The anatomy of Lottia gigantea Gray. 55 



from the left pleural ganglion is the subintestinal ganglion. This 

 gives rise to the right osphradial nerves. Between the above two 

 ganglia is the visceral ganglion (abdominal or subanal) which supplies 

 several very important nerves to the alimentary canal, nephridia, 

 and heart. 



Three main nerves can be distinguished. These supply (first 

 nerve) heart (presumably) and pericardium ; (second nerve) the ureters, 

 nephridia, rectum, afferent ctenidial vessel, and visceral mass; (third 

 nerve) visceral mass. The nerves to the heart and pericardium (Cd.N, 

 Cd. N) lie along the dorsal wall of the aorta. The larger nerve arises 

 from the visceral ganglion close to the main visceral nerve but the 

 smaller one usually about midway between the left stomatogastric and 

 the larger nerve. As the aorta is about to enter the pericardium the 

 two nerves join. Then an immediate division takes place (Pd. N' and 

 Pd.N") passing into the dorsal wall of the pericardium, while Cd.N" 

 continues along the aorta, but was not traced onto the ventricle. 

 Another branch (Pd.N) passes backward and to the right, thence 

 turns again to the left and lies along nearly the whole length of the 

 ventral wall of pericardium, giving off a branch or two into the dorsal 

 wall of the right kidney (cul-de-sac). This nerve is joined to a branch 

 of the main visceral-nephridial nerve by a short cross nerve (j). It 

 will ;be seen from the foregoing that no nerve was actually traced 

 into the heart. 



The visceral nerve (Vn) is the largest arising from the visceral 

 ganglion. It passes backward and slightly to the right, over a loop 

 of the intestine, and soon gives off two branches (Vn' and Vn") to 

 either side. The latter passes to the left where it is joined by the 

 cross nerve j from the heart nerve (Cd.N), then turns backward 

 under the rectum, and divides into three branches, two of which 

 spread out in the membrane covering the visceral mass while the 

 third reaches the cul-de-sac of the right kidney, on the left side of 

 the body. The other ( Vn') of these two branches of the visceral nerve 

 has a course backward over a portion of the intestine best shown in 

 Fig. 39. A branch is given off to the liver, and the main nerve sup- 

 plies not only the portion of the intestine alluded to, but likewise 

 the anterior half of the stomach. 



From the origin of these two divisions, the main visceral nerve 

 (Vn) passes backward then turns upward and forward around the 

 inner side of the body wall, bounding the pallial cavity at the rear 

 (Fig. 40). In other words the nerve passes onto the floor of the 



