190 ILLINOIS BIOLOGICAL MONOGRAPHS [190 



der or reservoir. This reservoir opens in the middle of the rounded 

 posterior margin of the end-proglottid. 



The genital aperture is marginal, irregularly alternating, situated 

 at the end of the anterior l^ to y^ of the proglottid. A genital papilla 

 is not present tho the margin of the genital sinus is slightly swollen. 

 In structure and arrangement the sexual organs agree thoroly with the 

 general relations of Proteocephalus. Riggenbach mentions a receptacu- 

 lum seminis as being new to Ichthyotaenia but it has been found in 

 several species of Proteocephalus. 



The testes number about 100. They measure 0.054 by 0.045 mm. 

 They lie in a single layer in the medullary parenchyma, between the 

 viteUaria and anterior to the ovaries. The vas deferens forms a volumi- 

 nous knot of coils outside the cirrus-pouch. The ductus ejaculatorius 

 forms a few coils in the cirrus-pouch and then, undergoing a change in 

 histological structure, it passes over into the cirrus, the basal part of 

 which is much broadened to form a roomy ovoidal vesicle. The cirrus 

 somewhat resembles the cirrus of Monticellia malopteruri (Fritsch). 

 Riggenbach did not see the protruded cirrus. The cirrus-pouch is a 

 large pear-shaped and muscular sac extending into the segment perpen- 

 dicular to the margin. Its length is about 0.34 mm. Since the ripe 

 proglottids measure about 0.70-1.0 mm. broad the cirrus-pouch must 

 reach from l^ to % across the proglottid. 



The vagina opens into the common genital sinus anterior or poste- 

 rior to the cirrus-pouch. In old proglottids the beginning part of the 

 vagina is swollen into a sac nearly as large as the cirrus-pouch but in 

 young proglottids the diameter of the vagina is uniform. In its course 

 to the middle of the proglottid it describes an arc, then it bends sharply 

 and passes to the interovarial space in a spiral or sinuous course. The 

 convolutions of vas deferens are crossed by the vagina only when the 

 latter opens anterior to the cirrus-pouch. A receptaculum seminis is 

 present near the mid-piece of the ovary. This is more than a broaden- 

 ing of the vagina at this point for in Riggenbach 's drawing there is 

 shown a change in the histological structure of the vaginal wall. The 

 relations of the organs with the interovarial space is similar to that in 

 species of Proteocephalus and need not be discussed here. The bilobed 

 ovary is in the posterior region of the proglottid. The lobes are un- 

 branched saclike structures united by a mid-piece from which the ovi- 

 duct arises. The vitelline glands are lateral follicular structures ex- 

 tending the fuU length of the segment. They occupy a broad zone 

 laterad to the excretory vessels and the nerve trunks. The uterus is a 

 median longitudinal tube with a large number of lateral outpocketings 

 on either side. The uterine eggs are 0.021 mm. long by 0.016 mm. 



