Principles of Heredity 111 



ment which brings into a single focus all the complex 

 lines of hereditary influence. If Darwinian evolution be 

 natural selection combined with heredity, then the single 

 statement which embraces the whole field of heredity must 

 prove almost as epoch-making as the law ^of gravitation 

 to the astronomer*." 



As I read there comes into my mind that other fine 

 passage where Professor Pearson warns us 



"There is an insatiable desire in the human breast 

 "to resume in some short formula, some brief 

 "statement, the facts of human experience. It leads 

 " the savage to ' account ' for all natural phenomena 

 "by deifying the wind and the stream and the tree. 

 " It leads civilized man, on the other hand, to express 

 "his emotional experience in works of art, and his 

 "physical and mental experience in the formulae or 

 "so-called laws of science f." 



No naturalist who had read Galton's paper and had 

 tried to apply it to the facts he knew could fail to see 

 that here was a definite advance. We could all perceive 

 phenomena that were in accord with it and there was no 

 reasonable doubt that closer study would prove that accord 

 to be close. It was indeed an occasion for enthusiasm, 

 though no one acquainted with the facts of experimental 

 breeding could consider the suggestion of universal applica- 

 tion for an instant. 



* I have searched Professor Pearson's paper in vain for any con- 

 siderable reservation regarding or modification of this general state- 

 ment. Professor Pearson enuntiates the law as " only correct on 

 certain limiting hypotheses," but he declares that of these the most 

 important is " the absence of reproductive selection, i.e. the negligible 

 correlation of fertility with the inherited character, and the absence 

 of sexual selection." The case of in-and-in breeding is also reserved. 



f K. Pearson, Grammar of Science, 2nd ed. 1900, p. 36. 



