ILLUSTRATION OF STATISTICAL RESULTS 335 



reversion (i.e. the reappearance of a character which occurred 

 in a definite ancestor). In exclusive inheritance, in which the 

 offspring inherits the full character of either parent, and does 

 not blend the two , the law of ancestral inheritance in the strict 

 sense ceases to hold, for it presupposes a blend. Thus eye- 

 colour in man rarely, if ever, blends, and it is in regard to such 

 characters that we should look for reversion. 



By statistical methods Pearson has sought to ascertain how 

 far the inheritance of the duration oj life extends, and has reached 

 the important conclusion that in a large percentage of cases 

 there is evidence in the death-rate that discriminate selection is 

 at work. It is no longer possible to say of natural selection, 

 as Lord Salisbury did in 1894, that "no man, so far as we know, 

 has seen it at work. " " It is at work, and at work among civilised ' 

 men, where intra-group struggle i.e., autogeneric selection 

 is largely suspended, with an intensity of a most substantial 

 kind. Of the existence of natural selection there can be no 

 doubt ; we require careful experiments and observation to indi- 

 cate the rapidity of its action. In a few years we may hope no 

 longer to hear natural selection spoken of as hypothetical, 

 but rather to listen to a statement of its quantitative measure 

 for various organisms under divers environments " (Grammar 

 oj Science, p. 500). 



