65 



thomasi, and one Anureea ; the tenth had taken eight Diap- 

 tomus, two Cyclops, and an Anuraea ; and the twentieth, seven 

 Diaptomus and three Cyclops thomasi. In two of these 

 examples were small clusters of orange globules, probably rep- 

 resenting unicellular Algae. 



Summarizing these data briefly, we find that of the one hun- 

 dred and six specimens dissected, sixty-three had taken food, 

 and that the ratio of those which were eating increased rapidly, 

 the longer the fishes were kept in the aquarium. Only one- 

 fourth of those examined on the fourteenth of the month had 

 taken food, while more than five-sixths of those bottled ten days 

 later had already eaten. The entire number of objects appro- 

 priated by these sixty-three fishes was as follows : Cyclops tho- 

 masi, ninety-seven ; Diaptomus sicilis, seventy-eight ; AnnrcEa 

 striata, twenty-nine ; Daphnia hyalina, one. Seven of the 

 fishes had eaten unicellular Algse, two had eaten diatoms, and 

 one, filamentous Algae, 



From the above data we are compelled to conclude that the 

 earliest food of the white-fish consists almost wholly of the 

 smallest species of Entomostraca occurring in the lake, since the 

 other elements in their alimentary canals were evidently either 

 taken accidentally, or else appeared in such trivial quantity as 

 to contribute nothing of importance to their support. In fact, 

 two species of Copepoda, Cyclops thomasi and Diaptomus sicilis, 

 are certainly very much more important to the maintenance of 

 the whitefish in this earliest stage of independent life than all 

 the other organisms in the lake combined. As the fishes increase 

 in size, vigor, and activity, they doubtless enlarge their regimen 

 by capturing larger species of Entomostraca, especially Daph- 

 nia and Limnocalanus. 



A few words respecting the relative abundance of these 

 species at different seasons of the year and their distribution in 

 the lake will have some practical value. We may observe here 

 an excellent illustration of the remarkable uniformity of the life 

 of the lake as contrasted with that of smaller bodies of water. 

 While in ponds minute animal life is largely destroyed or 

 suspended during the winter, the opening spring being attended 

 by an enormous increase in numbers and rate of multiplication, 

 5 



