588 



CEPHALOPODA. 



every one of these canals contains a cirrus or tentacle rather smaller 

 than those of the external digitations, although their structure is 

 precisely similar (h h, Tc fc). These cirri, like the former, receive large 



Fig. 291. 



Nervous system of Nautilus Pomp ilius (after Owen): a a, b 6, cut edges of the mantle; 

 d, ,/. ; g, retractile tentacula; h, presumed olfactory organ ; 1, the supraoasophageal ganglion; 

 2 2, optic ganglia; 3 3, 4 4, subcesophageal ganglia; f>, 6, 7, 8, 9, nerves supplying the retrac- 

 tile tentacula; 10, nerves supplying olfactory organ ; 11, 12, 13, nerves supplying the muscular 

 integument ; 14, 15, 16, nerves representing the sympathetic system. 



nerves, those supplying the external labial tentacles being derived im- 

 mediately from the brain (fig. 291, 6 6), while those distributed to the 



