CESTODARIA 443 



posterior end of some four or five main longitudinal canals 

 which unite into two or three to open into the excretory 

 bladder (texb) ; more anteriorly these canals apparently 

 branch into ten or more (PI. 24, fig. 12, excv). All these main 

 longitudinal trunks are connected by a network of finer vessels. 

 In the head region (PI. 24, fig. 6), especially at the base, a large 

 number of peripheral canals are visible under the subcuticula, 

 apparently belonging to a complicated dense network (cf. 

 C . 1 a t i c e p s), and a few canals of about the same size are also 

 visible in the centre of the medullary region, i.e. internal to 

 the zone of longitudinal muscle-fibres. I could observe no 

 distinction between ' ascending ' and ' descending ' vessels, 

 and my material was not sufficiently well-preserved to allow 

 me to detect flame-cells for certain. 



The eggs (PI. 24, fig. 11) contained in the uterus are ovoid and 

 thin-shelled, and measured, when mounted in balsam, 37-6- 

 41-3 microns in length and 20-1-25-6 microns in breadth. 

 They are thus nearly half the size of the eggs of C. 1 a t i c e p s . 



In addition to mature specimens of W. virilis I possess 

 five immature specimens all about 5 mm. in length (PI. 24, 

 figs. 1, d, 14, 15). In the youngest of these (fig. 14) the only 

 signs of developing organs are a strand of thickened tissue 

 with expanded ends (vagut) representing the future vagina 

 and uterus (this latter arises as a straight tube), the genital 

 openings and the isthmus of the ovary, and cell-thickenings 

 representing the future testes (tes). In an older stage 

 (fig. 15) the uterus has become convoluted, the genital openings 

 are distinct, the vas deferens is forming, and the rudiments 

 of the vitellaria are apparent. It is noteworthy in these 

 immature specimens that the post-ovarian region is evidently 

 not a mere secondary outgrowth, as is shown by the anterior 

 position of the rudiments of the hind ends of the vagina and 

 uterus. It is also noteworthy that these very immature forms 

 occur in the fish and not in a worm, and that they show no 

 signs of a ' caudal ' appendage comparable with that of the 

 larva of C . 1 a t i c e p s . The form of the post-ovarian region 

 in the next two species of Wenyonia to be described clearly 



