Mr. Garner on the Nervous System of Molluscous Animals. 489 



feient position, but where one might expect to find them, at the base of the 

 branchiae on the back. Perhaps we might infer from Cuvier's description that 

 the nervous system in HaHotls is similarly disposed. In Lottia, which has 

 a single branchial appendage over the neck, and a branchial circle besides 

 around the mantle, the ganglia are unaltered in tiieir position. Besides eyes, 

 we have in Gasteropoda another important part more than we find in Conchi- 

 fera, the pharynx or manducatory apparatus at the commencement of the oeso- 

 phagus, consisting of a muscular cavity, with a curious spiniferous tongue at 

 its floor, often supported by two or more cartilages, and sometimes furnished 

 with one or tM'o iiorny maxillae. Either a transverse band or two ganglia 

 supply this complicated apparatus with nerves, this band, or these ganglia 

 being always suboesophageal, forming another ring around the digestive 

 canal. In Patella this band (D.) is connected with two ganglia (E.), which 

 supply the fleshy lip of tiie animal, and not with the cerebral ganglia. 

 Thus the second part of the digestive canal has its ganglion connected with 

 those supplying the nerves of the entrance, and through them with the brain ; 

 the functions of the parts appearing thus naturally combined. The Patella 

 appears to be the only Gasteropodous animal where these labial ganglia exist 

 separate from the superior or cerebral ganglia. In the Cephalopoda, however, 

 there are distinct labial and pharyngeal ganglia, the latter, as in Patella, only 

 connected to the superior ganglion tiirough the former. These pharyngeal 

 ganglia, besides supplying the pharynx, give origin to superior visceral or sym- 

 pathetic nerves {h, I,), very fine and delicate, ascending and descending on 

 the oesophagus and getting upon tlie salivary ducts and glands. 



In Chiton (fig. 1. & 2.), there being no eyes nor tentacles, the upper portion 

 of the ring has no evident ganglia. The branchial (C.) and pedal ganglia (B.) 

 are sometimes distinct, sometimes conjoined on the inferior portion of the 

 ring. The pharyngeal ganglia are also developed on the ring. 



In ScylloEu (fig. 4.), an animal not covered, like Patella and Chiton, with 

 hard, insensible, testaceous parts, but with a delicate and sensible dorsal 

 integument, bearing also the branchiae (the muscular foot having almost 

 disappeared), we find the brain entirely supraoesophageal from the change 

 above mentioned. It appears composed of four imited ganglia (A.), probably 

 the cerebral and branchial, which latter might be appropriately named 



VOL. XVII. 3 s 



