EARLY DAYS AND EARLY WAYS 23 



attain maturity until five-and-twenty,or according to others 

 between thirty and forty years of age, and consequently 

 its period of infancy is a prolonged one : we may assume [ 

 a similar prolonged infancy in the case of the whales. ' 

 And this because, as we have just indicated, the greater 

 an animal's bulk the longer the time necessary to attain 

 maturity — that is to say to attain to the reproductive 

 period. 



This latter phase must similarly be prolonged, partly 

 because of the parental care necessary for the well-being 

 and survival of the young, and partly because each pair 

 of individuals must produce sufficient offspring to ensure 

 the continuance of the race, for of the number born only 

 a fraction can attain maturity. 



The elephant affords us an instructive illustration of 

 this rule. It certainly cannot begin the duties of repro- 

 duction, which Nature forces upon every living thing, 

 until from twenty-five to thirty years of age ; and the 

 period of gestation is nearly two years, consequently it 

 must continue fruitful for at least fifty or sixty years, 

 and some authorities place this estimate still higher. 

 The pig may attain the age of twenty-five years, the horse 

 of forty, or even more. But we cannot take into account 

 the maximum age of the individual ; all that counts from 

 our present point of view is the period which extends 

 from birth to the end of the reproductive period, which 

 is considerably less than the maximum life period. 



How vital to the race is this matter of reproduction 

 may be gathered from the fact that sexual maturity is 

 attained before physical maturity : even in the human 

 race this is the case ; and this fact is commonly lost sight 

 of in estimating the severity of the struggle for existence. 

 It evidently stands in direct relation to another fact no 



