44 



Memoirs of the Indian Museum. 



[Voi,. V, 



(both in the outer channel and in the main area) in September, but several sponges 

 from oyster- shells from Manikpatna taken in that month do not contain these bodies. 

 They are only present in specimens on leaves and stalks. Possibly the stimulus 

 necessary for the development of gemmules in this species may be set up by the decay 

 of vegetable matter, but more evidence is necessary before a definite opinion can be 

 expressed. In structure the gemmules differ considerably from those of L. lacustris 

 (fig. ii, p. 48) and are hardly distinguishable from those of the less robust phase of 

 Suberites senceus (fig. 7, p. 40), having thin shells without foramina and being arranged 

 in a single adherent layer at the base of the sponge. 



L. aquae-dulcioris differs in colour in different circumstances. Often it is hyaline 



Fig. 9. — Laxosuberites aquae-dulcioris (Annandale). 

 Part of the skeleton of a sponge on a leaf of Halophila, x 100. 



and quite colourless; sometimes it is of a more or less deep orange-yellow, and 

 occasionally bright green. The yellow colour seems to be due, probably in all cases, 

 to the accumulation of food-material in cells that have taken part or are about to 

 take part in the formation of eggs or gemmules, while the green is due to the 

 growth in the substance of the sponge of a branching alga of simple structure, which 

 only grows if the organism is exposed to light. As the sponge usually affects 

 sheltered situations, this is not very often the case. 



I will discuss the affinities of this sponge together with those of L. lacustris on a 

 subsequent page (p. 50). 



