The Food of Fi,shes. 29 



where the free waters play in ceaseless torrents, and there 

 they have wrested from stubborn nature a meager living. 

 Although diminished in size by their continual struggle 

 with the elements, they have developed an activity and 

 hardihood, a vigor of life and glow of high color almost un- 

 known among the easier livers of the lower lands. 



The following table (see page 30) will facilitate a com- 

 parison of the records of the different genera. The per- 

 centages were obtained by estimating carefully the ratios 

 of each element of the food of each individual, and aver- 

 aging these ratios for all the individuals of a species. 



Family PEROID^. The Perches. 



This family consists, in this state, of three species — the 

 common yellow perch and the two si^ecies of pike-i^erch or 

 "wall-eyed pike." I have examined the food of seventy- 

 five specimens of this family, so distributed in time and 

 space as to give a satisfactory idea of the usual food. 



Perca AMERICANA, Sclirauk. The Common Perch. Ringed 

 Perch. 



This exceedingly well-known species is most abundant 

 along the shores of Lake Michigan and in the small streams 

 and lakes of the northeastern part of the state, becoming 

 less common to the south and west. In the Illinois River 

 at Peoria and Henry it occurs in limited numbers, but in 

 southern Illinois disappears so completely that even its 

 name (there generally pronounced "pearch") is trans- 

 ferred to a different family, the sunfishes (Oentrarchidae). 



My knowledge of the food of this sijecies is derived from 

 the study of the contents of forty-nine stomachs, of which 

 thirty were from adults and the remaining nineteen from 

 fishes ranging from II inch to four inches in length. Ten lo- 

 calities and as many dates are represented by these speci- 

 mens. Some were taken in the Illinois River, others in Lake 

 Michigan and its southern tributaries, and still others in Fox 

 R. at McHenry, and in the lakes connected with that stream. 

 One lot included in these notes was bought in the Chicago 

 market. They were evidently of the river form of the 

 species, and judging from the contents of their stomachs, 



