Correlation and Application of Statistics to Problems of Heredity 65 



the population. This is not generally correct; Gal ton is confusing the regres- 

 sion coefficient with the correlation coefficient. As long as both relatives have 

 equal variability, which we may suppose to be the case with father and son 

 or uncle and nephew, the two coefficients are numerically equal ; but when 

 the two variates have not equal variability, this formula is of course incorrect. 

 In the first entry in the table we have the regre ssion of sons on midparent 

 given as §, and Galton calculates from pj\—uf the probable deviation of 

 the array of sons to be 1 '27. The variability of midparents is, however, not 

 equal to that of sons, but is in the ratio of 1 to v2; accordingly r = w/s/2 

 must be used here instead of w, and the probable deviation of the array of 

 sons is 1"50 and not 1*27. 



Further the equality of the regressions of sons on midparents and of 

 brothers on brothers is made by Galton to be f in both cases. I think this 

 value is too low in the case of midparents and too high in the case of brothers, 

 the regressions being much more nearly in the ratio of 1*0 to 0"5 than in a 

 ratio of equality. Other regressions entered in this table are very doubtful. 

 We have to look upon the numerical values given as suggestions of the 

 relative degrees of resemblance of various kinsmen, rather than conclusive 

 values founded on observation of adequate numbers (see our pp. 23-4). 

 The main result of Galton's work was to indicate the mechanism by which 

 a population could remain stable notwithstanding variation and inheritance. 

 It was a great direct achievement, and in the indirect light it cast on the 

 general idea of correlation of still greater importance. 



Chapter VIII contains the Discussion of the Data of Eye- Colour. This 

 corresponds to the Royal Society paper, which I have already analysed on 

 pp. 34-40 above. The same criticisms must be considered as still valid, and 

 need not be repeated here. 



Chapter IX deals with The Artistic Faculty. I do not think the contents 

 of this chapter had been previously discussed by Galton. The data were 

 deduced from the answers in Records of Family Faculties to the questions : 

 " Favourite Pursuits and Interests ? " and " Artistic Aptitudes ? " 



The object of this chapter is not to give a reply to the simple 

 question, whether or no the Artistic Faculty tends to be inherited. A man 

 must be very crotchety or very ignorant, who nowadays seriously doubts 

 the inheritance either of this or of any other faculty*. The question is 

 whether or no its inheritance follows a similar law to that which has been 

 shown to govern Stature and Eye-Colour, and which has been worked out 

 with some completeness in the foregoing chapters (p. 155). The conclusions 



* It may be interesting with regard to these words to cite a few sentences from an obituary 

 notice of Francis Galton which appeared in Nature, February 2, 1911 (Vol. lxxxv, p. 441). 

 The writer says : 



"Only once do I remember on a public occasion a slight severity in his usually gentle tone. A medical man 

 of distinction [Dr Charles Mercier], speaking obviously without any knowledge of the literature of the subject, 

 had asserted that the supposition that the children of parents with certain mental and moral peculiarities would 

 reproduce these features, arose from a totally false conception of what the laws of heredity are. The mental and 

 moral aptitudes were for the speaker outside the purview of hereditary investigation. Galton's reply was very 

 simple : Much of what his critic had said 'might have been appropriately urged forty years ago, before accurate 

 measurement of the statistical effects of heredity had been commenced, but it was quite obsolete now.' " 



P G III 9 



