STRUGGLE FOR EXISTENCE 1-165 



another being, been perfected? We see these beauti- 

 ful 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 ulti- 

 mately 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 follow from the 

 struggle for life. Owing to this struggle, variations, 

 however slight and from whatever cause proceed- 

 ing, if they be in any degree profitable to the indi- 

 viduals of a species, in their infinitely complex re- 

 lations 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 indi- 

 viduals 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 Natural Selection, in order 

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



