168 Wisconsin Academy of Sciences, Arts, and Letters, 
swampy lakes. Unknown visceral cysts were most common in the 
sandy, deep lakes. 
According to their degree of average infection the sixteen lakes 
rank in the following order: Green 59.1; Monona 42.1; Beaver 
32.7; Poygan 32.2; Mendota shallow 31.1; North 30; la Belle 30; 
Oconomowoc 25.5; Butte des Morts 19.2; Pine 17; Mendota deep 
15.3; Okauchee 14.5; Puckaway 14.1; Wingra 9.5; Wauhesa 6.5; 
Winnebago 3; Kegonsa 0.5. If Diplostomum cysts are disregarded 
the order is as follows: Beaver 32.1; Poygan 30.7; North 26; Men¬ 
dota, shallow 23.3; Butte des Morts 19.1; Mendota, deep 14.7; 
Oconomowoc 14.2; Puckaway 14; Pine 10.8; Wingra 9.4; Monona 
7.1; Green 7.1; la Belle 6.5; Okauchee 2.9; Wauhesa 2.5; Winne¬ 
bago 1; Kegonsa 0.2. There is no apparent relation between river 
systems, depth, fertility, character of shore and the general abund¬ 
ance of parasites. This appears to indicate that all parasites are 
not influenced by the same factors. There is also no apparent rela¬ 
tion between the size of the perch in various lakes and the degree 
of parasitic infection, but when there are more fishes per unit of 
area there is a heavier infection. 
Phyllodistomum superhum Stafford was found in the urinary 
bladders of many perch in the lakes along the Fox Kiver, but 
was never observed in any of the two thousand perch that the 
writer has examined in the lakes on the Mississippi drainage. This 
parasite is apparently confined to the St. Lawrence drainage system. 
The food of the perch examined was carefully recorded during 
August, 1917. For the three river systems it may be summarized 
as follows; the figures after the foods indicating the average per¬ 
centage eaten: 
Number examined. 
Average length. 
Insect eggs. 
Fish remains. 
Chironomid larvae. 
Caddis-fly larvae. 
Unidentified insect larvae 
Chironomid pupae. 
Corixa . 
Orasshoppers . 
Sialis larvae. 
Mites ... 
Crayfishes . 
Amphipods, unidentified.. 
iTahara 
Oconomowoc 
Fox 
58 
30 
32 
157 
160 
180 
0.1 
10.3 
32.7 ‘ 
6.8 
42.6 
1.0 
1.1 
1.8 
2.3 
7.0 
0.4 
0.2 
1.3 
0.1 
6.0 
2.5 
14.4 
+ 
0.1 
0.7 
22.0 
43.6 
7.1 
0.2 
