160 ILLINOIS BIOLOGICAL MONOGRAPHS [160 



vessel is very prominent on account of its very large lumen. At fre- 

 quent intervals branches may be seen to be given off from the ventral 

 vessel and a lesser number from the dorsal. Many of the ventral 

 branches communicate to the exterior by means of small ducts through 

 the cuticula. These branches are more numerous and more prominent 

 than in any other Proteocephalid examined by the writer. One branch 

 opens quite regularly at the posterior angle of the proglottid. Other 

 branches (by far the largest number) open on the ventral surface. A 

 few branches of the ventral vessel open on the dorsal surface. No duct 

 connecting the ventral excretory ducts in the posterior part of the pro- 

 glottids has been observed, nor have the relations of the excretory vessels 

 been observed in the end-proglottid. 



There is no genital papilla. The genital pore is marginal, irregu- 

 larly alternating, and situated at the end of the first third or two-fifths 

 of the proglottid. Vagina and cirrus open into the common genital 

 sinus, the vagina always anterior to the cirrus. In all the general 

 features of the sexual organs these are typical of the genus. The testes 

 are ovoidal or spheroidal in shape, 0.04-0.06 mm. broad by 0.07-0.10 

 mm. long. They are arranged (Fig. 85) in a single layer which fills 

 the dorsal region between the vitellaria anterior to the ovaries. The 

 region in which the coils of the vas deferens lie is free from them. They 

 are 75 to 85-90 in number. The vasa efferentia can very readily be 

 made out just below the layer of longitudinal muscles of the dorsal side. 

 These empty into the vas deferens which makes a large mass of coils in 

 the middle of the proglottid and reaching over to the cirrus-pouch. 

 This knot is relatively thick for it extends from dorsal to ventral wall 

 of the dermo-muscular sac. Entering the cirrus-pouch (Fig. 84) the 

 vas deferens which now becomes the ductus ejaculatorius passes over 

 almost immediately into the straight cirrus. The ductus ejaculatorius 

 is usually straight but sometimes it is thrown into from one to three 

 small coils. The cirrus itself has not been seen protruded. It is always 

 slender, straight, and muscular. The cirrus-pouch (Fig. 84) is slender, 

 nearly straight, and quite muscular. It measures 0.185-0.200-0.265 mm. 

 long. Its length goes 21/2-3 times into the proglottid width. 



The vagina (Fig. 84) in its first part has a narrow lumen. This 

 region extends about 0.100-0.110 mm. from the vaginal opening. It is 

 characterized by its rich covering, of gland cells and its weak longitudi- 

 nal and circular muscles. The vaginal sphincter which is poorly devel- 

 oped is situated just at the end of this first region. The sphincter is 

 about 0.025 mm. long. Immediately following this region with the 

 narrow lumen is a dilated portion which may extend clear to the vesic- 

 ula seminalis. There is no ciliated region of the vagina. The vagina 



