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A LABORATORY GUIDE
FOR BEGINNERS IN
ZOOLOGY

BY

CLARENCE MOORES WEED, D.Sc.

RALPH WALLACE CROSSMAN, A.B., M.Sc.

BOSTON, U.S.A.
D. C. HEATH & CO., PUBLISHERS
1902

: Corvricut, 41902,
By CLARENCE M. WEED
AnD RALPH W. CROSSMAN.

Plimpton Press
He. M. PLIMPTON & CO., PRINTERS & BINDERS,
NORWOOD, MASS., U.S A.

‘PREFACE

Ir is generally conceded that a satisfactory course in
zoology requires both laboratory study of animal forms
and lecture or-text-book presentation of the laws of animal
life. The teachers most conversant with pedagogical
principles also contend that the greatest educational value
of the subject lies in the opportunity it gives to furnish
the student with an adequate first-hand knowledge of
organic evolution. To accomplish this a course in which
the pupil begins with the lower forms and works gradually
upward is necessary. For the pupil thus follows the de-
velopment of living things, seeing how each succeeding
form is an improvement over the one that went before,
and getting some idea of the great laws which govern the
growth and sequence of animal life.

In his study of these forms of life the pupil needs a
guide which shall lead him wisely without telling him too
much, and which shall stimulate him to see and to think
without bewildering. him with questions that he cannot
answer. In this little book such an attempt is made.
Since the directions were first used in my own classes
some ten years ago modifications have been made every
year, until in their present form I have found them thor-
oughly workable with average classes of beginners in
zoology.

iii

iv Preface

The directions in the introductory chapter are designed
to help the teacher in getting material for study; they are
not intended for the pupil, although the figures should be
helpful in enabling the teacher to show the class what to
look for in the case of the microscopic specimens.

In the preparation of a few of the chapters valuable
assistance has been rendered by Mr. Albert F. Conradi,
while the drawings have been made by Mr. Robert A.
Cushman. The authors are also under great obligations
to Professor J. H. Gerould of Dartmouth College, who has
kindly read the proof, and made many valuable sugges-
tions for the improvement of the Guide.

Cc. M. W.

NEW HAMPSHIRE COLLEGE OF
AGRICULTURE AND MECHANIC ARTS,
DURHAM, August, Ig02.

1

CONTENTS

PAGE
INTRODUCTION . E . , ; ‘ - iii
The Laboratory and its Baiionieat 3 : P ; - ix
The Cultivation and Preparation of Material < 7 - xi
CHAPTER
I. BRANCH PROTOZOA: THE ONE-CELLED ANIMALS I
The Ameeba . ‘ 5 . ‘ I
The Euglena. A 3 e ri . 7 3
The Paramecium . 7 2 3 . : . . 5
The Vorticella. ‘ 5 . . . F . 8
The Stentor . : 9 A . 2 7 . 7 9
The Stylonychia . : é i ‘ : - Io
The Classification of the Bint - : 2 :
I]. BRANCH PORIFERA: THE SPONGES . . - 15
The Fresh-water Sponge : . ‘ ‘ : - 15
The Marine Sponge. . ‘ . 7 - 16
The Classification of the Bonne : E 3 ; - 18
III. BRANCH CdELENTERATA: THE HypRAs AND SEA-
ANEMONES . : ; : : i 3 - 20
The Fresh-water Hyde : . 7 ‘ 2 - 20
The Campanularian Hydroid c ‘ - 7 e233
The Hydro-medusa_. 7 2 F ‘ : - 26
The Tubularian Hydroid - : . é e 27
The Classification of the Ceelenterata . : . - 29
IV. BRANCH TROCHELMINTHES: THE ROTIFERS AND
THEIR ALLIES . A : 7 . - 31
The Rotifer, or Wheel Aaitinstenlie: 5 3 « 31
The Classification of the Rotifers and their iAllies . - 33

v

vi Contents

CHAPTER PAGE
V. BRANCH ECHINODERMATA: THE STARFISHES AND
SEA-URCHINS. . : ; : : : - 35
The Starfish . ‘ : ‘ . : . : en 35
The Sea-urchin . 3 ; ‘ : 3 : . 40
The Sea-cucumber . 3 2 2 « 42
The Classification of the Heiiiaenniala 5 i - 44
VI. BRANCH ANNULATA: THE TRUE Worms . . 46
The Earthworm . . 2 - : 8 : . 46
The Marine Annelid.. : . . . - 49
The Classification of the Anoubta : : a. G2)
VII. BRANCH ARTHROPODA: ‘THE ANIMALS WITH
JOINTED LEGs . p 5 2 ij - ~ 153
The Wood-louse, or re . . . : 2 53
The Lobster, or Crayfish : : : . : . 54
The Crab. a‘ c - 5 : . : - 60
The Cyclops . ‘ ‘ : i é . . 62
The Flattened Chinibede : . ‘ . 64
The Locust, or Grasshopper . i ‘ . . 65
The Dragon-fly . F : . : . : - 68
The Butterfly : : : : : ‘i ; Hl
The Spider . : P 2 ‘ a. 9
The Classification of die Aetitiopeds 7 ‘ 3 &. 74
VIII. BRANCH MOLLUSCA: THE OysTER, ei AND
SNAILS. 7 ‘ 5 : - e 97
TheClam . ‘ : : . , : 5 ao OF
The Snail. . ; ; ; a : : . 82
The Squid . : : : - . 83
The Classification of fie iifellosea . . r ‘ . 85
Ix. BRANCH CHORDATA: THE VERTEBRATES . . 87
The Perch . : r : , ‘ é . 87
The Frog. ’ E a . : : : - 92
The Bird. ‘ . ‘ : - 98

The Classification of the Weacimies fi i : . 102

INTRODUCTION

THE LABORATORY- ITS EQUIPMENT AND THE
PREPARATION OF MATERIAL

1

Fic. 1.

U

A Movable Laboratory Table.

viii

INTRODUCTION
THE LABORATORY AND ITS EQUIPMENT

THE zoological laboratory should be a well-lighted room,
with sufficient space for each student to work comfortably.
When possible it is better not to have direct sunshine
through the windows during the hours of work.

The laboratory must be fitted with some form of desks
or tables, at which the student can work with ease. When
good-sized laboratory tables were not available, I have
found individual tables, like the one shown in Figure 1,
fairly satisfactory, especially for rooms which cannot be
permanently fitted up with more expensive desks. Such
tables have many advantages. On the one hand they are
readily movable, so that the space can be divided accord-
ing to the size of the class, no more desks being kept in
the room than are needed for use; they are made of differ-
ent heights, so that they can be adapted to individual stu-
dents; they may be shifted about as the conditions of the
light may demand; they enable the teacher to insist that
each student shall work alone, without assistance from
others; and they prevent the joggling of the microscope of
others when a pupil uses the eraser, or is restless at his
desk. On the other hand, they are liable not to rest
squarely upon the floor if it is not carefully laid, or has
become worn through use, and in the form I have used
there is no drawer in which to keep appliances. The
addition of a drawer would render them more useful.

1x

xX Introduction

The desk illustrated in the figure is twenty-seven inches
high, and is made of pine boards, one inch thick; the top
board is eighteen inches wide by thirty-two inches long.

Whenever possible, each pupil should be provided with
a compound microscope, magnifying to about five hundred
diameters. There are, of course, many forms of micro-
scopes to choose from. In selecting them, the aim must
generally be to get the best instrument for the least money.
In my own laboratory I have used with satisfaction the
Leitz Stand No. 2, with objectives 3 and 7 and eye-pieces
1 and 3, an outfit costing $17 when imported duty free.
The stand has no rack and pinion adjustment, but it
serves its purpose admirably. Similar simple forms of
American makers will probably prove equally satisfactory,
and there should be no difficulty in getting a microscope
suitable for work in elementary zoology at the price named.

If the pupils have not before used the compound micro-
scope, a preliminary exercise should be given before the
work in zoology is taken up. An excellent guide to such
an exercise will be found in Dr. Charles H. Clark’s “ Prac-
tical Methods in Microscopy,” in which there are also given
plain directions for preparing the few staining solutions
called for in this manual.

A few glass slides, cover glasses, and two or three watch
glasses are necessary for each desk. A pair of small,
sharp-pointed scissors, forceps, and scalpel are also needed,
as well as a shallow tray or dish for the dissections that
are to be done under water. Shallow pans of granite-ware,
with sheet cork embedded on the bottom in plaster of Paris,
serve very well; but the wax-lined dissecting trays now on
the market are the best of all.

The teacher should be provided with the admirable
“Text-book of Zoology,” by Parker and Haswell, the

Introduction xi

classification of which is followed in this guide, and should
have for reference as many other books on the subject as
possible. Among the more important of these, mention
may be made of the following :—

Thomson’s “ Study of Animal Life.”

“The Riverside Natural History.”

“The Cambridge Natural History.”

Claus’s “ Text-book of Zoology.”

Lang’s “ Text-book of Comparative Anatomy.”
McMurrich’s “ Invertebrate Morphology.”
Packard’s “ Text-book of Entomology.”
Comstock’s “ Manual for the Study of Insects.”
Parker’s “Elementary Biology.”

Hertwig’s “General Principles of Zoology.”
Jordan and Kellogg’s “ Animal Life.”

Jordan and Heath’s “ Animal Forms.”

It is very desirable that some book should be studied
by the class as a text-book to supplement the knowledge
obtained through the laboratory study.

THE CULTIVATION AND PREPARATION OF MATERIAL

Perhaps the greatest difficulty that confronts the inexpe-
rienced teacher of zoology is found in obtaining the mate-
rial to be studied, in sufficient quantity and in good
condition for class use. Success with the laboratory
method of instruction in biological subjects renders it im-
perative that the organism selected should be on hand in
the right conditions and at the right time. To accomplish
this, however, is no light task. The subjects are to be
taken up in a certain definite order and at certain definite
times, and the specimens studied, to be of the most value,

xii Introduction

must show the different phases of their growth. In those
cases where the organisms are sufficiently abundant in the
outer world to be available in quantity, it seldom happens
that they present the desired phases of their existence at
the time when it is necessary to study them. In a large
proportion of cases they are not sufficiently abundant out
of doors to be readily obtained in the needed quantity.

Fortunately these difficulties may to a great extent be
overcome by indoor culture of the organisms required.
For several years I have been experimenting with such
cultures, and in the following pages I have summarized
such of the results as seem likely to be of assistance to
those who use this book. The apparatus required for such
cultures is simple and easily obtained. For the aquarium
cultures, glass dishes and jars of almost any size and shape
may be used. Perhaps no one general form is so cheap
and satisfactory as the special aquarium jars recently
placed upon the market by the dealers in microscopes and
laboratory supplies. These are of convenient size and
shape for cultures of many kinds, and a dozen or more of
them are of the greatest value to the work of any zoologi-
cal laboratory. Glass covers for them should be pur.
chased. But in case these aquarium jars are not at hand,
wide-mouthed museum jars or beakers, or even fruit cans
and jelly glasses, will serve the purpose very well.

THE AMCEBA

Amcebzee may be found in the waters of ponds and
ditches, but one is more certain to have them when wanted
by providing aquarium cultures. Almost any of the
small aquaria described in these pages are likely to furnish
good amcebe, if one examines the sediment that gathers
on the sides or bottom of the vessel. I have often obtained

Introduction Xiit

with pseudopods extended; D, shape

Tue AMcaEBA: A, B, C, shapes assumed
when encysted; 2, shape when dividing. Magnified.

xiv Introduction

an abundance of fine specimens by placing small pieces
of bark from trees or pond sides in small aquaria. , After
the culture vessel has stood in a warm room two or three
weeks, remove the piece of bark from the water, and with
a fine brush scrape off on to a glass slide some of the
liquid adhering to it. Frequently there will be dozens of
amoebe in a single mount. By floating a cover glass on
the surface of the water of a jar containing amcebe and
kept in a diffuse light for a day or two, specimens may
be obtained free from sediment.

In studying the amceba, one should not be content with
small amoeboid creatures having no contractile vacuole.
The large typical specimens showing contractile vacuole
and the nucleus may be obtained by a series of such
aquarium cultures as are here described. If the aquarium
is in a north window, it is well to put it in a warm sunny
situation a few hours before studying, as the amcebz thus
become much more active, and are of greater value for study.
With such specimens the vacuole may be seen to contract,
the distinction between the endosarc and the ectosarc may
be made out, the ingestion and egestion of food particles
may be observed, and my latest classes in zoology saw the
whole process of reproduction by fission.

The nucleus may be brought out in the amoeba by
staining with iodine, methy] green, or blue, and with various
other reagents.

If the water in a culture jar in which amcebe are abun-
dant is allowed slowly to evaporate, one will often be
able to get good examples to illustrate the process of
encystment. If the jar is finally allowed to become dry
and is then stored away, the culture may be started again
months later by adding water— a method first suggested,
I believe, by Professor Herbert Osborn.

Introduction XV

THE EUGLENA

I have generally been able to get the Euglena by this
method :, place pieces of bark an inch or more square,
preferably from the edge of a pond, in the middle of a
beaker or jar holding a pint or more
of water. Set the culture vessel in a
north window and let it stand. Ina
few weeks examine the upper and under
surfaces of the pieces on the bottom,
and you are likely to find ZAuglena
viriats.

Euglenz are also likely to be found
on the sides and bottoms of many small
aquaria. I have had fine lots of them
develop in closed glass plant boxes,
which had been temporarily used for
keeping frogs. In small salt-water
aquaria containing horse-shoe crabs
they have also developed in great abun-
dance. THE GRUEN EUGLENA:

I have also obtained a fine lot of Active form. Magni-
Euglena viridis in this way: a glass net:
dish two inches high by six inches in diameter was two-
thirds filled with vegetable debris — largely pond scum —
from an old spring. It was then filled with water, covered,
and placed near a window. After standing undisturbed
nearly two months, a thick whitish scum had developed on
top, and on the sides of the dish at the surface of the
water there was a green growth composed almost entirely
of euglene.

In summer and autumn the standing water in the
vicinity of barnyards is frequently full of euglenze in

XVI Introduction

THE PARAMECIUM: 4, normal active form; 8,after treatment with acetic acid
to bring out trichocyst threads; C, conjugating specimens; JD, early stage of
fission. Magnified.

Introduction XVIl

excellent condition for study. Water from such a situa-
tion may be placed in jars indoors, and allowed to stand
some time with good results.

THE PARAMECIUM

Paramecia may commonly be developed by putting an
excess of pond-scum or other water plants in a vessel
containing water and setting the vessel in a warm, dark
closet for a week. There will then probably be a whitish
film on top of the jar; in this film you are likely to find
an abundance of paramecia. Keep the jar in a warm,
dark situation and they will continue to develop for some
time.

One of the finest lots of paramecia I have ever seen
was developed in the following way: a cylindrical jar
holding about two gallons (six inches wide by about fifteen
inches high) was nearly filled with water and then was
stocked with a mass of Cedogonium and other fresh-water
alge, obtained from a spring, October 22. An excess
of this was put in, and the jar was placed in a well-lighted
room, six feet from a window. Five days later a rather
thick film had formed on the top; it contained an abun-
dance of large bacteria of various forms, a number of

‘ ciliate and flagellate protozoa, a few desmids and diatoms,
as well as an occasional protococcus-like form. The sides
of the jar showed bacteria, desmids, diatoms, Protococ-
cus, Hzematococcus, and a few euglene. The bottom
showed an abundance of the same forms. After this
examination (October 27) I covered ‘the jar and put it
in a dark closet. On November 1 another examination
was made. ‘The white film showed many ciliate infusoria,
including some fine paramecia. Ten days later the water

Xviil Introduction

was alive with splendid examples of typical paramecia,
white in color, which showed plainly the details of structure.
Along the sides of the glass, just below the surface of the
water, a white ring was visible to the naked eye, which
under the lens was seen to be composed entirely of these
paramecia, and the sides of the jar were also covered with
colonies of Stentor polymorphus. In many. cultures since
then I have obtained these rings of paramecia. From
such rings, hundreds of specimens may easily be transferred
to the slide by means of a camel’s-hair brush or a medicine
dropper.

Paramecia are also likely to be found in many small
aquaria; they are often abundant in those in which clams
have been kept. But they can be studied to much better
purpose when they are so abundant that one can have
the large typical specimens in quantity.

The course of the food-balls in the body may be admir-
ably shown by this method: place a lot of paramecia in
a watch glass with a small quantity of water; add a little
powdered carmine to the water; cover, and examine fresh
specimens at intervals of ten minutes for an hour or more.
You will be able to trace the whole course of the food-balls
in this way.

The nucleus of Paramecium may be brought out by
staining with iodine, magenta, methyl-green, or other stains.
The trichocyst threads may be brought out by running
under the cover glass a dilute solution of osmic, picric, or
acetic acid. The form of the body is sometimes well
shown when Schultze’s solution is added.

Paramecia should be first studied under the low powers
with little or no cover-glass pressure. The normal shape
can then be seen. The pressure of the cover glass flattens
the body.” By placing a little cotton-wool beneath the

Introduction XIX

cover glass the movements of the paramecia may be
restricted so that they are more easily studied.

THE VORTICELLA

Vorticellz occur in nature in ponds and sluggish streams,
but are difficult to find in such situations in sufficient
quantity for class use.
They may be cultivated
in aquaria without diffi-
culty. They are likely
to develop in shallow
dishes containing
aquatic plants of any
kind, especially if the
dish be placed in a dark
situation. In the aqua-
rium in which such a
great quantity of para-
mecia were developed,
as described above, large
numbers of vorticelle
were also produced.
Several cultures of vor-
ticellae are desirable in
order to get the divid-
ing, the free-swimming,
and the encysted stages.
I have repeatedly ob-

P : THE VORTICELLA: 4, stalked form; B, free-
tained cultures showing swimming form; C, encysted form. Mag-

each of these forms, the "ified.

seeing of which adds much to the value of the study by
the class.

XX Introduction

THE STENTOR AND STYLONYCHIA

Stentors are generally harder to develop in indoor cul-
tures than the common infusoria. But I have usually
had them present in some one of the culture jars, frequently
in those in which paramecia are found. Stylonychia is
also generally present in Paramecium cultures.

SPONGES

Fresh-water sponges occur as bright green growths
attached to stones and wood in shallow streams. The
shade of the green is different from anything else in the
environment, and together with the distinct spongy feeling
of the organism will enable any one to recognize it. It
frequently spreads over a considerable surface.

These sponges are common in brooks, and may generally
be found in abundance in the little pools between the
large stones where the stream is rapid. They should
be studied fresh, as they do not bear confinement -in
standing water very well. The gemmules occur late in
autumn.

The salt-water sponges are common along the coast,
and may easily be gotten from pools when the tide is out.
For inland schools they may be purchased of dealers in
biological supplies.

HYDRA

This creature has a small cylindrical body, by the base
of which it attaches itself to various objects in the water,
and from the other end of which project a number of
tentacles. Both the body and the tentacles are capable
of being expanded and contracted, so that sometimes they

Introduction XxI

are long and slender, and at other times short and
thick. Their appearance when slightly magnified is
shown in the figure herewith. Two species are com-
monly found: in one the body is green; in the other it
is light brown.

Hydras are common in ponds and ditches, but are
difficult to obtain in quantities under natural conditions.
To collect them the following method is recommended :

THE HyDRA. Magnified.

Bring in from various situations in ponds or sluggish
streams small quantities of water-weeds,—as Nitella,
Spirogyra, or Vaucheria,— collecting them with a small
quantity of water in jars or cans, and labelling each so as
to know where it came from. Place the material of each
collection in a jar of clear water near a window, and let it
stand fora day or two. Then examine the jar carefully,
especially the sides near the window, for hydras. In this
a reading glass is very helpful. In case hydras are found

XX11

Introduction

in one jar, get more of the material from the same place

and treat it in the same way.

The hydras may be trans-

ferred to covered aquaria containing Vaucheria, Nitella, or
similar plants, where under favorable conditions they
will multiply and be available when wanted.

With a dozen or more aquaria containing water plants

CYCLOoPs.

Magnified.

in good condition in the
laboratory, hydras are
pretty sure to be present
in some of them. Water
snails should not be al-
lowed in hydra jars. Cy-
clops or other minute
crustacea are also likely
to be found in some of
these jars.

Marine Animals. —The
various marine forms
treated of in this book
may be purchased in
good condition for study,
at small expense, from
the Supply Department,
Marine Biological Labora-
tory, Woods Holl, Mass.,
as well as from various
other dealers in such ma-
terials.

INSECTS

It is of course necessary that insects should be collected
during the season when they are abundant. Some of them,

Introduction XX111

like beetles, grasshoppers, and crickets, may be preserved in
alcohol; while others, like the butterflies, may be kept dry,
although part of these may well be preserved in alcohol.
To collect many of the insects a net is needed. To make
it, obtain an iron wire about a fifth of an inch in diameter,
bend it into a ring about a foot in diameter, with the ends
projecting two or three inches at right angles; solder the
ends into a short piece of brass tubing. Then sew over the
wire a strip of strong muslin an inch or two wide, and to
this muslin sew a bag of mosquito netting, Swiss muslin,
or some similar fabric, about thirty inches deep. When
in the field ready to collect, cut a handle for the net, or
make one beforehand that will fit into the piece of brass
tubing.

The most convenient method of killing insects is by the
use of the cyanide bottle. To make this, take almost any
wide-mouthed glass bottle with a tight-fitting cork. Place
on the bottom two or three lumps of cyanide of potassium
(a virulent poison to be handled with great care), the size of
a hickory nut, cover these with fine sawdust, and over the
sawdust pour in sufficient plaster of Paris mixed with water
to make a layer half an inch thick. Let the bottle dry out
before inserting the cork. As already stated this cyanide
of potassium is poisonous, and of course must be handled
carefully. If desired, the bottles may be prepared at drug
stores at small cost. After the plaster is set, there is prac-
tically no danger unless the fumes of the bottle be directly
inhaled, for which there is no excuse. Keep the bottle
closed except when putting in an insect. The cyanide
fumes rising through the porous plaster will kill it almost
instantly. This cyanide bottle is to be used especially for
butterflies and moths, as well as for bees, wasps, and similar
insects, but should not be used for worms and caterpillars,

XXIV Introduction

which are more successfully killed and preserved in
alcohol.

Insects which have been kept dry for some time should
be placed in a moist chamber (a tight jar with a little water
or a damp sponge in it) for several hours to soften them
before being used.

Crayfishes for class use are easily obtained in many
parts of the United States. In the Eastern States, where
it is more difficult to get them, they may be bought of the
following firms: Middleton, Carman & Co., Fulton Market,
New York, N.Y., or Shattuck and Jones, Faneuil Hall
Market, Boston, Mass.

Live lobsters may also be bought of these or other
merchants, but the crayfishes are less expensive and more
convenient for study. —c. M. w.

LABORATORY GUIDE IN ZOOLOGY

CHAPTER I _

BRANCH PROTOZOA: THE ONE-CELLED ANIMALS

THE AMC@BA

Ir is very desirable that good-sized specimens be pro-
vided for the study of the Amoeba. Under the high
power of the microscope look for a small, granular, nearly
transparent object, which changes its outline either con-
stantly or at frequent intervals. .

I.— Notice the general nature of the movements. Are
they slow or fast? Does the Amceba always move in a
definite direction? Does it ever happen that different
parts of the body move in different directions at the
same time? Make five outline sketches showing the
changes undergone by one Amceba.

II. — Study the method by which movement takes place.
See that the outer colorless layer of protoplasm — the
ectosarc — rolls out into one or more blunt projections,
called pseudopodia, or false feet. See whether the inner,
more granular protoplasm—the endosarc—is forced
into the pseudopods by the lateral pressure of the
ectosarc. Observe the changes in the outline of the
body due to the movement of the pseudopods. In

I

2 Laboratory Guide in Zoology

case the Amceba is moving in a definite direction,
notice whether the progress is being made by means
of a single broad pseudopod or by more than one.
Determine whether a change in the direction of move-
ment is made by pushing any part of the surface of
the protoplasm outward. Is it true that the body of
the animal is thus temporarily differentiated into an-
terior and posterior parts?

III.— Watch the Amceba as it approaches some small,
one-celled plant. Wait patiently to see, if possible, the
plant-cell taken into the body of the Amceba. How is
this accomplished? Is any water taken into the body
with the plant-cell?

IV.— Focus carefully upon a round, nearly transparent
spot generally to be seen in the ectosarc: this is the
contractile vacuole. Watch this spot patiently to see
whether it ever disappears. If it does thus disappear,
watch for its reappearance.

V.—In the largest specimens look for the roundish
nucleus, more granular than the endosarc surrounding
it. If it is not visible in the living Amceba, stain the
specimen with iodine or carmine to bring it out.

VI. — One is rarely fortunate enough to see the process
of fission in the Amceba, but sometimes this happens.
If a large Amceba is seen partially divided near the
middle, watch it closely to see if division is taking
place; if so, continue watching until the process is
completed.

VII.— Draw an Ameeba, making the sketch at least an
inch in diameter: show its form, the distinction between
the ectosarc and endosarc, the contractile vacuole, and
the nucleus.

Branch Protozoa 4

THE EUGLENA

The Euglena may be found in a resting or active condi-

tion ; if resting, its form is generally almost or quite spheri-
cal. In finding and studying it, use the high power of the
microscope.

I

II.

.— Study the free-swimming movements of the active

organisms: do they always move straight ahead, or do
they sometimes twist and turn about? Watch the eugle-
noid contortions of the body; make five outline sketches
showing the changes undergone by a single specimen.
See whether the shape assumed when swimming freely
straight ahead is generally the same in different indi-
viduals: Distinguish between the anterior and poste-
rior ends of the body. Watch the animal turn round
and round on its longitudinal axis: does it show any
differentiation into dorsal and ventral regions ?

—- The direct cause of locomotion will be found in the
constant vibratory movement of a single hair-like pro-
cess, about one-half as long as the body and projecting
from the anterior end. It is to be seen most plainly in
the largest specimens. This is the flagéllum: it is a
part of the protoplasm of the body, differentiated for
the purpose of locomotion ; it is permanent in the active
form of the Euglena, and cannot be withdrawn like
the pseudopod of the Amceba. By careful focussing,
one can get glimpses of the cone-like cavity with the
apex pointing inward, from the inner end of which
the flagellum arises. This cavity serves the purpose
of mouth and gullet, into which the vibration of the
flagellum brings particles that serve as food. See
the vortex in the water caused by the movement of
the flagellum.

4 Laboratory Guide in Zoology

III.— Notice the green color of the Euglena due to chlo-
rophyl—the green coloring-matter of plants. By
means of this the creature is able to build up its sub-
stance as plants do. Add a little alcohol, and notice
what effect it has upon the color of the Euglena.

IV.— After the alcohol has thus been added, notice the
oblong bodies near the middle of the Euglena: these
are paramylum grains.

V.—In a freshly mounted specimen study the proto-
plasm at each end of the body. How does its color
differ from that of the central part of the body? Near
the front end see a distinct red spot, often called the
eye-spot. Near this eye-spot distinguish the large clear
reservoir with the vacuole beside it. The distinction
between these may be plainly seen only in the largest
and best specimens.

VI.— Stain the specimens with iodine or carmine; then
look for the nucleus, a round spot near the middle of the
body. If it does not show clearly, take a fresh slide,
treat with alcohol to dissolve out the chlorophyll, and
then stain.

VII.— Make a drawing at least an inch long, showing an
outline of a free-swimming Euglena and all the struc-
tural details you have seen.

VIII. — Study as many stages of the round Euglenas under-
going fission as youcan find. Make sketches of two or
three specimens showing different phases of the process.

Branch Protozoa 5

THE PARAMECIUM, OR SLIPPER ANIMALCULE

For a successful study of the Paramecium we must ob-
serve the animal alive in water. Find it with the low
power: it will appear as a slipper-shaped creature swim-
ming rapidly about. To prevent its escape from the field
of vision so that it may be studied with the high power, it
is often desirable to put a few fibres of cotton under the
cover glass. The same end may also be accomplished by
drawing off much of the water on the slide by means of
blotting-paper, but one should remember that the pressure
of the cover glass may thus flatten the Paramecium.

I.— Determine whether the animal moves in a definite
direction without changing its outline. Does it move
both backward and forward? By focussing carefully,
with light from the small opening of the diaphragm,
determine the cause of movement. The short delicate
hair-like processes around the margin of the body are
called cilia. Do they vibrate when the animal moves?
Can you see any difference in the motion of the cilia
when the animal is going forward and backward ?

II.— Study the animal as it swims: does it revolve on
its longitudinal axis? Can you see a spiral groove on
one side of the body? It is called the buccal-groove.
How long is this groove as compared with the body?

III. — Watch the Paramecium as it moves in and out
among the particles on the slide. How does its flexi-
bility compare with that of the Amceba? See whether
the liquid endosarc flows back and forth within the body
in response to the pressure of the ectosarc.

IV. — Determine whether locomotion is made with either
end foremost. Is the blunter or the more pointed end

6 Laboratory Guide in Zoology

usually ahead? In case either of these is generally
in advance there is a differentiation into anterior and
posterior parts of the body.

V.— As the Paramecium turns on its longer axis, notice
whether the edges of the buccal-groove are covered
with cilia; are these longer than those on the rest of
the body? Are they constantly in motion? Focus
carefully to see the gullet connecting the buccal-groove
with the interior of the body. Is this also lined with
cilia in motion?

VI.— Run some powdered carmine under the cover glass:
when the particles have reached the Paramecium,
watch carefully to see some of them taken along the
buccal-groove through the gullet and into the body.
Notice that a little water goes in also, forming a
small, round food-ball that stops near the inner end
of the gullet, surrounded by the semi-liquid endosarc.
When another food-ball is taken in, the first one will
be forced along, keeping near the side of the body.
When a third mass is taken in, both the others will be
pushed along, and thus the process will continue, the
masses following a definite course around the outer
border of the endosarc.

VII.— The course of the food-balls in the body may be
easily shown in this way: Place a lot of Paramecia
in a watch glass with a small quantity of water; add
a little powdered carmine to the water; cover, and
examine fresh specimens at intervals of ten minutes
for an hour or more. You will be able to trace the
whole course of the food-balls by this method.

VIII. — See the two round, nearly transparent contractile
vacuoles near the side of body, each about halfway
between the middle and the end. Watch them care-

Branch Protozoa 7

fully, to see the contraction: as the round spot dis-
appears see the radiating canals surrounding it. Then
see the expansion by which the vacuole resumes its
former shape and size.

IX. — The egestion of indigestible material may sometimes
be seen by patient observation. Watch one or more
particles that have completed the circuit which the
food-balls follow, and have come to rest near the pos-
terior end of the body. If you are fortunate, you will
see a slight movement of the inner protoplasm, and the
particles in question will suddenly be seen lying on the
outside of the animal. As no opening in the body
wall is visible, it is evident that the particles passed
through a temporary opening. Since this usually takes
place at the same spot, it is probable that the body wall
is adapted at this point to the performance of this
function.

X. — Stain the Paramecium with iodine by putting a drop of
the coloring-matter on the slide, and drawing it under
the cover glass with blotting-paper. This will bring
into view a large nucleus, generally near the gullet:
and perhaps also the smaller micronucleus, lying beside
the nucleus.

XI.— With a fresh mount, focus carefully along the side
of the body to see the short, dark, oval trichocysts, per-
pendicular to the surface. Run a little dilute acetic
acid under the cover glass, and watch the long, hair-
like processes —the trichocyst threads — thrown out
from the surface of the body.

XII.— Should you see one of the Paramecia with a con-
striction on each side of the body at the middle,
observe it closely: it is undergoing fission, the simplest
method of reproduction employed by this species.

8 Laboratory Guide in Zoology

XIII.— Draw a Paramecium, sho'ving the structure as
you have observed it. Make the sketch at least two
inches long.

THE VORTICELLA, OR BELL ANIMALCULE

The Vorticella is usually attached by one end to some
stationary object. Its movements thus being confined to
a narrow range, it is comparatively easy to study under
high powers of the microscope.

I. — Notice the two principal divisions —body and stalk.
Compare the animal with a bell, and see at what part
of the bell the stalk is attached: this part is called the
proximal end. Tap the cover glass gently, and notice
the sudden contraction of the stalk into a spiral and
the change in the shape of the body. Watch the
creature as the stalk straightens out and the body
resumes its previous shape.

II. — Focus carefully on the stalk to determine its structure.
Can you see a slender band — the axial fibre—on the
inside of the cylindrical outer portion ?

III. — Study the outer or distal end of the body. Watch
the ring of cilia immediately within the enlarged edge
of the bell—called the peristome — within and partly
attached to which is a flattened disk. Between the
edge of the disk and the peristome on one side, is the
mouth, which leads into the gullet. The latter is lined
with cilia, and leads directly to the inner protoplasm
of the body. Add a little powdered carmine to the
slide, and see if you can observe the taking in of the
food.

IV.—A contractile vacuole may be seen in the body near
the gullet. Watch its action. Distinguish also, if you

Branch Protozoa 9

can, in the living Vorticella the long, curved, horseshoe-
shaped nucleus. If it is not seen, stain the specimen
to bring it out.

V.— You are likely to find sometimes two Vorticellas upon
the same stalk: this represents the last stage of fis-
sion. Sometimes other stages of division will be found,
and occasionally a free-swimming Vorticella may be
seen, with a ring of cilia around the posterior margin.

VI.— Make a good-sized drawing of a Vorticella, and
sketches of any of the reproductive phases you may
have found.

THE STENTOR

Although at times the Stentor is a free-swimming body,
moving around as readily as the Paramecium, when
found attached it may be studied as easily as the Vorticella,
which it resembles somewhat in shape. It is one of the
largest of the Infusoria, being easily visible to the naked eye.

I.— Find the Stentor and study its movements with the
low power. Note the various shapes that it assumes:
sometimes it appears as a long, blunt, revolving cylin-
der, swimming through the water; at others, it stretches
out and becomes pear-shaped, usually being attached
at such times to some object by its smaller end.

II. — When a Stentor thus becomes attached, study it care-
fully. See the movements of expansion and contrac-
tion. Observe the anterior disk, and the cilia encircling
it. Add a little powdered carmine to the slide to
demonstrate the manner of feeding; see the particles
pass down the spiral groove into the endoplasm, where
they become a food-ball which is pushed farther into
the protoplasm as time goes on.

ite) Laboratory Guide in Zoology

III. — Study the contractile vacuoles. How many can you
find?

IV.— Near the middle or front of the body find a mass
of food material contained in a well-defined spherical
cavity, somewhat larger than the contractile vacuole.
This is called the excrement vacuole. Indigestible
matter from all parts of the body is forced into this
vacuole, whence it is extruded through the body wall.
Egestion may, however, take place at other points.

V.— By careful focussing, make out the longitudinal stria-
tions of the Stentor. These are due to a differentiated
portion of the ectosarc, by the contraction of which
shortening of the body takes place. Determine whether
there are cilia all over the surface of the body.

VI. — See the remarkable chain-like nucleus along one side
of the body. It can frequently be distinguished before
staining, but if it is not visible in your specimen, add
some staining solution to bring it out.

VII. — Make a good-sized drawing of the Stentor, showing
the parts visible when it is stretched out. Make also
a sketch showing its shape when contracted.

THE STYLONYCHIA

In the first search for Stylonychia remember that it is
shorter than the Paramecium, although it resembles the
latter somewhat in general shape.

I.— Observe tHe quick, jerking movement in its locomotion.
By the use of a bit of blotting-paper, draw out some of
the water on the slide, to restrain its movements so that
it may be studied with the high power. Watch the ani-
mal carefully to determine its anterior and posterior ends.
Try to see if there is a rotary movement of the body.
Determine whether it has a dorsal and a ventral side.

Branch Protozoa Il

II. — Watch the motion of the cilia on the surface of the
body, and see the effect produced by such motion. If
the Stylonychia forces itself along among the particles
on the slide, notice the flexibility of the body.

III. —Find two or three groups of spine-like processes much
larger than the cilia. Are they movable? See if you
can determine their use.

IV. — Find the gullet, appearing as a light streak near the
centre of the body. Notice the motion within the gul-
let. Trace the buccal-groove from the gullet to the end
of the body. Observe the enlarged cilia along it. Ob-
serve the relation between the buccal-groove and the
direction in which the creature moves.

V.— Run a little powdered carmine under the cover glass.
Wait a little until it reaches the Stylonychia; then see
if you can observe the passage of some of the particles
into the body. By patient watching, the course of the
food masses through the body may be traced, the pro-
cess being similar to that already seen in the Paramecium.

VI. — The indigestible particles are forced out through the
ectosarc near the posterior end. Find if you can a
mass of particles to be egested; observe intently the
surface near the base of the spines, and quick, jerky
twitchings of the protoplasm will be seen; this forces
out the particles.

VII. — Observe the contractile vacuole and the two large
nuclei; to see the latter, it may be necessary to use a
staining solution.

VIII. — Draw a Stylonychia, showing the structural char-
acters you have seen. Make the sketch at least an
inch long.

12 Laboratory Guide in Zoology

THE CLASSIFICATION OF THE PROTOZOA

The lowest branch of the animal kingdom is the Pro-
tozoa. The members of this branch are nearly all aquatic,
microscopic animals of very simple structure. They con-
sist of a single cell, or in some cases of an association of
cells, which are not, however, distinctly differentiated into
tissues. The animals of this branch consist essentially of
bits of protoplasm, each capable of absorbing food and
reproducing its kind. Food is taken into the body; its
digestible portions are assimilated, and its indigestible
parts are rejected. The food so utilized may be either
animal or vegetable in its nature.

The Protozoa may be reproduced by fission, a process of
simple division; by budding, a process in which a small
portion of the animal is divided off, separating from the
parent cell, and finally developing into a new organism ;
and by conjugation, a sexual process by which in certain
forms two or more individuals fuse together, become en-
cysted, and later split up into a large number of spores,
each of which develops into an adult organism. There
are various modifications of each of these processes.

The Protozoa are now divided by leading authorities
into five classes, namely : —

I. Rhizopoda.
II. Mycetozoa.
III. Mastigophora.
IV. Sporozoa.

V. Infusoria.

The members of the lowest class of Protozoa, the
Rhizopoda, are usually characterized by the presence of
an outer layer of protoplasm which frequently sends out

Branch Protozoa 13

temporary processes. The Ameceba is a typical example
of this class, having a nucleus, nucleolus, and contractile
vacuole. Under unfavorable conditions the Amoeba may
become encysted and remain in that condition for a long
time. Many Rhizopods are marine, secreting a covering
or shell of carbonate of lime. The shells, falling to the
ocean bottom when the animals die, in the course of geo-
logic ages form vast areas of rock. Some of the most
important animals carrying on this work are members of
the order Foraminifera.

The second class, Mycetozoa, consists of a group of
organisms which are often included by botanists among
plants, and called “slime-fungi.” They so combine the
characters of animals and plants that it is very difficult
to say definitely to which kingdom they belong. They
live upon decaying organic matter—such as leaves or
damp wood, where they appear spread out in thin sheets
of jelly-like protoplasm.

The Euglena is a typical example of the third class,
Mastigophora. The members of this group were formerly
united with the Paramecium and similar animals to form
the class Infusoria. Now, however, those creatures fur-
nished with flagella are included in the Mastigophora.

The fourth class, Sporozoa, consists of microscopic
creatures living as parasites within other animals. The
best known examples belong to the order Gregarinida,
and live in the intestines of various insects and other
Arthropods and worms.

The members of the fifth class, the Infusoria, repre-
sent the highest Protozoa. In these the protoplasm of
the cell is generally differentiated on the outside into a”
somewhat hardened covering, inside of which is the more
fluid protoplasm. All the members of’ this class are pro-

14 Laboratory Guide in Zoology

vided with short filamentous processes called cilia, which
are outgrowths of the ectosarc. In some species, these cilia
remain during the entire life of the animal, while in others
they are present only in the young, being replaced in later
life by peculiar organs called tentacles. The Paramecium,
Vorticella, Stylonychia, etc., are examples of this class.

CHAPTER II

BRANCH PORIFERA. THE SPONGES

THE FRESH-WATER SPONGE

Upon the stones of clear running streams one can
commonly see a greenish growth which at first sight is
likely to be taken for an aquatic plant. If you rub
your fingers upon it, however, you will notice a peculiar
spongy feeling, and looking closely will find it very different
from a plant. It is rather an example of the Fresh-water
Sponge. Its more important features may be determined
by means of the following outline : —

I. — Study and describe the living sponge: its color, shape,
size, surface appearance, and mode of attachment to
the object on which it rests. In living specimens or
those preserved in formalin, notice with a lens the
minute openings in the surface, and see that there are
two sets of holes, one larger than the other. Water
containing food material enters the internal cavities
through the smaller and goes out through the larger
openings, the currents being produced by ciliated cells
lining the passages. Observe also the tiny projecting
spicules which form the skeleton of the sponge.

II. — Feel the sponge with the tips of your fingers, noting
the peculiar spongy texture.

III. -— Place a very small piece of the living sponge upon
a glass slide; tease it out with needle points, put on the
cover glass, press it down firmly, and examine under

15

16 Laboratory Guide in Zoology

.the high power the margins of the sponge. You are
likely first to see great numbers of very small, round,
greenish cells; these are a species of one-celled alga —
a microscopic plant—which develops in connection with
the sponge. Notice, also, certain much larger, spheri-
cal, granular cells, having somewhat the appearance of
a resting Amoeba. Imbedded in the protoplasm of
these cells, there are likely to be many of the micro-
scopic algz just mentioned. These larger cells are
the ones that form the sponge “flesh.” Some of them
are likely to show movements similar to those of the
Ameeba, and in consequence they are called ameboid
cells. Make drawings of one or more of them.

IV.— Examine the margin of the particle of sponge:
notice the soft cells connected with the whitish, needle-
like spicules.

V.— Place a small piece of sponge in caustic potash in a
watch glass for an hour, then study the spicules under
the microscope, after they have become separated from
the tissues. Make drawings of three or four of them.

VI.— Sponges collected during autumn and winter are
likely to show peculiar yellowish spherical gemmules
in the body. These are reproductive bodies by means
of which the sponge passes through the winter.

THE SIMPLE MARINE SPONGE
(GRANTIA SP.)

This sponge is a marine animal, found commonly along
the Atlantic coast of the United States.

I.— Make a careful drawing of your specimen as seen
through a hand lens of low power. Show in the
drawing these parts :—

Branch Porifera 17

a. The general outline of the body, with its surface
roughened by the presence of innumerable spicules.

6. Beneath the rough surface of the spicules see the
inhalent pores, scattered thickly over the wall of
the sponge.

c. The expansions at the basal end by which it is
attached to the object upon which it grows.

d. The terminal osculum, the opening at the upper or
distal end surrounded by a funnel-like circlet of
spicules.

II. — Make with a sharp scalpel a longitudinal section of
the sponge. Observe : —

a. The central cavity into which the osculum opens;
this cavity is called the cloaca.

é. The many minute openings through the inside wall ,
of the sponge are called the gastric ostia.

c. In the cut surface of the sponge the numerous
parallel canals, which connect the inhalent pores
with the ostia. Make a diagrammatic drawing
showing the structure of the sponge when thus
seen in a longitudinal section.

III. — Mount some of the spicules from the inside and out-
side of the sponge and examine with compound micro-
scope. Is there any difference in the appearance of
those from the two situations? Draw specimens of each.

This is an example of sponge life. The body is supported
by the skeleton of spicules. Water containing microscopic
plants or animals which serve as food is drawn through the
inhalent pores into the parallel canals, where some of the
food particles are taken up by certain cells. Then the water
goes on through the ostia into the cloaca, and later passes
out through the large osculum.

18 Laboratory Guide in Zoology

THE CLASSIFICATION OF THE PORIFERA

The animal kingdom as a whole is broadly divided into
two great groups, — the Protozoa, or one-celled animals, and
the Metazoa, or many-celled animals. The examples
treated of in Chapter I. all belong to the Protozoa, while
the sponge is the first example of the Metazoa.

The Porifera (formerly called sometimes Spongida) is
the second phylum or branch of the animal kingdom, and
the lowest of the Metazoa.

For a long time in the early history of science the real
nature of sponges was not understood. Naturalists could
not agree as to whether they were plants or animals, or
part plant and part animal. It has, however, been
acknowledged for many years that they belong to the
animal kingdom. After this point was reached there was
much discussion as to their place in the kingdom. Some
zoologists believed that they were simply masses of single-
celled individuals living together, each for and by itself:
consequently they placed the sponges in the Protozoa. It
is now known, however, that a single sponge individual is
made up of a great number of cells, all working for a com-
mon end —the existence of the sponge individual. To do
this well, some of the cells perform the function of protec-
tion, some that of nutrition, while others serve the purpose
of reproduction. In other words, the cells of the sponge
organism are differentiated into tissues, those doing the
same kind of work forming the same tissue.

Sponges are aquatic animals of wide distribution:
although most abundant in salt water, a few small chloro-
phyl-bearing species live in fresh-water brooks and other
streams. Their lives, except when they are very young,
are spent attached to some submerged object where micro-

Branch Porifera 19

scopic animal and plant life is abundant. Sponges as we
ordinarily see them, either while living or after they have
been treated for commercial purposes, convey to us no
idea of the typical structure of the sponge. A bathing
sponge, for instance, instead of being a sponge individual,
is a colony of individuals formed by the budding and
branching of an original sponge individual. The typical
sponge has but one large crater-like opening at its top, and
several smaller openings on its sides. Water currents
enter the smaller openings, pass through the canals to an
interior cavity and escape through the large opening called
the osculum. Food contained in the water is absorbed by
the cells as it passes through the water-courses. The
outer covering of the body, the ectoderm, is a delicate
membrane composed of a single layer of flat cells. A
similar layer, the endoderm, lines the interior cavity and
the canals leading to it. Between these is the mesoderm,
some of the cells of which have developed horny fibres, or
siliceous or calcareous spicules, which serve the purpose of
a skeleton that is seen in commercial sponges, the living
cells having been rotted and washed away.

CHAPTER III

BRANCH CELENTERATA: THE HYDRAS AND THE SEA-
ANEMONES

THE FRESH-WATER HYDRA

ErTHer the green or the brown Hydra may be used for
this study. Before the specimen is placed upon the slide
beneath the microscope it is desirable that the student
examine the specimens in the culture vessel. Notice their
color, general shape, and mode of attachment. With a
camel’s-hair brush or small glass tube, remove the Hydra
to a watch glass or a glass slide with a hollow cell, holding
a little water, and study it with the low power of the
microscope.

I.— Observe the general form of the Hydra, noticing the
shape of the body and of the projections, called tentacles,
at its upper end. See that the most noticeable move-
ments are the gentle lashings of these tentacles.

II. — Study and describe the contraction and expansion of
the body and of the tentacles. These movements are
caused by the contractile power of muscle processes
attached to the inner ends of those cells which form
the outer layer of the body wall.

III. — Sometimes the Hydra moves from place to place by
bending the body into a loop and using each end as a
foot. This is not usually to be seen, however.

IV.— Watch again the slow sweeping movements of the
tentacles. Possibly you may see one tentacle lay hold
upon a small water-flea or other particle of food. If so,

20

Branch Ccelenterata 21

it is likely to pass the food to the base of the tentacle,
where, in the middle of a round projection, the mouth,
opening into the body cavity, may be seen.

V.— Make another careful study of the Hydra, endeavoring
to see the hollow nature of its body and tentacles. This
may sometimes be done by strong light when the
animal is extended. Is the body cavity continued into
the tentacles? Encircled by the bases of the ten-
tacles, see a cone-shaped extension of the body, the
hypostome. How is the mouth situated with reference
to the hypostome? Unless you are fortunate in retain-
ing the specimen in the right position, it will require
careful manipulation with needles or other instruments
in order to see clearly the mouth opening.

VI. — See that the walls of the Hydra’s body and tentacles
are made up of two layers of cells: the inner layer is
called the endoderm, and the outer layer, the ectoderm.
The colored appearance of the green Hydra is due
to the pigmented chlorophyl. Focus carefully with
strong light along the edge of the body or tentacles, to
determine whether this chlorophyl is contained within
the ectoderm or the endoderm. Make a drawing to
show the double or diploblastic nature of the body wall.

VII. — Notice that the mouth furnishes the only entrance
to the body cavity, which serves as a stomach. Food
is pushed in by the tentacles through the mouth, and
through it the indigestible matter is ejected by the
contraction of the body. Note the fact that the food
comes in contact with the endodermal cells only.
These cells alone perform the function of digestion, and
thereby exhibit a true division of labor among the cells
of the organism. The ectodermal cells obtain their
food only after it has been digested and passed through

28 Laboratory Guide in Zoology

the endoderm. True excretion, or the removal of waste
material produced by chemical changes within the cells,
is performed by the general surface of the body.

VIII..— In the ectoderm of the tentacles try to find small,
well-defined oval bodies near the margin. They are
called nematocysts, are contained within nettle cells,
and correspond in function to the trichocysts of the
Paramecium. Within this oval sac there is a long,
spirally coiled thread which the Hydra has the power of
throwing out to wound its prey. Doubtless some poison
ejected with the thread produces the wound. These
organs are put to great use in capturing food, though
none can be used a second time. You may see the
threads by drawing acetic acid under the cover glass.

IX.—Observe the Hydras in the culture jar once more.
Try to find one that has a blunt projection on the side
of its body or one that hag a small Hydra attached to it.
These are doubtless stages in the process of reproduction -
by the asexual method. There is also another way in
which Hydras reproduce their kind — the sexual method.
These processes are explained in the following sections.

X.-— Asexual Reproduction. Multiplication by this pro-
cess is called budding. A blunt process or bud appears
on the Hydra’s side, formed at first only of ectodermal
cells. This is gradually pushed out and filled with endo-
dermal cells. As the bud increases in size, a cavity,
continuous with that of the main’ body cavity of the
parent Hydra, is developed within the mass of endo-
derm. Later a mouth and tentacles are formed at the
outer end of the bud; its stalk is then constricted at its
union with the parent, and the free-swimming young
Hydra moves away. Some stages of this process of
budding may be easily found by examining all the
specimens at hand.

Branch Coelenterata 23

XI.— Sexual Reproduction. Light-colored blunt processes
formed only of ectodermal cells appear on the body
near the tentacles. Such structures are the male
reproductive bodies and are called spermaries. Their
inner cells change into sperms, and when the thin wall
holding them bursts, they go forth as free-swimming,
pointed masses of protoplasm.

XIJ. — Elevations similar to the spermaries also occur near
the basal end of the body. These are the ovaries, and
are at first similar in structure to the spermaries. Their
inner cells soon disappear, with the exception of one
large amoeboid cell, called the ovum. This soon be-
comes freed from the Hydra, and is penetrated by a
single sperm from some other Hydra. The process is
called fertilization, and the fertilized ovum sinks to a
sheltered place and soon develops into a Hydra.

You will probably be unable to study this process by
actual observation, since it is much more hidden and
complex than that of budding. Any slight swellings
on the side of the Hydras should, however, be care-
fully studied, although it may be hard to distinguish
between ovaries, spermaries, and young buds.

THE GAMPANULARIAN HYDROID
HYDRIFORM STAGE :

This little animal lives in colonies in shallow water along
the seashore.

T. — Examine through a hand lens or with the low power
the specimen in your watch glass. Notice its general
appearance. Is it attached to anything? Is there
any variation in the color? Observe the size of your
specimen.

24 Laboratory Guide in Zoology

II. — Mount the specimen on a glass slide and observe it
through the low power. Notice that the animal is
composed of two general parts; namely : —

a. A firm outer covering, called the perisarc.

é. An inner protoplasmic part — the living substance.

III. — Identify the following five general divisions of the
perisarc : —

a. The root-like expansion, called the hydrorhiza, by
which the stem is attached to whatever object it
grows upon.

6. The upright stem portion, forming the linear cylin-
drical part of the colony. This is the hydrocaulus.

c. The branches that have an open, conical, bell-like
projection on the outer ends, inside of which are
small hydra-like bodies with numerous tentacles:
the projecting parts of the perisarc are called hydro-
theca, and the hydra-like bodies are called zooids or
hydranths.

ad. Branches like those just described, but closed at the
outer ends and having protoplasm inside: these are
young hydranths in process of development.

é. Branches that have a club-shaped tip, the gonan-
gium, inside of which are small, rounded bodies, the
medusa-buds. ,

Make a drawing showing each of these parts and
label them distinctly.

IV. — Study the structure of the perisarc. Notice its thick-
ness. Is it perfectly cylindrical throughout its length?
If not, where are the variations ?

V.— Make a careful drawing of a single zooid or hydranth
with the tentacles extended. Show these points : —

a. The relation of the hydranth to the bell-like projec-
tion of the perisarc, which is called the hydrotheca.

Branch Ccelenterata a¢

6. The connection of the base of the hydranth to the
protoplasm in the stem of the perisarc.

c. The shape of the body, including its basal part, its
central part, the tentacles, the proboscis or manu-
brium upon the tip of which is the mouth.

VI.— Compare this hydranth with a Hydra. In what re-
spects does it resemble the Hydra? In what respects
does it differ from it?

VII. — Study the tentacles carefully, using as high power
as necessary. How many are there? Is the number
always the same on different hydranths? How does
their length compare with the length of the body of
the hydranth? See the little nettle cells. How are
‘these arranged?

VIII. — Study the different stages of the young hydranths.
Make drawings of two or three of these stages. Are
these young hydranths able to get food for themselves?
If not, where does the material for their growth come
from ?

IX.— Trace the connection between a hydranth and the
one next above it and next below it on the stem. Is
the protoplasm continuous? Can you find any in
which a fully developed hydranth with tentacles is next
to a partially developed hydranth?

X.— Make a careful drawing of a gonangium, showing the
club-shaped perisarc portion and. the round or oval

’ bodies inside, as well as the protoplasmic connection
with the main stem. The bodies inside are medusa-
buds. In due time they escape from the club-shaped
perisarc into the sea, where they develop into small,
free-swimming jelly-fishes, very different from the hy-
droid colony. There are thus two sorts of generations
of this animal —the fixed colony you have been study-

26 Laboratory Guide in Zoology

ing, and the free-swimming jelly-fish form. For this
reason the species is said to have an alternation of
generations.

XI.—In what part of the gonangium are the medusa-buds
largest ?

XII.—Are there any tentacles in connection with the
gonangium, or is there any way in which it can get food
from outside? If not, where does the substance of
which the medusa-buds are built up come from?

MEDUSOID STAGE OF A CAMPANULARIAN HYDROID

I. —In your study of the hydriform stage of the Campanu-
larian Hydroid you observed, in the gonangia, small
bodies called medusa-buds. If you saw well-developed
medusa-buds, you found them to be bell-shaped. When
mature, these buds break away and escape through the
opening in the distal end of the gonangium into the
water, where they become at once independent, free-
swimming animals.

II. — Compare this free-swimming Medusa to an umbrella
with the handle broken off short. The short handle is
the manubrium. In its end there is an opening, which
is the mouth. From the base of the manubrium to the
margin of the circle run four ribs of the umbrella:
these are radial canals. They open into a circular canal.
Stretching horizontally from the circular canal toward
the middle is a thin white membrane: this is the velum.
The convex side of the umbrella is called the exumbrella
or aboral surface, and the concave side is the subumbrella
or oral surface.

III. — Projecting downward from the outer margin of the
umbrella are many rather long threads: these are the.
tentacles. About how many of them are there?

; Branch Ccelenterata 27

IV.— Mount one of these tentacles on a glass slide, and
observe its structure with the low power. How are
the nettle cells arranged along the tentacles? Is there
any difference in their arrangement near the basal end
of the tentacle and near its distal end? Make a care-
ful drawing of a section from the basal part and of
one from the distal part, including in the latter the end
of the tentacle.

V.— Now examine the tentacles with the high power.
Notice the structure of the nettle cells. Make a draw-
ing showing a bit of the edge of the tentacle with these
cells imbedded in it.

VI.— See the wart-like projections along the sides of the
radial canals: these are the sexual reproductive organs.
In some specimens these produce spermatozoa ; in others
they produce eggs. The sexes are therefore distinct.

. The eggs are fertilized by the spermatozoa which have
come from other medusz. Then each develops into a
Campanularian Hydroid.

VII. — Make a careful diagrammatic sketch of a side view

of the Medusa, labelling the parts distinctly.

THE TUBULARIAN HYDROID

HYDRIFORM STAGE

* This is an animal living in salt water in rather good-
sized colonies. It resembles in many respects the Cam-
panularian Hydroid.

I. — Examine the specimen in your watch glass through
a hand lens. Is the branching different from that of
the Campanularian Hydroid? Does the colony seem
larger?

28 Laboratory Guide in Zoology

II.— Mount a small part of the specimen ona glass slide,
and observe it through the low power. Notice that
like the Campanularian Hydroid it is composed of two
general parts, viz. : —

a. A firm outer covering, the perisarc.

6. An inner protoplasmic part —the living substance.

III. — Spread the colony out upon a flat surface and make
a sketch of the whole of it. Identify the following
divisions of the colony, and label them in your drawing :
a. The root-like expansion — hydrorhiza — by which

the colony is attached to the permanent support.

6. The upright branching stem, the hydrocaulus.

c. The terminations of the branches of the hydrocaulus,
without the bell-like expansion of the perisarc which
is present in the Campanularian Hydroid.

ad. The projecting zooids or hydranths on the ends of
the terminal branches.

IV. — Examine with the low power an individual zooid.
Make a good-sized drawing in which you show clearly
the following parts, labelling them carefully: —

a. The basal connection with the perisarc.

&. The ring of long tentacles near the base of the
zooid.

c. The ring of short tentacles toward the distal end.

ad. The projecting “ proboscis” or manubrium on the
distal side of the short tentacles.

e. The mouth upon the tip of the manubrium.

V.— Study several other hydranths to see what variations
exist. Are there always the same number of long
tentacles? of short ones?

VI. — Study the tentacles under a higher power. Are there
nettle cells present?

VII.— Compare this hydranth with the hydranth of the

Branch Ccelenterata 29

Campanularian. In what respects are the two alike?
In what respects are they different ?

VIII.— Find two or three hydranths with medusa-buds
growing upon the body wall. Make drawings of these,
showing different stages of the development.

THE CLASSIFICATION OF THE CEHLENTERATA

The third phylum or branch of the animal kingdom, and
the second phylum of the Metazoa, is the Ccelenterata.
This phylum is characterized by individuals having a dis-
tinct body cavity with but one external opening, the mouth,
and a body wall composed of two layers of cells, the ectoderm
and the endoderm. Sometimes a thin or thick layer called
the mesoglea occurs between the other two. The mouth
corresponds to the mouth of higher animals, and the
body cavity into which the mouth opens corresponds to
the alimentary canal of the higher animals. The endoderm
of the Coelenterata is homologous in general with the lining
of the alimentary canal, and the ectoderm is homologous
with the skin of the higher animals.

The Ccelenterata are universally aquatic animals, occur-
ring most abundantly in salt water. There is generally a
row of tentacles around the mouth, the cavities of these
tentacles being continuous with the main body cavity ; they
aid in the capture of food’ and in locomotion. Another
characteristic feature of the branch is the possession of
nettle cells, within each of which is a minute sac containing
a fluid and a barbed filament capable of being thrown out
for stinging purposes. They reproduce by budding, by
fission, and by eggs.

The Coelenterata are divided into four classes, of which
the Hydrozoa and the Actinozoa are the most important.
The members of the first class, the Hydrozoa, are the most

30 Laboratory Guide in Zoology

typical and easily understood. Their structure is well
illustrated by the common Fresh-water Hydra. Members
of this class reproduce by budding, sometimes by fission,
and sometimes by eggs. Many marine jelly-fishes belong
to this class, although a majority of the large jelly-fishes
are included in the second class, the Scyphozoa, and a few
peculiar forms known as Comb-jellies are included in-the
Ctenophora, which forms the fourth and highest class of
the Coelenterata.

The members of the third class, called the Actinozoa,
greatly resemble, and were long thought to be, marine
plants. Here belong the sea-anemones and other soft-
bodied polyps. The coral polyps, which secrete a kind
of calcareous framework, also belong to this class. These
animals, living a fixed life, constantly reproducing by fis-
sion, have been the chief agency in building up our vast
coral reefs and islands.

CHAPTER IV

BRANCH TROCHELMINTHES: THE ROTIFER AND ITS
ALLIES

THE ROTIFER, OR WHEEL-ANIMALCULE

Finp the specimen with the low power : some are likely
to be moving about the field too rapidly to be studied;
others may be temporarily fixed at the base, and simply
moving within an area represented by the length of the
body. These are the ones to study. If none such are
found, extract the surplus water from beneath the cover
glass with a piece of blotting-paper, to quiet some of the
active Rotifers. In the study use both the high and low
powers of the microscope.

I.— Can you see two different ways of locomotion — one a
crawling movement, the other a free-swimming move-
ment? Describe each. Do the Rotifers always go
forward when moving? How does the locomotion of
the Rotifer compare with that of the Amoeba? Is there
a distinct differentiation into anterior and posterior
parts? Is the movement in a definite direction ?

II. — What decided difference can you see between the gen-
eral structure of this creature and the other microscopic
animals (like Paramecium, Stentor, or Stylonychia) you
have studied? Is the Rotifer a one-celled animal ?

III. — Study and describe the tail-like structure on the pos-
terior end of the body. Does it move from side to side,
or disappear within the body, or both?

31

32

Laboratory Guide in Zoology

IV. — Learn whether the Rotifer revolves frequently on its

longitudinal axis. Do you conclude that the animal
has a dorsal and a ventral surface ?

V.—The cause of the free-swimming movement will be

VI.

easily made out. Notice that the head appears as if a
revolving wheel were attached to its surface: in many
species there are two disks showing this motion. This
appearance is caused by the rhythmical motion of one
or two bands of cilia encircling the disks of the head.
These revolving cilia form one means of locomotion.
Notice how the contraction of the body affects its
movement.

— Study the hard, vase-shaped case into which the
extremities of the body are drawn. Observe the
degree of its flexibility as the Rotifer moves about.
This case is called the lorica; in it are crowded the
organs for ingesting, masticating, digesting, and assimi-
lating food, and for egesting waste material; also the
organs of reproduction.

VII. — Watch again the head and foot as they are drawn

in, and notice that it is then much more difficult to
distinguish the parts inside. Observe the Rotifer as it
stretches out; you will be able to see narrow bands
passing along the body beneath the lorica. Similar
bands encircle the body. These two sets form the
muscular system of the Rotifer: the movements of the
body are due to the contractile power of the muscles.

VIII. — Adda few grains of powdered carmine to the water

on the slide. When the particles come near an active
Rotifer, see the vortex caused by the movements of the
cilia. Watch for the swallowing of some of these
grains when the head is suddenly drawn into the body.
When two disks of cilia appear, the mouth may be seen

Branch Trochelminthes ‘33

between them. Distinguish if you can the gullet leading
from the mouth, and lined with cilia. The so-called
teeth are visible at the inner end of the gullet; behind
the teeth lie the stomach and intestine; the latter ends
in an opening on the under side of the lorica near its
posterior border.

IX. — Make a good-sized drawing of the Rotifer.

THE CLASSIFICATION OF THE ROTIFERS AND THEIR ALLIES

Early in the history of zoological science the Rotifers
were classified with the Infusoria. But as soon as it was
seen that they were multicellular animals, it was necessary
to remove them from the branch Protozoa and to find for
them another resting-place in the system of classification.
No place seemed more fitting than the branch Vermes,
which was formerly made to include the worms and various
related creatures. It has long been recognized, however,
that the Vermes was too heterogeneous a collection to sat-
isfy the requirements of our knowledge, so that the latest
authorities have divided it into several groups, each with
the rank of a branch or phylum. The Rotifers, and two
other less abundant classes of minute animals somewhat
resembling the Rotifers, have been united to form the phy-
lum Trochelminthes. The young of these creatures exist
in the form of a trochosphere, which becomes modified dur-
ing the development of the animal. The class Rotifera is
much the most important one in this phylum. .

Four other groups have been separated from the Vermes
and raised to the rank of independent phyla. One of these,
the Annulata, is considerably higher than the rest and is
discussed later in this book in connection with the earth-
worm.

34 Laboratory Guide in Zoology

The lowest of these branches into which the old group
Vermes has been broken up, is the branch Platyhelmin-
thes, which includes the so-called Flatworms. These are
soft-bodied, bilaterally symmetrical animals in which the
body is generally compressed above and below so as to
give a flattened appearance. There is not a distinct body
cavity. This group includes many species, some of which
live free in water of ponds and streams, while. others are
parasites; the tapeworm of man is an example of the
latter.

The next higher branch is called the Nemathelminthes,
and includes the so-called Roundworms or Threadworms,
the “ Hook-headed worms,” and the “ Arrow-worms.” In
general the body is cylindrical. The most important class
is the Nematoda, which includes the “vinegar eels” and
various small worms that live as parasites in the roots of
plants, as well as the Zrichina spiralis found in pork and
often causing disease in man.

The third group which has been separated from the
Vermes is the Trochelminthes already discussed, while
the fourth is the Molluscoida. This is composed of three
classes; namely :—

I. Polyzoa. The “Sea-Mats” and “Corallines.”
II. Phoronida. Phoronis, a worm-like animal living in
the sea.

III. Brachiopoda. The Lamp-shells.

CHAPTER V

BRANCH ECHINODERMATA: THE STARFISHES AND SEA-
URCHINS

THE STARFISH

STARFISHES furnish excellent objects for study, whether
freshly killed or preserved in alcohol or formalin. The
internal structure is best made out by dissecting under
water. Of course the larger the specimens are the more
satisfactory will be the results. Dried specimens are
desirable for the study of the outer surface.

EXTERNAL ANATOMY

I. — What gives the animal its star-like appearance? Dis-
tinguish the flat ventral surface from the more rounded
dorsal surface. To understand that the body is pentag-
onal-shaped, imagine the rays cut off at their bases.

II. — Compare the animal’s symmetry with that of the frog.
Notice the apparent absence of anterior and posterior
ends. Such an arrangement may be called radial sym-
metry. The following method, however, will enable
you to understand that the arrangement of parts ap-
proaches a bilateral symmetry, or such an arrangement
of parts that the whole may be divided into two similar
halves: Find a smooth circular white, yellow, or orange
spot — the madreporite — near one side of the dorsal
disk and near the angle formed by two adjacent rays.
Will an imaginary line drawn from the madreporite
across the starfish divide it into two similar parts?

35

36 Laboratory Guide in Zoology

III. — With a pocket lens observe quite carefully the ap-
pearance of the rough dorsal and lateral surfaces. Find
as many kinds of projections as you can. The hard-
pointed projections, or spines, are developments of the
body wall, and are used for purposes of protection.
Around the bases of the spines are the forceps-like
pedicellariz.

IV. — The soft blunt projections are hollow processes of the
body wall. They allow the fluid of the body cavity —
visceral fluid — to come into contact with the external
water and air, and are called papule or respiratory ceca.

V.— Find a small anal opening, lying near the centre of the
dorsal disk on a line drawn from the centre of the
disk to the angle formed by two rays.

VI. — Place the animal upon its back, and observe its ven-
tral surface. Notice the five grooves, one in each ray,
terminating internally at the side of a pentagonal-’
shaped depression. Because these grooves contain
organs of locomotion they are called ambulacral
grooves.

VII. — Notice that beneath this pentagonal-shaped depres-
sion a colorless membrane with a small opening in its
centre is stretched. This is the peristome, and the
opening in the peristome is the mouth. The peristome
is connected with the wall of the alimentary canal.

VIII. — Observe the kind of organs that fill the ambulacral
groove. They are short, cylindrical structures called
ambulacra or tube feet. How many rows in each groove?
The tube feet are a part of quite a complicated system
which serves the function of locomotion and possibly
of respiration.

IX. — With the forceps, push aside the two inner rows of
tube feet, so that you can look down into the very roof

Branch Echinodermata 37

of the groove. See if you can find there a small,
white thread-like structure —a nerve trunk — sending
out branches to the feet. Follow this to the end of the
ray, where it ends in the midst of a little bunch of
spines. Look at this bunch of spines carefully with a
pocket lens. Examine the termination of each ray in
this way. Is there any connection of the nerve trunk
with the red spot at the end of the arm? This spot is
sensitive to light, and for that reason is called the eye-
spot. Follow the nerve trunk to its inner termination
at the base of the ray. Is it connected with the circu-
lar nerve ring, surrounding the peristome and the
mouth ?

INTERNAL ANATOMY

X.— With sharp-pointed scissors, remove the integument
from the dorsal surface of one of the rays, being very
careful not to disturb any of the underlying parts.
Remove also the body wall from the main dorsal sur-
face, leaving the madreporite untouched. Be espe-
cially careful to harm none of the internal organs when
removing this part of the body wall.

XI.— Observe the following structure: Two long pointed,
brown, lobulated bodies lie side by side, nearly filling
the ray from base to tip. These are digestive glands
(that is, organs the cells of which secrete a digestive
fluid); they are called hepatic ceeca.

XII. — Notice the colorless ducts running along the centre
of these masses, uniting near the bases of the ray.
Follow up this common duct, and see that it empties
into a flat, membranous, pentagonal-shaped sac, a part
of the stomach called the pyloric sac. Below this is
the stomach proper, with which the pyloric sac is con-
tinuous.

38 Laboratory Guide in Zoology

XIII. — Above the pyloric sac is the intestine, but on ac-
count of its small size it was probably torn away with
the body wall. Make out a similar connection between
the pyloric sac and the digestive glands in the other
rays.

XIV.— Upon the surface now exposed, muscles were ar-
ranged which lifted the rays and moved them from
side to side. They were probably cut away when the
integument was removed. Try to find parts of them
extending from the centre of the body along the me-
dian line of each ray.

XV.— Turn back both hepatic coeca and observe the
stomach carefully. Notice its large, blunt projection,
the cardiac pouch, extending into each ray a short dis-
tance. Push this carefully aside, and see the narrower
part below, corresponding to an esophagus or gullet,
into which the mouth opens.

XVI.—On each side of the ray, at its very base, and
attached to the walls separating that ray from the adja-
cent rays, find two small white or orange colored lobed
bodies, shaped something like a single digestive gland:
these are the reproductive bodies. At the place of
attachment, there is an opening in the body wall for the
passage of the contents. See if there are two, similarly
placed, in each of the other rays. These organs are
either ovaries or testes; that is, the sexes are separate.
The eggs are fertilized, and the development of the
young starfish takes place outside of the body.

XVII. — You will notice a very interesting arrangement of
the parts now exposed on the floor of the ray. Keep
the specimen constantly under water. See four rows
of colorless, inflated, closed tubes: they resemble in
arrangement the tube feet just below them on the

Branch Echinodermata 39

under side of the ray. These structures are called
ampulle (a single one is called an ampulla), and are
directly connected with the tube feet. In fact, an
ampulla is an enlarged extension of a tube foot. At
the junction of the ampulla and the tube foot, there is
a short tube connecting them with a-long one which
passes close to the nerve trunk along the roof of the
ambulacral groove.

This long tube passes the entire length of the ray,
and connects with a pentagonal, or rather circular, tube
around the peristome. Carefully push aside the parts
lying beneath the madreporite, and you will see a long,
hard, white tube extending downward. This is called
the stone canal. Does it connect with the circular
tube just mentioned? The madrepgrite is very finely
perforated, and through these openings water passes
down the stone canal, filling the circular tube. From
the circular tube the water passes along the radial
tubes in the arms, and from them into the short branch
tubes leading to the ampullze and tube feet. The
whole system is called the water-vascular system. A
patient study is required to understand well the ar-
rangements of parts in this system.

XVIII. — Learn how locomotion is performed by the water-
vascular system. As has been said, the system is filled
with water through the pores of the madreporite.
Water is forced from the ampullz into the tube feet,
throwing them forward. The contracting walls of the
tube feet then force the water back into the ampulle,
and suction makes the feet stick to the surface upon
which they were lying. The body may be then drawn
forward and the operation of extending the feet re-
peated. From what you know of the animal’s mode

40 Laboratory Guide in Zoology

of locomotion, would you say that it possesses anterior
and posterior parts?

XIX.— The blood system you will probably be unable to
make out. It has the same general arrangement as
the nervous and water systems, that is, a circular ring
around the peristome, which sends out five branches of

1 vessels, one to each ray.

XX. — Dissect each of the remaining rays, varying the
operation to suit the necessity of clearing up any
points not at first understood. Make drawings.

THE SEA-URCHIN

The Sea-urchin lives along the seacoast, and may often
be found abundantly in pools among the rocks when the
tide is out. Two species are common along the Atlantic
coast.

I.— Notice the general appearance of the animal — the
spheroidal shape of the body, and the spines with
which it is covered. See that one side is more flat-
tened than the other; this is the oral surface, while
the other is the aboral surface.

IT. — Examine the oral surface carefully. See the central
mouth opening, with its five projecting calcareous teeth,
and the more or less membranous area surrounding it;
this area is the peristome. See whether that part of
the peristome next to the mouth opening is thickened.
Find also the small calcareous ossicles which give
strength to the membranous peristome. Make a draw-
ing of the peristome and mouth.

ITI. — Find along the outer margin of the peristome a great
many of the movable ambulacra or tube feet, each end-
ing in a sucker-like disk. Each of the ambulacra con-
sists of a cylindrical basal portion, which in the living

Branch Echinodermata 41

animal can be greatly lengthened, and the disk-like tip
by means of which it holds on to objects. Make a
drawing showing the structure of the sucker-like tip.
The flat central disk is supported by a calcareous plate.

IV.— In addition to the numerous ambulacra on the outer
margin of the peristome, find five pairs with somewhat
larger tips surrounding the mouth. See between the
pairs of ambulacra the groups of pedicellarie, appearing
as miniature forceps on slender stalks. Are these
present on other parts of the body?

V.— Find other ambulacra among the spines over the rest.
of the body. How generally are they distributed ?
VI.— Extract at its base one of the long spines with which
the body is covered. Study it with a hand lens and
make a careful drawing showing the following parts : —

a.
é.

a

da.

The basal piece extracted from the body wall.

The membranous part by which the spine is attached.
The long spine proper, with its tapering surface
fluted longitudinally.

The flattened tip, with its polished tooth-like
surface.

VII. — Dissect out the flexible basal part of the spine to see
the ball and socket joint. Make a diagrammatic sketch
showing the structure accurately.

VIII. — Describe the arrangement of the spines with ref-
erence to the mouth, noting especially the differences in
the length and the structure of the tips.

IX. —

Make a careful drawing of the spineless aboral area

on the side opposite from the mouth. Show the four
anal plates; these form the periproct.

X.— Study now a specimen on which the spines and soft
parts have been removed by soaking for a few days in
a strong solution of caustic potash. On the aboral sur-

42 Laboratory Guide in Zoology

face notice the space formerly occupied by the peri-
proct. Notice that around it are five genital plates,
each having a small hole near the apex; these are the
reproductive openings. See that one of the plates is
larger than the others and is full of minute perforations ;
this is the madreporic body. Make a drawing of the
aboral surface of this specimen.

XI. — Study the oral surface of the same specimen. Notice
the large opening formerly occupied by the peristome.
What shape is it? Notice the five interradial sutures”
from the tip of each genital plate to the corresponding
angle of the mouth pentagon. See the double rows of
polished prominences for the attachment of the spines.
See also the zigzag ambulacral suture running between
each double row, and the double rows of ambulacral
pores on each side of the double rows of spines.

THE SEA-CUCUMBER

The Holothurians or Sea-cucumbers are strange crea-
tures that live in the ocean. They form a separate class
(Holothuroidea) of the great group to which the starfish
and sea-urchin belong. They have a water-vascular sys-
tem similar in general to that of the starfish.

I.— Make a drawing showing the general shape of the body
and the position of the tentacles, as well as of the mouth
and of the anal opening.

II. — Describe the number, size, shape, and position of the
tentacles.

II]. — Examine with a hand lens the ambulacral suckers with
which the body is covered. Make a drawing of one of
these, considerably magnified. Are these more abun-
dant on the lower side of the animal? On the upper
side, are they more abundant near each end than in the

Branch Echinodermata 43

middle of the body? Can you see that these ambulacral
’ suckers are arranged in five broad bands?

IV. — Cut the body wall longitudinally on one side to lay
open the central cavity. See the long much-coiled ali-
mentary canal. Notice the structure of this canal; next
the mouth is an esophagus ; below this is a well-defined
stomach; next comes the long, convoluted intestine,
which is small in size throughout until it opens into
the larger cloaca, at the posterior end. Make a sketch
of the alimentary canal, labelling each part.

V.— Remove the intestine, leaving the other parts of the
canal intact. The most noticeable objects now visible
are the genital gland, the respiratory tree, and, the five
sets of longitudinal muscles.

VI. — The genital gland is near the middle of the upper half
of the body cavity. It looks like a sort of brush, being
composed of many slender filaments lying side by side.
Notice that the duct leading from these extends to an
opening between two of the tentacles. (The genital
gland may be the ovary or the testes, as the sexes are
separate. )

VII.— Trace out the two main divisions of the respiratory
tree with their many branches. Notice the connection
of each half with the cloaca. In this way fresh sea
water reaches them.

VIII.— Study the five sets of longitudinal muscles, extend-
ing up and down the body walls. Trace these out
carefully and describe them. Notice also the circular
fibres which strengthen the body wall.

44 Laboratory Guide in Zoology

THE CLASSIFICATION OF THE ECHINODERMATA

The starfish is perhaps the most typical representative
of the branch Echinodermata, which includes also the sea-
urchins, the sea-slugs or sea-cucumbers, the sea-lilies or
feather-stars and the brittle-stars. In the members of this
phylum the arrangement of the parts in a circle around a
common centre is the’ most striking general character.
This is obvious in the starfish, and may easily be seen in
the other members of the group. There is also a calcare-
ous outer skeleton which varies much in its texture, but
the frequency with which it is furnished with spiny pro-
jections led to the name Echinodermata. All members of
the phylum live only in salt water. There are two open-
ings to the alimentary canal. There is also a distinct
nervous system, a circulatory system, a water system for
locomotion, and other complicated organs.

There are five principal classes of the Echinodermata,
namely :—

I. — Asteroidea. The starfishes are the typical representa-
tives of this class. They abound in almost every sea,
and may be found partly buried in the sand or con-
cealed beneath the shelter of the rocks. As the name
implies, they are star-shaped, generally with five rays.
In color they vary considerably, but they are com-
monly some shade of yellow, orange, or red.

II. — Ophiuroidea. This class is made up of the peculiar
sand-stars and brittle-stars, which have the arms longer
and more distinctly separated from the central portion
of the body than do the starfishes.

III. — Echinoidea. The spiny sea-urchins form this group.
In these the arms are absent, the body being rounded,

Branch Echinodermata 45

and covered with a shell made up of closely united plates
of a calcareous nature, to which stiff spines are attached.
Sea-urchins live in rocky holes and crevices along the
borders of the ocean, where they feed upon molluscs and
seaweeds. Their mode of locomotion is similar to that
of the starfish, although the movement is much slower.

IV. —Holothuroidea. The strange sea-cucumbers or sea-
slugs belong to this'class. In these the body is elon-
gated and covered with a thickened leathery wall.

' Around the mouth is a ring of tentacles. These slug-
gish creatures live in the ocean, especially in tropical
regions.

V.— Crinoidea. The members of this class are commonly
known as feather-stars or sea-lilies. They are com-
paratively few in number, and for the most part being
fixed to the bottom of the sea, they are seldom found.
The star-shaped body is usually attached to a stalk.
In former geologic times crinoids were very abundant ;
the formation of vast limestone areas is attributed to
the gradual accumulation of their remains.

CHAPTER VI

BRANCH ANNULATA: THE TRUE WORMS

THE EARTHWORM

For the purposes of this study both living and dead
earthworms should be provided. The larger the specimens,
the more satisfactory will be the results. Kill some of the
worms by enclosing them in a covered dish containing a
little ether or chloroform. If the internal anatomy is to
be studied in such freshly killed specimens, they should be
dissected under water in a shallow dish having the bottom
covered with wax or sheet cork. The internal anatomy
may also be studied in specimens hardened in alcohol,
although some of the more delicate parts are likely not to
show so well as they do in fresh specimens.

MOVEMENTS AND EXTERNAL ANATOMY

I.— Place a living earthworm on a sheet of paper.
Watch its movements. Determine which is the anterior
end and which the ventral surface. Is it able to move
backwards? By what means does it move? Is there
a decrease in diameter when the worm stretches out?

II.— Find the bristle-like seta on the ventral surface.
How many rows of them are there? Toward which
end of the body do the tips of the setee point?

III. — Notice how the earthworm is divided into narrow
rings, or segments, throughout its length. Study the
first segment; the lip-like projection above the mouth
is called the prostomium.

46

Branch Annulata 47

IV.—A few segments back of the head find a ring-like
swelling of the body: this is the clitellum. It is more
prominent in some specimens than in others.

V.— Examine the external surface carefully for openings
through the skin. The mouth and anal openings are
easily found. Find a small pore in the grooves between
successive segments behind the tenth along the mid-
dorsal line; these communicate with the body cavity
and will sometimes emit a milky fluid when the animal
is irritated. On the ventral side of the fourteenth seg-
ment find two small openings, the external terminations
of ducts leading from the ovaries. The external open-
ings leading to the seminal vesicles will be found in the
fifteenth segment. Draw a side-view of the earthworm.

INTERNAL ANATOMY

VI.—Pin the specimen to the bottom of the dissecting
dish with its ventral surface downward, by inserting
one pin through the prostomium and another through
the posterior segment, stretching the body a little.
With sharp-pointed scissors cut through the very thin
body wall, near to and parallel with the dorsal median
line. Be careful not to cut too deep. Notice the
many transverse partitions joined to the inner surface
of the body wall. Determine whether they correspond
to the constrictions between the segments. Cut these
partitions carefully down each side close to the body
wall, and pin down the flaps of skin thus laid open.

II.— The alimentary canal is now exposed. Notice that
it passes directly through the partitions between the
segments. See the dorsal blood-vessel along the top
of the alimentary canal. Near the eighth and ninth
segments, find branches running from this dorsal blood-

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Laboratory Guide in Zoology

vessel around the alimentary canal to join the longi-
tudinal ventral blood-vessel. These aortic arches form
the centres of the blood system.

VIII. — The most conspicuous bodies now exposed are the

IX.

white-lobed seminal vesicles in the tenth and eleventh
segments. They are connected by ducts with external
openings on the ventral surface of the fifteenth seg-
ment.

— The alimentary canal is composed of five parts,
named as follows, beginning at the anterior end:
pharynx, esophagus, crop, gizzard, and intestine: Dis-
tinguish each. The pharynx is continuous with the
mouth and has light-colored muscular walls; it extends
to about the seventh segment. The esophagus is a
straight tube, generally extending from the eighth to
the sixteenth segments. Near the sixteenth segment
the alimentary canal is enlarged, forming a sort of thin-
walled pouch; this is the crop. Directly back of it is
the muscular gizzard. The rest of the canal forms the
intestine. Make a drawing of the canal.

X.— Over the pharynx, near the anterior end, find two

XI.

small white oval bodies, which form the central part of
the nervous system: they are the cerebral ganglia. Re-
move the intestine carefully, and find a white ventral
nerve cord extending longitudinally.

—The ventral blood-vessel will be found extending
longitudinally below the alimentary canal. It may be
necessary to use another specimen in order to demon-
strate it.

XII. — Carefully push aside the alimentary canal from

about the eighth to about the fourteenth segment. The
very small white bodies to be seen in the base of the
thirteenth segment are the ovaries. Near these are two

Branch Annulata 49

short funnel-shaped tubes, the oviducts, which pass
through the partition to the fourteenth segment, and
thence through the body wall to the outside. These
furnish an exit for the contents of the ovaries.

XIII. — Between the ninth and tenth, and between the tenth
‘and eleventh segments, find two pairs of white pear-
shaped bodies; these are the seminal receptacles.

XIV.— Beginning with about the fourth segment, find in
the base of each segment except the last, and attached
to the posterior surface of the septum in front, long,
somewhat coiled, tubular organs. One end is free, but
terminates in thenextanterior segment by passing directly
through the partition : the other end communicates with
the exterior. These are excretory organs called nephridia.
They are brought out distinctly by blowing alcohol upon
them through the tube of a wash bottle.

THE MARINE ANNELID
(NEREIS VIRENS)

This curious worm lives in the mud along the seashore
and the bottoms of tide marshes. It is of special interest
because it shows a more highly differentiated structure than
does the earthworm.

I.— Study and describe the general shape of the body.
What are the most important ways in which it differs
from the earthworm? How many segments are there?

II. — How do the appendages along the sides of the body
compare with the segments in number? Is it easier to
distinguish the anterior and posterior ends than in the
earthworm ?

III. — Study the head: it has no appendages that project
laterally from the sides, and is divided into two general

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Laboratory Guide in Zoology

parts —a small anterior part, the prostomium, a large
posterior part, the peristomium. Make careful draw-
ings of the upper and lower views of the head and the
first three segments back of it.

IV. — Study the prostomium. Is it distinctly differentiated

from the peristomium? Notice the central lobe btar-
ing in front the two club-shaped tentacles. Are they
segmented? See on each side of this central lobe the
large conical palpi, distinctly segmented. Find the
small black spots which are the eyes. How many are
there?

V. — Study the peristomium : on each side in front are the

VI.

two cirri, each double. Find the mouth. Sometimes
this is extended and shows the two black, serrated
mandibles.

— Study the lateral appendages of the body segments,
—they are the parapodia. Are they of the same size
throughout the length of the animal? Remove with
forceps one of the parapodia, and examine it with a
low magnifying power —a simple lens will do. Dis-
tinguish two general parts—the dorsal and ventral
lobes. On which is a large subtriangular blade — the
gill? Which bears the most spinose sete? Treat a
parapodium with caustic potash solution to bring out
the spinose acicula. Make a careful drawing of a para-
podium showing its parts and its basal connections.

VII. — Lay the worm on the-bottom of the dissecting tray,

ventral side down. Cut longitudinally along the median
dorsal line, and pin down the cut edges on each side.
See how the body cavity is segmented.

VIII. —Study the alimentary canal: see how the mouth

opens into the pharynx, which in the living worm can
be protruded; and how the pharynx leads into the

Branch Annulata 51

cesophagus, and the latter into the long intestine which
extends to the posterior end. Can you see a small gland
on each side of the cesophagus? Where do these glands
empty? Do the constrictions of the intestines corre-
spond to the divisions of the segments? Notice the
mesentery below the intestines, binding it to the body
wall. The mesentery of the upper part was: probably
destroyed when the body was cut open.

IX. — Cut open the pharynx: notice the powerful muscles
and the two conspicuous black teeth which may be
seen on the outside in those specimens in which the
pharynx is protruded.

X.— Trace out as well as you can the blood-vessels and
the nerve system.

52 Laboratory Guide in Zoology

THE CLASSIFICATION OF THE ANNULATA

The earthworm is atypical representative of the phylum
Annulata, nearly all the members of which have an elon-
gate body divided into numerous segments, with an internal
partition between each of the segments. There is a well-
developed alimentary canal, a distinct body cavity, a system
of blood-vessels, and a nervous system with cerebral
ganglia and ventral nerve cord which is double, and gener-
ally shows a series of ganglia along the segments. The
members of the phylum also have nephridia, or pairs of
tubes leading from the body cavity through the body wall
and serving as organs of excretion.

This phylum is divided into four classes, namely : —

Class I. Chetopoda. The Earthworm and Nereis.
Class II. Gephyrea.

Class III. Archi-annelida. Polygordius and its Allies.
Class IV. Hirudinea. The Leeches.

Of these four classes the first and fourth contain the most
generally known members of the branch. The second
class, Gephyrea, is exceptional in its characters, in that the
members of it are not segmented when adult, although they
show the segmented condition during their development.

CHAPTER VII

BRANCH ARTHROPODA: ANIMALS WITH JOINTED LEGS

THE WOOD-LOUSE OR SOW-BUG

THESE curious creatures may be obtained in abundance
under boards and stones, especially in moist situations.
For this study, get as large specimens as you can find.

I. — Notice the segmented character of the body. See if
you can easily distinguish the three divisions of the
body — head, thorax, and abdomen.

II. — When the animal is viewed from above, the head is
what appears to be the first segment. Determine the
limits of the head by looking at it from both sides.
Notice its mode of attachment to the first segment of
the thorax.

III. —To distinguish between the thorax and abdomen, look
for a place where there is a decided difference in the
size of two adjoining segments as seen from above.
How many segments has the thorax? How many has
the abdomen ?

IV. — Returning now to the head, study the long, jointed
antenne. Compare the segments of these with the seg-
ments of the legs. Istherea similarity? Notice the ag-
gregation of simple eyes near the base of each antenna.

Unless the specimens are quite large, the mouth parts
are not easily distinguished by beginners. The jaws,
maxilla, and upper and lower lips come close together in
a point. The tips of the jaws are black.

53

$4 Laboratory Guide in Zoology

V.— How many legs has each segment of the thorax?
Make a drawing of one of the legs as it appears under
the lens, showing distinctly in the drawing the parts of
which it is composed. In female specimens, there is a
thin membrane or covering —the egg pouch — on the
ventral surface of the thorax at the bases of the legs.

VI.— Study the plate-like gills on the ventral surface of the
abdomen. Why should these creatures be found only
in moist situations?

THE LOBSTER, OR CRAYFISH

The lobster is one of the most satisfactory animals to
study. It is better to have fresh specimens that have not
been boiled, but if these are not easily obtainable, boiled
specimens may be substituted. In regions where cray-
fishes are abundant, these may be used instead of the
lobster.

EXTERNAL ANATOMY

I.— Does the lobster show a more marked bilateral sym-
metry than the earthworm? Study the hard, strong
covering of the body; this is a true outer skeleton or
exoskeleton. Notice the soft, pliable places in the
skeleton which permit the bending of the body. These
places differ from the rest of the skeleton only in
having no calcium.

IJ. — Axial Arrangement. In the axial arrangement of
parts what resemblances can you find between the
earthworm and the lobster? Both have a ringed or
segmented structure, but in the lobster this is shown
only in the posterior part of the body. Notice that
the body axis is separated into two great divisions.
The anterior one includes the head and thorax, closely
united, and is called the cephalothorax. The posterior

Branch Arthropoda Re

division comprises the remaining part of the animal,
and is called the abdomen. Fix carefully in mind the
precise boundary of these two great divisions, by bend-
ing the abdomen back and forth to see its mode of union
with the cephalothorax. The braad, unsegmented cov-
ering of the cephalothorax is the carapace, and its
toothed projection between the eyes is the rostrum.
Near the middle of the carapace find a distinct trans-
verse suture ; this represents a somewhat indistinct divi-
sion between the head and thorax, and for that reason
is called the cervical suture. ’

III.~—- Abdominal Somites. Find the seven distinct ring-
like segments, or somites, that form the abdomen. In
any single somite distinguish the following parts:
(1) The broad, dorsal part is the tergite. (2) The nar-
row, ventral part of the ring is the sternite. (3) The
pointed, somewhat curved part which forms each side
is the pleurite. Notice how the seventh, or the last,
segment, the telson, differs from the others.

IV.— Abdominal Appendages. On the sternite of each
segment find a pair of jointed movable organs, the
swimmerets. Examine a single one of these, and find
that it is made up of a basal part, the protopodite and
two branches; the outer branch is the exopodite and
the inner branch is the endopodite. Examine other
swimmerets to confirm this structure. Those of the
first and second abdominal segments are usually modi-
fied, and in the female are sometimes wanting. The
swimmerets of the sixth segment are so much enlarged,
and so like the hard parts of the skeleton, that they
will not at first be recognized as swimmerets. The
exopodites and endopodites of these swimmerets to-
gether with the telson form the tail fin of the lobster.

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Laboratory Guide in Zoology

V.—Somites of the Cephalothorax. From a ventral view
notice how small are the sternites of the thoracic seg-
ments. This is caused by the enlargement of the
basal joints of the appendages. The unbroken sides
of the carapace wepresent the united pleurites of the
various thoracic somites. Follow carefully the irregu-
lar outline of the carapace, and indications of the seg-
mented structure will be seen. In general it may be
said that each pair of limbs on the cephalothorax repre-
sents a single somite.

VI.— Appendages of the Cephalothorax. Study carefully
the following parts : — ‘

a.

é.

The four posterior, nearly uniform, appendages are
the legs used for walking.

The much larger pair, just anterior to these, are
used for capturing and crushing food, and are called
chelz,

Directly in front of the chelz find three pairs of
appendages drawn closely to the body. These are
of the nature of legs, but since they serve to pre-
pare the food for the mouth, they are called
maxillipeds.

. The two appendages directly anterior to the maxilli-

peds are the true maxilla. Notice the scoop-like
structure held by the second maxilla: it is called the
gill scoop.

In front of, and beneath the maxillz, are the hard-
toothed jaws, or mandibles. Move them back and
forth to see their mode of action. Is it from side
to side, or up and down?

The long tapering structures with large basal segments
are the antenne: they serve as organs of touch.

. The somewhat similar, but two-branched and shorter,

Branch Arthropoda 57

pair directly in front of the antenne are the anten-
nules, serving the same function as the antenna and
probably that of smell. Each also contains in its
basal part an organ of equilibration.

hk. The jointless stalks protruding from either side of
the rostrum are the eye-stalks, tipped with the
eyes. Examine them to learn the field of vision pos-
sessed by the lobster.

VII. — Breathing Apparatus. With strong scissors remove
one side of the carapace. The light-colored, many-
lobed organs thus exposed are the gills, or breathing
apparatus of the lobster. They are bathed in the water
that flows under the overhanging carapace. Move the
legs back and forth, and see the relation between the
legs and gills. Move the maxilla to which the gill-
scoop is attached, and observe how a stream of water
may thus be made to pass under the carapace. The
blood passes through the gills, thus coming into very
close contact with the water, to which it gives up its
carbonic acid and from which it receives its oxygen.

VIII.— External Openings. Find the mouth, tightly cov-
ered by the mandibles and maxilla. On the ventral
side of the telson, find a short longitudinal slit, the anal
opening. Examine the basal segments of the third and
fifth legs, to find the small external openings of the
reproductive organs. Those of the female will be
found in the basal segments of the third pair, and those
of the male in the basal segments of the fifth pair. But
one kind of reproductive organs will be found in an
individual. Compare this with the case of the earth-
worm. On the basal segment of each of the antennz
find a single small opening, the outlet of the excretory
organs. On the upper surface of the basal segment

58 Laboratory Guide in Zoology

of each of the antennules find a peculiar structure,
the organ of equilibration.

IX.— Comparison of Appendages. Remove one of the
chele, study and number its parts. Remove, study
in the same way, and compare with the chelz, one of
the first or second walking legs. Go through the same
process with one of the fourth walking legs. Review
the entire row of appendages, and note that all are in
pairs, and that they are nearly all jointed, and possess
branched terminations. Regarding each pair of ap-
pendages as representing a single somite, determine the
number of somites of which the lobster may be said to
be made up. Draw a side view of the animal.

INTERNAL ANATOMY

X.— Muscular System. Remove, with strong knife or scis-
sors, the tergites of the abdominal segments, cutting
away the muscles attached to them. The white masses
filling the abdomen are the strong muscles, and form
the edible flesh of the lobster.

XI.— Blood System. Remove in a similar manner the
entire top of the carapace, being very careful to dis-
turb none of the organs below. Near the centre of
the thorax, find exposed a soft, plastic, somewhat angu-
lar body, the heart. Find the colorless, hence some-
what indistinct, arteries, running forward, laterally, and
backward from the heart. Follow the artery running
backward, by pushing aside the muscles between which
it lies, and observe its branches supplying the surround-
ing tissues. The straight tube below, and attached to
the blood-vessel, is the intestine.

XIT. — Reproductive System. Carefully remove the heart,
and find directly below it either the testes or the ova-

Branch Arthropoda 59

ries, The testes are a pair of three-lobed bodies, gen-
erally white. If testes are present, find the ducts
leading from them to the external openings which
have already been found. The ovaries are a pair of
long, two-lobed bodies. If these are present, find their
ducts. Remember that only ovaries or testes will be
found in an individual, never both.

XIII. — Digestive System. Remove the reproductive
organs, and the most conspicuous portion now ex-
posed will be the digestive glands. Find the ducts by
which their contents are emptied into’ the small intes-
tine. The stomach is the hard-walled receptacle just
in front of these glands. It passes anteriorly into the
cesophagus, and posteriorly into the small intestine.
Pass the forceps through the mouth into the cesopha-
gus, and watch its passage to the stomach. The
very short small intestine expands into the large intes-
tine which terminates in the anal opening in the telson.
Remove the stomach and open it, to find an apparatus
for crushing the food. Make a sketch of the digestive
system.

XIV.—Nervous System. Beginning with the posterior
part of the abdomen, carefully remove the body
muscles from the abdomen and thorax. Left plainly
exposed between the muscles will be found the nerve
cord with its branches. Follow that forward to the
head. In the thorax it enters a hardened passage,
to remove which will require some care. Just posterior
to the cesophagus, find a large ganglion into which the
nerve passes. Find a similar ganglion in front of
the cesophagus. You may be able to see how these
are connected by the nerve cord passing around the
cesophagus.

60 Laboratory Guide in Zoology

The fact that the digestive canal passes at its ante-
rior end through a ring of the nervous system is an
important characteristic of animals below the verte-
brates, or back-boned animals. Find, if you can, nerves
passing from the forward ganglion to the eyes, antenne,
and antennules. Make a sketch of the nerve system.

XV.—Excretory Organs. Directly under the antenne, see
the green bodies, the excretory glands, whose openings
are found in the basal segments of the antennz.

XVI. — Compare the structural plan of the lobster with that
of the earthworm, remembering that both are analogous
to a tube within a tube, the edges of both tubes being
united at both ends. With this structure in mind, tell
which tube the mouth and the anal opening are con-
nected with. In which tube do the reproductive and
excretory organs lie? Where do their ducts lead? In
which tube does the liver lie, and into which do its
ducts pass? What is the relation of the skeleton and
body muscles to the system of tubes?

THE COMMON CRAB

Crabs are familiar to all who have wandered along the
sea-shore at low tide. They run sideways over the exposed
rocks, or crawl leisurely along the bottoms of the pools.
They are closely related to the lobster, although very dif-
ferent in appearance.

I. — Study the body as to its general shape. What modifi-
cations in the size, shape, and arrangement of the
cephalothorax and abdomen make it appear so different
from the lobster? Where is the abdomen situated?
Draw the view presented as you look down upon the
back,

Branch Arthropoda 61

II. — Study the carapace. Is its front margin denticulate?
Are there any sutures? Distinguish these parts, which
are marked off by the sutures : —

a. The gastric lobe, a large, elevated, subtriangular
area in the middle of the front half.

b. The cardiac lobe, a somewhat similar area, back of
the gastric lobe.

c. The hepatic lobes, one on each side of these median
lobes. :

III.— Study the ventral surface; make a drawing of it.
See the large plastron which forms the under side of
the body. Notice the plates of which it is composed.
Notice the broad groove in which the abdomen rests.
In male specimens the abdomen is narrow; in female
it is broad and rounded, its concave ventral surface
forming a chamber in which the eggs may be carried.
How many segments in the abdomen?

IV. — Study the six pairs of appendages attached to the
sides of the plastron. Beginning posteriorly, find four
pairs of walking legs, one pair of large chele, and one
pair — the third — of maxillipeds. Are the appendages
similar in general structure to those of the lobster?
Study the appendages of the head.

V.— Immediately in front of the third pair of maxillipeds
are the second and first pairs of maxillipeds. In front
of the latter are the large mandibles. Find the eyes.
How are they situated? Find the antennules and the
antenne.

VI. — Find a large orifice on each side of the head, opening
into the branchial chamber. Notice a membranous
flap on each side. See if this is a part of the second
maxilliped.

VII. — Should you say that the crab is to be placed higher

62 Laboratory Guide in Zoology

in the scale of classification than the lobster? Does it
show greater differentiation in its structure?

THE CYCLOPS

The Cyclops is a microscopic crustacean of the same
class to which the lobster belongs. It may be found in the
water of almost any aquarium where aquatic plants have
been growing ; it appears to the naked eye as a small white
speck swimming rapidly about with a peculiar, jerky move-
ment. The large specimens usually found are females.
The males are much smaller, and generally are less abun-
dant, and therefore are not so well adapted to study. Pre-
paratory to a study with a low power, several specimens
should be removed from the culture jar to a watch glass.
To do this, place a finger on the end of a short glass tube,
and inserting the other end in the water as near the speci-
men as possible, remove the finger; the animals will be
drawn into the tube with the surrounding water, and by
again covering the exposed end of the tube they may be
transferred to a watch glass. If a little ether is placed in
the water containing the animals, their rapid actions will
be checked, giving a better opportunity for observation.
Place the watch glass on the stand of the microscope and
study with the low power.

I. —Dorsal View. By careful manipulation, find a specimen
showing a good dorsal view. Observe the oval body,
tapering rapidly toward the posterior end. Study the
segmentation of the body axis; since the head and
thorax are united, as in the lobster, the body axis may
be divided into the two great divisions, — the cephalo-
thorax and abdomen. The cephalothorax is composed
of the first five segments beginning with the anterior

Branch Arthropoda 63

end. The remaining tapering segments make up the
abdomen. Observe the broad dome-shaped carapace
making up the anterior part of the cephalothorax.
Compare this with the carapace of the lobster in posi-
tion and shape. If the specimen is a female, a pair of
egg sacs may be seen attached to the first abdominal
segment. Study the greatly developed posterior seg-
ment of the abdomen, with its branched projections.
Observe the yellow outline of the intestine showing
through the wall of the abdomen. Dark masses show-
ing through the carapace are the reproductive organs.
Near the anterior edge of the carapace on the median
line, find the dark purple eye-spot: this is really made
up of two disks which may be seen with the high
power.

JI. —Lateral or Ventral View. Obtain a good lateral or
ventral view, if necessary using the needles in manipu-
lation. The most noticeable appendages of the cephalo-
thorax are the long-jointed antennae. Just back of
these another smaller pair, the antennules, may be |
found. Just below the two pairs of antennz the
mouth parts surrounding the mouth are grouped,
although it may be quite difficult to distinguish clearly
the pair of mandibles and the two pairs of maxilla.
At some distance behind the mouth parts are the four
pairs of thoracic appendages, the legs. Study the
segmentation of the legs, and try to make out a fifth,
rudimentary pair.

64 Laboratory Guide in Zoology

THE FLATTENED CENTIPEDE, OR THOUSAND-LEGS

,

The common “ thousand-legs,” or centipedes, are found
under boards and logs. For this study those with flattened
bodies should be selected.

I, — Observe the jointed nature of the body. See that the
head is easily distinguishable. Is there any distinct
division between thorax and abdomen? From a dorsal
view, count the segments back of the head. Are all
the segments of the same size?

II.— Count the pairs of legs. Does each segment bear
one or two pairs? Study the legs carefully. Are
they jointed? If so, how many segments has each?

III.— Find the breathing pores, or spiracles: one on each
side of a segment, just above the coxa, the first leg-
joint.

IV. — Examine the antenne — the most noticeable append-
ages of the head. Directly behind the antennz find
the eyes — blackish clusters made up of many ocelli,
or single eyes, crowded near together.

V.— Directly in front of the base of the antenne, find
two pairs of mouth parts, or jaws, one pair being much
smaller than the other. But first distinguish carefully
the front pair of legs, so much modified that they look
like sharp claws. In poisonous species the poison is
secreted in these claws.

VI.— Make a good-sized sketch of the centipede as seen
from the dorsal side, and another of the head as seen
from the ventral side.

Branch Arthropoda 65

THE LOCUST, OR GRASSHOPPER

Collect as large specimens as you can find. Have the
dead grasshopper pierced with a pin or held with small
forceps so that the examination may be quickly and easily
made. Examine first with the naked eye, and then with a
hand lens or a dissecting microscope.

I.— Take a general but careful view of the external feat-
ures of the grasshopper. Lift the wings; note their
number and place of attachment. Observe the num-
ber of pairs of legs and the location of the anterior
and posterior pairs.

II.— There are three principal divisions of the body, —
head, thorax, and abdomen. Move the head gently
from side to side to see the line of division between it
and the rest of the body. Examine the long tapering
posterior part of the body: this is the abdomen.
Between it and the head lies the third great division
of the body, —the thorax. The anterior margin of the
thorax passes directly in front of the first pair of legs,
and the posterior boundary is just back of the third
pair of legs. Study the thorax carefully, remembering
that the two pairs of wings and the three pairs of legs
are all attached to it.

III.— You have already noticed that the abdomen is
divided into segments, or somites, in a way some-
what similar to the abdomen of the lobster, but
with less freedom of motion. Look for a similar but
less marked series of divisions in the thorax. There
are really three segments in the thorax, each bearing
a pair of legs. See the first of these, — the prothorax,
— easily distinguished by the separation from the head
in front and from the rest of the thorax behind. The

66

Laboratory Guide in Zoology

second and third divisions are not so well defined,
and do not move upon each other. The division may
be made out, however, by observing certain lines which
represent the union of the two. On the ventral surface
this line will be found behind the second pair of legs;
trace it up along the sides and back. The middle seg-
ment thus distinguished is the mesothorax, and the hind
segment is the metathorax.

IV.— Notice that the position of the head is at right

angles to: the body axis. Compare it in this respect
with the lobster. Study the long slender projections
—the antenne, or feelers — on the front of the head.
See with a lens their jointed structure. Notice the
peculiar surface of the large compound eyes. Between
the compound eyes, find three small ocelli, or simple
eyes.

V.— Begin the study of the mouth parts by finding on the

lower side of the face a movable flap —the labrum, or
upper lip. Observe this carefully, then remove it and
see directly beneath it the mandibles, or jaws, — one on
each side; these are hard, black, toothed structures.
Press them apart, and then pull them out carefully with
pointed forceps. You thus bring into view a dark brown,
spindle-shaped organ in the centre of the mouth: this
is the ligula, ortongue. The entrance to the gullet is a
small round opening above the base of the tongue.
Below where the mandibles were, the maxill# are now
to be seen, one on each side. Pull one of these out,
being careful to get the whole of it, and by the aid of
a lens identify the following parts : —

a. The basal segment.

6. The jointed appendage on the outside, called the

maxillary palpus.

Branch Arthropoda 67

c. The large thin plate-like blade.

ad. The more slender inner portion, which is the true
maxilla.

e. Directly below the maxillz lies the labium, or lower
lip. On each side a palpus is attached: these are
the labial palpi.

Make good-sized drawings of each of the mouth parts,
labelling each.

VI.— Observe carefully the general nature of the legs
and their attachment to the body. Remove one of the
front legs and identify the following parts: the coxa,
the short segment next the body ; the trochanter, a short
segment connecting the coxa with the femur, the first
long segment; beyond the femur is another long seg-
ment, the tibia, which articulates with the tarsus, or foot,
a series of short segments, the last of which is tipped
with claws and has peculiar pads on its under surface.

VII.— Remove one of the hind legs and make a careful
drawing showing each of its parts. Why should the
femur and tibia be so much longer in these legs than in
the front and middle pair?

VIII. — Carefully turn back the outer pair of wings. Note
that they are the anterior pair. To which division of
the thorax are they attached? Lift one of the under
wings and notice its attachment to the thorax. Spread
it out and observe its fan-shaped appearance. See that
it is composed of a membrane stretched over a frame-
work of veins.

IX. — On each side of the mesothorax, over the second pair
of legs, find the spiracle, a slit-like opening to the air-
tubes. Find another spiracle on the prothorax.

X.— Bend the abdomen and notice the play of the seg-
ments upon each other. Theoretically each segment

68 Laboratory Guide in Zoology

is divided into four parts: the tergite is the dorsal
portion, a pleurite is on each side, and the sternite forms
the ventral surface. See if you can distinguish these
parts. Remember the structure of the segments in the
lobster.

XI. — Study the first segment; that is, the one next to the
thorax. Its sternite is not easily seen, but’on each side
above you will find a nearly circular cavity covered by
a thin membrane. This structure is believed to serve
as an ear. On the side of the abdominal segments
find spiracles similar to those on the thorax. Are spir-
acles found on all of the segments? Is there more
than one pair on any somite?

XII.— Notice that the somites at the posterior end of the
abdomen are greatly modified. In the case of female
specimens the abdomen ends in two pairs of pointed
processes curving outward. When these are brought
together they form a device for burrowing into the
ground, and they serve as the ovipositor of the insect.
In the male the end of the abdomen is much blunter.

XIV. — Draw a side view of the grasshopper.

THE DRAGON-FLY

Dragon-flies are abundant about ponds in summer.
Large specimens serve admirably for showing the general
structure of an insect.

I.—Find the three great divisions — head, thorax, and
abdomen — into which the body axis is separated.

II. — Compare the relative sizes of each of these divisions
with the relative sizes of the same parts in the grass-
hopper.

III. — Between which parts does the division line show
most plainly?

Branch Arthropoda 69

IV. — Notice that the head, convex in front and concave
behind, is given its peculiar shape by the very large
compound eyes.

V.— Using the lens, find the short antenne. How many
segments has each?

VI.— Near the base of the antenna find two small simple
eyes, the ocelli.

VII. — Find a third ocellus between and above these two
ocelli.

VIII. — Notice a slight projection covered with hairs,
sheltering the ocelli.

IX. — In examining the mouth parts, first observe the large
size of both upper and lower lips.

X:— Push these parts aside so that the mandibles — the
large toothed jaws— may be seen. Find beneath the
mandibles another pair of jaws, the maxille; these
consist of several parts, as in the grasshopper, and
should be carefully removed and studied under the
microscope.

XI.— Examine the thorax carefully, to find its three
segments, —the prothorax, the mesothorax, and the
metathorax. The lines of division may most easily
be seen on the ventral surface. Remember that each
of these divisions bears one pair of legs.

XII.— Note the relative size of the thoracic segments.
The enlargement of which one gives the insect its
peculiar hunchbacked appearance?

XIII. — Demonstrate the truth of the statement that the
anterior and posterior pairs of wings are attached to
the mesothorax and metathorax respectively. Reflect
upon the attachment of the wings in the other insects
studied, and remember that the place of attachment is
constant.

70 Laboratory Guide in Zoology

XIV. — Note the structure and size of the dragon-fly’s wings
as compared with those of’ other insects. Notice the
relative size of the front and hind wings. What bear-
ing do these characters have upon the habits of life of
the dragon-fly ?

XV. — Study the veins of the wings. Near the middle of
the front margin find a slight notch connected with a
short transverse vein. This structure is called the
nodus. Its presence is an important characteristic of
this group of insects.

XVI. — Notice the legs. Are they large or small? Does
the dragon-fly walk much?

XVII. — Beginning with the segment next the body find
the following parts of one of the legs: coxa, trochanter,
femur, tibia, and tarsus.

XVIII. — Study the claws on the tarsus. To what special
use are they likely to be put?

XIX. — Find the ten segments which compose the abdo-
men. The division between the segments is indicated
by ridges which completely surround the joints. Bear
this in mind when determining the segments nearest the
thorax.

XX.—In any single segment point out the parts, called
the tergite, pleurite, and sternite. (Refer if necessary
to page 68.)

XXI. — Find the spiracles, or breathing pores, on the pleu-
rites. What is their position ?

XXII. — Study the terminal segment. In the female this
segment is large and rounded; in the male it has four
pointed appendages.

XXIII. — Make a drawing of a dragon-fly as seen from
above.

Branch Arthropoda 71

THE BUTTERFLY

Before mutilating the specimen, study carefully its gen-
eral structure. Notice the relative sizes of the wings and
body, the markings on the wings, and the hairy covering
of the body.

I. — Note the relatively large size of the compound eyes ;
examine the outer surface of one with a lens to see its
honeycomb appearance.

II.— Are there any ocelli? If so, where are they situated ?

III. — Examine the antenna. What is the general shape ?
About how many segments are there in each? Which
segments are the longest? How does the basal seg-
ment differ from the others ?

IV. — Notice the long coiled sucking organ — the proboscis
—atthe mouth. Is it composed of one or two pieces?
Notice the two jointed hairy organs beside the probos-
cis: these are the labial palpi. The proboscis is formed
of the modified maxill. -

V. — Notice the small thorax in close connection with the
head. Compare the connection with that found in the
dragon-fly.

VI. — Observe the large mesothorax bearing the front pair
of wings. Find the suture between it and the meta-
thorax which bears the posterior wings.

VII. — Notice the fragility of the legs. Give a reason for
their small size as compared with those of the grass-
“hopper.

VIII. — Are the front legs as large as the others? When
you have a chance to see a large butterfly walking, see
how many feet it uses.

IX. — Place a piece of the wing under the low power of
the microscope. Observe the shingle-like arrangement

re: Laboratory Guide in Zoology

of the scales. What difference is to be seen at the edge
of the wing?

X. — Scrape off a few of the scales ona glass slide and
study with the high power of the microscope. Notice
the structure and the difference in shape. Draw five
specimens, each different from the others.

XI.— Scrape off a few of the hair-like scales from the
thorax and study them in the same way. Can you find
any scales intermediate between the short, broad ones
and the long, hair-like ones?

XII.— Count the abdominal segments. If necessary,
remove some of the hairy covering to show the joints.

XIII. — Rub off the scales from the sides of the body
and find the spiracles. How many are there?

XIV. — Is each segment made of four parts — tergite, two
pleurites, and sternite — as in other insects ?

XV. — Make a drawing of the butterfly as seen from above
when its wings are expanded.

THE SPIDER

I. — Segmentation of the Spider. Notice how the body axis
is divided into two great divisions by a deep constric-
tion near its middle. The anterior division is made
up of the head and thorax, and is called the cephalo-
thorax. The posterior division is the abdomen. How
does this division of the body axis compare with that
of the lobster? Notice the entire absence of any
segmentation either in the thorax or abdomen.

II. —Appendages of the Head. The parts of the head
must be studied with the low magnifying power. Are
there any antennz? Scattered over the anterior part
of the head find the small black ocelli, —generally four

Branch Arthropoda 73

pairs. Directly below the eyes is the pair of broad,
thick mandibles, or jaws. Find a sharp-pointed claw
on the tip of each mandible. It is within these claws
that the poison glands are situated. Directly below the
mandibles is another pair of jaws, or maxille. The
maxille themselves are short and thick, but each pos-
sesses a long jointed appendage, or palpus, which looks
very much like a foot. See the mouth between the
pair of mandibles and the pair of maxilla.

III. — Appendages of the Thorax. The thorax bears four
pairs of legs, a number characteristic of spiders. The
maxillary palpi just mentioned, though smaller than the
legs, are sometimes taken for a fifth pair of legs. See
that this point is clearly understood. Determine the
number of segments in the legs. Beginning with the
one next the body, they are coxa, trochanter, femur,
patella, tibia, metatarsus, and tarsus. The trochanter
and patella are generally very small.

IV. — Appendages of the Abdomen. Near the posterior end
of the abdomen, notice a blunt bunch of finger-like pro-
jections, the spinnerets, usually six in number. To see
them well it will be necessary to use a low magnifying
power. The spinnerets are the organs that form the
spider’s silken thread. In the end of each spinneret
there are a great number of small tubes. A peculiar
fluid is forced out through these tubes which hardens as
soon as it strikes the air, thus forming the silk thread.

Try to find a hard rough structure surrounding a
pore or spiracle just in front of the spinnerets. This
opening leads to a breathing apparatus. Two small
openings to another breathing system may be found on
the ventral side of the abdomen, near its union with
the thorax.

74 Laboratory Guide in Zoology

THE CLASSIFICATION OF THE ARTHROPODA

The branch Arthropoda which includes the jointed-footed
animals, is one of the largest and most important zoolog-
ical divisions. Its members differ from the Annulata in
having jointed legs or other appendages attached to the
body segments, and from the Mollusca in having the body
definitely divided into segments. They have an exoskel-
eton composed of chitin or of chitin and calcium combined.
They possess a specialized nervous system, composed of a
dorsal brain and a double row of ganglia along the ventral
side of the body cavity. In general, the body is bilaterally
symmetrical. :

The following classes of Arthropoda are now recognized
by leading authorities : —

Class I. Crustacea. Lobsters, Crabs, Shrimps, and
Barnacles.

Class II. Onychophora. Peripatus.

Class III. Myriapoda. Centipedes and “Thousand-legs.”

Class IV. Insecta or Hexapoda. Bees, Beetles, Butter-
flies, and other insects.

Class V. Arachnida. Spiders, Scorpions, and Mites.

The first class, the Crustacea, includes the smallest as
well as the largest forms of the Arthropoda ; forms which
vary in size from the microscopic Cyclops to the huge
crabs, some of which are of enormous size. The typical
crustacean is made up of twenty-one segments, divided
between the three great divisions of the body, —head,
thorax, and abdomen. The segments of the head and
thorax have become united, forming the cephalothorax,
while the individual segments of the great divisions of the
body have become so fused together that it is difficult
to distinguish the typical number. There are two pairs

Branch Arthropoda 75

of antennz, the smaller of which are called antennules.
The body is covered with a chitinous integument, a large
part of which is usually hardened with lime. This cover-
ing is cast off at frequent intervals during the growth of
the animal. During development many crustaceans pass
through a series of peculiar changes of form which are
called metamorphoses. Nearly all are water breathers ;
some live in fresh water or in moist situations on the
land, but the great majority are marine.

The second class, Onychophora, includes only the single
remarkable genus Peripatus. The members of this genus
are peculiar creatures, which appear to be a connecting
link between the Annulata and the Arthropoda. Only
a few species are known, all inhabiting tropical regions.

The members of the third class, Myriapoda, have a dis-
tinct head, but the segments of the thorax and abdomen
form a continuous series. The number of these segments
is indefinite. Each bears one or sometimes two pairs of
legs. They breathe air by means of trachee. The centi-
pedes and millipedes or ‘“ thousand-legs”’ are typical rep-
resentatives of this class.

The fourth class, Hexapoda, differs from the preceding
classes in having three distinct divisions of the body, —
head, thorax, andabdomen. The headis composed of several
united segments; the thorax of three segments; and the
abdomen of from seven to eleven segments. There are six
legs, one pair being borne by each thoracic segment. The
thoracic segments also bear on their dorsal surface one or
two pairs of wings. The nervous system has a wonder-
fully complex specialization, furnishing the insect with
great instinctive powers. Growth takes place only during
the early or larval life, and in many forms complicated
transformations occur.

76 Laboratory Guide in Zoology

The class Arachnida includes the spiders, scorpions,
and mites. In these there are two chief divisions of the
body, — the cephalothorax and abdomen, eight legs, no
antenne, and generally no distinct transformations. With
unimportant exceptions they breathe air either by means
of trachez or of book-lungs, and have a varying number
of simple eyes upon the cephalothorax.

CHAPTER VIII

BRANCH MOLLUSCA: THE OYSTER, CLAMS, AND THEIR
ALLIES

THE FRESH-WATER CLAM

EXTERNAL ANATOMY

I.— Place a clam in a glass of tepid water and observe
the gradual opening of the shell, and the protrusion
from one end of a white, blunt, muscular projection,
the so-called foot. This marks the anterior end of
the animal, and by its protrusion and retraction the
clam steadily moves along the sand, leaving grooves
made by the sharp edges of the shell. In removing
the creature from the water in preparation for the
study of its structure, notice how the two halves of the
shell are quickly brought together and the foot with-
drawn.

II. — The lateral surfaces are easily distinguished. They
are the broad oval surfaces upon which the clam rests
when placed upon the table. The sharp edges of the
two parts of the shell form the ventral surface. It is
this surface that makes the groove markings in the
sand, mentioned above. The opposite thicker edge is
the dorsal surface.

III. — With a clear idea of the lateral, dorsal, and ventral
surfaces in mind, determine the anterior and posterior
ends by the aid of the following directions. On the

7

78 Laboratory Guide in Zoology

dorsal surface find two prominences, the umbones, near
together. Notice that the umbones are nearer one
end than the other. The end to which they are nearer
is the anterior end, and the opposite extremity is the
posterior end.

IV.—We have noticed that the entire shell is divided.
equally into two parts, or valves. It is for this reason
that the term Bivalve was given to the class to which
the clam belongs. Find a strong, hard hinge or liga-
ment near the umbones that joins the valves.

V.— With some sharp instrument carefully force the
ventral edges of the shell apart, putting some object in
the space to hold them in position. Then pushing
aside the ruffled edge of a membrane, insert the knife
edge close under the valve and carefully push away the
soft membrane clinging to its inner surface.

VI. — By forcing open the valves a little farther, you will
be able to see near each end a hard, smooth, white pil-
lar of muscle fastened to the inner side of the valve.
These pass directly through the body, and are attached
in similar positions to the opposite valve. Carefully cut
out these muscles close to the valve. The springing
open of the latter shows why the muscles are called the
adductors. Without disturbing any of the parts, force
the two valves together, and notice the spring ex-
erted by the ligament, or hinge. Remember to study
the mechanism causing this action after the soft parts
have been removed, or on other shells.

VII.— Study the concentric rings radiating from the
umbones. These are the growth lines of the shell as
it was gradually secreted by the soft membrane first
seen when the valves were opened.

ee

Branch Mollusca 79

INTERNAL ANATOMY

VIII. — The shell is a true exoskeleton, and its removal
does not expose the interior or body cavity of the clam.
On account of the size of the animal and its lateral
compression, we can do no more than indicate the rela-
tions of the body cavity and alimentary canal.

IX.— The membrane above mentioned as found closely
adhering to the inner side of the shell is the mantle.
This has two lobes, corresponding in shape to the valves
of the shell. Demonstrate this fact. Lift the upper-
most lobe carefully to determine its place of attachment.
It is simply an outgrowth of the body wall. At the pos-
terior end find two well-defined oval openings, formed
by the two mantle lobes coming together. These two
openings together form the siphon. In the salt-water
clam the two lobes of the mantle have developed into
a siphon that extends outward, sometimes an inch or
more beyond the shell: a black, hard, elongated pro-
jection, through which these openings pass as wholly
closed tubes. Water containing food material passes
in at the ventral or lower opening, and out from
the dorsal opening. It may be necessary to remind
the student that we are still talking about the posterior
end of the animal, and that we have not yet penetrated
its body wall.

X.— By raising the mantle lobe examine the exposed,
hard, white, muscular foot. This is also an extension
of the body wall, and within its base (the visceral mass)
are embedded the long coils of the stomach region of
the alimentary canal.

XI.— On either side of and posterior to the abdomen find
the gills, a pair of ribbed membranous organs. Just

80 Laboratory Guide in Zoology

anterior to the foot, and below the anterior adductor
muscle, search for the mouth, a small opening, some-
times difficult to find. Force a bristle into this up to
the stomach coils.

XII. — Attached to the walls of the body, and on each side
of the mouth find a pair of soft triangular flaps, the
labial palpi.

XIII. — Gently detach the body of the clam from the shell
close under the hinge. Where the two mantle lobes
unite to form the dorsal body wall, the latter is so thin
that you may look through it into the body cavity and
see the straight intestine passing from endtoend. Try
to see the pulsing, colorless, ventricle of the heart,
through which the intestine passes, though the cavities
of the two have no connection. With pincers and
sharp-pointed scissors carefully lift and cut the body

wall so that the boundaries of the body cavity and its
organs may be more easily seen.

XIV.— Trace the intestine forward toward the mouth.
Examine the dark brown mass surrounding the coils of
the stomach. This is the liver (very evident in stews
of the edible clam). As is the usual function of that
organ, it secretes a digestive fluid that passes into the
interior of the alimentary canal.

XV.—Trace the intestine backward, and notice that it
ends in a space into which the dorsal opening of the
siphon opens. This space is called the cloacal chamber.

XVI.— Determine the course taken by the water that
passes in at the ventral opening. Notice that it bathes
the gills, the lower part of the body wall and foot, and
the inner side of the mantle lobes; then it passes for-
ward to the labial palpiand the mouth. The cilia which
cover the labial palpi keep up a constant vibratory

Branch Mollusca 8I

motion, causing currents in the water to pass into the
mouth, so that the food in such currents may be taken
by the clam. The gill chamber is the large cavity in
which the gills are suspended: it is bounded mainly
by the mantle. The lower end of the siphon opens
into it.

XVII. — It was stated above that currents of water enter-
ing the lower opening of the siphon escape through
the dorsal. To make this evident and to demonstrate
the relation between the cloacal and the gill chambers
hunt for small openings in the floor of the former.
Water passes through these from the gills into the
cloacal chamber and thence out.

XVIII. — The Nervous System may be very difficult to
make out ina fresh specimen. Better results are likely
to be obtained by hardening the specimen in alcohol.
Remove the mussel entirely from the shell, and with
the needles search in the median ventral line between
the gills and directly under the posterior adductor
muscles for a pair of yellowish masses, or ganglia. Still
another pair of these nerve centres may generally be
seen, lying near the surface, one on each side of the
mouth, close to the bases of the labial palpi. The pedal
ganglion may be found in front of the intestine in the
foot. These nerve centres are connected by nerve
threads called connectives. Trace out as much of the
connecting system as possible.

XIX. — The Reproductive Organs will not be easy to study.
They lie in the abdomen, below and behind the liver.
They open by ducts into the gill chamber.

XX.— Make two drawings of the clam: a side view of
the shell, and a diagrammatic view of the internal
structure.

82 Laboratory Guide in Zoology

THE FRESH-WATER SNAIL

Fresh-water snails may be easily found at almost any
season of the year. In summer they are abundant on the
vegetation in ponds and slow-running streams, while in
winter they may be easily procured by scraping the bottom
of the pond with a collecting net. This is especially feasi-
ble in springs that do not freeze over. This outline is for
one of the species with conical, pointed shells. Have one
or more specimens in the hand, and one or more live ones
in a beaker aquarium.

I.— Study the specimen as a whole. Notice the three dis-
tinctive characters of the molluscs, — the foot, the mantle,
and the shell secreted by the mantle. Make a drawing
of a side view of one with its body and tentacles
extended.

II.— Study the shell. Can the animal part with it?
Notice the pointed end: this is the apex. Notice the
open end: this is the aperture. Notice the spiral
groove: this is the suture. Notice the divisions of the
shell made by the suture: these are the whorls; the
large anterior one is the body whorl, while the others
together form the spire. The axis from the centre of
the aperture to the apex is the columella. Notice lines
around the shell parallel to the lip: these are the lines
of growth.

III.— Hold the shell with the apex toward you: if the
suture turns to the right, the spire is a right-hand or
dextral spire; if it turns to the left, it is a left-hand or
sinistral spire. Or hold the shell with the aperture
toward you: if the aperture is to the right, the shell is
dextral; if to the left, it is sinistral. Which is your
specimen ?

Branch Mollusca 83

IV.— Study the locomotion of the living snail: how is it
effected? Can the snail move in any direction in the
water or on a damp surface outside? How does the
large foot on which it moves differ from that of the
clam? Can you detect any motion of the different
parts of the foot while the snail is moving?

V.— Where are the tentacles? How many are there?
Can you see a small spot at the base or the tip of the
tentacles? These spots are the eyes.

VI.— As the snail crawls up the wall of the aquarium or
-along the surface film of the water, you can see the
mouth. Is it longitudinal or transverse as compared
with the direction of the body? Describe its move-
ment in opening and closing. When it is open, can you
see a black object moving back and forth? This is the
tongue. When magnified this tongue is seen to be
jagged in outline.

VII.— Do snails in the water come to the surface occa-
sionally? If they do, can you see a bubble of air escap-
ing from an opening in the mantle of each under the
lip of the shell? This is the opening to the curious
lung these snails have.

VIII. — The eggs of snails may be frequently found on the
sides of the aquarium. They appear as small granules
imbedded in a gelatinous mass, Examine some of
them through a lens.

IX. — Make a drawing of a side view of the snail and its
shell.

THE SQUID
The squid isa marine mollusc which is frequently
caught by fishermen in their nets.

I. — Study the animal as a whole. What characters should
you say ally it to the class Mollusca? Notice the long

84 Laboratory Guide in Zoology

cylindrical body, covered by a mantle and tapering to
a point. See the distinct, slightly movable head. Find
the large eyes, the arms or tentacles, and the mouth be-
tween the bases of the arms. Find a fold in the mem-
brane directly back of each of the eyes: these are the
olfactory lobes. See the opening in the siphon tube
back of the head on the lower side of the body, and
the wide terminal fins toward the posterior end of
the body.

II. — Study the tentacles. How many are there? How
do they vary in size? Notice the two rows of suckers
on the inner margin of the tentacles: how are they
arranged? Of what especial use are the suckers?
The pair of long arms are called the grasping arms:
what is their shape? What is the arrangement of the
suckers upon them?

III. — Study the mouth. What is its shape? Notice the
peristome. Open the mouth and notice the large chitin-
ous jaws. Which is the larger? The mouth is sur-
rounded by projections of the skin: how many and of
what use are they?

IV. — Study the large eyes. Is their position an advan-
tageous one?

V.— Study the siphon tube, beneath the head and pro-
jecting from between the mantle and the neck. Study
the structure of the orifice.

VI.—The body is enclosed in a mantle. From what do
the large terminal fins on the posterior third of the
body arise? These fins are used for swimming.
Around the neck you will find a cavity. This is the
external part of the mantle cavity. A small projection
of the mantle over the middle of the head is the pen.
The squid can take water into the mantle cavity

Branch Mollusca 85

and forcibly expel it through the siphon tube, and
this enables it to dart through the water with great
rapidity.

VII. — Make a drawing of the ventral view of the squid.

THE CLASSIFICATION OF THE MOLLUSCA

The Mollusca is the great branch, or phylum, to which
belong the mussels, snails, limpets, and cuttlefishes. Many
of its members are believed to be closely allied to worms,
though the members of the two branches differ widely in
external appearance. In the development of the Mollusca
the segments have been fused together, while the skin has
secreted a calcareous shell; the relative length of the body
has decreased, and in the lower groups there is no distinct
head. The alimentary system is greatly developed, espe-
cially the liver. The phylum includes terrestrial, fresh-
water, and marine forms. There are three principal
classes : —

I. —Pelecypoda. Oysters and Clams.

This class includes “laterally compressed Mollusca
without separated head, with bilobed mantle and bi-
valve shell, composed of a right and left half and con-
nected by a dorsally placed ligament.” The sexes are
generally separate, and there are large gill-plates on
account of which the class has commonly been called
Lamellibranchiata. The locomotive organ consists of
a single median muscular foot, and the parts of the
body are arranged with bilateral symmetry. Both
salt and fresh water forms are included, all of which
breathe by means of gills.

II. — Gastropoda. Snails, Slugs, and Limpets.

The members of this class usually have a shell ina

single piece which commonly has the shape of a spiral

86 Laboratory Guide in Zoology

cone. The body is not symmetrical, and in front of
the foot there is a head which bears the tentacles and
eyes. These animals are widely distributed: the
largest number live in salt water, but many live in fresh
water, and many are: terrestrial. Some breathe by
means of gills; others by means of lungs.

III. — Cephalopoda. Cuttlefishes and Squids.

This class includes the highest molluscs, the most
important examples being the Cuttlefish, Squid, Octo-
pus, and Nautilus. The members of it are bilaterally
symmetrical with the head separated from the body by
a slight constriction. There are two well-developed
eyes, a rasping tongue, a beak, and eight or more
tentacles. The ganglia of the head are somewhat pro-
tected by a covering.

CHAPTER IX

BRANCH CHORDATA: THE VERTEBRATES

THE PERCH
EXTERNAL ANATOMY

I.—General Form. Study the graceful outline of the fish
from a side view. From a dorsal view, see how the
body is compressed laterally. Observe how the head,
‘although flattened at the tip, passes with graceful
curves into the body. Account for the compressed
body, flattened head, and the absence of a neck by refer-
ence to the animal’s habitat and locomotion. Notice
the absence of any segmented division of the body axis.
Segmented structures will be found to exist, however,
when we study the skeleton and muscles. Study the
coloration of the fish. Account for its dark dorsal and
light ventral surface by reference to its needs of self-
protection. Notice the alternating perpendicular bands
of black and white along the sides. Explain how this
arrangement of color also makes the fish less conspicu-
ous in its natural haunts.

II.— Exoskeleton. Study the scales of the perch. Re-
move some of them, and with the low power of the
microscope see the thin covering. Draw one. The
scales themselves are the outgrowths of the inner or
true skin, while their covering corresponds to the outer
skin or epidermis of the higher animals.

87

88 Laboratory Guide in Zoology

III. — Appendages. Study the two fins running along the
dorsal median line. They are made up of a web sup-
ported by hard spines. How do the spines in the two
fins differ? The tail is called the caudal fin. What
kind of rays has it? When the caudal fin is symmetri-
cal, it is said to be homocercal; when it is bent so that it
is unsymmetrical, itis said to be heterocercal. Which is
the case in the perch? On the mid-ventral side of the
body, just in front of the caudal fin, find the anal fin.
Note the fact that all fins studied above are median or
single, z.c. never in pairs. Next observe a pair of fins
(pectoral) just back of the head, one on each side of the
body. They correspond to and indeed are homologous
with the fore legs or arms of the higher animals. Back
of the pectoral fins, and nearly on the ventral line, find
the pair of pelvic fins, corresponding to the hind legs of
the higher animals. Take a general view of the fins
with reference to their uses. Tell which keep the ani-
mal in an upright position, and which give it propelling
power and guidance.

IV.— Other Organs. Study the action of the jaws, noticing
that both have movement. Is the action up and down
or from side to side? Place a finger in the mouth to
feel the teeth, noticing their slanting direction. Study
the size and position of the eyes. Find with the for-
ceps the bony socket encasing the eyes. Move the
eye itself to find its field of vision. Are there any
eyelids? Find the nasal opening in the upper lip.
Find the anal opening just in front of the anal fin.

V. — Breathing Apparatus. Find a large, slit-like opening
on each side of the head just back of the mouth which
communicates directly with the mouth cavity. These
are the gill-chambers, and the flaps closing over them

VI.

Branch Chordata 89

are the gill-covers. The gill-arches are the four bony
arches standing side by side within the gill-chambers.
Attached to the gill-arches are the red filamentous
structures, the gills. Are the gill-chambers in direct
communication with the exterior from both sides; if so,
are the gills constantly bathed in water? As the blood
passes through the many filaments of the gills, oppor-
tunity is given for it to exchange its carbonic acid for
the oxygen of the water.

INTERNAL ANATOMY

— Body Cavities. Insert the point of the scissors just
in front of the anal opening, and cut through the body
wall to the gill-slits. Push the flaps aside, and observe
the main body cavity. Notice how the cavity with its
organs is crowded forward, leaving the posterior parts
for the strong muscles. Notice the shining membra-
nous lining, the peritoneum. Near the anterior end of
the body cavity you may find a membranous partial
partition corresponding to the diaphragm of the higher
vertebrates.

VII. — Blood System. Near the middle of the smaller

anterior cavity a dark reddish body, the heart, will be
found. There are but two cavities in the heart, — the
rather angular, thick-walled ventricle and the dark, irreg-
ular auricle. You may be able to find connected with
the auricle a dark, thin-walled vessel, the venous sinus,
extending across the body cavity. The venous sinus
receives the blood from the veins, and passes it on to the
auricle. Find and trace as many vessels as you can
connected with the heart or venous sinus.

VIII. — Digestive System. Pass a blunt instrument down

go Laboratory Guide in Zoology

the cesophagus to observe its union with the stomach.
Then follow the intestine from the stomach in its not
long course to the anal opening. The large, reddish
lobed object lyingin the anterior part of the body cavity
is the liver. Try to make out its connection with the
intestine. The gall-bladder is a small, greenish body,
partly concealed by and closely connected with the
liver.

IX.—Reproductiveand Excretory Organs. Inthe vertebrates,
as in many invertebrates, the sexes are separate. So in
the fish we must look for testes or ovaries, never both.
The appearance of the female organs or ovaries varies
greatly with the season. In spawning time the ovaries
may be so distended that they cover all the other organs.
At other times they have the appearance of a single
white body lying near the intestine. A delicate tube leads
from this to an opening toward the posterior end of the
body. If the specimen is a male, the testes will be
found to be a pair of white bodies lying in the posterior
dorsal part of the abdominal cavity. Ducts may be
found passing to an opening toward the posterior end
of the body. After clearing away the intestine and
reproductive organs, a broad, flat, membranous sac may
be seen, if it has not already been punctured: this is
the air-bladder ; it is connected with the cesophagus.
Its function is to decrease the specific gravity of the fish
by filling it with air. Remove the air-bladder, and find
two long, dark, slender bodies, the kidneys. Trace their
ducts to the outlet near the anal opening. Near the
outlet a pinkish sac, the urinary bladder, will be found.

X.—Endoskeleton and Central Nervous System. Cut the
flesh away from the dorsal surface of the fish, expos-
ing the backbone as completely as possible. Notice

Branch Chordata gi

that this flesh is composed of muscle segments or
myotomes. Observe the jointed or segmented nature
of the backbone or spinal column. Its lateral bony
processes are analogous to the ribs of the higher verte-
brates. Each separate segment is a vertebra. Passing
along a closed tube within the spinal column is the
spinal cord, ending anteriorly in the brain. The two
(spinal cord and brain) constitute the central nervous
system. Nerves pass from this through openings
between the vertebra to various parts of the body.
Break the connection between two of the vertebre to
see the cavity filled by the spinal cord. Open the
cranium, or brain case, by removing carefully the dorsal
surface of the head just back of the eyes. Study the
lobes of the brain now exposed. Follow the continua-
tion of the brain into the spinal cord. Without injuring
the lobes of the brain, carefully dissect away sufficient
surrounding tissue to see the large optic nerves passing
to the eyes. If the lobes of the brain still remain com-
plete and uninjured, follow out the different parts.
The small median lobe extending backward is the
cerebellum. The pair of large rounded lobes directly
in front of the cerebellum, constituting the broadest
part of the brain, are the optic lobes. The cerebral
lobes, or hemispheres, are much smaller, and lie directly
in front of the optic lobes nearly on the median line.
The somewhat flattened posterior part of the brain,
passing from the cerebellum into the spinal cord, is
the medulla oblongata. Make a drawing of the brain.

92 Laboratory Guide in Zoology

THE FROG

EXTERNAL ANATOMY

I.—General. Feel of the frog’s skin, noting its smooth, slimy
nature. The moisture is a secretion from the glands
in the skin. Note the general temperature of the body.
It is cold even in life. Study the color markings of the
dorsal and ventral surfaces, and give reasons for such
coloring. The frog has the power to change its color,
bringing it into closer harmony with its surroundings.
The frog is placed in the group of animals called Am-
phibia. All Amphibians belong to the larger group
called Vertebrata. Fishes, reptiles, birds, and mam-
mals, besides Amphibians, are vertebrates. Fishes and
reptiles, like Amphibians, are cold blooded. Notice
that the frog has no outer skeleton. Note the absence
of an external division of the body axis.

A segmented condition will be found to exist, how-
ever, when we study the skeleton. Examine the limbs
with special reference to the animal’s habit of locomo-
tion. Is the animal well adapted to its environment
in this respect? Remember that the number of limbs
possessed by the frog is the maximum for verte-
brates.

II. — External Openings. Examine the nature and position
of the mouth and cloacal opening. Study the position
of the eyes with reference to their field of vision and
protection. In the anterior parts of the upper jaw find
two small openings into the nasal cavities. Push the for-
ceps or some blunt instruments through them into the
mouth. Behind each eye find a circular disk of tightly
stretched membrane, the external apparatus of the ear.

Branch Chordata 93

Inside the mouth at the back find the eustachian tube,
a passage leading to the drum of the ear.

INTERNAL ANATOMY

III. — Dissection. With scissors or sharp scalpel cut the

IV.

skin from the edge of the lower jaw along the median
ventral line to the cloacal opening. Notice how loosely
the skin is attached to the body. Where is the prin-
cipal place of attachment? Make lateral slits in the
skin and pull away the flaps, pinning them if necessary.
Remove the skin from the legs in the same manner.
Observe the development of the powerful chest muscles ;
also the muscles in the hind legs used as the propelling
power in long leaps. Next, cut the body wall from end
to end, in a similar manner to the incision of the skin,
being very careful not to disturb any of the viscera
beneath. Make lateral slits and pin back the flaps of
the body wall, exposing the internal organs. A circlet
of bones to which the legs are attached passes over the
chest just above the heart. Cut these with strong
scissors.

—General. Recalling the general plan on which the
earthworm and lobster are built, you will remember
that it is a tube within a tube. The wall of the outer
tube, being the body wall, encloses the body cavity ;
while the inner tube is the alimentary canal, with its
two openings. Find a similar structure now revealed
in the case of the frog. The large cavity holding the
various organs, or viscera, is the body cavity, or outer
tube, and through this passes the alimentary canal, or
inner tube. The latter is now partly visible as the
light-colored stomach or intestine.

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Laboratory Guide in Zoology

V.—Blood System. Just beneath the position of the

VI.

chest bones the heart may be seen. It is a cone-shaped
body, darker at the apex. There are only three cham-
bers, — one ventricle and two auricles. The ventricle
forms the apex of the cone and has walls much thicker
than those of the auricles. Give reasons for this.
Notice that there is no blood fluid in the body cavity.
The blood circulates in a closed system, passing from
the heart in arteries and returning in veins, instead of
being left to find its way back to the heart by con-
tractions of the body. Observe the large vessels leaving
the heart; the arteries cannot be easily distinguished
from the veins. Follow the vessels as far as you can
without disturbing the other organs.

— Digestive System. Without removing the viscera,
study the entire alimentary tube and its appendages,
with the aid of the following directions: Move the jaws
up and down. Do they move in the same direction as
the jaws of insects or crustaceans move? Notice the
attachment of the tongue at its anterior end. The
posterior end is moistened by a sticky secretion from
the roof of the mouth, and protruded for the prehen-
sion of food. The mouth opens into the esophagus,
and thence into the stomach—the elongated, thick-
walled enlargement of the tube. -Pass some blunt
instrument down the cesophagus, or inflate with a
tube to observe the relation of the mouth, esophagus,
and stomach. From the stomach follow out the small
intestine, large intestine, and cloaca, the last enlarge-
ment. Into the cloaca pass the contents of the repro-
ductive organs.

VII.— Appendages of the Tube.. Find the liver, a dark-

lobed, very conspicuous body, lying near the heart.

Branch Chordata 95

Partly concealed by the lobes of the liver, find a small,
spherical, dark green body, the gall-bladder. Is it con-
nected with the liver and intestine? Find somewhat
closely connected with this a long, irregular, pink-
colored body, the pancreas. Trace out the ducts of the
pancreas, gall-bladder, and liver as well as possible.
The red spleen is farther back in the abdominal cavity.

VIII. — Respiratory System. Find the dark, thin-walled,
inflated bodies, the lungs, one on each side of the
heart. Through their walls runs a network of blood-
vessels, thus bringing the blood into close connection
with the air filling the lungs. In the floor of the
mouth, just back of the tongue, find the slit-like open-
ing of the larynx, a chamber which connects with the
lungs. Pass something down the larynx to see the
relation to the lungs.

IX.— Reproductive System. The frog, like all vertebrates,
and many invertebrates, is unisexual, z.e. an individual
possesses but one kind of sexual organs. If the speci-
men is a female, large, irregular bodies, the ovaries,
will be found on each side of the posterior part of the
abdomen. Within these are found the cells which
develop into eggs. During the breeding season the
eggs pass from the ovary into the body cavity, and
from there to the exterior by oviducts. These are
coiled, tubular organs, with a funnel-shaped opening,
and they pass to the cloaca. The openings of the ovi-
ducts possess small cilia, whose vibrations guide the
eggs into them, and as the eggs pass through they
gather a mucus secreted by the walls of the duct.
This mucus swells greatly on striking the water, and
we may thus account for the appearance of the frog’s
eggs when seen in ponds.

96 Laboratory Guide in Zoology

X.— If the specimen is a male, two small, oblong, light-
colored bodies, the testes, will be found, one on each
side of the median line just anterior to the cloaca.
They produce sperm cells that pass directly by minute
tubes into the kidney and thence by the ureter to the
cloaca and to the exterior, where they fertilize the eggs
from the female.

XI.—Excretory Organs. Excretory organs are used to
throw off the waste material of the body. Hence the
lungs, kidneys, and skin may be grouped together as
parts of the excretory system. We have here only to
study the kidneys. These are two flat, oblong bodies,
lying one on each side of the median line in front of
the cloaca and dorsal to the testes. As the blood passes
through the walls of these bodies, it is relieved of certain
waste materials that pass through ducts, the ureters, into
the cloaca by openings in its dorsal wall. The bladder
is a colorless bag which opens into the ventral side
of the cloaca. Find the ureters.

XII. — Skeleton. Cut away the viscera already studied,
leaving the backbone, or spinal column, exposed on its
ventral side. Cut away the muscles on the fore and
hind legs without severing the ligaments that bind the
bones. Notice that in its general plan the skeleton
is made up of a central axis (spinal column) and its
appendages (limbs, etc.). Notice the segmented char-
acter of the backbone. Each segment is a vertebra.
The unsegmented posterior part of the axis represents
the fused segments that form the tail in other verte-
brates.

XIII. —Nervous System. This may be divided into two
great divisions, — the cerebrospinal and the sympathetic.
The cerebrospinal system is made up of the brain and

Branch Chordata 97

the spinal cord, and is now wholly invisible within the
cranium and the spinal column. The sympathetic sys-
tem may be seen in the shape of white cords lying
on the dorsal floor of the body wall on each side of the
spinal column. It is connected with the cerebrospinal
system by branches between the vertebrae. The func-
tion of the cerebrospinal system is to govern the
action of the muscles attached to the skeleton (skele-
tal muscles), while the sympathetic system controls
the action of the visceral organs. By bending, sever the
connection between the vertebra, in order to see the
spinal cord lying in a cavity within the solid bone of
the spinal column. Carefully remove the bone from
the dorsal surface of the cranium to see how the spinal
cord terminates in the brain.

The position of the central nervous system (cerebro-
spinal) lying ina tube parallel to and wholly separated
from the main tube (body cavity), and on the dorsal
side of the body is an important characteristic of verte-
brates as distinguished from invertebrates.

XIV.—Study again the pectoral arch,—the circlet of
bones supporting the forward legs. It corresponds
to our collar bone and shoulder blade.

XV.— Study the pelvic arch—the bones supporting the
hind legs. Study the bones of the fore and hind limbs,
noticing the similarity between the two pairs in the ar-
rangement of the bones. Make comparisons between
the bones of the limbs of the frog and those of the
higher vertebrates by aid of the following outline :—

In the fore legs, beginning with the segments next to
the body, the names and homologies are: (a) humerus,
which corresponds to the upper arm in man; (4) ulno-
radius, which corresponds to the ulna and radius of our

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Laboratory Guide in Zoology

forearm united; (c) the small bones following, gener-
ally six, correspond to the bones of the wrist and may
be called the carpus; (@) next to the carpus there are
five bones, corresponding to the bones of the palm of
the hand (one is much smaller than the others and
corresponds to the thumb) and all together compose
the metacarpus; (¢) the remaining bones making the
four fingers are called the phalanges.

XVI.—In a similar manner follow out the bones in the

hind legs: (a) the femur corresponds to the thigh bone;
(6) the tibio-fibula corresponds to the shank; (c) the
tarsus corresponds to the bones of the ankle; (d@) the
metatarsus corresponds to the bones of the foot; and
(e) the phalanges correspond to the bones of the toes.

THE BIRD

The English sparrow will serve very well for the follow-

ing study of the structure of a bird.

EXTERNAL ANATOMY

I,—General. Study the general structure of the body,

II.

noting that it may be easily divided into head, neck,
trunk, and tail. In the trunk find the thoracic and the
abdominal regions. In what ways does the bird differ
from the frog?

— Observe the hard beak composed of two mandibles.
Which of these is movable? Find the tongue, extend-
ing it with a pair of forceps. Describe its surface
above and below. Are there any projections upon it?
Of what use might they be? Behind the hard part of
the tongue find an opening — the glottis.

III. — Study the inner surfaces of the jaws. Find what

Branch Chordata 99

appears to be a longitudinal opening in the roof of the
back part of the mouth.. Push a pin through the
nostrils from the outside. Where does its point enter
the mouth? '

IV.— Study the eyes and eyelids. How are the latter
attached? See if you can find the nictitating mem-
brane which sometimes covers the eye of the living .
bird.

V.— Study the ear-opening. Describe its size and shape.
VI. —Study the wings. How does their length compare
with that of the body? How many joints in them?
VII. — Observe the kinds of feathers and their distribu-
tion over the body. Do you find on the trunk any
feather tracts beside comparatively bare places? Take
a long feather from wing or tail: see its central stem
or axis, and the vane which is made up of a vast num-
ber of barbs which in turn branch into barbules. The
barbules hold the barbs together. Are they more
effective toward the basal or the apical end of the
feather? Compare a feather from the ear and one from

the breast with the long one. How do they differ?

VIII. — Study the legs: what bones should you think are
covered by the feathers? Is there any system in the
arrangement of the scales on the tarsus and toes?
Notice the shape of the claws on the toes, and the pro-
tection along the under surface of the toes.

INTERNAL ANATOMY

IX.— Lay the specimen on its back in the dissecting
dish with its head pointing toward you. Cut the skin
along the median ventral line, beginning at the pos-
terior extremity of the lower mandible. Pushing back

100 Laboratory Guide in Zoology

the cut skin, notice over the thorax the large and
powerful pectoral muscles which control] the movement
of the wings. Which way do the muscle fibres
extend?

X.— Circulatory System. Cut through the pectoral mus-

XI.

cles and soft breastbone (sternum), extending the
incision back through the abdominal walls, thus expos-
ing the viscera of the thorax and abdomen. In the
thorax see the heart. Lift it carefully and cut the
connective tissues in such a way as to enable you to
study the important blood-vessels. From the front
of the heart on the left see the large aorta which
comes from the left ventricle. Before turning back-
ward this gives off the innominate arteries— one to
the right and one to the left. Each innominate artery
in turn has three branches; namely, a carotid, extend-
ing forward toward the head; a brachial, extending to
the wings, and a pectoral, extending to the pectoral
muscles. The large aorta extending backward may be
studied a little later when the thoracic and abdominal
viscera are removed. On its course it gives off various
branches, — to the stomach, to the liver, and to the legs.
Find three good-sized veins which pass into the right
auricle, and the right and left pulmonary arteries
which go from the right ventricle to the lungs.

— Study the structure of the heart itself. By cutting
transversely across the lower end see whether the ven-
tricles are completely separated from each other. Now
make a longitudinal section and study the structure of
the valves that connect one chamber with another.

XII.— Mount a drop of blood upon a glass slide, and

study the shape of the corpuscles as seen with a high
power of the microscope. Make drawings of them.

Branch Chordata IOI

XIII. —Digestive System. Study the alimentary canal.
. Beginning at the mouth see the straight tube, the
cesophagus, extending backward to the enlarged crop,
and then continuing to the muscular walled gizzard.
Open this: what is inside? What is the chief use of
the gizzard? Back of the gizzard see that the alimen-
tary tube continues as the duodenum, more or less curved
and looped. Within this loop see the pancreas—a
yellowish gland. Lift the pancreas and find where its
ducts enter the duodenum. At this time study also the
liver with its two large lobes, and find the greenish
gall-bladder between them. Directly under the gizzard
see the small, flattened, red spleen. The alimentary tube
continues backward from the duodenum as the small
intestine, much convoluted, until it enlarges in the
cloaca near the posterior end. Notice the ceca on the
small intestine. Make a sketch of the alimentary tube
and its connections.

XIV.— Respiratory System. The cartilaginous trachea is
easily seen extending from the mouth to the thoracic
cavity, where it divides into the bronchi, one passing to
each lung. Inflate the lungs through a tube inserted
into the trachea through the glottis, where it opens into
the mouth.

XV.— Reproductive System. If your specimen is a male,
the oval glandular testes will be readily seen in the
abdominal cavity after the alimentary system is re-
moved. Find a convoluted vas deferens running from
each'to the cloaca. If your specimen is a female, you
will see the glandular ovary. A single oviduct on the
left side of the body opens into the cloaca. Only a
vestige of the right oviduct remains.

XVI.—Renal System. When all the abdominal viscera

102 Laboratory Guide in Zoology

are removed, the kidneys are to be seen as dark-colored,
flattened bodies, fitting closely against the bones of the
back, one on each side the spinal column. Find a
tubular ureter running from each kidney to the cloaca.

XVII.—Nervous System. If the head is cut off and placed
in alcohol for a day or two, the brain will be hardened
so it can more readily be studied.. Remove the upper
part of the skull by cutting with strong scissors from
the beak over the eyes and around the back of the
head, thus exposing the brain. Note these parts of it:
the large cerebral hemispheres with the elongated
cerebellum immediately behind on the dorsal side; the
two olfactory lobes beneath the front part of the cerebral
hemispheres, and the two optic lobes in front of and at
the sides of the cerebellum. Make a drawing showing
the parts of the brain as seen from above and another
as seen from the side.

THE CLASSIFICATION OF THE VERTEBRATES

The highest branch in the animal kingdom is called
the Chordata. “It comprises all the Vertebrate Animals
(Fishes, Amphibians, Reptiles, Birds, and Mammals),
together with the Urochorda, or Ascidians, and the Adelo-
chorda, or Balanoglossus, and its allies. The name Chor-
data is derived from one of the most important of the few
common features by which the members of this extensive
phylum are united together — the possession either in the
young condition or throughout life of a structure termed
the chorda dorsalis, or notochord. This is a chord of cells,
typically developed from the endoderm, extending along
the mid-dorsal line above the enteric tube on the ventral
side of the central nervous system. It becomes enclosed

Branch Chordata 103

in a firm sheath, and forms an elastic supporting structure.
In the Vertebrata (with the exception of Amphioxus and
the Lampreys and Hagfishes) it becomes in the adult
replaced more or less completely by a segmented bony
or cartilaginous axis—the spinal or vertebral column.”
(Parker and Haswell.)

The branch or phylum Chordata is divided into three
subbranches or subphyla, namely : —

Subphylum I. Adelochorda. Balanoglossus.

Subphylum II. Urochorda. Ascidians and Sea-squirts. :

Subphylum III. Vertebrata. Fishes, Amphibians, Rep-

tiles, Birds, and Mammals.

The first of these includes the remarkable worm-like
animals belonging to the genus Balanoglossus. The
second comprises the Ascidians or Sea-squirts, which are
often called Tunicates and grouped together under the
name Tunicata. The third includes the vertebrates proper,
in which are found the highest animals.

In the subphylum Vertebrata, some of the very lowest
fish-like forms have no skull, or development of the ante-
rior end of the vertebral axis. These are classed under
the head of Acrania. All the others, or those with a skull,
are called Craniata. These are divided into six great
classes, named below in the order of their natural develop-
ment. The first four are cold blooded, and the other two
are warm blooded.

Class I. Cyclostomata. Lampreys.

This class comprises comparatively few forms, which
have in place of jaws a suctorial mouth; they have no
fins or other lateral appendages, and only one nasal
aperture. The Lampreys and Hagfishes belong to this
class.

Class II. Pisces. Fishes.

104 Laboratory Guide in Zoology

The members of this and the preceding classes are the
lowest of the true vertebrates, not only in structure, but
also in strength, intelligence, and sensibility. As a class,
however, the fishes are superior to all the others in number
and variety of forms. They live always in the water, are
cold blooded, and breathe by gills. Their fins are homolo-
gous with the limbs of the higher vertebrates.

Class III. Amphibia.

The Amphibia are cold-blooded animals, having gills
when young, and lungs when adult. In the early stages
the tail is modified into a swimming organ. The eggs are
deposited in the water or upon moist surfaces, the skin is
soft and naked, and the skeleton is bony or ossified.
There is no distinct neck. There are a number of orders
of Amphibia, the lower including the newts and salaman-
ders, or the tailed Amphibians, while the higher include
the frogs and toads.

Class IV. Reptilia. Reptiles.

These are cold-blooded animals, distinguished from the
Amphibia by never having gills, and from birds by the
absence of feathers. With the exception of some of
the turtles, they are carnivorous. The Reptilia includes
the snakes, the lizards, the turtles, and the crocodiles.

Class V. Aves. Birds.

This is the most clearly defined class in the animal king-
dom. Its members are air-breathing, egg-laying, feathered
vertebrates with the front limbs developed for flying or
swimming, and the hind limbs for perching, walking, or
swimming. The bones are light and compact, and the neck
is usually long. The birds are a group of great interest
and of the greatest economic importance, whether we con-
sider their direct value to man as food, or their indirect
benefits in checking insect and other animal pests.

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