823
IS 73

UC-NRLF

DDM

THE LIBRARY

OF

THE UNIVERSITY
OF CALIFORNIA

PRESENTED BY

PROF. CHARLES A. KOFOID AND
MRS. PRUDENCE W. KOFOID

ILLUSTRATIONS

OF

COMPARATIVE ANATOMY,

VERTEBRATE AND INVERTEBRATE,

FOE THE USE OF STUDENTS IN THE MUSEUM OF
ZOOLOGY AND COMPARATIVE ANATOMY.

SECOND EDITION.

AT THE UNIVERSITY PRESS.

; CAMBRIDGE WAREHOUSE, 17, PATERNOSTER Row,
: DEIGHTON, BELL, A^7D CO.

1875.

Cambridge :

PRINTED BY C. J. CLAY, M.A.
AT THE UNIVERSITY PRESS.

PKEFACE.

THE specimens and dissections described in the following
pages have been prepared to illustrate the most important
forms in Invertebrate and Vertebrate Anatomy.

When the first edition of these descriptions, entitled 'List
of Dissections/ was published in 1871, Invertebrate Anatomy
alone was illustrated. We have now included four representa-
tive Vertebrate forms — Rat, Pigeon, Frog, and Perch : and
have increased the series of Invertebrata from 55 to 90; adding
to it several specimens, with detailed descriptions, of the Exo-
skeleton in those forms where such descriptions are not to be
met with in the text-books that are commonly used by English
students.

All the descriptions have been carefully revised. As in the
former edition, we have not attempted to give a complete
account of each dissection, but merely an indication of its
leading features, to enable students more readily to recognise
the points dwelt upon in the literature of the subject, or in
lectures; and to shew them clearly the position and relation
of the organs which they will subsequently have to examine
when they begin to dissect. For this reason the very language
used by Prof. Rolleston, Prof. Huxley, and others has been

IR37Q337

IV PREFACE;

reproduced where it has been possible to do so. Our obligations
to Prof. Rolleston are however far greater than mere passages
of description, for it is to his work that our own owes its exist-
ence.

For the sake of brevity we have cited as '.Rolleston,' Forms
of Animal Life, by G. ROLLESTON, M.D., Oxford, 1870.

J. W. CLARK,

Superintendent.

T. W. BRIDGE,

Demonstrator of Comparative- Anatomy.

MUSEUM OF ZOOLOGY AND COMPARATIVE ANATOMY,
CAMBEIDGE, May 20, 1875.

ILLUSTRATIONS OF COMPARATIVE ANATOMY,
VERTEBRATE AND INVERTEBRATE.

SUB-KINGDOM PROTOZOA.

1. A piece of the common Freshwater Sponge (Spongilla,
fluviatilis), exhibiting its siliceous skeleton.

Rolleston, p. 163.

SUB-KINGDOM OELENTERATA.

CLASS HYDROZOA.

2. A Sea-Fir (Sertularia abietina).

It consists of a slender pinnately-branched 'coenosarc' in-
vested by a chitinous 'periderm.' Both the main stem and
the lateral pinnae are beset by numerous sessile or sub-sessile
more or less flask-shaped chitinous ' hydrothecae,' in which the
'polypites' are lodged. In addition to these, larger but similarly
shaped vesicles are to be observed studding the pinnae. These
are the 'gonotbecse' and contain the generative zooids. The
animal when mature is non-locomotive and is attached to its
base by a ' hydrorhiza.'

3. A Sea- Anemone (Tealia crassicornis), from which the
base has been removed. The tentacles and the space round the
mouth — ' peristomial disc ' — are too much retracted to be well
seen. On the other side of the preparation the internal surface
of the digestive cavity is exposed, marked with fine radiating
lines, which correspond with the attachments to it of the
vertical muscular lamellar plates termed 'mesenteries.' These

CL. 1

2 COMPARATIVE ANATOMY.

radiate from the outer surface of the stomach to the inner wall
of the outer integument, and thus divide the space between the
two — the body cavity — into a number of wedge-shaped com-
partments. Some of these ' mesenteries ' fail by greater or less
intervals to reach the outer surface of the stomach, and are
therefore called 'secondary' or 'tertiary' mesenteries, while
those that are attached to that organ and to the outer in-
tegument are called 'primary.' Between them are seen some
of the generative glands. The cord-like ' craspeda ' are also to
be seen, attached to the inner edges of the mesenteries.
Bolleston, p. 158.

SUB-KINGDOM ECHINODERMATA.

4. A Common Cross-Fish (Asterias rubens).

The animal consists of a discoid body, produced horizontally
into five radial prolongations. The ventral surface of the disk
is depressed into a cavity having a pentagonal outline, and
which is further continuous with the mesial lanceolate grooves
extending along the ventral surfaces of each ray. The dorsal
surfaces of the disk and rays, on the other hand, are convex and
not grooved. In the middle of the ventral surface of the disk is
the mouth: and on the corresponding part of the dorsal surface,
the anus. Protruding from the radial grooves or avenues are the
csecal tube-feet : arranged in four rows, two on either side of a
line running down the centre of each ray. There are two sets
of spines bounding each avenue, 'one of which is placed in-
ternally and consists of two rows of long and slender spines:
while the more externally placed is made up of three rows of
shorter and blunter spines.' Externally to the latter is a third
series of spines, marking the line of junction of the dorsal and
lateral surfaces. Furthermore the dorsal surface of both rays
and disk is studded with variously shaped spines, some short
and obtuse, while others carry a small bunch of calcified setae
at their free extremities. None of the spines are moveable.
On the extreme edge of the dorsal surface of the disk, and in
one of the inter-radial spaces, there is a porous elevation — the
madreporic tubercle — through the medium of which, and of the
'sand canal' with which it is in relation internally, the sea-

ECHINODERMATA. 3

water finds its way to the circular water-vascular canal sur-
rounding the oasophagus. The tube-feet being restricted to the
ventral surface of the rays and disk, that surface is distinguished
by the term 'ambulacra!' from the dorsal and lateral surfaces,
which do not possess tube-feet, and are therefore called ant-
ambulacral. Though the radial symmetry of the disk and arms
is apparently very evident, yet the animal is really bilaterally
symmetrical, thus : — the madreporic tubercle is inter-radial, and
as both mouth and anus are central, a vertical plane drawn
through tubercle, mouth and anus, will divide the animal into
two symmetrical halves, each half including two rays and one
half of the bisected ray. The two rays between which the
madreporic tubercle lies are distinguished as the 'bivium/ while
the remaining rays constitute the 'trivium.'

5. Another specimen, to shew the structure of the in-
vesting coriaceous test, and the disposition of the ossicles com-
posing it.

The whole of the disk, with the exception of that portion on
which the madreporic tubercle is situated, has been removed:
— and, with a single exception, the cavity of each ray has been
laid open by a longitudinal incision on the ant-ambulacral surface.
Four rays have been divided transversely. Each ray consists of
a solid axis and of the calcified arch supported by it. The axis
itself is composed of a longitudinal series of ossicles, apposed
to each other after the mariner of vertebrae, and forming a solid
though flexible rod extending along the ventral surface of each ray
from the mouth to the tip. Each ossicle is double — that is, it is
composed of two lateral halves, closely applied in the mesial line,
and retained in position partly by a tendinous investment — and
partly also by the longitudinal muscular fibres, which, in the
fresh condition, pass from ossicle to ossicle. Each lateral ossicle
gives off from its outer side a transverse process, which is
slightly sinuous, or emarginate on opposite sides: so that by
the apposition of the concavities of contiguous processes two
alternating rows of foramina for the exit of the tube-feet are
formed on each side of the median ossicles. The external
extremity of each of the transverse processes abuts upon a
small ad-ambulacral ossicle, which in addition to contributing
to form the prominent margin of the ambulacral groove, and

1—2

4 COMPARATIVE ANATOMY.

to supporting the innermost row of slender spines described in
the preceding preparation, also marks the junction of the
ambulacral and ant-ambulacral areas. The ad-ambulacral ossi-
cle is best seen in the transverse section. Externally to the
ad-ambulacral ossicles is a series of stout, rib-like rods, fewer in
number than the transverse processes, as there is but one of the
former to three of the latter. These form the lateral boundaries
of the ad-ambulacral region. These 'ribs' are connected with
each other by at least two well-marked rows of cross-bars on
each side; extending from one 'rib' to the other. The 'rib' is
not a single ossicle, but composed of several pieces joined to-
gether by oblique surfaces: so as to admit of some amount of
sliding motion upon one another, in order to allow the consequent
dilatation or contraction of the cavity, the walls of which they
contribute to form. Towards the dorsal region, or roof of the
ray, the 'rib' breaks up, and the pieces cross in all directions,
forming an irregular network of ossicles imbedded in the thick
integument. The first axial ossicle in each ray is much larger than
the rest : and by their abutment upon each other a strong cal-
cified ring is formed, encircling the mouth. The skeleton of
the disk in no way differs from the structure of the rays : as
it is in fact formed by the confluence of the ant-ambulacral
integument of the five rays: and the axial ossicles themselves
with their transverse processes are continued to the margin of
the mouth, and only then abut upon each other. In the fresh
state the radial ambulacral canal would lie in the ambulacral
groove immediately beneath the axial series of ossicles, and
still more superficially the radial nerve-cord: — while in the
cavity of the ray the digestive and generative systems are
contained. In the peristomial depression, and external to the
calcified oral ring, the pentagonal nerve-collar would lie. It
will thus be seen that from its relation to the nervous system
and the radial ambulacral canals, the skeleton is really an in-
ternal one, and does not correspond to the ambulacral and
inter-ambulacral plates of the Echinus, which form a true exo-
skeleton.

6. A Common Cross-Fish (Asterias rubens], dissected to
shew its digestive system.

The whole of the integument has been removed from the

ECHINODERMATA. 5

upper or anal surface. In the centre is the membranous
stomach, which has been stained pink, as also have been the
five csecal tubes — ' diverticula ' — radiating from it. A portion
of the integument has been preserved round the anus, into
which a black bristle has been inserted. From the intes-
tiniform portion of the digestive tract arise some tufted caecal
appendages. The tubes which are given off from the stomach
in the direction of each of the rays very soon divide into two,
each of which gives off a number of arborescent caeca, filling
up the whole cavity of each ray. At the base of each ray is
placed a pair of generative glands. Each gland is made up of
numerous caeca, converging to a duct opening at the base of the
ray. The madreporic tubercle is between the first and second
rays on the right of the preparation, counting from the top. In
each ray, and on each side of the median longitudinal ossicles,
may be seen numerous ' ampullae.'
Kolleston, pp. 141—145.

7. A Common Cross-Fish (Asterias rubens}, dissected to
shew its generative system.

The dorsal portion of the integument, with the whole of the
digestive apparatus, has been removed. The generative organs,
ovaries or testes (the Echinodermata being 'dioecious'), are seen
to consist of bundles of arborescent caeca, two to each ray, each
bundle being attached at the base of the cavity which contains
the digestive caeca, one on each side of the median longitudinal
ossicles. The attached extremity of each gland indicates the
position of its duct, which opens at the base of each ray in the
inter-radial space.

8. A Common Cross-Fish (Asterias rubens}, dissected to
shew its nervous system.

The tube-feet have been removed. The nervous system
lies on the ventral surface of the animal, and consists of a
pentagonal ganglionated ring surrounding the mouth, from
which a single cord passes down the centre of each ray.

9. A crinoid Echinoderm (Pentacrinus caput-medusce),
dredged off Barbadoes, 1869.

10. A Sea-Urchin (Echinus sphcera), divested of its spines,
and dried.

The exo-skeleton is an immovably articulated, inflexible

6 COMPABATIVE ANATOMY.

shell, composed of numerous — upwards of six hundred — calcined
pieces, arranged in a definite pattern. The shape of the test is
that of a sphere with flattened poles. One pole however, the
oral one, is much more flattened than the other, — the anal one.
With the exception of small circum-anal and circum-oral areas
the remainder of the body, ' corona ' as it is called, is composed
of numerous calcified plates, disposed in twenty longitudinal
series. These are furthermore arranged in ten double rows,
radiating from one pole to the other. The five double rows of
plates, which are perforated by the external apertures of small
canals, constitute the ambulacra, while the remaining five
double rows, alternating with the foregoing, and imperforate,
form the inter-ambulacra. The ambulacral and iriter-ambu-
lacral plates in converging towards the poles of the shell be-
come much smaller, and do not quite reach the poles, but
leave small areas round the mouth and anus, in which the
calcified plates have a different arrangement.

In the neighbourhood of the anus this space is occupied by
two concentric rows of plates, the anal plates. The much larger
circum-oral space — the 'peristoma — is in the fresh specimen filled
up by a leathery membrane strengthened by irregularly shaped
calcified plates, in the centre of which is the mouth. Each
ambulacral row of plates is separated from the adjacent row of
inter-ambulacral plates by a tolerably straight but not very well
defined suture. On the other hand the suture separating the
two rows which together make up an ambulacrum or an inter-
ambulacrum is a zigzag one: being formed by the alternation of
the triangular internal extremities of the component plates.
There is consequently such a suture running down the middle
of each ambulacrum and inter-ambulacrum. The plates com-
posing an ambulacrum are pentagonal, and transversely elongate.
Each is perforated by six obliquely disposed apertures or pores,
affording a passage to the tube-feet : and each carries on its
surface conical tubercles varying in size. Furthermore each
plate is subdivided by faintly visible oblique transverse sutures
into three primary divisions or pore-plates, each pore-plate con-
taining a pair of obliquely set pores : and the whole six aper-
tures are situated close to the outer or inter-ambulacral edge of
the plate. ' There is therefore a pore-plate or subdivision of

ECHINODEKMATA. 7

the ambulacral plate corresponding to each pair of pores : and
this arrangement would appear to hold good for all the EM-
noidea except the Clypeasteridm, where the pores of the loco-
motive feet are grouped together on a single plate.' (Huxley.)

Each row of ambulacral plates carries two rows of alternating
conical tubercles, and in addition there are inner tubercles of
various sizes scattered between the larger ones : these tubercles
carry the spines, which beset the external surface of the skeleton.

The inter -ambulacral plates, though similar in shape, and
carrying tubercles, are larger in size than the ambulacral, and
imperforate. If an ambulacrum be traced upwards towards
the apical pole of the shell, it will be found to abut upon
one of the five smaller ossicles which form the outer row of
circum-anal plates. Each of these angular plates is perforated,
and supports an eye- spot. Hence they are called 'ocular plates.'
The apical extremities of the inter-ambulacra are similarly
related to the larger plates which form the inner series of cir-
cum-anal ossicles, and alternate with the ocular plates. These
plates, of the inner row, are likewise perforated with a small
aperture for the passage outwards of the generative products.
Hence they have been termed ' genital plates.' One of these
is much larger than any of the others, and is marked by a
porous elevation, the madreporic tubercle : which internally is
in relation with the sand canal.

The small area within the ocular and genital plates is
occupied by small calcified tubercles and granules, within
which the anus is situated. The growth of the shell in the
Ecliinidc& is effected in two ways : partly by addition to the
circumference of existing plates, and partly by the interposition
of new ambulacral and inter-ambulacral plates at the apical end
of each series. The tubercles which cover the plates terminate
in rounded, ball -like summits, either simple, or marked by a
small pit. The spines articulating with these tubercles have a
cup-shaped depression at their attached extremity, which re-
ceives the rounded end of the tubercle in such a manner as to
form a ball and socket joint. The spine is attached to the
tubercle partly by a ligament which passes from the bottom of
its articular surface to the pit in the tubercle : and partly by
the muscular fibres which connect the neck of the spine with

8 COMPARATIVE ANATOMY.

the base of the tubercle, and in addition produce all the
motion of which these organs are capable.

It will be noticed that in addition to the absence of any
lateral prolongation of the body into rays, an Echinus differs
from a Starfish in the enormous development of the ambulacral
at the expense of the ant-ambulacral region : so that the latter
eventually becomes reduced to a very small space round the
apex. As in the Starfish, the test is bilaterally symmetrical,
for on each side of the vertical plane in which the mouth,
anus, and madreporic tubercle lie, there are two and a half
ambulacra, and two and a half inter-ambulacra. The dis-
position of the ambulacra into bivium and trivium is also
obvious.

11. Two Sea-Urchins (Echinus sphcera), with the spines and
tube-feet intact.

The spines cover the whole of the ambulacra and ant-ambu-
lacra. They fail however to be developed for some little distance
round the mouth, though they extend up to, and even arch
over, the anus. Though they vary much in size, they are all of
one shape. Each spine is cylindriform, striated longitudinally
as well as transversely, and tapers gradually towards its
apex, which is tipped with purple. The spines that form a
continuous series from one end to the other of an ambulacrum
or inter-ambulacrum are distinguished as 'primary' spines, while
the smaller and less regularly arranged are, in proportion to
their size, termed 'secondary' or 'tertiary.' The five pairs of
rows of tube- feet are to be seen protruding from the pores.
Each foot is a tubular csecal process, terminating distally in a
slightly expanded, disk-like extremity: — while internally it is in
connection with the 'ampullae' and one of the 'radial trunks' of
the water-vascular system. In the peristomial area, and im-
mediately surrounding the mouth, the tube-feet become modified
into a circle of more or less plumose appendages, which may
be regarded as the aborted rudiments of the tentacular crown
of the Holothuroidea.

12. A Sea-Urchin (E. brevispinosus\ bisected horizontally,
to shew the internal surface of the shell.

The ambulacral plates are produced into five short truncated
processes, so perforated as to form five small vertical arches,

ECHINODERMATA. 9

which arch over the ambulacra, and are called 'auriculae/
Through these apertures the radial nerve-cords and the radial
canals of the water- vascular system pass from the nerve-collars
and water-vascular ring. From the relation which these ' auri-
culae ' bear to the nervous and water-vascular systems it would
seem as though they represented the ambulacral ossicles of the
Starfishes.

13. A Clypeaster bisected to shew the great development
of the 'auriculae/ which here are so large as to unite the oral
and apical walls of the ' corona/

14. A Spatangus (8. purpureus), bisected to shew the total
absence of ' auriculae/

15. A Sea-Urchin (Echinus sphcera), prepared to shew its
generative and digestive systems.

The test has been horizontally bisected, and the apical half
of the shell suspended above the oral half.

The oesophagus, as it emerges from the arrangement of
calcified jaws called Aristotle's lantern, to be described in the
next specimen, is of moderate calibre, but subsequently it
somewhat abruptly expands into a large and thin-walled in-
testine, which, after turning twice round the inside of the
test, passes along an inter-ambulacral space to the anus. At
the commencement of its second and superior convolution
round the shell it bends upon itself and runs in an opposite
direction to its first circuit, to which however it still remains
parallel. The two convolutions are attached by a much-
fenestrated mesentery to the inside of the test, and are disposed
in festoons. Two pseud-haemal vessels can be seen in relation
with the intestine, one running along its inner, and the other
along its outer or mesenteric border.

The ovaries are five in number, and are arranged round the
apical area, one in each of the five inter-ambulacral spaces. A
short tubular oviduct conveys the ova to the apertures before
described as existing in the five genital plates.

The ampullae are seen on the internal surface of the shell in
the ambulacral areas ; and mesially between each of the two
rows of ampullae in an ambulacral area one of the five radial
nerve-cords can be seen.

Rolleston, p. cl.

10 COMPARATIVE ANATOMY.

16. The oral skeleton, whole and separated into its com-
ponent parts.

17. The lower half of an Echinus (E. sphcera), prepared
to shew the mouth, and the muscles that move the jaws.

"The apparatus consists of five hollow wedge-shaped cal-
careous pieces, the ' alveoli,' each of which is composed of two
halves united together in the mesial line, while each half again
consists of a superior epiphysis and an inferior principal portion.
Each ' alveolus ' serves as the socket to a long tooth shaped like
the incisor of a rodent, harder externally than internally, so as
always to develop a sharp edge with wear, and constantly grow-
ing from its upper extremity. The five alveoli, fitted together,
form a cone, whose applied surfaces are united by strong trans-
verse muscular fibres, while superiorly the epiphyses of each
pair of alveoli are connected by long radial pieces, the ' rotulae.'
To the inner extremity of each 'rotula' finally a slender
arcuated rod presenting indications of a division in the
middle of its length is articulated, and running outwards
parallel to the ' rotula' terminates in a free bifurcated ex-
tremity. This is the 'radius' or ' compass' of Valentin. Al-
together the ' lantern' consists of twenty principal pieces, five
teeth, five ' alveoli,' five ' rotulae,' or ' falces,' and five ' radii ' or
'compasses:' of which the alveoli are again divisible into four
pieces each, and the radii into two: making a total of forty
pieces. In their normal position it must be remembered that
the alveoli and teeth are inter- ambulacral, while the 'radii' and
'rotulae' are ambulacral. Besides the inter-alveolar muscles
this complex apparatus has protractor muscles arising from the
inter-ambulacral region of the oral edge of the 'corona/ and
inserted into the upper part of the alveoli; slender oblique
muscles, with a similar origin, but inserted into the radii ; trans-
verse muscles connecting the radii together; and retractor
muscles arising from the arches of the 'auriculae,' and inserted
into the oral ends of the 'alveoli.'"

Huxley, Medical Times and Gazette, 1856, vol. xiii. p. 587.

The next three preparations illustrate the anatomy of the
Holothuroidea. In each a blue rod has been placed in the
znouth : a red rod in the anus.

18. A Great Sea-Cucumber (Cucumaria frondosa), verti-

ECHINODERMATA. 11

cally laid open. In this specimen the animal has contracted
so much, that the whole of the tract round the mouth — 'the
peristomial space/ — with the tentacles, has been withdrawn
within the body-walls, and hangs down like a bag, which
has been laid open so as to expose the tentacles, of a black
colour.

Five pairs of longitudinal muscular bands, radiating from
mouth to anus, are seen to divide the body-walls into a corre-
sponding number of crescent-shaped divisions, in which the
muscular fibres, which encircle the animal transversely, are well
seen. In the interval between the two elements of each pair of
muscular bands lies the longitudinal water- vascular ambulacral
vessel. In this family — the Dendrochirotce — each longitudinal
muscle gives off a long slip which inserts itself into the corre-
sponding radial ossicle of the calcareous ring encircling the
mouth, and acts as a retractor. The water- vascular ring sur-
rounds the muscular pharynx, a little way posteriorly to the
calcareous ring. In the centre of the preparation are the
muscular pharynx and stomach. On the exterior may be
noticed the longitudinal rows of apertures for the tube-feet,
which, however, are now partially retracted.

Rolleston, p. 145 sq., and p. cxlvii.

19. A specimen of Psolus phantapus with part of the dorsal
and ventral surfaces removed. The animal is contracted as in
the last preparation. The longitudinal and retractor muscles,
and the calcareous ring with its two Polian vesicles, are well
seen.

On the ventral side of the preparation is seen the whole of
the digestive tract, spread out upon a sheet of mica. The anal
end receives the ducts of the so-called respiratory trees, which
in the preparation depend downwards from the cloaca, one on
each side. These organs consist of hollow stems carrying some-
what scanty ramifications; they reach a considerable distance
into the body, to the walls of which they are attached by
mesenteries.

On the dorsal surface is the generative gland — a bundle of
simple unbranched caeca of various lengths. The mesentery, by
which it was attached to the body-walls, has been removed. A
single efferent duct passes from these ca?ca to open inside the

12 COMPARATIVE ANATOMY.

circle of oral tentacles, above the calcareous ring. The ventral
surface is covered with calcareous scales, and is destitute of
tube-feet : though these latter do exist in other parts of the
body.

20. A specimen of Holothuria tubulosa, dissected to shew
the generative system and * respiratory tree/ The greater
portion of the left side of the body has been removed, together
with the whole of the digestive tract, except the pharynx and
cloaca. These are well displayed, as also are the mesenteric
bands by which the cloaca is attached to the body-walls.

The generative caeca have been spread out on a piece of
mica. They are disposed in two groups, but are shorter and
much less subdivided than in P solus, and end in dilated casca.
The two ducts, one from each group, shortly unite to form the
common efferent duct, appended to which, at about the level of
the calcareous ring, is a number of minute pyriform vesicles.
The external opening of the generative duct has a black bristle
inserted into it. The respiratory tree consists of a hollow stem
extending from the cloaca, with which it is in communication,
as far forwards as the pharynx. Numerous filiform and arbo-
rescent caBcal appendages are given off from it. The mesen-
teric fibres by which the stem is attached to the body-wall are
well seen.

On the left of the preparation is the 'respiratory tree,'
attached by mesentery to the body-wall. A green rod has
been inserted into the orifice by which it opens into the
'cloaca/ Depending from the calcareous ring are the 'ampulla'
of the water- vascular ring surrounding the mouth.

SUB-KINGDOM VERMES.
DIVISION ANNULATA.

Class I. ANNULATA PROPER.

21. An Amphinome. The body, though elongated, is of
considerable transverse width, and is divided by numerous
transverse constrictions into about 60 segments. With tlie

VEKMES. 13

exception of the cephalic the whole of the segments differ
from each other in little else than their comparative calibre.
The integument is not hardened by the deposition of chitinous
or calcareous matter, and the appendages attached to the
different 'somites' are soft, and devoid of segments or of joints.
A typical 'somite,' from the middle region of the body, may
be said to consist of dorsal and ventral arcs — each arc ter-
minates on each side in a conical eminence, constituting with
its appendages ('cirri' and 'setae') a 'notopodium' or 'neuro-
podium' according to the arc with which it is in relation. The
appendages attached to the * notopodium' are; first, a tuft of
branching caeca dorsally placed ; secondly, a fasciculus of
chitinous setse; thirdly, a small 'cirrus.' The neuropodial ap-
pendages are separated from the notopodial by a well-marked
interspace, and consist of, (1) a small fasciculus of setae, and
(2) a cirrus: but no branchiae. Towards the head and anal
extremity the branchiae become very small and are absent al-
together on the first two post-cephalic segments: and the setae
are also insignificant in size. The mouth and anus are ter-
minal: the former is situated on the ventral surface of the
third somite.

22. A Common Earthworm (Lurribricus terrestris), dissected
to shew its digestive system.

The transversely annulated integument has been divided
down the medio-dorsal line and pinned out on either side. The
digestive tract is seen in the middle line of the preparation,
and extends, without any convolutions, direct from mouth to
anus.

The mouth (formed by a modification of the first segment)
leads into an oval pharynx, whose external surface has a
coarsely villous appearance, due to the breaking away of the
delicate muscular bands by which it was attached to the body-
wall. The oesophagus, in length about five-eighths of an inch,
and of much smaller calibre, leads from the pharynx to the
large and globular crop. Immediately succeeding this latter
cavity, and of slightly smaller size, and lighter colour, is the so-
called gizzard. Posteriorly to the gizzard the intestine is con-
tinued as a slightly sacculated tube of even diameter to the
anus. Attached to the oesophagus immediately anterior to the

14 COMPARATIVE ANATOMY.

crop are three pairs of minute glands of unknown function
called cesophageal glands.

The membranous partitions extending from the body-wall to
the alimentary canal, and dividing the perivisceral cavity into a
series of inter-communicating spaces, are well seen in the
middle third of the preparation. In the inter-mesenteric spaces
of the middle third of the body are to be seen the ' segmental
organs/ consisting in each space of a looped internally ciliated
tube, communicating by its internal extremity with the peri-
visceral cavity, and by its other extremity opening externally.

Rolleston, p. 119.

23. The same, dissected to shew its nervous system.

The integument, divided in the medio-dorsal line, has been
pinned out on either side, and the whole of the digestive and
generative systems removed. The nervous tract is seen occu-
pying the medio-ventral line, and extending from the oral to
the anal extremity of the body. The supra-oesophageal mass is
seen to consist of two pear-shaped lobes applied together in the
median line by their broad ends, their apices pointing outwards.
From the outer end of each of these two lobes a large nerve
passes forwards to supply the upper lip, and a bristle has been
placed underneath them. A commissural cord on each side
proceeds downwards from the supra-cesophageal ganglia, en-
circling the oesophagus and connecting these ganglia with the
ventral nervous cord.

The anterior portion of the cord is of considerable thickness,
and, on close inspection, may be seen to be composed of two
distinct strands ; the ganglionic enlargements are, however, with
difficulty recognizable. In the middle third of the body the
cord becomes much thinner, but assumes a beaded appearance
owing to the greater comparative size of the ganglia and the
wider interspaces which separate them. In the posterior third
of the body it again becomes of considerable size, but the
ganglia are less distinctly visible and more closely apposed.

A pair of nerves is given off from each pair of ganglia, and
a single nerve on each side from the segments of the cord
interposed between each pair of ganglia.

24. A Sea-Mouse (Aphrodite aculeata), dissected to shew
its digestive organs.

VERMES. 15

The animal has been laid open along the ventral surface,
the nervous system having been removed.

The mouth, into which a black bristle has been inserted,
leads into a thick, cylindrical, muscular sac, called by some a
gizzard. The posterior extremity of this opens by a narrow,
sigmoid segment, into a funnel-shaped stomach, which gradually
diminishes in size, and insensibly passes into an intestine, ter-
minating at the anus. Throughout the whole length of the
stomach, caecal processes are given off on each side to the
number of about twenty pairs. They are slender at their
origin, but gradually enlarge, and give off lateral ' diverticula,'
which again, in their turn, divide and subdivide, terminating
finally in fusiform dilatations. These caeca are probably homo-
logous with the gastric caeca of the leech ; and the so-called
* gizzard,' which is capable of protrusion, has been considered to
be homologous with the projectile proboscis of other Annelids.

The stomach has been filled with red injection, and the
caeca partially so. They have been dissected and pinned out on
the left side. On the right they remain in situ, lying among
the transverse muscles. On this side also may be seen the
delicate muscular bands, which pass from the base of the
bundles of setae to the integument, and effect their protrusion.

25. The same, dissected to shew the ' elytra/

A longitudinal strip of the dorsal coating of ' felt ' has been
removed and the ' elytra ' displayed.

The 'elytra' are broad membranous plates developed as
appendages from the notopodia, and, arching inwards over the
back, form two lateral series on either side of the medio-dorsal
line. Beneath the elytra is the membranous partition forming
the dorsal boundary of the visceral cavity. The nervous sys-
tem may be seen on the ventral surface of the body, through
the integument.

It is to be observed that the ' Sea Mouse ' is much less dis-
tinctly annulated than the Earthworm : and that the ' setae,'
which in the Earthworm are almost microscopic, are here of
large size and iridescent.

26. A Leech (Hirudo medicinalis), dissected to shew its
nervous and generative systems.

The nervous system consists of a longitudinal ganglionated

16 COMPARATIVE ANATOMY.

ventral cord containing about twenty-four ganglia, from which
delicate nerves radiate on either side. The ganglia are more
approximated at both ends than at the middle of the animal.
From the foremost, or sub-cesophageal, ganglion pass the nerves
to the oral muscles and the cords on either side of the oeso-
phagus. These, meeting above, join the super -cesophageal
ganglion from which radiate nerves to the ten ocelli and other
parts of the head.

The testes are nine spherical bodies on either side of the
nervous cord connected by their ducts with a common canal, or
' vas deferens/ which runs external to them and communicates
in front with a receptacle or 'vas deferens.' The two receptacles
are connected with the muscular ball from which the penis is
continued. The ovaries, smaller than the testes, are situated,
one on either side, just behind the 'receptacula seminis,' and
are connected by short oviducts with the muscular bag or
vagina.

DIVISION ANNULOIDA.
Class II. NEMATELMINTHES.

27. The generative organs of a male and female Ascaris
(Ascaris lumbricoides, L.), taken from the duodenum of a
young woman. The male, on the left, is smaller than the
female. It — the male — has been opened longitudinally, and
the intestine, a straight tube, is seen passing from the mouth to
the anus. It has been pinned somewhat to the left of the
specimen. The testis is a long curling tube, very attenuated at
its commencement. It gradually becomes thicker, and is dis-
posed in numerous coils round the alimentary canal. About
three inches from its termination it suddenly dilates into a
larger tube or receptacle, which, narrowing again, is continued
to the posterior extremity of the animal. Its lowest part,
beneath which a slip of blue paper has been placed, admits of
protrusion, and is called the penis.

The female has also been laid open longitudinally. The
intestine, like that of the male, is a straight tube, extending
the whole length of the animal, but it expands much more

VERMES. 17

near its anal end. The ovarian tubes commence as thin fili-
form caeca arranged in complicated coils round the intestine.
Near the anus however these tubes become suddenly expanded,
and extend as far forwards as the anterior third of the body :
where they unite to form a short and very narrow oviduct,
which opens outwards. This, turning round the intestine and
becoming narrow, terminates at the genital aperture one-third
from the anterior end of the animal.

Class III. PLATYELMINTHES.

28. A Tape- Worm (Tcenia solium).

The specimen, a mature worm (Strolilia), is a flattened,
ribbon-shaped organism, divided by transverse constrictions into
numerous well-defined segments — the * proglottides,' — which are
for the most part of large size, but on approaching the head
they become gradually smaller, and the constrictions less evi-
dent, till in the vicinity of the head the body becomes reduced
to a mere flattened thread, and the constrictions are only repre-
sented by faintly marked ' striae.' A short, smooth, faintly-
striated neck is succeeded by the head. This is about the size
of a pin's head, and is armed with a double circlet of minute
spines, and carries in addition four minute suckers. The ' pro-
glottides ' in the hinder part of the specimen are of a whitish
colour, opaque, and three or four times as long as they are broad.
The head, 'nurse,' or 'scolex/ is asexual. The segments succeed-
ing are sexual, but immature : that is, their generative organs
and their products are but imperfectly developed. The segments
which succeed and make up the bulk of the organism, are
sexually mature, hermaphrodite ' proglottides.' The new seg-
ments are produced by a process of gemmation from the head :
and the segments thus produced are intercalated between the
head and the segments already formed. The apertures of the
efferent ducts of the male and female organs are situated on
small cup-shaped eminences placed on the lateral margins of
the 'proglottides,' the side alternating in adjoining segments.
The specimen is eight feet in length, and was taken from a
human intestine.

CL. 2

18 COMPARATIVE ANATOMY.

SUB-KINGDOM ARTHROPODA.

Division TRACHEATA.

Class MYRIAPODA.

29. A Centipede, Scolopendra, a Chilopodous Myriapod.

The segments of the exo-skeleton differ from those of In-
secta and Crustacea in not being definitely marked out into
cephalo -thoracic, abdominal, and post-abdominal regions. There
are twenty- three post-cephalic segments, to each of which a
single pair of appendages is attached. Any one of these append-
ages consists of a dorsal and ventral arc, united together late-
rally by the soft integument from which the appendages take
origin. On either side of the mesial line of the ventral arc are
two very faint lines, which mark off a median portion, or 'ster-
num/ from two lateral elements, or 'episterna.' These faint
lines are best seen in the sterna of the anterior segments. Im-
bedded in the lateral integument are one or two chitinous plates
or tubercles, representing the rudimentary 'epimera' or lateral
elements of a typical 'somite.' Each appendage is many-jointed.
The proximal joint is the 'coxa,' and the distal one carries a
sharp curved claw. Each segment is to be regarded as being
composed of two sub-segments, which at first are equally deve-
loped, but as development proceeds, one of them increases in
size more rapidly than the other; and moreover develops a pair
of appendages which the other does not. .This latter, the
anterior one, becomes abortive, though in the Chilognatha it
develops equally with the posterior one, with which it event-
ually coalesces, and moreover carries a pair of appendages.
Nevertheless in this specimen the remains of the anterior sub-
segment are to be seen. Immediately in front of each sternal
piece, and on each side of the mesial line, are three small
angular chitinous plates. The pair nearest the mesial line are
the two uncoalesced halves of the sternum of the aborted anterior
sub-segment. The pair external to these are the episterna,
and the most external and smaller pair are the epimeral plates.
Epimeral plates are also situated, one pair on the hinder edges
of the sternum, and two small plates just in front of the coxa,
imbedded in the lateral integument. The two sub-segments,

ARTHROPODA. ID

one of which in Chilopoda is abortive, are equally developed in
Chilognatha, and each carries a distinct appendage. The terga,
however, are confluent, so that the double nature of each body-
segment is only evident when the ventral surface is examined,
where two pairs of appendages will be found attached to each
segment. The segmental appendages are composed of six
joints, coxa, tibia, femur, metatarsus, tarsus, and claw. The an-
terior appendages are the smallest, but they gradually increase
in size posteriorly; and the hindermost pairs are directed back-
wards and not outwards, as is the case with the anterior ones.
The last pair is very much larger than any of the rest, curves
inwards, and by mutual apposition forms an efficient clasping
apparatus. The anus opens on the under surface of the last
segment. In several of the segments a pair of small, crescentic,
laterally placed slits surrounded by prominent chitinous lips
is to be seen a little inferior to the dorsal arc : these are the
' stigmata.'

The head is probably formed by the fusion of at least five
of the most anterior segments. The superior surface is formed
by a broad, shield-like plate, quite smooth, and devoid of
sutures, with the exception of a faint median groove. To the
anterior margin of this plate is attached a pair of multiarti-
culate antennae consisting of not fewer than seven segments.
In this respect the Order Chilopoda, to which this species
belongs, differs from the Order Chilognatha, in whicb the
antennas are composed of fewer than seven segments. At the
base of the antenna?, and external to them, are four sessile
'oculi.' On the inferior surface of the head, in addition to the
antennas already described, the following appendages are to be
seen. First, a pair of mandibles, toothed on their inner edges,
and carrying small rudimentary palpi on their outer edge.
Secondly, two pairs of maxillss, of which the anterior pair is
jointed, palpiform, and forms the external elements of the
labium, while the posterior pair is composed of two small
conical pieces applied together in the mesial line, but not
united, and constituting the mesial part of the 'labium.'

The appendages hitherto enumerated belong to the head,
the remainder, proceeding backwards, to regions which in the
Lobster are termed thoracic, abdominal and post-abdominal.

2—2

20 COMPARATIVE ANATOMY.

Succeeding the maxillae is a pair of jointed appendage*,
armed with a small claw. The next are the large cheliform
poison -fangs. These are armed with claws, and the extremity
of each claw is perforated by the aperture of a small duct lead-
ing from a poison-gland. The basal joints are confluent, so
that by this union a second labium is formed posterior to the
first. The two last-mentioned appendages may be taken as cor-
responding to two of the three pairs of maxillipeds in the
Lobster, and to the two anterior pairs of legs in Insects.

The segment to which the large 'chelae' are attached is
larger than the segment immediately succeeding it.

30. A Centipede (Scolopendra), dissected to shew the
digestive and female generative systems.

The animal has been laid open along its dorsal surface, so as
to expose the alimentary canal, which is simple, and passes in
almost a straight course from mouth to anus, the terminal por-
tion of the intestine alone indicating any approach to a con-
volution. It is distended with food. The stomach, which
occupies the central third of the body, is the widest part of
the canal : it communicates anteriorly with the mouth by a
narrow oesophagus, and posteriorly is marked off from the intes-
tine by a slight constriction. The intestine, at its j unction with
the stomach, though of less calibre than the latter, is yet of
considerable size; but diminishes as it proceeds, and after de-
scribing a sigmoid flexure terminates in an anus.

The ovary is a long and simple tube, attached above to
about the middle of the stomach, and gradually diminishing
in size till it reaches its vaginal outlet. The ovi-sacs may be
seen through its semi-transparent wall throughout its whole
extent.

The white caeca pinned on either side of the lower part of
the preparation are the ' accessory glands.'

31. A Centipede (Scolopendra), dissected to shew the male
generative organs.

The animal has been laid open along its dorsal surface, and
the digestive tract removed. The testes consist of a series of
pairs of fusiform vesicles, each vesicle being applied along its
whole length to its fellow, from which however it can be easily
separated. They occupy a considerable portion of the abdomen,

ARTHROPODA. 21

and extend forwards as far as the anterior fifth of the body.
Each end of each vesicle communicates by a duct with a
minute common longitudinal canal. There would thus be
twenty pairs of ducts passing from the testes to the central
canal. Posteriorly this canal becomes of considerable size, and
is disposed in spiral coils before it reaches its external opening.
Beneath it, and in the last two segments of the body, are
seen the 'accessory glands.' The long dorsal vessel has been
pinned on the left of the specimen.

32. A Centipede (Scolopendra), dissected to shew its
nervous system.

It has been laid open along its ventral surface. A black
bristle indicates the position of the oesophagus.

The nerve-system consists of a double cord placed medially
in the body. The cephalic ganglion supplies the antennas and
eyes. Posteriorly to this the cords divide to admit of the
passage of the oesophagus. Subsequently there are ganglia
at regular intervals, corresponding in number to the segments
of the body. From each nerves are given off to supply the
legs. The first ganglion is oval in form, the- others are round.

Class INSECTA.

1. Order Coleoptera.

33. A Goliath Beetle ( Cetonia cacicus), disarticulated and
mounted on wires to shew its segments- and their appendages.

34. Digestive system of an Oil-Beetle (Meloe proscarabceus).
Nearly the whole of the exoskeleton, together with the

other organs, has been removed.

The oesophagus, which is very short, leads into a large
elongated oval stomach, occupying the greater part of the ab-
dominal cavity. On, leaving the stomach the intestine becomes
suddenly extremely narrow, and is slightly convoluted. Its
terminal segment is dilated into a rectum.

Near the posterior end of the stomach the hepatic vessels, a
number of thread-like caBcal tubules, may be seen.

35. A Stag Beetle (Lucanus cervus), dissected to shew its
nervous system.

22 COMPAKATIVE ANATOMY.

The supra-cesophageal mass consists, as usual, of two cephalic
ganglia, from which are derived the nerves which supply the
eyes. These ganglia are connected with the ventral cord by a
double nervous cord encircling the oesophagus. Three large
ganglia supply the thorax. The first pair of abdominal ganglia
are very large, but the remaining six, with the exception of the
last, are small. This ganglion sends off a bundle of nerves which
supply the segments posterior to it.

3(j. A Common Cockchafer (Melolontlia vulgaris), female,
dissected to shew its generative and digestive systems, which
have been arranged on the left and right sides of the tablet
respectively.

Generative organs. Each ovary is composed of a single
fasciculus of egg-bearing caeca. These cseca, or tubules, at their
commencement are small and slender, but as they descend they
dilate and assume a granular appearance, eventually fusing to
form the oviduct. The caBca composing the right ovary have
been partially separated. The two oviducts combine to form
the common vaginal canal, which opens externally. On the
right of the 'vagina,' and opening into it by a short duct, is the
pyriform 'speraiatheca:' on the same side and with the same
termination is the glandular accessory caecum.

Digestive system. This is seen to be a canal of great length
in proportion to the size of the insect, of tolerably uniform
diameter throughout, and much convoluted.

2. Order Orthoptera.

37. A Common Cock-Roach (Periplaneta orientalis), dis-
sected to shew its digestive system.

The oesophagus opens into a large pear-shaped crop. On
either side of the oesophagus may be seen the two-lobed salivary
gland. Posterior to the crop, and separated from it by a slight
constriction, is the muscular gizzard. The true chylific stomach
which succeeds receives at its anterior extremity a whorl of
eight casca; and a cluster of much longer and more slender
tubules is similarly arranged round its lower end. The first
eight caeca are regarded as analogous to the liver of higher
animals, while the tubules are probably renal. The ' colon,'

ARTHROPOD A. 23

which is connected with the stomach by a short segment of in-
testine, of small calibre, is large, and bent upon itself. The
terminal portion, or ' rectum,' is marked by longitudinal mus-
cular bands.

Rolleston, p. 86 and p. 199.

38. A Locust (Locusta), dissected to shew the female
generative system and the digestive system.

The insect has been opened on its dorsal surface, most of
which has been removed.

The ovigerous caeca form two bundles, one on each side. The
tubules composing them unite to form an oviduct. The two
oviducts join in the median line, and form the short and wide
vaginal canal which opens externally at the base of the large
ovipositor. Communicating with this canal by a short duct is
the ' sperm atheca' (pinned to< the left side), and also a long
thread-like accessory caecum (pinned to the right side).

The digestive system of the insect has been arranged on the
right of the preparation. It closely resembles that of the Cock-
Roach; but the hepatic caeca are unusually large, and the
renal tubes are small.

39. A Locust, dissected to shew the male generative
organs.

The insect has been prepared in the same way as the last.
The testes are two large oval compressed bundles of sperm-
secreting tubules, one on each side of the body. Between them
is a mass of accessory glands, which have taken the form of
minute, much convoluted tubes.

3. Order Diptera.

40. A Common Flesh-Fly (Sarcophaga carnaria), dissected
to shew its digestive and female generative organs.

The insect has been laid open along its dorsal surface.

The alimentary canal has been pinned to the right, It
consists of a long tube, in which scarcely any difference between
stomach and intestine can be observed. The ovaries are seen
to be clusters of white caeca, arranged spirally. In this species
the female is viviparous.

Packard on Insects, p. 408.

24 COMPARATIVE ANATOMY.

4. Order Lepidoptera.

41. Larva of Privet Hawk Moth (Sphinx lig-ustri).
Bristles have been inserted into the spiracles of the right

side.

Rolleston, p. 73.

42. Pupa of the same.

43. Larva of the same, dissected to shew the nervous
system.

It has been laid open on its superior surface, and the
digestive system removed, with the exception of a piece of
the oesophagus, which has been pinned back, in front of the
head.

The nerve-system consists of twelve ganglia, arranged in a
linear series along the ventral surface of the larva. The first
pair of these are the cerebral ganglia, situated immediately
above the oesophagus. They are connected by the usual nerve-
collar, embracing the oesophagus, with the first post-oral ganglion.
The terminal ganglion of the series is composed of two ganglia,
closely opposed to ea^h other, from which a leash of nerves is
given off to the terminal segments of the body.

Rolleston, p-. 82.

44. Larva of Goat Moth (Cossits ligniperda), dissected to
shew the internal organs.

The integument has been- divided down the medio-dorsal
line and pinned out on each side.

Occupying the greater part of the body-cavity and investing
the contained viscera is a mass of lobulated adipose tissue,
known as the ' fat body ' or ' rete,' which disappears almost com-
pletely in the c imago' of those insects whose metamorphosis is
complete.

In the median line is the digestive tract, which passes,
without forming any convolutions, direct from mouth to anus.
The walls of the oesophagus are thin, and thus readily distin-
guish it from the thick-walled, opaque, corrugated stomach.

A little way below the pylorus the intestine receives the
common ducts of the tubular renal organs, the so-called 'Mal-
pighian vessels.' The common duct on each side bifurcates, and

ARTHKOPODA. 25

the branches so formed extend anteriorly and form two loops on
either side of the stomach ; the trunk forming the outermost of
the two loops in descending bifurcates again on each side.
There are thus three trunks on each side of the stomach, form-
ing an intricate plexus round the pylorus, and finally terminating
blindly. The long, convoluted, and much larger tubes seen on
each side of the digestive tract are the silk-glands; they
commence blindly in the posterior part of the body, and termi-
nate in a common duct opening on the modified ' labium ' or
' spinneret.'

On the left side of the stomach is seen a thin-walled,
transparent sac, the posterior end of which is connected with a
much-convoluted tubular gland, which bends forwards, and in
the preparation lies on the outer side and in advance of the sac.
This sac is connected anteriorly with the mouth by a wide duct.
The tubular gland, bladder,, and duct correspond with the
smaller salivary glands of the imago.

In the intervals of the fat body fasciculi of tracheae are seen
diverging to distribute themselves upon the viscera.

The following points in which the viscera of the larval form
differ from those of the imago may be noticed in this prepara-
tion : — the presence of the 'fat body/ the larger calibre and lesser
length of the digestive canal, and the absence of convolutions,
and the presence and large size of the silk-glands.

RoHeston, p. 79.

Class ARACHNIDA.

45. A Scorpion (Scorpio afer), to shew the exo-skeleton.

The exo-skeleton presents a well-marked division into
cephalo- thoracic, abdominal, and post-abdominal regions, and
with the exception that the abdominal segments are here distinct
from each other, these divisional areas approximate closely to the
same parts in the lobster. The cephalo-thorax is a broad and
but slightly convex plate marked by a median antero-posterior
groove, and with a deeply emarginate anterior border. At the
commencement of the posterior fourth of its extent there is a
shallow transverse groove curving forwards on either side,

26 COMPARATIVE ANATOMY.

dividing the cephalo-thorax into a large anterior and a much
smaller posterior division, and bearing some resemblance to the
cephalic suture, to be subsequently described, in the lobster. In
the centre of the cephalo-thorax, and situated upon a little
eminence, is the medio-dorsal pair of 'oculi,' one on each side of
the median groove. There are also three additional 'oculi' at each
antero-external angle, on each side of the anterior median notch.

The segmental appendages, of which there are six pairs,
namely, counting from before backwards, antennas, mandibles,
and four pairs of ambulatory legs, are entirely confined to the
c ephalo-thorax. Functional antennas are absent: but thehomo-
logues of the antennas of Insecta are the large and strong cheli-
form appendages situated in front of the mouth, and so modi-
fied from their ordinary structure as to become efficient
prehensile organs. The first post-oral pair, the mandibles, are
in this species remarkable for the extraordinarily dispropor-
tionate development of the mandible proper and its 'palpus.'
While the former is a small, internally flattened, slightly serrated
plate, the latter, absent in Insects and with the exception of a
rudiment, in Myriapods also, is enormously elongated, and carries
huge 'chelae' at its distal extremity. The two succeeding pairs of
appendages correspond to the two pairs of 'maxillae' in the lobster.
In the first pair the 'maxillae' themselves are small, somewhat
conical, curved inwards, and form the external lateral elements
of the ' labium.' The ' palpi,' on the contrary, are greatly elon-
gated, six-jointed appendages, with two small claws attached to
their distal segment. In the second pair a similar arrangement
exists. The maxillae are two triangular processes, applied by
their straight internal edges to each other in the median line,
and so forming the mesial elements of the ' labium.' The palpi
resemble those of the first pair of maxillae. The next two pairs
of feet, representing the two pairs of 'maxillipeds' in the
Lobster, and the two anterior pairs of legs in Insects, resemble
the maxillary palpi just described, with the exception that they
are longer, and have much larger basal segments.

The next segment, which in the Crustacea would carry the
third pair of 'maxillipeds/ is, as in the Chilognathous Myriapods,
the genital segment. In the centre of the sternal surface of this
segment is the opening of the efferent duct of the reproductive

ARTHilOPODA. 27

organs. An opereular process, attached in front, and free poste-
riorly, hangs like a flap over this aperture. This may probably
be regarded as the sternal element of this segment. The
sternal elements of the two maxillary segments of the 'cephalo-
thorax' are aborted, but in the two succeeding segments the
sterna, though small, are still sufficiently obvious.

The segments and appendages hitherto described belong to
the cephalo- thorax: the five succeeding ones to the abdominal
region. The abdominal segments are distinct from each other,
and, with the doubtful exception of the first, carry no append-
ages. Each consists of a broad tergal and sternal arc, united
laterally by non-chitinous membrane. The sternal element of
each segment is divided into a median division, 'sternum/ and
two lateral divisions, *episterna,'by two well-marked grooves, one
on each side of the median line. On each ' episternum,' with
the exception of that of the first pair, is a small oblique slit,
the external opening of the pulmonary sacs. In addition to the
absence of pulmonary apertures, the first abdominal segment
further differs from the rest in the small size of the sternum, and
in the presence of a pair of pectiniform appendages. Each ap-
pendage presents indications of being composed of several seg-
ments, and carries on its hinder border a row of close-set filaments.

The six segments which succeed the abdomen are the
post-abdominal segments. With the exception of the first,
which resembles the abdominal segments in its general
shape, each segment is more or less cylindriform, completely
chitinized, convex above and concave below, and marked with
longitudinal serrated ridges. Attached to the last post-abdomi-
nal segment is a conical, somewhat tumid segment, which
carries a strong curved spine upon its distal extremity, and may
represent the 'telson' of the Crustacea. On the ventral surface,
and in the interspace of the last two segments, is the anus.

46. A Scorpion (Scorpio ), dissected to shew its

digestive tract.

The alimentary canal is seen to be a straight tube,
destitute of convolutions, and passing directly from mouth
to anus. The liver is very large, occupying four-fifths of the
thoracic cavity, and from it numerous ducts pass to the stomach.
The anus is situated on the under surface of the last segment

28 COMPARATIVE ANATOMY.

but one. The nervous system is seen at intervals underlying
the digestive tract in the abdomen.

47. A gravid female Scorpion, dissected to shew the posi-
tion of the embryos in an ovi-viparous Arachnid.

The dorsal surface of the animal has been removed. The
embryos, differing from the parent only in size, are seen occupy-
ing the ovarian tubes, which overlie the liver or are even em-
bedded in its substance.

48. A Spider, dissected to shew its nervous system.

The whole of the post-oral ganglia are seen to be con-
centrated into a single stellate mass, occupying the larger
portion of the ventral surface of the cephalo-thorax. From
this mass, which may be taken to represent the confluent
thoracic and abdominal ganglia of Insecta, radiate, on each
side, five principal nerves to supply the legs and maxillary
palpi. Several nerves pass posteriorly from its hinder edge to
supply the abdomen. The cephalic ganglia (two in number)
are situated on the anterior edge of this stellate mass, between
which and the former the oesophagus passes. From this pair
of ganglia nerves are seen passing forwards to supply the eyes
and mandibles.

Division ARTHROPODA BRANCHIATA.

Class CRUSTACEA.
1. Order Decapoda.

49. A Lobster (Homarus vulgaris), disarticulated, so as
to shew its segmentation.

The different segments with their appendages have been as
far as posible separated from each other, and serially arranged
in their natural order. The segments have been numbered
from the first, or ophthalmic segment, backwards. The carapace
has been removed, and fixed on the right of the sub-abdominal
segments.

The skeleton consists of a broad, shield-like carapace,
1 cephalo-thorax/ and of the six segments, or 'somites/ which enter
into the composition of the post-abdomen. Attached to the
ventral surface of these different segments are the variously

AETHROPODA. 29

modified appendages, to the number of twenty pairs. These are
named in order from the first segment as follows. In front of
the mouth are a pair of eyes, a pair of antennules, and a pair
of antennae. Behind the mouth are a pair of mandibles, two
pairs of maxillae, three pairs of maxillipeds, five pairs of ambu-
latory legs, and six pairs of swimmerets: while to the last
sub-abdominal segment is attached a median azygos element,
the 'telson.'

A sub- abdominal 'somite,' which may be regarded as a
typical one, is made up as follows. It is nearly semicircular
in vertical section, the dorsal wall or 'tergum' being very con-
vex, and the ventral wall or 'sternum' nearly straight or
but slightly convex. At the infero-lateral angle both the ' tergum ?
and the 'sternum' are produced downwards and outwards into
a lobate hollow process, termed the 'pleuron.' In the angle
between the 'sternum' and the inner surface of the 'pleuron/ on
each side, is an articular cavity, which receives the proximal
extremity of the appendage attached to this 'somite.' A trans-
verse groove marks off a crescentic area on the anterior surface
of the 'tergum,' which is overlapped by the hinder part of the
'somite' in front of it. This area is the tergal facet. A similar
flattened surface exists on the anterior portion of each 'pleuron.'
This is the pleural facet. Each appendage consists of a basal
attached portion (divided longitudinally into two segments), the
'protopodite.' Each' pro topodite' (sometimes called 'basipodite')
carries at its distal extremity an external and internal fila-
ment, to the former of which the term 'endopodite,' and to the
latter 'exopodite/ has been applied.

This description will in the main apply to the four central
sub-abdominal segments, but the first and the sixth of these
segments have their appendages somewhat modified for special
purposes. In the sixth sub- abdominal segment, the 'exopodite'
and 'endopodite' are enormously expanded into flat setose plates,
and the exopodite is further divided by a transverse joint.

The 'telson' is a flattened conical setose plate, attached
to the hinder margin of this * somite,' and forms, with the
expanded ' exopodite ' and ' endopodite,' a powerful swimming
tail.

In the first sub-abdominal 'somite ' each appendage consists of

30 COMPARATIVE ANATOMY.

two elements, the distal one of which is grooved on its inner
face, and is capable, by being applied to its fellow, of forming a
short cylindrical tube which probably conveys the male semen
to the vulva of the female.

The ' cephalo-thorax ' is formed by the fusion of the terga of
the cephalic, the thoracic, and the abdominal segments. The
cephalo-thoracic pleura are well developed, and extend so far
downwards as to hide the bases of the appendages.

The sternal portions of the pleura are membranous and are
reflected upwards to the roof of the cephalo-thorax, and then,
after being deflected, become continuous with the partially
calcified ' epimera.' In this specimen this membranous por-
tion has been torn through by the separation of the tergal half
of the cephalo-thorax from the coalescent sterna, which form the
ventral surface of this part of the animal.

On the dorsal surface the ' cephalo-thorax ' does not present
any indications of division into distinct terga, corresponding to
the sterna and appendages of the ventral surface, but neverthe-
less contains areas more or less distinctly marked out. A groove
commences at the base of the antennae, and, after passing
directly backwards for a short distance, curves upwards and
fuses with the corresponding curve of the opposite side at about
the middle of the dorsum. The part in front of this suture has
been called the ' cephalo-stegite,' and the portion behind the
' homo-stegite.' The ' homo-stegite ' is further divided by two
lateral linear depressions, one on each side of the median line,
called the ' brancho-cardiac sutures,' and by a very faint trans-
verse ridge, which is to be seen a little way behind the
cervical suture, into a quadrangular area which corresponds
externally with the position of the heart internally. In this
specimen this area is tolerably well indicated by a boundary
line of irregularly shaped white spots. The cervical suture indi-
cates the line of separation between the cephalic and thoracic
segments. The area between the cervical suture in front,
and the faintly marked ridge behind, represents the confluent
terga of the three thoracic segments, while that part of the
'homo-stegite' posterior to this corresponds with the terga of the
five abdominal segments. The lateral areas which lie on the side
of these median divisions represent the conjoined pleura of the

ARTHROPOD A. 31

eight thoracic and abdominal 'somites : ' and from the fact that
these areas cover in and protect the branchial chamber, they
have been called ' branchio-stegites/ Anteriorly the ' cephalo-
stegite' is produced into a long serrated rostrum. The sterna cor-
responding to the ' cephalo-thorax ' are, like the terga, confluent,
owing to the calcification of the membrane connecting the sterna
and epimera of adjacent somites. The sterna which are in rela-
tion to the three posterior pairs of ambulatory legs are tolerably
wide, but the sterna anterior to these become so narrow as to
allow the bases of the appendages to meet in the median line.
The calcified inter-epimeral, and inter-sternal membranes send
inwards calcified processes, which, after dividing, reunite with
each other in such a manner as to divide the floor of the
cephalo-thorax into a series of inter-communicating chambers.
A median canal is also formed by these processes, called the
' sternal canal.' It contains the thoracic portion of the ventral
nervous cord, and is indicated by the insertion into it of a red
glass rod.

The abdominal segments which have been already described
are tolerably simple, and only slightly modified : but those
appended to the 'cephalo-thorax' exhibit much greater diver-
sity of form, and subserve a variety of functions.

Taking the segments in order, from behind forwards, and
beginning with the first sub-abdominal or fifteenth body-
segment, which has been already described, we find the fol-
lowing cephalo-thoracic appendages.

XIVth pair. (Ambulatory legs.)

Each appendage consists of a right ' protopodite ' and a long
segmented ' endopodite,' the ' exopodite ' being absent. The
joints of the appendage are named by Milne-Edwards as fol-
lows: 'coxopodite' ['protopodite'], which is attached to the
'somite,' and pierced by the external aperture of the 'vas
deferens,' into which a black arrow has been inserted : — ' basi-
podite,' ' ischiopodite,' ' meropodite,' ' carpopodite,' 'propodite/
and ' dactylopodite.'

32 COMPARATIVE ANATOMY.

XIIIth, XIIth, XIth, Xth pairs, (ambulatory legs,)

are similar to the fourteenth pair, but each possesses a
long curved membranous appendage, which ascends from the
' coxopodite,' and in the natural condition penetrated into the
branchial chamber. This is the ' epipodite.' Attached to each
' coxopodite ' may also be seen a lamellar gill.

In the twelfth, eleventh, and tenth segments the 'propodite'
is prolonged outwards into a process which bites against the
' dactylopodites,' and so forms the chelaB, which in the tenth
pair are of great size,

IX*, VIIIth, VIIth pairs. (Maxillipeds)

Each maxilliped is composed of three divisions, articulated
to a ' coxopodite/ In the first maxilliped [No. ix.], the outer-
most of these three divisions, the ' epipodite ' is a curved lanceo-
late lamina. A little in front of it is a gill, likewise attached to
the ' coxopodite.' The middle division is a many-jointed palpi-
form filament, which corresponds to the ' exopodite.' The
innermost element is the seven-jointed ' endopodite.' The
second pair of maxillipeds [No. vill.] much resembles the first,
but the ' endopodite ' is smaller and somewhat flattened, re-
sembling the foliaceous ' endopodite ' of the first pair. In the
third pair [No. vn.] the ' endopodite ' has been split into an
inner flattened plate-like lamella and an outer flattened fila-
ment. The ' exopodite ' is small, but the ' epipodite ' is large, and
in the specimen directed backwards.

VIth, Vth pairs. (Maxillce)

In the first pair [No. VI.] the ' endopodite ' has been split into
five divisions, and is in consequence somewhat foliaceous. The
' exopodite ' is a flattened filament. The ' epipodite ' is curved in-
wards. The ' endopodite' of the second pair [No. v.] differs
from that of the first in having only three divisions. The ' exo-
podite ' and ' epipodite ' are absent.

ARTHROPODA. 33

IV* pair. (Mandibles)

Each mandible carries a jointed palp, which corresponds to
the terminal joints of the mandibular ' endopodite ' (Huxley).
The calcified rod projecting outwards is the tendon of the ad-
ductor muscle of the mandibles.

IIId pair. (Antennce.)

The antennae are composed of a short basal ' protopodite/
which carries a long multi-articulated 'endopodite' and a short
flattened scale-like 'exopodite.' The black arrow is inserted into
the orifice of the duct of the 'green gland.'

IP pair. (Antennules.)

A three-jointed ' protopodite ' is succeeded by two long
multi-articulated filaments, the 'exopodite' and 'endopodite.'
An aperture protected by membrane in the proximal joint, and
towards which the arrow points, is the auditory organ.

/" pair. (Ophthalmic peduncles)

The eye-peduncles are composed of two segments, the distal
one of which carries the eye itself.

On the left of the specimen is a portion of the skeleton of a
female, with the ventral surface turned upwards, so as to shew the
openings of the oviducts on the ' protopodite' of the third pair of
ambulatory legs. The two orifices are indicated by two black
arrows. The first pair of post-abdominal appendages differs
from those of the male in being simple unmodified filaments.

The structure of the stomach is illustrated by the two
specimens marked A and B. In B the greater portion
of the cephalothorax has been removed so as to expose
the cavity of the thorax, with the stomach in its natural
position. This viscus occupies nearly the whole of that part of
the cavity which lies in front of the cephalic suture, and its
membranous walls are supported and strengthened by a some-

CL. 3

34 COMPARATIVE ANATOMY.

what complicated arrangement of calcified bars and plates. It
is divided transversely by a rather deep fissure into an anterior
layer or cardiac portion, and a posterior smaller or pyloric
division. The structure of the calcified gastric skeleton is as
follows.

Crossing the stomach transversely, at the hinder border of
the cardiac division, is a broad and slightly arcuated plate, the
' cardiac ossicle.' Attached to each extremity of this 'cardiac
ossicle ' is a curved triangular ' ptero-cardiac ossicle/ On each
side a large elongated ' supero-lateral ossicle/ wider posteriorly
than anteriorly, is connected with the lower end of the ' ptero-
cardiac ossicle/ and passing upwards and backwards articulates
by the anterior part of its hinder extremity with a small
transverse rod, which forms the medial part of the anterior
boundary of the pyloric portions, and is termed the ' pyloric
ossicle/ The posterior part of the superior extremity of the
' supero-lateral ossicle ' is connected with a triangularly shaped
imperfectly calcified plate, the ' meso-pyloric ossicle/ An-
teriorly this ossicle becomes continuous with the hinder edge
of the pyloric ossicle. " These pieces, it will be observed, form
a sort of hexagonal frame whose anterior and lateral angles are
formed by moveable joints, while the posterior angles are
united by an elastic meso-pyloric plate." From the middle
of the cardiac piece a strong calcified process passes downwards
and backwards underneath the ' meso-pyloric ossicle/ termi-
nating in a broad thickened extremity, which may be termed
the post-cardiac process, and to which is attached internally a
broad and flat chitinous plate. This plate has its postero-
lateral and internal angles slightly nodular. These nodules
represent the cardiac teeth of the Common Cray-fish. A very
narrow and uncalcified band connects the end of the post-cardiac
process with a broad calcified process, the ' uro-cardiac ossicle/
This ossicle carries on its inferior surface a strong conical tooth,
which projects into the cavity of the pyloric divisions of the
stomach. Finally, connected in a similar manner with the end
of the uro-cardiac piece, is a broad somewhat triangularly
shaped ossicle, convex above and concave beneath, the 'pre-
pyloric ossicle/ This passes upwards and forwards, and connects
the uro-cardiac with the pyloric ossicle. In A the greater

ARTHROPOD A. 35

part of the meso-pyloric ossicle has been removed, so as
better to exhibit the 'pre-pyloric ossicle' which lies beneath
it. The post-cardiac process and the uro-cardiac ossicle, with
its teeth, are also best seen in this specimen. The supero-
lateral ossicle sends inwards from its inferior border a strong
calcined process, which carries on its internal face the large
lateral gastric tooth. On the infero-lateral parietes of the
stomach there are several rod-like ossicles. To the inferior
extremity of one of these, the ' lateral cardiac/ stretching down-
wards and backwards from the 'ptero- cardiac,' is attached a
small ossicle, which internally bears a bifid tooth. The under
surface of the stomach is strengthened by two nearly parallel
rods, which extend from the pylorus forwards to the cardiac
division, where they become divergent and more or less mem-
branous. Their posterior extremities, also slightly divergent, are
somewhat thickened, and each articulates with two rods, one
of which is connected with the ossicle just described as bearing
the bifid tooth, while the other joins the ' supero-lateral ossicle.'
There are thus five gastric teeth, one median, and two lateral
on each side.

In A, on looking into the gastric cavity and towards the
pylorus, we can see, situated beneath the median gastric tooth,
a bilobed valvular process; and on either side, immediately
beneath the great lateral teeth, is a similar cushion-like process.
These processes are beset with hairs, and by their mutual
apposition form an efficient sieve to prevent the undigested
food from passing into the intestine.

For an account of the structure and functions of the stomach
of Astacus fluviatilis, which differ but little from that of the
specimen described above, see Huxley, "Medical Times and
Gazette" 1857, Vol. xiv. p. 255 : also Rolleston, p. 90.

50. The cephalo-thorax and the first fourteen segments
of a Langouste (Palinurus vulgaris.)

The same numbers have been affixed to the same parts as in
the preceding specimen : and the description is in the main
equally applicable.

51. A Lobster (Homarus vulgaris), dissected to shew its
nervous system, which is of the type termed ' homogan-
gliate:' that is, it consists of a longitudinal series of ganglia

3—2

3G COMPARATIVE ANATOMY.

of various sizes, united by nerve-cords, termed ' commissural
cords,' and occupies the ventral surface of the body.

The total number of ganglia is thirteen. Of these, the first
is the pra3-oral or cephalic ganglion, from which are derived the
nerves supplied to the eyes, antennae, and antennules. Black
bristles have been placed under these nerves. The remaining
and post-oral twelve are equally divided between the thoracic
and abdominal segments. The first post-oral ganglion (formed
by the fusion of six embryonic ganglia) is of large size, and
supplies six pairs of appendages, viz. the mandibles, two pairs
of maxillaB, and three pairs of ' maxillipeds.' The five succeed-
ing ganglia, smaller in size, and comparatively close together,
supply the five pairs of ambulatory legs. The abdominal
ganglia, still smaller in size and separated by greater inter-
vals, supply the powerful abdominal muscles, and the segmental
appendages. The last of these ganglia is of larger size than the
rest, and gives off a leash of nerves to supply not only its own
segment and appendages, but the 'telson.' The longitudinal
commissural cord is double in the segment anterior to the abdo-
men, but in the latter region it is reduced by fusion to a single
thread. Between some of the abdominal ganglia may be seen
the 'nervi transversi.' These are small nerves given off from
the longitudinal cord, at a point about midway between the
ganglia.

52. A Cray- Fish (Astacus fluviatilis), dissected to shew
the male generative system.

The whole of the heart and the greater part of the liver
have been removed. The testes are situated immediately
behind the posterior end of the stomach, and consist of two
lateral halves, which posteriorly fuse into a long thin mass,
situated in the median line. On either side the 'vasa defe-
rentia' quit the gland at the junction of its three apparent
lobes, and after describing a mass of convolutions on either side
of the hinder part of the thoracic cavity, terminate by a small
prominent orifice on the basal joint of the last pair of thoracic
legs. A slip of blue paper has been placed under the terminal
segment of each ' vas defercns.'

Rolleston, p. 106, sq.

ARTHROPODA. 37

2. Order Stomapoda.

53. A Stomapod (Squilla mantis'), dissected to shew the
same parts.

The double ' commissural cord T connecting the prse-oral with
the post-oral ganglion is remarkably well seen. The remaining
thoracic ganglia supply the thoracic legs. The abdomen con-
tains six ganglia, each of which gives off two or more nerves
on each side to supply the muscles of its segment. The longi-
tudinal commissural cord connecting the different ganglia is
more or less distinctly double throughout.

Sub-Class CIRRIPEDIA.

54. A Barnacle (Lepas anatifera).

The body of the animal consists of 'capitulum' and 'peduncle.'
The peduncle is soft and fleshy, and invested externally with a
tough rugose skin, which by its distal, clavate extremity serves
to attach the animal. The 'capitulum' is somewhat triangular,
consisting of two lateral valves, strengthened externally by
several calcified plates, and encloses the major part of the body
of the organism. The calcified pieces composing the valves are
four in number, two in each valve. The superior or distal
plates are called ' terga,' and the lower or proximal plates, also
the largest, are called 'scuta.' The two valves are connected
with each other along one side, through the intermediation of a
mesial curved piece, the ' carina.' Within those valves the body
of the animal is to be seen : — its dorsal surface in relation with
the inner surface of the ' carina/ The body consists of a ' prosoma'
which includes the cephalic segments — of six thoracic segments
— and a tubular extension from the hinder edge of the last
thoracic segment, which functionally is a penis, but morphologi-
cally may be the aborted representative of the abdomen, or
post-abdomen, of other Crustacea. The mouth is bounded
anteriorly by a tumid, transversely extended labrum. Behind
this we find, first, a pair of mandibles, each armed with a setose
palp, and two pairs of maxillae. Six pairs of appendages are
attached to the thorax, each consisting of a basal 'protopodite'
terminating clistally in a long multiarticulated 'exopodite' and
'endopodite.' That part of the body which lies in front of the

38 COMPARATIVE ANATOMY.

mouth, together with the whole of the peduncle, is the result of
an extraordinary development of the pre-oral 'somites' — and
the only appendage to be found in relation with these segments
is a pair of sucker-like antennae, to be seen by careful examina-
tion of the attached surface of the peduncle.

55. A Barnacle (Lepas fascicularis) , dissected to shew its
digestive system.

One half of the calcareous carapace has been removed, to-
gether with the investing membrane and the left testicular
mass. A black bristle has been inserted through the mouth and
oesophagus into the stomach, and a white one into the anus.
The mouth, encircled by its mandibles and maxillae, leads by a
short oesophagus into a large oval or sub-globular stomach.
The intestine is a simple tube of considerable size at its com-
mencement. It bends upon the stomach, and proceeds along
the dorsal aspect of the animal, gradually diminishing in size,
to the anus, which is situated at the base of the penis.

Upon the stomach is a mass of dark-coloured glandular
caeca, probably hepatic in function, — (a portion has been re-
moved with the wall of the stomach,) — which communicate
by several large orifices with its cavity. The cuticular lining
of the oesophagus is continued for some distance into the
stomach, and terminates therein by a well-defined serrated
edge.

56. The same, dissected, to shew its hermaphrodite genera-
tive system.

In the upper of the two specimens on the tablet the cara-
pace and investing membrane have been removed, and the
organs displayed in situ, on the left side.

The testis, of irregular shape, is composed of minute branch-
ing caeca, and not only overlies the pyloric end of the stomach,
but also gives off prolongations which enter the pedicels, and
the basal segments of the rami of the cirri.

In the lower specimen a great part of the testis has been
removed, so as to shew the ' vas deferens,' or dilated portion of
the efferent duct of the testis, ascending parallel to the terminal
portion of the intestine. It gradually diminishes in size to the
base of the penis, where it joins the corresponding duct of the
opposite side to form the common canal, which, after traversing

MOLLUSCA. 39

the penis, opens at its end. A black bristle has been placed
under the two ducts.

The ovaria are disposed in the peduncle and in the body.
In the peduncle they may be seen as a tangled mass
of branching tubes, filled with granular matter and immature
ova. From the peduncle two main ducts (not seen in this
specimen), one on each side, enter the body at the anterior
corner of the rostrum, whence they curve round towards the
base of the first pair of cirri. There they form two glandular
masses resting on the upper edge of the stomach, of an orange
colour, and generally subdivided near the mouth. These masses
were thought by Cuvier to be salivary glands, but are now
known to be true ovaries. No proper oviduct has yet been dis-
covered. In the uppermost of the two specimens, between the
body of the animal and the peduncle may be seen one of the
ovigerous lamellae in which the ova exist previous to their ex-
pulsion.

Darwin, " Monograph on the Cirripedia," p. 55, sq.

SUB-KINGDOM MOLLUSCA.

Division I. MOLLUSCOIDEA.
Class TUNICATA.

In the following preparations of Ascidians a Hue rod has
been placed in the inhalent, a red rod in the exhalent, aperture.
Eolleston, p. 66.

57. A simple Ascidian (Cynthia microcosmus.)

One half of the test, which in this species is of a leathery
consistency, has been removed, to shew the animal suspended
within it. The mantle is attached to the test at the two aper-
tures, and is very muscular. Fibres may be seen passing in a
longitudinal, oblique and transverse direction across its surface.
The two apertures are regarded by some as homologous with
the inhalent and exhalent siphons of the Siphonate Lamelli-
branchiates; and by others, as the mouth and anus.

58. One-half of the test, mantle, and branchial sac has been
removed, so as to expose the cavity of the latter. The branchial

40 COMPARATIVE ANATOMY.

sac is of considerable size, with its walls produced into a series of
parallel longitudinal folds, radiating from the inhalent orifice
to the mouth. A black bristle has been introduced into the
aperture leading from the branchial sac to the stomach — an
aperture which has been regarded by some as the mouth, while
others maintain that the mouth is better represented by the
inhalent aperture.

5.9. To shew the nervous system.

The single nerve-ganglion is situated in the substance of the
mantle on one side of the inhalent aperture, between it and the
exhalent aperture, and is indicated in the specimen by the inser-
tion of a black bristle behind it. The ganglion is fusiform in
shape, and from its anterior and posterior ends nerves are seen
passing towards the inhalent and exhalent apertures respec-
tively.

The genital ducts are seen emerging from the lower margin
of the first intestinal coil, and following the course of the intes-
tine open into the atrium in close contiguity to the anus.

60. An Ascidian, of a different species, dissected to shew its
digestive tract.

The external test has been removed, and the mantle and wall
of the branchial sac reflected.

A black bristle has been passed through the inhalent aper-
ture, branchial sac, and mouth, into the stom,ach, and a red rod
through the exhalent aperture and atrial chamber. The
mouth is situated at the bottom of the branchial sac, and leads
by a short cesophageal canal into an oblong stomach. Proceed-
ing from the stomach the intestine describes two curves, the
first of which has its convexity directed towards the nerve-
ganglion (marked by a black bristle being placed under it), and
its concavity towards the heart. Hence the primary flexure of
the intestine is said to be haemal. The second curve has its
concavity towards the ganglion, and terminates in a rectum
which has its anal orifice in the atrial chamber. The floor of
the stomach is seen to be marked by a longitudinal ridge, which
is prolonged into and along the intestine, so as partially to divide
the tube into two canals, by which arrangement the absorptive
surface is much increased. On the side of the branchial one
opposite to the mouth is to be seen a portion of the 'endostyle.'

MOLLUSC A. 41

Family Salpidce.

61. A Salpa maxima, the asexual form. A green rod
has been passed through the body-cavity, so as to protrude from
the anterior and posterior orifices. The test is double, being
composed of an inner and an outer layer : of which the latter is
semi-transparent, uniform in texture, and almost colourless:
the former is more opaque, of a yellowish tint, and provided
with numerous transverse muscular bands. The two are seen
to be united at one point on the right side near the posterior
orifice.

Extending across the body-cavity diagonally, from right to
left, are the branchiae. In the left-hand lower corner is the
liver, close to which is a young chain of sexual salps.

62. In this specimen the chain of sexual salps is nearly
mature, and will shortly separate from the animal.

63. A chain of sexual forms of the same species. In
the centre are two specimens, chained together, of JSalpa

pinnata.

Bay of Naples, 1874. F. M. Balfour.

Class POLYZOA.

64. A Sea-Mat (Flustrafoliacea).

The zooids in the living specimen are contained within the
ovoidal corneous cells of which the ramose and lamellar
' csenaecium ' or ' polyzoarium ' is composed. These cells are
arranged on both sides of the frond in parallel longitudinal
rows ; examined with a lens, from four to eight short and blunt
spines are seen to surround the broad end of each cell. The
stone to which these fronds are attached is encrusted with these
cells.

Class BRACHIOPODA.

65. Two specimens of Lingula anatina.

They have been attached to a sheet of mica. The valves
are of a horny texture, and of nearly equal size, differing in this
respect from the majority of the class, which have equilateral
but inequivalvc shells. Furthermore, the valves are not lateral,

42 COMPARATIVE ANATOMY.

as in the Lamellibranchiata, but dorsal and ventral in relation
to the animal they contain. Between the margins of the
umbones the long muscular peduncle by which the animal
is attached is protruded. The dorsal valve and mantle of the
right-hand specimen have been removed, but the ventral mantle-
lobe, with its margin and fringe of setse, is left intact, adhering
to the inner surface of the ventral valve. Little of the body,
which occupies but a small part of the shell, can be distinguished,
with the exception of a white glandular central mass, the liver,
and the various muscles by which the adduction and adjustment
of the valves is effected. The lateral margins of the mouth
are produced outwards into two muscular ciliated ' arms/ which
occupy quite one-half of the shell, and are curved inwards to-
wards each other. ,The bases of the arms are connected with
each other by a vertical membranous partition.

Division II. MOLLUSCA PKOPER.

Class LAMELLIBRANCHIATA.

66. A Fresh-water Mussel (Anodonta cygnea), removed from
its shell, so as to shew the general relation of the mantle and
branchiae. The two strings by which the animal is suspended
are attached to the mantle, one to each of its lobes. Bristles
are inserted into the mouth and anus.

The mantle consists of two lateral lobes, confluent with each
other along the medio-dorsal line, but free throughout the whole
of their ventral margins. With the exception of the free, thick-
ened, glandular, and shell-secreting ventral margin, which is
homologous with the ' collar ' of Gasteropoda, each pallial lobe is
comparatively thin, and in the fresh condition nearly trans-
parent. In the vicinity of the anus the free edge of each
mantle-lobe is beset with a fringe of minute papillae. This
papillose border corresponds with that part of the mantle which
in the siphonate Lamellibranchiata is produced into the cylin-
drical exhalent and inhalent siphons. There are two pairs of
branchiae on each side of the central body-mass ; each gill is a
flattened bag composed of longitudinal and transverse fibres,

MOLLUSC A. 43

and richly ciliated. By the fusion of the two inner gill-lamellae
through the hinder third of their extent, the mantle-cavity is
divided into a superior or anal chamber, into which the anus
opens, and an inferior or pallial chamber. The anal chamber,
indicated in the preparation by a white bristle, corresponds to
the exhalent siphon. Anterior to this union the two laminae are
free, but are united to the body-mass anteriorly to this. On
each side of the mouth is a pair of lamellar labial palpi.

67. A vertical section of an Anodon. The section has been
taken through the heart and intestine, the organ of Bojanus,
the visceral mass, and the foot. A white bristle has been in-
serted into the ventricle, through which the intestine is seen to
pass. Immediately beneath the heart a black bristle is inserted
into the great dorsal sinus, and right and left of this, a white
bristle has been placed in the secretory portion of the organ of
Bojanus, which overlies the excretory portion. The preparation
also shews the relation of the mantle and the two pairs of gills
to the median visceral mass. The three inferior bristles indicate
sections of the intestine which have been cut through in the
specimen.

68. The same, prepared to shew its digestive system.
The right lobe of the mantle and the right gill have been

removed, and part of the muscular foot and liver cut away to
shew the convolutions of the alimentary canal, which has been
filled with a light blue injection. A blue glass rod has been
placed in the mouth.

69. The same, prepared to shew the two muscles which
serve to draw the valves of the shell together (the anterior
and posterior adductor muscles). The strings by which the
proportion is suspended are attached to the posterior extremity
of the shell. Rolleston, p. 54.

70. The same, to shew its nervous system.

The animal is suspended on mica with its mouth upwards.
Part of the muscular foot has been removed on the left side to
shew the pedal ganglion in situ. Part also of the organ of
Bojanus has been cut away to shew the nervous commissure
connecting the cephalic with the parieto-splanchnic ganglion,
and posteriorly the two inner lamellae of the two inner gills
have been separated so as to shew the commissure last men-

44 COMPARATIVE ANATOMY.

tioned throughout its entire length. The ' labial ' ganglion is
seen lying on the anterior retractor muscle of the foot, and
immediately below the anterior adductor. Three commissural
cords, under each of which a slip of blue paper has been placed
pass off from it. The one which is seen passing vertically
downwards along the base of the inner gill and through the
organ of Bojanus, connects the labial with the parieto-
splanchnic or branchial ganglion, which is seen lying on the
posterior adductor. A little way to the left may be seen the
terminal portion of the corresponding commissural cord of the
opposite side. A slip of blue paper has been placed beneath
it. A second cord is seen passing obliquely to the left, into the
substance of the foot, to join the pedal ganglion. The third
cord passes upwards towards the anterior adductor, and
connects the labial "ganglion with its fellow of the opposite
side. From the pedal ganglion several nerves may be seen ra-
diating to supply the muscular foot. A black bristle has been
placed beneath a bundle of them. The two parieto-splanchnic
ganglia of the two sides of the body are closely apposed, so as
to form a transversely oblong mass. Nerves from these ganglia
may be noticed passing to the mantle and inner gills.

71. Two Oysters (Ostrea edulis).

The upper specimen shews the single adductor muscle; the
lower, the hinge-ligament, which causes the valves to open.
Each valve is composed of a series of concentric calcareous
laminae, overlapping each other by their free margins.

72. A specimen of PJiolas dactylus, to illustrate the ar-
rangement of the mantle in a Siphonate Gasteropod.

A red rod has been placed in the exhalent orifice, and a
blue rod in the inhalent.

The valves of the shell have been partially opened, so as to
shew the union of the ventral margins of the mantle. In front
the mantle-lobes are widely separated, so as to allow of the
protrusion of the muscular foot between them. In front of the
foot they are again united. Inferiorly the mantle-lobes are
prolonged downwards into a cylindrical tube, divided into two
canals by a median attachment. These canals are the exhalent
and inhalent orifices.

MOLLUSCA. 45

Class GASTEROPODA.
Order 1. Opistho-lranchiata.

73. A Sea- Hare (Aplysioi), dissected to shew the general
disposition of its organs.

In the upper of the two specimens on the tablet the rudi-
mentary shell has been displaced to the right side of the
animal, and the left mantle-lobe deflected, thus exposing the
heart, branchia3, and terminal segment of intestine.

The arborescent branchiae, protected by the rudimentary
shell, are situated behind the heart and towards the rear of
the body (hence the position of the animal in the order
Opistho-branchiata), but in front of the anus, into which a
black bristle has been inserted. A black bristle has also been
placed under the bilocular heart and the rectum.

In the lower preparation, the muscular envelope of the
animal has been separated from the foot along the left side,
and reflected to the right, together with the heart, branchiae,
and parts of the generative system. The digestive tract has
been arranged mainly on the left side.

The ribbon-like salivary glands (two in number) have been
pinned to the left of the animal's head. Posteriorly to the
buccal mass the oesophagus is seen communicating with the
stomach, which is divided by certain constrictions into three
compartments, the last of which, from the muscularity of its
walls, has been termed a gizzard. Surrounding the gizzard
and communicating with it by a large duct is the liver. The
intestine, on emerging from the liver, curves round the lower
border of the specimen, and passes to the anus. On the ex-
terior of the liver is the hermaphrodite gland, a white, irregu-
larly shaped, granular mass. From it a slightly convoluted
hermaphrodite duct passes forwards to the albuminiparous
gland; and after this junction and the reception of the duct of
a minute vesicle (seen near the anterior margin of the gland),
the duct passes upwards as a much larger tube to its external
opening, prior to reaching which it communicates with a
globular spermatheca. A little to the right of this part are
the heart and branchiae. A bristle has been placed under the
former.

46 COMPARATIVE ANATOMY.

The nervous collar, consisting of supra-cesophageal and sub-
cesophageal ganglia, connected by commissural strands, is seen
surrounding the oesophagus. From the sub-cesophageal ganglia
two nervous chords pass obliquely to a ganglion on the right,
(indicated by a black bristle), situated immediately in front of
the spermatheca : from this ganglion nerves are given off to the
genitals, liver, and branchiae. From the cephalic ganglia nerves
are seen passing to the tentacles.

Order 2. Prosobranchiata.

74. A Common Whelk (Buccinum undatum}.

The proboscis has been extended to its full length, and a
blue rod inserted in the mouth. The foot and operculum are
in the positions which they would assume when the animal is
in motion.

75. Another specimen, to shew the structure of the pro-
boscis, which has been laid open. A blue rod has been inserted
into the oesophagus. At the end of the proboscis is seen the
strap-like tongue, armed with a treble row of horny teeth. At
the end of the proboscis nearest to the head it is marked
horizontally with numerous striations, indicating the mode in
which it is folded upon itself within the body of the animal.
Its termination, which is not so marked, remains unfolded
when the organ is drawn in. The movements of the tongue
are effected by the longitudinal muscles seen beneath the oeso-
phagus.

76. Another specimen, to shew the penis and the sperm-
duct.

The penis has been protruded, and a portion of the shell
taken away so as to shew the sperm-duct, under which, where
it emerges from the body of the animal, a black bristle has
been placed. The penis is a very large, flattened organ, and
when laid open is found to be composed of interlacing muscular
fibres. The sperm-duct, having pursued a tortuous course
through the penis, terminates by opening externally at the
extremity of a projection near its blunt end.

77. Another specimen, to shew the digestive tract.

The whole of the mantle has been removed, the animal sus-
pended by its penis and proboscis, and the alimentary canal

MOLLUSCA. 47

partially filled with red injection. The proboscis has been
unfolded and laid open so as to display the commencement
of the alimentary canal, into which a blue rod has been in-
serted.

The oesophagus is of considerable length. At the base of
the proboscis it is clasped by large, coarsely-lobed, irregular,
salivary glands whose ducts open into it, as does a long and
apparently glandular cascum, which is coiled round its subse-
quent portion. Before it reaches the stomach there is a small
conical crop. The stomach is somewhat peculiar in shape, of
moderate size, and has its oesophageal end produced into a
short conical cascum. A black bristle has been placed under
this portion. The intestine, compared with the preceding por-
tion of the digestive tract, is remarkably short. Its primary
flexure is hsemal, and its terminal segment, or ' rectum,' very
large and capacious. The anus opens into the pallial cavity,
and is indicated by the insertion into it of a red rod. Near the
pyloric end of the stomach is the bi-locular heart.

78. A specimen of Triton rugosus, prepared to shew the
relation of a Branchio-gasteropod to its shell, when it is re-
tracted within its shell, and the mouth closed by the oper-
culum.

The first whorl of the shell, being broken away, shews the
broad muscular foot ; the tentacles behind; and further still the
proboscis, much retracted, which has been made visible by
removing a portion of the overlying integument. Behind this
again is seen the mantle, a large portion of which has been cut
away, so as to expose its cavity, in which are contained the
gills, the exhalent siphon, and the intestine. The branchiae
are seen as a fringe, depending from the lower border of the
mantle-cavity. A blue rod has been placed in the anus, a red
rod in the exhalent siphon. At the termination of the bran-
chiae the liver commences, and occupies the last two whorls of
the shell.

Order 3. Pulmonifera.

79. The upper specimen on the tablet, a Garden Snail (Helix
aspersa), shews the position and relations of the aperture of the
pulmonary sac when the animal is in motion. The aperture,

48 COMPARATIVE ANATOMY.

into which a white bristle has been inserted, is situated imme-
diately within the peristomial margin of the shell, a little to the
right side of the animal, but to the left of the anus, which is
indicated by a black bristle.

In the lower of the two specimens, a Roman Snail (Helix
pomatia), nearly the whole of the shell has been removed, and a
red injection thrown into the auricle and pulmonary vessels.
An incision has been made transversely through the roof of the
pulmonary sac, and its interior exposed by turning back the
posterior flap. A black bristle has been passed through the
external orifice into its cavity. Attached to the displaced
posterior half of the sac is the pale-coloured and triangular
kidney, and close to it on the left side the bilocular heart.

The floor of the respiratory cavity is non- vascular, being
composed of muscular fibres arranged transversely and lon-
gitudinally: and functionally representing a diaphragm. On
the right side of this floor the rectum may be seen passing for-
wards to the anus, which is situated to the right of, but in close
proximity to, the respiratory orifice.

80. A Roman Snail (Helix pomatia), dissected to shew
the general disposition of its organs.

The shell has been removed. The liver, heart, and pul-
monary sac have been arranged on the left side of the prepara-
tion, the stomach and salivary glands in the middle, and the
generative system mainly on the right side.

Posteriorly to the buccal mass, and on emerging from the
nerve-collar through which it passes, the oesophagus expands
into a long and fusiform stomach. The salivary glands overlie
the stomach about the middle of its length, and the two ducts
therefrom pass forwards through the nerve-collar and pierce the
buccal mass anteriorly to it. Posteriorly the stomach diminishes
in size, and at its point of junction with the intestine receives
the single large hepatic duct. The first segment of the intestine
ascends towards the heart, and, together with the stomach,
makes up a curve having its concavity towards the pedal
ganglia. Hence its primary flexure is said to be neural.
Below the heart the intestine describes certain convolutions
in the substance of the liver, and reappearing on the extreme
left of the preparation, proceeds straight to the anus, which is

MOLLUSC A. 49

indicated by a black bristle. The nerve-collar (through which
a black bristle has been passed) encircles the oesophagus. From
the supra- cesophageal portion delicate nerves pass forwards to
supply the tentacles, lips, &c. A little to the left of the left
salivary duct may be seen the left parietal nerve, double at
its termination, passing from its origin in the parieto-splanchnic
ganglion to its peripheral distribution in the body-walls. Be-
tween the left salivary duct and the stomach the central
portions of three other nerves may be seen in connection with
the same ganglia, viz. the two parietal nerves of the right side
and the great visceral nerve in connection with the aorta. The
second black bristle (the lower one) is inserted into the anterior
aorta, which passes through a foramen between the upper or
parieto-splanchnic, and the lower or pedal portion of the sub-
cesophageal mass.

On the left of the preparation is the pulmonary sac. The
greater portion of its diaphragm-like floor has been removed,
and its highly vascular roof exposed. At the lower edge of
the sac, and on the right side of it, is the bilocular heart.
To the left of the heart is the pale triangular kidney.

The hermaphrodite gland is lodged in the concavity of the
penultimate and ante-penultimate coils of the liver, which
occupy the lowest part of the preparation. From this gland
a convoluted hermaphrodite duct passes upwards to a tongue-
shaped body, the albumin iparous gland; and after this junction
the duct passes upwards again as a thicker and much plicated
tube, having closely applied along it a ribbon-like glandular
prostatic mass. At about the level of the animal's head this
hermaphrodite duct divides into the oviduct and the vas defe-
rens. The vas deferens passes forwards and joins the base of
the penis at the point where the long whip-like flagellum also
joins it. On the extreme right of the preparation is the globular
spermatheca with its duct leading to the oviduct into which it
opens. Connected with the vagina is the 'dart sac,' and
between the latter and the oviduct are seen the 'multifid
vesicles.'

The external generative opening is on the right side of the
animal at the base of the right superior tentacle.

CT, *

50 COMPARATIVE ANATOMY.

81. A Roman Snail (Helix pomatia), dissected to shew its
nervous system.

The viscera have been removed, with the exception of the
buccal mass, oesophagus, and portions of the generative system.

The oesophagus has been drawn through the nerve-collar
and pinned in front of the animal's head.

As in other Gasteropoda the central nervous system forms a
collar encircling the oesophagus. The supra-cesophageal part of
the collar is composed of the two cephalic ganglia and the broad
commissural band connecting them. The sub-cesophageal gan-
glia, which are connected with the former on each side by a
double nervous cord, consist of a lower or pedal, and an upper
or parieto-splanchnic element. From the former of these ele-
ments nerves may be seen passing to the muscular foot, while
from the parieto-splanchnie portion three large nerves pass off
to supply the parietes. Of these, two pass to the right side, and
one, which bifurcates, to the left. Arising from the same source
is the great splanchnic nea-ve. This nerve proceeds posteriorly,
in close proximity with the anterior aorta, as far as the al-
buminiparous gland, at which point it divides into two branches,
one of which goes ,to the liver, and the other to the herma-
phrodite gland. The anterior aorta passes forwards through a
foramen between the parieto-splanchnic and pedal ganglia to
supply the anterior part of the body. This fact, together with
the distribution of the nerves of the two ganglia respectively,
enables these two elements of the sub-cesophageal mass to be
differentiated.

From the cephalic ganglia nerves, under which a slip of blue
paper has been placed, may be seen passing forwards to supply
the superior or eye-bearing tentacles, together with the upper
lip and adjacent sensitive surface.

From each cephalic ganglion a nerve passes to join a small
stomato-gastric ganglion, situated on either side of the point at
which the oesophagus joins the buccal mass. The two stomato-
gastric ganglia are connected by a commissural strand, and from
each nerves are given off to supply the buccal mass, salivary
glands, and oesophagus.

82. A Grey Slug (Limax cinereus), dissected to shew the
general distribution of its organs.

MOLLUSCA. 51

The muscular envelope of the animal has been separated
from the foot proper along the left side, and turned over to the
right, together with the shield-shaped mantle, heart, and pul-
monary sac. The digestive tract and the glandular organs
in connection with it have been displaced from their natural
positions and pinned to the tablet on the left side of the prepa-
ration, while the generative organs, similarly displaced, occupy
the right side. The superior tentacles have been pinned by
their retractor muscles in front of the animal's head.

On the left side of the head are the salivary glands, two
lobulated organs connected with the mouth by two ducts which
pass forwards through the nerve-collar and pierce the buccal
mass anteriorly to it. The glandular mass which encircles the
anterior margin of the buccal mass is 'Semper's organ,' sup-
posed by its discoverer to be olfactory.

The oesophagus, emerging from the buccal mass, passes
through the nerve-collar, and almost immediately expands into
a long fusiform stomach, the posterior segment of which,
separated from the anterior three-fourths by a slight constric-
tion, receives the two biliary ducts, one from each of the two
principal lobes into which the liver is divided. A convoluted
intestine succeeds the stomack, passing to the middle line of the
body, where, after a short retrograde course posteriorly, it bends
sharply upon itself, ascends, and terminates at an anus situated
on the right side of the respiratory aperture.

In the upper portion of the specimen, and on the right side,
is seen the reticulated structure of the roof of the pulmonary
sac, the floor having been removed.

A little posterior to this point is seen the bilocular heart,
together with portions of the two trunks into which the aorta is
divided. Beneath the heart is the sub -triangular yellow kidney.
In the natural position of these parts the kidney would of course
overlie the heart. Immediately posterior to the buccal mass,
and encircling the oesophagus, is the nerve-collar, consisting,
superiorly, of the two cephalic ganglia connected with each other
by a broad commissural band, and inferiorly of the parieto-
splanchnic and pedal ganglia. The supra-cesophageal and sub-
cesophageal masses are mutually connected by a double commis-
sural strand embracing the gullet.

4-2

52 COMPARATIVE ANATOMY.

From the cephalic ganglia nerves may be seen passing
anteriorly to supply the tentacles, 'Semper's organ,' and the
adjacent parts. From the upper or parieto - splanchnic seg-
ment of the sub-cesophageal mass nerves are given off to the
parietes and viscera. Of the visceral nerves, the peripheral
divisions have been removed, their origins alone remaining.
From the lower or pedal segment a leash of nerves passes
off to supply the muscular foot. A black bristle (the longest
of the two) has been inserted into the foramen which gave
passage to the anterior branch of the aorta.

In the angle which the gullet makes with the buccal mass,
and situated on the latter, is the right stomato-gastric ganglion
of the sympathetic system.

Of the generative organs, the hermaphrodite gland (situated
at the bottom of the right side of the tablet) is connected by
a single convoluted duct with the large, somewhat irregularly
shaped, and coarsely lobulated albuminiparous gland.

The duct, on emerging from the gland, is of much larger
size and plicated. It has associated with it throughout
the greater portion of its length a ribbon-like granular pros-
tatic mass. Immediately above the pulmonary sac this sub-
divides into a long thread-like -duct, or 'vas deferens,' which
joins the root of the penis, and a short, thick oviduct which
opens outwards.

In the re-entering angle between the penis and the oviduct,
and communicating with the latter, is the globular spermatheca.
The penis, pinned by its retractor muscle a little to the right
of the right superior tentacle, is seen to communicate by its
saccular portion with an aperture common to it and the oviduct.
The 'inultifid vesicles,' and 'dart sac,' so characteristic of the
majority of the European Helicidae, are absent.

83. A Black Slug (Arion empiricorum), dissected to shew
its general anatomy.

The structure of this species differs in no very important
respect from the last. The most noteworthy points of dis-
tinction are the following: — the extremely lobulated and dif-
fuse character of the salivary glands and liver; the large
and compact hermaphrodite gland, and the smaller and more
finely lobulated albuminiparous gland. The spermatheca also

MOLLUSCA. 53

is larger, and connected by a much shorter duct with the
vagina.

On the right side of the preparation the heart is well dis-
played, and proceeding from it the aorta, divided into its anterior
and posterior branches, the former of which passes anteriorly to
supply the organs of that part of the body, while the latter
passes posteriorly to supply the liver and intestine.

A yellow glass rod has been placed under the cephalic gan-
glia, and a red rod under the sub-cesophageal mass.

84. A wax model of a Grey Slug (Limax cinereus), pre-
pared to shew its general anatomy.

A. The animal entire.

B. Anterior half of the animal. A portion of the mantle
has been removed in order to expose the rudimentary shell
which would not otherwise be seen.

C. General disposition of the internal organs, in their
natural position, on the removal of the integument.

D. The organs have been partially separated in order that
the general disposition of the alimentary canal and the genera-
tive organs may be seen.

E. Designed to shew the salivary glands, the nervous
system, and the pulmonary sac; together with the heart and
kidney.

F. The generative system.

G. The buccal mass laid open to shew the odontophore and
the nervous system.

The numbers affixed denote the different organs as follows :

1. Buccal mass.

2. Salivary Glands.

3. Stomach.

4. Intestine.

5. Liver.

7. Rectum.

8. Anus.

9. Renal organ.

10. Duct of Renal organ.

1 1 . Ventricle.

12. Auricle.

13. Anterior Aorta.

14. Posterior Aorta.

15. Pulmonary vessels lining
roof of pulmonary sac.

16. Branches of posterior aorta
supplying viscera.

17. Supra-cesophageal ganglion.

18. Sub-cesophageal ganglion.

19. Right and left stomatogas-
tric ganglia.

20. Buccal mass laid open -to
show odontophore.

21. Duct of salivary gland.

54 COMPARATIVE ANATOMY.

22. Hermaphrodite gland. | 27. Hermaphrodite duct.

23. Shell. i 28. Yas deferens.

24. Shield-shaped mantle.

25. Albuminiparous gland.

29. Oviduct.

30. Spermatheca.

26. Penis.

Class CEPHALOPODA.

85. A Cephalopod (Eledone).

A blue rod has been inserted into the mouth, a red rod into
the funnel.

The body is symmetrical, the organs being arranged sym-
metrically with reference to an imaginary vertical plane drawn
from before backwards through the centre of the body. The
animal is divided into an anterior or cephalic portion, 'pro-
soma,' and a posterior, or 'metasoma.' In the centre of the 'pro-
soma' and surrounded radially by the arms, is the mouth, and
on the opposite sides of it are the sessile eyes. The eight mus-
cular arms which surround the mouth correspond to the anterior
portion of the foot, 'propodium,' of the Gasteropoda, and are
formed by the- extension of the antero-lateral parts of the foot
forwards in front of the head, and their union with each other
in front of the mouth-: so that this aperture, from its position in
front of the anterior margin of the foot, comes to lie in the
centre of it. The margins are produced into long muscular
processes or arms;, which, in this species, are set with a single
row of suckers, by means of which the animal can attach itself
to foreign bodies, seize its prey, or move from place to place.

The 'metasoma/ which contains the chief organs of vegeta-
tive life, is invested externally with a thick muscular coat, or
mantle. This terminates in front freely, and so allows the
entrance of water into the pallia! cavity. On the dorsal surface
of the specimen a muscular tube may be seen emerging from
the pallial cavity: this is the 'Funnel.' It is formed by an
extension of the 'epipodda* upwards, and their subsequent
fusion in the medio-dorsal line. The Funnel is broader pos-
teriorly than it is anteriorly, and its base is covered by the
superior margins of the mantle.

The Octopoda, to which this species belongs, have no internal
skeleton of any kind. The specimen was taken at Algiers.

MOLLUSCA. 55

86. A Calamary (Loligo vulgaris), dissected to shew it->
internal skeleton, the 'gladius' or 'pen.' The 'gladius' ex-
tends throughout the whole length of the dorsal portions of the
mantle. It is of a horny texture, dark in colour, and consists
of a median shaft with two lateral alse. It lies loosely in the
cavity, so as easily to fall out when the integument is cut
away. This species represents the family Teuthidce.

87. A Sepia (Sepia officinalis), dissected to shew the posi-
tion of the internal skeleton, or ( cuttle-bone.' The ' cuttle-
bone ' is imbedded in the dorsal integument. It is a light,
cellular, calcareous body, peculiarly characteristic of the genus
Sepia. Its form is an elongated oval, convex, and marked by
a slight median keel on the dorsal surface, and partly convex and
partly concave on the ventral surface. The margin of the
' bone ' is seen to be more or less horny, and darker in colour.
This species represents the family Sepiadce.

88. Portion of 'cuttle-bone' from a Sepia, treated with
acid to remove the earthy matter, and shew the laminated
structure of the residual animal matter.

89. The lips and jaws of a Sepia (Sepia officinalis).

A portion of the lips has been removed, and a black and
white bristle passed through the mouth into the oesophagus.

The lip, which surrounds the mouth loosely, is beset with
numerous elongated papillae. The jaws consist of two horny
beaks of a brown colour, in shape not unlike those of a parrot.
They are embedded in a mass of muscular fibres by which the
movements of the jaws are regulated. The margin of the lower
one overlaps that of the upper. Between them is seen the
tongue with its serrated surface. From the hinder portion of
the buccal mass the oesophagus may be seen passing downwards
through the cartilaginous ring towards the stomach.

90. A Cuttlefish (Eledone), dissected to shew its digestive,
respiratory, circulatory, and generative organs.

The bag containing the viscera has been laid open, and the
mantle pinned back. An incision has been carried through the
cartilaginous ring at the base of the tentacles and the muscular
mass surrounding the jaws, so as to expose the origin of the
oesophagus. This is a narrow tube, which, after a course of
uniform diameter for about an inch, suddenly expands into a

56 COMPARATIVE ANATOMY.

large, easily dilateable, 'crop' (pinned to the right in the pre-
paration). A short passage leads thence to the stomach, a small
muscular organ which has been called ' gizzard,' from its muscu-
larity. Close to, and opening into, the stomach is the spiral
caecum; a little beyond this the intestine receives the duct
of the liver, and then proceeds in an upward direction to
the anus, which is situated near the ' funnel.' The liver is a
large globular organ, containing within its substance the inkbag,
the duct of which opens- into the intestine near the anus. There
are two sets of salivary glands. The uppermost are closely
attached to the under surface of the buccal mass, and open by a
single duct into the oesophagus. The lower pair are larger and
have each a duct, which shortly unite to form a common canal,
opening into the buccal mass at the base of the tongue.

On either side of the lower part of the preparation are the
branchiae, each with its venous heart attached. The great ven-
ous trunk has been removed, but the cut end of one of the two
veins that u?nite to form* it has been stitched back in the centre
of the preparation. A piece of red glass indicates the aorta.
On the left of this is the great pallial ganglion, from which
numerous nerves may be seen radiating into the substance of
the mantle. Between tbe two venous hearts, arching over the
systemic heart, are the two venae cavae, furnished with clusters
of 'spongy cellular bodies/ At the bottom of the preparation
is the ovary, with its ducts, of which one is pinned out to the
right.

91. Circulatory system of the same species. The arterial
portion has been injected with blue. The systemic heart is in
the centre; on either side of it are the venous dilatations into
which the blood is received from the branchiae, prior to its
reception by the ventricle. Pinned on the right and left sides
of the preparation, and uninjected, are the pulmonary hearts,
with their so-called ' appendages.' From the systemic ventricle
the anterior and posterior aortas may be seen passing respectively
upwards and downwards.

From a specimen taken at Wey mouth.

VERTEBRATA. 5 7

SUB-KINGDOM. VERTEBRATA,

Division I. ANALLANTOIDEA.

Sub-division I. ICHTHYOPSIDA.

Class PISCES.
Order TELEOSTEI.

92. A common Perch (Perca fluviatilis).

The roof of the cranial cavity and the greater part of the
left wall of the abdomen have been removed, exposing the
brain and most of the internal viscera. The following external
features may be noticed : the absence of distinct divisions be-
tween cephalic, thoracic and caudal regions; the imbricated
scales of the variety called ctenoid; the paired, and median
unpaired fins supported by hard, unbranched, non-striated rays,
and by soft, branching, striated rays ; the large size of the eyes ;
the absence of distinct eyelids; the presence of persistent
visceral clefts interposed between the visceral arches, and pro-
tected partly by a long operculum and partly by a membrane
supported on a series of branch io-stegal rays. Bristles are
inserted into the paired caecal nasal sacs, each of which has
two apertures. The pectoral fins are situated a little behind
the free edge of the operculum ; and behind these again are
the paired ventral fins. All the rays of the pectoral fins are
soft, but the first ray of the ventral fin is hard. The mesial
fins are the dorsal, divided into two divisions, the anterior of
which is composed entirely of hard rays, as is the rule in
Acanthopterygian fishes, the caudal, and the anal. "A series
of scales perforated by mucous ducts supplied with nerves forms
a lateral line along the trunk, the contour of which corresponds
with that of the upper line of the back." (Rolleston.) A portion
of the skin has been removed from the lateral surface in the
vicinity of the head — thus exposing the lateral branch of the
pneumogastric nerve, which passes posteriorly in relation with
the lateral line. A slip of blue paper has been placed beneath
this nerve. The tendinous intersections dividing the great
lateral muscles into a series of segments, may also be noticed.

58 COMPARATIVE ANATOMY.

A blue injection has been thrown into the gills, which are
four in number on each side. Each gill carries on its outer
or convex edge a double row of short, flattened, vascular fila-
ments, and on its inner or concave side a row of short bony
tubercles. In the angle between the converging gills are to be
seen the central parts of the circulatory system, consisting of a
triangular ventricle, leading into the pulmonary aorta anteriorly,
an auricle which slightly overlaps the ventricle, and a 'sinus
venosus,' into which the great veins pour their blood. The
heart is separated from the subjacent liver by a transverse
peritoneal partition. The latter viscus is of large size, rounded
in front and above, or divided inferiorly by a deep fissure into a
right and left lobe. Depending as it were from beneath the
inferior edge of the liver is the caecal stomach, with the intes-
tine, to which are appended three pyloric caeca passing out of it
at right angles. After describing an S-shaped convolution, the
intestine expands into a dilated, thin- walled, and transparent
rectum. Behind the rectum is the single large, pear-shaped
ovary, and still more posteriorly the small oval bladder. The
spleen lies in a loop of intestine, and a portion of it, stained
with the blue injection, is to be seen between the lower edge of
the stomach and the ovary. The large semi-transparent air-sac,
closely applied to the hinder wall of the abdomen, has been
left intact in the greater part of its extent ; but the posterior
third has been removed, in order to expose a portion of the
kidney, which lies between it and the vertebral column
throughout the whole extent of the abdomen. A slip of blue
paper has been placed beneath one of the ureters. The anus is
situated anteriorly to the openings of the generative and urinary
ducts, and not posteriorly, as in the higher Yertebrata.

In the brain the cerebral hemispheres are small, and their
surfaces are slightly corrugated. From their anterior extremi-
ties the olfactory nerves are given off. The optic lobes, which
succeed them, are the largest divisions of the brain : and by their
opposition to the hemispheres in front, the optic thalami are
hidden from view. The next division is the small, smooth cere-
bellum, and the fourth ventricle which it bounds anteriorly is
widely open. (Rolleston, p. 40.)

VEKTEBRATA. 59

Class II. AMPHIBIA.
Order BATRACIHA.

93. A Common Frog (Rana temporaries), dissected and in-
jected to shew the reni-portal system, and the chief trunks of the
arterial and venous systems.

A white bristle has been placed beneath the crural vein ;
if this vein be traced upwards from the leg it will be seen that
in the groin it divides into two branches, and that one of them,
the outer one, passes upwards to the kidney, along the outer
side of which it runs, and ultimately breaks up into capillaries
in that organ. This is the reni-portal vein. The second
branch of the crural curves round the front of the groin,
towards the medio-ventral line, where it unites with the cor-
responding branch of the crural vein of the other leg to form
the epigastric or umbilical vein. The latter vein, after receiving
one or two small twigs from the large and persistent allantois,
passes up the median line of the abdomen till it reaches the
liver, where it joins the portal vein, and subsequently ramifies
through that organ. It will thus be observed that the whole of
the blood in the hinder extremities of the body, after passing
through the capillaries proper to these parts, traverses in addi-
tion one of two sets of capillaries, either going by the reni-portal
vein to those of the kidney, or by the epigastric to those of the
liver. The hepatico-portal system is also shewn. A loop of
intestine has been pulled out and fastened to the right side of
the animal. The veins of the intestine are seen to unite and
re-unite, and by successive unions to form the portal vein which
passes upwards to the liver. The left superior vena cava is,
as usual, formed by the union of the jugular and subclavian
veins. A black bristle has been placed beneath it, just before
it curves round the base of the heart to reach the right auricle.
The large inferior vena cava is formed by the confluence of
the veins from the two kidneys, between which it is to be
seen. It passes forwards in relation with the posterior surface
of the liver, and, after receiving the hepatic veins, enters the
right auricle, (The liver has been displaced to the right so
that the posterior surface has, in this specimen, become the
anterior.)

60 COMPARATIVE ANATOMY.

Arterial System. — On the left side of the heart the three
trunks into which the ' bulbus arteriosus' divides on that side
are also to be seen. A slip of blue paper has been placed be-
neath them : the most anterior of the three is the carotid. The
central one, which is the systemic aorta, after giving off the
subclavian and vertebral arteries (the roots only of these are
seen), passes downwards and joins its fellow of the opposite side,
to form the abdominal aorta. The mesenteric artery which sup-
plies the intestines is given off immediately below this junction.
The third trunk is the pulmo-cutaneous artery — the pulmonary
branches, proceeding to the lungs, only being seen, as the cuta-
neous branch has been removed. After giving off the mesen-
teric artery, the abdominal aorta disappears behind the kidney,
though at some distance interiorly one of its branches, the
crural artery, passes downwards over a black bristle, to supply
the right leg.

94. A Frog, dissected to shew its nervous system.

The nervous system consists of a brain and spinal cord. The
cerebral hemispheres are much, elongated, and are, as in all Ver-
tebrata except fishes, the largest division of the encephalon.
Olfactory nerves are given off from their anterior extremities to
the nasal sacs. The optic thalami which succeed are largely
exposed between the hemispheres and the corpora bigemina.
The latter are comparatively small. The fourth ventricle is
widely exposed, and the only representative of a cerebellum is
the narrow band of transverse fibres which is to be seen crossing
over the anterior part of the ventricle. The spinal cord is short
and stout, and nerves are given off from it to the number of ten
pairs. The pia mater of the cord is continued as a thin sheath,
destitute of nervous matter, to the extremity of the neural canal.
The last two or three pairs of spinal nerves pass backwards in
the spinal canal for some little distance before passing out to
their peripheral distribution. The ganglia on the posterior
roots at the point where they join the anterior roots are to be
seen. A slip of blue paper has been placed under the two
ganglia. On the ventral surface of the throat slips of blue
paper have been placed beneath two cranial nerves and the first
spinal, viz. the glossopharyngeal, pneumogastric and hypoglossal.

95. A Frog, dissected to shew certain features not shewn,

VERTEBRATA. 61

or but imperfectly shewn, in the previous preparations. The
greater part of the stomach and intestine has been removed, a
portion of the dilated rectum alone remaining. The heart, con-
sisting of two auricles and a ventricle, is seen in the mesial line
at the base of the throat. The carotid with its bulb-like carotid
gland and the lingual artery which it gives off, the systemic and
pulmonary trunks, into which the aortic bulb divides on each
side, are perhaps better seen. The same remark will also apply to
the left musculo-cutaneous vein, which is to be seen returning the
blood from the vascular and respiratory skin to the left superior
vena cava. On each side of the heart are the simple sac-like but
internally vesicular lungs. Below the heart are two lobes of the
liver, the third having been removed to shew the large gall-
bladder and the root of the epigastric vein. A little to the
right of the darkly stained gall-bladder is the globular spleen.
The two oval white bodies seen beneath the liver are the testes.
The vasa deferentia emerge from and pass through the substance
of the anterior part of the kidney, and finally open into the uro-
genital duct, which can be traced down the outer edge of the
latter organ. To the terminal part of each of these ducts is
appended a large lateral dilatation, the vesicula seminalis. The
large bifid allautois hangs down in front of the rectum.

Division II. ALLANTOIDEA.
.Sub-division. SAUROPSIDA.

Class AVES.
Order CARTNAT.E.

9G. A Pigeon (Columba livia), dissected to shew the chief
features by which it differs from a Mammal.

The roof of the cranial cavity has been removed and the brain
exposed. The right wall of the chest and abdomen has also been
removed. The origins of -the well-developed pectoralis major and
pectoralis minor muscles are to be seen along the edge of the
sternal keel. The skin has been removed from the front of
the throat, and the crop, after having been distended with spirit
and hardened, has been laid open and its cavity displayed. The
cerebral hemispheres are pear-shaped, with a smooth surface,

02 COMPARATIVE ANATOMY.

and differ from the corresponding parts of the Reptilian brain in
being in contact with the cerebellum, and also by reason of
their much greater size. The cerebellum is large, and divided
by numerouj transverse ' sulci ' into well-marked lobules. It
has no lateral lobes. The ' corpora bigemina,' instead of being
in contact with each other mesially, as is always the case in
other Vertebrates, are thrown down towards the infero-lateral
surface of the brain, so that they appear as rounded lateral
projections. The other points to be noted about the head,
which is supported upon a long neck consisting of more than
seven vertebrae, are the presence of feathers ; the absence of
a ' concha ' to the external auditory meatus ; a well-developed
third eyelid, which can be drawn vertically across the eye ;
the edentulous character of the mouth ; the horny and non-
prehensile tongue ; and the absence of an epiglottis. The
widely dilated oesophagus expanding below into a bi-sacculated
crop occupies the front of the flexible neck. The cartilagi-
nous tracheal rings are complete. Between the chest and the
abdomen the absence of a diaphragm is to be remarked. In
the chest, and occupying a mesial position, is the long, acutely
conical heart. The short, thick aorta which it gives off, is seen
to divide into three large trunks, two 'arteriae innominate?,'
and a descending aorta. The aorta curves over the right
bronchus and not over the left, as in the Rat. Behind the crop,
and lying in close apposition with each other, in a deep groove
formed on the anterior surfaces of the cervical vertebrae by the
inferior transverse processes, are the two carotids. A piece of
blue paper has been placed beneath them. The right lung is
also seen in section. It is not divided into lobules, nor is it
suspended in a pleural cavity ; but is so firmly connected by
connective tissue to the back and side- walls of the chest as to be
marked by deep grooves, the impressions of the ribs. Each
innominate artery divides into three branches — the carotid, sub-
clavian, and pectoral arteries. Below the heart is the liver,
composed, as in most reptiles, of a large right lobe and a smaller
left one, the two being connected by a transverse lobe. The
apex of the heart is received into a mesial depression between
the two lobes. Overlapped by the left lobe, and partially con-
cealed by it, is the thick-walled and muscular gizzard ; the

VERTEBRATA. 63

intestine, with the exception of part of the duodenum and
the rectum, has been removed. The duodenum hangs down from
the gizzard, and contains within its primary convolution the
compact pancreas, with the three ducts by which its secretion is
poured into the intestine. In addition, two other ducts, one of
considerable size, and the other very small, are seen leaving the
liver and joining the duodenum. These are the hepatic ducts.
The right testis is also to be seen, as a large ovoid whitish body.
A little beneath and behind the testis is the tri-lobed kidney.
Each of its lobes lies in a depression in the under surface of
the ischium. The ureter emerges from its inner edge, and
passes posteriorly to its cloacal outlet. A little to its outer
side is the sinuous vas deferens. The rectum hangs down
from the bottom of the specimen, and about an inch from the
anus two small conical caeca join it. On the dorsal surface of
the extreme tip of the tail is the uropygial gland, consisting of
two pear-shaped lobes. The biceps muscle of the right leg should
be noticed passing downwards from the ischium. It passes
through a pulley-like loop of tendon at the back of the knee to
its insertion in the tibia.

Class MAMMALIA.
Order EODENTIA.

97. A Rat (Mus decumanus), dissected to shew the dis-
tinctive features of its class.

In addition to the more important anatomical details, the
following external points should be noticed : the hairy skin,
the existence of distinct outlets for the urinary and generative
organs as well as for the intestine, the vibrissaa on the snout,
the distinctly annulated tail, the cleft upper lip, the moveable
muffle, and the ungulate digits. To expose the viscera, the
greater part of the right side of the abdomen and thorax has
been removed. A red injection has been thrown into the
arteries and veins. The general visceral cavity is divided by
the transverse tendino- muscular diaphragm into a thorax,
containing the heart and lungs, and an abdomen, in which the
liver, stomach, intestines, &c. are situated. The lungs are freely
suspended within a pleura! cavity, and are not closely adherent

64 COMPARATIVE ANATOMY.

to the posterior walls of the thorax, as they were in the Pigeon ;
the right lung is divided into three lobes, and the left into two.
The heart is mesially placed between the two lungs, and its
anterior surface is about equally divided between the two ven-
tricles. The aorta is seen curving over to the left side, and
from the summit of the arch the three following vessels take
origin : first, the right arteria innominata which soon splits
into a right subclavian and carotid arteries ; a little to the left
of this the left carotid arises directly from the arch ; and still
more to the left the left subclavian, but this is hidden from view
by the left superior vena cava. On each side of the root of the
neck the jugular and subclavian veins are to be seen converging;
and subsequently by their union they form the right and left
superior venae cavse. In order that these vessels might be better
displayed, the thymus, or hibernating gland, has been displaced,
and turned forwards over the front of the heart. Descending
the neck, in close relation with the carotid artery, is the
pneumogastric nerve, and a little to the outer side of the same
artery the cervical portion of the sympathetic may be seen ;
while in close proximity with the trachea is the delicate recurrent
laryngeal. Subsequently to giving off the arteries to the head and
fore limbs, the aorta passes downwards through the chest just in
front of the vertebral column, and gives off numerous intercostal
arteries in its course : eventually it pierces the diaphragm and
becomes the abdominal aorta. A little to the outer side of the
thoracic aorta a rather large vein passes upwards to the left
superior vena cava, receiving during it ascending course small
veins from the intercostal spaces ; this is the azygos vein. The
phrenic nerves in their course downwards from their origins in
the cervical portion of the spinal cord to their distribution in
the diaphragm, of which they are the motor nerves, pass a little
to the outer side of the superior vena cava, and afterwards in
front of the roots of the lungs ; the right phrenic nerve is in
close relation with the inferior vena cava. Behind, and a little
to the left of the last-mentioned vein, is the thoracic portion of
the oesophagus. Beneath the concavo-convex diaphragm, and
attached to it by a peritoneal process — the suspensory liga-
ment— is the five-lobed liver. This again is rounded above and
adapted by its convex upper surface to the concave inferior

VERTEBRATA. 65

surface of the diaphragm, while inferiorly it more or less conceals
the shrunken stomach. The stomach has a large cardiac pouch
with a thin wall, and a pyloric division with much thicker and
glandular walls : the oesophagus opens into it about midway
between the two divisions. The epiploon, a special process of
peritoneum peculiar to this class, depends from the inferior
border of the stomach, and in its natural position would hang
in front of the small intestines. To the left of the stomach, and
attached to it by the gastro-splenic omentum, is the spleen, while
below the stomach the great mass of the large and small in-
testines lie. Of the large intestines, the darkly stained and
dilated caecum is the most prominent, though smaller in the Rat
than in most Rodentia. In the first convolution which the duo-
denum makes after leaving the stomach, the ramifying and
diffuse pancreas lies. A black bristle has been placed beneath
the hepatic duct near to its opening into the intestine at a point
about an inch and a half from the stomach. On each side of
the vertebral column, the slightly asymmetrically disposed
kidneys are to be seen lying on the psoas muscles. Three
vessels may be noticed passing out of the hilum of the
right kidney; of these the anterior one is the renal artery
and the posterior one the ureter, while the median and largest
of the three is the renal vein. The small, buff-coloured and tri-
angular masses attached to the anterior ends of the kidneys are
the supra-renal bodies; the left one only is seen, as the right one
is hidden by the hepatic lobes. Immediately below the kidney
the right ovary can be seen and from it the Fallopian tube passes
to the right cornu of the uterus. At a point just behind the
bladder the two cornua converge to form an extremely small
corpus uteri which opens into the large vagina. ' The vagina,
rectum and bladder have each of them separate and independent
outlets,' and into each of the three bristles have been inserted.

In the. interspace between the gastric and mesenteric veins
and close to the aorta from which these vessels are derived is the
small, pale-coloured, semilunar ganglion : and from it two small
nerves are to be observed passing obliquely upwards across the
aorta to connect this ganglion with the chain of sub vertebral
ganglia which together constitute the sympathetic system.

The following points arc to be noticed about the head in

CL. 5

GO COMPARATIVE ANATOMY.

addition to those already mentioned, viz. the large submaxillary
salivary glands bounding the angle of the lower jaw, and the
much smaller and more diffuse parotid gland placed behind and
beneath the external ear. On the right side of the animal's
head and situated at a point just in front of the ear, the extra-
orbital factor of the right lachrymal gland can be seen ; from
this portion a duct, with a slip of blue paper beneath it, passes
forwards to join a second duct from the intra-orbital part which
is situated at the posterior angle of the eye and inside the orbit.
Near the inner and anterior angle of the eye there is another
small gland about the size of a pin's head ; this is the Harderian
gland. Of the third eyelid, or membrana nictitans, with which
this gland is always correlated, a rudiment exists and can be
seen covering the anterior third of the eyeball.

A black bristle has been placed beneath one or two of the
external branches of the seventh or facial nerve, as they cross
the largely developed masse ter muscle.

The characteristic Kodent dentition should be noted : the
large, scalpriform, incisor teeth, of which there are two in each
jaw, growing from persistent pulps; the absence of canines, and
the large interval which separates the incisors from the molars.

The roof of the skull as well as the neural arches of the
cervical vertebrae have been removed in order to expose the brain
and spinal cord. The hemispheres are pear-shaped, thin, and
tapering in front, but broad behind ; their surfaces are smooth.
In the median longitudinal fissure which separates the hemi-
spheres, the longitudinal sinus, filled with red injection, can be
seen. The olfactory lobes are very large and are altogether
uncovered by any anterior extension of the hemispheres. The
cerebellum has a large median and two smaller lateral lobes.
In the transverse slit between the hemispheres and the cerebel-
lum the corpora quadrigemina are partially exposed. The
medulla oblongata is wide and passes behind into the spinal
cord.

CA31L1UDGE : naXTED BY C. J. CLAY, M.A. AT THE UN1VEKS1TY PJUESS.

In the Press.

A CATALOGUE

OF

EROTYLID^

BY THE LATE

GEORGE ROBERT CROTCH, M.A.,

ST JOHN'S COLLEGE, CAMBRIDGE.

CAMBRIDGE :
AT THE UNIVERSITY PRESS.