170 S. GOTO. 



the direct continuation of the oviduct, and the vagina as an accessory 

 duct. JFrom a physiological point of view this, conception is quite 

 correct — the ovum in fact passes from the ovary into the uterus. 

 But, as I. have already explained above, this mode of conception seems 

 to me morphologically not correct. I regard the vagina as the direct 

 continuation of the oviduct, and both the yolk-duct and the uterus as 

 accessory ducts opening into the former. ' And in accordance with 

 this view I regard that portion of the genital duct in Taenia and 

 CaryophjllcBus'^^ (Ph XXVII, figs. 5 &.6) which lies between the 

 beginning of the vagina and the beginning of the utei'us as 'the yolk- 

 duct. It may be objected that the position of the shell-glands, which 

 are in other forms always situated around a portion of the oviduct, is 

 against such a view. But the shell-glands being evidently a special 

 physiological provision, I believe that their position must not be regard- 

 ed as constant; in fact, they do vary considerably in position even 

 among the monogenetic Trematodes; and if they can be displaced in 

 one direction there seems to me to be no reason why they can not be dis- 

 placed in another, provided only that thei-e be a physiological necessity 

 for it or an advantage gained thereby. I therefore believe that in 

 Tmnia the shell-glands have shifted position from the initial portion of 

 the vagina (or its homologue, as in the Trematodes) towards the 

 uterus, in consequence of the changed functions of these two canals 

 (i.e., their respective homologues) in the Trematodes and the Cestodes — 

 assuming for the time being that the monogenetic Trematodes present 

 a more primitive state of things. This granted, let us compare the 

 uterus of the Cestodes with the vagina of the monogenetic Trematodes. 

 The. most striking difference between these two structures is that 

 one of them is cleai-ly seen to have been originally paired, while the 



1). Cf. Monticelli's "Appuuti 'etc." and Will's " Caryophyllaeus mutabilis" (PI. II, 

 fig- 17). •• " ■ 



