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the distribution of aquatic animals, especially that of fishes. Ti we 
examine the fishes of the rivers of the United States, peculiar species 
will be found im 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 versd, 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 wnaffected 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 that “‘ Time and developement change all things” (page 94, ) 
yet is very bitter on the absurdity of supposing that accipEenT has 
anything to do with such changes. Knox on Race, page 90, ‘“‘ When 
T 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 i.—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 accedent. By accident a child darker 
than the rest of the family is born; when this happens in the present 
day, it is also by courtesy called an accident, but its nature is well — 
