CORRELATION OF IIOMOTAXIAL STAGES 



289 



gion F from the center of dispersal. The line of direct genetic sequence 

 at the center of dispersal will be represented by A, A 1 , A 2 , A 3 , etcetera. 

 According to the theories set forth above, we will have at region B 

 first the descendants of A, becoming modified by the B environment; at 

 region C the descendants of A, partly modified by B and C environments, 

 and so on. The next mutation in region B will consist of the incoming 



Geoyrapfiic R a n y e 



Figure 1. — Relations of homotaxial and synchronous Stages in a widely dispersed 



Phylum 



migrants of the A 1 stage, mixing with and partially displacing the origi- 

 nal B, derived from A. Assuming as a special case that the newcomers 

 displace three-fourths of the earlier stage and absorb the remaining 

 fourth, then the B 1 mutants will contain (as an average) 3/4 of A 1 

 blood, 1/4 of A blood already somewhat modified by B environment or 

 B 1 = 3/4 A 1 , 1/4 A. 



Carrying on the same special case, we will have 



C 1 = 9/16 A 1 + 3/16 A + 1/4 AB. 



The modifying influence of the B environment is really somewhat 

 greater than this. 



At F 1 the approximate figures will show 



1/4 A 1 influence (23.73 per cent). 

 1/6 A blood. 



The remainder is A blood modified by the environments B, (\ D, and E, 



