Chap. IV.] THE NERVOUS SYSTEM OF MOLLUSKS. 



83 



of jerks, occasioned by the reaction of the respiratory 

 currents upon the surrounding water " — these currents 



Fig. 29.— Nervous System of the Common Cuttle-Fish {Sepia officinalis). (Owen.) 

 1, DoTible supra-oes -phageal ganglion developed from upper commissure; %> p, cut 

 surfaces of the cartilaginous cranium ; 2 2, optic ganglin ; 4 4, posterior sub-oeso- 

 ph igeal ganglia (anterior sub-cesophageal ganglia in connection with nerves of feet 

 and tentacles, 6 6, not seen in this view) ; 7 and 8, ganglia in connection with the 

 pharynx and mouth, connected by nerves (5 5) with the cerebral lobes ; 13 13, great 

 motor nerves, of the mantle and other parts, with {(I their gnnglia ; 14, e c, respiratory- 

 nerves ; k k, small tubercles in connection with optic ganglia. 



being produced by the expulsive contractions of a powerful 

 muscular funnel continuous with a portion of the mantle. 

 In the Cuttle-fish one of the most striking character- 



