-866 



SCIENCE. 



[N. S. Vol. XII. No. 310. 



y = 



Xy/- 



-- A-"'"^- 



At about this time also, the anthropol- 

 ogist Stieda called attention in Germany 

 to the application of the probability methods 

 to anthropological statistics. His paper 

 published in the Archiv fur Anthropologie, 

 Band XIV., entitled ' Ceber die An wen- 

 dung der Wahrscheinlichkeitsrechnung in 

 der anthropologischen Statistik,' 1883, has 

 ' had great influence in extending the use of 

 the method. In this work the measure of 

 variability is the probable error, here called 

 the ' Oscillations Index. ' 



Daring the eighties, Galton, in a remark- 

 able series of papers, developed the quanti- 

 tative theory of individual variation. In 

 1885 he introduced a graphic method of 

 determining the probable error, using his 

 ' ogive ' or normal curve of distribution of 

 error. In connection with his studies on 

 pedigree peas he developed the theory of 

 the mid-parent, the law of regression of the 

 progeny of extraordinary parents toward 

 mediocrity, and the law of ancestral inher- 

 itance, according to which the mid-parent 

 contributes one-half, the mid-grand-parent 

 one- fourth, the mid-great-grand-parent one- 

 eighth, and so on, of the whole heritage. 

 In 1888, Galton made another important 

 step. He obtained a method — somewhat 

 rough, to be sure, because chiefly graphic — 

 for measuring correlation between two or- 

 gans. The measures of one organ, called 

 subject, were taken, the mean found and the 

 measures grouped into classes expressed in 

 terms of the deviation from the mean divided 

 by the probable error of the subject. The 

 average of the corresponding measures of 

 the other organ, called relative, was found, 

 and the deviation of the average from the 

 mean size of the organ was expressed in 

 units of the probable error of the relative. 

 The average (found graphically) of the 

 ratios of the deviation of the relative divided 



by the deviation of the corresponding sub- 

 ject class gives the correlation-index sought. 



The culmination of this epoch-making 

 work of Galton was his ' Natural Inheri- 

 tance,' 1889, which applied the quantitative 

 methods he had elaborated to the data of 

 human inheritance which he had himself 

 gathered. The book is important, not so 

 much for its new material, for much of the 

 matter had appeared elsewhere, but because 

 it called attention to the possibilities of the 

 quantitative method applied to biology gen- 

 erally. But probably of even greater effect 

 were Galton's personal suggestions to biolo- 

 gists such as Weldon and to mathemati- 

 cians such as Pearson. At any rate, the 

 beginning of the new decade saw the begin- 

 ning of a wider interest in the quantitative 

 study of variation ; and the source of this 

 wider interest can be traced directly to one 

 man — Francis Galton. 



While the impetus to the modern quanti- 

 tative variation studies came from Galton, 

 quantitative studies, in zoology at least, 

 were not unknown before 1890. In our 

 own country, Baird, Cones and J. A. Allen 

 had measured numerous individuals of each 

 of many species of mammals and birds 

 and had published tables of measurements. 

 Allen, in particular, had grasped the im- 

 portance of the quantitative study of varia- 

 tion, had compared the average dimensions 

 of mammals and birds from different parts 

 of the country and had established* a law 

 of relation between the size of individuals 

 and their distribution which has proved 

 very fertile. 



As long ago as 1829, H. Milne-Edwards f 

 gave a table of variations in size of various 

 parts of the body of fourteen individuals of 



* J. A. Allen, ' On the Mammals and Winter Birds 

 of East Florida,' etc.. Bull. Museum Comparative 

 Zoology at Harvard College, 1871 , and ' Geographical 

 Variation among North American Mammals,' Bull. 

 U. S. Geol. and Geog. Survey, Vol. 11., 1876. 



f Annates des sciences naturellea (1), 16, p. 87. 



