I9I5-] 



Fauna of the Chilka Lake : Sponges. 



33 



The free microscleres are slender, spindle-shaped, sharply pointed, slightly curved 

 amphioxi, covered fairly uniformly with short, straight, blunt spines. They are 

 numerous both in the parenchyma and in the dermal membrane. 



The gemmules, though the sponge is never bulky enough to contain many of 

 them, are fully formed and relatively large. They possess a thick pneumatic coat 

 including many spicules. The single foramen is armed with a horny cup or short 

 tubule. The spicules are for the most part tangential to the inner coat but a large 

 number stand upright or nearly upright, giving the surface an irregular appearance 

 like that of the gemmules of the form of 5. alba that I called travancorica. There are 

 also a few horizontal spicules on the surface. 



Diameter of gemmule 



Length of macrosclere (average) 



Thickness , , , , 



Length of gemmule -spicule (average) 



Thickness 



Length of free microscleres (average) 



Thickness 



0.27 mm. 



0-192 ,, 



o-oio „ 



0-098 „ 



0-005 ,. 



0-OI02 ,, 



O'OOI .. 



Type. No. Z.E.V. 6455/7 Ind. Mus. 



Locality. In a small bay at the base of Patsahanipur promontory, Chilka 

 Lake, Orissa, 26-1-14. Salinity of water approximately i-oo6: depth not more than 

 2 feet. 



We found this sponge on one occasion only, but then in considerable numbers. 

 The little spheres or cushions were attached to the free stems of a water-plant. As 

 they were in a small backwater behind a rock where there was much decaying 

 vegetation, I was at first inclined to regard them merely as abortive or abnor- 

 mal individuals of 5. alba which, owing to unfavourable conditions, had developed 

 prematurely. This view would be supported by the fact that in general structure 

 they resemble a little sponge from an aquarium in Calcutta that I regard as an 

 abortive form of S. {Eunapius) carteri. 1 Although, however, the skeleton- spicules of 

 young sponges of S. carteri are often irregular in outline, this feature is by no means 

 strongly marked in the abortive sponge. Both in it and in some forms of S. lacustris 

 that have been found growing in unfavourable environments the gemmules are poorly 

 developed, being not only small but devoid or practically devoid of special micros- 

 cleres; this is also the case in large sponges of S. carteri induced by confinement in 

 an aquarium to produce gemmules prematurely. It is, therefore, an important point 

 in considering the status of 5. nana that its gemmules are fully developed and 

 relatively large : it is clear that the sponge, in the case of the type-specimens, has 

 produced the gemmules and not the gemmules the sponge, for their surface shows no 

 signs of wear or of having been exposed unprotected to the water and many of them 

 were actually in the course of formation when killed, the outer part of their coat not 



1 Faun. Brit. Ind., Freshw. Sponges, etc., p. 126, etc., pi. i, fig. 4 (1911). 



