155] PROTEOCEPHALIDAE—LA RUE 155 



and extremely heavy sphincter vaginae while in P. singularis the 

 sphincter vaginae resembles that of P. perplexus. Throughout its 

 length as far as the receptaculum seminis the inner surface of the vagina 

 is heavily ciliated. The vagina does not cross the cirrus-pouch, but 

 after reaching the mid-field of the segment it takes a sinuous course 

 posteriad to the interovarial space. A small receptaculum seminis lies 

 just anterior or posterior to the mid-piece of the ovary. The vagina 

 forms no coils anterior to the ovary. The vitellaria (Fig. 64) are 

 voluminous, the follicles are of good size and closely packed together. 

 They extend not only to the extreme posterior margin of the proglottid 

 but are bent around and lie parallel to the posterior margin nearly to 

 the mid-field. This is particularly noticeable in ripe proglottids. The 

 paired vitelline ducts pass through this posterior continuation of the 

 vitellaria. 



The ovary is bilobed. The lobes are thick and heavy, with a some- 

 what irregular outline due to protuberances. In sections it is noted that 

 the ovary is not a solid organ but is made up of smaller parts more or 

 less fused together. An oocapt, ootype, shell gland and other organs 

 usually found in the inter-ovarial space in Proteocephalids are found 

 here and in the relations characteristic of the genus. The uterus (Fig. 

 64), a median tube in mature proglottids, is made up in ripening pro- 

 glottids of a median tube and 20-25 narrow lateral pouches. These 

 pouches occupy the entire ventral field between the vitellaria and the 

 anterior and posterior proglottid limits. There are 2-4 ventral uterine 

 pores. The uterine eggs have three membranes, an inner one closely 

 investing the embryo, a middle membrane, quite thick and granular 

 and frequently partially or completely split into two layers, and an 

 outer membrane thin and hyaline. The embryo measures 0.013-0.014 

 mm. by 0.014-0.156 mm., being usually somewhat elongated but at times 

 spheroidal. The second membrane measures 0.019-0.030 mm. and the 

 outer one 0.024-0.036 mm. in diameter. 



The excretory system is made up of four main lateral canals which 

 traverse the length of the strobila. The two ventral vessels are larger 

 than the two dorsal. At intervals small branches arise from the main 

 vessels and lead to the exterior. No transverse excretory commissure 

 was observed. In the head and neck the anastomoses of the excretory 

 system are very complex. The main trunks are nearly straight. 



This species is closely allied to P. amhloplitis yet it differs from 

 that species in size, in the lack of a vestigial fifth sucker, in the size and 

 location of the vaginal sphincter, in the posterior prolongation of the 

 vitellaria, in the smaller cirrus-pouch, in the fewer coils of ductus ejac- 

 ulatorius within the cirrus-pouch, in the greater number of testes and 



