Food BcJations of Firsh-Wdfrr Fishes. 497 



While small lishes of all sorts are evidently competitors 

 for food, this competition is relieved to some extent by differ- 

 ences of breeding season, the species dropping in successively 

 to the banquet, some commencing in very early spring, or even, 

 like the white-tish, depositing their eggs in fall, that their 

 young may be the first at the board, while others delay until 

 June or July. The most active breeding period coincides, 

 however, with that of the greatest evolution of Entomostraca 

 in the backwaters of our streams; that is, the early spring. 



That large adult fishes, with fine and numerous rakers on 

 the gills — like the shovel-fish and the river carp — may com- 

 pete directly with the young of all other species, and tend to 

 keep their numbers down by diminishing their food supply — 

 especially in times of scarcity — is very probable, but is not 

 certainly true; for these larger fishes have other food resour- 

 ces also, and may resort to Entomostraca only when these are 

 superabundant, thus appropriating the mere excess above 

 what are required for the young of other groups. 



ON THE DEFINITENESS AND PERMANENCY OF 

 THE FOOD HABITS OF FISHES. 



It is always posssible that the seemingly specific differences 

 of food exhibited by data derived from miscellaneous collec- 

 tions not strictly comparable as to dates and localities, are 

 really due to differences of circumstance affecting the represent- 

 atives of the species, and not to differences in the food habits 

 or the regimen of the species in general. Date, locality, and 

 other circumstantial conditions, may have more to do with the 

 distinctions of food detected than structure and specific habit. 

 It is true that the probability of such errors of inference is 

 reduced to a minimum where alimentary peculiarities can be 

 clearly correlated with peculiarities of structure, as has usually 

 been done in my discussions; but to test still further the dis- 

 tinctness of species and genera with respect to food habits and 

 preferences, I have assorted my observations according to dates 

 and localities of the collections on which they were made and 

 have compared species with species as occurring under the 



