780 PROF. G. C. BOURNE ON THE 



flattened sac and extends some way behind the posterior end of 

 the V-shaped duct. 



Of the Pacific and Oriental genera, Aphanoconia (PI. XXXV. 

 fig. 27) most nearly resembles Alcadia and Eutrochatella. The 

 descending limb of the V-shaped duct is large ; the ascending limb 

 short and scarcely differentiated from the hinder end of the 

 ootype ; it bears a relatively large globular receptaculum seminis. 

 The vagina is fairly long, and opens b}'- a very short transverse 

 duct rather high up into the ootype. The vaginal sac is short. 

 There is no cpecum to the ootype. The female ducts are very 

 similar in all the four species of Aphanoconia that I have examined, 

 differing chiefly in the relative length of the vaginal sac and 

 the position of the vagino-ootypal connection. 



On the other hand, Palceohelicina (fig. 28) and Orohophana 

 (fig. 29), while resembling one another, differ in some important 

 respects fi-om the West Indian genera and from Aphanoconia. 

 In Palmohelicina idm the ascending limb of the V-shaped duct is 

 wide and scarcely differentiated from the hinder end of the ootype. 

 There is no receptaculum seminis, but the ootypal caecum is large, 

 bilobed at its extremity, lined by an epithelium of peculiar cha- 

 racter, and filled with spermatozoa. It evidently functions as a 

 receptaculum seminis. The vagina and vaginal sac are normal. 

 In Orohophana ponsonhyi the descending limb of the V-shaped 

 tube is unusually long ; the ascending limb very narrow and short, 

 and does not bear a receptacLilum seminis. The csecum of the 

 ootype is large, bilobed, full of spermatozoa, and in every respect 

 similar to that of PakEohelicina. The vagina is long ; the vaginal 

 sac leaves it about halfway between its external aperture and its 

 connection with the ootype. 



I am unable to give a description of the female organs of 

 Lucidella aureola, as all my specimens were males. 



Summing up the above facts, we see that as regards the 

 structure of the gonaducts there are two types in the genera dealt 

 with. In the first type there is a receptaculum seminis on the 

 ascending limb of the V-shaped duct. This type is divisible into 

 two sub-types : the one, found in Alcadia and Uiotrochatella, is 

 characterized by the lai^ge csecal appendage of the ootype ; the 

 other, found in Aphanoco7iia, has no such csecum. In the second 

 type, represented in Palceohelicina and Orohophana, there is no 

 receptaculum seminis on the ascending limb of the V-shaped duct, 

 but this organ is replaced functionally by the modified bilobed 

 caecum of the ootype. According to Wagner (12) Palceoheli- 

 cina stands nearest to Helicina sensu restricto, and therefore 

 nearer to Alcadia than other Oriental and Pacific forms, but in 

 the structure of the female gonaducts, Aphanoconia stands nearest 

 to Alcadia, but Palceohelicina with Orohophana stand somewhat 

 apart. 



The gonaducts of the Helicinidfe evidently undergo great histo- 

 logical changes at the onset of sexual maturity. In sections of 

 immature females of Alcadia and Eutrochatella the ootype is a 



