
such a perfect operculum as they do in the Brachj'urous. Posteriorly
to the ' epistoma,' we see the upper lip or ' labium,' and between
it and the first pair of thoracic appendages, or ' maxillipeds,' we
have the three cephalic appendages essentiall}'- concerned with the
preliension of food, and assisted in that function in the Hedri-
ophthalmatous or fourteen-footed Crustaceans by two, and here in

Common Crayfish.

93

the Decapods by all three pairs of thoracic limbs. Of the three
true jaws the most anteriorly placed^ the so-called ^mandible/
carries a tri-articulate palp with an expanded terminal joints and
corresponds as a whole to an ambulatory leg, or to the endopodite
of a foot-jaw. The palp, as being of great use in directing
floating food towards the mouth, is rarely absent in Crustacea,
except in the terrestrial Isopods and Amphipods. The basal portion
of the mandibular appendage* appears to correspond to the four
basal joints of the ambulatory legs ; and it may be remarked that
the denticulation and anchylosis of the second and third segments of
the third pair of foot-jaws alFord an instructive example of transi-
tion towards the modification of the basal segments seen in the
mandible. The two pairs of foliaceous maxillae, the posterior one of
which remains mesially divided, probably in rela,tion to the ingestion
of floating food, and does not form a ' labium^ as in air-breathing
Arthropoda, are not seen in this preijaration, being closely appressed
by the foot-jaws in apposition with them. Of the five pairs of
'ambiilatory' or ' abdominal' legs, whence the order Decapoda take
their name, the first has its two terminal joints or tarsus modified,
so as to form a large pair of pincers, by having the posterior distal
angle of the penultimate joint, or propodite, prolonged so as to be
parallel with and commensurate with the dactylopodite. Similar
but smaller pincers are developed similarly upon the second and
third pairs of feet ; the fourth and fifth are not so armed, the
penultimate joint not being prolonged beyond its distal articular
surface. It may be noted that the chela of the Scorpion, which
bears a considerable resemblance to the largest of the three chelae
of the Astacus, has its pincer-like portion somewhat difierently
constituted, the anterior or interior angle of the propodite being
produced instead of the posterior or exterior; and the smaller of
the two blades of the prehensile organs lying exteriorly, instead
of interiorly as in the Crustacean. The large pincers of the scor-
pion are homotypical, as representing the two terminal joints of an
appendage with the large pincers of the crayfish, but they are not

* See figure of edentulous mandible oiMatuta Victor in ' E^gne Animal,' Crustacds,
pi. vii. fig. i. c, where the palp has six joints, the three proximal ones of which are
very small, whilst the three distal have the proportions of those which make up the
ordinary tri-articulate palp.

94

Descriptions of Preparations.

its exact homologues, inasmucli as they correspond in strictness
with the two terminal joints of its mandibular palp. The four
posterior of the five abdominal legs of either side consist each
of seven joints, seven being considered by Mr, Spence Bate to
be the typical number of the joints in the normally developed
appendage of every kind in Crustaceans. The second and third
joints are anchylosed in the anterior of these five appendages, as
they are in all the five of the Brachyura, so as to reduce the
number of separate joints to six. The proximal joint is known
as the ' coxopodite f a black bristle is in this (female) specimen
introduced into the oviduct, which opens in Macrurous and Ano-
murous Decapods, as also in Hedriophthalmata, in the coxopodite
of the third abdominal appendage. The second joint is known
as the 'basipodite/ or 'basis.^ It is in the interval between the
' basi-"* and ' coxopodite^ that the separation of the limb takes place
when a Crustacean throws it ofi" in consequence of fright or injury.
The third, or ^ischiopodite/ is marked by an annular constriction a
little way distally to its articulation with, when it is distinct fi-om,
the basipodite. This constriction may perhaps represent the aborted
exopodite, which in the three posterior abdominal legs of Squilla
is articulated to the third segment of the appendage ; by observing
its presence we are enabled to identify the various segments in the
appendages of the abdomen in Brachyura. The fourth, the longest
of all the segments in all the five appendages except the first, is
known as the ^meropodite,^ and has been compared with the 'femur'
of insects ; the fifth is known as the ' carpopodite,' and the two
terminal are known as 'propodite' and ' dactylopodite,' and have
been compared to the ' tibia' and ' tarsus' of insects. The append-
ages on the first post-abdominal segment are rudimentary; to
the hairs upon the appendages of the succeeding segments, some
of the large ova of this fresh-water Decapod may be observed to
be attached. The appendages of the second, third, fourth and
fifth post-abdominal segments consist of a biarticulate * protopo-
dite,' the proximal segment of which is small and annular, and
the distal cylindriform ; and of two multiai-ticulate filaments repre-
senting an ' exopodite ' and an ' eudopodite,' the basal segment
of the latter of which is much the largest in either series. The
appendages of the sixth abdominal segment form the powerful
' swimmeret' of the crayfish. The lateral elements of this organ

Common Crayfish.

96

correspond to the appendages already described in the five ante-
rior post-abdorainal segments^ and consist each of an uniarticulate
' protopodite/ which carries on its apex a biarticulate ' exopodite'
and a uniarticulate ' endopodite/ The mesial element of the
' swimmeret^ is constituted by the so-called ^ telson/ an azygos
plate divided in the crayfish into an anterior and posterior portion
by a transverse suture, immediately anteriorly to which the anus
opens on the ventral surface of the body. The telson has some-
times been reckoned as a seventh post-abdominal segment, but
as it, with scarcely an exception, is without appendages ; as it is
generally aborted, or rudimentary, or fused with the sixth segment
in Hedriophthalmata ; and as, finally, it is developed after the other
segments and from the dorsal surface of the body, it is better to re-
gard it as being simply an outgrowth from the sixth segment of the
post-abdomen, in the same way as the rostrum may be considered to
be an outgrowth from the carapace. The proximal segment of the
'telson' is not calcified continuously across its ventral surface,
whereas the true post-abdominal segments have each of them a
horizontal calcified chitinous chord, connecting, without the inter-
position of any suture, the opposed internal surfaces of the arc
represented by their dorsal wall. At the junction of the chord
and arc are the articular surfaces for the post-abdominal append-
ages already described. The portion of the dorsal wall which
is prolonged downwards beyond the level of the junction of the
ventral and dorsal portions of the external skeleton of each segment
is known as the ' pleuron.-' There is no such element in the telson.
The pleura of the sixth, fifth, foiirth and third segments, and the
convex tergal surfaces whence the pleurae arise in all the segments,
have facets developed upon them anteriorly, which are overlapped
by processes of the segments next in front. The pleura, however,
of the second and first post-abdominal segments, develope processes
which are not overlapped by, but themselves overlap, the one the
pleuron of the first post-abdominal segment, and the other the
posterior pleural edge of the carapace.

A quadrangular area, corresponding pretty accurately with the
position of the subjacent heart, is marked off* in the posterior portion
of the carapace, or ' omo-stegite,' by two linear depressions on
either side the middle line, and by an anterior faintly marked line,
curving concentrically with the convexity of the cervical suture.

96

Descriptions of Preparations.

and uniting the anterior extremities of the two laterally placed
lines. The area on the omo-stegite intercepted between the curved
line and the cervical suture represents the terga of the three
thoracic segments j the area posteriorly to this line represents the
terga of the five abdominal segments. The portions of the omo_
stegite which lie laterally to these mesial areae are the connate
pleura of all the eight segments just mentioned ; from their
function they are called ' branchio-stegites.' Their free border con-
sists of a smooth rim, thickly fringed vnth hairs, arising along its
inner edge ; between which and the coxopodites of the thoraxjico-
abdominal segments, water can find free access to the branchial
chamber. The branchial portions of the carapace may be considered
as representing the fused pleura of the eight thoracico-abdominal
segments. The cervical suture which separates the omo-stegite
from the cephalo-stegite begins anteriorly opposite the middle line
of the antennary sternum. From this point it passes at first
horizontally backwards ; then it turns almost vertically upwards,
bounding a surface of the omo-stegite, which is slightly convex
forwards, and beset with from four to five spines ; finally, it bends
boldly backwards, describing a curve the mesial portion of which
bounds the cardiac area anteriorly. The cephalo-stegite is pro-
longed anteriorly into a triangular mesial rostrum, terminating
anteriorly in a sharp point, about on a level with the commence-
ment of the antennary flagellum. The cephalo-stegite carries a
sharp spine on either side, just externally to the basis of the
rostrum. Immediately posteriorly to this spine is seen a convex
surface, which is conspicuous even in early stages of development,
and marks the origin of the powerful adductor mandibulae muscle.
Inferiorly the cephalo-stegite is connected, though it is not anchy-
losed, with the antennary sternum, as it is in the Brachyura, and
indeed in the much more nearly allied species Eomarus V ulgaris.

For a full description of the external and internal anatomy of
Astacus Fluviatilis, see Huxley, Medical Times and Gazette,
Feb. 7, 1857 seqq. ; and for the tegumentary skeleton and
morphology of Decapodous Crustacea generally, see Milne-
Edwards, Ann. Sci. Nat., Ser. iii., tom. xvi., p. 22\, 1851.

For the development, see Rathke's Monograph, ' Ueber die Bildung
und Entwickelung des Flusskrebses,' 1829; and for the de-

Common Crayfish.

97

velopment of the 'telson' in particular, p. 27, and ' Zur Mor-
phologies Reisebemerkung-en aus Taurien/ 1837, pp. 113-115.
In this latter work about fifty pages are devoted to general
remarks on the development of Crustacea.
For the development of other Crustacea, see Spence Bate, Phil.
Trans., 1858; Fritz . Miiller, Archiv. fiir Naturgeschichte,
1862, 1863; Van Beneden, Recherches sur la Faune Lit-
torale de Belgique, Crustaees, 1861 ; Claparede, Beobach-
tungen iiber Anatomic und Entwickelungsgeschichte wirbel-
loser Thiere, 1863, ihique citata.
For the morphology of the appendages, see Savigny, Memoires
sur les Animaux sans Vertebres, 1816, vol. i., p. 4<S, Mem. ii.,
pi. iii. and iv. ; Erichson, Entomographien, 1840, where, at p.
28, attention is drawn to the fact of the relative prominence of
the thoracic appendages in the larval (Zoea) stages of Crustacea
which undergo metamorphosis, and to the illustration which
this peculiarity in the development of Crustacea affords of
their essential affinity to other Arthropoda which possess the
same hexapod arrangement permanently as adults in the class
Insecta, or, it may be added, pass through a hexapod larval
stage, as lulus among Myriapoda, and Hydrachna among
Arachnida. That the prolegs of Insect larvae are rightly con-
sidered as homologous with the abdominal and post-abdominal
limbs of Crustacea, though the proleg, even when greatly elon-
gated as in the anal appendages of the Puss Moth {Gernra
Schrank), is still an annulated rather than a segmented and
articulated outgrowth, may be seen from the fact that prolegs
and true legs may replace each other. In the Coleopterous
Insect SpiracIitJia Mir?/meclusa, described by Schiodte in the
Ann. Sci. Nat., Ser. iv., tom. v., 1856, p. 178, pi. i., fig. 19^
we have the first, second, and third prolegs of the Lepidop- ■
terous larva replaced by biarticulate appendages; whilst in the
Coleopterous CurcuUonidae we have the thoracic legs replaced
by prolegs.

For excellent figures of the appendages; see Brandt and Batzeburo-
'Medizmische Zoologie,' Bd. ii., Taf. xi., p. 58; or, Victor
Carus, ' leones Zootomicae,' Taf. xi.
See also Milne-Edwards, ' Suites d BuiTon,' Crustaces, tom. i. ii.
and m ' Begne Animal,' Crustaces, Atlas, pi. iv.

lU.,

H

98 Descriptions of Preparations.

For generalizations as to the homologies of the appendages in the
various orders of Crustacea, see Spence Bate, ' History of British
Sessile-eyed Crustacea/ Spence Bate and Westwood, 1868,
Introduction, pp. vii-xx.

For the bibliography of memoirs upon the anatomy of the Fresh-
water Crayfish, see Brandt and Ratzeburg, ' Medizinische
Zoologie,' Bd. ii., p. 65, note i ; or. Ley dig, < Handbuch der
A^ergleichenden Anatomic/ p. 253.

For the differences between Macrurous and Brachym-ous Crustacea,
see Dana, ' Crustacea, U. S. Exploring Expedition/ pt. i., p. 49.

32. Common Crayfish {Astacus Fluviatilis),

Male,

Dissected so as to show the nervous, circulatory, and digestive systems in situ, and in
the relatious they hold to each other and to the external tegumentary skeletal
system.

The nerve system underlies the sternal elements of the various
segments ; the heart, the dorsal portion of the omo-stegite, giving
off both anteriorly and posteriorly an azygos artery which may
represent the more elongated and vasiform heart, which is more
usual in Arthropoda than the compressed irregularly polygonal
organ seen here ; and the digestive tract occupies a position be-
tw^een those of the two other systems. A white bristle has been
introduced through the mouth into the oesophagus and stomach,
and shows that this latter organ is prolonged as far forwards in-
ternally as the antennary sternum is externally, and to a point,
therefore, much in front of the plane of entrance of the oesophagus.
In order to show these points, the external skeleton and its append-
ages, with the exception of the eyes, antenuule, and antenna, have
been removed on the animaPs left side, together with the muscles
in connection with them, and together with the two lobes of the
liver and the ' green' or ' antennary' gland of the same side. A slip
of blue paper has been placed under the nerve cord in the post-
abdominal region, in the interval between its penultimate and ante-
penrltimate ganglia ; a second has been placed in the same region,
but in its dorsal portion, under the azygos caudal artery and above

Common Crayjish.

99

the intestine ; a third is placed underneath the sternal artery^ just
at its origin from the bulbus arteriosus^ at the posterior extremity
of the heart, from which the post-abdominal artery just mentioned
is continued directly backwards ; the fourth and most anteriorly
placed slip of blue paper occupies an interval between the coecal
process, the rudiment of the embryonic yelk-sac, which marks the
commencement of the intestine, and the hepatic artery of the left
side, just as it emerges from under the cover of the testis, and
passes down on to the pylorus. The anterior wall of the stomach,
finally, has been displaced a little backwards, and the commissural
cord between the suprg,- and the infra-oesophageal ganglia, which
was rendered visible by the removal of the antennary gland, has
had its various connections made more evident.

The twelve post-oral and the supra-oesophageal ganglia are here
seen in profile, and the great lengths of the commissural cords
passing between the last-named ganglia and the first of the post-
oral series whence the three pairs of foot-jaws as well as the three
pairs of true jaws are supplied, is well seen, corresponding with the
elongated antennary sternum. Visceral nerves are seen passing
from the commissural cords and from the supra-oesophageal mass
on to the stomach. A sub-circular raised area on the anterior
aspect of the stomach as displaced backwards, and about midway
between its upper and lower border, marks the position of the
so-called ' eye,-" a. circular calcareous disc periodically developed in
the Crayfish. A convex protuberance marks the pylorus, imme-
diately behind which is seen, the two hepatic lobes having been
cut away, the opening of the left ductus choledochus into the
commencement of the intestine. The inferior portions of the
^ hepatic lobes of the right side come into view beneath the pyloric
portion of the stomach and the duodenum, along the middle line of
which they come into the apposition with the homologous portions
of the left hepatic lobes. The convolutions of the vas deferens
of the left side fill up the space between the two slips of blue
paper which are placed under the hepatic and the sternal arteries,
and which abut by their upper angles upon the anterior paired
and the posterior azygos testicular lobe respectively. Superiorly
to the testicular lobes, and, as in all Arthropoda which possess
it, immediately underneath the dorsal integument, is seen the
heart. In the interior of the post-abdominal region are seen,

100

Descriptions of Preparations.

besides the straight intestine, the nerve cord, and the post-abdo-
minal artery ah-eady mentioned, the powerful and complex flexor
muscles of the post-abdominal segments and the ' swimmeret ; '
fascicles from which are observable passing to find attachment
to ' apodemata/ as far forwards as the entrance of the oesophagus.
It is by these muscles that the more rapid movements of these
animals are executed. For their slower crawling movements, the
ambulatory legs are employed, and the muscles which act upon
the limbs of the right side, may be seen passing upwards through
the apodematal cells to take origin from the epimera as seen in
Prep. 34. Some muscular fasciculi not ordinarily described pass
backwards from the sternal regions, anteriorly to the mouth on to
the anterior surface of the stomach, decussating thus with the
commissural and stomato-gastric nerve cords.

As a sexual peculiarity, the modifications of the first and second
post-abdominal appendages should be noted. But the testis itself
does not extend further backwards than the posterior border of the
carapace, and the outlet of the vas deferens, as being placed in the
basal joint of the last ambulatory leg, justifies the application of
the term 'post-abdomen' to the segments placed posteriorly to it.

For figures of the Crayfish as thus dissected and described, see
plate vii.

For a detailed account of the flexor muscles of the post-abdominal
segments, see Milne-Edwards, ' Suites k Buffbn,' Histoire Na-
turelle des Crustaces, tom. i. p. 157, tom. iii. pi. xiii.

For the late period at which the digestive tract is developed in
Arthropoda, and the possibility of thus accounting for its
comparative simplicity and the straightness of its course, see
Zaddach, Untersuchungen viber die Entwickelung und den
Bau der Gliederthiere, p. 42.

33. Common Crayfish {Astacus Fluviatilis),

Dissected so as to show the heart, its six arteries, and two of its six venous inlets,

in situ.

The cardiac and part of the cephalo-stegal portion of the carapace
has been removed, as well as a flattened venous sinus which was

Common Crayfish.

101

interposed between the shell and the heart, and the terga of the
two anterior post-abdominal segments. The heart in the Deca-
podous, as also in some of the lower Crustacea such as Daphnia,
differs in its compressed shape from the vasiform structure which
is observable in the other classes of Arthropoda, and indeed in such
Crustaceans as Squilla and the Hedriophthalmata. From the an-
terior border of the heart a single artery is given off in the middle
line, and supplies the eyes and antennules. On either side of this
artery is given off the trunk which supplies the antennae ; and
finally, from either outer angle of the front border of the heart, an
artery passes downwards, between the testicular lobe of either side
and the intestine, over the pylorus to the hepatic lobes. A slip of
blue paper has been placed under the post-abdominal artery, which,
passing immediately beneath the middle dorsal line and above the
intestine, may be taken as representing the posterior segments of
the forms of heart more usually seen in Ai-thropoda. The sternal
artery, which is larger than the post-abdominal, and is given olf
from the same short trunk, is not seen in this Preparation. Two
venous inlets are seen in the anterior fourth of the upper surface
of the heart ; the two laterally placed and the two inferiorly placed
are not seen in this view. The cavity in which the heart is lodged
has been sometimes called ' a pericardium,' and sometimes an
'auricle/ It is formed by a reflection of the membrane which
lines the general visceral cavity ; and it receives the blood returned
from the branchiae, so as functionally at least to represent a bran-
chial auricle. Six elastic ligaments, the ' alae cordis,' pass from
the cardiac aspect of this ' pericardiaF or ' auricular' membrane, to
attach themselves to the walls of the heart, their main function
being probably to reopen by their recoil the six venous orifices
which each systole of the ventricle closes. These ligaments may
serve also to suspend the heart in the pericardial sinus, but the
arteries which pass off" from it are probably in these, as in other
animals, the chief means whereby the heart is maintained in situ.

The five arteries arising along the anterior edge of the heart,
and the sort of bulbus arteriosus into which the posterior end of
the heart tapers, give it the polygonal appearance which distin-
guishes the heart of the Decapodous Crustaceans from the similarly
unilocular and non-vasiform heart of the Entomostracous order
which gives off no arteries. The anterior edge of the heart corre-

102

Descriptions of Preparations.

spends more or less exactly with the curved line already described
at page 96 supra, as limiting off in the omo-stegite an area repre-
senting the coalesced terga of the thoracic segments anteriorly
from one similarly representing the coalesced terga of the five
abdominal segments posteriorly. In having thus its anterior edge
or boundary not prolonged beyond the region of the abdomen, the
heart of Crustacea corresponds with the heart of all other Arthro-
podaj and furnishes an excellent illustration of the value in mor-
phology of identity in the relative positions of organs which may
differ very widely in external shape, and appearance.

For a figure of the heart of a Decapodous Crustacean, see Professor
Owen, Comp. Anat. Invert., p. 318.

Eor a discussion as to the venous system, and as to the prolong-
ation or non-prolongation of the branchio-cardiac vessels as
distinct tubes through the pericardial srnus into the ventricle,
see Straus Durckheim, Considerations generales sm* FAuatomie
Comparee des Animaux Articules, p. 346 ; Milne- Edwards,
Histoire Naturelle des Crustaces, p. 103, 1834; Le9ons sur
la Physiologic et FAnatomie Comparee, tom. iii., p. 183, 1857,
where the views of Straus Durckheim are adopted.

For the Alae Cordis and their functions, see Verloren, Sur la Circu-
lation dans les Insectes Mem. Couronn et Mem. Sav. Etrang.
Acad. Roy. Belgique, tom. xix., pp. 68-70, 1844, where the
alae cordis are said not to be muscular even in insects.

34. Common Crayfish {Astacus Fluviatilis),

Male,

Dissected so as to show its stomach, intestine, reproductive and respiratory

systems, in situ.

The greater part of the tergal elements of all the segments of
the body have been removed, together with the venous sinuses
which underlaid them, as also the heart and its arteries. An
arcuated plate, the 'cardiac ossicle,' is seen crossing the cardiac
portion of the stomach, and receiving the insertion of the anterior
gastric muscles, which arise from the ventral base of the triangular

Common Crayfish.

103

rostrum. Between these gastric muscles anteriorly is seen the
azyo-os stomato-gastric nerve entering a small ganglion. From
this ganglion it is continued onwards, after giving off a nerve on
either side, across the cardiac ossicle, posteriorly to which it bifur-
cates, and joins one of the lateral stomato-gastric nerves to supply
the liver lobes. A small ossicle, the ' pterocardiac,' articulates
with either outer angle of the cardiac ; and from the base thus
constituted the supero-lateral ossicles pass backwards so as to form
with it anteriorly, and with the 'pyloric ossicle' distally, a tri-
aiigular framework, into the apex of which two other muscles are
inserted, which take origin posteriorly from the carapace. Imme-
diately in apposition with the portion of the stomach thus strength-
ened, is seen the end of the adductor mandibulae muscle, separated
from its attachment to the carapace ; and exteriorly again to the
muscle, are seen on either side the two lobes of the liver. In the
middle line between the hepatic lobes are seen the paired lobes of
the testis. Where these lobes join an azygos lobe placed pos-
teriorly to them in the middle line, and superiorly to the in-
testine, the vasa deferentia are seen taking origin as slender tvibes,
the calibre of which rapidly widens, and the lengthy convolutions
formed by which intrude some way into the post-abdominal cavity,
before they turn downwards to open in the basal joint of the last
abdominal limb on either side. Posteriorly, the comparatively
small strata of extensor muscles having been removed, we see the
intestine taking a straight course, as always in Crustacea, to the
anus. Externally to the vasa deferentia and hepatic lobes are seen
the branchial organs, arranged in three rows, the outermost con-
sisting of the branchiferous epipodites, which are developed upon
the coxopodites of the two posterior maxillipeds and upon the four
anterior^ ambulatory legs; and the two innermost of simple tree-like
upgrowths, developed in pairs from the third maxilliped to the
fourth ambulatory leg inclusively, and singly upon the second
maxilliped and the last ambulatory leg. The branchiferous epipo-
dites are in shape like a leaf, with the two halves of the blade or
lamina folded backwards, and with the mid-rib looking forwards.
Both halves are longitudinally plicated, but the branchial filaments
are developed only upon the half which looks outwards. The bi-an-
chiae proper are sessile, internally to the epipodites, upon the cpimera,
and the membrane intervening between them and the basal joints

104

Descriptions of Preparations.

whence the epipodites spring. The seven brauchiferous segments,
which, it may be remarked, correspond with the seven segments
carrying ambulatory legs, in Amphipoda and Isopoda, carry ten
branchiae in the pairs which all of them except the first and last
support, and a single branchia upon the first and last of their
number. To these twelve respiratory organs we may add six, by
counting the brauchiferous epipodites as such.

In the American species of the genus Astacus, with one exception,
there is no branchia upon the fifth abdominal leg ; and with the absence
of this branchia a lesser width of the cardiac area on the carapace has
been observed to be correlated. In the genus Homarus, on the other
hand, the branchiae are much more numerous than in Astacus, and
indeed without counting the epipodites which, as may be seen in the
common lobster, are setigerous rather than branchiferous, and act mainly
as the scaphognathite does, by changing the water in the neighbourhood of
the true branchiae, they out- number all the branchial organs of the Astacus,
whilst the cardiac area on the carapace is relatively much less clearly
indicated than in the smaller Decapod. Most of the anatomical points
upon which weight has been laid in these descriptions of the fresh-water
Crayfish, may be illustrated in the structural arrangements of the common
lobster, in places where the Astacus may not be procurable. The marine
species will however be found to diflFer from the fluviatile in the following
points. Its hepatic coeca are shorter, and the anterior portion of the
entire gland is larger, whilst the vasa deferentia are shorter, the testes are
very long and only joined by a commissure. The coecum at the commence-
ment of the intestine, which has already been spoken of as the rudiment
of the yelk-sac, is smaller and bilobed in the lobster, whilst it is simple in
the Astacus. The duodenum itself is smooth, and the rectum plicated
internally in the lobster, and the duodenum, where it ends in the rectum,
has an azygos coecum appended to it dorsally, as in Amphipoda, and
most other Decapoda except Astacus. The nervous system differs mainly
in having the ganglionic mass, whence the jaws and foot-jaws are inner-
vated, more distinctly constricted at the sides, and less in size I'elatively to
the five abdominal ganglia which succeed it, than we find the homologous
stmctures to be in the Crayfish. Of external points of difference, perhaps
the two most important are presented by the telson, which is uniarticulate
in the lobster, and the second ahdominal appendage in the male, which
is much less modified, and differs much less in appearance from those
which succeed it, than the same appendage does in the male Astacus.

Commo7i Cratifish.

105

For the points of difference between Astacus and Homarus, see
Milne-Edwards, Histoire des Crustaces, vol. i., pp. 329-333.
For the American subgenus Cambarus, to which the species
inhabiting the mammoth cave in Kentucky belongs, see Dana,
Crustacea, United States Exploring Expedition, 1852, p. 522.

For the nervous systems of the common lobster, see Swan, Comp.
Anat. Nerv. System, pi. iii. and iv., where the endophragmal
arch formed by the mandibulo-maxillary apodema, and inter-
posed in the natural position of the parts between the stomach
and the cords of the nerve collar, and the first sub-oesophageal
ganglion is well seen. See also Newport, Phil. Trans. 1834,
pi. xvii., fig. 40.

For an account of the development of the common lobster, Homarus
Vulgaris, see Rathke, Wiegman^'s Archiv. fiir Naturgesehichte,
1840, p. 24 T, translated in Annals and Magazine of Natural
History for 1841, vol. vi., p. 363, where the embryo on the
point of hatching is shown to differ from the adult mainly by
the presence on the ambulatory legs of an exopodite, such as
the two posterior maxillipeds retain in the adult Decapod, and
the ambulatory legs themselves in Mysis and Squilla.

For the correlation of large size of ova with the completion of
development before hatching, see Bergmann and Leuckart,
Vergleichende Physiologic und Anatomic, p. 647 ; and for an
exemplification of this law, in the instance of Mysis, where
the eyes are few (fifty) in number and large, and where the
development is direct and without metamorphosis, as com-
pared with such cases as those of the Palinuri and Carcini,
where the eggs may be from one to three hundred thousand,
and are of small size, and where the well-known metamor-
phoses with forms known as ' Zoea.' and 'Megalopa^ are
gone through, see Van Beneden, Recherches sur les Crustaces,
PP- 53' 57- The fresh-water congeners of marine species
which go through metamorphoses, are very frequently ameta-
bolous in the sub-kingdoms of Mollusca and Vermes as well
as in that of Arthropoda. In the instances here under com-
parison, of the fresh-water Astacus and the marine Homarus,
it should be borne in mind that the ova of the former animal
are larger than those of the latter, though the adult Crayfish
rarely attains one-third of the size of the lobster.

lOG

Descriptions of Preprtratlons.

35. Common Crayfish {Astacus Fluviatilis),

Dissected so as to show its nerve system ; the gi-eater part of all the terga of the
aninial, and the viscera of organic life, with the exception of the commencement
and the tennination of the digestive tract, having been removed.

Besides the prae-oral or so-called ' supra-oesophageaV ganglionic
mass, supplying the eyes^ antennules and antennae, there are twelve
post-oral ganglia in the Crayfish, of which six belong to the seg-
ments anterior to the post abdomen, and six to these terminal
segments. The first post-oral ganglion is the largest of the series,
and supplies no less than six pairs of appendages, viz. the man-
dibles, the two pairs of maxillae, and the three pairs of foot-jaws.
In the developing Crayfish, as shown by Uathke", this mas? which
irilius'"fusid in the adult is represented by six pairs of white^
spTcfe: — Posteriorly to it we see filve ganglia, remaining distract,
and corresponding in the adult as they do in the embryo of the
Macrurous Decapods, and also of the Hedriopthalmatous Crustacea,
with the five paii-s of abdominal feet. Each of these six ganglionic
masses presents a perfectly fused and continuous surface, but traces
of the primitive antero-posterior bifidity of the nerve chain are
still faintly visible, even to the unassisted eye, in the commissural
cords passing between the ganglia. The wide opening which is seen
in the commissural cord connecting the third and fourth abdominal
gangha, gives passage to the sternal artery seen iu Prep. 32, p. 99,
and the cord which connects the fourth with the fifth, differs from
the cords which connect the pairs anteriorly placed in being shorter
th an any one of them. There are six post-abdominal ganglia, undei \
the third and fourth of which, as also under the cord of commissurci j
between the fifth and last, slips of blue paper have been placed.
Each of the five anterior post-abdominal ganglia gives oflT two
pairs of nerves, the sixth, which is the largest of the series and
alone of the six connected with the one preceding it by a double
commissure, gives oif a considerably larger number of nerves,
supplying as it does both the anus and the tolson, in addition to
the parts homologous with those supplied by the five anterior

u Ueber die Bildung und Entwrickelung des Flusskrcbses, pp. 32, 33.

Common Crayfish,

107

ganglia. This ganglion has been said to represent two ganglia,
which were separate and distinct in the embryo. Rathke, however,
informs us, 1. c, that he has not been able to observe anything as
to the mode of origination of the post-abdominal ganglia; and
though the distribution of the nerves of the sixth ganglion may
seem to make it probable that it was so developed, the comparative
anatomy of the homologous series in other Crustacea would appear
to militate against such a view. A system of nerves homologous
with the nervi transversi or ' brides Spinier es' of Lyonet, described
under Prep. 29, p. 84, in the insect, is represented by a nerve
which arises in each segment, as seen with the naked eye in the
third post-abdominal segment over the slip of blue paper placed
there, from the commissural cord, and bifurcates into two lateral
nerves. The bilaterally symmetrical and the azygos stomato-
gastric system of insects are represented in the Crayfish by a
system of nerves which arises symmetrically on either side of the
oesophagus from a thickening on the commissures of the nerve
collar, and by an azygos nerve which arises from the supra-oeso-
phageal mass ; but which has not any separate prae-cerebroid gan-
glion frontale developed upon it as in insects. A slip of blue paper
has been placed between the commissural cords of the nerve collar,
and the antennary sternum with which they are commensurate
in length ; and in the interval between the commissural cords, the
various trunks of the stomato-gastric system are seen. The com-
missural cords are connected anteriorly to the first post-oral gan-
glion by a transverse cord, which is in apposition with the posterior
wall of the oesophagus, and represents, probably, an anterior frag-
ment of the backwardly displaced ganglionic mass which supplies
the jaws and foot-jaws. The prae-oral ganglionic mass, which in
embryonic life was seen by Eathke to be made up of two ganglia
on each side, of which the posterior or the one more nearly placed
to the mouth was the larger, and supplied the antennae and anten-
nules, sends nerves to these organs, to the auditory organ lodged
m the antennule, to the antennary gland, and finally to the eyes.
The ocular portion of the prae-oral mass has not assumed the
degree of relative importance which it has in air-breathing Ar-
thropoda.

The distinctness of the fibrous chords from, and their position
superiorly to the ganglionic elements of the ventral chain, can

108

Descriptions of PreiKirations.

be recognized in Astacus as well as in other Arthropoda, when the
specimen has been^ as in this case, sufficiently hardened in alcohol.
The summits of the branchial plumes are well seen in this Prepa-
ration, between the omo-stegite and the epimera of the abdominal
segments. From the internal aspect of the epimera, the muscles
which move the limbs are seen passing- downwards and bifurcating
as they pass through the apodematal cells to their insertions in the
upper segments of those appendages. In the cephalo-stegite, the
adductor mandibulae is seen taking origin from the internal aspect
of the protuberance already described, at page 96, as existing on
its outer surface.

On the ventral surface a packet of spermatozoa, aggregated in
their passage along the convolutions of the vasa deferentia into the
so-called ' spermatophore/ may be observed adhering to the cox-
opodite of the last abdominal segment, in which the vas deferens
opens. These structures, which are of comparatively small size
as compared with those of some much smaller Crustacea, but which
are produced in great numbers in the Crayfish, are by no means
found exclusively in the neighbourhood of the generative outlet
of the male, but may be seen adhering to various parts of the
animaFs body. In the Chilopodous Myriapoda they may be at-
tached even to foreign bodies.

It may here be noted that though in many Hedriophthalmata, or four-
teen-footed Crustacea, the number of post-oral ganglia may be tlie same,
or nearly the same, as in such Macrurous Decapods as the Crayfish or
Lobster, it is never made up of the same pre-thoracic, thoracic, abdominal,
and post-abdominal factors in the same proportions as in the higher
order. The ganglia supplying the ambulatory appendages, which in the
Hedriophthalmata correspond with the two posterior maxillipeds or
foot-jaws of Decapods, escape fusion with the first post-oral mass con-
sisting of the coalesced ganglia belonging to their three pairs of foot-
jaws and single pair of foot-jaws ; and maintain their typical distinct-
ness, just as the appendages which they supply maintain their primordial
locomotor functions. Having thus two more ganglia in the anterior
portion of their segmented bodies, the Amphipods and Isopods have
fewer than the Decapods ih the post-abdominal region ; and by a re-
duction of the number of the ganglia of this region from six to five or
four, the entire uuml)cr of their ventral ganglia comes to be thirteen
or twelve, as in Homarus or Astacus. In some of the air-breathing

Common Crayfish.

109

Isopocla, the post-abdominal may be represented by but a single mass.
Though, as already stated, we know that in the earliest periods of de-
velopment of the nerve system, at least in the Crayfish and Scorpion,
the single ganglionic centre which innervates the first six post-oral
segments, consists of an equal number of pairs of ganglia, it has been
shown in other cases, as by Weismann in the developing Dipterous larva,
and Metschiuow in Apliis Eosae, that the nerve centres of many typically
distinct segments may from the very earliest periods be connate. As,
indeed, the nerve system is specialized in Arthropoda at a very late
period as compared with that of the segmentation of the body and the
development of the appendages, it may seem that when it does thus
come into being, it must adjust itself to any secondary arrangement or
disposition which these organs may have assumed in the course of their
evolution, rather than to any typical relations of distinctness or of one-
ness which they may have manifested in earlier periods. In cases such
as those of the larvae of Muscidae, as described by Weismann, where the
nerve centres of the entire series of post-maxillary segments are, if no
earlier and rapidly transitory period of distinctness has been overlooked,
connate from their first appearance, the number of nerves given off from
the connate mass may serve to indicate its really compound nature. But
though in the larvae specified, as many as eleven pairs of nerves are given
off from the single mass corresponding to eleven post-maxillary ganglia
of such larvae as Gorethra plumicornis or Phalaena neustria, it is well
to note that in the perfect insect, even this indication of the typical
plurality of nerve ganglia is wanting, and that the ventral cord of the
adult fly, exclusively of its first sub -oesophageal mass which supplies the
modified jaws, gives off only four pairs of nerves, and one terminal
azygos abdominal cord.

As in the Myriapoda the jaws are supplied from a single gang*-
lion, just as in the other three classes of this sub-kingdom, we
may say that in all Arthropoda, the first three post-oral segments
upon which the mandibles and maxillae are developed, are inner-
vated, at least in the adult state, by a single ganglion. In Crustacea
and Myriapoda, this, which may be spoken of as the manducatory
ganglion, is always fused with more or fewer of the succeeding
ganglia accordingly as more or fewer of the thoracic appendages
are converted into auxiliary jaws. In the fourteen-footed Hedrioph-
thalmata therefore, where only the anterior pair of thoracic limbs
is converted into an accessory oral organ, we should say that the

110

DescriiJtions of Preparations.

first post-oral ganglionic mass consists of the manducatory g-ano-
hon fused with one thoracic ganglion; whilst in the D.capoda
all three thoracic centres have coalesced with the manducatory
In msects, on the other hand, we should say that even wlien the
nerve gangha attain the very extreme of concentration, the man-
ducatory ganglion is always distinct from the rest of the ventral
gangha; and that the thoracic gangha, as might be expected from
the ^importance of the parts they supply, have a much greater
relative size and independence than the homologous ganglia in
Crustacea. The first abdominal ganghon in insects very frequently
coalesces with the third thoracic, which is rarely the case in the
Crustacea, m which the nerve centres of what Fritz Miiller has
called the 'middle body/ very ordinarily are the best developed
m their entire ganghonic series. The Arachnida resemble, on
the one side, Crustacea, in having their manducatory fused mth
their thoracic gangha, and on the other, Insecta, in having more
or fewer of the abdominal ganglia coalesced with the thoracic.
Ihe Arthrogastrous Arachnida, as the scorpion, may have as many
as four post-abdominal ganglia; Insecta appear never, even in the
larval state, to have more than three; whilst Crustacea may have
as many as six; or may, in the air-breathing Isopoda, as Oniscus
Mnranns, have a single ganghonic mass partially coalesced with
the last abdominal to represent the entire caudal series, which,
together with the post-abdominal segments, may be wholly lost
m Laemodipoda.

On the other band, though fusion and connation even may be carried
out to the extreme degi-ee witnessed in Diptera, as also in Carcinm
Mamas amongst Crustacea, and the Araneae amongst Arachnida, it
would be wrong to hold that the nerve system of Artliropoda is in no
case a guide towards the determination of the homologies of their seg-
ments and appendages, or that the necessity existing in particular in-
stances for the establishment of consentaneous muscular action in seg-
ments and appendages, entirely obliterates all traces of a common typical
aiTangement of the elements of this system. The innervation of tlie
so-called 'mandibles' or 'cheliceres' in the Arachnida from the supra-
oesophageal mass, must be held to prove that these organs are essentially
antennae ; and a study of the appended Tables will show, that if we make
allowance for the (possible) connation of the three ganglia, which should
typically be developed in correspondence with the three manducatory

Table of Post-oral Nerve Ganglia of Decapodous Crustacean, op Macrurous Arachnidan, and op Lepidopterous
Insects, as observable in developing and in adult individuals of the genera

AsTACus, Scorpio, and Sphinx.

Dcrdbping Astaeus.
Eathke, 1. c.

Adult Astaeus.
Brandt, 1. c.

1.

it
iii.
ir.

T.

tL
vii.

vs.

X.

si.

xii.

Tiii.

sir.

rv.

xri.

rvii.

Post-oral ganglion.

Mandible
1st Maxilla
2nd Maxilla
1st Maxilliped
2nd

3rd „
1st Abdominal

Clieliferous
2nd Abdominal lej

leg

Ganglion, described
as two in Lobster

= u. Ganglion

Srd
4th
5th

1st Post-abdominal leg •

2nd

Srd

4th „

5th

6th

: IV.
: V.
: Vi.

: vii.
: viii.

XI.

: xii.

Developing Scorpion.
Eathke, 1. c.

Adult Scorpion.
Phil. Trans., 1843.

i. Post-oral gangUon. CheUferous mandibles

ii. „ „ 1st pair of legs

iii. „ „ 2nd pair of legs

iv. „ „ Srd pair of legs

v. „ „ 4th pair of legs

vi. Genital segment

vii. Pectiniferous segment

viii. 1st Puhnoniferous segment

ix.

2nd

X.

Srd

xi.

4th „

xii.

1st Caudal

xiii.

2nd „

xiv.

Srd „

XV.

4th „

xvi.

5th „

xvii.

6th „

Ganglion, laterally
conatiioted

: ii. Ganglion observed
by L6on Dufour, Ann.
Soi. Nat. XV. 1851.

= iii. Ganglion

: iV.
: V.
: vi.

: vii.
; viii.

: ix.

not developed

Lama of Lepidopterous Insect.
Newport, Phil. Trans. 1832.

Imago of Sphinx.
Phil. Trans., 1834.

Post-oral ganglion.

Mandibles, Spinnerets,
Salivary gland

Post-oral ganglion. 1st leg
„ „ 2nd leg

„ „ 3rd leg >

Vll.

viii.

xi. Bilobate.

Each two pairs of nerves,
one lai'ge and one
small.

Five pairs of nerves, four of which
are large.

= u.

= Aborted

Aborted

= IV.
= V.

= vi.
= vii.

Table of Post-oral Nerve Ganglia as observable in Amphipodous and Isopodous Crustacea and in

Orthopterous Insects.

Amphipodous Crustacea, Talitrus, Milne-Edwards
and Spence Bate, AmphitJwe, Bruzelius, Hyperia,
Straus Durckheim, Gammarus Pulex, mihi.

u.
iii.

iv.

V.

vi.
vii.
viiL

XI.

xii.

Post-oral gangUon gives branches to jaws, !s not figured
by Straus Durcklieim in Mem. du Museum, 1829,
tom. xviii., in Hyperia Galba. But s«e Bruzelius'
figures. Arch, fur Naturgeschichte, 1859, Taf. x., fig.
18. 1

1st Ambulatory foot] Fused in Hyperia with each other
r and mth i. approximating De-
" " capodous arrangement.

Srd „ „ Distinct ganglion
«h „
5th „
6th „
"h „

Ist Pleopodos „ „

2nd >.

Srd „ „ „

4th Pleopodos. Distinct ganglion accordii|g to Spence
Bate in Talitrus Locusta ; but in Talitrius, Hypem,
and Amphithoe, as figured by Milno-^dwards, De
la Valettc, and Straus Durckheim, and, in Gamma-
rus Pulex where it is much elongated, silpplying the
5th and 6th Pleopodos also. '

5th Pleopodos. Distinct gangUon in Talit^is Locusta,
Spence Bate, in British Association Eopoiit, 1855, p. 56,
PI. xxii.

xiv. 6th

Isopodous Crustacean, Oniscus Asellus, Woodlouae,
Leydig, 1. c. Taf. iv. 7.

i. Post-oral ganglion, very small and ordinarily overlooked.

The nerves for the manducatory organs ai'e said to
come from the commissures of the collar. Nova Acta,
XX., p. 35, in Idothea and iEga, as also in the Scolo-
pendra.

ii. 1st Ambulatory foot

iii. 2nd „ „

iv. Srd „ „
V. 4th

vi. 5th

vii. 6th „ „

viii. 7th „ „

ix. Supplies terminal segments, being itself distinguish-

able fi'om the eighth ganglion by a foramen placed
mesially. This ganglion represents the free terminal
ganglia described by Rathko and Milne-Edwards
in the marine species Idothea Entomon, Mga, Bicar-
inata and Cymotlioe, and by Leroboullet in the air-
breathing and closely allied Ligidium Persoonii.
See Nova Acta, xx., Pt. i. p. 34 ; Hist. Crustac^s, Taf.
xi. 2 ; Ann. Sci. Nat. xx. PI. v. 24.

Orthopterous Insect. Periplaneta Onentalis.
See Plate vi.

Post-oral ganglion supplies mandibles and bifid labium ;
is closer to supra-oesophageal mass than in Crus-
tacea.

1st pair of feet

2nd

3rd

This ganglion is probably to be considered as having

become fused with No. iv.
1st abdominal ganglion
2nd
Srd
4th

5th abdominal ganglion, coiTesponding as the tenth
post-oral of the Larva) of Lepidoptera and tenth post-
oral of the embryo Scorpion do with the first post-
abdominal of the Crustaceans.

6th, bilobed terminal ganglion, corresponding to the
three terminal ganglia of Gammarus Pulex.

Common Crayfish.

HI

segments in the insect, a veiy close, even if not complete, correspondence
exists between tbe arrangements of the ventral ganglionic chain in
Insecta, Arachnicla, and Crustacea.

In this Table the series of gang-lia as observable in the developing-
and in the adult forms respectively of AstacuSj Scorpio^ and Sphinx,
have been placed side by side in six columns, the maximum number
of divisions in which is seventeen, the typical number, according
to the view here adopted, of the post-oral segments in Arthropoda.
Each actually existing ganglion is placed in the particular division
of the scale of seventeen which is regarded as its homological
relation to the complete series furnished by the developing Astacus.
Thus a glance shows both where coalescence has taken place and
where ganglia have failed to be developed,

lu a second Table the ganglionic series of an Amphipodous, of an
Isopodous Crustacean, and of an Orthopterous insect, have been similarly
arranged in parallel columns, the Amphipodous Gammarus making the
transition from the Decapodous Astacus to the Isopodous Oniscus easy,
and the Oniscus in its turn approximating perhaps more closely than
most or all other Crustaceans to the insects ^. The anatomical points

^ The order Ortboptera is believed to be the earliest representative of the class
Insecta in geological times, see Gerstaecker, Klassen und Ordnungen des Thier-reichs,
Bd. v., p, 292 ; and as an order they are distinguished by the possession of a number
of characteristics which approximate them to the Crustacea, the earliest geological
representatives of the sub-kingdom Arthropoda. Amongst these may be mentioned
the possession of the processes figured at c in pL vi., and known as ' cerci anales,'
which appear to be homologous with certain processes which Eathke has spoken
of in Crustacea, e. g. Apus, BrancMpus, Cyclops (Morphologie, p. 115); the retention
by the second pair of maxillae of something of their typical distinctness as opposed
to fusion, as in other insects, into a 'labium ;' the presence of three basal joints
as a support to the multiarticulate antenna which thus resembles the antennule
of Crustacea; and, lastly, the functional peculiarity of ecdysis, which attaches even
to adult Ephemeridae in this order of insects, and the pedunculate jDosition of the
central eyes in certain male Ephemeridae, CJdoe diptera s. Ephemera hioculata,
Linn. The internal structural arrangements of the order Isopoda, irrespective of
those of their nervous system, present some points of interesting resemblance
to those of Insecta, and especially of Orthoptera. Their long non-ramified hepatic
coeca are essentially similar to those seen in the Orthoptera ; see above, p. 86,
and pi. vi. h, and description; Leydig, Lehrbuch der Histologic, pp. 362,
fig. 194 ; whilst in their air-breathing genera, Oniscus and Tylos, a system of
canals has been discovered in the opercula of their branchial plates, which has been
supposed to be a rudimentary tracheal apparatus. As these peculiarities do not
relate to the nervous system, it is of the more importance to note that a sympathetic

112

Descriptions of Preparations.

embodied in this Table can be illustrated by dissection of the readily
procurable animals, Gmnmarus Pulex, Oniscus Murarius, and Peri-
])laneta Orientalis.

Much has been written as to v/hether twenty or twenty-one is the
typical number of segments in the Arthropoda. The gi'cat number of
homonomous segments which in Myriapoda are developed posteriorly
to their thoracic region, enables us to eliminate them from consideration,
except so far as the thoracic and cephalic segments are concerned ; but
in all other Arthro])oda, with the exception of the Trilobites and Phyl-
lopoda amongst Crustacea, the number of actually, if not of homologically
distinct segments, appears to be very definitely limited. The typical
number of segments has been considered here as being twenty, in ac-
cordance with the views of Professor Huxley, and in opposition to those
of Professors Milne-Edwards and Van Beneden ; inasmuch as the ' telson'
or terminal so-called segment of the Crustacea does not appear to possess
the characteristics of a true segment. In the Sessile-eyed Crustacea, the
telson is, according to Mr. Spence Bate, 1. c. p. xxi., who however appears
to reckon it as making a twenty-first segment, " generally an abortive,
and frequently a rudimentary part and in the Isopoda, with the excep-
tion of two genera, it is always fused with the preceding segment. With
one, or perhaps two exceptions, the telson never carries appendages,
" whereas it is a law common to all Crustacea, that every segment has
its appendage and Kathke, from whom however Van Beneden differs,
describes it as being developed after the other segments, and from the
dorsal aspect of the body.

Even if it should be proposed to regard it as representing in a rudi-
mentary form the very gi-eat or all but indefinite number of homo-
nomous segments which we meet Avith in Apus amongst Crustacea, and
in the Myi'iapoda, we should still be justified in eliminating it from the
number of the typical segments of Arthropoda ; that is to say, from the
number of segments to which some of the best marked representatives of
three out of the four gi-cat classes into which the sub-kingdom is divided,
can all alike be shown to conform. The history of the development,
and to a considerable though lesser extent, that of the comparative

ganglion corresponding in position and connections to the azygos ' ganglion frmiiaJe'
of Insecta and Mjn-iapoda has been discovered by Leydig in Oniscus. In other
Crustacea, the nervus recurrens has no ganglion fronfalc develojied, but ajipears to
take origin from tlie supra-oesopliageal ganglia. Brandt has figured a lateral paired
system of sympathetic ganglia in this Crustacean, see Med. Zool., Bd. ii. Taf. xv.
fig- 27 ; but Leydig declares the structures thus described to be merely glands in
connection with the stomach.

Common Crayfish.

113

anatomy of the antennae and jaws in ^Vi-thropoda, pi'ovc that they are
appendages in just the same sense as any of the ventrally placed append-
ages attached to segments posterior to the cephalic ; and with them,
most authors, with the exception of Glaus and Fritz Miiller, would be
inclined to rank the eyes. The facts of the pedunculation of these organs
in the Podophthalmatous, and indeed in some other Crustacea ; of the
occasional replacement of their facets by a flagellum such as the antennae
caiTy ; of their having a separate pair of lobes developed in connection
with them in the supra-oesophageal ganglionic mass in ordinary De-
capods, as shown by Rathkey, see p. io8, supra, in Amphipoda, and also

y Bruzelm3, Archiv. fur Naturgeschiclite, torn, xxv., 1859, p. 306 ; Beitrag zur
Kenntniss vom innern Baue der Amphipoden, has described the supra-oesophageal
mass of an Amphipod, Amphithoe Podoceroides, as consisting of three pairs of ganglia,
the most anterior of which is in relation with the eyes, the middle one with the
antennules, and the one nearest the mouth with the antennae. Similarly Mr.
Newport, Phil. Trans., 1834, p. 422, pi. xvii. fig. 40, a, h, c, has figured and de-
scribed the supra-oesophageal nerve-mass in the common Lobster, Homarus Vulgaris,
as consisting of three pairs of ganglia in relation with the three pairs of sensory
organs specified. Though no air-breathing Arthropod has at any one period of its
life more than a single pair of antennary organs, Rathke's figures of the cerebroid
mass in the developing Scorpion, Morphologie, Eeise nach Taurien, Taf. i. fig. 10,
and his description of it in contras't to the brain of the adult animal, as * composed
of several pairs of ganglia lying one behind the other,' and also Metschnikow's
figures, Zeitschrift fiir Wiss. Zool., Bd. xvi. Taf. xxx., figs. 31, 33, though not his
description of the brain in Aphis Rosae, lead us to think that the brain, even in
these classes, may make its first appearance as a bilaterally trilobed mass, indicating
thus the presence of three prae-mandibular segments.

Mr. Newport indeed has put on record, Phil. Trans., 1843, p. 245, an observation
to the effect that in the embryo of a Chilopodous Myriapod, Geophilus Longicornis,
the brain is at the moment of its bursting its shell composed of four double ganglia.
But here it is probable that one of the p;iirs, as Metschnikow I. c. has shown to be
actually the case in Aphis Bosae, corresponded to the ' lobi optici,' which are lateral
outgrowths of the cerebroid gangha, and do not therefore indicate the presence of a
separate segment, though they may have been displaced inwards by lateral com-
pression. See Leydig, Vergleich. Anat., p. 183. The brain in adult Myriapoda is
very obviously quadrilobular, as has been noted by Newport, locc. citt., of Scolopendra,
Polydesmus, Geophilus Subterraneus when adult, and by Zaddach of Lithohius Forfi-
catus. This point is particularly well shown in the brain of Glomens Marginata, a
Myriapod closely resembling the Oniscus in external appearance. It has been
figured by Brandt, MiUler's Archiv., 1837, Taf. xii. fig. 7, p. 324, as consisting of
two irregularly quadrangular masses, prolonged at either outer angle into ocular
and antennary nerves respectively, and united at either inner angle to each other by
commissures passing over the oesophagus, and inclosing a wide open space between
them. For the development of the prae-oral ganglia in Astacus, see Rathke, Fluss-
krebs, p. 50, For the segmentation of the head, Rathke, Morphologie, pp. 126,

I

114

Descriptions of Preparations.

in Myriapocla, Geophilus, Lithohius and Scolopendra ; and finally, that of
tlieir having an all but independent annular segment, as well as a pe-
duncle, developed for their support in Squilla, appear to justify us iu
regarding the eyes aa either being or, when sessile, as representing ar-
ticulated appendages, and, by consequence, a distinct cephalic segment 2.
The apparent paradox of speaking of the eyes, which ordinarily have a
more or less completely dorsal position as homologous not with such
dorsal outgrowths as the wings of insects or the shells of certain Crus-
tacea, but with the ventrally placed articulated appendages, is to be
justified by the history of the development of the pro-cephalic lobes,
which at an early period are bent upwards at a right angle to the rest
of the blastoderm, and even backwards, so that the roof of the skull,
which is really a sternal, appears to be a tergal surface. Taking then
the eyes as indicating one segment, and the two pairs of antennae and
the three pairs of jaws as indicating five segments, we find that the
typical number of segments in the head of the Arthropod amounts to
six. The segments anterior to the maxillae, together with that part of
the body which ultimately becomes the swimmeret, in the Astacus,
Fritz Miiller has called the ' primitive body,' as being that which makes
up the 'Nauplius' form of larva, and which carries the sensorial appa-
ratus, as, for example, the ear, which is lodged ordinarily in the scale
of the second pair of antennae, but sometimes in the ' uropodos,' as in
Mijsis. The sections of the body which are intermediate to these
extreme points, he divides into a ' fore-body,' which corresponds to what
is here spoken of as ' thorax,' and which is second in order of develop-
ment ; into a 'hind-body,' the 'post-abdomen,' deducting the sixth
segment, which is third in order of development ; and finally the ' middle
body,' the ' abdomen' in the language here employed, which in Crustacea
always puts forth limbs immediately after its segments are developed.

1 2 7. The demonstration of the points relating to the brain of Amphipoda, is made
much more easy if acetic acid is added to the alcohol employed for hardening the
specimens to be dissected.

' Two pairs of articulated appendages have been observed in the larval forms of
Cirripedia anteriorly to the superior pair of their natatory antennae ; and if the
posterior of these be taken as equivalent to the 'olfactory filaments' of the superior
antennae, the anterior, the 'larger antennae' of Darwin, the so-called 'horns of the
carapace' would still indicate the presence of a third pre-mandibular segment. For
an account of these outgrowths, see Gerstaecker, Klassen und Ordnungcn des Thier-
reichs, Bd v., p. soS ; Rpencc Bate. Ann. and Mag. Nat. Hist., Ser. ii., vol. viii.,
i8.ni, p. .^27; Fritz Miiller, Archiv. fiir Naturgeschichte, 186:, p. 7. 1863, p. 25,
note 2 ; Darwin, Lepadidae, iS.m.p. 9; Balanidae, 1854, p. 105.

Common Craijjish.

115

and which has a high degree of independence manifested by its nerve
ganglia in Podoplithahnata and Hedriophthalmata.

The number of the prae-oral segments being thus taken as three, and
the so-called ' lips' of certain Crustacea being eliminated from tlic enu-
meration as not i-epresenting appendages, but being merely indurations
of the lining membrane of the digestive tract homologous with the 'jaws'
of the leech, we obtain, by omitting, for the reasons above stated, to
count the telson as a segment, seventeen as the typical number of post-
oral, and twenty as the typical number of the entire series of segments
in Artliropoda. The appended Table shows how these views may be
applied to the Insecta, tlie Arthrogastrous Arachnida, Myriapoda, and
to the two above-named orders of Crustacea, as also to the Coi^epoda ;
which, in spite of their small size, with which inferiority of organization
has been supposed to be commonly correlated in Crustacea, present many
important points of affinity to the highest order in the class. Amongst
these may be mentioned the degree to which heteronomy or diflferentia-
tion is carried out in the various regions of the body ; and the external
similarity which these small animals thus obtain to such Crustacea as
Peneus and Mysis is made tlie more striking, when we recollect that
they all alike leave the egg with no other appendages than those of the
'Nauplius ;' and that the adult Copepod corresponds very closely, if not
exactly, as to the number of articulated appendages on its 'fore-' and
' middle-body,' with certain ' Zoea' stages in the development of Podoph-
thalmata. See Spence Bate, Phil Trans. 1858, pi. xl. figs. A and B;
Claus Die frei Lebenden Copepoden, 1863, Taf. xxxiii. fig. 6; Dias
Longiremis, Taf. xix., fig. 2, Thalestris har23actoides ^. The non-seg-
mentation of the post-abdomen in many of the parasitic Copepoda, as
also in the Cladocera, Daphnis, the Ostracoda, Cypris and the Cirripedia,
eliminates them as it does the non-Arthrogastrous Arachnida from con-
sideration, except as to the anterior regions of the body. The Myriapoda
together with a few Branchiopoda, Apus, and the extinct Trilobites, are
similarly eliminated for the opposite reason.

The term 'Hedriophthalmata,' Schiodte, Ann. and Mag, Nat. Hist.,
Ser. iv., vol. i., 1868, p 6, is employed in the following Table in the
same restricted sense as its etymological equivalent, by Professor West-
wood and Mr. Spence Bate, in their work on the Sessile-eyed Crustacea.

* The internal anatomy of the Copepoda is well illustrated in the former of these
two figures ; the dorsal opening of the anus being especially noteworthy, as corre-
sponding with a condition observed by Rathke, in the early stages of the develop-
ment of the Astacus, sec p. 97, saijra.

1 2

IIG

TABLE OF
OF POST-ANTENNARY SEGMENTS

Nnmher
of

8c{))iient.

Insecta.

Arachnida.

Myriapoda.

Crustacea.

I.

Mandible, never pal-
pate.

'Chelae' of Scorpion
are the palps of its
mandible. The so-call-
ed * maxillae' of Spiders
are also palpate.

Mandible, with rudi-
mentary palp in Chilo-
poda; not palpate in

Oil 1 1 r»o^ 1 fi i"!! fi
LLLLUg I iiX t XIU *

Mandible, ordinarily
carrying a tri-artit-u-
late palp, except in
tpTTP^tiHjil TsoDods and
Ampliipods.

II.

Maxilla, palpate.

First pair of legs are
the palps of the 'la-
bium.'

Outer element of * La-
bium/ in both orderSj

Q o in T , pni fl nnf .PTrti i s

cLj ill JJC^^LUU^IA^J. WUij

larva.

'Maxilla' i. or 'SLig-
onopodos ' i. Westwood
and Bate in ' Sessile-
eyed Crustacea,' p. 3.

III.

' Labium,' palpate.

Second pair of legs.

Mesial elements of
' Labium.'

' Maxilla' or ' Siapono-
podos' ii. Bifid, Cyclops.

IV.

First pair of legs.
First spu'acle in Cater-
pillar.

Third pair of legs.

Basal jomts forming
a Labiiun by junction.

* Maxilliped ' i. Audi.
'Siagonopodos' iii.
Westwood and Bate.

V.

Second pair of legs.

Foui'th pair of legs.

Basal joints as in vii,
and in Chilopoda arm-
ed with claw and poi-
son duct.

'MaxilUped' ii. or
' Gnathopodos ' i. Last
foot of early Zoea Lar-
va.

VI.

Third pair of legs.

Genital segment m
Scorpion.

Grcnital opemng ni
some Chilognatha.
Simple pair of legs in
Chilopoda.

HXIl A 1 1 1 1 J itrU. 111. KJl

' Gnathopodos ' ii.
Third swimming foot,
Cyclops.

VII.

First abdominal seg-
ment. Second spiracle
in Caterpillar.

Pectiniferous seg-
ment in Scorpion.

Sunple pair of legs m
both Cliilognatha and
Chilopoda.

First ambulatory ap-
pendage of Astaeus:
third of AmphiiKxi.
' Pereiopodos ' i. West-
wood and Bate.

VIII.

Second abdominal
segment.

First piilmoniferous
segment in Scorpion.

Ditto, ditto.

• Pereiopodos' ii.

IX.

Third abdominal seg-
ment. Carries first pro-
leg of Caterpillar.

Second pulmoniferous
segment in Scorpion.

Ditto, ditto.

' Pereiopodos ' iii. In
basal joint of append-
age or in stcnnnn of
segment we find the fe-
male generative outlet.

X.

Fourth abdominal
segment. Second pro-
leg of Caterpillar.

Third pulmoniferous
segment in Scorpion.

Simple pair of legs in
Chilopoda and female
Chilognatha. Penis in
male Chilognatha,

' Pereiopodos'iv.abort-
ed. as also iii. and v. in
Coi^epoda.

XI.

Fifth abdominnl seg-
ment. Third prolog of
Caterpillar.

Fourth juilmoniferous
segment in Scorpion.

Simple pair of legs in
Chilopoda. Double pair
m Chilognatha.

' Pereiopodos ' v. In
basal joint of append-
age or in sternum of
segment male penen-
tive outlet in Podoph-
tlialmata and liodri-
oplitlialmata.

HOMOLOGIES

MARKED BY APPENDAGES IN ARTHROPODA.

117

Number
of

Segment.

Inseda.

Araehnida.

Myriapoda.

Crustacea.

xn.

Sixth abdominal seg-
ment. Fourth proleg
of Caterpillar.

Eirst caudal segment
in Scorpion.

Simple pair of legs in
Chilopoda. Double pair
in CMlognatha.

First post-abdominal
segment. 'Pleopodos'
i. Generative outlets
in Copepoda.

XIII.

Seventh abdominal
segment. Last gang
Uon in larva.

Second caudal seg-
ment in Scorpion.

Ditto, ditto.

'Pleopodos' ii.

XIV.

Eighth abdominal
segment. Ninth spi-
racle and horn of
Sphinx larva.

Third caudal seg-
ment in Scorpion.

Ditto, ditto.

*"Plof\T»nrlnci in
XT ICUputlUo

XV.

Ninth abdominal seg-
ment. Vulva opens m
front of it and outlet
of Spermatheca upon
its sternum in Cock-
roach. Symmetrical
depression on the me-
sial ventral hue in
pupae of Sphingidae.

Fourth caudal seg-
ment in Scorpion.

Ditto, ditto.

' Pleopodos' iv. or
'Uropodos' i.

XVI.

Tenth abdominal seg-
ment. Orifice of col-
leterial glands of Cock-
roach.

Fifth caudal segment
in Scorpion.

Last segment in Pau-
ropus, see Lubbock,
Linn. Soc. Trans, xxvi.
pp. 1S2, 184.

' Pleopodos ' V. or
' Uropodos ' ii.

XVII.

Eleventh abdominal
segment. Anal orifice.
The ' cerci anales ' are
carried by it in Panor-
pa, and are supposed
to belong to it in other
insects by Lacaze Du-
thiers, Ann. Sci. Nat.
iooi, iooo. xney aie
probably homologous
with tlie caudal ap-
pendages of Apus and
Brauchipus, see p. Ill,
supra.

Sixth caudal segment
of Scorpion carrying
sting on its apex. An
appendage homologous
probably with mesial
element or 'telson' of
Astacus.

' Pleopodos ' vi. or
'Uropodos' iii. This seg-
ment has the lateral
elements of the swim-
meret articulated to it
just as the other post-
abdominal appendages
are articulated to their
respective segments.
The mesial portion of
the swimmeret or ' tel-
son' may be articu-
lated to it or fused
mth it, and may be of
very various forms.

The 'furca' of Cope-
poda, Cyclops, p. Ill, is
held by Claus to repre-
sent this segment.
Compare trifid append-
ages of Chloeon Di-
midiatum. Linn. Soc.
Trans, xxiv., 18C5.

118

Descrijptions of Preparations.

A very clear account of the nerve system of the various orders of
Crustacea may be found in Frey and Leuckart's Lelirbuch
der Zootomie, 1847, PP- ^95? ^^3-

For an account of the development of the nervous system of the
Crayfislij see Eatlike, Ueber die Bildung und Entwickelung
des Flusskrebses, 1829, pp. 32, 33, 50, 61, 6^, 85. For that
of the Scorpion, see E-atbkCj Morphologic Reise nach Taurien,
p. 2S, cit. Huxley, Linn. Soc. Trans., vol. xxii., pp. 227,
228.

For a figure of the nervous system in tbe common Lobster, Homarus
Vulgaris, see Newport, Pbil. Trans., 1834, pi. xvii. fig. 40;
where, however, the evident constriction of the first post-oral
ganglionic mass has caused the writer to count it as two, and
to speak of the entire number of ventral ganglia as being
thirteen. The relative superiority in size of this first post-oral
ganglion is not so marked relatively to those which come
posteriorly to it in the marine as it is in the fluviatile species
here contrasted.

For the nervous system in the Decapodous Crustacea generally, see
Leydig, Vergleichende Anatomic, Bd. i. p. 253, ihique citata.

For the stomato-gastric system, see Huxley, Medical Times and
Gazette, April 11 1857, p. 353; Brandt, Ann. Sci. Nat.
Ser. ii. torn, v, 1836, p. 87, pi. 4, figs, i, 2, 3.

For the nervous system of Myriapoda and Macrurous Arachnida,
see Newport, Phil. Trans., 1843, pt. ii. pp. 243-272 ; and for
the structure of the cord, p. 248, and Phil. Trans., 1834,
p. 406, pi. xvii. fig. 42; Leydig, Vergleich. Anat., pp. 229-
241 ; and Helmholtz cit. in loc; Carpenter, Comp. Physiology,
p. 669.

For various views as to the homologies of the segments, see
Savigny, Memoires sur les Animaux sans Vertebres, 1816;
Milne-Edwards, Histoire Naturelle des Crustaces, 1834, p. 50;
Ann. Sci. Nat., 1851; Erichson, Entomographien, 1840;
Lacaze Duthiers, Ann. Sci. Nat., Ser. iii. torn, xvii., 1852,
pp. 227, 232, 233, torn, xix., pp. 34, 40, 229-233 ; Dana,
Crustacea, U. S. Exploring Expedition, 1852, p. 19 seqq. ;
Zenker, Archi v. fiir Naturgeschiehte, 1854, p. 118; Van der
Hoeven, nandl)ook of Zoology, English translation, vol. i.,
1856, p. 557, ihique citata; Huxley, Linn. Soc. Proc, vol.

Common Earthworm.

119

xxii., 1858, p. 238; Van Beneden, Recherches sur les Crus-
taees, 1861, p. 29; Glaus, Copepoden, 1H63, pp. 13-J8;
Gerstaecker, Klassen uad Ordnung-en des Thier-reiclis, 1866,
Bd. v., pp. 38, 48, 333, 339 ; C. Spence Bate and Westwood,
British Sessile Crustacea, 1868, vol. i. pp. viii.-xxi., 3-7,
vol. ii. pp. 102-105.
For the reclconing of the eyes as appendages indicating the presence
of a distinct segment, see Zaddach, Untersuchungen liber die
Entwickelung und den Bau der Giiederthiere, pp. 78, 87 ;
Gerstaecker, Klassen und Ordnungen des Thier-reichs, Bd. v.,
pp. 203, 343 ; Aiphonse Milne-Edwards, Comptes Rendus,
lix., p. 710, f.

36. Common Earthworm (Lumhricus Terrestris),

Prepared so as to show the external organs which subserve locomotion

and reproduction.

The epidermis forms an iridescent capsule for the animaFs body,
the tissues of which have shrunk a little away from it under the
action of spirit. The integument is at various points to be here-
after specified, thickened and intumescent, but these thickened
portions are all developed in relation to the function of repro-
duction, there being no specialized organs of respiration. A
thickened white ring, the ' clitellus,^ made up of the fusion of the
dorsal and lateral portians of about six segments, may be seen in
the middle third of the body. The thickened glandular three-
fourths of these segments are separated off from the ventrally
placed and unthickened fourth, by a hyaline slightly elevated
ridge, which is muscular and more constant in its characters from
species to species than the glandular portion of the clitellus. On
either side of this ridge may be seen the rows of setae, the inner
one of which has its spines much lengthened. An orifice with pro-
minent tumid lips produced similarly to the clitellus by the de-
velopment of the glandular layer of the integument, is seen on the
fifteenth segment of the body, and corresponds to the termination
of the vas deferens on either side. A somewhat similar but smaller
prominence may be observed on either side the middle line of a

120

D(iscri])tions of Preparations.

segment sixth in order anteriorly to the clitellus. In this pro-
minence there is no foramen_, but two spines modified so as to
co-operate with the clitellus as an organ of adhesion in the act
of copulation may be observed to be implanted in it. These
spines belong to the inner series of locomotor spines, which are
prolonged from the third or fourth or fifth segment of the body
anteriorly, down to the posterior segments, upon the last of which
they, as well as the spines of the outer series, fail to be developed.
The outer row of spines is very visible along the line where the
darker coloured dorsal region shades off into the lighter coloured
ventral. Each series is represented in the Lmnbricidae by two
spines only ; the multiple or fasciculate arrangement not being
found in this family, which are therefore pre-eminently 'oligo-
ehaetous.^ The external series is wanting not rarely upon the
anterior segments, and may be wanting even as far back as the
clitellus inclusively. The spines of the inner series are modified
so as to subserve the mutual adhesion of the allotriandrous Lum-
brieus in the act of copulation, not only in the segment ah-eady
specified, but also in the entire series of segments occupied by the
clitellus, and in the tenth and fifteenth segments, where they are
thinner and twice as long as in other segments. The oviducts
and the vasa deferentia open in the fourteenth and fifteenth seg-
ments respectively, just externally to the outer of the two setae of
the inner row. In large specimens of Lumbricus communis, an
orifice may often be noted in the median dorsal line, in the inter-
space between the rings from the tenth segment or so backwards.
From this orifice, which opens into the interior of the posterior of
the two segments between which it is placed, in a recently killed
animal, the peri-gastric fluid may be seen to escape in small jets
upon pressure. Much variety is observable in the condition of
development of the clitellus, and even the number of segments
composing it and interposed between it and the head are by no
means unifoim within the limits of the same species.

For the zoological characters of the family Lumbricidae, sec British
Museum Catalogue of the British Non-parasitical Worms, by
George Johnston, M.D., 1865, pp. 57, 318, and especially
p. 323 for the variability in external anatomy just mentioned.

For the anatomy of Lumbricus, see E. Ray Lankester, Esq., Quar-

Coinmo7i Earthivorm.

121

terly Journal of Microscopical Science, 1864-1865, ihique
citata.

See also D-'Ukedeui, Memoires de FAcademie Royale de Belgique,
torn, xxxvi.j 1865.

A monog'raph on the natural history and anatomy of the Lum-
bricus Terrestris, of considerable merit, was published in Latin
by C. F. A. Morren in 1829, under the title ' De Lumbrici
Terrestris Historia Naturali necnon Anatomia Tractatus/

37. Common Earthworm [Lumbricus Terrestris),

Dissected so as to show its gangliated nervous system consisting of a bilobed supra-
oesophageal mass and a ventrally placed nerve-cord, connected with each other
by commissures, which give off numerous branches on either side to the large
sympathetic ganglionic mass lying ujjon either side of the pharynx.

The integuments having been divided down the middle dorsal
line and fastened out on either side, the entire digestive tract with
the exception of the commencement of the pharynx, through which
a black bristle has been passed, has been removed, together with
the pseud-haemal vessels in connection with it ; the segmental
organs, and the muscular dissepiments dividing the body into
compai-tments. The organs of reproduction have been similarly
removed, with the exception of the two receptacula seminis of the
right side, two globular white sacs which are seen opening in the
line of the outer rows of setae, in the intervals between the ninth
and tenth, and between the tenth and eleventh segments respect-
ively. The two lobes making up the supra-oesophageal mass are
pyriform, and have their broader ends apposed to each other in the
middle line. From their outer and narrower ends a thick nerve
passes off, bifurcating almost immediately, to supply the pro-
boscidiform and tactile anterior segment or upper lip. These
nerves would appear to be homologous with those given off from
the post-oral ganglia, and the anterior or upper surface of the
ganglionic mass whence they are given off to be homologous with
the under surface of the ventral ganglia. The cords of commissm-e
to the first ventral ganglion pass downwards and form the nerve

122

Descriptions of Preparatio7is.

collar in which a part of the pharynx is still left. Upon either
side of the pharynx a reticulation of ganglionic masses may be seen
with a lenSj one_of which masses is much larger than the rest^ and
running parallel with the commissural cords is connected with
them by six or more nerve branches. Two distinct strands may
be distinguished in the anterior portion of the ventral cord^ and
they are underlaid by a continuous stratum ofjvesicjilajc gubstauce,
which at intervals is aggregated into more or less distinct gangliaj
from each of which a pair of nerves is given off on either side,
whilst a single nerve is given off on each side from the portion
of the cord interposed between each two pairs of ganglia. These
latter nerves may probably be considered as homologous with the
nervi transversi of the Arthropoda, and as serially homologous with
the branches of the plexus already described as existing upon the
pharynx. They are given off in each segment anteriorly to the
paired nerves, and take a course outwards in relation with the
posterior aspect of the anterior dissepiment of each segment. They
are accompanied by a branch from the sub-neurally placed pseud-
haemal vessel, whilst the paired nerves are similarly accomj^anied
by a branch from one of the pseud-haemal vessels on either side of
the nerve cord. The ventral cord takes the shape of a thick band
in which the ganglionic enlargements are difficultly recognizable
for a space corresponding with that occupied by pharynx oeso-
phagus and reproductive organs ; posteriorly to the fifteenth seg-
ment it becomes much slenderer, but the ganglia become much
more distinguishable, though separated by wide interspaces up to a
point a little way posterior to the middle of the entire length of
the body. Finally, for a length nearly equal to that of the pos-
terior half of the animal, the cord becomes much more distinctly
moniliform, its ganglionic enlargements being very plainly marked
though very closely apposed. The terminal ganglion of the chain
is, contrary to what is seen in some other Annelids, as also in many
Arthropoda, smaller than those which precede it. The ganglia do
not maintain the same numerical equality with the segments in
other Annelids as in Lumbricus, exceeding their number in some,
as Aphrodite, and falling below it in others, as Hirudo, see Preps.
41, 4^. The two rows of paired setae are well seen on either side
of the middle line ; the inner setae in the two segments fifth and
sixth in order anteriorly to the clitellus are seen together with the

Common Earthworm.

123

g-landular follicle secreting- them to be considerably enlarged in re-
lation to their function as accessory generative organs.

In the anterior fifteen segments in the interval between the inner row
of setae and the nerve cord, a white jmuscular, fascicle is ^een passing
forwards and finally upwards alongside of the commissural cords of the
nerve collar, and dorsally to the nerves given off from the first ventral
ganglion, to be inserted partly in the capsule of the cephalic ganglia, and
partly in the muscular and tegumentary tissues above them. No mus-
cular fibres are developed upon the commissural cords connecting the
ventral chain with the supra-oesophageal ganglia, as there are upon the
ventral cord itself ; and the function of retracting the supra-oesophageal
ganglia, together with the structures above them, is performed by the
muscle here described, which from its origin and course acts at great
advantage. These two muscular bands have at first sight an appearance
closely similar to that presented by the two somewhat widely separated
halves of the ventral cord of the Tubicolar Annelids, and of Peripatus, or
to that of the accessory nerve-chains, developed in the Amphinomidae in
relation with the locomotor organs.

For an excellent account of the nerve system of the Earthworm,
see Lockhart Clark, Royal Society^s Proceedings, 1857, pp.

344-351-

Eor figures of the general arrangement of the nerve system, see
pi. viii., and Description. Quatrefages, Regne Animal An-
neles, pi, i. e, fig. 2«, and Ann. Sci. Nat., Ser. iii., tom. viii.,
1847, p. 36, for discovery of sympathetic system in Lumbricus.
See also D^Ukedem, I. c, pi. iii. fig. 4.

For the histology, see Leydig, Tafeln zur Vergleich. Anat., iv.,
fig. 8, and the various authors cited in the letter-press of
that work at pp. 138 seqq., 168 seqq.

For figures of the nerve cord as existing in two separated halves,
see Grube, in Miiller^s Archiv. for 1853, Taf. x., 14. Quatre-
fages, ' Suites a Bufibn,^ Anneles, pi. iii., figs. 7 and 8 ; in
Peripatus Edwardsii, and Sabella and Serpula.

124

Descriptions of Preparations.

38. Anterior Segments of Earthworm
{Lumhricus Terrestris),

In number about forty, and inclading three placed posteriorly to the clitellus ;
dissected so as to show the reproductive system, the whole of which, together
^•ith the various accessory organs, is contained in or constituted by modifications
of the structures of these segments ; as also the portions of the pseud-haemal and
the digestive system which are contained in this part of the animal's body.

The integument having been divided down the middle dorsal
line and pinned out on either side^ the digestive tract is seen to
occupy the middle line of the Preparation, and to have in con-
nection with it the vascular system, which is called ' pseud-haemal/
because though the fluid which it contains is coloured and prob-
ably respiratory in function, it is not corpusculated, and therefore
not morphologically blood. The digestive tract manifests a very
considerable degree of heteronomy, consisting of a pharynx which
extends through the first six segments ; an oesophagus which
extends through the succeeding ten ; a crop which occupies a large
space in the sixteenth and seventeenth; a gizzard which is seen
in the seventeenth and eighteenth ; and finally, the intestine which
is laterally sacculated for its first eight segments, and posteriorly
to them more evenly cylindriform. The pharynx has a coarsely
villous exterior, owing partly to the breaking away in the dis-
section of the muscular bands by which it was connected with the
muscular dissepiments and with the body-walls, and partly to the
salivary gland-tissue which composes part, and especiall}" the outer
part, of its walls. The oesophagus is of much smaller calibre than
either of the two segments of the digestive tube, the pharynx and
the crop which it connects. The so-called 'hearts' are in close
connection with it in the anterior segments of its course, and the
reproductive and certain oesophageal glands are seen at its sides
in the middle and posterior. Tlie crop is considerabl}'^ distended
with dark coloured contents, and forms a larger mass than the
thicker coated lighter coloured gizzard which comes next behind it.
The dorsal pseud-haemal vessel is well seen along the median
dorsal line of the crop and intestine, where owing to the con-
traction of its muscular walls it has a moniliform appearance.

Anterior Segments of Earthworm.

125

Posteriorly to the gizzard the dorsal vessel is seen to give off two,
or sometimes three, vessels in each segment on each side, which
pass round the intestine, in close connection with its walls, and
indeed invested by the glandular hepatic tissue which forms here
the exterior layer of the coats of the tube, to join a sub-intestinal
vessel. This vessel is not so closely attached to the digestive tube
as is the dorsal vessel, but is loosely suspended between the nerve
cord and the intestine. It gives off branches to the segmental
organs, and is connected with a third set of longitudinal vessels
which are in close relation with the several aspects of the nerve
cord, one inferiorly and two laterally, and send branches outwards
with the nerves. In possessing this vascular supply to the seg-
mental organs, and this third set of longitudinal vessels, the
Lumbrici differ from other Oligochaetous worms. The commis-
sural vessels connecting the dorsal and the sub-intestinal are
reduced in number to a single pair in each segment, anteriorly to
the crop and posteriorly to the pharynx; but they are so much
enlarged in size as to have been called ' hearts,'' in about six
segments posteriorly to the pharynx. In the first six segments of
the body corresponding with the pharynx, both the dorsal vessel
and the commissural vessels are resolved into plexuses.

Anteriorly to the crop and in the line of the outer row of setae
are seen the large pendulous lobes which are the vesiculae seminales,
increasing in size from the ninth segment, where the first of the
three is attached, backwards. On the left side, the posterior
having been displaced a little backwards from the middle vesicula
seminalis, the corrugated funnel-shaped opening of the posterior
of the two branches of the left vas deferens is seen in the interval
between them. Immediately exteriorly to the line of attachment
of the vesiculae seminales are the so-called ^capsulo-genous' glands,
which appear to be due to the development in these segments of
the setiparous glands of the inner row of setae ; and more ex-
teriorly again, in the intervals between the ninth and tenth and
the tenth and eleventh segments, are seen the two globular recep-
tacula seminis in the line of the external series of locomotor setae.
On the walls of the oesophagus, in the segments corresponding
to the two posterior vesiculae seminales, may be seen the oeso-
phageal or ' calciferous' glands, structures said to attain a great
development in the Perichaetous worms. On the internal surface

126 Descriptions of Preparations.

of the body-walls are seen the remnants of the muscular dissepi-
ments which gave to the body and to the digestive tract their
annulate appearance. Near the line of the inner row of setae,
a little way exteriorly to which they ordinarily but not invariably
have their external outlet, are to be seen the ' segmental organs/
which are muciparous glands forming complexly convoluted coils,
attached by a sort of mesenteric membrane to the muscular dis-
sepimental walls of the segments in which the greater part of
their length is lodged, and prolonged through the anterior wall
of this segment into the segment next in front, to end by ex-
panded and ciliated infundibula near the middle line and the
ventral surface.

For a description and figure of the reproductive organs of the
Lumbricus Terrestris, see pi. viii. infra; and Heriug, Zeit-
schrift fiir Wiss. Zool. viii., 1857, p. 400. See also D'Ukedem,
Memoii'cs Couronnes Acad. Belg., 1856, torn, xxvii., p. 9
seq^q. ; Mem. Acad. Roy. Belg., torn, xxxv., 1865, pi. ii.,
figs. 2 and 3.

For the ' segmental organs/ see Gegenbaur, Zeitschrift fiir Wiss.
Zool. iv., 1853, p. 221. See also a note by Hering, I. c.
p. 40 T, and for the homologies of these organs with the
efferent ducts of the reproductive glands, see Claparede, R,e-
cherches Anatomiques sur les Annelides, Turbellaries, &c.,
1861, p. 28; and Lankester, Journal Micr. Soc, 1865, p. 7.

For the oesophageal glands, see Lankester, I. c, 1864, p. 265; and
D^Ukedem, Mem. Acad. Roy. Belg., torn, xxxv., pi. i. fig. 10,
p. 23.

For the Perichaetous Worms, see D^Ukedem, I. c, pp. 30, 31;
Schmarda, Neue Wirbellose Thiere, 1861, i. i, p. 13.

For the classification of the Annelids generally, see Grube, Die
Familien der Anneliden, 1851; Ehlers, Die Borstenwiirmer,
1 864- 1 868, vol. i., pp. 52—57 ; Clapaiede, Annals and Maga-
zine of Natural History, Ser. iii., vol. xx., 1867, p. 337.

Medicinal Leech.

127

39. Medicinal Leech (Ilirudo Medicinalis),

Showing the terminal suckers, the segmentation and annulation of the body, and
the distinctively coloured dorsal bands which difiFerentiate the variety Uirudo
medicinalis from the variety Ilirudo officinalis.

The number of annuli may be taken as about one hundred ; but
these aunuli appear to be due merely to secondary corrugation of
the primary segments of the body^ each of which comprises from
three to five of the secondary annuli. The primary segments are
not so readily distinguishable as the smaller rings ; but in a freshly
killed specimen^ two white spots on either side the median line
and in a line with the central pair of eyes are considered to mark
out the anterior boundary of each segment ; whilst the posterior
boundary is given by the openings of the two muciparous or seg-
mental organs on the ventral surface, from which jets of fluid can
be made to issue by pressure, especially on the posterior part of
the body. The black pigment specks which are seen in this
variety upon the outer and middle of the three tawny stripes
on either side of the dorsum seem, by attaining a great size and
prominence on every fifth annulus, to point in the same direction
as those more constant land-marks just specified, and to mark out
in each case a segment consisting of five annuli. Fewer annuli
are interposed between each pair of the dorsally placed white specks
at either extremity of the body, than in the intervening space
occupied by the middle regions of the body. Upon the anterior
sucker a pair may be found upon almost every one of four half-
circles of which it is made up, whilst the posterior sucker appears
at certain periods of its development to be made up of no less than
seven segments, to which seven ganglia subsequently fased to-
gether correspond, just as in the rest of the body each pair of
white specks on the dorsal surface corresponds to the nerve ganglia
on the ventral. This aggregation of segments at either end of
the body corresponds firstly to the externally visible concentra-
tion of the animal functions of special sense, prehension of food,
and locomotion in the region of either sucker ; and secondly to a
concentration of nerve ganglia and an abortion of the reproduc-
tive and depuratory or muciparous organs which are vegetatively

4

128

Descriptions of Preparations.

repeated in each of the intervening segments of the body's length.
The anterior sucker is perforated centrally by the mouth, and is
prolonged superiorly into an obtusely lanceolate lip consisting of
four rings. It is not separated by any constriction from the rings
immediately succeeding it, whilst the posterior sucker is very
markedly so separated, has the anus opening in the line of this
constriction, and differs consequently still farther from the anterior
sucker in being imperforate and having an evenly circular un-
interrupted rim. Ten eyes are carried in pairs upon the three first
rings of the upper lip-like portion of the anterior suckers, and also
upon the fifth and eighth segments, the ten eyes as thus arranged
forming an ellipse.

The male generative orifice from which the penis is sometimes in
this species, and very ordinarily in the common Horse-leech,
Aulostoma g%lo, protruded when the animal has been killed with
chloroform, is visible in the interval between _th£.J\ve]^
and twenty-fifth segments ; and at an inteiwal of five segments
posteriorly, the female generative orifice is seen in the interval
between the twenty-ninth and the thii-tieth segments.

A series of raised granular but minute tubercles may be observed
crossing the dorsal line in many segments, and representing in
miniature the warty exterior of Pontobdella.

The external colouration of the Leech is very variable, and hence
the more or less strikingly regular development of black patches at
intervals of five rings in the rust-coloured line on the dorsal is of
the greater morphological importance. The amount of pigment
specks on the ventral surface is especially variable, and there does
not appear to be any regularity as to their distribution when
present.

For an excellent monograph of Ilirudo Medicinalisy see Brandt and
Katzeburg, Medizinische Zoologie, 1833, Bd. ii., pp. 230-297,
Taf. xxviii., xxix. A, xxix. B, xxx. See also Moquin Tandon,
Monographic de la Faraille des Hirudinees, 1 846 ; Lcuckart,
Die Menschlichen Parasitcn, 1863, pp. 634-739 ; Claus, Grund-
ziige der Zoologie, pp. 154-161; Gratiolet, Ann. Sci. Nat.,
Ser. iv., tom. xvii., 1862, pp. 177-182, for the general out-
lines of the body.

For certain organs of which as many as sixty may be found upon

Medicinal Leech.

129

the cephalic, and some upon other segments of the body,
and which, as resembling the ' becher-formige Organe"" of fish,
may be supposed to be sensory in function, and concerned
possibly with the perception of chemical rather than of other
stimuli, see Leydig, Archiv. fiir Anatomic und Physiologic,
1861, p. 599 j Tafeln zur Vergleich, Anatomic, iii. 1 ; F. E.
Schultze, Zeitschrift Wiss. Zool. xii., 1863, p. 232.

40. Medicinal Leech {Hirudo Medicinalis),

Prepared and dissected so as to show its laterally sacculated stomach and its in-
testine, in their natural relations to the ventral chain of ganglia inferiorly, and
the pharynx anteriorly,

A STIITENING injection having been thrown into the digestive
tube, the specimen was hardened in spirit. After this, the in-
tegument having been divided down the middle dorsal line and
reflected outwards, the portions of the j)seud-haemal system which
were interposed between the digestive tract and the dorsal surface
were removed, and the entire cavity of the ' stomach'' and of its
diverticula exposed by the removal of its upper wall. Anteriorly
to the stomach is seen the pharynx with a villous exterior, much
resembling that in the earthworm'' as seen by the naked eye, as
also when its constituent elements, unicellular gland cells and
involuntary muscular fibre, are examined under the microscope.
Partly concealed by this villous exterior of the commencement of
the digestive tract, may be seen the prae-oral ganglionic mass.
The walls of the portion of the digestive tube which comes next
after the pharynx, are much thinner than those of the pharynx
itself, and consist mainly of a structureless basement membrane and
an internal layer of pavement epithelium ; its muscular coat being
almost wholly aborted, as in the Ophidia (see p. 30), and its func-
tions discharged by the muscular layer of the body-walls. This
portion of the digestive tube has a much larger calibre than the
pharynx, and has lateral diverticula appended to it on either side,
which occupy five-sixths of the entire cavity of the body. These

See Plate viii. b.
K

130

Descriptions of Preparations.

lateral diverticula are eleven in number, the two anterior being
smaller than the nine succeeding' ones^ and differing from them
also in not having their outer angles prolonged backwards. The
last pair of diverticula are twice the length of any other pair, and
bending sharply back almost immediately at their commencement,
so as to become apposed to each other along the middle line, are
prolonged backwards up to a point on a level with the commence-
ment of the rectum, and nearly up to the termination of the body.
The digestive tube is of very small calibre posteriorly to the point
of origin of the two last diverticula, and lies in the interval
between them superiorly. The diverticulate portion of the di-
gestive tract is called a ' stomach by most writers, but it is
considered to be homologous and analogous with a crop or dilated
oesophagus by Gratiolet, on account of its resemblance to the crop
of the Horse-leech {Aulostoma gulo), and on account of its functions,
which appear to be merely the squeezing out the watery part of
the blood which the animal swallows, and allowing it to be dis-
charged by the segmental organs. Dissepiments run transversely
across the body, and interpose themselves between the apposed
walls of the several diverticula. The central emargination in each
of the septa thus formed, corresponds to what was the antero-
posterior part of the digestive tube in the region of the diverticula ;
the method of preparation has given the shape of an ellipse to
what was, in the natural state of the parts, a circular foramen in a
diaphragm. A rudimentary dissepiment passes off from the pos-
terior aspect of each of the eight larger dissepiments, inwards and
backwards, within the cavity of each diverticulum towards the
middle line ; J)ut it is not prolonged quite up to the line of the
chain of nerve-ganglia. An accessory compartment is thus added
on to each of the diverticula from the third to the tenth inclu-
sively; whilst the eleventh pair has five pairs of accessory im-
perfect dissepiments, iutrodigitating along their interior. The
ganglia of the ventral chain are seen towards the posterior part of
each compartment, constituted by the median portion of the di-
gestive and its lateral appendages ; and in some cases they are m
immediate relation with the anterior face of the dissepimental wall.
A black bristle has been introduced into the segments of the di-
gestive tract, posteriorly to the point where the last diverticula
are given off. The ' oesophageal' portion of the tract projects and

Medicinal Leech.

131

opens as a nipple-shaped process^ into the bilobed commencement
of what Gratiolet calls the ' gastroileaF intestine^ the mucous
membrane of which is prolonged into spirally-arranged valvular
folds. This ' gastroileaP intestine ends in an ovoidal colon; and
this again in a short rectum of very small calibre^ which terminates
in a dorsally-placed anus, as in all Hirudineae except Acanthob-
della.

For description of digestive tract, see Gratiolet, Ann. Sci. Nat.

Ser. iv., vol. xvii., pp. 182, 188, 197 ; Brandt, Medizin.

Zoolog., Bd. ii., p. 246.
For figures of the digestive tract of the Horse-leech, see Moquin

Tandon, Monographic des Hirudinees; Atlas, pi. v. fig. u ;

Gervais and Van Beneden, Zoologie Medicale, 1859, p. 186.

41. Medicinal Leech (Hirudo Medicinalis),

Dissected so as to show its nervous system.

A PAET of the pharynx and the jaws are still left in situ, and
a black bristle has been passed through the remaining part of the
pharynx, where it is embraced by the nerve collar. There are in
the Leech twenty-two ventral ganglia, the most anteriorly placed
one of which is connected by commissures with the supra-oeso-
phageal mass. This mass is seen above the pharynx, part of the
glandular and muscular walls of which have been removed to show
it, in situ, and immediately posteriorly to the middle one of the
three jaws. In the narrow interspace between these two structures
is seen a minute mesial stomato-gastric ganglion, which is con-
nected with the supra-oesophageal ganglia, and sends nerves to
the semilunar saw-like jaw and its muscles ; and a similar gang-
lion similarly connected with the supra-oesophageal mass, may be
seen on either side, sending nerves similarly to either of the two
lateral jaws. Each lobe of the supra-oesophageal mass gives off
three other nerves, whence the five eyes of either side and certain
other, probably sensory, organs, the ^ becher-formige Organe' of
Leydig, are supplied. The first sub-oesophageal ganglion is much

K 2

132

Descriptions of Preparations.

larger than any which come after it; it gives off five pairs of
nerves, and is connected by very short commissural cords to the
supra-oesophageal ganglia anteriorly, as also to the second ventral
ganglion posteriorly. The commissures between the second and
third, and the third and fourth ventral ganglia increase in length,
though they are shorter than those connecting the ganglia be-
longing to the middle region of the body j the ganglia at the
posterior extremity of the animal are again closely aggregated
together. The last ganglion of the ventral chain is much larger
than any of the series except the first, and gives off from seven
to nine branches to the posterior sucker ; the other ganglia give
off each two trunks, which distribute themselves to the muscles of
the body, with the exception of the penultimate ganglion, which
gives off only a single nerve on either side. The paired nerves
are given off very close to each other, and the one which ramifies
nearer to or in connection with the anterior wall of each disse-
piment, and takes a dorsal rather than a ventral direction, arises
above rather than behind the other. This latter nerve has, just
at the point of its bifurcation, a small ganglionic mass developed
upon it, which may represent the accessory ganglia seen upon the
pedal nerves in Nereis, and called ' ganglions de renforcement ' by
De Quatrefages. With a microscope, a small detached ganglion,
probably homologous with the lateral ganglia of the system of the
nervi transversi in insects, may be seen apposed to but not inclosed
within the capsule of each ventral ganglion, in the interval between
the points of origin of these paired nerves. A second element
homologous to a portion of the Arthropodous system of nervi
transversi is presented to us in the Leech by an 'intermediary'
nerve, which runs in the interval between the two fibrous strands
connecting the several pairs of ganglia, but which does not give
off any branches. The bilateral character of the chain of nerve
ganglia is as plainly seen in the Leech as in the worm but there
are no nerves given off from the inter-ganglionic commissural cords
in the Hirudineae. A third nerve of the sympathetic class exists
in the Leech, in the form of an azygos nerve trunk, with ganglion
cells appended to it throughout its course, which corresponds to
the ventral aspect of the digestive tract, and has two lateral arms
prolonged in relation with the two posterior lateral coeca of the
'stomach' or 'oesophagus.' The removal of the digestive tract

Medicinal Leech.

133

prevents us from seeing this structure in this Preparation. It is
figured, however, by Brandt, its discoverer. Tab. xxix. B, 7 d. e.,
where it is seen not to be distinctly prolonged upwards into con-
nection with the stomato-gastric or supra-oesophageal ganglia.
Its relation would appear to correspond to the nermis recurrens
of Ai-thropoda, but that it is in relation with the ventral rather
than with the dorsal aspect of the digestive tube.

For the ' intermediary nerve,'' see the memoir of Faivre, its dis-
coverer, in the Ann. Sci. Nat. Ser. iv., torn, vi., p. 129. In this
author^s previous memoir, published in the volume of the
Annales des Sciences Naturelles, immediately preceding the
one just referred to, will be found, at p. 361, an account
of the various chemical reagents which may be employed in
the microscopic investigation of the nervous system of An-
nelids. For methods of preparation of entire specimens for
the dissection under a lens, without which much of what
is here described cannot be made out by the student for
himself, see Leydig, Vergleich. Anatomie, pp. 164, 165; and
Gratiolet, Ann. Sci. Nat. iv. 17, pp. 177, 178, 181.

For the lateral ganglia in apposition with the ventral ganglia, see
Leydig, Vergl. Anat., Taf. ii., fig. 3 e.

For the lateral ganglia developed upon the inferior pair of nerves,
see Leydig I. c, p. 146 ; Quatrefages, Histoire Naturelle des
Annales, tom. i., p. 81, pi. iii., fig. i, i. k., Nereis regia.

42. Medicinal Leech {Hirudo Medicinalis),

Dissected so as to show its reproductive and segmental organs in situ, the digestive
and pseud-haemal systems having been in great part removed, and the integuments
fastened out on either side.

At about the point of junction of the first with the second sixth
of the body^s length, is seen a globular body partly overhanging
and partly projecting to the left of the nerve cord, communicating
mesially with a siphon-shaped muscular tube, and receiving on
either side two tubes of smaller calibre but similar structure. The
globular organ is constituted partly l)y muscular and partly by

134 Descriptions of Prepayations.

glandular tissue^ and is called consequently the prostatic part of
the male intromittent apparatus; the mesial siphon-shaped tube
representing- a penis, and the lateral ducts being ductus ejaculaiorii.
Tracing the vas deferens of the right side outwards, we see that it
passes under the nerve cord, to join a convoluted epididymis -like
mass of a yellowish colour, which from its contents appears to be
analogous to a vesicula seminalis. A slightly tortuous duct enters
the organ from behind forwards, after receiving on its inner side
the short transverse ducts passing to it from each of the nine
globular testes which are seen close to the nerve cord, arranged
one in each of nine segments, beginning with the one next but
one in order to that in which the convoluted vesicula seminalis
is lodged. The female generative apparatus is lodged in the seg-
ment interposed between that which contains the first testis and
that which contains the vesicula seminalis; and four secondaiy
aunuli are seen to be interposed externally between those in which
the outlets of the two sets of generative organs are pierced. The
vagina has the form of an oval sac with thick muscular walls.
From its apex a single tortuous oviduct arises which has its coils
enveloped in loose tissue, the microscopic elements of which furnish
us with large and beautiful specimens of unicellular glands dis-
charging their secretion by isolated ducts. The oviduct divides
into branches, one of which is seen passing under the nerve cord,
on the apices of which the ovaries are carried. Externally to the
line of the vasa deferentia and alternating in position with the
testes, we see a row of globular sacs only a very little less in size
than these organs. These sacs communicate with the exterior
by the orifices already spoken of, Prep. 39, p. 127, as marking
the posterior limit of each of the primary segments of the body.
Exteriorly to each of these sacs we see a loop-shaped gland, the
outer convex end of which is directed upwards, and in the natui'al
condition of the parts almost vertically so, whilst internally it is
connected with the globular sac by a short duct passing from the
anterior limb of the loop backwards; and in the region of the
testes has a coecal process prolonged on to each of those organs.
The connection which subsists in the Lumbricidae between the
open mouth of a modified segmental organ and the reproductive
glands, may be regarded as represented in the Leech by the ar-
rangement just described. There are eight of these segmental

Medicinal Leech.

135

organs arranged opposite the interspaces of the testes, and two in
the two anterior genital segments. Four more are to be seen in
the segments anterior to those last named^ and the three first of
these are in closer proximity than the rest of the series. There
are three segmental organs in the segments posterior to that
containing the last testis ; and they possess a coecal process pro-
longed inwards beyond the line of the globular sac, by which their
excretion is discharged on the exterior of the body. The coecal
process of the most anterior of the three, comes into apposition
with the posterior testis, but its homologue is not developed in
the six anterior segmental organs. The segmental organs are
much larger in the Medicinal Leech than in tlie Horse-leech ; and
Gratiolet connects the greater power which the former animals
have of living out of the water with the greater power of moist-
ening the skin thus attained. Hirudineae, such as Branchellion,
which possess only two pairs of segmental organs, and Nephelis
and Clepsine, in which these organs attain but a small develop-
ment, appear never to leave the water, as the other genera do,
spontaneously; and in them, it should be added, the segmental
organs open, which they do not in either of the Leeches men-
tioned, by ciliated infundibula into the general cavity of the body.
The various portions of the loop-shaped constituent of the seg-
mental organs of the Leech, communicate with each other very
freely by lateral branches of anastomosis, which make the gland
to be labyrinthiform rather than merely tubular. It is of im-
portance both to the morphology and- to the physiology of these
animals, to observe that the failure of the organs of vegetative
life here described to be developed at either end of the body,
coincides with an aggregation both of segments and of animal
organs in the same two regions. The azygos character of the
generative ducts is noteworthy, as is also the development of an
intromittent organ ; a structure not found in other Annelids,
though existing both in Platyelminthes and Nematelminthes.

For the segmental organs, see Gratiolet, Ann. Sci. Nat. iv. 17,
p. 19a, pi. vii., fig. 4 ; Leuckart, Die Menschlichen Parasiten, i.,
p. 672.

For the reproductive organs, see Leuckart, I. c, p. 673; and for
the antagonism which subsists between the evolution of these

136

Descriptions of Preparations.

organs and that of those of animal life, ibid., p. 549, and
Art. ' Zeugnmg' in Wagner's Handworterbuch fiir Physiologie,
Bd. iv., pp. lig-i^SS-

43. Many-headed Bladder-worm
{Caenurus Cuniculi),

In its cystic stage, from the region of the masseter muscle of a rabbit

{Lepus Cuniculus).

This specimen illustrates the cystic stage in the metamorphoses
of the true Taeniadae. It belongs probably to the same species
as the one individuals from which are, when in the cystic stage,
lodged usually in the brain of the sheep, and are the cause of the
disease commonly knoAvn as the ''sturdy/ 'gid/ ''staggers/ or ''turn-
sick.-' The specimen consists of a white walled semi-transparent
sac ; and a large part of its walls having been removed, one end of
it is seen to be beset on its interior surface with a number of closely
apposed but distinct opaque white bud-like bodies, the area occupied
by which is prolonged out laterally into lobes indicating the conti-
nuing proliferation of the cyst. Two smaller cysts, one of which
is similarly bestudded internally, are attached by mere filaments
of tissue to the lower parts of the large cyst, to the proliferation
of which they may also be considered to be due. For, though it
is possible to suj)pose that these all but perfectly isolated out-
growths may have been produced by the pinching off from the
mother vesicle of small portions of its walls, the large cyst having
been necessarily subjected to much pressure from time to time
by the masseter muscle; cysts of this tapeworm showing a ten-
dency to form or forming similar accessory vesicles, have been
figured from parts such as the brain, or lungs and liver, where
no constriction could be effected by muscular pressure ; and the
analogy of certain of the forms of the proliferating cysts of the
Taenia Echinococcus would ajipcar to indicate that the formation
of such jiedunculate outgrowths is one of the normal modes of
self-multiplication in the C3'stic stage of the Taenioid metamor-
phoses. The white gemmules represent the ' heads,' or ' nurses'

Many-headed Bladder-worm.

137

of the cestode many-jointed tape-worms which this cyst might
have given rise to if it had found its way into the intestines
of a dog- ; and it is therefore as truly a social animal, or rather,
a colony of animals in this its cystic, as it is in its cestode
form. Each of these heads is called by helmintholog'ical writers
a 'scolexj' and the sac upon which they have developed them-
selves, and upon which the remnants of the six hooks of the
embryo might be detected, is the result of the growth of such
microscopic embryo, or ' proscolex,^ as the one figured pi. xii. fig. 6,
when by the aid of its hooks it has bored its way from the intes-
tinal canal into the blood-vessels of its 'host.' The 'scolices'
possess two sets of organs for adhesion upon their proboscis ; viz.
four suckers placed proximally to the sac, and two rows of hooks
placed near their free apical extremity. The heads themselves, as
well as the parent vesicle, are endowed with considerable contractile
power; a layer of muscular tissue existing in their walls by the
action of which the heads with their armature can be retracted as
in this Preparation, or protruded. The cystic stage of the bladder-
worm is passed in the organism of some herbivorous animal, and
ordinarily in the brain of the sheep; and it has been shown by
actual and repeated experiments with dogs, that when the cystic
form of this Taenia is swallowed by them, its various heads will
develope in their intestines into cestode worms, attaching themselves
by their armed proboscides, and producing sexual hermaphroditic
segments, the so-called ' proglottides," in the interval between the
remnants of the embryonic vesicle and the asexual adherent head.
The entire colony is called a ' strobile.'' The asexual character of
its ' head" may remind us of the similar exclusion of the generative
organs from the anterior segments of Hirudo Lumbricus ; and the
successive repetition of the testes in nine segments, as described in
the former of those animals, bears a distant resemblance to the
successive antero-posterior development of sexual deuterozoids, as
presented to us in the 'proglottides' of the 'strobile' in a Taenia.
A process, however, all but identical with the budding off of sexual
zooids by an asexual 'head' or 'nurse' as seen in the cestoid
stage of the parasitic Taenia, takes place in Autolijtv,s (Grube),
Nereis prolifera (O. F. Miiller), Mynanida (M. Edwards), which
are Vermes of the most highly organized order of the Polychaeta ;
and the resemblance pointed out in the preceding sentence, as

138

Descriptions of Preparatiom.

existing between the Leech and the Tapeworm, must not be taken
as justifying- the views of writers who would class Hirudineae with
the Platyelminthes''.

= The class Platyelniinthes is here taken as comprehending three orders — the
Cestodes, Trematodes, and Turbellarians ; and it is with the Trematodes that the
Leeches have been supposed to be so closely allied as to justify the removal of them
from the class Annulata, which comprehends the Polychaeta, Gephyrei, and Oli-
gochaeta. The principal reasons for this dissociation are those furnished by the
absence of external appendiculate organs such as locomotor setae or gills, and the
presence of suckers in both Trematodes and Leeches ; by the sacculate character of
the digestive tract ; by the absence of a body cavity ; and by the structure of its
skin. In answer it is to be said that the absence or presence of such organs as
setae or giUs is not to be considered as of such consequence as the similarity or
dissimilarity of such systems as the reproductive or nei-vous ; and that even if only
external characters are to be compared together, the definite segjnentation of the
Hirudineae differentiates them veiy sharply from the Trematodes, which are not
even annulated. With reference to the similarity which the dendritic digestive tract
of certain Trematodes presents to the diverticulate tube of the Hirudineae, it must
be borne in mind that amongst the Polychaeta, forms with more complexly diver-
ticulate intestinal tubes, Aphroditea, are to be found than amongst the Leeches ;
whilst the presence of an anal sucker in other members of the same order, Leucodore
and Clymejie, furnishes a similar answer to the argument for classing the Hirudineae
with the Platyelniinthes which is based upon their common possession of these
organs of adhesion. Another answer is furnished by the fact that the construction
of the suckers is, as Leuckart has pointed out, by no means identical in the two
classes under comparison ; and that the possession of suckers is a point of physio-
logical rather than of morphological importance, is even more clearly shown by their
existence on the caudal extremity of the free, and the ventral surface of the para-
sitic Nematoids, which belong to a class very distinct from both Annelids and
Platyelminthes. Neither are the Hirudineae truly ' parenchj-matous' or ' sterel-
minthous' Vermes in the same sense as the Trematodes. For Leuckart has shown
that in all Hirudineae more or less of a perivisceral cavity remains, after the full
development of the large digestive tract, and of the ' dorso-ventral' muscles which
encroach so much upon it. In Branchiobdella there exists a large perivisceral
cavity, as well as a system of vessels, which appear to be homologous with the
so-caUed 'pseud-haemal' vessels of the common Leech and other Annelids, though
at the same time they are continuous with, and must be supposed to represent a
part of the perivisceral cavity. And by consequence, therefore, the pseud-haemal
vessels of other Hirudineae must be taken to represent the remnant of the peri-
visceral cavity, when such a space appears to have become obliterated. So that
the true way of expressing the facts would be to say, not that the Hirudineae re-
semble the Trematodes in not possessing a perivisceral cavity, but that they differ
from them in possessing a system of vessels which, as beijig continuous with a peri-
visceral cavity in Branchiobdella, may be regarded as actually being in the species
mentioned, and as representing in other species a part of a perivisceral ca^^ty. To
this interpretation the fact that in certain Polychaetous Annelids, Glyccra and
Phoronis Uippocrepia, the pseud-haemal vessels have been observed to contain true

Many -headed Bladder-worm.

139

For a further account, with figures of the metamorphoses, of the
Taeniadae, see Description of the semi-diagrammatic figures,
1-6/ in plate xii. infra. See also Gobbold's Entozoa, 1864,
pp. 104 seqq. et passim; Leuckart's Menschlichen Parasiten,
pp. i8i-a3o; and p. 251 for the formation of the proglottides
by the development of annular constrictions in the vermiform

corpusculated blood, appears to lend considerable probability. On the other hand,
the Hirudineae do to a certain extent resemble the Treniatodes, in possessing a
muscular system which is more complex, and more closely connected with the
glandular and epithelial elements of the integument, than is usually the case in other
Vermes. It may be suggested however that the changed relations of the contractile
and other elements of the integument in the Leeches, may be correlated with the
other changes which are ordinarily produced in subordination to the special habit of
parasitism ; and which, in this sub-kingdom, appear to entail the loss of the setae,
the gills, and the cilia. And the development of an additional transversely crossing
set of muscles in addition to the external circularly arranged and the internally
longitudinally arranged muscles of other Vermes, seems similarly referrible to com-
munity of habits, and not to any morphological affinity subsisting between the
Trematodes and Leeches. For a similar layer of muscles has been observed by
Dr. Charlton Bastian to exist in the Nematoids (see Phil. Trans., 1866, p. 564) ;
and as in all three orders alike, the special need for some such arrangements, for
propelling and otherwise acting upon the contents of a digestive tube, altogether
or nearly devoid of muscular fibres, may be considered to account for its presence,
it cannot be held to furnish a good basis for classification.

On the whole, the Hirudineae appear to be rather Annelida degraded by the special
habit of parasitism, than to be intermediate forms in a series which should represent
the various stages in progression upwards from the lower Platyelminthous Vermes
to the highly organized Annelids. The characters which appear to approximate
them to the Platyelminthes, relate mainly to such external points as the shape of the
body, and the modifications of the tegumentary system ; and whilst these characters
are probably to be regarded as explicable by reference to a community of habit, and
therefore as devoid of classificatory value, those which connect the Hirudineae with
the Annelids possess a real morphological importance. Among these we may
mention the segmentation of the body not merely in the way of external annulation,
but in that of internal division into more or less completely separated compartments
by the development of dissepiments ; the possession of a chain of nerve ganglia, and
in most cases of a similarly multiple series of segmental organs ; and the presence of
the so-called 'pseud-haemal' system. And it should be further noted, that whilst in
all these points the organizations of the Hirudineae and the setigerous Annelids
resemble each other, and differ fi-om those of the Platyelminthes in the direction of
greater complexity and perfection, they still further resemble each other but in the
reverse direction, and as presenting lesser complexity and importance, when we come
to compare their reproductive systems, which never possess either the high degree of
morphological differentiation, or the actual bulk relatively to the rest of the body,
which distinguishes the generative organs of the Platyelminthes. See pi. viii., ix.,
and pi. xii., figs. 2 and 4 with descriptions, infra.

140

Descriptions of Preparations.

appendage of the -liead, and the constant intercalation of new
seg-ments formed in the same way between the head and the
earlier formed segments. See also Van Benedenj Memoire
sur les Vers Intestinaux, 1858, pp. 235-251; and for an
account of similar processes observed in the Polychaeta^ see
Huxley, Edinburgh New Phil. Journ., Jan. 1855; Ehlers,
Die Borstenwiirmer, Bd. i. 207 seqq., ibique citata ; and for
the Oligochaeta, see Lankester, Linn. Soc. Trans, xxvi.,
Quart. Journ. Microsc. Science, 1869.

For a special history of this Tapeworm, Caenurus Cerelralis s.
Cuniculi, see Van Beneden, I. c, pp. 146-148 ; Cobbold, I. c,
p. 116; Gamgee, Fifth Report of the Medical Officer of the
Privy Council, 1862, pp. 234-237; Thudichum, Seventh Re-
port of the Medical Officer of the Privy Council, i 865, p. 335;
Numan, Verhandelingen der eerste Klasse van het Koninklijk.
Nederlandsche Instituut, 1850, where many figures, micro-
scopic and other, are given of this animal.

For the classificatory relations of the Platyelminthes and the Hiru-
dineae, see Grube, Die Familien der Anneliden, 1851, pp. 3-8 ;
Schneider, Monographic der Nematoden, 1S66, p. 329; Leuc-
. kart, Die Menschlichen Parasiten, pp. 156, 157; Claparede,
Bibliotheque Universelle, tom. xxii. Bull. Sci., pp. ZA'^~2>SS^
1865; Ann. and Mag. Nat. Hist. Ser. iii. xvii., 1866, p. 100;
and M. de Quatrefages, p. 108; Claparede, vol. xx., 1867,
P- 337 5 ^3.n Beneden, Turbellaries, p. 48, i860.

For the structure of the integument in the Platj^elminthes, see
Leuckart, I. c, pp. 459, 645 ; Schneider, I. c, 333.

For their *■ parenchymatous'' or ' sterelminthous ^ character, see
Leuckart, L c, pp. 157, 666, 713; and for the presence in
the pseud-haemal vessels of true corpusculated blood, such as
is ordinarily found only in the perivisceral cavitj'', see Leuc-
kart, I. c, p. 670; and Dyster, Linn. Soc. Trans., xxii., p. 254,
1858.

Common Crossfish.

141

44. Common Crossfish [Asterias Ruhens),
Linn. (Dried.)

The animal consists of a central disk which is prolonged into five
lobes, the so-called ' arms' or ^rays/ One surface of the specimen
is hollowed out into a deep central cavity corresponding with the
mouth, and made pentagonal by the abutment upon its edge of
the rows of spines bounding the five ' avenues/ which radiate out
from it on the same surface, and, from lodging the locomotor feet,
have given this aspect of the animal the name of ' ambulacral.'
The other surface is more or less convex, and beset with spines ;
and in one of its interradial spaces it carries the concentrically
striated disk known as the "^madreporic tubercle.' The two surfaces
are nearly equally developed in Asteriae and Ophiurae. Along the
middle line of each radial avenue there runs a central furrow,
formed by and at the junction of the ^vertebral' ambulacral os-
sicles. In this central furrow were lodged first and most superiorly
the water- vascular canal supplying the ambulacral sucker-feet;
then some transverse adductor muscles; and thirdly and most
superficially, the gangliated nerve cord, the ' Ambulacral-gehirn '
of the German writers. Externally on either side to this central
furrow, the lateral processes of the ambulacral ossicles form, by the
apposition of their emarginated edges, two alternately placed series
of conjugate foramina, for the vessels bringing the sucker-like
exteriorly- placed portion of the feet into communication with in-
ternally placed ampullae as seen in Preparation 45. These am-
pullae are wanting in the Ophiurae, as also in the ambulacral
tentacles of certain Holothurioidea, for which see Preparation 47.
Each of the five radial avenues tapers up to its distal extremity
where the eye was lodged, and where in the fresh specimen the
suckers may be observed to attain a considerable relative length.
On each side of each avenue we see two sets of spines, one of
which is placed internally, and consists of two rows of long and
slender spines ; whilst the more externally placed one is made up
of three rows of stouter, shorter, and blunter spines. Towards the
apex of each ray the external set of spines attains a greater de-
velopment relatively to the internal ; and out of it is there evolved

142 Descriptions of Preparations.

the circlet of specialized spines, which protect the eye and the
contractile tactile organ in relation with it. A third set of spines
marks the line of junction of the vertical and dorsal surfaces in
each ray ; and the middle line of the anti-ambulacral surface has
more or less of a keeled appearance^ from the more or less regular
longitudinal arrangement there of the spines with which the dorsal
surface generally is beset. Remnants of the organs known as
pedicellariae/ which appear to be spines modified so as to be
mobile and prehensile, are to be seen in the interspaces between
the spines, and some, though of smaller size and not in especial
abundance, may be seen also round the bases of the spines. The
spines themselves are immobile in the Asteriae, and, though they
may carry a coronet of numerous calcified setae on their apices
when they are called paxillae,-' when modified into pedicellariae,''
they rarely carry more than two terminal processes, which make
up a pincer-like organ. In the Echinidae, on the other hand,
the spines are themselves mobile, and provided with a muscular
apparatus j and the ' pedicellariae,^ which are mainly distributed
about the oral region, are trivalved. Opposite one of the inter-radial
spaces is seen a whitish, circular, raised, concentrically striated
disk, the so-called ' madreporic tubercle.' In a fresh specimen
of any one of the Asteriae which is provided with sucker-like and
not with conical feet, the anus may be found near the centre
of the dorsal surface a little to the left of a line drawn from this
madreporic tubercle, down the longitudinal axis of the ray, oppo-
site to the inter-radial space in which it is lodged. The same
line will enable us to divide the five rays into a ' bivium,' between
which the madreporic tubercle lies, and a 'trivium,' the two
lateral arms of which lie on either side of the arm which is opposite
to that tubercle. But we cannot speak properly of an anterior
or posterior radius or inter-radius in these Echinodermata, inas-
much as, like Echinidae and Ophiuridae, they move in locomotion
indifferently in the direction of any one radius or inter-radius. The
radius which lies to the right in the madreporic bivium in this
specimen, when the central ray of the trivium is placed so as to
point away from the observer, is much shorter than any one of the
other four; having been reproduced after some injur}'-, l)ut not
liaving attained the size of its fellows. The power of reproduction
of injured parts is very great in these animals, having indeed

Common Crossfish.

143

scarcely any limit short of the retention of the stomach, and of at
least one coecal appendage uninjured. As the Echinodermata, on
the one hand, all go through more or less complex metamorphoses,
and, on the other, never when adult multiply by gemmation, it is
obvious that the power of repairing injuries cannot be, as it has
been held to be, correlated either with the absence of metamor-
phosis, or with the power of reproduction by metagenesis strictly
so called.

For the account of the structure of the Echinodermata generally,
see Johannes Miiller, Abhandlungen Kon. Akad. Wiss., Berlin,
for 1853, translated in part by Professor Huxley in the Annals
and Magazine of Natural History for 1854, Ser. ii., vol. xiii.;
Professor Sharpey, Article ' Echinodermata/ in Todd's Cyclo-
paedia of Anatomy and Physiology.

Eor a monograph of the Asteroidea, see Miiller und Troschel,
System der Asteriden, 1 842.

For an excellent account of the nerve system of the sensory organs,
and of the power of reproduction of lost parts in the common
Cross-fish {Asterias richens), as also of that of the Solaster
papposa, and Crihella oculata, see Wilson, Linn. Soc, Trans.,
J 860, vol. xxiii., pt. i., p. 107.

For an analysis of the tegumentary skeleton, see Gaudry, Ann.
Sci. Nat. Ser. iii., tom. xvi., 1851.

For reviews of Miiller's researches into the anatomy and develop-
ment of the Echinodermata, see Huxley, Ann. and Mag. Nat.
Hist., Ser. ii., vol. viii., 1851; Baur, Nova Acta, 1864,

PP- I7> 57-

45. Common Crossfish {Asterias Ruhens),

Linn.

Dissected so as to show its digestive and motor systems.

One of the rays, the central one of the trivium, has been cut
short, and more or less of the anti-ambulacral integument removed
from each of the other four, and from the central disk. In the
inter-radial space which is opposite to the ray which is cut short.

144

Descri'ptions of Preparations.

is seen the madreporic tubercle ; and a little to the left of a line
producing- the long- axis of that ray to the centre of the madreporic
tubercle^ and near the centre of the disk, is seen the small piece of
the apical integ-ument in which the anus opens. From the intes-
tiniform portion of the digestive tract immediately following upon
the anuSj two diverticula arise, and efflorescing into two or three
coecal ampullae, reach a short way into each of the two inter-radial
spaces in the disk, which lie on the left of the madreporic or anal
inter-radius. In this species there are only these two inter-radial
coeca; the one nearest the madreporic inter- radius is the larger
of the two ; both have their internal surface plicated longitudinally,
and from this it may be seen that, like the ' respiratory trees' of
the Holothuriae, with which they are homologous, they are highly
extensible. In a starfish which has died with its stomach pouted
out, as it often is during life, these coeca may be observed to be
drawn down much farther than the much longer coeca, which are
prolonged into the interior of the rays from a lower level in the
digestive tract, but are attached to the anti-ambulacral surface by
a mesenteric membrane. These latter coeca are seen to take their
origin from a much wider portion of the digestive tract as single
trunks ; and very shortly after entering the rays they break up into
two trees, which, with their foliaceous glandular ampullae, fill up,
in this specimen in w^hich the generative glands are in a state of
quiescence, the greater part of the interior of the ca\dty of each
ray. At a lower level again than the plane whence the stems
of these arborescent coeca take origin, the saccular dilatations of
the stomach proper are seen bulging ifor a short distance into each
radial space to the vertebral ossicles in which they are braced by
ligaments. The Asteriae are the only Echinodermata in which
any radial arrangement attaches to the digestive system beyond
that of the calcareous apparatus set around the mouth in all of
them, and subservient to the prehension or manducation of food
in most except the Crinoidea. In the interior of each ray, and
between the ramifications of the digestive coeca, which are here
and there slightly divaricated to show them, are to be seen the
bilaterally symmetrical biserial rows of ambulacral ampullae on
either side of the central stem, resembling that formed by the
bodies of a true vertebral column, and made up by the apposition of
the mesially articulated ossicles called ' vertebral' from this resem-

Angular Sea-Cucumber.

145

blance. The feet with which these ampullae communicate are seen
to be provided with sucker-like ends, thoug-h not with calcareous
terminal supports, as in the Echinoidea and Holothurioidea, In
the three genera of Asteriae, Astropecten, Ctenodiscus and Luidia,
the locomotor feet end by conical and not by sucker-like termina-
tions; and with this point of inferiority is correlated also the
absence of an anus. In the Ophim-idae, the digestive tract is a
simple coecal sac, bulging somewhat like the true stomach of the
Cross-fish radially, but not prolonged into the interior of the arms,
as in all the Asteriae including the three aproctous genera just
mentioned and Brisinga ; and with this increase of inferiority in
the digestive apparatus, an increase of inferiority in the locomotor is
found to correspond, as the feet are devoid not only of true suckers
but also of ampullae. It is in the Asteroidea alone that the nerve-
system lies externally to the ambulacral plates, which form thus an
'internal skeleton,'' absent in the Crinoidea, and existing in the
Echinoidea and, possibly, in the Holothurioidea also, only as ru-
diments. The nei"ve-cord is further protected in Ophiurae by a
row of dermal ventral scutes.

For a figure of the digestive tract, see pi. x. infra.
For figures of the locomotor feet in Ophiurae, see Sars, Norges
Echinodermer, 1861, tab. i., fig. 1-5.

46. Angular Sea-Cucumber (Cucumaria Pentactes),

Forbes,

Prepared so as to show the external characters of the class Holothurioidea ; and
the traces of a bilateral symmetiy, the co-existence of which with the more obvious
appearance of a radial arrangement is very well seen in these Echinodermata.

The five rows of ambulacral feet and the ten arborescent circum-
oral tentacles, which are merely modifications of ambulacral feet,
give the Sea-Cucumbers at first sight a very markedly radiate
appearance. But upon looking closely at these structures, both
will be seen to admit of being divided into two bilaterally symme-
trical halves, each of which is composed of heteronomous elements.
The five rows of ambulacral feet are seen to fall naturally into a
ventrally placed trivium, the feet in each of the rays of which
are more numerous, more perfectly developed, and more regularly

L

146

Descriptions of Preparations.

disposed than those of the two rays of the dorsally placed bivium ;
and of the ten tentacles the two which are placed immediately
opposite the central ray of the dorsal trivium, and one of which
is placed therefore on either side of the medio-ventral line, are veiy
much smaller than any of the other eighf^. The ventral trivium
gives the surface of the body which it occupies a somewhat flatter
surface than is possessed by the surface corresponding to the dorsal
bivium ; and this, together with the diminution in nvmiber and
importance of those two rows of ambulacra, appear to constitute
a transitional arrangement between the more perfectly pentagonal
appearance which nearly allied species may present, and the close
adumbration of the form of an ordinary Gasteropod which we note
in Psolus (Cuvieria), where the dorsal bivium is wholly aborted.
The ten tentacles are seen to be carried upon the outer rim of a
cylindriform prolongation of the body-walls, which is transparent
and carries no ambulacral feet. The anti-ambulacral surface is
reduced in Holothurioidea as it is in Echinoidea to the small region
immediately surrounding the anus ; in Cucumaria communis, indeed,
the ambulacra almost abut upon that orifice ; and it may be here

d Systematic zoologists differ as to whether the smaller size of the pair of ambu-
lacral tentacles, which are placed opposite the central ray of the ventral bivium,
is of generic, of specific, or even of less classificatory importance. Troschel, in the
Archiv. fiir Naturgeschichte for 1846, speaks of this difference as being of generic
value, and as separating Cladodactyla (Cucumaria) doliolum, Brandt ; Cladodadyla
Dicquemarii, Cuvier and Brandt, and Cladodactyla Syracusana from the species
here described. Forbes, however, in his 'History of British Star-fishes,' 184 1, saya
of Cucumaria pentactes, ' It is extremely variable in colour ; generally of a deep
purple, sometimes altogether white, sometimes purplish white. The tentacula and
head of both varieties vary equally, either purple or white. It varies also in the
pinnation of the tentacula, and in their relative size and number. The Holothuria
Montagui of Dr. Fleming, founded on a white variety described by ]SIontagu,
has eight full-sized tentacula and two small ones, which are alternately in motion
covering the mouth. The tentacula of this form are not so pinnate as in the
common or purple state.' It has been said that the ' Cuvierian organs,' certain
structures of various fonns and doubtful function attached to the stem of the
respiratory trees or inserted upon the cloaca, are wanting in all Cucumariae with
unequal tentacles ; but the readiness with which these organs are ejected by the
Holothurians, when they are alarmed or irritated, is such as to make it unsafe to
base a conclusion as to a specific difference upon their absence or presence. Semper,
on the other hand, Reisen im Archipel der Philippiuen, p. 47, assigns this smaller
size of the two medio-ventral tentacles as a generic property to the Cucumariae ;
but he also specifies the presence of this peculiarity in individual cases of particular
species as though it were not universally present.

A^igular Sea-Cucumber.

147

remarked that the two classes just mentioned, though they may
at first sight, owing to the great differences of their external tegu-
mentary organs appear to be entirely unlike each other, are in
reaHty more closely allied by structural, if not by developmental
history, than any other two classes in this sub-kingdom. The
Holothm-ians with rows of ambulacral feet are divided into two
families, according to the shape of their ambulacral tentacles ;
those in which the tentacles are, as in the Cucumariae, dendritic
in appearance, and carried upon a cylindriform stem of different
texture from that of the rest of the body, being called ' Dendro-
chirotae •/ and those in which the tentacles are shield-, or rather
shovel-shaped, and in which the integument is continued without
any alteration in its texture up to the tentacles, being called 'Aspi-
dochirotae/ With these external differences a considerable number
of points of difference in their internal structures are correlated,
for which see description of next Preparation. In all Holo-
thurians, but especially in the otherwise apodal Synaptidae, the
ambulacral tentacles are used as locomotor organs ; and in the
Aspidochirotae they are also used for bringing the sand, in which
these animals very ordinarily live partly immersed, into their
digestive tract. The intestinal tract, on the other hand, of the
Dendrochirotae, in which the tentacles could not be used for this
purpose, is ordinarily found to contain no sand or stones.

For an excellent account of the anatomy of the entire class Holo-
thurioidea, see C. Semper^s beautifully illustrated Monograph,
Reisen im Archipel der Philippinen, Theil ii. ; Wissenschaft-
liche Resultate, Bd. i., Hft. i. 1867, pp. 1-6, Hft. iv. 1868,
pp. 101-778; Emil Selenka, Zeitschrift fiir Wissenschaftliche
Zoologie, Bd. xvii., Hft. 2, 1867.

For the anatomy and development of the Synaptidae, see a me-
moir by Dr. Albert Baur, Nova Acta, vol. xxxi., 1864; where,
at p. 50-60, Ab. ii., some valuable remarks will be found upon
the ' so-called alternations of generations in the Echinoderms
and at p. 17, Ab. i., certain less convincing views as to the
homologies of the calcareous ring in the Holothurioidea with
the auriculae of Echinoidea.

^ For a note as to the existence of an Echinus with a soft integument, see Semper,
I. c, p. 163, citing Grube.

L 2

148

Descriptions of Preimrations.

47. Angular Sea-Cucxjmber {Cucumaria Pentactes),

Forbes,

Dissected so as to show its motor, digestive, respiratory, and reproductive systems.

The integument has been divided down the middle line of the
inter-radial space of the dorsal bivium, and fastened out on either
side. Five double longitudinal muscular bands are seen to divide
the bodj-walls into a corresponding- number of antero-posteriorly
running zones, upon which the external circular muscular coat
is very well seen. In the interval between the two factors of
each double band is lodged the longitudinal water- vascular ambu-
lacral vessel in all the pneumonophorous Holothurioidea, whether
they possess ambulacral feet, or, as the Molpadidae, are devoid of
them ; and, as in all Holothurioidea without exception, the longi-
tudinal nerve-cord is to be found lying in the longitudinal plane
corresponding to the interval between the two muscular bands im-
mediately beneath the cutis ; and, as in the families which possess
longitudinal ambulacral vessels, between the cutis and those vessels.
The longitudinal muscles are prolonged from the region of the
mouth, where they are inserted into the integument near its
junction with the commencement of the digestive tract, down to
the anus ; and in the Dendrochirotae, to which family the Cucu-
mariae belong, each longitudinal muscle gives off a long slip,
which passes to insert itself into the corresponding radial ossicle
of the calcareous ring. In this specimen the slip given off is much
thicker than the radial muscle itself; indeed, the slightness of the
radial muscles, as well as the possession of these slips, is one of the
many points in which the Dendrochirotae differ from the Aspi-
dochirotae. On either side of the radial muscles the ampullae,
which in Dendrochirotae are not usually present in their tentacular
ambulacra, arc seen arranged alternately. The radial water-vessels
with which these ampullae and the sucker-like feet are in con-
nection, pass forward to join the circumoral water-riug, through
an emargination in the anterior end of each of the radial ossicles
in the calcareous ring; and as the radial nerve-cords hold the
same relation to these ossicles, they have been viewed as homo-

Angular Sea-Cucumber.

149

logons, not, as they really are, with the masticatory apparatus, the
so-called ' Aristotle's Lantern,' of the Echinoidea, but with the
* auriculae' of these Echinodermata, and with the proximal pair
of 'vertebral ossicles' (see p. 144, S74,pra) of Star-fishes. The
water- vascular ring surrounds the muscular pharynx a little
way posteriorly to the calcareous ring ; two long air-bladder-like
Polian vesicles are seen hanging down from it, and ending freely
in the body cavity on the left side ; whilst the madreporic plate
and the pedicle upon which it is placed are seen to join it in the
medio-dorsal line. The internal position of the madreporic tubercle,
characteristic of the Holothurioidea., renders it necessary that the
water in the locomotor water- vascular system should be obtained
from the fluid in the perivisceral cavity, from which the pores of
the madreporic disk are, however, said to be separated by a layer
of epithelium, continuous with that lining the perivisceral cavity ;
so that the fluid they receive enters them not directly but by
difi'usion through and by the intermediation of these cells. In
immediate relation with the water-vascular ring is seen an annular
plexus of pseud-haemal vessels, which represents the circular pseud-
haemal sinus of the other Echinodermata. Erom it two principal
vessels pass backwards ; one along the dorsal, the other along the
ventral line of the digestive tract, in the substance of the walls
of which they are connected with each other by plexuses. Of
these two vessels, the ventrally-placed one is always comparatively
simple and devoid of any ramifications of importance, though the
segment of it in connection with the first descending convolution
of the intestine communicates with that in connection with the
first ascending, by one or more transverse commissural vessels;
whilst the dorsal vessel may have a considerable rete mirabile
developed in connection with it, which in Aspidochirotae comes
into relation with the left ' respiratory tree' arising from the cloaca.
This rete mirabile may be seen in this specimen in connection with
the dorsal vessel in the first segment of the intestine ; it must not,
however, be confounded with the reticular muscular mesentery,
the very abundant fenestration of which gives it the appearance
of a plexus of blood-vessels. The muscular pharynx is succeeded
by a muscular stomach, which is much smaller in calibre and a
little shorter in length than the portion of the pharynx which
intervenes between the commencement of the stomach and the

150

Descriptions of Preparations.

water-vascular ring anteriorly. The commencement of the intes-
tine proper is seen to be connected with the convex portion of the
second convolution of the tube by a considerable number of vessels
passing between the segments of the ventral vessel in connection
with each portion of the tract. The first convolution of the in-
testine has its concavity looking forwards, its convex aspect being
in relation with the posterior extremity of the animaFs body ; the
second convolution or the first ascending segment of intestine
reaches about as far forwards as the middle of the body, where
it turns backwards to end in the ^cloaca/ This term may be
applied to the terminal segment of the intestine, inasmuch as,
though it does not receive the duct of the generative organs, it
does receive those which lead from or into the so-called respiratory
trees, the functions of which, there is good reason to think, are as
much depuratory or renal as respiratory. These organs are seen
to take origin on either side of the cloaca as hollow stems carrying
somewhat scanty ramifications, and reaching a considerable but
varying distance forwards in various specimens into the cavity of
the body. They are both attached to the body-walls by mesen-
teries, which are, however, reduced by extreme fenestration to mere
series of filaments inserted along the left and right borders respect-
ively of the ventral trivium. In the Dendrochirotae there is not, as
in the Aspidochirotae, any connection between the respiratory tree
of the left side and the pseud-haemal plexus developed upon the
vessel in connection with the dorsal surface of the intestinal tube ;
and in this sense, though not in that in which the word has been
applied to them, the Dendrochirotae may be called ' Adetopneu-
mones.'' The arborescent form of the tentacles of the Dendro-
chirotae may, by exposing a greater surface to aeration than the
short shield-shaped tentacles of the Aspidochirotae, compensate for
this less perfect evolution of the internal aerating apparatus ; and
with the greater evolution of the tentacular apparatus and its
division into delicate twigs, we may connect again the evolution
of the special system of retractor muscles already noticed. Accord-
ingly as these respiratory trees are absent or present, the class
Holothurioidea is divided into the two orders of Apneumona and
Pneumonophora ; the Apneumona, Synaptidae, having, like such
of the Gephyraean Vermes, Sipunculidae, as are similarly devoid
of respiratory appendages to their cloacae, certain ciliated infundi-

Angula7' Sea-Cucumher.

151

buHform organs developed upon their mesenteric membranes, tlie
functions of vvhicli may be supposed to be identical with those of
tlie organs they replace. With the absence of lungs the pecu-
liarity of monoeciousness or hermaphrpditism is correlated in the
Holothurioidea. On the right side in this Preparation is seen the
generative gland, which consists of two bilaterally symmetrical
fascicles of coeca, attached on either side of a thickened portion of
the dorsal inter- radially placed mesentery. A single efferent duct,
under which a slip of blue paper is passed, passes along in this
mesentery to open inside the circle of oral tentacles, at the anterior
end of the dorsal inter-radial ossicle ; and it is seen just posteriorly
to it in the interval between the madreporic canal, which is "also in
relation with the dorsal mesentery, and one of the retractor muscles
which is passing to be attached to the radial ossicle on its right.

Tlie structural arrangements of the Dendrochirotae, as illustrated by
this Preparation, differ in the following particulars from those of the
Aspidochirotae, as illustrated in the Hunterian Catalogue, vol. i. pi. iii.,
vol. iv. pi. xlix. Their arborescent tentacles are carried upon a cylin-
driform prolongation of the body, which is differentiated from the part
which carries the five rows of arabulacral feet, and thus comes to be
not wholly unlike the proboscis of certain marine Annelids ; special
retractor muscles are developed in correlation with this apparatus ; a
muscular stomach is more commonly found in them than in the Aspi-
dochirotae ; their respiratory trees are less developed in length and
complexity, and the pseud-haemal system does not come into relation
with them ; the ' Cuvierian organs,' certain structures developed upon
the stem of the respiratory trees or upon the cloaca, and of various
shapes, appear to be very commonly wanting in them, as are also the
ampullae of the ambulacral tentacles nearly invariably, though their
Polian vesicles are more prominently developed than those of the Aspi-
dochirotae. In the peripheral part of the water -vascular system, the
Dendrochirotae differ from the Aspidochirotae, in never having suckers
or calcareous disks developed upon their tentacles : these structures
may be absent also in the feet of the ambulacral, and especially of the
dorsal ambulacral, rows, but they may be both present there.

The generative gland is bilaterally symmetrical in the Dendrochirotae,
consisting of two fascicles of short and non-bifid coeca, attached on either
side of a thickened portion of the inter-radially attached dorsal me-
sentery, and communicating with a single efferent duct of great length,

152

Descriptions of Preparations.

which opens inside of the crovm of tentacles ; whilst in the Aspido-
chirotae, the generative gland is made up of a single fascicle of long,
sometimes bifurcating, coeca, which are attached on the left side of the
dorsal mesentery, much nearer the oral end of the body, where they open
posteriorly and exteriorly to the crown of tentacles, in the dorsal inter-
radius opposite the medio-ventral line. The GvAivmxaria pervtactes here
described, differs from the common Sea-Cucumber {Gucwmaria commtmia)
in its smaller size, smoother inter-ambulacral areae, and in not having its
rows of ambulacra prolonged so closely up to the anus. Internally the
larger of the two species differs from the smaller in having a much
longer intestine, more numerous generative coeca, and longer respiratory
trees

' The two next Preparations are intended to illustrate some of the characteriBtics
of the Coelenterata as seen in the two chief classes of that sub-kingdom, the An-
thozoa s. Polypi, and the Hydrozoa ; and it may be well here to give some of the
reasons which have induced Naturalists to accept the separation of the Echino-
dermata, illustrated in the last four Preparations, from those animals with which,
until the publication of Leuckart's views in 1848, they were classed under the
common name of Radiata or Zoophytes. The resemblance connoted by the name
Kadiata has no more than a superficial basis in the organization of the Echino-
dermata. Not only are their radial divisions ordinarily pentamerous, whilst those
of the Coelenterata are ordinarily four or six or some multiple of these even
numbers, but they always in developmental, and usually in adult life show marks of
bilateral symmetry. The plant-like character of fixation to one spot which the
name Zoophyta may be taken to refer to, attaches to a very large number of
Coelenterata, but to only two genera of existing Echinodermata throughout life,
and to a third temporarily. The deposit of calcareous spicula in greater or less
abundance within the perisoma, and the absence of any but histological sexual
difierences, are points common to the majority of Coelenterata and to all Echinoder-
mata, and both sub-kingdoms are exclusively aquatic and all but exclusively marine
in habit ; but these points are probably the only points of real resemblance between
the two subjects of comparison. The integumentary system of the Echinodermata never
shows any traces of the possession of the 'nettle-cells,' all but universally found in
Coelenterata, as also in certain Turbellarians and Nudibranchiate Mollusks, and not
always absent in the higher Vermes, with which the Echinodermata are probably
more closely connected than is usually supposed. They possess a large peri\4sceral
cavity, in which not only an intestinal tract, but two other well-defined tubular sys-
tems, the paeud-haemal and the water-vascular, are always, and a generative system
with well-differentiated outwardly opening ducts, is almost always, contained ;
whereas in the Coelenterata, as is shown in the next Preparation, the digestive
tract is directly continuous with the body-cavity, and the generative products are
set free from the generative glands directly by dehiscence, either into the perivisceral
cavity or at once into the external water. The Echinodermata are multiplied ex-
clusively by the intermediation of the congress of the two sexual elements ; and in
this absence of agamogenesis of all kinds, they contrast as strongly with the Ar-
thropoda and Vermes as they do with the Coelenterata ; the metamorphoses which

Angular Sea-Cucumber.

163

For the danger which, owing to the habits of the Holothurioidea
of ejecting their viscera when alarmed, may attend upon the
basing of specific or other differences npon the presence or
absence of the internal organs, see Forbes, History of British

they do go through differing essentially from the phenomena known as 'alternation
of generations/ in that a part, and usually a large part, of the larval organism, is
worked up into the composition of the sexually perfect individual, WhUe the
characters of the Coelenterata are such as to make them into a sub-kingdom with
more sharply circumscribed boundaries than those of any other, except the Verte-
brate sub-kingdom, it must be confessed that the characters of the Echinodermata,
as presented to us not only in their life-history but also in their structure, ap-
proximate them so closely and at so many points to the sub-kingdom Vermes, as to
throw some doubt upon the propriety of separating them, as has been done here,
and as is all but universally done by foreign Naturalists, from the Vermes, and
elevating them to the rank of a separate and co-ordinate sub-kingdom. For viewing
the Echinodermata as a sub-kingdom co-ordinate with the sub-kingdoms Arthropod*
or Vermes the following justification may be offered. No Echinoderm ever presents
any trace of transverse, as opposed to antero-posterior segmentation of its body,
unless the jointed character of the peduncle of the Crinoidea constitutes a real ex-
ception to this rule ; whilst the perhaps most nearly allied order (or class?) of Vermes,
the Gephyrei, do occasionally, Phascolosoma Cumanense, Keferstein (Zeitschrift fiir
Wiss. Zoologie, xvii. , 1867, p. 53), show rudiments of the same division of the body
into transverse compartments, which we have so well marked in the typical Annelids.
They never multiply except through gamogenesis ; gemmation, to the existence
of which, actually or potentially, the presence of the transverse compartments just
mentioned may be considered to speak, being aa entirely unknown in them as is
parthenogenesis, whilst both forms of genesis are common in Vermes. The rarity
of hermaphroditism amongst the Echinodermata, and the non-existence in them
of any sexual differences except those of the ultimate histological structure of the
respective sexual glands, are minor points of difference between the two groups
of animals under comparison. Their possession in common of the power of repairing
great mutilations and injuries, as also of maturing sexual products before attaining
their full size, may be connected probably with their common aquatic habit, and
may be considered as constituting a point of physiological rather than of morpho-
logical affinity.

On the other hand, there can be no doubt that the Echinodermata as a whole
present, both in their life-history and in their anatomical structure, many points
of affinity, firstly, to the Vermes as a whole, and secondly, to each of the four great
orders into which they are here divided. The passing through a larval stage, in
which locomotion is effected by zones or circlets of cilia, is common to the majority
of Vermes and to almost every Echinoderm ; and the clothing of the interior of the
perivisceral cavity and of the digestive tract with the same microscopic element
is a second point common to the majority of Vermes and to all known Echinodermata.
Thirdly, all Echinodermata and almost all Vermes possess a system of vessels, which
in either may be either locomotor or depuratory in function, but which are distinct
from the cavities in which the true blood is lodged, though they may communicate

154

Desc7'iptions of Prepara tions.

Star Fishes, p. 199 ; and Peach, Annals and Mag-azine of
Natural History, vol. xv. p. 171, 1845, for an account of one
of the Aspidochirotae, belonging to the British Fauna, Holo-
tTiuria nigra, which, from its constantly obsei'ved ejection of

more or less indirectly with them as also with the exterior. And fourthly, the
antithesis which might be supposed to exist between Vermes and Echinodermata
by virtue of the chitinogenous character of the integumentary system universally
found in the one, and the calcificatory character of the same system as observed
in the other of the two sub-kingdoms, vanishes when we observe that amongst the
Vermes at least, the integumentary system of the same animal in both the highest
and the lowest orders, is competent to secrete or excrete both these chemical sub-
stances. All the three orders of the class Platyelminthes, the -Taeniadae and
Trematodes (Leuckart, Die Menschlichen Parasiten, p. 475), and the Turbellarians
(Schmarda, Neue Wirbellosen Thiere, 1859, i., pp. xi. xiii. 29), have calcareous
particles deposited abundantly in, as well as chitinous armature developed upon, their
integument. And the secretion of a calcareous vermidom by certain of the Tubicolar
Annelids (Serpulaceae), a family which, in their history as well as their structure,
appear to combine the peculiar characteristics of the sub-kingdom Vermes in the
most distinctive manner, points very clearly in the same direction.

The relationship of the Rotifera to the Echinodermata is founded upon their
resemblance to the larval forms of these animals, and upon their possession of a very
well developed water-vascular system. The resemblance of the adult Rotifera,
which it should be borne in mind do not themselves go through any metamorphosis,
beyond that of attaining in some cases a few appendages wanting in the young
state, to the larvae of various Echinodermata and Vermes, is very clearly shown in
a series of semi-diagrammatic figures appended to Professor Huxley's Paper on
Lanicularia Socialis, in the Transactions Microscop. Society, New Series, vol. i,
1853, pi. 3. But striking as this resemblance is, it may be said to approximate the
Rotifera to the Vermes as much as to the Echinodermata, and may be, by persons
who demur to allowing that a close parallelism exists between the two latter subjects
of comparison, expressed as amounting to nothing more than a permanent retention
by the Rotifera of certain of the characteristics of the larval state of higher Annelids.

Tlie affinities again of the Echinodermata to the Platyelminthes must be held to
be overstated by Semper, when I. c, p. 197, he speculates in a controversy with
Haeckel as to the 'Phylogenie' of the Echinodermata, whether the Dendrocaelous
Planarian may not have been the parent stock of the Gephyrean Sipnnculidae and
of the Echinodermata. The Platyelminthes as a class do, it is true, present a singular
resemblance in their developmental stages and metamorphoses to the Echinodemiata ;
some of them possessing a pseud-embryo, as Pilidium, which may compare for com-
plexity and importance with Bipinnaria Asterigcra, whilst others have their larval
stages marked merely by the possession of some external ciliated integument, which
is got rid of by ecdysis or absorbed, and may have as direct a development as Uoh-
thiiria tremida. To this point of resemblance may be added the dislocation of the oral
orifice from the anterior eye-carrying part of the body which the Turbellarians
present us with, and which even in the face of the fact that in some Annelids every
segment of the body may carry an eye, as in Polyophthalmus, bears no inconsiderable

Angular Sea-Cucumber.

155

the ' Cuvierian organs/ has received the trivial name ' Cotton-
spinner/

For figures of the Cuvierian Organs^ see Hunterian Catalogue,
vol. i. pi. 3 ; J. Miiller, Abhandlungen Konigl. Akad. Wiss.,
Berlin, 1853, p. 208.

resemblaDce to the relation Bubsisting between the compound eye of a Star-fish,
carried at the apex of one of its rays, and its centrally-placed mouth. A double
nerve-cord beset with pairs of ganglia has been figured by Schmarda, I. c, Taf. viii.,
fig- 83, c, in a TurbeUarian, Sphyrocephalus dendrophilus, as extending from the
region of the eyes and frontlet backwards to that of the pharynx, and lends an
additional feature of resemblance to the two sets of structures just compared to each
other. On the other hand, the Turbellarians, with the exception of the Nemertinea
(see Keferstein, Zeitschrift fiir Wiss. Zoologie, xii. p. 68), and all the other Platyel-
miuthes are sterelminthous^ and contrast herein very strongly with the Echino-
dermata.

Several points of resemblance have been pointed out by Dr. Charlton Bastian,
as existing between the Nematoids and the Echinodermata (see Phil. Trans., 1866,
pp. 622-627), and amongst these, the arrangement of the nervous system and of the
various systems of vessels and integmnental pores, deserve especial notice. The
Nematoids further resemble the Echinodermata in the large size of their perivisceral
cavity, and the absence fi-om it of any of the transverse compartments which are
so common amongst Annelids, and which so plainly show that they are, in Mr.
Herbert Spencer's language, 'tertiary aggregates.' But they diflfer from them, as
indeed fi-om the Vermes also, very markedly, in not going through any metamorphosis,
and in the absence of ciUa from their entire organism at all times of their existence.
The Acanthocephali, which have been placed together with the Nematoids and
Chaetognatha as forming the class Nematelminthes, differ from both these orders,
and resemble the Echinodermata in having their adult forms originating with a
provisional larva or pseud-embryo.

Perhaps more points of afiBnity exist between the Echinodermata and the highest
class of Vermes, the Annelids, than between them and the lower classes just com-
pared with them. The resemblance of the Gephyrean Vermes to the Holothurioidea
is so striking as to have caused certain members of the order (or class ?), the Sipun-
culidae, to be ranked in former times with the Echinodermata ; and this resemblance
relates to matters of greater morphological importance than the resemblances of
external form and of habits which are so obvious as existing between the Synap-
tidae and the Sipunculidae. The absence or presence of cloacal respiratory trees
is similarly correlated in the Holothurioidea and the Gephyrean Vermes with the
presence or absence of certain ciliated infundibula opening into the perivisceral
cavity. The existence however in the Sipunculidae of a system of internally ciliated
vessels, which, from throwing a ring round the oesophagus, whence prolongations are
given off into the interior of their peculiar tentacles, and to the skin, and upon
which contractile Polian vesicle-like sacs are developed, must be taken to be homo-
logous with as well as partly analogous to the peculiar ambulacral system of the
Echinodermata, is of the very greatest importance as showing the real afiinity
in question. It must here be said that the Tubicolar Annelids, which attain a

156

Descriptions of Preparations.

For a discussion as to the nature of the functions of the Cuvierian
organs, whether they are to be considered as weapons of
defence, or as exciting organs in connection with reproduction,
or as dej)uratory glands, see Semper, 1. c, pp. 136-142.

considerable external resemblance to the lower Echinodermata, and especially to the
Crinoidea, by the peculiar (Capitibranchiate) arrangement of their respiratory organs,
possess structures which may with probability be considered to be rudimentary
representatives of the tentacular vascular system of the Gephyrei, and, by con-
sequence, of the ambulacral system of the Echinodermata. Professor Huxley, who
(Edinburgh New Philosophical Journal, Jan. 1855), has drawn attention to the resem-
blance of the branchial organs of a Tubicolar Annelid, described by him under the
name of Prolula Dysteri, to the pinnate arms of the Crinoids, has figured from the
same animal, I. c, fig. 3 b, a structure exceedingly like a rudimentary circum-oral
water-vascular ring, with two stunted saccular appendages. This structure is de-
scribed by its discoverer in the following words : ' On the dorsal surface of the head,
a longitudinal canal, which sometimes appears to be ciliated, was visible at b. fig. 3 ;
posteriorly it divided into two branches, which dilated into granular coeca, arranged
in a kind of festoon in the first segment of the thorax.' The presence of cilia is of
importance as difierentiating this structure from the non-ciliated pseud-haemal vessels
both of Vermes and Echinodermata. It is possible that the somewhat similarly
situated and similarly obscure organ in Arenicola piscatorum (see Grube in V. Cams'
Icones Zootomicae, Taf. ix., fig. i x), may be, as has been suggested (Nat. Hist.
Rev., Oct. 1 86 1, p. 487), a rudimentary structure of the same import ; at any rate,
it is plain that the transition from the ' calcareoiis ring ' with a Polian vesicle
appended to it, which has in the new Holothurian species, Rhabdomol^us rvier,
described by Keferstein (Zeitschrift fiir Wias. Zoologie, xii., 1862, p. 34), taken the
place of the entire water-vascular system of other Echinodermata, to the glands
supposed to secrete the calcareous tubes of many Serpulaceae, and the homologous
excretions of certain Terebellaceae and their alUes is but very slight.

Grube has (Miiller's Archiv., 1853, Taf. ix. x., pp. 340-342), described in the
aberrant terrestrial Annelid, Peripatus Edicardii, a system of vessels, one of which
is dorsal, and two lateral, but none of which are branched or connected with each
other. The two lateral canals lie each on the outer side of the halves of the nerve
cord, which are in this Annelid, as in many Tubicolar species, widely divaricated ;
their calibre is considerably larger anteriorly than posteriorly ; the stnicture of
their walls is grumous or glandular, and no other contents than clear fluid could be
found in them. In relation with and probably in connection with these canals on
their under surfaces anteriorly, was a delicate looped tube ; and similarly constructed
tubes were to be seen also in the posterior part of the body in relation with the feet.
The lateral canals appear to be of diflferent structure from the dorsal ; at any rate,
the absence of continuity between the two sets of vessels in a terrestrial Annelid
goes far towards doing away with the difficulty of homologizing the, probably, simi-
larly discontinuous pseud-haemal and ambulacral vessels of the Echinodermata with
the ordinarily continuous and closed system of pseud-haemal vessels in Annelids.

The divarication of the nerve-cord into two halves observed in Peripatm Edwardii,
appears to correspond with the divarication from each other on the ventral surface

Angulai' Sea-Cucnmber.

157

For a good figure of the pseud-haemal system, and the commis-
sural junction between its ventral factors upon the first and
second segments of the intestine, see Sars, Oversigt af Norges
Echinodermer, 1861, Tab. xv. fig. i m, I.

For the homology of the ' auriculae' of the Echinoidea, of the

of the rows of feet which it supplies, and to be more or less physiologically similar to
the allocation of a series of ganglions de renforcement (for which see p. 132, supra,
ibique citato^, to the line of insertion of the feet as seen in Nereis regia. An exactly
similar separation of the nerve-cord into its two component halves, is to be seen in
many Serpulaceae ; see Quatrefages, Hist. Nat. Annel^s, pi. iii., fig. 7, 8 ; Ann.
Sci. Nat., Ser. iii., tom. x., pi. a, torn, xiv., pi. ro ; and when we couple these facta
of comparative anatomy with the fact, that whenever the development of the%ierve
centres of Invertebrata has been observed, that is to say, in Mollusca, Arthropoda,
and Vermes, these centres have been observed to be differentiated at a late stage
in the series of developmental changes (see page 109 supra, and Claparede, Beobach-
tungen iiber die Anatomie und Entwickelungsgeschichte wirbeUoser Thiere, 1863,
p. 87), it will appear probable that the physiological necessity which the already
radiate Echinoderm has for a radiate nerve-system, may be the regulating condition
of its peculiar arrangement, and that they are therefore, pro tanto, and as regards
their nerve system, approximated rather to the highest Annelids than to the Ne-
matoids, as suggested by Dr. Charlton Bastian. A truer homology for the trifid
nerve-system of the Nematoids, may be found in the nerve-cord of the singular
Annelid, Sphaerodorum peripatus, as figured by Claparede, I. c, pp. 50-53, pi. xi.,
fig. 17, where the super-addition to an organism, in other respects closely akin to
that of aNematoid, of motor organs, in the shape of numerous pairs of comparatively
simple setigerous uniramous feet, has been accompanied by a corresponding addition
of trifid nerve-ganglia, which are united by commissures into a continuous cord.
Coming finally to the indications of affinity which the history of the various stages
of development is properly held to point to, we may say that what is known of the
development of the Polychaetous and especially of the Tubicolar or Capitibranchiate
Polychaetous Annelids, shows that a closer relationship subsists between them and the
Echinodermata than between even the Gephyrean Vermes and these latter animals.
To judge of this similarity, it may be well to compare such figures as are given of
the development of Antedon Rosaceus {Oomatula Rosacea) by Professor WyviUe
Thomson, Phil. Trans., 1865, pi. xxiv., xxv., and xxvi. ; of Synapta digitata by
Baur, Nova Acta, 1864, pi. iv. ; or such figures as are given of various forms of
Echinoderm larvae, from the memoirs of Miiller and others, in Bronn's Klassen und
Ordnungen des Thier-reichs, Taf. xxxv., xxxvi., xxxvii., and especially Taf. xlvi.,
with the figures given by Claparfede, I. c. ; of the development of Leucodore, Spio,
Terebella and Magelona, Taf. vii., viii., ix., x., xi., and those given by Keferstein
and Ehlers, in their Zoologische Beitrage, Taf. viii. of Sipunculus. See especially
C'laparfede's remarks as to the Tubicolar Annelids going in their early stages through
more typical forms than those they ultimately rest in, and as presenting us therefore
with instances of retrogressive metamorphosis, a possibility which is not rarely lost
sight of in such discussions as these.

158

Descriptions of Preparations.

'calcareous ring' of the Holothurioidea^ and the 'vertebral
ossicles'' of the Asteriae, see Semper, I. c, pp. 161-163 ; Baur,
I. c, p. 18 j Miiller, Anatom. Studien, 1850, p. 154.
For the compensatory relation which exists between the respiratory
trees and the ciliated infundibula upon the mesentery, see
Brandt, Prodromus, Fascic. i., 1835, p. 59, who, in describing'
the genus Chiridota, says, ' Respirationis organum ramorum
nullum,- sed ejus loco corpuscula cylindrica, apice saepissime
fissa, illae mesenterii parti, quae primam seeundamque in-
testini curvaturam retinet afiixa/ See also Semper, I. c,
pp. 4, 132. For figures of these organs in the Synaptidae,
see Bronn, Die Klassen und Ordnungen des Thier-reichs,
Bd. ii., Taf. xliv., fig. i a, ; Sars, I. c, tab. xv.j xvi.

48. Sea-Anemone {Actinia Crassicornis),

Dissected so as to show its various external and internal organs.

A VERTICAL section having been made through the entire length
of the sub-columnar body, one of the halves thus obtained has
been suspended, so as to show the direct continuity, firstly, of the
cavity of the stomach with the general cavity of the body, and
secondly, of the general cavity of the body with the cavities of the
tentacles. These latter organs are arranged in four rows, within
the circumference of the oral disc, which forms a low parapet
externally to them ; they are shorter than the diameter of the oral
disc, even when fully extended ; in this specimen they are not fully
retracted, the animal having, probably, been killed by the addition
of fresh water; and their natural short and conical form is well
seen. Each tentacle tapers somewhat abruptly to a point, appa-
rently under the action of the muscular fibres, which act as a
sphincter to the foramen in its apical extremity. The peristomial
disc, internally to the inner row of tentacles, is divided into two
concentric areae by a line of depression corresponding with the
strong oral sphincter, which is seen in section at the entrance of

Sea-A7iemone.

159

the digestive cavity. Both the peristomial disc and the internal
surface of the dig-ostive cavity are marked by fine radiating lines,
which are seen to correspond with the attachment to their under
and outer surfaces respectively of the vertical muscular lamellar
' mesenteries/ which, radiating- from a point in the centre of the
hydrorhiza to the outer wall of the body, as well as to the roof
of the perigastric space, and to the outer sm'face of the tubular
stomach, divide the body cavity into a number of radially-arranged,
mutually inter-communicating, wedge-shaped compartments. Some
of these mesenteries fail by greater or less intervals to reach the
outer surface of the stomach, and they are called ^secondary* or
' tei-tiary^ mesenteries, whilst those which attach themselves to that
organ as well as to the outer wall are called ' primary.'' The
greater part of the external warty integument having been re-
moved, the lines of attachment of the mesenteries to it are as
plainly seen as those similarly produced on the digestive and
peristomial surfaces. At the lower part of the Preparation one of
the mesenteries has been reflected back, and the decussating
muscular fibres which make up a large portion of its substance
are well seen. At a little distance internally to this mesentery, and
in connection with the free border of another similar lamella, where
it projects into the general cavity of the body below the level at
which the stomach opens into it, we see some of the generative
glands surmounted by certain long convoluted filamentous organs,
the so-called ' craspeda/ which are richly furnished with thread-
cells; but which are often spoken of as renal organs, as concretions
in which guanin is said to exist have been found in connection
with them. The lower orifice of the digestive tube is seen to be
of about the same size as the oral inlet, but it is not seen in this
preparation to be guarded with a muscular sphincter as the mouth
is. In Actiniae there exists a demi-eanal on each of the opposite
sides of the mouth, which is prolonged down the inner surface
of the stomach, and is continued a little way beyond the termi-
nation of the sub-cylindrical organ, so as to project as a free
languet into the general cavity of the body. The external surface
of the body is similarly furrowed in this specimen, and an appear-
ance of bilateral symmetry is thus produced. The Actiniae and
Cerianthidae are the only Polypi s. Antljozoa in which the external
integument is not more or less indurated by inorganic deposit.

160

Descriptions of Preparations.

For the anatomy of the Actiniae, see Hollard, Ann. Sci. Nat.,
Ser. iii., torn, xv., 1851, p. 257; Huxley, Med. Times, June,
1856.

For a zoological description of Actinia Crassicomis, see Johnston,

British Zoophytes, 1847, 2nd edition, p. 226.
For the anatomy and morphology of the entire sub-kingdom

Coelenterata, see G-reene's Manual of the sub-kingdom Coe-

lenterata, 1861.

For the points of distinction between the Coelenterata and the
Echinodermata, see Van Beneden, Recherches sur la Faune
Littorale de Belgique Polypes, 1866, pp. 55-62.

4^. Sea-Fib, {Sertularia Ahietina).

A COMPOUND Hydroid Polype, plant-like in form, and differing
from the preceding specimen in being fixed to one spot in adult
life, and from the entire class to which the Sea-Anemones belong,
by the much smaller size and simpler structure of each of its
constituent zooids. The specimen consists of a number of regu-
larly branched stems, which arise near to each other from a
creeping stolon ; and are beset by series of closely arranged subal-
ternate cells, the ^ hydrothecae^ containing the zooids. In the
upper half of the specimen, the main stems and the pinnae may
be observed to carry, besides the regularly arranged hydrothecae,
certain larger cells, irregularly arranged along their upper surfaces.
These latter cells are the 'gonophores' of Hincks, the 'teleophores'
of Van Beneden ; they differ from the other cells or hydrothecae,
in that their contents are the sexual products developed within
processes of the ' coenosai'e,'' which possess neither the digestive
cavity nor the prehensile tentacles of the smaller hydrothecae.
Appended to the apices of some gonophores, may be seen the
marsupial pouch, into which the ova are transferred' at a certain
stage of their development. The gonozooids, or the contents of
the gonophores, we may call 'medusiform buds,' but they never
in the family Sertulariidae take tbe shape of Medusae. The em-
bryos are at first spheroids richly covered with cilia ; subsequently

Sea -Fir.

161

they become cylindriforin ; and finally they attach themselves by
one extremity which widens into a Miydrorhiza/ and develope a
circlet of tentacles and a digestive sac at the other. In the family
Campanularidae, which difiers from the Sertularidae mainly in the
pedunculation of its cells^ many species have Medusae set free from
their gonophores. The outer layer of the ectoderm has secreted
a firm but flexible polypary^ which is continued into the cups
for the lodgment of the digestive and generative zooidsj as ' hydro-
thecae^ s. ^calycles'' 8. 'cells/ and as 'gonothecae^ s. 'capsules/ in
the language of different writers. The digestive or alimentary
zooids are known as 'polypites/ their cavity^ which is not a
distinct sac freely suspended, but a mere hollow scooped out in
the part of the coenosarc which is prolonged into each cell^ is
continuous with that of the coenosarc or ' coenenchyma^ by a
narrow tubular passage^ the ' transition piece'' of Reichert, passing
inwards from the bottom of the stomach. Representations of two
other sub-kingdoms may be seen to have afiixed themselves semi-
parasitically to the main stems of this zoophyte. One of them is
the Spirorbisj a small Tubicolar Annelid, with a discoidal shell,
somewhat like that of the fresh- water mollusc Planorbis ; the other
is one of the Cyclostomatous Polyzoa, Ttibulipora patina, which with
its aggregated calcareous cells presents an appearance not unlike
that of a small tubiflorous flower belonging to a plant of the order
Compositae.

Coelenterata, with an external polypary, and a uniserial circlet
of tentacles such as this specimen possesses, bear a superficial re-
semblance to many Polyzoa, which indeed were formerly classed
with them. But beyond these more- or less unimportant points of
resemblance, the Hydroid Polypes and the Polyzoa have scarcely
any points of real similarity, unless we reckon as such the absence
of ducts to the generative glands, and the power of multiplying by
gemmation, properties which attach to them however in common
with representatives of several other classes of Invertebrata. In
the absence of a digestive tube difierentiated from the peri-visceral
cavity; in the absence of muscles differentiated into distinct fas-
cicles and crossing that cavity ; in the absence of any nerve-centre,
and in the presence of thread-cells (all points to be made out, and,
Avith the exception of the one relating to the nerve system, with
very little trouble, under the microscope, with a fresh specimen of the

M

162

Descriptions of Preparations.

present species) — the Hydrozoa differ widely and essentially from the
Polyzoa. It may be further added that it is very usual in Polyzoa
to have each cell cut off by a diaphragm or septum, into the forma-
tion of which both ectocyst and endocyst enter, from continuity
with the rest of the colony ; whilst it is only in the few cases such
as Hydra, Corymorpha, Vorticlavaj Myriothela, in which the hy-
drosoma consists of but a single polypite, that such independence
is attained to in the Hydroid Zoophytes. In the form of ' Poly-
morphismus/ which the 'medusoid bud-* presented to us in the
'gonophore' of the Sea-Fir exemj)lifi.es, we have the connecting
link between the distinct testis and ovary of the Hydra, (for which
see pi. xii., fig. 7, and description), and the free sexual zooids
known as ' Medasae/ and exemplified in genera as nearly akin to
the Sea-Fir as the Campanularia gelatinosa. And, as has been
well observed, a study of such histories as those of the various
modes of development of this class of Coelenterata, shows how
impossible it may become to draw sharp lines of distinction be-
tween individual animals or zooids and simple organs on the one
hand; and on the other between asexual generation and simple
growth.

For a monograph of the British Hydroidea Diplomorpha, V. Carus,
see Hincks, History of the British Hydroid Zoophytes, 1868,
where a general account of their structure and life-history is
given in the Introduction, pp. i.-lxv. For the Siphonophora,
see Professor Huxley, Oceanic Hydrozoa, Eay Society, 1859.
For the Hydrozoa generally, see Professor Huxley, Medical
Times and Gazette, June 7, 1856, p. 563.

For an account of the particular species to which the specimen
here described belongs, see Hincks, I. c, i., 226.

For an account of the development of the Sertularia cupressoides,
see Van Beneden, Recherches sur THistoire Naturelle des
Polypes, 1866, pp. 179-184, pi. xvi., where what is spoken
of above as a ' marsupial sac,' and described and figured as
such by Hincks, I. c, p. xvi., is figured at fig. 3, but spoken of,
p. 180, as a 'hernie au bout de la capsule/ and for the de-
velopment of the Hydroidea generally, see Allraau, British
Assoc. Rep. for 1863, p. 351.

For a short account of the Histology of this class, see Professor

Fresh-water Sponge.

163

Reichertj on the contractile substance and intimate structure
of the Campanularidae, Sertularidae and Hydridae, translated
in the Annals and Magazine of Natural History for Jan. 1867,
from the Monatsbericht der Akademie der Wissenschaften zu
Berlin, July 1866, p. 504; and for the Histolog-y of the entire
sub-kingdom Coelenterata, see Kolliker, Icones Histiologicae
ii., Abtheilung, Hft. i., 1866.

50. Fresh-water Sponge (Spongilla Lacustris),

From the Isis, growing on the wall of a lock.

This specimen, like the preceding, is plant-like in appearance,
consisting as it does of a root-like basis of attachment, and two
upright stems arising close together from it. The stems are about
five inches in height, and of the thickness of a drawing-pencil, but
the Spongilla Lacustris not rarely attains a greater size than this.
Owing to its having been preserved in spirit, this specimen has its
surface more fenestrated than it was in the living condition ; its
protrusible bladder-like cloacae are no longer visible ; and its eme-
rald-green colour is nearly lost. Its exterior is hispid with fascicles
of spicula, and the orifices in which the cloacal oscula were lodged
are very plain; though the smaller inhalant orifices or 'pores'
are not distinguishable, and indeed can only be seen in small
and transparent specimens under the microscope. Towards the
lower part of the stem, numbers of reddish globular seed-like
bodies, the asexual reproductive gemmae, formed towards the close
of the summer, are to be noted. The coriaceous capsule of these
gemmae is strengthened in this species, not by the birotulate
spicula known as ^amphidiscs' from their resemblance to a couple
of toothed wheels connected by an axle, and existing in the other
fresh-water Sponge, Spongilla fluviatilis, but by simple curved
acicular spicula which lie in it parallel to its surface. These
spicula are abundantly spinous, as are also the spicula which
are to be found in the dermal membrane of this, though not of
the other fresh-water species ; the spicula of the skeleton proper

M 2

164 Descriptions of Preioarations.

are smooth in both species. It is, of course, necessary to have
recourse to the use of the microscope for the verification of these
points ; and for the detection of the finer spicula, the specimens
must be mounted in Canada balsam. Owing to the neglect of
this latter method of investigation, the existence of spicula has
frequently been overlooked, as, for example, in the case of the
Halisarca Dtijardinii, which, on account of the supposed absence
of these structures, has been elevated to the rank of a distinct
genus.

Discussions have been frequently raised, firstly, as to the claim of the
Sponges to be considered animal organisms at all ; secondly, as to what
is to be considered the unit of their organisms ; and thirdly, as to the
rank which the class is to take relatively to other divisions of the animal
kingdom. With reference to the first of these questions, which is now
all but universally answered in the affirmative, it may be said that the
motile phaenomena noticeable in these creatures, and their great need
for, and rapid consumption of oxygen, without which, as supplied by
constant additions of fresh-water, the SpongiUae may be observed to
die and putrefy with very gi-eat rapidity, are, from the physiological point
of view, very strong evidence for their animal character. The histo-
logical evidence however drawn from the detection in them of ciliated
as°well as non-ciliated epithelium, of cells for the formation of the
spicula, and above all of contractile fibre-cells which, though not
detected in Spongillae, do exist in the more highly organized Sponges,
Cerato-spongiae and Corticatae, is, as Kolliker has remarked, quite con-
clusive upon the question.

It is not possible to give as distinct an answer to the second question,
as to whether the Spongiadae are to be considered as colonies made up
of uni-cellular but polymorphic organisms, or whether we ought not
rather to regard each exhalant osculum as marking out a correspondmg
zooid, into the constitution of which, as of all higher animals, a mul-
titude of polymorphic 'cells' enter. For, as has been already said, with
reference to the Hydroidea, it is not easy always in the lower sub -
kingdoms to draw a sharp line of demarcation between what in a higher
and indeed sometimes also in a lower organism would be unhesitatingly
spoken of as an 'organ,' and what in nearly alUed genera to one which
may chance to be under examination would be spoken as a specia ly
modified ' zooid.' It is agreed upon all hands, that, in addition to the
nucleated cells, ordinarily but not always, destitute of a cell wall, and

Fresh-ivater Sponge. 165

capable of amoeboid movements, which make up the greater part of the
non-skeletal elements of the Sijongiadae, there are to be found in them
several other kinds of cells, and even tissue, which however readily re-
assumes the form of the independent cells by the fusion of the sarcode of
which it was composed ; and it is not therefore necessary to say more
than that the better mode of expression for the facts acknowledged by
both parties is the one which speaks of each exhalant osculum as corre-
sponding not to an individual Sponge, but to an individual colony.

With reference to the third question, that of the position which the
Spongiadae may be considered to hold relatively to the Protozoa on the
one hand, to which sub-kingdom they are ordinarily referred, and to
the Coelenterata on the other, it is perhaps more correct to regard them
as exemplifying the highest stage of evolution of the former, rather than
as i)eing a transition towards the latter of these two types. The distinct-
ness indeed of their 'oscula' from their 'pores' would appear to place
them in a position of superiority as regards the Coelenterata, in which
there is but a single orifice both for the ingestion of aliment and for
the ejection from the system of refuse matter. KoUiker has thrown
doubt upon the view that certain of the sclerous elements of the organ-
isms of the Anthozoa are due to epidermal excretion, and thus one
point of distinction between them and the Spongiadae would be done
away with ; but the external chitinous polypary of the Hydroid Zoophyte
will serve always to differentiate it from the Sponge, in which the skeletal
elements are always internal. This, however, is perhaps a point of
merely secondary importance, as is also the non-secretion by Coelenterata
of the siliceous deposits so common in the Sponges.

For the anatomy and physiolog-y of the Spongiadae^ see Dr. Bower-
bank, Monograph of the British Spongiadae, 1864-1866,
pp. 1-153.

For the methods to be employed in the examination of Sponges,
thicl. \., 225 ; and for their apphcation in the cases of Halisar-
cina Bujarclinii and Sjoongilla lamstris, ibid, n., 225, and Zool.
Soc. Proc 1863, p. 462.

For the physiology of the ' oscula' and 'pores/ see Dr. Bowerbank,
British Assoc. Report for 1857, p. 125, pi. i., ligs. r-7.

For a diagrammatic representation of the mutual relations of the
various parts of a Sponge, see Professor Huxley, Introduction
to the Classification of Animals, 1869, p. 1 5, fig. 4.

166

Descriptions of Preparations.

For the liistolog-y of the Spong-iadae, see Kolliker, Icones Histio-
logieae, 1864, i,, p. ^6, and Dr. Bowerbank^ I.e., passim.

For the various views which have been taken as to the position of
the Spongiadae in the animal kingdom^ see KoUiker^ I. c,
p. 73 J ihique citata ; Van Beneden^ Polypes^ 1866, p. 198;
Claparede et Lachman, Etudes sur les Infusiores, i., p. 421,
1858-1859; Haeckelj Generelle Morphologie, 1866, ii.^ p.
xxix. J Natiirliche Schopfungsgeschichte, 1868^ p. 396.

For the different views which may be taken as to the ' indivuaV
organism in the Spongiadae, see O. Schmidt, Handbuch der
Vero-leichenden Anatomic, 1865, p. 25; Lieberkiihn, Archiv.
fiir Anatomic und Physiologic, 1863, p. 728; Glaus, Grund-
ziige der Zoologic, 1868, p. 52.

DESCEIPTIO¥ OF THE PLATES

PLATE 1.

Common Rat (Mus Deciimanus),

Dissected so as to show, superiorly, the cerebrospinal nervous system lodged in the
craniospinal cavity, and, inferiorly, portions of most of the organs of vegetative
Ufe.

The distinctive characteristic of the Vertebrate type^ the pos-
session^ namely, of an internal skeleton specially connected with
the organs and functions of animal life^ is clearly shown in this
figure. The internal skeleton is seen forming a separate chamber
for the central nervous system which presides over motion and
sensation, apart from the larger cavity in which the organs of
vegetative life are lodged. By virtue of this arrangement Ver-
tebrata may be spoken of as ^ Bicavitary animals, in contradis-
tinction to Invertebrata which are ordinarily ' Unicavitary.^ Se-
condly, we see that it is the internal, and not as in Invertebrata
an external, skeleton which gives origin and support to the active
and passive organs of locomotion. Thirdly, the limbs, which are
never more in number than two pairs, are directed towards that
surface of the body in apposition with which the heart, the great
centre of the circulatory or haemal system, is placed (m) . Hence
Vertebrata may be spoken of as ' Haemapods,''' in contradistinction

* The Description of the figure given in this plate will be found to coincide in
many particulars with the Description given at pp. 1-5 supra of the first series of
Preparations. The Descriptions of plates vi. and vii. stand in a somewhat similar
relation to the Descriptions of the Preparations 30 and 32. But in none of these
cases are the Descriptions mere repetitions, but will be found to be complementary of
each other. In the present Description, for example, the upper part of the figure
has been drawn from a dissection distinct from that described at pp. 1-5 supra; and
the structures lettered here g and </' will be found not to have been described before.

168

Description of the Plates.

to Invertebrata which are 'Neuropods/ having their main nerve
centre placed in the same relative position as that occupied by the
heart in the former class

Above the heart we see the digestive canal, and above the
digestive canal the craniospinal, and the nervous centres it
contains. But the great vessel, known as the aorta (7;), which
carries blood from the heart to the organs of the body generally,
interposes itself in all Vertebrata between the lower surface of the
craniospinal and the upper surface of the digestive tube.

A minor point distinctive of Vertebrata is the presence of a
spleen.

The peculiarities of the tegumentary system are distinctively
mammalian, as are also the following points in the anatomy of
the internal organs shown in this figure : the suspension of the
lungs freely in closed cavities, the so-called pleural' cavities;
the presence of a perfect diaphragm (c) supplied by a phrenic
nerve originating in the region of the neck; the smoothness of
the external surface of the kidney ; the persistence of the aortic
arch of the left side (^j) ; and the presence of an omentum or
epiploon {w).

The scalpriform incisors characteristic of the order Rodentia
are concealed in this profile view by the lips, but the figure shows
well the great size of the masseter muscle, by the contraction of
which the characteristic anteroposterior movement of the lower
upon the upper jaw is effected. The great size of the organs of
special sense relatively to the entire bulk of the animal, and of
the hind relatively to the fore limbs, are characteristic, though not
universally nor exclusively, of Rodents.

b These two latter names are more strictly accurate than the two former, for in
some Invertebrata the main nerve-centres are separated from the viscera of organic
life by more or less perfect septa, formed by separately calcified ossicles in the Aste-
roidea, or by the prolongation inwards of processes from the external skeleton, as in
many Crustricea and Insecta. But in all such cases the neural still remains the
motor surface, and the term 'Neuropod' applies to them as strictly as it does to any
of the Vermes or INloIlusca. For the ossicles of Asteroidea, see pi. x., -infra; and
for the 'endopliragmal' skeleton, in Crustacea, see Huxley, ]\Iedical Times and
Gazette, Feb. 21, 18.S9. V- 181; Nov. 7, i857. P- 467: in Insecta, sec Burmeister
Manual of Entomology, translated by W. E. Shuckard, p. asfi; and for figures of
it see Spence Bate, British Association Report for 1855, pl- %«• i and 2 :

Slraus Durckheim, Considerations gdn,$rales sur I'Anatomie Compar6e des Animaux
Articul^s, pl. ii., i-

Common Rat.

169

Points of less classificatory importance are furnished to us by
the presence of a vena cava descendens on the left side, of smooth
cerebral hemispheres (/i); of a uterus all but completely bifid (y
and /), of a Harderian gland of a hibernating gland {/c),
and of a double lacrymal gland {(/ and /).

The left halves of the parietes of the craniospinal^ thoracic,
abdominal, and pelvic cavities were removed to expose to view
the parts shown in this figure. The integument has been re-
moved from the greater part of the facial region, but a narrow
strip has been left connecting the concha of the ear with the
upper eyelid. A similar strip has been drawn as left in siiu
overlying the costal attachment of the diaphragm.

a. Left eye.

h. Left ear. Both eye and ear are largely developed in most
Rodents, and markedly so in this family.

c. Diaphragm forming a contractile dome-shaped floor between

the abdominal cavity below and the thoracic above.

d. Eleventh dorsal vertebra, counting from before backwards. The

ten anterior dorsal vertebrae have their neural spines directed
more or less obliquely backwards ; the two vertebrae — one
only of which is seen in the figure — immediately behind d,
have their spines pointing forwards. The spine of the
eleventh dorsal vertebra has a vertical direction, and it
marks the point of greatest mobility between the segments
of the vertebral column, as also the point whence the size
of the vertebrae progressively increases both towards the
cervical and towards the sacral regions. The spine of the
second dorsal vertebra is of great length, and in the natural
condition of the parts it had an ossicle articulated to it,
homologous to the ligamentum nucJiae of longer-necked ani-
mals, and running ^forwards amongst the muscles of the
nape of the neck. The dorsal vertebrae are thirteen in
number, as is very commonly the case in this order, as
also among the Ruminantia and Carnivora. The first two
cervical vertebrae are, as is usual, though not invariable,
among mammals, much larger than any of the five which
succeed them in the neck.

e. Spinal cord. The part where it widens into the medulla ob-

longata, a part of considerable transverse dimensions in

170 DescrijJtion of the Plates.

this and other Eodents, is concealed by the large external

ear.

/. Part of Harderian gland, which discharges its secretion by
a duct opening under the rudimentary third eyelid or nicti-
tating membrane. This gland is found in most mammals,
with the exception of Chiroptera and Simiadae.

ff. Intra-orbital portion of lachrymal gland. Its duct joins that
of a second portion of the lachrymal gland (/), which lies
without the orbit.

/. Extra-orbital portion of lachrymal gland, lying upon the
masseter muscle, and sending a duct with some glandular
tissue inlaid in its walls to enter the orbit at its posterior
angle, and receive the duct of the intra-orbital portion {ff).

h. Cerebral hemisphere of right side. The external surface

of the two hemispheres is not convoluted ; at their poste-
rior aspect the longitudinal venous sinus is seen to divide
into the two lateral sinuses. A small triangular portion
of the large cerebellum comes into view at this point;
the sinuses prevent the mesencephalon or corpora quadri-
gemina from being seen.

i. Vagina.

j. Parotid gland. Its ducts are seen to converge from its
constituent lobules, whicb_are Iposely aggregated from the
neighbourhood of the_ carlo thit of the acromion, and to
cTo'ssTwTien united, th^ ramifications into which the motor
nerve of the facial muscles is seen to break up. The buccal
pouch is wanting in the true Mures, but some lymphatic
glands have been removed from the space between the
masseter muscle and the parotid gland.
L Portion of 'hibernating gland;' a gland found in many
Rodentia, Chiroptera, and Insectivora, and spreading m
them into the axillary, the nuchal, the thoracic, and
occasionally even into the abdominal regions.
I. Submaxillary gland and duct.

m. Heart; the line ends upon the left ventricle. The apex of
the heart is not turned so much to the left as in man and
in some of the lower mammals, as, for example, the mole.
-fhTfoid immediately below the poliil wliefe the line abuts
upon the ventricle is formed by the cut edge of the

Common Rat

171

pericardium,, the upper four-fifths of which have been
removed. Between the inferior surface of the heart and the
diaphragm the fourth lobe of the right lung intervenes
posteriorly ; and between the apex of the heart and the
diaphragm and sternum anteriorly^ a process of serous mem-
brane entangling lobules of fatty tissue is interposed^ and
connects thus the apex of the pericardium with the sternum
and diaphragm.
n. Left amicle.

0. Phrenic nerve lying in relation with the left superior cava
and passing down from its origin in the neck, in front of
that vessel and between the root of the left lung and the
pericardium^ and by the side of the fourth lobe of the right
lungj to distribute itself in the diaphragm.

p. Aorta. A bristle has been passed between it and the left ^
azygos veinj and abuts on the diaphragm where the left
phrenic nerve enters it. Behind this bristle are seen from
behind forwards, firstly, the third lobe of the right lung;
secondly, the oesophagus, which is seen to be of a small
size in correlation with the scalpriform incisors of the
Eodent j thirdly, the fourth lobe of the right lung within
its own pleural cavity, in relation with which is the phrenic
nerve; and, lastly, the lobules of fatty tissue, already
spoken of, in apposition with the fourth and fifth of the
six sternal bones.

q. Left azygos vein joining the vena cava superior of the same
side, and receiving some veins from the masses of fat just
mentioned in connection with the pericardium.

r. Root of left lung : the lung of this side has been re-
moved; it consisted of a single lobe, as is often, though
not always, the case in Rodentia, Marsupialia, and Insecti-
vora, though very rarely in Carnivora and Quadrumana;
see Cuvier, Legons d'Anatomie Comparee, tom. vii. ed. sec,
1840, pp. 156-163.

s. Kidney ; lying in the angle between the diaphragm and the
psoas and quadratus lumborum muscles. The smoothness
of its external surface is a mammalian character.

t> Spleen.

lu Stomach.

172

Description of the Plates.

V. Liver; the line abutting- upon its left lobe.
to. Omentum or epiploon^ a process of the peritoneum peculiar
to mammalia.

w. Coecum. The entrance of the small intestine into the coecum
is not seen, but we may observe that the coecum becomes
smaller in calibre where it is bent on itself superiorly. It
passes thus into the 'large intestine/ which does not
however contrast so markedly either in its relative shortness,
or in the thickness of its walls, or in its calibre with the
' small intestine/ in the Rodentia, as in many other orders.
These omnivorous Rodents, and also the Sciuri, have smaller
coeca than the Rodents which live on less nutritious and
coarser food and have rootless molars.

w'. Convolutions of intestines.

Upper end of left cornu of pregnant uterus, passing into the
Fallopian tube, which together with the ovaiy fills up the
space between this convolution of the uterus and the kidney.
The ovary and tube are connected by a ligament to the
peritoneum covering the diaphragm, the 'ligamentum
diaphragmaticum ^ connected with the 'Wolffian body'
in the foetus.

/. Lower portion of same uterine cornu distended with foetuses.
z. Bladder contracted into a conical shape and recei%^ng the

ureter at its base on the left side.
z. Outlet of urinary organs through a perforated clitoris distmct

from the vagina.
77. Rectum.

A. Flexor muscles of the tail, which arise from the internal surface
of the pelvic bones.

8. Anterior portion of ilium, the posterior part of which has been
removed, together with the pubis and ischium. Froni its
internal surface the caudal flexors are seen to take origin,
and in front of them and in a line with the point on which
the letter 8 is placed, the cut end of one of the great veins
returning blood from the hind limb is seen.

The following peculiarities in the tegumentary system deserve
notice:— the absence of hair from a part of the anterior portion of
the snout, the so-called < muffle,' in which we see the orifices of

Common Rat.

173

the nostrils; the presence on the snout, as also over the eyes,
of long tactile bristles, which, like the larg-e eyes and ears, are
correlated with the nocturnal habits of the creature ; the presence
of a nail on the rudimentary thumb, which is occasionally over-
looked or lost in adult specimens; the coarseness of many of the
hairs along- the middle line of the back ; and the annular arrange-
ment of the scales on the tail, and the outgrowth of hair in the
intervals of the rings thus formed.

For an account of the ' hibernating glands,^ see Hirzel and Frey,
Zeitschrift fiir Wissenschaftliche Zoologie, xii., %, 16^, 1862;
Ecker, Wagner^s Handworterbuch der Physiologic, iv., p. lai,
1853, ibigiie citata.

I

I

I

PLATE II.

PiGEON; Columba Livia.

PLATE II.

A-e*. Common Pigeon {Columha Livia),

Dissected so as to show, firstly, some of the main points of agreement and difierence
between Aves, Reptilia, and Mammalia respectively ; and, secondly, the arrange-
ment of the principal muscles of flight.

In the possession of a single aortic trunk, as seen in tlie figure
a little internally to the letter p, and above the letter birds re-
semble Mammals, as they do also in the physiological peculiarity
of being warm blooded, or ' homoeothermal.-' A few Mammals
resemble all Birds in being testicondous, see h in figure, and in
the possession of two coeca, see / in figure, as also in the possession
of a coraeoid prolonged down to the sternum, see place of origin of
muscle % in figure. But all Mammals difier from all Birds in that
their single aorta crosses their left and not, as shown at g in this
figure of a Bird, the right bronchus ; in the absence of any indent-
ations of the lungs' surface to correspond with the ribs; and in
the absence of any external conformation of the kidney in relation
to the pelvic bones. In all Mammals there is a sinus urogenitalis,
in none do the genital and urinary ducts open separately, as shown
here at k and g, into a cloaca common to genital, urinary, and
faecal products. These points are as constant as the possession by
Mammalia of a hairy integument and of non-nucleated coloured
blood corpuscles. The relation of the pancreas to the duodenum,
as seen at e, is a minor point, but probably equally distinctive of
Birds in opposition both to Mammals and Reptiles.

In being testicondous ; in the absence of differentiation of the
structures of the kidney into cortical and medullary portions, and
in the supply of blood-vessels to the gland ; and in the absence of

176

Description of the Plates.

a perfect diaphrag-m, and also of a corpus callosum^ — Birds and
Eeptiles resemble each other as closely as they do in the micro-
scopic character of their blood-corpuscles. In two points of second-
ary importance Birds resemble the Loricate and differ from the
Squamate Reptiles ; in this latter class there is a rudimentary
urogenital apparatus^ and the genital gland is situated a certain
distance anteriorly to the kidney ; whilst in Birds, Crocodiles, and
Chelonia, the genital and m-inary glands have separate outlets,
and the glands themselves are more or less completely in appo-
sition with each other. On the other hand, all Birds possess a
quadrilocular heart, and a single aorta belonging to the left ven-
tricle, an arrangement by which they are secm-ed against any
direct admixture of venous with arterial blood, and in which they
differ as widely and constantly from Reptiles as in the peculiarity
of their integumentary system.

No Reptiles possess a true crop, such as is seen at b in the figure,
nor two coeca ; but these structm-al arrangements are by no means
constant in Birds.

a. Right cerebral hemisphere. Its surface is smooth, contrasting

herein with that of the transversely laminated cerebellum
seen behind in the median line.

b. The crop, which is bilocular in the Columbidae. It is con-

tinuous above with an artificially distended oesophagus, and
a window has been made in its right wall to show its divi-
sion into two compartments.

c. Right lobe of liver, on which the right side of the heart

rests.

d. Heart. The ventricular portion is more acutely conical in

most Birds than in Mammals, and the auricles are smaller
in relation to it.

€. Loop of duodenum in which are contained the longitudinally
arranged lobes of the pancreas. Into this loop of intestine
three ducts open from the pancreas and two from the liver,
which has no gall-bladder in this species. Two of the pan-
creatic ducts open near the middle of the distal segment of
the duodenum close to each other and to one of the gall-
ducts; the third pancreatic duct opens near the distal end
of the loop, and the second gall- duct near its proximal end.

Common Pigeon.

177

e. I. Terminal segment of small intestine ending in the large
intestine at f, whichj together with it, has been turned over
out of the abdominal cavity, on to the animal's left. Two
long coils of small intestine have been removed between its
terminal segment and the distal end of the duodenum ; the
first coil being a fold of great length spirally arranged, and
the second a much shorter one arranged like the duodenal
fold, which however it exceeds in length.

f. Large intestine, two small coeca marking its commencement.

In the small size of the two coeca the Columbidae contrast
with the great mass of the Gallinaceae.

g. Terminal dilatation of the large intestine which receives the

vas deferens and ureter posteriorly and superiorly on each
side. In this cloacal arrangement Birds resemble Keptiles
and Amphibia ; in all mammals there is a sinus urogenitalis
developed, into which these ducts open. In the absence of
a urinary bladder Birds resemble Snakes and Cartilaginous
Fishes, as also many Lizards.

h. Testis.

i. Kidney divided into three lobes, which are conformed to the

sinuosities of the pelvic bones. Between the lower and
middle lobes the large ischiatic artery and some nerves pass
out to the lower limb. The artery gives a supply of blood
to the gland. Between the middle and upper lobe of the
kidney the small femoral artery passes outwards, and a
large vein passes inwards. This vein, besides acting as a
'renal-portal' vein and supplying the glandular structure
of the kidney, communicates directly also with the renal
efferent vein. This latter branch is not possessed by cold-
blooded Ovipara a.

j. Vas deferens, dilating before its termination in the cloaca.
k. Ureter.

I. Teres major muscle, the subscapularis and great part of the

scapula having been removed.
m. Eight jugular vein receiving the veins from the oesophagus,

and by virtue of these vessels, as also of a branch of anasto-

» See Jourdain, Sur la Veine Porte Ednale, Ann. Sci. Nat. Ser. iv., torn. 12, i860,
pp. 156 and 359, and plate 4, fig. 2.

N

178

Description of the Plates.

mosis with the left juguLar, attaining, as is usual in birds,

a larger size than that vessel.
n. Right jugular vein in thorax. The junction of the subclavian

with the jugular vein is not effected until some way below

the point on which this line terminates ; a portion of the

former vein is seen in connection with the very short vena

cava superior just above the right bronchus.
0. Vena cava inferior, entering the auricle to the right of and

posteriorly to the entrance of the vena cava superior of the

right side.

p. Lung, showing on its exterior surface indentations correspond-
ing with the ribs.

q. Eight bronchus entering the lung. The right pulmonary
artery and the pulmonary veins which held the same relation
to the bronchus on this side which in the mammal they
hold on the left have been cut away, together with a con-
siderable portion of the spongy tissue of the lung on its
internal aspect. The aorta is seen arching over the bron-
chus, in its singleness contrasting with the aorta of Reptiles,
and in its dextral flexure with that of Mammals. Between
the bronchus and the vena cava inferior we see a portion
of the glandular proventriculus, and immediately above the
bronchus and below the arch of the aorta, which has been
a little displaced upwards, the junction of the fragment
of vein left to represent the subcla\dan trunk with the
jugular.

r. Right innominate artery, which is seen to break up into three
main divisions, the common cai-otid, the axillary and the
pectoral arteries.

s. Great pectoral muscle, the main depressor of the humerus and
wing seen in section on the right side as it arises from the
lower portion of the keel of the sternum and from the
clavicle. Its origin from the external lateral portion and
processes of the sternum is not seen, those parts having
been removed in the dissection; its main tendon is seen
turned back at x ; two other tendons which it gives, one
to the long extensor, the other to the short extensor of the
alar membrane, are not shown in this figure.

t. Second pectoral, the main elevator of the humerus, seen in

Common Pigeon.

179

section along the upper part of the keel of the sternum and
much of its lateral portion. It tapers anteriorly as it passes
along the internal surface of the coracoid to enter the canal
formed for it by that bone together with the furculum and
scapula. This muscle is homologous with the comparatively
insignificant ' subclavius^ of anthropotomy,

Coracobrachialis inferior^ a muscle arising from the inferior
and outer three-fifths of the distal part of the coracoid, and
inserted into the internal and proximal lip of the cup-shaped
pneumatic cavity of the humerus. The opposite lip of this
cavity receives the tendon of the teres major I; and from
the triangular space between the muscular bellies of these
two muscles the subscapularis muscle, together with the
upper portion of the scapula, and a small muscle, the ser-
ratus anticus, which passed between the fibres of the sub-
scapularis to be inserted into the inferior edge of the scapula,
have been removed.

Coracobrachialis superior, a bicipital muscle with a very ex-
tensive origin ; arising, superiorly, from the inner surface of
the vertebral end of the clavicle; inferiorly, from a facet
on the lateral aspect of the upper surface of the sternal
rostrum ; and between these two points of origin from the
upper and inner surface of the fascia connecting the cora-
coid, clavicles, and sternal rostrum. (See Descriptions of Pre-
parations, p. 32.) Its tendon, which is joined by that of the
subscapularis, is inserted proximally and anteriorly to that
of the preceding muscle u. The relations which these
muscles hold to each other are much the same as those
subsisting between the obturator externus and internus,
with which these muscles are serially homologous.

One head of the extensor plicae alaris anterioris longus,
arising from the upper end of the clavicle in continuity
externally with a head of the extensor brevis. These
muscular bellies appear to be divarications of the deltoid,
and to be serially homologous with the outer head of the
pectineus of anthropotomy.

Muscle in connection with the long alar extensor tendons.
Its fibres have in the natural condition of the parts much
the same direction as those of the muscle and of the

N %

180 Description of the Plates.

deltoid; but its orig-in is mainly from the fascia which
covers the biceps in front, and being iaterposed between
that muscle and the tendon of the great pectoral, it is con-
tinued up into the tendinous expanse by which the posterior
layer of the tendon of the great pectoral connecting itself
more or less intimately with the coracoid head of the biceps
obtains an insertion into that bone. The muscle i// is
inserted mainly into the inner of the two tendons at its
distal extremity. This tendon is prolonged down to be
inserted into the radial process of the carpometacarpal bone
which carries the poUex. It is more or less intimately
connected with the two other long extensor tendons from
the muscle w and from the great pectoral, which are here
drawn as one ; as also with the short extensor which is not
shown in this figure.

SO. Tendon of great pectoral muscle turned back and seen to
be folded upon itself so as to form a pouch with its con-
cavity upwards. The posterior portion of this tendon
receives at its lower edge the tendon of a cutaneous muscle
which is figured as attached to its outer angle, and higher
up it receives the main tendon of origin of muscle w , and
is ultimately prolonged either separately or in connection
with the tendon of the biceps up to the coracoid.

X. Biceps. Its tendon is seen running upwards to be inserted
into the internal anterior process of the upper end of the
coracoid; it had a small insertion into the humerus also,
which is not shown here.
Portion of inner tuberosity of humerus which overhangs the
pneumatic foramen of the bone.

z. Gizzard.

For the bibliography of memoirs upon the Anatomy and Physi-
ology of Aves, see Selenka in Bronn's Klassen und Ordnungen
des Thier-reichs, Bd. vi. Abtheilung iv. i, pp. ia-13, 1869.

For the homologies of the Muscles of the Shoulder Joint, see Linn.
Soc. Trans., vol. xxvi., p. 609, 1869.

Common Feog, Rnna Temjmaria.

PLATE III.

Common Frog {Rana Temporaria),

Injected and dissected so as to show its circulatory organs, and especially its two
systems of veins supplying the liver and the kidney, and known as the 'portal'
and the ' renal portal' systems.

The ramifications of a subcutaneous vein^ which must, like
the renal and hepatic systems, have a depuratory action on
the blood in these animals with transpirable skin; the renal,
reproductive, and parts of the muscular, lymphatic, and other
glandular systems of the creature are also shown in the figure.
An injection having been thrown into the ' renal portaF or renal
afferent vein of the left side, in a direction the reverse of that
which the blood took in it during life, that is to say, towards and
not away from the lower extremities, the figure shows that by this
means the greater part or the whole of the main venous system
can be injected. And it shows, secondly, that a very free anasto-
mosis exists, not only between the two renal inferent veins of the
two sides of the body, but also between each renal inferent vein
and the epigastric, one of the main factors of the hepatic inferent,
or true portal system in all cold-blooded air-breathing vertebrata.
Hence the blood from the deeply-placed parts, muscular and other,
whence the radicles of these vessels arise, can return to the heart
tlirough the venous system of either liver or kidney, as circum-
stances may require; whilst the blood of the more .superficially-
placed organs, glandular, cutaneous, and other, is aerated to a con-
siderable extent in the vascular network of the musculo-cutaneous
vein seen at d in the figure. By these arrangements the functions
of the lungs, which are lowly developed, and, in correlation with
the periodically recurring vast turgescence of the generative organs,
of small size in the Amphibia, are efliiciently supplemented.

182

Descri2)tion of the Plates.

The integument has been turned back on the right side, together
with the musculo-cutaneous vein, the superficial branches of which
extend from the knee to the shoulder ; part of the muscular wall
of the body has been removed on that side, but part has been left
in situ J and the main trunk of the musculo-cutaneous vein is seen
crossing" a slip which the obliquus externus muscle receives from the
scapula ; on the left side the muscular and cutaneous elements of
the wall have been turned back whilst remaining in their natural
connection with each other and with the epigastric vein; the
shoidder girdle has been cut through the middle line, and fastened
out on either side so as to expose the lungs, heart, and great
vessels j the liver has been removed with the exception of a small
part of its substance, as have also the stomach and intestines down
to the lower end of the rectum.

a. Intermandibular space. The skin is left in situ anteriorly in

the symphysial angle; immediately posteriorly to its cut
edge is seen part of the mylohyoid or submaxillaris muscle ;
and posteriorly again, and at a deeper level, tlie converging
hyoglossi in the middle line, and on either side of them the
geniohyoids, with a glandular body resting upon each of
them.

b. Tetradactyle hand. The thumb has its basal joint more or less

tumid in this, a male, specimen.

c. Muscles of thigh. The line points to the sartorius, which is

bordered externally by the vastus internus, and internally
by the adductores and recti interni. See Ecker, Die Ana-
tomic des Frosches, p. ii5-

d. Point where the musculo-cutaneous veins, constituted by

factors from the regions of the head and face, as also and
mainly from those of the back and flanks, turn inwards to
pass over a slip going from the scapula to the external
oblique muscle and join the axillary vein. See Ecker, 1. c,
p. 81 ; Gruby, Ann. Sci. Nat., Ser. ii. torn, xviii., p. 224.

e. Vein, called 'epigastric' by Rathke, ' umbilical' by Bojanus

and Jourdain, ' vena portae accessoria' and ' vena abdominalis
inferior s. anterior,' by other authors. This vein is mainly
constituted by the convergence of the two descenduig
branches from the femoral veins seen at / in the figure,
but it receives twigs also from the abdominal parietes, and

Common Frog.

183

a factor of especial significance in the shape of the hypo-
gastric vesico-hemorrhoidal vein from the allantois and
rectum. The occasional pathological distension in liver
diseases of the veins of the anterior abdominal parietes
in the human subject shows that an arrangement may exist
in a rudimentary condition in the higher vertebrata
similar to that shown here to exist functionally between
the epigastric and the parietal veins; and its connection
with a vesico-hemorrhoidal vein, whilst it may be held to
foreshadow the arrangement of the umbilical vein in the
foetus of mammals, puts prominently forward the fact that
anastomoses exist between the portal and systemic veins.
For the 'renal portal' of the Fi'og, see Jourdain, Ann. Sci.
Nat., Ser. iv., tom. xii., p. i8o.
/. Point where the descending branch of the femoral vein of
either side fuses with its fellow to form the trunk of the
epigastric.

g. ' Renal portal/ or renal inferent vein of the right side, being

the other branch of the bifurcating femoral vein, which is
thus seen to be freely and indifferently continuous with the
portal systems of both liver and kidney.

h. Bifid allautoid bladder distended, with ramifications upon it

of the vesico-hemorrhoidal veins which are seen to have
radicles of origin upon

i. The rectum, which is cut short. Cf. Quain and Sharpey,

vol. ii., pp. 478, 479, fig. 325, ed. 7th.

j. A vesicular dilatation developed upon the duct, by which both
testicular and renal products pass down to the cloaca. From
it a vein passes directly into the kidney.

Jc. Vena cava inferior, constituted mainly by the efferent kidney
veins, but receiving also those of the testes and fat bodies.

/. Testis of left side. It has, together with its fellow and with
the kidneys, been displaced a little to the right side. The
vasa efferentia of the testes are seen to pass inwards to the
internal edge of the kidneys, which they enter, 'and some
veins pass in the same transverse direction inwards to join
the vena cava inferior. Between the lower ends of the kidneys
we see a reticular appearance produced by a plexus of arterial
blood-vessels, each accompanied by two lymph vessels, closely

184

Description of the Plates.

apposed to and so appearing to surround it. See Langer,
Lymphgefasssystem des Frosches, 1 866-1 867, Wien. Akad.
Wiss. Sitz. Bericht.
m. Fatty bodies.

n. Spleen. To the left and a little above the spleen are seen the
cut ends of two vessels, one of which receives a factor from
that organ, coming itself from the intestine, and the other
of "which took its origin in the stomach, and, like the
former, joined a branch of the epigastric, and was distri-
buted to the liver, a small portion of which is seen as left
immediately above them.

0. Gall bladder left attached to the epigastric vein by a vein
which passes from it to that vessel.

^. Lung of left side. The cavity seen on the outer side of either
lung has its outer wall constituted by the internal abdominal
muscle, homologous with the internal oblique and transver-
salis which arches inwards in a dome shape, and is connected
with oesophagus, pericardium, and the coracoid and hypo-
sternal bones. In the natural condition of the parts these
cavities are however mainly occupied by the lobes of the
liver, wliich nearly entirely cover the lungs in an anterior
view.

q. Heart. From the base of the ventricle the muscular bulb is
seen to take origin, a constriction known as \he:f return Hal-
leri marking the line of separation of the two organs. The
bulb bifurcates into two great divisions, which again are each
firstly subdivided by two imperfect internal partitions into
three canals, and then subsequently into three perfect tubes,
the carotico-lingual, the aortic, and the pulmonary trunks, of
which the first is most internal and anterior, and the last the
most external and posterior.

q. Musculus bulbus arteriosus, with the auricles one on each
side. It inclines to the left, and is attached on that side to
the ventricle by the frenulum hulhi of Briickc. Denkschrift.
Akad. Wien. Bd. iii., p. 355, 185a.

r. Lingual branch of the first of three trunks arising just inter-
nally to a caverno -muscular dilatation of the artery known
as the ' carotid gland,^ from the outer side of which the
carotid artery, called sometimes the ' ascending pharyngeal,'

Common Frog.

185

passes to the back of the oesophagus in close apposition with
the second main trunk or aorta, with which it is usually-
connected by a duchis JBotalli.
s. Convergence of hyoglossi muscles, which, together with the
diverging arterial trunks, enclose a diamond-shaped space, in
the anterior angle of which a large glandular mass, and
posteriorly in which several smaller masses of similar cha-
racter, are lodged. Into the posterior angle of this space
the right auricle, which is here, as in all cold-blooded verte-
brata, possessed of two auricles, the larger of the two, pro-
trudes itself from behind the arterial trunks. Underneath
these structures the recurrent laryngeal nerve passes to the
larynx.

t. Thyroid proper, of which the glandular masses just spoken of
may be considered as divarications. It is placed just inter-
nally to the jugular vein. The Thymus is not seen in this
figure, lying far back as it does near the angle of the jaw.
See Ecker's Icones Physiologicae, tab. vi., fig. 5 ; Remak,
Entwickelungsgeschichte der Wirbelthier, tab. viii., fig.
8. a. ; Kolliker, Entwickelungsgeschichte, p. 391.

u. Left jugular vein passing down to receive the subclavian, and
thereby constitute the left cava of that side.

Eor the continuity of the lymphatic vessels with the various serous
cavities of the body, see V. Recklinghausen, Handbuch der
Lehre von den Geweben, herausgegeben von S. Strieker,
ii. Lieferung, 1869, p. 22a; Virchow^s Archiv., 1863, Bd. 26,
p. 172; Dybkowsky, Schweigger-Seydel, Dogiel, and Ludwig
in Ludwig^s Arbeiten aus der Physiologischen Anstalt zu
Leipzig, 1867.

PLATE IV.

PLATE IV.

Cellar Slug {Limax Flavus s. Variegatus),

Dissected so as to show its digestive, circulatory, respiratoiy, nervouSj and

reproductive systems.

The muscular envelope has been separated from tlie foot
proper along tlie left side, and turned over to the right, together
with the shield-shaped mantle and the organs it overlies. The
buccal mass and nerve collar, together with the salivary glands,
have been displaced a little to the left, on which side of the animaFs
body the stomach and bilobed liver have been fastened out, as the
generative apparatus has been upon the right. Some of the nerves,
muscles, and arteries have been cut away, but most of the organs
in the animaFs entire system have been displayed in this view. The
oesophagus and buccal mass have been pulled a little forward
through the nerve collar, and occupy much the same position
relatively to it as they do when in life the buccal mass and head is
thrust forward. The two first convolutions described by the intes-
tine have been uncoiled, and the intestine has thus been drawn as
taking a much less sinuous course than it does in nature from its
commencement at the pylorus to the point where it comes into
relation with the dorsal integument and shield, and hooks round
the stem of the muscle which retracts the buccal mass and the
tentacles. The generative organs have been detached from their
normal connections, and are arranged on the right side of the
animaFs head. Their volume, as drawn here, is but small in
comparison with that which it attains in the breeding season.
The upper tentacles, together with the nerves which supply and
the muscles which retract them have been cut through, and turned

188 Description of the Plates.

forward so as to lie between the generative apparatus on the right
and one of the salivary glands on the left hand. One of the lower
tentacles is seen on the right side in the interspace between the
right eye-bearing tentacle and the vestibulum of the reproductive
system.

a. Locomotive disk or ' foot' passing upwards at the sides into
the general muscular envelope of the various organs of the
animal's body, from which it is limited off by a furrow.
Its internal circular coat is raised into two corrugated
ridges along the middle line for the greater part of the
length of the body by the underlying mucous gland. This
gland has its bilaterally symmetrical halves arranged on
either side of a single duct, which again is underlaid by a
large venous sinus, very visible in the living animal along
the middle line of the foot inferiorly.

h. Shield and organs in connection with it projecting out
beyond and above the general muscular envelope of the
body.

c. Stomach arranged, together with the two lobes of the liver,

upon the animal's left.

d. Generative apparatus arranged upon the animal's right.

e. Nerve collar, consisting of two ganglia placed above, or rather

at the sides of, the oesophagus, and two pairs of ganglia
placed below it, and connected with the upper pair by com-
missural cords. The two superiorly placed ganglia are con-
nected with each other by a flat commissural band; and
with the suboesophageal ganglia by a double commissure,
the posterior cord of which joins the upper or parieto-
splanchnic part of the mass formed by the fusion of the
two inferiorly placed pairs of ganglia into a single centrally
perforated body, whilst the anterior cord joins the more
inferiorly placed or pedal portion from which nerves are seen
to pass off" to the foot. The functions of the supra-oesopha-
gcal ganglia may be judged of by the distribution of its
nerves to sensory organs. The nerves which the parieto-
splanchnic ganglia gave off to the retractor muscles, as well
as to the parts their name denotes, have been removed in
the dissection.

/. Stomatogastric ganglion of right side placed in the angle

Cellar Slug.

189

formed by the inferior surface of the oesophagus with the
buccal mass just where it enters it, together with the duct
of the salivary gland. The ganglion is connected by a long
and delicate commissural cord with the supra-oesoj)hageal
ganglion of its own side, and it gives off nerves to the buccal
mass, to the oesophagus, and to the duct of the salivary
gland.

g. Salivary gland.

h. Buccal mass containing the ' tongue.^

i. Semper^s organ ; a structure consisting of cells like those of a

salivary gland, but devoid of a duct, and very richly sup-
plied with nerves from the supra-oesophageal mass, and
supposed by its discoverer to be, possibly, an olfactory
organ. See Semper, ' Beitrage zur Anatomic und Physio-
logic der Pulmonaten,^ in the Zeitschrift fiir Wissenschaft-
liche Zoologie, Bd. viii., 1857, p. ^66. It is large in Li-
maces, though small in the other aii-breathing Gastero-
poda.

j. Coecal projection at pyloric end of stomach. - ^

k. Liver, consisting of two main lobes opening each by a single
duct into the digestive tube along the line of the opening
of the stomach into the intestine.

I. Intestine passing from pylorus to end close by the respiratory
inlet, but a little in front and above it. Its two first convo-
lutions have been uncoiled in separating it from the liver
and reproductive apparatus, but as it approaches the dorsal
integument and shield it describes a curve like that of an
Italic 8. In the first concavity of this curve we see the
stem of origin for the retractor muscles of the buccal mass
and labial tentacles, and at its opposite extremity we see a
straight coecum y pass ofi" and extend nearly to the posterior
extremity of the body.

m. Respiratory orifice, with the 'rectum' curving round it
to open a little above and anteriorly to it. To the
right of the rectum again is seen the duct of the renal
organ.

n. Portion of dorsal integument, by making an incision imme-
diately to the right of which the shell would be found.
Internally to it we see the respiratory sac, with the rami-

190

Description of the Plates.

flcations of the pulmonary veins. The cavity of the respi-
ratory sac is seen to be formed simply by the divarication
of the two layers of the general muscular envelope of the
viscera.

0. Renal organ, placed to the right of the heart in the natural
position of the parts, and giving off a duct which passes
backwards and curves round, inclosing between itself and
its gland a portion of the pulmonary sac, to run in company
with the rectum to open near the anus. See enlarged figure
by Professor Leidy in Binney's Terrestrial Molluscs of the
United States, vol. i., pi. i., fig. iv.

p. Ventricle of bilocular heart.

q. Hermaphrodite gland.

r. Hermaphrodite duct.

s. Albuminiparous gland.

t. Vas deferens becoming distinct from oviduct v sooner than
in Helix or Ai-ion, and richly beset with prostatic glan-
dules.

w. Penis, with part of its retractor muscle left attached to it; the
origin of the muscle having been at a spot on the under
surface of the muscular envelope of the viscera, close to the
arterial outlet of the heart.

V. Oviduct, like the vas deferens, glandular above, and membra-
nous below j and opening into a dilated vagina.

V). Beceptaculum seminis, opening in this species, though not in
the closely allied Limax Cinereus into the vagina.

X. Pedal portion of the suboesophageal nerve mass, enclosing,
together with the parieto-splanchnic, an orifice through
which the anterior aorta passes. The line is drawn to a
spot where in Helicidae the otic vesicle is readily found,
but where in Limax it is not easy to convince oneself that
it exists, even as a rudimentary organ, without the use of
reagents, such as the oxalic acid recommended by Lacaze
Duthiers.

V Coecum passing off from intestine just before it passes into rela-
tion with the pulmonary cavity, and reaching down nearly
to the termination of the body cavity.

z Retractor muscle of the buccal mass and the tentacles. Its
fascicles distributed to the parts mentioned passed with the

Cellar Slug.

191

oesophagus through the nerve collar, being separated from
the aorta by the parieto-splanchnic portion of the suboeso-
phageal mass. They have been cut away in this Prepar-
ation.

For the anatomy of the Pulmonate Gasteropoda generally, see
Semper, in Zeitsehrift fiir Wiss. Zoologie, Bd. viii., 1857.

For figures of the anatomy of Limax, see Leidy, in vol. i. of
Binney's Terrestrial Molluscs of the United States, pi. i.

For the reproductive system, see Baudelot, Ann, Sci. Nat.,
tom. xix., pi. 3, fig. 17, 1863.

For the essential connection of the acoustic nerve with the supra-
oesophageal ganglia, which has been overlooked on account of
the close apposition to the pedal ganglia of the vesicles ap-
pended to those nerves, see Lacaze Duthiers, L^Institut, No.
1 831, translated in Monthly Microscopical Journal, Feb. i,
1869 ; and for instances of the otic vesicle and its nerve
maintaining in actuality those morphological relations undis-
guised by approximation to the pedal ganglia, see Gegenbaur's
and Souleyet's figures of the Heteropodous Carinaria and Pte-
rotrachea in V. Carus' Icones Zootomicae, tab. xx., fig. 1%-
Gegenbaur, Untersuchungen iiber Pteropoden, und Heteropo-
den, 1855, tab. vii., fig. ij Vergleichende Anatomic, p. 325,
fig. 83.

The two sets of organs of special sense, the auditory and the
ophthalmic, are thus seen in Gasteropoda to be both in connection
with the same nerve-centres. The attachment, howevei-, of the otic
vesicle and nerve can scarcely be different in reality from what it
is in appearance in the Lamellibranchiata (for which see pi. v. j') ;
and the multiplicity of the ' eyes' in Peeten and Spondylus set
along the border of the mantle, to the nervous supply of which
both cephalic and parieto-splanchnic ganglia contribute, would lead
us to expect variability rather than fixity in the connections of the
organs of special sense in Mollusca. The varying allocation of the
organs of special sense in the two sub-kingdoms, Arthropoda and
Vernus, would appear to point in the same direction.

I

I

PLATE V.

Fresh-water Mussel (Anodonta Cygnea),

Dissected so as to show its muscular and nervous systems, as well as certain other

organs in relation with them.

The animal has been taken out of tlie shell ; the gills have been
removed on the left side, as also the mantle, together with the
labial tentacles and parts of the pericardium, and of the organ of
Bojanus of the same side.

a. Right mantle lobe, free along its ventral edge.

a . Fimbriated portion of mantle corresponding to the inlet by

which water is drawn into the branchial cavity.
a" . Dorsal raphe along which the two halves of the mantle

meet, and are more or less united.
h. Foot.

c. Gills of right side.

c'. Process passing from external gill to join the mantle, just
where its fimbriae cease and its anal region commences.

d. Anterior adductor.

e. Posterior adductor.

f. Posterior retractor of the foot, passing to be inserted into

either valve, anteriorly and superiorly to the posterior ad-
ductor, the scar or muscular impression of the two being
more or less confluent. Its muscular expansion in the foot
is especially well developed along the free or ventral edge of
the foot, but it inter-digitates very freely with the pro-
tractor pedis, though it lies for the most part at a lower
level than that muscle.

o

194

Description of the Plates.

g. Protractor of the foot. This fan-shaped muscle spreads over
the external surface of the foot^ from an insertion into the
shell, a little superiorly to the point where the pallial line
joins the impression for the anterior adductor. It must
act consequently, as an antagonist to the preceding and suc-
ceeding muscles. Its impression is distinct in this animal
from that of the adductor.

Ti. Anterior retractor of the foot. The fibres of this muscle take
origin from a point in the shell, towards the dorsal aspect
of the anterior adductor, though some way from its dorsal
border. They spread thence into the foot especially along
its anterior edge, and down as far as its anterior angle, oc-
cupying for the most part a deeper level than the preceding
muscle. Some of its fibres, however, spread superficially
over the liver region dorsally. Its action is that of a
powerful retractor of the foot mass.

K. Smaller retractor muscles with insertions just anteriorly to
the umbones, whence they radiate over the regions of the
stomach, and towards the pericardium.

i. Labial ganglion lying upon the anterior retractor, and in the
angle between that muscle, the anterior adductor, and the
protractor pedis, above the entrance to the mouth.

j. Cord of commissure passing from labial ganglion to pedal.
The pedal ganglion of each side gives off twelve nerves, six
from its neural, and six, more slender, from its lateral surface.
They are not figured in this plate.

/. Auditory vesicle appended to pedal ganglion. This vesicle
is ordinarily found to be appended to a branch given oflf
from the most backwardly-placed but one of the posterior
branches given oflE" from the pedal ganglion. It is not
always to be found symmetrically developed on both sides,
and, when found on one side only, it has been found to con-
tain two otoliths. It is situated in a part of the foot narrow
from side to side, at the junction of its anterior two-thirds
to its posterior third, and near to the purely muscular
portion of the foot, into which the viscera do not enter.
Cf. Moquin Tandon, Hist. Mollus. i., p. 136; Duvernoy,
Memoires de I'Institut, torn, xxiv., p. 96.

Tc. Cord of commissure between labial and parieto-splanchnic

Fresh-water Mussel.

195

ganglia. It passes between the fibres of tbe retractor pedis
anterior and those of the protractor through the upper part
of the foot, just internally or inferiorly to the generative
orifice, t ; then through the glandular portion of the organ
of BojanuSj s ; and across the tendon of the retractor pedis
posterior just where it bifurcates for insertion into either
shellj to end in the parieto-splanchnic ganglion.

I. Parieto-splanchnic ganglion. The two ganglia of the two
sides of the body are closely apposed, so as to form a trans-
versely oblong mass, which however still retains an in-
dication of its morphological duality in the bilobed con-
formation, which is somewhat exaggerated in this figure,
and is much less definite than that of the pedal centres
between j and f. Two nerves are figured in connection
with it, one, a parietal nerve, going to the mantle, the
other, a splanchnic nerve going to the gill.

m. Rectum ending in the anal compartment of the mantle, a
little beyond the posterior free edge of the posterior ad-
ductor. A delicate nerve is figured by Duvernoy, I. c, as
passing to it from the parieto-splanchnic ganglion.

n. Heart ; the letter pointing to the slit left by removal of the
left auricle. The rectum passes through the heart, having
commenced by emerging from the foot-mass, in close con-
nection with the aorta anterior, which lies above it and
below the mantle raphe, at a point corresponding to the
vertical plane of the orifices of the generative gland and
of the organ of "Bojanus.

0. Pericardial space into which open the glandular portions of the
organ of Bojanus, as also certain orifices belonging to the vas-
cular system ; see V. Hessling, ' Die Perlmuscheln/ p. :339.

p. Opening by which the excretory portion of the organ of
Bojanus communicates with the branchial cavity.

q. Opening by which the excretory portion of the organ of
Bojanus communicates with the secretory.

r. Wide opening by which the excretory portion of the organ
of Bojanus of one side communicates with that of the other.
This opening does not exist in Unio margaritifer. The
two secretory sacs are similarly connected at a deep level
in the same plane.

o 1

196

Descrijption of the Plates.

s. Secretory or glandular portion of tlie organ of Bojanus,
reaching from the level of the anterior end of the peri-
cardial space to the under surface of the posterior adductor.
It opens into the pericardium hy a canal along which a
bristle has been drawn as passing. It is seen to be covered
by the excretory half of the bisacculate organ for a space
corresponding with the under surface of the pericardium.
With this sac it is seen to communicate by a very fine
orifice at q. Posteriorly to this point it is prolonged into
a convolutionary mass^ roughly drawn here in section as
sub-triangular, in relation with the posterior adductor and
the tendon of the posterior retractor. These glandular
lamellar sacs communicate freely with each other_, as do
also the excretory sacs in this species.

t. Orifice leading to ramifications of the duct of the generative
gland. This orifice is in the Anodon, though not in the
Unios, concealed by the attachment of the inner gill-lamina
to the visceral mass. See V. Baer, Meckers Ai-chiv., 1830,
p. 318.

From this semi-diagrammatic figure, the course which the ova
take in passing from the generative orifice, f, to the external
gill-cavity, where they meet with the spermatozoa inhaled
with the water they breathe, and where they go through
certain stages of development, may be understood. The ova
are extruded from the orifice specified by the contraction of
the several muscles, ff, h, //, and /; the shell valves being
appressed by the adductors, cl and e. When they pass out
from this orifice, they pass along a canal, which for the
first part of its course corresponds in direction with the
nerve cord seen passing through the organ of Bojanus to the
parieto-splanchnic ganglion, I. This first part of the canal
is divided into three portions. The first of these is formed
by the attachment of the innermost gill-lamina to the vis-
ceral mass, and into it the orifice t opens. The second is
under ordinary circumstances only a demi-canal, but is
completed during the act of the extrusion of the ova, by
the close apposition of the inner gill-lamina to the side of
the visceral mass, which under these circumstances becomes
more globidar superiorly than when quiescent. The third

Fresh-ioater Mussel.

197

portion begins immediately posteriorly to the tendon of the
posterior retractor pedis, and extends as far back as the
entrance of the branchial nerves into the gill. It is bounded
below by the commissure of the two internal gills of the
two opposite sides of the body, and above, like the rest
of the canal, by the organ of Bojanus. Just beyond the
line of entrance of the gill-nerves, the canal thus made up
of three segments opens into a space, into which the ex-
ternal gill's cavity also opens ; a canal having been left
along the dorsal attached border of that gill by the failure
of the dissepimental bands which connect the lower three-
fourths of its two lamellae together, to be developed there.
And as the rectum m also opens into this space, it may be
called a ^cloaca/ Now it is easy to see how, under the
extruding action of the foot muscles, the ova will succes-
sively be pressed through the canal described into this
small cloacal space. When there, if the shell or the mantle
lobes are kept appressed posteriorly, or, as in the natural
position of the animal, superiorly, it is plain that they
must regurgitate, as additional relays of ova find their
way into the cavity, into the external gill-cavity from the
point c' forwards.
In this figure the nerve system is of a somewhat smaller size
than it is seen to possess, except when viewed in strict
profile, in nature ; and it has been owing to the necessity
for maintaining this position, which the demonstration of
the relations of the pericardium, and the two sacs of the
organ of Bojanus involved, that the distinction between the
muscular free border and the main mass of the mantle has
not been shown. The muscular portion of the foot is
figured in a condition of extretne contraction.

For excellent figures of the nerve ganglia seen from below, with
their branches and commissural cords, see Duvernoy, Mem.
Acad, des Sciences, tom. xxiv., 1854, pi. 7, fig, 2, pi. 8 and 9,
figs, I and 2,

For a diagrammatic figure of the organ of Bojanus, see Lacaze
Duthiers, Ann. Sci. Nat,, Ser. iv,, tom, iv,, 1855, reproduced
by V. Hessling, I. c, pi. v., fig, 6.

198

Description of the Plates.

For a full account of the anatomy of the organ, see Langer,
Denkschviften Akad. Wiss. Wien. xii., Bd. 1856, p. 39, Taf. i.,
figs. 3 and 4.

For figures of the muscular system, see Poll, Testacea Utriusque
Siciliae, tab. ix., fig. 2 ; and for the heart and rectum, the
same plate, fig. 12 ; and Langer, I. c, Taf. ii., fig. 8,

For an explanation of the route taken by the ova and spermatozoa,
in these dioecious animals, see V, Baer, Meckel''s Archiv.,
1830, p. 313; and also V. Hessling, Zeitschrift Wissenschaft
Zoologie, X., i860, p. 358.

For the various parts of the Lamellibranchiate organism, which in
different species may be modified so as to serve as marsupia
for the lodgment of ova and embryos, see Bronn, Klassen und
Ordnungen des Thier-reichs, Bd. iii., p. 442, ibique citata.

V

I

i

PLATE VI.

CocKEOACH^ Perijdaneta Orientalis.

PLATE VI.

Common Cockroach {Feriplaneta Orientalis),

Female,

Dissected so as to show its digestive, nervous, and reproductive apparatus ; the
'fat body,' and a considerable portion of the dorsal integuments having been
removed.

Of the external organs are seen tlie multi-articulate antennae^
the segmented anal appendages or ' cerei/ the compound eyes, por-
tions of the epicranium, of the pronotal, mesonotaJ, and metanotal
elements of the thoracic segments, and of the eight dorsal elements
of the abdominal segments ; and finally, the three legs articulated
to the three thoracic segments on either side, and consisting each
of a proximal segment known as the coxa, a second and much
smaller segment, distinct in these, though not in the saltatorial
Orthoptera, from the coxa, and known as the trochanter ; a third,
the fermir, beset below with spines ; a fourth, the tibia, more richly
armed with spines than the femur ; . and the fifth, the tarsus itself,
which is quinque-articulate.

a. Antennae consisting of three elongated basal segments, and

a multi-articulate appendage made up of as many as ninety-
two joints. The antennae of Insects correspond to the
so-called ' antennules' of Crustacea, and they are here made
up of large and small joints in similar proportions, see
p. Ill, supra.

b. I, b. 2, b. 3. Tibiae, sub-quadrangular in shape, and beset

along their two narrower sides with spines.

c. ' Cerci anales,"* consisting of twelve segments, the terminal

one conical, the others thickly beset with liairs. As sexual
characters may be noted the absence of the sub-anal styles

200

Description of the Plates.

possessed by the males^ and the median emargination of
the supra-anal dorsal plate with which the cerci articulate.
These cerci appear to represent the processes which the last
segment of the post-abdomen so frequently gives off in
certain lower Crustacea, as e. g. Apus, Cyclops, Lynceus,
Caligus ; and, like the line of fission between the second
pair of maxillae and the three basal joints supporting the
antennary flagellum, to be structures by possessing which
the Orthoptera resemble the Crustacea, see p. iii, supra;
and Rathke, Morphologic, p. 115.

d. Nerve ganglion developed upon the nervus recurrens, and

seen to give off a nerve on either side, which passes back-
wards upon the crop and has itself fusiform dilatations of
a ganglionic character developed upon it. From the tri-
angular ganglion, a nerve has been figured and described
as passing off to the salivary glands.

e. Common duct communicating with the two lobes of the

dendritic salivary gland. The ducts of the two salivary
glands fuse mesially vdth each other, in the angle formed
by the convergence of the ducts of the two salivary bladders
or reservoirs; and the common duct thus formed by the
ducts from the two glands, fuses subsequently with the
common duct from the two reservoirs, so that the two
compound ducts find an outlet into the mouth by means
of a short common canal. The figure does not accurately
reproduce this arrangement, which cannot be demonstrated
to the unassisted eye. All the four ducts and the compound
ducts have their internal chitinized coat spirally thickened
so as to resemble tracheae.

f. Salivary bladder.

g. Gizzard communicating inferiorly with the chylific stomach,

through the intermediation of a short segment of small
calibre.

h. Whorl of eight coeca, analogous probably to a liver, arranged

round the commencement of the chylific stomach, and re-
sembling the simple hepatic coeca of Hedriophthalmatous
Crustacea.

i. Chylific stomach, smooth externally as is the upper half of

the homologous segment in the Gryllotalpa, and limited

Common Cockroach.

201

inferiorly by the insertion of the Malpighian tubules in a
circle around the digestive canal.

j. Malpighian tubules, in number from twenty-four to thirty;
and by their insertion in a zone around the lower end of
the chylific stomach, marking- the commencement of the
short segment which may be spoken of as the small in-
testine.

k. Small intestine.

I. Large intestine or colon j found ordinarily to be in its upper
part distended with the refuse of the ingesta, and to be
below of smaller calibre, a:nd corrugated so as to present a
beaded appearance.

m. Rectum divided into longitudinal areae by muscular bands,
which alternate with internally placed lamelliform produc-
tions of the intestinal walls. The ridges thus developed
upon the rectum receive in the larvae of certain of the
Libellulidae a very rich supply of tracheae, and, together
with a valvular apparatus developed from the caudal tegu-
mentary skeleton, constitute their aerating organ.

%. First abdominal ganglion, closely approximated to the third
thoracic, and placed at a little greater distance from the
second abdominal ganglion posteriorly. The sixth abdo-
minal ganglion should have been drawn as somewhat heart-
shaped, but laterally constricted so as to have the appearance
of being made up, as the history of its development, of its
comparative anatomy, and of the distribution of its nerves
shows it to be, of two distinct ganglia. The two oviducts
pass to their point of fusion from the outside of the angle
bounded by the nerves, seen to pass ofi' from this ganglion ;
the receptacula seminis, which are small, and not given in
this figure, are situated within that angle and at its apex ;
distally to them, but within the angle, the two ducts of the
numerous colleterial glands pass to the orifice within which
they open on the sternum of the tenth segment. The first
sub-oesophageal ganglion is not seen in this figure, being, as
always in insects, in such close apposition to the supra-oeso-
phageal or cerebroid ganglia, as to have been sometimes,
but inconveniently, described, as together with them making
up a ^ brain.' Counting however this ganglion whence the

Description of the Plates.

mandibles^ maxillae and labium receive their nerve supply,
we find that the entire ventral cord is made up of" ten
ganglia^ the last of which may be taken as representing
two. This number is less by one than that of the Lepi-
dopterous larva^ and^ on account of the large size of the
third thoracic ganglion, we may suppose that in the Cock-
roach, the ganglion homologous with the fifth post-oral
ganglion of the Caterpillar has become fused, if it was not
originally connate, with the posterior thoracic ganglion.
Thus the thoracic ganglia of the Orthopterous insect, which
remain always as distinct masses in this order as also in
the Coleoptera, will correspond, as to the elements out of
which they are composed, with the bilobular centrally per-
forated mass whence the three pairs of legs and the wings
are innervated in Lepidoptera. The six posteriorly placed
ganglia of the Orthoptera and of the Caterpillar will corre-
spond with each other ; and, allowing for the disappearance
in the butterfly of the sixth and seventh post-oral ganglia
of the larva, with the four posterior ganglia of the perfect
Lepidopterous insect.
' Verticillate' ovary of right side, consisting of eight egg-
tubes, connected by a suspensory ligament, which is made
up by the fusion of filaments given off from their respective
apices, and prolonged up to an attachment in the dorsal
region of the thorax. The ovarian tubules are here figured
as opening into the convex end of a pear-shaped oviducal
infundibulum ; and this apical insertion has been supposed
by Leon Dufour and Fischer to constitute an important
difference between the arrangements of the female repro-
ductive apparatus, as existing in the Blattinae and in other
Orthoptera. The pyriform shape however of the oviducal
infundibula depends merely upon temporary distension;
and when these receptacles are not in this condition, the
egg-tubes may be seen to have the same lateral insertion as
those of other Orthoptera ; as, for example, the Forficula,
as figured by Fischer in his work, Orthoptera Europaea,
tab. i., fig. 4; or the Mantis Religiosa figured by Leon
Dufour in his work, Recherches Anatomiques et Physiolo-
giques sur les Orthopteres, les Hymenopt^res et les Neurop-

Common Coch'oach.

203

teres^ pi. iv.^ fig". 42. The two infundibula pass ventrally
to the terminal nerve structures and oviscapt, to form a
common vagina, which opens between the sterna of the
eig-hth and ninth abdominal segments.
p. ' Colleterial ' or ^ sebaceous^ glands of the left side. These
glands consist of long* delicate tubules, the contents of
which are by no means always uniform in colour. The
very numerous tubules of either side join a single stem,
and the two ducts thus formed pass down near the middle
line, and within the angle bounded by the nerves of the
last abdominal ganglion, to end within a single orifice on
the sternum of the tenth abdominal segment. Anteriorly
to the two coUeterial ducts, and occupying the apical
portion of the angular space limited by the nerve structures,
may be found the receptacula seminis, which consist of two
short tortuous coeca, opening by a very short common duct
upon the sternum of the ninth segment. Spermatozoa are
said by Siebold to be found in both these coeca ; otherwise,
as one is of smaller calibre than the other, we might have
considered one to be a receptaculum seminis and unpaired,
as usual in insects, and the other to be a ^ glandula appendi-
cularis,^ such as is so frequently attached to the recepta-
culum seminis in other insects. In thus possessing two
receptacula seminis instead of one, as also in having eight
ovarian tubuli instead of twelve, as is usually the case in
Orthoptera, the Cockroach presents us with more or less
aberrant arrangements. Figures of the various forms which
the female generative organs may assume in the Orthop-
terous Termes Lucifngum, may be found in the plates ap-
pended to M. Lespes-" memoir upon that species, in the
Annales des Sciences Naturelles, Ser. iv., tom. v., pi. 6,
figs. 34-27, where the colleterial glands and receptaculum
seminis will be seen to present much the same arrangement
as that which has here been described in the Cockroach.

For the morphology, anatomy, and development of Insecta, the
numerous memoirs by Sir John Lubbock, in the Transactions
of the Royal and Linnaean Societies from 1857 onwards,
should be consulted. Amongst these, see for Parthenogenesis

204 Description of the Plates.

in the Articulata generally, Phil. Trans., for 1857, vol. 147,
pp. 95~99 '} foi' tliG structure of the ova, pseud-ova, ovaria,
and pseud-ovaria of Insects, ibid., 1858, vol. 148, pp. 341-369,
1 861, vol. 151, pp. 620-623; for the functions and structure
of the tracheae. Linn. Soc. Trans., 1865, vol. xxv., p. 480;
and for the subject of insect-metamorphosis generally, ihid.^
pp. 485-491.

For the asexual propagation of Diptera, which takes place in
larvae, and was at first supposed to do so by metagenesis inde-
pendently of any ovarium or pseud-ovarium, see N. Wagner,
Zeitschrift fur Wiss. Zool., xiii., 1863, p. 513 ; Pagenstecher,
I.e., xiv., 1864, p. 410; Leuckart, Wiegman^s Archiv., 1865,
p. 286, translated in the Ann. and Mag. Nat. Hist., iii., 17,
March, 1866.

For an account of the internal and external anatomy of the order
Orthoptera and of the family Blattinae, see Fischer, Orthop-
tera Europea, pp. 5-32, pp. 84-88, pis. i., ii., and vii.

For an account of the receptacula seminis, see Siebold in Miiller's
Archiv., 1837, p. 408. For the opening of these and the
other ducts of the reproductive apparatus, see Huxley, Linn.
Soc. Trans, ii., vol. xxii., p. 231, 1858.

For number of joints in antennules of Crustaceans, see Spence Bate,
British Sessile-eyed Crustacea, Introduction, p. xi. ; and for
correspondence of the antennae of Insects, with imperfect
metamorphosis both in the larval and in the adult state with
the antennules of Crustacea, see Zaddach, Die Entwickelung
des Phiyganiden Eies, p. 86.

For the anal respiratory apparatus of the Libellulidae, which may
be considered to be foreshadowed in the longitudinal folds
developed upon the rectum of the Cockroach, see Dufom*,
Ann. Sci. Nat., Ser. iii., torn, xvii., 1852, p. 65, pis. iii., iv., v.;
Leydig, Lehrbuch der Histologic, p. 337.

1

PLATE VII.

Common Crayfish {Astacus Fluviatilis),

Male,

Dissected so as to show its nervous, digestive, circulatory, and reproductive systems
in situ J the various organs having been exposed in an antero-posterior vertical view,
by the removal of the teguraentary skeleton, the muscles, and the hepatic lobes of
the left side.

a. Oesophagus leading vertically upwards from the moutli into

the stomach. The labrum^ the free edges of the mandibles,
and of the two maxillae, are faintly indicated on the right
side of the mouth anteriorly to the three foot-jaws.

b. Cardiac portion of stomach. Superiorly and anteriorly the

stomach is still retained in its natural position a long way
anteriorly to the line of the entrance of the oesophagus,
the anterior gastric muscles which took origin superiorly to
the supra-oesophageal ganglia, o, from the under surface of
the ventral wall of the .\ollow rostrum, and attached them-
selves to the cardiac plate, having been left intact ; whilst
the anterior wall of the stomach has been displaced a little
backwards in order to give a better view of the stomato-
gastric nerves.

c. Lateral valvular prominence of pyloric portion of stomach.

d. Hepatic lobes of right side where they came into apposition

with those of the left side which have been now removed
along the infero-median line.

e. Orifice by which the hepatic lobes of the left side opened into

the digestive tract immediately posteriorly to the pylorus,
and below the coecal process, n.
f Intestine passing with the straight course characteristic of
Crustacea, with the exception of Lynceus, to the anus.

206

Descnption of the Plates.

g. Anus, opening on the inferior surface of the ' telson^ in uncal-

cified membrane, just anteriorly to the line of junction of
its anterior and posterior halves.

h. Heart, showing one of the lateral venous orifices, and its

posteriorly placed bulbus arteriosus dividing into two main
branches, the larger one of which passes vertically down-
wards at j, and is known as the sternal artery ; whilst the
other passes along the dorsal surface of the intestine at j,
and may be called the post-abdominal artery, and taken to
represent the posterior chambers of the elongated vasiform
heart seen in many lower Crustacea.

i. Post-abdominal artery, taking a course superiorly to the intes-

tine, and inferiorly to the extensor muscles of the posterior
segments.

y. Sternal artery passing down towards the orifice in the com-
missural cord connecting the third and the fourth abdominal
ganglia.

k. Hepatic artery of the left side, passing down from the heart
on to the pylorus towards the hepatic lobes of that side
which have been removed.

I. Anterior left lobe of testis.

I'. Azygos lobe of testis placed posteriorly to the paired lobes
of the two sides with which it is continuous.

m. Convolutions of vas deferens of left side, in length equal to
that of the entire body. ' They probably secrete the agglu-
tinating matter of the spermatophores. There are in most,
if not all, Crustacea and Myriapoda, and in the higher
Arachnida, two separate outlets for the vasa deferentia, one
on either side of the body, howsoever much intercommuni-
cation of the glands or ducts may take place distally to the
outlets. The Insecta, on the other hand, have ordinarily a
single ductus ejaculatorius, as also a single vagina, into
which the generative ducts of both sides of the body open.
In both Decapodous and Hedriophthalmatous Crustacea, the
male generative outlet is to be found in relation with the
last segments, and the female with the last but two of the
ambulatory or abdominal segments.

n. Coecal sac, the rudiment of the yolk-sac of the embryo. This
sac is apparently the homologue of the two coeca, which in

Common Crayfish.

•207

Bracliyura oiDen into the upper part of the pyloric part of
the stomach, just posteriorly to its valvular apparatus, and
close to its opening" into the duodenum. In Brachyura there
is a third sac homologous with the single sac observable in
some, and the two sacs observable in other Amphipoda as
opening into the duodenum just before its junction with the
rectum, and sometimes called a ^ renal organ/ It is not
found in the Fresh-water Crayfish, though it is in the
Lobster.

0. Supra-oesophageal ganglionic mass, immediately posteriorly to
the scaphocerite or squamiform exopodite of the inferior or
externally placed pair of antennae, the ^ antennae properly
so called. The likeness which this ' scale' of the antennae
bears to the exopodite of the sixth abdominal segment is, as
Fi'itz Miiller has remarked, curiously illustrated by the fact
that its ordinary function of lodging the auditory organ is
sometimes, as in Mi/sis, transferred from it to that appendage.
Both facts find their explanation in the view which regards
both segments and both sets of appendages as belonging to
a 'primitive body' corresponding with that which the
Naupliiform larvae of Cirripedia, Copepoda, and Phyllopoda
bring with them out of the egg. The greater relative size
of the scaphocerite is one of the external points of difierence
between the Crayfish and the common Lobster.

p. First post-oral ganglion, supplying the mandibles, the two
pairs of maxillae, and the three pairs of foot-jaws, or thoracic
appendages. In the developing Astacus this mass consists
of six pairs of ganglia, in correspondence with the six sets
of appendages it innervates. In Insects, the first post-oral
ganglion is always distinct from the thoracic ganglia, whilst
in all other Arthropoda it is fused with more or fewer of them.

q. Nervus reeurrens, formed by the junction to an azygos nerve,
homologous to the nervus reeurrens of Insects, and repre-
sented by the single trunk q', of two pairs of nerves, which
arise from the nerve-collar on either side of the oesophagus.
This compound nervus reeurrens of the Crayfish passes up
the anterior face of the oesophagus and stomach, and on
the angle formed by the junction of this anterior with the
dorsal wall of the organ, it has a ganglion developed upon

208

Description of the Plates.

it between the anterior g'astric muscles, from which, as also
from its posterior prolongation, nerves are given off down-
wards on either side of the stomach.
q. Azygos nerve, passing downwards from the middle of the
posterior edge of the supra-oesophageal mass to meet two
pairs of nerves given off from the thickenings developed
upon the commissural cords of the nerve collar as they cross
the oesophagus, and form with them the compound nervus
recurrens, q. The forward position of the supra-oesophageal
ganglionic mass would appear to render it impossible for the
Crayfish to have any ganglion fi-ontale developed upon
such as Insects possess. Leydig, however, appears to have
discovered such a ganglion in the Oniscus. This nerve, q',
seems to correspond with the nerve-cord passing backwards
from the ganglion frontale in Insects before it receives any
branches of communication fi-om the paired ganglia; the
compound nerve, q, would then correspond to the similarly
compounded nerve of Insects, upon which gangha are
frequently developed successively from before backwards
in relation with the digestive tract, whilst the ganglion
frontale must be considered to have coalesced with the
supra-oesophageal mass.
r. Fifth abdominal, or sixth post-oral ganglion. It is more
closely approximated to the ganglion next in front of it
than any of the ganglia either in front of or behind it are
to each other. Posteriorly to it are the six post-abdominal
ganglia. From this ganglion and the two in front of it,
long nerves pass off upwards to the reproductive organs and
the superiorly placed muscles.
s. Multi-articulate flagellum of inferior or outer pair of antennae,
the ' antennae,' strictly so called, supported by a peduncle
consisting of five joints, to which the scaphocerite and a
smaller calcified nodule are laterally articulated.
i. Paired flagella of upper pair of antennae, or anteuuules, carried
by a triarticulate peduncle, as are the antennae of Orthop-
tera. On the larger of these two flagella certain delicate
membranous cilia are to be found, which, though of very
various forms, are yet constant in Crustacea, and are sup-
posed to be olfactory organs by many authors.

Commo7i Crayrfish.

209

u. Second joint of posterior thoracic appendage^ or ' maxilliped,^
or ' foot-jaw/ This joint, as in the large cheliferous append-
age V 1, next behind it, represents two joints, the basipodite
and the ischiopodite of the normal seven-jointed endopodite,
as seen in v 2, v v v 5. Its antero-internal edge is den-
ticulate^ as in the Lobster, but its serratures are concealed
by a fringe of setae.

V I. First abdominal appendage, modified terminally by the pro-

duction of the distal outer angle of its penultimate joint or
propodite so as to form a pair of pincers with the opposed
last joint, or dactylopodite. Two other joints, the ^carpo-
podite^ and ^ meropodite/ are shown in this figure ; the two
basal joints are not seen. The two first abdominal legs are
not symmetrically developed in the Crayfish, nor in the
Marine Lobster, foreshadowing thus the extreme inequality
seen in the Hermit-Crabs.

V 2 and V 3. Second and third pairs of abdominal or ambulatory

legs, differing ft-om v i in their smaller size, and in not having
the second and third joints fused. It is at the interval
between the first and second joints, the 'coxopodite' and the
'basipodite,'' that the power of casting ofi" a limb, in conse-
quence of a fright or injury, is put in play by Crustacea.

V 4 and V 5. Fourth and fifth pairs of the ambulatory legs of the

Decapod. The two terminal joints do not form pincers,
otherwise they resemble v 2 and v 3. The vas deferens opens
in the coxopodite or basal joint of v 5.

w I and w 2. The appendages of the two first post-abdominal seg-
ments modified so as to form an accessory copula tory organ,

w 3, w 4, and to 5. Appendages of the third, fourth, and fifth post-
abdominal segments, consisting each of two basal joints,
which serve as a pedicle to two multiarticulate filaments
representing an exopodite and an endopodite. The inner of
these two filaments has its first joint longer and larger than
the other joints in either filament. This greater relative
importance of the endopodite is more plainly seen in the
antennae and thoracic limbs, where the exopodite is markedly
smaller than the endopodite, and most plainly in the abdo-
minal limbs where it is absent, or only represented by the
constriction marking the third joint, or ' ischiopodite.-'

210

Description of the Plates.

w 6. Appendag-e of sixth post-abdominal segment, forming the
right Literal element of the swimmeret. It consists of a
single basal joint, supporting a biarticnlate squamiform exo-
podite and a uniarticulate endopodite, which reverse thus
the positions of relative size held by these elements in the
segments anterior to the swimmeret. The telson is interposed
mesially between the two appendages of the sixth post-
abdominal segment.

X. Flexor muscles acting on the swimmeret and post-abdominal
segments in the animaFs rapid movements ; its slower
movements being dependent upon the ambulatory feet.

y. Extensor muscles^ in two layers like the flexors, but of
much smaller size.

For a full account of the anatomy of the Crayfish, see Huxley,
Medical Times and Gazette, Feb. 7, 1857, et seqq.

For figures of the various systems and organs of the animal, see
Brandt, Medizinische Zoologie, Bd. ii., tab. xi., pp. 63-64.

For the stomatogastric system, see Brandt, Ann. Sci. Nat., Ser. ii.,
torn, v., 1836, pi. iv., figs. I, 3, pp. 87-91.

For the olfactory (auditory?) organ, as carried by the internal or
superior pair of antennae, see Gerstaecker, Bd. v., p. 357, and
La Valette, Leydig, and Fritz Miiller, cit. in loc. See also
Spence Bate, Sessile-Eyed Crustacea, vol. i., p. ix.

For the formation of the coecal sac opening into the commencement
of the duodenum out of the yolk-sac, see Rathke, Entwick-
elungsgeschichte der Flusskrebses, p. 64. For other coecal
appendages to the digestive tract of Crustacea, see ISIilne Ed-
wards, Hist. Nat. des Crustaces, 1834, pp. 76, 77; and for the
formation of the liver by a bilateral out-pouching of the yolk-
sac, see Rathke, c. p. 49, and Abhandlungen zur Bulduugs-und
Entwickelungsgeschichte, Theil, i., 1832, p. 15; Theil. ii., 1833,
p. 78, in which latter memoir the relation of intestinal tract and
yolk-sac is shown to be different in Oniscus and Astacus.

PLATE VIIT.

PLATE VIII.

Earth Worm {Lumhricus Terrestris).

The fifteen anterior segments of an Earth Worm {Lumbricus Terrestris), numbered
from before backwards, the upper lip counting as the first segment.

The integument lias been divided^ except in the first segment,
down the middle dorsal line, and the greater part of the digestive
tract has been removed, together with the pseud-haemal vessels,
so as to show the nervous, muciparous, and reproductive organs.

a I. Bilobed supra-oesophageal ganglionic mass; giving off from
either outer angle a nerve which bifurcates very soon after
its origin, and passes to distribute itself in the tactile upper
lip.

a 2. Visceral or stomatogastric system of the right side, con-
sisting of a long ganglion lying upon the lateral wall of the
pharynx, and running parallel with the cord of commissure
between the supra-oesophageal and the sub-oesophageal gan-
glia, with which it communicates by several roots anteriorly,
as it does posteriorly with a reticulate ganglionic plexus upon
the posterior part of the pharynx. This plexus lies imme-
diately externally to the mucous lining of the pharynx,
and some of the glandular and muscular tissues of its
outer walls must be cleared away in order to demonstrate
it clearly. Figured roughly by Morren, I. c. Tabs, xix.-xxi.,
figs. I and 2 /c. I. ; and described more accurately by Qua-
trefages, Ann. Sci. Nat., Ser. iii., tom. viii., 1847, p. 36.

a 3. Commencement of chain of ventral ganglia. The ventral
chain consists here, as in Arthropoda, of fibrous elements

p 2

Description of the Plates.

placed superiorly, and vesicular placed inferiorly. The latter
form a continuous stratum with ag-g-regations at intervals
corresponding to the middle of each segment, whicli are
called ganglia, and give off two pairs of nerves on either
side. The nerve-cord gives off in each segment anteriorly
to the two pairs arising from the ganglioniform intumes-
cence a single pair, which distributes itself along the line
of the anterior dissepiment of each segment, and appears to
correspond to the Nervi transversi of the Ai-thropoda. The
four nerves given off in the middle of each segment are
accompanied by branches from the pseud-haemal vessels
which run on either side of the nerve-cord ; the two nerves
given off anteriorly to them are similarly accompanied by
branches from the azygos pseud-haemal vessel which under-
Hes the nerve-cord. These nervous and vascular branches
are not given in this Plate.
Pharynx, turned aside to the left, the right half of the organ,
except the small portion upon which the right stomato-
gastric plexus, a 3, is seen, having been removed. The
walls of the pharynx are of great thickness superiorly,
glandular tissue forming the exterior, and muscular the
middle layers, whilst the mucous membrane forms the inner-
most, and attains a considerable thickness where it lines the
saucer- or sucker-shaped cavity which opens from above into
the cavity of the tube.
I. First muciparous gland, or ' segmental organ,' opening
externally in segment iv. Ordinarily the thickened mus-
cular portion of the tube of the convolutions of which these
glands are made, opens externally in the segment imme-
diately posterior to that in which its internal funnel-
shaped opening is situated, this internal funnel-shaped
opening being carried upon a short hollow stalk prolonged
through the anterior muscular dissepiment of each postenor
segment of the two with which each segmental organ is
connected. But as segment iv. is not limited off from seg-
ment iii. by any such perfect or nearly perfect dissepiment
as limits the "^segments after segment v. from the seg-
ments next in front of them, the anterior funnel-shaped
termination is not seen so distinctly to be in a different

Earth Worm.

213

segment from the one in which tlie mass of the coils of the
gland are lodged.

c 2. Segmental organ similarly modified to c i.

c^,c4.,c^. Normal segmental organs^ the opening on to the
exterior being usually close to the inner row of setae, and
in the anterior portion of each segment, though it may
vary considerably, and even come to lie exteriorly and
superiorly to the outer row of locomotor spines. The
funnel-shaped internal opening is seen a short way from
the outer edge of the nerve-cord, and near the ventral
surface in the segment anterior to that in which the gland
communicates with the exterior. The coils of the posterior,
which is much the larger part of these organs, are connected
by a mesentery-like lamina to each other and to the disse-
piments of the segments.

d. Muscle passing up from one of the ventral muscles to attach
itself to the capsule of the supra-oesophageal ganglia and
the circumjacent parts, to which it stands in the relation of
a powerful retractor.

ei, e%, e ^, e^, e ^. ' Capsulogenous glands.' These bodies
appear to be specially-modified and greatly-developed seti-
parous glands, which attain this prominence in the segments
connected with the essential, and with the accessory organs
of generation ; amongst the latter of which the inner setae of
many segments may be reckoned, besides those here lettered
e I to e 5. At (? 2 we see a slip of muscle passing across the
glandular mass, and connecting the inner with the oviter row
of setae. Over the capsulogenous gland lettered e 4 is seen
the vas deferens passing forward and through the dissepi-
ment separating segment xi. from segment x., to end in an
infundibulum closely similar in form, relations, and connec-
tions to the more delicate tubular stalk carrying the funnel-
shaped ending of an ordinary segmental organ. On the
capsulogenous gland labelled e 5 are seen the junction of the
stem of a second vas deferens with the anterior one seen at
(?4, and the commencement of the common duct.

fi. Outer row of setae. Each seta is secreted by a separate
gland, and has a separate insertion The setae of the aquatic
Oligochaeta are, on the contrary, ' fasciculate' in their inser-

214

Description of the Plates.

tion. The outer row of setae is often wanting in the anterior
segments; in the others it is usually connected with the
inner row by a transverse muscular slip, such as that seen
here^ or at e 2. In the region of the elitellus the outer row
of setae may be adapted to serve as accessory copulatory
organs ; elsewhere they are purely locomotor.
/2. Inner row of setae. The spines are solitary in their inser-
tion as in the outer row, but they are in many segments, as,
for example, in the tenth and fifteenth, besides the segments
constituting the elitellus, modified so as to serve as organs
of adhesion.

g I . Anterior receptaculum seminis of the left side, opening in
the interval between the ninth and tenth segments, and
between the lateral and dorsal muscles in the line of the
outer row of setae.

g 1. Posterior receptaculum seminis, opening in the interval
between the tenth and eleventh segments. These organs
are very variable in size, and have had their existence over-
looked and denied. Their outer opening is marked by a
small elongated- papilla; but their development is not
always exactly correlated with that of the rest of the gene-
rative apparatus.

Ti\. Anterior vesicula seminalis of the left side, attached to the
posterior dissepiment of the ninth segment, and communi-
cating, as does the middle vesicula seminalis h 2, with the
anterior compartment of a sac with delicate walls which
occupied a space in the tenth and eleventh segments cor-
responding to that underlaid by the azygos ventral muscle,
and received the openings of the vesiculae of both sides.

h 2. Middle vesicula seminalis of left side.

7^3. Posterior and largest vesicula seminalis, opening into the
posterior compartment of the azj^gos central atrial sac just
described.

i I. Funnel-shaped orifice of vas deferens anterior of left side.

11. Similar orifice of vas deferens posterior of left side.

23. Similar orifice of vas deferens anterior of right side.

^4. Similar orifice of vas deferens posterior of right side. Ex-
ternally and interiorly to each of these infundibula there
exists in each of these segments a segmental organ's

Earth Worm.

215

posterior and larger portion; and posteriorly to each of
these infundibula there exists also in each of these segments
the funnel-shaped opening of the segmental organ of the
segment next behind it. The coexistence therefore of the
vasa deferentia with the very similarly constructed seg-
mental organs would appear to be inconsistent with a view
which should regard them as modihcations of those glands.
Still the great development and increase of mass observable
in other organs in these segments may_, as suggested by
Mr. Lankesterj induce us to hold that the typical number
of segmental organs in any one segment is four, and that
this number is attained to in those generative segments only
on account of their superabundant nutrition. Upon this
view the vasa deferentia, as also the oviducts n, would be
serially homologous with the segmental organs.
j 1. Vas deferens from anterior spermatic infundibulum of left
side.

j2. Vas deferens from posterior spermatic infundibulum of left
side. The junction of the two vasa deferentia to form one
common canal is well seen in the twelfth segment on the
right side, and the ending of the common canal there
formed is well shown on both sides in the fifteenth seg-
ment. The external opening of the common vas deferens
has the shape of an oval slit, with its long axis transverse
to that of the animaFs body, guarded at the breeding season
by prominent tumid lips.

k J . Anterior testis of right side.

k 2. Posterior testis of right side.

L The single ovary of the right side_, occupying the same posi-
tion relatively to the nerve-cord and the inner row of setae
as the testes.

m. Infundibular ciliated mouth of oviduct, holding a similar
position to that held by the infundibulum of the segmental
organ c 5, which opens both internally and externally in the
same segments.

n. Oviduct in the posterior of the two segments in which its
various parts are found. After passing through the dissepi-
ment separating the thirteenth from the fourteenth segment^
the oviduct has a saccular dilatation, ordinarily found to

216 Description of the Plates.

contain ova, appended to it. It then passes outwards in
relation with the dissepimentj to end by opening externally
immediately externally to the internal row of setae. It is
crossed just before its termination by a part of one of the
tubular muciparous or segmental organs which is passing
forwards to pierce the dissepiment, and end in its infundi-
bulum in the segment next in front.

For the nerve system, see Lockhai't Clarke, Royal Society's Pro-
ceedings, vol.viii.j 1857, p. 343 ; see also Quatrefages, Ann. Sci.
Nat., Ser. iii., tom. viii., 1847, p. 36; Morren, De Lumbrici
Terrestris Historia Naturali necnon Anatomia Tractatus, 1829,
tabs, xix.-xxi., figs, i and. 2, p. 1 1 9 ; and Leydig, Hand-
buch Vergleich. Anatomic, tab. iv., p. 168.

For the reproductive system, see Hering, Zeitschrift Wiss. Zool.,
vol. viii., 1 857 j Lankester, Quarterly J ournal of Microscopical
Society, vol. v., 1865, p. 10.

For the segmental organs, see Gegenbaur, Zeitschrift Wiss. Zool.,
vol. iv., 1853, p. 22,1 ', Hering, I. c, p. 401 ; Ehlers, Die Bors-
tenwurmer, i., pp. S7~45> 1864; Claparede, Introduction to
work on Annelids of Bay of Naples, translated by W. S. Dallas,
Ann. and Mag. Nat. Hist., Ser. iii., vol. x:x., 1867, p. 355.

i

r

11

I

(

I

!

H

PLATE IX.

Medicinal Leech^ Tlirudo 3fedicinali,9.

PLATE IX.

Figure of Medicinal Leech (Hirudo Medicinalis),

Dissected so as to show its nervous, digestive, reproductive and segmental organs,
as seen from below ; sliglitly altered from Moquin Tandon's figure, pi. viii., fig. lO,
Monographic des Hirudin^es, 1846.

The integuments are drawn as divided down the middle ventral
line, from the posterior border of the anterior sucker to the an-
terior border of the posterior sucker ; two of the testes and two
of the segmental organs have been displaced outwards in the
segmentj lettered 3, e 2 ; the rest of the organs have been left
undisturbed in situ, after the fastening out of the integuments on
either side.

a I . Anterior sucker, formed by the proboscidiform upper lip,
which is made up of four incomplete annuli, representing
however probably at least as many segments, and by the first
complete annulus surrounding the mouth. The mouth opens
in the middle of this sucker ; six of the eyes are carried by
the first, second, and third of the rays of the upper lip.

a 2. Posterior sucker, formed by the fusion of seven distinct
annuli, to which seven distinct ganglia subsequently fused
into the single posterior ganglion of the ventral chain,
corresponded at one period of the animaFs development.
The stellate spot in the centre of the sucker must not be
taken as representing the opening of the anus, which is
situated anteriorly to the sucker in the line of constriction
marking it off from the posterior annuli, which are not
similarly modified. The amis does however open in the
centre of the anal sucker in Acanthobdella, as also in the
Polychaetous Annelid, Leucodore

218

Description of the Plates.

h I. First and second pairs of sub-oesophageal ganglia, very
closely apposed to each other. From the first sub-oeso-
phageal ganglion, five pairs of nerves are given ofi"; from
the second only two, as from all the other twenty ganglia
placed posteriorly to it, with the exception of the two last.

b 2. Last ganglion, the twenty-second of the ventral chain.
This ganglion gives ofi' from five to nine pairs of nerves,
which are distributed to the posterior sucker. The penulti-
mate ganglion gives ofi" only one pair of nerves. The supra-
oesophageal ganglion, with the three stomato-gastric gang-
lia connected with it and supplying the jaws, is not shown
here; nor the azygos sympathetic nerves with a course
above the ventral nerve-chain, and between it and the
digestive tract upon which it forms gangliated plexuses,
and sends branches along its lateral diverticula,

CI. First lateral diverticulum of the portion of the digestive
tract, which comes next after the pharynx, and which is
called ' oesophageal by Gratiolet, inasmuch as its functions
are, according to him, merely those of a reservoir for the
more solid parts of the animaFs food, from which the watery
part is squeezed out hj the muscular contractions of the
body-walls whilst it is contained there; and which, after
remaining there thus condensed for several months, still
retains the faculty of reddening, when exposed to the
oxygen of the air.

C2. 'Small intestine^ of most authors, gastroilear portion of
dio-estive tube of Gratiolet, in which the blood undergoes
the alterations ordinarily effected in it by digestion. It
ends posteriorly in a short ovoidal colon, which again ends
in a short rectum, which turns slightly upwards to end at
the anus. The small intestine is a little dilated at its
commencement in the interval between the two terminal
sacculi c 3 ; this dilatation representing the much larger
bilobed dilatation, with which the homologous segment of
the digestive tract commences in the Horse-leech {Aulostoma
Gulo) .

c^. Eleventh lateral diverticulum of right side prolonged down-
wards on either side of the small intestine and colon, as far
as the point where the rectum begins. The calibre of either

/

Medicinal Leech. 2 1 9

of these terminal coeca is much larger than that of the
segment of the digestive tube which lies between tliem,
and which further differs from the homologous segment in
the Horse-leech, in not possessing any lateral sacculations.
di. The most anteriorly placed of the nine testes of either side,
communicating by a short transverse duct passing outwards,
with a common vas deferens, which receives posteriorly the
secretion of the eight posterior testes, and anteriorly leads
into a convoluted epidymis-like vesicula seminalis, which is
seen in this figure in the space bounded by the lines lettered
i and y.

d2. Last testis of right side. The segments between this one
and the most anterior of the genital segments /, have their
cutaneous glands greatly enlarged at the time of ovi-
position, and secrete the external chitinous shell of the
' cocoon'' in which the eggs are lodged ; whilst the glands
of the female generative apparatus secrete the albuminous
matter which fills the shell and surrounds the eggs.
Sixth testis, displaced outwards so as to show its own con-
nection with the vas deferens, and the relation of apposition
with it, into which a coecal process from one of the seg-
mental organs, e 2, comes.

e I. Segmental organs consisting of one portion, which is tu-
bular and loop-shaped to the naked eye, but so mutually
inter-communicating when examined with the microscope
as to be really labyrinthiform ; of a second portion, which
is vesicular and opens on to the exterior ; of a third, which,
as a slender but resistent duct, connects the loop-shaped
with the vesicular portions; and, in the eleven posterior
segments, of a fourth portion, in the shape of a coecal
process, which is prolonged inwards in the two most pos-
terior up to the nerve-cord ; in the ante-penultimate up to
the vas deferens from the last testis ; and in the eight
others up to the eight anterior testes.

e2. Segmental organ, shown with all the four constituent por-
tions just mentioned; the testis with which its coecal
process comes into apposition, though not into any tubular
continuity, having been displaced outwards. The vesicular
part of the segmental organ lies in every case posteriorly

Description of the Plates.

to the looped portion, with the anterior element of which
it is connected hy the duct ; and in the seg-raental organs,
which are in the relation mentioned with the testes, the
vesicular portions occupy the angle bounded by the vasa
deferentia and the inner parts of the looped portions, and
alternate in position with the testes. The eoecal process
constituting a fourth portion in the segmental organs in
relation with the nine testes, is always brought into relation
with the anterior one of the two testes, with which the
segmental organ alternates, except in the case of the last
testis, in which the coecal process appears only to reach the
vas deferens of that last gland. In this figure four seg-
mental organs are represented as existing posteriorly to the
last testis ; in nature there are only three, the most ante-
riorly placed one of which is connected with the male
organs as just mentioned j whilst the two posterior ones
have their coecal processes prolonged nearly up to the middle
ventral line occupied by the nerve-cord. The seven seg-
mental organs situated anteriorly to the most anterior
testis, are represented in this figure by four. None of these
seven possess the inwardly prolonged coecal process, but
consist of a simple loop-shaped portion, the outer and larger
end of which lies almost vertically in the natural condition,
whilst the inner and smaller is prolonged inwards, and
more or less horizontally, beneath the digestive tube, as
in the other segmental organs, a duct and a vesicle open
exteriorly. The coecal process when present may be taken
to be homologous with the open infundibulum of the ovi-
ducts, and vasa deferentia of tlie Lumbricidae (see pi. viii.,
*3, i 4, m). In some Hirudineae, the segmental organs may
resemble those of other Annelids, in opening by ciliated
infimdibula into the general cavity of the body (Branchio-
bdella), or into the interior of one of the pseud-haemal canals
(Clepsine), but they never are subordinated, as in those orders,
to the function of conveying the generative products. In
the middle regions of the body, the segmental organs are
repeated at regular intervals, five annuli being interposed
between the outlets of each pair ; and the annulus imme-
diately posterior to these outlets carries a nerve ganglion on

Medicinal Leech.

221

its inferior and inner, and a pair of white spots on its supe-
rior outer surface. The colouration also, it may be observed,
of some varieties of the true Medicinal Leech, as also and
more markedly of Hiruclo troctina, a distinct but closely-
allied species, appears to indicate similarly that five smaller
or secondary annuli enter into the composition of the
primary segments, by the aggregation of which the middle
body is made up. At the anterior part of the body the
segmental organs are arranged with less regularity. The
segmental organs of one family of marine Annelids, the
Capitelleae, are said to resemble those of the Leech in
having no inner orifice ; and in a few Annelids they may
be absent, or represented simply by apertures in the body-
walls.

/. Muscular ductus ejaculatorius of left side, leading from the
convoluted vesicula seminalis into the base of the flask-
shaped intromitteut organ. It is by the secretion of the
vesicula seminalis that the spermatozoa are agglutinated
into a spermatophore.

g. Club-shaped end of intromittent apparatus, glandular at its

coecal convex end, and tapering off into the muscular penis
below.

h. Penis, surrounded where it passes out of the integument by

a strong sphincter. This orifice is separated by an interval
of five secondary annuli from that of the female organs.

i. Ovary of left side, carried upon one of the short oviducts.

The ovary of the other side is seen on the farther side the
nerve-cord, underneath which its oviduct passed.
j. Muscular vagina, in which after sexual congress the sperma-
tophore is found. Between the vagina and the two oviducts,
a common oviduct intervenes, which takes a tortuous course,
and has its coils surrounded by a mass of loose tissue, com-
posed of unicellular glands, which are probably the main
agents in the secretion of the albumen which envelopes the
eggs in the cocoon. The azygos character of the two gene-
rative outlets is especially noteworthy. In all other Annelids
the generative glands discharge their products by dehiscence
into the perivisceral cavity, whence they are taken up by
the open mouths of infundibular ducts, as in Ganoid Fishes,

222

Description of the Plates.

and in the females of all higher Vertebrata; but in the
Hirudineae the walls of the generative glands are continuous
with the capsules of the generative glands; and, with
the exceptions above stated, p. 220, the segmental organs
have no opening internally. In the possession of accessory-
sexual organs, the Hirudineae and Oligochaeta resemble each
other^ and differ from the other Annelids.

For the general anatomy of the Leech, see Brandt, Medizinische
Zoologie, Bd. ii., pp. 239-253; or Leuckart, Die Menseh-
lichen Parasiten, Bd. i., pp. 634-720.

For the ^segmentar organs, see Gratiolet, Ann. Sci. Nat., Ser. iv.,
torn, xvii.j 1862, p. 192, pi. vii., fig. 4.

For the nervous system, see Leydig, Vergleichende Anatomic,
p. 162, ihiqite citata ; and Taf. i., figs. 4 and 6; Taf. ii., figs.
1, 2, 3, 5 ; Taf. iii., fig. i ; Taf iv., fig. i ; and for the sensory
organs called by him ' Becheiformige Sinnesorgane,^ see Ai'chiv.
fur Anatomic und Physiologic, 1 861, p. 60T, For the ' ganglions
de renforcement'' developed upon the inferior pair of nerves
given off" by each ganglia of the ventral chain, except the first
and the two last, see, in addition to the references given at
p. 133 supra, G. E,. Treviranus, Zeitschrift fiir Physiologic,
Bd. iii., Hft. 2, 1829, pp. 157-172; cited by Claparede, I. c,

For the development, see Leuckart, I. c, 686 ; and Rathke, Bei-
trage zur Entwickelungsgeschichte der Hirudineen (Nephelis,
Clepsine), cit. in loco.

For the existence of blood-coi-puscles in the pseudhaemal system, see
Quatrefages, Hist. Nat. Annales, 1865, i., p. 63, ii., p. 168,
where Sy/llidea armata is stated to possess blood-corpuscles in
those vessels ; and the statement as to Glycera made in the
Ann. Sci. Nat., 1850, iii. 14, p. 288, appears to be withdrawn.

For a statement as to their presence in the ' pseudhaemaP system
of some other Annelids, see Claparede, Ann. and Mag. Nat.
Hist., Ser. iii., vol. xx., 1867, p. 350, where Glycera is stated
to be devoid of the vascular S3'stcm in question. For the pro-
priety, however, of classing Plioronis as an Annelid, as is done
at p. 138 supra^ see Allman, Fresh-water Polyzoa, pp. S^—^*],
and Dyster, cit., p. 138.

PLATE X.

Common Star- Fish. Asterias Rubens. Linn.

*

PLATE X.

Common Starfish {Asterias Ruhens),
Linn.,

Dissected so as to show its motor, digestive, and reproductive systems.

The dorsal integument, with its multitudinous imbedded ossicles,
has been removed from the central ray of the trivium, I ; from its
left ray ; and from both rays of the anal bivium, a part of it being
left attached to the right ray of the bi\'ium at its apex, to show the
attachment to it of the radial digestive coeca. 'The digestive and
other viscera have been in great part removed from the interior of
the two rays of the bivium and the ampullae d 2, and the ambulacral
ossicles k 1 exposed in situ. The digestive coeca have been displaced
from their attachments in the left ray of the trivium ; they have
been left undisturbed in the central ray; and in the right ray all
the organs, with the exception of a small part of the dorsal inte-
gument next to the central disc, have been left undisturbed.

The Roman numerals I, II, and III, denote the central and the
right and left rays of the trivium, which is distinguishable from
the bivium numbered IV and V, by the position of the raadreporic
tubercle cj and the anus /, opposite to its central ray I, and to the
interradial space between rays IV and V. In the irregularly-shaped
Echinodermata, such as the Spatangidae, among the Echinoidea,
and Cuvieria, the functions and structure of the bivium and
trivium respectively may be very different, and may not only make
it easy to demonstrate the existence of a bilateral symmetry, but
may also constitute a ventral and dorsal surface respectively. .But

224

Description of the Plates.

the regular Echinodermata, such as the Asteridae, Ophiuridae, and
the regular Echinoidea^ to the ambulacral regions in which all the
five rays contribute equally, do not in adult life keep, when in loco-
motion, any one of these always pointiug anteriorly ; and it is by
the relations of the anus in the proctuchous forms and of the
madreporic tubercle when the anus is absent, that we are enabled
to divide the five rays into two sets of them and two rays respec-
tively. In the Ophiuridae, in which there is no anus, and in which
the madreporic tubercle is not always visible externally, being fused
with one of the interradially-placed circumoral plates, the adult
animal may seem to be perfectly radiate, and we have to refer to
the pluteiform larva for proof of its essentially bilateral character.

I. Central radius of trivium; a line drawn along the long axis

of this ray to the madreporic tubercle ff, w^ould, in the undis-
turbed condition of the parts, have the anus a little on its
left ; and if prolonged, would pass down the interradial space
of the bivium IV and V.

II. Right radius of trivium, with the greater part of the tegu-

ment left in situ. The inward prolongation of the external
ossiferous envelope is well seen in the interradial space be-
tween arm I and arm II and the generative gland of either
ray is seen on either side of the septum thus constituted,
with w^hich it is connected by a single efferent duct with a
cribriform opening on to the exterior. The dorsal integu-
ment contains a large number of ossicula imbedded in its
substance, some of which carry small conical prickly spines,
whilst others simply connect the spinigerous ossicles into a
reticulation. Down the centre of each ray the spinigerous
tubercles are in this species arranged with considerable regu-
larity, so as to form a mesial series ; in the other portions
of the dorsal area, they are scattered irregularly. The in-
tervals between the dorsal ossicula are perforated by respi-
ratory pores, through which coccal processes of the pen-
visceral sac protrude, and are exposed to the circumambient
aerating medium. Pcdicelhiriae of considerable size are
scattered over the interspinal areae, and smaller and incon-
spicuous ones surround many of the spines in a circle. They

Co7nmon Starfish.

225

may be so numerous in this species as to give the surface a
villous appearance.

III. Left radius of trivium. The two digestive coeca have been
displaced from their normal connections within the cavity
of the ray, and are displayed in the interradial space on
either side. Towards the apex of the ray are seen the
ambulacral ampullae belonging to one of the two biserial
rows of locomotor feet, in the middle line are seen the
ambulacral ossicles, and on either side the generative glands,

IV and V. Left and right rays of bivium. The greater part of
the digestive and reproductive organs have been removed,
and the ambulacral ampullae, d i, forming four rows, corre-
sponding to the two rows of sucker-like feet arranged on
either side of the ventrally-placed ambulacral furrows, are
seen on either side of the middle line occupied by the mesial
articulations of the successive pairs of ^ vertebraF or ' ambu-
lacral ossicles, ki, hi. Externally on either side to the
rows of ampullae, are shown diagrammatically the more or
less regularly quadrangular reticulations, formed by the
^ interambulacraF ossicles. Of these interambulacral ossicles,
there are in this species eight rows, interposed between the
ambulacral ossicles and the less regularly disposed ^ tergal ■*
ossicles. Of the interambulacral rows, the first, third, and
sixth carry spines on their ventral surfaces ; the second,
fourth, fifth, seventh and eighth are devoid of them, and
act simply as commissural bars uniting the whole series
into a quadrangularly reticulate skeleton. Of the tergal
ossicles, some are spinigerous and some simply connective;
the ambulacral never carry spines.

a. Intestinal cavity, communicating freely with the stomach
proper, seen below at c, and giving off a stem which bifurcates
as it enters each ray.

h 1 . One of the arborescent divisions into which the radial diver-
ticulum of radius I divides. It is only in the Asteriae that
this digestive tract has this radial arrangement of digestive
or ' hepatic' coeca.

226

Description of the Plates.

b %. Arborescent coecum of radius IIIj displaced, as is its fellow,
into the next interradial space.

b 3 and b 4. Terminations of coeca of radius V attached to the
dorsal integ-umentary skeleton by a mesentery.

c. Stomach proper, bulging* into the cavity of the several rays
at a lower level than the coeca, b, but only for a short dis-
tance. Ligaments may be observed passing up on either
side of c from the ambulacral ossicles, by means of which
the stomach can be retracted after being protruded, as it
often is by the animal when feeding. To the right of c is
seen one of the interradial septa to which the ducts of the
generative coeca on either side are attached.

d I . Ampullae of ambulacral feet of radius IV ; they are biserial
on either side, in correspondence with the four sucker-like
feet which communicate with them through conjugate fora-
mina formed by the alternating apposition of emarginations
of the ambulacral ossicles j for which see fig. 3, pi. i.,
Wright, British Fossil Echinodermata from the Oolite, 1862 ;
Gandry, Ann. Sci. Nat., Ser. iii., torn, xvi., pL 13, fig. i.

d 1. Ampullae of radius V.

e. Subcentrally-placed anus.

f. Origin of extensor muscle of radius I from inner surface of

centre of dorsal integument. It is by the action of this
muscle that the distal extremity of the rays and the com-
pound eyes they carry, have their ordinary up-turned direc-
tion, as shown in this figure, given to them.
fi. Distal termination of extensor muscle of radius V.

g. Madreporic canal and plate displaced backwards into the inter-

radial space of the bivium, opposite to whicli it is placed in
the natural position of the parts. The madreporic plate
being porous, and the madreporic tube, in spite of a some-
what complicated internal structure, being very readily
permeable by fluid, it is easy to see how the sea- water can
find its way into the water-vascular ambulacral system vdth.
which the madreporic canal is connected by its junction to
circum-oral water- vascular ring. The ' heart' of the pseud-
haemal system is inclosed in the same membranous sheath
with the madreporic canal, and, like it, communicates with
a circura-oral annular vessel, which lies inferiorly to the

Common Starjish.

227

water- vascular ring-, between it and the commissural ring,
or rather commissural pentagon, formed by the nervous
bands connecting the proximal ends of the gangliated radial
cords.

' Polian vesicles muscular sacculi appended to the water- vas-
cular circum-oral ring. There are in this species ten Polian
vesicles, one corresponding to each biserial row of ampullae ;
their functions, however, cannot be here of the importance
which they may possess when of the proportions observed
in the Holothurians (see Description of Preparation 47).
Corresponding again to the Polian vesicles is to be foimd,
on the internal aspect of the water- vascular ring, a series of
glandular sacculi, the so-called ' racemose vesicles.'' Of these
there are nine in this species, one being aborted at the point
of insertion of the madreporic canal into the ring.

j I andy a. Eeproductive glands of radius III, consisting of mul-
tiramified coeca appended to a single efferent duct, as in
many but not all proctuchous Asteriae, and in Ctenodiscus
amongst the aproctous. The efferent duct of each gland
comes into relation with the corresponding interradial sep-
tum, and the small ova find their way into the sea-water
through a cribriform external opening, which may be found
on the corresponding side of the apex of each interradial
angle on the dorsal surface of the body. See Miiller and
Troschel, Die Asteriden, pi. xii., fig. 2, p. 133.

J 3. Point of attachment of efferent generative duct of right
generative gland of radius V to interradial septum, which
is formed by the prolongation inwards of the external
envelope containing a number of small flat ossicles.

h I and k 2. Ambulacral ossicles forming by their mesial abut-
ment the commissural ambulacral arches. There may be
as many as 140 ambulacral arches in each ray, but as
each arch is never in relation with more than a single pair
of ampullae, and as the ampullae in Asteracanthion form
two biserial rows, these rows are only half as numerous as
the ambulacral arches. The apposition of the ambulacral
arches forms inferiorly the ambulacral furrow, in the upper
part of which is lodged the ambulacral water- vessel, and in
the lower part of which, immediately beneath the integument,

Q 2

228

Description of the Plates.

runs the gang-liated nerve-cord. Eacii ambulacral ossicle
abuts upon its fellow by a facet a little below the level to
which the lines k z, k 2, are drawn, the interval between
this level and that of the ai-ticular facets being filled up by
muscular fibres, which by contracting must act as divari-
cators of the ambulacral ossicles. Adductor muscular fibres,
on the other hand, are found in the concavity of each ambu-
lacral arch, crossing from one ossicle to the other in the
interval between the radial water- vessel and the nerve-cord.
The structui-es in the Ophiuridae, which are homologous
with the ambulacral ossicles of the Asteriae, are the two
immoveably Articulated halves of a vertebral ossicle, which,
in the absence of any prolongations of the digestive or
generative organs into the arms, occupies a much larger
space relatively than the ambulacral ossicles of the Asteriae.
The structures in the Echinoidea, which are homologous
with the ambulacral ossicles of the Asteriae, are the so-
called ' Auriculae' of Echinus, which in Echinanthus are
repeated upon each ambulacral plate. The ambulacral
plates, again, of the Echinoidea are not represented by any
calcification in the Asteriae, being developed in the layer of
perisoma which lies externally to the radial nerve-cords,
and which remains free from induration in the order just
named ; though it carries fom' rows of scutes, one dorsal,
two lateral, and one ventral, in the Ophiurae.

For the digestive system of the Asterim {Aster acantMoii) rubens,
see Miiller and Troschel, System der Asteriden, Taf. xi., fig. i,
p. 132.

For the reproductive system, see Miiller and Troschel, ibid., pp.
133^ 134-

For the motor and skeletal system, see Professor Sharpey, Cyclo-
paedia of Anatomy and Physiology, article ' Echinodermata,'
figs. 9 and 1 2, pp. 32, 34; Wilson, Linn. Soc. Trans., vol. xxiii.,
i860, p. 107, tab. 14, fig. 7.

For the skeletal system, see Gaudry, Ann. Sci. Nat., Ser. iii., torn,
xvi., 1851, pi. 3, fig. I.

For the homology of the Auriculae of the Echinoidea and the cal-
careous ring of the Holothuroidea with the ambulacral ossicles

Common Starfish.

229

of the Asteroidea as invalidating-, pro tanto, Miiller's dictum,
that this latter class alone of Echinodermata possesses an
internal skeleton, see Semper, Eeisen in Archipel des Philli-
piden, Theil. ii., Hft. iv., p. i6% ; see also Wright, British Fossil
Echinodermata of the Oolitic Formations, Palaeontographical
Society's Memoirs, 1862, vol. ii., p. 14. For a comparison of
the osseous skeleton of Asterias {Uraster) ruhens vf\i\i that of
a fossil species from the Middle Lias, Uraster Gaveyi, Forbes,
see Wright, I. c, p. 1 00, pi. i.

an account of the Pedicellariae, see Sars cit. Wright, 1. c,
p. 19. The pedicellariae of the Asteriae and Echinoidea are
not homologous with the avicularia of the Polyzoa, to which
they bear a considerable resemblance. The pedicellariae are
modified spines ; the avicularia are specially modified or poly-
morphic individuals of the compound Polyzoan colony. The
two sets of structures appear however to be analogous, being
both alike prehensile organs.

i

i

1

I

f:

PLATE XI.

o.oEvvnr.ifcZ ^ iTc

Fie 1 Diagram of Cephalopod. Fig. 5. Rotifek. Eydatma Senta

2. Bkachiopob. BJ.jnciu>nclla Fig. 6. Tukbellabian. Moc<elum
P 'ttacea Nausicm.

Fig 3 Dinim of AsclD.AK. Kg- GR^oar™b. %forAy«?«« OK-
rig.4. Diagram of POLVZOON. yac<.«(to.

PLATE XI.

Figure i.

Diagram of Cephalopod, from V. Carus' Icones Zootoinicae, p. iii., fig. 30-

The following points, characteristic of the class, are embodied in
this figure ; the formation of ' arms/ a, by the division and elonga-
tion of the margins of the ' foot' proper ; the formation of a funnel,
/, by the coalescence of the epipodia ; the relations of the mantle, h,
to the funnel, branchiae, and anus ; the presence of a cephalic carti-
lage, of highly-developed eyes, and of a digestive canal which, though
provided with accessory organs not shown here, is never, in this
class, complexly convoluted.

a. The arms, which in the more highly-organized Dibranchiate

subdivision of the class are provided with suckers.

b. The mantle, which not only protects the branchiae, and brings

them into relation with the aerating medium, but also whilst
doing so, by its contracting and expelling the water from its
cavity through the funnel enables the creature to swim
backwards.

c. Eyes, sessile, as in the Dibranchiata.

d. Auditory vesicle, contained, together with the main nerve

centres, in a cartilaginous capsule.

e. Intestinal tract, not forming complex convolutions.

f. Funnel formed by the coalescence of the epipodia posteriorly to

the 'foot'' proper, which here takes the shape of 'arms' at a.
Below the funnel are seen the gills, and between them and
the rectum one of the inter- viscerally placed ganglia, which
are so abundantly developed in this class.

For a figure giving full details of the anatomy of a Cephalopod,
Octopus Vulgaris, see Milne Edwards, Ann. Sci. Nat., Ser. iii.,
torn, iii., pi. 13, p. 341 ; or in Regne Animal; or in Victor
Carus' Icones Zootomicae, tab. xxiii. 6.

For the nervous system in Cephalopoda, see Hancock, Ann. and '
Mag, Nat. Hist., 185a, Ser. ii., vol. i., pp. 1-14.

232

Description of the Plates.

Figure 2.

Lateral view of viscera of Bracbiopod, Bhynchonella Psittacea, together with portions
of the mantle, peduncle, and arms; after Huxley, Proc. Roy. Soc, 1854.

The view here given shows that a section of the animal in the
plane of the aperture of its two valves would not divide it into two
symmetrical halves, as in the LamelKbranchiata, and that its
valves consequently cannot be spoken of as right and left, as- in
those animals. The two valves of the shell, the posterior third
only of the cavity of which was occupied by the body of the animal,
have been removed, as have also the anterior two-thirds of the
mantle lobes which were in relation with, though they did not,
as in Terebratula, send coecal processes into them. The spirally
coiled mass which the arms made up, and which filled up the
greater part of the mantle cavity, has been removed ; the arm of
the right side has been cut away from its origin, and only a small
part of the arm of the opposite side left on the other side of the
mouth.

Ms. Lobe of mantle which was in relation with the valve ordi-
narily called ' dorsal.^

Mi. Lobe of mantle which was in relation with the so-called
' ventral valve. Both valves in the Brachiopoda arise from
the ' dorsal or ' haemal' aspect of the animal, as they do in
the Lamellibranchiata, but in the former class they are
articulated across, whilst in the latter they are articulated
along the dorsal ridge. It is the ventral' valve which,
either by becoming adherent to some marine object, as in
Thecidium and Crania, or, as in the species before us, by
giving attachment on its inner surface to the peduncle p,
furnishes the entire shell with a fixed point for its limited
movements in the adult state. And Brachiopoda, whilst
still free in certain stages of their development, have been
observed to move from point to point by means of a pair
of rigid spines, one of which was inserted on either side of
the ventral pallial lobe. During the free stages of the life
of such larvae the dorsal valve, as being the heavier, has
been ordinarily observed to be inferior in position ; it is so

Viscera of Brachiopod.

233

in the adult condition of the pedunculate, though, as it is
always the free valve, it occupies the reverse position in the
adnate Brachiopoda.
X. Heart, unilocular as in all Brachiopoda, and globular as in
the articulate division of the class. Its position justifies the
application of the term ' dorsaP to the valve in relation
with it.

0. Mouth, immediately posteriorly to which the main nerve
ganglia, three in number, one placed mesially and two
laterally, were situated, forming the under side of an oeso-
phageal collar, completed by commissural cords passing" up
to join on either side a ganglion of small size at the base of
either arm.

Oe. Oesophagus ; of considerable length, the mouth being so near
the ventral valve.

A. Liver, surrounding the stomach, into the cardiac end of which
it opens by four ducts. Immediately below the posterior
lobe of the liver the intestine is seen passing downwards,
and slightly tapering in its course towards the ventral valve.
Having reached the valve it turns a little upwards and back-
wards, to end at a' in a coecal extremity, as in other articulate
Brachiopoda.

a. Coecal extremity of digestive tube. The simple curve de-
scribed by the digestive tube of the Rhynchonella has its
concavity directed towards the ventral valve, just as the
primary curve of the digestive tract of the inarticulate
Lingula, which differs however from it by not ending
coecally, and by having convolutions superadded to it, of
which the intestine in the articulate species is desti-
tute.

T. Tentacular cirrhi upon portion of left arm. The mouth, as in
all Brachiopoda, is situated between the points of junction
of the two arms to the visceral mass.

T. Sac, or ampulla, in connection with the great brachial canal ;
serving probably to increase the surface through which the
fluids in the perivisceral cavity and in the brachial canals
can act upon each other.

17. Crural lamina, arising from hinge process of upper valve in
Rhynchonella for the support of the right arm, which has

234

Description of the Plates.

been removed. The shell having been removed, the hinge

process is figured as broken.
c. Laminated portions of oviducts, opening by an expanded orifice

into the perivisceral cavity. In Rhynchonella there are four

oviducts, one pair within the ventral, the other within the

dorsal valve. The dorsal oviducts open into the perivisceral

cavity by orifices looking forwards and upwards ; the ventral

by orifices looking backwards,
c'. Tubular portions of oviducts, opening downwards. Those of

the dorsal oviducts open above the mouth, those of the

ventral below, into the mantle cavity.
p. Peduncle passing through a foramen, which is incomplete in

young shells, to be attached by a pair of muscles vrithin the

umbo of the ventral valve.
m. Occlusor muscle.

m 2. Divaricator muscle, passing fi'om ventral valve to cardinal

process of dorsal.
m^. Adjuster muscle, passing from hinge process in the dorsal

valve into the peduncle.
m4. Adjuster muscle, passing from ventral valve into peduncle.
ms. Mesenterial lamina, connecting the two limbs of the bent

tube made up by the digestive tract, and supporting the

expanded inner segments of each of the four oviducts.

For a figure giving more details of the anatomy of Rliynchonella

Fsittacea, see Hancock, Phil. Trans., 1 858, pi. Ixi., fig. 2.
For figures of the nerve system, see Hancock, ibid., p. 845, pi. Ixii.
For the various names which have been applied to each of the two

valves, see Lacaze Duthiers, Ann. des Sciences Natm-elles,

Ser. iv., tom. xv., i86r, p. 266.
For the various views which may be taken as to the relationship of

the class, see Lacaze Duthiers, Comptes Rendus, 1865, ii.,

p. 800 ; Hancock, I. c, p. 848.
For the entire organization of the Brachiopoda, see Hancock, /. c,

ibique citata, and Lacaze Duthiers, II. ciii.
For a description of a larval form of Brachiopod, see Fritz Miiller,

in Reichert and Du Bois Reymond's Arcliiv., t86o, p. 72;

Mc Crady, Silliman's Journal, i860, xxx., p. 157.

Plan of Ascidian.

235

Figure 3.

Plan of Ascidian ; from Bronn's ' Klassen und Ordnungen des Thierreichs,' pi. xvii.,
fig. 9, after Allman, * Fresh-water Polyzoa,' p. 44, fig. 6.

Arrows mark the directions taken by the inhaled and exhaled
currents^ and a figure of a heart has been placed in a line with the
ventral margin of the branchial sac, with which one end of the
vasiform heart is very directly connected by means of a vessel in
relation with the structure known as the ' endostyle/ and indicated
in this figure by the thick vertical line passing down the left side
of the branchial net- work. Functionally, the direction of the heart's
action, and of the currents of blood it propels, are alternately reversed
in the Ascidians, as shown by Mibie Edwards (Memoire sur les
Ascidies Composees, Mem. de FInstitut, tom. xviii., 1842, p. 228);
but homologically, this vasiform prolongation along the line [of the
endostyle is probably to be considered as representing the veins
which in the Lamellibranchiata bring blood back to the heart from
various parts of the mantle, as well as from the gills (see p. 60, supra).
The concavity of the curve described by the first segment of the
intestine, together with the stomach, looks in most Ascidians
towards the line of the endostyle, and away from the single nerve
ganglion seen in this figure between the inhalant and exhalant ori-
fices. This disposition however of the parts is not constant in the
Ascidians, not being, for example, maintained in Ascidia affinis, the
species described under Preparation 22, p. 66 supra.

If this figure be so viewed as that the nerve ganglion shall occupy
the same relative place as the branchial or parieto- splanchnic gan-
glion I, of the Lamellibranchiate figured on Plate V, and the arrow
at the inhalant orifice occupy the same position as °the line a, and
the arrow at the exhalant the same position as the line c' in that
figure, the theory here adopted as to the homologies of the several
structures in the two classes of animals under comparison will be
made plain. The single nerve ganglion of the Ascidian will then
be seen to hold much the same relations to its exhalant and inhalant
tubes as the parieto-splanchnic ganglia of the Lamellibranchiate do
to the anal and branchial compartments of its mantle cavity; the
branchial sac of the Ascidian will correspond with the inferior or

236

Description of the Plates.

ventral, and the atrial chamber ^^^th the superior or dorsal com-
partment of the mantle cavity of the bivalve. The generative duct
is not figured in this diagram ; it opens however ordinarily, together
with the anus, into the free cloacal space which is seen between the
anus and the nerve ganglion, and which corresponds very closely Avith
the space called ' cloaca in the descrij)tion of Plate V; differing
indeed from it mainly in not being traversed by muscles such as
the posterior adductor and retractor. The vessels passing in the
non-cloacal portions of the atrial chamber from the pallial and
visceral plexuses through the tubular ties described by Mr. Hancock
to be distributed over the branchial net-work, would, possibly, cor-
respond to the vascular system of the organ of Bojanus, which is
interposed between the systemic and the branchial vessels. The
absence of a foot, and with it of a pedal ganglion, and the asymmetry
and less perfect evolution of the branchial sac in the Ascidians, must
be borne in mind as being the main points which mask the fun-
damental unity of type existing between the two classes under
comparison.

For views more or less in accordance with those adopted here,
see Cuvier, Memoires du Museum, torn, ii., 1815, pp. 13-34)
or Memoires pour servir a FHistoire et k F Anatomic des
Mollusques, 1817; V. Baer, Meckel's Archiv., 1830, p. 341 ;
Hancock, Journal of Proceedings of Linnaean Society, June
30, 1867.

See also Allman, ' Freshwater Polyzoa,' pp. 43-55 ; Quarterly Jour-
nal of Microscopical Science, Jan., 1869, p. 62 ; Nitsche, Dubois
Reymond und Reichert's Archiv., 186.S, Hft. iv., p. 518; La-
caze Duthiers, Ann. Sci. Nat., Ser. v., tom. iv., 1865; Sur un
genre nouveau d'Ascidian Le Chevreidius Callensis, L.D.

For the view according to which the branchial sac of the Ascidian
represents the dilated pharynx of a Lamellibranchiate Mollusc,
see Milne Edwards, Observations sur les Ascidies Composees,
Memoires de FInstitut, xviii., p. 274; Huxley, Phil. Trans.,
1 85 r ; British Association Reports, 1 852 ; Transact. Linn. Soc,
i860, xxiii., p. 202.

For the structure of the external test, see Huxley, Cyclopaedia of
Anatomy and Physiology, article ' Tegumentary Organs F. E.
Schultze, Zeitschrift fiir Wiss. Zool., xii., p. i75> i^^S-

Plan of Polyzoon.

237

Figure 4.

Plan of Polyzoon, from Bronn's ' Klassen und Ordnungen de8 THerreichs,' iii. i,
Taf. xviii., fig. I. after Allman, ' Fresli-water Polyzoa/ figs, i and 2, p. 7, fig. 8,

P- 45-

The animal is figured as it is seen when its lophophore, with the
tentacles it supports, the lower segment and outlet of the intestine,
and the single nerve ganglion which is situated between them, are
retracted into a cavity a, formed for their reception by the invagi-
nation of the endocyst into the ' cell/ The double arrow above a
indicates that the cavity thus temporarily formed is common to both
inhalant and anal orifices.

h. Nerve ganglion, situated between the two openings of the
digestive canal.

c. Lophophore, representing in this figure only one-half of the
horseshoe-shaped or ' hippocrepian' structure, distinguishing
all fresh-water species, except Paludicellea and Urnatellea,
and replaced in all marine species, except Rhabdopleura and
Pedicellina, by a simple orbicular collar. The hippocrepian
form of lophophore may be considered as constituted by the
prolongation into two arms of the simple circlet of the
marine species. The mouth opens between the two lips of
the lophophore in all species, marine and fresh-water alike ;
and in all, except Pedicellina, both lips are beset with a row
of ciliated tentacles. The two arms of the lophophore are
attached to the polypide around its mouth, of which they
appear to be a development, and they form thus the roof of
its perivisceral space, with which their interior freely com-
municates. They are free in the rest of their length, and
project from the oral over towards the neural and rectal
aspect of the animal. Hence in this diagram the anal
orifice occupies the right, and the oral the left side of the
nerve ganglion. There is no gizzard in fresh-water Polyzoa,
but the stomach has a large pyloric coecum ; from the lower
end of this a cord is figured as passing to the bottom of the
cell. This cord represents the cylindrical granular 'fani-
culus in connection with which the testis of the Polyzoa,

Description of the Plates.

and also in the fresh -water species^ certain non-sexual repro-
ductive gemmae are developed. The ovary is figured on the
oesophageal side of the cell, and towards its upper part.
From the bottom of the cell, where in most cases a distinct
septum separates the several polypides, retractor muscles are
figured as passing upwards and attaching themselves to the
sides and upper part of the oesophagus. As the nerve gan-
glion has been described as sending filaments to these
muscleSj as also to the evaginable endocyst, lophophore,
tentacles, epistome, and digestive tract, it would appear to
correspond not only to the cerebroid ganglia of higher
molluscs, but also to the parieto-splanchnic. A nerve collar
has also been figured as passing round the oesophagus from
the infra-oesophageal mass. The Polyzoa are devoid of a
heart ; and the blood contained in their perigastric cavities
is aerated and kept in motion partly by the ciliary action of
the inner surface of the endocyst; partly by its muscular
contractions; and partly by the muscular movements re-
tracting and protracting the entire polypide; which cause
the contents of the perivisceral and of the tentacular cavi-
ties to be freely interchanged.

For a figure giving full details on a large scale of the lophophore,
and its relations to the mouth, anus, nerve-ganglion, and
epistome, see Allman^s Monograph, ' Fresh-water Polyzoa,'
published by the Ray Society, pi. ii., fig. 24 ; and passim for
information as to the entire class, and especially as to the
fresh-water representatives of it.

For an enlarged view of the nerve-ganglion, drawn as surrounding
the oesophagus with a collar, see Nitsche, Dubois Reymond,
and Reichert, Archiv., 1868, Taf. xiii., fig. 23. See also Du-
mortier and Van Beneden, Mem. Acad. Bruxell., torn, xv.,
pi. iv., fig. 5, p. 85; Hyatt, Proceedings of Essex Institute,
Salem, U. S. A., v. 4, Oct., 1867, p. 107.

For a figure of a marine species, showing its orbicular lophophore,
ovicell, and avicularia, see Bronn, Klassen und Ordnungen des
Thierreichs, iii. 9, Taf. v., fig. 3.

For the existence of a nerve-system common to an entire colony,
see Fritz Miiller, Archiv. fur Naturgeschichte, i860, p. 311.

Figure of Rotifer.

239

FrGriRE 5.

Figure of Rotifer {Hydatina Smta), Female, fi-om Pritchard's Infusoria.
Natural size, ^ to of an inch.

The body is divided into nine zonular segments by eigbt annular
muscles ; its anterior extremity, which is much the larger of the
two, carries the ciliated apparatus, from the appearance produced
by the action of which the name of the class is taken, and its
posterior end is a pincer-like foot.

a. Emargination of ciliated border of anterior extremity of body,

leading into digestive tract.

b. Mouth, opening directly "into a muscular pharynx or 'mastax'

c, armed with chitinous teeth, which leads, by a short and
narrow canal d, into
e. The stomach, a large sacculated and ciliated organ, with the
upper end of which two large glandular organs are in rela-
tion, one only of which, that of the right side, is here
jBgured.

/. Cloaca, into which open, not only the rectum and the oviduct,
but also

ff. The contractile vesicle, which receives the lateral terminations

of the two water- vascular tubes.
k. Ovary.

i. Water-vascular tubes, convoluted at intervals, and giving off
also certain pedunculate infundibula, which are richly
ciliated, and open into the perigastric cavity, as do the
segmental organs of the Annelids. There are never less
than five of these ciliated infundibula in Rotifers.

Jc. Nerve ganglion, on the side of the body away from which the
mouth opens.

I. Tentacular organ, consisting of a setigerous pit, situated on
the dorsal surface of the body, and receiving filaments from
the nerve ganglion. There are no eyes in the genus Hy-
datina. The surface upon which the tentacular organ is
developed, and which corresponds in genera provided with a
lorica, to its convex portion, is kept upwards by the animal
in moving.

240

Description of the Plates.

m. Longitudinal muscles, the action of which, as also of the
circular muscleSj giving* the body its annulated appear-
ance, is counteracted by the elasticity of the chitinous
integuments.

For a description of the Hyclatina Senta, see Cohn, Zeitschrift fiir
Wiss. ZooL, 1 855 ; or Huxley, Med. Times and Gazette, J uly
26, 1856.

For the anatomy and relationships of the Rotifera generally, see
Huxley, Trans. Micros. Soc, 1853, 1-19; Moxon, Linn. Soc.
Trans., xxiv., 1864, p. 459 ; Pritchard, ' Infusoria,^ 4th ed., pp.
468, 656.

Figure 6.

Figure of Turbellarian Worm (Dendrocoehom Nausicaa), after 0. Schmidt, Zeitschrift
fiir Wissenschaftliche Zoologies Bd. xi., Taf. ii., fig. i.

This figure is intended to show, firstly, the general external
appearance of this Turbellarian, which bears a strong resemblance
to that of the common Dendrocoelnm lacteum, which is found
abundantly in the streams and ditches of the south of England,
especially in masses of the American weed {Anacharis Alsinastrum) ;
and secondly, the peculiarities of the digestive system, whence the
Dendrocoelous sub-order of Turbellarians takes its name. The
cilia which cover the whole of the bodies of these worms, and from
which the order takes its name, as also the nervous system, and
the complicated organs of generation, with the exception of the
intromittent organ with its capsule, and an organ of obscure func-
tion but of similar outer form to the male organ, have been omitted
in this figure.

a. Muscular pharynx, communicating with the mouth, which
lies a little posteriorly to the middle of the body. The
pharynx is in this species so long as to require to be thrown
into convolutions when retracted into its sheath, and it
attains thus a deceptive similarity to the proboscis of the
Nemcrtines or Rhynchocaelous Turbellarians. Probably in
no true Turbellarian does the mouth open quite terminally
at the cephalic extremity of the mouth, and the organ which

Figure of Rotifer.

241

is described as sucli in V, Carus' Icones Zootomicae, Taf, viii.,
fig. i6j in Prosiomum lineare, is really homologous with the
proboscis of the Nemertines, and probably also with a
rudimentary structure which by careful focussing can be
seen in the central lobe of the three into which the frontlet
of many Dendrocoela is divided, as in this specimen. The
Turbellarians never possess suckers^ differing herein from the
two other orders of Platyelraiirthes, the Trematodes and the
Cestodesj and the structure which has been described in
FrostovHum lineare as being a sucker, has been shown by
Claparede to communicate with its comparatively simple and
aproctous digestive sac. See Claparede, Beobaehtungen iiber
Anatomic und Entwickelungsgeschichte Wirbellos. Thiere,
1863, pp. 16, 17, Taf. iii., fig. 3.
Anterior coecal end of intestine, passing upwards between the
two eyes, and seen very clearly in the marine species allied to
this one to be underlaid by a band of nervous tissue, passing
across as a commissure between the two nerve-ganglia in
relation with the eyes. Of the presence however of even
the nerve-ganglia it is not always easy to convince oneself
with the semi-transparent fresh-water species Denclrocoelum
lacteum under the microscope, and it must be borne in mind
that in comparative anatomy, as in development, the evolu-
tion of the organs of special sense may take precedence of
the differentiation of central nerve-organs (see p. 157, supra).
The digestive tract between the opening into it of the
pharynx and this anterior coecal end gives off from eight to
eleven lateral branches ; two other branches pass back from
the point of junction of the digestive tract with the pharynx,
and surround the area in which that organ, as also the
orifice of the bisexual generative glands, and the male in-
tromittent and another organ of uncertain function, are
seen to be situated. These two branches fuse posteriorly,
and from the arch formed by their anastomosis numerous
branches pass backwards and outwards. This arborescent
form of intestine is always correlated with the absence
of an anus in the Turbellarians; and in the K,habdocoelous
Prostomum and Vortex, where the digestive tract is aproc-
tous, indications of a tendency to form lateral diverticula,

242

Description of the Plates.

as in tlie Dendrocoela, and less markedly in Uhynchocoela,
are not wanting to careful inspection.
c. Orifice of female organs. The penis, and a pear-shaped organ
which is of doubtful function, but which may be supposed
to be concerned in the formation of the shell of the ova,
have their openings distinct from, and placed posteriorly to,
this orifice instead of within it, as in the genus Planaria,
which is on this account separated from the genus Dendro-
coelum. For detailed descriptions and for figures of the
reproductive organs, see O. Schmidt, Zeitstfhrift fur Wiss.
Zoologie, X., 1859, p. 34, Tafs. iii. and iv., xi., 1861, p. ii,
Tafs. i., ii., iii., iv.
The Turbellarian Worms show in various parts of their organisation
points of affinity to several other orders of animals besides the Trematodes
and Taeniadae, with which they have been here classed as Platyelminthes.

In some of the smaller and almost microscopic forms of Ehabdocoelous
Turbellarians the oesophagus opens into the general cavity of the body,
no distinct intestinal wall being developed ; the resemblance of such forms
to the larger Infusoria, and indeed also to the Coelenterata, is very close,
so far as the digestive and tegumentary systems are concerned. Still even
in a young Turbellarian, in which the digestive tract might not be distin-
guishable within, nor the generative organs differentiated fi-om the general
parenchyma of the body, the presence of such organs as the otohthic cap-
sule would point to the real character of the animal. The presence of ' thread
cells' in the integument is a point common to the Turbellarians, with
the Coelenterata and many of the Holotrichous Infusoria {Parmmecium
bursaria), but it has been noted also in certain Polychaetous Vermes, and
in the Nudibranchiate Mollusca, which by their dendritic digestive tract
present a real resemblance to the Dendrocoelous Turbellarians ; as also
to some extent by their complex reproductive organs. The singular
aproctous parasitic Mollusc Entoconcha mirabilis, which appears to be
nearly allied to the Nudibranchiate Molluscs, is, as figured and described
by Baur, Nova Acta, 1864, p. 35, by no means unlike, in the general rela-
tions of its various systems, to an aproctous Khabdococlous Turbellarian.

It is of more importance perhaps to note that the order Turbellarians
comprises forms which, whilst inseparably connected with each other by
connecting links, are yet so various as to present, at either end of the
series they make up, close approximations both to the highest and to the
lowest of the Vermes, to the unity and real compactness of which sub-
kin-dom they thereby appear to speak very distinctly. Dinophilus, for
example, has been ranked by Schmarda with the Naidina (see Nene Wn--

Figure of Rotifer, 243

bellosc Thiere, i. 2, p. 9), whilst by most othei- authors, as Van Beneden,
V. Carus, and 0. Schmidt, it is ranked as a Turbellariau. Such a form as
Macrostomiwi setosum (Schmarda, I. c, p. 7, Taf. i. 15 and 15 a) is espe-
cially instructive as showing how direct the transition may be from the
cihated integument, whence the Turbellarians take their name, to the
setigerous exterior of the Annelids. The ISTemertina s. Khynchocoela,
with which these minute worms are more or less closely allied, are by
almost universal consent ranked as Turbellarians, and they by their pos-
session of a perivisceral cavity, which is wanting in the Ehabdocoelous
and Dendrocoelous sub-orders, bring the entire order into still closer
relationship with the Annelids.

On the other hand, the kinship of the Turbellarians with the lowest of
the Vermes, the Trematodes and Taeniadae, is even more obvious, and by
virtue of it these three orders are ordinarily classed together ; and it
may be sufficient here to refer to the description of the class given in the
Introduction, some of the chief points of resemblance specified in which
may be illustrated from Schmarda's work, pp. xi., xiii., Taf. ii. 22.

Tor the classification and for many points in the anatomy of the
Turbellarians, see Max Schnltze, Archiv, fiir Naturgeschichte,
1849, p. 280 J Archiv. fiir Anatomic und Physiologie,
p. 351; O, Schmidt, Sitzungsbricht. Akad. Wiss, Wien. xxii.,

1857. p. 347-

For the anatomy of tlie Nemertina s. Turbellaria Rhynchocoela, see
Keferstein, Zeitschrift fiir Wiss. Zool.j xii., 1 862, p. 66.

Figure 7.

Gregarine {Etylorhynchus Oligacanthus), a Parasite found in the intestinal tract
of Callepteryx Vvrgo ; after Stein, in V. Carus' Icones Zootomicae, tab. i., fig. 3.

This animal consists of two unequal parts, the smaller being the
anterior, and armed with a coronet of spines ; the larger being the
posterior. It contains a large nucleus. The division between
the two parts of the body is formed, according to Kolliker, not
by an involution of the integument, but by an induration of the
hyaline cytoplasm or protoplasm, which, together with the nucleus
and the fatty granules which in all but young specimens give a
milky colour to these animals, make up its contents or paren-
chyma. Gregarinae, therefore, even when ' dicystideous,^ as in this
case, are really unicellular organisms. There are no sensory,
circulatory, digestive, or other specialized organs in this animal.

244 Description of the Plates.

Its power of executing active movements is due to the contractility
of its amorphous protoplasm or cytoplasm.

a. Anterior part of body or ' head.' The part upon which the

line a abuts is of dark colour, to denote the presence there
of the opaque fatty granules which give the adult Grega-
rines their milk-white appearance.

b. Posterior half of body, the integument or cell-wall being

slightly removed from the contained parenchyma, as it may
be by imbibition of water, though in the normal condition
of the parts it is not very sharply limited off from it.

c. Proboscis, into which it will be observed the granular opaque

element of the parenchyma does not extend.

d. Apical expansion armed with excretions of the cell-membrane

in the form of spines.

e. Should have pointed to the line of compartmental severance

between the two halves of the body, and this diaphragm
should, according to Kolliker, have been drawn as produced
by the contained protoplasm, not by the enveloping cell- wall.
/. Nucleus containing a number of brightly refracting granules.
It is not known to be directly concerned with the reproduc-
tion of these Protozoa, as is the ' nucleus' of Infusoria, or at
least not more directly than by being involved in the general
solution and rearrangement into small round masses, and ulti-
mately into ' pseudonavicellae,' which the entire parenchyma
undergoes after encystation, and which constitutes most of
what we know of the developmental history of Gregarinae.

See, for a general account of the Gregarinae, KoUiker, Icones His-
tiologicae, i., p. 7. See also Lieberkuhn, Archiv. fiir Anatomie
und Physiologic, 1865, p. 508 ; Lankester, Quarterly Journal of
Microscopical Society, vol. vi., p. 23 ; Stein, Der Organismus
der Infusionsthiere, ii., 1867, pp. 6-8, 19, 20.

For the possibility of a subsistence of a relationship between the
organisms known as ' psorospermiae' and ' pseudentozoa' and the
Gregarinae, see Lenckart, Die Menschlichcn Parasiten, pp. 14 f,
743 ; Bcale, Third Report of Cattle Plague Commissioners,
1866, Appendix, pp. 141-144; Cobbold, On the Nature of
Pseudentozoa found in Diseased and Healthy Cattle, Entozoa,
Supplement, 1869, p. 40.

PLATE Xn.

Fig. 1. Diagram of Tapewobm in Cestoid or Fig.

Strobile Stage.
Fig. 2. Halfof a young segment or Proglot- Fig.

tis of Tapewokm {Tccnia Cccnu-

rus) magnified.
Fig. 3. Diagram of entire segment as de- Fig.

tached when ripe or adult. Fig,
Fig. 4. Ripe segment, twice the natural size, Fig

of Tivnia Solium.

5. Embryo of Tapeworm wntliout the

shell.

6. Diagram of Mant-headed Bladder

WouM {Twnia Canuriis) in cystic
stage.

7. Hydra Viridis.

8. Infusorium. Prororlon Teres,
g. RuizoPOD. Amoeba Badiosa.

PLATE XIL

The figures i to 5 are intended to show semi-diagrammatically the
different stages of the metamorphosis or the ' alternation of genera-
tions' in the life of one of the typical Taenioid Flatworms or Platy-
elmiuthes. Figure i represents the perfect animal as it is found
in the compound form, called ' strobile/ from the analogy of the
cone of a fir, in the intestinal canal of ordinarily a carnivorous or
omnivorous vertebrate ' host/ such as the dog, or the human sub-
ject. Figure 2 represents one of its segments, the so-called ' pro-
glottides/ as it may be seen before the great development of the
ova in the uterus has overwhelmed and caused the disappearance
of the other sexual organs, female and male, which each segment
after the sexless adherent ' head^ or ' nurse^ contains. Figures 3
and 4 represent ripe segments of the compound animal, so dis-
tended with ova as to have caused the ripe proglottides, which
retaia considerable locomotor powers, to be called 'ovaria ambu-
lantia.'' Figure 5 shows one of the microscopic embryos, the
so-called ' proscolex/ as it appears when set free from its shell by
the action of the digestive secretions of the intestinal tract, into
which it is introduced ; the entire ovum having been set free from
the substance of the 'proglottis' by its spontaneous or other dehis-
cence, inside or outside of the digestive tract of the animal, which
is to be its host. Figure 6 shows the cystic stage into which such
a proscolex as that shown in Figure 5 developes into, when it has
belonged to Taenia caenunis, which diflFers from other Tapeworms
except Taenia echinococcus , in having its proscolex proliferating as
shown in the figure, instead of producing a solitary ' new head' or
' scolex/ This cystic stage is passed in the parenchyma of some
solid organ, such as the liver or the muscles ; and in the particular

246

Description of the Plates.

case of Taenia caemirus, in the brain of tlie sheep, most usually,
though not rarely, in other parts of the body of this ruminant, as
also of rodents. (See Description of Preparation 43, p. 136^ supra.)

Figure i.

Tapeworm, as found in the intestinal canal of man or of a dog, semi-diagrammatic ;
after Van Beneden, M^moire sur les Vers Intestinaux, Paris, 1858, pi. xxvi.,

fig- 25.

The asexual ' head' or ' nurse' is armed with a double circlet of
spines, as is the case with Taeniae which are harboured in the in-
testines of Birds and of carnivorous mammals ; whilst the Taeniae
of fish, batrachians, and herbivorous mammals are not possessed
of this armature. Posteriorly to the circlets of spines is seen a
circlet of four suckers. The definition of the segments* begins to
be evident a short way posteriorly to the head; the segments
increase in size and ripeness from before backwards; the most
posterior may be takeft to have been such segments as are figured
at 3 and 4. " The entire compound animal as seen in this figure
is trimorphic, consisting of a sexless armed adhesive 'head' or
' scolex ;' of unripe ' proglottides' secondly j and of ripe proglottides
thirdly.

FlGTJEE 3.

Half of an unripe segment of Taenia Caenurus, to show the generative organs, male
and female ; after Leuckart, Die MenschUchen Parasiten, p. 179. ^g- 3°.

a. Water-vascular or excretory system. Two longitudinal vessels,
one of which is often much larger than the other, and is
not shown in this diagram, run along either side of each
segment, parallel with and close to each other, and are
connected with their fellows on the opposite side of each
segment by a transverse annular anastomosis. This trans-
verse connecting vessel takes in the last segment the shape
of a median vesicle into which the lateral vesicles converge,
and through which they open on to the exterior. In some
cases similar openings have been observed in the anterior
portions of the Tapeworm, posteriorly to the suckers, and

Taenia Caenurus,

247

communicating- with the lateral trunks by short transverse
anastomoses. These vessels are both contractile and ciliated.
In their ramifications, besides other excretory matters which
they may be supposed^ from the analogy of other allied
animals (g-uanin having- been found in the water-vascular
system of Trematodes) to contain, crystals of carbonate and
phosphate of calcium are founds and sometimes^ as in both
the other classes of Platyelminthes^ in great abundance.
These calcareous corpuscles are found both in the central
parenchyma and in the cortical layers of the Taenia, but in
greatest abundance in the latter strata^ into which a dense
reticulation of capillary vessels^ in which the corpuscles are
lodged, may be observed to spread from the larger quadri-
laterally arranged vessels which lie in the central paren-
chyma.

b. Uterus, in the unripe segment running as a straight tube

from the posterior part of each segment to its anterior.

c. Ovary, or rather, as the yolk is furnished in these as in other

Platyelminthes by a separate set of glands, the 'germi-
genous'' gland. This organ occupies a place quite at the
posterior end of each segment, and has a reticular arrange-
ment.

d. Bilaterally symmetrical yolk-secreting gland or ' vitellarium,'

lying anteriorly to the germigenous gland. The two stems
carrying the digitate processes of either side unite into one
common duct ; this common vitelliferous duct joins the
vagina just above the spot where it dilates into a recepta-
culum seminis. The common duct formed of these three
factors carries its two kinds of contents into the dilated
end of the uterus, just where it receives the duct from the
germigenous gland, the products of which are thus brought
at once into relation with the yolk and the spermatozoa.
The granular layer of the cortical stratum which immedi-
ately underlies and secretes the chitinous ' cuticular'' struc-
ture of the cortex, and overlies the muscles, has been
sometimes mistaken for the true vitelligenous glands here
described.

e. Testes appended in a racemose manner by very delicate ducts

to the vasa deferentia. They were more abundant in the

248

Descrijption of the Plates.

anterior half of the segment which is removed, than in this,
the posterior.

f. Intromittent organ, essentially a specialization of the muscular

ductus ejaculatorius. It is armed with spines, which favour
its retention in the vagina, in the act of self-impregnation
ohservable in these ' heautandrous' hermaphrodites. It is
here figured as retracted and coiled up spirally ; it is figured
as protruded in Figure 3.

g. Vagina dilating into an oval receptaculum seminis, before

joining the duct of the two vitelligenous glands. The
vagina opens externally in the posterior half of a saucer-like
depression on one side of a segment ; in the anterior half of
each the male outlet is situated. The generative outlets are
similarly arranged in the Taenia cuc^imerina, a tapeworm
commonly found in the dog; and in the Taenia ellijdica, a
tapeworm which infests the cat; hut the glandular organs
being double, the outlets are double also, and exist on both
lateral edges in each segment. In the Taenia medioca-
nellata of the human species, the common generative de-
pression is situated some way behind the middle of the
lateral border of each segment; in the Taenia solium it is
nearer to the middle line, whilst in Bothriocephaliis latus,
which, like the two tapeworms, infests the human subject,
both orifices are situated on one of the flat aspects of the
segment they belong to. In other species, the male orifice
may be situated on the edge, and the female on the flat
aspect of each segment.
A segment with the generative organs in the condition here
figured, would be found in either Taenia solium or Taenia
mediocanellata, the two common human tapeworms, at about
the 450th segment counting backwards from the head ; and
the segments would assume the appearance given in Figures
3 and 4, after about aoo more segments in Taenia solium^
and 360 to 400 in Taenia mediocaiiellaia.

Diagram of Proglottis.

249

Figure 3.

Diagram of a ripe Proglottis, as cast free from the posterior end of the compound
colony ; one of the 'Vermes Cucurbitini' of the older authors.

Its edges are rounded off ; the penis is figured as protruded from
the orifice into which the generative ducts open ; but the rest of
the generative organs are overwhelmed by the abundant ova. But
such a proglottis as this might retain, even when detached from
the strobile, the power both of vegetative growth and of locomo-
tion ; and whilst moving freely in the contents of the digestive
tract it was infesting, might grow to be as large as the entire
strobile. Such proglottides have been mistaken for Trematodes,
or for Taeniae without segments. By means of the three muscular
layers of the cortex, the proglottis can move with considerable
power and effect from place to place, when discharged from the
intestinal canal of its host, so long as it is in an atmosphere
saturated with watery vapour. Such proglottides have been aptly
styled ' ovaria ambulantia.'' The ova are ultimately set free by the
spontaneous dehiscence of the cortical walls.

See Van Beneden, Memoire sur les Vers Intestinaux, 1858, p. 249,
and pi. xxvi., fig. 26, whence this figure is taken. For the
muscular layers in the cortex of the Taeniadae and Trematodes,
see Leuckart, Die Menschlichen Parasiten, Bd. i., p. 459.

FlGTJUE 4.

Segment of Taenia Solium, to show the dendritic outgrowing of the uterus, about
twice the natural size ; after Leuckart, I. c., p. 177, fig. 29.

This segment is not so far advanced towards maturity as the
segment figured at 3, its angles not being rounded off; but the
uterus and its contents have increased and encroached so much
upon the rest of the generative organs, as to have caused their
disappearance. In Taeriia solium, these dendritic ramifications
would have a yellowish colour, and be found to be made up of
aggregations of embryos, such as the one figured at 5, enclosed in
a hard resistent shell. It has been remarked that the proglottides

250

Description of the Plates.

of different species of Taeniae differ often very little or not at all
from each other, even though their ova would give rise to as
different a series of phaenomena as are presented by the histories
of the Taenia caenzmis and the Taenia serrata, the ova from the
former of which would produce in a sheep such an organism as that
figured at 6 ; whilst the ova of the latter would produce in a sheep
no appreciable effect at all. The Medusae of different species of
Polypes are similarly much ahke ; and in each case it is possible
that the similar mode of life which the sexual zooid in each set of
cases goes throughj accounts for the loss at that particular stage
of its specific and distinctive characteristics. The reverse is the
case in the developmental history of the parasitic Crustacea, in
which the larvae are alike, and the sexual animals very different
in structure. See Van Beneden, I. c, pp. 113, 148; Polypes,
Introd., p. 7-

Figure 5.

Embryo or proscolex of an ordinaiy Taenia, armed, as is the case except in certain
marine fish-infesting Taeniae {Tetrarhynchus) with six spines ; after Van Beneden,
I. c, pi. xxvi., fig. 27.

Such an embryo as this would be of about three times the size
of a human blood-corpuscle, o-022-o-028 Mm, and when set free
from the hard shell, which is not drawoi in this figure, by the action
of the digestive fluids of its host, it would bore and push its way
from the mucous surface of the intestinal tract into the blood-vessels,
and so pass along them into the liver, a very common place for the
development of the cystic stage, or, subsequently, into other organs.
The two spines of the central pair of the three are symmetrical, and, in
piercing the portal radicles, they have an antero-posterior movement
analogous to that executed by the oral stylet of certain parasitic
Crustaceans. The two spines again on the extreme right and left
of the series are symmetrical with each other, as are the two re-
maining ones, which, in numbering the whole series from left to
right, would stand as 2 and 5. These two latter pairs move in the
piercing of the tissues much as the fore limbs do in swimming.
The wound made is, on account of the small size of the embryo,
readily overlooked ; and it has been incorrectly supposed that the
embryos found their way into the liver by the way of the bile-

Many-headed Bladder-ivorm.

251

ducts. The six spines are to be recognised again, though scattered
and dislocated from their position as given here, in the more or less
distended, cystic or cysticercoid vesicle, into which the proscolex
expands when it reaches its place of lodgment in the tissues.

See fig. 6 h for Caemirus cerehralis, Van Beneden, 1. c, pi. xxvi.,
fig. 34 ; for the six spines as seen in the cystic stage of Taenia
ecUnococcus, Leuckart, I. c, fig. 51, Micrographic Dictionary,
pi. 16, fig. 3 ; for the six spines in Taenia solium, Cysticercus
cellulosae, see Cobhold, Entozoa, p. 235, fig. 48 ; for those in
Cysticerms limacis, and Stein, for similar organisms from the
perivisceral cavity of the larvae of Tenehrio molitor, which must
be supposed to gain the cestoid form in the digestive tube of
some insect-eating bird or mammal, Zeitschrift fiir Wissen-
schaftliche Zoologie, Bd. iv., 196, Taf. x., figs. 12, 13, 14, 16,
and V. Carus' Icones Zootomica ■, Taf vii., fig. 20.

For a history of the migration of these embryos, see Van Beneden,
I, c, p. 238 ; Leuckart, I. c, p. 198.

FlGUEE 6.

Cystic stage in the development of Many-headed Bladder-worm, Caenurus Cerehralis,
after Van Beneden, I. c, pi. xxvi., fig. 31.

The embryonic hexacanth embryo, figured at 5, has become greatly
distended after coming to rest in the organ, ordinarily the brain of
a sheep, into which it is carried by the blood after penetrating these
vessels. The six hooks are observed to be scattered and dislocated
over its surface at 6, and a number of *■ scolices/ the potential
' heads^ or ' nurses ' of a future tapeworm, are observed to be
developed upon one of the poles of tbe enlarged vesicle. The way
in which these heads are formed in the Taeniadae appears to be as
follows. In the innermost submuscular cellular layer of the cyst,
a proliferation of cells takes place, and forms a thickened disc. Into
this a single depression in the monocephalous Taeniadae, and from
3 or 4 up to 300 or 400 in the Caenuri, make their way from the
outside of the mother cyst inwards. On and out of the thus
inverted external layer, the cuticular layer of the future scolex, with

252

Description of the Plates.

its spines and suckers, is developed; whilst out of the thickened
disc the deeper layers of the cortex are formed. Each head thus
at first points inwards towards the interior of the parent cyst ; but
by the contractions of the muscular layers of this cyst, as also by
those of the intrinsic muscles of the cortex of each head, it may
come to have its apex pointing in either direction, either outwards
towards the circumambient tissues of its host, or inwards towards
the interior of the maternal vesicle.

a. Wall of embryonic dilated cyst, containing, as do the homo-

logous structui-es in the other Platyelminthes, calcareous
corpuscles.

b. Hooks of embryonic vesicle scattered and dislocated by its

distension.
c I. Scolex fully protruded.
c %. Scolex half protruded.

d. Scolex as developed with its apex pointing inwards and its
tubular body in communication therefore, not with the
parent cyst, but with the cavity of the adventitious cyst
thrown round the entire organism by the irritated tissues
of its host. The central parenchymatous portion of none
of these scolices is as yet developed, the sexual organs of
which the central parenchyma is all but exclusively made
up, not being developed except in the cestoid stage attained
to in the intestine of the dog.

For history of Caenunis cereh-alis, see Van Beneden, I. c, p. 146;
Cobbold, Entozoa, p. 1 16 seqq, ; Gamgee, Report on the Para-
sitic Diseases of Quadi-upeds used as Food (Med. Officers'
Privy Council Office Report, v. 1862) ; Thudichen, ibid., vii.,
1865.

For other figures illustrating the various stages in the development
of these Taeniadae, see Cobbold's Entozoa, p. a 16, pi. xii., et
passim.

Common Hydra.

253

FiGUKE 7.

Common Hydra (Hydra Viridis) showing the perfectly free communication or con-
tinuity vnth the body cavity which the digestive tract possesses ; the continuity of
the cavities of the tentacles with the digestive sac, and their contractility, as indi-
cated by the annulation of their external surface as at a ; and the reproductive
organs in situ. After Greene ; Manual of Coelenterata, 1861, p. 24.

The animal is di-awn as attaclied bj its ' hydrorliiza' to a piece
of weed with the oral end downwards^, as in the position very ordi-
narily assumed by it during life. It is much enlarged, its natural
size being, at the greatest, little over three quarters of an inch in
length. The Hydra differs from most other Hydrozoa, except the
free forms of the class,, in the three following particulars : firstly,
in consisting of but a single polype, in which point only a few
Corynidae resemble it; secondly, in. being totally destitute of any
external polypary; and, thirdly, in possessing the power of loco-
motion as well as that of fixation to one spot. It differs again from
all Coelenterata, with the exception of Cordi/lop/wra lacustris, by its
fresh- water habitat.

a. One of the tentacles, externally annulated, owing to the con-
traction of the external layer or ectoderm, which, in the
terminal part of the tentacles, can be very well seen to be
bounded internally by a structureless ' basement membrane"*-
like layer, which again forms here the innermost layer, the
cellular endoderm not being developed. The ectoderm is very
richly bestudded with the thread cells, so characteristic of
all Coelenterata (except Ctenophora?), but, besides a few
pigment cells, it is said by Keichert to contain no other
morphological element, its contractility depending upon a
perfectly homogeneous and hyaline substance, as in Rhizo-
poda. The basement-like membrane is an excretion from
the ectoderm, just as the chitinous external polypary is also
in other Hydroid Zoophytes, but has been supposed to be
muscular in character. As this figure shows that con-
tractility resides in parts of the organism of the Hydra,
where the purely cellular endoderm is absent, that layer of
the body at all events may be supposed with some prob-
ability to be devoid of this faculty.

254

Description of the Plates.

b. Moutli, ^trompe buccale' of Van Beneden; a clear line mark-

ing- the line of junction of endoderm and ectoderm.

c. Body-cavity, directly continuous with the digestive, and so,

indirectly, with the tentacular cavities.

d. Conical testicular glands, which set free their spermatozoa by

dehiscence outwards, and can be approximated by flexion of
the animaFs body to the inferiorly placed ovaria.

e. Large protuberance containing a single ovum, as seen in the

autumn, proliferation taking place in the way of gemmation
and separation of the buds during the summer months, just
as agamogenesis prevails during the same period in the

Daphnidae and Botifera, but is replaced by the sexual im-
pregnation of the ' winter ova'' at the latter end of the year.
In the Spongilla, and the fresh-water Polyzoa, on the other

• hand (see pp. 163 and 238, supra), this history is reversed,
agamogenesis by means of gemmules inclosed in a resistent
capsule, taking place towards the close of the warmer months
of the year, whilst a true sexual process takes place during
the summer months. The ovum here is seen to be sur-
rounded by a polygonally-shagreened capsule, which, how-
ever, is not spinous here as in Eijdra vulgaris. The ovum is
still enclosed within another capsule, furnished to it by the
substance of the body-walls, in which, between the endo-
derm and ectoderm, the generative products are developed.

The Hydra is not always monoecioug, as figured here; most ordinarily
the Hydroid Zoophytes are dioecious ; and as the Hydra possesses a cer-
tain power of movement from place to place, while the other Hydroids
do not, we should, cl i^riori, have expected to find the allocation of her-
maphroditism to be the reverse of what it actually is. The history, how-
ever, of Cerianthus, one of the Anthozoa Avhich possesses some slight power
of locomotion, which is rare in the class it belongs to, and is at the
same time hermaphrodite, which no other Anthozoou is known to be, is
similarly surprising. The analogy of the language universally employed
by us when speaking of animals in any one of the higher sub-kingdoms,
would cause us to speak of the structures here lettered d and e, as
' orcrans whilst the history of the development of the various Hydroid
Zoophytes, or an observation of the unbroken chain of gradations which
connects these 'organs,' through such fixed gonozooid forms as those of

Common Hydra.

265

the sea-fir, Sertularia ahietina (for which, see Description of Prei)ani-
tion 48, p. 160), with the free 'Medusae,' would induce ua to speak of
them as 'individuals.'

/. Hydrorhiza, forming the single point of attachment of the
animal, and supposed by some to be perforated so as to give
passage outwards to certain secretions from the body cavity,
the mouth being undoubtedly the channel by which the
refuse of the ingested alimentary matter is ejected. The
external layer of integument covering the adhering disc^ is
made up of sub-cylindrical cells, larger and more closely set
than those on the rest of the polype- stem.

For the histology of the Hydridae, see Huxley, Miiller's Archiv.,
i85i,p. 381; Oceanic Hydrozoa, 1859, p. I^^J^^g'j MulWs
Archiv., 1854, p. 276; Professor Rei chert, Monatsbericht der
Akademie der Wissenschaf . en zu Berlin, July, 1866, translated
in the Annals and Magazine of Natural History for January,
1867, p. 54. For the intermediate excretionary layer, see
Claus, Zeitschrift fiir Wiss. Zoologie, x.. 1 860, p. 300. See also
KoUiker, Icones Histiologicae, ii. Abtheilung, pp. 88, 100, 1866 ;
Leuckart, Archiv. fiir Naturgeschichte, 1 854, i. 369 ; Leydig, I. c.

For the discussions as to the individuality of the various Zooids, see
Claus, I. c, pp. 326-329 ; Gegenbaur, Vergleichende Anatomic,
pp. 94-103, where, as also in V. Carus^ Icones Zootomicae, p. ii.,
exceedingly instructive semidiagrammatic figures of those
organisms in the Hydrozoa are given. See also Hincks, His-
tory of British Hydroid Zoophytes, pp. xxxv— xxxix ; Leuckart,
Polymorphismus der Individuen oder die Erscheinungen der
Arbeitstheilung in der Natur., 1851.

FiGTJEE 8.

HolotrichouB Infusorium (Prorodon Teres), from Stein, in V. Carus' Icones
Zootomicae, Taf. i., fig. 27.

We see its armed oral inlet at one pole of the . body, its con-
tractile vesicle at the other, the cilia which in the sub-order
Holotricha clothe the entire surface with a uniform covering, the
sexual organs, and the globular masses of nutriment, which having
been ingested by the mouth have been distributed throughout the
parenchyma of the body.

256

Description of the Plates.

a. Cilia, of uniform size all over the body. These organs are
supposed to belong to the parenchyma of the body, and to
be protruded through innumerable very fine orifices in the
indurated integument. The integument in the ciliated
Infusoria is sufficiently resistent to give their bodies the
definite outline which distinguishes them from those of the
other Protozoa; but it is not ordinarily demonstrable as
distinct from the contained parenchyma without the use of
reagents.

h. ' Nucleus' or ovary, with adherent ' nucleolus' or testis.

c. Contractile vesicle, probably representing rudimentarily a

water-vascular or depuratory system, and opening on the
exterior of the body. It is always situated in the cortical
layers of the parenchyma, but does not appear to have defi-
nite walls of its own, as distinct from the contractile cyto-
plasm in which we find it. Tubular ramifications exist in
connection with it in some genera.

d. Particles of alimentary matter, which, together with the struc-

tures lettered b, c, e, and with pigment granules, oil globules,
and very fine cortically-placed granules, malce up the mor-
phological elements contained in the hyaline ' sarcode' or
' cytoplasm.'

e. Oral inlet placed in this species, though not ordinarily in

others, at the apical pole of the body. It is prolonged into
an oesophagus lined by a prolongation inwards of the cuticle,
and strengthened by the development upon it of longitudinal
teeth forming a circlet. The oesophagus opens directly into
the central parenchyma of the body, which is less closely
compacted together than the cortical layers, and in which
the particles of food, together with such water as is swal-
lowed with them, can freely circulate. The undigested
refuse of the alimentary particles are ultimately extruded
by the anus, which has a fixed position in all Infusoria
except the aproctous Opalinae and Acinetinae, and which in
this species is near the contractile vesicle c, at the aboral
pole of the body. It is ordinarily visible only at the moment
of the extrusion of the faeces, except in the few cases, of
which Prorodon is not one, in which the cuticle is prolonged
inwards at that, as it is at the oral orifice. Tlie excess of

Fresh-water Rhizopod.

257

ingested water must be supposed to be got rid of by passing
into the vessels in connection with the contractile vesicle, and
by being thus expelled from the body.

For an account of the anatomy of the Protozoa, see Kolliker's Icones
Histiologicae, Abtheil. i., pp. 9-24, 1864; Stein, Organismus
der Infusionsthiere, Abtheil. ii., pp. 1-140, 1867; Claparede et
Lachmann, Etudes sur les Infusoires et les Ehizopodes, vols. i.
and ii., 1 858-1 861 ; Extr. des tomes v. et vii. I'Institut
Genevois; Leuckart, Die Mensehlichen Parasiten, p. 135.

For an account of the genus Prorodon, see Claparede et Lachmann,
/. c, vol. i., 318.

ElGUEE 9.

Amoeba Radiosa, a fresh-water Bliizopod ; after Auerbach, Zeitschrift fur Wiss.

Zoologie, viii., Taf. xxi.

Showing its pseudopodia, its contractile vacuoles, its nucleolated
nucleus, and the algae and navicellae which it has enveloped in the
substance of its parenchyma. The central portion of the body is
very ordinarily of about the size of a human white blood-cell, and
the pseudopodial processes may be as long as from twice the length
of the diameter of the central mass up to as much as five times as
long ; but the size and shape both of body and of pseudopodia are
very variable, and make the distinction of species a matter of
much uncertainty.

a. One of the pseudopodia. The pseudopodia differ fi'om those

of most other Ehizopoda in not being branched at their
apices ; in not anastomosing with each other ; and, as this
figure shows, in not having the granular substance of the
central parenchyma body circulating within them. The
' sarcodic expansions,' as the pseudopodia have been called,
are very usually more broadly lobate than those figured
here ; it is by their alternate protrusion and retraction, from
which these animals take their names, that locomotion is
effected.

b. Nucleus and nucleolus.

c. Contractile vacuole. The possession of vacuoles, as also of the

s

Description of the Plates.

nucleus and nucleolus, by the Amoebina and Actinophryna,
differentiates them from the other Rhizopoda, and has
caused them to be placed in a separate order, as ' Infusoria
Ehizopoda,' or ' Rhizopoda Sphygmica,' The Actinophryna
differ from the Amoebina in having- their granular cen-
tral parenchyma carried by circulation into the interior of
their pseudopodia, which also are delicate and filamentous,
and anastomose apically, like those of the Foraminifera and
Radiolaria; but they resemble the shelless Rhizopod here
figured, not only by possessing the structures h and c, but
also by enveloping alimentary substances within their paren-
chyma, as the Amoeba is seen to do at d and e. At the
same time, the circulation which takes place in the pseudo-
podia of the Actinophryna is to be borne in mind as favour-
ing endosmosis, and thus^ though it is much less ener-
getically carried on in them than in the typical Rhizopoda,
enabling them to extract nutriment from their prey by the
same suctorial process which is the single method by which
those animals absorb nutriment.

d. Navicula, one of the Diatomaceae, swallowed as food.

€. Spore of conferva enveloped as nutriment by the parenchyma
of the body. It is only in the larger specimens that these
' vegetable remains are found ; and it is rare in any Amoeba
to find any traces of any other kind of nutriment. The
action of digestion is shown by the decolorization of the
chlorophyll, as well as by other changes effected in the
ingesta. It does not seem possible to demonstrate the pre-
sence of an external enveloping membrane in the Amoebina,
except in Amoeba bilimbosa, unless reagents be employed,
which themselves probably cause the differentiation observ-
able after their use. And there does not seem to be any
positive reason for supposing that these animals possess a
mouth which is only opened at the moment of swallowing,
and has its lips so closely appressed at other times as to
make the aperture invisible, as is the case in the Infusorial
genus Amphileptus. The absence of mouth, anus, differen-
tiated tegumentary envelope, and cilia, must be held to
justify the separation of Amoebina from the Infusoria, with
which however they are placed by Kolliker and V. Carus,

Fresh-iuate7' Rhizopod.

259

on the g-roiindthat they not only possess, as do the Actino-
phryna, a nucleolated nucleus and a contractile vesicle, but
also differ, which the Aetinophryna do not, from the other
Rhizopoda in having* no anastomoses between^ and no circu-
lation of granular sarcode within their pseudopodia.

For the anatomy and physiology of the Amoebae, see Auerbach,
Zeitschriffc fiir Wiss. Zoolog-ie, vii., 1855, p. 365 ; Claparede et
Lachmann, Etudes sur les Infusoires et les Ehizopodes, vol. i.,
P.4i3-

For other figures of Amoeba radiosa, see Auerbach, I. c, Taf. xxi.,
and for descriptions^ p. 400 ; Pritcbard's Infusoria, pp. 204,
.548.

For the relationships of the Actinophrjoia to the Amoebean and
the more typical Rhizopoda, see Claparede et Lachmann, 1. c,
p. 418.

For the recent Foraminifera of Great Britain, see Professor Wil-
liamson's Monograph, published by the Ray Society, 1858.

For the organization and classification of the Rhizopoda generally,
see Carpenter's Introduction to the Study of the Foraminifera,
(published by the Ray Society), 1862, pp. 12-17; and for the
Rhizopoda of the deep sea^ see Carpenter, Royal Society's Pro-
ceedings, JunCj 1869, vol. xviii,, p. 1 14.

For the sarcodic substance of the Rhizopoda, see Professor Hackel,
Zeitschriffc fiir Wiss. Zoologie, xv., 1865, p. 342.

s 2

ADDITIONS AND EERATA.

Page 8, 5 lines from bottom of the page ; in accordance with the language employed
by Mr. William K. Parker, in his work on the ' Shoulder Girdle,'
pp. 145, 209, 210, which was not in my hands when the first pages of
this part of this book were printed off, for "There are two lateral
episternal," read "There are two lateral omosternal ;" and at 3 lines
from bottom of page, /or " there is no central epistemum," read "The
praesternum does not develope a pro-osteon, as in Helamys and Coelo-
genys."

Page 9,11 lines from bottom of the page, add reference to Mr. Parker's work, " A
Monograph on the Structure and Development of the Shoulder-Girdle
and Sternum in the Yertebrata," by "W. K. Parker, F.R.S., F.Z.S.,
London, published for the Eay Society by Robert Hardwicke 102'
Piccadilly, 1868. ^

Page 13, II lines from bottom of the page, add reference to Mr. Darwin's work,
which, like Mr. Parker's, was not in my hands when these pages were
struck off, " The Variations ot Animals and Plants under Domesti-
cation," vol. i., pp. II 5-1 30, Osteological Characters of Rabbits.

Page 39, 15 lines from top of page, add reference to Professor Huxley's Paper
"On the Alectoromorphae," Proceedings of the Zoological Society,
May 14, 1868, p. 294.

r'age 33, 16 lines from bottom of the page, for "The Ophidia differ," read "The
Ophidia and the apodal Sauria differ." See V. Carus, Handbuch der
Zoologie, i. B''. p. 372.

Page 138, note c, 7 lines from top of the page, dele " Gephyrei ;" — and 2 lines from
bottom of page, erase words " Glycera and Fhoronis Mppocrepia,'" and
substitute " Opheliae and Cirratulidae." See Claparfede, Ann^lides
Ch^topodes du GoLfe du Naples, p. 19, 1868.

Page 147, note e, for " an Echinus," read " an Echinoid."

Page 149, line i, for "with the masticatory apparatus," read "with the radial
elements of the masticatory apparatus."

Page 152, note f, 32 lines from top of the page, after words " of the ' nettle-cells,' "
add words, " See, however, p. cxliv supra, ibique citata."

Page 153, 4 lines from the bottom of the page, for " to the majority of Vermes," read
" to many Vermes, such as Apliroditca, Glyccrea, and Polycirrida." See
Claparfede I. c. supra, and Ann. and Mag. Nat. Hist., 1867, vol-
p. 348.

Page 177, 8 lines from bottom of page, for "This latter branch is not," read "This
latter branch, by which the blood from the posterior limlDs can find its
way directly back to the heart, is not."

INDEX.

AbrancMata.

Abranchiata, xl.
Acanthobdella, 131.
AcaBthocephali, 155.
Acanthopteri, Ixxviii ; 40, 45.
Accipitres, lii, liv.
Acherontia atropos, 73, 78, 79.
Acranial Vertebrata, xxxiii, Ixxxiv.
Actinia, 158.

Air-bladder, Ixxv ; 41, 43.
Air sacs, 16.
Agassiz, xxiii.
Alae cordis, cv, cxx ; 10 1.
Albuminiparous gland, 50, 190.
Allantoid bladder, 183.
Allantoidea, xl, xU.
Allman, 70, 72.

Ambul^cral system, cxlvii ; 141.
Amniota, xxxix, xl.
Amphibia, Ixv-lxvii ; 181-185.
Amphidiscs, 163.

Ampbinomidae, accessory nerve system

of, 123.
Amphirrhina, Ixxviii.
Amphisbaenoidea, Ivii.
Ampullae of feet in Echinodennata,

141, 144.
Anallantoidea, xli.

Animals, characters of, as opposed to

Vegetables, clxii.
Annelides, 119.
Annulata, cxxii, cxxvii ; 138.
Annuloida, cxxiii.
Anodon, 54-66.
Antedon rosaceus, 157.
Antennae, homologies of, 75.
Antennulea, 91.
Anthozoa , clviii ; 152.
Anticlinal vertebra, 7.
Aorta of Mammals, xlv ; 168.

— of Birds, xlix ; 176.

— of Reptiles, lix.

Botalli ductus.

Aorta of Fishes, Ixxii.
Aphis, 109-113.
Aphrodite, 122.
Apteryx, liv, Iv.
Apus, III.
Acarina, cxviii.
Arachnida, cxvi; 110, 115.
Archaeopteryx, 1.
Arion, 190.
Armadillo, xliv.
Arthropoda, civ; 73, iig.
Ascidia, c ; 66-71.
Aspidochirotae, 147.
Astacus, 90-119.
Asterias, 141-145, 223-229.
Asteriae, cliii.

Asteroidea, cliii ; 141-145, 223-229.
Astropecten, 145.
Aulostoma gulo, 128, 130.
Auriculae of Echinoidea, homology of,
clii.

Autolytus, 137.

Autophagi, Iv.

Aves, xl-xlix, lix, Ix ; 175.

Axolotl, xlii.

Azygos nerve, 132.

— vein, 2, 171.

B.

Baer, v, xxi ; 65, 69.
Barkow, 15.

Bastian, Dr. Charlton, xvii ; 157.

Bate, Mr. Spence, 94.

Beneden, Van, 71, 119.

Bipinnaria asterigera, 154.

Bojanua, organ of, the renal organ of
Mollusca, Ixxxvi, xc, xciii, xciv,
xcvii, xcix ; 54, 60-62, 64, 69,
67.

Botalli ductus, 185.

262

INDEX.

Brachiopoda.
Brachiopoda, xcviii ; 232.
Brachycephalus, Ixii.
Bradypoda, xlv.
Branch ellion, 135.
Branchiate Vertebrata, xli.

— Arthropoda, cv, cxviii.

— Vermes, cxxviii.
Branchiae of Fishes, Ixxiv.

— of Cephalopoda, xc.

— of Lamellibranchiata, xcvi.

— of Crustacea, cxx.

— of VeiTnes, cxxix.
Branchiobdella, 138.
Branchipus, ill.
Brisinga, 145.
Bronn, 48, 70.
Briicke, 32.
Bruta, xlv.
BruzeHus, 113.

Buccal mass in MoUusca, 48, 189.

Bugle CoralHne, 73.

Bulbus arteriosus, Ixiii, Ixxii ; 40, 99.

Bursa Entiana, Ixxii.

Busk, 73.

C.

Caddis flies, 76.

Caducibranchiate Amphibia, Ixvi, Ixvii.
Caeciliae, Ixii, Isiii, Ixvi.
Calciferous glands, 125.
Camelidae, xlv.
Campanularidae, 161, 162.
Canalis temporalis, 8.
Capsulogenous glands, 125.
Carapace, 91.
Carcinus moenas, no.
Carinatae, Iv.
Camivora, xlvi ; 7, 169.
Carotid gland of frog, 184.
Carpenter, Dr., 259.
Carpus, of Mammals, 9.

— of Birds, xlix ; 17, 23.
Carus, C. G., 13, 16.
Carus, v., clxvi.
Casuarius, Iv.
Cauda equina, i.
Centetes, xlv, xlviii.
Cephalopoda, 49 ; Ixxxvii.
Cephalostegite, 96.
Ceratophrys, Ixii.
Ceratospongiae, 164.
Cerianthidae, clviii ; 159.
Cestodes, cxl ; 136.
Cetacea, xliv, xlv, xlvi ; 5.
Chaetognatha, cxxxvii.
Chamaeleonoidea, Ivii.
Chealiodes, Ixxviii.
Chauveau, xvii.
Chelonia, Ivi-lviii, Ix, Ixi.
Chiaama optic, Ixxii.

Cytoplasm.
Chilopoda, cxiv, cxvi ; 108-113.
Chimaerae, Ixix-lxxi.
Chimpanzee, 9.
Chiroptera, 9, 170.
Chondrostei, Ixxxii.
Choroid gland, Ixxviii.
Cilia, absent in Arthropoda, cviii.

— present in a Sagitta, cxxxvii.
Ciliated sac of Ascidian, 67.
Cirrhostomi, Ixxxiv.
Cirripedia, clxiii.
Cladodactyle, 146.
Claparfede, xviii ; 97, 157, 259.
Claus, clviii.

Clepsine, 135.

Clitellus of earthworm, 1 19.
Cloaca, in Mammals, xlv.

— in Birds, lii ; 175.

— in Reptiles, Ixi.

— in Eishes, Ixxii.

— in Lamellibranchiata, xcvi ; 65, 197.

— in Tunicata, c ; 67, 236.
Clymene, 138.
Clypeastridae, clii.
Cockroach, common, 86, 199.
Cod, common, 45, 46.
Coeca of Birds, 177.

— hepatic, of Arthropoda, cxx ; 104.

— pyloric, of Fishes, xxxiv ; 40.
Coecum of rodent, 4, 172.

— azygos of Crustacea, 104.
Coelenterata, clvi-clx ; 152, 158-163,

165.
Coenosare, 160.
Coenurus, 136.
Coleoptera, 75.
Colleterial glands, cxi.
Coliunba livia, 12-25.
Copepoda, 115.
Corethra, 109.
Craspeda, 159.
Cremaster, 76.
Crinoidea, cliv ; 144.
Crocodilina, Ivi ; 176.
Crop, 14.

Crustacea, cxviii; 90-119, 205-210.
Cryptobranchus, Ixiv.
Cryptogamia, clx.
Ctenocyst, chnii.
Ctenodiscus, cliv ; 145.
Ctenophorae, clvii, clviii.
Cuchia, bixiv.
Cucumaria, 145.

Cuvier, xxi ; 9, 14, 15, 4i> 5i» 54-
Cuvierian ducts, Ixxiii.

— organs, 146.
Cyclas, xcvii.

Cyclostomi, xxxv-xxxix ; 46.
Cyprinoids, Ixxii ; 45.
Cystic stage of Tapeworm, 136.
Cytoplasm, clx.

INDEX.

263

Daphnidae.
D.

Daphnidae, cxlvii.
Darwin, xxiv ; 114.
Dart sac, 50.

Decapodous Crustacea, 92.
Deciduate Vertebrata, xlviii.
Dendrocliirotae, 147.
Derotremata, Ixvi.
Deuterozooids, 137.
Development of Vertebrata, xxxviii.

— Amphioxus, Ixxx, Ixxxv.

— Amphibia, Ixvi.

— Fishes, Isxix.

— Echinodermata, cxlvi.

— Cephalopoda, xci.

— Gasteropoda, xciii.

— as a basis of Classification, xxi.
Diaphragm, 2, 168, 1 76.

Dias longiremis, 115.
Dibranchiate Cephalopoda, xci.
Dicystidea, clxviii.
Didelphia, xlviii.
Dinosauria, 1.
Dipnoi, Ixviii, Ixxxi.
Diphyodont Mammals, xv.
Dominant systems, 35.
Dondera, xviii.
Dromaeus, Iv.
Ductus Cuvieri, Ixxiii.
Duodenum, 15.
Duvemoy, 15, 32-66.

E.

Echinococcus, 136.
Echinodermata, cxliii ; I4I, 223.
Echinoidea, cl.
Ecker, 173, 185.

Edwards, Alphonse Milne, xxi ; 119.

— Milne, xxi; 2, 16, 67, 70.
Ehlers, cxxxiii.
Elasmobranchii, Ixvii, Ixxxii.
Endoskeleton, Ixviii.
Endostyle, 67.
Entomostraca, loi.
Ephemeridae, 89.
Epigastric vein, 36, 181, 183.
Epipodites, 103, 104.
Esocidae, 45.
Exoskeleton, Ixviii.

Eyes of Insects, 74.

— of Crustacea, 113.

— of Vermes, Ixxx.

F,

Eat-body in Snakes, 32.

— in Frog, 184.

— in Caterpillars, 73, 79, 81.

— in perfect Insects, 86, 89.

GuaniM.

Fierasfer, xlii.

Fins, function of, 43.

Flagella, distal elements of antennules

in Crustacea, 92.
Flagellum, replacing eye-facets in a

Crustacean, 113.

— secretes epermatophore in certain

Molluscs, 50.
Flustra, 71.

Foramen Pannizzae, Ivi.
Fowl, common, bones of, 25-29.
Frenulum bulbi in Amphibia, 184.
Frog, 35-40, 181-185.

Gadus morrhua, 45, 46.
Gall-bladder, 184.
Gallus Gallinaceus, 25-29.
Gammarus pulex, 112.
Ganglia ofTunicata, 67, 68.

— Gasteropoda, 48, 49, 52, 54.

— Lamellibranchiata, 62-64.

— MoUusca and Molluscoidea, Ixxxvii,

Ixxxviii.

— Arthropoda, 83, no.

— accessory of Annulata, 123, 132, 133.

— of Lamellibranchiata, xcvii.

— of Cephalopoda, xc.

Ganglia, stomatogastric, of Gastero-
poda, 53.

— of Arthropoda, 87, 103, 107.

— de renforcement, 132.
Ganglion, frontali, 79, 87, 1 12.
Ganoidei, Ixxiv, Ixxxii.
Gasteropoda, xcii; 48-54, 187-191.
Gaudry, 143.

Gephyrea, cxxxi; 155, 156.
Gerstaecker, 119.
Giraldds, organ of, xxxv.
Glands, antennary, 98.

— carotid, 184.

— choroid, Ixxviii.

— Harderian, 3, 1 70.

— hermaphrodite, 50.

— hibernating, 3, 1 70.

— salivary, 3, 49, 87.

— silk, 75, 80.

— uropygial, 16.
Glycera, 138.
Gnathostoma, Ixxxiii.
Goat moth, 79.
Gonophore, 160.
Gonozooid, 160.
Gratiolet, 135.
Gregarinae, clxvii, clxviii.
Gromida, clxv.

Grube, cxlvi.
Guanin, 159.

264

INDEX.

Haeclcel.
H.

Haeckel, civ, clxii.

Haemal flexure, 68.

Haeraapodous character of Vertebrates,

167.
Halisarca, 164.
Hancock, Mr. Albany, 69.
Harderian gland, 3.
Heart of Vertebrata, xxxi.

— Mammalia, xlv.

— Birds, lii.

— Reptiles, Iviii.

— Amphitiia, Ixiii.

— Fishes, Ixxii.

— Arthropoda, cv.

— Insecta, ex.

— Crustacea, cxx; 98, 100, loi.
Hedriojihthalmata, 92, loi.
HeUx, 47-54> 190-
Helmholtz, xvii ; 118.
Hepatic Cocca, cxx ; 104.
Heptanchus, Ixxiv.

Hering, 216.

Hermaphrodite gland, 191.
Hessling, Von, 60, 65, 198.
Hexanchus, Ixxiv.
Hibernating gland, 3, 169.
Highly specialized as opposed to high
types, 42.

Hincks, British Hydroid Zoophytes,
162.

Hirudo, 122, 127-136.
Holostean Ganoids, cxxxii.
Holothurioidea, cxlviii ; 145.
Homarus, 96.

Homologies, tables of, appendages and
segments in Arthropoda, 116, 117.

— ganglia in Arthropoda, 110.
Horse-leech, 135.

Huxley, Professor, 48, 49, 57, 69, 75,

90, 96, 162.
Hyatt, 72.
Hydrotheca, 160.
Hydrothiza, 160.
Hydrozoa, clix.
Hymenoptera, 75.
Hyperoartii, Ixxviii-lxxxiv.
Hyperotreti, Ixxviii-lxxxiv.

I.

Ichthyobatrachia, Ixvii.
Icthyopsida, Ixvii.
Imago of Insects, 78.
Impregnation of ova in Fishes, Ixxix.
in Amphibia, Ixv.

— in LameUibranchiata, xcvii ; 65.

— in Tunicata, c.
Infusoria, clxiv.

Insecta, cviii ; 73-9°. i99-'i°4-

Macdonnell, Dr.
Insectivora, 170.
Intermaxillary bone, 6.
Intermediary nerve in leech, 132.
Interparietal bone, 8.
Tsopoda, 92, 93, 110, III.

J.

Jourdain, 177.

Jugular, external jugular vein, 3.

— left jugular vein, 185.

K.

Keferstein, cxxxiii ; 156.
Kidney in Vertebrata, xxxv.

— in Mammals, xlvi ; 3, 168.

— in Birds, liii ; 16, 177.

— in Reptiles, Ix.

— in Amphibia, Ixiv ; 183.

— in Fishes, Ixxv.
Kolliker, clxvi ; 46, 163.
Kowalevesky, ci.
Kupfier, ci.

L.

Lacaze Duthiers, cxxxiii ; 190.
Lacrymal gland, double, of rat, 3, 1 70.
LameUibranchiata, xcv ; 54-66.
Languettes in Ascidians, 67.
Lankester, Mr. E. Ray, 120, 126.
Lantern of Aristotle, cli.
Lateral ganglia in Annulata, 132, 133.

— line, system o^ in Fishes, l»i, Ixviii,

Ixxviii ; 41.
Leydig, cxlix ; 1 1 1 .
Leidy, 51.
Lepidoptera, 74.
Lepidosiren, Ixv.
Leptocardia, cxxxiv.
Lepus cuniculus, 10.
Leuckart, 255, 257.
Leucodore, 138.
Libellulidae, 89.
Ligamentum nuchae, 11, 169.
Limacidae, 50.
Limax, 187-191.
Lister, Professor, xviii.
Lithydrodea, clix.
Loricate Reptiles, Ivi.
Lubbock, Sir John, 117, 204.
Luidia, 145.
Lumbricus, 1 19-126.
Lungs of Mammals, xlvi.

— of Birds, liii.

— of Reptiles, Ix ; 3.

M.

Macdonald, Dr., 70.
Macdonnell, Dr., 42.

INDEX.

265

Macleay, Mr.

Macleay, Mr., x.\i, sxiv.
Madreporic tubercle, cxlvii ; 141.
Malacopteri, 43.
Malacopterygii, Ixxv.
Malpighiau vessels, cx ; 80-86.
Mammalia, xlii-xlix.
Marsipobrancliii, Ixx-lxxxiii.
Marsupialia, xlviii ; 171.
Masticatory apparatus of Mammals, 6.
Matuta victor, 93.
Medusae, clix ; i6r.
Medusiform buds, 160.
Membrana nictitans, Ixviii.
Metagenesis, xxxviii, cviii, cxxvi, cxlvi ;
147. 153-

Metamorphosis of Insects, cxiii ; 79.

— of Echinodermata, cxlvi.

— of Platyelminthes, cxlii.

— of Vermes, cxxvi.

— relation of fresh-water habitat to,

cxlii ; 105.

— parasitism to, cxxvii.

Mollusca, Ixxxv; 47-66, 187-191, 231.
Molluscoidea, Ixxxvii ; 60-73, 232-238.
Monitor, Ivii.
Monodelphia, xlix.
Monophyodont Mammals, xlv.
Monorrhina, Ixxviii, Ixxxiii.
Monotremata, xlvii.
Morphology as opposed to teleology,
xxii.

Morgagni, cyst of, xxxv.
Moth, death's-head, 73.
Muffle, 172.

Muller, Fritz, 72, 97, 114.
MiiUer, H., 55.
Muller, J., cli.

— duct of, XXXV, Ixiv.
Mus decumanus, i, 167.
Muscidae, 84, 109.
Muscles of Birds, 13.

— of Ophidia, 30.

— compensatory relation of muscles of

body-wall to internal muscles in
Ophidia, 30.

— in Hirudineae, 129.

— of Helix, 48, 49-51.

— of Anodon, 56, 193.

— of Insects, 85.

— of Crustacea, 108.

— of Lumbricus terrestris, 123.

— of Cucumaria, 148.

— of Asterias rubens, 225.
Mustelus laevis, Ixxv.
Mycetozoa, clxii.
Myrianida, 137.
Myriopoda, cxiv-cxvi; 115.
Myriothela, 162.

My sis, 115.

Myxinoids, Ixxviii- Ixxxiii.

Ob en charrue.
Myxogastres, clxii.
Myxomycetes, clxii.

N.

Nauplius, 114.

Nematelminthes, cxxxiii ; 135.
Nematoids, 138.
Nephelis, 135.
Nereis, 132, 137.
Nervi transversi, 106, 122, 132.
Nervous system in Vertebrata, xxxi,
XXXV.

— in Mammals, xlvi.

— in Birds, Hii.

— in Reptiles, Ix.

— in Amphibia, Ixv.

— in Fishes, Ixx-vi.

— in MoUusca, Ixxxvii.

— in Molluscoidea, Ixxxviii.

— in LameUibranchiata, xcvii.

— in Brachiopoda, xcix. ■

— in Polyzoa, ciii.

— in Arthropoda, cvi ; iii, 116, M17.

— in Vermes, cxxv ; 121,133.

— in Cestodes, cxlii.

— in Nematelminthes, cxxxv.

— in Echinodermata, cxlv.

— in Rotifera, cxxxix.

— in Coelenterata, clvi.

— as a basis of classification, xxi.

— late development of, in Arthropoda,

109.

— development of, in Ascidians, ci.
Nervus recurrens, 79, 87.
Neural flexure, 49, 58.
Neuropodous character of Invertebrata,

xxH ; 168.
Neuroptera, 75.

' Nurses ' in ]?latyelminthes, 136, 137.

— in Vermes generally, cxxvi.

0.

Occipital condyle in Birds, 25.

— in Mammals, xliii.

— in Amphibia, Ixii.
Odontophorous MoUusca, Ixxxvii ; 63.
Oesophagus in Ophidia, 30.

— in Rodents, 2.
Oligochaeta, cxxviii ; 120, 125.
Omentim], peculiar to Mammals, 4, 168.
Omostegite, 95.

Oniscus miirarius, llo, 112.

Ophidia, 29-35.

Ophiuridae, cxlv.

Orbit of Rodents, 7.

Ornithodelphia, xlv.

Orthoptera, 86, iii.

Os en cJiarrue of Birds, 21, 26.

T

266

INDEX.

Otic vesicle.

Otic vesicle, 190.
Ovary, 88.
Oviscapt, 88.

Owen, Professor, 13, 24, 35, 102.

P.

Pancreas, 15.

Pai-asitism in Vertebrata,'xlii.

— in Mollusca, Ixxxvi.

— in Nematelminthes, cxxxvi.

— in Gregarinae, clxi.

— entails morphological degradation,

xi.

Parker, Mr. W. K., 39.
Parosteal bones, 36.
Parovarium, xxxv.
Patagia, 78.
Paxillae, 142.
Pecten, liv, Ix ; 191.
Pectoral muscles, 13.

— muscle, second, in birds, homology

of, 179.
Pedicellariae, 14 a.
Pelodytes, cxxxv.
Pelvis in Birds, 28, 29.

— in Reptiles, Ivii.
Peneus, 115.
Penguin, 1.

Perca fluviatiHs, 40-45.
Perennibranchiate Amphibia, Ixvii.
Perichaetous Annelides, 125, 126.
Peripatus, 156.

Periplaneta orientailis, 86, 112
Petromyzontidae, Ixxviii, Ixxxiii.
Phalaena, 109.
Pharyngobranchii, Ixxxiv.
Pharyngognathi, Ixxv.
Pharynx, externally villous in earth-
worm, 124.

— in leech, 129.
Phascolosoma, cxxxi ; 153.
Phoronis, 138.

Phrenic nerve, 171.
Phylactolaematous Polyzoa, ci.
PhyUopoda, 112.
Physoklisti, Ixxxiii.
Physostorai, bcix, Ixxxiii; 46.
Pipa, Ixiii.
Pisces, Ixviii, Ixxxv.
Plagiostomi, Ixix ; 46.
Planaria, 154-
Planula, clx.

Platyelminthes, cxl; 138, 154, 240.

Plectognatlii, Ixxv.

Polian vesicles, 149.

Polychaeta, cxxviii.

Polymorphismus, 162.

Polypterus, Ixxiii.

Polyzoa, ci; 71-73. '^37> '38-

Beproduction.
Pontobdella, 128.
Porifera, clxvi.

Portal system of Vertebrata, xxxiv,

— rudimentary, Ixxxv.
Priapulaceae, cxxxi.
Privet Hawk-Moth, 82.
Processus uncinati, li ; 20, 26, 27.
Proglottis, 136.

Prolegs, 64.
Proscolex, 136.
Proteus, Ixiii.

Protisticum Regnum, clxiii.
Protoplasm, clx.
Protozoa, clx.
Pro tula, cxx.

Pseudhaemal vessels, cxxiv, cxlv ; 122,

124, 149.
Psittacidae, li.
Psolus, 146.
Pteropoda, xciii.
Pterylography, xlix.
Ptilocercus, xliv.
Pupa, 73, 76.

Pyloric coeca in Pishes, Ixxii ; 40.

— in Orthoptera, 86.

— portion of stomach in Reptiles, Iviii.

Q.

Quadrate bone, 18, 38, 43.
Quekett, 46.

R.

Rabbit's vertebrae, 10.

Radiolaria, clxii.

Rana, 35-46, 181-185.

Rasores, 20, 25, 29.

Rat, i-^, 167-173.

Ratitae, liii, liv.

Rathke, 106, 107.

Recurrent nerve, 133.

Reichert, Professor, 163.

Regnum Protisticum, clxii.

Renal-portal system. Hi, lis, Ixiv; 177,

181, 183.
Renforcement, ganglions de, 132.
Reproduction in Fislies, Ixxix,

— in Amphibia, Ixvi.

— in Mollusca, Ixxxvi.

— in Artliropoda, cvi.

— in Vermes, cxxv.

— in Echinodenuata, cxlv.

— in Coelenterata, clvn.

— in Protozoa, clxi.
Reproduction of lost organs in Coelen

terata. clx.

— in Echinodermata, 143.

— in Amphibia, Ixvii.

— in Arachnida and Crustacea, cxvii.

INDEX.

■267

Jleproduction,
Reproduction in Beptiles, Ixi.
Eeptiles, Iv.

— relation of, to Bii'ds, 175.
Retia mirabilia, 61, 149.
Rhabdocoelous Turbellaria, cxli.
Rhea, li.

Rhinocryptis, Ixxiii.
Rhizopoda, clsv, clxvi.
Rhynchocoelous Turbellaria, cxli.
Rodentia, xlv.
Rotifera, cxxxviii-cxl.
Ruminantia, 169.

S.

Saccobranchus, Ixxiv.
Salicornaria, 73.

Salivary glands, xlv, lii, Iviii, Ixxi.

Salmonidae, Ixxix ; 45.

Sarcode, clx.

Sars, 145, 229.

Sauria, Ivii.

Sauropsida, xlvii, Iv.

Savigny, c.

Scaphirhynchus, Ixxxii.

Sclunarda, 155.

Schmidt, 0., xxi.

Schneider, cxxxv.

Schultze, F. E., 129.

Sciuri, 172.

Sclerotic, bony, 18.

Scolex, 136.

Scolopendridae, cxv.

Scorpionidae, cxi ; 109, no, 117.

Scutigera, cxv.

Segmental organs in Annulata, cxxv;
126.

— modified to serve as efferent genera-

tive ducts, cxxx ; 215.
Semper, xviii; 154, 229.
Semper's organ, 53, i8g.
Sensory organs in lateral line of Fish,

Ixxvii.

— on anterior segments in Leech, 128,

129.
Sepia, Ixxxix.
Serialaria, ciii.
Serpula, cxxviii.
Serranus, Ixxix.
Sertularia abietina, t6o.
Setae, 122.

Setiparous glands, 125.

Sharks, Ixix.

Sharpey, Dr., 143, 228.

Shell in Mollusca, 47, 48, 54-57.

Siluroideae, Ixxv.

Simiadae, xlv ; 170.

Siphonizantia, cxv.

Siphonostomum, cxxviii.

Sipunculidae, cxxxii ; 1 54.

Slug, 187-191.

Solenobia, cxii.

T 2

TeetJi of Bodents,

Spencer, Mr. Herbert, cxxii, civ,
Sphaerodorum, 157.
Sphaerularia, cxxxvi.
Sphingidae, 74.
Sphyi'ocephalus, 155.
Spicula, 163.
Spinneret, 75-80.
Spio, cxxviii.

Spirachtha, abdominal appendages of,

cix.
Spiracle, 74.
Spirorbis, 161.
Spirula, Ixxxix.
Spleen, 3, 168, 171, 184.

— absent in Marsipobranchii, Ixxxiii.
Spondylus, xcvii ; 191.
Spongiadae, clxvi.

Spongilla, 163.
Squalidae, Ixxix.
Squamata, Ivi.
SquUlina, loi.
Staurocephali, cxxix.
Sternaspidea, cxxxii.
Sternum in Amphibia, Ixiii.

— absent in Fishes, Ixviii.
Stomatogastric nerves, absent in Ano-

dontophorous Mollusca, xcvii.

— present in Odontophora, xc.

— in Arthropoda, cvi.

— undergo little change in the metamor-

phosis in Insects, 79-

— peculiarities of in Crustacea, 107.

— in Oniscus, 112.
Stomias, Ixxviii.
Strepsiptera, cxi.
Strobile in Tae.niadae, 137.
Strombidae, xcii.
Strongylostoma, cxxvi.
Struthio, li.

Sturgeon, Ixix.
Suspensorium, Ixii, Ixx ; 43.
Swimmeret, 90.

Sympathetic nerve-system in Verte-
brata, xxxvii.

— in Fishes, Ixxvii.

— absent in Marsipobranchii, Ixxxiii.

— absent in Lamellibranchiata, xcvii.
SyUidea, cxxvi.

Synapta, Ixxxvi, cxxviii.
Synaptidae, 147.

T.

Tables of Classification, xxvii-xxx.

— of Homologies, no, 116, ii7-
Taeniadae, 136-140.

Tarsus of Birds, li ; 17, 18.
Teeth of Mammals, xliv.

— of Reptiles, Ixviii.

— of Amphibia, Ixiii.

— of Fishes, Ixxi.

— of Rodents, 6.

268

INDEX.

Teeth, embryonic, in Birds.

Teeth, embiyonic, in Birds, li.
Tel^ophores, i6o.
Teleostei, Ixxii, Ixxxiii.
TelsoHj as segment, 95.
Testis, with a rudimentary ovary com-
bined with it, Ixv.

— supei-added to an ovary in certain
Fishes, Ixxix.

Thalestris, 115.
Thread-cells, cxxviii ; 1 59.
Thymus of Frog, 185.

— homologue of, in Fish, 41.
Thyroid of Frog, 185.
Toad, skeleton of, 39.
Tomopteris, cxxviii.

Tongue, sheath of, in Ophidia, 30.
Tracheata Arthropoda, cv, cvi.
Transition piece in Hydroid Zoophytes,
161.

Trematodes, cxl ; 1 38.
Trilobites, 112.
Tropidonotus natrix, 39.
Tubicolar Annelides, 123, 157.
Tubulipora, 147.
Tunicata, c.

— classed with Vermes by G-egen-

baur, ci.

— supposed similarity of development

into that of Vertebrata, ci.

— Turbellarian Vermes, cxl; 138, 155.
Turner, Professor, i.

U.

Umbilical vein, 182.

Unsymmetrical viscera of Ophidia, 29.

Zooids.

Unionidae, 54-66, 192-198.
Uterus, 169, 172.

V.

Vas deferens, 177.

Vegetables, distinction of, from Ani-
mals, clxii, clxiii.
Vena azygos, 2.
Vena cava, 169.
Vermes, cxxii ; 152, 153.
Vertebrae, Ixix.
Vertebrata, xxxi ; 167.
Vesicular seminales, 125.
Vibrios, xvii.
Vibrissae, 4.
Volvocineae, clxii.
Vorticlava, 162.

W.

Waterhouse, Mr., 4.
Water vascular system in Mollusca,
Ixxxvi.

— in Vermes, cxxiv, cxxxiv.

— in Echinodermata, cxlv, cliv.
Wolffian body, Ixv, Ixxv; 172.

Z.

Zaddach, 75, 85-113, 119,
Zenker, 118.

Zoea, larval foi-m in developing Crus-
tacea, 115.
Zooids, 164.

— relation of, to organs, 162.

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Also, to follow : Part 11. The Civil War : by the same Editor.

Cicero's Philippic Orations. With Notes, by J. R. King, M. A.,
formerly Fellow and Tutor of Merton College, Oxford. Demy 8vo. cloth, los. 6d.

Cicero pro Cluentio. With Introduction and Notes. By W. Ramsay,
M.A. Edited by G. G. Ramsay, M.A., Professor of Humanity, Glasgow. Ext.
fcap. Svo. cloth, 3s. 6d.

Cicero. Selection of interesting and descriptive passages. With Notes.
By Henry Walford, M.A., Wadham College, Oxford, Assistant Master at Hailey-
bury College. In three Parts. Extra fcap. Svo. cloth, 4s. 6d.

Also sold separately :
Part I. Anecdotes from Grecian and Roman History. Cloth, is. 6d.
Part II. Omens and Dreams : Beauties of Nature. Cloth, is. 6d.
Part III. Rome's Rule of her Provinces. Cloth, is. 6d.

Cicero. Select Letters. By Albert Watson, M.A., Fellow and Tutor

of Brasenose College, Oxford. In the Press.

Cicero de Oratore. With Introduction and Notes. By A. S. Wilkins,
M.A., Professor of Latin, Owens College, Manchester.

Cornelius Nepos. With Notes, by Oscar Browning, M.A., Fellow of
ling's College, Cambridge, and Assistant Master at Eton College. Extra fcap. Svo.
cloth, 2s. 6d.

Cicero and Pliny. Select Epistles (for Schools). With Notes by
C. E. Prichard, M.A., formerly Fellow of Balliol College, Oxford.

Horace. With Introduction and Notes. By Edward C. Wickham,
M.A., Fellow and Tutor of New College, Oxford.
Also a small edition for Schools.

Livy, Books I-X. By J. R. Seeley, M.A., FeUow of Christ's College,
and Regius Professor of Modern Histoiy, Cambridge. In the Press.
Also a small edition for Schools.

Ovid. Selections for the use of Schools. With Introductions and
Notes, and an Appendix on the Roman Calendar. By W. Ramsay, M.A.
Edited by G. G. Ramsay, M.A., Professor of Humanity, Glasgow. Ext. fcap. Svo.
cloth, 5s. 6d.

i8

Clarendon Press Series.

Fragments and Specimens of Early Latin. With Introduction,
Notes, and Illustrations. By John Wordsworth, M. A., Fellow of Brasenose
College, Oxford.

Selections from the less known Latin Poets. By North Finder,
M.A., formerly Fellow of Trinity College, Oxford. Demy 8vo. cloth, 15s.

Passages for Translation into Latin. For the use of Passmen and
others. Selected by J. Y. Sargent, M.A., Tutor, formerly Fellow, of Magdalen
College, Oxford. Second Edition. Ext. fcap. 8vo. clotb, 2s. 6d.

II. MENTAL AND MORAL PHILOSOPHY.

The Elements of Deductive Logic, designed mainly for the use of
Junior Students in the Universities. By T. Fowler, M.A., Fellow and Tutor
of Lincoln College, Oxford. Third Edition, with a Collection of Examples.
Extra fcap. 8vo. cloth, 3s. 6d.

The Elements of Inductive Logic, designed mainly for the use of
Students in the Universities. By the same Author. Extra fcap. Svo. cloth, 6s.
Just Published.

A Manual of Political Economy, for the use of Schools. By J. E.
Thorold Rogers, M.A., formerly Professor of PoUtical Economy, Oxford. Second
Edition. Extra fcap. Svo. cloth, 4s. 6d.

III. MATHEMATICS, &c.

An Elementary Treatise on Quaternions. By P. G. Tait, M.A., Pro-
fessor of Natural Philosophy in the University of Edinburgh ; formerly Fellow of
St. Peter's College, Cambridge. Demy Svo. cloth, 12s. 6d.

Book-keeping. By R. G. C. Hamilton, Accountant to the Edu-
cation Committee of the Privy Council, and John Ball (of the Firm of Messrs.
Quilter, Ball, and Co.), Examiners in Book-keeping for the Society of Arts
Examination. Second Edition. Extra fcap. Svo. limp cloth, is. 6d.

A Course of Lectures on Pure Geometry. By Henry J. Stephen
Smith, M.A., F.R.S., Fellow of Balliol College, and Savilian Professor of Geometry
in the University of Oxford.

A Treatise on Electricity and Magnetism. By J. Clerk Maxwell,
M.A., F.R.S., formerly Professor of Natural Philosophy, King's College, London.

Acoustics. By W. F. Donkin, M.A., F.R.S., SaviUan Professor of Astro-
nomy, Oxford. Just ready.

A Series of Elementary Works is being arranged, and will shortly be announced.

IV. HISTORY.

A Manual of Ancient History. By George Rawlinson, M.A., Camden
Professor of Ancient History, formerly Fellow of Exeter College, Oxford. Demy
Svo. cloth, 14s. Just Published.

A History of Germany and of the Empire, down to the close of the
Middle Ages. By J. Bryce, B.C.L., Fellow of Oriel College, Oxford.

A History of Germany, from the Reformation. By Adolphus W.
Ward, M.A., Fellow of St. Peter's College, Cambridge, Professor of History,
Owens College, Manchester.

Clarendon Press Series,

19

A History of British India. By S. W. Owen, M.A., Lee s Reader in
Law and History, Christ Church, and Reader in Indian Law in the University of
Oxford.

A History of Greece. By E. A. Freeman, M.A., formerly Fellow of
Trinity College, Oxford.

A Constitutional History of England. By W. Stubbs, M. A.,
Regius Professor of Modem History in the University of Oxford.

A History of Prance. By G. W. Kitchin, M.A., formerly Censor
of Christ Church.

V. LAW.

Commentaries on Roman Law; from the original and the best modern
sources. By H. J. Roby, M.A., formerly Fellow of St. John's CoUege, Cambridge;
Professor of Law at University College, London. 2 vols. Demy 8vo.

VI. PHYSICAL SCIENCE.

Natural Philosophy. In four Volumes. By Sir W. Thomson, LL.D.,
D.C.L., F.R.S., Professor of Natural Philosophy, Glasgow ; and P. G. Tait, M.A.,
Professor of Natural Philosophy, Edinburgh; formerly Fellows of St. Peter's
College, Cambridge. Vol. I. 8vo. cloth, il. 5s.
By the same Authors, a smaller Work on the same subject, forming
a complete Introduction to it, so far as it can be carried out with Elementary
Geometry and Algebra. In the Press.

Descriptive Astronomy. A Handbook for the General Reader, and
also for practical Observatory work. With 224 illustrations and numerous tables.
By G. F. Chambers, F.R.A.S., Barrister-at-Law. Demy 8vo. 856 pp., cloth, il. is.

Chemistry for Students. By A. W. Williamson, Phil. Doc, F.R.S.,
Professor of Chemistry, University College, London. A new Edition, with Solutions.
Extra fcap. 8vo. cloth, 8s. 6d.

A Treatise on Heat, with numerous Woodcuts and Diagrams. By
■ Balfour Stewart, LL.D., F.R.S., Director of the Observatory at Kew. Extra
fcap. 8vo. cloth, 7s. 6d.

Forms of Animal Life. By G. Rolleston, M.D., F.R.S., Linacre Pro-
fessor of Physiology, Oxford. Illustrated by Descriptions and Drawings of
Dissections. Just ready.

Exercises in Practical Chemistry. By A. G. Vernon Harcourt,
M.A., F.R.S., Senior Student of Christ Church, and Lee's Reader in Chemistry ;
and H. G. Madan, M.A., Fellow of Queen's College, Oxford.

Series I. Qualitative Exercises. Crown Svo. cloth, p. 6d.

Series II. Quantitative Exercises.

The VaUey of the Thames ; its Physical Geography and Geology.
By John Phillips, M.A., F.R.S., Professor of Geology, Oxford. In the Press.

Geology. By J. Phillips, M.A., F.R.S., Professor of Geology, Oxford.

Mechanics. By Bartholomew Price, M.A., F.R.S., Sedleian Professor
of Natural Philosophy, Oxford.

Optics. By R. B. Clifton, M.A., F.R.S., Professor of Experimental
Philosophy, Oxford ; formerly Fellow of St. John's College, Cambridge.

Electricity. By W. Esson, M.A., F.R.S., Fellow and Mathematical
Lecturer of Merton College, Oxford.

20

Clarendon Press Series.

Crystallography. By M. H. N, Story-Maskelyne, M.A., Professor of
Mineralogy, Oxford ; and Deputy Keeper in the Department of Minerals, British
Museum.

Mineralogy. By the same Author.

Physiological Physics. By G. Griffith, M.A., Jesus College, Oxford,
Assistant Secretary to the British Association, and Natural Science Master at
Harrow School.

Magnetism.

VII. ENGLISH LANGUAGE AND LITERATURE.

A First Reading Book. By Marie Eichens of Berlin ; and edited by
Anne J. Clough. Extra fcap. 8vo. stiff covers, ^d.

Oxford Reading Book, Part I. For Little Children. Extra fcap. 8vo.

stiff covers, 6d.

Oxford Reading Book, Part II. For Junior Classes. Extra fcap. 8vo.

stiff covers, 6d.

On the Principles of Grammar. By E. Thring, M.A., Head Master
of Uppingham School. Extra fcap. 8vo. cloth, 4s. 6c?.

Grammatical Analysis, designed to serve as an Exercise and Compo-
sition Book in the English Language. By E. Thring, M.A., Head Master of
Uppingham School. Extra fcap. 8vo. cloth, 3s. 6d.

Specimens of Early English ; being a Series of Extracts from the
most important English Authors, Chronologically arranged, illustrative of the
progress of the EngUsh Language and its Dialectic varieties, from a.d. 1250 to
A.D. 1400. With Grammatical Introduction, Notes, and Glossary. By R. Morris,
Editor of "The Story of Genesis and Exodus," &c. Extra fcap. 8vo. cloth,
7s. 6d.

The Vision of William concerning Piers the Plowman, by

William Langland. Edited, mth Notes, by W. W. Skeat, MA., formerly Fellow
of Christ's College, Cambridge. Extra fcap. 8vo. cloth, 4s. 6d.

The Philology of the English Tongue. By J. Earle, M.A., formerly
Fellow of Oriel College, and Professor of Anglo-Saxon, Oxford. In the Press.

Typical Selections from the best English Authors from the Sixteenth
to the Nineteenth Century, (to serve as a higher Reading Book,) with Intro-
ductory Notices and Notes, being a Contribution towards a History of English
Literature. Extra fcap. 8vo. cloth, 4s. 6d. Just Published.

Specimens of the Scottish Language ; being a Series of Annotated
Extracts illustrative of the Literature and Philology of the Lowland Tongue from
the Fourteenth to the Nmeteenth Century. With Introduction and Glossary.
By A. H. Burgess, M.A.

See also XI. below for other English Classics.

VIII. FRENCH LANGUAGE AND LITERATURE.

Brachet's Historical Grammar of the French Language. Trans-
lated into English by G. W. Kitchin, M.A., formerly Censor of Christ Church.
Extra fcap. 8vo. cloth, 3s. 6rf.

Corneille's Cinna, and Moliere's Les Femmes Savantes. Edited, with
Introduction and Notes, by Gustavo Masson. Extra fcap. 8vo. cloth, 2s. 6d.

Clarendon Press Series.

21

Racine's Andromaque, and Corneille's Le Menteur. With Louis
Racine's Life of his Father. By the same Editor. Extra fcap. 8vo. cloth, 2s. 6d.

Moli^re's Les Fourberies de Scapin, and Racine's Athalie. With
Voltaire's Life of Molifere. By the same Editor. In the Press.

Selections from the Correspondence of Madame de Sevigne and her
chief Contemporaries. Intended more especially for Girls' Schools. By the same
Editor. Extra fcap. 8vo. cloth, 3s.

Voyage autour de ma Chambre, by Xavier de Maistre ; Ourika, by
Madame de Duras ; La Dot de Suzette, by Fiev^e ; Les Jumeaux de I'Hotel
Corneille, by Edmond About; M^saventures d'un ficolier, by Rodolplie
TopfEer. By the same Editor. Extra fcap. 8vo. cloth, 2s. 6d.

A French G-rammar. A complete Theory of the French Language,

with the rules in French and English, and numerous Examples to serve as first
Exercises in the Language. By Jules Bud, Honorary M.A. of Oxford ; Tay-
lorian Teacher of French, Oxford ; Examiner in the Oxford Local Examinations
from 1858.

A French Grammar Test. A Book of Exercises on French Grammar ;
each Exercise being preceded by Grammatical Questions. By the same Author.

Exercises in Translation No. i, from French into English, with

general rules on Translation ; and containing Notes, Hints, and Cautions, founded
on a comparison of the Grammar and Genius of the two Languages. By the same
Author.

Exercises in Translation No. 2, from English into French, on the
same plan as the preceding book. By the same Author.

IX. GERMAN LANGUAGE AND LITERATURE.

Goethe's Egmont. With a Life of Goethe, &c. By Dr. Buchheim,

Professor of the German Language and Literature in King's College, London;
and Examiner in German to the University of London. Extra fcap. 8vo. cloth, 3s.

Schiller's Wilhelm Tell. With a Life of Schiller; an historical and
critical Introduction, Arguments, and a complete Commentary. By the same
Editor. In the Press,

Lessing's Minna von Barnhelm. A Comedy. With a Life of Lessing,
Critical Commentary, &c. By the same Editor.

X. ART, &c.

A Handbook of Pictorial Art. By R. St. J. Tyrwhitt, M.A., for-
merly Student and Tutor of Christ Church, Oxford. With coloured Illustra-
tions, Photographs, and a chapter on Perspective by A. Macdonald. 8vo. half
morocco, iSs.

A Treatise on Harmony. By Sir F. A. Gore Ouseley, Bart., M.A.,
Mus. Doc, Professor of Music in the University of Oxford. 4to. cloth, los.

A Treatise on Counterpoint, Canon, and Fugue, based upon that of
Cherubini. By the same Author. 4to. cloth, 16s.

A System of Physical Education : Theoretical and Practical. By
Archibald Maclaren, The Gymnasium, Oxford. Extra fcap. Svo. cloth, 7s. 6d.

22

Clarendon Press Series.

XI. ENGLISH CLASSICS.

Designed io meet the wants of Students in English Literature: under the
superintendence of the Rev. J. S. Beewer, M.A., of Queen's College,
Oxford, and Professor of English Literature at Kittgs College, London.

There are two dangers to which the student of English Literature is
exposed at the outset of his task ; — his reading is apt to be too narrow
or too diffuse.

Out of the vast number of authors set before him in books professing
to deal with this subject he knows not which to select: he thinks he
must read a little of all ; he soon abandons so hopeless an attempt ; he
ends by contenting himself with second-hand information ; and profess-
ing to study English Literature, he fails to master a single English author.
On the other hand, by confining his attention to one or two writers, or
to one special period of EngUsh Literature, the student narrows his view
of it ; he fails to grasp the subject as a whole ; and in so doing misses
one of the chief objects of his study.

How may these errors be avoided? How may minute reading be
combined with comprehensiveness of view ?

In the hope of furnishing an answer to these questions the Delegates
of the Press, acting upon the advice and experience of Professor Brewer,
have determined to issue a series of small volumes, which shall embrace,
in a convenient form and at a low price, the general extent of EngUsh
Literature, as represented in its masterpieces at successive epochs. It is
thought that the student, by confining himself, in the first instance, to
those authors who are most worthy of his attention, will be saved from
the dangers of hasty and indiscriminate reading. By adopting the course
thus marked out for him he wiU become familiar with the productions of
the greatest minds in English Literature ; and should he never be able to
pursue the subject beyond the hmits here prescribed, he will have laid
the foundation of accurate habits of thought and judgment, which cannot
fail of being serviceable to him hereafter.

The authors and works selected are such as ^vill best serve to Ulus-
trate English Literature in its historical aspect. As " the eye of history,
without which history cannot be understood, the literature of a nation
is the clearest and most intelligible record of its life. Its thoughts and
its emotions, its graver and its less serious modes, its progress, or its
degeneracy, are told by its best authors in their best words. This view
of the subject will suggest the safest rules for the study of it.

With one exception all writers before the Reformation are excluded
from the Series. However great may be the value of literature before
that epoch, it is not completely national. For it had no common organ
of language; it addressed itself to special classes; it dealt mamly with

Clarendon Press Series.

23

special subjects. Again ; of writers who flourished after the Reforma-
tion, who were popular in their day, and reflected the manners and
sentiments of their age, the larger part by far must be excluded from our
list. Common sense tells us that if young persons, who have but a
limited time at their disposal, read Marlowe or Greene, Burton, HakewiU
or Du Bartas, Shakespeare, Bacon, and Milton will be comparatively
neglected.

Keeping, then, to the best authors in each epoch — and here popular
estimation is a safe guide — the student wifl find the following list of
writers amply sufiicient for his ptupose : Chaucer, Spenser, Hooker,
Shakespeare, Bacon, Milton, Dryden, Bunyan, Pope, Johnson, Burke,
and Cowper. In other words, Chaucer is the exponent of the Middle
Ages in England ; Spenser of the Reformation and the Tudors ; Hooker
of the latter years of Elizabeth ; Shakespeare and Bacon of the transition
from Tudor to Stuart; Milton of Charles I and the Commonwealth;
Dryden and Bunyan of the Restoration ; Pope of Anne and the House
of Hanover ; Johnson, Burke, and Cowper of the reign of George IH to
the close of the last century.

The list could be easily enlarged ; the names of Jeremy Taylor,
Clarendon, Hobbes, Locke, Swift, Addison, Goldsmith, and others are
omitted. But in so wide a field, the difficulty is to keep the series from
becoming unwieldy, without diminishing its comprehensiveness. Here-
after, should the plan prove to be useful, some of the masterpieces of the
authors just mentioned may be added to the list.

The task of selection is not yet finished. For purposes of education,
it would neither be possible, nor, if possible, desirable, to place in the
hands of students the whole of the works of the authors we have chosen.
We must set before them only the masterpieces of Literature, and their
studies must be directed, not only to the greatest minds, but to their
choicest productions. These are to be read again and again, separately
and in combination. Their piirport, form, language, bearing on the
times, must be minutely studied, tifl the student begins to recognise the
fiall value of each work both in itself and in its relations to those that go
before and those that follow it.

It is especially hoped that this Series may prove useful to Ladies'
Schools and Middle Class Schools; in which English Literature must
always be a leading subject of instruction.

A G-eneral Introduction to the Series. By Professor Brewer, M.A,

1. Chaucer. The Prologue to the Canterbury Tales; The Knightes

Tale; The Nonne Prestes Tale. Edited by R. Morris, Editor of "Specimens
of Early English," &c., &c. Second Edition. Extra fcap. 8vo. cloth, as. 6d.

2. Spenser's Faery Queene. Books I and II. Designed chiefly for

the use of Schools. With Introduction, Notes, and Glossary. By G. W. Kitchin,
M.A., formerly Censor of Christ Church. Extra fcap. 8vo. cloth, is. 6d. each.

3. Hooker. Ecclesiastical Polity, Book I. Edited by R. W. Church,

M.A., Rector of "Whatley; formerly Fellow of Oiiel College, Oxford. Extra
fcap. 8vo. cloth, 2s,

24 Clarendon Press Series.

4. Shakespeare. Select Plays. Edited by W. G. Clark, M.A., Fellow

of Trinity College, Cambridge, and Public Orator ; and W. Aldis Wright, M.A.,
Librarian of Trinity College, Cambridge.

I. The Merchant of Venice. Extra fcap. 8vo. stiff covers, is.
II. Richard the Second. Extra fcap. 8vo. stiff covers, is. 6d.

III. Macbeth. Extra fcap. 8vo. stiff covers, is. 6d.

5. Bacon. Advancement of Learning. Edited by W. Aldis Wright, M. A.

Extra fcap. 8vo. cloth, 4s. 6d.

6. Milton. Poems. Edited by R. C. Browne, M.A., and Associate of

King's College, London. In the Press.

7. Dryden. Stanzas on the Death of OUver Cromwell ; Astraea Redux ;

Annus Mirabilis; Absalom and Achitophel; Religio Laici ; The Hind and
Panther. Edited by W. D. Christie, M.A., Trinity College, Cambridge. In the
Press.

8. Bunyan. Grace Abounding; The Pilgrim's Progress. Edited by

E. Venables, M.A., Canon of Lincoln.

9. Pope. With Introduction and Notes. By Mark Pattison, B.D.,

Rector of Lincoln College, Oxford.

I. Essay on Man. Extra fcap. 8vo. stiff covers, is. 6d.

II. Epistles and Satires.

10. Johnson. Rasselas; Lives of Pope and Dryden. Edited by C. H.
O. Daniel, M.A., Fellow and Tutor of Worcester College, Oxford.

11. Burke. Thoughts on the Present Discontents; the tw'O Speeches
on America ; Reflections on the French Revolution.

12. Cowper. The Task, and some of his minor Poems. Edited by
' J. C. Shairp, M.A., Principal of the United Colleges, St. Andi-ews.

Published for the University by
MACMILLAN AISTD CO., LONDON.

T/ie Delegates of the Press tnvile suggestions and
advice from all persons interested in education ; and
will be thaftkfiil for hints, &c. addressed to either the
Rev. G. W. KiTCHiN, St. Giles s Road East, Oxford,
or the Secretary to the Delegates, Clarendon
Press, Oxford.

fix ^jXaa^