LETTER TO MR, GEORGE TICKNOR. 685 



TO MR. GEORGE TICKNOR. 



Nahant, October 24, 1863. 



My dear Sir, — Among the schemes which 

 I have devised for the improvement of the 

 Museum, there is one for the reahzation of 

 which I appeal to your aid and sympathy. 

 Thus far the natural productions of the rivers 

 and lakes of the world have not been com- 

 pared with one another, except what I have 

 done in comparing the fishes of the Danube 

 with those of the Rhine and of the Rhone, 

 and those of the great Canadian lakes with 

 those of the Swiss lakes. 



I now propose to resume this 'subject on 

 the most extensive scale, since I see that it 

 has the most direct bearing upon the trans- 

 mutation theory. . . . First let me submit 

 to you my plan. 



Rivers and lakes are isolated by the land 

 and sea from one another. The question is, 

 then, how they came to be peopled with in- 

 habitants differing both from those on land 

 and those in the sea, and how does it come 

 that every hydrographic basin has its own in- 

 habitants more or less different from those of 

 any other basin ? Take the Ganges, the Nile, 

 and the Amazons. There is not a living being 



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