ON DISTRIBUTION. 21 



The range of species is much, mere closely restricted 

 than that of genera. As before remarked, very few 

 species that occur in India are to be found elsewhere, 

 though most of the Indian species are met with all 

 over the Indian continent. There are a few local 

 species; some that are found only in Assam, some 

 only in the Himalayan streams, some only in the 

 streams of the Neilgherry hills in Madras, and so on, 

 but these are generally species that live in rapid hill 

 streams ; those that inhabit still water, tanks, and 

 the larger rivers of the plains are to be met with all 

 over India. 



A number of interesting questions suggest them- 

 selves in connection with this subject. How can a 

 fish, take, for instance, Easbora daniconius, have spread 

 from India to the islands of the Eastern Archipelago, 

 or vice versa ? Does this point to a time when these 

 islands were connected with the main land? If 

 this question is to be answered in the affirmative, we 

 have here data for inferring the comparative antiquity 

 of this species, as it is evident that it must have ex- 

 isted before the separation of these islands from the 

 main land took place, and cannot have undergone any 

 perceptible variation since that time. 



Again, take a genus, Labeo, for instance, of which 

 some species are confined to India, while others closely 

 allied are found in Africa. This is essentially a tro- 

 pical genus, which fact accounts for its not spreading 

 northwards into Europe, but it would seem as if the 

 relative positions of land and sea must have been dif- 



