T^NIOID CESTODES OF NORTH AMERICAN BIRDS. 



29 



in width. It is located about in the center of the segment nearer 

 the ventral than the dorsal surface, and in contact with the inner 

 side of the inner longitudinal muscle layer. Immediately behind 



cir . 



sph. vag.' 



v.det. 



sem. recept. 



lOOjuu- 



Pig. 20. — Rhabdojietea nullicollis : Section through vagina, .seminal receptacle, 

 AND EXTRUDED CIRRUS, cir., CiBEus. sem. recept.. Seminal receptacle, sph. vac/.. 

 Sphincter of vagina, t.. Testicles, ut.. Uterus, vag.. Vagina, v. def., Vas 



deferens. 



the ovary is the rounded yolk gland (fig. IT, y. g.) which measures 

 100 to 130/x in diameter. Dorsal of the yolk gland is the shell gland 

 slightly smaller. The uterus (figs. 18, 20, 21, 22, ut.) develops im- 



vag. 



1 mm. 



Fig. 21. — Rhabdombtea nullicollis : Gravid segment, c. p., 

 Cirrus pouch, par. ut., Para-uterine organ, ut., Uterus. 

 vag.. Vagina, v. def., Vas deferens. 



mediately in front of and dorsal of the ovary, as a simple sac-like 

 organ. As the uterus develops, growing anteriorly and posteriorly, 

 the ovary disappears. The parenchyma in front of the uterus 

 becomes dense and fibrous, and develops into a prominent para- 



