CLASS OF THE CEPHALOPODA. 



513 



603. The disposition of the organs of locomotion and 

 prehension, fixed around the mouth, varies in these mollusca. 



Fig. 537, Nervous System of the Cuttle Fish (Sepia).* 



* a, the nervous collar surrounding the gullet, the course of which is indi- 

 cated by a bristle (s] ; c, the nervous mass situated before the gullet, and 

 generally called brain : its superior surface is surmounted with a very large 

 cordiform tubercle, and there proceed from its anterior part nerves, which 

 soon terminate in a circular ganglion, which in its turn gives origin to 

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