364 L. Agassiz on Fishes of the Tennessee River. 
than the western and_southern parts of the Union. In this iso- 
tated region of North America, in this zoological island of New 
England, as we may well callit, we find neither Lepidosteus, nor 
Amia, nor Polyodon, nor Amblodon, nor Grystes, nor Centrar- 
chus, nor Pomoxis, nor Ambloplites, nor Calliurus, nor Carpiodes, 
nor Hyodon, nor indeed any of the characteristic forms of North 
American fresh-water fishes, so common everywhere else, with 
the exception of two Pomotis, one Boleosoma, and a few Catos- 
tomus. The study of these features is of the greatest importance, 
inasmuch as it may eventually lead to a better understanding of 
the intentions implied in this seemingly arbitrary distribution of 
animal life. 
Before closing this notice I would remark that there is still 
another very interesting problem respecting the geographical dis- 
tribution of our fresh-water animals, which may be solved by 
the further investigation of the fishes of the ‘Tennessee River. 
This water course, taking the Powells, Clinch and Holston Riv- 
ers as its head waters, arises from the mountains of Virginia 10 
latitude 37°, it then flows S. W. to latitude 34°-25, when it turns 
W. and N. W., and finally empties into the Ohio under the same 
latitude as its sources in 37°. The question now is this: Are 
chief condition of the geographical distribution of our fresh-water 
fi 
o they differ in different stations along its course! 
and if so, are the differences mainly controlled by the elevation 
of the river above the level of the sea, or determined by climatic 
influences corresponding te differences of latitude? We should 
assume that the first alternative was true if the fishes of the upper 
course of the river differed from those of the middle and lower 
course in the same manner as in the Danube, from its source '0 
esth, where this stream flows nearly for its whole length under 
the same parallel. We would on the contrary suppose the secont 
bserved 
circumstances upon the surface of the globe. Nothing, however, 
short of such collections, compared closely with ove ane 
will furnish a reliable answer. I know already from a mere 
alogue of the vernacular names of the fishes from the vicinlt 
Jonesboro, sent me by Dr. Cunningham, and from a few ve 
mens collected by Prof. Erni, late of Knoxville, that the fishes 
the upper and lower course of the Tennessee differ greatly from 
y of 
