BIOMETRICS 171 



that, as we draw our geniuses from the great mass of 

 population, and not from a specially selected stock, the 

 average genius we meet is more likely to be an exceptional 

 variation of a mediocre stock than a common variation 

 of an exceptional stock. This accounts for the fact that 

 the sons of geniuses are often so disappointing. 



A great deal of controversy has arisen as to how far 

 the Law of Ancestral Inheritance holds good, its value 

 being altogether denied by the most thoroughgoing Men- 

 delians. There is no doubt that the Law of Ancestral 

 Inheritance, as stated by Galton and Pearson, is not 

 applicable to every kind of inheritance, for it presupposes 

 that each ancestor contributes some quota towards the 

 total heritage of a given characteristic, while in prepotent 

 and Mendelian inheritance certain ancestors may have no 

 share whatever in the production of such character in 

 certain offspring. But, as we said already at the con- 

 clusion of our chapter on Mendelism, it may well be that 

 the'.e are two or more series of phenomena needing explana- 

 tion. While Galton's law would apply to cases of intra- 

 Tftcial heredity (inheritance between members of the same 

 vace), it would not cover the cases of Mendelian hybrids. 

 A reconciliation between these laws may in the near future, 

 perhaps, not be impossible, seeing that G. Udny Yule has 

 expressed the conviction that " Mendel's Law and the Law 

 of Ancestral Heredity are not necessarily contradictory 

 statements, one or the other of which must be mythical 

 in character, but are perfectly consistent one with the 

 other, and may quite well form parts of one homogeneous 

 theory of heredity." 



