Matopo, the zebra stallion from which Professor Ewart had, some eight years ago, bred eleven zebra-hybrids from mares of various breeds and sizes, belongs to the widely distributed group of Burchell’s zebras. Many sub-species or varieties are included in this group, which, as regards the pattern of the stripes, passes—in certain varieties found in Nyassaland—into the second species, the mountain zebra, once common in South Africa. The third species is the Grévy’s zebra of Shoa and Somaliland; it is probably this species which attracted so much attention in the Roman amphitheatres during the third century of our era. A pair of Somali zebras were presented to the late Queen some years ago by the Emperor Menelik, and for a time were lodged in the Zoological Gardens, Regent’s Park. This species measures about fifteen hands high, is profusely striped, and stands well apart from the other two groups. It is important to note that in Professor Ewart’s opinion it is the most primitive of all the existing striped horses.
There is no direct evidence that the ancestors of horses were striped. Certain observers think that some of the scratches on the life-like etchings on bone, left us by our palæolithic cave-dwelling ancestors, indicate such stripes; but little reliance can be placed on this. On the other hand there is much indirect evidence. Every one who has an eye for a horse, and who has travelled in Norway, is sure to have noticed the stripings, often quite conspicuous, on the dun-coloured Norwegian ponies. Colonel Poole assured Darwin that the Kathiawar horses had frequently ‘stripes on the cheeks and sides of the nose.’ Breeders are well aware that foals are often born with stripes, usually on the shoulders or legs, less frequently on the face. Such stripes as a rule disappear as the colt grows up, but can often be detected in later life for a short time after the coat has been shed; they are sometimes only visible in certain lights, and then produce somewhat the same impression as a watered silk. From the facts that more or less striped horses are found all over the Old World; that in Mexico and other parts of America the descendants of horses which were introduced by the Spaniards and which afterwards ran wild are frequently dun-coloured and show stripes; that foals are frequently striped; and that mules not uncommonly have leg and shoulder stripes, the inference is largely justified that the ancestors of all our horses were striped.
The hypothesis of reversion has recently been called in question, and no doubt the term has been much abused. Animals and plants have been said to revert to some remote ancestor when they have varied in some particular, and this variation has then been described as a primitive character possessed by the ancestor; thus there has been much arguing in and about a vicious circle. But the fact that a term has been illogically applied does not destroy the existence of that which the term signifies, and there can be no doubt that reversion exists. That it exists in the Equidæ is shown by the following proofs: (1) The ancestors of the horse had four premolar teeth in the upper jaw; the modern horse has lost, or is losing, the first of these, and as a rule has only three. When the first is present—the so-called wolf-tooth—it is small, and soon disappears. Zebras usually retain the ancestral number. A few years ago Professor Ewart had a Shetland pony in which the first premolar was relatively nearly as large as it is in hipparion, one of the supposed ancestors of the horse. (2) There is no doubt that the horse is descended through three-toed ancestors from five-toed ancestors. All trace of the latter condition is now lost in development, but an embryo horse six weeks old has three toes as completely formed as those of a rhinoceros. The outer toes then begin to dwindle, and the newly-born foal supports itself on its central digit alone; but horses are occasionally born with two digits, each encased in a hoof, and at very rare intervals with three. Cæsar’s favourite horse was polydactylous, and so was Alexander’s Bucephalus. Major Waddell, in his book on the Himalayas, refers to a creamy fawn-coloured pony, which ‘had a black stripe down the spine ... broad black stripes over the shoulders, flanks, and legs, and dappled spots over the haunches.’ Many other instances might be quoted, but enough has been said to show that reversion is found in the Equidæ, as in other families of animals.
We now pass to the experiments made at Penycuik in crossing the zebra Matopo with various mares of different breeds.
1. Matopo was first mated with Mulatto, one of Lord
Arthur Cecil’s black West Highland ponies. The result was the hybrid Romulus, which on the whole, both in mental disposition and bodily form, took more after his father than his mother. His striping was even more marked than that of his sire. He had a semi-erect mane, which was shed annually. The pattern of the markings, on both body and face, resemble the stripes on a Somali zebra—which, as we have seen, is regarded by Professor Ewart as the most primitive type—more than they resembled that of any of Burchell’s zebras. The profuse striping is a point of difference between this hybrid and Lord Morton’s. The quagga-hybrid was less striped than many dun-coloured horses (see illustration).
The mother Mulatto was next mated with a highly-bred grey Arab horse, Benazrek. The offspring agreed in all respects with ordinary foals; it had, however, a certain number of indistinct stripes which could only be detected in certain lights. The stripes were not nearly so clear as in a foal bred by Mr. Darwin from a cross-bred bay mare and a thoroughbred horse, and they disappeared entirely in about five months.