26 THE TREND OF THE RACE 



tion of circumstances. He might ascribe much importance to 

 each of these events, and think how largely the destiny of the 

 stick had been governed by a series of trifling accidents. Never- 

 theless all the sticks succeed in passing down the current, and in 

 the long-run, they travel at nearly the same rate. So it is with 

 life, in respect to the several accidents which seem to have had a 

 great effect upon our careers. The one element, that varies in 

 different individuals, but is constant in each of them, is the natu- 

 ral tendency; it corresponds to the current in the stream, and 

 inevitably asserts itself." 



REFERENCES 



The reader who wishes to inform himself on the present status of the science of 

 genetics will find a number of good recent books among which may be mentioned 

 Castle's Genclics and Eugenics; Babcock and Clausen's Genetics in Relation to 

 Agriculture; Bateson's, MendeVs Principles of Heredity; Plate's Vererbungslehre; 

 Goldschmidt's EinfUhrung in die Vererbungswissenschaft; Morgan's Physical Basis 

 of Heredity; Morgan's et al. Mechanism of Mendelian Heredity; Walter's Genetics 

 and Punnett's Mendelism. Thomson's Heredity, although not brought up to 

 date is still a useful general treatise. Of more special connection with the preced- 

 ing chapter are the following: 



Harrington, A., and Pearson, K. A First Study of the Inheritance of Vision and of 

 the Relative Influence of Heredity and Environment on Sight. Eugen. Lab. 

 Mems., 5, 1909. 

 Conklin, E. G. Heredity and Environment in the Development of Men. Prince- 

 ton Univ. Press, 3d ed., 1919. 

 Darwin, L. Heredity and Environment. Eugen. Rev. 5, 153-154, 1913. See also 



1. c. 8, 93-122, 1916. 

 Davenport, C. B. Heredity in Relation to Eugenics. Holt and Co., N. Y., 1911. 

 Elderton, E. M. The Relative Strength of Nurture and Nature. Eugen. Lab. 



Lect. Series, 3, 1909. 

 Galton, F. Natural Inheritance. Macmillan Co., London and N. Y., 1889. In- 

 quiries into Human Faculty. Macmillan Co., London, 1883, and subsequently 

 in Everyman's Library. 

 Pearl, R. Modes of Research in Genetics. Macmillan Co., N. Y., 1915. 

 Pearson, K. The Grammar of Science, 2d ed. A. and C. Black, London, 1900; 

 Nature and Nurture. The Problem of the Future. Eugen. Lab. Lect. Series, 

 6, 1910. 

 Popenoe, P. Nature or Nurture? Jour. Hered., 6, 227-240, 1915. 

 Weismann, A. Essays on Heredity, 2 vols., Clarendon Press, Oxford, 1891, 1892. 

 The Germ Plasm, W. Scott, London, 1893. The Evolution Theory, 2 vols., 

 Arnold, London, 1904. 



