MORPHOLOGY OP THE HELICINID^. 777 



epithelium. The ureter is a widish tvibe which after leaving the 

 glandular sac turns back to run round the hinder wall of the 

 pericardium, interposing itself between it and the lower sui^face 

 of the visceral mass. After passing from the left to the right 

 side it mounts upwards again, passes under the reno-pericardial 

 canal, and opens into the right-hand side of the mantle-cavity 

 by a thick-lipped slit-like uropore. As is shown in fig. 23, the 

 mantle-epithelium is invaginated at the lips of the uropore, and 

 this invaginated portion is ciliated, but there is no ui^opore-sac 

 such as I have described in the Neritidte. 



The reno-pericardial canal (figs. 19 & 22) opens out of the 

 lower part of the right-hand recess of the glandular part of the 

 kidney, and runs straight into the right side of the pericardium 

 opposite the middle of the expanded base of the auricle. The 

 canal is short, straight, and narrow, lined by a cubical ciliated 

 epithelium, the component cells of which are small and bear no 

 resemblance to the very large ciliated cells lining the long twisted 

 reno-pericardial canal of the Nei'itidje. The cilia are fine and 

 directed towards the kidney. A thickening of the epithelium at 

 the pericardial opening of the canal is suggestive of the presence 

 of a pericardial funnel. The structure and relations of the kidney 

 and the reno-pericardial duct are remarkably uniform in all the 

 species of Helicinidse that I have examined. 



The Generative Organs. 



Thiele (10) has shown that the female ducts ai-e monaulic in 

 Hydrocena cattaroensis, but diaulic in Helicina ktiharyi. Before 

 my memoir on the Neritidfe was published I had discovered the 

 diaulic ducts in Alcadia and Euirochatella, but, as I omitted to 

 make mention of them in that place, I must yield priority to 

 Thiele, whose diagrammatic figure {loc. cii. text-fig. 2) gives a 

 coiTect representation of the general relations of the various sub- 

 divisions of the ducts. But it is almost impossible to construct a 

 life-like picture of such complicated organs from a study of 

 sections, and as I have dissected out the gonaducts, both male and 

 female, in a number of species and have checked my observations 

 by the study of sections, I may be pardoned for again taking up 

 the subject and entering into it at some length. From the 

 analogy of the Neritidfe, in which family the gonaducts exhibit a 

 considerable range of variation, I expected to discover equally 

 great diflerences in these organs in the various genera of Heli- 

 cinidfe, but have been disappointed. There are difl^'erences, it is 

 true, biit they are slight and do not throw much light upon the 

 systematic aflinities of the various genera studied. 



The gonads in all Helicinidas lie above and to the right side of 

 the liver. The ovaries are follicular, and the follicles open into a 

 large thin-walled chamber which in Alcadia and Eutrochatella is 

 situated on the right side of the visceral mass, just behind the 

 posterior end of the right columellar muscle and in front of the 



