160 KANSAS UNIVERSITY SCIENCE BULLETIN. 



Ohio, 201,700 miles, twenty-seven species. 



Arkansas, 185,700 miles, twelve species. 



Faxon ('85) says: "The distinction between the species of 

 the upper waters and the lower waters is most marked in rivers 

 that have a heavy fall from their source to their mouth." I 

 have found it interesting to compare the number of species in 

 a stream with its profile. The Mississippi river, exclusive of 

 its tributaries, has a fall of 1462 feet in 2296 miles, and has 

 thirteen species. The Tennessee river, including its principal 

 tributaries, has a fall of 5214 feet in less than half the number 

 of miles, and contains twenty-one species. The Wabash river, 

 in a length of 517 miles, has a fall of 689 feet, and yields twelve 

 species. Of the streams emptying on the south Atlantic coast, 

 the Cape Fear river, with a fall of 130 feet in 172 miles, has 

 three species; the Santee, with its tributaries, a fall of 2658 

 feet in 479 miles, and six species ; the Savannah river, with a 

 length of 314 miles and a fall of 577 feet, three species. Com- 

 jDaring the distribution by states, we find that in the southern 

 United States, where differentiation into species is the greatest, 

 Florida, with a maximum elevation of 828 feet, has five species ; 

 Louisiana, reaching a height of 362 feet, has five ; Mississippi, 

 602 feet, has ten ; Georgia, ranging from sea-level to over 5000 

 feet, has fourteen ; Alabama, sea-level to 2018 feet, has sev- 

 enteen species ; and Texas, sea-level to nearly 8000 feet, has 

 ten species. The range of elevation can give no idea of the 

 profile of a stream or a state, and the reasons for the differences 

 may be much more clearly seen by a glance at a curve plotting 

 the elevation of the stream at different points. In the examples 

 given a profile will show that there is a very great difference 

 in the amount and relative proportion of the mountain, upland 

 and flood-plain portion of the river in each case. Theoretically, 

 other things being equal, the stream offering the most diverse 

 conditions of environment would be expected to have the great- 

 est number of species, and it is evident that even in a river of 

 considerable length a stream with but a small fall can offer 

 comparatively few conditions, while a stream with a heavy fall 

 during the first part of its course may offer a great number. It 

 is very easy to select from the tables illustrations which do not 

 agree with those here given, and I am perfectly aware that the 

 problem is by no means simple or without complications, but 



