EFFECT OF SELECTION II5 
statement which follows, ancestors are supposed to 
have been selected showing in each generation a devia- 
tion h from the general mean of the population. Thus, 
suppose the character selected to be stature: suppose 
the mean height of the population to be 6 feet, and 
the selected individuals to be 6 feet 6 inches high; h is 
then 6 inches, and only individuals of a height of 
6 feet 6 inches would be selected as parents in each 
generation, so that after three generations of selection 
we should be dealing with children whose parents, 
grandparents, and great-grandparents were all of this 
particular height. 
Pearson calculates that after one generation of 
selection the immediate offspring will show 0'62 of 
the character selected (0°62 h). After two generations 
they will show 0°82 h, after three 0-89 h, and after a 
great number of generations 0:92 4. Thus in a com- 
paratively small number of generations the development 
of a character may be raised to within 90 per cent. 
of the value selected, but, after this, further selection has 
very little effect. If selection is stopped after one 
generation, and the selected stock is then inbred, it 
was calculated that the first generation of inbred stock 
would show 0'59 h, the second 0°56 h, the third 0°52 h, 
and the tenth 0-35 &. If, on the other hand, in- 
breeding was started after the selection had continued 
for a large number of generations, the first generation 
of inbred stock will show 0°86 fh, the second o-81 &h, 
the third 0-77 h, and the tenth 0°51 &. So that in- 
breeding of a selected stock is followed by a very 
8—2 
