78 ILLINOIS BIOLOGICAL MONOGRAPHS [78 



neck, more numerous and larger proglottids, fewer testes, a shorter cir- 

 nis-pouch, and fewer uterine pouches. The embryos are larger than in 

 P. exiguus. This species resembles P. pusUlus Ward. It differs from 

 that species in the character of the segmentation, in the smaller size of 

 its suckers, in the position of the genital aperture, in the smaller number 

 and size of testes, in its longer cirrus-pouch and in its fewer uterine 

 pouches. P. fallax resembles P. agonis Barbieri but it differs from that 

 species in being somewhat larger, in having a fifth sucker, fewer testes, 

 and more uterine pouches. P. fallax is larger than P. esocis (Schneider) 

 and it has a fifth sucker. It moreover has smaller and less numerous 

 testes than P. esocis. P. fallax most closely resembles P. duhius but it 

 differs from that species in having smaller and much fewer testes, a 

 relatively shorter cirrus-pouch, fewer uterine pouches, a slightly smaller 

 embryo, and a smaller middle egg membrane. In size, in size of head, 

 and size of suckers they resemble each other remarkably. 



PROTEOCEPHALUS NEGLECTUS La Rue 

 [Figs. 81, 82] 

 1911 : Proteocephalus neglectus La Rue 1911 :477 



Specific Diagnosis: Characters of genus. Strobila incomplete. 

 Head, suckers, neck not observed. Outline of proglottid rough. Seg- 

 mentation evident. Genital pore on a slight prominence. Ripe proglot- 

 tids 0.5 mm. long by 0.93 mm. broad to 0.75 mm. long by 1.53 mm. broad. 

 Young and mature proglottids not observed. 



Genital pores irregularly alternating, situated near middle of lat- 

 eral margin of proglottid. Cirrus-pouch frequently contracted, 0.185- 

 0.265 mm. long by 0.080 mm. broad. Normal cirrus-pouch 0.340 mm. 

 long. Cirrus and ductus ejaculatorius straight. Vas deferens a mass 

 of coils in mid-field of proglottid. Testes about 75, spheroidal, 0.042- 

 0.064 mm. in diameter, situated in a single layer in space between vitel- 

 laria. Vagina anterior to cirrus-pouch, its opening dorsal to opening 

 of cirrus-pouch. Sphincter vaginae poorly developed, situated near 

 vaginal opening. Vagina crosses cirrus-pouch near middle. Receptacu- 

 lum seminis not observed. Ovary bilobed, lobes with smooth outlines, 

 clubshaped. Organs of interovarial space not observed. Vitellaria lat- 

 eral, follicular. Vitelline follicles small, compacted. Uterus with 7-9 

 lateral pouches on either side. Uterine pores not seen. Embryo 0,026- 

 0.0265 mm. in diameter. Outer egg membrane 0.042-0.047 mm. 



Habitat: "Forelle" (Trutta fario), type host, probably from Lake 

 Geneva or Lake Lucerne, Switzerland. 



