PROTECTIVE COLOURING. 26 3 
sciously and without a plan. If we had not thoroughly 
considered the interaction of Inheritance and Adaptation 
under the influence of the struggle for life, we should not 
at first be inclined to expect such results from this natural 
process of selection as are, in fact, furnished by it. It may 
therefore be appropriate here to mention a few especially 
striking examples of the activity of natural selection. 
Let us first take Darwin’s homochromic selection of 
animals, or the so-called “sympathetic selection of colours,” 
into consideration. Earlier naturalists have remarked that 
numerous animals are of nearly the same colour as their 
dwelling-place, or the surroundings in which they per- 
manently live. Thus, for example, plant-lice and many 
other insects living on leaves are of a green colour. The 
inhabitants of the deserts, the jerboa, or leaping mice, foxes 
of the desert, gazelles, lions, etc. are mostly of a yellow or 
yellowish-brown colour, like the sand of the desert. The 
polar animals, which live on the ice and snow, are white or 
grey, like ice and snow. Many of these animals change their 
colour in summer and winter. In summer, when the snow 
partly vanishes, the fur of these polar creatures becomes 
brownish-grey or blackish, like the naked earth, while in 
winter it again becomes white. Butterflies and insects 
which hover round the gay and bright flowers are like them 
in colour. Now, Darwin explains this surprising circum- 
stance quite simply by the fact that such colours as agree 
with the colour of the habitation are of the greatest use to 
the animals concerned. If these animals are animals of 
prey, they will be able to approach the object of their 
pursuit more safely and with less likelihood of observation, 
and, in like manner, those animals which are pursued will 
