334 BULLETIN OF THE BUREAU, OF FISHERIES. 
have remained attached to its wall. The commonest intestinal distome, Bunodera 
nodulosa, lives in the bile ducts and gall bladder during early stages, but no regular 
examinations were made to discover its presence at seasons when it was not in the 
intestines. Every parasite observed was not identified as to species, but practically 
all, if not all, will fall in the list which follows. No routine record was kept of the 
occurrence of the skin parasite, Diplostomulum cuticola. 
The results of the routine examinations for parasites are summarized in Tables 31 
and 32. Nematodes were never present as intestinal parasites during December; in 
Lake Mendota they were most abundant in summer; in Lake Wingra, from March to 
May and from August to November. In Lake Mendota no trematodes were found in the 
intestines during September, October, and November; and in Lake Wingra none were 
found at any season. ‘The cysts of larval proteocephalid tapeworms were prevalent in 
the liver, and often in the peritoneum elsewhere, during every month of the year. Larval 
proteocephalids were most abundant in the intestine from March to May in Mendota 
but were irregularly distributed through the year in Wingra. Acanthocephalans were 
most abundant in spring in both lakes. Leeches and adult tapeworms were uncommon 
and irregular in their occurrence. 
The most striking difference in regard to parasites between the perch of Lake 
Mendota and those of Lake Wingra is in the complete absence of intestinal trematodes 
from the latter. This may be due to the absence of a proper intermediate host in Lake 
Wingra. The following list includes all the parasites known to occur in the perch from 
Wisconsin lakes: 
PROTOZOA. 
Henneguya wisconsinensis Mavor and Strasser.—This myxosporidian was first described from speci- 
mens taken from the urinary bladder of a male perch caught in Lake Mendota and examined on April r5, 
191s. During the present investigations no examinations for this parasite have been made. 
CESTOIDEA. 
Proteocephalus pearsei La Rue.—Specimens of larval cestodes, cestode larval cysts, and adult tape- 
worms were sent to Dr. G. R. La Rue, of the University of Michigan, who was kind enough to describe 
them (1919). One of the larval cysts was found in the body muscles on October 13, 1916. 
TREMATODA. 
Bunodera luciopercae (O. F. Miiller).—This fluke was common in the intestines, particularly in the 
ceca, in perch collected from Lake Mendota but was absent from those collected from Lake Wingra. 
It has previously been reported in the perch from this country by Stafford (1904) at Montreal, Canada, 
and by Marshall and Gilbert (1905) from the lakes near Madison, Wis. 
Clinostomum marginatum (Rudolphi).—This trematode was observed twice in the perch from Lake 
Mendota. On September 25, 1915, a cyst containing a nearly mature specimen was found beneath the 
skin in the flesh at the base of the tail. On January 10, 1917, the gills of 20 perch, which had been 
caught at a depth of 17 m., were examined and one small larval cyst was discovered, embedded in a gill 
filament. These isolated observations, of course, give no idea of the prevalence of this parasite in 
Wisconsin. 
Diplostomulum sp.—This skin parasite was observed now and then in the lakes near Madison and 
was always more abundant in the young fish than in adults. It was very prevalent in the perch from 
Oconomowoc Lake. An idea of the difference in infection in perch from two Wisconsin lakes may be 
gained from the following statistics: 
Fourteen perch, collected from Lake Mendota, near the base of Picnic Point, August 24, 1916 
(length—maximum, 69; minimum, 52; average, 61 mm.), were infected to the degree shown by the 
following ‘‘number of infected individuals—total number of parasites—average”’ figures: Tail, 5-5-3.5; 
fins, 0; head, 8-16-1.1; ventral region, 9-18-1.3; dorsal region, 14-15-1; whole body, 1455-4. 
