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* of it

eaebORATORY COURSE

INVERTEBRATE ZOOLOGY

BY

HERMON C. BUMPUS, Pu.D.

PROFESSOR OF COMPARATIVE ANATOMY IN BROWN UNIVERSITY, PROVIDENCE, R.I.,
INSTRUCTOR AT THE MARINE BIOLOGICAL LABORATORY, Woops Ho tt, Mass.

SECOND EDITION, REVISED

OF CONG,
Prernans | “Se
Syou | 14 33 ke

oy we
Y¥ of wast’ -

134 y
NEW YORK ;
HENRY HOLT AND COMPANY

1893

CopyYRIGHT, 1808,
By HERMON C. BUMPUS.

CopyRIGHT, 1893,
By HENRY HOLT & C@

-
/
TypoGRAPHY BY J. S. CusHinc & Co., Boston.

PREPAC E.

In the preparation of this book the author has had in
mind the requirements of a class of students who are
pursuing a course of laboratory work in Invertebrate
Zoology. An effort has been made to direct the work,
without, at the same time, actually #¢/zng the student all
that there is to be learned from the specimen. It is
taken for granted that an instructor is present to assist
when there is trouble, and to demonstrate many things
that written descriptions might only render more con-
fusing.

The animals that have been selected are not always
the most typical, but they are generally forms that can
easily be secured and preserved.

In the Appendix a few words have been given regard-
ing laboratory methods, etc. It has not been thought
advisable to introduce any considerable treatment of the

microscope as an optical instrument, nor have the modern

iii

iv Preface.

and valuable methods of microscopical research been more
than outlined. The former will be found in numerous
text-books; for the latter, it 1s expected that the stu-
dent will consult Whitman’s ‘Methods of Microscopical
Anatomy and Embryology” and Lee’s “ Microtomists’

Vade-Mecum.”’

PROVIDENCE, R.L.,
March, 1892.

CONTENTS:

Legge om
PAGE
PREFACE ........ eee tatters el yo) saterarers eels aie ace atayols tel aiatcrs eas ili
PROTOZOA —
ae otal a. era! = inna ap\n\ s" w/o! mysi'c\ no: pict «10.00 ac) eave a a's dais I
aA Aan cls Dias, wn) Sicie! oie! dine = ole's/ wie! a) s'@ aie <6 seipla's e-sie se 3
C@LENTERATA —
MPSA IED one cee vin see ete nvsisecarevce URanica. 2 - 5
eet ots crate diane Coo a icin waicieis; oS: wich ne. wre wid ialals, nielaea 9
RN ales ear orale oh uidy's = Wiel el} sioi's.cia'cce'vis ome 'etad ins slate 12
RM es otrctr ge aver aw’ oi 66 Gi pi sl'wiake <.a)et-sve'a Biv, sie elm ete. d aes U7
I ire craic sora sts ais aia, sific, soc ole e's eca°.s 6, 0'e"e's dele's and 19
REN oel fafa jo, cela! 0) afets at sl ava, alain a's 0'si/e's/e "a6 ovis a's) Giese 23
RENE estes Oe Ante oles oncaa's cies wines sina 6 bees wo ate E 26
ECHINODERMATA —
Et oats alla aime! y's) acne) alte dips. eleiat's/a'o\ dete ¢ «bie a ewe de a 29
tia celina ad jee a's s\n ais s oie s 0/9 ae'y sian ole fiainie ¥ a's 33
Maia ald o'atn's Gd o's w'ns ccg'e a tte'd.e cece 0 6 pas aa newt
VERMES —
RMA id Fete eimai wien nie'uic'e oo ic creie(a me's subse ee ss 39
MT etd aon gla iah a edie aval aye ateindie Ware! e'besw' wack net eelb ewes 42
Er clethin's <Misi Wein aad psoas visas es vale ee vies e es vies 47
MT ESE ea 'oin wis 'n'c.@ weieie' plaid nies a's ole.s'e bs s.¢ i» ua, 6's\8 0's\e,s 51

V

vi Contents.

MOLLuscA — PAGE
VOUS oc oe Sean Mae alas Vea e ek oe ee ee cececscerse 53
SVC PUS . i ev wale See stn ok Veleigt as see eer 59
LOW GO. oon aioe Vi neha es teas Hoek + oe cn ee 70

CRUSTACEA —

LLOMATUS 0s vee tale'e staves os vos he dink ok eee 78
BYUUCHIPUS | ccto eee ee ast sees wie segs Ce eee QI
CY LOPS Ase Seas, Soins asia oor Ge lve Sire! os oe 95
Pandar as Oe Pg an oe 98
LYASE a ein Vaal ewe | opts 3 OES Gove cen eae IOI
CANCER. basis ain aa esa eine swiss a be Ge ove os ae 105
FLOUR CSU ps oe sien 0 0 yh0 nibs aie \tov.0's pide olayerncielsen ee Kole)

LIMULUS AND ARACHNOIDEA —

LUIRUTUB 6 os snap ak a slain de is shin d Cae Pee - 1E3
LPO Bie o\e nie Sun's sien gi sein¥ ive okdualesnieinneoughice Gee, Ae 118

ANTENNATA — :

SPUEIR ois 2's 5's vis, als owe sh old else os o.0'e sei eee 123
ACEUAENM Es a vss shad wbvewddvese sss bcuae oo ee 129
ME OTRO ain a's a xn 6 oie sic! bs'n'a holy 0 8a tues be 134

APPENDIX |
A. Use of Laboratory and Laboratory Apparatus... eee 143
B. List of Instruments and Reagents..........) 02 seeeee 145
C. Miaerescopes : i)... ficu ne uale'sc ss auly een re 146
D. Directions for Dissection, ......./ 0...) 148
E. Methods of Killing, Fixing, and Hardening... eee 150
F. Methods of Preservation.......73.0 2.44.9 one I51
G.. Methods. of. Staining... 0. oa...) <c!.» don pee I51
Hi.. Methods of. Mounting ............0/202 0) ee 152

I. Methods of Imbedding and Section Cutting... <3 vce 153

INVERTEBRATE ZOOLOGY.

Se
tf

mI RHIZOPOD PROTOZOAN
(Ameba Ssp.).

PLACE a drop of water that is known to contain Ame@ebe
upon a slide and cover with a thin cover-glass. Having
found an Ameéa, note the following points :

The outline is irregular, and, if the animal is active, con-
stantly changing. The ray-like prolongations of the body
are called pseudopodia. Are the pseudopodia simple, or are
they branched? How many are there ?

The body of the animal is apparently made up of two
portions, —an inner granular portion, the exzdosarc, and an
outer clear layer, the ecfosarc. Is there endosarc in the
pseudopodia? Careful observation will reveal the presence
of a circulation of the granules of the endosarc.

Examining the endosarc with more care, it will be found
to contain food vacuoles, a vesicle, and a nucleus.

The food vacuoles are small, generally spherical bodies, in
color depending on the food that has been ingested. Around
certain vacuoles a clear enveloping space may be noted.

The xucleus, not often clearly seen in the living animal,
may be definitely demonstrated by adding a drop of one per

I

2 Invertebrate Zovlogy.

cent acetic acid to the water holding the Ameba. The acid
kills the animal and colors the nucleus light brown.
Make drawings illustrating the points above considered.
Observe a living specimen as it crawls about, and see if it
advances one portion of its body in preference to another.
Jar the slide. Is the animal sensitive? If possible, observe
the animal feed. It may be fed with powdered carmine,
indigo, or Bismarck brown.
- At times, by a process of fission, or self-division, the
Ameba divides into two smaller Ameba, which may in turn
again divide. This method of multiplication is asexuad.

A Ciltate Protozoan. 3

me CILIATE PROTOZOAN
(Paramecium caudatum).

PREPARE slides in the same way as was directed for
Ameba. If the animals have been fed for some hours with
carmine or Bismarck brown, the internal structure will often
be more clearly shown.

Under the compound microscope the Paramecia are seen
to glide rapidly about, lashing their way through the water
by means of innumerable ca. MWHave they an anderior and
a posterior end? Find an animal that is quiet, and see if
you can distinguish between an external membrane and the
enclosed granular cytoplasm.

Are all the cilia of about the same 2 each Note their
arrangement along the edges of the opening that leads into
the animal from the side. This opening leads into the
vestibule.

The vestibule is the ciliated passage down which food is
forced on its way tothe cytoplasm. Is there a definite flow-
ing of the cytoplasm? Are the contained food vacuoles dif-
ferent from those of the Am@eba? The food-balls, after
losing their nutritious portions, are ejected from the body at
a point, the aus, situated a little way posterior to the vesti-
bule.

Do you find pulsating vacuoles? Wow many? What is
the outline in diastole? In systole?

4. Invertebrate Zoology.

Use dilute acetic acid, and note the form and arrangement
of the zvichocysts, defensive bodies comparable to the nema-
tocysts of Coelenterates.

A ciliate infusorian contains a pe and one or
more micronuclei. The former is a comparatively large
body and can readily be observed by the use of dilute acetic
acid. ‘The micronuclei are smaller and, in some cases, diffi-
cult to find.

FParamecia are often to be observed attached in pairs by
their vestibular surfaces, in process of conjugation. After
remaining attached for some little time, the two become
free and undergo division by /fsszon.'

Make a drawing of Paramecium, naming the parts.

1 Conjugation is completed by disappearance of the macronuclei, which
are supposed to be nutritive bodies for use during this period of inac--
tivity. The micronuclei, during conjugation, are actively dividing, and
previous to separation one of these divisions in each organism passes
over into the body of the other.

An Ascon Sponge. 5

AN ASCON SPONGE
(Leucosolenia sp.).

General Anatomy. — Specimens of Zeucosolenia may be
abundantly found along the New England shores, attached
to rocks, seaweed, and submerged wood-work near the low-
tide mark. ‘The specimens submitted for examination will
be found to vary considerably in size and to not infrequently
occur in little groups or clusters. !

- Examine the specimens with a hand lens and note the fol-
lowing : —

Each sponge body is cylindrical and is attached by one end,
the proximal, to some foreign support, while its /vee end
presents a large opening, the “ oscu/um.” Press the sponge,
and note that its wa// is flexible. The larger sponges bear
buds or branches. Do the buds or branches have oscula?
Do the walls of the sponge become in any way different as
they approach the rim of the osculum?

Carefully lay open the sponge its entire length, cutting
from the osculum to the base. ‘The simple central cavity or
cloacal chamber is thus exposed. Does the cloacal cham-
ber communicate with the smaller cloacal chambers of the
buds? |

Place one half of the sponge where it will quickly dry, and
‘the other half, after washing it for a moment in water, place
in alum or borax carmine, where it may remain from one to

1 Specimens preserved in alcohol are more desirable for laboratory
work than the living animals.

6 Invertebrate Zoology.

several hours. Utilize the time while the piece is drying, by
drawing a cluster of the sponges (natural size, and also some-
what enlarged), illustrating such characters as have been
considered.

Place the now dry piece of sponge upon a clean slide and
examine the cloacal surface, using a low-power objective.
The sponge appears to be made up of a multitude of needle-
like bodies or sficules. ‘The spicules are clearly of two
kinds, radiaze and “near. ‘The radiate spicules form a some-
what regular lattice, each spicule producing its three longer
rays parallel to the wall of the cloacal chamber. A fourth
and shorter ray extends, from the common point of origin
of the three longer, perpendicularly into the cloacal chamber
and, as the sponge now lies, towards the eye of the observer,
as may be demonstrated by the use of the fine adjustment.
The “near or biradiate spicules are somewhat curved. Do
they lie in a plane mainly without or within the “ guadr-
radiate spicules”? ?

Make drawings of the spicules, giving them their relative
dimensions.

Remove the specimen from the stain, wash it for a
moment in water and then carry it through grades of alco-
hol to absolute. Clear in clove-oil and mount in balsam,
cloacal surface uppermost. (Do not allow the cover-glass
to rest too heavily upon the specimen.) Examine under
compound microscope.

The spicules will now be found to lie below (outside of)
a layer of small cells, the exdoderm, the nuclei of which are
clearly defined. The endoderm entirely covers the inner
surface of the cloacal chamber, and its cells, during life, are
provided with flagella and “ collars,” the activity of the for-
mer producing a current of water, which enters the chamber

An Ascon Sponge. ,

through numerous fores and leaves through the osculum.
The pores are easily determined, in the preparation under
consideration, as small round openings free from nuclei and
surrounded by the rays of the spicules.

Outside the endoderm (below in the present specimen),
and surrounding the spicules, are the mesoderm cells. The
mesoderm cells are not arranged as a single layer, but occur
irregularly through the mass of spicules. ‘Their nuclei are
often seen as granular bodies along the rays of the spicules,
and their protoplasm appears as a faintly stained reticulum.
While the endoderm cells have a definite outline, the meso-
derm cells are irregular and multipolar. ‘The spicular skele-
ton is formed by the activity of the mesoderm cells.

Still a third layer of cells, the ectoderm, has been described.
Its cells form a very thin tissue, easily destroyed, and too
difficult of demonstration to be here considered. It covers
the outer surface of the animal, and is probably somewhat
soiled with foreign matter.

Make a drawing illustrating the points above mentioned.

Reproduction. — Many of the larger specimens prepared
and mounted as above directed will be found to bear reproduc-
five cells. ‘These cells appear as large, deeply stained bodies
resting in the mesoderm and covered by the endoderm.
They are of two kinds, the male and the female. The male
cells or spermatozoa occur in spheres, each sphere containing
several hundred sperm-cells. The nuclei of the sperm-cells
give to the surface of the sphere a peculiar dotted appear-
ance, and are considerably smaller than the entodermal
nuclei. The sperm-spheres, however, are large, their diame-
ter being about one-third the length of a long ray of a
quadriradiate spicule.

8 Invertebrate Zodlogy.

The ova or ege-cells, though often as large as the sperm-
spheres, are provided with only a single large nucleus. In
this latter may rest a zucleolus. ‘The egg-cells are often
amceboid in form. ‘They are seldom spherical.

Make drawings of ova and sperm-spheres.

Segmenting eggs are not infrequently found. Such eggs
often have a clear space around them and _ between their
several segments or Jd/astomeres. Two- and four-celled
stages are most abundant. Are all the blastomeres provided
with nuclei? Can you find an unsegmented ovum that has
two nuclei ?

If a cluster of clean sponges be placed in two per cent
chromic acid for a day and then carefully washed, stained,
imbedded in celloidin and cut transversely, the arrangement
of the cell-layers and the structure of the segmenting ova
will be more clearly shown. ‘The endoderm will be found
to consist of closely appressed, somewhat columnar cells,
forming a layer considerably thinner than the outer, less dis-
tinct mesoderm. The delicate ectoderm will probably be
destroyed.

The spicules have been dissolved by the chromic acid,
but the cells once surrounding them are now seen to be
quite irregular in outline and to hold in their meshes the
ova and the sperm-spheres.

Make a drawing of the transverse section.

A Sycon Sponge. 9

mam SYCON SPONGE
(Granta sp.).

General Anatomy. — Simple sponges, which have been
described under the name Granta, are found associated
with Zeucosolenia along the Atlantic coast. Specimens vary
considerably in size, the larger sometimes reaching one inch
in length.

Examine a dry specimen with a lens and note the general
outline of the Jody, the somewhat expanded dase, the ter-
minal osculum, surrounded by a funnel of spicules, and the
numerous zucurrent pores, distributed over the external sur-
face of the body, and more or less hidden by the numerous
spicules. Are there duds attached to the sponge body?

Make a drawing illustrating the above points of the exter-
nal anatomy.

With a sharp scalpel open the sponge by making a longi-
tudinal stroke from base to osculum. ‘The central cavity or
cloaca will be exposed, and its walls will be found pierced
with numerous openings, the gastric osta. Note that the
cut edges, much thicker than in Lewcosolenia, are traversed
by parallel tubes, those entering the central chamber through
the gastric ostia being called radial canals, while the shorter,
which enter from without through the incurrent pores, are
called the zzcurrent canals. The incurrent canals commu-
nicate with the radial canals through certain small openings

10 Invertebrate Zovlogy.

which cannot be seen at present. Do you find anything
that might strain the water as it enters the incurrent canals?
Do the buds communicate freely with the cloaca of the
parent ?

Examine with lowest power of compound microscope.
The outer lighter-colored layer of the sponge is now seen
to be made up of innumerable, needle-like szcules, while
the inner portion is supported by radiate spicules.

Make enlarged drawings of the parts thus far considered.

Cut a thin transverse section of a dry sponge and note
the radial canals, and the smaller and also straight incurrent
canals lying parallel with them. Are the needle-like spicules
arranged more abundantly over the peripheral ends of the
radial canals? Note the arrangement of the triradiate
spicules in the walls of the tubes. ‘T-shaped spicules are
arranged around the cloacal chamber, each sending one ray
into the cavity. Recall the spicules of the Ascon. Do any
of the incurrent canals pass through the wall of the sponge
from the periphery to the cloacal chamber ?

Make a drawing showing the arrangement of the spicules.

Examine now a specimen that has been decalcified, stained
and cut into transverse sections by means of a microtome.
The spicules will not be present though their surrounding
mesodermal cells will appear as a delicate nucleated retic-
ulum extending between the parallel tubes and into pyram-
idal masses at the peripheral ends of the radial canals.
Endodermal cells, as a single layer, line the cloacal chamber
and the radial canals ; but while the cells of the former are
flattened out and form a “pavement epithelium,” those of
the radial canals retain the flagella and collars present in
the Ascon, and by their activity induce the circulation of
sea-water. Note that the incurrent canals are lined with

A Sycon Sponge. II

pavement epithelium, ectoderm, quite different from the
lining cells of the radial tubes.’ The incurrent pores through
which the sea-water enters the radial tubes are small and
somewhat difficult to demonstrate. They may frequently
be found in section, as interruptions of the even course of
the endodermal lining along the peripheral portion of the
radial tubes. They are more easily determined as minute
openings in such portions of the section as permit the exam-
ination of the szvface of the entoderm.
Make a drawing of the cross-section just examined.

Reproduction. — In the stained specimens there will fre-
quently be found large amceboid cells in the substance of
the mesoderm. Such cells, as was the case in the Ascon,
are the reproductive cells, male or female, and in a single
sponge may occur in varying stages ef development. The
sperm-spheres and the segmenting ova are clearly covered
by a layer of epithelial cells. The sexes are usually not
united in the same sponge-individual.

Draw one of the reproductive cells and show its nucleus
and nucleolus. Draw also a sperm-sphere or a segmenting
ovum, showing its position in the mesoderm and its epithelial
covering.

1 The difference in the lining of incurrent and radial canals is clearly
seen in specimens that have been cut at right angles to the axes of
these canals. While the endodermal tubes appear as circles of broad
outline, the ectoderm of the incurrent canals forms a most delicate
circle.

I2 Invertebrate Zoology.

THE HYDRIFORM STAGE OF A Cali
NULARIAN HYDROLD

(Campanularia sp.).

External Anatomy. — Examine with a low power and
note the more or less branching hydrocaulus or stem. It is
supported upon a root-like expansion or hydrorhiza. What
is the order of the branching? Note any structures that
may give flexibility to the horny, tube-like covering or fev7-
sarc. Do you find the perisarc enlarging at its free extremi-
ties into bell-shaped cups or hydrothece? ‘The hydrothecze
give protection to the zodzds or hydranths. Observe that
certain of the hydrothecze may become considerably en-
larged, forming govangia. Each ripe gonangium may con-
tain a number of medusa buds.

Make an enlarged drawing, naming the several parts.

Examine a single expanded hydranth under a higher
power and note the position of the terminal mouth. The
mouth is supported upon a proboscis or manubrium. Around
the base of the manubrium are arranged the ¢endacles which,
during life, are capable of considerable movement. Below
the circle of tentacles, and quite enclosed by the hydrothece,
the Jody of the hydranth is to be noted. What is the
arrangement of the tentacles in a contracted zooid or
hydranth ? |

Use a still higher power. Do you find certain wart-like

Campanularian Hydrotd. 13

batteries of nematocysts or “ lasso-cells” at varying positions
along the tentacles? In the living specimens (or in a living
fy dra, held under a light cover-glass and treated with dilute
acetic acid), note that each nematocyst has a rounded dod),
an elongated f/ament, and, at the base of the latter, a few re-
curved sf7nes.

Make a drawing of an expanded and of a contracted
hydranth.

Internal Anatomy.—TIf a clean, living specimen is
selected there will be little difficulty, by focussing through
the transparent perisarc, in making out the internal anatomy.
If alcoholic specimens are used, portions of the colony should
be stained, cleared, and mounted as described in the Appen-
dix. Observe that the perisarc of the hydrocaulus contains
a fleshy axis or cwenosarc. The ccenosarc is made up of
three layers, and encloses, as a tube, the centrally lying
celentertc or “ body-cavity.” Of the three layers the ectoderm
is the most external. It is made up of transparent, nucleated
cells, and is separated from the innermost and more granular
endoderm by a very delicate, third, transparent, supporting
layer.

If the specimen is still alive, note the circulation of the fluid
in the body-cavity. How is the circulation brought about?

Examine one of the tentacles and determine the just de-
scribed layers. ‘To which layer are the nematocysts con-
fined? The body-cavity does not extend into the tentacles.
Demonstrate, if you can, the presence of the three layers in
the body-wall of the hydranth. Is the cavity of the hydranth
in direct communication with the cavity of the hydrocaulus ?

Make a drawing of the stem, of a tentacle, and of a
hydranth, illustrating the three layers.

14 Invertebrate Zoology.

The Digestive System.— Nutritive material entering
the mouth is reduced to a semi-fluid condition, and, by
the action of the endodermal cilia lining the body-cavity
of the hydranth and hydrocaulus, is carried to the various
portions of the colony, where it is appropriated and digested
by the individual endodermal cells.

The Circulatory System is not specially differentiated
from the digestive system.

The Muscular System. —At certain points in the ten-
tacles of favorable specimens, elongated ‘ muscle fibres”
have been described. ‘They he on the outer surface of the
supporting layer.

The Nervous System.—In the present stage of the
Hydroid a nervous system has not been found.

The Reproductive System. — The fertilized ovum of a
Hydrozoan ordinarily develops into a colony of zooids.
Such a colony we have just been considering. ‘Through a
process of branching, new colonies are asexually produced,
and from the colonies medusa-buds are also produced.
A brief search will probably reveal the presence of several
gonangia or specialized hydranths. Each gonangium, some-
what larger than a hydranth, contains a fleshy central axis or
blastostyle, which is morphologically equivalent to the body
of a hydranth. The blastostyle is produced distally into
a manubrium. Is there a mouth? Are there tentacles?
Do you find the same layers that were present in the
hydranthe Is there a central body-cavity? Along the side
of the blastostyle are medusa-buds, in varying stages of de-
velopment. Which are larger, the terminal or those nearer
the base? How many are there?

Draw a gonangium with its contents.

Campanularian Hydrotd. 15

THE MEDUSOID STAGE OF A CAMPANU-
EAKIAN HYDEOID.

General Anatomy.— The medusa-buds were observed
to be produced asexually along the sides of a specialized
hydranth, the blastostyle. If some of the older buds are
examined, they will be found to be shaped like an umbrella.
The concavity of the umbrella is turned towards the exterior,
and the margin is provided with numerous marginal fen-
facles. Stretched across the opening of the umbrella, as a
perforate diaphragm, is the so-called velum. ‘The presence
of a velum is characteristic of the Hydromedusz and gives
to them the name Cvasfedo/a.

By the convex surface the medusa-buds are held to the
blastostyle, through which, for a time, they receive their
nourishment. When finally mature, the buds break away,
and, passing through a terminal opening in the gonangium,
reach the sea-water as free-swimming medusz.*

If possible, examine a living medusa and note its peculiar
movements. How many tentacles are there along the mar-
gin of the disc? Do you note a centrally projecting tube,
the manubrium? At its free end the mouth is situated.

1 The terms exumbrella and subumbrella designate the aboral and
oral portions respectively. The attachment of the blastostyle is at the
aboral or exumbrella portion, while the concavity, surrounded by the
marginal tentacles, is formed by the subumbrella portion.

16 Invertebrate Zoology.

Can you trace an opening leading from the mouth into
a central cavity? ‘There are radiating chymiferous tubes
leading from the base of the cavity of the manubrium to the
periphery of the disc, where they open into the very delicate,
circular, circumferential canal Is the arrangement of the
chymiferous tubes and the marginal tentacles correlative?

The Sexual Reproductive Organs lie one on each radiating
chymiferous tube, and appear, when viewed from below, as
wart-like projections. ‘Their contents, as eggs or spermatozoa,
are dehisced into the sea-water.

The Nervous System and Sensory Organs. —A circu-
lar nervous tract consisting of a plexus of nerve cells extends
entirely around the margin of the umbrella. Fibrillze extend
from the edge of this “ring” to muscle fibres and to certain
marginal sense-organs. ‘The latter may be dactle, “ audt-
tory” or visual. The tentacles are the principal iene
organs. The so-called “auditory vesicles”? are probably
organs of equilibration, and medusz being thus provided are
called vesiculate, while those having pigmented vzsual spots
are called oceHate. ‘The visual spots are more frequently
found at the bases of the perradial tentacles.

Make drawings that will show the important points in the
anatomy of the Hydromedusa.

1 The chymiferous tubes are more frequently four in number and
determine four radii ( Jerradiz) of the umbrella. In certain Campanu-
larians, however, there are eight or more of these radiating tubes.

Tubularian Hydroid. 17

fee YORIFORM STAGE OF A TUBULA-
RIAN HYDROID

(Pennaria tiarella).

External Anatomy. — Examine with a low power, and
note how the present specimen differs from the Campanula-
rian in its order of branching, in the disposition of its
hydrorhiza, and in the termination of the branches of the
hydrocaulus. No hydrothecz are present. How do the
zooids or hydranths differ from those of the Campanularian?
Specialized gonangia are not present, but medusa-buds will
be found as globular swellings along the sides of certain
hydranths."* :

Make an enlarged drawing, naming the several parts.

Examine a single expanded hydranth under a higher
power, and locate the manubrium, the terminal mouth, the
somewhat irregularly placed ‘‘ shorter tentacles,’ and the
whorl of “ longer tentacles’ arranged around the base. Is
the number of tentacles constant in different hydranths ?
Are batteries of nematocysts present?

Make an enlarged drawing of a hydranth.

Internal Anatomy. — Does the internal anatomy essen-
tially differ from that of the Campanularian? Do you find

1 Hydroids that are thus unprovided with hydrothece and gonan-
gia are united in the group Gymmnobdlastea, while the Campanularian
Hydroids (provided with hydrothece and gonangia) are united in the
group Calyptoblastea.

18 _ Luvertebrate Zoology.

ectodermal, endodermal, and supporting layers? Does the
body-cavity extend into the tentacles?
Illustrate the internal anatomy by diagram.

The Digestive, Circulatory, Muscular, and Nervous
Systems are not essentially different from the same of the
Campanularian.

The Reproductive System. — As in the Campanularian,
reproduction may be asexual (branching and budding) or it
may be sexual.

Though, as already noted, gonangia are not produced,
medusa-buds are abundantly found attached, as was the case
in the previously examined specimen, to the body or manu-
brium of the hydranths. An examination of medusa-buds
in varying stages of development will show that they arise
as simple outpushings, or evaginatons, of the body-wall.
The more mature buds (about one-sixteenth of an inch in
diameter) have all the essential characters of the same of
the Campanularian, though the umbrella is here strongly
four-ribbed and considerably elongated. The chymiferous
tubes are four in number, and lead from the cavity of the
manubrium. ‘The velum has but a small opening leading
into the cavity of the umbrella, and the marginal sense-organs
are visual (ocellate). Either eggs or spermatozoa are devel-
oped from the wall of the manubrium and are often in such
quantity as to distort the medusa. One or two of the eggs
are frequently much larger than the others, and may be
thrown off before the medusa-bud breaks away from the
hydranth.

Make a drawing of a mature medusa-bud.

An Actinian. 19

XN ACTINIAN

(Metridium marginatum).

External Anatomy. — Observe in the expanded animal
that the body is made up of a cylindrical column, terminated
above by a more or less flattened asc and resting below
upon an irregularly shaped dase. ‘The column is pierced
with small pores, cizclides, and is limited above by a ring-
like fold, which contains a marginal sphincter or ring-muscle.
The disc is capable of considerable expansion, and may
present a regular number of /odes. It bears numerous rows
of contractile sezzacles, the older and larger of which form
the innermost circles. ‘These tentacles are simple outpush-
ings of the substance of the disc. In the centre of the disc
is the elongated mouth or stomodeal opening, the lateral
lips of which often rest against each other, and may even be
united, while the terminal angles are somewhat thickened
and form the szphonoglyphes. (In certain specimens but a
single siphonoglyphe is present.) The elevated area imme-
diately surrounding the mouth is the pevzstome. The base,
or area of attachment, is an adhesive organ, expanded later-
ally into a 4mdbus, and capable of producing a considerable
amount of motion. In the living animal the internal struc-
ture is often to be seen through the transparent walls.

Make a drawing of the specimen as seen from the side,
and also as seen from above.

20 L[uvertebrate Zoology.

‘If the living animal is irritated, the tentacles are with-
drawn, the disc is lowered, and by the contraction of the
ring-muscle, the walls of the column are drawn together
over the free end. If the contraction goes still further,
numerous white, thread-like bodies, acont#a, are seen to
ooze from the cinclides.

Make a drawing of the contracted animal.

Internal Anatomy. — With a sharp knife divide the
animal from disc to base, through a plane at right angles
to the stomodzeal opening, and then remove from one of the
halves the thin tissue of the base. The mouth will be
found to lead into an elongated, thick-walled, and more or
less wrinkled tube, the wsophagus. Is its wall in any way
differentiated at the siphonoglyphes? Below, the cesopha-
gus opens directly into the ca@lenteric chamber, a general
cavity limited externally by the walls of the column and
divided, or partially divided, into numerous smaller cham-
bers by delicate, radially arranged partitions, the mesendertes
or s¢pda. Only six pair of mesenteries extend entirely across
the ccelenteric chamber and unite with the cesophagus.
They are called the primary mesenteries, and are definitely
arranged. ‘Two pair of primary mesenteries, the dvrectve
septa, occupy the plane of the longer axis of the mouth,
and are attached to the walls of the siphonoglyphe. They
divide the animal into two lateral halves. Between each
pair of primary mesenteries — indeed, between any pair of
mesenteries — is a limited chamber, the zz¢ra-vradial cham-
ber, while between two pair of mesenteries are the zz/er-
radial chambers. There are six primary inter-radial
chambers, three on either side. Between the primary
septa are the secondary and tertiary sepia, partially divid-

An Actinian. i |

ing the primary chamber into smaller secondary and ter-
tiary chambers.

Excretory and Respiratory System. — The waste pro-
ducts of digestion are ejected through the opening of the
mouth. Certain mesenterial filaments may (?), however,
perform excretory and respiratory functions. These fila-
ments are arranged along the free edges of the mesenteries,
at the upper part appearing as an undulating line, while lower
down each filament is coiled into a tangle of considerable
size. Lying near the base of the mesenteries, in the deeper
part of the ccelenteric chamber, are greatly elongated mes-
enterial filaments, the coiled acontia.

The Reproductive Organs lie near the free edges of the
mesenteries on each side of the mesenterial filaments. . Each
gland is a somewhat convoluted structure that dehisces its
contents, eggs or spermatozoa, into the ccelenteric cavity.
Are mesenterial filaments, acontia and sexual organs present
on the primary septa?

The Muscular System. — Though muscle fibres are pres-
ent in the walls of the column, around the disc and around
the mouth, the most characteristic muscles are developed
along the septa, where they run vertically as longitudinal
retractors. Are they on the inter- or intra-septal wall? Does
the arrangement on the primary mesenteries differ from the
arrangement elsewhere ? *

The Digestive and Circulatory System. — The sea-
water freely mixes with the products of digestion, and the

1 The tentacular retractors are arranged on the inter-septal walls of
the directive septa; on the other septa they are on the intra-septal
walls. |

22 Lnvertebrate Zoology.

resultant nutritive fluid is carried, by the action of cilia, to
all parts of ccelenteric -cavity. At the upper portion of
each mesentery circular openings are to be found, placing
the contiguous chambers in communication, and thus allow-
ing free circulation. ‘These openings, the sepfa/ stomata,
form imaginary rings around the upper end of the cesopha-
gus, and are possibly comparable with the circumferential
canal of the Hydromedusa.’ |

Make drawings that will illustrate the more important
points in the internal anatomy.

1 The zxner septal stomata are placed just below the peristome near
the cesophagus and pierce only the primary septa. The outer septal
stomata are near the outer-wall and pierce all the septa.

The Medusoid Stage of a Scyphozoan. 23

fee MENDUSOID STAGE OF A SCYPHO-
ZOAN

(Cyanea arctica).

External Anatomy.—In many points of its general
anatomy the present form agrees with the medusa of the
Campanularian Hydroid. A rounded aboral, abactinal, or
exumbrella surface is distinguishable from an ora/, actinal,
or subumbrela surface. The former is generally convex,
while the latter is more often concave. ‘The margin is
divided into eight large lobes.

The mouzh will be found in the center of the subumbrella,
but surrounded and probably hidden by a mass of delicate
fringe-like tissue, which, in life, may hang from the lower
surface of the animal in four pleated folds. These folds,
which are known as the ora/ fentacles, are capable of con-
siderable extension and contraction, and direct the food to
the mouth.

The oral tentacles may now be cut away, leaving only
their line of attachment along the margin of the oral open-
ing or mouth. This opening is elevated upon ashort manz-
érium, and has four radiating angles which determine four
main radii of the animal, the so-called perradiz. The four
radii that might be drawn between the perradii are known
as interradi. ‘Yhe perradii and interradii extended to the
margin pass directly through eight “ marginal sense-organs,”

24 Invertebrate Zoology.

tentaculocysts, or rhopaha. Each sense-organ is borne in a
median sinus of one of the eight large lobes, — four perradial,
and four interradial.

Four perradial pillars are now to be observed as supports
of the angles of the mouth. They are arranged radially, and
at their proximal ends rest against the cz7cular muscle of the
subumbrella. This muscle is a broad, flat band of parallel
fibres extending as a circle midway between the mouth and
the margin. A pair of radial muscles extend into each of
the eight lobes from near the peripheral edge of the circular
muscle. There are, then, sixteen radial muscles, — four
pairs of perradial and four pairs of interradial. }

Between each pair of contiguous perradial and interradial
muscles (adradially) a collection of highly contractile fen-
tacles will be noted. ‘These tentacles take their origin from
near the peripheral edge of the circular muscle, and, during
life, may be extended to an enormous degree. ‘They are
richly supplied with zemazocys¢és and are the more essential
prehensile organs. 3

The sexual glands (ovaries or destes) are four large lobu-
lated organs located interradially and separated from each
other by the perradial pillars.

The velum, characteristic of the Hydromeduse, is not
generally present in the Scyphozoa, and the term Acraspeda
has hence been applied to the members of this group in dis-
tinction to the term Craspedota as defined for the Campanu-
larian medusoid.

Digestive System. — If a blunt probe is passed through
the oral opening, the wsophagus will be found to be short,
and, in cross-section, quadrangular. The openings into the
four spacious interradial reproductive sacs lead from the

The Medusotd Stage of a Scyphozoan. 25

enlarged gastric cavity, the peripheral boundary of which
extends as far as the circular muscle. Four clusters of ten-
tacle-like interradial gastral filaments, or phacelli, are to be
found encircling the deeper portion of the short cesophagus.
They mark the dividing line between the cesophagus and
the true gastric cavity. It is from the latter cavity, imme-
diately within the phacelli, that the reproductive sacs take
their origin.

In injected specimens the chymzferous tubes or gastro-
canals can be followed, in their ramifications, through the
substance of the disc and into the marginal lobes. Four
main canals extend perradially and four interradially, finally
opening into enlarged terminal cavities, located between the
radial muscle bands and below and around the marginal
sense-organs.

Alternating with the perradial and interradial canals are
eight adradial canals which expand into as many terminal
chambers, one above each cluster of tentacles. The central
cavity of each tentacle communicates with the terminal
adradial chamber.

The Nervous System. — Near the base of each mar-
ginal sense-organ ganglia have been found, though a mar-
ginal nerve-ring has not been discovered.

26: Invertebrate Zovlogy.

A CTENOPHORAN
(Mnemiopsis leidyt).

External Anatomy.— The elongated gelatinous body
will be observed to have a broader, two-lobed oval pole and
a narrower a@boral pole. From the latter eight series of
combs, ctenophoral rows, or swimming plates extend meri-
dionally towards the broader end, the two lobes of which
(zerminal lobes) may be folded together and cover certain
structures. The mouzh is a slit-like opening which extends
from lobe to lobe, its major axis thus determining the first
perradius, and the plane (sagz¢fal or median plane) passing
through it and the axis of the body would divide the animal
into symmetrical lateral halves.

A pair of small papilli-form organs will be noted, one on
either side of the mouth. These are the centacular lobes,
and a plane passing through them and the axis of the body
at right angles to the sagittal plane, would divide the animal
into an anterior and a posterior half, the one an exact coun-
terpart of the other. Such a plane may then be called the
transverse or lateral plane. It lies in the second perradius.

The true ¢enfacles are considerably reduced. Each ap-
pears as a small opaque spot, lying in a small pocket, midway
between the lateral ctenophorial rows and a little aboral to
the tentacular lobe.

The ctenophoral rows are of different lengths. ‘The four
longer lie near the sagittal plane and extend over the ter-

A Ctenophoran. 27

minal lobes, and may be called the zerminal plates, while the
four shorter lie nearer the transverse plane, and may be
called the lateral plates.

As the eight ctenophoral rows approach the aboral pole,
each terminal pair become united at the margin of an aboral
crater-like depression, and form a single line which passes
down the wall of the depression in the plane of the first per-
radius. The four /ateral rows, however, preserve their indi-
viduality until they have reached the deeper portion of the
depression.

At the base of the depression is a small opaque spot, the
“ sensory body.”

If each lateral ctenophoral row is followed orally, it will
be found, at its lower end, to change its character somewhat
abruptly. At this point, four long finger-shaped processes
will be noted which extend freely between the terminal
lobes. These processes are the “ auricles,” and they lie
interradially. Each auricle is somewhat flattened, its two
richly ciliated edges being directed one away from and one
towards the terminal lobe. The cilia of the first-mentioned
edge continue, orally, the line of the true ctenophoral row.
This continuation extends from the free end of the auricle
aborally along the edge that is turned towards the terminal
lobe until it has reached a point near the “‘sensory body ’”’
midway between the neighboring terminal and lateral rows.
At this point it unites with a much larger fringe that has
extended aborally along the inner surface of each terminal
lobe from near the sagittal end of the mouth. There are
four of these large fringes.

Internal Anatomy.— The opening of the mouth has
been already observed. It leads into an @sophagus, which

28 Invertebrate Zoology.

is laterally compressed often to such an extent that its walls
are actually in contact. A double plate is thus formed
which lies in the median plane (perradially). ‘The flattened
cesophagus opens near the aboral pole into a much smaller
stomach.

The thick layer of jelly-like tissue that lies between the
walls of the cesophagus and stomach and the external integ-
ument is traversed by certain gastro-canals, which, as diver-
ticula, radiate from the stomach.

If a living animal has coloring matter forcibly injected
into the opening of the mouth, the course of these canals
will be beautifully demonstrated.

There are eight large gastro-canals that take their origin
from the stomach, of which four arise laterally and in the
second perradial plane and four arise interradially. A single
pair of very small canals extend aborally in the first per-
radial plane from the stomach to the region of the “ sensory
body.” |

Of the four lateral canals, one pair, the more external
(tentacular vessels), extend directly to the tentacles, while
the other, deeper pair, run along the wall of the cesophagus
as the wsophageal or gastric vessels. Each of the four inter-
radial canals branches dichotomously soon after leaving the
stomach. Eight meridional vessels are thus formed which
lie under and parallel to each ctenophoral row.

It is on the walls of the meridional vessels that the eggs
and spermatozoa are developed. ‘These reach the sea-water
after passing through the stomach and cesophagus.

The Starfish. 29

Ge SLARFISH
(Asterias sp.).

External Anatomy. — Note the small, cylindrical docy,
the radiating arms, the centrally placed mouwzh, and the
red madreporic plate. <A vertical plane passing through
the madreporic plate and thence across the body and along
the median line of the opposite arm will divide the animal
into a right and a left half. There is then bilateral sym-
metry.

Do you find specialized sfzzes surrounding the mouth?
How many? Are the spines specially developed on other
portions of the animal? Note the ambulacral furrows,
grooves, which extend along the orva/ surface of each arm.
Each groove is filled with two zigzag rows of ambulacral
suckers. Do you find any structure on the adbora/ side of
the arms that suggests a median radial line? Find the
pedicellarie, minute pincer-like organs around the bases
of the aboral spines. On what other portions of the animal
are they present?

Draw the animal as seen from above, and again, as seen
from below.

With a strong pair of scissors remove the entire aboral
surface of the animal and without in any way injuring the
underlying “ soft-parts.”

30 L[uvertebrate Zoology.

The Digestive System. —The mouth leads through a
short esophagus into a thin-walled stomach, the five lobes of
which normally lie in the cavities of the five arms, though
certain lobes, and indeed at times, while feeding, the entire
stomach, may be completely everted through the mouth.
Do you find the gastric retractors, bands of muscle which
draw the lobes of the stomach into the cavities of the arms?
The lobulated digestive glands appear in each ray as a pair
of voluminous masses of a light olive-color. Each gland
unites with its fellow, centripetally, and opens, through a
common pore, into the stomach. Note the suspending
mesenteric fold.

Inflate the stomach by blowing into the oral opening.
The organ will be found to lead, above, into a short cone-
shaped izfestine, which opens to the exterior through a
minute pore, the azuws. Leading from the left wall of the
intestine is a somewhat branched organ, the vespirafory
tree. It is made up of two main divisions, separated by
an interradius. The organ may perform an excretory
function.

The Reproductive System. — Though the ¢szs and
ovaries bear a superficial resemblance to each other, the
sexes are separate. ‘The sexual glands appear in mature
specimens as a pair of light-colored, grape-like masses,
extending from near the body out into each ray.’ Trace
the ducts to their external openings. (The openings may
be found well into the angles between the arms.)

Draw the reproductive system.

1 The testes are in living specimens of a whitish color, while the
ovaries are pale yellow.

The Starfish. 31

The Water-vascular System should be studied in a
specimen that has been artificially injected. The ambulacral
suckers were noted above as a series of tube-like organs
lying along the ambulacral furrows. Each sucker passes
upward, aborally, through a pore, the ambulacral pore, and
expands within the cavity of the arm, into an amdbulacral
vesicle or ampulla. ‘The ampulle of each arm are in com-
munication with a common radiating water-tube, which lies
in the median line of each ray beneath the ridge of calcare-
ous ambulacral ossicles. Follow the radial tube centripe-
tally. It will be found to arise from a circum-oral ring.
The Fohan vesicles, ten in number, are enlarged ampulle,
arranged in a circle around the mouth. The racemose vest-
cles, nine in number, have their axes lying at right angles to
the Polian vesicles and extend horizontally into the cavity
surrounding the cesophagus. At the place where the tenth
vesicle might occur a rigid tube, the szome-cana/, takes its
origin. The stone-canal extends to the lower side of the
madreporic plate.

Make a drawing of the water-vascular system.

The Circulatory System.— A delicate sac, the “ pervicar-
dium,” will be found lying immediately posterior to and be-
neath the stone-canal. Careful injecting will show that from
this sac certain minute blood-vessels pass to varying parts of
the body, following, in the main, the course already taken by
the water-vascular system.

The Nervous System. — Part the ambulacral suckers
from the median line of each furrow, and note the deeply
lying nerve-cord, the “vadiating nerve.” It extends from a
circum-oral nerve-ring to a red eye-spot. The latter occu-
pies a position at the tip of the arm.

32 Invertebrate Zoology.

Draw the nervous system.

With a strong knife, make a cross-section of one of the
arms. Note the perivisceral cavity and identify the con-
tained organs. Observe the arch of the aboral integument,
and below, the large furrowed ambulacral ossicles. Where
the ambulacral ossicle of the right meets that of the left, do
you find the cross-section of the radiating ambulacral water-
(UO Oe)

Remove the aboral integument from one of the arms and
note that the ambulacral plates form an unbroken 7zd¢e.
Trace this ridge to the tip of the arm and draw it, some-
what enlarged.

Remove the aboral integument from the body, taking care
not to disturb the madreporic plate. Clean the skeleton
and note any local specializations of the ambulacral plates.
Do you find znxéter-radial partitions ?

Draw the skeleton of the body.

An Echinord. 33

AN ECHINOID
(Arbacia punctulata).

External Anatomy.—Compare the oral and aboral
surfaces with the same of the starfish. Note that there are
five ambulacral areas, separated by five znuter-ambulacral
areas. Both areas bear numerous regularly arranged sfzves.
Note the “ball and socket” joint that permits movement
of the spines. Are all the spines, of different parts of the
body, of the same general structure? Where are they most
elongated ?

The aboral region is centrally free from spines, and is
called the feviproc¢, in contradistinction from the mem-
branous tract around the mouth, the feristome. Find ten
large ambulacral suckers on the peristome. Are pedicel-
/arie to be found on the peristome? On other portions of
the body? How do they differ from the same organs of the
starfish? ‘The periproct will be found to be perforated at its
centre by the opening of the azus which is covered by
four triangular valves.

Forming the periphery of the periproct, are five radiating
plates, the genztal plates. ach genital plate will be found
to form the apex of the zzzer-ambulacral series, and to be
perforated by a small opening leading from the sexual glands.
One of the genital plates will be found to be larger than its
_ fellows and to appear more or less granular. It is the

34 Invertebrate Zoology.

madreporic plate, and is directly comparable with the same
of the starfish. Arranged between the genital plates, and
consequently at the apex of the ambulacral areas, are the
five small ocular plates.

Make drawings of the animal as seen from above and from
below, naming the parts; also make enlarged drawings of a
spine with its “ ball and socket”’ joint and of a pedicellaria.

Remove the spines and thoroughly wash the shell. The
ambulacral and inter-ambulacral areas will be clearly shown.
Find the openings through which the ambulacral suckers
may be thrust out. What is the arrangement of these open-
ings, the ambulacral pores ?

Make a drawing of the denuded shell.

The Digestive System.— Around the margin of the
mouth the five hard ¢ee/h will be observed. With a pair
of scissors carefully remove the membranous peristome and
wash out the body-cavity with clean water. The wsophagus,
after passing through the complicated dentary apparatus,
inclines to the wall of the shell, where it passes into
the somewhat enlarged and elongated stomach. Break- .
ing the shell if necessary, follow-the course of the Jair
mentary tract to the anus, noting any mesendery that may
hold it in place, and observing the structure of its free
border.

By a diagram illustrate the course of the alimentary tract.

The Reproductive System.— The sexes are separate,
though, as in the starfish, the sexual glands superficially
resemble each other. The glands appear as five radially
arranged masses, and are closely attached to the perzvisceral
walls. ach gland opens to the exterior through the pore
already noted in the genital plate. |

An Echinotd. 35

Draw the reproductive system.

The Water-vascular System. — A tube, the szone-canal,
leads from the madreporic plate to a circum-oral canal sur-
rounding the cesophagus. From the circum-oral canal a
radiating tube passes along each ambulacral tract, giving off
branches to the several amfulle. ‘The ampulle in turn
supply the suckers. A so-called heart is to be found near
the upper end of the stone-canal.

The Nervous System.—A delicate nerve forming a
circum-oral commissure surrounds the cesophagus inside the
dentary apparatus. Nerves extend from it radially, along
the inner surface of each ambulacral series, to the terminal
ocular plates, where they end in the eye-spots.

The Muscular System. — A number of minute muscle
fibres will be found at the base of each spine, and a more or
less complicated series is associated with the dentary appa-
ratus. Find the protractors and retractors of the dentary
apparatus. ‘The zzzer-alveolar muscles are arranged between
the alveolar plates, which latter hold the teeth.

Make drawings illustrating the arrangement of the muscles.

36. Invertebrate Zoology.

A HOLOTRURIAN
(Zhyone briareus).

Note the general shape of the Jody, the point of origin
of the ¢enfacles, their number, and the ova/ and anal open-
ings. The body is covered with papilliform améulacral
suckers, which, by careful observation, will be found to be
arranged in five broad, meridionally disposed bands. On the
upper side of the animal the suckers are less abundant than
on the lower side. In the angle between the upper ten-
tacles, the opening from the genital duct will be found.
Examine the oral opening. Are there teeth? Are the ten
large circum-oral ambulacral suckers of the sea-urchin rep-
resented ?

Make a drawing of the animal as seen from the side.

With a pair of scissors open the animal longitudinally
along the middle of the lower surface. Why is it not strictly
correct to here speak of the “ ventral surface ”’? |

The Digestive System is greatly elongated and extends
as a coiled tube which partly fills the body-cavity. It is poorly
suspended to the body-walls by a delicate ‘‘ mesentery,”
and in certain portions of its course becomes somewhat
glandular. The mouth opens into an esophagus which is
surrounded by a cartilaginous structure that recalls the dentary —
apparatus of the urchin. The cesophagus soon enlarges into

A Holothurian. 37

a thin-walled crop or stomach, from which the coiled zn-
testine takes its origin, and continues to its posterior open-
ing into the cloaca. After making a careful drawing, remove
the alimentary tract, cutting it just back of the stomach and
anterior to the cloaca.

The Respiratory and Excretory Systems. — Lying lat-
erally in the body-cavity are the two main divisions of the
many-branched zespiratory tree. Each half of this organ
will be found to open directly into the cloaca, through
which it may receive fresh sea-water and become greatly
distended.

Make a drawing of the respiratory tree and the cloaca.

The Reproductive System. — The ovaries and ¢estes
superficially resemble each other. ‘The sexes are separate.
The genital gland (ovary or testis) occupies a median
position in the upper part of the body-cavity, and is made
up of a multitude of delicate filaments which collectively
forma brush. ‘The organ is divided into a right and into
a left half, and its duct leads directly to the opening already
noted, between the two uppermost tentacles.

Make a drawing of the reproductive system.

The Water-vascular System. — In certain specimens
the circum-oral water-tube or ring-canal will be found to sur-
round the deeper portion of the cesophagus, and to give off
one or two large and elongated Pohan vesicles. Commu-
nicating with the tentacles, the ring-canal gives them their
power of expansion, and it also gives off five radiating canals,
which extend over the body and supply the innumerable
ambulacral suckers. Elongated filiform ampule are abun-
dant and hang from the inner surface of the body-wall. The

38 Invertebrate Zoology.

madreporic plate and stone-canal are much reduced. The
former will be found, as a small calcareous sphere, in the for-
ward part of the body. It communicates with the ring-canal
by a slender tube (szone-cana/), lying below and parallel to
the genital duct.

Make a drawing of the water-vascular ic so far as
you have been able to determine its course.

Muscular System. — Note five meridional bands of
muscles extending the entire length of the animal. Is the
median band above or below? How are the vetractors of
the tentacles and of the @wsophagus arranged? What is the
arrangement around the cloaca? ‘The body-wall is tough-
ened by the presence of many czrcular muscle fibres. How
are they arranged?

Make a drawing that will illustrate the muscular arrange-
ment of the fore and of the hind end of the body.

The Nervous System is not easily dissected. There is
a circum-oral nerve-ring, from which extend five radial
divisions.

A Turbellarian Worm. 39

A TURBELLARIAN WORM
(Bdelloura candida or Bdelloura propingua).

Two species of BdeHoura are abundantly found attached
to the under surface and in the “gill-books” of Limulus.
The larger species (candida) may reach a length of 15 mm.,
while the smaller, often found aggregated in clusters on
the cephalothoracic appendages, does not exceed a length
of 8 mm. Certain internal characters also separate the
species.

External Anatomy. — The body is broad and flat, the
anterior end elongated and pointed, the posterior wide
and provided with a ventral sucker. The eyes are deeply
pigmented, and the brownish zz/estine often gives a darker
color to the middle region of the body. On the lower side
the proboscis hangs freely from near the middle of the
animal, bearing at its extremity the mouzh. In the living
animal active cilia will be found especially abundant along
the margin of the body.

The Digestive System. — The opening of the mouth
leads into the pharyngeal cavity, contained in the proboscis,
and from the proximal portion of the cavity the branching
intestine takes its origin.

The intestine should be examined in a specimen that
has been compressed under a heavy cover-glass. It will

40 Invertebrate Zovlogy.

appear as a greatly lobulated organ, extending nearly from
end to end of the animal, its lateral subdivisions giving
a segmented appearance. It is built on the Tricladid
type, one main branch or ramus extending anteriorly, and
two extending posteriorly. Both anterior and posterior
rami give off lateral lobes, the dzverticula above mentioned,
the rounded ends of which frequently becoming further
subdivided.

The Nervous System. — The pigmented eyes are sur-
rounded in the living animal by a halo-like area, which
marks the location of the drazm. This organ consists of a
pair of lobes, united across the median line by a commissure.
From the brain certain semsory nerves extend anteriorly, as
transparent lines, while extending posteriorly, as transparent
bands, are the Jongztudinal nerve trunks, one on either side.
Note that each longitudinal nerve trunk, after extending
almost the full length of the animal, is united to its fellow
of the opposite side by a broad posterior commissure. Other
commissures will be found in certain favorable specimens
to pass transversely across the animal, and to extend later-
ally beyond the longitudinal trunks, nearly to the margins.
These are the fransverse commtssures, and their number
is about the same as the number of pairs of intestinal
diverticula.

The Reproductive System. — The Turbellaria are
mostly hemaphrodite. In the present species the ovaries
are to be found in adult animals as a pair of rounded organs,
located in the anterior portion of the body between the
second and third or third and fourth intestinal diverticula.
They are ‘often more readily found if the mirror of “the,
microscope is shielded by the hand, thus viewing the

A Turbellarian Worm. Al

animal with reflected light. Frequently the ovzducts may
be traced as a pair of straight lines leading directly back-
wards from the ovaries. The “#sf#s appear as rounded
bodies, abundantly clustered along the margin near the
ends of the intestinal diverticula, and in Bdelloura propingua
extending inwards between these lobes. The seminal ducts
lead finally into elongated seminal vesicles, which extend
posteriorly parallel to the sides of the pharynx, and finally
curve towards the median line. They are quite easily
found, being of an opaque gray color. ‘The seminal vesicles,
often filled with spermatozoa, open into a median pocket,
the atrium, which in turn opens to the exterior from the
oral or ventral side of the animal through a single pore.
The ova are conveyed to this atrium through the oviducts,
which are often difficult to follow. Lying lateral to the
seminal vesicles, one on either side, are certain disc-shaped
organs, somewhat larger than the ovaries, though often
less distinct. The function of these organs is at present
unknown.

The Muscular System. — Both species of Bde/oura are
active swimmers, and the muscular system is especially de-
veloped, though too difficult of demonstration to be now
considered. :

Drawings should be made of the several systems.

———

42 Lnvertebrate Zoology.

A POLYCHA TOUS ANNELED

(LVerets virens).

External Anatomy. — The elongated body is terminated
anteriorly by a triangular piece, the Avostomium, which
bears certain sezse-organs, and forms the most anterior part
of the “head,” while the posterior end is terminated by a
pair of flexible caudal cirrt. Of how many segments or
metameres does the body consist? What is the arrange-
ment of the lateral appendages? Note, through the trans-
parent skin, the median dorsal blood-vessel, and on the lower
side the median ventral nerve-chain. ‘The latter appears
as a whitish line, extending almost the entire length of the
animal, and presents enlargements, ganglia, for each body-
segment.

The prostomium is borne on an enlarged ring, the fevz-
stomium or buccal somite. The zentacles are small and fusi-
form; and take their origin near the terminal point of the
prostomium, from which they abruptly diverge. Immedi-
ately lateral to and below the tentacles are the much larger
and clearly segmented pa/és. In the furrow between the
pro- and peristomium the czrvrz, four on each side, take
their origin. Are they segmented? ‘The eyes or ocel@ are
somewhat difficult to find in alcoholic specimens. ‘They are
four in number, and are arranged in pairs on the dorsal sur-
face of the prostomium. |

A Polychetous Annelid 43

The mouth will be found as a transverse fold of the
integument of the antero-ventral surface of the peristomium.

Make a drawing of the dorsal and of the ventral side of
peristomium.

Observe the varying size of the lateral appendages, espe-
cially at the two ends of the animal. Carefully remove one
of the larger bundles of lateral appendages and examine
under a simple microscope. The bundle will divide itself
into a dorsal and into a ventral parapodium. The former
bears a large triangular blade, the gz. From the upper
edge of the gill projects a small movable crrus. Do you
find ramifying blood-vessels in the gill? Do you find two
fleshy /odes immediately beneath the gill? The dorsal lobe
bears a large number of sezz.

The ventral parapodium is divided in much the same way
as the dorsal. Do you find a ventral cirrus? Ventral sete?
Closer examination will reveal the presence in each para-
podium of a supporting chitinous rod, aczculum.

Draw, naming the parts.

Examine the posterior end of the animal and note how
the lateral appendages become reduced. Which elements
are first lost? What is the point of attachment of the ter-
minal filaments? Does the azuzs open dorsally or ventrally ?

The external openings of the segmental organs will be found
on the ventral side of each body-segment, near the bases of
the parapodia.!

In a specimen that has been killed with extended probos-
cis note the large, laterally opening jaws.

1 These openings are often difficult to find. They are placed at the
summit of the rounded elevation that lies just medially of each ventral
cirrus. The segmental organs themselves are often to be seen through
the transparent integument of smaller specimens. They are opaque
white in color, and lie just lateral to the longitudinal muscle bands.

44 Invertebrate Zoology.

Draw.

Open the animal along the mid-dorsal line, and, after
gently pinning the cut edges apart, note the regular seg-
mentation of the body-cavity. The transverse partitions or
adissepiments correspond in position to the constrictions
between the successive rings or metameres.

The Digestive System.— Cutting through the dissepi-
ments, partially reflex the body-walls from the alimentary
canal. The mouth will be found to lead into a protrusi-
ble pharynx which, in turn, leads into a somewhat smaller
and less muscular cvop. The crop, separated from the
pharynx by a marked constriction, is in turn separated in
the same way from the elongated and thin-walled stomach-
intestine. The latter extends the remaining length of the
animal. Do you find muscles connecting the pharynx to the
inner walls of the peristomium ?

These muscles are -the “ prozraciors.” "Their pomigaa
origin and insertion should be clearly established. ‘The
lesser protractors are also longitudinally arranged, but are
not attached otherwise than to the walls of the pharynx.
The vetractors, unless the pharynx is extended, will be ob-
served as fine fibres in the region of the first and second
metameres. Determine their distribution.

?

The Crop. — Are there muscle fibres extending from the
crop to the body-walls? Do you find a g/and on each side
of the crop? ‘Trace its duct. How do the walls of the
crop compare with those of the pharynx ?

The Stomach-Intestine.—JIs this portion of the ali-—
mentary tract regularly constricted throughout its entire

A Polychetous Annelid. 45

length? Do the constrictions invariably correspond to the
surrounding body-rings? Are there any local changes in
the texture or color of the stomach-intestine that might
argue changes in function? Do you find a ventral mesen-
tery attaching the tube to the mid-ventral line? (The dor- |
sal mesentery has probably been destroyed in opening the
animal.)

Make a drawing of the dorsal view of the alimentary
tract, naming the parts.

With a pair of sharp scissors open pharynx, crop and in-
testine, along the mid-dorsal line. The interior of the
pharynx will be found to present an anterior, tooth-bearing
and a posterior, undifferentiated portion. Note the internal
lining of the crop, and the small opening leading from it to
the much thinner-walled stomach-intestine. Is the lining
membrane of the latter different from that of the crop?

The Circulatory System in /Verezs consists of a closed
system of tubes in which the 40d, holding in suspension
numerous red Jdlood-cells, circulates. The median ventral
blood-vessel extends nearly the entire length of the animal.
It lies ventrally to the alimentary tract and sends out lateral
branches to each segment of the body. These Méeral
blood-vessels ramify through the gills and over the organs,
uniting again, above, in a median dorsal blood-vessel. ‘The
latter rests upon the intestine. In the anterior portion
of the animal, due to the presence of the complicated
pharyngeal apparatus, the circulatory system is somewhat
less regularly arranged. — The dorsal vessel is contractile,
and forces the blood from the posterior towards the head.

46 Invertebrate Zoology.

The Muscular System. — How many distinct bands of
muscle bundles are there? ‘Their location? Are they seg-
mented? How are the muscles arranged around the acicula?

Make a drawing of the muscle bands of six segments, and
give special attention to the acicula and their muscles.

The Reproductive System. — The sexes are separate,
and the reproductive glands periodically develop from the
endothelium of the body-cavity. During the breeding
season the eges, or spermatozoa, often fill, as a granular or
creamy mass, many of the chambers of the body-cavity.
The eggs are fertilized after extrusion.

The Excretory System.—The external openings of
the segmental organs or nephridia have already been noted.
By gently displacing the lateral edge of a ventral muscle
band, a series of small flask-shaped bodies will be exposed,
lying somewhat below the ventral acicula. They are the
nephridia. ‘Trace the nephridia anteriorly and posteriorly,
and see if they are present in each segment.

Make an enlarged drawing of one of the segmental organs.

Nervous System. — Find the ventral chain of ganglia.
Do the ganglia of the several segments occupy the same
relative position? Can you find nerves leading from them
to the organs or to the body-walls? Is there anything to
show that the ventral chain was originally double? Im-
mediately back of the cesophagus, note the enlarged znfra-
esophageal ganglion. Extending laterally and anteriorly
from it are the @wsophageal commissures which unite above
the cesophagus in the drain, or supra-esophageal ganghon.
Do you find nerves passing from the brain, or commissures,
to the eyes, tentacles, or palps?

Make an enlarged drawing of the nervous system.

A Polyzoan. 47

na LORVZOAN
(Bugula Spey:

AFTER a colony of this Polyzoan has remained in a solu-
tion of caustic potash for a little time, all fleshy matter will
be removed, and the skeleton may be washed in water and
examined with a low power of the compound microscope.

The skeleton is somewhat hardened by a deposit of lime,
and is known as the cenecium. It is made up of a multi-
tude of little cups, zowcza, which are arranged in double
rows, back to back, each zocecium having its opening or
“mouth” directed distally. The margin of the mouth is
provided with one or two spines, and on one side a deep
indentation or sizus will be found. This sinus is on the
upper surface of the double row. For convenience, the
side of the zocecium that is directed towards the median line
of each double row may be called the zzmer, the side
directly opposite (lateral), the ouzer, the side marked by
the deep sinus, the wer, and the side opposite the sinus,
the Jower. The end of the zocecium which bears the
“mouth” is the asfa/, and is directed towards the free
growing point ; that directed towards the attachment of the
double row is the proxima/. It will be noted that the
branching of the ccencecium is always dichotomous.

On the outer margin of the sinus of the older zocecia,

48 | Invertebrate Zoovlogy.

“‘bird’s-head ” structures, or avzcu/aria, will be found. Near
the proximal ends of certain older zocecia, on the upper
surface, spherical bodies will be found. They are egg-caf-
sules, or oecia, and have a diameter about equal to that of
the zocecia.

By focussing deeply into the distal portion of one of the
zocecia, an irregular oval opening will be observed to lead
from its inner side. ‘This opening is the vosetfe or commu-
nication plate and leads into the proximal end of the zoce-
cium next above and on the opposite side of the double
row.

In an alcoholic specimen that has been properly killed
and preserved, the walls of each zocecium will be found to
extend distally and to be terminated by a circle of fourteen
long zenzacles, the zocecitum together with the fleshy parts
being known as a folyfide. The knob-shaped body bearing
the tentacles is the phophore. It is pierced by the mouth
opening, which is placed in the centre of the tentacular
crown. In life, the cilia covering the tentacles whip the
food into the mouth, the pharyngeal cilia there carrying it
still further into the digestive tube. The anal ofenting is to
be found on the inner side of the lophophore just below the
citcle of tentacles. It is often more readily found i tie
zocecium be examined from the lower side. Make a drawing
of a polypide.

Digestive System. — The digestive tract is V-shaped.
The pharynx leads into a stomach, which is provided with a

1 The jaws of the avicularia, during life, are frequently closed upon
small animals, the decaying bodies of which may attract smaller —
organisms upon which the Bugula feeds,

A Polyzoan. 49

proximally directed pouch, the cwcum. The ccecum forms
the lower curve of the V. The znzestine, richly ciliated,
extends from the ccecum to the rectum, the latter is often
better seen on the lower side of the zocecium. A loose
mass of non-muscular tissue, the /wmzculus, extends from
the lower end’ of the ccecum to the deeper portion (prox-
imal) of the zocecium. Make a diagram of the digestive
tract.

The Circulatory System.—A vascular circulatory sys-
tem is not present in Polyzoa, though the fluid contained in
the body-cavity bears numerous cellular corpuscles. It
probably becomes purified in the thin-walled, hollow tenta-
cles.

The Muscular System. — During life the lophophore,
together with the tentacles, is often forcibly retracted into
the cavity of the zocecium. This contraction is brought
about by the action of certain retractor muscles, which may
be seen in favorable specimens extending across the body
or coelomic cavity from the inner surface of the zocecium to
the inner walls of the pharynx and lophophore.

The Nervous System is represented by a supra-ewsopha-
geal ganghon, situated between the mouth and the anus.
From it certain nerves go to the tentacles. There are no
differentiated special sense-organs, and the entire system is
too difficult of demonstration to be considered in the present
course.

The Reproductive System. — The increase in the num-
ber of polypides in the colony, or zoarium, is brought about
asexually by “ budding,” though the more mature polypides

50 Invertebrate Zoology.

are provided with true sexual glands. The ova are often
found in varying stages of growth lying in the body-cavity
near the ccecum. ‘They are yellowish in color and oval
in outline. The stermatozoa lie deeper, near the proximal
end of the funiculus and form a cloudy mass.

A Gephyrean Worm. 51

A GEPHYREAN WORM

(Phascolosoma gouldit).

External Anatomy.— The elongated body shows no
external traces of segmentation, and lateral appendages
are not present. ‘The anterior end is often deeply with-
drawn, though in specimens killed with considerable care
the mouth will be found to occupy a terminal position, and
to be surrounded by a crown of tentacles. The anal open-
ing is not at the posterior end, but at the apex of a median
papilla, situated near the middle of the animal, and marking
the dorsal surface.

Make a drawing of the animal as seen from the side.

Internal Anatomy. — With a pair of scissors open the
specimen along the median line a little to one side of the
anus and pin the body-walls so as to expose the internal
organs. Note the dorsa/ and the ventral pharyngeal retrac-
tors. ‘They are large muscle bundles, longitudinally arranged,
and retract the anterior portion of the animal.

The Digestive System. — Locate the mouth and follow
the coiled stomach-intestine to the “ posterior” end of the
body, thence back to its final opening on the dorsum. Do
you find mesenteries? Are there dissepiments ?

52 Invertebrate Zoology.

The Circulatory System is with difficulty followed out.
There is a dorsal and a ventral vessel, much as in /Vereis.

The Muscular System. — What is the arrangement of
the muscle fibres of the integument? How many longitu-
dinal bands are there? Examine again the pharyngeal
retractors.

Draw.

The Reproductive System. — The sexes are separate.
The sexual glands are situated near the base of the ventral
pharyngeal retractors. The eges or spermatozoa reach the
exterior through the single pair of hia Fertilization
occurs after extrusion.

The Excretory System. — The zephridia are a pair of
large brown tubes which lie, somewhat freely, in the neigh-
borhood of the retractors. Their openings to the exterior
lie a little in front of the origin of the dorsal retractors.

Draw.

The Nervous System. — The zentra/ cord lies along the
mid-ventral line. Examine with a lens and see if it is pro-
vided with ganglia. Do nerves leave the ventral cord?
Find the wsophageal commissures and trace them to the
brain or supra-esophageal ganghon. Are there pigmented
eye-spots ?

Draw.

A Lamellibranch. 53

m LAMELLIBRANCH

(Venus mercenaria).

External Anatomy.— The sei is composed of two
bilateral halves or valves, the Ainge, or their common line
of union, marking the dorsal side. ‘The anterior end is
less elongated than the posterior. The wmdo is the dome-
shaped elevation along the dorsal edge of each valve. Lying
dorsally, between the valves, and extending posteriorly, is the
igament. Which is the right valve, and which the left?
Note the parallel Aes of growth.

Draw.

Pry the shells apart and note the thickened mande-
edge, running parallel to the free margin of the shell.
It is partly divided into a right and a left half, by lon-
gitudinal openings. The anterior and ventral opening
( pedal) gives opportunity for the protrusion of the foot
while the posterior or siphonal permits the ingress and
egress of salt water.

Internal Anatomy. — Remove the left valve of the shell,
taking care not to injure any of the underlying soft parts. If
the animal has been killed by being allowed to stand in
warm fresh water for a little time, the valves will naturally
gape apart, and the attachments of the strong adductor
muscles may be pressed from the shell with the handle of

54 Invertebrate Zoology.

the scalpel. Note the left mantle-lobe covering the whole
surface of the animal, except the muscles. Through the
semi-transparent mantle, the outlines of the underlying
viscera may be seen.

Along the dorsal edge, midway between the muscles, por-
tions of the dark green “ver, the cream-colored reproductive
gland, and the brownish Keder’s organ are to be noted, in
the order named. Further posteriorly and dorsally, between
Keber’s organ and the posterior adductor muscle, the heart
may be observed, lying in the delicate pericardial sac. If
the animal is still alive, the pulsations of the organ may be
noted. Immediately in front of the posterior adductor, and
lying somewhat lateral to the heart, the yellowish ovgan of
Boanus is to be noted.

The foot is a plough-shaped organ, pointed at its anterior
end, and supported from the lower margin of the great,
swollen, soft-bodied wzsceral mass.

With a pair of scissors remove the left lobe of the mantle,
cutting around the anterior and posterior adductors. ‘The
visceral mass nearly fills up the cavity between the two mantle-
folds (mantle or pallial chamber) and is crossed on each side,
diagonally, by two fringe-like gz/s. If the gills are followed
anteriorly, they will be found to end near two small gill-like
organs which lie just posterior to the anterior adductor.
These organs, of which there are two on each side, are the
palps. They lie, one pair above, and one pair below, the
mouth-opening.

Examine the szphonal region. ‘The mantle will here be
found to be specialized in such a way as to form two pro-
trusible tubes, of which the lower leads from without into
the mantle chamber.

Make a drawing of the above-mentioned organs.

A Lamellibranch. 55

The Muscular System. — The strong anterior and pos-
terior adductor muscles have already been noted. Is there
any difference in their relative size? Can you discover the
retractors of the foot, smaller muscles lying near the adduc-
tors? The siphonal muscles lie around the base of the
siphon. Note any lines of attachment on the inner surface
of the removed valve that correspond to the muscles just
mentioned. :

The Respiratory System. — Pass a probe into the
lower siphonal canal (the zzcurrent canal) and note that
the canal may convey water into the mantle chamber. Into
this chamber, which is also known as the 7nzfra-branchial
chamber, the gills or dvanchig hang. Each gill is made up
of two parallel plates of rods or bars. Study carefully the
attachment of the two pairs of plates of each side to the
mantle, without, and to the body-wall, within.

Inject water into the upper siphonal opening and notice
that it fills a certain chamber lying above each pair of gill-
plates or lamelle. This chamber is the supra-branchial
chamber, and on each side, above the outer and inner gills,
has an owzer and an izmer division. The outer subdivision
may be exposed by cutting along the line of attachment of
the outer lamella to the mantle. The inner sub-chamber
may be exposed by turning back both gills and cutting along
the line of attachment of the inner lamella of the inner gill
with the body-wall.’ Look into these chambers and note
the numerous openings of the zwater-pores, tubes which lead
from between the giil-lamellz.

Carefully slit open a gill in such a way as to separate its
lamelle and, floating one of the lamelle on a slide, exam-
ine with a compound microscope. If the gill is still alive, a

1 The inner lamella is only partially united to the body-wall.

56 Invertebrate Zoology.

most beautiful ciliary motion will be observed. Note the
supporting bars and the openings through the gill-lamella
for the passage of water. ‘This passes from the infra-
branchial chamber into the water-tubes between the lamel-
le, and thence into the supra-branchial chamber. ‘The
supra-branchial chambers of the right and of the left side
open into a common cloaca, below and behind the pos-
terior adductor. From the cloaca the water reaches the
exterior through the upper siphonal or excurrent canal.

Make drawings of all the parts of the respiratory appa-
ratus. The arrangement of the supra-branchial chambers
may be well shown by imaginary cross-sections.

The Circulatory System. — The location of the heart
within the delicate pericardium has already been noted. The
organ will be found to consist of a median and strong-walled
ventricle into which opens, from each side, through an a@z-
riculo-ventricular opening, a thin, triangular-shaped auricle.
The lower side of the auricle, corresponding to the base of the
triangle, lies above the supra-branchial chamber and receives
the purified blood from the gills. The rectum, or posterior
portion of the intestine, passes through the ventricle. In-
jected specimens will clearly show the course of the arteries
as they pass anteriorly and posteriorly from the heart. The
bulbus arteriosus will be noted on the posterior aorta as a
large contractile sac.

The Excretory System. — The dney, or organ of
Bojanus, has already been noted. Examine under the
organ and near its anterior end. ‘Two small openings will be
found. The more posterior is the opening of the wvezer, and
leads from the kidney. It lies inside’ the second, the 7efvo-
ductive opening. If a hair is carefully passed into the open-

1 Nearer the median plane.

A Lamellibranch. 57

ing of the ureter, and the outer wall of the kidney is then
dissected away, the probe will be found to have reached
what is called the “ upper Amd” of the kidney. This cavity
is a comparatively smooth and thin-walled sac. It is con-
tinuous with the “ ower 4imé,” which lies posteriorly, and is
provided with more glandular walls. This ower Amd finally
communicates, through a funnel-shaped opening, with the
cavity of the pericardium. ‘The opening into the pericardial
space is small and somewhat difficult to demonstrate. These
renal organs are comparable to the nephridia of /Vere7s.
Make a careful drawing of the parts just studied.

Reproductive System. — The reproductive gland (testis
or ovary) is a somewhat delicate and voluminous organ, par-
tially enfolding the coiled intestine. The opening of its duct
has already been noted.

The Nervous System. — The &/ cerebral ganglion will
be found as a small body, about the size of a pin’s head,
lying just behind the upper portion of the anterior adductor.
Find the short, transverse commissure that connects it with
its fellow of the opposite side. The visceral ganglia lie on
the lower surface of the posterior adductor. They are yel-
lowish masses, from which numerous nerves radiate. A
larger nerve may be followed from the left visceral to the
left cerebral ganglion. It is the cerebro-visceral connective,
and lies for the most of its extent near the surface. The
pedal gangha \ie side by side in the substance of the ante-
rior portion of the foot, and just below the visceral mass.
Cerebro-pedal connectives may be traced through the visceral
mass from the pedal to the cerebral ganglia.

Make a drawing of the nervous system.

58 Invertebrate Zoology.

The Digestive System. — The mouwth, already noted, is
provided with an wpfer and an wander ip, two transverse
folds that apparently connect the upper and the under
palps. (The position of the mouth can be very clearly seen
if the clam is carefully removed from its shell and pinned
out under water.) The posterior portion of the alimentary
tract passing through the ventricle has already been noted
as the vectum. Follow the rectum in its further course over
the posterior adductor to its final opening into the cloaca.

To now trace out the course of the entire digestive tube
considerable care must be exercised. — Carefully pick or
cut away, piece by piece, the side of the visceral mass. The
short @sophagus will be found to lead upward and _ back-
ward into the stomach. ‘The latter is an irregular sac situ-
ated dorsally and anteriorly, and has, opening into it, the
ducts from the digestive gland or ver. The liver almost
entirely surrounds the stomach.

The znuzestine is long and coiled. It begins at the poste-
rior end of the stomach, passes to the lower posterior por-
tion of the visceral mass, and then curves to the left and
forward, soon to again bed itself deeply into the surrounding
viscera and take on several convolutions. Finally the intes-
tine passes upward, posterior to and nearly parallel with the
first section until, at the level of the stomach, itememas
sharply backward to pass through the ventricle of the heart.
During a portion of its course the lumen of the intestine is
partially filled by a fold, the AAh/osole. The tract does not
lie in a “ body-cavity.”

During the dissection of the digestive tract a long gelati-
nous cord has doubtless been noted. This is the crystalline
style. Its function is not known.

Make a drawing of the alimentary tract.

A Cephalophorous Mollusk. 59

meer MALOPHOROUS MOLLUSK
(Sycotypus canaliculatus).

External Anatomy.— Examine an animal enclosed
within its shell and note the following points : —

The she//, unlike that of the Lamellibranch, consists of but
a single piece (Univalve). It is twisted towards the right,
around a central axis, the co/vmella, and makes several
revolutions or whor/s from its apex or spire, to its lower
opening or “mouth.” The side of the mouth nearer the
columella is called the zuzernal 4p, while the outer, thin,
convex edge is the outer 4p. Extending from the mouth
downwards (away from the spire) is an elongated groove,
the canal. The line of union between two whorls is called
the suture. Lines of growth extend as parallel series, at
right angles to the suture, and parallel to the edge of the
outer lip. Frequently the shell is covered externally by a
felt-like horny epidermis.

Draw the shell from the side, naming the parts.

From the “mouth” of the shell the soft parts of the
snail may be protruded, the large foot being the last to
disappear during contraction and the first to leave the shell
as the animal again expands. To the upper side of the
foot a horny lid, or operculum, is attached, which may effec-
tually close the opening of the mouth.

As the animal crawls about, the shell is carried upon its

60 Invertebrate Zoology.

back, the canal being directed forward, the spire backward.
The opening of the shell is then on the right side.

Examine an animal that has been removed from the shell,
and compare the number of whorls made by the body with
the same of the shell.

The lower surface of the foot is somewhat wrinkled. It
has, leading from its centre, an opening from the “ pedal
gland.” At the posterior and dorsal part of the foot, observe
the attachment of the operculum. Extending anteriorly and
dorsally, the substance of the foot merges into the “ead.
The head is anteriorly provided with two laterally projecting
and triangular flaps, the ¢enfacles.\ Midway between the
tentacles, but somewhat below them, is the opening of the
mouth. Frequently the elongated proboscis projects from the
mouth as a flexible tube, an inch or more in length. If the
specimen being examined is a male, the large intromittent
organ, or fens, will be observed. It is situated a little to
the right of and above the right tentacle.

The coMar is a circular fold of the mantle that entirely
surrounds the body just posterior to the head. In life, it
was applied to the lips of the shell, and by its activity the
body of the shell (middle layer as well as the epidermis)
was elaborated. At a point corresponding to the canal the
inner part of the collar is produced into a groove-like szphon.

If the collar is elevated along its antero-dorsal portion, a
large chamber, the mantle cavity, will be exposed.

The soft parts of the animal, extending into the spire, are
collectively spoken of as the “zzsceral mass.” It should be
borne in mind that the outer surface of each whorl corre-
sponds to the left side of the animal, while the inner surface,
next the columella, is the right side.

1 On the lateral edge'of each tentacle is the small deeply-pigmented eye.

A Cephalophorous Mollusk. 61

The outlines of the following organs may be distinguished
through the somewhat transparent walls.

The 4ver or digestive gland extends as a dark green mass,
from the apex of the spire, of which it forms the larger
part, to a point two revolutions lower down. It bears on
its dorsal surface the lighter sexual gland, fests or ovary,
the sexes in this univalve being separate.

On the external surface of the liver the stomach is often
to be seen as a curved body somewhat less than the sexual
gland in size. Extending anteriorly from the liver, and con-
fined more to the outer portion of the whorl, is the dark-
colored renal organ or kidney. ‘The outline of this organ,
when viewed from above, is triangular, the apex being di-
rected towards the columella, while the base extends laterally.
Viewed from the side, the base of the triangle is seen to rest
upon the liver, posteriorly ; upon the pericardial chaméer,
ventrally ; and upon the roof of the mantle chamber, ante-
riorly. ‘The renal organ is divided into a smaller svbuliferous
portion, which lies against the pericardium, and a larger acin-
ous portion, which lies above and around the first." The line
separating the two runs parallel with the upper edge of the
pericardium. The pericardial chamber is somewhat cres-
centic in outline, and is about the size of one of the tentacles.

If the specimen being examined is a female, the roof of
the mantle chamber presents on its dorsal surface a long,
large elevation of light cream-color, extending from the
liver, and internal to the kidney, nearly to the free edge of
the collar. This elevation is the zzdamental gland. ‘Through
its activity the long egg-st77ngs are manufactured. Lying
parallel to, but outside of and below the nidamental gland
(nearer to the siphon tube), the location of the gill is clearly

1 The function of the tubuliferous portion is uncertain. It is prob-
ably not excretory.

62 Invertebrate Zodlogy.

seen. It is a large crescentic area, often slightly depressed.
On the inside of the visceral mass, and extending somewhat
parallel to the nidamental gland, is the large columelar mus-
cle, by means of which the animal retains its hold upon the
columella of the shell.

Make drawings of the animal as seen from in front and
as seen from the outer and inner sides.

The Anatomy of the Mantle Cavity. — With a pair of
scissors slit open the roof of the mantle chamber along a
median line extending parallel to the upper edge of the
pill. Reflect the flaps and observe, on the mmer side of
the left, the extent of the single large lamellate gz What
is the arrangement of the dranchial lamellae ? Immediately
below the gill is a smaller organ, somewhat similar in out-
line and structure. It is the osphradium or olfactory organ.
On the inner surface of the right flap the external opening
of the vectum will be noted. It is at the apex of a short
anteriorly directed tube. i

If the specimen is a female, the exéernal opening of the
oviduct will be found at the apex of an elevation near, though
a little lower than, the anal papilla. Pass a flexible probe
(a guarded bristle) into the opening.

Males are somewhat smaller than the females, and may
be readily distinguished by the intromittent organ. Lead-
ing out from the base of the pezzs, and inclining towards
the right, until it finally reaches the groove made by the
union of the roof of the mantle chamber to the body, is a
clearly defined ridge which marks the course taken by the
vas deferens. Trace the vas deferens to the upper portion
of the mantle chamber.

In both sexes a large gland, the hypobranchial or adrectal

A Cephalophorous Mollusk. 63

gland, occurs as a series of tranverse folds along the roof
of the mantle chamber. In the female the gland extends
between the gill and the nidamental gland.

At the very apex of the mantle chamber a slit-like open-
ing will be found. ‘This opening leads from the cavity of
the renal organ.

Make a drawing that will illustrate the anatomy of the
mantle chamber.

Internal Anatomy. — The systems of organs may be
dissected in the following order : —

(2) The Circulatory System. — Though it is well to
use a hypodermic syringe with some colored liquid for trac-
ing out the arteries and veins, the larger blood-vessels may
be located in the uninjected specimen.— The branchial
vein, seen from without, is a transparent line running
along the lower side of the area which we know to be that
of the gill. It may be followed nearly to the pericardium,
where it unites with a veval vein that returns the blood
from the lower, tubuliferous portion of the renal organ.
The common vein empties into the auricle of the heart.

With a pair of scissors carefully open the pericardial
chamber, and gently lift the heart from the cavity. The
auricle will appear as an anterior division, thin-walled and
collapsed. The ventricle, lying posteriorly, is much larger,
and is provided with strong muscular walls. From the ven-
tricle arise two arteries. These pass from its posterior
end and convey blood to all parts of the animal. ‘The zs-
ceral artery passes upwards, through the substance of the
liver, giving off branches to the stomach and reproductive
gland. By the careful use of probes the visceral artery
is not difficult to trace. The aorta, the second artery,

64 Invertebrate Z oblogy.

makes an abrupt turn downwards and forwards, and passes
towards the head. It soon enlarges and forms a secondary
heart which lies, as dissection will show, to the left of, upon
and to the right of, the cesophagus. Large branches are
given off to the muscles of the foot, siphon, and to the head.

Make a drawing of the heart and principal blood-vessels.

Cut the heart in two and reflect, exposing the pericardial
chamber. Note the serous lining, and especially the open-
ing which leads into the renal organ. ‘This opening, which
is of considerable morphological significance, will be found
somewhat below and inside of the point of entrance of the
branchial and the renal veins, and near the deepest point of
the pericardial chamber.

Make a drawing of the interior of the pericardium.

(6) The Excretory System. — The location of the glan-
dular and of the tubuliferous portions of the kidney have
already been noted. With a small pair of scissors cut along
their common line of union, opening the chamber of the
kidney. Observe the numerous parallel lines of sudules
which make up the substance of the lower, cvbuliferous por-
tion. The larger, acinous portion of the kidney is made up
of large lobules over which blood-vessels ramify, on their
course from the upper part of the body to the gill. Look
for the large opening leading from the renal to the mantle
chamber, and also for the smaller opening which leads from
the pericardial chamber. |

Make a drawing of the glandular organs of the kidney.

Carefully remove the acinous portion of the renal organ.

(7) Lie Reproductive System. — If the specimen being
examined is a female, the ovary will be found as already
noted. ‘Trace the oviduct as it leaves the lower inner side

A Cephalophorous Mollusk. 65

of the ovary and passes down to the nidamental gland. In
the living animal it rests against the columella. Follow the
course through the lumen of the nidamental gland to the
exterior. Open the ovary and note the ultimate branches of
the oviduct and the numerous eggs.

Make drawings that will illustrate the anatomy of the
ovary and the course of the oviduct.

The zest#s of the male lies in the same place as does the
ovary of the female, and its duct, the was deferens, pursues a
similar course along the inner surface of the liver to that
taken by the oviduct. The course along the floor of the
mantle chamber has already been noted.

Draw.

(72) The Digestive System.— Select a specimen that has
been killed while the proboscis remained protruded and
note the terminal mouth-opfening, and the Angual ribbon or
odontophore, projecting slightly from its lower side. Witha
pair of scissors slit open the proboscis along its mid-dorsal
line, taking care to cut only through the skin. Immediately
below the incision, the light-colored wsophagus will be seen
as a straight tube. It extends from its opening into the
pharyngeal cavity, immediately over the end of the odonto-
phore, to the upper end of the proboscis, where it abruptly
dips into the substance of the body. Note the small fibres
that attach it to the integument, and which, at its outer end,
are deeply colored, and may, by their contractility, give the
organ a pumping function. Extending from the base of the
proboscis into the substance of the body are a pair of white
muscle bundles, the righ? and left retractors of the proboscis.

Below the cesophagus lies the deep-colored muscular mass
that brings about the movement of the lingual ribbon.

66 Invertebrate Zoology.

Draw. :

The odontophoral or radular protractors are muscle
fibres which extend from the lower side of the muscular
mass to the inner surface of the integument, near the free end
of the proboscis. The vadular retractors are a series of
fibres extending dorsally from the proximal end of the
cylinder to the inner surface of the integument, near the
base of the proboscis.

Having opened the oesophagus, free it from the underlying
muscular mass, and note the transverse fibres of a thim
muscle sheet that rested below the middle third of the
cesophagus and gives attachment to the radular protractors
along its lateral edge. Observe that the radula extends
under the muscle from near the base of the proboscis to its
free end, and that the obliquely disposed radular retractors
also extend under the muscle sheet.

Carefully slit open the muscle sheet and note the place of
insertion of the radular retractors along the sides of the
radula. |

The lower surface of the radula rests upon a pair of
elongated odontophoral cartilages, the retractor muscles
of which extend proximally and below the radular retractors
to a tendinous ring, which also gives attachment to the white
fibres of the retractors of the proboscis. On the ventral
side of the muscular mass the ventral retractor of the radula
will be noted. It is a small muscle, lying between the
odontophoral cartilages, and by its contraction the dorsal
surface of the radula is brought down over the pulley-like
ends of the odontophoral cartilages.

Make a drawing that will illustrate the structure of the
radular apparatus.

The cesophagus passes between the mass of white re-

A Cephalophorous Mollusk. 67

tractors of the proboscis and midway between the large yel-
low salivary glands. The ducts from the salivary glands
appear as two delicate tubes extending one on either side of
the cesophagus as it passes down the proboscis.

Draw.

At a short distance beyond the salivary glands the cesoph-
agus is surrounded by the orange-colored gangla of the ner-
vous system. A little posterior to the cesophageal nerve-
ring, the alimentary tube receives the duct from a delicate,
elongated gland, the ‘‘ pancreas,” which lies to the right side
of and upon an enlarged section of the alimentary tract, the
crop. ‘The crop becomes smaller in diameter as it ap-
proaches the liver, into the lower portion of which it courses,
and becoming again enlarged, forms the “ stomach.” ‘The
walls of the stomach may be seen without dissection as a
whitish tract on the outer surface of the liver.

If the stomach is opened and the contents washed away,
the large hepatic ducts will be found. How many ducts are
there? After passing along the lower side of the liver, the
stomach bends abruptly upward and forward, and thence, as
the zz¢estine and rectum, runs to its external opening parallel
to the crop and cesophagus. Is the epithelial lining of the
rectum in any way specialized?

Make drawings that will illustrate the course of the ali-
mentary tract.

(e) The Nervous System. — The nervous system of the
Cephalophorous or Gasteropod mollusks consists of a series
of ganglia, chiefly arranged around the cesophagus, and of a
number of radiating zerve-cords. — The circle of ganglia. sur-
round the cesophagus somewhat in front of the duct of the
“pancreatic gland,” and when viewed from above present

68 Invertebrate Zoology.

considerable bilateral asymmetry. If the anterior part of
the cesophagus is turned back, however, the lower side of
the ganglionic mass will be found to be made up of two

nearly equal halves.

Lying ventrally are the small duccal gangha, a pair of
spherical bodies somewhat in front of the remaining ganglia
and giving origin to a number of nerve-strands that pass to
the pharyngeal apparatus. A duccal commissure runs beneath
the oesophagus and connects the right with the left ganglion.

Also, on the ventral side of the cesophagus are the much
larger pedal ganglia. ‘These lie, fused together, a little pos-
terior to the buccal ganglia, and from them large strands of
nerves pass to the right and left halves of the foot.

Cerebro-pedal connectives pass from the pedal ganglia
dorsally, partially encircling the cesophagus, and uniting with
the cerebral gangha. ‘The cerebral ganglia rest dorso-later-
ally upon the cesophagus, and are united dorsally by the
cerebral commissure. Nerves pass from the cerebral ganglia
to the region of the head. Cevebro-buccal connectives unite
the buccal and cerebral ganglia.

The left cerebral ganglion is in union ventrally and pos-
teriorly with the /e/t pleural ganghon, which rests anteriorly
upon the posterior part of the left pedal ganglion.

The right cerebral ganglion at first appears to be some-
what larger than its fellow. Examination will show that this
is because of its partial fusion with the 77gh¢ plural ganghon,
which lies immediately ventral and posterior to it.

At the posterior edge of the right pleural ganglion, the
pear-shaped right visceral or supra-intestinal ganglion 1s
seen to be attached. It lies almost directly upon the dorsal
surface of the cesophagus, and gives off several branches, of -
which two go to the osphradium, and a third passes pos-

A Cephalophorous Mollusk. 69

teriorly in a line nearly parallel to the course taken by the
digestive tract. ‘This posterior band forms one half of the
so-called wisceral loop and leads to the abdominal gan-
glion, located far up in the substance of the body near the
nephridial opening.

The ft visceral or sub-intestinal ganglion lies on the right
side of the cesophagus, below the right pleural ganglion, and
posterior to the right pedal ganglion. A broad band, the
left viscero-pleural commissure, will be observed to lead from
the left visceral ganglion to the left pleural ganglion, passing
below the cesophagus just back of the pedal ganglia. The
left visceral ganglion gives rise to the left half of the visceral
loop, which passes posteriorly to join the abdominal ganglion
already noted. On its course it gives off a branch to the
columellar muscle.

The pleural ganglia give off nerves which pass to the
lateral walls of the body and to siphon and collar.

Make a series of drawings of the nervous systems.

70 Invertebrate Zoilogy.

A’ CEPHALOPODOUS MOLiEUss
(Loligo peal).

External Anatomy. — Note the elongated body, sepa-
rated from the movable head by a constricted zeck. The
integument is abundantly supplied with chromatophores.
Though not of the usual morphological significance, observe
that there is an anterior and a posterior end, and a dorsal
and a ventral surface. What is the shape and attachment
of the terminal 7s 2 Demonstrate that there is an opening
between the neck and the “ co/ar” into a central chamber,
the mantle cavity. What is the position of the eyes? Are
they provided with Z¢ds? How many arms are there? Are
all of the arms of the same structure? How many rows of
suckers axe there on the shorter.arms? .On the longer:
Do you find the mouth? The opening of the szphon-tube ?
Just back of each eye, note the fold of the olfactory organ.
What is its extent? Note the median, dorsal projection of
the collar. Turn it back, and note that it is stiffened by the
presence of a horny structure.

Open the animal along the mid-dorsal line. The horny
structure, pen, will be found to extend the entire length.
Remove the pen.

Make a drawing of the animal as seen from the left side,
putting in as much detail as possible and naming the parts.
Also make a drawing of the pen.

A Cephalopodous Mollusk. 71

Examine one of the larger suckers. Is it sessile or
mounted on a peduncle? Note the horny vwg. Is the
margin of the ring entire or serrate? Make a longitudinal
section through the sucker and its fleshy fzszon.

Draw the side view of the section.

Internal Anatomy. — Carefully open a male specimen,
a little to one side of the mid-ventral line, exposing the
mantle cavity. Pass a large probe through the opening of
the siphon. Do you find the large retractor muscles of the
siphon? ‘Trace them to their posterior points of attach-
ment. On each side of the siphon note the lateral szphonal
_ blind-sacs. What is their function? Immediately posterior
to the siphon note the tube-like rectum.

The anus, at the most anterior point of the rectum, will
be found guarded by two lateral, leaf-like valves. Carefully
inject water into the rectum, and note the outline of the
organ.

Immediately dorsal to the rectum is a dark-colored sac,
the znk-sac. Slit open the anterior end of the rectum,
along its mid-ventral line, and note the point of entrance of
the tube from the ink-sac.

Lying along each side of the mantle cavity, and parallel
to the retractors of the siphon, are the g7//s. How is each
gill attached? Do you find, at the base of each, a disc-
shaped branchial heart? The median mantle artery will be
noted, as a cord-like tube, extending from a point midway
between the branchial hearts, across the mantle cavity to the
inner side of the mantle. It marks the anterior limit of a
median mesenteric fold that extends from it posteriorly.

Looking through the transparent tissue that covers the
viscera, a pair of underlying urinary organs, or nephridia,

72 Invertebrate Zoology.

will be seen. Anteriorly, each organ opens through a small
pore that thus leads from the nephridium to the mantle
cavity. Each pore lies near the median line, some little
distance in front of the branchial heart, and marks the
anterior end of the nephridial chamber. ‘The posterior and
broader end of the chamber lies just medially of the branchial
heart, the night and left nearly meeting in the median line.

Two arteries, Zateral mantle arteries, will be noticed (one
on each side), extending laterally and posteriorly, from near
the point where the median mantle artery leaves the visceral
mass, to the internal surface of the mantle. Lying laterally
to each lateral mantle artery is a much larger thin-walled
posterior vena cava. ‘This organ is often filled with blood
that has been received from the posterior mantle veins which
lie parallel to the mantle artery. The cone-shaped posterior
portion of the mantle cavity is filled up with the voluminous
visceral sac and the sexual organs.

Make an outline drawing of the organs as they naturally
lie in the mantle cavity.

The Circulatory System. — By the use of a hypodermic
syringe the circulatory system may be injected and the fol-
lowing points determined.

Each post-cava empties its blood into the branchial heart of
the same side, which also receives the blood that has been re-
turned from the anterior portion of the animal through the fre-
cave. ‘The latter traverse the glandular walls of the nephridial
chambers. Each branchial heart also receives an anderior
mantle vein, returning blood from the anterior portion of the
mantle. Impure blood is forced from the branchial heart
to the gills along the afferent branchial vessel which traverses
the edge of the gill that is directed towards the mantle.

_

A Cephalopodous Mollusk. 73

The pre-cave unite just in front of the nephridial organs
and form the common vena cava. This vessel lies an-
teriorly in the median line, just dorsal to the ink-sac and
midway between the siphonal retractors. It returns the
blood from the ink-sac, liver, cesophagus, and head.

The systemic heart lies in the median line between the
posterior ends of the nephridial organs and receives blood
from the vzght and left efferent branchial vessels, which
course along the free edge of the gill.

The systemic heart gives off an anferior and a posterior
aorta. ‘he former passes directly to the head, dividing at
the neck into a ~7gh¢ and a &ft branch. On its course it
gives off certain branches to the digestive organs. The
posterior aorta soon divides into the median and lateral
mantle arteries already noted.

The cave rest dorsally on a delicate flask-shaped bilateral
organ of considerable size, the “‘ sA/een.”

Make drawings illustrating the course of the blood-vessels.

The Digestive System. — Note the large chitinous jaws,
situated at the base of the circle of arms. Which jaw is
larger? Open the mouth and note the Angual ribbon or
odontophore. What is its position? Pass a probe down the
narrow @sophagus, and cutting along the mid-ventral line of
the head and neck, follow the cesophagus to its entrance into
the stomach. On its way it is accompanied for a short dis-
tance, along its ventral side, by the duct from the median
salivary gland, a small body which may be found enfolded
in the anterior end of the liver. The /ateral salivary
glands lie on the posterior surface of the buccal-mass. The
fiver is a large gland that extends posteriorly from near the
spherical buccal-mass to a point dorsal to the nephridial

74 Invertebrate Zoology.

openings. It lies between and dorsal to the siphonal re-
tractors, and is pierced at its anterior end by the cesophagus,
which courses along its dorsal surface.

The cesophagus finally enters the smaller, more muscular,
cardiac portion of the stomach. By blowing with a blow-
pipe into the cardiac portion, the much larger and thin-—
walled gastric sac will become inflated. This organ is a
“‘blind-sac ”’ and extends to the posterior end of the mantle
cavity. It often contains partially digested food — bits of
AS ete:

Trace the ¢azestine from its origin, near where the cesopha-
gus enters the stomach, to the rectum. If the gastric sac is
already filled with water, it may be rolled from its original
position, clearly showing its relations to the other neighbor-
ing organs.

Make a drawing of the entire digestive system as seen from
below, and also as seen from the side, naming all the parts.

The Muscular System. — The Cephalopods are most
active Invertebrates and the muscular system is correlatively
developed. Muscle tissue largely makes up the outer sub-
stance of the animal, though there is a remarkable lack of
clearly defined muscle bundles. The retractors of the head
and siphon are, however, more definitely isolated.

Reproductive System of the Male.—As the gastric
sac 1s partly removed, note on the posterior dorsal wall of
the mantle cavity the large ¢es#s. It is firm in texture and
somewhat elongate-oval in outline. Leading to the testis
from the region of the cardiac stomach is an artery which
pierces the delicate capsule in which the organ lies. At
the left of the testis, the accessory reproductive organs of the
male are to be observed. They form an irregular mass

A Cephalopodous Mollusk. 75

from which a tube, the sfermatophoric sac, passes anteriorly
to open through the fenzs. The latter is a tube of consider-
able size, lying parallel to, and along the left side of, the
rectum. ‘The penis finally opens at a point about even with
the anus.

There extends from the spermatophoric sac, which is
often filled with numerous small worm-like sfermazophores,
to the capsule of the testis, an elongated and much convo-
luted tube, the vas deferens. It is, in places, considerably
swollen and highly glandular. |

Make a drawing of the male sexual organs, naming the
parts.

The Reproductive System of the Female. —If the
mantle cavity of a female specimen is opened in the mid-
ventral line, the sex may be at once determined by the
presence of two large nzdamental glands, each about the
size of one’s little finger and lying side by side along
the median line, well towards the anterior of the mantle
cavity. Each gland has an anterior opening through which
the gelatinous substance of the egg-capsule is extruded.
Lying in front of the nidamental glands are the smaller,
reniform accessory glands, which rest laterally upon the sides
of the rectum and ink-bag.

The large funnel-shaped opening of the oviduct will be
seen at the left, on a line with the openings from the nida-
mental and accessory glands. Pass a probe into the ovidu-
cal opening, and trace the duct below the left gill into the
large oviducal gland. It is situated on the left of the pos-
terior end of the nidamental gland. From the central point
of the oviducal gland the more constricted oviduct will be
seen. It passes posteriorly towards the mid-ventral line.

76 Invertebrate Zoology.

Follow the oviduct far back and note the abrupt turn in
its course as it bends anteriorly. Trace it to its opening
into the capsule of the ovary. The ovary lies along the
dorsum and extends anteriorly from near the posterior end
of the animal to a point dorsal to the external opening of
the oviduct. In its substance are to be seen the eggs or ova,
in varying stages of maturation.

The Excretory System. —The cavities and the external
openings of the wephridia have already been noted. Such
glandular tissue as ts present is concentrated along the sides |
of the venz cave. |

The Nervous System. — Observe on each side of the
animal, at a point on the inner surface of the mantle just
anterior to the attachment of the retractors of the head, the
large stellate gangha. From these ganglia radiating zerves
may be traced to different portions of the mantle and, run-
ning anteriorly from each, through the retractor of the same
side, and thence to the 7zufra-wsophageal ganglon, are the
right and the “ft pleural nerves. Carefully trace these
nerves to the cartilaginous support of the head, and then
remove the tissue from the ventral side of the eyes until the
enormous optic ganglia are exposed.

Lying ventrally, between the optic ganglia, and bro
by cartilage, are the fused pedal, pleural, and visceral gangha.
They form the z22/ra-esophageal mass.

With a sharp scalpel carefully slice away the ventral carti-
lage, exposing the deep-lying nervous mass. Note, as the
cartilage is being removed, the central cavities or auditory
chambers.

The infra-cesophageal mass is prolonged anteriorly into
the pro-pedal ganglha, which give rise to ten radiating

A Cephalopodous Mollusk. 77

nerves which pass to the arms. The siphonal nerves are
given off from the lower portion of the infra-cesophageal
mass, while the Aleuwral and visceral nerves arise more
posteriorly.

From the smaller supra-cesophageal ganglion a pair of
very minute connectives extend to the posterior surface
of the buccal-mass, where they end, immediately over the
cesophagus, in a pair of small swpra-buccal gangha. From
the supra-buccal ganglia fibres extend around the cesophagus
to the zufra-buccal gangha. ‘The latter are of about the
same size as the supra-buccal pair, and are united below the
cesophagus by a commissure.

Make drawings of the ventral, lateral, and dorsal views of
the brain.

78 Invertebrate Zovlogy.

THE LOBSTER?

(Homarus americanus).

External Anatomy. — Is the animal perfectly “ bilater-
ally symmetrical’’? What characters distinguish the anterior
portion of the animal from the posterior? It will be ob-
served that the latter, the abdomen, is segmented. Look
carefully and see if there are traces of segmentation in the
anterior portion, the cephalothorax. Is the number of ab-
dominal segments constant ?

Has each abdominal segment a pair of appendages? Do
they all take their origin from similar points of the several
segments? ‘The ventral piece lying between each pair of
appendages is called the sternum. The dorsal portion is
the ¢exgum. The ventrally projecting lateral lobes are the
pleurons. The epimeron.is a piece, more clearly seen on the
first abdominal segment, that lies ventrally between the ap-
pendage and the pleuron. Note any specialization of any

1 The lobster has been here introduced for several reasons. — Its gen-
eralized structure, large size, and the easiness with which its organs may
be dissected make it a most convenient animal for the demonstration
of not only arthropod morphology, but of general Invertebrate anatomy.
It is, moreover, a typical crustacean, and in a shorter course might be
studied as a representative of the entire Class. The crustacea considered
farther on are especially valuable for comparative study.

The Lobster. 79

abdominal segment and, if possible, give a reason for the
same.

Is there anything to show that the last cephalothoracic
appendage is homologous with the abdominal appendages?
The latter have been called Aleopoda. If the homology
can be shown for the last, it must also be claimed for the
remaining cephalothoracic appendages of equivalent origin
and structure. How many such appendages are there?
(Answer the question by comparing points of origin, num-
ber of joints, position of sensitive hairs, and number and
position of protective spines. It will probably be concluded
that there are five pairs closely resembling each other.) Why
the remarkable enlargement of the anterior pair, the forceps?
Do the five pairs of appendages arise from five segments?
Will you admit of the “ Rule of Savigny”’: “A pair of ap-
pendages represents a segment, though segments may occur
without appendages”? How many segments, then, are there
from the posterior end of the body to the forceps ?

The appendages lying immediately anterior to the forceps
are more or less specialized. They may be pressed down
one after the other, like leaves of a book, and if found
homologous with the appendages already examined, their
number will indicate the number of supporting segments.

The most posterior, the #iird maxilliped, is in part like one
of the ambulatory appendages already studied. Examine
its point of origin, count its joints, etc. The immediately
anterior, second maxilliped, is not remarkably different from
the third, though the fi7s¢ maxillifed is considerably altered.

The line separating the maxillipeds from the anteriorly
lying second maxille divides the head from the thorax.
There are two pairs of maxille, the second, broad and leaf-
like ; the 7rs/, smaller and tricleft,

80 Invertebrate Zoology.

In front of the first maxillse are the strong 7aws or man-
dibles, each provided with a jointed accessory portion, the
palpus.

Two pair of anzztenne lie somewhat in front of the jaws.
The jrst antenne are shorter and biramous; the second,
longer and with only a single filament.

The compound eyes are borne on stalks which are, by —
some, considered to represent appendages. Beginning with
the eye-stalks, enumerate the segments of the entire animal.

Find the following openings: (@) The openings of the
auditory organ, each situated at the base of the first antennee
and opening from the upper surface, (4) Of the excretory
organs or evcen glands, on the lower side of the second an-
tenn. (c) The mouth, between the mandibles. (d) The
oviducts, in females at the base of the third pair of ambula-
tory appendages. (e¢) The openings into the receptive afp-
paratus, if the specimen is a female, in the angles of the
heart-shaped structure between the next succeeding pair of
appendages. (/) The seminal openings of the male, at the
bases of the last pair of thoracic appendages. (g) The anal
opening in the last segment (ze/son) of the abdomen.

Is there anything to show that some of the paired open-
ings may be homologous?

Comparative Study of the Appendages. — Examine
one of the appendages of the fourth abdominal segment. It
will be found to consist of an elongated basal portion, the
protopodite, bearing two blades, the endopodite within, and
the exopodite without. Remove the left appendage where it
joins the body and draw it as seen from in front, naming the
parts. Compare with the appendages of the second, third,
and fifth abdominal segments. Compare now with the first

The Lobster. SI

and sixth. The appendages of the first abdominal segment
are different in the two sexes. Do you find any trace of
appendages on the terminal segment or telson?

Examine one of the thoracic appendages and endeavor to
homologize the parts with the parts of the pleopoda. Pass
to the third maxilliped and see if it has a protopodite, an
exopodite, and an endopodite. Return now to the ambula-
tory appendage and see if you are better able to homologize
its parts, so far as they are present, with parts of the abdomi-
nal appendage. (The ambulatory appendage is really an
endopodite supported on a strengthened protopodite.)

Carefully remove the second ambulatory appendage of the
left side and draw it as seen from the front, naming the
parts. The proximal part of the protopodite bears a finely
lamellate gz// and a posteriorly directed membranous out-
growth, the fadbellum. :

Remove the remaining ambulatory appendages of the
same side and see if all agree in structure. (Other gills sit-
uated higher up, on the epimera, will be considered later.)

Has the “hird maxiliiped a gill? A flabellum? Remove,
and draw as seen anteriorly, naming the parts.

After carefully removing the second maxilliped and noting
the rudimentary condition of the gill, the reduced flabellum,
and the number of divisions of the entopodite, draw as
above directed. 7

The first maxilliped is without a gill, though its flabellum
is remarkably developed. ‘The flattened, elongated exopo-
dite and endopodite extend anteriorly from the lateral
angle, while the internal part of the protopodite is greatly
enlarged and lobe-like.

Draw.

The second maxilla is even further altered: no gill is

82 L[uvertebrate Zoology.

present. The flabellum is indurated by a deposit of lime and
stiffened by its fusion with the exopodite. What is the
probable function of this the most anterior flabellum? The
endopodite resembles the same of the first maxilliped. The
protopodite is divided into four long inwardly-projecting
lobes.

Draw.

After identifying the parts of the fvs¢ maxilla, draw and
name, taking care not to be confused by the fan-like out-
growths of the lower “ip.

The body of each mandible represents the protopodite,
while the palpus represents the endopodite.

Draw as seen from in front, naming the parts.

The second antenna presents a modification of the same
double structure that has been noted in the other appen-
dages. The protopodite bears an exopodite, a mere mov-
able scale, and a much elongated endopodite, which func-
tions as a tactile organ.

Draw.

The first antenna, the antennud/e, is in the adult also bira-
mous, though primitively it is uniramous.

Draw.

Morphology of the Carapace. —It has probably been
noted that a transverse groove divides the anterior portion
of the cephalothorax from the posterior. ‘The carapace,
then, probably represents the fusion of terga, and cur prob-
lem is to find out which have become fused. -

If the groove be followed ventrally and anteriorly, it will
lead to a septum between the second antennee and the man-
dibles. It is probable, then, that the groove marks the
dividing line between these two segments, second antennal

The Lobster. 83

and mandibular. We know that in front of the groove
three segments are represented, because related Crusta-
ceans (Sguilla, Hupagurus, Gebia, Calanassa) show these
three segments more or less free, and in the lobster there
are three pairs of appendages. It is probable that in the
lobster the terga were also once free though now consolidated.

Elevate the free edges of the carapace and give reasons,
if you have any, for considering them homologous with the
pleura. Note the marginal hairs. Where are they most
abundant? ‘Their function? With a strong knife cut away
all the right side which lies posterior and ventral to the
groove. Note that the inner layer is membranous. Is it
continuous at the margin with the outer layer? How far
dorsally does the membranous part extend? Follow the
line of its union with the epimera.

The space between the pleural piece and the epimera is
the gill or branchial chamber. Wow many gills are there
arising from the thoracic protopodites? Carefully remove
these podobranchie with their associated flabella, keeping a
record of their position. Above each exposed protopodite
is a membranous 7zterarticular membrane which bears the
arthrobranchig. Record the number and position of the
arthrobranchiz. Above, are the four pleurobranchia. They
belong to which segments?

Granting that the transverse groove marks the dividing line
between two segments, it is reasonable to suppose that the
part lying immediately behind it must represent a portion of
the tergum and pleura of the mandibular segment. The
fused thoracic epimera now being exposed, it is clear that
the posterior portion of the carapace is certainly independent
of the six posterior thoracic rings. To just which of the
remaining segments, mandibular, maxillary or maxillipedal,

84 Invertebrate Zoology.

the posterior part of the carapace does belong is somewhat
doubtful.

Internal Anatomy. — With a strong pair of shears care-
fully remove the calcareous shell from the dorsal half of the
body, from the zostrum to the telson, noting the points
where the muscles are attached. Have the attachments in
any way affected the even contour of the exoskeleton?
Examine still further the internal face of the removed por-
tion of the carapace and see if there is anything to show that
there are represented in it certain segments posterior to the
groove.

Remove the dorsally lying pigmented zutegument, and
also the superficial muscles, exposing the viscera. Note
the large, anteriorly lying horny stomach. It is held in
place by certain gastric muscles. Just back of the depres-
sion in the carapace formed by the groove, the Aear¢ will be
seen. In outline it is somewhat shield-shaped, three angles
being directed anteriorly and a single rounded angle project-
ing posteriorly. Two small, oblique openings will be noticed
on its dorsal side, near the median line.

Do you find the elongated sexual glands extending on
either side from near the lateral angles of the stomach to
about the middle of the abdomen? Is the right gland in
communication with the left? If the specimen is a female,
the eggs may be seen through the transparent ovarian
walls. Examine the outer border of the organ and find
ducts leading ventrally.

Can you follow a blood-vessel, the superior abdominal
artery, leading posteriorly from the heart and extending to
the telson? Immediately below, and somewhat covered by
the sexual organs, is the zzfestine.

The Lobster. 85

The “ver is the voluminous organ, of light green color,
that fills up the greater part of the thorax. Note the seg-
mental arrangement of the “roracic and abdominal muscles.
Carefully remove the tissues at the base of the second
antennz, exposing the green glands.

Draw the animal as seen from above, using only the
lightest outlines, as the details are to be put in after further
study.

Remove the muscular and skeletogenous tissue from the
lateral third of the left side of the body, thus giving a new
view of the viscera. Lay the animal in water and note the
boundaries of the organs already studied.

Probe through the mouth into the stomach. What direc-
tion does the short w@sophagus take? The larger, more chiti-
nous, anterior or cardiac portion of the stomach is separated
from the posterior or pyloric portion by a groove running
diagonally from the dorsal to the ventral line. Do you find
that the insertion of muscles is in any way related to the
hardened areas of the stomachic walls? Are there any
pouch-like out-pushings of the pyloric portion? Is the
pyloric portion chitinous? The whole organ resembles the
exoskeleton and is, indeed, formed from an in-pushing of
the outer covering of the body.

Pass to the posterior end of the alimentary tract and note
that the vec/wm, the section lying behind the middle of the
penultimate segment, is somewhat different from the straight
mesenteron or intestine, which connects it with the pyloric
portion of the stomach. Inject water through the anus and
distend the intestine. Do you find a dorsally projecting
sac, the cecum, arising from the hinder end of the mesen-
teron ?

Find the duct which leads from the left lobe of the

86 Invertebrate Zoology.

liver, or mesenteric gland, into the intestine. What is its
extent? Cut the gland open and see if it has a lumen.
Does the lumen communicate with the intestine? What is
the plan upon which the organ is built up.

Carefully finish the drawing of the alimentary tract and
its diverticula.

Remove the entire alimentary tract and float it out in
clean water. Dissect away the anterior wall of the stomach
and wash out the contents. Artificially work the gastic
teeth together, thus demonstrating their function. Do you
notice any apparatus that prevents the larger fragments of
food from entering the delicate intestine? Do you find any
organs which might, in function, distinguish between the
nutritious and non-nutritious contents of the stomach? Are
sensory hairs present in the cesophagus?

Slit open the intestine, czecum, and rectum. Do you find
any local differences in the lining. membrane of the three
portions ?

Make a drawing of the interior of the right half of the
stomach.

Excretory System. — With great care remove the left
green-gland. Do you find the following parts: A smaller,
ventral, glandular portion, of a deep green color in the
living animal? A very large saccular portion, the deli-
cate diverticula of which extend as lobes over the ante-
rior and lateral walls of the stomach? The wrimary
duct, leading to the opening at the base of the second
antennee P

Reproductive System. — This may be worked out on
the side of the animal which has not yet been injured. If the

The Lobster. 87

specimen is a female the essential reproductive organs are
the ovaries. ‘Their position, color, and relation to the other
viscera, should be clearly determined. How are they held
in place? Can water be injected into them through the
openings at the bases of the ambulatory appendages?
Examine the ovzduc¢t and note its course. Are the eggs in
different portions of the organ of about the same size?

Make a longitudinal incision through the ovarian wall
and examine the interior. How are the eggs held in place?
Is the wall of the oviduct in any way different from the
same of the ovary? It is probable that it secretes a cover-
ing for the eggs, as they are being extruded, which attaches
them to the hairs of the abdominal appendages.

Open the receptive apparatus and place some of the con-
tained fluid on a microscope slide. Do you find, on exam-
ining the preparation with a high power, that spermatozoa
are present? If the specimen which is being dissected
measures ten inches in length, it will in all probability con-
tain many of these ma/e-cells, the structure of which is given
below.

Draw the ovary.

Examine a male specimen. Note the position, color, and
extent of the zeszes, the essential reproductive organs of the
male. In what respect do they differ from the correlative
structures of the female? Endeavor to inject through the
external openings. Is the course taken by the vasa defer-
entia im any way different from that taken by the oviducts ?
Do you find the median portion of the vasa deferentia
enlarged? Can you induce the extrusion of the contents
(spermatophore) of this enlarged portion? Slit open one of
the testes and place some of the contained fluid on a slide.
Cover, and examine as above directed.

88 Invertebrate Zoology.

Each of the spermatozoa, or male-cells, will be found to
consist of a somewhat cylindrical body, which is terminated
at one end by a series of long spines.

Make a drawing of one of the testes as seen from the side,
representing the vas deferens, and the external opening.

The Circulatory System. — The position of the heart
has been already noted. In a specimen having the circula-
tory system artificially injected with a colored fluid, note the
pericardial sac, a delicate tissue surrounding the heart. It
receives the blood from the édranchiz,' which then enters
the heart through six cardiac apertures. ‘The dorsal, lateral,
and ventral apertures occupy positions as suggested by their
names.

The origins of the arteries, as they leave the heart, are as
follows : —

The superior abdominal artery passes directly posteriorly
from the heart, resting on the sexual organs, intestine, and
deeper muscles. How many branches does it give off to
each abdominal segment? Does it send branches to the
sexual organs? Intestine? Czcum? Note any terminal
bifurcation.

The sternal artery has its origin from the most anterior
point of the superior abdominal artery. It passes ventrally
to supply the lower portions of the body. On which side
of the intestine does it pass?

The ophthalmic artery runs from the heart anteriorly.
Does it give off branches to the stomach? Can you deter-
mine its distribution in the anterior part of the head ?

The anéennary arteries arise from near the antero-lateral

1 Tater dissection will show that the blood is returned from the
branchie through six dranchio-cardiac canals.

The Lobster. 89

angle of the heart. Each, in its course to the region of the
antenna, gives off, besides others, a branch to the lateral
walls of the stomach. Do you find the renal branch, dis-
tributed to the green-glands ?

Draw in the circulatory system on the dorsal view of the
animal already made, using a brush with light carmine paint.

Press to one side the viscera, which hide the duct of the
mesenteric gland. A large artery, the Aepazc, will be seen.
From what part of the heart does it take its origin? .Does
it give off branches to other organs ?

By the use of dots, rather than lines, designate its position
on the drawing.

Turn the animal on its back, and through the transparent
wall of the abdomen note the 7xzferior abdominal artery.
With a strong knife or with scissors, cut away the abdominal
sterna, and see if the artery sends out metameric branches.
Follow the artery anteriorly. It will be found to receive its
blood from the sternal artery, which also gives rise to an
anterior branch.

The antero-ventral artery passes along the mid-ventral
line of the thorax. Name in order the branches fhat it
gives off to the thoracic appendages. What is its anterior
termination ?

From the ultimate subdivisions of the main arteries, above
noted, the blood passes into certain szzzses, and from these
is sent to the subdivisions of the gills, through the afferent
branchial vessels, and there purified. Does your specimen
show the afferent vessels? After being purified, the
blood from the minute gill-filaments empties into the
efferent branchial vessels which unite to form the dranchio-
cardiac canals. ‘The latter lead from the region of the
thoracic epimera to the pericardium, where they empty

90 Lnvertebrate Zovlogy.

their contents. Does your specimen show the efferent
branchial vessels? ‘The branchio-cardiac canals?

In the injected gills note the course taken by the large
afferent and efferent vessels. Is the flabellum also supplied
with axial blood-vessels? Examine the gill with a lens and
note the slender filaments.

Make a drawing that will show the structure of the gill.

The Nervous System. — The specimens have had many
of the internal organs removed, but as the greater portion
of the nervous system lies ventrally, it has not been injured.
The system consists of a series of nervous centres, or ganglia,
connected together by longitudinal and transverse commis-
sures. Work out the following : —

The supra-esophageal gangha will be found beneath the
rostrum at the base of the antennz. ‘The right is intimately
connected with the left. Extending posteriorly and sur-
rounding the cesophagus, are the circum-wsophageal commis-
sures, which are soon united by |

The infra-ewsophageal ganghon which lies immediately
behind the cesophagus.

From the infra-cesophageal ganglion the longitudinal com-
missures or connectives may be followed to the region of the
telson.

How many thoracic ganglia are there? How many
abdominal ganglia? Are the ganglia of one series more
closely approximated than those of the other? Does the
number of ganglia in anyway correspond with the number
of associated body segments? Do you find nerves running
from the ganglia to the surrounding tissues?

Make two drawings of the nervous system, one as it is
seen from above, the other as it is seen from the side.

A Phyllopod Crustacean. QI

mtr Y LEOPOD CRUSTACEAN

(Branchipus vernals).

External Anatomy. — Observe the elongated dody. Is
it distinctly segmented? Is it separated into a head, a
thorax, and an abdomen? ‘The appendages are leaf-like
(Phyllopod). They occur on which main division of the
body? Are they represented on the other regions? Observe
the pair of flexible anterior antenne. In the males the
second antenneé are enormously developed and form “ clasp-
ing organs.” Large at the base, each second antenna soon
becomes constricted, and forms an elongated chitinous rod.
Find the homologues of the second antennz in the female.

The upper lip, Zzadrum, will be found as a median fold
extending posteriorly from between the bases of the second
antenne. Elevate the labrum and note that it covers the
jaws or mandibles. In what plane do the mandibles move?
Are the cutting edges specially hardened? Note the open-
ing of the mouth. The maxilla, relatively poorly developed,
lie immediately posterior to the mouth.

How many pairs of thoracic appendages are there? Care-
fully remove one of the first pair, and note that there is a
basal portion, profopodite, which is extended distally by cer-
tain lobes. ‘The internal lobe, exdopodite, is the largest and
bears numerous se/@ along its inner and distal edge. Of the
same general structure is the outer lobe or exopodite, which

Q2 Invertebrate Zoology.

bears several longer setze. External to and above the exop-
odite is a small sac, the gz//-sac. Above the gill-sac is the
broad, paddle-shaped gz.

Examine the remaining thoracic appendages. Are they
all built upon the same plan? What functions do they
perform? Recall the parapodia of JVerezs.

At the anterior end of the abdomen are the external
sexual organs. In the female they will be seen to enclose
the eggs. In the male a tubular organ is formed. Are the
terminal fin-like organs comparable with the thoracic ap-
pendages?

Make drawings of the specimen as seen from the side,
and of the more important and characteristic parts.

Digestive System. — Open a specimen along the mid-
ventral line, and observe the course of the alimentary tract.
It extends as a tube from the mouth to the augsy “Does
the anus open dorsally or ventrally? Note any local en-
largements of the alimentary tract.

Make a drawing of the tract.

The Circulatory System consists of an elongated dor-
sally lying tube, the Aear¢. It is provided with numerous
lateral s@¢s, a pair for each surrounding segment, and
extends from near the anterior end of the thorax to the
posterior part of the abdomen. ‘The blood enters the heart
through the lateral slits, and is forced out throngh the
antertor aorta into the sinuses of the body, finally reaching
the lamellated gills, where it is aerated. After being purified,
a system of channels conveys the blood to a pericardial
sinus, from which it passes through the slits or vs#a@ into the
heart.

A Phyllopod Crustacean. 93

The Excretory System. —A pair of so-called “ shed/-
glands”’ may function as renal organs, and have been com-
pared with nephridia. ‘They open to the exterior through
two papille, near the bases of the second maxille.

The Muscular System is well developed. Observe the
extensor and retractor muscles of the abdomen. Also note,
in the thorax, the presence of regularly arranged muscle
bundles. Recall the arrangement in JVerezs.

The Nervous System. — Observe the minute, median
ocellus. Below and on each side of it are the first antenne,
the tactile organs. The compound eyes are large and promi-
nent. Are they stalked? Examine carefully and note the
Jacets.

Make a drawing of the head, paying particular attention
to the organs of special sense.

Carefully remove the appendages from another specimen,
using a pair of fine scissors. Cut the animal open along the
mid-dorsal line, and remove the lateral walls of the thorax
and abdomen, together with all. but the most anterior portion
of the alimentary tract. Wash out the cavity with ninety-
five per cent alcohol, and then place in absolute alcohol for
one quarter of an hour. Remove from absolute alcohol and
place in xylol. The delicate ventral chain of gangla will
soon take on a different appearance from the rest of the
specimen. Note that there are two ganglia in each thoracic
segment, each connected with its fellow by a cross commus-
sure. ‘The ganglia lying anterior and posterior to each other
are united by /ongitudinal connectives. Follow the chain
into the abdomen and also anteriorly into the head. As
in JVereis, it will be found to surround the cesophagus and

94 Invertebrate Zoology.

to pass above into the supra-wsophageal ganglion or brain.
Trace the nerves from the brain to the oce//us and to the
compound eyes. |

Make a drawing of the nervous system.

The Reproductive System. — The “ brood-pouch” of
the female has already been noted. The ovavies are paired
organs, each lying parallel to the alimentary tract, and extend-
ing through a considerable portion of the thorax and abdomen.
They are beautifully brought out by the adoption of the xylol
method above described. Note, in the brood-sac, the large
eggs. Do you find any pore through which the eggs may
pass from the sac to the exterior?

Make drawings of the female reproductive system.

The external reproductive organs of the male are situated on
the anterior portion of the abdomen. LE ach consists of a
somewhat complicated apparatus, which is used in placing
the spermatophores in the sacs of the female. The ¢ésées
will be easily found as paired organs, of the same general
structure as the ovaries, though of not equal extent.

Draw the reproductive system of the male.

A Free-Living Copepod. 95

A FREE-LIVING COPEPOD

(Cyclops sp.).

SELECT a large female specimen (the females generally
have a pair of ovisacs suspended from the body), and exam-
ine under a compound microscope. The doy will be found
to be well rounded, neither depressed nor compressed, con-
siderably elongated, and clearly segmented. The divisions
into cephalothorax and abdomen are at once apparent. The
former consists of an anterior, unsegmented carapace, behind
which are four movable thoracic segments. Has the cara-
pace a rostrum? Are the edges of the carapace free?
Are the several thoracic rings all of about the same size ?

In the present sex the abdomen has four segments, though
the first is in reality formed from two. Do you find any-
thing to suggest that fusion has actually occurred? In the
smaller male there are five abdominal rings, the original
structure being retained.

How many filaments are there arising from the terminal
abdominal styles? Are there thoracic appendages ? Abdom-
inal appendages? Note the position of the enlarged jfrs¢
antenne. Are they provided with hair-like se¢e (olfactory
hairs)? Compare them with the smaller second antenne.
In the males the antennz are reduced in size and functionize
as clasping organs.

Examine the swimming appendages of the posterior por-

96 Invertebrate Zoology.

tion of the cephalothorax. Four well-developed pairs will
be found, each consisting of a basal portion and two free
terminal blades. The fifth pair are reduced. The mouth
parts, consisting of a pair of mandibles and two pairs of
maxille, are too small to be profitably studied at this time.

Digestive System. — Specimens that have been feeding
upon some colored substance (carmine) should be selected.
They may be rendered inactive by placing a drop of ether
in the watch-glass that contains them. The moz/h, situate
on the lower surface, just behind the origin of the antenne,
will be found to lead into a large, somewhat thick-walled
crop. .From the crop the zazestime extends in a direc:
course to the azus. Does the anus occupy a dorsal or a
ventral position? ‘Through which abdominal segment does
it open?

Circulatory System. — Though in certain related forms
there is a dorsally situated contractile ear¢, in the present
form, and, indeed, in the greater number of Copepeds
rhythmic contractions of the entire alimentary tract produce
the circulation of the surrounding c@lomic flurd.

Excretory System. —A pair of coiled tubes, the shed/-
glands, occupy lateral positions in the thorax and open to
the exterior through pores at the bases of the maxillipeds.
They are only to be seen in specially favorable specimens.
The intestine probably has some excretory power, while the
entire surface of the body may permit the escape of injurious
gases, combining excretory and respiratory functions.

The Muscular System is somewhat difficult to demon-
strate. It consists of a series of regularly arranged fibres,

A Free-Living Copepod. 97

which bring about the movement of the second antenne,
and other less important locomotor appendages. There
are also two large muscular bands that forcibly flex the
body.

The Nervous System is too difficult of demonstration
to be here considered. The offactory hairs of the first
antennz have been noted. The oce//us is the visual organ.

The Reproductive System. — In the female the ovary
is found to occupy a median dorsal position, extending as a
somewhat elongated organ about two-thirds the length of
the cephalothorax. Leading from the ovary to the external
ovisacs are the oviducts. Each oviduct is a coiled structure,
lying laterally to the ovary and often containing ova. Its
external opening is through the first abdominal segment.
The ova are fertilized from a zecepiaculum seminis, as they
pass into the large ovisacs. How many eggs does each
ovisac contain? ‘The young hatch in the interesting “ Nau-
plius stage.”

The sexual organs of the male consist of a median fests
and two coiled, laterally extending vasa deferentia. Each
vas deferens finally opens into a terminal receptacle, where
the spermatozoa are collected, and form a spermatophore.
At time of coitus the spermatophore leaves the body of the
male, through an opening in the first abdominal segment,
and passes into the recepfaculum seminis.

Make drawings of the dorsal and lateral views of the male
and female.

98 Invertebrate Zoology.

A PARASITIC COrEPO@D
(Pandarus sinuatus).

THE species under consideration leads a parasitic life upon
the external surface of the shark. Only females have been
collected. Parasitism has wrought many interesting changes.

External Anatomy.— When compared with the free-
living Copepod, Cyclops, the present form will be found to
have the Jody depressed, the cephalothorax enlarged, and
_ the posterior portion of the addomen somewhat reduced.
Compare the general outline with that of Cyclopss. sik:
rostrum present? Observe the location of the wsual organ,
and compare with Cyclops. Note the outline of the poste-
rior three thoracic segments. ‘The first abdominal segment
is greatly enlarged, and within its transparent walls the coiled
ovary and oviducts are to be seen. A rounded, flap-shaped
piece terminates the body posteriorly.

Make an enlarged drawing of the dorsal view.

Examine the ventral surface and note its concavity. The ©
jirst antenne appear as free, blade-like organs along the most
anterior edge of the cephalothorax. Do they have flexible
tips? Are they provided with sexsory hairs? At the base
of each is a sucking disc.

Having their origin nearer the median line, and bearing,
laterally and posteriorly, a pair of suckers, are the small,
hook-shaped second antenne. What is their function? »

A Parasitic Copepod. 99

The sucking proboscis, which is in part made up of the
greatly modified mandibles, arises as a styliform organ, mid-
way between the second antennz. It surrounds the ora/
opening.

The first maxille are very much reduced in the parasitic
crustacea. In the present form they appear as a pair of
minute palp-like organs, situated laterally on the flaring base
of the proboscis.

The second maxille are well developed, and appear as a
pair of long, slender-jointed appendages arising posterior to
the second antennz. ‘Their free extremities are seen to be
provided with hooks, while a pair of suckers will be found
between their points of attachment.

The maxzllipeds are considerably larger, directed poste-
riorly rather than laterally, and bear, at their free ends, a
peculiar attachment organ. Behind the maxillipeds are four
pairs of szuzmming appendages, of which the first are some-
what reduced. Note the. median sucker, between the first
and second pair of swimming feet.

The body is terminated below by a flap-like segment that
bears a pair of laterally projecting s#/es. Compare with
Cyclops.

The greatly elongated ege-stvings will be found to take
their origin laterally from a point midway between the
dorsal and ventral terminal flaps.

Make drawings of the ventral surface and of the several
appendages.

Naupli, the free-swimming young of many crustacea,
may be secured from the present form and in large num-
bers. Tease one of the egg-strings and place its contents
under a compound microscope. Each Nauplius will be
found to bear three pairs of jointed appendages, which repre-

100 Invertebrate Zoology.

sent the firs¢and second antenne and the mandibles of the
adult. Are the appendages biramous? Is the body of the
Nauplius segmented? Are there posteriorly directed ter-
minal styles? Is there a median oced/us ? Can you trace
out the aimentary tract ?

Make a drawing of the Nauplius.

A Cirriped Crustacean. IOI

m-CIRRIPED CRUSTACEAN
(Lepas fascicularis).

External Anatomy. — The highly specialized animal is
attached at its azzevtor end by an elongated peduncle, and is
protected laterally by a mussel-like shell. Of how many
pieces does the shell consist? Do you find an elongated
opening between the two halves of the shell? The opening
is on the ventral side. The median, dorsal piece of the
shell is the carina, while lying laterally are the more pos-
terior fervga and the more anterior and ventral scw/a. ‘The
scuta join in the mid-ventral line. From the ventral open-
ing the six pairs of biramous appendages are thrust out for
the securing of food.

Draw the animal as seen from the right side, naming the
parts.

Stretch apart the valves and note that the integument of
the animal, externally indurated with lime, passes, within
the ventral opening, into a more delicate transparent fold,
which completely separates the soft parts of the animal
from the exterior. Note in particular the deeply lying
oral cone,’ the attachments of the dzramous appendages,
the aborted abdomen, and the greatly elongated Zn/vo-
mittent organ, which occupies a position just back of

1 The oral cone is a large knob-like mass which is made up of the
mouth-parts, and bears, at its apex, the mouth.

102 Invertebrate Zoology.

the last pair of thoracic appendages.’ Do you find the
anus ?

Remove and make a drawing of one of the appen-
dages. :

Before the body has been opened, the transparency of the
integument permits the location of several internal organs.
A large dark-colored area on either side, near the base of
the cone, marks the position of the “ hepatc glands.” A
smaller, orange-colored area near the base of the most
anterior filament is the anterior end of the vas deferens.
On the ventral side the muscular apparatus and the gan-
glonic chain are beautifully shown.

Carefully remove the right half of the shell, and trace
the folds of the integument into the peduncle. The pedun-
cle is a prolongation of the head, the anzertor ( first) anten-
ne of the larva having entered into its formation.” The
second antenneé are, in the adult, aborted.

At the summit of the oral cone a large transverse fold will
be found to bound the mouth anteriorly and to bear at each
end a triangular ‘‘scale-shaped”’ piece. The mandibles and
first maxille bound the mouth laterally, while the second
maxille are partially fused and form a lower lip. Both
mandibles and first maxillz have strong cutting edges.

Digestive System. — Carefully opening the animal along
the lateral line, note that a funnel-shaped tube leads from

1 The abdomen is greatly reduced. It is represented on the dorsal
side by a pair of small terminal flaps which cover the anal opening,
while on the ventral side it supports the intromittent organ.

2 The first antenne bear the so-called “ cement glands,” the secre-
tion of which enables the larva to attach itself. In the adult these
glands are to be found in the substance of the peduncle occupying a
position in its dorsal portion.

A Cirriped Crustacean. 103

the mouth to the short, straight wsophagus. The latter opens
suddenly into a large sfomach. Numerous dark hepatic
glands will be seen on the walls of the stomach. The
intestine is a straight tube of uniform size, extending from
the stomach to the anus.’

Make a drawing of the alimentary tract as seen from the
side.

Excretory System. — Glandular bodies, possibly excre-
tory in function, have been described as opening from the
second maxille. The cement glands of the first antennz
may also belong to the category of excretory organs.

A closed Circulatory System is not present in the Cirri-
pedia. Near the base of the oral cone, on either side of the
animal, five elongated f/amenzs are to be noted. These
organs are probably respiratory in function.

The Muscular System is developed chiefly for the
movement of the divisions of the shell, the waving of the
appendages, and the retraction of the soft parts. The young
(Nauplii) are active swimmers.

The arrangement of the muscles that move the mouth
parts can often be seen through the transparent integument
of the oral cone.

The Nervous System.— Remove the stomach and
intestine from the opening already made in the side of the
animal. The nervous system occupies, as a chain of ganglia,
a median ventral position. Anteriorly it surrounds the
cesophagus (esophageal ring or collar), and unites with the

1 On either side of the cesophageal end of the stomach is a whitish
glandular organ, which may be called the “ pancreas.”

104 Invertebrate Zoology.

supra-esophageal ganglion, from which nerves pass to a pair
of minute, pigmented eye-spods.
Draw.

The Reproductive System. — The barnacle is hermaph-
rodite. The ovaries will be found in the peduncle, the ova
appearing as a collection of minute spheres loosely held
together. The ovzducts pass from the ovaries to the bases
of the anterior thoracic appendages, and are difficult to
follow."

The zestes may be seen through the transparent integu-
ment of the body and appendages. Each gland, in alcoholic
specimens, appears as a racemose structure of pale yellow
color, the lobes extending from a larger antero-dorsal mass
into the more anterior thoracic appendages, and into the
filaments.

If the six pairs of thoracic appendages be spread apart, the
vasa deferenta will be observed entering the base of the
intromittent organ. These ducts will be found to lead from
the anterior end of the testis and to unite in the penis and
form a common ductus ejaculatorius.

Make a drawing of the reproductive system.

1 The opening of the oviduct is on the anterior surface at the point
where the appendage joins the body.

A Brachyuran Crustacean. 105

A BRACHYURAN CRUSTACEAN

(Cancer trroratus).

External Anatomy.— Are the cefhalothorax and abd-
domen built upon a new plan, or is the plan presented by
the lobster again adopted? Which region of the body has
been specially elaborated? The abdomen of the female is
much wider than that of the male; to which sex does the
specimen belong ?

Count the abdominal appendages of a female, and see if
they agree with the same of the lobster. Count the same
of the male. Why are there more appendages on the abdo-
men of the female than on that of the male? (Examine
a specimen that bears eggs.) Is the number of abdomi-
nal somites different in the two sexes? Does the male show
any traces of coalescence of abdominal segments? How
does the number compare with the abdominal segments of
Homarus ?

Is the number of amébulatory appendages the same as in
the lobster? The number of appendages bearing pincers?
In what main feature does the carapace differ from the cara-
pace of the lobster? Do you find the homologue of the
rostrum? The transverse groove is more clearly shown in
many related forms. Can you easily follow the groove to
the margin of the carapace? Is this a free margin, as in
flomarus? Note the opening at the base of the first am-
bulatory appendage, through which the water enters to bathe

106 Invertebrate Zoology.

the ez//s. Do you find the external openings of the ovizducts ?
Of the vasa deferentia ?

Draw the animal as seen from above.

Remove the lower portion of the left thoracic pleuron,
and expose the bases of the appendages. Podobranchie
and arthrobranchie are not present. Are there fladella at
the bases of the ambulatory appendages?

Carefully remove the “rd maxilliped of the left side.
Compare it with the same of the lobster.

Draw.

The second maxiliped will be found to have endopodite,
exopomdite, and flabellum, of the same general structure as in
Homarus. Only two gills are present.

Draw.

The first maxiliped is foliaceous and gill-less. Note its
greatly elongated flabe/lum, which extends far back into the
branchial chamber.

Remove the appendage and draw.

Examine the right (uninjured) side, and see if you do
not find at the base of the first maxilliped, and extending
anteriorly, a large opening that leads from the branchial
chamber.

The second maxilla, as in the lobster, has a specially de-
veloped flabellum for bailing the water out of the branchial
chamber. Note how its protopodite is divided almost pre-
cisely as in Homarus. The rudiment of the endopodite is
especially interesting.

Draw.

Remove the first maxilla and draw, and do the same with
the mandible.

Examine the antennae, and see which are jrs¢ and which
second.

A Brachyuran Crustacean. 107

Remove the second antenna. Do you find the elongated
filament that was specially developed in the lobster? Can
-you find the openings of the green-glands ?

Draw a second antenna.

Carefully remove the frst antenna. Find the position of
the auditory sac. Do you find the representatives of the
terminal filaments of Homarus? Which filament is provided
with numerous sensory hairs?

Draw.

Do the compound eyes differ from the same of the lobster?

Draw.

Without injuring the gills, remove the nght branchial
wall. Pleurobranchie will be found on the fifth and
sixth thoracic segment; arthrobranchig, one on the sec-
ond, two on the third, and two on the fourth; while
podobranchig are found only on the second and third
thoracic segments.

Remove one of the gills, and see how its structure differs
from that of the gill of the lobster.

Internal Anatomy. — Carefully remove the dorsal por-
tion of the carapace. Cut away the underlying integument,
and expose the viscera. Cover the specimen with water,
and, without displacing or injuring the organs, note as fol-
lows :—

The heart and its two pairs of cardiac apertures or
valves; the pericardial sinus ; the openings into the sinus of
the dranchio-cardiac canals; the ophthalmic artery; the
antennary artery; the hepatic artery; the superior abdom-
inal artery.

Somewhat anterior to the heart lies the stomach. Com-
pare with Homarus. Note the arrangement of the dorsal

108 Invertebrate Zoology.

gastric muscles. ‘The lobes of the “ver, or mesenteric gland,
extend laterally until they reach the limits of the shell.
Each lobe, as in the lobster, is composed of a multitude of
tubules.

Lying anteriorly to the heart, and extending laterally over
the mesenteric gland, are the voluminous sexua/ organs.
The ¢zesfes appear as a coiled filament, extending from
near the lateral walls of the stomach to the lateral angles of
the shell. In the region of the pyloric end of the stomach
the filament enlarges into a coiled duct, the vas deferens.
Expose the gveen-gdands, and trace out their ducts.

The comparison of the zervous system of the Brachyuran
with that of the Macruran (Homarus) will prove most in-
teresting.

Draw the animal as seen from above.

An Amphipod Crustacean. 109

AN AMPHIPOD CRUSTACEAN

(Zalorchestia longicornis).

External Anatomy.— Select a large male specimen.
(The males are generally larger and have antennz which
almost equal the body in length.) Note the laterally com-
pressed body and the numerous jointed appendages. Dis-
tinguish between the /ead, the thorax, and the abdomen.

Projecting anteriorly from the head are the smaller firs
antenne. How many joints has each? Immediately be-
neath the first antennz are the long second antenne. Of
how many joints does each consist? Compare with the
same organs of the female.

Remove the head and examine from the side. Are there
any suture-like lines that might lead one to suppose that
the head is really composed of several fused segments?
Note the lobe-like upper lip or Zaérum. In what plane
does it move? Is there a somewhat similar organ (the
united first maxillipeds), covering the mouth-parts from
behind ?

Remove both labrum and the fused maxillipeds. The
remaining mouth-parts move laterally.

Lying immediately anterior to and under the maxillipeds
are the second maxille. Each is a delicate, foliaceous,
bilobed organ, and bears numerous sete along its free

edge.

ii (Oe Invertebrate Zoology.

Remove the second maxillz, and expose the more rigid
bilobed frst maxilla. The large, irregular zaws work
between the first maxi@e and the labrum.

Open the jaws and note the opening of the mouth.

Make drawings of the several appendages of the head.

The first thoracic segment, bearing the first maxillipeds,
has, as already noted, become fused with the head. The
second thoracic segment bears a pair of fair-sized second
maxillipeds, while the third, homologous with the third max-
illipeds of the lobster, bears a pair of enormous chele.
Behind the chelee are five pairs of ambulatory appendages
supported on as many separate thoracic rings.

Note the expanded coxa/ joints of the thoracic append-
ages, the efimeral plates. Spread the appendages apart,
laterally, exposing the gz//s. Each gill arises from the pos-
terior side of an appendage, near where the latter is inserted.
How many gills are there? Do you find the same number
in the female? In the latter do not confuse the gills with
the odstegites, or lamellar plates, which form the bvood-pouch.

Attached to the anterior part of the abdomen are three
pairs of szwzmming-feet, while the posterior portion bears the
same number of sumping-feet. Are there six separate seg-
ments bearing the six pairs of appendages? Note the small
terminal plate. Are all the abdominal appendages biramous?

Digestive System. — Remove the appendages from a
large specimen, and, after opening along the mid-ventral
line, pin the animal out under water or alcohol, and wash
any cloudiness away.

The short wsophagus will be found to lead into a somewhat
rounded crop, from which extends, posteriorly, the straight
intestine. Vhe hepatopancreatic ceca appear as four elongated

An Amphipod Crustacean. III

sacs extending from their attachment at the anterior end of

the intestine, two-thirds the length of the body. Howare they

held in place? Does the azus open dorsally or ventrally?
Draw.

Excretory System. —A pair of small, somewhat coiled
diverticula, the mesenteric tubules, are to be seen lying along
each side of the more posterior portion of the intestine.
Trace out their course and see where they open into the
intestine. The external openings of the anfennal glands
may be observed, near the median ventral line, as two small
pores, each on the basal joint of a second antenna.

Draw, as seen from the side.

The Reproductive System.—The “szs are to be
observed as a pair of delicate tubes lying longitudinally,
immediately above the middle portion of the intestine.
Follow both to their external openings. Are the testes in
the thoracic or in the abdominal cavity ?

Draw.

The ovavies occupy a position similar to that of the testes.
The openings of the oviducts may be found at the bases of
the fifth pair of appendages. Each is a small pore between
the gill and the oostegite.

Draw.

The Circulatory System. — The ears will be found as
a delicate elongated sac lying along the dorsal part of the
thoracic cavity. The blood enters the organ through cer-
tain lateral os#a and is then forced, through anzertor and
posterior aorte, into the various lacune of the body. The
blood finally reaches the g7//s, situated, as has been observed,
on the thoracic segments. It is from them returned to the
heart.

112 Invertebrate Zoology.

The Muscular System. — The Amphipods are active
jumpers. Observe the strong extensor muscles of the tail.
Determine also the general arrangement of the muscles
which move the appendages.

The Nervous System. — What is the position of the
compound eyes ? Are they stalked or sessile? Certain spec-
imens clearly show, through the transparent sterna of the
thorax and abdomen, the ventral ganghonic chain. Is it
clearly made up of two strings? Do you find longitudinal
and ¢ransverse commuissures 2? Do nerves leave the gangha ?
Does the number of ganglia correspond to the number of
segments? Carefully dissect in the region of the head,
noting the zzfra- and supra-esophageal gangha and the
esophageal ring or collar.

‘Make a drawing of the nervous system, naming all the
parts.

The King Crab. 113

THE KING ‘CRAB
(Limulus polyphemus).

External Anatomy. — Note, on examining the animal
from above, that the chitinous shell is divisible into a large
anteriorly lying cephalothorax and a smaller, polygonal aé-
domen, terminated posteriorly by a rigid caudal spine.

The cephalothorax bears a pair of lateral, compound eyes,
and a pair of median oce/z. ‘The latter occupy positions,
one on each side of the frontal spine. |

Is there anything on the dorsal surface of the abdomen
that would show that it might possibly be made up of sev-
eral fused segments or metameres? How many movable
spines are there along the margin? How many pairs of Zzés
each side of the median line?

Draw.

Examining the lower, concave surface of the specimen,
observe the seven pairs of cephalothoracic Lmbs. ‘The first
(chelicere), smaller than the remaining, are followed in
immature specimens and in females by four pairs of pincer-
bearing /egs. Do the pincers open and close as in Homa-
rus? ‘The sixth pair of appendages are directed posteriorly.
Have they anything that might be of assistance in forcing
the animal through the mud? Note the exopodite-like
process at the base of each. <

The chidarta are supposed by some to represent a pair

114 Invertebrate Zoology.

of appendages. ‘They are small unjointed processes lying
between the bases of the pair of appendages just considered.

The seventh pair of cephalothoracic appendages are con-
siderably modified and form the operculum or cover for the
abdominal appendages. The two are united in the median
line. Certain transverse lines mark their lines of original
segmentation.

The mouth opens in the median line between the bases of
the four pincer-bearing appendages. In front of it is a conl-
cal elevation, the upper Lp.

The abdomen bears five pairs of modified appendages, each
pair resembling the operculum, and covering the large g//-
books. By the movement of the abdominal appendages and
the gill-books the animals can slowly swim through the water.

, At the base of the caudal spine the opening of the anus
will be observed. The external openings of the genital organs
will be found on the posterior surface of the operculum.
The external openings of the coxal glands have been found
in embryos on the basal joints of the fifth pair of cephalo-
thoracic legs.

Internal Anatomy. — With a strong knife remove the
entire upper portion of the shell of both cephalothorax and
abdomen.

The Muscular System. — The strong flexor muscles will
be seen to have a longitudinal course along each side of the
median plane. The muscles which move the legs are dis-
posed laterally to the flexors, and their fibres are arranged,
for the greater part, dorso-ventrally.

The Circulatory System. — Along the mid-dorsal line,
just below the flexor muscles, the elongated Aeart will be

The King Crab. II5

found. It extends from a point under the median eyes to
the posterior half of the abdomen. It has, extending ante-
tiorly, a frontal artery which divides into a right and a left
anterior marginal artery... The marginal arteries bend out-
wardly, laterally, and posteriorly, following the curve of the
margin of the cephalothorax. The fostertor marginal arte-
ries are the abdominal continuations of the anterior marginals.
Extending laterally from the heart are the /azera/l arteries.

The “ aortic arteries” take their origin from the anterior
end of the heart, and pass, one on either side of the cesopha-
gus, to the czrcum-oral reservoir, below mentioned.

The frst lateral arteries branch off from about the middle
of the cephalothorax ; the second and third lateral arteries,
from the posterior portion of the cephalothorax. From the
second, branches communicate with the marginal arteries
and with the hepatic arteries. The latter lie parallel to the
anterior marginal, and supply blood to the liver.

The collateral arteries \ie longitudinally, one on each side,
parallel to the heart. ‘They connect the several lateral arteries.

The heart is continued posteriorly by the superior abdomt-
nal artery.

Branchial arteries pass from the abdominal collaterals to
the gills.

The arteries of the ventral side cannot be now dissected.
They enclose the nervous system and consist of a circum-
oral reservoir, from which the crural arteries are given off
to the legs. Extending posteriorly from the reservoir is
the ventral artery, which gives rise to branchial and anal
branches.

The blood is returned from the gills and all parts of the

1 The frontal artery extends anteriorly to the margin of the cephalo-
thorax before dividing into the marginal arteries.

116 Invertebrate Zoology.

body, through certain irregular channels, to the pericardial
sac, from which it passes into the aorta through a series
(eight pairs) of osta.

Make drawings illustrating the course of the heart and
principal blood-vessels. |

The Digestive System. — Remove the heart and expose
the more ventrally lying alimentary tract.. The mouth will
be found to lead into an anteriorly and upwardly directed
esophagus which opens into a strong-walled anterior stomach
or crop. Cut the crop open and note the character of its
lining. The crop opens posteriorly into a thin-walled stom-
ach, which extends, without any remarkable change, to the
short proctodeum or rectum, the latter opening to the ex-
terior through the anus.

Carefully open the stomach and note the entrance of the
bile-ducts. These bile-ducts lead from the voluminous “ver,
which nearly fills the cavity of the cephalothorax.

Make a drawing of the digestive system.

The Reproductive System.—The sexes are separate.
The ovaries or ¢estes form a network of tubes which ramify
over and through the substance of the liver. Their ducts
may be traced to the external openings already noted.

The Excretory System.—The coxa/ glands lie along
both sides of the stomach, each consisting of a longitudinal
portion, from which project laterally four finger-shaped
lobes. In life they are “ brick-red” in color, Wine ammee
tion of these organs 1s not definitely known.

Draw.

The Nervous System.— Remove the alimentary tract
from the beginning of the crop to the anus, and expose,

The King Crab. Vk

immediately under the stomach, the cartilaginous s#rna/
plate. Note the outline of the plate and remove it with
care, as a portion of the nervous system lies immediately
beneath.

The nervous system consists of a drain, a circum-oral ring,
and a ventral, posterior continuation, the ventral cord. ‘The
brain is a rounded body lying in front of the cesophagus.
Trace the nerves leading from it. The circum-oral ring is
a flattened disc which innervates the ambulatory appen-
dages. The posterior part of the ventral cord gives off
branches to the abdominal appendages. The more central
portions of the nervous system are surrounded by a blood-
sinus.

Make a drawing of the nervous system.

118 Invertebrate Zoology.

AN ARACHNID
(Lpeira riparia).

External Anatomy.— The Jody is here again divided
into a cephalothorax and an abdomen, the two being united
by asmall peduncle. ‘The cephalothorax is flattened above
and bears six pairs of appendages. The most anterior pair,
the chelicereg, are provided with strong cutting jaws and are
pierced, near their tips, by a small opening which leads from
a poison-gland, ‘They lie anterior to the mouth.

The pedipalps, which lie immediately behind the chelicere,
and on each side of the mouth, are more leg-like. They
consist of a strong-bodied, basal portion and of an elongated,
many-jointed /feeler or palpus. In the males the palpi are
specialized into organs for bearing the spermatophores.
Compare this pair of appendages with the same of Zzmutus.

The four pairs of /egs take their origin from behind the
mouth, along the lateral portion of the cephalothorax. Do
they all agree in having the same number of joints? Note
the hook-like organ terminating each.

Examining the abdomen from above, do you find any-
thing (grooves or transverse bands) that might suggest that
it was once segmented ?

The lower surface of the abdomen presents several organs
of interest. — The external openings of the lung-sacs appear
as two transverse slits, one on either side of the anterior por-
tion of the abdomen. In the median line, between them, 1s

An Arachnid. | 119

the external opening of the sexual organs, in the female
highly elaborated. The sfennerezs will be found at the pos-
terior end of the abdomen as three pairs of papille. They
are jointed, and probably represent specialized abdominal
appendages. The smaller middle pair of spinnerets are
covered by the much larger anterior and posterior pair,
while the aza/ papilla is closely folded against the latter
as a transverse chitinous elevation. If the anal papilla is
pressed back, the opening of the aus will be found.

A small pore, or sfzvac/e, lying in the median line, imme-
diately in front of the spinnerets, leads from a series of
branched abdominal trachee. ‘This pore is often difficult to
find. It lies just in front of a thorn-like process which rests
just between the first pair of spinnerets. If the integument
at this point be carefully picked away, the trachez will be
found.

Make a drawing of the spider as seen from above, and
another as seen from below.

Internal Anatomy.— Carefully remove the integument
from the upper half of the thorax and abdomen.

The Circulatory System. — The /eart is an elongated,
thin-walled tube which extends along the dorso-median por-
tion of the abdomen and is continued anteriorly, as the azze-
rior aorta, through the peduncle, into the cephalothorax.
The heart is really enclosed in a very delicate pericardium,
which holds the blood as it is returned from the acune of
the body, finally pouring it into the heart through certain
lateral ost#a. The blood, leaving the heart through the ante-
rior and posterior aortz, is conveyed in arteries for only a
short distance. It soon enters lacunz and sinuses, in which
it pursues a definite course until it gathers in a large reservoir

120 Invertebrate Zoology.

near the lung-sacs. In the lung-sacs it is purified, and from
thence passes directly to the pericardium.

The Reproductive System. — The ovarves of the female
often nearly fill the abdominal cavity, the ova being very
irregular in outline, as a result of their mutual pressure.
The oviducts may be traced to the external opening already
noted. Lying on either side of the external openine is7a
coiled tubular organ, the vecepfaculum seminis, that receives
the spermatophore of the male, and retains the spermatozoa
until the time of egg-laying. The estes of the male are
elongated tubular glands, which lie longitudinally along the
lower portion of the abdominal cavity. Before opening to
the exterior each gland is continued into a coiled vwas
deferens."

The Digestive System. — The straight zzdestine will be
found to lie immediately under the heart and to give off lat-
erally several cecal diverticula. Followed posteriorly, the
intestine opens into an enlarged vectum, which also receives
the ducts from certain many-branched tubes, the /a/~ighian
vessels.

Followed anteriorly, the intestine passes through the
peduncle and enlarges within the cephalothorax into a
stomach. From the stomach, ccecal diverticula extend out
as loops into the bases of the legs. Certain gastric muscles
are so arranged that they can enlarge the central portion of
the stomach, which thus acts as a sucking-organ.

The esophagus may be followed as a tube leading from
the mouth to the stomach.

1 The spermatic fluid is collected in the pedipalps and retained in
spermatophores until transferred to the receptacula of the female.

An Arachnid. I21

The pozson-glands, which are probably modified salivary
glands, will be observed in the anterior portion of the cephalo-
thoracic cavity, immediately over the cheliceree. ‘Trace
their ducts to the terminal openings already noted.

Make an imaginary drawing of the viscera, thus far studied,
as they would appear in side view.

Carefully remove the digestive tract and note, lying imme-
diately below it in the cephalothorax, the ‘‘ diaphragm,” a
thin sheet of tissue extending horizontally almost entirely
across the cavity. Recall the sternal plate of Zzmulus.

The Respiratory System. — The external openings of

the lung-sacs have already been noted. Each /ung-sac con-
tains a cavity into which a series of /ame//e, like the leaves
of a book, project. In these thin-walled lamelle the blood
circulates and is purified. Recall the gill-books of the king
crab.

The spivacular opening of the tracheal system of air-tubes
has been already noted. The arrangement of the ¢rachee
or aiv-tubes is much as in insects. It is through them that
the air is conveyed to many of the tissues.

The sz/k glands. In the abdominal cavity, immediately
over the spinnerets, the silk glands will be observed. Each
gland is composed of a brush of tubular organs of which the
more anterior are the larger.

The Nervous System. — The drain or supra-esopha-
geal ganglion occupies a position in front of the cesophagus
and innervates the ocelli and the chelicere.'| The wsopha-

1 The arrangement of the ocelli is different in different species. In
the present type two pairs of median ocelli form a quadrant, while a pair
of lateral ocelli will be found on elevations just above the base of each
chelicera.

122 Invertebrate Zoology.

geal colar connects the brain with a large thoracic ganghonic
mass from which nerves extend to the lateral appendages
and into the abdomen.

Finish the drawing already begun, representing the dia-
phragm, lung-sac, tracheee, silk glands, and nervous system.

A Lepidopterous Insect. 123

A LEPIDOPTEROUS INSECT

(Sphinx sp.).
LARVAL STAGE.

External Anatomy. — The body of the Zavva or caéer-
pillar is elongated and vermiform and, like that of Arthro- -
pods already studied, is made up of serially arranged seg-
ments or metameres. |

The head bears, anteriorly and laterally, a pair of large,
convex parietal plates which meet above in the median line
and enclose, lower down, a smailer, median, triangular /ronfal
plate. The ocefi are found as a series of pigmented dots at
the lower anterior portion of each parietal plate. How
many ocelli are there?

The first pair of cephalic appendages, the anzenne, take
their origin from the lower anterior angles of the parietal
plates. Each antenna is made up of several joints.

The opening of the mouth will be found midway between
the antennze. It is bounded anteriorly by a two-lobed uffer-
Lip or labrum, and laterally by a pair of strong chitinous jaws
or mandibles. In what plane do the mandibles move?

The maxill@ lie immediately posterior to the mandibles.
Each is provided with a small jointed organ, the palpus. In
the median line between the maxillz is the cone-shaped
lower-lip or labium. It bears the external opening of the
duct leading from the sz/k-g/ands.

124 Invertebrate Zoology.

Make drawings of the head as seen from the side and from
below.

The segments immediately following the head, the f7-,
meso-, and meta-thoracic, are each provided with a pair of
jointed appendages, the thoracic legs.

Behind the thoracic region, the abdomen extends as a
series of ten segments. Do the first two abdominal seg-
ments bear appendages? ‘The fleshy appendages of the
third, fourth, fifth, and sixth abdominal segments are called
the prolegs. Note that each is terminated at its free end by
a series of hooks. The seventh and eighth segments are
not provided with appendages, though the eighth frequently
bears a median dorsal spine. The ninth segment is short
and somewhat suppressed, while the tenth is pierced by the
. anus and bears a pair of anal prolegs. In the embryo all
the abdominal segments are provided with rudimentary
appendages.

Extending along each side of the animal are a series of sfz7-
acles, openings which lead within the animal into an elabo-
rate system of branched vesfiratory tubes or trachea. ‘The
spiracles do not occur on every segment, but are present
upon the first thoracic and upon all the abdominal segments
except the ninth and tenth.

Make a drawing of the animal as it appears when viewed
from tie side:

Internal Anatomy. — With a fine pair of scissors cut
through the integument, along each side of the animal a little
above the line of spiracles, from the side of the head to the
ninth abdominal segment. Remove the dorsal piece without
disturbing the underlying viscera.

A Lepidopterous Insect. 125

The Circulatory System. — The “ear? will be observed
as a median tube extending along the mid-dorsal line of the
animal, immediately below the integument. The dod,
which contains amedboid corpuscles, enters the organ through
certain lateral os¢#za, and is forced anteriorly, where it enters
the aorta, from whence it is distributed to the various
sinuses of the body.

The Muscular System. — Many parallel bands of mus-
‘cles, segmentally arranged, will be observed immediately
under the integument. In the head they become specially
developed in the neighborhood of the mouth parts.

Remove the heart and the laterally lying muscle bands. —
The dody-cavity will be found to be apparently filled with the
subdivisions of the fazdody, though more careful examination
with a lens will reveal the presence of other organs of some-
what the same appearance.’

The Digestive System. — The mesenteron or stomach
will be observed as a large, rather thick-walled cylinder extend-
ing antero-posteriorly through the body-cavity. Followed
anteriorly, the stomach is found to lead from a thinner-walled
esophagus. Posteriorly, the stomach becomes abruptly con-
stricted and passes into the zzéestine, which in turns opens
through the rectum to the exterior. The sazvary glands will
be found lying anteriorly, along the sides of the cesophagus.
Their ducts open into the mouth. Associated with the sali-
vary glands are the s/k glands or serictaria, a pair of elon-
gated organs which may be found lying side by side along
the lower surface of the anterior portion of the mesenteron.’

1 The substance of the fat-body is loose and flocculent.
2 Both salivary and silk glands are elongated tubular organs. Each
salivary gland extends as a coiled thread from the dorsal region of the

126 L[nvertebrate Zoology.

The external opening of the silk glands has already been
noted. |
Make a drawing of the alimentary tract.

The Excretory System. —A series of irregular tubes
will be observed lying upon the posterior half of the mesen-
teron, each pursuing a somewhat irregular course and pre-
senting, when seen under the lens, a beaded appearance.
These organs are the Malpighian tubes, six in number. Each,
after pursuing a tortuous course, empties into the intestine.

Make a drawing of the excretory system.

The Respiratory System. — The spiracular openings
have already beennoted. Each leads into a series of branch-
ing tubes, the ¢-achee, which subdivide into very minute
subdivisions, carrying the air to the most remote tissues.
The tracheze are lined with chitin and are strengthened by a
spirally coiled chitinous ridge.

third thoracic or first abdominal segment along the lateral surface of
the anterior portion of the digestive tract, in its course being partly
covered by the lobes of the fat-body.

The salivary duct passes down the posterior surface of the bundle
of muscles that works the jaws.

The silk glands are much larger than the salivary glands and occupy
avery different position. Their ducts lie immediately below the cesopha-
gus and the anterior portion of the stomach. The greater portion of
each gland appears as a coiled cord, more or less surrounded by the fat-
body and lying on a level with the spiracular openings, in the middle
and posterior portions of the body-cavity.

The salivary and silk glands should not be confused with the much
more delicate Malpighian tubes, which are arranged in more nearly
parallel lines along the outer surface of the stomach.

A Lepidopterous [nsect. 127

The Reproductive System. — The sexual glands are
somewhat difficult to find in alcoholic specimens. They lie
in the fifth abdominal segment, immediately beneath the
dorsal integument. In favorable specimens a delicate duct
may be traced from each, around the intestine, to the lower
side of the body-cavity.

The Nervous System. — The nervous system has the
same general disposition that has already been noted for
related Arthropods. The drazn will be found far for-
ward, immediately over the mouth, and uniting with the
infra-esophageal ganglion through the circum-cesophageal
collar.

From the brain, which is divided into a right and a left
half by a median furrow, nerves may be traced to the ocelli,
antennze, and to the cesophagus.

The first or infra-esophageal ganghon innervates the man-
dibles, the labium, and the silk glands, and by its two con-
nectives unites with the next following ganglia.

The second ganglion is of relatively small size. It inner-
vates certain muscles of the head and neck and the first pair
of legs.

The third ganghon innervates the second pair of legs, while
the fourth ganglion supplies the third pair.

The abdominal ganglia are seven in number, —the first
abdominal segment bearing the 7///, the second segment
the szxth, the third segment the seventh, the fourth segment
the ezghth, the fifth the #zzth, the sixth the senzh, and the
seventh the eleventh ganglion. The eleventh ganglion is,
moreover, clearly divided into an anterior and posterior half,
and is, hence, probably composed of two fused ganglia.

128 Invertebrate Zoology.

There are no nerve-centres in the remaining abdominal
segments.

While the connectives leading from the second to the
third and from the third to the fourth ganglia are free and
form loops, those leading between the remaining ganglia
are more or less united together.

Make a drawing of the dorsal view of the nervous system.

An Orthopterous Insect. 129

me OR THOPTEROUS INSECT

(Acridium americanum).

ApULE STAGE.

External Anatomy. — Observe that the three divisions
of the body, head, thorax, and abdomen, are here much
more definitely outlined than they were in the caterpillar.

The head bears a pair of antenne, each made up of sev-
eral joints; a pair of large compound eyes; a median and
two lateral ocelZ; a bilobed labrum or upper-lip; a pair
of strong mandibles or jaws which move laterally ; a pair of
maxille lying immediately behind the mandibles, and each
bearing a lateral, jointed apparatus, the faljus; and a
bilobed Zower-Zip or labium, which lies posterior to the max-
ill, and is also provided with palpi. As the mouth-parts
are opened and the mouth exposed, the fongue will be
noticed as a chitinous papilla on its floor.

The ¢horax has the same segments that were present in
the caterpillar. The prothorax is the largest of the three
and bears the first pair of /egs. Its sevgum or dorsal por-
tion is enlarged and forms a shield. ‘The meso- and meta-
thorax are somewhat united together. The mesothorax
bears the second pair of legs and the first pair of wings, while
the metathorax bears the much larger “hird pair of legs and
second pair of wings.

The legs will be found to consist of a series of joints a
to be terminated by a pair of hook-like organs. ‘The joints

130 Invertebrate Zoology.

of the legs are as follows: The coxa, short and ring-like,
bears at its free end the ¢vochant¢er, which is a little smaller
than the coxa, to which, in the third leg, it becomes fused.
The trochanter bears a long joint, the femur, which, at its
free end, bears another long joint, the #éza. The darsus
is made up of a series of small movable joints which bear
pads on their lower surfaces. The tarsus is terminated by
the claws.

The /fore-wings or wing-covers differ from the ¢rue wings.
Note the arrangement of their vezzs, the rib-like lines which
strengthen them and which are in communication with the
circulatory and tracheal system. The second or ¢rwe-wings
are, when at rest, folded like a fan. Note the arrangement
of the veins and see if the wing-covers, when expanded, do
not support the anterior edge of the true-wings.

The abdomen is composed of a series of ten segments or
metameres, all but the last two or three of which are very
evident. ‘There are no abdominal appendages.

The first abdominal segment 1s somewhat modified from
its association with the metathorax. Laterally, it is pierced
by two large openings, one on either side, which lead into
the auditory organs. The abdominal segments of the two
sexes from the first to the eighth closely resemble each
other.

The ninth abdominal segment of the female is only about
one-fourth as wide as the eighth, and is not provided with an
independent sternal piece, the sternum of the eighth extend-
ing to the posterior end of the mid-ventral line. ‘The pos-
terior edge of the #enth abdominal segment follows a line
parallel with posterior edge of the eighth. There project
posteriorly from the tenth segment a series of more or less
flexible pieces of which the dorsal is the larger and may

An Orthopterous Insect. 131

represent the tergum of an eleventh segment. This dorsal
piece rests laterally upon a pair of triangular plates, the
podical plates, the lower edges of which follow the course
taken by the lower edges of the ninth and tenth segments.
Resting laterally upon the podical plates are short pointed
processes, the cevcz. The ovipositor fills up that opening at
the posterior end of the body, which is bounded by the free
edges of the podical plates and the eighth sternal piece.
The ovipositor is made up of two dorsal and two ventral
pieces, all of which have sharp chitinous points. The anus
opens between the dorsal pieces, and the ovzduct between the
ventral.

The abdomen of the male is relatively smaller than that of
the female. The ninth and tenth segments are provided with
a common sternal plate. ‘The podical plates are reduced,
while the cerci are relatively larger. A swdgenital plate lies
below the podical plates and continues posteriorly the ven-
tral series of sterna.

Spiracles will be observed as follows: The most anterior
is on the posterior edge of the prothorax, under the lateral
fold of the shield-like piece. The second is at about the
same level, behind the edge of the mesothorax. The third
pierces the first abdominal ring just within the anterior mar-
gin of the auditory organ. ‘The seven succeeding abdominal
rings are each provided with spiracular openings. Spiracles
do not occur on the ninth and tenth segments.

Internal Anatomy. — Carefully open the animal along
the mid-dorsal line.

The Circulatory System. — The ear? will be found
occupying the same place that it has occupied in many
_ other Arthropods, and presents no remarkable features.

132 Invertebrate Zovlogy.

The Muscular System. — Lying either side of the heart
are the longitudinal abdominal muscles. ‘The thorax con-
tains several bundles of a/ary muscles. Are those which move
the fore-wings separate from those which move the larger
posterior wings? Fazbodies may be found forming a loose
tissue throughout the cavity of the abdomen.

The Respiratory System. — The external openings of
the respiratory organs, or ¢rachee, have been already noted.
They will be found to lead, within the body-cavity, to a
many-branched system of tubes which convey the air to the
tissues, as has already been observed in the caterpillar.

The Reproductive System. — The reproductive gland
rests in the upper part of the abdominal cavity. The ovary
is a bilateral organ which is continued posteriorly into a pair
of oviducts. ‘The oviducts pass to the lower side of the
abdomen, where they unite and form the vagina. ‘The vagina
opens to the exterior between the ventral pieces of the
ovipositor. Slightly above and anterior to the external open-
ing of the vagina, the much smaller opening which leads
from the dursa copulatrix will be found. The bursa is a
small sac which receives the spermatozoa. It is situated
beneath the rectum.

The Digestive System. — The wsophagus leads into a
large crop which extends from the mesothorax to the anterior
part of the abdomen. Lying laterally to the crop are the
branched safvary glands, the ducts of which may be traced
to their openings into the mouth. In the abdomen the crop
opens into the stomach which extends over half the length of
the abdominal cavity. The stomach opens into the zzéestine.
The gastvic ceca are a series of pouches which lie parallel to

An Orthopterous Insect. 133

the stomach and open into it. How many are there? The
intestine is somewhat less than the stomach in size. It
receives the ducts which lead from the Malpighian bodies.
The latter appear as a tangle of minute tubes. The intestine
opens into the vectum, which in turn opens through the anus
to the exterior.

The Nervous System. — The 4razn occupies the same
position that it has been found to occupy in all the Arthro-
pods that have been studied. The esophageal collar and
ventral nerve-chain present no new features. Is there a
ganglion for each thoracic segment? There are five abdom-
inal gangha. In which segments do they rest?

134 Invertebrate Zoology.

A SIMPLE TUNICATE
(Moleula manhattensis).

THIS species is quite abundant along the New England
shores, attached to submerged stones and woodwork.
Though occasionally solitary, the individuals are more often
found in clusters of varying sizes. It is our most common
Simple Tunicate, and is related to the Czova so frequently
mentioned in the European text-books.

External Anatomy.— Though individual specimens
vary, the more general shape of the present species is that
of a two-necked flask, the larger neck or siphon serving for
the entrance of water and food, the other, slightly smaller
and often abruptly curved, serving for the escape of the
strained water, the waste products of digestion and excre-
tion, and also for the egress of the ova or embryos. ‘The
incurrent opening or mouth is surrounded by a series of
circum-oral lobes or tentacles, which may be folded in such
a way as to completely close the orifice. Are similar lobes
arranged around the excurrent or cloacal opening? ‘The
outer surface of the animal has a felty appearance, due to
the presence of innumerable papiw/e. ‘The papille entangle
foreign matter, and thus the animal secures a protective
coloring. In certain specimens the deeply colored vis-
cera are to be seen through the semi-transparent body
walls.

A Simple Tunicate. 135

Note that the only plane that will divide the animal
bilaterally passes through the long axis of each neck. Sub-
sequent study will show that this plane actually separates
the right from the left. The incurrent siphon arises from
the morphological anterior end, while the cloacal tube
extends from the fosterior end. ‘The shorter distance
between the two is along the mzd-dorsal line, while the
greater distance marks the ventral fine. ‘Through the walls
a light-colored band will be observed, extending along the
anterior portion of the mid-ventral line. It is the endostyle,
and, as subsequent dissections will show, lies along the floor
of the pharynx.

ee veuter covering of the animal, “¢zazc” or “test,”
should now be partially removed from the left side. This
covering will be found to be thick and tough: its outer sur-
face, except where the specimen was attached to others,
rough and dirty; its inner surface smooth and easily sepa-
rated from the transparent underlying “ mane.”

The entire tunic may now be removed, and its only points
of firm attachment to the underlying mantle are found at
the margins of the incurrent and excurrent openings.
Through the transparent mantle the contained deeply
colored viscera are to be seen, while the mantle itself is
found to be provided with certain clear white bands of
muscle tissue. ‘These muscle bands are especially abundant
on the tubes, where they are arranged in longitudinal bundles
and d¢ransverse fibres. How are they arranged on other
parts of the mantle? It is through the activity of these
muscles that the animals contract and forcibly eject the
contained sea-water. ‘The transverse fibres form sphincters
around the mouth and at the base of each siphon, and move
the six oral and four anal flaps.

136 Invertebrate Zoology.

Internal Anatomy. — Viewing the specimen from the
left side, the course of the S-shaped digestive tract may
readily be followed. ‘The tract is made up of two parallel
portions, the wsophagus and stomach forming the lower
limb, and the zzzestine forming the upper. Lying just
above the, often dark-colored, intestinal loop is the light-
colored sexual gland. ‘The delicate sexual duct extends
dorsally and posteriorly, parailel with the posterior section
of the intestine.

Lying deeper than the just mentioned viscera are six
nearly parallel light-colored bands. ‘They are the dranchial
folds, and will be considered later on.

At a point on the dorsal surface, about midway between
the siphons, the gang@on will be observed as a small opaque
spot. Notice the zevves, and, if possible, trace them to the
siphon tubes.

Again follow the course of the opaque endostyle. It ex-
tends along the mid-ventral line, from near the base of the
oral siphon to a point removed nearly 180°. Its posterior
termination is near the point of origin of the cesophagus.'

Through the transparent mantle of the right side six
branchial folds and a large sexual gland will be at once
recognized. The duct leading from the Sexual’ elama
extends in a nearly horizontal direction towards the cloacal
siphon. It often contains eggs or embryos. Lying parallel
to and below the sexual gland, enclosed in a pericardium, is
the heart. (In alcoholic specimens the circulatory system
is not easily dissected.) Below (ventral to) the heart is a
crescentic sac of considerable size. It is the zenal organ,
and often contains brownish flakes and concretions.

1 The endostyle may be the homologue of the hypobranchial groove
of Amphioxus, and of the #hyrozd gland of higher Vertebrates.

A Simple Tunicate. EX7

If the specimen is viewed from the dorsal side, a circular
line will be found to extend from the anterior end of the
endostyle around either side of the oral siphon to the
ganglion. This line marks the position of the pevipharyn-
geal bands.

Drawings of the right and left side of the animal should
now be made.

By gently pressing upon the mantle it will be shown that
there is a space between it and the deeper lying branchial
bands. ‘This space is the afvzum or peribranchial chamber,
and can be beautifully seen if one now carefully removes the
cloacal siphon by cutting around its base, beginning just
above the ganglion. ‘The cavity thus opened is actually the
cloacal chamber, though the right and left halves of the peri-
branchial chambers are seen to lead directly from it as we
look down through the artificial opening. The branchial
folds are now seen to form the longitudinal ribs of a reticu-
lated sac, the dranchial sac or pharynx. Crossing the bands
at right angles are certain ¢vansverse vessels, and stretched
between vessels and ribs is a delicate membrane pierced by
minute openings or stigmata.

On the branchial sac a dorso-median line will be observed
to extend from near the ganglion to near the posterior end
of the endostyle. The anal opening will be found near the
lower end of this line. The zzéestine lies along the floor of
the left peribranchial chamber, and is often deeply colored
from the presence of contained feecal matter. The ofenings
of the genital ducts are to be seen on the right and left
external branchial walls respectively. The cloacal chamber
receives then the waste products of digestion, the secretion
of the sexual glands, and also the water which flows into it
directly through the stigmata of the posterior wall of the

138 Invertebrate Zoology.

branchial sac as well as the water which flows from the two
large laterally lying peribranchial chambers.

Slt the mantle from the opening already made, along
the upper edge of the left peribranchial cavity and thence
ventrally along a line midway between the endostyle and
the lower loop of the digestive tract, cutting through the
strands or ¢rabecule that connect the mantle with the
pharyngeal sac. The external wall may be now lifted and
turned down and the extent of the left branchial chamber
definitely established. On its external wall the exact course
of the alimentary tract will be noted from the origin of
the cesophagus at the point where the branchial bands con-
verge, to the anus. Again note the transverse vessels and
stigmata.

In the same way as above directed open the right peri-
branchial chamber and note the course taken by the sexual
gland and renal organ. ‘The two peribranchial chambers
are not confluent along the ventral line.

Passing the point of a fine pair of scissors into the oral
siphon, carefully cut along near the ventral line of the
branchial sac midway between the endostyle and the ventral
branchial band. The pharyngeal cavity will thus be opened.
The twelve branchial folds converge from their origin, just
below the peripharyngeal bands, to the opening of the cesoph-
agus. Each lateral half of the pexipharyngeal bands, tak-
ing its origin from the anterior end of the endostyle, passes
dorsally to meet its fellow in the mid-dorsal line just back of
the ganglion. Thus united, the bands continue posteriorly
to the opening of the cesophagus as the dorsal lamina.

The endostyle now appears as a gutter-like structure,
extending the entire length of the ventral side of the pharyn-
geal chamber. A circle of dranched tentacles form a crown

A Simple Tunicate. 139

around the siphonal canal, just outside the peripharyngeal
bands.

Drawings should now be made of the structures thus shown
on the interior of the pharynx.

Carefully remove the ganglion together with the immedi-
ately surrounding tissues, and examine it carefully in a watch
glass.

From its inner surface a funnel-shaped process will be
observed. This is the dorsal tubercle, and is a part of a
small glandular mass, the neural gland. The course of the
nerves can be readily determined by the adoption of the
xylol method described for the nervous system of the Phyl-
lopod Crustacea.

Make a drawing of the ganglion and of its associated
structures.

General Remarks. — The outer covering of the Tuni-
cates is variously described as the test, tunic, outer mantle,
or sac. It varies considerably in different types, being in
some delicate and transparent, in others tough and opaque.
It is produced by the activity of a lining layer of epithelial
cells, and is consequently comparable with the covering of
many Invertebrates. It is peculiar in that it contains cellu-
lose. The mantle or muscular sac (integument, second or
inner muscular tunic) is also subject to considerable varia-
tion. In life it is attached throughout to the inner surface
of the tunic, though in alcoholic specimens it is often
partially free.

The Digestive System. — Food that is drawn into the
pharyngeal sac by the activity of the cilia of the pharyngeal
walls is collected by the mucus secreted, probably by the
endostyle or by the sub-neural gland, and is carried along

140 Invertebrate Zoology.

the peripharyngeal bands to the dorsal lamina, and thence
posteriorly along the “roof” of the pharyngeal sac to the
opening into the cesophagus. In certain species the cesoph-
agus opens into an enlarged stomach, and _ frequently
accessory digestive glands are present. A median fold, the
‘yphlosole, partially divides the lumen of the intestine.

The Excretory System. — Besides the renal organ
already noted, there are certain small anomalous collec-
tions of vesicles around the intestine and in the tunic that
are supposed to perform excretory functions. The neural
gland is also supposed by some to function as a renal organ.

The Circulatory System. — In the Tunicata there are
no true arteries or veins. The heart is a sac-like organ
which forces the blood intermittently towards the posterior
dorsal portion of the animal, and then in the opposite direc-
tion towards the anterior ventral. It is surrounded by a
fold, the pericardium. During the respiratory circulation, a
ventral trunk conveys the blood from the heart along the
ventral portion of the animal, below the endostyle, and gives
off lateral branches to the ¢-ansverse vessels of the branchial
sac. From these vessels the blood passes into’ Haeame,
irregularly disposed interstigmatic vessels, the meshes of
which surround the stigmata. The /ongitudinal vessels in
Moleula are arranged on the branchial folds already noted.

When the current is from the ventral towards the dorsal
portion of the animal, the blood passes through certain
vessels to the mantle, the digestive and reproductive organs.
The blood from these organs is then collected in a dorsal
trunk, which lies along the mid-dorsal line of the branchial sac,
and from thence it passes into the transverse vessels. There
are then, during this cycle, three systems. 1st, Branchio-

A Simple Tuntcate. 14!

cardiac, conveying pure blood to the heart along the ven-
tral trunk; 2d, Cardio-splanchnic, conveying blood from
the heart to the viscera and other parts of the body; 3d,
Splanchno-branchial, conveying impure blood from the
viscera, etc., through the dorsal trunk to the branchial
sac.

The test is supplied with blood through vessels that leave
the main trunks near the heart.

The Nervous System. — The nerves from the ganglion
may be traced to certain sense-organs. ‘The ocelii are sit-
uated around the oral and cloacal orifices. The sentacles
have already been noted.’

The Reproductive System. — The Tunicata are her-
maphrodite, though probably not self-fertilizing, as the ova,
often reach maturity much earlier than the spermatozoa.
In Molgula the ovary and testis unite and form a pair of
hermaphrodite glands; in other forms the glands may be
separate. Reproduction by ,budding is not infrequent.
This process may give rise to small colonies, the individuals
of which may have a common circulatory system. Such
Tunicates are called Social in distinction from the Solitary
Tunicates, of which A/o/guwla is a type.

1 For a long time the dorsal tubercle was supposed to function as a
sense-organ, and was called the olfactory tubercle. It is now known
to be the funnel-shaped extremity of a ciliated duct, leading from
the neural gland. It has been compared to the pituitary body of
Vertebrates.

APPEND EX.

as

THE USE OF THE LABORATORY AND LABORA-
TORY APPARATUS.

OBSERVANCE Of the following regulations will facilitate lab-
oratory work : —

During laboratory hours work, walk, and talk quietly, that
your co-laborers may not be annoyed.

Handle microscopes and other instruments with care,
keeping them clean and in order, and always, after using,
return them to their proper places.

Instruments that are the property of the laboratory should
be used with especial care, and never retained longer than
is necessary for the immediate work in hand. On returning
the same, be sure that it is to the proper place.

Reagents should be used sparingly, corks or stoppers
returned to the bottles to which they belong, and the bottles
returned to their proper places. Never pour back into the
“stock bottle ” any reagent that has been once made use of.
Take care that your hands do not soil the label of the bottle.
(It is well to wipe the lip of the bottle before and after
pouring out the liquid.)

143

144 Invertebrate Zoology.

After each day’s work, clear up your table and return
everything that has been borrowed.

All organic refuse should be placed in the receptacle that
has been provided for the same, and as free from liquid as
possible. |

Pour nothing but liquid into the sinks. Be especially
careful that sand and shreds of flesh are not left in the sinks.

After using laboratory sponges, rinse them out and leave
them in their racks. Never use them for absorbing grease
or oil.

Paraffin chips or wax should not be allowed to fall on the
floor. |

Your own books, and certainly laboratory books, should
not be handled with soiled fingers.

Keep the lockers, drawers, etc., that have been assigned
to you in an orderly condition.

Finally, if you are so unfortunate as to injure laboratory
instruments, books, or other property, inform the instructor
of the extent of damage done.

Appendix.

B.

145

LIST OF INSTRUMENTS AND REAGENTS.

[Those marked with an asterisk should be owned by the student. ]

* Large scalpel.
* Small scalpel.
* Large tweezers, with serrated

points.

* Small tweezers, with smooth
points.

* Large scissors, with “lock”
joint.

* Small scissors, with fine points.

* Vial of entomological pins.

* Pair of needle holders and as-
sorted needles.

* Small package of bristles, white
and black.

* Hand lens or, better, a dissecting
microscope.

* Assortment of small brushes.

* Drawing pencils, one hard and
one medium.

* Note book.

* Erasing rubber.

* Bristol drawing-board.

* Slides and covers for micro-
scopic work.

GLASS WARE.
* Several small and one large
pipette.
Water bottle.

Assortment of heavy and light
watch-glasses.
Spirit-lamp.

REAGENTS.

50% alcohol.

70% alcohol.

95% alcohol.

100% alcohol.
Acidulated alcohol.
Corrosive sublimate.
Perenyi’s fluid.
Picro-sulphuric acid.
10%, nitric acid.
Aceto-carmine.
Borax carmine.
Alum cochineal.
Alcohol carmine.
Turpentine.
Chloroform.
Chloroform and paraffin.
Collodion.

Collodion and clove oil fixative.
Clove oil.

Cedar oil.

Thyme oil.

Canada balsam.
Glycerine.

Vaseline.

146 Luvertebrate Zoology.

&
MICROSCOPES.

THE microscopes required for ordinary biological work
should be “simple” and “ compound.”

The szemple microscope may be either a pocket lens or one
of the more elaborate dissecting microscopes figured in cat-
alogues of optical instruments, etc. Pocket lenses of a very
convenient form are made in German silver mountings. For
laboratory work each lens should be provided with a long-
arm support, that it may be held, if need be, over a dissect-
ing dish, allowing the free use of both the operator’s hands.

The compound microscope should be provided with eye-
pieces and objectives that will give a magnifying power
ranging from fifty to six or seven hundred diameters. The
mechanical and optical parts of the microscope, and their
uses, should be familiar to the student. ‘The more impor-
tant parts are as follows: The heavy foot, or dase, often
made in the shape of a horseshoe ; the upright Azar, which
may be supplied with a oz, allowing inclination of the in-
strument. The s¢age, generally black in color, is the hori-
zontal support upon which the object to be examined is
placed. The stage is often provided with a pair of com-
pressors or clips, which need not be used in ordinary work.
Immediately under the stage, and a part of it, is the szd-
stage. The sub-stage is generally provided with a perforated
apparatus — the daphragm—for limiting the amount of
light. In the more expensive instruments the sub-stage has
also condensing glasses for increasing the intensity of the
light. The mzrror is provided with a plane and a concave
surface. ‘Though a more simple part of the instrument, the

Appendix. 147

mirror is most important. Successful observation frequently
depends on the origin and intensity of the light and also upon
the direction from which the mirror throws light upon the
object. The arm of the microscope, reaching out from the
pillar, supports more or less directly the zzde, which in turn
carries, partly within itself, the draw-tube. The tube may
be moved up and down either by a rack and pinion —
“ coarse adjustment’ —or by sliding easily through a colar
supported by the arm. More delicate motion is secured by
the use of the “fine adjustment,’ a small milled wheel, gen-
erally placed at the apex of the pillar.

The parts of the microscope thus far mentioned are gen-
erally included in the term “‘ microscope stand.” ‘The opti-
cal parts consist of a series of eye-pzeces or oculars, which fit
into the upper part of the draw-tube, and a series of much
more expensive odjectives which screw into the lower end of
the tube. A very convenient, though not essential, appara-
tus is the “#7fle nose-piece, by means of which ¢hree objec-
tives, revolving around a common centre, may be attached
to the lower end of the tube, permitting an instantaneous
change of magnifying powers. A little careful experiment-
ing with the eye-pieces and objectives, under the direction
of the instructor, will soon show their relative values as
magnifying agents. One rule for adjusting the focws has no
exceptions. ‘ A/ways place the front of the objective near
the object before looking in the ocular, and then move the
tube wpward in focussing.”” By observing this rule the objec-
tive will not be ruined by being forced into the object.

Objects may be examined as they float in watch-crystals,
or they may be mounted on s&des and covered with cover-
glasses.

In case objectives or oculars become soiled, it is well to

148 Invertebrate Z oology.

call the attention of the instructor. An objective may be
ruined by being wiped with a dirty cloth. If, through acci-
dent, fluid runs on to the stage of the microscope, be sure
that it is a carefully removed from around the sub-stage.
Be especially careful of acids, and do not let them long
stand under the objective. Never wet the mirror. Do not
allow the instrument to stand in strong sunlight. Always
dust and put the instrument away after using.

D.
DIRECTIONS FOR DISSECTION.

VERY small objects are studied by “ teasing,” which con-
sists of gently tearing them apart under a lens, or of placing
them under a cover-glass and tapping the cover lightly with
a needle, the result being observed under the compound
microscope. All teasing should be done while the object is
covered with liquid, generally water, glycerine, or alcohol.

With somewhat larger animals the small scissors, scalpel,
and tweezers may be used, the object being pinned out
under water. As the water becomes cloudy it should be
renewed, or the cloudy portions may be removed with the
large bulb-pipette.

It is only the larger animals that are ordinarily dissected
without being flooded with water. The sponge should be
freely used and, if possible, the animal should be frequently
placed under the tap.

Nerves may generally be more easily separated from the

Appendix. 149

surrounding tissue if the specimen is allowed to stand for
two or three days in 10% nitric acid. The acid, however,
injures the other tissues.

Muscles are generally more easily studied in alcoholic
specimens. Small blood-vessels should be injected either
with a pipette or with a hypodermic syringe. ‘The use of
strong acetic acid will frequently aid in separating organs
that are firmly held together with connective tissue.

Xylol may at times be advantageously used with small
objects that have been preserved in strong alcohol. The
xylol frequently clears the object in a most instructive way,
presenting in the process one organ-system after another.’

Glycerine may be advantageously used as a teasing
medium with many objects. Fragments of tissue thus iso-
lated may be kept under the cover-glass for a considerable
time.

Schneider’s aceto-carmine is a penetrating stain that can
be used with fresh tissues, either during the process of teas-
ing or after the objects are under the cover-glass. Material
thus stained may be washed in water and kept for a short
time by being mounted in glycerine.

1See page 83.

150 Invertebrate Zoology.

EK.
METHODS OF KILLING, FIXING, AND HARDENING.!

UNLESS animals or tissues are killed by some one of the
recognized agents, they will not give the best histological
results and the organs themselves will be often distorted and
unnatural. The killing agents that are more ordinarily used
are the following: Hot water (80° C.), weak alcohol, corro-
sive sublimate in hot or cold saturate solution, acetic acid,
Kleinenberg’s picro-sulphuric acid, Perenyi’s fluid, and the
varying chromic solutions. |

While the above reagents may be successfully used with
many animals, there are nevertheless many organisms that
violently contract on coming in contact with them. Such °
organisms must first be rendered insensible by being anzesthe-
tized and then plunged into the killing agent.

Chloral hydrate, weak alcohol, cocaine, chloroform, hydro- |
xylamine, etc., have been used as anzsthetizing agents.

Objects that have been killed by the use of many of the
above-mentioned agents are still soft and flabby and would,
if allowed to remain for any considerable length of time,
disintegrate. Several so-called “ fixing” and “ hardening
agents” have been adopted which are also frequently the
same as are adopted for killing. Such are corrosive subli-
mate, picro-sulphuric acid, Perenyi’s fluid, and the chromic
solutions. Alcohol, used in regularly increasing grades of

1The methods of killing, fixing, hardening, preserving, staining, etc.,
are only given in the briefest possible way. It is taken for granted
that the students have at hand either an instructor or the admirable
text-books of microscopical technique which have been written by
Dr. C. O. Whitman and A. B. Lee.

Appendix. 151

strength from 50 to 95%, is also frequently used as a fixing
and hardening agent. To these might be added osmic
acid and cupric sulphate.

The length of time that objects should be allowed to
remain in the fixing fluids varies according to the fluid used
and the tissue or animal being treated. As a general rule,
a large quantity of fluid, two or three times the bulk of the
object, should be used, and this renewed as soon as it
becomes cloudy.

FF.
PRESERVATION.

Opjects that have been sufficiently fixed or hardened are
thoroughly washed in water, excepting such as have been
treated with picro-sulphuric acid or alcohol, and placed in
70% alcohol. An abundance of alcohol should always be
used. Picro-sulphuric preparations should be repeatedly
washed in alcohol of 70% before being finally placed in the
cabinet.

G.
METHODS OF STAINING.

OrGANISMS that when living are brightly colored are gen-
erally bleached by the action of the fixing or preserving
media, and tissues which are really very dissimilar in struc-
ture not infrequently appear to be quite similar. To reveal
these masked or hidden structures, microscopists have made
use of certain stains.

Stains are either diffuse or selective. “The former dye the
tissues throughout, while the latter stain only certain parts of

152 Invertebrate Zodlogy.

the tissue and leave other parts unaffected. Selective stains
are for this reason spoken of as “ differential stains.” Cer-
tain tissues will absorb a certain color in a certain fixed way
and may be quite unaffected by another stain.

The stains more commonly used are made from carmine,
cochineal, hematoxylin, or from some of the numerous ani-
line dyes.

Stains are also either aqueous or alcoholic. Alcoholic
specimens may be placed directly into alcoholic stain, but
should be first washed with water before being placed in
aqueous stain. The length of time that an object requires
for proper staining depends on the object, the way it has
been hardened, the length of time it has been preserved, and
the stain that is adopted.

The objects are taken from the alcoholic stains, washed
in acidulated alcohol for a short time, and then placed, until
wanted, in 70-90% alcohol. If an aqueous stain has been
used, the excess of stain is washed out with water, often acid-
ulated, and then the object is placed successively in 50, 70,
and 90% alcohol.

FE.
MOUNTING.

Many small organisms, and portions of larger, may be
mounted on glass slides and retained, if properly prepared,
indefinitely. ‘The mounting medium most commonly used is
Canada balsam. ‘The order of procedure is as follows : —

The object, stained or unstained, is carried up through
the grades of alcohol, and is finally placed in absolute alco-
hol, that the last trace of water may be withdrawn from it.
This is the process of dehydrating.

Appendix. 153

After dehydrating, the object is cleared, 7#.e., an oil, which
will mix with alcohol on the one hand and with Canada bal-
sam on the other, is allowed to take the place of the abso-
lute alcohol. ‘This change for all small objects may be made
by lifting the object from the alcohol and, after draining off
the excess of alcohol, placing the specimen for a few minutes
in oil of clove, or oil of cedar, or turpentine, or organum oil.
After remaining in the oil for a few moments, the object will
become quite transparent. It is now ready to be placed on
the slide and, after the oil is drained off, covered with a drop
of Canada balsam.

A clean cover-glass is now warmed for a moment over the
spirit-lamp and allowed to gently rest on the balsam and
object. If there is an excess of balsam, it may be removed
with a cloth dampened with turpentine. If there is not a
sufficient quantity of balsam,.a drop may be placed on the
slide near the edge of the cover, when it will run under by
capillary attraction.

If the object is rather thick and does not well support
the cover-glass, the latter may be supported with rubber
or glass rings made for the purpose, or with small pieces
of a broken slide. ‘“ Wax feet’ have been recommended by
Kukenthal.!

r.

METHODS OF IMBEDDING AND SECTION
CUTTING.

THOUGH sections of certain tissues may be cut without
previous preparation, the best results are to be obtained by
the adoption of one of the following methods : —

1 To three parts of wax are added one part of vaseline and one part
of Canada balsam.

154 Invertebrate Zoblogy.

The Paraffin Method. — The object, which should be
of small size, not often exceeding 1 cu. cm., having been
stained, is thoroughly dehydrated as previously directed.

From absolute alcohol the object is to be placed in some
fluid that will mix on the one hand with alcohol and on
the other with paraffin. Such fluids are oil of cedar, oil of
clove, oil of creosote, turpentine, chloroform, etc. Immer-
sion for two hours in any one of these will often be sufficient.

Flakes of paraffin are now whittled into the oil, or chloro-
form, until the point of saturation is reached, and the speci-
men allowed to stand for an hour or longer. If the fluid is
warm, a less time may suffice.

The object is now taken from the saturated oil or chlo-
roform, and placed in melted paraffin, the temperature of
which should not exceed 35° C. In from one to two hours’
time the object will be thoroughly infiltrated.

Make now a paper box, somewhat larger than the object,
and by means of a warm pipette fill the box with paraffin,
and place the object therein, noting the position in which it
lies.

In a few moments a film will have formed on the surface
of the paraffin, when the box may be placed in a glass of
water until thoroughly cold.

Remove the box, wipe dry, and with a sharp knife trim
off the paper from around the block of paraffin. Bearing in
mind the position of the object when dropped into the box,
scratch on the block a line that will designate the plane in
which the object is to be sectionized.

If the object is not to be immediately cut, it should be
properly labelled and placed away for safe-keeping.

Appendix. 155

Objects imbedded in paraffin may be cut, by a steady
hand, with no other instrument than a sharp razor. Of late
years, however, some form of mechanical section-cutter —
microtome —is to be found in every biological laboratory.
Such microtomes are the Minot, which is the best for paraf-
fin work, and the Thoma, which may be used for paraffin
or for celloidin.

If paraffin has been used as an imbedding mass, the
object-holder, metal or wood, is warmed, and the block at-
tached by cool water being allowed to run over block and
holder until a firm union has been obtained. The position
of the object in relation to the cutting-plane of the knife
has, of course, been observed.

Adjust the paraffin block, and cut off thin sections of par-
affin until the neighborhood of the object is reached. Trim
the remaining portion of the block so that it will be in the
form of a cube, the edges of which are parallel to or at right
angles with the cutting edge of the knife. Adjusting the
gauge so that thin sections of equal thickness will be cut,
proceed until as many slices are secured as are needed.

The following annoyances may arise : —

ist. The sections roll. — Correct, by cutting thinner sec-
tions, or by using softer paraffin, or by cutting in a warmer
room. Sections sometimes roll when the knife is dull.

2d. As the knife passes through the object, the tissue
appears granular and the section porous. — The trouble is
either that the imbedding was not properly done or the
knife is not properly sharpened.

3d. The block at its upper portion becomes white and
broken. — See if the cutting edge is not set so that it is fur-
ther from the block than the back part of the knife.

4th. The sections crimp, the section of paraffin being

156 Lnvertebrate Zodlogy.

somewhat smaller in area than the block from which it is
cut.— The sections are too thin, or the room is too warm, or,
quite likely, the knife has become smeared with dirt or par-
affn. Clean the knife on both sides by stroking it from the
back toward the edge with a clean cloth dampened with
chloroform.

The Celloidin Method of Imbedding and Cutting. —
The object 1s first stained zz zo¢o, dehydrated, infiltrated with
thin, medium, and thick celloidin or collodion, and finally
placed in a paper tray filled with the thick collodion. Ina
few minutes a film will form over the exposed surface of
the collodion, when the paper tray and its contents are
placed in a jar of strong chloroform, in which, after a few
hours, the collodion becomes quite hard.

The tray is now taken from the chloroform and, after the
paper has been removed from the hardened block, the col-
lodion with its enclosed object is placed in a vial of white
oil of thyme or some similar oil. If the block of collodion
is not large, in a few hours it will become as clear as glass,
the stained object appearing as if suspended in a transparent
fluid.

For the process of orienting, the block of collodion may
be taken from the oil, placed in a watch-crystal, and, after
covering with the oil of thyme, examined with a lens or, if
very small, with a compound microscope. The side of the
block that is to be attached to the object-holder of the micro-
tome is now selected, wiped dry of the oil, and immersed
for a moment in ether, and then smeared with thick collo-
dion. The object-holder, a block of wood rather than cork,
is smeared in the same way, and the two collodionized sur-
faces are brought together.

Appendix. 157

The holder and collodion block are now immersed for a
few minutes in chloroform, or long enough for them to
become firmly united.

The object-holder is finally screwed between the jaws of
the microtome, and covered, by means of a camel’s-hair
brush, with oil of thyme. The microtome knife is flooded
with the same oil.

After a few sections have been cut from the block of col-
lodion, the relative position of the plane of the knife to the
axis of the object can be definitely established, and the
object definitely oriented.

The sections are now cut and may be at once transferred
to the slide, covered with balsam, and mounted ; or if they
are not immediately needed they may be kept indefinitely,
together with the block, in a vial of thyme oil.

Che Hmerican Science Series.

The two principal objects of this series are to supply the
lack—in some subjects very great—of authoritative books
whose principles are, so far as practicable, illustrated by
familiar American facts, and also to supply the other lack
that the advance of science perennially creates, of text-
books which at least do not contradict the latest generali-
zations. The scheme outlines the field of science, as the
term is usually employed with reference to general education.

Barker’s Physics. ADVANCED COURSE.
By GEORGE F. BARKER, Professor in the University of Pennsylvania.
x+go2 pp. 8vo.

A comprehensive text-book, for higher college classes,
rigorous in method, and thoroughgoing in its treatment of the
subject as distinctly the science of energy. The matter is
presented under the general heads of Mass Physics, Molecular
Physics, and Physics of the A‘tther. The last division, which
occupies half of the volume, is subdivided into Energy of
Aéther Vibration (Radiation), Energy of AXther Streess (Elec-
trostatics), Energy of A‘ther Vortices (Magnetism), and
Energy of Aither Flow (Electrokinetics). hes most
approved mathematical methods of deriving the formulas
are given, but the student unacquainted with the Calculus
must of course be content to take the formulas on faith.
The illustrations are largely diagrammatic, and most of them
have been prepared especially for this work.

London Chemical News:—The| Francis H. Smith, Professor in
best truly modern manual of phy-| University of Virginia:—The work
sics in our language, is up to date as regards facts. It

Chas. R. Cross, Professor in| shows excellent judgment, in my
Massachusetis Institute of Tech-\ opinion, as to what it leaves out.
nology:—There is no other text-|.. . It is judicious in its scientific
book that seems to me so well| “ perspective,” giving due relative
adapted for high-grade teaching in| prominence to the several subdi-
general physics, visions,

2 Henry Holt & Co.
Remsen’s Inorganic Chemistry. ADVANCED CouRSE.

By IRA REMSEN, Professor in the Johns Hopkins University. xxii + 827
pp. 8vo.

A manual for higher courses. The material is arranged
according to the Periodic system. ‘The significant relations
existing between different reactions and different compounds
are constantly indicated. ‘The dynamical aspect of the science
and the constitution of compounds are carefully treated.

Remsen’s Introduction to the Study of Chemistry.
BRIEFER COURSE. xix+435 pp. 12mo. TZ%ird and enlarged edition.

This book represents the elementary course in general
chemistry in the Johns Hopkins University. The main
principles of the science are developed in the study of a
carefully planned series of experiments employing at first
only the commoner gases. After the fundamental laws, and
as an explanation of them, the theoretical aspects or geme
subject are presented. The elements and them pamem
compounds are then treated in groups, arranged upon the
Periodic scheme. Both in the discussion and in the experi-
ments, so far as practicable, questions are made to do duty
for direct statements... One chapter is devoted to gn. amie
duction to qualitative analysis and two to organic chemistry.

Remsen’s Elements of Chemistry. ELEMENTARY
COURSE. x+272pp. 12mo.

Upon the same plan as the foregoing book, but materially
simpler. It utilizes the facts of every-day experience to show
what chemistry is and how things are studied chemically, and
offers a rational course of lessons in which the endeavor is to
help the pupil to think as well as to see.

Remsen’s Laboratory Manual. xii+196 pp. 12mo.

Intended for the ‘‘ Elements,’ but can be used with the
“Introduction.” There are blank pages for students’ notes.

The American Science Series. 3

Newcomb & Holden’s Astronomy. ADvANcED Course.

By SIMON NEWCOMB, Professor in the Johns Hopkins University, and
EDWARD S. HOLDEN, Director of the Lick Observatory. xii+ 512 pp.
8vo. .

The portions in large type form a complete course for the
use of those who desire only such a general knowledge of the
subject as can be acquired without the application of advanced
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for the use of those students who either desire a more detailed
and precise knowledge of the subject, or who intend to make
astronomy a special study. A college text-book.

Newcomb & Holden’s Astronomy. Brirrer Course.
x-+ 366 pp. I2mo.

Aims to furnish a tolerably complete outline of the as-
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same matter into less space, but by omitting the details of
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greater relative prominence.

Chamberlin & Salisbury’s Text-books of Geology.
ADVANCED CoursE and BRIEFER COURSE.
By THomMAs C. CHAMBERLIN, Head Professor in the University of
Chicago, and ROLLIN D. SALISBURY, Professor in the University of
Chicago. [/z preparation.|
The general scope and character of these works may be
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college work and suited in one edition to higher, anu in the
other to lower-class men, thoroughly modern in matter and
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A Henry Holi Gc Co.

Sedgwick & Wilson’s General Biology. Parr I.
By WILLIAM T. SEDGWICK, Professor in the Massachusetts Institute
of Technology, and EDMUND B. WILSON, Professor in Columbia
College. viili-- 193 pp. 8vo.

This work is intended for college and university students
as an introduction to the theoretical and practical study of
biology. It discusses broadly some of the leading principles
of the science on the substantial basis of a thorough examina-
tion of two typical forms, a fern and an earthworm.

Bessey’s Botany. ADVANCED COURSE.

By CHARLES E. BESSEY, Professor in the University of Nebraska.
x+611 pp. 8vo.

This manual offers a general survey of vegetable life,
adapted to higher collegiate work. The first 200 pages give a
comprehensive account of the general anatomy and physiology
of plants, proceeding from the simplest to the most complex
in structure. Then comes classification, with a systematic
examination, in some detail, of all the orders. The presenta-
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Bessey’s Essentials of Botany. Brirrer Course.
xlii+ 292 pp. 12mo.

A guide to beginners. Its principles are, that the true aim
of botanical study 1s not so much to seek the family and
proper names of specimens as to ascertain the laws of plant-
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The American Science Sertes. 5

Packard’s Zoology. ADVANCED CouRSE.

By A. S. PACKARD, Professor in Brown University. viii+722 pp. 8vo.

Designed for college classes, to be used either in the recita-
tion-room or in the laboratory. It will serve asa guide to
the student who, with a desire to get at first-hand a general
knowledge of the structure of leading types of life, examines
living animals, watches their movements and habits, and
finally dissects them. He is presented first with the facts,
and led to a thorough knowledge of a few typical forms, then
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principles or inductions growing out of the facts.

Packard’s Zoology. BRIEFER COURSE. viii+338 pp. 12mo.

The distinctive characteristic of this book is its use of the
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vertebrate structure as a basis of comparison. Beginning
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whole animal kingdom until man is reached. As each of its
great divisions comes under observation, he gives detailed
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class, and bases the study of other forms on this.

Packard’s First Lessons in Zoology. ELemMentary
COURSE. viii+290 pp. 12mo.

In scope this book differs considerably from those men-
tioned above. Since it is meant for young beginners, it de-
scribes but few types, mostly those of the higher orders, and
discusses their relations to one another and to their surround-
ings. The aim, however, is the same with that of the others ;
namely, to make clear the general principles of the science,
rather than to fill the pupil’s mind with a mass of what may
appear to him unrelated facts. Classification is fully treated.

6 Henry Holt & Co.

Martin’s The Human Body. Apvancep Course.

By H. NEWELL MARTIN, sometime Professor in the Johns Hopkins
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Reproduction will be supplied when spectally ordered.

While intelligible to the general reader, it is accurate and
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The work is in use in such medical schools as those of Harvard
University and the University of Michigan.

Martin’s The Human Body. Brierer Course.
xii+377 pp. 12m0. With a chapter on Stimulants and Narcotics.

A clear, accurate, and coherent statement of the ascertained
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illustrations of, or deductions from, the doctrine of the Con-
servation of Energy and that of the Physiological Division of
Labor. The discussions are supplemented by simple directions
for demonstrating the fundamental truths of the science.

Martin’s The Human Body and the Effects of
Narcotics. viii+ 399 pp. I2mo.
An edition of the foregoing book in which. at the solicitation
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relating to narcotics has been rearranged and augmented.

Martin’s The Human Body. ELrementary Course.
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A simple and accurate outline of those broad facts con-
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which make clear the reasons, as regards health, for following
or avoiding certain courses of conduct. The action on the
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The American Science Series. ”

James’s Principles of Psychology. ApvancEep Course.

By WILLIAM JAMES, Professor of Psychology in Harvard University.
Vol. I., xii-++- 689 pp. Vol. II., vi+-704 pp. 8vo.

Treats psychology from the point of view of natural science,
leaving strictly metaphysical questions in abeyance. The
works on psychology of the older school give little or no
account of the facts recently brought to light in the laboratory.
Recent works on physiological psychology, on the other hand,
give an abundance of physical facts, but fail to trace much
connection between them and mental laws. In this book
experimental facts and theoretical inferences are treated of in
combination, so as to give to each of the successive topics a
rounded form, and to avoid pure anatomy and physiology on
the one hand, and on the other pure metaphysics.

E. H. Griffin, Johns Hopkins |
University: —An important con-
tribution to psychological science,
discussing its present aspects and |
problems with admirable breadth,
insight, and independence.

John Dewey, University of M-
chigan :— A remarkable union of
wide learning, originality of treat-
ment, and, above all, of never-fail-

ing suggestions. To me the best
treatment of the whole matter of
advanced psychology in existence.
It does more to put psychology in
scientific position both as to the
statement of established results and
a stimulating to further problems
and their treatment, than any other
book of which I know.

-James’s Psychology. BRIEFER COURSE.

xiili+478 pp. 1I2mo.

This is not simply an abridgment of the “ Principles of

Psychology.”
rewritten.

About two fifths of the book is either new or
All the polemical and historical matter and purely

speculative passages of the larger work have been omitted.

Brief chapters on the various senses have been added.

The

purpose has been to make the book directly available for

class-room use.

H. N. Gardiner; Professor in
Smith College, Mass :—\t is within
the simple truth to say that a better
text-book of psychology for college
use, one clearer, simpler, more
stimulating, does not exist.

Williston Hough, Professor in
the University of Minnesota:—
This is the book we have been
wailing for—a competent, authori-
tative treatment of physiological
psychology which is suitable for
use as a text-book.

8 Henry Holt & Co.

Walker’s Political Economy. Apvancep Course.

By FRANCIS A. WALKER, President of the Massachusetts Institute of
Technology. vilit 537 pp. 8vo. fevzsed and Enlarged.

The peculiar merit of this book is its reality. The reader is
brought to see the application of the laws of political economy
to real facts. He learns the extent to which those laws hold
good, and the manner in which they are applied. The subject
is divided, as usual, into the three great branches of pro-
duction, exchange, and distribution. An interesting and
suggestive ‘‘ book” on consumption is added which serves to
bring in conveniently the principles of population. The last
part of the volume is given to the consideration of various
practical applications of economic principles.

Walker’s Political Economy. Brirrer Coulise.
vill+ 415 pp. iI2mo.

The demand for a briefer manual by the same author gor
the use of colleges in which only a short time can be given to
the subject has led to the publication of the present volume.
The work of abridgment has been effected mainly through
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notably in the parts relating to distribution and consumption.

Walker’s First Lessons in Political Economy.
ELEMENTARY COURSE. x+332pp. rI2mo.

This book is addressed to pupils fifteen or sixteen years of
age. What has been attempted is a clear arrangement of
topics ; a simple, direct, and forcible presentation of the ques-
tions raised; the avoidance, as far as possible, Of cextama
metaphysical distinctions which the author has found per-
plexing; a frequent repetition of cardinal doctrines, and
especially a liberal use of concrete illustrations, drawn from
facts of common experience or observation.

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