no Records of ihe Indian Museum. [Vol. XVI, 



or resting stage in its life-histor}^, perhaps with the structure of a 

 minute hydroid, or more probably encysted in a form that would 

 not be recognizable with our present knowledge. 



The most interesting results obtained in the streamlets at 

 Khandalla were those bearing on adaptation to environment in 

 fish and molluscs. 



Notes resulting from a tour of the kind cannot be exhaustive, 

 but our knowledge of the bionomics and environment of the aqua- 

 tic fauna of India is still in its preliminary stage, in which it is, 

 in my opinion at any rate, worth while to publish notes of the 

 kind, even at the risk of being superficial. 



I must be held wholly responsible for all statements made in 

 those sections of the paper in the superscription of which no 

 author's name is given. 



I. The Limnocnida pool in the Yenna river at Medha. 



The Yenna or Vena is a stream of a type very common in 

 hilly districts in Peninsular India. In the wet season it may be 

 described as a small river in which deep pools alternate with 

 rapids obstructed by rocks of irregular shape. In dry weather, 

 however, the pools shrink considerably, while the rapids are re- 

 duced to a mere trickle of water or even disappear altogether, 

 leaving the pools completely isolated. The bed of the stream is 

 for the most part rocky, with gravelly reaches , but in the pools 

 it is covered with a la3^er of mud and vegetable debris. As in all 

 the smaller tributaries near the source of the Kistna, the water 

 contains an abundance of very finely divided silt never com- 

 pletely deposited, and is, therefore, opaque and brownish. After 

 heavy rain it is further contaminated with red mud, from the 

 Mahableshwar plateau, that seems to be particularly inimical to 

 animal life. The pools are practically devoid of aquatic vegeta- 

 tion. The temperature of the water of the pools must rise to a 

 considerable height in the hot season ; at other times of year it is 

 strictly temperate. 



The pool in which Limnocnida indica was originally found is, 

 including the gorge at its upper end, about 50 yards long and a 

 stone's throw across ; its width must vary slightly with the sea- 

 sons. A photograph of it is published by Gravely and Agharkar in 

 Rec. Ind. Mus. VII. In March the water is 7 to 12 metres deep, 

 but must be considerably deeper in the " rains." In March there 

 is very little current, as the rapid above the pool is then small 

 and feeble. A tall man could stride across the outlet. The rocky 

 bottom is very irregular ; in the lower part of the pool it is 

 covered with a fairly deep layer of gravel mixed with mud, but in 

 the upper part, which is the deepest, there is onh' a sparse 

 coating of small pebbles and vegetable debris. A large irregular 

 rock rises far above the surface in the lower part and a foot-bridge 

 spans the upper part at a considerable height above the water. 

 It is impossible, owing to the opacity of the water, to see the 



