CEPHALOPODA. 



429 



ally the great optic nerves (A;), and 

 is continued at the sides of the 

 oesophagus as a broad commissure, 

 which leads to the sub-oesophageal 

 mass. The sub-oesophageal mass is 

 indistinctly divided into a posterior 

 part, which is supposed to consist 

 of the pleural and visceral ganglia 

 (i.e., ganglia of the visceral com- 

 missure) fused (g\ and an anterior 

 comparable to the pedal of other 

 types (d\ the anterior aorta passing 

 ventralwards between the two. The 

 pedal portion is generally divided 

 into two parts, a portion behind 

 the pedal proper supplying the 

 funnel, and a brachial part (b) in 

 front, supplying the arms. 



The cerebral ganglion is connected 

 by two thin cords, or by one soon 

 dividing into two, with a ganglion 

 on the buccal mass called the supra- 

 Imccal ganglion (Fig. 344, n; Fig. 

 345, b). This is to be regarded as 

 a detached portion of the cerebral; 

 it gives off the stomatogastric com- 

 missure, which is completed ven- 

 trally to the oesophagus in the 

 infra-buccal ganglion (Fig. 344, m; 

 Fig. 345, a), or buccal ganglion 

 proper. The cerebral and the supra- 

 buccal are both connected with the 

 brachial or anterior part of the pedal 

 by separate commissures (Figs. 344 

 and 345). In Octopus the supra- 

 buccal ganglion is not separated 

 from the cerebral. 



The pleuro-visceral portion of the 

 sub-oesophageal gives off from the 

 pleural portion two large pallial 

 nerves (Fig. 344, j; Fig. 345, m) 



FIG. 345. Central nervous system of 

 Ommatostrephes, dorsal view (after 

 Hancock, from Pelseneer). o stomato- 

 gastric (buccal) ganglion ; b anterior 

 part of cerebral ganglion (suprabuccal) ; 

 c optic ganglion ; d visceral ganglion ; 

 e rectal nerve; / stellate ganglion 

 (mantle ganglion) ; g commissural gan- 

 glion of the visceral nerves ; h brachial 

 ganglion ; i viscero - stomatogastric 

 anastomosis; j stomach ganglion; k 

 oesophageal stomatogastric nerves ; I 

 commissure of the mantle ganglia ; m 

 pallial nerve ; n visceral nerve ; o cere- 

 bral ganglion, beneath which a probe 

 indicates the passage of the oesophagus, 

 and of the stomatogastric nerve from 

 q to k; p brachial ganglion; q oeso- 

 phageal stomatogastric nerve. 



