[48] "On the Inheritance of Some Characters in Wheat," A. and G. Howard, _Mem. Dep. of Agr. India_, V: 1-46, 1912. This careful and important work has never received the recognition it deserves, apparently because few geneticists have seen it. While the multiple factors in wheat seem to be different, those reported by East and Shull appear to be merely duplicates. [49] "The Nature of Mendelian Units." By G. N. Collins, _Journal of Heredity_, V: 425 ff., Oct., 1914. [50] Dr. Castle, reviewing Dr. Goddard's work (_Journal of Abnormal Psychology_, Aug.-Sept., 1915) concludes that feeble-mindedness is to be explained as a case of multiple allelomorphs. The evidence is inadequate to prove this, and proof would be, in fact, almost impossible, because of the difficulty of determining just what the segregation ratios are. [51] In strict accuracy, the law of ancestral inheritance must be described as giving means of determining the probable deviation of any individual from the mean of his own generation, when the deviations of some or all of his ancestry from the types of their respective generations are known. It presupposes (1) no assortative mating, (2) no inbreeding and (3) no selection. Galton's own formula, which supposed that the parents contributed 1/2, the grandparents 1/4, the great-grandparents 1/8, the next generation 1/16, and so on, is of value now only historically, or to illustrate to a layman the fact that he inherits from his whole ancestry, not from his parents alone. [52] Johnson, Roswell H., "The Malthusian Principle and Natural Selection," _American Naturalist_, XLVI (1912), pp. 372-376. [53] Karl Pearson, _The Groundwork of Eugenics_, p. 25, London, 1912. [54] "Let _p_ be the chance of death from a random, not a constitutional source, then 1-_p_ is the chance of a selective death in a parent and 1-_p_ again of a selective death in the case of an offspring, then (1-_p_)^2 must equal about 1/3, = .36, more exactly 'therefore' 1-_p_ = .6 and _p_ = .40. In other words, 60% of the deaths _are selective_." [55] _Archiv f. Rassen-u. Gesellschafts Biologie_, VI (1909), pp. 33-43. [56] Snow, E. C., _On the Intensity of Natural Selection in Man_, London, 1911. [57] _Biometrika_, Vol. X, pp. 488-506, London, May, 1915. [58] Pearson, Karl, _Tuberculosis, Heredity and Environment_, London, 1912. Among the most careful contributions to the problem of tuberculosis are those of Charles Goring (_On the Inheritance of the Diathesis of Phthisis and Insanity_, London, 1910), Ernest G. Pope (_A Second Study of the Statistics of Pulmonary Tuberculosis_, London, Dulau & Co.), and W. P. Elderton and S. J. Perry (_A Third Study of the Statistics of Pulmonary Tuberculosis. The Mortality of the Tuberculous and Sanatorium Treatment_), London, 1909. See also our discussion in Chapter I.