102 Memoirs of the Indian Museum. [Voi,. V, 



that are allowed to die iu water the pigment of the spots begin to f< run" imme- 

 diately, staining the surrounding medium. The Ennur specimens were of all sizes 

 from a diameter of about 3 cm. to about 20 cm. 



These facts, taken in conjunction with the observations recorded on Halianthus 

 limnicola and Edwardsia tinctrix on pp. 91, 95 of this paper, justify an expression of 

 the belief that some individuals of certain coelenterate species, if forced to live tempora- 

 rily in water of very low specific gravity (i.e. greatly decreased salinity), are able to 

 survive in a state of quiescence or torpidity for considerable periods, and that the 

 most obvious direct structural effect of such conditions is a shrinkage of the mesogloea. 

 If unduly prolonged these conditions cause the deaths of many individuals. The 

 more marked results at Ennur, as compared with those noticed in the Chilka L,ake, 

 were probably due to the greater suddenness of the change. 



In the Chilka L,ake, but not at Ennur, a small amphipodous crustacean was 

 almost invariably observed among the tentacles on the mouth-arms of large indivi- 

 duals of A . rabanchatu and occasionally also on the subumbrellar surface. It was 

 not present on very young medusae. In the gastric cavity of these latter, among 

 the gastric filaments, ova were frequently observed, giving, together with the large 

 relative size of the filaments, a false appearance of sexual maturity. The ova, 

 however, were not confined to the gastric cavity but occurred scattered through- 

 out the vascular system and in particular in the circular canals; they are shown 

 as white spots in the photographs of young medusae reproduced on plate vi. 

 A microscopic examination revealed no ovarian tissue, and there can be no doubt 

 that the ova were not proper to the medusae. Mr. T. Southwell has been kind 

 enough to examine a series of well-preserved specimens. He agrees with me in 

 thinking that the eggs are not those of the commensal amphipod but probably 

 belong to some helminth parasite. They are in various stages of segmentation and 

 the formation of a blastula, but unfortunately have not reached in any case a" higher 

 stage of development and have not as eggs any distinctive structural character. In 

 size and shape, however, they closely resemble eggs found with immature Distomid 

 Trematoda in the canals of a Ctenophore common in the Chilka Iyake (p. 118). No 

 eggs of the kind were observed in adult medusae. 



The main breeding season of A. rabanchatu occurs in the Chilka Lake, to judge 

 from the condition of the gonads in specimens, towards the end of the cold weather, 

 i.e. in February and March. 



HYDROZOA. 



(Plate ix, in part.) 



We obtained in the Chilka L,ake specimens of eight or nine species of Hydrozoa, 

 representing four orders, seven families and eight or nine genera. The alternative 

 numbers in species and genera are due to doubt as to the association of a medusa 



