THE VAGINA AND UTERUS. 319 



of both sides open. The testes are apparently always present in great 

 numbers and pretty equally distributed over the middle layer. 



The vagina and uterus (Fig. 170, B) have, on the whole, the same 

 course as the seminal duct, only differing from it in so far as they lie in 

 another plane. This is especially true of the vagina, which lies upon 

 the ventral surface, very much as the vas deferens lies upon the dorsal 

 surface. These three canals cover one another in their course, and this 

 must be to a large extent the reason why the vagina the narrowest 

 and most insignificant of the three, in spite of its contents of semen 

 has remained only imperfectly known, and was often wholly 

 overlooked till after Stieda's researches. It runs downwards in a 

 pretty straight course, while the uterus, at least in the older joints, 

 forms on each side a number of oval loops. These project a consider- 

 able distance towards the sides, and are all the more conspicuous 

 since they are stuffed full of eggs, and from their dark colour stand 

 out in sharp contrast to the other organs. Only in the narrow 

 posterior part does the uterus exhibit less regular windings, and a 

 more simple structure. Although the hinder portion of the vagina is 

 not unfrequently distended into a sort of caecum, no proper sperm- 

 pouch seems to be present, the whole vagina being, as we have men- 

 tioned, usually filled with semen. 



At the connection of the vagina with the uterus there is also a 

 fertilising canal, which ends in a shell-gland the so-called "coiled 

 gland" of which the real nature was first understood by Stieda, and 

 which I erroneously held to be the ovary. This canal, as in the 

 Taeniadae, receives the efferent canals of the proper reproductive organs. 

 Although there are instances of a more or less marked simplification 

 (Caryopliyllceus) the ovary is, as a rule, of a hand-like or wing- 

 shaped structure, and, except in Ligula, generally exhibits the already 

 familiar symmetrical arrangement. This is the structure which I 

 formerly identified in Bothriocephalas and in the Tcenice as the 

 yolk-gland, which is, however, really represented by the organs de- 

 scribed by Eschricht as ventral and dorsal granules. These yolk- 

 glands are, indeed, the most striking and important characteristics of 

 the Bothriadae, not only on account of their size, but because, unlike 

 the other sexual parts, they belong to cortical layers of the body. In 

 many species they run down the sides of the joint in the form of a 

 pretty large caecal tube, abundantly provided with lateral protube- 

 rances, especially on the outer side. They open ultimately into the 

 vaginal canal by means of an efferent canal, which runs transversely 

 from the middle line, and close beside the shell-gland. They thus 

 exhibit conditions similar to those which we shall afterwards find in 

 the Trematodes conditions, moreover, which may undergo many 



