160 LECTURES ON BIOLOGY 



gradually reach a time when there would be only snow-white 

 hares. That this is no mere imagination is proved by experi- 

 ence, for we actually find in the Arctic regions and high 

 mountains that our common hare is there represented by a 

 white variety. 



The soft, white fur of the Polar fox has in recent years become 

 fashionable with ladies. How can the origin of white foxes be 

 explained ? Apart from man the fox has not so many enemies 

 that he should stand in need of protective coloration. Here the 

 theory of selection provides an easy explanation. Dark foxes 

 may be distinguished on the white snow at great distances, and 

 their colour thus becomes a warning to their prey to escape to 

 safety. A red fox would therefore be severely handicapped in 

 searching for food, an all-important reason for putting into 

 motion the forces of natural selection. From century to century 

 increasingly less numbers of red foxes would be able to 

 reproduce their kind, whilst the light-coloured foxes would 

 steadily increase in number and transmit their useful charac- 

 teristics to subsequent generations ; thus the process would go 

 on until natural selection had left only pure white foxes. 



Whilst the human breeder must usually content himself with 

 being able to breed or change one definite feature, natural selec- 

 tion begins at the most different points. To resume our illus- 

 tration, Nature would not be satisfied with selecting only 

 light-coloured animals, but among these again the best runners, 

 the most intelligent, the strongest, and those who possess any 

 other useful quality in a higher degree. Natural selection 

 employs the same methods as man, but in its effects leaves man's 

 work far behind. 



But there are other animals in the Arctic regions which are 

 distinguished by a white colour. The brown bear would on the 

 vast snowfields of the Far North be doomed to die from hunger, 

 whilst the Polar bear is easily able to stalk his prey, the seals, 

 and obtain abundant food. All our owls are brown, grey, or 

 spotted, but their Polar relative, the great snowy owl, has 

 white plumage. The sable of the Far North forms the only 

 exception, for it has dark fur. A look at its life-habits will 

 explain this seeming inconsistency. It lives and seeks its prey 

 on trees. A white colour would therefore not only be no ad- 



