THE EVOLUTION OF LIVING BEINGS. 8l 



dominants, pure dominants and dominant-hybrids will 

 profit equally by their protective coloring. 



Suppose we have an F 2 generation consisting of I AA 

 plant 2 Aa plants and i aa plant and of these aa Plants 

 50 % perish on account of their conspicuousness, then 

 we will have 1 AA plant 2 Aa plants and \ aa plant 

 left. If we assume now, as in the example on p 76 that 

 each plant forms 4 gametes, we get 4 A gametes from 

 the A A plant, 8 gametes from the two Aa plants of 

 which 4 are A and 4 a, and 2 a gametes from the \ 

 aa plant, which will combine: 



8 A 6 a 

 8 A 6 a 



x 



64 AA 48 Aa 



48 Aa 36 aa 



64 AA 96 Aa 36 aa 



consequently in the proportion 16 AA : 24 Aa : 9 aa 

 against the proportion 16 AA : 32 Aa : 16 aa in the 

 preceding generation. 



Or, if we count AA and Aa together as phenotypi- 

 cally indistinctible, we get the proportion 40 : 9 

 against 48 : 16 or 4f : 1 against 3:1. But not only has 

 the number of phenotypically dominant forms increa- 

 sed considerably, as compared with the recessives, 

 but also the number of pure dominants, as compared 

 with the number of dominant-hybrids, this being in the 

 preceding generation 16 : 32 or 1 : 2 and in this ge- 

 neration 16 : 24 or 2 : 3 in other words an increase 

 from | to |. 



6 



