EVOLUTION 503 



field of evolution by natural selection, combined with sexual selection and 

 heredity, seem especially to centre round differentiation of maximum fertility 

 and the actual rate of selection with change of environment. But even here 

 the quantitative method suggests how in the near future we can hope for 

 definite solutions. It is not a question of whether Darwinism is or is not an 

 hypothesis describing progressive change in living forms — practically all its 

 factors have been now shown to have quantitative reality. It is a question of 

 the rate of effective change, and when the biologists are in a position to make a 

 definite draft on the bank of time, their credit will be just as substantial as 

 that of the so-called exact sciences. 



LITERATURE 



Besides the works of Charles Darwin, cited at the end of the previous 

 chapter, I may specially mention : — 



Galton, Francis. — Hereditary Genius, London, 1869. English Men of 

 Science, London, 1S74. Inquiries into Human Faculty, 1883. Natural 

 Inheritance, London, 1889. The Average Contribution of Each Several 

 Ancestor to the Total Heritage of the Offspring. Roy. Soc. Proc. vol. 

 Ixi. p. 401, 1897. 

 Most of the remaining statements of this chapter are extracted from memoirs 

 of the author and his collaborators. See especially : — 



Pearson, Karl. — Mathematical Contributions to the Theory of Evolution — 

 HI. Regression, Heredity, and Panmixia. Phil. Trans, vol. clxxxvii. pp. 



253-318, 1896. 

 VI. Genetic (Reproductive) Selection. Inheritance of Fertility in Man 

 and of Fecundity in Thoroughbred Race-horses (with A. Lee and 

 L. Bramley-Moore). Phil. Trans, vol. cxcii. pp. 257-330, 1899. 

 VII. On the Inheritance of Characters not Quantitatively Measurable. 

 The Inheritance of Eye-Colour in Man and Coat-Colour in 

 Thoroughbred Race-horses. Phil. Trans. 1900. 

 On Telegony in Man (with A. Lee). Roy. Soc. Proc. vol. Ix. pp. 273- 



283, 1899. 

 On the Law of Ancestral Heredity. Roy. Soc. Proc. vol. Ixii. pp. 386- 



412, 1898. 

 A First Study of the Inheritance of Longevity and the Selective Death-rate 

 in Man (with M. Beeton). Roy. Soc. Proc. vol. Ixiv. pp. 290- 

 305, 1899. 

 The Chances of Death and other Studies in Evolution, London, 1897. 

 Particularly the essay on Reproductive Selection. 



