MORPHOLOGY OF THE HELICINID^. 783 



and between these ai^e very attenviated supporting cells. I could 

 not detect any cilia on the latter. 



The proximal two-thirds of the vagina and the vaginal sac 

 are lined by a non-ciliated epithelium of uniform character, the 

 details of which were not well preserved in my sections of Alcadia 

 and Eutrochatella : apparently they had been injuriously aflected 

 by the action of Perenyi's fluid. In Orohojyhana ])onsonhyi the 

 epithelial cells of the lower part of the vagina and of the vaginal 

 sac are squarish in outline, non-ciliated and clearly glandidar, for 

 each contains a number of coarse non-staining spherules. The 

 cavity of the sac contains a number of spherules of similar 

 character and among them ropy masses of some coagulable sub- 

 stance staining faintly in htematoxylin. 



In Orobopliana the epithelial lining of the ootj'pe differs in some 

 respects from that described for Alcadia. The supporting cells are 

 attenuated towards their bases, have long compressed nuclei 

 about the middle of their length, and are distinctly ciliated. The 

 gland-cells of the distal part of the ootype resemble those of 

 Alcadia, but are apparently differentiated to some extent, for the 

 granular contents of those on the inner side of the ootj^e nearest 

 the mantle-cavity are eosinophilous, those on the outer side are 

 not. Just above the entrance of the vaginal duct the eosinophilous 

 cells ai-e replaced by mucinogenous cells staining deepl}' in 

 heematoxylin. A large spiral flap or valve separates the opening of 

 the caecum from that of the ascending limb of the V-shaped duct. 

 The last named is very narrow and invaginated for some distance 

 into the terminal part of the ootype : it has no spiral epithelial fold, 

 such as is seen in Alcadia. The gland-cells of the distal limb of 

 the V-shaped tube are highly eosinophilous. 



Thiele (10) has shown that the female ducts of Hydrocena are 

 monaulic. The external aperture leads into a thick-walled glan- 

 dular duct, which is clearly homologous with the ootype of the 

 Helicinidee. The lumen of this duct is continued posteriorly into 

 a fairly wide canal lined b)' a columnar epithelium devoid of 

 glandular cells, and this ends in a saccular dilatation of consider- 

 able size, which is apparently glandular ; " sein Epithel enthalt 

 Kliimpchen von Kornchen." Thiele identifies this sac and its 

 duct with the vaginal sac and vagina of Helicina, and regards it 

 as the homologue of the right kidney of the Trochidse, which in 

 this case has not acquired an independent opening into the mantle- 

 cavity. In addition to this sac, three other structures open into 

 the hinder end of the " ootype " in Hydrocena : on the right a 

 thick-walled glandular c^cum ; on the left the oviduct ; and 

 between the two and dorsad of the " right kidney sac " a tubular 

 receptaculum seminis. Thiele's homologies seem to be perfectly 

 just, and after his discover}'- of the conditions obtaining in Hydro- 

 cena, I must agree with him in regarding the vaginal sac of the 

 Helicinidpe and the spermatophore sac of the Neritidse as the 

 representatives of the right kidney. But I still beg leave to 

 differ from his interpretation of the vaginal aperture as the 



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