The anatomy of Lottia gigantea Gray. 57 



service. Usually only one specimen in ten shows the network on the 

 stomach satisfactorily. 



The nerve supply to the oesopagus and stomach is derived from 

 all three centers mentioned. From the stomatogastric ganglia there 

 are two nerves (ipn) following the base of the lesser folds of the oeso- 

 phagus, and two others (spn) pursuing a similar course under the 

 dorsal or greater folds. These nerves reach the proventriculus. The 

 left stomatogastric (Stg.N') nerve supplies the left side of the oeso- 

 phagus, but I was unable to find any branches reaching the stomach. 

 From the left pleural ganglion there are three nerves (?, m, w), which 

 branch profusely, spreading over the ventral, lateral, and dorsal walls. 

 From the right pleural ganglion there are two nerves {x, y) to the 

 oesophagus. All these reach the proventriculus, where the mesh work 

 of nerves first clearly becomes evident (because the lining is smooth), 

 and thence they continue out onto the stomach. The forward curve 

 of the stomach receives nerves {Vn\ Int.N) from the visceral ganglion, 

 but no nerves from the visceral ganglion appear to reach the oeso- 

 phagus. 



The intestine just beyond the stomach is supplied from conti- 

 nuations of the stomach nerves, besides the following, the nerve y'^ 

 a branch of y^ from the right pleural ganglion, and branches of the 

 nerve I from the left pleural ganglion. The loops on the anterior and 

 right side of the body are supplied principally by the nerves Vn' and 

 Int.N from the visceral ganglion, and by nerve a, a branch of the 

 right stomatogastric (Stg.N). That portion of the intestine on the 

 left side of the body, lying under the stomach and over the oeso- 

 phagus (Fig. 39), is plentifully supplied by the left stomatogastric 

 {Stg.N', g, h), by the right stomatogastric and its branches (Stg.N, d), 

 and by the nerve y which lies along the ventral wall, when the in- 

 testine is in the natural position. It is wholly probable that the 

 nerves m', c and z, lying in the wall of the visceral artery, all contri- 

 bute to the supply of the lower layers of the intestine. Nerves sup- 

 plying the rectum arise from the main visceral nerve (Vn). There is 

 no portion of the alimentary canal on which at least a few nerves 

 cannot be made out, either running parallel, as on the rectum, or 

 forming a net, as on the stomach and on the greater part of the 

 intestine. 



Special sense organs. The organs of special sense are the 

 osphradia (Spengel's organs), the otocysts, and eyes. The inner- 

 vation and position of these structures have already been described. 



