: t*M vm. <^~, _ >^ THE UNIVERSITY OF ILLINOIS LIBRARY S10.5 XLL ••*;* ■ The person charging this material is re- sponsible for its return to the library trom which it was withdrawn on or before the Latest Date stamped below. Theft, mutilation, and underlining of books are reasons for disciplinary action and may result in dismissal from the University. UNIVERSITY OF ILLINOIS LIBRARY AT URBANA-CHAMPAIGN m 2 i 1! NOV 2 9 MAR 14 6 9Bf L161 — O-1096 ILLINOIS BIOLOGICAL MONOGRAPHS PUBLISHED QUARTERLY UNDER THE AUSPICES OF THE GRADUATE SCHOOL BY THE UNIVERSITY OF ILLINOIS VOLUME X Urbana, Illinois 1926 Editorial Committee Stephen Alfred Forbes William Trelease Henry Baldwin Ward £ 7 . £ _ i— • L— i TABLE OF CONTENTS VOLUME X NTTMBERS PAGES 1. Studies on the Avian Species of the Cestode Family Hymenolepididae. By R. L. Mayhew. With 9 plates and 2 text figures 1-120 2. Some North American Fish Trematodes. By H. W. Manter. With 6 plates, 2 charts, and 1 text figure 127-264 3. Comparative Studies on Furcocercous Cercariae. By H. M. Miller, Jr. With 8 plates and 2 text figures : 265-370 4. A Comparison of the Animal Communities of Coniferous and Deciduous Forests. By I. H. Blake. With 16 plates and 25 tables 371-520 Digitized by the Internet Archive in 2011 with funding from University of Illinois Urbana-Champaign http://www.archive.org/details/somenorthamerica10mant SOME NORTH AMERICAN FISH TREMATODES WITH 6 PLATES, 2 CHARTS AND 1 TEXTFIGURE BY HAROLD WINFRED MANTER Contributions from the Zoological Laboratory of the University of Illinois under the direction of Henry B. Ward No. 287 THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY IN ZOOLOGY IN THE GRADUATE SCHOOL OF THE UNIVERSITY OF ILLINOIS 1925 TABLE OF CONTENTS Introduction Material and Methods General Distribution of Entozoa in Hosts Examined 8 Historical Survey 12 The Morphology of Otodistomum cestoides 14 Thickness of Regions of Body Wall 18 Otodistomum vdiporum 21 Otodistomum cestoides 22 Variation in Posterior Extent of Vitellaria in O. cestoides 27 Growth Changes in Otodistomum cestoides Within the Final Host 29 Chart I — Showing Relations Between Body Length and Distance from the Anterior End to Ventral Sucker in O. cestoides 31 Chart n — Showing Relations Between Body Length and Body Width in O. ces- toides 32 Sucker Size in Relation to Growth in O. cestoides 34 Comparison of Uterus Region with Posterior Body Region in Young Specimens of Otodistomum cestoides 36 Comparison of Uterus Region with Posterior Body Region in Adult Specimen of Otodistomum cestoides 37 Comparison of Neck Region with Posterior Body Region in Young Specimens of Otodistomum cestoides 38 Comparison of Neck Region with Posterior Body Region in Adult Specimens of Otodistomum Cestoides 39 Diagram to Show Growth Changes in Otodistomum cestoides 40 Comparison of Otodistomum cestoides and O. vdiporum 41 The Miracidium of Otodistomum cestoides 44 Notes on the Life History of Otodistomum cestoides 50 A Systematic Review of the Family Azygiidae 54 Azygia angusticauda (Stafford 1904) 60 Azygia acuminata Goldberger 1911 61 Azygia longa (Leidy 1851) 63 Azygiasebago 67 Azygia bulbosa 68 Cooper's Azygia lucii from L. masquinongy 68 Cooper's A zygialucii from the pike 69 Azygia robusta Odhner 1911 73 Azygia perryii Fujita 1918 74 Azygia volgensis (v. Linstow) Odhner 1911 77 Synopsis of the Genus Azygia 78 A General Study of Some Marine Fish Trematodes 79 The Genus Podocotyle 80 Podocotyle atomon (Rudolphi 1802) 81 Podocotyle olssoni Odhner 1905 82 Stephaochasmus baccatus Nicoll 1907 83 Lepidapedon rachion (Cobbold) Stafford 1904 84 Lepidapedon dongatum (Lebour 1908) 85 Homalometron pallidum Stafford 1904 86 Steganodermaformosum Stafford 1904 88 The Hemiuridae 90 Eemiuriis levinseni Odhner 1905 92 Brachylhallus crenatus (Rudolphi 1802) 94 Lecitkaster gibbosus (Rudolphi 1802) 95 Aponurus sphaerolecithus Manter 1925 96 Genolinea laticauda Manter 1925 100 Gonocerca phycidis Manter 1925 101 Derogenes various (Muller 1784) 103 Eirudindla fusca (Poirier 1885) 104 Siphodera vinaledwardsii (Linton 1899) 107 Deroprislis inflata (Molin 1859) 110 Acanthocotyleverrilli Goto 1899 110 Dactylocotyle minor (Olsson 1868) 112 Summary and Conclusions 115 Bibliography 117 Explanation of Plates 122 Index to Scientific Names 135 133] SOME NORTH AMERICAN FISH TREMATODES—MANTER INTRODUCTION The study of the parasites of North American fish, especially marine species, offers a comparatively new field to the investigator. Linton has opened this field in a broad sense by his papers on fish parasites of the Woods Hole region and of the Atlantic waters of Southern United States. This pioneer work has been necessarily incomplete in some respects. On the parasites of fishes inhabiting the colder waters of the northern Atlantic, almost no work has been done in America. Stafford and Cooper have made small collections in these regions. On European shores considerably more research has been done, and here the early work of Van Beneden, Olsson, and Levinsen has been followed by valuable contributions from Looss, Odhner, Lebour, Nicoll, and others. The present paper is based very largely upon studies of marine fish parasites from the Maine coast. These studies were first undertaken at the Mount Desert Island Biological Laboratory during the summer of 1924, although some material was also collected in the same region in 1923. Early in the work of collection, attention was directed to a common trematode (Otodistomum cestoides) of the barn-door skate. Considerable time was devoted to the structure of this form and its life history. Later, a large series of fresh-water forms related to this species were also studied and compared. A brief report of the trematodes collected from marine fish has already been published (Manter, 1925). Sincere appreciation is here extended to Professor Ulric Dahlgren for the use of the laboratory facilities at the Mount Desert Island Biological Station. Acknowledgment is also rendered to the Hygienic Laboratory of the U. S. Public Health Service and to the U. S. National Museum for the loan of valuable material. Above all, is the writer indebted to Dr. Henry B. Ward, under whose direction these studies were undertaken. To him appreciation is extended, not only for his constant interest, but also for the loan of material from his personal collection of parasites, and for the use of his extensive library. To others, who, like fellow-students, have been less intimately associated with this work, but who have gladly cooperated in many ways, gratitude is likewise expressed. MATERIAL AND METHODS The collection of parasites was not limited to any particular group. In general, a broad collection of metazoan fish parasites was attempted. The final collection included trematodes, cestodes, nematodes, acantho- ILLINOIS BIOLOGICAL MONOGRAPHS [134 cephala, copepods, leeches, an ectoparasitic turbellarian, and an ecto- parasitic isopod. From this collection the trematodes were chosen for special study. The most common shore fish such as sculpin, flounder, herring, and skates were obtained from Frenchman's Bay in the immediate vicinity of the Laboratory. Most of the fish examined, however, were obtained at the small fishing village of Manset on the south side of Mount Desert Island. Here specimens of the larger food fish such as cod, haddock, and hake were available in large numbers. Identification of the host was usually simple as most of the fish examined were common and well known species. Some uncertainty was unavoidable in the correct identification of a few forms, such as the sculpins. The following table (Table 1) shows the general occurrence of the different groups of parasites according to hosts. Table 1 General Distribution of Entozoa in Hosts Examined Name c f Host Common Number of Hosts Scientific Examined With Trema- . todes With Nema- todes With Ces- todes With Acantho- cephala Acanthias vulgaris Common dog fish 12 2 12 Raia erinacea Bonnet skate 8 1 1 8 Raia diaphanes Big skate 2 2 1 Raia stabuliforis Barn-door skate 20 18 7 20 Raia scabrata (?) Skate 1 1 1 AnguiUa chrysypa Common eel 2 2 Clupea harengus Herring 28 9 6 Osmerus mordax Smelt 5 3 2 Scomber scombrus Mackerel 5 5 Fundulus heteroclitus Killifish, minnow 25 9 6 23 Tautogolabrus adspersus Cunner 4 3 1 135] SOME NORTE AMERICAN FISH TREMATODES—MANTER Table 1 (continued) Name c >f Host Common Nun iber of Hosts Scientific Examined With Trema- todes With Nema- todes With Ces- todes With Acantho- cephala Myxocephalus octodecimspinosus Sculpin 11 3 7 4 9 Pholis gunnellus Butterfish 9 2 Anarrhichas lupus Wolf-fish 2 1 1 Zoarces anguillaris Eel pout 1 1 Pollachius virens Pollack 4 2 3 2 Gadus callarias Cod 10 8 9 2 10 Melanogrammus aeglifinus Haddock 17 4 9 5 17 Urophycis tenuis Hake 3 3 1 1 2 Urophycis chuss Squirrel hake 6 5 6 1 4 Hippoglossus hippoglossus Halibut 2 1 2 2 Pseudopleuronectes americanus Flounder 19 3 3 2 15 Limanda ferruginea (?) Sand dab 2 2 2 1 Total 198 72 70 66 90 The barn-door skate (Raia stabuliforis) was found to furnish the most varied and interesting parasites. Ecto-parasitic on this skate were found; Micropkarynx parasitica (a tri-clad turbellarian), Aega psora (an isopod), and a large leech, Oxyostoma typica* In the nasal cavity was found Charopinus dalmanni (Retz.) a large parasitic copepod. The stomach was usually heavily infected with the trematode, Otodistomum cestoides. Large numbers of cestodes occurred in the spiral valve. Although only a part * For the identification I am indebted to Prof. J. Percy Moore who reports that the leeches "are representatives of Oxyosloma typica Malm or possibly a closely related species of the same genus." 10 ILLINOIS BIOLOGICAL MONOGRAPHS [136 of this cestode material was examined, two forms were identified as Rhynchobothrius erinaceus (van Ben.) and Acanthobothrium coronatum (Rud.). One interesting case of Acanthocephalan infection was found in Fundu- lus heteroclitus. The livers of these minnows were almost invariably heavily infected with a juvenile form of Neoechinorhynchus. These parasites were sometimes free in the liver tissue but usually were coiled in a very thin- walled cyst. In one liver 25 or 26 such cysts could be counted. Only two of about 25 specimens failed to show the cysts macroscopically. In one case, this same form of juvenile Acanthocephalan was found in the intestine. This possible occurrence of the parasite in the intestine led to feeding experiments. A Fundulus was isolated and fed liver containing cysts from other minnows. As some of the material was disgorged, it could not be ascertained exactly how many cysts were ingested. The fish was fed again on the following day, and killed and examined on the third day. Three of the Acanthocephala were found in the intestine. This experiment was repeated by again feeding an isolated Fundulus the cysts on two days, and examining it on the third day. This second fish contained six of the Acanthocephala in its intestine. It is evident that the parasite can be transmitted from the liver to the intestine of the same species host. A possible explanation of the rare occurrence of this type of transfer in nature is found in the fact that the viscera of dead minnows in the aquaria are readily devoured by the other minnows. No evidence was found that the parasite ever reaches sexual maturity in this host. The final host of the parasite was found to be the common eel, Anguilla chrysypa. The locality from which the minnows were caught harbored numerous eels. Two of these fish were caught and examined for parasites. The first contained large numbers (about 50) of a Neoechinorhynchus in the lower part of the intestine. The parasites were apparently identical with the young form taken from the minnow, differing only in beingsexually mature. The second eel contained three minnows in the stomach. One of these minnows was practically digested. From the stomach content in this region one of the Acanthocephalan cysts was recovered. Furthermore, there was found free in the upper part of the intestine one of the juvenile Acanthocephalans without the cyst. Lower down in the intestine occurred large numbers of the adult parasite attached to the intestine wall. The species of Acanthocephala was kindly identified by Dr. H. J. Van Cleave as Neoechinorhynchus cylindratns (Van Cleave). The demonstration seems to be quite complete that the eel (at least in this particular locality) acquires (at least in part) its infection through the minnow, Fundulus heteroclitus. Whether the minnow is a necessary fink in the life-history of the parasite is very doubtful. Van Cleave (1920) in explaining juvenile forms of Acanthocephala encysted in various fish, 135] SOME NORTH AMERICAN FISH TREMATODES—MANTER 11 suggests that they may result from ingestion of the larva when it is too young to maintain itself in the intestine, the immature larva developing to an infective juvenile form in some tissue outside the digestive tract. In the course of the present work, no new methods of technique were discovered. The finding of the larger parasites such as most cestodes, acanthocephala, and nematodes is simple. To collect the smaller forms such as many trematodes, the content of the digestive tract of the host must be minutely examined. Best results were obtained by diluting a small amount of material with considerable water in a large glass dish. A chang- ing from light to dark of the background below the dish is often helpful. Careful scraping of the wall of the digestive tract is usually necessary to remove many of the smaller parasites. Cestodes were killed in HgCl2 solution. Agitation by shaking or the actual stretching by hand of cestodes is necessary to prevent excessive contraction. Trematodes were killed according to the Looss method (Looss 1901) by first shaking in water and then in a 50% solution of HgCh. A modified Gilson's solution (Petrunkevitch solution) was also found very satisfactory for trematodes. Nematodes were killed by placing in hot 70% alcohol or hot Petrunkevitch solution. Acanthocephala from the marine fish were first placed in fresh water which causes complete extension of the proboscis. When the Acanthocephala no longer respond to stimuli they are removed to the killing solution. Some difficulty was experienced by some forms, especially trematodes, later becoming quite black, due apparently to a precipitation of metallic mercury. This condition might be due to insufficient or delayed treatment with iodized alcohol. A semisatisfactory method of reclaiming such specimens was found to consist of treating them with a weak solution of nitric acid. The acid removes the mercury but slightly stains the tissues. In staining trematodes for total mounts, Ehrlich's or Delafield's hematoxylin or a mixture of the two was found to be very satisfactory. Alum cochineal also gave good results. Sections were stained with the ordinary reagents such as hematoxylin, iron hematoxylin, safranin, eosin, orange G, and Lyon's blue. The present studies can be divided into three rather distinct parts as follows. First, an intensive study of Otodistomum cestoides, its first larval form, its growth changes within the final host, and its morphology. Some data was also obtained from an attempt to trace the life history of this form. Second, a comparative study of the entire family of the Azygiidae, and a revision of the American representatives of the genus Azygia. Third, a briefer account of each of the other forms of marine trematodes in the collection. This last account also includes data on several forms from the collection of Dr. H. B. Ward. These latter were collected from the Woods Hole region. 12 ILLINOIS BIOLOGICAL MONOGRAPHS [138 HISTORICAL SURVEY Van Beneden (1858 and 1871) was one of the earliest workers to deal particularly with fish parasites and many of the more common species were first described by him. His collections were made along the coast of Belgium. Olsson in 1868 records 32 different trematode parasites from Scandinavian fish. Twenty-seven of these parasites were distomes, and eight were reported as new. Olsson's work covered a wide host range, the trematodes being collected from 42 different species of fish. Levinsen published in 1881 results of his studies on trematodes of arctic fish. This work is the product of two years spent on the west coast of Greenland and constitutes the first comprehensive record of trematodes from strictly arctic marine fish. The number of host species examined was small (six), but the trematode fauna of a few fish such as the sculpin was thoroughly studied. Nine different species of trematodes were recorded from this host. Levinsen lists thirteen different sexually mature forms, most of which are distomes. Seven species are described as new. Early work on the fish trematodes of the Mediterranean was done by Rudolphi, Monticelli, Stossich, and Looss. The detailed and accurate morphological observations of Looss have been of special service, and his (1899) conception of the genus among distomes has resulted in a complete systematic reorganization of that group. Probably the most important paper on trematodes of arctic fish is Odhner's contribution (1905) to the Fauna Arctica, Trematoden des arktischen Gebietes. This critical monograph of the arctic trematode fauna is not limited to fish parasites but includes a few forms from avian and mammalian hosts. Odhner also restudied Levinsen's material. As the paper deals with considerable change in the "natural system" of trema- todes, short descriptions are given of some forms outside the arctic regions. Twenty-two different trematodes, 19 of which are Digenea, are recorded from fish. Among these fish trematodes, four new genera and three new species are described. Several previously known species are redescribed, and some important systematic reorganizations are made. In a series of later short papers under the general title, Zum naturlichen System der digenen Trematoden, Odhner has made numerous subsequent additions to our knowledge of relationships among the trematodes, and his conclusions have been largely accepted by Nicoll (1915) and others. The trematodes of the British marine fish are probably better known than those of any other particular region. This is largely due to the re- searches of Lebour, Johnstone, T. Scott, A. Scott, and Nicoll. According 139] SOME NORTE AMERICAN FISH TREMATODES— MANTER 13 to Nicoll, up to 1915 nearly 100 species of trematodes had been recorded from British marine fish. Nicoll's (1915) list of trematodes from marine fish contains 241 different species of trematodes belonging to 119 genera. Of these trematodes, 157 species and 73 genera are distomes. In America the work of Linton at Woods Hole, Beaufort, N. C, and the Tortugas stands almost alone. The last named region is especially interesting in revealing a very rich and varied trematode fauna (Linton 1911) with forms differing considerably from most of the more northern forms. Stafford (1904) gives a list of 37 trematodes from 32 different Canadian marine fish. Cooper (1915) gives more complete data on a few forms from the same region. A large amount of the literature is, of course, in the nature of special studies on individual or few forms. Examples of papers of this type are found in the works of Poirier (1885), Villot (1879), Pratt (1898), Darr (1902), Buttel-Reepen (1903), and Mtihlschlag (1914). 14 ILLINOIS BIOLOGICAL MONOGRAPHS [140 THE MORPHOLOGY OF OTODISTOMUM CESTOIDES OTODISTOMUM CESTOIDES (VAN BENEDEN 1871) Otodistomum cestoides (van Ben.) Syns.: Dislomum cestoides van Ben. 1871 Otiodistomum vcliporum of Stafford 1904 Otiodistomum veliporum of Lebour 1908 Otiodistomum veliporum of Lonnberg 1891 From stomach, Raia stabuliforis ( = R. loads) Reported hosts: Raia batis Raia laevis Raia fullonica Raia lintea Raia clavata Raia radiata Raia macrorhyncha Cldamydoselache anguinea Dist. cestoides was first obtained by van Beneden (1871) from Raia batis. The genus Otodistomum was named by Stafford (1904) for a form he obtained from the stomach of Raia stabuliforis ( = R. laevis). This form he called Otodistomum veliporum, identifying it as the Dist. veliporum of of Creplin. The close resemblance between the two species cestoides and veliporum has been a cause of general confusion, and, indeed, the two have been considered synonymous. Odhner (1911b) first showed that 0. cestoides (van Ben.) had been incorrectly identified as 0. veliporum by previous workers including Stafford, Lebour, and Lonnberg. In the course of the present studies both species were available for comparison. Specimens of 0. veliporum were obtained from the collection of Dr. H. B. Ward* and were collected by him from Raia binoculata in Alaska in 1909. Further material of this same form was collected by a fellow-student from the same host at Friday Harbor, Washington, in 1924. Frequent reference will be made to this species in connection with the following discussion of the morphology of O. cestoides. The host records of the two species are doubtless somewhat confused. According to the literature, O. veliporum appears to have a much wider host range among the Selachians, O. cestoides being almost entirely re- stricted to Raia species. In the region of Mount Desert Island O. cestoides occurs abundantly in Raia stabuliforis, but was never found in any other species of skate. Both Stafford and Cooper report it from Canadian waters. * Collection of Dr. H. B. Ward, vial No. 48a from Excursion Inlet, Alaska, July 22, 1909. 141] SOME NORTE AMERICAN FISH TREMATODES—MANTER IS Linton also records it from Woods Hole but there it seems to be a rare parasite. The trematode was found in the lower part of the pyloric stomach of Rata stabuliforis. It is one of the most common fish trematodes in the region of Mount Desert Island as almost all the skates of this species we re- infected, sometimes heavily. Only two individuals among twenty examined in 1924 were uninfected, while all of the several examined in 1923 contained the trematode. The average degree of infection is about 21, although the number varies from only 2 or 3 to about 150. In a number of cases only young immature forms were found. It is also common, especially if the infection is light, to find only mature forms or at least no very young specimens. Several instances were found wherein all stages were present. Table 2 shows a record of the collection of this parasite. The trematode is one of the largest known. Stafford records worms as long as 80 mm. when extended. There is a remarkable size variation. The longest specimen in the present collection measured about 65 mm., while several were found only 2 or 3 mm. in length. Sexual maturity is reached when the worm has a length of about 11 mm. The body form is elongate and somewhat flattened dorso-ventrally especially in the posterior region. The anterior end tapers slightly in front of the ventral sucker and is bluntly pointed. Behind the ventral sucker the body tapers only very gradually and the posterior end is usually blunt. In some cases, however, when the worm is extended the posterior tip is sharply pointed. In this case, the body form is spindle-like. The two suckers are close together near the anterior end. The ventral sucker is the larger and very powerful. When in use this ventral sucker may be protruded from the body very prominently. The worms cling tenaciously by means of the ventral sucker and may extend the anterior end of the body for some distance, feeling about in a leech-like manner. When removed from their host the worms cling to each other by means of their ventral suckers, and it is often difficult to separate individuals after they have become attached in this manner. There is a marked tendency for the worms to bend slightly inward, (i.e., ventrad), so that in profile they assume a curved or crescentic shape. This shape is especially marked when the trematodes are killed unless they are prevented by some mechanical means from so curling. The color of the worms is a translucent white when alive, becoming opaque white when killed. The region of the uterus just posterior to the ventral sucker is dark brown in color, due to the presence of many eggs which possess a light brown shell. The oral sucker is smaller than the ventral sucker and the size ratio of the two does not show any progressive change with growth, averaging the same in very small individuals as it does in the largest. The anterior sucker averages slightly over .6 the size of the ventral one, or a proportion of 10 ILLINOIS BIOLOGICAL MONOGRAPHS [142 Table 2 Individual Infection of Raia stabuliforis with Olodistomum cestoides Date Content of Stomach Number of parasites Condition July 16 Empty Several Mostly mature Sculpin a " 27 Emptj' 4 None August 5 Empty Few Immature u u u u 8-10 u 30-35 a 15-20 a 10-15 " S Crab, shrimp 16-20 Mature Remains of flounder 16 Small, immature " 12 3 herring, part of lobster 16-20 Mature Empty 17 Small u 4-5 ■ 19 u Many All sizes, 10 or more mature 8-10 small crabs, shrimp None Empty 12-15 Mostly mature u 160-170 Heaviest infection. 100 immature Remains of fish, Buccinum Several All sizes « 28 Flounder 2 Mature about 3 : 5. Odhner (1911b), however, gives a ratio of 3 : 4 for 0. cestoides and 3 : 5 for 0. veliporum. Miss Lebour's single specimen with a ratio of 1 : 2 must have been (as Odhner suggests) an abnormal condition. For the measurements of the suckers see Table 4. The circular opening of the oral sucker may be directed anteriorly, but is usually ventral. The ventral sucker is very deep, extending nearly to the dorsal surface of the body when the worm is extended. The cavity of this sucker extends posteriorly as well as dorsally, a condition due to the 143] SOME NORTH AMERICAN FISH TREMATODES— MANTES. 17 greater development of its muscles in the posterior region. While interest- ing because of the high degree of muscular development, the structure of the two suckers is like that already described for similar forms by Poirier (1885) and for 0. veliporum by Miihlschlag (1914). From the ventral anterior rim of the ventral sucker two muscle bands pass dorsally and can be traced nearly to the longitudinal body muscles of the dorsal wall. Crossing them obliquely a strong band of muscles can be seen to extend ventrally and anteriorly from the central dorsal border of the sucker to the longitudinal muscles of the ventral body wall. There are also muscle fibers extending laterally from this anterior ventral border of the sucker. Muscle bands at the posterior border of the sucker extend laterally on each side, and other bands extend dorsally to the dorsal body wall. Short muscles are attached to the anterior margin of the oral sucker and course anteriorly and dorsally where they seem to join longitudinal body muscles of the dorsal side. Just posterior to these occur lateral oblique muscles running dorsally and laterally from each side of the sucker. They also are closely related with the dorsal longitudinal body muscles. Some of these fibers extend to the outer edge of the sucker. Finally, from the posterior edge of the sucker oblique muscle bands run dorsally and pos- teriorly and attach themselves to the pharynx. The body wall consists of the cuticula, a layer of circular muscles, and a layer of longitudinal muscles (Fig. 12). The cuticula is a thick structureless layer surrounding the entire body. In a specimen about 25 mm. in length, this cuticula was about 17yu thick on the ventral surface of the neck region and about 28/j. thick on the ventral surface of the posterior region. The thicknesses on the dorsal surfaces of the same regions were 34 and 37^. Hence, the same relative thicknesses are found that Miihlschlag noted for 0. veliporum. For the latter species, Miihlschlag's measurements are all much smaller than were found in the present species, but the size of the specimen was not given in the former case. The cuticula is much thinner over the inner surfaces of the two suckers. Here it measures only 5 to 8/i in thickness. The body wall is thrown into circular folds which are more prominent with increased degree of contraction. These folds give the ringed appear- ance characteristic of this group of trematodes. Sections show that these folds involve the cuticula, and the layer of circular muscles, but not the layer of longitudinal muscles. The thickness of the circular layer, therefore, varies greatly. The layer is very thick in the center of the folds, and is greatly reduced in the furrows between the folds. In the following table a medium condition is represented as far as possible. 18 ILLINOIS BIOLOGICAL MONOGRAPHS [144 Thickness of Regions of Body Wall (Specimen about 25 mm. long) Ventral Surface Neck Region Testis Region Posterior Region Cuticula 17 M 2S-30 M 28-30 M Circular muscles 40-50 50-55 50-55 Longitudinal muscles 34 17-20 17 Dorsal Si irface Cuticula 34 M 40 M 35-i5v Circular muscles 50 50 38 Longitudinal muscles 22 J!) 16 The parenchyma presents no unusual features. It consists of a spongy tissue, filling in the regions between organs. Small nuclei are common, and also larger cells which are possibly nervous in function. The parenchyma is set through with muscle bands. Many of these, especially near the body wall, and within the neck region are oblique or diagonal, but the majority run in longitudinal bands throughout the length of the body. In species of Azygia (a related genus) a very definite and relatively narrow band of these longitudinal muscles occurs. In cross-section, the body is separated by them into medullary and cortical regions. Various Azygia species were available for comparison with O. cestoides in this respect. The localization of the muscles is much more pronounced and definite in Azygia where they form a rather compact layer. Here also the follicles of the vitellaria are outside this layer, that is, in the cortical region. In Otodistomum, the longitudinal parenchyma muscles are not limited to such a narrow layer and their formation is much less compact (Fig. 23). The region of their occurrence is, however, definite enough so that it can be noted that the follicles of the vitellaria lie largely internal to them, a condition to be contrasted with that occurring in Azygia species. The nervous system could not be worked out in detail, only its more prominent features being noted. These agreed with data already known for similar forms. The pharynx is ovoid or egg-shaped. It is located just posterior and slightly dorsal to the oral sucker. Its size is about 0.5 mm. by 0.3 to 0.4 mm. in average sized specimens. The largest examples measured about 0.75 mm. in length. In a specimen 24.5 mm. in length the pharynx measured 0.56 by 0.37 mm., and the thickness of its walls was about 0.18 mm. There is no pre-pharynx and the pharynx itself may protrude slightly into the cavity of the oral sucker. The pharynx usually extends obliquely dorsally and posteriorly. The opening between pharynx and oral sucker is therefore facing obliquely between a dorso-ventral and a posterio-anterior direction. The walls of the pharynx are very muscular and show the same sets of muscles found in the suckers. Circular or equatorial muscles are especially 145] SOME NORTH AMERICAN FISH TREMATODES—MANTER 19 powerful in the posterior region where the esophagus joins the pharynx and these may act as a sphincter muscle between the two (Fig. 10). Special muscle bands run obliquely forward from the dorsal and ventral sides of the pharynx to the oral sucker. These bands are much more prominent on the ventral side. The degree of contraction of these muscles no doubt accounts for the varying position of the pharynx especially its tip in the dorso-ventral direction in relation to the oral sucker. Sometimes the pharynx entirely overlaps the sucker dorsally and rarely it extends almost directly posteriorly. The pharynx leads directly into the esophagus. In a specimen about 25 mm. long the anterio-posterior length of the unpaired region of the esophagus adjacent to the pharynx is only about 57/u, but the organ divides immediately into two lateral stems and is actually a tube running laterally and perpendicular to the long axis of the pharynx. The length of each lateral stem is about 0.4 mm. Each stem bends toward the anterior and extends in that direction about 0.3 mm. before opening into the intestine proper (Fig. 10). The esophagus lies dorsal and partly lateral to the pharynx. Outside the cuticula layer of the esophagus occurs a layer of circular muscles covered in turn by a thin coat of longitudinal muscles. The circular muscles are more prominent in the region where the esophagus joins the intestine, and serve here as a sphincter muscle usually giving rise to a slight constriction in this region. Usually at about the level of the middle of the pharynx the esophageal stems on each side open into the ceca of the intestine proper. The internal cuticular layer of the esophagus ends abruptly at this point (Fig. 10). The intestinal ceca continue forward for a short distance, then bend abruptly and lead posteriorly. The intestine shows no special regions. The two branches stretch nearly to the posterior tip of the body. They spread apart in the region of the ventral sucker, but approach each other closely immediately posterior to the sucker. They are also forced somewhat laterally by the ovary and testes. Just behind the posterior testis they again approach each other slightly. As in other related trematodes (Azygia and Leuceruthrus), the ceca are thrown into small folds throughout their length, the folds being more pronounced the higher the degree of body contraction. Each branch of the intestine ends blindly. There may be a slight difference in their length. That no significance can be attached to the frequently unequal length of the ceca is shown by the fact that the right is sometimes longer and sometimes shorter than the left. The intestine is lined internally by a layer of cuboid or low cylindrical cells from which long wavy protoplasmic processes stream out into the lumen usually nearly filling it (Fig. 10). The internal boundary of these intestinal cells is very indefinite. The size of the cells is the same in very 20 ILLINOIS BIOLOGICAL MONOGRAPHS [146 small specimens and in the largest. A thin membrane surrounds the intestine which is also provided with a thin circular (internal) and longi- tudinal (external) muscle layers. The excretory system is like that of similar forms. It consists posteriorly of a large single median tube which may be much swollen, lying between the branches of the intestine, and opening by means of a short duct at the posterior tip of the body. This tube branches a short distance behind the posterior testis, its two branches crossing the intestinal ceca ventrally and proceeding anteriorly lateral to these ceca. The two branches are con- tinuous anterior to the oral sucker. . The main excretory system consists then, of a Y-shaped tube with the two forks of the Y continuous. This tube may be thrown into folds comparable with those described for the intestine. Its outline in cross-section is very irregular and it can be seen to be con- tinually receiving minute lateral branches. Its thin membraneous lining is obscured by many deeply staining spherical granules which thickly adhere to the wall of the main tube throughout its length. These con- cretions are generally considered as waste products, and are commonly known in many trematodes. Flame cells are numerous. They are small cells oval in shape, with prominent nuclei. Favorable sections show that they occupy ends of minute excretory ducts and that their tips are prolonged into a tuft of cilia about equal to the cell body in length. The cells measure about 14 by 8/*. The genital pore is ventral, median, between the two suckers and much closer to the oral sucker. It leads into a roomy genital atrium within which usually projects the nipple-shaped genital cone or papilla (Fig. 5). Both the genital atrium and the papilla are lined with cuticula which, however, becomes very thin at the tip of the cone. Just beneath this cuticula the wall of the atrium is strengthened by a thick layer of circular muscles. These muscles continue about the base of the papilla but gradually dis- appear toward its tip. Outside these circular muscles is a layer of longi- tudinal muscles, that is, muscles running in the direction of the long axis of the papilla. These muscles are continuous from the wall of the atrium into the papilla where they are internal to the circular muscles. Oblique muscles run off from the region of the longitudinal muscle layer of the atrium. In the solid-appearing tissue of the cone occur numerous nuclei which are more numerous near the tip of the papilla. What at first appeared to be a marked difference in the size and occur- rence of this papilla in the two species of Otodistomum led to a study of the permanency and variability of this organ. In the related genus Azygia, the genital atrium is usually without a papilla, the common sex duct opening at its base. This base of the atrium is, however, protrusible so that it can be thrust out papilla-like. Thus, here the genital papilla is only a momentary or temporary structure. Odhner (1911b: 518) says in 147] SOME NORTH AMERICAN FISH TREMATODES—MANTER 21 regard to this condition; "Dies konnte den Verdacht erwecken, dass es sich bei Otodistomum am Ende in derselben Weise verhielte; doch scheint mir dort die Papille einen mehr 'soliden' Eindruck zu machen." Sections through 0. veliporum from the Pacific showed the genital papilla almost always entirely absent or quite rudimentary in size. In 0. cestoides the papilla was usually of robust form filling most of the atrium, or even entirely protruded from it (Fig. 6). In the latter case, the atrium itself is practically eliminated. In order to determine the constancy of the papilla, specimens of various sizes and degrees of body contraction were sectioned. Specimens collected in different years and killed in different solutions were also compared. The usual and contrasting conditions found are represented in Fig. 8 (0. cestoides) and Fig. 7 (0. veliporum). Of the specimens of 0. veliporum sectioned, six showed the papilla absent, or a condition as in Azygia, three showed a small papilla (Fig. 7), while one showed a prominent papilla partially protruded from the pore (Fig. 29). Among eight specimens of 0. cestoides sectioned, one showed the papilla entirely protruded (Fig. 6), six showed a robust papilla largely filling the genital atrium (Figs. 5 and 8), while one showed the papilla entirely absent (Fig. 28). Odhner's suspicion is therefore correct. Although the genital papilla has always been described and figured as a prominent feature in Otodistomum species it is capable of being entirely withdrawn as is normally the condition in Azygia. What appeared, then, to be a clear distinction between the two forms studied becomes a weak taxonomic character since it is variable and inconstant. The atrium in 0. veliporum from the Pacific almost constantly led very sharply posteriad and only slightly dorsad, while in the Atlantic form (0. cestoides) the slope of the atrium was almost directly dorsad and only slightly posteriad. This degree of slope of the atrium is probably associated with the condition of the papilla as when this structure was completely withdrawn in 0. cestoides the atrium led sharply posteriad (Fig. 28). Measurements on the size of the atrium and papilla in different speci- mens are as follows: Otodistomum veliporum Genital atrium Genital cone 1. 0.845 0.093 mm. 2. 0.9 by 0.06 3. 0.935 0.112 4. 0.935 0.168 5. 0.935 0.149 6. 2.04 0.32 7. 1.57 0.3 8. 1.57 0.28 9. 1.25 0.23 10. 0.9 0.5 0.102 by 0.08 mm 0.075 0.035 absent 0.056 0.093 absent absent absent absent absent 1.25 0.43 22 ILLINOIS BIOLOGICAL MONOGRAPHS [148 Olodistomum ccstoides Genital atrium Genital cone 1. 0.243 X 0.187 mm. 0.168 X 0.149 mm. 2. absent 0.71 0.52 3. 0.33 0.28 0.28 0.2 4. 0.617 0.355 0.317 0.317 5. 0.37 0.187 0.187 0.187 6. 0.6 0.6 0.39 0.54 7. 0.94 0.62 0.39 0.54 8. 1.25 0.15 absent It is certain that trie size of the papilla is independent of general body contraction. Measurements No. 4 in the above table represent a strongly contracted specimen of 0. veUporum and an extended specimen of 0. cestoides. The size of this structure is also independent of the killing fluid. Sometimes the body wall projects lip-like about the genital pore. This condition also is not associated with the size of the papilla. A definite system of muscles about the papilla and in the neck region seems to be responsible for the protrusion and withdrawal of the papilla. The exact mechanism for the protruding of the papilla is difficult to determine and probably depends upon a rather complex system of muscles. The longitudinal muscles about the wall of the atrium have processes which attach themselves to the anterior (or ventral) part of the atrium (Fig. 28). At the other end these muscles are continuous with the longi- tudinal body muscles. Contraction of these muscles of the atrium would have a tendency to widen and to pull forward the anterior part of the atrium. The actual pushing out of the base of the atrium to form the papilla is probably brought about by the numerous diagonal and dorso- ventral muscles of the neck region. Contraction of these muscles causing a compression of body tissue in that region would provide a pushing force at the base of the atrium. Once the movement of the extrusion has started, it would be aided by the contraction of the circular muscles in the wall of the atrium and base of the papilla. Of the two specimens with papilla protruded O. cestoides showed the ejaculatory duct somewhat coiled even in the papilla itself, while this duct was straight in the papilla of 0. veU- porum. The duct is always coiled between the cirrus sac and the papilla, and in unprotruded papillae. The sudden projection of sperm and seminal fluids through this muscular duct would have a tendency to straighten its coiled condition just as such an effect is brought about by sudden pressure of water in a coiled hose. This influence is, of course, an uncertain one in this case and even if present would probably have a negligible effect in elongating the papilla. The retraction of the papilla doubtless results from the contraction of the longitudinal muscles which it possesses. The papilla probably functions as a copulatory organ. In the specimen of 0. veUporum with protruded papilla (Fig. 29), a large mass of sperma- 149] SOME NORTH AMERICAN FISH TREMATODES—MANTER 23 tozoa was emerging from the genital duct at the tip of the papilla. Sperma- tozoa were also found crowding the distal tip of the vagina for a short distance, as well as in the genital atrium outside the papilla. None were found in the vagina posterior to the papilla. Eggs were frequently found in the atrium but only when the papilla was completely withdrawn, a fact which indicates that egg laying occurs while the papilla is completely subsided. The two testes lie one immediately behind the other in the median line at about the center of the body. They are close together and very com- monly are in contact with each other. This condition depends, however, upon the state of body contraction. The posterior testis is always slightly larger than the anterior testis. Each testis is surrounded by a fibrous-like membrane containing a few flattened nuclei. In adult forms from the Atlantic collection (0. cestoides) the size of the anterior testis was 0.62 to 1.25 mm. by 0.8 to 1.12 mm., while the posterior testis measured 0.8 to 1.37 mm. by 0.8 to 1.2 mm. The organs seemed to be rather consistently somewhat larger in O. veliporum. The duct from the anterior testis leads from the ventral side of that organ near its anterior end, and extends anteriorly in the right half of the body. The other male duct leads from the ventral side of the posterior testis about 1/4 the length of the organ from its anterior end. Thus, in the specimen studied, the posterior testis measured 1.235 mm. and the duct opened 0.365 mm. from the anterior end. This condition may be at least partially due to the angle at which the sections were cut. The duct from the posterior testis leads anteriorly in the left half of the body. Both ducts at first lie ventral to the uterus but like the uterus pass dorsal to the ventral sucker, and in this region they also gradually become dorsal to the uterus. Slightly anterior to the posterior margin of the cirrus sac both ducts swing ventrally. The two do not unite until just before they empty into the seminal vesicle. Relations of the ducts were found to be the same in both O. cestoides and O. veliporum. Miihlschlag, however, gives the ducts as arising from the median anterior borders of the testes and uniting into a common duct dorsal to the cirrus sac. The diameter of the vas deferens varies but when expanded measures 26 to 39,u with a very thin mem- braneous wall except in regions where the wall expands into prominent cells. (Fig. 25.) The cirrus sac is large and elongate-ovoid in shape. It lies between the two suckers somewhat nearer the oral. In average sized specimens (23 to 35 mm.) it measures 0.84 to 1.02 mm. by 0.65 to 0.84 mm. It may attain a length of 1.3 mm. It is somewhat larger in O. veliporum where it reaches a length of 1.4 mm. The sac is definitely bounded by a thin membrane about which is an inconspicuous coat of circular muscles. Both seminal vesicle and prostate gland are contained entirely within the sac. 24 ILLINOIS BIOLOGICAL MONOGRAPHS [150 The seminal vesicle is a large swollen tube almost filling the posterior half of the cirrus sac. It is somewhat curved in shape and always packed with sperm cells. The sperm cells are thread-like in form with minute round heads. The wall of the vesicle is made up of flattened cells with large nuclei. The pars prostatica of the male duct leads from the anterior end of the seminal vesicle, proceeds posteriorly and dorsally, then bends anteriorly and runs diagonally forward to the anterior end of the cirrus sac. It is surrounded by the large prostate gland which fills the remainder of the cirrus sac. Just before the duct leaves the cirrus sac its character changes very abruptly into that of the ejaculatory duct. The ejaculatory duct follows a much winding course leading to the tip of the genital papilla. Distally, it is joined ventrally by the vagina. The coiling of the duct in O. cestoides continues in the genital cone itself even when the latter is fully extended. The duct is lined by a thick layer of cuticula-like material continuous with the body cuticula. This layer attains a thickness of 10 to I3n and shows a folded irregular outline in cross-section. It is surrounded by a thick coat of circular muscles which becomes 20 to 25m in thickness near the cirrus sac. No longitudinal muscles could be noted. In development the male reproductive system precedes that of the female. The seminal vesicle is filled with sperm cells some time before eggs appear in the uterus and before the vitellaria appear at all. The ovary lies immediately in front of the anterior testis and usually in contact with it. In both organs the surface of contact is somewhat flattened. The ovary is therefore flattened on its posterior surface and its longest dimension is in the right and left direction. It may lie a little to one side of the testis, either to the right or to the left. (Figs. 13 to 18.) Its position in this respect is very inconstant and the various descriptions of the position of the ovary in this and similar forms is probably without significance. It is normally almost directly in front of the anterior testis. The size of the ovary in fully mature forms is 0.43 to 0.6 mm. by 0.78 to 0.9 mm. It is slightly larger in O. veliporum where it reaches 0.8 by 1 mm. The ootype lies immediately anterior and slightly dorsal to the ovary with which it is in close contact. Both organs are surrounded by a common fibrous tissue which also separates the two. The ootype is somewhat smaller than the ovary. In an average sized specimen where the ovary measured 0.5 by 0.84 mm., the ootype measured 0.35 by 0.53 mm. The oviduct leads from the middle anterior aspect of the ovary. It projects into the ovary in the form of a funnel-like structure with thick walls. This condition was found in both species (Fig. 11). The walls are composed of fibrous tissue which is continuous with the tissue covering the ovary and the ootype. This tissue is quite thick between ovary and ootype, and in it occur the two lateral vitelline ducts. As these ducts 151] SOME NORTH AMERICAN FISB TREMATODES—MANTER 25 approach each other they also tend to encroach upon the ootype so that they give the impression of pushing into it from the rear. Since the fibrous lining tissue becomes very thin between the yolk duct and the cells of the ootype, it is difficult to determine the exact point of penetration of the ootype by the yolk duct on either side. Frontal sections of 0. cestoides indicate that the lateral ducts may penetrate the ootype before uniting to form the common yolk duct. More commonly, however, the two lateral ducts unite while still within the fibrous tissue close to the ootype and only the common duct actually penetrates into that organ. Almost immediately after entering the ootype proper the oviduct is joined by the common vitelline duct and by Laurer's canal. The common vitelline duct is very short. A rather unusual condition was found in at least two cases where Laurer's canal instead of joining the oviduct opened at the point of union of the two yolk ducts, so that the three canals opened together into the oviduct (Fig. 24). In other cases noted, Laurer's canal was slightly to the right and appeared to join the right vitelline duct. Again, Laurer's canal may join the oviduct at about the same point as does the common yolk duct. Laurer's canal is very well developed. It is lined with cuticula 4 to 6/j. in thickness. In medium-sized specimens the duct is about 25/j. in diameter. A circular layer of muscles surrounds it but no special longitudinal muscles could be made out. The tube is much coiled and leads dorsally and either anteriorly or posteriorly as will be shown later. Within the lumen of the canal are many sperm cells. In some cases, in the region adjacent the oviduct a few yolk cells were noted. A seminal receptacle is absent. After receiving the yolk duct and Laurer's canal, the oviduct, now the uterus, becomes a small tube only about 26/x in diameter with a thick wall made up of very definite cells with large nuclei. Into the lumen of this tube project cilia-like processes. The tube very shortly enlarges and the nature of its wall becomes one of large cuboidal and heavily granular cells (13 to 23fi in thickness). This part of the tube coils about more or less within the ootype for a short time and continues also outside of that organ. All stages in formation of the egg shell can be traced from the point where the yolk duct joins the oviduct. The shell material can be first seen as a shapeless irregular mass surrounding an egg cell and a group of yolk cells. Within the cellular-walled uterus region the eggs still lack their characteristic shape. The inner surface of the forming shell often shows vacuole-like spaces (Fig. 26). The cellular region of the uterus as it coils anteriorly soon passes over into a region characterized by a thin simple membraneous wall. By the time the eggs have reached this region they possess hardened and fully formed shells. The uterus contains thousands of eggs and extends anteriorly in many transverse coils. It passes dorsal to the ventral sucker and ventral to the 26 ILLINOIS BIOLOGICAL MONOGRAPHS [152 seminal vesicle. At about the level of the ventral sucker it becomes less coiled and the nature of its wall changes to produce a region which may be called the vagina. The vagina like the male ejaculatory duct is lined internally by cuticula. It possesses two layers of conspicuous muscles, an inner circular layer and an outer longitudinal layer. The vagina contains few eggs and above the ventral sucker is almost a straight tube. It leads to near the tip of the genital cone where it unites with the male ejaculatory duct. There is a common duct for a distance of about 25//. In development the uterus first appears as a solid string of cells without a lumen. Sections of a very young specimen seem to show a lumen appear- ing first within the ootype the start of which appears early with the beginning of the ovary. It is an interesting fact that in slightly older specimens when the uterus can first be made out in toto-mounts but before eggs are being produced, this string-like beginning of the uterus assumes the coiling which characterizes the organ when filled with eggs. It winds transversely back and forth between the ovary and ventral sucker, crossing the body as many as 40 to 50 times, approximately the same degree of folding that is found in the adult. The first eggs to be produced are abortive. A specimen 11.5 mm. in length showed the earliest egg still in the region of the ventral sucker. The most anterior eggs (15 to 20) were only about half the size of the others and were almost spherical with very thin shells. They measured from 22.8 to about 30/x, the smallest being most anterior. The eggs nearer the ovary were larger but still showed a very thin shell, in striking contrast to the thick shell found in the adult egg. No eggs in this specimen measured over 6S;u, a measurement slightly below the average adult size. The vitellaria are interesting because of the variation of their extent and arrangement. They are of the follicular type and consist of separate spherical bodies grouped in two longitudinal rows along the sides of the body. The follicles lie mostly ventral to the digestive system. They do not appear until relatively late in development, or just before eggs begin to be formed. At this time the follicles are very small, approximately the size of the eggs (about 50yu in diameter), but in the adult they reach a diameter of 150 to 190/x. Several hundred of these follicles are connected by ducts which unite into a common lateral duct on each side at the level of the ootype, and these two lateral ducts unite in the ootype as described. The rows of follicles are usually narrow, but the width of the rows often increases to such an extent that the two approach each other medianly. Thus, Miss Lebour (1908) figures the vitellaria massed together posterior to the testes. Such variations are not common, however, the two rows being usually distinctly separate. Irregular breaks or spaces free of follicles are common, and certainly can have no specific significance within the 153] SOME NORTH AMERICAN FISH TREMATODES—MANTER n genus Otodistomum. Even the differences in the vitellaria given by Odhner (1911b) to distinguish 0. cestoides from 0. veliporum are quite useless. He gives the vitellaria in 0. veliporum as beginning behind the middle of the uterus and as being compressed into narrow rows, while in Table 3 Variation in Posterior Extent of Vitellaria in 0. cestoides Body length Distance from Extent of right Extent of left posterior testis to vitellaria beyond vitellaria beyond b b posterior tip posterior testis posterior testis c i a b c d 31. mm. 16. mm. 6.4 mm. 7.6 mm. 2.5 2.1 38. 21. 12.8 13.2 1.6 1.5 24.5 13.5 crosses over to left side 7.9 1.7 1.7 20. S.3 8.3 7.3 1. 1.1 28. 13.5 10.6 9.8 1.2 1.3 17. 7.5 5.6 6.25 1.3 1.2 19. 9. 4.8 3.7 1.8 2.4 29. 14. both unite in center 8.4 1.6 1.6 38. 18. 9.3 12.1 1.9 1.4 16. 8. 4.6 4.6 1.7 1.7 18. S. 5.5 7.1 1.4 1.1 16. 6. both unite in center 5. 1.2 1.2 11. 5.3 2.9 2.9 1.8 1.8 10.5 5. 2.4 3.1 2.1 1.6 10.8 5. 3.3 3. 1.5 1.6 10.5 5. 3.7 3.7 1.3 1.3 11.5 6. 3.9 3.9 1.5 1.5 11. 5.3 2.5 2.5 2.1 2.1 26. 10.5 7.4 7.2 1.4 1.4 26. 14. united for 2.8 mm. 8.7 1.6 1.6 28. 15. 6. 6. 2.5 2.5 31. 17. unites with left 7.4 2.2 2.2 28. 13. unites with left 8.7 1.5 1.5 28. 15. 6. 6. 2.5 2.5 29. 15. 9.4 9.4 1.5 1.5 32. 16. 8.2 10.7 1.9 1.5 0. cestoides the follicles ordinarily begin in front of the middle of the uterus and are not as compressed. This distinction cannot be maintained. In 0. cestoides, while the vitellaria have their anterior limit between the ovary and ventral sucker, approximately half way between these two organs, they may extend clearly beyond this mid-uterine point or may fail to reach it by some distance. Posteriorly, the vitellaria always extend considerably beyond the posterior testis and practically always reach at least half the distance 28 ILLINOIS BIOLOGICAL MONOGRAPHS [154 between the hind testis and the posterior end of the body. Two cases (one in 0. veliporum and one in 0. cestoides) were noted wherein the vitellaria extended to the extreme posterior tip of the body. One row of the follicles may be several millimeters longer than the other. The rows may unite and run together for several millimeters either medianly or on one side. As such variation in these organs is unusual a table has been prepared to show more detailed measurements (Table 3). The average egg size for 0. cestoides was 69.4 by 46.2ju as derived from over 50 measurements. This size agrees with data by Odhner (1911b) who gives 0.065 to 0.072 by 0.043 mm., and Cooper (1915) who gives 0.070 by 0.042 mm. The thickness of the egg shell measured under oil immersion lens averaged about 4.5/j. This thickness is somewhat above the measure- ments of Odhner, who gives 0.003 mm. and Cooper, who gives 0.0028 mm. The eggs of 0. veliporum averaged 85.5 by 57.8,u. 155] SOME NORTE AMERICAN FISH TREMATODES—MANTER 29 GROWTH CHANGES IN OTODISTOMUM CESTOIDES WITHIN THE FINAL HOST Since it is clear that the trematodes must be slightly under 2 mm. in length when first entering the skate, there is a growth within that host to about 40 times. Moreover, the parasite increases its size by six or seven times after it has become sexually mature. This growth of the worm within the skate is marked not only by degree, but also by a regional localization, which results in very different conditions of body proportions in the young and in the adult. The growth is largely in the region posterior to the ventral sucker, and consists mostly in body elongation. A study was made of this localized growth and its effects upon various body proportions. The material at hand was especially favorable for such study not only because the extremes in size were conspicuous, but also because all intermediate sizes were available. Regional growth in trematodes has been noted in a general way by various workers. Braun (1894:567) says of trematodes in general: " — junge Exemplare sind nicht nur absolut, sondern auch relativ kurzer, indem besonders das hintre Korperende mit der Entwicklung der Geschlecht- sorgane bedeutend an Lange zunehmen kann. Gleichzeitig treten auch andre Veranderingen der Gestalt auf, die so bedeutend sind, dass es oft der Uebergangsstadien bedarf, um eine Jugendform zu diagnosticiren." As early as 1870 van Beneden stated that the young form of Dist. hispidium was entirely different from the adult. A proportionally greater increase in length than in width was indicated by von Linstow (1890) for Dist. cylindraceum, but only a few forms were measured. Specimens measured were 4.5 by 1.4 mm., 6-7 by 1.5 mm., and 13 by 2 mm. The liver fluke (F. hepatica) shows a very marked increase of the posterior regions at the time of sexual maturity as shown by both Thomas (1883) and Leuckart (1886). This growth change also affects the ventral sucker which increases its size ratio to the oral sucker. Thus, according to Thomas (1883:132) the suckers are of nearly equal size in the cercaria while in the adult the diameters of the oral and the ventral suckers have the ratio 1 : 1.35. In F. hepatica the body form also increases rapidly in width. Barlow (1923) gives measurements of hundreds of individuals of Fasciolopsis buski. While the size changes in this form are interesting, there does not appear to be conspicuous changes in proportions. 30 ILLINOIS BIOLOGICAL MONOGRAPHS [156 Cort (1921) has given the changes in body proportions with growth in Schistosoma japonicum. It is interesting that these changes parallel very closely the changes in 0. cestoides, an entirely unrelated form. Like the fish trematode, the adult blood fluke is elongate, whereas the young are short and wide. The adult Schistosoma japonicum may increase its size as many as 100 times over that of the cercaria. The changes "consist in a very great increase of the length in ratio to the width, an enormous increase of the post-acetabular region of the body as compared with the pre- acetabular, and a gradual assumption of the secondary sexual character- istics which produce the sexual dimorphism of the adult." Especially interesting are changes in the size ratio between the two suckers. "In the cercaria the ventral sucker is only about 1/3 the diameter of the oral sucker. In an early stage of development, the suckers become about equal in size, and in later stages the ventral sucker is constantly larger than the oral sucker." This progressive change in sucker ratio is to be contrasted with the constancy of this ratio in 0. cestoides as will be shown later. Growth phenomena have been noticed in the Azygia group by Ward (1910) for A. sebago and by Muhlschlag (1914) for Otodistomum veliporum. Ward says (of -4. sebago): "The anterior region assumes the form of an ellipse surrounding the two suckers. This region changes relatively little in size with growth. In one of the smallest specimens (measuring 1.6 mm.) the distance between the centers of the two suckers was 0.5 mm. In one 10 mm. long, this distance measured 1 mm." Muhlschlag found by measuring the largest and smallest specimen of his collection of Otodistomum veliporum that the neck region compared with the body region was 1 : 4 in the young forms and 1 : 7.8 in the largest individual. He concludes: "dass bei verschiedener Grosse der Tiere der Hinterkorper relativ starker wachst als der Vorderkorper." In Otodistomum cestoides the contrast in form between a very young and a sexually mature individual can be seen by comparing Fig. 1 and Fig. 2. Measurements were made on over 200 specimens varying in size from 2.3 mm. to 65 mm. The measurements (taken on alcoholic specimens) included length, width at broadest point, and distance from anterior end to the posterior margin of the opening of the ventral sucker. The margin of the opening was chosen because the outline of the ventral sucker itself is usually not distinct in unmounted specimens. The position of the opening varies somewhat in relation to the outline of the sucker, but, in general, approximates very constantly the true position of the sucker. All measure- ments can be considered only as approximate as most were taken with a millimeter rule which necessitated estimations of half and quarter milli- meters. The smaller specimens were measured microscopically. The youngest specimens (which very probably represent the earliest condition in the skate) are strikingly unlike the adult in body proportions. /(I ; J I f / f j ,, / f J | / J j / / j 1 r A * 1 r J ~" \ '3 : / 1 r 4 } \ — -H - 1 B, •r B C '_ O _ y. - Z - C — — ~ — a d :. is _ - .. - C - _ ~ 2 — !ti — rt O § c 3 ;_ — ^ £ « a'-S cu - H "ft <2 •_ . en in ° § > A Vit. on right beyond testis 8.* 1.68 1. 0.75 2.6 3.3 0.4 1.37 0.31 0.31 11.3* 2.5 1.3 1. 3.9 0.65 2.56 1.56 0.96 10.9* 2.5 1.3 0.93 3.4 3.87 0.37 2.5 0.63 1.01 9.75* 1.3 1. 0.68 3.3 3.1 0.5 2.4 0.5 1.5 * 2.5 1.25 1. 3.87 0.74 9.68* 2.5 1.3 1. 3. 3.75 0.3 9.87* 2.6 1.25 1.06 3.56 3.62 0.35 1.4 0.65 1.15 6.87 1.8 1.18 0.9 1.9 2.5 0. 1.6 0.78 0.84 6.56 1.75 1.06 0.74 2.3 1.75 0.5 1.6 0.95 0.76 6.3 1.5 0.93 0.78 2. 2.18 0. 1.4 0.84 0.13 7.5 2. 1.18 1. 2.68 2.75 0. 1.68 0.88 1.03 8.87f 1.4 0.87 0.812 2.93 3.3 0.3 2.18 1.5 1.56 9.37f 1.3 0.87 0.812 3.75 3.3 0.75 2.18 0.87 1.18 11. t 0.93 0.75 3.87 4.12 0.5 2.8 1.87 1.9 189] SOME NORTH AMERICAN FISH TREMATODES—MANTER 63 arrangement of internal, longitudinal parenchyma muscles than was found in the other Azygia species. Table 9 (page 60) gives measurements of the available A. acuminata specimens. Those marked * were collected by Cooper; those marked f are from the Ward collection and were obtained at Fairport, Iowa, in 1916 by T. B. Magath. In each case the host was Amiatus calvus. Pearse (1924) records A. acuminata from the "wall-eyed pike" in Lake Pepin, Wisconsin, but gives no further data. AZYGIA LONG A (LEIDY 1851) [Figs. 19, 20 and 30] Synonyms: Dist omum longum Leidy 18S1 Dist omum tereticolle of Leidy 1851 Megadistomum longum (Leidy) Stafford 1904 Azygia tereticolle of Stafford 1904 Azygia sebago Ward 1910 Azygia bullosa Goldberger 1911 Hassalliits hassalli Goldberger 1911 Azygia lucii of Cooper 1915 Authentic material of all these forms (with the exception of Stafford's) was obtained. A careful comparative study of this material has led to the acceptance of the above list of synonyms. The occurrence of intermediate conditions between somewhat extreme types, and the high degree of variability of some factors, necessitates the extension of the limits of the species as will be shown. In view of the high degree of contractility and marked growth changes of trematodes in this group, all comparisons were made relative to body length and on the basis of body proportions. Even on this basis consideration must be given to relative changes in proportions with growth. Azygia sebago Ward (1910) from the Sebago salmon is the best described of American species. Leidy's Dist. longum reported in 1851 and the various other species recorded from America since 1910 have appeared to differ more or less markedly from A. sebago. These differences will now be critically examined. In separating A. sebago from the European species, A. lucii ( = A. tereti- colle) Ward emphasized the posterior extent of the vitellaria. Although Odhner (1911b) is partially justified in discounting dependence upon vitellaria in this genus, the distinction seems to be a valid one. Not only in A. sebago, but in all American forms of Azygia examined, the vitellaria always extend appreciably beyond the hind testis, usually at least half way from this point to the posterior end, and may even reach to the extreme posterior tip as was observed in one case. According to descriptions and figures of A. lucii, the vitellaria end in the region of the hind testis and 04 ILLINOIS BIOLOGICAL MONOGRAPHS [190 rarely extend appreciably posterior to it, although van Beneden (1858) says the vitellaria reach "depuis la ventouse posterior jusqu'en dessous du second testicule." His figures show the vitellaria extending beyond the hind testis to a point about 1/4 the distance between that organ and the posterior end. Looss (1894:16) describes their extent for the European species as follows: "Die Dotterstocke erstrecken sich in den Seitentheilen des Leibes ausserhalb der Darmschenkel nach vorn hin nicht bis an den Bauchsaugnapf — sie endigen ungefa.hr die Lange seines Durchmessers vorher-, nach hinten zu kaum jemals bis tiber hintere Grenze des zweiten Hodenshinaus." Further distinction between American species and A. lucii can probably be found in pharynx shape, a point upon which Odhner separates a new species, A. robust a. The pharynx of American species is more globose than the elongate pharynx of A. lucii. This point will be considered in more detail under A. robusta. A. sebago averages about 6 to 8 mm. in length. Specimens were found as small as 1 mm. and no ova were present in forms 2.85 mm. long. In regard to sucker proportions: "The ventral sucker or acetabulum is usually distinctly smaller than the oral. In the extreme case it appears about equal in size or, on the other hand, only about half as large" (Ward, 1910:1177). The questions of body size, size at sexual maturity, egg size, and sucker proportion are important points of comparison in American Azygia species. Of the other Azygia species, A. bulbosa Goldberger is most evidently identical with A. sebago. The descriptions of the two forms show no important differences. Type material of both species was studied. Refer- ence to comparative tables (Tables 15 to 18) shows almost identical body size and proportions, as well as similar position and arrangement of organs. Goldberger gives the egg size of A. bulbosa as 56 by 25ju. Although the eggs may reach a length of 57/*, the average of my 110 measurements gave the egg size as 48.3 by 28.7yn. Ward gives the egg size of A. sebago as 48 by 27 M . The original type material of Hassallins hassalli Goldberger was also examined for comparison. That all of this material was strongly contracted was made very evident by the ring-like foldings of the cuticula and the excessive foldings of the intestine. Goldberger himself explained the "numerous transverse sulci" of the cuticula as "apparently due to con- traction of the worm." The high degree of body contraction is also evi- denced by the longitudinal compression of the organs, especially the uterus, gonads, and vitellaria. The pharynx is brought down closer to the ventral sucker than is normal. Yet, in spite of the evident body contraction, Goldberger separates his genus from Azygia on a thicker, shorter body form, and a lateral position of the ovary in relation to the anterior testis, both of which characters would be caused by body contraction. The only 191] SOME NORTH AMERICAN FISH TREMATODES—MANTER 65 comparison Goldberger makes between the two genera is in these words: "This new genus, aside from its external characters, differs from Azygia in the position of the ovary, which here is by the side of, that is in the same transverse plane as the cephalic testis, instead of cephalad of the latter as in Azygia." The shorter and thicker body shape is directly due to con- traction. In regard to the position of the ovary, reference need only be made to Goldberger's figure of Azygia acuminata (his Fig. 8) and to the following sentence from his description of this Azygia species: "In one of four press preparations, the ovary bears exactly the same relation to the testes as that in Hassallius hassalli; that is, it is within the zone of the cephalic testis." In Azygia species as in Otodistomum (see Figs. 13-18), the ovary may be located slightly to the right or to the left of the anterior testis, and is consequently forced into the "zone"of this testis when the body is contracted. Until the ovary can be shown to be lateral to the testis in uncontracted specimens, this character cannot be given even specific significance. In fact, after allowance is made for body contraction, this form cannot be distinguished from the other common American forms as represented by A. sebago and A. bulbosa. Goldberger's own description and figures show the terminal genital apparatus in his A. bulbosa and Hassallius hassalli to be exactly similar. Study of his publication and original material reveals not a single point of difference between the two forms, except differences that might be due directly to body contraction. Comparison of sagittal sections of this species with sagittal sections of A. sebago and the A. lucii of Cooper shows no differences that can in any sense be considered specific. Goldberger gives an egg size of 48 by 26jx measured from sections. My measurements of eggs from toto mount gave about 49 by 24/i, but the larger eggs measured from sections were from 54 to 57^ in length by about 24^ in width, or practically exactly the measurements for A. bulbosa. The internal parenchyma muscles in Hassallius hassalli are prominent and are exactly as in A. sebago and the A. lucii of Cooper. Leidy in 1851 described Distomum longum from the mouth of Esox estor ( = E. lucius). Stafford (1904) designates as "Megadistomum longum Leidy" forms which he collected from the mouth, esophagus, and stomach of Esox masquinongy. These trematodes are very long, Leidy's speci- mens being up to 76. mm. (3 inches) in length, while Stafford reports living worms as extending to 127. mm. (5 inches), a truly prodigious length. Stafford gives a normal length of 75 mm. Both Leidy and Stafford give the oral sucker as slightly larger than the acetabulum. Odhner (1911b) expresses the view that this trematode should be considered as a large Azygia species. Cooper (1915) collecting material from L. masquinongy considers his form the same as that reported by Stafford and identifies it as Azygia lucii. 66 ILLINOIS BIOLOGICAL MONOGRAPHS [192 Study of Leidy's original Distomum longum and Cooper's material clearly shows that they represent members of the genus Azygia. Their large size is certainly not sufficient basis to warrant Stafford in forming a genus, Megadistomum. Leidy's Dist. tereticolle (from Esox reticidatus) also was compared with them, and in the single specimen available in the Leidy collection, the oral sucker, contrary to Leidy's description, was found to be slightly larger than the acetabulum. In Dist. longum, Leidy describes the genital opening as "just anterior to the middle of the neck, or nearer the oral acetabulum." Such was not the condition in the two specimens of this form available. In each case the genital aperture was close in front of the ventral sucker, as is, indeed, characteristic of the genus Azygia. In the most elongate specimen the esophagus was unusually extended longitudinally and at its base a swollen region showed a marked resemblance to the cirrus sac. It is possible that Leidy mistook this appear- ance for the end-apparatus of the genital system. The true position of the terminal genital-apparatus in Dist. longum is seen in Figure 30. Cooper also collected Azygia species from the pike (L. lucius). These latter trematodes were much smaller in size, and apparently a different species, but Cooper, after a careful comparison of his smallest examples from the maskinonge with those from the pike, concludes that they repre- sent a single species. He also points out the highly variable size at which egg production begins. A 14. mm. trematode showed less mature eggs than one 6. mm. long from the same host. "On the other hand," Cooper adds, "examples of intervening lengths may have their uteri distended with ripe eggs!" (Cooper 1915:192). Forms from the trout were all immature although they reached a length of 11 mm. This variable size at which eggs are first produced in Azygia species is in contrast with the fairly constant size at sexual maturity in Otodistomum species. The large number of different hosts in which Azygia species occur may be associated with this variability. Another possible factor is the season of the year, but the influence of this factor would be difficult to determine. Eleven different fish hosts have been reported for the present Azygia species. Ward collected his material in July and August and found that those forms from the smelt although attaining a length up to 11 mm., were always immature. Cooper does not indicate the season of his collection but found all forms from the trout and from the small-mouthed black bass immature. Stafford examined his fresh water fish in the spring and fall. One specimen of his "Megadistomum longum" measured 18. mm. long but contained no eggs; and the largest individuals of his "A. tereticolle" were smaller than immature individuals of Megadistomum. He found that most of his "Mimodistomum angusticaudum" were immature, but "towards the end of October" found a few sexually mature. 193] SOME NORTH AMERICAN FISH TREMATODES—MANTER 67 Whatever effect the season of collection may have, it is certain that what is evidently the same Azygia species does not attain sexual maturity at the same time in the different hosts in which it occurs. Thus, while average sized forms are producing eggs in such hosts as pike, pickerel, and salmon, specimens fully as large are still immature in such hosts as smelt, trout, small-mouthed black bass, and perch. That variation in body size at sexual maturity may occur within a single host is shown by Cooper's report of a 14 mm. trematode with less mature eggs than were commonly found in specimens 6 to 14 mm. in length. Further data is needed, however, to show the extent of this variation. It has not been noted by other workers, and certainly is not so conspicuous as the marked differences found in specimens from different hosts. The maximum body size which the trematode attains also seems associated with the host. In those cases wherein the greatest size is reached (as in the maskinonge and pike) there also seems to be considerable growth before sexual maturity (e.g. Stafford's immature 18 mm. specimen), and it is very possible that the ultimate size which the trematode may reach is associated with the amount of growth before eggs are produced, and this latter condition may, in turn, depend upon the fish host. The following tables (Tables 10-13) show absolute measurements on these different forms. The 66 mm. specimen of Dist. longum was very highly extended and had apparently been stretched in killing. Moreover, the body was not equally extended but was more elongate in the uterus region just posterior to the acetabulum. The 37 mm. specimen therefore probably furnishes the more normal proportions. Table 10. Azygia sebago Measurements in millimeters ■3 to c -a ■a H o § S "3 .a 03 CD (J < Post, edge acet. to mid. ovary Post, edge acet. to ant. end Post, edge acet. to most ant. vitellaria •a & s "2 3 - t/i (2 3 in c -a o c . o *i >> > -Q a t3 o a . o > J3 5.9 0.9 0.65 0.59 2. 1.4 0.31 2.12 0.72 0.72 5.9 0.9 0.65 0.59 2. 1.4 0.31 2.12 0.72 0.72 10. 0.93 0.65 0.58 4.37 1.9 0.65 2.75 2. 2. 6.7 1.06 0.65 0.56 2.25 1.5 0.41 2.18 1.31 1.18 11.5 0.75 0.67 0.56 4.06 2. 0.5 3.75 2.3 2.4 13. 0.5 0.74 0.56 5.3 2.5 0.9 3.25 1.9 1.9 9. 1.5 0.68 0.62 2.9 1.8 0.4 2.8 1.12 0.55 12. 1.1 0.8 0.5 4.8 3. 2.12 3.43 1.9 1.9 10. 0.81 0.71 0.52 4.18 2.56 1.3 3.18 1.93 2.28 10.5 0.81 0.65 0.56 3.6 2.4 1.06 3.37 2.12 1.87 OS ILLINOIS BIOLOGICAL MONOGBjIPHS Table 11. Azygia bulbosa Measurements in millimeters [194 J3 to a u t-3 -a h W 1 s ^ en a "3 2 u < Post, edge acet. to mid. ovary Post, edge acet. to ant., end Post, edge acet. to most ant. vitellaria as HJ O • m (2 2 t/1 "2 3 ° § — >> IT* <" > J2 4-> . W ° § > -Q 5.68 l. 0.81 0.62 2.43 1.68 0.65 1.49 0.75 0.75 6.3 1.37 0.87 0.62 2.2 1.8 0.65 1.5 0.75 0.75 6.2 1.25 0.81 0.68 2.4 2.1 0.58 1.6 0.7 0.7 8.4 2.9 1.25 1. 2.6 2.5 0.84 2.5 1.32 1.25 3.9 0.9 0.66 0.54 1.25 1.5 0.37 0.78 0.28 0.28 5.6 0.9 0.69 0.54 2. 1.6 0.58 1.6 0.73 0.92 7.1 1.1 0.87 0.63 2. 2.5 0.69 2.1 1.2 1.2 5.1 1. 0.75 0.56 1.68 1.62 0.9 1.3 0.74 0.74 4.18 0.9 0.56 0.35 1.3 1.49 0.5 1.12 0.55 0.55 6.9 1.1 0.81 0.62 1.9 2. 0.8 2.3 1.43 1.43 5.9 1.1 0.75 0.63 1.9 1.8 1.56 1.6 0.85 0.85 Table 12. Cooper's Azygia lucii from L. masqidnongy Measurements in millimeters •a 60 a u M (5 h o g a "3 $ U < Post, edge acet. to mid. ovary Post, edge acet. to ant. end Post, edge acet. to most ant. vitellaria "0 as -a o VI "■*-> o yi S 3 en •.a ju 3 « "3 ° § > J3 f-1 -M c "3 ° § > J3 29. 2.06 1.06 1.06 15.3 4. 4.8 6.87 3.27 4.07 29. 2.1 1.1 1.1 12.3 4.4 7.5 9.6 4. 6.1 39. 2.18 1.25 1.25 17. 4.3 8.2 9. 5.6 4.4 31. 1.8 1. 1. 14. 3.68 5.3 9.1 5.23 3.3 2.3 1.25 1.37 5.12 9.7 1.87 8.4 6.22 5.9 1.68 1.18 0.87 1.18 0.87 9.6 5.3 6.8 3.4 0.5 0.48 0.5 * The large size of DisL longum and the form from the maskinonge seems at first to separate them from most of the other forms. Leidy's Dist. tereticolle, however, somewhat bridges the gap. The equal size of the suckers in the form from the maskinonge is distinct in these tables, but Cooper himself reports the oral sucker as larger than the acetabulum. In DisL longum which this form most closely resembles, the oral sucker is larger. Moreover, Ward reports occasional equality of sucker-size in A. sebago. In view of these facts, the apparently constant equality of the size of the suckers in the above form is probably a coin- cidence, and at any rate could not alone justify a new species. 195] SOME NORTH AMERICAN FISH TREMATODES—MANTER 60 Table 13. Cooper's Azygia hicii from the pike Measurements in millimeters M to a hJ ■3 1 3 S 3 3 ■M 4> U < Post, edge acet. to mid. ovary Post, edge acet. to ant. end Post, edge acet. to most ant. vitellaria -o T3 O O w tfl ° § > J2 142 1.6 0.93 0.75 4.18 2.7 0.25 5. 2.8 2.5 14. 1.12 0.78 0.56 6.3 2.9 0.89 5. 2.7 2.3 8. 1. 0.5 0.43 3.75 1.8 0.48 1.75 0.75 0.68 11. 0.75 0.68 0.56 4.75 2.5 1.5 2.68 1.18 1.37 7.5 0.87 0.67 0.52 2.9 1.6 0.28 2. 0.9 0.87 8.5 0.68 0.5 3.4 1.8 0.43 1.4 0.8 0.8 12. 0.93 0.75 0.62 5.5 3.9 0.9 2.1S 1.5 1. Leidy's Disiomum tercticolle 20.3 0.97 I 0.8 | 0.71 | 9.3 3.9 2.5 7.1 3.6 I 3.6 Dislommn longum 66. 1.56 1.42 1.3 38. 6.8 18.7 12.1 7.1 7.1 37. 1.56 1.37 1.18 19.7 5.68 9. 4. 4. The egg size is larger in the larger forms, but intermediate sizes were found in some of the material from the pike as shown by the following measurements. Table 14 Average egg sizes in American forms of Azygia Azygia sebago 48 by 27/i Azygia bulbosa 48 " 28 Leidy's Disiomum teretkolle 45 " 28 Distomum longum 62 " 34 Cooper's Azygia lucii from maskinonge 63 " 33 Cooper's A zygia lucii from pike 51 " 28 Cooper's Azygia lucii from pike 56 * 28 Two measurements are given in the last case as one trematode from this collection showed larger eggs. The following tables (Tables 15-18) show the ratios of body length to: (1) width, (2) "neck" region, (3) uterus region, and (4) distance between ventral sucker and most anterior vitellaria. 70 ILLINOIS BIOLOGICAL MONOGRAPHS [196 Table 15 Proportion op Body Length to Width in Azygia Species Body Length in Millimeters is Given in Parentheses A. sebago A . bulbosa A . anguslicauda A. acuminata 6.5 ( 5.9) 5.68 ( 5.68) 7.7 ( 5.25) 3.8 ( 6.8) 11.7 (10.5) 4.6 ( 6.3) 7.9 ( 4.9) 3.6 (6.5) 6.2 (6.7) 5. ( 6.2) 4.2 ( 6.3 ) 11.8 (10. ) 3. ( 8.4) 3.7 ( 7.5) 15.3 (11.5) 4.3 ( 3.9) 4.7 ( 8. ) 26. (13. ) 6.2 ( 5.6) 4.5 (11.3) 6. (9. ) 6.5 ( 7.1) 4.3 (10.9 ) 10.9 (12. ) 5.1 7.5 ( 9.75) 12.3 (10. ) 4.6 ( 4.1) 5.3 ( 6.9) 4.4 ( 5.9) 3.8 6.3 7.2 ( 9.68) ( 9.87) ( 9.37) Cooper's A. lucii Cooper's A . lucii Dist. Ion gum Leidy's Dist !. terelicoll from pike from maskinonge 8.7 (14. ) 14.5 (29. ) 42.2 (66. ) 20.8 (20.3) 12. (14. ) 14.5 (29. ) 23.5 (37. ) 14.6 (11. ) 17.8 (39. ) 8.6 ( 7.5) 6.8 ( 3.4) 12.9 (12. ) 8. (S. ) Table 16 Proportion of the Total Body Length to the Distance from Ventral Sucker to Anterior End in Azygia Species Body length in millimeters is given in parentheses A . sebago A. bulbosa A . anguslicauda A. acuminata 4.2 ( 5.9) 3.3 ( 5.6) 2. ( 5.25) 2.4 (8. ) 5.2 (10. ) 3.5 ( 6.3) 2. (4.9) 2.9 (11.3 ) 4.4 ( 6.7) 3. ( 6.2) 2.8 (10.9 ) 5.7 (11.5) 3.3 (8.4) 3.1 ( 9.75) 5.2 (13. ) 2.6 (3.9) 2.6 ( 9.68) 5. ( 9. ) 3.5 ( 5.6) 2.7 ( 9.87) 4. (12. ) 3. ( 7.1) 2.7 ( 6.87) 3.9 (10. ) 2.7 (4.1) 3.7 ( 6.56) 4. (10.5) 3.4 ( 6.9) 2.8 ( 6.3) 3.3 (5.9) 2.7 ( 7.5 ) Cooper's A . lucii Cooper's A . lucii Dist. longum Leidy's Dist . terelicoll from pike from maskinonge 5.2 (14. ) 7.2 (29. ) 9.7 (66. ) 5.2 (20.3 ) 4.8 (14. ) 6.6 (29. ) 6.7 (37. ) 4.4 ( 8. ) 9. (39. ) 4.7 ( 7.5) 8.3 (31. ) 4.4 (11. ) 4.7 ( 8.5) 4. (12. ) 197] SOME NORTH AMERICAN FISH TREMATODES—MANTER 71 Table 17 Proportion of Total Body Length to Length of Uterus Region in Azygia Species Body length in millimeters is given in parentheses A . sebago A.balbosa A.angusticauda A . acuminata 2.9 ( 5.9) 1.9 ( 5.68) 2.8 ( 5.25) 3.6 ( 6.87) 2.2 (10. ) 2.8 ( 6.3 ) 2.9 (4.9) 2.8 ( 6.56) 2.9 ( 6.7) 2.5 ( 6.2 ) 3.1 ( 6.3 ) 2.9 (11.5) 2.5 ( 8.4) 2.8 ( 7.5 ) 2.4 (13. ) 2.3 (3.9) 3. ( 8. ) 3. (16. ) 2.8 ( 5.6) 3.2 (10.9 ) 2.5 (12. ) 3.5 ( 7.1 ) 2.95 ( 9.75) 2.3 (10. ) 3. ( 5.1 ) 3.2 ( 9.68) 2.6 (10.5) 3.2 3.6 3. (4.18) ( 6.9 ) ( 5.9) 2.7 ( 9.87) Cooper's A . lucii Cooper': ; A . lucii Dist. longum Leidy's Dist . tcrclicoll from pike from maskinonge 3.3 (14. ) 1.9 (29. ) 1.7 (66. ) 2.2 (20.3 ) 2.2 (14. ) 2.3 (29. ) 1.8 (37. ) 2.1 (8.) 2.3 (39. ) 2.3 (11. ) 2.2 (31. ) 2.6 ( 7.5) 2.5 ( 8.5) 2.2 (12. ) Table 18 Proportions of the Body Length to the Distance from Ventral Sucker to t ut. Most Anterior Vitellaria in Azygia Species Body length in millimeters is given in parentheses A. sebago A . bulbosa A . angusticauda A. acuminata 19. ( 5.9) 8.7 ( 5.68) 26.2 ( 5.25) 20. (8. ) 14.4 (13. ) 9.7 ( 6.3 ) 27.2 (4.9) 17.3 (11.3 ) 16.7 ( 6.7) 10.6 ( 6.2 ) 29.4 (10.9 ) 22.5 (9.1) 10. ( 8.4) 19.5 ( 9.7 ) 15.5 (12. ) 9.6 ( 5.6) 28.2 ( 9.8 ) 5.6 (19. ) 10.5 (3.9) 3.2 ( 9.68) 23. (11.5) 10.2 ( 7.1 ) complete ( 6.8 ) 7.5 (10. ) 5.7 (5.1 ) 13.1 ( 6.56) 9.9 (10.5) 8.3 ( 4.18) 28.6 ( 8.87) 8.6 ( 6.9 ) 12.5 ( 9.37) 10.5 ( 5.9 ) 22. complete complete (11. ) (6.3 ) ( 7.5 ) Coope :r's A . lucii Cooper's i A . lucii Dist. longum Leidy's Dist. tercticolle from pike from maskinonge 45. (14. ) 6. (29. ) 3.5 (66. ) 8.1 (20.3 ) 15.7 (14. ) 3.8 (29. ) 16.6 (8. ) 4.7 (39. ) 7.3 (11. ) 5.8 (31. ) 26.7 ( 7.5) 19.7 (8.5) 13. (12. ) 72 ILLINOIS BIOLOGICAL MONOGRAPHS [198 The relative width of the body is seen to be quite variable. Differences can be explained by different degrees of contraction, and by growth changes. The closely related genus, Otodistomum, has been shown to increase greatly in length but very little in width with growth. This condition is well shown by reference to the 39 mm.- and the 3,4 mm. specimens (Table 12) from the maskinonge. In the former case the length is 17.8 times the width while in the latter the length is only 6.8 times the width. Dist. longum and the form from the maskinonge have body lengths 7 to 9 times the neck regions, while in the other forms this ratio varies from about 3 to 5. But this difference is of no specific significance, being clearly due to the larger size of the former trematodes and representing a change in ratio which has been shown to occur with growth in similar forms. That is, the proportions shown in the table are what would be expected if all the forms represented different stages of growth of the same species. In the 66 mm. specimen of Dist. longum some allowance should perhaps be made for artificial extension which the other specimens did not receive. The tables dealing with the uterus length and with the anterior extent of the vitellaria both indicate a slight tendency in Dist. longum to differ from the other species. In regard to uterus length, however, the smallest ratio (1.7) or longest uterus is in the specimen already described as showing a localized extension in that region. Furthermore, a tendency for this region normally to increase slightly its proportion to the remainder of the body was shown to be true in Otodistomum. The anterior extent of the vitellaria is highly variable, as the body may be from 3.5 to 45 times the length of the distance between vitellaria and the acetabulum. Because of this high variation and because there is no consistency in any single group outside of A. acuminata, this point cannot be urged in separating species. Thus, in spite of the great difference in size, a consideration of the possible features which might separate these species shows that there has been found no valid basis for distinction between them. It is especially significant that, except for characters which vary and overlap in the different forms, all the differences are in the direction taken by normal growth changes, and are moreover -commensurable with such changes. Therefore, one feels justified in concluding that so far as can be determined morphologically, all these forms are representatives of the single species, Azygia longa (Leidy), and that this species manifests a variety of states, the extremes of which differ widely, but all of which are in accordance with growth changes and capacities known in related trematodes. The following fish are known hosts: Salmo sebago, Osmerus mordax, Esox reticulatus, Anguilla chryspa, Perca flavescens, Esox lucius, Amiatus calvus, Esox masquinongy, Salvelinus namaycush, Lucioperca sp. ; Micropterus dolomieu. 199] SOME NORTH AMERICAN FISH TREMATODES—MANTER 13 AZYGIA ROBUSTA ODHNER 1911 Odhner (1911b) established the species, A. robusta, "mit einer gewissen Reserve." This form (from the salmon) differs from A. lucii apparently in attaining a somewhat greater length (to 47 mm.) and in possessing a spherical although "mitunter etwas langer als breit" pharynx. The latter feature is the chief one upon which the species is founded. Odhner in his "ziemlich reichlichen Material" never finds the pharynx twice as long as wide, while in the material (A. lucii) from the pike, the pharynx is never spherical but always elongate. In a postscript, Odhner claims a substantia- tion of this new species on the character of the pharynx. As he gives no further specific differences between the new species and A. lucii it is to be inferred that the two are similar in other respects. This distinction on pharynx shape introduces a new possible taxonomic factor for the group. The following measurements from favorable total mounts and cleared specimens might help in estimating the value of this character. The longitudinal axis of the pharynx is the first measurement given in each case. All measurements are in millimeters. 0.54X0.39 0.56X0.37 0.46X0.41 0.18X0.18* 0.24X0.16 0.20X0.18f 0.18X0.16f 0.22X0.16 0.18X0.15 0.46X0.37 Olodistomum cestoides 0.48X0.39 0.71X0.56 0.54X0.50f 0.50X0.29 0.18X0.15 0.56X0.39 0.24X0.18 0.52X0.43 0.46X0.35 0.37X0.29 0.37X0.24 0.35X0.26 0.43X0.37 0.37X0.37* 0.35X0.28 0.56X0.46 0.74X0.56 0.74X0.74* 0.44X0.31 A. sebago 0.35X0.20 0.28X0.37* 0.18X0.11 0.37X0.20 0.46X0.28 0.28X0.18 0.37X0.28 0.28X0.22 0.28X0.20 0.20X0.14 A. bulbosa 0.31X0.31* 0.20X0.22* 0.37X0.41* 0.29X0.22 0.29X0.28f 0.41X0.41* A. acuminata 0.41X0.26 0.37X0.35f 0.37X0.31 0.18X0.18* 0.27X0.27* 0.31X0.24 0.46 X 0.45 f 74 ILLINOIS BIOLOGICAL MONOGRAPHS [200 A. loossii Cooper's A. lucii Dist. longum Leidy 0.18X0.14 0.62X0.37 0.65X0.50 0.18X0.14 0.65X0.43 0.65X0.46 0.18X0.13 0.48X0.29 0.37X0.27 0.40X0.31 0.37X0.34f 0.32X0.27 * indicates that the pharynx is at least as wide as long, f indicates that the pharynx is practically as wide as long. A study of these figures shows that in no American species does the pharynx measure twice as long as wide; that it is ovoid rather than cylindri- cal; and that in all cases it may assume an almost spherical shape. For the European species, A. lucii, Looss (1894) describes the pharynx as cylindrical and his figure shows its length to be twice its width. Of this species Odhner (1911b:520) says: "Pharynx immer langgestreckt, etwa doppelt so lang wie breit, bei 18-22 mm. langen Exemplaren 0.6-0.8 mm. lang und 0.35- 0.45 mm. breit." Accepting these records, there appears to be rather definite difference between A. lucii and all American species in the shape of the pharynx. Odhner's A. robust a resembles the American species in this respect. In view of the range of variability shown by the above measure- ments, this feature becomes of questionable specific value, particularly when considered alone. But until further comparisons with numerous specimens of European forms are made, the conclusions of Odhner will be accepted. AZYGIA PERRYII FUJITA 1918 Fujita (1918) described this species from a fresh-water fish, Hucko perryi Breevoort, sent him by a friend. Fujita found the trematode attached to the external surface of the fish especially to the pectoral fin, oral cavity, buccal cavity, and outer and inner surfaces of the operculum and gills. This location of the parasite, although emphasized by Fujita, is, of course, of no significance since Azygia species normally inhabiting the anterior regions of the digestive system often migrate forward into the oral cavity and hence to the exterior. Such migration was noted as conspicuous in A. sebago by Ward (1910). Fujita compares a few relative measurements of his form with A. lucii and A. sebago. His table of comparison follows. The figures are in per- centages presumably based upon body length. 201] SOME NORTH AMERICAN FISH TREMATODES—MANTER 75 A. perryii Average A. sebago Average A . lucii Distance between oral and ventral suckers 18 19 17 IS 18 18% 16 22 24 11 19 18% 24 Distance from an- terior tip to center of ovary 54 53 47 50 49 51%* 54 56 54 63 66 59% 63 Center of ovary to center of post, tes- tis 62 59 59 57 58 59%* 65 65 66 77 74 69% 74 Breadth behind ventral sucker 14 14 14 12 15 14% 16 21 17 6 19 16% 8 * These two numbers are interchanged in the original table, but it is obvious that this is due to misprinting. Fujita concludes from these figures that his species "has a resemblance to the American species in the distance between suckers and breadth of body, but in the location of the reproductive organs, which is very im- portant, it is entirely different from the American species. On the other hand, the European species resembles closely the American species in positon of reproductive organs, and on other points it differs from both American and Japanese forms." He does point out that these percentages are of comparative value only, since they will vary according to the methods used in preserving the specimens. But Fujita's conclusions from his table are open to still more serious objections. The number of specimens compared is small as measurements of the single case of A. lucii were calculated from the figure by Looss (1894). Furthermore, all of the characters considered are influenced by different degrees of contraction and a contraction of any particular region of the body would alter such percentages. This fact might account for the high variation in the figures for A. sebago. But still more important, an analysis of the figures as they stand shows no valid differences between the three forms. The figures for A. sebago cover a range which includes figures for both the other forms in every character considered except "center of ovary to center of posterior testis" where 62% in A. perryii is the nearest approach to 65% in A. sebago. It is quite unexplained how "the position of the re- productive organs" in A. perryii is "entirely different" from the other two species. The derivation of the percentages in the character dealing with this distance from the ovary to the posterior testis is also not clear. The percentages (62% to 74%) certainly cannot be in relation to body length as the other figures appear to be, and 6.2% to 7.4% likewise are inappro- priate for such ratio. 76 ILLINOIS BIOLOGICAL MONOGRAPHS [202 Two type specimens of A . perryii in the Ward Collection* were available for study. Measurements of these specimens are as follows: Length 8.6 mm. 5 . 6 mm. Width 1.3 0.8 Oral sucker 0.78 0.58 Acetabulum 0.6 0.48 Post, edge acetab. to mid. ovary- 2. 1.06 Post, edge acetab. to anterior end 2.18 1.8 Post, edge acetab. to most ant. vitellaria right: left: 0.18 0.56 0.09 Post, edge testis to post, end 3.1 1.9 Vit. on left beyond testis 0.74 0.84 Vit. on right beyond testis 0.2 •1.3 Pharynx 0.317 X 0.28 0.24 X 0.11 Fujita figures the vitellaria as terminating posteriorly in the immediate neighborhood of the posterior testis. I found that the posterior extent of the vitellaria was only slightly beyond the testis in the 8.6 mm. specimen, although they extended slightly over 1/2 the distance between this point and the posterior end on one side only in the 5.6 mm. specimen. In respect to this important point, Fujita says: "The posterior extent (of the vitel- laria) extends somewhat farther down than the posterior testis" and adds that the vitellaria "do not extend posteriorly as far as in the American form." Since it has been seen that the vitellaria in A. lucii may extend some distance beyond the hind testis, it is apparent that A. perryii is like A. lucii and different from the American species in this respect. Concerning the anterior extent of the vitellaria, Fujita says they reach "to near the posterior end of the ventral sucker," and concludes that this limit is further anterior than is reached by the European species. Looss describes them (in A. lucii) as failing to reach the acetabulum by a distance about equal to its diameter (his figure shows them ending posterior to such a point), and this is about their anterior extent as figured by van Beneden (1858). Although in the Japanese material they reach somewhat nearer * Collection of Dr. H. B. Ward, vial No. 18.83. 203] SOME NORTH AMERICAN FISH TREMATODES—MANTER 77 the acetabulum, the slight difference in this extent could not separate Fujita's form from the European. Pharynx measurements of the two specimens in the above table showed one elongate pharynx and one ovoid. Fujita gives 0.29 by 0.2 mm. Fujita's egg measurement was 0.058 by 0.033 mm. which is larger than the egg size in A. sebago, but about the size attained in the American form from the pike. Looss gives 0.045 by 0.023 mm. for A. lucii. Hence, in egg size the Japanese appears to differ from the European form, but that this distinction may not be a valid one has been indicated in the preceding comparison of American forms. Fujita records the presence of the internal longitudinal muscles as described by Ward. He noted also that these muscles were located much more deeply (i.e., farther from the surface) on the dorsal side than on the ventral side. Thus, dorsally the cortical body region measured 0.21 mm., while on the ventral side this same region measured only 0.13 mm. in thickness. Such a condition was not true in American forms I studied. Leuckart's diagram of a cross-section of A. lucii is like A. sebago in respect to position of these muscles. Some variation in their position is probably accidental. AZYGIA VOLGENSIS (V. LINSTOW) ODHNER 1911 Synonyms: Ptychogonimus volgensis v. Linstow 1907 Distomum volgense (v. Linstow) Liihe 1909 Odhner states that this species (from Lucioperca sandra) appears to be a true form. Apparently only very few specimens are known, v. Linstow studying only one. "Luhe's (1909) description is based on von Linstow's. Odhner (1911b) does not state the number or source of specimens he studied. His description is, however, very brief." It is certainly very close to A. lucii and no important distinction can be determined between the two from their descriptions. The length of A. volgensis is 5 mm. according to Odhner, and 6.2 mm. according to v. Linstow. Odhner contrasts "Eipro- duktion" in A. volgensis at 2 mm. with this condition at 5 to 6 mm. in A. lucii, an entirely meaningless feature, in view of the variation the condition shows in American forms. These two European species should be further studied. On the basis of present evidence A. volgensis must be regarded as a doubtful species. 78 ILLINOIS BIOLOGICAL MONOGRAPHS [204 SYNOPSIS OF THE GENUS AZYGIA A key to the species of Azygia (including the several doubtful European species which might represent the single form, A. lucii) follows: Vitellaria not extending appreciably posterior to the hind testis Body length about 6 mm.; sexually mature at 2 mm A. volgensis (v. Linst.) Body length up to 30 mm. or more Pharynx elongate, twice as long as wide; eggs 45 by 23/jl A. lucii (Muell.) Pharynx globose; eggs? A. robusla Odhner Eggs 58 by 33/ji A. perry ii Fujita Vitellaria extending considerably posterior to the hind testis, usually at least half way between this point and posterior end of body Acetabulum near middle of body; gonads near posterior tip. .A. angusticauda (Staff.) Acetabulum distinctly nearer the anterior end; gonads anterior from posterior tip by about 1/3 ot 1/4 the body length Body relatively wide; vitellaria beginning close behind acetabulum; neck usually constricted; internal parenchyma muscles weak; eggs about 64 by 33/t.... A . acuminata Goldberger Body often extremely elongate; vitellaria usually beginning some distance posterior to acetabulum; internal parenchyma muscles strongly developed; eggs variable in size (up to 63(i in length), usually about 48 to 55^ by 28 to 30/z A . longa (Leidy) 205] SOME NORTH AMERICAN FISH TREMATODES— MANTES. 79 A GENERAL STUDY OF SOME MARINE FISH TREMATODES Most of the following trematodes were collected at the Mount Desert Island Biological Laboratory during the summer of 1924. A brief account of these parasites has already been published (Manter 1925). The following descriptions give more complete data on them. A few trematodes from fish of the Woods Hole region are also considered. The study of these forms is based on specimens from the collection of Dr. Henry B. Ward. Extended descriptions are given only to those forms which are new or which have been briefly or incompletely described in the literature. Following the systematic arrangement adopted by Nicoll (1915) for trematodes of British fish, the forms studied would be grouped as follows: Order: DIGENEA Sub-order: Prostomata Super-family: Distomata Family: Allocreadiidae Sub-family: Allocreadiinae Genus: Podocotyle 1. P. alomon 2. P.olssoni Sub-family: Stephanochasminae Genus: Stephanochasmus 1. S. baccatus Sub-family: Lepocreadiinae Genus: Lepidapedon 1. L.rachion 2. L. clongatum Genus: Homalometron 1. H . pallidum Family: Zoogonidae Sub-family: Lecithostaphylinae Genus: Steganoderma 1. S.formosmn Family: Siphoderidae* Genus: Siphodera 1. S.vinaledwardsii Family: Azygiidae Genus: Otodistomum 1. O.cestoides Family: Hemiuridae Sub family: Hemiurinae Genus: Hemiurus 1. H.lcvinscni * Odhner may be correct in not recognizing this family. 80 ILLINOIS BIOLOGICAL MONOGRAPHS [206 Sub-family: Sterrhurinae Genus: Brachyphallus 1. B. crenatus Sub-family: Lecithasterinae Genus: Lecithaster 1. L. gibbosus Genus: Aponurus 1. A.sphaerohcithus Sub-family: Syncoeliinae Genus: Derogenes 1. D. various Genus: Genolinea 1. G.laticauda Genus: Gonocerca 1. G.phycidis Sub-family: Accacoeliinae Genus: Hirudinella 1. H. fusca Unclassified genus: Deropristis 1 . D. inflata Order: MONOGENEA Family: Tristomidae Sub-family: Acanthocotylinae Genus: Acanthocotyle 1. A.verrilli Family: Octocotylidae Sub-family: Octocotylinae Genus: Dactycotyle 1. D. minor THE GENUS PODOCOTYLE Stafford (1904) records "Sinistroporns simplex Rud." from seven different Canadian marine fish. He comments: ". . . . genital pore to the left from the origin of the caeca in all specimens examined," and on this basis seems to found the new genus, Sinistroporus. The species is evidently the Dist. simplex Rud. that Linton describes from various fish of the Woods Hole region. The sinistral position of the genital pore is not sufficient, however, to separate the form from the genus Allocreadium in its older sense. Odhner (1905) considers Dist. simplex Rud. as probably synonymous with Podocotyle atomon (Rud.) and he also includes Dist. simplex Rud. of Levinsen (1881) as a synonym. Odhner redescribes the genus Podocotyle with Dist. atomon Rud. as type. Podocotyle, originally a sub-genus of Dujardin's, was listed as a genus by Stossich in 1892. Stiles and Hassall (1898) established as type of this genus Dist. angulatum Duj. This species is, however, a species inquirenda, and Liihe (1900:491) remarks: Das endgultige Schichsal der Gattung ist demnach abhangig davon, dass diese Spec, inquir. einmal wieder gefunden 207] SOME NORTH AMERICAN FISH TREMATODES—MANTER 81 und dann auch wieder erkannt wird." According to Odhner (1905:321) this type material has been permanently lost, and the species is insufficiently described. He therefore assign: Dist. aiomon Rud. as type species of Podocotyle. At any rate, the forms described as Sinistroporus are without doubt members of this genus as separated from Allocreadium. Such a synonymy is recognized by Nicoll in 1909 when he lists Sinistroporus Staff, as synonymous with Podocotyle (Duj.) Odhner. In an earlier paper Odhner (1901) had considered Allocreadium atomon (Rud.) as a highly variable species and recognized three varieties. In 1905, he determines Podocotyle atomon (Rud.) ( = Allocreadium atomon (Rud.) Odhner 1901, e.p.) as a fixed species and his earlier varieties he considers as true species. The diagnosis of the genus Podocotyle as given by Odhner (1905) is as follows: "Body elongate, quite evenly wide, sometimes flattened and ribbon-like, sometimes cylindrical. Esophagus at most twice as long as pharynx, forking in front of the ventral sucker. Genital pore to the left, lying at the level of the esophagus. Excretory vesicle reaching to the ovary. Cirrus-sac elongate, reaching at maximum as far as half way between ventral sucker and ovary. Seminal vesicle long, coiled. Pars prostatica lacking. Cirrus of marked length, straight. Ovary three-lobed. Vitellaria normally not reaching anterior to ventral sucker. Eggs without filament. In intestine of marine fish. Type species P. atomon (Rud.) Other species, P. reflexa (Crep.), P. olssoni Odhner ( = Dist. simplex Olss. 1868 e.p.)." Odhner refers to Linton's form as either identical with P. olssoni or closely related to it. Two species of Podocotyle were found in the present collection and these tend to confirm the constancy of the specific nature of the characters given by Odhner. In P. atomon the vitellaria are unbroken and do not come together between the testes; the testes are relatively small, not occupying over one half the cross-section of the body; the esophagus is longer than the pharynx; and the cirrus sac over-reaches the ventral sucker by a short distance. In both P. reflexa and P. olssoni, the vitellaria are broken near each testis and come together between these organs; and in both species also the testes are large, occupying a great part of the body in cross-section. P. reflexa differs in being cylindrical. It also has an esophagus longer than the pharynx. P. olssoni possesses and esophagus only as long or even shorter than the pharynx; and has a seminal vesicle reaching about half way between ventral sucker and ovary. PODOCOTYLE ATOMON (RUDOLPHI 1802) [Fig. 49] From intestine, Pholis gunnellus (Butterfish) From intestine, A narrhichas lupus (Wolf fish) One specimen of this species was taken from each of two butterfish of ten examined. These trematodes measured 2.37 mm. and 2 mm. in length. 82 ILLINOIS BIOLOGICAL MONOGRAPHS [208 Both of the specimens agreed in detail with Odhner's description of the species, with long esophagus, small testes, and unbroken vitellaria (Fig. 49). In one specimen the body was somewhat contracted and in this case the esophagus coiled somewhat instead of shortening with contraction, so that its length could be easily distinguished as about twice that of the pharynx Cooper (1915) reports one young specimen of Sinistroporus simplex from the butterfish, but it is very probable that he was dealing with the same species now being considered. Both of the present specimens were fully mature. The single specimen from the wolf-fish measured 3.06 mm. in length and 0.57 mm. in width. The esophagus was twice the pharynx length. The testes occupied about half the body width and were slightly lobed or crenulated as Cooper noted for Sinistroporus simplex. There was a slight break in the vitellaria opposite the hind testis, and the follicles approached each other between the testes. In these respects, the form showed a tendency to assume characters of P. olssoni, although these features are more marked in the latter species. In view of this possible variation of the vitellaria, the esophagus length seems to be the most useful distinction between the species. PODOCOTYLE OLSSONI ODHNER 1905 [Fig. 50] From intestine, Urophycis tenuis (Hake) " " Myxoccphalus groenlandicus (?) (Sculpin) " " Gadus callarias (Cod) " " Microgadus tomcod* (Tomcod) Woods Hole This trematode is a very common species. Fig. 50 shows the typical appearance of the material from the hake. The differences between this species and P. atomon have already been pointed out. The specimens from the hake show these differences most constantly and clearly. The esophagus is short (not longer than the pharynx); the seminal vesicle reaches to a point about half way between ventral sucker and ovary; the testes are large; and the rows of vitellaria are broken opposite each testis. The size was from 2.8 to 4 mm. in length by 0.4 to 0.58 mm. in width. The ventral sucker is prominent, usually somewhat protruded, and longer in its cross- diameter. It is almost exactly twice the size of the oral sucker. In one specimen the body wall about the sucker formed a slightly projecting fold around the sucker. Material from the cod (which were of small size) agrees with the Woods Hole material from the tomcod. These forms show a few slight differences from the clear-cut specific characters of the form from the hake. The short * Collection of Dr. H.B.Ward, vial No. 13.75. 209] SOME NORTH AMERICAN FISH TREMATODES—MANTER 83 esophagus, however, is a constant character in which all agree. The breaks in the rows of vitellaria can usually, but not always, be discerned in the cod trematodes. The one or two cases wherein the follicles appeared con- tinuous were of somewhat contracted specimens. The forms from the cod were all small in size. They measured 1.28 to 1.6 mm. by 0.26 to 0.3 mm. The seminal vesicle did not quite reach to a point half way between ventral sucker and ovary. All of these forms also show two regions of slight body contraction, one about at the level of the posterior testis, the other usually slightly in front of the anterior testis. Figure 50 shows this condition only slightly evident. Sometimes it is conspicuous. Odhner does not mention it, nor does Linton, although the condition is shown in the figure of his Dist. simplex from the tomcod (Linton 1898, pi. 47, fig. 3). From Linton's description and figures there can be no doubt that his Dist. simplex (Linton 1898:525) is the same species as the present form from the tomcod. Linton records a length up to 2.4 mm., which approaches the size of the material from the hake. The egg size in all forms agrees, being 70 to 80 by 37 to 40^. Considering the above characteristic features, there can be little doubt that all the forms belong to the species, P. olssoni. STEPHANOCHASMVS BACCATUS NICOLL 1907 [Figs. 51-521 From intestine, Hippoglossus hippoglossus (Halibut) Five specimens of this trematode were obtained from the intestine of a single halibut. The largest specimen containing about 12 eggs measured 2.18 mm. in length. The smallest containing one imperfect egg was about 1.3 mm. in length. Measurements on the large specimen are as follows: Length 2.187 mm. Width 0.467 Oral sucker 0.176 Ventral sucker 0.256 Pre-pharynx 0.2 Pharynx 0.199 by 0.119 Eggs 85 to 91 by 45 to 51 M Length of spines in posterior row 34m Length of spines in anterior row 28m In two specimens the number of spines in the oral ring was 29, but that this number may vary is shown by the fact that only about 25 spines were found in a third specimen. Nicoll found from 28 to 30 spines. The ring is unbroken, and the spines in the posterior ring are larger than those in the anterior ring. The characteristic shape of the egg with one pole flattened was noted (Fig. 52). This condition at first seemed due to contraction, but Nicoll 84 ILLINOIS BIOLOGICAL MONOGRAPHS [210 reports it as specifically characteristic. In cross-section the eggs show a peculiar star-shaped outline (Fig. 52), which is evidently characteristic for all species in the genus. LEPIDAPEDON RACHION (COBBOLD) STAFFORD 1904 [Figs. 45-46] Syn.: Lepodora rachiaea (Cobbold) Odhner 1905 From intestine, Melanogrammus aeglifiuus (Haddock) This trematode is fairly common and well known. Nicoll and Lebour each report it as common in the haddock of the English coast. Infection, however, is always light, usually only from one to three trematodes being found in a host. Its presence might accordingly be easily overlooked. In the present collection, two specimens were found from one host, and one each from two others. It is reported by Stafford (1904) from the same host. Stafford gives it the new generic name, Lepidapedon (for the form pre- viously known as Dist. Tachion Cobbold), but gives no description. Odhner (1905) gives a complete and carefully worked out description of the form which he named Lepodora rachiaea (Cobbold). In spite of the extent of Odhner's work, Stafford's name, Lepidapedon, holds priority and has been accepted by Nicoll and others. Stafford gives the measurement of 5 by 1 mm., but my specimens agree more nearly with those of Odhner who gives a length of 1.5 to 3.5 mm. with a width varying from 1/5 to 1/4 this measurement. The following measurements show general proportions: Length 2 . 59 mm. Width 0.46 Oral sucker 0.24 Ventral sucker 0.18 Pre-pharynx . 285 Pharynx 0.19 by 0.17 X-diameter, ovary 0.11 X-diameter, ant. testis 0.17 X-diameter, post, testis 0.17 Length, sem. ves . 285 Cirrus sac 159 by 114/i Eggs 65 by 34ji The morphology of the species is well known and the present material showed no new features. Most characteristic is the glandular mass of cells surrounding the seminal vesicle, and the location of the vitellaria ventral to the intestinal ceca. Two other species of this genus have been described. Leiper and Atkinson (1915) describe a trematode which they name Lepodora garrardi. The corrected name would be Lepidapedon garrardi (Leip. and Atkin.). The description is not complete in regard to some points and indicates 211] SOME NORTH AMERICAN FISH TREMATODES—MANTER 85 (as the figure also shows) that their form approaches the genus Lepo- creadium which it resembles in body shape and shortened pre-pharynx. No mention is made of any glandular cells surrounding the seminal vesicle. Odhner mentions one other species but does not describe it. Miss Lebour in 1908 names a species Lepodora elotigata ( = Lepidapedon elongatum (Lebour)), and this species she suggests might be the form mentioned by Odhner. It differs from L. rachion by being more elongate in form, possess- ing a long esophagus, and with somewhat less extensive vitellaria. Several specimens, agreeing in most of these points are found in the present collection and were referred to this species. LEPIDAPEDON ELONGATUM (LEBOUR 1908) [Figs. 47-48] Syn.: Lepodora elotigata Lebour 1908 From intestine, Urophycis tenuis (Hake) Five specimens were collected from one out of three fish examined. The trematode shows close resemblance to L. rachion in general form, shape, arrangement of organs, and spiny cuticula, but differs from it in the length of the esophagus, extent and position of the vitellaria, and develop- ment of the glandular cells about the seminal vesicle. Also, the genital pore in this species is closer to the ventral sucker than in L. rachion. These same differences separate Miss Lebour's Lepodora elongata from L. rachion. The present form differs only in not being more elongate than L. rachion, but this point is one which may be influenced by age of the parasite or by body contraction. Typical measurements are as follows: Length 2.4 mm. Width 0.54 Oral sucker 0.119 Ventral sucker 0. 14 Pre-pharynx 0. 125 Pharynx 0.09 Esophagus 0.091 X-diameter, ovary 0.29 X-diameter, ant. testis 0.31 X-diameter, post, testis 0.37 Miss Lebour does not record the position of the vitellaria in relation to the ceca. As has been noted, in L. rachion the vitellaria are ventral to the ceca. In the present form, this condition did not hold but the vitellaria were found distributed on both sides of the intestine. They extend an- teriorly at least to the ventral sucker in L. rachion, but fail to reach the level of this sucker in L. elongatum. Another conspicuous difference between the two species is found in the character of the glandular mass surrounding the seminal vesicle. The cells in this mass are large, globular, 86 ILLINOIS BIOLOGICAL MONOGRAPHS [212 and numerous in L. rachion (Fig. 46), but are much reduced in L. elongatum where they are very inconspicuous (Fig. 47). In this respect, L. elongatum approaches the related genus Lepocreadium. My material also resembles Miss Lebour's and differs from L. rachion in that the testes are separated from each other by a distinct space. The pharynx is considerably smaller than in L. rachion. HOMALOMETRON PALLIDUM STAFFORD 1904 [Figs. 54-56] From intestine, Fiindulus heieroclitus This species is the same form referred to by Linton (1901:422, pi. 32, Fig. 354) and named Uomalome.tr on pallidum by Stafford in 1904. Stafford does not describe the genus or species, merely referring to Linton's paper. Linton's description is as follows: "Body very minutely spinose, white translucent; acetabulum and oral sucker about the same size; outline of body, long oval; neck short, continu- ous with body; greatest breadth in region of testes, near posterior end; ecaudate; acetabulum sessile; rami of intestines simple, elongate; esopha- gus as long as pharynx; testes two, in median line behind uterus; seminal vesicle dorsal to ovary and posterior border of acetabulum; ovary between acetabulum and testes, on right side; pharynx sub-globular; genital aperture in front of acetabulum, on median line; vitelline glands lying at posterior end and along sides of body as far as acetabulum; ova, few, relatively large. Dimensions of specimen in formalin, given in millimeters: Length 2.72; breadth, anterior 0.43, at acetabulum 0.89; middle 1.07, near posterior end 0.36; diameter of oral sucker 0.26; diameter of acetabulum 0.29; diameter of ovary 0.21; diameter of testes 0.33 and 0.39; ova 0.11 and 0.07 in the two principle diameters." Looss (1907:613-14) criticizes Stafford for establishing a genus without description. As Looss shows, the trematode seems to agree with the genus Lepocreadium Stoss. This genus was established in 1903, or prior to Stafford's Homalometron. The genus Lepocreadium contains the following species: L. album (Stoss.), L. pegorchis (Stoss.), L. India (Lint.) and L. levinseni (Lint.). Odhner (1905) erects a new sub-family of the Allocreadiidae, Lepo- creadiinae, for this genus and Lepidapedon ( = Lepodora). In a later paper (1914) Odhner identifies the cercaria of Lepocreadium album, the type species, and gives an account of the morphology of the adult As is common, some of the most distinctive characters of the genus are found in the distal male genital apparatus. The present form is strikingly like the genus Lepocreadium. It shows similar size, form, spiny cuticula, suckers, digestive system, excretory 213] SOME NORTH AMERICAN FISH TREMATODES—MANTER 87 system, vitellaria, and position of the gonads. So far as the description of Linton shows, the form could easily belong to this genus, the chief point of difference being the median location of the genital pore instead of a position to the left, as in Lepocreadium. This pore was clearly median also in my material. The most important features were found in the male reproductive apparatus. In Lepocreadium a prominent cirrus sac is present. It encloses the prostate gland and an anterior region of the seminal vesicle, which is thus divided into two parts. In the form from Fundulus, however, the cirrus sac is entirely absent. The seminal vesicle is globular and swollen in form and is not divided into two regions (Fig. 55). It opens directly into the pars prostatica, the glandular cells of which lie free in the parenchyma at about the level of the ventral sucker. The prostate gland is poorly developed. The vagina seems to join the male duct shortly beyond the prostate gland and there is a long genital sinus. The absence of a cirrus sac would seem to be of generic significance and, in fact, together with the median genital pore, violates the sub-family diagnosis. Other features of the trematode are so similar to Lepocreadium that it must be considered a very closely related genus. The seminal receptacle is large and located close behind the seminal vesicle, as in Lepocreadium. A short Laurer's canal is present. No spines could be detected in the cirrus or vagina. The yolk reservoir is large and located posterior to the ovary. The eggs are very large. A specimen with only two eggs showed them to be fully as large or even larger than the ovary. The spiny or scaly cuticula layer is very evanescent as has been noted for Lepocreadium, and may be lost in preserved material. It is most conspicuous on the dorsal anterior regions and thins out in the tail region. The glandular mass about the posterior tip of the excretory vesicle is present as in Lepocreadium. Very young forms of this distome were sometimes found in large numbers embedded in the intestinal folds of the host. Moreover, from the stomach of the fish cysts were found which clearly contained this trematode as shown by the finely spined cuticula of the cercariae within the cysts. As the Fundulus had been in salt water aquaria for some time, the indica- tion is that infection is derived from marine rather than from fresh water sources. In spite of the fact that immature specimens were sometimes found in large numbers, infection with the adult form was never heavy, and many uninfected fish were found. Usually not more than two or three specimens were taken from one host. 88 ILLINOIS BIOLOGICAL MONOGRAPHS [216 STEGANODERMA FORMOSUM STAFFORD 1904 [Figs. 58-60] From pyloric ceca, Hippoglossus hippoglossus (Halibut) Six specimens of this interesting trematode were obtained from the ceca of a single halibut. The only description of the form seems to be by Stafford who also found it in the ceca and intestine of the halibut. The taxonomic position of this trematode is very close to the genus Lecithostaphylus Odhner 1911 (Odhner 1911a) which it markedly re- sembles, but from which it differs in certain distinct characters. The genus Lecithostaphylus is placed by Odhner in the family Zoogonidae, and, indeed, is used as a basis for a new sub-family, Lecithostaphylinae. In- cluding the present genus, the family contains the following genera: Family: Zoogonidae Sub-family : Lecithostaphylinae Genus: Lecithostaphylus Steganoderma Proctophan tastes Lepidophyllum Sub-family: Zoogoninae Genus: Diphterostomum Zoogonoides Zoonogenus Zoogonus Odhner places Lecithostaphylus "an die Spitze der Familie" and from this genus assumes that the entire family might be derived from the, Fellodistominae (Steringophorinae of Odhner*) with which it agrees in genital and digestive systems. In the Fellodistomidae, the cirrus is short and wide, a condition occurring also in Lecithostaphylus but differing from its elongate form in the remaining genera of the Zoogonidae. Stegano- derma combines the elongate cirrus with marked similarities to Lecitho- staphylus, and hence represents a step between the latter and other genera of the sub-family. An outline of the genus based on Stafford's description with some additions might be as follows: Body elongate, regular in outline, flattened, both ends regularly rounded, anterior end slightly broader. Scale-like spines covering body to near the posterior end. Suckers about equal in size, ventral sucker a little more than 1/3 from the anterior end. Very small pharynx, long esophagus, ceca extending slightly more than half the body length. Ovary median or to one side, just posterior to the ventral sucker. Testes side by side at ends of ceca. Uterus between testes and filling posterior body. Cirrus sac somewhat elongate, almost straight, * Nicoll (1913) is correct in pointing out that Odhner is not justified in changing Fello- distominae Nicoll to Steringophorinae. 215] SOME NORTH AMERICAN FISH TREMATODES—MANTER 89 reaching posteriorly to and sometimes overlapping the ventral sucker, crossing left cecum between ventral sucker and the forking of the intestine. Genital opening ventral and to the left about half way between cecum and margin of body. Vitellaria lateral, reaching only from ventral sucker to the testes, composed of a few large follicles. Laurer's canal present. Type species: S. formosum Stafford. This genus is like Lecithostaphylus Odhn. in body shape, size, spiny cuticula, intestine, gonads, vitellaria, and uterus; but differs from it in possessing a very small pharynx, long esophagus, elongate cirrus, well developed excretory bladder, and Laurer's canal with pore. The following measurements are from an average sized specimen: Length 3.25 mm. Width 0.86 Thickness 0.2 to 0.28 Oral sucker 0.224 Ventral sucker 0.24 Diameter of ovary 0. 26 Diameter of testes . 355 Pharynx 97 by 68/x Esophagus 0.285 Eggs 34 by 17/x There is no pre-pharynx. The posterior end of the esophagus splits into two short branches each about 46/x long. That is, the intestine proper does not begin at the point of bifurcation, but the esophagus histologically extends slightly beyond this point. The excretory system is simple, expanded tube-like in form, and extends from the posterior tip almost to the posterior border of the ventral sucker where it spreads out laterally, T-like. It lies mostly dorsal to the uterus. Near its anterior end it becomes so swollen as to fill the larger part of a cross-section of the body in that region. It here comes in close contact with the intestinal ceca from which it is separated by a very narrow distance (Fig. 59). An excretory duct at the posterior tip of the vesicle is lined by a cuticula-like layer continuous with the external body cuticula. In the parenchyma about this duct appear what seem to be gland cells, pyriform in shape and with large nuclei (Fig. 60). Within the parenchyma, in the anterior body region, especially in the vicinity of the esophagus, numerous, conspicuous, round to oval bodies occur. They are without nuclei and their content is very finely granular and homogeneous. They exhibit a very strong affinity for eosin stain, which colors them immediately and tenaciously. These bodies which almost fill the parenchyma anteriorly thin out posteriorly, and disappear at about the level of the ventral sucker. Their size varies, being about 13 to 39/i in longest diameter. The nature and function of these bodies could not be determined. They were not found in any other trematode 90 ILLINOIS BIOLOGICAL MONOGRAPHS [216 of the present collection. The cells in the neck region of Siphodera de- scribed by Linton (1911) differ markedly from these bodies in appearance. In Siphodera, the cells have definite nuclei. The position of the ovary is just posterior to the ventral sucker, but it may be either median or slightly to one side. The ootype is small, without membrane, and lies posterior to the ovary. Laurer's canal is present, is only slightly coiled, and opens dorsally just posterior to the ovary. A sem- inal receptacle seems to be absent. The uterus leads posteriorly, coiling between the testes, filling the hind body, and returning to course ventrally over the ovary. The vagina begins at about the level of the ventral sucker, leads anteriorly and obliquely to the left parallel with the cirrus sac, to which it is at first lateral on the left and then dorsal. The male duct joins the vagina ventrally and there is a common genital sinus for a short distance about 60/x. The number of follicles in the vitellaria is fairly but not exactly constant. It is sometimes difficult to determine the exact number, as some follicles are seen to be double in nature, an indication of an evolutionary change either toward a more compact or a more diffuse condition of these organs. Eight or nine follicles were found on the right side and ten to twelve on the left. The two ducts from the testes arise from the anterior aspects of these organs and course anteriorly lateral to the excretory vesicle and between this organ and the ceca. The ducts unite just posterior to the termination of the excretory vesicle, and continue forward for some distance as a single duct in the mid-body region. At about the level of the anterior border of the ventral sucker this duct enters the muscular cirrus sac and becomes the seminal vesicle. This vesicle is poorly developed. It is scarcely, if any, coiled. A slight constriction separates it from the well-developed pars prostatica which, surrounded by gland cells, occupies most of the cirrus sac. The ejaculatory duct is unarmed. In the 3.25 mm. specimen the cirrus sac measured about 0.69 mm. in length and 0.19 mm. in width at its widest point. The seminal vesicle extended about 0.176 mm., the pars prostatica 0.34 mm., and the ejaculatory duct 0.17 mm. THE HEMIURIDAE The Hemiuridae include many of the most common marine trematodes. Typical members of the family are those forms with a "tail appendage" such as Hemiurus, Brachyphallus, and Dinurus. Liihe founded the family in 1901, and included in it also such forms as Derogenes and Accacoelium. Looss (1907a) later limited the conception of the family, excluding the two latter genera. Odhner (1911b) points out that Derogenes is so closely related to the other Hemiuridae that separation from that family is impossible. The inclusion of Derogenes necessitates the adoption of 217] SOME NORTH AMERICAN FISH TREMATODES—MANTER 91 Genarches and other Syncoeliinae. Odhner also included the Accacoeliinae and the HirndineUa clavata group. Nicoll reviews the status of the family and agrees with Odhner in accepting its broader conception according to which "Looss's Hemiuridae takes the position of a sub-family" (Nicoll 1913:245). Nicoll also extends the boundaries of the family slightly to include his genera, Hemipera and Derogenoides. The family has thus become so broad as to be very difficult to describe. At present, it must be considered as a large variable group, containing (Nicoll 1915) the following sub-families: Hemiurinae, Diurinae, Sterrhurinae, Lecithasterinae, Syncoeliinae, and Accacoeliinae. Considering Hirudinella as belonging in the last sub-family, members of each of these sub-families except Dinurinae have been met with in the present studies. A few words should be said in respect to the use of the term "cirrus sac" in this group (Hemiuridae). In the Hemiuridae, the two sex ducts unite to form a more or less elongate tube-like "ductus hermaphroditus" or genital sinus which leads to the common genital pore. This condition of the terminal genital region in the Hemiruidae has been rather fully discussed in the literature. Pratt (1898) reviews the situation and gives its history to 1898. Levinsen (1881) and Juel (1889) termed the common terminal portion of the genital tract the genital vestibule. It is perhaps now more commonly known as the genital sinus. Pratt and Juel both believe that the terminal portion of this vestibule or genital sinus has arisen as "an invagination of the body wall and is homologous to the genital cloaca of other trematodes." Juel believes that the remainder of the duct represents the distal end of the uterus which has come to serve as a genital sinus by the dropping back of the ejaculatory duct. Pratt, however, believes that it has been the uterus that has dropped back and hence that most of the sinus is homologous with the forward end of the ejaculatory duct. Whatever its origin, it is known that this genital sinus can function as a cirrus, and is protrusible. Looss noted such a functioning in 1896 for Apoblema mollis simum. Because the genital sinus functioned as a true cirrus, the muscular sac surrounding it he considered as a true cirrus sac. He says (p. 125): "Or, en ne tenant compte que de ses rapports avec le canal renferme, je crois deja pouvoir la considerer avec raison comme une veritable poche du cirrhe: ces fonctions viennent parfaitment a l'appui de cette interpretation." In the same discussion, however, Looss himself notes that the term is not strictly correct. Thus, in regard to "la poche du cirrhe," he says (p. 127): .... "a proprement parler ce terme n'est pas tout a. fait exact; mais connaissant maintenant ses rapports avec le reste des organes genitaux, nous pouvons nous en servir pour plus de simplicite." Other authors (e.g., Liihe 1901, Lander 1904, Odhner 1905, 92 ILLINOIS BIOLOGICAL MONOGRAPHS [218 Lebour 1908) agree in calling the muscular sac around the genital sinus a true cirrus sac. Strictly speaking, it does not seem appropriate to refer to this structure as a true cirrus sac. The cirrus is a definite organ belonging strictly to the male genital system. The genital sinus in Hemiuridae, although functioning as a cirrus and although probably homologous with the cirrus, cannot be termed a true cirrus, since it is a duct common to both male and female systems. It has never been referred to as a cirrus, but as the "genital sinus" or "ductus hermaphroditus." To call the sac surrounding it a cirrus sac is then a misnomer. Since this structure surrounds the genital sinus, it seems more appropriate to refer to it as a sinus sac. This sinus sac in Hemiuridae certainly functions as a cirrus sac, and is probably homologous with the cirrus sac. The difference is, however, a distinct one. For the expression of the association of the sac with a common sex duct instead of with the male duct alone, it is felt that the term "sinus sac" is justified. It has already been used by the present author in an earlier paper (Manter 1925). Some such term seems all the more advisable in view of the fact that in Nicoll's genus Hemipera a true cirrus sac appears to be present, containing "not only the ductus ejaculatorius but also the pars prostatica" (Nicol! 1913:245). HEMIURUS LEV IN SEN I ODHNER 1905 [Figs. 62-63] From stomach, Gadus callarias (Cod) From stomach, Urophycis chuss (Squirrel hake) Species of the genus Hemiurus are among the most common trematodes of marine fish. Distinction between species is, however, rather difficult. Looss in 1907 perhaps drew the most careful lines between species. It has been customary, especially previous to 1907, to refer most specimens which are clearly Hemiurus to the species appendiculatus. Thus, Stafford (1904) lists H. appendiculatus from ten different fish of Canadian waters. His only comment is: "Suckers of equal size." Looss shows that true H. appen- diculatus up to 1907 had probably been found only in Alosa finla. He adds the additional hosts, Gadus euximis and Mugil capito, in the latter of which the parasite might be accidental. The following are some of the most distinctive characters of B. ap- pendiculatus as given by Looss: Ventral sucker about twice as large as oral sucker; ringing of the cuticula disappearing dorsally at about the level of the pharynx; cirrus sac elongate, reaching a length about 3/4 the diameter of the ventral sucker; anterior part of the seminal vesicle very muscular; coils of uterus can stretch relatively far into the tail appendage, and come near the ends of the ceca. 219] SOME NORTH AMERICAN FISH TREMATODES—MANTER 93 All of the material collected from the Mount Desert Island region and belonging to the genus Hemiurus apparently belongs to the species, E. levinseni. The almost equal size of the suckers, with the oral sucker slightly larger is a constant character and one which separates the species from E. appendicualtus, E. communis, E. liihei, and E. rugosus. Since all of Stafford's representatives of this genus collected from Canadian fish show this character, it is very probable that they should belong in this species rather than in E. appendiculatus. Odhner reports E. levinseni from Gains morrhua f. ovak, Cottns scorpius, and "many northern fish." It seems to be the most common Hemiurus species in arctic marine fish. In temperate waters the other species showing larger ventral suckers and small oral suckers are common. Thus, Linton's Dist. appendiculatnm from Woods Hole fish shows a sucker proportion of about 1 : 2. Hemiurus levinseni also differs from E. appendiculatus in possessing a shorter prostate tube, in a more constantly retracted tail appendage into which the uterus does not commonly extend, and in the cuticular rings extending dorsally to the level of the ovary. In the present material, as in Odhner's, the tail was almost always completely retracted. The ceca may enter the tail slightly. In a single specimen the tail was fully extended and in this case both the ceca and a portion of the uterus extended into it (Fig. 62). The genital pore is median just behind the mouth opening. The genital sinus is long, and in contracted specimens the prostate tube does not begin until about the level of the ventral sucker. This tube is long and more or less curved according to body contraction. The seminal vesicle is large and divided into two sections, the anterior of which is surrounded by a muscular coat. The sizes of the specimens vary from 0.7 mm. to 1.68 mm. in length. Eggs measure- ments of 23 to 26 by 10 to 13,u agree well with Odhner's measurements of 26 to 28 by 12 to 13//. Eighteen specimens were taken altogether from the stomachs of six squirrel hake examined. Eight specimens were collected from three cod. Cooper (1915) reports this species encysted in the muscles of small herring. Measurements on four typical specimens are as follows: Length 1.68 mm. 1.12 mm. 1.06 mm. 0.99 mm. Width 0.467 0.37 0.374 0.37 Oral sucker 0.176 0.176 0.142 0.159 Ventralsucker 0.188 0.17 0.136 0.142 Pharynx 91by91/i 91by74/x 68by62/. 85by74 M Eggs 23 12/. 23 13/i 26 10-13/. 94 ILLINOIS BIOLOGICAL MONOGRAPHS [220 BRACHYPHALLUS CRENATUS (RUDOLPHI 1802) [Fig. 53] From stomach and intestine, Osmerus mordax (smelt) " a « Pollachias virens (Pollack) Chpea harengus (Herring) Lander (1904) has described the morphology of this form in detail. His material was also obtained from the smelt. In the present collection thirteen specimens were obtained from the stomachs and intestines of three smelt. Two other fish examined d.id not contain the trematode. The worms usually occur in the stomach. Looss (1907:158) expresses the view that the American form of this parasite represents a new species which he names B. affinis. He finds the chief distinction to be the elongate and less lobed condition of the vitellaria and that the host and geographical occurrence differ widely from the European B. crenatus from Salmo salar. Lander figures the vitellaria as about twice as long as wide in an extended specimen, and his description indicates that this is the usual condition. In regard to lobation of these organs, Lander says: "They are commonly slightly lobulated, though they sometimes have a regular oval outline." Cooper (1915) describes and figures one specimen from a small herring. This specimen agreed with B. crenatus in having definitely lobed vitellaria (right, four lobed; left, three lobed). He also points out that either gland may appear entire when viewed obliquely. He suggests that the herring may represent an inter- mediate host and that the trematode might be discovered in Salmo salar from America. The present material from the smelt agrees with descriptions of B. crenatus (Rud.). It is probably the same species collected by Lander from the same host. The vitellaria, however, in my specimens from the smelt were always distinctly lobed (Fig. 53), usually one being four-lobed, the other three-lobed. In none of the specimens were the vitellaria noticeably longer than wide. On the basis of these thirteen specimens from the smelt, it would appear that the American species is not distinguishable from the European species, B. crenatus. For hosts of Brachy phallus crenatus Odhner gives: Cottus scorpius, Pleuronectes limanda, Gasterosleus aculeatus, Ammodytes tobianus, Salmo salar and truita, and Osmerus eperlanus. Lander's material was from Osmerus mordax and Anguilla chrysypa. The smelt from which the present material was collected occurred in large numbers, together with small cod and pollack beneath the fishing wharf at Manset. All these fish were about the same size and evidently had similar feeding habits. The same trematode, Brachyphallus crenatus, was obtained from the stomach of the pollack, Pollachius virens, but not from the cod. Specimens from the pollack agreed in every respect with 221] SOME NORTH AMERICAN FISH TREMATODES—MANTER 95 those from the smelt. They were relatively small and usually contracted. The vitellaria were constantly lobed. Four fish yielded eleven trematodes. Eight or nine specimens were obtained from the examination of 28 herring (Clupea harengris). The much larger size of most of these trema- todes gave the impression of a different species, but the details of anatomy agreed with Brachyphallus crenatus. Moreover, the sizes agree with known limits for the species (Odhner recording a variation of 0.8 mm. to 2.5 mm. in body length, while Olsson gives 5 mm. as maximum length). Cooper (1915) found one small specimen in the stomach of the herring. The present collection of large mature specimens from this host indicates that the herring is a normal host for the parasite and not, at least exclusively, an intermediate host as suggested by Cooper. Only in material from the herring was variation in vitellaria shape noted. In these specimens, lobing of the vitellaria was not common. The characteristic four- and three-lobed condition was clearly evident, how- ever, in one specimen. The material from the herring agrees in this respect with Lander's description, although an elongate condition of the vitellaria was not common. LECITEASTER GIBBOSUS (RUDOLPHI 1802) [Fig. 61] From intestine, Myxoceplialus octodecimspinosus (?), Sculpin Looss (1907) gives the following synonyms for this species: Distomum mollissimum Lev. 1881 1 nee Distomum mollissimum Stoss. 1889 nee Apoblemamollissimum'Lss. 1896 Odhner (1905) reports this species from various northern fish (including Cottus scorpius). He separates the species from Lecithaster confusus Odhner. This latter species has the following synonymy: Apobhma mollissimum Lbs. 1896 nee Distomum mollissimum Lev. 1881 Hemiurus bothryophorus Lss. 1899 nee Distomum botryoplwron 2 Olss. 1868 3 A single specimen was collected from the intestine of one fish out of eleven examined. Stafford (1904) reports a species as Lecithaster bothryo- phorus Olsson ( — Apoblema mollissimum) from the salmon and herring. 1 This date printed 1891 was evidently a misprint. 2 Olsson originally spelled this name botryoplwron, but the word has been very commonly referred to as bothryophoron. Liihe (1901) called the species Lecithaster bothryophoron using it as type of the genus Lecithaster. Odhner (1905) shows this species to be actually Lecith- aster gibbosus (Rud.). 8 Given as 1S69. 96 ILLINOIS BIOLOGICAL MONOGRAPHS [222 Odhner (1905) assigned Lecithaster bothryophorus as the type of a new genus Lecithophyllum. As Apoblema mollissimum is a synonym of Lecithaster njusus, the actual identification of Stafford's material which is undescribed is unknown. Linton (1901 and 1905) reports Dist. bothryo- phoron from various fish, but to which species of Lecithaster his form belongs cannot be determined from his descriptions or figures. The two species Lee. confusus and Lee. gibbosus are closely related. The present specimen was assigned to the latter species because of the thickness of the ovarian lobes, the length of the vitelline lobes, and because the seminal vesicle did not extend posterior to the ventral sucker. Accord- ing to Looss, these three points are the chief means of distinction between the two species. Measurements on the specimen are as follows: Length 1.12 mm. Width 0.4 Oral sucker 0.17 Ventral sucker 0. 256 Pharynx 0.09 by 0.09 Eggs 23 to 26 by 15/i APONURUS SPHAEROLECITHUS MANTER 1925 [Figs. 70-74] From stomach, Urophycis tenuis (Hake) The genus Aponurus is considered by Looss (1907) as most nearly related to Lecithaster, although showing relationships to Brachyphallus. The only other species in the genus is A. laguncula Lss. The trematodes of this genus are small in size (about one millimeter in length) and almost cylindrical in form, tapering anteriorly but broadly rounded posteriorly. The ventral sucker, located about l/3 from the anterior end, is almost exactly twice the size of the oral sucker. The genital pore is about at the level of the pharynx. The genital sinus is surrounded by a conspicuous pear-shaped sinus sac. Vagina or metraterm is lacking or very short. Seminal vesicle rather short, swollen, mostly anterior to the ventral sucker. Testes, ovary, and vitellaria globular. The vitellaria are in two groups, one of four, another of three follicles. They are more or less spherical, and are located just posterior to the ovary. Coils of the uterus fill the body posterior to the vitellaria, but anterior to the ovary are more limited to the space between the intestinal ceca. The genus Aponurus bears close relationship to Lecithaster and Lecithophyllum. Lecithophyllum was created by Odhner (1905) for Olsson's Distoma botryophoron. Odhner studied Olsson's type material. The following table, showing differences between the three genera is based on data as given by Odhner and Looss. 223] SOME NORTH AMERICAN FISH TREMATODES—MANTER 97 Leciikophyttum Genital pore rather close to oral sucker Ovary entire Posterior end broadly rounded Pars prostatica shorter than genital sinus Genital sinus reaching al- most to ventral sucker Eggs large (60/j) thick- shelled Vitellaria elongate in 7 con- nected parts Aponurus Genital pore rather close to oral sucker Ovary entire Posterior end broadly rounded Pars prostatic as long as genital sinus Genital sinus reaching only about half way to ventral sucker Eggs small (26ju) Vitellaria rounded in 7 separate parts Lecithaster (1) Genital pore rather distant from oral sucker (2) Ovary 4-lobed (3) Posterior end tapering (4) Pars prostatica much longer than genital sinus (5) Genital sinus reaching about to ventral sucker (6) Eggs small (15 to 25m) thin- shelled (7) Vitellaria elongate in 7 con- nected parts The significance to be attached to the distinctly separated nature of the follicles of the vitellaria might be questioned and perhaps should not be considered as of generic value. Looss himself brings up this question. In his discussion of Lecithaster he says (Looss 1907:161): "Einen gewissen Anklang an die bei den Verwandten herrschenden Verhaltnisse kann man vielleicht darin erblichen, dass die 7 Schlauche nicht selten so gelagert sind, dass mehr oder weniger deutlich eine Gruppe von 4 und eine von 3 Schlauchen ensteht." Yet in Lecithaster and Lecithophyllum the follicles are described as distinctly united centrally. Again, Looss seems to express some doubt as to whether the vitellaria in Aponurus are all actually un- connected. He says (p. 168): "Bei der Pressung frischer Tiere geht die Kugel-form in eine Birn- oder Keulenform liber, die Gruppen von 3 und 4 bleiben meist deutlich sichtbar, verschinden manchmal aber ebenfalls, und dann ahneln die Dotterstocke vollkommen denen von Lecithaster, da die Schlauche alle von einem Punkt auszugehen scheinen. Ich glaube auch, dass dies tatsachlich der Fall ist, obwohl der direkte Nachweis an ganzen und aufgehellten Individuen wegen der ungiinstigen Lagerung der Follikel nicht zu erbringen ist." Yet, if it be true that the vitellaria are actually as in Lecithaster then there is much less justification for separation of Aponurus from Lecithophyllum. The condition of the vitellaria in the present material will be discussed below. Two specimens of this form were obtained from the stomach of one fish. These specimens agree in the main with the characters of the genus. Both seemed fully mature and their size measurements were 1.47 by 0.29 mm., and 1.1 by 0.245 mm. The greatest thickness is about the same as the greatest width, so that at the ventral sucker and posterior the worm is cylindrical. The body is broadly rounded at the posterior end. The cuticula is smooth and there is no tail appendage. The sucker proportion is almost exactly 1 : 2. Pre-pharynx lacking, pharynx globular; esophagus short; wide ceca reaching to the posterior end of the body. 98 ILLINOIS BIOLOGICAL MONOGRAPHS [224 The excretory system is as in other Hemiurids. Posteriorly it is con- cealed by egg masses. The unpaired vesicle branches between the ovary and testes, and the two lateral branches unite dorsal to the pharynx. The genital pore is ventral, median, at about the level of the middle of the pharynx. The pear-shaped muscular sinus-sac extends dorsally and posteriorly from the pore and surrounds the genital sinus. It reaches about half way to the ventral sucker. In this posterior extent of the genital sinus the form differs from Lecithophyllum. The wall of the sac consists of an outer layer of longitudinal muscles and an inner layer of circular muscles. Between these layers and the sex duct is a space filled by parenchyma tissue containing a few cells. The width of this parenchyma-filled space is about equal to the combined thickness of the muscle layers. The common genital duct coils somewhat within the sac, at the posterior end of which it splits into the male and female sex ducts. The testes are located a short distance posterior to the ventral sucker. In both specimens the right testis was slightly anterior to the left. Their size is relatively small, and in this respect they differ from the condition in A. laguncula, where the testes fill a large portion of the body cross-section. The seminal vesicle is large, and ovoid or simple-sac like in shape. In A. laguncula it is bent slightly at each end. In the present species it extends posteriorly to near the middle of the ventral sucker. In A. laguncula, it does not extend very far beyond the anterior margin of the sucker. The duct of the pars prostatica leads from the ventral surface of the seminal vesicle near its anterior end, bends directly dorsally over the anterior end of the vesicle, reaches to the dorsal wall, and then bends again ventrally to unite immediately with the uterus to form the genital sinus. The wall of the duct is composed of small flat cells apparently without ciliary processes. The form of the pars prostatica is S-shaped in lateral view (Fig. 70), and the gland does not run directly posteriorly as in A. laguncula. The cells of the prostate gland are large in size and somewhat angular in shape. The total length of the gland is just about equal to the length of the sinus sac. Thus, in length it agrees with A. laguncula and differs from Lecithophyllum botryophoron. In a 2 mm. specimen of the latter species, the genital sinus was 0.3 mm. long and the pars prostatica 0.17 mm. or about 1/2 as long. In the 1.1 mm. specimen of A. sphaero- lecithus the pars prostatica was about 0.19 mm. in length. In this same specimen the sinus sac was about 0.2 mm. in length measured from the lateral aspect. This proportional length is about as in Lecithophyllum, but due to the dorsal slant of the organ its posterior edge only reached a point about half way to the ventral sucker. The ovary is located a short distance posterior to the testes and slightly to the right. It is spherical in form and smooth in outline. The globular 225] SOME NORTH AMERICAN FISH TREMATODES—MANTER 99 seminal vesicle is located anterior and slightly dorsal to the ovary. It is about one half the size of the ovary. Laurer's canal is absent. The vitellaria consist of seven follicles, globular in shape a smooth with outline, and located close together just posterior to the ovary. They are in two groups. One group of four is located to the right and just posterior to the ovary, while the group of three is located to the left (Figs. 73-74). The follicles in the group of four are larger, being almost as large as the ovary. This size of the follicles is greater than in A. laguncula, where they are about one half the size of the ovary. The position of both ovary and vitellaria is near the ventral surface of the body. In regard to the separate or connected condition of the follicles, a series of sections through the larger specimen gave no indication that the follicles are united at any point. While some were in close contact with each other, others were clearly isolated. In spite of Looss's question, this condition seems definitely distinct, certainly from the normal condition in Lecithaster and from the condition described for Lecithophyllum. More material will be necessary to settle the point finally. The coils of the uterus are as in A. laguncula. The terminal region of the uterus is surrounded by the cells of the prostate gland. The uterus runs close to the male duct in this region and with it swings dorsally over the anterior end of the seminal vesicle (Fig. 72). The male and female ducts do not unite outside the sinus sac. The male duct opens into the extreme posterior tip of the sac, while the female duct enters from the left at practically the same spot. The eggs are very large and this character forms a conspicuous differ- ence between the two species of Aponurus. Looss gives the eggs of A. lagun- cula as about 0.027 mm. in length and 0.016 mm. in width. Eggs in the present species were 0.056 to 0.065 mm. by about 0.026 mm. This size and the thick egg shell agree with Lecithophyllum. Measurements are as follow T s: Length 1 . 47 mm. 1 . 1 mm. Width 0.296 0.245 Oral sucker 0.137 0.1 Ventral sucker 0.264 0.19 Ant. end to post, edge ventral sucker 0.617 0.43 Pharynx 63 by 63^ 57 by 57^ Diameter, ant. testis 68^ 57,u Diameter, post, testis 79^ 68m Diameter, ovary 91m 85m Diameter, vitellaria 85 to 91m 62 to 72m Eggs 58-62 by 26m 56-65 by 26/* 100 ILLINOIS BIOLOGICAL MONOGRAPHS [226 GENOLINEA LATICAUDA MANTER 1925 [Figs. 64-66] From stomach, Hippoglossus hippoglossus (Halibut) Small to medium-sized forms, with flattened body tapering slightly anteriorly, at which end it is roundly pointed; body broadly rounded posteriorly. Body almost uniformly wide. Cuticula smooth. Tail ap- pendage lacking. Oral sucker embedded in body, overlapped dorsally by fleshy lip. Ventral sucker about one and a half times the size of the oral sucker, located anterior to the middle of the body and about at the end of the first body third. No pre-pharynx, pharynx broad, esophagus vepy short, ceca broad, extending to posterior tip of body. Excretory system as in Hemiuridae, branches uniting dorsal to pharynx. Genital pore median, ventral, at about the level of the forking of the intestine. Testes compact, globular, obliquely behind one another some distance behind the ventral sucker. Ovary large, compact, globular, located behind testes. Vitellaria behind one another posterior to ovary, compact, globular. Uterus sends two lateral coils posterior to vitellaria to near body tip. Between ovary and ventral sucker the uterus is in large transverse coils. Genital sinus short, seminal vesicle much coiled, just anterior or slightly overlapping the ventral sucker. Eggs 28 to 31 by 12 to 15yu. The Hemiurid affinities of this form are seen in the digestive and excretory systems, the general form, shape, and position of the gonads, the genital sinus, prostate gland, and oral lip. It is most closely related to Genarches Lss. and Derogenes Liihe. which are grouped under the Syn- coelinae. It differs from both in body shape which is not markedly tapering at either end, and in position and proportional size of the ventral sucker which is distinctly anterior to mid-body. None of the three specimens showed contraction of the neck region, so that this sucker position can be assumed as normal. The course of the uterus in Genolinea is distinctly different than it is in either Genarches or Derogenes. Genarches is, of course, also clearly separated by the union of the two intestinal ceca posteriorly. Genolinea, in addition to points already mentioned, is distinct from Derogenes in possessing a very short prostate gland, a much coiled seminal vesicle, and a more linear arrangement of the reproductive organs. Measurements on two of the specimens are as follows: Length 1.87 mm. 1.32 mm. Width 0.336 0.299 Oral sucker 0.136 0.125 Ventral sucker 0.239 0.199 Ant. end to post, edge ventral sucker 0.617 0.5 Pharynx 57 by 79 M 57 by 74 M Ant. testis 0.136 mm. 0.1 mm. 227] SOME NORTH AMERICAN FISH TSEMATODES— MANTES 101 Post, testis 0.136 0.13 Ovary 0.165 0.15 Ant. vitellarium 0.114 0.12 Post, vitellarium 0.142 0.12 Eggs 31 by 13 to IS/t 28 to 31 by 12 M GONOCERCA PHYCIDIS MANTER 1925 [Figs. 67-69] From gills and branchial cavity, Urophycis chuss (Squirrel Hake) Body elongate, both ends bluntly rounded, cuticula smooth, not ringed, body only slightly flattened, oval in cross-section, tail appendage lacking. Ventral sucker posterior to middle of body, almost twice as large as the oral sucker, about as wide as body. Mouth opening sub-terminal, over- lapped dorsally by lip-like projection of body, oral sucker embedded in body. No pre-pharynx, short esophagus, intestinal ceca reaching to posterior end of body. Excretory vesicle branching just posterior to the ovary, the branches running forward laterally and uniting dorsal to the oral sucker near the anterior tip. Gonads crowded together posterior to the ventral sucker and filling most of the body space in that region. Genital aperture median and ventral, close behind mouth opening. Ovary median just behind ventral sucker, anterior to the testes. Vitellaria compact, un- lobed, lateral and very slightly posterior to the ovary. Testes large, just posterior to the ovary, obliquely behind and in contact with each other. Ootype without membrane, dorsal and anterior to the ovary. Eggs com- paratively large. Seminal vesicle comma-shaped, pointed anteriorly, located at about the level of the pharynx. Prostate gland little developed, free, short, located ventral to the oral sucker just anterior to the seminal vesicle. The covering of the seminal vesicle seems to be non-muscular, hence the cirrus sac is absent or at most weakly developed. There is a short genital sinus. No localized seminal receptacle. Region of the uterus just anterior to the ovary often crowded with sperm cells. About 15 specimens were taken from the gills and branchial cavity of a single host. The fish had been caught but a few hours and it is possible that (as is true of some other Hemiurids) the gill region is the normal habitat of the parasite. Two specimens altogether, however, were obtained from the stomach of this fish. That this trematode belongs to the non-appendiculate Hemiuridae there can be no doubt. Its features characteristic of the family are seen in the excretory system, projection of upper lip, position of genital pore, and character and form of the gonads. It differs from most members of the family in the reversed position of the ovary in relation to the testes. Still more marked distinctions are found in the location of the uterus entirely anterior to the ovary, in the position of the seminal vesicle far 102 ILLINOIS BIOLOGICAL MONOGRAPHS [228 distant from the ventral sucker, in the position of the prostate gland, and in the crowded localization of the gonads and vitellaria in the tail region. The occurrence of the parasite on the gills and in the branchial cavity of the host is not unique among the Hemiuridae. Odhner gives the follow- ing as "gill parasites": Accacoelium contortum, Syncoelium, Otiotrema, Bathycotyle, and Liocerca. Of these forms, the present species resembles most closely Liocerca. Liocerca is also one of the few members of the family with testes posterior to the ovary. Gonocerca differs markedly, however, from Liocerca in the following points: position of the genital pore, which is considerably more posterior in Liocerca; position of the seminal vesicle, which is close to the ventral sucker in Liocerca; length of the prostate gland, which is elongate in Liocerca; and in uterine coils, which extend posterior to the ovary in Liocerca. Liocerca shows more resemblance to Hemiurus than does Gonocerca. Nicoll in 1913 describes the genus Hemipera which he considers most closely related to Liocerca. It resembles this genus in inverted position of the ovary. In this respect, it is also like the present form with which it shows further similarity in position of the ventral sucker. The body form of all three genera is very similar. In Hemipera, the testes are lateral to each other, instead of behind one another, as in the other two genera. Hemipera shows the widest divergence in possessing a cirrus sac inclosing both prostate gland and seminal vesicle, and in having egg with polar filaments. A tabular comparison of these genera follows: Habitat Position of genital pore Position of ventral sucker Testes Cirrus sac Prostate gland Seminal vesicle Eggs Liocerca gills Somewhat distant from oral sucker About mid-body Behind one another Inclosing only male duct Free, elongate Near ventral sucker Numerous, non- filamented Gonocerca gills Close to oral sucker Posterior to mid- body Behind one another Absent Free, short Near pharynx Numerous, non- filamented Hemipera stomach Somewhat distant from oral sucker Posterior to mid- body Lateral to each other Inclosing prostate gland and sem. ves. Inclosed Between suckers Few, filamented Form, shape, size, cuticula, excretory and digestive systems are similar in all three genera. Gonocerca differs from Derogenes in extent and position of prostate gland, position of genital pore, course of uterus, and inverted position of ovary in relation to testes. These same differences except extent of prostate gland separate it from Genarches. -MANTER 103 1 . 4 mm. 1.4 mm. 0.37 0.4 1. 1. 0.2 0.22 0.33 0.35 0.12 0.125 0.23 0.23 0.114 0.114 96 by 51 M 85 by 7pus von Copulationsorgen bei Dist. megastomum. Central. Bakt. Par., 27:68-74, 4 text figs. Juel, H. O. 1889. Beitrage zur Anatomie der Trematodengattung Apoblema (Dujard.). Beih. k. Svenska Vet.-Akad. Handl., 15:3-46, Taf. 1. Kendall, Wm. C. 1908. Fauna of New England: List of Pisces. Boston Soc. Nat. Hist., Occas. Papers, 7:152 pp. Lander, C. H. 1904. The Anatomy of Hemiurus crenatus (Rud.) Liihe, an Appendiculate Trematode. Bull. Mus. Comp. Zool. Harv. College, 45:1-28, 4 pis. Lebour, M. V. 1908. Fish Trematodes of the Northumberland Coast. Rept. Northumberland Sea Fish., 1907, 3:3-47, 5 pis. Leidy, Jos. 1851. Contributions to Helminthology. Proc. Acad. Nat. Sci. Phila., 5:205-210. Leiper, R. T. and Atkinson, E. L. 1915. Parasitic Worms, British Antarctic ("Terra Nova") Expedition, Zoology. 2:19-60, 11 text figs., 5 pis. Leuckast, R. 1886. Die Parasiten des Menschen. 2te Aufl. Leipzig. 897 pp. Levinsen,G. M.R. 1881. Bidrag til Kundskab om Grj^nlands Trematodfauna. Overs. Danske. Vidensk. Selsk. Forhdl., 1 :49-84, tab. 2-3. LlNSTOW, O. VON 1890. Ueber den Bau und die Entwicklung des Distomum cylindraceum Zed., Arch, mikr. Anat., 36:173-191, Taf. 7-8. 1907. Zwei neue Distomum aus Luciperca sandra der Wolga. Ann. Mus. Zool. Acad. Imp. Sci. St. Petersbourg, 12:201-202, 1 text fig. Linton, E. 1889. Notes on Entozoa of Marine Fishes of New England. Ann. Rept. Comm. Fish and Fisheries for 1886:453-498, 6 pis. 1898. Notes on Trematode Parasites of Fishes. Proc. U. S. Nat. Mus., 20:507-548, pis. 40-54. 1900. Fish Parasites Collected at Woods Hole in 1898. Bull. U. S. Fish Comm. for 1899, 19:267-304, pis. 33-43. 1901. Parasites of Fishes of the Woods Hole Region. Bull. U. S. Fish Comm. for 1899, 19:405-492, 34 pis. 1905. Parasites of Fishes of Beaufort, North Carolina. Bull. U. S. Bur. Fish., 24:321- 428, 34 pis. 1911. Helminth Fauna of the Dry Tortugas. II. Trematodes. Carnegie Inst. Wash., Pub., 133:15-98, 28 pis. Looss, A. 1894. Die Distomen unserer Fische und Frosche. Bibliotheca Zool., 16: 296 pp., Taf. 1-9. 1896. Recherches sur les faune parasitaire de 1'Egypte, I. Mem. 1'Inst. Egypt., 3 : 252 pp., 16 pis. 245] SOME NORTH AMERICAN FISH TREMATODES—MANTER 119 1899. Weitere Beitrage zur Kenntniss der Trematoden-Fauna Aegyptens. Zool. Jahrb., Syst., 12:521-784, Taf. 24-32. 1901. Zur Sammel und Conservierungstechnik von Helminthen. Zool. Anz., 24:302-304, 309, 318. 1907. Beitrage zur Systematic der Distomen. Zool. Jahrb., Syst., 26:63-180, Taf. 7-15. 1907a. Zur Kenntnis der Distomenfamilie Hemiuridae. Zool. Anz., 31 :585-620. LtJHE, M. 1900. tlber die Gattung Podocotyle (Duj.) Stoss. Zool. Anz., 23:487-492. 1901. UberHemiuriden. Zool. Anz., 24:394-488. 1909. Parasitische Plattwiirmer, I. Trematodes. Siisswasserfauna Deutschlands, Heft 17. Manter, H. W. 1925. Some Marine Fish Trematodes of Maine. Jour. Parasit., 12:11-18, pi. 2. Marshall, W. S. and Gilbert, N. C. 1905. Three New Trematodes Found Principally in Black Bass. Zool. Jahrb., Syst., 22:477-488, pi. 15. MONTICELLI, F. S. 1899. II Genere "Acanthocotyle." Arch. Parasit., 2:75-120, Tav. 1-3. 1904. Osservazioni intorno ad alcune specie di Heterocotylea. Boll. Soc. nat. Napoli, 18:65-80, 5 text figs. MtJHLSCHLAG, G. 1914. Beitrage zur Kenntnis der Anatomie von Otodistomum veliporum (Creplin), Distomum fuscum Poirier, and Distomum ingens Moniez. Zool. Jahrb., Syst., 37:199-252 16 text figs., Taf. 9-10. Nicoll, Wm. 1907. A Contribution towards a Knowledge of the Entozoa of British Marine Fishes. Part I. Ann. Mag. Nat. Hist., ser. 7, 19:66-94, 4 pis. 1909. Studies on the Structure and Classification of the Digenetic Trematodes. Quar. Jour. Micr. Sci., 53:391-487, pis. 9-10. 1909a. A Contribution towards a Knowledge of the Entozoa of British Marine Fishes. Part II. Ann. Mag. Nat. Hist., ser. 8, 4: 25 pp., 1 pi. 1910. On the Entozoa of Fishes from the Firth of Clyde. Parasit., 3:322-359, pi. 29. 1913. New Trematode Parasites from Fishes of the English Channel. Parasit., 5:238-246, pi. 11. 1913a. Trematode Parasites from Food-Fishes of the North Sea. Parasit., 6:188-194, pi. 13. 1914. The Trematode Parasites of Fishes from the English Channel. Jour. Mar. Biol. Assn., 10:466-505. 1915. A list of the Trematode Parasites of British Marine Fishes. Parasit., 7:338-378. 1915a. The Trematode Parasites of North Queensland. III. Parasites of Fishes. Parasit., 8:22-41, pis. 4-5. NORDMANN, A. VON 1832. Mikrographische Beitrage zur Naturgeschichte der wirbellosen Thiere. Ersles Heft. Berlin. 118 pp., 10 pis. Odhner, T. 1901. Revision einiger Arten der Allocreadium Lss. Zool. Jahrb., Syst., 14:483-520, Taf. 33. 1902. Mitteilungen zur Kenntnis der Distomen, II. Central. Bakt. Par., 31:152-162, 3 text figs. 1905. Trematoden des arktischen Gebietes. Fauna Arctica, 4:291-372, 4 text figs., Taf. 2-4. 1911. Zum natlirlichen System der digenen Trematoden. II. Zool. Anz., 37:237-253, 2 text figs. 120 ILLINOIS BIOLOGICAL MONOGRAPHS [246 1911a. Zum natiirlichen System der digenen Trematoden. III. Zool. Anz., 38:97-117, 8 text figs. 1911b. Zum natiirlichen System der digenen Trematoden. IV. Zool. Anz., 38:513-531, 2 text figs. 1914. Cercaria setifera von Monticelli- die Larvenform von Lepocreadium album Stoss. Zool. Bidr. Uppsala, 3 :247-255, Taf . 6. Olsson, P. 1868. Entozoa, iakttagna hos Skandinaviska hafsiskar. Lund's Univ. Arsskrift, 4:1-64, Tab. 3-5. 1876. Bidrag till Skandinaviens Helminthfauna. Kongl. Svenska Vet.-Akad. Handl., 14:3-35, Taf. 1-4. Pearse, A. S. 1924. The Parasites of Lake Fishes. Trans. Wis. Acad. Sci., 21 :161-194. Poirier, J. 1885. Contribution a l'histoire des trematodes. Arch. Zool. experm., ser. 2, 3:465-624, pis. 23-34. Pratt, H. S. 1898. A Contribution to the Life-history and Anatomy of the Appendiculate Distomes. Zool. Jahr., Anat. u. Ont., 11 :3-40, pis. 25-27. Saint-Remy, G. 1892. Synopsis des trematodes monogeneses. Rev. biol. nord. France, 4: 92 pp., pi. 10. 1898. Complement du synopsis des trematodes monogeneses. Arch. Parasit., 1:521-571. Schauinsland, H. 1883. Beitrage zur Kenntnis der embryonalen Entwicklung der Trematoden. Jen. Zeit. Naturwiss., 16:465-527, Taf. 19-21. Scott, T. 1909. Some Notes on Fish Parasites. 26th Ann. Rept. Fish. Bd. Scot., 3:73-92, pis. 3-7. SlF.BOLD, C. TH. VON 1837. Zur Entwickelungsgeschichte der Helminthen. K. F. Burdach's: Die Physiologie als Erfabrungswissenschaft. Bd. 2, 2 Aufl. Leipzig. Stafford, J. 1904. Trematodes from Canadian Fishes. Zool. Anz., 27:481-495. Stiles, C. H. and Hassall, A. 1898. An Inventory of the Genera and Subgenera of the Trematode Family Fasciolidae. Arch. Parasit., 1:81-99. 1908. Index-Catalogue of Medical and Veterinary Zoology. Subjects: Trematodes and Trematode Diseases. Bull. Hyg. Lab., 37 : 401 pp. Stossich, M. 1886. I distomi dei pesci marini e d'acqua dolce. Prog. Ginnasio comm. sup. Trieste, 3-66. 1890. Brani di elmintologia tergestina, VII. Boll. Soc. adr. sci. nat. Trieste, 11:23-30, pis. 13-14. 1892. I distomi dei mammiferi. Prog. d. civ. scuola r. sup., Trieste, 42 pp. 1898. Saggio di una fauna elmintologica di Trieste e provincie contermini. Prog. d. civ. scuola r. sup., Trieste, 162 pp. 1900. Osservazioni elmintologiche. Boll. Soc. adr. sci. nat., Trieste, 20:S9-103, Tav. 6. 1903. Note distomologiche. Boll. Soc. adr. sci. nat., Trieste, 21:193-201. Thomas, A. P. 1883. The Life History of the Liver Fluke. Quart. Jour. Micros. Sci., 23 :99-133. van Cleave, H. J. 1920. Notes on the Life Cycle of Two Species of Acanthocephala from Fresh Water Fishes. Jour. Parasit., 6:167-172, pi. 14. 247] SOME NORTH AMERICAN FISH TREMATODES—MANTER 121 VlIXOT, M. A. 1879. Organization et developpement de quelques especes de trematodes endoparasites marins. Ann. sci. nat., ser. 6, 8: 40 pp., pis. 5-10. Wagener, G. R. 1857. Beitrage zur Entwicklungs-Geschichte der Eingeweidewiirmer. Naturk. Verhandl. Holland. Maatsch. Wetensch. Haarlem, 2 Verzamel., 13: 112 pp., pis. l-36a. Ward.H.B. 1910. Internal Parasites of the Sebago Salmon. Bull. U. S. Bur. Fish., 28:1153-1194, pi. 121. 1917. On the Structure and Classification of North American Parasitic Worms. Jour. Parasit., 4:1-11. Ward, H. B. and Whipple, G. C. 1918. Fresh Water Biology. New York. 1111 pp., 1547 figs. WlLLEMOES-SUHM, R. VON 1871. tjber einige Trematoden und Nemathelminthen. Zeit. wiss. Zool., 21:175-203 Taf. 11-13. 122 ILLINOIS BIOLOGICAL MONOGRAPHS [248 EXPLANATION OF PLATES With the exception of Figs. 3, 76, 77, and 81, all figures were drawn with the aid of a camera lucida. The scale projected is equal to 0.1 mm. unless otherwise indicated in the explanation of figures. The following abbreviations are used: a tail appendage Im longitudinal muscles ac accessory sucker mf meridional fibers as anterior sucker mo male sex opening c cuticula ovary cd common sex duct od oviduct cm circular muscles ot ootype cs cirrus sac ov ovum dm diagonal muscles t genital papilla dp duct of prostate gland ph pharynx e excretory system pp prepharynx *f equatorial fibers pr prostate gland ej ejaculatory duct rf radial fibers es esophagus s spermatozoa f genital fold sr seminal receptacle fo female sex opening sv seminal vesicle ga- genital atrium t testis ge gland cell u uterus gP genital pore V vagina gs genital sinus 1>S ventral sucker i intestine vt vitellaria Ic Laurer's canal yd yolk duct 249] SOME NORTH AMERICAN FISH TREMATODES-MANTER 123 PLATE I 124 ILLINOIS BIOLOGICAL MONOGRAPHS [250 Fig. 1. Fig. 2. Fig. 3. Fig. 4. Fig. 5. Fig. 6. Fig. 7. Fig. 8. Fig. 9. Fig. 10. Fig. 11. Fig. 12 EXPLANATION OF PLATE I Otodislomum cestoides. Ventral view of adult. Scale = 1 mm. O. cestoides. Ventral view of young specimen. Copy of Nicoll's figure of cercaria of O. cestoides from cyst from flounder. Enlarged to same proportion as Figure 2. O. cestoides. Ventral view of young specimen. Scale = lmm. Sagittal section through anterior region of O. cestoides showing normal condition of genital papilla. Scale = 1 mm. Same, with genital papilla protruded. Scale = 1 mm. Sagittal section through genital atrium of O. veliporum. Same of 0. cestoides. Sagittal section through a position of ventral sucker of 0. cestoides. Frontal section through pharynx region of 0. cestoides. Scale = 1 mm. Cross-section through edge of ovary of O. veliporum showing beginning of oviduct. Sagittal section through portion of body wall of 0. cestoides. Scale = 0.5 mm. ILLINOIS BIOLOGICAL MONOGRAPHS VOLUME X o ■ §3; T ^M •5V — V ?■« '01 ) V ?* II . . «V'. Jl »■' p^t- fe ys j .. 1 r-'¥~ 1 22" I ** 1 MANTER FISH TREMATODES PLATE I 138? OF THE .■- ■ ' .i;* Jaw 251] SOME NORTH AMERICAN FISH TREMATODES—MANTER 125 PLATE II 126 ILLINOIS BIOLOGICAL MONOGRAPHS [252 EXPLANATION OF PLATE II Figs. 13-18. Outline drawings of gonads in 0. cestoides to show changes in relative position of ovary. Figs. 19-20. Cross-sections of Azygia sebago to show inner parenchyma muscles. Figs. 21-22. Same of A. acuminata. Fig. 23. Same of Olodistomum cestoides. Fig. 24. Ootype region of O. cestoides to show relations of ducts. Semi-diagrammatic. Fig. 25. Cross-section through vas deferens of 0. cestoides. Scale = 0.05 mm. Fig. 26. Sections through early eggs of 0. cestoides before shell has assumed regular form. Fig. 27. Frontal section through uterus region of Azygia angusticauda, showing inner parenchyma muscles. Fig. 28. Sagittal section through genital atrium region of 0. cestoides showing genital papilla retracted. Fig. 29. Same of O. vcliporiim showing genital papilla protruded. Fig. 30. Ventral view of anterior body region of Azygia longa showing position of genital pore. Scale = 1 mm. ILLINOIS BIOLOGICAL MONOGRAPHS VOLUME X MANTER FISH TREMATODKS PLATE II T '.:'- i""!-uny ' OF THE ibhversity of illihqe 253] SOME NORTE AMERICAN FISH TREMATODES—MANTER 127 PLATE III 128 ILLINOIS BIOLOGICAL MONOGRAPHS [254 EXPLANATION OF PLATE III Fig. 31. Mature egg of Otodislomum cesloides. Drawn from live egg. Scale = 0.05 mm. Fig. 32. Same, showing three lobes in internal organ. Scale = 0.05 mm. Fig. 33. Miracidium and empty egg shell of O. cestMes. Drawn from toto-mount. Length of larva 9h<. Fig. 34. Recently dead miracidium of O. cestoides showing bristle plates detached. Scale = 0.05 mm. Fig. 35. Cross-section through mature egg of 0. vdiporum showing the five bristle plates. Diameter of egg 50w. Fig. 36. Longitudinal section through mature egg of O. cesloides, showing paired glands. Fig. 37. Cross-section of same. Fig. 38. Longitudinal section through mature egg of O. vdiporum. Fig. 39. Recently hatched miracidium of O. cesloides. Drawn from live specimen. Scale = 0.05 mm. Kgs. 40-41. Cross-sections through mature eggs of O. vdiporum. Diameter of eggs about 60«. Figs. 42-43. Recently dead miracidia of O. cesloides, showing bristle plates. Scale = 0.05 mm. Fig. 44. Longitudinal section of mature egg of Azygia acuminata showing four nuclei in internal organ. Length of egg 60;<. Fig. 45. Lepidapedon rachion. Ventral view. F'ig. 46. Sagittal section through region of ventral sucker of L. rachion. Fig. 47. Same of L. dongatum. Fig. 48. Lepidapedon clongalum. Ventral view. ILLINOIS BIOLOGICAL MONOGRAPHS VOLUME X MANTER FISH TREMATODES TLATE III THE LlBRMlK OF T5SE ■vci: ..." > ,i.vjj 255] SOME NORTH AMERICAN FISE TREMATODES—MANTER 129 PLATE IV 130 ILLINOIS BIOLOGICAL MONOGRAPHS [256 EXPLANATION OF PLATE IV Fig. 49. Podocotyle atomon. Ventral view. Fig. 50. Podocotyle olssoni. Ventral view. Fig. 51. Stephanochasmus baccatus. Ventral view. Fig. 52. Sections through eggs of S. batcatus. Fig. 53. Brachyphallus crenatus. Ventral view. Fig. 54. Homalometron pallidum. Ventral view of young specimen. Fig. 55. B. pallidum. Sagittal section through region of seminal vesicle. Fig. 56. H . pallidum. Ventral view of adult. Fig. 57. Derogates varicus. Ventral view. Fig. 58. Steganoderma formosum. Ventral view. Fig. 59. S. formosum. Cross-section through body just posterior to ovary. Fig. 60. S. formosum. Sagittal section through posterior body region. Fig. 61. Lecithaster gibbosus. Ventral view. ILLINOIS BIOLOGICAL MONOGRAPHS VOLUME X MANTER FISH TREMATODES PLATE IV Of ff|f 257] SOME NORTH AMERICAN FISH TREMATODES—MANTER 131 PLATE V 132 ILLINOIS BIOLOGICAL MONOGRAPHS [258 EXPLANATION OF PLATE V Fig. 62. Ventral view of Hemiurus levinseni with tail appendage extended. Fig. 63. Same, with tail appendage retracted. Fig. 64. Ventral view of anterior body region of Gcnolinca laticauda. Fig. 65. Ventral view of entire body of G. laticauda. Fig. 66. Same view of another specimen. Fig. 67. Ventral view of Gonoctrca phycidis. Fig. 68. Ventral view of anterior body region of same. Fig. 69. Sagittal section through posterior body region of G. phycidis. Fig. 70. Lateral view of anterior body region of A ponurus sphaerolecithus. Fig. 71. Ventral view of entire body of .4. sphaerolecithus. Fig. 72. Cross-section through body of A . sphaerolecithus just posterior to sinus sac Fig. 73. Ventro-lateral view of body of A . sphaerolecithus in region of gonads. Fig. 74. Ventral view of same. ILLINOIS BIOLOGICAL MONOGRAPHS VOLUME X MANTER FISH TREMATODES PLATE V THE LfBRARY OF THE 259! SOME NORTH AMERICAN FISH TREMATODES—MANTER 133 PLATE VI 134 ILLINOIS BIOLOGICAL MONOGRAPHS [260 EXPLANATION OF PLATE VI Fig. 75. Sagittal section through anterior body region of Birudinella fusca. Scale = 1 mm. Fig. 76. Free-hand drawing of H . fusca, lateral view. Fig. 77. Same, ventral view. Fig. 78. Composite drawing from three sagittal sections through ootype region of B. fusca. Fig. 79. Sagittal section through anterior body region of H. fusca, showing detail. Scale = 0.5 mm. Fig. 80. Ventral view of Siphodera vinaledwardsii. The eggs are omitted. Fig. 81. Diagrammatic representation of relationship of female ducts with the oviduct in 5. vinaledwardsii. Fig. 82. Cross-section through region of ventral sucker of 5. vinaledwardsii. Fig. 83. Sagittal section through same region. Fig. 84. Outline drawing of Dactycolyle minor, showing body regions. Scale = 1 mm. Fig. 85. Genital sucker of D. minor. Scale =0.05 mm. Fig. 86. Posterior sucker of A canthocotyle verrilli. Fig. 87. Accessory posterior sucker of A. verrilli. Scale = 0.05 mm. Fig. 88. Ventral view of A verrilli. Scale =1 mm. ILLINOIS BIOLOGICAL MONOGRAPHS VOLUME X MANTER FISH TREMATODKS PLATE VI THE LIBRARY Of THE 261] SOME NORTH AMERICAN FISH TREMATODES—MANTER 135 INDEX TO SCIENTIFIC NAMES Acanthias vulgaris, 2 Acathobothrium coronation, 10 Acanthocotyle, 79 Acanthocotylinae, 79 Acanthocolyle lobianc!u>i, 111 verilli, 80, 110 Accacoeliinae, 79, 91 Accacoelium, 90 Accacoelium contortum, 102 aculeatus, Gasterostetts, 94 acuminata, Azygia, 57, 61, 72, 78, 116 odsPersus, Tautogolabrus, 8 Aega psora, 9 aeglifinus, Melanogrammns, 9, 84 ajfinis, Brachy phallus, 94 album, Lepocreadium, 86 Allocreadiidae, 79 Allocreadiinae, 79 Allocreadium atomon, 81 Atosafinta, 92 amencantts, Pseudoplcuronectes, 3 ^mio ca/fa, 61 Amiatus calvus, 61, 72 ^mwotljto tobiatius, 94 ampullaceum, Distomum, 104 Anarrkickas lupus, 9, 81, 103 Anguilla chrysypa, 9, 72, 94, 110 anguillaris, Zoarces, 9 anguinea, Chlamydoselache, 14 angulalum, Distomum, 80 angusticauda, Azygia, 60, 78, 116 angusticaudum, Mimodhtomv.m, 60, 116 Apoblema mollissimum, 91, 95 Aponurus, 79 Aponurus laguncula, 98 Aponurus sphaerolecithus, 80, 98 appendiculatum-, Distomum, 93 appendiculatus, Hemiurus, 93 atomon, Allocreadium, 81 Distomum, 80 Podocotyle, 79, 81 Azygia, 18, 54 Azygia acuminata, 57, 61, 72, 78, 116 angusticauda, 60, 78, 116 &w/ta, 61, 68, 116 /e#s, Pollachius, 9, 94 vitreum, Stizostedion, 61 volgense, Distomum, 77 volgensis, Azygia, 77 Ptychogonimus, 77 vulgaris, Acanthias, 2 Xenodistomum mclanocystis, 53 Xyphias gladius, 104 Zoarces anguillarts, 9 Zoogonidae, 79, 88 Zoogonoides, 79, 88 Zoogonus, 88 Zoonogenus 88 *"\ W t : *c- ./ '•■ J ■ ■ A £ .. 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