THE PERIOD OF INCUBATION 75 



the maintenance of the average number of the species. 

 Of these young, by far the greater number must always 

 perish from generation to generation, for want of space, 

 of food, of air, of raw material. The survivors in each 

 brood must be those naturally best adapted for survival. 

 The many would be eaten, starved, overrun, or crowded 

 out ; the few that survive would be those that possessed 

 any special means of defence against aggressors, any 

 special advantage for escaping starvation, any special 

 protection against overrunning or overcrowding foes. 

 Animals and plants, Darwin found on inquiry and in- 

 vestigation, tended to vary under diverse circumstances 

 from the parent or parents that originally produced 

 them. These variations were usually infinitesimal in 

 amount, but sometimes more considerable or even 

 striking. If any particular variation tended in any 

 way to preserve the life of the creatures that exhibited 

 it, beyond the average of their like competitors, that 

 variation would in the long run survive, and the indi- 

 viduals that possessed it, being thus favoured in the 

 struggle for existence, would replace the less adapted 

 form from which they sprang. Darwinism is Malthusian- 

 ism on the large scale : it is the application of the 

 calculus of population to the wide facts of -universal life. 

 In one sense, indeed, it may be said that, given 

 Malthus on the one hand and the Lamarckian evolu- 

 tionism on the other, some great man somewhere must 

 sooner or later, almost of necessity, have combined 

 the two, and hit out the doctrine of natural selection as 

 we actually know it. Quite so ; but then the point is 

 just this : Darwin was the great man in question ; he 

 did the work which in the very essence of things some 



