DISPERSION OF FRESH-WATER FISHES. 123 



River to the James, or from the Neuse to the 

 Santee, by descending to the lower courses of the 

 rivers, and thence passing along either through 

 the swamps or by way of the sea. The lower 

 courses of these streams, warm and muddy, are 

 uninhabitable by such fishes. Such transfers are, 

 however, possible farther north. From the rivers 

 of Canada and from many rivers of New England 

 the Trout does descend to the sea and into the sea, 

 and farther north the White-fish does this also. 

 Thus these fishes readily pass from one river 

 basin to another. As this is the case now every- 

 where in the North, it may have been the case 

 farther south in the time of the glacial cold. We 

 may, I think, imagine a condition of things in 

 which the snow-fields of the Alleghany chain might 

 have played some part in aiding the diffusion of 

 cold-loving fishes. A permanent snow-field on the 

 Blue Ridge in western North Carolina might ren- 

 der almost any stream in the Carolinas suitable 

 for trout, from its source to its mouth. An in- 

 creased volume of colder water might carry the 

 trout of the head-streams of the Catawba and the 

 Savannah as far down as the sea. We can even 

 imagine that the trout reached these streams in 

 the first place through such agencies, though of 

 this there is no positive evidence. For the pres- 

 ence of trout in the upper Chattahoochee, we 

 must account in some other way. 



It is noteworthy that the upland fishes are 

 nearly the same in all these streams, until we 

 reach the southern limit of possible glacial in- 

 fluence. South of western North Carolina, the 



