76 STRUGGLE FOE EXISTENCE. [Chap. III. 



part, and to the conditions of life, and of one organic 

 being to another being, been perfected ? We see these 

 beautiful co-adaptations most plainly in the woodpecker 

 and the mistletoe; and only a little less plainly in the 

 humblest parasite which clings to the hairs of a 

 quadruped or feathers of a bird; in the structure of 

 the beetle which dives through the water : in the 

 plumed seed which is wafted by the gentlest breeze ; 

 in short, we see beautiful adaptations everywhere and 

 in every part of the organic world. 



Again, it may be asked, how is it that varieties, 

 which I have called incipient species, become ultimately 

 converted into good and distinct species, which in most 

 cases obviously differ from each other far more than do 

 the varieties of the same species ? How do those 

 groups of species, which constitute what are called 

 distinct genera, and which differ from each other more 

 than do the species of the same genus, arise ? All 

 these results, as we shall more fully see in the next 

 chapter, follow from the struggle for life. Owing to 

 this struggle, variations, however slight and from 

 whatever cause proceeding, if they be in any degree 

 profitable to the individuals of a species, in their 

 infinitely complex relations to other organic beings and 

 to their physical conditions of life, will tend to the 

 preservation of such individuals, and will generally 

 be inherited by the offspring. The offspring, also, will 

 thus have a better chance of surviving, for, of the many 

 individuals of any species which are periodically born, 

 but a small number can survive. I have called this 

 principle, by which each slight variation, if useful, is 

 preserved, by the term Xatural Selection, in order to 

 mark its relation to man's power of selection. But the 



