32 Records of the Indian Museum, [Vol. XXIV, 



of animals inhabiting these streams ; it was at his suggestion that 

 the work here published was undertaken. 



Apart from their natural position in the animal kingdom, hill- 

 stream fishes maybe divided bionomically into two primary groups. 

 The first group comprises those forms that migrate upstream at 

 certain periods of their lives for spawning, etc.; these may be 

 called the temporary inhabitants of these streams. Fishes of 

 this group travel against the current by muscular effort and do 

 not show, to any great extent, special modifications for life in 

 rapid waters. The members of the second group are the perma- 

 nent residents of the streams and of still smaller torrents and 

 many exhibit extreme adaptations. It is with the latter group 

 that the present paper is concerned. 



The greatest handicap in dealing with the subject was the 

 paucity of material available in the Museum or to be obtained 

 from the streams. Species of many of the genera dealt with 

 in this paper were not only poorly represented, but the specimens 

 often consisted of old and badly preserved individuals quite unfit 

 for detailed morphological investigation. In the hill-streams, on 

 the other hand, there may be plenty of fish, but the readiness 

 with which they seek shelter" underneath stones or the swiftness 

 with which they dart away makes it extremely difficult to obtain a 

 good series of specimens. Most of the species are, therefore, known 

 from very few individuals. Through the kindness of the Director, 

 Zoological Survey of India, I was allowed to make tours in the 

 Naga Hills, the Manipur Valley, the Khasi Hills, the Kumaon 

 Hills, the Kharagpur Hills and the Darjiling Himalayas. Good 

 collections were made at all these places. For histological 

 investigation the material, wherever practicable, was fixed 

 either in f or mol- alcohol or corrosive sublimate ; haematoxylin and 

 eosin have chiefly been used in staining sections of the adhesive 

 apparatus. 



The taxonomy of the Indian hill-stream genera has hitherto 

 been involved in a state of great confusion and this factor greatly 

 impeded the progress of my work. In a series of papers, 1 chiefly 

 dealing with hill-stream forms, I have tried to elucidate the taxo- 

 nomy of those genera of which sufficient material was present 

 in the collection of the Indian Museum, and I have also worked 

 out completely the collections made by myself in Manipur * in 

 order to find out the correct names of the fishes with which this 

 paper is concerned. Besides these I have published recently a 

 paper on some rare and new forms kindly sent to us by Mr. G. E. 

 Shaw from the base of the Darjiling Himalayas. In. interpreting 

 the generic position and specific limits of the various species 

 assigned by Day to Erethistes and Psilorhynchns, I have derived 

 great help from this collection. 



' Hora, Rec. hid. Mus. XXIX, pp. 195-215, pis. x, xi (1919); ibid. XXII 

 pp. 13-19, ibid., XXII, p. 633, pi. x\iv-xxvi (1921). 

 2 Hora. Rec. Ind. Mas. XXII, pp. 165-214(1921). 



