SECOND TYPE OF SEXUAL ORGANS. 317 



number of eggs. The latter are further generally enclosed in a 

 common more or less firm envelope, as we shall afterwards see in the 

 case of Tcenia elliptica and others. 



If, however, there be two pori genitales in every joint, the uterus 

 always remains simple, but instead of a simple vagina, it then possesses 

 two (each with a receptaculum). In Tcenia elliptica (Fig. 143), T. 

 denticulata, and others, each vagina has a special germ-producing organ, 

 whilst in the " biporous " proglottides of Tcenia solium the ovary and 

 yolk-gland are developed as usual along with two symmetrical vaginse 

 (p. 279). According to Moniez, the two receptacula of T. Giardi (a new 

 form found in the intestine of the sheep, and nearly related to T. denticu- 

 lata) send each a fertilising canal to the ovary of the opposite side. 1 



The second typical form of the sexual organs is much more widely 

 distributed among the Cestodes than the one which we have considered, 

 and indeed apparently occurs in all the species which remain after 

 the exclusion of the Tseniadse (i.e., in the Bothriadae), being found in 

 the forms where the genital pore is marginal, as well as in those where 

 it is situated on the surface. As the former have a very general re- 

 semblance to the Tcenice in regard to the structure of the male appar- 

 atus, vagina, and ovary, and as none of them are found in man, we 

 need not give them special attention. 2 Further, their distinctive 

 characteristics, and especially the structure of the yolk-gland and the 

 presence of a special uterine opening, 3 will be sufficiently elucidated 



1 Comptes rendus, t. Ixxxviii., p. 1094, 1879. 



2 Compare, regarding the sexual organs of these forms, the statements of van Beneden 

 (" Vers Cestoides," p. 53), and of Sommer and Landois (loc. cit.) Moniez's recent reports 

 (loc. cit. ) on these structures, as specially observed in a new form, Leuckartia, are indeed 

 very divergent, for he disputes the independent existence of nearly all the parts except 

 the yolk-gland, but particularly of the uterus, shell-gland, and ovary. He thinks that, 

 as in Tania, the eggs originate in a cellular mass found in the meshwork of the paren- 

 chyma, provide themselves with yolk-granules, which reach them by ways of their own 

 making, and lastly become surrounded by a shell. My own investigations, which had 

 partly to do with the same objects (Ligula), do not lead me to agree with Moniez's inter- 

 pretation and description, but, on the other hand, I do not deny (p. 312) that the sexual 

 organs and the later formed connective substance both originate from the primarily quite 

 undifferentiated cellular mass of the parenchyma. 



3 I may, however, expressly mention that the presence of this uterine opening has as 

 yet only been observed in few Bothriadse, although its general presence may be presumed 

 from the essential uniformity in the structure of the sexual organs. I am also convinced 

 that a similar opening is to be found in Ligula and Schistocephalus two species, which in 

 spite of the many differences which they exhibit in the organization of their sexual appara- 

 tus, are essentially allied to the Bothriadae. Donnadieu's statements regarding the 

 sexual organs of these animals (Archiv. pJiysiol., 1878), rest upon a complete misconception 

 of their real structure : see the above -cited memoir of Kiessling. Further, if the Tseniadae 

 possessed a uterine opening like the Bothriadae, it would be situated on the at present 

 closed anterior extremity. At least it would be so in the species with a perpendicular 

 uterus, and in those where the uterus assumes a transverse course it would presumably 

 occupy a lateral position. 



