TELEGONY AND EEVERSION. 131 



— in some respects a small edition of Mulatto — is especially 

 interesting. This hybrid filly suggests Romulus when at a 

 corresponding age, but she is smaller and more compact 

 and more self-assertive, but less docile. The general plan 

 of the striping and the coloration is the same as in Romulus ; 

 and, as in Romulus, there are fourteen frontal arches (but 

 the pattern is somewhat different), and there are nine 

 vertical stripes across the body behind the shoulder stripe. 

 Over the hind quarters, instead of numerous more or less 

 transversely arranged spots, there have been from the first 

 numerous nai-row somewhat zigzag bands. In other words, 

 unlike Romulus and the three other hybrids, in Norette 

 the croup and rump have been from birth decorated by 

 narrow transverse stripes such as we find on the Somali 

 zebra. But although there have been since birth numerous 

 distinct transverse narrow stripes extending well down the 

 hind quarters in the Shetland hybrid, this is no argument 

 in favour of discontinuous variation. In this case what 

 might be termed the Somali stage in the ancestral histoiy 

 has been reached about a year sooner than was the case 

 with Romulus. 



The fact that all the hybrids differ so decidedly in the 

 markings over the hind quarters fi-om their common sire 

 while they agree more or less accurately with the Somali 

 zebra, seems to me to support the revei'sion hypothesis. 

 Further evidence in favour of reversion is afforded by 

 the neck stripes. Not very long ago, from a geological 

 point of view, there were two types of three-toed horses in 

 existence, one (Protohippus) in the New World, the other 

 (Hipparion) in both the New and the Old. Protohippus 

 was probably the ancestor of all our recent breeds of 

 horses ; Hipparion I look upon as the common ancestor of 

 the asses and zebras. The asses I believe parted com- 

 pany at an eai'ly stage with the zebras — before the zebras 

 had acquired their extravagantly striped coat. If asses 

 were never as fully and distinctly striped as horses, hybrids 

 between a common ass and a zebra might very well in their 

 markings present a simpler and more primitive arrange- 



