TJilNIOID CESTODES OF NORTH AMERICAN BIRDS. 



33 



shape, and measure about 50/x in diameter. The vas deferens (fig. 28, 

 V. def.)^ formed by the junction of efferent canals from the testicles, 

 extends forward near the median line to the anterior end of the seg- 

 ment, then turns and passes outward and backward in a tortuous 

 course toward the cirrus pouch. The cirrus pouch (figs. 23, 24, 25, 

 c. p.) is comparatively small, measuring but 80 to 90/x in length by 

 40/* in diameter. The outer muscular wall is rather thick (8 to 

 10/x,) compared to the size of the pouch. The cirrus pouch is not sup- 

 plied with a retractor muscle, but numerous muscle fibers extend from 







@- 









ut 



ut , 





0mmm. 



lOOjx. 



Fig. 26. — Rhabdojietra sijiilis : Gravid segment, par. ut., Para-uterine organ. 



vt._. Uterus. 



the base of the pouch outward to attach to the cuticula surrounding 

 the genital pore. The cirrus (fig. 25, cir.) in the retracted condition 

 is very slender (2/x,) and is apparently without spines. When evagi- 

 nated it measures about 4fi in diameter. 



Female reproductive organs. — The vagina (figs. 23, 25, v<2^.), which 

 opens into the genital cloaca immediately behind the cirrus, is at 

 first rather thick-walled. It has no definite sphincter. Before cross- 

 ing the lateral nerve the vagina becomes a thin-walled tube with nar- 

 roAv lumen, and after passing the excretory canals is dilated to form 



3264— Bull. G!»— 09 3 



