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 " iLepus sylvaticus) of the 

 How the hare . ^\, c t> i ■ j ^i 



, . region south of Pennsylvania, and the 



becomes white. . . "^ ' 



white rabbit \Lepus 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 descendants 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 



