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 
