Japanese Ti-icladida Maricola. 07 



found to be filled with a granular substance, evident!}' the 

 secretory product of the uterine wall. Besides, I have nowhere 

 been able to find out ova and yollc cells. In my opinion, this 

 organ has perhaps no functions in connexion with the union of 

 the sexual elements and also with the formation of the cocoon, 

 but it seems doubtless to act as a seminal receptacle. As already 

 stated, it seems beyond doubt probable that fertilization takes 

 place in the lumen of the tuba of the oviduct. I think, therefore, 

 I am justified in showing the organ in question as the primary 

 seminal receptacle against the tuba. As to the function of secre- 

 tion of the uterine wall it is difficult to account for the presence 

 of a secretion in the uterus unless it serves as a nutrient jnedium 

 for prolonging the activity of the male elements. 



Vagina. — In Fr. lacfca the vagina arising from the anterior 

 part of the receptaeulum runs anteriorly and obliquely downwards 

 to join tlie vestibular part of the genital atrium from l^ehind, and 

 undergoes a small outbulging at the postero-inferior part. Its 

 wall is of cuboidal cells resting upon a fine basement membrane, 

 just outside which there exist internal circular and external 

 longitudinal muscular layers. As I have already stated, the wall 

 •of the outbulging is perforated by the efferent ducts of the eosi- 

 nophil glands, which are scattered in sparse numbers in the 

 parenchyma around the same. 



In ^St. trigonocephala the receptaeulum give rise at its antero- 

 , superior part to the vaginal canal which runs down to open into 

 the genital atrium from behind. As is shown in fig. ~) (PL I), the 

 vagina has special epithelial cells in the wall, eacli being wholly 

 destitute of nucleus. In sections the cell-boundaries can be clear- 

 ly made out, being cuboidal. The epithelium rests upon a 

 ^delicate basemejit mem})rane, exterior to which are distinctly seen 

 the strong circular and weak longitudinal muscles. Moreover, 

 •outside the muscular layers there exi-sts a cellular coating which 

 proba1)ly partly represents the insunken parts of the lining 

 epithelium. Processes from the cells are occasionally seen to 

 extend to, and to join the epithelium. The vaginal part just in- 

 ierior to the point where it receives the openings of the oviducts is 



