228 THE ORIGIN OF SPECIES 



see sevenil distiiu't 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 coloring 

 y)f 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 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 color, with 

 certain bars and other marks; and when any breed as- 

 sumes 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 tru- 

 est breeds of various colors are crossed, we see a strong 

 tendency for the blue tint and bars and marks to re- 

 appear 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. And we have just seen that 

 in several species of the horse-genus the stripes are either 

 plainer or appear more commonly in the young than in 

 the old. Call the breeds of pigeons, some of which have 

 bred true for centuries, species; and how exactly parallel 

 is the case with that of the species of the horse-genus! 

 For myself, I venture confidently to look back thousands 

 on thousands of generations, and I see an animal striped 



