This sea-anemone, which has only been found in the delta of the Ganges, offers a most remarkable instance of what appears to be rapid adaptation of a species to its environment. The typical form, which was described in 1869 by Stoliczka from specimens taken in tidal creeks and estuaries in the Gangetic area and in the ponds at Port Canning, is found attached to solid objects by its basal disk. The race (subsp. _exul_), however, that is now found in the same ponds has become elongate in form and has adopted a burrowing habit, apparently owing to the fact that the bottom of the ponds in which it lives is soft and muddy. In addition to these four species a minute hydroid belonging to the order Gymnoblastea and now being described by Mr. J. Ritchie has been taken in the ponds at Port Canning. It is a very aberrant form. FRESHWATER COELENTERATES OTHER THAN HYDRA. _Hydra_ is the only genus of coelenterates as yet found in fresh water in India, but several others have been discovered in other countries. They are:-- (1) _Cordylophora lacustris_, Allman (1843). Hincks, Hist. Brit. Hydr. Zooph. p. 16, pl. iii, fig. 2 (1868). This is a branching hydroid that does not produce free medusæ. It forms bushy masses somewhat resembling those formed by a luxuriant growth of _Plumatella fruticosa_ (pl. iii, fig. 1) in general appearance. _C. lacustris_ is abundant in canals, rivers, and estuaries in many parts of Europe and has recently been found in the isolated salt lake Birket-el-Qurun in the Fayûm of Egypt. (2) _Cordylophora whiteleggei_, v. Lendenfeld (1887). Zool. Jahrb. ii, p. 97 (1887). A species or race of much feebler growth; as yet imperfectly known and only recorded from fresh water in Australia. _Cordylophora_ is a normal genus of the class Hydrozoa and the order Gymnoblastea; the next four genera are certainly Hydrozoa, but their affinities are very doubtful. (3) _Microhydra ryderi_, Potts (1885). Potts, Q. J. Micr. Sci. London, l, p. 623, pls. xxxv, xxxvi; Browne, _ibid._ p. 635, pl. xxxvii (1906). This animal, which has been found in N. America and in Germany, possesses both an asexual hydroid and a sexual medusoid generation. The former reproduces its species by direct budding as well as by giving rise, also by a form of budding, to medusæ that become sexually mature. The hydroid has no tentacles. (4) _Limnocodium sowerbii_, Lankester (1880). Lankester, Q. J. Micr. Sci. London, xx, p. 351, pls. xxx, xxxi (1880); Fowler, _ibid._ xxx, p. 507, pl. xxxii (1890). There is some doubt as to the different stages in the life-cycle of this species. The medusa has been found in tanks in hot-houses in England, France and Germany, and a minute hydroid closely resembling that of _Microhydra ryderi_ has been associated with it provisionally. (5) _Limnocodium kawaii_, Oka (1907). Oka, Annot. Zool. Japon. vi, p. 219, pl. viii (1907).