342 



NERVOUS SYSTEM OF CEPHALOPODA. 



which the animal fixes itself with great force to any body which 

 it embraces. In the Poulp we find eight of these appendages, 

 and in the Cuttle-fish ten. Sometimes two of them are expanded 

 into flattened mem- 

 branes, as in the Ar- 

 gonaut (Fig. 546) ; 

 or are elongated so as 

 to become filiform^ 

 or threadlike, as in 

 the Calamary, and 

 particularly in the 

 Loligopsis (Fig. 

 543). In the four- 

 gilled Cephalopods 

 these appendages are 

 quite slender, and 

 unprovided with 

 suckers; but they 

 are extremely nu- 

 merous (Fig. 548). 

 882. Most Mol- 

 lusca of this class 

 are remarkable for 

 the development and 

 perfection of their 

 eyes, which are ex- 

 ceedingly like those 

 of Vertebrated ani- 

 mals. Many possess 

 also an apparatus 

 for Hearing ; but 

 this organ is reduced 

 to a little membra- 

 nous sac repre- 

 senting the vesti- 

 bule, and receiving 

 a nerve (ANIMAL 

 PHYSIOL. 512). 



FIG. 544. a, nervous collar embracing the oesophagus, 

 the passage of which is marked hy the bristle * ; c, ner- 

 vous mass, apparently analogous to the Cerebrum of 

 Vertebrata, from whose under side proceed connecting 

 cords to two ganglia situated in front, which send nerves 

 to the mouth, lips, pharynx, &c. ; 6, tentacular ganglia, 

 sending nerves to the arms ; o, optic nerves ; g, sub-ceso- 

 phageal ganglion ; v, great nerve of the viscera, of which 

 one of the branches possesses an elongated ganglion, r, 

 and enters the gills ; i, another branch, having the same 

 origin, and furnished with a star-shaped ganglion, e, that 

 sends nerves to the mantle. 



Lastly, the nervous system of these animals 



