DISTOMUM OIRRIGEKUM. 279 



basement membrane are circular muscles, and outside of 

 these longitudinal muscles, thus recalling the condition seen 

 in a Chastopod. 



The R e p r o d n c t i V e vS y s t e m . — The testes are two large 

 rounded bodies lying ventrally to the gut-cteca. The right- 

 hand one is in front of the left, but nevertheless the slender 

 vasa deferentia are of about equal length, the right one 

 becoming looped upwards as the testis is thrust forwards 

 during development. In the quite young individual the two 

 testes are at the same level (Figs. II and XII). 



The vasa deferentia open together into a very large 

 vesicula seminalis, which is a thin-walled sac bent sharply on 

 itself, and leading by a short tube into the protrusible 

 muscular cirrus. The Avhole structure, including the vesicula 

 seminalis and the cirrus, is enclosed in a muscular sheath, 

 which may be called the cirrus-sac (Fig. III). 



In the space between the wall of the sac and the cirrus are 

 large glandular cells {jrr. gL), which are supposed to act as 

 prostate gland. The position of the cirrus-sac varies con- 

 siderably in different individuals. It may be either practically 

 in the middle plane or, more usually, well on the left side ; 

 occasionally it is on the right, A similar variation has 

 been noticed by Looss ^ iu various species. 



The ovary (Fig. V, o. v.) is a rounded structure lying nearly 

 centrally in the body. From it there springs a short, wide 

 oviduct, which meets (I) the duct from the receptaculum 

 seminis (r. s.), which is a thin-walled vesicle lying to the right 

 of the ovary ; (2) the common duct from the yolk-glands ; 

 and (3) the uterus. Laurer's duct (L. d.) extends from the 

 commencement of the duct of the receptaculum to the ex- 

 ternal aperture. Its close connection with the receptaculum 

 would seem to indicate that its function is to keep the vesicle 

 clear of waste yolk and cement substance, for otherwise the 

 vesicle might readily become blocked with extraneous matter. 

 At the place of meeting of these ducts there is the usual 



• Looss, A., " Weitere Beitiiige zur Kenntniss der Trcmatoden-Fauna 

 aegyptens," ' Zool. Jalirbiicher (Systematik)/ Bd. xii, 189S-9. 



