852 



Tin: AMERK'W NATURALIST 



[Vol. XL. 



But the absence of these powers is almost equally fatal to small ani- 



Bulk must therefore be considered in relation to (1) disadvan- 

 tage of the large amount of food required by a large animal, which 

 is offset by the advantage that many large animals can travel long 

 distances; (2) diminished birth rate, which is a characteristic of 

 large animals, is a point to be noticed; as a rule, the larger the 

 animals, the fewer the young, and the less able a species would l)e 

 {juickly to regain numerical strength after some widespread 

 diminution in number; (3) by the fact that the diminished birth- 

 rate is offset by longevity and power to protect young from enemies. 

 "The elephant," observes Darwin, "is reckoned to be the slowest 

 breeder of all known animals, and I have taken some pains to 

 estimate its probable minimum rate of natural increase: it will 

 he under the mark to assume that it breeds when thirty years old, 

 and goes on breeding till ninety vears old, bringing forth three 

 pair of young in this interval; if this be so, at^the end of the fifth 

 century there would be alive fifteen million elephants, descended 



