39. 



the pattern quite simple. 



The gr* i t ^noaledge of the excretory ay tern of 

 trematodea as stated is comparatively mender. In nearly 

 every oercnria described the bladder ind larger tubules 



are shown, ^rh-sreae the collecting tubules, accessory 

 ccll<-ctin ( 'T tubules, capillaries 3nci flame cells are 



missing or nearly sc This is, as stated before, due to 

 wcr^ing on preserved material* But evn tho the larger 



V 



parts of th* system have been long ^nown, yet for con- 

 Pid"rVbl time they ?#re confused with blood vessels, 

 parts cf the digestive tract, the oviduot and other parts 

 of the genital system (ITraipont, 1880, pp. 415-420). The 

 rL-xrae cell itself wrva perhaps firnt eeen by Biitohli in 

 1879, sc it is impossible that earlier reeearcliers could 

 t have conaeived of a unified pye teia. ilven after the flame 

 cells and capillaries had been found, they were considered 

 f o r -a time as distinct' fxv-m the larger tubules ind bladder. 

 Thr^t this confuBion could readily exint can now be v/ell 

 undor^tood, because of tJie minutenens and complexity of the 

 parta of this system. 



In reviewing the literature on excretory oyptema of 

 cercariae that have been completely worked cut this 

 conclusion, I believe, can be safely made, that there is a 

 definite plan of arrangement of the collecting tubules, 

 necessary coll acting tubules, i^ien developed, and th:i.t the 



capillaries and flame oells are found in groups, nearly 



throughout 

 always of an e^unl number / the body* Thie grouping 



of the fl'une celli, naturally can occur in cercariae only 

 where the excretory system in the crcaria approximates or 



