166 LAWS OF VARIATION. Chap. V. 



to ask Colonel Poole whether such face-stripes ever 

 occur in the eminently striped Katty war 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 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. 

 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 ! 



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