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Prof. Karl Pearson. 



common. Thus, Mr. Galton writes in his * Natural Inheritance '(p. 139) : 

 " Parents of different statures usually transmit a blended heritage to 

 their children, but parents of different eye-colours usually transmit an 

 alternative heritage if one parent has a light eye- 

 colour and the other a dark eye-colour, some of the children will, as a 

 rule, be light and the rest dark ; they will seldom be medium eye- 

 coloured like the children of medium eye-coloured parents." 



Again, in his paper on "Basset Hounds,""^ Mr. Galton classifies these 

 hounds as tricolour (T) and non-tricolour (N), remarking, " I am assured 

 that transitional cases between T and N are very rare, and that experts 

 would hardly ever disagree about the class to which any particular 

 hound should be assigned." In other words, Mr. Galtoa appears to 

 assume exclusive inheritance.! Eoughly, in such exclusive inherit- 

 ance, the offspring takes after one or other parent, or reverts to more 

 distant ancestry. It becomes accordingly somewhat difficult to see 

 how the law of ancestral heredity, which applies to blended inherit- 

 ance, can be transferred to this different field. Yet Mr. Galton in his 

 'Natural Inheritance' (p. 153) writes: "The broad conclusion to 

 which the present results irresistibly lead, is that the same peculiar 

 hereditary relation that was shown to subsist between a man and each 

 of his ancestors in respect to the quality of stature, also subsists in 

 respect to that of eye-colour." Further, in the paper on Basset 

 Hounds, he actually endeavours to demonstrate the truth of the law 

 on the exclusive colour of these hounds. Now I think we must keep 

 these two matters quite apart. The average stature of an individual 

 is a blend of all his progenitors' characters ; even in a single individual 

 we find contributions from many ancestors ; this is not the case 

 with an exclusive inheritance, and it does not accordingly seem to me 

 possible that " the same peculiar hereditary relation that was shown 

 to subsist between a man and each of his ancestors " for a blended 

 character can also hold for an exclusive character. 



It is no longer of the proportions of a character in one individual 

 that we speak, but of the frequency of various types of individuals 

 among the total offspring of a given ancestry. The one statement is a 

 law of blending characters, and the other is a law of distributing the 

 exclusive characters among a group of individuals. In the first case 

 we deal with regression, in the second with reversion. What Mr. 

 Galton really asserts is, that the proportions of reversion in an array 

 of offspring are identical with the proportions of blend in the average 



* * Eoy. Soc. Proc.,' vol. 61, p. 403. 



f A remark in the 'Natural Inlieritance ' (p. 139) that "Stature is due to its 

 being the aggregate of the quasi-independent inheritances of many separate parts, 

 •while eye-colour app'^ars to be much less various in its origin," -would seem to 

 indicate that Mr. Galton considers that blended inheritance is ultimately based 

 upon exclusive inheritance of parts— a suggestion well worth investigation. 



