202 DISTINCT SPECIES PRESENT [Chap. V. 



vinced 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 hemionus 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, liow ob- 

 serve 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 reappear- 

 ance of very ancient characters, is — that there is a ten- 

 dency in the yoiing of each successive generation to 

 produce the .long-lost character, and that this tendency, 

 from unknown causes, sometimes prevails. And we 



