The First Food of the Common White-Fish. 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 accordiug to the time of day, coming 
to the surface by night, and sinking again when the sun is bright. 
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 sunk 
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 North ville, 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. 
