178 THE THEORIES OF EVOLUTION 



begets a son who is as richly endowed as himself, and 

 still more if he has a son who is endowed yet more 

 largely." * The hereditary transmission of talent or 

 high qualities is therefore very doubtful, but so is, 

 on the other hand, the transmission of individual 

 blemishes. 



A salient character, whatever it may be, is never 

 transmitted in its entirety but is always attenuated in 

 the following generation. This is the law of "regres- 

 sion" or reversion to the average, which is partly due 

 to the fact that the average represents the most stable 

 equilibrium and partly to the fact that we inherit not 

 only our parents' but our grandparents' and our an- 

 cestors' characters. And thus we arrive at Galton's 

 second great generalisation known as the law of ances- 

 tral inheritance. 



Galton's theory of ancestral inheritance not only 

 postulates the continuity of the germ plasm, but 

 figures mathematically the amount contributed by 

 each generation to the make-up of one given indi- 

 vidual. A near ancestor bequeathes to the individual 

 more elements than a remote ancestor. Galton deter- 

 mines as follows the respective contributions of an 

 individual's ascendents: the parents determine one- 

 half of an inherited character (the father one-quarter 

 and the mother one-quarter) ; the grandparents' share 

 is one-quarter, that is one sixteenth for each, and so 



i Natural Inheritance, p. 106. 



