414 Oil the Anatomy of 



The kidney is situated just behind the heart, is of elonga- 

 ted forni; curved upon itself so as to form nearly a complete 

 circle, leaving an open space in the centre, which is partly 

 occupied by the heart. 



Nervous System. This system closely resembles that of 

 the Helices and Limaces ; its central portion consisting of a 

 ganglionic ring, through which passes the oesophagus, salivary 

 ducts, and some of the retractor muscles of the mouth. Fig. 

 6 represents the ganglia and nerves as seen when viewed on 

 the posterior face. Above, the ring consists of two ganglia, 

 from a process at the outer angles of which the nerves to the 

 upper tentacles are given off. (fig. 6, a.) The pair of nerves 

 going to the lower tentacles, and numerous minute filaments 

 going to the parts about the mouth, are given oflf from the 

 anterior face of the ganglia. The infra-oesophageal ganglia 

 are four in number, but so united as to form a ring (fig. 6, c 

 and cJ,) through which passes a large arterial trunk distributed 

 to the parts about the mouth. The nerves arising from the 

 supra-oesophageal ganglia appear to be, for the most part, 

 nerves of sensation and those from the infra-oesophageal 

 ganglia are almost if not entirely distributed to the organs of 

 motion. These two sets of ganglia are united by commis- 

 sures, from which last a few minute filaments are given oflf 

 on each side. 



Organs of Generation. The male organs consist of a 

 testis, vas deferens and penis ; the female of an ovary, oviduct, 

 and spermatheca ? or vesicle ; both sets of organs terminate 

 in a common receptacle, which opens externally by a single 

 orifice just behind the upper tentacle on the rigiit side. The 

 testis (fig. 7, a,) has an irregular spheroidal form, is of an ash 

 gray color, and composed of numerous lobules, each lobule 

 consisting of minute granules. It is in part enveloped by the 

 posterior lobe of the liver (fig. 1, c/.) The vas deferens (fig. 7, 

 b,) is a whitish duct, slightly convoluted at its commencement, 

 and becoming more so as it approaches the ovary. It is 

 closely united to the oviduct throughout the convolution of 

 the latter, and as it separates from it (fig. 7, e,) it reaches the 

 male organ in the form of a long and slender tube without 



