Type in the Indian Museum; a co-type in the British Museum.
Geographical Distribution.—All over Eastern India and Burma; also in Cochin on the west coast; Ceylon; W. China; Java, Flores and Celebes. Localities:—Bengal, Calcutta and neighbourhood (Annandale); Berhampore, Murshidabad district (R. E. Lloyd): Assam, Mangal-dai near the Bhutan frontier (S. W. Kemp): Madras Presidency, Madras (town) and neighbourhood (J. R. Henderson); Rambha, Ganjam district (Annandale); Bangalore, Mysore (alt. ca. 3000 ft.) (Annandale); Ernakulam and Trichur, Cochin (G. Mathai): Burma, Rangoon (Annandale, J. Coggin Brown); Prome, Upper Burma (J. Coggin Brown); Kawkareik, Amherst district, Tenasserim (Annandale): Ceylon, between Maradankawela and Galapita-Gala, North Central Province (Willey). Mr. J. Coggin Brown has recently brought back specimens from Yunnan.
Biology.—S. proliferens is usually found in ponds which never dry up; Prof. Max Weber found it in small streams in Malaysia. It is common in India on the leaves of Vallisneria and Limnanthemum, on the roots of Pistia stratiotes and on the stems of rushes and grass. So far as I have been able to discover, the life of the individual sponge is short, only lasting a few weeks.
Sexual reproduction occurs seldom or never, but reproduction by means of buds and gemmules continues throughout the year. The former is a rare method of reproduction in most Spongillidæ but in this species occurs normally and constantly, the buds being often very numerous on the external surface. They arise a short distance below the surface as thickenings in the strands of cells that accompany the radiating fibres of the skeleton. As they grow they push their way up the fibres, forcing the external membrane outwards. The membrane contracts gradually round their bases, cuts off communication between them and the parent sponge and finally sets them adrift. No hole remains when this takes place, for the membrane closes up both round the base of the bud and over the aperture whence it has emerged.
The newly liberated bud already possesses numerous minute pores, but as yet no osculum; its shape exhibits considerable variation, but the end that was farthest from the parent-sponge before liberation is always more or less rounded, while the other end is flat. The size also varies considerably. Some of the buds float, others sink. Those that float do so either owing to their shape, which depends on the degree of development they have reached before liberation, or to the fact that a bubble of gas is produced in their interior. The latter phenomenon only occurs when the sun is shining on the sponge at the moment they are set free, and is due to the action of the chlorophyll of the green bodies so abundant in certain of the parenchyma cells of this species. If the liberation of the bud is delayed rather longer than usual, numbers of flesh-spicules are produced towards the ends of the primary skeleton-fibres and spread out in one plane so as to have a fan-like outline; in such buds the form is more flattened and the distal end less rounded than in others, and the superficial area is relatively great, so that they float more readily. Those buds that sink usually fall in such a way that their proximal, flattened end comes in contact with the bottom or some suspended object, to which it adheres. Sometimes, however, owing to irregularity of outline in the distal end, the proximal end is uppermost. In this case it is the distal end that adheres. Whichever end is uppermost, it is in the uppermost end, or as it may now be called, the upper surface, that the osculum is formed. Water is drawn into the young sponge through the pores and, finding no outlet, accumulates under the external membrane, the subdermal cavity being at this stage even larger than it is in the adult sponge. Immediately after adhesion the young sponge flattens itself out. This process apparently presses together the water in the subdermal cavity and causes a large part of it to accumulate at one point, which is usually situated near the centre of the upper surface. A transparent conical projection formed of the external membrane arises at this point, and at the tip of the cone a white spot appears. What is the exact cause of this spot I have not yet been able to ascertain, but it marks the point at which the imprisoned water breaks through the expanded membrane, thus forming the first osculum. Before the aperture is formed, it is already possible to distinguish on the surface of the parenchyma numerous channels radiating from the point at which the osculum will be formed to the periphery of the young sponge. These channels as a rule persist in the adult organism and result from the fact that the inhalent apertures are situated at the periphery, being absent from both the proximal and the distal ends of the bud. In the case of floating buds the course of development is the same, except that the osculum, as in the case of development from the gemmule in other species (see Zykoff, Biol. Centrbl. xii, p. 713, 1892), is usually formed before adhesion takes place.
The sponge of S. proliferens is usually too small to afford shelter to other animals, and I have not found in it any of those commonly associated with S. carteri and S. alba.
Owing to its small size S. proliferens is more easily kept alive in an aquarium than most species, and its production of buds can be studied in captivity. In captivity a curious phenomenon is manifested, viz. the production of extra oscula, often in large numbers. This is due either to a feebleness in the currents of the sponge which makes it difficult to get rid of waste substances or to the fact that the canals get blocked. The effluent water collects in patches under the external membrane instead of making its way out of the existing oscula, and new oscula are formed over these patches in much the same way as the first osculum is formed in the bud.
3. Spongilla alba*, Carter.
Spongilla alba, Carter, J. Bombay Asiat. Soc. iii, p. 32, pl. i, fig. 4 & Ann. Nat. Hist. (2) iv, p. 83, pl. iii, fig. 4 (1849) Spongilla alba, Bowerbank, P. Zool. Soc. London, 1863, p. 463 pl. xxxviii, fig. 15. Spongilla alba, Carter, Ann. Nat. Hist. (5) vii, p. 88 (1881). Spongilla alba, Petr, Rozp. Ceske Ak. Praze, Trída, ii, pl. i, figs. 3-6 (1899) (text in Czech). Spongilla alba, Annandale, Rec. Ind. Mus. i, p. 388, pl. xiv, fig. 2 (1907).
Sponge forming masses of considerable area, but never of more than moderate depth or thickness. Surface smooth and undulating or with irregular or conical projections; sponge hard but brittle; colour white or whitish; oscula of moderate or large size, never very conspicuous; radiating furrows absent or very short; external membrane adhering to the substance of the sponge.