Page:EB1922 - Volume 32.djvu/440

422 were for some time slightly below 1,040, which, though about the same as the proportion in Japan, is somewhat low in comparison with Germany, several European countries, and the white popula- tion of the United States, in which the males are about 1,060. On the other hand for the coloured population of the United States the male births aie still less in proportion (in the year 1890, 1,024) and occasionally fall actually below the female number (998 in 1900). In all countries for which data can be obtained the proportion of males among still-births is very largely in excess of the females. Such divergences usually point to differ- ential mortality or to the action of lethal factors, but in view of the large excess of males among still-births this account is not readily applicable here. The excess of males (surviving infancy) is exceptionally large in certain, though not all, of the families affected with the tendency to bleed profusely from trifling in- juries, known as haemophilia. This is one of the sex-linked ab- normalities appearing in males which follow much the same system of descent as colour-blindness. Illegitimate births in most countries show a distinct diminution in the excess of males.

Since the publication of Diising, the proposition which he (following earlier writers) developed, that war produces an in- crease in the proportion of male births, has been widely dissemi- nated. S. Newcomb investigated data as to births in the United States during the Civil War but found no positive result, and other parts of the evidence have been declared to be fallacious. Nevertheless, statistics for Great Britain and also those for Germany during the World War show a progressive rise which can scarcely be deemed insignificant. It should be remarked, however, that this rise had begun in Prussia some years before the war. On the other hand, no similar change has taken place in the neutral countries. For an adequate consideration of the facts many concomitant phenomena must be taken into account; for example, the fact that the total birth-rate of Prussia fell in the war period to less than half. Whatever be the immediate cause of the rise in male births, it is likely that it should be referred to the incidence of a differential pre-natal mortality rather than to any more fundamental genetic process.

Sex in Plants. The attempt to make a factorial analysis of sex in the higher plants has not led to clear conclusions. Dioe- cious plants suitable for experiment are few. Correns, from results obtained in reciprocal crosses made between Bryonia dioica and the monoecious B. alba, inferred that the male of dioica was heterogametic, but the argument did not amount to proof. Shull's experiments with Lychnis dioica and a variation having the elements of both sexes present together were also beset with many complications and obscurities. In dioecious mosses the Marchals proved that segregation, in respect of sex, normally occurs at spore-formation, but both their experiments and those of Collins gave indications of further complexities. Sphaerocar- pos, a liverwort, produces spores in tetrads, and of the four, two became males and two females. C. E. Allen states that the female spores each receive an accessory chromosome larger than that which passes to the male spores. Blakeslee showed that Mucors consist of several strains which may be called + and, and that conjugation only takes place when a + culture comes into contact with a culture. These strains may with great probability be regarded as two sexes, but the results were complicated by the discovery of other strains which are indifferent. We meet here the same difficulty noted in the case of animals, that the factorial relations between hermaphrodite plants and the dioecious forms have not yet been successfully represented. Varieties having the stamens to a greater or less degree aborted are not uncom- mon among the species of flowering plants which are normally hermaphrodite. If the deficiency is extreme, the variety is not merely in function female, but it is in a condition morphologically not distinguishable from the females of plants dioecious in the strict sense such as Lychnis dioica or tiespertina. When such female varieties are fertilized with pollen from the hermaphrodite type the resulting family may be a mixture of hermaphrodites and females, but not rarely females only are produced. As the hermaphrodite is a dominant this evidence demonstrates that the hermaphrodite factor must thus be relegated to the female side,

the male side taking the recessive in which the anthers are aborted. Such " unilateral " distribution of the factors may exist in regard to colour, double flowers and probably many other factorial distinctions, and the conception of sex-linkage is in a special and limited sense applicable to them (C. Pellew). Other- wise nothing comparable with the sex-linkage of animals has yet been discovered in plants. It must always be remembered that, on account of the complications created by the existence of a syncopated alternation of generations in the higher plants, no direct parallel between sex, as manifested in them, and that of animals can be instituted.

BIBLIOGRAPHY. Text-books: W. Bateson, Mendel's Principles of Heredity (3rd. ed.. 1913); L. Doncaster. The Determination of Sex (1914); R. Goldschmidt, Mechanismus und Physiologic der Geschlechtsbestimmung (1920); T. H. Morgan, Heredity and Sex (2nd. ed., 1914). References to most of the authorities named are given in these works. Special references: C. E. Allen, " The basis of Sex inheritance in Sphaerocarpos," Proc. Amer. Phil. Sac., 58 (1919) ; VV. Bateson and R. C. Punnett, " The Inheritance of the peculiar Pigmentation of the Silky Fowl," Jour. Genetics, I (1911) ; W. Bate- son, "Genetic Segregation," Proc. Roy. Soc., B, 91 (1920); F. Baltzer, " Die Bestimmung des Geschfechts nebst einer Analyse des Geschlechtsdimorphismus bei Bpnellis," Mitt. Zool. Stat. Neapel, 22 (1914); C. B. Bridges, " Non-disjunction as proof of the Chro- mosome Theory of Heredity," Genetics, I (1916), see also his ar- ticle " Triploids in Drosophila," Science, Sept. 29 1921 ; E. J. Collins, "Sex-segregation in the Bryophyta," Jour. Genetics, vih. (1919); C. Correns " Die geschlechtliche Tendenz d. Keimzellen gemischt- geschlechtiger Pflanzen," Zts. f. Bot., xii. ; F. A. E. Crew, "Sex- reversal in Frogs and Toads," Jour. Gen., xi. (1921) ; J. A. Detlefsen, " Genetic Studies on a Cavy Species Cross," Carnegie Institution Publication No. 205 (1914); L. Doncaster and G. H. Raynor, " Breeding Experiments with Lepidoptera," Proc. Zool. Soc. (l, 1906); R. Goldschmidt, " Untersuchungen iiberdie Intersexualitiit," Zts. f. ind. Abst. u. Vererbungslehre, 23 (1920); F. R. Lillie, "The Free-martin, a study of the action of Sex hormones in the foetal life of Cattle," Jour. Exp. Zool. (1917); T. H. Morgan and C. B. Bridges, " Sex-linked Inheritance in Drosophila," Carnegie Institu- tion Publication No. 237; T. H. Morgan, C. B. Bridges and A. H. Sturtevant, " Contributions to the Genetics of Drosophila Melano- gaster," ibid. No. 278 (1919); T. H. Morgan, "The Genetic and operative evidence relating to Secondary Sexual characters," ibid., No. 285 (1919) ; H. H. Nevyman and J. T. Patterson, " Development of the nine-banded Armadillo," Jour. Morph., 21 ; J. Th. Oudemans, " Falter aus castrirten Raupen," Zool. Jahresb., xii. (see also J. Meisenheimer, Verh. Deut. Zool. Soc., xviii.) ; J. T. Patterson, " Studies on the Biology of Paracopidospmopsis," Biol. Bull., 32-35 (1917-8) ; C. Pellew, " Types of Segregation," Jour. Gen., yi. (1917) ; J. Seller, " Das Verhalten d. Geschlechtschromosomen bei Lepidop- teren," Arch. z. Zellfprschung, xiii. (1914); and Zts. f. ind. Abst. u. Vererbungslehre, xviii. (1917). For evidence as to human statistics: H. Lucht, " Das Geschlechtsverhaltniss d. Gebprenen in Preussen wahrend des Krieges," Zts. d. Preuss. Statistischen Landesamts, Jahrg. 60 (1920) ; B. Mallet, " Pres. Address," Jour. Roy. Stat. Soc., 81 (1918); J. B. Nichols, Mem. Amer. Anthrop. Assn., i. (1907); A. A. Tschuprow, " Zur Frage d. sinkenden Knabeniiberschiisses unter d. ehelich Geborenen," Bull, de L'Insl. internal, de Statistique, xx. (1915). (W. BN.) SGAMBATI, GIOVANNI (1843-1914), Italian composer (see 24.757), died at Rome Dec. 15 1914. SHACKLETON, SIR ERNEST HENRY (1874-1922), British polar explorer, was born at Kilkee Feb. 15 1874. He was educated at Dulwich College, and afterwards entered the merchant service, subsequently becoming a lieutenant in the R.N.R. In 1901 he joined the Antarctic expedition of Capt. Scott in the "Discovery," but had to return home on account of ill health. In 1908 he organized his first Antarctic expedition, largely fitted out by himself, which started from New Zealand in the " Nimrod," and achieved important results, reaching a point on the Antarctic continent about 97 m. from the South Pole (see 21.968). For this he was knighted in 1909, also receiving the C.V.O., while the Government contributed 20,000 towards the expenses of the expedition. He equipped a second expedition which left England in the " Endurance," Aug. 1 1914, with the idea of approaching the Antarctic continent from Weddell Sea and ultimately joining hands with another party whose ship, the "Aurora," was to start from Australia and approach by way of Ross Sea. Owing largely to bad ice conditions, the expedition was almost uniformly unfortunate (see ANTARCTIC REGIONS). The story of this expedition was related by Sir Ernest Shackleton in South (1919). He received the King's