IV] THE ORIGIN OF THE LIBYAN HORSE 467 



dark colour, even on those parts of the body which are covered 

 with Avhite hair, as for instance in the star on the forehead. 

 On the other hand, the skin of white horses is usually white, 

 though in grey horses it is generally dark. But it has been 

 shown that grey horses are especially common where the North 

 African blood is mixed with the Asiatic, whilst the white horse 

 is essentially the child of the regions lying north of the great 

 central mountain ranges of Europe and Asia, where it has been 

 specialised under conditions analogous to those which make the 

 stoat and the ptarmigan turn white in winter, and have perma- 

 nently clothed in white the Arctic hare and the Polar bear. 

 Moreover, it is a fact well known in India that white horses 

 have not the same power of enduring heat as bay and grey. 

 But, as the latter have dark skins, while the former have a white 

 skin, we may reasonably infer that the pigmentation of the skin 

 helps to give the bay and grey horses their power of withstand- 

 ing tropical heat. It follows that the dark skin of the African 

 horse, like that of the negro, has been developed in a hot 

 climate. But this specialisation cannot have been produced by 

 the residence of the Asiatic horse in North Africa from the 

 date of its importation already domesticated into Egypt about 

 B.C. 1500, for it might just as well be argued that a fair-haired, 

 light-skinned people from Europe, if transported to Africa 

 would in an equally short period develope the peculiar skin 

 of the negro. It is of the highest importance to note that 

 the zebras, which have admittedly been specialised in Africa, 

 have dark skins like that of the Libyan horse. The skin 

 of the Burchell zebra Matopo is described by Prof. Ewart^ 

 " as dark throughout ; under the white hair the skin is of 

 an iron-grey colour, elsewhere it is nearly black, owing to the 

 pigment in the hair roots." Thus the skin of the zebra is dark 

 beneath his light as well as his dark parts, exactly as the skin 

 of the Al-Khamseh horse is dark under its white markings as 

 well as under the gi-ound colour. We are therefore led in- 

 evitably to conclude that the dark skin of the Libyan horse is 

 the result of its having been domiciled in North Africa for long 

 ages before it was ever domesticated. 



^ Penycuik Experiments, p. 75. 



30—2 



