ZOOLOGY 



SECT. 



O/ 



The cc-rcln-al, ^nlnl. and pleuro-msceral 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 (rcr. 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 <>pf/r nerves 

 or c.ptic stalks (opt. st.) which expand 

 almost immediately into large masses 

 the optic ganglia (<,pt. g.} in immediate 

 contact with the eyes. At the sides 

 and posteriorly a pair of very thick com- 

 missural bands of nerve matter puss 

 round the oesophagus to unite with the 

 pedal and pleuro- visceral ganglia, which 

 lie behind. The j>c</a/ ganglia (Fig. (J30) 

 are, like the cerebral, united into a 

 single mass: orally this is prolonged 

 forwards and expanded into a broad 

 mass from which the ten lirca-liinl nerves 

 (In-, /i.) are given off to the arms. The 

 pleuro-viscci-tr/ 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 1m mil ganglia (Fig. (>2!), 

 /".), situated close to the buccal cavil v 

 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 < if ganglia, 

 the stomatogastric (Fig. 623, #. sfom.), 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 

 Irarlinil 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 n'.s'vm/ nerves (Fig. li-SO. vise. //.) supplying the various 

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



^-w 



Kin. il-j;. -Sepia officinalis. 

 longitudinal section of ink- 

 sac, n. anus ; <'. ink-duct ; 

 i. i.i. ink-gland ; i. /. cavity 

 i'f ink-sac; o. orifice of ink- 

 n'land ; T. rectum ; s/>. sphinc- 

 ter muscles. (From the Cam- 

 !,!;, i<i, x<it iii-iii nistrii-ii, after 

 Girod.) 



