A guide to the shell and starfish galleries (Mollusca, Polyzoa, Brachiopoda, Tunicata, Echinoderma, and worms)

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& GUIDE

TO THE

SHELL AND STARFISH
Gro 1b 101 Eee

(MOLLUSCA, POLYZOA, BRACHIOPODA, TUNICATA,
ECHINODERMA, AND WORMS),

“DEPARTMENT OF ZOOLOGY,

BRITISH MUSEUM (NATURAL HIS

feud

CROMWELL ROAD, LONDON,

FIFTH EDITION.

JAN 25 1988

WITH NUMEROUS ILLUSTRATIONS.

LONDON:
RENE Di bas ORDER OH SE Ey RU Sm EsS
OF THE BRITISH MUSEUM.
1908.
(All rights reserved.)

LONDON:

4)

PREFACE TO THE THIRD EDITION.

—1>e——_.

One of the large north galleries approached from the Bird Gallery
is devoted to the exhibition of the extensive Class of Mollusca.
Specimens of the types of all the principal divisions of this Class
are exhibited, either entire and preserved in spirit, or as models.
However, as not the animals, but their shells have always been a
favourite object of study, and a popular source of pleasure to
collectors, the exhibition of the species of shells has been made as
complete as the space of this Gallery admitted. It has thus proved
adequate for the requirements of the majority of visitors and students
who consult this Collection. A separate series of British Shells is
exhibited in some small table-cases along the west wall.

This Gallery also contains the exhibited series of Polyzoa,
Brachiopoda, and Tunicata.

The Starfish Gallery, so called from one of the best-known types
of the Echinoderma, contains an exhibition of the animals of this
Class, as well as of the somewhat heterogeneous assemblage of
creatures which are comprised under the popular name of Worms
(Vermes). ‘These animals possess greater attraction to students of
Natural History than to the general public, and many, from their
small size or the soft nature of their body, are not suitable for

exhibition. Therefore no attempt has been made to show more than

lV PREFACE.

a carefully selected number of the types of the larger groups. But
the exhibition of very complete series, supplemented by models or
figures, to illustrate the remarkable life-history of some of these
animals, also of specimens of the Worms which possess a special
interest from their relation to man, render this Gallery particularly

instructive to the student.

This guide has been prepared by Mr. E. A. Smith, Mr. F. J.

Bell, and Mr. R. Kirkpatrick, who have special charge of the
collections described.

Thanks are due to Messrs. A. & C. Black, Messrs. F. Warne & Co.,
Messrs. Macmillan & Co., Crosby Lockwood & Son, and the Linnean
Society for kindly allowing the use of cliches from illustrations in
various works published by them.

April, 1901.

THE present issue is, to a great extent, a reprint of the fourth
edition. 7

Some important corrections, however, have been made, and
further information given where necessary, especially in the part of

the Guide which has reference to the Echinoderma.

British Museum (Naturau History),
Lonpon, 8.W.

August, 1908.

- eee

TABLE OF CONTENTS.

THE SHELL GALLERY.

GENERAL Notes oN MoLiLusca

SYSTEMATIC ARRANGEMENT

AMPHINEURA (Chitons, etc.)

GASTROPODA (Marine Univalves, Land Sheth etc.)
PELECYPODA (Bivalves, Oysters, Cockles, etc.)
CEPHALOPODA (Octopus, Cuttlefish, etc.)
INDEX TO PRINCIPAL GENERA OF MOLLUSCA
GENERAL NoTES ON POLYZOA .
CLASSIFICATION ‘ :

AN ACCOUNT OF THE BRACHIOPODA
CLASSIFICATION ; :

AN ACCOUNT OF THE TUNICATA
ARRANGEMENT

THE STARFISH GALLERY.

GENERAL ACCOUNT OF THE HCHINODERMA.

CRINOIDEA (Lily Stars, etc.)

ASTEROIDEA (Starfishes)

OPHIUROIDEHA (Brittle-Stars)

ECHINOIDEA (Sea-Urchins)

HOLOTHURIOIDEA (Sea-Cucumbers)
PLATYHELMINTHES (‘T'apeworms, etc.)

VerRmMES j NEMATODES (Roundworms, etc.) .

ANNULATA (Marine Worms, Earthworms, Leeches) .

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Ee SAR GALLERY.

GENERAL NOTES ON MOLLUSCA.

THE Mo.uusca constitute one of the principal divisions of the
Animal Kingdom, and include such animals as the Octopus, Cuttle-
fish, Snail, Slug, Whelk, Cockle, and Oyster.

They may be characterized as soft, cold-blooded animals, without
distinctly marked external division into segments (as in Worms) ;
their cerebral ganglia (the centre of the nervous system) lie above
the commencement of the gullet, and are connected with the inferior
ganglia by nerve-chords. Their heart consists of two or more
chambers, and is situated on the dorsal side of the animal; it drives
the blood into spaces between the various organs of the body. Only
the Cephalopods possess internal cartilages, but all are without a
bony internal skeleton ; in the majority this is compensated for by
an external hardened shell which is formed (secreted) by the outer
covering of the animal termed the mantle. The shell may consist
of two parts (valves), as in the Oyster, or may be single, as in
the Whelk and Limpet, or composed of a series of plates, as in
the “ Coat-of-mail”’ shells or Chitons; when well developed it is
hardened by a rich deposit of carbonate of lime; but it may be

gelatinous, as in Cymbulia, or altogether absent, as in Polypus; it

may cover and protect the body, as in the Oyster, lie within the
folds of the mantle, as in the Sea-hares (Aplysiid@) and the Slugs,
or it may be quite internal, as in the horny “pen” of the Squid.
It may be elongated, as in the Elephant Tooth-shell (Dentalium),
cup-shaped, as in the Limpet, or spirally coiled, as in the Snail.

The mantle may form a free fold on either side of the body, as
in the Bivalves, or it may become largely attached to the body-wall,
as in the Snail or the Slug, and so give rise to an air-chamber,

B

Defini-
tion.

The
shell.

Descrip-
tion of the
animal.

The oper-
culum.

The
breathing
organs.

2 SHELL GALLERY.

which, when its walls are richly supplied with blood-vessels, serves
as a lung. The ventral surface of Molluscs is produced into the
so-called ‘“ foot,” which may be very variously modified. The foot
may be more or less hatchet-shaped, or curved and capable of serving
as a leaping-organ, or sole-shaped and adapted for creeping ; its
margins may be produced into elongated processes, as the so-called
arms of the Octopus, eight in number and provided with suckers,
or of the Nautilus, where the arms are much more numerous, but
shorter and without suckers. In the Cephalopods, also, another
part of the foot may fold over from either side and form a median
funnel, through which the water of respiration is driven outwards,
causing the animal to move in the opposite direction—this part of
the foot having, therefore, still the function of an organ of loco-
motion. By means of their muscular foot the Solenid@, or Razor-
shells, burrow in the sand, the Pond-Snails (Limneide) crawl on
aquatic plants and swim reversed on the surface of the water, the
Limpet clings to the rock, and the Cockles and Trigonias take
surprising leaps.

Upon the upper surface of the foot, in many Gastropods, a flat
hard structure termed the operculum is situated, which, when the
animal is retracted, partly or entirely closes the aperture of the
shell. In some cases, as in the Turbos, it is very strong and
of a stony nature, but in most instances it is horny. It is
differently constructed in distinct families: it may be annular
and multispiral, annular and paucispiral, subannular and ovate, or
subannular and unguiculate. In the Nerites it is shelly, somewhat
semicircular, closes the aperture of the shell, and is furnished with
a stout projection on the straight edge, fitting like a hinge under
the inner lip of the shell. A series of opercula is exhibited in side
table-case C.

Thread-like processes on either side of the body, the so-called
gill-filaments, often unite with those in front of and behind them,
and so give rise to plates; these, when well developed, are best
seen in the division to which the Oyster and the Mussel belong.
Where the body is coiled or twisted on itself, as so often happens,
the gills of one side may be altogether lost. Sometimes, as in
Phyllirhoé, when the body is small and its wall thin, the gills
(ctenidia) disappear altogether, and there is no special breathing-
organ; in others the loss of the gill is compensated for by the
formation by the mantle of a lung; this is most often seen in the
forms that live on land.

GENERAL NOTES. 3

But these so-called gills may have other functions : in the Lamelli-
branchs, where there is no head and no special means by which the
creature can obtain food, the delicate waving filaments or ci/lva with
which they are covered cause currents in the surrounding water, by
means of which minute organisms are brought to the mouth.

Nearly all Molluscs, except the Pelecypods, have a very remarkable
structure developed in the floor of their mouth-cavities ; on a basis
of cartilage, which may be moved backwards and forwards by muscles,
there is developed a horny plate, which may be of considerable length,
and which has its upper surface covered with a number of more or
less fine, flattened, or spiny outgrowths, which are known as teeth.
This is the odontophore, tongue, radula, or lingual ribbon (see fig. 3).*

Eyes may be absent, as in nearly all the headless Pelecypods ;
but in other Molluscs they are generally present, and may be more or
less well developed. An instructive series of stages is exhibited by the
Cephalopoda. In Nautilus the eye remains an open pit ; in Omma-
tostrephes two chambers appear, the anterior of which is bounded
posteriorly by the lens, and is open to the exterior, so that sea-water
enters it; in Sepia, finally, the anterior chamber becomes closed in
front. We may observe that the eyes of all Cephalopods are at
first pit-like, or pass through a stage which is permanent in Nautilus,
one of the geologically oldest types.

Cephalic eyes have been noticed in Mytilus and the Pterude.

Eyes of a more complicated structure, which are modified ten-
tacles, are sometimes found on the edges of the mantle in Pelecy-
pods (e.g. Pecten) ; these eyes resemble those of Vertebrates,
and differ from those of most invertebrate animals in having the
fibres of the optic nerve entering the distal and not the proximal
ends of the retinal cells. yes of a similar construction are to be
found on the back of the shell-less Oncidiwm, and may be about
one hundred in number.

Hyes of a remarkable character on the shells of some of the
Chitons appear to be modified from tactile organs, and are in-
nervated like the ordinary molluscan eye ; they sometimes occur in
enormous numbers, more than ten thousand being present on one
animal (see wax-model, Case 2).

In Cephalopods the ear, like the eye, is known to make its first
appearance in the form of an open pit, the mouth of which gradually
closes up, leaving only a narrow slit in communication with the

* A framed series of photographs, illustrating different kinds of radule, is
placed on the east wall of the gallery.
B 2

The
radula.

The eyes.

Organ of
hearing.

Sense of
smell.

The sexes
and repro-
duction.

4 SHELL GALLERY.

exterior. It is probable that in many forms the so-called ear is an
organ by means of which the mollusc becomes acquainted with
changes in the surface over which it is passing ; it is generally found
deeply imbedded in the substance of the foot, where it forms a
closed vesicle.

There is no doubt that the carnivorous Gastropoda are gifted
with a sense of smell, and throughout the series we observe patches
of modified cells of the body-wall (the osphradium) which serve
either as olfactory organs or as an apparatus for testing the nature
of the water of respiration.

The sexes are distinct in the most highly organized Mollusca,
but are united in the same individual in some of the lower forms,
such as Land-Snails, the Opisthobranchia (including the Bubble-Shells,
Sea-Slugs, &c.), and in some Bivalves. The reproduction of Mollusca
is in all cases effected by means of eggs. In some instances the
young are actually hatched within the oviduct of the parent, as in
the Freshwater Snails (Vivipara) ; and apparently in many Bivalves
the eges are also retained within the valves until hatched.

The ova of many molluscs are deposited in masses enclosed in
capsules. Some of them are very wonderful and complicated
structures. Those of the Cuttles and their allies are clustered
like grapes, each capsule containing but a single embryo; but in
the Calamaries or Squids they form a radiating mass of elongated
sacks, each containing from thirty to two hundred eggs, and it
has been estimated that one of the spawn-clusters of the Common
Squid (Loligo vulgaris) contains as many as 40,000 ova. Everybody
knows the spawn-cases of the Common Whelk, found so abundantly
on the sea-beach, consisting of a large number of yellowish capsules,
heaped one upon another and forming an irregularly rounded mass.
As many as five or six hundred capsules may be piled together in
a single heap, each capsule containing several hundred eggs, of
which perhaps only thirty or forty are hatched.

In other genera, as TVethys, Doris, Kolis, &c., the eggs are
contained in a spirally rolled ribbon or strap-like structure; and
some of the Natice build a somewhat similar capsule, composed of
the eggs cemented together by sand and a gelatinous material, the
whole forming two-thirds of a circle narrowed at the upper part.

Terrestrial Molluscs deposit, in comparison with their marine
relations, but very few eggs. They are sometimes covered by a
thin soft skin, but in certain groups, such as the large South-
American Strophochili and the African Achatine, which include the

GENERAL NOTES. 5

largest of known land-molluscs, they are protected by a hardened
calcareous shell, in some instances fully an inch in diameter. The
freshwater forms (Limnea and Physa) deposit from thirty to a
hundred eggs enveloped in a gelatinous mass.

The number of eggs produced by some Bivalves is enormous.
The Common Oyster is said to produce a million or more, and the
American variety ten, or even sixty, times as many. Some of the
River-Mussels are also very prolific, as many as two millions being
sometimes the product of a single individual. A small series of
the eges of Land-Snails and of the egg-capsules of some marine
Gastropods is exhibited in side-table case C at the side of the
Gallery. )

The ova of Mollusca may be gradually developed into the form
of the parent, or there may be a free-swimming larva, which has
a circlet of cilia near the anterior pole of its body (so-called
“ Veliger” larvee), or there may be special larvee, as in the case of
the Freshwater Mussel, the ‘“ Glochidium,” as it is called, which
has a toothed bivalve shell by which it can fix itself to fishes.

The limits of age of molluscs has been definitely ascertained in
a few instances only. Most Land-Snails probably live about two
years, although in confinement some have been kept alive for a
much longer time. Some of the marine forms live for a considerable
period, the Common Oyster not attaining full growth until about
five years old, after which it may continue to live for many years.
The Giant Clam, a specimen of which is placed in the upright cases
near the entrance to the Gallery, must, one would think, have a very
long existence, judging from the size and thickness of the shell.
All terrestrial molluses hibernate in cold climates, hiding themselves
away in the ground between roots and in similar sheltered places.
In tropical countries some assume a state of torpidity (eestivate)
during the hottest and driest season of the year, closing up the
aperture of their shells with a temporary lid or door (epiphragm),
in order to resist the dryness of the atmosphere. Some of these
“‘ summer-sleepers”’ are endowed with a remarkable tenacity of life.
An Australian Pond-Mussel has been known to live a year after
being removed from the water; several Land-Snails have revived
after a captivity of from two to five years, without any food what-
ever. One of the most remarkable instances of this kind occurred
in the British Museum. A specimen of Helix desertorum, the common
Desert-Snail of Egypt, was fixed to a tablet in March, 1846, and in
the same month of the year 1850 it was discovered to be alive.

Duration
of life.

Hiberna-
tion and
torpidity.

Economie
uses.

Geological
history.

General
distribu-
tion.

6 SHELL GALLERY.

It must have come out of its shell in the interval, and finding it
was unable to crawl away, had again retired within it, closing the
aperture with a new epiphragm, but leaving traces of slime upon
the tablet, which led to its immersion in water and subsequent re-
vival, having passed a period of four years in a dry museum with-
out the smallest particle of food.
It lived till October, 1851, then
became torpid, and was found to
be dead in May, 1852. The
actual specimen is here figured,
Fig. 1.

The economic uses of molluscs
to man are manifold, and will be
mentioned in the course of the de-
scription of the several families ;
but here may be the place to direct the attention of visitors to
side table-cases B and D at the side of the room, containing some
specimens of articles manufactured from shells, such as cameos,
flowers, bracelets, brooches, &c.

Mollusca made their appearance on the globe at a very early
epoch in the history of the development of animal life, a large
number of Cephalopoda, such as Litwites, Orthoceras, &c., being:
found in the oldest Paleozoic formations. Probably all these
belonged to the Tetrabranchia, of which one descendant only, the
Pearly Nautilus, has survived to our period. Some Gastropods
and Bivalves coexisted with those ancient Tetrabranchs ; but these
types abounded more in the later geological epochs, many Tertiary
forms being undistinguishable from species which now exist.

The greater number of Mollusca are inhabitants of the sea,
some passing their whole life at the surface hundreds or thousands
of miles away from land ; others at the bottom of the ocean at all
depths, some having been dredged at five miles from the surface.
Many are found in much shallower water, and a large number
between tide-marks. Rivers and lakes furnish an immense variety
of forms, and vast numbers live on land in all situations—on
mountains, in valleys, forests, and deserts.

Molluscs are generally either animal or vegetable-feeders, the
former preying principally upon other members of their own class.

Helix desertorum.
(See black table-case 1.)

* From Woodward’s ‘Manual of the Mollusca,’ published by Lockwood
& Son.

AMPHINEURA. 7

The following Table shows the systematic arrangement of the
Mollusca adopted in the Shell Gallery :—

Class I—Amphineura.
Order 1.—Polyplacophora. Chitons.
», 2.—Aplacophora. Neomenia, Chetoderma, ete.
Class IIl.—Gastropoda.
(Section Streptoneura, ) s
Order 1.—Scutibranchia. Nerites, Top- ‘shellg, Ear-shells, iLAbmpet.

» 2.—Pectinibranchia?~ Rock- -snails, Whelks, Olive-shells, Harp- shells
Cones, Strombs or Wing-shells, Periwinkles, Carrier-shells, ete.
b ‘ i

(Section Euthyneura.)
Order 1.—Opisthobranchia. Bubble-shells, Sea-hares, Umbrella-shells.
5, 2—Pulmonata. Land and freshwater Snails, False Limpets.
Class III.—Seaphopoda. Tooth-shells (Dentaliwm).

Class [V.—Pelecypoda. Bivalved Molluscs.
Order 1 —Protobranchia. Nucula, ete.
, 2.—Filibranchia. Anomia, Common Mussel, Ark-shells, ete.
», 3.—Hulamellibranchia. Freshwater Mussels, Cockles, Razor-shells,
Oysters, Ship-worms, ete.
» 4-—Septibranchia. Poromya, etc.
Class V.—Cephalopoda.
Order 1.—Tetrabranchia. Pearly Nautilus.

» 2.—Dibranchia. Octopus, or Poulp, Argonaut, Squids, and Cuttle-
fishes.

Class I-—AMPHINEURA.

The Molluscs of this class are characterized by bilateral symmetry.
The head and anus are situated at the opposite extremities of the
elongated body, the gills, genital ducts and circulatory organs being
paired and similar on both sides. The first order belonging to this
division, the Polyplacophora, includes the ‘ Coat-of-mail shells,”

“ Sea-woodlice ” (Chitomde). They have their back protected with
eight shelly plates which overlap one another like tiles, and, like
woodlice, have the power of rolling themselves into a ball. These
plates are imbedded at the sides into the fleshy mantle, beneath
which, on each side of the foot, are arranged the gills. A Chiton
differs in many respects from other Mollusca. It has a shell like an
Isopod' Crustacean, a heart down the back like a sea-worm, sym-
metrical organs of reproduction on each side like the bivalves, a
head and crawling foot like a true Limpet, and a posterior anal

Syste-
matic
arrange-
ment.

Cases 1-3.

8 SHELL GALLERY.

orifice. These several anatomical peculiarities at one time induced cer-
tain eminent authorities to hesitate in considering them molluscs ; but
now that the development from the egg has been investigated, their
association with the Mollusca may be considered definitely settled.
Chitons are found in all parts of the world, the finest inhabiting
tropical countries. They live chiefly on rocks and under stones at
low-water or at moderate depths ; but a few forms have been dis-
covered by the ‘Challenger’ Expedition at depths exceeding 2000

Coat-of-mail Shells, or Chitons.

1. Chiton squamosus (upper surface).
2. Chiton elegans (lower surface): a, mouth; b, foot; c, mantle; d, gills.

fathoms, The numerous sections of the group are principally dis-
tinguished by differences in the edges of the plates or valves which
are inserted in the mantle, and in the different kinds of ornamenta-
tion upon the upper surface of the mantle-border. This, in some
Species, is quite smooth, in others covered with a dense mass of
minute grains or scales, and in others armed with short prickly
spines. In the giant Cryptochiton of Kamtschatka the plates are
entirely covered over by the thick leathery granular mantle, and in
another set, Cryptoplaz, which consists of long slug-like animals, the
plates are very small, and placed at intervals along the back.

Five or six hundred living species are known, and about one-

GASTROPODA. 9

fourth that number has been found fossil from the Ordovician age
upwards.

The second order of Amphineura, namely, the Aplacophora,
comprises a few somewhat worm-like Molluscs which are devoid of a
shell, but have instead the dorsal surface more or less studded with
numerous minute calcareous spines or spicules. Neomenia, Pro-
neomenia, Chetoderma are genera belonging to this order.

Class II1.—GASTROPODA.

In contradistinction to the preceding class these Molluscs are
asymmetrical, especially in respect of the gills and the spiral coiling
of the viscera and most of the shells. They may be divided into
two sections, Streptoneura and Huthyneura, distinguished by differ-
ences in the arrangement of the visceral nerve-loop.

Section STREPTONEURA.

The Molluscs of this section are bisexual and furnished with a
shell, and generally with an operculum. The gills are in front of
the heart and the visceral nerve-loop is twisted into a figure of 8.
The section contains two groups or orders, Scutibranchia and
Pectinibranchia.

Order 1.—ScUTIBRANCHIA.

The Scutibranchia have a free bipectinate gill, or the gill may
be absent (Lepeta, Helicina), and generally exhibit traces of bilateral
symmetry.

The Acmeide are called False impets, because, although the
shells are identical with the true Limpets, the animals differ in
having only a small gill on the left side of the neck, whilst the
Patelle have the gills greatly developed all round the sides of the
foot. Both the true and the false Limpets are littoral and found
on rocks between tide-marks. They have the power of excavating
the surface to which they attach themselves, and adhere so firmly
that it is easier to break the shell than detach the animal. The
largest known Limpet (Patella (Ancistromesus) meaicana, case 7) in-
habits the west coast of Central America, its shell having sometimes
a length of 12 inches. The Limpets are vegetable feeders and fond
of seaweeds of various kinds, which they rasp with their remarkable

Case 3.

Cases
4-135.

Cases
4-94,

Case 4.

10

SHELL GALLERY.

7
1. Radula of the Common British Rock-Limpet (Patella vulgata), natural
size.
2. Two transverse series of teeth: a, median teeth; b, laterals; c, uncini or
marginals.

The Common Rock-Limpet (Patella vulgata). British.

1. Animal: a, foot; b, fringed mantle; c, tentacles; d, mouth; e, eyes;

f, gills.
2. Side view of shell, showing the impression or scar of the attachment-
muscle, g.

3. Upper surface of the shell.

fee is

GASTROPODA. idl

spiny tongues. ‘That of the common English Limpet (P. vulgata,
Fig. 3) is longer than the shell itself, and armed with as many as
1920 glassy hooks in 160 rows of twelve teeth each. ‘The Limpet
is commonly used for bait in the sea-fishing off the Scottish coast,
and vast quantities are consumed as food in some parts of Ireland.
Some Limpets, such as P. compressa, P. mytilina, etc., are found on
the stems of floating seaweeds, and have the shells usually thinner
and smoother than the Rock-Limpets, which have to resist the fury
of the breaking waves.

The “ Keyhole Limpets” and “Slit Limpets” (/isswrellidw) Case 8.
resemble in external shape ordinary Limpets, but are perforated at
or near the apex, or more or less slit at the front margin. The
hole or slit gives passage to a tubular fold of the mantle, through
which the water apparently flows to the gills. The largest species
are from California and South America, and others are found, but
not abundantly, on most shores. ‘The animal of the large Lucupina
crenulata from California is eight or ten inches in length, and almost
conceals the shell, and the shell of the South-African Pupillea aperta
is also all but hidden beneath the mantle of the animal.

Pleurotomaria adansoniana. Case 9.
4 natural size.

The Pleurotomarie are extremely rare in recent times, only six Case 9.
Species being known, whereas over a thousand fossil forms have

* From ‘The Cambridge Natural History,’ Messrs. Macmillan & Co.

Cases
9-1].

Cases
12-18.

12 SHELL GALLERY.

been described. The specimens of P. adansoniana and P. beyrichi
exhibited in case 9, are among the finest acquisitions to the shell
collection of recent years.

The “ Har-shells” or “ Ormers” (Haliotide) are found adhering
to rocks in most parts of the world, with the exception of South
America. ‘They are lined with pearl, and many exhibit splendid
colours and sculpture externally. Like the Limpets they hold on
to the rocks with such tenacity that it is absolutely impossible to
remove some of the larger species by force without injuring the
shell. Boiling water or mustard and water poured over them will,
however, soon compel them to relinquish their hold. The shell of
Haliotis is pierced by a series of holes parallel with the left margin.
Through such of them as are open the animal protrudes a slender
filament or feeler, and the water also finds its way through them
to the gills beneath. ;

The Single British species (1. tuberculata) is not actually found
on the English coast, but is common on rocks and stones at low-water
in the Channel Islands. It is frequently eaten by the poor of those
islands and the north of France; other species in New Zealand,

China, Japan, West Africa, and elsewhere, constitute a common —
article of diet among the natives. Haliotis-shells are largely used in —

the manufacture of pearl ornaments, and in all kinds of inlaid work.
The Zrochide and Turbinide are two extensive families, the
animals: of which are very much alike, and mainly distinguished by

Fig. 6.

Top-shell (Turbo petholatus). (From the Indo-Pacific Ocean.)

a. Inner surface of operculum. b. Exterior of ditto.

the operculum, which in the former is horny, and shelly in the
latter. The shells of these families are beautifully pearly within,

a
ee eee

GASTROPODA. 13

and the external shelly coat is generally brightly coloured and
highly ornamented. Several very pretty species are found on our
own shores. The opercula of Turbo petholatus (Fig. 6), from the
Indian and Pacific Oceans, are frequently mounted in gold and
silver as scarf-pins, ear-rings, &c.

The Nerites are mostly found in tropical countries, and, like the
Winkles, are very strongly made, to resist the force of the breaking
waves. The Neritinas are found both in the sea, and in fresh
water, and are less solid shells. The third section of Neritide,
the Septariw, are shaped very much like Limpets, except that the
apex is at one end instead of central. They are, however, very
different animals, and furnished with a shelly operculum imbedded
in the foot.

Order 2.—PECTINIBRANCHIA.

In most cases the molluscs of this order have an attached
monopectinate gill and a single osphradium. A few are fresh or
brackish water forms, but the majority are marine.

The “ River-Snails” (Viviparide) might be termed freshwater
Periwinkles, as the animals of both are very similar. The true

Fig. 7.

The Common British River-Snail (Vivipara vivipara).
a, head; b, tentacles; c, eyes; d, foot; e, operculum.
Vivipare are viviparous. 'They are rather sluggish, and found at

the bottom of ponds and rivers feeding on decaying animal and
vegetable matter.

Cases
18-20.

Cases
22-94,

Case 22.

The Cyclophoride are land-shells, which, however, cannot properly Cases

be considered true lung-breathers like ordinary snails. They have
not the closed lung-chamber of the Pulmonates, their eyes are

23-25.

Cases
25-26.

Cases
27-28.

Cases
31=32:

Cases
32-35.

14 SHELL GALLERY.

placed at the base of the tentacles instead of at their tips, they
have a long proboscis armed with a different rasping tongue (radula),
a spiral operculum, and the sexes are distinct, whereas the true
Snails are hermaphrodite.

The operculated air-breathers have been divided into many
sections, chiefly on account of differences in the apertures of the
shells and in the opercula. They most abound in hot countries, but
a few species are met with in temperate regions.

The ‘“Apple-Snails” (Ampullariide) live in the rivers and
marshes of tropical regions, and, although represented by a large
number of species, exhibit comparatively slight variations in form
and colour. The animal has both a pectinated gill and a lung
cavity, being thus enabled to breathe either water or air.

Fig. 8.

Ampullaria canaliculata.

The “ Periwinkles” (JLittorinide) are found almost on every
known shore; they feed upon all kinds of marine vegetation.
Some species are met with at low-water mark, others on rocks
almost beyond the reach of the sea, and some have been discovered
inland nearly half a mile away from the shore. It is calculated that
1900 tons of the ‘“‘Common Periwinkle” (Littorina littorea), of the
value of £15,000, are annually consumed in London alone.

The family of Calyptreide includes the “ Slipper-Limpets ”
(Crepidula) and the “Cup-and-saucer Limpets” (Crucibulum).
Although furnished with a foot, they rarely crawl about, but
remain attached to rocks, stones, or other shells, sometimes
forming a shelly plate under the foot by which they become
fixed to the spot where they have taken up their abode. —

The “ Cowry-shells” (Cypreide) are remarkable for their varied

GASTROPODA. 15

markings and splendid polish, which is produced and preserved by
two flaps of the mantle, one on each side, which fold over the back,
a line down the centre of which usually marks where the flaps meet.
The animals are even more brilliantly coloured than the shells.
They have no operculum, but a large foot, which they can withdraw

The Tiger Cowry (Cyprea tigris). (From the Indo-Pacific Ocean.)

a, the shell; b, the mantle; c¢, foot; d, siphon; e, proboscis; f, tentacles ;
g, eyes.

entirely within their shell, although the aperture is usually very
narrow. Cowries, as is well known, are sold as ornaments ; and a
small yellow species, “the money-cowry”” ((. moneta), which is very
common in the Indian and Pacific Oceans, passes current as coin
among the negro tribes of certain parts of Africa. The specimen
of Cyprea leucodon figured on p. 16 is extremely valuable and sup-
posed to b2 the only one hitherto discovered. The “ orange cowry ”
(Cyprea aurora) is worn by chiefs in the Friendly Islands, and is
considered the highest order of dignity. Only one small species,
Trivia europea, is found on the British coast, and numerous fossil
forms have been discovered in Jurassic, Cretaceous, and Tertiary
rocks.

Of the Ovulide, the most curious is the ‘‘ Weaver’s-shuttle ”’
(Radius volva), in which the shell is peculiarly beaked at both ends.
It is found living on barked corals (Gorgonide), and some of the
smaller species exhibit differences of coloration, resembling the tints
of the Gorgonias upon which they are found.

The Naticas are mostly blind, and have a very large foot, suitable
for burrowing in the sand when in quest of bivalves. They are very

Case 35.

Cases
35-37.

16 SHELL GALLERY.

voracious. This is one of the groups of shells that have continued
to exist from Paleozoic times.

Case 38. The “ Violet Snails” (Janthinide) are found floating about in
every ocean, excepting in cold regions, with the spire of the shell i
downwards, and the bottom, being more exposed to the action of
light, is more deeply tinted than the upper part. They feed upon

i

ses

Cyprea leucodon. Case 32. c

Jelly-fish, and construct a gelatinous raft, filled with air-bubbles,
to the underside of which the females attach their eggs.

GASTROPODA. 17

The Melaniide are freshwater Snails which abound in most tropi-
cal and subtropical countries ; about 1000 species are known. They
are mostly of dark colours, and are fond of muddy places.

The Cerithiide are chiefly marine forms, some, however, entering
brackish water. About five hundred fossil species have been described,
some of them gigantic in comparison with any now living, of which
more than two hundred are known.

The Scala scalaris was formerly considered a great rarity, as
much as £40 having been given for a single speci-
men, which might now be purchased for as many
pence.

The “ Worm-shells” (Vermetide) are a very
peculiar family. Their shells can scarcely be dis-
tinguished from the shelly tubes which are formed
by certain species of marine worms, Serpula, &c.
They are free and spiral in early life, but after-
wards become distorted and generally attached to
rocks, stones, &c. A foot for walking purposes
therefore would be of no use; consequently it
is more or less obsolete, serving only as a support = Scala scalaris.
to the operculum. Case 44.

The “ Screw-shells ” (Z'urritellide) have elongate tapering shells ;
about 100 recent and 200 fossil species are known. One species only
(Turritella communis) is now found living on the British coasts.

The Xenophoride have the singular habit of cementing to the
exterior of their shell, stones, pieces of coral, and fragments of other
shells ; hence they have been called ‘‘ Carrier-shells,” and, according
to the kind of material chosen, have been named ‘‘ Conchologists ”
and “ Mineralogists.”” Beyond acting as a disguise, and consequently
as a protection, there does not appear to be any special utility in
thus adding to the weight of their own shells. The animals do not
glide like most other molluscs, but scramble along like the Strombs,
the form of their foot being small, divided into a front, expanded,
and a hind, tapering portion admirably adapted to the nature of the
ground on which they live, which usually consists of broken and dead
shells.

The “ Wing-shells ” (Strombide) are the largest of the Gastro-
pods with a proboscis or non-retractile snout. They do not crawl
like most other Gastropods, but progress bya sort of jerking move-
ment. They act as scavengers, feeding on decomposing animal matter.

The Strombus gigas, or “ Fountain-shell,” occurs in great numbers

Cc

Fig. 11.

Cases
388-41.

Cases
42-43,

Case 44.

Cases
46-47.

Case 48.

Case 49.

Cases
49-52.

Cases
51-52.

Cases
a= os

Cases
55-56.

Cases
56-57.

Cases
57-60.

Cases
61-64.

Cases
64-66.

18 SHELL GALLERY.

in the West Indies, and is a very heavy solid shell. It is a favourite
ornament for rockwork and fountains in gardens, and, like the
Helmet-shells, is used for cameo-carving. At one time it was also
employed in the manufacture of porcelain, as many as 300,000 having
been imported into Liverpool in one year for that purpose.

The Scorpion-shells, or “ Spider-claws,” as they are sometimes
called (Pterocera), possess singular claw-like projections, which are
developed on the outer lip of the shells.

The “ Trumpet-shells” (Septide@) have varices or strengthening
ribs at intervals, like the Murices; the largest species, Septa
variegata, is used by South-Sea Islanders as a horn or trumpet.
A hole is made in the upper part of the spire to blow through, and
the sound produced can be modulated or varied by inserting the hand
in the aperture or mouth of the shell.

The “ Helmet-shells” (Cassidide) are used for cameo-carving ;
they consist of differently coloured layers, so that the ground-colour _
of the carving is of a different tint from the subject engraved. The
most artistic shell-cameos are produced in Italy, whence the art has
been introduced into France and England. The Cassis madagas-
cariensis (Fig. 12 on p. 19) is in special request by shell-carvers on ac-
count of the strong contrast of the white upper layer with the dark
eround beneath. Extinct forms of Cassis are found fossil in Tertiary
formations, but none of them equal in size the largest living species.

The * Tun-shells ” (Doliid@) are remarkable for the globoseness
of the shells, which are covered with very regular revolving ribs.

The fasciolarude contains two of the largest living Gastro-
pods: Megalatractus aruanus, from North and West Australia, and
Fasciolaria gigantea, which is found off the coast of South Carolina,
and attains at times a length of two feet.

The Mitras (Witride) are great favourites with shell-collectors,
on account of their beautiful colours and varied sculpture. There
are about 600 living species already known, and between one and
two hundred have been found in a fossil state. Shells of this group,
like the Fasciolarie, are distinguished by a few plaits or folds on
the inner side of the aperture (the columella). Mitras are almost
exclusively found in tropical or subtropical regions, the majority
being met with either at low-water mark or in comparatively shallow
water.

The family of Buccinide also contains a very large and varied
assemblage of forms. Among them may be mentioned the Whelks
(Buccinum). (See Fig. 13 on p. 19.)

GASTROPODA.

Cassis madagascariensis, with cameo engraved upon it.
Side table-case B.

Fig. 13.

5

The Common Whelk (Buccinum undatum).

a, siphon ; 6, foot; c, tentacles; d, eyes; e, operculum.

19

Cases
70-76.

Cases
74-75.

Cases
78-81.

Cases
81-83.

Case 84.

Cases
85-87.

20 SHELL GALLERY.

The family of Muricide, or ‘ Rock-shells,” is another extensive
eroup, containing many very handsome and peculiar forms. The
animals of this family have a long protractile proboscis, at the end
of which is the spiny tongue (radula). The true Murices produce at
intervals ribs or varices, which in some species are ornamented with
long spines or foliations, and which indicate periods of growth, but
of what duration we do not know. ‘They are all carnivorous,
feeding chiefly on other Mollusca, boring through the shells of
bivalves with their spiny tongue, and slowly devouring the unfor-
tunate inhabitant piecemeal. From certain species of Murex (I.
brandaris, &c.) found in the Mediterranean, the ancients manufac-
tured the celebrated Tyrian purple dye.

The “ Purples” (Purpura) are found between tide-marks all
over the world. JMJagilus, belonging to the family Coralliophilide
(Case 77), is found among coral-reefs in tropical seas, and has the
remarkable habit of lengthening the aperture of its shell into an
elongate tube, in order to keep pace with the growth of the coral,
and to prevent its being overgrown and killed.

The “ Volutes” (Volutide) are a group of shells also much
sought after by shell-collectors. Some of these attain to a very large
size, the animals inhabiting them being enormous. The Boat-
shells (Cymba) and Melons (Cymbiwm) are ovo-viviparous, the young
being carried about by the parent until they are an inch in length.
Volutes are found chiefly in the warmer parts of the Atlantic and
Indo-Pacific Oceans, and occur in the greatest variety on the coasts
of Australia.

The Olives (Oliwide) are common in most tropical seas, and are
remarkable for their beautiful polish and various patterns of colour-
ing. In structure and form they are very similar to each other.
They burrow in sand in quest of bivalves for food, and some species |
are said to have the power of swimming by expanding the lobes of
the foot.

The Harps (Harpide) form a small well-marked group, of which
probably nearly all the existing species have been discovered. The
animals inhabiting these beautiful shells are also brightly coloured.
They have the remarkable power of casting off a portion of the foot
when disturbed. The species are known from the Indo-Pacific Ocean,
the west coast of Central America, and West Africa. -

The next family, the ‘“Slit-lips” (P/leurotomide), consists of
very numerous species, over a thousand living forms having been
discovered, and almost as many fossil species from Cretaceous and

GASTROPODA. 21

Tertiary strata have been described. The typical forms are charac-
terized by a slit in the outer side (lip) of the aperture. Species
of Pleurotoma are found in every sea, although most abundant in
the tropics, and, although so numerous in species, the number of
specimens is small in comparison with some other genera.

The “ Auger-shells”’ (Zerebrid), like the Cones, present a great Cases
; 87-89.

Al
The “ Glory-of-the-Sea ” Cone (Conus gloria-maris). Case 94.
(From the Philippine Islands.)

similarity in form, but, unlike them, have a great diversity of “ sculp-
ture” or external ornamentation. They are all elongate shells, with
a deep notch at the base of the aperture. Owing to the length and
comparative solidity of the shells, the animals of many of the species
do not carry their shelly structures on their backs, like most other
species, but drag them along the sandy sea-bottom.

The Conide, or Cones, form one of the most beautiful portions of Cases
the collection of Shells. This family, of which between 400 and 500 %9-94.

Case 94.

OD) SHELL GALLERY.

distinct kinds are known, is a great favourite with collectors on account
of the brilliant colours and various patterns of the shells. Some, owing
to their beauty and rarity, have been sold at very high prices, as
much as £50 having been paid for a single shell. The Cones are
found in all tropical seas, but are rare in cold or temperate latitudes.
None are met with on our own shores, one species alone being known
from the Mediterranean. They occur fossil in the Chalk and Ter-
tiary strata. These animals are all carnivorous, and live usually in
shallow water among rocks and coral-reefs. Some of them are said
to bite when handled, and to be dangerously poisonous, the bite in
some instances having been all but fatal.

The Atlantide, Pterotracheide, and Carinarude, at various times
recognized as forming a distinet sub-class or order of Gastropoda,

Fig. 15.

Glassy Nautilus (Carinaria lamareh‘).

a, proboscis; 6, tentacles; c, shell; d, gills; e, foot; 7, sucker.

under the name of Heteropoda or Nucleobranchiata, are now regarded
as families of aberrant Gastropods organised for swimming in the
open sea. The Atlantas are found in great numbers in warm lati-
tudes, and are provided with a glassy, thin, flat, spiral shell, not
unlike a keeled Ammonite. The glassy shell of the Carinaria is one
of the most beautiful structures of any mollusc, and at one time was
such a rarity that £100 are said to have been given for a single
specimen, which at the present time is perhaps worth only from five
to ten pounds. Species of Carinaria are found in the Mediterranean
and warmer parts of the Atlantic and Indian Oceans. The animal
is large, semitransparent, and elongate, with a compressed fin-like
foot which projects from the body, and is used in swimming. The
gills are placed towards the hinder part of the back and covered by
the shell. They feed on jelly-fish of various kinds, and probably on
other soft animals.

GASTROPODA. ao

Section EUTHYNEURA.

The Gastropods belonging to this sub-class have the visceral Cases
nerve-loop straight and not twisted as in the Srrepronnura. All 94-189.
the HuTHYNEURA are hermaphrodite, and their radula is generally
composed of numerous similar denticles on each side of a median
tooth. Scarcely any of these forms are provided with an operculum
in the adult state. The HurHyneura may be divided into two
orders, Opisthobranchia and Pulmonata.

Order 1.—OPISTHOBRANCHIA.

All the Molluses of this order are marine, some (7ectibranchia) Cases
breathing by means of the ordinary Gastropod ctenidium, which is oe
generally behind the heart, whereas others (Mudibranchia) have
developed a different type of respiratory organs.

The Opisthobranchia include the ‘ Pteropods” formerly con-
sidered as a distinct class, the ‘‘ Bubble-shells ” (Lullide), the “ Sea-
Hares” (Aplysiide), the ‘“ Umbrella-shells” (Umbraculide), the

Nudibranchs and some others.

. The Pteropods* are sometimes called Sea-butterflies, and are
organized for swimming freely in the ocean. They have a pair of

- Shell-bearing Pteropod (Cavolinia tridentata). Case 96.

a. Shell and animal. 0b. Side view of shell. c¢. Dorsal view of shell.

fins developed from the sides of the mouth or neck, which perform a
flapping movement during progression. Some Pteropods (Thecoso-

* From the Greek: pteron, wing, and pous, foot.

24 SHELL GALLERY.

mata) are provided with small glassy shells ; others (Gymnosomata)
are naked. They exist in countless millions in some parts of the

Shell-less Pteropod (Clione limacina).

a. Dorsal view. 6b. Ventral aspect.

ocean, discolouring the water for miles. They constitute the princi-
pal food of the Baleen Whales.
About a hundred species are known.
Case 96. The Sea-Hares, so called on account of a slight resemblance to a
crouching hare and not for their nimbleness of foot, are found in

Fig. 18.

Sea-Hare (Tethys (Aplysia) punctata). British.

a, labial tentacles; b, upper tentacles or rhinophores; c, siphonal fold
of the mantle near the shell; d, eye.

most parts of the world, in pools at low water. At the hinder part
of the back two flaps of the mantle partly conceal a thin horny shell
which serves as a protection to the gills and vital organs beneath.
When molested, these animals discharge a large quantity of a purple
fluid, discolouring the surrounding water for a distance of more than
a yard.

Case 97. The shell of Umbraculum is shaped very like that useful article,
an umbrella, of the Chinese pattern. The animal is very large,
having its breathing-organs on the right side below the shell.

Case 97. The Mudibranchs or Naked-gilled Molluscs comprise some of the

GASTROPODA. 25

most beautiful and strange forms. They are unprovided with shells
except in the earliest stages of their existence, when they dwell in a
minute nautiloid shell, furnished with an operculum, both of which

The Umbrella-shell (Umbraculum mediterraneum).
a, shell; b, gills; c¢, tentacles; d, mouth; e, foot.

are subsequently cast off. Unfortunately the colours of these beauti-
ful creatures cannot be preserved after death, and therefore a small
series of glass models is exhibited, which will give some idea of

Fig. 20.

Naked-gilled Mollusc, or Nudibranch (Doto coronata).
a, head; b, foot; c, gills; d, tentacle-sheath; e, tentacle.

their great variety in form and colouring. They are found in most

\ parts of the world, chiefly in shallow water, but a few species live
upon floating’ seaweed in the open sea. Over a hundred species
exist on the British coast, the majority of which are, however, very
small. They are chiefly carnivorous, feeding on other molluscs,
sea-anemones, &c.

Order 2.—PULMONATA.

The Pulmonata are furnished with a lung-cavity in place of the Cases
ordinary gill of other Gastropods, and may be termed true air- 97-199.

Cases
97-98.

Cases
98-99,

Cases

99-101.

26 SHELL GALLERY.

breathers. Most of them are provided with shells, and, with the
exception of the Amphibolide never possess an operculum. They
are divisible into two groups or sub-orders, Basommatophora and
Stylommatophora, characterized by the difference in the position of the
eyes. ‘The Basommatophora, including the Auwriculide, Amphibolide,
Siphonaride, and Limneide, have a single pair of non-retractile
tentacles, at the base of which the eyes are situated. The Stylom-
matophora (Land-snails, Slugs, &c.), are provided, save in a few cases,
with two pairs of retractile tentacles, with the eyes at the summit of
the upper pair. Over ten thousand species of Pulmonata are known.

(Basommatophora.)

The first group of the aquatic air-breathers, the Awriculide,
chiefly inhabit salt or brackish water. The largest forms are tropical
and found at the mouths of rivers, among the roots and stems of
mangrove-trees, or in damp woods near the sea.

The ‘‘ Limpet-Snails” GSiphonariide) seem at first sight to be
out of place among the Snails and Slugs, and more nearly allied to

Fig. 21.

ay aie ©

: “ae Maer serene oe :
2 oop ee ra

=pyyrvyyy YBBYYIINIANN 9 ARERR RRRING me

Three Rows of Teeth of the Radula of Siphonaria.

ce, central ; J, lateral teeth.

the Rock-Limpets ; but the character of the tongue (radula) and
the closed respiratory cavity indicate a close relationship with the
present group.

The shells of Siyhonaria may be known from Limpets by a slight
bulging on one side, caused by a radiating groove which interrupts
the muscle of attachment. They are marine. and are found on rocks
between tide-marks, chiefly im tropical countries.

The Limneide are only found in fresh water. Most of them
occasionally rise to the surface to breathe, where they glide along
foot uppermost, at times suspending themselves by a glutinous
thread, after the fashion of a spider. All countries appear to have
their peculiar species.

GASTROPODA. 27

The freshwater Limpets (Ancylus) live attached to stones and
leaves of plants, and have not the habit of floating, but, like the

Fig. 22.

0

s
British Pond-Snail (Limnexa stagnalis).

1. Upper view: a, foot; b, tentacles: ce, eye; d, muzzle.
2. Lower view: letters a, b, ¢ as above; e, mouth; /, respiratory orifice.

rest of the Limnwide, feed on freshwater alge, confervee, and
decayed vegetable matter.

(Stylommatophora. )

True Snails (Helicide, etc.) have a distinct head furnished with
eyes, tentacles, cutting upper jaws, and rasping teeth, and nearly all
are protected by a spiral shell. They are almost exclusively vegetable-
feeders, subsisting chiefly on leaves. The sexes are not distinct.
Many of the species are beautiful objects on account of the brilliancy
of their colouration, and some are remarkable for the variation they
exhibit in this respect. Species of Helicide are found in nearly
every part of the world and in all situations, from sea-level to an
altitude of 12,000 feet. They are fond of moisture, and in hot and
dry weather retire within their shells, remaining torpid until the
return of dew and rain. Helix pomatia (Case 119), which is found
on the chalk in the south of England and on the Continent, is
commonly eaten in Austria, France, and Belgium.

Cages
102-135,

28

SHELL GALLERY.

The eggs of Land-Snails vary in texture, size, and in numbers ;
they are usually white, but in some instances yellow and pale green.
Those of some of the large South-American forms are as hard as
that of a hen, and more than an inch in length (Case 120).

Slugs (Cases 106, 107) are very like Snails without external shells ;
most of them, however, possess a small internal shelly plate, or a few

a, eye-bearing tentacles (“horns”); b, lower or smaller tentacles.

calcareous granules hidden beneath the skin of the back. Some have
a large slime-pore at the end of the foot, and others are slightly

Fig. 24.

Case 136.

British Tooth-shell
(Dentaliwm tarentinum).

a. The shell. b. The an-
imal, removed from
its shell; 7 the foot.

phosphorescent. Like the Snails, they are fond
of damp localities, and at times become great
pests to farmers in devouring the young shoots
of the growing corn. Testacella, which is found
in this country, differs from the Slugs in having
an external shell at the tail-end of the foot.
It is not slimy, and lives under ground, feeding
upon earthworms.

Class IIT.—SCAPHOPODA.*

The ‘“ Tooth-shells”? (Dentalude) form a
distinct group, the shells of which are very
unlike those of any other mollusc, but closely
resembling the shelly tubes constructed by
certain kinds of marine worms. The Dentalia

* From the Greek: scaphe, a small boat, and pous,
a foot—the foot of some Scaphopods being somewhat
pointed like the prow of a vessel.

PELECYPODA. 29

have neither eyes nor tentacles, nor a distinct head like Gastropods ;
their organs of circulation and respiration are of a rudimentary
kind, and they have no heart. The sexes are separate. Their foot
is adapted for burrowing in sand, in which they live and obtain
their food, which consists of Yoraminifera and minute Bivalves.
One species, Dentalium pretiosum, found on the shores of North-
West America, was until recently used as money by the Indians.

Class [V.-—PELECYPODA.*

The Molluscs belonging to this Class have neither head, nor,
with a few exceptions, cephalic eyes, nor jaws nor tongue like those of
the other Classes, and are enclosed in a shell which consists of two
plates or valves held together on one side of the margin by a horny,
elastic substance, called the ‘“‘ gament.” Bivalves do not creep about
in search of food, but find their means of existence in the shape
of minute particles, both animal and vegetable, which happen to be
contained in the water which they breathe. Some, however, are
capable of locomotion by means of a well-developed foot, and a
few swim through the water by alternately opening and shutting
their valves. The body is enclosed within two lobes of the mantle
which line the interior of the valves, and which at their base are
firmly attached to the shell, producing on the shell a scar or impres-
sion called the ‘pallial line.” The gills are lamellar or leaf-like, and
placed on each side of the body. Hach gill or ctenidium consists of an
axis which is partly attached to the body of the Molluse. This axis
generally gives off two plates consisting of hollow filaments which
are parallel with one another, directed downwards towards the
ventral side, and in most cases long and refolded upon themselves, so
that each plate becomes in reality a double lamella. In a few
instances, however, the filaments are simple and not reflected. They
are connected with one another sometimes by microscopic cilia, some-
times by vascular junctions, and the dependent and reflected portions
(amelle) of each filament may be connected by “ interlamellar
vascular junctions.” The mouth is merely an oval aperture at the
anterior end of the body, and generally furnished on each side with
soft thin flaps, or labial palps, which have the function of conveying

* This name has priority over the term Lamellibranchia, often applied to
this class of Mollusca, and is also in uniformity with the nomenclature of the
other classes, Gastropoda and Cephalopoda.

Cases
137-204.

30 SHELL GALLERY.

the food to the mouth. The mantle secretes the substance out of —
which the shell is formed. The two valves are always in contact at |
the hinge, which is generally formed by small interlocking projections
or hinge-teeth, and they are closed by large adductor muscles, which
are attached to impressions in the interior of the shell. When these
muscles cease to act, as after death, the valves of the shell open in ~

consequence of the elasticity of the ligament on the dorsal margin. |

The majority of species have two principal adductors, one at each end, —
like the Venus-shells, Cockles, Razor-shells, &c.; but in Oysters, —
Scallops, and a few others, there is but a single central muscle. All —
Bivalves are aquatic, and the majority marine. They are found

mostly burrowing in sand or mud or attached to rocks. Some

perforate stones and corals, others wood and other substances, and
Lima constructs a sort of nest of fragments of shells, stones, &c.
Many schemes of classification have from time to time been pro-
pounded, based upon the presence or absence of respiratory siphons, —
the number and position of the adductor shell-muscles, the character —

of the shell-hinge, &c. The most recent arrangement is founded

principally upon the structure of the gills. The value of such a —
classification has yet to be fully tested. Dr. Paul Pelseneer has
suggested four orders of Pelecypods: Protobranchia, Filibranchia,
Eulamellibranchia, Septibranchia; but Dr. W. G. Ridewood has
proposed to limit the main divisions te three, namely, Protobranchia,
Eleutherorhabda, and Synaptorhabda.

Fig. 25.

Tow

SOS

(From the ‘Cambridge Natural History.’ Messrs. Macmillan & Co.)

A. Protobranchia. B. Filibranchia. C. Eulamellibranchia. D. Septibranchia.

m. Mantle. v. Body. f. Foot. e. Outer gill-lamella; ¢. Inner gill-lamella;
e’. Reflected portion of outer lamella; 7’. Reflected portion of inner lamella.
s. Septum-like gill.

PELECYPODA. 3l

Fig. 26.

0 0 9000°0 0 6

Gill of Mytilus edulis.*

A. Part of four filaments showing ciliated interfilamentar junctions (cj).

B. Diagram of a single filament showing the two lamelle connected at intervals
by interlamellar junctions (ilj) and the position of the interfilamentar
ciliated junctions (ep).

PROTOBRANCHIA. (Fig. 25, A.)

In this order the filaments of the leaf-like gills are not reflected,
but arranged in two divergent rows, the foot being expanded and

flattened beneath with crenulated margins and with the byssal gland

very slightly developed. The Nwcwlide and Solenomyide are the
only families belonging to this order. The shells of the former are
remarkable for the numerous fine interlocking hinge-teeth, and those
of the latter on account of the strong, fringed periostracum.

* From the ‘ Encyclopedia Britannica.’ Messrs. A. & C. Black.

Case 137.

Cases
137-138.

Case 138,

Cases
139-141.

Case 141.

32 SHELL GALLERY.

FILIBRANCHIA. (Fig. 25, B.)

In this group the gills are smooth, with the filaments directed
downwards, reflected, and connected one with another by inter-
filamentar ciliated junctions, but the lamelle are not connected.
The foot is usually provided with a well-developed byssal gland.
Anomia, Arca, Trigonia, Mytilus, Pteria (= Avicula), Spondylus,
and Pecten belong to this order.

The family of Anomiude contains a number of more or less pearly
shells remarkable for a deep notch or hole in the lower or flat valve
through which a shelly plug passes, by means of which the animal
attaches itself to other shells, stones, &c. Anomia enigmatica is
found adhering to leaves in mangrove-swamps.

The Placunide, sometimes called Window-shells and Saddle-
Oysters, are very flat pearly shells with a remarkable hinge, which.
consists of two long divergent teeth, like a A, to which the ligament
is attached. ‘The species are few in number, and inhabit sandy
shores of India, China, and North Australia.

The Arcide are a family of strong ponderous shells varying much
in form and sculpture. The animals have a longish pointed foot,
deeply grooved along the bottom, no labial palpi, and free margins
to the mantle, which are not prolonged into breathing-siphons.
Many of the Arks often anchor themselves by means of a strong
byssus. The shells of this family are usually radiately ridged ; and
the hinge is composed of a number of teeth arranged along the
hinge-line, which is generally straight. Arca tortuosa, from China,
has the valves curiously twisted. The section Barbatia is remark-
able for the coarse fibrous character of the periostracum ; Scapharca
for its unequal valves ; and Cwcullea, from the Indian Ocean, for the
elevated ridge bounding the posterior muscular impression. Glycy-
meris (better known as Pectunculus) has the hinge-teeth arranged in
an arched series, and the shells are more regular in growth than in
many other forms of Arcide.

The family Zrigonide is one of those which have all but disap-
peared during our period. Only three or four living species are known,
whilst more than a hundred fossil forms have been described from the
Jurassic and Cretaceous formations. Australia, where some of the
oldest types of animal life persist, furnishes also the existing species of
Trigonia (Fig. 27). The animals have a long, sharply-bent, pointed
foot like the Cockles, with which they take surprising leaps. The
shells are beautifully pearly within, and ribbed and noduled exteriorly.

PELECYPODA. 33

The Mytihde, or Mussels, are too well known to need descrip-
tion. The small foot, which is brown in the common species, is
not much used in creeping about, but has
the power of spinning a byssus or bundle
of tough threads, by means of which the
animals attach themselves to rocks and one
another, forming colonies of vast numbers.
Mussels have always been much eaten in
this and other maritime countries, and large
quantities are brought to the London market
from the Dutch coast. At times they are
unwholesome; but all the exact causes of
this are not known. Mussels seem to be
found on every shore, and some of the Trigonia margaritacea.
species are very widely distributed — the Case 141.
common edible Mussel, J/. edulis, being found on every European
coast, on the shores of North and South America, in the Arctic
and Antarctic Oceans, and probably on the coasts of Australia.

One group of Mussels (Lithodomus, Case 144) burrow in rocks and
other shells, forming holes just large enough to contain their shells.
L. dactylus is sold as an article of diet on the shores of the
. Mediterranean.

The large family of Ptertide includes the ‘ Wing-shells”
(Pteria), the “Pearl” and ‘ Hammer-Oysters” (Margaritifera
and JJalleus).

The “ Hammer-Oyster” (J/alleus) is so called from its rude
resemblance toa hammer. The “ Pearl-Oysters ” Margaritifera mar-
garitifera, Fig. 28) possess rather heavy strong shells, lined with very
thick layers of ‘‘ mother-o’-pearl.” Hundreds of tons of these shells
are annually collected at the great pearl-fisheries of North and West
Australia, and imported into Europe. The pearl-oyster of Ceylon
(IW. vulgaris, Case 147) is a smaller species, and collected more for the
pearls than the shells. The origin and formation of pearls has from
ancient times, even until now, been a subject of much discussion,
and many theories upon this subject have been propounded. Perhaps
that most generally accepted has been the “ grain-of-sand ” theory.
A particle of sand or other foreign substance getting between the
animal and its shell, or in the soft parts of the animal itself, was
supposed to produce irritation, and thus cause deposits of nacre upon

Fig. 27.*

* From ‘The Cambridge Natural History.’ Messrs. Macmillan & Co.
D

Cases 142-
145.

Cases 145-
147.

34 SHELL GALLERY.

it. Recent investigations, however, prove that pearls are chiefly due
to the presence of the larval stages of Nematode Worms. ‘These
become enclosed in minute sacs in the skin of the mantle of the
mollusc, and in course of time are surrounded with superimposed
layers of nacre. Pearls thus formed in the Pearl Oyster are the
round pearls, which are so highly valued.

‘‘ Blister-pearls,” or ‘‘attached-pearls,” as they are sometimes
called, are those which are attached to the inner surface of the
shells, and are produced either by the intrusion of extraneous bodies

Pearl-Oyster (Margaritifera margaritifera). Case 147.

between the animal and the shell, or by the secretion of nacre over
holes in the shells made from the outside by boring molluscs, worms,
or sponges. These pearls, as a rule, are of comparatively little
money value.

The nacre is generally of the well-known pearly-white colour,
very rarely dark, and occasionally almost black. The action of the
animal in secreting successive layers of nacre over any foreign body
which intrudes between the mantle-folds, and thus converting it
into a pearl, is strikingly illustrated by two specimens in which, in

PELECYPODA. By)

the one case, an entire fish, and in the other a small crab, have
been so enclosed (see side table-case E).

The most ancient and, even at the present day, one of the most
important of the pearl fisheries is that carried on on the western
shores of Ceylon. “The Banks,” or spots on which the oysters
grow, are at an average depth of 30 to 60 feet, and extend several
miles along the coast. The oysters, which should be six or seven
years old when collected, are gathered in baskets by native divers
and hauled up by ropes into small boats. The shells are then
brought to land and placed upon the ground to die and putrefy,
and then minutely examined for the pearls. As many as two
‘million oysters have been brought ashore on one day; but the
number obtained varies very much according to the state of
the banks. A small proportion of the oysters contain pearls ;
in some only very small ones (seed or dust-pearls as they are
called) are found, and very few contain pearls larger than a pea,
that are so highly valued. In his account of the pearl-fishery
of Ceylon the Rey,.JamecCovdkiner says that; ne -saw ‘the
gpérution of sorting the pearls performed; the produce of
17,000 oysters weighed only ?# lb. and was contained in a vessel
smaller than a common soup-plate. Out of that quantity there
were not found two fine perfect pearls; all of the largest were
slightly deformed, rugged and uneven, but of the smaller sizes many
were round and perfect. The chief qualities which regulate the value
of pearls are size, roundness, and brilliancy of lustre. Of the smallest
kind several may be bought for a shilling, whilst many thousand
pounds have been given for a single fine pearl of surpassing beauty.

Other important pearl-fisheries besides that of Ceylon are carried
on in the Persian Gulf, on the west coast of Central America, and
especially North-west Australia, where diving-dresses are now
employed in collecting the shells.

The Chinese obtain pearls artificially from a species of fresh-
water Mussel (Dipsas plicata). In order to do this they keep them
in tanks and insert between the sheli and the animal either small
shot or small round pieces of mother-of-pearl, which soon receive
regular coatings of nacre and assume the look of ordinary pearls.
They also insert small metal images of Buddha, which also soon
become covered with pearl and firmly cemented to the shell, the
production being to the uninitiated a supernatural testimony to the
truth of Buddhism. (A shell treated in this way is exhibited in one
of the small cases (E) at the side of the room.)

D 2

Cases 148-
149.

Cases 150-
153.

Cases 153-
204.

36 SHELL GALLERY.

ae !

a wee

The Spondylide, or Thorny Oysters, closely resemble the Scallops,
but the shells are more spiny, heavier, united by interlocking teeth,
and they are attached by one valve to rocks, corals, etc. Many of the
species are very brightly coloured ; and from the fact that small quanti-
ties of water are sometimes enclosed in cavities in the inner layer of
the shell, they have been called “* Water-Clams ” or “ Water Spondyli.”

The Scallops or Fan-shells (Pectinide) are well known for their
beautiful colours, sculpture, and excellent flavour. The animal has

Mile

Common Edible Oyster (Ostrea edulis).

a, labial palpi; b, gills; ¢, mantle; d, junction of the two folds of the mantle;
e, large adductor muscle ; f, the shell.

a distinct foot, which is not, however, used as a locomotive organ,
but employed in spinning a byssus of attachment when required.
The young Pectens dart through the water by opening and suddenly
closing their valves. The species are very numerous, world-wide in
their distribution, and may be found at depths from a few to three —
thousand fathoms. -

EULAMELLIBRANCHIA. (Fig. 25, ©.)

In this order the gills have interfilamentar and interlamellar
vascular junctions, and there are generally two adductor muscles.

PELECYPODA. 37

The order is very extensive, comprising nearly sixty families, of
which only the more important can be referred to.

The Limas (imide) are very like the Pectens, but the inner
edge of their mantle is fringed with very long thread-like filaments.
The shells are always white, generally more or less oblique, and
radiately ridged. They appear to be found in most seas, and either
swim about freely like the young Scallops by flapping their valves,
or attach themselves by a byssus, sometimes forming a sort of nest,
consisting of pieces of coral and shell or small stones, in which they
are completely concealed. |

The Ostreide, or Oysters, undoubtedly take the first rank among
molluscs as regards usefulness io mankind as an article of food.
They have no foot ; the mantle is entirely open, with double edges,
each being bordered by a short fringe, and the labial palps are large
and somewhat triangular. There are on each side a pair of simple
gills, which appear closely striated ; the single adductor muscle is
large and nearly central (see Fig. 29). The Oyster is, except in the
very young state, entirely incapable of locomotion, and always
attached by the deeper valve to other shells, rocks, or other sub-
stances. The common British species is not full-grown until it is
about five or seven years old. A series of different ages, from the
“spat” to the adult form, is exhibited in Case 154. During the
months of May, June, and July the eggs are discharged into
the gills, where they remain until hatched; and it is during
this period that oysters are “out of season.” In the American
Oyster (O. virginica), on the contrary, the eggs are said to be
hatched outside the parent shell. Oysters of different kinds are
found on nearly every shore. The gigantic O. gigas is said to
grow to the length of three feet in the Bay of Taichou, Japan,
where it is commonly eaten. About two hundred fossil species have
_ already been described.

Some specimens of Pinna attain to a length of two feet. They
are found imbedded in the sand with the narrow pointed end down-
wards. They form a large silky byssus, which can be woven or
knitted into gloves, socks, etc. (see side table-case B).

The Carditide and Astartide have strong solid shells, frequently
ornamented with radiating or concentric ribbing, and usually are
coated with a dark epidermis. They have the general appearance
of certain Veneride ; but the animal has no prolonged siphons, but
merely a fringed opening in the mantle. One very remarkable species,
Thecalia concamerata (Case 161), has an internal cup-like process

Case 153.

Cases 154-
155.

Cases 156—
160.

Cases 162-
163.

Cases 166-
177.

38 ; SHELL GALLERY.

within the valves, which serves as a nursing-pouch for the
young.

The Lucinide are almost invariably white shells, and may
eenerally be recognized by the very long muscular scar in front
on the inner surface of the valves. They occur in all parts of the
world; and the fossil forms, which are still more numerous
than those now living, have existed at every epoch from the
Silurian. ;

Of the freshwater Mussels or Unionide more than 1200 species

Fig. 30.

British “‘ Fan-Mussel” (Pinna pectinata): a, the byssus. Case 157.

have been already discovered ; they are found in most parts of the
world, the greatest number having been described from North
America. In Unio the edges of the mantle are not structurally
united along the bottom and not prolonged into siphonal tubes ;
but are closely apposed save at the posterior end, where there are
two openings, of which the upper or excretal orifice is simple, and
the lower or branchial fringed at the edge. The foot is very large
and adapted for crawling and burrowing. The sexes are distinct ;

PELECYPODA. 39

and the shells of the females are somewhat more tumid than those
of the males. Jlargaritana margaritifera (Case 168), which is found
in this country and in Hurope, sometimes produces handsome pearls,
but not equal to those obtained from the pearl-oyster of tropical
seas. The hinge in this family is extremely variable, being in some
instances delicate and toothless (Anodonta, Fig. 31, B), whilst in
others it is enormously thickened and furnished with strong inter-
locking teeth (see Fig. 31, A).

B. Anodonta anatina.

The family Mtherude, or freshwater Oysters, consists of but Cases 178-
three genera : Wtheria contains African, and Miilleria and Bartlettia 1.
Indian and South-American forms. When young the shells of
Aftheria (which are common in the Nile) are free and not unlike
an Anodonta, but when adult they become attached and irregular
and look like an olive-green Oyster ; they are, however, provided
with two muscular impressions instead of one, as in ordinary marine

Cases 179-
181.

Cases 183-
185.

Cases 185-—
192.

Cases 192-
194.

40 SHELL GALLERY.

Oysters. Still more remarkable is Miilleria lobata of Colombia, which,
when young, freely moves about and has two adductor muscles, but
in time becomes attached and stationary, and then possesses but a
single adductor.

The Tellinas have usually thin shells, and their two siphons are
longer and more completely separated from each other than in the

many other Bivalves. The pallial line is widely and deeply sinuated, —

and the ligament generally external. In the genus Semele of the

family Scrobiculariide, it is placed within the hinge-margin. They

live in great numbers beneath the sand in shallow water, and are
occasionally used as food.

The Mactride have an internal ligament to the hinge, the
siphons are joined together and fringed at the ends, and the pallial
line is more or less sinuated. Spisula solidissima (Case 184), the
largest species found on the coast of the United States, is a common
article of diet.

The next family, Venerid@, have long respiratory siphons and
a sinuated pallial line. Many of this tribe are very beautiful in
form and colouring, and most of them have very hard strong shells.
The valves are united above by an external ligament, and the hinge-
plate is toothed. Nearly all of them live buried an inch or two
beneath the sand or mud, but a few are
found burrowing in rocks. Probably the
majority of the species of this family
might be used as food. Venus verrucosa,
of our own southern shores, is frequently
eaten both in this country and abroad ; and
Venus mercenaria (Case 189) is commonly
sold in the markets of Philadelphia and
New York. Meretrix lusoria (Case 185)
also forms a favourite article of diet among

Zs the poorer classes in Japan, and several

Common British Cockle kinds are eaten by the natives of New

(Cardium edule). Zealand and other countries.

a, foot; b, exhalant siphon ; Some of the ‘“Cockles” (Cardiide)
e, branchial or inhalant from warm latitudes are highly coloured
siphon ; d, edge of mantle; . :

4, WReainents ff, aimlbones and adorned with most beautiful sculpture.
an bealks of ne Gael. Probably the majority are edible, like
the common cockle (Cardium edule) of the

British coast. The foot of these molluscs is very large, bent, and

used for leaping. The siphons are short and fringed at the margins.

PELECYPODA. 41

The Zridacnide, or true Clams, differ from other Bivalves with
united mantle-margins in having but a single central adductor muscle.
In the typical species the animal is attached to the rocks by a
“byssus,” a strong fibrous structure which passes through an
aperture at the upper part of the shell. A species found in the
Red Sea, 7’. elongata, is eaten by the natives, and the shell employed
for the manufacture of lime. TZridacna gigas, the largest known
bivalved mollusc, sometimes weighs over 500 lb., that exhibited in

Left valve of the Giant Clam (Tridacna gigas).
Length, 36 inches. Weight, 154 lb.; weight of the two valves, 310 lb.

the upright cases at the entrance of the Gallery being 310 Ib. in
weight. A large pair bordered with gilt copper are used as béndtiers
or holy-water vessels in the church of St. Sulpice in Paris. Tridacne
are found associated in large numbers in lagoons, among coral-reefs
in the Eastern and Pacific Seas. The animals are described as pre-
senting a beautiful iridescent glare of blue, violet, and yellow
variegated with fantastic markings.

The genus Chama consists of tropical species, which are found
fixed to corals, rocks, etc. Nevertheless, they have a small bent foot,
but what purpose it serves is difficult to conceive.

In this place attention should be called to the Hippuritide and
Radiolitide, very remarkable extinct families of bivalved molluscs
which occur abundantly in the cretaceous strata of southern and
eastern Hurope, Egypt, etc. They are remarkable for the solidity
of the shells, the relatively small space occupied by the animal, and
the complicated character of the hinge and processes bearing the
adductor muscles. They are usually classed near to the Chama,
but their true position as regards living Mollusca is very pro-

Cases 195-
196.

Case 196.

Cases 198-
199.

Case 198.

Cases 199-
201.

49, SHELL GALLERY.

blematical. A fine series of these shells is exhibited in Gallery VIII.,
wall-case 5, in the Geological Department.

The Iyide, popularly known as “ Gapers,” on account of their
valves being open at one or both ends, have the mantle united all
round, except where the small foot is protruded. The siphons are

Fig. 34.

British Gaper (Mya truncata).

a, foot; b, siphon-sheath; ce, exhalant siphon; d, inhalant siphon; e, umbones
or beaks; f, anterior, g, posterior end of shell.

very long, united almost to the ends, and covered with a coarse
wrinkled outer skin. They bury themselves in mud and sand at low-
water mark or in shallow water. The species are few in number, and
chiefly from the shores of northern countries. J/ya arenaria of our
own coasts is largely eaten in some parts of Europe and North America.

The Corbule (Case 198) have one valve larger than the other
and are like little Wya, but the valves are almost closed and their
siphons are very short.

Many of the Solenidw, or Razor-shells, possess very elongated
shells, and are remarkable for the great development of the foot,

Fig. 35.

_—-@1

w
British Razor-shell (Solen stliqua).

a, foot; b, mantle; c, inhalant siphon; d, exhalant siphon; e, shell.

which can be extended or contracted as may be required for boring
into sand. By means of this powerful foot the animals, when

PELECYPODA. 43

disturbed, bore with such rapidity and to such a depth that their
capture is a matter of great difficulty ; and even when seized they
hold on so tightly that at times they suffer their foot to be torn off
rather than be captured. They not only burrow in sand, but also
have the power of darting through the water, like the Scallops.
Solens were considered a dainty dish by the ancient Greeks, and
numbers are still eaten by the poorer coast-population of this
country and abroad.

The Pholadide, or Piddocks, are very remarkable shells, of an
unusually complicated structure, some having the power of boring
into rocks, wood, mud, sand, etc. Their shells are white, adorned with
prickly sculpture, and, although thin, are strong. The foot is believed
to be the principal excavating instrument, but the shell appears
to be used as a file to enlarge the hole as the creature grows.
These animals are brightly phosphorescent ; and certain species are
eaten at many places on the shores of the Mediterranean. They

Fig. 36.

Piddock, or Borer (Pholas dactylus). (From the British coast.)

1. Animal in the shell: a, foot; 6b, siphons; ¢, inhalant orifice; d, exhalan
orifice.
2. Shell: e, accessory valves or plates.

appear to be indifferent as regards the material they bore into ; for
the common Pholas dactylus (Fig. 36) of our own shores has been
found in slate-rocks, mica-schist, coal-shale, new red sandstone
chalk, marl, peat, and submarine wood. The siphons are long in the
Piddocks, united except near the end, and enclosed in tough skin.
The species are world-wide in their distribution, and several are
found fossil in some of the Tertiary and older formations.

The Teredinide, or Ship-worms, are also borers, like the Pholads,
but do not perforate rocks. They are principally wood-borers ; the
large Kuphus arenarius, which is an exception, living buried in the
sand. The ship-worm has a long worm-like body, from 6 to 12

Cases 201-
202.

Case 202.

44

inches in length, which is more or less enclosed in a thin shelly tube
or sheath. The true bivalved shell is at the thicker end, and pro-
tects the mouth, labial palps, the liver, and
other internal organs. At the opposite, or
more slender, end of the animal, the mantle
is produced into two small tubes, one of which
conveys the water to the gills, whilst through
the other the water is expelled, charged with
the woody pulp excavated by the foot. At
the end there is a pair of pallets, or paddles

Fig. 37.

Ship-worm
(Teredo norvegica).
Case 202.

a, animal, removed
from its shelly tube:
p, p, pallets; s, ex-
halant siphon; s’, in-
halant siphon.

b,c, different aspects
of the shell.

SHELL GALLERY.

as they are sometimes
termed, which are probably
used as a means of defence,
in closing the shelly tube
after the contraction of the
siphons.

These animals are
most destructive to
wood which is not pro-
tected by metal, and
when once attacked, it is
soon riddled through and
through. They work either
with or across the grain,
and although the holes
may be all but touching,
they seldom appear to run
into one another.

The ‘“ Watering - pot
shell” (Brechites), of the
family Clavagellide, is a
very remarkable structure,
and unlike the shell of an
ordinary bivalved mollusc.

On looking carefully, however, near the per-
forated end (the rose), two small valves will be
seen imbedded in the surface. These shells are
found with the rose downwards buried in mud
or sand at low water on the shores of the Indian and Pacific

Oceans.

Watering-pot Shell
(Brechites vaginifer).
Case 203.

a, bivalve shell of
the very young
animal.

CEPHALOPODA. 45

SEPTIBRANCHIA. (Fig. 25, D.)

The members of this order differ from other Pelecypods in
having the gill-plates represented by a muscular septum. 'They are
provided with two respiratory siphons and two adductor muscles,
and the edges of the mantle-lobes are connected at three points.
The families Verticordide, Poromyide, Cetoconchide and Cuspidar tide
belong to this order. ‘The species are all small, without colour-mark-
ings, are world-wide in their distribution and occur at all depths.

Class V.-CEPHALOPODA.*

This Class includes the Octopus or Polypus, Cuttlefish, Squid,
Spirula, the Paper and Pearly Nautilus. The body of the animal con-
sists of a muscular sac, in the cavity of which the viscera are placed.
In front of the body projects the head, which, in species belonging to
the two-gilled section of the Class, is surrounded by eight or ten fleshy
arms. A wide aperture below the head admits the water to the gills
or branchie, which are situated in the interior of the sac, whilst a
short tube, the so-called funnel or siphuncle, projects from the open-

Fig. 39.

A, the upper, B, the lower beak of Architeuthis monachus; one-third
natural size.

ing of the mantle—the water and various excretions being expelled
through this tube, especially also an ink-like fluid, which is dis-
charged by nearly all Cephalopods when disturbed, in order to
darken the water and thus escape their enemies. The centre of
the head, between the bases of the arms, is occupied by the mouth,
which is armed with two horny jaws, similar in shape to the
beak of a parrot (Fig. 39). In Nautilus the cutting edges are
covered with a calcareous deposit. The two large eyes are placed on
the sides of the head. The arms or feet are more or less elongate,
capable of movement in any direction, and, except in Nautilus,
furnished on one side with numerous suckers, by means of which the

* From the Greek: kephale, head, and pous, foot.

Case 204.

Cases 205-
208, and
Wall-case.

46

SHELL GALLERY.

animal attaches itself most securely to anything it may seize; they
are employed in capturing food and in walking. Cephalopods walk
in any direction head downwards, but chiefly swim backwards,

The Common Octopus (Polypus vulgaris), resting.

being propelled in that direction by the water which they discharge
with force through the funnel out of their branchial cavity. They
are divided, according to the number of their gills (which is either

Fig. 41.

Sepiola scandica
(Natural size). British.

two or four), into Dibranchia and Tetra-
branchia. Of the latter but one representa-
tive now exists, viz., the Pearly Nautilus, all
other living Cephalopods being provided with
but two gills, placed one on each side of the
body within the mantle, as may be seen in the
wax model of Sepia officinalis (Case 207). The
two-gilled section comprises forms with eight
arms as the Paper-Nautilus (Argonauta) and
the Octopus (Polypus), and others with ten
arms, viz., the Cuttlefishes (Sepia) (Fig. 43),
the Squids (Loliyo, Ommatostrephes, Sepiola,
Chiroteuthis, etc.), and Spirula. The “shell”
of the Paper-Nautilus, or Argonauta, is too

well known to require any description. Unlike the shells of other
Mollusca, it is not attached to the animal by a special muscle, but is

CEPHALOPODA. AT

held on to the body by two of the arms, which are dilated and
specially adapted for this purpose. Only the female Argonaut is
provided with a shell, the male being shell-less and a much smaller
creature. The Argonaut-shell is therefore not a true shell, but
simply a receptacle for the ova, serving at the same time for the
protection of the parent.

Chiroteuthis Veranyi is remarkable on account of the great length

Fig. 42.

Chiroteuthis Veranyt (much reduced).

a, general view of animal; b, magnified view of pedunculated sucker of the
terminal club of the tentacular arms; c, internal shell or gladius.

of the tentacular arms. These are non-retractile and are employed
to seize their prey when at a distance.

Species of Polypus are found on the shores of almost all temperate
and tropical seas ; they do not attain to a large size, and are without
the internal shell or “bone” which is found in the mantle of many
Cephalopods. That of the Cuttlefish or Sepia (Fig. 43 @) is found in
abundance on our coasts ; it is composed of numberless layers of a
friable calcareous substance. That of the Squid tribe, termed the
gladius, is of quite another character, consisting of an elongate thin
horny plate, and strengthened by one or more thickened ribs, in some
species somewhat resembling a quill-pen. Some species of this pen-
bearing class related to the Common Squid attain an immense size.

48 SHELL GALLERY.

One was captured off the Irish coast in June, 1875 (probably Archi-

teuthis harveyi), with the shorter arms 8 feet in length and 15 inches _
in circumference at the base, each of the two tentacular arms having a
length of 30 feet. The powerful beak measured about 4 inches —
across. Thus from the tip of the tail to the end of the tentacular
arms this wonderful monster must have measured something like 40
feet in length. Other very large specimens of Architeuthis have
been captured on the coasts of Newfoundland and Labrador. Two
specimens stranded on the south coast of Newfoundland, in the winter

Fig. 43.

The Common Cuttlefish (Sepia officinalix), and its shell or bone (a).

of 1870-1871, measured respectively 40 and 47 feet. Another, cast
ashore at Bonavista Bay in December, 1873, had a very stout body
14 feet long, arms 10 feet, and tentacles 24 feet in length. These
are only a few of the many instances of the capture of gigantic
Cephalopods, which occur not only in the North-Atlantic Ocean, but
also in tropical seas. Their appearance in mid-ocean may, in some
instances, have given rise to the tales of ‘‘Sea-serpents.” Specimens
much smaller than those mentioned above have attacked men, and
pearl-fishers are in constant fear of them. One of the arms of a
large Squid (Architeuthis harveyi ?), which is supposed to have been
found off the coast of South America, is exhibited in the wall-
case on the east side of the room.

CEPHALOPODA. 49

The shells of Spirula (Fig. 44) have been long known, and are
scattered in thousands on the shores of New Zealand and other
islands in the Pacific Ocean, and they are also found in the Indian
and Atlantic Oceans, occasionally drifting on the coast of Devon and
Cornwall. Notwithstanding the abundance of the shells, very few
specimens of the perfect animal have been captured. The loosely-
coiled shell resembles a ram’s horn, and is divided into a number of

The Spirula (Spirula peronii). (From the Indian and Pacific Oceans.)

1. Animal: a, portions of the shell exposed in front and behind; 6, the funnel
or siphunele. 2. Side view of shell. 3. Shell in section, to show partitions
or septa. [Wall-case on east side of gallery. ]

seoments by fine concave partitions, like the shell of Nautilus, each
one pierced by a slender tube or siphon. It is almost entirely
enclosed within the hinder end of the body, only a small portion
of it being exposed in front and behind. Absolutely nothing is
known of the habits of this very interesting creature, although
probably they are somewhat similar to those of other Cephalopods.
Tt is possible that it may live at a considerable depth.

The Nautilus (Fig. 45), of which several shells (Case 208) and a
perfect animal in spirit (black upright case A) are exhibited, is an
inhabitant of the Indo-Pacific Ocean, and differs from all other
living Cephalopods in being provided with four instead of two gills,
and, instead of eight or ten arms with suckers and hooks, has a

E

50 SHELL GALLERY.

number of small retractile feelers. The Nautilus occasionally swims,
like other members of its class, at the surface of the sea, but mostly

4
<
$
4
#

The Pearly Nautilus (Nautilus pompilius).

a, body ; b, siphunele; ¢, eye; d, hood; e, tentacles; f, muscle of
attachment to the shell; g, siphon.

crawls about leisurely on its feet at the bottom in search of food,
which consists chiefly of small crabs or Mollusca, which it crushes
with its strong parrot-like mandibles.

The chambered shell is pearly within, and covered with an ex-
ternal calcareous layer. The chambers are connected by a slender
tube or siphon, the function of which is not at present thoroughly
understood. The septa, or partitions across the shell, indicate periods
of growth. When the Nautilus outgrows the capacity of the outer
chamber, in which it resides, it constructs a new one of larger size,
separating the additional chamber from the preceding one by a
transverse partition.

A series of Cephalopods preserved in spirit is exhibited in the
black upright case at the side of the room.

ALPHABETICAL INDEX

OF THE

FAMILIES AND PRINCIPAL GENERA OF MOLLUSCA
EXHIBITED IN THE SHELL GALLERY.

This Index has been compiled to assist the numerous visitors, who wish to
examine and determine specimens of shells, in finding, without trouble or loss
of time, the Cases in which the genera are placed. Subgeneric terms are
omitted, as they do not fall within the scope of this “ Guide.”

Acanthina . . 75
Achatina 130-132 |
Achatinella. .134,135
Acmea . : 4
Actions.) - 94
Aitheria. . . 178
_Amphibola. . 98
Amphiperas. . 35
Ampullaria . 25, 26
Amussium . . 153
Anatina. . . 203
meAncylusis. 9.) = 99
Anodonta . 166, 167
Anomia . . 137-138
Anostoma . . 128
Aplacophora . 3
Aplustrum . . 96
Aplysia
= Tethys ge
Aporrhais . . 49
Arca. . 139-140
Argonauta . .205, 206
ATION ss 107
Aspergillum
Goncaiiton} als
Astarte =. 161
Atlantean 94

Auriculide . 97, 98

Avicula = Pteria 146 |

Batissaer sews 165
Brechites . . 203 |
Bryopaw 202 |
Buccinum . . 65
pee = 128
na
Bulimulus . . 122
Bulimus= “a 120
phocheilus -
Bullide. . . 95
IBUTSaGe ee one 3
Calyptreeidee 31, 32
Cancellaria. . ia
Capulus. . . 31
(Chine, 6 6 « 160
Cardium. 192 194
Carinaria . . 94
Cassis 55-56
Cemion 5 6 6 129
Cerithiidee 42-44
Chetoderma . 83
Chama . ._ .196-197 |
Chitonide . . 1-3 |
Chrysodomus . 64 |
MRED, 26 6 187 |
Clausilia . 129-130

Clavagella= \ 204
Bryopa

Columbella . . 69
Conus . . . 89-94
Coralliophila . 76
Corbicula . . 164
CoAgKh 6 5 0 163
Corbulayeeee 198
Crassatella .. 161
Crenatula . . 146
Crenella. . . 145
Cucullea . . 140
@umapeeaee ee 75
Cuspidaria . . 204

Cyclophoridss . 23-25
Pe paaeene 28, 29

= Pomatiide
Cylindrella . .127-128
Cypreea . 82-35
Cyprina = :

Cypriniadea \ Ie
Cyrendes 4) 164
Cytherea = .

Meretrix } HS
Delphinula . . 12
Dentalium . . 136
Despoena . . 22
Diplodonta . . 1638
Dolium . 5 0,07
IDES 5g 6 6 182

52

Dosinia . 188
Dreissensia . 179
Eburna . 67
Kmarginula . 7
Ena . 128
Ennea ‘ 103
EKucalodium. 129
Eulima . 40
Fasciolaria . 59
Ficula=Pirula . 57
Fissurella 8
Fulgur 61
Fusus 97, 58
Gadinia . 99
Galatea . 165
Galeomma . 163
Gastrochzna 201
Gena. a Des 11
Glandina =

Oleacina \ N02
Glauconome. 192
Glycymeris . 141
Haliotis. . . 9-11
Haminea 95
Harpa : 84
Helicarion : 104
Helicidse .107-121
Helicina . : 21
Hemifusus . 61
Heteropoda 94
Hinnites. 159
Hydatina 96
Tanthina. 38
Isocardia 5 162
Isognomon=

Melina \ les
Kellia 163
Latiaxis . 74
Latirus . f 59
Heds =Nucu- \ 137

ana

Lepeta 4
Lepton 163
Lima. 153
Limax j 106
Limneidee . 99-102
Limopsis 141
Lithodomus . 144
Littorina 27
Loligo : 207
Lucinide . 162, 163
Lutraria . 199
Lyonsia . 204

SHELL GALLERY.

Mactride . 183-185
Magilus . 77
Malletia . 137
Malleus . 146
Marginella . . 83,84
Melaniidze 38-41
Margaritifera 147
Melina 145
Melongena . 61
Meretrix. 185
Mesodesma . 182
Mitride . . 61-64
Modiola. . .148,144
Modiolarea . 145
Modiolaria . 145
Monoceros = \ 75

Acanthina
Montacuta 163
Murex 70-73
Mutela 177
WIV 9 a 198
Myodora. 204
Mycetopus 176
Myochama . . 204
Mytilus . 142, 143
Nassa 67, 68
Naticidee 35-37
Nautilus. 208
Navicella=

Septaria \ Dye.
Gee a 204.

aria

Neomenia 3
Nerita 18,19
Neritina . 19-20
Nucleobranchi-

ata = Hetero- 84

poda
Nucula . 137
Nuculana 137
Nudibranchiata 97
Octopus =

Polypus \ 208
Oleacina. 102
Olividee . 81-83
Ostrea 154, 155
Ovulum = Am- \ 35

phiperas
Paludina = \ 99

Vivipara
Paludomus .
Pandora . 204
Panopea 201
Partula . 127 |
Patella 4-7

gall) |

Pectinide . .
Pectunculus=
Glycymeris
Pedum
Periploma
Petricola.
Philine = 2%
Pholadide . .
Pholadomya. .
Pholas . . .
Phorus (=
Xenophora)
Physa
Pinna
Pirula
Placuna .
Planaxis.
Planorbis
Pleurotomaria .
Pleurotomids
Plicatula
Polypus .
Pomatiidz
Proserpina= \
Despoena
Psammobia .
Pteria
Pterocera
Pteropoda
Puncturella .
Pupilla=Pupa .
Purpura. . .
Pyramidellide .

Sm’

Ranella = Bursa
Ricinula=Sis-
trum
Ringicula
Rissoiide
Rocellaria
Rostellaria .
Rotella .

Saxicava

SBI, 5 oo
Scalaria=Scala
Scaphander .
Scaphopoda .
Scintilla .
Scutum .
Semele

Sepia

Septa

Septaria .
Septifer .
Siliquaria
Siphonaria .
Sistrum, .

149-153
141

201, 202
204
201, 202

49

Solarium
Solenidee
Solenomya .
Spherium
Spirula .
Spondylus
Stenogyra
Stilifer ..
Stomatella .
Streptaxis
Strombus
Strophia =
Cerion

Strophocheilus .

Struthiolaria
Succinea.
Sunetta .
Sycotypus

Tapes.
Tellinide

191

"179-181

INDEX.

| Terebellum .
Terebridz
Teredo
Testacella
Tethys
Thracia .
Trichotropis.
Tridacna
AUBEOMBG 5 6

| Triton=

| Septa }

Trochidz

Trophon .

Truncatella .

| Tugonia. .

| Turbinellide

Turbinide .

Turritella

Typhis

| Umbraculum

Se)
a

Umbrella = 97
Umbraculum \ :
Ungulina 168
Unionidee 166-178
WENN 6 6 c 3
Vanicoro 49
Welutinaze 37
Veneride . .185-191
Venerupis .. 192
Venus . ._ .188-189
Vermetide . 46,47
Verticordia . 204
Vitrina . 106
Vivipara. . . 22
Volutidsera, 2. 7S—sil
Vulsella . 146
Xenophora . 49
Yoldia 137

Upright
Table-
Cases

A and B,

at south
end of
Shell
Gallery.

54 SHELL GALLERY.

POLYZOA.

(*) An asterisk against names of species denotes that specimens of these species
are in the upright part of Case A and preserved in spirit.

From a casual glance at the contents of these cases, it might be
supposed that many of the specimens exhibited therein were sea-
weeds ; but a closer inspection, especially with a lens, will reveal
structure of a kind not to be found in any plant.

Let us select for examination Flustra foliacea, the Broad-leaved
Hornwrack or Sea-Mat (Fig. 1), (Case A 1), commonly to be found

Fig. 1.

y i;

| ‘i }

ia
ae

Flustra foliacea. A, natural size; B , portion magnified in B;
B, magnified 30 diameters.
a, avicularium; 0, ovicell.
[‘ The Cambridge Natural History.’]

among heaps of sea-weed cast up on sandy shores round our
coasts.

The brown horny fronds, which vary in width, branch upwards
from a narrow flat stem attached at its base to stones and shells.
Both surfaces of the fronds show a fine network pattern formed by

POLYZOA. 5d

the edges of little oblong boxes or cells termed zocecia,* arranged in
longitudinal parallel rows and forming a double layer back to back.
The cells are broad and rounded above, narrow and truncate below,
and each is roofed in by a transparent membrane with a semicircular
lid or operculum situated near the upper end; four short stout.
spines spring from the margin in this neighbourhood. When the
surface of a living frond is examined in sea-water, here and there
a bundle of tentacles may be observed pushing up a lid, slowly
emerging and expanding into a bell-shaped coronet; on the least
alarm the tentacles are rapidly withdrawn into the cell and the lid

Figs. 2, 3, diagrams representing polypide in cell. Fig. 2, tentacle-sheath pro-
truded. Fig. 3, ditto, retracted; a, tentacles; b, tentacle-sheath; ¢, mouth:
d, gullet; e, stomach; f, vent; g, retractor muscle; h, funiculus; 7, ovary ;
k, testis; 1, lid or operculum; nerve ganglion is between mouth and vent.
Fig. 4, polypide extracted from cell; d, pharynx; e, stomach; f, vent (after
Van Beneden). Fig. 5, section (partly diagrammatic) of frond of Flustra,
showing cells back to back.

shut. The flexible protrusible region of the cell is termed the
tentacle sheath. The relation of the cell to the tentacle sheath
(Figs. 2, 3) may be roughly compared to a glove finger, stiff below,
but flexible at the end, and surmounted by a crown of bristles ; on
pulling down the glove-finger tip, the tentacles will also be drawn
in, and will lie in a sheath formed by the invaginated portion of
glove finger. The lid which closes over the tentacle sheath is only
found in the Sub-order Chilostomata to which Flustra belongs. The
area of the tentacle sheath whence the tentacles arise is termed the
lophophore.t

* Zoon, animal; oikos, house.

+ Lophos, plume; pherein, to bear.

56 SHELL GALLERY.

The mouth is situated in the centre of the lophophore, surrounded
by the circle of tentacles ; and the latter, by the action of their cilia,
set up currents which convey food to the mouth.

The mouth leads into a pharynx and gullet, the latter opening
into a stomach, whence the intestine ascends to terminate in the
vent opening below and outside the circle of tentacles; the in-
testines, in fact, form a U-shaped tube (Figs. 4, 5) suspended in
the body cavity in the interior of the cell. A cord, the funiculus,
passes from the stomach to the base of the body-cavity. A small
nerve ganglion is situated within the upper part of the loop of
intestine.

The tentacles, intestines, and other organs constitute the “ poly-
pide,” the cell being simply the protective house formed by the
latter.

The body-cavity, which contains fluid, is in direct communication
with the interior of the tentacles, which are hollow, and which act
as respiratory organs by bringing the fluids of the body-cavity in
proximity to the water. In Flustra the body-cavities of the cells
are shut off from each other, but pores and sieves in the partition
walls allow of the junction of the inner linings of these cavities.
The male and female reproductive elements are formed in the body-
cavity. The egg develops in a helmet-shaped brood-pouch, the
ovicell, situated at the summit of the cell and almost immersed in
the cell above. The ciliated embryo swims about for a few hours
and settles down to form the first polypide and cell; from the
latter there arise buds which remain attached, and produce other
buds, till a colony like that of /lustra results.

Among the ordinary cells are certain smaller cells (Fig. 1, a)
slightly raised above the general level, different in shape from the
ordinary kind and with thicker lids. These peculiar cells are termed
avicularia, and chiefly contain muscles for opening and shutting the
lid. ‘They arise by modification of the ordinary cells, whereby all
the organs of the polypide have become atrophied except the muscles.
The Polyzoa * were so named by Vaughan Thompson, who, in 1820,
discovered that certain plant-like animals, which had previously been
classed with the zoophytes, possessed a much higher organisation,
in that the intestine was separate from the body-cavity and not con-
tinuous with it as in Sea-Firs, Sea-Anemones, and Corals. In 1834,
Ehrenberg named the group Bryozoa t or Moss Animals.

* Polus, many; zoon, animal. t Bryon, moss.

POLYZOA. 57

With the exception of one genus (Lozosoma), all Polyzoa form
colonies, which arise by the continual budding of the cells, the buds
remaining attached to the parent cells. The colonies vary endlessly
in form and habit, occurring as crusts on rocks, etc., masses, broad
fronds, branching tree-like growths, bushy tufts, etc.

The texture and consistency may be gelatinous, cartilaginous,
horny and flexible, or stony.

The great majority of species are marine, but a considerable
number inhabit fresh water. The Polyzoa are classified as follows :—

Sub-order 1. Chilosto-

mata.||
Order I. Gymnole- Orifice of cell with a
horny lid.
mata.
Lophophore and tenta-

Sub-order 2. Ctenosto-
mata.9
Orifice of cell closed
by a membranous
comb.- like frill.
Always fleshy or
horny.

cular crown circular.
Without a lobe over
Group I. Ectoprocta.* the mouth.
Vent opens outside
the circle of tenta- | Order II. Phylactole- }
cles. mata.§

Lophophore and tenta-
cular crown horse-
shoe shaped. With
lobe over the mouth.
Fresh water forms,

Sub-order 3. Cyclosto-
mata.**

Without lid or frill;
orifice of cell usu-
ally circular; <eils
always calcareous.

Group II. Entoprocta.t .
Vent opens inside circle of tentacles.

Sub-order 1.—CHILOSTOMATA.

The Chilostomata, which contain many more species than all
the other groups put together, are divided into three sections :—
A. Cellularina, in which the cells are more or less boat-shaped or
cornucopia-shaped, and joined together to form flexible branching
colonies; 6. Flustrina, in which the cells are typically shaped like
oblong boxes with membranous front walls; and C. Escharina, in
which the whole front wall is calcified.

* Ektos, outside ; proktos, vent. + Entos, inside; proktos, vent.
t Gumnos, naked ; laimos, throat. § Phulassein, to guard; laimos, throat.
|| Chetlos, lip; stoma, mouth. q Ktenos, of a comb.

** Kuklos, circle.

Cases,
Aand Bl.

58 ; SHELL GALLERY.

Case A 1. Section A. CELLULARINA.—Bugula turbinata, or the Bird’s-head
Coralline (Fig. 6) grows attached to rocks near low water mark in
the form of spiral tufts about two inches in height, composed of
narrow flat branches in which the cells are arranged from two to six
abreast and all facing upwards. Each cell is boat-shaped and with

Fig. 6.

A, Bugula turbinata, natural size. B, portion x 50.
a, avicularia; m, mouth; 0, ovicell.
[‘ The Cambridge Natural History.’]

nearly the whole front surface membranous ; the globular bodies at -
the head of certain cells are the ovicells. Attached to the outer edge
of each cell is a remarkable object resembling a bird’s head, and
hence termed avicularium, seated on a short stalk. The head and
beak contain powerful muscles for opening and shutting a horny lid

POLYZOA. 59

or mandible hinged on below. In life, the avicularium sways to and
fro on its stalk, with the lower “jaw” continually snapping up and
down in the most ludicrous fashion. The beak is capable of seizing
and holding quite large objects.

The function of these curious appendages is partly to warn off
trespassers and partly to capture and retain small animals till de-
composition has set in; in the latter case, the currents set up by
the tentacles draw in the particles to the mouths of the poly-
pides. The avicularia have arisen by modification of the ordinary
cells, in which the muscles have developed at the expense of the
degenerated polypides, the cells have become much smaller, of
different shape, and separated out from the rest; the mandible
represents the lid or operculum of the ordinary cell. The avicu-
laria vary greatly in size and shape in the different genera; in
Flustra, for instance, these organs closely resemble the ordinary cells.

In Bugula bicornis* (Fig. 7), from 1950 fathoms in the Southern Case A.
Upright
Fig. 7. part.

Bugula bicornis. Cells magnified. (After Busk.)

Indian Ocean, each cell is provided with two avicularia with remark-
ably long stalks. The graceful vase-shaped Kinetoskias cyathus *

Case A.
Upright
part.

Case A 1.

60 SHELL GALLERY.

(Fig. 8), one of the treasures of the “ Challenger ” Expedition, was
dredged from 1525 fathoms off Cape St. Vincent. The stem, which’
tapers gradually upwards, rises from a tuft of root fibres. The cup
is formed of slender branches supported at the base by a delicate
membrane. The branches are composed of biserial rows of cells
(Fig. 9) opening towards the interior of the cup. The avicularia are

Vig. 9.

Kinetoskias cyathus. A branch magnified.
a, an ayicularium. (After Busk.)

pear-shaped and pedunclate. Probably, in life, the cup is capable of
being opened out toa considerable extent. Specimens of this species
were also obtained from 2160 fathoms in the South Atlantic.
Scrupocellaria reptans, or the Creeping Coralline (Fig.10 A, B) forms
branching colonies, creeping over rocks and seaweeds, and attached
by horny fibres often provided with curved hooks. The branches
are composed of cells arranged in a double row Hach cell has the
membranous area of its front surface protected by a branched flattened
spine or operculum, and is produced and narrowed below; at the
upper outer margin is a minute triangular avicularium. At the base
of the back surface is a small sack-shaped cell with a cleft at the
upper end, in which a horny bristle is articulated. The little cell
is termed a vibracular cell, and the bristle a vibraculum.* This

* Vibraculum, a bristle.

POLYZOA.

\
Wy ae

Kinetoskias cyathus. (¥ Joy. Challenger, Atlantic :; Wyv. Thomson.)

Case
Al, 2.

Case A 1.

Case A 1.

62 SHELL GALLERY.

organ has arisen by a further modification of an avicularium, whereby
the horny lid of the latter has become a long bristle. The bristles

Fig. 10.

Scrupocellaria reptans. A. Creeping over seaweed, natural size; B. Front
surface, magnified.
a, branched spine covering front of membranous area; b, avicularium ;
ec, Vibraculum.
C. Back surface; a, vibracular cell; 6, vibraculum.

by their motion keep off intruders, and possibly act as scavengers by
sweeping the surface of the cells.

In Caberea ellisii the vibracular cells are very large. The
vibracula, which are long and serrated, have been observed to move
in unison like a double row of oars.

Section B. Fuustr1nA.—In this group the colonies form leafy
lamellee, crusts, etc., in which the individual cells are typically in
the form of oblong boxes with their front walls wholly or
partly membranous. /7ustra foliacea has already been described. In
Flustra carbasea the fronds are formed of only one layer of cells, and
not of two layers back to back as in /’. foliacea. The fine specimen
of Flustra nobilis from 8. Africa is so called from the large size of its
long hexagonal cells which form a honeycomb pattern clearly visible
to the naked eye.

In Flustra cribriformis* (Fig. 11), from Torres Straits, the
fenestrated frond forms a beautiful spiral. /Justra florea, from 8.
Australia, grows in the form of branching tufts of narrow spiral
fronds. Llectra pilosa [dry and spirit specimens exhibited | (Fig. 12)

POLYZOA. 63

forms a delicate silvery lace-work, encrusting shells and seaweeds
(especially red algze) on almost every shore. The long horny spine
at the base of the membranous area of each cell gives the crust a

Fig. 11.

Flustra cribriformis.

Fig, 12.

|

Dias

i" fe, AMIS? S|
W204 fabiay Ly

Electra pilosa. A, incrusting a seaweed, natural size; B, cells
magnified ; a, lid or operculum.

pilose appearance. In Electra verticillata from West Africa, the cells
form an elegant branched colony, the branches being composed of
regular verticils of cells.

Membranipora membranacea occurs in the form of horny incrusta-

Case A 1.

Case A 2.

64 SHELL GALLERY.

tions on bladder-wrack, which, owing to their flexibility, are able to
adapt themselves to the swaying of the fronds of the Fucus.

The Selenarudae (Case B 2) form free colonies, usually orbicular
in shape, convex above and concave below. In Lunulites capulus
alternating rows: of cells and vibracula radiate from the centre of
the colony.

Section C’. ESCHARINA.—In this group, the front walls of the cells
are wholly calcareous. Many species form patches or crusts on shells
etc., and hence the name of the section ; other species, again, form
stony tree-like growths, or thick plates. Frequently one and the
same species occurs in the form of crusts or of erect lamelle, the
identity being recognised by the characters of the individual cells.

Often a large number of species may be found on one shell.
Two good examples of this are exhibited in Case A 2.

Leprahia pallasiana (Fig. 13) forms sub-circular vitreous patches
on stones and shells; the cells are rather large, broadly oval, and |

Fig. 13.

Lepralia pallusiana, incrusting a shell. A, natural size; B, cells magnified.

with the front wall punctured with pores; the aperture is squarish
and with a slight indentation on each side.

Lepratia foliacea forms a massive coral-like growth composed of
thin contorted plates which fuse to form labyrinthine cavities, the
plates being constructed of a double layer of cells back to back. A
large specimen from the English Channel is exhibited in Case B,
upright part. In Lepralia the orifice and lid of the cell have a
straight lower margin, but one large group, M/yriozoide, is characterised

POLYZOA. 65

by having a notch in the lower margin of the orifice (Fig. 14, Case A 2.
Schizoporella wunicornis).

In many of the Escharina, the front wall of the cell is produced Case B 1.
into a stout process or mucro at the lower margin of the orifice (genus
Mucronella), or, again, a collar or tube grows up round the primary

0 eis
me FE GKey

Schizoporella unicornis, magnified.

Retepora beaniana.

orifice, thus giving rise to a secondary orifice (Smittia, Porella, etc.,
Case B 1). :
In the Celleporide (Case B 1) the cells are typically pitcher-shaped Case B 1.
and arranged vertically, and tend to be heaped up from overcrowding.
Cellepora pumicosa forms thick pumice-like masses composed of
F

66 SHELL GALLERY. E

Case B1. succeeding layers of cells. The Reteporide (Case B 1) form delicate
stony networks. The reticulate fronds may be expanded out, or
may form tubular or contorted growths (Fig. 15, Retepora beaniana).
The beautiful Retepora phenicea from Torres Straits is of a rich —
purple colour.

The Adeonide form thick fenestrated plates which unite to form
cavernous masses usually attached to rocks by a thick jointed
stem. Several very fine examples from Port Phillip, Victoria, are
exhibited in the upright part of Case B.

Case A 2. The Catenicellide are represented by a fine series of specimens
from Australia. The colonies form dense clusters of finely beaded
branches. The cells are arranged in single series, each cell being
united to those above and below by a horny joint. The cells are
usually urn- shaped with a triangular avicularium at each upper
angle, and with the front surface variously sculptured with pores or
bands (Fig. 16, Catenicella ventricosa).

Fig. 16.

B
Catenicella ventricosa. A, natural size; B, magnified. (After Busk.)
-
Case B 2, Sub-order 2.—CTENOSTOMATA.
and A
upright The Ctenostomata are fleshy, horny, or membranous; never
part.

calcareous. When the tentacles of a polypide are retracted imto

POLYZOA. 67

the cell, they are protected above by a membranous comb-like
frill.

The cells either bud off from each other or arise as buds on a
stolon or stem.

Alcyomdium gelatinosum* (Fig. 17), so called from its resemblance
to the zoophyte Alcyonium, forms fleshy translucent growths
occurring in the form of nodulated branched masses, or of long

Fig. 17.

Hable 'y del

Aleyonidium gelatinosum. A, «small piece, natural size; B, the
same magnified.

finger-like growths. The species is common round our coasts
where it grows attached to stones and shells near low-water
mark.

Amathia forms bushy growths composed of slender horny branches.
The cells, which are cylindrical or squarish, rise from the branches
in biserial rows like Pan’s pipes. In Amathia lendigera* (Fig. 18) the
groups of cells are well separated from each other, but in A. spiralis*
and A. convoluta* the cells form a nearly or entirely continuous series
winding in a spiral round the slender stems. In Sowerbankia
imbricata* the cells are clustered on the stems. Vesicularia spinosa*,

KF 2

Case A,
upright
part.

Case A,
upright
part.

68 SHELL GALLERY.

or the Silk Coralline, forms delicate brown tufts resembling a
filamentous alga; the cells arise separately in a single series from

Amathia lendigera. A, natural size; B, magnified.

the hollow tubular stems and are contracted at their point of
attachment.

Nearly all the Ctenostomata are marine, but a few species live
in brackish and fresh water.

Sub-order 3.—CYCLOSTOMATA.

Case B 2. In the CycLostomatTa, which are all calcareous, the usually ~
tubular zocecia have plain circular orifices without a lid or frill
closing over the retracted tentacle-sheath. There are two sections
in this group, viz., Articulata, in which the cells form branching
colonies, the branches being connected by horny joints; and In-

POLYZOA. 69

articulata, in which the colonies may be encrusting, or erect and
branching, but are without joints.

The first section includes the Cristide.

Crisuat denticulata (Fig. 19) forms delicate white tufts, in which Case B 2.
the flat slender branches are composed of a double row of tubular

Fig. 19.

Highley, del

Crisia denticulata. A, natural size; B, branches magnified.

cells. The horny joints between the branches are black. The
Inarticulata occur as crusts or branching growths. In T'ubulipora Case B 2.
labellaris (Fig. 20) the colonies form little fan-shaped crusts on sea-
weeds. Lichenopora hispida forms little white disks, in which rows
of tubular cells radiate from the centre. In Jdmonea, the colony is
branched, the tubular cells being arranged in parallel rows on each
side of the middle line of the branch.

The Cyclostomata are all marine.

Table
Case A,
upright
part.

70 SHELL GALLERY.

Fig. 20.

Tubulipora flabellaris.

a, half of an incrusting colony, x 8; b, a few cells, x 44: ¢, a colony,
natural size.

Order I].—PHYLACTOLAMATA.

All the forms in this group inhabit fresh water, where, in the
form of creeping or erect branching growths or masses, they grow
attached to fresh-water plants, tree-trunks, old wood, etc. ; two species
are capable of slow movement from place to place. The lophophore
and tentacular crown of the polypide are, with one exception,
horseshoe-shaped. ‘The Order owes its name to the presence of a
lobe guarding the mouth.

In addition to the sexual, there is an asexual reproduction by
means of peculiar internal buds termed statoblasts (Fig. 21). When
the colony dies in the autumn the liberated buds, securely protected
in a horny capsule, retain their vitality till the spring; im due
season the valves of the statoblast burst open, and the contents
develope into a new colony. The statoblasts, which resemble small
seeds, are usually provided with a ring of air cells, which act as a
float, and in some species spines are present.

Pea e& a8

POLYZOA. ral

Fig, 21.

Statoblasts of Freshwater Polyzoa. A, Fredericella sultana x 38; B, Plumatella
repens X 38; C, Lophopus erystallinus x 28; D, Cristatella mucedo x 28.

(‘The Cambridge Natural History.’]

Fig. 22.

A, Plumatella repens, partly free, partly incrusting stem of water-weed.
B, Cells magnified. (After Allman.)

Case A,
upright
part.

ie, SHELL GALLERY.

Plumatella repens* (Fig. 22) forms brown branching colonies,
wholly or partly adherent to the surface of leaves of water plants, old
wood, etc. The individual cells are club-shaped, and about a quarter
of an inch long, each cell being attached to the upper back part of
the cell below; the statoblasts (Fig 21, B) are simple oval bodies
with a zone of air cells.

Plumatella (Alcyonella) fungosa forms thick masses, composed of
closely packed vertical tubes. A small specimen * surrounding a
stick from Hampstead Ponds is exhibited, and also a slice of another
specimen, prepared and presented by Mr. C. F. Rousselet, showing
the polypides expanded.

Lophopus crystallinus* occurs in the form of translucent gelatinous
blobs, often attached to the slender stems of duck-weed. The
statoblasts (Fig. 21,C) are elliptical and pointed at each end. The
polypides are comparatively large, and can be easily observed through
the transparent surface. When its delicate plumes are fully expanded,
Lophopus forms a beautiful object.

Cristatella mucedo* (Fig. 23) occurs in the form of greenish
translucent oval or worm-like colonies with the polypides on the

\ sat) Qin ‘ yi
Sa QQNy_ e
\ Mi

Cristatella mucedo, creeping over a stem of water-weed; x 6. (After Allman.)

a, polypides with horseshoe-shaped crown of tentacles; 6, statoblasts seen
through the tissues ; c, muscular sole by means of which the animal creeps;
d, stem of water-weed.

convex upper surface. The animal slowly creeps about on its
flattened under surface.

Freshwater Polyzoa usually prefer dark places, but Cristatella
creeps along on the stones and pebbles in clear water, and in the
sunlight. The polypides form three or more concentric rows on the

POLYZOA. 73
upper surface. The statoblasts (Fig. 21, D) are circular, provided
with a zone of air cells, and with hooked spines, the total diameter

being about 3), of an inch.

Sub-class I].—EntToprocta.

In this small group, both orifices of the alimentary canal open
within the circle of tentacles, and there is no tentacular sheath.

The polypides are borne on contractile stalks. In the Pedicel-
linide the stalks arise from a creeping stolon. In Pedicellina cernua*
(Fig. 24) a stolon, creeping over sea-weeds, etc., gives rise to stalked
cups, the movements of which are vigorous: ‘the polypides, when
excited, dash themselves vehemently from side to side. The heads

Table
Case A,
upright
part.

Pedicellina cernua. X 27.
[‘ The Cambridge Natural History.’ ]

are easily knocked off, but the decapitated stalks develop fresh ones.”
In Ascopodaria the stalks are swollen at the base ; A. fruticosa*, from
Port Phillip, Victoria, forms beautiful tree-like colonies. The
Loxosomide do not form colonies, owing to the buds becoming
detached from the parent. The species of Loxosoma are always found
associated with some other animal, such as a worm or Tunicate.
The tentacles of the polypide are arranged obliquely to the long
axis of the body, hence the name of the family (Jovos, oblique).
Loxosoma phascolosomatum * occurs, in the form of delicate tufts, on
the caudal end of the Sipunculid worm Phascolosoma. The individuals
resemble pins with little white heads, and are capable of vigorous
movements to and fro; occasionally a stalk coils itself up into a
spiral.

74 SHELL GALLERY.

BRACHIOPODA.
Small THE Brachiopoda, though presenting a certain outward resemblance
Ben to bivalved Mollusca, are quite distinct from this group. They are

against all marine, and all possess a bivalve shell. They grow attached to
the west rocks (Fig. 1), usually by a horny peduncle or stalk passing between
wall to left : :
of main the two valves, or through a foramen in one of the latter; or,

entrance.* peduncle and foramen may be absent, one of the valves adhering by

British Brachiopods (Terebratula and Crania).

its surface to the rocks ; some species of Lingula live in tubes in the
sand or mud. They occur at all depths, from shallow water up to
2900 fathoms, but the largest number of species live at a depth of
about 350 fathoms. Though found in all seas, the localities whence
they have been obtained are comparatively few in number; but
specimens are usually congregated in considerable numbers, in places
where they do occur. The surviving species of Brachiopods con-

* The Davidson Collection of Recent Brachiopoda is placed along with the
Fossil forms in the Geological Section.

BRACHIOPODA. TD

stitute only a small remnant of a group that flourished abundantly
in former epochs. There are about 150 recent, and over 6000
fossil species.

THE SHELL.—The valves of a Brachiopod shell differ from each
other in size and shape, but each valve is in itself symmetrical, i.¢.,
similar on each side of a middle line.

The valve through which the peduncle passes is termed the
peduncle or ventral valve (Fig. 2, A), the other being the brachial or
dorsal valve. ‘The peduncle valve, which is usually the larger and
uppermost, contains the bulk of the viscera; in the higher genera,

Fig. 2.

Meg
Magellania flavescens. Australia. Interior of valves.

A. Peduncle valve: f, foramen for peduncle, below which are the two small
deltidial plates; ¢, hinge teeth; a, b, c, muscle scars. B. Brachial valve,
showing the reflected loop for support of the “arms.”

calcareous bars or loops (Fig. 2, B) attached to the inner surface of
the brachial valve form a support for the “arms” of the animal.
The inner surface of the valves presents certain markings and
depressions where the muscles have been attached (Fig. 6).

The shell is constructed of very minute prisms of calcareous
substance imbedded in an organic matrix. In Lingula the shell is
formed of alternating layers of horny and calcareous substance.

The shell-valves are either hingeless, or joined by a hinge in
which teeth in the peduncle valve fit into sockets in the brachial
valve. The Brachiopoda are primarily divided into two sections,
Inarticulata and Articulata, based on the absence or presence of a
hinge.

The division into Orders is based on the relation of the peduncle

76 SHELL GALLERY.

to the valves in its passage between them or through one of them.
In the most primitive Brachiopoda (Lingulide), the peduncle
simply passes out between the valves and not through a foramen or
pore in one of them; hence the group is named Afremata (a, not,
trema, pore). In the next group, including the families Discunide
and Craniide, the peduncle passes through a fissure in the edge of
the peduncle valve, the fissure in recent forms becoming closed round
to form a slit-like foramen ; this group is named NEOTREMATA (ne0s,
new, /rema, pore). In the third group, PROTREMATA (pro, in front
of, trema, pore), which includes the Thecidudce, the peduncle lies at
the apex of a triangular fissure in the peduncle valve, and secretes a
calcareous plate to fill in the gap. In the fourth group, TELo-
TREMATA (¢elos, final or complete, trema, pore), including the Tere-
bratulide, etc., the triangular fissure in the peduncle valve is filled
in by two calcareous plates termed deltidia, secreted by the edges of
the mantle.

The valves are hingeless in the first two Orders (Inarticulata),
and hinged in the last two (Articulata).

THE Bopy.—The body usually occupies only a comparatively
small space in the posterior or peduncle end of the shell. From
each side of the body there is given off a thin expansion, the mantle
which lines the inner surface of the shell. The space between the
valves is termed the mantle-cavity. The mouth is situated in the
centre of the front wall of the body or floor of the mantle-cavity.
The front wall gives rise to a horseshoe-shaped platform surrounding
the mouth and bearing on its upper edge ciliated tentacles, or cirri,
which set up currents carrying food towards the mouth. In many
genera the platform is produced into two coiled “arms” (Figs. 3
and 5), which fill up the mantle-cavity.

The name Brachiopoda (brachion, arm, pous, foot) was given to
the group because these “arms” were supposed to be homologous
with the Molluscan “ foot.”

The mouth leads into a gullet, which opens into a stomach and
intestine. In the more primitive forms the intestine terminates in
a vent, but in the higher forms the distal end of the intestine has
become atrophied, and consequently the gut ends blindly.

The body-cavity contains fluid, and is in communication with a
system of sinuses in the lobes of the mantle (Fig. 5). Bands of
muscles pass across from valve to valve. The peduncle consists of
a horny outer sheath surrounding longitudinal and transverse bands
of muscles.

BRACHIOPODA. 12

The sexes are usually separate. The reproductive cells are
formed in the body-cavity. The embryo swims freely for a short

Magellania flavescens. (After Davidson.)

A. Interior of dorsal valve to show the “arms”; some of cirri removed on right
side; v, mouth. B. Longitudinal section, with a portion of the animal.

time before settling down and becoming fixed. The specimens
exhibited in the case are arranged according to the following
classification :—

Order 1. Atremata. Fam. Lingulide.

Section I. INARTICULATA.
Fam. Discinide.

Order 2. Neotremata. pee Baresi

Order 3. Protremata. Fam. Thecidiide.

selion UL, venucomiven. Fam. Rhynchonellide.

Order 4. Telotremata. Fam. Terebratulidz,
Kam. Terebratellidz.

Section J.—INARTICULATA.

Order 1.—AtTREMATA. Family Lingulide.—The Lingulas possess
emerald green or golden brown duck-bill-shaped shells. Having no

78

SHELL GALLERY.

hinge, the dead valves of dried shells easily fall apart. The peduncle,
which is sometimes over six inches in length, passes between the

Lingula anatina in tubes
in the sand ; upper figure
shows trilobed opening on
surface of sand. Dotted
line in lower figure indi-
cates position in retrac-
tion. (After Francois.)

pointed posterior borders of the valves. Dr.
Frangois gives a very interesting account of
the habits of Lingula anatina which he found
living in the sand at Noumea, New Hebrides.
The sole evidence of the animal’s existence
is the presence, on the surface of the sand
or mud, of a small, three-lobed slit (Fig. 4,
upper figure). The tube (Fig. 4) in which
the Lingula lives is about four inches deep,
flat in the upper half, rounded below. The
walls of the upper flat portion simply con-
sist of the sand with a surface coating of
mucous secretion ; but in the lower end the
sand grains are agglutinated so as to form a
distinct tube.

The edges of the mantle-folds are pro-
vided with sete (bristles), which form three
funnels protruding through the three lobes
of the slit-like mouth of the sand-tube;
currents enter by the lateral funnels and
leave by the central.

On the least alarm the animal is rapidly
withdrawn as far as the centre of the tube
(see the dotted line of the shell in the figure),
the surface slit and upper part of the tube
being obliterated. Hach of the arms forms
a spiral with several coils (Fig. 5). The
Lingulide are of exceptional interest, in that
they furnish a very remarkable example of
“persistence of type.”

Shells of Zingula occur in the earliest
Paleozoic strata, and so closely resemble
those of the present day, that often no
difference can be observed either in the shape
of the valves or in the muscular impressions
on their inner surface (Fig. 6).

Lingula occurs in the Indo-Pacific, Aus-
tralia, China, Japan, and the Pacific Islands.
Glottidia, a smaller form, with two small

:

BRACHIOPODA, 79

Lingula anatina, removed from shell, mantle reflected, coiled arms separated
slightly; a, mouth. (Marginal setae omitted.) Ventral aspect, three-quarter
face.

Lingula anatina. Interior of valves showing muscle scars.
V. Peduncle valve. D. Brachial valve.

80 SHELL GALLERY.

curved plates on the brachial and a ridge on the peduncle valve,
is found on the American coast of the Pacific, and in the Atlantic.

Order 2.—Nerorremata. The Discinide includes two genera,
Discina and Discinisca (Fig. 7), with orbicular conical shells, of
horny calcareous composition ; both valves are conical in the former

Discinisca lamellosa. Peru. (After G. Sowerby.)

A group of old and young specimens; largest showing foramen in peduncle
valve, the rest showing brachial valves.

genus, but in the latter the peduncle valve is flattened. Sometimes
the embryos settle down on the parent shells, and we see a mass of
shells in various stages of growth, as in the specimen of Discinisca
lamellosa from Peru.

The Cranude form small limpet-like shells (Fig. 8) closely
adherent to the rocks by the whole surface of the peduncle valve;

Three specimens of Crania anomala on a stone. Loch Fyne.

although this valve is so named, no peduncle or foramen is found in
this family. ‘The Neotremata, like the Lingulide, are remarkable

BRACHIOPODA. 81

examples of persistence of type, since forms very similar to the present
day Discinas and Cranias occur in the Paleozoic Ordovician and
Silurian strata.

A piece of rock, with several specimens of Crania anomala
attached, is exhibited.

Section I[I.—ARTICULATA.

Order 3. ProrrEMATA.—This group, formerly very abundant, is
now almost extinct, the Family 7hecidiide representing the Order at
the present day. Zhecidium mediterraneum (Fig. 9) forms little oval
boxes about a third of an inch in length, shaped somewhat like a

Magnified.

pear cut in half (peduncle valve), and with a semicircular lid
(brachial valve) working on a hinge on the upper flat surface. The
foramen and peduncle are absent ; but between the pointed end of
the peduncle valve and the hinge is an area filled in by a caleareous
plate characteristic of the Protremata.

The brachial valve opens like the lid of a snuff-box, and shuts
down on the least alarm with the rapidity of lightning. The
peduncle valve is fixed on the rocks by its convex surface. The
Species is common in the Mediterranean in from 30 to 300 fathoms,
and is also found in the West Indies.

82 SHELL GALLERY.

Order 4. TELOTREMATA.—This group, which at the present day
contains the largest number of species, includes the Lamp shells,
so called from their resemblance to an ancient lamp. The valves
are joined by a well-marked hinge, the peduncle passes through the
peduncle valve through a foramen completed by two plates secreted
by the mantle edges, and the brachial valve has attached to it a
calcareous scaffolding of processes or loops for the support of the
STanmaseu

The shells in this group are frequently ridged. Their colour
is usually white, but sometimes red or yellow; deep-sea forms are
generally vitreous.

Rhynchonella psittacea has a black shell with a pointed incurved
beak ; each of the arms forms a many coiled spiral and can be pro-
truded beyond the shell; the brachial skeleton is comparatively small
and simple, consisting of two separate processes.

In Terebratulina the brachial skeleton forms a simple loop; in
Magellania the loop is reflected on itself (Fig. 2).

The beautiful and unique specimen of Dyscolia wyvillu, from
390 fathoms W. Indies, is remarkable for its size, being over two
inches in length. The small vitreous specimens of Terebratula
wyvillii were obtained off Chili from a depth of 2160 fathoms ;
specimens of the same species were obtained also from a depth of
2900 fathoms in the North Pacific.

( So)

TUNICATA.

THe Tunicata are marine animals, the majority of which live, in
their adult stage, a stationary life, fixed to the rocks or sea-bottom,
but a comparatively small number are free-swimming.

They occur in the form of cartilaginous or leathery sacs, fleshy in-
crustations, solid fleshy masses, free-swimming, barrel-shaped animals,
solitary or united into chains or hollow cylinders ; or, lastly, of minute

Ascidia mentula from the right side.
at, atrial aperture; br, branchial aperture; ¢, test.
[After Herdman: Tunicata, Encyc. Britannica. ]

free-swimming tadpole-shaped organisms. To explain briefly the
structure of a Tunicate, Ascidia mentula (Fig. 1), is selected. The
6)

a

Wall Case
to left

of main
entrance
to Shell
Gallery.

84 SHELL GALLERY.

animal, which lives on a muddy bottom, in from five to twenty fathoms,
resembles a conical sac fixed by the broader end, of grayish green
colour and about 4 inches in height. At the narrower end are two
orifices, one terminal—the branchial orifice or mouth, and the other
a little lower—the atrial orifice : the former has eight lobes and the
latter six.

When the Ascidian is undistubed, the orifices are wide open, and
currents enter by the branchial and leave by the atrial orifice. On
the least alarm, the orifices close, jets of water being at the same
time squirted out; hence the popular name “ Sea-squirts” given to
these animals.

The Ascidian is orientated as follows: hold the animal with the
branchial orifice pointing forwards and the atrial upwards; the
branchial orifice will be anterior and the opposite end posterior ; the

Diagrammatic section of Ascidia representing the three sacs, and the branchial
sac as the pharynx or throat. :
a, branchial; and }, atrial orifice; c, tunic or test; d, mantle; e, branchial sac;
f, gullet; g, stomach ; h, anal orifice; 7, dorsal lamina; dotted line indicates

the endostyle.

atrial orifice will lie on the upper or dorsal aspect, the opposite
aspect being lower or ventral, and the sides right and left. The
aspects, in fact correspond with those of a vertebrate animal. A

TUNICATA. 85

vertical section roughly shows the animal to be formed of three
concentric sacs (Figs. 2, 3). The outermost, which is tough and

Diagrammatic dissection of A. mentula.
at, atrial orifice; br, branchial orifice; a, anal orifice; brs, branchial sac;
dl, dorsal lamina; end, endostyle; m, mantle; ng, nerve ganglion; oea,

orifice of gullet; pbr, peribranchial cavity; st, stomach; ¢, test; tn,
tentacles.

(After Herdman : Tunicata, Encye. Britannica.)

membranous, is called the Test or Tunic, the whole group owing
its name to the presence of this protective covering.

The middle sac, termed the Mantle, which almost corresponds
in shape to the outer, is composed of connective tissue, muscle-fibres,
blood-vessels, etc. ; in spirit specimens, the mantle is shrunk away
from the test except at the orifices and at a point behind, where
vessels enter the test.

The innermost or Branchial Sac is attached behind the branchial
orifice and along the ventral edge, but otherwise hangs free in the

86 SHELL GALLERY.

interior, the space around and outside of the sac being termed the

atrial or peri-branchial cavity.
The delicate walls of the branchial sac, which resemble fine

Fig. 4.

Ascidia mentula. Part of wall of branchial sac showing stigmata.
Magnified.

muslin, are perforated by innumerable vertical slits, termed stigmata,
arranged in transverse rows (Fig. 4).

The margins of the stigmata are lined with cilia which set up
currents ; and the water which enters by the branchial orifice, passes
through the stigmata into the atrial cavity, and thence out through
the atrial orifice. The walls of the branchial sac are chiefly composed
of asieve-like meshwork of fine blood-vessels arranged in transverse
and longitudinal rows. The currents of water passing through the
stigmata aérate the blood in the vessels. Besides the stigmata, the
branchial sac has two relatively large orifices, viz., the branchial
orifice or mouth, and, at the opposite end, the opening into the
gullet. The branchial sac is, in fact, a capacious throat or pharynx
(Diagram Fig. 2 and Fig. 14). Inside the branchial orifice is a circle
of fine tentacles, which guard the entrance to the branchial sac. The
food of the animal consists of minute animal and vegetable organisms.

It may be wondered how this food is secured, seeing that the
currents of water are continually passing through the sieve-like
walls of the branchial sac to the exterior again. Within the
branchial orifice and above the branchial sac are two circular
ciliated ridges with a groove between, which is full of viscid
secretion ; the cilia on the ridges direct particles into the groove
where they are retained by the mucus.

ns epee

Sa aaa

TUNICATA. 87

Passing backwards along the ventral edge of the branchial sac
is a thick-lipped furrow, which appears like a rod in the thin-walled
sac, and hence is called the endostyle. This organ secretes the
mucus which is carried up by ciliary action to the circular groove
in front of the branchial sac, and thence to the gullet along a fold
or crest, termed the dorsal lamina, situated along the dorsal edge of
the branchial sac.

The gullet opens into a large stomach situated posteriorly on the
left side of the branchial sac. The stomach opens into the intestine,
which, after forming a loop, terminates in the anal orifice or vent
opening into the atrial cavity.

The tubular heart lies below the stomach, a remarkable feature
in the circulation consisting in the periodic reversal of the blood
current. An elongated nerve ganglion is situated between the
branchial and atrial orifices.

Ascidia mentula is hermaphrodite. The egg develops into a
minute tadpole-like larva which swims about by means of its tail.
Water entering by the mouth passes out through the gill-slits. A
nerve-tube extending along the back and tail is swollen in front into
a brain-vesicle; and underneath the long nerve-tube behind the

Ascidian Tadpole with part only of the tail C. Magnified section.
N, nervous system with enlarged brain in front and narrow spinal cord behind
n; N’, cavity of brain; O, the single cerebral eye lying in the brain ;
a, auditory organ; K, pharynx; d, intestines; 0, rudiment of mouth ;
ch, notochord or primitive backbone.
(From Gegenbaur’s ‘ Elements of Comparative Anatomy.’)

brain is a stiff skeletal rod or axis—the notochord—which constitutes
the rudiment of a backbone. Inside the brain are two unpaired sense
organs, an eye and an organ of hearing (Fig. 5). After swimming
freely for a few hours, the larva settles down head foremost and

88 SHELL GALLERY.

fixes itself by papillee on the anterior end (Figs. 6,7). Presently
the tail becomes absorbed, and the posterior end of the nerve-tube,

NOTOCHORD

Degeneration of Ascidian Tadpole to form the adult. The black pieces represent
the rock or stoue to which the Tadpole has fixed its head.

é
Very young Ascidian with only two gill-slits. Ee
(Figs. 6, 7, from Lankester’s ‘ Degeneration.’ )

and the brain with its eye and hearing organ, undergo atrophy, the
nerve-ganglion of the adult alone representing the cerebrospinal
axis of the larva. The branchial sac and intestines develop greatly,

TUNICATA. 89

and growth proceeds in such a manner that the mouth is pushed
round to a position opposite to the fixed area, and gradually the
animal becomes the adult ascidian.

This wonderful metamorphosis presents a striking example of
DEGENERATION resulting from the adoption of a fixed mode of life.
The active free-swimming larva with its brain, eye, hearing organ,
and muscular tail becomes transformed into a comparatively inert sac.

The tadpole of an Ascidian resembles that of a frog (Figs. 8, 9),
not merely superficially, but also in its general structure and mode
of development. The Tunicata are now generally regarded as a

TAIL

yey

) my) mn)
wr

MH]
LTT
UU HH

@)//!//})
LT

MH
ASCIDIAN
Tadpole of Frog and Ascidian. Surface view.

(Lankester’s ‘ Degeneration.’ )

Fig. 9.

SPINAL CHORD

NOTOCHORD

CILL SLITS
Tadpole of Frog and Ascidian. Diagram representing the chief internal
organs. (Lankester’s ‘ Degeneration. A chapter in Darwinism.’)

degenerate offshoot from the ancestral stock of the Vertebrata, in
that the larva possesses a skeletal rod (rudimentary backbone)
separating the dorsally situated nerve-tube (cerebro-spinal axis) from
the ventrally situated intestinal tube, the existence of the cerebral

90 SHELL GALLERY.

eye in the Ascidian tadpole further tending to confirm the truth of
this theory. Apart from a knowledge of the course of their develop-
ment, Tunicata would have been classed among the Invertebrata,
but the structure of the larva clearly reveals the affinities of the
group to the backboned animals.

Ascidia mentula belongs to the group of SIMPLE ASCIDIANS which
are all fixed, and are either solitary or joined into colonies in which
each individual or ascidiozooid has a distinct test of its own. In the
CompounD AScrpIANs, which form colonies by budding, the ascidio-
zooids are buried in a common investing mass and have no separate
tests. Ina third group, the SALPA-LIKE ASCIDIANS, the ascidiozooids
are united to form free-swimming colonies shaped like hollow cylinders
open at one end. The above three groups belong to one great
Order—the AscrprackaA. A second Order, THALIAcEA, includes
the free-swimming Salpa and Doliolum, which exhibit alternation
of generations in their life history. A third Order Larvacna,
includes very minute free-swimming forms which possess a tail in
the adult stage. There are sixteen families of Tunicata.

The following is a tabular view of Prof. Herdman’s classifica-

tions :—
Sub-order 1. Ascidize Simplices, 4 Families.

Order I. Ascidiacca . Sub-order 2. » Composite, 7 Families.
Sub-order 3. » Salpiformes, 1 Family.
Order II. Thaliacea . . 3 Families.

Order III. Tarvacea. . . 1 Family.

Order I.—ASCIDIACEA.

The Ascidiacea include the great majority of species. With the
exception of the one genus Pyrosoma, they lead a fixed or stationary
life.

Sub-order 1.—ASctp1a@ SIMPLICES.

The Simple Ascidians are mostly solitary ; in a few forms, however,
colonies arise by budding from stolons, but each individual has a dis-
tinct test. The four families into which the sub-order is divided are
chiefly characterised by the nature of the test, the number of lobes round
the branchial and atrial orifice, and the character of the branchial sac.

In the family Molgulide the tough membranous test is often
coated with sand; the branchial aperture is six-lobed, the atrial
four-lobed, the branchial sac has long folds or pleats, and the
stigmata are curved or arranged in spirals.

sal

TUNICATA. 91

Molgula gigantea, which is one of the largest of the Ascidians,
and which attains a leneth of over thirteen inches, forms a tough
conical sac; the branchial and atrial orifices at the upper end
have six and four lobes respectively. The test is leathery, smooth
above, but coated with sand below. The exhibited specimen,
which comes from the Straits of Magellan, has several specimens
of the stalked Boltenia legumen attached to the lower part of the
test.

The curious Molgula oculata (Fig. 10) has a soft oval or rounded
body coated with sand. The branchial and atrial orifices have res-
pectively six and four lobes. Specimens grow attached to the rocks
and also live free in the sand. The surface of the test is provided
with hairs, which adhere to the rocks and collect particles of sand.
The adhesion not being very firm, specimens are easily detached by

Fig. 10.

Molgula oculata.

a, branchial; b, atrial orifice.

currents and collected into heaps by the eddies ; when living in the
sand only the two dark orifices are visible. The sand coating has
been supposed to confer protection by mimicry of the environment ;
but Professor Lacaze Duthiers found, much to his chagrin, that
the sandy tests of his specimens were of no avail in securing them
from being devoured by crabs who seemed to scent their prey
from afar.

In the family Cynthude the test is usually leathery, the
branchial and atrial apertures four-lobed, and the branchial sac
folded into longitudinal pleats.

92 SHELL GALLERY.

The genera Goltenia and Culeolus include species in which the
body is attached to a peduncle.

The large exhibited specimen of Bollenia pachydermatina is 28
inches in length, the head being 4 and the stalk 24 inches long.
The two four-lobed apertures are along one edge, the branchial
being the lower ; the body is marked with long deep furrows, and
the stalk with transverse wrinkles. Culeolus perlucidus, from 1600
fathoms in the Southern Ocean, isin the form of a small pear-
shaped head on a slender stalk, the total length being 44 inches.
The branchial orifice forms a transverse slit with raised lips near the
stalk, the slit-like atrial orifice being near the rounded end of the
body. Culeolus moseleyi, another slender-stalked form, was obtained
from 2425 fathoms in the Central Pacific.

The little Cynthiid Styelopsis grossularia (Fig. 11), popularly
known as the “ Currant Squirter,” occurs in the form of bright red
hemispherical blobs on stones and shells; when undisturbed, the

Fig. 11.
Lf
7

al f
cone 4y
}
/ B

/

A

A. Styelopsis grossularia on shell. B. Tadpoles of same, x 9.
a, branchial; 6, atrial orifice. (B, after Sir J. Dalyell.)

branchial and atrial orifices expand and project upwards. The eggs
are brilliant red in colour. Sir John Dalyell was the first to discover
the tadpole form, which is about 5 inch long (Fig. 11, B), and to

TUNICATA. 93

observe the tadpoles become fixed and develop into fixed Ascidians.
He calls the active little swimming larve “Spinule,” from their
resemblance to small pins.

The family Ascidiide includes forms with a gelatinous or
cartilaginous test ; the branchial and atrial orifices usually have 8
and 6 lobes respectively ; the branchial sac is without folds.

Ascidia mentula, described above, belongs to this family.

Chelyosoma is characterised by the test forming tortoise-like
horny plates on the upper surface. The exhibited specimen of

Fig. 12.

Chelyosoma macleayanum, slightly enlarged.
a, branchial; b, atrial orifice.

C’. macleayanum (Fig. 12) comes from Greenland ; the upper hemi-
spherical part of the test is divided into 8 plates; the branchial and
atrial orifices are situated in the joints between the plates.

The fine specimen of Phallusia mammillata from Naples consists
of several individuals partly fused together; the branchial and
atrial orifices are wide open, and the mantle can be seen through the
thick knobby translucent test.

In Fhodosoma the test is modified so as to form stiff plates recall-
ing the valves of a bivalve shell. One plate is attached to the rocks,
the other closing against the first like a lid; the anterior end of the
animal with its branchial and atrial orifices is visible only when the

94 SHELL GALLERY.

lid is open. The Mediterranean species A. callense (Fig. 13) grows
attached to the rocks. The little exhibited specimen is on a fragment

Fig. 13.

%

Rhodosoma callense, x 10. A, “valve” open; B, shut.
a, branchial; b, atrial orifice. (After Lacaze Duthiers.)

of shell in front of a black patch. The figure shows specimens with
the lid open and closed.

Family Clavelinide. The body is attached to a creeping
stolon or mass of stolons, from which new individuals arise by
budding. The other three families of Simple Ascidians included
solitary forms, but the Clavelinide are social, and form colonies
wherein each individual has its own test.

Clavelina lepadiformis (Fig. 14) forms graceful crystal vases about
an inch in height. The figure shows one individual, but usually
the processes at the base extend out as stolons whence other
individuals arise.

Diazona violacea, from Cornwall, forms beautiful purple disk-
shaped colonies in which the ascidiozooids arise from a basal mass
of stolons. Sometimes the ascidiozooids die down, leaving only a
smooth violet pad, which in due time produces a new crop of ascidio-
zooids.

a

TUNICATA. 95

Clavelina lepadiformis; diagrammatic, showing the anatomy. The oyal bodies
are the eggs; at lower end lies the tubular heart; the root-like processes at
the base grow into stolons, whence other ascidiozooids arise.

Perophora listeri; A, slightly, B, further magnified. Ascidiozooids in right,
left, and lateral aspects.
a, branchial; b, atrial orifice,

96 SHELL GALLERY.

The remarkable Ahopalea neapolitana, from Naples, may be
roughly compared to an hour-glass with a very long constriction.
The test is smooth in the upper part, but knobby and encrusted with
foreign bodies below. The upper or thoracic end contains the
branchial sac, and the lower or abdominal portion the stomach,
heart, and reproductive organs, the gullet and intestine traversing
the whole length of the narrow central region. Although from its
general structure Rhopalea is a Clavelinid, it is not certainly known
to produce buds.

Perophora listert (Fig. 15) occurs in the form of little jelly-like
transparent blobs rising by short stalks from a silvery thread-like
stolon. Owing to their small size and transparency, it is possible to
examine specimens alive under the microscope, the currents passing
through the stigmata in the walls of the branchial sac, and the
beating of the heart being distinctly visible. The rapid motion of
the cilia surrounding stigmata gives the appearance of dark wheels
all rotating in the same direction. The heart beats so as to drive
the blood current so many times in one direction, and then after a
short pause, in the reverse direction.

The exhibited specimen growing on an oyster shell, is from
Plymouth.

Sub-order 2.—AscipIa@ COMPOSIT A.

The Compound Ascidians are fixed forms, which give rise to
colonies by budding, the individuals being immersed in a common
mass and not possessing separate tests.

Although reduced to an extremely small size each individual or
ascidiozooid of a colony possesses the same organs as a large Simple
Ascidian, excepting that the former does not possess a separate test.
Frequently the individuals of a colony are grouped into systems, m
which the atrial orifices open into a common cloaca. The little
ascidiozooids vary greatly in shape in the different families. In the
Polyclinide, for instance, they are long, the organs being, so to speak,
drawn out, and being arranged in three regions, the thoracic, ab-
dominal and post-abdominal, the first region containing the branchial
sac, the second the stomach, and the third the heart and repro-
ductive organs. In the Distomide, the body exhibits two regions,
thoracic and abdominal, the heart and reproductive organs lying
alongside of the stomach. The Botryllide comprise only one region,
the stomach and the other organs being situated by the side of the
branchial sac.

TUNICATA. 97

The Compound <Ascidians include seven families which are
characterised chiefly by the method of bud formation, and by the
arrangement of the organs into one, two, or three regions.

It is only possible, from limits of space, to refer to a few interest-
ing forms.

The species of Botryllus are those most commonly met with.
They form richly coloured gelatinous incrustations on rocks and sea-
weeds. #. violaceus (Figs. 16, 17, and 18 D) is blue with white lines ;
B. smaragdus, green ; B. marionis, brown with white and carmine ; B.

Botryllus violaceus on seaweed. (After H. Milne-Edwards.)

castaneus, purple, and so on. The individuals are arranged in circular
systems with the branchial orifices round the circumference and the
atrial orifices opening into a common central cavity (Fig. 17), the
whole colony being composed of groups of systems.

The exhibited specimen of B. violaceus was grown in the tanks
of the Biological Station at Plymouth. The red specimen of B.
aurolineatus, from Naples, shows well the branchial and cloacal
orifices. In Botrylloides, the individuals form elliptical or elongated
Systems.

Colella thomsont was obtained near the Philippines at a depth
of 10 fathoms. The specimen, which is about 7 inches in length,

. H

98 SHELL GALLERY.

resembles an elongated head of clover on a thickened stalk. The
individuals which compose the head are arranged in spiral lines,

Fig. 17.

A. Botryllus violaceus, magnified, showing two systems of 6 and 7 ascidiozooids.
B. One ascidiozooid extracted.

a, branchial; b, atrial orifices ; c, branchial sac ; d, stomach.
(After H. Milne-Edwards.)

the atrial orifice of each ascidiozooid opening separately and not
into a common cloaca.

Colella quoyi (Fig. 18 A), from 25 fathoms off Kerguelen Island,
forms a rounded head on a short peduncle, the total height being

Fig. 18.

Colonies of Ascidix composite, natural size. A. Colella quoyi. B. Leptoclinum
neglectum. ©. Pharyngodictyon mirabile. D. Botryllus.

(After Herdmar, Challenger Report and Encyclopedia Britannica.)

one inch. The ascidiozooids are arranged in vertical lines in the
“head,” each line consisting of a double zigzag series.
Julinia ignota, from the Antarctic regions, forms long narrow

TUNICATA. 99

colonies, which attain a length of nearly three feet. One end is
attached, the rest of the colony apparently lying along the sea-
bottom.

Amaroucium roseum from Naples forms translucent gelatinous
masses; a slice is exhibited, showing the long slender ascidiozooids
immersed in the mass.

Pharyngodictyon mirabile (Fig. 18 C), from 1600 fathoms in the
Southern Indian Ocean, resembles a small mushroom, and is about
one inch in height. This species is one of
the few deep-sea Compound Ascidians.

Leptocinum albidum is a common and
widely distributed species ; it occurs in the
form of thin white crusts. The glistening
white appearance is due to the common test
being densely crowded with minute stellate
spicules of carbonate of lime.

The specimen of Leptoclinum neglectum
(Fig. 18 B) encrusts a fragment of sponge.

Goodsiria pedunculata from the Straits of
Magellan, forms a rounded cartilaginous mass
attached by a short peduncle; sometimes
several masses are attached to each other.
Each of the small dark oval areas on the
surface corresponds to the branchial and
atrial orifices of one ascidiozooid.

Sub-order 3.—AscIpa SALPIFORMES.

The Salpiform Ascidians comprise only
one genus, Pyrosoma, which occurs in the
form of free-swimming colonies shaped like
hollow cylinders closed and rounded at one
end and open and truncate at the other
(Fig. 19). The wall of the cylinder is formed pyrosoma et Pathe, OEE
of a single layer of ascidiozooids (Fig. 20), size. A. Side view of
so arranged that all the atrial orifices open entire colony. B. End
into the interior of the cylinder, and all the Vie of open extremity.
branchial orifices on the exterior, the two _ “Herdman : Tunicata,
kinds of orifices being at opposite ends of pogiacee dia Driennica
the body, and not close together, as in most simple and compound

Ascidians.

1s 4

100 SHELL GALLERY.

Specimens vary in size from a few inches to upwards of four feet
in length, and, as the name of the genus implies,* they are brilliantly
phosphorescent. Sometimes they occur in innumerable multitudes,

Fig. 20.

Section through wall of Pyrosoma, magnified, showing a single layer of
ascidiozooids.

br, branchial ; at, atrial orifice; tp, process of the test; br s, branchial sac.
(Herdman: Tunicata, Encyclopedia Britannica.)

giving rise to a zone of greenish light extending for miles. Professor
Moseley records that during the voyage of the Challenger in the
North Atlantic a huge specimen of Pyrosoma spinosum, four feet
in length, was captured. On tracing his name on its body, the word
came out in letters of fire.

In Pyrosoma elegans (exhibited), from Naples, the ascidiozooids are
arranged in verticils, and the mouth of the cylinder is surrounded
by a movable diaphragm; the outer end of each ascidiozooid is
provided with a membranous spine. Six species of Pyrosoma are
known. Pyrosoma atlanticum is found in the tropical Atlantic and
Antarctic ; P. giganteum in the Atlantic, Pacific, and Antarctic ; and
P. spinosum in the South Atlantic.

Order IJ.—THALIACEA.

The Thaliacea are free-swimming Tunicates, which exhibit
alternation of generations in their life history. There are three
families, Salpide, Octacnemide, and Doliolide.

Salpide.—The Salpas are transparent barrel-shaped organisms,

* Pyrosoma—pur, fire; soma, body.

TUNICATA. 101

which occur in abundance at the ocean surface. They are so
transparent that they are rarely seen, except in calm weather
from the side of small boats; yet they frequently swarm in
countless multitudes. From five to ten bands of muscles partially
or entirely surround the body, like hoops. The branchial and
atrial openings are at or near the opposite ends of the body.
The branchial sac has almost disappeared, the dorsal lamina and
ventral gutter (or endostyle) alone remaining, the interval be-
tween the two on each side representing an enormous stigma; the
dorsal lamina, or “gill” is the transversely striated band passing
obliquely across the body and forming the only barrier between the
branchial and atrial cavities. Water enters at the mouth, and, by
the contraction of the muscle-hoops, is driven out through the atrial
aperture at the opposite end, which is then closed by a sphincter
muscle. The elastic walls of the body expand, and water again
enters through the mouth, the valve-like lips of which prevent its
being driven out that way. The Salpa swims along in jerks, and
along with each gulp of water takes in Radiolaria, Foraminifera, etc.,
which are retained by the mucus of the endostyle and carried to the
cullet. The Salpa, in fact, lives, as Professor Brooks observes, in a
“living broth,” so abundant is the food supply.
The intestines usually form an oval mass termed the “ nucleus,”
which is a conspicuous object at the posterior end.
~The solitary Salpa above described is asexual. In the ventral

Posterior part of solitary form of Salpa democratica-mucronata, showing a chain
of embryos nearly ready to be set free.
gem, young chain of Salpx; st, stolon; ¢, test; vise, visceral mass.

region of its body it forms a stolon which becomes segmented into a
series of buds (Fig. 21). As the stolon grows the end series of buds

102 SHELL GALLERY.

breaks off in the form of a chain and swims away, other chains being
detached in succession. A chain is formed of individuals arranged
in two rows, the individuals in each row being alternate (not opposite).

Each individual of a chain differs from the solitary individual in
shape, arrangement of muscle bands, etc., but especially in having re-
productive organs. The chain Salpid is hermaphrodite ; the embryo
develops into a solitary asexual Salpa which produces the chains by
budding. The wonderful life history of Salpa was discovered by the
poet Chamisso during a voyage round the world in 1819. He
observes : “ A Salpa mother is not like its daughter or its own mother,
but resembles its sister, its granddaughter, and its grandmother.”
Here we have an example of ‘alternation of generations,” a sexual
generation (chain form) giving rise to an asexual generation (solitary
form), which latter produces the sexual generation.”

Most of the species of Salpa have double names owing to the
chain and solitary forms having been regarded as distinct species
before they were known to be phases in the life history of one and
the same species. Salpa runcinata-fusiformis, solitary form (Fig.
22 B), is barrel-shaped, truncated at each end, with terminal orifices,
and with nine muscle-bands on the dorsal surface, some of which
converge towards each other. An individual of a chain (Fig. 22 A)
is fusiform, with six muscle-bands, and with the orifices not terminal,
but at each end of the dorsal surface.

The solitary form of S. africana-marima is barrel-shaped,
with truncated ends and terminal orifices, and with nine broad
parallel muscle-bands. The chain form is conical at one end, with
six bands, and with orifices on the dorsal surface. The exhibited
specimen of the chain form, which is in an early stage of growth,
contains 202 individuals. The solitary and chain individuals of
Salpa costata-tiles attain a length of six to eight inches. The
solitary form has eighteen muscle-bands and two large spines at the
posterior end. The individual of the chain has five muscle-bands.
A chain of three individuals is exhibited.

Salpa pinnata produces a circular chain ; the exhibited specimen
of the solitary form shows a small chain about to be detached; a
circular chain of six individuals is also exhibited. Species of Salpa
abound in all seas, but specimens from Naples have alone been
exhibited on account of their good preservation. |

* Tt should be mentioned that one high authority, Prof. W. K. Brooks, does not
regard the life history of Salpa as an example of alternation of generations, but
considers the solitary Salpa to be, not asexual, but a female which produces a chain
of|males ; but it is impossible to enter into a difficult question of controversy kere.

TUNICATA. 103

Family Octacnemide includes O. bythius, a deep-sea Salpid, in which
the body forms a flattened disk produced into eight radiating lobes.

Fig. 22.

|
gem --}i

Salpa runcinata-fusiformis. A. Chain form. B. Solitary form. 1-9, muscle
bands; em, embryo; m, mantle; visc, visceral mass or nucleus.

(Herdman : Tunicata, Encyclopedia Britannica.)

Fig. 23,

tg
dt Vi sel

Tin

br.
br IL: at
“atl
sO

end i se p ee: . .
br's tes h oy “ ou
Doliolum denticulatum, sexual generation, from the left side.
m'—m8 muscle bands; at, atrial; br, branchial apertures; br s, branchial
sac; sg, stigmata; st, stomach ; ng, nerve ganglion; so, sense organs.

(After Herdman, Encyclopedia Britannica.)

Family Doliolide. The body is cask-shaped and surrounded by
circular hoops. The branchial and atrial orifices are at the opposite

104 SHELL GALLERY.

ends. The branchial sac is pierced by two oblique bands of stig-
mata (Fig. 23 sy). The life history is very complicated. The egg
develops into a tailed larva, which develops into a “nurse” ; the
latter is asexual, and produces three kinds of buds on a stolon, viz.
(1) nutritive buds which provide the “ nurse ” with food, (2) foster
forms which are set free as cask-shaped bodies with eight broad
muscle-bands, and (8) sexual forms which are attached for a time
to the foster forms, but which later become free and give rise
to the egg.

Order IJ].—LARVACEA.

The Larvacea are very minute Tunicata which live at the surface
and swim by means of a tail-like appendage, resembling in this and

Fig. 24.

Oikopleura cophocerca in its “house” (after Fol); seen from right side, x 6.
Arrows indicate course of the water; «, lateral reticulated parts of the “ house.”

certain other respects the tadpole larva of other Tunicata. They
are able to form a temporary test or “ house” many times larger
than the body (Fig. 24). The organism itself, which is almost lost

TUNICATA. 105

in its large test, is the little hammer-shaped body in the centre of
the figure ; the streaked areas bound a space in which the tail lashes
vigorously. The animal can leave its test and secrete another in a
few hours.

The tail is attached to the under or ventral surface of the tiny
little barrel-shaped body, and usually points forwards ; a skeletal rod,
the urochord, runs along its length. The branchial sac has two
ciliated openings or gill-clefts leading directly to the exterior, and
not opening like the stigmata of the other orders into an atrial
cavity.

The order contains one family, the Appendiculartide, and four
genera, and is represented in all seas.

Oikopleura cophocerca, one of the largest forms, is about half an
inch in length. The exhibited specimens came from St. Andrews,
Fife. Professor McIntosh reports that occasionally specimens of this
species occur in immense quantities, the tow-nets being filled with
them.

106 STARFISH GALLERY.

TEES Aon Sieh Go Awe iene

—00595,00—.

In the SrarFisH GALLERY is exhibited a series of ‘the animals
belonging to the class Hchinoderma; of these the Starfishes are the
best known, while others are the Sea-Lilies, Sea-Urchins, and Sea-
Cucumbers or Sea-Slugs (Wall-case IV.).

A small collection of various kinds of Worms is also exhibited in
this Gallery (Wall-cases I.—-III.).

ECHINODERMA.

Six table-cases contain the dried Echinoderms arranged in
systematic order. The seventh is devoted to preparations, models,
and figures illustrative of the structure and life-history of various
members of the group.

An inspection of that Case and the accompanying woodcuts will
make clear the distinctive characters of the Echinoderma. Unlike
that of a Crayfish or a Mussel, the body does not appear to be divided
into two equal or symmetrical halves, though it really is ; this is due
to the possession of a number of rays, of which there are ordinarily
five. The skin is strengthened by the deposition in it of carbonate
of lime, which may be in the form of continuous plates or bars,
or of separate scattered spicules. A series of tube-feet or suckers
(podia) are generally developed along each ray, and these are
supplied by a system of water-vessels peculiar to Starfish and their
allies. These rays are often called “ ambulacra.”

In the body of the Starfish (Fig. 3) the arms are seen to be
continuous with the disk and to contain portions or prolongations
of the chief organs. The middle of the arm is occupied by two
rows of hard pieces (ambulacral ossicles), the fellows of which make
an open angle with each other, and so form an open ambulacral
groove; along this we find the suckers, the water-canal that
supplies them, the blood-vessel of the arm, and a nerve-cord. At

ECHINODERMA.

107

A. Anchor and plate of Synapta. B,C. Tables of Holothuria impatiens; and

D. Holothuria atra: from various aspects. E. Spicule from sucker of
Stichopus variegatus, magnified about 200 times.

Diagram of Water-vessels.

e.c. Circular canal, with p.v, its Polian vesicles; from it a radial canal (v.c.) is
given off along the lower surface of each arm; this supplies, by side
branches, the suckers, s; connected with each sucker is a contractile
swelling or ampulla (a). The circular canal is in connection with the
exterior by s.c, the stone-canal, and opens to it by the madreporite (m).

108 STARFISH GALLERY.

WANA:

five

ab

et
pase

ox

woo
arn,

Sant
te

Figure of a Starfish (Asterias rubens).

In the ray marked I. the skin has been removed from the upper surface, and
the ambulacral ossicles (ao) and the podia (s) are seen in situ; the
blind outgrowths (¢) from the central stomach (sp) have been dissected
out. In If. the gonads (q) are exposed; and in the centre above the

stomach the rectal glands (7g) are to be seen. The anus (@) is seen to be
subcentral in position.

ECHINODERMA. ; 109

the centre of the disk is the mouth. The ossicles at the sides of
the arms bear spines, which vary in different species ; the surface
of the back is supported by a network of hard pieces, and through
the intervening spaces there project membranous pouches, which
are respiratory in function. The modified plate on the upper
surface opens into a tube by means of which the water-vessels
communicate with the exterior; this plate is known as the madre-
porite (Fig. 2, m).

The organs for. masticating the food are most highly developed
in the regular Echinoids, where the complex apparatus known as
the ‘‘ Lantern of Aristotle’ is found (Case 38) to consist of five
sets of pieces; the tooth is strong and bevelled at its free end ; it
is supported by triangular jaws on either side, a pair uniting and
having the form of an inverted pyramid ; these alveoli are con-
nected with their neighbours by oblong pieces (falces) ; above these
there are elongated bars, which are hinged on to the inner end of
the falces and have their outer ends free. The whole lantern is
connected to the test by muscles which pass from its sides to the
auricles or upstanding pillars which lie round the mouth ; and, owing
to this muscular apparatus, the teeth are capable of complicated and
various movements.

In the Ophiuroids the edges of the mouth-slits are provided with
short spinous processes, varying a good deal in arrangement, but
never having, apparently, any other function than that of a filtering-
apparatus ; in the Starfishes the plates round the mouth have a sup-
porting function only ; in Crinoids and Holothurians the mouth is
unarmed ; the latter are often remarkable for a deposit of calcareous
plates in the walls of the gullet, and in the former the grooves on the
arms are the lines along which food is passed to the mouth.

EKchinoids live on seaweeds and the animals that are found on them ;
such as have no teeth, like Spatangus (Case 32), use their spout-like
mouth to take up the sand and débris on which they move, and from
which they extract some nutriment. Ophiuroids live on the smaller
foraminifera ; Asteroids on dead fishes (as line-fishermen well know),
oysters, and other molluscs, and even on specimens of their own
particular species; Holothurians on shell or coral débris and the
minute organisms it contains; and Crinoids on small tests of
foraminifera and on the adults of small and larve of larger
crustacea.

In a number of Echinoids and Asteroids some of the spines are
specially modified to act as seizing-organs—the free end being

110 STARFISH GALLERY.

divided into two, three, or rarely four pieces, which are moved on
one another by special muscles. These minute organs were regarded
by earlier observers as parasites, and were named pedicellarie ; they
may be movable, when they have a stalk, or the stalk may be absent
and the valves sessile. Considerable difficulty attaches to the deter-
mination of the use that these organs may be to their possessors ;
but there is reason to suppose that they may act as cleansing-organs
by removing minute particles of dirt, and as temporary organs of
fixation, while M. Prouho has observed their use as organs of defence.

Echinoderms move but little; the unstalked Crinoids, if they
cannot find stones or worm-tubes around which to attach themselves,
swim by beating the water with their delicate arms, five being
raised and five depressed alternately. The Echinoid or Asteroid is
able to move by the aid of its podia or so-called ambulacral feet,
which become erected by being filled with water, and are then
contracted ; by means of this contraction movement is effected ; a
similar kind of locomotion obtains with the pedate Holothurians ;
in the Ophiuroids the flexible arms either serve as the organs of
movement, or act as an apparatus whereby the creature becomes
coiled round the branches of corals (see Case 20).

Echinoderms are often of exceedingly bright colours, as is shown
by the pictures on the wall, and are very conspicuous objects ; this
may, apparently, be associated with disagreeable tastes or odours ;
sometimes they cover themselves over with seaweed, and so hide their
brilliancy ; the spines of some forms are exceedingly painful to the
touch, and the stout plates of some of the Gonzasters must form
admirable organs of protection. The power of restoring lost or in-
jured parts is one of the most remarkable points in the Echinoderm
organization (see Case 6).

Echinoderms are of great geological age, and were very abundant
in earlier periods of the world’s history. Two groups (the Blastoids
and Cystids) have completely disappeared, and the Stalked Crinoids
(Lily-Encrinites) are far less common than they used to be. The
visitor should make a point of seeing the specimens exhibited in
Gallery VIII of the Geological Department. Echinoderms are now
found in all seas, and extend to great depths of ocean; many of
the species have exceedingly wide areas of distribution, and most are
characterized by their gregarious habits, a large number of specimens
of a single species being generally obtained by the dredge. They are
most abundant in the tropical seas.

Most Echinoderms lay their eggs in the water, where the larvee

ECHINODERMA. 111

are developed and swim about freely; but in a few (Hemiaster,
Opluacantha vivipara, and others) the young do not pass through
any metamorphosis, for the eggs are placed in special pouches of
the body of the parent, in which they are hatched. The free-
swimming larve of the other Hchinoderms pass through a series
of remarkable changes (Figs. 4 and 5) ; these are illustrated by the

Developing larvee.
Pluteus. Bipinnaria.

twelve models of various forms of larve exhibited in Case 36; in
Case 35 is a set of models showing in detail the changes under-
gone by a single species (Asterina gibbosa). A portion only of the
body of the larva is converted into the substance of the perfect
animal; the rest is either absorbed by the growing animal, or
shrivels up and disappears.

Below the twelve models in Case 36 may be seen a representation
of three stages in the history of the Feather-star (Antedon bifida).
The larvee of this Echinoderm are not free, but are attached by a
stalk (Fig. 6); in the common Feather-star and other Comatulidee
the stalk is found during larval stages only ; in others, such as
Pentacrinus, it persists throughout life.

The presence or absence of this stalk has been taken as the first
character of importance in the classification of Hchinoderma which
may be divided into two groups :—

A. Pretmatozoa,* or Echinoderms provided with a stalk through-

* From the Greek pelma = a stalk.

12 STARFISH GALLERY.

out life or in the larval stages only. To this group belong the
Crinoidea, and the extinct Blastoidea, and Cystidea.

Fig. 6.

Pentacrinoid stage of Antedon rosacea.
a, arms; b, basals; 7, radials; s, stalk.

B. Ecurnozoa, or Echinoderms without stalks at any time of
their existence. To this group belong the Asteroidea, Ophiuroidea,
Echinoidea, and Holothuriovdea.

CrINoIDEA.—This Order may be described as stalked, globular,
or cup-shaped Echinoderms, in’ which the oral surface of the calyx
or disk looks upwards, and in which five jointed and generally
branched rays arise from the central disk. Their joints have jointed

ECHINODERMA. 113

pinnules at their sides, and the sucking-feet have the form of
tentacles.

The stalked representatives of this Order (714-732) are placed on
tables and brackets near the south door, and are worthy of being
particularly noticed for their fine preservation, size, and beauty.
The largest specimen of Pentacrinus decorus (717-719) was taken
on a telegraph-wire, to the covering of which the stalk of the Crinoid
is still attached. Metacrinus (726-729) is a more lately discovered
genus, which appears to be confined to the eastern seas.

A few dried unstalked Crinoids are shown in Table-case 1 ;
these show the leading modifications of structure in the two great
genera Antedon (270-274, 276) and Actinometra (277, 278).

ASTEROIDEA.—This Order comprises Hchinoderms with a de-
pressed body of pentagonal or star-like shape, to the ventral surface
of which the ambulacral feet are confined. The rays are more or

Comet form of Linckia.

less elongate movable arms, with skeletal structures, which consist
of transversely arranged, paired, calcareous plates, articulated with
I

114 STARFISH GALLERY.

each other like vertebree, the series extending from the mouth to the
end of the arms. The groove in which the ambulacral feet are
arranged is uncovered.

Typical specimens of this Order are exhibited in Cases 2 & 3, in
which the great variety of form in the genus Asterias (283, 286-292)
and beautiful examples of Acanthaster (295) are shown. Cases 6 & 7
contain specimens illustrating the curious habit of self-mutilation
possessed by so many Echinoderms. Specimens (317-324) illustrate
the power possessed by some Starfishes of throwing off their arms, and
forming from each separate arm a new individual. The end of the
arm nearer the disk is capable of giving rise, by budding, to a fresh
central disk, and to four or more arms. From the appearance
presented by such Starfishes in an early stage of the process, the
term Comet-form is usually applied to them.

It is not known whether the setting free of an arm requires an
external stimulus, but it is obvious that this process of reproduction
- is of great advantage to the species; it may, moreover, be noted
that it is seen at its best in forms that have no protecting plates, or
defensive spines; it has not, in other words, been observed in
Pentaceros (361-370) or in Astropecten (390-401). Cases 9-11
contain a fine series of Pentaceros.

OPHIUROIDEA, or “ Brittle-stars.”—These Echinoderms appear to
resemble the ordinary Starfish * ; but they differ in having the organs
of digestion, respiration, and reproduction confined to the disk, the
arms having merely the function of locomotor organs. The arms
therefore are more slender and cylindrical in form, and are sharply
distinct from the disk; the separate joints consist of two central
ossicles, which leave only a narrow canal between them, and these are
covered above, below, and at the sides by specially developed investing
plates ; the lateral plates bear spines, which are always comparatively
short and delicate, as compared with the spines found at the sides of
the arm in starfishes.

The ambulacral ossicles appear to be formed on three types. The
simplest condition is that in which one surface of an ossicle has two
pairs of slight convexities, and the opposing surface of the neigh-
bouring ossicle has two pairs of slight concavities. This allows of
a moderate amount of movement of the ossicles, while uniting the

* The Asteroidea and Ophiuroidea may be united under the name Stelli-
formia.

ECHINODERMA. iLL)

whole series of each arm into an articulated organ. In some others
the faces of the arm-joints are saddle-shaped, and admit of the
arms being coiled and twisted, as in Astroschema. These conditions
may be known as Streptospondyline.

The OpHiurorps that possess the simpler streptospondyline type
of ossicle never have branched arms, and to them the term Strept-
ophiurae may be applied ; those that have saddle-shaped ossicles tend
to have branching arms, and may be called Cladophiurae.

In the great majority of Ophiuroids the extent to which the
arm-ossicles can be moved on one another is much reduced by the
development of processes and corresponding cavities, which limit the
motions of the arm-joints in very much the same way as do the
zygosphenes and zygantra of a snake’s vertebral column. These,
then, are known as the Zygophiurae.

The principal types of this Order are exhibited in Cases 17-22 ;
the most exquisite of them are the forms whose arms are divided and
subdivided till they end at last in the finest threads, as in Astro-
phyton (481-486), the so-called Basket-fish or Gorgon’s heads.

Ophiacantha vivipara (438) carries its young about with it,
and they grow into the adult condition without passing through
a free larval stage.

The EcHrnorpkEA (489-711), or “ Sea-Urchins,” are Echinoderms
of a globular, heartshaped, or flattened form in which the rays are
not free arms; the primitive possession of five rays may be seen
even in those which, like the Heart Urchins, appear to be bilaterally
symmetrical. The calcareous covering generally consists of a series
of closely applied plates which form a continuous test ; at the upper,
or apical, pole there are five radial and five interradial plates, and
five pairs, or more, of calcareous plates are found on the membrane
which borders the mouth.

The Echinoidea are either (1) Regular, when the vent is at the
opposite pole of the body to the mouth, or (2) Irregular, when the
vent is more or less posterior in position.

The regular Echinoidea have or have not external gills in the
form of five pairs of folded outpushings of membrane set in slits
round the margin of the mouth (488, A); such as have them are
known as the Ectobranchiata. Those in which there are no external
gills are the Endobranchiata, and they always have well developed
sacs connected with the mouth which appear to be internal gills
(488, B), and are called, after their discoverer, the Organs of Stewart.

I 2

116 STARFISH GALLERY.

The Cidaridee (489-495) are the only known living Endobran-
chiata. Other distinctive characters of the family are the large size
of the apical area (488, C); the auricles (488, D) to which the
Lantern of Aristotle is attached, are incomplete, or do not meet in
the middle line, and they are placed in the interradial areas. The
membrane (488, E) which bounds the mouth is covered by a large
number of both radial and interradial plates of small size. The
perforated radial plates remain separate, and do not form compound
plates as in most Hctobranchiata.

The EcropraNCHIATE EcHINorps (496-611) are divisible into
several groups, but all have external gills, radial auricles, and radial
plates only on the mouth membrane. Some have the apical area
large, and some possess the Organs of Stewart.

The ARBACIIDA (498-502) differ from the Cidaride in being
ectobranchiate, and from the Echinothuriide in having only five
pairs of buccal plates (decalepid series).

The SaLentIDaA (497) resemble the Cidaridze and the Echino-
thuriidz in having, as a rule, simple plates in the ambulacral regions.
In all other regular Echinoids several of the separate primary plates
are set in an arc, or fuse to form a compound secondary plate.

The EcHINOTHURIID® (496) differ from all other Ectobran-
chiata in having more than five pairs of plates on the mouth mem-
brane, but they differ from the Cidaridz in not having interradial
plates carried on to that membrane. The Organs of Stewart are
sometimes large, sometimes lost. The test is thin and flexible, and
the paired plates overlap one another, so that the creature is able to
change in form. For evidence that the genera of this group are
extremely specialised and not primeval forms, see Prof. Gregory,
Quart. Journal Geol. Soc., vol. li.

The Ecuinrp@ have the auricular arch complete, the apophysis
of the jaw is united in the middle line, the internal gill is generally
altogether lost, and three or more primary unite to form a secondary
plate.

These may be strengthened by a process of interlacing, and
illustrations of sections through the test of a Temnopleurid (554) are
given to show the knobs and depressions, by means of which the

ECHINODERMA. i197

constituent plates of the test are the more firmly united. (For details,
see Prof. Martin Duncan, in Journal Linnean Society, vol. xvi.
past):

Some, for protection, when exposed to great waves live in hollows
of the rocks, and a fine photograph shows Purple Sea-Urchins
(Strongylocentrotus lividus) (596) in hollows made by them in lime-
stone rocks, Bundoran, South Donegal.

The Irregular Hchinoids (613-711) are distinguished from the
regular forms by never having the vent at the pole of the body
opposite to the mouth, but posterior to it; it is also interradial in
position.

The mastigatory apparatus (Lantern of Aristotle) is reduced or
lost ; in the former case the Urchins are known as Gnathostomata,
and in the latter as Nodostomata.

The GNATHOSTOMATA (613-710) are largely fossil ; they have a
central mouth with teeth and jaws, the ambulacra are simple or
petal-like, and are all similar.

The Nopostomata (652-711) have the mouth either central or
pushed forwards, and there are no teeth or jaws. The circular form
of the regular Echinoid is often hidden by a bilateral symmetry
produced by a special modification of the anterior ambulacrum.

The genus Hemiaster (707) offers an example of an Echinoderm in
which the eggs are laid in special pouches ; the hinder ambulacra are
deepened to form pits, which are guarded by specially elongated
spines (see Case 34); in these pits the young pass through all the
stages of their development.

The minute structure of the spines of Sea-Urchins is illustrated
by a series of figures on the wall (713).

The HoLoTHURIOIDEA, or Sea-Cucumbers, form the last order of
Echinoderms. Their body, as indicated by their English name, is
elongate, subcylindrical, with a more or less flexible integument,
according to the extent of the reduction of the calcareous skeleton ;
the mouth is at one end of the body and surrounded by tentacles,
the vent at the opposite end.

As these animals cannot be shown in a dried state, some of them,
preserved in spirit, are placed in Wall-Case TV. (150-188). According
as they have or have not the sucking-feet of the Echinoderma, they

118 STARFISH GALLERY.

are ordinarily divided into the Pedata and the Apoda; the latter
are represented by Synapta, which may attain to a great length, and
by Chiridota ; the Pedata are illustrated by the genera Cucumaria,
Psolus, and Holothuria. Deep-sea investigations have revealed the
existence of another group of specially modified Holothurians—the
Elasipoda; these are remarkable for their well-marked bilateral
symmetry and the distinctness between the dorsal and ventral
portions of the body ; the prominent processes on the dorsal surface
are not contractile.

An exhibition of some interest is to be found in a Table-Case
against the wall (189-219), in which there are various specimens of
the edible Holothurians—trepang or béches-de-mer; these were all
bought in the market at Canton, and may be taken to be typical
of the kinds offered for sale in various eastern countries.

( U9 -)

WORMS.

By the name ‘ Worms,” people commonly indicate a number of
different forms whose relations with one another are by no means
so close as those of a Holothurian and a Crinoid, or a Mussel and
an Octopus. There are not, indeed, any common characters by the
possession of which the worm-like animals can at once be distin-
guished from other animals. We take the divisions, examples of
which are here represented, either by drawings, models, or specimens
preserved in spirit separately.
The groups referred to may be enumerated as follows :—

Platyhelminthes.

Nemertinea.

Nematoidea.

Chetopoda.

PLATYHELMINTHES, or Flat-Worms.—These form the lowest and
simplest division of the group; they never have bristles, and are
often parasitic in habit. The parasitic have been derived from free
forms, but parasitism is a habit that leads to great changes in
structure ; the Tapeworm, for example, has no mouth.

They are divided into—

I. Turbellaria, free Flat- Worms (1, 2, 36, 37).
II. Trematoda or Flukes (29-35).
III. Cestoda or Tapeworms (8-28).

The parasitic Platyhelminthes—the Tapeworms (Cestoda) and the
Flukes (7rematoda)—occupy Case I. ; the life-history of the common
Tapeworm (7wnia soliuvm) is shown by the aid of models and figures.
A model of the anterior end of the common Tapeworm shows the
four suckers and the crown of hooks; the unjointed neck is followed
by the joints (proglottids), which increase in size the farther they
are from the neck. Several entire specimens of Tania follow,
showing the size of the whole worm and the form of its joints.
The structure of the body is shown in the models of two joints.
The growth and development of the Tapeworm is dependent on a
migration or a change of the hosts which it inhabits in the various
stages of its life; and although the different kinds of Tapeworm
differ from each other somewhat in certain details of their migration
and development, their life-history exhibits, on the whole, the same

120 STARFISH GALLERY.

events which we find in Tenia solium, a common Tapeworm of man
in Northern Europe (9-15). This worm is matured in the intestines

Txnia solium: showing the
head (h) with its suckers
(s’) and crown of hooks
(s), the unjointed neck
(m), and a few of the
succeeding joints (7).

of man ; its final joints consist merely of
fertilized ova which have already passed
through the earlier stages of development ;
when the joints are detached and dis-
charged, their contents escape in the form
of embryos contained in a thick chitinous
shell. If these are now swallowed by a
pig, the shell is digested by the gastric
juices of the new host, and a rounded
embryo, which is provided with three
pairs of hooks, is set free; by means of
these hooks the guest makes its way
through the wall of the stomach or
intestine, and finally settles down in the
muscles of its host. The embryo now
loses its hooks, and gradually acquires a
bladder-like form, the central cavity of
which is filled with fluid. This bladder-
worm (Cysticercus) has its outer wall
pushed inwards at the anterior end, and
on this hooks and suckers become de-
veloped. We have now a narrow head
and neck with an attached bladder, the
head being at this time hollow. If during
the long time that these bladder-worms
remain alive, the pig is killed for food,
its flesh is found to be ‘‘ measly”; if it
is afterwards insufficiently cooked and
eaten, the worms are conveyed into the
human stomach. Here the bladder-like
termination becomes absorbed, and, the

neck beginning to grow, we have the commencement of the form
from which we started, and the completion of that “vicious
circle ” which is so curious a characteristic of many forms of parasitic

life.

In other Tapeworms the cyst may be more complicated than that
in the pig, as, for example, the form found in the sheep’s brain (25)

or the liver of the horse.

Of the other Cestode parasites mention should specially be made

WORMS. 121

of those of Fishes; the vulgar notion that the parasites of these
animals are dangerous to man has been shown to be entirely
erroneous.

The Flukes infest animals of all kinds; that which is most
dangerous to sheep, and the cause of much pecuniary loss (Déstoma
hepaticum), is selected here asa type; its structure is shown by a large
model (32), and its life-history by a series of diagrams (Figs. 10-13).
Here, again, we have a creature which infests two hosts. If the
larvee which escape from the sheep fall on wet
ground in or near a pool, they make their way :
to a small pond-snail (Limnea truncatula, Fig. 9), jar
into the lung-chamber of which they bore their We
way. On leaving them the larva may be, and pemnea truncatula.
is, too frequently, eaten by a sheep, and makes
its way into the liver of that animal, where it causes the disease
known as the “liver rot.”

The damage done by the liver-fluke may be imagined from the
fact that in the winter of 1879-80 no less than three millions of
sheep died of rot in the United Kingdom ; this heavy loss is no
doubt largely due to the immense number of eggs to which a single
fluke may give rise. It has been estimated that every fluke may
produce, during its life, several thousands of eggs ; and in one case
Prof. A. P. Thomas found as many as 7,400,000 eggs in the gall-
bladder of a sheep which was suffering from rot, and which, at that
time, had in its liver about 200 flukes.

The non-parasitic Flat-worms are shown, magnified, in the upper
parts of Cases I. & II. The Twrbellaria proper, without any or
with a simple or a branched intestine, but without a vent, are
represented by Convoluta and Thysanozoon : the general structure is
shown by a diagram in Case II., which is here reproduced (Fig. 14).
Planaria, Thysanozoon, and Bipalium serve to illustrate the forms
of members of this group.

The Nemertine Worms (Nemertinea), with a straight intestine,
with a vent, and with a proboscis, may attain to a very considerable
length ; Lineus marinus, for example, varies from 15 feet to 30 yards
in length ; Carinella and Lineus are represented by large figures, and
various species are shown in spirit (88-49). These forms, which used
to be very unsatisfactory to exhibit, on account of the great difficulty
of preserving them complete and uninjured, are now, with improved
methods, very satisfactorily shown, as the specimens purchased from
the Marine Biological Laboratory at Plymouth prove.

Fig. 9.

aun

12? STARFISH GALLERY.
Fig. 10.

Nit

On|
SO.

)
MOO Z. ~Cs
<0) |

Stages in the life-history of the Fluke.
Fig. 10. Ege of Fluke, showing the operculum and the contained yolk-spheres.
Magnified 340 diams.
Fig. 11. An embryo forcing its way by its boring-papilla (p) into the wall of
the lung of a Snail (e.p). Magnified about 340 diams.
Fig 12. A young Redia (natural size, } millimetre or #4, inch): pl, pharynx ;
g, contained germs; , characteristic posterior processes of the Rédia.
Fig. 13. Free-swimming Cercaria, before the commencement of the formation of
the cyst. Magnified 100 diams.

ei ae

7

WORMS. 23

Nematopes (Thread-Worms or Round-Worms).—These are for
the most part parasitic, and infest plants as well as animals; the
common Round-Worms living parasitically in man (Ascaris, Stron-
aylus, Trichocephalus) belong to this Order (50-72). Sometimes they

Fig. 15. Fig. 16.

(xe)
iD
eG

il

Fig. 14. Diagram of the structure of a Turbellarian: ng, nerve- (cerebral)
ganglia; nb, nerve-branches; yg, yolk-glands; t, testis; 0, ova; ov, ovary ;
¢, cirrus; m, mouth; ph, pharynx.

Fig. 15. Diagram of a Nemertine: b, brain; m, mouth; m, renal organs ;
id, diverticula of intestine; g, gonads; sn, side nerve-trunk; pr, proboscis in
its dorsal sheath.

Fig. 16. Diagram of the structure of a Nematoid; m, mouth; ph, pharynx ;
a, anus; 0, orifice of genital tube.

are parasitic in their early stages and later live a free life—such are
Gordius and Mermis. A specimen of a Mantid is exhibited from which
half the body of the infesting Gordius (70) has already protruded
(Fig. 17). One of the most remarkable Gord#i is the great elongated

STARFISH GALLERY.

124
G. fulgur, or “ Lightning Snake,” from Celebes (72). Another very
large Nematode is the so-called Guinea-worm, or Dracunculus
Fig. 17.
\i

Gordius escaping fone Mom
medinensis (64), which is found beneath the skin of the leg ; itis very
possible that this worm was the cause of the illness which afflicted the

Israelites in their journey through the desert from Egypt to the

Promised Land.
Fig. 18.

7 TT
Do OMNI
Dahm AMAT

at

nu

a

a

A)

ANDAMAN

fund)

iu

nD

piralis, showing the worms encysted in muscle.

G3

Figure of Trichina s
Of all Nematodes the most dangerous to man is the small worm
which is known as 7’richina spiralis (Fig. 18); a series of models are

WORMS. 125

shown which give a good idea of the structure of the female and the
smaller male (78). The young make their way through the walls of
the stomach of their host, and encyst themselves among its muscles : a
piece of a sternothyroid muscle is shown (59), taken from a man in
whose body it was calculated there were forty millions of encysted
Trichine.

Other Nematodes infesting man, such as Faria sanguinis
hominis, are too small for exhibition.

Plants are not free from the attacks of Nematodes, and examples
are shown, accompanied by an illustrating fieure, of the Ear-cockle
gall of wheat (66); this gall is due to the injuries inflicted by a
minute Thread-worm—Tylenchus tritici. Wheat is, of course, by no
means the only cultivated plant that is attacked by these minute
worms ; the history of most has, however, still to be made out.

Holding a somewhat uncertain position in relation to the Round-
worms are the parasitic Acanthocephali (Thorn-headed Worms) (73,
74) and the free-swimming Chetoygnatha, or Bristle-jawed Worms
(75, 76); examples of both of these groups are shown, together
with diagrams illustrative of their general structure.

ANNULATA or Cheetopoda.—So-called because consisting of a
series of rings, and being provided with cheete or bristles; they
are to be associated with the Arthropoda, under the one head
“ Appendiculata,” a better name than “ Articulata,” since Cuvier did
not include worms in his group. The creatures that are most
familiarly called worms are to be found in Case III.; here area
few examples of the numerous kinds of worms that are found living
freely in the sea, of earth and freshwater Worms, and of Leeches.
All these worms are distinctly characterized by the fact that they
consist of a number of definite rings (somites), whence they have
been called Annulata. The marine Worm and the Earthworm differ
from the Leech in that these rings are provided with cheete or
bristles, of which there are a number in each bundle in the marine,
and a few only in the terrestrial or freshwater form: hence the
marine Worms are called Polycheta and the latter Olugocheta.

The former are divisible into two great groups. There are those
that are free-swimming and are able to forage for themselves, such
as the lovely Sea-mouse (Aphrodite aculeata) (96), the large Halla
parthenopera (87), the common Nereis pelagica (104), or the exquisitely
coloured Chloeia fava (100). Others live a more retired life, dwelling
_ in tubes, which they fashion for themselves ; they lead either a solitary
or asocial life. Here we have examples of Terebella (226), Sabellaria

126 STARFISH GALLERY.

(224), Serpula (249); a number of forms of worm-tubes, showing

their great variety and beauty (see especially the delicate Filograna)

(239), are to be seen in the small Table-cases placed against the north
Tig. 19.

Home of Panthalis oerstedi.
wall of the Gallery. Attention should be especially directed to Mr.
A. T. Watson’s beautiful preparations of Terebella littoralis (226).
Fig. 20.

Section across the body of an earth-worm to show the disposition of the more
important organs; the body wall (2) consists cf dermis, circular, and longitu-
dinal muscles; the body cavity is divided by membranes (c) into a series of
chambers, in each of which opens the mouth of a coiled nephridium (m). The
axis of the cavity is occupied by the intestine (7); above and below it isa
longer blood-vessel (v), and below it is also the central nerve-cord (ne).

We givea figure (Fig. 19) after a drawing by that gentleman of the
home of Panthalis oerstedi, the tube-forming habits of which have
been carefully observed by him.

WORMS. 127

The Oligocheta are represented by the common Harthworm
(92), the influence of which in the formation of mould and in the
general ploughing of the soil was carefully investigated by Mr. Darwin,
and by a few other worms (122-127) ; the little Tubifex rivulorum
(Bloodworm), which owes both its red colour and its ability to dwell
in mud, which is so poor in oxygen as to be unfit for respiration, to
the same chemical compound as that which gives the red colour to
our blood and carries the oxygen of respiration all over the body.

The Hirudinea, or Leeches, are often said to be distinguished
from the Chetopoda by the absence of bristles; but, as a fact,
Acanthobdella (Figs. 21 and 22) has very well marked bristles. They

Fig. 21. Fig. 22.

Acanthobdella: e, eyes; ch, cheetee ; s, sucker.

always have asucker at the hinder end of the body by which they are
attached to their prey ; they are found in fresh water (Pescicola), on
sea-fishes (as Pontobdella), or in moist places, as the Leech (Hirudo)
(130-134). The last-named has three jaws, armed with as many

128 STARFISH GALLERY.

as ninety denticles. Trochetia subviridis (land-Leech) (96) is a
species which is found rarely and sporadically in England.

The Myzostomata (128, 129) form a division of Polycheeta, all the
members of which live parasitically on Crinoids, and otherwise present
great differences in their habits. Some move about freely on the
Crinoids they infest, others are more sluggish and rarely move,
others produce galls or cysts on their host, and yet others are internal
parasites, and live in the alimentary canal. It is of interest to
note that there are corresponding degrees of difference between the
young and old specimens of the different groups of species.

The general organisation of Myzostomata is shown in the
accompanying figure (Fig. 23) in which the dorsal wall of the body

Diagram of Myzostomum to show the general form of the body and the marginal
extensile cirri (¢); within these and on the ventral surface are four pairs of
suckers, and more internally five pairs of appendages each bearing two
hooks; the proboscis (p), the digestive tract and its ramifications, and the
reproductive organs are outlined as if seen through a transparent wall ;
a, anus.

is supposed to be transparent so as to allow of the chief internal
organs being seen.

WORMS. 129

The last group of Worms here represented is that of the
Gephyria (94, 1385-144); with the advance of our knowledge it is
probable that they will be found to be more intimately allied to the
Annulata than is now generally supposed; it will be seen indeed
that Lchiurus has bristles at its hinder end ; Sipunculus is the best
known representative of the unarmed Gephyria ; Bonellia is inter-
esting both from the fact that it owes its green colour to a matter
closely resembling the chlorophyll of green plants, and from the
possession by the female of a proboscis, which is protruded from
the hole in the rock occupied by the worm : the male is very much
smaller than the female, and is not nearly so well developed. Owing
to the mode of lighting the Gallery, the visitor may have to shift
his position several times before gaining a good view of the whole
length of the proboscis.

PAGE
ACANTHASTER . 114
Acanthobdella 127
Acanthocephali 125
Acmeide . 9
Actinometra 113
Adeonide . 66
/Jitheriide . 39
Aleyonidium . 67
Amaroucium . 99
Amathia 67, 68
Amphineura 7-9
Ampullariide . 14
Ancylus 27
Annulata . . . 125
Anodonta . 0 ae)
Antedon 111-113
Aphrodite . 5 | LBS
Aplacophora 9
Aplysiide . 23
Apoda . a oo UNG
Appendiculariide. 105
Apple-Snails . 14
Architeuthis 48
Argonauta . 46
Ascaris . 123
Ascidia 83, 93
Ascidiacea . 5 0
Ascidise Composite: 96
Ascidize Salpi-
formes 6 o
Ascidiz Simplices. 90
Ascopodaria 73
Astartide . 37
Asterias 108, 114
Asterina ote: JUL
Asteroidea. . 112,118
Astrophyton 115
Atlantide . 22
Auger-shells 21
Auriculide 26
BARTLETTIA 39
Basket-fish. 115
Basommatophora . 26

facso1e

INDEX.

nd

PAGE

Béche-de-mer . 118
Bipalium 121

Bird’s head Coral-
liner 2Bige vie oe 58

Bladder-worm . 120
Blastoidea . 112
Blood-worm Seal:
Boat-shells. . . 20
Boltenia 91, 92
Bonellia 5 dee)
Borer. pe, ca eee to
Botryllidee 96, 97
Botrylloides . . 97
Botryllus 97, 98
Bowerbankia . . 67
Brachiopoda 74-82
Brechites . . . 44
Bristle - jawed
worms . 125
Brittle Stars 114
Bubble-shells .. 23
Buccinide . 18, 19
Bugula . 58, 59
Bullid=eeceecnaes 3
CABEREA . . . 62
Calamaries. . . 4
Calyptreide . . 14
Cardiide . . . 40
Carditidse . . . 37
Carinariide . . 22
Carinella 121
Carrier-shells . . 17
Cassidide . . .18,19
Catenicellide . . 66
Cayvoliniay eases 23
Cellularina. . . 58
Cephalopoda 45-50
Cerithiide . . . 17
Cestoda 119
Cestode parasites . 119
Cetoconchide . . 45
Chetoderma . . 9
Chetognatha . 125

PAGE
Chetopoda. . 119,125
Chama; <0 4a) eel
Chelyosoma . . 98
Chilostomata . . 57
Chiridota . . . 118
Chiroteuthis . . 47
_Chitonide. . . 7,8
Chloeia 125
Cladophiure . . 115
Clams:.) =. Saal
Clavagellide . . 44
Clavelina . 94,95
Clayelinide . . 94
@hione. . 5 2 24
Coat-of-mail shells 0
Cockle. . . . 40
Colella . 97, 98
Comatulidse Thal
Comet-forms . 114
Conchologists. . 17
Conidz emis. 2a
Conyoluta. . . 121
Coralliophilide . 20
Corbula. . . . 42
Cowries 2.5) <0 nl:
Crania . . .74, 80
Creeping Coralline 60
Cro, ¢ . o 4
Crinoidea . 112
Crinoids 109
Cristal eS
CGmmmcks 5 5 . GY
Cristatella. . .71, 72
Cryptochiton 8
Cryptoplax. . . 8
Ctenostomata . .57, 66
Cucumaria . 118
Quiles o .o . $B
Cup - and - saucer
IOINOENS 5 6 5 A
Currant Squirter . 92
Cuspidariide . . 49
Cuttlefish:
Cyclophoride . . 13
Cyclostomata . .57, 68

PAGE
Cynthiide . 91
Cypreide . 14
Cysticercus 120
Cystidea 112
DENTALIIDH 28
Desert-snail 6
Diazona 94
Dipsas . 39
Diseinids . 80
Distoma alt
Distomide . 96
Doliide ees 18
Doliolidze - 100, 103
Doliolum 90, 103
Dracunculus 124 |
Dyscolia 82
Ear-cockle gall 125
Ear-shells . 2
Earth-worms 5 D7
Wehinoderma . 106-118
Hehinoidea. . 112,115
Echinozoa . 112
Echiurus 129
Ectobranchiata 115
Ectoprocta o7
Elasipoda . 118
Electra 62, 63

Elephant - tooth

shelly) 1
Endobranchiata 115
Entoprocta. 57, 73
Escharina . 64

Eulamellibranchia 36
Euthyneura

Fase Limpets g
Fan-Mussel . . 38
Fan-Shells 35
Fasciolariide . 18
Feather-star TL
Wilaria. . 125
Filibranchia 32
Filograna . 126
Fissurellide 11
Flat-worms 119
Flukes . 12 122
Flustra. 04, 62
Flustrina 62
Fountain-shell 17
Fredericella “Al
Freshwater. Lim-

PetSmeraee- snes) eli

INDEX.
PAGE
Freshwater Mus-

selsic a; 38
Freshwater Oyster 39
Freshwater Poly-

WAU) ase 70
Freshwater Snails 7, 26
Freshwater Worms 125
CAS gg to
Gastropoda . 9-28
Gephyria . 129
Giant Clam 41
Glassy Nautilus 22

“Glory - of - the -

Sea” Cone . 21
Glottidia 78
Goodsiria . 99
Gordius 123, 124
Gorgon’s head . 115
Guinea-worm . 124
Gymnolemata. o7
Gymnosomata . 24
Hatrotripz . . 12
Jee 5 5 op NS
Hammer Oyster . 33
Harpidee 20
Harp-shells 20
Helicidze 27, 28
Helmet-shells . 18

| Hemiaster . TWISTS wate
Heteropoda 22
Hippuritidee 41
| Hirudinea . 127
Hirudo. . a lee
Holothuria . 107,118

Holothurioidea 112,117 |

TANTHINIDZ 16
Kdmonea) ys 69
JULINIA

KeyHoLe Limpets 11
Kinetoskias .09-61
Kuphus 43

LAMELLIBRANCHIA 29-45

Land Snails 26
Larvacea 104
Leeches 127

98 |

TAGE
Lepralia 64
Leptoclinum .98, 99
Lichenopora 69

| “Lightning-

Snake” . 124
Lily-Encrinites 110
Limide. Sh Geol
Limnea trunca-

tula . 121
Limneide . 26
ILO 6 a 6 g)
Limpet Snails . 26
liane) 5g Ul}
Lineus . Seal

| Lingula 74, 75, 77-79
Lithodomus . . 33
Littorinidse 14
Liver-fluke 121
Loligo . 46
Lophopus . 71, 72
Loxosoma . 73

- | Lucinide . 38
Lunulites . 64
MactTRID® . 40
Magellania. “75, 77, 82
Magilus 20
Malleust ery nae 3
Margaritana a) ee
Margaritifera . .33, 34
Marine worms. 125
Melaniide . Ie
Melons . 20
Membranipora 63

| Mermis 123

| Metacrinus. 113
Mineralogists . 17
Mitridee 18
Molgula 91
Molgulidz 90
Mollusca 1-53

| Money-Cowry . 15
Moss Animals . 56
Mucronella 65

| Miilleria 39, 40
Muricidee 20

| Mussels ee oo
Mussels (fresh-

SE) cg a o Be)
WAGES G6 6 og See
Mytilide . . . 33
Myzostomata . 128
Nakep-gilled Mol-

luses . : 24
Natica . 5 LS
Nautilus .45, 49

132

PAGE
Nematodes. . 119, 123
Nemertinea 119, 121, se
Neomenia .

Nereis . oe
Neritidee 13
Non parasitic
Worms 121
Nucleobranchiata . 22,
Nuculide . . . 31

Nudibranchia . .23, 24

OCTACNEMID® . 100
Octopus . 46
Oikopleura. . 104,105
Oligocheeta 125, 127
Olivide. 20)
Ophiacantha . 111,115
Ophiuroidea 112, 114
Opisthobranchia . 23
Orange Cowry. 15
Ormers . 2,
Ostreidee 37
Ovulide 15
Oyster . 36
PANTHALIS. 126
Paper-Nautilus . 46
Ratellaye = seamen 9
Pearl-Oyster . 33, 34
Pearly Nautilus 00
Pectinibranchia . 13
Rectinidsca-se aaa

Pedata . 118
Pedicellinidee . 73
Pelmatozoa 111
Pentaceros. . 114
Pentacrinus . 111, 113
Periwinkle. 14
Perophora . 95, 96
Phallusia . o | «OB
Pharyngodictyon .98, 99
Pholas a7 43
Phylactolemata 70
Piddocks 43
Pinna 37, 38
Piscicola 127
Planaria . eli
Platyhelminthes o dlil)
Pleurotomaria 11
Pleurotomide.. 20
Plumatella Ti, 7
Polycheta . 125
Polyclinidse o Oe
Polyplacophora . 7
Polypus . 46
Polyzoa 04-73

Pond-Mussel . . 5

INDEX.

Pond-Snails
Pontobdella
Poromyide.
Poulp
Proneomenia .
Protobranchia .
Psolus .
Pterocera
Pteropoda .
Pterotracheidee
Pulmonata.
Purpura
Pyrosoma .

RADIOLITIDA .
Razor-shells
Retepora
Rhodosoma
Rhopalea ..
Rhynchonella .
River-Snails
Rock-shells
Round-Worms.

SABELLARIA
Saddle-Oysters
Salpay 90)
Salpide

Scala

Scallops
Scaphopoda
Schizoporella .
Scorpion-shells
Screw-shells
Scrobiculariidee
Scrupocellaria .
Scutibranchia .
Sea-Butterflies

125

32
100-103
100

17

60, 62
9
93

Sea-Cucumbers 106, 117

Sea-Hare
Sea-Lilies .
Sea-Mat
Sea-Mouse .
Sea-Slugs .
Sea-Urchins
Sea-Woodlice .
Selenariidee
Semele .

Sepia

Sepiola .
Septibranchia .
Septidee
Serpula.
Ship-worm .
Silk Coralline .
Siphonariide .
Sipunculus. .

.23, 24

106

- 106, 115

PAGE
Slipper-Limpets 14
Slit-Limpets 11
Slugs 28
Snails . 27
Solenidee 42
Solenomyida . 31
Spatangus . 109
Spirula.. 49
Spondylidee 36
Squid 46

Stalked Crinoids 1] 110, 112
Starfishes . . . 108

Stichopus . 107
Streptoneura . . 9
Streptophiure 115
Strombide . V7
Strongylus 120
Styelopsis . 92
Stylommatophora . 27
Synapta SL ONee ats
TANIA . O20
Tapeworm . 119
Tectibranchia . 23
Tellina. 40
Terebella . 126
Terebratula TA, 82
Terebratulina . 82
Terebride . 21
Teredo . 43, 44
Testacella . 28
Tethys . 24
Thaliacea . 100
Thecalia 37
Thecidium . 81
Thecosomata . 23
Thorn - headed
Worms . . « 125
Thorny Oysters . 36
Thread-worms. . 123
Thysanozoon 121
Tooth-shells 28
Top-shells . 12
Trematoda 119
Trepang 118
Trichina ; 124
Trichocephalus 123
Tridacnide 4]
Trigonia 33
Trochetia . 128
Trochide 12
Trumpet-shells 18
Tubifex 127
Tubulipora 69, 70
Tunicata 83-105
Tun-shells . 18

Turbellaria 119, 121, ue
Turbinide . 3

Turritellidee
Tylenchus .

UMBRACULID2.
Umbraculum .
Umbrella-shells
Unionide .

VENERIDZ .
Venus-shells
Vermetide.

INDEX.

Verticordiide .
Vesicularia.

| Violet Snails .

Viviparide.
Volutes .
Volutide

Water-Clams .
Watering pot-shells
Water Spondyli
Weaver’s-shuttle .
Whelk .

PAGE
Window-shells . 32
Wing-shells . . 33

Winks 6s sm.) ae 14
Worms). see) LG=029
Worm-shells . . iL7/
Worm-tubes

XENOPHORIDE. . 17

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A guide to the shell and starfish galler

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