108 Evolution and Adaptation 
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 subspecies or varieties; what rank, for in- 
stance, 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 adaptions of one part of the organization to 
another part, and to the conditions of life, and of one organic 
being to another being, been perfected? We see these beau- 
tiful coadaptions most plainly in the woodpecker and the 
mistletoe; 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 adaptions 
everywhere 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 converted 
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 con- 
stitute 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, variations, however slight and from whatever cause 
proceeding, if they be in any degree profitable to the individ- 
uals of a species, in their infinitely complex relations to other 
organic beings and to their physical conditions of life, will 
tend to the preservation of such individuals, and will gener- 
ally be inherited by the offspring. The offspring, also, will 
thus have a better chance of surviving, for, of the many 
