Variation and Heredity 271 



to find all the individuals of a community very much alike, 

 except for the fluctuating variations close around the mode ? 



As a result of his studies on the stature of man, and on 

 the coat color of the Basset hounds, Galton has shown that 

 the inheritance from the parents can be represented by the 

 fraction \ ; that is one-half of the peculiarities of the individ- 

 ual comes from the two parents. The four grandparents 

 together count for \ of the total inheritance, the great-grand- 

 parents \, and so on, giving the series \, \, \. Pearson, taking 

 certain other points into consideration, believes the following 

 series more fully represents the inheritance from the ances- 

 tors, .3, .15, .075, .0375, etc. He concludes that, "if Dar- 

 winism be the true view of evolution, i.e. if we are to describe 

 evolution by natural selection combined with heredity, then 

 the law which gives us definitely and concisely the type of 

 the offspring in terms of the ancestral peculiarities is at 

 once the foundation stone of biology and the basis upon 

 which heredity becomes an exact branch of science." 



The preceding statements give some idea of what would 

 occur in a community in which no selection was taking 

 place. The results will be quite different, although the same 

 general law of inheritance will hold, if selection takes place in 

 each generation. If, for instance, selection takes place, the 

 offspring after four generations will have .93 of the selected 

 character, and without further selection will not regress, but 

 breed true to this type. 1 " After six generations of selection 

 the offspring will, selection being suspended, breed true to 

 under two per cent divergence from the previously selected 

 type." 



If, however, we do not assume that the ancestors were 

 mediocre, it is found that after six generations of selection the 

 offspring will breed true to the selected type within one per 

 cent of its value. Thus, if selection were to act on a race 



1 In this statement the earlier ancestors are assumed to be identical with the 

 general type of the population. 



