how species arise in niture. How have all those exqui- 

 site adaptations of one part of the organization to an- 

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

 being to another being, been perfected? * * * 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 caises obviously differ 

 from each other far more than do the varieties of the same 

 species? How do those groups of species which consti- 

 tute what are called distinct genera arise? All of these 

 results follow from the struggle for life. Owing to this 

 struggle, variations, however slight and from whatever 

 c ause proceeding, if they be in any degree profitable to the 

 mdividuals of a species, in their infinitely complex rela- 

 tions to other organic beings, and to their physical condi- 

 tions of life, will tend to the preservation of such individ- 

 uals 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 period- 

 ically 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." Mr. Darwin 

 adds that his meaning would be more accurately expressed 

 by a phrase of Mr. Spencer's coinage, "Survival of the Fit- 

 test." 



It may be observed that neither "natural selection" 

 nor "survival of the fittest" gives very accurate expression 

 to the idea which Darwin seems to wish to convey. Nat- 

 ural selection is at best a metaphorical description of a 



11 



