50 Journal of the Asiatic Society of Bengal. [February, 1912. 
being subjected to the heat of summer. It igs therefore 
probable that there is a mean temperature which, in the case 
ere are, however, a considerable number of simply 
organized aquatic animals which in this country undergo the 
annual crisis in their life-cycle not at the beginning of the 
hot weather, but at the beginning or during the course of 
the dry, that is to say, the cold weather. Without exception 
these animals either live in very shallow water or are fixed 
to solid objects near the surface. They are obliged t 
tect themselves from desiccation, but it is possible that the 
actual cause of the change in their case also is a rise in the 
we find different sponges growing side by side but in an 
entirely different physiological state. The most striking in- 
stance I know is that of the sponges Spongilla bombayensis and 
Corvospongilla lapidosa in Bomba, Thes 
are found together on the lower surface of stones. In the 
month of November, however, C. lapidosa ig in full vegetative 
vigor, while S. bombayensis, in absolutely identical! conditions 
blasts or 
IV. 
The last topic on which I 
that of the direct effect of cha 
propose to touch to-night is 
nges In environment on simply 

et eee 


! Annandale, Rec. Ind. Mus., I, p..267 (1907). 
