This article must not close without a word or two more about the zebra-hybrids. It is mentioned above that only two out of the eleven which have already been born took strongly after their father. This is no proof that the wilder animal is not prepotent. Recent experiments in hybridizing echinoderms, star-fish, seaurchins, etc., show that the hybrid tends to resemble that species whose germ-cells are most nearly approaching maturity; and thus the nutrition of the germ-cell is but another thread in that complex tangle of heredity which must not be overlooked in attempting to estimate the part played by prepotency and reversion.
Those who have seen the young hybrids playing about in the fields at Penycuik must agree that they are the most charming and compactly built little animals possible; ‘marvellous steeds, striped as a melon is, all black and white,’ as the poet has it. Of Romulus, the eldest of the herd, Professor Ewart says:
‘When a few days old [he] was the most attractive little creature I have ever seen. He seemed to combine all the grace and beauty of an antelope and a well-bred Arab foal.... What has struck me from the first has been his alertness and the expedition with which he escapes from suspicious or unfamiliar objects. When quite young, if caught napping in the paddock, the facility with which he, as it were, rolled on to his feet and darted off was wonderful.’
The writer can fully confirm all the praise Professor Ewart lavishes on his pets; in truth Romulus has been well described as a ‘bonnie colt with rare quality of bone ... and with the dainty step and dignity of the zebra.’ Remus, the offspring of the Irish mare, was from the first more friendly than his half-brother; he objected less to the process of weaning, and promised to be the handsomest and fleetest of the existing hybrids.
On the whole the hybrids are unusually hardy; at the time of writing only two have been lost—one, a twin, which died almost as soon as it was born, and
another which lived some three months and then succumbed. It is only fair to say that the dam of the latter, who was only three years old when the hybrid was born, had been much weakened by attacks of the strongylus worm, and that she was the victim of close inbreeding. Both the zebras and the hybrids which have been under observation at Penycuik show a remarkable capacity for recovering from wounds. Accidental injuries heal with great rapidity. On one occasion the surviving twin was discovered with a flap of skin some five inches long hanging down over the front of the left fetlock. The skin was stitched into its place again, during which operation the little hybrid fought desperately, and cried piteously; but it soon recovered, the wound healed, and now scarcely a scar remains. There was no lameness and no swelling either at the fetlock or above the knee. Some time ago four hybrid colts and three ordinary foals were attacked by that scourge of the stable, the strongylus worm. One of the latter died and another was reduced almost to a skeleton: the hybrids, though obviously affected, suffered much less than the others, and soon recovered. It is further noticeable that the hybrids suffer less from colds and other slight ailments than the mares and horses amongst which they live. Thus it seems that Colonel Lugard’s hope has to some extent proved true. Some years ago, when administering British East Africa, he strongly recommended the breeding of zebra mules from both the horse and the donkey, believing that they would prove exceptionally hardy and possibly impervious to the tsetse fly. So far as Professor’s Ewart’s experiments go, the first part of the forecast has proved correct. Unfortunately, the latter half has not been justified.
The much dreaded tsetse fly, which has interfered so seriously with the colonization of whole tracts of South Africa, is now known not to be the direct cause of the disease which follows its puncture, but to be the means by which the organism which causes the disease is introduced into the body. In this respect the tsetse fly resembles the malarial mosquito. It is not thought that the organism—a hæmatozoon—passes through any of the stages of its life-history within the body of the fly, but that the proboscis of that insect merely acts like an inoculating needle. An answer to the important question, Are zebra-hybrids fly-proof or not? has been attempted. Professor Ewart generously allowed an experiment to be tried on two of his hybrids, which were inoculated with the hæmatozoon, supplied from the Pathological Laboratory at Cambridge. The result was unfortunate, for, although the hybrids resisted the disease far longer than a mare which was also inoculated as a control experiment, both ultimately succumbed.