Chap. 111.] STRUGGLE FOR EXISTENCE. 1^5 



CHAPTER III. 



STSUGGLE FOB EXISTENCE. 



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

 Geometrical ratio of increase— Rapid increase of naturalised 

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

 petition universal— Efiects 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 

 stru ggle for existence bears on JsTatural 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 mul- 

 titude 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 individuafl 

 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- 



