6o 



only those whose young were toothless fed to any considerable 

 extent upon other forms. The discovery of teeth in the young 

 whitefish, therefore, placed this species definitely in the group 

 of those carnivorous when young. The fact that the adult was 

 itself toothless interfered in no way with this inference, because 

 other toothless fishes (Dorosoma) whose young were furnished 

 with teeth, had been found carnivorous at an early age. 



The inconclusive character of the results thus far obtained, 

 made it necessary to attempt to imitate more closely the natural 

 conditions of the young when hatched in the lake. In Febru- 

 ary, i88i, r obtained, through the kindness of Mr. Clarke, 

 twenty-five specimens of living young whitefish, saved from a 

 lot which he was planting in the waters of Lake Michigan, oft" 

 Racine, Wisconsin. I succeeded in conveying them to the labo- 

 ratory without loss, and there kept them for several days in a 

 glass aquarium and supplied them with an abundance of the 

 living objects to be obtained by drawing a fine muslin net 

 through the stagnant pools of the vicinity. These consisted of 

 many diatoms and filamentous fresh-water Alga^, of two or 

 three species of Cyclops, of Canthocajtiptus illijwiscusis, and 

 Diaptomiis sanguineus among the Copepoda, and of two rather 

 large Cladocera, Simocep/ialns vetu/us dind S. americamis. These 

 little fishes were kept under careful observation for several days, 

 the water in the aquarium being frequently aerated by pouring. 

 Many of them had, however, been injured by handling, and 

 eleven of the specimens died without taking food. It was soon 

 evident that the larger Entomostraca (the SiinocepJialus, and 

 even the Diaptomns) were quite beyond the size and strength 

 of these little fishes, and that only the smaller Copepoda, 

 among the animals available, could aftbrd them any food at 

 first. These they followed about from the beginning with 

 signs of peculiar interest, occasionally making irresolute at- 

 tempts to capture them. Two days after their arrival, one of 

 the young whitefish had evidently taken food, which proved, 

 on dissection, to be a small Cyclops. During the next two days 

 nine others began to eat, dividing their attentions between the 

 Cyclops above mentioned and the Canthocamptus, and on the 

 22d two other took a Cyclops each and a third a Canthocamptus. 



