6go Memoirs of the Indian Museum. [Vol. V, 



extensive evaporation from the surface. As Anuandale and Kemp point out (loc. 

 cit., p. n). " In a lagoon of the size and shallowness of the Chilka Lake evaporation 

 must, especially in a tropical climate, be more than considerable and doubtless plays 

 a great part in the phenomena we have been discussing. We have no means of 

 estimating the exact influence of this factor, but it is not unreasonable to suppose 

 that beyond compensating for the comparatively small amount of fresh water that 

 comes from the Mahanaddi system in the dry season, it also plays an important part 

 in inducing an inflow from the sea. ' Any inflow from the sea must, however, de- 

 pend on the existence of a free channel between the two areas, and although I have 

 been unable to obtain any direct evidence that such was actually the case, the serang 

 of the launch informed me that this channel was closed in November, 1919. 



Part II. FAUNA. 



By N. Annandale. 



The chief object of these notes is to put on record changes in the invertebrate 

 fauna of the south-western extremity of the Chilka Lake that took place between 

 the years 1914 and 1919-20. I have also added one or two particulars that sup- 

 plement statements made in former parts of this volume. My observations were 

 made in August, September, October and December, 1919, and in April and June, 

 1920. A few notes were also obtained in July and August of the latter year. 



Porifera. 



Three species of sponge were found in Rambha Bay in 1914, namely Cliona 

 vastifica Hancock, Suberites sericeus Theile, and Laxosuberites lacustris (Annandale). 

 All of these belong to marine genera. In the rainy season and in December, 1919, 

 Laxosuberites lacustris was still common on the lower surface of stones in the landing 

 stage at Barkuda, but no specimens of the other two sponges were found, and by 

 April, 1920, the Laxosuberites had also disappeared. One of the most noteworthy 

 changes in the fauna of the bay was the appearance in it of the freshwater sponge 

 Spongilla alba Carter in great abundance. In 1915 I wrote of this sponge, " In the 

 Chilka Lake its distribution is somewhat remarkable. It occurs on all the rocks of 

 the northern region, often growing luxuriantly and covering considerable areas, and 

 is found among loose algae in the outer channel. In sheltered inlets among the 

 rocks its gemmules often form a scum on the surface. South of Kalidai I. it is not 

 present in the lake, although many rocks apparently suitable for its growth are si- 

 tuated round Rambha Bay. . . . We found it growing actively and producing larvae 

 in water of sp. gr. of 1-0065, but it cannot exist in water that never becomes fresh or 

 practically fresh." 



At the end of July, 191 9, and on several occasions in the next month I found 

 dead sticks on both the north and the south shore of Barkuda covered with dead 

 sponge of this species containing numerous gemmules. In September and October 

 small sponges were common on the lower surface of stones on both sides of the bay. 

 and my nets were on several occasions completely blocked up by masses of weed 



