STRUGGLE FOR EXISTENCE 99 



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 con- 

 verted 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 spe- 

 cies 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, how- 

 ever slight and from whatever cause proceeding, if they 

 be in any degree profitable to the individuals of a spe- 

 cies, 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 prin- 

 ciple, by which each slight variation, if useful, is pre- 

 served, by the term Natural Selection, in order to mark 

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

 sion often used by Mr. Herbert Spencer of the Survival 

 of the Fittest is more accurate, and is sometimes equally 



