28 SCIENCE FROM AN EASY CHAIR 



a far larger number of young than can possibly grow up 

 to maturity, since the kind of food and the situation 

 necessary to each kind are limited and already occupied. 

 Only one oyster embryo out of every five million pro- 

 duced (the reader may refer to p. 137 on this subject) 

 grows up through all the successive stages of youth to 

 the adult state. The total number of a species of animal 

 or plant on the whole area where it is found does not 

 increase. Even in those which produce a small number 

 of young, there is great destruction, and taking all the 

 individuals into consideration, only a single pair of young 

 arrive at maturity to replace their parents. There is no 

 exception to the rule that every organic being naturally 

 multiplies at so high a rate that, if not destroyed, the 

 progeny of a single pair would soon cover the earth. 

 The elephant is reckoned the slowest breeder of known 

 animals ; it commences to breed at 30 years of age, dies 

 at 100, and has six young in the interval. After 750 

 years, supposing all the offspring of a single pair fulfilled 

 the rule and were not destroyed in an untimely way, 

 there would be nearly nineteen million elephants alive 

 descended from the first pair. There is then no doubt 

 as to the enormous excess in the production of young 

 living things, nor as to their necessary competition with 

 one another of the most severe and inexorable kind; 

 nor again as to the necessary death, in many species, 

 of hundreds and thousands, for every one which survives 

 to maturity and in its turn breeds. 



(2) The second great fact is that among all the young 

 born to a pair of parents, no two are exactly alike, nor 

 are any exactly like their parents ; nor are any two taken 

 from all produced by all parents of that species exactly 

 alike. They all resemble their parents at the corre- 

 sponding age, in a general way and even very closely ; 

 but the resemblance is far from amounting to identity. 



