Chap. III. 
STRUGGLE FOR EXISTENCE, 
61 
plainly in tlie woodpecker and missletoe; and only a 
little less plainly in the humblest parasite which clings 
to the hairs of a quadruped or feathers of a bird; in the 
structure of the beetle which dives through the water; 
in the plumed seed which is wafted by the gentlest 
breeze; in short, we see beautiful adaptations every¬ 
where and in every part of the organic world. 
Again, it may be asked, how is it that varieties, which 
I have called incipient species, become ultimately con¬ 
verted into good and distinct species, which in most 
cases obviously differ from each other far more than do 
the varieties of the same species ? How do those groups 
of species, which constitute what are called distinct 
genera, and which differ from each other more than do 
the species of the same genus, arise ? All these results, 
as we shall more fully see in the next chapter, follow 
from the struggle for life. Owing to this struggle for 
life, any variation, however slight, and from whatever 
cause proceeding, if it be in any degree profitable to an 
individual of any species, in its infinitely complex rela¬ 
tions to other organic beings and to external nature, 
will tend to the preservation of that individual, and 
will generally be inherited by its offspring. The off¬ 
spring, also, will thus have a better chance of surviving, 
for, of the many individuals of any species which are 
periodically born, but a small number can survive. 
I have called this principle, by which each slight vari¬ 
ation, if useful, is preserved, by the term of Natural 
Selection, in order to mark its relation to man’s power 
of selection. We have seen that man by selection can 
certainly produce great results, and can adapt organic 
beings to his own uses, through the accumulation of 
slight but useful variations, given to him by the hand of 
Nature. But Natural Selection, as we shall hereafter 
see, is a power incessantly ready for action, and is as 
