A laboratory guide for beginners in zoology

Front matter

QL w.

■a fi« o \

V * i I j ^ ° * * t'N O

Preface

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

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

iv Preface

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

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

C. M. W.

New Hampshire College of

Durham, August, 1902.

Contents

The Laboratory and its Equipment-

The Cultivation and Preparation of Material

CHAPTER I. BRANCH PROTOZOA: The One-celled Animals The Amoeba

The Euglena .

The Paramecium The Vorticella The Stentor .

The Stylonychia The Classification of the Protozoa

II. BRANCH PORIFERA: The Sponges The Fresh-water Sponge The Marine Sponge ....

The Classification of the Porifera .

IV. BRANCH CCELENTERATA : The Hydras and Sea

ANExMONES .

The Fresh -water Hydra

The Campanularian Hydroid

The Hydro-medusa

The Tubularian Hydroid

The Classification of the Ccelenterata

PAGE

iii ix xi

I I 3

9 io

15 15 16

20 20

23 26 27 29

BRANCH TROCHELMINTHES : The Rotifers and

their Allies 31

The Rotifer, or Wheel Animalcule . . . 31

The Classification of the Rotifers and their Allies . . ^ vi Contents

CHAPTER PAGE

V. BRANCH ECHINODERMATA: The Starfishes and

Sea-urchins 35

The Starfish 35

The Sea-urchin 40

The Sea-cucumber 42

The Classification of the Echinodermata ... 44

VI. BRANCH ANNULATA: The True Worms . . 46 The Earthworm . . . . . . . .46

The Marine Annelid 49

The Classification of the Annulata .... 52

VII. BRANCH ARTHROPODA: The Animals with

Jointed Legs 53

The Wood-louse, or Sow-bug ..... 53

The Lobster, or Crayfish 54

The Crab 60

The Cyclops 62

The Flattened Centipede ...... 64

The Locust, or Grasshopper 65

The Dragon-fly 68

The Butterfly 71

The Spider 72

The Classification of the Arthropoda .... 74

VIII. BRANCH MOLLUSCA: The Oyster, Clams, and

Snails . 77

The Clam 77

The Snail 82

The Squid 83

The Classification of the Mollusca 85

IX. BRANCH CHORDATA: The Vertebrates . . 87

The Perch . 87

The Frog 92

The Bird 98

The Classification of the Vertebrates . . . . 102

THE LABORATORY: ITS EQUIPMENT AND THE PREPARATION OF MATERIAL

Fig. i. A Movable Laboratory Table.

vm

THE LABORATORY AND ITS EQUIPMENT

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

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

x Introduction

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

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

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

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

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

Introduction xi

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

Thomson's " Study of Animal Life."

"The Riverside Natural History."

"The Cambridge Natural History."

Claus's " Text-book of Zoology."

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

Hertwig's " General Principles of Zoology." Jordan and Kellogg's " Animal Life." Jordan and Heath's " Animal Forms."

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

THE CULTIVATION AND PREPARATION OF MATERIAL

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

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

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

THE AMCEBA

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

Xlll

THE AMCEBA: A, B, C, shapes assumed with pseudopods extended; B, shape when encysted ; £, shape when dividing. Magnified.

xiv Introduction

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

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

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

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

xv

THE EUGLENA

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

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

I have also obtained a fine lot Of Active form. Magni-

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

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

XVI

THE Paramecium: A t normal active form; B, after treatment with acetic acid to bring out trichocyst threads ; C, conjugating specimens ; D t early stage of fission. Magnified.

Introduction xvii

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

THE PARAMECIUM

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

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

: dance of large bacteria of various forms, a number of ciliate and flagellate protozoa, a few desmids and diatoms, as well as an occasional protococcus-like form. The sides of the jar showed bacteria, desmids, diatoms, Protococcus, Haematococcus, and a few euglenae. The bottom showed an abundance of the same forms. After this examination (October 27) I covered the jar and put it in a dark closet. On November 1 another examination

J was made. The white film showed many ciliate infusoria, including some fine paramecia. Ten days later the water

i xviii Introduction

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

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

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

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

Paramecia should be first studied under the low powers with little or no cover-glass pressure. The normal shape can then be seen. The pressure of the cover glass flattens the body. By placing a little cotton-wool beneath the xix cover glass the movements of the paramecia may be restricted so that they are more easily studied.

THE VORTICELLA

Vorticellae occur in nature in ponds and sluggish streams, but are difficult to find in such situations in sufficient quantity for class use.

They may be cultivated in aquaria without difficulty. They are likely to develop in shallow dishes containing aquatic plants of any kind, especially if the dish be placed in a dark situation. In the aquarium in which such a great quantity of paramecia were developed, as described above, large numbers of vorticellae were also produced.

Several cultures of vorticellae are desirable in order to get the dividing, the free-swimming, and the encysted stages.

I have repeatedly obtained cultures showing each of these forms, the seeing of which adds much to the value of the study by the class.

V A

THE VORTICELLA : A, stalked form; B, free-swimming form; C, encysted form. Magnified.

xx Introduction

THE STENTOR AND STYLONYCHIA

Stentors are generally harder to develop in indoor cultures than the common infusoria. But I have •usuallyhad them present in some one of the culture jars, frequentl) in those in which paramecia are found. Stylonychia is also generally present in Paramecium cultures.

SPONGES

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

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

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

HYDRA

This creature has a small cylindrical body, by the base of which it attaches itself to various objects in the water, and from the other end of which project a number of tentacles. Both the body and the tentacles are capable of being expanded and contracted, so that sometimes they xxi are long and slender, and at other times short and thick. Their appearance when slightly magnified is shown in the figure herewith. Two species are commonly found : in one the body is green ; in the other it is light brown.

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

TxitT i t x t.o..yLUxrLaxLrtx

The Hydra. Magnified.

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

XX11 in one jar, get more of the material from the same place and treat it in the same way. The hydras may be transferred to covered aquaria containing Vaucheria, Nitella, or similar plants, where under favorable conditions they will multiply and be available when wanted.

With a dozen or more aquaria containing water plants

in good condition in the laboratory, hydras are pretty sure to be present in some of them. Water snails should not be allowed in hydra jars. Cyclops or other minute Crustacea are also likely to be found in some of these jars.

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

Cyclops. Magnified.

INSECTS

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

Introduction xxiii

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

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

which are more successfully killed and preserved in alcohol.

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

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

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

A LABORATORY GUIDE FOR BEGIN- NERS IN ZOOLOGY

LABORATORY GUIDE UN ZOOLOGY

CHAPTER I BRANCH PROTOZOA: THE ONE-CELLED ANIMALS

THE AMCEBA

It is very desirable that good-sized specimens be provided for the study of the Amoeba. Under the high power of the microscope look for a small, granular, nearlytransparent object, which changes its outline either constantly or at frequent intervals.

I. — Notice the general nature of the movements. Are

they slow or fast ? Does the Amoeba always move in a definite direction ? Does it ever happen that different parts of the body move in different directions at the same time? Make five outline sketches showing the changes undergone by one Amoeba.

II. — Study the method by which movement takes place. See that the outer colorless layer of protoplasm — the ectosarc — rolls out into one or more blunt projections, called pseudopodia, or false feet. See whether the inner, more granular protoplasm — the endosarc — is forced into the pseudopods by the lateral pressure of the ectosarc. Observe the changes in the outline of the body due to the movement of the pseudopods. In case the Amoeba is moving in a definite direction, notice whether the progress is being made by means of a single broad pseudopod or by more than one. Determine whether a change in the direction of movement is made by pushing any part of the surface of the protoplasm outward. Is it true that the body of the animal is thus temporarily differentiated into anterior and posterior parts ?

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

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

V. — In the largest specimens look for the roundish

nucleus, more granular than the endosarc surrounding it. If it is not visible in the living Amoeba, stain the specimen with iodine or carmine to bring it out.

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

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

THE EUGLENA

The Euglena may be found in a resting or active condition ; if resting, its form is generally almost or quite spherical. In finding and studying it, use the high power of the microscope.

I. — Study the free-swimming movements of the active organisms : do they always move straight ahead, or do they sometimes twist and turn about ? Watch the euglenoid contortions of the body ; make five outline sketches showing the changes undergone by a single specimen. See whether the shape assumed when swimming freely straight ahead is generally the same in different individuals. Distinguish between the anterior and posterior ends of the body. Watch the animal turn round and round on its longitudinal axis : does it show any differentiation into dorsal and ventral regions ? II. — The direct cause of locomotion will be found in the constant vibratory movement of a single hair-like process, about one-half as long as the body and projecting from the anterior end. It is to be seen most plainly in the largest specimens. This is the flagellum : it is a part of the protoplasm of the body, differentiated for the purpose of locomotion ; it is permanent in the active form of the Euglena, and cannot be withdrawn like the pseudopod of the Amoeba. By careful focussing, one can get glimpses of the cone-like cavity with the apex pointing inward, from the inner end of which the flagellum arises. This cavity serves the purpose of mouth and gullet, into which the vibration of the flagellum brings particles that serve as food. See the vortex in the water caused by the movement of the flagellum.

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

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

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