(50 



That tlic study here set forth should give us details not to l>e otherwise 

 ohtained of the strugKlc ff>r existence among fishes themselves, goes with- 

 out saying: and tliat it may thus explain some peculiarities of distribu- 

 tion, seems also iMohaljIe. I have thought it not impossible that by tak- 

 ing into account all the data collected, and the mass of related facts. 

 structural, biological, and other, that materials might be found bearing 

 on the interesting question of the pre/;edence in time and the relative 

 evolutionary -importance of desire and effort on the one hand and struct- 

 ural aptitudes on the other. 



Among the purely practical results to be anticipated, are a more accurate 

 knowledge of the conditions favorable to the growth and multiplication 

 of the more important species: the ability to judge intelligently of the 

 fitness of any body of water to sustain a greater number or a more profit- 

 able assemblage of fishes than those occurring there spontaneously; guid- 

 ance as to the new elements of food and circumstance which it will be 

 necessary to sui)ply to insure the successful introduction into any lake or 

 stream of a tish 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 varieties of condition likely to 

 arise. We should derive, in short, from these and similar researches, 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 maintain the supply of food and the incitement to 

 healthful recreation afforded by the waters of the State. 



As a contribution to the general subject, I present herewith a summary 

 account of the food of twelve hundred and twenty-one fishes ot)tained from 

 the waters of Illinois at intervals from 1876 to 1887, and in various months 

 from April to November. These fishes Ijelonged to eighty-seven species of 

 sixty-three genera and twenty-five families. They were derived from 

 waters of every description, ranging from Lake Michigan to weedy stag- 

 nant ponds and temporary pools, and from the ]Mississii)pi and Oliio 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 

 practically adult, so far as the purposes of this investigation are concerned, 

 the remaining three hundred and seven being young, in the first stage of 

 their food and feeding habits. More than lialf these young belonged to a 

 single species, — the common lake white-fish.— but the remainder were well 

 distributed. 



I have arranged the matter under the following general heads: il) a 

 summary statement of the food, so made as to exhibit (a) the kinds and 

 relative importance of the ])rincipal competitions among fishes and {b) the 

 relative value to the principal species of fishes of tlu^ major elements of 

 their food; (2) a brief account of the food of the young: (.3) an examina- 

 tion of the permanency and definiteness of distinctions with respect to 

 food, between different species, and also between higher groups: (4) a re- 

 view of the structures of fishes related to food prehension and to their 

 feeding habits: and. finally. (.")) a classified list of the objects detected in 

 the food of fisiies, with a statement, against eacli object, of the species 

 feeding on it and the number of specimens in which it was found. 



The Food of Adult Fishes. 



An analysis of our facts made with reference to the kinds of fishes eat- 

 ing each of the principal articles in the dietary of the class, and showing 

 the relative importance of these elements in the food of the various 

 species, will exhibit the competitions of fishes for food more clearly and 

 precisely than my earlier discussions, and also the nature and the e'nergy 

 of tlie restraints imiiosed by fislies on the nndtiplication of their principal 

 food species. 



