Spongilla meyeni, Carter, J. Bomb. Asiat. Soc. iii, p. 33, pl. i, fig. 1, & Ann. Nat. Hist. (2) iv, p. 84, pl. iii, fig. 1 (1849). Spongilla meyeni, Bowerbank, P. Zool. Soc. London, 1863, p. 448, pl. xxxviii, fig. 4. Spongilla meyeni, Carter, Ann. Nat. Hist. (5) vii, p. 93 (1881). Ephydatia fluviatilis, Weber, Zool. Ergeb. Niederländ. Ost-Ind. i. pp. 32, 46 (1890). Ephydatia mülleri, Weltner (partim), Arch. Naturg. lxi (i), p. 125 (1895). Ephydatia robusta, Annandale, J. Asiat. Soc. Bengal, 1907, p. 24, fig. 7. Ephydatia mülleri subsp. meyeni, id., Rec. Ind. Mus. ii, p. 306 (1908).
Sponge hard and firm but easily torn, usually of a clear white, sometimes tinged with green, forming irregular sheets or masses never of great thickness, without branches but often with stout subquadrate projections, the summits of which are marked with radiating grooves; the whole surface often irregularly nodulose and deeply pitted; the oscula inconspicuous; the membrane adhering closely to the parenchyma. The parenchyma contains numerous bubble-cells (see p. 31, fig. 2).
Skeleton dense but by no means regular; the radiating fibres distinct and containing a considerable amount of spongin, at any rate in the outer part of the sponge; transverse fibres hardly distinguishable, single spicules and irregular bundles of spicules taking their place.
Fig. 21.—Gemmule and spicules of Ephydatia meyeni (from Calcutta).
a, Skeleton-spicules; b, gemmule-spicules.
Spicules. Skeleton-spicules entirely smooth, moderately stout, feebly curved, sharply pointed. No flesh-spicules. Gemmule-spicules with the shaft as a rule moderately stout, much longer than the diameter of one disk, smooth or with a few stout, straight horizontal spines, which are frequently bifid or trifid; the disks flat, of considerable size, with their margins cleanly and deeply divided into a comparatively small number of deep, slender, triangular processes of different sizes; the shaft extending not at all or very little beyond the disks.
Gemmules spherical, usually numerous and of rather large size; each covered by a thick layer of minute air-spaces, among which the gemmule-spicules are arranged vertically, often in two or even three concentric series; a single short foraminal tubule; the pneumatic coat confined externally by a delicate membrane, with small funnel-shaped pits over the spicules of the outer series.
I think that the gemmules found by me in Bhim Tal and assigned to Potts's Meyenia robusta belong to this species, but some of the spicules are barely as long as the diameter of the disks. In any case Potts's description is so short that the status of his species is doubtful. His specimens were from N. America.
E. meyeni is closely related to the two commonest Holarctic species of the genus, E. fluviatilis and E. mülleri, which have been confused by several authors including Potts. From E. fluviatilis it is distinguished by the possession of bubble-cells in the parenchyma, and from E. mülleri by its invariably smooth skeleton-spicules and the relatively long shafts of its gemmule-spicules. The latter character is a marked feature of the specimens from the Malay Archipelago assigned by Prof. Max Weber to E. fluviatilis; I am indebted to his kindness for an opportunity of examining some of them.
Type in the British Museum; a fragment in the Indian Museum.