MORPHOLOGY OF THE HEUCIXIDJl. 779 



homologous in the two forms, as is also the vagina. The vaginal 

 sac of Alcadia coiTesponds to the spermatophore sac of Paranerita, 

 but in the former genus the duct connecting the vagina with the 

 ootype has been shortened to such an extent that it is merely a 

 passage between the two. The V-s^haped duct of Alcadia is only 

 a modification of the oviduct and has no exact homologue in 

 Paranerita ; the position of the receptaculum seminis is also 

 somewhat difterent. There is no trace of an oviduco-coelomic 

 funnel in any Helicinid. nor is there any representatiA"e of the 

 crystal-sac. On the other hand, the c^cum of the ootype is not 

 represented in the Xeritidse, for it would be straining homology 

 too far to suggest that it is the equivalent of the lower dilated 

 part of the ductus enigmaticus. But if the morphological com- 

 parison between the female gonaducts of the Keritid?e and 

 Helicinidfe is faii-ly obvious, a physiological comparison is by no 

 means so clear. In the specimen of A . hoUandi whose ducts are 

 drawn in fig. 25 the hinder moiety of the ootype wa^ filled and 

 greatly distended by a large mass of spermatozoa held together by 

 a coagulable substance, and, as shown in the figure, a string of the 

 same mass of spermatozoa and coagulum extended into and filled 

 the cfecum of the ootype. The vaginal sac was empty, but the 

 receptaculum was full of spermatozoa. Tliis suggests that the 

 '• oot3'pe " is the copulatory canal or functional vagina, and that 

 the •• vagina " may serve for the passage of the ova into the 

 mantle-caA"ity. But the probability of such a conclusion is 

 lessened by the fact that in Ajjhanoconia merguiensis and A. 

 goiddiana I found the vagina and vaginal sac full of spermatozoa. 

 I have not found ova either in the oviduct or in the ootype of any 

 of my specimens ; and apparently in the Helicinidse fertilization is 

 not effected by means of spermatophores, for I have found no 

 ti'ace of such structures. The mass of spermatozoa and coagiilum 

 in AlcaAia koUandi caimot be called a spermatophore. The 

 evidence as to the function of the several parts being slender, and 

 what there is conflicting. I offer no definite theory on the matter, 

 but may add that the " vagina " is evidently a distensible duct, as 

 it has thin walls, with a veiy feeble coat of cii'cular muscle-fibres, 

 but with a number of muscular slips passing from its walls to be 

 attached to adjacent organs. On the other hand, the ootype has 

 a thick muscular coat, especially in its hinder moiety, and the 

 contraction of this muscular coat would expel any contained 

 material through the external aperture. 



A comparison of the gonaducts of the seveial genera shows 

 certain differences in detail. The female gonaducts of Eutro- 

 ehaieUa. a ^"est Indian genus, are shown in PI. XXXV. fig. 26. 

 Their arrangement is clearly very similar to that of Alcadia. The 

 ascending limb of the V-shaped duct is shorter in Eutrochatella 

 and has more the appearance of a direct posterior continuation of 

 the ootype. The receptaculum seminis is small and ovoid, but in 

 the same position as in Alcadia. The vagina is short : the vaginal 

 sac of moderate length. The caecum of the ootype is a Iso^ge 



