Enteropneusta from Madras.

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1 BNTEROPNEUSTA FROM MADRAS. 123 Enteropneusta from Madras. K. Kamiuini Meiion, Assistant Professor, Presidency College, Madras. With Plate 10. DURING the last few months I have been able to dredge on a small scale off the Madras Coast. The specimens already obtained include a number of interesting forms, and I was especially gratified to find a few specimens of Bnteropneusta, the occurrence of which had been rendered almost certain by the presence in great abundance of Tornarias in the Madras Plankton. Among other types may be mentioned Amphioxus, Lingula, Edwardsia, Pennatulids, Sphenopus, etc. The Enteropneusta form the subject of the present paper. I gladly take this opportunity of expressing my great indebtedness to Mr. Edgar Thurston, Superintendent of the Government Museum, Madras, who was so very kind as to place a small sum of money at my disposal for the purpose of dredging. I also wish to express in this connection my most grateful thanks to His Highness the Rajah of Cochin and to His Highness's late Prime Minister, Mr. P. Eajagopalachari, for their great generosity in enabling me to purchase much valuable zoological literature. The Enteropneusta were dredged at depths of six to nine fathoms in mixed sand and mud. The specimens obtained were all imperfect. They belong to three different species belonging to the three families established by Spengel. The Ptychoderidae are represented by a single specimen, a

124 K. KAM[TNN[ MENON. fragment 7 mm. long, and consisting of the proboscis, collar, and part of the branchial region. Unfortunately, the specimen was not of much use for anatomical purposes.

2 124 K. KAM[TNN[ MENON. fragment 7 mm. long, and consisting of the proboscis, collar, and part of the branchial region. Unfortunately, the specimen was not of much use for anatomical purposes. Its external features (and what little it was possible to make out of its internal anatomy) agree so closely with Spengel's description of Grlossobalanus minutus (Ptychodera minuta) notably in the possession of the triangular " Kiemenfeld," which Spengel regards as characteristic of the species that, notwithstanding the slight difference in colour, my specimen being more nearly white than the corresponding portion in Spengel's drawing, I have no hesitation at present in identifying it as a small specimen of that species. A form identical with G-landiceps haekii represents the Glandicipitidfe. It is interesting to find this Japanese species here. A few specimens (all male and incomplete) of this were obtained; the largest of them measured about 45 mm. in length. The animal is drawn in fig. 1. When alive, the body of the animal was very contractile. I have very little to add to the descriptions of the animal given by Spengel and by its discoverer Marion. The proboscis is conical, and has a thick base and a pointed anterior end. Its dorsal surface is arched, and the ventral flat. Fig. 1 shows the proboscis in a fairly extended condition. A well-marked longitudinal groove is present on the dorsal side at the base, and a similar but less marked one on the ventral. The length of the proboscis when moderately extended is 6J mm., its basal breadth about 4 mm., and its basal thickness (dorso-ventral) a little over 3 mm. The collar is short, broad, and slightly depressed, its length, breadth, and thickness being 24 mm., 44 mm., and 4 mm. respectively. The anterior end of the collar is broader than the posterior. A little in front of the posterior end there is a ring furrow. The trunk immediately behind the collar is narrower than the collar, and compressed. Its breadth is, in this region, about 3 mm., and its thickness about 4 to 4 mm. It gradually becomes flatter and broader posteriorly, the posterior end of the largest fragment being 5 mm. broad.

3 ENTEROPNEQSTA FROM MADRAS. 125 The dorsal surface of the trunk is marked by two subinedian ridges, which are correctly described by Spengel and Marion. In the posterior region of the trunk, at some distance behind the branchial region, two similar ridges (due to the thickening of the longitudinal muscles) make their appearance on the ventral side on either side of the median ventral groove. These ridges become narrower posteriorly. The lateral portions of the trunk that is, the portions lying outside the submedian Hues are thicker in front than behind. The surface of the truuk is marked by transverse grooves and ridges both above and below. The colour of the animal agrees generally with that given by Spengel. The general colour is white or yellowish white on the ventral surface, which changes into yellowish brown on the dorsal, especially in the branchial region. Irregular dark brown patches are present on the dorsal surface of the proboscis and the collar. The ridges between the transverse grooves are marked by yellowish-brown pigment, especially on the dorsal side. The internal organisation agrees very closely with Spengel's account. Spengel was able to see only the proximal portion of the vermiform process, having utilised the anterior portion of the proboscis for longitudinal sections. This, however, seems to be the only portion present. In one large specimen examined by me the process was only a little over -J.L- mm. in length. The dorso-vontral septum of the proboscis stretches much farther forwards than the process. The vermiform process of this species is thus in a very reduced condition. As pointed out by Spengel, the chondroid tissue of the proboscis skeleton is very highly developed ; the posterior limbs of the skeleton reach to the hind end of the collar. In the collar Spengel mentions a posterior epidermal invagination, bind in his figure of a median longitudinal section he indicates a similar anterior invagination. This latter I have found in my sections, and one like it at the posterior end of the collar cord. They are both of them depressions into the actual nerve-tissue, and it is not clear to me why they are not called neuropores (the

4 126 K. RAMUNNI MBNON. rest of the axial canal of the collar-cord being broken up into the smaller spaces of the cord). They are certainly not like the anterior dermal pit which is present in the new species described here, and which has a proper epidermal wall. The arrangement of the intestinal pores is quite different in my largest specimen (the only one which possessed the post-branchial region) from that given by Spengel. Spengel mentions uine unpaired intestinal pores, the first being placed on the right side and the rest on the left, and, some distance behind these, three pairs of paired intestinal pores. In my series of transverse sections I counted about sixty of the former aud six pairs of the latter. The arrangement of the unpaired pores is very irregular. They lie now on the left side, now on the right; some of them are paired, but the majority are unpaired. The gonads begin a little behind the anterior end of the branchial region, and extend into the commencement of the liver region. Marion's statement that they are confiued to the branchial region is thus certainly not true of the males. The testes are paired, irregularly lobed, and transversely elongated bodies. These dorsally placed masses bend at the sides of the body, and extend into its ventral portion. They open by ducts along the submedian grooves. Dolichoglossus bournei. Two specimens of a new species of Dolichoglossus were obtained. The proboscis, collar, and a portion of the branchial region were alone present. The animal is small. What at once enables one to assign it to its proper place is the great length of the proboscis. When moderately extended, it measured about 9 mm. in length, and after preservation about 6 mm. It is depressed, and its base is twice or three times as broad as the tip, its greatest breadth at the base being nearly 2 mm. The deep longitudinal groove present on the dorsal surface in the species sulcatus and otagoensis is absent. But in pi - e- served specimens there is a shallow longitudinal depression on the dorsal side, extending forwards some distance from the base of the proboscis; there is a similar but less marked

5 ENTBROPNFiUSTA FROM MADRAS. 127 one on the ventral side. As in other forms, these are, no doubt, caused by the contraction of the dorso-ventral septum of the pi'oboscis. The anterior extension of the groove shows that the septum is not confined to the base of the proboscis. The proboscis is connected with the collar by a very thin neck. The collar measures nearly 1 mm. in length and nearly 1 mm. in breadth. Three annular grooves are present. The branchial region, which, like the collar, is nearly cylindrical, measures about 1^ mm. from side to side. The larger of the specimens possessed about 18 mm. of this region, which was coiled ventrally, as shown in fig. 2. The sides of the trunk were transversely ridged, the ridges becoming more mai'ked posteriorly. The dorsal surface of the trunk is slightly flattened, and has a shallow, median, longitudinal groove containing the nerve-cord, and on either side of it a submediau groove containing the branchial pores and the openings of the gonads. Both specimens were female, and were of a light brown colour. The tip of the proboscis and the collar were yellowish in colour. I have not been able to make a complete study of the internal anatomy, but certain interesting points may be noted. Proboscis. The circular muscle is, as is usually the case in this genus, feebly developed. The longitudinal muscle forms a very thick layer, the fibres of which are not arranged in concentric rings. In this latter point, the present species agrees with otagoensis. The fibres have a remarkably straight course, as they are almost all represented by dots in transverse sections. The cavity of the proboscis is not merely confined to the base, but is present throughout the whole length of the proboscis. It is fairly wide half as wide as the proboscis itself in its anterior third, but between it and the base is reduced to a very narrow canal. At the base, the cavity is present as a very narrow space investing the basal organs in the usual way. The basal organs project a very short distance about one tenth of its length into the proboscis. The median mesen-

6 128 K. RAMUNNL MENON. tery, however, extends farther forwards, and reaches up to the wider anterior portion of the proboscis cavity. The mesentery is more muscular in its posterior part than in its anterior, which is practically a band of connective tissue. It may be doubted whether this portion can be really called a mesentery, but there can be no doubt that the mesentery proper extends a considerable distance beyond the basal organs. This anterior extension of the mesentery is regarded as far as I have been able to make out as characteristic of the genera with a vermiform process, viz. Glandiceps and Schizocardium, and it is interesting to find it in Dolichoglossus, in which no vermiform process has been detected. The tip of the proboscidial diverticuluin is bent dorsally, as in D. Kowalevski. The diverticuluin is hollow, but the cavity of the anterior portion is extremely narrow. In mediau longitudinal sections the neok of the diverticulum is seen to be very long, and to open into the buccal cavity far behind in the collar region. This posterior position of the opening (fig. 3) may be partly due to a slight retraction of the proboscis into the collar during preservation. The central blood-sinus is very conspicuous, and is distended dorsally just behind the heart vesicle. The heart vesicle is remarkably small. In a series of longitudinal sections each about ^-{iy- mm. thick, the heart vesicle covers only ten sections. Its other dimensions can be gathered from fig. 3. Its posterior wall does not touch the wall of the proboscis. A similar reduction in the size of the heart is also mentioned in Stereobalanus (Balanoglossus) Oanadensis. The body of the proboscis skeleton is long, and extends into the posterior region of the collar; the chondroid tissue is very poorly developed. Its posterior limbs reach to the hind end of the collar. The proboscis pore is placed on the left side of the median line at the posterior end of the neck of the proboscis. Collar. The collar has the usual structure. The dorsal mesentery is present throughout the whole extent of the collar, the ventral only in its posterior half. Transverse muscles are present in the ventral wall of the periheenial

7 BNTBROPNPiDSTA FROM MADRAS. 129 cavities. Peri branchial cavities are absent. The nerve-cord of the collar does not contain a central cavity, but numerous small spaces are present in it. The antei'ior end of the collar is sunk into a deep pit with folded walls and lying above the collar-cord. In transverse sections it appears as a crescentic space lying above, and extending laterally over the nerve-cord. The pit extends posteriorly more than half-way into the collar. The collar pores have the usual structure. Trunk. The body-wall is marked, as in other species of the genus, by the absence of a circular muscle. The longitudinal fibres form a thick band below the epidermis. Ventrally, on either side of the ventral mesentery, these fibres are scattered in the body-cavity, and a few are closely applied to the gut-wall, forming a feeble longitudinal musculature to it. Radial muscles are well developed between the outer walls of the branchial pouches and the body-wall; they are also scantily developed between the dorsal portion of the gut-wall and the body-wall. In the hypobranchial wall in the posterior part of the branchial region, outside the basement membrane of the alimentary epithelium, a thin circular muscular layer, consisting of extremely thin fibres, is visible. These fibres are also present in the epibranchial region. They have not been traced round the branchial pouches. In the branchial system there is a histological detail which seems worth noting. A similar condition has been described only in one other Bnteropneust, Balanoglossus Kupferi. The ciliated epithelium, instead of forming a single layer of low cells, consists of a layer of very thin columnar cells which have their numerous minute nuclei arranged in different levels. In stained preparations the epithelium shows a closely-packed mass of coloured dots, and gives a characteristic appearance to the branchial portion of the alimentary canal. As in other forms, this epithelium is restricted to the anterior and posterior faces of the branchial septa and tongues. The outer wall of the branchial tongue is not folded into the cavity of the tongue. VOTJ. 47, PAET 1. NEW SERIES. I

8 130 K. RAMONNl MENON. The ovaries reach quite to the anterior end of the branchial region. Median gonads are not present. The ovary (which is solid in the young stages) is a hollow sac : in specimens in which the ova are not fully developed, they are arranged round the lumen. Certain globular, fat-like bodies of varying sizes are also found among the ova. The ovary opens by the oviduct to the outside, externally to the branchial pores. There can be no doubt that the form here desci-ibed is different from the three species of the genus described by Spengel, and from the one described subsequently by Benham. I dedicate it to one to whom I owe much. Of the two species of Tornaria found in the Plankton, one is T. Krohnii and is very common. This has been previously recorded from the Mediterranean and from the European and American Coasts of the Atlantic. Grlossobalanus mitiutns, which occurs here, has also been recorded from the Mediterranean and from the American Coast of the Atlantic. This may be a mere coincidence, of course; but it may also be that T. Krohnii is the larva of Grlossobalanus minutus. The other species of Tornaria cannot be identified with any of those described by Spengel. Figs. 5 and 6 represent the larva from the ventral and dorsal aspects. It is about 1^ mm. long. With the help of Spengel's terminology, this form inay be characterised as follows : The ventral lobes of the oral area are shallow and broad, and are secondarily lobed. The portion of the pre-oral area which lies below these ventral lobes and to the sides of the mouth is also encroached upon on its outer side by secondary lobes of the oral area. The upper dorsal lobes have secondary and tertiary lobes. Lower dorsal lobes are well developed. There are no.lateral lobes. The ventral saddle of the postoral area is long and narrow, as in T. agassizi. There is no secondary perianal ring of cilia. Round patches of yellowish-brown pigment are found along the course of the ciliated bands. They are placed on the side of these bands, turned away from the oral area. They are also found along

9 ENTEROPNEUSTA FROM MADRAS. 131 tlie periaual band of cilia_, on the side turned towards the month. A smaller ring of such patches, often appearing as slight elevations, is present round the anus. These, no doubt, represent a vestigial secondaiy perianal ring. These patches agree in colour with the transversely elongated patches found on the body of Grlandiceps haekii, and possibly the larva belongs to this species. It may be added here that, in his monograph, Spengel mentions two forms, Ptychodera (Chlamydothorax) Ceylonica, and Tornaria grenacheri, which were obtained in Ceylon. MADRAS ; October 2nd, EXPLANATION OF PLATE 10, Illustrating Mr. K. Ramunni Menon's paper on " Enteropneusta from Madras." FIG. 1. Dorsal view of Glandiceps haekii. X 3. Tlie gonads were sketched from preparations cleared in clove oil. FIG. 2. Dolichoglossus bournei. X 6. The gonads were sketched from clove-oil preparations. Dorsal view. FIG. 3. Median longitudinal section of Pig. 2. con. Us. Connective tissue. pr.ca. Proboscis coelom. d.v.s. Dorso-ventral septum. N.B. The dorsoventral muscle-fibres ought not to have been drawn in tlie anterior portion. //I. Glomerulus. bl. sin. Blood-sinus. v. div. Ventral diverticulum of tlie proboscidial divertieulum. ep.div. Anterior epidermal pit. c.c. Collar-cord. sk. Body of the proboscis skeleton, p. h. Perihsemal cavity, h. Heart vesicle. FIG. 4. Transverse section of the branchial region of Fig. 2. d. n. c. Dorsal nerve-cord, v.n.c. Ventral nerve-cord, g.p. Genital pore. r.m. lladial muscle-fibres, br. s. Branchial septum, br. t. Branchial tongue, ov. Ovary, cm. Circular muscle-fibres of gut wall. I. m. Longitudinal muscle. FIG. 5. New species of Tornaria. Seen from the ventral aspect, x 40. The oral area is shaded. FIG. 6. New Tomaria, from the dorsal side. Oral area shaded.

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Title. Author(s)Okuda, Shiro; Yamada, Mayumi. CitationPublications from the Akkeshi Marine Biological Stat. Issue Date Doc URL.

Title. Author(s)Okuda, Shiro; Yamada, Mayumi. CitationPublications from the Akkeshi Marine Biological Stat. Issue Date Doc URL. Title The Fauna of Akkeshi Bay : XXIII. Enteropneusta (Wit Author(s)Okuda, Shiro; Yamada, Mayumi CitationPublications from the Akkeshi Marine Biological Stat Issue Date 2017-12-27 Doc URL http://hdl.handle.net/2115/68004