MULES AND OTHER HYBRIDS 237 



was deeply forked at the extremity, and in another 

 instance was double, although united in the middle. 

 Mr, Martin gives a figure of a Spanish mule with 

 strong zebra-like marks on its legs, and remarks 

 that mules are particularly liable to be thus striped 

 on their legs. In South America, according to 

 Roulin, such stripes are more frequent and con- 

 spicuous in the mule than in the ass. In the 

 United States, Mr. Gosse, speaking of these 

 animals, says that in a great number, perhaps in 

 nine out of every ten, the legs are banded with 

 dark transverse stripes." In a later paragraph 

 Darwin continues as follows : " From these facts 

 we see that the crossing of the several equine 

 species tends in a marked manner to cause stripes 

 to appear on the legs. As we do not know whether 

 the parent -form of the genus was striped, the 

 appearance of the stripes can only hypothetically 

 be attributed to reversion. But most persons, after 

 considering the many undoubted cases of variously- 

 coloured marks reappearing by reversion in my 

 experiments on crossed pigeons and fowls, will 

 come to the same conclusion with regard to the 

 horse-genus ; and if so, we must admit that the 

 progenitor of the group was striped on the legs, 

 shoulders, face, and probably over the whole body, 

 like a zebra." 



While fully admitting the cogency of this argu- 

 ment, it may be suggested that the striping may 



