184 s. GOTO. 



the absence of any membrane in the ovum of Tristomum ; so also 

 Wierzejski'' in that of Calicofiße Kroijcri ; and I believe the same is true 

 of the ova of all ectoparasitic Trematodes. As we proceed nearer the 

 smaller end of the ovary, the ova and their nuclei become smaller 

 and smaller, the vacuoles within the nucleolns disappear and finally 

 the nucleolns itself, until we see only spherical nuclei crowded to- 

 gether and surrounded by a common mass of uniform protophi>;m. 

 Fig. 22 shews a section through this part. 



The oviduct proceeds from the larger end of the ovary and takes 

 its course posteriorly and to the right, ventral to the vas deferens and 

 the testis. At a short distance from its origin, it receives a canal 

 (Fig. 2, cc) which proceeds anteriorly and, after making a slight wind- 

 ing or two, opens into the intestine (Figs. V & XIX). This is the 

 " Laurer's canal" of Zeller which he represents as standing in direct 

 connection with the vas deferens of the other individual. In Poljisto- 

 inuni integer rimuur^ he asserts a direct connection between the ovary 

 and the testis ; and in proof of this he alleges his observation of the 

 ova passing through the oviduct and Lanrer's caiial and entering the 

 cavity of the testis. But it has been pointed out by Ijima'"' that the 

 canal in question distinctly opens into the intestine, and that a similar 

 canal is present in many other species of the group ; and I can con- 

 fidently state from my own study that the ''dritte Dottergang" of 

 Lorenz in Axineixwà Microcotyle distinctly opens into the intestine. A 

 similar connecting canal is also present in a species of Octohothrinm 

 which I have examined."*' The fact cited by Zeller can be explained 



1) Wierzejski— 1. c. p. 558. 



2) Zeller— Weiterer Beitrag z. Kenutniss d. Poljstomeen. Ztschr. f. w. Z. Bd. XXVII. 

 1876. p. 245. 



3) Ijima — Über den Zusammenhang d. Eileiters mit d. Verdauungscanal bei gewissen 

 Polystomeen. Zool. Anz. Jahrg. VII. 188i. p. 635. 



4) Voeltzkorw (Arb. a. d. zool.-zoot. Inst, in Würzburg. Bd. VIIT. 1888. p. 267) describes 

 an evidently homologous canal in Aspidogaster conchicola. According to him it ends blindly 

 near the dorsal surface of the worm. He calls it Receptaculum vitelli. 



