160 Nerve Structure and Force. [April, 



or those disturbing emotions of the mind, implanted with more or 

 less intensity in all the vertebrate sub-kingdom. 



The predacious habits of the Cephalopods, involving definite and 

 rapidly executed powers of locomotion and prehension, with sight, 

 hearing, and the exercise of choice, imply the necessity of a very 

 different kind of nervous system. The central mass, it is true, 

 forms an oesophageal ring, which consists of a superior and an 

 inferior ganglionic mass, connected by lateral commissures. The 

 superior is small, and sends some delicate nerves to the parts of the 

 mouth. But the inferior portion is very large, and extends along 

 the sides of the oesophagus in order to be directly connected with 

 the broad commissures. An olfactory and two optic nerves arise 

 from the lateral portion of this ganglion, while the auditory nerves 

 have then origin from its inferior surface. From its anterior 

 border pass off four or five pans of large nerves to the arms, 

 and also others to the muscles of the head. From its posterior 

 border arise small nerves for the funnel, and also two large trunks 

 for the back of the mantle. 



The eye is composed of numerous membranes and is covered by 

 the skin, which becomes transparent in passing over it, and some- 

 times forms folds that supply the want of eyelids. The ear is 

 merely a little cavity excavated on each side near the brain, without 

 semicircular canals or external passages, and in which there is 

 suspended a membranous sac containing an otolite. The fleshy 

 point of the tongue is undoubtedly a gustatory organ. There are 

 olfactory organs situated in the neighbourhood of the eyes. The 

 organ most highly developed is the organ of sight. 



In the cephalopods we find well-marked " pneumogastric 

 nerves." They arise from the middle of the inferior cerebral mass 

 between the two pallial nerves, or nerves of the mouth ; they 

 descend along the neck behind the funnel, the posterior wall of 

 which tbey pierce, and thence pass under the peritoneum, sending 

 several nerves to the ink-sac and ramifying upon the heart; the 

 large vascular trunks, the branchial hearts, and the branchiae. 

 There is moreover a distinct splanchnic nervous system. 



A nervous system thus highly developed implies the active 

 exercise of the organs with which it is supplied. The parrot- 

 beaked mouth, the prehensile suckers, are structures which even 

 the larger vertebrata would shrink from encountering. We read 

 of the " Sejpia octopodia" of the early naturalists, attaining in hot 

 climates such a size as to measure twelve feet across its centre, and 

 to have each of its arms between forty and fifty feet long ! " When 

 the Indians go out in their canoes," says Bingley, "in places 

 frequented by these sepia, they are always in dread of their flinging 

 their arms over and sinking them; on which account they are 

 careful to take with them an axe to cut them off."* Without 



* ' Nat. Biography,' p. 519. 



