The anatomy of Lottia gigantea Gray. 53 



and d). One of these branches (d) supplies the ventral wall, while 

 the other (Stg.N) curves around to the dorsal wall, keeping quite 

 distinct from branches of the left stomatogastric (Stg.N'). 



The left stomatogastric nerve, like the right follows the salivary 

 duct to the posterior septum of the head cavity, and here divides into 

 at least two parts. The smaller (e) supplies the ventral wall of the 

 oesophagus. The main branch passes backward, between the gonad 

 and the oesophagus, to both of which fine branches are given off. It 

 here lies in the thin buccal gland. A fine branch (f) is given off to 

 the genital artery, and follows the vessel, along its ventral floor, into 

 the pericardium. From this point the main nerve passes diagonally 

 across the dorsal wall of the oesophagus, and reaches the left limb of 

 the first anterior loop of the intestine (Fig. 39). Here it divides, on 

 the lateral wall, into two branches, one going forward to supply the 

 lateral and dorsal walls of this portion of the intestine, keeping di- 

 stinct apparently from branches of the right stomatogastric. The other, 

 or posterior, branch (Stg. N') runs along the lateral wall, where it divides. 

 One division (g) keeps on the lateral wall while the other passes to 

 the dorsal. 



Visceral nerves arising from the pleural ganglia 

 (Figs. 39 and 41). 



Each pleural ganglion is prolonged dorsally into a sort of horn 

 from the summit of which the visceral commissure or loop arises. It 

 is from this dorsal or visceral tract of each pleural ganglion that the 

 visceral nerves arise. 



From the right pleural ganglion fine nerves reach the pharynx, 

 oesophagus, visceral artery and dorsal aorta. There are two nerves 

 which ultimately reach the oesophagus. The largest (y, see also Fig. 3) 

 leaves the ganglion near its upper end, and passes through the visceral 

 loop, over the little knob-like distal end of the radula tube, pierces 

 the septum of the buccal sinus, after following it for some distance 

 to the side of the oesophagus. Then the nerve goes backward dia- 

 gonally across the dorsal wall of the oesophagus, reaching the left 

 side about where the left stomatogastric crosses obliquely to the in- 

 testine. Thence the nerve passes backward along the lateral wall of 

 the oesophagus to the proventriculus, where it is lost. On the way 

 it anastomoses with other nerves near the hind end of the oesophagus. 

 Before this nerve reaches the oesophagus it gives off at least one 

 branch (y 1 ) which following the right side of the oesophagus inner- 

 vates that portion of the intestine of a bluish tint in Fig. 1. This 



