THE DEVIL-FISH OF FICTION AND OF FACT 21 



■ The cups themselves, by their internal mechanism for air ex- 

 haustion, and consequent pressure of the outer atmosphere, adhere 

 firmly to any substance to which they are applied, whether stone, 

 fish, crustacean, or flesh of man ; but in the octopus they have no 

 power to puncture or lacerate the skin, or to cause blood to flow. 

 They are merely pneumatically prehensile organs, by which the 

 animal's prey is caught and held ; not by " harpooning," as the 

 novelist supposes, but by their atmospheric adhesion to the surface 

 of its body. In this genus the sucking discs 

 are composed of a muscular membrane, the 

 circumference of which is thick and fleshy, 

 and in some species cartilaginous, but in all 

 unarmed, and only adapted to secure close, 

 air-tight contact with any object it may touch. 

 When experimenting on the holding force of ^^^ ^ Suckerofthe 

 an octopus I have allowed it to fix its suckers Xo^luS'aris). 



firmly on my arm and the back of my hand, 

 and by pretending to try to pull them away 

 from its grasp have caused it to exert its utmost power of resistance 

 and retention. The only eftect of this has been that the vacuum 

 produced an almost indistinguishable circular mark, corresponding 

 with the edge of the larger discs, and not nearly so distinct as 

 would be caused by the application of a glass tube to the skin, 

 and the partial exhaustion of the air in it by drawing it from the 

 other end by the mouth and tongue. In some of the Cephalo- 

 pods the outer circle of the cups is a horny ring, sharply serrated 

 or dentated around its edge ; and in others— for instance, Oiiycho- 

 teuihis—\hQ centre of each cup is provided with a sharp, strong 

 hook, capable of being extended or sheathed, like the claws of a 

 cat, which is plunged deeply into the flesh of slippery prey for the 

 better security of its hold ; but the cuttle-fishes thus furnished are, 

 unlike the octopus, habitually swimmers, instead of rock-crawlers. 

 The sessile arms of the octopods are considerably longer than 

 those of the decapods, or ten-armed cuttle-fishes ; but the latter 



