MENDELISM AND BIOMETRY 211 



way a knowledge of the characters shown by the grand- 

 parents adds something to the certainty of the pre- 

 diction as to the proportionate numbers of offspring of 

 the two kinds which are to be expected, when the 

 average of a number of cases is taken according to the 

 usual statistical method. 



Yule therefore regarded the case of the dominant 

 character as showing conformity with the law of 

 ancestral heredity, according to his own statement of 

 that generalization, which was to the following effect : 

 The law that ' the mean character of the offspring can be 

 calculated with the more exactness, the more extensive 

 our knowledge of the corresponding characters of the 

 ancestry, may be termed the law of ancestral heredity.'* 



It may be remarked in passing that Yule's dis- 

 tinction of the problems of genetics into those of 

 intra-racial heredity and those of hybridization cannot 

 now be regarded as holding good, unless the term 

 hybridization is to be extended to many cases e.g., 

 that of the inheritance of coat colour in thoroughbred 

 horses, which would have been classed unhesitatingly 

 as instances of heredity by all biometricians in 1902. 

 Bateson's instinct did not fail him when he divided 

 these problems into those of continuity and those of 

 discontinuity respectively, although at the present time 

 the realm of continuous variation and inheritance is 

 being steadily encroached upon owing to the analysis 

 of complex characters into definite constituents. 



In 1904 Karl Pearson struck a blow at the prospect 

 of conformity between biometrical and Mendelian 



* ' Nevr Phytologist,' vol. i., p. 202. 



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