700 



THE ANATOMY OF BOTHEIOCEPHALUS LATUS. 



their considerable size (up to 0'25 mm.), to be regarded as degenerated 

 testicular vesicles. This supposition is at least more probable that the 

 interpretation of Landois and Sommer, according to which they are 

 " portions of the vas deferens or of the large seminal ducts " which 

 have been constricted off, and whose contents have undergone fatty- 

 metamorphosis. 



The Female Beproductive Organs. — The Vagina, as above noted 

 (Fig. 363), opens just below the cirrhus-pouch into the bottom of the 

 genital cloaca. In spite of the approximation of their apertures, 

 their mutual position is such that the possibility of self-fertilisation 

 uo ulo seems all but excluded. Por such 



a purpose the cirrhus would have 

 to bend at an acute angle backwards 

 and downwards, for which it is the 

 less capable, since the cloaca is 

 flattened out when extruded, and 

 external pressure cannot therefore 

 act upon it, as in the Tcenice (p. 309). 

 The vulva is a somewhat wide 

 (0-06 to 0-085 mm.) and funnel- 

 shaped, but yet short, invagination 

 of the external envelope of the 

 body, which is directly continued 

 into the much narrowed vaginal 

 canal (0024 to 004 mm.). The 

 latter extends, as can be seen in 

 longitudinal sections, for some dis- 

 tance below the cirrhus-pouch to- 

 wards the dorsal surface (Fig. 367). It bends, however, before it 

 reaches the opening of the vas deferens, at an acute angle towards the 

 ventral aspect, and finally extends almost straight backwards, in the 

 middle line, upon the transverse muscle layer of the joint. Eeaching 

 the anterior border of the ovary, it leaves the ventral muscle-layer, 

 passing on to its dorsal surface, on which it continues its course for 

 some distance further. The posterior end of the vagina usually forms 

 a more or less large (0-12 to 0-2 mm.) saccular dilatation, filled with 

 semen. This is to be regarded as a receptaculum seminis, although it 

 is not in any way histologically different from the rest of the canal, 

 and is further so slightly separated anatomically, that when quite 

 filled it is for some distance quite continuous with the adjacent 

 portion of the canal. This csecal vaginal receptacle communicates by 

 a narrow duct, as we shall presently see, with the hinder end of 



the uterus and with the. other portions of the female apparatus. 

 Digifizecrby Wlicroson® 



Fie. 366. — Female generative organs of 

 Bothriocephalus Jatus, from the ventral 

 surface, ov., ovary; r.s., receptaculum 

 eeminis ; s.g., shell-gland ; ut., uterus ; 

 ut.o., uterine opening; v., vagina; v.o., 

 vaginal opening, (x 20.) 



