fiicecssaeeese Poppi siphiretiarteeyiy e perieres phere eed er Saaeeits “¥) Bee i jae! erat = : tt se aatete ety orks? 15 a ee et siast agrees . ot Spspnnasases SY Th) sie erst evashby bese cess d, Livi sgentirses ease corp eer Geers sptheremte etn ssitietton oi ty Statete renee ey aisle iste By ME seers tt ress Batabattatey Rea schatetei etree iat ate Hiatt testinceaaarataecreaetia 3 Me titan, fTeeiseeniy ey, seater seca bopsiaiedese at tires eam seeaieentepieetaredas ne a ratitaatiete tats terstes ie 5 3 ea pgtatita asthe iat eets te a Sati sSetliegtascretete i : ahs sg ataetey ayes rapa es pratt isles Ey 13 tefagsoatgidtabeeceee ta paceatics Digitized by the Internet Archive in 2010 with funding from University of Toronto htto://www.archive.org/details/memoirs45harv MEMOIRS OF THE MUSEUM OF COMPARATIVE ZOOLOGY HARVARD COLLEGE. VOL. XLV. CAMBRIDGE, MASS, U.S. A. Printed for the duseum. 1911-1918. CONTENTS. No. 1.— REPORTS ON THE SCIENTIFIC RESULTS OF THE EXPEDITION TO THE TROPICAL PACIFIC, IN CHARGE OF ALEXANDER AGASSIZ, BY THE U.S. FISH COMMISSION STEAMER “ALBATROSS,” FROM AUGUST, 1899, TO JUNE, 1900, COMMANDER JEFFERSON F. MOSER, U. 8S. N., COM- MANDING. XIV. THE SOLENOGASTRES. By Harotp Hears. 40 plates. June, 1911 No. 2.— SOLENOGASTRES FROM THE EASTERN COAST OF NORTH AMERICA. By Harotp Heatu. 14 plates. October, 1918 ; ‘ 4 5 Memoirs of the Auseum of Comparative Zodlogy AT HARVARD COLLEGE. Wore, MIDS INR UIE REPORTS ON THE SCIENTIFIC RESULTS OF THE EXPEDITION TO THE TROPICAL PACIFIC, IN CHARGE OF ALEXANDER AGASSIZ, BY THE U. S. FISH COMMISSION STEAMER “ALBATROSS,” FROM AUGUST, 1899, to JUNE, 1900, COMMANDER JEFFERSON F. MOSER, U. 8S. N., COM- MANDING. XIV. THE SOLENOGASTRES. By HAROLD HEATH. WITH FORTY PLATES. {Published by permission of GEorce M. Bowers, U. 8. Commissioner of Fish and Fisheries. | /4YE 16Y 3y fi Nae CAMBRIDGE, U. S. A.: Printed for the Museum, JUNE, 1911. a - # > ; Vale ; a * y. a WW oN : al Ce ihe 4 ‘ r ; POU Sy : ag , Uy TTR ; GIO | : 11 - » be : - : 7 a - a > <= et « f « ‘ : set : x rs * 7 e, ~ ie j - i y =e V' — TABLE OF CONTENTS Page. INTRODUCTION 9 HISTORICAL REVIEW 5 ce, ala GENERAL FEATURES, METHODS, BYRON eae ey) he ees, 19 EXTERNAL CHARACTERS 19 INTERNAL ANATOMY 19 MetHops 22 OccURRENCE 23 Mops oF Lirp, Foop 24 Cotor, SIzE 25 LenetuH INDEX 26 COMPARATIVE ANA’ rOMY 26 Foor AND GLANDS 26 HypoprRMIS AND PRopuctTs 27 SprcuLE DrevELOPMENT 28 Digestive TRActT 32 Muscubar System : 32 Primary Bopy Caviry AND Sc P 33 CrrcutatTory AND Respiratory Sys- TEMS : NERVOUS SysTEM SENSE ORGANS CorLom PHYSIOLOGY CLASSIFICATION APLACOPHORA ce Wt Chaetodermatidae . Chaetoderma Limifossor Neomeniidae Drepanomenia Pachymenia Proneomeniidae Proneomenia Driomenia Dorymenia Strophomenia . Pruvotiniidae Lophomenia Alexandromenia Halomenia . Dondersiidae Herpomenia Dondersia Ichthyomenia DESCRIPTION OF SPECIES Chaetoderma hawaiiensis C. attenuata C. erudita C. montereyensis . C. argentea C. seabra C. californica C. nanula C. japonica . C. robusta Limifossor talpoideus L. fratula j Pachymenia abyssorum Drepanomenia vampyrella Proneomenia hawaiiensis P. insularis Driomenia pacifica Dorymenia acuta Strophomenia scandens S. ophidiana S. regularis 5. fareimen S. spinosa S. triangularis . Lophomenia spiralis Alexandromenia agassizi A. valida Halomenia gravida Herpomenia platypoda . Dondersia californica Ichthyomenia porosa GENERAL CONSIDERATIONS BIBLIOGRAPHY : EXPLANATION OF PLAT ES DDD OO x) “I J Non wh ¢ oo | pe { THE SOLENOGASTRES. INTRODUCTION. THE present paper embraces the results of the study of a collection of over three hundred specimens of Solenogastres, which have been taken in the Pacific during the various expeditions of the U.S. Fish Commission Steamer “ Alba- tross.”’ Based primarily on material from the Museum of Comparative Zodlogy, it includes, through the generosity of the late Mr. Alexander Agassiz, the deseription of other species collected during recent years. The territory embraced in these explorations is very extensive, including the entire coast of North America from Lower California to Bering Sea, the Kurile Islands, the Japanese Archipelago, and the Hawaiian Islands. The major portion of the material was collected by the following expeditions: Tropical Pacific, 1899-1900; Hawaiian Exploration, 1902; Alaska Investigations, 1890 and 1903; California Coast Exploration, 1889 and 1904; Japanese Expedition, 1906. | NUMBER Deprru SPEcIES | SvTarron OF IN LocaLity SPECIMENS FatHoms Chaetoderma argentea 4231 1 82-1138 | Alaska, near Naha Bay. r 4244 1 ye attenuata {4250 5 50-201 “vicinity of Pr. Wales Id. | 4252 2 californica 4381 1 618-667 | California; S. pt. N. Coronado Id. eh : { 4258 10 Alaska, Lynn Canal. ae l4c64 | 4 282-313 “ Chatham Strait. : ee) (8992) 1 es * apes 3 hawaliensis 1 4130 1 283-528 Hawaiian Ids.; near Kauai Id. a japonica 321 1 207-250 | Japan, 8. of Honshu Id. A485 | | ; 4508 | ao eae Ate re montereyensis 4522- | 39-356 California, Monterey Bay. 4525 | 139 ae nanula | 4369 1 260-284 | fe off San Diego. s robusta 3210 4 483 |S. of Alaska Peninsula seabra 4538 | 1 795-871 | California, Monterey Bay. 10 INTRODUCTION | Numper | Depru Species | Station | OF IN Locaity > | SPECIMENS FarHoms ‘9: : { 4258 4 aty Pe Alaska, Lynn Canal. Limifossor talpoideus | 1 4264 | 6 282-313 “ Ghathant Sterna HE fratula 4369 | 2 | 260-284 | California, off San Diego. Drepanomenia vampyrella 3907 | 1 304-315 | Hawatian Ids., off Oahu Id. Pachymenia abyssorum | 4397 | 1 | 2196-2228 | Off southern California. . ‘ Sail aieeso tes be | 2 eee, Proneomenia hawaiiensis ? 4001 | 1 | MGS 2 (eS rr arias: ' g insularis 4157 | 1 | 762-1000 x “near Bird Id. Driomenia pacifica | eee | : 65-125 Japan, Ose Zaki; vicinity of Misaki. 44.07 2 | Dorymenia acuta {ans 6 | 302-638 | Off southern California. 4416 | Show) Strophomenia fareimen | 3748 2 73-200 Japan, 8. of Honshu Id. * ophidiana 3755 1 52-77 a Bg a a . regularis 3717 1 63-100 |} “ SAE a os oh scandens 4156 3 286-568 | Hawaiian Ids., near Bird Id. 3748 1 My spinosa | 4935 2 | 3-200 Japan, 8. of Honshu Id. 4936 2 (3716 2 me triangularis 4935 2 65-125 SENSE AES ae Lark nd 4936 1 Lophomenia spiralis 4176 2 | 537-672 | Hawaiian Ids., near Niihau Id. Alexandromenia agassizi 2992 6 460 Revillagigedo Ids. off Mexico. , 2980 1 , : | | 4382 1 : alee eee valida | 1389 1 | 603-1350 | Off S. California. ' oy \agon 1 Halomenia gravida | 4804 2 229 Kurile Ids., near Simushir Id. Herpomenia platypoda | 4781 11 482 Aleutian Ids., near Agattu Id. Dondersia californica 4303 1 21 California, off San Diego. Ichthyomenia porosa | § noe a 500-542 oe A ‘ =r | 4402 2 | a Up to the present time none of these molluses has been described from the North Pacific. A few species are known to occur about Australia and the Philippines, and an extensive collection was made in the East Indian Archipelago by the Siboga Expedition. The present collection embraces thirty-one species of which all are new with the exception of Limifossor talpoideus Heath; the species belong to fourteen genera of which eight are new. From this material it becomes increasingly evident that this group of molluses is cosmopolitan; but there is no evidence of a bipolarity or any indication that the north and south poles were centres of distribution. And furthermore there is no apparent relation between size and geographical distribution. In concluding this section of the paper it becomes a most pleasant duty to express my obligation to those who have aided in its completion. To Hon. HISTORICAL REVIEW. 11 G. M. Bowers, Dr. D. 8. Jordan, and Dr. C. H. Gilbert I am indebted for a portion of the material, to certain data relating to a few of the species and for many courtesies while on board the ‘‘Albatross.’”” I am likewise under deep obligation to Drs. E. J. Nolan and H. A. Pilsbry for the use of the magnificent library of the Philadelphia Academy of Sciences, and for several suggestions of a most helpful character. To Dr. W. K. Fisher I am indebted for the identi- fication of the aleyonarian hosts and for a specimen of Chaetoderma hawaviensis. I also wish to express my gratitude to my assistants, Miss R. M. Higley, and Mr. F. W. Weymouth who have greatly lessened the burden necessarily involved in such a study as this. And finally my indebtedness to the late Mr. Alexander Agassiz is very great; in every way possible he helped the work along. HISTORICAL REVIEW. The first known reference to any species of Solenogastre occurs in the works of Loven, who in 1844 briefly described as a gephyrean worm Chaeto- derma nitidulum. During the next thirty years a number of systematists adopted this scheme of classification though there was some difference of opinion concerning the exact position of the species within the group. Diesing (’59), Keferstein (’65), Quatrefages (’65), and Baird (’68) allied it to Sipunculus or Priapulus; Theel (’75) created for it a new family (Chaetodermidae), while M. Sars (’69) placed it among the gephyreans without any comment. Dalyell (53) in ‘The Powers of the Creator” gives under the name Vermiculus crassus an abbreviated description and one figure of an undoubted Chaetoderma, ac- cording to Koren and Daniellssen (’77) C. dalyelli, but the description is much too indefinite to make the determination certain. During this time M. Sars discovered another species of Solenogastre, be- longing to a new genus and ultimately to a new family, which he placed (’69) among the Mollusca without any comment whatever, merely giving it the name Solenopus nitidulus. Some years later Tullberg (’75) described what is considered to be the same species under the name Neomenia carinata. This last named author’s investigations mark a distinct advance in our knowledge of these forms, since they are concerned not only with the study of the external char- acters but with the internal organization as well. In certain respects, especially in the treatment of the urogenital system, the work is seriously at fault, but never- theless it was thoroughgoing enough to lead Tullberg to conclude that, while the species is vermian in what he considered to be probably the most important characters, it is on the other hand decidedly similar to certain of the Mollusca. 12 HISTORICAL REVIEW. In 1876 von Graff subjected Chaetoderma nitidulum to an examination, which considering the amount of material and the methods then in vogue, was more than ordinarily searching; and while he, like Tullberg, fell into error regarding the urogenital organs, his results relating to the other systems, espe- cially the nervous, were of the greatest importance. While not entirely com- mitted to any particular belief regarding the animal’s relationships he was inclined to uphold Keferstein, Diesing, and others; and yet he drew attention to the fact that the spicules, gills, mode of egg development, and musculature are so unique that. the genus may in reality belong elsewhere, possibly in close proximity to the Turbellaria owing to the close correspondence in the nervous systems. In 1877 and the following year von Ihering proposed a new classification of the Mollusca based on extensive anatomical researches largely concerned with the nervous system. He drew attention to the very important fact, not pre- viously recognized, that in many fundamental respects the Solenogastres are allied to the Chitons. In his opinion the ancestral neomenian was probably not distantly related to the gephyreans or nemerteans and accordingly lacked a true shell, and Chitonellus, with its small shell and extensive girdle, is thus more closely related to the Solenogastres than other Chitons and must there- fore be lookedupon as a connecting link. Owing to the presence of lateral nerves the Chitons, Chitonellus, and the Solenogastres are clearly differen- tiated from the gephyrean worms and annelids, so that in this and other respects they approach the molluses. On this account a new phylum of Vermes, the Amphineura, was created for their reception. The following year (’78) this same author reviewed the work of Tullberg, Koren and Daniellssen, and von Graff in a suggestive paper, and was more strongly convinced than before that his conclusions were justified. These papers of von Ihering’s created much criticism, some of it decidedly hostile, but it is undoubtedly true that, while some of the results have not proved to be correct, the work as a whole had a stimulating effect and has been productive of much good. During this same period (77) Koren and Daniellssen described a number of species collected along the Scandinavian peninsula. In most cases the descriptions are so brief that they are not even of generic value, and the animals remain practically unknown down to the present day. Neomenia carinata (Solenopus nitidulus) is described at some length, but the facts adduced are not strikingly different from those presented by Tullberg. By these authors the Solenogastres were considered to be true molluses, and were placed among the opisthobranchs in a new order, Telobranchiata. HISTORICAL REVIEW. 15 During this same year Lankester (’77) placed himself on record to the effect that members of the genus Neomenia are among the most generalized molluses, related to the Chitons and Chitonellus, yet belonging apart in a phylum which he termed Scolecomorpha, the first division of Mollusca eucephala. Another of the important papers which appeared during this year came from the hand of von Graff, who investigated the anatomy of Neomenia carinata and reexamined Chaetoderma nitidulum. From the facts disclosed this author was convinced that not only are the two forms constructed upon the same plan, but that the establishment of the Amphineura as a separate phylum by von Ihering was wholly justified. ‘‘Wir erkennen in Neomenia und Chaeto- derma Modificationen einer sehr alten Urform, vom denen die letztere niher den Wiirmer, die erstere néher den Mollusken ankniipft.”” In quite a remarkable way the facts discovered in the study of these two species supported von Iher- ing’s contention that the Solenogastres and the Chitons are allied forms, though they did not force one to the belief that the Amphineura are necessarily to be placed in the phylum Vermes, and von Ihering himself abandoned this position a short time later. About the same time Hansen (’77) published a most important paper on the anatomy of Chaetoderma nitidulum, and in the treatment of all the systems, especially the urogenital, advanced our knowledge to a considerable extent beyond the old position. For the first time the mode of development of the sex products was determined, and their route traced to the exterior; in other words the broader features of the anatomy of Solenogastres now became com- prehensible. In the opinion of the author, Chaetoderma does not clearly belong to any definite place in the existing system of classification; that while certain molluscan characters appear, others are strongly suggestive of annelid relation- ships, so that its exact position is yet in doubt. The following year Gegenbaur (’78) in the ‘‘Grundrisse”? made a few very guarded statements regarding the relationships of Neomenia and Chaetoderma which may, provisionally at least, be designated the Solenogastres and may be regarded as a division of the group Vermes. The ventral groove of Neo- menia ‘“‘represents the first stage in the formation of that pedal surface of the body which is seen in the lowest Mollusca.”’ On the other hand the nervous system, while decidedly different from that in the worms, nevertheless presents some fundamental resemblances. With the exception of two or three short notices no other papers appeared until 1881, which in some respects is the most important year in the history of 14 HISTORICAL REVIEW. the group. At this time Spengel described the innervation of the osphradium, and in several species of molluses discovered deep-seated resemblances in the elements of the nervous system and their arrangement. On the basis of this work, which includes the examination of Neomenia, Chaetoderma, and two unidentified species of Solenogastres, and with the additional help afforded by the work of Tullberg, von Graff, and Hansen he emphatically claimed, in oppo- sition to von Ihering and Gegenbaur, that the Amphineura are true molluscs. Accordingly he established the Amphineura (Chitons and Solenogastres) as a class of the Mollusca. A very short time afterward the masterly work of Hubrecht appeared, and in some respects it continues to be the most important work that has ever been published on the subject. The study was based chiefly upon a gigantic species, Proneomenia sluiteri, which occurs in Barents Sea north of Scandinavia, and embraced a careful examination of its external and internal anatomy. The results, with a few relatively unimportant exceptions, have been confirmed by the study of many other species, and form a most substantial foundation for studies of more recent date. Concerning the relationships of Proneomenia, Neomenia, and Chaetoderma the author has no hesitancy in agreeing with Spengel that they constitute one order (Solenogastres) of the class Amphineura, the Chitons belonging to the other (Polyplacophora). In a number of suc- ceeding publications this position is held without modification, and the few additional facts of importance that are presented still further emphasize the correctness of the theory. From this time forth scarcely a year has elapsed without one or more papers appearing on the subject of the Solenogastres. Deep-sea researches or work along the shore line beyond the littoral zone have brought to light an ever increasing number of species whose anatomy is now for the most part fairly well known. Without exception all are built upon essentially the same funda- mental plan though in detail each species presents, as is to be expected, some new and interesting modifications. To the majority of zodlogists the aecumu- lated results point unmistakably to the true molluscan nature of these animals, but a glance through some of the succeeding paragraphs will show that there is far from being a unanimity of opinion regarding their position in the phylum and their relation to other groups. The great mass of anatomical details which have been published during the past twenty-five years, serving chiefly to dis- tinguish genera and species, new and interesting though they may be, can be but briefly considered in a review of this character. HISTORICAL REVIEW. 15 In 1882 Kowalevsky and Marion called in question the work of all pre- ceding authors, claiming that they in every case had wrongly oriented the ani- mals, that the anterior end is in reality posterior and vice versa. Tullberg’s lateral glands (portion of the coelomoducts) are accordingly the salivary glands, the penis with its appendages is clearly the radula, the mouth cavity is the rectum, the “egg bag” (pericardium) is the intestinal coecum above the pharynx, the branchia are the buccal cirri and finally the protrusible pharynx is the com- bined uterus and oviducts. This paper called forth an immediate rejoinder on the part of Hubrecht, who reviewed the work of the authors in question, and showed that the orienta- tion of the animals in question is correct, and that Kowalevsky and Marion have created confusion worse confounded owing, for one reason at least, to the fact that they had not seen the species under discussion. During the next four or five years Kowalevsky and Marion published, either separately or conjointly, several papers preliminary to their chief work which appeared in 1887. In this study the authors describe to a certain extent the habits of five new species of these molluses collected along the shores of France, and accompany it with a very detailed description of the external and internal anatomy. Some of these last named results are referred to else- where in the present paper. In the meantime Selenka (’85) published an account of the gephyrean worms collected by H. M. 8. Challenger, and therein briefly described Chaetoderma militare from the Malay Archipelago, adding the remark that he was unable to give any data that might settle its systematic position. In 1888 Hubrecht described a new genus of Solenogastres (Dondersia) taken in the vicinity of Naples. It is a fairly close relative of Proneomenia and Neomenia, and the anatomical characters are accordingly not strikingly differ- ent from those presented in the paper on P. sluiteri. In this same year Hansen (’88) made a study of several species of Soleno- , gastres long before described by Koren and Daniellssen (’77). His researches chiefly concern Neomenia carinata, which is shown more conclusively than be- fore to be similar to P. sluitert. Chaetoderma nitidulum was found to pass the sex products into the pericardium from whence they pass through ducts into the anal cavity (Hubrecht) or branchial cavity (Hansen). Pruvot (90) denied the existence of a heart, or pericardium or dorsal aorta in the Solenogastres. The blood moves in lacunae of which a large one passes dorsally along the mid line propelled by contractions of the body. The paired 16 HISTORICAL REVIEW. gonad, posteriorly becomes single, and opens into what has been termed the pericardium, in reality an accessory part of the reproductive system; while the dorsal sinus courses in a tube (hanging partially in the so-called pericardium), which is called, by other authors, the heart. In Dendersia banyulensis sperma- tozoa develop on the external walls of what has been termed the heart, while the lateral walls of the pericardium are ciliated and serve to convey the sperms as in many hermaphroditic gastropods. Eggs are temporarily stored in the “poche accessoire’’ (pericardium), and the kidneys are in reality genital ducts without renal function. In a later paper (90) the same author describes a few very interesting stages in the development of Dondersia banyulensis, and two years afterward adds some further observations regarding the embryology of Proneomenia aglaopheniae. Ova in the pericardium (of other authors) lack membranes; as these are present in extruded eggs it follows that the supposed kidneys are in reality shell glands. The segmentation stages resemble those of scaphopods and pelecypods, and to some extent this similarity is visible in the later develop- ment. A gigantic coat of ciliated cells (a highly developed velum probably) is formed, and within this the embryo forms by a process certainly not primitive or at all events unlike that of other molluses studied up to the present time. When the velum is thrown off the larva resembles to some extent a young Chiton, possessing seven imbricated calcareous plates along the dorsal surface and later- ally situated flattened spines in what appears to be the girdle. The internal organs at this stage are practically undeveloped, and as the later growth is wholly unknown the present results throw but little light upon the important subject of the phylogenetic development of the group. Pelseneer (’90) considered (contra Hubrecht and others) that Chitonellus is not a primitive form intermediate between the Solenogastres and more typical Chitons, but on the other hand is highly specialized. These conclusions were based on data supplied by a study of the branchia, nervous system, and shell. In an introduction to the extensive work of Blumrich (’91) Hatschek seconds Von Ihering in his attempt to place the Chitons and the Solenogastres apart from the gastropods, and agrees also with Pelseneer in regard to the position of Chitonellus. Owing to the studies noted in the preceding paragraphs the broader fea- tures of the anatomy of these animals have been settled beyond dispute, and consequently the papers from this time forward serve in large measure to supply details, and to a limited extent indicate the phylogenetic relationships of this HISTORICAL REVIEW. 1 group of animals. The more special features relating intimately to the various systems are noted to some extent in the main body of the present paper, while the general considerations are discussed on p. 164-173. Among the more exten- sive of these works are those of Pruvot (91), who has described several species from the shores of France; Wiren (’92) whose study of several species from the Scandinavian coast is among the best that has ever appeared; Simroth (’93) and Pilsbry (98) whose systematic works are of the highest value; Thiele whose various papers during the past fifteen years have added materially to our knowl- edge of the anatomy of molluscs, including several species of Solenogastres; Nierstrasz (1902, ete.), who with an abundance of material collected chiefly by the Siboga Expedition, has added extensively to our information of these animals; and finally the present writer who has contributed some data relating especially to the nervous system. Since the above was written Nierstrasz has published an important report (1908) reviewing the work of various investigators since the appearance of Sim- roth’s paper in 1893. It is a valuable contribution, and the scheme of classifica- tion there adopted will be of much service. Turning now to the broader features of the classification of these animals we find that practically every investigator in this field of research is agreed with Spengel that among the Mollusca their nearest relatives are the Chitons; but regarding their more accurate position within the phylum differences of opinion appear. Von Ihering in 1877 called attention to the fact that the Solenogastres and the Chitons are not distantly related, especially if we consider Chitonellus to be a connecting link and therefore a primitive animal. According to this line of reasoning the Solenogastres, devoid of a radula (none had been discovered at that time) and shell, are the more ancestral and are so closely related to the worms that both they and the Chitons constitute a special phylum (Amphineura) of Vermes as noted in a previous paragraph. Hubrecht, without laying much stress on the ancestry of the Amphineura, though he hints at their derivation from a platyhelminth ancestor, was likewise of the opinion that the Soleno- gastres are primitive, and that Chitonellus is a link connecting them with the more highly modified Chitons. It may be mentioned also that Haller in ’94 modified some of his previous ideas, having become convinced of the correctness of von Ihering’s and Hubrecht’s position. The above idea was combated by Pelseneer (’90) who claimed that Chito- nellus is nothing more than a highly modified Chiton and in no direct way related to the modified group of the Solenogastres. Hatschek (’91) agreed with this 18 HISTORICAL REVIEW. theory though he did claim with von Ihering (a theory abandoned by him in 90) that the Amphineura are Vermes. Grobben (’94) likewise considered this the correct view though he believed the Amphineura to be true molluses. This notion is implied in the work of Haller (’82), who made the claim that the Chitons and the Solenogastres are distinct groups of animals which have been derived from a common vermian ancestor. In a more vigorous fashion Thiele argues from the same standpoint. With one or two exceptions those who argue along the line just indicated regard the Solenogastres as primitive animals, and are accordingly opposed to several investigators who hold a diametrically opposite view. Simroth, Wiren, and Heath believe that the Solenogastres early branched off from some primitive polyplacophore and while retaining several primitive features are in other re- spects degraded organisms. Pelseneer and Garstang take practically the same view. Marion, in a sense, does the same as he compares the adult Solenogastre to the larva of the Chiton. Plate traces the Solenogastres and Chiton lines of descent to some ancestral molluse which may have given rise also to the present classes. In regard to the derivation of the molluses, and the Solenogastres especially, from some premolluscan ancestor there are a number of widely divergent theories. In 1877 von Ihering believed that among the worms the gephyreans are most closely related to the Solenogastres. Haller (’82) on the other hand regarded them as more closely allied with the nemerteans. Hubrecht, Thiele, Plate, and a number of other writers consider that the molluscs, or at all events the Soleno- gastres, arose from a turbellarian-like ancestor. This idea has been most fully developed by Thiele. According to him the progenitor of the molluscs and the Solenogastres (which are considered to be worms) was in the fundamental characters of its organization similar to the modern cotylean polyclad. The often frilled sensory margin of the body became the mantle, which for purposes of protection, developed a cuticular covering and ultimately a shell, while the ventral sucking disc expanded into the molluscan foot which in its least modified form occurs in Haliotis and similar species. GENERAL FEATURES, METHODS, ETC. 19 GENERAL FEATURES, METHODS, ETC. EXTERNAL CHARACTERS.— The Solenogastres constitute a group of marine animals, which combine with features more primitive than in any other molluses numerous others indicating a high degree of modification. All are bilaterally symmetrical, worm-like in form, usually nearly round in cross section, and vary in shape from short thick set to very slender greatly elongated types. While the average length is not far from twenty-five millimeters several species such as Notomenia clavigera and Kruppomenia minima are from one to four or five millimeters long, and on the other hand Proneomenia sluitert reaches the giant size of one hundred and forty-eight millimeters. The mouth, or more’ properly the atrial opening, usually in the form of an elongated slit, holds an antero-ventral position, and is clearly separated from a ventral median furrow, in the Neomeniina extending throughout the entire length of the body. This latter structure is generally considered to be a true pedal groove, the small fold included therein and abundantly provided with glands being the foot. In the Chaetodermatina no external trace of these organs exists, but a gap in the ventral musculature, and a thickening of the muscle bands on each side of the mid line, and in Limifossor a definite pedal sinus, indicate that they were present at a former time. In what must be con- sidered a primitive condition the ventral furrow is posteriorly continuous with what has usually been termed the cloacal cavity, which contains the openings of the urinogenital apparatus, anus, and the respiratory organs. As is more fully shown in a succeeding paragraph, the cloaca is in reality a mantle cavity, and the two branchiae it contains in the Chaetodermatidae are undoubtedly true ctenidia. On the other hand the folds of the cloacal wall, sometimes ex- cessively developed and highly vascular, do not appear to be rudimentary nor degenerate ctenidia. A cuticular sheath, often of great thickness, envelops the body, and con- tains from one to seven or eight layers of calcareous spicules. Where more than one layer is present groups of cells constitute papillae or organs of prob- lematical use. In the adult condition all traces of a shell are absent, but in the development of Myzomenia (Dondersia) banyulensis, as determined by Pruvot, a stage occurs in which the embryo bears on its dorsal surface seven slightly imbricating, calcareous plates. InTeRNAtL ANATOMY.— In regard to the internal organization there are numerous features that indicate a degraded condition, due probably to parasitic 20 GENERAL FEATURES, METHODS, ETC. habits or an adaptation for a life in the bottom ooze. In Chaetoderma the ali- mentary tract is a comparatively simple tube passing directly through the body, (as with other Solenogastres), provided with a radula, reduced to a single median tooth, and a voluminous unilobed liver. In other genera (Prochaetoderma, Limifossor) of the family the radula is of large size, and is typically formed and placed. In the Neomeniina this system is more complex. The first division of the digestive tract, which may be termed the atrium, probably corresponds to a highly modified buceal plate, and though usually connected with the mouth (Diagram p. 20, A) may be separated from it. The walls are modified into Ss Diagrams illustrating structure of a neomenian. A anterior end. b brain; dsg dorsal salivary gland; f foot; gon gonad; im, om inner and outer atrial ridges enclosing the cirrose area; int stomach- intestine; s subradular organ; sg ventral salivary gland. B posterior end. el cloacal cavity; ep dorsal limb of gonoduct; do dorso-terminal sense organ; pem pericardium; r seminal receptacle; sgl ventral limb of gonoduct or shell gland. ridges and cirri, probably sensory structures. A radula is generally present though often greatly reduced in size. In addition to the dorsal salivary glands, probably existing in certain Chaetodermatina as well, a ventral pair is usually GENERAL FEATURES, METHODS, ETC. PAA attached near the radula. A definite digestive gland is wanting, the mid-gut pouches being lined with hepatic cells. Owing to the great reduction of the foot and correlated changes, several peculiarities appear in connection with the circulatory system. As in the Chitons the heart is posterior, and the aorta passes along the mid line dorsal to the gonad to connect with the head cavity, which in Limifossor is limited posteriorly by a well-developed septum. In this genus there are indications also of a pedal sinus, but behind the head region it largely disappears, the blood flowing between the gut and body wall to the branchial region. Passing through the ctenidia, or the folds in the cloacal wall, when these are present, the blood makes its way to the posterior end of the heart. The nervous system bears a striking resemblance to that of the Chitons. There is a greater concentration of the nerve cells to form well-differentiated ganglia, but otherwise there are, in such species as Proneomenia hawaviensis, no especially unique features. The supraoesophageal mass originates three pairs of nerves, which innervate the buccal and neighboring body walls and three pairs of connectives, the labiobuceal, pedal, and lateral. The first named, in a typical condition, is decidedly Chiton-like both as regards its position and elements. The other two, passing backward throughout the entire length of the animal, are united frequently by commissures and connectives, and may fuse completely (Chaetodermatidae) in the cloacal region. In a number of other species the pedal cords, after diminishing in size in the hinder regions of the body, may lack any connection with the lateral ganglia, or they may termi- nate in ganglionic enlargements (ganglion posterius inferius of Wiren) united by connectives with similar swellings (gang. post. superius) on the end of the lateral cords. The latter ganglia are invariably united by a heavy commissure passing dorsal to the rectum, and the pedal cords likewise may be connected by a subrectal commissure, thus completing a circumrectal nerve ring. In the Solenogastres the secondary body cavity comprises that of the gonad, pericardium, and the ducts leading from this latter space to the cloaca. In the Neomeniina the species are hermaphroditic; in the Chaetodermatina dioecious. The sexual elements pass through the pericardial cavity ito the coelomoduets, which in an immature condition are relatively simple, and in some species at least are not fused before they open into the cloacal cavity, characters which the Chaetodermatina retain throughout life. In the Neo- meniina, on the other hand, various modifications may occur which produce a high degree of complexity. Two or more seminal receptacles are usually present, 22 GENERAL FEATURES, METHODS, ETC. and the walls of the median undivided section and a portion of the canals leading on to the pericardium become greatly thickened to form the shell gland. Whether these canals ever function as kidneys is an unsettled question. In the Chaetodermatidae there are indications that they do, but at the present time there is no experimental evidence in support of such a view. Our knowledge of the development of this group of animals is very incom- plete. From Pruvot’s work on Myzomenia banyulensis, and my own on Halo- menia, it is evident that the early history resembles that of certain lamellibranchs and theseaphopods. Pruvot’s interesting discovery of astage where the embryo bears seven calcareous shell plates indicates, as a number of authors maintain, that the Aplacophora have descended from polyplacophorous ancestors. Mernops. — On several occasions I have tried the effects of various killing fluids, and am convinced that for general histological work alcohol is the most satisfactory and is easily controlled. Specimens from deep water are usually in a moribund condition when they come up in the dredge, and undergo prac- tically no contraction when plunged directly into 70% alcohol. Where the animals are more hardy or have been taken in comparatively shallow water it is advisable to add gradually chloretone (aceto-chloroform) dissolved in aleohol until they are completely narcotized. They may then be placed in 70% alcohol for a few hours and preserved permanently in an 80% solution. In warm weather it is sometimes necessary to keep the specimens in a cool place until thoroughly fixed, and in any case it is necessary to use considerable quantities of alcohol. In the study of the nervous system I have found vom Rath’s fluid highly satisfactory especially when the material is treated subsequently with a 1% solution of pyroligneous acid. When sufficiently oxidized the nerve fibres remain grayish in color and are usually quite distinct among the yellow muscle and connective-tissue fibres. For staining I have generally used Delafield’s haematoxylin, rarely using rubin as a secondary stain. In connection with certain features of the nervous system the specimens used were of sufficient size to allow of dissection. Under such circumstances paraffine was poured into a small dissecting pan and while it remained soft the molluse was partially imbedded in it, thus obviating the use of pins. Dissection was done under alcohol by means of a needle mounted on the end of the arm of an instrument for mounting diatoms. In removing the cuticle from about the spicules eau de Javelle is preferable to caustic potash which frequently exerts a decided corrosive action on the more delicate spines. GENERAL FEATURES, METHODS, ETC. 23 OccuRRENCE. — Owing to the methods employed the Solenogastres de- seribed by the earlier authors, and a small fraction of those subsequently dis- covered, have been taken in comparatively shallow water, in a very few cases within the littoral zone. However it cannot be said that they are essentially shore forms, for the various deep-sea explorations of recent years have demon- strated that, in certain localities at least, they are a characteristic feature of the deeper regions of the sea and only exceptionally extend into habitats along shore. With the publication of the present paper the number of species of Soleno- gastres reaches a total of ninety-two. In most instances these have been de- scribed from one or at most a very few specimens, but the scantiness of material appears to be the combined result of habitat and mode of capture. As men- tioned in a succeeding paragraph, these animals are either attached to some coelenterate host or they burrow in the bottom ooze. In the first case they may be readily dislodged and lost; in the second they are usually out of reach. On several occasions, while acting as temporary naturalist on the U. 8. F. C. Str. “ Albatross,” I have been able to examine carefully large quantities of mud, which has been scooped from the bottom, and have secured unusually large numbers of individuals of a few species. In Alaska (Sta. 4264), for example, the dredge load contained forty-seven specimens belonging to two different genera (Limifossor talpoideus and Chaetoderma erudita). Again in Monterey Bay, California, one haul (Sta. 4522) contained fifty-nine Chaetoderma monterey- ensis, while in a neighboring locality (Sta. 4523-4525) eighty were taken. In the National Museum I recently examined a large number of small animals taken by the ‘‘ Albatross” in the Atlantic, and discovered no less than thirty specimens of these molluses belonging to two genera. From such data and considering that the amount of territory explored is but a tithe of the entire sea floor, it is reasonable to suppose that in point of numbers and of species these animals will far surpass their nearest allies, the Chitons. Owing to the fact that up to the present time no Solenogastres have been reported from the North Pacific, and since the species described in the present paper have usually been collected from widely separated stations in a single dredge haul, it follows that there is little to be said definitely regarding their general distribution. It is an interesting fact that of the eight species taken in Japan six belong to the genus Strophomenia.. The genus Limifossor is represented by two species off Alaska and California respectively. This last named region is likewise the home of Alexandromenia agassizi and A. valida. Species of Chaetoderma occur in the ooze in all of the carefully explored terri- 24 GENERAL FEATURES, METHODS, ETC. tory mentioned in the introduction. However, it cannot be said that in any case we have any very definite information regarding the geographical limits or relative abundance of a single species. There is little to be said regarding the vertical distribution of the species described in the present paper. Where several individuals have been secured from a number of stations each species appears to be restricted to a fairly definite depth. Chaetoderma nitidulum is reported to have a range of from 14-1250 meters. A much greater depth may be possible for C. hawatiensis from Station 4130 where the initial sounding recorded 1362 fms.; but since the closing sound- ing was 358 fms. it is probable that the latter figure is more nearly correct, as a second specimen was taken at a depth of 528 fathoms (Sta. 3992). In many places the ocean floor is exceedingly rough and characterized by high almost vertical cliffs bounding fissure-like valleys. Under such circumstances a num- ber of soundings are desirable in order to avoid the necessity of accepting great extremes in vertical distribution though these may in reality exist with certain species. Mope or ure, Foop.— The species belonging to the Chaetodermatidae are, so far as known, inhabitants of the sea bottom where they excavate burrows which they rarely leave. Wiren (’92) who kept over one hundred specimens of C. nitidulum in captivity says they progress through the ooze by means of the alternate contraction and expansion of the prothorax aided by movements of the entire body; and that when at rest they ordinarily direct the body vertically with the cloacal chamber widely expanded, and the branchiae fully exposed at the opening of the burrow at the surface. When disturbed they disappear instantly several inches into the mud. In most respects these observations answer for C. erudita which I kept some time in captivity. This animal from, time to time advanced through the ooze in the manner described by Wiren but it never appeared at the surface. For hours together it remained quietly in its burrow with the gills fully expanded and when disturbed retreated but slowly, though the gills were at once retracted and the cloacal chamber closed. The individuals acting in this manner were apparently in a normal condition since the alimentary canal of several kept in captivity for nearly one month contained quantities of food. The members of the suborder Neomeniina, on the other hand, are not known to burrow, but are usually found on some species of hydroid, coral, and exceptionally (Proneomenia vagans, P. desiderata), on plants. Now and then specimens have been dredged unattached and it may be that they, like Neomenia GENERAL FEATURES, METHODS, ETC. 25 carinata and Stylomenia salvatori, crawl about freely over the sea bottom, though it is possible also that they have been loosened from some host. The relation of molluse and coelenterate has not been thoroughly worked out, but there are many indications and some definite proof that it is a genuine ease of parasitism and not an accidental association or a case of commensalism. In Drepanomenia vampyrella from the Hawaiian Islands the proboscis of one individual was inserted into the body wall of some species of Epizoanthus, many of whose reproductive and other cells had been withdrawn so that here there is no doubt that this Solengastre is a parasite. The presence of nematocysts in the alimentary canal of several other species, including most of the species of Strophomenia, indicates that they likewise are in the same category.* Hubrecht (80) states that a bit of aleyonarian coral was found in the mouth of P. sluiter7, but he calls attention also to the fact that diatoms and entomostracans occurred in the faeces in the cloacal cavity, and Heuscher (’92) records the presence of Entomostraca in the gut itself. It thus develops that the diet of such species is varied, and it is possible that such forms as P. vagans and P. desiderata which were found crawling about on plants belong to this same class. So far as known the food of the Chaetodermatidae consists of microscopic organisms and organie remains which they scoop up while burrowing through the ooze. ~ Wiren (’92) believes that the buecal plate (Mundschild) acts as a digging organ, and this may indeed be the case but the exceedingly small amounts of inorganic material, which make their way into the digestive tract, indicate that in addition to functioning in a purely mechanical fashion it manifests a decided selective action. When selected the food is carried backward by the great conical tooth in the genus Chaetoderma, and in the form of a more or less spherical bolus, mixed with the secretion of the salivary glands, is carried into the mid gut. In Prochaetoderma and especially Limifossor the radula and its supports are of large size and indicate active, predatory habits, but the contents of the gut are essentially the same as in Chaetoderma. Cotor, Size. —In a preserved state the skin of the Solenogastres is usually unpigmented, the light yellow or yellowish brown tint of the animal being due to the cuticle investing the body. In many species, especially of the Chaetoder- matidae, this may be obscured to a greater or less degree by the multitudes of refringent spicules imbedded in it or by some of the internal organs. The liver for example is often dark brown, and shining through the translucent body wall and the overlying cuticle and spicules, gives a decided frosted gray tint to several species. The red color of the blood plasma may impart a pinkish tinge espe- 26 COMPARATIVE ANATOMY. cially in the head and cloacal regions. An incrustation, rusty red or black, may cover the entire animal though it is usually restricted to the posterior extremity. In a very few species some of the hypodermal cells contain pigment, red, yellowish red, lilac, or yellow in color. Echinomenia coralliophila, a species living on Coralliwm rubrum, is provided with movable scales which when de- pressed give the body a whitish tint resembling the tentacles of the host, and this may possibly be the case with Strophomenia spinosa. Upon raising the spines the pigmented hypodermis becomes less obscured and the animal assumes a reddish color similar to the coral stalk. The smallest sexually mature Solenogastres are not over 5 mm. long, and on the other hand Proneomenia sluiteri attains, as previously stated, the great length of 148 mm. The average length is probably not far from 30 mm. LenetH Inpex.—In the discrimination of species the so-called length index, or the ratio of length to breadth of body, has been used to a considerable extent, but from several experiments in the preservation of fresh material, I am convinced that it is of little use, certainly not with closely related forms. For example nearly sixty Chaetoderma montereyensis, which had come up in the same dredge haul, were treated with slow alcohol in precisely the same fashion and yet the length indices varied fully twenty per cent. Some specimens must invariably be subjected to a greater pressure than others in the dredge load, and these are more flaccid and less contractile and with them the length index is relatively greater. COMPARATIVE ANATOMY. Foor anp Guanps.—It is now a generally accepted fact that the ventral furrow and its included fold represents a greatly reduced pedal furrow and foot. In the Chaetodermatina all external traces of these structures have disappeared completely, but internally a gap in the ventral musculature and a thickening of the longitudinal muscles on each side of the mid ventral line and in Limifossor a well-developed pedal sinus in the head region indicate their former existence. In what appears to be the least modified species, the foot consists of a single fold, but in several other species this is accompanied on each side by a fold of almost equal height and length, and in the Necmeniidae the creeping surface is often comparatively broad and is developed into several folds. Whether one or more of these plaits exist each is bounded by a single layer of ciliated COMPARATIVE ANATOMY. 27 epithelium which as a rule is continuous with the lining of the cloaca. The last named space is certainly a true mantle cavity and the plume-like branchia it contains in the Chaetodermatidae are ctenidia. On the other hand it is questionable if the folds developed in the cloacal walls, as in Alexandromenia for example, are homologous organs. As in the Chiton embryo two sets of pedal glands exist, termed by Hubrecht (80) the anterior and posterior pedal. The first named is a highly developed organ filling the greater part of the space between the body wall and gut in the head region. It is composed of pyriform cells whose ductules lead into the anterior end of the pedal furrow, which is usually developed into a cavity of considerable size, where they make their exit by separate intercellular openings. The posterior pedal gland is situated above and slightly to each side of the foot throughout its entire extent. Its cells are likewise pear shaped and open inter- cellularly into the pedal furrow. HypopERMIS AND Propucts. — What is sometimes termed the skin consists of two main elements, the hypodermal cell layer and the overlying spiculose cuticle. In the majority of species the hypodermis consists of a single layer of cells, and exceptionally (Paramenia palifera, Ichthyomenia ichthyodes, for exam- ple) forming a more or less irregular many cell layer. Concerning the nature of the elements entering into its formation there are numerous differences judg- ing from the accounts of the various authors, and the functions ascribed to them are equally diverse. The ordinary hypodermal cells, those responsible for the formation of the cuticle, are usually cubical or low columnar in form with round or oval nuclei imbedded in a finely granular cytoplasm pigmented in a few spe- cies (e. g. C. nitidulum) which blends with the overlying cuticle. In the same general situation gland cells are present in several species together with more slender elements which may perform a sensory function. The papillae occur in all Neomeniina in which there is more than one layer of spicules imbedded in the cuticle. Generally speaking each consists of a comparatively slender stalk which is attached to the hypodermis, and on the other hand expands into a more or less globular mass in contact with the free surface of the cuticle or may even project above it. The cells composing the swollen portion are apparently filled in life with a highly spongy, possibly vacuo- lated protoplasm which in preserved material may shrink greatly, producing radiating pseudopodia-like processes. In Halomenia gravida outpouchings of the gut occur at fairly regular intervals along the dorsal side of the animal on each side of the mid line. These penetrate the somatic musculature (Plate 32, 28 COMPARATIVE ANATOMY. fig. 5) and come in contact with the under surface of modified papillae, which appear to be capable of a certain amount of protrusion owing to the agency of a surrounding blood sinus. The significance of this remarkable state of affairs is very obscure; and for that matter the various functions such as excretion, touch, and pressure relations which have been ascribed to these organs as yet rest upon no direct experimental evidence. That they are the homologue of the aesthetes in the Chiton’ shell is a reasonable assumption, but this carries with it no trustworthy evidence regarding their office. The spines form from one to several layers in the cuticle, and present a great variety of forms. In the Chaetodermatina spearhead-types prevail, and in the Neomeniina, where there is but one layer, this shape may likewise occur. In those species with more than one layer the usual type is needle-shape, and with it may be associated radially directed spicules usually with truncated bases. : SprcuLE DeveLopMENT. — In a number of species of the present collection, notably Proneomenia hawariensis, Strophomenia scandens, and Halomenia gravida, certain of the more important details of the formation of the spiculose investment of the body appear with unusual distinctness, and to avoid needless repetition the results are discussed once for all in the following paragraphs. Speaking first of Proneomenia hawaiiensis, in the earliest stages of the spicule formation, where the calcareous product is no larger than the neighboring hypodermal elements, several cells are seen to be taking part. One of somewhat larger size than the others, and with clear finely vacuolated cytoplasm and distinct granular spherical nucleus, rests underneath the base of the spine. Its general appearance is_ essentially like that of the cell beneath the spicules of C. nitidulum as figured by Wiren or the spicule forming cells in the mantle of certain species of Chitons, and is par excellence the lime secreting element. Wiren is of the opinion that the basal cell is a modified wandering cell that has left the blood stream and migrated to the hypodermis. In all of the Soleno- gastres under discussion the wandering cells are of a granular character with no distinct cell membrane and clearly different from any of the hypodermal cells. Furthermore in the species under discussion I have never seen these plasma cells outside of the somatic muscle layer, and there are never any indications that the spicule forming elements are derived from any other source than the hypodermis. In very early stages, perhaps from the first, the spicule is surrounded by a delicate cuticular sheath whose reaction to the ordinary stains indicates a com- position unlike the material in which the spicules are imbedded. This spicule COMPARATIVE ANATOMY. 29 sheath is probably formed by seven or eight cells, slender in form, indistinct in outline, with dense nuclei and attenuated bases which are imbedded in the hypodermis proper. They entirely surround the basal cell, and distally their membranes become continuous with the spicule sheath, which as Plate 36, fig. 5, shows, is thus interrupted a short distance above the base of the spine. At a relatively early stage in the development of the spine a minute cell (Plate 36, fig. 11) may be detected between the basal cell proper and the spicule sheath. At first it appears to be connected with the deeper portions of the hypodermis by a single stalk that passes to one side of the basal cell; but in later stages such a connection disappears and the cell in question becomes closely applied to the base of the spine. It appears to be responsible for the formation of the spicule sheath immediately above it and in the following way for the cavity of the spicule itself. At first the cuticle above this small basal sheath cell is of uniform thickness and the lime salts, deposited presumably by the basal cell proper completely fill the spicule sheath, but very soon a minute knob-like elevation appears on the basal part of the sheath, and, perhaps owing to this increased thickness of the cuticle, it interferes with the deposition of calcareous material, for from this time on a cavity develops in the spine that in size and position corresponds to the cuticular knob. As the latter increases in size the spicule cavity enlarges, and when in later stages there is a decrease the cavity becomes proportionately narrowed until both finally disappear together. In the earliest stages of its existence the long axis of the spine is at right angles to the hypodermis, but as development progresses it becomes more and more inclined until it reaches the final horizontal position. This rotation is probably due in large measure to the unequal elongation of the attached cells, while the continual advance of the free tip of the spine through the surrounding cuticle is due to the addition of new material basally. During this whole forma- tive period and after its completion the entire spicule is migrating also toward the free surface of the body. Hubrecht and several other subsequent observers consider that this movement is caused by the continual cuticular current, so to speak, brought about by the perpetual addition of new material in contact with the hypodermis, a belief with which I concur for on any other supposition it would be difficult to account for the perfectly vertical, unbent position of the slender remnant of the matrix cells in late stages. Until the spine has been carried outward for a distance equal to one fourth or one third the thickness of the cuticle the matrix cells retain their usual con- nections and generally are fairly distinct though showing more or less shrinkage . 30 COMPARATIVE ANATOMY. (see Plate 36). This latter feature becomes strongly marked beyond this stage and as the cells shift to a distinctly subterminal position their boundaries dis- appear, and in the neighborhood of the spine they become dense and fibrous. Still later they migrate to a point fully one eighth the length of the spicule from a terminal position, their attachment to the spicule sheath becomes reduced to a minute knob-like dise and all but the basal portions of the cells themselves be- come transformed into a slender fibrous stalk, which elongating as additions are made to the cuticular investment of the body, maintains its attachment with the spine as long as the latter remains in the cuticle. In the region of the hy- podermis the outlines of the matrix cells remain distinct and unmodified with the exception of the enclosed basal cell which becomes distinctly fibrous. In certain slightly abnormal cases the stalk is sometimes unusually broad and under such circumstances the basal cell in later stages becomes distinetly fibrillar throughout its entire length, while the surrounding ensheathing cells assume rather a cuticular appearance and never so far as I have seen assume a fibrous character. In a very considerable number of cases the fibres, of unknown nature, that have developed in the original basal cell may be seen to extend beneath the level of the hypodermis, or to unite with others that may be traced for varying distances into the somatic muscles beneath. In the region of the buceal cavity, in Proneomenia hawaviensis, they may be followed through spaces in the muscle layer into close proximity to the ganglionic masses bordering on the cirri. So long as the spicule remains imbedded in the cuticle the stalk is in connection with it, and appearances suggest that after the basal cell ceases to be functional as a spicule forming agent it may transmit impulses to the central nervous system as the spines and scales in the mantle of the Chitons are sup- posed to do. In Halomenia, Lophomenia, Dorymenia and all of the species of Stroph- omenia described in the present paper this type of development prevails. In some species the matrix cells become detached from the fully formed spine, but otherwise no fundamental differences exist. Regarding the species described by other authors, Hubrecht and Heuscher agree that in Proneomenia slwiteri a cup of several cells clasps the base of the spicule, and Kowalevsky and Marion and to a certain extent Pruvot, and Wiren have made similar observations on other species. Through the generosity of Professor Hubrecht I have been able to examine a portion of the type of P. sluiteri and though the cells are not so clearly defined as in P. hawaiiensis there is no doubt that in both the spines follow the same course of development. Nierstrasz writes of Cyclomenia holo- COMPARATIVE ANATOMY. dl sericea ‘The spicula remain in connection with the hypodermis by thin threads, met with everywhere in the spicula’’ (cuticula?) and of P. discovery he states that ‘‘The spicules are formed in small accumulations in the epidermis” though one cell only is said to be active. Thiele has consistently argued in favor of one matrix cell and it is probable that he has focussed his attention on the type of spine I am about to describe. As noted in a preceding paragraph, there are in addition to the tangentially placed spicules in some species others that from the beginning to the close of their development are directed radially. This latter type of spine, so far as I have determined, has a mode of development completely different from the one just described. In Strophomenia triangularis for example as soon as it becomes clearly recognizable it rests upon what appears to be a single cell, and as long as it remains in the cuticle no additional elements put in an appearance. In the later stages the matrix cell usually becomes more cup-like closely clasping the base or side of the spine (Plate 36, fig. 18), and it may elongate to form a slender stalk but it is always unicellular. It is to be noted, however, that in this species, and perhaps in others, there are additional, radially directed spines of much larger size which appear to be formed by more than one cell though this is not certain owing to the fact that the base of each spicule is crowded against the somatic musculature. In the Chaetodermatidae Wiren has shown that but one formative cell exists though in its early stages the spine is surrounded by three hypodermal cells which may exercise a moulding influence. From my studies I doubt this last statement. In both Chaetoderma and Limifossor the formative cell is surrounded by hypodermal elements but there is no evidence that in the develop- ment of the spine they take any active part. It thus becomes evident that there are various types of spicule formation among the Solenogastres just as there are among the Chitons, but it is a most interesting and significant fact that the most common type of Chiton-spine development (according to Plate, 01, Theil C, p. 372) is almost the precise counterpart of what exists in P. hawaiiensis and several other species. Wiren is inclined to the belief that after the spicule forming cells have performed their function they become transformed into the hypodermal papillae. There is confessedly no definite evidence to substantiate such a theory, and on the other hand there are one or two facts that tend to discredit it. In the first place there is no definite relation between the number of papillae and spines; in the majority of species the latter considerably outnumber the former, notably 32 COMPARATIVE ANATOMY. in Alexandromenia. And again where the spicule retains its connection with the original formative cells such a fate is out of the question. And finally a few authors, notably Heuscher, have observed the origin of these organs directly from the hypodermis. I have seen many times papillae-like elevations (Plate 36, fig. 18) such as Heuscher figures, and I am strongly of the opinion that they have no connection with the matrix cells. Digestive Tracr.—The anterior division of the alimentary canal consists of a cavity whose walls are provided with two folds ( Mundleisten), usually of a horseshoe-shape that define the cirrose area where the wall is modified into numerous finger-shaped filaments. In the greater number of species this and the succeeding portions of the gut are intimately united, but in Rhop. aglao- pheniae, Dondersia, and a few other species they are distinctly separated by a ridge covered with the spiculose cuticle investing the body generally. Thiele considers that this sensory atrium is an ectodermic invagination of the integu- ment corresponding possibly to the Chiton snout. Accordingly where the separation is complete the true mouth is posterior to the opening of the atrial cavity, and where the latter is fused with the gut the mouth is situated behind the internal buccal ridge. In the Chaetodermatidae this anterior division is absent or is represented, as Thiele assumes, by the buccal sensory plate and possibly the semicircular groove (halbmondformige Grube). The limits of the pharynx are difficult to define but it is generally assumed that it contains the radula and the outlets of the salivary glands. Asa rule its epithelial lining is unmodified though it may be greatly folded and, in some spe- cies form papillae, which afford an outlet for the dorsal salivary glands. If an oesophagus exist it is usually not clearly differentiated from the pharynx, and in the following pages I have disregarded it. , In the Neomeniina the digestive gland or “‘liver”’ is not differentiated from the stomach or intestine. This last named organ may possibly be represented by the ciliated tract attached to the under surface of the gonad. In the Chaeto- dermatina the digestive gland, stomach, and intestine are clearly defined and are not essentially different from what exists in other molluses. The cloacal chamber is probably an ectodermic invagination and a true mantle cavity. There is no evidence that it is an expanded rectum. Musctunar System. — This system has been described in a very few species though most authors refer to the more obvious features especially the nature of the body wall. This consists of an outer circular layer, resting in some spe- cies upon a layer of diagonal fibres that in turn is in contact with a system of COMPARATIVE ANATOMY. 33 longitudinal bundles. In the anterior and posterior regions these are subject to various modifications, forming mouth and ‘cloacal sphincters and dilators, and affording attachment for the gill retractors or anteriorly for the multitudinous muscles operating the forward section of the digestive tract. These last named muscles have never been fully studied in any species though they are fairly well known in Chaetoderma nitidulum and Limifossor talpoideus. As the matter rests at present there is a similarity between the various species with respect to the somatic musculature and to certain of the more conspicuous bundles elsewhere in the body, but beyond this our data are too insufficient to permit -of close comparisons. Primary Bopy Caviry AND Smpra.— The space between the alimentary canal, gonad, and body wall, the primary body cavity, reaches a varying height of development according to the species. In the Chaetodermatina it constitutes a comparatively limited pseudovascular system and in some of the Neomeniina it is likewise much reduced, but in several species it becomes much more extensive. This haemocele is divided by a horizontal septum that extends between the longitudinal fibres on each side of the body beneath the gut and so forms a ventral blood sinus. In the Neomeniina it is small, but is bounded, in every species described in the present paper, by connective-tissue fibres per- forated here and there to permit of communication with the overlying blood spaces. In Chaetoderma a vertical septum separates heart, gills, and pallial complex from the remainder of the primary body cavity. It is not present in the Neomeniidae nor in Limifossor. In the last named genus there is an addi- tional partition, essentially the same as in the Chitons, which separates the head cavity from the succeeding portions of the haemocele. It is perforated by the aorta, alimentary canal, and a pedal sinus which passes forward into close proximity to the mouth. CrrcuLATORY AND Respiratory Systems.— The heart is developed as a fold of the dorsal pericardial wall reinforced by a varying number of muscle fibres, and in some species differentiated into an auricle and ventricle. From its anterior end the aorta arises and passing dorsal to the gonad leads into a more or less definite head cavity. In the Chaetodermatina and a very few Neomeniina this vessel possesses definite walls; in the others it is part of the general lacunar network. In Limifossor a distinct connective-tissue septum bounds the head cavity posteriorly, but in the greater number of other species the blood spaces in the head region communicate directly with those surrounding the mid gut. These last named sinuses are in communication also with a ventral 34 COMPARATIVE ANATOMY. median pedal sinus even though the foot be absent. In the posterior end of the body the blood is collected in a branchial sinus, if gills be present, or is con- veyed to the posterior end of the heart by means of clearly defined channels in the neighborhood of the rectum. In the Neomeniina the haemoglobin is contained in the corpuscles, and in the Chaetodermatina by the plasma. In the Chaetodermatina two plume-like respiratory organs, which spring from the anterior wall of the cloacal chamber, are in all essential respects like those of the Chitons and are doubtless true ctenidia, the space wherein they are contained being the mantle cavity. In the Neomeniina such organs are absent, though the cloacal wall may be developed into folds in some species of large size, penetrated by numerous sinuses and covered with a richly ciliated epithe- lium. It is believed by some investigators that such lamellae are incipient or degenerate ctenidia but there is little to support such a theory. Apart from these organs it is probable that respiration takes place over the surface of the body, especially along the ventral furrow if such be present. It has been suggested also that the great buccal folds may possess a combined respiratory and sensory function. Nervous System.— In the Solenogastres there is a more pronounced con- centration of the nerve cells to form definite ganglionic enlargements than in the Chitons, and the nerves supplying the mantle-cavity complex arise from a more restricted section, but in the arrangement of the brain, pedal and lateral ganglia, and the labio-buceal system there is a very distinct fundamental resem- blance between the two orders. In every case the brain, usually if not always bilobed, is situated on the dorsal side of the alimentary canal about the inter- section of the mouth and pharynx. From its anterior face three pairs of nerves originate in the Neomeniina and innervate the buccal wall and the adjacent regions of the body. About the bases of the atrial cirri these fibres connect with accumulations of nerve cells which may be the homologue of the great ganglionic masses in contact with the brain in the Chaetodermatina. In this last named group these accessory nerve masses, ten in number in Limifossor, are connected with the brain by several nerves, and on the other hand give rise to fibres which innervate the sensory buccal plate (Mundschild). In what appears to be the most primitive condition three pairs of connectives, the pedal, lateral, and labio-bucecal, take their separate origin from the brain as in the Chitons. Such a state of affairs is the rule in the Neomeniina. In Chaetoderma erudita these cords unite immediately before plunging into the accessory gangli- onic masses attached to the brain but retain a delicate connective-tissue sheath, COMPARATIVE ANATOMY. 39 and hence a perfect individuality, until they pass into the brain. In some other species of the genus, as for example Chaetoderma nitidulum, they fuse indistin- guishably as they enter the brain. Finally in Limifossor the pedal and lateral cords fuse a comparatively long distance from the brain, and at a less remote position are completely united with the labio-buccal connective. In every case the pedal ganglia are almost as long as the animal and hold a ventral position on each side of the pedal furrow though not always in close proximity to it. In several species commissures at fairly regular intervals have been seen uniting these cords, and equally numerous connectives have been traced to the lateral nerves which hold a more dorsal position along the sides of the body. In the posterior end of the animal the relation of these elements varies considerably in the different species. In Proneomenia hawaiiensis, for example, the pedal cords become reduced in calibre, and finally break up into small nerves which have not been shown to have any connection with the lateral cords though they come into the neighborhood of some of the small nerves originating from them. In Strophomenia scandens the last two or three latero-pedal connectives are of relatively large size and the union of the lateral and pedal ganglia is clearly established. Furthermore in several species, such as Lepidomenia hystrix, and Neomenia carinata, the posterior ends of the pedal cords terminate in ganglionic enlargements (ganglion posterius inferius, Wiren) united by a commissure of more than usual size situated ventral to the rectum. The posterior ends of the lateral ganglia are also frequently enlarged (ganglion posterius swperius) and are invariably united above the rectum, thus completing in several species a circum- rectal nerve ring. In the Chaetodermatidae the lateral and pedal ganglia are united, at least in the anterior end of the body, by commissures and connectives but more posteriorly these main ganglionic cords terminate in a large nerve mass, the so-called gill ganglion, continuous across the mid line above the rectum. In what probably represents a typical condition the sublingual or buccal system, in reality the labio-buceal, holds essentially the same relations as in the Chitons. Connectives lead from the brain along the pharyngeal wall and unite with ganglia about opposite the forward end of the radula or in the neighborhood of the openings of the ventral salivary glands. These nerve masses probably represent the labial and buccal ganglia of other molluses, and in at least one species, Strophomenia scandens, are united by three commissures and the sub- radular system. One of these commissures, the dorsal buccal, crosses the dorsal side of the pharynx, while two pass ventral to it. In Proneomenia hawaiiensis, where the subradular system is most highly developed, a connective arises from 36 COMPARATIVE ANATOMY. the inner face of each labio-buceal ganglion and unites with a small subradular ganglion which is in close contact with a subradular organ. These two ganglia are in turn united by a subradular commissure. In the genus Chaetoderma also there is a well-defined subradular system (p. 57). In several species of Solenogastres various authors have found what corre- sponds to the labio-buecal connectives and ganglia, and in most of these cases have found one commissure which is either the ventral buccal or labial. In the Neomeniidae the subradular organ is usually wanting together with the customary nerve supply; and in most species it is impossible to find more than one buccal commissure. However these nerves are usually very small and difficult to trace so that negative evidence in this case may not be entirely trust- worthy. SENSE oORGANS.— In the majority of Solenogastres a dorsal sense organ exists in the mid line in the cloacal region. In the Neomeniina it consists of a circular depression, naked or covered with a thin cuticular layer, and surrounded by spicules which in its contracted condition overarch it. When expanded by an underlying blood sinus a dise-like projection is elevated from the bottom of the depression and is raised above the surrounding spines. In the Chaetodermatina * a groove, likewise overarched by spicules when contracted, is probably a homol- ogous structure. In both families these organs are innervated by nerves from the dorsal commissure uniting the lateral nerve cords. Various functions have been assigned, but without any experimental evidence. a Thiele believes that the ventral furrow may be tactile but no sense cells have been shown to exist. In the gills on the other hand stiff hairs have been found among the cilia and are considered to be parts of sensory elements. Osphradia are unknown. In the Chaetodermatidae the anterior sensory plate is innervated by a heavy set of nerves and probably acts as a tactile organ. Owing to the heavy cuticular covering it may act also as a digging organ, operating in a general way like a hog’s snout. In Proneomenia hawaziensis a low sensory ridge encircles the atrial wall immediately within its outer opening. It is composed of high columnar cells whieh rest throughout their entire extent upon a rod-like mass of nerve cells. Internal to this are the usual atrial ridges (Mundleisten), of which the more external closely parallels the sensory tract just mentioned, while the inner one passes nearly around the canal at the commencement of what is probably the mouth cavity. Both are usually well-developed ciliated folds, capable, in some COMPARATIVE ANATOMY. 37 species, of great distention owing to the large blood sinuses contained within. Between the ridges the lining of the atrium is developed into simple or branched, finger-like processes termed cirri. Each is composed of glandular and sensory cells frequently pigmented, and is penetrated by a slender canal traversed by a nerve fibre. Regarding the function of these organs and the ridges it is vari- ously considered that they are gustatory, olfactory or tactile, or even respiratory. The cirri may be protruded from the opening, and this fact in connection with their glandular character has suggested that they may serve also to collect food; but judging from Drepanomenia vampyrella (page 79) there are times when they are Inoperative in this respect. Regarding the papillae in the hypodermis of the Neomeniina various hypotheses have been suggested. They appear to be connected with nerve fibres, and may reasonably be considered the homologue of the aesthetes in the shell of the Chitons, but up to the present time there is no proof that such is the case, nor that they are tactile, or secretory, or excretory, organs as some authors have maintained. A subradular organ, normally located and innervated, is known to exist in a few species (page 86). In its finer details it bears a striking resemblance to its homologue in the Chitons and perhaps functions in the same way. Corniom.— The secondary body cavity comprises the gonad, pericardium, and gonoducts whose relations have been determined in most of the known species of Solenogastres although their physiological significance remains very incomplete. The gonad, usually paired, is situated along the dorsal side of the animal between the body wall and alimentary canal. Posteriorly it is econtinu- ous, by means of two ducts, with the pericardium which in turn is in communica- tion with the cloacal cavity by means of two canals, the coelomoducts. So far as known all the Chaetodermatina are dioecious while the Neomeniina are hermaphroditic, and generally speaking the gonad is of the same length as the liver and therefore nearly as long as the body in members of the first named suborder. In the young the reproductive gland is paired, and in the adults with the exception of the genus Chaetoderma this condition of affairs persists, though sometimes partially obscured by the development of numerous germinal folds. In the Neomeniina the sperms arise along the outer walls of the gland while the ova, in some species surrounded by a follicle, are more inwardly placed. In the mature state the ova and spermatozoa make their way through the short, ciliated canals terminating the gonad posteriorly, and enter the pericardium from whence they pass to the outside through coelomoducts of various degrees 38 COMPARATIVE ANATOMY. of complexity. In the young of some of the Neomeniina these last named canals are simple tubes of about equal calibre throughout, but in later life they become modified into a shell gland and one or more seminal receptacles. In adult Chaetodermatina these canals remain comparatively simple, and there is some evidence that they function as excretory organs as well as genital ducts. In every case the coelomoducts originate from the hinder wall of the peri- eardium as comparatively small, ciliated tubes which pass anteriorly to about the level of the forward wall of the pericardium where they make a sharp bend and join the so-called shell gland in the Neomeniina. At the intersection of these two divisions from one to twenty-five vesicular appendages are usually attached, which have usually been considered seminal receptacles though the arrangement of the sperms in a few species indicate that for at least a part of the breeding season they may function as seminal vesicles. As the distal or ventral portions of the coelomoducts usually unite before entering the cloaca the shell gland which they form is a bicornuate, comparatively swollen structure with excessively thick walls and contracted lumen. It is reasonably certain that this organ functions as a nidamental gland, forming possibly an albumenous envelope before the egg passes to the exterior. In intimate connection with the genital apparatus just described there are a number of problematical organs which in some cases at least appear to have some role to play in the reproductive process. These include the genital spicula or penes such as oceur in Neomenia carinata, Dorymenia acuminata, Pararhopalia pruvoti, Stylomenia salvatori, and several other species. These are either rela- tively large caleareous paired spines, which ordinarily are concealed in sheaths formed as anteriorly directed diverticula of the cloacal wall, provided with pro- tractor and retractor muscles and in some cases with a gland, or similar diver- ticula, may conceal numerous spines of much smaller size. While the function of these organs is unknown it is reasonable to believe, with several authors, that they are excitants and possibly in a few species they may serve to attach the animals in covtu. The preanal gland (Hubrecht), which is attached to the anterior face of the cloacal wall in Proneomenia sluiteri, and opens at the end of the pedal furrow or right and left under the cloaca, may be associated in some way with the repro- ductive process. PuystoLocy.— Several authors, notably Wiren, have called attention to the striking resemblance between the Chiton kidney and the ccelomoducts of certain species of Chaetoderma; and again the presence of crystals has been . COMPARATIVE ANATOMY. 39 noted in these same organs. It thus becomes very probable that they aid in the removal of waste matters, and as noted on page 169 the fact that the male and female glands are identical in form and structure indicates that they play no especially important part in the egg-laying process, merely conveying the ova from the pericardium to the exterior. In the Neomentina there are certain indica- tions that the coelomoducts do not serve as kidneys, and the fact that they are non-glandular in immature individuals points also to their non-excretory character. In other parts of the body of several other species of Solenogastres there are organs of widely different character which are believed by various authors to hold the office of excretory organs. These include a number of structures which are in close proximity to the cloacal wall or are modifications of it. Among them are anal, preanal, or byssus (improbable) glands probably not in all cases homologous and evidently in some species playing a part in the process of repro- duction, especially where they are muscular, vesicular invaginations of the cloacal wall. Pruvot described a mass of spongy, glandular cells in Myzomenia banyulensis, forming a low elevation on the floor of the cloacal cavity, and con- taining yellow granules similar to others of larger size in the free cells of the underlying tissue. The supposition is that these last named elements are leucocytes, which, collecting materials from the blood, pass them to the cloacal wall from whence they are voided to the exterior. Thiele states also that in Proneomenia neapolitana there is an accumulation of cells irregular in form, forming a preanal gland between the hypodermis and the somatic musculature. Similar elements are attached to the cloacal-wall, the rectum, and coelomoducts, and others of somewhat like character are found in the intestinal sinus. Their resemblance to chlorogogue cells is marked, and for this reason chiefly they are believed to exercise the same function. Heath also has noted the presence of certain cells, along the ventral sinus of Limifossor talpoideus, whose shape and granular contents suggest the connective-tissue, concrement-bearing elements in the Chitons and other molluscs as noted by Brock. The papillae have been looked upon as glandular bodies by several authors and of these a few consider them to be excretory. On the other hand they may function as organs of special sense (see page 40). Respiration to a certain extent probably occurs over the general surface of the body, especially in those species with thin cuticle or where the cuticle is provided with blood sinuses. The ventral groove, as several authors have suggested, certainly permits the interchange of gases. The walls of the atrial cavity, especially the cirri and ciliated folds are believed also to take a share in 40 COMPARATIVE ANATOMY. = the process, and it has even been suggested that the entire stomach-intestine may be active. In the Chaetodermatina definite ctenidia perform the respira- tory function, while in the Neomeniina the thin walls of the cloacal cavity, often thrown into folds, sometimes of enormous size, and in contact with extensive blood sinuses, are undoubted active agents in this respect. In some species, such as in Alexandromenia the atrial ridges are of large size and their superficial extent is increased by the development of secondary folds and papillae. As these are penetrated by large blood sinuses it is probable that they act to a certain extent as respiratory organs though it is doubtful if this is their chief duty. The cirri on the other hand never, or very rarely, con- tain blood spaces and are very probably special sense organs. As the functions ascribed to the various sense organs, real or supposed, have been tested experimentally in a few cases only, it is not surprising that the opinions of authors differ widely. Considering first the sense of touch it is probable that it is located over the general body surface, for living specimens of Chaetoderma erudita and C. montereyensis respond to mechanical stimuli applied at any point. A number of investigators have noted the presence of nerves in contact with the hypodermis in other species and Wiren has traced some of them into the deeper portions of the cuticle where they are supposed to function in the sense of touch. In those species with thin cuticle and freely projecting spines it is likewise supposed that the latter serve as tactile organs. This same activity is ascribed a'so by Thiele to sense cells which he has detected in the foot of certain Neomentidae (Neomenia grandis, Proneomenia vagans). Of the various activities which have been connected with the much discussed papillae of the hypodermis is the ability to distinguish vibrations, amount of water pressure, or more generalized stimuli affecting the tactile sense. It is to be noted, however, that on the other hand these organs are said by several authors to be strictly glandular. A remarkable problematical relation of some of the papillae, considerably modified, to the anterior coecum of the stomach-intestine in Halomenia gravida (p. 147) is difficult to explain on any hypothesis. From experiments Wiren finds the gills of Chaetoderma to be very sensitive, and considers that the stiff hairs situated among the cilia are probably tactile. The buccal papillae are said by Heuscher to be organs of touch; they are cer- tainly not universally, if ever, food collecting organs. In close connection with the anterior border of the mouth of a few species in a living condition Pruvot, and Kowalevsky and Marion have detected sensory hairs, that in some species are attached to elevations, apparently the homologue of the sensory ridge, that CLASSIFICATION. 41 I have found paralleling to some extent the outer buccal sensory fold (p. 84). Pruvot has noted that as some of these animals progress they move the anterior end of the body from side to side, and appear to be using the organs in question to detect the character of their surroundings, so that they may be tactile. In Ichthyomenia there are many pits, apparently ciliated, in the anterior end of the body. These are probably sense organs, but of unknown function. The buccal sensory plate in the Chaetodermatidae with its enormous nerve supply may very probably function also as a tactile organ as Wiren and others have assumed, but it is to be noted that while this structure takes an active part in the excavation of burrows it is probable that it serves to detect the pres- ence of food. At all events the alimentary canal of these animals is singularly free from inorganic materials, and in the absence of any other well-defined organs In or near the buccal cavity it is not improbable that the plate acts as an olfactory or more than usually delicate tactile organ. These same activities or possibly the sense of taste have been assigned to the frontal sense organ noted in the preceding paragraph. The dorso-terminal groove in the Chaetodermatidae and its homologue in the Neomeniidae is usually considered to be an organ of special sense, Heuscher alone alleging the contrary owing to the fact that the depression in Proneomenia sluiter’ was filled with detritus. This condition is not infrequently encountered in animals which have been excavated from the material in a dredge, but it is certainly not a normal state of affairs. Concerning its function we have abso- lutely no positive evidence. It is reported by Pruvot that it may hold the same office as the frontal sense organ though the belief appears to rest upon nothing more tangible than a certain similarity of structure. CLASSIFICATION. While the modification, by Nierstrasz, of Simroth’s scheme of classification doubtless fails of necessity to indicate accurately the phylogenetic relationships of the Solenogastres it has the virtue of being more convenient than any other now in use and hence has been adopted in large measure. The family name Para- meniidae must be discontinued. Cockerell (’03) has shown that Pruvot’s genus Paramenia is preoccupied and has proposed the name Pruvotina, hence in the following table I have used a new family name Pruvotiniidae. The family 42 CLASSIFICATION. Lepidomeniidae Nstr. containing Dondersia must retain Simroth’s name Dondersiidae. As has been noted by other authors the genus Proneomenia as created by Hubrecht, has been much enlarged to include a number of species some of which probably belong to other genera. Proneomenia weber appears to be very closely related to Dorymenia acuta and may in reality belong to Dorymenia. In the genus Strophomenia the long pharynx, the papillae and the numerous seminal receptacles are so characteristic and similar in the species of the present collection that I have no hesitancy in placing all in the same genus. Pruvot’s material was poorly preserved, as he states, and under such circumstances the peculiar condition of the ventral salivary glands is readily explained as I know from experience. The radula sac is likewise incorrectly placed, being much too far forward. Evidently in Pruvot’s species all traces of this organ have dis- appeared. With this revision the species are quite similar. It is probable that Rhopalomenia indica Nierstrasz belongs to this genus. Order APLACOPHORA vy. [HERING. Suborder. I. Chaetodermatina Simroth. Spiculose integument continuous all around the body. Chaetodermatidae, p. 42. Suborder II. Neomeniina Simroth. Spiculose integument interrupted beneath by a longitudinal ventral furrow. Neomeniidae, p. 44. Proneomeniidae, p. 45. Piuvotiniidae, p. 47. Dondersiidae, p. 48. . CHAETODERMATIDAE Srimroru. Opening of mouth and anal chamber terminal. Body with more or less sharply marked regions. Ventral furrow and fold lacking. Two highly devel- oped plume-like gills. Radula distichous, polyserial or strongly reduced to a large unpaired cuticular tooth. The mid-gut possesses, in most cases, a well- developed digestive gland. Copulatory apparatus lacking. Coelomoducts remain separate. Cuticle thin, spicules flat, often needle-form, but solid. Inhabit jbottom ooze. CLASSIFICATION. 43 Chaetoderma Loven, 1845. Body vermiform, without ventral groove; mouth and anal chamber ter- minal. Two gills. Sexes separate. Radula reduced to conical peg. Type of genus C. nitidulum. C’. argentea, sp. nov. Length 24 mm. by 1.6 and 2.6 mm. through the metathorax and preabdomen respectively. Silvery white. Spines, in side view, usually bent. Alaska. (p. 62.) C. attenuata, sp. nov. Body long and slender, measuring 61 mm. in length by 1.5 through the metathorax and 2.7 through the preabdomen. Buccal plate relatively small. Alaska. (p. 55.) C. californica, sp. nov. Body measuring 24 mm. in length by 1.6 mm. greatest diameter. Larger spines with expanded bases. California. (p. 64.) C. erudita, sp. nov. ° Average length, in preserved state, 27 mm. by 2.5 mm. average thickness of preabdomen. Buccal plate deeply cleft by mouth opening. Brain of large size. Alaska. (p. 59.) C. hawaiiensis, sp. nov. Body slender, measuring 12-19 mm. in length by 0.5-0.6 mm. greatest thickness. Buccal plate broadly elliptical, perforated in centre by mouth. Hawaii. (p. 49.) C. japonica, sp. nov. Length 17 mm. by 1.5 mm. greatest thickness, buecal plate shield-shape, perforated by mouth opening. Japan. (p. 67.) C. montereyensis, sp. nov. Length 45 mm. by 3 mm. greatest diameter. Buccal plate unusually large. Tooth stout. Monterey Bay, California. (p. 61.) C. nanula, sp. nov. Body small, comparatively stout, measuring 9 mm. in length by 1.4 mm. greatest diameter. Spines keeled and of heavy appearance. California. (p. 66.) C. robusta, sp. nov. Body heavy, measuring 60 mm. long by 3.5 and 4.7 mm. through the meta- 4d CLASSIFICATION. thorax and preabdomen respectively. Buccal plate shield-shape. Largest spines relatively slender without definite keel. Alaska. (p. 68.) C. scabra, sp. nov. Small, measuring 12 mm. in length by 2 mm. greatest diameter. Body wall relatively thin. Brownish, becoming olive-green in region of digestive gland. Monterey Bay, California (p. 63.) Limifossor Hearn, 1904. Body short. Radula very large, distichous, with twenty-eight transverse rows in L. talpoideus (about the same number in L. fratula). Dorsal salivary glands present. Stomach and digestive gland well developed, and distinet from intestine. Type of genus, L. talpoideus. L. fratula, sp. nov. Slaty gray with yellowish cast. Spines from middle of body 0.5 mm. long. Length index 1.38-4.7. California. (p. 72.) L. talpoideus. Slaty gray in color. Spines, from all parts of the body, 0.02—0.38 mm. in length. Length index 1-6. Alaska. (p. 69.) NEOMENIIDAE Simrorn. Body compressed, more or less crescent-shaped, without distinet divisions. Index 7 at most. Opening of atrium ventral, of the anal chamber ventral or terminal. Ventral furrow present, usually with several folds. Cuticle some- times comparatively thick, spines mostly needle-like, flat, grooved, or hollow. A cirelet of gills in the anal chamber. Radula and salivary glands usually lack- ing. Epidermal papillae, of simple structure, usually present. Fore gut pro- trusible. Coelomoducts separate or united to form shell gland or copulatory organ. Digestive gland lacking. Penial spines usually present. Free, creep- ing about over bottom. Drepanomenia, gen. nov. Body short and thick. Hollow needle-like spines with truncated bases; slender stalked papillae. Ventral salivary glands long and tubular. Coelomo- ducts simple, without appendages. No copulatory apparatus. Type of genus D. vampyrella, sp. nov. With characters of the genus. Hawai. (p. 77.) CLASSIFICATION. 45 Pachymenia, gen. nov. Body stout, measuring 27 by 4.5 mm. One layer of awl-like spines, papillae multicellular with broad bases, posteriorly ill defined. Pharynx very large and muscular with numerous glands some of which open by one pair of ducts at forward border of pharynx. Dorsal and ventral limbs of coelomoducts provided with numerous glands. One pair of small seminal receptacles. Cloacal wall covered with glands except region of branchial folds. No copulatory spines. Type of genus P. abyssorum, sp. nov. With characters of the genus. California. (p. 72.) PRONEOMENIIDAE Simroru. Worm-like. Radula distichous or polystichous, sometimes lacking. Sali- vary glands tubular, lobed or lacking. Cuticle thick, spicules mostly needle- like in several layers. Epidermal papillae present. Gills usually lacking. Coelomoducts usually united into shell gland, sometimes separated. Copulatory apparatus may be present. Free living, partly or entirely parasitic. Proneomenia Husrecurt, 1880. Body elongated, vermiform, the length 9-50 times the diameter. Cloaca opening ventral. Foot present, the groove passing into the cloaca. Cuticle thick with crowded spicules. No gills. Radula multidentate. Two salivary glands. Copulatory organs present or absent. Type of genus, P. sluiteri. P. hawaiiensis, sp. nov. Length 36 by 2 mm. Dorsal and ventral salivary glands. Radula with 38-40 teeth in each transverse row. One pair of seminal receptacles. No copulatory organs. Hawai. (p. 82.) P. insularis, sp. nov. Anterior end similar to the foregoing species (posterior end missing). One pair long, tubular salivary glands. Radula polystichous with 28 transverse rows. Hawai. (p. 90.) Driomenia, gen. nov. Measurement 9 by 1 mm. Cuticle thick, papillae present, spines needle- shaped, slightly curved. Atrium separate from mouth opening, no radula, one pair globular ventral salivary glands. Antero-lateral pericardial wall prolonged 46 CLASSIFICATION. into a pair of horn-like pouches. One pair seminal receptacles. No copulatory spines. Gills absent. Type of genus D. pacifica, sp. nov. With characters of the genus. Japan. (p. 93.) Dorymenia, gen. nov. Vermiform, body terminating posteriorly in a finger-shaped elongation. Radula polystichous, with 48-51 longitudinal rows of 22 teeth each. One pair of seminal receptacles. A pair of long copulation spicules closely associated with a pair of globular coeca likewise opening separately into the cloaca. Type of genus D. acuta, sp. nov. With the characters of the genus. California. (p. 95.) Strophomenia Pruvor, 1899. Body elongated, cylindrical, the thick cuticle penetrated by acicular spicules and closely crowded vesicular papillae; radula and salivary ducts, caudal sense organ sometimes absent (?); two distinct genital openings into the cloaca. Type of genus, S. lacazev. S. farcimen, sp. nov. é Length 18 by 2 mm. Papillae smal, closely crowded. Radula with 15 transverse rows of 24-28 teeth. 19 seminal receptacles. Japan. (p. 119.) S. ophidiana, sp. nov. Length 43 by 2.5 mm. Papillae fairly numerous. No radula. 23 small seminal receptacles. Japan. (p. 112.) S. regularis, sp. nov. Anterior end missing. Papillae small, closely crowded. 12 seminal recep- tacles. Japan. (p. 116.) S. scandens, sp. nov. Length 32-39 by 1.6-2.1 mm. diamter. Papillae crowded. No radula. 15-18 seminal receptacles. Hawaii. (p. 106.) S. spinosa, sp. nov. Length 28 by 1 mm. Papillae few. Radula small, monoserial or biserial with 8 transverse rows. 12-31 seminal receptacles. Japan. (p. 122.) S. triangularis, sp. nov. Length 12 mm. by 1.6 mm. diameter. Triangular in cross section. Radula CLASSIFICATION. 47 distichous, apparently comb-like with 16 cusps in each row. Seminal receptacles 10-12. Japan. (p. 125.) PRUVOTINIIDAE, nom. nov. Worm-like. Cuticle, as a rule, thick; spines as in Proneomeniidae or hook-like. Epidermal papillae present or absent. Radula distichous, simple or double comb-form, or lacking. Salivary glands globular, lobed or tubular. Gill folds present. Coelomoducts united to form unpaired shell gland. Copu- latory apparatus may be present. Ventral furrow and fold present. Free or living on coral, ete. Lophomenia gen. noy. With dorsal keel; length 24 mm., diameter 1.5 mm.,3 ventral folds. Cuticle thick, with numerous needle-like spines in several layers; papillae few, club- shaped. Radula distichous, 20 transverse rows. Dorsal salivary gland large; ventral globular. 2 seminal receptacles, 2 bundles of many copulatory spines. Type of genus L. spiralis, sp. nov. With characters of the genus. Hawai. (p. 128.) Alexandromenia, gen. noy. Body relatively short and thick, length 25-32 mm. by 3.5-5 mm. diameter. Spicules small needle-like associated with larger radially directed ones. Papillae very large, multinucleate. Foot, 5-9 folds. Gill folds 20-40. Numerous pharyngeal glands and enormous lobulated glands opening on the sides of the pharynx. Radula monoserial. 1 pair seminal receptacles. Type of genus A. agassizi, sp. nov. Posterior end truncated, gills exposed. Monoserial radula with slightly curved rectangular teeth. 40 gill folds. California. (p. 133.) A. valida, sp. nov. Posterior end rounded, cloaca opening ventral. Teeth with two horn-like projections. 20 gill folds. California. (p. 142.) Halomenia, gen noy. Body short, length index 7:1. Spicules needle-like. Papillae large, in places resting upon diverticula of the mid gut. 2 ventral folds. Gills 26-80. Radula distichous. 1 pair seminal receptacles or vesicles. Type of genus H. gravida, sp. nov. With the characters of the genus. Kurile Islands. (p. 146.) 48 CLASSIFICATION. DONDERSIIDAE Srimroru. Body often worm-like. Cuticle thin; spines flat and solid. Papillae lack- ing. Radula distichous, monoserial or lacking. Salivary glands globular, sac- or tube-like. Gill folds lacking. Coelomoducts united or separate. Copulatory apparatus may be present. Ventral fold and furrow may be absent. Living free, or on corals, ete. Herpomenia, gen. noy. Length 11-18 mm. by 0.6-0.9 mm. Foot smoothed out, ciliated. Ventral salivary glands very large, encircling the thick walled very muscular pharynx. Radula lacking. 1 pair seminal receptacles. Shell gland almost globular. Type of genus H. platypoda, sp. nov. With the characters of the genus. Aleutian Ids., Alaska. (p. 151.) Dondersia Husrecnut, 1888. Body long, length index 10-48. 1 ventral fold. Spicula needle- or spatula- shaped, flat. Cuticle very thin, no papillae. Dorso-terminal sense knots present. 1 pair of short ventral salivary glands, which unite before opening out into the pharynx. Radula small, monoserial or biserial. Mouth cavity and pharynx opening separated from each other. No copulation spicula. Type of genus, D. festiva. D. californica, sp. nov. Dorsal salivary glands very scant; ventral small. Radula with at least 12 pairs of teeth. Immature. California. (p. 155.) Ichthyomenia Piussry, 1898. Body eylindric-conic, broader behind, narrowed in front. Cloaca opening a terminal transverse slit, a prominence in front of it. Foot groove and foot present, disappearing posteriorly. Cuticle not papillose, the ventral spicules leaf-shaped, the rest scale-like, imbricating. No gills. Radula well developed or rudimentary, with apparently two rows of teeth. Length 5 to 13 times the breadth. Type of genus, I. ichthyodes. I. porosa, sp. nov. Body pale yellowish white, 16 mm. long by 1.2 mm. thick. Seales fish-like and elub-shaped. Upwards of 50 sensory pits in the anterior end. No radula. California coast. (p. 159.) CHAETODERMA HAWAITIENSIS. 49 DESCRIPTION OF SPECIES. Chaetoderma hawaiiensis, sp. nov. Two specimens of this species were dredged in the vicinity of Kauai Island. The first came from the western end (Sta. 4130) at a depth of 283-309 fath.; the second from the northern extremity, Mokuaeae Islet (Sta. 3992), at a depth of 528 fath. The first specimen was found in a mass of polyps of Epizoanthus (Plate 2, fig. 3) elevated at least a foot above the bottom, and densely matted together in such a manner as to preclude the possibility of accidental lodgment. The second individual was found by Dr. W. K. Fisher among the spines of a species of starfish (Odinia pacifica Fisher) also in such a position that it could scarcely be due to accidental shifting. There is no especial reason for considering this species a parasitic form nor indeed a commensal, for the food in the alimentary canal consisted of small quantities of plant spores, sponge spicules, and organic debris such as is ordinarily found in those species that burrow in the ooze. It seems more probable that it, like Chaetoderma nitidulum, as described by Wiren, may leave its burrow to crawl about on the bottom, or as in the present case even on the bodies of other animals. In its external features this species displays the usual characteristics of other members of the family. The body including the globular and apparently non-retractile prothorax, itself about 2 mm. in length, is 12 mm. long. Imme- diately behind the swollen part of the prothorax the diameter of the body is 0.65 mm., and this continues with little change through the anterior half of the ani- mal. Beyond this point the calibre gradually increases to 13 mm. in the neigh- borhood of the cloaca, beyond which a slight decrease occurs that continues to the end of the body. In the other specimen the size of the prothorax is the same, but the length of the metathorax (19 mm.; diameter 0.5 mm.) and the abdomen (7 mm.; diameter 1 mm.) is considerably greater and bears witness to the futility of using the length index in the discrimination of some species. The color of both specimens is a slaty gray, though this is usually obscured by an inorganic incrustation covering the body generally. In the region of the metathorax the larger spines are completely hidden in a granular deposit that gives this part of the animal a brick-red shade. The same substance, in one case black in color, is present in several other species of Chaetodermatidae in my possession, and may perhaps be an excretory product thrown out from the coelomoducts. 50 CHAETODERMA HAWAIIENSIS. The cuticular plate covering the frontal sense organ is almost circular in outline and is elevated above the general surface of the prothorax. This is especially the case with the lateral portions which assume the form of pronounced folds decreasing in height as the centre of the organ is approached. The boun- dary between the cuticle and the underlying epithelial cells is not sharp and the outlines of the cells themselves are not clearly visible. The greater number appear to be sensory elements and are distinguished by their relatively slender appearance (the diameter being to the height as one to four) and by darkly staining elongated nuclei placed-in the basal half of the cell. Among these are a few cells of the same height, but of greater diameter, which contain spherical centrally placed nuclei with a small amount of chromatin. Great numbers of ganglion cells are situated in immediate contact with this sensory plate, and some of the more deeply seated clearly connect with nerves passing out from the precerebral ganglia (as I have termed the great accumulations of ganglion cells in contact with the brain in the Chaetodermatidae), and on the other hand originate fibres that pass down to the frontal organ (Plate 28, fig. 1). A very few small pyriform gland cells, staining almost black in haematoxylin, extend from the midst of the ganglion cells to the sense organ where they probably open to the surface. Large numbers of muscle fibres attach also to the sensory epi- thelium and at several points there are indications that they pass between the hypodermal cells and connect directly with the overlying cuticle. The hypodermis is practically the same as in other species and not particu- larly favorable for the solution of any of the several problems connected with it. Its cells differ considerably in form and appearance. In the swollen part of the prothorax they are slightly higher than broad; in the metathorax the reverse is true; while in the abdominal region the height is about twice the diameter. Everywhere their boundaries are indistinct, and thus unlike the sharply defined central nuclei. Here and there are more slender elements with elongated darkly staining nuclei, and somewhat more numerous are the basal cells in contact with the base of the overlying spicules. These latter cells vary widely in general appearance from very small compact elements to others large, globular, and much vacuolated, owing to different stages of development and probably to some extent to mechanical compression. No pigment cells exist, nor wandering cells nor other elements that are sufficiently different from the usual constituents to be placed in a separate catagory. The spicules are of the usual spearhead shape, and form a continuous series of increasing size, from those of the prothorax with a length of .0275 mm. CHAETODERMA HAWATIENSIS. ol to others on the postabdomen .225 mm. long. Plate 37, fig. 12, gives an accurate idea of the usual type of spine, these being from the middle of the metathorax. The mouth opening is situated about the centre of the frontal sense organ and is remarkable for its minuteness. From here to the region of the radula the canal is relatively small, not exceeding one seventh of the greatest diameter of the prothorax. It is invested by a thin layer of muscles and is attached also to a considerable number of scattered fibres that pass outward and are inserted in the body wall. Ganglion cells arranged in groups as in the Neomeniidae are also fastened to the buccal mass. The epithelial lining consists of high columnar cells with basal nuclei imbedded in moderately dense cytoplasm, that more distally becomes filled with a finely granular colorless secretion. In one speci- men particles of a golden yellow color occurred in, or between, some of these elements, but whether they were developed in situ, or had been produced by cells more externally placed, it is impossible to determine. While in one specimen the digestive tract continues of about the same calibre throughout, the other expands widely in the region of the radula, and at the anterior end of this enlargement a circular fold is present that is probably homologous with the proboscis of Drepanomenia, for example. In one indi- vidual this swollen section is almost completely filled with diatoms, plant spores, sponge spicules, and organic remains some of which appear to have been mixed with some viscous secretion and moulded into globular masses. From a point corresponding to the hinder border of the globular part of the prothorax to the anterior end of the preabdomen, the wall of the digestive tract is relatively thin due to the scarcity of muscle fibres and the lowness of the epi- thelial cells. The latter are columnar elements of medium height with spherical basal nuclei and an abundance of a finely granular, light yellow substance filling the entire distal half. At various points throughout the prothorax and meta- thorax this substance is in the act of escaping in the form of droplets constricted from the cell, and all stages exist between this and the development of a finely granular secretion filling the canal. Cells freed of this secretion are cubical in form and are usually relatively dense. Cleared specimens show that while in this part of the gut true pouches do not exist the canal is by no means entirely straight, wrinkles and folds occurring throughout, though they lack the definite- ness and regularity of the dilations in the Neomeniidae. At the level of the front end of the gonad the development of digestive fluids becomes relegated to a set of cells that form a large diverticulum extending to the hind end of the body. In this digestive gland, judging from the material 52 CHAETODERMA HAWATIENSIS. in hand, two distinct kinds of material are secreted, but in widely differing quantities according to the locality. The cells attached to the gonad are usually more or less pyriform with comparatively small, dense almost homogeneous nuclei placed basally, while the remaining protoplasm is closely packed with innumerable granules. By far the greater number of these are spherical and of yellow or slightly greenish yellow tint. They are liberated, as is the secretion in the more anterior parts of the gut, by the constriction of droplets from the distal end, and may be seen undergoing disintegration and solution in many different places. Among the granules of this character are others in the form of small particles of a distinct pink or violet color after treatment with haematoxylin. They have every appearance of being an end product and not a stage in the development of the more abundant secretion. Elsewhere in the gland the cells are of looser texture, the basal nuclei are relatively larger and granular and many if not all contain the two species of secretion just described. Generally the yellowish product is scant in amount, while in many cells the violet tinted substance accumulates in spherical or elliptical masses, surrounded by a vacuole in preserved specimens, that almost fills the cell. These secretory products are passed out entire, and in a single section as many as twenty-five may hold positions in the lumen of the gland. Making their way forward many if not all pass into the intestine, and here may be seen in various stages of solution, forming at first a vacuolated product that before dissolving completely transforms into a finely granular material of maroon color after treatment with haematoxylin. The cells of the intestine are cubical in form and in front of the pericardium show signs of slight glandular activity. Behind this point this phase of activity disappears, and cilia become developed and continue to the opening into the cloacal cavity. The large size of the ganglia and the abundance of the nerve cells that envelop them and also the sharpness of even the smaller nerves renders it pos- sible without much effort to gain a very clear idea of the nervous system of this species (see Plate 7, fig. 2). As is there shown the brain, located some dis- tance above the digestive tract, is distinctly enveloped in a delicate connective- tissue sheath and is clearly bilobed in form though its outlines are somewhat obscured by great masses of ganglion cells (forming the precerebral ganglia) attached chiefly to its lateral and anterior surface. A considerable number of delicate fibres, passing out from the brain, attach to these ganglionic bodies which in turn are connected with large numbers of nerve fibres that pass chiefly to the walls of the mouth and the frontal sense organ. lt cae i SS Bi i ee eee ee ee 0 Gee a a ee ne = oan ee CHAETODERMA HAWATIENSIS. 53 This part of the nervous system is thus essentially as we find it in other Solenogastres. In Proneomenia hawaiiensis, for example, the supraoesophageal ganglia are connected with several nerves some of which unite with groups of ganglion cells attached to the bases of the cirri, and from these again other nerves pass to the digestive tract and probably to the body wall. In Chaetoderma the chief difference is that the nerves uniting the brain and precerebral ganglia are very short. In the present species the pedal and lateral connectives unite immediately ‘before plunging through the precerebral ganglia, and as Plate 7, fig. 2 shows the labio-bueceal cord unites with them before the brain is reached. This same condition of affairs exists also in two species of this genus taken in Alaska, though much more obscured than in the present species. At the posterior end of the prothorax the pedal and lateral cords that have gradually approached each other actually come in contact and in one specimen even fuse for a short distance and lose the usual sheath of ganglion cells. Anterior to this point two pedal com- missures exist, but until the hindmost part of the body is reached no farther trace of such nerves has been found. On the other hand latero-pedal connectives are present throughout the entire length of the animal. The relations of the labio-buccal ganglia are represented in Plate 7, fig. 2. The non-ganglionic connectives imbedded in the pharyngeal wall unite with the superficially attached ganglia, that are also united by a commissure passing behind the median tooth. In front of the radula there are connectives giving rise to nerves passing dorsally to what is probably the subradular organ and in addition attaching to a ganglionic mass in the mid line. As this part of the nervous system appears with greater distinctness in C. attenuata it is more fully described in that connection. Throughout the entire metathorax the lateral and pedal cords pursue their course almost in contact, here and there giving rise to nerves that soon disappear, and finally join in the extreme posterior end of the body. Shortly after their union they are connected by a heavy ganglionic commissure passing dorsal to the intestine. In the mid line it develops a single nerve that makes its way into the tissue of the rectum, while on the dorsal side four fibres originate, two of which pass at once into the gills while the others attach to the inner side of the cloacal epithelium, and branching repeatedly supply this membrane and the dorsal body wall and a well-marked fold of the hypodermis to be described presently. At the junction of the latero-pedal cord and the commissure a nerve arises that passes backward and appears to supply the ventral body wall of the cloacal region. 54 CHAETODERMA HAWAIIENSIS. Owing to the debris encrusting the posterior end of the body it is impossible to determine the position of the dorsal sensory groove in entire specimens. In sections it is seen to occupy the usual position, that is from the extreme hinder end of the animal forward to a point almost immediately above the level of the anal opening. As is represented Plate 6, fig. 8, it consists of a relatively deep fold of the hypodermis, that anteriorly rapidly disappears but is continuous with a ridge-like elevation in the mid dorsal line extending for a short distance more anteriorly. Some of the spines of the immediate neighborhood are of compara- tively small size and overarch the depression, which is also covered by a thin continuation of the cuticle investing the body. The cells of this organ consist of those common to the hypodermis, and others which are much more slender and compact with spindle-shaped nuclei usually subcentrally placed. The latter elements are probably sensory and connect with small groups of ganglion cells holding positions immediately beneath the circular somatic muscles in the neighborhood of the organ, and on the other hand are undoubtedly related with nerves from the branchial ganglia. That this is a definite sense organ and the homologue of the dorsal organ of the Neomeniidae, as maintained by various authors, there is little doubt, but there is nothing that more definitely establishes its function. The gonad extends from the front end of the metathorax to the pericardium with which it is united by two short and comparatively wide ducts. Both speci- mens were sexually mature males and considerable quantities of spermatozoa occupied positions in the pericardial cavity, and at various points in the coelomo- ducts. These last mentioned organs arise from the postero-lateral borders of the pericardial chamber in the form of clearly defined tubes, whose cells are nearly cubical in form and support an abundance of large cilia. Bending sharply inward each becomes continuous with a canal, of much larger size and different structure, that after extending forward for a short distance pursues an irregular course opening symmetrically on each side of the rectum. The large non-ciliated por- tion of the ducts is composed of rather low cells with well-defined, basally placed nuclei, in which the chromatin exists in the form of a moderate number of sharply defined granules. In the more distal part of each cell is a sharply defined vacu- ole, in which are one or two light greenish yellow bodies, having the appearance of concrements such as occur in the kidneys of several molluses. At various places these are in the act of escaping through the ruptured or dissolved end of the cell or having become free are undergoing a process of solution. Such an appearance in the kidney of other molluses would not in any way appear unusual, - =_ —- CHAETODERMA ATTENUATA. 55 and leads to the irresistible conclusion that here the coelomoducts are not only morphologically related to the renal organs in the Chitons or other molluses, but physiologically also as Wiren first clearly stated. Chaetoderma attenuata, sp. nov. Eight specimens of this species were dredged near the southern limit of Alaska, buried in glacial mud brought down chiefly by the Stikine River. One from Kasaan Bay (Sta. 4244) oecurred in green mud at a depth of 50-54 fathoms; five opposite the mouth of the Stikine River (Sta. 4250) were in the same habitat at a depth of 61-66 faths.; while two in the waters of Stephens Passage (Sta. 4252) were buried in gray mud at a depth of 198-201 faths. Their appearance in life, Plate 4, fig. 3, answers closely for preserved material. The type specimen measured 45 mm. in length by 1.7 mm. through the metathcrax, and 2.6 mm. through the abdomen. The color of aleoholic material, which is the same as the living save for the pinkish tinge due to haemaglobin in the head and gill region, is almost white with a tinge of yellow, becoming grayish where the liver is located. The body wall, including muscular, hypodermal, and cuticular layers, is of median thickness and is typically located, but in specimens killed in vom Rath’s fluid certain elements appear that have not been fully described, though they probably occur in all species of the genus. These are the so-called giant cells (Riesenzellen Wiren) which in ordinary material present the form of empty vesicles with the nucleus imbedded in the wall. In life this cavity is filled with a secretion, that after treatment with fluids containing osmie acid, is granular as Wiren has remarked. In favorable situations it may readily be seen that fibres, muscular at least in part, extend from the somatic musculature and penetrating the hypodermal layer attach to the sides of these cells (Plate 25, fig. 7). Ap- pearances suggest that the secretion, upon the contraction of the fibres, is forced into the neighboring lacunae, but in no case has this been actually observed though proximally the cell may be produced into a comparatively slender, short stalk. Distally the cells are usually in close contact with the free surface of the cuticle and present a sharply defined rounded appearance. Posteriorly these elements become somewhat less numerous and of smaller size. In alcoholic killed material the fibres may be distinguished, but their attachment to the cell body is very indistinct. Wiren (’92) states that these giant cells are not sharply differentiated from the basal matrix cells of the spicules, but this refers, so far as I am able to judge, 56 CHAETODERMA ATTENUATA. merely to their form as the spicule mother cells do not contain any clearly de- fined granular secretion. On the other hand the matrix cells shade much more perfectly into the cubical elements that probably form the cuticle. The mouth, placed in a cleft on the dorsal side of the buccal plate, opens into a tube whose form and general appearance are represented (Plate 25, fig. 1). The lining epithelium consists of the usual high columnar cells produced into several irregular longitudinal folds, through which the outlets of the buccal glands make their way. These last named organs are comparatively abundant, especially on the ventral side of the pharynx, and extend from the region of the brain to the radula. A subradular organ certainly exists in this and several other species, if position and innervation be any criterion. In material killed in vom Rath’s fluid it appears with the greatest distinctness as a sharply defined median area composed of high columnar cells situated immediately in front of the peg-like tooth (Plate 25, fig. 10). In alcoholic material the appearance is not so striking, and yet there is very little difficulty in distinguishing the organ. However, with such material it is sometimes a task to determine its innervation. Nerves in the immediate vicinity are usually visible, but to trace these into the ganglia is frequently a perplexing operation. In vom Rath’s material on the other hand the entire system is clearly differentiated (see section on nervous system). The radula and its supports (Plate 25, fig. 2) are of comparatively large size but are typically arranged and require no especial description. Beyond the radula the gut becomes circular (Plate 25, fig. 3), the epithelium relatively high and a finely granular secretion fills the distal two thirds of the component cells. Among these are a very few more globular elements with a darkly staining more granular secretion. Beyond the pharynx the gut widens, the cells become lower and slightly glandular with the exception of a very few cells containing a yellow secretion. Beyond this point the relations of stomach, intestine, and liver are typical and require no detailed description. The brain and anterior portion of the nervous system closely resemble what is found in C. erudita, and so require but little additional description. It appears that the labio-buccal connectives have an origin independent of the lateral and pedal, which as in C, erudita unite before entering the brain. The commissures of the pedal cords are relatively more slender than those of C. erudita, save the anterior one which is of exceptional thickness. In some cases nerves arise from the commissures and are distributed to the body wall. The labio-buccal system is of unusual interest since it possesses what may CHAETODERMA ATTENUATA. 57 be considered to be a subradular system with ganglia and connectives with fibres passing into the above described organ in front of the radula. The labio-buccal connectives pass backward as usual and unite with the well-known ganglia imbedded in the pharyngeal musculature: and these bodies are in turn united by a cord in which two small ganglia are intercalated. A nerve which appar- ently has escaped observation arises from the posterior surface of each of the larger ganglia (Plate 13, fig. 3), and imbedded in the pharyngeal wall may be traced to the forward border of the stomach. A short distance in front of the labio-buccal ganglia a clearly defined fibre arises from each of the connectives (Plate 13, fig. 3), and, imbedded in the muscle of the pharynx, courses downward and inward and Joins a ganglionic mass that gives slight evidence of being paired (Plate 25, fig. 10). To the outside of the ganglion (or ganglia) a nerve arises from each of these connectives uniting with the labio-buccal connectives, and coursing dorsally attaches to the base of the subradular organ. There is absolutely no doubt of the existence of this system, the grayish nerves showing with great distinctness against the yellowish muscle fibres in material killed in vom Rath’s fluid. In material fixed in aleohol on the other hand it is sometimes difficult to trace. The ganglionic mass may closely re- semble a salivary gland and the nerves from it counterfeit muscle fibres; never- theless with an oil immersion lens I have been able to demonstrate its presence in all the species of the genus described in the present paper, and in a specimen of C. nitiduium kindly sent me by Professor Hubrecht. As is more fully noted on page 172 I believe that the ganglion and its connectives constitute a subradular system the homologue of the one I have described in some of the Neomeniidae. Posteriorly the pedal and lateral ganglia unite in the customary fashion, and at the, point of union give rise to two small nerves which become closely applied to the body wall, and after branching are lost to sight among the longi- tudinal somatic muscle fibres. From the suprarectal ganglionic mass (Plate 12, fig. 4), several branches arise some of which appear to have escaped observation, or at all events have not been traced to any considerable extent. Of these the larger pair originate from the ventral side of the ganglion and make their way ventrally to the sides of the rectum, where according to Wiren’s figures and description they diminish very rapidly in diameter and form a delicate subrectal commissure. In the present species this is certainly not the case, nor is it true of C. erudita, for arriving at the rectum each follows it posteriorly to the anal opening, and then passes outward almost at a right angle and becomes imbedded 58 CHAETODERMA ATTENUATA in the ventral gill retractors and in this position may be traced almost to the apex of the gill. Between its point of origin and its attachment to the rectum at least four small nerves arise and extend fan-like into the ventral gill retractors which they probably innervate. I have been unable to find any subrectal commissure. From the dorsal side of the suprarectal commissure four nerves arise, of which the outermost pair extends dorsally through the superior gill retractors, and imbedded in the dorsal cloacal wall, which it probably innervates, may be followed for a very considerable distance. The inner pair pursues much the same route at first, but upon emerging from the dorsal retractors and while imbedded in the cloacal wall each nerve turns sharply upon itself, and bending slightly toward the mid line and somewhat ventrally it enters the dorsal gill retractor and in this position may be followed close to the tip of the gill. Each of the branchia thus has a double nerve supply as in the ctenidia of the Chitons for example. The gonad, with the usual characteristics, opens into the pericardium by means of very short dorso-ventrally compressed tubes separated by the aorta. The pericardium is of unusual size, extending behind the heart nearly to the posterior end of the body. As may be seen Plate 36, fig. 2, it is interrupted by the dorsal gill retractors, but behind these muscles the cavity again becomes continuous across the mid line, extending down the sides of the cloacal cavity (Plate 25, fig. 5) and posteriorly forming a horn-like extension in the mid line. The heart is the usual tubular organ but posteriorly it unites with an atrium, which may be considered an auricle or an invagination of the ventral pericardial wall continuous posteriorly with the efferent branchial sinus. The openings of the coelomoducts hold the usual position, at the sides of the suprarectal commissure, but the tubes with which they communicate are in the first part of their course very slender, ciliated, and somewhat convoluted. In this condition they extend ventrally and join the glandular portion (Plate 36, fig. 2). The cells of this secretory portion are of the usual type, almost cubical vacuolated elements containing a small concrement. The position of the external opening is shown (Plate 25, fig. 5). Wiren (’92) has accurately described a patch of glandular epithelium, a modification of the cloacal wall, which on each side of the body surrounds the openings of the gonoducts and extends to a certain extent over the base of the gills. The cells composing it are high and consist of very slender supporting cells and glandular elements filled with an almost homogeneous substance, con- CHAETODERMA ERUDITA. 59 taining in favorable preparations groups of small prismatic crystals. This description answers for the present species with the exception of the crystals which have not been found. Wiren compares this glandular area with the shell gland of the Neomeniidae, though claiming it acts as an excretory organ. Be- yond certain histological resemblances there are no cogent reasons for accepting such a theory. Chaetoderma erudita, sp. nov. Ten specimens of this species were taken in Lynn Canal, Alaska (Sta. 4258) at a depth of 300-313 fathoms; and forty-one were dredged in Chatham Strait, Alaska (Sta. 4264) at a depth of 282-293 fathoms. In both cases the bottom consisted of very tenacious green mud. A number of individuals were kept in an aquarium aboard ship and lived apparently in a normal state, burrowing extensively and in some instances feeding on organic debris. Two males gave off considerable quantities of sperms during a period of over an hour. It escaped from the sides of the cloacal cavity, lateral to the gills and soon diffused into the surrounding water. Much care was taken in the preservation of these animals, and yet the shrinkage was considerable, in the case of some of the more active ones, amounting in six individuals to a decrease in the body length of one fourth. It thus becomes apparent that the length index or ratio of length to diameter is not to be depended on in the discrimination of species. . The entire animal is represented (Plate 4, fig. 9); the buceal plate (Plate 4, fig. 11), and the spicules (Plate 37, fig. 15). The hypodermis comprises three fairly distinet types of cells. Of these the most conspicuous, in alcohol killed material, is the basal cell of each spine whose nucleus is placed considerably above the level of the other types. In material killed in vom Rath’s fluid the Reizenzellen of Wiren, well-defined globular cells, are very distinct and con- tain a highly vacuolated material which almost totally disappears in alcohol killed specimens. In some cases fibres, probably muscle, attach to these ele- ments as in C. attenuata, but their relations are difficult to determine. The remaining cells are simple low columnar elements of the usual appearance. The mouth, a relatively wide opening in the deeply cleft buccal plate, opens into a laterally compressed buccal tube that beneath the brain develops longi- tudinal folds and a more circular outline (Plate 29, fig. 4). As far as the forward end of the radular supports buccal glands in great abundance are attached to its walls. The subradular organ is not as sharply defined as in C. attenuata, yet is clearly distinguishable as a median ventral elevation composed of slender 60 CHAETODERMA ERUDITA. columnar cells of greater height than those of the adjoining epithelium. In one specimen killed in vom Rath’s fluid the protoplasm of the component cells is much vacuolated or in a very small number contains a granular secretion. Poste- rior to the radula, whose general appearance is sufficiently shown (Plate 29, fig. 8), the pharynx becomes dorso-ventrally compressed, then circular and opens into the stomach. This is a relatively spacious organ with thin unfolded walls that posteriorly become thicker and folded. The relation of intestine and liver are typical and require no description. In the proximal part of the liver, and throughout the major portion of the intestine, there are considerable quantities of organic remains, diatoms, sponge spicules, a few fragments of entomostra- cans, and several chambered Foraminifera whose protoplasm was only partially digested. The nervous system of this species is exceptionally clearly defined in one specimen killed in vom Rath’s fluid and for this reason has been more thoroughly studied than any other species of the genus described in the present paper with the exception of C. attenuata. The brain is very distinctly bilobed, a deep indentation occurring on its anterior surface. From its lateral and forward borders nerves pass into the precerebral ganglia which in turn send tremendous bundles of fibres to the buccal sensory plate. In some species the connectives to the pedal, lateral, and labio-buceal systems have distinct origins in the brain, but in the present case they are united for a considerable distance (Plate 13, fig. 3). Each of these compound connectives after leaving the brain and pass- ing forward a short distance gives rise to the labio-bueccal connective and con- siderably farther on the pedal and lateral connectives become differentiated. The pedal and lateral ganglia are in the usual positions and are united by frequent connectives and commissures. At the points of origin of these nerves there are no very clearly defined enlargements though anteriorly the pedal and lateral cords are of large size and gradually taper posteriorly, attaining their average size about the hinder border of the prothorax. As these ganglia diminish in size the connectives and commissures become reduced in calibre and are difficult to follow yet they may be traced here and there throughout the entire length of the animal. As in C. attenuata a nerve arises from each labio-buccal connective about the level of the forward border of the radula and passing inward and downward joins a small subradular ganglionic mass. In this species the gan- glion shows no indication of being paired. Each of these subradular connectives gives rise to a nerve distributed to the subradular organ and more laterally swells CHAETODERMA MONTEREYENSIS. 61 somewhat though ganglion cells are lacking. From each of these enlargements a nerve is developed, and after branching in the pharyngeal musculature becomes lost to view. This subradular system does not appear with the diagrammatic clearness of the one in C. attenuata, but there is no especial difficulty in determin- ing its relations which are essentially the same in the two species. In the posterior regions of the body the nervous system very closely resembles that of C. attenuata. The gonad, with the usual characteristics and relations, opens into the for- ward end of the pericardium by means of comparatively large tubes in sexually mature animals. In some animals, possibly owing to killing fluids, the peri- cardial cavity is greatly distended with spermatozoa which have made their way into the proximal half of the coelomoducts. These last named tubes com- municate by wide openings with the pericardium and on the other hand extend forward as ciliated tubes for a short distance. Beyond this point their walls become glandular and are thrown into numerous convolutions which render it impossible, without much effort, to determine their exact relations. Posteriorly each duct becomes more simple, though of fairly large calibre, so that it con- tracts the cavity of the cloacal chamber; and on the ventral border of the fold thus developed the outlet canal is formed (Plate 29, fig. 5). Chaetoderma montereyensis, sp. noy. This species is evidently abundant in the deeper waters of Monterey Bay, California, as 155 were taken distributed through the following stations: nine from 4485, seven from 4508, fifty-nine from 4522, fifteen from 4523, thirty-one from 4524 and thirty-four from 4525. In every case the bottom was mud and the depth varied from 39 to 356 fathoms. Chloretone (aceto-chloroform) was used with good results as a narcotizing agent and 70 % alcohol served as a fixing agent. The length of a medium sized specimen' is 45 mm. with an average diameter of 2 mm. through the prothorax and 3 mm. through the preabdomen. The color in life and preserved material is yellowish white. The hypodermis very closely resembles that of C. attenuata. The spines are represented in Plate 37, figs. 2, 3. The mouth opens through a slit in the subelliptical buccal plate (Plate 4, fig. 17) and leads into a laterally compressed tube which becomes circular in 1 Generally speaking the larger specimens come from the shallower depths. This is very marked in comparing those from Sta. 4525 with others from Sta. 4508. These size differences, however, do not appear to be correlated with any constant structural peculiarities. 62 » CHAETODERMA ARGENTEA. outline slightly in front of the radula (Plate 27). Throughout its entire course to the hinder borders of the radula its walls, more than commonly muscular, afford lodgment for numerous salivary glands whose secretion stains darkly with haematoxylin. The radula, its supports and musculature are typically situated but are exceptionally heavy and powerful. The remaining divisions of the digestive tract are related as usual and are represented on Plate 27. Countless thousands of diatoms, together with nondescript organic and inorganic remains, fill the intestine and in some specimens, the stomach. The pericardium is a comparatively spacious chamber, extending backward some distance over the cloacal cavity (Plate 27, fig. 9), and is perforated by the superior gill retractors; but otherwise neither it nor the tubular heart and the connecting sinuses are peculiar in any important particular. The nervous system has been studied in considerable detail, and in all essential respects has been found to resemble that of C. attenuata for example. The gonad, with the usual characters, opens into the pericardium by com- paratively wide, dorso-ventrally compressed tubes. The inner openings of the coelomoducts are likewise of large size (Plate 27, fig. 8) and the adjacent ciliated section also though the latter is unusually short. This ciliated section unites with a division of the glandular part (shown on the left, Plate 27, figs. 2,8). The outlet (Plate 27, fig. 9) occurs in the customary position and is sur- rounded by the glandular modification of the cloacal epithelium as in C. atten- uata and a few other species. Chaetoderma argentea, sp. nov. One specimen (Plate 4, fig. 7) of this species was taken in southern Alaska in the green mud of Behm Canal (Sta. 4231) at a depth of 82-113 fathoms. It was ina moribund condition and with the exception of slight movements of the body and gills gave no signs of life. 'The measurements are, total length 24 mm. diameter of the prothorax 1.6 mm. while the greatest diameter of the preabdomen was 2.6mm. The color in life and in a preserved state was a silvery white. The cuticle is scant in amount and the hypodermis is comparatively low and is composed of small cells cubical or low columnar in form. Among these are the giant cells (Reisenzellen) from which the secretion has disappeared but they are attached to faintly staiming fibres whose exact relations have not been determined. The spines are represented (Plate 37, fig. 6). Although the animal when captured was alive it never relaxed sufficiently to allow the buccal sensory plate to become exposed. In sections this last named CHAETODERMA SCABRA. 63 organ appears to be typical though the glands that open along its margin are more than usually developed. The preradular section of the gut is of average diameter, fairly muscular and is provided with numerous glands uncommonly compact except on the dorsal side behind the brain. Violent contractions of the prothorax have apparently been responsible for the dislodgment of the epithelial lining of this part of the digestive tract; but there are indications that a subradular organ exists and the nerve supply is distinctly evident. The radula is constructed on the usual plan as may be seen (Plate 26, fig. 2). Beyond the radula the gut becomes narrow, circular in section and very soon unites with the capacious stomach whose relations to the intestine and liver are of the usual type. The stomach and especially the intestine contain a considerable amount of inorganic and organic material, diatoms being especially abundant. The single specimen is a male with the gonad distended with sex products in all stages of development. Violent muscular contractions have forced a mass of sex cells, many of them immature, into the pericardium; and at various points along the coelomoducts fully developed sperms are present. The reno-peri- cardial openings, at the level of the posterior border of the suprarectal commis- sure, are relatively wide and lead into correspondingly spacious, highly ciliated tubes which pass almost directly ventrally to a point about opposite the mid lateral line where they unite with the glandular portion (Plate 36, fig. 1). This last named section extends as a slightly convoluted tube to a point about oppo- site the posterior border of the gonad where it bends sharply upon itself and ventral to the dorsal ciliated section opens into the cloacal chamber at the usual point. The nervous system shows with distinctness and has been traced in con- siderable detail, but as the results show it to be essentially the same as in C. attenuata and C. erudita it demands no especial description. The subradular ganglion with the usual connections is clearly a single mass. Gland cells in the gills are very definitely distributed, in cross sections being disposed along the transverse axis of the body (Plate 26, fig. 5). Chaetoderma scabra, sp. nov. One individual was dredged in Monterey Bay, California at a depth of 795-871 fath. It measures 12 mm. in length, 1 mm. through the metathorax and 2 mm. through the greatest diameter of the preabdomen. The expanded portion of the prothorax is light brownish yellow; more posteriorly the brown shade is more pronounced, becoming olive-green in the region of the liver which 64 CHAETODERMA CALIFORNICA. shows through the translucent body wall. An orange-brown substance incrusts the spines about the cloacal opening. The spicules are represented (Plate 37, fig. 19). The form of the buccal plate and the position of the mouth opening are shown (Plate 4, fig. 16). The adjacent section of the digestive tube rapidly as- sumes a circular form in section, and a few compact groups of gland cells become applied to the dorsal, and to a less extent the lateral walls. Immediately behind the brain these lobules become larger (Plate 30, fig. 3), but soon disappear more posteriorly. The radula was cut obliquely and it is therefore somewhat difficult to determine its exact relations. The tooth appears to be relatively slender, but its supports and musculature are typical. Behind the radula the pharynx again becomes circular and in this form joins the stomach (Plate 29, fig. 9). This last named organ is at first thin walled, but the epithelium soon grows higher, becomes folded and soon smooths out at the level of the posterior end of the prothorax (Plate 29, fig. 11). Again becoming thick walled and of small calibre it unites with the liver and intestine. From this point onward these last mentioned organs are of the usual type. The pericardial cavity is of more than average size (Plate 29, fig. 10) and the heart is highly muscular; otherwise neither these organs nor the connecting sinuses are unusual. The specimen is sexually mature and multitudes of sperms have made their way from the gonad through wide tubes into the pericardium and the proximal portion of the coelomoducts. The openings of these latter organs into the peri- cardial cavity are comparatively large and the ducts themselves are relatively simple. As in some other small species the glandular portion is a simple canal extending as far forward as the posterior end of the gonad where it bends abruptly and making its way posteriorly opens by an inconspicuous pore into the cloacal chamber. The nervous system is distinct and sharply defined and has been carefully examined, but it does not differ in any important respect from that of C. erudita for example. Chaetoderma californica, sp. nov. One specimen was collected in the neighborhood of San Diego, California, (Sta. 4381) at a depth of 618-667 fathoms. It measures 24 mm. in length by 1.6 mm., the average thickness of the metathorax, and 2 mm. the average diame- ter of the preabdomen. The general appearance of the animal and the relative length of the various divisions of the body are shown (Plate 4, fig. 6). The color CHAETODERMA CALIFORNICA. 65 ‘of the protrusible portion of the prothorax is yellowish brown, while the remainder of the body is yellowish green. A rusty red substance, possibly excreta, incrusts the spines in the cloacal region. The cuticle is of moderate thickness and rests upon a hypodermal layer whose nuclei, placed at various levels in the region of the prothorax, have at first sight the appearance of being more than one cell thick. The most common type of cell is relatively slender and contains an oval granular nucleus. Among these are other elements, probably spicule matrix cells, each of which contains a spherical nucleus larger in size than those of the foregoing class of cells and placed in the neighborhood of the base of a spine above the general level of the hypodermis. As in C. attenuata spaces exist at frequent intervals in the hypo- dermis and from the vicinity of each fibres pass into the underlying muscular layer. As noted on page 55 there are reasons for the belief that these are gland cells, of unknown function, whose secretion is dissolved through the agency of aleohol when used as a fixing agent. The shape of the spines is shown (Plate 37, fig. 14). The alimentary canal opens through the dorsal half of the buccal plate; its first section (Plate 27) is a narrow canal that rapidly widens in the neighbor- hood of the brain. To its lining epithelium the usual muscles attach and afford lodgment for numerous buccal glands. These last named organs extend from the mouth to the level of the brain and are similar to those of C. nitidulum save that the cells are less compact and of larger size. In the neighborhood of the radula the walls of the pharynx become more folded than in C. nitidulum and are unique in possessing a pouch (Plate 31, fig. 8) of considerable extent, into which the glands of the dorsal side open. Behind the radula the canal gradually narrows, its folds become smoothed out whereupon it unites with the stomach. The salivary glands consist of several globular cells surrounding a small lumen that in some instances is in direct communication with the digestive tract. However each cell communicates with a small ductule which gives evi- dence, not of passing the secretion into the lumen of the gland, but directly into the digestive tract through intercellular channels of the lining epithelium. The radula presents no especially noteworthy features. Its conical tooth is slightly more slender than is usual (Plate 31, fig. 1), but the cuticular wing- like supports and musculature are entirely typical. As usual the pharynx opens by a comparatively narrow pore (Plate 31, fig. 2) into the stomach whose relations to the liver and intestine are normal. Large quantities of organic remains occur in the gut, Radiolaria, diatoms, and sponge 66 CHAETODERMA NANULA. spicules being distinguishable. Associated with these are numerous rounded cells (Plate 35, fig. 11) that occur also in the digestive gland. In most cases these are free but occasionally one may be seen that is encysted in the cells of the organs mentioned. Rarely they are associated in pairs as though in the process of conjugation. The gonad holds the usual position and like the sperms, in all stages of development, presents no noteworthy characters. Posteriorly the halves of the organ diverge, become rather indistinct though their route may be traced with certainty, owing to the presence of spermatozoa, passing lateral to the heart or the expanded base of the aorta and opening into the pericardium. This last named space lacks the almost diagrammatic outline as in C. nitidu- lwm and is much more limited in extent, but its relations to the gonoducts are very similar. Chaetoderma nanula, sp. nov. One specimen of this species was dredged off the coast of southern California (Sta. 4369) at a depth of 260-284 faths. It is 9 mm. in length by 0.9 and 1.2 the average diameter of the metathorax and preabdomen respectively (Plate 4, fig. 1). The color of the globular, protrusible portion of the prothorax is light brownish yellow (though this may have been produced by tannin from the cork), while the metathorax and preabdomen are considerably darker, the latter region becoming olive-green. A dark brownish substance incrusts the spines about the cloacal opening. The hypodermal layer is comparatively thin, the cells small and somewhat indistinct, yet are typical so far as may be determined. The spines are represented (Plate 37, fig. 18). The mouth opening represented (Plate 4, fig. 12), leads into a relatively spacious tube lined with slender columnar cells except along the dorsal side where they are almost cubical. A median fold, located immediately in front of the radula, probably represents a subradular organ since it is typically innervated. Salivary glands are almost wholly lacking, a small group attached to the pharyn- geal wall adjacent to the radula being all that is visible in the present specimen. The radula is small but typical. Beyond it the tube narrows considerably, the lining becomes folded and in this form it unites with the stomach. At the outset this last named organ is plain walled but near its union with the liver becomes considerably sacculated. The intestine is distended with fragments of Radiolaria, sponge spicules, and organic debris. Parasitic Protozoa, resem- bling those from Chaetoderma californica, are abundant and are imbedded in the epithelial lining of the stomach, intestine, and liver throughout their entire extent. CHAETODERMA JAPONICA. 67 The animal is a female, not perfectly mature, and the ducts leading into the pericardium are accordingly small. The openings into the coelomoducts are likewise minute, and the ciliated tube with which each connects is relatively long and slender. The glandular division with which it unites is a comparatively simple tube, at first directed forward until it reaches the level of the front end of the heart whereupon it bends abruptly and makes its way to the opening into the cloacal chamber (Plate 28, fig. 10). The nervous system is in an excellent state of preservation and is clearly defined, but a careful study has failed to disclose any noteworthy feature. It may be mentioned that a subradular system exists similar in all respects to that of C. attenuata. Chaetoderma japonica, sp. nov. One specimen (Plate 3, fig. 7) was dredged off Honshu Island, Japan (Oi Gawa, Sta. 3721) at a depth of 207-250 fathoms. The body is comparatively slender, measuring 17 mm. in length by 1.3 mm. through the metathorax and 1.5 mm. through the preabdomen. The color is almost white with a slight tinge of yellow. A slight incrustation, brick-red in color covers the spines in the cloacal region. The spines are of the usual type. The mouth opens through a distinct pore in the buccal plate (Plate 3, fig. 8) which, like the neighboring section of the digestive tube, is abundantly supplied with glands, small celled and more than commonly compact. These continue, for a considerable distance behind the radula, apparently unchanged in character though in many cases closely applied against the bases of the buccal and pharyn- geal epithelium. This first named organ with its supports and musculature is typical, as may be seen in Plates 30, 31. As the major portion of the body was not sectioned the union of liver and stomach has not been seen; otherwise these organs conform to the usual plan. The prerectal portion of the intestine is lined with an exceptionally high epithelium so that the lumen is very small where it is not distended with pellets of faecal matter consisting principally of diatoms and sponge spicules. The nervous system is not especially favorable for study and accordingly only its more general features have been examined. In this respect it is typical. The specimen is a female and the fully formed ova present the customary appearance and are developed in a gland holding the usual position. The ducts leading into the pericardium, are large and as in the case of the last named space, and the gonoducts, are filled with eggs mostly disintegrated, due perhaps to violent movements of the somatic musculature. The gonoducts open by rela- 68 CHAETODERMA ROBUSTA. tively large pores into the pericardium and as moderately spacious tubes without any marked convolutions, extend to their openings into the cloaca (Plate 30, fig. 7). Surrounding these pores the cloacal epithelium is modified to form the glandular area similar to that of C. attenuata. Chaetoderma robusta, sp. nov. Four specimens of this species were taken south of the Alaskan peninsula (Sta. 3210) in green mud at a depth of 483 fathoms. The largest specimen (Plate 4, fig. 5) is 60 mm. long with an average diameter through the metathorax and preabdomen of 3.5 and 4.7 mm. respectively. The smallest is 35 mm. long with an average metathorax diameter of 2 mm. and 3 through the preabdomen. Where the spines have not been dislodged the general color of the body is slaty gray shading to buff at the anterior end of the body. A yellowish brown sub- stance incrusts the spines about the cloaca. The hypodermis consists of numerous small cells rather closely crowded so that the cells lack distinctness. However giant cells are visible and faint fibres, connective tissue or muscle, springing from the underlying body wall appear to attach to them. Spicule-matrix cells in all stages of development are visible, and in each ease the spines are attached to only one cell so far as it is possible to judge. The remaining elements are comparatively slender, compact and lack any noteworthy features. The spines are represented in Plate 37, fig. 4. The buccal plate is shield-shaped in outline (Plate 4, fig. 19), and is pierced by the mouth opening. The buccal and pharyngeal cavities are slender, and the walls of more than average thickness (Plate 30). The lining cells are accordingly very slender, ciliated and are thrown into a few prominent folds. The ductules of a very large number of salivary glands make their way between the cells and in some cases are in the act of pouring their secretion into the canal. A sub- radular system is present, and as usual two nerves are distributed to a median fold of pharyngeal epithelium that probably functions as a subradular organ. However with the exception of affording scarcely any outlet for the salivary glands its cells are not clearly distinguishable from the general epithelium. The radula consists of the usual conical tooth, rather heavier than usual, but with supports and musculature of the customary type. Beyond the radula the tract becomes circular in cross section before uniting with the stomach whose relations to the liver and intestine are typical. The circulatory system presents no noteworthy features beyond the fact that the heart is suspended by a fold of the pericardial wall reinforced by a few LIMIFOSSOR TALPOIDEUS. 69 connective-tissue fibres, and is surrounded by a pericardial cavity that posteri- orly extends as a slit-like space between the cloacal and body walls far along toward the posterior end of the body. In its general features the nervous system closely resembles that of C. erudita and C. attenuata. The labio-buccal system has been worked out in detail, but it is no exception to the statement just made. The gonad is of large size and is distended with spermatozoa that have made their way through wide canals into the pericardium. As usual the pericardial openings are situated close to the suprarectal commissure, and lead into clearly defined ciliated ducts which very soon unite with the glandular portion. In this species the glandular portion is at first relatively slender, and but little convoluted yet it soon enlarges greatly, becomes much folded and extends as may be seen in Plate 30, figs. 5, 7, from the posterior limit of the gonad to its opening into the cloacal cavity. Limifossor talpoideus Hearn. Zool. Anz., 1904, 5, p. 28. Zool. Jahrb. Abth. Anat. Ontog., 1905, 5, p. 21. Several specimens of this species were taken in Alaska in the Lynn Canal (Sta. 4258) and in Chatham Strait (Sta. 4264) at depths ranging from 282-313 fathoms. The general appearance of these animals is shown (Plate 10, fig. 1). The length ranges from 6-12 mm. and the diameter from 1-2 mm., the ratio 1:6 being constant. The mouth, almost terminal in position, is bounded by the sensory plates (Mundschild) and more dorsally by the type of spine covering the prothorax generally. The plates in life undergo rapid changes in form, but histologically and in their innervation they resemble their homologue in Chaetoderma. The deep semicircular groove (halbmondférmige Grube) situated beneath the mouth and sensory plates, is lined throughout with the spiculose integument of the body. The spines are triangular or leaf-like and range in length from 0.02 mm. in the region of the mouth to those about the cloacal chamber 0.38 mm. long. The hypodermis is relatively very thin, the boundaries of the cells indis- tinct and similar in general to that of other species of Chaetoderma. The somatic musculature likewise is very similar in the two genera. The mouth leads into a comparatively narrow canal with longitudinal folds covered with a well-defined cuticle. In the region of the radula the canal enlarges, develops a subradular pocket (Plate 10, fig. 4) and dorsally continues as a cir- cular tube to its junction with the stomach. Attached to a dorsal diverticulum numerous cells pour their secretion into the pharynx. A clearly defined subradu- 70 LIMIFOSSOR TALPOIDEUS. lar organ does not exist and yet the fact that in the mid line the cells are more . than usually high and slender and are in close proximity to nerves from the labio- buccal ganglia indicates that the area exercises a sensory function. The radula and its supports and attendant musculature are enormously developed and indi- cate active predatory habits, but in every case the alimentary canal contains little besides a few diatoms, sponge spicules, and a small quantity of inorganic detritus. The radula with twenty-eight transverse rows is of the distichous type (Plate 34, figs. 3, 6), the long claw-like teeth being united while in the radula sheath by a clearly defined basement membrane. When freely exposed this membrane splits along the mid line and the teeth become located on each side of a deep cleft in the forward end of the radular supports (Plate 10, fig. 10). Odonto- blasts, in typical fashion, form the teeth which are subsequently enveloped by numerous enamel cells. The radular supports comprise two great masses of muscle and connective tissue which together form an ovoid mass grooved dorsally to hold the radula tube. To these numerous muscles attach that are in part responsible for the movements of the teeth. A detailed description of these and other muscle bands has been given in another place (Heath ’05) and an attempt has been made to determine their functions. The stomach is sharply differentiated from the remainder of the digestive tract (Plate 10, fig. 4) and occupies practically all of the space between the end of the radular supports and the forward border of the gonad and digestive gland. Its epithelial lining is produced into a number of heavy folds that gradually blend with those of the oesophagus. In most cases the intestine leaves the pos- terior end of the stomach in the mid line, and immediately ventral to this union the liver opens by a single pore. This last named organ is relatively voluminous, filling much of the space beneath the gonad between the stomach and forward cloacal wall where it ends blindly. The intestine, of practically the same calibre throughout, makes its way by a fairly direct route to the front end of the peri- cardium. Here it bends abruptly downward and passing under the cloacal wall opens to the exterior in the mid line. A clearly defined connective-tissue septum bounds the head cavity pos- teriorly as in the Chitons. It passes immediately behind the radular supports and is penetrated by the alimentary canal, dorsal aorta, and pedal sinus. The pericardial cavity is of trihedral form and encloses a tubular and more than usually muscular heart without any distinet subdivisions. The aorta passes out from its forward border, and as a distinct tube with definite walls LIMIFOSSOR TALPOIDEUS. fA makes its way between the halves of the gonad to an opening in- the septum bounding the head cavity. This latter space communicates with a well-defined pedal sinus, which perforates the septum and pursues its course posteriorly, communicating here and there with the general visceral cavity, to the neighbor- hood of the cloacal cavity. Here both sinuses unite on their way to the gills from which the blood passes above the dorsal gill retractor to enter the heart. The brain, clearly bilobed, develops fibres which unite with five pairs of precerebral ganglia that in turn give rise to nerves passing to the sensory plate. The lateral, pedal, and labio-buccal connectives unite before entering the brain. The last named are first to be differentiated and holding the usual position at the sides of the pharynx, they unite with the ganglia lateral to the dorsal salivary glands. These nerve masses are united by the usual commissure and by another passing dorsal to the pharynx in the neighborhood of the salivary glands. What appears to be a complete one passes ventrally into the neighborhood of the subradular organ. A nerve from each ganglion passes backward and probably innervates a portion of the digestive tract. The lateral and pedal ganglia, with the usual relations, extend to the region of the cloaca where they unite to form on each side a well-defined enlargement connected by a suprarectal commissure. From each swelling several nerves arise that are distributed to the cloacal and body walls; while from the commissure branches are developed, dorsally and ventrally, that innervate the ctenidia. The gonad extends from the stomach to the pericardial cavity into which it opens by relatively long and slender ducts. The coelomoducts have the form of simple tubes extending from the pericardium to separate exits in the cloacal chamber. ‘Their inner openings are situated in the infero-lateral angles of the pericardial cavity and are guarded by high pyriform cells devoid of cilia. On the other hand the succeeding portion of the canal, of very small calibre, is composed of cubical elements covered with a heavy ciliated coat. This division makes its way forward to the outside of the dorsal gill retractor and unites abruptly with the glandular portion, which although a single tube is so con- voluted that it becomes a relatively voluminous structure. Its walls are com- posed of more or less cubical cells of which the cytoplasm is scant in amount owing to the presence of one or two great vacuoles. The general structure bears a fairly close resemblance to certain kidney tissue yet there is no positive proof that it possesses an excretory function. The outer openings are on each side of the anus a short distance anterior to it, and though very minute in pre- served material they are nevertheless clearly defined, 72 : PACHYMENIA ABYSSORUM. Limifossor fratula, sp. nov. This species is represented by two individuals taken off the coast of southern California (Sta. 4369) at a depth of 260-284 fathoms. In general it so closely resembles the foregoing species that a very brief description will suffice. The body, slaty gray in color with a slight yellowish cast, is shorter and thicker than in L. talpoideus, and owing to a heavier body wall is much firmer. The spines of the two species are very similar in form, but in the present species they are of considerably larger size. Spicules from the middle of the body are 0.5 mm. in length while in L. talpoideus the largest of the body do not exceed 0.38 mm. The hypodermis is also proportionately thick and what are probably matrix cells are frequent and sharply differentiated from the other elements of the hypodermis, and hence different from L. talpoideus in this respect. The digestive tract in the two species is, neglecting minor differences, built upon the same plan. Heavy as is the radula and its supports in ZL. tal- poideus it is even heavier in the present case, and the teeth are of larger size, making it so difficult to section them that at present there are no clear indications of their exact shape though it appears certain that the smaller cusp of each tooth is larger than in the preceding species. The muscles that operate the radula are typical but are unusually heavy. The nervous, circulatory, and reproductive systems are very similar in the two species. This species is readily distinguished from the foregoing by the size of the spines, the structure of the hypodermis, and the heavier musculature and con- sequent firmness of the body. Pachymenia abyssorum, sp. nov. One specimen of this species was dredged off the southern coast of Cali- fornia (Sta. 4397) in 2196-2228 fathoms, the greatest depth recorded for any Solenogastre. In bringing the animal to the surface the consequent decrease in pressure upon the body resulted in the active release of gases from the blood, causing the displacement of the cuticle to a considerable extent, the shrinkage of the hypodermal cells and the partial destruction of the foot at various points; otherwise the tissues are in a good state of preservation. The body is thick set, externally resembling Alexandromenia valida, and measures 27 mm. in length by 4.5 mm. average thickness. The color is a light yellowish white. As is indicated (Plate 39, fig. 4), the foot is exposed for a considerable distance, and is unusually broad and doubtless in life is capable of forming a relatively large PACHYMENIA ABYSSORUM. 73 surface possibly enabling the animal to crawl about on the bottom ooze. As in the case of Alexandromenia this individual is unattached and may be accord- ingly a roving form. The cuticle is approximately three times the thickness of the hypodermis, but is scant in amount owing to the vast numbers of needle-like spicules, of varying sizes, imbedded in it. As noted above the hypodermal layer is not in a good state of preservation, but it may readily be discovered that the cells are unusually slender, and laterally and ventrally form papillae in the head region. There are low elevations at other points over the body but it is not certain that they are definite papillae. The external opening of the anterior pedal gland is a cavity of large size whose walls are provided with folds of unusual height. On the posterior wall these are approximately seven in number, the outermost on each side being very large. Behind the cavity the five included folds disappear while the large lateral ones unite in the formation of a foot with a creeping surface of greater width than in any other known species of Solenogastre. In the posterior end of the body the foot decreases in size and becomes continuous with small folds of the cloacal wall. The anterior pedal gland is a voluminous organ lying at the sides of the body opposite the external outlet. The cells composing it are exceptionally small but otherwise present no noteworthy characters. Behind it shades into the posterior pedal gland without any appreciable change in the character of the cells. Throughout the entire extent of the foot the gland is unusually large and the ductules appear to open over the entire creeping surface. The external atrial opening is subterminal and large, and leads into the customary cavity provided with ridges and cirri typically situated. As may be seen in Plate 39, fig. 1, the external ridge is continuous across the mid line in front of the external opening of the atrium and though relatively small at this point it rapidly increases in height, finally becoming of such a size that it may be seen in external view. The inner ridge is likewise small anteriorly but behind becomes as extensive as the external fold. Behind these two folds are con- tinuous with each other and are connected with several long plaits in the hypo- dermis which extend to the external opening of the pedal gland. The cirri are simple unbranched processes, slightly pigmented and contain a muscle or nerve fibre extending, in some cases at least, throughout their entire extent. The atrium communicates dorsally with the succeeding section of the digestive tract whose general relations may be determined from an examination 74 PACHYMENIA ABYSSORUM. of Plate 39, figs. 1, 6. The walls of this division are provided with numerous muscle bundles of irregular distribution between which are multitudes of glands staining actively when treated with Delafield’s haematoxylin. The cells com- posing these glands are without distinct cell boundaries, are made up of vacuo- lated protoplasm containing droplets of various sizes and are grouped into lobules of various bulk. In many places they extend into the folds of the epi- thelial lining of the pharynx and give evidence of opening through intercellular channels. Some distance toward the dorsal side of the animal a fold of large size ap- pears in the wall of the digestive tract which narrows the pharyngeal cavity to a relatively small tube. At this point the epithelial lining becomes thicker, a char- acter which it retains to the stomach-intestine, and the walls become surrounded by a heavy sheath of circular muscles to which vast number of gland cells attach. These gland cells are grouped into slender lobules, and owing to the fact that they are much vacuolated their tint is fainter than in the case of those of the pre- ceding division of the tract. The nuclei also are of larger size and more distinct, but the secretion presents the same general appearance. A slender duct on each side of the pharynx (Plate 40, fig. 6) extends from the region of the ventral labio-buccal commissure (Plate 39, fig. 8), to its outlet (Plate 39, fig. 6). Poste- riorly each ends blindly and anteriorly is provided, as in the case of Alexandro- menia, with a papilla which is doubtless capable of being protruded into the pharyngeal cavity. Throughout its entire extent the ductules from these glands attach to the canal, but behind it they connect with intercellular channels and so pour their secretion directly into the pharyngeal cavity. The glands with this last named outlet present the same appearance as those communicating with the ducts except in the neighborhood of the stomach-intestine where they become more compact. No trace of a radula or radula sac exists. The pharynx or oesophagus projects for a great distance into the stomach- intestine which is provided with several longitudinal ridges instead of the cus- tomary sacculations. The middle portion of the body was not sectioned but as these ridges are present in the posterior end of the animal it is probable that they extend throughout the entire length of the gut. Many of these folds contain blood sinuses which often produce a marked distention. The lining epithelium is composed of more than usually slender cells many of which con- tain more or less spherical, granular masses. Posteriorly the intestine narrows, passes between the coelomoducts and opens into the cloacal chamber. No PACHYMENIA ABYSSORUM. 75 traces of food were found in the tract and accordingly we are without any knowl- edge of the animal’s feeding habits. The walls of the cloacal chamber are provided with a number of slender outpouchings and to these are attached multitudes of gland cells grouped into lobules of different sizes. Each cell is pyriform and contains a somewhat granu- lar slightly vacuolated secretion that makes its way by a delicate ductule through an intercellular opening into a diverticulum of the cloacal wall. The general arrangement of these structures is shown in Plate 39, fig. 2. The pericardial cavity is comparatively spacious and the contained heart, consisting of two divisions, is moderately muscular. The aorta in the present specimen is of small size but in its relations to the gonad and the anterior end of the body it is typical. Owing probably to the size of the foot the ventral sinus is large and connects in the usual fashion with the head sinuses and here and there throughout the body with the visceral sinus. In the posterior part of the body it divides, passes dorsally on each side of the intestine and after passing posteriorly for a short distance breaks up into a small number of lacunae which connect with the gills. From these organs the blood passes through rather ill-defined channels in the somatic musculature to the posterior end of the heart. Five or six pairs of relatively large folds appear in the cloacal wall running more or less parallel to the outer opening near which they are situated (Plate 39, fig. 2). Here and there these develop numerous minor wrinkles (Plate 40, fig. 7) which pass from one main fold to another or extend some distance over the cloacal wall. As usual they all contain blood sinuses but otherwise are not especially modified. The brain, imbedded in the numerous glands attached to the forward wall. of the pharynx, is an unusually elongated structure and without distinct signs of being bilobed. From its anterior face the usual nerves, heavy in appearance, are distributed to the body wall and the ganglionic masses about the bases of the cirri. The lateral, pedal, and labio-buccal connectives arise from the ex- treme lateral boundaries of the brain and follow the usual course. A very slight enlargement marks the point of union of the lateral ganglion with the corre- sponding connective, while one of twice the diameter occurs in the case of the pedal cords. The last named structures are united at fairly definite intervals by clearly defined commissures and about the same number of connectives attach to the lateral ganglia. A nerve from the anterior pedal enlargement passes to the wall of the outlet of the anterior pedal gland, and two branches originate from a corresponding point on the lateral ganglia and applied to the 76 PACHYMENIA ABYSSORUM. somatic musculature extend far forward into the anterior end of the body. The labio-buccal connectives, imbedded in the pharyngeal glands, pass backward about half the length of the pharynx where they join the ventrally placed ganglia (Plate 39, fig. 8). These masses are in turn united by a strong commissure provided in its mid section with several ganglion cells from which a nerve arises and extends backward for a considerable distance attached to the pharyngeal glands. What appears to be a dorsal commissure springs from the upper side of the ganglia, passes dorsally and may be traced here and there amid the glands over the dorsal surface of the pharynx. It has not been followed throughout its entire extent yet I have but little doubt that it is a definite commissure. From the posterior borders of each labio-bucecal ganglion a nerve arises and imbedded also in the glands of the pharynx extends for a considerable distance posteriorly before it becomes lost to view. Finally it may be said that the arrangement of the brain and anterior portion of the nervous system is more regular than in the case of Alexandromenia for example, but otherwise there is no fundamental difference. In the posterior end of the body the pedal ganglia continue to be united by commissures of large size and practically the same number of connectives unite them with the lateral ganglia placed high up on the sides of the body. In front of the anterior cloacal wall the pedal cords bend dorsally and provided through- out with ganglion cells attach to the lateral nerve masses at the sides of the peri- cardial cavity (Plate 40, fig. 4). From the posterior end of the lateral and pedal ganglia nerves arise and extend backward along the body wall and in some places pass into the cloacal folds. A well-defined dorsal sense organ is present whose location is represented (Plate 39, fig. 2). Owing to the fact that it is of small size, that the cells like those of the hypodermis are not well preserved and because of the oblique direction of the sections its structure has not been accurately determined yet so far as the examination has gone it appears to conform to the usual type. The ovo-testis occupies the usual position on the dorsal side of the animal and extends forward to the posterior end of the pharynx. The ova are unusually large and are surrounded by a chorion, but with these exceptions neither they nor the spermatozoa present any especially noteworthy features. The ducts leading from the gonad into the pericardium are of comparatively large calibre. In several respects the coelomoducts are remarkable structures and unlike those of any other known Solenogastre. In the vicinity of their inner openings DREPANOMENIA VAMPYRELLA. ree the pericardial wall becomes thickened and numerous small folds appear which converge and in some cases at least become continuous with the adjacent sec- tion of the duct. A short distance beyond the pericardial cavity and as far distally as the seminal receptacle each duct affords attachment for a vast num- ber of glands of unknown function. These are slender diverticula (Plate 40, fig. 2), composed of very small cells with indistinct boundaries filled with a finely granular faintly staining secretion. In the present specimen large quantities of spermatozoa are present in the coelomoducts and frequently these have made their way into some of the diverticula where they form masses without definite arrangement. Whether this is a normal occurrence or a post mortem effect cannot be definitely decided with the material in hand. Beyond these glands the dorsal section of the coelomoduct becomes thin walled, without folds and soon joins the ventral division which as Plate 39, fig. 2, indicates is of large size, thin walled, with few folds and is crowded with sperms. Immediately ventral to the union of the dorsal and ventral limb of each duct there is a small globular outpouching to whose internal wall large numbers of spermatozoa are attached so that in position and function it is to be considered as a seminal receptacle. Sperms with the same mode of attachment are found in considerable numbers adjacent to the seminal receptacles and rarely at much greater distances, even as far as the undivided section or shell gland. The cavity of this last named organ is not much larger than that of the dorsal section and its epithelial lining is relatively thin but a multitude of glands, attached throughout its entire extent, give it a heavy appearance. These glands are composed of compact, pear-shaped cells arranged in lobules that open by intercellular channels in the epithelial lining of the shell gland. As may be seen in Plate 339, fig. 2, the shell gland pushes inward the anterior wall of the cloacal chamber so that its outlet is far within this last named cavity. Drepanomenia vampyrella, sp. nov. This species is represented by a single specimen dredged off the southern coast of Oahu Island (Sta. 3907) at a depth of 304-315 fath., where the tempera- ture was 43.7 F. It was coiled tightly about a solitary polyp of Epizoanthus, and further examination showed that the proboscis of the molluse was protruded through the body wall of the coelenterate, whose reproductive and other tissues had been drawn into the alimentary canal of its captor. There is therefore no doubt that this species is carnivorous and that its association with the actinian is not an accidental one or a case of commensalism. 78 DREPANOMENIA VAMPYRELLA. The body (Plate 2, fig. 2) measured 9 mm. in length, was slightly compressed laterally, particularly its anterior half, and in form was somewhat spindle shaped, being largest about the middle section of the body and gradually tapering off toward each end, especially posteriorly where the body becomes quite slender before terminating in a truncated extremity. A well-defined keel extends along the entire animal in the mid dorsal line. The color was faint yellowish white. The cuticle surrounding the body is of medium thickness, measuring 0.35 mm. in the keel and 0.28 mm. elsewhere in the dorsal region, but gradually decreasing to half this amount on the ventral surface. It includes a single layer of radially directed spicules (Plate 32, fig. 6), ranging in size from those in the first stages of formation to others of the keel 0.129 mm. long. All are of the same general form represented in Plate 37, fig. 7. It is to be noted that many of the spicules are not in contact with the hypodermis, even the matrix cells having disappeared, but are situated far out toward the surface of the body. Beneath each developing spine are several cells apparently instrumental in its formation. The cells of the hypodermis are very small and indistinct and accordingly have been examined only superficially. The prevailing cells are slender with subcentral nuclei, and are developed into numerous small elevations, some of which connect by strands with the overlying papillae (Plate 32, fig. 6). These last named organs contain upwards of eight cells in the enlarged portion; none appear to exist in the exceedingly slender stalk. As in other species of the family the ventral furrow commences close to the hinder border of the lip, and extending the entire length of the animal becomes continuous with the cloacal opening. Anteriorly it contains a relatively deep excavation into which the anterior pedal gland opens by the usual numerous intercellular ducts. This last named gland occupies practically all of the vis- ceral cavity between the region of the brain and the anterior end of the gonad. The cells composing it are generally pyriform, with an average diameter of .021 mm. and are filled, save for the small compact nuclei, with a finely granular substance that stains intensely with logwood dyes. In some eases this secretion appears to be undergoing solution, and presents a vacuolated appearance, a character that is very pronounced among the cells of the posterior pedal gland. These latter elements are related also to the-foregoing in general form, size, and appearance, and extending to the cloaca and opening on each side of the foot, are thus seen to hold the usual position. At the hinder border of the crypt into which the anterior pedal gland opens, DREPANOMENIA VAMPYRELLA. 79 the foot arises as a single, small prominence and rapidly assumes its fully devel- oped condition. Posteriorly it gradually decreases in size, disappearing, so far as may be judged from longitudinal sections, at a point immediately in front of the gonoduct openings. The general relations of the anterior section of the digestive tract are fully represented in Plate 7, fig. 4. As will be seen the atrial opening is subterminal in position and of medium size. The relations of the succeeding parts, while much the same as in Proneomenia, for example, are somewhat obscured by the protrusion of the pharynx. An outer ridge, composed of the usual type of col- umnar cell though apparently lacking cilia (Mundleist), is present. The inner ridge, probably related as in other species, has in the present specimen been carried out on the tip of the pharynx, an interesting fact as it indicates that these cells may be sensory, and of service in determining the character of the animal’s food or surroundings. Between these two prominences the usual cirrose area is present, the cirri being of relatively large size and unbranched. It has been suggested that the cirri, secreting a viscous material, may serve in the capture and retention of food. Here, however, is an animal killed in the act of feeding with its proboscis penetrating its host. The material drawn into the pharynx does not come into contact with the cirri, which in this case must certainly have some other function, though it is difficult to say what this may be. In its present extended condition the pharynx is relatively slender, almost wholly devoid of longitudinal folds and is relatively muscular. Heavy retractor muscles attach to the buccal wall and serve to withdraw the pharynx, that ap- pears to lack special retractors of its own. In some species of Neomenia the ventral salivary glands are described as being more or less coiled; in the present species this would probably be the case, but with the protrusion of the pharynx their openings into the canal have been carried forward until they are very close to the end of the proboscis. Each gland is unbranched, composed of excessively spongy cells and is possessed of a relatively large lumen, and a length of fully one fourth that of the body. In view of the fact that Drepanomenia has no radula it appears probable that the salivary secretion exercises a solvent action on the tissues of its victim, and the liquified material is then sucked in. The digestive tract in the present case is well filled with a finely granular substance in which one may recognize here and there the remains of cells, chiefly repro- ductive, belonging to its host. As may be seen (Plate 7, fig. 4), the stomach-intestine extends forward a considerable distance in front of its union with the pharynx, thus forming an 80 DREPANOMENIA VAMPYRELLA. extensive anterior coecum. On this sack a number of short outgrowths are developed chiefly on the dorsal side. A short distance behind the front end of the gonad gut pouches appear arranged with great regularity, and from this point on digestive cells attain their fully developed condition. In the region of the pericardium the sacculations vanish, the canal narrows rapidly and the liver cells are replaced by low eolumnar cells thrown up into longitudinal ridges extending to the opening into the cloacal chamber. In this specimen the pericardial cavity is relatively large (Plate 6, fig. 3), and the heart it contains is considerably distended with blood, rendering it possible to some extent to determine the course of the circulation. The blood returning from the gills, and another smaller portion that appears to come directly from the hinder portions of the body, pours into a well-defined auricle situated at the hinder end of the pericardial cavity beneath the ventricle. Its walls are only slightly less muscular than those of the ventricle, and owing possibly to muscular contractions, are developed into several pouches that do not have the appearance of blood glands. From the auricle the blood passes into the ventricle through a comparatively large opening guarded by a well- developed muscular flap probably functioning as a Valve. From the front end of the ventricle a clearly defined vessel arises, and passing forward unites with the dorsal aorta. This latter vessel holds its usual position between the body wall and gonad, but it extends backward over the dorsal side of the pericardium as far as the posterior end of the ventricle. Anteri- orly the relations of the vessels in the gonad and of the aorta to the head cavity are essentially as they are in P. hawatiensis. This appears to be the case also with the sinuses in other parts of the body, though using longitudinal sections through the somewhat twisted body, it is not possible without much labor, to determine their connections accurately. With the protrusion of the pharynx the brain has been carried some dis- tance ventrally, but under ordinary circumstances its position and the relations of the nerves which it develops are probably not unusual. As Plate 7, fig. 4, shows three pairs of nerves pass to the atrial wall as in other of the Neomeniina, and are probably destined, here as there, to supply the cirri, anterior muscula- ture, and hypodermal sense organs. So far as may be judged from sections, the labio-buccal connectives originate some distance from the pedal and pallial, and may be clearly seen to pass down to ganglia situated on the sides of the pharynx where it unites with the buccal wall. From the hinder border of each ganglion a fibre originates that may be the inferior or ventral commissure, but DREPANOMENIA VAMPYRELLA. 81 owing to innumerable muscles it was not possible to determine this conclusively. Neither was it possible on this account to determine if any subradular system exists. The relations of the pedal and lateral ganglia call for few special remarks. In some places it was possible to demonstrate pedal commissures, and to trace connectives between the pedal and lateral cords, especially in the hinder regions of the animal where the cords are closer together. The most posterior connective is especially heavy (Plate 11, fig. 1), and develops two or three fibres whose branches may be traced to the musculature of the body wall. On the inside a very few exceedingly delicate nerves pass to the terminal section of the coelomo- ducts. From the posterior swollen section of the lateral cords (ganglion superior posticus) several nerves arise chiefly distributed to the body wall. The dorsal commissure is relatively heavy and closely applied to the dorsal wall of the rectum. In the median line it gives rise to a nerve that may be traced to a point near the dorso-terminal portion of the body. In position it corresponds to the nerve supplying the dorsal sense organ in other Solenogastres described in this paper, but no such well-defined sensory area appears to be present in this species. In this species the paired gonad, without any special peculiarities, terminates rather abruptly at a point about as far forward as the hinder border of the atrial opening, and on the other hand passes by two relatively large ducts into the spacious pericardial chamber (Plate 11, fig. 1). From the lateral portions of a small recess at the posterior end of this cavity each coelomoduct arises, and after passing downward for a short distance then passes forward, gradually increasing in size until it reaches a position about level with the hinder tip of the gonad. Here it bends abruptly and coursing backward unites with the one of the opposite side, and as a short common duct makes its way to the cloaca. Each canal commences its course with an epithelial lining essentially like that of the pericardial wall, being composed of low flat cells entirely devoid of cilia and lateral cell boundaries. These deficiencies are soon overcome, however, and there are evidences in some of the cells a short distance from the pericardium of a slight glandular activity. In proportion to the increasing diameter of the duct the cells show a greater width and height and the cilia become a strongly marked feature. This holds true for only a portion of the canal however for at a point slightly below the level of the lateral nerve the character of the lining changes abruptly. At this point the cells become high and columnar along the dorsal side of the tube and form a ridge, extending forward to the most anterior 82 PRONEOMENIA HAWAIIENSIS. turn in the duet. The cilia with which this part of the tube is provided are probably operative in driving the sex products toward the exterior. There are no evidences that they ever form a groove such as has been described in a few other species, and it must rather be supposed that both sex products travel much the same path. At the anterior sharp turn of the coelomoduct the ciliated ridge passes, so far as may be judged from sections, into a ciliated patch that occupies the anterior wall of the canal, and extends a short distance down the posteriorly directed section, corresponding to the shell gland in other Solenogastres. This patch, roughly circular in outline, is composed of low columnar cells provided with very long, powerful cilia. Posteriorly the cells of this region blend with others of the same general appearance, but without cilia, and filled with an abundant secretion in several cases in the act of being discharged. This glandular area is limited to a narrow girdle encircling the duct, and is sharply defined from the succeeding portions of the canal, whose walls are developed into numerous folds obscure at first but in the neighborhood of the cloaca of considerable height. The cells in all of this corrugated section, the shell gland of other Neomeniina, vary in height according to the size of the fold of which they form a part, but all agree in being relatively slender with central dense nuclei external to which the cytoplasm is filled with some glandular product of yellow tint. In the terminal section of the cloacal passage this substance is present in considerable quantities and at various points has made its escape in an unchanged condition into the neighboring duct. Proneomenia hawaiiensis, sp. noy. This species is represented by three individuals, one perfect and two muti- lated. The first was dredged in the neighborhood of Kapuai Point off the west- ern extremity of Kauai Island (Sta. 4001) at a depth of 230-277 fath. where the bottom consisted of coarse sand and the temperature was 44.3° F. The imperfect specimens were taken in the vicinity of Mokuhooniki Islet (Mokuo Niki), a small island close to the eastern border of Molokai Island (Sta. 3864) at a depth of 163-198 fath. where the temperature was 57.5° F. and the bottom con- sisted of shells and fine voleanic sand. All the specimens came in unattached and without any food in the digestive tract so that nothing is known of their mode of life. The perfect individual measured 36 mm. in length and 2 in average diameter, and this proportion of 1:18 appeared to be the same in the imperfect specimens. The body (Plate 3, fig. 10) is elongated, tapering gently from the forward to the hinder end, and is slightly elliptical in cross section. A rusty red incrusta- PRONEOMENIA HAWAIIENSIS. 83 tion covered the entire animal save the anterior tip and the lips, where the color was light lemon-yellow. As in other members of the genus the atrial opening is subterminal and pre- sents the appearance of an elongated slit encircled by rounded lips. Immediately behind it the ventral furrow takes its rise and extends to the posterior end of the body where it becomes continuous with the subterminal cloacal opening. Sections show a well-defined dorsal sense organ with small surrounding spines (Plate 32, fig. 10) but owing to the debris encrusting the body this was not exter- nally visible. With the exception of the ventral furrow the body is covered by a relatively thick cuticle that must be an efficient means of protection and at the same time render the animal relatively sluggish. As usual innumerable calcareous spicules are imbedded in the cuticle, forming five or six irregular layers. These spines are of two distinct types; one, the larger and more abundant form with rounded extremities (Plate 37, fig. 5a) is placed more or less parallel with the hypodermis while the second (b) extends at right angles to it and projects slightly above the external body surface. Spines of somewhat this same general form are located along the ventral furrow and about the atrial and cloacal openings; but in their mode of development and owing to numerous intermediate stages it may be seen that they belong to the first class. A more detailed description of the position and development of the spines of this species is given on page 28. The cuticle is penetrated also by many papillae whose arrangement and general appearance are shown (Plate 33, fig. 3). As Hansen has noted they appear like so many baloons situated inmediately below the external surface of the cuticle and connected with the hypodermis by a slender fibre. This distal expanded part appears to consist of several cells each with basally placed nucleus and an outer vacuolated section which usually fuses with the correspond- ing part of the other cells. These elements pass without any sharp line of de- marcation into the stalk that contains from four to six elongated nuclei and in turn unites without definite cell boundaries with a small number of cells of the hypodermis. In many cases delicate fibres may be traced from these hypodermal cells into the deeper tissues of the body, and at the anterior end of the animal they may occasionally be followed into close proximity to the ganglionic layer surrounding the atrial wall; nevertheless while appearances seem to favor the belief that these are nerve fibres and the papillae are sense organs the evidence is not complete. The pedal gland is coextensive with the foot and consists of two long slender 34 PRONEOMENIA HAWAIIENSIS. bands of cells situated a short distance within the body on each side of the ventral furrow into which their secretion is poured. In the body proper the position, size, and number of the component cells in cross section is shown (Plate 14, fig. 3). This condition of affairs exists to the front end of the gonad where the gland cells become more abundant and of larger size, occupying approximately one fourth of the visceral cavity at the level of the posterior end of the radula. Their outlets still continue in the ventral furrow and in addition occur throughout the region of the anterior division of the foot, which contains extensive blood lacunae and may probably be protruded at times beyond the ventral furrow. The anterior pedal gland abuts against the front end of the pedal gland proper and, occupying more than half of the space between the buccal mass and the body wall, extends as far forward as the brain. The main body of each of its cells consists of spongy cytoplasm containing an abundant secretion that stains faintly in Delafield’s haematoxylin. The included nucleus is relatively very small, granular and very irregular in form. Several cells are usually grouped together and surrounded by a few connective-tissue fibres. Each cell is attached by a duct with the ventral furrow chiefly in front of the foot. All of the ductules of both pedal glands open between the cells of the ventral furrow. The atrial opening leads into a cavity of relatively generous proportions (Plate 5, fig. 2) with walls abundantly supplied with sense organs of several different types. The most external of these, which I have termed the outer atrial ridge (Plate 14, fig. 1), presents the appearance of a low prominence situ- ated just within the lips and encircling the atrium except in the mid line behind. Its cells are comparatively slender and in addition to the darkly staining and usually basally situated nuclei, they contain numbers of greenish yellow pig- ment granules. Lying in contact with the inner ends of these cells is an accumu- lation of ganglion cells forming an elongated mass coextensive with the ridge itself. From it nerve fibres may readily be traced to the sensory cells adjoining, and in an opposite direction large nerves occasionally pass inward, and soon be- come confused with the ganglionic elements attached to the bases of the cirri above. That this is a highly sensory structure there is no reasonable doubt, but to define its function more accurately is at present impossible. Of almost identically the same length as the sensory ridge just described and directly in contact with its inner border is another inwardly projecting fold of much greater height and widely different character. It likewise encircles the atrium save on the posterior side where its free extremities unite with another ridge of corresponding height and appearance that farther within the body also PRONEOMENTA HAWAIIENSIS. 85 encircles the atrial cavity. The epithelial cells bounding these ridges (Mund- leisten) are columnar, richly ciliated and besides the centrally placed spherical nucleus contain a small quantity of greenish yellow pigment. Within the ridges are a few connective and muscle elements and an occasional nerve fibre, all loosely arranged and permitting the entrance of multitudes of blood cor- puscles that probably cause the distension of these organs. The area bounded by these two sensory prominences is the cirrose region characterized by the presence of numbers of hollow finger-shaped projections each attached by its base and extending into the atrial cavity. The cells com- posing these organs differ to some extent in different specimens but agree in being low, non-ciliated, and charged with a considerable quantity of the usual greenish yellow pigment and a varying amount of some hyaline secretion that often covers their external surface. More slender elements, scant in numbers, occur among these ordinary cells; they may be sensory but some at least appear to be cells from which the secretion has recently been discharged. The cavity within each cirrus is usually very slender and is traversed by a muscle and nerve fibre. In very exceptional cases there are one or two blood corpuscles; but neither in this nor in other species of Solenogastres have I found any indication that these play an important part in the process of respiration. Beneath the cirri is a felt-work of muscle, connective and nerve fibres together with blood corpuscles and leucocytes beyond which is a mass of ganglion cells connected with the central nervous system and on the other hand with sense organs of the atrium and probably of the hypodermis. A very short distance within the inner ridge the digestive tract narrows rather abruptly, the character of the epithelial lining changes radically, and since it marks the point of entrance of the dorsal salivary gland it may be con- sidered the line separating the mouth and pharynx. According to such an in- terpretation the pharyngeal wall, lined with a relatively heavy cuticle, is thrown into a series of ridges that course more or less longitudinally throughout its entire extent. In the majority of cases the cells are high, with central oval nucleus and a slight secretion that had escaped at various points through some of the exceedingly minute pores passing through the lining cuticle. The so-called dorsal, or accessory, salivary gland is attached to the dorsal wall of the pharynx immediately behind the brain (Plate 5, fig. 2). The cells composing it are one layer thick, and as the duct itself is short and unbranched the gland is necessarily compact and globular in form. The epithelial lining of the pharynx is continued inward to form the lining of the duct between whose 86 PRONEOMENIA HAWAITIENSIS. cells the secretion is discharged. The cells of the gland are comparatively large, with small nuclei and an abundance of a lightly staining secretion, and are grouped into several clusters separated from each other by a small amount of connective tissue. The paired ventral salivary glands are long tubular unbranched structures opening into the pharynx on each side of the front end of the radula. Their position and general appearance are represented (Plate 14, figs. 7, 9). Each constituent cell is high and columnar in form, composed of vacuolated cytoplasm and possessed with nuclei ranging from spherical to slender spindle-shaped forms correlated with different stages of glandular activity. The secretion within the main duct is finely granular and has only a slight affinity for logwood dyes. In this species the radula is relatively well developed and is located as in other members-of the genus. The teeth are formed by odontoblasts of the usual high columnar type characteristic of the Chitons and prosobranchs and are of the form represented (Plate 34, fig. 13). All the teeth are of essentially the same form and number not less than from thirty-eight to forty-five in each transverse row. There is no indication of a median tooth so far as the sections show but each tooth adjacent to the mid line is somewhat smaller than its fellows (Plate 34, fig. 13). In some species of Solenogastres the teeth are reported to be merely thickenings of a continuous cuticular plate, but in this species they are clearly distinct, a well-defined suture not only separating each tooth from the others but from the basal plate as well. Immediately in front of the radula and somewhat covered by its forward border are two areas of high columnar cells (Plate 34, fig. 2) that are more or less sunken in a well-defined sheath. In another place (Heath ’04) it has been shown that these organs probably correspond to the subradular organ in the Chitons and some of the prosobranchs. Their innervation is discussed in the section on the nervous system. The usual relation of pharynx and stomach-intestine are shown (Plate 5, fig. 2). In another specimen the anterior dorsal coecum is considerably more developed and there is also a small ventral one that extends forward between the salivary glands. A short distance behind the pharynx the cells of the di- gestive tract shade gradually into the relatively high pyriform hepatic cells of the stomach-intestine. There are strong evidences that the distal part of these cells loaded with secretory products separates from the remaining nucleated portions and dissolves in the alimentary tract and that the process is repeated indefinitely, the basal nucleated parts developing anew the glandular distal portions. PRONEOMENTA HAWAIIENSIS. 87 Upon reaching the front end of the cloacal passage (slime gland) (Plate 14, figs. 5, 6) the alimentary canal becomes crescent-shaped in cross section, the concave surface being in contact with the gonad. Before reaching the cloaca it becomes elliptical and the epithelial lining is developed into longitudinal folds that persist to the anal opening. The heart is irregularly cylindrical in form, lacks any clear subdivisions and is attached to the dorsal wall of the pericardium. From its anterior end the dorsal aorta takes its origin and coursing forward between the gonad and the body wall finally makes its way into the roughly defined head cavity. At irregular intervals it gives rise to small ventral branches that pass between the halves of the reproductive gland and enter a sinus lying along the under side of the organ. From this vessel lateral branches extend around the sides of the gonad and open into the visceral cavity dorsally. This relation of aorta and gonad continues as long as any trace of the latter exists, and anterior to this point the aorta gradually enlarges and finally in the neighborhood of the brain passes into the ‘‘head cavity.”’ This last named space is not bounded posteri- orly by a septum, but is well defined by the front end of the pedal gland through and around which the blood passes backward by small channels into the visceral cavity proper. This large sinus surrounding the digestive tract is subdivided into two roughly defined spaces, a relatively large sinus lying beneath the in- testine and a very much smaller one located between it and the foot. At irreg- ular intervals these two communicate and small lateral canals also connect the pedal sinus with the main section of the visceral cavity. The latter also com- municates with the ventral intestinal sinus by fairly well-defined lateral canals that occupy positions between the gut. pouches. In the neighborhood of the cloacal passage these minor sinuses unite with the larger and the blood, that has travelled backward in all of them, makes its way dorsally to open into the hinder end of the heart. In a foregoing account (Heath ’04) the nervous system of this species has been described and in this connection it is only necessary to mention the more prominent features. As is represented (Plate 5, fig. 2), the brain is situated in a depression immediately in front of the dorsal salivary glands. Anteriorly it develops six nerves whose branches supply in large measure the sense organs of the buccal wall and probably the hypodermis and the musculature of adjoin- ing regions. Posteriorly it gives rise to three pairs of nerves, the lateral, pedal, and labio-buccal connectives. The lateral cord almost immediately takes up its permanent position at the sides of the body; the pedal passes downward and 88 PRONEOMENIA HAWAITIENSIS. backward to unite with the pedal ganglia that occupy the usual ventral position ; while the labio-buccal connectives pass backward along the sides of the pharynx and unite with the labio-buccal ganglia that are placed at the sides of the radula. About mid way between the brain and ganglia the labio-buccal connectives are united by a commissure (dorsal buccal) that passes across the dorsal side of the pharyngeal wall, while a second (ventral buccal) passing over the radula unites the buccal ganglia. Each of these last named nerve masses, connected by the well-known commissure dorsal to the radular sac, gives rise to a prominent nerve that passes inward and unites with a ganglion situated near the base each of the subradular organs mentioned in connection with the radula. Hach sub- radular ganglion is in turn connected with a commissure imbedded in the tissue beneath the pharynx. The relations of these ganglia and the attendant sense organs is essentially the same as in the Polyplacophora. They are much more concentrated in the latter group but the various elements may be readily homologized. Through the body proper the pedal and lateral cords are united by con- nectives corresponding roughly to the number of gut pouches. About the same number of commissures also unite the pedal cords. These connectives and commissures disappear about the middle of the slime gland and a short distance beyond this point the pedal cords disappear apparently without forming a posterior connective (Plate 13, fig. 4). The lateral cords on the other hand pass into the posterior ganglia that give rise to many nerves supplying the surround- ing tissues and are united by a strong commissure dorsal to the intestine. In the mid line this commissure develops a nerve that supplies the dorsal sense organ. The dorsal sense organ is located on the mid dorsal line a short distance from the hind end of the animal. Sections show that the cuticle in this region is almost wholly lacking and that the neighboring spines bend over and protect the otherwise naked sensory area. In each specimen the spines were much worn and the upper part of the sensory hollow was filled with debris so that no outward sign of this organ was visible. In one individual, probably abnormal in this regard, there were two dorsal sense organs, one a short distance in front of the other in the mid line. The posterior one corresponds most closely to the single one of the other individuals and will be first described. The cuticle over the sensory region is almost wholly absent and the hypo- dermal cells, that ordinarily are small and distinet, become clearly defined, columnar, and depressed below the general level of the hypodermis. To the PRONEOMENIA HAWAIIENSIS. 89 bottom of this hollow are attached a group of ganglion cells that connect in turn with a nerve from the postpallial commissure. Several muscle fibres are also united to the base of this organ. Judging from appearances the pressure of the blood beneath causes an eversion of the cells of the sensory pit bringing them to the level of the general body surface while the contraction of the muscle fibres produces their withdrawal and, if of sufficient strength, the overarching of the surrounding spicules. The anomalous sense organ mentioned previously as occurring slightly in front of the dorsal organ proper consists of two sensory pits in all essential respects like the one Just described. They are separated by a ridge (Plate 32, fig. 10) on which the spines are relatively small and the hypodermal epithelium only slightly different from that found over the body elsewhere. Nerves from the post lateral (pallial) commissure pass to the depressed area that thus appears to be the sense organ proper. As in other Solenogastres the hermaphrodite gland is in the form of two greatly elongated sacs closely appressed along the mid line and extending nearly as far forward as the brain. As usual the ova are developed along the inner wall while the spermatozoa are produced more externally. In the region of the heart each half of the gonad becomes narrowed to a small duct that communi- cates with the front end of the pericardium, which in one of the specimens was of large size and filled with sex products. From the postero-lateral borders of the pericardium the coelomoducts arise (Plate 13, fig. 4) as relatively slender tubes, and coursing forward and down- ward make their way by a fairly direct course to a point near the front end of the shell gland into which they open. Each canal is in the form of a greatly elongated spindle lined throughout the first part of its course with low flat cells, having indistinct boundaries like those of the pericardial cavity. In the middle enlarged section they attain a greater height becoming nearly cubical, a shape they retain throughout the remainder of this section of the genital canal. The shell gland or slime gland is a comparatively voluminous organ roughly U-shaped in form (Plate 11, fig. 5). Anteriorly each limb communicates with the spiral seminal receptacle and the section of the gonoduct just described while posteriorly both unite and enter the cloaca by a comparatively narrow opening. In striking contrast to the low epithelium of the dorsal limb of the genital canal the lining cells of this section possess clearly defined walls, are high and slender, and are glandular in character. Those in the neighborhood of the seminal receptacle differ considerably in the nature of their secretion from those of the 90 PRONEOMENIA INSULARIS. succeeding portions. With the exception of a small mass of protoplasm contain- ing the spherical granular nucleus the cytoplasm is charged with a product apparently muciform, staining intensely with logwood dyes. In many cases the material has been discharged leaving a relatively spongy protoplasmic matrix. When relieved of their load the cells show no sign of degeneration but continue to elaborate the secretion which forms as minute granules uniformly distributed throughout the protoplasm. As these increase in amount they unite, finally becoming one confluent mass that almost completely fills the cells. In the only other specimen which was sectioned this portion of the gonoduct is composed of cellular elements of the same appearance, but the secretion is hyaline and unaf- fected by Delafield’s haematoxylin, a condition of affairs due in all probability to a different phase of glandular activity. In both specimens these cells of the anterior third of the shell gland blend rather gradually with those of the succeeding section of the duct. As Hubrecht notes in Proneomenia sluiteri the cells are very slender elongated elements with basal nucleus and a secretion, developing at first in the form of minute granules which subsequently fuse and form particles of larger size until one great droplet occupies almost the entire cell often crushing the nucleus into an almost indis- tinguishable mass. It is worthy of note that all the cells in a fairly well-defined area are usually in the same stage of activity, perhaps discharging their burden while those of neighboring regions may be entering into the first stages of the process. In many cases where the secretion has recently been discharged it acts as a highly viscous fluid that only gradually undergoes liquifaction and fills the lumen of the cloacal passage. Proneomenia insularis, sp. nov. This species is represented by a small portion of the anterior end of one individual including the radula and the comparatively long ventral salivary glands. The specimen was found in the bottom of a jar containing some aleyonarian corals that were dredged near Bird Island (Sta. 4157) at a depth of 762—-1,000 fath. where the bottom consisted of white mud and foraminiferous sand with a temperature of 38°. In external appearance and especially in the relations and structure of the cirri, atrial ridges, the radula, salivary glands, and other of the more important organs this species shows a very close resemblance to the species of Proneomenia just described; accordingly I have very little hesitancy in placing it in this genus. The present fragment, cylindrical in cross section PRONEOMENTA INSULARIS. 91 save for a slight flattening of the ventral surface, measured about 1.5 mm. in diameter and terminated anteriorly by a rounded extremity (Plate 8, fig. 4). There is no crest. Its enveloping cuticle, of the usual yellow color, is compara- tively thick and contains large numbers of tapering spicules with rounded ends (Plate 37, fig. 16). Another type of spine occurs in the deeper layers of the cuticle in the form of relatively short basally truncated bodies which are in contact with a stalked cell of the hypodermis. In the case of the larger spicules of this character the sharp distal point may protrude freely above the cuticle. The anterior pedal gland is relatively voluminous, extending forward as far as the cirrose area, posteriorly to the front end of the oesophagus and filling nearly all of the visceral space between these two boundaries. As has been noted in other species of the genus this gland opens separately into a comparatively large space situated behind the mouth opening and continuous with the front end of the pedal furrow. Posteriorly this organ passes without a sharp line of demarca- tion into the pedal gland proper that holds the same relation to the animal as in the preceding species, but in bulk and in size of its cells it is probably twice as large. Behind the opening into which the anterior pedal gland pours its secre- tion the foot commences as a low median ridge that gradually assumes its full size though this is considerably short of that of the foregoing species. The opening of the atrium holds the same position and is of the same rela- tive size as in P. hawaiiensis (Plate 8, fig. 4). The ridges and the cirrose area are likewise very similar in the two forms. The ciliated ridges are not so high in this species owing possibly to the amount of contained blood and the cirri, somewhat more slender than in the foregoing species, are united by their bases into groups of two or three. The junction of the atrial cavity and the pharynx is characterized by a ridge similar to that of the preceding species, but is not farther marked by the presence of a dorsal salivary gland. A very few relatively large cells are situated among the nerve fibres passing out from the brain, but while they are in the correct position for the unpaired gland no ducts have been discovered. The paired salivary glands present the same general appearance as in P. hawaviensis. In the present specimen each organ extends from its opening at the sides of the forward end of the radula backward twice the distance from the front end of the animal to the opening of the salivary duct. Beyond this point the remaining portions of the body are missing. The cells are of the usual high columnar type and are more vacuolated than in any specimens of the preceding species. 92 PRONEOMENIA INSULARIS. After extending backward for about half its length the pharynx bends abruptly upwards and unites with the stomach-intestine. In the angle thus formed is placed the radula that is considerably shorter than in the foregoing species. The teeth also are much smaller though of somewhat similar shape and judging entirely from longitudinal sections there are probably not less than twenty-eight transverse rows with at least twenty-four teeth in each row and possibly more. On the other hand the radular supports, in the form of several transverse rods of compact connective tissue, are more highly developed. The relation of the pharynx and the stomach-intestine are sufficiently shown (Plate 8, fig. 4). The anterior coecum, the gut pouches, and the digestive cells are also essentially like those of P. hawatiensis and require no comment. In connection with the circulatory system there are no unique characters. Every blood space was crowded with corpuscles, spherical in form, with dense nuclei and cytoplasm, colorless after treatment with Delafield’s haematoxylin, and containing several refringent granules. In this species the brain is of medium size, its greatest diameter equaling one eighth the average diameter of the body, and is situated some distance behind the union of the pharynx and mouth. As usual three pairs of nerves pass from its forward and lateral regions to the front part of the body, becoming lost to view in the region of the cirri or more laterally among the body muscles. The connectives passing backward are completely ensheathed in the anterior pedal gland whose granular substance renders it very difficult to follow them to their destination. It has been possible to trace the relatively large pedal fibres to the pedal ganglia, and the lateral connectives to their position along the sides of the body, but the labio-buccal connectives are exceedingly difficult to differen- tiate. However with the aid of high magnification their course has been traced beyond question to the ganglia situated on each side of the pharynx about the level of the radular supports. Each is characterized by a much elongated spindle shape, the connective uniting with its anterior end and the ventral commissure attaching posteriorly. This latter nerve arches over the dorsal side of the radula and otherwise presents the usual appearance. A dorsal buccal commissure, subradular system, and labial commissure were not found. Immediately in front of the radula is a ridge of columnar cells that may correspond to the subradular organ. In several sections it is also possible to distinguish fibres that have the peculiar refraction of other undoubted nerves; yet in spite of persistent effort it has not been possible to determine their relations. Three pedal commissures have been proven to exist and eight palliopedal connectives, all with the usual relations. DRIOMENIA PACIFICA. 93 The paired gonad extends forward to a point slightly behind the level of the hinder end of the radula supports. Anteriorly its cells are entirely male, minute ova appearing only in the most posterior part of the fragment. Driomenia pacifica, sp. nov. Three individuals of this species were taken off the southern end of Japan, two from Ose Zaki (Sta. 3716) at a depth of 65-125 fms. and one from Kago- shima Gulf (Sta. 4935) at a depth of 103 fathoms. All were imbedded in a mass of hydroids belonging to the genus Sertularella. The body is of uniform diam- eter, measuring 1 mm. by 9 mm. in length. The color in alcohol was a yellowish white. No dorso-terminal sense organ has been discovered. The cuticle is thick and contains an innumerable number of hollow spicules of varying sizes but with the general form represented in Plate 39, fig.5. The usual hypodermal cells are not especially favorable for study, but on the other hand those of the papillae (Plate 38, fig. 10) are exceptionally clear. In the distal portion of each papilla the cells are spindle shaped, usually compact and finely granular, and appear in many cases at least to be continuous with a slender fibre which traverses the stalk and may be followed readily into the tissue beneath the hypodermal layer. Beyond this point their course cannot be determined with certainty and accordingly there is no clear evidence as to whether they are muscle or nerve. The anterior pedal gland, occupying the customary position, is composed of the usual pyriform cells of average size. Posteriorly it passes without any change, except a decrease in the number of cells, into the posterior pedal gland which accompanies the foot throughout its entire extent. The outlet of the anterior pedal gland (Plate 38, fig. 1) is a plain walled, globular cavity heavily ciliated. Posteriorly two lateral and one median fold arise on its walls and soon unite to form the foot which continues to the cloacal opening though the two lateral folds become of small size. The atrial chamber, distinctly separated from the remainder of the digestive tract by a spiculose ridge, is a cavity with walls fashioned into the usual sensory organs. ‘Fhe inner and outer ridges are moderately low, horseshoe-shaped ciliated folds nearly encircling the chamber and bounding the cirrose area. Each cirrus is very slender, without a distinct cavity and is usually united at its base with one or two others. The true mouth opening is borne on the summit of a low yet broad pro- boscis which is separated by a very narrow spiculose ridge from the outlet of 94 DRIOMENIA PACIFICA. the anterior pedal gland. From external view this proboscis is not visible, the ventral furrow appearing to extend to the atrial chamber. The mouth leads into a slender tube, with irregular longitudinal folds, and becoming gradually larger as it courses dorsally it opens into the stomach-intestine. About midway it connects with two short ducts from the salivary glands wedged between the stomach-intestine and the anterior pedal gland in the general position represented (Plate 38, fig. 1). Each salivary gland cell is pyriform, slightly vacuolated with distinct compact nucleus and unites with the main outlet by means of a very slender ductule. The anterior coecum and the adjoining section of the gut, is a plain walled tube lined with the usual vacuolated, granular digestive cells. More posteriorly lateral pouches of irregular form appear (Plate 38, fig. 1) and may be found at fairly regular intervals as far as the anterior end of the pericardium. Here the canal rapidly narrows, becomes circular in outline (Plate 38, figs. 7, 9) the epithe- lial lining is reduced in height and by a slender pore it opens into the cloacal chamber whose form and relations are represented (Plate 38, fig. 2). It may be added in this connection that the walls of the cloaca are devoid of folds, glandu- lar appendages, or modifications of any definite character. The pericardial cavity is of moderate size but in one respect differs from that of any other Solenogastre. Immediately behind the opening into the gonad the pericardial wall forms two latero-ventral outpouchings of considerable length (Plate 38, figs. 2, 7). The component cells are low columnar in form, without definite signs of glandular activity and contain relatively large dense nuclei. It is impossible to determine their function though they may be seminal vesicles since cells of the same general appearance compose the lateral peri- cardial wall and connect these diverticula with the inner openings of the coelo- moducts. The heart is of average size and consists of two distinct divisions. The anterior one, without any sharp boundary line is continuous with the aorta which, throughout its entire length, is a tube of more than usually great size. Its connections with the gonad and the anterior end of the body are normal as are those of the visceral sinus. Large blood spaces occur about the cloacal cavity and as the walls of the latter are thin the exchange of gases may readily take place at this point. The blood corpuscles vary considerably in shape, in some cases being similar to the elongated type found in Strophomenia and at other times appearing almost globular. This may be a post mortem effect but the cells are very well preserved. DORYMENIA ACUTA. 95 The nervous system is difficult to trace and accordingly has been examined in its broader features only which show it to be of the usual type. The single specimen examined is sexually mature and the reproductive gland extends as far forward as the level of the salivary glands. While the eggs are attached as usual to the median wall of the gonad the sperms develop in lateral pouches. In the posterior end of the body these crypts are of large size, extending in some cases far down the sides of the intestine, and they are connected with the gonad by small pores (Plate 38, fig. 2). The coelomoducts arise as relatively small tubes from the posterior border of the pericardium and extend forward to the region of the seminal receptacle where as usual they unite with the shell gland. The lining epithelium is low, the cells cubical and ciliated and without indications of being glandular. Each seminal receptacle is a comparatively large club-shaped sae provided with several small outpouchings especially on its distal extremity. In these small pouches multitudes of spermatozoa are attached to the lining epithelium which is com- posed of slender columnar cells. The shell gland is in the form of a thick set Y and as may be seen, Plate 38, it contains a cavity of moderate size. The greater number of gland cells are of one type, high columnar elements containing, large numbers of spherical granules. In the neighborhood of the opening into the seminal receptacle these are associated with a small number of cells containing, after treatment with Delafield’s haematoxylin, a homogeneous violet colored substance. In close proximity to the opening into the cloacal chamber the dorsal wall of the gland contains a considerable number of cells, which secrete a coal black substance when treated with the above mentioned stain. All of these glandular elements are in contact with slender supporting cells containing mesially placed spindle- shaped nuclei. Dorymenia acuta, sp. nov. Eleven specimens of this species were dredged in the vicinity of the Santa Barbara Islands, off southern California, at depths ranging from 302-638 fathoms. The three largest specimens measure 35 mm. in length by 1.25 average diameter, with one exception having a thickness of 2.25 mm. The two smallest indi- viduals are 14 mm. in length by 1 mm. average diameter, and with one excep- tion, a slightly spindle-shaped individual, all of the specimens are slender and of about uniform diameter throughout (Plate 3, fig. 11). Their color varies from a grayish white, where the brick-red color of the liver shines through the cuticle, to light lemon-yellow. The head is rather sharply pointed, and but slightly 96 DORYMENIA ACUTA. differentiated from the body proper, which posteriorly terminates in a very pointed extremity as in Proneomenia weberi Nierstr. The atrial opening is relatively small, subterminal and surrounded by tumid lips which separate it from the ventral furrow. As noted in a succeeding paragraph, the anterior pedal gland is highly developed, but its outlet is not especially modified externally. Posteriorly the pedal groove is continuous with the cloacal cavity. The cloacal opening is relatively large, ventral and is overarched by the posterior pointed end of the body, whose lateral margins are involuted, but may perhaps be flared occasionally to expose the genital spicula, the appearance of the hinder end of the animal resembling at such a time /chthyomenia ichthyodes Pruvot. A well-developed dorsal sense organ (Plate 15, fig. 11), visible in sections only, is present a short distance from the posterior end of the body, and is sup- plied with special nerves and blood sinuses as in P. hawaziensis. The cuticle investing the body is relatively thick (Plate 33, fig. 4), and is developed by a hypodermal layer in which the component cells are of small size. Those not instrumental in the formation of the spicules or papillae are more or less cubical in form and consist of vacuolated cytoplasm in which the nucleus, usually spherical, holds a central position. At various points the nuclei are dense and elongated and may possibly belong to sensory cells. The spicules are hollow needle-like structures (Plate 37, fig. 10), those of the alternate layers crossing the others almost at right angles. In their forma- tion no points of especial interest appear. As usual several cells take part in the process as in P. hawaiiensis. The papillae are of average number and present the appearance represented (Plate 33, fig. 4). Three or four spindle-shaped nuclei occur in the slender fibrous stalk while from five to seven are present in the swollen distal portion. In this last named situation the nuclei are frequently of two sizes, small dense bodies, and one or two of twice their size with a more vesicular appearance. Judging from many sections both the number and character of these elements are due to different stages in the development of the papillae. In advanced stages these latter organs may open to the exterior and become so filled with debris that the cellular elements save those of the stalk, become obliterated. This, however, is undoubtedly an abnormal condition and marks the close of an active functional existence on the part of the papilla. The anterior pedal gland, as in various other species of Neomeniina, is a voluminous organ extending anteriorly as far as the brain, posteriorly as far as the forward border of the radula and filling practically all of the space between — DORYMENIA ACUTA. 97 the gut and the body wall. The cells, where not compressed, are pear shaped with a diameter ranging from .0185-.0351 mm. In the early stages of their existence the cytoplasm is vacuolated and not affected with haematoxylin but with the assumption of glandular activity the secretion, in the form of fine darkly staining granules, appears in the peripheral portions of the cell gradually filling the more central portions with the exception of the small, and at this stage, much shrunken nucleus. Delicate ducts, as usual, lead from the cell body to their intercellular opening into the anterior end of the pedal furrow. From external view the opening of the anterior pedal gland is not marked by any noteworthy peculiarity, but from sections it may be seen that the pedal groove soon expands inwardly into two extensive lateral diverticula (Plate 15, fig. 1), whose anterior walls, in some specimens, are thrown into low folds and more posteriorly are supplied with very heavy cilia, ranging from one to three times the length of the supporting cell. Along the median dorsal line a large fold exists which more posteriorly is continuous with the foot. Everywhere throughout this fold and over the anterior folds of each crypt the secretion makes its exit in the form of a very finely granular almost homogeneous substance and after treatment with haematoxylin of a slightly pinkish tint. The posterior pedal gland is also well developed and consists of a rod of cells on each side of the mid ventral line continuous in front with those of the anterior pedal gland with which they are identical save for their slightly smaller size. Posteriorly they gradually diminish in bulk and number, and in the region of the cloaca finally disappear. . The foot consists of very little more than a V-shaped epithelial fold, the included muscle and connective tissue being very scanty, and entirely devoid of blood sinuses or at all events those of sufficient size to include blood corpuscles in preserved material. Throughout its entire extent it is accompanied by two small epithelial ridges which are to be considered special modifications of the hypodermis. The inter-cellular openings of the pedal gland occur in the angle formed by these ridges and the foot. The atrial opening, holding the usual subterminal position, leads into a cavity possessing essentially the same relations as in various species of Neo- menidae. Like Proneomenia hawaiiensis, for example, there are two conspicu- ous ridges surrounding the cirrose area, and external to the outer buccal ridge a low elevation encircles the cavity save in the mid line posteriorly. From this elevation numerous delicate fibrils may be traced to a rod-like accumulation of ganglion cells coextensive with the ridge itself. On the other hand these 98 DORYMENIA ACUTA. nerve cells connect by relatively large nerve bundles with the ganglia located near the bases of the cirri. Of the ciliated ridges (Mundleisten) the more external are in the form of two elevations which approach each other very closely in front and behind, at which points they become low and inconspicuous though in their mid section they are comparatively high. The inner ridge has the form of a horseshoe, the free extremities connecting posteriorly with the ends of the outer ridge. This inner prominence is relatively short yet high, and like the outer con- tains a loose meshwork of muscle and connective-tissue fibres among which are numerous blood corpuscles. The cells composing them present much the same appearance as those of the outer low elevation described in the preceding paragraph. Practically all are slender and contain small amounts of pigment and elongated nuclei. Nerve fibres may be followed into the ridges which thus seem to be sensory. In P. hawatiensis these cells are richly ciliated, but in this species all traces of cilia are absent and, it may be added, the material is excellently preserved. Within the cirrose area and lying behind the innermost ridge the atrial wall in the mid line is developed into a fold, of large size, which is closely packed with multitudes of blood corpuscles. If the buceal ridges serve as respiratory organs, as some authors would have us believe, this structure is. certainly more efficient since it is not only voluminous but its epithelial covering is not more than one third as thick as that of the general atrial cavity. The cirri are prominent structures in this species, being not only numerous but of considerable length and calibre. Each is composed of cubical or low columnar cells filled to a considerable extent with the usual yellowish pigment. which more or less conceals the small centrally placed spherical nucleus. At various points these organs may arise singly from the buccal wall, but usually the bases of from four to six are fused, and into this stalk muscle and occasionally nerve fibres may be traced. The cavity of the single cirrus is usually so small that the relation of these fibres remains unknown and, it may be noted, effec- tually blocks the entrance of blood cells, so that these organs are rather to be considered retractile sensory organs with little respiratory function. A short distance behind the cirrose area the pharynx originates as a tube with somewhat smaller diameter than the atrial cavity. However, immediately behind the region of the brain the canal from external view expands considerably, but sections of this region show that a great fold develops in the pharyngeal wall which it entirely encircles reducing the cavity to a crescentic slit (Plate 15, DORYMENIA ACUTA. 99 figs. 1, 7). Numerous muscles inserted in the tissue of the fold and on the other hand to the body wall doubtless serve to dilate the canal when the animal is in the act of feeding. Immediately behind this fold, and therefore in the region of the radula, the canal becomes much wider but more posteriorly again narrows and by a comparatively small opening communicates with the stomach-intestine. Throughout the entire extent of the pharynx its epithelial lining is thrown into numerous longitudinal folds, especially in the neighborhood of the radula where they become wavy and in sections present a most complicated appearance. In general the cells of the pharyngeal epithelium are low columnar elements devoid of cilia and overlaid with a clearly defined cuticular layer. Two sets of salivary glands are present, a ventral pair and a group of cells imbedded in the large fold just mentioned. The cells of the last named gland, which is probably the homologue of the dorsal salivary gland of several other species of Solenogastres, are not grouped compactly as in P. hawaviensis, for example, but are scattered throughout the tissue of the fold and open by separate pores over its entire extent. All the cells are pyriform and in early stages are composed of a finely vacuolated cytoplasm in which the secretion ultimately makes its appearance in the form of distinct granules of comparatively large size. These rarely accumulate to a sufficient extent to hide the nucleus but make their way by well-defined ducts to open by intercellular channels into the pharyn- geal cavity. The ventral salivary glands open into the pharynx at the sides of the extreme tip of the radula, and in the form of tubular outgrowths extend backward for a distance of 3.5mm. As may be seen (Plate 15, fig. 2), the ducts are of large size and are bounded by slender cells densely filled with a secretion having much the same appearance as that developed in the dorsal set. The radula is of the polystichous type, and judging wholly from sections consists of 48-51 rows with twenty-two teeth in each row. All the teeth are of essentially the same shape (Plate 34, figs. 7, 11) and size with the exception of those on each side of the mid line which appear to be slightly smaller. 7, Alexandromenia agassizi. x 4, Limifossor fratula. x 7. Chaetoderma seabra. X 7. Chaetoderma attenuata. Living specimen. x 2, Chaetoderma montereyensis. 1.3. Chaetoderma robusta. X 1.3, Chaetoderma californica. 3. Chaetoderma argentea. Livingspecimen. > 2.5. Chaetoderma montereyensis. X 2. Chaetoderma erudita. Living specimen. 2. Chaetoderma attenuat a, front and side views. Living specimen. Chaetoderma erudita. 15. Chaetoderma nanula. 15. Limifossor fratula. >< 13. Chaetoderma montereyensis. X 15. Dondersia californica. Anterior end. X 2: Chaetoderma scabra. 15. Chaetoderma montereyensis. X 10. Dondersia californica. Posterior end. »X 22, Chaetoderma robusta. 8. i) x 10. » ‘ALBATROSS’ PACIFIG SOLENOGASTRES. LY fo SESPERY ITE PEARS ERMC Ur Gne B Meisel ith Boston H Heath del. If ? £. 2. g. 3. g. 4. ). 6. PLATE 5. Posterior end of Chaetoderma attenuata, living specimen. Reconstruction of anterior end of Proneomenia hawaiiensis. Same of Halomenia gravida. Same of Dondersia californica. Posterior end of Alexandromenia agassizi. Anterior end of Ichthyomenia porosa. “ALBATROSS” PACIFIC SOLENOGASTRES BMeisel lith Boston PLATE 6. Fig. 1. Reconstruction of posterior end of Ichthyomenia porosa. Fig. 2. Same of Dondersia californica. Fig. 3. Same of Drepanomenia vampyrella. Fig. 4. Same of Dorymenia acuta. Fig. 5. Same of anterior end of Lophomenia spiralis. eae Fig. 6. Junction of pharynx and stomach-intestine in Strophomenia scandens, showing opening of the ventral salivary gland and a portion of the labio-buccal system. Fig. 7. Reconstruction of posterior end of Strophomenia scandens. Fig. 8. Same of Chaetoderma hawaiiensis. dso dorso-terminal groove; gn suprarectal com- missure; nd, coelomoduct; rpo reno-pericardial opening. “ALBATROSS” PACIFIG SOLENOGASTRES. HHeath del. B Meisel lith. Boston. Wig. Vig. Vig. Fig. lig. PLATE 7. Reconstruction of anterior end of Strophomenia farcimen. Same of anterior end of Chactoderma hawaiiensis. Same of anterior end of Alexandromenia agassizi. Same of anterior end of Drepanomenia vampyrella. Same of posterior end of Alexandromenia agassizi. “ALBATROSS” PAcIFIG SOLENOGASTRES. HHeath del. BMeasel lith. Boston Fig. Fig. Fig. Fig. Fig. Fig. — Lo or) PLATE 8. . . 7 . Reconstruction of anterior end of Herpomenia platypoda. Same of anterior end of Strophomenia spinosa, small specimen. Same of posterior end of Herpomenia platypoda. Same of anterior end of Proneomenia insularis. Same of anterior end of Strophomenia ophidiana. Same of posterior end of Lophomenia spiralis. “ALBATROSS” PACIFIG SOLFNOGASTRES. PLarz 8. F B Meisel ith Boston. PLATE 9. Reconstruction of the posterior end of the body from transverse sections. Fig. 1. Strophomenia ophidiana. Fig. 2. Dorymenia acuta. Fig. 8. Strophomenia triangularis. Fig. 4. Strophomenia spinosa. Fig. 5. Lophomenia spiralis. “ALBATROSS” PACIFIG SOLENOGASTRES HHeath del. B Meisel lith. Boston PLATE 10. PLATE 10. Figs. 1-7, 9-10. Sections of Limifossor talpoideus; Fig. 8. Chaetoderma erudita. ies le Hig. 42: Fig. 3. Fig. 4 Fig. 5. Tig. 6. Fig. 7. its supports. Vig. 8. Fig. 9. Fig. 10. Side view, living specimen. X 5. Anterior end, living specimen, showing extremes of motion of frontal sense organ. Lateral view of organs of posterior end of body. Same of organs in anterior part of body. Diagram of radula and muscles that open and close the teeth. Section through dorsal sense organ. X 13d. Lateral view of buccal mass, showing more important muscles that operate the radula and Brain and labio-buecal nervous system. Spicules from middle of body, front and side views. X 110. Dorsal view of radula and its supports; portion of dorsal pharyngeal wall removed. “ALBATROSS” PACIFIG SOLENOGASTRES H Heath del. B Meisel lith. Boston PLATE 11. Reconstruction of the posterior end of Drepanomenia vampyrella. Same of anterior end of Strophomenia spinosa, large specimen. Same of anterior end of Alexandromenia valida. Same of posterior end of Strophomenia farcimen. Same of posterior end of Proneomenia hawaiiensis. “ALBATROSS” PAcIFIG SOLENOGASTRES. “Stayer, HHeath det. B Meisel lith. Boston PLATE 12. Fig. 1. Reconstruction of anterior end of Strophomenia scandens. Fig. 2. Section through dorso-terminal sense organ of Alexandromenia valida. Fig. 3. Reconstruction of posterior end of Strophomenia spinosa, small specimen. Fig. 4. Reconstruction of posterior end of Chaetoderma attenuata, showing principal nerves, two (brn) passing into the gill. Fig. 5. Reconstruction of anterior part of nervous system of Alexandromenia agassizi. Fig. 6. Same of posterior end. “ALBATROSS” PACIFIG SOLENOGASTRES PLatel2. HHeath del B Meisel lith. Boston TA ies ' Pee WA iy — I i ; vi 1 : : ; ) ‘ - Mat a A ii PLATE 13. Fig. 1. Reconstruction of anterior end of Dorymenia acuta, showing nervous system. Labio- bueeal system heavily shaded. Fig. 2. Same of posterior end of Strophomenia scandens. Fig. 3. Same of anterior end of Chaetoderma erudita. Tig. 4. Same of posterior end of Proneomenia hawaiiensis. “ALBATROSS” PACIFIG SOLENOGASTRES. PLATE 13, aan asa H.Heath del. B Meisel lith. Boston A a), | PLATE 14. — PLATE 14. Cross sections of Proneomenia hawaiiensis. 33. Tigs. 1, 2, 7 correspond to lines A, B, C in fig. 2, pl. 5 (anterior end) and figs. 5, 6, 8 to D, E, F in fig. 4, pl. 13 (posterior end). In fig. 1. im, om represent inner and outer atrial ridge; os, external sensory ridge. Fig. 3. Section through middle of body. Fig. 4. Section through animal about one fifth body length from anterior end. Fig. 9. Section through body a short distance behind pharynx. LL “ALBATROSS” PAGIFIG SOLENOGASTRES. Plate 14. rt) \ % 4 i sy, SUEEUN oS Ni, B Meisel lith. Boston PLATE 15. Figs. 1-7, 9-12. Sections of Dorymenia acuta. > 50; Fig. 8. Halomenia gravida. Figs. 1, 2 correspond to lines A, B indicated in fig. 7, pl. 15 (anterior end), and figs. 4, 6 to D, C, in fig. 4, pl. 6 (posterior end). Fig. 3. Section through dorso-terminal sense organ. . Fig. 5. Cross section of penial spine. X 205. Fig. 7. Longitudinal section of anterior end of body. Tig. §. Cross section corresponding to line D, fig. 5, pl. 3. Fig. 9. Cross section of young animal, posterior end. Fig. 10. Longitudinal section through base of penial spine. 205. Fig. 11. Section through dorso-terminal sense organ. XX 205. Fig. 12. Section through atrial cavity. “ALBATROSS” PACIFIG SOLENOGASTRES Me iD) QI MAY cs < HHeath del. B Meisel lith Boston PLATE 16. Fig. Fig. Fig. lig. Vig. Fig. Fig. Tig. \s Pig. PLATE 16. Cross sections of Strophomenia scandens. In region of brain. Behind pharynx. In middle of body. Through pharynx opposite anterior pedal gland outlet. Through seminal receptacles. Through mid section of coelomoduets. Opposite junction of pharynx and mid gut. Through junction of coelomoducts. Through outlet of coelomoduets into cloaca. xX 33. “ALBATROSS PACIFIG SOLENOGASTRES. HHeath del. B Meisel litt Boston PLATE 17. ligs. 1-7. Strophomenia spinosa, X 33. Figs. 8, 9, 13. S.ophidiana, X 24. Figs. 10-12, 14-17, S. farecimen, X 33. Figs. 1, 2, 3 cross sections of 8. spinosa (large specimen) along lines A, B, C indicated in fig. 2, pl. 8 (the lines A, B should be perpendicular to the cuticle). Fig. 4. Cross section through radula and salivary gland outlet, S. spinosa. Figs. 5, 6, 7 are through fig. 4, pl. 9 (posterior end). Figs. 8, 9, 13 are cross sections of S. ophidiana along lines A, B, C of fig. 5, pl. 8. Figs. 10, 11, 16 are cross sections of 8. farcimen along lines, A, B, C indicated in fig. 1, pl. 7 (ante- rior end), Figs. 14, 15, 12, of same species, correspond to lines D, E, F, of fig. 4, pl. 11 (posterior end). Fig. 17. Spines of Strophomenia farcimen. X 210. PLATE 17. “ALBATROSS” PACIFIG SOLENOGASTRES i aloe ,\. w ne B Meisel lith Boston HHeath del. PLATE 18. Figs. 1-4. Strophomenia ophidiana X 24. Figs. 5-12. 8S. triangularis. farcimen. X 60. Fig. 1. Cross section of 8. ophidiana along line D of fig. 5, pl. 8. Figs. 2, 3, 4 of same species are along lines, E, F, G, fig. 1, pl. 9. Figs. 8, 12, 10, 11 of S. triangularis correspond to lines D, E, F, G, fig. 3, pl. 9. Figs. 5, 6, 9 correspond to lines A, B, C, fig. 6, pl. 36. Tig. 7. Section through mid gut behind pharynx. Fig. 13. Section through mid gut of S. farcimen in region of salivary glands. x 55. Fig. 13. “ALBATROSS” PACIFIG SOLENOGASTRES. PLATE 18. HHeath del. B Meisel lith Boston fod, ha ae PLATE 19. PLATE 19. Figs. 1-3, 5,6,9. Lophomenia spiralis. X 35; Figs. 4,7,8, 10-15. Herpomenina platypoda. X 60. Figs. 1, 2, cross sections of much curved specimen of Lophomenia spiralis. X 45. Fig. 3. Section behind pharynx. Figs. 5, 6, 9 (same species) correspond to lines B, C, A, fig. 6, pl. 8. Figs. 4, 7, 8, cross sections of Herpomenia platypoda along lines A, C, B in fig. 1, pl. 8. 60. Figs. 10, 14. Sections through posterior end of H. platypoda along lines D, E, (which should incline to left) fig. 3, pl. 8. Fig. 12. Section through dorso-terminal sense organ. X 205. Fig. 13> Section through salivary ducts, showing entrance of ductules from gland cells. Figs. 11, 15. Longitudinal sections through posterior end of H. platypoda. “ALBATROSS” PACIFIG SOLENOGASTRES. HHeath del. Pate 19, B Meisel lith Boston PLATE 20. PLATE 20. Alexandromenia agassizi. XX 25. Figs. 1, 2, 4, 9 correspond to lines A, D, B, C of fig. 3, pl. 7 (anterior end). Tig. 3, 5, 7, 8, are along lines I’, G, H, E, of fig. 5, pl. 7 (posterior end). Fig. 7, 20. Fig. 6. Cross section of heart at junction of its two divisions. es Caer Te PLate 20. “ALBATROSS” PACIFIG SOLENOGASTRES. B Meisel lith Boston HHeath del. Figs. 1-6. 2 Fig. 11. Fig. 12. Fig. 13. ? ) PLATE 21. Alexandromenia valida. > 28. Figs. 7-13. Limifossor talpoideus. X 33. 4. Cross sections along lines A, B, C in fig. 3, pl. 11 (anterior end). 6. Through posterior end of body. Chlorogogue or concrement bearing cells of L. talpoideus, from sides of ventral sinus. Section through brain. Hypodermis of L. talpoideus. > 255. Section through heart and pericardium. X 50. “ALBATROSS PAGIFIG SOLENOGASTRES Prateel HHeath del B Meisel lith Boston PLATE 22. Cross sections of Halomenia gravida. ™X 55. Figs. 1, 2, 3 correspond to lines A, B, C in fig. 3, pl. 5 (anterior end). Fig. 4. Section through body behind pharynx. Fig. 5. Salivary gland lobules opening into main duct. Figs. 6, 8, 11 (see fig. 8, pl. 15) correspond to lines 1, 1’, G in fig. 5, pl. 8 (posterior end). Tig. 7. Longitudinal section through advanced Jarva, showing cerebral ganglion chain of nuclei, stomodaeum, st, and early stage in the development of the anterior pedal gland and outlet, f. Fig. 9. Section through anterior division of heart. Fig. 10. Section through junction of two divisions of heart. Fig. 12. Section through dorso-terminal sense organ Vig. 13. Spines from middle of body. > 300. “ALBATROSS” PACIFIG SOLENOGASTRES PLATE 22. H.Heath del. B Meisel lith, Boston PLATE 23. Cross sections of Dondersia californica. X 60. Figs. 1, 2, 3, 5 correspond to lines A, B, C, D, fig. 4, pl. 5 (anterior end). Fig. 4. Through anterior end of mid gut. Figs. 6, 9 are along lines G, F of fig. 2, pl. 6 (posterior end). Fig. 7. Though middle of body. Fig. 8. Section through radula. X 555. ) B Meisel lith. Boston PLATE 24. Figs. 1-5, 11. Sections of Ichthyomenia porosa. > 55. Fig. 6-10, 12-14. Strophomenia regu- lenis >< +55; Figs. 1, 4, 11 of I. porosa, correspond to lines B, C, A, fig. 6, pl. 5. _ Figs. 2, 5 are along the lines E, D, fig. 1, pl. 6 (posterior end). Fig. 3. Seetion through middle of body. Figs. 6, 8, 9, 10, of S. regularis, are along the lines, C, D, B, A in fig. 8, pl. 26 (in fig. B read el in place of ct). Fig. 7. Section of cuticle and hypodermis of 8. regularis. X 205. Fig. 12. Section through one sense organ of anterior end of I. porosa. > 555. Fig. 18. Section through one seminal receptacle and several stalks of 8S. regularis. X 255. Vig. 14. Blood corpuscles of 8. regularis. » 555. “ALBATROSS PACIFIG SOLENOGASTRES. H Heath del. BMeisel lith Boston Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Figs. 9, 10. Two successive sections through the subradular ganglion and connectives. il 2 3. 4. 5 6 7 8. PLATE 25. Sections of Chaetoderma attenuata. X 33. Section through brain. Section through radula. Section through junction of stomach and intestine. Section through suprarectal commissure. Section through outlet of coelomoduct (pores omitted in figure). Section through posterior end of prothorax. X 60. Hypodermis, showing gland cells and attached fibres. > 555. Section through heart. X 135. = « “ALBATROSS” PAcIFIG SOLENOGASTRES. : we B Meisel lith. Boston « 0 ato bi be “ PR pts barr ian pa 2 i Wea. PLATE 26. Figs. 1-7. Chaetoderma argentea. X 33; Fig. 8. Strophomenia regularis. Fig. 9. Alexan- dromenia agassizi. Fig. 1. Through brain region. Fig. 2. Through radula. Fig. 3. Through heart and coelomoducts. Fig. 4. Through suprarectal commissure. Fig. 5. Through region of outlet of coelomoducts. Fig. 6. Through posterior end of prothorax. Vig. 7. Through junction of pharynx and stomach. Fig. 8. Reconstruction of posterior end of Strophomenia regularis. Fig. 9. A portion of the ventral salivary glands and duct in Alexandromenia agassizi. = 7’. = a : —— “ALBATROSS” PACIFIG SOLENOGASTRES Heath del. BMaycel lth Roe? DS. Meisel ith, Boste PLATE 27. Figs. 1,2,4-11. Cross sections of Chaetoderma montereyensis. (X 40.) Fig. 3. C. nanula. Fig. 1. Through brain region. Fig. 2. Through heart and coelomoducts. Fig. 3. Through junction of pharynx and stomach. Fig. 4. Through radula. Fig. 5. Through labio-buccal ganglia and glands entering pharynx. Fig. 6. Through heart and coelomoducts. Fig. 7. Dorso-terminal sense organ. Fig. 8. Through suprarectal commissure. Fig. 9. Through outlet, on left, of coelomoduct. Fig. 10. Through junction of pharynx and stomach. Fig. 11. Through brain and anterior buccal plate of small specimen. PLATE 27, eee B.Meisel lth Boston aS pdigh acs) ah ora PLATE 28. Figs. 1-6, 8,9. Cross sections of Chaetoderma hawaliensis. > 55; Figs. 7, 10-12. Chae'oderma nanula. X 33. Fig. 1. Through brain and buceal plate. Fig. 2. Through radula. Fig. 8. Through junction of pharynx and stomach. Vig. 4. Through suprarectal commissure. Fig. 5. Through heart and coelomoducts. Vig. 6. Through outlet of coclomoduct, on left, and origin of pericardial opening. Vig. 7. Through brain region. Fig. 8. Through posterior end of prothorax. Fig. 9. Longitudinal section of posterior end. Fig. 10. Section through outlet of coelomoduct, on left. Fig. 11. Through radula. Fig. 12. Through suprarectal commissure. HHeath del. Ey AV ma} di B Meisel lith Boston PLATE 29. Figs. 1-5, 8, 12. Cross sections of Chaetoderma erudita. X 33. Figs. 6, 7, 9-11. seabra. XX 20. Fig. 1. Through heart and coelomoducts. Fig. 2. Close to junction of pharynx and stomach. Fig. 3. Posterior end of prothorax. Fig. 4. Through brain. Fig. 5.- Through outlet, on right, of coelomoduct. Fig. 6. Suprarectal commissure. Fig. 7. Through gills and cloacal chamber. Fig. 8. Through radula. Fig. 9. Through junction of pharynx and stomach. Fig. 10. Through heart and coelomoducts. Fig. 11. Through posterior end of prothorax. Fig. 12. Through suprarectal commissure. Chaetoderma “ALBATROSS” PaciFIG SOLENOGASTRES. PLATECS, nes 9090S of. lite Ure sie 24 SEO CAINS Sea S33 ea, B Meisel lith Boston ua Vigs. robusta. Vig. Fig. Fig. lig. Fig. Vig. Fig. Vig. Fig. Fig. Tig. Fig. Vig. PLATE 30. 13) x 33. Chaetoderma scabra. 33. Figs. 2, Vigs. 7-9, 11, 12. Chaetoderma japonica. 1. Through brain region. 2. Through radula. 3. Same. Through radula. 4. Through brain region. 5. Through suprarectal commissure. 6. Through posterior end of prothorax. 7. Though outlet, on left, of coelomoduct. 8. Through heart and coelomoducts. 9. Through suprarectal commissure. 10. Through junction of pharynx and stomach. 11. Through posterior end of prothorax. 12. Through junction of pharynx and stomach. 13. Through outlet, on left, of coelomoduct. 4-6, 10, 13. xX 33. Cross sections of Chaetoderma “ALBATROSS” PAciFIG SOLENOGASTRES. awa Tae PLate30. B Meisel ith. Boston > PLATE 31. Figs. 1-4, 7, 8, 10. Cross sections of Chaetoderma californica. (XX 33.) Figs. 5, 6. Chaeto- derma japonica. XX 33. Fig. 9. Proneomenia hawaiiensis. Fig. 1. Through radula. Fig. 2. Through junction of pharynx and stomach. Fig. 3. Through heart and coelomoducts. Fig. 4. Through brain region. Fig. 5. Through brain of Chaetoderma japonica. Fig. 6. Through radula, same species. Fig. 7. Through outlet of coelomoduct, on left. Fig. 8. Pharynx and glands in front of radula. Fig. 9. External sensory atrial ridge of Proneomenia hawaiiensis; os, ridge resting upon gan- glion cells; om, outer atrial ridge; c, cirrus. Fig. 10. Through suprarectal commissure. “ALBATROSS” PaciFic SOLENOGASTRES. PLATESI. E.Heath del. ———— B Meisel ith Boston PLATE 32. Cuticle and hypodermis from side of head unless otherwise stated. Fig. 1. Hypodermis and its products in Strophomenia spinosa, large specimen. XX 205. Fig. 2. Same in Lophomenia spiralis. > 255. Fig. 3. Same in Strophomenia scandens. X 155. Fig. 4. Same in Halomenia gravida. X 225. Fig. 5. Perforation of the somatic musculature in H. gravida by a diverticulum of the mid gut which comes in contact with a modified hypodermal papilla; s, blood sinus. XX 255. _ Fig. 6. Hypodermis of Drepanomenia vampyrella. X 255. Fig. Same of Ichthyomenia porosa. X 330. Fig. Same of Dondersia californica. X 555. Same of Proneomenia hawailensis; ne, nerve. > 180. 7 8. Fig. 9. Section through the dorsal sense organ of Strophomenia scandens. > 300. 0 1. Same of Lophomenia spiralis; ne, nerve. X 150. “ALBATROSS” PAGIFIG SOLENOGASTRES. HHeath del B Meisel lith. Bosten a) = * . *¥ a . = ( =, e . 2 = Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. CON CONE SoC CO NODE PLATE 33. Cuticle and hypodermis from side of head unless otherwise stated. Strophomenia triangularis. > 200. Strophomenia farcimen. > 300. Proneomenia hawaiiensis. > 300. Dorymenia acuta. X 330. Alexandromenia agassizi. > 200. Proneomenia insularis. x 400. Strophomenia spinosa, dorsal side. 200. Alexandromenia valida. > 260. Strophomenia ophidiana. Xx 200. “ALBATROSS” PACIFIC SOLENOGASTRES. aie — = eae oe Ss z SEE rare aye B Meisel (ith. Boston, PLATE 34. Cross section through radula sae of Lophomenia spiralis. > 57. Longitudinal section through radula and subradular organ of Proneomenia hawaiiensis. Dorsal view of radula of Limifossor talpoideus. > 135. Two rows of teeth of Strophomenia triangularis. X 330. Portion of radula of Alexandromenia agassizi. X 255. Side view of radula of Limifossor talpoideus. X 135. Teeth of Dorymenia acuta (mid line to left). x 330. Teeth of Strophomenia spinosa, large individual. X 555. Same species, small individual. X 330. Same species, small individual. > 330. Side view of teeth of Dorymenia acuta. > 330. Cross section of radula of Halomenia gravida. X 330. Proneomenia hawaiiensis, showing 7 of the 40 teeth of each transverse row; m, mid line. Tooth of Alexandromenia valida. > 200. Portion of radula of Strophomenia farecimen. X 255. “ALBATROSS” PAGIFIG SOLENOGASTRES. PLATE 34. i, af i} Yi, y Mejunt’ } LS. a HHeath del. . B Meisel lith. Boston. eats Fig. 1 Fig. 2. Fig. 3. Fig. 4 Fig. 5. PLATE 35. Limifossor fratula. Section through region of salivary glands. » 28. Same through muscle 17 (fig. 4, pl. 10). Same through posterior end of radula support. X 28. Same in region of heart. Same through opening of digestive gland. Figs. 6, 7, 9. Development of ova in Herpomenia platypoda. In fig. 6 the nuclei of probable follicle cells (fe) are intact; in fig. 7 the membrane has dissolved and the scattered chromosomes are becoming vesicular; in fig. 9 the ovum is almost mature and the vesicles (er) of relatively large size. x 555. Fig . 8. Longitudinal section through region of radula of Chaetoderma erudita, showing sub- radular ganglion, sn. X 135. Fig Fig Fig Fig lig - 10. callie . 12. eles pike Section through brain of Limifossor fratula. 28. Protozoa encysted in wall of digestive tract of Chaetoderma californica. Section through dorso-terminal sense organ of Dondersia californica. 333. Blood corpuscles of Proneomenia hawaiiensis. X 450. Section through Proneomenia insularis. “ALBATROSS” PAGiFIG SOLENOGASTRES. fel Ki of oy iM B Meisel lith, Boston, a a an | = Fig. Fig. Us 2. 3. the spine. Fig. Fig. Fig Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. 17. 18. PLATE 36. Reconstruction of posterior end of Chaetoderma argentea. Same of Chaetoderma attenuata. Advanced stage in spicule development, the matrix cells retaining their attachment to Proneomenia hawaiiensis. X 555. Somewhat earlier stage than fig. 3. > 555. Completion of spicule development and commencement of shifting of matrix cells. > 555. Reconstruction of anterior end of Strophomenia triangularis. Early stage in development of spine in Proneomenia hawaiiensis. > 555. Hypodermis in Limifossor fratula. X 255. Posterior end of Alexandromenia agassizi. X 3. Papilla and outlet of salivary gland in A. agassizi. Very early stage in development of spine in Proneomenia hawaiiensis. X 555. Blood corpuscles of Strophomenia scandens. > 450. Same of Chaetoderma hawaiiensis. X 450. Same of Lophomenia spiralis. XX 450. Spines of Strophomenia triangularis. 150. Same of Strophomenia spinosa. X 205. Same of Strophomenia ophidiana. > 205. Completed development of radially directed spine of Proneomenia hawaiiensis; and developing papilla. > 555. Fig. 19. Base of gill plates and attached gland cells (gc), Alexandromenia agassizi; ne, nerve. “ALBATROSS” PAcIEIG SOLENOGASTRES ' PLATE 36, DN AN \ Ye B Meisel lith. Boston Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. ee BPODONDNRPA PWN _ ~) b Ot ell eel aed Oo ed _ ~ i > wa ~] S t PLATE 37. Spicules of Ichthyomenia porosa. X 480. Of Chaetoderma montereyensis, small specimen. X 80. Of Chaetoderma montereyensis, large specimen. X 80. Of Chaetoderma robusta. X 80. Of Proneomenia hawaiiensis. a X 330; b X 130. Of Chaetoderma argentea. X 135. Of Drepanomenia vampyrella. X 135. Of Chaetoderma attenuata. X 135. Of Alexandromenia agassizi. XX 335. Of Dorymenia acuta. X 135. Alexandromenia valida. X 180. Of Chaetoderma hawaiiensis. X 255. Of Lophomenia spiralis. X 335. Of Chaetoderma californica. X 135. Of Chaetoderma erudita. X 135. Of Proneomenia insularis. X 135. Strophomenia scandens. X 300. Of Chaetoderma nanula. X 135. Of Chaetoderma scabra. X 100. Of Chaetoderma sp.? Unidentified fragment, Alaska. a Cr. Teer = 4 : “ALBATROSS” PACIFIG SOLENOGASTRES. ay PLATE 38. Fig. 1. Reconstruction of anterior end of Driomenia pacifica. Fig. 2. Same, posterior end. Fig. 3. Entire animal enveloped in small portion of hydroid colony, Sertularella sp. Figs. 4, 5, 6, 8. Sections along lines A, C, B, D, in fig. 1. 50. Figs. 7,9. Along lines E, F, of fig. 2. X 50. Fig. 10. Section of hypodermis and cuticle. X 260. Fig. 11. Same of Pachymenia abyssorum. X 60. x 5. “ALBATROSS” PACIFIG SOLENOGASTRES. PLATE 38. HHeath del.” 7 ‘eee te ‘op te eo 2 ee ee “aif ' t a _ PS ae od ee te 4 cael = ; , ee ae Es ary woe @ Ns ? NOarPwwr 8. PLATE 39. Reconstruction of anterior end of Pachymenia abyssorum. Same, posterior end. Foot, same species, in middle of body. Pachymenia abyssorum. X 3. Spines of Driomenia pacifica. Section of Driomenia pacifica along line G, fig. 2, pl. 38. Sections of Pachymenia abyssorum along lines B, D, fig.1. 25. x 50. .., RAMEN Nae = GAR ane Hieeth del. B Meisel lith, Boston PLATE 40. gs. 1-4, 6-10. Cross sections of Pachymenia abyssorum. Fig. 5, Driomenia pacifica. Figs. 1, 2, 4, 7, along lines E, F, G, H, posteriorend. X 25. Figs. 3, 6. Sections along lines A, C, anterior end. Fig. 5. Section of Driomenia along line H, fig. 2, pl. 38. Fig. 8. Spines of Pachymenia abyssorum. X 140. Fig. 9. Section about the posterior end of gonad. Fig. 10. Section through body behind pharynx. “ALBATROSS PACIFIG SOLENOGASTRES. HHeath del. B Meisel lit. Boston Memoirs of the Museum of Comparative Zodlogy AT HARVARD COLLEGE. Vou. XLV. No. 2. SOLENOGASTRES FROM THE EASTERN COAST OF NORTH AMERICA. By HAROLD HEATH. WITH FOURTEEN PLATES. {Published by Permission of E. Lester Jones, Superintendent U. S. Coast and Geodetic Survey and of H. M. Smira, U. S. Commissioner of Fish and Fisheries]. CAMBRIDGE, U.S. A.: Printed for the Museum. OctospeEr, 1918. il * retina TABLE OF CONTENTS. INTRODUCTION . CLASSIFICATION . APLACOPHORA Chaetodermatidae Chaetoderma . Neomeniidae . Neomenia Proneomeniidae . Proneomenia Dorymenia . Strophomenia . Dondersiidae . INTerstrassiay 2-913 to sues DESCRIPTION OF SPECIES | Chaetoderma nitidulum Pace. 187 189 189 189 190 191 191 191 191 192 192 192 193 193 193 Chaetoderma caudatum . C. vadorum C. lucidum C. bacillum C. squamosum Neomenia verrilli Proneomenia acuminata . Dorymenia peroneopsis Strophomenia agassizi . Nierstrassia fragile . EMBRYOLOGY GENERAL CONSIDERATIONS . BIBLIOGRAPHY tee EXPLANATION OF PLATES Pace. 193 195 198 201 204. 206 215 222 229 235 240 251 261 263 SOLENOGASTRES FROM THE EASTERN COAST OF NORTH AMERICA. INTRODUCTION. The present report deals with a collection of upwards of one hundred and twenty-five Solenogastres dredged at various times by Coast Survey or U. S. Fish Commission vessels along the eastern coast of the United States. The greater number of these were placed at my disposal by the late Mr. Alexander Agassiz, who generously granted permission to include the descrip- tions of additional species based upon material kindly forwarded by: Prof. A. E. Verrill and by the officials of the National Museum. The territory embraced by these explorations, with the exception of a single station off the south coast of Florida, another in the Gulf of St. Lawrence and a third off the coast of Newfoundland, extends from the Gulf of Maine on the north to the mouth of Chesapeake Bay on the south. The larger num- ber of dredge hauls were made along shore in comparatively shallow water; thirty-four were at depths ranging from one hundred to five hundred fathoms, three were from five hundred to one thousand fathoms, two from one thousand to fifteen hundred fathoms and one from seventeen hundred and fifty-three fathoms. The appended table indicates the habitat with greater exactness. The following abbreviations have been employed to indicate the vessels engaged : A Albatross, B Bache, Be Blake, Bt Bluelight, Fk Fishhawk, Sp Speedwell. Number Depth _ 3 2 x Locality Species Station of in Specimens | Fathoms Het Ne Hess. Wie | Chaetoderma bacillum 2076A 3 906 41 13 — 66 — 50 200m. E. of Cape Cod. i Ky caudatum 2588A 8 479 39 02 — 72 36 — 240m. E. of Cape May. « lucidum 2212A 15 428 39 59 30 70 30 45 240m.N.E.of Cape May. 8 ss! 2588A 15 479 39 02 — 72 36 — 240m.E. of Cape May. 188 INTRODUCTION. Number Depth Species Station , of in Lat. N: Taneawe Specimens} Fathoms Chaetoderma nitidulum | 2458A 89 | 46 48 30 52 34 — S. E. of Newfoundland. “ “ 20B 95 | 43 01 — 7010 — NearBoonls. Light, Me. “ a 31B 56 | 42 19 — 70 29 — Massachusetts Bay. ee S 38-43B 27-68 | 42 57 — 70 35 — Gulf of Maine. “ “ 62-65B 42-58 | 43 38 — 69 22 — Gulf of Maine. “« ss 69B 32 | 43 11 — 69 35 — OffS. coast of Maine. (: bs 892Fk. 36 | 40 33 — 70 45 — Off Martha’s Vineyard. “ « 895Fk. 238 | 39 56 30 70 59 45 Off Martha’s Vineyard. u . 898Fk. 50 300 | 37 24 — 74 17 — Chesapeake Bay, Mass. Cs i 943Fk, 157 | 40 — — 71 14 30 Off Martha’s Vineyard. « us 18Sp. _ 45 | 42 29 — 70 38 — Near Salem, Mass. « e 293Sp. 27 | 42 03 — 7019 — Cape Cod Bay, Mass. “ & 2968p. 26 | 42 02 — 70 26 — Cape Cod Bay, Mass. & Os 3015p. 27 | 42 01 — 70 20 — Cape Cod Bay, Mass. iB s 3175p. 25 | 42 02 — 70 14 — Cape Cod Bay, Mass. ~ “ 322Sp. 67 | 42 12 — 7001 — Off Cape Cod, Mass. eo ‘ 3508p. 31 | 42 08 — 70 25 — Massachusetts Bay. & squamosum | 2534A 1 1234 | 40 01 — 67 29 15 200m.8.E. of Cape Cod. vadorum = 5 — |——— —-—— Casco Bay, Me. S fs 3B 1 64 | 43 38 — 69 17 — OffS. coast of Maine. « 20B 1 95 | 43 10 — 7010 — NearBoonls. Light, Me. & fe 3178p. 1 25 | 42 02 — 70 14 — Cape Cod Bay, Mass. Neomenia verrilli — 1 313 | — — — ——— Gulf of St. Lawrence. Proneomenia acuminata 5Be at 150-229 | 24 15 — 82 13 — Straits of Florida. a « 893Fk. 1 372 | 39 52 20 70 58 — S.of Martha’s Vineyard. cd 25474 1 390 | 39 54 30 70 20 — S. of Rhode Island. Dorymenia peroneopsis 2715A 1 1753 | 38 29 30 70 54 30 S.of Martha’s Vineyard. Strophomenia agassizi 2046A 5 407 | 40 02 49 68 49 — S.E.of Nantucket, Mass. co « 2528A 4 677 | 41 47 — 65 37 30 E. of Cape Cod, Mass. Nierstrassia fragile 2588A ll 479 | 39 02 — 72 36 — Off coast of New Jersey. Up to the present time very few Solenogastres have been collected along the Atlantic coast of North America. Chaetoderma canadense Nierstr. has been taken off Port Hood, Canada, Neomenia carinata Wiren came from the North Atlantic, and Neomenia microsolen Koren & Danielson is recorded from the West Indies; but none of these species is represented in the present collection, and accordingly nothing further can be said regarding their geographical range. The discovery of Chaetoderma nitidulum off the New England coast indicates that this species is relatively abundant throughout the North Atlantic Ocean north of the fortieth parallel. Proneomenia acuminata was originally described from specimens collected in the West Indies. The material in hand extends its distribution along the Florida coast and the Atlante seaboard as far north as Rhode Island. Other species in the present collection are new, and thus far their known range is very limited, CLASSIFICATION. 189 CLASSIFICATION. Judging from the material already described, it is evident that not only is the genus Chaetoderma very widely distributed, but the individual species are difficult to differentiate, especially where we are compelled to rely solely upon descriptions and figures. Externally and internally there is considerable variation within a given species, and suitable diagnostic characters are difficult to discover. The relations of the gut to the somatic musculature and the ventral blood sinus at the junction of the pro- and metathorax are of considerable value in the specimens I have thus far examined, and with figures of this region and others of characteristic sections it is believed that it will be possible, without great difficulty, to recognize the species described in this and the earlier Pacific Ocean report. The validity of the genus Dorymenia Heath has been questioned by certain investigators, but the discovery of a second species, with all of the character- istic features of the first (Dorymenia acuta), indicates that the genus was well founded. Order ApLacopHora v. lhering. Suborder I. Chaetodermatina Simroth. Spiculose integument continuous all around the body. Chaetodermatidae, p. 189. Suborder II. Neomeniina Simroth. Spiculose integument interrupted beneath by a longitudinal ven- tral furrow. Neomeniidae, p. 191. Proneomeniidae, p. 191. Dondersiidae, p. 192. CHAETODERMATIDAE Simroru. Opening of mouth and anal chamber terminal. Body with more or less sharply marked regions. Ventral furrow and fold lacking. Two highly devel- oped plume-like gills. Radula distichous, polyserial or strongly reduced to a large unpaired cuticular tooth. The mid-gut possesses, in most cases, a well- 190 CHAETODERMA. developed digestive gland. Copulatory apparatus lacking. Coelomoducts remain separate. Cuticle thin, spicules flat, often needle-form, but solid. Inhabit bottom oo ze. CHAETODERMA Loven, 1845. Body vermiform, without ventral groove; mouth and anal chamber ter- minal. Two gills. Sexes separate. Radula reduced to conical peg. Type of genus C. nitidulum Loven. Head, cylindrical or pear-shaped, bounded posteriorly by a circular groove. Spines with keel absent or but slightly developed. North Atlantic (p. 193). C. caudatum, sp. nov. ’ Length from 3.3 mm. to 7.75 by 1.3 mm. greatest diameter. Greatest thickness of body in preabdomen; the postabdominal region narrows abruptly to a tail-like appendage. Northeast coast of the United States at a depth of 428-499 fathoms. (p. 193). C. vadorum, sp. nov. Length 12.5 mm. by 1.1 thickness of preabdomen to 15.2 by 1.45 mm. Spines strongly keeled and at junction of metathorax and abdomen measure from 0.1 to 0.14 mm. in length. Mouth occupies a cleft in the buccal plate. Off coast of Maine at a depth of 25-95 fathoms. (p. 195). C. lucidum, sp. nov. Body size variable, ranging from 1.2 mm. width by 11.25 length to 0.75 mm. width by 25 mm. length. Spines with keel slight or undeveloped, with average length on preabdomen of 0.12 mm. Mouth occupies a cleft in the buccal plate. Off coast of New Jersey at 428-479 fathoms depth. (p. 198). C. bacillum, sp. nov. Length 11-17 mm. length by 0.9-1.07 mm. greatest diameter. Spines moderately keeled with a length of 0.11-0.16 mm. at the junction of the pro- and metathorax. Mouth perforates the buccal plate. Off the Massachusetts coast at a depth of 900 fathoms. (p. 201). C. squamosum, sp. nov. Length 25.7 mm. length by 1.3 mm. greatest thickness. Mouth pierces the buccal plate. Spines unusually thin, weakly keeled. Off Massachusetts at 1,234 fathoms depth. (p. 204). PRONEOMENTA. 191 NEOMENIIDAE Simrornu. Body compressed, more or less crescent-shaped, without distinct divisions. Index 7 at most. Opening of atrium ventral, of the anal chamber ventral or terminal. Ventral furrow present, usually with several folds. Cuticle some- times comparatively thick, spines mostly needle-like, flat, grooved or hollow. A circlet of gills in the anal chamber. Radula and salivary glands usually lacking. Epidermal papillae, of simple structure, usually present. Fore gut protrusible, coelomoducts separate or united to form a shell gland or copulatory organ. Digestive gland lacking. Penial spines usual present. Free, creeping about over bottom. NEOMENIA Tutwpera, 1875. Body thick-set and usually compressed laterally, 2-3 em. long, with anterior and posterior ends similarly shaped. Cloacal opening subterminal. Ventral fold present with the groove extending to the cloacal chamber. Spic- ules needle- or spearhead-shaped, projecting from the cuticle. Broad stalked papillae present. Branchial folds in the cloacal chamber. Copulatory spines usually present. Radula absent. Type of genus, N. carinata. N. verrilli, sp. nov. Body thick-set, unkeeled, 25 mm. in length by 8 mm. greatest thickness. 8 ventral folds, 30-40 branchial folds. Accessory copulatory apparatus present. Gulf of St. Lawrence, 313 fathoms. (p. 206). PRONEOMENIIDAE Simrorna. Worm-like. Radula distichous or polystichous, sometimes lacking. Sali- vary glands tubular, lobed or lacking. Cuticle thick, spicules mostly needle- like in several layers. Epidermal papillae present. Gills usually lacking. Coelomoducts usually united into a shell gland, sometimes separated. Copu- latory spicules may be present. Free living, partly or entirely parasitic. PRONEOMENIA Huvsrecurt, 1880. Body elongated, vermiform, the length 9-50 times the diameter. Cloacal opening ventral. Foot present, the groove passing into the cloacal chamber. Cuticle thick with crowded spicules in several layers. No gills. Radula 192 DONDERSIIDAE. multidentate. Two salivary glands. Copulatory spines present or absent. Type of genus, P. sluitert. P. acuminata WIReEN. Length index 9.3. Radula present. (p. 215). DORYMENIA Hearn, 1911. Vermiform, body terminating posteriorly in a finger-shaped elongation. Radula multidentate with 9-51 longitudinal rows of from 9-22 teeth in each transverse row. One pair of seminal receptacles. A pair of long copulatory spicules closely associated with a pair of globular coeca or deep pits likewise opening separately into the cloacal chamber. Type of genus, D. acuta. D. peroneopsis, sp. nov. Body 25 mm. in length by 2 mm. in greatest thickness. Radula with 9 longitudinal rows of teeth and 22 teeth in each transverse row. Accessory copulatory apparatus present. Off the Massachusetts coast at a depth of 1,753 fms. (p. 222). STROPHOMENIA Provor, 1899. Body elongated, cylindrical, the thick cuticle penetrated by acicular spic- ules and closely crowded vesicular papillae. Radula and salivary ducts present. Two distinct genital openings into the cloacal chamber usually present. Type of genus, S. lacazev. S. agassizi, sp. nov. Worm-like, 22-37 mm. in length by 1.1-1.5 mm. average diameter. Papillae stalked, numerous; spicules needle-like. Radula very small. Ventral salivary glands tubular. Nine pairs of seminal receptacles. Off Massachusetts coast, 677 fms. (p. 229). DONDERSIIDAE Simroru. Body often worm-like; cuticle thin; spines flat and solid. Papillae lacking. Radula distichous, monoserial or lacking. Salivary glands globular, sac- or tube-like. Gill folds lacking. Coelomoducts united or separate. Copulatory apparatus may be present. Ventral fold and furrow may be absent. Liv- ing free upon corals, ete. CHAETODERMA CAUDATUM. 193 NIERSTRASSIA, gen. nov. Body short, 2.5-5 mm. in length by 0.75-1 mm. thick. Single layer of leaf-like keeled spines as in Chaetoderma; no papillae. Epithelium of atrium (?) composed of long, slender cells without cirri and ciliated ridges. Radula dis- tichous, 15 transverse rows. Dorsal salivary glands diffuse, ventral small, lobulated. Coelomoducts with three pairs of diverticula, two bundles of copu- latory spines (5 in each bundle) opening into terminal part of shell gland. Repro- ductive opening on large papilla. Posterior walls of cloaca with 5-6 glandular folds. Type of genus JN. fragile, sp. nov. with characters of the genus. Off New Jersey coast, 479 fms. (p. 235). DESCRIPTION OF SPECIES. Chaetoderma nitidulum Loven. This species is represented by over fifty specimens dredged from various comparatively shallow water stations between Newfoundland on the north to Virginia on the south. Whether this last named locality represents the southernmost limit of distribution it is impossible to state as the work of explora- tion south of 37° north latitude is largely confined to deep water. In the present case the bathymetrical distribution ranges from 25 to 300 fathoms; elsewhere it is reported to range from 25 to 2,250 meters. Specimens in the present collec- tion have been taken at the stations noted on page 183. A careful comparison of these western Atlantic specimens with the descrip- tions given by various authors and with a single individual from the Kara Sea discloses no essential differences. One of the Atlantic specimens is unique in being monocious. Throughout its entire extent the gonad is distended with vast numbers of spermatozoa, mature and in various stages of development. The ova are also in different stages of growth, and roughly speaking are developed on the surface of an inconspicuous septum separating the halves of the ovo- testis, while the sperms arise from more lateral positions. Chaetoderma caudatum, sp. nov. Eight specimens of this species were dredged off the coast of New Jersey (Sta. 2588A) in 479 fathoms of water where the bottom consisted of green mud. In every case the posterior end of the body rapidly narrows in the vicinity of the cloaca to form a tail-like appendage of approximately even calibre through- 194 CHAETODERMA CAUDATUM. out. The largest specimen (Plate 9, fig. 1), measures 7.75 mm. in length by 1.3 in greatest diameter, while the smallest is 3.3 by .75 mm. In several indi- viduals the anterior end of the prothorax is considerably swollen, giving the entire body a decided trumpet-shape. The color, especially of the older individuals, is a slaty gray in the meso- thorax and the posterior part of the prothorax, owing to the dark colored liver showing through the translucent body wall. The postabdomen is of the usual light yellow tint save the posterior half or third which is very dark brown owing to an incrustation consisting apparently of faecal matter or substances from the coelomoducts. A dark brown or black band encircles the prothorax and this peculiarity together with the shape of the body readily distinguishes the species. The dorsal sense organ, in the form of a deep groove, holds the customary position at the posterior end of the body, but owing to the overarching spines it is in large measure invisible in whole specimens. In sections it is seen to be composed of slender cells whose general arrangement and appearance are typical of the genus. The mouth opens through the centre of the buccal plate whose general appearance is represented (Plate 9, fig. 4). Between this point and the anterior border of the brain the buccal tube is of moderate size, is folded to form four or five longitudinal ridges, and supports a considerable number of gland cells attached to its outer surface. These last named organs, grouped into lobules (Plate 8, fig. 7), whose general size and shape depend upon the spaces between the longitudinal and radial muscles of the buccal tube, are composed of small cells containing after treatment with Delafield’s haematoxylin an abundance of some golden yellow, finely granular secretion. The subradular organ is moderately distinct and the tooth (Plate 9, fig. 5) of average size. Behind the radula the canal rapidly narrows, becomes thick walled and the component cells, slender in form, are filled with a dense, finely granular secretion. This condition of affairs continues to the opening borne on the summit of a short papilla (Plate 8, fig. 10) projecting into the gastric cavity. The stomach is a capacious sac, with highly folded walls especially in the neighborhood of the oesophageal opening where the cells are packed with a finely granular, yellowish secretion. In the vicinity of the bile duct the walls are much thinner, nearly smooth and the epithelial cells are approximately cubical and contain but a small quantity of secretory products. The liver presents in general the usual appearance, possessing yellowish brown Ké6rnerzellen and moderately staining Keulenzellen. The intestine, CHAETODERMA VADORUM. 195 with walls of the usual character, pursues its course to the end of the preabdomen where it becomes unusually narrow and contorted before opening in the cus- tomary fashion into the cloacal chamber. Food products, among them rela- tively long and slender tubular fragments of some unknown organism, are present in considerable quantities in the stomach and the proximal part of the hepato-pancreas and in a more or less digested condition throughout the intes- tine. So far as could be determined the circulatory system is typical of the genus. As noted in connection with the reproductive system the aorta at its origin is unusually heavy walled and of large calibre. In the region of the gonad its walls become thinner yet distinct so that they may be traced readily to the neighborhood of the radula where it disappears as a distinct vessel. The nervous system is very distinct and has been examined with more than usual care, but in all essential respects it is practically the same as in C. attenuata for example. The single specimen sectioned is a female with the sex gland, filled with ova in all stages of development, holding the customary position. At the junction of the preabdomen with the tail-like postabdomen the ovary rapidly narrows to form the paired canals leading into the pericardium. These, however, are of unusual extent, traversing almost the entire extent of the postabdomen, and are separated from each other by the large dorsal aorta (Plate 8, fig. 11) whose walls in this region are relatively heavy. In the neighborhood of the peri- cardial cavity they become somewhat enlarged but otherwise they exhibit no unusual features. The pericardium is of moderate size and the coelomoducts open in the usual position (Plate 9, fig. 6) by very distinct, ciliated funnels connected with a short non-glandular section directed anteriorly. At the level of the dorsal commissure they unite with the glandular portion which though it is of large size relatively, lacks the sacculations and tortuous course characteristic of larger species and passes directly backward to open at the usual point in the cloacal chamber. The cells lining this main division of the canals are com- posed of highly vacuolated protoplasm frequently in the process of liberating its products by means of constriction of the distal end of each cell. Chaetoderma vadorum, sp. nov. One specimen (Plate 13, fig. 1) of this species was taken off the south coast of Maine (Sta. 3B) at a depth of 64 fms., another from the same general locality 196 CHAETODERMA VADORUM. (Sta. 20B) was dredged at a depth of 95 fms., and a third came from Cape Cod Bay, Mass. (Sta. 317 sp.) at a depth of 25 fms. Two additional specimens, of approximately the same size, bear the label ‘‘Casco Bay, Maine, U. 8. Fish Com., Aug. 5th. 1873.’ No other data are forthcoming but it may be assumed that they are shallow water forms. The length of the largest (sectioned) speci- men was 15.2 mm. with a diameter through the abdomen (Wiren) of 1.45 mm.; the smaller specimen is 12.5 mm. long by 1.1 in diameter. The color is light brownish yellow though this may be due to long preservation or to tannin from the cork. The buccal plate (Plate 13, fig. 2) is somewhat distorted, but appears to be elliptical in outline or broadly shield-shaped with the mouth occupying a deep indentation in the dorsal two thirds. The spines examined were taken from the neighborhood of the union of the metathorax and abdomen, and range in length from 0.1 to 0.14 mm. They present the usual spearhead appearance (Plate 12, fig. 3), and are strongly keeled throughout nearly their entire length. The cells composing the hypodermal layer (Plate 13, fig. 8) comprise two distinct types, the matrix cells of the spic- ules, and those probably responsible for the development of the cuticle. The first exist in the form of flattened disc-like bodies attached to the basal portion of the spine, and indicate that in this genus every spicule is the product of a single cell. The cells of the second class possess spherical nuclei, and a columnar form though as a general rule they are without clearly defined boundaries. In the region of the union of the pro- and metathorax especially the hypo- dermal layer is seen to rest upon a felt-work of connective-tissue fibres, forming a species of basement membrane that stains intensely in haematoxylin. A short distance removed from this region the meshwork becomes less compact and less darkly staining. Under fairly high magnification fibres may be seen to traverse the underlying somatic muscles and to enter the basement mem- brane whose elements they resemble closely; but in no case have they been seen to extend into the hypodermal layer, and it may be added the material appears to be excellently preserved. As usual the buccal plate is composed of a heavy cuticular layer (Plate 13, fig. 4) resting upon the hypodermis in which the cell elements are very indefi- nitely defined. About the margins of the plate the cells possess fairly distinct nuclei and cell boundaries, but in the more central regions bordering the mouth they become distorted, owing apparently to numerous nerve and muscle fibres that either attach to or pass between them to the cuticular plate. Darkly staining ductules open to the exterior close to the margins of the plate, and for the first time in my experience have been traced to definite cells. CHAETODERMA VADORUM. 197 In sections these are seen to occupy a position adjacent to the buccal tube, and along the path traversed by the nerves destined to the buccal plate and originating in the great precerebral nerve masses (buccal ganglia of Wiren). In several other species of the genus ductules lead to cells in the same general position, but the lack of a clearly defined secretion in these cells and owing to their resemblance to ganglion cells it has never been possible heretofore to make the identification certain. In the light of the state of affairs in the present case it is altogether probable that gland cells are normally present and in the position described above. These gland cells are usually arranged in the form of lobules, though sepa- rate cells are occasionally met with in the neighborhood of the buceal plate. Each, in a fully developed condition contains numbers of darkly staining gran- ules, though not in sufficient numbers to mask the nucleus. This last named body occupies a central position, and contains a well-defined though faintly staining nucleolus. In a few instances the ductules perforate the margins of the buccal plate; more generally they pass to the exterior without the borders of the plate but in close proximity to it. As noted previously the mouth occupies a cleft in the buccal plate, and sections show that it leads into a canal of average dimensions and with typical relations. Generally speaking the epithelial lining rests upon a circular muscle layer, but as this is pierced by numerous radial or diagonal fibres the line of de- marcation is by no means sharp, a state of affairs that is accentuated by the presence of several glands. These last named organs (Plate 12, fig. 2), in the form of lobules, encircle the tube and are in all stages of glandular activity. Those in an inactive state bear a fairly close resemblance to the neighboring ganglion cells, but in a fully developed condition they become distended with a vacuolated, moderately staining secretion that escapes into the buccal tube or pharynx by intercellular canals, though these are usually difficult to demonstrate. The radula of this genus, together with its supports and muscles, is a remarkably constant structure, and this species is no exception to the rule (Plate 12, fig. 1), there being no marked characteristics of diagnostic value. Immediately posterior to the radula the digestive tract narrows rapidly, and becomes elliptical in outline (Plate 12, figs. 9, 12). The cells of the lining are greatly elongated and glandular, the secretion appearing as a finely granular, moderately staining mass that may in rare instances become so abundant and closely packed that it appears to be homogeneous. This state of affairs rapidly changes as the canal is followed backward. The cells become lower, and in most instances have been dislodged, evidently due to the decreased pressure attendant upon coming to the surface. Where they have remained they are 198 CHAETODERMA LUCIDUM. likewise glandular, and continue in this condition for a considerable distance beyond the union of the pro- and metathorax (Plate 12, fig. 14) where the ali- mentary canal attains a greater diameter (Plate 12, fig. 5). Sections were not made of the mid region of the body. Posteriorly the intestine pursues the usual course and opens in typical fashion into the cloacal chamber. The cloacal cavity, so far as shape and relations are concerned, is not unusual, but its epithelial lining, especially near the posterior end of the ani- mal, is highly glandular, the cells staining intensely in haematoxylin. Gland cells with similar staining reaction occur in the branchiae, and are limited to very definite zones (Plate 12, fig. 13). A comparatively small number occur in the external epithelial layer immediately dorsal to the dorsal branchial sinus, and a much larger proportion is imbedded in the lamellae, forming in sections a horizontal band passing through the dorsal limit of the ventral gill retractors. The circulatory system presents no unusual features. The sinus returning the blood from the branchiae to the heart is unusually large and clearly defined and the pericardial chamber (Plate 12, fig. 15) is more spacious than common, but otherwise the heart, aorta, and sinuses are fashioned upon the usual plan. The coelomoducts open into the pericardial cavity beside the posterior dorsal commissure by means of well-defined, ciliated mouths, and from this point extend anteriorly, rapidly losing the ciliated coat and assuming the char- acteristic vacuolated appearance, until they have traversed on half of the length of the main or ventral portion of the organ with which they unite. This main division presents no especially noteworthy peculiarities. The lining epithelium is composed of very clearly defined cells with basal nucleus, and in living material the distal two thirds was evidently filled with some non-staining material that in sections has escaped leaving only the ruptured cell membrane. The openings into the cloaca (Plate 12, fig. 13) are normally placed and are not surrounded by the high columnar cells encountered in several species of this genus. The nervous system, in its broader details at least, conforms closely to the usual type, and therefore calls for no description beyond that afforded by the figures. Chaetoderma lucidum, sp. nov. Fifteen specimens of this species, the majority of them mutilated, were dredged approximately one hundred and forty miles to the eastward of Cape May, New Jersey (Sta. 2588A) at a depth of 479 fathoms. Fully as many more were taken on another occasion slightly to the northeast of this point (Sta. 2212A) at a depth of 428 fathoms, but unfortunately all from this last named locality CHAETODERMA LUCIDUM. 199 had dried prior to coming into my possession and are useless for the study of the internal anatomy. The smaller specimens from both stations agree in being relatively slender, and the larger specimens may retain this character- istic or become relatively thick-set (Plate 9, fig. 12). The longest specimen measures 25 mm. in length by 0.75 mm. in greatest diameter, while the individual with the greatest diameter, 1.2 mm., is 11.25 mm. long. The color of the specimens from the two stations is strikingly differ- ent, though I am of the opinion that this is due to methods of preservation and not to habitat. What appears to be the normal shade in a preserved state is a glistening light yellowish white somewhat darkened by the slaty gray liver shining through the translucent body walls. A reddish yellow or reddish brown incrustation, usually shading into dark brown in the larger individuals, gathers on the spines about the cloacal opening. Bordering on the union of the pro- and metathorax the spines are in the form of very thin flattened scales without any well-defined keel (Plate 9, fig. 15). In length they range from 0.094 to 0.13 mm., while the width, even in spines of the same length, varies as much as 30 per cent. The hypodermal layer presents no peculiarities whatever save that the giant cells of Wiren are more abundant than is usual in the region of the pro- and metathorax where the hypodermis shows to the best advantage. In these cells the nucleus is usually basally placed while the cell body contains little save a finely granular coagulum adhering to the cell wall. As the spines in this species have no clearly defined matrix cells in this species the possibility presents itself that these larger hypodermal elements may play a part, but there is nothing to prove conclusively that such is the case. On the other hand they may correspond to the gland cells occurring in Chaetoderma attenuata, but the absence of attached fibres penetrating the somatic muscles renders the identification uncertain. The remaining hypodermal elements are generally cubical in form though the cell boundaries, unlike the sharply defined spheri- cal nuclei, are very indistinct. The buccal plate is broadly shield-shaped with the mouth occupying a deep cleft in the upper two thirds (Plate 10, fig. 11). In sections it is bounded as usual by a heavy cuticular plate (Plate 10, fig. 2) resting upon a modified hypodermal layer in which the cells appear with marked clearness though without any especial peculiarities. In a number of different species of this genus there is a muscle bundle, probably acting as a sphincter oris and appear- ing clearly in cross sections, and in the present species it is situated immedi- ately internal to a well-defined sensory area that likewise encircles the mouth. 200 CHAETODERMA LUCIDUM. The sense cells are exceedingly long and slender with spindle-shaped nuclei, and internally may be followed into the vicinity of the great nerve bundles passing from the brain into the region of the buccal sensory plate. Gland cells, attached to the great ganglionic masses applied to the brain or scattered irregularly anterior to the mouth opening, communicate with clearly defined ductules leading to the margins of the buccal plate. Even in moderately stained (Delafield’s haematoxylin) material these cells are almost black while the ductules are purple. The mouth, whose position has been described in a foregoing paragraph, communicates with a canal of moderate size in which the elements, muscular and epithelial, present the customary appearance. Buccal or pharyngeal glands are present in an unusually restricted area. On each side of the mid line a very short distance posterior to the brain they appear as a single lobule (Plate 9, fig. 13) or as two or three closely appressed lobules in which the cells are unusually compact owing to an abundance of a finely granular, moderately staining secretion. A median ventral ridge immediately anterior to the radula probably repre- sents the subradular organ of other species. The cells are not so distinctly columnar as in Chaetoderma attenuata for example, and consequently are not sharply differentiated from the adjoining cells. Nevertheless the absence of folds in the ridge and the fact that it rests upon a typical ganglion with con- nectives marks it as a definite sense organ. In several species where the subradular organ and the related nerve supply have been well preserved a lobule of gland cells attaches to the ventral side of the digestive tract on each side of the subradular ganglion. This happens - so invariably that it furnishes some evidence for the belief that these organs correspond to the ventral salivary glands in the neomenians, while the scattered yet compact glands attached to the dorsal or even lateral surface represent the dorsal salivary glands. There is at present no more cogent reason than their position for such an opinion, but their constancy indicates that they are structures of long standing. The radula and its supports and musculature are relatively heavy (Plate 10, fig. 1) but otherwise typical. Posterior to the radula the alimentary canal narrows rapidly and unites with a highly enlarged section with very thin walls. The outer or proximal boundaries of the lining cells are clearly defined, but the presence of large quan- tities of a granular secretion in the neighboring lumen suggests that in the act of bringing the animal to the surface or owing to the method of fixation the CHAETODERMA BACILLUM. 201 distal, glandular products of the cells have become dislodged. Passing through the union of the pro- and metathorax (Plate 9, fig. 18) the epithelial lining becomes thicker. In the anterior end of the metathorax it again grows thin (Plate 9, fig. 16) save in the immediate neighborhood of the dorsal aorta, and where folds appear, especially on the ventral side, the cement substance between the cells assumes the form of minute granules (Plate 10, fig. 7). Intercellular bridges may exist, judging from certain cells, but the state of preservation of the material renders this uncertain. The liver, gonad, and intestine arise at practically the same level in the posterior end of the metathorax (Plate 10, fig. 4), and are of typical structure and arrangement. The latter statement is likewise true of the entire intestine and of its outlet into the cloacal chamber. A careful examination has been made of the nervous and circulatory sys- tems, but the results do not call for a description beyond that afforded by the figures. The single specimen sectioned was a male with mature sex products in the gland itself and to a slight extent in the pericardial cavity. The cloacal chamber may likewise be passed with a few words only. Gen- erally speaking the epithelial lining is composed of low cubical cells that become somewhat more elongated in the neighborhood of the external openings of the coelomoducts. There are, however, no extended patches of columnar epi- thelium in this region such as occur in Chaetoderma nitidulum for example. Each branchia is provided with 11-12 plates so far as can be determined from cross sections. The coelomoducts communicate with the pericardial chamber by clearly defined ciliated openings in the customary position beside the strong dorsal commissure. Extending anteriorly each canal rapidly loses its ciliated coat, assumes the characteristic glandular appearance and extends anteriorly about one third the entire length of the ventral section with which it then unites. The ventral division is provided with comparatively simple walls, the greatest outpouching occurring at the level of the pericardial openings. The external pores (Plate 10, fig. 3) are located in the usual position in the cloacal cavity. Chaetoderma bacillum, sp. nov. Three specimens (one mutilated) of this species were dredged in 906 fath- oms in the neighborhood of 200 miles southeast of Cape Cod, Massachusetts (Sta. 2076A). All were silvery gray in color with a slight tinge of buff due to the underlying somatic musculature, and are further characterized by a bright 202 CHAETODERMA BACILLUM. brick-red incrustation restricted to the spines surrounding the cloacal opening. The two perfect individuals measure 11 mm. and 17 mm. respectively in length by 0.9 mm. and 1.07 mm. in greatest diameter; the mutilated specimen was approximately 13 mm. in length by 1.2 mm. greatest diameter. = The spines are of the customary spearhead-type (Plate 11, fig. 4), with moderate keels, and in the immediate neighborhood of the junction of the pro- and metathorax range from 0.11 mm. to 0.16 mm. in length. In this same region, at least, the hypodermal layer is clearly one cell thick, and gener- ally speaking is composed of cells with clearly defined nuclei but invisible cell boundaries (Plate 10, fig. 13). Among these are nuclei of the same general appearance, but of twice the bulk, that are in contact with, and appear to belong to, spherical or spheroid cavities containing in a preserved state a very small quantity of a finely granular coagulum. What these spaces are it is impossible to state definitely. They may contain calcareous salts in life or, as in several other species, notably Chaetoderma attenuata, they may be gland cells. At the base of each is a disc-like darkly staining body, presenting the appearance of a nucleus though this is not conclusive. Delicate fibres traverse the underlying muscle layer at frequent intervals, and come in contact with the hypodermal layer and at several points appear to pass between the cells and then become lost to view. The nature of these fibres has not been determined. They react somewhat as connective tissue elsewhere in the body, and it may be mentioned are distributed to all of the hypodermal elements alike. The buccal plate is partially exposed in one specimen only (Plate 11, fig. 6), and appears to resemble a shield in form with the mouth holding a central - position. In sections the shield consists of the usual thick cuticular plate rest- ing upon cells of several different types, judging by their form and arrangement. Numerous muscle and large sized nerve fibres pass into the neighborhood of the epithelial cells, but the absence of distinct cell boundaries renders it impos- sible to determine their exact relations. Darkly staining masses, probably cells though their details are aggravatingly difficult to determine, are attached to the precerebral masses of ganglion cells, and from them delicate ductules make their way to the margins of the buccal plate. In some instances they open through the cuticular plate; in other cases they pass to the outside of its borders. The mouth opens into a tubular canal without any particularly charac- teristic features. The lning epithelium, consisting of columnar epithelium CHAETODERMA BACILLUM. 203 fashioned into a few rather ill-defined folds, is surrounded by the customary muscle sheath in which a relatively few gland cells find lodgement. These last named elements are arranged in small lobules, and the component cells are occasionally charged with considerable quantities of a darkly staining secretion, though this is much more often greatly limited in quantity. Immediately anterior to the radula a prominent fold appears in the mid ventral line of the digestive tract that is probably a subradular organ. The cells, unlike those elsewhere in the neighborhood, are sharply defined externally and are separated here and there by ductules from two masses of gland cells situated immediately ventral to the ridge in question. That the organ is sensory is evidenced by the fact that it rests upon a ganglion resembling in every important respect the one found in Chaetoderma attenuata for example. The radula (Plate 10, fig. 9) comprises the single tooth, relatively heavy in this species, and the wing-like supports together with matrix cells and mus- cular attachments that. follow closely the arrangement of these organs in other species of the genus. Posterior to the radula the digestive canal narrows rapidly, becomes cir- cular in outline and after a brief course posteriorly unites with a more expanded portion, probably the commencement of the endodermal section. This enlarged division rapidly develops a variable number of small longitudinal folds — from 18 to 25 — that as the gut gradually narrows upon approaching the metathorax (Plate 10, fig. 12), become correspondingly reduced, finally disappearing alto- gether. The cells throughout are clearly defined elements with spherical nuclei, and especially on the dorsal side beneath the aorta are distinctly glandular. This state of affairs continues for at least 1.5 mm. into the metathorax. Beyond this point sections were not made of the central portion of the body. In the posterior end of the animal the intestine, somewhat larger in cross section than common, maintains the usual relations and opens into the cloaca. Its cells, in favorable situations, appear to be more cubical than those of the anterior end of the mid-gut, and present a denser appearance owing to a finely granular secretion they enclose. Diatoms and other substances, organic and inorganic, are present in abundance. The circulatory system is typical in all essential particulars. The heart (Plate 10, fig. 14) is distinctly more muscular than the average, and the dorsal aorta is not only larger than usual but it is lined with an endothelium uncom- monly distinct especially in the anterior end of the body. Beyond this point no other distinctive features have been recognized. 204 CHAETODERMA SQUAMOSUM. The openings of the coelomoducts into the pericardium occur slightly behind the level of the posterior dorsal commissure. From this point the dorsal section of each of the ducts extends anteriorly and unites with the mid section of the main portion of the organ. This main, glandular or ventral section is character- ized by great simplicity. Faint lobes occur in its walls accentuated by a very few internal septa. The nervous system is normal in all of its essential features. Chaetoderma squamosum, sp. nov. A single specimen (Plate 11, fig. 5) of this species was dredged at a depth of 1,234 fathoms (Sta. 2534A) about 200 miles southeast of Cape Cod, Massa- chusetts. The total length of the body was 25.7 mm. with a width of 1.3 mm. in the prothorax and of 1.2 mm. and 1.7 mm. through the metathorax and abdomen respectively. The color is grayish white due in part to a grayish colored incrustation particularly over the pro- and metathorax and to the lead colored liver partially visible through the translucent body wall and over lying spicules. The buccal sensory plate, roughly elliptical in outline, is some- what concealed in the semicircular groove; it is apparent, however, that the mouth opening is comparatively small and is entirely surrounded by the plate. In the neighborhood of the junction of the pro- and metathorax the spines (Plate 11, fig. 9) measure from 0.11 to 0.19 mm., and are further characterized by unusual thinness and the absence of a sharply defined keel. The hypodermis (Plate 13, fig. 7) lacks any distinguishing features. In many places, especially in the anterior end of the body, the nuclei are arranged in two or three layers although the cells to which they belong may actually constitute a single layer. - Occasionally the more external nuclei are spindle-shaped, but it is not certain that this characteristic is correlated with any especial function. The nuclei of the spicule-matrix cells are conspicuous objects, nearly twice the size of the ordinary hypodermal nuclei, and are further distinguished by staining a lighter shade. The buccal plate comprises a thick, external cuticular plate secreted by the underlying hypodermis whose cell boundaries are very difficult to deter- mine. For this reason it is impossible in the present instance to accurately relate these elements to the numerous nerve and muscle fibres and to the duc- tules of deep seated gland cells. Generally speaking the hypodermal cells are relatively slender, often unusually high in the vicinity of the mouth and at various places muscle cells appear to pass between them to attach to the cutic- ular plate, while nerve fibres have been undoubtedly seen to attach to the bases of a few cells with spindle-shaped subcentral nuclei. The ductules perforating CHAETODERMA SQUAMOSUM. 205 the plate, or opening adjacent to it, are usually closely associated with nerve fibres originating in the precerebral ganglia attached to the brain; but they have not been definitely traced to any special set of cells. Several groups of gland cells, of shrunken appearance probably owing to reagents, are imbedded in the wall of the digestive tube in the neighborhood of the mouth. These may be connected with the ductules in question, but on the other hand there are signs that they are in reality buccal glands opening by ill-defined passages into the digestive tract. In common with other members of the genus, this species possesses a diges- tive tract comparatively simple in its structural details. The mouth opens into a well-defined buccal tube of average size and with slightly folded walls in which the lining epithelium consists of slender cells possibly ciliated and without very distinct cell boundaries. Immediately anterior to the peg-like tooth the ventral wall becomes modified to form a well-defined patch of slender, ciliated cells —the subradular organ, judging by position and innervation. Here and there, especially in the ventral half of the tract, gland cells are imbedded in the muscular walls, and in some instances at least open into the digestive tract by intercellular ductules. These glands become relatively abundant in the neighborhood of the radula where they chiefly open on prominent folds of the lateral walls of the gut. The radula (Plate 11, fig. 10) is, as usual, a slender conical structure 0.4 mm. in length, and in its relations, muscular attachments, and matrix cells conforms closely to other species of the genus. A very short distance posterior to the radula the digestive canal narrows rapidly, becoming elliptical in cross section, whereupon it almost immediately unites with a dilated portion whose walls have been largely stripped of their lining epithelium due apparently to the reduction of pressure upon being brought - to the surface. Where it remains the cells agree in being relatively large columnar elements in which the centrally placed nuclei are unusually conspicu- ous. A darkly staining secretion covers their free surface, but its origin is uncertain, though it may have been elaborated by these cells as they generally show traces of glandular activity. This dilated section of the canal narrows considerably in the posterior end of the prothorax (Plate 11, fig. 8), and as an almost perfectly circular tube extends into the metathorax where it unites in characteristic fashion with the stomach and liver. In the abdomen a mass of diatoms, sponge spicules, and inorganic debris prevented sectioning; in the cloacal regions the position of the gut was typical. The coelomoducts are comparatively simple structures, holding the usual 206 NEOMENIA VERRILLI. position and presenting the customary appearance. Beyond this statement there is little to be added that will aid in diagnosing the species. From its opening into the pericardial cavity each duct, slender in outline pursues a course anteriorly and at the same time assumes a position dorsal to the main or ventral portion of the duct. In this situation, considerably enlarged and with three or four slight folds springing from its inner surface, it extends anteriorly for a considerable distance and becomes continuous with the ventral section. This last named division, relatively large in diameter and likewise supplied with a few folds, extends posteriorly until it has traversed approximately one third the length of the cloacal chamber into which it then opens by a conspicuous pore. As in several other species of this genus the walls of the cloacal cavity are modified to form a well-defined area surrounding the external openings of the coelomoducts. The component cells comprise slender supporting cells and elongated gland cells sharply defined from the cubical elements that at other points line the chamber. The nervous and circulatory systems were studied in detail, but no espe- cially noteworthy features were encountered. Neomenia verrilli, sp. nov. A single specimen of this species occurs in the present collection, bearing the label ‘‘Gulf of St. Lawrence, 313 f’ms. J. F. Whiteaves, 1872.” The animal has been decalcified and cut open along the mid dorsal line, an opera- tion that has destroyed some of the organs though their general plan is still discernible. The body is thick-set (Plate 3, fig. 6), bean-like in form and measures approximately 25 mm. in length by 8 mm. greatest diameter. The ‘color in a preserved state is light yellow. The work of decalcification is complete, not a sign of a spicule being evi- dent, yet it is certain that, as in other species of Neomeniidae, one layer of spines was present originally. While the papillae differ in detail among themselves, these variations appear to be due to growth and possibly to some extent to fixation. Little if any pigment is present in the component cells, and no clearly defined nerve supply has been traced to them. It may be added that these organs are comparatively numerous (Plate 3, fig. 8). The remaining hypodermal cells are comparatively small, without clearly defined boundaries and are devoid of features of special interest. No dorsal keel exists. A well-defined spiculose, cuticular bridge separates the atrial cavity from NEOMENIA VERRILLI. 207 the external opening of the anterior pedal gland. Anteriorly this last named space appears as a narrow slit, when viewed from the mid line, but in cross section it is seen to extend far outward on each side and to possess plain though highly glandular walls. About midway its dorsal wall loses its glandular char- acter and develops numerous folds, large and small, which more posteriorly decrease to seven or eight. In the middle of the body the foot has been cut away, but in the posterior third it reappears with this reduced number of folds. Whether this condition continues to the cloacal chamber cannot be determined owing to slight mutilations. As noted previously the anterior, plain-walled section of the anterior pedal gland outlet is composed of highly glandular cells whose secretion, after treat- ment with Delafield’s haematoxylin, stains a uniform lavendar tint. With the appearance of the folds on its dorsal surface the component cells lose their glandular character, and the deeper seated cells, pyriform in shape and opening by delicate ductules through the folds, stain intensely and probably represent the anterior pedal gland of other neomenians. Posterior to the anterior pedal gland outlet these last named glandular elements decrease in size and number and shade into the posterior pedal gland. The extremities of the body presented almost identically the same appear- ance, and it was only from the study of sections that the atrial opening was definitely located. The cirrose cavity into which it leads is relatively small, and is almost completely separated into two subdivisions crowded on each side of the body against the body wall (Plate 4, fig. 7). While there are no clearly differentiated sensory ridges bounding the cirrose area, the entire atrial cavity, with the exception of the cirri themselves, is lined with an epithelium composed of high and slender cells similar to those composing the ridges in other species. Appearances indicate that these cells are sensory in character, but the absence of undoubted nerves renders the identification uncertain. Along the inner boundary of the cirrose area is an unusually high fold that like a curtain shuts off to a large extent these lateral cavities from the median space, which may represent the buccal cavity. If this fold represents the inner atrial ridge of other Solenogastres its cells, low in form and non-ciliated, give no indi- cation of possessing any sensory function. At the commencement of the buccal or pharyngeal cavity, a great fold, seamed with numerous minor corrugations, springs from the dorsal side, and in the first part of its course almost fills the cavity. More posteriorly it becomes subdivided into three or four lesser folds, that, with others which have arisen 208 NEOMENIA VERRILLI. on the lateral and ventral surfaces of the pharynx, extend longitudinally to a point probably corresponding to the posterior end of the pharyngeal tube where they terminate as abruptly as they began (Plate 3, fig. 4). All of these folds are deeply furrowed with secondary ridges, and are supported by an abundance of muscle and connective tissue, which likewise give support to a large number vo: gland cells. These last named elements appear to be grouped in the form of slender lobules, but the protoplasm of which they are composed stains but faintly, and their relations with the overlying epithelium are obscure. At several points what appear to be ductules are evident, and a darkly staining secre- tion on the exposed surface of the pharyngeal epithelium indicates that the products from these cells escape as usual by intercellular channels. As noted in the foregoing paragraph the large pharyngeal folds end abruptly posteriorly; and immediately behind them a large circular fold arises com- posed of muscle and connective tissue penetrated by blood sinuses. This fold appears to be capable of a certain amount of protrusion, but owing to the lack _ of well-defined protractors and retractors its movement is probably limited. The lining epithelium is composed of high, slender cells charged distally with a granular secretion not encountered elsewhere in the digestive tract. Distinct ventral salivary glands are absent, and it is possible that these cells are homolo- gous or at all events that they perform a similar function. No radula is present. Beyond this circular fold the stomach-intestine appears with walls fash- ioned into numerous longitudinal folds lined internally with digestive cells without distinct boundaries and densely packed with innumerable granules. Along the mid-ventral line the cells of this character blend insensibly with others, almost cubical in form, and non-glandular, that anteriorly form a narrow trough-like tract which nearer the middle of the body develops folds and in this condition extends to the region of the seminal receptacles. Here the intestine narrows to pass between the limbs of the coelomoducts, and this non-glandular portion of the gut gradually extends toward the dorsal side until at the anal opening it comprises fully half of the digestive tube. The mutilation of the specimen renders it impossible to state with certainty, but it appears that the dorsal glandular tract does not disappear until the cloacal chamber is reached. The cloacal cavity is a spacious chamber, and as in other species of the genus its walls are provided with extensive branchial folds (Plate 4, fig. 5), numbering apparently between fifteen and twenty pairs. These in turn are’ often supplied with many secondary folds, the appearance in cross section reminding one strongly of ctenidia. NEOMENIA VERRILLI. 209 Between the bases of these folds and the somatic musculature are large numbers of gland cells separated into small lobules by connective-tissue septa between which blood sinuses make their way. No traces of ductules are appar- ent though there are evidences here and there, possibly a post mortem effect, that some of the cells have released their hold and are free in the blood stream, while others, attached by very slender stalks, appear to be in process of libera- tion. In a general way these elements remind one of the concrement cells as described by Brock (1883), but there is no definite evidence that they are homologous or that they function similarly. The circulatory system has suffered to a greater extent from the mutilation of the specimen than any other set of organs, but so far as determined it con- forms closely to the neomenian type. The pericardial cavity is of moderate size only, and the ventral displacement indicated in the reconstruction (Plate 3, fig. 1), may be an abnormal state of affairs. As indicated there is a shallow pouch-like expansion of the forward wall in the neighborhood of the reno- pericardial openings, but with the exception of a somewhat thicker, slightly corrugated wall there are no indications that it may play any especial function. The heart is a two-chambered organ, the blood from the branchiae and the dorsal part of the posterior end of the body entering the hindmost section. There are indications of a valve guarding the union of the two divisions. The clearly defined dorsal aorta, holding the usual position and supplying the cus- tomary organs, makes its way to the head cavity, and there communicates with an extensive system of spaces which in turn soon combine to form the median ventral sinus and that of the general visceral cavity. In the posterior end of the body, about the level of the anterior end of the shell gland, the first named of these canals rapidly diminishes in size, while the other communicates with spaces leading into the branchiae and beyond them into the heart. The nervous system is more than usually well-defined, and for this reason more than ordinary care has been taken to determine the position of the vari- ous ganglia and their more important branches. The brain occupies the usual position above the atrial cavity, and with the exception of its comparatively small size presents no especially noteworthy features. As usual it originates on its anterior face several nerves that are distributed to the atrium and the adjacent body wall; and laterally it gives rise to the connectives passing to the labiobuccal, lateral, and ventral ganglia. The last named connectives like the brain, are of exceptionally small calibre, and lying loosely in the visceral cavity may be traced to the region of the outlet of the anterior pedal gland where they unite with the ventral ganglia. Close to the point of union the ganglia 210 NEOMENIA VERRILLI. are strongly enlarged, and are united by two commissures of considerably larger size than those in a more posterior position. With the exception of the most anterior, the connectives uniting the lateral and ventral ganglia are spaced at fairly definite intervals. The exception arises on each side from what appears to be the connective to the ventral ganglion since no nerve cells occur in its vicinity, and on the other hand it unites with the anterior swollen extremity of the lateral cords. The last named enlarge- ment gives rise to two strong branches of which the smaller, directed anteriorly, makes its way into the vicinity of the bases of the cirri. The other makes its way ventrally and is distributed in part to the somatic muscles, while a com- paratively large nerve extends between the lobules of the anterior pedal gland where it becomes lost to view. Another nerve destined to the same organ arises from the lateral cords about midway between the first and second latero-ventral connectives. As usual nerves spring from the dorsal side of the lateral ganglia, and though clearly defined and of relatively large size none have been traced as far as the mid-dorsal line. They branch repeatedly over the internal face of the somatic muscles which they probably innervate together with the overlying hypodermis. The labiobuccal connectives are so closely associated with the lateral for a short distance beyond the brain that though they are fairly distinct they nevertheless occupy the same sheath. Beyond this point they may be fol- lowed with unusual clearness, and owing to this fact more than ordinary care has been exercised in determining the relation of the principal elements. Loosely attached to the muscular coat of the digestive tract each connective extends posteriorly to the labiobucecal ganglion placed about opposite the posterior end of the outlet of the anterior pedal gland. At approximately two thirds of its length from the brain two or three branches are developed of which the largest, crossing the dorsal surface of the pharynx, forms a commissure. The others, imbedded in the muscular pharyngeal walls, have been followed to a greater or less extent until their subdivisions become so small in cross sections that they disappear from view. At many points minute nerves appear in the pharyngeal wall, and give the impression that they are parts of an extensive plexus such as is known to ensheath the digestive tract in several other molluses. Other nerves of this same character occur at a short distance anterior to the labiobuceal ganglia. Immediately in front of the ganglia a simple, ventral commissure occurs. NEOMENIA VERRILLI. 211 A few small nerves arise from it, but soon become lost to sight in the ventral pharyngeal musculature. The labiobuccal ganglia are sharply defined spheri- cal structures, and each is connected by a dorsal and ventral commissure. There are thus two dorsal and two ventral commissures, but no signs whatever of a subradular complex. This is not surprising as a radula is lacking completely, and a subradular organ, if such exists, is far from being a sharply differentiated structure. The nervous system in the posterior end of the animal has been partially destroyed so that only the broader features have been worked out. Its gen- eral configuration, however, is essentially the same as in Drepanomenia vampy- rella. The pedal cords continue to a point about opposite the middle of the cloacal coecum or vagina (Wiren) where they bend abruptly, and coursing dorsally and posteriorly unite with the lateral cords slightly ventral to the open- ings of the coelomoducts into the pericardium. From this point of union, on one side, a heavy nerve, doubtless the dorsal commissure, extends for a con- siderable distance toward the mid line. The commissures uniting the pedal cords appear to be more numerous than the latero-pedal connectives, but beyond this fact no especially interesting features have been observed. As usual the animal is monoecious, and in this instance is sexually mature, the swollen gland extending from the pharyngeal region to the pericardium being distended with sex products in all stages of development. Anteriorly the ovo-testis contains sperms only, but a very short distance behind the for- ward tip of the organ ova appear attached as usual to the inner faces of the tubes. The canals leading into the pericardium are comparatively short, though of more than average diameter, and are richly ciliated throughout. As is more fully described in the section on the circulation, the pericardium is provided on each side of the body with two relatively wide diverticula with which the coelomoducts connect. The reno-pericardial openings are unusually wide and conspicuous, and are further distinguished by being surrounded by cells of greater height than is encountered elsewhere in the pericardial wall and by bearing a ciliated coat. The upper section of each coelomoduct, pursuing its way anteriorly to the region of the seminal receptacle, is of more than ordinary length and is fashioned into a number of short turns (Plate 3, fig. 4) that give it a some- what complicated appearance in cross section. Throughout its entire extent each canal is provided with a dozen or more high, longitudinal ridges sup- ported by muscle and connective-tissue fibres penetrated in many instances by blood sinuses. The component epithelial cells are relatively slender, of 212 NEOMENIA VERRILLI. moderate height and in addition to containing small amounts of some finely granular substance support a well-defined ciliated coat. At the junction of the dorsal and ventral divisions of the coelomoducts on each side is a large vesicular appendage (re) that probably functions as a seminal receptacle since each contains a very few spermatozoa together with a small amount of some glandular secretion. The walls of the neck-like duct are similar to those of the dorsal limb of the coelomoduct, and are heavily cili- ated, as are the cells of the receptacle adjacent to it. On the other hand the walls of the expanded portion comprise cells of two types, goblet-shaped glandular elements with basal or subcentral nuclei, and exceedingly slender supporting cells. The secretion of the first named class is restricted to the distal half of the cell, and from its homogeneous appearance and seemingly viscous character probably exists in the form of a fluid in living material. The ventral limbs of the coelomoducts hold the customary relation to the other organs in the posterior end of the body, and are not only of relatively small diameter but the walls are comparatively thin. From the quantities of secretion imbedded in the walls it appears probable that this is the usual state of affairs. The epithelial lining is thrown into folds of varying sizes each supported usually by fibres sent in from the sheath surrounding the organ. The cells are high, slender elements with the distal portion containing groups of small granules staining moderately with Delafield’s haematoxylin. This state of affairs continues to the median, undivided section where the cells become more nearly cubical especially in the neighborhood of the opening into the cloacal chamber. The external reproductive pore does not communicate directly with the general cloacal cavity, but with a compartment of it that in turn gives rise to the diverticula responsible for the development of the penial spines. Ventrally this same space leads into a heavy tubular outgrowth termed by Wiren (1892) the vagina or copulation organ. The so-called vagina (co) is a diverticulum of the anterior cloacal wall reinforced with a heavy muscular sheath. The muscular elements comprise three classes, an innermost, heavy circular layer external to which is a thin covering of longitudinal fibres, while here and there small, radiating bundles extend through these layers from the neighborhood of the inner epithelial lin- ing. The internal bounding membrane consists of slender, ciliated cells, appar- ently slightly glandular, produced into numerous small folds. Along the mid- ventral line the muscular sheaths are pushed inward, thus producing a species of typhlosole that continues throughout the greater part of the organ. Distally the vagina opens into a pair of relatively large sac-like organs NEOMENIA VERRILLI. 213 symmetrically placed on each side of the mid line. From sections, which pass longitudinally through these structures, it is very difficult to gain a clear idea of their character, and, as will be seen, it is equally trying to ascribe to them a definite function. The epithelial lining appears to be fashioned into a large number of heavy folds (Plate 3, fig. 3), and occasionally where the walls are bare they appear golden yellow in color after treatment with haematoxylin. This seemingly is due to large quantities of secretion, though even with high magnification cell boundaries and nuclei are invisible. Generally speaking the lining epithelium affords attachment for myriads of spermatozoa, which, with great regularity of arrangement, seem to be imbedded in the cells them- selves, while the tails extend outwardly and together with the above mentioned secretion practically fill the lumen of the organ. Even in portions of the vagina and the expansions of the cloacal wall, into which the penial spines emerge, sperms find attachment to the lining epithelium though their numbers per unit area are considerably less than in the vesicles themselves. It may be men- tioned that the golden yellow secretion occurs at intervals throughout the vagina and lateral to it, having apparently passed into these locations from the sac-like expansions or vesicles. Regularity of arrangement of spermatozoa within a vesicle is usually considered to be an indication that the organ in question functions as a seminal receptacle, while the reverse condition indicates that the structure plays the role of a seminal vesicle. If such a line of argument be followed in the present instance then these pouches are seminal receptacles. It is a very unusual thing, unique in fact, to find organs such as these in such a situation, and it is the more difficult to look upon them as receptacles since a pair of these last named organs occurs in the usual position at the junction of the dorsal and ventral limbs of the coelomoducts. It is possible that they function as such temporarily, and that the sperms take up their final position in the usual recep- tacles, but nothing short of a series of specimens in different stages of sexual maturity will indicate the true solution of the problem. Wiren (1892) has described a vesicular attachment, filled with sperms, of the dorsal limbs of the coelomoducts in the neighborhood of the pericardial openings in Neomenia carinata. In sections they hold the same general position that the sperm sacs do in the present species, but in our specimen the dorsal limbs are unmutilated, and a careful examination of them throughout their entire length fails to disclose any spermatozoa, much less any noticeable enlarge- ment. 214 NEOMENIA VERRILLI. Each penial spicule sheath and the included spine are of unusual length and girth, and with the accompanying muscles form a very conspicuous element of the accessory reproductive apparatus. In addition to these elements there exists a trough-like guide or groove (Plate 4, fig. 8) in which the spicule rests. As in the case of the spine this guide appears to be cuticular in character, but whether in life this serves as a matrix for calcium salts it is impossible to state at present. Both of the structures are secreted by numerous slender cells, clear and well-defined at the distal extremity of the sheath, but growing indis- tinguishable near the free opposite end. The external sheath is composed largely of connective tissue to which the retractor and protractor muscles are attached. The first named are of larger size and are united with the sheath in the neighborhood of its distal extremity. On the other hand they become inserted chiefly in the cuticular trough though small slips extend to the spine that thus is possessed of a certain amount of independent action. The protractors attaching to the spine are comparatively thin and delicate, and, so far as may be judged from sections, are attached both to the grooved guide and to the sheath. Another protractor, of much larger size, is inserted in the grooved plate near its outer end, and extending in a postero-ventral direction fuses with the somatic musculature lateral to the posterior termination of the foot. In addition to these elements the spicular apparatus comprises: a pair of highly developed glands (pgl) that in the present instance are fully as large as the shell gland. Each of these is placed somewhat above and to the inside of the ventral limbs of the coelomoducts or shell gland (Plate 4, fig. 1), and presents the appearance of an inflated sac ellipsoid in form. Internally well- defined septa spring from the walls, and in the anterior end of the organ these become so united that they form a number of diverticula communicating with the main cavity of the gland. The cells of the epithelial lining are more or less goblet-like in shape, and distally contain vacuoles in which are occasional globules of some secretion. In the neighborhood of the free extremity of the retracted spine a duct opens into the surrounding space, and on the other hand passes laterally then dorsally and toward the mid line to enter the mass of connective tissue ventral to the shell gland. » In this position, close to the gland just described, it becomes lost to view owing to the mutilation of the specimen. Two possibilities present themselves; either it opens into the shell gland or into this large, overlying gland. The former course appears unlikely, especially in view of the fact PRONEOMENIA ACUMINATA. 215 that in Neomenia carinata Wiren (1892) has described a large accessory penial gland whose relations bear a close resemblance to the state of affairs in the present case. In conclusion it may be added that the members of the genus Neomenia ean searcely be considered primitive. The complexity of the reproductive system especially, with its penial spines and glands, seminal vesicles, and recep- tacles, appears to indicate that the genus stands in about the same relation to the primitive molluse that the pulmonates do to the prosobranchs. Proneomenia acuminata WIREN. One specimen of this species was dredged in the Straits of Florida (Sta. 5 Be) at a depth of 152-229 fathoms; a second was taken south of Martha’s Vineyard, Mass. (St. 893 Fk) at a depth of 372 fathoms; while a third came from practically the same location (Sta. 2547 A) at a depth of 390 fathoms. The first is somewhat distorted, and in a normal state probably measured not far from 20 mm. in length by 1.7 mm. in thickness: the second is 23 mm. long by 1.8 mm. thick; the third measures 30 mm. in length by 1.7 mm. in diameter. The anterior end is bluntly rounded (Plate 5, fig. 3), while the posterior extremity terminates in a rounded point, and owing to the large size of the cloacal opening it is probable that in life its borders can be widely expanded as in the case of Ichthyomenia ichthyodes. The atrial opening, surrounded by rounded, prominent lips, is distinctly separated from the ventral groove whose anterior excavation, the outlet of the anterior pedal gland, is invisible externally though in decalcified material it shows faintly through the translucent cuticle. While the outline of the outlet is somewhat irregular in form it consists, generally speaking, of hemispherical diverticula extending laterally a short distance from the ventral groove. The anterior pedal gland is a voluminous organ occupying most of the visceral cavity between the region of the radula and the outlet of the dorsal salivary gland. Although the cells are of varying size, owing to age or the amount of secretion they contain, all agree in being more or less pyriform with an irregular somewhat varicose ductule leading to the exterior of the body. The secretion itself is invariably finely granular, staining intensely in Delafield’s haematoxylin, and usually fills the cell. As is the case generally with the Neomentidae the ductules open by intercellular channels into the anterior end of the ventral furrow. 216 ‘PRONEOMENIA ACUMINATA. The posterior pedal gland is directly continuous with the anterior from which it differs in no essential particular, save in the smaller size of the cells and their lesser number. The ductules lead to the median fold, or rudimentary foot, and in addition are distributed to the epithelium of the ventral groove generally as far as the spiculose cuticle. With the posterior termination of the foot in the neighborhood of the external reproductive pore, these cells dis- appear, but close behind the gonoduct exit the wall of the cloaca is supplied with a scattering band of cells of the same character opening along the border of the spiculose cuticle. The cuticle is of moderate thickness only and the hypodermis is exception- ally thin and its cells difficult to interpret. The spicules, with which the cuticle is crowded, are of the customary proneomenian type, slender, slightly curved needle-shaped structures (Plate 5, fig. 4) arranged in approximately seven layers. Radially directed spines appear to be lacking excepting in the region of the ventral groove. The papillae (Plate 5, fig. 6) appear in life to have been filled with a highly fluid substance that after treatment with reagents largely disappears, leaving the few component cells in a much shriveled condition. In the expanded por- tion five to seven nuclei are usually visible; none appear in the stalk. As noted previously the hypodermis is a very thin sheet, and the compo- nent cells are very inconspicuous. The spicule-matrix elements on the other hand are relatively distinct, and maintain essentially the same relations as in Proneomenia hawariensis for example. The cells retain their attachment to the spine until the latter has travelled halfway to the surface of the body, and in some eases they retain their connection for a longer period. The position of the dorso-terminal sense organ was discernible in surface view, owing to the presence of numerous, small overarching spines though the cavity itself was not visible. In sections it presents the appearance of a hemi- spherical depression composed of very slender cells resting upon the somatic musculature. A unique feature appears in the form of a comparatively large number of gland cells filled with a darkly staining secretion, located about the rim of the pit adjoining the spiculose cuticle. In some instances the cells are in the general hypodermal layer; in other cases they are in the underlying tissue, but in any case they open through intercellular spaces about the margin of the depression. There are strong reasons for the belief, first expressed by Thiele, that the anterior enlargement of the digestive tract, with its ciliated ridges and finger- PRONEOMENIA ACUMINATA. 217 shaped cirri, is in reality a modified snout homologous with that in the Chitons, and perhaps with the sensory shield in the Chaetodermatidae. On such an assumption the true mouth is deeply seated, and in the present case is in the neighborhood of the outlet of the dorsal salivary gland. In the specimen in hand the atrial opening, subterminal in position is a relatively long narrow slit leading into a spacious chamber, the atrial cavity, whose limits are fairly well-defined by two prominent horseshoe-shaped ridges, which fuse posteriorly (Plate 5, fig. 1). The first of these, the outermost and continuous across the mid line, courses parallel to the borders of the outer opening, and is bounded externally by slender cells bearing a well-defined coat of cilia. Internally it is supported by an abundance of connective tissue and is penetrated by a blood sinus distended by blood corpuscles. It thus appears, as has been suggested, that these organs may play a part in the process of respira- tion, but the nature of the overlying epithelium and the presence of nerve fibres beneath it indicates also that it is a sense organ though its office is unknown. As in Proneomenia hawariensits and some other neomenians, this external atrial ridge is bounded on its outer side by a lower prominence (Plate 5, fig. 1) whose slender cells are fully twice as high and are evidently sensory. In this species fibres may be traced into its neighborhood, but it is not so evident that they are sensory as in a few other species. In P. hawaiiensis a cord-like group of ganglion cells is situated in close proximity to the overlying ridge, which it supplies with numerous delicate fibres, and in the opposite direction is united at fairly frequent intervals with some of the ganglia located about the bases of the cirri. There thus appears to be little doubt that in such cases we are dealing with a definite sense organ, and it is probable that in Proneomenia acumi- nata the same is true. Throughout its entire extent this external sensory ridge contains a small number of gland cells, whose slightly vacuolated secretion stains intensely in haematoxylin. In the posterior third of its course additional cells of the same character appear in the outlying hypodermis beneath the spiculose invest- ment, and in this position they continue to the posterior border of the atrial cavity. The inner atrial ridge, in form and structure and perhaps in function, is the counterpart of the external one (Plate 5, fig. 1). In the area circumscribed by these prominences the cirrose area is located, and is characterized in the present instance by numerous slender diverticula of the atrial wall. These arise singly, and are further distinguished by multi- 218 PRONEOMENIA ACUMINATA. tudes of slender, lightly staining cells containing small quantities of yellowish pigment. The contained cavity is extremely slender, preventing the entrance of blood corpuscles but allowing the entrance of slender fibres from the under- lying tissue. In certain species these fibres appear to be in part branches of nerves and such may be the case here, but the contorted appearance of these organs leads to the belief that contained muscle fibres are, at least in part, responsible for their condition. Immediately behind the union of the atrial ridges the wall of the digestive tract is smooth, but rapidly develops folds, as the pharynx is approached, of irregular appearance and bounded by the cubical cells characteristic of the pharyngeal epithelium generally. The accompanying figure (Plate 5, fig. 1) represents approximately the existing state of affairs, but the folds though generally longitudinal are somewhat diagrammatically shown. In this species the dorsal salivary gland (Plate 4, fig. 11, Plate 5, fig. 1) is a marked feature, owing to its size and compactness. It comprises numerous globular or pear-shaped lobules of various sizes bounded by a connective-tissue sheath, and in every instance these are without central cavities. The compo- nent cells are pyriform, and their ductules open by intercellular channels in the epithelium of the prominent diverticulum on the dorsal wall of the pharynx. Vacuoles are abundant in their cytoplasm, and in life they are doubtless filled with a secretion that in preserved material stains very faintly in haematoxylin. From the outlet of the dorsal salivary gland to the forward end of the radula the pharynx is approximately circular in outline, and is reinforced by a layer of circular muscles and more externally by a longitudinal set. Radiat- ing bundles, acting as dilators, pass from this muscle sheath to the body wall. - The ventral salivary glands are tubular, paired organs about 3 mm. in length, situated throughout the greater part of their course on the ventral side of the body between the stomach-intestine and the body wall. The component cells, all bordering on the narrow centrally placed lumen (Plate 5, fig. 2), are without definite cell boundaries, and the secretion they elaborate occupies numerous vacuoles in the cytoplasm except in the immediate vicinity of the basal or subcentral nuclei. In close proximity to its outlet into the pharynx this glandular portion passes abruptly into a much more slender, non-glandular duct leading to the opening at the side of the exposed portion of the radula. In this non-glandular section the lumen is eccentrically placed, the ventral cells being three or four times longer than those of the dorsal side. The radula is a well-defined structure, normally placed, and is of the poly- PRONEOMENIA ACUMINATA. 219 stichous type. The teeth (Plate 4, fig. 9) are comparatively small and delicate, and as far as may be judged from cross sections number approximately twenty- eight in each transverse row of which there appear to be about forty-five, though this last estimate is difficult to prove definitely. The radular supports lack the vesicular structures found in several other species of neomenians, and con- sist entirely of a compact mass of muscle and connective-tissue fibres far too intricate to define accurately from the study of sections alone. It may be said, however, that close to the posterior end of the radula fibres pass to the overlying pharynx or oesophagus, and others, much more powerful, extend from the extreme posterior tip to the overlying radula sheath. In addition to these, numbers of others extend from the radula sheath to the walls of the pharynx. It thus appears that the radula, by reason of its intrinsic muscles, is capable of considerable movement but probably, during the feeding process, the great- est motion is produced by the protrusion and retraction of the pharynx which carries the radula forward and backward. In Proneomenia hawaiiensis two well-defined subradular organs exist innervated by fibres from ganglia, connectives, and commissure essentially the same as in the Chitons for example. In the present specimen two patches of modified cells, of the same character, exist and as they are in close proximity to a pair of small ganglia it is reasonable to believe that here likewise we are dealing with a definite sense organ. The component cells (Plate 4, fig. 10) form knob-like elevations, surrounded by a shallow groove, on each side of the forward border of the radula. Posteriorly they become continuous with the ventral wall of the short, non-glandular ducts from the ventral salivary glands so that the secretion from these organs pours over them in escaping into the pharynx. In addition to these two modified areas the epithelium, continuous with them across the mid line, is also of unusual height, being fully three times thicker than that bounding the pharynx elsewhere (Plate 4, fig. 10). Its cells appear, though not clearly, to contain small amounts of some faintly staining secretion, but whether this is associated with a special sensory function has not been determined since no definite nerve supply has been detected. Immediately behind the radula the pharynx unites with the stomach- intestine without any material change in the character of the epithelial lining or the nature of its longitudinal folds. And furthermore the stomach-intestine itself with its glandular lining and regular outpouchings does not differ from the usual neomenian type, though certain features demand a brief description, 220 PRONEOMENIA ACUMINATA. The first of these concerns the anterior dorsal coecum, which extends as far forward as the brain. Throughout its entire course it is dorsoventrally com- pressed, and is totally devoid of pouches though its lining epithelium resembles that of the stomach-intestine. Ventral to its base (Plate 5, figs. 1, 2) is a much smaller, anteriorly directed coecum similar, in the character of its lining cells, muscular sheath and folds, to the pharynx with which it is directly continuous. Finally the pharyngeal epithelium extends along the ventral side of the digestive tract as far as a dorsoventrally compressed ventral coecum whose cells are identical with those of the stomach-intestine. It is thus apparent that the pharynx or oesophagus dilates posteriorly into a funnel-shaped structure and in this form unites with the stomach-intestine. The stomach-intestine, with its lateral sacculations, dorsal ciliated tract, and lining of digestive cells, presents no especially noteworthy features. As it passes between the limbs of the gonoducts it becomes triangular, then more or less elliptical as it crosses the undivided section and finally as an almost circular canal it opens into the cloaca. The cloacal chamber is of moderate size only (Plate 5, fig. 5), and its plain or only slightly folded walls exhibit no especial peculiarities though it may be said that the cells forming the lateral walls are heavily ciliated. Undigested material, associated with some darkly staining secretion, fills the cavity with the exception of that held by a parasitic or commensal worm, apparently a rhabdocele. The condition of the present specimen indicates that the breeding season was close at hand, as the gonad is greatly distended with sex products and the gonoducts are in a condition of great glandular activity. The reproductive © gland, distinctly paired throughout, extends anteriorly as far as the level of the radula, and on the other hand unites, as usual, with the front end of the pericardial cavity. With the extreme forward tip of each division of the gonad the organ is filled laterally with male products, in all stages of development while large numbers of what appear to be nearly mature ova attach to the wall along the mid line. Posteriorly the conditions are peculiar. The halves of the gland diverge widely until in the region of the pericardium they are separated by a space nearly equal to one third the diameter of the body. This intervening space is spanned dorsoventrally by muscle fibres, and is filled with blood corpuscles and furthermore is directly continuous with the heart so that it is doubtless a greatly expanded aorta. Close to the posterior end of each half of the ovo- PRONEOMENIA ACUMINATA. 221 testis a small duct arises from the dorsal side and coursing ventrally to a slight degree it then pursues a direct path (about once again as long as is represented in Plate 5, fig. 5) to the forward end of the pericardium. The lateral walls of these small canals are folded to a slight degree, and the slender cells support a ciliated coat. Toward the mid line the walls are relatively smooth and serve for the attachment of small numbers of spermatozoa that have also made their way into the front end of the pericardium. Posteriorly the walls of the pericardium are continuous with the coelomo- ducts that arise as slender tubes with plain walls consisting of cubical, ciliated cells. During the first part of their course each is crowded between the shell gland and the somatic musculature, but after extending upwards of one third the distance to their anterior attachment they shift into the angle between the shell gland and the seminal receptacle and become considerably enlarged. The walls show slight signs of glandular activity and here and there the cells form slight folds. The opening into the shell gland is borne on the summit of a hemispherical papilla, and is further marked by a yellowish secretion (unstained in haematoxylin) that has escaped from the dorsal section and may be traced some distance posteriorly in the lumen of the shell gland. Each seminal receptacle is an elongated sac, of sinuous outline when viewed dorsally, resting upon the anterior horn of the shell gland. The walls are rela- tively thick with slight folds here and there and present a dense appearance due apparently to the presence of a finely granular secretion. A very few spermatozoa find attachment to the walls. The union with the shell gland is made by means of a very slender, short tube placed slightly in front of the union of the dorsal and ventral sections of the coelomoduct. The shell gland, or ventral division of the coelomoduct, is of the usual horseshoe-shape, and as may be seen in the figures is a massive affair. For a distance equal to half the length of the seminal receptacle its epithelial lining is charged with a darkly staining granular secretion that in many places has escaped into the adjacent relatively large lumen. Posterior to this point the nature of the cells changes abruptly for not only do they become of greater height but the secretion, practically unaffected by haematoxylin, acts as though in life it had been of a highly viscous character. This is especially true of the elements of the ventral half of the organ which continue to present this appear- ance throughout the median, undivided section of the shell gland as far as the point where it narrows to form the small, non-glandular tube communicating with the cloacal chamber. On the other hand the dorsal cells of the median 222 DORYMENIA PERONEOPSIS. division of shell gland become charged with a darkly staining, partially granu- lar, secretion which likewise extends to the narrow canal communicating with the cloaca. The terminal section of the coelomoducts is a tube of comparatively small diameter (Plate 5, figs. 5, 8) composed of slender cells fashioned into several inconspicuous folds. Circular muscles form a sheath about it, and radiating bands, probably functioning as dilators, pass from it to the body wall. In sections it may be seen that the spiculose investment of the animal extends within the body as far as the external reproductive aperture (Plate 5, fig. 5). What probably function as copulatory spicules occur at the sides of the ventral furrow (openings shown in Plate 5, fig. 8) a short distance in front of the posterior end of the foot. These organs present the form of needle-like bodies, so far as can be judged from decalcified specimens, are probably derived from the usual type of spine occurring everywhere in the region of the ventral furrow, and form two groups of from 12-14 on each side of the mid line. Each spine occupies its individual sheath, which extends anteriorly and laterally from the outer opening, and ends blindly where a single matrix cell is located. While no definite muscles appear to attach to these bodies, the region in which they occur, and in fact the entire border of the cloacal chamber, is highly mus- cular and doubtless can be opened widely, thus bringing these penial spines into an exposed position. The type-specimens of this species was taken in the “West Indies” at a depth of 540 meters, practically the same as the habitat of the present speci- mens. Some of Wiren’s reconstructions and drawings of various organs appear to be somewhat diagrammatic and do not entirely accord with what exists in the specimens in hand. Accordingly the foregoing detailed description has been arranged with the hope that it may be compared with Wiren’s account and the type-specimen. Dorymenia peroneopsis, sp. nov. A single, unattached specimen of this species was dredged south of Martha’s Vineyard, Massachusetts (Sta. 2715A) at a depth of 1,753 fathoms. The body measuring approximately 25 mm. in length by 2 mm. in greatest thickness, is broadly elliptical in cross section with a slight flattening of the ventral surface. The anterior end is bluntly rounded while the posterior extremity tapers abruptly to a point. From external view no line of separation exists between the atrial opening and the ventral furrow, and sections show that the usual spiculose bridge is lacking. The outlet of the anterior pedal gland is accordingly located DORYMENIA PERONEOPSIS. 223 immediately behind the external opening of the atrium, although otherwise it is not especially modified externally. The ventral furrow is continuous with the cloacal chamber. The cloacal opening is relatively large, ventrally placed and is overarched by the posterior pointed end of the body, whose lateral mar- gins may perhaps be separated in life to expose the genital spicula, the appear- ance of the hinder end of the animal at such times resembling [chthyomenia ichthyodes. A well-developed dorso-terminal sense organ (Plate 7, fig. 7), visible in sections only, is present about the level of the anterior margin of the cloacal opening. It presents the usual cup-shaped appearance, is adjacent to the median dorsal sinus entering the posterior end of the heart, and is innervated by two nerves springing from the mid section of the suprarectal commissure lying immediately posterior to the pericardium. The cuticle investing the body is of more than average thickness (0.1 mm.) and is developed by a hypodermal layer whose component cells are not clearly defined and therefore are unfavorable for study. So far as could be determined they comprise three types, columnar elements seemingly responsible for the development of the cuticle, spicule-matrix cells which in early stages are indis- tinguishable from the foregoing, and those forming the papillae. These last named structures are stubby bodies (Plate 8, fig. 9), resembling an inverted cone composed of highly vacuolated protoplasm in which nuclei are usually visible throughout the entire organ. The spicules are hollow, needle-like bodies (Plate 8, fig. 2) those of alter- nate layers crossing the others almost at right angles. In their formation no points of especial interest have appeared. As usual several cells take part in the process, and after functioning appear to shrink back into the hypodermal layer without retaining any visible connection with the spicule. The average length of fully developed spines from the sides of the body about the middle of the animal measure from 0.4 to 0.48 mm. The anterior pedal gland is an organ of moderate size occupying the major portion of the visceral cavity between the level of the mid section of the atrial cavity and the posterior border of the brain. The component pyriform cells, measuring from 0.017 to 0.0216 mm. in greatest length, are early filled with a stringy, violet colored secretion, after treatment with Delafield’s haematoxylin, which becomes finely granular in the later stages of its development. Each cell is continuous, as usual, with a delicate ductule which opens by an inter- cellular channel to the exterior. 224 DORYMENIA PERONEOPSIS. The outlet of the anterior pedal gland, when viewed laterally from the mid line, presents the appearance of a fairly long, narrow slit (Plate 7, fig. 5). In cross sections this slit is seen to expand laterally into a well-developed chamber with corrugated walls composed of columnar cells furnished with a heavy coat of cilia. The folds of the dorsal wall merge into a single median fold which more posteriorly becomes continuous with the foot. Everywhere through- out this fold, and over the entire surface of each crypt, the secretion of the anterior pedal gland makes its exit in the form of a finely granular, almost homogeneous substance with a strong affinity for haematoxylin dyes. The posterior pedal gland is moderately developed, and in the form of a slender rod of cells on each side of the mid line continues from the anterior pedal gland to the cloacal opening. The foot itself presents the usual wedge- shaped form, accompanied on each side by a non-spiculose hypodermal layer, both structures serving as the outlet for the secretion of the gland. The atrial opening, holding the customary subtérminal position, leads into a cavity possessing essentially the same relations as in various other species of neomenians. ‘Two horseshoe-shaped ridges, an internal and external, sur- round the cirrose area and after uniting posteriorly gradually shade into the folds of the pharynx. The component cells are slender, columnar elements moderately ciliated and are supported by a framework of muscle and connective- tissue fibres penetrated by slender blood sinuses and a few nerve bundles from the adjacent ganglionic mass. The cirri are prominent, finger-shaped struc- tures, arising from separate bases or united into groups of from two to four, and are composed of low columnar or cubical cells ranged about a slender cavity too small to admit of the entrance of blood corpuscles though containing deli- cate fibres of unknown character. A short distance posterior to the cirrose area the pharynx arises as a circu- lar tube of somewhat smaller diameter than that of the atrial cavity. At the outset its walls are fashioned into numerous longitudinal folds, especially along its lateral and dorsal surfaces. Approximately halfway back to the radula a heavy fold develops in the dorsal wall, and sections show it to be packed with innumerable lobules of what probably is the dorsal salivary gland. These lobules are cirrus-like masses composed of relatively small cells whose secretion stains a light pink after treatment with haematoxylin. Slender ductules from the component cells make their way through the adjacent muscle fibres and open by intercellular pores throughout the entire surface of the dorsal fold. The pharynx beneath the outlet of the dorsal fold is ventrally produced DORYMENIA PERONEOPSIS. 225 into a deep pocket, which posteriorly develops a slit-like cavity functioning as the outlet of the ventral salivary glands. In the mid line between the salivary ducts the epithelium becomes more columnar and may function as a subradular organ, as in Proneomenia hawatiensis for example. A commissure from the labiobuccal system passes in close proximity to it, but beyond this fact there is nothing to indicate its function. The ventral salivary glands are long, tubu- _lar organs, about one eighth the diameter of the body in thickness, and contain a lumen of unusually large size. The component cells, on the other hand, are relatively small and are densely packed with granules staining a dull pink after treatment with haematoxylin. The mid section of that portion of the pharynx posterior to the outlet of the dorsal salivary gland is the seat of the radula whose musculature and relations to other organs are unique in this genus. In common with other Glossophora the teeth are developed by clearly differentiated odontoblasts on a well-defined basement membrane, and as far as can be judged from a careful examination of cross sections number nine in each row. There are probably not less than twenty-five rows. The median tooth is triangular with a base whose length is approximately twice the height. Each admedian tooth is likewise triangular with the base not over half that of the foregoing but with a height fully as great. The lateral teeth are more spike-like, and like the admedian are slightly twisted. These data, however, are largely derived from the study of fragments and are doubtless incomplete. Beyond the narrow section where the fully developed teeth are fully exposed in the pharynx the remaining portion, comprising fully half the total length of the lingual ribbon, is bent backward and occupies the cavity of a large diverti- culum of the pharynx ventral to the radula proper (Plate 7, fig. 5). As noted presently this ventral sac is operated by several heavy muscles, whose relations have been determined with a fair degree of accuracy, though their mode of operation is not wholly clear. The position of this entire radular system in the present specimen indicates that it is in a contracted state, and it is probable that in the act of feeding the pharyngeal tube is not only widened considerably, but that the radula is projected anteriorly borne on the summit of the ventral diverticulum. This will become more intelligible after the muscles concerned have been described. The entire outer surface of the ventral diverticulum is in contact with a sheath of circular muscles of great thickness especially in the mid section (Plate 7, fig. 4,6). This sheath is pierced at the blind end of the diverticulum by two 226 DORYMENIA PERONEOPSIS. well-defined muscle bundles (Plate 7, fig. 6) which are attached to its wall and on the other hand are fastened to the two pairs of globular radular supports located beneath the posterior end of the radular sac. The blind extremities of the radula and the ventral diverticulum are thus closely bound together. It is probable therefore that the contraction of the circular muscle sheath results in a lessened diameter and an increased length of the diverticulum whose free extremity is thus pushed forward into the anterior section of the pharynx. This process is doubtless aided by the action of two pairs of muscles that appear to act as protractors. The more conspicuous of these is attached to the globular radular supports and extends forward, expanding in a fan-like fashion, before becoming inserted in the radular sac (close to the exposed teeth), the adjacent wall of the pharynx and to a greater extent in the anterior end of the ventral diverticulum. The second pair of protractors is relatively small, and from their insertion in the circular coat of the mid section of the diverticulum extend forward and downward to become attached to the ventral wall of the small cul-de-sac into which the ducts of the ventral salivary glands open. The retractors are likewise four in number. The first and most posterior pair is attached to the median radular supports and extending posteriorly and ventrally unites with the body wall. The more ventral pair is attached to the ventral diverticulum, close to the insertion of the ventral protractors, and after pursuing a ventral and backward course also fuses with the somatic musculature. The stomach-intestine presents no especial features of interest beyond what is sufficiently illustrated in the reconstructions of the anterior and pos- terior ends of the body (Plate 7, fig. 5, 7). A well-developed, non-sacculated anterior coecum extends from the termination of the pharynx to the brain region. The main gut is provided with the customary ciliated tract adjacent to the gonad, and elsewhere is furnished with high columnar cells charged with a granular secretion which is periodically discharged by constricting off the distal extremities of the cells. In the region of the pericardial cavity the sacculations disappear, the gut becomes approximately circular in outline and as a relatively wide canal opens into the cloacal chamber. | The pericardial cavity is a comparatively large space typically located in the posterior end of the body. The heart likewise is well developed (Plate 7, fig. 7), and is fashioned into two chambers communicating by a narrow pore apparently guarded by a valve. The posterior division, presumably the auricle, is comparatively thin-walled, distinctly less so than the anterior division, and both are spanned by delicate trabecular muscles, DORYMENIA PERONEOPSIS. 227 The vessels to the gonad, and the communication of the dorsal vessel or aorta with the channels in the head region are of the usual type. These last named sinuses are relatively small yet can readily be followed past the anterior pedal gland and about the buccal wall to a small ventral median sinus originating immediately posterior to the outlet of the anterior pedal gland. Above the forward end of the foot this median sinus is of more than usual width, but throughout its entire extent to the posterior end of the body it communicates here and there with the overlying visceral sinus. As the hinder end of the animal is approached these two blood spaces unite at more frequent intervals and finally fuse completely. The single channel thus formed communicates with the posterior end of the heart. No distinet branchial apparatus exists in this species. The walls of the cloacal chamber are smooth and ciliated, and as they are in intimate contact with the visceral sinus they may function in the respiratory process. The present specimen, although of considerable size, is sexually immature, and it is altogether possible that during the breeding season the general appear- ance of the accessory reproductive apparatus may be considerably altered, though the configuration of the component organs will probably remain about as that shown in the reconstruction (Plate 7, fig. 7). The gonad exists in the form of two slender tubes ending blindly anteriorly and separated widely by the dorsal aorta. Posteriorly they enter the pericardium, whose size and general appearance in sections are similar to what has been found to exist in Strophomenia. The gonoducts, in the form of slender tubes, arise from the posterior border of the pericardial cavity and extending downward and forward join the shell gland or ventral section. The dorsal section of each coelomoduct is a tube of approximately even calibre throughout (Plate 8, fig. 6), and is composed of cubical cells, possibly ciliated and certainly without any signs of glandular activity. The ventral section is of somewhat larger size, and is likewise formed of cubical cells in which there are very small quantities of a darkly staining secretion. At the junction of the dorsal and ventral sections a small sacculation may represent the char- acteristic seminal receptacle though it contains no spermatozoa. Ventral to the coelomoducts are two diverticula each of which communi- cates with the cloacal cavity and probably contains a spicule though the process of decalcification has wiped away all traces. Retractor muscles attach to the outer surface of the blind end and on the other hand extend anteriorly to become inserted in the body wall. Protractors likewise attach themselves to the sheath, 228 DORYMENIA PERONEOPSIS. though more posteriorly, and following along the walls of the sheath are inserted in the forward border of the cloacal chamber wall. Owing to the fact that the sheath surrounding the larger nerve bundles stains with unusual clearness, considerable care has been taken to trace out the more important trunks. The brain, holding the usual position dorsal to the pharynx, is more than usually globular and lacks the customary groove in the region of the commissure connecting the nerve cells of the two sides. From its anterior face the usual three pairs of nerves take their origin, and after connecting immediately with small, spherical ganglia are distributed to other ganglionic masses attached to the external surface of the atrial wall. From the sides of the brain the lateral, pedal, and labiobuccal connectives originate as separate, distinct roots. At the point of union of each lateral connective with the ganglion there is a well-defined enlargement which ante- riorly gives rise to a strong fibre passing forward and closely applied to the somatic musculature. In the neighborhood of the atrium and atrial ridges it branches repeatedly and the resulting subdivisions give evidence, in some instances at least, of uniting with ganglia in the neighborhood of the cirri. From this same anterior enlargement a small nerve arises and passing ventrally becomes lost in the region of the outlet of the anterior pedal gland. The anterior end of each pedal ganglion is likewise developed into a globular enlargement from which one or two nerves arise that soon become lost in the surrounding muscle tissue. It may be mentioned that the lateral and pedal connectives are each united by a small connective in close proximity to the brain. The labiobuceal ganglia are ellipsoidal bodies occupying a space between the muscles of the radula and the lateral portions of the overhanging stomach- intestine. There is developed, from the anterior surface of each, a strong nerve, the labiobuceal connective, which in the contracted state of the present speci- men is considerably twisted throughout its course to the brain. About one fourth of the distance from the ganglion to the brain each of these connectives enlarges considerably, though apparently without the presence of ganglion cells, and gives rise to three distinct nerves. One of these pursues a course anteriorly, and imbedded in the muscles of the gut unites with a corresponding branch from the opposite side, thus forming a commissure. Throughout its course at least three pairs of small nerves are developed which often branch repeatedly before being lost to view in the surrounding muscles. The other two nerves springing from the labiobuccal connective pass ventrally where one becomes lost when lateral to the outlet of the ventral salivary gland. The STROPHOMENIA AGASSIZI. 229 other passes beneath the duct and forms a commissure. No signs of ganglia exist along this ventral commissure, and accordingly there are no indications that it forms a subradular system as might be suspected from its position. The labiobuccal ganglia are also united by the usual commissure crossing over the dorsal surface of the radula. In the posterior end of the body both the lateral and pedal ganglia terminate in well-defined enlargements which are united in typical fashion by connectives. A few small nerves from the pedal enlargements extend posteriorly and become lost in the somatic musculature. In addition to the suprarectal commissure the posterior end of each lateral ganglion gives rise to two main nerve bundles whose ultimate ramifications form a plexus over a considerable portion of the posterior end of the animal. Only a small portion of this network has been followed in detail, but there are indications that it exists beneath the somatic musculature, behind the level of the posterior end of the pericardium. Small ganglionic masses occur at the nodal points. It may be added that this net extends across the mid-dorsal line, at least in the neighborhood of the dorso- terminal sense organ, thus forming a species of suprarectal commissure though of a diffuse type. A careful examination of the nerves innervating the dorso- terminal sense organ shows that they have their origin in the more anterior of the dorsal commissures, which accordingly corresponds to the usual one in neomenians generally. Simroth mentions two dorsal commissures in Pro- neomenia but as no figure is given a further comparison is not possible. Strophomenia agassizi, sp. nov. Five specimens of this species were dredged southeast of Nantucket, Mass. (Sta. 2046A) at a depth of 407 fms., and four additional specimens were taken to the northeast of this point (Sta. 2528A) in water 677 fms. deep. In every case the animal was coiled about the branches of an aleyonarian coral, Acantho- gorgia armata. Two of the specimens from Sta. 2046A are in the act of copula- tion, the posterior ends being applied to each other so that the cloacal openings are in communication with each other (Plate 1, fig. 1). In alcohol the color is light brownish yellow. The largest specimen is 37 mm. in length and 1.5 mm. in average diameter, while the smallest is 22 mm. long and 1.1 mm. in thickness. In the only specimen sectioned two dorso-terminal sense organs are present (see section on nervous system). The cuticle surrounding the body measures, along the sides of the animal, approximately 0.19 mm.; along the dorsal side it is slightly thicker. 230 STROPHOMENIA AGASSIZI. Innumerable spicules are buried beneath its surface and form, roughly, seven or eight layers. The greater number of spines, hollow, needle-like, slightly curved structures rounded at both ends (Plate 1, fig. 3) form two series crossing about at right angles. Among these are many radially directed spicules, likewise hollow but with the basal extremity truncated or slightly rounded (Plate 1, fig. 3). The hypodermal cells are small and their boundaries indistinct, yet there are many examples of spicule formation where several cells may be seen attached to the base of the spine, and again many cases where but one cell has been detected attached to the radially directed spicules. In examples of the first class the matrix cells lose their connection when they become non-functional. The papillae (Plate 1, fig. 2), each attached to the hypodermis by a rela- tively thick stalk, are numerous and are crowded together at the surface of the body. In the expanded portion are a number of nuclei, twenty is the average of six examples, and with these there are frequently darkly staining globular masses that appear to be some glandular product. The anterior pedal gland, while extending from the brain to an even greater distance beyond the outlet posteriorly, is in reality not a voluminous structure as the cells are not compactly arranged nor do they fill to any great extent the visceral cavity. Owing to the fact that the secretion stains an inky hue in haematoxylin nothing has been determined regarding the finer structure of this organ, which otherwise presents no especially noteworthy features. The outlet of the anterior pedal gland (Plate 1, fig. 4), though not espe- cially voluminous, is of considerable length. Its walls, as usual, are ciliated but otherwise are unmodified save that they are produced into a fold, on ° each side of the cavity, that becomes gradually lower and finally disappears posteriorly. Halfway back the foot appears as a low ridge in the mid line, that soon reaches its average size, and posteriorly is continuous with the cloacal chamber. The posterior pedal gland differs from the anterior merely in size, and otherwise requires no further description beyond the statement that it disappears an unusually long distance from the posterior end of the foot (in the specimen studied, opposite the posterior end of the pericardium). The atrial opening, subterminal in position, leads into a relatively large cavity provided, in typical fashion, with ridges and cirri. Of the former the innermost is considerably larger though the cells composing it are on the average of less height than those of the inner ridge. As may be seen (Plate 1, fig. 4) STROPHOMENIA AGASSIZI. 231 these folds unite posteriorly and bound the cirri, relatively thick, finger-shaped processes that appear, with very few exceptions, to be attached separately to the atrial wall. What is probably the true mouth opening occurs in the postero-lateral atrial wall and leads into the long pharynx characteristic of Strophomenia. At the outset the walls of the pharyngeal tube are relatively thin, numerous radial muscles attach it to the body wall, its epithelial lining is developed into many low folds and a very few gland cells are scattered over its surface. Passing backward one third of its length it will be found that the radial muscles dis- appear, the circular and longitudinal muscles become more abundant, the tube grows more circular and multitudes of pyriform gland cells, arranged in lobules, appear upon its outer surface. This state of affairs continues to the stomach-intestine. A radula is present, but it is of small size and stains so faintly that even under high magnification it is difficult to interpret its true form. It contains a small number of transverse rows, appears to belong to the distichous type, and in one section there are evidences that each tooth is comb-like with five sharply pointed cusps. As in other members of the genus there are two, long tubular ventral sali- vary glands opening on each side of the radula into a shallow depression in the pharyngeal wall. Each of these organs consists of two divisions (a) aslender duct leading from the pharynx to the distal end of the gland where it ends blindly, and with the exception of a small division in close proximity to its outlet this canal is covered by (b) a sheath of gland cells which probably pour their secretion through intercellular channels into the central canal. While the transition from the pharyngeal epithelium to that of the stomach- intestine is abrupt the muscular coat about the pharynx passes for a consider- able distance over the ventral surface of the stomach-intestine proper and the anterior intestinal coecum. This last named organ is highly developed, pos- sesses digestive cells and lateral pouches like those of the succeeding sections of the gut and extends anteriorly as far as the forward border of the atrium. Throughout the body the character of the mid-gut is constant, the pouches especially being remarkably regular. Ventral to the gonad the digestive cells are replaced by low, cubical ciliated elements that beneath the pericardium form an extensive tract. As the gut narrows this tract grows circular as it forces its way between the halves of the shell gland and the ciliated elements approach the mid-ventral line of the gut to become the only lining of the rectum. Near its 232 STROPHOMENIA AGASSIZI. outer opening the intestine becomes almost square in cross section (Plate 2, fig. 7) and opens with the shell gland into the cloacal chamber. The heart is a long tubular organ that near its posterior end falls into two divisions as in a few other species of this genus. The aorta, as it springs from the forward end of the heart, is of large size but as it courses anteriorly it assumes normal proportions, and the route it follows and that of the blood after leaving the head region, are typical in all essential particulars, save that the visceral cavity is of more than usual proportions owing to the absence of the usual amount of connective tissue. In the midst of connective tissue and muscle fibres tracing out the dis- tribution of the smaller nerves is an arduous and time consuming task but when these last named elements are free in the visceral cavity they may be fol- lowed with exceptional facility and their study has yielded some interesting results. The brain (Plate 1, fig. 4) not only holds the usual position but gives rise to the customary three pairs of nerves leading to ganglia about the bases of the cirri and in addition originates the lateral, pedal, and labiobuccal con- nectives. Those passing to the cirri are in nowise peculiar and the same is true for the connectives save that they are more than usually separated as they pass out from the brain, the lateral and pedal laterally and the labiobuccal close to the mid line near the posterior border of the brain. The lateral ganglia are of approximately even calibre, showing no especial enlargement where they unite with the connective from the brain. In the case of the ventral cords, on the other hand, such a swelling occurs and marks the point from which the first latero-pedal connective takes its rise. Beyond this point connectives and ventral commissures occur with considerable regularity, the latter being usually of slightly larger diameter. In practically every case in the anterior and posterior ends of the body (the middle portion of the body was not sectioned) delicate branches pass from the connectives to the body wall where they disappear from view among the somatic muscles. Other nerves, usually of larger size, originate from the lateral cords and may pass dorsally or ventrally, but in every case they become lost in the body wall without being continuous across the mid line. The labiobuccal connectives, lightly resting against the sides of the pharynx, pursue their course to the neighborhood of the radula where they join the labio- buceal ganglia united by the usual heavy commissure passing ventral to the pharynx and dorsal to the radula. Anterior to these ganglia an enlargement occurs in each connective and from them two connectives arise, one situated STROPHOMENIA AGASSIZI. 233 beneath the pharynx the other imbedded in the diffuse salivary glands passes dorsal to the gut. At one or two points between this region and the brain nerves arise from the connectives and form seemingly either dorsal commissures or a very delicate network which it is impossible to trace from sections. In the posterior end of the body the lateral and ventral ganglia continue to hold the usual positions and to be united by connectives and commissures at fairly regular intervals. A short distance behind the level of the posterior end of the pericardium both of these ganglionic cords enlarge considerably and are united by one especially heavy pair of connectives as may be seen (Plate 1, fig. 5). Slghtly in front of this another pair occurs of about half the diameter of the one behind. The remainder in this region present the usual slender appearance and are sometimes difficult to follow. In many cases they give off delicate fibres that pass to the body wall where they probably supply sense organs or are distributed to the somatic muscles. The suprarectal commissure is long (Plate 2, fig. 6), not especially heavy and gives rise to a few very small nerves that pass at once to the rectal wall where they spread out fan-like and disappear from view among the muscle fibres. Here and there are indications of a nervous network over the surface of the rectum but from sections: neither its origin nor its configuration has been determined. The ventral commissures in the posterior end of the body are without excep- tion of large size and are readily followed. In a few cases fibres have been seen to leave them and pass into the ventral body wall, especially lateral to the ventral furrow; and in one specimen (Plate 1, fig. 5), one such nerve unites with the ventral ganglion and originates a fibre, in the nature of a connective that follows the body wall and resting upon the accessory reproductive organs, passes dorsally and unites with the lateral cord. The pedal cords, behind the last connective, give rise to a very few nerves that disappear at once in the mass of muscle surrounding the cloacal wall at this point. The lateral ganglia likewise are continued behind the last connective as a heavy cord apparently distributed in large measure to the cloacal wall though some branches may pass to the neighboring body wall. As in the case of Proneomenia vagans this species is in possession of two dorso-terminal sense organs (Plate 1, fig. 5). Both present the same as well as the customary appearance, but their innervation is unique. In Proneomenia hawaviensis a nerve leaves the exact centre of the suprarectal commissure and pursuing its course along the mid line passes into the base of the single terminal 234 STROPHOMENIA AGASSIZI. sense organ. In the present case a nerve arises from the suprarectal commissure. on each side of the body near each lateral ganglion. These two nerves extend dorsally then posteriorly and a short distance in front of the more anterior sense organ they unite to form a single fibre that may be traced, without especial difficulty to the base of the organ. The nerve to the posterior organ arises from the lateral cord, on the left side only, behind the suprarectal commissure and making its way across the visceral cavity it finally comes into close contact with the body wall yet may be distinctly followed to the organ in question. Whether innervation from one nerve or two is the more primitive, it is impossible to say at present, but it certainly appears to be a fact that such an asymmetrical innervation, as in the case of the posterior organ, indicates that it is either an abnormality or is from a phylogenetic standpoint a late formation. While the presence of copulatory spines and seminal receptacles, filled with sperms, have led to the conviction that copulation takes place among the neo- menians no actual example has been noted up to the present time. Definite proof, however, is now at hand, for two individuals from Sta. 2046 were in the act of copulating (Plate 1, fig. 1). Their posterior extremities were in contact so that the cloacal openings were opposite each other, thus placing the two cham- bers in direct communication with each other, and a whitish secretion appears to have aided the attachment in life, or at all events to have prevented the loss of sperms during the copulatory process. It was thought best not to destroy these specimens so that nothing is known regarding the course pursued by the sperms on their way to the seminal receptacles nor of the appearance of the organs most intimately concerned in the process. In the sectioned specimen several eggs are present in the pericardial cavity and other indications suggest that the egg-laying season was at its height. Fully formed ova are in the gonad along with multitudes of sperms in all stages of development, and the canals leading from the pericardial cavity are of very large size. In common with the other species of the genus the pericardium is spacious and the coelomoducts, leaving its postero-lateral borders, are of unusu- ally large calibre. As may be seen (Plate 1, fig. 5) the dorsal limb of each canal is externally a simple unmodified tube uniting with the shell gland close to its anterior extremity. In close proximity to the pericardial opening there is a small, short ridge of cells of larger size than those adjoining and the nuclei are correspondingly large and the cilia longer. This soon disappears and the cells throughout the dorsal limb are lightly staining, cubical, or low columnar, ciliated, and possess NIERSTRASSIA FRAGILE. 235 indistinct cell boundaries. The ventral section, on the other hand consists of high, ciliated elements filled with a darkly staining, granular secretion. Close to the outlet and extending a short distance along the mid-ventral line of the rectum the cells become lower and the secretion changes, in a fully developed con- dition, to a granular, highly refractive, yellowish product not effected by haema- toxylin. The cells of the seminal receptacles are columnar, and the secretion, consisting of droplets of varying size, is of a lavendar tint. Multitudes of sperms are crowded against their free surfaces and in many cases have produced a vacuolation and even disintegration so that spermatozoa may enter such cells. Nierstrassia fragile, sp. nov. Eleven specimens of this species, all unattached, were dredged off the coast _ of New Jersey (Sta. 2588A) at a depth of 479 fms. where the bottom consisted of green mud. The smallest measures 2.5 mm. by 0.75 mm., while the largest is 5 mm. long by 1 mm., the greatest thickness. This material, very well pre- served, was taken in 1885, and for over twenty years remained in an ordinary cork stoppered bottle so that its yellowish brown tint is probably due to tannin. A silky layer of delicate spicules, rather easily dislodged, gives the animal a light frosted appearance. While the spines adjacent to the ventral furrow over- arch it the greater number are directed diagonally away from the furrow in a postero-dorsal direction, those along the mid-dorsal line meeting each other without, however, forming any marked keel. While a dorso-terminal sense organ appears to be present the obliquity of the sections (the posterior end of the longitudinally sectioned specimen was lacking) and a number of small folds in the hypodermis renders it difficult to definitely decide this point. In some respects the hypodermis, cuticle, and single layer of spines show a striking resemblance to the same elements in species belonging to Chaetoderma. The spicules show this most clearly, having the characteristic leaf-like form with a longitudinal keel. By far the greater number of hypodermal cells (Plate 6, fig. 2) are unmodified more or less cubical elements. In some instances a small, compact mass, attached to the base of some of the spines, may represent a degenerate spicule-matrix cell, but in most instances these have disappeared. At rare intervals slender cells, possibly sensory, occur among the larger hypo- dermal elements but no especial nerve supply has been detected. No structures corresponding to papillae are present, the general appearance of hypodermis and cuticle over the body being represented in the drawing (Plate 6, fig. 2). The outlet of the anterior pedal gland consists of a simple, hemispherical 236 NIERSTRASSIA FRAGILE. depression provided with long cilia (Plate 6, fig. 8), lying behind the mouth or atrial opening from which it appears in surface views to be separated by a very narrow cuticular bridge continuous with the general investment of the body. The gland itself, occupying the visceral cavity halfway up the sides of the body, extends from the anterior end of the animal to a point about level with the posterior end of the radula. The cells composing it are pyriform, filled with a darkly staining secretion, among which are larger, lavendar colored masses, apparently consisting of more than one cell. This may be one stage of glandular activity though it appears to be a different secretion. The foot (Plate 7, fig. 1) arises immediately behind the outlet of the anterior gland in the form of a single fold that, accompanied by the usual pyriform gland cells, extends to a point a short distance in front of the cloacal opening. The mouth opening is, as usual, subterminal in position (Plate 6, fig. 3), and in some specimens is reduced to a very small pore scarcely larger than in some species of Chaetoderma, while in other cases it is more or less open. In any event it leads into a small chamber holding the position usually occupied by the atrium, but it is somewhat doubtful if it should be interpreted as such. So far as can be detected after careful examination there is no trace whatever of any cirri or atrial ridges, and as the cells lining this space are in large measure at least clearly modifications of those present in the undoubted oesophagus or pharynx it would appear that the atrial chamber is wholly wanting. On the other hand it is important to note that the usual nerves passing out from the forward surface of the brain connect with masses of ganglion cells, probably the homologue of those about the bases of the cirri in other species, and from these masses fibres may be distinctly followed to the bases of some of the cells” lining the cavity in question. According to the nerve supply the atrium exists, but judging from cell characters alone it is absent. On which of these criteria dependence is to be placed it is difficult to say though personally I am inclined to take the first named position. As may be seen (Plate 6, fig. 9) the cells of this first section of the canal are of two, possibly three distinct varieties, club-shaped elements, usually long and slender especially on the dorsal surface, and thread-like supporting or sense cells. In the first type the distal portion is almost wholly occupied in pre- served material by a vacuole, the nucleus occupying the basal section. The supporting or sensory cells likewise usually possess basal nuclei, but especially near the antero-dorsal boundary of the cavity some are more distally situated. Often the free surfaces of all of these cells are covered with a yellowish brown, NIERSTRASSIA FRAGILE. 237 homogeneous substance which extends between the cells far down toward their bases. The origin of this substance could not be determined. Neglecting differences in size these types of cells form the epithelial lining as far as the opening into the stomach-intestine. As far back as the stomach-intestine, the digestive tract is surrounded by a layer of circular muscles among which numerous radial strands occur, extend- ing to the body wall. Among these elements, from the anterior end of the animal to a point a short distance behind the brain, numerous solitary, pyri- form gland cells occur and open by intercellular pores into the digestive tract. In some instances the secretion is abundant, the small spherical granules staining intensely, but especially behind the brain the granules become relatively smaller in size and amount, vacuoles occupying a considerable portion of the cell. A radula, of the distichous type, is present, and so far as may be determined from sections comprises 15 rows. The form of each tooth is represented in Plate 2, fig. 10, while the radula sac and odontoblasts are faintly shown in Plate 6, fig. 3. In this last figure a small ridge, composed of slender cells, occupies the position of the subradular organ, but while it presents the appearance of a sensory area no definite ganglia have been found in connection with it. Paired ventral salivary glands are present in the form of small, globular sacs (Plate 6, fig. 3) that on one side at least develop small lobes. One of these is unusually swollen in the longitudinal section and appears to contain a few parasites. The cells are relatively small, vacuolated and in some instances contain a finely granular secretion. The stomach-intestine exhibits the usual sacculated form and relations to other organs; and the glandular epithelium is not essentially different from that of other neomenians. In the longitudinal sections large numbers of some parasitic protozoan are present in various stages of development and may be responsible for the unusual size of some of the epithelial cells. Posteriorly the canal narrows, becomes laterally compressed as it passes between the limbs of the shell gland and then in the form of a very slender canal makes its exit into the cloacal chamber. As these animals came in unattached with no food in the digestive tract there is nothing to indicate the nature of their habitat. Owing to the abundance of connective tissue in the visceral cavity it is very difficult to accurately trace the course of the blood, but in its main features the circulatory system is typical. The heart, much contracted, is a tubular structure (Plate 6, fig. 5) in two divisions possibly separated by a valve though this was not clearly demonstrated, and throughout much of its extent it is free 238 NIERSTRASSIA FRAGILE. from the pericardial wall. In the first part of its course the aorta is of rela- tively large size, but later becomes greatly compressed and difficult to follow between the halves of the gonad. In the head region it loses its walls, the blood entering sinuses that apparently have the usual relations. As in the case of the circulatory system the abundance of connective tissue masks the course of the smaller trunks of the nervous system so that the broader features only have been worked out. The brain presents the usual characters, giving off laterally the pedal, lateral, and labiobuccal connectives, and anteriorly, nerves which at once attach to groups of ganglion cells. As noted in connection with the digestive tract these last named ganglia probably correspond to those located about the bases of the cirri in other neomenians, and in the present species they send off fibres that pass to the anterior section of the alimentary canal whether it be an atrium or not. The pedal, lateral, and labiobuceal ganglia and their connectives are normally placed, and as many points throughout the body the first two are united by the usual commissures and connectives. In the case of the labiobuccal ganglia the commissure was fol- lowed posterior to the radula, but the abundance of muscle and connective- tissue fibres makes it impossible to determine if there be other commissures or a subradular system. In the posterior end of the body the pedal ganglia gradually diminish in size and finally disappear from view. Almost to the end of their course they con- tinue to be united by connectives with the lateral ganglia, but these show no unusual development and the pedal ganglia lack the posterior enlargements characteristic of some neomenians. The lateral ganglia, on the other hand, terminate in globular masses, in the neighborhood of the pericardial-coelomoduct openings, that are united by a commissure passing dorsal to the rectum where the latter unites with the more expanded section of the gut. The paired gonad, containing both ova and spermatozoa, extends as usual, from about the level of the anterior end of the foot to the pericardium. In both specimens the ova appear to be somewhat immature while the spermatozoa are in all stages of development and especially in the mid section of the gland are so numerous that they distend its walls to a considerable degree. Posteriorly the halves of the organ gradually narrow, diverge slightly and communicate with the small pericardium. The opening of each gonoduct is borne on the summit of a small papilla (Plate 6, fig. 5) on the postero-lateral walls of the pericardium, and leads into a tube which passes laterally and then posteriorly to unite with the ventral NIERSTRASSIA FRAGILE. 239 section, or shell gland. For a distance equal to about one fourth of its length the dorsal half of the gonoduct is a simple, very slender tube but at this point it enlarges somewhat and develops a short pouch-like diverticulum composed of cubical, ciliated cells without any special signs of glandular activity. Contin- uing its way forward for a short distance another diverticulum, finger-shaped in appearance, arises and on both sides of the body is directed backward and down- ward. In the usual position for the seminal receptacle a very slender tube appears, on each side of the body, that is directed anteriorly for a short distance and terminates in a slight enlargement. These three pairs of diverticula are empty and accordingly afford no clue as regards their possible function. The cells of this dorsal section of the gonoduct are all more or less cubical, ciliated but without ridges or other modifications. The shell gland, (Plate 6, fig. 5), composed of the usual long and slender cells, occupies the usual position. Posteriorly the halves unite to form a single median section with folded walls, but the union is unusually near the opening into the cloaca. Lying ventral to this portion of the reproductive system there are two bundles of spicules, five in each group, that are developed and concealed in two diverticula, arising not from the cloaca, as is usual, but from the undivided ‘section of the shell gland. Each of these spicules is rod-shaped, apparently straight with the base rounded and the distal extremity pointed, and during the act of copulation is probably protruded through the reproductive opening into the cloaca. As may be seen (Plate 6, fig. 7), the median section of the shell gland and the adjoining undivided portions together with the bundles of spicules are imbedded in a relatively large diverticulum, rich in muscles, that in life may doubtless be protruded beyond the opening of the cloaca. In reality the cloacal chamber is comparatively large but usually it is almost completely filled by the great diverticulum bearing at its tip the reproductive opening. In some specimens it is partially closed and in other cases its margins are widely expanded. Throughout the greater part its walls are smooth and unmodified but beyond the reproductive and anal openings five or six low ridges (Plate 6, fig. 4) make their appearance, and while they may be respiratory they certainly possess some additional unknown function since the pyriform cells are highly glandular and their distal extremities are filled with a colorless secre- tion after treatment with haematoxylin. In the neighborhood of the anal open- ing additional groups of cells occur, and in some instances appear to open into the cloacal cavity, but the supposed ductules may in reality be delicate strands of connective tissue. 240 EMBRYOLOGY. EMBRYOLOGY. In the report of the Solenogastres of the North Pacific a species of neome- nian, Halomenia gravida, was described that carried in the spaces between the branchial folds of the cloacal chamber twenty-five embryos in various stages of development. As the single specimen was sectioned before these were dis- covered it is obvious that the following account of the early growth of this species has been based solely on sections and reconstructions. It may be said, however, that unusual care has been exercised in their study, and while certain details, to be noted later, are doubtless faulty, the broader features are fairly clear and intelligible. In the earliest stage two distinct nuclei are present (Plate 13, fig. 5) together with four other bodies that may be nuclei, though appearances (Plate 13, fig. 10), suggest that more probably they are unusually large yolk granules super- ficially coated with a dense layer of protoplasm or some glandular secretion. The egg measures at this time 0.32 mm., assuming that a slight elongation is due to the pressure of the neighboring branchial folds. A single polar body (Plate 14, fig. 10) is attached, and it is a peculiar fact that in every case where these cells have been seen there is never more than one. A delicate membrane, cuticular in appearance, surrounds the egg, and where it has remained undis- turbed it is closely adherent to the yolk granules beneath. At other points on the surface it may be thrown into folds, but as these lack regularity and any signs whatever of nuclei, it is probably a vitelline membrane and not a chorion, though this last named structure occurs normally in the Chitons and several Solenogastres. Furthermore in developing ova within the reproductive gland of Halomenia there are no traces, even in early stages, of a chorion though the cuticular membrane just described is well defined. Immediately within the membrane, and adjacent to the polar body, a clearly defined nucleus exists closely surrounded by yolk with the exception of an excentrically placed archi- plasm mass. It is probably the female pronucleus, while the remaining one of similar appearance is the sperm nucleus. In the only other early stage two undoubted nuclei hold the same relative positions, and again there are four bodies that as before may be either nuclei or yolk granules. It is worthy of note that one or two similar bodies may occur in fairly advanced embryos, and on the other hand none of these bodies has ever been detected in mature ova within the gonad. Furthermore in these early stages no cleavage planes have been noted. EMBRYOLOGY. 241 In the next stage segmentation has commenced, resulting in twenty-eight cells (Plate 13, fig. 13). These show no differentiation into micromeres and macromeres, and so far as may be judged from sections the inequality of size noticed among the cells is irregular and not confined to a definite hemisphere. All of the cells are closely crowded together and consequently no sign of a blasto- cele exists (Plate 14, fig. 11). These facts together with the absence of polar bodies in this particular embryo and the uniform distribution of yolk renders it impossible to distinguish the principal axes. In the succeeding stage (Plate 13, fig. 6) approximately one hundred nuclei are present and an elongation of the larva defines the principal axis. There are, however, no definite signs of blastopore or blastocele, and the size and arrangement of the cells does not certainly define the dorsal and ventral surfaces. Sections (Plate 14, fig. 8) show that at this stage several cells are wholly enclosed within the partially formed external layer whose component cells are of unequal size and irregular arrangement. In a few cases the position of karyokinetic spindles indicates that the internal cells are formed by tangential divisions, a species of delamination, while other cleavages at right amen to these further increase the number of cells on the exterior. In advance it may be said that in the larvae of this species test cells partially enclose the body as Pruvot (’90) has shown to be the case in Myzomenia banyu- lensis. While no definite reliance can be placed on reconstructions for determin- ing the exact shape and arrangement of cells it nevertheless appears fairly well established that in the stage under consideration the external cells are not so definitely arranged as in the later stages, and even there they are not so diagrammatically placed as in Pruvot’s figures. In the next stage (Plate 13, fig. 12) a single polar body remains in hoe held by the vitelline membrane, and the animal pole is thus determined, together with the probable point of origin of the cerebral ganglia though these last named structures have not as yet put in an appearance. The differentiation of the test cells has become evident to a certain extent, although their exact limits have not been determined from reconstructions. Granted that the polar body has not shifted from its point of origin, it does not appear to mark the centre of the test cells which may be seen (Plate 14, fig. 1) to extend over nearly the entire dorsal surface. Furthermore while the test cells may form rows or definite bands about the embryo, reconstructions give no clear evidence of this fact up to the present point in the development. In sections the cells, exclusive of those forming the test, that is those destined 242 EMBRYOLOGY. to develop into the fully formed animal, are much more numerous than before, and are as yet without signs of differentiation into the fundaments of the various organs. This statement may perhaps be modified in one particular, for on the ventral side immediately posterior to the large test cells is a group of several elongated cells extending from the surface to a considerable distance into the interior. Their external position is marked by a shallow depression (Plate 14, fig. 9), and appearances suggest that this is the region of the blastopore, and that the cells are stomodeal elements destined to become much more numerous and prominent in later stages. As may be seen in the figures no definite blasto- cele is evident. Later stages are ushered in with the development of the test (Plate 13, fig. 11), the great increase in the number of the remaining ectoderm cells, and the appearance of a definite stomodaeum, mid-gut, and cerebral ganglia together with the appearance of recognizable mesodermal elements. In other words, differentiation has now advanced to a stage where the three germ layers are clearly defined, and certain systems broadly outlined so that the following account will probably gain in clearness if these various systems are considered individually rather than parts of the whole. The Test:— As has been noted some of the test cells have been seen to arise at an early stage by tangential divisions of the relatively few cells com- posing the body of the embryo. Concerning the cleavages of cells left in the interior there is nothing known. The differentiation of the test itself from the remainder of the ectoderm of the trunk region is accomplished by a slower rate of division that is soon brought to a complete standstill. As may be seen in the figures (Plate 13, fig. 11, Plate 14, fig. 3), the test extends at the outset farther over the ventral side than on the dorsal, but in the latest stage in the present collection (Plate 14, fig. 4) a shifting has evidently occurred as the brain is placed at the anterior end of the embryo, and the mouth is well forward on the ventral side. Even yet the organ is asymmetrical in position, but more radially adjusted than at first. Judging from the amount of yolk, contained in the test cells of the oldest embryo it is evident that a very considerable time must elapse before the nutritive material is absorbed and the remnants cast off. While the nuclei present an irregular, somewhat shrunken appearance the cyto- plasm is not vacuolated, as are functional test cells of Chitons or Yoldia for example, and it is probable that a much greater diminution in size occurs before these elements become wholly non-functional and worthless. That a diminution in the size of the test has already ensued in the oldest EMBRYOLOGY. 243 larva is evident from a comparison with the figures of earlier stages. In the oldest larva the increase in the size of the body is not especially marked, and yet the test does not compose more than half of the external surface. Measure- ments, somewhat roughly made, indicate that a shrinkage of approximately two fifths of the original superficial extent of the test has taken place. To what extent this progresses is not known; nor is it known what means are employed to increase the area of the remaining ectoderm. In a few cases cells of the trunk ectoderm have been seen, containing karyokinetic spindles thus indicating one source of increase. On the other hand there are certain large, yolk containing cells in the anterior end of the body of the oldest larva (Plate 14, fig. 4) that do not appear to belong to the mid-gut. From their position it is altogether pos- sible that products of these are added to the external layer as the free border of the test advances toward the apical pole. There is no indication other than this of an ectodermic layer beneath the test, and the indication is that at the time of its dehiscence the test is a comparatively insignificant organ. Nervous System:—In the earliest recognizable stage the cerebral ganglia appear (Plate 14, fig. 6) as a set of cells bordering a depression in the test. It is evident that originally one or more cells, indistinguishable in sections from those of the test, underwent cleavages in which the plane of division cut the surface of the body at right angles. The resulting elements migrated some distance into the interior of the embryo, and at a later time other cells were cut off from these parent cells that remained in contact with the depression. By the successive divisions of daughter and parent cells a large accumulation is produced, extending from the exterior to the neighborhood of the stomodaeum. Within a comparatively short time wing-like prolongations are developed which encircle the stomodaeum and still later these are continuous with a rod-like mass resting against the ventral ectoderm and extending to the posterior end of the body (Plate 4, fig. 3, 4). Unfortunately all of the sections of the later stages are longitudinal, and it is not possible to determine if this ventral band is double, as it ultimately must become if my belief is correct that it forms the ventral cords. While the evidence goes to show that the cerebral ganglia arise at one point in the outer layer of cells, later stages indicate that the depression undergoes a considerable lateral expansion, and in one case the two accumulations, destined to form the halves of the brain, become almost if not completely separated from each other, there being two external pits in contact with the surface. In another example the nerve masses are at opposite ends of a transverse groove 244 EMBRYOLOGY. and are thus incompletely separated. In the oldest stage the nerve mass is in contact with the anterior surface at one point only, and its double character does not appear until it divides to surround the stomodaeum. Apical Sense Organ:— An apical sense organ may exist in this anterior depression from which the cerebral ganglia arise. One is present in Myzomenia banyulensis according to Pruvot, but in the present series of embryos there are, with one possible exception, no especially developed apical cells nor tuft of cilia. The exception is the oldest embryo where a small band of cells extends in the mid line from the ganglionic enlargement bordering upon the stomodaeum to the surface where it ends in a slight pit. The material is excellently preserved yet it is not possible to detect apical cells, and cilia have never been seen at this point or anywhere else on the body. The Terminal Ring:— In Pruvot’s figures of Myzomenia there appears a circular group of relatively large cells surrounding the posterior end of the body. This organ, somewhat resembling an annelid telotroch, is ciliated and a diffuse tuft of cilia projects from the enclosed, terminal depression. In some of the oldest embryos of Halomenia the same structure, minus the cilia, holds a corre- sponding position (Plate 13, fig. 11). The cells are comparatively large yolk- laden elements (Plate 14, fig. 1, 2), resembling small test cells, and are arranged about a saucer-shaped depression. At first they form two rows as in Myzomenia, but in the oldest embryo in my possession the ring-like arrangement has become lost, the cell boundaries have seemingly disappeared and I have not been able to detect any nuclei that may with certainty belong to these cells. The depres- sion is likewise lacking and the yolk granules merely form a confused mass (Plate 13, fig. 9) at the posterior end of the body. In this same section the — ectoderm adjacent to the ‘‘telotroch” appears to be passing beneath the yolk granules, leaving them upon the exterior, but the absence of definite cell boundaries renders this somewhat uncertain. Appearances suggest that the terminal ring is a larval organ that, like the annelid telotroch, is cast off. The fate of the cells within the terminal ring is uncertain. In early stages (Plate 14, fig. 2) the depression is composed of yolk-bearing elements similar to those of the ring itself though of smaller size. At a considerably later stage (Plate 14, fig. 3) the cells in the corresponding position are relatively small, without yolk granules and with indistinct boundaries, and it is reasonable to conclude that they are the progeny of the cells originally included within the terminal ring. Anteriorly they are continuous with the ganglionic cord extend- ing along the ventral side of the body. In the oldest stage the nerve cord comes EMBRYOLOGY. 245 in contact with the epithelial layer in the posterior end of the body (Plate 13, fig. 9), and the only tenable theory that suggests itself is that the terminal cells of the ganglionic cords, those adjacent to the epithelium, have originated from the elements at first surrounded by the terminal ring. While the cells of the epithelium with which the ganglionic cords come in contact form a fairly distinct group, they are not depressed and otherwise give no indication of constituting a special sense organ, although I am inclined to look upon them as the future dorso-terminal sense organ characteristic of many adult neomenians. The Foot:— The oblique direction of the sections through the oldest embryo renders it practically impossible to determine the exact arrangement of the cells of the ventral surface. Immediately beneath the ventral rod of ganglion cells, and therefore in the mid line, the cells are clearly defined columnar elements placed approximately at right angles to the surface of the body. A short dis- tance removed on each side the cells of this character become replaced by others of more slender appearance that are inclined toward the posterior end of the body. It thus appears that along the mid-ventral line there is a strip of cells about one sixth of the body diameter in width, that probably becomes the future ventral groove and included fold although there are no indications that these structures exist as yet. At the anterior border of this strip, and con- sequently immediately posterior to the mouth opening, is the anterior pedal gland, consisting of several cells bordering upon a slight depression (Plate 14, fig. 4) —the future pit-like outlet prominent in the adult. Five or six cells contain small quantities of a moderately staining secretion, and are relatively conspicuous objects. Shell (?): As just noted the cells bordering upon the mid-ventral line are inclined posteriorly with reference to the surface of the body, and this appears to be generally true of the whole trunk region. Especially along the mid-dorsal line they are comparatively slender, columnar elements (Plate 14, figs. 3, 4), con- taining distinct spherical or ellipsoidal nuclei and one or two yolk granules each. In the oldest larva these have separated at fairly regular intervals, and originally I was inclined to consider the spaces thus formed as the seat of cal- careous products. There is, however, a lack of any definite cuticular sheath, and no perforation or elevation of the membrane bounding the body, and accord- ingly I am now of the opinion that these spaces are due to methods of prepara- tion of the material. In the posterior end of the embryo there is a distinct slit (Plate 13, fig. 9), extending through three sections or about one fifth the diameter 246 EMBRYOLOGY. of the trunk, that is bounded by a delicate though none the less definite cuticular sheath. It has the appearance of a developing spine, scale or plate of calcareous material, but with one specimen only it is not possible to form a definite opinion. It is very evident that the oldest larva of Myzomenia as figured by Pruvot with its many scale-like plates is much more highly developed than any embryo in the present collection. Stomodaeum: — As previously noted a few of the cells on the ventral side of the body, at the posterior border of the test, rest against a shallow depression (Plate 14, fig. 7, 8) in relatively early stages, and extend for a considerable dis- tance into the interior of the embryo. They thus occupy identically the same position as the future stomodaeum, and it therefore becomes practically certain that the depression is the first indication of the blastopore and that the slender cells are stomodeal elements. In the next stage (Plate 14, fig. 3) in the present collection the yolk-laden mid-gut, communicating with the exterior, is directly in contact with the test cells anteriorly, but posteriorly it connects with the yolk free stomodeal cells which extend for a considerable distance within the body. The stomodaeum is thus a semitubular structure largely confined to the pos- terior side of the digestive tract. This same state of affairs continues in the oldest stage (Plate 14, fig. 4). Mesoderm:— After the formation of the ectoderm the remaining cells form a confused mass within the interior. Order, that is regularity of arrangement, is not established until relatively late in development (Plate 14, fig. 3) when the mid gut is distinctly outlined. Between the gut and the ectoderm are several fairly large yolk-laden cells whose exact nature is open to question. Anteriorly, between the test and the gut, several of these appear (Plate 14, fig. 3), and — in the latest stage represented (Plate 14, fig. 4) these appear in even greater abundance. They ultimately may become incorporated with the mid-gut, or in part at least they may form the ectoderm of the anterior end of the body as the test diminishes in size, or in whole or in part they may be mesoderm. In the posterior end of the body similar cells appear, of somewhat smaller size, that IT am inclined to consider true mesoderm. Unfortunately the question cannot now be decided. Endoderm:— The endoderm, as indicated in the preceding paragraph, does not become clearly differentiated until relatively late in development, judging from the material in hand. At the time that the stomadaeum com- municates with the succeeding section of the digestive tract the mid-gut is clearly defined as a blind sac filling practically all of the interior of the body. EMBRYOLOGY. 247 The component cells at this time are comparatively large, and as they are filled with yolk granules they are clearly distinguished from the stomodeal elements. In the latest represented stage (Plate 14, fig. 4) the mid-gut in its central portion appears as a confused mass of cells owing apparently to great irregularities in the position of the component cells. The general outline of the organ, it is believed, is correctly indicated. No trace of a proctodaeum or cloacal chamber has been discovered. Comparisons.— The only other accounts of the development of a Soleno- gastre comes from the hand of Pruvot who investigated two species, Myzomenia banyulensis and Proneomenia aglaopheniae. The two reports are very brief, and in some respects the observations coincide with those of the foregoing paragraphs; on the other hand there are certain statements that are open to question. These agreements and differences will now be considered in brief. In Myzomenia the eggs as they leave the gonad and enter the coelomoducts are naked. A membrane is present when the eggs leave the body, and it there- fore follows that the shell gland forms the envelope. It does not follow, how- ever, that the ducts are not at the same time excretory organs though this may indeed be the case. In Halomenia the ova in the gonad are surrounded by envelopes of the same character as surround the eggs stored in the cloacal chamber. The shell gland is highly developed in this species, but what part it plays in the reproductive process is not clear. The four-cell stage comprises one large and three small cells; successive divisions of the smaller cells enclose the products of the larger. At a later period the embryo becomes cap-shaped and a large pit in the ventral half of the embryo is believed to represent the blastopore. The test now becomes clearly defined, an apical tuft of cilia arises, the trunk region, button-like in form, protrudes beyond the margin of the test and a ciliated terminal ring encloses a pit-like depression termed the blastopore. Calcareous plates arise at various points upon the surface of the body, whereupon the metamorphosis ensues. Turning now to the development of Proneomenia it is evident that in several respects it bears a close resemblance to Halomenia. The blastomeres are described as being slightly unequal, surrounding a small blastocele. Invagi- nation occurs and a large blastopore is formed. The larva now elongates and, covered with a ciliated coat borne on five tiers of cells forming three zones or segments, the resemblance to the Myzomenia larva is fairly complete. There 248 EMBRYOLOGY. are, however, certain details of the process that are difficult to comprehend. A brief summary! will make this fact clear. “The layer forming the primary invagination (? archenteron) does not correspond to the definitive entoderm, but gives rise to all the tissues of the trunk. By the tangential division of its cells, it gives rise to a superior ento- dermic mass resting upon a single layer of cells; the latter increases by the radial division of its cells and becomes infolded, forming three invaginations; of these the middle one, which remains open, becomes the future proctodaeum, while the two lateral ones close and are transformed into the masses of mesoderm, the lateral mesoderm-bands. The lower layer, which now has the form of a vault, represents the ectoderm of the trunk. The lips of the proctodaeum now grow out to form the caudal button which first projects into the cavity of the ecto- dermal vault, but later, together with the entire vault, becomes evaginated through the depression at the posterior end of the larva. This conical protu- berance with the caudal button and the proctodaeum at its extremity represents the trunk of the young Proneomenia. The entoderm still remains as a solid mass with the mesoderm-bands on either side and in contact with the procto-: daeum behind. The next important change is the appearance of three ventral invaginations of the larval ectoderm, just. behind the circle of large cilia on the middle segment; the median of these invaginations, the larval stomodaeum, is merely transitory, while the two lateral ones are concerned in the formation of the ectoderm and mesoderm of the head. These two unite, forming a trans- verse band capping the anterior end of the entodermic mass and prolonged posteriorly at two points to meet the mesoderm-bands of the trunk; this por- tion appears to form the muscles, while the more dorsal elements of the invagi- ‘ nation form the cerebral ganglia. The cells of the apical plate seem to take no part in the formation of the nervous system. The ectoderm of the head appears to form entirely from these anterior invaginations, while that of the trunk de- velops from the primary posterior invagination. The latter is now completely evaginated, and has developed the provisional imbricated spicules. In this way the young Proneomenia is developed under cover of a provisional ectoderm which serves as a locomotory organ and is thrown off at the moment of meta- morphosis. The adult does not exhibit a distinct head but, during development, this structure is perfectly distinct and arises quite independently of the trunk.”’ Upon first thought it appears difficult to correlate some of these observa- 1 From a note by M. IF’. Woodward in the English translation of Korshelt and Heider’s Text-book of the embryology of invertebrates. 1900, 4, p. 19. EMBRYOLOGY. 249 tions with those pertaining to the development of any other class of animals, but the difficulty, it appears to me, arises at the outset when the cells included within the test are declared to be wholly endodermic. I shall endeavor to show that they comprise the elements of all three germ layers, and that the Solenogastre development may be derived from that obtaining in the Chitons for example. In the first place I am in entire accord with those authors, notably Drew (1901), who look upon the test as a highly developed velum. In Ischnochiton it is a relatively insignificant structure forming an equatorial band around the embryo and dividing the animal hemisphere from the vegetative, or, roughly speaking, the head from the trunk. Until the metamorphosis it remains functional when it is cast off. Remodelling such a type of larva into that of Halomenia it is necessary merely to greatly widen the band. This well nigh obliterates the usual head vesicle, leaving only those cells at the animal pole that develop the cerebral ganglia. In the vegetative half of the animal the cells responsible for the development of the trunk ectoderm are likewise greatly reduced though by no means wiped out entirely. In both types the blastopore is situated on the ventral side adjacent to the velum or test, and the ectoderm that forms the future trunk is continuous with the margins of the test. The absolute proof of this theory rests upon a knowledge of the history of the early blastomeres, and this unfortunately is almost totally lacking. We know that the early cleavages may be nearly equal or highly unequal, but to assume that because one or more cells become partially withdrawn into the interior at an early stage it is therefore endodermal is certainly not justified. Furthermore it is unfortunate that the terms micromere and macromere have been introduced in describing the Solenogastre development since these terms apply to the history of the cells in question rather than to its size. We know that in the majority of the’ Trochozoa that have been carefully examined, the original four cells divide three times forming three quartettes of micromeres, some of which as a matter of fact may be larger than the remaining parent cells or macromeres which are now endodermal. Whether this is true of the Solenogastres we do not know, but the arrangement and fate of many of the cells suggests strongly that something akin to this has taken place. Considering now the gastrulation of Myzomenia and Proneomenia it is evident at the outset that the test is of such large size that when viewed from the side it conceals within its borders the entire trunk. The so-called blasto- pore is accordingly nothing more than a temporary shallow depression bordered 250 EMBRYOLOGY. on all sides by the test. The same effect may be produced in Halomenia (Plate 13, fig. 11 for example) by slightly extending the borders of the test. The layer forming this ‘‘primary invagination” is therefore no archenteron, and Pruvot is quite correct in claiming that its cells do not correspond to the defini- tive endoderm and that they give rise to all the tissues of the trunk. By tan- gential divisions of the cells of this depressed area there is produced a ‘‘superior ectodermic mass resting upon a single layer of cells,” that is to say the ectoderm of the trunk becomes distinct from the endoderm that later forms the mid-gut (Plate 14, fig. 5). In this area circumscribed by the borders of the test are ‘‘three invagina- tions; of these the middle one, which remains open, becomes the proctodaeum, while the two lateral ones close and are transformed into ‘‘masses of mesoderm.” The proctodaeum is evidently the mid-gut, but that it is open to the exterior or is derived from this species of invagination is certainly an erroneous con- clusion resulting from a failure to detect the true blastopore. The mesoderm bands are evidently the ventral cords of ganglion cells as will appear more clearly later on. Concerning the formation of the trunk it may be said that the “‘lips of the proctodaeum”’ evidently refers to the rim of the terminal depres- sion in the trunk of comparatively old larvae and the ‘‘terminal button which first projects into the cavity of the ectodermal vault” probably refers to the group of cells that in one stage in the development of Halomenia (Plate 14, fig. 4) lie at the base of this depression. Later the button ‘‘together with the entire vault becomes evaginated”’ beyond the borders of the test, and the presumption is that the button corresponds therefore to the dorso-terminal sense organ. . In the anterior half of the body three invaginations are said to exist in the midst of the test cells. The first, a transitory structure, is said to repre- sent the stomodaeum. If such is actually the case it occupies a very different position from what it does in Halomenia. That it is transitory makes it appear to be a misinterpretation. The two lateral invaginations that ultimately meet to form a transverse band are said to supply material for the ectoderm of the head, the cerebral ganglia and the mesoblastic bands that are ‘‘prolonged pos- teriorly to meet the mesoderm-bands of the trunk.” I am not certain regarding — the head ectoderm formation but the mesoderm bands are clearly the ganglionic trunks that continue to the posterior end of the body. GENERAL CONSIDERATIONS. 251 GENERAL CONSIDERATIONS. Since the completion of the report on certain species of Solenogastres from the Pacific Ocean (Heath, 1911) the excellent paper of Nierstrasz (1908) and several objections (in litt.) on the part of various investigators open up the dis- cussion of certain questions not fully treated in the earlier paper. It is evident, however, that some of these protests, ike many of my own theoretical con- clusions, are very largely based on personal opinion. The same material in the hands of these or other students would perhaps be interpreted in various ways from a theoretical standpoint, and accordingly the following paragraphs are very largely a confession of faith with some of the grounds upon which it rests. The first of these criticisms is directed at the section treating of the forma- tion of the spicules imbedded in the cuticle, which, like the papillae when such are present, is a product of the hypodermis or epidermis as Nierstrasz prefers to term it. At the outset it is important to note that there are two distinct modes of spicule formation, and the confusion that my account appears to have created is largely due to the fact that this has not been kept in mind. In all of the Chaetodermatina, so far as my observations go, each spine is the product of one, and only one, cell, and it may be, indeed it usually is, crowded between adjacent hypodermal (or epidermal) cells. But that these surrounding cells are limited to three, or that they perform a molding function as Wiren main- tains (Wiren, ’92) is open to serious question. In those sporadic cases where the matrix cell is raised above the general level of the remaining elements of the hypodermal layer the minute spine is clearly seen to rest solely upon this formative cell, and is not in intimate contact with any other cell element. The same method of growth also appears to be characteristic of the families Neo- meniidae and Dondersiidae. In those species of the suborder Noemeniina where the spicules form more than one layer a relatively small number of spines are usually directed radially and at the completion of their development project beyond the external surface of the cuticle. So far as I have been able to follow the development of all such radial spicules each is the product of a single cell, which is either attached directly to the base or close to the base at one side. In the families Proneomentidae and Pruvotintidae the development of the tangentially placed spines follows a different course of development, at least in several carefully studied species belonging to the genera Halomenia, 252 GENERAL CONSIDERATIONS. Dorymenia, Lophomenia, and Strophomenia. At its first appearance the minute, cone-shaped calcareous product rests upon a relatively large cell that probably may be considered the homologue of the matrix cell in the foregoing types. In this case, however, the matrix cell is surrounded by ‘‘seven or eight cells, slender in form, indistinct in outline, with dense nuclei and attenuated bases which are imbedded in the hypodermis proper.’ The cell membranes of these accessory elements are distally attached to a membrane or sheath enveloping the spine which accordingly is interrupted near the base. The part played by these different cells is obscure. The basal cell doubtless acts as a lime-secreting agent, and the remaining subsidiary cells form the spicule sheath, but whether they likewise supply calcareous material remains unde- - termined. The important point, however, is clear that all of these cells, eight or nine in number, are attached to the spine, diminish in size as the spine increases, and in many instances retain their attachment permanently. There is therefore nothing to indicate that they are other than matrix cells. Hssen- tially the same mode of development has been described by Plate in his study of the formation of the spines of certain species of Chitons, and it furnishes another line of evidence for the belief that the Solenogastres and Chitons have had a common ancestor. One point noted in the Pacific report remains obscure. In early stages a minute body rests between the basal matrix cell and the base of the spine. The point in question is whether it is a cuticular product or a cell. In a late stage it undoubtedly is cuticular, and appears to prevent the passage of lime salts from the matrix cell and by its increase and subsequent decrease and final disappearance is responsible for the development of the cavity within the spine.’ At the suggestion of Professor Nierstrasz I have made a careful examina- tion of the heart in all of the species of Solenogastres described in the Pacific and in the present report; asa result I cannot feel that much dependence can be placed on this organ as indicating relationships or relative primitiveness consid- ering our scanty knowledge of the group. To me it appears clear that the dorsal blood vessel in the pericardial region has been provided with a highly developed muscular coat, has thus become a pulsatile organ which frequently comprises two divisions, a ventricle and auricle or atrium, as certain authors prefer to term it. In some species this muscular section lies in a dorsal fold of the peri- cardial wall; in other cases it has severed its connection with the wall and lies freely in the pericardium. In certain species the auricular or atrial division is very short, as in Chaetoderma argenteum, or it may be more pronounced as in — GENERAL CONSIDERATIONS. 253 Chaetoderma attenatwm, and again it may be entered by two vessels but this bipartite condition ends at the pericardial wall. The impression given is that the heart is a relatively simple tube, usually with two divisions, sometimes sacculated, but I have never found more than one auriculo-ventricular opening or any other evidence to show that the heart is a paired organ. Whether the auricle or atrium is the homologue of the auricles in other species of molluses is likewise uncertain; there is no clear evidence for or against such a view. And we are, it seems to me, equally in the dark when we approach the subject of the most primitive type of Solenogastre heart. In my opinion the heart which lies in a fold of the pericardial wall as in some of the Proneo- meniidae appears to be among the most primitive. On the other hand where it lies freely in the pericardial cavity, as in Chaetoderma or Alexandromenia, it must have arisen from a simpler embryonic condition, and a simpler phylogene- tic stage is equally conceivable. Here again the matter rests upon few data and personal opinion and must accordingly remain as an unsettled problem for the present. The digestive system, like the circulatory and muscular systems, is most susceptible of change, and the wide variations of form and component elements, correlated with differences in habits of life of the different species, renders it difficult to differentiate coenogenetic from palingenetic characters. I believe, however, that in the ancestral Solenogastre the fore gut was provided with both dorsal and ventral salivary glands and a radula, while the mid-gut, as in the modern neomenians, was a relatively simple tube without clearly defined stomach, digestive gland, and intestine. The hind gut appears to me to be a relatively small section of the digestive tract in the Chaetodermatidae, and forms no part of what has been termed the cloacal, anal, or mantle chamber, a point to which I shall return. As Thiele maintains the atrium of the Neomeniina is no part of the fore gut, and it is possible that it is the homologue of the buccal shield in the Chaetodermatina and the snout of the Chitons. Dorsal and ventral salivary glands clearly appear in several species, such for example as Proneomenia hawaviensis and Lophomenia spiralis. On the other hand the ventral set may disappear completely as in Limifossor and several species of Strophomenia. Since dorsal glands exist in Limifossor I am inclined to look upon the diffuse glands attached to the fore gut of Chaetoderma as a modified homologue. Whether this is the case with the equally diffuse glands surrounding the walls of the fore gut in Strophomenia it is impossible to determine. In Alexandromenia there are three distinct groups of salivary glands one of 254 GENERAL CONSIDERATIONS. which with paired ducts is doubtless the counterpart of the ventral set of other species. The possible homologue of the dorsal gland here exists as a diffuse band encircling the fore gut in the neighborhood of the brain. The third set is attached to the fore gut between the radula and mid-gut, and in appearance and staining qualities differs from the other two. It is altogether possible that this posterior set is of more recent, independent origin, and it is also pos- sible that the diffuse glands existing in various species of Strophomenia may have had a similar origin. But at the same time it should be kept in mind that these pharyngeal glands in Strophomenia lie in front of the radula and ventral salivary glands and accordingly may represent a diffuse dorsal gland. Since a radula exists in Limifossor talpoideus and Halomenia gravida, for example, with odontoblasts and basement membrane typically located, and the entire organ holding essentially the same position with reference to the ventral salivary glands and the pharynx generally as in the Chitons, it is difficult to avoid the belief that it was present before the Solenogastres became an inde- pendent group. The radula may indeed have originated as a cuticular product of the fore gut with separate teeth or as minute projections of a more or less extensive buccal lining, but that this has been its history since the Solenogastres branched off from the parent stock is highly improbable. It is true that the radula in present day species is a highly variable structure — distichous, poly- stichous, with or without a basement membrane, reduced to a conical peg, or absent. altogether — but in my opinion the Limifossor and Halomenia types of radulae have preserved their ancestral characters, while the others represent different stages of degeneration. This is wholly aside from the discussion as to which is the more primitive, the polystichous or distichous plan, a matter it - appears to me which cannot be settled considering the small amount of com- parative anatomical data we now possess. As to the mid-gut there are wide variations and here again it is difficult to follow the ancestral history. Where the digestive gland is not clearly differ- entiated or the stomach or intestine sharply defined we certainly have the least complicated state of affairs and it appears to me to be the more primitive. The Chaetodermatina are therefore more highly modified in this respect than are the Neomeniina. In this connection the so-called anal, cloacal or branchial chamber may be considered to be a development of the anus, as certain authors maintain, and nowise the homologue of the mantle cavity. The lamellae on its walls in the Neomeniina are therefore modified anal folds and according to Thiele GENERAL CONSIDERATIONS. 255 and Plate are not homologous to the branchiae of the Chaetodermatidae, which though a coenogenetic development have nevertheless had an independent origin. Nierstrasz likewise considers the neomenian branchiae to be anal folds, but holds that the Chaetoderma type of gill is the most extreme development of such lamellae. In the Pacific report I have argued in favor of the complete lack of homology between the neomenian type of gill and that found in members of the family Chaetodermatidae. Concerning the true significance of the first named I have no evidence to offer. Plate and Nierstrasz have described cer- tain species (Notomenia clavigera, Archaeomenia prisca, Proneomenia discovery?) in which the coelomoducts do not open into the branchial cavity, and for the present at least I am not inclined to argue for or against the theory that the neomenian gill is a derivative of the anal wall. But when it comes to the Chae- toderma type of gill the evidence that it is a development of the anal or procto- dael walls is far from being conclusive. If such a type of gill were to be found among the Gastropoda I venture to say it would unhesitatingly be considered as a ctenidium. It has the same macroscopic and microscopic structure, the same blood circulation, musculature, and innervation as the Chiton or Haliotis gill for example, and the space in which it is held contains the outlets of the coelo- moducts and digestive tract. So far as appearance and general relations are concerned the gills of the Chaetodermatidae are true ctenidia, and the sur- rounding space is a mantle cavity. Here again we must have embryological evidence to definitely settle the question. Regarding the nature of the ventral fold there is little to add to the observa- tions of other authors and the comments made in the Pacific report. A detailed study of the most advanced larvae of Halomenia gravida, in which the anterior pedal gland comprises three or four cells, shows no line of demarcation between the cells of the mid-ventral line and those more laterally placed; and even if all stages in the development of this organ were present it is doubtful if it would afford convincing evidence that the ventral fold is a foot with a long ancestral history to those opposed to such a view. Thiele, Plate, and Nierstrasz admit that the fold is an organ concerned in the function of locomotion, but that it, with the anterior and posterior pedal glands, is the homologue of the foot of other molluscs is vigorously denied. To them the organ in question has had an independent origin, and where the furrow stops short of the branchial chamber we have a primitive state of affairs. As a matter of fact the groove passes into the branchial chamber in the larger number of neomenians I have studied, and has led me to suspect that at least a portion of this last named space may 256 GENERAL CONSIDERATIONS. be a true mantle cavity, though at present there is no more actual proof for such a view than for the one which considers it to be an anal space. In my opinion this fold, lying in the mid-ventral line and supplied with two glands, holding essentially the same position as the glands and creeping surface in the young Chiton, is a true foot, the homologue of the Chiton foot, and has been derived from a common ancestor. In the Chaetodermatidae there are few traces of its existence; in the Neomeniina it varies from an exceedingly small organ to one relatively wide and comprising several folds, but so far as I can judge these are secondary features having to do solely with modifications within the group. That the ventral nerve cords cannot be considered pedal ganglia because they innervate the ventral side of the body as well as the ventral fold, and in this respect are unlike other molluscs, appears to me inconclusive evidence. The supraoesophageal ganglia in both molluscs and annelids are probably derived from homologous groups of cells of the head vesicle, and there is a strong probability that the anterior pair of ventral or suboesophageal ganglia in the annelids is the counterpart of the pedal ganglia of molluscs, the repetition of the ventral ganglia in the annelid being correlated with metameric segmenta- tion. The ventral ganglia of annelids innervate the ventral suface, the entire body wall in fact, but with the development of the mantle and its associated complex in the molluscs a new set of ganglia, the pallial, appeared which inner- vate these typically molluscan organs. Whether this theoretical view is accepted or not it is certainly true that the ventral surface of the body of the molluscan ancestor, before a definite creeping surface became differentiated, was innervated and continues to be innervated whether the foot includes the entire ventral side of the body or not. Where the foot is small, as in the modern Solenogastre, and the body wall continues to form a portion of the under surface both continue to be supplied by this ventral set of nerves. Where the foot constitutes the entire ventral side of the body it alone is so supplied. The broader features of the nervous system have been described in the Pacific report, and the study of the various species in the present collection merely confirms the general belief that in the Solenogastres it is reducible to one fundamental plan. In every ease the brain is attached to three connectives, the lateral, pedal, and labiobucecal, and anteriorly develops nerves which pass into ganglionic masses (precerebral ganglia) in close proximity to the brain (Chaetodermatina) or attached to the bases of the atrial cirri (Noemeniina). The lateral and pedal cords course to the posterior end of the body where they GENERAL CONSIDERATIONS. 257 may unite directly or become closely associated by means of unusually heavy connectives. At frequent intervals the pedal cords are united by commissures, while an approximately similar number of connectives unite them with the lateral ganglia. These last named elements are united posteriorly by a heavy suprarectal commissure. The labiobuccal connectives pass to ganglia in the neighborhood of the radula, which are united by a ventral commissure. A dorsal commissure has also been demonstrated in certain species of neomenians (for example, Dorymenia acuta and Strophomenia scandens) arising from the labiobuceal ganglia or on the labiobuccal connectives. A second ventral commissure may also exist. In a few species of both suborders a subradular system has been demonstrated with ganglia, commissure and connective unit- ing them with the labiobuccal ganglia. With these general features in mind the innervation of the various regions of the body will now be described, the description being based solely upon data derived from the study of species I have personally examined. In the Chaeto- dermatina the nerves from the great precerebral ganglionic masses attached to the anterior surface of the brain innervate the frontal sense organ and the anterior end of the digestive tract. Nerves from the lateral cords, and in some instances from the latero-pedal connectives, attach to the somatic musculature dorsally and laterally, while fibres from the pedal cords pass to the more ventral portions of the body. In the posterior end of the animal the ventral section of the cloacal wall and the adjacent region of the body wall are supplied with nerves originating at the posterior end of the united lateral and pedal cords. The ventral gill retractor and the ventral half of each gill is supplied with a nerve from the ventral side of the suprarectal commissure, while the dorsal half of the gill is penetrated by a nerve arising close to the mid line on the dorsal side of the suprarectal commissure. Another pair of nerves, originating on the dorsal side of this same commissure but more laterally situated, spread over the dersal cloacal wall and the neighboring portions of the body wall probably including the dorso-terminal groove. In Chaetoderma hawatiense a nerve from the suprarectal commissure, in the mid line, has been followed into the tissue surrounding the rectum. Nerves from the labiobuccal ganglia extend pos- teriorly along the wall of the fore gut, and in Chaetoderma eruditum have been followed as far as the stomach. The subradular organ is supplied with nerves from the subradular ganglia. In the Neomeniina the six nerves leaving the anterior surface of the brain are in part distributed to ganglia, about the bases of the cirri, from which deli- 258 GENERAL CONSIDERATIONS. cate fibres pass into the cirri themselves. Other branches of these same cerebral nerves, though apparently independent of the atrial ganglia, pass to the anterior end of the body where they doubtless innervate the body wall including the hypodermis. In Pachymenia abyssorum and Dorymenia acuta the body wall of the anterior end of the body (and possibly the atrial ganglia, cirri, and atrial ridges) is also supplied with nerves from the anterior end of the lateral ganglia. In Dorymenia acuta nerves from the anterior end of the pedal cords and from each anterior latero-pedal connective have been followed to the external atrial ridge. The pharynx is supplied, at least in part, with nerves from the labio- buccal ganglia or from some of the labiobuccal connectives, and in Dorymenia acuta a pair of small nerves, having an independent origin from the sides of the brain, have been followed a short distance into the pharyngeal musculature. In Alexandromenia agassizi and Pachymenia abyssorum the walls of the out- let of the anterior pedal gland are furnished with nerves from the anterior end of the pedal ganglia. The dorsal side of the body is supplied with nerves from the lateral cords, the sides are furnished with branches from the lateral and pedal ganglia and to some extent by delicate offshoots from the latero-pedal connectives, while the ventral surface is innervated by nerves from the pedal cords. In rare instances slender branches from the pedal commissures have been followed into the foot or ventral fold. In the posterior end of the body the terminal section of the shell gland or ventral section of the coelomoducts in Strophomenia ophidiana and Alexandromenia agassizi are supplied with nerves from the posterior end of the pedal ganglia or from the posterior latero-pedal connective in Drepanomenia vampyrella. Nerves to the pericardial wall and heart in Strophomenia ophidiana have their origin in the posterior end of each lateral ganglion. Nerves from the same source enter the gill lamellae in Pachymenia abyssorum and Alexandro- menia agassizi which in the first named species at least are also innervated by other nerves from the posterior end of the pedal ganglia. The body and cloacal walls are furnished with nerves from the posterior end of the pedal and lateral cords and in Drepanomenia vampyrella an additional supply originates in the most posterior latero-pedal connective. In several species the suprarectal commissure gives off one nerve (two in Strophomenia regularis) which enters the dorso-terminal sense organ. In Alexandromenia agassizi the nerve to the sense organ is a relatively small offshoot of a branch having the usual attach- ment to the suprarectal commissure, but more posteriorly it passes into some of the more dorsally placed gill lamellae. GENERAL CONSIDERATIONS. 259 Regarding the fragmentary knowledge we have of the embryonic develop- ment of the Solenogastres and the light which this throws on the question of the primitive characters of the group, it must be admitted that very little con- clusive evidence has appeared. In an earlier paper (Heath, 1911) it was shown that the Chiton and annelid in their development up to the trochophore stage follow practically the same course. The great test or modified velum in the Solenogastre larva cannot therefore be looked upon as a primitive mark; nor can the posterior invagination which may represent a dorso-terminal sense organ against which the nerve band abuts. Unfortunately we have no conclusive evidence regarding the presence of a true shell nor any data relating to the form and size of the foot. Whether adult characters are to be considered primitive or secondarily modified must accordingly largely rest upon comparative ana- tomical studies and the personal factor in interpreting such evidence. As Nierstrasz has maintained the various species of Solenogastres show a truly surprising amount of variation, and while it is possible to find a fundamental plan upon which all are constructed it is most difficult to decide which features are the most primitive. Personally I am strongly of the belief that the ancestral Solenogastre was provided with a mantle cavity containing a pair of ctenidia and the openings of the coelomoducts and digestive tract, and a creeping sur- face or foot provided with two sets of glands. Whether a shell was present or absent cannot be decided. The digestive tract was provided with a typical radula, dorsal and ventral salivary glands, while the mid-gut lacked a clearly defined digestive gland. The heart, in the posterior end of the body, communi- cated on one hand with a sinus from the ctenidia and in the other direction connected with the dorsal aorta, which supplied the gonad and opened through a septum limiting the head cavity. This septum was also perforated ventrally to allow the flow of blood into the visceral cavity and probably a ventral sinus from which it passed to the ctenidia. The coelom comprised a genital section opening into the pericardium, which in turn communicated with the exterior by means of two simple, distinct coelomoducts. The nervous system, having essentially the same configuration as it now possesses, was probably more diffuse. If such indeed does represent the general plan of the ancestral Solenogastre then it follows that the members of the Chaetodermatidae are highly modified in most respects. They have retained their ctenidia, their relatively simple coelomoducts, and in Limifossor there is an anterior septum and a well-developed radula. In the neomenians the foot and glands still persist, and in certain 260 GENERAL CONSIDERATIONS. species a typical radula is present together with dorsal and ventral salivary glands and a diffuse digestive gland. In the posterior end of the body great coenogenetic changes have ensued. The coelomoducts are usually united, semi- nal receptacles have appeared, and a highly glandular epithelium has developed at least in the terminal section. Penial spines and branchial folds are, in my opinion, likewise recent developments. Where the spines imbedded in the cuticle investing the body develop from a single matrix cell it probably represents the most primitive condition, but since certain neomenians develop some of their spicules in the same general fashion as the Chitons do in part it appears probable that both modes prevailed in the ancestral Solenogastre. As noted above the Solenogastres are a highly variable group, and such genera as Alexandromenia, Pachymenia, and Neomenia appear to me to stand among the most highly modified members of the order Aplacophora. The Chitons on the other hand are a remarkably conservative group, the differences between the most diversified genera, such as Cryptochiton, Chitonellus, and Ischnochiton, being far less than those differentiating Limifossor and Chaeto- derma belonging to the same family. When I made the claim that the Chitons represent the most archaic type of modern mollusc I had in mind the highly modified Solenogastres just noted which appear to me to have departed more widely from the ancestral molluse than any of the Chitons. It doubtless is possible to select a character here and there from the various species of known Solenogastres and produce a list of primitive features of greater length and more importance than in the case of the Chitons. On such a basis of selection the Solenogastres may be considered to be the more primitive group, but where a single species of Solenogastre (especially from one of the genera noted above) is compared with a single species of Chiton it appears to me that more primitive features will be found to exist in the last named. However this is not a matter upon which I would lay great stress since it appears to rest upon much less con- clusive evidence than does the theory whereby the Solenogastres are considered to be more closely related to the Chitons than to any other group of molluscs. BIBLIOGRAPHY. Brock, J. 1883. Untersuchungen iiber die interstitiellen bindesubstanzen der mollusken. Zeit. f. wiss. zool., 39, p. 1-63, pl. 1-4. Heatu, H. 1911. The solenogastres. Mem. M. C. Z., 45, p. 1-182, pl. 1-40. KorscuHett, E. 1893. [Mollusken]. Korschelt & Heider’s Lehrbuch, 3, p. 909-1177, fig. 541-687. Niersrrasz, H. F. 1908. Die amphineuren. 1. Die Solenogastren. Ergebn. zool., 1, p. 240-306. Pruvot, G. 1890. Sur le développement d’un Solenogastre. Comptes rendus Acad. sci., 111, p. 689-692. 1892. Sur l’embryogénie d’une Proneomenia. Comptes rendus Acad. sci., 114, p. 1211-1214. Smmrotu, H. 1893. Amphineuren. Bronn’s Thier-reichs, 3, abth. 1, p. 128-233. WrrEN, A. 1892. Studien iiber die Solenogastres. 1. Monographie des Chaetoderma nitidulum Loven. Svenska vet. akad. Handl., 24, p. 1-66, pl. 1-17. II. Chactoderma productum, Neomenia, Proneomenia acuminata. Svenska vet. akad. Handl., 25, p. 1-100, pl. 1-10. EXPLANATION OF THE PLATES. anus aorta anterior pedal gland brain buccal commissure labiobuceal ganglion gill nerve to gill intestinal coecum cloacal chamber cloacal coecum coelomoduct dorsal aorta dorsal salivary gland buceal plate glands of pharynx gonad heart intestine labiobuceal connective liver mouth nerve to buceal plate oesophagus pedal ganglion precerebral ganglion pericardium pharynx lateral ganglion pedal sinus radula seminal receptacle radular support anterior vertical septum subradular commissure ventral salivary gland shell gland subradular ganglion sense organ spicule dorsal gill retractor subradular organ stomach seminal vesicle ventral gill retractor ventral diaphragm PLATE 1. Fig. 1. Two individuals of Strophomenia agassizi in the act of copulation; the posterior ends in contact near left side of figure. X 6. Fig. 2. Hypodermis and papillae in head region. 135. Fig. 3. Spicules from middle of body. X 100. Fig. 4. Reconstruction of anterior end of body. Fig. 5. Reconstruction of posterior end of body. Fig. 6. Section across outlet of anterior pedal gland of Neomenia verrilli. PLATE 1. Meise! lith.Co..Besion. PLATE 2. Fig. 1. Strophomenia agassizi. Section along line C of fig. 4, pl. 1. Fig. 2. Same along line B of fig. 4, pl. 1. Fig. 3. Same along line A of fig. 4, pl. 1. Fig. 4. Section along line H of fig. 5, pl. 1. Fig. 5. Section along line D of fig. 4, pl. 1. Fig. 6. Section along line F of fig. 5, pl. 1. (One third reduced). Fig. 7. Same along line G of fig. 5, pl. 1. Fig. 8. Same along line E of fig. 5, pl. 1. X 360. Fig. 9. Nierstrassia fragile. Ventral fold. Xx 360. Fig. 10. Section through radula. X 555. PLATE2, Meisel lith.Co.,Boston 3 a : 4 PLATE 3. Reconstruction of posterior end of body of Neomenia verrilli. pgl. penial gland. — Section through posterior end of body along line of D of fig. 1. oe. Section through seminal vesicle. Reconstruction of anterior end of body. ; Section through accessory penial spines and glands. X 85. Lateral view of entire animal. X 2. Section through accessory penial spines and glands. Hypodermis and papillae. 190. X 46. PLATE 3. Meisel lith.Co, Boston i : a PLATE 4. Neomenia verrilli. Section through penial gland and junction of dorsal and ventral limbs of coelomoduct. »X 85. Fig. 1. Fig. 2. Fig. 3 Fig. 4 Fig. 5. Fig. 7. Fig. 8 Fig. 6 Fig. 9. Fig. 10. Fig. 11. Fig, 12. Section through posterior end of body along line E of fig. 1, pl. 3. Section through pharynx along line B of fig. 4, pl. 3. Section through pharynx along line C of fig. 4, pl. 3. Cloacal folds and attached glands. X 215. Section through brain along line A of fig. 4, pl. 3. Section through distal end of penial spine, sheath, and attached muscles. X 29. Proneomenia acuminata. Section through middle of heart. 85. Teeth to left of mid line. Section through pharynx (ph) at level of subradular organ. Section along line B of fig. 1, pl. 5. Section along line E of fig. 5. pl. 5. PLATE 4. ss ATLANTIC SOLENOGASTRES Meisel lith.Co., Boston. ms ‘ at : aha ms ” i aoe ‘i ad ee. 2 oe * ! x ives ae e PLATE 5. PLATE 5. Fig. 1. Reconstruction of anterior end of body of Proneomenia acuminata. Fig. 2. Section through pharynx along line C of fig. 1. Fig. 3. Entire animal. X 2. Fig. 4. Spines from sides of body. X 100. Fig. 5. Reconstruction of posterior end of body. Sg, shell gland. Fig. 6. Hypodermis and papillae. X 190. Fig. 7. Section through pharynx (ph) at level of subradular ganglia (srg) above which are ducts of the ventral salivary glands. Fig. 8. Section along line F of fig. 5 int, intestine. Fig. 9. Section along line A of fig. 1. Fig. 10. Section along line D of fig. 5. da, dorsal aorta; ht, heart; sr, seminal receptacle. Fig. 11. Section through cloacal chamber along line G of fig. 5. PLATE 5, WS ) | NUN w MANS H Heath de : Meisel lith.Co.,Boston PLATE 6. Bigs Fig. 2. Fig. 3. Fig. 4. Fig. 5. Fig. 6. Hig. 7. Fig. 8. 9. eae gaa a = © PLATE 6. Entire animal of Nierstrassia fragile. X 13. Hypodermal layer. X 800. Reconstruction of anterior end of body. Section through posterior end of body along line F of fig. 5. Reconstruction of posterior end of body. Section through posterior end of body along line C of fig. 5. Same along line D of fig. 5. Section through region of brain along line A of fig. 3. Longitudinal section through brain and anterior end of alimentary canal. Section through posterior end of body along line E of fig. 5. Posterior end of body, ventral view. x 180. PLATE6. 08S "ATLANTIC SOLENOGASTRES Rema REN i Meisel lith. Co.,Boston. . = A PLATE 7. PLATE 7. Fig. 1. Nierstrassia fragile. Cross section at level of B of fig. 3, pl. 6. Fig. 2. Dorymenia peroneopsis, entire animal. X 3. Fig. 3. Section through brain at level of line B of fig. 5, pl. 7. | Fig. 4. Section through anterior end of body corresponding to line E of fig. 5, pl. 7. Salivary glands in natural position. Fig. 5. Reconstruction of anterior end of body. The main portion of the ventral salivary gland has been shifted ventrally to show radular mechanism. Fig. 6. Reconstruction of radular apparatus. Fig. 7. Reconstruction of posterior end of body. er eee Boston Meisel {ith.Co.,B nm STRE ANTIC SOLENOGA r SATROSS "AT PLATE 8. . My “ae 8 ie. ry” > ek 2: i =o eet ine ~ F ! » ' Fig. 1. Fig. 2. Fig. 3. Fig. 4. Fig. 5. Fig. 6. Fig. 8. Fig. 9. Rips, 7. Fig. 10 Fig. 11. PLATE 8. Dorymenia peroneopsis. Section through posterior end of body along line G of fig. 7, pl. 7. Spines from side of body. X 190. Section along line H of fig. 7, pl. 7. Section along line A of fig. 5, pl. 7. | Section along line C of fig. 5, pl. 7. Section along line F of fig. 7, pl. 7. Section along line D of fig. 5, pl. 7. Papilla and hypodermis, head region. X 255. Cross section of pharyngeal (salivary) gland of Chaetoderma caudatum. X 91. Section close to junction of pharynx and mid-gut. 88. Section slightly anterior to forward border of pericardium showing alimentary canal, two lateral gonoducts and dorsal aorta. Fig. 12. Section through mid-gut or stomach. ioe] [ss] : FS : fh fas S = 3 a ans \ 6 ize} a ty [oxy / in / 4 fy f ‘S | i is) gp) \ iS) \ 1 I OSS "ATLANT é eS is 5 AY :S SOMNAa RON — —_ a OOF CFE CTECO SNS =a PLATE 9. Chaetoderma caudatum, entire animal. xX 8. Head region of same specimen. X 12. Side view of another specimen. X 12. Anterior view of same animal as fig. 1. X 12. Section at level of radula. X 88. Section through pericardium and coelomoducts. Section at level of external coelomoduct openings. Section at level of brain. Hypodermis of prothorax. > 360. Junction of stomach and liver. Spines from mid section of body. X 190. Section through outlets of pericardium into coelomoducts. Two specimens of Chaetoderma lucidum. X 4. Section through a pharyngeal gland. X 330. Spines. X 146. Cross section of metathorax. X 46. Section through dorso-terminal sensory groove. X 190. Cross section at junction of pro- and metathorax. is TROSS ATLANTIC SOLENOGAS?RES : Prare 9 Meisel ith Co Seston H.Heath del. PLATE 10. PLATE 10. Chaetoderma lucidum. Section through head at level of radula. > 46. Cross section through brain. Section through posterior end of body at level of coelomoduct outlets. Junction of digestive gland and midgut or stomach. Junction of pharynx and stomach. Section at level of suprarectal commissure. Gastric epithelium, showing supposed intercellular bridges. Anterior end. Chaetoderma bacillum, entire animal. X 7. Section through anterior end at level of radula. > 46. Section at level of brain. Section through junction of pro- and metathorax. Portion of hypodermal layer. Section at level of posterior end of heart. PLATE 10, ATROSS ATLANTIC SOLENOGASTRES Co.,Boston MeiseMith PLATE 11. SOP OMOG ET Coat sao Nes PLATE 11. Chaetoderma bacillum. Section near junction of pharynx and stomach. Section at level of suprarectal commissure. Section at level of coelomoduct openings to exterior. Spicules from middle of body. x 146. Chaetoderma bacillum. Anterior end. Section slightly anterior to opening of gut into cloaca. Chaetoderma squamosum, entire animal. X 3. Section slightly anterior to junction of pro- and metathorax. X 35. Spines from mid section of body. X 91. Cross section of body at level of radula. Section at level of brain. Section about level of middle of pericardium. Section near junction of pharynx and stomach. Section through anterior end of metathorax. Section at level of dorso-terminal groove and coelomoduct outlets. Junction of pro- and metathorax. Anterior end of young specimen of Chaetoderma vadorum. PLATE IL ROSS ATLANTIC SOLENOGASTRES Meisel lith. Co. Boston PLATE 12. = b a eee esl ted LS) a PLATE 12. Chaetoderma vadorum. Section through anterior end at level of radula. Section through one group of pharyngeal glands. X 255. Spines from middle of body. X 146. Oblique section through metathorax. Section through middle of prothorax. Section through brain. Section at union of pharynx and stomach. Section through anterior end of metathorax. Section through pharynx slightly behind the radula. Section through junction of stomach and liver. Section through anterior end of pericardium. Same region as fig. 9 in another specimen. Section at level of openings of gut and coelomoduct into the cloacal chamber. Section through union of pro- and metathorax. Section at level of suprarectal commissure. Gland cells near mid-ventral line of body in preabdomen. X 255. Same region as in fig. 1 of another specimen. _Meiseliith.Co.Boston le. o% PLATE 13. Chaetoderma vadorum. Same species, anterior end. Section through dorso-terminal groove. 330. Section at level of brain. Hypodermis. Ovum showing male and female pronucleus of Halomenia eae Reconstruction of segmentation stage in the development. Longitudinal horizontal section through posterior end of larva of about the same stage Nuclei-like bodies in egg; also shown in fig. 5. Reconstruction of an advanced larva. Reconstruction of another stage about midway between those represented in figs. 6 and 13. Reconstruction of early stage somewhat flattened. Hypodermis of Chaetoderma squamosum. X 290. “ALBATROSS” ATLANTIC SOLENOGASTRES PLATE 13. Co. Boston HHeath de). ” Me aN hd - , mre ay, { ‘ i Leo Ai.) pw Sa 1 hy a Ne ty - : ‘ i? a ae ie can bene anes pte @ ee, aay i tab Shee oO) ean cra BD tg PRLS ro? ae) Oe ah he 4 ¥, 1. PLATE 14. Longitudinal horizontal section through posterior terminal depression in an advanced larva of Halomenia gravida. Fig. Fig. 2. surfaces. Fig. 3. Fig. 4. Fig. 5. cide. Fig. 6. Fig. 7. Same; younger than stage represented in fig. 3. > 330. D, v, dorsal and ventral Longitudinal horizontal section through larva of about the same stage as fig. 11, pl. 13. Longitudinal horizontal section through oldest larva. Next section to the one represented in fig. 1. The horizontal lines in this and fig. 1 coin- Early stage in the development of the cerebral ganglia. X 360. Longitudinal horizontal section of about the same stage as fig. 12, pl. 138. Arrow indi- cates position of polar body. Fig. 8. Longitudinal horizontal section of about the same stage as fig. 6, pl. 13. x 91. Fig. 9. Longitudinal horizontal section of about the same stage as fig. 12, pl. 138. X91. Arrow indicates position of polar body. Fig. 10. Polar body and female pronucleus; same stage as fig. 5, pl. 13. X 330. Fig. 11. Section through larva of about the same stage as fig. 13, pl. 13. 7 =~ CO rh eh at”. “ALBATROSS ATLANTIC SOLENOGASTRES PLATE 14. =i a 22 & ° ° et © 45 5 Sam % Meisel lith. Co. Boston. H.Heath dei BOUIN ESEINA SE i. JUN YD QL Harvard University. 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