166 Wisconsin Academy of Sciences, Arts, and Letters. 
of Lake Mendota have more parasites than those at greater depths 
and that Lake Mendota has a higher percentage of infection than 
any of the other lakes. If the highest percentage of infection with 
a particular parasite makes a lake ‘‘first/’ the lakes rank about 
as follows: 
Mendota, shallow: 6 firsts; 6 seconds; 2 thirds; all species pres¬ 
ent. 
Mendota, deep: 5 firsts; 1 second; 2 thirds; 4 species absent. 
Wingra: 3 firsts; 1 third; 1 fourth; 1 fifth; 2 sixths; 6 species 
absent. 
Waubesa: 1 first; 2 seconds; 3 thirds; 2 fourths; 2 fifths; 4 spe¬ 
cies absent. 
Kegonsa: 1 first; 2 seconds; 2 thirds; 1 fourth; 3 fifths; 3 spe¬ 
cies absent. 
Monona: 1 first; 2 seconds; 1 third; 1 fourth; 2 sixths; 6 spe¬ 
cies absent. 
That Monona ranks last is probably explained by the fact that 
it is heavily contaminated with organic matter from the city of 
Madison. It is on the whole the most barren of the lakes and 
contains fewest fishes. 
Glochidia, leeches, intestinal proteocephalids, and acanthoceph- 
alans are apparently more abundant in shallow water. All en¬ 
cysted parasites are somewhat more abundant in deep water. Lake 
Kegonsa has a much higher infection with bothriocephalids than 
any other lake, and also has many Dacnitoides. 
The data in table 1 are rearranged in table 3 to show the av¬ 
erage infection of the perch in the Yahara lakes by months. It 
will be noted that the maximum infections were in spring. This 
was due largely to the increase of acanthocephalans at that season. 
Winter came next, autumn was third, and summer showed the 
lowest infection. The different parasites reached their seasons 
of greatest numbers as follows: 
Spring: acanthocephalans; Bunodera. 
Summer: glochidia—^which were found at no other season. 
Autumn: bothriocephalids, Diplostomum, Clinostomum, Icthy- 
onema, and proteoeephalid cysts. 
