150 ON THE ORIGIN OF SPECIES 



nevertheless had all four legs barred, and had three 

 short shoulder-stripes, like those on the dun Welch 

 pony, and even had some zebra-like stripes on the sides 

 of its face. With respect to this last fact, I was so con- 

 vinced that not even a stripe of colour appears from 

 what would commonly be called an accident, 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 occur 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 very 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 dis- 

 played 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 varia- 

 tion a bluish tint, these bars and other marks in- 

 variably reappear ; but without any other change of 

 form or character. WTien 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 hypo- 

 thesis 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 char- 

 acter, 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 



