234 THE MECHANICAL FUNCTIONS. 



So great is the force with which the teiitacula 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 re- 

 markable family of Sepice, which comprehends 

 three principal genera, namely, the Octopus, the 

 LoUgo, or Calamary, (depicted in Fig. 121), and 

 the common Sepia, or Cuttle-tish. The first of 

 these, the Octopus, which was the animal denomi- 

 nated Poll/pus by Aristotle, has eight arms of equal 

 length, and contains in its interior two very small 

 rudimental shells, formed by the inner surface of 

 the mantle. This shell becomes much more dis- 

 tinct in the Loligo, where it is cartilaginous, and 

 shaped like the blade of a sword. (Fig. 123.) The 

 internal shell of the common Sepia is large and 

 broad, and composed wholly of carbonate of lime : 

 it is well known by the name of the cattlejish bone. 

 Its structure is extremely curious, and deserves 

 particular attention, as establishing the universality 

 of the principles which regulate the formation of 

 shells, whether internal or external, and from which 

 structures differing much in their outward appear- 

 ance may result. It is composed of an immense 

 number of thin calcareous plates, arranged parallel 

 to one another, and connected by thousands of 

 minute hollow pillars of the same calcareous mate- 

 rial, passing perpendicularly between the adjacent 

 surfaces. This shell is not adherent to any internal 



