BLASTOGENIC VARIATIONS. 129 



theory of heredity is rendered simple, straightforward, 

 and luminous. Pearson points out that we no longer 

 need to know the characters of parents, grandparents, 

 etc., to test the law, for any single relationship, near or 

 far, direct or collateral, will bring its cjuota of evidence 

 for or against it. 



Galton's principle of " Regression towards Medi- 

 ocrity ' has been spoken of occasionally as if it were 

 something abnormal and unexpected; something, in- 

 deed, unexplained and inexplicable. It is clearly noth- 

 ing of the kind, however, but only what might readily 

 be deduced from his law of Ancestral Heredity, sup- 

 posing that this and this alone were known to us. 

 Thus we have seen that offspring derive certain por- 

 tions of their heritage from their grandparents and 

 more remote ancestors, and as these are likely to be, on 

 an average, more mediocre than their parents, they 

 water down the parental characters transmitted to the 

 offspring. Supposing all the grandparents and more 

 remote ancestors of any given parents were absolutely 

 mediocre, then, as the offspring receive only half their 

 heritage from these parents, they would exhibit their 

 characters in only half strength, or the coefficient of 

 regression would be .5, and not .6. The reason why 

 the regression reaches, on an average, the higher figure, 

 is of course that the grandparents and other ancestors 

 are not, as a rule, absolutely mediocre. They possess 

 the characters exhibited by the parents, though in a 

 diminished degree. Grandparents regress on parents 

 to just the same extent as offspring do. 



It may perhaps be enquired how it is that, if off- 

 spring are on an average more mediocre than their 



