276 rROCEKDIXGS OF THE MALACOLOGICAX SOCIETY, 



on as the oviduct (ovd.) or vagina and opens into the genital cloaca. 

 Eefore doing so it receives tlie openings of two blind tubes : one com- 

 municates with the long spermatheca {■sp.), which is closely bound by- 

 connective tissue to the hermai)lirodite duct and ends finally in an 

 oval saccular enlargement situated close to the heart, as in Jlelix ; 

 wliile the other leads into a blind diverticulum [c.) of the oviduct, 

 which runs back in the thickness of the hermaphrodite duct, and is 

 only seen on cutting open these parts. A similar structure has been 

 found by Pace in N. Quekettiana. It possibly serves as a recepiaculum 

 ovorum. 



The 7iervotis system. — There is a well-marked nerve- collar composed 

 of cerebral, pedal, and pleural ganglia surrounding the anterior 

 portion of the alimentary canal, and giving off the usual branches 

 to the head, foot, and rest of the body. Its composition calls for no 

 special comment, but its position is more interesting, for even in my 

 practically uncontracted specimens it is situated in front of the main 

 portion of the buccal mass, and gives off posteriorly two nerves, which, 

 running backwards, end in two large and normally situated buccal 

 ganglia, i.e. just under the oesophagus, where they are united by 

 a commissure as in Helix, and close to the salivary ducts. Now in 

 most snails the nerve-collar, save when the body is retracted, is behind 

 the buccal mass, and the buccal nerves run forwards. The modifi- 

 cation here met w^ith is obviously due to the enormously enlarged 

 buccal mass, which must cither push the nerve-collar right back, a 

 condition necessitating a groat elongation of the nerves supplying the 

 head, or else it must push it forward so as to surround the slightly 

 narrower buccal cavity : the latter condition appears to be the usual 

 one for the xVgnatha. The nerve-collar is, however, fairly loose, and 

 sufficiently so, I think, to permit the buccal mass passing through it if 

 the animal be very fully extended, as would be the case when feeding. 

 The pair of small ganglia situated on the buccal mass in fi'ont of the 

 nerve-collar in N. Quekettiana, described by Pace, cannot be regarded 

 as the homologue of the large buccal ganglia of Helix, which are 

 situated at the side of the oesophagus, ancl united underneath that 

 structure by a transverse commissure, as is the case with the ])uccal 

 ganglia of N. Caffra. I have seen no trace of an anterior pair in that 

 species. 



EXPLANATION OF PLATE XVIL 



Adbheviations. 



cm. columella muscle, 



d.c. dorsal constrictor muscle, 

 d.l. ,, lorjiitiulinal muscle. 



e.l.m. external lonfjitudinal muscles, 



g.c. genital cloaca. 



, , I hermaphrodite I pr. prostatic portion 

 '■' ■ j duct. 1 ov. oviducal ,, 



h.g. ovotestis. 

 i. intestine. 



k. kidney. 



