THE EVOLUTIONIST AT WORK.

Otago Witness, Issue 2400, 1 March 1900, Page 63

THE EVOLUTIONIST AT WORK.

"THE PENYCUIK EXPERIMENTS." By J. C. Ewart, M.D., F.R.S., Regius Professor of Natural History, University of Edinburgh. London : Adam and Charles Black, In justice to this volume an epitome of the history of the evolution theory ought to preface a notice' of it. Forty years have elapsed since Charles Darwin gave wheels to that theory by the publication of his • <c Origin of Species " ; an event followed by such explosions of animosity as have seldom <if-ever) been caused by the appearance of ft mere book. Subsiding after a time, these ructions were followed by more definite if less vigorous attempts to combat the new doctrine — that of natural selection — as well j,s the theory of evolution itself, which had .been immensely strengthened by the labours of Darwin. This fight went on for a good many j^ears, and, according to some, is not yet ended. But in so far as the broad conception of evolution is concerned effective opposition is undoubtedly at an end, the educated world having accepted the new explanation of the known universe and its living denizens with a degree of unanimity as unparalleled in itself as giatifying to what may be called the army of evolutionary, workers. The big battle being to all intents and purposes over, most of the combatants have found themselves free to engage in the lesser combats springing from it. "These go on merrily, and are waged chiefly over vexed questions - connected with the factors of evolution. It is evolution itself no longer, but the how and the why of it, that worries thinking heads. The Geiman biologist Weismann hers stands supreme as yet, though by no means unassailed. His denial of the transmission to offspring of characters acquired by the parent, and his ultraDarwinian insistence upon the idea that all evolution of higher forms springs from natural selection acting on conjugating sperm and germ, has shaken every investigator who has work in him into activity, but as ] yet there is little agreement over results. Dr Ewart's Penycuik experiments •have evidently been made with intent to throw light upon some of these knotty problems hedging round the subject of organic variation. His establishment at the quiet little village of Penycuik (near Edinburgh) •must be a veritable up-to-date zoological I garden, meant, however, for work, not chow. In his aims, Dr Ewart is practical as well as scientific, and hopes, for instance, to produce zebra-horse hybrids, climateproof and fit for efficient transport service in Africa find India. He hopes, also, to produce a tsetse-fly hybrid, which would be a great achievement. In addition to experiments, in crossing zebras, horses, and donkeys, numerous interesting results, bearing upon telegony, ! reversion', etc., have also been got from dogs, rabbits, pigeons, ducks, and fowls. • Without attempting to. grapple in detail with this account of a well-informed essay in experimental evolution I musjb say that a large amount,, of the fresh evidence as herein presented will be found of extreme interest and value by both evolutionist and breeder. Professor Ewart's results will go far to strengthen the growing scientific belief that race is of more importance than ' parentage in the long run, and the passages wherein he deals \sith the theory of " re- : capitulation" will take a deal of refuting , from recent critics of that matter. " | " The subject of " telegony " — or 'the ten- j dericy of subsequent offspring to exhibit characters not derived from their sire, but ' due to previous matings of their dam — is the chief thesis of the present problem, j The views of Darwin, Romanes, Herbert j Spencer, Agassiz, Weismann, and many , others are here given, and it is seen that a fine field for all stock-owners to expeiiment in is here displayed. British breeders and sportsmen are almost unanimous supjporters of the belief in telegony, and have •been so for a century at least. On the other hand, German breeders of acknowledged eminence express complete denial of the doctrine. The experiments of Penycuik eeein to favour the positive view, but results are as yet too few to be conclusive. • Further investigation under stringently sci- ; entitle conditions can alone decide the mat- ', ter, and a cataloge of suggested experiments ; is given at the end of the book. Another important and much vexed subject fully dealt with is " reversion " — the occurrence in offspring of characters that seem due to remote ancestral influence, and which, at any rate, are very difficult otherwise to be explained. Even the highest i class breeders are continually vexed by the ' tendencies of stock to go back— to " retrogress toAvards mediocrity,'' and revert to j primitive types, to use the scientific phraseology. Common in the animal kingdom, ! this tendency (unlike telegony, which Dr •Ewart says he never knew to occur among ' human beings) is equally visible in the human species, and Galton and others have j shown clearly the great part it seems to play in maintaining the equilibrium or safe average of races. Many attempts have been made to discredit the reversion hypothesis, j but multitudes of fact go to support it, "and >Dr Ewart is confident that certain aberrant offspring of his zebra-horse hybrids, pigeons, and rabbits are only to be understood as instances of reversion. Of nine hybrids which he bred by crossing his zebra stallion ■with marcs, he says : " Some of the hybrids in make and disposition strongly suggest their zebra sire, others their respective 'dams ; but even the most zebra-like in form are utterly unlike their sire in their markings. It is not a case of taking after a. grandparent, but after an ancestor in all probability thousands of generations removed " Closely connected with reversion is the question of prepotencj-. It is generally as sumed that an old species or variety is prepotent over a more recent species or variety. It is impossible to say whether zebra 'hybrids in their markings take after a reimote zebra ancestor, or after an ancestor common to both zebras and horses, or after a hypothetical mid -parent combining the

characters of the less remote ancestors o: both zebras and horses. There is, how ever, no difficulty in seeing that while some zebra hybrids, apart from their stripes 'closely resemble the zebra parent, other.' take after their horse parent, thus show ing that the wild parent is not necessarilj , the most prepotent. But even when the 'hybrids are distinctly horse-like they nevei repeat recently acquired peculiarities, suet 'as a blaze or short ears, high withers, or a small head and long neck." I Full of interesting particulars as it is, , this volume does not purport to be a record j of completed work — it is merely a bulletin in answer to those who have " frequently 'asked when an account is likely to be published of the telegony 'and other experi- . ments " being carried on at Penycuik. As yet these experiments are more important from their aim than from their achievement, though that is considerable. As their origi- , nator saj r s, some years must elapse befoi'e a ) 'complete and systematic account is pos- ! sible. Though not of a kind to captivate the attention of the general reader, this book will be found full of sterling interest to breeders on the one hand and scientifically inclined stxidents on the other. Many finery done photo-engravings illustrate the text, and in a binding which closely imitates zebra skin " The Penycuik Experiments "' appears outwardly a very striking volume. | DINORNIS.