419] PSEUDOPHYLLIDEA FROM FISHES— COOPER 131 



The vagina opens immediately behind the cirrus at the bottom of the 

 genital cloaca with an aperture which forms an arc of a circle. It passes ven- 

 trally in the median hne close to the posterior wall of the cirrus-sac and then, 

 after taking a few coils on a level with the lower border of the isthmus, it joins 

 the oviduct a short distance from the origin of the latter. Thruout its course 

 it is considerably flattened anteroposteriorly, its dimensions being alongside 

 the cirrus-sac about 46 by 18ju. It is provided with a cuticula, 3/x in thickness 

 and thrown into longitudinal folds. It gradually diminishes in size until a 

 diameter of about 15;u is reached — at the ventral border of the ovary — and 

 then enlarges somev.'hat before joining the oviduct in a dorsoventral transverse 

 plane, but without forming a distinct receptaculum seniinis, altho a consider- 

 able length of this portion of the duct is often found filled with spermatozoa. 

 Unlike that of B. scorpii the ovary of this species is a compact organ, 0.60rrLm. 

 wide, 0.10 long (the wings) and 0.13 deep. The elongated oval shaped wings 

 (Fig. 86), usually directed forwards, since the whole organ is situated right 

 at the posterior border of the proglottis and close against the uterus-sac of the 

 next proglottis, are attached by narrow necks to the somewhat wider and bul- 

 bous isthmus. Ova from the latter are oval in shape, measure about 15 by \2n 

 and have nuclei 6/x in diameter with nucleoli 2.5^. As in B. scorpii the wings 

 occupy the whole of the dorsoventral diameter of the medulla, while the median 

 bulbous portion of the isthmus almost reaches the same level dorsally. The 

 oviduct arises dorsolaterally from the isthmus in the somewhat elongated 

 oocapt which has a diameter of 20 to 25^ and a length of from 25 to 30^. Im- 

 mediately beyond the oocapt it gradually enlarges from a diameter of 7 to 20/1 

 where it is joined by the vagina only a short distance either to the right or 

 left from its point of origin. At the junction of these two ducts there is only 

 a very small vestibule, as in the foregoing species, into which, nevertheless, 

 the oviduct may be seen to open by a longitudinal slit, and from one corner 

 of which it proceeds with a diameter of 6.5/x. After continuing almost directly 

 dorsally with only a few very open coils it is joined at about the level of the 

 upper edge of the isthmus by the common vitelline duct. Thruout its course 

 the epithelium of the oviduct is poorly provided with ciha and is surrounded 

 by only a comparatively small number of circular muscle fibres. The common 

 vitelline duct has a diam.eter just beyond its point of origin with the oviduct of 

 25ai or more. It is directed transversely above the generative space from the 

 dorsal edge of one horn of the ovary to about the median line, where the separate 

 vitelline ducts unite. In sections it is usually filled with yolk cells. The vitel- 

 line ducts, themselves, pass laterally close in front of the wings of the ovary, 

 and hence between them and the vas deferens and uterine tube. When empty, 

 they have a minimum diameter of only 3^t. The vitelline foUicles, as shown in 

 figure 86, occupy almost the whole of the cortical parenchyma between the 

 longitudinal muscles and the nuclei of the subcuticular cells. They are ellip- 

 soidal in shape, their longest diameters being directed at right angles to the 

 surface of the strobilia. They are longest near the median line and smallest 

 at the edges of the strobila. In general they may be said to be arranged in two 



