The First Food of the Common White -Fhh. 109 



more densely populated by these animals than the lake itself, as 

 has been particularly evident at Racine and South Chicago. Nei- 

 ther are they commonly equally distributed throughout the waters 

 in which they are most abundant, but like most other aquatic ani- 

 mals, occur in shoals. In the deeper portions of the lake, 

 many species shift their level according to the time of day, coming 

 to the surface by night, and sinking again when the sun is briglit. 



These facts make it important to the fish-culturist that the par- 

 ticular situation where it is proposed to plant the fry should be 

 searched at the time when these are to be liberated, to determine 

 whether they will find at once sufficient food for their support. A 

 little experience will easily enable one to estimate the relative 

 abundance of the Entomostraca at any given time and place, and 

 they require nothing for their capture more complicated or difficult 

 of management than a simple ring net of cheese-cloth or similar 

 material, towed behind a boat. This may be weighted and siuik 

 to any desired depth, so that the contents of the water either at 

 the surface or at the bottom, may be ascertained by a few minutes' 

 rowing. 



In conclusion, I wish again to express my great obligation to 

 the United States Fish Commissioner, Prof. S. F. Baird, and to 

 Frank N. Clark, Superintendent of the United States Hatchery 

 at Northville, Mich., through whom, as already stated, the speci- 

 mens were derived upon which these studies were made. My best 

 thanks are also due to the Exposition company of Chicago, and 

 especially to their secretary, the Hon, John P. Reynolds, for the 

 use of a tank in the Exposition building, and for many courtesies 

 received while the experiment there was in progress. 



