840 PROF. G. C. BOURNE ON THE [KoV. 17, 



fundus into the egg-duct. The dorsal side of the egg-duct is 

 capped by a considerable glandulai^ mass {m.gl.), whose contents 

 stain deeply in ha3matoxylin : it may therefore be identified as a 

 m.itcous gland. Beyond this is a narrow ring of glandular tissue 

 whose cell-contents stain bright rose-red colour in eosin and 

 carmine dyes : for this reason I shall refer to it as the rose- 

 coloured gland (figs. 12-14, rc.gl.). Beyond the rose-coloured 

 gland the egg-duct dilates to form a distinct chamber with thick 

 glandular walls. This chamber corresjwnds to the " premiere 

 ampoule " of Lenssen ; 1 shall call it the thalamus (figs. 14, 15, 16, 

 th.). It occupies the right-hand posterior corner of the genital 

 complex, and the gland surrounding it may from its position and 

 staining-properties be identified as the vitelline gland. The 

 oviduct, a nari'ow tube lined by a columnar ciliated epithelium, 

 emerges from the lower left-hand corner of the thalamus, runs 

 towards the left, is thrown into a few convolutions, then turns 

 sharply backward and downward and enters the connective-tissue 

 layer forming the floor of the large right extension of the gonadial 

 coelom. In its passage below this coelomic space it gives ofli" a 

 short branch to the right, which immediately opens into the 

 coelom by a ciliated oviduco-coelomic funnel (figs. 3 & 4, od.c.f.). 

 Beyond the oviduco-ccelomic funnel the oviduct branches 

 repeatedly ; the branches subdivide and end in a number of 

 claviform acini lined by a germinal epithelium and containing ova 

 in all stages of development. The ovary, thus constituted, is a 

 fairly extensive organ lying to the right of the liver and sjai-eading 

 for some distance over its dorsal surface. 



The second passage leading out of the fundus of the ootype is a 

 narrow thin-Avalled tube Avhich passes to the right and immediately 

 dilates to form a sac of considerable size lying between the 

 posterior end of the ootype and the rectum. As this sac always 

 contains free spermatozoa in greater or less abundance, it may be 

 called the sperm-sac. Its walls are thin, usually much folded, and 

 lined by a simple cubical ciliated epithelium without any trace of 

 glandular structure. In longitudinal section it is seen to be' 

 'U-shaped. 



Fi-om the bend of the U a short duct is given off posteriorly. 

 It has thick muscular walls, and ends in a thick-walled dilatation, 

 filled with speinnatozoa. This is the recejitacidum seminis 

 ( = spermatheca of Gilson). The limbs of the U are prolonged 

 forward as two narrow ducts, which acquire thick muscular walls 

 and open separately into the mantle-cavity. The outer or right- 

 hand duct corresponds to the "connecting duct" of Gilson and 

 Lenssen. I shall call it the vaginal canal. The inner or left-hand 

 duct is not represented in Nerita or in Neritina fltiviatilis, 

 and as its function is obscure I have named it the ductus 

 enigmaticus. The two ducts run forward close to one another and 

 to the rectum. The ductus enigmaticus is relatively short and 

 straight, and eventually opens into the mantle-cavity by a minute 

 pore situated on the ventral side of the genital complex and some 



