The First Food of the Common White-Fish. 
103 
The inconclusive character of the results thus far obtained, made 
it necessary to attempt to imitate more closely the natural condi- 
tions of the young when hatched in the lake. In February, 1881, 
I obtained, through the kindness of Mr. Clark4, twenty-five speci- 
mens of living young white-fish, saved from a lot which he was 
planting in the waters of Lake Michigan, off Racine, Wisconsin. 
I succeeded in conveying these to the laboratory 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 Algae, of two or three species of Cyclops, of Ganthocamp- 
tus illinoisensis , and Diaptomus sanguineus among the Copepoda, 
and of two rather large Cladocera, Simocephalus vetulus and S. 
americanus. These little fishes were kept under careful observa- 
tion 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 Sim- 
ocephalus, and even the Diaptomus), were quite beyond the size 
and strength of these little fishes, and that only the smaller Co- 
pepoda among the animals available, could afford them any food 
at first. These they followed about from the beginning with signs 
of peculiar interest, occasionally making irresolute attempts to 
capture them. Two days after their arrival, one of the young 
white-fish had evidently taken food, which proved, on dissection, 
to be a small Cyclops. During the next two days nine others be- 
gan to eat, dividing their attentions between the Cyclops above 
mentioned and the Canthocamptus, and on the 22d two others 
took a Cyclops each and a third a Canthocamptus. One of these 
fishes contained still a large remnant of the egg-sac, showing that 
the propensity to capture prey must antedate the sensation of hun- 
ger. On the 25th the fourteenth and last remaining fish captured 
its Cyclops and was itself sacrificed in turn. As an indication 
of the efficiency of the raptatorial teeth, it may be worth while to 
note that I saw one of the smallest fishes make a spring at a Cy- 
clops, catch it, give three or four violent wriggles, and drop it dead 
to the bottom of tank. 
As a general statement of the result of the observations made 
