80 THE EXISTING EQUIDAE [CH. 



of Africa have far outstripped their congeners of the northern 

 latitudes. From these considerations it follows that the presence 

 of manifold stripes all over the body in any member of the 

 genus Equus is a strong indication that it has been long 

 domiciled in Africa, where its progenitors for protective or 

 other purposes either retained and modified the gaudy coat 

 of a common ancestor of all the Equidae, or else put on 

 stripings differing in different species and varieties according 

 to the nature of their environment. That in either alter- 

 native such modifications have taken place as I assume, on 

 African soil, is rendered highly probable by Prof. Ewart's 

 careful study of the markings of the zebras, from which he 

 has been led to conclude that the Somali Zebra represents 

 the oldest type, ''that the plan of marking in the common 

 zebra might be easily derived by a modification of the stripes 

 in the Somali Zebra, and that by further modifications in the 

 same direction the various patterns presented by the stripes 

 in the Crawshayi, Chapmani, and Burchelli types of zebras 

 might also be obtained. I do not wish it to be inferred that 

 the Burchell Zebras have been derived from the common zebras, 

 but simply that the ancestors of the Burchell Zebras once upon 

 a time more or less resembled in their markings the common 

 zebra of to-day, and that their still more remote ancestors 

 probably resembled in their markings the Somali Zebra 1 ." But 

 it by no means follows that the peculiar markings of the 

 Somali Zebra represent the original livery of the common 

 ancestors of horses, asses and zebras, for we are not more justified 

 in making such an assumption than zoologists five-and-thirty 

 years ago before the discovery of the Somali Zebra would have 

 been warranted in assuming that as the markings of BurchelPs 

 Zebra and the quagga could be derived from those of the Moun- 

 tain Zebra, the latter therefore represented in its striping the 

 livery of the common ancestor of all the Equidae. Moreover, 

 the GreVy Zebra from Shoa differs in the transverse stripes 

 of the croup, and in its coloration (p. 59), from that from 

 Somaliland. In other words, since it is highly probable that 

 much modification has taken place in the stripings of the 

 1 Penycuik Experiments, p. 90. 



