730 ON SOME TREMATOUK PARASITES 



the anterior surface of each testis respectively ; that from the pos- 

 terior skirts round the lateral aspect of the ovary and anterior 

 testis (Fig. 5), and joins its fellow just after it leaves the 

 anterior testis. The tube, formed by their union, shortly enters 

 the vesicula seminalis, which is a coiled tubular body, of compara- 

 tively considerable length, not enclosed in the cirrus-sac, but lying 

 free in the parenchyma. The cirrus-sac, a moderately developed 

 muscular sac, surrounding the cirrus with its ejaculatory duct, does 

 not extend inwards beyond the junction of the ejaculatory duct 

 with the vesicula seminalis. The prostate cells lie free in the 

 parenchyma. The cirrus-sac and vagina, Avhich has thick muscular 

 walls, are surrounded by modified parenchyma cells. 



The ovary(0'39 x 0-31 mm.) is smaller than the testes, and lies 

 either median or slightly lateral. Like the testes, it is a smooth 

 oval body. The oviduct leaves it in the middle of its ventral sur- 

 face (Fig. G), and runs to its posterior edge; here the ootype is 

 situated, and just in front of this, Laurer's canal takes its origin, 

 and curves round to the dorsal surface, where it opens on tlie 

 exterior (Fig. G). There is no receptaculum seminis. The "shell- 

 glands" round the ootype are not well developed. The yolk-reservoir 

 lies close to the ootype. From the ootype, the female duct runs 

 forwards in a slightly coiled course to the level of the genital open- 

 ing, and this part of it, which is stuffed full of sperms, is the recep- 

 taculum seminis uterinum; it then runs, in a series of transversity 

 placed loojjs in the ventral surface of the body, as far forwards 

 as the middle of the ventral sucker, returning in the dorsal part of 

 the body by a series of complex folds to end at the genital open- 

 ing. The loops of the uterus laterally lie strictly within the inner 

 boundary of the intestinal limbs. 



The yolk-glands consist of numerous, quite small, oval follicles 

 (average size 0-038 x 0-023 mm.), wliicli lie in the lateral aspect of 

 tlie body outside the intestinal limbs; in front, they just reach the 

 level of the posterior edge of the ventral sucker, while posteriorly, 

 they do not pass beyond tlie level of the anterior testes. Their 

 ducts form tAvo conspicuous lines that at first gradually, then more 

 quickly, converge on the yolk-reservoir. 



