14 r ca , 4 Cornell Mniversity Library BOUGHT WITH THE INCOME FROM THE SAGE ENDOWMENT FUND THE GIET OF Henry W. Sage 1891 Aeon MEADS 22/b/14 5474 lark anniversary volume; Cornell University The original of this book Is in the Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924024546347 a 7 a4 Ge go> MARK ANNIVERSARY VOLUME TO | a sEowatd ‘Laureng Math eee 2 Bien Professor of Anatomy at oo oe a ae M “‘Directa of the 2oilogieal Laboratory at Harvard 1 Unters ee ee in Celebration. of | Yar a. Swe Work. ‘Tor the Advancement oF Zobiogy hat ee from bis former S tudenis 2 1877-1903, ° ‘al a oe NEW YORK - pire HRC! HOLT AND ‘COMPANY = oe 3 1903, 7 MARK ANNIVERSARY VOLUME Ge G : L- le vi MARK ANNIVERSARY VOLUME TO woward Laurens Mark Hersey Professor of Anatomy ana Director of the Zoblogical Laboratory at Harvard University’, “in Celebration of Twenty-five Years of Successful Work for the Advancement of Zoology from his former Students 1877-1902 NEW YORK , HENRY HOLT AND COMPANY 1903 & Copyright, 1903, BY HENRY HOLT AND COMPANY. COMMITTEE OF MANAGEMENT. CHARLES B. Davenport, University of Chicago; C. H. Eigenmann, University of Indiana; HERBERT HavitaND Fievp, Concilium Bibliographicum, Zurich, Switzerland; SerraRo Goto, First High School, Tokyo, Japan; Wiuu1am A. Locy, Northwestern University; GerrRitt 8. Mituer, United States National Museum; MarGaretT Lewis Nickerson, University of Minnesota; JacoB RercHarD, University of Michigan; Wiiu1am E. Rirrer, University of California; Henry B. Warp, University of Nebraska. EXECUTIVE COMMITTEE. JacoB REIGHARD, Chairman; CHARLES B. DAVENPORT; Henry B. Warp, Secretary-Treasurer. EDITOR. G. H. PARKER. ili ESTEEMED MASTER: On the completion of your twenty-five years of service at Harvard University, we your pupils seek through this volume to express our devotion to you as our erst- while teacher, as the advocate of the highest ideals in scientific work, and as the trainer of investigators and teachers in zodlogy. We recall with pride the service that was done science by the publication of your work on the Maturation, Fecundation, and Segmentation of the Egg of Limax—a work that introduced into America the then new cytological methods in the application of which this country has since reached an elevated position. It likewise introduced into zodlogy a proper fulness and accuracy of citation and a convenient and uniform method of referring from text to bibliography. It marked a step forward, also, in thoroughness and detail, and in the full recognition that, even in zodlogy, as in physics and chemistry, method is hardly less important than matter. These ideals in produc- tive scholarship have been retained throughout the series of researches issued by yourself and your pupils. Much more personal and more precious to us has been your work in training zoblogists. We call to mind your rigorous preliminary methods that gave us self- reliance, and your constant advice and encouragement; and we have keen and grateful recollections of the critical skill with which you discussed with us our completed studies. But the memories that we cherish most, the inspiration and the stimulus that have abided longest, depend on certain traits of your character of which this is not the fitting place to make analysis, and of which only your students fully appreciate the influence. Your geniality, your sympathy, and especially your scientific honesty and justice—the influence of these on your pupils no less than your scholarship have inspired this tribute of affection and loyalty. GLovEeR Morritut ALLEN, Secretary of the Boston Society of Natural History, Boston, Mass. James ALDERSON BalItey, Jr., Barristers Hall, Boston, Mass. -Francis Noyes Baucu, Jamaica Plain, Mass. Frank Watts Bancrort, Instructor in Physiology, University of California, Berke- ley, Cal. Harry GARDNER BarsBer, Teacher of Biology, DeWitt Clinton High School, New York, N. Y. Vv vi MARK ANNIVERSARY VOLUME. Tuomas Barzour, Student of Zodlogy, Harvard University, Cambridge, Mass. CuaRLes RusseLt Barpeen, Associate Professor of Anatomy, Johns Hopkins Univer- sity, Baltimore, Md. Wiu1aM Barnss, Physician, Decatur, Ill. ELizABETH Emma BickFrorD, Teacher of Biology, Newton High School, Newton, Mass. Henry Bryant BicEtow, Student of Zodlogy, Harvard University, Cambridge, Mass. Maurice ALPHEUS BicELow, Adjunct Professor of Biology, Teachers College, Colum- bia University, New York, N. Y. Rosert Payne Bicetow, Instructor in Biology and Librarian, Massachusetts Insti- tute of Technology, Boston, Mass. Mary Atice Bowers, Instructor in Zoélogy, Wellesley College, Wellesley, Mass. Rosert STANLEY BREED, Professor of Biology and Geology, Allegheny College, Mead- ville, Pa. Epwin Tenney Brewster, Instructor in Natural Sciences, Phillips Academy, Ando- ver, Mass. Epita Nason Bucxineuam, Teacher of Science, Concord High School, Concord, Mass. CHARLES BULLARD, Cryptogamic Herbarium, Harvard University, Cambridge, Mass. Epwarp Aneus Burt, Burr Professor of Natural History, Middlebury College, Middlebury, Vt. WENDELL T. Busu, Brooklyn, N. Y. WaLtTeR BRADFORD CANNON, Assistant Professor of Physiology, Harvard Medical School, Boston, Mass. BENJAMIN FRENCH CARPENTER, Merchant, Chicago, III. FREDERIC WALTON CARPENTER, Edward Austin Fellow in Zodlogy, Harvard Univer- sity, Cambridge, Mass. Wii11aM Ernest Cast ie, Assistant Professor of Zodlogy, Harvard University, Cam- bridge, Mass. Lron Jacos Cots, Austin Teaching Fellow in Zodlogy, Harvard University, Cam- bridge, Mass. Ernest Lez Conant, Attorney at Law, New York, N. Y., and Havana, Cuba. Francis WHITTEMORE CraGin, Professor of Geology, Mineralogy, and Paleontology, Colorado College, Colorado Springs, Col. Howarp Craw.ey, Wyncote, Pa. CuarLes Aucustus Crows lL, Jr., Teacher of Science, Winthrop High School, Win- throp, Mass. CHARLES BENEDICT Davenport, Associate Professor of Zodlogy, The University of MARK ANNIVERSARY VOLUME. vii Chicago, Chicago, Ill.; Director of the Biological Laboratory, Cold Spring Harbor, Long Island, N. Y. GERTRUDE Crorry Davenport, Chicago, Ill.; in charge of Microscopic Methods at the Biological Laboratory, Cold Spring Harbor, Long Island, N. Y. Hersert Spencer Davis, Assistant Zodlogist, College of Agriculture and Mechanic Arts, Pullman, Wash. Mase Lavinia Harte, Teacher of Science, Miss Winsor’s School, Boston, Mass. CHARLES Rocuester Eastman, Assistant in Vertebrate Paleontology, Museum of Comparative Zoélogy, Harvard University, Cambridge, Mass. Cart H. E1rgenmann, Professor of Zodlogy and Director of the Biological Station, University of Indiana, Bloomington, Ind. HERBERT KimBaLu FauLKNeER, Physician, Keene, N. H. HERBERT Havitanp Fievp, Director of the Concilium Bibliographicum, Zurich, Switzerland. Witit1am Lusk WesstTER Frexp, Instructor in Natural Sciences, Milton Academy, Milton, Mass. JEFFERSON BuTLER FLEetTcueEr, Assistant Professor of Comparative Literature, Har- vard University, Cambridge, Mass. Roure Fioyp, Physician, New York, N. Y. Justus Watson FotsoM, Instructor in Entomology, University of Illinois, Urbana, III. WALTER FoRCHHEIMER, Physician, Cincinnati, Ohio. Peter FRANDSEN, Assistant Professor of Zodlogy and Bacteriology, Nevada State University, Reno, Nev. Tuomas Watton GatLoway, Professor of Biology, Milliken University, Decatur, II. Wiiu1aM Francis Ganona, Professor of Botany and Director of the Botanic Garden, Smith College, Northampton, Mass. FrEDERIC GARDINER, Head Master, Yeates School, Lancaster, Pa. JoHN Hiram GEROULD, Instructor in Zoélogy, Dartmouth College, Hanover, N. H. Srrtaro Goro, Professor of Biology, First High School, Tokyo, Japan. FrepERIc Putnam GULLIVER, Science Master, St. Mark’s School, Southboro, Mass. CLARENCE Wixson Hann, Teacher of Science, Little Falls High School, Little Falls, N. Y. Ropert Witu1AM Hatt, Instructor in Zodlogy and Biology, Lehigh University, South Bethlehem, Pa. Joun Irwin Hamaker, Professor of Biology and Geology, Trinity College, Durham, N. C. CHARLES STEDMAN Hanks, Lawyer, Boston, Mass. RouaNnp Haywarp, Boston, Mass. Anniz Parker HEencuMan, Cambridge, Mass. viii MARK ANNIVERSARY VOLUME, Frank Harris Hircucock, Department of Commerce and Labor, Washington, D. C. Artur TenNEY Hoiprook, Physician and Surgeon, Milwaukee, Wis. FREELAND Hows, Jr., Biologist, Board of Public Works, Harrisburg, Pa. Ipa HenrierreE Hype, Associate Professor of Physiology, University of Kansas, Lawrence, Kan. Rozsert Tracy Jackson, Assistant Professor of Paleontology, Harvard University, Cambridge, Mass. HERBERT SPENCER JENNINGS, Assistant Professor of Zodlogy, University of Penn- sylvania, Philadelphia, Pa. Hersert Partin JoHNson, Associate Professor of Bacteriology, University of St. Louis, St. Louis, Mo. Cuancry JupAy, Boulder, Col. Harry McCormick KE.ey, Professor of Biology, Cornell College, Mount Vernon, Iowa. Harris Kennepy, Physician, Roxbury, Mass. Linus Warp Kuinz, Department of Education, State Normal School, Farmville, Va. CHARLES Atwoop Kororp, Assistant Professor of Histology and Embryology, Univer- sity of California, Berkeley, Cal. CLARENCE HasKELL LANDER, Teacher of Biology, East High School, Cleveland, Ohio. Witu1AM Cooniper Langs, Librarian, Harvard College Library, Cambridge, Mass. Tuomas GeorGeE Lez, Professor of Histology and Embryology, University of Minnesota, Minneapolis, Minn. Freperic THomas Lewis, Instructor in Embryology and Histology, Harvard Medical School, Boston, Mass. Henry Ricuarpson Linvinie, Instructor in Biology, De Witt Clinton High School, New York, N. Y. Wiuu1am AuBeErtT Locy, Professor of Zoélogy, Northwestern University, Evanston, Ill. Grorce Grant MacCurpy, Lecturer in Anthropology, Yale University, New Haven, Conn. ALFRED GOLDSBOROUGH Mayer, Curator of the Natural Sciences, Museum of the Brooklyn Institute of Arts and Sciences, Brooklyn, N. Y. FLORENCE Mayo, Physician, Philadelphia, Pa. Gerrit SmirH Miter, Jr., Assistant Curator, Division of Mammals, United States National Museum, Washington, D. C. Wiu1am J. Momnxuavs, Assistant Professor of Zodlogy, Indiana University, Bloom- ington, Ind. CHARLES Henry Morss, Superintendent of Schools, Medford, Mass. Hersert Vincent Neat, Professor of Biology, Knox College, Galesburg, III. MARK ANNIVERSARY VOLUME. ix MarcareT Lewis Nickerson, Instructor in Histology and Embryology, University of Minnesota, Minneapolis, Minn. WinFIELD Scorr Nickerson, Assistant Professor of Histology and Embryology, University of Minnesota, Minneapolis, Minn. ADELE OPPENHEIMER, Teacher of Biology, Wadleigh High School, New York, N. Y. BERNARD SuTRO OPPENHEIMER, Physician, New York, N. Y. HERBERT OsBorN, Professor of Zodlogy and Entomology, Ohio State University, Columbus, Ohio. JAMES LEONARD Patnz, Merchant, Boston, Mass. GrorceE Howarp Parker, Assistant Professor of Zodlogy, Harvard University, Cam- bridge, Mass. Wit11AM Parren, Professor of Zodlogy, Dartmouth College, Hanover, N. H. GEORGE JAMES Perrce, Associate Professor of Botany and Plant Physiology, Leland Stanford Junior University, Stanford University, Cal. HELEN Prrxins, Boston, Mass. JoHN WALTER Perkins, Surgeon, Kansas City, Mo. Amos Wi.u1AM Peters, Instructor in Zoélogy, University of Illinois, Urbana, III. JOHN CHARLES PHiuuies, Student of Medicine, Harvard Medical School, Boston, Mass. Newton B. Pierce, United States Department of Agriculture, Division of Vegetable Physiology and Pathology, Santa Ana, Cal. JAMES Foster Porter, Architect, Lakeside, Il. FREDERICK HAVEN Pratt, Student of Medicine, Harvard Medical School, Boston, Mass. Henry SHERRING Pratt, Professor of Biology, Haverford College, Haverford, Pa. CHARLES WILLIAM Prentiss, Instructor in Biology, Adelbert College, Cleveland, Ohio. HERBERT WILBUR Rann, Instructor in Zodlogy, Harvard University, Cambridge, Mass. JacoB REIGHARD, Professor of Zodlogy, University of Michigan, Ann Arbor, Mich. HerRsertT Mave Ricwarps, Adjunct Professor of Botany, Barnard College, Columbia University, New York, N. Y. . Witi1AM Emerson Ritter, Professor of Zodlogy, University of California, Berkeley, Cal. THEODORE HitGARD RomeEtsER, Physician, New York, N. Y. THEODORE RoosEVELT, President of the United States, Washington, D. C. Witu1amM Henperson Ruppick, Physician, South Boston, Mass. Barney Sacus, Physician, New York, N. Y. Ernest Sacus, Student of Medicine, Johns Hopkins Medical School, Baltimore, Md. Porter Epwarp SarGEnt, Teacher of Natural Sciences, Brown and Nichols School, Cambridge, Mass. x MARK ANNIVERSARY VOLUME. Witi1am Martin Smatiwoop, Associate Professor of Zodlogy, Syracuse University, Syracuse, N. Y. Frank Situ, Assistant Professor of Zodlogy, University of Illinois, Urbana, III. Grant Surry, Austin Teaching Fellow in Zodlogy, Harvard University, Cambridge, Mass. THORNDIKE SPALDING, Attorney at Law, Cambridge, Mass. RevuBEN Myron Srrone, Carnegie Fellow in Zodlogy, The University of Chicago, Chicago, IIL. RatpH Stockman Tarr, Professor of Dynamic Geology and Physical Geography, Cornell University, Ithaca, N. Y. JoHn Exiot THayer, South Lancaster, Mass. Martin Bue Tinker, Physician, The Sanitarium, Clifton Springs, N. Y. Witi1AM LAWRENCE Tower, Associate in Embryology, The University of Chicago, Chicago, IIl. WILLIAM TRELEASE, Director of the Missouri Botanic Garden, St. Louis, Mo. ALBERT HENRY TuTTLe, Surgeon, Cambridge, Mass. THoMAs WAYLAND VauGHAN, Assistant Geologist, United States Geological Survey, Washington, D. C. Wituiam Scott WapswortH, Coroner’s Physician, Philadelphia, Pa. FREDERICK CLAYTON Wairs, Assistant Professor of Histology and Embryology, Western Reserve University, Cleveland, Ohio. Rosert Wa tcott, Boston, Mass. ERNEST DE WoLFEe WALES, Physician, Boston, Mass. Henry BaLpwin Warp, Professor of Zodlogy and Dean of the College of Medicine, University of Nebraska, Lincoln, Nebr. FREDERIC LEONARD WASHBURN, State Entomologist of Minnesota, Agricultural Experiment Station, University of Minnesota, St. Anthony Park, Minn. FRANK ELBERT WATSON, Teacher in Biology, Springfield High School, Springfield, Mass. Puitie RexForp WavuGuHop, Physician to Kealid and Hanalei, Hawaii Kealia, Hawaii. Houuis WesstTER, Teacher of Botany, Cambridge, Mass. ArtTuuRr WisswaLp WeyssE, Instructor in Zodlogy, Massachusetts Institute of Tech- nology, Boston, Mass. Epity HELEN WHEELER, Boston, Mass. Francis Bracu Wuits, Master, St. Paul’s School, Concord, N. H. WorRALLO WHITNEY, Instructor in Zodlogy and Botany, South Chicago High School, Chicago, III. MARK ANNIVERSARY VOLUME. xi Epwin Meap Witcox, Professor of Vegetable Physiology and Pathology, Alabama Polytechnic Institute, Auburn, Ala. Witu1am ALBERT WILLARD, Adjunct Professor of Zodlogy, University of Nebraska, Lincoln, Nebr. StepHEN Riggs WiuiaMs, Professor of Biology and Geology, Miami University, Oxford, Ohio. Joun GrrrisH Woop, Superintendent of the Twine Mills of the McCormick Harvester Machine Company, Chicago, II. Freperick Apams Woops, Physician, Brookline, Mass. Witi1am McMicuarL Woopworts, Keeper of the Museum of Comparative Zodlogy, Harvard University, Cambridge, Mass. AutFrRED WorcesstTER, Physician, Waltham, Mass. Rospert Mearns YeERKES, Instructor in Psychology, Harvard University, Cam- bridge, Mass. TABLE OF CONTENTS. PAGE I. Szrraro Goto; The Craspedote Medusa Olindias and some of its Natural Allies. (Plates I-III.) 1 II. Henry S. Prarr: Descriptions of four Distomes. (Plate IV.).......... cece cee eee e eens , 23 TI. Wiii1am A. Locy: A New Cranial NerveinSelachians. (Plates V-VI.)............0.eee eee 39 IV. Jacos Retcuarp: The Natural History of Amia calva Linneus. (Plate VII.).............. 57 V. Cuaries A, Kororp: On the Structure of Protophrya ovicola, a Ciliate Infusorian from the Brood-sac of Littorina rudis Don. (Plate VIII.).............0ceceeececeeeeeseeeuens 111 VI. C. B. Davenport: A Comparison of some Pectens from the East and the West Coasts of the tired Sites. Pits Ie soa wt a lal ai ela hale eseces CoRR pm ie cake 121 VII. Gerrrupe Crotry Davenport: Variation in the Number of Stripes on the Sea-anemone, Saari Wclase CP Wits: ay te dosne te dee ee Un ee doves eae Ge and hee ee 137 VIII. Franx W. Bancrorr: Aistivation of Botrylloides gascoi Della Valle. (Plate XI.).......... 147 IX. Car. H. Eigenmann: The Eyes of the Blind Vertebrates of North America. V. The His- tory of the Eye of the Blind Fish Amblyopsis from its Appearance to its Disintegration in Old -Avge:., (Plates: XTIAXV |) iviz-.o-0s. cece ce tie tage ne Sate Maa eee 167 X. Herpert Pariin Jonnson: Fresh-water Nereids from the Pacific Coast and Hawaii, with Remarks on Fresh-water Polychetain General. (Plates XVI-XVIL.).................. 205 XI. Henry R. Linvitte: The Natural History of some Tube-forming Annelids (Amphitrite ornata, Diopatra; cupres) ncciscivias esd sed goes Vee ea ee we eee Osa Ia ewe cme ee em ees 225 XII. Wituram E. Ritrer: The Structure and Affinities of Herdmania claviformis, the Type of a New Genus and Family of Ascidians from the Coast of California. (Plates XVIII-XIX.)...... 237 XIII. R. M. Strona: The Metallic Colors of Feathers from the Sides of the Neck of the Domestic Pigeon... (Plate 2X.) ccc vc caaday dadutave pid oleae aw ete R eae dae 263 XIV. C. R. Eastman: On the Nature of Edestus and Related Forms. (Plate XXI.).............. 279 XV. H. V. Neat: The Development of the Ventral Nerves in Selachii. I. Spinal Ventral Nerves. Ce lntes Se OD ect oe te eee as RAR ae Cae eae TANNA aaa wae 291 XVI. H.S. Jennines: Asymmetry in certain lower Organisms, and its Biological Significance....... 315 XVII. Rotre Fiorp: A Contribution to the Nervous Cytology of Periplaneta orientalis, the Common Cockroneh, “(Plates SOR VSO VIL) oy petites anes eae E eee ewe eENAe ree 339 XVIII. Roperr Mearns Yerkes: Reactions of Daphnia pulex to Light and Heat.................. 359 XIX. W. E. Castiz and Guover M. ALLEN: Mendel’s Laweand the Heredity of Albinism........... 379 XX. Porter Epwarp Sarcent: The Torus longitudinalis of the Teleost Brain: Its Ontogeny, Morphology, Phylogeny, and Function. (Plate XXIX.).......-. 0. cs eee cece eee eee 399 XXI. Tuomas G. Lez: Implantation of the Ovum in Spermophilus tridecemlineatus Mitch. (Plates ay ecco see sa emma ee en ee Ras 417 XXII. Joun H. Geroutp: Studies on the Embryology of the Sipunculide. I. The Embryonal En- velope and it Homologue. (Plate XXXIL.)............ eee cece cece cent ence tenes 437 XXIII. G. H. Parker: The Phototropism of the Mourning-cloak Butterfly, Vanessa antiopa Linn. CPI TUL eae Sunn sead cece ie etes oases eee eee aaa 453 XXIV. Iva H. Hype: The Nerve Distribution jn the Eye of Pectenirradians. (Plate XXXIV.)...... 471 XXV. Henry B. Warp: On the Development of Dermatobia hominis. (Plates XXXV-XXXVI.).. 483 xn THE CRASPEDOTE MEDUSA OLINDIAS AND SOME OF ITS NATURAL ALLIES. (PLATES I-III.) Seitaro GoTo. I. OLINDIOIDES FORMOSA gen. nov., sp. nov. For some years past one species of veiled medusa, in particular, has been attract- ing the notice of the members of the Misaki Biological Station, by its large size, the beautiful variety of its colors, and some peculiarities in the form and arrangement of its tentacles. Attending, among other things, to the study of the veiled medusz, my attention was naturally drawn to the above-mentioned species, and with the generous assistance of the Director of the Station, I have been enabled to collect enough material for study, the principal results of which are given in the following lines. It is a great pleasure to me to extend my best thanks to Professor Mitsukuri, the Director of the Station. The medusa in question has proved on study to possess many striking points of resemblance to the Mediterranean species Olindias miilleri Haeckel; but for reasons which will appear farther on I have decided to form a new genus for it, and propose the name of Olindioides formosa for the species. Further, I have come to the con- clusion that the genera Gonionema and Halicalyx are closely, and the fresh-water genera Limnocodium and Limnocnida more distantly, related to the new genus, and these relationships will be discussed. There are some facts connected with the occurrence of the medusa that deserve notice. So far as my experience goes it is found only from December to June or July. The examples collected in December are all immature, with the diameter of the disk not over 20 millimetres or so, and although a few stragglers may be met with in July and August, they generally appear to be in a dilapidated condition. It must, however, be remembered that these limits are subject to variation from year to year. Another fact worth noting is that Olindioides formosa is a bottom species, and none but weakened or injured examples have been caught at the surface. The best season for collecting the medusa is March and April, when a large number of fishermen do trawling at various depths off the Station, and by sailing from one boat to another as the trawls are hauled in, one can, on. successful occasions, easily get a few dozen specimens. The medusa appears to confine itself to the depth of from 20 to 30 fathoms, although my experience has not been varied enough to enable me to make any very positive statement on this point. 3 4 THE CRASPEDOTE MEDUSA OLINDIAS AND SOME OF ITS NATURAL ALLIES. The umbrella is moderately high, measuring nearly one-half as much as its largest diameter, which is found slightly above the margin (Pl. I, Fig. 1); but in younger examples (Fig. 2) it is relatively higher, as in many other veiled meduse. The jelly is thick and very consistent. The manubrium is quadrate with distinct lips, and when expanded hangs down into the umbrella cavity about two-thirds the height of the latter. Of some forty specimens that I have examined for the purpose, only three had four radial canals, and all the rest had six, so that there cannot be any doubt that six is the normal number for the species. Two of the canals start from two of the opposite corners of the manubrium, and of the remaining four two together from the other opposite corners. A comparison of a few examples is, however, suffi- cient to show that the number six is due to the bifurcation of two of the four original radial canals. This is easily seen on the apical view of almost any example, as shown in Figure 7, where two of the radial canals are seen to unite just before enter- ing the central stomach, or as in Figure 8, where four of the radial canals forming opposite couples are seen to have a common root for each couple. Examples with two simple and two Y-shaped radial canals are not rare, and cases of five radia canals are also met with, though seldom. The gonads are foldings of the subumbrellar walls of the radial canals, and extend the greater part of their lengths, leaving only a small proximal portion and a much smaller distal portion free (Fig. 6). In young examples these foldings are very simple and are clearly continuous (PI. II, Fig. 13), but in older ones they become more complicated and are sometimes divided into numerous lobes, which are again subdivided into secondary lobes (Pl. I, Fig. 9). In the case of Y-shaped radial canals, the gonads extend upwards only as far as the point of division, and are therefore V-shaped. If the point of division lies very near the manubrium, however, the gonads leave a smal] proximal portion free, as in the normal case. The endoderm of the radial canals presents different aspects on the oral and aboral sides. On the latter the cells approach nearly to the cubical form, and the cytoplasm is usually deeply stained and contains a comparatively small number of minute granules, while on the former the cells are tall and contain numerous large granules, which are probably a product of assimilation and form a reserve material. It must be remarked in this connection that the amount of these granules varies a good deal according to the nutritive condition of the example, and that in a specimen which in some way or other had lost its manubrium these granules were almost wholly absent. The endodermal lining of the gonads is composed entirely of these cells con- taining large granules. The circular canal is very large, and the endoderm presents the same difference of THE CRASPEDOTE MEDUSA OLINDIAS AND SOME OF ITS NATURAL ALLIES. 5 aspect on the inner (oral) and outer (aboral) sides. On the former the cells are nearly cubical, stain deeply, and contain numerous fine granules, while on the latter side the cells are exceedingly tall and are at places almost clogged with large granules, which are exactly similar to those found in the lower walls of the radial canals (PI. II, Figs. 15, 16; Pl. III, Figs. 17, 18). In some examples these cells are so tall as to project into and considerably narrow the lumen of the canal. There are numerous centripetal canals of varying lengths in each sextant, lying, as in most other cases where these are found, close to the ectoderm of the subumbrella. They increase in number with the age of the medusa, and the longest lie midway between the radial canals, the next longest between the longest and the next radial canal, and so on. As the centripetal canals increase in number, however, this law is apt to be disturbed. In the specimen represented in Figure 6, for instance, this law holds good only for a short way; and even in small specimens the centripetal canals are not frequently found so regularly graded as in Figure 5. In one and the same specimen the number of centripetal canals varies from sextant to sextant, although within a limited range. To give only two examples, in a specimen with the disk of 75 millimetres in diameter, which is about full grown, the maximum number of centripetal canals was 23, and the minimum 18; in another of 15 millimetres in diameter the centripetal canals varied between 11 and 14; the total number for the former being some 120, for the latter 78. The centripetal canals are, in structure, repetitions on a smaller scale of the radial canals, and their endoderm presents exactly the same features as in the former. The radial, circular, and centripetal canals are connected with one another and with the central stomach by the endodermal, or vascular, lamella. In younger exam- ples this is a layer of strictly one cell in depth, but in a very large one of about 100 millimetres in diameter the nuclei lay without any order, forming irregular tiers across its thickness. The cell boundaries could not be detected usually, except in very young specimens. The endodermal lamella runs close to the subumbrellar ectoderm, but is separated from it by a thin layer of jelly, and meets the radial, circular, and cen- tripetal canals along the line that separates the different kinds of endodermal cells described above. There are two sets of tentacles different in structure and position, and presumably also in their main function. From their position I shall call them velar and exum- brellar; both are very numerous. The exumbrellar tentacles may arise from the exumbrella at any level, from very near the apex to a short distance from the velum, but they are provided with endodermal roots, traversing the jelly and connecting them with the circular canal. 6 THE CRASPEDOTE MEDUSA OLINDIAS AND SOME OF ITS NATURAL ALLIES. The majority of these tentacles arise just outside the velar tentacles, and in these the roots are very short; but several of them spring at various levels from the surface of the exumbrella (PI. I, Figs. 1, 2), and in these the roots are not only correspond- ingly long, but are accompanied by streaks of thickened ectodermal cells loaded with ivory-black pigment granules. These streaks as well as the endodermal roots are narrow near the circular canal, but become broader higher up, and the black streaks are continued for some distance on to the free portion of the tentacles. In younger specimens these exumbrellar tentacles with long roots are very few, and there is no doubt that they increase with age; and the black pigment above mentioned appears to be developed always in conjunction with the union of these tentacles to the exum- brella; for those tentacles which arise a little above their fellows have their prox- imal portion tinged with black (Fig. 1). The ectoderm of these black streaks contains nettle-cells, and is the direct continuation of the marginal nettle-ring. There is no objection to calling these streaks “peronia#.” The number of exumbrellar ten- tacles in an example 15 millimetres in diameter was 72, and in one 75 millimetres in diameter 264. The exumbrellar tentacles have numerous elongated warts arranged across their lengths, formed by tall ectodermal cells containing nettle-capsules. They are slightly enlarged at the tip, where there is an elliptical patch of mucous gland-cells. The terminal portions of the exumbrellar tentacles are slightly curved inwards in a charac- teristic way, and the glandular patch just mentioned may be found indifferently at the tip or on the oral or aboral surface of the tentacles. In the aquarium the medusa has been observed to anchor itself to the bottom by means of these glands, stretching out and using the exumbrellar tentacles very much in the same way as the tie-ropes of a half-filled balloon. As it is a bottom species there can hardly be any reasonable doubt that these tentacles are used in the same way in its natural sur- roundings. The tentacles that spring from well up on the exumbrella probably serve to fasten the animal to seaweeds or rocks lying over it. The cells of the glandular patch above mentioned are very tall, and the cytoplasm contains numerous minute granules which stain well with hematoxylin (aqueous glycerin-alum solution after Rawitz), and the secretion is usually seen forming a row of rounded masses, each corresponding to a gland cell and connected with it (Pl. III, Fig. 20). The endodermal roots of the exumbrellar tentacles lie directly underneath the exumbrellar ectoderm, to which they are closely applied. The cells are large and vacuolated, and are directly continued into the endoderm of the circular canal. On the inner side of these tentacle roots there is a layer of scattered ectoderm cells. The THE CRASPEDOTE MEDUSA OLINDIAS AND SOME OF ITS NATURAL ALLIES. 7 exumbrellar ectoderm lying about the tentacle roots is conspicuously thickened, and contains black pigment granules and nettle-cells. The velar tentacles are very long, slender, and contractile when fully formed, but are found in all stages of development from a mere bulb to a long contractile filament armed with numerous stinging batteries. They are always found close to the base of the velum, and their endoderm is directly continued into that of the cir- cular canal, without the intervention of what may be called “roots.” In younger examples, of about 20 millimetres or a little more in diameter, the velar tentacles are all in the condition of bulbs, exactly like the basal bulbs of Gonionema; but in mature specimens (70 millimetres or more in diameter) some of the velar tentacles are exceed- ingly long and contractile, and are armed with numerous nettle batteries in the form of incomplete rings. These incomplete rings are arranged all with the open point turned towards the oral side, so that there is formed a longitudinal groove on the inner side of the filiform velar tentacle. The ectodermal muscle fibres of these tentacles are at least three times as thick as those of the exumbrellar tentacles and are cross- striped. This is in entire accord with their great contractility in life. These filiform velar tentacles are never very numerous, there being some ten or so in an example of about 60 millimetres in diameter. In the aquarium these tentacles are dragged along passively when the animal swims forwards, but when at rest they are loosely laid out on the bottom and occasionally contracted. I believe they are the principal organs for capturing prey. When strongly contracted, they tend more or less to form a spiral. In an example of 15 millimetres in diameter there were about 100 velar tentacles, all in the condition of bulbs, and in one of 75 millimetres some 325, of which a dozen or so were filiform. The velar tentacles are very different in structure in the bulbular and filiform conditions. In the bulbular condition the ectoderm is so clogged with nettle-cells in all stages of development that it is hard to recognize the individual ectoderm cells. It is also to be remarked that none of the numerous nettle-cells are found fully devel- oped. The endoderm is a direct continuation of the external part of the endodermal wall of the circular canal, with which it presents the same histological characters, and the mesoglea is very thin. In the filiform condition the mesoglcea is tolerably thick, the endoderm cells are large and vacuolated, though less so than those of the exumbrellar tentacles. The stinging batteries contain numerous fully developed nettle-cells, and between the ectodermal cells close to the mesogloea are found numer- ous nettle-cells in the later stages of development. These are placed with their long axes parallel or only slightly oblique to the length of the tentacle, and are, in my opinion, on the way to their destinations, the earlier stages having been passed in the 8 THE CRASPEDOTE MEDUSA OLINDIAS AND SOME OF ITS NATURAL ALLIES. bulbular velar tentacles. All suspicion that the bulbular and the filamentous forms may be fundamentally different has been dispelled by the presence of numerous intermediate stages. The bulbular velar tentacles as well as the ectodermal thick- enings that connect them are then the nisi formativi of the stinging cells, whence they travel in opposite directions, up along the peronia into the exumbrellar tentacles, or down into the filiform velar tentacles. The wandering nettle-cells are much less numerous in the exumbrellar than in the velar tentacles. The marginal organs are all otocysts, and are present in large numbers, two at the base of the endodermal root of each exumbrellar tentacle. In younger exam- ples they form a single row along the umbrella margin and are situated close to the circular canal (Pl. I, Fig. 3), but in larger ones they no longer keep the same front, and, generally speaking, the older ones are pushed up into the jelly of the umbrella (Fig. 4). They are either spherical or ellipsoidal, and some of the larger ones measure no less than 160 micra across. The vesicle is lined by a flattened epithelium, which presents a local thickening at a place turned towards the circular canal, where prob- ably the sensory cells are found. The otolith is surrounded by some granular proto- plasm containing nuclei, and is attached to the wall of the vesicle by means of a short stalk consisting of some granular, well-staining protoplasm containing nuclei. The otolith itself is highly refringent, and, when fully formed, consists of somewhat irregu- larly concentric layers arranged around a centre. It appears to be very hard and is apt to be detached from sections. Haeckel says that the structure of the marginal vesicles of Olindias shows it to belong to the Trachomeduse, but as both Olindias and Olindioides as well as the closely related genera before mentioned appeared to me to present several features which are not commonly met with among the Trachomeduse, I have paid special attention to the development of the otocyst, which, in the absence of any knowledge of the life history, must be considered the most reliable criterion by which to decide the natural relationship of the veiled meduse. I have shown in Figures 15 to 19 (Pls. II, III) some stages in the development of the otocyst. The endodermal roots of the exumbrellar tentacles start from the circular canal at the place where the two kinds of endodermal cells already mentioned meet each other, and the first rudiment of the otocyst is seen in process of formation close to this root. It consists of a small segregation of ectodermal cells hardly dis- tinguishable from the rest, closely applied to the endoderm of the circular canal at the point where the two kinds of cells meet (Pl. I, Fig. 15). At this stage it would be very apt to be overlooked, were it not for the presence of the root of a very young exumbrellar tentacle. There cannot be any reasonable doubt that the rudiment THE CRASPEDOTE MEDUSA OLINDIAS AND SOME OF ITS NATURAL ALLIES. 9 consists exclusively of ectoderm cells, since the boundary line between the two cell- layers is always distinguishable with a good objective (Zeiss apochromatic oil-immer- sion), and there is no sign of proliferation in the endoderm. On the contrary, the latter is usually found pushed in by the otocyst rudiment—just the contrary of what one would expect if the endoderm took part in its formation. The first rudiment just described forms, as will appear in the sequel, the otolith and the parts that di- rectly surround it. In the next stage (Fig. 16) the endoderm is generally found pushed in somewhat more by the otocyst rudiment, and around the latter on the outer side has been formed a cup-shaped cavity lined by a layer of cells, some of which are flattened, while others can hardly be distinguished from the surrounding ectoderm cells. This cavity is the beginning of the vesicle, and the layer of cells around it becomes its lining epi- thelium. In this stage the cells that formed the first rudiment are all alike. The next change that takes place consists in the enlargement of the cavity and the differentiation of the central cells into two sorts, namely, those that are trans- formed into the otolith and those that form its investment and stalk. In the section reproduced in Figure 18 (Pl. III) this differentiation has hardly begun, and the deeply and faintly staining nuclei are found mixed together, although some of the more cen- tral ones are larger and clearer than others. It may also be noted that in this section many of the peripheral nuclei are vesicular in appearance. These differences taken by themselves appear to me to afford only a dubitable clue to the destination of the respective cells, depending as they do on the changing conditions of the nuclear substance. For example, even in one and the same otocyst some nuclei of its lining epithelium are clear and vesicular, while others are darkly stained. In a later stage the cells that are destined to be transformed into the otolith and those that remain as its investment and the stalk are clearly distinguishable, the central nuclei being generally larger, clear and vesicular, while the peripheral ones are deeply stained and are more or less flattened. It must be borne in mind, nevertheless, that these differences are by no means absolute. Sometimes, as is seen in Figure 17, the dif- ferentiation of the central cell mass appears to be effected at a very early stage, and in such a case the difference between the two kinds of cells is very striking. In the last stage described the central cell mass was sessile, resting as it did directly against the endoderm of the circular canal by a broad base. If double staining is resorted to at such a stage, the cells that are destined to become the otolith stain of the same color as the endoderm, while the lining epithelium and the investing cells stain like the ectoderm; for example, with fuchsin and methyl green the endoderm and otolith cells are violet, and the epithelium, investing cells, and ectoderm are green. 10 THE CRASPEDOTE MEDUSA OLINDIAS AND SOME OF ITS NATURAL ALLIES. And one is very apt to interpret such a different behavior towards stains as proving different origin. This is the fundamental principle of double staining, but if applied too liberally it is very apt to lead one into unwarranted conclusions. The researches of Fischer (99) have taught us that this principle must be checked and rechecked constantly by other considerations to afford justifiable and reliable conclusions. The origin of a structure can be regarded as definitely proved only by being traced to its first beginning. The cells that are destined to form the otolith gradually undergo histolysis; the cytoplasm becomes more and more attenuated, and the nuclei enlarge and become clearer and vesicular; finally they disintegrate and disappear, leaving in their stead a sparsely granular substance, which at first stains tolerably well, and in which small blocks of chromatin and some irregular fibres can be observed. At this stage the stalk is very distinct and consists of a deeply staining, finely granular protoplasmic mass containing several nuclei (Fig. 19). The otolitic substance gradually becomes more refringent, at the same time losing its affinity for stains, and finally comes to consist of numerous concentric layers. The otolith is surrounded by a nucleated protoplasmic investment to the last. In the stage shown in Figure 19, the lining epithelium of the otocyst is separated from the ectoderm only an exceedingly thin layer of mesogloea; but in older stages the entire organ is pushed far into the jelly and has usually no cellular connection with the ectoderm. Exceptionally, however, such a connection persists through life. The otocysts are throughout life more or less closely applied to the endoderm of the circular canal, from which they are frequently separated by a very thin layer of jelly. The colors * of the medusa are as follows: for the tips of the exumbrellar tentacles a beautifully transparent, shining lilac, for the next adjoining portion a shining sma~- ragdine-green, and for the peronia and the basal portion of those exumbrellar tentacles that arise some way up the umbrella ivory-black, the latter thinning out and passing into the green portion or separated from it by a short colorless stretch; for the radial and circular canals a deep scarlet, and for the centripetal canals a lighter scarlet. There is also a small smaragdine-green triangular area at each corner of the base of the manubrium, on either side of which is a lilac area of the same color as that of the tips of the exumbrellar tentacles; there is in addition one or two somewhat irregu- lar longitudinal streaks of lilac along the middle of each side of the manubrium. The tips of some of the filiform velar tentacles are occasionally just tinged with green and lilac. The gonads are egg-yellow. In small specimens the more axial portion of the manubrium is egg-yellow, but in larger ones it is almost entirely colorless. * The names of the colors used in this description are in accordance with the system proposed by Saccardo (’94). THE CRASPEDOTE MEDUSA OLINDIAS AND SOME OF ITS NATURAL ALLIES. 11 Some histological notes other than those mentioned heretofore may now be added. The velum is very strongly developed, its mesogloea is very thick in full-grown examples, and on the subumbrellar side is thrown into numerous vertical folds, form- ing muscular lamelle. The subumbrellar musculature is also vigorously developed, and there is a special muscular ring just inside the base of the velum, adjacent to the nerve-ring. This is due to a special development of the muscular lamellae, which are here very numerous and closely set, and are also exceptionally tall. The muscu- lar lamelle are found here and there in all parts of the subumbrella, but they are inconspicuous elsewhere. The nettle-cells are exceptionally large and cylindrical, and are in general form like those of many actinians. When fully formed they are as large as 30 micra by 7 micra, and the protoplasmic mantle and the nucleus can always be distinguished very clearly. The latter is usually found near the more slender end of the organ and is frequently horseshoe-shaped. When the nettle-cells are placed in their defini- tive position this slender end is invariably directed inwards, being the closed end of the urticating vesicle. As before mentioned, the nettle-cells are comparatively few in the exumbrellar tentacles, but are especially numerous in the ring-shaped warts of the velar tentacles, and in these they are imbedded between exceedingly tall ectodermal cells, which are very conspicuous in sections even under a low power. These ectodermal cells are provided with very long stalks which stain deeply with hematoxylin, are more or less undulating, and are attached below to the mesogloeea. The body of the cell consists of a granular or a somewhat fibrous cytoplasm with a distinct membrane and a deeply staining nucleus situated near the centre. Under ordinary objectives the transition between the stalk and the body of the cell appears sudden, but with a high-power apochromatic system it is seen to be more gradual. These stalks were at first suspected to be muscular in nature, but further observations revealed many transitional forms between these and the ordinary tall ectodermal cells; and further, these stalks look very different from the muscular fibres lying immediately below. It is evident, how- ever, that the protoplasm of the stalks of these cells has undergone a special modifica- tion, but-its nature has so far remained obscure to me. These cells with deeply stain- ing stalks are also present in the warts of the exumbrellar tentacles; but they are less numerous there and the stalks are shorter. Olindioides formosa has been observed in the following localities: Misaki; Kan- agawa (practically identical with Yokohama, Prof. Mitsukuri); Bay of Tateyama, southeastern extremity of the Bay of Tokyo (Dr. Oka). 12 THE CRASPEDOTE MEDUSA OLINDIAS AND SOME OF ITS NATURAL ALLIES. II. GONIONEMA DEPRESSUM sp. nov. This is a pretty species common among the eel-grass growing within the wharves of Yokohama, and specimens can easily be obtained at any hour of the day by towing in such situations by means of a weighted net. I have never seen the medusa on the surface of the water during the daytime. The Woods Hole species, for which Mayer has recently proposed the name of G. murbachii, is stated to come to the sur- face at night, and the towing for the medusa appears to be performed there only in the evening; but it is probable that the animal never quits the eel-grass entirely, since it is known that the grass grows rank in the eel-pond, where it is always hunted for. The Yokohama species has a rather shallow open umbrella, which may measure 20 millimetres by 8 millimetres or a little more. The smaller examples have the umbrella relatively deeper; one of 4 millimetres in diameter measures just as much in height. The jelly is only moderately thick. The swimming movements are vigorous, but only a few pulsations are made consecutively at a time, after which the animal slowly sinks with expanded umbrella and outstretched tentacles until it touches some object, when it attaches itself to it by means of the adhesive disks of the tentacles. The manubrium is quadrate with distinct lips, and hangs down close to the level of the umbrella margin. The radial canals are four, and the gonads are developed on their lower walls along nearly their entire lengths, leaving only a small proximal and an equally small distal portion free. In very young examples the gonads are simple thickenings of the wall of the radial canals, but in larger ones they are thrown into folds which are arranged alternately on either side of the canal. These folds remain, however, very simple, and, so far as I have observed, are never divided into lobes (Pl. II, Fig. 18). The tentacles are numerous; in an example of 18 millimetres in diameter there were 59, and in another of 4 millimetres there were 32; 64 was the largest number of the tentacles I have observed so far. They are very flexible, but are not as con- tractile as the velar tentacles of Olindioides; they are armed with incomplete ring- like warts,-in which the nettle-cells are found. The. most characteristic feature of the tentacles, however, is that they bear at some distance from the tip each an adhesive disk, by which the animal can securely attach itself to any external object. When the tentacles are expanded, these disks are nearly flat and elliptical, but in contracted tentacles they are more or less saucer-shaped, and are compressed along the length of the tentacle (Pl. Il, Fig. 11; Pl. III, Fig. 21). They consist of tall THE CRASPEDOTE MEDUSA OLINDIAS AND SOME OF ITS NATURAL ALLIES. 13 cylindrical cells very similar to those of the adhesive disks of Olindioides, and the secretion can be observed almost at any time, forming rounded or elongated masses each corresponding to a mucus cell. The cells stain well with hematoxylin, but espe- cially so near their free ends. These disks have been described as “sucking,” but a study of their structure reveals nothing capable of exercising a pumping action. In all the known species of Gonionema these disks are situated on the inner side of the tentacles, and cause the characteristic angular bend, which has given rise to the generic name. On a cursory observation, the tentacles appear to arise from the margin of the umbrella, but a closer inspection shows that they spring always from the exum- brella at a short distance from the margin, just as do the exumbrellar tentacles of Olindioides; and one can easily observe the endodermal tentacle roots traversing the jelly to join the circular canal. In Gonionema these roots are very short, and as a consequence the peronia do not come into view, although the ectoderm lying over these tentacle roots is slightly thickened. On the inner side of the tentacles, close to the base of the velum, are the basal bulbs of the tentacles, exactly corresponding both in position and number to the former. These bulbs are exactly similar in structure to the rudimentary velar tentacles of Olindioides, that is to say, they contain hollow prolongations of the endoderm of the circular canal, and the ectoderm is clogged with developing nettle-cells. In Gonionema these bulbs never become elongated and filiform, but there is no doubt that they are the homologues of the velar tentacles of Olindioides. The marginal organs are all otocysts, and are present two at the base of each tentacle. In structure they are also exactly like those of Olindioides; they are, however, generally smaller, a fully developed vesicle measuring only 75 micra in diameter. Again, the majority remain close to the marginal ectoderm containing the outer nerve-ring, and retain a cellular connection with it; but some of the oldest otocysts are pushed far into the jelly, and the cellular connection with the ectoderm disappears. They remain, however, more or less closely appressed to the endoderm of the circular canal (PI. III, Fig. 22). The otolith, when fully formed, shows a radial arrangement of its constituent pyramids. The endodermal lamella remains one-layered throughout life, and joins the cir- cular and radial canals along the line that divides the two kinds of cells as in Olindi- cides. It is separated from the subumbrellar ectoderm by a thin layer of jelly. The coloration of the medusa is as follows: radial canals, basal bulbs, and the adhesive disks of the tentacles a transparent chestnut-brown; tentacles, gonads, the larger part of the manubrium, and the circular canal a lighter brown, marginal 14 THE CRASPEDOTE MEDUSA OLINDIAS AND SOME OF ITS NATURAL ALLIES. area of the manubrium pale green. At the very base of each tentacle there is a speck of shining emerald-green, of the same color as the green portion of the exumbrellar tentacles of Olindioides. These are not eyes. The musculature is well developed, but less so than in Olindioides, and the muscular lamelle are confined to the subumbrella. There is, however, a strong mus- cular ring exactly in the same position as in Olindioides, namely, near the base of the velum, just internal to the inner nerve-ring. Here the mesoglcea, or, as it may be called, the supporting lamella, is thrown into extensive irregular folds, on either sur- face of which the muscular fibres are closely arranged in a row. III. REMARKS ON OLINDIAS? MULLERI HAECKEL. There are some points in Haeckel’s description of this medusa that require com- ment. The following remarks are based on an examination of an excellently pre- served museum specimen of about 50 millimetres in diameter from Naples, that has been in the possession of this school for several years, and of a few examples that have recently been obtained from the Naples Zodlogical Station, fixed according to my directions. The latter material is, so far as I have examined, in a rather unsatis- factory condition histologically, due, as I believe, to histolysis having set in before fixing. But so far as the general structure is concerned, these specimens can be safely depended on, the more so as there is the perfect specimen as a control. The general form of the medusa is very well represented in Haeckel’s figure, but the filiform velar tentacles (Fangfdiden) are too numerous. In the perfect speci- men above referred to there were only some 35, irregularly distributed along the entire margin, and these are of very unequal length and thickness. There can also be observed various stages in their development from the bulbular to the filiform condition, the bulbular forms being about four or five times as numerous as the fili- form ones. Haeckel (’79) also speaks of numerous ocelli situated between the velar tentacles, which, according to him, appear to contain a biconvex lens. These so- called ocelli are nothing but the bases of the exumbrellar or of the filiform velar ten- tacles, which contain a red pigment in the endoderm, and the supposed biconvex lens is simply the axial cavity of the tentacle viewed in optical section. The exumbrellar tentacles are armed with incompletely ring-shaped or horse- shoe-shaped nettle-warts, and are provided each with an adhesive patch of mucous cells at the tip. The patch extends on the inner side more than on the outer. The endodermal roots of the tentacles are not very long, but are quite conspicuous. THE CRASPEDOTE MEDUSA OLINDIAS AND SOME OF ITS NATURAL ALLIES. 15 In the fully developed condition the gonads consist of numerous lobes, each of which looks somewhat acinous, but a closer examination shows that these lobes are continuous with each other; and a comparison with the lobed condition of the gonads of Olindioides already described leaves no doubt that each gonad of Olindias must have been formed as a single continuous thickening of the subumbrellar wall of a radial canal and became lobed only secondarily. An examination of Haeckel’s figure (79, Pl. XV, Fig. 10) of a young example of about 8 millimetres in diameter bears out this view. As to the habitat of Olindias miilleri, I have not been able to ascertain it. Haeckel (79, p. 253) says that it appears to be rather rare, or perhaps to be confined to certain localities, and I am informed by the authorities of the Naples Station that it occurs especially in the months of October and November and then disappears. Consider- ing that the exumbrellar tentacles are provided with adhesive disks, and judging from analogy, it is very probable that Olindias miilleri is a bottom species like Olindi- oides; and its comparative rareness must at least in part be attributed to this pecu- liar habit. It appears, however, that the medusa can be obtained without difficulty at the Naples Station in the proper season. The material lately sent me appears to have been collected late in August or very early in September. IV. NATURAL RELATIONSHIPS OF THE DESCRIBED SPECIES. On looking through the published descriptions of the veiled meduse it will at once be evident to any one that the genera Olindias, Halicalyx, and Gonionema, and the new genus Olindioides must be put together into a natural group, for which we may adopt the name Olindiade used by Haeckel. The common characters are very simple and clear: jelly tolerably consistent, radial canals four or six, manubrium well developed and quadrate, with distinct lips, velum well developed, gonads originally a continuous fold of the subumbrellar wall of the radial canals, which may secondarily become lobed, with two sets of tentacles, the velar and the exumbrellar, with an adhesive disk somewhere on each exumbrellar tentacle, at the base of which there is a pair of otocysts. The exumbrellar tentacles are provided with endodermal roots, which more or less traverse the jelly to join the circular canal. Bottom species or living among seaweeds. The genus Halicalyx, with one species, H. tenuis, was originally described by Fewkes (’82) and recently redescribed by Mayer (:00), who says that it is closely allied to his genus Gonionemoides, but that it differs by the absence of “suctorial” disks on 16 THE CRASPEDOTE MEDUSA OLINDIAS AND SOME OF ITS NATURAL ALLIES. any of the tentacles. I may, however, be allowed to suggest that the exumbrellar tentacles (stiff tentacles standing out sharply at right angles to the bell and sprinkled over with wart-like protuberances of a deep purple color) will probably be found on a closer examination to be provided with an adhesive disk near the tip. The mucous glands in similar positions of Olindias have been overlooked. Haeckel says that he at first placed Olindias in the Aiquoride, but that the structure of the marginal vesicles shows it to belong to the Trachomeduse. Mayer (99) also regards Gonionema as a trachomedusan; but Murbach (’95), who has stud- ied its development, says that there is true alternation of generations, the larva pass- ing through a hydrula stage. Haeckel places Gonionema in his leptomedusan family Cannotide, which is characterized by the absence of marginal vesicles, the possession of four- or six-branched, forked or pinnatifid radial canals, in the course of which the gonads lie. On the systematic position of Halicalyx neither Fewkes nor Mayer says anything. It is evident from a perusal of their works that Haeckel and Mayer have been led to regard Olindias and Gonionema as belonging to the Trachomeduse by the struc- ture of the otocysts, and the only peculiarity of these organs that could have impressed them appears to me to be that the otolith is provided with a stalk, by means of which it is attached to the wall of the vesicle. But the presence of a stalk taken by itself seems to me to be of no systematic importance, since, in all the Leptomeduse thus far described or observed by me, the otoliths are attached to the wall of the vesicle, and it is simply a question of the comparative length of the intervening portion that deter- mines the presence or absence of the stalk. Further, if one compares the stalk of the vesicle of any of the medusze above mentioned with that of such undoubted Tracho- meduse as Glossocodon or Liriope, there are some differences, which, taken in conjunc- tion with the observations on the development of the otocyst, point to a fundamental difference between the two. The otolithic stalk in Glossocodon and Liriope is very distinctly set off both from the protoplasmic mass surrounding the otolith and the wall of the vesicle; but in all the genera of Olindiade the stalk passes on gradually into the periotolithic mass on the one hand and the vesicle wall on the other. We have also seen that in Olindioides the endoderm takes no part in the formation of the otocyst. Among the differences set up by the Hertwigs (’78) for the two types of otocysts, one characteristic of the Trachyline and the other of the Leptoline, is one of innerva- tion. According to the observations of the two brothers, the otocyst is innervated in the former group by the upper (outer) nerve-ring, and in the latter by the lower (inner). In Olindioides and Gonionema the otocysts appear to be supplied from THE CRASPEDOTE MEDUSA OLINDIAS AND SOME OF ITS NATURAL ALLIES. 17 the outer nerve-ring; ‘but this coincidence with a character of the Trachyline must be due to convergence, and the difference of innervation must not be regarded as absolute for the two types of otocysts. In Olindioides, moreover, the two nerve- rings are seen in several places to be directly continued one with the other through breaks in the mesogloea separating the two. The presence of centripetal canals is another point of resemblance between Olin- diade and some Trachomeduse; but it is evidently of no systematic moment, since these canals may be present or absent in closely related genera. I have spoken of the marginal nettle-ring; but it must be borne in mind that it is unlike the nettle-ring of the genuine Trachomeduse. For, while in the latter the ring is a very distinct structure continuous throughout, in the Olindiade it is brought about merely by the close proximity of the velar tentacles, and in such a form as Gonionema, where the intervening spaces are wider, the ring tends to become more or less discontinuous, and in some sections through such a space the nettle-cells are totally absent. We must also remember that in some Leptoline there is a well-devel- oped nettle-ring, as in Laodice (Brooks, ’95). The presence of endodermal tentacle roots in the Olindiade is another feature of resemblance to the Trachomeduse, but we must also remember that these struc- tures may be present in forms which undoubtedly belong to the Leptoline (Brooks, 95). The unsatisfactoriness of Haeckel’s system of the meduse has been pointed out by Brooks (’86, ’95), but accepting it we must place the subfamily Olindiade in the Lep- todmeduse. It is impossible to put it under the Cannotide, to which Gonionema is referred by Haeckel. It appears, to me that it comes with least violence under the Eucopide, where our meduse may find their temporary resting-place. The genus Gonionemoides formed by Mayer (:00) is evidently nearly related to our genera, but less so than these are among themselves, and it will perhaps be found advisable to place it in a distinct subfamily. The fresh-water medusze Limnocodium and Limnocnida have not found a satis- factory place in the system. Allman (’80) and Fowler (90) think that Limnocodium should be placed in the Leptoline, while Lankester (’80) and Gunther (94) bring it under the Trachylinz, in which the latter also places his genus Limnocnida from Lake Tanganyica. It appears to me that these genera present some features which point to their affinity to the Olindiade, near which they can, in my opinion, be placed most naturally. But as I am not able to examine any material of these medusz, I shall confine myself to some critical remarks on the statements of previous authors concerning points of fundamental importance. 18 THE CRASPEDOTE MEDUSA OLINDIAS AND SOME OF ITS NATURAL ALLIES. The point of greatest importance in determining the position of these medusz is of course, in the absence of a definite knowledge of the life history, the origin of the otolithic cells, which, according to Lankester (’80) and Gunther (’94, ’94a), are produced from the endoderm of the circular canal. Lankester made his observations on the marginal vesicles exclusively by means of optical sections, and it is no discredit to the author to say that none of his figures touching the point in question can be con- sidered as decisive. Gtinther (’94), on the other hand, carried on his observations on actual sections prepared from materials killed with osmic acid, and by means of the best optical appliances, and he reproduces several figures intended to show the endo- dermal origin of the otolithic cells. It must, however, be remarked that the figure (Fig. 1) he gives us of the earliest stage that came under his observation in the development of the otocyst represents a somewhat advanced stage, when its constituent parts have all been formed, and these parts have only to enlarge, multiply, and undergo a little differentiation to arrive at the definitive condition; and it is exceedingly improbable that any additional endoderm cell should at this stage wander out to reinforce their precursors, even if these were derived from that source (com- pare Figures 17 and 18 in the present paper). The absence of the intervening meso- gloea must net be taken by itself as a proof of the morphological continuity of the two cell layers, and it is necessary to exercise constantly self-criticism not to be misled into taking appearance for reality. The question of morphological continuity or dis- continuity in such a case comes very near to splitting a hair, and it is only by the closest scrutiny that one can draw a safe conclusion. It may be added in passing that the structure of the otolith which Lankester and Gunther regard as unique represents only a developmental stage in other forms, and it is possible that these authors have observed only comparatively young otocysts, and that in older ones the otolith loses its cellular structure. Should the ectodermal origin of the otolithic cells be granted, the structure of the marginal vesicles of Lim- nocodium and Limnocnida is exactly like that of the same organs of the Olindiade, except for the peculiar prolongations into the velum of the vesicles in the first-named genus. The presence of tentacle roots, though of secondary importance, is another fea- ture common to the Olindiade and the two fresh-water genera. The young stages of Limnocodium described by Lankester (’80, ’81) are sup- posed by him to have developed from the egg-cell, although he did not observe any mature females, but only males. On examining them, however, one is struck with some features in their anatomy that point strongly to their origin as medusa buds either from a hydroid stock or, more probably in this case, from young female meduse. THE CRASPEDOTE MEDUSA OLINDIAS AND SOME OF ITS NATURAL ALLIES. 19 the presence of a closed subumbrellar cavity, a manubrium, and the radial canals at a stage corresponding in other respects to that of the Trachomeduse, in which there is as yet none of these parts, is a point that seriously interferes with the supposition that the young medusz studied by Lankester were derived from the egg-cell (Brooks, ’86). Some leptoline meduse proliferate by budding when young, and produce ova when older. As to the hydroid described by Parsons, Bourne, and Fowler, it is not known for certain whether it is a member in the life-history of Limnocodium, although this supposition must be allowed to be very probable. Some light will perhaps be thrown on this point by the French naturalists who have recently observed the medusa in a lily tank in the Zoological Garden of Lyon (Vaney et Conte, :01), or by the collection from Mr. Moore’s expedition to Lake Tanganyica. Any one who is acquainted with the Narcomedusa, and especially with their marginal sense-organs, will hardly agree with the proposal of Gunther to place Lim- nocnida, even provisionally, in that group. In conclusion I shall add a synopsis of the Olindiade, which will bring forth their distinctive characters and their natural relationships more clearly, though neces- sarily in a schematic way. Subfamily: Olindiade.—Eucopide with two sets of tentacles, velar and exum- brellar, the former springing close to the base of the velum, and the latter at variable distances from it, but always from the exumbrella and connected with the circular canal by endodermal roots. Marginal vesicles numerous, two on either side of the base of the exumbrellar tentacle. Manubrium well developed and quadrate, with distinct lips. Radial canals four or six. Gonads primarily continuous folds of the walls of the radial canals. With an adhesive disk on each exumbrellar tentacle. SYNOPSIS OF THE GENERA. 1. Velar tentacles just as numerous as the exumbrellar.................. 3. 2. Velar tentacles more numerous than the exumbrellar.............. 5, 6. 3. Velar tentacles all rudimentary, in the form of basal bulbs... .Gonionema. 4, Velar tentacles all flilorii.c¢ ic asgoges sei Geeeaeseriweneees Halicalyx. 5. Radial canals four. ....0.s0008ews see aee te ee ere ee Olindias. 6, Radial canals six icc e lc cngi ss Lean sinawe ve neeeeeneee ca Olindioides. Gonionema (= Gonionemus) A. Agassiz. Agassiz, 62, p. 350. Haeckel, 79, p. 146. 20 THE CRASPEDOTE MEDUSA OLINDIAS AND SOME OF ITS NATURAL ALLIES. G. vertens A. Agassiz. Agassiz, ’62, p. 350. Haeckel, ’79, p. 147. G. murbachii A. G. Mayer. Murbach, ’95. Mayer, :01,p.5. Morgan, ’99. G. suvaénsis A. G. Mayer, ’99, p. 164. G. aphrodite A. G. Mayer, ’94, p. 237; :00, p. 62. The last two species belong in my opinion to Gonionemoides, since they posesss only four otocysts in each quadrant. Halicalyx J. W. Fewkes. Fewkes, ’82, p. 277. Mayer, :00, p. 63. H. tenuis J. W. Fewkes. Fewkes, ’82, p.277. Mayer, :00, p. 63. Olindias F. Miller. Miller, ’61, p. 312. Haeckel, ’79, p. 252. O. sambaquiensis F. Miller. Miiller, 61, p. 312. Haeckel, ’79, p. 254. O. mulleri E. Haeckel. Haeckel, ’79, p. 253. Olindioides 8. Goto. O. formosa 8. Goto. V. BIBLIOGRAPHY. Agassiz, A. 62. [Description of Gonionemus vertens.] In Contributions to the Natural History of the United States of America by Louis Agassiz, vol. 4, p. 350. Agassiz, A., and Mayer, A. G. 99. Acalephs from the Fiji Islands. Bull. Mus. Comp. Zodél. Harvard Coll., vol. 32, no. 9, pp. 157-189, pls. 1-17. Allman, G. J. ’80. On “Limnocodium victoria,” a Hydroid Medusa of Fresh Water. Nature, vol. 22, pp. 178-179. Brooks, W. K. ’86. The Life-History of the Hydromeduse: A Discussion of the Origin of the Meduse, and of the Signifi- cance of Metagenesis. Mem. Boston Soc. Nat. Hist., vol. 3, no. 12, pp. 359-480. Brooks, W. K. 95. The Sensory Clubs or Cordyli of Laodice. Jour. Morph., vol. 10, no. 1, pp. 287-804, pl. 17. Fewkes, J. W. 782. Notes on Acalephs from the Tortugas, with a Description of New Genera and Species. Bull. Mus. Comp. Zoél. Harvard Coll., vol. 9, no. 7, pp. 251-289, pls. 1-7. THE CRASPEDOTE MEDUSA OLINDIAS AND SOME OF ITS NATURAL ALLIES: 21 Fischer, A. 99. Fixirung, Farbung und Bau des Protoplasmas. Jena, 8°, x+362 pp. Fowler, G. H. 90. Notes on the Hydroid Phase of Limnocodium Sowerbyi. Quart. Jour. Micr. Sci., vol. 30, no. 120, pp. 507-514, pl. 32. Gtinther, R. T. 794, Some Further Contributions to our Knowledge of the Minute Anatomy of Limnoeodium. Quart. Jour. Micr. Sci., vol. 35, no. 140, pp. 539-550, pl. 40. Gtinther, R. T. 94a, A Further Contribution to the Anatomy of Limnocnida tanganyice. Quart. Jour. Micr. Sci., vol. 36, no. 142, pp. 271-293, pls. 18-19. Haeckel, E. "79. Das System der Medusen. Erster Theil einer Monographie der Medusen. Denkschr. med.-naturw. Gesell. Jena, Bd. 1, Abt. 1, pp. 1-360, Taf. 1-40. Hertwig, 0., und Hertwig, R. 78. Das Nervensystem und die Sinnesorgane der Medusen monographisch dargestellt. Leipzig, 4°, 186 pp., 10 Taf. Lankester, E. R. 80. On Limnocodium (Craspedacustes) Sowerbii, a new Trachomedusa inhabiting Fresh Water. Quart. Jour. Micr. Sci., vol. 20, no. 79, pp. 351-371, pls. 30-31. Lankester, E. R. 81. On Young Stages of Limnocodium.and Geryonia. Quart. Jour. Micr. Sci., vol. 21, no. 82, pp. 194-221, Fpl. 13. Mayer, A. G. 794, An Account of some Meduse obtained in the Bahamas, Bull. Mus. Comp. Zoél. Harvard Coll., vol. 25, no. 11, pp. 235-242, pls. 1-3. Mayer, A. G. :00. Some Meduse from the Tortugas, Florida. Bull. Mus. Comp. Zoél. Harvard Coll., vol. 37, no. 2, pp. 13-82, pls. 1-44. Mayer, A. G. :01. The Variations of a newly-arisen Species of Medusa. Sci. Bull. Mus. Brooklyn Inst. Arts and Sci., vol. 1, no. 1, pp. 1-27, pls. 1-2. Morgan, T. H. 99, Regeneration in the Hydromedusa, Gonionemus vertens. Amer. Nat., vol. 33, no. 396, pp. 9389-951. Miiller, F. 61. Polypen und Quallen von Santa Catharina. Arch. f. Naturg., Jahrg. 27, Bd. 1, pp. 312-819, Taf. 9. (Not accessible to the writer.) Murbach, L. 95. Preliminary Note on the Life-History of Gonionemus. Jour. Morph., vol. 11, no. 2, pp. 493-496. Saccardo. P. A. " 94, Chromotaxia seu nomenclator colorum polyglottus, additis speciminibus coloratis ad usum botanico- rum et zoologorum. Patavii, 8°, 22 pp., 2 tav. Vaney, C., et Conte, A. :01. Sur le Limnocodium Sowerbii Ray Lankester. Zool. Anz., Bd. 24, No. 651, pp. 533-534. 22 THE CRASPEDOTE MEDUSA OLINDIAS AND SOME OF ITS NATURAL ALLIES. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. EXPLANATION OF PLATES I-III. ABBREVIATIONS. can.crc. Circular canal. ot’cys’. Otocyst. ec’drm. Ectoderm. rz. ta. Endodermal tentacle roots. en’drm. Endoderm. ta. ex’ubr. Exumbrellar tentacle. gl. go. CON oaPr wn > 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. muc. Adhesive mucous gland. ta. vel. Velar tentacle. Gonads. PLATE I. OLINDIOIDES FORMOSA. Adult medusa in natural colors; diameter 55 mm. Young medusa in natural colors; diameter 15 mm. at mouth of umbrella. Portion of umbrella margin; diameter of umbrella 30 mm. Exumbrellar view; Xx 27 diameters. Portion of umbrella margin; diameter of umbrella about 100 mm. Exumbrellar view; x 13 diameters. One sextant with manubrium; diameter of umbrella 15 mm. Subumbrellar view. One sextant with manubrium; diameter of umbrella 75 mm. Subumbrellar view. Apical view of radial canals; diameter of umbrella 10 mm. Apical view of radial canals; diameter of umbrella 15 mm. Portion of gonad, showing three lobes which are subdivided into lobules; diameter of umbrella 90 mm. PLATE II. GoNIONEMA DEPRESSUM. Adult medusa in natural colors; diameter 18 mm. Portion of tentacle, showing the adhesive gland disk. X54 diameters. Portion of umbrella margin including a radial canal; diameter of umbrella 18mm. X13 diameters. Radial canal with gonad and manubrium; nearly adult. OLINDIOIDES FORMOSA. Terminal portion of a longitudinal section of tentacle, showing the adhesive glandular patch; diameter of umbrella 60 mm. X54 diameters. Portion of a radial section of umbrella margin, showing the first traces of otocyst; diameter of umbrella 10mm. 570 diameters. Portion of a radial section of umbrella margin; diameter of umbrella 10 mm. 420 diameters. PLATE III. OLINDIOIDES FORMOSA. Portion of a horizontal section of umbrella margin; diameter of umbrellal0 mm. 420 diameters. On one side of the tentacle root the otocyst is just cut tangentially. Portion of a radial section of umbrella margin. 420 diameters. Otocyst in a later stage of development. 420 diameters. Portion of adhesive glandular patch; diameter of umbrellal0 mm. X730 diameters. The mucus is seen as exudations at the free ends of the cells. GONIONEMA DEPRESSUM. Portion of a longitudinal section of tentacle, showing the adhesive disk. 240 diameters. Otocyst fully developed; diameter of umbrella 18mm. 420 diameters. SS fa. excuby a. vel. SG del MaRK ANNIVERSARY VOLUME. | glue. Meisel, lith. Boston SG del MARK ANNIVERSARY VOLUM PEA LT: ea) Codsin. CAMMETE, 19 COMCTTC 3 , 20 endrim. LIne 5G del GoTo-GRASPEDOTE MEDUSAE III 3) i: DESCRIPTIONS OF FOUR DISTOMES. (PLATE IV.) Henry S. Pratt. I. RENIFER gen. nov. The first three worms described in this paper, of which two are new to science, are all very closely related to one another and were found in similar localities, the mouth and air-passages of common North American snakes. They are also so closely allied to a worm recently described by Looss (99, p. 708) under the name of Styph- lodera solitaria, which was found by him in the intestine of Thalassochelys corticata, a sea-turtle, and to one recently described by Volz (’99, p. 231) from the lung of Heterodon platyrhinus and named by him Distomum zschokkei, that no doubt exists in my mind that all five species should be included in the same genus. This genus cannot well be Styphlodera, for reasons I shall give later on, and I have, therefore, created a new genus to contain them. The new genus may be given the following characterization. Renifer gen. nov.—Small distomes with body more or less elliptical and cov- ered with minute spines or scales. Mouth subterminal; acetabulum somewhat larger than oral sucker and in anterior half of body. Pharynx present; cesophagus short or wanting; intestinal ceca reach about to the middle of the body or a little past it. Excretory vesicle very large, Y-shaped, extending into the forward end of the body. Genital pore in front of the acetabulum often to the left or the right of the median line. Testes two, usually lobate, in the same transverse plane near the middle of the body; cirrus-sac often long, containing a vesicula seminalis which bends on itself. Ovary just posterior to the acetabulum and in front of the testes; yolk-glands lateral in position and occupying the middle third of the body; Laurer’s canal present; uterus composed of a descending and an ascending limb, and extend- ing to the hinder end of the body; receptaculum seminis absent or minute. Parasitic in the mouth or air-passages of snakes and in the intestines of turtles. Type: Renifer ellipticus Pratt. Additional species: R. elongatus Pratt, R. variabilis (Leidy) Liihe, R. solitarius Looss, R. zschokkei Volz. II. RENIFER ELLIPTICUS sp. nov. This worm (Pl. IV, Fig. 1) was found in the mouth of Heterodon platyrhinus, a common non-poisonous snake. It is a small worm, elongated in form and elliptical in outline; its dorsal surface is cylindrical, its ventral surface flat, the cross-section 25 26 DESORIPTIONS OF FOUR DISTOMES. forming thus a semicircle. The body of the worm is widest at about its middle, from which region it tapers towards both ends. These are rounded and blunt, the posterior end being, however, less so than the anterior end. The length of the worm varies from 3 millimetres to 4.2 millimetres, its breadth from 1.1 millimetres to 1.6 millime- tres, its greatest thickness 0.8 millimetre. The entire body is thickly covered with minute scales, set in transverse rows, except towards the hinder end, where their arrangement is irregular. The suckers are of good size and are sessile. The oral sucker is subterminal, with a diameter of 0.35 millimetre. The acetabulum is situ- ated almost in the centre of the body, but somewhat nearer the anterior than the poste- rior end and is 0.73 millimetre from the oral sucker in a small worm. It is larger than the oral sucker, measuring 0.41 millimetre in diameter. The genital pore is about half-way between the two suckers, although slightly nearer the anterior one, and is very near the left edge of the body, being 0.07 millimetre from that edge, and in the ventral surface. The excretory pore is at the posterior end of the body. The digestive tract is made up of pharynx, oesophagus, and intestinal ceca. The pharynx has a length of 0.10 millimetre and the csophagus is of moderate length and measures 0.24 millimetre; both are surrounded by gland-cells. The intestinal ceca are simple tubes without lateral branches; their width is about 0.2 millimetre. They extend about to the middle of the body, reaching the middle or posterior portions of the testes, and being somewhat longer in the larger specimens than in the smaller ones. The excretory vesicle is unusually long and voluminous. It is a Y-shaped tube with such delicate walls that it can be traced only in sections. The median portion is very long and wide. It extends forward as far as the ovary, lying dorsal to the uterus and between the testes. Its width in the posterior portion of the body be- hind the testes is about 0.5 millimetre, and it here occupies a quarter or more of the space within the body walls. The excretory crura are also wide and extend for- ward, one on each side of the acetabulum, to a position a little in front of the yolk- glands. Their width is about 0.17 millimetre. The testes are two slightly lobate bodies situated side by side near the centre of the body. They measure about 0.3 millimetre in length and width and 0.4 milli- metre in thickness. The right testis is a trifle in advance of the left one. The vasa efferentia pass forward to a position just dorsal to the anterior edge of the acetabulum, where they unite to form the vesicula seminalis. This organ, together with the pros- tate gland and the cirrus, is enclosed in a large cirrus-sac, which measures 0.8 milli- metre in length and 0.19 millimetre in width, and passes diagonally across the body to the genital pore at the left. The vesicula seminalis bends on itself in the posterior DESCRIPTIONS OF FOUR DISTOMES. 27 portion of the cirrus-sac and is continued in a short pars prostatica. The cirrus which follows is a large organ, about 0.4 millimetre in length, and occupies more than half of the cirrus-sac. , The ovary (Pl. IV, Fig. 3) is an ovoid body about 0.26 millimetre in length and lies partly behind and partly dorsal to the acetabulum and a little to the right of this organ. It is immediately beneath the dorsal body-wall. The oviduct is a short canal which leaves the left side of the ovary and passes to the odtyp; it is entirely surrounded by the shell-gland. A receptaculum seminis is wanting. Laurer’s canal, which is present in the form of a delicate tube, passes from the odtyp near the median line first to the right towards the ovary, then dorsally and posteriorly to the external opening, which is to the right of the median line. The yolk-glands consist of about forty rounded or elongated bodies on each side. They lie just beneath the ventral body-wall and immediately ventral to the intestinal ceca and extend from the posterior end of the testes forward a short distance anterior to the acetabulum. They are thus lateral in position and occupy about the middle third of the body. Five or six ducts arise from each yolk-gland at different regions and pro- ceed dorsally to a common point, where they unite to form the transverse yolk-duct. These two vessels, which are dorsal in position, meet in the midst of the shell-gland in the median line, and form a very short median yolk-duct which joins the o6typ. The shell-gland is a rather extensive group of glandular cells that lie against the dorsal body-wall to the left of the ovary with which they are in contact. It encloses the oviduct, Laurer’s canal, the transverse and median yolk-ducts, and the beginning of the uterus. This last-named organ is not very voluminous and consists of a descending and an ascending limb. The former passes posteriorly with a serpen- tine course to within a short distance of the hinder end of the body; the latter passes in a similar way to a point dorsal to the acetabulum and near the posterior end of the cirrus-sac. From this point it passes diagonally alongside the cirrus- sac to the genital pore on the left side of the body. The diameter of the two limbs is the same in young worms, but in the older and larger ones the ascending limb is much the larger and may become a third as wide as the body itself posterior to the testes. It is filled with a dense mass of dark-colored eggs. The egg measures 0.03 millimetre by 0.019 millimetre. A metraterm is not developed. The following is a specific diagnosis of Renifer ellipticus: Small, elliptical, semi- cylindrical worms averaging 4 millimetres in length and 1.4 millimetres in breadth. Oral sucker subterminal, 0.35 millimetre in diameter; acetabulum 0.41 millimetre in diameter, sessile, about 0.73 millimetre from the oral sucker. Body covered with minute scales. Pharynx and cesophagus of moderate size; intestinal ceca extend 28 DESCRIPTIONS OF FOUR DISTOMES. to the middle of the body. Excretory vesicle very long and voluminous, Y-shaped, with a long median portion and long crura. Testes two, side by side, in the middle of the body, behind the acetabulum and the ovary. Ovary immediately behind the acetabulum; yolk-glands lateral, occupying the middle third of the body. Cirrus-sac large, lying diagonally across the body from the acetabulum to the geni- tal pore at the left edge of the body. Egg measure 0.03 millimetre by 0.019 milli- metre. Parasitic in the mouth of Heterodon platyrhinus. This worm shows a remarkable resemblance to R. zschokkei Volz (’99), a worm found in the lung of a specimen of Heterodon platyrhinus which died in a private terrarium in St. Gall, Switzerland. In size the two forms are alike. They are also almost identical as to their anatomy, but the Swiss form differs from the American in the following particulars: it is found in the lung instead of the mouth of the snake; it is without an cesophagus; the genital pore is at the right side of the body instead of the left; and the folds of the uterus in the hinder part of the body have a lateral direction, which is not the case in the American form. III. RENIFER ELONGATUS pp. nov. This worm (Pl. IV, Fig. 2) was found in the mouth of Heterodon platyrhinus together with the one just described. It is a smaller worm than R. ellipticus, and is relatively more slender; the suckers are relatively longer, the intestinal ceca are also longer, the yolk-glands are less voluminous, and the genital pore is near the median line instead of being near the edge of the body; in other respects, however, the worm is very similar to its neighbor. The length of Renifer elongatus is about 3 millimetres; the greatest breadth is at the beginning of the second third of the body, where the large acetabulum is situated, and is 0.68 millimetre. From this place the body tapers slightly towards the anterior end, to which the large oral sucker gives a rounded form. Towards the posterior end the body tapers to a blunt point. The body has a thickness in the region of the acetabulum of 0.4 millimetre. As is the case with R. ellipticus, the worm is flat on the ventral side and cylindrical on the dorsal. The entire body is thickly covered with minute spines arranged in trans- verse rows, except towards the hinder end where the spines become less numerous and regular. The suckers are of large size and are sessile. The oral sucker is sub- terminal and has a length of 0.32 millimetre and a width of 0.33 millimetre. The opening is noticeably small, having a width of 0.06 millimetre. The acetabulum DESCRIPTIONS OF FOUR DISTOMES. 29 is situated about at the beginning of the second third of the body and has a length of 0.4 millimetre and a width of 0.36 millimetre. The genital pore is on the ventral surface near the posterior end of the pharynx, a little to the left of the median line. The excretory pore is at the posterior end of the body. The digestive tract is made up of the pharynx, the cesophagus, and the intes- tinal ceca. The pharynx has a length of 0.06 millimetre. A very short cesophagus with a length of 0.02 millimetre follows. The intestinal ceca are simple tubes with- out lateral projections and have an average width of 0.04 millimetre. They are longer than in R. ellipticus, extending beyond the testes; the right cecum is some- what longer than the left one. ' The excretory vesicle is very long and voluminous. It has the shape of the letter Y, the median portion extending forward as far as the ovary, and the crura almost reach the branching of the digestive tract. The median portion is not only of great length, but also of great width and depth. Posteriorly to the testes it occu- pies at least half of the space within the body-wall. Near the ends of the intestine, for instance, it has a width of 0.41 millimetre and a depth (dorso-ventral) of 0.13 millimetre (Pl. IV, Fig. 4), while at the posterior end of the uterine loop it measures 0.20 millimetre by 0.05 millimetre. At the hinder end of the animal the excretory vesicle occupies practically the entire space within the body-walls. Between the testes this vesicle is contracted to a fraction of its width behind those organs, but immediately anterior to them it again expands so that it measures 0.41 millimetre by 0.2 millimetre, the body of the worm itself at this region having a width of 0.66 millimetre and a thickness of 0.29 millimetre. Just behind the ovary the excretory vesicle branches, and each branch has a width of about 0.13 millimetre and a depth of 0.2 millimetre. The branches gradually become smaller toward the anterior end of the animal, where they run alongside the cirrus-sac, to terminate a short distance in front of the acetabulum. Throughout its entire course the excretory vesicle is dorsal in position. The testes are two elongate, slightly lobate bodies situated side by side near the centre of the body. The right testis is slightly in advance of the left one. They measure about 0.32 millimetre in length, 0.16 millimetre in width, and 0.24 millimetre in thickness, lacking but little of being as thick as the body itself. The vasa efferentia pass from their anterior ends forward to a position dorsal to the posterior edge of the acetabulum, where they unite to form the vesicula seminalis. This organ together with a long pars prostatica and a short cirrus is enclosed in the large cirrus-sac, the length of which is 0.7 millimetre and the width 0.16 millimetre. The vesicula semi- nalis bends on itself in the posterior portion of the cirrus-sac. The pars prostatica 30 DESCRIPTIONS OF FOUR DISTOMES. is an elongated organ that occupies three-fourths of the space within the cirrus-sac. The cirrus is short and weak. The ovary is a small ovoid body 0.16 millimetre in length that lies partly behind the acetabulum and partly dorsal to it. It is just to the right of the median line and is dorsal in position. The oviduct is a short tube which proceeds towards the me- dian line through the shell-gland to the odtyp. The shell-gland lies next to the left side of the ovary and in contact with the dorsal body-wall. It is about half the size of the ovary. The yolk-glands consist of about twenty-five glandular bodies on each side. They extend from the anterior end of the testes to the anterior end of the acetabulum. Their position in the body is ventral and between the intestinal exca and the ventral body-wall. Three or four yolk-ducts leave the yolk-glands on each side and proceed to a common point posterior to the ovary in the dorsal portion of the body, where they meet to form the transverse yolk-ducts. These ducts meet in the median line and form a short median yolk-duct which proceeds to the odtyp. Laurer’s canal arises in the odtyp and extends through the shell- gland to the external pore a little to the right of the median line. The uterus consists of a descending and an ascending limb, both of which have a serpentine course. The descending limb proceeds from the odtyp between the testes to the hinder end of the body; the ascending limb, which is much the larger of the two, proceeds anteriorly along the median line, and on the left side of the cirrus-sac to the genital pore. The terminal portion of the uterus forms a metraterm. The egg measures 0.035 millimetre by 0.02 millimetre. The following is a specific diagnosis of Renifer elongatus: Small, elongated semi-cylindrical worms whose length is 3 millimetres and breadth 0.68 millimetre. The oral sucker is subterminal and 0.33 millimetre in diameter. The acetabulum is sessile and 0.36 millimetre in diameter. Body covered with minute spines. The pharynx is of moderate size; the cesophagus is very small; the intestinal ceca extend beyond the testes into the beginning of the posterior third of the body. The excre- tory vesicle is very long and voluminous, Y-shaped, and with a long median por- tion, and long crura. The testes are two, situated side by side, in the middle of the body, behind the acetabulum and the ovary. The ovary lies immediately behind the acetabulum. The yolk-glands are lateral, between the testes and anterior end of the acetabulum. A Laurer’s canal is present, but a receptaculum seminis is wanting. The genital pore, nearly median, lies near the pharynx. The eggs meas- ure 0.035 millimetre by 0.02 millimetre. Parasitic in the mouth of Heterodon platyrhinus. DESCRIPTIONS OF FOUR DISTOMES. - 31 IV. RENIFER VARIABILIS (LEIDY) LUHE. ~ Three specimens of this worm were found in the lung of Tropidonotus sipedon, a common non-poisonous. snake. In 1856 Leidy (’56, p. 44) described very briefly two distomes which he named Distomum variabile, Variety a and Variety b. His description was as follows: “Var. a. Body white, variegated with black in the course of the oviduct, clavate, posteriorly obtuse, minutely echinated.” “Oral and ventral acetabula nearly equal; the latter one prominent, situated at the base of the neck. Length to 6 lines; breadth of body 4 line.” ‘Attached to the sides of the cavity of the lungs of Tropidonotus sipedon.”’ “Var. b. Body flattened, ovate, continuous with the head, anteriorly narrowed, posteriorly obtuse, color and echination as in the preceding variety. Length 24 lines; breadth 2 lines.”’ Found detached in the mucus of the lungs and trachea of Tropidonotus sipedon. Variety b has also been described, briefly and without figures, by Max Liihe (:00, p. 559), who obtained his specimens from the Museum fiir Naturkunde in Berlin. Lihe proposes to confine the specific name variabile to this worm and to consider Variety a a distinct species. Although the worm found by me differs in some slight degree from Distoma variabile as described by Lithe, I have no hesitation in ascribing it to that species. The following is a description of it. Renifer variabilis (Pl. IV, Fig. 5) is a broad, flat worm between 3 millimetres and 4 millimetres in length and between 1.50 milli- metres and 2 millimetres in width; the average thickness is 0.5 millimetre, the dorsal and the ventral surfaces being approximately parallel. The greatest width is just posterior to the middle of the body, from which region it tapers towards the anterior end, while the hinder end is rounded and semicircular in outline. The entire body is thickly set with minute spines which are arranged anteriorly in rows and are more numerous there than posteriorly. Lithe found only the anterior portion of the worm examined by him to be covered with spines, but it is not impossible that the spines had been present on the hinder portion, but had disappeared as a result of poor preservation, for the worm was an old museum specimen. The suckers are of good size and are sessile. The oral sucker is subterminal and has a diameter of 0.5 millimetre in a large specimen. The acetabulum is about 0.4 millimetre distant from the oral sucker and has a diameter of 0.6 millimetre in a large animal. The 32 DESCRIPTIONS OF FOUR DISTOMES. genital pore is about half-way between the two suckers and very nearly on the median line. The excretory pore is at the posterior end of the body. The digestive tract consists of pharynx, cesophagus, and intestinal ceca. The pharynx has a length of about 0.2 millimetre. The cesophagus is very short. The intestinal ceca extend posteriorly to about the beginning of the posterior third of the body. In a large worm they extend to the posterior end of the testes; in the smaller one to the anterior end of those organs. They are not simple tubes, but they send out short lateral projections that are most numerous and longest toward their posterior ends. The excretory vesicle is a long Y-shaped structure, the diameter of which remains approximately the same, 0.08 millimetre, throughout its entire course. The median portion is very long, extending from the excretory pore forward to a point just behind the shell-gland and near the anterior end of the testes, between which it passes. The excretory crura are also long and extend forward to a point near the pharynx. The excretory vesicle is not a simple tube, but, like the intestinal cxca, it sends out short lateral projections which are especially noticeable towards its anterior ends. The testes are two large, deeply lobate organs situated near the middle of the body, and in very nearly the same‘transverse plane. The length and width of a testis is about 0.8 millimetre, the thickness is very nearly that of the body itself. The narrow space between the two testes is occupied by the median limb of the excretory vesicle and the ascending and descending limbs of the uterus. The vasa efferentia pass forward to a point near the anterior margin of the acetabulum, where they join to form the vesicula seminalis. This is an organ of the considerable length of 0.6 millimetre. It bends on itself in the cirrus-sac, and from its anterior end a pars prostatica and a short cirrus extend to the genital pore. These organs are contained in a cirrus-sac 0.4 millimetre in length and 0.15 millimetre in width. The ovary is an organ of irregularly ovoid form about 0.33 millimetre in length. It lies immediately behind and to the left of the acetabulum, its anterior portion lying dorsal to the ventral margin of that organ. The oviduct is a short, delicate tube which passes directly from the ovary to the centre of the shell-gland. A recep- taculum seminis is wanting. The shell-gland is a little behind and to the right of the ovary and almost exactly in the median plane. Laurer’s canal passes from the odtyp dorsally and to the right, where it meets the dorsal surface to the right of the median line. The yolk-glands consist of about forty rounded or elongated bodies on each side. They lie mostly lateral to the intestinal ceca, and extend from the anterior end of the testes to the level of the genital pore. In a small specimen they occurred DESCRIPTIONS OF FOUR DISTOMES. 33 posteriorly to about the posterior end of the intestinal cxeca, as described by Lithe, but in a large worm, in which the ceca are relatively longer, they do not reach the posterior ends of those organs. Two or three yolk-ducts leave each yolk-gland and proceed towards the centre of the body. They join on each side to form a single duct, the transverse yolk-ducts, which meet and form a median yolk-duct. This duct, which proceeds posteriorly, is very short and widens at once to form a small yolk-reservoir 0.06 millimetre long and 0.03 millimetre wide, beyond which it im- mediately joins the odtyp. The uterus leaves the odtyp near the centre of the body and proceeds towards its hinder end. This organ is very voluminous and forms a descending and an ascend- ing limb, the former on the left and the latter on the right side of the body. These limbs are both thrown into transverse folds which, posterior to the testes, extend from the centre to the sides of the body. Anterior to the testes the folds do not. extend laterally beyond the intestinal ceca. The broad hinder part of the body is entirely filled with these uterine folds. The ascending limb finally passes forward, dorsal of the acetabulum, to the genital pore. No specialized metraterm is present. The uterus is crowded with small dark-colored eggs, the average length of which is 0.034 millimetre, and the average width 0.018 millimetre. The affinities of R. variabilis were indicated by Lihe (:01, p. 561), who called attention to the similarity of structure that exists between it and Styphlodora solitaria Looss. There seems to me little doubt that these two species belong to a common genus, but I would not ascribe them to the genus Styphlodora. The principal points of differ- ence between them are the possession of a receptaculum seminis by 8. solitaria, which is wanting in R. variabilis, and the shortness of the median limb of the excretory vesicle in S. solitaria, as compared with that of R. variabilis. As regards the first point of difference, the minute size of the receptaculum in S. solitaria deprives it of importance. As regards the second, Looss (’99, p. 708) was unable from lack of material (he possessed but a single specimen) to determine the exact course of the excretory vesicle in S. solitaria, and he mentions the possibility that its median portion may be long instead of short or wanting, as he describes it. He says: ‘‘ Es hat mir geschienen, als ob ausser diesen Schenkeln noch ein medianer Stamm nach vorn liefe, doch war wegen der Fiillung des Hinterleibes mit den Schlingen des Uterus etwas Genaueres nicht zu erkennen.”’ Looss (’99, p. 592) also seems to express a doubt that S. solitaria belongs to the genus Styphlodora. He states that “Dieser Gattung scheint noch zuzuzéhlen zu sein St. solitaria.”’ Its generic identity with S. serrata, the type-species ‘of this genus, 34 DESCRIPTIONS OF FOUR DISTOMES. may well be questioned, as a study of the two species will show. If, however, its excretory vesicle proves to possess a long median stem, the essential identity of its characters, with those of Renifer variabilis, as well as with those of R. ellipticus and R. elongatus, justifies the creation of this new genus to contain them. The affinities of Renifer are with the genera Styphlodora and Astia as described by Looss (’99, pp. 592, 590), and forms a connecting link between them. With Astia it agrees in the great length of the median stem of the excretory vesicle and the ex- tent and structure of the yolk-glands. It differs from it in the form and extent of the excretory crura, which are peculiarly formed in Astia and do not extend in front of the acetabulum, in the relative size of the acetabulum, which is smaller than the oral sucker in Astia, in the position of the cirrus-sac, the form of the vesicula seminalis, and the form and position of the testes. Renifer is similar to Styphlodora in the course and extent of the intestine, and in the general disposition of its organs. It differs from Styphlodora in the structure of the excretory vesicle, the position of the testes, the size of the yolk-glands, and the absence of a large receptaculum seminis. V. OSTIOLUM FORMOSUM eget. nov., sp. nov. Several specimens of this worm were given me some years ago labelled “from the frog.”’ I do not know from what organ they were taken or from what species of frog. It is an elongated, graceful animal (PI. IV, Fig. 6) between 7 millimetres and 10 milli- meétres in length, and about 1.5 millimetres in width in the widest region. The thickness averages 0.33 millimetre; the cross-section is elliptical. The outer surface is without spines or scales. The broadest portions of the worm are posterior to the middle. Towards the forward end the body tapers very gradually to the oral sucker; the hinder end is rounded and blunt. The oral sucker is nearly terminal, but slightly subterminal, and measures 0.3 millimetre in width in a large worm. The acetabulum is situated about 2.5 millimetres distant from the anterior end and is distinguished by its small size (Pl. IV, Fig. 8). It is only 0.07 millimetre in diam- eter, which is about a twelfth of the width of the worm in this region. It is besides very shallow and its musculature is so weak that it can hardly be a functionally active organ. It is much more likely that it is a rudimentary organ which is in process of retrogression; in fact until I sectioned the worm I supposed I was study- ing a monostomid. . The genital pore is near the anterior end on the ventral surface, a little to the DESCRIPTIONS OF FOUR DISTOMES. 35 left of the posterior end of the pharynx. The excretory pore is at the posterior end of the body. The digestive tract is made up of pharynx and intestinal ceca. The former is 0.19 millimetre in length and 0.13 millimetre in width. There is no esophagus. The intestinal ceca are wide tubés, without lateral projections, which reach into the posterior extremity of the body. The average width of each is 0.16 millimetre. The excretory vesicle is Y-shaped, with a very long median portion and short crura. The former extends from the excretory pore forward to the region of the ovary and shell-gland. Its course lies close to the ventral body-wall as far as the posterior testis; it then winds between the testes, near the centre of the body, and passes to the left of the receptaculum seminis and ovary. The excretory crura extend forward, one on each side of the body, parallel and dorsal to the intestinal ceca. They terminate near the anterior ends of the yolk-glands. The diameter of the median portion is about 0.1 millimetre; that of the crus is about 0.07 milli- metre. The testes are two large, ovoid, but somewhat irregular organs situated near the middle of the body. Each testis measures about 1.14 millimetres in length and 0.8 millimetre in width. In thickness they measure about 0.32 millimetre and entirely fill the body of the worm between the dorsal and ventral body-walls. The testes are situated one diagonally behind the other, the anterior testis being on the right side of the body. The vas efferens from the anterior testis leaves its anterior border and passes forward between the receptaculum and the ovary, ventrally to the former and dorsally to the anterior end of the latter. The vas efferens from the posterior testis passes to the left of the anterior testis and of the receptaculum seminis, and meets its fellow near the anterior end of the ovary. The vas deferens, which is formed by their union, runs forward between the intestinal ceca to the genital pore, enclosed the entire distance in a cirrus-sac. The greater portion of the vas deferens functions as a vesicula seminalis. This organ is thus very long, and is still further increased in length by its serpentine course. It is also very broad, having an average width of 0.06 millimetre, and is constantly filled with spermatozoa. The anterior end of the vas deferens forms a short cirrus, which can be protruded from the body. The cirrus-sac is peculiar because of its great length, and also from the fact that it is almost entirely filled by the voluminous vesicula seminalis. The posterior portion of that organ, in fact, exactly fills the cirrus-sac; its anterior portion, however, has a slightly smaller diameter, and leaves a small space within the cirrus-sac. The ovary (Pl. IV, Fig. 7) is an elongated body which lies in front of the recep- taculum seminis and the testes and just behind the acetabulum. It has a length 36 ‘DESCRIPTIONS OF FOUR DISTOMES. of 1 millimetre, a breadth of 0.4 millimetre, and a thickness of 0.28 millimetre. It lies transversely or diagonally across the body, with its posterior end on the right side. The oviduct is a short narrow canal 0.013 millimetre in diameter which leaves the ventral surface of the ovary near its anterior end and proceeds to the odtyp in the centre of the shell-gland. The receptaculum seminis is a large sac about the size of the ovary and is constantly filled with spermatozoa. It has also the shape of the ovary and lies immediately posterior to it. Its duct is a narrow tube, similar in size to the oviduct, which proceeds from the anterior surface and joins the oviduct. The shell-gland is an extensive group of glandular cells situated between the ante- rior ends of the ovary and the receptaculum seminis, and enveloping the proximal portion of the uterus and also portions of the oviduct and the median yolk-duct. Laurer’s canal could not be found. The yolk-glands are extensively developed and are situated at the sides of the body mostly lateral to the intestinal ceca. They consist of a number of distinct follicles on each side and are joined by a longitudinal duct. The number of these follicles varies from six to eleven on a side, and each follicle is made up of from five to ten rounded glandular bodies. Most of the follicles are between the intestinal ceca and the lateral edge of the body; the extreme posterior and anterior ones, how- ever, may be situated in the centre of the body between the intestinal ceca. The anterior and posterior portions of the yolk-ducts on each side meet ventral to the receptaculum seminis and form thus the two transverse yolk-ducts. These ducts meet near the median plane and form the median yolk-duct. This duct in a large worm measures about 0.3 millimetre in length. It runs anteriorly to the odtyp. About midway in its course it expands to form a small yolk-reservoir, the diameter of which is 0.06 millimetre. The uterus begins its course at the odtyp, and passes first towards the hinder end of the body. It proceeds, as a small and moderately straight tube, between the testes to the space behind those organs, which it entirely fills with its numerous irreg- ularly transverse folds. It then runs forward, winding in transverse folds between the testes, filling the space between them and the receptaculum seminis, and passing to the genital pore near the anterior end of the body. The uterus is thus very volu- minous. It is filled with small dark-colored eggs which measure 0.039 millimetre by 0.017 millimetre. No specialized metraterm is present. The following is a specific diagnosis of Ostiolum formosum. Elongated, flattened worms. Length between 7 and 10 millimetres; breadth 1.5 millimetres; thickness 0.33 millimetre. No spines or scales are present. Oral sucker subterminal, 0.3 milli- metre in width. Acetabulum sessile, minute, 0.07 millimetre in width. Pharynx of DESCRIPTIONS OF FOUR DISTOMES. 37 moderate length, esophagus wanting; intestinal ceca extend nearly to the posterior end of the body. Excretory vesicle Y-shaped, with a very long median portion and short crura. Testes two, of large size, in the anterior portion of the posterior half of the body, one diagonally behind the other. Ovary immediately behind the acetab- ulum and in front of the testes; yolk-glands lateral, distributed in six to eleven follicles on a side, extending nearly the length of the body; receptaculum seminis present and very large; vesicula seminalis very long, enclosed in the cirrus-sac; cirrus small. Genital pore at the posterior end of the pharynx. Egg measures 0.039 millimetre by 0.017 millimetre. Parasitic in the frog. The affinities of Ostiolum are with the genus Hematolcechus, as described by Looss (94). It resembles that genus in the shape and size of the body of the worm, the form and extent of the digestive tract, the form of the excretory vesicle, the position of the testes, the position of the genital pore, the form and length of the cirrus-sac and of the vesicula seminalis, the large size of the receptaculum seminis, the absence of Laurer’s canal, the form and distribution of the yolk-glands, the great length of the uterus, the weakness of the acetabulum, and the host which harbors the animal. It differs principally from Hematolcechus in the position of the acetabulum, which is farther forward than in that genus, the size of the testes, which are much smaller than in Hematolcechus, in the arrangement of the uterine folds, which have a general longitudinal direction in Hematolcechus, and in the length of the excretory vesicle, which extends much farther forward than in Hematolcechus. In that genus, also, the worms are often covered by spines, while in Ostiolum these structures did not appear in any of the specimens examined by me. VI. BIBLIOGRAPHY. Leidy, J. 756. A Synopsis of Entozoa and some of their Ecto-congeners observed by the Author. Proc. Acad. Nat. Sci. Philadelphia, vol. 8, pp. 42-58. Looss, A. 194. Die Distomen unserer Fische und Frésche. Bibl. Zool., Heft 16, 296 pp., 9 Taf. Looss, A. 799. Weitere Beitrage zur Kenntniss der Trematoden-Fauna Aegyptens. Zool. Jahrb. Abt. f. Syst., Bd. 12, pp. 521-784, Taf. 24-32. :00. Ueber einige Distomen aus Schlangen und Eidechsen. Centralbl. f. Bakt. Parasit. u. Infek., Abt. 1, Bd. 28, No. 17, pp. 555-566. 99. Beitrag zur Kenntniss der Schlangendistomeen. Arch. f. Naturg., Jahrg. 65, Bd. 1, pp. 231-240, Taf. 20. 38 Fig. 1. Fig. 2. Fig. 3. Fig. 4. Fig. 5. Fig. 6. Fig. 7. Fig’ 8. act. can. Lau. cir. cia. dt, vt. gl. cnch, gl. phx. gl. vt. im mht. mu. lg. 0a, o’dt. Renifer ellipticus, ventral view. 30. Renifer elongatus, dorsal view. X33. DESCRIPTIONS OF FOUR DISTOMES. EXPLANATION OF PLATE IV. All the figures except 3 and 7 were made with the aid of a camera lucida. Acetabulum. Laurer’s canal. Cirrus. Cuticula, Yolk-duct. Shell-gland. Pharyngeal gland. Yolk-gland. Intestine. Metraterm. Longitudinal muscles. Ovary. Oviduct. ABBREVIATIONS. oes. or. phx. po. exe. po. gen. prs. prost. rcp. sem. rsv. vt. sac. cir. te. ut. vsl. exc. vsl. sem. PLATE IV. Csophagus. Mouth. Pharynx. Excretory pore. Genital pore. Pars prostatica. Receptaculum seminis. Yolk-reservoir. Cirrus-sac. Testis. Uterus. Excretory vesicle. Vesicula seminalis, Diagram showing the arrangement of the female genital organs of R. ellipticus. Outline of a cross-section of R. elongatus just posterior to the testes. 78. Renifer variabilis, dorsal view. x24. Ostiolum formosum, ventral view. X14. Diagram showing the arrangement of the female genital organs of O. formosum. Cross-section of the ventral body-wall of O. formosum showing acetabulum. X10. MARK ANNIVERSARY VOLUME, PLATE WV. x = DO.GYEN. NP Os C A pers Bs ; Ve : aN cnet By \ ia mrt Jo IER SOC FUL +: SY Aa ee . pan" > (| aS SS LO ee RSS ut-ff a, ARN ABIL wn) \ Jt’ oe T3V.ves a bs \Geananioeeioen Soa ‘ T CPSC ALVE a HSPdel 2 Meisel, lth 6ysten PRATT.- DISTOMES. jII. A NEW CRANIAL NERVE IN SELACHIANS. (PLATES V-VI.) Wiuuiam A. Locy. I. INTRODUCTION. Explorations in the field of morphology are continually bringing to light new facts which modify our ideas regarding structural features already recognized, and also make it necessary to take account of new ones. ‘This progress is the result of intensive work with, of course, better instruments and better technique. One result of this work has been to concentrate the attention within relatively narrow limits, so that one observer often misses that which will lie in the path of another working on the same material. Of this there is no lack of illustrations, and another case in point is now found in the. brain of the selachians. From the time of Busch (’48) through Leuret and Gratiolet (’389-57) to the publication of Fritsch’s classical memoir (’78), the brains of various selachians had been carefully examined and figured. From Fritsch’s time to the present the brains of Squalus acanthias and other selachians have been among the most frequently examined nervous systems both from the standpoint of structure and of development. In the study of the selachian head the present writer also had a modest part (’95), but a pair of cranial nerves was continually overlooked. I found them first in Acanthias embryos about six ‘years ago, and, published (Locy, 799) an account of their embryonic development in that selachian. At first, very naturally, I looked upon these nerves as of exceptional occurrence, possibly transitory in existence, and probably confined to a very limited number of species. I have, however, continued to find them in all the different adult selachians that I have had opportunity to dissect. In this paper it is proposed to describe these newly observed nerves in six genera of adult selachians and their de- velopmental history in one. Their occurrence in the adult stages of six genera is sufficient to show that they are not transitory structures, nor are they confined to a very limited number of species. It is a great pleasure to the writer to prepare this paper as an expression of high regard for Professor Mark, under whose stimulating guidance he received his training in morphological method and took his first steps in independent work. The nerves in question are connected, peripherally, with the olfactory epithelium and terminate, centrally, in the upper part of the corpus striatum. One’s first im- pulse would be to look upon them as possibly representing a pair of bundles of the olfactory system run wild, rather than as new elements in that system, or as inde- 41 42 A NEW CRANIAL NERVE IN SELACHIANS. pendent nerves. But the chief bundles (Edinger) recognized as belonging to the olfactory system are present simultaneously with these nerves, and the anatomical descriptions which follow will make it clear that their fibres have no connection with the olfactory glomeruli, and throughout their course have a striking independence. This, taken in connection with their embryonic history, is what to my mind justifies calling them a pair of “new cranial nerves.” It is my hope to be able to complete in the near future observations on the bundles in the olfactory tract, and to publish them in another connection, with a critical examination of the entire olfactory system. II. DESCRIPTIONS OF THE NEW NERVE IN ADULT SELACHIANS. 1. In Squalus acanthias.—The brain of an adult Squalus acanthias is repre- rented in Figure 1 (Pl. V). A brief general description of the parts of the forebrain will be given first in order to make clearer the course of the new nerve. In front are the olfactory cups, two hollow bodies in the interior of which the nasal membrane is thrown into plate-like folds. The fila olfactoria, or fibres of the olfactory nerves, arise in cells of the nasal membrane and pass backward, uniting just below the capsules into distinct bundles. The smaller bundles of the fila olfactoria are gathered into two great divisions, one more lateral (n. olf. 1.) and one more median in position (n. olf. m. in other figures). This partition of the olfactory fibres into two large complex divisions seems to be general among the selachians. The complete separation of the two divisions is well shown in Scoliodon terre-nove (Fig.9); in 8. acanthias the sepa- sation is not so distinct, but it is nevertheless complete. The fibres composing each division cross and mingle in a complicated manner and enter the enlarged end of the olfactory tract (Fig. 1, irt. olf.). There is thus formed a rounded enlargement at the base of the capsule called the bulbus olfactorius. The ends of the fila olfactoria divide into brush-like tufts which come into communication with similar brush-like endings of dendrites, belonging to a different series of cells, situated in the base of the bulbus. The rounded masses formed by the union of the tufts of the filia olfactoria and those of the dendrites are designated glomeruli olfactorii, and they mark the di- vision between the neurons of the first and second order respectively. The neuraxons of the neurons of the second order pass backward in the tractus, and, entering the forebrain, they separate into the various tracts or bundles of the olfactory system. The front part of the forebrain in 8. acanthias is divided by a median furrow into two parts. This extends backward only about one-half the distance to the thalam- A NEW CRANIAL NERVE IN SELACHIANS. 43 encephalon and, therefore, the hinder portion of the forebrain is undivided. The epiphysis is not represented in the drawing. Connected with the base of the thalam- encephalon are the optic nerves (n. opt.). Behind the thalamencephalon come the midbrain (ms’ence.), the cerebellum (cbl), and the medulla oblongata. The course of the new nerve (Fig. 1, . nov.) may now be described. It may, for convenience, be spoken of as passing from the brain to the olfactory cups with- out prejudicing the question of the source of origin of its fibres. Starting deep in the median furrow, it passes forward across the anterior surface of the forebrain; it then curves in the angleformed by the union of the olfactory tract and the fore- brain, and finally passes along the inner margin of the tract to reach the median division of the fila olfactoria. It crosses this obliquely and enters the fissure between the two divisions of the fila. These are unequal in breadth—the median one being broader—so that the point at which the nerve disappears in the furrow is about two- thirds the space across. Just as the nerve reaches the fissure it branches, unequally, into three stems (not shown in the drawing); a small one passing obliquely back- ward and downward to unite with the lateral division near its base, another slender one curving upward and inward to unite with the median division, and the chief central stem which runs forward and laterally, uniting with the outer bundle of the lateral division of the fila olfactoria (n. olf. 1). This chief stem breaks into anumber of small branches that pass among the fibres constituting the lateral division. This stem also dips downward into the furrow and reaches about the level of the median horizontal plane of the olfactory cup. By separating the fila olfactoria it can be traced close to the membranous covering of the olfactory capsule, and well out along the lateral portion of the olfactory cup. Here it penetrates the connective-tissue covering of the cup and enters (in connection with the fila olfactoria) the nasal epithe- lium. All this, with the exception of the last item, can be made out by careful work under a dissecting microscope, and has been many times confirmed by repeated obser- vations. One point that forcibly strikes the observer is that this new nerve pre- serves its independence, often mingling with the fila olfactoria. Actual anastomosis could not be made out. The two sets of fibres commingle very intimately, but in no case have they been seen to unite with each other. There are two ganglionic enlargements on the nerves in Squalus acanthias that vary in position in different specimens. The more prominent one (Fig. 1, gn.) is near the base of the bulbus, and the other near the angle of union between forebrain and tractus. The nerve is composed of two bundles united within the same enve- lope of connective tissue. The distinction between the two bundles is well seen in sections at the angle between tractus and forebrain, and, again, within the median 44 A NEW CRANIAL NERVE IN SELACHIANS. furrow. In the latter position the two bundles of each nerve separate and penetrate the brain-wall at different points. Having described the course of the nerve from the median furrow to the olfactory cup, let. us now consider its central connections. Near the bottom of the furrow the divided bundles of the nerves penetrate the brain-wall. They enter this a little below the level of the median horizontal plane, and, rising slightly (Pl. VI, Fig. 18, n. nov.), pass toward the inner wall of the brain-ventricle. Sections made in the horizontal plane (Pl. VI, Fig. 17, n. nov.) show that the nerves on each side pass backward in the brain substance, dividing into two or three chief branches, which in turn are greatly subdivided. The median branches of each side cross the median plane and spread into a number of twig-like terminations, while the other branches spread out in the brain substance of the same side as that on which they entered. The minuter branches of these nerves terminate near the epithelial cells which form the lining of the brain ventricle. The portion of the brain substance in which these fibres end apparently corre- sponds to the epistriatum (Edinger) of the brains of reptiles, etc., although it is on the median wall rather than the lateral wall of the brain ventricle. In the forebrain of Squalus two thickened masses of cells meet in the median plane on the base of the brain, and also unite vertically with an infolding of the cortex from the roof of the brain. In cross-section this presents the appearance of a short pillar with an enlargement above, the cortical infolding, and another below, the corpus striatum; the fibres terminate in the region between the two (the epistriatum?). The fibres can be traced very close to the brain ventricle, but I have not been able to make out the nature of their final terminations. Figure 18 (Pl. VI) shows the course of the nerve within the brain substance as seen in a sagittal section; Figure 17 shows a partly diagrammatic reconstruction of sections made in the horizontal plane; and Figure 19 shows the position of the nerve in a cross-section. As to peripheral connections, the study of serial sections shows that the fibres of the new nerve are mainly distributed to the olfactory membrane in the antero-lateral portions of the olfactory cup. There is in 8. acanthias, as in other selachians, an obvious division of the olfactory chamber into two parts, one median, the other lateral. The olfactory membrane of these two parts is continuous and, in both, is thrown into similar folds, but membranous flaps, or valves, developed from the firm ring surrounding the entrance to the cavity, are so arranged as to make two openings and separate the chamber into two parts. The separation of the fila olfactoria into two divisions apparently has reference to these two parts. The fibres of the new A NEW CRANIAL NERVE IN SELACHIANS. 45 nerve are mainly, but not entirely, distributed to the outer lateral portions of the olfactory membrane, inasmuch as the chief branch of the nerve takes a course to that portion of the olfactory cup. Here the fibres can be traced between the folds of the olfactory epithelium. The nature of their termination within that membrane or their possible connection with cells of it will be especially difficult to determine. After the divisions of the fibres become very minute they are easily confused with the smallest bundles of the fila olfactoria and the tracing of individual fibres is very uncertain. Small bundles of the fibres of the new nerve can, however, be traced between the folds of the olfactory membrane and as far as the base of the epithelial cells. Since writing the above my attention has been called by one of my students, Miss Effie Thayer, to a series of sections in which a fortunate differentiation with iron-hemotoxylin staining has made a distinction in appearance between even the small fibres of the fila olfactoria and those of the new nerve. Iam indebted to her not only for making the sections, but for tracing these fibres, thus seen with greater distinct- ness than was possible in other sections, into contact with the olfactory epithelium. The next question in reference to this nerve would naturally be, What is its embryonic history? This has been worked out in Squalus acanthias, and the main facts will be given, after considering the anatomical condition of the nerve in the adult stages of other selachians. 2. In Mustelus canis.—The brain of the smooth hound, Mustelus canis, seen from above is represented in Figure 2 (Pl. V). The olfactory cups are relatively of enormous size, showing that the olfactory apparatus is doubtless of great impor- tance in the life of this animal. The tractus olfactorius is shorter than in Squalus, and the forebrain is not divided by a median furrow as in that selachian. The new nerve is more easily detected in Mustelus than in Squalus, for it lies more freely in the membrane of the cranial cavity and is not so closely applied to the tractus. Its point of entrance into the brain-wall is on the ventral surface as shown in Figure 3. Here the nerve enters a small depression on the base of the brain, considerably in front of the optic nerve. From this point it passes towards the olfactory cup, in a course nearly parallel to the tractus, but it does not come to lie close to that structure. As seen from above, it traverses the relatively short space between the anterior wall of the forebrain and the bulbus and then crosses obliquely the median division of the fila olfactoria (Fig. ,2 n. olf. m.) and enters the furrow between the two great divisions. Just as it reaches this furrow it branches unequally, the main branch taking a similar course to that described for Squalus. The nerve is, therefore, mainly distributed to the antero-lateral portions of the olfactory membrane. No well-marked ganglion was observed on the course of the nerve in Mustelus. 46 A NEW CRANIAL NERVE IN SELACHIANS. 3. In Raja.—I have observed this nerve in three species of the genus Raja. Its point of connection with the brain is on the anterior dorsal surface instead of the ventral surface as in Mustelus and other forms to be described later. From its point of attachment to the brain-wall (Pl. V, Fig. 4, n. nov.) it passes over the surface of the forebrain, along the inner margin of the slender tractus, and upon the olfactory cup. Here it runs along the anterior border of the fila olfactoria and dips among the fibres of the latter about midway between the posterior end and the anterior tip of the olfactory cup. In the skate there is no very obvious separation of the fila olfactoria into two divisions as in the other forms described. There is, however, a median blood-vessel that partly separates the fila into two divisions which corre- spond, I think, to the lateral and median divisions already described. I have not traced the nerve-fibres in the skate into connection with the nasal membrane. 4. In Carcharias littoralis—Of all the selachians I have examined, the new nerve is most readily seen in the sand-shark, Carcharias littoralis. It is always more or less difficult to see this nerve before the brain has been stained. I have uni- formly immersed the entire brain in borax carmine from ten to twenty-four hours in order to secure a surface stain before completing its dissection in alcohol under a dissecting microscope. In Carcharias (Pl. V, Fig. 5) the nerve can readily be de- tected before staining. It is connected with the ventral surface of the brain (Fig. 6) as in Mustelus, considerably in front of the optic nerve. The course of the nerve from this ventral connection is nearly in a straight line to the olfactory cup. It runs obliquely towards the long slender tractus and, after reaching it, runs for a part of its course directly upon the tractus. The result is that the nerve enters the fissure between the bundles of the fila olfactoria from behind, instead of crossing the median division (n. olf. m) as in Squalus and Mustelus. In the Carcharias there is a bundle of the fila olfactoria connecting the two divi- sions of the olfactory nerve. The new nerve as it enters the fissure branches une- qually, sending a small twig to the connecting bundle, and a main stem to the lateral division. This main stem dips into the mass of fila making up the lateral division and, after coming into contact with the enveloping membrane of the capsule, con- tinues its course along the latter in an antero-lateral direction. From time to time it gives off small branches, which penetrate the investing membrane of the capsule and enter the folds of the nasal epithelium. The chief part of the nerve reaches the antero-lateral portions of the cup and there disappears within the nasal membrane. As in other cases, it preserves throughout its course a striking independence. The nerve has a small ganglionic enlargement near the base of the bulb. 5. In Sphyrna.—A part of the brain of the bonnet-head, Sphyrna tiburo, A NEW CRANIAL NERVE IN SELACHIANS. 47 is represented in Figure 7 (Pl. V). The forebrain is expanded laterally, but is short antero-posteriorly. The olfactory cups are elongated and shaped somewhat like a long seed-pod. The tractus is relatively slender. The new nerve unites with the brain on the ventral surface (Fig. 8, . nov.) in a depression much nearer the optic nerve than in the other forms described. From this point the nerve passes directly to the base of the fila olfactoria and mingles with them in a manner I was unable to make out clearly in the single specimen of this shark at my command. There are very well marked ganglia (Fig. 8, gn, gn’) on the nerves. In the speci- men observed the ganglia were not symmetrical in position. The one on the left side could be seen from above just in front of the brain (Fig. 7, gn’). The one on the opposite side was on the base of the brain, and could be seen only in ventral view (Fig. 8, gn). 6. In Scoliodon terrea-nove —In a shark from Florida, identified by Mr. A. D. Howard as probably Scoliodon terre-nove, the new nerve (PI. V, Fig. 9, n. nov.) is likewise present. In this shark the separation of the great divisions (n. olf. L., n. olf. m.) of the fila olfactoria is very striking. Each division is of course made up of a number of bundles of fila. The nerve enters the brain substance on the ventral surface, in the median plane about midway between the optic nerve and the anterior tip of the forebrain. It is flattened on the ventral surface of the brain, and has an enlargement which is possibly ganglionic. Beyond this swelling the nerve is slender and passes directly to the lateral division of the fila olfactoria, with which it unites. It does not branch in the fissure between the two great divisions as described in several other forms. Near the base of the median division there is a slight enlargement which is also possibly ganglionic. 7- In Other Selachians.—I have also determined the existence of this nerve in embryos of the torpedo, and, as mentioned above, in three species of Raja. This makes a total of nine species of selachians in which this nerve has been found. It will be interesting to determine whether it is present or absent in others.* The anatomical descriptions show that there is considerable variation as to the position on the external surface of the brain at which this nerve enters. In the skate it enters on the anterior dorsal surface; in Squalus it enters the brain in the median furrow, midway between the dorsal and ventral surfaces; and in the other forms examined it enters on the ventral surface, rather posteriorly in Sphyrna, and further anteriorly in the others. As to internal connections there is doubtless * Since the above was sent to the printer I have identified this new nerve in 19 genera and 24 species of adult selachians. 48 A NEW CRANIAL:«.NERVE IN SELACHIANS. greater uniformity. The fibres have been traced into the epistriatum in Squalus, Mustelus, and Carcharias, but they have not yet been studied in the other forms. There is also much variation as regards the ganglionic enlargements on the nerve. III. EMBRYONIC HISTORY OF THE NEW NERVE IN SQUALUS. The embryonic history of this nerve was described by me (Locy, 99) some four years ago, and the main facts are repeated here. It can be found in embryos of Squalus acanthias about 10 millimetres in length running from the apex of the fore- brain near the neuropore to the olfactory epithelium. Its previous history is difficult to clear up. I have given much attention to sections of embryos from 6 to 8 milli- metres long, and I have repeatedly observed that there exists a cellular connection between the olfactory plate and the brain-wall as described by Hoffmann (’96). The new nerve has at first a connection (placode) with the thickened surface exist- ing just above the shallow depression that marks the beginning of the olfactory pit. This connection is a group of closely packed cells in which I have failed, at this stage, to recognize fibres. In embryos about 10 millimetres long, however, fibres are to be seen that run from the sides of the neuropore to the olfactory epithelium. These I take to be fibres of the new nerve, but have not been able to satisfy myself as to the position of the neuroblasts that give rise to them. The neural crest is dis- appearing in this region, and my observations incline me to the view that the neuro- blasts of the fibres of the new nerve are derived from the cells of that structure. For a short time there is a single connection, on each side, between the brain- wall and the nasal epithelium. Very soon a second fibrous connection, more lateral in position, is established between the brain-wall and the olfactory pit. The two connections are entirely independent as to their union with the brain-wall, but are close together in the olfactory epithelium. The earliest of these fibrous tracts repre- sents the new nerve, the later one the main olfactory. The latter is present in em- bryos 13 millimetres long * (and perhaps in still smaller ones). By the time the embryo has reached a length of 16 millimetres the two inde- pendent brain connections are clearly differentiated. The connection belonging to * The length is, of course, no sure criterion as to its age. Those who have compared a large assortment of embryos of any animal must have been impressed with their variations. Some embryos are longer than others which are clearly more advanced in development, and there is variation as to the number of gill-clefts broken through on the two sides of the body as well as in other anatomical landmarks. The difference between embryos 10 millimetres and 18 millimetres in length is slight, and in individual cases the longer one might be the younger. The chief point is that my sections show stages in which the median fibres are present and the more lateral ones absent. A NEW CRANIAL NERVE IN SELACHIANS. 49 the main olfactory is more lateral in position and is composed of two roots; that belonging to the median nerve is on either side of the neuropore and shows a gan- glionic enlargement. A frontal view of a Squalus embryo that had reached a length of 25 millimetres is shown in Figure 10 (Pl. VI). At this stage the median nerve is well established, as is also the main olfactory. To obtain this view, the front surface of the brain was completely exposed by first removing the overlying layer of ectoderm, and then sweeping away the mesoderm by the use of an artist’s brush and a needle when necessary. ‘The olfactory cups have been left in position. The mark of the closed neuropore is seen in the median plane, and on each side of it the new nerves (n. nov.) with a ganglionic enlargement (gn.). From these positions the nerves pass laterally across the front surface of the brain and join the main olfactories, being principally connected with their outer or lateral roots (n. ol.1.). It is to be noted that the main olfactory consists of two divisions (n. olf. l., n. olf. m.), each of which is composed of smaller bundles. This condition persists in the adult, as already indicated above. A frontal view of the right half of the brain of an older embryo, 38 millimetres in length, is shown in Figure 11 (Pl. VI). Part of the olfactory cup has been broken away, exposing the olfactory membrane, which is already thrown into folds. The new nerve (n. nov.) is relatively long and slender; its course and relationships are the same as shown in Figure 10. The two chief divisions of the olfactory nerve (n. olf. l., n. olf. m.) are more complex and composed of several small bundles. The olfactory pit is imperfectly divided into two parts, a median and a lateral portion, and the fibres of the two great divisions of the olfactory nerve are mainly distributed to the corresponding portions of the pit. The new nerve, as it approaches the main olfactory, becomes flattened and there- fore broader. It passes in front of the median division (n. olf. m.), then underneath two slender bundles of the lateral division (n. olj. l.), and enters into connection with the largest bundle of that division. It branches very unequally just before passing behind the bundles of the lateral division. As far as I can make out by sections its fibres do not anastomose, but commingle in a very intimate manner with the fila olfactoria. They subdivide and pass mainly to the lateral portion of the nasal mem- brane in close association with the fila olfactoria. Figure 12 (Pl. VI) is an almost ventral view of the brain of an embryo 40 milli- metres long. On the left the olfactory cup has been completely broken away, while only the anterior part of the right cup has been removed. The new nerve isseen, as in former cases, to cross the forebrain, pass in front of the median division of the olfactory, and behind two slender bundles of the lateral division, to come into con- 50 A NEW CRANIAL NERVE IN SELACHIANS. nection, finally, with the large outer bundle of the lateral division. On the left side the principal blood-vessels (va. sng.) are indicated. In the other sketches they have been omitted. The ganglionic enlargement has not been represented in Figure 12. The brain of an embryo 47 millimetres long is seen from above in Figure 14. On the right side the surface of the olfactory cup and the various bundles of the olfactory nerve have been exposed by dissection, while on the left the tissue covering these parts has not been removed. The new nerve (n. nov.) is seen on both sides, and on the right side its connection with the lateral division of the olfactory is represented. This lateral division (n. olj. 1.) has been broken free from the olfactory lobe in order to show better the point of union. In Figure 13 is seen the brain of an embryo 68 millimetres long viewed from above. f decd. / eas FELON TCU. ce cee CHOP, = trl.tor tet, eee ae i ~~ lec. d bal >. e Sa ees Wert a Fo ne 4 i coms.p. ms'cocl. poe SELL Ce: s : 2 let.opt, ¥ be = trt.opl,.- A \ dec. d.-pe2 tlopt. \ Uri. lor tet. SS C0 MS. p. 2) “oprs.i'cal. Ut for. Reis.a, = , cb. a f plehr. iy) 4 yy © it fbr, Reis.y, | \ , Bi Ugo é . : ms'coel, 2 LL crds.€end. qu ha 10 IrLopl. >. for. Kets. : trt.tor. lel, K fet opt. yn hab, Dy trt.tor.cbl. Ay rt for, Neils. p. int. ont COMMS. P, prs. Vcd, & of tee evphy, \"¢ : \ \\ \ placbl, bd. ‘ms coel, irt.lornich, .—_ i Bae tel. opt. », ae Y, ( PAS tor, Iq. lv. cht —_- a. . 1 ay 2 = ——_ da'e.cot v SS co'ms.p. 3 dev. d. = ce - cb, * lech. wi mscoel, 23 ITS ONTOGENY, MORPHOLOGY, PHYLOGENY, AND FUNCTION. 415 EXPLANATION OF THE PLATE. ABBREVIATIONS. ax. Axon. prs. vcal. Pars intercalatus (Schaltstiick). ebl. Cerebellum. rec. ms’ cel. Mesencephalic recess, dorsal and anterior co’ms. p. Commissura posterior. to the posterior commissure. cras. e’end. Ependymal thickening. tct. opt. Tectum opticum. ernu. lL. a. Anterior lateral horn of the mesoccele. tor. lg. Torus longitudinalis. da’e cel. Diaccele. tor. sv’ ere. Torus semicircularis. dec. d. Dorsal decussation of the tectum irt. fbr. Reis. a. Tractus toro-fibre Reissneris anterior. opticum. irt. for. Reis. p. Tractus toro-fibre Reissneris posterior. dec. e’phy. Epiphysial decussation. trt. opt. Tractus opticus. jor. Reis. Reissner’s fibre. irt. tor. cbl. Tractus toro-cerebellaris. fis. Vtor. Median ventral fissure between the lat- rt. tor. ict. Tractus toro-tectalis. eral lobes of the torus longitudi- lv. cbl. Valvula cerebelli. nalis. a. Mesal edge of tectum opticum (con- gn. hab. Ganglion habenula. sidered by Auerbach the “Anlage” of ms’ cel. Mesoccele. the torus). pl. chr. Plexus choroideus. B. Mesencephalic groove above the torus. PLATE XXIX. In all figures the dorsal edge of the section is uppermost. All figures are from transverse sections, except Figures 20 to 24 inclusive which are from parasagittal sections. In Figures 20 to 23 inclusive the anterior end is at the left. In Figure 24 the anterior end is at the right. All the figures were outlined with the camera lucida. Fig. 1. Salvelinus fontinalis, at time of hatching. Section through the anterior portion of the mesencephalon caudad of the posterior commissure, showing the median longitudinal fold from which the torus develops. The median sulcus of the torus is indicated by the absence of cells in that region. X87. Fig. 2. Salvelinus fontinalis, one day older than that shown in Figure 1. The section was taken a little anterior to that for the preceding figure. 87. Fig. 3. Salvelinus fontinalis, 4 cm. long. Section through the same region as that shown in Figure 2. x40. Fig. 4. Acanthocottus eneus, newly hatched. Section through the anterior part of the mesencephalon showing the torus longitudinalis in an early stage of development. ‘Fig. 5. Acanthocottus zeneus, a little older than that seen in Figure 4. Section through the same region as in the preceding figure. X87. Fig. 6. Tautogolabrus adspersus, young specimen 6 cm. long. The torus presents the adult condition. x15. Fig. 7. Tautogolabrus adspersus. Section from the same specimen as that from which Figure 6 was taken, but from a position considerably posterior to that of Figure 6. The torus is seen in an early stage of development. X15. Fig. 8. Amiurus nebulosus, young specimen. Section through the anterior portion of the mesencephalon, caudad of the posterior commissure. X30. Fig. 9. Amblyopsis spelzeus, adult. Section through the same region as in the preceding figure. 30. Fig. 10. Menidia notata, young specimen. X20. Figs. 11-14. Pseudopleuronectes americanus, adult. Four sections from the median portion of the mesencephalon. Figure 11 represents the most posterior of the four sections, and the others follow in sequence. X15. Figs. 15-19. Cynoscion regalis, adult. Five sections of the mesencephalon; that shown in Figure 15 is the most anterior, and the others follow in sequence. X10. 416 Fig. 20. Fig. 21. Fig. 22. Fig. 23. Fig. 24. Fig. 25. THE TORUS LONGITUDINALIS OF THE TELEOST BRAIN. Salvelinus fontinalis, adult. Parasagittal section through the mesencephalon, cutting the right lobe of the torus longitudinalis. The anterior end is toward the left. x10. Morone americana, adult. Section as in Figure 20. X10. Gasterosteus bispinosus, adult. Section as in Figure 20. X30. Notropis cornutus, adult. Section as in Figure 20. X30. Tautogolabrus adspersus, adult. Parasagittal section through the anterior portion of the roof of the mesencephalon and left lobe of the torus longitudinalis. The anterior end is toward the right. The details of this and the next figure are filled in diagrammatically. 50. Tautogolabrus adspersus, adult. Transverse section through the anterior portion of the mesencephalon; torus longitudinalis, and posterior commissure. X50. XXI. IMPLANTATION OF THE OVUM IN SPERMOPHILUS TRIDECEMLINEATUS MITCH. (PLATES XXX-XXXT.) Tuomas G. LEE. I. INTRODUCTION. Desirous of making a study of the so-called inversion of the germinal layers in rodents, and wishing for purposes of comparison to use a family of the order other than those usually studied, I determined several years ago to work upon the sub- order Sciuromorphi, for the reason that it had been almost entirely neglected. There- upon I began collecting Spermophilus as the most easily obtained representative. In the first collections there were many stages lacking; but I soon discovered that Spermophilus was not in accord with the descriptions of inversion then published, and that it had developmental features peculiar to itself, which were far from being easily understood owing to want of material. For several seasons I collected specimens in large numbers, believing that in this way I could secure a series with few stages lacking. This has proved to be the case, and I now have material from which I am working out in detail the complete development of this animal. In a preliminary notice (Lee, :02), read before the American Morphological Society, Dec. 29, 1901, I briefly outlined the subject-matter of this paper. 1. Material.—The small striped gopher, Spermophilus tridecemlineatus Mitch., is found abundantly throughout Minnesota living in burrows in pasture-lands and grain-fields. While a timid animal, it has a fatal curiosity which is of the utmost service to the collector, for, after retreating, it soon reappears at the mouth of its burrow to be caught in the snare or shot with the rifle. At the imitation of its shrill whistle the gopher will often stop when running to its burrow and stand erect to dis- cover the source of the whistle; or, if in its burrow, its reappearance may be hastened by this means. In the breeding season the whistle acts as a challenge to the males, and one can often bring them within a few yards. In this way needless shots are avoided. The gopher has the habit of sitting at the margin of its burrow so that it can tumble in at the least alarm. It has astonishing powers of vitality, for even when mortally wounded it often reaches its burrow. One should endeavor to shoot them through the head or back, as otherwise a large percentage is lost. It breeds in the spring, the males making their appearance as soon as they cease hibernating, usually between April 10 and 25. The period of gestation, as near as I can determine, is about one month. I have not been able to breed it in captivity, consequently I do not know the exact duration of this period. At any given time the majority of 419 420 IMPLANTATION OF THE OVUM IN females are at about the same stage of gestation. While the later stages of preg- nancy are quite easily obtained, it has taken much labor in the field at the beginning of the breeding season for a number of years to secure a complete series of stages. The preplacental stages have been by far the most difficult to secure, as there are only a few days in each season in which they can be obtained. During this period the majority of the animals killed are males, the females for the most part remain- ing under ground. Again a day or so of cloudy or rainy weather at this particular time may almost ruin the chances of securing early stages for that year. However, the fact that they carry a large number of young is a compensating feature. The following tables may prove of interest in showing the number and distribu- tion of embryos in the uterus. They are compiled from notes based on collections made at the height of the season of 1900, an unusually favorable year for this purpose. Tasie II. Tass I. DISTRIBUTION OF EMBRYOS IN RIGHT AND LEFT NUMBER OF EMBRYOS PER ANIMAL. HORNS OF UTERUS. etal Sseabes ant ae ronal . Sore ber of of Embryos umber o ‘umber o: mbryos . in on Animals. Embryos ne Namaberot Left Horn. | Right Horn. orn. 5 1 5 6 7 42 0 2 1 1 7 26 182 1 10 7 3 8 36 288 2 24 14 10 9 31 279 3 43 18 25 10 14 140 4 79 33 46 11 11 121 5 53 26 27 12 2 24 6 22 14 8 13 1 13 7 13 10 3 oes sores 8 5 2 3 129 1094 9 7 4 3 129 129 It will be seen from these tables that the 129 pregnant females averaged nearly 8.5 embryos with a total variability of from 5 to 13. As regards the distribution in the two horns of the uterus, the right horns had 537 embryos and the left 557, averag- ing over 4 for each horn, the range of variability being the same, from 0 to 9 for each side. This record is based on one week’s collecting during the middle of May, all the embryos being fairly well advanced. Only 4 non-pregnant females were taken during this week, showing that most of the females are pregnant at this time. It is also interesting to note that in 14 cases some one embryo was abortive, and, acting as a plug, effectually prevented the delivery of the remaining embryos in the ovarial SPERMOPHILUS TRIDECEMLINEATUS MITCH. 421 portion of that horn and would-unquestionably have caused the death of the mother. The mortality of old and young from a variety of causes must be enormous, as the number of adults does not materially increase from year to year. 2. Methods.—Most of the material was obtained by shooting with a small rifle. The body was opened at once, and, cutting through the vagina and mesometrium, the whole uterus, oviducts, and ovaries were removed and transferred to a jar of fixing-solution.