THE DONKEY. 1 13 



would at once catch the eyes of his fellows, 

 because he is so conspicuously marked, and they 

 would either join in protecting him, or flee, as the 

 occasion required. The sharp vision of every 

 pair of eyes in the herd is thus made to contribute 

 to the safety of the whole community. I ought 

 to add that Mr Francis Galton has shown the 

 curious and interesting fact that, in the twilight, 

 when the zebra approaches the dangerous drink- 

 ing-places, his mixed colour seems to render him 

 much less visible than if he were all of one hue. 



Most mountain animals go in small bands, the 

 members of which have to scatter over a wide 

 area to find food, and so have to exercise great 

 personal vigilance. To such, therefore, an in- 

 conspicuous colouring is advantageous, and in the 

 case of an ass it is an imitation of the rocks of 

 his ancestral domain. We do not know the 

 colour of the three -toed horse (which, after all, 

 was probably a donkey) which at one time roved 

 in enormous numbers over Europe, Asia, and 

 America, but there are some reasons for thinking 

 that it was a striped animal somewhat similar in 

 markings to the quagga. The chief reason for 

 believing this is that all its descendants show a 

 tendency to stripe -like markings. The ass is 



H 



