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BIOLOGY

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LABORATORY DIRECTIONS
IN

PRINCIPLES OF ANIMAL BIOLOGY

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LABORATORY DIRECTIONS

IN

PRINCIPLES OF ANIMAL BIOLOGY

BY

A. FRANKLIN SHULL

ASSOCIATE PROFESSOR OF ZOOLOGY IN THE UNIVERSITY OP Jp3HIGAN

WITH THE COLLABORATION OF

GEORGE R. LARUE

ASSISTANT PROFESSOR OF ZOOLOGY IN THE UNIVERSITY OF MICHIGAN

ALEXANDER G. RUTHVEN

PROFESSOR OF ZOOLOGY AND DIRECTOR OF, THE MUSEUM OF ZOOLOGY

IN THE UNIVERSITY' «)r»

PETER 0. , O&BEBIffei?,.1 «\> j ,%

ASSISTANT PROFESSOR OF ZOOLOGY IN THE UNIVERSITY* 6F MitHIOAN

AND OTHERS

McGRAW-HILL BOOK COMPANY, INC.

239 WEST 39TH STREET. NEW YORK

LONDON: HILL PUBLISHING CO., LTD.

6 & -8 BOUVERIE ST., E. C.

1919

55-

BIOLOGY

LlBRf
G

COPYRIGHT, 1919, BY THE
MCGRAW-HILL BOOK COMPANY, INC.

THE MAPLK PRESS YORK PA.

Our ^fceinttin Students

FOR WHOM A KNOWLEDGE OF PRINCI-

PLES AFFORDS, IN OUR OPINION,

THE BEST APPROACH TO

ANY SCIENCE

403321

PREFACE

The course for which this book of laboratory directions was prepared
is a recognition of the growth which the science of Zoology has made
in the past several decades. No longer a purely morphological subject,
zoology is not in the opinion of the authors properly treated in a purely
morphological course. Good teachers have long recognized that dis-
section and classification alone would not make a zoologist, and have
striven in lectures and recitations to provide the larger outlook which the
-science has come to possess. But this recognition seems hardly adequate.
If in the lectures and recitations due attention is paid to the type dis-
sections in the laboratory, morphology can scarcely avoid receiving an
emphasis it does not deserve. If to avoid this over-emphasis the recita-
tions and lectures are devoted exclusively to evolution, distribution,
ecology, genetics, etc., the laboratory exercises and recitations must seem
unrelated to one another. Recitations and laboratory work thus become
two courses which the student pursues simultaneously.

The only solution has appeared to be to make the laboratory work
itself bear on the large questions of biology. The laboratory work may
thus have a balance of its own, it does not need to be averaged with the
recitations. This book contains directions for first-hand exercises which
we believe have the emphasis properly placed. Morphology still receives
more attention than any other division of the subject, but it is nearly
everywhere directed to some end which is not merely structure.

The large number of inquiries received concerning this course, indi-
cating a widespread belief that some plan of this kind is preferable to
the usual type course, have led us to make the book available for use in
other institutions. Many details of the course may well be altered. One
form will often illustrate a point as well as another form. In a number of
instances alternative tasks are provided; others will occur to the experi-
enced teacher.

In the preparation of the laboratory directions every member of the
Zoology Department of the University of Michigan has had a share,
either in original organization or subsequent revision. Besides those
mentioned on the title page as authors, special mention is due to Pro-
fessors Jacob Reighard, E. C. Case, R. W. Hegner, and Paul S. Welch,
and Mr. George E. Johnson.

A. FRANKLIN SHULL.

August, 1919.

vii

CONTENTS

PAGE

PREFACE vii

INSTRUMENTS, SUPPLIES & TEXTBOOKS 1

SCHEDULE 1

LABORATORY ARRANGEMENTS AND REGULATIONS 2

LABORATORY RECORDS 2

FILING AND CORRECTION OF THE RE-PORT 4

EXERCISE

I. USE OF THE MICROSCOPE 5

II. THE CELL 8

III. ACTIVITIES OF PROTOPLASM 13

IV. MITOSIS (Karyokinesis) 20

V. CELL AGGREGATION, DIFFERENTIATION, AND DIVISION OF LABOR .... 23

VI. REPRODUCTION 32

VII. BREEDING HABITS OF VERTEBRATE ANIMALS 37

VIII. EMBRYOLOGY OF TYPICAL ANIMALS 40

Xr HOMOLOGY 46

X. TAXONOMY 51

XI. ECOLOGY AND ADAPTATION 62

XII. ZOOGEOGRAPHY 67

XIII. PALEONTOLOGY 70

INDEX 76

IX

LABORATORY DIRECTIONS

IN

PRINCIPLES OF ANIMAL BIOLOGY

A. INSTRUMENTS, SUPPLIES, AND TEXT-BOOKS

Students electing the course in Principles of Animal Biology should
furnish themselves with the following :

1 "Principles of Animal Biology" (by Shull, LaRue and Ruthven).

1 "Laboratory Directions in Principles of Animal Biology."

2 Teasing Needles.

% Ib. note paper, 2 doz. drawing sheets, 1 piece press board, all in strong manila

envelope.
1 Pair Fine Forceps, milled tips, 5 inch.

1 Millimeter Rule. I ,J

3 Medicine Droppers.

Y2 doz. Slides. > '* ,

2 doz. %-inch Cover Glasses No. 2, Sqi*ase«Qfc C^ircuiar; '• ^D> % ° . ,
1 Piece Absorbent Cloth for Cleaning Slides and Covers: ' > • • '1 „' /•>
1 5H Venus Drawing Pencil.

1 Eraser with Beveled End.

1 Tablet Fine Emery Paper for Sharpening Pencils.

1 Case for Instruments is desirable.

13 Manila Envelopes Printed for Zoology.

These instruments and supplies may be obtained in sets at the various
dealers.

B. SCHEDULE

An attempt will be made to maintain a definite schedule in the work
of the laboratory. Fill in the blanks below, from the notice posted on
the bulletin board showing the date for beginning each subject and the
number of periods allowed for it. Plan your work so that you may finish
it in the time allotted.

1

LABORATORY DIRECTIONS IN

Report
Number

Subject

Date of
Beginning
Study

Number of
Periods
Allowed

1.

Relation of object and image .

2.

The cell

3.

Activities of protoplasm

4.

Mitosis

5.

Cell aggregation, differentiation, division of
labor

6.

Reproduction

7.
8.

Breeding habits of vertebrate animals
Embryology of typical animals.

9.

Homology. .

10.

Taxonomy

11.

Ecology and adaptation

12.

Zoogeography

13.

Paleontology

C. LABORATORY ARRANGEMENTS AND REGULATIONS

1. General Laboratory Directions. — Each student on leaving the
laboratory should leave his place and instruments in good condition.
Return the microscope, dissecting microscope, trays, etc., in good con-
dition to their proper places. Clean your place at the table. Push the
stool under the table. Do your part to leave the laboratory in good order
for the next section.

2. Laboratory Notes Must not be Removed from the Laboratory
Without Permission.— At ohe conclusion of each laboratory period put
all your work, complete or incomplete, in an envelope, properly labeled
and deposit it in tho plaps indicated by the instructor.

3. Always put your name, section and laboratory seat number on your
text-book, laboratory manual, and envelopes so that they may be easily
identified.

4. Report immediately to the^instructor or his assistant any part of
the laboratory equipment that is missing or out of repair.

D. LABORATORY RECORDS

The laboratory records consist of notes and drawings which should
supplement each other. If laboratory records are to be accurate they
must be recorded at the time the observations are made, not hours or
days afterward.

1. Notes. — The laboratory work of the course consists of 13 exercises.
With the exception of the first, which is a preliminary drill in the use of
the microscope, each exercise is designed to illustrate certain generaliza-
tions. The facts upon which these generalizations are based can, in

PRINCIPLES OF ANIMAL BIOLOGY 3

many cases, best be recorded in the form of notes. Such notes, recorded
while the observations are being made, will usually be isolated state-
ments, often without connection with those that precede or follow. How
frequently such notes should be made is left to the judgment of the
student. They are intended solely as an aid to the memory . Obviously,
therefore, these disconnected notes need not repeat statements made
in the laboratory directions. Likewise, it is superfluous to write in the
notes what the drawings show equally well. Unless called for by the
instructor, these notes need not be handed in for inspection.

2. Summary. — When an exercise is completed, with his notes and
drawings before him, the student should be able to draw certain conclu-
sions from them, or to state the principles which they illustrate. In
most of the exercises, those conclusions or principles will be capable of
clear expression in the form of a summary. If the student is in doubt as
to what this summary should contain, it probably means that he has not
grasped the significance of the exercise, and he should ask help. How-
ever, not all the exercises lend themselves equally well to recapitulation,
and the instructor may indicate, in connection with each one, whether a
summary is expected. When a summary is written, it is to be handed in
with the drawings for inspection.

3. Drawings form a very essential part of the laboratory records.
They should therefore accurately fulfill the purpose for which they are
made. Many of them must be detailed, not caricatures of the general
appearance of the object; when detail is desired frequent comparisons
of drawing and object must be made during the process of drawing.
Drawings should in all cases be analytical, that is, should represent the
student's analysis of the structures seen. They should, therefore, be
made directly from the specimens themselves. Laboratory drawings
should not be considered from the standpoint of art, but from the stand-
point of faithful analysis. Sometimes brief sketches will suffice to illus-
trate a specific point; but even these must not be careless.

Special training in drawing is not presupposed, but any student can
attend to certain features. Always use a sharp, hard pencil. Very
lightly mark in the outlines and general features of the object to be
drawn, erasing and redrawing any parts which are out of proportion
or incorrect. Then carefully retrace the corrected outline leaving a clean,
sharp, single line. Leave no thick lines, nor double lines, nor loose ends,
nor gaps between the ends of lines where they do not belong. Draw
even small granules with complete outlines and of the proper shape and
relative size. If granules are actually irregular make them so. Remem-
ber that even minor errors offend the eye.

Make drawings large enough to show the required details.

Shade sparingly, and always with a definite purpose in view. Shading
is rarely needed. An excellent method of shading for scientific purposes

4 LABORATORY DIRECTIONS IN

is by the use of fine regularly placed dots (stippling) . In pencil work,
an artist's tool called a blender may be used to secure an even gradation
of shading.

4. Drawings and Legend. — The pages or " Plates" of drawings
should be numbered consecutively through the course with Roman
numerals, in the upper right-hand corner (Plate I, Plate II, etc.). The
student's name should appear in the upper left-hand corner. The indi-
vidual structures in a drawing may be labeled with the initial letter (or
first two letters) of their names, and an explanatory legend be placed at
the bottom of the plate; or, if preferred, the entire names may be written
beside the figure. In the latter case, the labeling must be neat and so
inconspicuous as not to overshadow the drawing. If the drawing is done
with a pencil, the labeling should be done with a pencil. A neat style of
lettering for free-hand work is shown in Fig. 1. Refer to it if in doubt as
to the correct form of letters.

ABCDEFGHIJ K L M
N 0 P 0 Ft S T U V W X Y Z
a b c d e f q h i j k I m

nopgrsfuvwxy z

FIG. 1. — The alphabet in suitable style for free-hand lettering.

Do not crowd the drawings on the plate but plan the plate so that there
will be ample room for the drawings, the lettering, and the legend.
Always take a fresh sheet of drawing paper when beginning a new exercise,
so that drawings of two different exercises will not be found on one sheet.

E. FILING AND CORRECTION OF THE REPORT

At the conclusion of each laboratory period place all notes and draw-
ings, finished or unfinished, in an envelope, fill in the blanks on the face
of the envelope, and file the report in the place designated by the in-
structor. Notes and drawings must not be removed from the laboratory
except by permission. They must be available for inspection at all times
except when the student is actually working on them. At the time indi-
cated by the instructor for the completion of the study on each exercise
the report will be taken up, graded, and returned. The student, while
in the laboratory, should make the corrections indicated and then place
the work in an envelope where it is to be kept until the end of the semester.
At that time the notes and drawings, arranged in proper order, must be
returned to the laboratory for inspection.

EXERCISE I
USE OF THE MICROSCOPE

Before beginning work, it is necessary to become familiar with the
microscope and the method of using it. The first laboratory period will
be devoted to this.

Identify the stand, the oculars, the tube, the objectives, the stage,
the diaphragm, the mirror, the foot, coarse adjustment, fine adjustment,
clips. Study the illustration, Fig. 2, for other features.

FIG. 2. — A modern microscope, with its parts named. (Courtesy Spencer Lens Co.)

Understand perfectly how to change from "low power" to "high
power," and the reverse; also which direction to turn the coarse adjust-
ment and the fine adjustment to raise or to lower the body tube.

In using the microscope, note especially the following points:

5

6 LABORATORY DIRECTIONS IN

1. Never focus downward while looking into the microscope as there is
great danger thus of driving the objective against the object examined,
to the great injury of both.

2. Never wipe off the ocular or objective with handkerchief, cloth,
or anything except lens paper, which will be furnished as needed.

3. In case the 'ocular or objective cannot be readily cleaned or is
injured in any way take it at once to one of the instructors. Do not
try to clean it yourself.

5. Report at once to the instructor any missing parts or injuries to
the microscope.

PREPARED SLIDE OF A PRINTED LETTER

1. Focusing. — Place the 4x ocular and 16 mm. objective in position
and adjust the mirror so that the light from the window passes up through
the tube of the microscope. Now so place the slide of the printed letter
on the microscope that its label may be read (that is, right side up) and
the letter is as nearly as possible in the center of the aperture in the stage.

Lower the tube of the microscope by means of the coarse adjustment
until the objective almost touches the cover-glass; then with the eye
at the ocular slowly move the tube upward until the letter on the slide
appears distinct.

2. Relation of Object and Image. — With the slide held as in (1)
make a drawing (on drawing paper) of the letter as seen with the unaided
eye, and another drawing of the image made by the microscope. Before
making your drawing, refer again to the instructions for labeling draw-
ings and plates.

These drawings should be made of the same size as the image and
object respectively. The image may be measured by laying a milli-
meter scale across the stage of the microscope at one side, and looking
into the microscope with one eye and at the scale with the other. The
scale will appear to lie over the image.

This sheet of drawings is your Plate I. Always follow this style in
making up your plates.

Now using note paper and ink state how the image differs from the
object.

3. Illumination. — Note carefully the brightness of the field of vision
and the appearance of the letter; it is illuminated by transmitted light.
Tilt the mirror and observe the change in the intensity and character of
the light. The object is now viewed by reflected light which must be
employed for all opaque objects.

4. Magnification. — Determine what combination of ocular and ob-
jective gives the lowest magnification, what combination the highest,
etc. Make a table showing all the combinations of objectives and oculars
arranged in the order of their magnifying power.

PRINCIPLES OF ANIMAL BIOLOGY 7

The student should note that the oculars are marked to denote their
magnification, thus, 8x and 4x, while the objectives are marked in terms
of their focal length, thus, 4 mm. and 16 mm. These terms should always
be used in designating the oculars and objectives rather than the ex-
pressions high power and low power, or large and small.

5. Other objects will be furnished for examination.

Note to the Student. — The work of this laboratory period constitutes
report number 1. Place all the notes and the plate (see that each sheet
of your work has your name on it) in an envelope, fill in the blanks giving
as the subject "of this report "The Relation of Object and Image," and
put the envelope in the place indicated by the instructor. Put every-
thing away in good order. Put waste paper in the waste basket; push
the chair or stool under the table; leave the table in as good condition
as you would like to find it. Take this book of laboratory directions
home with you and study carefully the general laboratory regulations,
the statements concerning the laboratory records, and the use of the
microscope.

Be ready for a quiz at any time on the work completed.

EXERCISE II
THE CELL

It is the purpose of this exercise by means of a study of actual mate-
rials to acquaint the student with the general facts in regard to the
structure of the cell and the extent to which the cell occurs as a unit of
structure in living things. In order to accomplish this object a general
problem is stated and this general problem is subdivided into minor
problems. Appropriate materials with suggestions for study are given
under each subdivision.

At the conclusion of the exercise the student should be able to formu-
late certain inferences in regard to the cell. He should realize that the
study of the relatively small number of materials suggested in the course
of this exercise do not furnish data sufficient for the confirmation of the
cell doctrine but that the facts observed belong to certain classes of
facts on which the modern cell doctrine is based.

A. THE GENERAL PROBLEM

To determine the structure of the cell and the extent of its occurrence
as a unit of structure in living things.

1. What Structural Features are Common to Cells?

A complete answer to this problem cannot be made until all the
materials in this exercise have been studied but a study of cells from
the four sources indicated below (la, 16, Ic, Id) will serve to introduce
certain structures and will give an idea as to the forms which a cell may
assume.

la. Place a drop of water on a clean slide and mount in it a small
piece of stratum corneum of frog skin (the outermost layer that is re-
peatedly shed). Spread the specimen flat, and cover with a cover-glass.
Examine with the microscope, trying out different light intensities.

Note the units of which the tissue is composed. These are the cells.
Each contains a dense mass, the nucleus (plural, nuclei), which is usually
visible. The remainder of the contents of the cell, besides the nucleus,
is to all appearances nearly structureless and is known as cytoplasm.
Both nucleus and cytoplasm are composed of protoplasm. The surface
layer of each of these cells is the cell membrane.

Now remove the cover-glass or mount a fresh piece of stratum cor-
neum. Draw off the excess water with filter paper or a blotter, and add a

8

PRINCIPLES OF ANIMAL BIOLOGY 9

drop of erythrosin, which is a staining solution. After half a minute
remove the surplus stain, add a drop of distilled water, and put on a
cover-glass. Which part of the cell is most intensely stained?

Draw a group of three or four cells, each one about half an inch in
diameter. An outline of the cells and their nuclei will suffice, but it
should be neat. Label nuclei and cytoplasm.

16. Examine a section of the liver of a frog or salamander which
you will find in the tray on the table. Is this made up of cells? What
part of the cell is most intensely stained? Is a nucleus found in each
cell? If not, explain its apparent absence.

Ic. Examine a slide of stained snake, bird, or salamander blood.
Draw an oval corpuscle in outline, showing the nucleus. This is one
of the corpuscles which gives the blood its red color but its present red
color is due to the fact that it has been stained.

Id. From a culture containing Protozoa (one-celled organisms)
mount a drop of water. Before putting on the cover-glass, examine the
slide with low power to see that the organisms are present. Then add
a drop of acetic methyl-green, mixing the stain with the drop containing
Protozoa, and put on the cover-glass.

This solution kills the organisms and stains the nucleus of each. How
many kinds of nucleated organisms do you find?

In the cells studied thus far the nucleus, cytoplasm and cell membrane
have been demonstrated. During the remainder of this study note
carefully whether these cell structures are present in the cells studied.

2. What are Some Other Structures Found in Cells?

2a. Examine a leaf from the growing tip of Elodea. Note the cell
wall which limits the protoplasm of the cell. Is this cell wall relatively
thick or thin? Draw the cell wall of a single cell showing also the con-
nections with the walls of neighboring cells. The figure should be 1J^
to 2 inches long.

Do all^cells have enveloping structures such as cell walls or cell mem-
branes? Reserve the answer to this question until you have examined
the cells in the remainder of this study and include your answer, which
should be in some detail, in the summary.

26. Examine Euglena or other green flagellate for colored bodies.
Mount in water a bright green leaf of Elodea taken from a growing tip
of a branch and examine it for colored bodies. These are plastids.
Search in Elodea for plastids shaped like two biscuits fastened together.
How do you explain this shape? Color of fruits and of many flowers may
be due wholly or in part to the presence of colored plastids. Chromo-
plast is'a general name for all colored plastids while the word chloroplast
is used to designate only green plastids.

Draw in outline one cell with its plastids. If Elodea is chosen for

10 LABORATORY DIRECTIONS IN

this sketch, the chloroplasts may be added to the figure of the cell wall
already drawn. In this case plastids shaped like two biscuits fastened
together should be included if they are found. Be on the lookout for
plastids in other unstained cells to be studied later.

2c. In mounted sections of Hydra study the cells of the innermost
layer. Hydra is a small many celled animal, having certain affinities
with jelly fishes, corals, sea-anemones and hydroids. Its body is com-
posed of two distinct layers of cells separated by a non-cellular layer.
Note particularly the large clear spaces within the inner cells. These
spaces are vacuoles. Draw in detail a group of three cells of this layer
showing structures present.

2d. Examine specimens or Phacus or Euglena (both green flagellate
Protozoa) for paramylum bodies. These are granules of stored food,
resembling starch in its chemical composition. They are colorless.
Their shape differs in various species, being discoid in some, ring-shaped,
rod-shaped, or polyhedral in others. If Euglena is used for this study
flatten the specimen by withdrawing water from the preparation and look
for minute colorless bodies among the green. Do not mistake the
rounded nucleus near the middle of the body and the reservoir of the
contractile vacuoles near the anterior end for the paramylum bodies.

2e. Remove a frog's egg from its jelly-like covering, then tease out
(tear up finely with needles in water) the substance of the egg upon a slide,
separating the particles until they form a very thin layer on the slide,
and mount under a cover-glass. Examine with the microscope. The
fine granules are yolk material (stored food). Sketch a group of them.

3. What are Some of the Structures of the Nucleus?

3a. In longitudinal sections of a dorsal root ganglion (a small mass
of nervous tissue occurring near the junction of spinal nerves with the
spinal cord) of a cat look for a single rounded body near the center of
many of the nuclei. This is the nucleolus. Note its color. Observe
the chromatin which occurs as granules in the nucleus. Compare the
colors of these granules. Sketch in detail a cell of the ganglion -to show
nucleolus or nucleoli and chromatin granules. The sections on these
slides were stained with two stains. All parts of each cell were sub-
jected to the same processes. On what basis may the difference in color
between the nucleolus and the chromatin granules be explained?

4. What is the Structure of a Simple Living Cell?

Amoeba furnishes an example of such a cell.

4a. Mount some ooze from a culture containing Amoeba. The
student should endeavor to find a specimen for himself. If an amceba
cannot be found ask help, but do not discard the slide. It may have
Amceba on it, even if the student has not been successful in identifying
one.

PRINCIPLES OF ANIMAL BIOLOGY 11

46. Describe the general appearance of. Amoeba, its color or lack of
color. Be specific.

4c. The blunt processes thrust out from the body are pseudopodia
(singular, pseudopodium) . Do they change shape or size? If so make
three sketches in outline only of the entire amoeba at intervals to show
these changes. What relation exists between the pseudopodia and the
movement of the body as a whole? In some species there is only one
pseudopodium.

4d. On using high magnification note the outer clear layer of proto-
plasm, often quite thin; this is the ectosarc. Within the ectosarc is the
granular endosarc. Note the movements within these two layers, es-
pecially in the formation of a pseudopodium. Which layer moves more
rapidly when free to move? What conclusion may be drawn regarding
the relative fluidity of ectosarc and endosarc? Give reasons for the
answer to this question.

4e. In large specimens vacuoles containing particles of food may be
seen. The larger food vacuoles may be recognized by their contents.
In which layer are they? What are their contents? These contents
are cell inclusions, not part of the cell.

4/. Look for one or more pulsating vacuoles. These are not always
visible but if the specimen be watched for a few minutes small vacuoles
may be seen which increase in size and finally move to the surface where
they collapse. Under certain conditions of light the contractile vacuoles
may have a slight pinkish cast. The disappearance of the vacuole is
one feature that distinguishes the contractile vacuole from the more
persistent food vacuoles. The latter also contain food particles.

40. Find the nucleus, a rounded, highly refractive somewhat grayish
body, occurring in some species in a vacuole-like structure. Is it in the
ectosarc or endosarc? If you do not see the nucleus clearly in your
specimen consult the demonstration of a stained specimen.

4/i. Make a careful drawing of Amoeba not less than two inches in
diameter, showing all the structures noted in the foregoing study. Ask
for instructions if in doubt on any point.

If on any point of structure or appearance your drawings fail to
give a proper idea, a description should be given also.

5. How May Cells be Modified?

5a. Cartilage Cells. — On the upper end of the humerus or femur of
a preserved frog note the glistening white cap. This is cartilage. Place
a drop of water on a slide. Then with a very sharp scalpel or safety
razor blade shave off a very small, thin piece of cartilage from the
surface, and touch the edge of the blade to the drop of water. Cover,
and examine the thin edge of the cartilage with the microscope. How
are the cells arranged ? Do the cells touch one another ? The intervening

12 LABORATORY DIRECTIONS IN

substance is the matrix. What inference may be made concerning its
origin? Draw a few groups of cells, showing the structure of at least two
of them, and representing also the matrix.

56. Bone Cells. — -Examine prepared sections of dry bone. The
dark spots are the spaces or lacunce (little lakes) formerly occupied by
the bone cells. Projecting from the lacunae are minute wavy channels, the
canaliculi (little canals) into which in life extend slender processes (like
pseudopodia) of the bone cells. Larger openings, for blood vessels, may
occur in the preparations. The remainder of the specimen consists of
the hard parts, mostly calcium salts, deposited in the matrix. The
fleshy parts of the bone are dried and shriveled in these preparations.
What is the origin of the matrix?

Draw carefully a lacuna with its canaliculi as representing the form of
a bone cell.

5c. Remove a hair from your eyebrow, mount it in water and examine
at different points along its length both on the margin and on the upper
surface. Can you detect anything that would indicate cells? Sketch a
segment of the hair to show them. In the sketch the diameter of the hair
should be one-half inch.

5d. Wool is similar to hair in its composition. Examine the minute
fibers from a woolen blanket. Are there any indications of cellular
structure?

5e. Human Blood. — This exercise is not required. Any one who desires
to examine his own blood will be shown how to do so with comparative
safety and with the minimum of pain. Mount the blood, and examine the
red corpuscles . What is their color when seen singly ? Is there a nucleus ?
Examine a demonstration of stained human blood.

6. Is the Whole Animal Body1 Made up of Cells?

6a. Examine a longitudinal section of a small salamander. The names
of most of the structures (organs) which you find there maybe determined
by consulting the wall chart. Make a list of all the organs which you
think are made up of cells? Do you find any organs not made up of cells?
If so make a list of them also. If you are in doubt as to the interpretation
of any of the observations consult the instructor or the assistant. (The
presence of nuclei may be taken as evidence of the existence of cells if
the cell outlines cannot be determined.)

66. Recall also in connection with this problem the parts of the animal
body studied la, 16, Ic, 2c, 3a, 4, 5a, 56, 5c, 5d, 5e.

B. SUMMARY

In your summary state the general conclusions in regard to the cell
which may be derived from the facts presented in this exercise.

1 To the teacher: By the addition of proper plant material this problem may be
made to cover all living things.

EXERCISE III
ACTIVITIES OF PROTOPLASM1

Living protoplasm exhibits certain properties which distinguish
it from non-living matter. Among these are independent movement and
metabolism. Independent movement is the result of the instability of
living substance and its reactiveness to chemical and physical forces.
'Metabolism includes the taking in of food, its transformation into energy
or into more living substance, and the elimination of waste formed during
the process.

Only a few of the more easily demonstrated functions of living matter
are studied in this exercise. Even a representative series of experiments
in physiology would require considerable time, and some previous
training in biology and related subjects.

Notes. — Much of the work outlined below is not recorded in drawings
Notes should be written with special care in such cases.

ir A. FUNCTIONS OF THE CELL

Vital phenomena are first studied in the cell since all activities of the
protoplasm are fundamentally cell activities.
1. Movements of Protoplasm.

la. Mount a young green leaf of Elodea, recently collected, under
a cover-glass. Under high magnification look for movements of the pro-
toplasm inside of some of the cells. If movements are not observed at
first they will usually begin after a few minutes. This form of movement
is known as "rotation." In what region of the cell does it occur? Note
the time required for a complete rotation. Compare the direction of
rotation in adjacent cells. Draw an outline of the cell and indicate by
arrows the direction of rotation.

16. Recall the movements of the protoplasm in the endosarc of
Amoeba, especially as it enters a newly formed pseudopodium. If
material is available this should be observed again. This movement of
the protoplasm is known as " streaming."2

Ic. Amceboid Movements. — Recall the movements of Amoeba by means

1 To the teacher : It is not essential that all of the experiments and observations
outlined in this exercise be employed. The ones to be selected may depend in part
upon the amount of time to be devoted to the subject, and upon the facilities of the
laboratory.

2 At the option of the instructor movements like those mentioned in la and 16 may
be observed in Paramecium, in hairs from the stem of the tomato plant, in stamen
hairs of Tradescantia, or in some other plant.

13

14 LABORATORY DIRECTIONS IN

of blunt pseudopodial processes. Such movements result in locomotion
or the engulfing of food.

Id. Ciliary Movements. — Paramecium. Examine specimens of Para-
mecium mounted on a slide. Note their movements. Introduce a small
drop of iodine along the edge of the cover-glass. The iodine kills the
animals and stains the cilia covering their surface. Study these cilia.
Approximately how much of the cell is devoted to ciliary movements?
Determine whether the whole surface is covered by cilia. Are the cilia
like the rest of the protoplasm or may they be regarded as specialized
for movement?

Rotifers. Place a number of rotifers (wheel animalcules) on a
slide and examine with a microscope. Observe the ciliary movements
at the broader end of the body. Describe the structure and arrangement
of the cilia. Do they beat with equal vigor in both directions, or more
strongly in one direction? If the latter, is the form of the cilium during
the stronger beat the same as during the weaker one? If you detect a
differ ence., make a drawing of a single cilium to illustrate 'the difference.

Gill of a freshwater mussel.1 Mount a small piece cut from the edge
of the gill of a freshwater mussel. The epithelium covering the gill is
ciliated. As the piece slowly dies, the movements of the cilia diminish.
Observe their movements as in the rotifer.

le. Flagellate Movements. — Examine Euglena or Peranema on a slide
and note its form of locomotion. Introduce some iodine along the edge
of the cover-glass. Now look for specimens which have been killed by the
iodine. A long whiplike thread at one end is the flagellum by means of
which the animal moves. Flagellate movements are less common than
ciliary movements in tissues of higher forms.

In which, if any, of the specimens so far studied is the moving proto-
plasm like the quiet protoplasm near it? In which, if any, does the moving
protoplasm appear to be differentiated for movement?

2. Metabolism.

2a. Ingestion. — Mount some paramecia on a slide and note the
color of the round bodies (food vacuoles) in them. Put a small drop of
carmine suspension (well shaken) along the side of the cover-glass.
(India ink may be substituted for the carmine.) After a moment note
the formation of red vacuoles inside of the animal. The small carmine
particles have been ingested. Study a chart or model of Paramecium
and determine how ingestion is accomplished.

26. Secretion and Digestion. — Find a specimen on the above slide that
is quiet. To quiet them it may be necessary to press down the cover-glass
slightly or put them into a jelly made by steeping crushed quince seeds in

1 The gill of a freshwater mussel may be used as a substitute for the rotifers or in
addition, at the option of the instructor.

PRINCIPLES OF ANIMAL BIOLOGY 15

water. Examine with high magnification and determine the structure
of the food vacuoles. What proportion of the vacuole is liquid and what
proportion is solid material? Where are the food vacuoles found?
What accounts for their distribution? Are the carmine vacuoles evenly
distributed? If not where are they most abundant? Do you observe
any difference in the various food vacuoles? What may be the object
of the liquid in the vacuoles? What may be its source?

Neutral red gives an opportunity to determine the nature of some of
the chemical processes taking place in the vacuoles since it stains acid
substances red and alkaline ones yellow. To prove this put a drop of
weak alkaline solution (NaOH) and another drop of weak acid solution
(HC1) at opposite ends of a slide resting on a white background. Add
a drop of neutral red (0.001 per cent, solution) to each of the drops on the
slide and note results.

Mount a fresh slide of paramecia and put a drop of neutral red along
the edge of the cover-glass. This will reach the paramecia after a few
minutes, with the usual result that some of the food vacuoles are stained
red, others will be found to be colorless, and still others will have a pale
yellowish tinge. What does this suggest as to the nature of the contents
of the three kinds of vacuoles? What is the source of the substances
indicated in the vacuoles? Other substances whose action may account
for the digestion of the food in the vacuoles may be inferred at the end of
the exercise.

2c. Absorption. — After food is rendered soluble by digestion it is
absorbed by the surrounding protoplasm. This process cannot readily
be demonstrated. How may it take place in Paramecium?

2d. Respiration and Oxidation. — This function is also difficult to
demonstrate in single cells. In Paramecium oxygen is taken in directly
through the surface of the body and carbon dioxide is given off in the same
way. What provision, if any, is made for bringing in oxygen to the vari-
ous parts of the body and for taking carbon dioxide out to the surface?
How is a constant supply of fresh water brought to the animal?

2e. Excretion. — Excretion takes place in Paramecium by means of
two clear pulsating vacuoles. Mount some paramecia and observe the
vacuoles in a quiet specimen. Note that they increase in size and dis-
appear at intervals. Where are they located? Observe the radiating
canals around them. At what stage in the pulsation of the vacuoles are
these canals most conspicuous? What do the vacuoles contain? What
is the relation of the canals to the vacuoles? What becomes of the
contents of the vacuoles when they disappear?

B. FUNCTIONS OF TISSUES AND ORGANS

The cell in one-celled organisms has a generalized function. In
multicellular organisms different cells have become specialized to perform

16 LABORATORY DIRECTIONS IN

different functions. Cells having similar functions combine to form
tissues and tissues unite to form organs of various kinds.

3. Movements. — Movements in higher animals are usually due
to the concerted action of numerous specialized cells known as muscle
cells.

3a. Examine a longitudinal section of the tail of a young sala-
mander. A considerable portion of the section passes through the
muscles. Note that the muscle mass is divided into segments, the
myotomes, by oblique septa of connective tissue. Muscle cells extend
lengthwise from one septum to the next. What is the relative length and
width of each cell? (The width can best be determined near the septa.)
How many nuclei in one cell? Observe the longitudinal threads or
fibrils in the cells. Note the transverse light and dark bands on the
fibrils. These are known as striations. Are the striations continuous
lines across each cell?

36. If time permits a bit of teased out preserved frog muscle should
be examined for the structures found in the above preparation. An
oil immersion demonstration will also be provided showing the structures
more in detail.

Muscular movements are due to changes in the muscle fibrils re-
sulting from a change in the relative size and shape of the light and dark
bands. The process is not very well understood. Approximately what
fraction of the muscle cell is given over to the function of movement?
Is the movement performed by the general protoplasm or by specialized
structures?

3c. A muscle removed from the body will respond to various forms
of stimuli such as mechanical, thermal, chemical, and electrical. The
last is usually employed in laboratory experiments. The contraction
of a muscle will be demonstrated by the following experiment :

The gastrocnemius muscle of a frog is removed and suspended by
means of a clamp attached to the leg bone. A small weight is attached
to the lower end by means of a hook. The muscle should be kept moist
with normal salt solution. Touch the muscle with platinum electrodes
attached to a dry cell. Note the contraction. Is the movement slow
or rapid? How does the muscle change in shape? How much does it
shorten? When does the contraction occur, at the application of the
stimulus, during the passage of the current through the muscle, or at the
removal of the stimulus?

3d. In the body the muscle usually responds to stimuli that come to it
through a nerve. The conduction of an impulse through a nerve may
be demonstrated by a nerve-muscle preparation of the gastrocnemius of
the frog. In such a preparation the nerve going to the muscle is left
intact. Apply the stimulus to the nerve some distance from the muscle
and compare the contractions with those above.

PRINCIPLES OF ANIMAL BIOLOGY 17

4. Metabolism.

4a. Ingestion takes place in higher animals through the mouth.

46. Secretion and Digestion. — Digestive juices and enzymes are se-
creted by specialized cells which often unite to form glands. Examine
the cross-section of the stomach of a frog. Note the layer of cells, the
mucosa, lining the interior. Note the elongated nucleus near the base of
each cell. At frequent intervals the mucosa dips down into the under-
lying tissue in the form of slender tube-like pits. These pits are the
glands. Find a gland which is cut throughout its whole length. At
some depth in it note a group of clear vacuolated cells. If the section is
cut from the anterior (cardiac) end of the stomach, the gland will extend
much deeper than the group of clear cells. The gland is everywhere
composed of a single layer of cells around a slender open canal. Draw
(without stippling) a stomach gland.

The glands of the stomach secrete hydrochloric acid and pepsin.
Test the action of these as follows: Place a small piece (half as large as
a pea) of hard-boiled white of egg into each of three test-tubes or dishes,
taking care to make the pieces of equal size. To one tube add 10 cc.
of a 0.2 per cent, solution of hydrochloric acid (2 cc. of the acid to a liter
of water); to another 10 cc. of a solution of pepsin in water (1 gram of
pepsin to a liter of water) ; to the third 10 cc. of a solution of pepsin in
0.2 per cent, hydrochloric acid. Put all the tubes into a water bath or
incubator, and keep at a temperature of 40°C. Observe the three
tubes at the end of the laboratory period, and daily thereafter. What
conclusion do you draw from the experiment?

Among other digestive glands found in higher animals may be men-
tioned the salivary glands opening into the mouth, the pancreas opening
into the intestine, and the intestinal glands in the walls of the intestine.
The enzymes secreted by these glands digest the various kinds of foods,
namely, proteins, carbohydrates, and /ate.

4c. Absorption. — Absorption is principally an osmotic phenomenon.
Osmosis may be briefly defined as the passage of water and dissolved
substances through a permeable membrane. If the membrane separates
two liquids of unequal density, the greater flow is toward the liquid of
greater density. Osmosis may be illustrated by the following demon-
stration experiment : Tie a wet piece of parchment paper or animal bladder
over the end of a thistle tube. Fill the tube with a concentrated solu-
tion of copper sulphate and support it in a beaker of water so that the
level of the water and the copper sulphate is the same. Examine at the
end of the laboratory period and also at succeeding laboratory periods.
Observe the results and explain.

The intestine and blood vessels are lined with permeable-membranes
through which osmosis takes place in a similar manner.

4d. Circulation. — This is accomplished in higher animals by the
2.

18 LABORATORY DIRECTIONS IN

blood system. Study the beating of a frog's heart in a demonstration
specimen. Also observe the circulation of blood in the blood vessels
of the web of a frog's foot. What are the formed objects in the blood?
Observe the thinness of the blood vessel walls. With what are they in
contact outside? Note differences in the size of the blood vessels. Does
the blood flow in a steady stream in all the vessels? Why?

4e. Respiration and Oxidation. — Oxidation with the liberation of
energy takes place in the tissues. The oxygen needed in the process is
supplied through the lungs in higher forms and usually through gills in
lower forms of animals. Carbon dioxide which is formed during the
process is eliminated through the same organs. Presence of carbon
dioxide in the expired air may be demonstrated by the following experi-
ment which can be performed by each student. Put a little lime water,
Ca(OH)2, in a test-tube and blow through it with a glass tube or blow
pipe. Note results. The C02 in the expired air combines with the
Ca(OH)2 to form an insoluble substance calcium carbonate, CaCOa. Now
pass some ordinary laboratory air through a fresh supply of lime water by
means of a large rubber bulb and a glass tube. Results? Conclusion?

4/. Excretion. — Most of the nitrogenous waste products are removed
by the kidneys. Study a cross-section of the kidney of a frog. The kid-
ney is made up of small tubes, much coiled, and the section cuts these
tubes at all possible angles. Note that the tubules are more distinct in
some parts of the section than in others. From a chart learn the arrange-
ment of the tubes and their connection with the ducts leading from the
kidney.

In one part of the section find a number of rounded bodies, the glom-
eruli. These lie within small capsules known as Bowman's capsules
at the end of the tubules. These are difficult to make out in the sections
and a chart should be consulted. A Bowman's capsule and its glomeru-
lus are together known as a Malpighian corpuscle. The glomeruli are
coiled blood vessels, and the yellowish cells in them are red blood cells.
Find red blood cells elsewhere in the section, outside of the glomeruli.
In a demonstration specimen of an injected kidney note again the glom-
eruli and the numerous blood vessels in the rest of the kidney. The
tubules are not easily made out in this section. What function may the
close proximity of tubules and blood vessels serve? What physical
phenomenon may account for the elimination of waste by the tubules
of the kidney?

From your reading be sure you understand the main facts of the struc-
ture of the kidney and the functions of the kidney.

C. SUMMARY

In your summary of the functions of protoplasm compare the func-
tions of one-celled animals and of other single cells with the functions

PRINCIPLES OF ANIMAL BIOLOGY 19

of many-celled animals. What functions have been studied in each?
Is cooperation or division of labor involved in either case? The guide
questions throughout the exercise will suggest valuable comparisons.

References

HUXLEY, THOMAS H., "Lessons in Elementary Physiology."
JENNINGS, H. S., "Behavior of Lower Organisms."-
VERWORN, MAX, "General Physiology."

EXERCISE IV

MITOSIS (KARYOKINESIS)
Also Called

INDIRECT CELL DIVISION

A. INTRODUCTION

In this type of cell division characteristic changes occur in the nucleus,
the cytoplasm, and the centrosome. The most important changes take
place in the chromatin, the deeply staining portion of the nucleus. The
nuclear membrane disappears, and the chromatin, which was -arranged
in a net-like reticulum, gradually rearranges itself into fine coiled threads
(fine spireme) which shorten and thicken into coarser, more loosely
coiled threads (coarse spireme). From the coarser threads are developed,
by further shortening and thickening, definite bodies called chromosomes.
The number of chromosomes is different for different species, and is
constant for any given species.

In the cytoplasm a spindle-shaped figure composed of thread-like
structures is formed. At the ends of the spindle, where the threads
converge, are two deeply staining bodies, the cenirosomes, from which
other threads radiate in all directions. These latter radiating threads
are the astral rays. Upon the middle of this spindle the chromosomes
take their place in a flattened group, the equatorial plate. Each chromo-
some splits longitudinally and equally and the two halves go to opposite
ends of the spindle.. Thus two new groups of chromosomes are formed,
each of the same number as was present in the group from which they
came. A cell membrane forms between the groups of chromosomes,
dividing the cell into two cells. The chromosomes of each group now
undergo a series of changes approximately the reverse of those in the
early stages of division; that is, they become diffuse again, spinning
out into a fine reticulum, thereby forming two new nuclei like the original
one.

For convenience the process of mitosis may be divided into four
intergrading stages: (1) the prophases, that is the early stages up to and
including the equatorial plate; (2) the metaphase, in which the chromo-
somes divide longitudinally; (3) the anaphases, in which the half chro-
mosomes are distributed to opposite ends of the spindle; and (4) the
telophases which include the division of the body of the mother cell and
the reconstruction of the daughter nuclei.

20

PRINCIPLES OF ANIMAL BIOLOGY 21

B. MITOSIS IN THE SEGMENTING EGG OF ASCARIS

Mitosis may be readily studied in the segmenting egg of A scaris
megalocephala (a round worm parasitic in the intestine of the horse),
in the skin of young salamander larvae, or less satisfactorily in the seg-
menting egg of the white-fish. The description below applies directly
to Ascaris, but may be modified to apply to the others.

A knowledge of the nature of the specimens of Ascaris in which
mitosis is studied will obviate some confusion. The salient features
follow :

(a) The segmenting eggs are in the uterus, a tubular organ, which
is cut in thin sections. If the sections are cut longitudinally, each rib-
bon shows the walls of the uterus at the edges, with the eggs between.

(6) The eggs have been fertilized, so that in the earliest stages two
nuclei (egg nucleus and sperm nucleus) are present.

(c) The eggs are turned in all possible positions, so that only one,
or both of the nuclei may show, also the later division figures may be
observed in various positions.

(d) Each section includes only fractions of the eggs, so that only
portions of the nuclei or spindles may be present, or these structures may
be wholly lacking.

(e) After the first division of the egg, only certain of the cells divide
in the same manner as the first segmentation. The directions below
apply to the first division and later ones of the same kind.

Directions for Study

1. Resting Nucleus. — Study a cell not undergoing division. Note
the nuclear membrane; the net-like arrangement of the chromatin in the
nucleus; and one or more net knots (thickenings in the chromatin network) .
How is the chromatin distributed through the nucleus? What is the
appearance of the cytoplasm?

Draw a cell with resting nucleus, showing also the nature of the cyto-
plasm. The thick membrane around the egg, and at some distance from
the egg may be omitted.
2. Prophases.

2a. Find a cell in which the chromatin is arranged in distinct but
still slender threads (fine spireme) . Where are these found in the nucleus ?
Observe the nature of the cytoplasm. Look for a darker mass, the
attraction-sphere, in the cytoplasm. A dark central granule may or may
not be visible in this mass.

2b. Select a cell in which the chromatin is in thick worm-like
strands (coarse spireme). Is the nuclear membrane still present? If
so, where in the nucleus are these strands? Observe the cytoplasm.
The attraction-sphere may be divided into two parts near together, each

22 LABORATORY DIRECTIONS IN

part with lines radiating in all directions into the cytoplasm. Each
part is an aster. The two asters may be connected by other lines, the
double structure being the amphiaster. If only one aster is present, how
do you account for the absence of the other? Draw a or b.

2c. Find cells in, which the nuclear membrane has disappeared, and
in which the chromosomes, now quite thick and distinct, have no definite
arrangement. Count the chromosomes. Look in the cytoplasm for
an amphiaster. Each aster should contain a central granule, the centro-
some. If only one aster is seen, where is the other? Draw.

2d. In a later stage the chromosomes are arranged in a flat group.
Seen on edge, they form a nearly straight line; viewed from the flat side
of the group, the chromosomes are readily distinguishable. How many
are there? This group of chromosomes is the equatorial plate. In a
cell in which the equatorial plate is seen on edge, note the two attraction-
spheres and centrosomes (that is, observe the amphiaster). The lines
connecting the asters with the chromosomes and with each other are
called spindle fibers.

Draw a cell with the spindle in side view; that is, with the equatorial
plate seen on edge. Draw another cell to show the equatorial plate as
viewed from one of the centrosomes.

3. Metaphase. — While in the equatorial plate, or earlier, the chromo-
somes split longitudinally. If you do not find this stage readily, ask
for a demonstration either in Ascaris, or in the skin of a salamander, or
in some other cell.

4. Anaphases. — Find cells in which the halves of the divided chromo-
somes have begun to separate into two groups of chromosomes. If pos-
sible, count the chromosomes in each group. Note the form of the
spindle. Are there fibers between the groups of chromosomes? Draw
either an early or a late stage; that is, one in which the groups of
chromosomes are still near together or are widely separated.

5. Telophases. — Search for a later stage than 4, showing the two
groups of daughter chromosomes separated by a cell membrane which
has divided the original cell into two cells. Is the nuclear membrane
present around the groups of chromosomes? Are the centrosomes
visible? Do any signs of the spindle remain? Draw.

C. SUMMARY

Give a brief but clear account of the whole process of mitosis. Do not
treat it as a series of stages, like the ones you have studied, but as a con-
tinuous process. That is, fill in the gaps between the stages studied,
using any reliable source of information.

EXERCISE V

CELL AGGREGATION, DIFFERENTIATION, AND
DIVISION OF LABOR

A. AGGREGATIONS OF CELLS

When a unicellular animal divides, two daughter animals are formed
which usually separate from one another. Thus one-celled organisms
are always of small size, in most cases invisible to the unaided eye. Ani-
mals that reach visible dimensions almost always consist of more than one
cell. Increase in size, in these, is due to accumulation of the cells as they
divide. A group of cells derived from one cell by division may be called
a cell aggregation. Various types of aggregation are described below.
Try to discover their fundamental differences while this study is in prog-
ress, and arrange them in a definite scheme at the end of the exercise.

1. Epistylis is a colonial protozoon usually found attached to small
freshwater animals. Examine demonstrations of stained specimens.
Note the method of branching. The oval-shaped bodies at the ends of
the branches are the individuals of the colony, and each one consists of a
single cell. Note the nucleus; what is its shape? Are the cells alike, or
distinctly different?

Reproduction in Epistylis takes place by a simple division of an indi-
vidual into two daughter individuals which remain attached to the colony
by independent stalks.

Sketch a small colony.

2. Carchesium and Zoothamnium are other colonial Protozoa.
Observe living specimens if obtainable, otherwise omit this section.
Study a colony in a salt cellar with a dissecting microscope. Note
that each individual is attached to the end of a long contractile filament
or stalk. Can it retract itself independently of its fellows? The con-
tractile element is absent in Epistylis. Note the result of touching one or
several individuals with the point of a needle.

In Carchesium and Zoothamnium as in Epistylis the cells are inde-
pendent of each other and each cell elaborates its own stalk, and carries
on the metabolic processes, movements and reproductive functions
independently of the colony as a whole.

Write out your observations on the living Carchesium.

3. Pleodorina calif ornica is a free-swimming organism found in fresh-
water ponds. Study preparations of stained specimens. Note the small

23

24 LABORATORY DIRECTIONS IN

spherical bodies. How many cells do they contain? How are they held
together? Note that the cells on one side are larger than those on the
other side. The large cells are the reproductive or germ cells; the small
ones are sterile, and are called somatic (body) cells. How many kinds of
somatic cells are there? How many kinds of germ cells?

Note if possible the slender whip-like structures projecting out from
each cell. These are the flagella, organs of locomotion. Do they pro-
ject beyond the jelly? Would movement of these flagella result in move-
ment of the individual cells, or of the whole group? Is the association
of the cells more close or less close than in the two preceding forms?

Sketch Pleodorina.

4. Volvox, like Pleodorina, is a free-swimming organism found in
fresh-water ponds. Study living specimens if available in a salt cellar
with the dissecting microscope. In case preserved material must be
used, place a few drops of liquid containing Volvox on a slide, add three
to ten grains of fine sand to support the cover-glass and then put on the
cover-glass. Compare with Pleodorina as to size, shape and number of
cells.

Are the cells all alike? Note the numerous small cells of nearly uni-
form size. These are the somatic cells, held together by a gelatinous sub-
tance. In what part of Volvox are these cells located? Connecting the
somatic cells are slender strands of protoplasm. By counting in several
instances (not less than six) determine how many of these connecting
strands project from each cell. If living Volvox is available, focus on the
edge of a specimen, and fmd flagella projecting from each cell. Does the
beating of these flagella result in movement of the individual cells, or of
the whole organism? From the structure of Volvox, would you say
the cells are independent of each other? -***••

Besides the small somatic cells, observe the larger bodies in Volvox.
These are either reproductive cells or daughter individuals derived from
them. Determine where they are located. The reproductive cells are
of three kinds: (a) parthenogonidia, which by cell division give rise to
daughter individuals asexually; (6) ova or eggs; and (c) spermatozoa (male
reproductive cells).

4a. Parthenogonidia. — Look for these in very small (young) individ-
uals. They are somewhat larger than the somatic cells and rarely as
many as a dozen in number. Some of them may be found to have divided
into two, four, eight or more cells forming small daughter individuals.
In older individuals look for daughters of various sizes. There may be
from four to nine of these. Eventually they break out of the parent.

46. Ova may be 30 to 100 in number in certain species or as few as four
to eight in others. They are considerably larger than the somatic cells.
Find ova with spiny shells covering them. The shell indicates that they
have been " fertilized" by a spermatozoon and have gone into a resting

PRINCIPLES OF ANIMAL BIOLOGY 25

condition. The fertilized ova later give rise to new Volvox. How many
ova in the specimens studied?

4c. Spermatozoa occur less frequently than ova. When present, they
are in bundles like sticks of wood in a rick. Several of these bundles may
sometimes be found together. If you do not find them, ask to have them
pointed out.

Draw a specimen having parthenogonidia or daughter Volvox, repre-
senting the whole organism in outline, and the parthenogonidia or daugh-
ter Volvox more in detail. The outline should be at least 3 inches in
diameter. Show the somatic cells in a portion of the figure. Draw a
similar figure of a specimen containing ova and spermatozoa, representing
some of the germ cells in detail, and showing somatic cells in part of the
figure. May any advance in complexity of Volvox over Pleodorina be
observed? If so, in what respects?

5. Hydra is a fresh-water animal found in lakes, ponds, and streams,
attached to the surface of dead leaves, aquatic plants, and other objects.
Two species are commonly found, the brown hydra (Hydra oligactis)
and the green hydra (Hydra viridissima) . Study a living specimen in a
salt cellar containing a small amount of water. Examine with the unaided
eye, with the dissecting microscope, and with the low power of the com-
pound microscope.

5a. Somatic Cells. — Focus on the margin of the body, and note a clear
outer layer of cells, the ectoderm. The darker part within is another layer
of cells, the endoderm.

Mount a specimen on a slide, supporting the cover-glass so as not to
crush it. Focus on the margin. The serrations found there indicate
roughly the extent of the principal cells of the ectoderm. Among these,
find numerous round bodies smaller than the ectoderm cells, the nema-
tocysts, or stinging organs. The' nematocysts are lodged in cells
called cnidoblasts which may not be visible in the living animal. In
what part of the animal are the nematocysts most abundant? Do you
find groups of them anywhere? The structure of the nematocysts
should be studied from specimens prepared for this purpose.

Examine mounted cross-sections of Hydra. Note the two layers
of cells, the ectoderm and the endoderm, surrounding the digestive or
g astro-vascular cavity. The bulk of the ectoderm is made up of the cells
previously observed as serrations at the surface, approximately rectangu-
lar in section and not very deeply stained. These are called epithelial
cells. Among the epithelial cells are pear-shaped or oval bodies, the
nematocysts. Look for the cnidoblasts in which the nematocysts are
contained. Numerous small deeply stained cells among the bases of the
epithelial cells are called sub-epithelial cells. From the sub-epithelial
cells are derived the cnidoblasts, and some other cells.

Study also the endoderm. Are there distinct types of cells in this

26 LABORATORY DIRECTIONS IN

layer, or are all approximately alike? How do the cells of the endoderm
differ from those of the ectoderm? What are the large clear spaces in
the endoderm cells?

Draw a small portion of a section, showing all the different kinds of
cells you have studied. Choose for drawing a portion of a section where
the cells are as diagrammatically arranged as is possible to find. The
figure should represent the thickness of the two layers as about two inches.

55. Germ Cells. — If available examine a living specimen bearing one or
more spermaries or testes. What is the shape of this organ? Do you note
any movement within the spermary? The moving bodies are the sperma-
tozoa. Sketch an entire specimen showing the spermaries. (Use a pre-
pared slide if a live specimen is not at hand.) Examine a cross-section of
Hydra through a spermary. The spermatozoa are deeply stained cells
in a dense mass. What is their relation to the ectoderm and endoderm?

Examine either a living or a stained specimen bearing an ovary.
Sketch to show this organ. What is the relation of the ovary to the ecto-
derm and endoderm? (When an ovum is fertilized by a spermatozoon,
it develops into an embryo. See demonstration.)

Are the somatic cells of Hydra all alike? If not, how many kinds
may be observed? Are the cells of one kind grouped together, or scat-
tered over the body? If the answer to the last question is different for
different kinds of cell, specify the difference in your notes. Are the germ
cells all alike?

Do you observe any advance in complexity of Hydra over Volvox?

6. The Earthworm (Lumbricus terrestris). — Study both living and
preserved specimens.

6a. External Features. — Note that the body is divided into segments
known as somites or metameres. A segmented animal is said to be
metameric, or to exhibit metamerism. '

Observe that the animal has a dorsal or upper surface, and a ventral
or lower surface. It has also an anterior end and a posterior end. Con-
sequently it has also a right and left side. Since the earthworm can be
divided by only one plane into two corresponding halves, it is said to be
bilaterally symmetrical. Where does this one plane pass?

The following external features are referred to in the dissection : ,

Seta, minute horny bristles arranged in rows on each side of the
body. Pass a preserved worm through your fingers in both directions.
What does the result indicate?

Clitellum, a swelling of the body in the region of metamere 32. On
its ventral side is a pair of thickened ridges, the tubercula pubertalis.

Prostomium, a small rounded projection at the anterior end, overhang-
ing the mouth.

Mouth, an opening at the anterior end leading to the buccal or mouth
cavity.

PRINCIPLES OF ANIMAL BIOLOGY 27

66. Internal Structure.— Handle the specimens with care. They must
not be cut up or destroyed except as indicated later in the instructions.

Find the dorsal side of the animal. Insert the point of the scissors
through the body wall a little behind the clitellum near the mid-dorsal
line. Be sure that the scissors do not pass into the internal organs.
Now cut the body wall backward to the posterior end, then forward to
the anterior end, the cut always passing close to the mid-dorsal line.
Be especially careful near the anterior end, about the third somite, not to
injure the brain.

Separate the cut edges a little, just behind the clitellum, and note the
transverse partitions or septa (singular septum), which divide the body
cavity or ccelom into compartments. The ccelom surrounds the digestive
tract. Note the relation between the septa and the intersegmental
furrows on the surface of the worm.

Now cut the septa carefully on each side for about an inch. The
best instrument for this is the point of a sharp dissecting needle. Lay
the worm ventral side down in the dissecting pan and pin the body wall
out flat as far as the septa have been cut. Slant the pins outward so as
to leave room to work between them. Then with the point of the needle
cut or tear the septa forward and backward, putting in pins whenever
necessary. When this dissection is completed the septa should have been
cut to the same depth on each side. Be careful not to injure any of
the internal organs. Remember the general rule in dissection, to cut
nothing unless you know what it is and why you cut it.

Readjust the pins in the anterior region so that they pass through
the walls of the fifth, tenth, and fifteenth somites. This will facilitate
counting them in locating the organs. Now study the following systems
of organs.

6c. Reproductive System. Male Organs. — In somites 9, 11, and 12
notice the three pairs of whitish bodies partly covering the alimentary
tract. These bodies are the seminal vesicles. In them are located the
testes which produce the spermatozoa.

None of the remaining male organs are visible without careful dis-
section. They may be omitted from the study of the dissection but
should be studied from a chart and from figures in the text-book ("Princi-
ples of Animal Biology," by Shull, La Rue and Ruthven).

Female Organs. — These consist of the paired ovaries in the 13th
somite and a pair of oviducts in the 14th. Both organs are small and
need not be found, but should be studied from a chart or text figures.

Close to the septa separating somite 9 from 10 and 10 from 11, are
two pairs of small whitish bodies, the seminal receptacles. Mature sper-
matozoa received from another worm are stored in these. Be careful
in the course of the dissection not to remove or injure the reproductive
organs.

28 LABORATORY DIRECTIONS IN

6d. Blood System. — The dorsal blood vessel may be seen in the
living worm. In favorable specimens it may be seen to pulsate. In the
dissected worm it is found imbedded on the dorsal side of the digestive
tract. Follow the dorsal vessel forward. In somites 7 to 11 inclusive,
will be found certain paired, tube-like red bodies (variously colored in
preserved worms), the hearts, which are connected with the dorsal blood
vessel. The hearts extend ventrad, forming semicircular loops on each
side of the digestive tract. They unite below with a ventral blood vessel,
which extends backward along the ventral side of the digestive tract.
If the hearts cannot be seen carefully dissect away the remaining portion
of the very prominent septa which obscure the hearts and other organs
of somites 7 to 12. The ventral vessel will be seen later in cross-sections.
In life the hearts propel the blood from the dorsal to the ventral vessel.
Smaller vessels are found throughout the body. Some of the more promi-
nent of these may be found in each segment back of the hearts connecting
the dorsal blood vessel with the body wall and the intestine. What is
the function of the blood system? How is this function served in Hydra?

6e. Digestive System. — This consists of a tube extending through the
whole length of the body. It is modified into various parts which may
be readily found. Beginning at the anterior end these are taken up in
order.

The mouth has already been found. It leads into the mouth cavity
or buccal pouch in the first three somites. Be careful not to injure the
brain, a whitish bi-lobed structure situated on the dorsal side of the mouth
cavity in somite 3.

The pharynx is the thick-walled portion following the buccal pouch.
It extends to about the 7th somite. The walls are firm and muscular.
Test the consistency of this structure with your dissecting needle.

The esophagus is a long slender portion behind the pharynx. It is
partly covered by the hearts and reproductive organs, and in the
anterior part by heavy septa. The hearts and reproductive organs must
not be removed or injured but the reproductive organs may be carefully
turned aside in order to reveal the esophagus.

The crop is an enlargement following the esophagus. It is situated
directly behind the last pair of seminal vesicles in somites 15 and 16
(usually). Feel of it to determine whether it is thick or thin walled.

The crop is followed by the whitish gizzard. Feel of this organ to
determine whether it is thick or thin walled. Behind the gizzard, the
intestine extends to the posterior end of the worm where it opens to the
exterior by means of the anus.

Compare the digestive system of the earthworm with that of Hydra.

6/. Excretory System. — Find, with the dissecting microscope if neces-
sary, a pair of coiled tubes in each somite except a few at the anterior and
posterior ends. They are located between the septa and partly beneath

PRINCIPLES OF ANIMAL BIOLOGY 29

the intestine. These tubes are the nephridia (singular nephridium), or
excretory organs. Does Hydra possess any definite excretory organs?

60. Nervous System. — In the third somite is a small whitish bi-lobed
structure, the brain, resting on the buccal pouch. In the posterior
part of the worm push the intestine aside, and note the white nerve cord.
How far does it extend forward and backward? The thickenings of the
nerve cord are the ganglia. Note the small nerves running out from the
ganglia. Find the connection between the brain and the nerve cord in
the anterior portion. The connecting cords are called the circum-
pharyngeal connectives.

Qh. Muscular System. — The longitudinal muscles are visible in the
dissection as glistening strands running lengthwise on the inner surface
of the body wall.

Make a drawing of the first 25 somites of the dissection three times
natural size, putting in all the organs that can be seen in a dorsal view.
Turn aside the seminal vesicles of one side so that the underlying organs
can be exposed and included in the drawing. Label all the parts identi-
fied and shown and indicate somites 1,5,10, 15.

62'. Examine prepared slides of cross-sections of the earthworm under
the dissecting 'microscope. Observe again the ccelom or body cavity
directly between the body wall and the intestine. The intestine is seen in
the middle of the section. Determine the dorsal and the ventral sides of
the section. This may be done by using some of the following organs as
landmarks.

In the intestine note the typhlosole which is an infolding of the dorsal
wall of the intestine. On the dorsal side of the intestine is the dorsal
blood vessel. Beneath the intestine is the ventral blood vessel, supported
by a thin membrane or mesentery seen in the cross-section as a wavy line.
Near the ventral blood vessel is the nerve cord. In the ccelom may also
be found portions of nephridia and sometimes portions of septa.

The body wall consists of four distinct layers. Lining the ccelom
is a very thin layer of cells, the peritoneum. Outside of this membrane
is a layer of more or less feathery appearing structures, the longitudinal
muscles. Outside of these is a layer of circular muscles. External to
these is the hypodermis. How many layers of cells in it?

The intestine also consists of four layers. On the inside is a single
layer of slender epithelial cells. Outside of this is a circular muscle layer;
then a longitudinal muscle layer reduced to a few fibers; and covering the
intestine is a layer of thick peritoneal cells.

Draw an outline figure showing the form and position of the various
layers of tissue and other organs in outline, but do not fill in details. The
boundaries of the layers and organs are sufficient. Be careful to make
this drawing with the dorsal side toward the top of the page.

Does the earthworm possess germ cells and somatic cells? If so,

30 LABORATORY DIRECTIONS IN

where are the germ cells? Are they of more than one kind? Examine
preparations of ovary and of seminal vesicles to secure facts for the
answers to these three questions. How many kinds of somatic cells
are there? Compare their distribution over the body with their dis-
tribution in Hydra. Which arrangement appears to you the more com-
plex? The more specialized? What are organs? Systems? Does
Hydra have any approach to organs? If so, where?

B. AGGREGATIONS OF MANY-CELLED INDIVIDUALS

7. Bugula belongs to a group of animals known as Bryozoa. They
are found in both fresh and salt water. Bugula is a salt water form.
Study a branch in a watch glass. Note the plant-like form. It lives
attached to rocks and other objects in the water.

Study the method of branching. In a stained branch on a prepared
slide, note how the individuals are arranged.

From a prepared slide examine a favorable individual with a low power
of the microscope. Note the transparent sheath surrounding the indi-
vidual, the tentacles surrounding the mouth, and the form of the re-
mainder of the body. Are all individuals alike?

Sketch several individuals including the sheath as seen under the
compound microscope.

8. Obelia is an animal related to Hydra (a member of the phylum
Coelenterata). It grows in plant-like colonies on wharves and rocks
in salt water. Under the dissecting microscope note the tree-like form
of a single branch. Specimens in watch glasses or mounted permanently
on slides may be used for this purpose and for the identification of the
kinds of individuals and their parts indicated below. Use the compound
microscope for parts of this study.

8a. Hydranths or zooids, bearing tentacles, are located at the ends
of the branches. Each hydranth is enclosed in a cup-like sheath or
hydrotheca which is a continuation of the tough membranous covering of
the whole colony (the perisarc).

In an expanded hydranth note the body with the hypostome, an elon-
gated projection in the midst of the tentacles. The fleshy continuation
of the hydranth into the stalk is the ccenosarc. The cavity in the body
of the hydranth continues through the coenosarc.

86. Gonangia (singular gonangium), club-shaped individuals usually
found in the angles between the hydranths and the main stalk. Note
that they have no tentacles, hence can capture no food. How can they
be nourished ? The sheath forming the outer portion of the gonangium is
the gonotheca. The fleshy core of the gonangium is the blastostyle.
Upon the sides of the blastostyle find

8c. Medusce, here in an immature form, mere rounded projections.
In the larger ones, the beginning of the tentacles may be seen at the margin

PRINCIPLES OF ANIMAL BIOLOGY 31

(see demonstration). The medusae detach themselves later from the
blastostyle, emerge from the gonangium through an opening at the tip
which in younger gonangia is plugged up by the broad end of the blasto-
style, and live a free swimming existence. Examine one of the free medusae
in a demonstration. Note the manubrium in the center. It is homologous
with the hypostome and contains the mouth. Four radial canals extend out
from the manubrium as far as the circular canal along the margin. The
reproductive organs are usually borne on the radial canals. The convex
side of the medusae is called the ex-umbrella and the concave side the sub-
umbrella. The medusae reproduce by eggs and spermatozoa. The
structure of a medusa may be better appreciated from an examination
of larger medusae belonging to other species sueh as Gonionemus or
Polyorchis.

The tree-like branch you have examined is not an entire colony. In
a demonstration, note that numerous such branches may be connected
by a horizontal creeping portion, the hydrorhiza, from which the branches
arise.

Obelia illustrates a simple form of polymorphism, in that it comprises
three kinds of individuals in differing form: (1) The hydranth or nutri-
tive individual; (2) The blastostyle which produces (3) Medusae, the
dispersing members of the species.

Draw a branch showing a hydranth and a gonangium in detail. Draw
also a medusa.

9. Physalia, the " Portuguese Man-of-war," will be on demonstration.
It is a very complex polymorphic colony. The various individuals cannot
be made out without more careful examination than the demonstration
will permit.

C. SUMMARY

What is the simplest form of aggregation into which cells may enter?
What animals show this simple collectivism? Are these aggregations
colonies, or individuals?

Arrange the animals you have studied in order of ascending complexity.
What is the first increase in complexity beyond the simplest condition
mentioned above ? Point out what are the further increases in complexity,
step by step, through the rest of the series.

Is there division of labor in any of these types of aggregation? If so,
which ones? Is division of labor lacking in any of them? Is there any
cooperation, not involving division of labor, in any of them? If so,
where ?

Is there any parallelism between aggregations of cells and aggrega-
tions of individuals? If so, in what respects?

Do you see any value in the construction of a scale of complexity
such as the foregoing? If so, indicate its use.

EXERCISE VI
REPRODUCTION

A. ABIOGENESIS

Living organisms come into existence only from other organisms
through some form of reproduction. It was once supposed that living
things were sometimes produced directly out of non-living matter, an
old theory now referred to as dbiogenesis.

The following experiment which is to be performed as a class demon-
stration represents in a simple way the kind of experiment by which
abiogenesis was disproved. Preparations for this experiment are to be
made as follows: Into each of several clean, sterilized petrie dishes or test-
tubes place a small amount of nutrient agar solution; put covers on the
petrie dishes and cotton plugs in the test-tubes and sterilize under 15-18
pounds steam pressure. One-half of the preparations are opened in the
presence of the class, exposing the agar to the air of the laboratory for
about fifteen minutes. The unexposed preparations are kept as controls.

Examine the dishes at frequent intervals for signs of growing organ-
isms (molds, bacteria colonies, and yeasts). On which cultures
do they appear first? Source of the growths? Discuss possible sources
of contamination in the controls1 if growths occur in them.

B. TYPES OF REPRODUCTION

Living organisms give rise to other organisms like themselves; that is,
they possess the power of reproduction. Since the life of the individual
is in every case limited, it is this reproductive capacity that prevents any
race from dying out.

Reproduction may be of two general kinds: (1) asexual and (2)
sexual. It is the purpose of this exercise to determine as far as possible,
from a limited number of examples, the essential features of each of these
types of reproduction.

A. Asexual Reproduction
1. Fission.

la. Fission in a protozoon (Paramecium). Try to find living para-
mecia that are dividing by means of transverse constriction about the
middle, but do not spend much time in search. If living animals under-

1 Note that air is not entirely excluded by the covers of the petrie dishes. A more
careful experiment is not needed, however, to illustrate the method of attacking
the theory^of abiogenesis.

32

PRINCIPLES OF ANIMAL BIOLOGY 33

going fission are found, note the position and depth of the constriction.
Look for contractile vacuoles. How many and where? If dividing
animals are found watch them at intervals until the process of division is
completed.

In specimens stained and mounted on slides, observe carefully the
condition of the nuclei. Note that each paramecium has two nuclei,
a large macronucleus and a minute micronucleus. The micronucleus
in paramecia which are not undergoing division occurs in or near a little
hollow on the side or surface of the macronucleus. Look for it carefully.
In fission each of the two nuclei divides, a half going into each of the
daughter cells. Each daughter gets one of the old contractile vacuoles
and produces a new one. This type of reproduction is called binary
fission because each animal divides into two equal parts. Since division
is transverse it may also be called transverse fission in contrast to longi-
tudinal fission which occurs in some Protozoa.

Make two drawings each two inches long showing an early and a late
stage of fission. Represent the body by an outline and make the nuclei
dark.

2. Spore Formation.

Spore formation in Monocystis. This is a protozoan parasite found
in the seminal vesicles of the earthworm.

Examine a specimen in the cyst stage. The spindle-shaped bodies
are the spores, contained in the cyst. Estimate the number of spores
and record it in your notes. All of the spores have been produced by
the multiple division of a single cell.

3. Budding.

3a. Budding in the metazoon Hydra. Select hydras which bear buds
of various sizes, representing stages in the growth of these buds. Note
that the cavity of the bud is directly continuous with the cavity of the
parent. The bud is formed by the simple outpushing of both layers of
cells of the parent's body and the subsequent development of tentacles
and mouth. Tentacles are produced by a process similar to budding.

Make an outline drawing of parent and bud.

36. Budding in a metazoon, a fresh water sponge. The fresh water
sponges exhibit a sort of internal budding. As autumn approaches
certain cells in the body wall aggregate into spherical groups and become
surrounded by a protecting shell. These spherical bodies are called
gemmules. Examine a specimen containing them. In some species
several gemmules may be enclosed in a common envelope. The adult
sponges die in the autumn, but the gemmules live through the winter and
develop into new sponges in the spring. Crush a gemmule under a cover-
glass. Distinguish the whitish cells of the interior from the brownish
protective coat. Examine gemmules that have been boiled in caustic

34 LABORATORY DIRECTIONS IN

soda to destroy the cells inside and to make the gemmules more trans-
parent. You should find a small plain or tube-like foraminal aperture
through which the small sponge emerges in the spring by an amoeboid
movement.

Using the compound microscope make a drawing of a gemmule an
inch in diameter, or show a group of gemmules in a common envelope.
Show the foraminal aperture in one of the gemmules.

3c. Budding in a metazoon (Nais, Aeolosoma, Chaetogaster, Dero, or
Microstomum) . When reproduction by budding occurs the elongated
body becomes constricted transversely and later separates into two parts.
In some cases the worm may show several budding zones. A demonstra-
tion will be provided (living if possible) . A sketch in your notes may be
helpful, but is not expected on your plates. Be sure to note the name
of the worm studied.

How many parents are concerned in each of the observed cases of
asexual reproduction?

B. Sexual Reproduction

4. Conjugation in Paramecium. — Look in the cultures for paramecia
swimming about in pairs side by side. Such specimens are conjugating.
The nuclei of conjugating specimens can be studied only with the aid of
prepared slides. The essential part of the process is the exchange of
portions of the micronuclei. Several demonstrations of this stage will be
provided. Draw carefully, representing the body in outline, and the
nuclei in detail. Read Chapter VIII in "Principles of Animal Biology,"
by Shull, La Rue and Ruthven, for an account of conjugation.

5. Reproduction in an Hermaphroditic Metazoon, the Earthworm. —
Recall your dissection of the earthworm. Each individual was found to
possess both male and female organs. Such an animal is called an
hermaphrodite. An earthworm does not, however, fertilize its own eggs;
each egg is fertilized by a sperm received from another worm and stored
in one of the seminal receptacles (spermathecae) . Make a list of the
organs which are classed as female and male and be sure that you know
the function of each.

Examine a demonstration of ova (female germ cells) in the ovary,
and also a demonstration of male germ cells in various stages of develop-
ment secured from the median seminal vesicles. Read Chapter VIII
in " Principles of Animal Biology" for a discussion of reproduction in the
earthworm.

How many parents are concerned in sexual reproduction in each
of the cases studied? Were the parents alike or unlike?

In a majority of species of animals the parents are unlike in structure,
each parent having but a single set (male or female) of reproductive organs.
Such species are known as dioecious while those which have both sets of

PRINCIPLES OF ANIMAL BIOLOGY 35

sexual organs in the same individual are known as monoecious or her-
maphroditic animals. Make a list of at least ten species of animals which
are dioecious. The anatomy of the sexual organs of a dioecious species
will be studied later, in the exercise on breeding habits.

C. Parthenogenesis

The eggs of certain species of rotifers, crustaceans, insects, and others
normally develop without fertilization.

6. An Aphid. — A laboratory experiment will be conducted using the
aphid or plant louse, Macrosiphum, and the chrysanthemum as a host
plant. Several chrysanthemum plants should be carefully examined to
discover if they are free from plant lice. If they are free then a single
immature plant louse should be placed on each plant, and the plant
should be covered with a lantern globe closed at the top with cheese
cloth or muslin. The plants will now be placed on a shelf and cared
for by an assistant. Make a record of date and just what was done.
After a time interval of a number of days count and record the number of
individuals on each plant, the date, the number of days elapsed since the
lice were put on the plants. If the interval has been long enough some of
the progeny may also have borne young.

7. Rotifer. — At the option of the instructor a second experiment to be
performed by each student may be instituted. Secure from the instruc-
tor or an assistant a Syracuse watch glass with a single immature female
rotifer in a small quantity of liquid. Examine under a dissector to make
sure that only a single rotifer is present. Now fill the dish two-thirds
full of distilled water and food materials as the instructor directs. Write
your initials with pencil on the ground edge of the watch glass and put
the dish on the shelf designated by the instructor. The assistant will
see that dishes are covered and food provided at proper intervals. The
record should consist of the date and the number of rotifers put in the
culture. After a certain time interval to be announced by the instructor
examine your watch glass culture, record the number of rotifers present,
date, and interval of time elapsed since the beginning of the experiment.

How many parents were concerned in the act of reproduction in
Macrosiphum? In the rotifer? How can you be sure? Why is this
glassed under sexual and not under asexual reproduction? If in doubt on
the latter point ask for a demonstration of a rotifer showing the egg.

C. COMBINATIONS OF ASEXUAL AND SEXUAL REPRO-
DUCTION WITH DIFFERENCES IN STRUCTURE.
ALTERNATION OF GENERATIONS OR
METAGENESIS

Alternation of generations is a phenomenon exhibited in the life cycle
of certain animals in which asexual individuals give rise to sexual indi-

36 LABORATORY DIRECTIONS IN

viduals, which in turn produce asexual individuals. The asexual and
sexual individuals are structurally unlike.

8. Metagenesis in a Colonial Hydroid Obelia. — Recall your drawings
of Obelia or if you failed before to work out its structure do so at this time.
Note especially:

8a. That the hydranths produce gonangia and hydranths by budding.

86. That the gonangia produce medusae by budding.

8c. That the medusae produce hydranths by means of eggs which must
be fertilized by spermatozoa.

Sd. That the kinds of individuals that reproduce asexually are struc-
turally very unlike the kind which reproduces sexually.

Therefore, Obelia exhibits " Alternation of Generations" or " Meta-
genesis."

D. SUMMARY

The summary should consist of discussions of abiogenesis, and of
asexual and sexual reproduction or a comparison of the two modes of
reproduction pointing out distinguishing or essential features of each.

EXERCISE VII
BREEDING HABITS OF VERTEBRATE ANIMALS

A knowledge of the anatomy of the reproductive organs is essential
to an understanding of the breeding habits of vertebrates. In order to
gain this knowledge the student should work out the structure of the male
and female reproductive systems in the frog, using for this purpose dis-
sections which are placed on the table. He should also consult the charts
which will show the relative location of the organs and their connections.
Examine also a model of the frog showing organs, and specimens partly
dissected.

A. ANATOMY

1. Male Reproductive Organs. — In the dissection furnished you note:
la. The kidneys, two flattened oval structures side by side. Near

their anterior ends find:

16. The testes (singular testis), two yellowish bodies of ovoid shape.
Push one of them aside and observe:

Ic. The vasa efferentia (singular vas efferens), delicate white tubes
passing between the testis and the median edge of the kidney.

Id. The ureters are tubes, one passing backward from the lateral
margin of each kidney. They connect the kidneys with:

le. The cloaca, a short passage which is a continuation of the large
intestine. (The large intestine and part of the small intestine are
included in your specimen.) The cloaca discharges to the exterior through
the anal aperture. If your demonstration specimen is from the species
Rana pipiens, find also :

If. The Muellerian ducts, two irregular white tubes extending from
the cloaca forward to a point in front of the kidneys. They correspond
to the oviducts of the female, but are functionless in the male.

Make a diagram of the male reproductive system. Discover if
possible how the spermatozoa reach the water.

2. Female Reproductive Organs. — In the demonstration dissection
furnished find:

2a. The ovaries, two large lobed masses containing black and white
eggs (or the ovaries may be much smaller and white).

2b. The oviducts, two thick convoluted tubes extending longitudinally
beside the ovaries.

2c. The uterus, a thin-walled portion of the posterior end of each
oviduct. Each uterus connects with:

37

38 LABORATORY DIRECTIONS IN

2d. The cloaca, a continuation of the large intestine, as in the male.
Try to discover how the eggs escape into the water.

Make a diagram of the female reproductive system. Indicate the
path of the eggs by means of arrows.

Compare your diagrams of the reproductive systems of the frog with
the charts showing similar diagrams for the other vertebrates. Be sure
that you understand the function of each organ in the frog and in a
mammal.

B. METHODS OF REPRODUCTION AND THE TYPES

OF EGGS

Full notes on this exercise are desired and particular attention must
be given to the conclusions or summaries called for under paragraphs
3c, 4d, and E.

3. Types of Eggs of Oviparous Forms.

3a. Examine the eggs of two fishes (perch and white-fish) and three
amphibians (a frog, a toad and a salamander Ambystoma tigrinum) which
are deposited in water and fertilized as laid. Describe the covering and
the differences in the way in which the eggs are held in a mass.

36. Examine the egg of a turtle, a crocodilian, a snake and a bird
which in each case is fertilized within the body of the mother and sub-
sequently laid in places exposed to air. Describe the difference in the
texture of the shell of the two types 3a and 36. Read the paragraph on
shell structure in the text-book.1

3c. Read the account of fertilization given in the text-book and ex-
plain the relation between the habits of the animals in 3a and 36 and the
nature of the egg-covering.

4. Types of Eggs of Animals Which Give Birth to Young (Ovo viviparous
and Viviparous Forms).

4a. Examine the demonstrations of the developing eggs in position
in the body of an ovoviviparous reptile (the garter snake). Describe
the position of the eggs in the genital system and their relation to the
body of the mother.

46. On slides prepared for the purpose locate the eggs in the ovary
of a viviparous species (the cat, for example). Note the relative size
of the eggs.

4c. Examine the demonstrations of a mammalian embryo (mouse)
in position in the uterus and describe the relation of the developing
young to the body of the mother.

4d. Give an explanation of the differences in the relative size of the
egg in oviparous, ovoviviparous and viviparous forms.

1 The frequent references to the text-book in this section apply to "Principles of
Animal Biology," by Shull, LaRue and Ruthven. Chapter IX.

PRINCIPLES OF ANIMAL BIOLOGY 39

C. BROODING HABITS

5. The Habit, Among Oviparous Forms, of Guarding the Eggs Without
Incubating Them.

5a. Read the section in the text-book describing this habit.

56. Examine the demonstration specimens, or in the absence of these
the figures of the marsupial frog (Nototrema) and a fish which carries
the young (Hippocampus), noting the position of the brood pouch.

6. The Habit of Brooding the Eggs (Incubation) and the Habit of Brood-
ing the Young.

6a. Read the section in the text-book describing these habits. Ex-
amine the series of bird and mammal nests in the laboratory, and describe
at least three nests representing different types of construction.

66. Note the position of the brood pouch in a marsupial (opossum),
or in the figures of a kangaroo in the text-book.

D. BIRTH STAGES

7. Oviparous and Ovoviviparous Species with a Larval Period.

Compare the young and adult of the common lamprey, a frog and the
salamander Ambystoma tigrinum. Describe the differences in the mouth,
eyes, form of body and appendages.

8. Species Without a Larval Period.

Compare the newly born young of a shark, a garter snake, two birds
(English sparrow and the chick), a mouse and a guinea pig. Describe the
differences in the stage of development at time of birth as shown by
the relative size, strength, the covering of scales, hair or feathers, and
the eyes.

E. SUMMARY

Do you discern any possible relation between the oviparity, ovovivi-
parity or viviparity of an animal and the number of eggs it produces?
Any relation of the same three phenomena to the certainty that the eggs
will be fertilized? Any relation to the mode of life of the animal? Dis-
cuss these relations if they appear to exist.

EXERCISE VIII
EMBRYOLOGY OF TYPICAL ANIMALS

A. MATURATION AND FERTILIZATION

The change undergone by the male and female germ cells previous to
fertilization is known as maturation.

1. Maturation of the Male Germ Cells. — The undifferentiated male
germ cells are known as spermatogonia. These multiply by ordinary mito-
sis. When mitosis stops each cell increases in size and is known as a
primary spermatocyte. Each primary spermatocyte divides into two
secondary spermatocytes. Each of these in turn divides into two sperma-
tids which metamorphose into spermatozoa. Thus out of each primary
spermatocyte four spermatozoa are formed. During the process of
maturation the number of chromosomes is reduced one-half. A wall
chart should be studied for the outline of the process.

la. Examine sections of the testis of the beach grasshopper, T rimer o-
tropis maritima. At one end of each section spermatogonia will probably
be found, at the other end mature spermatozoa, and between the two ends
spermatocytes in various stages.

16. Note the small size of the spermatogonia. Find some undergoing
mitosis. In a polar view of an equatorial plate determine as nearly as
possible the number of chromosomes. Record the number.

Ic. The spermatocytes are larger than the spermatogonia. Among
them find cells undergoing mitosis. From an anaphase of the division
of a secondary spermatocyte determine as nearly as possible the number
of chromosomes. If in doubt whether you are observing the correct
stage ask to have one shown to you. How does the number of chromo-
somes in each anaphase group in the secondary spermatocyte compare
with the number in the spermatogonia? The number in these anaphase
groups is the number that goes into the spermatozoa.

Id. Draw a group of mature spermatozoa, either from the grasshopper
or from a mammal, of which a demonstration may be provided.

2. Maturation and Fertilization of Female Germ Cells. — Since, in
the animal selected for the study of the female germ cells, the processes
of maturation and fertilization occur in large part simultaneously, they
are studied together. The chronological order of events is followed.

2a. Examine sections of the uterus of Ascaris megalocephala. See a
specimen of Ascaris. The large rounded bodies are oocytes or later stages.

40

PRINCIPLES OF ANIMAL BIOLOGY 41

The nature of these sections has been explained in Exercise IV. While
still in the ovary, before growth began, the female cells were oogonia.

26. In the uppermost row of sections which is from the inner part of
the uterus, find primary oocytes each containing a triangular dark body
with a distinct black nucleus. These triangular bodies are spermatozoa
which have already penetrated the primary oocytes. Some spermatozoa
may also be found among the oocytes.

2c. Note the nuclei of the primary oocytes. Some will have formed
spindles preparatory to the first maturation division.

2d. In the second row of sections, from a point a little lower down in
the uterus, observe oocytes undergoing their first maturation division.
The chromosomes are arranged in two quadruple bodies or tetrads.
Each tetrad is composed of two chromosomes brought together in a proc-
ess known as synapsis, the chromosomes of the pair having divided so as
to form four parts. The nucleus of the spermatozoon, surrounded by
more darkly stained protoplasm, may also be seen in some specimens.
Select a clear specimen, and draw.

2e. In the third row of sections are secondary oocytes undergoing the
second maturation division. The secondary oocyte is surrounded by a
thick membrane. Within this membrane, at the surface of the oocyte,
is found in some sections, a small dark object, the first polar body. This
and the secondary oocyte constitute the two daughter cells formed by the
first maturation division described in 2d. If the polar body is not
seen, explain its absence.

In the secondary oocyte observe the spindle, bearing two double bodies,
the dyads. Each dyad is half of one of the tetrads described in 2d. When
this second division is completed, two single bodies (chromosomes) will
have gone into the second polar body (a very small cell), and two remain in
the mature ovum. The nucleus of the spermatozoon may be visible in
some specimens.

Draw a specimen showing a spindle with clear dyads.

2f. In the fourth row of sections, the second maturation division is
already completed and the two polar bodies are visible at the surface of
the mature egg in some of the specimens. (The first polar body in some
instances adheres to the inner surface of the egg membrane.)

The first polar body in some animals divides so that out of the original
oocyte, four cells are formed, one of which is the mature egg and the
others the polar bodies which are without function.

Observe in the interior of the mature egg the two large vesicular
nuclei, containing scattered granules of chromatin. One of these is the
egg nucleus , the other the sperm nucleus. These fuse to form a cleavage
nucleus and this fusion constitutes the final step in fertilization.

2g. In the fifth row of sections, the fertilized ovum is undergoing
division or cleavage. Two-celled and four-celled embryos will be found.

42 LABORATORY DIRECTIONS IN

In a favorable specimen count the chromosomes in one cell. This num-
ber is the number of chromosomes found in all the body cells of Ascaris,
and is known as the somatic or diploid number. Recall the number of
chromosomes in the mature ovum (see 2e above), which is known as
the reduced or haploid number. The diploid number is restored at
fertilization.

Compare maturation in the male and female germ cells (see chart).

B. DEVELOPMENT
Development of the Frog

The developmental processes of the various groups of vetebrates are
quite similar. The development of one of them, therefore, serves to
illustrate the process in all, just as the formation of spermatozoa and ova
in the grasshopper and Ascaris are typical of the corresponding processes
in other animals.

Study the early development of the frog, using the following stages:

1. During the First Day.

la. Unsegmented Egg. Study with dissecting microscope, using
transmitted light and reflected light (the latter preferably with dark back-
ground). The middle of the black half is called the animal pole; the
middle of the white half the vegetative pole. Note the layers of jelly.
How many? Relative thickness? Draw an unsegmented egg, side view,
with the animal pole toward the top of the plate. Make the egg itself
% inch in diameter and the jelly in proportion. Label.

16. Two cell stage. Note the cleavage furrow. Where is it deepest?
Draw the egg without the jelly, side view, and with the animal pole above.
Label the poles and furrow.

Ic. Four cell stage. A second cleavage furrow is present. How is it
placed with respect to the first? Draw, without the jelly, inclining the
animal pole slightly toward you so as to show the intersection of the two
cleavage furrows.

Id. Either twelve cell or sixteen cell stage. The cells of the animal
half of the egg divide more rapidly than those of the vegetative half, so
that there may be eight cells in the region of the animal pole while there
are only four near 'the vegetative pole. This would be a twelve cell
stage. The four vegetative cells soon divide, making sixteen in all.

Note that the eight cells in the animal half are usually arranged roughly
in two rows of four cells each. Compare these cells in size with those
about the vegetative pole. Draw the twelve cell or sixteen cell stage,
inclining the animal pole toward you so as to show the entire group of
eight cells above, but still representing an oblique side view. Label the
animal and vegetative poles.

PRINCIPLES OF ANIMAL BIOLOGY 43

2. During the Second Day After Laying.

2e. Early gastrula. Previous to this stage the cells have through
successive division become small and numerous, the whole mass forming a
hollow ball known as the blastula. During the early gastrula stage the
cells near the border between the black and white areas begin to be tucked
into the hollow interior of the mass, along a crescent-shaped line. This
crescentic opening is the blastopore. Note that the cells on one side of it
are white, on the other side black. Draw, with the blastopore in the
middle of the figure, convex side up. Label animal and vegetative poles.

2/. Late gastrula. The invagination of the cells into the interior is
now occurring along a circular line, that is, the blastopore is now a circle.
The white cells within this circle constitute the yolk plug. The yolk
plug is all that is left of the vegetative half of the egg that has not retreated
into the interior. A neural groove may be present, but will probably not
be found at this stage. Draw, turning the blastopore nearly to the right
side. Label animal and vegetative poles.

2g. Neural groove stage. The neural fold is a ridge or elevation on the
surface of the embryo. The fold is continuous and in the form of an
elongated ring, wide at one end and narrow at the other. Later the wide
part forms the brain and the narrow part the spinal cord. The groove
between the neural folds is the neural groove. At a somewhat later stage
the neural folds of the two sides come together above the neural groove
and fuse, forming a neural tube, which differentiates into the brain and
spinal cord. Draw, with the dorsal side toward you, that is showing the
whole nervous system.

3. About the Fifth Day After Laying.

3h. Early larva. Note the prominent tail; the V-shaped sucker under
the head;&nd the rounded body, its form due to the yolk still present. At
each side of the neck there may be a prominence, the gill plate. Draw,
in side view, but tilt the ventral side up enough to show the sucker. Omit
shading.

4. About the Eighth Day, or the Time of Hatching from the Jelly.

4z. Tadpole. Note the external gills developed from the gill plate of
an earlier stage; the operculum, a fold of skin partially covering the gills
and extending entirely across the ventral side of the body; the broad tail
with its thin margin or fin; the V-shaped segments or myotomes into which
the muscles in the axis of the tail are divided ; the angular mouth beneath
the head; the two suckers formed by the division of the original one sucker;
and the eye, a whitish spot surrounded by a darker ring on each side of the
head above. The nasal pits, minute depressions at the anterior end of the
head, will be visible in clean specimens.

Draw a tadpole, tilting up the ventral side enough to show the mouth
and suckers. Omit shading.

44 LABORATORY DIRECTIONS IN

5. After Several Months or a Year (According to the Species Used).

5j. Tadpole with hind legs. Note the following external features
observed in the eighth day tadpole : tail, fin, myotomes, mouth, eyes, and
nasal pits or nostrils. In addition find:

The hind legs. The forelegs are present but concealed.

The spiracle, an opening on the left side. Its front edge is the edge of
the operculum (see stage 4) which has fused with the body everywhere
except at this point. Water passes out of the gill chamber through the
spiracle.

The horny jaws with which the tadpole scrapes off little particles of
food from objects in the water.

The myotomes or muscle segments along the sides of the body and
tail. Strip off the skin from a part of the tail and with a sharp needle
tease apart the muscle fibers of a myotome. Note whether the muscle
fibers extend beyond the connective tissue septa.

Internal Features. — Slit open J)he body wall on the ventral side and
turn the flaps back. Observe:

The much coiled intestine, and the mesenteries supporting its coils.

The liver, a brownish body to the right of the intestine (the observer's
left), and the gall bladder, on the posterior side of the liver.

The pancreas, along the anterior part of the intestine.

The heart with its whitish ventricle anterior to the intestine. Push
the intestine to one side and beneath it find:

The fat bodies, branching yellow organs.

The two kidneys lying against the dorsal wall in the posterior part of
the body cavity.

The small reproductive organs lying near the anterior ends of the kid-
neys. It is difficult to distinguish the sexes at this stage.

The lungs, two flattened black or grayish structures attached at the
anterior end of the body cavity and free at their posterior ends. They are
rudimentary and still functionless at this stage.

Open the gill chamber by slitting through the operculum and observe :

The brownish fluffy gills. Probe between them into the mouth. The
openings from the gill chamber into the mouth and pharynx are the gill
slits.

The fore legs inside of the opercular cavity behind the gills.

C. SUMMARY

Describe carefully, but without too much detail, the essential features
of (a) maturation and (6) development. Treat both phenomena as con-
tinuous processes, not as a series of stages. That is, fill in the gaps be-
tween the stages studied in the laboratory.

PRINCIPLES OF ANIMAL BIOLOGY 45

References

BAILEY, F. R. and MILLER, ADAM M., "Text-book of Embryology." Chapters I
to VI inclusive.

HEGNER, R. W., "The Germ Cell Cycle in Animals." Chapters I and II.1
HOLMES, SAMUEL J., "The Biology of the Frog." Chapter V.
KELLICOTT, WILLIAM E., "A Text-book of General Embryology."
KELLICOTT, WILLIAM E., "Outlines of Chordate Development."
MORGAN, THOMAS H., "The Development of the Frog's Egg."
PRENTISS, CHARLES W. and AREY, LESLIE B., "A Laboratory Manual and Text-
book of Embryology." Chapters I AND II.

EXERCISE IX
HOMOLOGY

Structures or organs having a similar embryonic origin irrespective of
their final form or their function are said to be homologous. All such
structures are believed to have been derived from some common ancestral,
more generalized type of structure and to have diverged in various direc-
tions. The generalization that the ancestral history of a structure is
repeated during embryonic development is known as the Biogenetic Law
or the Recapitulation Theory. It is one of the arguments in favor of the
theory of organic evolution.

A. EMBRYONIC ORIGIN OF VERTEBRATE LIMBS

1. Limb Buds of a Toad or a Frog Tadpole.

la. Examine tadpoles showing a very early stage in the development
of the hind legs. Note the rounded prominences, the hind limb buds,
at the base of the tail. Draw an outline of the whole animal, two inches
long, in side view, and make the limb buds dark.

16. In an older embryo observe that each limb bud is now elongated,
and that the distal end is broadened and shows signs of division into
several digits. How many? Draw the limb bud, considerably enlarged,
without the body.

Ic. Determine the number of digits in the hind foot of an adult frog.

2. Limb Buds of Chick Embryos.

2a. Examine a chick embryo after 72 to 80 hours of incubation. Note
that the body is in the form of a letter J (see wall chart). The shorter
and thicker limb of the J is the head, which bears the eyes, large rounded
prominences on each side. The longer and more slender limb of the J
is the trunk, the bend of the J being the neck.

The limb buds are two semicircular prominences on each side of the
trunk. Are they alike? Draw an outline of the body two inches long,
and represent the limb buds dark.

2b. Examine a chick embryo after 100 to 120 hours of incubation.
The general features may be recognized from the description above.
In addition observe that the limb buds are elongated, that their distal ends
are flattened, and that the division into digits has begun. (The latter
feature is best observed if the light falls obliquely on the flattened surface
of the limbs, so as to throw shadows in the hollows.)

46

PRINCIPLES OF ANIMAL BIOLOGY 47

Draw the limb, either wing or leg, omitting the body. Compare the
origin of the wings and legs of the chick with the origin of the hind legs
of the tadpole.

B. DIVERGENCE OF ADULT VERTEBRATE LIMBS

3. Hypothetical Pentadactyl (Five-toed or Five-fingered) Limbs.
Before comparing the adult limbs of the frog, pigeon, and man, study

a chart representing the skeleton of a hypothetical pentadactyl limb. The
limbs of vertebrates have diverged in various ways from this typical form.

3a. Fore Limb. — Note the following parts: The shoulder girdle, com-
posed of clavicle, scapula, and coracoid, with perhaps a precoracoid; the
upper arm or humerus; the fore arm composed of radius and ulna; the
wrist with its ten carpal bones; the body of the hand with its five meia-
carpals; and the digits or fingers composed of phalanges. How many
phalanges in each?

36. HindLimbs. — Note the following parts: The pelvic girdle composed
of ilium, ischium, and pubis; the leg bone or femur; the lower leg with its
tibia and fibula; the tar sals, ten in number, in the ankle; the five meta-
tarsals forming the body of the foot; the digits or toes, composed of
phalanges. How many in each toe?

4. The Limbs of Man.

4a. The Arm. — Compare the human arm bones with those of the
typical pentadactyl fore limb. Study the following structures: The pec-
toral or shoulder girdle, composed of the scapula or shoulder blade, the
clavicle extending from the shoulder to the sternum or breastbone, and
the coracoid, a hook-like process fused to the head of the scapula but
which in youth starts as a separate center of ossification; the arm bone
or humerus; the fore arm with its radius (on the thumb side) and the ulna;
the carpals in the wrist (number?); the metacarpals in the body of the
hand; and the phalanges. How many in each digit?

46. The Leg. — Compare the human leg bones with those of the typical
pentadactyl hind limb. Note similarities and differences.

The pelvic girdle is fused into a single bone, the innominate, on each
side. The ilium is the broad expanded portion above the hip socket
or acetabulum. The ischium projects downward and somewhat backward
from the acetabulum. The two pubes of the opposite sides meet in the
middle line in front, from which point two branches project, one upward
and outward to the acetabulum, the other backward and downward to
the lower end of the ischium.

In the leg proper observe: the femur or thigh bone; the tibia (larger)
and the fibula in the lower leg; the tar sals in the ankle (number?); the
metatarsals in the body of the foot; and the phalanges. How many in
each digit?

48 LABORATORY DIRECTIONS IN

5. The Limbs of a Frog.

5a. The Fore Limb. — Omit the pectoral girdle. Compare the bones
of the arm with those of the typical pentadactyl arm. Note the humerus
in the upper arm, and the radio-ulna in the fore arm. Which of the fused
bones is the radius? Study also the irregular carpal bones of the wrist
(number?) ; the metacarpals in the body of the hand, the one of the thumb
being rudimentary; the phalanges, present in the second, third, fourth,
and fifth digits, but wanting in the first. How many in each digit?

56. The Hind Limb. — Compare with the typical pentadactyl hind limb.
The pelvic girdle consists, on each side, of a long bone the ilium, extending
forward from the acetabulum; the ischium, a rounded flat bone behind
the acetabulum; and the pubis, a triangular bone below the acetabulum.
The latter is more or less translucent in fresh preparations. Each bone
forms part of the acetabulum. They may be readily distinguished in the
skeleton of a young frog. Observe the femur in the thigh, and the tibio-
fibula in the lower leg. Which edge of the latter represents the tibia?
There are four tar sals. Two of them are much elongated; beyond these
are the other two, small irregular bones. Study also the metatarsals in
the body of the foot, and the phalanges in the toes. How many in each
toe? A rudimentary^sixth^ toe may jDe^ present on the inner side of
the foot.

6. The Limbs of a Pigeon.

6a. The Fore Limb or Wing. — Compare the bones of the pigeon wing
with those of the typical pentadactyl fore limb as well as with the
other forms already studied.

The pectoral girdle consists of the scapula, a sword-shaped bone pro-
jecting back over the ribs; a coracoid, sloping downward and backward
and joining with the sternum or breastbone; and the two clavicles
fused to form the furcula or wishbone. Observe the humerus in the upper
arm and the radius and ulna (larger) in the fore arm. Only two free
car pals are present and they may be hidden in the ligaments of the wrist.
See a thoroughly cleaned skeleton to find them. The remaining carpals
are fused with three metacarpals to form a large irregular bone, the carpo-
metacarpus, consisting of two rods joined at the ends. The larger of the
two rods represents the second metacarpal. At its base, on the anterior
edge, is a tubercle which represents the first metacarpal. The third
metacarpal is represented by the more slender one of the two rods.

Only three digits are represented by phalanges. The first finger has
a single spine-like or triangular phalanx. The second has two phalanges;
and the third finger one, which may be closely applied to the first phalanx
of the second finger.

66. The Hind Limb. — Compare the leg of the pigeon with the typical
pentadactyl limb and with those of the other forms studied.

PRINCIPLES OF ANIMAL BIOLOGY 49

The pelvic girdle is fused into a single bone except in young birds.
The ilium is the broad flat part above. The pubis is the slender curved
rod at the lower margin of the girdle, behind the acetabulum. It is
partially separated from the rest of the girdle by a long cleft. The
ischium lies above this cleft and below the large opening behind the ace-
tabulum. Observe the femur in the thigh, and the tibio-tarsus [in the
lower leg. The fibula is a slender bone fused to the tibio-tarsus near its
upper end. The tar sals are not present as distinct bones, some of them
being fused with the tibia and some with the metatarsals. The latter
together with the fused metatarsals form the tarso-metatarsus of the foot.
Note that it is a triple bone, the second, third, and fourth metatarsals
being fused. At the proximal end they are fused with some of the tarsal
bones. The first metatarsal is a separate bone applied to the inner edge
of the tarso-metatarsus at its distal end. There are four digits. The
distal phalanx of each is modified for the support of the claw. The first
digit points backward, the second, third, and fourth forward. How many
phalanges in each digit?

Draw two of the limb skeletons studied and label fully.

Prepare a chart comparing the limbs of man, the frog, and the pig-
eon. In the first column place the names of all the bones found in the
limb skeleton of any of the animals studied; in three other columns state
whether the bone in question is in any striking way modified from the
hypothetical ancestral condition (3a, 36), such as fusion with another
bone, reduction in number, etc., in the three animals named.1 If not
so modified, leave the corresponding place in the chart blank. What does
this chart, when completed, show?

C. MODIFICATION OF LIMBS IN EVOLUTION

Animals possessing homologous structures, no matter how different
those structures are in the adult, are believed to be related to one another.
That is, they are believed to have descended from a common ancestor at
some more or less remote time. If this belief is well founded, these
structures must have become modified from the ancestral condition.

While it is easy to demonstrate, as has been done above, the similarity
of origin of such homologous structures, it is usually impossible to trace
the evolutionary changes by which the similar structures became different.
These changes can be certainly known only from the fossils of animals
from various points in the line of descent from the common ancestor, and
such fossils are usually wanting. For this reason the stages of modifica-
tion in the frog and bird are not thoroughly known. In the horse, how-

1 The student should have acquired in this exercise the ability to name most of the
bones found in the limbs of any vertebrate. At the option of the instructor, an addi-
tional form, such as the horse, may be introduced to test this ability.
4

50 LABORATORY DIRECTIONS IN

ever, a fairly complete series of fossils demonstrates the transition from
the many-toed ancestor to the one-toed modern horse,. This series of
fossils should be examined at the present stage of the work but a careful
study of them will be deferred until the exercise in paleontology.

D. SUMMARY

What is homology? What evidence of homology in the foregoing
study? Must adult structures be different from one another in order
to exhibit homology? Must embryonic structures be alike in order to
exhibit homology? Are the wings of two robins homologous with each
other? In what ways do the vertebrate limbs differ among themselves?
What is the commonest kind of modification from the supposed ancestral
type? Which of the limbs studied is the most modified from the ancen-
tral type? Which least modified? On the basis of the structure of the
limbs, does man stand high or low in the animal series? Of what use is
homology in other branches of zoology?

The above questions are a guide only to the contents of the summary
not to the order of presentation.

References

ROMANES, GEORGE J., "Darwin and After Darwin," Vol. 1, Chapters III and IV.
SCOTT, WILLIAM B., "The Theory of Evolution," pp. 42-73.

EXERCISE X
TAXONOMY

Taxonomy (Gr. taxis = arrangement + nomos = a law) is the
arrangement of known facts according to law. As applied to animals,
taxonomy has for its object the discovery of the pedigree of every animal
from an evolutionary standpoint; that is, its kinship or blood relationship,
and consequently its position in the animal series or genealogical tree.
The characters used in determining such relationship are the form and
structure of the adults, young and embryos, since these most nearly
indicate the degree of kinship among organisms. The discovery of homol-
ogous structures in two or more animals is regarded as a certain indication
of kinship.

In the work on taxonomy, numerous sketches should be made, but it
is left to the student to decide what forms shall be drawn. As aids to
memory, these sketches should serve two purposes. First, they should
recall those features of animals which place the animals in certain groups;
these features are listed in the following exercises under the heading
" Characteristics." Second, many animals should be simply remembered
as belonging to certain groups, without the necessity of recalling the
characteristics which put them in those groups. For this second purpose,
the drawings of one phylum or of one class, should be grouped together on
consecutive pages.

Drawings are to be made on note paper, not on the drawing sheets.

At the end of the exercise on Taxonomy, the student should be able
to place any animal studied in its proper group. Be prepared for a test
of your ability to do so.

A. THE PHYLA OF ANIMALS

All animals have been arranged according to their supposed relation-
ships into phyla (Gr. phulon = tribe, race, stock). All members of a
single phylum possess certain characteristics in common, and differ
in certain of these respects from the members of every other phylum.
The principal characteristics of each phylum are listed with illustrative
examples, in the following exercises.

1. Phylum PROTOZOA (Gr. protos = first -f zoon = animal).

Characteristics.

la. Unicellular. Examine stained specimens of Amceba. The single
nucleus, together with the absence of cell boundaries within the animal

51

52 LABORATORY DIRECTIONS IN

demonstrates that it is a protozoon. Living specimens of other protozoa
may be stained with acetic methyl green, if desired, to show the existence
of but one cell in each.

16. If cells are attached to one another, all are alike. Examine
stained preparations of Epistylis and Carchesium.

2. Phylum PORIFERA (Lat. porus = pore + ferre = to bear).

Characteristics.

2a. Aquatic, mostly marine. Spongilla is a fresh- water form.

26. Usually radially symmetrical. Examine Grantia or other
sponge. How many planes can be passed through the longitudinal axis,
each dividing the body into two parts that are mirrored images of each
other?

2c. Multicellular. Examine a cross-section of Grantia. Note that
many cells are present.

2d. Diploblastic. Note also in the cross-section of the body that
there are two layers of cells, with a gelatinous substance between.

2e. Numerous pores. Examine the surface of a dried specimen of
Grantia with a dissecting microscope. Also the inner surface of a
specimen split open (keep in alcohol or water).

2/. Skeleton composed of spicules or spongin. For spicules examine
the surface of Grantia, the skeleton of Euplectella, and a slide bearing
isolated spicules of Grantia. For spongin, tear off a minute portion of a
bath sponge, place between two slides, and examine with a compound
microscope.

3. Phylum CCELENTERATA (Gr. koilos = hollow + enteron =
intestine) .

Characteristics.

3a. Aquatic, mostly marine. Hydra, and at least one of the colonial
hydroids, are fresh- water forms.

36. Diploblastic. Examine a cross-section of Hydra. Note the two
layers of cells.

3c. Radially symmetrical. How many planes can be passed through
the longitudinal axis of Hydra, each dividing the body into halves approxi-
mately mirrored images of one another? How many such planes through
the jelly-fish Gonionemus? Through a hydranth of Obelia? The sea-
anemone Metridium? The coral Fungia?

3d. Single gastro vascular cavity. Note the hollow interior of Hydra
as shown in cross-sections. Observe also the coenosarc of Obelia.

3e. Nematocysts. Examine these in preparations of Hydra and
hydranths of Obelia. In the tentacles of Gonionemus. If living ma-
terial is available, examine nematocysts of Hydra that have been
discharged.

PRINCIPLES OF ANIMAL BIOLOGY 53

4. Phylum PLATYHELMINTHES (Gr. platus = broad + helmins =
an intestinal worm).

A. Characteristics

4a. May be (1) free-living in water or earth, or (2) parasitic in or on
other animals.

46. Bilaterally symmetrical. Examine Planaria. How many planes
may be passed through the center of the body, each dividing it into two
parts that are mirrored images of one another?

4c. Triploblastic. Examine sections. Note a middle tissue between
ectoderm and entoderm.

4d Single gastrovascular cavity (may be wanting in parasitic forms) .
Examine an entire planaria; note the gastrovascular cavity and its
branching form. It has but one opening, the mouth, as in the
Coelenterata.

4e. Unsegmented. In Planaria, note that the body is not divided
into a series of segments.

B. Special Features.

In the tapeworm observe:

4/. That the animal is not segmented, but is colonial, the members of
the colony being attached in a linear series. Each individual is called
a proglottis.

4gr. The head or scolex. The individuals of the colony are successively
budded off from the scolex. Note the hooks: also the suckers. What is
the use of these structures?

4/i. The absence of a gastrovascular cavity. Why is it not necessary?

4i. The reproductive bodies make up the greater part of the body.

5. Phylum NEMATHELMINTHES (Gr. nema = thread + helmins =
an intestinal worm) . One of the richest phyla in number of species, yet
seldom attracting general attention.

A. Characteristics.

5a. Cylindrical in form. See Ascaris or any other species available.

56. Bilaterally symmetrical. Meaning of this expression? Verify
in Ascaris or any other species.

5c. Triploblastic. Meaning of this term? Transparent living forms
can usually be had either in mother of vinegar (vinegar "eels") or in
old protozoan cultures. If the nematodes keep quiet enough, observe
the triploblastic feature. Or examine a cross-section.

5d. Unsegmented. See any nematode, e.g., Ascaris.

5e. Alimentary canal with both mouth and anus. Demonstrations
may be available.

5/. Coelom present. This is a cavity surrounding the alimentary
canal. Examine a dissection of Ascaris, and observe that the body wall

54 LABORATORY DIRECTIONS IN

may be cut through without opening the digestive tract. Was such a
cavity present in any of the preceding phyla?

B. Economic Representatives.

Some of the most dangerous parasites of man and other animals as
well as of plants are found among the Nemathelminthes. Among the
demonstrations are:

5g. Ascaris, parasitic in the intestine of pigs, horses, and man.

5h. Trichinella, which causes trichinosis in pigs, rats, and man.

5i. Necator, the hookworm, that causes a form of anemia in human
beings.

6. Phylum ECHINODERMATA (Gr. echinos = a sea-hedgehog +
derma = skin).

Characteristics.

6a. All marine.

66. Radially symmetrical. Meaning of this expression? Verify
in a starfish; in a sea-urchin. (There are exceptions to radial symmetry,
especially in minor features.)

6c. Parts usually arranged in fives. Verify in starfish; in sea-urchin;
in brittle-star.

6dL Generally covered with spiny exo-skeleton of calcareous matter.
Observe in starfish; in sea-urchin; in brittle-star. Compare, however,
with sea-cucumber.

6e. Possess tube-feet for locomotion. These are connected with a
water vascular system in the body, and operate by means of suction.

7. Phylum ANNELIDA (Lat. annellus = a little ring.)

A. Characteristics.

7 a. Mode of life is terrestrial (earthworm), or aquatic (Aeolosoma,
fresh water; the sandworm Nereis, marine), or parasitic (some leeches).

76. Segmented. Recall earthworm. Note also the sandworm
Nereis. Compare in this respect with the Platyhelminthes and
Nemathelminthes, which are also called " worms."

7c. Setae. Re-examine the earthworm. How are the setae arranged?
Observe the sandworm, with the flattened projections at the sides of the
body, upon which are bunches of setae.

B. Special Feature.

7d. Suckers in leeches. These attach the animals to the body of the
host whose blood they suck. Examine any leeches available.

8. Phylum MOLLUSC A (Lat. mollis = soft).

Characteristics.

8a. Body soft and unsegmented. Observe the razor-shell clam Solen,
Lampsilis, and Modiola, in which the shell is either open or partly removed.

PRINCIPLES OF ANIMAL BIOLOGY 55

86. Body bilaterally symmetrical (see Chiton, Anodonta, and the
cuttle-fish Sepia), though often apparently asymmetrical (the common
snail Polygyra, Natica, or any other snail).

8c. Locomotion usually by a fleshy, muscular foot. In Modiola,
Lampsilis, and the clams generally, the foot is wedge-shaped. In Poly-
gyra and other snails, it is flat and used for creeping along surfaces. In
Loligo, Sepia, and Nautilus, the foot is composed in part of a series of
arm-like projections.

Sd. Body usually protected by a calcareous shell which may consist
of two valves (Lampsilis, Pecten, Pinna), of a spirally wound tube (Helix,
Polygyra, Nautilus), or be concealed by the fleshy parts (Loligo, Sepia),
or wanting (Octopus).

8e. Possess a mantle, a thin membranous sheet that secretes the
shell. This may be a single piece (Polygyra, Loligo), in two flaps lining
the two valves of the shell (Lampsilis, Modiola), or wanting (the slug
Limax).

9. Phylum ARTHROPOD A (Gr. arthros = joint + pous = foot). The
Arthropoda include hundreds of thousands of species, probably a greater
number than any other phylum.

A. Characteristics.

9a. Segmented. Examine any insect; a crayfish; a centipede; a
spider.

96. Paired jointed appendages (legs, antennae, mouth parts, etc.).
How many pairs of legs in an insect? In a crayfish? In a centipede?
In a spider?

9c. An exo-skeleton of chitin covering the body. Observe in all the
forms mentioned in the preceding paragraphs.

B. Special Considerations.

9d. Although each arthropod has a definite number of segments in its
body, these segments are often fused in characteristic ways so that the
number is not easy to determine. The number of appendages, or the
embryonic development, is relied on in such cases to establish the
correct number.

In insects, a number of segments are fused to form a head, others are
fused to form a thorax, while the segments of the abdomen remain more
or less movable upon one another. Make out these regions in Polistes
(wasp) and Dissosteira (grasshopper), or other insects.

In the crayfish, the segments of both head and thorax are fused into
one immovable group called the cephalo-thorax, while those of the abdo-
men are movable. Make out these regions in Cambarus and Palinurus,
or other crayfishes.

In spiders, the cephalo-thorax is one group of fused segments and the

56 LABORATORY DIRECTIONS IN

abdomen is also a group of fused segments. Make out these regions in
Metargiope and Miranda, or other spiders.

In the centipedes, and millipedes on the other hand, all of the seg-
ments are movable except a small number in the head. Examine a
specimen of Scolopendra or Julus, and note that the region behind the head
is flexible.

10. Phylum CHORD ATA (Lat. chordatus= having a chord or cord).
The most commonly known animals because they are large and con-
spicuous and some of them are domesticated.

Characteristics.

10a. Backbone composed of vertebrae (or a notochord) present.
Examine skeleton of a bird, a cat, a frog, a fish, and a snake or lizard.

106. Typically two pairs of jointed appendages. Recall the modi-
fications of these appendages found in the skeletons studied in Homology.
Observe also the modifications of the limbs in the skeleton of a mole; of
a seal; of a porpoise; and (if available) of a snake.

lOc. Besides the above parts there is a general internal skeleton com-
posed of cartilage or bone.

B. SUBDIVISION OF THE PHYLA

Phyla are divided into subgroups called classes. Classes are dis-
tinguished from one another in the same way as are phyla, but by means
of characters less fundamental and less primitive than those used in
separating phyla. Note that this is true in the analysis of one sub-phylum,
the Vertebrata, in the following exercise.

The Classes of Vertebrates

1. Class PISCES (Lat. piscis = fish).

Characteristics.

la. Cold blooded, aquatic, respiring by gills. Observe the gills in
a fish.

16. Body long and pointed, and provided with dorsal fins, tail fin,
ventral fin, and two pairs of lateral fins. Verify in a specimen.

Ic. Scales cover the body; and a flap, the operculum, covers the gills.
Verify.

2. Class AMPHIBIA (Gr. amphi = both + bios = life). Frogs, toads,
salamanders, newts, etc.

Characteristics.

2a. Cold blooded animals usually spending part of their existence in
water, part on land, capable of living either in water or on land,

PRINCIPLES OF ANIMAL BIOLOGY 57

26. Usually possess two pairs of limbs with five digits each. Examine
a toad, a frog, and a salamander for verification of, or exception to, this
rule.

2c. Skin is without scales or other hard parts, and is slimy owing to
a mucous secretion. Handle a living frog to observe these features.

2d. Young breathe by gills (observe a tadpole); adults usually
breathe by lungs (see dissection of a frog, also the respiratory movements
of a living frog).

3. Class REPTILIA (Lat. repere = to crawl). Lizards, snakes, turtles,
alligators, etc.

Characteristics.

3a. Cold blooded.

36. Skin possesses scales or hard plates. Observe in a snake; in a
turtle; in a lizard.

3c. Body not slimy.

3d. Breathe by means of lungs throughout life. Note the lungs,
in a dissection of the snapping turtle, or other reptile.

4. Class AVES (Lat. avis = bird).

Characteristics.

4a Warm blooded. How does a fowl incubate her eggs?

46. Terrestrial. Even wading and swimming birds spend the major
portion of their time on land.

4c. Body covered with feathers. Examine one or more feathers
under a lens. Compare with figures.

4cL Fore limbs modified as wings. Examine the skeleton of a wing
and note its deviations from the typical vertebrate limb. Examine also
the character of the feathers which add to the wing expanse,

4:6. Absence of teeth in modern birds. Examine a bird skull.

5. Class MAMMALIA (Lat. mamma = a breast). Man, monkeys,
whales, bats, seals, and many common wild and domestic animals.

Characteristics.

5a. Warm blooded. What is your own temperature?

56. Mostly quadrupeds. Some, however, progress on two feet
(man), some by "wings" (bats).

5c. Skin covered with hair. Observe hair in squirrels, bats, or other
quadrupeds; also spines in hedgehog or porcupine.

5d. Young nourished after birth by secretion from mammary glands
of mother.

C. SUBDIVISION OF THE CLASSES

To illustrate the subdivision of the classes of animals into smaller
groups called orders, the Amphibia and Reptilia may be selected. There

58 LABORATORY DIRECTIONS IN

are but three orders of living Amphibia, and four orders of Reptilia.
Note, in the following exercises, that the characters used to separate
orders are less fundamenal than those used to separate classes.

The Orders of Amphibia

1. Order CAUDATA. Salamanders, newts, etc.

Characteristics.

la. Tailed. See Ambystoma, Diemictylus, Cryptobranchus, Pleth-
odon, Desmognathus, and others.

16. External gills sometimes present throughout life (Siren, Necturus,
Proteus), sometimes absent in the adult stage (Ambystoma, Triton, and
others).

2. Order SALIENTIA. Frogs, toads.

Characteristics.

2a. Tailless. See Rana, Hyla, Chorophilus, Acris, Bufo.

26. External gills absent in adult. See the forms listed under 2a.

3. Order APODA. Coecilians.

Characteristics.

3a. Without limbs. See Siphonops.

36. Eyes concealed. See Siphonops, and compare with any of the
Salientia.

The Orders of Reptilia

1. Order TESTUDINATA. Turtles.

Characteristics.

la. Body encased in a bony capsule composed of dermal plates.
Observe any turtle. In a cleaned skeleton note how the shell is attached
to the skeleton.

16. Jaws without teeth. Examine a cleaned turtle skull.

Ic. Quadrate bone immovable. Examine skull. The quadrate is
at the angle of the upper jaw, and forms the articular surface for the
attachment of the lower jaw.

Id. Usually five digits in each fore foot, and four or five in each
hind foot. Verify in as many specimens as possible.

le. Only one nasal aperture in skull. Observe in any cleaned skull.

2. Order RHYNCHOCEPHALIA. This order is represented by only
one species, which is found in the New Zealand region. Owing to the
rarity of the material, the internal features- listed below cannot be demon-
strated. A figure of the whole animal is desirable.

PRINCIPLES OF ANIMAL BIOLOGY 59

Characteristics.

2a. Vertebrae biconcave.
26. Quadrate bone immovable.

2c. Pineal eye fairly well developed. Examine the dorsal side of the
head of Sphenodon; note a whitish spot some distance back of the eyes.
2d. Anus a transverse slit.

3. Order CROCODILINI. Crocodiles and alligators.

Characteristics.

3a. Vertebraae usually concave in front. Material for demonstra-
tion will probably not be available.

36. Fore limbs bear five digits, hind limbs four. Verify in specimens.

3c. Anal opening a longitudinal slit. Compare with a Rhyncho-
cephalian in this respect.

3d. Quadrate immovable. See alligator skull.

4. Order SQUAMATA. Snakes, lizards, and chameleons.

Characteristics.

4a. Vertebrae usually concave in front. Verify on specimens.

46. Quadrate freely movable. See skull of snake; also of the " blind
worm" Anguis. Advantage of this feature? What is the food of
snakes?

4c. Anus a transverse slit. See Thamnophis, Bascanion, and Sis-
trurus or any other snake.

D. SUBDIVISION OF THE ORDERS

Orders are divided into families, on the basis of characters less funda-
mental than those which furnish the basis for the division of classes
into orders. To illustrate the features that distinguish families, a few
families of turtles1 may be used. All the families listed below belong to
one order, the Testudinata, and there are several families of this
order that are not mentioned.

Some of the Families of Testudinata

The characters exhibited by turtles are as follows:
1. Neck retractile in vertical plane, or (2) bending laterally.
3. Cervical vertebrae without (or with only small) transverse processes,
or (4) with strong transverse processes.

xTo THE TEACHER. — It is not necessary that all of the families of turtles listed here
be used in. this exercise. It is suggested that th'e families represented in the region
where the work is being done be used, and that if the teacher is more familiar with
other groups than with the turtles other keys be substituted. The main requirement
is that the characters used be the true family characters and not superficial ones which
merely happen to differentiate the families of a particular area.

60 LABORATORY DIRECTIONS IN

5. Last cervical and first body vertebrae articulated by centrum and
zygapophyses, or (6) articulated by zygapophyses only.

7. Marginal bones forming a complete series, or (8) absent or in an
incomplete series.

9. Squamosal and parietal bones separated, or (10) forming a suture.

11. Limbs not paddle-shaped, or (12) paddle-shaped.

13. Nuchal plate with costiform processes, or (14) without costiform
processes.

15. Plastron composed of nine bones, or (16) eight bones, or (16a)
eleven bones.

17. Caudal vertebrae mostly opisthoccelous, or (18) proccelous.

Some of the families are given below with the characters, and these
families are represented by specimens. Study the specimens with the list
of characters, determine the families to which they belong and describe
each family in your notes.

Family Cheloniidse.— Characters 1, 3, 5, 7, 10, 12, 14, 15, 18.
Family Trionychidse. — Characters 1, 3, 6, 8, 9, 11, 13, 15, 18.
Family Chelydridaj— Characters 1, 3, 5, 7, 9, 11, 13, 15, 17.
Family Pelomedusidse. — Characters 2, 4, 5, 7, 9, 11, 14, 16a, 18.
Family Kinosternidae. — Characters 1, 3, 5, 7, 9, 11, 13, 16, 18.
Family Testudinidae.— Characters 1, 3, 5, 7, 9, 11, 14, 15, 18.

E. SUBDIVISION OF THE FAMILIES

To THE TEACHER. — It is expected that the teacher will at this point
introduce keys to the genera and species of some one or a few groups of
animals. The group selected should preferably be represented in the
general region where the work is being done so that the exercise will both
acquaint the student with species with which he will come in contact and
with the characters used to differentiate the subdivisions of the family.
The teacher should select groups with which he is most familiar and of
which representative specimens can be most easily acquired. The keys
may be compiled from general systematic treatises or from state mono-
graphs. As examples of the works which may be used the following may
be cited:

GENERAL SYSTEMATIC TREATISES:

CHAPMAN, Handbook of Birds of Eastern North America.
BAILEY, Handbook of Birds of Western United States.
DICKERSON, The Frog Book.

JORDAN, A Manual of the Vertebrate Animals of the United States.
WALKER, A Synopsis of the Classification of the Fresh-water
Mollusca of North America, North of Mexico.

PRINCIPLES OF ANIMAL BIOLOGY 61

STATE MONOGRAPHS:

BARROWS, Michigan Bird Life.

FORBES and RICHARDSON, The Fishes of Illinois.

ORTMANN, The Crawfishes of Pennsylvania.

RUTHVEN, THOMPSON and THOMPSON, The Herpetology of

Michigan.

WALKER, An Illustrated Catalogue of the Mollusca of Michigan :
Part 1. Terrestrial Pulmonata.

To THE STUDENT. — Generic characters, that is characters which permit
of the breaking up of the families into groups of forms, are generally
structural and less variable than the so-called specific characters by means
of which the genera are in turn divided into species. The specific charac-
ters may be and generally are superficial, such as form and color of the
body or its parts, but the characters differ greatly in different groups and
may in fact be any difference which is sufficiently constant. As an aid in
identification "keys," that is simplified tabulations of characters, are
compiled by systematists. These keys do not necessarily show the actual
relationships of the forms in the groups which they analyze, but they
illustrate the characters used and the methods employed in analytical
systematic zoology.

F. SUMMARY

State the principles at the basis of classification. What differences
in degrees of relationship are expressed by groups of different rank, as
orders, families, etc.? How do the characteristics of the groups show
these differences? What is the relative age of groups of different ranks,
as orders, families, etc.? Give the reasons for the last answer.

The summary need not directly answer these questions, but the
answers should be included in the course of the discussion.

EXERCISE XI
ECOLOGY AND ADAPTATION

In this exercise will be studied two species of animal found in terri-
genous bottoms of lakes, with special reference to the structures and hab-
its which fit them for such habitat. Animal reactions will be studied
in forms from other habitats. Drawings, answers to questions, and a
summary should be handed in.

A. TERRIGENOUS BOTTOMS
Character of Terrigenous Bottoms

Examine photographs of portions of some lake showing (1) a consider-
able area of barren, sandy shoal, and (2) a photograph of a limited portion
of the bottom of such a shoal. If such habitat is easily available for
actual observation, this part of the work could be done in the field with
considerable profit. The first two animals to be studied were taken in
such a situation. Note:

1. The almost complete absence of vegetation. How is this feature

accounted for?

2. The waves, showing the beach to be wind-swept. What relation

does this fact bear to (1) above? On which shore of a lake
might such a beach be located?

3. The sand ripples. What causes them? Relation to (1) and (2)

above?

4. Flecks of foam on the surface of the water. Cause?

5. In such an environment what are the conditions with respect to

(a) dissolved oxygen content of the water, (6) carbon dioxide,
(c) decaying organic matter, (d) extremes of temperature as
compared with the deeper water, (e) light, (/) molar agents, (g)
materials for holdfasts, shelter, or abode.

6. By what methods can animals normally inhabiting such a situation
maintain their positions there?

Fauna of Terrigenous Bottoms

(a) Lampsilis or Anodonta (Fresh- water Mussels).

1. Study living specimens in shallow dishes or in small aquaria
containing water and provided with sand bottoms. Be careful not to
jar them.

62

PRINCIPLES OF ANIMAL BIOLOGY 63

la. Note the two siphonal openings with fringed borders at one end
of the shell. With a pipette carefully and without touching
the animal put some powdered carmine mixed with water
just opposite the openings and demonstrate that water enters
one (inhalent) and leaves the other (exhalent).

16. Observe the large fleshy, plow-like foot, buried in the sand.
It may be seen if the animal is near the sides of the glass dish,
or demonstrated by lifting the animal quickly before it
contracts.

Ic. Make a sketch or diagram of a mussel from the side, showing the
position of the long axis of the shell, that of the surface of
the sand, the siphonal openings (with direction of the current
for each shown by an arrow), and the outline of the extended
foot. The lower end is the head, or anterior end, the upper
is the posterior end. The dorsal surface is that bearing the
hinge with its dark brown ligament. Make a full page
sketch, since other structures are to be drawn in later.
2. Study fresh or preserved material, including some females with
young (glochidia) in the gills.

2a. Remove the right valve of the shell by cutting against its inner
surface, with a stout knife, the strong adductor muscles, one
near each end, and pushing the mantle from the valve to be
removed. Place the half of the shell containing the animal
in a dissecting dish and cover with water.

26. Note the mantle lining the other shell valve, and the mantle
cavity between the two lobes of the mantle. In the mantle
cavity find:

2c. The gills, two leaf-like structures on each side. Turn back the
upper pair and find:

2d. The hard, contracted foot near the anterior end on the ventral
side. It continues backward into the visceral mass which
contains alimentary canal, reproductive, circulatory and
excretory organs. These will not be dissected, but may be
seen in charts of typical mussels.

2e. The labial palps, triangular ridged flaps, two on each side just
anterior to the gills.

2/. The mouth opening between the labial palps of the two sides.
Probe it with the blunt end of a needle or other instrument.
Sketch in natural position the foregoing parts in the outline
already made.

2g. With dissecting microscope examine the surface of a living gill
and note the numerous small openings leading into its in-
terior. With compound microscope observe the cilia which
cause water currents to pass in through the openings. These

64 LABORATORY DIRECTIONS IN

can best be seen in a portion of a single lamella (half of one
gill) mounted in Ringer's solution between slide and cover-
glass, and studied with high magnification. Sketch a little
of the gill surface showing the cilia and their relation to the
openings.

2h. Tear apart the two lamellae of which each gill is composed, and
note that these enclose vertical tubes which extend from the
free edge of the gill to its attached dorsal edge. With scis-
sors cut thick cross-sections of the gill to show the lamellae
and tubes. Draw a small portion of the cut edge.

2i. Put a probe into the exhalent siphonal opening. It enters a
channel above the attached edge of the gills. Cut through
the gills by drawing a knife along the probe, and explore the
gill chamber into which the vertical tubes from the gills open.

2j. Trace the course of the water from the inhalent siphon into the
mantle cavity, thence through the gill tubes, and out at the
exhalent opening.

2k. How do you suppose the animal breathes? Gets its food?
Removes the waste products of respiration, digestion, and
excretion?

21. Examine a specimen containing glochidia and note how the ex-
panded spaces between the gill lamellae serve as brood pouches.

2m. Examine some of the glochidia of Anodonta in water under a
low magnification. Sketch to show:

1. The triangular valves of the shell.

2. The large tooth at the apex of each valve.

3. The strong adductor muscle.

4. The thread-like byssus (of uncertain function).

2n. By reading one of the following references, or by consulting the
instructor, learn how the glochidia attach themselves to fish
and are distributed by them.

LEFEVRE, G. and CURTIS, W. C., 1912. Studies on the Reproduc-
tion and Artificial Propagation of Fresh-water Mussels. Bull.
Bureau of Fisheries, 30: 107-201.

NEEDHAM, J. G. and LLOYD, J. T., 1916. The Life of Inland
Waters. Comstock Publ. Co. See pp. 287-292.

BAKER, F. C., 1916. The Relation of Mollusks to Fish in Oneida
Lake, Tech. Publ. No. 4., N. Y. State College of Forestry at
Syracuse University. See pp. 219-223.

2o. Examine the demonstration of towings made with a fine mesh
Birge cone net from the sandy shoal habitat where the mussels
were collected. In general, what kinds of minute organisms
occur there? Then:

PRINCIPLES OF ANIMAL BIOLOGY 65

2p. Examine (demonstration) contents of the anterior part of the
digestive tract. Can you recognize any of the organisms
observed in 20? Approximately what proportion of the con-
tents is composed of organisms ? If other materials are present,
what are they and what is their source? By what means
are the food particles brought to the mouth?

3. The mussel must maintain an upright position by means of the foot,
and have its siphonal openings uncovered in order to breathe and feed.
On what kind of a bottom would it thrive best? Why is it not found
on the ooze bottom in deep water far from shore? Why does it not occur
on a solid, clean swept rock bottom? What other animals must live in
the same body of water with it? In short, in what situations would you
be most likely to find fresh- water mussels and why?

(6) The Nymph of a Gomphine Dragon-fly (Gomphus).

1. Examine living specimens in a dish of water on sand bottom.
Note:

la. The tube-like tip of the abdomen with its open end thrust
up through the sand. Water enters this opening (anus)
to reach the gills which are contained in a rectal respiratory
chamber. The opening is guarded by an elaborate strainer.

Ib. That the animal burrows through the sand when disturbed.
Note if possible the method of burrowing.

2. Examine a specimen in a watch glass of water under a dissecting
microscope and note:

2a. The large grasping labium or lower lip with its hooks and
spines. This is hinged so that it may be extended forward
far beyond the head, and is capable of being thrust forward
and withdrawn with great rapidity. Pull it forward with
forceps. The animal is carnivorous and predatory.

26. The adaptations for digging:

1. The flattened head.

2. The flattened fore legs thrust forward.

3. The remaining legs pressed against the side of the body
where they are out of the way; the hind pair extended back-
ward against the side of the abdomen.

3. How does the form of the head and legs, and the structure of the
respiratory organs adapt the animal to burrowing in the soft bottom?

B. ANIMAL REACTIONS

Of importance in determining the habitat of animals is the manner in
which they react to different factors in their environment. A few reactions
will be observed here.

1. Place a number of living planarians (Planaria sp.) in each of several

66 LABORATORY DIRECTIONS IN

shallow dishes containing water and a moderate amount of algse or a few
small pieces of water weed (Elodea) . Allow these dishes to stand for some
time absolutely undisturbed and add no food. Where are the animals?
Why? What is the stimulus involved? As gently as possible, place
a small, recently excised portion of the body of an earthworm just below
the surface of the water. Watch the dish intently for signs of activity on
the part of the planarians. What kind of activity is manifested? What
is the end result of this activity? To what kind of stimulus is it a
response? Is it positive (going toward the source of the stimulus) or
negative (going in the reverse direction)? Of the stimuli referred to
above, which is the stronger? Evidences?

2. Observe land sow-bugs (Porcellio sp.) in a petrie dish half of which
is covered with black paper to exclude the light, leaving the other half
well lighted. Ten sow-bugs have been placed in this dish and left undis-
turbed so that they might come to rest. What is the distribution of the
animals and how do you account for it? What is the stimulus involved
and how do they react to it?

3. Observe ten land sow-bugs in another petrie dish half of which
contains loosely laid thin sheets of mica, the other half being clear.
In which half are most of the sow-bugs? Which of the following
factors, if any, are they reacting to: light, gravity, contact, moisture,
temperature? Reactions to these are called respectively, phototaxis,
geotaxis, thigmotaxis, hydrotaxis, and thermotaxis.

4. In a pan half of the bottom of which is covered with rather moist
soil and half with dry soil note the reactions to moisture in this species of
land sow-bugs.

Make records of observations. In what sort of environment would
you expect to find land sow-bugs? Do you conceive the reactions of
these animals to be advantageous to them?

C. SUMMARY

, How are the animals studied in this exercise adapted to their envi-
ronment? Is the adaptation morphological, physiological, or both?
Examples. Have you witnessed any adaptation to the biological en-
vironment (the other organisms in the vicinity)? How may animals
have become adapted to their environment? (Give alternative views
if you can.) What is ecology?

These questions are suggestive only, and are not intended to indicate
the order in which topics are to be discussed in the summary, nor to limit
the summary to these topics.

EXERCISE XII
ZOOGEOGRAPHY

The laboratory exercises in Zoogeography will be limited to the condi-
tions in North America. Their object is to develop a general knowledge
of the environmental conditions in North America, and their relations to
the ranges of animals. Vertebrates are principally used because the ranges
are better known. The maps should be carefully and neatly prepared as
otherwise their significance will be obscured.

A. GENERAL AREAS OF ENVIRONMENTAL CONDITIONS
IN NORTH AMERICA

North America may be divided into several regions which have
characteristic physical conditions. These areas support characteristic
floras which provide an easy means of establishing their boundaries.
It should be kept in mind that the boundaries of the different regions
are sharply drawn only at the seashore; where the regions come together
inland there is in every case a zone of transition due to the fact that the
environmental conditions change gradually and not suddenly.

1. On an outline map of North America indicate by shading or
symbols the location of the areas covered by the following floras : conif-
erous forests, deciduous forests, prairies, plains and deserts. The map
in " Principles of Animal Biology" (Shull, LaRue and Ruthven), Chapter
XIV, may be followed in preparing this map.

2. Compare the map just made with the map of the regions in eastern
United States given in " Principles of Animal Biology" and note the sub-
regions into which general regions may be divided. Note the transition
areas.

B. DISTRIBUTION OF SOME TYPICAL ANIMALS
OF NORTH AMERICA

3. Plot upon outline maps of North America the ranges of several
exclusively terrestrial animals. Any of the following forms are suitable.

3a. Two of the garter snakes, Thamnophis radix and Thamnophis
butleri. Their ranges1 are described by Ruthven, Bull. U. S. Nat. Museum,
No. 61. Plot the ranges of both species on one map.

1 The maps from these books may be duplicated and furnished to the students in
sufficient numbers.

67

68 LABORATORY DIRECTIONS IN

3&. The American Bison and the Moose, on one map. (From Seton,
Life Histories of Northern Animals).

3c. The Willow Ptarmigan, White-winged Cross-bill, and Road
Runner on one map. (From Chapman, Handbook of the Birds of Eastern
North America, and Bailey, Handbook of the Birds of Western United
States. These books contain descriptions, not maps, of ranges.) l

4. Plot upon outline maps of North America the distribution of one or
more semi-aquatic species. The North American minks are suggested
for this purpose (Seton, Life Histories of Northern Animals).

5. Compare the distribution maps which you have made with the map
showing the natural regions in North America as indicated by the domi-
nant vegetation and summarize the distribution of the species in terms of
natural regions and geographic location. (Example: The range of
species X is the coniferous forest region in eastern North America from the
Atlantic coast to the 100th meridian and from Hudson Bay on the north
to Lake Superior on the south.)

In which cases, if any, does the range approximately correspond to the
distribution of certain types of vegetation? (See map prepared in
paragraph 1 above.) In which cases, if any, does the range bear no
relation to the vegetation areas? Explain the difference in the two
cases.

It will be noted that the ranges of the animals do not correspond
exactly to the natural regions. There are several reasons for this, such as
incomplete knowledge of the extent of the range, too general summaries of
the distribution, the fact that the regions merge gradually into each other
or interdigitate where they come in contact, and the different effects of
the environments upon different animals.

The intermediate regions are characterized to some extent by inter-
mediate conditions, but at least frequently the environments interdigi-
tate. For an example of the latter phenomenon consult " Principles of
Animal Biology," by Shull, LaRue and Ruthven.

C. ADAPTATIONS OF ANIMALS TO THE CONDITIONS
IN THE REGIONS WHICH THEY INHABIT

As brought out in the exercise on ecology animals are adapted to the
conditions in which they live. It follows from this that a difference in
any conditions of the environment may serve to limit the distribution of a
form. Owing to the complexity of the relationship between animals and
their surroundings it is difficult to determine the exact factor or factors
restricting the distribution of a given species at a given point, but certain
very general adaptations may be easily recognized.

1 Other ranges of terrestrial animals may be substituted for the ones mentioned, or
used in addition to them.

PRINCIPLES OF ANIMAL BIOLOGY 69

6. Observe the following structural adaptations of animals:

6a. The locomotor appendages of a fish; two turtles, for example,
Chrysemys marginata and Gopherus polyphemus; three birds, for example,
a heron, a duck and a woodpecker; and two mammals preferably a mole
and a flying squirrel or a bat.

66. The pelage of the northern form and the southern form of the
woodchuck.1

6c. The color of a forest and a desert species of horned lark.

Qd. The molar teeth of a grazing animal (bison or cow) and a browsing
mammal (the elk).

Qe. The beaks of a duck, a woodpecker and a heron.

List the above-mentioned forms with the environmental conditions
in which the structures fit them to live and the changes in conditions
which would probably destroy the usefulness of the structures and there-
fore limit the distribution of the animals.

D. SUMMARY

Discuss briefly the relation of diverse environmental conditions to the
distribution of animals.

1 Certain other animals may be used equally well to show these regional differences.

EXERCISE XIII
PALEONTOLOGY

In the exercise on Homology it was found that the limbs of vertebrates
begin their development in the same way, as a simple outpushing of the
body wall, whereas the adult limbs of different vertebrates are quite unlike
in the details of structure. These and other facts are believed to show
that all vertebrate animals have descended from a common ancestor. If
this belief is well founded, vertebrates have changed (" evolved") greatly
in the generations subsequent to the common ancestor.

In the following exercises it is shown in the case of two typical groups
of animals, one vertebrate and one invertebrate, that such an evolution
has actually taken place. Either or both of these exercises may be used
at the option of the instructor. The change is demonstrated by the
remains of animals preserved in the rocks as fossils. In general, the
deeper rock strata contain the fossils of the more ancient animals, the
more superficial rocks the more recent animals. Why?

In the study of the fossils used, reference should be made to the geo-
logical time scale in "Principles of Animal Biology," by Shull, LaRue
and Ruthven, Chapter XV, or in Pirsson and Schuchert's " Text-book
of Geology." This time scale should be before the student throughout
the exercise.

A. EVOLUTION OF THE CEPHALOPODA

The cephalopods of the past lived within their shells, like the present
day Nautilus, but unlike the squid or cuttlefish, which are also cephalopods.

Examine a bisected shell of Nautilus, also a shell of Nautilus contain-
ing the animal. Note that the shell is divided into a number of chambers
by septa (singular, septum} . These were successively produced from the
center to the opening of the shell. The animal, as it grew, moved forward
in its shell at intervals, and formed new septa behind it.

The ancient cephalopods lived in shells somewhat similar to that of
Nautilus. The line of union of a septum with the outer wall of the shell
is called a suture. The sutures of Nautilus are not visible externally
because of a pearly layer, the nacre, on the outside. Fossil cephalopod
shells, however, usually show these sutures. Examine a fossil Loxoceras,
Orthoceras, or other orthocone.

Notes. — No preliminary notes on the cephalopods are required. The
questions asked below are intended chiefly to direct attention. The

70

PRINCIPLES OF ANIMAL BIOLOGY 71

drawings, and the summary (directions for which are given below),
will answer most of them.

1. Study an orthocone (Loxoceras or Orthoceras, for example). This
type of cephalopod was particularly common in the Ordovician and
Silurian periods. What is the form of the shell ? The form of the sutures ?
The specimen is usually only a fragment of the entire shell. Thus, in the
Museum of Geology at the University of Michigan is a fragment of an
orthocone 6J^2 inches in diameter at its larger end, 4J^ inches in diame-
ter at its smaller end. This fragment is 18 inches long. If the piece were
completed at its smaller end, how long would it be? Since the animal
lived only in the undivided chamber at the larger end of the shell, the
shell was many times larger than its occupant.

Modern cephalopods progress backward by means of the siphon.
(Examine the siphon of a squid and understand its operation.) How
would the long shell affect the animal's movements?

Draw an orthocone, giving its name, to show the form of the shell and
of the sutures. A line drawing is sufficient but should be carefully made.

2. Examine a gomphoceran (Poterioceras or some other). These
forms are recovered from the Ordovician to the Carboniferous periods.
What is the shape of the shell? Form of the sutures? How much of the
shell was occupied by the animal? Is this shell more cumbersome, or less
so than that of the orthocone?

Draw a gomphoceran carefully (line drawing).

3. In a nautiloid (Eutrephoceras is an example), what is the form of
the shell? Of the sutures? Examine a bisected fossil nautiloid, if
one is available, noting the form of the septa; compare it with the bisected
shell of the modern Nautilus. The nautiloids were most abundant in
Silurian and Devonian times, though some survived those periods, and
one of them, the pearly Nautilus, is still living.

Draw a nautiloid, showing all the visible sutures.

4. Compare the shell of a goniatite (Aganides or some other) with those
of the preceding forms, particularly the nautiloid. Note the form of the
sutures. Goniatites were most abundant in Carboniferous times (see
time scale).

Draw a goniatite, being careful to represent all the sutures in their
correct form.

5. Study a ceratite (Ceratites or any other). What is the form of
the suture? How do the sutures compare in complexity with those of a
goniatite? The ceratites were largely Triassic.

Draw a ceratite to show its sutures.

6. Study an ammonite (Scaphites or any other). These reached their
climax in the Jurassic to the Cretaceous periods. The sutures are
very crooked fine lines on the surface. Do not confuse the coarse ridges
on the surface with them. Trace very carefully at least one suture

72 LABORATORY DIRECTIONS IN

completely around one coil of the shell before attempting a drawing. The
chances for error are large, because adjoining sutures approach one
another very closely at various points. Examine other ammonites if
possible.

Draw an ammonite at least natural size, showing two of the sutures.
The latter should be very accurate pictures of the specimen used, not
merely a diagrammatic representation of the kind of sutures found in
ammonites in general.

B. EVOLUTION OF THE HORSE

The development of the horse, as far as known from fossils, took
place entirely in Tertiary time. The undiscovered ancestor was undoubt-
edly a small animal, with five toes on each foot, and nails instead of hoofs.
In the following exercise the evolution of the horse will be traced with
respect to (1) number of toes, (2) form of teeth, and (3) size of body and
skull.

Many of the specimens used in the laboratory are casts of fossils,
and must be handled with care. The student should see some of the
actual fossils also, if these are available.1

The Feet.

1. Examine casts of the bones of the fore and hind feet of Eohippus
or Orohippus. They are of natural size. How many digits in each foot?
Are any of the digits distinctly shorter than the rest?

From the wall chart note the geological age to which these forms be-
long. Draw both fore and hind foot, representing the proportions with
care, and carefully distinguishing the individual bones. Indicate by
Roman numerals which of the ancestral five digits are left (see Shull,
LaRue and Ruthven, "Principles of Animal Biology," Chapter XV).
The figure may be less than natural size.

2. Study a cast of the foot of Mesohippus. How many digits?
Which ones? What is the relative size of the various digits? Compare
in size with Eohippus or Orohippus.

To what geological period does Mesohippus belong? Draw the
foot of Mesohippus with care, indicating which digits are present.

3. Examine the fore foot of Hypohippus. Compare in size with the
foot of Mesohippus. Note the size of the third digit as compared with
the second and fourth. Is the third digit relatively larger, or relatively
smaller, than in Mesohippus? Did the lateral digits of Hypohippus
reach the ground? Observe the nodules at the back of the metacarpals

1 Other genera of similar nature may be substituted for the ones named below.
Hypohippus and Hipparion, which appear not to be in the direct line of evolution, may
be omitted if desired.

PRINCIPLES OF ANIMAL BIOLOGY 73

at their proximal end. What do they represent? Which nodule is the
larger? Does this relative size signify anything?
In what geological time did Hypohippus exist?

4. Study the fore or hind foot of Merychippus. Compare in length
with the fore foot of Hypohippus. Did the lateral toes reach the ground?
Are there any indications of the first and fifth digits (cf . Hypohippus) ?
How recent is Merychippus?

Draw a foot of either Hypohippus or Merychippus. If Hypohippus
is selected for this figure, view it obliquely from the side so as to include
the vestige of one of the lateral metacarpals. Represent the individual
bones carefully in their proper proportions.

5. Foot of Hipparion or Pliohippus. Compare in height with Mery-
chippus. How well developed are the second and fourth digits? Com-
pare with Hypohippus and Merychippus.

Geological period?

6. Equus, fore or hind foot, either fossil or modern. Compare in
size with the earlier forms. Look for vestiges of the second and fourth
digits.

Draw the fore or hind foot of Hipparion or Pliohippus or Equus with
care. Turn in such a position as to show one splint bone.

The Teeth and Skull.

1. Examine the skull of Eohippus. Note size of the jaws. Note
position of orbit of eye relative to teeth. Ask for a specimen, photograph
or cast of a tooth of Eohippus. What is the relative length of the crown
and the roots? (Note whether the roots are entire or not). Observe
the tuberculate surface of the tooth (that is, the cusps or prominences on

it).

2. Study the skull of Mesohippus. Compare with Eohippus.
Where is the orbit relative to the teeth? A fossil tooth, photograph or
cast will be furnished. What is the relative length of crown and root?
What is the nature of the surface? Draw the tooth of Mesohippus, either
from the original or from a cast or photograph, showing as accurately as
possible (a) the length of crown and root, and (6) the form of the upper
surface. Shading is desirable to show the latter feature. View the tooth
obliquely so as to include roots and upper surface in one figure.

3. In specimens, casts, or photographs of the tooth and skull of Mery-
chippus, note (a) the size of jaw, (6) position of orbit, (c) the size of the
crown of the tooth, (d) the character of the surface of the tooth. Draw
the tooth of Merychippus or copy the photograph in a line drawing.

4. Compare the skull and teeth of Equus (either fossil or modern)
with the preceding forms. Examine a bisected tooth and note the ex-
tent of the pulp cavity. Draw the tooth of Equus in oblique view to
show roots and upper surface in one figure.

74 LABORATORY DIRECTIONS

Size of Body.

1. From the casts or fossils of the feet, note the increase in size through
successive geological periods.

2. On a chart representing restorations of the entire animals, based
on measurements of the fossil bones, note the increase in stature from
Eohippus to Equus.

C. SUMMARY

State carefully the course of evolution of the cephalopods and of the
horse with regard to the features studied in the foregoing exercise. Make
reference to your figures. Note that some of the forms studied may not
be in the direct line of descent, but are probably offshoots. Which are
these? In which continents did the early, middle, and late development
of the horse chiefly take place? Make use of these points in your sum-
mary. The summary of the horse should include a table showing the
continents where its development took place, the geological periods, and
the changes in feet, teeth, skull, and stature.

Readings Concerning the Evolution of the Horse

1. SCOTT, W. B., "The Theory of Evolution," pp. 98-109.

2. LULL, R. S., "Evolution of the Horse Family," American Journal of Science,
March, 1907.

3. NICHOLSON, H. A., "Manual of Paleontology," pp. 335-340.

4. DENDY, A., "Outlines of Evolutionary Biology," pp. 307-312.

5. COPE, E. D., "Primary Factors of Evolution," pp. 146-149.

6. MATTHEW, W. D., "The Evolution of the Horse," supplement to American
Museum Journal, January, 1903.

Readings Concerning Cephalopod Evolution

1. LULL, R. S., "Organic Evolution," Chapter XXVI, especially pp. 429-433.

2. WILLIAMS, H. S., "Geological Biology," Chapter XIX, especially pp. 350-358.

INDEX

Numbers refer to pages.

Abiogenesis, 32, 36. '

Absorption, in metazoa, 17; in Para-
mecium, 15.

Acetabulum, in frog, 48; in man, 47; in
pigeon, 49.

Acris, 58.

Adaptation, 62, 68.

Adductor muscle, 63, 64.

Aeolosoma, 54; budding in, 34.

Aganides, 71.

Aggregations, of cells, 23, 31; of many-
celled individuals, 30, 31.

Alphabet, free-hand lettering, 4.

Alternation of generations, 35, 36.

Ambystoma, 58.

Ambystoma tigrinum, birth stage of, 39;
eggs of, 38.

Ammonite, 71.

Amoeba, 10, 13, 51.

Amphiaster, 22.

Amphibia, 56, 57, 58.

Anaphase, 20, 22.

Anguis, 59.

Animal pole, 42.

Annelida, 54.

Anodonta, 55, 62.

Anus, of earthworm, 28.

Aphid, parthenogenesis in, 35.'

Apoda, 58.

Arthropoda, 55.

Ascaris, 53, 54; cell division in, 21, 22;
maturation of eggs in, 40, 41, 42.

Aster, 22.

Astral ray, 20.

Attraction-sphere, 21, 22.

Aves, 57.

Backbone, 56.
Bascanion, 59.
Bilateral symmetry, 53, 55; in earthworm,

26.

Biogenetic law, 46.
Birge net, 64.
Birth stages, 39.

Bison, distribution of, 68; teeth of, 69.

Blastopore, of frog embryo, 43.

Blastostyle, of Obelia, 30, 31.

Blastula, of frog, 43.

Blood, 9; human, 12.

Blood system, of earthworm, 28.

Bone, 12.

Bowman's capsule, 18.

Brain, of earthworm, 29; of frog embryo,
43.

Brooding habits, 39.

Brood pouch, of frog, 39; of Hippocam-
pus, 39; of kangaroo, 39; of marsupial
(opossum), 39.

Bryozoa, 30.

Buccal pouch, of earthworm, 28.

Budding, in Hydra, 33; in Nais, Aeolo-
soma, Chaetogaster, Dero, Microsto-
mum, 34; in sponge, 33.

Bufo, 58.

Bugula, 30.

Byssus, 64.

Cambarus, 55.

Canaliculi, of bone, 12.

Carbohydrate, 17.

Carbon dioxide, 18.

Carboniferous, 71.

Carchesium, 23, 52.

Carpals, 47; of frog, 48; of man, 47; of

pigeon, 48.

Carpo-metacarpus, of pigeon, 48.
Cartilage, 11.
Caudata, 58.
Cell, 8; inclusions, 11; membrane, 8, 20;

structure of, 8, 9; wall, 9.
Cell aggregation, 23.
Centrosome, 20, 22.
Cephalopoda, 70, 71, 74.
Cephalothorax, 55.
Centrum, 60.
Ceratite, 71.
Ceratites, 71.
Chaetogaster, budding in, 34.

75

76

INDEX

Cheloniidse, 60.

Chelydridse, 60.

Chitin, 55.

Chiton, 55.

Chloroplast, 9.

Chordata, 56.

Chorophilus, 58

Chromatin, 10, 20.

Chromoplast, 9.

Chromosome, 20, 22, 40, 41, 42.

Chrysemys marginata, 69.

Circular canals, of Obelia, 31.

Circular muscles, of earthworm, 29.

Circulation, 17.

Circumpharyngeal connectives, of earth-
worm, 29.

Classes, 56, 57.

Clavicle, 47; of man, 47.

Cleavage, of frog's egg, 42.

Cleavage furrow, 42.

Cleavage nucleus, in Ascaris, 41.

Clitellum, of earthworm, 26.

Cloaca, of frog, 37, 38.

Cnidoblast, in Hydra, 25.

Ccecilians, 58.

Coelenterata, 30, 52.

Coelom, 53; of earthworm, 27.

Ccenosarc, 52; of Obelia, 30.

Color, regional differences of, 69.

Coracoid, 47; of man, 47; of pigeon, 48.

Costiform processes, 60.

Crocodilini, 59.

Crop, of earthworm, 28.

Cross-bill, white-winged, distribution of,
68.

Cryptobranchus, 58.

Cyst, of Monocystis, 33.

Cytoplasm, 8, 9, 21, 22.

Daughter individuals, of Volvox, 24.

Dero, budding in, 34.

Deserts, 67.

Desmognathus, 58.

Development, of frog, 42.

Devonian, 71.

Diemictylus, 58.

Differentiation, 23.

Digestion, in metazoa, 17; in Parame-

cium, 14.

Digestive system, of earthworm, 28.
Dioecious, 35.
Diploblastic, 52.
Diploid, 42.

Dissosteira, 55.
Distribution of animals, 67.
Division, of cells, 20.
Division of labor, 19, 23, 31.
Drawings, 3, 4.
Duck, adaptations in, 69.
Dyad, in Ascaris, 41.

Earthworm, 26, 54; reproduction of, 34.

Echinodermata, 54.

Ecology, 62.

Ectoderm, in Hydra, 25, 26.

Ectosarc, of Amoeba, 11.

Egg, digestion of white of, 17; maturation

of, 40; membrane, in Ascaris, 41; of

frog, 10; of Obelia, 31; of Volvox, 24;

types of, 38; yolk, 10.
Elk, teeth of, 69.
Elodea, 9, 13, 66.
Embryo, of Ascaris, 41; of Hydra, 26; of

mammal, in uterus, 38.
Embryology, 40.
Endoderm, in Hydra, 25, 26.
Endosarc, of Amceba, 11.
Enzyme, 17.
Eohippus, 72, 73, 74.
Epistylis, 23, 52.
Epithelial cells, in earthworm, 29; in

Hydra, 25.
Epithelium, 14.
Equatorial plate, 20, 22.
Equus, 73, 74.
Erythrosin, 9.

Esophagus, of earthworm, 28.
Euglena, 9, 10, 14.
Euplectella, 52.
Eutrephoceras, 71.
Excretion, in metazoa, 18; in Para-

mecium, 15.

Excretory system, of earthworm, 28.
Exumbrella, of Obelia, 31.

Family, 59, 61.

Fat, 17.

Fat bodies, of frog tadpole, 44.

Fauna, of terrigenous bottoms, 62.

Feathers, 57.

Femur, 47; of frog, 48; of man, 47; of

pigeon, 49.

Fertilization, 38, 39, 40, 41.
Fibril, in muscle cell, 16.
Fibula, 47; of man, 47; of pigeon, 49.

INDEX

77

Filament, of Carchesium and Zootham- Helix, 55.

nium, 23. Hermaphrodite, 34.

Fin, 56; of frog tadpole, 43. Heron, 69.

Fission, in Paramecium, 32, 33. Hinge, of mussel, 63.

Flagellate, 9, 14. Hipparion, 72, 73.

Flagellum, of Euglena or Peranema, 14; Hippocampus, care of eggs, 39.

of Pleodorina, 24; of Volvox, 24. Homology, 46.

Focusing, 6. Hookworm, 54.

Foot, of mussel, 63. Horned lark, 69.

Foraminal aperture, of sponge gemmule, Horse, evolution of, 49, 72-74; legs of

34.

Forest areas of North America, 67.

Fossils, 70-74.

Frog, development of, 42.

Fungia, 52.

Furcula, of pigeon, 48.

modern, 49.
Humerus, 47; of frog, 48; of man, 47; of

pigeon, 48.
Hydra, 10, 25, 26, 28, 30, 52; H. oligactis,

25; H. viridissima, 25.
Hydranths, of Obelia, 30, 36, 52.
Hydrochloric acid, 17.
Hydroid, metagenesis in, 36.
Hydrorhiza, of Obelia, 31.
Hydrotaxis, 66.

Gall bladder, of frog tadpole, 44.

Ganglia, of earthworm, 29.

Gastrocnemius, 16.

Gastrovascular cavity, 52, 53; in Hydra, Hydrotheca, of Obelia, 30.

25. 52. Hyla, 58.

Gastrula, of frog embryo, 43. Hypodermis, of earthworm, 29.

Gemmule, of sponge, 33, 34. Hypohippus, 72, 73.

Genera, 61. Hypostome, of Obelia, 30.
Geotaxis, 66.

Germ cells, in earthworm, 29; in Hydra, Ilium, 47; of frog, 48; of man, 47; of

26; in Pleodorina, 24; in Volvox, 25; pigeon, 49.

maturation of, 40, 41, 42. Illumination, of microscopic preparations,

Gill plate, of frog tadpole, 43. 6.

Gills, 56, 57; of frog tadpole, 43, 44; of Incubation, 39.

mussel, 63. Ingestion, in metazoa, 17; in Parame-

Gill slits, of frog tadpole, 44. cium, 14.

Gizzard, of earthworm, 28. Innominate, 47.

Gland, intestinal, 17; of stomach, 17; Interdigitation, 68.

salivary, 17.
Glochidia, 63, 64.
Glomerulus, of kidney, 18.
Gomphus, 65.

Gonangium, of Obelia, 30, 31, 36.
Goniatite, 71.
Gonionemus, 52.
Gonotheca,'of Obelia, 30.
Gopherus polyphemus, 69.
Grading of notes and drawings, 4, 5.
Grantia, 52.

Intestine, of frog tadpole, 44.
Iodine, 14.

Ischium, 47; of frog,' 48; of man, 47; of
pigeon, 49.

Jelly, of frog's egg, 42.
Julus. 56.
Jurassic, 71.

Karyokinesis, 20.
Keys, 61.

Grasshopper, maturation of spermatozoa Kidneys, of frog, 18, 37; of frog tadpole,
in, 40. 44.

Kinosternidse, 60.
Hair, 57; cellular structure of, 12.

Haploid, 42. Labial palps, 63.

Heart, of earthworm, 28; of frog, 18; of Labium, 65.

frog tadpole, 44. Laboratory regulations, 2.

78

INDEX

Lacunae, of bone, 12.

Lamella, of gill of mussel, 63.

Lamprey, birth stage of, 39.

Lampsilis, 54, 55, 62.

Larva, 39; of frog, in development, 43.

Limb buds, of chick embryo, 46; of frog

tadpole, 46.

Liver, cells in, 9; of frog tadpole, 44.
Loligo, 55.

Longitudinal muscles, of earthworm, 29.
Loxoceras, 70, 71.
Lumbricus, 26; L. terrestris, 26.
Lung, 57; of frog tadpole, 44.

Macronucleus, in Paramecium, 33.

Macrosiphum, parthenogenesis in, 35.

Magnification, 6.

Malpighian corpuscle, 18.

Mammalia, 57.

Mammary glands, 57.

Mantle, 55, 63.

Manubrium, of Obelia, 31.

Marginal bones, 60.

Marsupial frog, care of eggs, 39.

Matrix, of bone, 12; of cartilage, 12.

Maturation, 40.

Medusa, of Obelia, 30, 31, 36.

Merychippus, 73.

Mesentery, of earthworm, 29.

Mesohippus, 72, 73.

Metabolism, 13, 14, 17.

Metacarpals, 47; of frog, 48; of Hypo-
hippus, 72; of man, 47.

Metagenesis, 35, 36.

Metamere, of earthworm, 26.

Metamerism, in earthworm, 26.

Metaphase, 20, 22.

Metargiope, 56.

Metatarsals, 47; of frog, 48; of man, 47.

Methyl-green, 9, 52.

Metridium, 52.

Micronucleus, in Paramecium, 33.

Microscope, figure of, 5; use of, 5, 6.

Minks, distribution of, 68.

Miranda, 56.

Mitosis, 20, 22; in spermatogonia of grass-
hopper, 40.

Modiola, 54, 55.

Mollusca, 54.

Monoecious, 35.

Moose, distribution of, 68.

Mouth, of earthworm, 26, 28; of frog
tadpole, 43; of mussel, 63.

Movement, 13; amoeboid, 13; ciliary, 14;

flagellate, 14; muscular, 16.
Muellerian duct, of frog, 37.
Muscle, 16.

Muscular system, of earthworm, 29.
Mussel, 14.
Myotomes, 16; of frog tadpole, 43, 44.

Nacre, 70.

Nais, budding in, 34.

Nasal pits, of frog tadpole, 43.

Nautiloid, 71.

Nautilus, 55, 70, 71.

Necator, 54.

Necturus, 58.

Nemathelminthes, 53, 54.

Nematocyst, 52; in Hydra, 25.

Nephridium, of earthworm, 29.

Nereis, 54.

Nerve, 16.

Nerve cord, of earthworm, 29.

Nervous system, of earthworm, 29.

Nests, of birds, 39; of mammals, 39.

Net-knots, 21.

Neural fold, of frog embryo, 43.

Neural groove, of frog embryo, 43.

Neural tube, of frog embryo, 43.

Neutral red, 15.

Notes, 2.

Notochord, 56.

Nototrema, care of eggs, 39.

Nuchal plate, 60.

Nucleolus, 10.

Nucleus, 8, 9, 21, 51; chromatin of, 10;
membrane of, 21; nucleolus of, 10; of
Amoeba, 11; of Ascaris, 41; of Epis-
tylis, 23; resting, 21.

Obelia, 30, 52; metagenesis in, 36.
Oocyte, of Ascaris, 40, 41; primary, 41;

secondary, 41.
Oogonium, of Ascaris, 41.
Operculum, 56; of frog tadpole, 43, 44.
Opisthoccelous, 60.
Orders, 57, 58, 59, 61.
Ordovician, 71.
Organs, 16.
Orohippus, 72.
Orthoceras, 70, 71.
Orthocone, 70, 71.
Osmosis, 17.
Ovary, of earthworm, 27, 30, 34 ; of frog, 37 ;

of Hydra, 26; of viviparous animal, 38.

INDEX

79

Oviduct, of earthworm, 27; of frog, 37.

Oviparous, 38, 39.

Ovoviviparous, 38, 39.

Ovum, of Ascaris, 41; of earthworm, 34;

of Volvox, 24.
Oxidation, in metazoa, 18; in Parame-

cium, 15.

Paleontology, 70.

Palinurus, 55.

Pancreas, 17; of frog tadpole, 44.

Paramecium, 14, 15, 32; conjugation of,

34.

Paramylum, 10.
Parietal bones, 60.
Parthenogenesis, 35.
Parthenogonidia, of Volvox, 24, 25.
Pecten, 55.

Pelage, regional differences of, 69.
Pelomedusidae, 60.
Pelvic girdle, 47; of frog, 48, of man, 47;

of pigeon, 49.
Pentadactyl limb, 47.
Pepsin, 17.
Peranema, 14.
Perisarc, of Obelia, 30.
Peritoneum, of earthworm, 29.
Phacus, 10.
Phalanges, 47; of frog, 48; of man, 47;

of pigeon, 48, 49.
Pharynx, of earthworm, 28.
Phototaxis, 66.
Phyla, 51-56.
Physalia, 31.
Pineal eye, 59.
Pinna, 55.
Pisces, 56.
Plains, 67.
Planaria, 53, 65.
Plastid, 9.
Plastron, 60.
Platyhelminthes, 53, 54.
Pleodorina, 23, 25; P. calif ornica, 23.
Plethodon, 58.
Pliohippus, 73.
Polar body, first, in Ascaris, 41; second,

in Ascaris, 41.
Polistes, 55.
Polygyra, 55.

Polymorphism, in Obelia, 31.
Porcellio, 66.
Porifera, 52.
Portuguese Man-of-war, 31.

Poterioceras, 71.
Prairies, 67.
Precoracoid, 47.
Procoelous, 60.
Proglottis, 53.
Prophase, 20, 21.
Prostomium, of earthworm, 26.
Protein, 17.
Proteus, 58.
Protoplasm, 8, 9, 13.
Protozoa, 9, 33, 51.
Pseudopodium, 11.

Ptarmigan, willow, distribution of, 68.
Pubis, 47; of frog, 48; of man, 47; of
pigeon, 49.

Quadrate, 58, 59.
Quadruped, 57.
Quince seeds, 14.

Radial canals, of Obelia, 31.

Radial symmetry, 54.

Radiating canals, in Paramecium, 15.

Radio-ulna, of frog, 48.

Rpdius, 47; of man, 47; of pigeon, 48.

ftana pipien&, 37. '- , >'

Reactions, 65, 66. ,

Recapitulation ;ifieory .; 46/,

Rectal chamber, of dragorifly nymph, 65.

Reduced number of chromosomes, 42.

Reproduction, 32; asexual, 32, 36;

methods of, 38; sexual, 32, 34, 36.
Reproductive cells, of Volvox, 24.
Reproductive organs, of frog, 37, 38; of

frog tadpole, 44; of Obelia, 31; of tape-

worm, 53.
Reproductive system, of earthworm, 27;

of frog, 37, 38.
Reptilia, 57, 58.
Respiration, in metazoa, 18; in Para-

mecium, 15.

Rhynchocephalia, 58, 59.
Ringer's solution, 64.
Road runner, distribution of, 68.
Rotation, of protoplasm, 13.
Rotifer, 14; parthenogenesis in, 35.

Salamander, 12, 16, 21, 22.

Sahentia, 58.

Scaphites, 71.

Scapula, 47; of man, 47; of pigeon, 48.

Schedule of laboratory work, 1, 2.

80

INDEX

Scolex, 53.

Scolopendra, 56.

Secretion, in metazoa, 17; in Parame-

cium, 14.

Segmentation, of frog's egg, 42.
Seminal receptacles, of earthworm, 27,

30, 34.

Seminal vesicles, of earthworm, 27, 34.
Sepia, 55.

Septum, in Cephalopoda, 70; in earth-
worm, 27, 29; in segmented muscle,

16.

Setae, 54; of earthworm, 26, 54.
Sheath, of Bugula, 30.
Shoulder girdle, 47; of man, 47; of pigeon,

48.

Silurian, 71.
Siphon, 63, 64, 71.
Siphonops, 58.
Siren, 58.
Sistrurus, 59.
Skull, of fossil horses, 73.
Solen, 54.
Somatic cells, in earthworm, 29, 30; in

Hydra, 25, 26; in Pleodorina, 24; in

Volvox, 24, 25;,number of cfrrc>mGS>>mesf

42.

Somite, of earth worm, 2ft r*u<
Species, 61. ;\ ; ',/'• vHt<
Spermary, in Hydra, 26.
Spermatid, 40.
Spermatocyte, primary, 40; secondary,

40.

Spermatogonium, 40.
Spermatozoa, maturation of, 40; of As-

caris, 41; of Hydra, 26; of Obelia, 31,

36; of Volvox, 24, 25.
Sphenodon, 59.

Spinal cord, of frog embryo, 43.
Spindle, in mitosis, 20.
Spindle fibers, 22.
Spiracle, of frog tadpole, 44.
Spireme, coarse, 20, 21; fine, 20, 21.
Spongin, 52.

Spore, of Monocystis, 33.
Spore formation, in Monocystis, 33.
Squamata, 59.
Squamosal, 60.
Stalk, of Carchesium and Zoothamnium,

23.

State monographs, 61.
Stimuli, 16, 66.
Stratum corneum of frog skin, 8.

Striations, in muscle, 16.
Subepithelial cells, in Hydra, 25.
Subumbrella, of Obelia, 31.
Sucker, of frog tadpole, 43; of leech, 54;

of tapeworm, 53.
Summary, 3.
Supplies, 1.
Suture, in cephalopod shell, 70-72; in

turtle skull, 60.
Synapsis, in Ascaris, 41.
Systematic treatises, 60.

Tadpole, of frog, 43.

Tail, of frog tadpole, 43.

Tapeworm, 53.

Tarsals, 47; of frog, 48; of man, 47.

Tarso-metatarsus, of pigeon, 49.

Taxonomy, 51.

Teeth, of fossil horses, 73.

Telophase, 20, 22.

Tentacles, of Gonionemus, 52; of Hydra,

33; of Obelia, 30.
Terrigenous bottoms, 62.
Testis, of frog, 37; of Hydra, 26.
Testudinata, 58, 59.
Testudinidse, 60.
Tetrad, in Ascaris, 41.
Thamnophis, 59; T. butleri, 67; T. radix,

67.

Thermotaxis, 66.
Thigmotaxis, 66.
Tibia, 47; of man, 47.
Tibio-fibula, of frog, 48.
Tibio-tarsus, of pigeon, 49.
Tissues, 16.
Triassic, 71.
Trichinella, 54.
Trimerotropis maritima, maturation of

spermatozoa in, 40.
Trionychidse, 60.
Triploblastic, 53.
Triton, 58.
Tube-feet, 54.
Typhlosole, of earthworm, 29.

Ulna, 47; of man, 47; of pigeon, 48.
Unsegmented egg, of frog, 42.
Ureter, of frog, 37.

Uterus, of Ascaris, 21; of frog, 37; of
mammal, 38.

Vacuoles, food, in Amoeba, 11; food, in
Paramecium, 15; in Hydra, 10; pul-

INDEX

81

sating, in Amoeba, 11; pulsating, in

Paramecium, 15.
Vasa efferentia, of frog, 37.
Vegetative pole, 42.
Ventral blood vessel, of earthworm, 28,

29.

Ventricle, of heart of frog tadpole, 44.
Vertebrae, 59, 60; centrum of, 60.
Visceral mass, 63.
Viviparous, 38, 39.
Volvox, 24, 25.

White-fish, 21.
Woodchuck, 69.
Woodpecker, 69.
Wool, cellular structure of, 12.

Yolk, of egg, 10.

Yolk plug, of frog gastrula, 43.

Zoogeography, 67.
Zoothamnium, 23.
Zygapophyses, 60.

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