In the ponds of Calcutta a large number of animals are found associated in a more or less definite manner with _Spongilla carteri_. Only one, however, can be described with any degree of certainty as being in normal circumstances an enemy, namely the larva of _Sisyra indica_,[AD] and even in the case of this little insect it is doubtful how far its attacks are actually injurious to the sponge. The larva is often found in considerable numbers clinging to the oscula and wide efferent canals of _S. carteri_, its proboscis inserted into the substance of the sponge. If the sponge dies and the water becomes foul the larvæ swim or crawl away. If the sponge dries up, they leave its interior (in which, however, they sometimes remain for some days after it has become dry) and pupate in a silken cocoon on its surface. Hence they emerge as perfect insects after about a week. [Footnote AD: Needham. Rec. Ind. Mus. iii, p. 206 (1909).] An animal that may be an enemy of _S. carteri_ is a flat-worm (an undescribed species of _Planaria_) common in its larger canals and remarkable for the small size of its pharynx. The same worm, however, is also found at the base of the leaves of bulrushes and in other like situations, and there is no evidence that it actually feeds on the sponge. Injured sponges are eaten by the prawn _Palæmon lamarrei_, which, however, only attacks them when the dermal membrane is broken. A _Tanypus_ larva (Chironomid Diptera) that makes its way though the substance of the sponge may also be an enemy; it is commoner in decaying than in vigorous sponges.