62 Indian Gasteropoda. [No. 2, 



the distribution of aquatic animals, especially that of fishes. If we 

 examine the fishes of the rivers of the United States, peculiar species 

 will be found in each basin, associated with others which are common 

 to several basins. Thus the Delaware river contains species not found 

 in the Hudson. But on the other hand, the pickerel is found in both. 

 Now, if all animals originated at one point and from a single stock, 

 the pickerel must have passed from the Delaware to the Hudson or 

 vice versa, which it could only have done by passing along the 

 sea shore or by leaping over large spaces of terra firma ; that is to say, 

 in both cases it would be necessary to do violence to its organisation." 

 This last argument must of course stand for what it is worth, and 

 were it alone, would not be worth much, but we have here, with fish, 

 as I have shown to be the case with Gasteropods in India, the grand 

 fact of certain few species of enormous range, compared with the 

 limited extent of their more numerous congeners and the absurdity of 

 supposing that they have been thus widely distributed by any physical 

 agency, which has left the great majority unaffected by its operation. 

 Hence my reasons for leaning towards the " sporadic" theory, for 

 some species at least, not singly at all events, I am glad to see, if 

 however, in company with no other physiologist than Louis Agassiz. 

 I cannot conclude these observations without quoting a passage from 

 the vitriolic pen of Dr. Knox, in his work on Race, where, though 

 he holds tliat " Time and developement change all things" (page 94,^) 

 yet is very bitter on the absurdity of supposing that accident has 

 anything to do with such changes. Knox on Race, page 90, " When 

 I am told that there is a short-legged race of sheep somewhere in 

 America, the product of accident, my reply is simply, I do not 

 believe it, even although to make the story look better, it has been 

 added that from among the few short-legged sheep accidentally 

 produced in the flock, the owner was careful to extrude the long- 

 legged ones, and so at last his whole flock became short-legged, and 

 he had no more trouble with it. — It is the old fable of Hippocrates 

 and the Macrocephali reduced to something like a scientific formula. 

 Transferred from sheep, it has been made the basis of a theory of 

 race of mankind, reducing all to accident. By accident a child darker 

 than the rest of the family is bom; when this happens in the present 

 day, it is also by courtesy called an accident, but its nature is well 



