104 ILLINOIS BIOLOGICAL MONOGRAPHS [104 



DESCRIPTION OF PLATE 



Figs. 1-3. — Ccrcaria pdlucida; sketches of progressive stages of pigmentation; dorsal view, 

 showing two lateral eye-spots and one median spot. X 100. 



Fig. 4. — Cercaria pellucida; dorsal view, somewhat contracted. X 100. 



Fig. 5. — Cercaria pellucida; anterior tip, figuring details of pigmentation and contents of the 

 excretory tube. X 330. 



Fig. 6. — Cercaria pellucida; redia, characterized by extensive rhabdocoel gut and spinous 

 prepharynx. X 34. 



Fig. 7. — Cercaria pellucida; detail of the spinous prepharynx of the redia. X 540. 



Fig. 8. — Cercaria pellucida; young redia; precocious development of the cercariae before the 

 redia is mature. X 38. 



Figs. 9-11. — Cercaria pellucida; three stages in encystment. X 38. 



Fig. 12. — Young Cercaria pellucida; origin of posterior locomotor pockets within the caudal 

 pocket. X 170. 



Fig. 13. — Cercaria pellucida; transverse section thru the middle of the body. X 330. 



Fig. 14. — Cercaria pellucida; detail of cystogenous gland cells in the region of the lateral eye- 

 spot. X 330. 



Fig. 15. — Cercaria pellucida; contracted excretory bladder and posterior locomotor pockets. 

 X 238. 



Figs. 16, 17. — Cercaria pellucida; details of the posterior locomotor pocket; Fig. 16, con- 

 tracted; Fig. 17, relaxed; xx, retractor muscles; yy, reflexor muscles. X 540. 



Fig. 18. — The genitalia of Cercaria pellucida; regions of ootype and metraterm. X 238. 



Fig. 19. — Cercaria pellucida; transverse section thru tail, indicating arrangement of ordinary 

 parenchyma cells. X 540. 



Fig. 19a. — Cercaria pellucida; oblique section thru tail, indicating arrangement of muscle 

 fibers. X 540. 



