98 THE ORIGIN OF SPECIES 



CHAPTER III 



STRUGGLE FOR EXISTENCE 



Its bearinp: on natural selection — The term used in a wide sense— Geo- 

 metrical ratio of increase — Rapid increase of naturalized animaLs and 

 plants — Nature of Llie checks to increase — Competition universal — 

 Effei'ts of climate — Protection from the number of individuals — Com- 

 plex relations of all animals and plants throughout nature — Struggle for 

 life most severe between individuals and varieties of the same species: 

 often severe between species of the same genus — The relation of organ- 

 ism to organism the most important of all relations 



BEFORE entering on tlie subject of this chapter, I 

 must make a few preliminary remarks, to show 

 how the struggle for existence bears on Natural 

 Selection. It has been seen in the last chapter that 

 among organic beings in a state of nature there is some 

 individual variability: indeed I am not aware that this 

 has ever been disputed. It is immaterial for us whether 

 a multitude of doubtful forms be called species or sub- 

 species or varieties; what rank, for instance, the two or 

 three hundred doubtful forms of British plants are en- 

 titled to hold, if the existence of any well-marked varie- / 

 ties 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 \ 

 organization to another r)art, and to the conditions of f 

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



