The larvæ of _Sisyra indica_ are commonly found in the oscula of the typical form of _S. alba_ as well as in those of _S. lacustris_ subsp. _reticulata_, and _S. carteri_; but the compact structure of the sponge renders it a less suitable residence for other _incolæ_ than _S. carteri_. In the variety _bengalensis_, as it grows in the ponds at Port Canning, a large number of arthropods, molluscs and other small animals take shelter. Apart from protozoa and rotifers, which have as yet been little studied, the following are some of the more abundant inhabitants of the sponge:--The sea-anemone, _Sagartia schilleriana_ subsp. _exul_ (see p. 140), which frequently occurs in very large numbers in the broader canals; the free-living nematode, _Oncholaimus indicus_[W], which makes its way in and out of the oscula; molluscs belonging to several species of the genus _Corbula_, which conceal themselves in the canals but are sometimes engulfed in the growing sponge and so perish; young individuals of the crab _Varuna litterata_, which hide among the branches and ramifications of the larger sponges together with several small species of prawns and the schizopod _Macropsis orientalis_[X]; the peculiar amphipod _Quadrivisio bengalensis_[Y], only known from the ponds at Port Canning, which breeds in little communities inside the sponge; a small isopod[Z], allied to _Sphæroma walkeri_, Stebbing; the larva of a may-fly, and those of at least two midges (Chironomidæ). [Footnote W: O. von Linstow, Rec. Ind. Mus. i, p. 45 (1907).] [Footnote X: W. M. Tattersall, _ibid._, ii, p. 236 (1908).] [Footnote Y: T. R. R. Stebbing, _ibid._, i, p. 160 (1907); and N. Annandale, _ibid._, ii, p. 107 (1908).] [Footnote Z: Mr. Stebbing has been kind enough to examine specimens of this isopod, which he will shortly describe in the Records of the Indian Museum. _S. walkeri_, its nearest ally, was originally described from the Gulf of Manaar, where it was taken in a tow-net gathering (see Stebbing in Herdman's Report on the Ceylon Pearl Fisheries, pt. iv, p. 31 (1905)).] The peculiarly mixed nature (marine and lacustrine) of the fauna associated with _S. alba_ in the ponds at Port Canning is well illustrated by this list, and it only remains to be stated that little fish (_Gobius alcockii_, _Barbus stigma_, _Haplochilus melanostigma_, _H. panchax_, etc.) are very common and feed readily on injured sponges. They are apparently unable to attack a sponge so long as its external membrane is intact, but if this membrane is broken, they swarm round the sponge and devour the parenchyma greedily. In fresh water one of these fishes (_Gobius alcockii_, see p. 94) lays its eggs in sponges.