Diseases of Fishinthe Adirondacks 15 
the early part of this study, I am inclined to believe that the small 
worms about 3 mm, long may be considered as young worms and that 
they will grow longer before making their natural escape from the 
body of the perch in the late fall. The mere fact that the reproductive 
elements have developed does not necessarily mean that the worm is 
full grown, because I have found the gonads differentiated in some 
of the smaller specimens even before the anterior sucker is well 
developed. 
With a hand lens one can easily identify the two suckers, the oral 
Figure 4. Sketch of living animal in “suctorial pose” as seen 
from the ventral side, from bass taken at Nebish, Michigan. From 
Osborne. (Reproduced by permission of author and Biological Bulle- 
tin.) 
and ventral. Osborne says correctly that “the mouth opening lies 
in the center of the oral field and leads into the cavity of the oral 
sucker. The sucker is nearly spherical and is much smaller than 
the ventral sucker, measuring ¢.28 mm. long and 0.25 mm. across. It 
has the usual cuticular lining and heavy muscular walls composed of 
fibres running in various directions,” 
