k Report on the Zoological Survey of India 



that those I have sketched will be sufl&cient to indicate the nature and 

 extent of the work of the department in this direction. 



Special Lines of Eesearch. 



It is difficult on logical grounds to separate this section of my report 

 from that on touring and field-work. Observations made in the field 

 are just as much research as those made in the laboratory, but the 

 latter are naturally of a more elaborate nature and call for different 

 methods. It is impossible to discuss in detail all the more specialised 

 pieces of research work (rather the tesserae of a mosaic than the finished 

 picture) undertaken in our laboratories in the three years under 

 discussion, and I think it will give a better idea of the scope of our 

 investigations if I sketch the results of one or two special investi- 

 gations that are of greater general interest and more complete in them- 

 selves. The first two that I select were alluded to briefly in my last 

 report, at the time of publication of which they were incomplete. 



The Fauna o£ the Matlah River. — This so-called river is now merely 

 a tidal creek in the Gangetic delta. Its water varies greatly in 

 salinity and is always turbid on account of suspended silt. Dr. S. W. 

 Kemp on investigating its fauna was struck by the resemblance between 

 many of the animals, especially among the fish and Decapod Crustacea, 

 and deep-sea forms, with which he was already acquainted in a fresh 

 condition. The resemblances were in most species quite superficial, 

 depending mainly on colouration, outline and the production of elong- 

 ate filamentous appendages with a sensory function. In at least one 

 instance, however, that of the " Bombay Duck " {Harpodon nehereus), 

 there was a close morphological relationship to deep-water species. Dr. 

 Kemp was able to show that the physical factors in environment 

 common to the abysses of the ocean and a shallow creek in the delta 

 of such a river as the Ganges are a very soft muddy bottom and low 

 visibility. He regards the zoological phenomena, therefore, as mainly 

 due to convergence or parallel evolution, though the case of the 

 Bombay Duck cannot be brought under this heading. Dr. Kemp's 

 paper is published in Vol. XIII of the Records of the Indian Museum. 

 Two of the figures from it are here reproduced (Plate B) to illustrate 

 the superficial resemblance between a deep-sea prawn and one common 

 in the Matlah Eiver. It should be noted that the abnormally long 

 legs are differently constructed in the two species. 



The Fauna of the Inle Lake. — The Inle Lake occupies an isolated 

 basin hollowed out by the dissolving action of water rendered acid by 

 the decay of vegetation in the limestone of the Shan Plateau. It is 

 now very shallow and by no means large but was once probably both 

 much deeper and of much more extended area. The fauna is highly 

 peculiar, particularly so far as the fish and molluscs are concerned. 

 I have discussed it, with the aid of Tr. Kemp, the late Mr. Paiva, 

 Dr. Baini Prashad and other zoologists, in Vol. XIV of our " Kecords," 

 which is entirely devoted to the subject. The most interesting features 

 of the Mollusca are the plasticity and the individual variability of 

 certain forms and the exuberant sculpture of the shells of the 



