LAW OF ANCESTRAL HEREDITY 113 



every ancestor of a particular individual contributes 

 its quota to the heritable qualities displayed by that 

 individual. The law also states that the average 

 amount of resemblance between an individual and any 

 particular ancestor is capable of definite numerical 

 expression. Thus the mean amount of correlation 

 between (i) the two parents and the offspring, (2) the 

 four grandparents and the offspring, (3) the eight 

 great-grandparents and the offspring, and so on, is 

 believed to diminish in a geometrical series, which is 

 the same for all organisms and for all characters. The 

 actual amounts of these correlations were expressed by 

 Galton in the form of the series 0*50, 0*25, 0*125, etc - 

 Pearson regards them as being more nearly represented 

 by the more rapidly diminishing series 0-6244, 0*1988, 

 0-0630, etc. 



Now, there can be no doubt that the law as stated 

 above has been disproved in specific instances, and was 

 indeed disproved by the work of Gregor Mendel before 

 ever it was enunciated, although Mendel's work was 

 not generally known until later. According to Mendel's 

 theory of inheritance, certain ancestors contribute 

 nothing to the constitution of cerfain offspring in respect 

 of certain characters. Furthermore, the modification of 

 the law of ancestral heredity which applied to alterna- 

 tive inheritance, and which was assumed in working 

 out the inheritance of coat colour in thoroughbred 

 horses, has since been shown not to apply to that 

 particular case. 



Unfortunately, most of the further biometrical 

 generalizations which concern students of heredity 



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