584 



CEPHALOPODA, 



Fig. 231. 



Nervous System of the Pearly Nautilus. 



it affords a fixed point of attachment, and is 

 not extended upwards so as to inclose the 

 brain : this part is defended by a strong mem- 

 brane which loosely surrounds it ; but the ex- 

 tremities of the transverse band, the optic gan- 

 glions, and the anterior resophageal collars rest 

 in grooves of the cranial cartilage. 



The nerves which arise from the anterior 

 collar are very numerous : the larger branches 

 (6, 6) enter respectively the roots of the ten- 

 tacles which are lodged in the digital pro- 

 cesses : the ophthalmic tentacles are also sup- 

 plied from this source (5*); no lateral con- 

 necting filaments are found between these 

 nerves, corresponding to those which associate 

 the corresponding nerves of the Poulp for the 

 simultaneous action of the parts they supply. 

 Below the digital nerves small nerves are 

 given off (12), which enter the external labial 

 processes, and penetrate in a similar manner 

 the roots of the tentacles which are there 



lodged. The internal labial processes are, 

 however, supplied in a different manner : a 

 larger nerve (7, 7) comes off on each side near 

 the ventral extremity of the ganglion, and after 

 a course of half an inch swells out into a 

 flattened ganglion* (8, 8), from which nu- 

 merous filaments (9, 9) extend into the sub- 

 stance of the process, and are continued into 

 the tentacles as in the preceding case ; a larger 

 twig (10) inclines inwards and distributes fila- 

 ments to the olfactory laminae. The infundi- 

 bular nerves (11) come off near the lower part 

 of the anterior collar. 



From the ganglions composing the posterior 

 collar (4, 4) arise numerous nerves of a flat- 

 tened form, (13, 13,) which pass in a radiated 

 manner to the inner sides of the shell-muscles 



* These ganglions I believe, from subsequent 

 examination, to have been also connected with a 

 nervous twig from the fleshy mass of the mouth, 

 derived from the supra-oesophageal ganglion. 



