ANALOGOUS VARIATIONS. 145 



Mr. W. C. Martin, in his excellent treatise on the horse, has 

 given a figure of a similar mule. In four colored drawings, 

 which I have seen, of hybrids between the ass and zebra, 

 the legs were much more plainly barred than the rest of the 

 body ; and in one of them there was a double shoulder- 

 stripe. In Lord Morton's famous hybrid, from a chestnut 

 mare and male quagga, the hybrid and even the pure off- 

 spring subsequently produced from the same mare by a 

 black Arabian sire, were much more plainly barred across 

 the legs than is even the pure quagga. Lastly, and this is 

 another most remarkable case, a hybrid has been figured by 

 Dr. Gray (and he informs me that he knows of a second 

 case) from the ass and the hemionus ; and this hybrid, 

 though the ass only occasionally has stripes on his legs and 

 the hemionus has none and has not even a shoulder-stripe, 

 nevertheless had all four legs barred, and had three short 

 shoulder-stripes, like those on the dun Devonshire and 

 Welsh ponies, and even had some zebra-like stripes on the 

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

 convinced that not even a stripe of color 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 affirm- 

 ative. 



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 coloring 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 (in- 

 cluding two or three sub-species or geographical races) of a 

 bluish color, 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 colors are crossed, we see a strong 



