SURVIVAL OF THE FITTEST. 
MONG organic beings in a state of nature there is some 
individual variability. This is an admission about 
which there can be no dispute. But the mere existence of 
individual variability and of a few well-marked varieties, 
though necessary as the foundation for the work, assists us 
but little in understanding how species originate in nature. 
Those exquisite adaptations of one part of the organization to 
another part, and to the conditions of life, and of one organic 
being to another being, which we know to exist, seem as 
mysteries. We see them in the humblest parasite that clings 
to the hairs of a quadruped or the feathers of a bird, in the 
structure of the beetle that dives through the water, and in 
the plumed seed that is wafted by the gentlest breeze. In 
short, we see beautiful adaptations everywhere and in every 
part of the organic world. And yet, how few have paused 
while admiring these beautiful and wonderful co-adaptations 
to ask themselves the question: How have these been 
perfected ? 
If the existence of any well-marked varieties be admitted, 
how is it that these varieties, which may be denominated 
incipient species, become ultimately converted into good 
and distinct species, which in the generality of cases obviously 
differ from each in a greater degree than do the varieties of 
the same species? How do these groups of species, which 
constitute what are authoritatively called genera, and which 
differ from each other more than do the species of the same 
genus, arise? All these results, as will presently be seen, fol- 
low from the Struggle for Existence. Owing to this struggle, 
