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Gregor Johann Mendel (the first name was taken on entrance to his order), b. 22 July, 1822, at Heinzendorf near Odrau, in Austrian Silesia; d. 6 January 1884, at the Augustinian Abbey of St. Thomas, Brunn.

His father was a small peasant-farmer, and the pecuniary resources of the family were very meagre, as is shown by the fact that a younger sister of Mendel's voluntarily gave up a large part of her dowry in order that the plans which his family had formed for his education might be carried out. The debt was afterwards repaid, and more than repaid, by Mendel. After a period of study at the school of Leipnik, Mendel distinguished himself so much that his parents made a great effort and sent him to the gymnasium at Troppau, and subsequently, for a year, to Olmutz. At the former place one of his teachers was an Augustinian, and, whether post or propter hoc, at the end of his period of study at the gymnasium Mendel applied to be admitted as a novice in the Abbey of St. Thomas at Brünn, commonly known as the "Königskloster". This was in 1843, and in 1847 he was ordained priest and seems to have occupied himself in teaching until 1851, when he was sent, for a two years' course of study in mathematics, physics, and the natural sciences, to the University of Vienna. When this course terminated, in 1853, he returned to his abbey, and was appointed a teacher, principally of physics, in the Realschule. He continued in this position for fifteen years and appears to have been genuinely devoted to teaching and to have gained the reputation of being extraordinarily successful in interesting his pupils in their work. In 1868 he was obliged to relinquish his educational labours on assuming the position of abbot of his monastery, to which office he was then elected.

When appointed to this important post, Mendel, already much engrossed with his biological experiments hoped that he might have more time for his researches than was possible in the midst of his labours at the Realschule. But this was not to be. The jurisdiction and privileges of the abbey are somewhat extensive, and its abbot must, in ordinary times, find himself with plenty of occupation. Mendel, however, in addition to the multiplicity of his duties as abbot, became involved in a lengthy controversy with the Government which absorbed his attention and embittered the last years of his life. The Government had imposed special taxes on religious houses, and these Mendel refused to pay, alleging that, as all citizens were, or should be, equal in the eye of the law, it was unjust to ask one kind of institution to pay a tax from which another kind was free. At the commencement of the struggle several other monasteries sided with him but one by one they submitted, until at last Mendel was left alone in his opposition to the tax. Great efforts were made to induce him to yield but he refused, and even allowed the goods of the abbey to be distrained upon rather than submit. In the end — though not till after Mendel's death — the obnoxious tax was repealed. The result of all this strain, as may easily be understood, was a complete cessation in Mendel's scientific work. His appointment as abbot may have been an excellent thing for the monastery, but it cannot be denied that it was a great misfortune for science. The latter years of his life were rendered unhappy, not only by constant strife with the Government, and by the racial controversies which tore that part of Austria at the time in question, but also by constant ill-health due to the chronic nephritis of which he ultimately died. The result of these various troubles was to change that sunny cheerful nature, which had secured Mendel many friends, to a somewhat morose disposition and suspicious attitude of mind. A public monument to his memory was unveiled at Brünn, 2 October 1910.

Mendel's experiments, on which his fame rests, were commenced while he was still a novice, and carried out in the large gardens attached to his monastery. Dissatisfied with the Darwinian views, then commencing to be known, he undertook a series of experiments on peas which occupied his spare time for eight years. The results of these observations were published in the "Transactions" of the Brünn Natural History Society in 1866, and a further paper on Hieracium appeared in the same periodical in 1869. Two short papers of less importance were published during the period of study at Vienna, and this seems to complete the list of the communications which he gave to the world, with the exception of his annual meteorological records, also published by the same society. It is, however, known that he devoted himself to various lines of investigation, bestowing much labour on the heredity of bees. He collected queen bees of all attainable races, European, Egyptian, and American, and made many crosses between the various races. Unfortunately, the notes which he is known to have made on this subject have completely disappeared, and it is not impossible that he may have destroyed them himself in some of the dark hours which he was called upon to endure during the last years of his life.

The Brünn Society was not a wholly unknown organization, but its Journal was scarcely one which could be expected to give the widest publicity to a new discovery or theory. It is perhaps largely on this account that Mendel's views seemed for a third of a century to have been still-born. Bateson, however, thinks that this would not so long have delayed his recognition, but that "the cause is unquestionably to be found in that neglect of the experimental study of the problem of Species which supervened on the general acceptance of the Darwinian doctrines", and Bateson's opinion, as that of the man who has done more than any other to make Mendel's views known, is worthy of all consideration. Whatever may have been the cause, the fact remains that Mendel's work was unrecognized until, in 1899, three men of science — de Vries in Holland, Correns in Germany, and Tschermak of Austria-almost simultaneously called attention to his publications and started the interest in his line of investigations which has steadily continued to grow and increase since that date. Mendel himself, though grievously disappointed at the neglect of his views, never lost confidence in them, and was wont to exclaim to his friends, "Meine Zeit wird schon kommen". He was abundantly justified in his belief.

It now remains to give some account of the theory put forward by Mendel and the influence of his work during the past ten years. Mendel himself confined his experiments to plants, and his most important observations were made on the garden pea, Pisum sativum. Later observers have dealt, not only with a number of other members of the vegetable kingdom, but also with a variety of animals, using that word in the widest possible sense. With the details of their publications it is not possible here to deal, but a short account of Mendel's own work will suffice to show the lines of his theory. He did not, as others had done and have since done, direct his attention to the entire group of characteristics making up the individual, but concentrated his attention on certain pairs of opposed features observable in certain plants. In the case of the pea, he observed that some were tall, some dwarf in habit; some had round seeds, others wrinkled; some had green endosperm, others yellow. For the purpose of his own observations he selected seven such characters and studied their behaviour under hybridization. From what occurred he was led to believe that the progeny of the various crosses behaved in regard to these characters, not in a haphazard manner, but in one which was reducible to the terms of a so-called "Natural Law". One instance given by Bateson will explain what happens: there are tall and short (or "Cupid") sweet peas, and in them we have plants showing a pair of marked and easily recognizable opposite characters. The tall and short forms are crossed with one another, and the seeds collected and sown. The resultant plants will be found to belong entirely to the tall variety, which has apparently wiped out the short. If, however, this generation of seeds is sown and the flowers of the resultant plants be self-fertilized, the result is that, when their seeds are sown, and have sprung up into plants, it is found that these are mixed, and mixed in definite proportions, for on the average, it will be found that there are three tall forms for every one of the short. It follows that the dwarfishness was not wiped out, but that it was temporarily obscured in the second generation, though present all the time potentially. To the character which alone appears in the first cross is given the name dominant (in this instance tallness is dominant), and to the hidden character that of recessive (dwarfishness, in the example). When the talls and dwarfs of the third generation are allowed to be self-fertilized, it is found that all the recessives (dwarfs) breed true and, what is more, will go on breeding true as long as uninterfered with. Not so the dominants, which, after self-fertilization, produce both talls and dwarfs. Some of the talls of this generation will breed true and continue to breed true; others will not, but will produce a mixed progeny. Hence, out of the first plants, seventy-five will be talls (dominants), and twenty-five dwarfs (recessives), these last being pure. Of the seventy-five talls, twenty-five will be pure and will go on producing talls; fifty will be mixed, and their progeny will consist of pure dominants, mixed dominants, and recessives, as has been stated above.

Davenport thus enunciates the laws underlying these facts: "Of the two antagonistic peculiarities possessed by two races that are crossed, the hybrid, or mongrel, exhibits only one; and it exhibits it completely, so that the mongrel is not distinguishable as regards this character from one of the parents. Intermediate conditions do not occur. . . . Second: in the formation of the pollen, or egg-cell, the two antagonistic peculiarities re segregated; so that each ripe germ-cell carries either one or the other of these peculiarities, but not both. It is a result of the second law that in the second generation of mongrels each of the two qualities of their grandparents shall crop out on distinct individuals, and that the recessive quality shall appear in twenty-five per cent of the individuals, the remaining seventy-five per cent having the dominant quality. Such recessive individuals, crossed inter se, should never produce anything but recessive offspring."

Such, in brief, are the main outlines of Mendel's theory; but in the few years which have elapsed since it first engaged the attention of the scientific world, there has grown up an enormous literature on the subject which has much added to the complexity of the minor developments of the laws above enunciated, and has still more added to the difficulty of the terminology of Mendelism. With these developments it is impossible to deal here: they will be found very fully treated in Bateson's work (see below). It would, however, be negligent to omit all mention of the estimation in which the theory itself is held by men of science of the present day. Bateson claims that "his experiments are worthy to rank with those which laid the foundation of the atomic laws of chemistry"; and Lock, that his discovery was "of an importance little inferior to those of a Newton or a Dalton". Punnett also states that, owing to Mendel's labours, "the position of the biologist of today is much the same as that of the chemist a century ago, when Dalton enunciated the law of constant proportions. In either case the keynote has been Discontinuity-the discontinuity of atom and the discontinuity of the variations in living forms". It is a remarkable fact that Mendel's writings never appear to have come under the notice of Charles Darwin and many have speculated as to the effects which they might probably have exercised on that writer had he made their acquaintance. T.H. Morgan does not hesitate to say that Mendel's laws give the final coup de grace to the doctrine of Natural Selection, and others consider that his views, if finally proved to be correct, will at least demand a profound modification in the theories associated with the name of Darwin.

It would not, however, be by any means correct to suppose that Mendel's views have been received with complete acceptance by the scientific world; indeed there is a sharp, and at times even embittered, controversy between the supporters of Mendel and his opponents, amongst whom the late Professor Weldon may perhaps be considered to have been one of the most important. The end of the controversy is not yet in sight, nor is it likely to be for some time, judging by the extraordinarily varied results which observers have drawn from even identical series of facts. For instance, from the same materials afforded by the colours of thoroughbred horses given in the pages of Weatherby's "General Sudbook of Horses", a Mendelian (Mr. Hurst) has deduced evidence in favour of the view which he upholds, and an anti-Mendelian (the late Professor Weldon) has arrived at a diametrically opposite conclusion. This, at least, may safely be said: that Mendel's views have been endorsed by a number — it would probably be safe to say a steadily increasing number — of scientific men; that they seem to be likely to exercise a profound influence on agriculture and on the scientific breeding of horses and stock; and that, with such modifications as farther experience may suggest, the main underlying principles of the work will probably become more and more firmly established.

As above stated the papers in which Mendel's theories were made public are contained in the "Proceedings" of the Brünn Society. They have been made available for English readers by the translation which appears in Bateson's work (see bibliography below).