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Rh eties, is now scarcely open to question. Nevertheless the belief held very widely by systematists, that certain classes of differences are important as being more fixed, and others trivial as being more liable to variation, is scarcely consistent with genetiqal knowledge. The frequency and amplitude of variation and the perfection of segregation must be empirically determined for the various organisms and for the various characters. No general rules can be predicated. Anthropologists, for example, are accustomed to regard special features of anatomy as comparative- ly sure guides to racial origin. Knowing what we now do of seg- regation and recombination we suspect that no characteristic is incapable of segregation and so of transference to another race: given the possibility of cross-breeding, the shape of the skull or other bodily peculiarity may be transferred in its entirety to individuals descending by another parent from a different race, and hence to a resulting population, more slowly but not less completely than a language or a custom.

The classificatory dichotomies in common use in the systematic arrangement of animals and plants have no prerogative signif- icance except for mnemonic or demonstrative purposes; for the number of the dichotomies is merely an enumeration of the pairs of factorial differences, and the order in which they are taken into account, though often treated as a matter of cardinal im- portance, is purely arbitrary. Peas, for instance, are divided first into tall varieties and dwarf varieties, then into round and wrinkled, yellow and green, etc., but it would be logically as sound and physiologically as justifiable to divide them first into yellow and green, then into early and late, and so on. If the races of men could be crossed under experimental conditions we should find the same principles governing their distinctions.

(10) Applications. The applicability of genetic discoveries to the betterment of the human race is discussed in the article EUGENICS, but a few words as to the progress in the art of breed- ing animals and plants made possible by the development of Mendelism may be given here. The use and consequences of crossing in the search for new forms of economic value are now apparent. The reasons for preserving the first generation (Fi) though it may present no valuable feature and the desirability of raising from it as many individuals (F 2 ) as space will ac- commodate, are obvious. The breeder now knows what he is about and is able to interpret countless phenomena previously meaningless. Granting that the chief breeds of animals now in the keeping of civilized man are not capable of much ameliora- tion, experience has shown that enormous improvements can be made by applying accurate knowledge to the breeding of even such old-established crops as' wheat, oats, tobacco, etc. If this is true of the crops which have for ages been the object of un- remitting care, it will be understood that the cultivated plants of tropical regions offer limitless possibilities. The breeding of coconut, rubber, jute, cacao and many more has scarcely begun. These are all still raised from seed gathered almost promiscuously, the result of uncontrolled fertilization, and the produce is what we should see if our orchards were raised from seeds and those seeds gathered at random from garden varieties and from wildings in the hedgerows. At first, selection and fertilization under con- trol will suffice to make great progress. Even at that stage some genetic knowledge will be of value, but when the more difficult task of making genetic recombinations of desirable qualities is begun the breeder will require skill in the management and in- terpretation of the generations and the various terms in the series of forms which only accurate knowledge of principle can supply. Genetic science shows primarily what can be expected, providing the breeder with an aim, and also indicates how it may be attained. For example, a crop of sugar beet often con- tains 4% sometimes many more of plants which " bolt " or flower in the first year making no "bulb," and so worthless. This state of things has long been accepted as inevitable. But when the geneticist finds that the annual habit is a recessive, he suspects that the plants which produce the bolters are hetero- zygous in that respect, and that if he can raise plants homozy- gous in the biennial habit he will have eliminated bolting. The breeder, whether scientific or practical, ignorant of genetics, would never suspect the nature of the fault, still less could he devise a cure. Common sense in the art of seed-raising is an im- perfect guide. Apart from any question of making new races, the purification of existing varieties and their maintenance in a state of purity are exacting tasks. What has been done in these several phases of the industry, in ignorance of principle, is remarkable, but we may confidently foresee that the application of scientific method will in the case of the breeder's art effect a change in magnitude no less than that which has been witnessed in the other industries.

BIBLIOGRAPHY. W. Bateson, Materials for the Study of Variation (1894) ; Problems of Genetics (ed. 2, 1916) ; Presidential Address to Brit. Assn., Australia (1914); W. E. Castle, Genetics and Eugenics (1916); N. Heribert-Nilsson, " Variabilitat, Spaltung, Artbildung und Evolution in der Gattung Salix," Festskr. Lunds Universitet 200 Arsjubileum (1918); W. Johannsen, Elemente der exakten Erblich- keitslehre (ed. 2, 1913); J. P. Lotsy, Evolution by Means of Hybridiza- tion (1916); T. H. Morgan, A Critique of the Theory of Evolution (1916); The Mechanism of Mendelian Heredity (1915); O. Renner, " Versuche iib. d. gametische Konstitution d. Onotheren," Zts. fur indukt. Abstamms. u. Vererbungslehre (xviii., 1917); H. de Vnes, Die Mutationstheorie (1901-3). (W. BN.)

 MENÉNDEZ Y PELAYO, MARCELINO (1856-1912), Spanish scholar and critic (see ), was at the time of his death working at the second edition of his Historia de los heterodoxos espanoles. He died at Santander May 19 1912, and bequeathed his valuable Library of 40,000 volumes to that town.

 MENSDORFF-POUILLY-DIETRICHSTEIN, ALBERT, (1861- ), Austro-Hungarian diplomatist, was born at Lemberg Sept. 5 1861. He was the second son of Alexander von Mensdorff-Pouilly, Prince Dietrichstein von Nicolsburg, and Alexandrine, born Countess Dietrichstein-Proskau and Leslie. Entering the diplomatic service at an early age, he was assigned in 1886 to the Paris embassy and in 1889 transferred to London, where with short intervals he was ambassador from 1904 to Aug. 13 1914. He used his family relations with the English court, derived through the marriage of Count Emmanuel Mensdorff-Pouilly (1777-1862) with Queen Victoria's aunt, Princess Sophia of Saxe-Coburg, his friendship with Edward VII. and George V., and his popularity in English aristocratic circles, to establish and secure friendly relations between the Cabinets of Vienna and London. In the critical negotiations before the outbreak of the World War he supported every attempt to avert the danger. During the war he was repeatedly entrusted with missions directed towards the restoration of peace. He met Gen. Smuts in Switzerland in Dec. 1917, but these negotiations proved as fruitless as those which he conducted with the Entente representatives in the last days of the Habsburg Monarchy. At the end of 1920 he represented the Austrian Republic on the occasion of its reception into the League of Nations.

 MERCIÉ, MARIUS JEAN ANTONIN (1845-1916), French sculptor and painter (see ), died in Paris Sept. 12 1916.

 MERCIER, DÉSIRÉ (1851-), Cardinal Archbishop of Malines, Belgium, was born Nov. 21 1851 at Broine l'Allemt, in the Walloon portion of Brabant, of a bourgeois family. After finishing his course at the college of St. Rombaut at Malines, he entered the larger seminary of that town, and on April 5 1874 was ordained priest. He continued his theological studies at Louvain, and in 1877 was appointed professor of philosophy at the lesser seminary of Malines. In 1882 he was appointed to the recently created chair of Thomist philosophy at Louvain, and during the ensuing years was active in the scheme for founding the Institut Supérieur de Philosophie at Louvain, which was finally opened in 1894.

In Feb. 1906 Monsignor Mercier was appointed Archbishop of Malines in succession to Archbishop Goossens, and in 1907 he was created a cardinal. Soon after the outbreak of war in 1914 he was summoned to Rome to attend the funeral of Pope Pius X. and the election of his successor, and it was therefore not until his return to Belgium that he became fully aware of the incidents