GEXEOLOGICAL. 409 



like behind him, for we all know that this is not the 

 case. It is due to a regression which tends to bring 

 the offspring of extraordinary parents nearer the 

 average of the stock. In other words, children tend 

 to differ less from mediocrity than their par- 

 ents. 



This big average fact is to be accounted for in terms 

 of that genetic continuity which makes an inherit- 

 ance not dual, but multiple. " A man," says ]Mr. 

 Pearson, " is not only the product of his father, but 

 of all his past ancestry, and unless very careful se- 

 lection has taken place, the mean of that ancestry is 

 probably not far from that of the general population. 

 In the tenth generation a man has (theoretically) 

 102-i tenth great-grandparents. He is eventually 

 the product of a population of this size, and their 

 mean can hardly differ from that of the general 

 population. It is the heavy weight of this mediocre 

 ancestry which causes the son of an exceptional 

 father to regress towards the general population 

 mean ; it is the balance of this sturdy commonplace- 

 ness which enables the son of a degenerate father to 

 escape the whole burden of the parental ill." 



At this point one should discuss reversion or ata- 

 vism, but it is exceedingly difficult to get a firm basis 

 of fact. The term reversion is here used to include 

 cases where through inheritance there reappears in 

 an individual some character which was not ex- 

 pressed in his parents, but which did occur in an 

 ancestor. It includes abnormal as well as normal 

 characters, and even the reappearance of characters, 

 the normal occurrence of which is outside of the 

 limits of the race altogether, i.e., in some phyleti- 

 cally older race. In other words, the character 

 whose reappearance is called a reversion may be 



