MOLLUSCA CEPHALOPODA. 261 



the inner margin of which appears like a row of 

 teeth. It is evident that by this mechanism, 

 which combines the properties of an accurate 

 valve, with an extensive cavity for producing 

 rarefaction, or the tendency to a vacuum, the 

 power of adhesion is considerably augmented.* 



So great is the force with which the tentacula 

 of the cuttle-fish adhere to bodies by means of 

 this apparatus, that while their muscular fibres 

 continue contracted, it is easier to tear away the 

 substance of the limb, than to release it from its 

 attachments. Even in the dead animal I have 

 found that the suckers retain considerable power 

 of adhesion to any smooth surface to which they 

 may be applied. 



Our attention must first be directed to the 

 remarkable family of Sepice, which comprehends 

 three principal genera, namely, the Octopus, the 

 Loligo, or Calamary, (depicted in Fig. 121), 

 and the common Sepia, or Cuttle-fish. The 

 first of these, the Octopus, which was the animal 

 denominated Polypus by Aristotle, has eight 

 arms of equal length, and contains in its interior 



* The description I have here given is the result of my own 

 examination of a large Octopus, which I had lately an opportu- 

 nity of dissecting: and the annexed figures 123*, A, B, c, are 

 copied from drawings I made on that occasion. A represents 

 the sucker in its usual form when not in action : B shows the 

 sucking surface fully expanded: and c is a section of the whole, 

 which had become somewhat flattened by the opeiation of di- 

 viding it. 



