Page:The Zoologist, 4th series, vol 2 (1898).djvu/97

Rh measured without offering any resistance. At birth Norna generally resembled Romulus, both in colouring, markings, and shape; but her head was relatively smaller, and the ears relatively shorter. There was, however, a very important and interesting difference between Norna and the other hybrids. As already pointed out, the croup and rump of Romulus were at the outset marked by numerous rows of spots having on the whole a transverse direction. When his new coat was completed, in August last, I noticed that many of the spots had united to form somewhat zigzag bands that in their direction agreed closely with the stripes on the hind quarters of the Somali Zebra. In Norna, instead of spots over the hind quarters, there were from the first numerous narrow and hardly at all wavy stripes, which line for line almost agreed with the markings in the Somali Zebra. But, further, many of these all but transverse stripes reached, or all but reached, a stripe running obliquely across the hind quarters in almost the same position as the oblique stripe in the Somali Zebra which I have elsewhere referred to as the upper femoral stripe. The remarkable difference between the markings over the hind quarters of Norna and her sire Matopo, and the equally remarkable resemblance between these markings in Norna and the Somali Zebra, seem to me to throw a flood of light on the relationships of the stripes in the various species and varieties of Zebras, and at the same time strongly to support the view already advanced, that the difference between the stripes of the sire and his various hybrid offspring is in all probability due to atavism or reversion. If this is the correct explanation, it follows as a matter of course that at least in the markings the Somali is the most primitive of all the known recent Zebras.

That the hybrids have reverted in at least their markings towards a somewhat remote ancestor—it may be a common ancestor of both the Horses and Zebras—is also indicated by the presence of faint "shadow" stripes on the neck. From Matopo having twelve cervical stripes and some Zebras having in addition nine or ten "shadow" stripes, and from Romulus having twice as many stripes as Matopo, it may be inferred the typical number of cervical stripes in Zebras is twenty-four or thereabout. But in Norna, in addition to the twenty-four Zool. 4th ser. vol. II., February, 1898.