CHAP. III.] STRUGGLE FOR EXISTENCE. 45 



be admitted. But the mere existence of individual variability 

 and of some few well-marked varieties, though necessary as the 

 foundation for the work, helps us but little in understanding how 

 species arise in nature. How have all those exquisite adaptations 

 of one part of the organisation to another part, and to the con- 

 ditions of life, and of one organic being to another being, been 

 perfected 1 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 1 All these results, as we shall 

 more fully see in the next chapter, follow from the struggle for 

 Jife. 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 sur- 

 vive. 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 the expression 

 often used by Mr. Herbert Spencer of the Survival of the Fittest 

 is more accurate, and is sometimes equally convenient. We have 

 seen that man by selection can certainly produce great results, 

 and can adapt organic beings to his own uses, through the accu- 

 mulation of slight but useful variations, given to him by the hand 

 of Nature. But Natural Selection, as we shall hereafter see, is 

 a power incessantly ready for action, and is as immeasurably 

 superior to man's feeble efforts, as the works of Nature are to 

 those of Art. 



We will now discuss in a little more detail the struggle for 

 existence. In my future work this subject will be treated, as it 

 well deserves, at greater length. The elder De Candolle and 

 Lyell have largely and philosophically shown that all organic- 

 beings are exposed to severe competition. In regard to plants, no 



