A. H. Trow 



321 



This result may be reached more easily by making use of the general 

 formula on p. 319. 



For if AB : Ab : aB : ab :: n : 1 : 1 : n, 



and AD : Ad : aD : ad :: p : 1 : 1 : p, 



then BD : Bd : bD : bd :: np + 1 : n+p -.n+p: np + 1. 



Any number of derivative ratios may be ascertained in the same way by 

 this method. 



This more complex case may be represented graphically thus : — 



«mpABCD 



m aBcD 



m^;aBcd 



nm/j abed 



According to this scheme of segregation (which however must not 

 be regarded as the only possible one), each additional factor (or pair of 

 allelomorphs) Ee, Ff, Gg, etc. will necessitate a further dichotomy of 

 each branch. If these additional branches are equally developed it can 

 readily be shewn that reduplication does not take place. We have the 

 important rule that equal dichotomies produce normal segregation ; 

 uneipial dichotomies produce reduplications. These two types of behaviour 

 may occur in any order or at any stage in the phylogeny, but as 

 Bateson and Punnett have already stated, they cannot occur simul- 

 taneously. 



