WHALES' FOOD. 205 



rays, the only thing that will remain to testify to the 

 existence of this singularly graceful object is a thin 

 film, that a stroke of the sponge or finger will remove 

 in an instant. 



The most satisfactory explanation that has been 

 offered as to the use and purpose of the Medusae is, 

 that they serve as the principal food of whales and 

 other Getacea. To these marine monsters frequently 

 found from 70 to 110 feet long we can imagine a 

 few hundreds of jelly-fish would be considered a small 

 meal The supply, however, is ever equal to the 

 demand, as we shall see hereafter. 



I may here be permitted to explain that, in most 

 large fishes, the jaws are completely filled with for- 

 midable teeth, as in the shark, for instance. This 

 rapacious monster which has been aptly termed the 

 tiger of the sea by us, and which the French, in allu- 

 sion to the deadly character of its habits, have named 

 Requin, or Requiem, the rest or stillness of death 

 possesses a most marvellous dental apparatus. 



Its teeth are not, as might be supposed, fixed in 

 sockets, but attached to a cartilaginous membrane. 

 The teeth, in fact, are placed one behind the other 

 in a series of rows ; the first of which, composed 

 of triangular cutting teeth, stands erect and ready 

 for use. But as the membrane continues to grow 

 and advance forward, it slowly perishes, and the teeth 

 drop off, their place being taken by the next row 

 which formerly stood second. These, in the course 



