202 DISTINCT SPECIES PRESENT [Chap. V. 



that not even a stripe of colour appears from what is 

 commonly called chance, that I was led solely from the 

 occurrence of the face-stripes on this hybrid from the 

 ass and hemionns to ask Colonel Poole whether such 

 face-stripes ever occurred in the eminently striped 

 Kattywar breed of horses, and was, as we have seen, 

 answered in the affirmative. 



What now are we to say to these several facts ? We 

 see several distinct species of the horse-genus becoming, 

 by simple variation, striped on the legs like a zebra, or 

 striped on the shoulders like an ass. In the horse we 

 see this tendency strong whenever a dun tint appears — 

 a tint which approaches to that of the general colouring 

 of the other species of the genus. The appearance of 

 the stripes is not accompanied by any change of form 

 or by any other new character. We see this tendency 

 to become striped most strongly displayed in hybrids 

 from between several of the most distinct species. Now 

 observe the case of the several breeds of pigeons : they 

 are descended from a pigeon (including two or three 

 sub-species or geographical races) of a bluish colour, 

 with certain bars and other marks; and when any 

 breed assumes by simple variation a bluish tint, these 

 bars and other marks invariably reappear ; but without 

 any other change of form or character. When the 

 oldest and truest breeds of various colours are crossed, 

 we see a strong tendency for the blue tint and bars 

 and marks to reappear in the mongrels. I have stated 

 that the most probable hypothesis to account for the 

 reappearance of very ancient characters, is — that there 

 is a tendency in the young of each successive generation 

 to produce the long-lost character, and that this 

 tendency, from unknown causes, sometimes prevails. 



