STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAN. JJl 



other presents no trace of such a condition. This difference, how- 

 ever, appears to me to be not so fundamental as to effectually bar 

 the homology of the two ducts, since both the Cestodes and the mono- 

 genetic Trenlatodes must have undergone numerous modifications in 

 different directions since they have divei'ged from a common stock. 

 This difference, then, being eliminated as of secondary importance, 

 and the blind ending of the uterus in Tceniaheing assumed to be also 

 a secondary modification scarcely requiring further exposition here, 

 there is a remarkable coincidence between the vagina of the Monogenea 

 on the one hand and the uterus of the Cestodes on the other, in their 

 relation with the other genital ducts. Thus, both unite with the 

 yolk-duct at one end and open outwards at the other. It is indeed 

 true that in Bothrioceplmlus latus the uterine pore is situated on the 

 ventral side ; but the homologous pore is also on the same side in 

 many species of ectoparasitic Trematodes, as Trlstomum, Monocotijle, etc.; 

 and in many species of Botliriocephalus the opening is on the dorsal 

 side, as may be seen from the figures published by Matz'^ in his 

 paper on Bothriocephalus. After all, the position of the external 

 openings is, as Looss has justly remarked, of quite secondary 

 importance, and as already mentioned varies considerably in different 

 members of the same group. In Bothrioceplmlus the uterus can not 

 exactly be said to open into the yolk-duct; on the contrary, the uterus, 

 the oviduct, and the yolk-duct meet at one point ; but a similar case 

 occurs in Monocotijle among the mOnogenetic Trematodes. I there- 

 fore believe that the uterus of the Cestodes is homologous 

 with the vagina of the Trematodes. ' 



The view above explained seems to me to possess at least one 

 advantage over others,' which is that it leaves no residual pheno- 



1).. Matz — Beitriige zur Kenntniss der Bothriooephalen. ArcHv f. Naturgescluchte, 

 Jahrg. 58, 1. Bd. 



