of a process similar to perietal sis in the elimination of 

 excretory ?a*te as well as showing in this early stage that 

 toe bladder is quite decidedly muscular. tfhen the embryo 

 is 0.710 cam. long, th<* final sh^pe of the oercaria is nearly 

 attained* In this sta^e the union of the two tubules of the 

 primitive musculnr bladder is partially accomplished (fi* 40) 

 just at the juncture of the body and tail* At 0.765 mm. in 

 length (fig* 41) the process of union is nearly completed 

 extending i int<- the body and tail* Thus the tubule 



found in the tail of mature cercariae is really a part of 



the bladder. Principally upon this data in regard to the 



m 



ol :t (icier tubules in the tail Ssinitssin (1911), based his 



:? * . 



therry that the bcdy proper of rnany oercariae really extends 

 to the region of tho excretory pores in the tail and not 

 to wher^ the slender pnrt ordinarily called the tail joins 

 the body, he then holds th'it the triifs tail is an outgrowth 

 from tissue found just posterior to and between the excretory 

 pores. There is considerable evidence, aside from the work 

 of Ssinitzin to uphold this theory. Loss (1896, figs. 147, 

 lf>b, 172, 173, 174) shows that in both monostomer? and dis- 

 tomes such a bladder formation taJ-es place. Also Jx>oss 

 (1892, pi. XX) shows several stages in the aevelopmmt of 

 an arnchistoffle cercatia portraying th< sarae development of the 

 bladder. From this evidence it seems to me quite logical to 

 say that the body proper of such cer^-iriae extends to the 

 excretory opening* on the side of tho tail and th-*t the true 

 tail e-; tends only from this point on. 



Since the oladder R'*C is derived f rom the union of 

 two tubes in the atabryo, then certainly, if necessary, they 

 could unite for a longer distance and form a much larger 



