EXCRETORY SYSTEM IN DIGENEA. 



319 



Proof of the fundamental character of the groups and numbers 

 of flame cells in Cercaria convoluta is further established by the 

 analysis of the excretory system of the redia. Here (Fig. 4) 

 there are three groups of flame cells on each side of the body, 

 although the more primitive character of the redia is evidenced 

 by the single cell as representative of each group. 



DISCUSSION. 



The exact knowledge of the groups of flame cells and exact 

 grouping of these cells in Cercaria convoluta makes it possible to 

 understand the importance of the excretory system both in the 

 anatomy and systematology of the group. In his study of 

 Diplodiscus subdavatus Looss has shown that the miracidium of 

 his species has a single pair of flame cells at the anterior end of 

 the unbranched collecting tubules. With the metamorphosis 

 into a sporocyst the collecting tubules elongate but the single 

 flame cell on each side persists. In the redia of this species 

 Looss has found from two to four flame cells on each side of the 







TABLE I. 



SHOWING NUMBER OF FLAME CELLS RESPECTIVELY IN CERCARIA CONVOLUTA 

 AND C. DIPLODISCI SUBCLAVATI AT VARIOUS STAGES IN THE LlFE HISTORY. 



median line, although he is not sure if the number is constant. 

 In the writer's species there are always three flame cells on each 

 side of the redia. In the cercaria germ-ball in both C. diplodisci 

 subclavati and C. convoluta there is at first a single flame cell for 

 each lateral collecting tubule. The next stage recognized by 

 Looss in his species is one with four flame cells, each of which 

 appears to represent a separate group. A subsequent stage in 

 Looss's figures shows three cells for the cephalic group, two each 

 for the two groups in the middle of the body and eight (or nine) 

 for the acetabular group. This same number persists in the 



