f Laboratory Directions ^fv^l FOR AN Elementary Course IN GENERAL ZOOLOGY Seventh Edition BY' HARLEY J. VANJJ:LEAVE Published by THE U. OF I. Supply Store 1928 : '4 \ 53 V 29 J A fs /o ^ ')^, (^3J^ cr nj a a m □ a ^-iA^^g-^ !S C ^==2ra: Laboratory Directions FOR AN Elementary Course IN GENERAL ZOOLOGY Seventh Edition BY HARLEY J. VAN CLEAVE i Published by The U. of I. Supply Store 1928 FIRST EDITION, 1916 COPYRIGHT BY HARLEY J. VAN CLEAVE SECOND EDITION, 1918 THIRD EDITION, 1920 FOURTH EDITION, 1922 FIFTH EDITION, 1925 SIXTH EDITION, 1926 SEVENTH EDITION, 1928 TABLE OF CONTENTS Preface 5 Equipment 7 Directions for Laboratory Work 8 Use of the Microscope 11 Aquatic Collecting Trip 16 Directions for Using Key 18 Key to the Phyla, Etc. 19 Dragonfly and Damselfly Nymphs 29 Pond Snail 8] A Study of the Interrelations Between Birds and Forest Vegetation 33 Amoeba 38 Paramecium 41 vorticella 45 Euglena 46 Colonial Protozoa 48 VoLvox 48 Mitosis 52 Embryology of Cerebratulus 55 Hydra 58 Obelia 62 Gonionemus 64 Regeneration in Planaria 66 Earthworm 68 Crayfish 76 Starfish 87 Freshwater Mussel 92 Glossary 96 42003 \S^&; ^cOoS^^ O"^ «iAV^ '^.'-^ ^•^ >^^^ .ul LIBRARY^ PREFACE lg;\ ^*.45-H^ yJiai These laboratory directions represent the outline of the lab- oratory course in fj^eneral zoology as developed in the University of Illinois. The original plan of the course was formulated by Professors Henry B. Ward and Charles Zeleny. Individual out- lines throughout the course represent the work and suggestions of numerous persons who have, at various times, been connected with the instructional staff in general zoology. The form found in the present volume is the result of many revisions and altera- tions of the several mimeographed and printed editions which have been used with classes through a period of a considerable number of years. An attempt has been made to secure a fair distribution of emphasis through a number of the more important aspects of the subject. The directions are so organized that the field work and laboratory study based upon it may be used either at the open- ing or toward the close of the course, depending upon the time of year when the course is started. More work is outlined than is usually covered in a half-year course, thus allowing some choice of materials on the part of the instructor. A number of the outlines are intentionally brief. These offer opportunity of directing the student in a comparative study of forms closely related to others which have been treated in greater detail. The writer is indebted to Professor S. H. Gage for the use of the figure of the compound microscope. IIarley J. Van Cleave. Zoological Laboratory, University of Illinois, Urbana. EQUIPMENT The following equipment must be purchased at the supply stores- before your first laboratory period : I. Zoology I Packet, Containing: (1) 4H drawing pencil (2) Pencil eraser (3) Cloth for wiping glass slides, etc. (4) 3 microscope slides (5) 10 square coverglasses . (6) Note book; National Loose Leaf 38101/2 or 3810, or equivalent (7) 30 sheets Zoology drawing paper (8) 40 sheets ruled note paper II. Zoology Dissecting Set. Must contain the following: 1 pair fine-pointed dissecting scissors, 1 scalpel, 2 dissecting needles, 1 pair fine-pointed forceps, 1 millimeter rule. Students expecting to take Zoology II should get a larger set of better quality. III. Pen and Ink or Fountain Pen IV. Small Individual Towel V. Principles op Animal Biology by Siiull, LaRue and RuTHVEN, Second Edition. VI, Laboratory Outline por Zoology I 7 DIRECTIONS FOR LABORATORY WORK I. General Conduct 1. Work in the laboratory begins promptly on the hour. Attendance is recorded at the stroke of the bell. Late comers are reported absent, A student with a valid excuse for lateness should offer it to the instructor in charge of his section, 2. Remember that other people are working near you. Be careful to make as little disturbance of any sort as is absolutely necessary. 3. All work must be done independently, both in the field and in the laboratory. This applies to notes and drawings equally. Any work copied from any source other than your own direct observations will he rejected. 4. All ivork must he done in the laboratory. Under no condition will permission be granted to finish or make up work outside the laboratory, 5. The note book bearing name, section and desk number on the inside of the front cover is to be left gn the table at the end of each laboratory period, 6. In connection with the foregoing rule no notes may be removed from the laboratory until they have received a final grade except in rare cases under special arrangements with the instructor in charge, 7. Learn to work independently. When you have a ques- tion, the answer to which is not directly available from the study of your specimen, read ahead several sentences in the outline be- fore asking for information. Look in the Glossary before asking for the meaning of any term. 8. In getting material from the preparation table, always ask an Assistant for it. Very often the cultures and material are of such nature that great care must be exercised to prevent destruction. 8 DIRECTIONS FOR LABORATORY WORK II. Laboratory Records A. DRAWINGS 1. All laboratory drawings are to be in pencil and fully labelled in pencil. 2. Outline drawings showing boundaries of structures with clear cut, continuous lines (not sketched) are required except Avhere finer structure is to be shown. Indicate such finer struc- ture by fine dots. See Fig. B, page 14. No other kind of shad- ing will be accepted. 3. Drawings must be upon the approved paper included in the Zoology I packet. Use but one side of the drawing paper. 4. Each page of drawings should bear a general subject label at the top of the page. Use care in arranging the drawings. 5. Each individual drawing must be accompanied by a descriptive label, above or below the drawing, and in addition, details and individual parts must be pointed out. 6. All labels must be written or printed parallel to the top of the page. 7. Usually the size of drawings is specified in mm. In some instances, size of the drawing is indicated in terms of the actual size of the object. Thus X5 means that your drawing is to be five times the diameter or length of the object studied. 8. A solid or broken line should connect each structure with its special label. Study the drawing of the microscope (page 11) for method of labeling. 9. In laboratory drawings the name of a part should never be written upon the drawing of the part but should be to one side. B. NOTES 1. Notes are to be written only where indicated by "notes required." 2. The notes are to be in ink upon the ruled paper for that purpose included in the Zoology I packet. Use one or both sides of the ruled paper as you maj' pi*efer. 10 ZOOLOGY DIRECTIONS 3. Questions in the outline are not to be answered with "Yes" or "No," but in each case a full statement of observa- tions and conclusions must be given. Never copy parts of the laboratory directions in your notes. 4. Many questions in the outline are intended to direct the attention along definite lines and to stimulate thought. For these no notes are required. C. ARRANGEMENT OP WORK IN NOTEBOOK 1. Each page of finished drawings will be stamped with an official stamp. After the drawings have been graded a check mark will be placed after one of the words, "pass," "not pass," or "excellent," indicating that the work has received a final grade. 2. All drawings and notes not yet graded must be kept in the front of the book in the order in which the work was done in the laboratory. Drawings and notes on the same study must be kept together, the drawings preceding the notes. 3. All work which has received a final grade must be trans- ferred to the back of the book and kept in proper order. 4. Notebooks must be ready for inspection at all times. At each laboratory period the work should be entered properly. 5. Drawings and notes failing in any way to comply with any of these requirements will not be accepted and will not be graded. III. Absence and Unfinished Work 1. Absence, from any cause what-so-ever, does not excuse you from completing the work outlined for the class. 2. One week from the date upon which an exercise is finished by the class is the latest date on which completed work will be accepted for full credit except in instances of accepted excuses. 3. An excuse for absence, properly signed by the Dean of Women or the Dean of Men, constitutes the only basis for granting extension of time limit for finished work. USE OF THE MICROSCOPE (Materials: cotton, wool, water) I. Instruction to be Followed in Using the Microscope 1. Each student is responsible for the condition of the microscope with his desk number. If the microscope does not work properly at any time, the fact should be reported to the OCULAR Coerse Adjustment OBJECTIVE CONDENSER Substaga Figure A. A Coniponnd Mieroscope. From S. H. Gage, The Microscope. 1917. Comstock Publisliiiig Co. instructor in charge of the laboratory section at once. The mi- croscope is a delicate instrument and must not be handled roughly. All parts should work easily. Do not force parts at any time. 2. Before attempting to use the microscope become familiar with the names and uses of the parts. Study figure A carefully. 11 12 ZOOLOGY DTBECTIONS 3. Proper way to carry a microscope. In carrying a mi- croscope, it slionld be lifted by tbe arm and held in an approxi- mately upright position to prevent the ocular from dropping out. 4. Lenses. The lenses consist of (a) the ocular or upper lens, (b) a low power objective^ the shorter of the two objectives and (c) a high power objective, the longer of the two objectives. Before and after using see that the lenses are clean. Use lens paper for cleaning them. Do not use cloth. The low power objective is much more effective than the other for all ordinary work. Do not use the high power objective when you can make out the desired points with the low power. In using the high power, find the object under the low power first, move the part you desire to examine with the high power to the exact center of the field of the low power, and then if the lenses are "parfocal" swing the high power objective into place. In case you find the two objectives are not directly interchangeable (=parfocal) draw the tube of the microscope up by means of the coarse ad- justment and then swing the high power objective into place. Now with your eye at the side of microscope on a level with the stage, lower the lens until it almost touches the coverglass. With your eye at the ocular, focus upward until the object comes into view. 5. Focusing. The working distance of the fine adjustment is short and it is therefore always necessary to get the approxi- mate focus with the coarse adjustment before using the fine. In using the coarse adjustment ALWAYS FOCUS UPWARD. This relieves the possibility of ruining the lens or the slide. 6. Light. The proper adjustment of the light is essential. It is accomplished by giving the mirror the proper tilt and by changing the size of the opening in the stage. In some of the instruments there is a so-called iris diaphragm for this purpose, below the stage of the microscope. Study the operation of the mirror and of the diaphragm. Then with the eye at the ocular practice adjusting the mirror so as to secure a perfectly uniform illumination of the field of the miscroscope. THE MICROSCOPE 13 7. In looking through the microscope keep both eyes open. A little practice will enable you to neglect wholly the -image in the unused eye and will avoid the muscular strain due to the clos- ing of one eye. It is well to use right and left eyes alternately. 8. Keep the stage of the microscope horizontal. It is always better to adjust the height of your chair than to tilt the microscope. 9. Do not use the stage clips unless it is absolutely neces- sary. Turn them back so that they will not be in the way. II. Exercise in the Use of the Microscope 1. Inversion of the image in the microscope. Place the card which has been given you upon the stage of the mi- croscope in proper position for reading. Find a letter "e" and without shifting the position of the card draw, in outline, 40 mm. high. 2. On the slide containing mounted colored fibers determine the relative positions of the fibers by focusing up and down. Use the high power objective. In this exercise amount of color must not be confused with sharpness of focus. A dark color out of focus may strike the eye more forcibly than another color which is in the plane of focus. Distinctness of the margins or outlines of the fibers is the only safe point for comparison. In your notes indicate relative positions of the fibers beginning with the lower- most (1, 2, 3, etc.). While your slide is still on the microscope ask to have your observations verified. No drawings required, 3. Examine dry cotton fibers with low and high powers of miscroscope. Allow a drop of water to run under the coverglass by applying a pipette to the slide at the edge of the coverglass. Make a drawing of the wet fiber 10 mm. in diameter, being sure to include in your drawing at least one place where the fiber is twisted. If you have studied the fiber carefully you should be able to come to a definite conclusion regarding its form as an object with three dimensions. At the side of the drawing already made, place a diagram illustrating your conclusion re- garding the shape of a cross-section of this fiber. 14 ZOOLOGY DIEECTIONS 4. Place wool fibers on a clean slide. Apply coverglass and study when dry and when wet as for cotton. Examine the out- line of the fiber carefully. Draw a wet fiber, 10 mm, in diame- ter, and a cross-section as directed before. What diiferences do you observe between the dry and the wet fibers? Notes required. 5. Mount a drop of protozoan culture in such a way as to include minute air bubbles. The inclusion of cotton fibers with the drop of water will facilitate the formation of the air bubbles. Study air bubbles and Protozoa and other micro-org'anisms with special reference to the use of the focusing and lig-hting adjust- ments of the microscope. No drawings are required, 6. To determine the size of microscopic objects. One of the commonest means of measuring microscopic objects is by means of an ocular micrometer. The oculars for which these 0 '^^^^ Figure B. The use of an ocular mierometer. A cell under the low power of the microscope. Note that the cell is 14 of the smallest micrometer divisions in length. Its acutal length is then : 14x0.0078mm.=0.10& mm. Since the scale in the ocular remains the same regardless .of the objective used this cell under high power would be about 64 of the smallest micrometer divisions in length. Consequently each divi- sion would have a correspondingly smaller value. directions are given have a scale divided by fine lines into 100 units of length. The lines appear in the field of the microscope at the same time that the image to be measured is seen. Notice that the upper portion of an ocular micrometer may be pulled out or shoved in to permit of sharp focusing upon the ruled scale. THE MTCEORCOPE 15 Before inserting the ocular micrometer into the tube of the mi- croscope look through it toward the light and adjust the draw- tube until the lines and figures in the field of the ocular becomes most distinctly observable. These lines are always the same distance apart regardless of the power of the ohjective used but since the size of the image to be measured varies with the objective used it becomes necessary to find the value of the ocular divisions for the different objec- tives. When used with a low power (Spencer Lens Co. 16 mm.) objective a single one of the smallest divisions of the ocular scale has the value of 0.0078 mm. AVith the high power (Spencer Lens Co. 4 mm.) objective each of the smallest ocular divisions has the value of 0.0017 mm. To measure an object under the microscope find the number of smallest micrometer units in the length (or other dimension) of the image and multiply that number by the value, as given above, of a single ocular unit for the objective you are using. REFERENCE Gage, Simon Henry, 1925. The Microscope, An Introduction to Microscopic Methods and to Histology. Comstock Publ. Co. /^/^ ^•^ ^^<^A !uj|Lli?^ARYKJ W)v AQUATIC COLLECTING TRIP 1. The object of this work is to learn how to study and collect animals in the field, in their natural environment. 2. The field work is conducted on the same g'eneral plan as the laboratory work. 3. Each student is required to do individual work. 4. A full record of your observations is to be made in your note book while in the field. 5. Collect representatives of all kinds of animals found and large numbers of such forms as especially instructed to secure. 6. Absences do not excuse you from the work of these trips. The work must be made up as early as possible. This means inconvenience both to student and to instructor, therefore do not miss a field trip if it can be avoided. 7. Tardiness counts as absence on these excursions, as the class starts promptly on the hour. 8. For aquatic collecting each student should have the following equipment, the first two items of which are furnished by the laboratory : (1) A dip-net (2) A quart fruit jar with lid and rubber (3) A pair of forceps with string attached (4) CAR FARE (5) Notepaper and pen or pencil. 9. In the laboratory before the trip you will be given definite directions for note taking, and all field notes must conform with these directions. 10. The use of the dip-net will be demonstrated in the field 16 before the collecting begins. AQUATIC COLLECTING 17 11. Write a general descrij)tion of the region before you begin to collect. Describe fully and carefully the main features of the locality examined. This should be full enough to give a stranger a fair idea of the locality. It should include the ap- proximate size of the stream, character of its banks, bottom, depth of water, vegetation, etc. 12. Fill the jar two-thirds full of water before beginning to collect, and preserve the animals collected in the jar. 13. Wash the mud from the net as directed before attempt- ing to sort over and examine the collection. Sort the materials upon the bank of the stream, in the net, and throw the refuse back into the stream. 14. Rinse out the net before leaving the field. 15. Before returning to the laboratory be sure you have everything with which you started. REFERENCES Needham, Jas. G. and Lloyd, J. T. 1916. The Life of Inland Waters. Comstock Publ. Co. Shelford, Victor E., 1913. Animal Communities in Temperate America. Universitv of Chicago Press. KEY TO THE PHYLA AND THE MORE COMMON CLASSES AND ORDERS OF ANIMALS, CHIEFLY AQUATIC, IN THE REGION OP URBANA, ILLINOIS Directions For Using Key. The use of the following key involves a series of choices between two contrasting possibilities, thereby making necessary a complete chain of observations and conclusions. If any one of these is incorrect, there is no possibil- ity of making a correct final determination so the work must be started from the beginning again. For this reason care should be taken at each step to avoid "getting off the track." Always make direct observations upon the animal rather than rely on memor}' or on what some one else tells you. In using the key the two numbers at the left refer to the two contrasting possibilities. Thus an attempt to classify an earth- worm will start at 1 by reading the description there to see if it agrees with the facts of structure in the earthworm. The state- ment under 1 agrees with the facts discovered by examination of the specimen so the 3 at the end of the line indicates the next step to be tried. Since the earthworm is bilaterally symmetrical, step 3 must be disregarded and its alternative 6 used. Then comes the choice between 7 and 15, and so on until the name of the phylum is reached. After the name of the phylum, is given a page number which refers to a key for distinguishing the smaller subdivisions of the phylum. In most cases classes and orders are given. The limit beyond which this key must not be used is indicated by the lack of the reference number at the end of a line following the name of a class or an order. Laboratory notes on the work in classification are to be kept in the following manner : Make a record of the steps taken (dis- regarding the alternatives which have been discarded as not applicable to the specimen in question). Use a line for each number accepted and after the number indicate by a brief 18 KEY TO PHYLA 19 statement some one fact (or more) which led yoii to accept that particular step. In so far as possible make these statements in your own words rather than copy the words of the key. For example, the notes on the earthworm would be as follows : 1 — visible to unaided eye 6 — bilaterally symmetrical 15 — segmented 16 — like a worm, without appendages 17 — short bristles on segments ; Phylum Annelida V-4 — segmented 6 — setae regularly arranged around segments. Class Chae- topoda, Subclass Oligochaeta. Common name, Earthworm. After one or two specimens in the same general group have been identified, the descriptions may be omitted and numbers only given with the names of the Phylum, Class, Order, etc. For example, if a snail and a mussel are both identified the de- scriptions accompanying the numbers of the steps need be given in only one instance leading to the Phylum Mollusca. KEY TO THE PHYLA 1 (2) Animals composed of various organs and tissues, usually large enough to be seen without the microscope (the Meta- zoa) 3 2 (1) Animals consisting of single cells or of groups of cells, all of which perform the same functions. Microscopic in size. PHYLUM PROTOZOA (sec page 21) 3, (6) Body either very irregular in form or radially sym- metrical, but never arranged in spiral form 4 4 (5) Body more or less indefinite in form. Body wall pierced by numerous small openings (incurrent pores) which lead into internal cavities. The internal cavities also connect with the exterior by one or more larger openings, the oscula. PHYLUM PORiFERA (sec page 21) 20 ZOOLOGY DIRECTIONS 5 (4) Body radially symmetrical; body wall not pierced by pores. Body composed essentially of two layers of cells without a cavity between them. Inner layer forms digestive system. Anns wanting. Parts of the body not usually ar- ranged in five or multiples of five, phylum coelen- TERATA (see page 22) 6 (3) Body usually bilaterally symmetrical, or in part spirally coiled, never radially symmetrical 7 7 (15) Body not divided into segments. (In determining this point examine various surfaces of the body. Wings and other structures frequently obscure evidences of segmenta- tion on the dorsal surface) 8 8 (11) Body usually large, not worm-like. With a skeleton and sometimes with jointed appendages. If skeleton and appendages are both lacking, the body may be encased in a limy shell 9 9 (10) Completely or partially encased in a limy shell com- posed of one or two pieces. Soft parts of body inside shell either bilaterally^ symmetrical or in part spirally coiled. Ventral surface provided with a heavy muscular locomotor organ, the foot, phylum mollusca (see page 22) 10 (9) With an axial skeleton consisting of a skull and verte- bral column. Nearly always with two pairs of jointed ap- pendages. Central nervous system entirely dorsal to ali- mentary canal, phylum chordata, .subphylum verte- brata (see page 28) 11 (8) Body small, worm-like, not provided with shell, skeleton or jointed appendages 12 12 (13) Body flattened dorso-ventrally. Alimentary canal con- sisting of a pharynx and a branching intestine without any anus, phylum plzVthelminthes (see page 22) 13 (12) Body cylindrical or flattened. Alimentary canal al- ways terminating posterially in an anal opening 14 KEY TO PHYLA 21 14 (15) Body not segmented, covered with cuticula. phylum NEMATHELMiNTHES (see page 22) 15 (7) Body segmented 16 16 (19) AVithont jointed appendages; worm-like 17 17 (18) With bristles arranged on certain segments (if no bris- tles then a sucker on each end of body) ; without tracheae or spiracular openings, never with large tufts of bristles at one end of body, phylum Annelida (see page 22) 18 (17) With tracheae and tracheal gills or spiracular open- ings; often with large tufts of bristles at one end of body; with a head well differentiated and always with some form of antennae and mouth parts, phylum arthropoda, class iNSECTA (larvae) (see page 23) 19 (16) With jointed appendages at least on extreme anterior segments, phylum arthropoda (see page 23) I. Phylum Protozoa 1 (2) No locomotor structures in adult age; parasitic CLASS SPOROZOA 2 (1) Special structures for locomotion 3 3 (4) Temporary lobes (pseudopodia) protruded for locomo- tion CLASS RHIZOPODA 4 (3) Permanent processes (cilia or flagella) from the surface of body for locomotion , 5 5 (6) Numerous short protoplasmic processes (cilia) CLASS CILIATA 6 (5) Small number of long thread-like protoplasmic processes (flagella) class mastigophora II. Phylum Porifera The Phylum Porifera is represented in fresh water by sev- 22 ZOOLOGY DIEECTIONS eral g'enera of but a single family spongillidae belonging to the ORDER SILICISPONGIAE. III. Phylum Coelenterata Nematocysts present. Polyp without ectodermal esophagus. Solitary polyps without medusae or medusa buds CLASS HYDROZOA, ORDER HYDRARIAE IV. Phylum Plathelminthes 1 Free-living' flatworms with body covered with cilia, class TURBELLARIA 2 2 Digestive system with three main branches, one toward the head and two running posteriorly order tricladida V. Phyla Nematiielminthes and Annelida 1 (4) Worms with cylindrical bodies, not segmented. Covered with cuticula. phylum nemathelminthes 2 2 (3) A longitudinal lateral line on each side of body. Body usually tapering at one end class nematoda 3 (2) Without lateral line. Adults live in water, larvae are parasitic in insects. Body practically uniform diameter throughout class gordiacea 4 (1) Body segmented, without jointed appendages, phylum ANNELIDA 5 5 (6) Body with anterior and posterior suckers. Nearly al- ways without setae class hirudinea 6 (5) Setae present and regularly distributed around each segment class chaetopoda, subclass oligochaeta VI. Phylum Mollusca 1 (2) Body without a distinct head, usually bilaterally sym- metrical. Bivalve shell. Mantle bilobed class acephala KEY TO PHYLA 23 2 (1) Molluscs with body always asymmetrical, frequently spiral. Shell in one piece class gastropoda VTI. Phylum Arthropoda 1 (44) Head provided with not more than a single pair of jointed appendages in addition to any feeler-like organs which are attached immediately around the mouth open- ing 2 2 (3) Without distinctly jointed appendages on the thorax, often with non-jointed appendages. Entirely legless or with abdominal prolegs. Head frequently reduced and retracted within the pointed apex of the thorax CLASS INSECTA. ORDER DIPTERA (larvae) 3. (2) Thorax 'bearing jointed legs.. 4 4 (5) More than four pairs of legs class myriapoda 5 (4) With two, three, or four pairs of legs 6 6 (25) With one or two pairs of wings used in flight or at least capable of free movement. Immature insects having immovable, rudimentary wings, enclosed in sacs or wing- pads, are not included here, but under section 25. Usually three pairs of legs, class insecta 7 7 (10) Two pairs of wings, unlike in structure 8 Fig. 3 Back swimtner membranouB t\- tlp Fig. 1 Giant water bug 8 (9) Front wings leathery at base and membranous at Fig. 3 Water boatman Fig. 4 Water strider Fig. 5 Water scorpion 24 ZOOLOGY DIRECTIONS .tip, often overlapping. Month parts formed for sncking (see figs. 1 to 5) order hemiptera r^antermax 'Fig. 6 Fig. V Pig. 8 Fig. 9 Fig. 10 Larva of a water Water scaveng- Predacoous Larva of pre- Whirligig gcavenger beetle er beetle vra.ter beetle daceous beetle beetle 9 (8) Front wings of same texture throughout, horny or leathery (elytra) always meeting in a straight line down the middle of the back (see fig. 7) order coleoptera 10 (7) Two pairs of wings similar, membranous 11 11 (12) Last joint of the tarsi bladder-like or hoof -like in form and without claws order phtsopoda 12 (11) Last joint of tarsi not bladder-like 13 13 (14) Wings entirely, or for the greater part, clothed with scales. Mouth parts for sucking order lepidoptera 14 (13) Wings transparent and naked or thinly clothed with scales 15 15 (16) Mouth parts a jointed tube for sucking, arising from hinder part of ventral surface of head order hemiptera (Homoptera) 16 (15) Mouth parts not united to form sucking beak. Wings net veined with very numerous veins and cross veins.... 17 17 (24) Tarsi of less than five segments 18 18 (21) Antennae inconspicuous, awl-shaped, short, slender.. 19 KEY TO PHYLA 25 19 (20) First and second pairs of wings of nearly the same length. Tarsi three jointed order odonata 20 (19) Second pair of wings either small or wanting. Tarsi four jointed order ephemerida 21 (18) Antennae usually conspicuous 22 22 (23) Tarsi two or three jointed. Second pair of wings broader at base than first pair or at least as large as the first pair order plecoptera 23 (22) Tarsi four jointed. Wings equal in size order isoptera 24 (17) Tarsi with five segments. Abdomen with hair-like, many jointed, anal filaments.. ..order ephemerida (in part) 25 (6) Wings wanting, or in some cases immovable, rudimen- tary wings are enclosed in sacs, called the wing pads 26 26 (27) With typically three pairs of legs. Head, thorax, and abdomen usually distinct ; head always distinct. General body form resembling that of adult insects, class insecta (nymphs, larvae, pupae, and a few wingless adults) 28 27 (26) Usually with four pairs of legs; in some cases with two or three pairs, but in these, head, thorax, and abdomen are all fused together. Respiration never by means of gills. class arachnida 28 (33) Abdomen bearing prolegs on at least some somites.... 29 29 (30) Abdomen with five pairs of prolegs and with no spir- acles at apex of abdomen order lepidoptera (larvae) 30 (29) Prolegs on last abdominal somite only 31 31 (32) Abdominal segments each with a pair of long lateral filaments or provided with conspicuous tufts order neuroptera (larvae) 26 ZOOLOGY DIRECTIONS 32 (31) Abdominal segments without long lateral filaments or conspicuous tufts; often Avith minute gill filaments, Cyl- :.giiis caudal sataa tarsal claws - Fig. 11 Fig. 12 Fig. 13 Fig. 14 Stonefly nynrnh Dsunselfly nyn^ih Dragonfly nymph teyfly nynph indrical larvae, generally living in portable cases ORDER TRICHOPTERA (larvac) 33 (28) No prolegs on abdomen 34 34 (35) Labium, when extended, much longer than head; at rest folded upon itself like a hinge and extending backward be- tween the bases of the forelegs order odonata (nymphs) 35 (34) Labium not capable of extension beyond head 36 36 (43) Biting mouth-parts 37 37 (40) Two or three conspicuous caudal setae. (Some larvae with two projections from the posterior extremity of the ab- domen have no gills on either thorax or abdomen. These are Coleoptera (larvae). If gills are present along sides of either thorax or abdomen go on with 38) 38 38 (39) Three caudal setae; gills on sides of abdomen; tarsal claws single (see fig 14) order ephemerida (nymphs) 39 (38) Caudal setae usually two; gills mainly under thorax. Tarsal claws two (see fig. 11) order plecoptera (nymphs) 40 (37) With no caudal setae 41 KEY TO PHYLA 27 41 (42) Abdominal segments provided with long lateral fil- aments of tufts of hair-like projections along either side, or in some eases the last two abdominal segments only are sup- plied with lateral rows of hair-like projections (see fig. 9) ORDER COLEOPTERA (larvae) 42 (41) Abdomen ending in a median non-segmented, tail-like process order neuroptera (larvae in part) 43 (36) Mouth parts in the form of a jointed beak directed backward between the bases of the forelegs, often closely applied to body order hemiptera (nymphs) 44 (1) Head provided with two pairs of antennae in addition to an}^ feeler-like organs which occur in the region immedi- ately around the mouth opening. " Never with wings. Res- piration by means of gills, or in some small forms directly through the skin. Mostly aquatic, class Crustacea.... 45 45 (50) With a bivalve shell hinged along dorsal surface, cov- ering at least part of body and enclosing not only body w^all but also the appendages 46 46 (49) Entire body, including appendages and head, enclosed in a shell; resembling a small mussel 47 47 (48) With but two pairs of trunk appendages subclass ostracoda 48 (47) With ten or more pairs of trunk appendages subclass phyllopoda, order branchiopoda 49 (46) Bivalve shell covering only part of body and frequently ending posteriorly in a pointed spine. Head not enclosed in the shell and bearing large, fringed antennae used in swimming subclass phyllopoda, order cladocera 50 (45) Body covering firm and shell-like but not a hinged, in- dependent continuous shell covering the body 51 51 (58) Eyes paired 52 52 (57) Head, thorax and abdomen all bearing appendages. SUBCLASS malacostraca 53 28 ZOOLOGY DIEECTIONS 53 (54) Eyes on the end of a movable stalk. Head and thorax fused and covered on sides and dorsal surface by a single shell, the carapace. Five pairs of walking legs ORDER DECAPODA 54 (53) Eyes not stalked 55 55 (56) Body dorso-ventrally flattened order isopoda 56 (55) Body almost cylindrical or compressed laterally order amphipoda 57 (52) Abdomen lacking appendages; carapace lacking; ap- pendages flat, leaf -like SUBCLASS PHYLLOPODA, ORDER BRANCHIOPODA 58 (51) A single eye in front of the head subclass copepoda VIII. PHYLUM CHORDATA SUBPHYLUM VeRTEBRATA 1 (4) Body covered with scales or plates, (except in fishes with smooth skin) with or without rayed fins 2 2 (3) Scales or plates dry and hard. Breathe by lungs. With- out rayed fins class reptilia 3 (2) Scales or plates moist (rarely absent, in these cases dis- tinguishable by presence of rayed fins). Rayed fins always present. Breathe by gills class pisces 4 (1) Body not covered with scales 5 5 (6) Cold blooded, skin slimy class amphibia 6 (5) Warm blooded 7 7 (8) Body covered with feathers class aves 8 (7) Body covered with hair class mammalia references Alexander, C. P., 1925. An Entomological Survey of the Salt Fork of the Vermilion River in 1921, with a Bibliography of Aquatic Insects, 111. Nat. Hist. Survey Bull., 15 (art. 8). Lutz, Frank E., 1921. Field Book of Insects. Revised. G. P. Putnam's Sons. Ward, Henry B. and Whipple, George C, 1918. Fresh Water Biology. John Wiley and Sons, Inc. DRAGONFLY AND DAMSELFLY NYMPHS (Materials: Mason jars and jar lids, carmine suspension.) Classification, — Phylum Arthropoda, Class Insecta, Order Odonata. Distinguish two kinds of odonate nymphs, those with slender bodies and three flat plate-like gills at the posterior end of the abdomen ; and those which lack these plates and are stout bodied. The ones with the plate-like gills are called ''damselfly" nymphs and the stout bodied ones are "dragonfly" nymj^hs, though the name ' ' dragonfly ' ' is also often used as a general term for all in- sects of the Order Odonata. Keep your specimens under water. A Mason jar lid makes a convenient dish. Invert the jar and place the lid containing the specimen on the bottom of it. This brings the specimen to a convenient height for study with a hand lens. I. Dragonfly Nymph 1. Describe the resting habits and position of nymphs in an aquarium. Where do they usually rest ? Notes required. 2. Do the nymphs ever feign death or ' ' play possum ? " If so, under what conditions? Have you ever seen this habit in other animals 1 What kinds 1 Notes required. 3. Place a large nymph in a Mason fruit jar lid. Place a small drop of carmine suspension near the posterior end of the abdomen of a resting nymph and describe the result. Repeat the experiment until you are sure of the results. In connection with this experiment remember that carmine is inert and is used merely to show the presence of and direction of water currents State your observations. What conclusions may be drawn from this experiment ? Notes required. 4. Describe the methods of locomotion of the live animal. How many different methods? Describe each. Notes required. 29 30 ZOOLOGY DIRECTIONS 5. Note the adaptation of the labium (lower lip) for grasp- ing food. Examine preserved specimen and with forceps draw the labium forward to fully extended position. Draw side view and dorsal view of labium, fully extended, X5. 6. Draw the entire animal, dorsal view X4. Label the head, the thorax (the part bearing the legs), and the abdomen. 7. Into what kind of an animal does the nymph transform? See demonstration. Notes required. 8. Define metamorphosis. Notes required. 9. The three plate-like gills of the damselfly nymphs con- tain the air tubes (tracheae), while in the dragonfly nymphs the posterior part of the intestine is modified and contains tracheal filaments. Air and not blood fills these tubes, and aerates the tissues. II. Damselfly Nymph 1. Describe the habits of the live animal, its methods of locomotion, habit of resting, etc., while in an aquarium. De- scribe fully. Notes required. 2. Does the animal feign death? If so, under what condi- tions and for how long? Notes required. 3. Draw the entire animal X4, dorsal view. 4. Draw X5, a plate-like gill. 5. Examine the expanded labium from the side and from the ventral surface. Compare with labium of dragonfly. 6. Into what kind of an animal does the nymph transform? See demonstration. REFERENCE Wilson, C, B., 1920. Dragonflies and Damselflies in relation to pondfish culture, with a list of those found near Fairport, Iowa. Bull. U. S. Bur. Fish., 36 (Doc. 882) : 182-264. POND SNAIL Classification : — Phylum Mollusca, Class Gastropoda, Order Pulmonata, 1. Phvsa and Planorbis are two of the most common genera of pond snails found in this region. The two genera are readily distinguishable one from the other by the general shape of the shell, that of Physa being more or less cone shape while that of Planorbis is a practically flat coil. Indicate by labels which kind is being studied. 2. Place a snail in a Mason jar lid filled with water. Allow the snail to crawl onto the under side of a glass slide, one end of which is placed in the water. Notice that the hody protrudes from a single opening in the shell. Examine a fully extended body and on its ventral surface note a crosswise fold which sep- arates it into a small anterior region, the head, and a larger tri- angular posterior region, the foot. The head bears the mouth on its ventral surface and a pair of tentacles on the dorsal sur- face. 3. The mantle is a membrane which lines the shell. In fact the shell is formed by secretion from the mantle. In Physa the mantle may be seen best on the right side where it folds back upon the sitle of the shell in a series of small, pointed projections, 4. Both Physa and Planorbis breathe by lungs. Conse- quently they must come to the surface of the water occasionally for air. The lung opening is a small circular opening into the side of the body between the foot and the shell. It can be seen only when the snail is at the surface of the water taking air. 5. Draw X4 a side view of a fully extended snail, from the right side. Label all of the parts. Draw a ventral view X4. 6. Observe the method of feeding by looking through the side of the aquarium at the ventral side of the animal. Can you determine the nature of the food ? Notes required. 32 ZOOLOGY UIEECTIONS 7. When snails are not disturbed, in what part of the aquarium do they accumulate? Notes required. 8. Describe the method of crawling. Observe a snail crawl- ing on the lower side of the surface film of water. The lateral stretch or pull of surface tension supports the weight, just as an oiled needle may float upon the upper surface of the film. 3Iucus threads may usually be demonstrated when the animal is crawl- ing upon the surface film by drawing a dissecting needle across the path of the animal just a short distance behind the posterior end of the body. Such threads are frequently found extending between the bottom of the aquarium and the surface film thereby providing a path along which the snails crawl back and forth. 9. Have you observed other animals moving upon the sur- face film? If so, what kinds? Notes required. 10. Describe the masses of snail eggs. Examine them with the microscope and describe their general appearance. 11. The growth of the shell takes place in what direction ? Can you find evidence of periods of growth and rest? Notes required. 12. Observe carefully the lung opening, and determine by your watch how frequently and under what conditions air is taken in. Record in your notes six trials. What is the average ? REFERENCES Walter H. E., 1906. The Behavior of the Pond Snail, Lymnaeus eleodes Say. Cold Spring Harbor Monographs VI. Dawson, J., 1911. The Biology of Physa. Behavior Monographs. Vol. I, No. 4. A STUDY OF THE INTERRELATIONS BETWEEN BIRDS AND FOREST VEGETATION Materials required for trip : — Laboratory Directions, rough note paper, pencil or pen. This study is based upon a field trip to the University of Illinois Forestry. The same outline is adaptable for a field trip to any sort of a planted grove or to fence rows where the veg- etation is allowed to grow. Rough notes are to be taken in the field. Later these are to be written up in the form of a connected report which is to be organized under the following headings : I. Introduction. II. Facts observed and Inferences. III. Conclusions. The Introduction should bring into relation all information considered necessary for an understanding of the observed facts. A. Suggested Materials For Introduction 1. Aim of this study : An appreciation of the work of birds as agents in the distribution of vegetation and the effects of their work upon the plant and animal life of a region. 2. Before 1871 there were no trees of any sort in this plot now known as the University of Illinois Forestry. Originally there was a dense growth of grasses and low type of vegetation characteristic of the prairies but tliis sod was broken and the ground was put under cultivation for a considerable number of years before the first trees were planted. Since the breaking of the sod and the planting of the first trees by man in 1871, there have been many agencies at work bringing about changes in the plant and animal life of the region. One of the important agencies in bringing in new kinds of 33 34 ZOOLOGY DIEECTIONS plants, has been the wind, by whose action seeds of dandelion, thistle, maples, elms and of many other kinds of plants have been introdnced. Animals like dogs, horses and men have scattered the seeds of bnrs and other fruits which cling to the body or clothing. Squirrels and jays have buried many kinds of nuts, some of which have germinated. Birds and other animals have eaten the seeds of fruits which pass through the digestive tract uninjured. In this present study attention will be directed to the last of these agencies only. 3. Because of their greater range of movement and prefer- ence for fruit diet, birds have greater influence in distributing seeds than any other group of animals. The stomach contents of thousands of birds have been examined by experts and show that some fruits are favorite foods of many different species of birds. Thus elderberries have been found in the stomach of 67 different species of birds, raspberries and blackberries in 60 spe- cies ; mulberries in 48 species ; dogwood in 47 species ; nonpoison- ous sumachs in 44 species ; wild cherries in 39 species ; blueber- ries in 37 species; wild grapes in 29 species; pokeberries in 26 species; Virginia creeper in 25 species; juniper in 25 species; strawberries in 16 species; hackberries in 15 species; haws in 12 species; hose hips in 11 species; gooseberries and currants in 10 species. 4. Fruits are carried to nestling birds even in species the adults of which do not ordinarily eat fruits. 5. Not all seeds are capable of bird dispersal. A pulp at- tractive to the birds as food must be present, then if the seeds are small enough they will be swallowed along with the pulp. If the seeds are provided with hard or tough seed coats at least some will escape crushing in the gizzard and pass out along with the excrement. 6. The undergrowth of this forest is largely cut out each year. 7. Large flocks of blackbirds usually roost in this forestry in the spring and fall. GIRDS AND FOREST VEGETATION 35 B. Outline of Field and Laboratory Study To Be Based Upon Observed Facts and Inferences Throughout the report be careful to distinguish between actual facts that you observe and conclusions that you draw from these facts. Wherever possible give a definite statement of just what was observed, then a statement of the conclusions that are drawn from these observations. THE KINDS OF SEEDS SCATTERED In this study it is well to distinguish between the woody plants, as trees and shrubs, and those which do not have a woody stem, the herbs. 1. Plow can yoji distinguish the planted vegetation from that derived from other sources? Trees, shrubs, tree seedlings, and herbs? 2. List the trees which produce fruits eaten by birds. At demonstration table in laboratory examine fruits pre- served in formalin to determine if they possess the characters essential for distribution by birds. 3. List the shrubs which produce similar fruits and ex- amine fruits at demonstration table. 4. List the herbs in the same manner. At least 15 plants, including trees, shrubs, and herbs, must be included in the above three lists. Aid will be given in the identification of these plants. EVIDENCE OF THE SCATTERING OF SEEDS 1. Do you find wild cherry seedlings elsewhere than under cherry trees? Describe fully your observations, places where found, under what kinds of trees, size of seedlings, etc. 9. Under what kinds of trees do you find cherry stones? List them. Can dispersal by wind explain the location of these seeds? Direction of prevailing winds? 36 ZOOLOGY DIRECTIONS 3. Of the seeds that are scattered, do all of tliem grow, or, if so, to full size ? Is the above absence of plants proof that the seeds have not been scattered 1 4. Do you find any evidence of the location of bird roosts? Describe fully. C. Conclusions and Practical Applications (a) THE INFLUENCE OF THE SCATTERED SEEDS UPON THE FOREST 1. How have the introduced seeds and plants changed the character of the forest in its trees, shrubs, herbs? 2. How would the bird-introduced plants influence the present forest as a bird habitat if left uncut for a few years? 3. Do the seeds of the introduced plants germinate in open grass lands like the original prairie before the sod was broken? 4. Do the animals which now live and breed in the forestry regularly live in open meadows? 5. What effect has the planting of the first trees had upon the invasion of the area by new organisms? 6. State the composition of the forest which would succeed the present one if left uncut. Would it be denser or less dense? Would it favor the same or different kinds of animals? (b) PRACTICAL APPLICATIONS 1, What kinds of trees and shrubs should be planted if you wish to attract birds about an estate by means of bird food? 2. If you wish to protect cultivated fruits from the depre- dations of birds, what kinds of wild fruit should be planted to serve as food ? In this connection it is necessary to keep in mind the time of ripening of the cultivated and wild fruits. BIRDS AND FOEEST VEGETATION 37 3. Discuss injury or harm produced by seed plantings by birds ? Weeds ? Poisonous plants ? Choking out of cultivated plants ? REFERENCES Burrill, T. J., 1887. The Forest-Tree Plantation. 13th Report of Board of Trustees, University of Illinois, pp. 252-282. Burrill and McCluer, 1893. The Forest Tree Plantation. (Bul- letin No. 26, Illinois Agricultural Experiment Station.) McAtee, W. L., 1910. Plants Useful to Attract Birds and Pro- tect Fruit. Yearbook U. S. Department of Agriculture for 1909. pp. 185-196. AMOEBA Classification : Phjdiim Protozoa, Class Rhizopoda, Order Amoebina. There are numerous species which are commonly referred to as the "amoebas" but not all of these belong to the genus Amoeba in its technical or restricted sense. These differ from one another in the form and number of pseudopodia and in finer details such as size and structure of the nucleus in stained preparation. The large species. Amoeba proteus, is most com- monly used for laboratory study. If the same species is used throughout this study, care should be exercised to avoid making broad generalizations. Facts observed for one species are not always applicable for other members of this genus. While many amoebae lead independent lives, utilizing mi- croscopic plant and animal matter as food, others exist as para- sites. Especially important are those which parasitize man. One species (Endamoeha histolytica) is the cause of the amoebic dysentery. 1. Method of Examination : 1. Upon a clean glass slide mount a small piece of the ooze containing Amoeba. Cover with coverglass. Note appearance under low power. 2. If a full answer cannot be given at once, make tem- porary notes, reserving the final answer until all observations are completed. 3. From time to time, add a drop of water to the slide, at the margin of the coverglass, to replace loss by evaporation, II. General Form. Is the form constant? Is there any plane of symmetry? Anterior or posterior end? Is there a characteristic form? Notes required. III. Structures and Functions. 1. Study under high power. The outer clear or non-granular region is the ectoplasm. Structure? What part does it play in the movements of the animal ? 38 AMOEBA 39 2. The inner granular mass is the endoplasm. Structure? Movement? "Within the endoplasm distinguish food vacuoles, which are usually dark in color and maj^ be of any shape or size, and the small water vacuoles which appear grey or colorless and are alwaj^s perfectly spherical in form. 3. The blunt processes which are thrust out from time to time and retracted are pseudopodia (false feet). How are they formed? Do any of them branch? About how many can you count at any given time? Are they confined to any particular part of the body? Mention two functions which they perform. Notes required. 4. Describe in detail the method of locomotion in the Amoeba, telling what part the ectoplasm and the endoplasm each plays. Is there any coordination in movements? Notes required. 5. Find an Amoeba that is moving actively. Make six outline sketches of your specimen at intervals of approximately twenty seconds to show the changes of form. Each drawing should be at least 40 mm, in diameter. 6. Note differences in number and in arrangement of pseudopodia in an Amoeba that is floating free in the water and in one that is creeping upon the surface of the slide or cover- glass. 7. Watch an Amoeba feeding and describe the process of taking food. Watch and describe any changes in particles of food which have been engulfed. Where does digestion take place? What becomes of the food particles? Notes required. 8. Contractile Vacuoles. Find one or more. They are circular in outline and disappear from time to time. Note and describe carefully the method of disappearance and reappear- ance. Has the contractile vacuole any color? Any definite po- sition in the body? In which body layer? Source of its con- tents? Nature of its contents? What becomes of the contents when a vacuole disappears? Notes required. 40 ZOOLOGY DIRECTIONS 9. Nucleus. Find in living specimen. Describe its ap- pearance. Does its form change ? Does its position change ? Is there more than one nucleus'? Notes required. 10. Make a careful drawing 100 mm. in diameter, of the living Amoeba under the high power, labelling all parts. Stipple one pseudopodium to show structure of endoplasm and its in- clusions and in addition show structure of other important parts such as nucleus and vacuoles which may not be included in this pseudopodium. In the remainder of the body indicate division between ectoplasm and endoplasm by a dotted line, 11. AVith the aid of ocular micrometer find the approxi- mate size of an Amoeba (see page 14, section 6). IV. Experiment. Notes required. 1. Object : to determine the effect of a mechanical stimu- lus upon an Amoeba, Clamp slide firmly to stage and gently tap the coverglass with a needle. Results? V. While completing the work on Amoeba be on the look- out for specimens which are dividing and encysting. When found describe and draw, REFERENCES Dellinger, 0. P., 1906. Locomotion of Amoeba and Allied Forms. Jour. Exp, Zool, 3:337-358, Greenwood, M., 1886-87. On the Digestive Process in Some Rhizopods. Part I. Jour. Physiology 7:253; Part II, Jour. Physiology 8 :263. Sehaeffer, A. A., 1920. Amoeboid movement, 156 pp. Princeton University. Sehaeffer, A. A., 1926. Taxonomy of the Amebas, with descrip- tions of thirty-nine new marine and freshwater species. Carnegie Inst, of Washington, papers from the Dept, of Marine Biol,, 24:1-116. PARAMECIUM (Materials: Carmine suspension, Sanford's red ink, Water- man's blue fountain-pen ink, 15% alcohol, cotton, filter paper.) Classification : — Phylum Protozoa, Class Ciliata, Order Holotricha. 1. Method of Examination. 1. From the instructor se- cure a drop of water from a culture coHtaining Paramecium. After this has been placed on a slide, add a few cotton fibers, before applying the coverglass. The fibers help retard the movements of the Paramecia and thereby facilitate examina- tion especially with the high power. • 2. Examine with low power. From the instructor learn how to distinguish Paramecia from other Infusoria. There are several species of the genus Paramecium. The one most com- monly seen in laboratory cultures is Paramecium caudatum. II. General Observations. 1. Describe the shape. Is it constant ? Is there a plane of symmetry ? Anterior end ? How determined? How does it differ from the posterior end? Note a depression extending from the anterior end backward toward the middle of the bod3^ This is the ora? groove. Is there a dorsal (upper) and a ventral (lower) surface? Why? Notes required. 2. With ocular micrometer find length and breadth of a Paramecium. 3. Make a model in clay showing the form of Paramecium. 4. Look for the mouth at the posterior end of the oral groove. The surface bearing the mouth is called the oral surface. Make an outline drawing 60 mm. long, showing oral view. The mouth should be about equidistant from the lateral margins of the body in this drawing. The surface opposite the oral surface is called the aboral surface. 5. Draw lateral view in outline, 60 mm. long. 41 42 ZOOLOGY DIEECTIONS III. Structures and Functions. 1. Cilia are delicate protoplasmic projections from the bodies of ciliates. Their de- tection requires a very careful adjustment of the light through the microscope. Are they evenly distributed? Note the arrange- ment of the individual cilia as far as possible. Of uniform size? Do all move? What functions do the cilia perform? Compare Amoeba and Paramecium with reference to locomotion. Notes required. 2. The body of a Paramecium consists of three distinct parts; (a) a thin, non-living, external covering, or cell wall, the pellicle, (b) a thicker, fixed layer, the ectoplasm, in which the trichocysts are embedded, and (c) the more fluid, granular, in- ner mass, the endoplasm. 3. To demonstrate the trichocysts get from the preparation table a drop of culture to which red ink has been added. Run a drop of blue ink under the coverglass. This kills the animals upon contact, but in so doing the trichocysts are shot out from the body. Describe the effect the instant the ink reaches an ani- mal. Draw (60 mm. long). Thoroughly wash off your slide and coverglass and get a fresh preparation. Use high power on living specimens and look for unexploded trichocysts in the ectoplasm. Notes required. 4. To demonstrate the pellicle run a little fifteen percent, alcohol under the coverglass. Notice how the pellicle becomes separated from the ectoplasm. Does the pellicle swell away from the ectoplasm or does the ectoplasm shrink away from the pellicle ? Focus carefully on the surface of the loosened pellicle using the high power. Do you find any cilia? What are the markings that occur in definite arrangements on the surface? Draw (60 mm. long). Notes required. 5. To observe the endoplasm and its movements get a fresh preparation and before applying the coverglass add a little car- mine suspension to the water containing the Paramecia. The carmine is added here for use in a later part of the work. Car- mine particles, while of no food value, are taken into the body PARAMECIUM 43 along with food, thus by their color making the food vacuoles very conspicuous, 6. How does the endoplasm differ from the ectoplasm? Are the two entirely distinct ? Watch specimens crowd through narrow places. How are ectoplasm and endoplasm affected? Notes required. 7. Under high power watch the passage of carmine grains down the gullet. Describe the formation into food vacuoles. Where do the granules enter the endoplasm? Do the food vacuoles move in a definite direction? Compare motion with that of granules of endoplasm. Notes required. 8. Note the streaming of granules in the endoplasm. Di- rection ? Distinguish the spherical food and water vacuoles, the minute structural granules of the endoplasm, and the small crystals. 9. Describe the course of the oral groove. On what sur- face of the animal is it located? The groove continues at its posterior end into the gullet. Describe the course of the gullet. Is it lined with cilia? Notes required. 10. Solid waste material which accumulates in the body is discharged through a special opening called the anus. Ordin- arily this is not observable except when waste matter is being given off. There is neither mouth nor anus in Amoeba. Why are they necessary in Paramecium ? Note required. 11. Contractile Vacuoles. Look for large contractile vacuoles which disappear from time to time. How many do you find? Is the location definite? In which body layer? At certain stages in its functioning, each contractile vacuole has a more or less star-shaped appearance, caused by radiating lines from th& vacuole into the surrounding endoplasm. These radiating canaJs bring the fluid wastes into the vacuole. If you have trouble in locating the radiating canals in fresh preparations, draw some of the water from under the cover- glass, by use of a piece of filter paper, until the coverglass rests upon the paramecia and compresses them slightly. Under these circumstances canals are plainly visible. 44 ZOOLOGY DIRECTIONS 12. Nuclei. Division of labor is accompanied by a spe- cialization of the nuclear material in the Ciliates. Instead of a single nuclear mass there are two nuclei in each cell. The larger of these, called the macronucleus, seems to have control of the or- dinary bodily functions, Avhile the fnicronucleus is concerned chiefly in the reproductive process. These nuclei are not observ- able in the living animal. At the demonstration table examine stained specimens. 13. By use of the ocular micrometer measure the length of the entire animal, the macronucleus, and micronucleus. Use these measurements to insure correct proportions in drawing asked for in next paragraph. 14. Make a large drawing, 150 mm. long, of a living Para- mecium, side view, locating and labeling various structures. Show structure carefully in part of drawing 1 cm. back from the anterior end of the body. In remainder of body show division between ectoplasm and endoplasm by dotted line. Nuclei seen in stained demonstrations should be shown in this drawing. Indi- cate direction of protoplasmic currents by a series of arrows showing course through the entire cell. 15. Reproduction by simple transverse fission. If possible watch and sketch the process in living specimens. Time for process of fission ? How many mouths just before fission is completed? How many contractile vacuoles? Are the two re- sulting individuals alike? See stained demonstrations. 16. Look for pairs of Paramecia undergoing conjunction. See demonstrations. REFERENCES Calkins, G. N., 1926. The Biology of the Protozoa. Lea and Febiger, Philadelphia, Penn. Maier, H. N., 1903. Ueber den feineren Ban der Wimperap- parate for Infusorien. Arch, f . Protist. Bd. 2 :72-179. Minchin, E. A., 1912. An introduction to the study of the Pro- tozoa. Arnold, London. Woodruff, L. L., 1922. Foundations of Biology. Macmillan, N. Y. VORTICELLA Classification: — Phylum Protozoa, Class Ciliata, Order Peritricha. Make out: (1) Shape. Is it constant? (2) Cilia. Distri- bution and functions? Does Vorticella ever swim about? (3) Groove, mouth, and gullet. (4) Ectoplasm and endoplasm. (5) Food vacuoles. (6) Protoplasmic granules. (7) Contractile vacuoles. (8) Macronucleus. (9) Structure of stalk. (10) Reproduction. (11) Make a large drawing, 50 mm. across, show- ing the parts you have seen. With ocular micrometer determine the diameter of the bell. JLU L I i « A R Y 33 45 EUGLENA (Materials: filter paper, aqueous iodine) Classification : — Phylum Protozoa, Class Mastigophora, Or- der Eugienoidina. 1. Secure a drop of Euglena culture from preparation table. Euglena may be recognized as bright green spindle- shaped or cigar-shaped organisms though some of the largest species are rather distinctly flattened. 2. Is there a characteristic shape? If your specimen is undergoing changes in shape, make six sketches showing pro- gressive change of form. 3. Note that the body is composed of a thin outer layer of ectoplasm covering an internal mass of endoplasm. 4. Look for chromatophorcs or masses of chlorophyl which give the body its green color. Shape of individual chromato- phorcs? In which body layer? 5. Locate stigma or red eye spot near the anterior end of the body. 6. The clear area, not occupied by chromatophorcs, in con- tact with the eye spot is the reservoir of the contractile vacuoles. The numerous individual vacuoles are not distinguishable under ordinary magnifications. 7. The reservoir opens into the gullet but in most species the nature of the gullet is not recognizable under ordinary mag- nification. The external opening of the gullet, the mouth, is usually distinguishable as a small cleft in the anterior extremity of the body. 8. The flagellum passes through the mouth and under very high magnification an attachment to the wall of the gullet has been observed. Adjust light and focus carefully to see the long, very fine flagellum. If not observable after a reasonable search, add a drop of aqueous iodine to the water under the coverglass. This kills the Euglena but in so doing colors the flagellum and all other protoplasm brown. 4(> EUGLENA 47 9. The nucleus is located near the middle of the body. In living specimens absence of the chromatophores in this region marks the location of the nucleus. For its shape and structure see demonstration, 10. Paramylum hoclies, a form of stored animal starch, are readily seen in some species. Since they are not always present and assume different shapes in various species, the instructor will announce if special attention is to be directed to them. .11. Compare locomotion of Euglena with that of Paramecium and Amoeba. 12. With an ocular micrometer find length and width of a Euglena. Record these measurements beside the drawing called for in the next paragraph. 13. Make a drawing, 120 mm. long, showing the parts you have seen. 14. Though the Euglena possesses a mouth and gullet no one has ever seen it take solid food particles. In its metabolism it is distinctly plant-like. Through the energy of sunlight the chlorophyl bodies combine carbon-dioxide and water to form starch which is used as food. 15. Euglena reproduces by longitudinal fission which be- gins at the anterior end. The old flagellum is retained by one- half while the other half produces a new one. COLONIAL PROTOZOA Among the Protozoa are found some forms in which the individual cells do not separate immediately after fission but re- main attached to form either temporary or permanent groups of cells called colonies. The chief point wherein these protozoon colonies differ from true many-celled animals, the Metazoa, lies in the fact that while certain cells may be set aside and special- ized as sex cells or gametes for reproduction, all the other cells of the body, the somatic cells, remain similar one to another, i. e., they lack histological differentiation. Pandorina and Eudorina are two examples of such colonies consisting of a small number of similar cells held together by a jelly-like substance called the matrix. In reproduction, each cell of the colony may continue to divide by simple fission until it forms a new colony. This is the asexual method of reproduction. Some of the colonies may produce male sex cells and others female sex cells. In these cases a male gamete must unite with a female gamete to form a single cell called a zygote which is the starting point of a new colony. This is the beginning of true sexual reproduction. Observe under demonstration microscope stained mounts of Eudorina and Pandorina. Then as you take up the study of Volvox note how these serve as a transition from the forms with no colonial tendencies, such as Paramecium and Euglena, to the more highly specialized condition found in Volvox. VOLVOX Classification: — Phylum Protozoa, Class Mastigophora, Order Phytomonadina. 1. Read the entire Volvox outline before beginning to study the prepared slide. 2. In Volvox, is found a still higher type of colony life where several hundred, or even thousands, of cells have become associated to form a single layer of cells over the surface of a 48 VOLVOX 49 sphere. In such a colony some individual cells are commonly specialized to carry on the reproductive function while all of the remaining cells (somatic cells) are similar. 3. These colonies live in ponds and pools where they swim about freely by the action of the flagella with which the somatic cells are provided, progressing with a smooth rolling motion. Ordinarily in preserved material used for study these flagella are not distinguishable. 4. There are a number of different species of Volvox. These differ among themselves in details of structure as well as in methods of reproduction. The material selected for this study belongs to the species Volvox weismannia. In this species there are two different methods of reproduction involving three differ- ent types of individuals ; these are male colonies and two differ- ent kinds of female colonies. 5. The simplest and most characteristic method of repro- duction is found in the parthenogenetic female colonies. In these, some of the cells become set apart as reproductive cells and are called parthenogenetic macrogametes. Arising in the colony wall, they increase in size until they are shoved into the interior of the colony. ]\Iacrogametes of this sort are capable of undergoing development directly without being fertilized. Each gamete, by repeated divisions, forms a group of cells which become arranged as a small sphere within the parent colony. Only by rupture or disintegration of the wall of the parent col- ony are these young colonies liberated. This method of partheno- genetic reproduction continues as long as conditions are favor- able. 6. At certain times the young colonies instead of producing parthenogenetic gametes develop into true sexual individuals. Thus there are formed male colonies which develop only micro- gametes or male cells and sexual female colonies which produce only sexual m-acrogametes. In these true sexual individuals neither type of the reproductive cells is capable of undergoing reproduction independently, for fertilization is necessary. When fully formed the microgametes leave the male colony and pene- ZOOLOGY DIRECTIONS trate the wall of the female colony. When a microgamete unites with a sexual macrogamete within a female colony a fertilized egg called a zygote is formed. The zygotes thus formed do not undergo development immediately but each becomes encased in a firm, resistant membrane. When a female colony bearing these protected zygotes disintegrates, the zygotes fall to the bottom of the pond and remain there, inactive for some time. With the return of conditions favorable for development each zygote loses its protective shell and undergoes cell division to form a new colony. 7. Examine Volvox colonies with a microscope. Use low power and focus very carefully. The large, deeply stained masses on the interior of many of the colonies are the sex cells or gametes. In most of the female colonies each mass is a macrogamete. In the male colonies, each dark mass is a cluster of microgametes. Note that the clusters of microgametes near the equator of the colony are shown in side view. Look for clusters showing end view. The small, darkly stained spots rather uniformlj^ arranged in the wall of the sphere are the somatic cells. The less deeply stained material between these cells is the matrix. 8. Make a drawing of a small portion of the colony wall showing the relation of cells and matrix. 9. At demonstration table examine specially prepared slide of Volvox showing the fine protoplasmic threads which pass through the matrix connecting each somatic cell with the adjoin- ing cells. Draw a small portion, greatly enlarged, 10. In this species the relative numbers of somatic cells in the wall of the colony is one of the easiest means of distinguish- ing the two sexes. Find a colony in which the distance between two adjacent somatic cells is more than twice the diameter of a single somatic cell. This is a male colony. Because of the wide separation of the somatic cells such a colony appears much lighter in color than the other colonies. VOLVOX 51 11. Make a drawing, 60 mm, in diameter, showing a male colony in optical section. In such a drawing only a single ring of somatic cells should be shown but all of the clusters of micro- gametes should be drawn in outline. Detailed structure of one cluster of microgametes in side view and another in surface view should be brought out. 12. The two kinds of female colonies are much alike in structure. In them, the distance between two somatic cells is usually not more than the diameter of a single somatic cell. There is no reliable constant difference in the appearance of either the somatic cells or of the macrogametes in the partheno- genetic female colonies and the true sexual female colonies. Observations upon living material have demonstrated that the chief difference lies in the number of gametes. The sexual female colonies of this species contain sixteen or more gametes while female colonies containing twelve or fewer macrogametes are parthenogenetic female colonies. 13. Make a drawing of each kind of female colony showing colony wall in optical section and showing in outline the total number of macrogametes characteristic of each. Show at least one macrogamete in detail. 14. See demonstration of zygote and draw one, in optical section, about 20 mm. in diameter. MITOSIS Reproduction of the Cell All living organisms are built up of minute units called cells. The power of an organism to reproduce itself is dependent upon the ability of these protoplasmic units to divide and thereby re- produce other cells. Mitosis is the name applied to the long se- ries of intricately correlated changes which the nucleus under- goes during the division of the cell. Cell division is especially active and conspicuous in the early development of an individual from a fertilized egg. The structures involved in mitosis are so minute that they can not be studied easily in entire cells, con- sequently cells undergoing mitosis are preserved and cut into thin slices (sections) by the use of an instrument called the mi- crotome. These sections are then treated with stains or dyes. Various parts within the cell react differently to the stain and for that reason are easily distinguishable. Chromatin, one of the materials within the nucleus, is especially deeply colored by the stains frequently used. In interpreting sections of cells in this study keep the fol- lowing facts in mind : 1. The nucleus is much smaller than the entire cell, conse- quently many slices through a given cell will contain no part of the nucleus. 2. Before the mitosis has begun the nucleus is very con- spicuous as a large light colored body in which some darker granules of chromatin are found. 3. Early in the process of mitosis the membrane surround- ing the nucleus disappears, allowing the nuclear material to lie directly in the protoplasm. From this time there is no sharply defined light colored body to represent the nucleus. 4. The spindle formed by the centrosome has but one chief axis. The developing eggs are too small to be placed all in a uniform position, consequently when sections are cut only part of them will pass through the spindle and of these only a very 52 MITOSIS 53 small percentage will contain the entire spindle. Most of the sections passing through the spindle will cut it at various angles to its chief axis and will thus include only a portion of the mitotic figure. In sections of cells undergoing mitosis study the following stages in the process of mitosis and make one or more drawings of each. Divide the page into six parts and place drawings in proper order as the difiPerent stages are found. In this exercise, keep the drawings in sequence, six drawings to a page. Prepare a sheet of drawing paper by ruling a line down the middle of the page and then two cross lines to divide the sheet into six equal parts. This exercise requires 5 drawings. Before making any drawings, number the posi- tions for all 5 figures by labelling the respective squares "Fig. 1," "Fig. 2," etc., consecutively. Then as individual stages are located each should be drawn in its proper position in the series. The unused space at the end of the series may be used for drawings of demonstrations or additional stages if time permits. Caution ! Mitosis follows much the same series of steps or stages in many diflPerent kinds of animal and plant tissues. However, there are numerous individual points of difiPerence in the details of the process for every organism. Developing eggs of the roundworm (Ascaris megalocephala) and those of the starfish, sea urchin, and the marine worm (Cerebratulus) are favorable sources for the study of mitosis. The spermary of a salamander and of certain species of crayfishes and grasshop- pers are also valuable for the study of mitosis. In the labor- atory study be sure to draw figures of mitosis characteristic of the particular kind of cells provided by your instructor, with- out regard for the generalized diagrams of mitosis. For the resting stage (Fig. 1) and for the telophase (Fig. 5) draw the entire cell. In the remaining stages draw the nuclear structures and mitotic figure only. 1. Resting Stage. Chromatin scattered throughout the nucleus in the form of small granules. Fig. 1, 54 ZOOLOGY DIEECTIONS 2. Prophase. Chromatin becoming arranged in masses, usually forming a coiled thread, the spireme. Fig. 2. 3. Metaphase. The chromatin thread has broken into chromosomes which have become arranged in the equatorial plate. In this stage each chromosome has split longitudinally but because of their minute size in some kinds of preparations the individual chomosomes are not readily observable. Fig. 3. 4. Anaphase. Chromosomes moving toward each pole of the spindle. Fig. 4. 5. Telophase. The construction of the two daughter nuclei. This is usually accompanied by a cleavage of the cell, whereby the two daughter nuclei become the nuclei of two daughter cells. Fig. 5. reference Wilson, E. B., 1925. The Cell in Development and Heredity. Macmillan. EMBRYOLOGY OF CEREBRATULUS Classification : — Phylum Plathelminthes, Class Nemertinea, Order Heteronemertinea. Cerebratiiliis is a marine worm which lives in burrows on sandy beaches. Its reproduction is by the sexual method. When the females reach maturity they discharge enormous numbers of eggs into the surrounding water. At the same time the males discharge myriads of small, motile spermatozoa into the water. These spermatozoa, through their power of locomotion, come into contact with the eggs liberated by the females. Under nor- mal circumstances but a single sperm cell enters each egg cell. Before the union of the nuclei of these> germ cells each of the uniting cells has undergone a series of preparatory changes called maturation. The fusion of the two germ cells to form a single cell with a single nucleus constitutes the act of fertili- zation. From the egg thus fertilized a new individual is formed. The early stages in this development will be studied in prepared slides of preserved eggs and embryos. You will be given slides in which numerous eggs and em- bryos in various stages of development are mounted in a drop of balsam. These mounts are very tragile and should be HANDLED WITH UTMOST CARE. Evcu in wiping the dust from the coverglass be very careful that no pressure is brought to bear upon the coverglass. Number these drawings in sequence continuous with the drawings of the preceding exercises (Figs. 6-20). The drawing of the immature egg should be 50 mm. in diameter and all of the remaining drawings should be in pro- portion. 1. The Immature Egg may be distinguished because of its very large, light colored nucleus. A small, deeply stained spheri- cal body, the nucleolus, is usually conspicuous within the nucleus. 55 56 ZOOLOGY DIEECTIOXS Draw immature egg. With ocular micrometer find diameter of immature egg and record next to drawing Fig. 6. Orientation of the Egg. In Cerebratulus, the polar bodies are given off at the point directly opposite the original point of attachment of the egg in the ovary. The place where the polar bodies are given off is called the ^animal poJe,' while the opposite pole is called the 'vegetative pole.' The line passing from one pole through the nucleus and then through the other pole, is called the 'axis' of the egg. Any line on the egg (or of the embryo) running from pole to pole is called a 'meridional line,' while any plane including a meridian is called a 'meridional plane.' Any plane cutting the axis of the egg (or of the embryo) at right angles is called an 'equatorial plane.' The polar bodies of Cerebratulus always occur inside of the outer membrane of the egg. The egg is always slightly flattened at the point where they appear. 2. Maturation op the Egg. The process through which the amount of chromatin is reduced by the extrusion of the two polar bodies is called 'maturation.' Draw any two different stages. Figs. 7 and 8. 3. Fertilization. After maturation the sperm, nucleus, which had entered the egg previously, fuses with the nucleus of the mature egg to produce the first cleavage nucleus. See demon- stration microscope and draw, Fig. 9. 4. First Cleavage. By the process of mitosis the nucleus divides. In the cleavage of the cell which accompanies this in Cerebratulus three processes may be made out. Draw each : (a) The cell elongates slightly and begins to constrict, Fig. 10. (b) The constriction entirely separates the two daughter cells, leaving but a slight contact surface between them, Fig. 11. (c) The two cells become pushed together, forming a broad contact surface one with the other. Fig. 12. Observe immature egg and first cleavage stage in same low power field and compare sizes. 5. Second Cleavage. In succeeding cleavages each cell EMBEYOLOGY 57 undergoes the same stages outlined in the preceding paragraph. Make three drawings to show these stages in the second cleavage. Figs. 13 to 15. 6. Third Cleavage. Draw a polar and a lateral view. In this stage note that the four cells at the animal pole are not directly above the four cells of the vegetative pole. This shift- ing of the position of the cells indicates what is called the ' spiral type of cleavage.' Figs. 16 and 17. 7. Fourth Ci eavage. Draw a polar view. By focusing note that a cavity is already beginning to form in the center of the mass of cells. In Cerebratulus there is no morula stage. Fig. 18. 8. Blastula Stage. Draw in optical section showing the blastula cavity or blastocoel which is surrounded by a single layer of cells. Fig. 19. 9. Gastrula Stage. In optical section show relative thickness of ectoderm (outer cell layer) and entoderm (inner cell layer. The cavity between them is the hlastocoel. The cavity within the entoderm layer is termed the gastrula cavity or archenteron. It opens to the exterior through an opening, the blastopore. Determine the diameter of entire gastrula and compare with that of immature egg. Draw as Fig. 20. 10. During the gastrula stage the Cerebratulus is a free- living animal. By further development the gastrula becomes modified to form a small larva known as a pilidimn. The mature worm, several feet in length, results from the further growth and complicated transformation of this larva. . 11. Write a connected account of early development in Cerebratulus, bringing into relationship the processes of matura- tion of the egg, fertilization, mitosis, and cleavage. In describ- ing the first cleavage, give in full an account of the process of mitosis as it occurs in this animal. REFERENCE Wilson, E. B., 1903. Experiment on Cleavage and Localization in the Nemertine-egg. Arch. Entw.-mech. 16 :411-460. HYDRA (Materials: — Phylum Coelenterata, Class Hydrozoa, Or- der Hydraria. 1. Living Hydra. A living specimen will be given you in a watch glass with a small amount of water. Examine with dis- secting lens while still in the watch glass, using care in handling the specimen to prevent injuring it. Note that the animal is composed of a more or less cylindrical hody which near one end bears a ring of tentacles. At its opposite extremity the body is slightly modified as a foot by means of which it becomes attached. II. General Study. 1. Body, size and form. Does the form change. 2. The foot. See if any debris or foreign material is at- tached to the foot. See demonstration of longitudinal section through foot. (Glandular cells usually stain much darker than other cells.) Examine specimens clinging to the sides of an aquarium or bottle. How do you infer that attachment is eifected ? 3. The tentacles. How many? Where situated? Change of form? 4. You have observed that the tentacles are located a short distance back of the extreme tip of the body. The cone- shaped tip of the body which extends anteriorly beyond the bases of the tentacles is termed the hypostome. The mouth is located at the tip or apex of the hypostome. 5. If micro-crustacea are available, add a drop of water containing a few of them to the watch glass containing a living Hydra. Under the hand lens, watch the tentacles capture a crustacean and bring it into the mouth of the Hydra. 6. Draw the Hydra when the body is well extended and also when contracted. The extended drawing should be at least 58 HYDRA ■ 59 200 mm. long and approximately 15 mm. in diameter, and the other one in proportion. 7. With a pipette transfer the Hydra to a drop of water on a slide. Place two pieces of thread in the water so that when the coverglass is added they will be at two opposite sides of the coverglass for support. Study ectoderm and entoderm. 8. Study tentacles. Note small round bodies, the nettling cells, of at least two different types. Are they arranged in definite order? The short hair-like projections seen on the margin of the tentacle are the cnidocils mentioned under (b) on the next page. 9. On each of the two drawing called for above, show the arrangement of the nettling cells on a portion of one tentacle as seen in surface view. III. Transverse Section. A. Low Power. Examine trans- verse sections and see the outer, cellular ectoderm, the very thin middle non-cellular layer or mesoglea, and the inner cellular entoderm. Note the general appearance and the relative thick- ness of these layers. The space bounded by the entoderm is the coelentric cavity. This cavity serves for the digestion and dis- tribution of food. B. High Power. Study a transverse section under high power. (a) Examine cells of the ectoderm carefully. Note that the protoplasm does not fill the entire cell but usually sur- rounds a more or less conspicuous open space called a vacuole. With a little practice the nuclei of these cells may be readily distinguished from the nettling cells and other bodies lying in the protoplasm. Because the cells which cover the surface of the body of the Hydra have become partially specialized for movement they are called epithelio-muscular cells. In transverse sections that have been specially prepared note that each of these ectoderm cells shows a row of dark dots close to the margin 60 ZOOLOGY DIEECTIONS which lies next to the mesogiea. These are muscle threads cut in cross section, (b) The netting cells or cnidohlasts are peculiar in that they are included within the protoplasm of the epithelio-muscu- lar cells. The nematocyst may be distinguished as a clear blad- der-like structure which frequently encloses a solid elongated body. This last named structure is the series of barbs which be- come evident on one type of netting cells when they are dis- charged. A small nucleus is often present just outside the wall of the nematocyst. The nucleus with the protoplasm immedi- ately around the nematocyst constitutes the cnidohlast, or cell which produces the nematocyst. In a nettling cell which lies at the outermost surface of the ectoderm a small pointed projection called the cnidocil is frequently observable extending beyond the general surface of the body. The cnidocil used to be called the "trigger" on the supposition that it controls the explosion of the nematocyst. (c) Small wedge-shaped cells called interstitial cells are frequently found between the bases of the epithelio-muscular cells. It is from these cells that the nettling cells are formed. When fully formed the nettling cells migrate through the proto- plasm of the epithelio-muscular cells until they come to lie at the surface of the body where they are in a position to function. (d) The entoderm cells are much larger than ectoderm cells. The protoplasm of these cells is usually fiUed with rounded masses of stored food material which has been taken directly from the coelenteric cavity. These masses are frequently so numerous as to obscure the nucleus. Make a drawing of a part of the wall of the body as seen under high power. Show the structure very carefully in one or two cells of each kind. In your 200 mm. drawing of the entire animal, show in out- line the location and distribution of coelentric cavity, ectoderm, and entoderm. HYDEA 61 IV. Reproduction. The various species of Hydra undergo both asexual and sexual reproduction. The asexual method is by budding. In this process, a portion of the body wall bulges out and increases in size until a sac-like bud is formed. The ectoderm, entoderm, and cavity of the bud are continuous with those of the parent. In the early stages tentacles and a mouth are lacking but these soon appear and the bud is recognizable as a new Hydra attached to the body of its parent. Ultimately the bud breaks away and becomes independent. In the sexual method, the ectoderm of certain regions of the body forms spermaries and ovaries which contain the repro- ductive cells. After an egg is fertilized a resistant membrane is formed around it. After some time the fertilized egg is dropped from the surface of the body. It finally undergoes cleavage and gives rise to a new Hydra. V. Experiment. Run a little methylen blue under the coverglass. This acts as a chemical stimulus, causing the nem- atocysts to be shot out and at the same time stains them blue. If threads are not shot out from the surface of the body upon contact with the stain, tap lightly with a dissecting needle upon the coverglass immediately above the Hydra. Make out at least two kinds of nematocysts. Draw an 'exploded' specimen of each. The sac of the larger should be 10 mm. in diameter. In the exploded condition, the nettling cells have been com- pletely separated from the body so that each nematocyst may be seen to consist of a long thread-like tube, one end of which is attached to a small sac-like structure. Often some of the nem- atocysts which are discharged from the body are more deeply stained and more irregular in outline than the others. Such a nematocyst is surrounded by its cfiklohlast, the cell which forms the nematocyst. REFERENCE Hegner, R. W., 1916. An Introduction to Zoology. Macmillan, N. Y. Hyman, Libbie H., 1928. Miscellaneous Observations on Hydra, with special reference to Reproduction. Biol. Bull., 44 :65-108. OBELIA Classification : — Phylum Coelenterata, Class Hydrozoa, Or- der Leptomedusae. 1. Obelia is a marine colonial coelenterate which becomes attached to seaweed, piles, or other submerged objects. Study prepared slide (or a piece of a colony on seaweed). Each in- dividual of the colony is called a Jiydranth or zoo id. Is there any reo^ularity in the arrangement of the zooids upon the upright branches ? Each branch usually represents but a part of a colony. Several such branches may be united by a continuous root-like hydrorhiza which is the part by means of which attachment is secured. 2. Examine prepared slide with hand lens while holding slide up to the light-. Make a simple diagram to show arrange- ment of parts of the colony. In this diagram, the central stalk and each of its branches should be represented by a single line. Details of structure will be shown in another drawing. 3. Study specimen mounted on a slide and under low power compare the structure of an individual zooid with the structure of Hydra. Note, in addition to what was found in Hydra, a tough, membranous sheath, the perisarc, covering the surface of the colony. The vase-like expansion of the perisarc around each zooid is called the hydroiheca. 4. The fleshy continuation of the zooid down into the stalk is termed the coenosarc. Is it in close contact with the perisarc ? 5. In an expanded hydranth, note the mouth, the arrange- ment of the tentacles and the number of tentacles. The mouth opens into the coeJenteric cavity as in the Hydra. This cavity continues down through the coenosarc so the coelenteric cavities of all of the individuals of a colony are directly continuous with each other. 6. Do you notice any modifications of the perisarc below the hydrotheca ? Do these serve any purpose? Notes required. 62 OBELIA 63 7. Examine hydranth and stalk with low power and look for the cell-layers which you discovered in the study of Hydra. Draw a hydranth and part of the stalk as seen in optical section under the low power, making the hydrotheca 80 mm. long. Cell layers but not cytoplasmic contents should be shown in this draAving. 8. Find reprochictive individuals and draw one. These are large sac-like structures containing numerous huds formed asexually. These buds when fully developed, become small, free-swimming, jellyfish (see demonstration microscope) which reproduce sexually. The fertilized egg develops not into a jelly- fish, but into a hydroid such as you have been studying. This condition where the offspring is not like the parent but like the grandparent, is termed metagenesis or alternation of generations. The hydroids produce jellyfish; jellyfish produce hydroids, etc. 9. Examine demonstrations of undeveloped hydranths. These must not be confused with old or injured hydranths which have lost their tentacles. An undeveloped hydranth is a bud, the free end of which is covered by a continuous layer of the perisarc. GONTONEMUS Classification : — Phylum Coelenterata, Class Plydrozoa, Or- der Leptomedusae. Gonionemus is the medusoid or jellyfish form of a coelenter- ate. In fundamental structure it closely resembles the medusa of Obelia and is given as a type of medusoid instead of the medusa of Obelia because of its greater size which makes it more easily studied. The following study is to be made upon a speci- men preserved in formalin : 1. The convex face is called the aboral surface and the concave portion the oral surface. 2. The velum is a membrane on the oral surface which ex- tends from the margin of the body inward toward the center partially enclosing the bell. In many specimens that have been handled roughly this membrane may be torn. Normally it is perforated by a single circular opening in the center. 3. Hanging in the center of the bell is the manuhrmm, at the extremity of which is the mouth. 4. From the stomach, at the base of the manubrium, the four radial canals lead to the periphery of the disc where they open into the very delicate circular canal. What is the use of these canals? Study canals in specimen with aboral surface uppermost. 5. The gonads hang in folds from beneath the radial canals. The eggs or spermatozoa are discharged from these directly into the water. 6. Examine the tentacles. How are the nematocysts ar- ranged on them? Note the sucking disc some distance from the end of each tentacle. 7. Two kinds of sense organs can be made out on the edge of the medusa. See demonstration of : 64: GONIONEMUS 65 (a) Light-perceiving organs. These are large, round, pig- mented bodies at the bases of the tentacles, (b) Otocysts, or balancing organs, are small, transparent, ovoid bodies located between the tentacles. In Gonionemus each otocyst consists of a large vesicle surrounding the true sensory organ which is located at the end of a short stalk extending into this vesicle. The rounded structure at the end of the stalk con- tains a cavity, the secondary vesicle, within which a small cal- careous body called the otolith is located. 8. Make drawings, (a) from the oral surface, 70 mm. (without tentacles), filling in outline one comi)lete tentacle and bases of one-third of remaining tentacles, (b) Of an optical vertical section through the radial canals. (c) A portion of a tentacle much enlarged, showing sucking disc. (d) An otocyst much enlarged. 9. Make a brief word diagram showing in a circle the life history of a hydrozoan. REFERENCES Perkins, H. F., 1903. The development of Gonionemus mur- bachii. Proc. Acad. Nat. Sci, Phila. 54 :750-790. Thomas, L, J., 1921. Morphology and orientation of the oto- cysts of Gonionemus. Biol. Bull., 40 :287-296. REGENERATION IN PLANARIA (Materials: large pipette, watch glasses, pond or cistern water.) Classification : — Phylum Plathelmiuthes, Class Turbellaria, Order Tricladida, A fresh-water flat worm will be giA^en yon in a watch glass containing pond water. Make out the characteristics of struc- ture and movement. Make a 100 mm. drawing across the top of a page showing as many of the following parts as possible: (1) general body shape, (2) the pharynx is a cylindrical structure near the middle of the body (usually the pharynx is retracted within the body except when food is being taken) : (3) the mouth is at the pos- terior free end of the pharynx. (4) the intestine consists of three main branches leading off from the end of the pharynx, one anteriorly and two posteriorly, (5) the eye spots, (6) the sensory loles, ear-like structures on the sides of the head. The worm is to be cut into three pieces of as nearly equal size as possible. One transverse cut is to be in front of and the other behind the pharynx. Sharpen scalpel on knife stone. While the worm is crawling along on the bottom of the watch- glass place the point of the scalpel against the bottom of the dish at one side of the worm. With a fairly rocking movement roll the edge of the knife across the body of the worm; thus severing the body with one clean cut. On your first drawing indicate with broken lines the planes of the cuts. Make outline drawings of the three parts immed- iately beneath the drawing of the entire animal, placing the parts in the same relative positions. Next to these drawings record the date of the operation. ^ See that the watch glass is carefully covered. Change the water at each laboratory period. Make observations on struc- 6G EEGENEKATION OF PLANAEIA 67 ture and movements of each piece until regeneration is com- pleted. Make outline drawings of each piece as often as directed at the beginning of each laboratory period before taking up the advanced work of the day. Record the date of each set of drawings. After this experiment is completed write a connected ac- count of regeneration as it occurs in Planaria. REFERENCE Morgan, T. H., 1901. Regeneration. Macmillan Co. EARTHWORM (Lumbricus terrestris) Classification : — Phylum Annelida, Class Cliaetopoda, Sub- class Oligochaeta. There are numerous species and genera of earthworms. The one chosen for this study is not a native of this country but was introduced from Europe and has become established in some lo- calities. The small worms which are found in the soil and on walks after heavy rains are usually not the young of this same species but represent a number of separate genera and species differing considerably in internal structure. Information given in this outline does not apply to all earthworms. I. External Characters 1. Note that the body is composed of a series of similar rings placed end to end. Each of these divisions or rings is called a somite or segment. Notice that the body is almost cylin- drical in form but is slightly flattened on one surface. This flattened surface, which is also usually light in color, is the ven- tral surface of the worm. The anterior region is the more robust of the two body extremities, 2. The most anterior part, the prostomium, is not a true segment. How far does it extend through the next division, the peristomium, or first true somite? Make a drawing, X5, of the dorsal view to show the relation of these two parts. 3. The clitellum consists of several thickened segments forming a partial ring in the anterior region of the body. On which surface of the body is this ring incomplete in this species ? Count the number of segments anterior to the clitellum, in the clitellum, and posterior to the clitellum. Record the results of counting after your desk number on the table outlined upon the blackboard. What part of body has a constant number of seg- ments ? 68 EAETHWORM 69 4. Locate the mouth on the ventral surface just behind the prostomium. 5. The amis occurs in the last segment. Shape ? Position ? 6. Find the supermiducal pores on segment XV. Position and appearance? 7. The ovichical pores occur in similar positions on segment XIV, but are much smaller and visible only upon careful exam- ination with a lens. 8. Dorsal pores, very small, on dorsal median line at an- terior margin of all segments except a few at the anterior ex- tremity. 9. Find the setae or short bristles extending beyond the sur- face of the body wall. How many on a somite and how ar- ranged? In what direction do they point? This can be deter- mined by pulling the worm gently between the fingers. 10. Make an outline drawing X3, of the anterior forty segments as seen in lateral view. Label all of the parts. 11. Make a diagram of a cross section showing locations of the setae. II. Internal Anatomy The method of opening the body wall will be demonstrated to small groups in the laboratory. In dissecting the earthworm it is necessary to split open the body wall so it may be pinned out flat, thus revealing the internal organs. In the region just be- hind the clitellum insert one point of the dissecting scissors and cut forward along the mid-dorsal line of the body to about the second segment. While making this cut hold the one point of the scissors just inside the body wall stationary, moving only the free blade of the scissors. This will avoid injury to the in- ternal organs. Note that the space inside the body wall is divided into small chambers by partitions called septa. With what do these septa 70 ZOOLOGY DIRECTIONS correspond externally? Hold the worm in your left hand and with a dissecting needle note that these septa break away fairly readily. With the needle pressing outward from the cut against the body wall run it along the body until the septa have been broken along both sides of the body. Now with pins open the body wall out flat against the wax in the bottom of a dissecting pan, allowing the heads of the pins to point away from the body of the worm at a broad angle so as to be out of the way during later dissection and examination. Before beginning the study of individual organ systems, examine the opened specimen and locate the following land marks. At the anterior extremity of the body is the pharynx, the anteriormost part of the digestive tract. Posterior to this are several large white objects, the sperm sacs, which hide the digestive tract in this region. Behind the sperm sacs the large cylindrical tube which continues through the length of the body is the digestive tract the parts of which will be studied in detail. In all of this work remember that the septa may be crowded either forward or backward by some of the organs. For this reason it is necessary to observe in what cavities the organs lie, rather than observe the external body markings of segments in the region occupied by the organs. If a structure oc- cupies more than one segment, the places where the septa crossed it are fairly easily recognized. REPRODUCTIVE SYSTEM In studying this system be careful to prevent injury to the organs of other systems. A. Male Reproductive Organs 1. Three pairs of sper)n sacs, large white sacs at sides of and above esophagus. Some of them may not be very large be- cause the specimens were not at the height of sexual activity EAETHWOEM 71 when killed. Three pairs, in which somites? They contain spermatozoa. 2. Ventrally the sperm sacs are connected by a common seminal vesicle. 3. The testes, two pairs in X and XI, in positions corre- sponding to those of the ovaries in XIII, are small and being en- closed in the seminal vesicle they cannot be seen. B. Female Reproductive Organs 1. The ovaries are attached to the anterior septnm of XIII near the mid-ventral lines. They are generally difficult to find. 2. Oviducal funnels are on posterior septum of XIII op- posite the ovaries. 3. The oviducts lead from them backwards to the ventral wall of XIV. 4. Spermathecae, two pairs of small globular sacs lying close to the septa between IX and X, and X and XI. They open to exterior on ventral side and receive spermatozoa from another worm. Make a diagram of a side view showing the location of the reproductive organs found. Number segments. C. Reproduction in the Earthworm Because the earthworm has the reproductive organs of both sexes functional in the same individual it is said to be hermaph- roditic. During the breeding season earthv;orms come out of their burrows at night for the purpose of copulation. Two in- dividuals come together with their heads pointing in opposite di- rections. While in this position a mucus tube is secreted which holds the two worms with their ventral surface together. During this period of copulation, glands in each clitellura secrete a cocoon which surrounds the body of the worm. Into each cocoon, spermatozoa and eggs are deposited. Fertilization 72 ZOOLOGY DIKECTIONS takes place outside the body of the worm, within the cocoon. The cocoons are worked off the anterior extremity of the worms and are deposited in moist places. Here the eg'gs undergo develop- ment and give rise to minute immature worms which finally leave the cocoons and burrow in the soil. CIRCULATORY SYSTEM 1. The dorsal vessel may be seen as a small dark tube which runs along the dorsal surface of the digestive tube. How far forward does it extend ? 2. Large lateral branches, '^ hearts," pass around esopha- gus. At demonstration table examine a piece cut through the body in the region of the hearts to see connection with ventral vessel. 3. In your own dissection find at least four pairs of hearts. Draw a pair in optical vertical section to show their shape and communication with longitudinal vessels. 4. Parietal vessels may be found in the body wall and in the wall of the intestine. 5. Make a diagram of the main trunks of the circulatory system. Nnmher the hody segments shown. DIGESTIVE SYSTEM 1. The alimentary tract, a straight tube extending through the body, has the following parts arranged in order from anter- ior to posterior extremities: (a) Buccal cavity or mouth cavity, a thin-walled sac- shaped structure communicating with the outside through the mouth. (b) Pharynx, thick-walled region with muscles running to the body wall. (c) Esophagus, slender and extending through a number of somites, mostly hidden by the sperm sacs which may now be removed by picking away the pieces carefully with a pair of fine EARTHWORM 73 poinled forceps. The ralciferous glands occur on the sides of the esophagus as small lobular structures. See demonstration dissection. (d) Crop, an enlarged thin-walled sac. With the point of a needle note the difference in resistance of this and the gizzard. (e) Gizzard, thick-walled, muscular grinding organ. (f) Intestrnf, a tube of practically uniform diameter ex- tending through the remainder of the bodv. A laver of brown cells, the cMoragogue cells, covers the intestine. These are sup- posed to be associated with the excretory function. 2. Make a slit in one side of the intestine and fold back the dorsal half for the distance of about 10 mm. or more. If the in- testine is filled with dirt or other matter w^ash it out and observe the fyphlosole, a fold which hangs into the intestine from the dorsal surface. 3. Make a full-page drawing, dorsal view, of the digestive system found in the anterior part of the body, showing all struc- tures mentioned above. In your drawing number all segments. EXCRETORY SYSTEM For a distance of several inches behind the clitellum open the body wall as before and pin out flat. Remove the intestine carefully. Observe the paired structures lying loosely in each. somite, flat against the ventral body wall. These are the metanephridia. Each metanephridium is composed of two distinct parts lo- cated in different somites. The conspicuous white masses, one on each side of the nerve cord in each somite, are the nephridial tubes. Under the hand lens only a part of each mass shows its tubular nature. The tube leads forward to a transverse septum through which it passes and extends as a minute knob-shaped nephrostome into the segment next ahead. The other extremity of the tube is attached to the body wall through which it opens 74 ZOOLOGY DIRECTIONS as the nephridiopore. The location of this nephridiopore is best observed in the study of the cuticnla under Section IV, Note demonstration of stained nephridium. Draw three somites showing arrangement of nephridia as seen under hand lens. RESPIRATION In the earthworm there are no special organs for respiration. The moist conditions under which the animal lives and the deli- cate structure of the body wall make it possible for the entire body surface to function in the process of respiration. NERVOUS SYSTEM 1. The nerve cord lies against the body wall in the middle of the ventral surface. It is conspicuous, thread-like struc- ture, slightly enlarged in each somite. How many side branches of this cord in each somite? Do these lateral branches follow any definite plan of arrangement? 2. Trace the nerve cord toward the anterior end of the worm. 3. Very carefully lift the posterior end of the pharynx and tracing the nerve cord on forward locate the place where it di- vides and passes around the pharynx. The nerve cord around the pharynx is the circum-pharyngeal collar. 4. The small, whitish, two-lobed mass on the dorsal sur- face of the anterior end of the pharynx is the hrain. 5. Make a diagram of the nervous system. BODY WALL With the hand lens examine the cut surface of the body wall. Locate the muscle layers. Note the inner ends of the setae protruding through the body wall. III. Study of Prepared Slides Under the microscope examine cross sections of the body in the region of the intestine. EAETHWORM 75 Make an outline drawing of the cross section, properly oriented. This drawing should be 19 cm. in diameter. Show the exact structure of a strip 2 cm. wide from the center to the periphery and in addition show a portion of any other structures not included in this strip. The foliowinfy structures should be found: cuiicula (may have been removed by handling previous to sectioning) ; hupo- dermis, an epithelium frequently shoAving darkly stained unicel- Inhir )nucus glands; circuhv muscle layer; longitudinal muscle layer. Inside the body cavity find ; the dorsal vessel with occa- sionally a lateral branch, one of the parietal vessels; the intestine with its fyphlosole; the nerve cord ; the ventral vessel which is connected with the intestine by a membrane — the mesentery; nejihridia cut in various planes ; setae or at least breaks in the musculature indicating location of setae. IV. Study of C'uticula Cuticula, the delicate iridescent outer covering. Strip off a piece of the cuticula from the anterior end of the body. Float it on a drop of water on a slide. Apply coverglass. Examine prepared slide with the microscope and find : the seta sacs, little sleeves within which the setae work ; the nephridioporcs ; openings of the niKCus glands, numerous very minutes dark spots from which fine lines radiate ; and the cover- ing of sense organs. These last appear as small oval or rounded areas in which no mucus openings are present. Within these areas will be found groups of minute openings from which sensory hairs have protruded. Make a diagram of a complete segment showing the rela- tions of these parts as viewed under low power. REFERENCE Sedgwick, W. T. and Wilson, E. B., 1904. An Introduction to General Biologv. Henrv Ilolt and Co. CRAYFISH (Materials: Tags, carmine, pipettes, pins) Classification : — Phylum Arthropoda, Class Crustacea, Or- der Decaj)oda, This animal is studied as an example of a complex, seg- mented animal, with diverse kinds of jointed appendages which are built upon the same general plan, and thus clearly illustrates the principle of homologies. All crayfishes of the eastern United States belong to the single genus Cambarus. There are many species of this genus but all of them agree so closely in general structure that this outline is suited for the study of any member of the group, I. The Live Aniwal 1. Place a crayfish in a large dissecting pan and allow it to walk about. Determine the function of the different legs. Notes required on all questions upon live animal. 2. Place the crayfish in water and observe the movements of the swhnmerets on the ventral side of the abdomen. 3. Note the use of the tail fin when the animal is suddenly surprised in the water. 4. Turn the animal upon its back and describe the method of righting itself. This experiment should be tried upon a rough surface. 5. Keep the crayfish in the air for a few minutes, then return it to the water, back do^vnward, and describe where you find bubbles of air escaping. 6. Hold the animal, back downward, over a piece of white paper in the water and place a drop of carmine suspension on the ventral surface of the thorax in the region of the posterior pair of legs. Describe the result. What is the relation between what 76 CEAYFISH 77 3^011 observe and the bubbles, previously seen ? The carmine is used simply to show presence of and direction of water currents. 7. Why are not air bubbles constantly ejected while the crayfish is in the water ? 8. Examine a demonstration specimen prepared to show the *' (jin bailer" in action. The "bailer" is a part of the second maxilla. 9. Make a diagram of a side view of the carapace, and show by arrows the general course of the water currents. Explain your diagram. Briefly summarize the method of aerating the gills. 10. Observe to what degree the eye stalks are movable. What evidence can you give that the crayfish sees? IT. External Ciiaractees 1. Observe that the body is readily divisible into two re- gions. The large anterior region, which is covered on the dorsal and lateral surfaces by a non-jointed shell called the carapace, is the cephalotliorax. The remaining series of movable segments behind the cephalotliorax is the ahdomen. 2. Note the cervical groove, a slight depression extending from the ventral margin to the dorsal surface of the carapace. This groove marks the boundary between head and thorax. 3. Examine the lateral margin of the carapace. This marks the ventral boundary of the gill chamber. On the dorsal surface of the carapace the gill chambers and pericardial chamber are separated by a pair of grooves called the h ranch io-pericardial grooves. The rostrnm is the sharply pointed projection of the cephalothorax between the eyes. 4. Examine the ventral surface of the cephalothorax. Is there any evidence of segmentation? Notes required. 5. Note the texture of the skin. Where is it hard and where is it soft? What is the relation of the texture to movability? Notes required. ZOOLOGY DIEECTIONS 6. How many segments in the abdomen ? How many have appendages? These appendages are called the sivimmerets. III. Homologies of the Appendages In this entire section where drawings are asked for they are to be ventral views of the appendages from the left side of the body. 1. Study one appendage of the third abdominal segment. Distinguish the stem or profopodite, composed of a basal short segment, the coxopodite, and a long segment, the tasipodite. Of the two branches given off from the end of the protopodite the outer one is called the exopodite, while the one nearer the median line of the body is called the endopodite. Draw X4 and label all of the parts. 2. Such a two-branched appendage is called a diramous ap- , pendage, and constitutes the general plan upon which all of the appendages of the crayfish are built. In the following study, each appendage is to be studied in order to determine the modi- fications which have arisen in the various parts of biramous appendages. 3. The study of homology usually involves a comparison of organs or structures found in two different kinds of organ- isms. When repeated parts upon the same individual show the same fundamental plan of structure the term serial homology is used. 4. The terminal part of the abdomen is the ielson. The telson, together with the appendage of the sixth abdominal seg- ment, form the tail pi. Draw the entire tail fin X3, ventral view, labelling all parts and being especially sure to show what parts of the sixth abdominal appendage correspond to the parts worked out for the third appendage under section 1. 5. Remove carapace from the animal's left side exposing CEAYFISH 79 the gill chamber. In the dissection and study which follow, it is imperative for you to know what structures are associated with each of the legs. Begin at the posterior end of the thorax, grasp- ing the last walking leg with the forceps. Move this leg gently about so as to discover all parts attached to it. In like manner manipulate each of the remaining legs without removing or in- juring any of the attached parts. Move the cheliped slightly and note relation to gills. With a pair of strong forceps grasp the cheliped at its attachment to the body and by a firm, steady pull remove the entire appendage, being sure to get all the parts belonging to it. The various parts of all such appendages are studied to best advantage when under water. 6. The appendages directly associated with the mouth open- ing have become greatly modified in their adaptations to special functions. In these highly modified appendages relative position of the parts is not a safe clue to homology. From the study of these structures in their early development it is usually possible to determine the homologies with certainty. In these and other obsecure instances the information about homologies is given in this outline. 7. With the cheliped out of the way it "is easier to see the appendages immediately around the mouth. Before removing any other parts study the appendages just in front of the region from which the cheliped was removed. Note that there are three rather conspicuous maxiUipeds, two smaller maxillae, and an ex- tremely hard mafidible. Between the mandibles and the first max- illae there is a pair of very small structures, the jmraynatha, which occur at the sides of the mouth and form the posterior boundary of the mouth. They are outgrowths of the body wall and not true appendages. 8. A tabulated summary is of interest in showing the re- lationship of the parts in the variously modified biramous ap- pendages of the crayfish. The following table is prepared as a summary of the study of the head appendages. A plus sign 80 ZOOLOGY DIRECTIONS indicates that the structure is present, a zero that it is wanting. segment appendage exopodite endopodite protopodite epipodite gills prostomium antennules 0 + -f- 0 0 I. antennae + + + 0 0 II. mandibles 0 + + 0 0 III. 1st maxillae 0 + + 0 0 IV. 2nd maxillae + + + + 0 9. On your note paper prepare a table for the thorax and abdomen, using the same column headings as above. Data for filling out this table will be secured, in the course of the study and should be incorporated into the table only after the study has been made as directed and after drawings that are asked for have been prepared. The thorax includes segments V to XII and bears three pairs of maxillipeds and five pairs of walking legs. The abdomen comprises segments XIII to XVIII and the telson. 10. In the same manner as directed above study the third maxilliped which lies immediately anterior to the cheliped. Ex- amine carefully while still in place, to make sure of proper ar- rangement of parts, then remove and draw ventral view, X4 Distinguish protopodite (made up of coxopodite and hasipodite) , exopodite, endopodite, epipodite, and gills. 11. Remove, study, and draw second maxilliped. Continue the study, using the first maxilliped. Draw. Do you find gills on each of these ? 12. The second maxilla has a broad, thin protopodite near the median line of the body. The exopodite is fused at its poster- ior extremity with the epipodite to form a tough, membranous structure, the gill hailer. The endopodite is a very minute pro- jection between protopodite and exopodite. Draw. 13. The first maxilla consists of only two conspicuous, flat- tened lobes, the outer one of which is the endopodite and the other the protopodite. Draw. 14. All the hard part of the mandiMe and the basal joint CEAYFISH 81 of the small feeler-like structure attached to its outer margin are protopodite. The two remaining segments of the feeler-like ap- pendage are endopodite. Draw. 15. Examine the second pair of feelers, the antennae, and compare the parts with those of the third abdominal appendage. Draw left antenna X3. In this, as well as in other parts of the outline, the position of an appendage is determined by the point of its attachment to the body wall, not by the distance the ap- pendage extends beyond the body. 16. Note the small white elevation of the ventral side of the basal joint of each antenna. The small opening on each of these elevations is the excretory opening. 17. The first pair of feelers, the antennules, though two branched, are not "biramous." Their location upon the prosto- mium, which is not a true segment, their development, and their structure all indicate that they are not homologous with the other appendages. Note that three joints are interposed between the body and the two branches or flagella of each antennule, while but two joints are found in the protopodite of a true biramous appendage. 18. While the walking legs of the crayfish are not biram- ous in any stage of their development there are indications that they are biramous appendages which have lost the exopodite. The crayfish is a near relative of the lobster, but the develop- ment of the crayfish has been greatly shortened so that the young, when hatched from the egg, resembles the parent. On the other hand the lobster passes through a distinct series of free- living larval stages before acquiring the general body form of the adult. In these larval stages of the lobster the walking legs are typical biramous appendages made up of protopodite, exopodite, and endopodite. During later development, the exopodite dis- appears, leaving only protopodite and endopodite for each walk- ing leg. These same parts are recognized in the walking legs of the crayfish. 82 ZOOLOGY DIEECTIOXS Kemove the walking legs and study to secure data for com- pleting the table but no drawings are required. 19. The genital openings of the male occur on the basal segment of the fifth pair of Avalking legs, while those of the fe- male occur in a similar portion on the third pair of walking legs. Note that the first two pairs of abdominal appendages are dif- ferent in the two sexes. Examine both sexes but no drawings are required. 20. In the male the first two pairs of abdominal appendages are highly modified for use in copulation and are not easily hom- ologized. When at rest they lie in a groove directed forward be- tween the bases of the walking legs. In the female, the first pair of abdominal appendages is also modified. In the table asked for under section 9, do not try to work out the homologies for these modified structures of the first two or first abdominal ap- pendages. IV. Internal Organs Circulatory System 1. With scissors cut away the dorsal surface of the carapace, by two cuts which extend from the hind margin for- ward toward the eyes, and connect anteriorly by a transverse cut. Do not injure the underlying parts when removing the cut part of the carapace. 2. Remove the delicate skin along the median line and expose the pericardial sinus. This cavity receives the purified blood from the gills. 3. The heart, which lies within the pericardial sinus, is a thick-walled muscular organ. It receives the blood from the sinus by three pairs of valvular apertures, the ostia. 4. What is the function of the circulatory system? Notes required. 5. Five vessels pass anteriorly from the heart. The median one is the opthalmic artery. On either side of this is an CEAYFISH 83 antennary artery. The hepatic arteries are given off just poster- ior to and ventral to the antennary artery. Posteriorly from the heart runs the dorsal addominal artery from which the sternal artery passes to the ventral surface of the body. This is an open circulatory system because in the tissues of the body the blood leaves the capillaries and finds its way back to the heart by a series of spaces called the sinuses. 6. Draw side view of heart and main branches of circula- tory system. Reproductive Organs the female 1. The ovary lies below the pericardial sinus, and fre- quently contains conspicuous eggs. There are two anterior lohes and a median posterior lohe. 2. From the lower side of the ovary trace the large oviduct downward to the external openings on the basal segment of the third pair of walking legs. 3. On the external surface upon the median line between the fourth and fifth pairs of walking legs observe the annulus ventralis. Following copulation sperm is stored in this until the time for egg laying. THE MALE 1. The testes lie immediately below the pericardial sinus. They consist of two anterior lobes and one median posterior lobe. 2. The vas deferens is a long coiled tube extending along the side of the body, from the lower part of each testis to the genital opening, in the basal joint of the fifth walking leg. Before the breeding season has passed the vas deferens will be filled with a white mass of sperm. 3. Reexamine the appendages of the first and second ab- dominal segments, as it is by their aid that a tube is formed which conducts the sperm from the genital openings of the male ZOOLOGY I)I}?ECTIONS to the annulus veniraHs of the female. Make a drawing of the reproductive organs of your specimen. See demonstration specimen of female crayfish carrying eggs on the swimmerets. The eggs, after fertilization, become attached to the swimmerets where they undergo development. Digestive System 1. The digestive tube extends from the mouth to the anus. The liver (or more correctly the hepato-pancrcas) is a large bilobed organ which lies below the ovaries or testes. These lobes lie along either side of the digestive tube. Each lobe connects by a duct with the main digestive tube. 2. Turn the animal over and on the ventral side examine the mouth between the jaw^s. Insert a probe into the mouth. 3. A short wide passage, the esophagus, leads upward from the mouth. 4. The esophagus leads to a large dilated portion of the canal, the stomach. This occupies the main portion of the head region. The larger cardiac chamber lies in front and the smaller pyloric chamber lies behind. The two are separated by a nar- row constriction. 5. The region of the mouth, esophagus, and the stomach are lined with chitin and are formed by an infolding of the outer skin of the animal as it develops. These parts are collectively known as the fore-gut. 6. Posterior to the fore-gut is the mesenteron or mid- gut. This part lacks the chitinous lining and receives the ducts from the liver. 7. The hind-gut, which leads to the anus is the part of the digestive tube behind the mesenteron. Trace its course. This develops from an infolding of the outer surface and is lined with chitin. CRAYFISH 85 8. Make a drawing twice natural size of a side view of the entire digestive system. Label all the parts. 9. Remove the stomach. Cut longitudinally through the ventral Avail and examine the interior after pinning it out ex- panded. Examine the hard, tooth-like structures which make up the gastric mill. Distinguish the cardiac and pyloric chambers, and the constricted region of the gastric mill. What do you in- fer to be the main function of this mechanism? Note required. 10. The cardiac ossicle is a hard plate running across the roof of the cardiac chamber. 11. The median tooth is at the junction of the pyloric and cardiac chambers. Note the lateral teeth. 12. Manipulate these teeth to see how they crush the food. 13. The aperture between the cardiac and pyloric chambers is much narrowed by folds, as is also the entire pyloric chamber. These folds are fringed with hairs so that they form a strainer or filter which prevents the passage of large food particles into the intestine. Make drawing of gastric mill as dissected. 14. Manipulate the mandibles and learn where the large muscles are attached. Distinguish the tendons. Nervous System 1. The central nervous system consists of a chain of paired ganglia extending the length of the body close to the mid-ventral line. The ganglia of a pair are so closely applied that they ap- pear as a single ganglionic mass. Locate the nerve chain near the base of the abdomen. Trace it forward along the floor of the thorax to a point where it enters a small canal. With a pair of forceps pick away the parts of the endophragmal skeleton which form the canal surrounding the nerve chain. 2. The brain is a rather large white body just behind and above the bases of the antennules. This supplies nerves to the eyes, antennae, and antennules. 86 ZOOLOGY DIEECTIONS 3. The para-esophageaJ connectives are a pair of nerve cords which connect the brain, around the esophagus with the hinder part of the nervous system. Behind the esophagus they are connected by a transverse commissure. 4. The post-esophageal mass lies behind the mouth. It supplies the mandibles, maxillae, and first and second maxilli- peds with nerves. 5. The thoracic nerve chain consists of six ganglionic masses, which supply nerves to the third maxillipeds and the five pairs of walking legs. The first one lies very close behind the post-esophageal mass. 6. Trace the ahdoviinal nerve chain with its six ganglionic masses. 7. Make a drawing to show the nervous system and label all parts. 8. A statocyst occurs on the dorsal surface of the basal joint of each antennule. Remove the rostrum and locate opening of statocyst by means of a blunt probe. Excretory System 1. The kidneys or green glands lie in the ventral part of the head anterior to the mouth. Each kidney connects with the exterior on the posterior surface of the tubercle located upon the basal segment of the antenna. REFERENCES Andrews, E. A., 1906. The Keeping and Rearing of Crawfish for Class Use. Nature-Study Review: Vol. 2, pp. 296- 301. Herrick, F. H., 1911. Natural History of the American Lobster. Bull. U. S. Bureau Fisheries 29. STARFISH (asterias) Classification: — Phylum Echinodermata. Class Asteroidea. The preserved starfish is rigid and the arms are immotile but in the living animal the arms are flexible and capable of movement in all directions. The starfish is even able to tvirn completely over because of the mobility of its arms and in feed- ing, the arms enfold the mussel or other animal that is being devoured. The vivid colors characteristic of the living starfish are also lost in the preserved specimen. The starfish will be studied as a representative animal in which the organs are repeated, more or less perfectly, about a central axis, and therefore it is said to be radially symmetrical. During this study look for structures which prevent the starfish from being a perfectly radial animal. As this kind of animal differs so much in structure from the other animals you have studied it will be very important to keep in mind the functions of the different organs, as functional relations to other animals are more readily understood than its structural relations. The entire study, including the dissection, must he made from a single specimen. I. External Characters 1. Observe that the body is composed of a central disc from which the five rays or arms radiate. 2. Examine the two surfaces of the disc. The mouth is located in the center of one surface which is therefore named the ora^ surface. Most of the ahoral surface of the disc is covered with sharp spines except for a small rounded area be- tween the bases of two rays. The spineless region is termed the madreporite or sieve plate. 87 88 ZOOLOGY DIIiECTIONS 3. Examine madreporite with hand lens. Draw. X5. 4. For convenience of description, the two rays between which the madreporite is located are termed the hivlum, while the remaining three are the trivium. The central ray of the trivium (the ray directly opposite the madreporite) is called the anterior ray. 5. Place a specimen, ahoral surface uppermost, in suffi- cient water to cover it. The small, soft projections which cover the body wall between the spines are the gills. Each gill is a hollow finger-like process whose cavity is directly continuous with the body cavity. Sea water bathing the outer surface of the gills provides the means of respiration, for the gills and the body cavity are filled with the body fluids. 6. The pediceUariae, small pincer-like organs, protect the animal, and especially the gills, from injury and remove debris. They are especially abundant about the bases of the spines. Find them. Examine a prepared slide of pediceUariae under the mi- croscope. Find and draw two distinct kinds. In the larger type the basal portion is a distinct piece upon which the two jaws are hinged while in the smaller type the basal parts of the two jaws cross over each other like the handles of a pair of shears or tongs. 7. A line drawn from the center of the disc along the middle of an arm is a radius. One drawn from the same point exactly between two arms is an inter-radius. Do all radii inter- sect similar parts. All inter-radii? Are radii or inter-radii marked in any way on the aboral surface of animal? Notes required. 8. Make an outline drawing of the aboral surface show- ing details on the disc and a portion of one ray only, 9. With the oral surface uppermost notice : — The mouth. Position? Size? Is its margin smooth or rough? Note the clusters of spines projecting over it. Are they radial or inter-radial ? STAEFISH 89 The peristome or membrane surrounding the mouth is only imperfectly observable from the oral surface. Note this mem- brane again after the dissection has been made under section 8 of the Digestive System. The amhulaci^al grooves. One runs outward along the ven- tral surface of each ray. They contain : — The amhulacral feet or tuhe feet. Note their terminal suckers. 10. Draw the oral surface showing details of the disc and one ray. In determining the arrangement of the tube feet pull off the feet from a portion of one groove and note the openings from which the feet protrude. II. Internal Organs Kemove, under direction, the aboral wall of the anterior ray and the disc, being very careful to leave undisturbed those portions directly beneath the wall of the disc and in the vicinity of the madreporic plate. The Digestive System Note how the pyloric ceca are attached to the aboral walls of the arms and how the stomach is attached to the aboral wall of the disc. Note further : 1. Intestine, a very short tube, extending from pyloric sac to the anus. The anus is vestigal and cannot be seen from the aboral surface. 2. Intestinal ceca opening into the intestine. How many lobes ? It is doubtful if these ceca have any digestive function. Recent experiments have shown that the intestinal ceca pulsate and it is suggested that they may have a respiratory function. 3. The pyloric cecum is the conspicuous two-branched structure occupying most of the space within each ray. This 90 ZOOLOGY DIEECTIOXS organ produces digestive fluids. At its inner end each cecum is attached to the pyloric chamber of the stomach. 4. Pyloric sac or stomach. Shape ? Position ? How at- tached to body wall? How many and what openings from it? Into it ? {Extensor muscles of rays. Situated in the center of the lower face or aboral wall of each ray. What movement can be produced by their contraction?) 5. Cardiac division of the stomach. Remove the eeca from two adjacent rays and under the corner of the pyloric sac note one of the five cardiac pouches, the union of which makes the cardiac stomach. 6. Stomach retractor muscles. There are two to each pouch. Attachments? What effect would their contraction have ? Notes required. 7. Esophagus. Cut two of the stomach retractors and raise up the pouches so as to expose the esophagus. 8. Persitome or membrane around the mouth. Expose from inside. 9. Make a careful drawing showing the digestive system from aboral surface. 10. Study the chart and your specimen to make out the relations of the organs in side view. Reproduction The sexes are distinct. Have the gonads pointed out to you. Number in each ray? Position, Form? Examine with lens. Their ducts may be traced into the inter-radial partitions whence they pass up to the openings on the upper surface of the rays. Their external openings are very difficult to demon- strate. Starfishes live only in the oceans where their germ cells STAEFISH 91 are discharged directly into the water. Here development takes place resulting in the formation of minute larvae in no manner resembling the adult .starfish. The adult form is reached only through a complicated metamorphosis of the free-swimming larval stage. Nervous System Pull oE all the tube feet and interambulacral spines from one ray and note : — 1. The radial nerves, one at the bottom of each ambulacral groove. Trace it down to the peristome and find its connection with — 2. The circum-oral nerve ring. 3. Each radial nerve ends at the tip of the ray in an eye spot which is brightly colored in living animals but usually inconspicuous in preserved specimens. 4. Make a diagram of the nervous system. • Water Vascular System 1. The stone canal extends down from the sieve or madre- poric plate. Shape? Nature of it walls? Connection of its lower end with the ri7ig canal? 2. Amhulacral or tube feet. Position? 3. Ampullae. Occur inside the body cavity. Number of rows ? Are they connected with tube feet ? 4. Badial canals or ivatcr tnhcs. One on the aboral side of each radial nerve band. Expose one by scraping away a radial nerve. 5. Make out the connections between the different parts of the water vascular sj^stem. 6. Can you think of possible uses for it ? State j^our views 92 ZOOLOGY DIRECTIONS and have them criticized before incorporating them in your notes. How does the animal crawl? Notes required. 7. Draw the water vascular system of the disc and one ray. REFERENCES ■Coe, W. R., 1912. Echinoderms of Connecticut. Conn. Geol. and Nat. Hist, Survey, Bull. 19. Jennings, H. S., 1907. Behavior of the Starfish Asterias forreri. Uni. Calif. Pub. Zool. 4. Bull. U. S. Fish Coram, for 1899, 103-244. Mead, A. D., 1900. The Natural History of the Starfish. <^%^^ (ujIlisraryUxj fresh- water mussel %^^-w (Materials: aquaria, carmine suspension.) "v^ |^ )^ Classification : — Phylum Mollusca, Class Acephala. The mussel is studied as an example of a highly developed group of animals which are entirely without segmentation. Despite the very great diversity of size and form among the numerous species and genera of mussels, all follow the same plan of structure closely enough to permit the application of the fol- lowing outline of study to any of the common species found in our lakes and streams. I. The Live Animal 1. Note the general appearance and position of the animal when fully extended. 2. Identify the fleshy foot, and the tivo valves which com- prise the shell. Note the gaping valves caused by the tension of the hinge ligament. 3. The foot projects from the lower (ventral) anterior part of the shell and the hinge line is on the dorm.l surface. 4. At the posterior end of the animal distinguish the in- halent aperture by means of carmine suspension. Determine the function of this opening. Is there an exhalent aperture? If so, give the evidence for this. Notes required. 5. Examine the demonstration of a fragment of a gill under the microscope and observe the movement of the cilia. How is the water current produced? What are its main functions? The food of the mussles consists primarily of microscopic plant forms (plankton) and particles of organic matter suspended in the water. 6. Make an outline drawing, natural size, of the expanded condition of the animal and name all parts. 93 94 ZOOLOGY DIRECTIONS 7. From an assistant loarn how to cut the adductor muscles. Cut free the mantle from the pallial line and remove the left valve of the shell. 8. Below the hinge line of the shell is found a slowly pul- sating organ, the heart. Carefully cut through the surrounding pericardium, and expose the heart. Distinguish the median ven- tricle and the lateral auricles, the left one being uppermost. 9. Examine the left valve of the shell and distinguish the scars on the valve where the anterior and posterior adductor muscles were attached. 10. Examine the pallial line and note the corresponding part of the mantle. The mantle muscle and its mode of attach- ment may be seen on the right side of the animal. Compress the margin of the right mantle. What is the effect ? What is the function of the mantle muscle? Notes required. 11. Distinguish the umbo near the anterior part of hinge ligament. This is the older part of the shell, and concentric with this are the lines of growth. How are these formed? What do they indicate? Where is the newest part of the shell? II. The External Characters of the Soft Parts 1. Examine the soft parts of the mussel on the "half shell." Compare the cut muscles on the body with the scars on the shell, and also with those yet in place on the right side. Distinguish the following muscles and their scars : (a) The large anterior adductor, near the dorsal an- terior end. Posterior to this is a pair of muscles: — (b) The anterior retractor is the upper or dorsal one; (c) The protractor is the lower or ventral one. The protractor compresses the viscal m,ass and forces the foot from the shell. Determine the functions of the other muscles. At the posterior end are : (d) The large posterior adductor. FEESHWATER MUSSEL 95 (e) Dorsal and anterior to the preceding is the pos- terior retractor. (f) The mantle muscle is attached along the pallial line. 2. Note the right and left mantle lohes and their relation to one another. 8. Note the inhalcnt and exhalcnt apertures and the mar- gins of the mantle in this region. 4. Fold back the left mantle lohe and distinguish the two gills just beneath the mantle ; the foot, a heavy muscular struc- ture ; the visceral mass, the enlarged region dorsal to the foot ; the lahial palpi, two small triangular flaps at the anterior end of the body. 5. Make an outline drawing of the left side with the shell and mantle removed, to show the relation of parts. Label all parts. 6. Pass the probe into the exhalent aperture and note the cavity, the cloaca, which lies above the bases of gills and pos- terior to the posterior adductor muscles. Above the muscles is the anal opening of the intestine. The portion of the intestine leading to the anus is the rectum,. 7. Insert a probe into the mouth, which lies between the anterior adductor muscle and the anterior edge of the foot. De- termine the relation of outer and inner pair of palpi to the mouth. 8. Determine the relation of the two pairs of gills to one another. The gills ma^' be distended with eggs and larvae in some specimens. Locate the supra-brancliial chamber and de- termine its relation to the exhalent aperture. III. Examination of Cross Sections 1. Cut a section, about i/4 i^^ch thick, obliquely through the anterior part of the pericardial cavity and the foot. Distinguish ^6 ZOOLOGY DIEECTIONS the mantle, gills, visceral mass, intestine, foot, rectum and its typhlosole, and ureter. Draw and label all the parts. 2. Make a similar section through the region of the pos- terior adductor. Determine the relation of the suprabranchial chamber. Draw. IV. Economic Importance and Reproduction Freshwater mussels are of especial importance because of the use of many varieties in the manufacture of pearl buttons and novelties. In many localities in North America, the species of most value in the industries have become practically extermin- ated as a consequence of continued fishing operations. Practically all of the freshwater mussels (excepting the minute finger-nail shells) undergo a complicated development. The fertilized eggs are retained by the parents in a modified portion of the gills termed the marsupium. There they un- dergo development resulting in the formation of a larval stage known as a glochidium. This larva is unable to develop inde- pendently upon leaving the parent. Completion of the life cycle is possible only for the individuals which become at- tached to the fins or gills of a suitable fish. Not all fish may serve in this capacity. At the close of the parasitic stage the young mussel drops off from its host and undergoes its final growth to adult condition as a free animal at the bottom of the stream or lake. REFERENCES Brooks, W. K., 1882. Handbook of Invertebrate Zoology. S. E. Cassino, Boston. Coker, Robert E., 1919. Fresh-water Mussels and Mussel In- dustries of the United States. Bull. Bureau of Fisheries, 36:13-89. Lefevre, G. and Curtis, W. C, 1910. Studies of the Reproduc- tion and Artificial Propogation of Fresh- Water Mussels. Bull. U. S. Bureau Fisheries, 30. Simpson, C. T., 1899. The Pearly Fresh- Water Mussels of the United States. Bull. U. S. Fish Comm. for 1898, pp. 279- 288. GLOSSARY Ahoral surface — The surface opposite the one bearing the mouth. Ambulacral area — The series of skeletal plates bearing the open- ings through which the tube feet protrude. AmpuUae — Small, sac-like reservoirs connected with the tube feet of echinoderms ; located inside the body cavity. Anterior — That part of the body normally directed forward in locomotion. Anus — The posterior opening of the alimentary canal for the discharge of waste. Asexual reproduction — Any form of reproduction not involving the functioning of germ cells. Asymmetrical — Parts of the body arranged irregularly so that no plane could divide the body into equal parts with corre- sponding structures on the two sides of the plane. Bilaterally symmetrical — Parts of the body evenly disposed on the two sides of a plane which passes through the chief axis of the body. One-half of the body is the mirror image of the other half. Bivalve — A shell composed of two approximately equal parts hinged one on the other. Blastula — That stage in the development of a fertilized egg when the cells resulting from cleavage become arranged in a single layer usually surrounding a cavity. Budding — A method of asexual reproduction in which a small portion of the body gives rise to a new individual. Carapace — The shell covering the dorsal and lateral surfaces of head and thorax of a crayfish. Caudal — Located at the posterior tip of the abdomen. 97 98 ZOOLOGY DIEECTIONS Cephalothorax — A term applied to the anterior part of the body of an animal in which head and thorax are not separated from one another. Chela — The large claw of a crustacean. Cheliped — The crustacean leg bearing the chela or large pincher. Cleavage — The division of a cell following the division of the nucleus. Cloaca — The posterior region of an alimentary canal that holds the waste from the digestive and excretory organs. Coelenteric cavity — The single cavity of the body of a coelente- rate which at the same time serves as body cavity and di- gestive cavity. Conjugation — The fusion of two protozoans for an exchange of cytoplasm or of nuclear material. Cuticula — A thin, non-cellular body covering of many inverte- brates. Differentiation— The specialization of a group of cells for a definite, restricted function. Dorsal—' ' The back ; " or more strictly the part of the body di- rected away from the surface upon which the animal nor- mally rests. Elytra^The horny outer wings of the Coleoptera. Epipodite — In the crayfish, a membranous projection from the protopodite extending into the gill chamber. Fertilization— The fusion of two gametes to form a single cell, the zygote. Fission — A method of asexual reproduction in which the body of an individual becomes split into two equal parts. Gastrula— That stage in the development of a new individual GLOSSARY 99 from a fertilized egg in which the cells resulting from cleav- age become arranged in two layers. Gamete — A reproductive cell. Invasion — A term used in ecology to donate the entrance of new species into a habitat, usually due to changes produced by species already present. Labium — The lower lip of an arthropod. Larva — A young, free-living animal which has not yet completed its development. Lateral — Of or pertaining to the side of the body. Left — The lateral surfaces of any animal's body are determined by placing the animal in a position comparable to the posi- tion of the observer (i.e., with the anterior end uppermost and with the dorsal surface toward the observer). Then left and right of the animal correspond directly to left and right of the observer. Longitudinal section — A section taken to include the main axis of the body or parallel to the main axis. Madreporic plate — A finely perforated disc at the external open- ing of the water vascular system of echinoderms serving to keep out foreign matter. Matrix — A non-protoplasmic substance in which the cells of some tissues are embedded. Metamorphosis — A marked change in an animal between the time of hatching from the egg and acquiring adult bodj^ form, involving the loss of some structures characteristic of the larva and the acquisition of new structures charac- teristic of the mature adult. Metazoa — "Many-celled animals;" all animals higher than the Protozoa. Nymph — The young of those insects which at the time of hatch- 100 ZOOLOGY DIRECTIONS ing resemble the adult except for the lack of certain adult organs. The young of insects having incomplete metamor- phosis. Optical section — The reconstruction of what a slice through an object would look like. Oral surface — The surface on which the mouth is located. Organ — A group of cells or tissues which together perform some specific function. Parthenogenesis — Reproduction through unfertilized eggs. Parthenogenetic colony — A colony carrying germ cells which de- velop without fertilization. Pellicle — A thin, non-living cell wall covering the body of most Protozoa. Plane of symmetry — Any plane which passed through an object divides the object into two parts of corresponding size and form. Posterior — At or toward the hinder end of the body. Prolegs — Larval legs, without joints, upon the abdomen of some insect larvae. Pseudopodium — Temporary protoplasmic process thrust out from membraneless cells. Pupa — The inactive stage between the larva and adult of insects having a complete metamorphosis. Radially symmetrical — Having the parts of the body repeated around a central axis like the spokes of a wheel. Rayed fin — A fin, the membrane of which is supported by a series of spines or 'rays.' Right — (See definition of left.) Regeneration — The power of an organism to replace a lost part. GLOSSAEY 101 Rudimentary — Any organ or structure which has not yet reached its full development. Segm.ent — One of the successively repeated units of the body of a jointed animal. Seta — (pi. setae) : stiff "hairs" or bristles. Somatic — Pertaining to the body cells as contrasted with the reproductive cells. Somite — One of the divisions of the body of a segmented animal. Spiracles — External openings of the respiratory system of in- sects. Stalked — Extending beyond the margin of the body at the tip of a stalk. Stipple- — A method of portraying structure by the use of fine dots. Succeed — (See succession.) Succession — A term used in ecology to indicate the change in species present at any one point due to changes produced by organisms there or due to physiographic causes. Symmetrical — Parts of the body arranged in regular order with reference to one or more axes or planes. Tarsal claws — One or more claws or hooks at the end of an in- sect's foot. Tarsus — (pi. tarsi) : the foot. Thorax — In arthropods and vertebrates, that part of the body between the head and abdomen, usually bearing appendages. Tissue — A group of similarly differentiated cells. Tracheae — Air tubes within the body of an insect, serving for respiration. 102 ZOOLOGY DIRECTIONS Transverse section — A section taken at right angles to the main axis of the body. Trlchocysts — Minute, rod-like refractive bodies in ectoplasm of some ciliates. Umbo — The protuberance of a bivalve shell above the hinge liga- ment. Ventral — "The under side of the body;" or more strictly that part of the body directed toward the surface upon which the animal walks or comes to rest. Vertical section — A section running from dorsal to ventral sur- face through the main or chief axis of the body. Vestigial — Any organ or structure which never reaches full de- velopment and is consequently without function. Wing-pads — Rudimentary, sac-like wings on the thorax of many nymphs. X — preceding a number, indicates the number of times your drawing is to be greater than the dimensions of the original specimen. Zooid — One of the individuals in a united colony of animals. Zygote — A single cell resulting from the fusion of two gametes. Marriott & Miles, Printers Charapaifen, Illinois