296 



accidental in its denotation. It usually includes everything 

 which it was convenient or desirable to catalog under one ac- 

 cessions number, with a mention of the date, place, and body 

 of water from which the collection came, and, in the majority 

 of cases, particulars concerning the apparatus used and the 

 more notable features of the situation. It may cover at one 

 time the product of a single haul of a small minnow seine from 

 a rivulet or a pond, and at another time that of a number of 

 longer hauls with a larger seine from a great lake or from a 

 considerable stretch of the course of a great river; and in this 

 discussion no account has been taken of differences of condi- 

 tion, season, or time of day, represented by the several acces- 

 sions numbers. 



If each collection had been made as much like every other 

 as practicable in respect to the apparatus used, the proportion- 

 ate area covered, and the definiteness and distinctness of the 

 unit of environment from which it was drawn; if these ecologic- 

 al situations had been skilfully chosen, fully described, and 

 thoroughly "sampled" as to the contents in fishes; and if col- 

 lections, of moderate size but ample in number for the territory 

 covered, had been judiciously repeated for each situation at dif- 

 ferent seasons and under varying conditions— we should doubt- 

 less have obtained for our tables coefficients capable of yield- 

 ing a larger and more complex knowledge than I have here 

 presented of the local distribution of fishes under the influence 

 of their environment. 



In a later paper, in course of preparation, the writer intends 

 to discuss, in a similar manner, the local and ecological rela- 

 tions of all the species obtained from a limited area— that of 

 the Wabash valley in Illinois. 



Acknowledgments. 



For a large part of the materials of this paper, both speci- 

 mens and field observations, I am indebted to a considerable se- 

 ries of former and present assistants of the State Laboratory 

 of Natural History — most largely to Professor H. Garman, Pro- 

 fessor H. A. Surface, Mr. Wallace Craig, Mr. Thomas Large, and 



