Ill THE SERVICE OF TAILS 93 



" As regards the white tip of the tail of certain 

 mammals, there are some curious phenomena 

 connected with tips. . . . White and black are 

 interchangeable. There are many mammals which 

 have black tips to their tails, and this, in allied or 

 other individuals, may change to white. The 

 Arctic hare in its summer dress is brown with black 

 tips to his ears; and the ermine is also brown with 

 half the tip end of the tail black. When these 

 two animals get their snow-white winter clothing 

 the tips of the ears of the one, and the tip of the 

 tail of the other, remain black." 



These peculiarities of color may be correlated 

 with the fact that the tips of ears, occasionally, and 

 the tips of tails, very frequently, are adorned with 

 tufts of hair, in the case of animals not otherwise 

 long-furred. That is the case with all the hoofed 

 beasts that have long tails, as the horses and asses, 

 cattle, camels, giraffe, and several of the South 

 African antelopes ; the practical service of this as 

 a wisp to drive away biting insects is recognized by 

 every one ; and it results in the ability of such ani- 

 mals to stay on the plains all summer, while their 

 short-tailed relatives are obliged to migrate to moun- 

 tain-tops and other regions of sometimes poorer 

 pasturage in order to escape the flies. 



This phenomenon of marked color and increased 

 hairiness at "tips" may be further correlated with 

 the fact that in the tip of the tail, particularly, 

 seems to be centred or focalized, an unusual de- 



