Whatever answer the future may give to that question, it is clear from this moment that every case which obeys the Mendelian principle is removed finally and irretrievably from the operations of the Law of Ancestral Heredity.
At this juncture Professor Weldon intervenes as a professed exponent of Mendel’s work. It is not perhaps to a devoted partisan of the Law of Ancestral Heredity that we should look for the most appreciative exposition of Mendel, but some bare measure of care and accuracy in representation is demanded no less in justice to fine work, than by the gravity of the issue.
Professor Weldon’s article appears in the current number of Biometrika, Vol. I. Pt. II. which reached me on Saturday, Feb. 8. The paper opens with what purports to be a restatement of Mendel’s experiments and results. In this “restatement” a large part of Mendel’s experiments—perhaps the most significant—are not referred to at all. The perfect simplicity and precision of Mendel’s own account are destroyed; with the result that the reader of Professor Weldon’s paper, unfamiliar with Mendel’s own memoir, can scarcely be blamed if he fail to learn the essence of the discovery. Of Mendel’s conception of the hybrid as a distinct entity with characters proper to itself, apart from inheritance—the most novel thing in the whole paper—Professor Weldon gives no word. Upon this is poured an undigested mass of miscellaneous “facts” and statements from which the reader is asked to conclude, first, that a proposition attributed to Mendel regarding dominance of one character is not of “general”[52] application, and finally that “all work based on Mendel’s method” is “vitiated” by a “fundamental mistake,” namely “the neglect of ancestry[53].”
To find a parallel for such treatment of a great theme in biology we must go back to those writings of the orthodox which followed the appearance of the “Origin of Species.”
On 17th December 1900 I delivered a Report to the Evolution Committee of the Royal Society on the experiments in Heredity undertaken by Miss E. R. Saunders and myself. This report has been offered to the Society for publication and will I understand shortly appear. In it we have attempted to show the extraordinary significance of Mendel’s principle, to point out what in his results is essential and what subordinate, the ways in which the principle can be extended to apply to a diversity of more complex phenomena—of which some are incautiously cited by Professor Weldon as conflicting facts—and lastly to suggest a few simple terms without which (or some equivalents) the discussion of such phenomena is difficult. Though it is impossible here to give an outline of facts and reasoning there set out at length, I feel that his article needs an immediate reply. Professor Weldon is credited with exceptional familiarity with these topics, and his paper is likely to be accepted as a sufficient statement of the case. Its value will only be known to those who have either worked in these fields themselves or have been at the trouble of thoughtfully studying the original materials.
The nature of Professor Weldon’s article may be most readily indicated if I quote the summary of it issued in a paper of abstracts sent out with Review copies of the Part. This paper was most courteously sent to me by an editor of Biometrika in order to call my attention to the article on Mendel, a subject in which he knew me to be interested. The abstract is as follows.
“Few subjects have excited so much interest in the last year or two as the laws of inheritance in hybrids. Professor W. F. R. Weldon describes the results obtained by Mendel by crossing races of Peas which differed in one or more of seven characters. From a study of the work of other observers, and from examination of the ‘Telephone’ group of hybrids, the conclusion is drawn that Mendel’s results do not justify any general statement concerning inheritance in cross-bred Peas. A few striking cases of other cross-bred plants and animals are quoted to show that the results of crossing cannot, as Mendel and his followers suggest, be predicted from a knowledge of the characters of the two parents crossed without knowledge of the more remote ancestry.”
Such is the judgment a fellow-student passes on this mind
“Voyaging through strange seas of thought alone.”
The only conclusion which most readers could draw from this abstract and indeed from the article it epitomizes, is that Mendel’s discovery so far from being of paramount importance, rests on a basis which Professor Weldon has shown to be insecure, and that an error has come in through disregard of the law of Ancestral Heredity. On examining the paper it is perfectly true that Professor Weldon is careful nowhere directly to question Mendel’s facts or his interpretation of them, for which indeed in some places he even expresses a mild enthusiasm, but there is no mistaking the general purpose of the paper. It must inevitably produce the impression that the importance of the work has been greatly exaggerated and that supporters of current views on Ancestry may reassure themselves. That this is Professor Weldon’s own conclusion in the matter is obvious. After close study of his article it is evident to me that Professor Weldon’s criticism is baseless and for the most part irrelevant, and I am strong in the conviction that the cause which will sustain damage from this debate is not that of Mendel.