On the reproductive system of Planaria simplissima. 457 



(PI. 31, Fig. 4 S2)2). While it seems probable from this that fer- 

 tilization occurs in the oviduct a glance at the side view of the system 

 (PI. 31, Fig. 8) showing the relation of the common oviduct, uterus 

 and vagina will show that with a slight contraction of the strong 

 vaginal muscles the eggs coming out of the common oviduct would 

 find a ready entrance into the cavity of the uterus. 



The vagina formed by the union of the common oviduct and 

 uterus (PI. 31, Figs. 1 and 8 va) enters the atrial chamber in the 

 posterior upper region. It is lined by an epithelium continuous with 

 that of the genital atrium and similar to it in appearance. Through 

 this epithelium is poured out the secretion of a large number of uDi- 

 cellular glands situated some distance away. These correspond to 

 the long stalked "shell-glands" of the vagina which Bergendal ('92, 

 p. 316) distinguishes from the "Eiweissdriisen" of the uterus and 

 uterine canal and are the same in position and appearance as those 

 described by Lang ('81) for Gunda (tab. 14, fig. 56 ew) and Ijima 

 ('84) for Planaria polychroa and Dendrocoelum lacteum (tab. 21, figs. 1 

 and 5 edr). The cells lie on all sides of the genital atrium in the 

 periphery of an area bounded laterally by the two oviducts and an- 

 teriorly by the uniting vasa deferentia. Their long stalks converging 

 on the vagina, as indicated by the arrows in PI. 31, Fig. 1, unite 

 into a mass composed of many parallel threads which passes through 

 the epithelium on either side of the cavity. At these lateral areas a 

 small amount is found spreading over the surface and the granular 

 secretion is seen to cause the deeper staining which separates this 

 part of the epithelium so distinctly from that above and below. 

 Whether the secretion actually passes through the epithelial cells 

 I cannot determine. They are so surcharged with it that the cell-out- 

 lines are not visible and the nuclei quite indistinct. 



II. The Activity of tlie Reproductive System during 

 the Winter. 



Although specimens taken at frequent intervals from October to 

 April were examined for any decided change, the results obtained in 

 this line have been meagre and for the most part negative. The 

 testes in different animals collected at the same time presented various 

 degrees of development and the individual follicles of the same worm 

 often showed almost as great ditierences. The several steps in the 

 formation of the testes showing at first a solid compact mass of cells 

 already connected with the vas deferens or with a neighboring follicle 



30* 



