104 ILUNOIS BIOLOGICAL MONOGRAPHS (104 



DESCRIPTION OF PLATE 



Figs. 1-3. — Cercaria pellucida; sketches of progressive stages of pigmentation; dorsal view, 



showing two lateral eye-sp>ots and one median spot. X 100. 

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

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



excretory tube. X 330. 

 Fig. 6. — Cercaria pellucida; redia,^characteriz€d by extensive rhabdocoel gut and spinous 



prepharynx. X 34. 

 Fig. 7. — Cercaria pellucida; detail of the spinous prephar^Tix of the redia. X 540. 

 Fig. 8. — Cercaria pdlucida; 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 pdlucida; 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 pdlucida; detail of cystogenous gland cells in the region of the lateral eye- 



spot. X 330. 

 Fig. 15.— Cercaria pdlucida; 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 pdlucida; r^ons 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 pdlucida; oblique section thru tail, indicating arrangement of muscle 



fibers. X 540. 



