1 68 THE STORY OF THE LIVING MACHINE. 



We need do no more than outline the subject, 

 since it is well understood by all. The basis of 

 the method is natural selection, which acts in this 

 machine building something as follows : 



The law of reproduction, as we have seen, pro- 

 duces new individuals with extraordinary rapidity, 

 and as a result more individuals are born than 

 can possibly find sustenance in the world. Hence 

 only a few of the offspring of any animal or plant 

 can live long enough to produce offspring in turn. 

 The many must die that the few may live; and 

 there is, therefore, a constant struggle among the 

 individuals that are born for food or for room in 

 the world. In this struggle for existence of course 

 the weakest will go to the wall, while those that 

 are best adapted for their place in life will be the 

 ones to get food, live, and reproduce their kind. 

 This is at all events true among the lower animals, 

 although with mankind the law hardly applies. 

 Now, among the individuals that are born there 

 will be no two exactly alike, since variations are 

 universal, many of which are congenital and thus 

 born with the individual and transmitted by in- 

 heritance. Clearly enough those animals that 

 have a variation which makes them a little better 

 adapted for the struggle will be the ones to live 

 and hence to produce offspring, while those with- 

 out such advantage will be the ones to die. We 

 may suppose, for example, that some of the indi- 

 viduals had longer necks than the average. In 

 time of scarcity of food these individuals would 

 be able to get food that the short-necked indi- 

 viduals could not reach. Hence in times of 

 famine the long-necked individuals would be the 

 ones to survive. Now if this peculiarity were a 

 congenital variation it would be already repre- 



