THE KINSHIP OF LIFE. 25 
Nature, of “natural selection,” has saved the whiter 
rabbits and condemned the darker ones to destruction. 
In the summer these conditions are changed; those in- 
dividuals who retain the ancestral gray are then the 
ones best fitted to live. And so after many centuries, 
as we may conceive, there has come about a gradual 
change in the fur of our hares, until now in the northern 
species the fur is white in winter, while all are alike 
gray or brown in the summer. 
Precisely similar is the change in the plumage of the 
arctic partridge, or ptarmigan, as well as in the various 
other northern birds. But this is not all. A change in 
colour such as enables the hare or the ptarmigan to evade 
its pursuers would also aid these pursuers to steal un- 
aware on their prey. Nature has no preferences, and 
helps alike victim and victor. And so it comes about 
that predatory weasels and owls in winter assume a 
snow-white garb, and that this is laid aside in the sum- 
mer. It is doubtless true that other influences co-oper- 
ate in producing these changes in colour. White fur is 
warmest in cold weather, for it radiates less heat. We 
may say that all these animals are dressed in white in 
winter to keep them warm. But this again would be sim- 
ply a phase of “natural selection.” If the animals suffer 
from cold, the dark ones will be chilled first. Thus in 
more ways than one the white animal has the advantage 
of the other in the winter. This advantage enables it 
to outlive the other. It causes its descendants to outlive 
and eventually to displace those of its darker rival. 
To such causes as these we must ascribe the nice 
adjustment of each species to its surroundings. If a 
species or a group of individuals can not adapt them- 
selves to their environment, they will be crowded out by 
others who can do so. The former will disappear en- 
tirely from the earth, or else they will be limited to 
