v NATURAL SELECTION 123 



observe or think of, goes on also among the millions and 

 scores of millions of individuals which are comprised in almost 

 every species ; and must get rid of the idea that chance 

 determines which shall live and which die. For, although in 

 many individual cases death may be due to chance rather 

 than to any inferiority in those which die first, yet we cannot 

 possibly believe that this can be the case on the large scale 

 on which nature works. A plant, for instance, cannot be in- 

 creased unless there are suitable vacant places its seeds can 

 grow in, or stations where it can overcome other less vigorous 

 and healthy plants. The seeds of all plants, by their varied 

 modes of dispersal, may be said to be seeking out such places 

 in which to grow ; and we cannot doubt that, in the long run, 

 those individuals whose seeds are the most numerous, have the 

 greatest powers of dispersal, and the greatest vigour of growth, 

 will leave more descendants than the individuals of the same 

 species which are inferior in all these respects, although now 

 and then some seed of an inferior individual may chance to be 

 carried to a spot where it can grow and survive. The same 

 rule will apply to every period of life and to every danger to 

 which plants or animals are exposed. The best organised, or 

 the most healthy, or the most active, or the best protected, or 

 the most intelligent, will inevitably, in the long run, gain an 

 advantage over those which are inferior in these qualities ; 

 that is, the fittest will survive, the fittest being, in each particular 

 case, those which are superior in the special qualities on 

 which safety depends. At one period of life, or to escape one 

 kind of danger, concealment may be necessary • at another 

 time, to escape another danger, swiftness ; at another, intel- 

 ligence or cunning ; at another, the power to endure rain or 

 cold or hunger ; and those which possess all these faculties in 

 the fullest perfection will generally survive. 



Having fully grasped these facts in all their fulness and 

 in their endless and complex residts, we have next to consider 

 the phenomena of variation, discussed in the third and fourth 

 chapters ; and it is here that perhaps the greatest difficulty will 

 be felt in appreciating the full importance of the evidence as set 

 forth. It has been so generally the practice to speak of 

 variation as something exceptional and comparatively rare — as 

 an abnormal deviation from the uniformity and stability of the 



