144 ILLINOIS BIOLOGICAL MONOGRAPHS [432 



curve upward on each side, sometimes reaching ahnost to the dorsal boundary 

 of the medulla. The oocapt is almost spherical in shape with an average 

 diameter of 30/x, and is situated in the median line. The oviduct immediately 

 beyond the narrow outlet of the oocapt is 25/i in diameter. At the point of 

 union of the vagina with the oviduct there seems to be a vestibule, similar to 

 that of B. scorpii, but this was not made out to the writer's satisfaction. Two 

 vitelhne ducts, each about 15ju in diameter, unite at about the level of the oocapt 

 and continue dorsally with the same diameter as the common vitelline duct. 

 This turns downward again and quickly enlarges to form the vitelline reservoir, 

 which was found to have a maximmn diameter, when filled with yolk cells of 

 about 60fjL. The vitelline foUicles are extremely niunerous and very closely 

 arranged in the cortical parenchyma in two lateral fields, a median strip being 

 left" free of them on each surface of the strobila. They are ellipsoidal in shape, 

 with average maximimi lengths, widths and depths of 35, 60 and 85^1, respec- 

 tively. In the material studied they showed considerable tendency towards 

 stratification and on account of this fact, their very varying size and the poor 

 condition of their walls, no satisfaction was experienced in attemptmg to deter- 

 mine the approximate number for each segment; but it must be weU over one 

 thousand from a comparison of the sections with those of B. ciispidatus. 



The uterine duct begins approximately in the median line, quickly expands 

 between the cirrus pouch and the ovary, first in the direction of the coiled vas 

 deferens and as far laterally as the edge of the ovary, and then crosses the me- 

 dian Une to the opposite side where the mass of coils, occupying the whole dorso- 

 ventral diameter of the medulla, further enlarges gradually in all directions 

 and joins the comparatively large uterus sac. In toto preparations the duct 

 and sac are seen to form a continuous club-shaped mass gorged with eggs and 

 with the larger end, the sac, alternating irregularly from side to side. This 

 irregular alternation of the uterus-sacs was evidently not noticed by Linton 

 since he spoke of only "a dark brown median stripe made by the ripe ova in 

 the crowded ovaries [uteri] "; but Ariola (1900:410) said of them: "Le 

 masse ovariche spesso sono irregolarmente collocate da una parte e dall' altra 

 della linea mediana. " Only in sections can one distinguish the sac from the 

 duct, since the two are so closely apphed to each other. In dorsoventral view 

 the uterus-sac, itself, is somewhat circular in outline, when not pressed against 

 one of its fellows ahead or behind, and has a maximmn diameter of 0.45mm. 

 Ventrally, however, it is funnel-shaped. As shown in figure 73, it may become 

 so enlarged as to invade the adjoining proglottides to a considerable extent. 

 The aperture is located in the middle of the sac and consequently forms with 

 its f eUows two hues of irregularly alternating pores on the ventral surface of the 

 strobila, about 1.0mm. apart. It is only about 20^ in diameter, and is situated 

 towards the anterior border of the proglottis, often well under the overlapping 

 posterior border of the segment ahead. The lowermost or funnel-shaped 

 portion of the sac, Httle more than that which passes through the stratum of 

 longitudinal muscles, is surrounded by a thick layer of material, as shown in 

 figure 97, the nature of which was not determined satisfactorily. It appears 



