The Relation of Mollusks to Fish in Oneida Lake 191 
Mollusca, CnvtOn : Gn eareiea. - ite peta able Sia ) 
Spherium (Cyclas) .......... | 
ISCAS a 308) BSH CIS ere eeice $ 19 per cent. 
Physa heterostropha .......... 
Valvata tricarinata .........-. 
Pisces. Peacilichthys (eaten by one fish)..... 9 per cent. 
ADULT. 12 specimens examined from Lake Michigan. 
Crustacea. Cambarus wirilig ......-..:4.-+: 14 per cent. 
ised. Cyprinids: ys me woth eo ees ks alten 2 86 per cent. 
Hankinson (1908, p. 215) examined 32 stomachs. The 
contents of 15 are listed in his tables (pp. 245-251). Three 
of these were in the “ youth” stage (34-38 mill. long) and 
had eaten only copepods and other entomostracans. Of the 
balance, ranging from 4 to 6 inches (100-150 mill.) in 
length, 8 had eaten midge larve or pupe, 1, Hexagenta 
‘larvee, 1, May-fly larvee, 2, Daphnia (one contained only 
Daphnia), 1, copepods, and 1, crawfish and the remains of a 
small fish. Of the entire 32 stomachs, Hankinson says 13 
had eaten midges in several stages of development, and 11 
had eaten crawfish. These two groups, therefore, form the 
most important food of the Perch in Walnut Lake. The dis- 
tinction in food between the young and adult fishes is not 
here as marked as noted by Forbes for Illinois perch. J. E. 
Reighard (1915, p. 236-7) examined and tabled the food 
of 24 fish from Douglas Lake, Mich., 19 of which contained 
identifiable material. ‘‘ Of these, 11 contained insects only, 
one contained insects together with a crayfish, three con- 
tained crayfish only, and four contained fish only. The rela- 
tive importance of the three kinds of food is perhaps indi- 
eated by the frequency of the occurrence of each, which is 
the ratio: Insects 3, fish 1, crayfish 1.” Marshall and Gil- 
bert, (1905, p. 520-521) found the Perch of Lakes Men- 
dota, Monona, and Wingra, Wisconsin, to feed on a variety 
of material. Fifty-six specimens were examined of which 
39 contained insect larvae, 14 gammarids, 6 snails (mostly 
Physa ancillaria), 9, crawfish, 2, plant remains, 16, plank- 
ton, 2, minnows, and 3, fish spawn. In this locality insect 
larve appear to be the most important food element, in this 
respect resembling the Walnut Lake fish. Smallwood (1914, 
