tt2 ILLINOIS BIOLOGICAL MONOGRAPHS [382 



EXPLANATIOX OF PLATE 



POLYSTOMA MICROCOTYLE 



Fig. 28. Entire specimen, ventral view. X 27. 



Fig. 29. Ventral view of caudal disc, showing arrangement of musculature and 

 hooks. X43- 



POLVSTOM.\ HASSALLI 



Fig. 30. Entire specimen, ventral view, ceca connected posteriorly. X 45. 



Fig. 31. Entire specimen, ventral view, in which there is no posterior connexion 

 between the ceca. X 40. 



Fig. 32. Reconstruction of genital apparatus from frontal sections. X 135. 



Fig- 2Z- Frontal section thru the dorsal part of the uterus, showing oral sucker, 

 pharynx, nerve commissures, intestine, excretory vesicles and ducts, 

 vitellaria and smaller tubes of the ootype region. X 60. 



