286 Dispersion of Fresh-water Fishes 



materially differ in their evolution above the sea, but flow under 

 different latitudes. Now, a few collections from different sta- 

 tions along this river, like that sent me by Dr. Newman from 

 the vicinity of Huntsville, would settle at once this question, 

 not for the Tennessee River alone, but for most rivers flowing 

 under similar circumstances upon the surface of the globe. 

 Nothing, however, short of such collections, compared closely 

 with one another, will furnish a reliable answer. . . . Who- 

 ever will accomplish this survey will have made a highly valu- 

 able contribution to our knowledge." 



Conclusions of Cope. Certain conclusions were also sug- 

 gested by Prof. Cope in his excellent memoir on the fishes of 

 the Alleghany region* in 1868. From this paper I make the 

 following quotations: 



"The distribution of fresh- water fishes is of special impor- 

 tance to the questions of the origin and existence of species in 

 connection with the physical conditions of the waters and of 

 the land. This is, of course, owing to the restricted nature of 

 their habitat and the impossibility of their making extended 

 migrations. With the submergence of land beneath the sea, 

 fresh-water fish are destroyed in proportion to the extent of 

 the invasion of salt water, while terrestrial vertebrates can re- 

 treat before it. Hence every inland fish fauna dates from the 

 last total submergence of the country. 



" Prior to the elevation of a given mountain chain, the courses 

 of the rivers may generally have been entirely different from 

 their later ones. Subsequent to this period, they can only 

 have undergone partial modifications. As subsequent sub- 

 mergences can rarely have extended to the highlands where 

 such streams originate, the fishes of such rivers can only have 

 been destroyed so far as they were unable to reach those ele- 

 vated regions, and preserve themselves from destruction from 

 salt water by sheltering themselves in mountain streams. On 

 the other hand, a period of greater elevation of the land, and 

 of consequent greater cold, would congeal the waters and 

 cover their courses with glaciers. The fishes would be driven 

 to the neighborhood of the coast, though no doubt in more 



* On the Distribution of Fresh-water Fishes in the Alleghany Region of 

 Southwestern Virginia. Journ. Acad. Nat. Sci., Phila., 1868, pp. 207-247. 



