200 LAND AND FRESHWATER 



mottled. Generative organs (fig. 3/) : the uterus was gravid and 

 swollen, and while examining and turning the animal about in a 

 watch-glass the transparent membrane broke, and out rolled a 

 single very large oval egg, immature, granular, and with a dark 

 nucleus. It measured 12 mm. on the major axis, 6| mm. on the 

 minor. 



The buccal mass (fig. 3 b) is rather small and globose, its main 

 muscles joining the shell-muscle are of great size and strength. The 

 salivary gland is in one united, long, narrow mass lying some way 

 back upon the intestine. 



Jaw oxygnathic, curved (fig. 3 e). 



The radula (fig. 3 d) was got out complete. Its formula is : — 



18 . 18 . 1 . 18 . 18 

 36 . 1 . 36 



The admedian and centre teeth all alike, narrow plates with a single 

 tooth. The marginal have a more oblong plate and broad cutting- 

 teeth sloping inwards. Semper gives a drawing of the 24th tooth, 

 but at this distance from the middle line the characteristic oblong 

 plates are not seen. 



Genitalia (fig. 3/). The penis is simple, bent on itself at the 

 retractor muscle, which is short and attached to the wall of the 

 branchial chamber ; the vas deferens is very long and thick, tapering 

 very gradually to where it joins the sperm-duct. The spermatheca is 

 evideiitly very long, its thin walls were broken and mixed up with 

 the uterus. It had evidently contained the spermatophore (sp.ph.); 

 this consisted of a very long, thin, elongate tube somewhat flattened*. 

 The oviduct and sperm-duct as usual, the first passing into an empty 

 thin-walled duct, in which the embryonic shells are often present ; 

 the albumen-gland was large and elongate. There is nothing to 

 indicate the presence of an amatorial organ. 



It will thus be seen that the generative organs in Gorilla are 

 remarkably similar to those of Plectopylis : vide Ferdinand Stoliczka's 

 memoir " Notes on Terrestrial MoUusca from the Neighbourhood of 

 liloulmein (Tenasserim Provinces), with Descriptions of new iSi^ecies," 

 Journ. Asiat. Soc. Bengal, vol. xl. 1871, pp. 219-220, pi. xv. tig. 4. 

 Another striking character common to both genera is found in 

 the liver. Stoliczka says, p. 219 : " The liver very extensive and of 

 a peculiar, coarsely tubular, clustered appearance." In Gorilla this 



* If any doubt existed as to this being a spermatophore, and doubts do arise 

 in the course of anatomical work on small species, it was set at rest by the form 

 of the terminal end (fig. 3//), wliich, minute as it is, has the form of the same 

 part, i. e. the capsule, in such genera as Austenia {vide Plate XO. figs. 1 & 3). 

 Tlie genus .Corilla presents us with another form of spermatophore. Extremely 

 long and tube-like with no spines whatever. Their absence is very probably 

 due to the drawn-out attenuate form of all internal organs packed very tight, 

 and further constricted by the shell-barriers on the parietal and palatal sides, 

 there would be no room for them, whereas in a large form (such as in Girasia 

 and Atistenia), which cannot -withdraw itself into the shell at all, they reach 

 their maximum development. 



