: BIOLOGY ft G A LABORATORY MANUAL OF INVERTEBRATE ZOOLOGY BY OILMAN A. DREW, PH.D. ASSISTANT DIRECTOR OF THE MARINE BIOLOGICAL LABORATORY, WOODS HOLE, MASSACHUSETTS WITH THE AID OF FORMER AND PRESENT MEMBERS OF THE ZOOLOGICAL STAFF OF INSTRUCTORS AT THE MARINE BIOLOGICAL LABORATORY WOODS HOLE, MASS. SECOND EDITION, PHILADELPHIA AND LONDON W. B. SAUNDERS COMPANY 1913 D7 2JOUX2X* -. -••; -'• G Copyright, 1907, by W. B. Saunders Company. Revised, reprinted, and recopyrighted July, 1913 Copyright, 1913, by W. B. Saunders Company *N* PRINTED IN AMERICA PRESS OF PHILADELPHIA PREFACE TO THE SECOND EDITION THIS edition contains descriptions for the study of a few forms and a rather simple literature list that were not included in the first edition. There has been no attempt to make the literature list at all complete, but it seems desirable to refer students to some of the available papers, for by consulting them in connection with their laboratory work they become acquainted with methods of work and develop the spirit of research that is the beginning of real understanding. Certain text-books should be used freely for reference. These have not been mentioned under the special heads, as they apply to practically all groups. Among these may be men- tioned Parker and HaswelPs "Text-book of Zoology/' Macmil- lan; Lankester's "A Treatise on Zoology/' Black; Harmer and Shipley's "The Cambridge Natural History," Macmillan; Lang's "Lehrbuch der Vergleichenden Anatomie," Fischer; or the English translation, Macmillan; Korschelt and Heider's "Lehrbuch der Vergleichenden Entwicklungsgeschichte/' Fis- cher; or the English translation, Macmillan; and Delage et Herouard's "Traite de Zoologie Concrete," Schmidt. For the many suggestions and criticisms from zoological friends the author is deeply grateful. To Dr. Lorande L. Woodruff, who has given much attention to the revision of the Protozoa, and to Dr. Winterton C. Curtis and Dr. Caswell Grave, who, with the men associated with them as instructors in the Zoology Course at the Marine Biological Laboratory, have given much attention to corrections and additions through- out the manual, special acknowledgments are due, for they have not only saved the author much labor, but have added mate- rially to the value of the revision. THE AUTHOR. July, 1913. iii 313810 PREFACE. THE present manual has for its basis a set of laboratory direc- tions prepared by members of the staff of instructors to meet the needs of the class in general zoology at the Marine Biolog- ical Laboratory of Woods Hole, Massachusetts. Those who were associated with me in the preparation of the first notes were Dr. Robert W. Hall, Dr. James H. McGregor, Mr. Robert A. Budington and Dr. Caswell Grave. Other members of the staff who have either aided me in modifying the original notes or who have added others are Dr. Winterton C. Curtis, Dr. D. H. Tennant, Dr. Otto C. Glaser, Dr. Grant Smith, Dr. John H. McClellan and Dr. Lorande L. Woodruff. Each year for the past six years the directions have been changed where experi- ences indicated changes should be made. Probably few instructors will find it desirable for their stu- dents to follow closely all that is given in this manual, but it has seemed better to arrange the matter in a logical order, and in some of the forms to call attention to only the important points of anatomy or adaptation, than to try to make the directions for each form complete in themselves. To make the directions for each form complete would necessarily add much labor for the student and would, by the repetition of well-known facts, tend to blunt some of the new and important points to be gained. The type method of laboratory study has for many years been the prevailing method, but care needs to be exercised to keep students from making everything conform to type, and in lead- ing them to see the wonderful adaptations that fit the different animals for their particular lives. The manual is not intended to lead students to a knowledge of comparative anatomy alone, but to an appreciation of adaptation as well. It has fallen on me year by year to see that desirable changes were made in the directions, and it has finally been my lot to put them into their present form, but much of the credit be- longs to the men who have been associated with me in the instruction work at the Marine Biological Laboratory. THE AUTHOR. CONTENTS. PAOD PROTOZOA 1 RHIZOPODA 3 Amoeba proteus 3 Foraminif era 5 Actinosphserium or Actinophrys 6 MASTIQOPHORA 7 Euglena 7 Volvox 8 Ceratium 9 Noctiluca 0 SPOROZOA 10 Gregarina 10 INFUSORIA 11 Paramaecium 11 Spirostomum 12 Vorticella 13 Oxytricha 14 Euplotes 15 PORIFERA. 17 Grantia 18 CCELENTERATA 22 HYDROZOA 24 Hydra (Fresh-water Polyp) 24 Obelia 26 Parypha 28 Gonionemus 29 Hydrocorallina 31 Siphonophora 31 SCYPHOZOA 32 Aurelia 32 ACTINOZOA 34 Metridium (Sea-Anemone) 34 CTENOPHORA 37 Mnemiopsis 37 PLATYHELMINTHES 39 TURBELLARIA 40 Planaria maculata 40 Bdelloura or Syncoelidium 41 TREMATODA 44 Hsematolcechus (Distomum) 44 CESTODA 46 Crossobothrium laciniatum . . 46 Vlll CONTENTS. PLATYHELMINTHES (Continued). PAOB NEMERTINEA 49 Tetrastemma 49 NEMATHELMINTHES 51 Ascaris 51 Trichina 52 TROCHELMINTHES 54 ROTIFERA 54 Brachionus (A Rotifer) 54 MOLLUSCOIDA 56 POLYZOA 56 Bugula 56 Plumatella 58 BBACHIOPODA 58 Terebratulina 58 ECHINODERMATA 60 ASTEROIDEA 61 Asterias (Starfish) 61 OPHIUROIDEA 67 ^ Ophiura (Serpent-Star) 67 /ECHINOIDEA 68 1 _ Strongvlocentrotus (Sea-Urchin) 68 HOLOTHUROIDEA ~~'. . . . 74 Thyone (Sea-Cucumber) 74 ANNELIDA 78 CH^BTOPODA 79 Nereis virens (Clam-Worm) 79 Lumbricus (Earthworm) 82 Autplytus cornutus 88 Lepidonotus squamatus 89 Diopatra cuprea 90 Chsetopterus 90 Amphitrite ornata 91 Cistenides gouldii 92 Clymenella torquata 92 Arenicola cristata 93 Sabella microphthalma 93 Hydroides 94 Spirorbis borealis 94 GEPHYREA 95 Phascolosoma 95 MOLLUSCA 97 LAMELLIBRANCHIATA 99 Venus mercenaria (Quahog) 99 Yoldia limatula 107 Mytilus or Modiola (Mussels) 109 Pecten irradians (Scallop) 110 Ostrea virginiana (Oyster) Ill Solenomya 112 Mya arenaria (Long Clam) 112 Ensis directus (Razor-shell Clam) , 113 CONTENTS. IX MOLLUSCA (Continued). AMPHINEURA ............................................... 115 Chsetopleura ..... . ..................................... 115 GASTROPODA ......................... . ..................... 116 Fulgur (Sycotypus) .............. ....................... 116 CEPHALOPODA ............................................. 124 Loligo pealii (Squid) .................................... 124 ARTHROPODA ............................................... 133 CRUSTACEA ................................................ 137 Homarus americanus (Lobster) ........................... 137 Callinectea hastatus (Blue Crab) ......................... 144 Eupagurus (Hermit Crab) ............................... 148 Hippa (Sand Mole) ..................................... 148 Squilla ................................................ 149 Mysis ................................................. 151 Talorchestia (Beach-Flea) ............................... 151 Porcellio or Oniscus (Sow-Bug) .......................... 152 Caprella ............................................... 153 Branchipus (Fairy Shrimp) .............................. 153 Daphnia ............................................... 154 Cyclops (Water-Flea) ................................... 155 Argulus (Fish-Louse) ................................... 156 Lepas (Goose-Barnacle) ................................. 156 ARACHNOIDEA ............................................. 158 Limulus (Horseshoe Crab) .............................. 158 Buthus (Scorpion) ...................................... 159 Epeira (Round-Web Spider) ............................. 160 Phoxichilidium ......................................... 162 MYRIAPODA ................................................ 163 Lithobius (Centipede, Earwig) ........................... 163 Julus (Thousand-legs) .................................. 164 INSECTA ................................................... 164 Acridium (Grasshopper) ................................. 164 Apis mellifica (Honey-Bee) .............................. 170 CHORDATA .................................................. 174 UROCHORDA ............................................... 175 Dolichoglossus (Balanoglossus) ........................... 175 Molgula manhattensis .................................. 176 Perophora ............................................. 180 Botryllus .............. ................................ 180 Amaro3cium (Sea-Pork) ................................. 181 Salpa cordif ormis ...................................... 183 ACRANIA .................................................. 185 Amphioxus lanceolatus .................................. 185 NOTES FOR GUIDANCE IN MAKING PERMANENT PREPA- RATIONS .................................................. 187 GLOSSARY ...................... ............................. 193 INDEX.. . 207 INVERTEBRATE ZOOLOGY. PROTOZOA* Unicellular Animals. CLASS 1. Rhizopoda. With changeable pseudopodia during adult life. Reproduction by simple division and by spore- formation. Subclass 1. Amoebina. With lobose pseudopodia. (Amoeba, Arcella, Difflugia.) Subclass 2. Foraminifera. With fine branching and anastomosing pseudo- podia. Shells, when present, usually calcare- ous. (Lecythium, Globigerina.) Subclass 3. Heliozoa. Typically spherical in form. The pseudopodia, which radiate from the entire surface of the body, are ray-like, seldom changeable, and usually possess an axial filament. (Actino- phrys, Actinosphserium, Clathrulina.) Subclass 4. Radiolaria. With ray-like pseudopodia, and with a chitinous capsule inclosing the nuclei. The skeleton, when present, is formed of silica or acanthin. All are marine. (Thallassicolla.) CLASS 2. Mastigophora. Motile organs in the form of flagella. Repro- duction by longitudinal division. Colony for- mation is frequent. Subclass 1. Flagellidia. With a definite anterior end on which there are one or more flagella. The members of one order (Choanoflagellida) have one or more collar-like 1 1 . processes about the base of the single flagellum. (Mastigamceba, Trypanosoma, Euglena, Pera- nema, Prpterospongia.) Subclass 2. Dinoflagellidia. Usually with two flagella, one encircling and the other directed away from the body. (Peri- dinium, Ceratium.) Subclass 3. Cystoflagellidia. With two flagella, one of which is modified into a "tentacle," while the other is short and con- tained within the gullet. (Noctiluca.) CLASS 3. Sporozoa. Without flagella or cilia in the adult period of the life-cycle. Reproduction is by spore-form- ation. All are endoparasites. Subclass 1. Telosporidia. Sporulation phase of the life-cycle is distinct from and follows the trophic phase. Order 1. Gregarinida. The young stages are intracellular parasites, while the adults are free and motile in the di- gestive tract or body-cavity of the host. Sporulation occurs within a cyst during the free period of the life-cycle. (Gregarina.) Order 2. Coccidiidia. Without a free and motile adult stage. Sporu- lation occurs within a cyst during the intra- cellular period of the life-cycle. (Coccidium.) Order 3. Hsempsporididia. Living chiefly in the blood-corpuscles of verte- brates. In many forms the entire sexual period of the life-cycle takes place in an inter- mediate host, as the mosquito. (Plasmodium.) Subclass 2. Neosporidia. Sporulation takes place during the trophic phase of the life-cycle. Order 1. Myxosporididia. The initial free stage occurs in the tissues or the cavities of the organs of the host. The adult form is amoeboid. (Myxidium.) Order 2. Microsporidia. Amoeboid trophozoites. Spores very minute and with but one polar capsule. PROTOZOA. 3 Order 3. Sarcosporidia. The initial stage of the life-cycle occurs in the muscle-cells of vertebrates. (Sarcocystis.) CLASS 4. Infusoria. With motile organs in the form of cilia during all or part of the life-cycle. Nucleus dimorphic (macronucleus and micronucleus). Reproduc- tion is by simple transverse division or by bud- ding. Subclass 1. Ciliata. With cilia throughout the life-history. Order 1. Holotrichida. The cilia are of approximately equal length and thickness and equally distributed over the body. Trichocysts are present. (Prorodon, Paramse- cium.) Order 2. Heterotrichida. With a uniform covering of cilia, together with an "adoral zone" formed of cilia fused into membranelles. (Spirostomum, Stentor, Halte- ria.) Order 3. Hypotrichida. The cilia are limited to the ventral surface of a dorso-ventrally flattened body. Cilia often fused into cirri, membranelles, etc. (Oxy- tricha, Pleurotricha, Euplotes, Stylonychia.) Order 4. Peritrichida. More or less bell-shaped in form. Cilia usually reduced to those constituting the adoral zone. (Vorticella, Zoothamnium, Lichnophora.) Subclass 2. Suctoria. Usually possessing cilia only during the embry- onic stages of the life-history. Tentacles adapted for piercing and sucking are present. (Podophrya, Ephelota, Acineta.) Blochmann: Die Mikroscopische Tierwelt des Siisswassers. Abt. 1. Pro- tozoa, 1895. Biitschli: Protozoa. Bronn's Thierreich, 1889. Calkins: Protozoa, 1901. - : Protozoology, 1909. - : Marine Protozoa of Woods Hole. Bui. U. S. Fish. Com., 1901. -- : The Scope of Protozoology. Science, 1911. Conn: Fresh Water Protozoa of Connecticut. Bui. State Nat. Hist. Surv., 1905. d: PROTOZOA. Doflein: Lehrbuch der Protozoenkunde. 3d Auf., 1911. Edmondson: Protozoa of Iowa. Davenport Acad. Sci., 1906. Hartmann: Praktikum der Protozoologie, 1910. Jennings: Behavior of the Lower Organisms, 1906. : Old Age, Death, and Conjugation in the Light of Work on the Lower Organisms. (Harvey Lectures), Pop. Sci. Mo., 1912. Kent: Manual of the Infusoria, 1881. Lankester: Treatise on Zoology. 1. Protozoa. Leidy: Fresh Water Rhizopods of North America, 1879. Minchin: Protozoa, 1912. Prowazek: Einfuhrung in die Physiologic der Einzellgen (Protozoen), 1910. : Taschenbuch der Mikroskopischen der Protistenuntersuchen, 1907. Stokes : Contribution Toward a History of the Fresh Water Infusoria of the United States. Jour. Trenton Nat. Hist. Soc., 1, 1888. Whipple: Microscopy of Drinking Water, 2d ed., 1910. Woodruff: Observations on the Origin and Sequence of the Protozoan Fauna of Hay Infusions. Jour. Exp. Zool., 12, 1912. RHIZOPODA. AMOEBA PROTEUS. Amoebae are usually easily discernible under the low power of the microscope as irregular, semi-transparent, granular bodies. Find a specimen in the material provided, which is known to con- tain amoebae, and determine the following points: 1. With the high power observe the peculiar method of loco- motion, the constant but slow change in the shape of the body by means of projections, pseudopodia, or "false feet." Make sketches at intervals of one or two minutes to show the changes in the form of the body. 2. Observe the peripheral zone of hyaline protoplasm, the ectoplasm, and compare this with the inner protoplasm, the endo- plasm. Observe in detail the formation of a pseudopodium. Does the endoplasm extend into the pseudopodium? Can you explain how the movement is caused? 3. Find a clear space which appears and disappears at inter- vals; this is the contractile vacuole. Determine the length of time between successive contractions. Are the intervals regu- lar? When the vacuole contracts what becomes of the con- tents? What is its function? 4. Note the oval or rounded nucleus moving with the flowing endoplasm. What is its structure? THE FOBAMINIFERA. 5 5. Food materials in process of digestion are readily seen. Of what do they consist? They are contained in gastric vacu- oles. By careful watching, it is often possible to observe the man- ner in which food is ingested and the manner in which the undi- gested matter is egested. Make a careful drawing of an Amoeba. AmoebaB of various kinds represent in many respects the simplest type of protozoan, and are therefore placed in the first class of these animals, the Sarcodina. The individuals of this class all possess pseudopodia, but many are quite unlike those of Amoeba. Look over the figures of various Rhizopoda. If time and material permit, study Amoeba verrucosa, Arcella, and Difflugia, and compare them with Amoeba proteus. Do you understand how the shells of the last two genera are made, and of what service they are? Why are not shells good for all forms? Drawings of these forms are desirable. Calkins: The Fertilization of A. proteus. Biol. Bui., 13, 1907. Bellinger : Locomotion of Amoeba and Allied Forms. Jour. Ex. Zool., 3, 1906. Metcalf : Amoeba Studies. Jour. Ex. Zool., 9, 1910. Mast: Reactions in Amoeba to Light. Jour. Ex. Zool., 9, 1910. Popoff: Ueber den Entwicklungs cyclus von A. minuta. Arch. f. Protist., 22, 1911. THE FORAMINIFERA. With very few exceptions Foraminif era are marine and pro- vided with shells. Empty shells from deep-sea dredgings or from the sand beaches of such islands as the Bermudas may be had for study. Examine them with a low power by reflected light. 1. Carefully examine various shells, compare them with each other and with figures. Notice the great variety in size and shape and determine how the chambers must have been added during growth. 2. Observe a single opening in a shell, and determine whether the general surface has any finer perforations. Be sure to under- stand the relation of the live animal to the shell. Make drawings of several types of shells. Farmer: Foraminif era, pp. 133-139, Lankester's Treatise. Flint: Recent Foraminif era. Rep. U. S. Nat. Mus., 1897. PROTOZOA. ACTINOSPHAERIUM OR ACTINOPHRYS. Find, as usual, with the low power, and increase the magni- fication as occasion demands. 1. Note the many fine radiating pseudopodia. These are quite stiff compared with those of Amceba and for a considerable time show little change, not being pushed out and retracted constantly as in Amceba. Is the animal flat or spherical ? 2. Both ectoplasm and endoplasm are so filled with vacuoles that they present a frothy appearance characteristic of most Heliozoa. The endoplasm of all Protozoa is alveolar in struc- ture, but in Actinosphaerium the vacuoles are exceptionally large, though not as large as those in the ectoplasm. In Ac- tinophrys the endoplasm is not so sharply separated from the ectoplasm. 3. The nucleus of Actinophrys is present in the center of the organism, but it is somewhat difficult to demonstrate in the live animal. In Actinosphaerium there are many nuclei. 4. At some point near the periphery, the contractile vacuole can usually be seen. When it is found notice its action, and immediately after it has contracted look among the pseudopodia of that region for indications of its extruded contents. Draw a specimen, indicating all of the points observed. 5. When the contractile vacuole discharges, or when any foreign body touches the ends of the pseudopodia, notice the way in which this type of pseudopodium is moved. What does this indicate in regard to its structure? How far do the pseudo- podia extend? They may be seen to contain minute granules when studied with the high power and best light. 6. If possible, observe the process of catching food with the tips of the pseudopodia and the manner in which it is drawn toward the body. Note any motion on the surface of the body as the food is drawn closer, and also the manner in which the food is finally ingested. Are there any indications that the pseudopodia extend as still finer filaments beyond the point to which it is possible to trace them with the highest magnifica- EUGLENA. 7 tion at hand? If the capturing of food is observed, make a series of diagrams to illustrate the process. If possible, observe a specimen undergoing division. Draw. It is desirable to examine Clathrulina, noting the stalk and skeleton. Look over figures. R. Hertwig: Ueber die Kernteilung, Richtungskorperbildung und Befruch- tung bei Actinosphserium. Abt. d. Math. Phys. Kl. d. Ak. d. Wiss., Miinchen, 19, 1898. HASTIGOPHORA. EUGLENA. Understand its habitat and with what forms it is usually associated. 1. Observe the free-swimming movements of the organism, and the euglenoid changes in the form of the body. Make drawings showing the changes in the shape of a single in- dividual. 2. Distinguish anterior and posterior ends. Is there any dorso- ventral differentiation? Note the motile organ, the flagel- lum. Where is it attached? What relation does it bear to the gullet? How is it directed during locomotion of the organism. Does it serve any other purpose besides locomotion? (See Doflein, pp. 604, 33 and 207.) 3. The green color of Euglena is due to chlorophyl, and this enables it to live in clear water, being nourished like a typical green plant. (See Minchin, p. 14.) 4. Note the absence of color near the anterior and posterior ends of the organism. Near the anterior end also notice the red pigment spot, or stigma. What is its probable function? 5. Stain a specimen with'iodin and look for the nucleus. It is obscured by the chlorophyl. 6. Observe specimens in the resting stage. Make a drawing showing all of the points observed. Look through the stock cultures for other forms of Masti- gophora, such as Trachelomonas, Peranema, Phacus, etc. It is desirable to make drawings of the different forms. 8 PROTOZOA. Klebs: Ueber die Organisation einiger Flagellatengruppen und ihre Be- ziehungen zu Algen und Infusorien. Unt. Bot. Inst. Tubingen, 1, 1883. : Flagellatenstudien. Zeit f. Wiss. Zool., 55, 1893. Wager: On the Effect of Gravity upon the Movements and Aggregation of Euglena viridis and Other Micro-organisms. Phil. Trans. Roy. Soc., London, Series B, 201, 1911. VOLVOX. Volvox globator is better for study than V. aurens. It may be distinguished from the latter by the larger size of the colony, the greater number of cells that compose it (about 15,000), the angular shape of the individual cells, and the stout connecting processes of protoplasm, into which chromatophores may enter. Observe the movements of colonies in a watch-glass of water, with the naked eye and with a low power of the microscope. 1. Do the colonies tend to collect toward a particular side of the dish? What reason is there for the reaction? 2. Place a number of colonies on a slide with enough water to allow them to be covered without crushing them. Study first with the low and then with the high power and determine the species. Understand the relation of the individual cells to the colony. (See Doflein, p. 222.) Draw a figure showing several cells and their protoplasmic con- nections. 3. Compare in detail an individual cell with Euglena. 4. Observe, if possible, certain cells, called parthenogonidia, which are specialized for asexual reproduction. These divide and form the daughter colonies, which become detached and swim in the interior of the parent colony. They are finally liberated by the rupture of the wall of the parent colony. Make a figure of a parent colony that incloses several daughter colonies of different sizes. 5. V. globator is monoecious. Look for eggs and bundles of spermatozoa. Figure them. 6. Be sure to recognize the significance of the fact that the cells of Volvox are differentiated into somatic and germ cells, CERATIUM. NOCTILTJCA. 9 and to understand the resulting physiological division of labor. (See Calkins, Protozoa, p. 232.) 7. Consider the reasons for and against regarding Volvox and allied organisms as animals rather than plants. Meyer: Ueber den Bau von V. aurens und V. globator. Bot. Cent.. 63. 1895. CERATIUM. 1. Examine this form with a high power, and in a favorable specimen notice the sculptured outer surface of the cellulose test. The living animals are green or brown owing to the pres- ence of chromatophores in the protoplasm. 2. Note the furrow encircling the body. Does it extend completely around it? Is there a short furrow on one side at right angles to the first, or a depression of considerable size? Understand the position of the flagella. Draw the animal, showing the points observed. Look for examples of the earlier stages of division, and of later stages, which appear as chains of fully formed individuals attached together. Kofoid: Mutations in Ceratium. Bui. Mus. Comp. Zool., 52, 1909. NOCTILUCA. If living specimens are not to be had for study, material preserved in alcohol, after suitable fixation, can be used. Spec- imens are best examined in a cell-slide under a cover-glass. 1. Observe the nearly globular shape, and on one side a groove from which arises a large flagellum or " tentacle." Is there a deep groove near it ? At the bottom of this groove it is possible to see the mouth in a living specimen. Another smaller flagellum is visible in living specimens inserted at the bottom of the mouth, but in preserving the organism it is usually destroyed. 2. Note the appearance of the preserved protoplasm. The endoplasm appears parenchymatous. At one point a more com- 10 PROTOZOA. pact mass is seen, from which strands appear to radiate. This has been found to contain the nucleus. Noctiluca is phosphorescent, and frequently causes very bril- liant displays. Make a drawing. Calkins: Nuclear Division in Noctiluca. Jour. Morph., 15, 1899. SPOROZOA. GREGARINA. Remove the head and posterior end of a larval or adult meal beetle and pull out the digestive tract with a pair of for- ceps. Place the digestive tract on a slide, split it open length- wise with a sharp scalpel, and then spread it out, with the inner wall exposed, and cover. The operation should be per- formed rapidly to prevent the material from drying. If the beetle is infected, numerous gregarines will be visible under the microscope. Study with low and high powers. 1. Does the animal move? A great number of refractive granules are present in the protoplasm. They are regarded as reserve nourishment. They can be removed with acid. 2. Note that the body is covered with a membrane, and is divided into a dense superficial layer, the ectoplasm, and a cen- tral, more fluid mass, the endoplasm. 3. The endoplasm is separated into two parts by a portion of the ectoplasm. The anterior part is termed the protomerite, and the posterior part the deutomerite. In which is the nucleus situated ? 4. Is it possible to distinguish a layer of myonemes just ex- ternal to the endoplasm? 5. Is there another section of the body just anterior to the protomerite? If so, this is the epimerite. 6. Note that occasionally two (or more) individuals are united. These aggregations are termed syzygies. Before reproduction Gregarina throws off the epimerite, leaves it in the cell-host, and falls into the lumen of the digestive PARAMLECITJM. 11 tract. It then encysts, and the protomerite and the deutome- rite form one spore-producing individual. The attached stage in the life-history of Gregarina is termed the cephalont, and the detached stage, the sporont. (See Calkins' Protozoa, Fig. 77.) Make a drawing. Berndt : Beitrage zu Kenntnis der im Darme der Larve von Tenebrio moli- tor lebenden Gregarinen. Arch f. Protist., 1, 1902. Minchin: Sporozoa, pp. 177-179, Lankester's Treatise. INFUSORIA. PARAMAECIUM. Place a drop of the culture on a slide, cover, and examine with the low power. 1. In an animal not closely confined note the shape and movements. Is it possible to distinguish an anterior and a posterior end? A forward and backward movement? Is one side of the animal kept constantly uppermost? Is there a dorsal and ventral surface? Do the animals change their shape either permanently or temporarily? Individuals tend to collect about air-bubbles and at the edge of the cover-glass. Why? Indicate by a sketch all the paints which can be determined with the low power. 2. Draw off all superfluous water by means of filter-paper, add a trace of powdered carmine, and then find a specimen which is narrowly confined and examine it with the high power. The particles of carmine are taken into the body. Deter- mine how and where. Note that the carmine collects in gastric vacuoles. What do you think is probably the nature of the fluid in the vacuoles? In watching them do you notice any definite movement of the protoplasm? Try to see the undi- gested material ejected. 3. Determine the arrangement of the cilia, and the nature of their motion. Is there a reversal of the direction of the stroke, etc.?1 1 It is possible to decrease the rate of movement of both animal and cilia by placing it in a solution of gum arabic. Specimens so treated remain alive for some time. 12 PROTOZOA. 4. Observe the contractile vacuoles. How many are there? Is their position constant? What is their action? In com- pressed specimens the contractile vacuoles and their reservoirs are usually conspicuous. Note the order of appearance and disappearance of the vacuoles and reservoirs. 5. Focus carefully on the margin of the body and note a very thin outer cuticle. A thick layer, the ectoplasm, devoid of gran- ules but containing radially arranged, minute, oval bodies, the trichocysts, is just internal to the cuticle. The inner mass of protoplasm, containing the contractile and gastric vacuoles, and small granules, is the endoplasm. 6. If possible distinguish the clear, centrally located nucleus (macronucleus). Make a sketch showing all of the above points. 7. Kill the animal by running a drop of methyl-green under the cover-glass. What happens to the cilia? To the trichocysts? Sketch the trichocysts with the threads protruded, and also note and sketch the macronucleus and the micronucleus. 8. Observe, if possible, animals dividing and conjugating. 9. Study demonstrations of permanently stained specimens for finer structure. Calkins and Cull: Conjugation of P. caudatum. Arch. f. Protist., 10, 1907. Jennings and Hargitt : Characteristics of the Diverse Races of Paramsecium. Jour. Morph., 21, 1910. Metalinkow: Contributions £ l'6tude de la digestion. Arch d. Zool. Exp. et Gen., 9, 1912. Schaeffer: Selection of Food in Stentor cseruleus. Jour. Ex. Zool., 8, 1909. Woodruff: Paramsecium aurelia and Paramsecium caudatum. Jour. Morph., 21, 1910. : A Five Year (3000 generations) Pedigreed Race of Paramsecium without Conjugation. Proc. Soc. Ex. Biol. and Med., 1912 (also Biol. Centr., 33, 1913). SPIROSTOMUM. 1. Compare Spirostomum with Paramaecium, noting the method of locomotion, the shape of the body, the ciliation, the buccal groove and mouth, and the large excretory reservoir, fill- ing the posterior end of the body and in communication with the anterior end of the body by a canal. VORTICELLA. 13 2. Note the highly refractive, long, band-like (moniliform) macronucleus. In another species of Spirostomum the macro- nucleus is similar to that of Paramsecium. It is desirable to examine stained specimens of the two species of Spirostomum. 3. Note the sudden contractions of the body. When these occur spiral lines appear on the surface. Can you distinguish these lines when the animal is extended? These are primitive structures (myonemes) functioning as muscles. Make a drawing of the extended animal and a diagram show- ing the form when contracted. (See Doflein, p. 968.) VORTICELLA. Place a number of individuals on a slide and cover loosely to avoid crushing. As usual, study first with the low power and then with the high. 1. Notice that the body of Vorticella has the general shape of an inverted bell. The covering of the body is a very thin transparent layer, the cuticle, underneath which is the periphe- ral layer of ectoplasm enveloping the more fluid and granular endoplasm. 2. The peristome is the rounded rim about the base of the bell. 3. The elevated and inclined area included within the peri- stome, and ciliated around the edge, is the disk. It is some- what convex. 4. The marked depression between the disk and the peri- stome is the vestibule. It is also lined with cilia. The vestibule defines the ventral surface of the animal. 5. The gullet, a slender canal, leads from the vestibule toward the center of the body. 6. The anus occurs at the side of the vestibule. It is a tem- porary opening from which the undigested products are passed into the vestibule and so to the exterior. 7. Within the endoplasm are situated the clear contractile vacuole, several gastric vacuoles, the long U-shaped macronucleus, and the small round micronucleus. The macronucleus may be made more distinct by treating with methyl-green. 14 PROTOZOA. 8. The stalk is composed of a sheath, which is continuous with the cuticle of the body, and, within the sheath, the contractile axis or myoneme, which is continuous with the body ectoplasm. Notice that this myoneme is situated within the sheath in a very loose spiral, and that the stalk quickly contracts into a close spiral when the animal is stimulated. Observe also the manner in which the peristome folds over simultaneously with the contraction of the stalk. What purpose does the contrac- tion of the stalk serve? Vorticella is distinguished from its allied genera by its sim- ple unbranched stalk and also by the spiral form assumed by the contracted stalk. In which order of the Ciliata does the cilia- tion of Vorticella place it? Compare with Zoothamnium. Make a drawing of an expanded individual and a sketch to show the condition when contracted. (See Doflein, Fig. 816, p. 867.) 9. Study, by means of finely powdered carmine, the vortex currents set up by the cilia. Note how the particles are collected in the gullet, and at intervals are forced in rounded masses into the endoplasm to form gastric vacuoles. Is there a definite circulation in the endoplasm? 10. Endeavor to find several stages of reproduction by divi- sion. Large fresh-water species of Vorticella are preferable for study, but marine species may be substituted when necessary. If time and material permit, study Lichnophora, a marine peri- trichous form parasitic on Crepidula. (See Calkins' Protozoa, p. 203.) Schroder: Beitrage zur Kenntnis von V. monilata. Arch f. Protist.. 7, 1906. OXYTRICHA. Infusoria belonging to the genus Oxytricha, or the genera Stylonychia, Pleurotricha, Euplotes, etc. (see Doflein, Fig. 136, p. 138), may be used for the following study. These forms belong to the order Hypotrichida. Hypotrichous forms are ETJPLOTES. 15 among the most highly organized of the class Infusoria, as well as of the entire phylum of Protozoa, and present a complexity of structure and function which is not found probably within the limits of a single cell elsewhere in the animal series. 1. In an animal which is becoming quiet, note the mode of locomotion, the shape of the body, the buccal groove, the con- tractile vacuole, etc., as in other forms studied. Compare the dilation with that of other forms. Refer to Calkins' Protozoa, Fig. 98, and understand the relation of cirri, membranelles, etc., to cilia. Draw, showing the structure in detail. 2. Run some methyl-green under the cover-glass. What is the shape of the macronucleusf The shape varies considera- bly in the different genera. Is it possible to distinguish the micronucleus? 3. Prepare a fresh slide and observe in detail the character- istic movements and manner of creeping over various objects. As the animal turns sidewise, note the marked dorso-ventral compression of the body. Represent this diagrammaticalty beside the previous drawing. It is desirable to examine permanently stained preparations for division stages, finer details of the nuclei, etc. Wallengren: Zur Kenntnis des Neubildungs und Resorptionsprocess bei den Teilung der Hypotrichen Infusorien. Zool. Jahrb., 15, 1901. EUPLOTES. Mount a small piece of hydroid under a supported cover- glass and with a low power observe the suctorians attached by delicate stalks. Select a field where the animals are abun- dant and study under a high power. 1. Note the general shape of the cell and the distribution of the tentacles. Draw. Are all of the tentacles of one kind? Observe the movements of the tentacles and their use. Is there any morphological relation between tentacles and cilia? (See Minchin's Protozoa, p. 458.) 16 PROTOZOA. 2. Study the method of exogenous budding. What is the relation of this type to simple division? Is the number of buds in process of formation the same on all specimens? 3. Fix, stain, and mount in balsam a piece of hydroid with many Euplotes attached. Under the high power note the character of the macronucleus and its relation to the buds. Are micronuclei visible? 4. Examine carefully the relation of the stalk to the cell body. ' Compare with that of Vorticella. If the material is available study Podophrya and allied forms, with particular reference to the method of budding. Collin: Etude monographique BUT les Acine'tiens. Arch. Zool. Exp. et Gen., 1911 and 1912. PORIFERA. Cells not differentiated to form definite organs. Water admitted through surface pores and ejected through an osculum or through oscula. CLASS 1. Calcarea. With a skeleton composed of calcareous spicules. Subclass 1. Homocoela. With the gastreal layer continuous sb the col- lar cells line the whole gastreal cavity. (Leu- cosolenia.) Subclass 2. Heterocoela. Gastreal layer discontinuous. Collar cells restrict- ed to the flagellated chambers. (Grantia.) CLASS 2. Hexactinellida. With a skeleton composed of siliceous six-rayed spicules. Order 1. Lyssacina. Spicules separate or becoming united. (Euplec- tella.) Order 2. Dictyonina. Spicules united from the first into a firm frame- work. (Eurete.) CLASS 3. Demospongiae. Great diversity of structure. Dominant forms of today. Subclass 1. Tetraxonida. Typically with four-rayed spicules. (Corticella.) Subclass 2. Monaxonida. Simple, usually unbranched spicules. Spongin frequently present. (Cliona, Suberites, Chalina, Spongilla.) Subclass 3. Keratosa. Skeleton of spongin fibers. No true spicules. (Euspongia, Aplysina.) Subclass 4. Myxospongida. Without skeleton. (Oscarella.) 2 17 18 PORIFERA. Lankester: A Treatise on Zoology, Porifera, and Coelenterata, Pt. 2, 1900. Moore: A Practical Method of Sponge Culture. Bui. U. S. Bur. Fish., 28, 1908. : The Commercial Sponges and the Sponge Fisheries. Bui. U. S. Bur. Fish., 1908. Parker: The Reactions of Sponges, with a consideration of the Origin of the Nervous System. Jour. Ex. Zool., 8, 1910. H. V. Wilson: On Some Phenomena of Coalescence and Regeneration in Sponges. Jour. Ex. Zool., 5, 1907. : Development of Sponges from Dissociated Tissue Cells. Bui. U. S. Bur. Fish., 30, 1910. GRANTIA. This form is quite common along the New England coast, where it occurs attached to. rocks, seaweeds, and submerged woodwork from just below the lowest tide-mark to a number of fathoms in depth. You should visit an old wharf where speci- mens may be found, and study their relation to the forms with which they are associated. Specimens will be found to vary considerably in size. The largest sometimes reach an inch in length. 1. Examine a dry specimen and notice its general shape, manner of attachment, and osculum. The osculum is surrounded by a funnel of rather long spicules. Distributed over the gen- eral surface, more or less hidden by the numerous spicules, are many small pores. Their presence may be demonstrated more satisfactorily later. 2. Look for indications of budding. If your specimen does not show this, examine others. Make an enlarged drawing of a sponge. With a razor or sharp scalpel cut a dry specimen into halves, with a stroke from base to osculum, and notice : 3. The central cavity or cloaca. 4. Many apopyles, the inner openings of tubes that are em- bedded in the walls of the sponge, will be seen opening into the cloaca. Are the apopyles arranged in any order? 5. With the low power of your microscope (with the light turned off) examine the cut wall and find that it is traversed by parallel tubes. Determine that these tubes are of two kinds. GBANTIA. 19 (a) Regular, nearly cylindrical tubes that open into the cloaca through the apopyles and that bear tufts of spicules on their closed ends, at the surface of the body. These are the radial canals. It is frequently hard to see their openings into the cloaca, as the apopyles are narrow, so the section only occa- sionally passes through them. (6) Smaller and less regular tubes that open on the outer surface between the clusters of spicules, and do not open into the cloaca. These are the incurrent canals. In life there are small pores, prosopyks, that open from the incurrent canals into the radial canals. These openings are very minute and are apparently capable of being closed. They are never visible in dried material. 6. Examine thin, transverse sections of a dry sponge and determine the positions of radial and incurrent canals. Make a drawing that will show the arrangement of the canals. 7. Examine the spicules and determine their positions as regards canals. Boil a portion of a sponge in caustic potash until only the spicules remain and examine the spicules. See if more than one kind occurs. Draw specimens of the spicules. LIVING AND SECTIONED MATERIAL. 1. Place a living sponge in a watch-glass of sea-water, add a little powdered carmine, and examine it with the low power of your microscope for currents of water. See if particles are mov- ing in a definite direction near the general surface and near the osculum. 2. With a moderately sharp razor cut tangential sections of the wall, as thin as possible, mount in sea-water under a cover, and examine with a low power. This will show both incurrent and radial canals in cross-section. How can you distinguish one from the other? In a favorable place look for moving flagella. Are flagella in all of the canals? In favorable situa- tions it can be easily seen that the cells that have flagella possess collars also. (Collars may be withdrawn by cells so they pro- 20 PORIFERA. trude but slightly). You see now what causes the current of water. Do you understand how a sponge feeds? The choano- cytes of the sponge resemble choanoflagellate protozoons. Make a drawing showing the arrangement of choanocytes. Examine transverse sections of a specimen that has been decalcified and stained. 1. The cloacal chamber is lined by a pavement of epithelium. 2. The radial canals are lined by more conspicuous cells, the gastral epithelium, or choanocytes. 3. The incurrent canals and the outer surface of the sponge are covered with flattened cells, the dermal epithelium. 4. In a part of the section where a considerable area of choan- ocytes appear in surface view, look for the prosopyles, through which the water passes from the incurrent to the radial canals. (They may not be found.) 5. Make out any structures you can in the area lying between the dermal and gastreal layers. What cells are found here ? Make a drawing of several adjacent canals to show the above points and indicate the course of the water by arrows. 6. In the stained sections, look for single ova and for spheres containing many spermatozoa, the sperm-spheres. Look also for segmenting eggs, which are frequently to be found. The ova are fertilized while still lying where they have developed, just within the choanocyte layer. Remaining in place, they undergo cleavage and develop so far as the amphiblastula stage (see figures in the text-books). They then break through the choanocyte layer into the radial canals and pass out with the current of water. Living specimens are frequently found with such embryos issuing from the oscula in the outgoing current of water. The sperm-spheres, when fully developed, also break through the choanocyte layer and, separating into their com- ponent spermatozoa, pass out with the outgoing water. Ova and sperm are formed by the same individual, and the animal is therefore hermaphroditic, but the products ripen at different periods and are seldom both present in an individual at the same time. GRANTIA. 21 // the time allows, draw ova, sperm-spheres, segmenting eggs, and embryos. It is desirable to examine specimens of Leucosolenia, a still simpler sponge, and of some of the more complicated forms, like commercial sponges, Spongilla, Cliona, and Chalina. Why is more than a single osculum desirable in such forms? Under- stand the relation of the internal structure of the complicated forms to the more simple forms. What reason is there for the complication? COELENTERATA. With a single continuous coelenteron or gastro-vascular cav- ity. With the exception of the Ctenophora all have nettle cells. There are two cellular layers and a mesoglea. CLASS 1. Hydrozoa. Coelenteron simple, without septa. Gonads usu- ally ectodermal. Fully formed medusae have a velum. Order 1. Leptolinse. With a fixed zoophyte stage. Suborder 1. Anthomedusse. Without hydrothecse or gonothecse. The medusa bears gonads on the manubrium. (Hydra, Pary- pha.) Suborder 2. Leptomedusse. With hydrothecse and gonothecse. The medusa bears gonads on the radial canal. (Obelia, Goni- onemus.) Order 2. Trachylinse. Without fixed zoophyte stage. Suborder 1. Trachymedusse. Tentacles from the margin of the umbrella. Gonads on the radial canals. (Petasus.) Suborder 2. Narcomedusse. Tentacles from the exumbrella. Gonads on the manubrium. (JSginopsis.) Order 3. Hydrocorallina. Massive calcareous exoskeleton. (Millepora.) Order 4. Siphonophora. Pelagic. Colonial. Colony usually shows extreme polymorphism of its zooids. (Physalia.) CLASS 2. Scyphozoa. Body-wall of polyp thrown into four ridges (tsenioles) which project into the ccelenteron. Medusa generally without velum and with gas- tric tentacles. Medusoid form predominating. 22 CCBLENTERATA. 23 Order 1. Stauromedusse. Conical or vase-shaped umbrella. No tentacu- locysts. (Tessera.) Order 2. Peromedusse. Conical umbrella with transverse constriction. Four inter-radial tentaculocysts. (Pericolpa.) Qrder 3. Cubomedusse. Four-sided umbrella. With per-radial tentacu- locysts. Velum present. (Charybdea.) Order 4. Discomedusae. Saucer-shaped umbrella. Per-radial and inter- radial tentaculocysts. (Aurelia.) CLASS 3. Actinozoa. With a stomodseum, and with mesenteries ex- tending into the coelenteron. Fixed forms. Subclass 1. Zoantharia. Mesenteries and tentacles usually very numerous. Order 1. Actiniaria. Usually single. No skeleton. (Metridium. Sa- gartia.) Order 2. Madreporaria. Usually form colonies and always have calcare- ous exoskeleton. (Astrangia, Orbicella, Mean- drina.) Order 3. Antipatharia. Tree-like. Mesenteries and tentacles compara- tively few. Chitinoid skeleton. (Cirripathes.) Subclass 2. Alcyonaria. Mesenteries and tentacles eight in number. Ten- tacles branched. Order 1. Alcyonacea. Skeleton in the form of small, irregular bodies, frequently calcareous spicules. (Alcyonium, Tubipora.) Order 2. Gorgonacea. Tree-like, with calcareous or horny exoskeleton. No syphonoglyphes. (Gorgonia.) Order 3. Pennatulacea. Colony with one end usually embedded in the sea-bottom. (Pennatula, Renilla.) CLASS 4. Ctenophora. Single. Pelagic. Eight rows of meridional swimming plates. No nettle cells. 24 CCELENTERATA. Order 1. Cydippida. Nearly circular. Two tentacles, each of which may be retracted into a sheath. (Pleurobra- chia, Mnemiopsis.) Order 2. Lobata. Compressed in the vertical plane. Two large oral lobes. No tentacle-sheaths. (Deiopea.) OrderS. Cestida. Ribbon-shaped. Two tentacles with sheaths, and numerous other tentacles. (Cestus.) Order 4. Beroida. Laterally compressed. Without tentacles. (Berce.) Mayer: Mudusae of the World. Carnegie Inst., Wash., 1910. Nutting: The Hydroids of the Woods Hole Region. Bui. U. S. Fish. Com., 19, 1899. HYDROZOA. HYDRA. (Fresh-water Polyp.) Hydra, the 'only common fresh-water ccelenterate, is fre- quently found in jars of water taken from quiet pools or sluggish streams that contain lily-pads, decaying leaves, and other vege- table matter. The animals may frequently be found by examin- ing the surfaces of submerged leaves, but it is usually better to allow such material to stand in glass jars for a day or two, as the animals then tend to collect on the lighter sides of the vessels. They are easily kept in balanced aquaria. Examine specimens in an aquarium and find what you can about their mode of life. Do they form colonies? Place a specimen in a watch-glass of water and examine it with a lens. 1. What is its shape and color? Is it attached? If so, by what part of the body? Notice the circlet of tentacles. How many are there? Compare notes with others and see if all have the same number. How are they placed? 2. Does the Hydra move its body or tentacles? Is it sensi- tive? How do you know? HYDRA. 25 3. Examine with a low power of the microscope and review the above points. You may also be able to see the mouth around which the tentacles are arranged. Make two drawings, one showing the animal expanded and the other contracted. Place your specimen on a slide under a cover-glass that is supported by the edge of another cover-glass, so it can be exam- ined with a high power. Be careful not to crush it. Notice: 4. The outer layer, ectoderm. What is its color? Is it continuous over the whole outer surface ? Does it vary in thick- ness? Are the cells of which it is composed apparently all alike? 5. The inner layer, endoderm. What is its color? If color is present, is it evenly diffused or is it collected in special bodies? Are the cells of which the endoderm is composed apparently all alike ? Do they differ in appearances from those of the ecto- derm other than in color? If the specimen is not deeply colored, look for flagella moving in the internal cavity. 6. Examine the ectoderm of the tentacles carefully and notice that each of the large, rounded, clear cells, the nematocysts, shows a rather indefinite streak running from its outer end, back into the interior. See if you can find the trigger (cnidocil) on any of these cells. Draw a portion of a tentacle showing the distribution of the nematocysts. 7. Place your specimen under the low power of the micro- scope, carefully run in a drop of saffranin, and see if any of the nematocysts are discharged when the saffranin touches them. Examine with a high power and notice the appearance of the thread. Notice the change in the shape of the nematocysts that have discharged. See if you can find two kinds. Make an enlarged drawing of an exploded nematocyst. 8. Examine prepared transverse sections of Hydra. Notice that the body is composed of two layers of cells, between which is an almost structureless thin layer. Do the cells of the two layers differ in size, shape, and structure? Do you find more 26 CCELENTERATA. than one kind of cell in each or either of these layers? Where are they? What are they? Make a careful drawing of the section showing the arrangement as you see it. Examine longitudinal sections, for differences in the char- acter of the ectoderm and endoderm in different parts of the body. 9. Reproduction. Examine living specimens in a watch- glass of water for bud formation and for sexual organs. Sperm- aries are just beneath the tentacles; ovaries, lower down; buds may be found at different levels. What layers of cells is involved in the formation of each of these? Eggs are not formed at all seasons of the year and vary greatly in appearance according to their stage of development. Make drawings of the stages of reproduction that you find. Tannreuther: The Development of Hydra. Biol. Bui., 14, 1908. Whitney: Artificial Removal of the Green Bodies from Hydra viridis. Biol. Bui., 14, 1908. OBELIA. These small, colonial animals are common on submerged or floating wood, stones, and seaweeds, where the water is rather free from sediments. With the aid of a glass-bottomed pail they, in company with many other forms, may usually be seen about old wharfs.1 Note the appearance of large colonies of this form that are growing on stones or on pieces of board. 1. Notice the tree-like form of any single stem. Do the branches have a definite size and arrangement? 2. At the extremities of the branches are the single individuals, hydranths or zooids. Each is similar to a single Hydra in cer- tain ways, but is inclosed in a vase-like formation, the hydrotheca. 3. The latter is a continuation of a tough, membranous sheath, the perisarc, which covers each part of the whole colony. 1 Campanularia differs principally in that it does not set its medusae free. OBELIA. 27 Do you notice any modifications of the perisarc below the hydrotheca? Do the modifications serve any purpose? 4. Trace the stem down to the creeping, stolon-like portion of the colony, the hydrorhiza. Make a drawing of a colony. 5. The fleshy continuation of the zooid down into the stalk is termed the coenosarc. Is it in close contact with the perisarc? 6. In an expanded hydranth, note the mouth, the arrange- ment of the tentacles, and the number of tentacles. How is the individual supported in its cup? Can you trace the ccelenteric cavities down through the stalks, and prove them to be continuous with each other? Motion in the fluid contents of living speci- mens makes this easy to observe. 7. Examine a hydranth with a high power and look for the cell-layers characteristic of coelenterates. Determine how its tentacles differ from the tentacles of Hydra, and explode nemato- cysts as with Hydra. Make a drawing of a hydranth. 8. Look for certain extremities which show neither tentacles nor any opening in the perisarcal covering. Such a condition signifies either an undeveloped hydranth or a reproductive individual. If the latter, it is considerably swollen and is termed a gonangium. The central core or coenosarc of a gonangium, the blastostyle, should be examined for medusce buds. This may re- quire a high power. Make a drawing of a gonangium. 9. You may find free medusae swimming in the dish where material is kept. If you do, you should examine one, but it will not prove as satisfactory for study as a larger form, like Gonionemus, directions for the study of which are given further over. In comparing it with Gonionemus notice the small size of the velum, and the usual everted position of the bell, so the manubrium appears like a handle. It is not uncommon to find planulae escaping from gono- thecae of Campanularia. Frequently the medusse that are liberated have previously shed their eggs. 28 CCELENTEEATA. 10. Study the cellular structure of a hydranth and of a gon- angium, as seen in cross and longitudinal sections. Make a drawing of each. For comparison use any thecate forms, which may be offered as loose material or as demonstrations, such as Campanularia, Sertularia, and Plumularia. PARYPHA. This form is frequently abundant on the piles of old wharfs, where the colored colonies form conspicuous masses just below low-water mark. Examine the general form of a colony and note, either with a hand lens or with the naked eye, the stem, or hydrocaulus, as it arises from the branching, matted hydrorhizal portion of the colony. The parts of the colony will be seen to differ from the Leptomedusan (Campanularian) form studied, especially in branching, rigidity, hydrothecse, and gonangia. Make a drawing to show the formation of the colony. 1. How does a hydranth differ from the hydranth of Obelia in the matter of tentacles ? Is a hydrotheca present ? 2. The mouth is terminal and is situated at the end of a manubrium. 3. The short but rather large body of the hydranth passes back to the perisarc as the fleshy axis, ccenosarc. 4. Notice the medusa buds on the manubrium between the rows of tentacles. What is their arrangement? This is a form in which the medusae are not set free, but remain vestigial. The gonads ripen on the partially developed manubrium of the medusa. The sexes are separate. Make a drawing of a hydranth. 5. The arrangement of the attached medusae is best seen in sections. In the male medusae numerous spermatozoa will be found, while the female individuals have a much smaller number of large ova, which are likely to be in advanced stages of seg- mentation. The sections show the same body layers as Hydra, and the GONIONEMUS. 29 derivation of the medusa as an outpocketing of the wall of the hydranth is evident. Make drawings of sections of male and female reproductive organs (medusa buds). For comparison, study Pennaria, Margelis, Hydractinia, Clava, and Eudendrium. Hargitt: The Early Development of Penneria tiarella. Arch f. Entwick- lungsmech.^ 18, 1904. Pearse: Reactions of Tubularia crocea. Am. Nat., 40, 1906. Torrey: Biological Studies on Corymorpha. I. Jour. Exp. Zool., 1, 1904; II. Univ. Calif. Pub. Zool., 3, 1907. GONIONEMUS. As has been seen, the medusae buds are usually produced from the walls of a specialized hydranth (Leptomedusae) or from the manubrium wall of an ordinary hydranth (Anthomedusae). A series of these buds in various stages would show the formation of the umbrella-shaped individual with the growth of the marginal tentacles around the edge. The life-history of this form is not known, but from its structure we are led to believe that it belongs to the suborder Leptomedusse. It is found in con- siderable numbers throughout the summer in the border of eel- grass in the Eel Pond at Woods Hole, where it may be obtained with a dip-net. It is more satisfactory to study than the medusa of Obelia, as it is much larger and its movements and organs are more easily observed. In plan of structure the two are quite similar. Put a living specimen in a flat-sided jar containing sea-water, or in a finger-bowl, with a black tile beneath, and notice: 1. Its method of locomotion. To the contraction of what part of the bell is movement due ? How large is the jet of water that is delivered from the bell ? Why is the jet made narrow ? Does the jet necessarily leave at the center or may it be thrown from one side ? Should it be thrown from one side, what would be the result ? 2. Its position in the water when quiet. Why is this position 30 CCELENTEBATA. more desirable than the opposite? With a needle-point prove that various parts of the body are sensitive. With either fresh or preserved material notice: 1. Its flattened dome-shape. The convex face is called the ex-umbrella (aboral), while the concave portion is termed the sub-umbrella (oral). 2. The velum is the perforated diaphragm that partly closes in the sub-umbrella. All medusae possessing this structure are classed as Craspedota. Do you understand its use? 3. In the center of the sub-umbrella is seen the large pen- dent manubrium, at the extremity of which is a wide-lipped mouth. If the medusa is alive, feed it with small bits of clam meat. 4. From the capacious sac at the base of the cavity of the manubrium, the stomach, the four radiating chymiferous tubes, or canals, lead to the periphery of the disk, where they open into the very delicate circular circumferential canal. The four radii marked out by these canals are called the per-radii. Do you understand the use of these canals ? 5. The gonads hang from beneath the chymiferous tubes into the sub-umbrellar space. They are lobulated in structure, and more or less prominent according to maturity and the breeding season. The eggs or spermatozoa, as the case may be, are de- hisced from these into the water directly. 6. The tentacles. Is their arrangement a radially symmetrical one? How are the nematocysts arranged on them? Look for adhesive organs on them. Of what use are such organs? Turn your specimen with the velum side toward you and study the edge of the medusa with a low-power objective for the sense organs. These are of two kinds: (a) The larger, round bodies at the bases of the tentacles communicate with the circumferential canal (which may possibly be seen along the edge of the bell). They are filled with a layer of strongly pigmented endoderm cells and are probably light- percipient organs. HYDROCORALLINA. SIPHONOPHOKA. 31 (6) Other small sessile and transparent outgrowths, situated between the bases of the tentacles, are the so-called otocysts, which are probably static organs. All of the tentacles are abundantly supplied with tactile, sensory cells. There is a well-established circumvelar nerve ring (not easily determined in living material) derived from the ectoderm, also scattering nerve cells beneath the ectoderm in connection with the muscular tissue. Ex-umbrellar and sub- umbrellar layers of muscle fibers are also present. Make a drawing from the side, slightly tipped, to show the velum, and another as seen from the oral surface. Brooks: Life History of Hydromedusac. Mem. Bost. Soc. Nat. Hist., 3, 1886. Murbach: The Static Function in Gonionemus. Am. Jour. Physiol.. 10, 1903. Perkins: The Development of Gonionema murbachii. Proc. Acad. Nat. Sci., Phila., 1902. Yerkes: A Study of the Reaction Time of the Medusa Gonionema murba- chii to Photic Stimuli. Am. Jour. Physiol., 9, 1903. HYDROCORALLINA. To this group belong forms that have heavy calcareous exoskeletons. While material is generally not at hand to study the polyps, it is desirable to study and sketch the characteristic forms of colonies such as Millepora and Stylaster, and to note the difference in the distribution of pores. Later you will see how decidedly these differ from the ordinary stony corals. SIPHONOPHORA. Examine living or preserved specimens of Physalia, and sketch the type with reference to showing, if possible, the follow- ing structures: (a) pneumatophore, (b) dactylozooids, (c) gastro- zooids, (d) gonodendrons, (e) tentacles. It will be well to refer to a text-book to find the positions and functions of each of .these. Bigelow: The Siphonophorse. Mem. Mus. Comp. Zool., Harvard, 38, 1911. 32 CCELENTERATA. SCYPHOZOA. AURELIA. This form is one of the common jelly-fishes, and is found floating freely in the water. It is frequently washed up on shore. To be appreciated these medusae should be seen as they occur at the surface of the sea, before they have been handled or in- jured. Frequently vast numbers may be seen together, all gently pulsating and thus keeping near the surface. The move- ment is very different from that of most hydrozoan medusae, being very deliberate and graceful. If living material is offered, study the method of locomotion and compare it with the locomotion of Gonionemus. Like the latter, the discoid animal presents ex-umbrellar (aboral) and sub- umbrellar (oral) surfaces, but the edges of the disk are indented, fringed with very numerous short tentacles, and a velum is wanting. What difference does the velum make in locomotion? The ex-umbrellar surface presents little of interest. In the live specimens, however, prove that the animal is sensitive over this area as elsewhere. Preserved and hardened material is better than living for the study of the rest of the anatomy of this form. With a specimen in water in a finger-bowl, with a black tile for the background, find the following from the sub-umbrellar surface: 1. The shape of the animal. Is the margin perfectly circular or regularly indented? Are all of the marginal portions similar? 2. Four large, fringed oral arms or lips hang from the corners of the nearly square mouth, which is located in the center. No- tice how each arm is similar to a long, narrow leaf, with the sides folded especially along their margins. Examine the arms for nematocysts. Do you understand how the animal gets its food? If the arm edges appear to be covered with dark specks and granules, examine to see if embryos may not be entangled. 3. The mouth is found to lead by a short gullet into a rather spacious stomach, which is produced in the region between each two corners of the mouth to form a gastric pouch. Determine the shape of the stomach. AUKELIA. 33 4. The remaining parts of the digestive (and also in this case circulatory) system include the numerous radial canals and the single circumferential canal. (a) Directly beneath each oral arm a per-radial canal is given off, which, at a short distance from the stomach, gives off a branch on either side. The per-radial canal proper usually continues straight to the marginal circumferential canal, without further subdivision, but the two side branches above mentioned in turn subdivide several times. (6) From the peripheral wall of each gastric pouch three canals pass toward the margin; the middle one (inter-radial canal) branches somewhat after the manner of the per-radial canals, but the other two (ad-radial canals) continue to the circular canal without further branching.1 5. The position of the gastric pouches is made clearly mani- fest by the gonads, which lie on the floor of the pouches, as frill- like structures, horseshoe-shaped, with their open sides toward the mouth. The ova or spermatozoa are shed into the stomach and pass out of the mouth. Embryos in various stages of develop- ment may frequently be found adhering to the oral arms. The sexes are separate. On the sub-umbrellar surface, opposite each gonad, is a little pocket, the sub-genital pit, which opens freely to the outside. Whatever purpose this may serve, it does not function to conduct the genital products to the outside. 6. Parallel with the inner or concave border of each gonad is a row of delicate gastric filaments. These are supplied with stinging cells, and they may aid in killing live food taken into the stomach. These structures are not present in the Hydro- zoan medusa. 7. At the marginal extremity of each per-radial and inter- radial canal there is an incision on the edge of the animal, in which there are sensory organs. In each incision find : (a) A tentaculocyst in the form of a short, club-like struc- ture containing a prolongation of the circular canal. At its 1 In most cases the foregoing canals are very evident, but if they are not, they may be injected with water in which carmine is mixed, by insert- ing a large-mouthed pipet into the stomach. 3 34 CCELENTERATA. outer extremity are calcareous concretions or lithites, and a pig- ment-spot or ocellus. Each tentaculocyst is protected aborally by a hood-like projection, and on the sides by marginal lappets. (6) Two depressions, one above and the other below the tentaculocyst. These have been assigned olfactory functions, and are called the olfactory pits. Make a drawing showing the profile of the entire animal, and show the structure of at least one quadrant, as seen from the oral surface. If time permits study a developmental stage, "ephyra," and compare it with the adult. By way of comparison, examine demonstrations of Cyanea, Dactylometraf Lucernaria, or other forms belonging to this group. Hargitt: Variations among Scyphomedusse. Jour. Exp. Zool., 11, 1905. Hargitt, C. W. and G. T. : Studies in the Development of Scyphomedusae. Jour. Morph., 21, 1910. Mayer: Rhythmical Pulsation in Scyphomedusae. Carnegie Inst. of Wash- ington, 1906. ACTINOZOA: MBTRIDIUM. (Sea-Anemone.) Specimens are quite common on piles, as well as on rocky bottoms, and may be easily observed by means of a glass- bottomed pail. Most of the observations can be made much better on specimens in aquaria, but it is desirable to see their natural surroundings. 1. Notice the shape and attachment of expanded, living speci- mens in an aquarium, or in a deep finger-bowl. The free end, called the disk or peristome, is fringed with tentacles, and the elongated mouth is located in the middle of this area. At one or both angles of the mouth the lips are thickened into what is called a siphonoglyph. Make a drawing of the animal. 2. Feed a specimen with bits of mashed clam to ascertain its manner of taking in food. Drop bits on the tentacles at one time, and disk at another. METRIDIUM. 35 Endeavor also to determine whether there are currents constantly passing in or out of the mouth that are due to ciliary action. 3. Irritate the animal and observe its manner of contraction. When fully contracted, if the irritation is continued, thread- like structures, acontia, are thrust out through minute pores, cinclides, in the body-wall. Make a drawing of the contracted animal. Internal Anatomy.— Using preserved material, place the edge of a razor across the peristomial area, at right angles to the mouth-slit, and divide the animal from disk to base into halves. 1. Note the extent of the esophagus and siphonoglyphes; they lead into the coelenteric chamber. Find the extent of this chamber, and the method of its subdivision by delicate parti- tions, the mesenteries, or septa. Are all of the mesenteries alike ? 2. Forming the free edges of the mesenteries, below the esophagus, are the convoluted mesenteric filaments, which are secretory organs that are probably equivalent to the gastric filaments of the Scyphozoa. 3. Quite near the bases of the mesenteries are the attachments of the acontia. What relation have they to the mesenteric fila- ments? 4. Also located on the mesenteries, and arranged parallel to the filaments, but back from the edge a bit, are the repro- ductive organs or gonads. Are they found on all of the mesen- teries? The ova or spermatozoa are shed into the coelenteric chamber and pass out through the mouth. Cut one of the halves of your specimen transversely in the region of the esophagus, and study the arrangements of the mesenteries, their attachments, etc. 5. How many pairs of primary mesenteries, i. e., those attached both to the outer body-wall and to the esophagus, are there? The directive septa are those at the angles of the esophageal tube. The portion of the coelenteric cavity between any two pairs of mesenteries is termed an inter-radial chamber. The space between the two mesenteries of each pair is called an intra- radial chamber. 36 CCELENTERATA. 6. Carefully determine the disposition of the longitudinal retractor muscles on the mesenteries. Do they occupy similar positions on all of the mesenteries ? 7. Examine the upper parts of the mesenteries for openings, septal stomata, that put the chambers in communication 8. Are the tentacles solid or hollow? Make a drawing of a longitudinal section and another of a cross-section. Put into these all of the points of the anatomy you have seen. If time and opportunity permit, it is very desirable that this form should be compared with specimens of the order Madre- poraria, and later with the Alcyonaria. Such a form as Astran- gia may easily be obtained either alive or properly preserved, and will serve to show the relation of the hard parts of the coral to the polyp. You should understand the relation of the septa and the mesenteries, and of the polyps to each other. If speci- mens are at hand, compare such forms as Orbicella, Favia, and Meandrina, or any forms that show gradations from separate calices to fused groups, and understand the positions of mouths, the arrangement of the ccelenteric chambers, and the way in which the colony has come to its present form. You should also examine large branching colonies and determine why branches are formed and how they arise. Examine the structure of an Alcyonarian colony and see how the polyps are placed. The structure of the expanded polyps is nicely shown by Renilla. The spicules of such forms as Gorgonia may be obtained by boiling a portion of a colony in caustic potash. What purpose do such spicules serve? Parker: The Reactions of Metridium to Food and Other Substances. Bui. Mus. Comp. Zool. Harvard, 29, 1896. : The Mesenteries and Siphonoglyphes in Metridium marginatum. Bui. Mus. Comp. Zool., Harvard, 30, 1897. : Longitudinal Fission in Metridium marginatum. Bui. Mus. Comp. Zool., Harvard, 35, 1899. : The Reversal of the Effective Stroke of the Labial Cilia of Sea- Anemones by Organic Substances. Am. Jour. Physiol., 14, 1905. MNEMIOPSIS. 37 CTENOPHORA. MNEMIOPSIS. This form belongs to the group of 'animals popularly called "comb-jellies," and occurs along the coast in irregular abun- dance during the summer months. Specimens are very phos- phorescent when disturbed, so, when they are abundant, the display caused by them while rowing at night is sometimes bril- liant. They may frequently be seen during the daytime and can often be satisfactorily observed in the shade of a wharf when the water is calm. Unmutilated, living material can be studied to best advan- tage, but preserved material may be had that is quite satisfac- tory for anatomic study. 1. In general appearance a specimen resembles a hydrozoan medusa, with its aboral surface elongated until, as a whole, it approaches the shape of a fowl's egg. 2. The broader or oral end bears two heavy terminal lobes, between the bases of which is the slit-like mouth. We may con- sider the elongation of the mouth to be in the antero-posterior line. A bilateral symmetry is thus evident. 3. On each lateral surface of the animal, midway between the terminal lobes, at a short distance from the mouth, notice a small opaque spot, an undeveloped tentacle in its sheath. 4. At the aboral pole is a depression, in the bottom of which is the "sensory body." 5. Leading away from this and extending as meridional lines toward the oral pole, are eight ctenophoral rows, or swim- ming plates. Examine the plates with a hand-lens and deter- mine their structure and function. A pair of rows (arising from the pit of the sensory body as a single row) extends down over each terminal lobe. Another pair passes down each lateral surface of the animal. Each of these lateral rows, after passing half-way to the mouth, changes its appearance somewhat, and leaves the surface of the body proper, being continued down one edge and up the other of a finger-like process which hangs orally, 38 CCELENTERATA. called an auricle. Each ctenophore then possesses four auricles, which are somewhat covered over by the loose edges of the terminal lobes. The fringe of cilia which borders each auricle is continuous with a fringe which extends up and down the inner, lateral edge of each terminal lobe. Do you understand how the animal gets its food? Digestive System. — With a pipet inject a solution of carmine into the mouth opening. 1. You can then more plainly see the long ribbon-like esoph- agus, which leads to a very small stomach just beneath the sensory body. 2. From the stomach are given off the canals, which in a successful injection will be seen to be as follows : (a) Two short "excretory canals" opening into the pit where the sensory body is located. (6) Two esophageal canals, one on each side, passing down along the esophagus. (c) Two tentacular canals, one on each side, passing to the tentacular structure of that side. (d) Four meridional canals, each of which bifurcates. The eight thus formed pass down the animal superficially, just beneath the ctenophoral rows. Reproductive System. — The ctenophore is hermaphroditic and ova and spermatozoa are proliferated from the walls of the meridional vessels. A portion of a ctenophoral row should be cut off, and exam- ined under a microscope, to ascertain the arrangement and rela- tion of plates and cilia. Make a drawing of a side view. Make a diagram that will show the appearance of a merid- ional cross-section. Abbott: The Morphology of Coeloplana. Zool. Jahrb., 24, 1907. A. Agassiz : Embryology of the Ctenophorse. Am. Acad. Arts and Sci., 10, 1874. Mayer: Ctenophores of the Atlantic Coast of North America. Carnegie Inst. of Washington, 1912. Parker: The Movements of the Swimming-Plates in Ctenephores, with Reference to the Theories of Ciliary Metachronism. Jour. Exp. Zool., 2, 1905. PLATYHELMNTHES. Body elongated, flattened and unsegmented. Anus gener- ally absent. CLASS 1. Turbellaria. Outer surface ciliated. Free living. Order 1. Polycladida. Intestine complexly branched. No separate vitellaria. (Planocera, Leptoplana, Stylochus.) Order 2. Tricladida. Intestine with anterior median, and two posterior lateral limbs. Vitellaria numerous. (Planaria, Bdelloura, Synccelidium.) Order 3. Rhabdoccelida. Simple, sac-like intestine. Body usually elon- gated. (Polychcerus, Microstomum.) CLASS 2. Trematoda. Parasitic. Generally with sucking disks. Well- developed digestive system. Order 1. Monogenetica. Ectoparasitic. Direct development. Three or more suckers. (Polystomum.) Order 2. Digenetica. Endoparasitic. Complicated development. Never more than two suckers. (Distomum.) CLASS 3. Cestoda. Endoparasitic. Without digestive cavity. Usu- ally having a scolex, bearing clinging organs (suckers or hooks). Order 1. Monozoa. Body not divided into proglottids. (Caryophyl- Iseus.) Order 2. Polyzoa. Body consisting of scolex and proglottids. (Tae- nia, Crossobothrium.) 39 40 PLATYHELMINTHES. CLASS 4. Nemertinea. Elongated, ciliated, with eversible proboscis not directly connected with the alimentary canal. Intestine usually with lateral diverticula. Anus present. (Tetrastemma, Cerebratulus.) TURBELLARIA. PLANARIA MACULATA. This form is very common in fresh-water ponds throughout the United States. It is found during the day on the lower or shaded surfaces of stones and other submerged objects, a fact which suggests that it is nocturnal in its habits. Most fresh- water planarians have very opaque bodies and their internal organization cannot be studied in the fresh specimens. 1. Notice the general shape of the body. 2. The methods of locomotion. Look for cilia. 3. The pharynx and mouth near the middle of the ventral surface. 4. The eye-spots on the anterior dorsal surface. 5. Try feeding specimens by crushing a live pond-snail and putting the fragments in the dish with them. If any of the worms are at rest, set them in motion by lifting one end of each with a bit of wood or some blunt instrument. Observe the ani- mals at intervals of a few minutes and see if any of them begin to feed. If so, by turning them over quickly with a blunt instru- ment, try to see how the pharynx is used. If not successful, try turning a specimen ventral side up, and placing a small bit of snail meat on its body in the region of the pharynx. 6. Look among the specimens in the dishes on the prepara- tion table for animals that show marks of normal fission. 7. Clean a heavy watch-glass thoroughly and pour it about two-thirds full of clean pond-water from the jar on the prepa- ration table. Transfer all of the specimens to this dish, lifting each carefully with a bit of wood. With a scalpel mutilate them in various ways; cut one in two transversely, another longitu- dinally, another into several pieces of various shapes. Make BDELLOURA OR SYNCCELIDIUM. 41 memoranda, if necessary, of the shapes of the various pieces. Carefully cover the dish and set it away. Examine the pieces with a hand-lens every twenty-four hours for the next week or ten days. If the water in the dish begins to show signs of becom- ing foul, transfer the pieces to a clean dish of fresh pond-water. Do not use water from the tap. Curtis: The Life History, the Normal Fission, and the Reproductive Organs of Planaria maculata. Proc. Bost. Soc. Nat. Hist., 30, 1902. Morgan: Experimental Studies of the Regeneration of Planaria maculata. Arch. f. Entwickelungsmech., 7, 1898. Parker and Bennett : The Reactions of Planarians with and without Eyes to Light. Am. Jour. Physiol., 4, 1900. BDELLOURA OR SYNCOELIDIUM. Most triclads are free-living, but a few are ectoparasites. The above-mentioned forms are found upon the proximal joints of the walking legs and in the gill-books of Limulus. Owing to the absence of pigment, they are very favorable for the study of internal structure, and may be used to demonstrate the struc- tures not observed in Planaria maculata. 1. Observe the movements of the living worms in a watch- glass of sea-water; then place a specimen on a slide, dorsal side uppermost, and cover with a slip. If any of the points of structure mentioned for Planaria have not been observed, try to find them on this form. 2. Notice that the gut with its three main branches (triclad type) and many secondary diverticula is easily recognizable. The mouth can sometimes be made out as a small circular open- ing leading ventrally from the posterior end of the pharyngeal sheath. Compress the specimen as much as possible by drawing off the water with filter-paper and look for: 3. The cerebral ganglia, a bilobed structure beneath the eye- spots, that appears as a slightly lighter area. 4. From the cerebral ganglia two longitudinal nerve cords pass backward, and several smaller nerves pass off in front. Ex- amine the specimen by reflected light, looking particularly at 42 PLATYHELMINTHES. the nervous system and pharynx. What relation have the nerve cords behind? 5. With the high power and good light, look for the water- vascular tubules. The region anterior to the cerebral ganglia is a favorable place. They form a clear, branching tracery, a little lighter than the surrounding tissue. The flicker of the flame cells can usually be seen, but they may be more easily seen in Crossobothrium. Examine chart and text-book figures of the water-vascular system. Make a good-sized drawing of a worm, showing the above points. Reproductive Organs. — Turbellarian worms are hermaphro- ditic. In this form the various organs are so crowded together that it will be best to follow each system separately. Com- press a specimen under the slip and find the male organs as fol- lows: (a) The testes are the numerous rounded masses between the lateral branches of the gut. They are connected by means of fine tubes which cannot be seen in fresh specimens. (6) The vasa deferentiaf two large tubes, one on either side of the pharynx, that unite posteriorly near the base of the penis. (c) The genital atrium, within which the penis lies with- drawn, is situated behind the pharynx. The penis and atrium may be considered as a replica, in miniature, of the pharynx and its sheath. If the above structures cannot be satisfactorily seen, try preserved, stained, and mounted specimens.1 Draw the male reproductive system. Refer to charts and text-books for anything that is obscure. 1 Specimens may be readily killed by compressing under a slip, being careful to draw the excess of fluid out on one side so that the animal cannot contract, and running in killing fluid. (Sublimate acetic is good.) As soon as they become opaque white, put on enough killing fluid to float the slip off and transfer the specimens to a dish of the fixative for five minutes, then 50 percent alcohol a few minutes, 70 percent several hours, stain with borax carmine or Delafield's hematoxylin; dehydrate, clear and mount in balsam. (See directions in the appendix for making permanent preparations.) BDELLOURA OR SYNCCELIDIUM. 43 The female organs are as follows: (a) Opening into the genital atrium are the two large sacs, the so-called uteri, which lie near the margins, just posterior to the end of the pharynx. Each has a separate opening on the ventral surface of the body, but has no direct connection with any other part of the reproductive system. These may not be homologous with the single uterus found in most triclads. (See Wheeler.) (6) Place a worm ventral side up and look carefuly be- tween the second and third or the third and fourth anterior gut diverticula on either side of the main anterior ramus for the two ovaries. (c) The oviducts pass backward from the ovaries, parallel to the vasa deferentia, and unite posterior to the penis. The common duct thus formed enters the posterior part of the geni- tal atrium. The oviduct is difficult to demonstrate and it may be necessary to try both fresh and stained material. (d) Along the margins of the animal, between the divertic- ula of the gut, are rounded bodies, the wtellaria. These dis- charge their products into the oviducts. Do you know what they are for? Draw the female reproductive system. Study stained and mounted specimens for any points which have not been found, and particularly examine the ner- vous system. Look for the marginal nerve running along the edge of the body, and for numerous transverse commissural nerves. How many of these are there? How regular is their arrangement? * Wheeler: Synccelidium pellucidum, a new Marine Triclad. Jour. Morph., 9, 1894. 1 A Polyclad, Planocera, can be obtained without difficulty from the mantle chamber of Sycotypus. If Sycotypus is allowed to remain out of water for some hours the Planocera usually crawl out. The form is fairly satisfactory for study. 44 PLATYHELMINTHES. TREMATODA. Trematodes are flat worms which lead a wholly parasitic life, but which have retained, to a greater or less degree, those organs that characterize free-living animals. Some Trematodes are parasitic upon the outside (or ectoderm) of other animals, and are hence called " ectoparasites." HABMATOLOECHUS (DISTOMUM). This form is found as a parasite in the lungs of frogs. In some localities a large proportion of the frogs are infested and several specimens are frequently found in one frog. The host of the asexual generation of this species is not known, but in a closely allied species the asexual generation lives in the pond- snail. The living worm is cylindrical and pointed at both an- terior and posterior ends. With a low-power objective note : 1. The anterior sucker, surrounding the mouth. 2. The ventral sucker, near the middle. 3. Do you find eyes ? 4. The alimentary canal. (a) Mouth. (b) The muscular pharynx. (c) Soon after leaving the pharynx the intestine divides into two equal branches, which pass, one on the left and one on the right side, to near the end of the body. These intestinal branches do not send out lateral branches as they do in Bdel- loura. The Water-vascular System. — A small opening will be found at the posterior end of the body from which a duct passes forward in a median position to a point a little posterior to the median sucker. Here it divides and sends a branch on either side of the worm to near the anterior end. The Nervous System. — This is difficult to see, but on either side of the pharynx a small, deeply stained mass, the cerebral ganglia, may be visible. Three pairs of longitudinal nerves pass back to near the posterior end of the body. H^MATOLCECHUS (DISTOMUM). 45 Make a drawing showing the above structures as far as you have seen them. The Reproductive Organs. — Male: Two large bodies, the testes, very definite in outline, occupy the posterior end of the worm. A duct from each, the vas deferens, passes forward, and the two unite just posterior to the point where the intestine branches. By means of a median, common duct, they open to the exterior through the male genital opening. This is situ- ated on the ventral surface, just below the point where the intestine branches. Female: Some of the ducts are difficult to see, and in many cases they cannot be followed, but some of the organs can be found in most of the specimens. The ovary is a lobed organ lying a little to one side of the middle of the animal, and just anterior to the testes. Lying against it is the sac-like ootype, into which the ovary opens. From the posterior end of the ootype the long, coiled, duct- like uterus passes backward to near the posterior end of the worm, turns and passes forward, and finally opens, at a point on the ventral surface near the male opening. The uterus of an adult worm usually contains embryos and fills the body, so as to ob- scure the other parts. The vitellaria consist of numerous small, rounded masses that lie near the margins of the animal. The products of these organs are emptied into the ootype through a short common duct, just ventral to the ootype. Do you know what they are for? Laurer's canal is a short duct which leads from the ootype to the exterior. Its function is doubtful. Goto: Studies on the Ectoparasetic Tremetodes of Japan. Jour. Col. Sci. Imp. Univ. Tokyo, 8, 1894. Linton: The Process of Egg Making in the Trematode. Biol. Bui., 14, 1908. Leuckart: Die Blasenwurmer und ihre Entwicklung. 1856. : Die Parasiten des Menchen. Schauinsland : Beitrag zur Kenntnis der Embryonalentwicklung der Tre- metoden. Jen. Zeit. f. Naturwiss. Neue Folge, 9, 1883. Thomas : Development of the Liver Fluke. Quart. Jour. Mic. Sci., 23, 1883. 46 PLATYHELMINTHES. CESTODA. The Cestoda are endoparasites which possess very few of those organs that are characteristic of free-living animals. They have no alimentary canal, no organs of special sense, and, except in the head, the nervous system is feebly developed. On the other hand, the organs needed for the reproduction of the species are enormously developed, so that in the more mature portions of the animal, the ovaries, testes, and accessory organs occupy nearly the whole space. Can you explain why this is true? CROSSOBOTHRIUM LACINIATUM. This form passes its adult life in the intestine (spiral valve) of the sand-shark. Cestode larvae which may be the young of this species are abundant in the cystic duct of the squeteague. How the developing eggs and embryos are conveyed from the shark to the squeteague is not known. The transfer of the larvae from the squeteague to the alimentary canal of the shark can be easily understood. Adult Stage. — 1. Notice specimens that are attached to the wall of the intestine of the shark. 2. Observe movements of specimens in a dish of sea-water. Do the suckers have independent movements? 3. With a low power of the compound microscope, or with a hand-lens, note that the worm is made up of a head portion, the scolex, and of numerous segments, the proglottids. What is the relative size of the proglottids in the different regions of any specimen? Where are new proglottids produced? (See Curtis.) Are the proglottids attached to one another with equal firmness in all parts of the body? Note their peculiar shape, and how they are connected together. In the above ex- amination, if living material is used it will often be desirable to stretch portions of the animal very gently with your forceps. 4. Note the number and arrangement of the disk-like suck- ers. How are they borne on the scolex? Do you find each sucker to be entirely simple ? Draw the adult worm. CROSSOBOTHRIUM LACINIATUM. 47 5. Cut from the head-end of a living specimen a piece con- sisting of a scolex and not more than one or two proglottids. Place this on a slide, cover, being careful not to compress too much at first, and examine the scolex carefully again to make sure you understand its structure. 6. Look for transparent tubes coiling about in the scolex and Hs suckers. Compress the specimen by drawing off as much water as possible with filter-paper, and look again for the trans- parent tubes. These are portions of the water-vascular system. Recall the description of this system given in the lecture or in text-books. The finer branches which lead from the main trunks are difficult to identify with certainty, but by using the high power of your microscope, and focusing just below the surface in the more transparent portions of the scolex, the flame cells may easily be seen. The " flame " appears like a short, thick whip lost in con- tinual vibration. Find such flames and watch them carefully. If not found at once, let the preparation stand and examine in about half an hour. In the older preparation they are frequently easier to find. 7. In both scolex and proglottids of fresh specimens many clear, transparent, thread-like muscle fibers may be seen. There will also be found an abundance of clear, rounded granules of lime. 8. Watch the movements of the large, detached proglottids. Pull proglottids from the posterior end of the specimen to see how easily they may be detached. Very many tape-worms have these " motile proglottids," which in some cases remain alive for so long after being detached as to seem almost like independent animals. Mount stained specimens of proglottids in balsam and study the reproductive organs.1 1. On one side of the proglottid the lateral genital aperture will be seen. The penis is a long, slender organ, found pro- truding, or lying in its sheath near the lateral aperture. The vas deferens, a long, convoluted tube, extends from the penis 1 Specimens may be killed in the manner described for Bdelloura. Enough pressure should be used to flatten the proglottids decidedly. 48 PLATYHELMINTHES. to the testes, which form many rounded, deeply stained struc- tures that lie about the oval outline of the uterus. On leaving the penis the vas deferens extends toward the pointed end of the proglottid, along the side of the uterus, until it reaches a point anterior to it, where it may sometimes be seen sending branches to the testes, but is frequently lost. Throughout its length it is greatly convoluted and is generally filled with sper- matozoa. 2. At the base of the penis, in the lateral genital aperture, is the external opening of the female organs'. From this point a small tube, the vagina, leads to a point below the sac-like uterus, which is sometimes very large and sometimes collapsed and small. The vagina ends in a small pouch, the ootype, from which a short canal (sometimes visible, but more often obscured by the vagina, which lies above or below it) leads to the uterus. 3. The ovary consists of a large many-fingered mass in a median position, near the posterior end of the proglottid. It surrounds, more or less completely, the end of the vagina and ootype. 4. The vitelline glands occupy the posterior corners of the proglottid and may extend anteriorly along its margins, by the sides of the testes, nearly to its anterior extremity. The ducts from the vitelline glands unite and join the ootype. 5. The shell gland is a small median mass that is situated between the lobes of the ovary around the ootype. From the lecture and figures, understand the relation of the ducts of these glands and the vagina to the ootype and uterus, how and where the eggs are fertilized, and how they are finally lodged in the uterus. Why should hermaphroditism occur in this form? Draw a figure of the proglottid showing all of the parts you have seen. Larval Stage. — Examine and draw a specimen of the larva found in the cystic duct of the squeteague. The scolex with its suckers at the anterior end, and the opening of the water- vascular system at the posterior end, are readily seen. Compress TETEASTEMMA. 49 slightly if the trunks of the water-vascular system are not easily seen. They can always be seen in preserved and stained speci- mens that have been killed under pressure. If you have trouble in seeing them, examine such a specimen. Do you find pro- glottids? Understand the relation of this larva to a true cysti- cercoid. Curtis: Crossobothrium laciniatum and Developmental Stimuli in the Cestoda. Biol. Bui., 5, 1903. : The Formation of Proglottids in Crossobothrium laciniatum. Biol. Bui., 11, 1906. Linton: A Cestode Parasite in the Flesh of the Butterfish. Bui. U. S. Bur. Fish., 26. 1906. Tennent: A Study of the Life-history of Bucephalus haimeanus: A Parasite of the Oyster. Quart. Jour. Mic. Sci., 49, 1906. NEMERTINEA. Several representatives of this group are rather easily ob- tained. Some of these, as some species of Cerebratulus and Meckelia, are large, but they are generally unsatisfactory for anatomic study, as they are opaque and filled with a connective- tissue parenchyma that binds the organs together. Further- more, they are especially likely to cut themselves into small pieces by contraction of muscles in the body-wall. TETRASTEMMA. This small animal lives among the forms that are generally found attached to piles. Specimens can usually be found by plac- ing scrapings from piles in a glass jar with a little sea-water and allowing them to stand from a half hour to three hours. The animals may then be found, with the aid of a lens, on the sides of the dish, usually near the surface. With a pipet transfer a specimen to a slide, cover it, and examine with low and high powers of the microscope. Notice : 1. The shape of the body, the four eye-spots, and the ciliated grooves. 2. The straight alimentary canal. The diverticula of the intestine and the terminal anus. 4 50 PLATYHELMINTHES. 3. The enormous proboscis, consisting of a large anterior eversible portion, and a smaller posterior portion that is not eversible. When the proboscis is retracted it is bent upon itself. Stylets are present in the eversible portion, near its inner end. Can you determine how the proboscis is protruded and retracted? Does the proboscis have anything to do with the digestive system? 4. Beneath the posterior eye-spots are the cerebral ganglia, from which lateral nerve cords extend posteriorly. 5. If the specimen happens to contain eggs, they will lie between the diverticula of the intestine. They are compara- tively very large. Coe: Development of the Pilidium of Certain Nemerteans. Trans. Conn. Acad., 10, 1899. : On the Anatomy of a Species of Nemertean (Cerebratulus lacteus). Trans. Conn. Acad., 10, 1890. Verrill: The Marine Nemerteans of New England and Adjacent Waters. Trans. Conn. Acad. Sci., 8, 1892. C. B. Wilson: Habits and Early Development of Cerebratulus lacteus. Quart. Jour. Mic. Sci., 43, 1900. NEMATHELMINTHES. Body elongated, cylindrical, and not segmented. Many are parasitic forms. Anus usually present. Coelom not filled with parenchyma. The classes may not be genetically related. CLASS 1. Nematoda. Many are internal parasites, but others are found in fresh and salt water and in damp earth. Body pointed at both ends. Mouth terminal, anus ven- tral. (Ascaris, Trichina, Gordius.) CLASS 2. Acanthocephala. Formidable intestinal parasites. Proboscis bearing hooks. No alimentary canal. (Echinorhynchus.) CLASS 3. Chsetognatha. Marine, and all but one species pelagic. With caudal and lateral fins and bristle-like jaws. (Sagitta.) ASCARIS. Animals belonging to this genus are common in the intestine of the horse and pig, and are not uncommon in man. Examine specimens and see if they have any organs that would aid them in clinging to the intestinal wall. How can they retain their positions ? 1. Can you determine which is anterior and which is posterior? Is there any indication of segmentation? Can the ventral side be told from the dorsal? 2. Find the mouth and see that it is bounded by three lips. Notice how these are placed and find the papillae on the ventral ones. Find the anus and note its position. This serves also as a reproductive aperture for the male. In the female the repro- ductive aperture is situated about one-third back from the anterior end. It can be seen only in favorable specimens. 51 52 NEMATHELMINTHES. 3. Open a well preserved or fresh specimen along the dor- sal line and notice the definite codom, and the straight alimentary canal. If the specimen is a female, find the Y-shaped genital organs, the free, ovarian ends of which are slender and some- what tangled. The position of the external genital opening has already been noted. In the male there is a single, tangled, thread- like testis, which joins the enlarged seminal vesicle that extends to the cloaca. The nervous system consists of a circum-esopha- geal ring, six longitudinal nerves, the dorsal and ventral of which are larger than the others, and anterior nerves. It is not easily seen. A drawing is desirable. Montgomery : The Adult Organization of Paragordius varius. Zool. Jahrb., 18, 1903. TRICHINA. Encysted specimens may frequently be found by examining thin pieces of pig muscle obtained from the meat market. Pigs fattened in small pens and fed on table waste, or in slaughter- yards and fed on the offal of butchered animals, are much more likely to be infected than others. Scavenger rats and cats are frequently infected. 1. Flatten a piece of muscle containing trichinae between two slides in a little glycerin and notice the relation of the ani- mal to the muscle fibers. Notice the cyst that surrounds it and see if you can determine whether this was formed by the host or the parasite. There are frequently fat cells at the ends of the cyst. Just after the parasites are encysted, the cysts are surrounded by capillaries that may be injected by injecting the vessels of the host. These may be found only at a definite stage after encystment. Why are they formed? Do they indicate how the cysts were formed? If the trichinae are abundant see if you can find more than one in a cyst. 2. Notice the shape that is assumed by the parasite. Is the coiling always the same? If your material is fresh, mount some of fhe muscle between slides without glycerin, warm the slide, and see if the encysted animals will move. TRICHINA. 53 3. Are the anterior and posterior ends alike? Is there any indication of a mouth? The large cells that form the intestine can frequently be seen. It should be borne in mind that the encysted specimen is not fully adult and that the animal grows after reaching the alimentary canal of the next host. Make a drawing of an encysted animal. Glazier: Report on Trichinae and Trichinosis. U. S. Treas. Dept. Doc. No. 84, Marine Hospital, 1881. TRCXHELRHNTHES. Minute animals whose adult structure seems to be related to that of the trochophore larva. Mouth usually surrounded by a circlet of cilia. Three classes (Rotifera, Dinophilea, and Gastro- tricha) are referred to this phylum, but they may not be geneti- cally related. ROTIFERA. Mostly fresh-water forms, but a few are marine. All are of microscopic size. The pharynx is provided with a masticatory apparatus, and the anterior end bears a trochal disk. Most rotifers are free, but a few are permanently attached, and some, as Melocerta, live in tubes of their own formation. BRACHIONUS (A Rotifer). These animals are frequently quite abundant in ponds and aquaria. They are not very active, and spend most of their time near the bottom among the plants and debris. Owing to their minute size, they must be studied with a high power of the microscope. 1. The body is divided into a trunk, which is inclosed in a transparent cuticular lorica, and a movable tail or foot. The tail is tipped with two processes which form forceps, by means of which it attaches itself to plants. Can you see how these are used? Why does the animal need to attach itself? 2. Projecting anteriorly from the lorica is the retractile trochal disk. Notice the cilia on the margin of this disk. Is the disk used in locomotion? Does the animal always move when the cilia are active ? What other use has the disk ? Is the animal entirely dependent upon the cilia of the disk for loco- motion? 54 BRACHIONUS. 55 3. The mouth is at the ventral border of the trochal disk and leads by a short buccal cavity to the mastax, which is a muscu- lar apparatus provided with three chitinous trophi (a median incus and two mallei). It is used in grinding the food. The grinding movements are easily seen. A very short gullet leads from the mastax to the large stomach. The intestine is short and thick and opens into a cloaca. The anus is near the base of the tail, on the dorsal surface. 4. The reproductive and excretory systems are not easily seen. An ovary and a large vitellarium are present. The ovi- duct opens into the cloaca. Two long nephridial tubes open into a contractile vesicle that in turn opens into the cloaca. 5. There is a single ganglion in the anterior dorsal region, immediately beneath two red eye-spots. Anterior to the eye- spots is a dorsal feeler, which is a tactile organ. There are many common rotifers that have no lorica and some of them have the trochal disk two-lobed. Jennings: Rotatoria of the United States with Especial Reference to those of the Great Lakes. Bui. U. S. Fish Com., 19, 1899. Whitney: The Desiccation of Rotifers. Am. Nat., 42, 1908. MOLLUSCOIDA. Lophophore present. Mouth and anus closely approximated. Ccelom usually present. CLASS 1. Polyzoa. Usually colonial. Zooids of small size and pro- tected by a firm cuticle. Subclass 1. Ectoprocta. Anus outside of the lophophore. Order 1. Gymnolaemata. Marine. Circular lophophore. No epistome present. (Bugula, Membranipora.) Order 2. Phylactolsemata. Fresh -water. Horseshoe -shaped lophophore. Epistome present. (Plumatella, Pectinatella.) Subclass 2. Endoprocta. Colonial or solitary. Anus and mouth both in- side of the lophophore. (Loxosoma, Pedicellina.) CLASS 2. Phoronida. Marine. Solitary. Lophophore horseshoe-shaped with each end coiled. (Phoronis.) CLASS 3. Brachiopoda. Marine. Solitary. Bivalve shell. Usually at- tached by a peduncle. Order 1. Inarticulata. Valves not united by a hinge. (Lingula.) Order 2. Articulata. Valves hinged. Usually with a shelly loop to support the lophophore. (Terebratulina.) POLYZOA; BUGULA. The colonies are very common in shallow water along shore, attached to rocks and piles. They may be examined with the aid of a glass-bottomed pail in the positions they occupy on the 56 BUGULA. 57 sides of the piles of almost any old wharf. What must be the source of their food? What part of the colony is likely to be best nourished? Collect specimens by scraping the piles and see what forms are associated with them. 1. Examine a colony in a dish of water and see how it branches. Does it present any regularity? Make a drawing of a colony. 2. Remove one of the flat branches, place it in a watch-glass of water, and examine it with a low power. What more can be observed regarding the branches? How are the cups arranged? Are the cups on the two sides of a twig placed in definite rela- tions to each other? Where are the empty cups found? Why? Can you find connections between the cups of the two sides? Make a drawing showing the arrangement of the cups. 3. Allow a living branch to remain undisturbed for a few moments and with a microscope see how the thin outer mar- gins of the cups are unfolded as the zooids protrude. 4. Mount a specimen on a slide, cover, and compare the tentacles of an expanded zooid with those of the hydroids that you studied. How do they differ? How must the animal feed? 5. How are the tentacles arranged around the distal end of the body? How many tentacles are there ? Look for the mouth. 6. Can you see the parts of the alimentary canal? Is there food in the stomach ? How does the zooid pull itself back into its cup? 7. Look for avicularia and observe their movements and structure. Where is the jaw hinged? Where are the muscles that open it? Where are the muscles that close it? Of these muscles, which are largest? Why? See if " sense hairs" can be found between the jaws. What is their probable use? Draw an avicularium. 8. Ooecia with embryos will be found in some specimens. Where are they placed? 9. Put powdered carmine in the water with a living branch and see if the zooids will eat it. 10. Put a small living branch in a drop of sea-water under a supported cover-glass and see if any of the zooids will expand. 58 MOLLUSCOIDA. If any do expand they may be examined, with a high power, to good advantage. Study specimens that have been killed while expanded. Stain with iodin, wash in water, mount in glycerin, study with a high power. Find the retractor muscles, the funiculus, germ cells, and, if possible, the shape of the alimentary canal. As the alimentary canal bears a definite relation to the position of the zooid on the branch, its shape can be readily determined only when the branch happens to be twisted so the zooid is to be seen in side view. Make a drawing showing the structure. If time permits it will be desirable to examine an incrusting form to determine its method of branching and the way in which the cups are closed. Nitsche: Beitrage zur Kenntnis der Bryozoen. Ueber die Anatomic und Entwicklungsgeschichte von Flustra membranacea. Zeit. f. Wiss. ZooL, 21, 1871. PLUMATELLA.1 If the zooids of this fresh-water form will expand in a watch- glass of fresh water, notice the shape of the lophophore and the position of the epistome. In such a specimen the ganglion may be seen as a rounded mass just beneath the lophophore, between the mouth and the anus. Study the statoblasts with a micro- scope. Allman: Monograph of the Fresh-water Polyzoa. Ray Soc., 1856. BRACHIOPODA. TEREBRATULINA. Examine specimens on the demonstration table and notice : 1. Shell. The difference in the size and shape of the two valves and their position in relation to the body. How are the valves articulated? How are they opened? 1 Slices of the large gelatinous form, Pectinatella, placed in watch- glasses of fresh water, make very satisfactory objects for study, as the zooids will soon expand, and they are then hi the best possible position for study. TEREBRATULINA. 59 2. Peduncle. Its position. What is its use? 3. Muscles. Those used in opening and closing the shell. 4. Lophoph&re. Consisting of two elongated arms with a double row of tentacles on each. 5. Mouth. Notice its relation to the grooves running be- tween the rows of tentacles on each of the arms of the lophophore. Brooks: Development of Lingula. Ches. Zool. Lab. Sci. Results, 1878. Conklin: The Embryology of a Brachiopod, Terebratulina septentrionalis. Proc. Am. Phil. Soc., 41, 1902. Hancock : On the Organization of Brachiopoda. Trans. Roy. Soc., London. 148, 1858. Morse: Observations on Living Brachiopoda. Mem. Bost. Soc. Nat. Hist., 5, 1902. ECHINODERMATA. Radially symmetrical animals, with calcareous plates in the integument. Water-vascular system always present. CLASS 1. Asteroidea. With radiating arms not sharply defined from the central disk. Ambulacral feet in grooves on the oral side. Order 1. Phanerozonia. With large marginal ossicles. (Astropecten.) Order 2. Cryptozonia. Marginal ossicles inconspicuous. (Asterias.) CLASS 2. Ophiuroidea. With slender radiating arms sharply defined from the central disk. No ambulacral grooves. Order 1. Ophiurida. Arms not branched. (Ophiura.) Order 2. Euryalida. Arms branched. (Astrophyton.) CLASS 3. Echinoidea. Globular, or somewhat disk-shaped, spiny bodies. Shell or test composed of close-fitting plates. Order 1. Regularia. Nearly globular test. Spines rather large. Mouth and anus polar. Jaws present. (Ar- bacia, Strongylocentrotus.) Order 2. Clypeastroidea. More or less flattened test. Spines very small. Anus not polar. Jaws present. (Echinarach- nius.) Order 3. Spatangoidea. Somewhat flattened and elongated. Spines very small. Neither mouth nor anus polar. CLASS 4. Holothuroidea. Bodies soft, elongated and cylindrical. Mouth and anus polar, the former surrounded by a cir- clet of large oral tentacles. 60 ASTEKIAS. 61 Order 1. Elasipoda. Well-marked bilateral symmetry. Tube feet on ventral and papillae on dorsal surface. Deep sea only. Order 2. Pedata. Ambulacral feet in rows or scattered. (Thyone, Cucumaria.) Order 3. Apoda. Without tube feet. Worm-like. (Synaptula.) CLASS 5. Crinoidea. Temporarily or permanently attached by a stalk. With five branching arms radiating from a small disk. Order 1. Neo-Crinoidea. Characters as above. (Antedon, Pentacrinus.) Berry: Metamorphosis of Echinodenns. Quart. Jour. Mic. Sci., 38, 1905. Grave: Occurrence among Echinodenns of Larvae with Cilia Arranged in Transverse Rings. Biol. Bui., 5, 1903. ASTEROIDEA: ^ ASTERIAS. (Starfish.) Starfishes are rather common along most coasts and are among the worst enemies of oysters. They can generally be most satisfactorily examined on shallow-water mussel-beds or on rocks covered with barnacles. Places where starfish occur should be visited, and the conditions under which they live ex- amined. Determine : 1. Upon what and how they feed. 2. What their enemies must be. 3. How their arms are repaired when injured. Do you find specimens that are growing new tips to injured arms or are such arms apparently replaced ? When an arm is injured how must the animal proceed to repair it? 4. Do specimens ever conceal themselves? See if specimens can be found with pieces of grass and weeds covering them. Try picking these pieces off to see if they adhere. 5. Do the animals have other means of protection? Examine a specimen and notice: 1. That the surface by which the animal clings, the oral 62 ECHINODEEMATA. surface, is different from the other, aboral surface, and that both surfaces are covered with short spines. What is the use of the spines? 2. It consists of radiating arms and a central disk. 3. On the aboral surface of the disk, near the junction of the two arms, a small, frequently conspicuously colored, circular body, the madreporic plate. The two arms adjacent to this plate are sometimes referred to as the bivium, and the remaining three as the trivium. The radial symmetry of the animal is disturbed ex- ternally only by the madreporic plate. Examine this plate with a lens and determine its structure. 4. On the oral surface, the mouth. Note its size and see if it is provided with jaws of any kind. Would you expect jaws? Why? 5. Radiating from the mouth are the ambulacral grooves, one on each arm. In these grooves are the ambulacral or tube feet. Do they have a definite arrangement? Along the sides of the grooves are slender spines that differ from the general body-spines in being movable. 6. Scrape the tube feet from a portion of an ambulacral groove of a dried specimen and notice the pores through which the feet are attached to organs inside the arm. Notice also the exposed ambulacral plates and determine their relation to the pores. Draw figures of the aboral and oral surfaces of a starfish, and a diagram to show the relation of the ambulacral plates and pores. Place a living starfish in a dish of sea-water. 1. Study its method of locomotion. How are the ambu- lacral feet used? How far can they be protruded? 2. Tear the starfish quickly from the bottom. Do any of the feet remain behind ? Understand how they are attached. 3. Place the starfish on its aboral surface and watch it turn over. 4. Find the thread-like dermal branchice projecting through the body integument. Are they withdrawn when touched? What is their function? 5. Stroke the starfish with a camel 's-hair brush and notice how the hairs are caught. Can you determine by what and ASTEEIAS. 63 how they are held? With a hand-lens examine around the bases of the spines, and see the arrangement of the pedicellarice. Their function is obscure, but they enable the starfish to hold small objects firmly and they may be of service in dealing with possi- ble surface parasites. 6. Remove some of the pedicellarice with a scalpel and ex- amine them under the microscope. Is there more than one kind? Draw a pedicellaria. Internal Structure. — Make the dissection under water, and in cutting through the integument be careful not to injure the underlying soft parts. With strong scissors cut through the aboral body-wall near the tips of the rays of the trivium. Carry the cuts forward along the sides of the rays to the disk. The cavity thus opened is the ccelom or body cavity. Lift up the integument at the tip of each arm and carefully snip away the mesenteries which attach the organs to it. Cut the membranes that extend into the disk opposite the junc- tions of the arms, and remove the three-rayed flap of integu- ment thus freed, cutting as close as possible to the madreporite, but leaving this in place. Digestive System. — In studying this system you should con- stantly bear in mind the peculiar method by which the animal feeds, as the digestive system is highly modified to suit this method. 1. The short, cone-shaped intestine and the intestinal cceca were probably removed with the integument. The intestine probably does not function, and may be regarded as a vestige. It opens near the center of the disk, on the aboral side, by a very minute anus that is very hard to see. 2. The stomach, which occupies the greater part of the space in the disk, is composed of a small aboral portion, the pyloric division, that receives the ducts from the hepatic caeca, and a larger, lobed, cardiac division, into which the mouth opens. The cardiac portion may be everted through the mouth, thus being turned wrong side out. Five pairs of muscles, which draw this portion of the stomach back into place, may be seen at- 64 ECHINODERMATA. tached to the ridges formed by the ambulacral plates in each arm. How is it possible for the stomach to be everted? What reason is there for two divisions? 3. In each arm is a pair of long, glandular organs, the hepatic cceca. The ducts of each pair unite and join the pyloric divi- sion of the stomach by a common duct. These are digestive glands. What reason is there for having ten enormous digestive glands? Does this have anything to do with the method of feed- ing? Make a drawing of the digestive system of the disk and one arm. Reproductive System. — Turn the hepatic caeca to one side and notice the ovaries or testes. The sexes are separate, but the organs have the same general appearance in both sexes. They vary in size according to the season of the year, sometimes being so small that they are not easily found, and again being nearly or quite as large as the hepatic caeca. With a pair of forceps lift up one of these organs and see where it is attached. It is at this point that the reproductive cells reach the exterior. How many gonads are there ? Draw the gonads into another arm of your figure. Water-vascular System.1—!. Carefully remove the side of the stomach next to the bivium, being very careful not to disturb the stone canal, which runs from the madreporic plate to the margin of the membrane around the mouth. By the side of the stone canal is a thin band of tissue formerly supposed to be a heart. It is now generally believed to be connected with the reproductive system, and is frequently referred to as the axial organ. It has nothing to do with the system now under con- sideration. 2. The circular canal, which is joined by the stone canal at the outer margin of the peristomial membrane, follows the mar- gin of the membrane and so encircles the mouth. Originating 1 This may be injected in fresh specimens, either with gelatin or fine starch-mass, by picking up one of the radial canals with a hypodermic syringe and injecting toward the disk. ASTERIAS. 65 from it at points very near the ampullae of the first tube feet are nine small vesicles, Tiedemann bodies. They are smaller than the ampullae and project in toward the mouth. The posi- tion where the tenth Tiedemann body might be expected, is taken by the stone canal. 3. Leaving the circular canal are five radial water tubes, one for each arm. These tubes lie along the oral surfaces of the ambulacral plates, and are accordingly not visible on the inside of the animal. The position of the tube can best be understood by making a transverse section of an arm. It will then be seen either in injected or uninjected specimens, lying immediately below the ambulacral plates. In injected speci- mens it may be followed by dissecting from the oral side, from the circular canal to the extremity of the arm, where it ends in a small tentacle. 4. Along the sides of the ambulacral ridges, within the body- cavity, are rows of little bag-like ampullce. Determine their re- lation to the ambulacral pores. If the specimen is fresh, press a few ampullae and see if the corresponding tube feet are affected. Can you determine their function ? In a dissection it is hard to find the connecting tubes that join the radial tubes to the tube feet, but they can sometimes be seen in sections of arms of injected specimens. They can readily be seen in microscopic preparations. The water-vascular system is very distinctive for the Echi- nodermata, and you should understand perfectly: (a) How the tube feet are extended. (6) What causes them to adhere. (c) The connection between tube feet, ampullae, connecting canals, radial water tubes, circular canal, stone canal, and mad- reporic plate. (d) How it is possible to extend one foot without extend- ing others. Make a drawing showing the arrangement of the water-vascu- lar system, Nervous System. — This is not easily studied by dissection. 5 66 ECHINODERMATA. It consists of a nerve ring which encircles the mouth and lies just ventral to the circular water canal, and five radial nerves that extend down the arms just beneath the radial water tubes, to end at the tips of the arms in pigment spots, the eye- spots. The whole central nervous system is superficial and forms a portion of the outer covering of the body. The radial nerves can be seen by separating the rows of ambulacral feet, but it is much more satisfactory to study them in prepared sections. Muscular System. — Examine the walls of the starfish for its muscular system. If time permits, it will be desirable to macerate a portion of an arm to see the skeleton to which these muscles are attached. Study prepared sections of the arm of a small starfish and determine the relation of organs. 1. The hepatic caeca. How are they supported? What is their structure ? 2. The radial canal, connecting tubes, tube feet, and ampullae. 3. The thickened, deeply stained, radial nerve between the tube feet and below the radial water tube. 4. The perihaemal canal, divided by a thin partition, that lies between the radial water tube and the radial nerve. Make a drawing of a section of an arm that will show these points. Understand how a starfish can open an oyster or a mussel and how it digests it when open. How can it digest a barnacle or a small snail ? How does it respire ? Field: Larva of Asterias yulgaris. Quart. Jour. Mic. Sci., 34, 1892. Goto: The Metamorphosis of Asterias pallida, with Special Reference to the Fate of the Body Cavities. Jour. Col. Sci. Imp. Univ., Tokyo, 10, 1898. Harvey: Methods of Artificial Parthenogenesis. Biol. Bui., 18, 1910. Jennings: Behavior of the Starfish Asterias forreri. Univ. Calif. Pub. Zool., 4, 1907. Mead: The Natural History of the Star-fish. Bui. U. S. Fish Com., 1899. OPHIUBOIDEA. 67 OPHIUROIDEA. OPHIURA. (Serpent-Star.) These animals live more or less concealed in crevices, shells, eel-grass, etc., and may be obtained either by dredging or by pulling a dip-net through eel-grass. They are not conspicuous objects along the shore, as are starfish, and they differ essen- tially from starfish in their method of locomotion and their method of feeding. Examine a specimen and notice : 1. The appearance of the disk and arms. Are the spines similar to those of Asterias? The arms are more flexible. In what direction do they bend easiest ? 2. The five buccal plates, one of which bears a madreporic opening that is not easily seen. 3. The size and shape of the mouth. 4. The ambulacral groove. Is it distinct? 5. The ambulacral feet. Do they have suckers? How are they arranged? 6. The openings to the bursse, near the bases of the arms. Most Ophiurians have five pairs of these openings, one for each bursa, but Ophiura has ten pairs, two for each bursa. Draw an oral view of a specimen. Place a living specimen in a dish of sea-water and watch its movements. 1. Compare the rate and method of movement with Asterias. 2. Are all of the arms used in progressing in the same way? 3. See if the arms can be used interchangeably or if a cer- tain one is always directed forward. 4. Are the ambulacral feet of any service? Do they adhere? The internal structure shows that the stomach is not eversible and that the hepatic caeca do not extend into the arms. Is there any correlation between these two facts? The nervous and water-vascular systems are very similar to those of Asterias, but here the former lies within instead of 68 ECHINODERMATA. on the surface of the arm, the entire arm being encased with four or more rows of shields. They can be studied best in sections. Grave: Ophiura brevispina. Mem. Biol. Lab. Johns Hopkins Univ., 4, 1900. Mem. Nat. Acad., 8, 1899. ECHINOIDEA. STRONGYLOCENTROTUS.1 (Sea-Urchin.) In some localities sea-urchins can be found in tide pools or near low-tide mark, where they may be very abundant. In other localities they can be obtained only by dredging. When possible they should be observed in their native places and the conditions noted. 1. What apparently serves as food for the animal? Can you determine how this is obtained? 2. Do you find attempts at concealment? 3. Are the animals able to climb? Put a living sea-urchin in a dish of sea-water and study its movements. 1. When placed on its back, how does it turn over? 2. What is the normal method of progression? 3. How are the spines arranged when the animal is creeping on the bottom? 4. What difference do you note between the spines on the lower and upper surfaces? 5. How long are the tube feet? Are they used with the spines in moving or do both sets of organs act independently ? 6. Grasp a spine with your forceps and see if neighboring spines respond. Do they form a good defensive armor? 7. In what directions may a spine be moved? Remove a spine from a preserved specimen and determine how it was attached and how the muscles that moved it were attached to the spine and to the test. Make a diagram showing the arrangement. 1 These directions will serve for any of our common sea-urchins. STRONGYLOCENTROTUS. 69 8. Do the spines have any definite arrangement? 9. By means of the tube feet, notice that there are five awfrw- lacral areas, between which are five inter-ambulacral areas. 10. Notice an area on the aboral surface which is free from spines. This is the periproct. 11. Notice the membrane around the mouth, the peristome. 12. Look for pedwellarice on the peristome. In what other places are pedicellariae found? Do they differ from those of the starfish? Draw one. »*• 13. Notice the tentacles (modified tube feet) on the peristome. 14. The dermal branchice are shrub-like appendages at the outer edge of the peristome. They are situated opposite each inter-ambulacral area. Skeleton.1 — Examine the aboral surface of a cleaned "test" and note: 1. The periproct has scattered plates which cover the anal opening. (Four triangular ones in Arbacia.) 2. Around these anal plates are five large ones, that form the apices of the inter-ambulacral series of plates. These are the genital plates, and, each is perforated by a small opening, the genital pore. 3. That one of the genital plates is larger than the others and is full of very minute pores. This is the madreporite, which is homologous with the madreporite of the starfish. Determine its structure with a lens. 4. Between the genital plates are five smaller ocular plates, also perforated, which form the apices of the ambulacral series of plates. These plates and the genital plates, together form, what is known as the apical system. 5. In the ambulacral series of plates, the arrangement of the openings (ambulacral pores) through which the tube feet protrude. 1 If a preserved specimen of Strongylocentrotus be placed in a solution of nitric acid (about 15 percent) from five to ten minutes, the plates of the test can be more easily seen, especially after drying. This is apparently due to the coloring-matter in the animal itself. Arbacia is not helped by the treatment. 70 ECHINODERMATA. 6. Do all of the plates bear balls to which spines were artic- ulated? Are the balls of equal size? Do they have a definite arrangement ? Can you homologize the positions of the ambulacral, inter- ambulacral, ocular, and genital plates in the sea-urchin and starfish? What portion of the starfish is represented by the periproct of the sea-urchin? Make a drawing of the test, showing the ambulacral, inter- ambulacral, and apical systems of plates. 7. Around the peristome, on the inside of the test, note the five auricles forming arches or bridges over the bases of the ambulacral areas. Their purpose will be seen later. With a scalpel or strong scissors, cut around the equatorial region of an alcoholic specimen, taking care to cut through the test only. Break or cut the aboral portion away bit by bit until near the genital plates, freeing the fragments from the internal organs without disturbing their positions. ^ Reproductive System. — How were the gonads (their appear- ance is the same in both sexes) attached to the test? How many are there ? Opposite what areas of the test are they placed ? Where do they open to the exterior? Without mutilating, find the narrow strip of tissue that connects the gonads to each other near their aboral ends. This is the genital rachis. Connected with the genital rachis and lying alongside the stone canal, which leads from the madreporite, is the genital stolon, - Digestive System. — Remove the gonads from the three areas farthest from the madreporic plate, lift the remaining aboral portion of the test slightly, and examine the alimentary canal. 1. The large and conspicuous jaws, frequently called the lantern. They will be studied later. 2. The esophagus, passing between the jaws, and bending over to one side to join the intestine. 3. The intestine. Notice its size and its shape. Do its loops have any relation to the positions of the gonads? 4. The intestinal siphon, lying along the intestine and attached to it at both ends. STRONGYLOCENTROTUS. 71 5. The rectum, running from the end of the intestine to the anus. 6. The mesenteries which hold the various organs in place. Make a drawing to show the reproductive and digestive organs. — ^ <* Water-vascular System. — 1. The stone canal leads from the ( madreporite to the circular canal, which encircles the esophagus V at a point just above the lantern. 2. From the circular canal radial tubes pass over the top and down the sides of the lantern, to pass through the auricles and up the ambulacral tract, to the ocular plates. They can be easily seen along the si