1920.] R. B. Seymour vSewei.Iv : Mesocoelium sociale. 



89 



hrinum {I.e. 1912, p. 332). In mature specimens the ovary- 

 is considerably smaller than the testis : in all my examples its 

 outline is circular and from the median and posterior aspect 

 arises a short wide oviduct (fig. 3 ovd.). After a short course 

 the oviduct receives on its posterior aspect the duct from the large 

 pear-shaped receptaculum seminis {r.s.), and immediately beyond 

 this point it gives off Laurer's canal (/.c), which turns forwards 

 and upwards and opens on the dorsal surface above the aceta- 

 bulum : the oviduct is then continued on across the middle line 

 and receives posteriorly the common vitelline duct (vitd.) ; it 

 then enters MehUs' gland {Mg.) and dilates to form the ootype 

 (oGt.). On leaving the oot^-pe the uterus {n.) turns forwards for 

 a short distance and then bends sharply backwards towards the 

 posterior end of the body, which is almost completely filled with 



oa 



oi/cL 



7jit/d,. 

 r.s. 



Fig. 3. — The female reproductive system of Mesocoelium sociale (Liihe). 

 La., Laurer's canal; Mg., Mehlis' gland ; oot., ootype; ov., ovary; ovd., 

 oviduct; r.s., receptaculum seminis ; u., uterus; vitd., vitelline duct. 



its coils and convolutions (fig. i u) : it finally turns forwards 

 again and, passing ventrally to the testis on the side of the body 

 opposite to that on which the ovary lies, it bends inwards to- 

 wards the middle line and opens at the genital pore. The terminal 

 portion of the uterus or metraterm (fig. 2 met.) is thick-walled and 

 muscular ; internally is a layer of circular muscle-fibres and im- 

 mediately external to this is a la^'er of gland-cells, with oval or 

 rounded nuclei 



The viteUaria or yolk-glands (fig. i vit.) consist of a number of 

 oval or rounded follicles, and extend from the side of the oral 

 sucker, backwards along the sides of the body to the posterior 

 extremity of the intestinal caeca : as a rule they do not extend 

 backwards beyond this point, though in a few examples they 

 are slightly more extensive. In the anterior region of the body in 



