THE PAST AND PRESENT OF THE CUTTLEFISHES. 107 



is thus utterly wasted ; since his remarks apply to no cuttlefish what- 

 ever, and least of all to the argonaut, which, like its cephalopod 

 neighbours, creeps along the sea-bed by aid of its sucker-provided 

 arms, or shoots backwards in the sea by aid of the water-jets from 

 its funnel. 



Amongst the two hundred odd living two-gilled cuttlefishes, con- 

 siderable diversity of external form may be seen ; but the general 

 type already described is at the same time closely adhered to ; and, 

 save in the case of the paper nautilus or argonaut, in which the 

 characteristic shape of body is concealed by the shell, the cuttlefish 



FIG. 9. PAPER NAUTILUS. 



A, Female Argonaut showing shell, around which the two expanded arms are clasped : B, Female 

 removed from shell ; c, the Male Argonaut (shell-less). 



characters are readily apparent. The shell of the paper nautilus 

 (fig. 9, A) is termed " false" or "pedal/' because it is not formed by 

 the mantle, as all true shells are, but by the two expanded arms, as 

 already mentioned. In its homology it therefore coincides with foot- 

 secretions (such as the "beard" of the mussel), and not with the 

 shells of its neighbours. The female argonaut alone possesses a 

 " shell," the male (fig. 9, c) being a diminutive creature, measuring 

 only an inch or so in length. 



