THE SHAPES AND SIZES OF ANIMALS 155 



some other reptiles, we are probably not far wrong 

 in assuming that this size is somewhere near the 

 mechanical limit imposed by the strength of the 

 materials of which the animal frame is composed. 



With aquatic animals in which the body is 

 supported on all sides, and the specific gravity of 

 the entire animal is not greatly in excess of that 

 of the water in which it lives, the case is very 

 different ; and among the whales we meet with 

 genera which attain the length of ninety feet, and 

 whose weight is estimated at upwards of one 

 hundred tons, figures which according to some 

 authorities may in exceptional cases be consider- 

 ably exceeded. Whales are not merely the biggest 

 animals that live, they are probably also the biggest 

 that ever have lived, for we have no satisfactory 

 evidence of larger forms at any period in the 

 world's history. 



It is worth while also to note that the giants, 

 whether aquatic or terrestrial, are doomed to 

 extinction. Elephants have been tolerated because 

 of the readiness with which they can be tamed and 

 made to place their great strength at the service of 

 man ; but it is many centuries since the African 

 elephant was so employed, and no one of the 

 African tribes at the present day makes the 

 slightest attempt to so use him ; while with regard 

 to the Indian elephant, though large numbers are 

 still employed, experts are becoming more and 

 more doubtful as to the profitable nature of this 

 mode of labour. Elephants require much attention, 

 they consume enormous quantities of food, and 



