CEPHALOPODA. 459 



ganglionic mass, in Nautilus gives off nerves, 1st, to the ophthalmic 

 tentacles (fig. 212, 5*) ; 2ndly, to the digital tentacles (6). 

 Srdly, there arises from near the ventral aspect of the ganglionic 

 collar a pair of nerves (7), each of which soon dilates into a large 

 ganglion (8), from whence are derived the nerves of the internal 

 labial tentacles (9), and also other gangliform nerves (10), distri- 

 buted to what Professor Owen regards as the olfactory apparatus. 

 Lastly, the anterior collar gives off nerves (11) which penetrate 

 the muscular integument and supply the infundibulum. 



In the Dibranchiate Cephalopods the nerves derived from that 

 portion of the brain that may be regarded as analogous to the an- 

 terior collar of Nautilus, supply the locomotive sucker-bearing 

 arms, the labial apparatus, and also the auditory organs (fig. 215, 

 c, d) ; but the latter have not been found to exist in Nautilus 

 Pompilius. 



There is no possibility of doubting that the above nerves, dis- 

 tributed as they are to the complex sensitive tentacula connected 

 with the head and parts of the mouth, represent the fifth pair 

 of Vertebrata ; their general distribution and semiganglionic cha- 

 racter being, ccteris paribus, precisely similar : so that those por- 

 tions of the brain of vertebrate animals from whence the tri- 

 facial and auditory nerves originate, may reasonably be compared 

 with the anterior sub-cesophageal collar of the Cephalopoda. 



The posterior sub-cesophageal ganglionic ring (fig. 212, 4), 

 may be compared to the medulla oblongata of quadrupeds ; in 

 Nautilus it gives origin, 1st, to numerous nerves (13) which, after 

 a short course, plunge into the muscular parietes of the body to 

 which they are distributed : 2ndly, to two large cords (14), which 

 terminate by becoming gangliform (15), and supply the branchial 

 apparatus and the viscera ; thus representing the par vagum in their 

 distribution, and in like manner communicating with branches ap- 

 parently corresponding with the sympathetic nerves that are spread 

 out over the heart and ramifications of the vascular system. Lastly, 

 slender nerves (17), allied to the sympathetic, accompany the vena 

 cava into the abdomen. 



(501.) Such being the arrangement of the principal nervous 

 ganglia, and the general distribution of the nerves, we must now 

 turn our attention to the instruments of sensation possessed by 

 these comparatively highly gifted animals ; and these, as we shall 

 soon perceive, are in all respects correspondent in the perfection 

 of their structure with the exalted condition of the brain. 



