APLYSIA. 237 



branches supply the genital duct and accessory genital glands. 

 The largest branch emerges on the dorsal side of the accessory 

 mass, passes dorsal to the rectum and innervates the little 

 hermaphrodite duct and gland. 



4. A small nerve to the floor of the mantle cavity. 



F. Stomato-gastric or Buccal Ganglia. (Fig. 17.) 



The buccal ganglia (buc. g.) are small ganglia lying on the 

 ventral side of the buccal mass. They are slightly anterior 

 to the cerebral ganglia with which they are connected by 

 cerebro-buccal connectives (c. buc. conn.). A buccal commis- 

 sure is present. 



[Dissection. After dissecting the nerves from the 

 cerebral, pleural, and pedal ganglia, detach the* nerves as 

 near as possible to the organs they innervate. Dissect off 

 the connective tissue from the gut so that it can be pinned back 

 on the left side. Cut through the muscle bands that hold 

 the buccal mass in place and turn the latter over to expose 

 its ventral surface. The buccal ganglia are now visible. Or 

 cut through the oesophagus about half an inch from the buccal 

 mass, detach the muscle bands as before, and turn the whole 

 forwards so as to expose the ventral side of the buccal mass. 

 This method, however, involves cutting the visceral nerve 

 cords.] 



The following nerves arise from the buccal ganglia : — 



1. From the commissure is given off a median radular 

 nerve (rod. n.) 7 which runs forward, plunges into the muscles 

 of the buccal mass and enters the radular sac on its ventral 

 side. 



2. A small nerve (buc. n. 2) which supplies the basal 

 muscles of the buccal mass. 



3. A large nerve (buc. n. 3) which soon bifurcates to 

 supply the lateral muscles of the buccal mass. In some 

 specimens there appear to be two distinct nerves as the branch- 

 ing occurs at the root. On the posterior side of this nerve 



