14 College o Forestry 
The encysted Clinostomum has a characteristic appearance in the 
muscles of the fish where it occupies a space in the endomysium. 
The worm fills the cyst and has a whitish appearance. Within the 
cyst the worm is bent twice, both times with the ventral surface out- 
ward. When the living worm is released from the cysts, it begins to 
crawl about on the skin of the fish or on one’s hand. Osborne 
distinguishes two poses which he designates as the ‘“suctorial and 
swimming.” It does not seem to me that these are really as distinct 
as he points out, for when the animal is on the skin of the fish it 
makes a variety of movements, chiefly with the anterior end of the 
body, that might belong to any one of several poses. Unfortunately 
no experiments have ever been tried to determine just what the worm 
would do when brought in contact with another living fish in the water. 
Figure 3. Drawn from a specimen of Clinostomum marginatum 
which had been removed from the cyst after fixation in alcohol and 
relaxed by slight maceration; from a bass taken at Nebish, Michigan. 
From Osborne. (Reproduced by permission of author and Biological 
Bulletin.) 
The problem of how and at what spot these worms enter the body 
of the fish is still unknown. 
Osborne gives a table of measurements for the adult in which the 
length ranges from 3 millimeters to 8 and the width from .9 to 2. 
millimeters. The worms that I have taken from the perch, particularly 
those taken in September, are much longer, some being 10 mm. long; 
the width, however, ranges about as given by Osborne. The most 
of my specimens are from 5 to 8 mm. long with several Io mm. These 
long specimens were taken throughout the summer. As suggested in 
