60 
STRUGGLE FOR EXISTENCE. 
Chap, III. 
CHAPTEE III. 
Struggle for Existence. 
Bears on natural selection — The term used in a wide sense — 
Geometrical powers of increase — Rapid 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 be¬ 
tween species of the same genus — The relation of organism 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 amongst organic 
beings in a state of nature there is some individual vari¬ 
ability : 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 vari¬ 
eties ; what rank, for instance, the tw^o 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 organ¬ 
isation to another part, and to the conditions of life, and 
of one distinct organic being to another being, been per¬ 
fected ? We see these beautiful co-adaptations most 
