PLATE 20 



Figs. 10-16. Stages of development of miracidia. X 34. 14. pdt., primitive 

 digestive tract; 15. ap., anterior papilla; 16. ens., central nervous system. 



Fig. 17. Egg just after escape of miracidium, showing operculum attached 

 and waste material inside. X 34. 



Fig. 18. Eggshell with operculum detached. X 34. 



Fig. 18a. Operculum of egg. X 34. 



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