414 Mr. K. I. Pocock on the Colours of 



way, the dark marks they may exhibit being vestigial. 

 According to the accepted theory, the dark stripes of the 

 zebroid prototype have, apart from these vestiges, vanished, 

 leaving the dun, reddisli-fawn, or tan ground-colour un- 

 marked. According to Johnston, the pale stripes have in- 

 creased in extent until they have enveloped nearly the whole 

 body, fusing together and swamping the dark interspaces 

 representing the ground-colour, the sole remnants of which 

 are the spinal stripe and the stripes, when present, on the 

 legs, shoulders, or elsewhere. 



Johnston seems to think also that the uniformity in colour 

 may have been attained by a rather different process as well, 

 namely, by the fading of the dark interspaces and the 

 darkening of the light stripes until they were both of the 

 same brown or dun hue. 



There seems to me to be nothing extravagant in the view 

 of a pattern developing so as to overrun the ground-colour. 

 An instance of this is seen in the black leopards of Grahams- 

 town, where the spots have become broken up and multiplied 

 until there is scarcely a trace of the original yellow inter- 

 spaces left ; and, to cite an instance which is peculiarly 

 apposite, 1 may mention that of the quagga in the Vienna 

 Museum, the type of E. quagga lore^izi, in which the dark 

 markings, hitherto quoted by myself and others as stripes, 

 have expanded and spread to such an extent that the head, 

 neck, and fore-quarters of the animal are dark brown, relieved 

 by thin pale lines. If these dark marks, as has been 

 assumed, are stripes that have spread so as almost to crowd 

 out the pale interspaces, no reason can be alleged why white 

 stripes should not similarly spread and obliterate dark 

 interspaces. 



It seems to me indeed that we need not look beyond the 



subspecies of Equus quagga itself for justification of Johnston's 



belief. In these may be seen the passage from thickly striped 



legs to white legs by the thinning of the black marks, or, 



stating the same fact another way, by widening of the white 



marks. It is quite obvious, too, that the dark marks become 



not only reduced in width and length, but also toned in 



intensity of colour until they fade away and are replaced by 



white. This process goes on up to the shoulder and nearly 



to the root of the tail, and also takes place on the belly. 



Existing races only go to this stage, which is exhibited in 



Burchell's quagga [E. quagga hurchelii). But in extinct 



races the suppression of the dark marks at the expense of the 



light marks was carried still further, as is shown in the 



original quagga depicted by Edwards, in which the black 



