THE PAST AND PRESENT OF THE CUTTLEFISHES. 97 



of the plates wherewith he illustrated his " Mollusca." At the present 

 time, recent cuttlefish ink is said to be utilised in the manufacture of 

 ordinary artist's " sepia." 



The due regulation of cuttlefish existence is determined by the 

 action of its nervous apparatus. Every living being exercising the 

 functions of a nervous system may be said to perform the function of 

 " relation ; " that is to say, it is brought, through the operation of its 

 nervous apparatus, into relation with the outer world. The higher 

 the nervous system, the more perfect are the relations between its 

 possessor and the outer world. In comparing a mussel with a snail, 

 and the latter or both with a cuttlefish, the differences between a low 

 and a high nervous apparatus may be plainly seen. The mussel, 

 possessing a distinct nervous system, lives, nevertheless, a vegetative 

 existence. It exhibits little activity ; it has no distinct head ; its 

 energies are cabined, cribbed, and confined within the compass of its 

 shell ; it may " hear " dimly, it is true ; but its relations with the 

 outer world are limited to the sweeping in and to the reception of food 

 particles in the water it receives, and to the occasional closure of its 

 shell when alarmed. Mussel life passes, therefore, through an un- 

 eventful history. 



The snail, on the other hand, exhibits a livelier interest in the 

 affairs of the universe. Possessed of head, sense-organs, and motor 

 powers, its means of relating itself to the outer world are of an 

 infinitely superior kind to those possessed by the mussel. It quickly 

 retires into private life and into the cavity of its shell when alarmed'; 

 it hears and sees, and its capacities for acting and reacting upon 

 its surroundings are of a tolerably advanced nature. The cuttlefishes 

 in turn present us with a marked advance upon the innervation of 

 the snails and their allies. The cephalopods are infinitely more 

 active, in turn, than the slow-moving gasteropods, and their nervous 

 axis exhibits additional specialisation and development, as becomes 

 their more elevated position. 



The ordinary type of molluscan nervous system undergoes in the 

 cuttlefishes a decided change of form. In a snail or whelk, for ex- 

 ample, the nervous system exhibits an arrangement of three chief nerve- 

 masses or "ganglia," connected by nervous cords. Of these three nerve- 

 centres, one is situated in the head, a second in the " foot " or organ 

 of movement, and a third in the neighbourhood of heart and gills, or 

 amidst the viscera generally. Increased concentration of this type 

 of nerve- arrangement awaits us in cuttlefish organisation. Just as 

 the spider possesses a more concentrated and localised nerve-axis 

 than the insect, or as the gangliated chain of the latter becomes the 

 fused nerve-mass of the spider ; so in the cuttlefish, the molluscan 

 nerve-system, scattered and diffused in the snail, whelk, or mussel, 

 becomes localised in adaptation to the increased nerve-control and 



H 



