718 



ZOOLOGY 



SECT. 



The cerebral, pedal, and pleuro-visceral ganglia (Fig. 629), all of 

 relatively large size, are closely aggregated together around the 

 oesophagus, supported and protected by the cranial cartilage. The 

 cerebral ganglia (cer. g.) are fused together into a single rounded 

 mass, lodged in a hollow of the cranial cartilage, and covered 



over anteriorly by a strong fibrous mem- 

 brane. Laterally are given off a pair of 

 short thick processes the optic nerves 

 or optic stalks (opt. st.) which expand 

 almost immediately into large masses 

 the optic ganglia (opt. g.) in immediate 

 contact with the eyes. At the sides 

 and posteriorly a pair of very thick com- 

 missural bands of nerve matter pass 

 round the oesophagus to unite with the 

 pedal and pleuro-visceral ganglia, which 

 lie behind. The pedal ganglia (Fig. 630) 

 are, like the cerebral, united into a 

 single mass; orally this is prolonged 

 forwards and expanded into a broad 

 mass from which the ten bmchieil nerves 

 (br. n.) are given off to the arms. The 

 pleuro-visceral ganglia, also united into 

 one, are in immediate contact with the 

 pedal behind the oesophagus. 



Besides the optic nerves the cerebral 

 ganglia also give off a pair of slender 

 nerves which join a smaller pair of 

 closely united buccal ganglia (Fig. 629, 

 buc.), situated close to the buccal cavity 

 on the anterior aspect of the oesophagus. 

 The buccal ganglia again (which are 

 sometimes looked upon as separated por- 

 tions of the cerebral) are connected by 

 slender commissures with a pair of ganglia, 

 the stomatogastric (Fig. 623, #. stem.), also 

 closely united, situated on the posterior 

 aspect of the oesophagus. Besides the ten 

 brachial nerves, each of which, expand- 

 ing at the base of the arm into a 

 brachial ganglion, runs along the axis 

 of the arm to its extremity, the pedal ganglia also give off 

 nerves to the funnel, and also a pair to the otocysts; but the 

 latter are found, when their fibres are traced to their origin, to be 

 derived from the cerebral ganglia. The pleuro-visceral ganglia 

 give off two visceral nerves (Fig. 630, vise, n.) supplying the various 

 internal organs, one pair of branches, the brecnchieds, expanded into 



. 827. Sepia officinalis. 



longitudinal section of ink- 

 sac. . anus ; d. ink-duct ; 

 -/. </. ink-gland ; i. ,: cavity 

 of ink-sac ; o. orifice of ink- 

 gland ; /. rectum ; sp. sphinc- 

 ter muscles. (From the Cam- 



Girod.) " 



