MENDELISM AND BIOMETRY 213 



results, and being convinced that these facts must 

 have a very wide application, were thereupon driven 

 reluctantly to the conclusion that something was 

 seriously wrong with the methods adopted by biome- 

 tricians for determining the coefficients of correlation. 

 It seems, however, that this conclusion may have been 

 arrived at with undue haste. 



In August of the present year (1906) Mr. Yule read 

 a very interesting paper before the International 

 Congress of Hybridization assembled in London on 

 4 The Theory of Inheritance of Quantitative Compound 

 Characters on the basis of Mendel's Laws.' Though 

 some difficulty was then experienced in following 

 his argument by an audience unaccustomed to 

 statistical methods, Yule's conclusion is really very 

 simple. 



Yule points out that the only character dealt with 

 in Pearson's memoir is the number of protogenic or 

 allogenic couplets present in the individual, and it is the 

 proportionate number of these couplets present in the 

 parent and in the offspring respectively which is taken 

 as determining the value of the correlation coefficient. 

 Consequently Pearson's treatment of the subject does 

 not justify his statement that the Mendelian theory 

 gives a rigid value for the coefficients of parental cor- 

 relation for all races and characters a conclusion 

 which he regards as fatal to this theory, because the 

 coefficients for different characters and races, as found 

 statistically, show considerable individual differences, 

 and seem to cluster round a value considerably higher 

 than that indicated by his elaboration of the theory of 



