28 ILLINOIS BIOLOGICAL MONOGRAPHS [28 



this point the vas deferens is continuous with the ductus ejaculatorius 

 and the cirrus. 



Testes are numerous small ovoidal or spheroidal bodies which lie 

 toward the dorsal surface of the medullary parenchyma within the lon- 

 gitudinal muscle sheath. They occupy as a rule nearly the entire space 

 between the lateral vitellaria anterior to the ovary. They leave a small 

 free area in the region of the coils of the vas deferens. In the genus 

 Proteocephalus the testes form one or two layers which extend from one 

 vitelline field to the other. In one species, P. torulosus, they extend past 

 the ovary to the posterior margin of the proglottid. In the genus Coral- 

 lobothrium the testes form a single broad field anterior to the ovary. In 

 Ophiotaenia, Crepidobothrium, and Acanthotaenia they form two lateral 

 fields, one on either side of a free median zone. In rare cases some scat- 

 tered testes may be found in this median zone. In these genera, which 

 have been but little studied by the section method, the testes seem to form 

 a single layer in depth. The number of testes varies widely from about 

 25 in some to about 400, the upper limit for other species. For each 

 species there seems to be a characteristic number which is not constant 

 but varies within certain limits. This range is usually not great, being 

 5-10-15 for cestodes with the smaller number of testes and very much 

 greater for those cestodes which have very numerous testes. Crepido- 

 hothrium gerrardii has from about 200 to 400 testes, the range being 

 about 200. In mature proglottids the testes are most plainly seen. As 

 the uteri develop and the eggs fill the uterine pouches the testes are 

 pushed aside by the swollen uteri or they shrink and are lost to view 

 between the walls of the uterine pouches. 



The organs which comprise the female reproductive system are 

 vitellaria, vitelline ducts, vagina in all its parts, ovary, oocapt, oviduct, 

 ootype, shell glands, receptaculum seminis, uterine passage and uterus. 

 The vitelline follicles are small spheroidal bodies which are arranged in 

 two long bands which extend the full length of the proglottid near the 

 lateral margin of the latter. The follicles usually are rather compactly 

 grouped about the central conducting tubule. Rarely the vitellaria ex- 

 tend past the posterior edge of the ovarian lobes, and in only one known 

 case, (Proteocephalus perplexus), do they follow along the posterior 

 margin of the proglottid (Figs. 54, 55). The vitellaria are inside the 

 longitudinal muscle sheath and very near the lateral nerve trunks. The 

 central conducting tubules near the posterior end of the proglottid are 

 known as the paired vitelline ducts which lead to the middle of the pro- 

 glottid where they unite to form the common or unpaired vitelline duct. 

 This may dilate to form a vitelline receptacle. From the vitelline recep- 

 tacle the unpaired duct passes backward to join the oviduct just before 



