NATURAL SELECTION 



tion the case of colour, in the animal and vege- 

 tal kingdoms. 



Until after the publication of Mr. Darwin's 

 speculations, the colours of plants and animals 

 had never been made the subject of careful and 

 philosophical study. So far as any hypothesis 

 was held concerning these phenomena, it was the 

 vaguely conceived hypothesis that they are due 

 to the direct action of such physical conditions 

 as climate, soil, or food. But there are fatal 

 objections to such an explanation. When Dr. 

 Forbes Winslow, in his work on the " Physio- 

 logical Influence of Light," tells us that " the 

 white colour of animals inhabiting the polar re- 

 gions is attributable to the absence of intense 

 sunlight," it is an obvious objection that the 

 polar regions are not preeminent for darkness. 

 Though within the limits of the arctic circle 

 the sun is below the horizon for six months 

 together, it is none the less for the other six 

 months above the horizon ; and though its 

 slanting rays do not cause excessive heat in the 

 summer, the prolonged glare of light, intensified 

 by reflection from the snow and ice, is described 

 as peculiarly intolerable. The summer ought to 

 tan the polar bears as much as the winter can 

 bleach them. And to this it may be added that 

 the Eskimos and Greenlanders, living under the 

 polar circle, are not bleached. Several other 

 facts, ahke incompatible with the direct action 

 29 



