260 MOSTLY MAMMALS 



exists only in the species inhabiting the plains. Moreover, 

 it is only in South Africa that the transitional form is met 

 with, and only in the north of the continent that the 

 striping has been completely lost. 



But, as I have already mentioned in earlier articles, this 

 is only one phase of a general tendency among mammals 

 to replace their spots or stripes by a uniformly coloured 

 coat. 



So far as I am aware, no one has ever attempted to 

 give a philosophical reason for this remarkable tendency. 

 But till an adequate explanation of the phenomenon be 

 forthcoming, naturalists, to repeat the words of a well- 

 known ornithologist, have left half their work (and I am 

 inclined to think the more important half) undone. Without 

 ascertaining the reason for phenomena of this nature, our 

 zoological work is, indeed, as though a man were content 

 with describing the mechanism of a complicated machine 

 without an inkling as to its use. 



One word more, and I have done. To the systematic 

 zoologist, the quagga is an animal of special interest as 

 affording evidence of the intimate relationship between 

 the zebras and the wild asses. Although, judging from 

 its geographical distribution, it was probably not the actual 

 transitional form between the two groups, yet it serves to 

 show the manner in which the transition was effected. 



