xii PHYLUM MOLLUSCA 681 



buccal chamber. Also given off anteriorly from the cerebni] 

 ganglia are optic nerves to the eye, and tentacular nerves t<> the 

 tentacles. From each cerebral ganglion passes downwards and 

 forwards a stout cerebro-pcdal conned ire, and from each pleura 1 

 ganglion a pleuro-pcdal connective, to a large pair of closely-united 

 pedal </ Hi/lie (Figs. 579 and 580, pcd. g.) embedded in the 

 upper layers of the muscles of the foot, to which they give off 

 numerous nerves. The right pleural ganglion gives off behind a 

 supra-intestinal visceral connective, which bends across to the left, 

 over the oesophagus, and, some distance to the left of the ali- 

 mentary canal, expands into a triangular supra-intestinal visceral 

 ganglion, (supra, g.}, situated below the superficial layer of muscular 

 fibres. The left pleural ganglion gives off an infi-a-intcstinal 



cer.buc.con- 



].'!,:. ;,MI. Triton nodiferus. Lateral view of nerve-ganglia and related parts. Letters as in 

 Pig. 579 : in addition ant. no. anterior aorta; cc. crop; a-*, oesophagus; sal. da. salivary 

 ducts ; r. sal. fjl. salivary gland. 



visceral connective, which passes obliquely backwards and to the 

 right, below the alimentary canal, to a ganglion situated a little to 

 the right of the middle line the infra-intestinal visceral ganglion 

 (infra, g.). The supra-intestinal ganglion gives off a nerve which 

 runs towards the osphradium and ctenidium, which it supplies 

 with branch nerves, and unites with a stout mantle nerve (l.mant.n.\ 

 which is given off from the left pleural ganglion. The right 

 pleural also gives off a stout connecting nerve to the infra-intes- 

 tinal ganglion. From the supra- and infra-intestinal ganglia the 

 left and right visceral connectives are continued backwards and 

 unite behind in the neighbourhood of the stomach ; each ends 

 in a triangular aMominal ganglion (I. al<l. g.; r. aid. g.}, and these 

 are joined by a transverse commissure, from which a number of 

 visceral nerves are given off. A remarkable torsion of the nerve 

 connectives is here to be observed, the two visceral connectives 

 becoming twisted into the form of the figure 8. 



