94 ILLINOIS BIOLOGICAL MONOGRAPHS [374 



EXPLANATION OF PLATE 



POLYSTOMA ORBICULARE 



Fig. I. Entire specimen, extended, ventral view. X 35. 



Fig. 2. Hook from genital coronet. X 225. 



Fig. 3. Reconstruction of genital apparatus from frontal sections. X I3S. 



Fig. 4. Sagittal section thru caudal disc. X 87. 



Fig. 5. Frontal section thru caudal disc. X 7Z- 



Fig. 6. Sagittal section thru oral sucker and pharynx. X 140. 



