8 College of Forestry 
FieLp Notes ON CLINOSTOMUM MARGINATUM WITH A CONTRIBUTION TO 
irs Lire Hisrory. 
Preliminary Report —W. M. SMALLwoop. 
It is common knowledge among those who frequent the several 
Adirondack Ponds during the summer months that the perch and 
often the bass are considered unfit for food because of the numerous 
parasites in their skin and in their flesh. The usual term heard from 
the guides is “grubby” when referring to the summer perch. A 
number of woodsmen have been consulted in reference to the time 
of the spring when they have first noticed the “grubs” in the perch 
and as to how long they remain. The writer has yet to find any one 
who knows anything definite concerning either of these important 
phases of the problem but all agree that in the ponds that have the worst 
infected fish in summer, perch free from parasites are caught in the 
winter and early spring. 
For the past ten years the writer has usually reached the Adirondacks 
about the middle of June and by that time most of the perch are unfit 
for food as a result of parasitism. This is a condition, however, 
which seems to develop rather rapidly, possibly in about two weeks, for 
usually no trouble is experienced the last of May in securing plenty 
of perch entirely free from skin and flesh parasites. 
3efore any remedial measures of lasting benefit can be devised we 
must know the conditions under which these annoying parasites live 
and how they come to the adult stage. This is a report of a study of 
some of the more important biological conditions involved in an 
analysis of the problem. As a contribution to the life history, it is 
to be regarded as of a preliminary nature only. 
Two species of Trematode parasites are found, the larger being 
the common flat-worm, Clinostomum marginatum, and the smaller one 
“ 
of the genus Holostomum. The phrase “ grubby” perch has reference 
to the presence of Clinostomum which is usually imbedded in the flesh 
and shows as a whitish spot through the skin. Field studies covering 
hundreds of specimens show that these Trematodes (C. marginatum) 
