The Project Gutenberg eBook of Freshwater Sponges, Hydroids & Polyzoa, by Nelson Annandale

? Ephydatia fluviatilis, Lamouroux, Encyclop. Méthod. ii, p. 327 (1824). Spongilla fluviatilis, Bowerbank (partim), Proc. Zool. Soc. London, 1863, p. 445, pl. xxxviii, fig. 1. Ephydatia fluviatilis, J. E. Gray (partim), Proc. Zool. Soc. London, 1867, p. 550. Meyenia fluviatilis, Carter (partim), Ann. Nat. Hist. (5) vii, p. 92, pl. vi, fig. 11 a, b (1881). Ephydatia fluviatilis, Vejdovsky, Abh. k. Böhm. Gesellschaft Wiss. xii, p. 24, pl. i, figs. 1, 2, 7, 10, 14, 19 (1883). Ephydatia fluviatilis, id., P. Ac. Philad. 1887, p. 178. Meyenia fluviatilis var. gracilis, Potts, ibid., p. 224. Meyenia robusta, id., ibid., p. 225, pl. ix, fig. 5. Ephydatia fluviatilis, Weltner, Arch. Naturg. Berlin, 1895 (i) p. 122. Ephydatia robusta, Annandale, Journ. As. Soc. Bengal, 1907, p. 24, fig. 7. Ephydatia fluviatilis, Weltner, in Brauer's Süsswasserfauna Deutschlands xix, Süsswasserschwämme, p. 185, figs. 316, 317 (1909). Ephydatia fluviatilis, Annandale, P. U. S. Mus. xxxviii, p. 649 (1910).

[Many more references to this common species might be cited, but those given above will be sufficient.]

(iii.) the gemmule-spicules are longer, the shafts being as a rule longer than the diameter of the rotulæ;

(iv.) the gemmules are armed with a single row of regularly arranged spicules embedded in pneumatic tissue with minute air-spaces.

The sponge is a variable one and several "varieties" have been described from different parts of the world. My Indian specimens come nearest to the form described by Potts as Meyenia robusta, but have rather more slender skeleton-spicules and more elongate gemmule-spicules. The latter also appear to be less frequently "monstrous."

Geographical Distribution.—E. fluviatilis is widely distributed in Europe and occurs in N. America,^[BP] S. Africa (var. capensis, Kirkpatrick), Australia, and Japan. Specimens were obtained by Mr. Kemp from several lakes in Kumaon, namely Naukuchia Tal (alt. 4200 feet), Bhim Tal (4450 feet), Sat Tal (4500 feet), and Naini Tal (6300 feet). The gemmules from Bhim Tal referred by me to E. robusta (Potts) also belong to this species.

Biology. The external form of the sponge is due in great part to its environment. Specimens on small stones from the bottom of the Kumaon Lakes consist of thin disk-like films, often not more than a few centimetres in diameter and a few millimetres thick: others, growing on thin twigs, are elevated and compressed, resembling a cockscomb in appearance, while others again form nodules and masses of irregular form among the branches of delicate water-weeds. Some of these last are penetrated by zoaria of Fredericella indica.

Weltner has published some very interesting observations on the seasonal variation of minute structure in European representatives of the species (Arch. Naturg. Berlin, lxxiii (i), p. 273 1907) and has discussed the formation of the abnormal spicules that sometimes occur (ibid. lxvii (Special Number), p. 191, pls. vi, vii, figs. 27-59, 1901).

Sponge forming thin films of considerable area not more than 3 or 4 mm. thick, of a bright green colour, moderately hard but friable. The surface smooth; oscula inconspicuous, surrounded by shallow and ill-defined radiating furrows; a very stout basal membrane present.

Skeleton reticulate but almost devoid of spongin, the reticulations close but formed mainly by single spicules; skeleton-fibres barely distinguishable. A close layer of spicules lying parallel to the basal membrane.

Spicules. Skeleton-spicules variable in size and shape, almost straight, as a rule smooth, moderately stout, blunt or abruptly pointed; sometimes roughened or spiny at the tips, often sharply pointed. Flesh-spicules minute, few in number, with smooth, slender shafts which are variable in length, never very strongly curved; the terminal spines relatively short, not strongly recurved. Gemmule-spicules amphistrongylous or amphioxous, irregularly spiny, slender, of variable length.

Gemmules free in the substance of the sponge, spherical or somewhat depressed, very variable in size but never large, having a thick external pneumatic coat in which the air-spaces are extremely small and, inside this coat, a single rather sparse layer of spicules lying parallel to the gemmule. A single depressed aperture present.

Habitat. Hazratganj, Lucknow; on piers of bridge in running water (J. Caunter, 29-30. iv. 11).

The structure of the gemmules of this species differs considerably from that in any other known species of the genus, in which these structures are usually adherent and devoid of a true pneumatic coat. In some of the gemmules before me this coat measures in thickness about 1/9 of the total diameter of the gemmule. C. caunteri is the first species of Corvospongilla to be found in the Indo-Gangetic plain.

Mr. Kemp found this species common in Bhim Tal in May. His specimens, which were of a reddish-brown colour in life, appear to have been of more vigorous constitution than those taken by Major Stephenson in Lahore. Some of them had four buds but none were sexually mature.

This species is common in some of the Kumaon lakes, in which it grows, at any rate at the beginning of summer, much more luxuriantly than it does in the lakes of the Malabar Zone in autumn, forming dense bushy masses on the under surface of stones, on sticks, &c. The vertical branches often consist of many zoœcia. Mr. Kemp took specimens in Malwa Tal, Sath Tal, and Naini Tal (alt. 3600-6300 feet).

Mr. Kemp only found this species in Malwa Tal, in which (at any rate in May) it appears to be less abundant than it is in Bhim Tal in autumn. Mr. Kemp's specimens belong to the form called P. elegans by Allman.

Specimens taken by Mr. Kemp, somewhat sparingly, in Bhim Tal and Sath Tal in May exhibit a somewhat greater tendency towards uprightness of the zoœcia than those I found in autumn in Igatpuri lake. The ectocyst is, in the former specimens, of a deep but bright reddish-brown. The zoaria are attached to twigs and small stones.

This species may be distinguished from S. indica by (i) its entirely recumbent zoœcia, and (ii) the lateral branches of its zoarium.

Zoarium entirely recumbent, consisting of zoœcia joined together, often in groups of three, by slender, transparent, tubular processes. These processes are often of great relative length; they are formed by a modification of the posterior or proximal part of the zoœcia, from which they are not separated by a partition, and they increase in length up to a certain point more rapidly than the zoœcia proper. A zoœcium often gives rise first to an anterior daughter-zoœcium, the proximal part of which becomes elongate and attenuated in due course, and then to a pair of lateral daughter-zoœcia situated one on either side. As a result of this method of budding a zoarium with a close superficial resemblance to that of Paludicella is at first produced, but as the colony increases in age and complexity this resemblance largely disappears, for the zoœcia and their basal tubules grow over one another and often become strangely contorted (fig. 49).

Zoœcia elongate and slender, flattened on the ventral, strongly convex on the dorsal surface; rather deep in proportion to their breadth; the ectocyst colourless, not very transparent except on the stolon-like tubular part; dorsal keel and furrow as a rule absent; orifice unusually inconspicuous, situated on a tubercle on the dorsal surface.

Polypide stout and short; the tip of the fundus of the stomach capable of very complete constriction; the retractor muscles unusually short and stout.

Statoblasts. Only free statoblasts have been observed. They resemble those of S. indica, but are perhaps a little longer and more elongate.

The discovery of this species makes it necessary to modify the diagnosis of the genus, the essential character of which, as distinguishing it from Plumatella, is the differentiation of the proximal part of some or all of the zoœcia to form stolon-like tubules. From Stephanella, Oka, it is distinguished by the absence of a gelatinous covering, and by the fact that all the zoœcia are attached, at least at the base, to some extraneous object.

Biology. Mr. Kemp took three specimens, all attached to the lower surface of stones. They contained few statoblasts and were evidently in a condition of vigorous growth. Between the lateral branches new polyparia were developing in several instances from free statoblasts, each of which appeared to contain two polypides.

[BP] Most of the forms assigned by Potts to this species belong to the closely allied E. mülleri (Lieberkühn).

ALPHABETICAL INDEX.

When more than one reference is given, the page on which the description occurs is indicated by thickened numerals.