Chap, in.] S1KUGGLE FOB EXISTENCE. 75 



CHAPTEE III. 



Struggle for Existence. 



Its bearing; on natural selection — The term used in a wide sense — 

 Geometrical ratio of increase — Eapid increase of naturalised 

 animals and plants — Nature of the checks to increase — Com- 

 petition universal — Effects of climate — Protection from the 

 number of individuals — Complex 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 organism 

 to organism the most important of all relations. 



Before entering on the 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 amongst 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 

 entitled to hold, if the existence of any well-marked 

 varieties 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 



