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PUBLISHED BY THE COUNCIL OF THE COLLEGE AND EDITED BY PROFESSOR SYDNEY J. HICKSON. MANCHESTER : J. E. CoRNISH. 1899. PRICE TEN SHILLINGS. VACUA a ho N9.N9481-T ume ne PMELIGLR MUU WAYURAL bE TORY: STUDIES - FROM THE |S) S10L0GICAL DEPARTMENTS, YRAGE US EHX AO AWE UM MAOTE EMA VAC ESE AN PAL PAGE H. B. Pottarb.—‘‘ The oral cirri of Siluroids and the origin of the head in Vertebrates.” Plates land Il. Reprinted from the Zoologischer Jahrbiicher, Bd. VIIL. J. H. AsSHwortTH.—‘‘ On the structure and contents of the tubers of Anthoceros tuberosus, Taylor. Plate III. Reprinted from Vol. 41, pt. I., of Memoirs and Proceedings of the Manchester Literary and Philosophical Society, 1896-1897 T. Hick.—‘‘On Rachiopteris cylindrica, Will. Plate IV, Reprinted Vol. 41 of the Memoirs and Proceedings of the Manchester Literary and Philosophical Society, 1896-1897 EpirH M. Prarr.—‘‘ Contribution to our knowledge of the Marine Fauna of the Falkland Islands.” Plate V. Reprinted from Vol pt. V., of the Memoirs and Proceedings of the Manchester Literary and Philosophical Society, 1897-1898 F. W. GAMBLE and J. H. AsHworrH.—‘ The habits and structure of Arenicola marina.” Plates VI.—X. Reprinted from the Quarterly Journal of Microscopical Science. Vol. XLI. ... EpitH M. Prarr. —‘‘ The Entomostraca of Lake Bassenthwaite,” Le- printed from the Annals and Magazine of Natural History. Ser. Uo Woe Mule S. J. Hickson.—‘‘ On the species of the genus Millepora.” Reprinted From the Pr ase of the a as eo of London. April 5, 1898 : 3 ; : tk : : S. J. Hickson. —‘‘ A Crab-gall on Milena” Plate XI. aa ie Ie on the Bulletin Liverpool Museum. Vol. 1... IsA L. H1tLEes.—‘‘ Report on the Gorgonacean Corals collected by Mr. J. Stanley Gardiner at Funafuti.” Plates XII.—XV. Reprinted from the Proceedings of the Zoological Society of London. Jan. 17, 1899. O. V. DARBISHIRE.—‘‘ Chantranzia endozoica Darbish., eine neue Flori- deen-Art.” Plate XVI. Reprinted from the Berichte dev Deutschen Botan. Gesellschaft. 1899. Bd. XVII. Heft 1. O. V. DARBISHIRE.—‘‘ On Actinococcus and Phyllophora.” Plate XVII. Reprinted from the Annals of Botany. Vol. XIII. J. H. ASHworTH.—‘“‘ The structure of Xenia Hicksoni, nov. sp., with some observations on Heteroxenia Elizabethe.” Plates XVIIT.— XXII. Reprinted eee the Quar ey Journal of Microscopicat Science. Vol. XLII. : : % ae whe 5 49 or on 67 23 133 . 147 151 . 161 . 167 5 Utsji The Editor wishes to express his sincere thanks to the Council of the Zoological Society of London, the Council of the Manchester Literary and Philosophical Society, and to the editors of the ‘‘ Morphol. Jahrbiicher,” ‘Quarterly Journal of Microscopical Science,” ‘“ The Annals and Magazine of Natural History,” “The Annals of Botany,” “The Liverpool Museum Bulletin,” and of the “ Ber. d. Deutschen Botanischen Gesellschaft,” for permission to reprint the articles which appear in this volume. PRR HAL CHB THE present volume of the Studies includes most of the papers that have been published by the workers in our Biological departments during the past four years, and it may be taken as a sign of our earnest endeavour to maintain the reputation of our laboratories as places of original research as well as of sound learning. In our opinion these two functions of such an Institution as this are inseparable ; but the demands made upon our time by heavy teaching responsibilities makes a continuous and systematic investigation of a definite subject a matter of considerable difficulty. The stimulus which the teachers of our departments received in previous years from the presence of the Bishop Berkeley Research fellows, whose whole time was devoted to original work, was most valuable. In the Preface to Vol. II. of this series the late Professor Milnes Marshall said these fellowships ‘“‘ promise to rank among the most successful and most characteristic features of Owens College Institutions.” Now that the fellowships cannot be offered any more we may again express our appreciation of the generosity of the anonymous benefactor whose assistance has borne such good fruit. Biology is now left in our College without any fellowship or scholar- ship to enable a promising student to devote a year of his life to original investigation before commencing his career as a teacher or medical student, and our well-equipped Research laboratory has conse- quently to remain unoccupied during the greater part of the year. We cannot help feeling that if tkese facts were more generally known some help might be forthcoming from those who realise what Biology has done and is doing for the development of rational methods of modern medical research. It is probable that this volume of the Studies is the last of the series. Original work will be carried on as usual in the laboratories, but by increasing the list of institutions and persons to whom we send separate copies of our papers as they appear, we hope to avoid in future the necessity of reprinting them in a volume form. Works in exchange for the Milnes Marshall Zoological library and the library of the Botanical department will at all time be gratefully received. : We cannot allow this opportunity to pass without expressing our sense of the loss to Biological science by the death of our friends, Dr. Pollard and Mr. Hick. It was with a heavy heart that we read the proofs of their last contributions to Science. SYDNEY J. HICKSON. F. E. WEISS, Owens College, December 4th, 1899. Reprinted from the “ ZooLociscHE JAHRBUCHER Bp. VIII., Asru., F. Morpu.” THE ORAL CIRRI OF SILUROIDS AND THE ORIGIN OF THE HEAD IN VERTEBRATES. By Dr. H. B. Potuarn, Lerkeley Fellow in the Owens College, Manchester. With Plates I—II. CONTENTS. Introduction. Technique. On the occurrence of oral cirri. Descriptive part : Models of Auchenaspis, Silurus, Trichomycterus and Callichthys. Sensory tentacular nerves of Auchenaspis, Trichomycterus, Callichthys and Myxine. Comparative part : Nasal tentacle and nerve supply. Premaxillary tentacle and nerve supply. Maxillary and coronoid tentacles. Origin of the cranium. Labials and nerve supply. Mental tentacle and extramental. Submandibular tentacle. The Meckelian cartilage. Other parts of the head. Histology. Reversion and larval forms. Zoological position of Siluroids. INTRODUCTION. Nearly four years ago, I found in the cellar of the Anatomical Buildings at Freiburg i./B, a number of Siluroids, which Professor Wiedersheim openhandedly placed at my disposal, and I then began 2 H. B, POLLARD. my study of the head in this group. Being, however, engaged on Polypterus, [ did not actively investigate their anatomy till October, 189i. After Christmas of that year Professor Wiedersheim procured for me more material, through the kindness of Dr. Giinther, of the British Museum, and Professor Mobius, of Berlin, and I wrote a short paper on their lateral line system, though I also investigated other parts of their anatomy. Proceeding then to the Zoological Station at Naples, to occupy the Oxford University table, my work on this group was again interrupted, since I wished to make use of opportunities of studying the development cof the head in fish. At Naples, however, I also dissected quite a number of the more uncommon Selachii and Teleostei, and came to the conclusion that very little information could be gained as to the ancestral history of the head, from a study of its development. Before leaving the Zoological Station I made the wax plates for a model of Szlurus glanis from a valuable series of sections, which Professor Dohrn, knowing how widely my views differed from his, with generous magnanimity, handed to me for examination. On my return to England I continued the present work at University College, London, where Professor Weldon supplied me with some specimens of Myaxime. My study has been completed as Berkeley Fellow of the Owens College, Manchester. I am also greatly indebted to the Governing body of my Oxford College, Ch. Ch., which renewed a research scholarship. To the late Professor Milnes Marshall I owe a specimen of Protopterus, and to Mr. Hoyle, Keeper of the Manchester Museum, the opportunity of making a preparation of Ceratodus. In various museums I have taken every opportunity of studying fish, both recent and fossil. The wax models described in this paper were made from the following species : Auchenasprs biscutatus Geofftr., Cameroons. 4 Trichomycterus tenuis (Pygidium tenue) Weyenbergh, Sierra de Cordoba. Callichthys paleatus Jenyns, Porto Alegre. Silurus glanis. A small specimen of Chaetostomus guairensis Steind., Caracas, was unfitted for modelling. ORAL CIRRI OF SILUROIDS AND ORIGIN OF THE HEAD IN VERTEBRATES. 3 TECHNIQUE. The models have been made after the well-known method of Born, but with certain additions to the technique. The heads of the small fish were decalcified in picric acid, stained with alum carmine, and subsequently with bleu de Lyon. Camera drawings were made on ordinary tracing paper and then rolled in with the wax to make the plates. I used the cheap impure wax with a low melting point of the kind used, I am told, by printers. A large rectangular museum bottle proved the best table on which to cut out the plates. After reaching a certain size the models became extremely difficult to handle and it was necessary to find some method of strengthening them. I decided to electroplate them. The parts were wired together and then brushed with a suitable kind of blacklead. Then by applying in the copper sulphate bath, a current up to 5 or 10 ampéres, according to the size of the model, a deposit of copper of sufficient solidity was formed ia a few hours. Subsequently they were painted and photographed. For opportunity of carrying out these operations I am indebted to the Physical Department of the Owens College. By subsequent calculation I find that the models are an appreciable fraction too long in comparsion with the breadth, but that does not detract to any great extent from their value. The wax plates must be made considerably thinner than the calculated thickness, but how much thinner depends on the “ personal equation.” ON THE OCCURRENCE OF ORAL CIRRI. Oral cirri, barbels, barbules or tentacles occur in many fish, and form one of the characters diagnostic of the Siluroids (Wematognathe), in which they occur throughout, with the apparent exception of Plecostomus. Much information on them can be gained from systematic works, especially from Giinther’s Catalogue of Fishes, where the subject is treated from the systematist’s point of view. True barbels do not grow out indefinitely, but only with certain morphological relationships, and the maximum number in the Craniata is 6, or perhaps-7 pairs, which I term nasal, premaxillary, maxillary, coronoid, mental (and extramental) and submandibular. I attempted to draw up a list shewing the occurrence of the H. B. POLLARD. individual tentacles, but had to relinquish it from lack of morpho- logically precise observations. These tentacles may be bifid and per- haps completely split, or fringed, but nevertheless all processes from the skin round the mouth, e.g., those of Plecostomus may not be con- sidered proper tentacles, though they may in a remote way have been connected with tentacles. Such skin processes may be compared with the fringe round a lamprey’s mouth. Tentacles occur in Cyprinoids, and especially in Coé¢tidae, where they attain an equal development with the Siluroids. They appear also in Gladidae and other fish. JJotella trictrrata and Mullus barbatus: are familiar examples. Again they are found in Sturgeons, as the barbels under the snout, and in the larva of an Amphibian, Dacty/- ethra (Xenopus). Below the fish they appear in Myxinoids, and as I maintain, in the well-known form of the oral cirri of Amphioxus. A typical tentacle should consist of the following parts: (1) a skeletal axis connected with a root piece, the axis being accompanied. by (2) sensory nerves, which supply tactile organs in the skin, and worked by (3) muscles belonging to a special system and not homo- logons with the metameric body muscles, the (4) motor nerve supply being from nerves which have been shown to arise from the lateral cornu of the central nervous system, and to proceed out with the Sensory nerves. DescrIPrivE Part. Model of Auchenaspis (Figs. 1, 2, 8). The head of a specimen 5 cm in length, was cut in sections 30 u thick. Every second section was drawn with a camera with a magni- fication of 28 (Zeiss Oc. 2, Obj. aa, height above table of drawing 19 em). Thickness of wax plates 1°35 mm. 4 Model 23 cm long (or a little over 9 inches) by 20 cm broad. The head as far as reconstructed was about the size of a hazel nut. The specimen was no doubt a young one. The replacement of cartilage by bone has not occurred to any great extent. The head was not modelled further posteriorly than the anterior semicircular canal. The anterior semicircular canal is enclosed in cartilage, which does ORAL CIRRI OF SILUROIDS AND ORIGIN OF THE HEAD IN VERTEBRATES. 9 not however extend up as a tegmen cranil, nor is it prolonged down- wards to form the floor of the cranial cavity, and there is no appearance of resorption of cartilage, to indicate that at an earlier ontogenetic stage it extended further. A pterotic ridge is present, better developed in its posterior than in its anterior part, and it bears the moderately long articulation for the hyomandibular. The articulation is a very flat one, showing that there can be little movement of the hyoman- dibular on it. In the cranial floor, two blocks of cartilage occur, at the level of the anterior semicircular canal. The cartilage of the auditory region is con- tinued forwards as the wall of the orbital region, a bay in front of the anterior semicircular canal indicating where the facial and trigeminal nerves pass out. Slightly further forwards about the middle of the orbital region, the epiphysial bar (Hph) passes across the supracranial fontanelle, and somewhat further forward, there is a large open space in the cartilaginous wall. This is filled up by thin bone and does not transmit nerves or blood vessels. Below this a cartilaginous projection, directed backwards at each side of the pituitary body, forms a partial floor to the brain in this region. It leaves a deep notch below the orbital wall, filled up however by thin bone. Where the orbital joins the ethmoid region, a slit-like preorbital canal (Pr. orb. c.) can be seen. It transmits a vein and the Ophthalmicus superficialis, VII. The nerve runs in a foramen of the cartilage on the right side of the drawing, the opening being seen from the front, on the preorbital process. On the left side of the figure, a notch corresponds to this foramen, the cartilage being partly replaced by bone. The preorbital process is well developed, but not of great vertical extent. An extraordinarily well developed rostrum is present, triangular in section in its anterior part, the upper angle truncated in the posterior sections. This rostrum extends far back posteriorly, as a thick cartil- aginous septum between the olfactory nerves and lobes of each side, and from this septum a roof extends to the orbital wall and preorbital process, s) that the olfactory nerves and lobes lie in long tunnels of cartilage, except where this is placed irregularly, above and below, by thin bone. In the model these replacements appear as asymmetrical open spaces on each side of the rostral region. 6 H. B, POLLARD. The anterior narrower portion of the brain case, that is, from the epiphysial bar forwards, is drawn out to a remarkable length, as indeed are all the structures of the anterior part of the head. The hyoman- dibular cartilage (H./.) is triangular in form, the lower angle being produced into a strong process, which bears the operculum without the intermediation of an opercular cartilage. An extensive but thin block of cartilage (Qu) remains in the symplectic and quadrate region, and sends inwards and forwards a short pterygoid process. The cartilaginous terminal portions of the prepalatine piece (Prepal.) are shown in the figures, the part round about the articulation with the preorbital process being replaced by bone. ‘The prepalatine car- tilage reaches almost to the tip of the snout. A small round block (m.v.s.) between the ends of the prepalatine cartilages in the model represents, in a very diagrammatic fashion, the premaxillary piece and rudimentary median support of the velum. The Meckelian cartilage (Mck) has an inverted T-shape, the arms of the T being long. The posterior arm does not reach the quadrate, the quadrato-mandibular articulation being formed by bone. The upper process is the coronoid process (Proc. cor.) which bears the long and large procartilaginous coronoid piece (Cor. p.), which is continued into a tentacle combining characters of maxillary and coronoid tentacle (Mz. t.), in that it is continuous with the coronoid piece, and also supported by the maxilla, which is attached to the end of the prepalatine cartilage. The tentacle is directed outwards and backwards. The anterior arm of the Meckelian cartilage is the mentomeckelian process (M.mck.), which is very far from reaching its fellow of the opposite side. I am inclined to think that it has not, at an earlier ontogenetic stage, extended further. In the fleshy lower lip, there is a huge block of procartilage? (Ment. p.), with a projection directed posteriorly, while medially and somewhat below this block may be seen on each side the mental tentacle (Ment. t.), which is actually supported by a lamina of procartilage, lying superficially below the dentary bone. This supporting lamina is of considerable extent. A submandibular tentacle (Swbm. ¢.) lies below the coronoid process, also with a superficial supporting lamina of procartilage. 1Better termed Extramental. ORAL CIRRI OF SILUROIDS AND ORIGIN OF THE HEAD IN VERTEBRATES. 7 A stylohyal (Sty. hy.) bears the ceratohyal (Hy.) which is massive posteriorly. The thickened anterior end bears a hypohyal piece. Model of Silurus (Figs. 3, 4). Sections 15 » thick. Every third section drawn, with magnification 28 (Zeiss Oc. 2, Obj. aa). Height of drawing above table 19 cm. Wax plates 1 mm thick. Model, reconstructed as far as middle of horizontal semicircular canal (on one side), 11 em long and 15 broad. The drawings for this model were taken from sections belonging to Prof. Dohrn, which he kindly allowed me to use. The cartilage was at its maximum development, no replacement by bone having occurred. The skull wall, in the auditory region, is not completed on the in- ternal aspect, but on the contrary, a large fenestra is left, as is the rule in Teleostei. The cartilage of the side wall of the cranial cavity only extends back so far as to separate the anterior semi-circular canal from the brain, while above, in the same region, a cartilaginous roof extends towards the middle line very slightly beyond the level of the membranous labyrinth. The pterotic ridge, which is on a level with the external semicircular canal, is not specially strongly developed. Below the pterotic ridge is the articulation for the hyomandibular, which is a long narrow articulation, situated at an angle of 30° to the median axis. From the pterotic ridge, the floor of the auditory capsule slopes, at an angle of 30° with the horizontal plane, to the basicranial region where it is continuous across the middle line, behind the large pituitary fontanelle. As is well known, an interorbital septum is never formed in Siluroids, and at this young stage the orbital walls are very wide apart. The upper portion of the orbital wall (Parker’s supraorbital band) is a forward prolongation of the auditory capsule, and is triangular in section for some distance, the pterotic ridge being also continued forwards. ‘The pterotic ridge can in fact be traced on to the antorbital process. In front of, and partly below the auditory region, is a great foramen in the skull wall, through which many of the cranial nerves pass out, all from the optic to the facial. This is partly filled, in the adult, by the so-called prootic. The floor of the cranial cavity is con- tinuous cartilage, except for the large pituitary fontanelle, but, between this foramen and the pituitary fontanelle, the cartilage is much reduced in breadth and thickness. The skull wall in the anterior half 8 H. B. POLLARD. of the orbital region is complete and passes into the ethmoid region. At its anterior limit there is a foramen, the Canalis praeorbitalis (Pr. orb. c.). At the junction of the orbital and ethmoidal regions the epiphysial bar (Hph.) passes across the supracranial fontanelle, thus dividing the latter into pre- and post-epiphysial portions. The side wall of the skull is produced into a large vertical antorbital process, separating the nasal and orbital cavities, and the cranium is almost as wide in this region as in the auditory region. At its antero- lateral extremity, the antorbital process has an articulation for the prepalatine piece (Prepal.). The nasal cavities are wide apart, the rostral portion of the chondrocranium being very broad. The olfactory lobes and nerves lie, as it were, in two short tunnels, being separated by a thick internasal septum and roofed over by the bridge of cartilage, which extends from the anterosuperior orbital region to the rostral region. Between the antorbital process and the base of the rostral region lies the extensive floor of the nasal cavity. The shape of the rostral region is best shown by the figure (Fig. 3). The hyomandibular (H.2/.) articulates, as above mentioned, with the pterotic region of the auditory capsule. Its upper portion is in the form of an inverted triangle, the articulation being the base of the tri- angle. At the apex of this triangular part there is a notch in front for the hyomandibular nerve, while behind is attached the opercular cartilage which bears the operculum. From this level the hyomandibular cartilage broadens downwards and forwards to the quadrate and symplectic regions. At the posterior ventral angle, that is in the symplectic region, is attached the stylohyal, while at the most ventral, or quadrate region, is situated the articu- lation for the lower jaw. Inwardly and forwards, the quadrate is pro- longed into the small pterygoid process, which in Szlurus is attached by a ligament to the vomer. The prepalatine piece articulates with the antorbital process. It is an irregularly shaped block of cartilage. In some specimens there may be found at, its anterior edge accessory nodules of cartilage. Externally it bears the procartilaginous axis of the maxillary barbel (J/2. ¢.), which proceeds out at a right angle for a short distance, then turning backwards. The prepalatine piece has no connection with the ptery- goid process. In front of the rostrum is a small triangular block (Pmz. p.) repre- senting somewhat schematically the premaxillary block of procartilage. ORAL CIRRI OF SILUROIDS AND ORIGIN OF THE HEAD IN VERTEBRATES. 9 The Meckelian cartilage (M/ck.) passes horizontally forward from its articulation with the quadrate. An angular process, however, passes downwards aud backwards from the articulation. At some little distance forward, the coronoid process is given off. The coronoid process (Proc. cor.) projects vertically upward and bears the procartila- ginous, cylindrical, horizontally placed coronoid piece (Cor. p.), which reaches forward to the level of the prepalatine piece, its end, in fact, approaching the maxillary tentacle. Directly below the coronoid process lies the proximal portion of the submandibular tentacle (Subm. t.), and, some little distance in front of this, is seen the corresponding part of the mental tentacle { Ment. t.). Beyond the level of the mental tentacle, the Meckelian cartilage becomes distinctly more slender (m. Ack.) passing over con- tinuously, in the symphysial region, into the corresponding portion of the opposite side. Viewed from the front, the model reveals a most remarkable conformation of the edge of the rostral portion and the Meckelian cartilage, a bay being formed in the rostrum above, and in the Meckelian cartilage below. A nodule (m.v.s) attached to the rostral region, in the bay, represents a tentacle-like pro- cartilage support of the upper ‘‘ Velum,” or flap used to close the mouth in respiration, and a corresponding nodule (m.v.s) on the Meckelian cartilage represents the lower tentacle-like support of the lower velum. The stylolryal bears the enormous ceratohyal (//y.) which is much expanded at its anterior and posterior ends. The middle portion which is strengthened by perichondrial bone is thinner. Anteriorly are found the smaller hypohyals. Mode! of Trichomycterus (Figs. 5, 9). Specimen about 2°5 cm in length. Sections 20 p thick. Every second section drawn with magnification 48 (Zeiss Oc. 14 Obj. aa.). Height above table of drawing 19 cm. Thickness of wax plates 1°6 mm. Model about 13°5 cm long by 185 broad. Reconstructed so far as to show the hyomandibular. The head was about the size of a small pea. The replacement of cartilage by bone has gone on in places so far as to seriously interfere with the modelling although the specimen was very young, 10 H. B. POLLARD. the nerves being almost in an embryonic condition. Apparently in all the S. American Siluroids ossification begins at a remarkably early stage. The auditory region shows much replacement of cartilage by bone, only irregular and asymmetrical projections being left. Cartilage only remains in fact in the neighbourhood of the hyomandibular articulation. A pterotic ridge is little developed and the hyomandibular articulation, which is very great in extent anteroposteriorly, may be said to be on the pterotic ridge itself. The cartilaginous floor of the brain case is only represented by three isolated blocks, one unpaired and median at the level of the auditory labyrinth, and a pair situated below the foramen of exit of the Facial and Trigeminus nerves. The supraorbital band is the only remaining cartilage of the posterior part of the orbital wall. It is somewhat triangular in section. At the middle of the orbital region the epiphysial bar (Z’ph.) passes across the supracranial fontanelle. In the anterior border of the epiphysial bar at the median point is a notch where the epiphysis rests. In front of the level of the epiphysial bar a portion of the carti- laginous side wall is left and shown foreshortened in the figure (Fig. 5) but there is no antorbital process and no bridge above from the orbital to the rostral region (iu other words the olfactory lobes and nerves are not roofed over by cartilage). The internasal septum takes the form of a distinct rostrum which however does not project beyend the level of the anterior narial opening. In the cranial floor behind the rostrum is a pair of small fonta- nelles in the cartilage. One is indicated by the shading on the right of the drawing. These lodge minute projections from the base of the forebrain. Behind the epiphysial bar the skull cavity widens out very remark- ably. From the epiphysial bar forwards it is much smaller as shown in the figure. The hyomandibular (H.M/.) articulates with the skull by an enormously long articulation and only along the articulation does much cartilage remain. There is, however, a strong process downwards and backwards which supports the operculum without the intermediation of an opercular cartilage. Another block of cartilage remains in the symplectic and quadrate region, the intervening portion having been replaced by perichondrial bone, ORAL CIRRI OF SILUROIDS AND ORIGIN OF THE HEAD IN VERTEBRATES. 1! A small pterygoid cartilage (Pty. Fig. 9) is independently formed much further forward. It may be seen on the left of the figure partly hidden by the prepalatine piece. The cartilaginous apophyses of the prepalatine piece (Prepal.) remain as a small portion at the articu- lation near the base of the rostrum and a large distal block. Above the prepalatine cartilage is the nasal tentacle with a slight basal expansion. ‘This forms the outer wall of the anterior narial opening. The rostrum bears at its tip the upper tentacle-like support of the velum (m.v.s). A small nodule of procartilage is seen on the left between the prepalatine and the velar supports. The maxillary tentacle (Vz. t.) does not rest on the prepalatine piece but is supported by the intermediation of the maxillary bone. Its base is bifurcated on the left side of the figure. The Meckelian cartilage (J/ck.) is represented as a triangular block. The posterior portion has undergone partial resorption and the posterior angle is far from reaching the quadrate. The upper angle is prolonged into a vertical somewhat anteriorly directed coronoid process (Proce. cor.) to which is affixed the procartilaginous coronoid piece (Cor. p.) which is large and passes continuously into the coronoid tentacle. The tentacle (Cor. t.) turns downwards, outwards, and backwards. The anterior angle of the Meckelian cartilage is produced into the mentomeckelian process (m. ck.) which is short and very far from reaching its fellow of the opposite side. The distance of the mentomeckelian processes from each other is well shown in the figure. A stylohyal cartilage (Sty. hy.) is present and bears the ceratohyal which is very thick at its two ends. In the specimen the middle portion was replaced by perichondrial bone on one side. The distal extremity bears a hypohyal. The postero-ventral tip of the ceratohyal bears a procartilaginous prolongation (* Fig. 9) which supports the uppermost branchiostegal ray. It may perhaps be considered the homologue of one of the car- tilaginous branchiostegal rays of Selachii. Model of Callichthys (Figs. 6, 7, 10). Specimen 3 cm. in length. Sections 25 » thick. Every second section drawn, with magnification 28. (Zeiss, Oc. 2, Obj. aa). Height of drawing above table 19 cm. Wax plates 1:2 mm. thick. 12 H. B. POLLARD. Only the end of the snout reconstructed. The specimen was young but replacement of cartilage by bone has proceeded to a considerable extent, especially in the rostral region. The median cartilage of the rostral region slopes sharply downwards and forwards, and, viewed from the side, its profile is curved. The floor of the nasal cavity extends laterally as two wings, actually prolonged still more laterally by the prefontal bone. At the median anterior part of the rostral region there are abundant traces of resorption of cartilage, showing that a more distinct rostral prolongation was present at an earlier stage. This resorption is the cause of the irregular appearance of the anterior face as seen in the model. Below the junction of the lateral and medial portions, a remarkable though slight projection of cartilage (* Fig. 7) bears the prepalatine bones, of which the large cartilaginous apophyses are seen in the figure, placed curiously close together and, along with the so called ethmoid bone, reaching very near to the tip of the snout. Below and in front of the prepalatine cartilage is seen the three- rayed, procartilaginous premaxillary piece, forming the tip of the snout (Pma. p.). The maxillary tentacle (J/z. t.) is attached to the prepalatine car- tilage through the intermediation of the maxillary bone. The tentacle itself passes sharply downwards and backwards, below the coronoid tentacle. Behind the maxilla lie the paired, external tentacle-like supports of the velum (/. v. s.). Only the mentomeckelian portion of the lower jaw (m. Mck.) is seen in the model. A coronoid process is not developed, and the coronoid piece is only represented by a procartilaginous rudiment, not shown in the model. The coronoid tentacle (Cor. t.) proceeds backwards, almost parallel with the mentomeckelian cartilage, and it is fused with the distal portion of the mental tentacle (Ment. t.). The mental tentacles, which have a beautifully curved form, are fused with one another at their bases in the middle line, below the premaxillary piece. The junction is in front of, and slightly below the symphysis of the dentary bones. The distal fusion of the mental and coronoid tentacles deserves especial attention. a ORAL CIRRI OF SILUROIDS AND ORIGIN OF THE HEAD IN VERTEBRATES. 13 Sensory Tentacular Nerves of Auchenaspis (Fig. 8). The trigeminal nerve passes out from the skull, along with the Facial, in front of and below the hyomandibular articulation, thence passing downwards and forwards below and somewhat internal to the eye, which in Siluroids is small. Just below the optic nerve it divides into two great branches, the upper and internal shortly dividing into palatine (#. Pal.) and maxillary branches. The lower branch slightly further forwards divides into Ramus coronoideus and Ramus mandi- bularis. The palatine branch, after separating from the maxillary, passes inwards through an anterior portion of the adductor arcus palatini muscle, that part which stretches from the skull wall in the anterior orbital region to the posterior end of the prepalatine piece, and which moves the maxillo-coronoid barbule. The motor nerves to this muscle run along with the palatine aerve. Reaching the skull wall the pre- palatine nerve passes downwards and forwards, beneath and internal to the preorbital process, lying in fact beneath the lower wall of the passage of the olfactory nerves. Here it runs alongside the edge of the vomer and, reappearing in front of the postorbital process, proceeds, parallel to the edge of the rostrum and beneath the olfactory organ, to the end of the snout where, on reaching the premaxilla, it divides into several small twigs. The maxillary nerve (&. Mz.) runs forward almost horizontally above the edge of the posterior part of the prepalatine piece, giving off the premaxillary branch and passing just outside the postorbital process. It then takes a long course forward between the anterior part of the prepalatine and the coronoid piece, giving off above a small branch to: the skin and, below, another branch which supplies the skin at the base of the maxillo-coronoid tentacle. The main portion turns outward aud supplies the anterior face of the maxillo-coronoid tentacle. The premaxillary branch (2. pmz.) passes external to the preorbital process, crossing over the prepalatine piece to lie internal to this piece, runs forward parallel to the edge of the rostrum, and divides into twigs which run beneath and outside the olfactory organs to supply the premaxillary region. The coronoid branch (2. cor.) is given off from the mandibular nerve 14 H. B. POLLARD. and passes forward parallel to and just outside and below the maxillary nerve. It turns outward, still parallel to the maxillary nerve, and supplies the posterior face of the maxillo-coronoid tentacle. The mandibular nerve (2. md.) passes downwards and forwards and, some little distance behind the coronoid process, it divides into Ramus mandibularis externus and R. md. internus. The R. md. externas passes outside the coronoid process forwards and downwards outside the mento-meckelian process, and reaches the posterior edge of the mental piece (the large block of procartilage in the lower lip). Here it divides into a number of twigs which supply the fold of skin below and behind this piece. The R. md. internus passes inside the coronoid process and divides into two branches which I name mental and submandibular. The mental branch (2. ment.) passes forwards, outside and below the mento- meckelian process, internal to the R. md. externus. Proceeding horizontally forwards, it crosses internally the block of procartilage of the lower lip and, reaching the mental tentacle, passes down it, dividing them into two branches, which supply the anterior and posterior aspects of the tentacle. The submandibular branch (2. subm.), after parting from the mental, proceeds down outside the mento-meckelian process to the submandi- bular tentacle, dividing into two branches, which supply the anterior and posterior faces of the tentacle. The R. md. internus contains motor portions, which pass off where the nerve divides into mental and submandibular branches, and supply, the anterior branches, the muscles of the mental tentacle, and the posterior the muscles of the submandibular tentacles. More exact descriptions of the muscles and the motor supply must be reserved for a subsequent work. I have not observed any ophthalmic branch of the Trigeminus though some fibres may accompany the Ophthalmicus superficialis of the Facial. Sensory Tentacular Nerves of Trichomycterus (Fig. 9). The Ophthalmicus profundus (2. 0.p.) takes its exit from the cranial cavity independently of the maxillary branches, and is at first difficult to distinguish from the Ramus ophthalmicus superficialis of the Facial. It runs below the rectus superior, above the optic nerve, along the ORAL CIRRI OF SILUROIDS AND ORIGIN OF THE HEAD IN VERTEBRATES. 15 wall of the orbital region, proceeding forwards, outside the olfactory organ, to reach the nasal tentacle, then dividing into two branches which supply this tentacle. The great maxillary stem, taking its exit in front of the hyomandi- bular, proceeds downward and forward to below the eye. Behind the optic nerve it gives off the Ramus palatinus (7. pal.), which runs inwards and downwards, through the anterior portion of the adductor arcus palatini muscle (that part which moves the prepalatine piece and to which it gives motor fibres), Reaching the base of the skull it runs forward alongside the vomer and parallel to the edge of the rostrum, and then reaching the premaxilla it divides into several small twigs. Below the eye the great maxillary stem divides into two branches the Ramus maxillaris (#. mx.) and the Ramus mandibularis (#. md.). Almost immediately, the R. mavxillaris gives off a Ramus pre- maxillaris (2. pmx.) which runs outside the anterior portion of the adductor arcus palatini, outside the articulating cartilaginous part of the prepalatine piece, above the bony portion, and internal to the anterior cartilaginous part of the prepalatine. Here it runs below the olfactory organ, parallel to the Ramus palatinus, and dividing into fine twigs, is lost in the tissue above the premaxilla at the tip of the snout. The Ramus maxillaris runs forward horizontally, above and some- what internal to the coronoid piece, dividing in front into three branches, the innermost of which supplies the skin internally at the upper anterior angle of the mouth, the upper and outermost branch passing downwards in front of the coronoid piece, then dividing into two twigs which supply respectively the anterior faces of the maxillary and coronoid tentacles. The third middle branch runs down, internal to the coronoid piece, and supplies the posterior face of the maxillary tentacle. The Ramus mandibularis gives off a Ramus coronoideus (2. cor.) which runs forward, outside and parallel to the R. maxillaris, and turning down, proceeds to the posterior face of the coronoid tentacle. The Ramus mandibularis, passing downwards, runs internal to the coronoid process and divides into mental and submandibular nerves, besides giving off motor fibres. The Ramus submandibularis (f. subm.) turns backwards, outside the coronoid process, and supplies the skin below the Meckelian cartilage, while the R. mentalis (2. ment.) is continued forwards to the front of the dentary region. 16 H. B. POLLARD. Sensory Tentacular Nerves of Callichthys (Fig. 10). The main stem of the Trigeminus passes below the eye giving off behind that organ a palatine branch, which divides into several small twigs supplying the roof of the mouth. Below the centre of the eye the main stem divides into two branches, an upper and lower. The upper gives off shortly a Ramus premaxillaris (A. pmz.) and, as the Ramus maxillaris (2. mz.), runs forward along with the R. premaxillaris in a space between the adductor mandibulae and adductor arcus palatini muscles. The Ramus pre- maxillaris gives off small branches to the skin in the antorbital region and passes forward, lying near the skin outside the prepalatine piece, dividing into small twigs in the premaxillary region. The Ramus maxillaris, running forward, divides into (1) a small branch which passes outwards and downwards and along the posterior face of the coronoid tentacle, (2) a large branch which runs down outside the maxillary tentacle and divides into four twigs, two of which supply the anterior and lateral face of the ccronoid tentacle, and the other two the posterior face of the maxillary tentacle, (3) a branch which divides above the velar support, some twigs supplying the lateral part of the anterior region of the roof of the mouth, the remaining branch passing down inside the maxillary tentacle to supply its anterior face. The Ramus mandibularis (#. md.) gives off a Ramus coronoideus (FR. cor.), which is small and runs above and outside the adductor mandibulae muscle, turning down to supply the posterior face of the coronoid tentacle. Continuing forwards and downwards, through the adductor mandi- bulae muscle, the Ramus mandibularis divides into R. R. mandibulares externus (&. md. ext.) and internus. The R. mandibularis externus lies outside the muscle and gives off a small branch, which runs down- wards and backwards to the skin outside the Meckelian cartilage, thence, passing outside the anter‘or portion of the Meckelian cartilage, it continues forwards interual to the maxillary and coronoid tentacles, and reaching the mental tentacle, it divides into three small twigs, which supply the anterior face of this tentacle, the skin there being remarkably rich in sense organs. The Ramus mandibularis internus divides above the Meckelian cartilage into R. submandibularis (2. subm.) and R. mentalis (4. ment). ORAL CIRRI OF SILUROIDS AND ORIGIN OF THE HEAD IN VERTEBRATES, 17 The former turns down outside the mentomeckelian process, while the R. mentalis continues on above it and passing forward horizontally, parallel to the R. maudibularis externus, divides into small twigs which supply the posterior face of the mental tentacle. An Ophthalmicus profundus is only represented by certain fibres running in the course of the Ramus ophth. superficialis of the Facial. Sensory Tentacular Nerves of Myzxine (Fig. 11). For purposes of comparison and in view of the object of this paper, I venture to give a figure of the terminal distribution of the sensory branches of the Trigeminus in M/yaine, with some description, though I have only one point to add to the almost perfect account given by Johannes Miiller in his classical memoir. In the figure the anterior part of the irregular nasal skeleton is shown, and supplying the skin in this region are several twigs belonging to one of the branches of the Ophthalmicus profundus (2. 0, p.), the upper terminal branch of the first branch of the Trigeminus of Miiller, 5” in his figures. One twig also proceeds to the premaxillary tentacle (shown in my figure with an asterisk). The branch termed Ramus premaxillaris (2. pmx. in the figure) is Miiller’s ‘lower stouter branch of the first branch of the Trigeminus, 5””” Tt runs alongside the premaxillary piece, the ‘‘ vordere knécherne Sttitze der Schnauze,” and, after giving off motor branches, supplies the first or premaxillary tentacle. The above two branches form the “upper anterior branch of the Trigeminus” and both are said to run above the optic nerve in Ldellostoma. They are by most authors termed ophthalmic branches, and I have kept that name in my preliminary communication. The remaining branches belong to the “anterior lower branch” of Miller. The maxillary nerve (2.mz.) is his branch 6 and the coronoid (2. cor.) is his branch 6”. They supply the maxillary and coronoid tentacles. My Ramus mandibularis (#.md.) corresponds to the ‘‘ deeper finer branch, 6”, of the anterior lower branch.” Only the sensory part is shown in the figure. It divides into a Ramus mentalis (ZR. ment.) supplying the fourth or mental tentacle, and a Ramus submandibularis (R. subm.), not specially mentioned by Miiller, which supplies the skin B 18 H. B. POLLARD. in front of and below the anterior lateral piece of the ‘ Zungenbein ” of Miiller which I take to be the Meckelian cartilage. CoMPARATIVE PART. Nasal Tentacle. The most typical condition of the nasal tentacle is shown in Trichomycterus. The procartilaginous axis expands at its basal portion, and forms a partial wall outside the olfactory organ, being attached to. a small bone, one of the terminal antorbitals of the series surrounding the suborbital branch of the lateral line system, This small bone and the base of the tentacle are supported by the prepalatine piece. In Clarias the base of the tentacle is bifurcated, and the two prongs are attached to prefrontal and antorbital bones, at each side of the posterior of the nasal openings, the tentacle itself rising up in front of the opening behind the small nasal bone. The position of the tentacle in relation to the anterior and posterior nostrils has been used as a diagnostic of certain groups of the Siluroids (Giinther). In Motella tricirrata, one of the Gadidae, far removed from the Siluroids, the procartilaginous axis of this tentacle bears the anterior tubular opening of the nose, and the basal portion forms the roof of the olfactory chamber. In Callichthys though the tentacle is absent there is a procarti- laginous roof to the olfactory chamber, which helps to support the anterior narial aperture and is obviously the basal portion of a tentacle. Thus it is seen that when the tentacle is absent yet a basal portion of it may remain and form asupport for the wall of the olfactory capsule. As such it is known to anatomists as the “nasal labial” or ** Nasenfliigelknorpel.” ; According to Sagemehl, such a nasal labial occurs in many Cyprinoids and perhaps in all; and also in the Characinidae. No doubt on special search it might be found in very many other groups of Teleostei. The nasal labial of Selachii has been described in rich detail by Johannes Miiller and Gegenbaur. Many references to such structures. have been made by Parker, but subsequent investigation has shown his observations to be unfortunately unreliable. In many Selachii the nasal labial is fused with the edge of the nasal ORAL CIRRI OF SILUROIDS AND ORIGIN OF THE HEAD IN VERTEBRATES. 19 capsule, and indeed Gegenbaur concludes that it isa portion cut off from the cranium. That, however, is controverted by comparison outside the Selachii. In the Dipnoi there is a trelliswork of cartilage forming the wall of the olfactory capsule and, in view of the frequent fusion of the nasal labial with the cranium in Selachii, this trelliswork may perhaps be held to represent a nasal labial. The nasal capsule and tube of Myaine is surrounded by irregular rings of procartilage, which represent the nasal labials. Gegenbaur, in mentioning this view, concludes that it is a hasty one, but all doubt seems to be removed by the fact that the nasal tube is worked by a muscle, the Nasalis of Fiirbringer or “ Zuriickzieher der Nasenoffnung” of Miiller, which belongs to the tentacular system and is supplied by the Ophthalmicus profundus, while the nasal tube itself receives sensory branches from the Ophthalmicus profundus. The compressor narium M. ethmoideonasalis F., and a portion of the transversus oris F. are also attached to the nasal tube. On this point Miiller remarks that ‘Since two olfactory nerves proceed into the single olfactory capsule, the single olfactory capsule is to be explained rather by the apposition than fusion of the nasal capsules of cartilaginous fish, and this happens indisputably through the suppression of those parts which otherwise lie between the nasal capsules”. While agreeing with Miiller in principle, I regard the supporting elements of the nasal capsule of Myaine as corresponding only to the nasal labial of Selachii, not to the whole capsule. Furthermore no one, who has examined a series of sections of the head of Ayxine, can doubt that the plate supporting the posterior part of the nasal or hypophysial tube where it opens into the palate, the ‘“Gaumenplatte ” of Miiller or “posterior intertrabecula” of Parker is a posterior continuation of the nasal skeleton, and as such ultimately _ to be derived from a nasal tentacle. Miiller compared the nasal cartilages of Chimaera with the rings of the nasal tube of Myxine. This view is shown below to be untenable. Only the most anterior crescentic cartilage (f of Miiller) corresponds to the nasal labial of Selachii and the nasal rings of Myzine. Nerve Supply. The motor nerves, which have occasionally to be referred to in this paper as supplying the system of tentacular muscles, are, to follow the 20 : 153) 3 HB: POLLARD: distinction established by His, nerves of the lateral cornu. The sensory nerves of the oral cirri are branches of the Trigeminus, and a sharp distinction must be drawn between them and the nerves of the lateral line system. The nerves of the lateral line system develope quite differently from the trigeminal branches. Their ganglia are derived from cells proliferating along certain tracts of the ectoderm as shown by Beard, Froriep, and Kupffer. I have followed the process myself in Gobius. The evidence of comparative anatomy is not less clear as to distinctness of the lateral line nerves in fish. The topographical position and course of nerves is not of great importance.. This has been determined by Stannius for the palatine nerves. ‘It is to be established that in certain classes of animals a larger, in others a smaller portion of allied elements may be contained originally in the course of one or other of two allied nerves, and at the same time the same elements may frequently arise by an indifferent root, without distinctly belonging to the one or the other nerve.” Numerous examples of this phenomenon will occur in this paper, The most extreme case is that of the premaxillary nerve of Myxinoids. According to Fiirbringer the premaxillary nerve in Ldellostoma, runs over the eye-stalk and optic nerve, while in Myzxine (and all other vertebrates) it runs below the optic nerve. Fiirbringer indeed explains this by supposing the eye a later structure and capable of wandering, but an explanation on the grounds given by Stannius is more reason- able. Thus we see that the fundamental grounds for determining the homology of nerves are (1) origin from homologous nerve cells, (2) terminal distribution to definite structures. The course of the fibres is of less importance. It is hardly necessary to remark, however, that an absolutely strict conception of homology is incompatible with a theory of evolution. The sensory nerve of the nasal tentacle is the ophthalmicus pro- fundus, and it is shown best in Zrichomycterus where it takes the normal course of an ophthalmicus profundus, namely, below the rectus superior and obliquus superior, over the eyestalk. In Zvrichomycterus it runs on the outer side of the olfactory organ to reach the tentacle. In Clarias the nerve does not bear quite the same relation to the eye muscles, because the small eye, along with the muscles, is shifted very far laterally, while the nerve follows the skull wall more closely. It runs on the median side of the olfactory organ to reach the tentacle. ORAL CIRRI OF SILUROIDS AND ORIGIN OF THE HEAD IN VERTEBRATES. 21 In other Siluroids the ophthalmicus profundus may only be represented by some fibres running along with the ophthalmicus superficialis of the Facial. In some Siluroids e.g. Stlurus (Stannius) and Clarias the trochlear nerve runs along with the ophthalmicus profundus. That is purely a case of apposition. The comparative anatomy of the ophthalmicus profundas is fairly well known in the vertebrates, and need not be further entered into here, except as regards Myzxine. In Cyclostomi, Miiller and Stannius showed that it contains motor fibres, a fact of which most embryo- logists who have drawn up schemes of the head have been oblivious. The motor fibres supply muscles attached to and working the nasal tube and belonging to the tentacular system. Another feature in Myzxine is that a small twig from the ophthalmicus profundus supplies the premaxillary tentacle. Premaxillary Tentacle. A premaxillary tentacle occurs in Cobitidae (Misgurnus) and some Cyprinoids e.g. Barbus, where it is attached to the premaxilla. However, these forms are much modified as to histology and topographical relations and are not suited to form a basis for comparison, In Siluroids, though the tentacle itself is absent (except in Aspre- dinidae Giinther), yet there is usually present a block of procartilage at the tip of the snout in relation with the premaxilla. In Callichthys (Figs. 6 and 7 Pmzx. p.) this block is triradiate, occupying the tip of the snout below the prepalatine pieces, and on its lower surface developes the premaxilla. A corresponding block is present in Chaetostomus, differing somewhat in shape. With it articulate the anterior ends of the premaxillae which possess the remarkable form depicted by several authors in the Wypostomedae. The ventral position of the mouth in these South American Silu- roids is due to the large size of this piece and of the prepalatine, in addition to the presence of a rostrum. In Sturgeons it is due mainly to the rostrum, while in Selachii it is brought about by the position and size of the nasal capsules and the presence of rostral cartilages. In embryos of various vertebrates it is due merely to the mode of growth of the brain and olfactory organs, 22 H. B. POLLARD. In Silurus the premaxillary piece is represented by procartilage above and between the premaxillary bones. In many Teleostei it becomes a solid block of cartilage. It is mentioned by Staunius as a special part of the snout in front of the nasal septum. ‘In Cottus and Lelone, a small discrete cartilage, applied to the anterior end of the skull, is covered by the premaxillae.” ‘In Malthaea it forms a considerable free projection on the skull” (Stannius). Sagemehl gave the rather unsatisfactory name “ Rostrale” to this block and mentioned its existence in Scomberesocidae, Cyprinodontidae, Scopelidae, Cyprinidae, Anacanthini (Macrurus), Acanthopteridae and Plectognatht. ‘‘ From its relations to the premaxillae we have every ground for the supposition that it originally formed the basis (Grund- lage) of these bones. The fact that it occurs in far removed forms of Teleostei allows the conclusion that it is of great antiquity, and thus we may expect to find it in lower fish.” “It is found in most distantly related groups, and this points to its being an inheritance from a very remote ancestral form.” Sagemehl goes on to compare it to a small cartilage between the ends of the palato-quadrate in Heptanchus. This view cannot be correct. Since it is unpaired the piece cannot, according to Sagemehl, corres- pond to a labial of Selachii. A premaxillary block also occurs in the Pharyngognathi (Labrus) and probably in many others not yet investi- gated, especially where the premaxillae possess a vertical upward projection, sliding on the ethmoid region. Among the older anatomists this piece has apparently also received the name prenasal cartilage, but I have not succeeded in running this term down. An interesting feature in connection with this block is that the median velar support is shown by comparison to be a posterior prolonga- tion from it serving to support the velum or fold of respiratory function, which lies behind the premaxillae. ‘In many Teleostei, mucous folds, placed behind the jaws, hinder the outflow from the mouth of the water which has been gulped in” (Stannius). The median velar tentacle-like structure is shown in Silurus and Tricho- mycterus (Figs. 3 and 5) and it occurs in many Teleostei. There may be also a lower median tentacle-like support of a lower velum, and these two give the appearance shown in Si/urus (Fig. 3). It is the mode of development of these structures in the embryo which has given rise to the views of some embryologists on the paired nature ORAL CIRRI OF SILUROIDS AND ORIGIN OF THE HEAD IN VERTEBRATES. 23 of the mouth of Teleostei. These structures possess no great morpho- logical importance. A similar phenomenon is seen in the nose of Myzxine, where a small process forms a partial septum in the nasal tube. I propose to deal with the Selachii and some other forms later on. In the Sturgeon, the most median of the two pairs of tentacles appears, from its nerve supply, to be the premaxillary tentacle. The premaxillary tentacle of Myxine is the one which Miiller showed to be the first, though viewed externally it lies inside and below the morphologically second. It is continuous with the unpaired bar of hard tissue, which underlies the nasal tube, and which is its root piece. Miiller terms this premaxillary block the ‘“ knécherne Stiitze der Schnauze,” and has given full details. Nerve Supply. Two nerves supply the region of the premaxilla. They are the palatine and a branch of the maxillaris, which I term here the pre- maxillary. The R. premaxillaris occurs throughout the Siluroids, with comparatively unimportant variations. In Awchenaspis it runs along with part of the buccalis. The palatine nerve is also present in all Siluroids examined by me. It supplies the muscle which moves the prepalatine piece and, except in Callichthys, proceeds forward to the tip of the snout. The R. premaxillaris corresponds to the nerve supplying the pre- maxillary tentacle of Myxine. ‘This is usually considered to be an ophthalmic branch, and I have kept the old name in my preliminary communication, However, it is better to consider it a special branch, and not a mere portion of the ophthalmic. It is said to run over the optic nerve in Bdellostoma, and under it in Myxine, as in other verte- brates. It runs mainly in the substance of the palato-ethmoidalis superficialis muscle (Fiirbringer) the Retractor of the bony support of the snout (Miller), outside the premaxillary piece, beyond which it gives off a motor branch to one portion of the Depressor of the mouth (U’ of Miiller). It then supplies the premaxillary tentacle, which also receives a twig from the ophthalmicus profundus. Concerning the R. palatinus there are widely divergent opinions, which have been summarized by Stannius. In Silurus glanis he states that it is undoubtedly a branch of the Trigeminus. In other forms it 24 H. B. POLLARD. appears to be Facial, and finally in ‘‘ Ganoids,” elements of the Glosso- pharyngeus enter into its composition (v. Wijhe). Therefore, in considering its homologies, various components must be recognised in the palatine, and I consider the most anterior branches a dissociated portion of the R. premaxillaris. The most anterior tentacle of Cyprinoids is supplied by a nerve, of which Biichner bas given a most excellent description (in Barbus). He terms it maxillaris superior. ‘It springs from the anterior internal border of the ganglion, passes in a canal formed by the upper convex face of the body of the sphenoid (parasphenoid) and the base of the greater (prootic) and lesser wing (orbitosphenoid) and is directed along the internal wall of the orbit, passes between the anterior frontal (ectethmoid) and palatine along the vomer and forms a kind of plexus with a branch of the maxillaris inferior (R. mx. superior). From this plexus start three branches for the two barbels and for the fleshy lip along the inter- maxillary. That of the superior barbel passes through a foramen, hollowed out at the internal extremity of the maxillary bone.” Sagemehl has described the nerve as palatine in Cyprinoids and agrees with Biichner, and I have myself fullowed the course of the nerve by sections and dissections in Misgurnus fossilis. It takes a course intermediate between those of the R. premaxillaris and R. palatinus of Siluroids, inasmuch as it passes below the prepalatine piece. I take it therefore, that this nerve almost universally termed palatine contains palatine and premaxillary fibres and corresponds to the Premaxillaris of Wyzine. The R. palatinus has been described in detail in the Sturgeon by Stannius and v. Wijhe, ‘In Accpenser the N. palatinus has relations really corresponding to those of Teleostei” (Stannius). “It runs forward along the lateral edge of the parasphenoid, separated from the orbit by a paired outgrowth of cartilage from the basis cranii. In front of this the nerve forms a network with the Ramus maxilaris superior, and then sends branches to the snout and ends in the tentacles ” (vy. Wijhe). The barbels of Sturgeons are therefore premaxillary and maxillary tentacles. Maxillary and coronoid Tentacles. Maxillary tentacles are shown most typically in 7richomycterus and a ORAL CIRRI OF SILUROIDS AND ORIGIN OF THE HEAD IN VERTEBRATES. 25 Callichthys (Figs. 5, 6 and 7). They are supported, through the inter- mediation of a small maxillary bone (os labial Cuvier, adunasal MeMurrich), on the prepalatine piece and extend downwards and out- wards. They are also present in Cyprinidae. The coronoid tentacle is most typically shown in 7’richomycterus, where it is verylong. Its base passes continuously into a large procartilaginocus root piece, the coronoid piece, which is firmly attached to the cartilaginous coronoid process of the lower jaw. In Callichthys the tentacle is fused, near its base, with the mental tentacle, and the coronoid piece is only represented by a small mass of procartilage. The rudimentary tentacles of Hypostomidae are maxillary tentacles. The tentacle at the angle of the mouth in the majority of Siluroids combines the characters of the two tentacles, and may thus be termed maxillo-coronoid. In Auchenaspis this is well shown (Figs. 1 and 2). The coronoid piece is seen to be continuous with the tentacle, but on the other hand this tentacle is borne by the maxilla, which articulates with the prepalatine piece. In Szlurus (Figs. 3 and 4) the coronoid piece does not reach the tentacle actually, but approaches near it. What I think may be regarded as the proof of the fusion of maxillary and coronoid tentacles is given by the nerve supply. What occurs in the case of the mental and coronoid tentacle of Callichthys gives a clue as to how the fusion may have actually taken place. Judging from the nerve supply the outer pair of barbels of the Sturgeon are maxillary tentacles. The prepalatine piece requires careful observation. In the young Silurus it occurs as a squarish block of cartilage, articulating with the preorbital process. In my specimen of Auchenaspis ossification had set in around the articulation, and consequently only apophyses of cartilage are left. The anterior block always lies very far forward in the snout. The posterior end serves for the attachment of the adductor muscle proceeding from the ethmoid wall. The muscle is mentioned by Stannius. It works the maxillo-coronoid tentacle. In Trichomycterus a small cartilage remains in the posterior part of the articulation, and on comparing closely the sections of the young Callichthys, I found that a small projection of cartilage from the skull represented this free cartilage of Trichomycterus. Thus we have a stage when the prepalatine cartilage is continuous with the skull cartilage (the spot is marked with an asterisk in Fig. 7). 26 H. B. POLLARD. In all Siluroids, this prepalatine piece never enters into continuity with the pterygoid cartilage, the latter being attached by ligament to the vomer. The lateral velar supports which may, as in Callichthys (Figs. 6 and 7) be of considerable size are apparently derivatives of the maxillary tentacle. As to other Teleostei, Balfour remarks of the Salmon: ‘ The anterior bar of the upper arcade is known as the palatine ; but it appears to me as yet uncertain how far it is to be regarded as an element primitively belonging to the upper arcade of the mandibular arch which has become secondarily independent in its development ; or as an entirely distinct structure which has no counterpart in the Elasmo- branch upper jaw. The latter view is adopted by Parker and Bridge, and a cartilage attached to the hinder wall of the nasal capsule of many Elasmobranchs is identified by them with the palatine rod of Teleostei” (Prepal.). The development of this region in the Salmon has been worked out by Stohr, who finds that tissue in the anterior trabecular region gives rise to trabeculae, palatine cartilage (Prepalatine), and tissue underlying the maxilla. The fusion of palatine and ptery- goid elements occurs later. I have followed the process also in Gobzus. It might be considered that these ontogenetic stages recapitulate the condition in Siluroids, but that can only be in a very limited sense, inasmuch as the piece in Siluroids is moveable, with special muscles, and does not bear any close resemblance at all to this embryonic con- dition. Indeed the resemblance is really closer in the adults. In the Sturgeon free prepalatine cartilages exist, at any rate in the young animal, outside the basal angle (Basalecke) in front of the mouth. They may be the ethmo-palatines of Parker, but his lack of precision reduces the value of his observations. I cannot tell what Parker meant, since enthusiasm cannot replace accuracy. In Poly- pterus there is a separate ossification (autopalatine, v. Wijhe), in the upper jaw, where it articulates with the ectethmoid, and the cartilage projects forwards beyond this point. This is here called prepalatine. A similar projection occurs in Chlamydoselachus (Garman), so that, in this form, we must conclude that the prepalatine is really included in the jaw, in the region of the articulation with the preorbital process. In Heptanchus and Hexanchus, a posterior portion of the pre-palatine piece would appear to be represented by the “Lateral process of the ethmoidal region M,” of Gegenbaur, which the latter homologizes with the “ Schadelflossenknorpel ” of Rays. ORAL CIRRI OF SILUROIDS AND ORIGIN OF THE HEAD IN VERTEBRATES. 27 The second tentacle of Myaine is the maxillary tentacle. It lies outside and above the premaxillary and is connected by a bar of softer cartilage to the coronoid tentacle and to the antero-lateral piece of the tongue apparatus, the piece W of Miiller and my Meck (Fig. 11). To the base of this tentacle, but not fusing with it, extends the process from the cranium, which Miiller termed the cartilaginous process at the anterior end of the palatal ridges,” the Processus spinosus of Fiirbringer, or the Prepalatine of Parker. The coronoid tentacle extends downwards and has an expanded root piece of hard cartilage. The prepalatine piece is in continuity with the ethmoid region, and thence with the subocular bar (Gaumenleiste of Miiller), and the subocular bar is continuous with the auditory capsule and basilar part of the skull. Miiller makes the following remarks on the origin of the first cranium. On the fibrous membrane of the chorda tube arise paired cartilaginous rudiments of basilar pieces, running out into the auditory capsules and forwards as lateral wings. This is shown in Ammocoetes and Myxine. From this stage chondrification has proceeded further, and by various steps the condition of the chondro-cranium of higher vertebrates is attained. This is the simple view of Miller, and to me it seems still the most correct. Indeed where the conception of recapitulation in ontogeny has, in spite of the arguments of v. Baer, Gegenbaur and others, been introduced, there has often been great retrogression from the truth. Miiller does not come to any conclusion as to the origin of the subocular regions and of the prepalatine piece. The prepalatine piece I regard as the root piece of a tentacle, and since there is no break of continuity in the skull of Myxinoids we may perhaps regard the subocular bar and “ quadrate” regions as outgrowths aud extensions of fused vertebral and tentacular elements. This would mean that the autostylic condition of suspension of the jaws is the most primitive condition. To this conclusion I have come in a recent paper from quite different grounds. The Labials (sensu strictiorz). Comparison of the traces of premaxillary, maxillary, and coronoid tentacles brings us to the question of the labials, as the term is strictly used by Gegenbaur. I shall treat of the subject rather in a historic Way. 28 - Sete H. B. POLLARD. Cuvier (1814) dealt with the upper jaw of fish and came to the conclusion that the maxillary bones (labiaux ou mystaces) and inter- maxillaries correspond to the two labials of Squatina and other sharks, while in the Rays the intermaxillaries are represented by the small cartilage in the nasal lobe, and the maxillaries by the “ Schadelflossen- knorpel.” | On the maxilla of Teleostei he remarks: ‘‘Since the labial bone is unprovided with teeth in almost all the fish, it has little resemblance to the ordinary maxilla ; but in order to be convinced as to its nature, it is enough to observe it in the trout or salmon, and thence to follow it in its various forms” (I may here remark that the Teleostean maxilla only partly corresponds to the maxilla of other vertebrates e.g. Polypterus, where it is mainly a ‘ suborbital” bone. On the Siluroids he remarks: ‘ The intermaxillary, without a pedicle (ascending process), is situated under the anterior, more or less broad- ened edge of the skull and at each of its extremities is a small maxilla, which, becoming flexible, is prolonged into a long filament or barbel ; in a word, the principal barbel of Siluroids is their maxilla prolonged.” As to Chimaera: ‘“ In the thickness of the lip are found three bones (cartilages), which one recognises as the intermaxillary, maxillary, and the palatine arcade ; this last is entirely suspended by muscles and ligaments, without articulating with anything.” Subsequent investigation has confirmed the remarks of Cuvier to a wonderful extent. Rathke (1823) compared the labials of Petromyzon to the “‘ Knorpelriemen ” of Amphioxus (I quote from memory of the text). Johannes Miiller (1835) criticised Cuvier’s accounts and views and attempted to show that the labials are structures not belonging to the general plan of the vertebrates, and that the upper: jaw of sharks corresponds to the upper jaw of other vertebrates. ‘‘ The tooth-bearing cartilage of Plagiostomi can be nothing else than the upper jaw (maxilla), while the labial bones are, as we have already shown, accessory pieces. Probably in the tooth-bearing cartilage, maxilla and premaxilla are united.” The palatine arch of e.g. Teleostei is, according to Miiller, represented by accessory cartilages in Vareine and other fish. Miiller makes many valuable comparative. observations, and gives a complete account and figure of Callorhynchus. His views have not met with acceptance, and have been abandoned since Hertwig’s researches on dermal bones. ORAL CIRRI OF SILUROIDS AND ORIGIN OF THE HEAD IN VERTEBRATES. 29 Gegenbaur (1872) gave a complete account of the structures in Selachii, accepting Cuvier’s homology of the premaxillary and maxillary labials, drawing attention, however, to the distinction between the dermal bone and its subjacent tissue. The premaxillary bone must be imagined as developed phylogenetically, not from a cartilaginous substratum, but on such, the bone persisting while the cartilaginous substratum retrogrades and finally disappears. He then set forth his view that the labial arches are to be compared with arches of the inner visceral skeleton or branchial bars. This has been the basis for most of the modern German views. Huxley (1676) compared the lower labials of the frog to the annular cartilage of the lamprey and the “incomplete ring” of Amphioxus, while the upper labials of the frog are the anterior dorsal cartilages of the lamprey. Balfour (1882) says of the labials: ‘‘ The meaning of these cartilages is very obscure ; but from their being in part employed to support the lips and horny teeth of the Cyclostomata and the Tadpole I should be inclined to regard them as remnants of a primitive skeleton supporting the suctorial mouth with which, on the grounds already stated, I believe the ancestors of the present vertebrates to have been provided.” Howes (1891) has compared the labials of Chimaera and Marsipo- branchs. His figures of Myxinoids are partly erroneous as to facts, being apparently compounded from museum preparations. The question of the homology of the labials in Chemaera seems to me to be decided by the work of Vetter, the value of which can hardly be overestimated. | He describes in detail the musculature of the labials in Chimaera. These structures are worked by four muscles ; the Musculi labiales anterior and posterior, and two portions of the Levator anguli oris. The Labialis anterior is supplied by an anterior motor branch of the Trigeminus and corresponds closely to a portion of the Copulo- tentaculo-coronarius muscle of Myaine (Fiirbringer) the ‘“ Kopf U’ des zweiképfigen Herabziehers des Mundes” (Miiller) which, as I have shown, is innervated by a branch from the premaxillary nerve. The Labialis posterior is a portion of the Kopf U of Miiller, and is supplied by a most posterior branch of the motor part of the Trigeminus. The portions of the Levator anguli oris are the Retractores tentaculorum of Myaine. 30 H. B. POLLARD. We have therefore in these labials remnants of premaxillary, maxillary, and coronoid tentacles. To put the homologies, which I maintain, into unmistakeable form, I will refer to Miiller’s figure of Callorhynchus. I take his “ iusserer Nasenfliigelknorpel e” to be the remnant of the premaxillary tentacle, his ‘“‘oberer Seitenknorpel des Mundes c” to be a remnant of the maxillary tentacle, his ‘‘ unterer Seitenknorpel des Mundes 6” to be the coronoid tentacle, his ‘‘ innerer Nasenfliigelknorpel f” to be the nasal labial or remnant of nasal tentacle. Then the remaining piece, the “ Trager der Lippenknorpel und der Nasenfliigelknorpel d” can only be the prepalatine piece, precisely as Cuvier maintained. The labials of Selachii are then easily shown to be premaxillary, maxillary and coronoid tentacles.! Further, by comparison of Holocephali and Dipnoi it is rendered probable that the posterior upper labial of Ceratodus, as described by Huxley, and one of the antorbital cartilages of Protopterus, as repre- sented by Wiedersheim and Rose, and other authors, are homologous with the prepalatine piece, and to proceed outside the limits of the fish, > of the Anuran tadpole, as shown in the ‘“ Cartilago labialis superior’ the splendid work of Gaupp, is also a prepalatine piece. In Dactylethra larvae it bears a maxillo-coronoid tentacle. There still remain some few structures to be considered. Sagemehl has described certain small cartilages in the region of the articulation of the maxilla, which he terms submaxillaria, in Catostomidae, Gymnotus and Perca. He homologizes them with the upper labials of Selachii, giving, however, no figures, and adding that they correspond to the two small upper labials described by Parker in Salmon embryos, where always supposing Parker’s figures to be correct, they belong rather to the premaxilla. ; Then, also, there are the “ Mundwinkelknorpel” referred to by Miiller and Stannius. That of Polypterus is the coronoid labial, as it is attached to the coronoid process. In others more definite observations are needed to show whether these ‘‘ Mundwinkelknorpel ” are coronoid or mental pieces. 1The lower labial of Selachii may, however, prove to be extramental, in which case the coronoid would be absent as a rule. In Scymnus there is a mass of soft cartilage along the upper jaw which might then represent the coronoid. . : : ORAL CIRRI OF SILUROIDS AND ORIGIN OF THE HEAD IN VERTEBRATES. 31 Certain muscles in Teleostei, considered by Vetter superficial portions of the adductor mandibulae, proceed, not to the lower jaw but, to the maxilla and neighbouring parts. The Adductor tentaculi of Amiurus, described by McMurrich, is one of these. In Cobitidae (Misgurnus) they are very large, labial muscles also being present in correspondence with the presence of the tentacles. Vetter states that they are innervated by a special motor branch of the Trigeminus. They correspond to the Retractores tentaculorum of Myxinoids, and are a further proof of the correctness of the views here maintained. Nerve Supply. It is impossible in Siluroids to sharply define maxillary and coronoid nerves, inasmuch as many fibres rnnning along with the maxillaris supply the coronoid tentacle. However, there is always a coronoid branch arising from the mandibularis and supplying the posterior face of the coronoid tentacle. Where the coronoid and maxillary tentacles are fused, as in Auchenaspis, the branch is still present in exactly the same relation, and this, indeed, is one of the proofs that the maxillo- coronoid tentacle contains maxillary and coronoid elements, A similar coronoid branch is described as arising from the mandibular nerve in larval Salamanders, by von Plessen and Rabinowicz. As to Myzxine, the second branch of the Trigeminus divides into maxillary and coronoid branches, apart from motor nerves. They supply maxillary and coronoid tentacles and the skin between them. Stannius gives further descriptions of the distribution of the maxillaris superior in Silurus and Actpenser, mentioning the pre- maxillary branch in Sedurus. He states that the maxillaris superior supplies the upper labial cartilages in Spinaz. Biichner figures the maxillaris superior in Barbus as an upper branch of the maxillaris inferior, He describes its course and its anastomosis with the premaxillary nerve (his maxillaris superior). The literature of the cranial nerves is immense, but I do not think the facts need further reviewing here. Mental Tentacle. The mental tentacles of Callichthys are fused at their bases, the fused portion lying medially in front of the symphysis of the dentary bones, Thence the tentacle curves down on each side, and, never 32 H. B. POLLARD. really becoming free to the exterior, fuses distally with the proximal part of the coronoid tentacle. There is no special root piece. In Silurus the mental tentacle is situated some little way back from the symphysis along the lower jaw, being supported by a plate of pro- cartilage lying just internal to the skin. To this are attached muscles. The condition in Auchenaspis is similar, the basal plate being, however, very much larger. In Auchenaspis there is situated at the outside of the dentary bone a large block of procartilage (Ment. p.) with a posterior ventral projection running parallel with the tentacle as shown in Fig. 2. This block may be a derivative of the tentacle, possibly arising as a bifurcation of the proximal portion. Such a bifurcation is shown in the proximal part of the maxillary tentacle in T'richo- mycterus (Fig. 5, left side of the drawing), The outer prong of the bifurcation may have expanded secondarily so as to have formed this great block. The outer mental tentacle of Misgurnus is a continuation from a corresponding block just as if the backward projection of the piece in Auchenaspis were prolonged into a tentacle. A corresponding piece is found in Motella tricirrata, and no doubt in many other Teleostei, in fact this may be in some fish the ‘““Mundwinkelknorpel” of Stannius. A median unpaired mental tentacle is also present in Motel/a and Gadidae, but it shows few of the characters of a typical mental tentacle. This tentacle is paired in Jullus and Upeneus. The lower support of the velum may be a derivative of the mental tentacle though much modified. The mental tentacles of Callichthys show a remarkable similarity with the cartilage in front of the lower jaw of Protopterus, as figured especially well by Rose and of Ceratodus as figured by Huxley. I have, as in most cases, verified the observa- tions myself, by sections in Protopterus and dissection in Ceratodus. This cartilage however passes under the lower teeth and is continuous with the Meckelian cartilage showing in this respect no correspondence with Callichthys. The position of this cartilage led Huxley erroneously I think, to term the lower teeth splenial. The huge unpaired block of cartilage in front of the lower jaw in Callorhynchus is obviously a mental piece, corresponding to the mental cartilage of Dipnoi (lower labial of Giinther), and somewhat doubtfully to the mental piece of Auchenaspis. In Chimaera as shown by Hubrecht and Vetter it is represented by a small pair of cartilages below the ORAL CIRRI OF SILUROIDS AND ORIGIN OF THE HEAD IN VERTEBRATES. 33 coronoid labials at each side of the Meckelian cartilage. Howes has compared this mental piece with that of the Myxinoids and with the lower half of the annular cartilage of the lamprey, which Huxley homologised with the lower labial of the tadpole. Considering now the Selachii, I have to withdraw a hasty statement in my preliminary paper that no traces of mental tentacles occur in them. Gegenbaur describes in a few Selachii small cartilaginous blocks below the Meckelian cartilage, and these he considers to be rudiments of rays showing that the lower jaw once bore a gill. In accordance with my theory I consider them to be the rudiments of the mental and submandibular tentacles. Gegenbaur goes on to make the far reaching suggestion that on such cartilages the jugular plates of Crossopterygia may have arisen. On my view the jugular plates would, like the premaxillae and maxillae, arise in connection with tentacles. However direct evidence is still wanting, unless indeed certain phenomena in Ceratodus may be interpreted as such. Huxley has described an ensheathing bone at each side of the symphysis, on the ventral face of the mandible. This he takes to be the dentary element, setting aside Giinther’s determination of the tooth as the dentary. The bone in question however lies in front of and below the mental cartilage, and may be interpreted on Gegenbaur’s suggestion, as a paired anterior jugular plate. Jugular plates occurred in fossil Dipnoi but are usually stated to be absent in the living forms (Smith Woodward). This bone is absent in Protopterus. The mental tentacle in Myxinoids is represented by a hard root- piece, bearing a rudimentary tentacle and suspended only by ligaments. and muscles. It is fully described by Miller as the cartilage in the 4" or lowest tentacle. Nerve Supply. The nerve supply of the mental region is from the R. mentalis and the R, mandibularis externus. The Ramus mentalis in Siluroids runs outside or above the mentomeckelian process and forward, to run down outside the tentacle, where that is present, or to branch in the skin, when the tentacle is absent. The Ramus mandibularis externus may be a dissociated branch of the R. mentalis. It runs outside the coronoid process supplying in Auchenaspis the fold of skin below the mental block of cartilage. In Callichthys it is placed not so far forward. c 34 H. B. POLLARD. Other details are given by Stannius. In Misgurnus fossilis, the mental tentacle is supplied by a R. mentalis which crosses the Meckelian cartilage and then runs below that cartilage. In Motella tricirrata the unpaired mental tentacle is supplied by a R. Mentalis which takes a slightly different course. It crosses the lower jaw rather far back, and then proceeds along with the R. mandi- bularis of the Facial, which supplies the mandibular branch of the lateral line system. This close apposition led Zincone to the erroneous view that the mental tentacle was supplied from the Hyomandibular nerve of the Facial. The mental tentacle in Myxine is supplied by a mental branch proceeding forward as in Siluroids. Addendum.—l! must confess to not being able to speak with any feeling of certainty concerning the mental tentacle in Siluroids and Cyprinoids. | The independence of the R. mandibularis externus and the existence of the separate block in Auchenaspis may be taken to represent, as an alternative view to the above, a separate external tentacle or Extra- mental. Giinther, in the Catalogue of Fishes mentions two pairs of barbels as occurring in a number of Siluroids close to the chin. This is also stated for Cobitidae, but I am in doubt whether the inner smaller process is a real tentacle or only a fold of the skin. It has the form of a tentacle. The question may be decided by examination of fuller material or completer literature than has been accessible to me. Submandibular Tentacle. I have investigated the submandibular tentacle in Auchenaspis and Stlurus. It lies just below the coronoid process, being supported by a subdermal plate of procartilage, which is very large in Auchenaspis. It has no typical relation with a root piece, but from careful comparison Iam convinced that the Meckelian cartilage is the root piece of this tentacle, precisely as in the case of the premaxillary root piece, the prepalatine and the coronoid block. It is in Myazne that the Meckelian cartilage, or anterolateral piece of the tongue apparatus most closely resembles a root piece, a supposition strengthened by the disposition of the nerves. Occurrence of the submandibular tentacle is rare in fish. ORAL CIRRI OF SILUROIDS AND ORIGIN OF THE HEAD IN VERTEBRATES. 35 The nerve supply is from the R. submandibularis which in Siluroids is given off from the R. mandibularis, just at the point of origin of the coronoid process. The Ramus submandibularis then crosses outside the mentomeckelian process to supply the tentacle. At the branching of the R. mandibularis into R. mentalis and submandibularis, the motor nerves to the muscles, moving the mental and submandibular tentacles are given off. A similar disposition of the nerves is described by Gaupp in Amphibia. “In Urodela and Reptilia, the principal portion of the Inframaxillary nerve runs in the canal of the lower jaw, as the Ramus alveolaris, forwards at the upper edge of the Meckelian cartilage, but a branch of this Alveolaris inferior runs down on the outer side of the Meckelian cartilage, and round its lower edge inwards, reaching the inner side after proceeding through a foramen (in Svredon between the dentary and opercular) and then supplies the Mylohyoid.” “This branch is the Ramus circumflexus, and in the Frog it alone forms the terminal portion of the Ioframaxillaris.” (Gaupp). The R. submandibularis is present in Myxinoids, running, however, along with the mentalis outside the Processus coronoideus and supplying the skin in front of the Meckelian cartilage. This branch possesses a certain resemblance to the Ramus mandibularis externus but never- theless it appears to me to be really the submandibular. Meckelian Cartilage. The Meckelian Cartilage of Trichomycterus is of an irregular inverted T-shape, the crossbar of the T being horizontal, the coronoid process representing the stem. The process towards the quadrate does not reach the articulation, partly because the cartilage, even at this young stage, has been resorbed after the formation of the os articulare. Probably at no ontogenetic stage was this arm at all massive. The mentomeckelian process is also very short and far from reaching the symphysis, that being formed by the dentary bones only. The Pro- cessus coronoideus proceeds upwards and forwards accompanied by bone. It bears the procartilaginous coronoid piece. The demarcation between the hyaline cartilage of the coronoid process and the procar- tilage of the coronoid piece is quite clear. In Callichthys the coronoid process is wanting, and the coronoid piece is rudimentary. The mentomeckelian extends very little forwards 36 H. B. POLLARD. and to judge from the appearance of the cartilage there has been no resorption, so that probably it never extended further at earlier stages of its ontogeny. The mentomeckelian processes are as far from reach- ing the symphysis as in Tvrichomycterus. In Auchenaspis the condition is a little different from .that of Trichomycterus. The posterior arm is in the same state and the processus coronoideus passes up, and bears the coronoid piece. The mentomeckelian process is, however, longer, reaching halfway from the coronoid process to the symphysis, tapering away. In Stlurus, where the cartilage is more extensively present, the pos- terior arm extends beyond the articulation with the quadrate, as an angular process, and the mentomeckelian process is fused with its fellow and the symphysis. In Hypostomidae the whole rami of the lower jaw may be said to be free, there being no symphysis. A processus coronoideus is stated to be frequently present in fish by Stannius. “The lower jaw, varying to an extraordinary extent in shape, possesses often a special coronoid process.” It is indicated in Dipnoi by the shape of the jaw, and the cartilaginous coronoid process can well be seen in sections. The Selachii are not known to possess a coronoid process, the lower jaw in these animals being far from primitive. It is no part of the present paper to follow out the coronoid process in the Vertebrates, and indeed complete observations on the relative extent of cartilage and bone are still wanting. It may be remembered that the rami of the lower jaw of Teleostei are said to lie some way apart in embryos (Stohr), but this may have nothing to do with the existence of the space between the mento- meckelian processes in Siluroids. The anterolateral piece of the tongue apparatus in Myxinoids corres- ponds, to a certain extent, with the Meckelian cartilage. From its anterior upper corner a coronoid process proceeds to the coronoid piece and on to the maxillary tentacle, the relations in this respect being essentially the same as in Auchenaspis, where maxillary and coronoid tentacles are fused. The branches of the mandibular nerve run outside it however. No mentomeckelian:process is present, or only virtually so, and there is no articulation with the quadrate region. A number of muscles belonging to the tentacular system are attached to Meckel’s cartilage. In Myxinoids the number is consider- ORAL CIRRI OF SILUROIDS AND ORIGIN OF THE HEAD IN VERTEBRATES. 37 able. In Teleostei it is almost equally great, but in Selachii there has been much reduction and simplification. Vetter says of the adductor mandibulee of Teleostei: ‘‘ This muscular mass is nowhere found in the form of the relatively simple undivided adductor of Selachii or of Chimaera but always split into several portions. The Teleostei thus stand in regard to the jaw muscles much nearer to M/yxine than the Selachii. Many great authorities have held that the adductor mandibulae is the homologue of the adductores arcuum visceralium and that the jaws represent a visceral arch, yet this view appears to me to be entirely erroneus and to have turned subsequent investigations into a wrong path. In spite of the admirable researches of Johannes Miller, Fiirbringer and Vetter, much remains to be done, especially in the way of comparison, since the muscles yield most conclusive evidence of the correctness of the Cirrhostomial theory. The Cranium and other Parts. Concerning the skull it is not my intention to enter into any great amount of detail, A cartilaginous tegmen cranii is not formed. However across the great fontanelle runs the epiphysial bar, beneath and slightly in front of which the pineal organ terminates. It divides the fontanelle into an.anterior and posterior portion and the anterior part corresponds to the Selachian ‘ Praefrontalliicke” (Gegenbaur) inasmuch as a prolongation of the pineal organ is said to terminate at the anterior border of the tegmen cranii. Parker has described the tegmen cranii in the Salmon. An epiphysial bar is shown by Sagemehl in Characinidae and Cyprinidae. It is represented by a rudimentary block of cartilage, discovered by myself in Polypterus, and Gaupp has followed its development in the tadpole, terming it the Taenia tecti transversalis. The main fontanelle in the frog thus corresponds to the Praefrontalliicke of Selachii. It is interesting to note that the cartilage follows the wandering of the pineal organ backwards, but, the dermal bones do not, the pineal organ shifting from between the frontals to between the parietals. There is considerable variation in the floor of the brain, cartilages remaining only as blocks or processes, paired or unpaired. A preorbital process is not formed in 7richomycterus, but by various degrees it reaches a complete development as in Silurus. 38 H. B. POLLARD. One of the most remarkable features is the Rostrum or modification of the internasal septum. It is most marked in 7'richomycterus and Auchenaspis. It becomes invaded by the so called dermethmoid bone. We have only to consider the rostrum somewhat prolonged to obtain a typical Sturgeon rostrum. The Sturgeons cannot be very far removed from the Siluroids, more especially the Hypostomidae, as indeed is suggested by Huxley’s observations on the relation of the fossil forms. The comparative anatomy of the hyomandibular is of very great interest, but, since I have already dealt with the subject in a paper on the suspension of the jaws, I need not refer to it in detail here. The hyomandibular articulates with the pterotic ridge by a long articula- tion. The immobility of the suspensorium of /Hypostomidae is well known. In Claritas the pterotic ridge is produced far outwards, the arti- culation of the hyomandibular lying some way from the cranial wall. The Siluroids approach near to an autostylic condition, or, to speak more correctly, are little removed from it. HisToLoGy OF THE TENTACULAR SKELETON. I venture to give the following sketch of the varieties of cartilage present in the tentacular skeleton. Condensed embryonic tissue, known as procartilage, developes in various directions. It may give rise to an intercellular matrix with a tendency to become refractile. Such a tissue, for the sake of com- parison, I term soft Myxinoid tissue (A), inasmuch as it forms the axis of the tentacles of Myxime. The nuclei and protoplasm may dis- appear, and the intercellular matrix become very hard, as in the hard tissue of Myzxine. On the other hand the intercellular matrix may become fibrillar and and the cells and protoplasm degenerate as in the tentacles of Clarias (B). Or the procartilage may develope into hyaline cartilage (C) or persist to a considerable extent in its embryonic condition (D). The refractile matrix is stained blue by Bleu de Lyon, while the nuclei and protoplasm remain unstained. The core of the tentacle may attain very little developement, the tentacle then being very flexible, as in Misgurnus, or, on the other hand, as in Motella it may be formed by structureless bone, with a layer of osteoblasts round it. I have drawn ORAL CIRRI OF SILUROIDS AND ORIGIN OF THE HEAD IN VERTEBRATES. 39 up the accompanying scheme of the occurrence of these tissues, A stroke between two letters indicates that the tissue is intermediate between two variaties. Na. Pm. t. & p. Mz. t. & Prepal. Cor.t.& p, Mental t. & p. Subm. t. Clarias B B Cc (degenerate) Auchenaspis B Cc A B A B Trichomyc- C/D C/D C c/D A terus (young) ——— Callichthys D C/D Cc C/D D Cc/D (young) Chaetostomus A/D A/B Cc A (hard) (young) Acipenser D D Cc (young) Misgurnus (rudimentary) (0) D Extramental D (young) Motella D C (replaced Extramental D (young) by bone) Other forms Cc Cc c/D Cc (Teleostei) (Polypterus) (Dipnoi) From such a scheme it may be learnt that all parts are independently variable. Root piece and tentacle in Amphioxus are essentially similar in structure. In Myxinoids the root piece is differentiated from the tentacle by the great development of the intercellular matrix, the hardening of the same, and the degeneration of nuclei and protoplasm. In Siluroids much more complicated differentiations have arisen. The tentacles are not of similar histological nature in different families. The root piece differs from the tentacle in the same individual, the root pieces differ among themselves, some being of procartilage, some of the Myxinoid tissue, and some of true hyaline cartilage. Usually in one animal all the tentacles are of similar histological nature, but nevertheless this is not always the case, ¢.g., in Motella tricirrata. To a certain extent the grade of histological differentiation is a measure of the constancy of the piece. For example, Meckel’s cartilage and the hyoid cartilages occur in all the Craniata. The prepalatine piece, the hyaline premaxillary piece of Teleostei, the mental piece of Holocephali and of the Dipnoi are less omnipresent, but still run through whole orders, while less differentiated tentacles are present or absent in different genera. Of course there is no universal rule. In view of the extraordinary amount of variation in histology and structure, it is very remarkable that, when tentacles do occur sporadically, they can be referred to certain of definite 6 or 7 pairs. Following the conception of Wiesmann, it would seem that the archi- 40 H. B. POLLARD. tecture of the germ plasm is more constant than the quality of the determinants. Exceptions to this rule may be discovered. The embryonic development of the tentacles in /ctulurus albidus has been investigated by Ryder. Those present in the adult develope early in situ, and there is no parallelism with the phylogeny. REVERSION AND LaRvAL Forms. From comparison of long lists illustrating the occurrence of the individual tentacles, and from consideration of the fact that they appear sporadically, I have come to the conclusion that it would be extremely rash to maintain that the tentacles have come down in unbroken ancestral line from an early progenitor. In other words, their presence must often be due to reversion.' They are not always the most primitive and archaic forms that possess the tentacles most fully developed. All parts of an organ may not revert to the ancestral condition, or in other words the reversion may be only partial. Such is the case in the tentacles of Cobetidae where the skeletal axis is not developed. In the language of Weismann the reversion in this case is due to determinants in the skin, the skeletal determinants not being evolved, When once a structure has arisen by reversion and been rendered constant by natural selection, it will develope ontogenetically direct to the adult condition, and therefore it is useless to seek for information as to its ancestral history in its embryological history. It will I think be obvious, to anyone fully acquainted with the writings of Darwin and Weismann, that reversion may occur at any free living stage. Laval forms are often supposed to represent ancestral or existing adult forms. The resemblance has no doubt been greatly exaggerated. For instance I am not aware that Ammocoetes shows any approach in positive characters to Myxine or Amphiowus. Nevertheless such characters as the prepalatine piece of tadpoles, and the maxillo-coronoid tentacles of the larva of Dactylethra at its fancied ‘“Siluroid” stage, have to be accounted for. Tentacles do not 1Or, in many cases, inasmuch as rudiments of tentacles are almost always present, by ‘‘ re-development from rudiments” (Darwin). Nosharp distinction can be drawn between the phenomena of reversion and re-development from rudiments. ORAL CIRRI OF SILUROIDS AND ORIGIN OF THE HEAD IN VERTEBRATES. 41 occur so far as I know in other tadpoles nor in the larvae of Urodeles. Therefore probably we have here a case of larval reversion, but it is only an exceedingly incomplete reversion. THE ZooLtoGicaL POSITION cF SILUROIDS. The Siluroids are mostly freshwater fish with an extraordinary diversity of habits and structure and with a remarkably wide geo- graphical distribution. While however the group as a whole occurs in all the zoogeographical regions, yet certain families are confined to one. Thus, for instance, the Loricarina with peculiar anatomical features appear to be confined to the rivers of 8. America. (Certain forms from the oriental region have been allied with them by some ichthyologists. ) They are freshwater forms without any means of passing across seas, being heavily armoured with feeble powers of swimming, lying at the bottom of pools in the daytime, and creeping about at night on banks by means of their strong spines, and feeding on soft substances more or less putrified (Weyenbergh). We are justified by the principles of geographical distribution in attributing to Zoricarina an antiquity like that of Lepidosiren. Nor is there any reason, as far as distribution is concerned, for denying to other families, such as the Clariana, an immense antiquity. They are a now flourishing group, while the Dipnoi, with restricted range are a decadent group. The dermal skeleton of MHypostoma and Callichthys has been exhaustively investigated by Hertwig, who found that their dermal teeth are homologous with the placoid scales of Elasmobranchs. Therefore the dermal skeleton must be regarded as exceedingly primi- tive. From that of MHypostoma may be derived that of Acipenser, which, however, is considerably more modified. Recently Klaatsch has attempted to upset Hertwig’s conclusions, but I am not alone in thinking that in spite of the technical excellency of Klaatsch’s work, he has signally failed to prove his point. Another feature of considerable interest is revealed by the oral teeth of Hypostomidae. Some forms have been excellently figured by Kner. 1 would specially refer to his Fig. 1, Tab. 5. The bent hook-like teeth of the premaxillary and dentary bones all converge in the same direction, and the two premaxillae and the two 42 H. B. POLLARD. dentary bones are separate, thus forming four independently moveable blocks. Such teeth can only be used for hanging on to some object. Weyenbergh remarks “the fragility of these teeth is enough to show that the fish cannot use much force with them, and this is not necessary, because these fish feed on more or less putrescent organic substances. I have met, for example, with many specimens round a dead horse, which was decaying in the river Primero. It seems to me that their mode of feeding does not deserve the name of mastication, but rather of suction.” It is of no little importance to find that these archaic animals have a suctorial mouth. Possibly the symphysial teeth of Coccosteus may also have been used for hanging on. No doubt Coccosteus did not live on dead horses, but even in palaeozoic times, there can have been no lack of decaying organic matter. Coccosteus also possessed normal teeth in its jaws, so that it would appear to have been able, not only to hang on, but also to bite in the usual fashion. The Siluroids are almost throughout characterised by having a very small gape of the jaws. They will suck at bait and not swallow it suddenly like ordinary fish.’ Along with this is associated the fact that the suspensorium possesses little mobility and the suspension is little removed from autostylism, which I hold to be the primitive condition. Of late years it has become customary to look upon the ‘ Ganoids” as derived from Selachii, while the Teleostei are regarded as a flourishing offshoot from the least primitive of the Ganoids, Amza. When the Ganoids were established as a limited group by the weight of Miiller’s authority, and further when the primitiveness of Selachii was so strongly insisted on by Gegenbaur, it was but logical to assume that a Selachian form gave rise to a Ganoid, and this in turn to a Teleostean. . However, the Ganoids are now being given up as a natural group. Sagemehl’s work illustrates the progress of such views. This author directly compared Amuva with Selachii, and came to the conclusion that a form like Amza might be descended from an early Wotidanus-like shark. ‘Then he proceeded to show that the Characinidae are closely allied to Amza, while a group including Siluroids, Gymnotidae, Chara- 1This information I owe to my friend, Mr. E. T. Mellor, who has observed the habits of Australian species. ORAL GIRRI OF SILUROIDS AND ORIGIN OF THE HEAD IN VERTEBRATES. 43 cinidae, and Cyprinidae, must be founded under the term Ostari- ophyseae, since they possess in common the remarkable ‘ Weber's apparatus.” No weight can then be assigned to characters of the dermal armature or fins. Bridge and Haddon, also working on Weber’s apparatus, seem also to accept the modern origin of Siluroids. Thus, according to Sagemehl, the Siluroids are to be derived from Amia. Such a view seems to me inconsistent with all known principles of comparative anatomy and geographical distribution. Any discussion on the affinities of the Siluroids would be incomplete without reference to the paleontological evidence. Agassiz classed the Siluroids, on account of their dermal armature, with the Ganoids, from which they were removed by Johannes Miiller. Subsequently (1858-61) Huxley following up the investigations of Pander, compared certain of the Siluroids with Cephalaspidae. ‘No one can overlook the curious points of resemblance between the Siluroids, Callachthys and Loricaria, on the one hand, and Cephalaspis on the other, while in other respects, they may be still better under- stood by the help of the Chondrostean Ganoids.” ‘I am inclined to place the Cephalaspids provisionally among the Chondrostei, where they will form a very distinct family.” Ray Lankester at the con- clusion of his monograph on the Cephalaspidae remarks: ‘It cannot be too strongly asserted that these fishes are, as far as can be seen, by no means of a low type. At the same time there is nothing in the remains known to us which will indicate even approximately their affinities to any one of the large groups recognised in the classification of Amphirhine fishes.” ‘The series of scales or bones along the body of Cephalaspis—so strongly recalling the cinctures of Callichthys which has a complete endoskeleton—are, probably, morphologically of the same nature as those structures, but anteriorly I have not been able to detect any modification of the flanking ‘scales’ in Cephalaspis in the form of clavicular bones.” ‘It is best then to let the group of Cephalaspidae stand alone.” Pander, Huxley, and Ray Lankester are therefore agreed that the dermal armature of Loricarina is like that of the oldest known vertebrate fossils. Claypole (1892) has discovered Crossopterygian fins along with a Pteraspidian, Palaeaspis. As to the Silurine forms, Huxley compared Coccosteus with Clarias 44. H. B. POLLARD. and concluded that the structural coincidencies in the two forms “must lead us to assign a place near, if not among the Siluroidei to Coccosteus.” This view has not met with general acceptance and Traquair writes “Undoubtedly, the weakest point in Professor Huxley’s ‘ Essay’ is the attempt which he made to show by comparison of the exoskeletal plates of Coccostews with the bones visible on the exterior of the skeleton of many recent Siluroids, that there was a possibility at least of the enigmatical group of the Placodermata turning out to belong to the great order of Teleostei, or ordinary bony fishes, ‘ hitherto supposed to be entirely absent from formations of palaeozoic age.’ Recent dis- coveries in the palaeozoic rocks of America point, as we shall presently see, to another, and, perhaps more probable solution of the question.” > The “perhaps more probable solution” is given by the discovery of Dinichthys. Newberry discovered that Dinichthys has a dentition like that of Protopterus, and therefore concludes that it is allied to the Dipnoi. Dinichthys being also allied to Coccosteus, it follows that Coccosteus is allied to the Dipnoi. Nevertheless, too much stress must not be laid on a single feature. Fusion of teeth to form great dental plates has occurred over and over again in the Vertebrates as for example in Plectognathi: and in Hatteria. The jaws of Dinichthys have far less resemblance to those of the more archaic Ceratodus, where the teeth lie on the inside on the lower jaw, than to the more modified Protopterus. Therefore, the resemblance may be due to convergence. Other features forbid entirely the close alliance of Dinichthys and Protopterus. The latter has no structures corresponding to the spines of the former. The whole dermal armature is entirely different, and finally the distribution of the lateral line system, as figured by Cluiypole, is in no respect like that of Ceratodus or Protopterus (I have examined both of the latter animals on this point), while it bears a remarkable similarity to that of Clarvas, as figured by me, Returning to Coccosteus, I may state that I have examined a number of specimens and the dermal armature certainly shows no affinity with Dipnoi. lsewhere I have endeavoured to prove that the lateral line of Clarias closely resembles that of Coccosteus, thus offering confirmation of Huxley’s view. The Siluroids are therefore not classed with the Cephalaspidae and ORAL CIRRI OF SILUROIDS AND ORIGIN OF THE HEAD IN VERTEBRATES. 4) Coccosteidae mainly on negative evidence, such as the absence of pectoral fins or clavicular bones and the absence of internal ossification, Owens College, Manchester, Dec. 1894. 3IBLIOGRAPHY. BUCHNER, G., Mémoire sur le systéme nerveux du Barbeau, Strasbourg 1836. “ CLAYPOLE, E. W., On the Structure of the American Pteraspidian, Palaeaspis in: Quart. Jour. Geol. Soc., V. 48, 1892. “ _ The head of Dinichthys, in: Amer. Geologist, V, 10, 1892. ~CUVIER, Mémoire sur la composition de la machoire supérieure des poissons, 1814. 7 [DEAN, BASHFORD, The pineal fontanelle of Placodermata and Catfish, in : Rep. of Fish Comm. 19, New York. ] “ FURBRINGER, paw, Unters. z. vergl. Anat. d. Musk. d. Kopfskelets d Cyelo- stomen, in: Jena. Zeitschr., V. 9. GAupP, Primordialeranium von Rana fusca, in: Wo % ‘ GEGENBAUR, C. Wo (os tse “— Unters. z. vergl. Anat. d. Wirbelth Leipzig 1872. Morph. Arb. SCHWALBE, , Ueber die Kopfnerven von Hexanchus, in: Jena. Zeitsch., ., V. 3. Das Kopfskelet der Selachier, ~ GOLDI, E., Kopfskelet und Schultergiirtel von Loricaria cataphracta ete Jena. Zeitsch. 1884. “ GUNTHER, A., Catalogue of Fishes in the British Museum. " HERTWIG, O., Ueber das Hautskelet der Fische, in: Morph. Jahrb., V. 2, 1876. “Howes. G. B., Affinities ete. of Marsipobranchii, in: Proc. and Trans. Liverpool Biol. Soe., V. 6, 1891—92. V Husprecut, A. A. W., Beitrag zur Kenntniss des Kopfskelets der Holocephalen, in. Morph. Jahrb., V. 3, 1877. HUXLEY, T. H., The craniofacial apparatus of Petromyzon, in: Journ. Anat. and Physiol., V. 10, 1876. ~ — Preliminary essay on Devonian Fishes, in : Mem. Geol. Surv. of United King., Dec. 10, 1861. i V KLAATSCH, H., Zur Morphologie der Fischschuppen u. zur Geschichte der Harnsubstanzgewebe, in: Morph. Jahrb., V. 16, 1890. “ KLINCKOWSTROM, A. VON, Die Zirbel und das Foramen parietale bei Callich- thys, in: Anat. Anz. V. 8, 1893. 46 H. B. POLLARD. ~ Kner, R., Die Hypostomiden, in: Denkschr. k. k. Akad. d. Wiss. Wien, math.-naturw, Cl. 7, 1854. MULLER, JOHANNES, Vergleichende Anatomie der Myxinoiden, Berlin, 1835. “Newserry, J. S., Structure and relations of Dinichthys, in: Rep. Geol. “a Survey Ohio, V. 2, 1875. PANDER, C. H., Ueber die Placodermen des devonischen Systems, St. Peters- burg, 1856. PARKER, W. K., Numerous papers. POLLARD, H. B., On the anatomy and phylogenetic position of Polypterus in: Zool. Jahrb., V. 5, Anat. Abth., 1892. — The lateral line system of Siluroids, ibid. -— The “‘cirrhostomial” origin of the head in Vertebrates, in: Anat. Anz., V. 9, 1894. -— The suspension of the jaws in Fish, ibid. V. 1894. — Observations on the development of the head in Gobius capito, in: Quart. Journ. Mier. Se., V. 35, 1894. ~ POWRIE and LANKESTER, Monograph of the Fishes of the Old Red Sandstone, I. Cephalaspidae by E. RAY LANKESTER, 1870. RAMSAY WRIGHT, MCMURRICH and others, Anatomy of Amiurus, in: Proe. Canad. Inst. Toronto, V. 2, 1884. RATHKE, H., Bemerkungen iiber den innern Bau der Pricke, Danzig, 1825. ’ Rosk, C., Ueber Zahnbau u. Zahnwechsel der Dipnoer, in: Anat. Anz., V. 7, 1892. RYDER, Development of osseous Fishes (Ictalurus), in: U. 8. Fish Commission., 1885. ’ SAGEMEHL, M.. Das Cranium der Characiniden, in: Morph. Jahrb., V. 10, 1885. — Das Cranium der Cyprinoiden, ibid. V. 17, 1891. STANNIUS, H., Handbuch der Zootomie, 2. Ausg. Berlin 1854. — Das peripherische Nervensystem der Fische, Rostock 1849. Stour, P., Zur Entwicklungsgeschichte des Kopfskeletes der Teleostier, in: Festschrift, Wiirzburg, 1882. TRAQUAIR, R. H., On the structure of Coccosteus decipiens, in: Ann. and Mag. Nat. Hist. 1890. — History of Scottish fossil ichthyology in: Proc. Roy. Phys. Soe., 1879. VETTER, B., Unters z. vergl. Anat. d. Kiemen u. Kiefermusce. d. Fische, in: Jena. Zeitsch., V. 8 and 12. : WEYENBERGH, H., Hypostomus plecostomus VAL. Mémoire anatomique pour servir & l’/histoire naturelle des Loricaires, Leipzig 1876. WiEDERSHEIM, R., Das Skelet u. Nervensystem von Lepidosiren annectens, in: WIEDERSHEIM, Morph. Studien, Jena 1880. v. WiJHE, Ueb. d. Visceralskelet u. d. Nerven d. Kopfes d. Ganoiden, in: Nied. Arch f. Zool. 5, 1882. ORAL CIRRI OF SILUROIDS AND ORIGIN OF THE HEAD IN VERTEBRATES. 47 / Woopwarb, A. S., Catalogue of fossil Fishes in the British Museum, 1891. / ZINCONE, ANT., Osservazioni anatomiche su di alcune appendici tattili dei pesci, in: Rendiconti Accad. Sc. Napoli, 1876. / Cor. p. Cor. t. Eph. A.M. Hy. lv. 8. Mz. t. Mm. v. 8. Ment. p. Ment. t. Mck. m. Mck. Na. Na. t. Op. ¢. Pmx. t. Px. 9. Inia De Fig. 2. Fig. 3. Fig. 4. Fig. 5. Fig. 6. Enos ae Fig. 8. iota: Fig. 10. Fig. 11. ZITTEL, Handbuch der Paliontologie, V. 3, 1890. LETTERING OF FIGURES. Coronoid piece. Pr. orb. c. Preorbital canal. Coronoid tentacle. Prepal. Prepalatine cartilage. Epiphysial bar. . Proc. cor. Processus coronoideus, Hyomandibular. : Pty. Pterygoid cartilage. Hyoid. Qu. Quadrate cartilage. Lateral tentacle-like snp- Sty. Hy. Stylohyal. port of the velum. &. cor. Ramus coronoideus. Maxillary tentacle. R. md. Ramus mandibularis. Median tentacle-like sup- 2. md.ext. Ramus mandibularis ex- port of the velum. ternus. Mental piece. R.md.int. Ramus mandibularis in- Mental tentacle. ternus. Meckelian cartilage, Rk. mz. Ramus maxillaris. Mento - Meckelian _ pro- R. ment. Ramus mentalis. process. f. o. p. Ramus ophthalmicus pro- Nasal cartilage. fundus. Nasal tentacle. Lf. pal. Ramus palatinus. Opercular cartilage. R. pmx. Ramus premaxillaris. Premaxillary tentacle. R. subm. Ramus submandibularis. Premaxillary piece. Plates I., II. Model of Auchenaspis, front view. ae a side view. >» 9, Stdurus, front view. Spree tts 53 side view. » 9» L'vrichomycterus, front view. » 5, Callichthys, front view. > a5 side view. Sensory branches of Trigeminus of A wchenaspis. 39 39 5 at », Lrichomycterus. yy ny » »_ Callichthys. » ) 95 6p », Myzxine. WAG, OC LSnaidies = | | Corp. Proc.cor ' Sg Le: ‘ tne Ti | ; - i ! 1 | Hy. | mck | Ment.t. Subnet. Ment.p. Fig. Auchenasprs. Gls Fig, 7. | Callichthys. Corp. ‘ \Froc.cor: / fee | ie | He a BOISE” SS . mMck, ick, Hy. ‘ “Ment. Submt. Fig. 3. Srlurits. Cont. --F--- fo 8 @/ H.B Pollard sez. Verlag von Gust PA, Lph. Prorbe. Met. PS ' Ment.t. \ ‘ % COR Esai iA of 1 Subnet. \ Ment.t. Met. | Mek: m™m.Mck. Fig. 4. Fig? : Srlarias. Auchenasys. Ss Eph fig. 3. | Trichomycterus: Lig. 6. Caliichthys. TithAnstvK WessenJena ZL.OC Studres ) uy | Lig. . . Auchenaspis. | fig. 0 ( : tone Y Rmdiext. Calhihithys. } at Lnd.int. vi . Liye. ‘ : iv fae a ) / ‘ Z a / eee (ee er) Nea org } A \ | = \\ VS) | , F A \ \ ) x -}------ Ferment. Rime. Lt.cor Ley. ext. i} 1 1 i ‘ ' 1 oe Bay 228 eer oO HB Pollard gez. Verlag von Gust R.md Fe. subm..__ Fig 1. Rement. ~ Fe pies x Lm. Tig? jetahonee or Trichomycterus. her m Jena. TithAn stv KWesserJena. From Volume 41, Part I., of MEMorIRS AND PROCEEDINGS OF THE Man- CHESTER LITERARY AND PHILOSOPHICAL SocrEty, Session 1896-7. ON THE STRUCTURE AND CONTENTS OF THE TUBERS OF ANTHOCEROS TUBEROSUS, TAYLOR. By J. H. AsHworta, B.Sc. In the Synopsis Hepaticarum (Gottsche, Lindenberg et Esenbeck, 1847) the occurrence of tubers in Anthoceros tuberosus, Riccia vesicata, Riccia tuberosa and Petalophyllum Preissii is mentioned. The tubers of Anthoceros tuberosus were first described by Taylor in the London Journal of Botany (1846, p. 412), the specimens described being collected by Drummond on the banks of the Swan River in Western Australia. This account is quoted in the Synopsis, where the oval tubers are described (p. 792) as occurring chiefly, but not exclusively, in sterile plants, being formed at the ends of out-growths from the thallus, and containing a farinaceous mass within a deeply coloured envelope or cuticle. Attention is drawn to the presence of rootlets upon the tubers, and the latter, which are to be regarded as gemme, are said to serve as organs which can resist drying during the hot period of the year. In Kiccia vesicata (Taylor), the tubers are described as oblong or round and provided with rootlets (loc. cit. p. 795). In Riccia tuberosa (Taylor), the tubers are described as pale yellow, rounded or oblong, slightly curved bodies, provided with rootlets, and yielding, on compression in water, a small amount of farinaceous matter and opaque globules (loc. cit. p. 796). Nothing is said about the tubers of Petalophyllum Preissti (Gottsche) beyond the statement of their presence (loc. cit. p. 792). Recently Goebel’ has found tubers on a Fossombronia (n. sp.) from Tovar, which he finds are produced by the thickening, and filling with 1 Flora. 1893. Band 77. G. Ruge. Beitrige z. Kentniss der Vegeta tionsorgane der Lebermoose. p. 305. D 50) J. H. ASHWORTH, B.SC. reserve food materials, of a downward-growing apex, on entering the soil. In these tubers, Ruge (loc. cit. p. 306) finds that the reserve food materials contain considerable quantities of starch. Beyond these observations I have been unable to find any other references to the tubers of Liverworts. The object of my investigation was to ascertain the structure and the nature of the contents of the tubers of Anthoceros tuberosus.. Unfor- tunately, I have had at my disposal only dry herbarium material, but I have been able to make out several new points of interest. Anthoceros tuberosus. The tubers occur on the ventral surface of the thalloid expanse, and they lie embedded in the soil beneath the thallus. They are spherical or pear-shaped, their diameter being -15—--35 mm., and the length of the stalk attaching them to the ventral surface of the thallus -2—:35 mm. (Pl. IIL, Fig. 1). The wall of each tuber is formed of three or four layers of more or less rectangular cells, which are almost devoid of contents, there being only very small remnants of protoplasm found in some of the cells (Fig. 1, C). The walls of these cells are corky in nature, as they are coloured yellow by iodine, and are not swollen or turned blue by a subsequent treatment with strong sulphuric acid. Many of the cells of the outermost layer, and some of the cells of the stalk, are produced into hair-like processes, attaining a length of -25 mm. (Fig. 1, H.). These do not appear to be cut off by a cell wall from the cells from which they arise. The walls of these hairs, and also of the cells of the basal part of the stalk, differ slightly in composition from the corky cell walls, as on treating with iodine and sulphuric acid they stain slightly bluish-green, but do not swell appreciably. These cell walls appear to be cellulose which has become almost transformed to cork. The hairs are probably the remains of absorbing organs (the rootlets mentioned in the Synopsis) which performed some function during the formation of the tuber. Within the protective cells, lie closely-packed cells, all of which con- tain food materials. The cell walls of this portion of the tuber are thin, and of unchanged cellulose (Pl. 2, Fig. 2). Hach cell contains a large, central, usually elongated nucleus (N), a large number of colourless or slightly yellow round or oval granules (G), imbedded in the remains of the protoplasm (P), and numerous small oil drops (O), or one large one due to the coalescence of the smaller drops. THE TUBERS OF ANTHOCEROS TUBEROSDUS. 51 The oil is present in considerable quantity, as can readily be seen on crushing a tuber in water between a glass slide and a cover, when large fluid oil-drops exude. These are at once stained brown, or black, by osmic acid. The drops are readily soluble in chloroform, ether, benzene, but dissolve only slowly in absolute alcohol. The oil is not vaporised by heating for two hours to 120°—140°C., and it is not readily saponified with potash, even on heating for several minutes. The oil- drops are fluid at the ordinary temperature (12°C.), as can be seen on compression. The granules present in the cells are of different sizes (Fig. 2) ; a few are large, but the greater number are of smaller size. The larger granules have an average diameter of (006 mm., the diameter of the smaller granules being about ‘(002 mm. Both larger and smaller grains contain one, two, or three brighter and more refringent portions, which may be enclosed bodies or only specialised portions of the substance of the grains. The grains are swollen and dissolved by a weak solution of potash (27), and in some grains there is an inner portion which remains undissolved for a short time. The granules are not starch, as they are stained yellow by iodine. They give other reactions for proteids ; ¢.g., they turn bright yellow when treated with nitric acid and ammonia (xanthoproteic reaction), and they stain readily with picrocarmine hematoxylin, aniline blue, acid fuchsin, and other protoplasmic stains. The tests mentioned above prove that the grains consist of some proteid substance, and they appear to be aleurone grains. The food material stored up in the tubers of Anthoceros tuberosus differs, therefore, from that in the tubers of Fossombronia (n. sp.), which were found by Ruge to contain considerable quantities of starch. In the Synopsis, the tubers of Anthoceros tuberosus are said to contain a farinaceous mass ; but it is necessary to remember, in considering this statement, that the nature of aleurone grains was only discovered in 1855, that is eight years after the publication of the Synopsis. The small size of the granules in the tubers of Anthoceros tuberosus does not preclude the possibility of their being aleurone grains, as in some plants aleurone grains attain a diameter of only (001 mm. The occurrence of larger and smaller grains in the same cell is also known in other cases (e.g. Vitis). The occurrence of oil and aleurone grains together as reserve food materials is not at all uncommon, but they 52 J. H. ASHWORTH, B.SC. have not hitherto, to my knowledge, been found together in Liverworts, though oil-containing bodies have long been known to occur in them.’ The oil found in these tubers closely resembles that which Pfeffer found in other Liverworts in its solubility in various reagents, its fluid condition at a temperature of 12°C., the difficulty experienced in its saponification with potash, and in the fact that the oil is not vaporised on heating to 140°C, Besides these stalked tubers projecting ventrally into the soil, there are analogous structures formed in the substance of the thallus, which have not hitherto been described. These are produced by the forma- tion of a cellular mass (like that of the inner part of a stalked tuber) between the upper and lower lays of the thallus. The cells of these tuberous masses have the same structure and contents as those in the inner portion of the external tubers. These cellular masses are usually oval in shape, and their average length and breadth are ‘2 mm. and ‘15 mm. respectively. They are somewhat flattened dorsoventrally, their thickness being -1—‘15 mm. In several sections, I have found one of these internal masses at the base of the stalk of an ordinary (but small) tuber. This suggests that, possibly, the stalked tuber in question was in process of formation, and that the cells at the base of the stalk were storing up food materials, which would subsequently be passed into the tuber. Internal masses of considerable size occur in other places in the thallus where there is no sign of the formation of a stalked tuber, and these probably always remain in the thallus, and are independent of any external tuber. Regarding the function of the tubers, the Synopsis says they should be looked upon as gemme, and Ruge (Flora, 1893, p. 306) suggests that this process of vegetative reproduction is an adaptation to a mode of life in which the plants are subjected to periodic droughts. In support of this view he mentions the fact that the four plants which bear tubers, mentioned in the Synopsis, come from Western Australia. We may regard these tubers as gemme, the inner cells of which have become stored with food materials, and are protected by a corky envelope formed by modification, when the tuber is fully formed, of the cell walls of the outer cell layers. In Anthoceros tuberosus we may presume that the internal cellular masses, as well as the ordinary tubers, can give rise to new plants, and hence if the thallus becomes 1 Pfeffer. Die Oelkérper der Lebermoose. Flora. Jan., 1874. O.C. BL. Pica _ Vol. XL. Plate 2. Manchester Memoirs. Mintern Bros. lith.London J H.Askworth.del. ANTHOCEROS TUBEROSUS. THE TUBERS OF ANTHOOCEROS TUBEROSUS. 53 dry and dies there will still remain several living cellular masses, filled with food materials, which will be enclosed and protected by the remains of the dead thallus. These would probably be able to survive a con- siderable time and then give rise to new plants under circumstances favourable to their germination. It is possible that this plant forms the cellular masses in the thallus before it produces the stalked tubers, and, thus, early secures protection against extinction by drying during hot periods. That this is a possible explanation is supported by the fact that, in the dry herbarium specimens at my disposal, the histology of the cells of these internal food-laden cells is quite good, and the normal shape of the cells is retained, whereas the ordinary cells of the thallus are shrunk and collapsed. The specimens used in this investigation were obtained from the Carrington Herbarium in the Manchester Museum, Owens College, and the work was carried on in the Botanical Laboratory of the College during the Lent Term of this year, under the direction of Professor Weiss, to whom I am indebted for advice and criticism. EXPLANATION OF FIGURES IN PLATE III. Fig. 1.—Longitudinal section of a tuber (with its stalk) of Anthoceros tuberosus, x 100. Fig. 2.—Three cells from the internal portion of the tuber, x 1,000. In the two upper cells the proteid granules are shown, and in the lower one the oil drops. C. Cork cells. N. Nucleus. G. Proteid Granules. | O. Oil-drops. H. Hairs. P, Protoplasm. Reprinted from the MEMOIRS AND PROCEEDINGS OF THE MANCHESTER LITERARY AND PHILOSOPHICAL Socigty, Vol. 41. ON RACHIOPTERIS CYLINDRICA, WILL. By Tuomas Hick, B.A., B.Sc, A.L.S., Assistant Lecturer in Botany, Owens College, Manchester. In his ninth memoir “On the Organisation of the Fossil Plants of the Coal Measures,’”’! the late Professor Williamson described a series of plant remains from the Lower Coal Measures of Halifax, under the name of Rachiopteris cylindrica. The genus Rachiopteris he had previously adopted for the reception of a number of isolated Fern petioles whose connections were unknown, and in referring the speci- mens to it, he only did so provisionally, as he was “ far from certain ” at the time that they were “true Ferns.”* As to the nature of the fragments, he was undecided whether they were parts of roots or parts of stems. The description given by Williamson in 1878 is a brief one, based apparently upon a small number of microscopic preparations, and, so far as I can discover, no further observations have been published on the subject. In the present communication I propose to give a more detailed account of the plant than was possible when Williamson wrote of it, and then to consider whether or not the knowledge since acquired throws any light upon its affinities. The specimens on which I have mainly relied are a number of sections prepared by Mr. James Binns, of Halifax, and now in the Cash Collection at the Manchester Museum, Owens College, but these have been supplemented by others. Anatomy and Elastology. Transverse sections of Rachiopteris cylindrica have a circular or. elliptical outline. The diameter of the circular ones varies slightly 1Phil. Trans., 1878. 2Loe. cit. p. 350. 56 THOMAS HICK, B.A., B.SC., A.L.S. from an average of 2 mm. (,4 in.), while the elliptical ones are some- what larger, and measure for the most part 2°1 mm. (;4;in.) by 1-9 mm. (;;in.). It is obvious, therefore, that the objects to be dealt with are small, but there is nothing to show that they are in an immature state. In most of them one recognises without difficulty (Fig. 1) a central cylinder or stele, surrounded by a cortex, and a peri- pheral or epidermal layer. The stele, when single, is circular in transverse section, with a diameter varying between 0°4 and 0:75 mm. (j5 and ;2,in.). In many cases, however, it is preparing for, or in a state of, division, and is then more or less elliptical, measuring 1 by 08 mm. (5 by jyin.). The cortex, including the epidermis, varies in thickness from 0-4 to 0°8 mm. (3, to .j;in.). The Epidermis. The peripheral layer or epidermis is not usually quite distinct, but when it is, as in No. 115, it presents itself as a single layer of cells. No signs of stomata have yet been seen in it. In some sections, such as the one just referred to, it is provided with a covering of multi- cellular hairs, the density of which varies in different specimens, while in some no hairs are visible. In these last, however, it is not certain that the outermost layer is actually the epidermis. For the most part the hairs are seen only in transverse section. They are very rarely, and then for short lengths only, presented in longitudinal section. As in the epidermal cells, no cell contents have as yet been met with in the hairs. Putting together the details observable in various fragments, the hairs may be described as filaments made up of a single row of cells placed end to end. At the base, what appears to be a sort of pedestal is sometimes seen, but no indications of anything of the nature of a terminal gland have been found. From the fact that transverse sections of the stem show the hairs, when present, also cut, for the most part, transversely, it seems probable that the latter were appressed rather than spreading. 1 Here and throughout the figures refer to the Register of the ‘‘ Cash” Collection of sections of Carboniferous Plants in the Manchester Museum, Owens College. RACHIOPTERIS CYLINDRICA. ~°- 57 The Cortex. The cortex is, apparently, cellular throughout, but the outer part is usually more or less differentiated from the inner. The former, or hypoderma, consists of elements which in the transverse section are polygonal, or rounded in shape, and of relatively large size. The walls show some degree of thickening, which, however, diminishes from without inwards. Longitudinal sections show the elements to be much elongated in that direction, and, in form and appearance, to be sclerenchymatous, The inner part of the cortex is composed of cells which are some- what smaller and rounder in transverse section than the elements of the hypoderma. Towards the stele they diminish in size, become somewhat compressed radially (as was noted by Williamson),’ and are arranged in concentric layers. They show a certain amount of wall thickening, which increases from without inwards, and the innermost elements are elongated longitudinally. In the middle part of the cortex, where the hypoderma and the inner parenchyma run into one another, the cell walls are thinner and often much crumpled. In young specimens a complete zone of thin-walled elements occupies this region, but in older ones it is occupied by a series of radial lacune, separated by cellular partitions (Fig. 1). From the appearance of the tissues abutting on these lacunee, it seems probable that their origin was lysigenous rather than schizogenous. The contents of the cortical elements are somewhat remarkable, and present some interesting modifications. In one or two specimens the conterts of both hypoderma and inner parenchyma are in the form of contracted utricules, as may be seen in the marginal section on No. 102. But in the second section on the same preparation, as well as in other cases, the utricular form is restricted to the hypoderma, and the contents of the inner parenchyma are in the form of granules, which remind us of the stored starch of recent plants. In the majority of the preparations, however, the cortical cells contain certain sharply defined black bodies, of a rounded or ellipsoidal shape, and with an even contour (Fig. 2). Frequently they are seen to be enclosed in a sort of vesicle, the cavity of which they do not fill, and whose wall is, therefore, somewhat removed from the body itself. The bodies are 1 Loe. cit. p. 350. 58 THOMAS ‘HICK, B.A., B.SC., A.L.S. small compared with the size of the elements in which they lie, and two or more are frequently seen in the same element, especially in longitudinal sections like No. 113. In the specimen figured by Williamson? they are very numerous, and are carefully represented, but are not referred to in the description. In most instances where the black bodies are present, the granular and utricular forms of cell contents are absent, but not in all. Thus, in No. 115 the contents of the hypoderma are utricular, while those of the inner parenchyma are represented by the peculiar black bodies. In No. 106 we have both the black bodies and the granular contents, but the distribution of each is irregular. The nature and origin of these peculiar black bodies are points not easily determined. The first question that arises is whether they are actually portions of the cell contents or adventitious bodies that have found their way into the plant from without. Against the latter view must be set the fact that they are absent from the tissues of other plant fragments, and found in all preparations of Rachiopteris cylindrica which have been fossilised simultaneously and under the same con- ditions. Moreover, an examination of numerous sections of other species of Rachiopteris found in the same situations has so far failed to show their presence as regularly and as copiously as in the species under consideration. In some sections of the roots of Psaronzus black bodies are occasionally met with which might be compared with them; but they lack the uniformity of shape and the definiteness of contour of those found in Rachiopteris cylindrica, On the other hand, their frequency in this species is remarkable. Leaving out doubtful cases where fogsilisation has caused the disorganisation or disappearance of the cell contents, we have in the “Cash” Collection 17 preparations of the plant which show cell contents. Of these only three fail to show the black bodies, viz.: Nos. 102, 103 and 104, and they are all cut from the same specimen. It follows that out of 15 different specimens, we have only one in which these bodies do not occur. Lastly, there are reasons for regarding this specimen. as younger than the rest, and it may be that the contents of the cortical cell have not assumed their final form. It is not desirable to place too much weight on these points, but taking the whole of the facts together, they seem strong enough to warrant the 1 Loe. cit. Plate XXIV., Fig. 80. RACHIOPTERIS CYLINDRICA. 59 provisional conclusion that the bodies in question are really consti- tuents, or derivatives, of the normal cell contents and not alien immi- grants from without. On this view their mode of origin will have to be sought in the changes brought about in the process of fossilisation, but with regard to this I am not in a position to say anything. Finally, before leaving the subject, it may be worthy of notice that the general occurrence and peculiarities of these bodies have made it possible to use them to some extent as a diagnostic character of Rachi- opteris cylindrica, and with such good results that determinations first made by their aid have been subsequently confirmed by more rigorous methods. Endodermis. At the innermost part of the cortex, where it abuts on the central cylinder, one naturally expects to find an endodermis, and the sections have been carefully scrutinised for indications of its presence. The result is not so completely successful as could have been wished, since it still leaves some doubt whether a specially differentiated endodermis is or is not always present. The case appears to be somewhat similar to that of Lycopodium clavatum, for we find here also thick-walled elements abutting on the stele, and here a well-marked endodermis cannot always be clearly recognised. But in favourable sections, e.g., Nos. 104, 105 and 107, a layer of thin-walled elements is found on the inside of the thick-walled inner parenchyma, which, in the shape of its cells, their mode of union, and the appearance of the radial walls, bears some resemblance to an endodermis (Fig. 1). Its cells are larger than, and alternate with, those of the next layer on the cortical side; and they also alternate with those of the next layer within. Hence it may be regarded as the innermost layer of the cortex, or the phloeoterma of Strasburger.? : The Central Cylinder or Stele. If the layer of cells just referred to be really the phloeoterma, then all the tissues within it must be those which constitute the stele. On this view we can distinguish, more or less readily according to the state of preservation of the specimens, (i.) a pericycle, (ii.) phloem, and (iii.) xylem. 1Histologische. Beitrige, III. 60 THOMAS HICK, B.A., B.SC., A.L.S. The pericycle is seldom sharply defined, but when it is, it consists for the most part of a single layer of thin-walled cells, as large as those of the endodermis, but more variable in size and less regular in shape and arrangement. The cell contents have altogether disappeared or are too vague for determination. The phloem is composed of thin-walled, empty, and irregularly- shaped elements of different sizes, in which little differentiation has so far been detected. It forms a complete zone round the xylem, but the breadth of the zone is not always uniform. The reference of this zone to the phloem is based more upon its topographical position than upon its structure, but in one preparation, No. 104 (Fig. 1), larger elements are embedded in it, which in form, position, and arrangement resemble the sieve-tubes seen in transverse sections of recent Ferns. The xylem occupies the centre of the stele, and, as was pointed out by Williamson, the larger elements are usually at the periphery, while the smaller are in the centre (Figs. 1 and 2). In Williamson’s figure’ the larger and smaller elements are well differentiated, and this is not an unusual state of affairs, though in some sections the difference is less sharply marked (Fig. 1). In the majority of the transverse sections I have seen, the central elements include one or more groups of small ones, which resemble in appearance the protoxylems of recent vascular bundles. When two such groups are met with, the appearance is as ifa single group had, in some way, been divided. When three, four, or five groups are met with, as is often the case, they are arranged symmetrically round the centre, and look as though they had originated by division from a smaller number. As to the nature of the elements of the xylem, the sections at my disposal do not enable me to speak altogether without reservation. The larger are probably tracheides, as good longitudinal sections, No. 127 for instance, show. In this section the wall markings are scalariform, the pits stretching for the most part from one angle to another. But in some slightly oblique transverse sections, represented by No. 114, the pits appear to be much less elongated and approach an elliptical form. The case of the smaller elements is not quite so certain. In the longitudinal section just referred to, they present themselves as 1phil. Trans. 1878. Plate XXIV., Fig. 80. RACHIOPTERIS CYLINDRICA. 61 scalariform structures quite similar to the larger ones, save for the smaller diameter. The same may be said of the oblique transverse sections, where the markings of the large and small elements appear to be the same. In No. 127, however, there are suggestions at one or two points of a spiral marking, but whether these are actually spiral, or are really scalariform markings altered in some way, it is impossible to say. The position then as regards the xylem is this. In tranverse sec- tions we have one or more groups of small elements that may be interpreted as groups of protoxylem, but this interpretation has not so far been confirmed by satisfactory evidence that they have spiral or annular markings. Neither in transverse nor longitudinal sections have any cellular elements been met with in the xylem, so that the xylem may be said to be wholly vascular, so far as observation has at present gone. Division of the Stele. The description of the stele given above does not apply to all the preparations that have been examined. In the majority a condition is met with which does not appear to have presented itself to Williamson at the time he dealt with this plant, and which shows the stele in a state of division (Figs. 2, 3, 4,5). As this appears to be associated with the mode of branching of the plant, and the formation of lateral members, it deserves to be described with some detail. So far as has yet been seen, the division of the stele takes place in one of two ways, being either (1) an equal division, or (2) an unequal division. In equal division, the stele divides along a diameter in such a way that the two halves have, from the first, the same size, form, and ap- pearance, and when the process is completed we get two distinct steles of the type already described. An early stage of the process is well shown in No. 110, where we have two semi-circular masses of xylem, inclosed in a common zone of phloem, and separated by a narrow band of thin-walled parenchyma. This parenchyma cuts through the xylem in such a way as to have the small groups of elements, presumed to be protoxylem, abutting directly upon it. As the two moieties of the stele become more and more divergent, a centrifugal development of xylem would seem to take place on the inner side of these semi-circular 62 THOMAS HIOK, B.A., B.SC., A.L.S. masses until the circular contour is restored in each, and we have the appearance seen in No. 105 (Fig. 2). Here we have two normal strands of xylem, separated by a band of phloem, and enclosed in a zone of the same tissue. Ata later stage, shown in No. 107, the two steles are found to be completely formed, and are isolated from one another by the intercalation of cortical tissue. In this mode of stelar division we obviously have a true dichotomy of the same, and it can hardly be doubted that the process is associated with a dichotomy of the axis itself. If this inference be correct, it will follow that whatever be the nature of that axis, be it stem, petiole, or other structure, it is characterised by a dichotomous mode of branching. In unequal division the stele divides into two portions, which from the first, are conspicuously different from one another. Ultimately they become converted into perfect steles ; but they are not alike, one being of the normal type, and the other differing in important particu- lars. An early stage of this mode of division is met with in No. 103 (Fig. 3), where a segment of the xylem, whose height is not more than one-third of the diameter of the whole, is cut off from the rest by a narrow band of delicate parenchyma, resembling that met with in equal division. The dividing line passes through some of the smaller elements which have been referred to as probably protoxylem. 'The smaller seg- ment of xylem is composed mainly of large tracheides, with only a few smaller ones on the side turned towards the other segment. As the process advances, the larger segment appears to receive an accession of centrifugally-developed xylem on the inner side, by which the detached seoment is replaced, and the normal, circular form and appearance is restored. The smaller segment seems to develop little or no xylem on its inner side, and the typical form and appearance is not restored. Thus, in Nos. 101 and 102 (Figs. 5 and 4), where we find two complete steles quite separated from one another, which have arisen by unequal division, it is clear at a glance that the two strands of xylem are very different from one another. The normal stele needs no description. The other presents a xylem, semi-lunar in form, with small elements on the flattened side and much larger ones on the convex side. The number of preparations of this type of stele is not large, and their phloem is not clear enough to justify a definite statement; but two or three of them have raised the suspicion that the phloem is mainly, if not entirely, restricted to RACHIOPTERIS CYLINDRICA. 63 the convex side of the xylem. It is somewhat tantalising that the pre- parations should fail at this important point, because, as will be seen below, the nature of the: member to which this stele belongs depends, at least in part, upon the symmetry of the stele, It is important, therefore, to decide whether the latter is radially or bilaterally symmetrical. Lastly, in No. 115, we have two distinct and complete structures, lying near to one another, whose steles correspond respectively to those found in the same axis in No. 101. In No. 105 (Fig. 2), in addition to the two steles already described, a third structure is found in the cortex, which is obviously some organ which, originating at or near the bifurcation, is on its way from the central cylinder to the surface Coming off obliquely, its section is an oblique one, but in it we can easily distinguish both a central cylinder and a cortex. The cortical cells seem to have had thin walls and copious cytoplasmic contents, as if full development had not yet been attained. The central cylinder is not at all well defined, but I suspect it carried a diarch xylem strand. The real nature of this organ is not quite certain, but its endogenous origin leads me to thing it is a root, Moreover, in several preparations, Nos. 102 and 103, for example, sections of the principal axis are accompanied by sections of structures that are almost certainly roots, and have some resemblance to the organ in question. Division of the Axis. Looking at the whole series of sections with dividing steles, it seems scarcely open to doubt that while in equal division we have an indica- tion of dichotomous branching of the axis, in which the two members are strictly homologous with each other and their common podium, in unequal division of the stele we have an indication of the formation of some lateral organ which is not homologous with the axis from which it arises. As to the morphological nature of this lateral organ or appendage, the evidence to hand is not sufficient to justify any definite conclusion. The suggestion that it is a foliar organ naturally and readily occurs, and that may be its character. It would be in favour of this view if the suspicion expressed above that the stele is not radially symmetrical could be converted into certainty, and this view is supported by the 64 THOMAS HICK, B.A., B.SC., A.L.S. negative evidence that besides the appendages in question, there is nothing else that can be regarded as suggestive of leaves ; indeed the absence of anything like an ordinary leaf-trace bundle, both in the cortex and at the periphery of the xylem, is one of the pecularities of this plant. But of positive evidence, as just stated, there is not nearly enough to justify a conclusion. On the other hand, the large size of the detached portion, relatively to that of the whole stele, is hardly in accordance with the foliar hypo- thesis. In several of his Memoirs’ Williamson describes an unequal division of the stele of Lepidodendron, which in some respects resembles that met with in our plant. But in these cases it would seem that the detached smaller segment soon becomes changed into a radially symmetrical stele, similar, in essential points, to that from which it originates, a condition of things which has not been found in Rachiop- teris cylindrica. According to Williamson, this mode of branching in Lepidodendron is associated with the formation of fruit-spikes or strobili, into the axes of which the branches of the stele, successively formed by unequal division, are distributed. While there is a possibility, then, that in our plant the lateral appendage may be some form of fruit or an organ axial in its nature, the character of its stele is rather opposed to such an interpretation than in favour of it. Fig. 6, which is taken from No. 102, shows what are probably the relations in space between the axis and its offshoots. At A and B we have two normal axes which have apparently arisen by the dichotomy of a common podium. Just below A is a section, a, of what appears to be a root, while another, 7, is seen just above B. Below B, at s, is one of the unknown lateral appendages. Symmetry of arrangement would suggest a lateral appendage above A, but the periphery of the latter is at the extreme edge of the preparation, and it is impossible to say whether such an appendage was or was not originally present. The stele of B is undergoing unequal division in a plane at right angles to that which contains all the other sections. What is Rachiopteris cylindrica ? Whatever interest or importance may attach to the anatomical details set forth in the preceding pages, it must be admitted that they 1See Part II. Phil. Trans., 1872; Part XI. Phil. Trans., 1881 ; Part XII. Phil. Trans., 1883; Part XVI. Phil. Trans., 1889; and Part XIX. Phil. Trans., 1893. RACHIOPTERIS CYLINDRICA. 65 help us but little towards a kaowledge of the position which Aachiop- teris cylindrica should occupy in the Vegetable Kingdom. In the Memoir referred to at the outset, Williamson found it extremely difficult to form a reasonable conjecture on this point, and ultimately remarks, “it may be a Fern Stem, though I know no recent type of Fern which it resembles ; it may be the root of some type of Fern, an idea suggested by the tendency to a concentric arrangement of the cortical cells ; or it may belong to some dwarf type of Lycopodiaceous plants.” Whether in the last sentence Williamson meant that it might be the root or the stem is not certain. From what has been said of the histology of the stele, botanists will allow that its characters do not support the view that the axis of Rachiopteris cylindrica is a root. Nor is it otherwise with the mode of branching. We may conclude then with some confidence that it is either a stem structure—a caulome, in fact—of some kind, or the phyllopodium of a foliar organ. The further question as to whether it should be referred to the Lycopodiacee, or to the Filices, cannot be answered definitely. William- son tells us that “the entire series of [his] sections of this plant dis- plays a considerable resemblance’ to “sections of the aerial and subterranean stems of Psilotum triquetrum,” but those I have examined hardly confirm this. Indeed, if the small elements within the strand of xylem are, as I presume, protoxylem elements, that fact of itself would be evidence against Lycopodiaceous affinities. On the other hand, it would not be inconsistent with what we know of the xylem strands of Ferns. If, therefore, our choice is to be restricted to the Lycopodiacee and Filices, the latter seem entitled to the preference. As, however, there are other types of Carboniferous plants in addition to those mentioned, it will be well to leave this point for future in- vestigation, 66 Fig. Fig. re) THOMAS HICK, B.A., B.SC., A.L.S. EXPLANATION OF FIGURES ON PLATE IV. Transverse section of Rachiopteris, showing undivided stele. This photograph is taken from slide No. 104 of the Cash Collection in the Manchester Museum. Transverse section, showing division of stele into two equal parts (Cash Coll., No. 105). Transverse section, showing unequal division of stele (Cash Coll., No. 103). Transverse section taken a little higher up than section 3, showing beginning of separation of the two unequal steles (Cash Coll., No. 102). Transverse section, showing completion of division of the stele (Cash Coll., No. 101). Photograph of a larger portion of slide No. 102, than in Fig. 4 show- ing two stems, A and B, with their offshoots ; and 7 are probably lateral roots; and s is a lateral structure of unknown nature. RACHIOPTERIS CYLINDRICA. SB Bolas & Co Collotype ig Real aeaat F eee he Fiom Volume 42, Part V., of “‘Memorrs AND PROCEEDINGS OF THE MaNcHESTER LITERARY AND PHILOSOPHICAL Society,” Session 1897-8. CONTRIBUTION TO OUR KNOWLEDGE OF THE MARINE FAUNA OF THE FALKLAND ISLANDS. By Evita M. Pratt, BSc. (Vict.), Research Student in Zoology at The Owens College. The work in connection with this paper has been done in the Zoological Laboratories of the Owens College, Manchester, under the kind supervision of Professor Hickson. I must thank Dr. Harmer, of Cambridge, for his great kindness in placing at my disposal his collection of Bryozoa, and for his kind aid in identifying certain species. My thanks are also due to Mr. Kirkpatrick for assisting me in the examination of the “ Busk” Collection of Bryozoa, at the British Museum. The material at my disposal was collected by Miss Blake, at Hill Cove, West Island, Falklands, during the months of September and October, 1896, and the specimens may be regarded as forming a typical common shore collection of that region, the shore at Hill Cove being sandy with small rocks. Through the kindness of Mr. Standen, I have also had access to a collection of Mollusca, on some of which grew various Bryozoa, made by Miss Cobb at Lively Islands, Falklands. These were also shore forms. In the Collection were the following species of Bryozoa :— CHEILOSTOMATA. I. Beania magellanica MacGillivray = Diachoris magellanica Busk, Brit. Mus. Cat., 1., p. 54. 68 II. ITT. Wel XV. XVI. XVII. EDITH M. PRATT, B.SC. Beanwa costata MacGillivray = Diachoris costata Busk, Challenger, Vol. X., Polyzoa, p. 60. Cellaria malvinensis Busk, = Salicornaria malvinensis Busk, Challenger, Vol. X., Polyzoa, p. 91. . Cellepora pustulata Busk, Challenger Vol. X., Polyzoa, p. 200. . Cellepora pumicosa Busk, var. eatonensis Busk, Challenger, Vol. X., Polyzoa, p. 201. . Cribrilina labiosa Busk = Lepralia labiosa Busk, Brit. Mus. Cat. I1., p. 82; Challenger, Vol. X., Polyzoa, p. 133. Cribrilina monoceros Busk, Challenger, Vol. X., Polyzoa, p. 133 ; Hincks, Ann. Mag. Nat. Hist., (5) VIIL., p. 57. Lepralia adpressa Busk, Grit, Mus. Cat. IL, p. 82; Hincks, Brit. Mar. Polyzoa, p. 307. Membranipora membranacea Linn. Hincks, Brit. Mar. Polyzoa, p. 140. Micropora uncifera Busk, Challenger, Vol. X., Polyzoa, p. 71. . Microporella ciliata Pallas. Hincks, Brit. Mar. Polyzoa, p. 206. . Microporella malusti Audouin. Hincks, Brit. Mar. Polyzoa, p. 211. . Mucronella tricuspis Hincks, Ann. Mag. Nat. Hist., (5) VIIL., p. 66. . Schizoporella hyalina Linn. Hincks, Brit. Mar. Polyzoa, p. 271. Schizoporella hyalina (variety). Smittia landsborovit Johnston. Hincks, Brit. Mar. Polyzoa, p. 341. Porella tridentata, sp. nov. CTENOSTOMATA are only represented by some badly preserved frag- ments of the genus Bowerbankia, the species of which I have been unable to identify. THE MARINE FAUNA OF THE FALKLAND ISLANDS. 69 Of the preceding species, two are cosmopolitan in shallow water and are also found in some regions in deep water ; this fact is referred to later. I. Microporella ciliata, on weed, among debris, and on Mytilus. Il. Schizoporella hyalina, on weed and shell (Photinula). It is noteworthy that both these forms occur on weed. The following species are common to the northern hemisphere, in- cluding Britain, and the Falklands :— I. Lepralia adpressa, on shells (Photinula violacea and T'rophon muricijormts). Habitat: Britain (Torbay, Guernsey, Hastings). Mediter- ranean (Algiers, Naples, Bay of Gibraltar). Australia. Chiloe. Falklands. Mazatlan. Moderate to deep water. Fossil—Italian pliocene. Il. Membranipora membranacea. Habitat: Britain; universal and abundant, Hvidingsoe. Hougesund (Norway). Roscoff. -Finisterre (France). Adriatic. New Zealand. Australia. Range in time—coralline crag. Paleeolithic. Occurs only in temperate seas and shallow water. Ill. Microporella malusit. Habitat: Britain (widely distributed and abundant). Gull- maren. Bahusia, 10-20 fath. Bergen. Finmark (Norway). Greenland. Mediterranean. Adratic. France (S.W.). Black Sea. South Patagonia, 48 fath. Tierra del Fuego. Falklands. Valparaiso. New Zealand. Fossil—coralline crag, on Terebratula. Older pliocene (Castrocara). The following occur in north and south temperate seas, but not in Britain, nor the tropics :— I. Beanta magellanica, growing on an Ascidian (Molgula gregaria). Habitat: Adriatic. Australia, 2-10 fath. New Zealand. Kerguelen. Cape Horn. Falkland Islands. It appears to occur only in shallow water. Il. Cellepora pustulata, on Patella venosa. Habitat: Island of Capri (Italy). Victoria (Australia). New Zealand. Marion Island. The specimen, though fairly large, is much water-worn. 70 EDITH M. PRATT, B.SC. It is interesting to note that the only known northern habitat of these two species is the Mediterranean. The following species is the only one which occurs in north and south temperate and cold seas, and in the tropics (Florida). Smittra landsborovu, on shell (L'rophon muriciformis). Habitat: Britain. Florida. Greenland. South Africa. Falklands. Australia. Arctic Seas. Davis Strait. Fossil—var. erystallina—Scottish glacial deposits. The following species occur only in the southern hemisphere :— I. Beania costata, on weed, in shallow water. Habitat: Australia. Kerguelen. Cape Horn. Falklands. Il. Cellarva malvinensis, erect, in fairly shallow water. Habitat: Petane (New Zealand). Strait of Magellan. 45 fath. South Patagonia. Victoria (Australia). Kerguelen. Marion Island. New Hebrides (S. Pacific), 70 fath. Cape Horn. Falklands. Fossil in tertiary of New Zealand, Ill. Cellepora pumicosa, var. eatonensis, among debris, and en- crusting shell. Habitat: Kerguelen, 28 fath. and 45-127 fath. W. of 8. America, 45° 31’S., 78° 9’ W. Falklands. IV. Micropora uncifera, on weed. Habitat: Mid South Atlantic. Tristan D’Acunha. Night- ingale Island, Inaccessible Island. Cape Horn. V. Cribrilina labiosa, on shells (Mytilus magellanicus and Tere- bratula). Habitat: Falkland. Simon’s Bay (Cape of Good Hope). VI. Cribrilina monoceros, on Mytilus edulis. Recorded from :— Mid N. Pacific, 3,125 fath. Australia, 35 fath. New Zealand. Marion Island. Strait of Magellan, 175 fath. Between Strait of Magellan and Faiklands. Bass Strait. Cape Horn. Falklands, 12 fath. Fossil: tertiary depcsits. Bairnside, Victoria (Australia). Napier and Petane (New Zealand). VIL. Mucronella tricuspis, on shell (Mytilus ungulatus). Habitat: Australia, 38 fath. Simon’s Bay (Cape of Good Hope). Prince Edward Island. Tierra del Fuego. Chiloe. Falklands, 5-12 fath. S. America. THE MARINE FAUNA OF THE FALKLAND ISLANDS. 7(l VIII. Porella tridentata, sp. nov. On shell (4uthria antaretica) Falklands. Of the foregoing list of species, the following have not, I think, been hitherto recorded from the Falklands :— 1. Cellepora pustulata. Lepralia adpressa. Membranipora membranacea. Smittia landsborovit. Micropora uneifera. Do w bo Microporella ciliata. The variety personata was recorded by Darwin from the Falklands, but not the true species. Of 16 species of Bryozoa in this collection, eight have been found only in the southern hemisphere. Five have been found in the north and south temperate regions. One occurs in the north and south tem- perate regions and in the tropics, and two are cosmopolitan. Notes on the Specres of Bryozoa in this collection. The zocecia of Microporella ciliata seem larger than those of the British specimens. In structure I think they more closely resemble those of the Californian specimens. Lepralia adpressa var. Busk. The surface of the zowcium is strongly grooved, as described by Busk of the species occurring at Chiloe (see Busk, Brit. Mus. Cat., Vol. II., p. 82) but there are, in addition, certain large pores which occur round the margin of each zocecium at the base of each triangular furrow (see Figs. 1 and 2). These pores I have also seen in Busk’s “ Chiloe” specimen at the British Museum, but they are neither so numerous nor so well marked as in my specimen. Avicularia (Fig. 3) of two kinds occur, which have not hitherto been described ; one appears to be the ordinary beak-like form, but is often slightly irregular in shape (Fig. 3, a and 6); the other is circular in outline, with a spatulate mandible (Tig. 3, cand d). The avicularia are very irregularly distributed over a colony ; sometimes five or six neighbouring zocecia possess one or even two, whilst not one of the remaining zocecia of the colony bear any. In one or two cases, knobbed cells are seen (Fig. 1, a), which are characteristic of the British species (see Hincks, Brit. Mar. Polyzoa, p- 307). I have seen no trace of an ovicell. 72 EDITH M. PRATT, B.SC. Porella tridentata, sp. nov. Zocecia hexagonal, separated by fairly deep linear furrows ; surface convex and punctured by large irregular pores which, in some cases, are definitely arranged round the margin. Secondary orifice horse-shoe shaped or inversely subtriangular, with a lateral raised collar meeting in a sudden depression behind (Fig. 4, 6), often a sinus in front, containing a small avicularium with a rounded mandible (Figs. 4 and 5, 6). In many cases a spatulate avicularium is present to the right of the secondary orifice (Figs. 4 and 5, a). Deep down in the orifice can be seen a large median denticle with two lateral ones (Figs. 4 and 5, ¢ and d) ; because of this feature it has been thought fit to call the species “ tridentata.” The ovicell (Fig. 5, Ov.) is semicircular in outline, convex in front, somewhat granular, with one or two groups of irregular punctures. Zoarium encrusting shell (Photinula violacea) and of a dirty pink colour, | Porella tridentata is somewhat like P. concinna (Hincks, Brit. Mar. Polyzoa, p. 323). It differs from the latter in having two lateral denticles in addition to the median one which is present in P. concinna. It is also somewhat larger, and the pores are bigger and irregular in shape. The spatulate avicularium appears to be constant in position, while the general shape of the secondary orifice seems to be somewhat different. P. tridentata differs from Jullien’s P. malouwinensis (see Cap Horn Lixped., p. 57) in that the pores are larger and fewer in number. P. malouinensis appears to have no spatulate avicularium or denticles, and the secondary orifice is somewhat different. The ovicell agrees with Julliens description of that in P. malouinensis, which, however, he does not figure. A consideration of the geographical distribution of the Bryozoa in this collection from the Falkland Islands, is of special interest at the present time because of the controversy about the origin of the north and south extra-tropical marine faunas. 5 Murray? is of opinion that “if there were once a nearly universal climate over the whole of the ocean, then it is possible that there was ' Murray ‘‘ On the Deep and Shallow-water Marine Fauna of the Kerguelen Region of the Great Southern Ocean.” (Zrans. R. Soc. Ed., Vol. 38 (1896), p- 343 ; also Challenger Summary of Results). THE MARINE FAUNA OF THE FALKLAND ISLANDS. 73 a universal littoral marine fauna.” When cooling set in at the Poles, then the animals with pelagic larvee would be killed out, or be forced to migrate towards the warmer tropics. By limiting their reproductive process to the summer season, some of the organisms with free swimming larve would live on in the temperate regions. With the disappearance of the shallow-water fauna from the polar regions, its place would be occupied by organisms from the deeper mud line, few of which have pelagic larve. In this way the similarity and, in some cases, identity between the polar faunas, and the likeness of many shallow-water polar animals to deep-sea species, might be explained. The cooling of the waters at the Poles would cause vast migrations of forms towards the warmer seas, where metabolic changes would be greater; this would cause the struggle for existence to be intensely severe in the tropics, and would result in a rapid formation of species, while many would become extinct. On the other hand, the metabolism being less in the temperate and colder waters, and the struggle for existence being less severe here than in the warmer waters, there would be less tendency for the species to become modified, and many would remain true ; hence the similarity between the North and South tem- perate faunas. Ortmann,’ whilst acknowledging the possibility of the existence at one time of a universal fauna, contends that the cooling at the Poles did not arrest the capability of variation, but that the bipolar forms now existing must have passed through a greater range of variation than the tropical forms; in other words, that the tropical fauna has remained more or less true, while the temperate and bipolar forms are derivatives of ancestral forms. He admits that a form with a well-developed adaptative faculty may have passed through all the varying conditions of temperature, etc., without becoming extinct. The changes due to climatic conditions being similar at both Poles, two faunas resulted from the primitive material, one Arctic, the other Antarctic. He also holds that the likeness between the north and south polar faunas is in many cases a secondary reappearance, and is dependent on the adaptative capability of the inhabitants of the Poles. He does not think that identical species can result in both polar seas from a Ortmann ‘‘ Ueber ‘ Bipolaritit’ in der Verbreitung mariner Thiere.” Zool. Jahrb. (Abth. f. Syst.) Bd. 9 (1896), p. 571. 74 EDITH M. PRATT, B SC. common descent. He maintains that an exchange of both polar forms can take place through the deep sea, on the ground that, among Crustacea, the Cosmopolitan genus Pontophilus shows a decided tendency to retire into deep water, but only occurs in the tropics in deep water. He suggests that many forms which have been recorded from northern and southern seas, but not from the tropics, may occur in the tropics in deep water and have consequently escaped capture. Ortmann further maintains that the migration of forms may take place from the northern hemisphere through the tropics, to the southern hemisphere along the west coast of America and Africa, because of the comparative low temperature in tropical regions along these coasts. This is confirmed in the Decapods, and the reverse—z.e., the migration of forms from the southern to the northern hemisphere— in the case of the Isopod Serolzs. Before discussing the bearings of these two theories, it would be useful to consider the distribution of the genera in the collection. The genera represented are :— CHEILOSTOMATA. Beania, Cellaria, Cellepora, Cribrilina, Lepralia, Membranipora, Micropora, Microporella, Mucronella, Schizoporella, Smittia, Porella ; and, among the Crenostomata, Bowerbankia. All the species of Beania, with one exception (B. hirtissima), occur north and south of the tropics in temperate regions, but not within the tropics. B, hirtissima has been recorded from Cape Verde Islands. which lie within the tropics. All the species, except the British B. mirabilis, occur in shallow water. The genus Cellaria is cosmopolitan. It occurs in deep and shallow water in the temperate zone. The depths at which it occurs in the tropics I have not been able to ascertain. It occurs in the fossil tertiary strata. Cellepora. The Challenger obtained 30 or 31 species of this genus, of which the North Atlantic yielded three, from depths varying from 51-400 fath. The South Atlantic yielded 9 species, 5-600 fath. ekterguelen regions... 66 95,- 20-000 5 Po) PAWS URAL AT weyers ler eimai i 2-40 ,, THE MARINE FAUNA OF THE FALKLAND ISLANDS. (8 (One species, an aberrant form, doubtfully referred to this genus, was found in 2,600 fath.). The North Pacific region, 4 species, 10-30 fath. Pe SOUthe a5, ae Te » one from 45 fath., the other from 1,325 fath. The genus is cosmopolitan, and appears to belong to shallow water, yet evidence shows that it has a wide bathymetrical range. Cribrilina. This genus inhabits north and south temperate regions, but only one species (C. jloridana) has been recorded from the tropics (Gulf of Florida). The genus is fossil, occuring in the French cretaceous, Austro-Hungarian miocene (coral and red crag), Italian pliocene, boulder clay (Wick). The species C. monoceros is notable in that it occurs in very shallow as well as in very deep water. Off the west coast of the extreme south of South America it has been found at a depth of 1,325 fath., in the North Pacific at a depth of 3,125 fath., Strait of Magellan 25 fath., Tierra del Fuego and Patagonia 19 fath., Cape Horn 40 fath, Falklands 4-12 fath. My specimens were picked up on the beach. The facts of its occurring in the tertiary deposits, its presence in the north and south temperate regions, and its absence from the tropics, tend to support Murray’s argument, according to which Cribrilina may be looked upon as a true representative of a primitive, universal, marine, littoral fauna. On the other hand—and this is supported by the fact that this species does occur in very deep water elsewhere—it may be that this Species eXists in the tropics at great depths, and has thus escaped capture. Lepralia. This genus occurs in the north and south temperate zones, and within the tropics ; all the deep-sea forms occur in the temperate regions ; the forms living in shallow water occur in the tropics as well as in the temperate regions. ‘This is rather interesting, for it shows that the tropics do not form an insuperable barrier for all species, between the two temperate zones. Then, again, according to Ort- mann’s view, one would expect to find the deep-sea forms nearer the Equator, if the deep sea affords a passage between the two temperate zones. The species Z. adpressa occurs north and south of, but not within the tropics, in shallow and moderately-deep water. It occurs fossil 76 EDITH M. PRATT, B.SC. in Italian pliocene, Austrian miocene, and tertiary formations at Reggio (Italy). The distribution of this species gives evidence in support of Murray’s view. Membranipora. The genus is cosmopolitan, chiefly in shallow water, but it also occurs in deep water. M. albida, Tongatabu (Pacific), 21°S., 18-20 fath, Bermuda, 38° 37’N., 450 fath. Singapore. M. crassimarginata, Bass Strait, 38-85 fath. Heard Island, 75 fath. Tristran D’Acunba, 110-150 fath. Gulf of Florida, 13-60 fath. M. multifida, Cape of Good Hope, 450 fath. Challenger station 320, 37° 17'8., 600 fath., green mud. It is notable that the species occurring at great depths are found only in temperate regions. The tropical forms occur in fairly shallow water. Membranipora membranacea occurs in north and south temperate zones, but not within the tropics. Micropora. Genus extends back at least to the chalk period. It occurs in north and south temperate zones, as well as the tropics, in shallow to fairly deep water (greatest depth recorded, 150 fathoms). The species M.uncifera is recorded only from the southern hemisphere. Microporetia. Genus cosmopolitan. Microporella ciliata is also cosmopolitan ; the specimens taken at greatest depths have been limited to temperate regions, namely : Bahusia, on the Falmouth and Lisbon cable, 47° N., 89-205 fath. ; and the coast of Norway, 300 fath. The tropical specimens occur in fairly shallow water. The species 1. malusii occurs north and south of, but not within, the tropics in fairly shallow water (10-50 fath.). It occurs fossil ; coralline crag, older pliocene (Castrocaro). Mucronella. The genus is cosmopolitan, from fairly deep water, but the species JM. tricuspis appears to be restricted to the southern hemisphere, from shallow ‘to fairly deep water, 12-150 fath. Fossil— tertiary—New Zealand. The species occurring at the greatest depths occur also in temperate regions, with one exception — Challenger . Station 122, off East coast of South America, 9° 5'S.; the species M. castanea occurs from 32-400 fath., and, with this exception, all other tropical species occur in fairly shallow water. Many of the species of this genus are fossil, occurring in coralline crag, middle pliocene, upper pliocene, paleolithic, Scottish glacial deposits, &e. THE MARINE FAUNA OF THE FALKLAND ISLANDS. Ui Schizoporella. The genus is cosmopolitan. The species S. hyalina is cosmopolitan, it occurs on shells, stones, weed, etc., from shallow to deep water, it is fossil, and occurs in coralline crag, Scottish glacial deposits, post-pliocene deposits (Canada), Greatest depth: of species 100 fath. (Davis St.), of the genus 300 fath. (off Norway). Both the cosmopolitan species Schizoporella hyalina and Microporella ciliata occur fossil, and might be remnants of a once universal fauna. Evidence shows that these forms have been able to withstand all changes of temperature and altered conditions of life, without either becoming extinct or undergoing modification so far as the hard parts are concerned. Smittia. The genus appears to be cosmopolitan. It is found among the fossil tertiary deposits. It inhabits shallow and moderately deep water, the greatest recorded depth being 600 fath. (S. smzttiana). Smittia landsborovit appears to be characteristic of north and south temperate and cold seas, from shallow water to great depths. Fossil : Scottish glacial deposits. The species S. trispinosa occurs in temperate and tropical zones, in shallow water and at great depths. Porella. The genus is cosmopolitan, and is represented in the tertiary deposits. It occurs in shallow water chiefly, but does also occur at moderate depths. These results, as far as the Bryozoa are concerned, seem to support Murray’s theory on geographical distribution. Each genus represented in the collection occurs fossil, and also occurs in the north and south temperate zones, as well as in the tropics ; in fact, most of the genera are cosmopolitan, Many of the species are represented in the tertiary deposits. This shows that the changes of climate and altered conditions of life, have not affected their “ tertiary ” structure ; as many of these forms occur only in the two temperate zones, there is reason to believe that they have retained their common ancestral structure. The fact of many of the species occurring in the deep sea hardly supports Ortmann’s theory, for many of them occur at very great depths only in the temperate regions ; in the tropics they occur in shallow water. Their presence in the deep sea is, I think, the result of accident. 78 EDITH M. PRATT, B.SC. ANTHOMEDUSE. MaRrGELID&. Hippocrene macloviana Haeckel, Das System der Medusen, p. 9. Peculiar to Falklands. Soledad Bay (Lesson). Stanley Harbour. The genus (after allowing for Haeckel’s weeding out of synonyms) is curious in its distribution, in that the species H. macloviana is the only representative in southern seas, and even this has, as yet, only been recorded from the Falkland Islands. The other members of this genus are found in the temporate and cold regions of the northern hemisphere as well as in the north tropical zone. PoORIFERA. in the collection are two species of the genus Sycon :— Sycon ciliatum Fleming. Habitat: Europe. New to Falklands. Sycon ramsayt Lendenf. Habitat: Australia. New to Falklands. One small specimen. The genus is cosmopolitan in shallow to moderately deep water. POLYCHATA. NEREIDIFORMIA. I. Nereis catont M‘Intosh, Challenger, Vol. XIL, p. 223. Habitat: East of South America. Fernando Noronhia, 25 fath. Marion Island, 69 fath. Kerguelen, 20 fath. Falklands, 5—10 fath. Il. Nereis patagonica M‘Intosh, Challenger, Vol. XIL, p. 228. Habitat: East of Strait of Magellan. New to Falklands. Ill. Nereis kerguelensis Baird?, Challenger, Vol. XIL, p. 225. Hlalitat : Kerguelen New to Falklands. IV. Nereis atlantica M‘Intosh, Challenger, Vol. XII, p. 219. Habitat : Cape Verde Islands. New to Falklands. The genus is widely distributed in north and south temperate and tropical seas, from very shallow to very deep water (1,520 fath). The Polycheete species represented in the collection from the Falkland Islands appear to be peculiar to the southern temperate zone, although most of the genera are widely distributed in the north and south temperate and cold seas, as well as in the tropics. THE MARINE FAUNA OF THE FALKLAND ISLANDS. 79 V. Lagisca magellanica M‘Intosh, Challenger, Vol. XII, p. 82. - Habitat: Strait of Magellan, 175 fath. Kerguelen, 127 fath. The genus appears to belong to the southern hemisphere, being widely distributed in that region, and in the tropics. It occurs also in the northern hemisphere, but is rare. There were also present in the collection some fragmentary specimens belonging to the genera Zerebella and Cirratulus, but they were tco badly preserved for identification. GEPHYREA. Phascolosoma capsiforme Baird, Proc. Zool. Soc, 1868, p. 83; Selenka’s Sipunculiden, p. 27, Numerous specimens of this species were found on roots of basket kelp after storms. This species is peculiar to the Falkland Islands. The genus is cos- mopolitan in shallow to very deep water. Mo.Luusca. Out of 45 species of Mollusca from Lively Island, Falklands, which Mr. Standen’ has identified, 4 occur in the tropics as well as in the southern hemisphere ; one ranges through the southern hemisphere, the tropics and the northern hemisphere, Crepidula dilatata, which extends all along the west coast of America from Patagonia to Alaska, and also occurs in Kamtschatka ; 40 are found only in the southern hemisphere, 29 of which occur only in South America and the Strait of Magellan, whilst 5 are peculiar to the Falklands. EcHINOIDEA. Goniocidaris canaliculata Agassiz, Revision of Echint, p. 395. A single, young, somewhat damaged specimen. This species has an extensive distribution. Southern oceans, 1,600- 1,975 fath. Sandwich and Navigator Islands. Natal. Falklands, 5-12 fath. It ranges along the southern extremities of all the southern con- tinents and extends north of the equator to Japan. 1Melvill, J. C., and Standen, R., ‘‘ Notes on a Collection of Marine Shells from Lively Island, Falklands” (Jowrn. Conchol., IX., 4). 80 EDITH M. PRATT, B.SC. G. canaliculata has a wider distribution than any other species of this genus, which is restricted, with this exception, to the southern hemisphere and to the tropics. An interesting fact concerning this species is that it extends through the tropics to the northern hemisphere along the western shores of the Pacific, and not along the eastern shores, as one would expect. This is still more interesting when we note that this species occurs at the southern extremities of America and Africa. HoLOTHUROIDEA. Cucumaria mendax Théel, Challenger, Vol. XIV., Holothuroidea, p. 65. The specimens are young and under average size. The species is restricted to the Falklands. The genus is cosmopolitan. ASTEROIDEA. I, Asterias cunningham: Perrier, Arch, Zool. Hupér., t. IV., p. 339. Habitat: Falklands and Strait of Magellan. Peculiar to this region. The genus is cosmopolitan, from shallow water to 1,250 fath. II. Porania magellanica Studer, Challenger, Vol. XXX., p. 363. Young specimen. Habitat: W. of Patagonia. Peculiar to the southern portion of South America. The genus is widely distributed in north and south temperate and tropical seas, from 15 to 6,000 fath. OPHIUROIDEA. I. Ophiothriz magnifica Lyman, Challenger, Vol. V., Ophiuroidea, pp. 215, 216. Proc. Boston Soc. Nat. Hist., Vol. VIL, 1860, p. 254. Habitat - Coast of Chili, Not previously recorded from Falklands. Peculiar to South America. The genus is cosmopolitan, from very shallow to fairly deep water. IL. Ophiomyaia vivipara Studer, Monatsh. K. Akad. Berlin, 1876, p- 462,; Challenger, Vol. V., Ophiuroidea, p. 245. Habitat - Cape of Good Hope, 150 fath. Kerguelen. S. W. of South America. Strait of Magellan, 55-70 fath. Between Magellan and Falklands. Has not been recorded from the Falklands before. THE MARINE FAUNA OF THE FALKLAND ISLANDS. 81 Of the 4 species of this genus known :— I. O. vivipara is only found in the southern hemisphere. II. O. australis occurs in South Australia and south temperate region as well as the tropics. ILI. O. flaccida occurs off Bahia and off Bermudahg, 7.¢., in south tropical and north temperate zone. IV. O. pentagona occurs only in the northern hemisphere. From the preceding one may conclude that, while the genus is widely distributed in temperate and tropical regions, the species, though over- lapping each other to a certain extent, are somewhat limited in their distribution. Of 6 representatives of the Echinoderms in the collection, 3 species are pecular to South America, 2 of which are found in the Strait of Magellan, as well as the Falklands ; one is peculiar to the Falkland Islands. Two species are apparently distributed over the southern hemisphere, one of them extending beyond the Equator to the north temperate region. BRACHYURA, a) CATOMETOPA. PINNOTHERID. Halicarcinus planatus White, Ann. Mag. Nat. Hist., Vol, XVIIL, 1846, p. 178, is widely distributed over the Antarctic region, and is said.to be the only Brachy- urous Decapod proper to that wide area of distribution (Stebbing, Crustacea). (6) CYCLOMETOPA. CANCRINEA. CANCRIDE. Xantho crenatus Milne Edwards, Crustacea Vol. I., p- 396. Coasts of Peru. New to Falklands. MACRURA. ANOMURA. (a) LirHopEa. LITHODID&. Paralomis verrucosus Dana, U.S. Hupl. Haped., X IIT, Crust. Pt. 1, p. 428. Falklands. Common in E. portion of Strait of Magellan, not further W. than C. 82 EDITH M. PRATT, B.SC. Negro. Genus taken south and north of tropics, but not within tropics. : (b) PaguropEa. PaGURIDE. Hupagurus comptus White. Peculiar to Falklands, and Fuegian region. ISOPODA. IDOTEID#. ELdotia tuberculata Guérin-Méneville, Zeonoqgraphie du Reégne Animal de-G. Cuvier T. ITI. Crust., p. 34. Habitat : Con- fined to Strait of Magellan and the Falklands. SPH ZROMIDH. Spheroma gigas Leach, Dict. Sct. Nat. t. 12, p. 346; Miine- Edwards, Crustacea Vol. I11., p. 205. Habitat : Strait of Magellan. Falklands. Australia. New Zealand. Ker- guelen. Aucklands (Southern Hemisphere). AMPHIPODA. Orchestia chilensis Milne-Edwards, Crustacea, Vol. IL1., p. 18. Habitat: Mediterranean and coasts of Chili; not previously recorded from Falklands. Of the seven species of Crustacea in this collection of common shore fauna, one is common to the northern and southern hemispheres (Orchestia chilensis), two are distributed over the temperate portion of the southern hemisphere, and four are peculiar to the neighbourhood of the Falklands. Paralomis, The genus occurs north and south of the tropics but not within the tropics; of 3 species, 2 occur in moderately deep to deep water, 310-600 fath. ; the third, P, verrucosus, appears to be a shallow-water form. Halicarcinus. Vhe genus appears to be widely and universally distributed over the southern portions of the three great continents in the southern hemisphere. Xaitho. Genus cosmopolitan, and fossil. Hupagurus. The genus is distributed in north and south temperate THR MARINE FAUNA OF THE FALKLAND ISLANDS. 83 regions as well as the tropics, but the species of this genus appear to be very limited in their distribution. The depths vary from 0 to 700 fathoms. Edotia. The distribution of this genus appears to be somewhat doubtful. A species, #. bécuspida, occurs in the Arctic seas. 1 have been unable to ascertain if the genus is represented in the tropics. Spheroma. The genus appears to be almost universally distributed over the temperate and tropical areas, but the species appear to have a very limited distribution. Orchestia. The genus appears to be cosmopolitan in temperate and tropical littoral waters; the species of this genus, like those of other genera in this collection, are limited in their distribution. Regarding the seven genera represented in this collection: three (Eupagurus, Sphevroma, and Orchestia)-are widely distributed in temperate and tropical waters; one (Nantho) is cosmopolitan; one (Paralomis) has been recorded from the north and south temperate regions, but not from the tropics. One (Halicarcinus) is confined to the southern hemisphere: and the distribution of one (Zdotza) is doubtful. The distribution of the genus Paralonis in northern and southern temperate seas, but not in the tropics, cannot be said to support Murray’s view, for I do not think this genus has been recorded as occurring fossil. The tendency of this genus to retire into deep water might be said to support Ortmann’s view, but there is not much evidence to turn the balance in favour of either one or the other. There appears to be no evidence among the representatives of Crustacea in this collection of a passage from one temperate zone to the other, along the west coasts of America or Africa. SS UUINTOATIEA: Ascipim SIMPLICES. ~ Boltenva legumen Lesson, Centurie Zoologique, 1830, p. 149; Challenger, Vol. VI., Tunicata, p. 88. Habitat: Falk- lands, and southern extremity of South America. The genus appears to be specially characteristic of north and south temperate seas, but has not, I think, been recorded from the tropics. 84 EDITH M. PRATT, B.SC. Molqula gregaria Lesson=Cynthia gregaria, Cent, Zooloy.. p- 157; Challenger, Vol, VI., Tunicata, p. 73. Habitat: Limited to Strait of Magellan and the Falkland Islands. It appears to have been found only in shallow water. The genus appears to be almost universally distributed over the temperate portion of the southern hemisphere. Comparison of the common shore fauna of the Falkland Islands with that of Britain. It is interesting to note that there is a certain resemblance between these two faunas, but it is more clearly marked in some groups than in others. This may be due, to a certain extent, to the great or small number of species of the groups represented in the collection. Of the 16 species of Bryozoa represented, 6 (of which two are cosmo- politan) are also found on our shores. Of species belonging to other groups, one (Sycon ciliatum) is British. All the genera (13) of Bryozoa in the. collection are represented in the British fauna; of these, 8 are cosmopolitan, the remainder are found only in temperate and tropical waters. Of the 22 genera belonging to other groups, 15 are British, 2 are restricted to the southern hemisphere, 4 are found in the southern hemisphere, tropics, and northern hemisphere (Japan) ; the distribution of one ( Adotia) is doubtful. Of the 24 species, exclusive of the Bryozoa, occurring in this collec- tion, 19 have been found in the southern hemisphere only ; of these, 7 are more or less uniformly distributed over the temperate portion, and 12 (three of which are peculiar to the Falkland Islands) have been recorded from and about the southern portion of Sonth America. Three have been recorded from north and south temperate regions only ; one from north and south temperate regions and the tropics ; one from tropics and southern hemisphere only. The evidence gained from a study of the distribution ,of the common shore fauna of the Falkland Islands, points to a near and close relation- ship, among the majority of forms, between the faunas of the tem- perate portions of the three great continents, including the islands in temperate latitudes of the southern hemisphere. iz aay : 5 I g 6 8 I G ss ; en piivhath vinhjoyy| uaunfian pruajog es ov DyDjNILIQny DYOP A 2) sngduoo snanbndug 5 SNSOONALAL sohib puosanydy sesuapiya Dysayolg | gs srwmopnLng | sngounjpd 9 SnyDUata OYIUDY SNUIILNID FY a noyrubou ; = xrsyjoryd?) = xppuau povuppjabnu mandir DywnaypuUDa 5 DLADUNING DUIDLOT piehwmorydy SILDPVOWUOL) = aupyburcuuna 3 $p0.1098 F P sruofisdpo a6 DULOSOJOISDY T 25 ai nS povunjjabou a 3 - ee posiby'T = 8 DIQUDIID 820.13 NT pruUobpypnd 82a. Ay cepeeiuien : 1U07DA $29.0 AT ry Pa" AhDSUDA WOKS py uodliy| Fe t : oTele os. — mal ga pUnrWo?IDUL oes auasv0ddr yy Bs sot ‘ataydstmlay UlatyyNog ‘spurpyTeg “eoLoUry YyNog ‘aloydstmayy ulatyynog ‘sotdoay,-+ ‘oyerodwi94 pue sordory, 0 ‘aqraaduiay, ‘aqerod uta y, “dut9y "SP “NT ‘SRN "UO1}IIT[OD IY} Ul ‘eozoAIg Jo dAISNJIx—a ‘Saldads JO UOTINGII\sIG 86 EDITH M. PRATT, B.SC. EXPLANATION OF PLATE 5. Fig. 1. Lepralia adpressa, var. Bush. Group of zowcia, magnified about 260 dian. hk, knobbed cell. a, knobs. Characteristic of British species. s, spatulate avicularium. p, pores round margin between furrows. Fig. 2. Single cell, magnified about 380 dian. C. A., circular avicularium. Chiin., chitinous mandible. fig. 8. Avicularia, magnified about 380 diam. aand b are avicularia of the ordinary beak-like type. cand d are circular avicularia, showing mandible in two different positions. Fig. 4. Porella tridentata. Portion of colony showing disposition of zoecia, nuagnified about 260 dian. a, spatulate avicularium, b, lateral raised ollar, meeting behind in a depression. c, median denticle. d, lateral denticles. RA, median avicularium with rounded mandible. Fig. 5. Single cell, magnified about 380 diam. a, spatulate avicularium. b, median avieulariwn with rounded mandible. c, median denticle. d, tavo latcral denticles. Ov, vi cell, / IMEI Dy spouaye sopsoyouny" Mintern Bros. lith. EM.Pratt del. Reprinted from the “QUARTERLY JOURNAL OF MICROSCOPICAL SCIENCE, Vol ai. THE HABITS AND STRUCTURE OF ARENICOLA MARINA. By F. W. Gamers, M.Sc., and J. H. Asawortu, B.Sc., Demonstrators and Assistant Lecturers in Zoology, Owens College, Manchester. With Plates VI.—X. CONTENTS. 1. Distribution: Varieties : i Gulls: Habits. 8. Nervous System and Sense- 2. External Features: Segmenta- organs tion: Skin: Sete, 9. Nephridia. 3. General Anatomy of the Internal 10. Ccelom. Organs. 11. Reproductive Organs. 4. Musculature. 12. General Summary. 5. Alimentary Canal. 13. Literature. 6. Vascular System. | J.—DIstTRIBUTION: VARIETIES: HaBITs. The common lugworm and its coiled castings of sand are familiar objects on almost all the sandy and muddy shores of Western Europe, but the exact geographical range of the species is doubtful. It has been recorded from the shores of North Siberia, Spitzbergen, Iceland, and Greenland (Wirén, 1883; Levinsen, 1883). On the north-east coast of America it has been found from the Bay of Fundy to Long Island (Verrill, 1881). On both sides of the Atlantic, latitude 40° N. marks approximately the southern limit of Arenzeola marina. South of this it is replaced in the Mediterranean by A. Vlaparédi, Lev., and 88 F. W. GAMBLE, M.SC., AND J. H. ASHWORTH, B.SC. by A. cristata, Stimps., the latter also ranging on the west side of the Atlantic from Cape May (N.J.) to the Caribbean Sea. Its reputed occurrence on the north coast of Alaska (Murdoch'), at Vancouver Island (Marenzeller, 1887), Coquimbo, and South Africa requires confirmation. An abundant, widely ranging, and undoubtedly old form such as Arenicola, might be expected to vary considerably in its habits and structure, though it has not hitherto been ascertained how far this is the case. Having paid special attention to this point, we have found that there are (at least on the Lancashire coast) two varieties of A. marina, differing in habits, structure, and times of maturity, and that there is, in addition, considerable individual variability. (1) From high-water mark down to the beginning of the Laminarian zone, the common shore lugworms (or “lugs,” as fishermen call them, in contradistinction to the second variety, or ‘“ worms”) sink their U-shaped burrows to a depth of from one to two feet below the surface. One end of the burrow is marked by a casting, the other by a ‘‘ countersunk ” hole, through which the head of the lugworm is pro- truded when the tide comes in. The size and colour of the animal vary with the amount of muddy organic matter in the sand. Where there is comparatively little mud, the Arenicola average about seven inches in length and are somewhat transparent, so that the superficial blood-vessels can be clearly seen through the thin body-wall. The gills, which are not very strongly developed, are composed of nine to eleven branches, each provided with three to five pairs of short lateral twigs (Pl. VI., Fig. 3). The proboscis and prostomium are only slightly pigmented, and being very vascular, appear red in colour. Where, however, the amount of organic matter is consider- able, the worms are usually about ten inches long, and_ their prostomium, proboscis, gills, and epidermis are black. The gills are better developed than those of worms living in purer sand. These differences are probably due to more abundant nutrition. The time of maturity of both these forms of the littoral variety on the Lancashire coast is the summer, while at St. Andrews they are found mature from February to September. (2) The second variety occurs on the Lancashire coast at the upper 1 «Proc. U.S. Nat. Museum,’ Washington, vol. vii., 1884, p. 522. THE HABITS AND STRUCTURE OF ARENICOLA MARINA. 89 part of the Laminarian zone. Almost all the dvenicola from this zone (which can accordingly be obtained only at low spring tides) are of this kind, which when fully mature, as it is from February to May, is probably one of the largest Polycheets of our shores, measuring as much as fifteen inches in length and three in girth. It is almost black, the prostomium proboscis, and the base of the gills being markedly so. The tail is shorter in proportion to the length of the body than in the littoral variety. The burrows are of considerable length, three feet or more, and are not U-shaped, but simply vertical. Like those of the littoral variety, they are lined by a greenish coating of mucus.~ The dark ‘““worms ” appear to keep nearer the surface of the sand in cold weather than in summer—at least, during the winter of 1893-4 large numbers were thrown up on the beach at Blackpool. The most distinctive character, however, of this ‘ Laminarian ” variety is the gill (Pl. VI., Fig. 2), which presents a structure hitherto only known in Arenicola cristata, Stimps. Instead of the somewhat simple gill seen in the shore lugworms, there is in the “ Lamuinarian ” variety a highly developed pinnate structure, consisting of about twelve branches united by a connecting membrane at their bases, and bearing ten or more pinnules on each side of the main axis. Such a gill is undoubtedly a much more efficient respiratory organ than the gill of a shore lugworm, though it does not appear to possess the same power of contractility as the latter, and hence probably does not contribute so much to the movement of the blood. In some old specimens the gills lose many of their finer branches, perhaps owing to friction or to the attacks of enemies,’ and in such cases there is an approximation to the type of gill seen in the littoral variety, though a certain amount of difference is always observable. Thus there appear to be two varieties of the common lugworm on the Lancashire coast, distinguished by their habits, external features, and periods of maturity, but their are no important structural poits of difference. The habits of Arenicola marina at the breeding season are still to a large extent unknown, and developing eggs have not hitherto been obtained. It has been stated that, when mature, the animal is in the habit of swimming freely (Ehlers, 1892, a), but we are unable to confirm 1 See the curious account of the ravages of Corophium longicorne, by d’Orbigny, ‘Journal de Physique,’ 1821. 90 F, W. GAMBLE, M.SC., AND J. H. ASHWORTH, B.SC. this. The post-larval stage, however, appears to be, for a short time, pelagic (Benham, 1893). The curved burrow of the shore lugworm is formed by the combined action of the proboscis, the swollen anterior region of the body, and the waves of muscular contraction which pass along the body from behind forwards. When the proboscis is everted and pressed into the sand, the prostomium is slightly retracted into the body. The proboscis is withdrawn full of sand, again everted, and the body is thrust forward, partly by contraction of the longitudinal muscles, partly by a peristaltic wave produced by the circular ones. The anterior end is in this way rendered swollen and tense, and is able to enlarge the burrow, and thus a passage is gradually eaten through the sand, smoothened by contact with the skin, and lined by the mucus secretion of the epidermis. The oill-region being narrower than that which precedes it, is thus, to a certain extent, protected from friction, while, as if to ensure this, the notopodial pencils of bristles are directed so as to protect the gills. After burrowing vertically downwards for a depth of from one to two feet, the worm forms a horizontal or oblique gallery, and then a second vertical one which ends at the ‘‘ countersunk ” hole, through which the anterior part of the worm may protrude, and so bathe the gills in fresh sea water. The amount and value of the work done by lugworms has been estimated on the shore of Holy Island by Mr. Davison (1891), and has also been adverted to by My. Hornell under the name of ‘“ cleansing of the littoral.” Mr. Davison finds that the castings are larger and more numerous above than below half-tide; and as the result of several estimates and measurements he calculates that on the Holy Island Sands, the entire layer of sand, to a depth of two feet, passes through the bodies of the lugworms which live in it, once in twenty-two months, and that in a year the average volume of sand per acre, which is brought to the surface in the form of castings, is 1,911 tons, represent- ing, when spread out, a layer of thirteen inches in thickness over the surface of the sands. 2. EXTERNAL FEatuRES. Segmentation.—The body is divided into an anterior cheetigerous portion, a middle branchial one, and a posterior caudal region or tail. The first region begins with the prostomium, and is followed by a short EERE aman THE HABITS AND STRUCTURE OF ARENICOLA MARINA, 91 acheetous portion (Fig. 1, JZ#'7’), which in many specimens appears to be composed of four annuli, divided, however, by secondary circular markings. The first cheetigerous annulus is produced into a strongly marked ridge, just behind which the notopodial sete (Chn.") are inserted, the corresponding neuropodia (Viw.') being very short and containing only a few sete. The intervals between the chetigerous annuli are subdivided into rings, of which there are, in the “Lami- narian” variety, 22444... , and in the littoral variety 23444 respectively. The chetigerous annuli do not mark the true somites into which the body is divided. From a consideration of the internal anatomy (see p. 94) we have reasons for believing that, in the middle region of the body, the second groove behind each cheetigerous annulus marks the boundary between the somites. A somite is, therefore, composed of a cheetigerous annulus together with three annuli in front of, and one’ behind, it. The purapodia are not situated at the beginning, but slightly behind, the middle of the somites to which they belong, thus confirming Benhaim’s observations on the post-larval stage (1893). The anterior region of the body is thus composed of the prostomium, six cheetigerous somites, and a region between these, made up probably of two somites, but the exact number is somewhat doubtful. (See Plate VI., Fig. 1, and explanation, p. 120.) The second or branchial region of the body is composed of thirteen somites, and is distinguished by the presence of gills, a pair of which are attached to a slight fold of the skin Just behind the notopodia. The first gill is variable, usually fairly well developed, but always smaller than the rest and sometimes absent. The gills about the middle of the branchial region are frequently, but not always, the largest. Both the gills and notopodia are very sensitive, and are retracted from time to time on the application of stimuli, such as a strong light. This contraction of the gills proceeds sometimes as a wave down the body, and as Milne Edwards (1838) pointed out in his classical paper, considerably assists the circulation of the blood. The neuropodia in the branchial region extend towards the mid-ventral line, so as almost to meet, and are only separated by a groove which marks the line of the nerve cord. This groove is continued on to the prostomium by a pair of diverging arms (‘‘Metastomial grooves”) underlying the circum-cesophageal nerve connectives (PI. 4, Fig. 19, Co Wika 92 F. W. GAMBLE, M.SC., AND J. H. ASHWORTH, B.SC. The tail, which is devoid of sete and gills, is marked by a large number of secondary annuli, crowded together at first, but arranged in distinct somites of about five each, towards the hinder end. The caudal region varies much in length; some specimens have about thirty somites, but the number is not constant possibly owing to the tendency of the worm to throw off the last few segments when irritated. There is no change in the internal organs to mark the somite which bears the first gill, but the transition from the branchial to the caudal region is accompanied by the loss of parapodia, oblique mus-les, and branchial vessels. Kxternal Apertures.—The mouth (Pl. 1X., Fig. 19, C. M0O.), when the proboscis is withdrawn, is a slightly crescentic transverse slit, bordered by papille and somewhat overhung by an upper lip. The anus, which is terminal, is often protruded, and the thin vascular swollen lips of the aperture project behind the last caudal segment. The cpenivg of the “nuchal organ” is a fairly wide slit on the upper and hinder border of the prostomium (P]..IX., Fig. 19, a and s, .VV.). Through this aperture, sea water (or a mixture of sea water and the secretion of the surrounding glandular cells) is probably introduced. The openings of the otocysts are difficult to see. They lie behind the prostomium on each side of the anterior end in the position marked OT. (Pl. IX., Fig. 19, 4 and B). Each is placed at the point of inter- section of the first transverse groove following the prostomium, with the oblique “metastoumial” groove which marks the position of the nerve commissure. The nephridial openings (Fig. 1, NO), six in number on each side, though not so distinct as in some species (e.g. 4 Claparéedi), are not difficult to find. The first is placed behind at the upper edge of the fourth neuropodium, and the other five in corresponding positions on the succeeding somites. They are minute slightly oblique slits, some- times exhibiting tumid lips. Skin.—The skin is subdivided into raised polygonal areas separated by corresponding shallow grooves, and is noteworthy in being devoid of special glands, Wirén (1887) has shown that the grooves are composed of columnar cells containing pigment granules, the raised areas being made up partly of larger cells containing still greater quantities of pigment granules and partly of clavate mucus-forming cells, which produce the slimy covering of the a.imal with which the burrow is lined. THE HABITS AND STRUCTURE OF ARENICOLA MARINA. 93 The 5 per cent. formalin solution of the epidermal pigment is fluores- cent, but does not yield any absorption bands, merely cutting off the rays at the blue end of the spectrum. In successively thicker layers of this solution, first the violet, then the blue, and lastly the green portions of the spectrum were cut off. MacMunn (1889), however, has shown that the alcoholic extracts of the integumental pigment shows a band in the blue and green (A 503 —468); that the residue of this solution if dissolved in ether or chloroform yields two bands \ 503—474, and » 465—446; and that the residue of this solution again being dissolved in nitric acid gives two bands, \ 500—468, and \ 472—443, so that a chlorophan-like lipochrome is present. It is probable that the pigment (melanin) of the skin is derived from tke -lipochrome of the yellow “glandular” tissue of the stomach, since the alcoholic extract of the latter yields a siniilar absorption spectrum. Further investigation will be required to show in what way the transference of the pigment from the yellow peritoneal cells to the epidermis is brought about, and whether the dark coloured, hairy- looking investment of the ventral vessel and its branches (PI. VIL, Fig. 5) contributes to the melanin of the skin. In this connection the inter- muscular extension of the ccoelom, bringing it almost into contact with the epidermis at certain points, must be borne in mind (see p. 29). Selte.—The notopodial sete are long capillary structures averaging 6 mm. in length, and bearing several rows of minute free and pointed hair-like processes (Pl. VIII., Fig. 10). The neuropodia in the anterior somites, which at first contain few sete, gradually extend by addition of new ones at their ventral edge, so as to almost reach the mid-ventral line (Pl. 1, Fig. 1). By isolating the entire band of the sete the different stages in their development may be seen. The youngest setze are always at the lower end of the series; the point of each seta is formed first, then the toothed ridge, and lastly the shaft. The fully- developed ventral seta is frequently almost smooth, owing to the wearing down of the teeth behind the apex. The middle of the shaft is straight, the inner end bent ventrally, and the outer end bent slightly dorsally, ending with a finger-shaped process bordered on the convex side by a toothed ridge, while on the concave side it is slightly produced at one point into a minute process (Pl. VIII, Fig. 12, proc.). This process is more constant in the Laminarian than in the littoral variety. It 94 F, W. GAMBLE, M.SC., AND J. H. ASHWORTH, B.SC. appears to correspond, in position, to the characteristic tufts of hairs on the ventral setze of the Maldanide. According to the age of the specimen the ventral setze differ in shape, and in the development of the toothed ridge. In sete from a small specimen (17 mm. long) the apex was bent more sharply on the shaft than in old examples, and the teeth were very prominent (Pl. VIIL, Fig. 9). Apparently the production of fresh ventral setze goes on slowly throughout life, and the form which they assume before being cast out of the body, varies at different ages Their size of course varies with the age of the worm to which they belong (see Pl. VIII.), but ina worm of average size their length is about *5 to ‘8 mm. 3. GENERAL ANATOMY OF 1H# INTERNAL OreGans (PI. VIL). In opening the body-cavity by a dorsal incision, the middle part of the alimentary canal is usually forced out through the cut by the pressure of the somewhat viscous ccelomic fluid. Normally this portion of the canal, beg longer than the section of the celom in which it lies, is swung to and fro by the movements of the body. This freedom of motion is ensured by the absence of mesenteries, by the absence of any vessels running from the body-wall into the dorsal vessel, and by the length and flexibility of the branchial and nephridial vessels, which are the only conuection between the stomach and the body-wall. The coelem is exceedingly spacious, and continuous from one end of the body to the other. In front it is divided transversely by the origins of the buccal retractors (B. Sh.), which form a sheath round the proboscis, and by three septa or diaphragms (Pls. VIT. and VIIL, Figs. 5 and 6). The first of these septa (Dphin.) is placed obliquely, arising below behind the level of the first neuropodium, and being inserted dorsally in front of the first notopodial sacs. The result of this arrangement is that between the first and second diaphragms two pairs of setal sacs occur, caused by the forward shifting of the upper edge of the first diaphragm (Fig. 5). The second and third are inserted both above and below, opposite the second groove behind the second and third cheetigerous annuli. Between the first and second diaphragms, dorsal and ventral mesenteries occur, supporting the corresponding vessels ; and it will be noticed that the dorsal mesentery ends in front, exactly where the first diaphragm would be inserted if it corresponded with the othertwo. The third diaphragm is perforated by the funnels THE HABITS AND STRUCTURE OF ARENICOLA MARINA. 35 of the first nephridia. There are, then, three diaphragms and not, as so often stated, four; and, while affording valuable evidence of the extent of the first and second cheetigerous somites, they do not help in deter- mining the number of segments which compose the achzetous portion following the prostomium Behind the last diaphragm the body-cavity is unsegmented up to the base of the tail. The segmental arrangement of the organs, however, can be recognised by taking the funnels of the nephridia as marking the anterior ends of the somites. The slight amount of connective tissue supporting the long afferent and efferent vessels (segmental vessels) (Pl. VIL, Fig. 5) of the nephridia and gills, may be regarded as the remains of the septa. Allied species of Avenicola fully confirm this view. At the level of the thirteenth pair of notopodial sacs, the segmental afferent and efferent blood-vessels, which have hitherto run nearly parallel across the coelom, diverge. At the base of the tail, the connec- tive tissue between them increases slightly in amount, septa forming which are continued down to the end of the body (Fig. 5, C. Sp.). 4. MUSCULATURE. The muscles of the body-wall are arranged in (1) an outer circular sheath, subdivided in the anterior and middle regions of the body into hoops, which cause the annulation of the skin; and (2) an inner longitudinal sheath of considerable strength and thickness divided by the nerve-cord and lines of insertion of the notopodial sacs into three parts, two ventrolateral and one dorsal (Pl. IX., Fig. 23). The inter- muscular spaces are filled by coelomic fluid, and are probably lined by a delicate peritoneum. In the anterior region of the body there are a few circular muscle- bands which are stronger and more obvious than the rest (Fig. 5, M. Cire.). The oblique muscles, which divide the colom longitudinally into three compartments, commence behind the thiid diaphragm, and disappear at the base of the tail. ‘These muscles are arranged in thin broad bands, arising at the sides of the nerve-cord, and are inserted right and left into the body-wall at the level of the notopodial sacs. They partly cover the nephridia, and in some specimens a muscle-band is attached to each nephrostome. 96 F. W. GAMBLE, M.SC., AND J. H. ASHWORTH, B.SC. The musculature of the buccal mass consists of a strong sheath of fibres derived from the longitudinal layer just behind the first diaphragm. This sheath, which is loosely attached to the proboscis by slips which run through the coelomic space between the two structures (Pl. VIII. Fig. 6, Bb. Sh.), is inserted into the anterior part of the proboscis. Pressure of the coelomic fluid at this point causes eversion of the buccal mass, which is withdrawn by the contraction of its muscular sheath. The prostomium is retracted by a small sheet ef muscle which arises partly from the longitudinal layer dorsally, and partly from the muscular covering of the circumoesophageal connectives ventrally, and it is inserted into the ventral surface of the brain, and the ventral and hinder edge of the nuchal organ (Pl. VIIT., Fig. 6, Vu. 77.). The parapodial muscles are modifications of the longitudinal layer. One, the retractor of each notopodium, is remarkably long, reaching to the side of the nerve-cord (Pl. VIIT., Fig. 13, An.). The protractors (Pn.) of the notopodia are six to eight in number, three to four being placed in front of, and three to four behind, the setigerous sac, They arise from the body-wall just below the dorsal longitudinal vessel, and are inserted into the base of each sac. The position and relations of the three anterior septa or diaphragms, of the dorsal and ventral mesenteries between the first two of these, and the presence of regularly arranged septa in the tail region, have already been noted. It may be added that a pair of outgrowths from the first diaphragm lie under the cesophagus, opening anteriorly into the coelomic space in front of the first septum. They are very vascular, and contract rhythmically every three or four seconds during life, and are doubtless of use in everting the proboscis (Pl. VIL. and VIII. Figs. 5 and 6, Dph. Ph.). In the caudal region the intestine is attached both above and below to the body-wall by mesenteries, in which the dorsal and ventral vessels lie. 5, ALIMENTARY Canatu (PI. VII.). This consists (1) of an eversible buccal mass (Buce. M.), of a pinkish or greenish-brown colour, which lies in front of the first septum ; (2) of an cesophagus, of a light brown colour, provided with a pair of glandular pouches behind the third diaphragm; (3) of a gastric region, THE HABITS AND: STRUCTURE OF ARENICOLA MARINA. oi with yellow glandular walls, extending from the level of the heart to about that of the twelfth or thirteenth notopodium ; and (4) of an intestine, of a dark brown or almost black colour, folded in a concertina- like manner by the caudal septa, and opening at the terminal anus. During life the buccal mass (or ‘ proboscis”) is constantly being everted and withdrawn, carrying sand into the csophagus. During eversion several rows of curved, pointed, vascular papillae (2. Pap.) ave first extruded. These papille (Pl. VIIL, Fig. 7) in old specimens are tipped with chitin, and recall the armature of the proboscis in certain Sipunculids (e.g. Phascolion collare'). Then the more globular portion of the buccal mass, covered with minute rounded processes, is protruded. Finally, when fully everted, the buccal aperture is surrounded by a few pointed pigmented papille, which are continuous with the lining of the first part of the cesophagus. The cesophagus’ itself is slightly looped behind the second diaphragm. It is a thin-walled distensible tube, the first part of which is lined by non- ciliated mucus-forming cells. The middle portion is lined by a cuticle, and the posterior part by cells resembling those of the stomach in bearing cilia, The cesophageal pouches (Oe. G/.) are somewhat flask-shaped, and open into the cavity of the cesophagus by a short tubular stalk. They are usually greenish in colour, but have a slight reddish tinge on account of their very large blood-supply. ‘Their blood-vessels are connected with the lateral cesophageal and dorsal vessels. The cavity of the pouch is subdivided by twenty-five to thirty incomplete partitions, produced by in- folding of the wall of the pouch, and therefore covered on each side by the epithelial lining of the pouch (Pl. IX. Fig. 22). Between the epithelial lamellze is a blood-sinus, which is slightly enlarged at the inner end and slightly thickened at the edge of each partition. The cesophageal pouches are lined by ciliated epithelium, covered with a fairly stout cuticle, and contain glandular cells. The walls of the cesophagus are marked by longitudinal and circular muscular impressions. The stomach, marked out by the patches of yellow tissue on its walls, extends from the level of the heart to about the twelfth notopodial sete. As we have already stated (p. 94), the stomach is bent upon 1 Selenka, ‘ Die Sipunculiden,’ 1883, pl. vi., fig. 74. 2 The histology of the alimentary canal has been carefully investigated by Wirén (1887, p. 31), Our results agree very closely with his. G 98 F, W. GAMBLE, M.SC., AND J. H. ASHWORTH, B.SC. itself and loosely attached to the body-wall. The patches of ‘ chloro- gogenous” tissue are at first arranged in symmetrical oval areas right and left of the dorsal blood-vessel, while more ventrally they are placed in two or three less regular series, and are separated from one another by a network of blood-vessels.1. About the level of the tenth sete these yellow areas all become subequal and arranged in a spiral manner, ending at the level of the fourteenth setze. | Stomach and Intestine.—The muscular wall of the gastric region is exceedingly thin, and composed purely of circular fibres, which appear to confer very slight powers of peristalsis upon the stomach. The mucus lining is strongly folded, and is composed of several kinds of cells. Some of the cells in all parts of the stomach are ciliated, others are apparently digestive, and a large number appear to secrete a mucus similar to that of the cesophagus, the cells themselves being discharged into the mucus which they help to form. Commencing about the middle of the stomach (that is between the ninth and tenth segments) is a ventral groove formed by a couple of folds of its inner and lower surface. This groove’ (Pl. IX., Fig. 23, Gv.) is provided with specially long cilia, which produce a current of mucus from before backwards. There are other smaller grooves on the side walls of the stomach and the anterior part of the intestine, whose general direction is downwards and backwards, and which open into the median ventral groove. The direction of the current in all these is from before backwards. ‘The ventral groove is continued back to the anus. The intestine is dark brown or nearly black in colour externally. Its mucus lining is somewhat similar to that of the stomach, but is covered by a thin cuticle, and is not ciliated. The process of digestion in the lugworm has not been at all fully investigated, but the series of events appear to be somewhat as follows. The sand or mud is mixed with the mucus secretion of the cesophagus, and is slowly carried backwards by peristaltic contraction. At the junction of the stomach and cesophagus the secretion of ‘the cesophageal pouches is poured upon the sand. Wirén regards the contents of these pouches as acid and digestive. In several cases we have found the 1 This network is considered by Wirén and others to be parts of a continuous sinus. Weare not convinced, however, that this is really the case, and our reasons will be found on p. 101 infra. * This groove has only hitherto been noticed by Wirén (1887). THE HABITS AND STRUCTURE OF ARENICOLA MARINA, 99 fluid neutral. In the stomach several changes occur. The secretion of the gastric cells proper is probably digestive, and this, together with a further amount of mucus, is mixed with the sand, and shaken together by the swing of the loose gastric loop. In this way the food, which apparently consists of the organic sub- stances! in the sand is brought into contact with the digestive secretion. The ciliary action of the lateral and ventral grooves probably separates the digestive substances from the sand and carries them slowly downwards and backwards. The lining of the stomach is very thin, and the lateral and ventral grooves are in specially close contact with the blood plexus, in which the flow is, probably, slowly forwards, more rapidly in the sub-intestinal vessels. It seems probable, therefore, that the blood in the visceral plexus conveys the nutritive material to the hearts, which pump it along the ventral vessel to the various parts of the body. The action of the chlorogogenous tissue round the stomach, and particularly of that in the neighbourhood of the ventral vessel and its branches, is uncertain. 6. VascuLar System (Pl. VII. Fig. 5). The blood-vascular system of Arenicola attains a high degree of per- fection. The large size of the chief vessels, the great development of the capillary system (especially on the walls of the alimentary canal), and the mechanism for promoting the flow of the blood, are features that distinguish it. There are two chief vessels running, one above, and the other below, the alimentary tract from end to end,—the dorsal vessel, which con- tracts fairly rhythmically from behind forwards ; and the ventral vessel, which is feebly, if at all, contractile. The walls of the gastric and intestinal portions of the gut are enclosed in a blood-plexus, and the cesophageal region is supplied by lateral vessels. The gastric vessels are connected with the ventral vessel by a pair of “hearts” placed a short distance behind the cesophageal pouches (Fig. 5. V.). These hearts drive the blood from the gastric vessels into the ventral vessel. al So = The dorsal vessel (DV) arises near the anus, and as it runs along the a Saint Joseph found in an Arenicola a whole Nereis almost digested. ‘Ann. Sci. Nat.,’ series vii., t. xvii., 1894, p. 127. 100 F. W. GAMBLE, M.SC., AND J. H. ASHWORTH, B.SC. intestine gives off in each somite a pair of branches which are attached to the anterior face of the caudal septa, and which run downwards and forwards to open into the ventral vessel (Pl. VIL, Fig. 5). Of these there may be twenty-seven to thirty pairs. In front of the caudal region each of the last seven pairs of gills returns an efferent branch to the dorsal vessel, and between these there are three or two pairs of smaller branches which run round the alimentary canal from the ventral vessel to open into the dorsal one. From the level of the twelfth setze to the oesophageal pouches the dorsal vessel does not receive any segmental vessels from the gills or nephridia, nor does it open directly into the heart (Fig. 5). It merely receives numerous branches from the gastric plexus. In front of the heart it receives on each side a branch from the third nephridium and the fifth setigerous sac ; a branch from the csophageal pouches ; and one from the second nephridium and fourth setigerous sac. It then runs on and, piercing the third diaphragm, receives a branch running on the anterior face of the diaphragm trom the first nephridium aud _ third setigerous sac. On reaching the second diaphragm it receives a branch from the second setigerous sac, and after piercing the first diaphragm receives a branch from the muscles forming the bueeal sheath. Thence the dorsal vessel breaks up into capillaries around the buccal musculature, prostomium, and otocysts. From these capillaries the ventral vessel takes its origin. It gives off a small unpaired branch running in the first diaphragm and to its pouches ; a paired branch arising about midway between the first and second diaphragms to the neural vessels and second setigerous suc; a single small vessel supplying the second diaphragm and the neural vessels ; an unpaired vessel to the third diaphragm, to the neural vessels in that region, and to the first nephridia ; a pair of branches to the neural vessels and second nephridia ; and lastly, a pair to the neural vessels and third nephridia. From this point onwards the ventral vessel supplies the setigerous sacs, body-wall, nephridia (if present), and gills, by large segmental vessels. The ventral vessel is very large and turgid in the gastric region, and is surrounded by tufts of dark brown chlorogogenous tissue, which are also found in older specimens on the vessels running to the body-wall. This chlorogogenous tissue is first seen on the ventral vessel about the level of the eighth pair of setz. In the tail the ventral vessel ends in the obliquely placed intestinal vessels which THE HABITS AND STRUCTURE OF ARENICOLA MARINA. 101 encircle the intestine, and which form, along with the capillaries from its median terminal portion, the commencement of the dorsal vessel. Visceral Plexus.—Wirén (1887) maintains that the intestine and stomach are enclosed in a blood sinus, thickened along certain lines ““ vessels.” which have been call the dorsal, gastric, and subintestinal We are, however, of the opinion that the so-called sinus is a close plexus of vessels, some of which appear to have a distinct cellular lining. The dorsal vessel is, at any rate, a perfectly distinct structure with proper walls. ‘The subintestinal vessels (Fig. 5, S.V.), which commence just behind the heart and run backwards, are moderately large up to the level of the thirteenth setze, but then taper rapidly and gradually disappear. They each receive seven segmental vessels. The first of these comes from the fourth nephridium, the second from the fifth nephridium and the first gill, the third from the sixth nephridium aud second gill, and the other four from the third, fourth, fifth, and sixth gills. The subintestinal vessels open through the plexus into the lateral gastric ones, and so into the heart. The flow in these vessels is probably slowly forwards. The gastric vessels give off from the “auricle” into which they expand, a lateral cesophageal vessel (Oe. Lat.), which, after giving off a stout branch to the csophageal pouches, runs forwards to the buccal mass, supplying the wall cf the cesophagus, as it does so, with numerous small branches. Neural Vessels—These are a pair of small vessels lying one on each side of the ventral nerve-cord, and accompanying it from one end of the body to the other. They arise around the nerve-connectives from the brain from capillaries of the dorsal vessel, and receive several branches from the ventral vessel (1) midway between the first and second diaphragms (2) from the vessel running in the second diaphragm (3) from a vessel just behind the third diaphragm (4 and 5) from the vessels to the second and third nephridia. Near the middle of each somite the two neural vessels are united by cross connections, which also supply the nerve- cord (Pls! VII. and VII, Big. 13; 4. V., N.C_V... Behind the third diaphragm the neural vessels supply the oblique muscles by branches which run the whole length of the bands, and are connected with the outer longitudinal parietal vessel (Fig. 13). 102 F. W. GAMBLE, M.SC., AND J. H. ASHWORTH, B.SC. Vessels of the Body-wall.—This parietal system of true vessels is highly developed in Arenicola marina. It consists of two longitudinal vessels (1) the nephridial longitudinal vessel (Fig. 22, V. Z. V.) running just below the level of the nephridiopores, and (2) the more important dorsal longitudinal vessel (Fig. 13, D.L.V.), which runs just above the level of the insertion of the notopodial setal sacs. Both arise just behind the first setze, and increase in size as they pass backwards. The former receive vessels from the nephridia, just behind which they taper and disappear. The latter, which may be traced to the anus, and are Jargest in the branchial region, receive branches in each somite : (1) from the segmental vessels (2) from its fellow of the opposite side. The body-wall in the dorsal and lateral regions derives its blood-supply from the nephridial and dorsal longitudinal vessels, and in the ventral region from the neural vessels. These parietal vessels (Par. V.) run just within the layer of circular muscles in almost every groove between adjacent longitudinal muscle-bands of the body-wall, are chiefly longitudinal in direction, but at frequent intervals there are cross connections. Branches from these vessels ramify between the bases of the epidermal cells, and are accompanied by extensions of the coelom. Hearts.—The hearts are a pair of muscular bulbous swellings connect- ing the visceral plexus with the ventral vessel on each side. Each commences with the thin-walled expansion of the gastric vessel (“auricle,” Fig. 5, A.v.) which, after giving off the lateral cesophageal branch, opens into the ventricle (V.). The cavity of the ventricle is small and broken up by a spongy mass of cells. The ventricular walls are muscular, and contract from above downwards, forcing the blood into the ventral vessel. (We have sometimes seen an apparent reversal of the heart’s action.) The spongy cardiac body arises by ingrowths from the wall of the ventricle, chiefly in the middle and ventral regions. It gradually encroaches on the blood space, so as to reduce it considerably (Pl. X., Fig. 36, Card. B.) in an old specimen. The cardiac body in a young specimen (Fig. 38) is much smaller, and extends obliquely across the heart, its general direction being down- wards and backwards. The cells of the cardiac body in an old specimen which we have examined are loosely arranged, so as to cause the forma- tion of a large number of intercellular spaces, some of which are of considerable size, and which are in life filled with blood (Figs. 36—38, THE HABITS AND STRUCTURE OF ARENICOLA MARINA. 103 B.S.). Between the cells there are numerous fibres, which are probably muscular. The cells are apparently of two kinds, which, however, merge into each other: (1) cells whose protoplasm has a very yvacuo- lated appearance, and which contain few or no granules (Vac. C.); (2) cells which contain a large number of yellowish granules in the proto- plasm (G.C.). These latter cells are possibly granular, and correspond to those found in the cardiac body of other Polychets. The function of the cardiac body may be, as Schaeppi (1894) suggests, to prevent regurgitation of the blood from the ventral vessel into the heart when the diastole commences. The ‘‘cardiac body” of Polycheets, as hitherto described, is an unimpaired structure lying iu the dorsal vessel. That of Arenicola, however, is paired and in no way connected with the dorsal vessel. Hence a strict homology is scarcely probable. Blood,—As Professor Lankester was the first to point out, the blood of Arenicola is strongly impregnated with hemoglobin, but there has been no thorough investigation of the constituents of the plasma. Krukenberg (1882), it is true, made some experiments which led him to believe that there were no coagulable albumens in the blood of his specimens; but, as they were in a starving condition, a fresh examina- tion is very desirable. A large quantity of albumen is certainly present, which, when the specimens are fixed, becomes very hard and brittle. We have seen small cells (4 2 in diameter) in the blood-vessels of the nephridia, but it is doubtful if these are the blood-corpuscles which we have not been able to demonstrate.! General Remarks on the Circulatory System.—No other system of organs shows the true segmentation of the body of Arenzcola so well as this. The lines of demarcation between the somites from one end of the body to the other are marked by the segmental vessels passing from the ventral to the dorsal vessel and breaking up on their way in the body-wall, nephridia, or gills. Throughout the gastric region, however, this arrangement is somewhat disguised, owing to the less of the connection with the dorsal vessel, an alteration caused probably by the necessity for leaving this part of the alimentary canal freely moveable. 1 Since writing this we have discovered that these small cells are the blood-corpuscles. 104 F, W. GAMBLE, M.SC., AND J. H. ASHWORTH, B.SC. Wirén evidently believes that there is no capillary system except in the gills and the alimentary canal. He suggests that the assimila- tion of food and oxygen by the tissues is effected chiefly through the mediation of the celom, which he points out is parcelled off in the intermuscular spaces, by a channelling out of the subepidermic connec- tive tissue, into ‘‘periheemal canals.” Though this suggestion is a valuable and correct one, we have found a very perfect system of capil- laries in the skin in all parts of the body, and in the nephridia and septa the same is the case. The extension of the ccelom into the inter- muscular and subdermal spaces has, however, all the appearance of acting as the equivalent of lymph-spaces of higher forms. The trans- formation of the constituents of the blood into ccelomic fluid takes place in all probability with especial rapidity in the neighbourhood of the dark chlorogogenous processes of the ventral vessel (cf. Cuénot, 1891). 7. Tue Grits (Pl. VI, Figs. 2—4). The general characters of these organs have been mentioned in the introductory part of this paper, and little remains to be added. There are thirteen pairs of gills from the seventh to the nineteenth cheetigerous somites inclusive. ‘The shape varies from the short den- dritic type of the littoral form to the delicate, richly-branched gill of the Laminarian variety. The gills are hollow, being out-growths of the body-wall enclosing an extension of the ccelom, and what little evidence we have of their development (see Benham, 1893) points to their being independent structures, and not modified dorsal cirri. The walls of the gills, though thin, are muscular, and there are also muscular bands stretching across the cavity of the gill (Fig. 23) ; and Milne Edwards has pointed out that the contraction of the gills, which often proceeds like a wave from before backwards down the sides of the body, must exert a powerful influence in propelling the blood partly into the efferent vessels, and partly to the parietal capillaries. The ventral vessel supplies all the gills with their afferent branches. Tke first seven pairs return the blood to the sub-intestinal vessels, and so to the heart ; while the efferent branches of the remainder open into the dorsal vessel. THE HABITS AND STRUCTURE OF ARENICOLA MARINA. 105 8. NERVOUS SYSTEM AND SENSE-ORGANS, This system is composed of the brain, the oesophageal connectives, the ventral nerve-cord, and the nerves arising from these. We have not been able to demonstrate a visceral nervous system. The brain (Pl. X., Figs. 25, 26) is placed in the prostomium, of which it forms the chief part, being only separated from the epidermis by blood-vessels lying in extensions of the ceelom. It is a small elongated structure, measuring *75 mm. in length in ordinary shore lugs, and 1 mm. in the large “ Laminarian” variety. At its anterior end the brain is divided into two stout cornua (4. Cr.), separated by a cleft containing blood-vessels. About the middle of the brain the cornua unite, but only for a very short distance, a second connective-tissue partition dividing the smaller posterior cornua (P. Cr.), which gradually taper off and end at the hinder edge of the nuchal organ (RIX. Fig. 25). Sections of the prostomium of the littoral variety of bu Or Cs Baie Loic iaNe Quart Spurn Moor Se VAM NST 4 BrAff and ELF ag F Huth, Lith? Edin? Nea oe ~ a rrr srr ene co ert et a SE A CN E.W.G. & J.H.A. del. (9), Ca 18) Ily Jia 2X 4s NSGLE fed / fe LOOP, s UN. Au A oa frign tn a a Sn ¢ aoe vn revives I mo ea Ee A et 5 a fj From the “ ANNALS AND Macazine oF Naturau History, Ser. 7, Vol. ii., December, 1898. THE ENTOMOSTRACA OF LAKE BASSENTHWAITE, By Evira M. Pratt, BSc. With an Introductory Note by Sypney J. Hickson, M.A., F.R.S., Beyer Professor of Zoology in the Owens College, Manchester. Introduction. The splendid researches on the character of the fresh-water fauna which have of recent years been made by Zacharias at Plon, by Birge at Mendota, and by many others abroad, serve to remind us how ignorant we are of the fauna of our own English lakes. Investigations of the inland waters of Scotland have been conducted for some years by Scott’; but Beck’s? paper is the only one that gives a systematic account of the Entomostraca of the English lakes. As Beck’s investigations were chiefly made in the autumn months it occurred to me that it might be of interest to inquire into the character of the fauna earlier in the year, with the object of noting the principal differences that presented themselves in the early spring and in the autumn. Accordingly in April, 1897, when the weather was still very cold, and blasts of icy wind blew down in gusts from the snow-capped Skiddaw, I took a few samples of the Plankton as a preliminary step to further investigations. The material I then obtained proved to be of considerable interest, containing among other things the interesting Nauplius larva of Leptodora. In April of this year, the weather being decidedly warmer than in the corresponding time of 1897, I obtained the assistance of Mr. J. T. Wadsworth, and made with him a considerable number of gatherings in various parts of the Lake, so that it may be said that we obtained a fair sample of what the Plankton is at that time of year. 1 Scott, T., Scottish Fishery Reports. Scient. Invest, 1890 onward. Inver- tebrate Fauna of Inland Waters of Scotland. 2 Beck, C., J. R. Micr. Soc. (2) iii. p. 780. 124 EDITH M. PRATT, B.SC. Again, in June, with the assistance of Mr. J. H. Ashworth, B.Sc., another long series of tow-nettings were taken which show the remark- able change that takes place in the character of the Plankton during the first two months of the summer. I have to acknowledge here my thanks to Mr. Ashworth and Mr. Wadsworth for their skilled assistance in this investigation. As my time was fully occupied during the summer months I entrusted the duty of identifying the species to my former pupil, Miss Edith Pratt, B.Sc., of the Owens College; and the results of her investigations are recorded below, It cannot be supposed that the list of Entomostraca which is now given as occurring in Lake Bassenthwaite is by any means complete. A complete list will be drawn up only when a series of gatherings are taken every month for two or three years; but it may be hoped that the publication of this paper will act as a stimulus for further investi- gation. It is well known to fishermen that the lakes in Cumberland vary very considerably in their “trout” reputation. Bassenthwaite is not regarded as a very good lake for trout, but, on the other hand, it con- tains an abundance of perch and pike. It would be extremely interesting if in time a systematic study of the relations between the fish-fauna and the Entomostracan fauna could be undertaken. It would not be a very costly investigation, but it would require the whole time of a competent naturalist provided with a modest laboratory on the lake side for a period of two or three years. The results to be obtained might be of considerable value to the fishery.—S. J. H. Bassenthwaite Lake is particularly well suited for faunistic investi- gations, for while being one of the lowest of the English lakes, it has the largest drainage-area; it also receives the overflow from Derwentwater and Thirlmere; therefore in Bassenthwaite we should expect to find a typical lake-fauna, and, in addition, a concentration of the forms living within the drainage-area of the lake. Bassenthwaite! is the same size as Derwentwater—a little over ‘ For a complete description of Lake Bassenthwaite see ‘ Bathymetrical of the English Lakes,’ by H. R. Mill, D.Sc. THE ENTOMOSTRACA OF LAKE BASSENTHWAITE. 125 2 square miles in area. It is 3°83 miles in length, its average breadth is (054 mile or 950 yards. The widest part of the lake is exactly ? mile. The surface of the Jake is 223-4 feet above the sea-level ; the average depth is 18 feet: the greatest depth is 70 feet. Direct drainage-area 914 square miles; total catchment-area 154 square miles. The upper end of the lake is shallow, and depths over 25 feet are confined to a trough nearly 2 miles long in the middle of the lake. The section across the lake suggests a double-troughed depression separated by a broad central rise. Mill says:—‘‘ The steep slopes of the lake above and below water were always composed of smooth rounded stones, much smaller than the great blocks of Derwentwater ; the stones were only observed to be covered with mud on the shallow flats at the north-west and southern ends, and except for some rushes and water-lilies in the south-eastern corner, there were remarkably few water-plants, and no signs of a peaty floor. Well out in the lake the sediment was always found to be soft mud.” The soundings were taken on June 24th and 26th, 1893. On 4th April, 1897, a few tow-nettings were roughly made in the lake, with the view of ascertaining the nature of the fauna. The follow- ing forms were taken :—Coprpopa: Cyclops strenuus, and C. signatus were fairly common; Cyclops afinis was rather rare. DAPHNIDE: Bosmina longirostris and the larve of Leptodora hyalina were fairly common. On 21st and 22nd April, and 15th, 16th, and 17th June, 1898, the investigations were more thorough, and the middle and northern portions of the lake were carefully worked at. In April ten tow-nettings were taken, six at the surface and four at a depth of from 5 to 6 feet. The preservatives used were (1) a solution of corrosive sublimate, and (2) a mixture of formol, spirit, and osmic acid ; the latter obtained better results than the former. On 21st and 22nd April, 1898, it was noticed that the Copepods were most abundant some little distance below the surface, while the Daphnids were found in greatest numbers at the surface. The follow- ing forms were taken :—CopEpopa: Cyclops Kaufmannt' was very abundant ; Cyclops signatus and Diaptomus gracilis were abundant ; Cyclops imsigns, C. Hwarti, and CU. strenuus, were less abundant ; 1This form is believed to be the young male of C. strenuus by Mr. Scour- field, Nov. 20th, 1899. 126 EDITH M. PRATT, B.SC. Cyclops Thomast was rare. CLADOCERA—DapPHNiIDE: Bosmina longirostris and Sida crystallina were abundant; Chydorus sphoericus and the larve only of Leptodora hyalina were less abundant ; Bythotrephes longimanus, Polyphemus pediculus, and Daphnia pulex were rare. On 15th, 16th, and 17th June, 1898, sixteen tow-nettings were taken at different hours of the day at depths from 0 to about 10 feet from the surface. This collection was characterized by the presence of the rotifer “ Asplanchna priodonta” in immense numbers. As it occurred in the same proportion in all the tow-nettings, it must have been universally distributed. In April the Copepods outnumbered the Daphnids, but in June the Copepods had diminished remarkably in numbers and were replaced by those Daphnids (Bythotrephes, Polyphemus, Leptodora, and Daphnella) which were rare in April. The following Copepopa were taken :—Cyclops signatus was fairly abundant ; CU. phaleratus, C. strenwus, C. serrulatus were rather rare ; C. insignis was rare. Darunip&: Daphnella brachyura, Leptodora hyalina, Polyphemus pediculus were very abundant, with eggs, embryos, and young in various stages of development ; Aythotrephes longimanus with eggs and embryos was abundant ; Sida crystallina and Chydorus sphaericus were rare. A few water-mites were taken which have not yet been identified. The following species were abundant in April 1898, but were rare or not taken in June:—Cyclops Kaufmanni, C, insignis, C. Ewart, Diaptomus gracilis, Bosmina longirostris, Sida crystallina, Chydorus sphoericus. Cyclops Thomast and Daphnia pulex were fairly common in April and were not taken in June. The following species were common in June which were rare or not taken in April :-—Daphnella brachyura (absent in April), Leptodora hya- lina (only larvee were taken in April), Polyphemus pediculus, Cyclops phaleratus, and C. serrulatus (fairly abundant, but not taken in April), Bythotrephes longimanus. Cyclops signatus and C. strenuus were fairly abundant in April and in June. THE ENTOMOSTRACA OF LAKE BASSENTHWAITE. 127 Brief Statement of recorded Distribution in Britain of the Species taken in Lake Lassenthwaite. ENTOMOSTRACA. CLADOCERA. Bosmina longirostris, Baird. Bosmina longirostris, Baird, British Entomostraca, p. 105, tab. xv. Fig. iii. This species appears to be fairly ccmmon and widely distributed in Britain. In Bassenthwaite it was very common in all the tow-nettings in April, but rare in June. Seda erystallina, Straus. Sida erystallina, Baird, Brit. Entom. p. 107. Baird remarks that this species is of rare occurrence, but Scott records it as being common in Raith Lake in Scotland. Tt was the most common species taken in April 1898. In June very few specimens were taken, but these were of a large size, with well-developed ova and embryos. Chydorus sphericus, Baird. Chydorus sphericus, Baird, Brit. Entom. p. 126, tab. xvi. fig, 8. Common in ponds and ditches in Britain almost all the year ronnd. Leptodora hyalina, Lilljeborg, Leptodora hyalina, Bronn, Klass. und Ordn. des Thier., Arthrop. Crust., Erste Halfte, Tafeln, Taf. xxi. fig. 1. This species was first taken in England by Bolton! from the Olton reservoir, near Birmingham. Later it was taken by Beck in Lake Grasmere. Scott has taken it in the Scottish lakes (Loch Leven, Loch Morar), and remarks that while it is considered to be a rare species, it is not very rare in Loch Leven. In April only the larvee and very young forms were taken, chiefly at the surface in Bassenthwaite. In June this species was exceedingly abundant, with eggs, embryos, and young, but no young larve were taken. It was, moreover, confined to the middle of the lake, where the water is deep (see Map, p. 131). Very few mature specimens were 1Ann. & Mag. Nat. Hist. (5) vol. ix. p. 53. E. Ray Lankester, ‘‘On new British Cladocera discovered by Mr. Conrad Beck in Grasmere Lake, Westmoreland.” 128 EDITH M. PRATT, B.SC. taken at the surface, or at the depth of 2 to 4 feet; but from 6 to I0 feet (10 feet =greatest depth at which tow-nettings were taken) it was taken in great quantities. Bythotrephes longimanus, Leydig. Bythotrephes longimanus, Leydig, Naturgeschichte der Daphniden, p. 244, figs. 73—75, Taf. x. British Habitat.—Scotland (Scott): Loch Ness, Loch Morar (frequent at surface), Loch Leven (frequent). Perthshire Lochs (Sept.): Loch Oich (common), Loch Tay (frequent at surface). This species has not been recorded before from the English lakes. In Bassenthwaite it was very rare in April but very abundant in June, with eggs, embryos, larvee, and young. Beck describes the species ‘ cederstromi” from Grasmere and other English lakes, and remarks that it appears to be more abundant in the autumn than in the spring. Daphnia pulex, Latreille. Daphnia pulex, Baird, Brit. Entom. p. 89, tab. xvi., fig. 5. This species, while being widely distributed in ponds and ditches in Britain, occurs but rarely in large sheets of water; it was very rare in Bassenthwaite in April, and no specimens were taken in June. Daphnia longispina, Daphnia longispina, Baird, Brit. Entom. p. 91, tab. vii., figs. 3, 4. This species was taken by Beck in English lakes and by Scott in some of the Scottish lochs. It was rare in April, and no specimens were taken in June. Polyphemus pediculus, Straus. Polyphemus pediculus, Baird, Brit. Entom., p. 111, tab. xvii., fig. 1; Leydig, Naturg. der Daphniden, p. 232, Taf. viii., fig. 63, Taf. ix., fig, 71. Baird took specimens of this species in a ditch near Richmond-on- Thames ; he remarks that this species seems to be very limited in its range of habitat, as he only found it in one spot not more than 20 yards in extent. Scott, however, has taken it in many of the Scottish lakes, and describes it as being a fairly common species, especially in large sheets of water ; in Loch Morar, in Perthshire, it was taken by him in abundance near the surface all over the portion of the loch examined. Beck took this species in the English lakes. It was very rare in THE ENTOMOSTRACA OF LAKE BASSENTHWAITE. 129 Bassenthwaite in April, but very abundant and universally distributed at the surface and some little distance below the surface in June, with eggs, embryos, and larvee in all stages of development. CopEPODA. Cyclops signatus, Koch, Cyclops signatus, Brady, Brit. Copep. vol. i. p. 100, pl. xvii. figs, 4—12 ; id, Revision Brit. Freshwater Cyclopidee and Calanidee, p. 6, pl. ii. fig. 5. Examples with serrated and with simple ridge on antenna were taken. They are supposed to represent different stages in development (Herrick). This species is widely distributed and common in Britain. Cyclops strenuus, Fischer. Cyclops strenuus, Brady, Brit. Copep. vol. i. p. 104; id. Rev. Brit. Freshw. Cyc. and Cal, p. 8, pl. ii. Widely and generally distributed in Britain, but not very common. Cyclops Themasi, Forbes. Cyclops Thomast, Brady, Freshw. Cyc. and Cal. p. 15, pl. vi. figs. 1—4. This is not a common species. Scott has taken it in many of the Scottish lakes, but it seems to occur nowhere in great abundance. It was rare in Bassenthwaite in April, this being the first time that it has been recorded from the English lakes. No specimens were taken in June. Cyclops insignis, Claus. Cyclops insignis, Brady, Brit. Copep. vol. i. p. 108, pl. xxi. ; id. Rev. Brit. Freshw. Cyc. and Cal. p. 18, pl. vii. Brady describes it as being one of the less common species of Cyclops. I have not found it recorded from the Scottish lakes. Specimens of this species were fairly common in the middle of the lake in April, but rare in June. (I am inclined to believe now that this species is not distinct from C. Thomast. Nov. 20, 1899.) Cyclops Hwarti, Brady. Cyclops Ewarti, Brady, Rey. Brit. Freshw. Cyc. and Cal. p. 22. _ Scott has taken this species in a small bay near Queensferry, Firth of Forth. Brady remarks that this is the only undoubted member of this genus which has been found living in the sea. As it was first I 130 EDITH M. PRATT, BSC. found in the Forth, he thought that its habitat must be in ponds and ditches which flow into the Forth. Since then it has been taken by Scott in Loch Morar (Inverness-shire) and in Loch Moray. Only a few specimens of this species were taken in April and none were taken in June. Cyclops affinis, Sars. Cyclops affiinis, Brady, Brit. Copep. vol. i. p. 112, pl. xv. figs. Tess pl. xxiv. B, figs. 10—15; id. Rev. Brit. Freshw. Cye. and Cal. p, 21, pl. viiis Brady says that this species seems to be of rare occurrence. Scott records it from some of the Scottish lakes. It was taken in Bassenthwaite in April, 1897, and has not since been taken. Cyclops Kaufmanni, Uljanin. (See note, p. 125.) Cyclops Kaufmanni, Brady, Brit. Copep. vol. i. p. 113, pl. xxiv. figs. 6—12; id. Rev. Brit. Freshw. Cyc. and Cal. p. 24, pl. ii. fig. iii. This species, although very limited from all accounts in its distribution, was by far the most abundant species taken in April, 1898; in June it was rare. Cyclops phaleratus, Koch. Cyclops phaleratus, Brady, British Copepoda, vol. i. p. 116. This specics is not very common, though fairly widely distributed. It has been taken ina few of the Scottish lakes by Scott, in Ireland and North of England by Brady, but has not been recorded from the English lakes. It was taken in Bassenthwaite in April, 1898, when it was rather rare. No specimens were taken in June. Cyclops serrulatus, Fischer. 4 Cyclops serrulatus, Brady, British Copepoda, vol. i. p. 109, pl. xxii.; id. Rev. Freshw. Cyc. and Cal. p. 18, pl. vii. fig. 1. This is the most common species of the genus. It occurs almost universally over Britain, and has been recorded by almost all continental writers. Specimens were only taken in Bassenthwaite in June. THE ENTOMOSTRACA OF LAKE BASSENTHWAITE. 131 a LUM“ S 7K). 7, Ne 7 4; \ =, Yj Yj be C Scale 13 Inches bo the mile BASSENTHWAITE LAKE. (Reproduced from ‘‘Bathymetrical Survey of English Lakes,” H. R. Mill, D.Sc.) 132 EDITH M. PRATT, B.SC. Diaptomus gracilis, Sars. Diaptomus gracilis, Brady, Rev. Brit. Freshw. Cyc. and Cal. p. 29, pl. xi. figs. 7-9, pl. xii. figs. 1-8. This species is universally distributed and abundant throughout Britain in large sheets of water where there is little vegetation. (On making a revision of the material I feel doubtful if Diaptomus castor occurred, and I have consequently struck it out of the list. Noy. 20, 1899.) ROTIFERA. Asplanchna priodonta, Gosse. Asplanchna priodonta, Gosse, Ann. & Mag. Nat. Hist. ser. 2, vol. vi. 1850, p- 18, pls. i. & ii. ; Hudson and Gosse, Rotifera, p. 123, pl. xii. fig. 2. Gosse found this species not uncommon in the Serpentine, Kensington Gardens, and in ponds and ditches near Birmingham. It was very sparingly but generally distributed in April, but in June occurred in vast quantities in all the tow-nettings taken at the surface and moderate depths. In the Map accompanying this paper the areas of depth are signified by dotted lines. The weather was calm and fine when the tow-nettings were made in June, but there had been heavy rains a few days before. The tow-nettings were confined to the middle and northern portions of the lake. In the 10-fathom area six tow-nettings were made, and were characterised by the presence of Polyphemus in greater numbers than elsewhere, and the almost complete absence of Leptodora and Bytho- trephes (a few immature forms were taken). In the 25-fathom area four tow-nettings were taken from 6 to 8 feet, in which Leptodora and Bythotrephes were fairly common; In the 50-fathom area five tow-nettings were taken from 6 to 10 feet, and in these gatherings Leptodora and Bythotrephes were very abundant. (It is worthy of note that Leptodora and Bythotrephes very often occur together in great abundance.) The remaining forms were distributed more or less universally over the portion of the lake examined, From the “PROCEEDINGS OF THE ZooniocicaL Society or Lonpon,” fopril 5, 1598. ON THE SPECIES OF THE GENUS MILLEPORA: A PRE- LIMINARY COMMUNICATION. By Sypyry J. Hickson, M.A., D.Sc., F.R.S., F.Z.S. The phylum Ccelentera presents us with many families and orders of animals in which our knowledge of the characters which van be satisfactorily used for the purpose of systematic classification is singu- larly deficient. In the Madreporaria, the Gorgonacea, and the Mille- poridee the form of growth of the colony, the colour, and the structure of the hard skeletal parts are the only characters which have been used for the diagnosis of genera and species. In many cases it is probable that the diagnosis afforded by these characters should be considered to be satisfactory, but as the number of specimens in our museums increases it becomes more evident that in others no satisfactory classi- fication can be framed until we have a thorough knowledge of the anatomy of the polyps which construct these skeletons and of the canal- systems which bind them together into colonies. In some genera of Madreporaria, for example, of which the skeletal characters only are known, a long series of intermediate stages can be found between the type specimens of the different species, and every new collection of specimens that is examined increases the difficulty of deciding whether a particular intermediate form belongs properly to one species or another. Moreover, in this same group the outlying species of one genus resemble the outlying species of another so closely that it is often a matter of great difficulty to determine, on our present system, to what genus a particular specimen belongs. Nearly every important systematic work on these Ccelenterates. contains some remarks about the difficulty of determining species, and examples are quoted of series of intermediate forms connecting closely allied species. If it were possible to frame some general rule for the 1384 SYDNEY J. HICKSON, M.A., D.SC., F.R.S., F.Z.S. correct definition of a species, which would be agreed to by all system- atic zoologists, our task might be less difficult than it is; but, as matters stand, the conception of what is a species of one worker is so different from that of another that there is constantly going on a see- saw of construction and destruction of new species in our systematic literature. I do not propose to attempt to define the conception ‘‘ species” in Ceelenterates, but I think that all zoologists would agree that, if a form which is known as species A were proved to give rise to an embryo which grew into a form which had hitherto been known as species B, the two forms would have to be merged into one species with one specific name. Similarly, I imagine that all zoologists would agree that if a coral known as species X changed in the course of its life- history into a form known as species Y, then the forms X and Y should be regarded as one species and retain only one name. In the absence of any experimental proof that the embryo of one so-called species of coral gives rise, under any circumstances, to another so-called species, or that one so-called species changes in the course of its life history into another, it is necessary to examine with very great care the anatomy of the soft parts as well as the skeletal structures, in order to determine whether it is possible or even probable that such changes actually occur in nature. If we find, then, that the polyps or repro- ductive organs of a coral with one form of growth are essentially different from those of another form, we may consider there is good reason for believing that such changes do not occur and the species founded on the skeletons are good; but if, on the other hand, the polyps, reproductive organs, and other characters of the two forms are essentially the same, then there is reason for believing that the species founded on skeletal characters may not be good. Before proceeding further with this discussion of the characters which may be used for distinguishing species in Celenterates, it may be well to describe briefly the general results of my observations on the genus Millepora. This genus stands quite by itself among living corals. No one genus of the other Hydrocorallines can be confused with it, both the living tissues and the hard skeletal parts being perfectly distinct. It is widely distributed through the tropical seas, occuring in the Red Sea, Indian Ocean, Malay Archipelago, Tropical Australian waters, Pacific Ocean, and in the seas of the West Indies. It is essen- ‘THE SPECIES OF THE GENUS MILLEPORA. 135 tially a shallow-water genus, living in abundance in most of the coral- reefs, and not occurring in greater depths than 15 fathoms. The form varies immensely. It may be broadly lamellate or densely branched, or anastomosing, or it may form thin incrusting plates on dead corals. In all large collections of Millepores series of intermediate forms may be found between all the most prominent types. The difficulty of defining and describing the species of this genus has been commented upon by several authors. Dana, for example, says “There is much difficulty in characterizing the Millepores on account of the variations of form a species undergoes and the absence of any good distinctions in the cells. The branched species are often lamellate at the base, owing to the coalescence of the branches, and the lamellate species as wellas the branched sometimes occur as simple incrustations.” My own investigations confirm and amplify Dana’s statement on this point. Notwithstanding these difficulties a large number of species of the genus have been described. In the writings of the older naturalists many species were described which have since been relegated to other classes of the animal kingdom, and in palzeontological literature we find many species of fossil corals referred to the genus on erroneous or very unsatisfactory grounds. Apart from all these, which may be left out of consideration in this paper, no less than 39 species of the genus Jfillepora have been described. The characters which have been used for determining thes? species are :—(l) The form of the corallum. (2) The size of the pores. (3) The degree of isolation of the cycles. (4) The presence or absence of ampulle., (5) The texture of the surface of the corallum. (1) Lhe Form of the Corallum.—tThis feature is even more unsatis- factory than I anticipated at the beginning of my investigation. In the first place, attention has been called by Dana, Duchassaing and Michelotti, and others to the fact that M/illepora grows in an incrusting manner on many objects, and thereby assumes the form of the object on which it grows. It is quite easy to distinguish such forms as incrusting forms when they have only partially covered such objects as the horny axis of a Gorgonia, a glass bottle, or an anchor ; but in many cases the object is so completely overgrown by Millepore and other marine zoophytes that its presence is not discovered until a fracture is 136 SYDNEY J. HICKSON, M.A., D.SC., F.R.S., F.Z.S. made. To give only one example to illustrate this point :—A specimen in the Manchester Museum was named JMillepora intricata, and, on comparing it with the description of the species, I thought at first that the name was correct. On breaking it into two pieces, however, I found that the form it had assumed was due to the fact that it had grown over a small piece of wood. In a still greater number of cases, however, the Millepores grow upon the dead coralla of other Millepores or Madrepores or other white corals, and then the difficulty of determining whether the form of the specimen is due primarily to the living coral or to the one on which it has grown becomes extreme. There is a large specimen in the collection brought home from New Britain by Dr. Willey, of very irregular form, one part of which has a form like that attributed to the species WV. plicata, another part to the species J/. verrucosa, but a broken knob shows quite clearly that a part of this great mass has grown over a dead coral. It would consequently be quite impossible to determine with any degree of satisfaction to which of the already-described species it belongs, unless every knob and projection were broken off to see whether the dead coral extends as a basis through the whole piece. In the second place, the immense amount of variation in form which occurs in large specimens of Mzllepora, and, indeed, in many small specimens too, leads to very great difficulties in the determination of species which have been described on form as the principal character. In Dr. Willey’s collection there is a series of varieties of growth leading from a massive lamellate form to a complicated branching and anastomosing form. A careful study of these skeletons, then, points very definitely to the conclusion that the general form of the corallum of Millepora should be used, not as a primary, but as a very subsidiary character in the description of species. The form assumed by the corallum must depend upon many circum- stances connected with the exact spot on which it grows. Ifa Millepora embryo happens to become fixed on a large piece of dead éoral, it will form a large incrusting base, and such a base nearly always gives rise to a lamellate form of growth ; if, on the other hand, the embryo settles on a small stone or other object, lamellate growth is impossible, and the corallum will be ramified. The growth of the corallum must also be influenced by the propinquity THE SPECIES OF THE GENUS MILLEPORA. 137 of other corals. Its form must be adapted to the space left between its neighbours on the crowded reef. Again, its form must be modified by the depth of the water in which the embryo happens to develop, As Duchassaing and Michelotti pointed out long ago, MMzllepora often grows in very shallow water and is consequently unable to develop in height. Specimens that happen to fix themselves on foreign bodies on the edge of the reef at a depth of 5 or 6 fathoms can and do grow to a very great length without impediment. It is also extremely probable that the available food supply, the par- ticular set of the tides and currents, and the chemical composition of the sea-water, particularly as regards the amount of calcium carbonate it holds in solution, vary very considerably in different reefs and in different parts of the same reef. Such variations must affect the rate of growth of Millepores, and I think it is reasonable to believe the mode of growth also. (2) The Size of the Pores. Quelch have used the size of the pores as a specific character, but, with Dana, Milne-Edwards and Haime, and one exception, to be referred to presently, they give no measurements, being contented to use the expressions “very small,”. “large,” “minute,” &c. Unless the zoologist has an immense number of speci- mens from different localities to compare one with another, it is diffi- cult for him to understand what is meant by such expressions ; but even the naturalists of the great national collections would be mystified by the case of I. alcicornis, whose gastropores are, according to Quelch, very large, and according to Milne-Edwards and Haime, “ trés petits.” I have measured a very large number of gastropores, taking for each specimen an average of 6 or 12. The greatest average diameter of the gastropores I have found is 0°37 mm., the smallest is 0:13 mm., so that the difference between those pores which might legitimately be called “very large,” and those that are “very small” is 0°24 mm. But these “large ” pores are very rarely seen; the great majority of the gastropores are between 0°3 mm. and 0°2 mm. This general result agrees fairly well with the only measurement I have been able to find in the literature of the subject, namely, that of I. murrayt by Quelch, which is given as 0°25 mm. The question that had next to be considered was whether there is any other feature constantly associated with large pores and with small 138 SYDNEY J. HICKSON, M.A., D.SC,, F.R.S., F.Z.S. pores. The large pores are very constantly found in specimens with thick lamellz or branches, while the small pores are found on those of a more slender habit. A further investigation of the question yielded an explanation of the variation in the size of the gastropores, which proves that it cannot be of any real service for specific distinction. I found that in the gastropores of specimens of slender growth there are only 3 or 4 tabulee, while in those of more massive growth there may beas many as 9 or 10 tabule. This suggested that the size of the gastropore depends upon the age of the gastrozoid which lived in it, and, on measuring carefully a number of gastropores from the base, middle branches, and growing-points of a specimem in the Manchester Museum labelled J/. complanata, I found that the average diameter of the gastropores at the base, which we may assume in this case to be the oldest part, was 0°185 mm., on a middle branch 0:17 mm., and at the growing-edge, z.e., the youngest part, it is only 0:13 mm. This general result was confirmed by similar series of measurements on other specimens. I also found that the greatest average diameter of gastropores which I have given above was obtained from the base of a massive specimen, while the smallest was obtained from a growing-edge of a slender specimen. Moreover, it occurred to me that if the size of the gastropores is de- pendent upon their age or the rate at which the gastrozooids have erown, there ought to be, in some cases at any rate, a difference between the average size of the gastropores on one side of a branch or plate and that on the other ; those on the face most favourable as re- gards food supply in the living state should be larger than those on the other. Measurements confirmed my point, and I found a difference in two out of three specimens between the gastropores on one side and those on the other as great as 0:03 mm. (3) The Degree of Isolation of the Cycles.—Moseley noticed that in one specimen of Millepore taken at Zamboanga the cycles were much more distinct than in other specimens, and suggested that this feature might be of specific value. After very careful consideration I am con- vinced that it cannot be. In many large specimens it will be seen that the cycles are much more distinct in one part than another. Some- times the cycles are so crowded as to be indistinct at the edge, and perfectly clear on the face or at the base. The evidence points to the | Ss en THE SPECIES OF THE GENUS MILLEPORA. 139 conclusion that in slow-growing Millepores in unfavourable situations the cycles are distinct, and that in fast-growing specimens in good situations the polyps are formed in such great numbers that the cycles become confused. (4) The Presence or Absence of Ampulle.-—The ampulle of Jillepora were discovered by Quelch in a specimen obtained by the ‘ Challenger.’ He found a new species for the specimen, which he called M. murrayz, and used this feature as an important specific character. I have found that ampulle occur in plicate, ramose, and digitate specimens, and, as will be explained later, the absence of ampulle in any particular specimen merely means that at the time it was taken it was not in a state of sexual activity. It is greatly surprising how very rarely specimens are found in this particular condition, but I believe that it must occur in all varieties at one time or another in their life-history. (5) The Texture of the Surface of the Corallum.—The species J. verrucosa of Milne-Edwards, df. tuberculata of Duchassaing, and JZ. striata of Duchassaing and Michelotti have been named after the peculiarities of their surface. I have had an opportunity of examining a very fine specimen of a Millepore, resembling very closely the type of J. verrucosa, and I found that on the summit of a very large number of the verrucze there is a small hole of the shape of a keyhole, which leads into a cavity formed by a parasitic cirripede (probably Pyrgoma milleporce), On others, however, no such evidence of parasitic interference with normal growth is apparent from the surface, but nevertheless there is reason for be- lieving that the tubercle may have been due to hypertrophy of the Millepore at a spot which was irritated by some parasite, the parasite subsequently being overwhelmed or killed. Now it is not cirripedes alone which attack Millepores ; various alge, worms, crabs, and other creatures settle on the Millepores and cause profound modifications of their growth. I think there is very good reason for believing that the warts, tubercles, ridges, and the like which occur on the surface of these corals are primarily due to parasites or to some other irritant, and that itis very doubtful whether they are ever of specific value. If they are to be used, however, it will be found that they lead to many difficulties, as it is not infrequently the case that one side of a lamella is tuberculate 140 SYDNEY J, HICKSON, M.A., D.SC., F.R.S., F.Z.S. and the other is not, or that one lamella or branch is covered with wart- like processes and the others are smooth. (6) The Relative Number of Dactylopores and Gastropores.—Finding that all other characters derived from the skeleton are unsatisfactory for determining and distinguishing species, I thought it possible that a good character might be found by calculating the average number of dactylopores to each gastropore in a number of species. In many specimens the cycles are so close one to another that it is often difficult to determine to which cycle a particular dactylopore belongs. In order, therefore, not to be misled, I used only those cycles which were clearly defined from their neighbours. In the following table 1 have put together the results of my calcula- tions on this point :— eee Number of Average No. of Highest | Lowest cycles | dactylopores | number. | number. (The name of donor ae counted. | in each cycle. locality in parentheses. I. M. murrayi. 6 | 5°15 8 5 | (Haddon, Torres Str. ) IL M. alcicornis. 8 6°45 8 5 | (Brit. Mus., W. Indies. ' | TIL. M. alcicornis. 6 «56 7 5 , (Shipley, Bermudas. ) | IV. M. alcicornis. 12 6°7 Sime 6 (Lister, Tonga. ) 12 5:08 8 | V. M. plicata. 12 7:08 9 6 | (Hickson, Celebes. ) VI. Al. complanata. 7 6:28 7 5) (Man. Mus., W. Indies. | _ 100 | 5°82 a 4 VIL. MW. alcicornis. a 6°14 7 5 (Man, Mus., W. Indies.) VII. MW. alcicornis. 13 55 9 4 (Agassiz, Bahamas) It will be seen from these figures that there is not much variation in the average proportion of dactylopores to gastropores in the different forms examined. The largest number of cycles I was able to count on one colony gave an average of a trifle under 6. It is noteworthy that this is the exact mean of the highest and lowest averages obtained from smaller specimens on which only a few cycles could be counted. The extreme averages 5°08 and 7-08 (IV. & V.) do not show so great ? f | ‘ THE SPECIES OF THE GENUS MILLEPORA. 141 a range as may be seen on different parts of a single piece 9 and 4, and 8 and 3. On the basal incrusting regions of a specimen of Millepore in the Manchester Museum I have observed several widely-separated gastro- pores attended by only one, two, or three dactylopores, and a similar paucity of dactylopores I have more recently noticed in specimens from the collection made by Mr. Gardiner in Funafuti and Rotuma. I may point to the figures obtained from an examination of the specimens of M. alcicornis given to me by Mr. Lister to show the variability of this feature in the colony. The specimens were a number of broken branches, each a few inches in length, beautifully preserved in spirit. Two specimens were taken at random and twelve cycles counted on each, The average of one came out 6°7 dactylozooids to each gastrozooid, and of the other 5:08 dactylozooids to each gastrozooid. The only author who has referred to the number of dactylopores in each cycle is Moseley. He says that each group consists “of a centrally placed zastropore surrounded by a ring of five, six, or seven dactylopores,” and on counting the number of dactylopores in each cycle that are drawn in Mr. Wild’s picture in Moseley’s ‘ Philosophical Transactions’ paper I find that the average is 6. In Milne-Edwards and Haime’s figure of J, intricata there are 5 gastropores to 35 dactylopores ; of MW. verrucosa, there are 7 gastropores to 32 dactylopores (?); in -W. tuberculosa, 5 gastropores to 18 dactylo- pores ; but it is not certain that these figures can be absolutely relied upon. They are, however, on the whole, very similar to my own results. The general conclusions, then, that must be drawn from these obser- vations are :— That the number of dactylopores in each group is very variable in each individual colony of Millepora. There may be, in fact, any num- ber up to 8 or 9. That specimens of widely different forms of growth have approxi- mately the same average number of dactylopores in each group. That the average number of dactylopores, in each group for specimens of all kinds is about 6. That the average number of dactylopores to each gastropore cannot be used as a specific character. 142 SYDNEY J. HICKSON, M.A., D.SC., F.R.S., F.Z.8. Anatomy of the Soft Parts——I have examined the anatomy of the soft parts of a large number of specimens preserved in alcohol by mounting them whole and by making series of vertical sections. The following is alist of the specimens examined :— Form of growth. Donor. Locality. Digitate & palmate. Pref Haddon. Torres Strait. ‘* Alcicornis.” Mr. Shipley. Bermuda. “¢ Alcicornis.” Mr. Lister. Tonga. “ Alcicornis,” Prof. Agassiz. Bahamas. ‘¢ Alcicornis.” British Museum. W. Indies. Ramose. Mr. Gardiner. Funafuti. Plicate. » ” Foliate. - 5 Striate. 3 Rotuma. Ramose. Dr. Willey. New Britain Group. Plicate. si . if (Several small fragments). 3 a Complanate. Mr. Duerden. Jamaica. “¢ Wxaesa.” Dr. von Marenzeller. Red Sea. ‘** Dichotoma.” 45 45 And a specimen of “ Plicate” form obtained by myself in Celebes. The preparation and examination of these Millepores has extended over a period of twelve years, with the result that I have failed to find any constant difference between them that can be used for the separation of the genus into species. The structure of the gastrozooids and the dactylozooids is essentially the same in all the specimens examined, but the size varies some- what, according to the position from which the preparations are made —those at the growing-edges being smaller than those at the base, &e. The canal-system is the same in all specimens. /Zooxanthelle of exactly the same size are always present in the superficial canals. I have observed the two different kinds of nematocysts, the large and small figured by Moseley, in all my preparations. Many of the Mille- pores are known to sting badly, and have received popular names in various languages expressive of this feature, but Mr. Gardiner informs me that one form in Funafuti did not sting. “It was at its base THE SPECIES OF THE GENUS MILLEPORA. 143 rather overgrown by weed, and above, curiously enough, it did not sting, and was the only one in Funafuti that did not.” ? It is not known whether both the large and the small nematocysts possess the stinging-power, or whether it is confined to cnly one kind. The small nematocysts are confined to the tentacles of the gastrozooids and dactylozooids, and the large nematocysts, when ripe, occur in the superficial ccenosare between the pores, but are specially crowded in the neighbourhood of the gastropores. Moseley’s description of these features in Millepora is correct for all specimens I have examined. The size and the position of the small nematocysts render them difficult to measure, but the large nematocysts can be scraped off the surface of any preserved specimen in considerable numbers. The average size of these nematocysts when ripe in specimens from Celebes, Bermuda, Bahamas, Funafuti, Rotuma, the Red Sea, Jamaica, and New Britain is exactly the same—0°02 mm. x 0025 mm. The number of the nema- tocysts varies considerably, but as this must be influenced by the manner in which the specimens were killed, and by external conditions affecting them before they were killed, no differences of specific value can be framed from this feature. The general anatomy of all these forms is in other respects, as well as those mentioned, so much alike that I know of no means of dis- tinguishing one series of sections of well-preserved material from another, There are no features of the soft parts which indicate in the least the general character of the form and structure of the skeleton they secreted. By far the most interesting and in many respects the most important structures of these corals are the generative organs, and to them we should naturally turn for characters which might assist in distinguish- ing species. Unfortunately, however, our knowledge of these structures is very meagre and does not at present help us very much. In the specimen presented to me by Prof, Haddon from Torres Strait, I discovered that the male sexual cells migrate into dactylozooids which become converted intc medusz. These medusze, when ready to become free, are situated in ampullee, which are approximately 0:4 mm. in their greatest diameter: that is, in holes in the skeleton larger than the largest gastropores. In another specimen of a different mode of growth presented to me by Mr. Gardiner from Funafuti I found numbers Extract from a private letter. 144 SYDNEY J. HICKSON, M.A., D.SC., F.R.S., F.Z.S. of these medusze in ampullee of exactly the same size. The medusz of these two forms are quite indistinguishable one from another. It seems probable, then, that the Millepores from Zamboanga (Quelch), Jamaica, and several others from unknown localities in which ampullee of this character have been described bore in the living state medusee. No gaps similar to these can be seen in any of the preserved specimens which have been examined except those which contain or have contained medusee. The fact that the largest ampulle of all specimens are of approximately the same size, coupled with the fact that the medusz of such different forms as those given me by Mr. Gardiner and Prof. Haddon are exactly similar, suggests thut the medusee of all Millepores are similar. At any rate, there is no evidence at present that there is any difference between the medusze of the different forms. it is a very extraordinary fact that the ampulle are so rarely found I have had the opportwnity of examining carefully a very large collection of Millepores collected in the West Indies, and deposited in the Liverpool Museum. I failed to find a single ampulla in any one of them, but a small skeleton sent to me by Mr. Duerden from Jamaica exhibited an immense number of them. In the large collection at the British Museum only a few specimens exhibit ampulle. It seems to be certain, then, that the meduse are but rarely formed, but when they are they are formed in very great numbers. General Considerations.—It appears to me that these investigations present very strong reasons for believing that there is only one species of Millepora, That one species must, on the ground of priority, be called Millepora alcicornis. There are two courses open to us: either to assume that there are characters still undiscovered which distinguish one species from another, and on the strength of that assumption retain the old specific names ; or to wait until such assumed characters are discovered before recognizing more than one species. Of these two courses the latter appears to me to be preferable. If we consider a series of specimens, a, 6, c, d, &c., are distinct species, we assume that the embryo of a gives rise to a definite form of coral, so like its parent a that it can be easily distinguised from the forms b, c, d, &c. If, on the other hand, we consider them as modifications in the form of one species, then we may consider it possible that under different external conditions the embryo of d@ may give rise to a form THE SPECIES OF THE GENUS MILLEPORA. 145 similar to 0, or c, or d, or any intermediate or combined form of these varieties. By the former course we are practically denying the possibility of considerable plasticity ; by the latter course, while not assuming that it exists, we do not deny it. Now the evidence in favour of the view that the Millepores are extremely plastic in their growth increases with every new collection that is examined. Nearly every large specimen shows some branch or plate that is distorted, twisted, compressed, or bent into a different shape from the rest of the coral; its surface shows galls, cups, tubes, warts for the accommodation of crabs, worms, cirripedes, algze, and other so-called parasites. Nor is there any greater constancy of form in the smallest independent specimens that can be found. They may be simply incrusting, or may form a simple crest, or a short pointed process from the base, according to the character of the object on which they grow. It is therefore, in my opinion, not only extremely inconvenient, but positively erroneous, to consider those forms of erowth that may be grouped round one “type” as a species distinct from those that can be grouped round another ‘‘ type.” By this plan we either deny the extreme degree of variability which there is reason to believe does occur in nature, or else we employ specific names in a sense altogether different from that in which they are used in the other groups of animals and plants. It would be premature to propose to extend my remarks to other genera of corals, but I have already pointed out that there are some reasons for believing that there is not more than one species in the Alcyonarian genus Zwubipora and the Hydrocoralline Dvistechopora. Our knowledge of the soft parts of MJadrepora and cther genera of Zoantharian corals is so small that it is possible that im the future a very considerable reduction in the species of this genus will also be necessary. Madrepora itself is a genus with a very wide geographical distribution in shallow tropical waters, like Millepora. Its coralla are also subject to extraordinary variability in their form of growth, and the species have been founded on skeletal characters only. All the species, or many of them, may be good, but the classification of the genus must be considered to be unsatisfactory until our knowledge of the anatomy of the polyps of the different varieties has been consider- ably extended. J Reprinted from the “ Buuustin, Liverpoot Museum,” I. CRAB-GALL ON MILLEPORA. By Sypney J. Hickson, M.A., F.R.S., Beyer Professor of Zoology, Owens College, Manchester. With Plate XI. The occurrence of gall-like growths on certain genera of branched Zoantharian corals, belonging to the genera Srderopora, Seriatopora, and Pocillopora, has been known to zoologists for many years. The best description of them may be found in Semper’s interesting book, “The Natural Conditions of Existence as they affect Animal Life.’’! The Crab that causes the growth of the gall is called Hapalocarcinus marsupialis. These galls are by no means rare. In nearly every Museum which possesses several specimens of these genera, examples of such galls are sure to be found ; and in Serzatopora itself as many as nine or ten galls in different stages of formation are frequently seen in specimens less than a foot in diameter. The occurrence of Crab-galls on Millepora, however, has not, I believe, been hitherto recorded. It must, however, be of extremely rare occurrence, as it has never before come to my notice. During the past ten years I have examined the whole stock of Millepores in several Museums, and have received for examination from naturalists in various parts of the world the specimens of this genus that they have collected. I have noted the various parasites and commensals that are found on them, and the many variations and distortions of growth that they exhibit, and, therefore, have good reason for saying that the occurrence is a rare one. + Kegan Paul, International Scientific Series, 1881. 148 SYDNEY J. HICKSON, M.A., F.R.S. On the specimen in the Derby Museum, Liverpool (Fig., p. 80), there are three galls, two complete and one in process of formation. Of the three galls the lowermost (a) in the figure is the oldest. It is about 30 mm. long by 25 mm. broad, and the aperture is oval, 8 mm. by 6 mm. in size. The cavity is large, its diameter being considerably greater than the greatest diameter of the aperture. The dried crab remains in this gall, but as it would be impossible to extract it without injury, | am unable to say more about it than that it is very much smaller than the cavity in which it lives. The second gall (6) is smaller and much more spherical in shape, its diameters being approximately 20 mm. The aperture is relatively larger than that of the other, being 6 mm. by 7 mm. in size. It contains no crab. The imperfect gall at the top (c) is widely open, and is formed of a network of Millepore branches imperfectly woven together. The extent of the malformation produced by these crabs need not be described as it is adequately represented in the illustration, but, I may add, the surface of the coral forming the outer wall of the gall shows no signs of unhealthiness or weakness. The cycles of pores are as numerous and as regular as in other parts of the corallum with normal growth, and the pores themselves are just as large and as well defined there as elsewhere. These galls cannot, therefore, be regarded as a disease, although they effect a considerable alteration in the normal growth of the corallum. Norr.—The description of the gall-forming crab, given by Dr. Semper, and referred to above, is as follows :—“‘So long ago as the year 1837 Stimpson described a small crab, under the name of Hapa- locarcinus marsupialis, which had been discovered in the Pacific Ocean by Dana, in the course of his great voyage under the command of Wilkes. Irrespective of other peculiarities this was distinguished from all other crabs by a remarkable pouch, in which the female carries the young, formed by a prolongation of the lateral plates of the abdomen.” The singular mode of life of these crabs, which was first observed by Semper, who studied them alive in the Philippine Islands, is thus described by him. For gall-forming crabs “an association,” he says, “with living corals is indispensible, and the influence of the Corals on the Crabs is as direct and important as that of the Crabs on the Corals. PLATE XI. < (6) A.M. H. del. 3 CRAB-GALL ON MILLEPORA. 150 SYDNNY J. HICKSON, M.A., F.R.S. Hapalocarcinus has hitherto been detected only in pieces of branching corals of different genera . . . . On all these corals the crabs produce a peculiar excrescence on the twigs (so to speak) of a branch ; these growths . . . . grow opposite each other in such a way that the crab settled between them is perfectly surrounded, and thus enclosed, in the gall which gradually forms . . . . A diseased’ excrescence is first produced by the young crab establishing itself between the two branches, and the twig thus originating takes various forms according to the character of the species of coral In the first instance the two leaf-like twigs are, of course, far apart, so that the crab could easily get in and out ; but as it does not do this, it is soon so surrounded by the growing together of the twigs that it must remain a prisoner. The creature requires a constant and rapid renewal of the water in the gall in which it livesforrespiration . . . . Since in all the crabs of this group the current of water for breathing enters the body close to the mouth, and passes out again at the hinder margin of the branchial [respiratory] cavity, the stream passing through the gall must always flow in one and the same direction . . . . The two excrescences on the coral grow together quickest in those spots which are least exposed to the current through the gall at length only two fissures . . . . are left, which plainly show that it is through them that the current for respiration passes . . . . These two slits remain open so long as the crab is alive ; no living crab is ever found in a closed gall, and they are for the most part perfectly empty.” 1 The excrescences show, as stated above, no signs of disease. From the ‘‘ PROCEEDINGS OF THE ZooLoGicaL Society oF Lonpon,” January 17, 1899. REPORT ON THE GORGONACEAN CORALS COLLECTED BY MR. J. STANLEY GARDINER AT FUNAFUTI. By Isa L. Hives, B.Se. (Vict.), Owens College, Manchester. Plates XII.—XYV. Of the forms of Gorgonacean Corals sent to me by Mr. Gardiner for identification and examination the majority belong to the family Muriceidee. There is one Gorgonellid—Verrucella granifera Kolliker; two Sclerogorgic forms of Gorgonidee—Suberogorgia verriculata Esper, and Kereides korent Wright and Studer; and one Plexaurid Huplecaura antipathes Klanzinger. Among the representatives of the Muriceide there are three new forms—Villogorgia rubra, Acamptogorgia spinosa, and Muricella - flexilis. The specimens have been very carefully preserved in spirit, but un- fortunately in some cases the endoderm is not complete, and therefore they are not so useful for anatomical examination as they would other- wise be. I am much indebted to Professor Hickson for the great help he has given me, especially with regard to the literature. The classification adopted is that used by Wright and Studer in the ‘Challenger’ Report on Alcyonaria. 152 ISA L. HILES, B.SC. Section SCLERAXONIA. Family ScLeRoGoRGIDA. KeEra@IDES KORENI Wright and Studer. There are numerous fragments of this species, but no complete colony. The spicules are ‘92 mm.--'203 mm. in length, by -27 mm.—"13 mm. The colony is light red in colour, with yellow polyps. Hab. Outer slope of the reef. Depth 40--90 fathoms. Previously recorded from the neighbourhood of Japan (7), Section Houaxonta. Family Mvriceip@. ACAMPTOGORGIA SPINOSA, n. sp. (Plate XII., Figs. 3, 4, 5). There are several fragments of this form, but they are all rather small. The branches are ‘5 mm. in diameter. ‘The coenenchyma is fairly thick and very rough. The small branches arise at angles of from 60°-90°. The polyps are borne chiefly on the sides of the branches. They stand out fairly perpendicularly at intervals of about 2 mm. Each branch bears, close to the apex, two opposite polyps which are usually somewhat larger than the others. They are 1:05 mm. in height, by 1:1 mm. across the crown and ‘64 mm. across the base, The other polyps are ‘73 mm. x ‘62 mm., and ‘55 mm. across the base. Thus the terminal polyps are decidedly larger than the lateral ones. They are cylindrical in shape, somewhat wider across the crown. The operculum forms a low cone ; it consists of the basal spicules of the tentacles, each tentacle having 2 or 3 long-pointed spicules which divide into two at the basal end. They are 36 mm. x ‘09 mm. (length by breadth), and rest on a sunken collaret of spindles. The polyp spicules are of the three-rayed type, with foliaceous ex- pansions from two of the three rays, the third standing perpendicular to the others like a long sharp spike. They are -37 mm. in height by *36 mm. across the foliaceous basal portion. The coenenchyma spicules are bent spindles with short branched ex- pansions on the convex side, and also smaller forms of the polyp spicules. The spindles are ‘21 mm. x ‘11 mm. (length by breadth). The axis is horny, brown, with the central core divided into chambers The colour of the colony in spirit is light brown. REPORT ON THE GORGONACEAN CORALS. 153 Depth 40-90 fathoms. This form differs from A. arbuscula, A. alternans Wright & Studer, A. acanthostoma and A. fruticosa Germanos, in the structure of the polyps, their proportionate size to the width of the branch, and the shapes of the spicules. The spicules resemble most closely those of A. acanthostoma, but the polyps of the new species are much more spiny. AcanrHogorGia MuRIcATA Verrill. (Plate XII. Figs. 6, 7.) Verrill (4) gives no figures, but the specimen agrees fairly with his description of the species. The branching is in one plane. Height of the specimen 75 mm. ; breadth 8 mm. ; diameter at the base | mm. Length of the calyces 2°0-2°5 mm.; diameter at the base ‘6 mm. ; diameter of the head 1-2 mm. The spicules round the edge of the calyx are 1:01 x :06 mm. ; the spicules of the calyx-wall are ‘75x°:03 mm.; the spicules of the ceenenchyma are °3x 03 mm. Most of the spicules are crooked, and. some have the smaller end slightly branched. Depth 40-90 fathoms. Previously recorded from Barbados. Depth 76 fathoms. This is a good example of wide distribution, the same species being found at Barbados and at Funafuti, two widely separated localities. VILLOGORGIA INTRICATA Gray. There is one example of this species attached to the axis of a dead Gorgonid. Wright and Studer (7) describe the species among the ‘Challenger’ Gorgonide. Depth 40-71 fathoms. Previously recorded from a locality between the Fiji Islands and the New Hebrides. Depth 145 fathoms. This is a considerable difference in depth, but the specimen is undoubtedly V. intricata. VILLOGORGIA RUBRA, uu. sp. (Plate XIII. Figs. 1, 2, 3, 4.) There are two small colonies with much of the conenchyma rubbed off. 154 ISA L. HILES, B.SC. The basal attachment is present in both as a small, flat, calcareous expansion. , One colony gives off a broken branch at an angle of 90°, 10 mm, above the base; the main stem reaches a height of 40 mm., and 13 mm. from the apex gives off another branch at the same side, 8 mm long. The other colony is 34 mm. high and gives off three branches fairly perpendicularly. These are all on the same side; the lowest arises 11 mm. from the base and is broken off short; the second is 9 mm. long, and arises 3 mm above the first; the third is 4°5 mm. above the second, and is 13 mm. long. There are very few polyps, most of the coenenchyma having been rubbed off; but what remains of the coonenchyma is thin. ‘The polyps arise almost perpendicularly, and mostly on the two sides. The end of a branch bears two polyps, only slightly in advance of the other, but neither truly terminal. The polyps are ‘92 mm. in height by 1:3 mm. in breadth at the base. The spicules of the conenchyma are chiefly four-rayed stars and flattened curved spindles, giving off spines from the convex side. They are ‘12 mm. long by ‘2 mm. broad. The polyps are covered with broad flat spicules, somewhat triangular in shape, with branched lateral outgrowths. They are ‘22 mm. x ‘49 mim. (length by breadth). The operculum is eight-rayed; each ray consists of two broadish spicules, converging at the apex. Their bases rest on a horizontally placed spicule, curved in shape and somewhat spiny. The opercular spicules are *31 mm. x ‘07 mm. The axis is horny, flexible, with the centre divided into chambers. The colour of the colony in spirit is reddish brown. The spicules of the coonenchyma and polyps are bright red, those of the operculum white. Hab. Outer slope of Ellice Island. Depth 40-71 fathoms. This form differs from V. intricata Gray in the size of the polyps and of the spicules, the arrangement of the polyps, and the colour of the spicules It differs from V. mauritiensis Ridley (5) in the size of the polyps. the shape of the spicules of the verrucz, and the colour of the colony. REPORT ON THE GORGONACEAN CORALS. LS It differs from V. flabellata Whitelegge (9) in the colour and form of the spicules. It differs from V. nigrescens Duchassaing & Michelotti (1) in the form and size of the verruce and in the colour of the colony. MURICELLA FLEXILIS, n. sp. (Plate XIV. Figs. 1, 2.) There is one small specimen of this form. It is 130 mm. in height and 70 mm. across the widest part. The main stem is 1°5 mm. in diameter near the base. Branching takes place in one plane, the branching arising from two sides of the stem. Lateral branches are borne in the same plane. The branches are slightly flattened in the plane of branching ; they all end in a small flat expansion with two lateral polyps borne close to the apex, making it somewhat hammer-shaped. The calyces are ‘9 mm. by ‘8 mm. in diameter at the base. The polyps are only partially retracted, the heads, measuring 6 mm. x ‘5 mm. in diameter, being visible above the verruce. The spicules are spindle-shaped, with warts not very thickly placed. They are 1:105 mm. x 09 mm., ‘83 mm. x 073 mm., -18 mm. x ‘027 mm. The colour in spirit is dirty white, the brown axis showing through the thin white coenenchyma. Ha®. Outer slope of the reef of Funafuti. Depth 40-71 fathoms. This specimen differs from J/. tenerw Ridley (5) in the greater slenderness of stem and branches, the smaller size of the spicules, and the fact that they are much less warted. It differs from JM. wmbraticoides Studer' in the absence of the “halbseitig warzig” character of the spicules. It differs from MW. complanata Wright & Studer (7) in its much more slender appearance, the thinness of the coenenchyma, and the com- paratively smooth character of the spindles, and also in colour, being white, not rose colour. It differs from J. perramosa Ridley (5) in colour and in the absence of a divergent bend of the stem at the origin of the branches. It differs from /. nitida Verrill (4) in colour, in the size of the spicules, and the lateral position of the polyps. It differs from J. gracilis Wright & Studer (7) in the lateral arrange- 1 Studer, Th , Monatsber. d. k. Akad. d. Wiss. Berlin, 1878. 156 ISA L. HILES, B.SC. ment of the polyps at the ends of the branches, in the much less warted spindles, and in the colour of the coenenchyma, which is not red but white. It differs from M. crassa Wright & Studer (7) in the thinness of the cenenchyma, the lateral arrangement of the polyps, the slender character of the stem and branches, and in the much smoother character of the spicules. | MuriceLLa TENERA Ridley, (Plate XIV. figs. 3, 4.) There is one colony ; it is 115 mm. high by 55 mm. across the widest part. The main stem is 2 mm. in diameter at the base. It is ramified in one plane, giving off branches on two sides at angles of about 45° ; these again bear branches at angles of 45°-60°. The calyces are small and inconspicuous, °5 mm. high and 1 mm. in diameter at the base. They are borne on the two sides of the stem and branches about 2 mm. apart. The branches end in two laterally placed polyps, making the termina- tion triangular in shape. The coenenchyma is ‘thin and whitish in colour ; the brown axis shows through, making the whole appear fawn-colour. The polyps are brown. The spicules are long, wavy spindles, covered with warts, which are more prominent on one side than the other. They are 4°54 mm. x 29 mm., 2°34 mm. x 22 mm., -°29 mm. x’ 036 mm. Hab, Outer slope of the reef. Depth 40-71 fathoms. This specimen differs slightly from Muricella tenera as described by Ridley (5), but the differences are not very important. The calyces are smaller, and the spicules are from two to four times the size of those of Ridley’s form. The spicules of the calyx also are not arranged in such a regular row as Ridley figures; Wright and Studer (7. p. 124) say the same about these spicules in the forms examined by them. Otherwise the colony decidedly approaches J. tenera: I have seen the ‘Challenger’ specimen, and consider this to be the same form. Previously recorded from south of Papua, off the Ki Islands, depth 140 fathoms; and Port Molle, Queensland. Or ~I REPORT ON THE GORGONACEAN CORALS, 1 Family PLEXAURIDs. EUPLEXAURA ANTIPATHES Klunzinger. (Plate XV. Figs. 1, 2.) Plexaura antipathes Klunzinger. This specimen which is in a dried state, is pale fawn in colour. The colony is much branched, the branches arising approximately in one plane. ‘The branches are given off irregularly ; they, in their turn, branch repeatedly, and these branches bear further branches. There are no traces of anastomoses. The basal portions are slightly flattened, but the terminal twigs are round and thicken slightly towards the ends. The branches run close together and fairly parallel. The polyp-pores are scattered irregularly over the whole surface, and are not raised above the general level except on the terminal twigs, where they are at the summit of slight conical elevations. They are about 1 mm. apart. The cortex is friable, and somewhat thicker on the twigs than the older parts. It is comparatively smooth ; on the older branches there are slight longitudinal furrows which run somewhat spirally round the stem. The axis is of horn, with scattered particles of calcareous matter ; it is of a dense black colour in the thicker branches. The “root” portion of the colony shows a great development of a peculiar skeletal substance, hard, and looking like stone. It is dull grey in colour, and shows the same furrowings as the cortex of the stem which extended over it. On treating with acid the stony part is dissolved away, leaving a fine network of horny matter in which the CaCO, was contained. The grey substance which strengthens the base of attachment is clearly formed independently of the black axis, although it may rightly be regarded as being of the same nature. Judging from the dried specimen it is composed of spicules of lime embedded ina horny matrix, no processes of the coenosarcal canals extending into it, even superficially. It is extremely hard, and breaks with a clean fracture when struck with a hammer. The horny axis, on the other hand, can be cut with a pen- knife. The nature of the horny substance is not determined, but from its insolubility seems similar to the keratin of the axis. It is only rarely seen in specimens of Gorgonacea in Museums, although it is possible that it may be formed at the base of all large Gorgonids when exposed to strong tides. 158 ISA L. HILES, B.SC. In the centre the calcareous matter is white and friable, not having assumed the stony, solid appearance of the outer part. The basal enlargement is seen also in Plexaura principalis and P. suffruticosa, in the National Collection at South Kensington ; and Klunzinger, in his ‘ Korallthiere des Rothen Meeres,’ mentions it for Plezaura antipathes. The spicules of the cortex are small warty spindles and clubs, the spindles preponderating. They are colourless, and are ‘17 mm. in length by ‘07 mm. in breadth. There are also a few small irregular crosses. Hab, Funafuti Lagoon. Depth 6-7 fathoms. Family GORGONELLIDA. VERRUCELLA GRANIFERA KoOlliker. (Plate XII., Figs. 1, 2.) Syn. Verrucella flabellata Whitelegge. There are several fragments of this species. The largest is 170 mm. long ; the stem is 1 mm. in diameter at the base, and remains about the same throughout. Ata height of 70 mm. it gives off a branch, and 50 mm. farther another branch arises. The branches are about the same thickness as the stem. The whole is whip-like and very flexible. The verruce are numerous, alternate, nearly at right angles to the axis, and about 2 mm. apart. They are °5 mm. high by 1 mm. wide at the base, and bluntly conical in shape. The axis is very hard and brittle ; it shows a number of longitudinal grooves. The branches end in a small knob, with a laterally-placed polyp close to the apex. The spicules are double stars and spindles of the Gorgonellil type. The warts are compound, and arranged in rings, leaving a median zone free and smooth. The spindles are flat, and many of them have rounded ends. ‘The double spindles are ‘075 mm. x ‘036 mm., ‘082 mm. x ‘018 mm.; the double stars are (036 mm. x ‘018 mm. The colour, in spirit, is pale fawn. These specimens seem to approach most closely to Verrucella grani- fera Kolliker (2), except that the spicules are only faintly tinged with yellow. V. flabellata Whitelegge (9) seems to resemble Kélliker’s form, V. granifera, very closely, the only difference, apparently, being that some of the spicules have rounded ends; but others, as he figures REPORT ON THE GORGONACEAN CORALS. 159 (PI. XVII. Fig. 83), have pointed ends, and resemble those of V’. granifera. This seems a small difference on which to found a new species, especially when the character is not constant and found in all the spicules. In one of the pieces from Funafuti which I examined, the spicules are decidedly longer and more pointed than in the other frag- ments although in other respects they are similar. This may be due simply to a difference in locality. A slight variety of form and size in the spicules is of frequent occurrence in Gorgonacea, and must not be considered of specific value. Hab. Funafuti. Depth 40-71 fathoms. Previously recorded from the coast of Africa. This is another instance of the same species from two widely separated localities, and may be compared with the distribution of Acanthogorgia muricata Verrill, which occurs at Funafuti and has been recorded from Barbados. SUBEROGORGIA VERRICULATA Esper. There are two fragments of this species, drab in colour. The double star spindles are somewhat rougher than those figured in Kolliker’s paper (2), otherwise the form seems to belong to Esper’s species. Hab. Outer slope of the coral-reef at Funafuti. LITERATURE REFERRED TO. 1. DUCHASSAING, P., et MICHELLOTI, G.—Mémoire sur les Corailiaires des Antilles. Turin, 1860. . KOLLIKER, A.—Icones Histiologicee. Leipzig, 1860. . RIDLEY, S. O.—‘‘ Contributions to the Knowledge of the Aleyonaria, with Descriptions of new Species from the Indian Ocean and the Bay of Bengal.” Annals and Magazine of Natural History, ix., 1882. 4. VERRILL, A.—‘ Report on the Anthozoa, and on some additional Species dredged by the ‘Blake,’ 1877-79, and the U.S. Fish-Commission Steamer ‘Fish Hawk,’ 1880-82.” Bulletin of the Museum of Compara- tive Zoology, Harvard, vol. xi., No. 1, 1883. 5. RIDLEY, S. O.—Zoological Collection of H.M.S. ‘Alert.’ ‘ Aleyonaria,” Melanesian Collections. Part I., 1884. 6. Von Kocu, G.—‘* Die Gorgoniden des Golfes von Neapel.” Fauna u. Flora des Golfes von Neapel, xv., 1887. G2 WwW 160 ISA L. HILES, B.SC. 7. Wricut, E. P., and STUDER, TH.—‘ Challenger’ Report on Alcyonaria, Xxxi., 1889. 8. GERMANOs, N. K.—‘‘ Gorgonaceen von Ternate.” Die Abhandlungen der Senckenbergischen naturforschenden Gesellschaft, Band xxiii, Heft 1, 1896. 9. WHITELEGGE, TH.—‘ Aleyonaria of Funafuti.” Memoirs of the Aus- tralian Museum, iii., pt. 5, 1897. EXPLANATION OF THE PLATES. PLATE XII. Fig. 1. Verrucella granifera, p. 158. A branch, natural size. 2. Verrucella granifera. Some spicules. 3. Acamptogorgia spinosa, n. sp., p. 152. A small portion of a branch, magnified, to show the arrangement of the spicules. 4. Acamptogorgia spinosa. The crown of a polyp, magnified, to show the arrangement of the opercular spicules. 5. Acamptogorgia spinosa. Some spicules, (@) of the operculum, (4) of the ccenenchyma. 6. Acanthogorgia muricata, p. 153. A polyp, magnified. 7. Acanthogorgia muricata. Some spicules, (@) of the operculum, (6) of the ecenenchyma, (c) of the polyp. PLATE XIII. Fig. 1. Villogorgia rubra, n. sp., p. 153. The colony, natural size. 2. Villogorgia rubra. Some spicules, (@) of the operculum, (0) of the polyp, (c) of the ecenenchyma. 3. Villogorgia rubra. Three polyps, magnified, to show the operculum closed. 4. Villogorgia rubra. Two rays of the operculum. PLATE XIV. . Muricella flexilis, n. sp., p. 155. The colony, natural size. . Muricella flexilis. Some spicules. . Muricella tenera, p. 156. The colony, natural size. . Muricella tenera. Some spicules. mB who ee PLATE XV. Fig. 1. Euplexaura antipathes, p. 157. The lower part of the colony, x3, to show the stony basal enlargement. 2. Huplexaura antipathes. A small portion of a microscopical section of the basal part, decalcified, showing the horny matrix. NGO 24 Piss Mintern Bros imp. Fies 12 VERRUCELLA GRANIFERA. Fies 3-5. ACAMPTOGORGIA SPINOSA. N Of. Bue. Lee Xda AOA LD ATCA Vred n es 6), 7. ANCAIN TIsIO)|GOINEG1UA IMNONR I CARA. te: tas POPE PON BN GG Serre if ee eae pe fe 7 See y, ~foo- = : i , J od y } J.Smit hth. Bi Sk | | Se : bd 2 eo , NS : | a Et ai N | ag -Q O : q | ae aa 2) a i mae? “S : yaaa Oe RSS OF se UY 4 4 ae! A a 5 N = ay a Ba © fe) — | | Ete ae - plliefekelwled Mantern Bros. imp - Fies.3,4.M.TENERA. J Smut delet hth. Ise IL. IMRUBBUUG leh nile NL CII ALS) ONC Ibe I2/, 2M. PZ SalOo oe cla E Dust del. J.Smat bth. EUPLEXAURA ANTIPATHES Mintern Bros.imp. Reprinted trom the ‘‘BERICHTE DER DEUTSCHEN Bot. GESELLSCHAFT,” Jahrgang, 1899. Band XVII, Heft 1. CHANTRANSIA ENDOZOICA DARBISH., EINE NEUE FLORIDEEN-ART. By O. V. DARBISHIRE. Hingegangen am 16 Januar, 1899. Mit Tafel XVI. Die im Folgenden als neu beschriebene Art wurde mir zur Bestim- muug von Herrn Prof. F. E. Weiss tibergeben, der das Material bei Valencia an cer Stidkiiste von Irland gesammelt hatte. Durch die Freundlichkeit der Herren E. A. L. Batters und Dr. P. Kuckuck wurde ich in die Lage versetzt, die unserer neuen Art verwandt- shaftlich am niichsten stehenden Chantransien an conservirtem Material selbst untersuchen zu konnen. ODafiir sage ich diesen Herren hiermit meinen besten Dank. Chantransia endozoica Darbish. wuchert in der iusseren Wandung und auch im Innern von Alcyonidium gelatinosum L., eines marinen thierischen Organismus, der durch die Gegenwart des Gastes ein ganz rothes Aussehen bekommt und etwa folgenden Aufbau aufzu- weisen hat. Eine Anzahl Individuen bilden einen zusammenhingenden Stock, der durch eine gemeinsame, feste Schicht nach aussen be- grenzt ist. In grosser Anzahl stehen auf dieser Aussenwand kleine conische Hocker, deren aussere Schicht mit der des tibrigen Stockes fortlaufend ist. Der conische Hocker ist nur eine Ausstiilpung der gewohnlichen Wandung des Stockes. Es befindet sich in demselben ein Hohlraum, der auch nach dem Innern des Stockes zu durch eine Wand begrenzt ist. Auch das Innere des ganzen Stockes scheint durch Wande mehr oder weniger gekammert zu sein. Diese Wiande sind fast von derselben Dicke, wie die Aussenwiinde des ganzen Stockes. Zwischen den conischen Héckern finden sich Oeffnungen in der Aussen- wand, welche in das Innere des Thierstockes fiihren, In dem unter K 1602 O. V. DARBISHIRE. dieser Oeffnung liegenden Hohlraum befindet sich einer der vielen Polypen, welche den lebenden Theil des Gesammtorganismus aus- machen. Alcyonidium gehort zu der Klasse der Bryozoén. Diese kurze Beschreibung der Unterlage, welche Chantransia endozoica Darbish. bewohnt, wird gentigen, um die Lebensweise dieser kleinen Floridee im Folgenden klarlegen zu kénnen. Chantransia endozoica Darbish. kommt zuerst. nur in der fusseren Wandung des Thierstockes von Aleyonidium gelatinosum L. vor. Sie durchwuchert diesen Theil nach allen Seiten und dringt sogar schliesslich in den lebenden Theil des Thierstockes ein, ja befillt in einigen Fallen selbst die in demselben befindlichen Polypen. | Es muss hier bemerkt werden, dass bei dem untersuchten Material scheinbar nur ein Theil der Polypen in vollig gesundem Zustande war, in Fallen, wo die Thiercolonie von Chantransia endozoica Darbish. befallen war. In dem Innern des thierischen Substrates und in den Wandungen desselben wuchert nur der rein vegetative Theil der Alge, die fort- pilanzenden Thallusabschnitte entwickeln sich ausserhalb des Wirthes (Tafel XVI., Fig. 1). Die vegetativen Faden sind reichlich gabelig verzweigt. An Stellen, wo ein intensives Wachsthum stattzufinden scheint, sind die Zellen meist ziemlich lang gestreckt, wihrend sie an Stellen, wo das Wachsthum wegen Raummangels im Begriffe ist nachzulassen oder ganz aufzuhéren, kiirzer und breiter sind. Die letzteren findet man am zahlreichsten und am dichtesten in den schon mehrfach erwahnten conischen Ausstiilpungen, die ersteren mehr in dem inneren Gewebe des Thierstockes. : In dem conischen Answuchse bilden die Faden des Gastes all- miihlich ein ziemlich dichtes Gewebe, das die Wandung bald fast ganz ausfiillt. Normalerweise scheint diese Wandung etwa 5—6 p dick zu sein, durch das Wucherr unserer kleinen rothen Alge steigt ihre Dicke auf 17—20 up. 4 Die vegetativen Zellen in den conischen Ausstiilpungen sind 6,8—8,5 mw lang und bis 5 pw breit. Zwischen diesen lingeren Zellen finden sich viele, meist altere Zellen, welche von ziemlich runder Gestalt sind und 6,83—8,5 yp nach jeder Richtung messen. Daneben finden sich einige, die sebr schlank und bis 20 p lang sind. Diese scheineu meist nach dem Innern des Thierstockes hinzuwachsen. CHANTRANSIA ENDOZOICA, EINE NEUE FLORIDEEN-ART. 163 Die Auszweigungen des vegetativen Thallus im Innern von Aleyonidium bestehen in der Regel aus langen, schmalen, dusserst diinnwandigen Zellen, die 17—25 zu 2,5—13,6 y» messen. Dazwischen finden sich kiirzere von 5,1—13,6 yx Grosse. Hier im Innern ist die regelmiissige, gabelige Theilung am besten zu sehen (Tafel XVI., Fig. 2). An einigen Stellen dringen diese Faden bis zu einer Tiefe von 1 mm in das Innere des Thierstockes. Unsere Chantransia erreicht hier also eine ganz betrichtliche Lange. Die ganze iussere, lederartige Wandung des Thierstockes kann mit diesen Faden durchwuchert sein, indem von dem Chantransia- Pflinzchen eines conischen Auswuchses Faden in die benachbarten Hocker iibergehen. Die trennende Strecke legen die Ausliéufer in der tiefer liegenden Wandung zurtick (Tafel XVI., Fig. 1, bei b). Zahlreich entsteigen den flach verlaufenden vegetativen Faden aufrechte Aeste, welche die 4ussere Wandung durchbrechen und dann in’s Freie hinausragen. Es sind dies die fertilen Aestchen, welche eine Héhe von 85 yw erreichen koénnen. Ihre Zellen messen, 6,8 bis 8,5 w zu 10—15 pw. Auch hier findet nur eine einfache gabelige Theilung statt. Bis jetzt ist es mir nur gelungen, die Bildung von Fortpflanzungsorganen zu beobachten, die ich fiir Monosporen halte. Sie kommen reichlich zur Ausbildung und messen bei etwa eiformiger Gestalt 12 x 10 » im Durchmesser. Ist ein Monosporangium entleert, so dringt von den darunter sich befindlichen, das Sporangium tragen- deu Zellen von Neuem das Plasma in die alte Hiille des Sporangiums, mit einer neuen Membran umgeben. In iilteren Exemplaren sieht man oft drei Membranen ausserhalb der jiingsten Membran. Moglicher- weise liegen hier nicht Monosporangien, sondern Spermatangien vor. Das Material war in Spiritus conservirt, so dass die rothe Farbe nicht mehr zu sehen war. Weitere Fortpflanzungsorgane wurden nicht beobachtet. Die fertilen Aestchen entstehen sehr zahlreich auf der Wandung des ganzen Thierstockes. Am hiiufigsten scheinen sie jedoch auf den conischen Auswiichsen zur Ausbildung zu kommen. Nicht selten ist die basale Zelle des fertilen Aestchens besonders ausgebildet. Sie ist dann ziemlich gross, von fast gleichmissigem Durchmesser nach allen Richtungen und meist mit einer dickeren Membran versehen, als die iibrigen Zellen des vegetativen Thallus. 164 0. V. DARBISHIRE. Die dickere Wand kennzeichnet auch die anderen Zellen des fertilen Aestchens. Die Membran wird bis 1,5 w dick. Die basale Zelle sitzt meist noch in dem Substrat (Tafel XVI., Fig. 1, bei a). Allmahlich bildet sich in den ilteren Theilen von Aleyonidium gelatinosum L. in den conischen Ausstiilpungen eine fast pseudo- parenchymatische Zellplatte aus, die nicht selten bis zu zwei Zellen tief ist. Der urspriinglich fiidige Charakter des Thallus von Chan- transia endozoica Darbish. lisst sich dann meist nicht mehr erkennen. Nur einmal schien eine Endzelle in ein Haar auszulaufen, doch kann dieses irgend einem fremden Organismus angehort haben. In Gestalt von kleineren Algen und Bacterien u. s. w. bedeckten an solechen iilteren Theilen von Aleyonidium die verschiedensten Organismen in dichten Rasen den Thierstock. Ein Ursprung des Haares von dem niichsten Chantransia-Pflanzchen war nicht festzustellen. Fiir die eben beschriebene neue Art moéchte ich folgende kurze Diagnose geben : CHANTRANSIA ENDOZOICA DaARBISH. NOV. SP. Der Thallus, reichlich gabelig verzweigt, wuchert in der dusseren Wandung des marinen Thierstockes von Alcyonidium gelatinosum L. kann aber an Stellen bis zu 1 mm tief in denselben eindringen. Vor- nehmlich lebt der Gast in den conischen Auswiichsen der Oberfliiche des Wirthes, von wo aus sich Faden in die benachbarten Theile des letzteren ausbreiten. Die vegetativen Zellen sind 6,8 bis 25 pw zu 6,8 bis 18 w gross. Zahlreich entstehen senkrecht abstehende fertile Aestchen, welche die Wandung des Alcyonidiwm durchbrechen und so in’s Freie gelangen und hier Monosporangien (oder Spermatangien ?) bilden. Die fertilen Aestchen werden bis zu 85 » hoch und sind nur wenig verzweigt. Die Fortpflanzungszellen sind von etwa eiformiger Gestalt und messen 12x10. Haarformige Gebilde sind nicht mit Bestimmtheit beobachtet worden. Bei Valencia an der Siidwestkiiste von Irland gefunden (F. E. Weiss). UEBER EINIGE NAHE VERWANDTE ARTEN VON CHANTRANSIA. Chantransia microscopica (Niigeli) Batters (1, 8.3) und die hierzu eehorigen Varietiiten pygmaea Kuckuck (4, 8. 391) und collopoda Rosenvinge (3,8. 41) sind unserer Chantransia endozoica Darbish. nicht unahnlich. Die erste Varietiit wuchert in dem Thallus von Porphyra CHANTRANSIA ENDOZOICA, EINE NEUE FLORIDEEN-ART. 165 laciniata (Lightft.) C. Ag. Dem einfachen Bau der Wirthspflanze entsprechend hat auch der Eindringling einen sehr einfachen Aufbau aufzuweisen. Er erreicht keine grossen Dimensionen. Nach Kuckuck sind die vegetativen Zellen seiner neuen Varietat 3 bis 3,4 p breit, bei der Batrers’schen Art 4,5 bis 7 » breit, wahrend KoLprerup-RoseN- VINGE fiir seine Varietiat collopoda die Breite der vegetativen Zellen als 7 bis 8 p, die Liinge als 12 bis 28 » angiebt. Diese Varietiit kommt auf Chordaria jlagelliformis (Miill.) Ag. vor. Sie besitzt ein grosses Basalorgan. Bei unserer Art fehlt die Chantransza microscupica (Nag.) Batters und varr. kennzeichnende Bildung eines Basalorganes. Angedeutet findet sich das letztere bei Chantransia endozoica Darbish., indem man gelegentlich, wenn auch selten, eine etwas grdssere basale Zelle am Grunde der fertilen Aestchen findet, die sich auch durch eine dickere Wandung auszeichnet. Bezeichnend fiir unsere Art ist kurz das Fehlen von farblosen Haargebilden, sowie eines deutlich ausgepragten Basalorgans. Chantransia microscopica (Niig.) Batters befallt mit seinen Varietiiten nur Algen, wihrend Chantransia endozoica Darbish. in einem thierischen Organismus, Alcyonidium gelatinosum L., vorkommt. Fiir eine Floridee ist dieser Umstand von grossem Interesse. LaGerHEIM hat (6) eine Anzahl epizoischer Algen autgefiihrt, und auch die perforirenden Algen wiren vielleicht hierzu zu zahlen, obgleich diese meist nur auf alten Schalen vorkommen. Von diesen ist die Floridee Conchocoelis Batters auch nur wenig bekannt. In gleicher Weise wie unsere neue Chan- transia befallt auch die Chlorophycee Hpicladia Flustrae Rke. var. Phillipsts Batters (2, 8. 2) und die Phaeophycee Hndodictyon infestans Gran (3, 8. 47) Arten von A/cyonidiwm. Neben der eben beschriebenen neuen Art bemerkte ich noch auf der Aussenseite von Alcyonidium Arten von Delesserva, Polysiphonia, Hry- throtrichia, Chylocladia, Plocamium u.a, m., in Anfangsstadien. Oefters wurden auch gekeimte und ungekeimte Sporen von rothen Algen ebendaselbst beobachtet, die zum Theil wahrscheinlich zu Chantransia endozoica Darbish. gehérten. Es ist mir nicht gelungen, festzustellen, auf welche Art und Weise diese Alge in das Wirthsthier eindringt. Manchester, Owens College, Januar 1899, 166 O. V. DARBISHIRE. LITTERATUR. 1. BATTERS, E. A. L., Some new British marine Algae.—Journal of Botany, iw) January, 1896. . Batters, E. A. L., New or critical British marine Algae. —Ebendas., Nov., 1897. 3. GRAN, H. H., Kristiania fjordens Algeflora. I. Rhodophyceae og be Phaeophyceae.—Videnskabsselskabets Skrifter I. Mathem.-naturvid. Klasse 1896, n. 2.—1897. KOLDERUP-ROSENVINGE, L., Deuxieme mémoire sur les aleues marines du Groenland.—Meddelelser om Groenland, XX., 1898. Kuckuck, PAUL, Bemerkungen zur marinen Algenvegetation von Helgo- Jand, [I.—Wissenschaftl. Meeresuntersuch., herausgegeben von der Kommiss. zur Untersuch. der deutschen Meere in Kiel und der biolog. Anstalt auf Helgoland. Neue Folge, Band II., Heft 1, 1897. 6. LAGERHEIM, G. DE, Trichophilus Neniae Lagerh. n. sp., eine neue epizoische Alge.—Ber. der Deutschen Bot. Gesellsch., Band 10, 1892, S. 514 bis 517. ERKLARUNG DER ABBILDUNGEN. Habitusbild eines ganzen Pflinzchens, wie es in einer conischen Ausstiilpung der iiusseren Wandung von Alcyonidium gelatinosum L. wuchert. Man sieht auch, wie mehrere Fiden mehr nach der Mitte des ganzen Thierstockes vordringen. Bei a@ ist ein kleines, fertiles Aestchen in voller Entwickelung ausserhalb des Substrates. Bei 6 ist ein Faden im Begriff die iiussere Umwandung zu durch- brechen. Die zwei rechten fertilen Aestchen besitzen beide deutliche Basalzellen. Vergr. 400. Einige langzellige Faden ganz aus dem Innern des Thierstockes von Alcyonidium gelatinosum L. Vergy. 400. - Endstiick eines fertilen Astes mit zwei Monosporangien (oder Spermatangien ?). Vergr 800. O.C. BL, Phe 21am Berichte d. Deutschen Bot. Gesellsch. BA. XVM Ev Laue lth. PMC Dartishire ges Reprinted from the “ ANNALS OF Botany.’ Vol. XIII. ON ACTINOCOCCUS AND PHYLLOPHORA. By Orro VERNON DarpisHire, The Owens College, Manchester. With Plate XVIJ. and seven Figures in the Text. Credidi enim et etiamnune credo, tubercula illa nihil aliud esse quam para- siticum quid ...—LYNGBYE, Tentamen Hydrophyt. Dan., 1819, p. 11. In 1893 Schmitz published a paper, in which he discussed at some length the Actinococcus question. He maintained that all so-called forms of fructification of Phyllophora Brodiaei (Turn.) J. Ag. which he had so far been able to examine, belonged in reality to a different Floridea growing parasitically on the former species (5, p. 371). This paper was shortly after reviewed by Gomont, who expressed bis full agreement with the views held by Schmitz ; so that the true nemathecia of Phyll. Brodiae (Turn.) J. Ag. still remained to be found. Doubts had long been felt with regard to the true nature of the so- called nemathecia of Phyll. Brodiaet (Turn.) J. Ag. The few lines quoted at the head of this paper were written by Lyngbye in 1819 in describing these very same nemathecia. In the beginning of 1894 the author of this paper gave a preliminary account of some observations on the anatomy and development of the Baltic species of Phyllophora Grev., in which Schmitz’ assertions concerning the parasitic nature of the nemathecia of Phyll. Brodiaec (Turn.) J. Ag. were discussed and the accuracy of his conclusions was doubted (1, p. 47). A more detailed account of the author’s work on the Baltic Phyllophorae was published about a year later, but unfortunately Schmitz died in 1894. In the 168 OTTO VERNON DARBISHIRE. second paper just mentioned the author again expressed it as his opinion that the so-called nemathecia of Phyll. Brodiaei did really represent the true tetrasporic fructification of this Floridea (2, pp. 2 sq., 23 sq., 36). The subject has not been worked at by algologists since, and Schmitz’ theory has therefore naturally been most generally accepted. Kolderup Rosenvinge alone seems to have adopted an opposite view (4, p. 33). Since commencing work on the anatomy and development of Phyllophora in 1892, the author has devoted much time to the exami- nation of all forms of fructification found on it. Up to 1896 opportunity was however wanting for dredging and examining fresh material during the months of September and October, owing to the author’s absence from Kiel during that time. Practically all the material used in these investigations was collected in the Baltic near Kiel. The observations carried out up to this point indicated that the one conclusion to be drawn was that the so-called (Actinococcus) nemathecium of Phyll. Brodiaer was really the genuine tetrasporic fructification of that plant. Fig. 1. Nemathecia of Fig. 2. Nemathecia of Actinococcusroseus(Lyngh. ). Actinococcus roseus (Lyngb). Kold. Rosenv. on Phyllo- Kold. Rosenv. on Phyllo- phora Brodiae (Turn.)J. Ag. phora Brodiaei(Turn.) J. Ag. Nat. size. Nat. size. In 1896 for the first time specimens of Phyll. Brodiae were dredged and preserved at all times of the year. This was continued up to ON ACTINOCOCCUS AND PHYLLOPHORA. 169 September, 1898, when the author left Kiel. The development of the plant in question was followed out, and as a result the author has accepted Schmitz’ view of the parasitic nature of Actinococcus, the correctness of which view, however, Schmitz unfortunately was not able to establish, as he did not succeed in observing the entrance of the parasite into the host. The following is an account of the anatomy and development of Actinococcus subcutaneus (Lyngb.) K. Rosenv., which forms the ‘pseudo- nemathecium’ of Phyll, Brodiaei (Turn.) J. Ag. Actinococcus suBcuTANEUS (Lyngb.) K. Rosenv. Almost at every time of the year small, more or less spherical, dark reddish bodies are found on the flat expansions forming the thallus of Fig. 3. Phyllophora Brodiaei (Turn.) J. Ag, Sterile, Baltic forms. Nat. size. Phyll. Brodiae. They are sessile on the young shoots at the apex of 170 OTTO VERNON DARBISHIRE. the thallus, but often appear to be stalked, this appearance being pro duced by the shoots on which they grow (Figs. 1 and 2) being at first rather narrow. These red bodies are the nemathecia of Actinococcus subcutaneus (Lyngb.) Kolderup Rosenvinge, the Floridea mentioned above as growing parasitically on Phyll. Brodiazi. The young shoots of the latter Alga are not usually much modified by the presence of the parasite, but are on the contrary as a rule well developed. In the Baltic sea small detached portions of the thallus of Phyll. Brodiaet frequently occur lying on the sea-bottom. They are Fig. 4. Phyllophora Brodiaci (Turn.) J. Ag.“ I. Two spermophores. x 10diam. II. Longitudinal section of spermophore, showing the antheridial cavities in the cortical layer. 200 diam. characterized by being very narrow, elongated and always sterile (Fig. 3, forma, ligulata, elongata, &c., of various authors). They therefore never develop antheridia or procarpia. Furthermore they are never attacked, at any rate not successfully attacked, by the ON AOTINOCOCCUS AND PHYLLOPHORA. 171 germinating spores of Actinococeus subcutaneus. This parasite can only enter the host when the male (or the female?) organs of the latter are present. It has been known to the author for some time that the antheridial cavities of Phyll. Brodiaei often accompanied the presence of Actinococcus subcutaneus, but only during the last year has it become possible to explain definitely the significance of this appearance. As the presence of the antheridial cavities is so intimately associated with the relationship of the two red Algae which form the subject of this paper, it might be useful to recall the structure of the former 2a 2). The antheridia of Phyll. Brodiaez are developed in the cortical layer of the spermophores, the latter being shoots more or less modified tempora- rily for the production of the male organs (Figs. 4,5). They are slightly flattened near the lighter coloured apex, attaining a length of about 3 mm., being rarely broader than 0°5 mm., and they are borne on the apical margin of the flattened vegetative thallus. In the cortex of such a spermophore, close to its apex and not further down from it than 1:0—1:‘5 mm., we find the small cavaties which contain the antheridia. These cavities are flask-shaped and communicate with the exterior by a small ostiole. Their height is 24—34 p, their breadth about 20 «. From the flat bottom of the flask-shaped cavity arise a number of 2, 8, or even 4-celled antheridia, which produce the single male cells or spermatia, at their apex (Fig. 5). The spermatia pass out of the cavity through the ostioles, which measure about 6—10 Across. It is not necessary to describe the carpophores of Phyll. Brodiaer, on which the female organs are borne (vid. 2, p. 32, Figs. 46, 47). I have not been able to ascertain definitely whether our Actinococcus can enter its host by means of the opening caused by the projecting trichogyne. Very probably it does, as I have seen Actinococcus-bearing shoots of Phyllophora, in the cortical layers of which could be seen what were apparently remains of undeveloped carpogones. Antheridia and procarpia, moreover, do not occur on the same plant. In the autumn it is possible to observe the entrance of A ctinococeus into Phyll. Brodiaei by the small ostioles of the antheridial cavities. The spores (tetraspores or carpospores) which ultimately give rise to the nemathecia of Actinococcus subcutaneus germinate on the surface of the host about this time. ee OTTO VERNON DARBISHIRE. The immediate product of germination seems to be a small heap of perhaps 4—8 cells, one of which always comes to be near an ostiole leading to an antheridial cavity. The antheridial cavities are de- veloped in large numbers and very close together (Fig. 4, IL).