mZ ILLINOIS BIOLOGICAL MONOGRAPHS [382 



EXPLAXATIOX OF PLATE 



POLYSTOMA MICROCOTVLE 



Fig. 23. Entire specimen, ventral view. X 27. 



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

 hooks. X 43- 



Poi.YSTOMA HASSALLI 



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



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



between the ceca. X 40. , 



Fig. Z2. Reconstruction of genital apparatus from frontal sections. X 135- 

 Fig- 33- 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. 



