MORPHOLOGY OF THE HELICINID^. 781 



relatively nari-ow tube lined by a columnar epithelium, in which 

 glandular elements are hardly recognizable, and there is a similar 

 lack of differentiation of glandular cells in the V-shaped duct. On 

 the approach of sexual maturity the epithelium of the ootype is 

 enormouslj' thickened, is rich in glandular elements, and is thrown 

 into complicated folds ; at the same time, histological changes 

 occur in the V-shaped duct. In the breeding-season, when the 

 ootype is distended as shown in fig. 25 (PI. XXXV.), the epithelial 

 folds of the ootype disappear, the gland-cells have discharged their 

 contents, and the epithelium appears shrunken and thinner than 

 before. In consequence of these changes, it is difficult to give 

 a consistent account of the histological characters of the ducts : 

 what follows is based on a series of sections of a mature 

 specimen of Alcadia hollandi, in which the tissues, thanks to 

 Mrs. Longstaff 's care, are admirably preserved. 



In the distal half of the ootype, that is in the portion mai^ked a 

 in fig. 25, the epithelium is moderately long and of the mixed 

 glandular and ciliated kind. The ciliated cells are elongate 

 columnar, not much attenuated at their bases, their cytoj)lasm 

 clear and very finel}^ granular, their nuclei rather large, oval, 

 situated rather to the basal side of the middle of the length of 

 the cell. The gland-cells are of nearly the same shape, but of 

 rather greater diameter than the ciliated cells, their nuclei slightly 

 larger, situated nearer the bases of the cells, and the cell-body 

 filled with rather small highlj' refracting spherules of a greenish- 

 yellow colour in preparations stained with hfematoxylin and eosin. 

 The hinder moiety of the ootype — namely, that poi'tion filled with 

 the mass of spermatozoa in fig. 25 — shows somewhat diflerent 

 characters. The supporting epithelial cells are, as before, columnar 

 and finely granular, but of greater length : they appear to have 

 lost their cilia over the greater part of the inner wall of the 

 ootype and to end distally in rounded and somewhat vacuolated ex- 

 tremities, but as I can find cilia in patches this appearance may be 

 due to maceration. The gland-cells in this region (PI. XXXVII. 

 fig. 36) are not very abundant, but characteristic, and presumably 

 mucinogenous as they stain deeply in hsematoxylin. Their basal 

 ends, I'esting on the basal membrane, are broad and in each is a 

 rather small subspherical nucleus, above Avhich the cell tapers to 

 a fine tube filled with a darkly staining granular material : these 

 attenuated cell-bodies run between the supporting cells and ter- 

 minate in swollen extremities filled with coarse deeply staining 

 spherules. Throughout this region of the ootj^pe the epithelium 

 is thrown into ridges and furrows, which are partly due to the 

 folding of the walls, but chiefly to the unequal length of the 

 epithelial cells. At the hinder end the folds increase and there is 

 a prominent valve projecting into the lumen and making a com- 

 plete spiral turn just above the opening of the V-shaped duct. 

 This opening, guarded b}'^ the above-mentioned valve, is narrow. 

 The upper part of the V-shaped duct is lined by an epithelium of 

 the same character as that of the hinder moiety of the ootype, the 



Proc. ZooL. Soc— 1911, No. LIV, 54 



