HARRIS : CRAYFISHES GENUS CAMBARUS. 53 



the species of fishes occurring in the upper and lower part of 

 the courses of a stream, and in 1854" he pointed out more fully 

 the importance of such investigations. 



In 1868 Cope^ studied the distribution of the fishes of the Al- 

 leghany region and arrived at several very important conclu- 

 sions. Since that time various papers containing data and 

 conclusions on the distribution of the fresh-water fishes have 

 appeared/ and Jordan has presented^ in detail the facts as they 

 are known up to the present time. 



More recently work of much interest has been done in plant 

 and animal ecology. Cowles has published*' a paper of great 

 botanical interest in which he emphasizes the importance of 

 the genetic and dynamic in physiographic ecology. The rela- 

 tion of biology to physiography has been emphasized in papers 

 by Woodworth," Hays and Campbell,- Simpson,^ and Adams. ^^ 

 The results are well summarized by Adams. 



The conclusions and suggestions in these papers, as well as of 

 some others which have appeared, cannot be given in detail 

 here, but those who are acquainted with them will understand 

 my point of view in the compilation of the data dealing with 

 the distribution by river systems. A single genus of a moder- 

 ately large number of species of diverse habitat and wide dis- 

 tribution obviously offers advantageous material for a study of 

 ecological adaptations — more favorable material for comparison 

 than species taken from different genera. 



2. Agassiz, L. Am. Jour. Sci. and Arts, 2d ser., vol. XVII, p. 25, 1854. I have seen only quo- 

 tations from this paper. 



3. Cope, E. D. On the Distribution of the Fresh-water Fishes in the Alleghany Region of 

 Southwestern Virginia. Jour. Acad. Nat. Sci. Phila., n. s., vol. VI, pp. 207-247, lSt58. 



4. Jordan, D. S. On the Distribution of Fresh-water Fishes. Am. Nat., vol. XI, pp. 607-613, 

 1877. 



Jordan, D. S. On the Distribution of the Fishes of the Alleghany Region of South Carolina, 

 Georgia, and Tennessee, with Descriptions of New or Little-known Species. Bull. U. S. Nat. 

 Mus., vol. XII, pp. 7-95, 1878. 



Forbes, S. A. A Catalogue of the Native Fishes of Illinois. Ann. Rep. 111. Fish Com. 1884, 

 pp. 60-89, 1884. 



Jordan, D. S., and Gilbert, C H. List of Fishes Collected in Arkansas, Indian Territory, and 

 Texas, in September, 1884, with Notes and Descriptions. Proc. U. S. Nat. Mus. 1886, pp. 1-25, 1887. 



5. Jordan, D. S. Science Sketches, new ed., Chicago, 1896. 



6. Cowles, H. C. The Physiographic Ecology of Chicago and Vicinity: A Study of the 

 Origin, Development and Classification of Plant Societies. Bot. Gaz., vol. XXXI, pp. 73-108, 145- 

 1S2, 1901. 



7. Woodworth, J. B. The Relation between Base-leveling and Organic Evolution. Amer. 

 Geologist, vol. XIV, pp. 209-235, 1894. 



8. Hays, C. W., and Campbell, M. R. The Relation of Biology to Physiography. Science, 

 n. s., vol. XII, pp. 131-133. 



9. Simpson, C. T. On the Evidence of the Unionidse Regarding the Former Courses of the 

 Tennessee and Other Southern Rivers. Science, n. s., vol. XII, pp. 133-136. 



10. Adams ('01). 



