THE TURBELLARIA 



37 



opens into a short median tube or "egg duct" with muscular walls. 

 This duct on its way towards the exterior receives the necks of 

 numerous glands, and this region is the "shell gland" (ootype), (Fig. 



'i, 



en 



FIG. XVII. 



Plan of the anatomy of a Polyclad (from v. Graff) ; ventral view, en, brain ; i, intestinal 

 caeca ; i\, anterior, median, supra-cerebral caecum ; In, ventral nerve ; m, mouth ; od, oviduct ; 

 ot', ovary ; ph, pharynx ; phi, pharyngeal sac ; st, stomach or midgut ; t, testis ; tt, uterus ; vd, 

 vas deferens ; <$, penis; 9> vagina.^ 



XVIII.) ; lower down the duct enters the " antrum femininum " ; 

 but in its course it, in many cases, becomes surrounded by a thick 

 muscular sheath and then forms a bursa copulatrix (Leptoplanidae, 

 Planocera, and others), and in these forms the penis is " armed." 



