40 



office of reproduction, they do little but to search for food and 

 to eat, and avoid being eaten in turn ; consequently, if we seek 

 to measure or estimate their function in the general system 

 of life in any region or locality, we are limited chiefly to their 

 food relations, immediate and remote. 



Among the purely practical results to be anticipated from 

 such a study, are a more accurate knowledge of the conditions 

 favorable to the growth and multiplication of the more import- 

 ant species ; the ability to judge intelligently of the fitness of 

 any body of water to sustain a greater number or a more 

 profitable assemblage of fishes than those occurring there 

 spontaneously ; guidance as to the new elements of food and 

 circumstance which it will be necessary to supply to insure the 

 successful introduction into any lake or stream of a fish not 

 native there ; and a clear recognition of the fact that intelligent 

 fish-culture must take into account the necessities of the species 

 whose increase is desired, through all ages and all stages of 

 their growth, at every season of the year, and under all varie- 

 ties of condition likely to arise. 



We should derive, in short, from these and similar re- 

 searches, a body of full, precise, and significant knowledge to 

 take the place of the guess-work and empiricism upon which 

 we must otherwise depend as the basis of our efforts to main- 

 tain and increase the supply of food and the incitement to 

 healthful recreation afforded by the waters of the country. 



As a contribution to the general subject, I present herewith 

 a summary account of the food of twelve hundred and fifteen 

 fishes, obtained from the waters of the State of Illinois at in- 

 tervals from 1876 to 1887, and in various months from April 

 to November. These fishes belonged to eighty-seven species 

 of sixty-three genera and twenty-five families. They were 

 taken from waters of every description, ranging from Lake 

 Michigan to weedy stagnant ponds and temporary pools, and 

 from the Mississippi and Ohio rivers to the muddy prairie 

 creeks, and the rocky rivulets of the hilly portions of the State. 

 Nine hundred and fourteen of the examples studied were prac- 

 tically adult, so far as the purposes of this investigation are con- 

 cerned, the remaining three hundred and one being young, ini 



