PROFESSOR EWART’S PENYCUIK EXPERIMENTS.[A]
[A] Abstract from an article in the Quarterly Review discussing Professor Ewart’s ‘Experimental Investigations on Telegony,’ read before the Royal Society last year, and his book, ‘The Penycuik Experiments,’ published by Messrs. A. & D. Black.
The views and works of Darwin have influenced in an unexpected way the nature of the work carried on by biological investigators during the latter end of this fast-dying century. To a great extent, while generally holding the doctrines he held, they have forsaken his methods of inquiry.
If animals and plants have arrived at their present state by descent with modification from simpler forms, it ought to be possible by careful searching to trace the line of ancestry; and it is this fascinating but frequently futile pursuit which has dominated the minds of many of our ablest zoölogists for the last thirty years. To such an extent has this pedigree hunting been carried that there is scarcely a group of invertebrates from which the vertebrates have not been theoretically derived; and to-day one of the ablest of our physiologists is using his great powers in the attempt to trace the origin of the backboned animals from a spiderlike creature, and is exercising his ingenuity in a plausible but unconvincing effort to equate the organs of a king-crab with those of a lamprey. This appeal to comparative anatomy and the consequent neglect of living animals and their habits are no doubt partly due to the influence of Huxley, Darwin’s most brilliant follower and exponent. He had the engineer’s way of looking at the world, and his influence was paramount in many schools. The trend which biology has taken since Darwin’s time is also partly due to a fervent belief in the recapitulation theory, according to which an animal in developing from the egg passes through phases which resemble certain stages in the past history of the ancestors of the animal. For example, there is no doubt that both birds and mammals are descended from some fishlike animal that lived in the water and breathed by gills borne on slits in the gullet, and every bird and mammal passes through a stage in which these gill-slits are present, though their function is lost and they soon close up and disappear. In the hope, which has been but partially realized, that a knowledge of the stages through which an animal passes on its path from the ovum to the adult would throw light on the origin of the race, the attention of zoölogists has been largely concentrated on details of embryology, and a mass of facts has already been accumulated which threatens to overwhelm the worker.
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 can not 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, a few years ago, shows that there exists a small but active school of workers in this field; and the recent congress on hybridization, held in London under the auspices of the Royal Horticultural Society, is 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. Prof. 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 can not be regarded as final, they mark an important stage in the history of the subject.
Five years ago Professor Ewart began to collect material 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 among these is the view widely held among 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 place 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 this 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 afterward Lord Morton sold his mare to Sir Gore Ouseley, who bred from her by a fine black Arabian horse. The offspring of this union, which were 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 color 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 upward 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 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 its 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 the opinion “that the act of fecundation is not an act which is limited in its effects, 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.”