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. Clarke, twenty-five speci- 

 mens of living young white-fish, saved from a lot which he was 

 planting in the waters of Lake Michigan, oflF 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 AlgiB, of two or three species of Cyclops, of Canthocamp- 

 tus illinoisensis, and Diaptoinus sanguineus among the Copepoda, 

 and of two rather large Cladocera, Simocephalus vetuhcs 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 tliat 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 al)out from the beginning with signs 

 of peculiar 'interest, occasionally making irresolute attempts to 

 capture them. Two days after tlieir arrival, one of the young 

 white-fish had evidently taken food, which proved, on dissection, 

 to be a small Cyclops. During the next two davs nine others be- 

 gan to eat, dividing their attentions between the Cyclops above 

 mentioned and the Cantliocamptus, and on the 22d two others 

 took a Cyclops each and a third a Cantliocamptus. One of these 

 fishes contained still a laro-e remnant of the eofof-sac, showino- that 

 tlie propensity to capture prey must antedate the sensation of hun- 

 ger. On the 25th the fourteenth and last remaining fish captui'ed 

 its Cyclops and was itself sacrificed in turn. As an indication 

 of the efficiency of the raptatorial teeth, it niay 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 o-eneral statement of the result of the ol)servations made 



