28 



THE TURBELLARIA 



(Lang, Francotte (17), and Chichkoff (7)), and the external pores 



are known even now in only a few cases. 



The male generative organs present further advance on that 



follicular arrangement which is 

 just commencing in Alloiocoela. 

 In the female organs the differen- 

 tiation into germ -producing and 

 yolk'-producing organs, of which 

 every stage is presented by the 

 Khabdocoelida, has in the Tri- 

 cladida only reached half-way. In 

 fact, we have a branched "germ- 

 vitellarium," of which the most 

 4n anterior lobe or follicle produces 

 small egg cells, whilst the remain- 

 ing follicles give rise only to yolk 

 cells but all these follicles open 

 into a common " oviduct " (Fig. 

 XII.). This organ thus differs 

 from the "germ-vitellarium " of 

 Rhabdocoelida, merely by being 

 " follicular " instead of " compact.' 7 

 The two oviducts unite to form 

 a shorter or longer common duct, 

 into which numerous unicellular, 

 albuminiparous glands pour their 

 secretion. This region may be 

 muscular, and is termed " vagina.' 7 

 In its turn it opens into the 

 atrium genitale, which is common 

 to both sexes. The "uterus" 

 (Fig. XIII.), probably originally a 

 dilatation of the lower part of the 

 . oviduct ' becomes a diverticulum of 



g, germ-producing follicle of the ovary; tj, the Vagina (XIII. 1), (GuncUt. Plan- 

 anterior branch ; i%, i^, the right and left . -ff, 7 7 rf 7 j?\ / e , i 



posterior branches of the intestine; In, ven- ana, EhynckodemuS Scharfi), (cf. the 



FIG. XII. 



common genital pore. 



i/'; accessory sac of Polyclads) ; or it 



i T y T n , in c to , the atrium in - 



dependently of the oviduct, as in 

 various species of Planaria and 



Polycelis (XIII. 2) ; the process is carried further in Uteripoms, 

 where the organ opens outside the area of the atrium, and in the 

 parasitic Bdelluridae we find the same condition, but the uterus 

 is paired (XIII. 4). 



In addition to the normal male and female copulatory organs 

 the genus Artioposthia possesses elaborate accessory copulatory 



