240 The Under-Water World 



guins so grotesquely helpless ashore can 

 swim at a high speed below water. When 

 pursued by the Killer they make a dash 

 for the nearest ice floe and leaping clear 

 of the water often land six or twelve 

 feet above the surface. The Killer, how- 

 ever, swims beneath the floe and hump- 

 ing its back endeavours, often success- 

 fully, to bump the penguin back into the 

 water. 



The Narwhal, or Sea Unicorn, of 

 Arctic Seas, is remarkable for the develop- 

 ment of the two upper incisor teeth. In 

 the female these teeth remain concealed, 

 but in the male the left and sometimes 

 the right attain a great length five to 

 seven feet. When both tusks are de- 

 veloped they are twisted spirally in the 

 same direction in marked contrast to 

 the spiral horns of antelopes, in which 

 one always turns to the left the other to 

 the right. The tusks were once much in 

 demand by apothecaries, being supposed 



