With six size-characters, the extreme size of a 

 grandparent would reappear no oftener than 

 once in 4000 times, while with a dozen such 

 independent characters it would recur only 

 once in some 17,000,000 times. It would be 

 remarkable if under such conditions the ex- 

 treme size were ever recovered from an ordi- 

 nary cross. 



There is one means by which we can deter- 

 mine with certainty whether in a particular 

 case of seemingly blending inheritance segre- 

 gation does or does not occur, namely, by com- 

 paring the variability of the F l and the F 2 

 generations. If segregation does not occur, F 2 

 should be no more variable than F x , whereas 

 if segregation does occur, F 2 should be more 

 variable. For, in a segregating system, the F 

 individuals should all fall in a middle, inter- 

 mediate group, but the F 2 individuals should 

 be distributed also in classes more remote from 

 a strictly intermediate position, that is, they 

 should be more variable. But, in a non-segre- 

 gating system, F t and F 2 individuals alike 

 should fall in the same intermediate group, 

 that is, they should have the same variability. 



137 



