42 Memoirs of the Indian Museum. [Vol. V, 



interesting as suggesting a reason, or rather as supporting a suggestion already 

 advanced, 1 for the fact that sponges of different kinds frequently grow over molluscs 

 or their eggs 2 and that the shells or egg-cases are found full of sponge-substance. 



The case of hydroid colonies buried in sponges is somewhat different. In in- 

 stances such as the present one their vital parts may serve as food for the sponge, but 

 in others the association is apparently symbiotic and the two organisms afford mutual 

 support the one to the other without suffering in consequence. 3 



Genus LAXOSUBERITES, Topsent. 

 1896. Laxosuberites , Topsent, Mém. Soc. zool. France, IX, p. 126. 

 1900. ,, id. , Arch Zool. expêrim. (3) VIII, p. 184. 



Topsent (1900) defines this genus as having the skeleton composed of ascending 

 columns in which the spicules are all orientated in one direction. Neither of the two 

 species found in the Chilka I v ake agrees precisely, when fully developed, with this 

 definition, for the spicule- fibres that form the main element in the skeleton are to a 

 large extent horizontal and there are also many non-fasciculated horizontal spicules 

 in the choanosome and basal membrane that may be regarded as a part of the 

 skeleton. However, the peculiarities of these species are obviously correlated with 

 the method of growth and certainly do not justify generic separation from L. rugosus 

 (Schmidt) , the type-species of the genus. Their relationship to it is discussed 

 on p. 50. 



According to Topsent, Schmidt' s Suberites pallidum, which was originally 

 described from a Mediterranean lagoon, is synonymous with L. rugosus. The genus 

 is also represented in the fauna of the Black Sea and other enclosed waters and 

 would seem to be one peculiarly capable of adapting itself to life in such situations. 

 A remarkable adaptation of the gemmules of one of the Chilka species is described 

 here (pp. 48, 49). 



Laxosuberites aquae-dulcioris (Annandale). 



(Plate iv, figs. 5,6.) 



1914. Suberites aquae-dulcioris , Annandale, Rec. Ind. Mus., X, p. 157, pi- xi, 

 fig. 1. 



I have little to add to the description of this sponge published in 1914, so far 

 as its structure is concerned. Attention may be invited, however, to the peculiar 

 spiral arrangement of the spicules round the broader vertical canals (pi. iv, 

 fig. 6a) and to the fact that the sponge occurs in two somewhat distinct phases 

 of growth in accordance with the nature of the surface to which it is attached. 

 When it is growing on an oyster-shell or a stick it is rather more robust and has 

 the skeleton distinctly better developed than when it is attached to the leaves and 



1 Annandale, Faun. Brit. Ind., Freshw. Sponges, etc., p. 94 (1911). 

 1 Herdman, lourn. Linn. Soc. (Zool.) XXXII, p. 271 (1914). 

 8 Alcock, Ann. Mag. Nut. Hist. (6) X, p. 208 (1892). 



