24 FOOT-NOTES TO EVOLUTION. 
In the eastern United States there are two native 
species of hare or wild rabbit. These are the gray rabbit 
or “cotton-tail ” (Lepus sylvaticus) of the 
region south of Pennsylvania, and the 
white rabbit (ZLepus americanus) of the 
woodlands of the North. The southern hare is smaller 
than the other; it is much less shy, and its winter dress 
is not very different from its summer dress, the fur 
which comes in after the autumn shedding being of the 
same grayish colour. The northern hare is in summer 
not very different in colour from the other, but when it 
renews its fur in the fall its winter coat is pure snow- 
white. There are some other distinctions between the 
two species, but we need notice simply the difference in 
colour as showing the principle of “ natural selection.” 
We may presume the two species to have had one com- 
mon origin, probably in a form not very different from 
the gray rabbit as we know it. In every dozen rabbits 
which we may examine we shall find a considerable 
variation in shade of colour. Some will be darker than 
the average, some grayer, some browner, and others 
evidently paler. We shall find also differences in size 
and proportions, besides other differences, but for the 
present we need only consider the matter of colour. 
In the South, where the ground is mostly free from 
snow, even in winter, whiteness would be of no sort of 
advantage to a rabbit. The nearer the animal is in 
colour to the dead grass and dried leaves about him, the 
better are its chances of escaping detection, the greater 
the likelihood that it may elude its enemies and live out 
its days, leaving descendauts to inherit its peculiarities. 
Not so with the northern species. The nearer it is in 
winter to the colour of the snow, the less likely it is to 
fall a prey to carnivorous animals or birds. And so for 
ages in the northern winter the action of competition in 
How the hare 
becomes white. 
