[21] For a review of the statistical problems involved, see Karl Pearson. An attempt to correct some of the misstatements made by Sir Victor Horsley, F. R. S., F. R. C. S., and Mary D. Sturge, M. D., in their criticisms of the Galton Laboratory Memoir: First Study of the Influence of Parental Alcoholism, etc.; and Professor Pearson's various popular lectures, also A Second Study of the Influence of Parental Alcoholism on the Physique and Intelligence of Offspring. By Karl Pearson and Ethel M. Elderton. Eugenics Laboratory Memoir Series XIII.
[22] A First Study of the Influence of Parental Alcoholism on the Physique and Intelligence of Offspring. By Ethel M. Elderton and Karl Pearson. Eugenics Laboratory Memoir Series X. Harald Westergaard, who reëxamined the Elderton-Pearson data, concludes that considerable importance is to be attached to the selective action of alcohol, the weaklings in the alcoholic families having been weeded out early in life.
[23] Prohibition would have some indirect eugenic effects, which will be discussed in Chapter XVIII.
[24] Chapter XXX, verses 31-43. A knowledge of the pedigree of Laban's cattle would undoubtedly explain where the stripes came from. It is interesting to note how this idea persists: a correspondent has recently sent an account of seven striped lambs born after their mothers had seen a striped skunk. The actual explanation is doubtless that suggested by Heller in the Journal of Heredity, VI, 480 (October, 1915), that a stripe is part of the ancestral coat pattern of the sheep, and appears from time to time because of reversion.
[25] Such a skin affection, known as icthyosis, xerosis or xeroderma, is usually due to heredity. Davenport says it "is especially apt to be found in families in which consanguineous marriages occur and this fact, together with the pedigrees [which he studied], suggests that it is due to the absence of some factor that controls the process of cornification of the skin. On this hypothesis a normal person who belongs to an affected family may marry into a normal family with impunity, but cousin marriages are to be avoided." See Davenport, C. B., Heredity in Relation to Eugenics, p. 134. New York, 1911.
[26] Its eugenics is to be effected through the mental exertion of mothers. And we have lately been in correspondence with a western attorney who is endeavoring to form an association of persons who will agree to be the parents of "willed" children. By this means, he has calculated (and sends a chart to prove it) that it will require only four generations to produce the Superman.
[27] Life and Letters of Charles Darwin, Vol. I, p. 302, New York, 1897. The letter is dated 1844.
[28] Goddard, H. H., Feeble-mindedness, p. 359. New York, the Macmillan Company, 1914.
[29] For a review of the evidence consult an article on "Telegony" by Dr. Etienne Rabaud in the Journal of Heredity, Vol. V, No. 9, pp. 389-400; September, 1914.
[30] It will be recalled that the coefficient of correlation measures the resemblance between two variables on a scale between 0 and-1 or +1. If the correlation is zero, there is no constant relation; if it is unity, any change in one must result in a determinate change in the other; if it is 0.5, it means that when one of the variables deviates from the mean of its class by a given amount, the other variable will deviate from the mean of its class by 50% of that amount (each deviation being measured in terms of the variability of its own class, in order that they may be properly comparable.)