102 The First Food of the Common White -Fish. 



better opportunity for the development of animal life, to which 

 fact was doubtless due th^ occurrence of insect larva3 and Ento- 

 mostraca in the intestines of the fishes reared in it. The situation 

 of the spring, on the other hand, was particularly unfavorable, as 

 it was under the hatchery, and consequently in the dark. 



The observations above described on the specimens kept in 

 spring water, have but little value for the reason that evidently 

 very little food was contained in the water flowing through their 

 cage. The vegetation in the streams being chiefly filamentous 

 Algae and the number of Entomostraca apparently trivial, very 

 little of either vegetable or animal food could reach the little 

 prisoners. It is not surprising, therefore, that notwithstanding 

 their greater age and the higher temperature of the water in which 

 they were kept, a much smaller ratio of the specimens had taken 

 food than of those captured in the hatchery. From the contents 

 of their intestines we can only infer that these fishes, reduced to a 

 desperate strait by starvation, will snatch at almost anything con- 

 tained in the water. The result obtained by a study of those from 

 the hatching house was more significant, but still unsatisfactory. 

 It seemed to indicate that in confinement white-fish fry will feed 

 upon both animal and vegetable structures to some extent, and 

 that they can be induced to take minute fragments of the higher 

 crustaceans, but not in sufficient quantity to keep them alive. 

 The fact that animal food was more abundant than vegetable in 

 this last lot, indicates nothing of their natural preference, since it 

 was doubtless also more abundant in the watet containing them. 



More light was thrown upon the earliest food habits of these 

 fishes by the discovery of raptatorial teeth upon the lower jaw, 

 than by these dissections of their alimentary canals. All the fam- 

 ilies of fishes which I had previously studied whose young were 

 provided with teeth were found strictly dependent at first upon 

 Entomostraca and the minuter insect larva?; while only those 

 whose young were toothless fed to any considerable extent upon 

 other forms. The discovery of teeth in the young white-fish, 

 therefore, placed this species definately in the group of those car- 

 nivorous when young. The fact that the adult was itself tooth- 

 less interfered in no way with this inference, because other tooth- 

 less fishes (Dorsoma) whose young were furnished with teeth, had 

 been found carnivorous at an early age. 



