54 



SUMMARY OF CUERENT RESEA.RCHES RELATING TO 



collecting- tubes of the fully developed system. In further development 

 each of these flame cells with its capillary first divided into two flame 

 cells and capillaries, one going to the dorsal and the other to the ventral 



The excretory system of Cercaria polyadena, ventral view ; body 

 spines, stylet, and cystogenous glands are not shown ; acct, accessory 

 collecting tube ; act, anterior collecting tube ; h, bladder ; c, capillary ; 

 cct, common collecting tube ; exp, excretory pore ; /, flame cell ; os, oral 

 sucker ; pet, posterior collecting tube ; ph, pharynx ; st, stylet ; vs, ventral 

 sucker. 



side of the body. One of these two flame cells again divided, making 

 the groups of three found in the fully developed system in which the 

 common collecting tubes, entering the horns of the bladder, receive- 



