Chap. V. LAWS OF VARIATION. 163 



here, as before, I lie under a great disadvantage in 

 not being able to give them. I can only repeat that 

 such cases certainly do occur, and seem to me very 

 remarkable. 



I will, however, give one curious and complex case, 

 not indeed as affecting any important character, but 

 from occurring in several species of the same genus, 

 partly under domestication and partly under nature. 

 It is a case apparently of reversion. The ass not rarely 

 has very distinct transverse bars on its legs, like those 

 on the legs of the zebra : it has been asserted that these 

 are plainest in the foal, and from inquiries which I have 

 made, I believe this to be true. It has also been as- 

 serted that the stripe on each shoulder is sometimes 

 double. The shoulder-stripe is certainly very variable 

 in length and outline. A white ass, but not an albino, 

 has been described without either spinal or shoulder 

 stripe ; and these stripes are sometimes very obscure, or 

 actually quite lost, in dark-coloured asses. The koulan 

 of Pallas is said to have been seen with a double shoulder- 

 stripe. The hemionus has no shoulder-stripe ; but traces 

 of it, as stated by Mr. Blyth and others, occasionally 

 appear: and I have been informed by Colonel Poole 

 that the foals of this species are generally striped on 

 the legs, and faintly on the shoulder. The quagga, 

 though so plainly barred like a zebra over the body, is 

 without bars on the legs ; but Dr. Gray has figured 

 one specimen with very distinct zebra-like bars on the 

 hocks. 



With respect to the horse, I have collected cases in 

 England of the spinal stripe in horses of the most dis- 

 tinct breeds, and of all colours ; transverse bars on the 

 legs are not rare in duns, mouse-duns, and in one 

 instance in a chestnut : a faint shoulder-stripe may 

 sometimes be seen in duns, and I have seen a trace in a 



