32 



Records of the Indian Museum. 



[Vol., VIII, 



It is noteworthy that the means whereby the fishes of the 

 streams of the Himalayas adhere to rocks are analogous to those 

 adopted by the tadpoles which live in the same environment. 

 N emachilus rupicola, as has already been stated, clings to rocks 

 b}^ means of the smooth skin of its belly and of its enlarged lips, 

 just as the tadpole of Megalophrys parva does; several other 

 mountain Cyprinidae have their mouths modified in a manner that 

 would suggest their being used in the same way as the lips of Rana 

 liehigii, while Discognathus lamta certainh^ adheres to the bottom 

 in rapid water very largely by means of its lips, which recall those 

 of the unidentified Ranid tadpole of the Abor foot-hills. The 

 Silurid genera Pseudecheneis and Glyptosternum , on the other hand, 

 cling by means of a separate abdominal sucker as the tadpole of 

 R. afghana does. 



There can be no doubt that these are instances of convergence, 

 and there is some evidence that even in the case of the tadpoles of 

 mountain streams, the same method of adhering to fixed bodies in 

 rapid- running water has been acquired independently in some 

 instances by different species. The lips of the tadpole of Bufo 

 penangensis ,^ for example, appear to resemble closely those of the 

 unidentified Abor larva, which must certainly be assigned to the 

 Ranidae, and enlarged lips like those of Rana liehigii are found in 

 different species the adults of which are by no means closely allied. 

 It can hardly be that the adaptation of such tadpoles, striking as 

 it is, has been brought about b}^ genetic relationship between the 

 different species that possess it. The adults of most of the Abor 

 frogs and toads have developed adhesive disks on their fingers 

 without being in all cases closely related to one another, and we 

 must suppose that the development of special abdominal suckers 

 or of greatl}^ enlarged lips is a similar phenomenon due, directly 

 or indirectly, to environment rather than to the possession of a 

 common ancestry by animals which have undergone parallel evo- 

 lution in one particular. 



Part III— GEOGRAPHICAI.. 



GEOGRAPHICAI, IvIST of the species in the COLI.ECTION. 



1 Flower, P.Z.S., 1899, p. 909. 



