Pearls & Parasites

by Sir A. E. Shipley

The two chief factors which play a part in the origin of species are heredity and variation, and until we know more about the laws which govern these factors, we cannot hope to arrive at any satisfactory criteria by which we can estimate the importance of the data accumulated for us by comparative anatomists and embryologists. Signs are not wanting that this view is beginning to be appreciated. The publication of ‘Materials for the Study of Variation’ by Mr. Bateson some years ago shows that there exists a small but active school of workers in this field; and recent congresses on hybridization give evidence that in America, on the Continent, and in Great Britain, one of the most important sides of heredity is being minutely and extensively explored. Professor Cossar Ewart’s experiments, which we shall attempt to summarize, deal with heredity and cognate matters, and although they are so far from complete that the results hitherto obtained cannot be regarded as final, they mark an important stage in the history of the subject.

Twelve years ago Professor Ewart began to collect materials for the study of the embryology of the horse, about which, owing to the costliness of the necessary investigations, very little is at present known. At the same time he determined to inquire into certain theories of heredity which have for centuries influenced the breeders of horses and cattle, and the belief in which has played a large part in the production of our more highly bred domestic animals. Foremost amongst these is the view widely held amongst breeders that a sire influences all the later progeny of a dam which has once produced a foal to him. This belief in the ‘infection of the germ,’ or ‘throwing-back’ to a previous sire, is probably an old one, possibly as old as the similar faith in maternal impressions which led Jacob to placed peeled wands before the cattle and sheep of his father-in-law Laban. The phenomenon has recently been endowed with a new name—Telegony. Since the publication of Lord Morton’s letter to Dr. W. H. Wollaston, President of the Royal Society, in 1820, it has attracted the attention, not only of practical breeders, but of theoretical men of science. The supporters of telegony, when pressed by opponents, having almost always fallen back on Lord Morton’s mare, it will be well to recall the chief incidents in the history of this classic animal.

It appears that early in last century Lord Morton was desirous of domesticating the quagga. He succeeded in obtaining a male, but, failing to procure a female, he put him to a young chestnut mare of seven-eighths Arab blood which had never been bred from before. The result was the production of a female hybrid apparently intermediate in character between the sire and the dam. A short time afterwards Lord Morton sold his mare to Sir Gore Ouseley, who bred from her by a fine black Arabian horse. The offspring of this union, examined by Lord Morton, were a two-year-old filly and a year-old colt. He describes them as having

‘the character of the Arabian breed as decidedly as can be expected where fifteen-sixteenths of the blood are Arabian, and they are fine specimens of that breed; but both in their colour and in the hair of their manes they have a striking resemblance to the quagga.’

The description of the stripes visible on their coats is careful and circumstantial, but the evidence of the nature of the mane is less convincing:

‘Both their manes are black; that of the filly is short, stiff, and stands upright, and Sir Gore Ouseley’s stud-groom alleged that it never was otherwise. That of the colt is long, but so stiff as to arch upwards and to hang clear of the sides of the neck, in which circumstance it resembles that of the hybrid.

This is the classical—we might almost say the test—case of telegony: the offspring resembled not so much the sire as an earlier mate of the dam. The facts related tended to confirm the popular view, and that view is now widely spread. Arab breeders act on the belief, and it is so strongly implanted in the minds of certain English breeders that they make a point of mating their mares first with stallions having a good pedigree, so that their subsequent progeny may benefit by his influence, even though poorly-bred sires are subsequently resorted to.

The evidence of Lord Morton’s mare convinced Darwin of the existence of telegony. After a careful review of the case, he says: ‘There can be no doubt that the quagga affected the character of the offspring subsequently got by the black Arabian horse.’ Darwin, however, latterly came to the conclusion that telegony only occurred rarely, and some years before his death expressed the opinion that it was ‘a very occasional phenomenon.’ Agassiz believed in telegony. He was strongly of opinion

‘that the act of fecundation is not an act which is limited in its effect, but that it is an act which affects the whole system, the sexual system especially; and in the sexual system the ovary to be impregnated hereafter is so modified by the first act that later impregnations do not efface that first impression.

Romanes also believed that telegony occasionally occurred. He paid a good deal of attention to the matter, commenced experiments in the hope of settling the question, and corresponded at length on this subject with professional and amateur breeders and fanciers. The result of his investigations led him to the conclusion ‘that the phenomenon is of much less frequent occurrence than is generally supposed. Indeed, it is so rare that I doubt whether it takes place in more than 1 or 2 per cent. of cases.’ He adds that his professional correspondents regard this as an absurdly low estimate. Tegetmeier and Sutherland believe that telegony exists in dogs and other animals; and Captain Hayes, whose opinion probably coincides with that of the majority of veterinary surgeons, takes for granted that it occurs in horses. A controversy some years ago in the Contemporary Review shows us that Mr. Herbert Spencer was a firm upholder of telegony, and that he had a theory of his own as to the mode in which it is brought about.