ll ) ) | l wali 3 1761 03673237 8 ) | I | | fo) —_ 2G tc a O =O © t= ww os N= z —_ \| II! ELEMENTARY “SSONS IN ZOOLOGY JAMES G. NEEDHAM , | cP ee 132%, Ss 7) mma SEES 555555550 505050505050:502:502:5:5b5b5:56 OZ6L 0} 8Z6L Woy ABO[OOZ jo JUIW}Iedaq dU} JO IaquIaUI Be SEM ap] JOSsajOlg O}UOIO] Jo AjIsJaAtuc) A30]007 jo JUaWIedaq ‘ATeIgr] ay} 0} ap] ‘d Mepel{ snpaury 10ssajoi1g WOOL; HIS V7 oN a.™ > e e QE ES 555555555555E5 (GG) ) &) S) G) S)} S)} S) S) G) S) G)G)G)S)6)E)E)5} eet ict A. wv a 7 rn! ae i at | ir Ra Wan 4 Bites 4 7 = ee Peay a Ts fra” an ‘ f en ie en Wan By. ite ny hud heat HLEMENTARY LESSONS ZOOLOGY 4A GUIDE IN STUDYING ANIMAL. LIFE AND STRUCTURE IN FIELD AND LABORATORY BY JAMES G. NEEDHAM, Px.D. PROFESSOR OF BIoLoGy, LAKE FOREST COLLEGE NEW YORK -:. CINCINNATI -:. CHICAGO AMERICAN BOOK COMPANY “ The invariable adaptation of an animal to the life it leads is one of nature’s most instructive lessons, and can be discovered and appreciated by every pupil, but never through oral teaching or from reading of books. Better a child should learn to handle one animal, to see and know its structure and how it lives and moves, than to go through the whole animal kingdom with the best text-book under the best teacher, aided by the best charts ever made. The former would have learned what real knowledge is and how to get it, while the latter would have simply learned how to pass at his school examination.” ALPHEUS Hyatt, “* Therefore I would, in the name of education, urge students to begin naturally with what interests them, with the near at hand, with the practically important. A circuitous course of study, followed with natural eagerness, will lead to better results than the most logical of programs, if that take no root in the life of the student.”’ J. ARTHUR THoMsON, in ‘ The Study of Animal Life,’’ p. 361. CopyRigut, 1895, 1896, By AMERICAN BOOK COMPANY. NEED. ZOOLOGY. E-P 12 , al oo ee ee a PREFACE. Tuis book is intended for that increasing class of moderately equipped schools in which it is desired to make a beginning in the study of zoology after the scientific method. Its aim is to put the student in the way of acquiring for himself a knowledge of animal — life and structure. It is not intended to supersede the teacher, but rather to relieve him from doing that part of the work for the stu- dent which the student should do for himself, and to give the teacher a wider opportunity. It is written in the firm belief that the student will receive that benefit which belongs peculiarly to this study in just so far as he comes into touch with nature through actual contact with facts. The plan presented has been adopted after due deliberation and repeated trial. In the belief that the simplest animal structures are best for illustrating the fundamental ideas of zodlogy, as well as being easiest understood, four simple types are introduced first. These are for microscopic study, from material to be provided by the teacher, and prepared by him for examination. From the study of these the student may learn the purport of the terms cell, protoplasm, tissue, organ, differentiation, sexuality, etc. With these fundamental ideas mastered, he is prepared to study intelligently any of the higher animals. The novelty of the introductory microscopic work will be a sufficient guaranty of interest in it, and the succeeding work is out- lined in accordance with the tastes and in avoidance of the prejudices of the beginner. Insects are taken up next in order, and the most attractive insects are studied first. This is a deliberate but not a purposeless violationof the logical order. Systematic zoology may well be neglected, so long as the student is ignorant of the material to be classified. To start the beginner where the specialist leaves off is an error too often repeated in the teaching of this as of other sciences. Wherever, in the arrangement of the subject-matter of this book, the choice has seemed 3 4 PREFACE. to lie between being logical and being serviceable, the author has preferred that the arrangement should be serviceable. The study of animals alive, and in their biological relations to their environment, is made a prominent feature. It is not morphology, or physiology, or natural history alone, that constitutes a proper ele- mentary zodlogical course, but a comprehensive study of animals, that develops these sciences in their proper relations, and gives the ele- mentary student a general view of the whole field,—a correct “zoological perspective.” Morphology may, perhaps, like chemistry, be learned in the laboratory alone, but zoology may not. It has been a popular delusion that a term of dissections constitutes a proper ele- mentary course. Such a course was an improvement on former methods: the study of dead animals is infinitely better than no con- tact with animals at all. But to study animals with nature and life left out is to omit a phase of the subject of deepest scientific interest, of highest educational importance, and of greatest pedagogical utility. This book is written primarily for use in the interior: hence forms of life obtainable only at the seashore receive less attention than those found inland. The study of animal life is best begun with forms nearest at hand. The custom of sending to the seashore for specimens with which to begin the study, and neglecting a wealth of material at home, does not deserve to be encouraged. At the sug- gestion of many teachers who live where fresh marine material is available, a study of the starfish is inserted as the last chapter in the book. Believing that it will be used in some cases where material tq illustrate it is insufficient, it contains fewer interrogation points, and more of explicit statement, than preceding chapters. A few diagrams of structures are inserted for the same reason. All the work outlined in the following pages has been tested in the classroom, and has been repeatedly performed by the author while drawing up these lessons; and it is hoped by him that they may prove reasonably free from ambiguity and error. No animal is studied exhaustively: each one lends itself to some special purposes of illus- tration, and to such ends only is it used. Care has been taken to introduce no work beyond the capacity of the beginner. The illustra- tions given are intended to guide the student in finding and identify- ing for himself the animals recommended in the text for study. Few drawings are given of things which the student may reasonably be expected to draw for himself. If such are wanted, the reference books recommended are filled with them, and may be consulted with profit. In the material presented herein the author can lay no claim to ad Se =e a — a a ee ee ee PREFACE. 5 originality: he only wishes to be given credit for an honest effort at selecting, from the most available materials offered, that best calcu- lated for introducing the beginner to the ideas and principles of zodlogical science. He respectfully invites the correspondence of teachers who find difficulty in using the book. Finally, the author would gratefully acknowledge the assistance of many friends and teachers and of books which were teachers. He would speak of the cut on p. 212, which was kindly loaned by Professor Forbes of the Illinois State Laboratory of Natural History: and he would especially remember the assistance of Dr. E. A. An- drews of Johns Hopkins University, who read the manuscript of the text; of Professor J. H. Comstock of Cornell University, who read the proof sheets of the pages relating to insects; of Professor E. A. Birge of the University of Wisconsin, who read the proof sheets of the pages relating to crustaceans, mollusks, and vertebrates; of Mr. Edward Potts of Philadelphia, who read the manuscript of the pages relating to the fresh-water sponge; of his honored friend and teacher, Professor Hurd of Knox College, who revised the etymological list of technical terms; and, last but not least, ‘of his wife, Anna Taylor Needham, who made pen drawings for most of the illustrations. J. G. N. én CONTENTS. INTRODUCTION Ae! No toa hatae= Se PCAN 4 w.« © « 6 -« The Amceba . The Slipper Animalcule. . C@®LENTERATES The Fresh-water Sponge The Hydra. ES 0 ee er Hexapod Insects The Butterfly . The Dragon Fly . The Grasshopper. The Squash Bug . ; The Two-year Cicada . The Back-Swimmer. The Bumblebee . The Mud Wasp . The Paper Wasp. The Honeybee The Black Blister Beetle . The Bluebottle Fly . The Bee Killer The Cabbage Butterfly The Life Process in Insects A Review Exercise. A Lesson in Classification . Arachnid Insects . DG TMGGE:. See 6 8 CONTENTS. Myriapod Insects . .. . cbs 6 ek 2 te The Chilopod or Cacined PPM omr eerie CRUSTACEANS. 7). 3 we ee ne The Crawfish 2 6 wc eee a The Asellus . . ..... + +s wb eBay eee The Cyclops . . .) ..k a ces Witwer Further Classification § ..0 6 sca sn pe og Worms <0... ese wert The Harthworm 9... 4%. 9s". Sige ee «wi 10 PIOLLUSES os. ac. rene teem The River Muséel . errr tran ne erg The Pond Snail. >. 1 4) he wt ag ce VERTEBRATES .9. 2 es 0s pee isn ee a a The Catfish . .0. v6 3 se ew te > a The Frog... 88 ce es ee es Oe The Turtle. 20. ss) 0 we in oe ca en ee The Snake 2... 6 ee we Beem oe ee a me The English Sparrow. «0:40 «0 3! 80 ol ee The Rabbit... 2). ss oes ba es eee eee The Life Process in Vertebrates.” .° 2-3). 0.) a. ECHINODERMS . .0 5s) 6 wean se es ee ne The Starfish 0. 6000. ee ee mee APPENDIX .o. wee ee) ak) See en ge elaine = tsi nen Prerequisites. 0.0. 29.5 a ee se Reagents . 2.0. ss gee oe eros Directions for the Preparation of Material for Study . . . . 278 Accentuated List of Technical Terms ... . . . 2 9s) enue Suggestions to the Teacher . . oe we INDEX... 60 8 0 ce om re en a Sten a INTRODUCTION. The Study of Animal Life is begun when we first learn the names of our household pets, and begin to note the differences between them. It is continued so long as our eyes and ears are open to observe the nature and capacities of the animals with which our daily life brings us in con- tact. The horses that draw our carriage, the dogs that answer our call, the birds that delight our ears with their songs from the tree tops, the insects that flit before our eyes among the flowers of the garden, — all are continually illustrating phases of animal life, some of which cannot escape the notice of the most casual observer. Every one knows that animals must have food. When they are young, they require food for growth; and when they are grown, they require food to furnish bodily strength. They require air also, — fresh air, containing oxygen, for the oxygen is the essential thing. A bird inclosed in an air-tight box with plenty of food, ora fish placed in a small quantity of clean water, soon dies, because the available supply of oxygen is soon exhausted. Every one knows that, sooner or later, animals die, and that they leave descendants to perpetuate their race upon the earth; and every one should know that not all their young come to maturity, and that the number of their prog- eny is proportioned to the vicissitudes to which their life is exposed. Every one knows that animals move, that most of them move freely from place to place, and that those which are 9 10 INTRODUCTION. fixed in their location, like the oyster, move freely some parts of their bodies in obtaining their food. Every one knows that animals feel, that they respond to stimuli from without and to impulses from within, and that the most familiar animals exhibit varying degrees of instinct and intelligence. These plain facts are fundamental. All the phenomena of animal life may be grouped under four heads : — 1. All those processes which are concerned with feeding and growth, — the taking of food, the preparation of it for the use of the body, the carrying of it in solution to the various parts, the building of it into the body structure, the exposure of it to oxygen derived from the air, and the removal of useless portions and of waste materials from the body (whether performed by simple means or by com- plex, whether without organs or by means of many separate organs), —all may be called phenomena of Nutritzon. 2. All the phenomena connected with the reproductive process may be called phenomena of Reproduction. 8. All the phenomena of free and spontaneous move- ment may be called phenomena of Voluntary Motion. 4. All the phenomena of the senses of instinct and of intelligence may be called phenomena of Sensation. It will then need to be borne in mind that this fourfold division is made for convenience; that the four groups of phenomena are not entirely distinct, but interrelated and interdependent. In the beginning we must distinguish between that which is necessary and that which is only accessory in animal structure. The robin has a beak for eating, and wings for getting about; but beak and wings are not necessary for animal existence. Eating and moving are necessary, but these might be effected in other ways. The robin is a bird because of its beak and wings, an animal only because it eats and moves at will. INTRODUCTION. 11 In studying each animal, if we ask, (1) What is its food, how obtained and how used? How does it get oxygen from the air? How does it get rid of waste and worn-out mate- rial from its body? (2) How does it reproduce its kind ? How numerous are its progeny and to what danger exposed ? (8) How does it move? What are its specially movable parts? (4) What powers of sense, of instinct, and of intel- ligence has it, and what sort of a nervous system as the seat of these powers? —and if we follow patiently where Nature leads until we have found satisfactory answers to these questions, — we shall arrive at a better comprehension of the animal’s activities, and in the end shall have learned many lessons of perennial interest and profit. This four- fold division of animal phenomena will be of service as an outline for our future study, leading us to learn for each animal all we can about I. Nutrition, and its subservient organs. II. Reproduction, and the adaptation of the reproduc- tive process to varying conditions of life. Ill. Voluntary Motion and motor organs. IV. Sensation, as manifest through a nervous system in senses, instinct, and intelligence. PROTOZOANS. THE AMGBA. The Ameba is selected as the first animal for study, because of its extreme simplicity. In it we are dealing with animal life at its lowest terms. It is very small, usually less than a hundredth of an inch in diameter, and can be studied only with the aid of a microscope. Examine one that has been taken up in a drop of water, mounted on a glass slip, covered, and placed in the field of a microscope.t First find it. This will be task enough for a moment for a beginner, even if the ameba be in the field; for it presents so little likeness to familiar animals, that it might as readily be taken to be anything else. It appears like a little drop of jelly spreading out on a flat surface, trans- lucent in its central portion, and very transparent around its border. Reference to the accompanying figure will aid in recognizing it. ‘That it is alive will not be ascertained at the first glance, but may be learned from watching its slowly changing outline for a moment or two. After find- ing it, and after learning by a few trials how, by moving the glass slide, to bring it back into the center of the field when it moves out, and how to keep it in focus by turning the adjustment screws on the microscope, then study its general structure and its movements. 1 Tf the student be working alone, he will follow the directions given to the teacher (see Appendix, p. 278) for collecting amcbas, and’ pre- paring them for examination. 12 THE AMCEBA. 13 Observe: 1. A granular, translucent central portion (the endosarec), with something of the appearance of ground glass. 2. A transparent outer border (the ectosarc), so clear it is liable to be overlooked the first time an amceba is seen, and the endosare taken for the whole animal. 3. Irregular, blunt projections (pseudopodia, or false feet), which are slowly pushed out from the body wall, or drawn into it. Observe that in all of these there is the AMBA (X 500), drawn while moving in the direction of the arrow: nu, nucleus; v, vacuole; ps, pseudopodia. same clear border and granular central portion; and this is true of their appearance when they protrude vertically, as well as when extended laterally. If we can roll an amoeba over, we shall see the same arrangement of parts; so that we must conclude that the ectosarc forms a com- plete outer layer about the whole animal. Pseudopodia.— Watch the formation of pseudopodia. See first a protrusion of the clear ectosarc, then the flowing of the more fluid granular endosare out into it. Observe 14 PROTOZOANS. that, while pseudopodia are pushed out in all directions, they grow principally in one direction, and that the direc- tion in which the ameeba is traveling. Observe that about as fast as pseudopodia are formed in one direction, the body follows them, all its granular content flowing into their bases, swelling them, and uniting them. Watch also the withdrawal of pseudopodia, first a flow- ing toward the center of the granular part, leaving an emptied projection of ectosarc, which follows on in the rear. Such is ameeba’s primitive method of locomotion. The pseudopodia which are pushed out on one side hold their ground; and, when the semifluid body begins to follow, they advance, and the whole mass is seen setting forward in an exceedingly slow, flowing or gliding motion. If an active amceba be watched a short time, it may be seen to change its direction. To do this it does not need to turn around: it simply puts out pseudopodia in the new direction, and follows them. It has neither head nor tail. All parts are alike, and one is as well adapted as another to go first. It may be seen to avoid large objects with which it comes in contact in its course. If it meet a conveniently small object, it may sometimes be seen to encircle it with pseudopodia, and ingulf it into its soft body mass,—swallow it, so to speak,—after which the object may be seen within the granular endosarc, where it is lodged as food for digestion. If it prove indigestible, it is gotten rid of in a correspondingly simple way. The body mass flows away from it, and it is left behind. If the amceba be irritated in any way, as by touching the cover glass, it immediately draws in its pseudopodia, and assumes a more or less spherical form. If not injured in any way, it soon resumes activity. Make a series of half a dozen outlines of an ameba, drawn at intervals of a minute or two, or less if it be ° moving actively, to show the changes in form. THE AMCBA. 15 Minute Structures. — If the currents in an active amcba have been watched carefully under high power, certain minute structures will have been discovered within the body. Three of these are normally present, though not always easily made out : — 1. A nucleus, a discoid or spherical body slightly more transparent than the surrounding endosarc, and usually located toward the posterior end of a moving ameceba. 2. A contractile vesicle, a round clear spot within the ectosarc. It may sometimes be seen to contract, and dis- appear temporarily, and will then be certainly recog- nized. 3. Ingested food particles. These appear darker than the surrounding endosarc; or if colored food particles have been taken, microscopic green plants, etc., the color will shine through. These are of various sizes. These structures may be more readily made out in a specimen that is stained with iodine. Place a drop of iodine solution on the slide at one edge of the cover glass, and place a bit of blotting paper at the opposite edge. The blotting paper, by its absorbent action, will draw the iodine solution under the cover glass, where it will pene- trate and stain and kill the ameba. The nucleus will be more brightly stained than the other parts. Make an enlarged drawing of an amceba prepared in this way, showing all the points of structure you have been able to see. , By mixing some very finely powdered carmine or indigo in the drop of water containing amcebas before covering, their feeding may sometimes be better observed. Occasionally an amceba may be found dividing into two. Such should be watched carefully. - The Life Process. — The jelly-like living substance which makes up the body of the ameceba is protoplasm. It is 16 PROTOZOANS. an almost structureless and colorless substance, in chemi- cal composition much like the albumen of an egg. It is the physical basis of life. Neither animal nor vegetable life is known to exist apart from it. It is everywhere present in the growing: parts of animals and plants. It is capable, as life’s agent, of producing the most complex structures. The nucleus within the amceba is but a bit of the protoplasm of slightly firmer consistency than the rest; but it is, perhaps, the most essential part. Simple as the amceba is, and wanting in parts, it yet leads an animal life, and exercises all the essential animal functions. I. Nutrition. — That the amceba takes food has been seen already. Having neither mouth nor stomach, it ingests and digests its food at the most convenient point. Its proper food consists of the smallest microscopic plants. These, when found within the body of a living ameceba, may, by continued watching, be seen to dissolve away as they are digested. The small amount of mineral food and the larger amount of oxygen necessary for the amceba are already in solution in the water in which it lives, and need but to be absorbed. These dissolved foods penetrate freely to every part of the protoplasmic mass, and by a process called assimilation they are incorporated into it, and become a part of it. But this process means more than the mere storing of digested food: it means that the food is built up into complex chemical compounds, like those which are the constituents of protoplasm, and that. it then becomes a part of the protoplasm, like any other part, in all its properties. The necessary result of this process is that the animal grows. But this process also makes possible the animal’s activi- ties. The complex chemical compounds formed in this constructive process are highly charged with potential energy and are very unstable, like a single tier of bricks % THE AMCEBA. 1 that is piled too high, or like a train of gunpowder that is ready to be discharged. As a light touch will upset the bricks and cause them to fall with great force, or as a spark will ignite the gunpowder and cause a violent explo- sion, so, in a small way, a slight stimulus to the ameba will cause some of these complex molecules in the proto- plasm to break up into simpler ones with the liberation of the forces manifested in the animal’s activities. The simple compounds (carbonic-acid gas, water, etc.) formed in this destructive process are of no use to the amoeba, and must be removed. ‘The name of the process is excretion. ‘These waste products pass out directly through the body wall into the surrounding water. It should be noted that there is an important difference between this true process of excretion and the mere egesting of an indi- gestible bit of carmine: the latter does not become a part of the animal’s structure at all. Many such particles are ingested in the course of feeding. It shows little choice in the selection of food, ingulfing any object of convenient size with which it may come in contact. II. Reproduction.— The common method of reproduc- tion in amceba is simple division. First the nucleus divides into two. Then the body elongates, and the nuclei move apart toward the ends. A furrow then appears across the body, between the nuclei. This furrow deepens until it entirely separates the body into two pieces, each of which is at once an independent, perfect amceba. 3 The converse of this process has been observed. ‘Two amcebas have been seen to fuse together into one. It is believed that this process (conjugation) is necessary for the continued existence of amcebas. It has been proved to be necessary in the case of some other microscopic animals which reproduce ordinarily by dividing. III. Voluntary Motion. — Protoplasm is contractile, i.e., capable of extending in one direction by shortening in NEED. ZOOL. —2 18 PROTOZOANS. another. But the movements of amceba, simple as they are, are yet more than the independent automatic contrac- tions of protoplasm; for they are controlled and codrdi- nated to certain ends, — to reaction in response to stimuli from without, to locomotion and to securing food in response to impulses from within. IV. Sensation. — These latter acts indicate spontaneous activity, and show that the amceba possesses in a low degree sensibility, the dawning of faculties which are the highest endowment of animal life. The Cell. — The cell in biology is a minute mass of pro- toplasm containing a nucleus with or without a cell wall. The ameba is a single cell that has developed about itself a very delicate and pliant cell wall. The cell is the unit of all organic structure. Every plant and every animal begins its existence as a single cell. This cell grows and divides repeatedly; and the cells thus formed remain together, and with their products compose the bodies of the higher plants and animals. The cellular character of the growing parts of all animals may be easily recognized under the microscope. When the amceba divides, its parts separate. It there- fore retains this simple condition, never becoming more than a single cell. THE SLIPPER ANIMALCULE. (Parameciunt.) Study of Live Specimens. — Examine a drop of water containing slipper animalcules. They appear as minute white specks rapidly moving to and fro through the water, just large enough to be seen without a lens. Examine under the microscope a drop that has been mounted on a slide in cotton fibers, or, better, in cherry- THE SLIPPER ANIMALCULE. 19 gum solution, and covered.'_ Use low power at first, and make a general survey of the contents of the drop. Sev- eral kinds of animalcules may be present. The slipper animalcule (Paramecium) may be recognized by its elon- gated, somewhat slipper-shaped form, and by its rapid pro- gression with one end always forward. Study its actions. Observe that paramecium, unlike amoeba, when it reverses its direction of travel, turns around; that it has anterior and posterior ends. Yet it can and does move backward when cornered, as may be seen when one swims into a narrow space between two cotton fibers, and has to back out. Find one that may be retained within the center of the field, and examine it, magnified 300 to 500 diameters. Observe : — 1. That paramecium has a definite, permanent, though unsymmetrical shape. 2. That its body is a single minute mass, without par- titions or divisions; 1.e., that it is a single cell. 3. That its body mass is made up of two layers, — (a) An outer, transparent ectosare. (6) An inner, granular, and more fluid endosare. 4. That the whole body is covered over with delicate, transparent processes, shaped somewhat like eyelashes, and hence called cilia. In an active paramecium, these cilia are moved so rapidly, they may be seen but dimly, like the spokes of a rapidly revolving wheel. It is by means of these cilia that the paramecium swims. They are used as a boy’s arms are used in swimming: they are struck back- ward quickly and forcibly, and are drawn forward again more slowly. It must be noted that they are not baits, but only delicate projections from the body wall. . Observe also, focusing up and down to bring into view the parts at different levels, — 1 See Appendix, p. 279. PARAMECIUM (300). 20 PROTOZOANS. 5. An oblique groove ( peristome) extending from the anterior end halfway along one side of the animal, and so TTR yy es SASS <2 SY The water current is driven in the direction of the large arrow by the lashing ac- tion of the cilia of that re- gion. Food particles pass down the funnel-shaped esophagus (e), and col- lect in little round pellets at the bottom. Then they circulate about the body in the direction of the arrows, and indigestible portions are ejected at a. Two contractile vacuoles (v) are seen near the ends of the body, and an elon- gate nucleus (2) may be seen after staining. twisted that its edges form an elongated 8-shaped figure when viewed from the side (see cut). 6. A fringe of cilia, longer and stronger than those of the body, all around the edge of this groove. These set up currents in the water, which may be seen, if there be any loose sediment in the water, set- ting toward the posterior end of this groove. 7. A funnel-shaped chamber (vestibule, or mouth) in the poste- rior end of this groove. Toward this the currents in the water tend, and into it they drive the particles they sweep along. Near to this chamber, and in the central portion of the body, is an elongated, often spindle-shaped nucleus, often hardly visible with- out staining. In one or two places in the body there is a clear, round spot of con- siderable size (usually one near each end), which regularly ap- pears and quickly disappears sev- eral times a minute. Each of these is a contractile vesicle. If one of these be watched very closely, it will be seen to have minute, radi- ating tubes appearing around it when it contracts. The remaining objects seen in the endosare are food THE SLIPPER ANIMALCULE. 21 balls and minute fat globules, and various foreign bodies that have been swept into the mouth with food. The feed- ing habits of the animal are best studied after putting some finely powdered carmine or indigo into the drop of water with it. Bits of these indigestible substances will be seen swept along the groove by its cilia, through the mouth, if they be small enough, for this is the only entrance requirement, and down a sort of short rudimen- tary esophagus, at the bottom of which they collect into a little pellet before being ingulfed by the protoplasmic mass of the interior. Then they may be seen to circulate slowly about the body, and, after considerable time, to collect at a point about halfway between the mouth and the posterior end of the body, where they are egested directly through the body wall. . The Life Process. — This is essentially as in ameeba; but there are some interesting differences in its details. When any part of an animal becomes so modified as to be better fitted for doing some one thing, that part is said to be specialized. Thus in paramecium the cilia are specialized for locomotion. One circlet of cilia — that fringing the groove leading to the mouth —is still more highly specialized for setting up currents -in the water as a means of capturing food. A mouth and short esophagus are specialized for receiving food, and contractile vesicles are specialized for circulating the fluids of the body. Every time a vesicle contracts, it drives its liquid contents out into the surrounding body mass. These specialized parts in the one-celled paramecium foreshadow the locomotor, digest- ive, and circulatory systems of the many-celled animals. Ameeba and paramecium are representatives of the Pro- tozoa, a large group of microscopic unicellular animals of wide distribution. CaRLENTERATES. THE FRESH-WATER SPONGE. (Myenia fluviatilis. ) Study of Live Specimens. — Examine fresh specimens.? Note: — | 1. Their form. 2. Their attachment: upon what kind of surfaces they are found growing. 3. Their color. 4. Their odor, pecul- lar, not unpleasant in life, but rapidly becom- ing very disagreeable if any specimens have died. E This rapid decomposi- tion of the sponge flesh betrays its animal na- ture. Examine the surface of the sponge with a Sercunt oF Reeseovaren Sroxce (Y- sood lens to find the oste the others, gemmulespiculesseensidewise oles (or exhalent open- at 6 and d, endwise at c and e. ings), out of which, in life, currents of water are continually flowing. Examine it still more closely to find the minute but multitudinous pores (or inhalent openings) which cover 1 Directions for collecting are given in Appendix, p. 279. 22