106 THE SEAS 



ally, the octopus, which possesses only eight arms 01 

 tentacles, al] of the same length. 



Within the body is a curious flat shell, which serves to 

 support the animal when it is swimming. In the cuttlefish 

 this shell is hard and limy ; it is that white object which we 

 so often find cast up amongst the drift weed on the sea 

 shore, and which we put to such various uses as removing 

 ink stains from our fingers and giving to canaries to sharpen 

 their beaks upon (Plate 32). In the squid, however, the 

 shell is very thin and transparent and is commonly known 

 by the fishermen as a " pen" on account of its resemblance 

 to the old-fashioned quill pen of our ancestors (P]ate 32). 



Both animals are active swimmers. Usually they move 

 slowly along by a slight wavy motion of the fins, which run 

 along the sides of their bodies ; but they can also dart 

 rapidly backwards. To secure the necessary propulsion 

 they draw water into their body cavities and then squirt 

 it out with considerable force through an opening under 

 the head. 



Both the cuttlefish and the squid have within their 

 bodies a little sac containing a black inky powder. This is 

 the sepia that is used in the manufacture of certain brown 

 paints. When alarmed or attacked by an enemy this ink 

 is squirted out into the surrounding water, where it spreads 

 out into a great dark cloud behind which the animal 

 darts rapidly away and so eludes its foe. This method of 

 escape is exactly that used by our battleships when they 

 send out masses of black smoke to form a smoke screen, 

 which drifts out between themselves and the enemy and 

 so hides their movements. 



In appearance the cuttlefish is stumpy compared with the 

 squid, whose body is long and tapering and carries a big 

 triangular fin along its hinder end (Plate 39). In our 

 coastal waters none of the species that occur reach much 



