PAEASITES ON CYPKINOID FISHES IN OHIO. 
361 
of tlie psorosperms. In the sections they are evidently undisturbed and lie as they 
did in the cyst. They appear to lie in all positions. Edge, side, and end views are 
presented by individuals lying side by side. 
These cysts differ from those found on the short minnow {Cyprinodon 'variegatus) 
in the absence of connective tissue and calcareous bodies in their substance. They 
agree closely with those described by Zschokke from Coregonus fera of Europe. The 
psorosperms, however, appear to be different. I am unable to determine from the 
material at hand whether the absence of polar vesicles is to be interpreted as a specific 
character or simply due to the immature condition of the psorosperms. The real 
nature of these peculiar forms is as yet little understood and their life history is not 
known. 
A list of the more important contributions on the psorosperms is given in an 
article by the author entitled “ On certain Wart-like Excrescences occurring on the 
Short Minnow, Cyprinodon variegatus^ due to Psorosperms.” Bulletin U. S. Fish Com- 
mission, 1889, p. 99. 
EXPLANATION OF THE FIGURES. 
Fig. 1. Cypriuoid {Notropis megalops) with dermal cysts caused by psorosperms. X lb 
Fig. 2. Psorosperms liberated from cysts and highly magnified, a, side view of specimen in caustic 
potash ; a', same more highly magnified ; h, view of edge ; h', same more highly magnified ; 
c, specimen treated with sulphuric acid. 
Fig. 3. Portion of thin section of cyst, a, pigment spot ; h, granular protoplasm ; c, psorosperms ; 
d, wall of cyst and dermis. X about 150 diameters. 
