78 
On the Food of Young Fishes. 
rium, Cosmarium, Staurastrum and various diatoms 
among the Algae, were the principal genera. A minute 
Agrion larvae, a very young Amphipod, and larval Co- 
pepoda (nauplii), were the only other kinds recognized. 
It was obviously impossible to make any estimate of the 
ratios of such minute and varied objects occurring in 
such great quantity, and I have contented myself with a 
simple enumeration. 
A specimen three inches long, from Peoria Lake, in 
October, had eaten only Copepoda (Canthocamptus) 
with a trace of Chironomus larvae. 
Ten specimens of red-horse (Myxostoma), varying in 
length from an inch to two and three-fourths, taken in 
July and August, from the Fox and Illinois rivers and 
-from Mackinaw Cr., show no important differences of 
food. 
In the smaller specimens, taken from the Fox and Illi- 
nois, Entomostraca, especially Cyprids, were relatively 
more important, sometimes constituting nearly the whole 
food; but no attempt was made to fix precise ratios. In 
the four larger specimens from Woodford Co., tests of 
Difflugia were estimated to form eighty-five per cent, of 
the contents of the intestines. These specimens were 
taken one at a time, several miles apart, along a rocky 
part of the stream. Besides the species of Difflugia and 
Arcella given in the foot note, various desmids and dia- 
toms were abundant, with filamentous Algae, rotifers 
(Squamella and Rotifer vulgaris ), Cyclops, Alona, Pleu- 
roxus and water mites, Chironomus and other Diptera 
larvae, some indeterminable vegetable matter and a single 
Thrips (Hemiptera). The small percentage of Chiron- 
onius larvae shows that this species has not the habit of 
the stone-roller. 
Two specimens of the common sucker ( Castostomus 
commersonii) , six inches and six and three-fourths in 
length, taken from Mackinaw Cr., in August and June, 
had eaten food so similar to that of the preceding genus 
that detailed description is unnecessary. 
Two specimens of the commonest huffalo-fish (Ichthyo- 
bus ), seven-eighths of an inch long, had eaten most freely 
