from the topmost branches of one tree to the lower branches 
of another, after the mode of the “‘ flying-squirrels,” and 
“ flying-lemur’”’ of to-day. The wing, at this primitive stage 
of its evolution, was even then, probably, a three-fingered 
limb, provided with a broad fringe of incipient feathers along 
its hinder border. At this stage the body would have been 
less bird-like than that of Archeopteryx, and have been still 
more like that of the ancestral reptilian stock from which the 
birds have sprung. That feathers are, so to speak, glorified 
reptilian scales cannot be certainly demonstrated, but men 
of Science are generally agreed that this was their origin. 
By the time that Archeopteryx had come into being, 
true flight had been arrived at, though probably it could not 
have been long sustained. As these primitive birds increased 
in numbers, and spread from the woodlands to the open 
country, life became more strenuous. New enemies had to 
be evaded, longer journeys had to be made for food. Only 
the very best performers on the wing could survive, and thus, 
in each generation, the failures would be speedily weeded 
out, while competition among the survivors would raise the 
standard. We see thé result of this “ struggle for existence ”’ 
in the many and varied types of wings, and of flight, which 
are presented in this book. 
154 
