100 
from the specimens from the Chicago market. Insects are also an 
important item,—amounting to twenty-four per cent., nearly all be-— 
ing the larve of Neuroptera,—May-flies (Hphemeride), dragon-flies. 
and case-flies (Phryganeide). A single specimen from Peoria Lake 
had eaten one small fish—a ‘‘darter” of the genus Peecilichthys. + — 
The second group, of twelve specimens from Lake Michigan, pre-_ 
sents a curious and instructive contrast in food to the foregoing. 
Mollusks and insects wholly disappear, and Crustacea are limited — 
to the commonest crawtish of the lakes (Cambarus virilis, Hagen), — 
which forms fourteen per cent. of the food. The remaining eighty-— 
six per cent. consisted wholly of fishes, all minnows (Cyprinid) as ~ 
far as recognized except one, and that was some undetermined per-— 
coid,—probably itself a perch. i 
It will thus be seen that the common perch has a food history” 
of three periods,—the periods of infancy, youth, and mature age.” 
In the first it lives wholly on Entomostraca and the minutest larva 
of Diptera; in the second, commencing when the fish is about an 
inch and a half in length, it takes up first the smaller and then 
the larger, kinds of aquatic insects in gradually increasing ratio, the 
entomostracan food at the same. time diminishing in importance ;_ 
and in the third it appropriates, in addition, mollusks, crawfishes_ 
and fishes—in the lake specimens depending almost wholly on the 
last two elements. . ‘ 
- We have here the first instance of a fact which we shall see 
again and again illustrated—that the young, having at first an™ 
alimentary apparatus too’ small and delicate to dispose of any) 
insects but the minutest larve, live almost wholly on minute crus-— 
taceans. 
It is proper to note that the lake and river perch are by some 
good authorities regarded as separate species—the latter being” 
much more highly colored than the former. I have not found so 
strict a separation of the two forms as that described by Mr. HK. 
W. Nelson, but have frequently taken both in the same haul of 
the seine in different parts of Calumet R. and in Lake George, 
Ind.,—a body of water communicating with Lake Michigan by an 
outlet three or four miles long. Occasional pale specimens are also 
taken far from the lakes, in the Fox and Illinois Rivers. The differ-_ 
ence of color is probably due partly to thé smaller amount of light” 
to which those inhabiting the deeper waters of the lake are exposed, — 
and partly to their piscivorous habit combined with the compara-— 
tively few lurking-places afforded them. There is some evidence that) 
fish food bleaches a fish directly, and a good deal that it does so, 
indirectly, by increasing the importance of an inconspicuous ap-. 
pearance.:. . 
STIZOSTETH.UM CANADENSE, Smith. Gray Pike-PERcH. SAUGER. “Jack, 
SALMON.” 7 : : 
Fourteen specimens of this excellent fish were examined, all of 
which were from the Illinois R., ten taken in October, 1878, one 11 
June, 1577, and three in November, 1877. It is evidently a very 
destructive species. ‘hese specimens had eaten nothing but fishes. 
