DESCRIPTION OP EPHYDATIA BLEMBINGIA. 71 A Description of Ephydatia blembingia, with an Account of the Formation and Structure of the Gemmule. By Richard Evans, M.A., B.Sc. With Plates 1—4. CONTENTS. PAGE PAKT I.—THE MORPHOLOGY, ETC., OF BPHYDATIA BLBMIUNGIA. I. Introduction . .72 II. Description of Ephydatia blembingia. - .72 (1) Colour, habits of growth, and external form . 72 (2) Skeleton . .73 A. Spicules . .73 B. Arrangement of spicules to form fibres . 76 c. Spongin . .76 (3) Canal system ...... 77 (4) The structure of the mature gemmule . .78 III. Affinities of Ephydatia blembingia . .79 IV. Summary ........ SI PART II.—THE FORMATION OF mi GEMMULE OP EPHYBATIA BLEMBINGTA. I. Introduction . ...... SI II. Historical review ....... S2 III. Descriptive account of the development of the gemmule of Ephy- datia ble in bi ngi :i . 89 (1) Origin, elc., of the reproductive part of the gemmule . S9 (2) Origin, etc., of the cells which form the chilinous layers, etc. 9] (3) Origin, etc., of the scleroblasts and amphidiscs . 92 (4) Structure, etc., of the " trophocytes "... 94 (5) General conclusions . .95 IV. Critical review of previous accounts ... 96 V. Bibliography ....... 103 Description of Plates ....... 105 72 JtTOHARD EVANS. Part I.—The Morphology, etc., of Ephydatia blembingia. I. INTRODUCTION. Ephydatia blembingia is a fresh-Avater sponge which Mr. Annandale came across in a small pool of water while in search of snails. It was collected and preserved by me on the 23rd of July last year. The specific name blembingia has been applied to it on account of its locality. Blembing is a small Malay village which was visited by the members of an expedition sent out by Cambridge University to the Siamese Malay States, and which is situated on a small river of the same name. The river Blembing is a tributary of the Pergau, which in its turn empties itself into the Kelantan River. The pool of water in which the sponge, now desci'ibed for the first time, was found, was situated in a comparative]}' dense jungle at a distance of a few yards from the bank of the river. The trees growing around it were so big, and their foliage so thick, as to admit of only a small amount of light ever passing through them. Consequently the pool of water in which Ephydatia blembingia was found was always in a deep shade. The material which I collected was preserved in the following reagents: (1) Plemming's solution (weak fluid). (2) Saturated solution of corrosive sublimate (92 volumes) and glacial acetic acid (8 volumes). (3) Absolute alcohol. (4) Rectified 70 per cent, spirits. II. DESCRIPTION OF EPHYDATIA BLEMBINGIA. (1) Colour, Habits of Growth, and External Form.— Ephydatia blembingia is almost colourless, or to use a term which was used many years ago by Professor Lankester (11) to describe the colour of Spongilla from the Thames, it is "pale flesh-coloured/' Knowing as we do that Spongilla DESCRIPTION OF EPHYDATIA BLEMBINGIA. 73 lacustris and Epliydatia fluviatilis, denizens of our own rivers, are green in colour only when they grow in bright sunlight, this is what we would have expected in the case of a sponge which grew in a pool of water scarcely ever brightened by direct sunlight. The habits of growth of Bphydatia blembingia are peculiar. In reality it is an encrusting sponge, though some specimens have a massive appearance. But this is due to the habit of growing on such supports as blades of grass and branching weeds of various kinds which inhabit the same pool of water as the sponge. It never seems to produce independent branches, which, when present, give a sponge a kind of bush-like appearance, as Spongilla lacustris does. If, at first, a specimen appeal's to branch, on closer examina- tion the apparent branching reveals itself as the result of creeping over a branched support. Consequently, in spite of its massive appearance, Ephydatia blembingia is an encrusting sponge. The biggest specimens measure no more than about an inch across (PL 1, fig. 1). The surface texture of the preserved sponge is somewhat woolly, an appearance caused by the spicule fibres which sup- port the otherwise smooth dermal membrane. The fibres often penetrate the membrane, owing undoubtedly to its being rubbed off their extreme points. To sum up, Ephydatia blembingia may be described as a pale flesh-coloured sponge, with encrusting habits, creeping over branched vegetable supports, and consequently irregular in shape and woolly in texture. The oscula, not to speak of the dermal ostia, are so small as to be invisible without the aid of the microscope. The openings represented in fig. 1 are those of the inhalant canals seen through the dermal membrane. (2) Skeleton.—The skeleton consists almost entirely of spicules, which I shall now proceed to describe. A. Spicules.—In order to facilitate the description of this most important element of the skeleton, I shall arrange the spicules under three heads. 74 EIOHABD EVANS. (a) The first group of spicules consist of diactinal monaxons or amphioxea, which are usually curved, though straight speoimens are occasionally seen (PI. 1, fig. 3, a—e). (6) The second group also consists of curved aiuphioxea,.. but for reasons which will be stated further on they are sepa- rated from the first group (PL 1, fig. 3, /). (c) The third group consists of amphidiscs, which may be present in a fully developed or in an immature form (PI. 1, figs. 3, g—m, 4, a—c). (a) The amphioxea belonging to the first group taper gradually to a sharp point. They are never provided with a swelling at the middle point of the shaft, and scarcely ever are they malformed or modified in any way. In both respects, therefore, they differ most strikingly from the spicules of Spongilla moorei, a description of which was published in this journal a year and a half ago. They appear to be in- variably covered with small spines. (b) The amphioxea belonging to the second group are invariably curved and-covered with small spines. In fact, they present the same characters as the spicules of the first group, but differ from them in being only half as long and less than half as thick. They are not found in the general tissues of the sponge or in its membranes, but are grouped together round small bodies1 which are embedded in 1 The bodies above mentioned seem to possess a definite outline, and to lie in cavities of their own, much in the same way as the gemmulcs (PI. 4, fig. 17). I have no conception what these bodies arc, but several solutions have suggested themselves. Unfortunately T have been unable to find them in thin sections, and consequently cannot speak of their internal structure. The first suggestion, with regard to their nature, to present itself was that they were a second kind of gemmule. The arrangement of the spicules round them reminds us of that of I lie spicules round the gemrnules of Spongilla lacustris, and is, so far, in favour of the supposition that these bodies are some kind of gemmules. But apart from the f;ict that Ephydatia blem- bingia possesses another kind of gemmule, these structures are much more transparent than ordinary gemmules are at any stage in their development or when they are mature. If they were gemmules their basket-like shape could be easily explained as the result of contraction under the action of preserving reagents, owing to the cuticular coat being extremely thin. Apart from the DESCRIPTION OF EPHYDATIA. BLEMBINGIA. 75 the deeper tissues, and which present a kind of basket- shaped form. (c) The last class of spicules to be considered consists of the amphidiscs (PL 1, fig. 4, b). The diameter of the hat- shaped disc is about three times that of the shaft. The two discs are exactly similar in size and shape. The surface situated away from the shaft is smooth and convex, while the other surface is concave. Their margins are very finely serrated. The shaft is covered with spines which are conical in shape and placed at right angles to the axis of the amphi- discs. Tn addition to the fully mature forms, all the stages of development are represented, from the simple rod slightly fact that, if the supposition here made were true, it would cut at the very root of the system of division into subfamilies, now adopted, of the so-called Spongillidae, the reasons given above seem to bo sufficiently weighty to compel us to lay aside this possible view of the nature of these enigmatical bodies. The second supposition that suggests itself as a solution of the problem is that these structures are a kind of symbiotic or parasitic 3ponge. This supposition is not so unreasonable as it would at first appear, for we already know that Spongilla bohmii is parasitic on Spongilla nitens (17). Be- sides, it must be remembered that all the spicules in connection with these bodies are quite different from those which form the sponge skeleton, being, as has been stated already, only half as long and less than half as thick. It is no argument to say that they are incompletely developed, for they are all of equal size, which would not be the case if they were merely young spicules. However, if these bodies are of the nature of a parasitic sponge, there are, at present, no data by which its position among the Spongillidse can be determined. There is still left another possible solution of the problem,namely, that the bodies hero discussed are the result of parasitism on the part of some animal other than a parasitic sponge.