96 ILLINOIS BIOLOGICAL MONOGRAPHS [376 



EXPLANATION OF PLATE 



POLYSTOMA ORBICULARE 



Fig. 7. Frontal section. X 35- 



Fig. 8. Frontal section of ootype and beginning of uterine duct. X 185. 



Fig. 9. Frontal section of ootype and end of right vitello-vaginal canal, five 

 sections ventral to Figure 8. X 185. 



Fig. 10. Frontal section, ootype region of same specimen as Figures 8 and 9, 

 showing ovary, uterus, oviduct, uterine duct, genito-intestinal canal 

 and vas deferens. X 140. 



Fig. 11. Frontal section showing vitellaria and origin of vitelline ducts with 

 granular secretion in the cells and duct. X 87. 



Fig. 12. Frontal section thru cirrus sac at the juncture of the shanks and roots of 

 the genital hooks, showing the genital papillae cut across, and a sec- 

 tion of the duct from the uterus at the bottom of the figure. X 250. 



Fig. 13. Reconstruction of male genital apparatus from sagittal sections. X 140. 



Fig. 14. Frontal section thru uterus showing embryo in stage of a morula-like 

 mass of cells. X 700. 



