90 Reduplication Series in Sweet Peas 



coupling between D and F, together with repulsion between N and F 

 and between N and D. The figures here given shew that the first part 

 of the anticipation was realised. 



There is coupling between D and F and this is not far removed from 

 the expected 15 : 1 : 1 : 15 system. But there is no repulsion evident 

 between either N and F. or between N and D. 



Instead of this the figures accord closely in both cases with an 

 ordinary 9:3:3:1 ratio. The possibility of a similar ratio has already 

 been referred to in the case of other families where these factors are 

 concerned (p. 86) and it is hoped that a further study of this interest- 

 ing case may give us the clue as to the relation between normal and 

 reduplicated gametic series. But it is evident that several years must 

 elapse before the necessary experiments can be completed. 



Primary and Secondary Reduplications. 



In an interesting paper which has just appeared (16) Trow dis- 

 cusses the problems offered by reduplicated series of gametes, and 

 draws a distinction between what he has termed primary and secondary 

 series. Starting with the case where there are three factors A, B, C 

 such that any two may form a reduplicated series, he has shewn theo- 

 retically that if the reduplication between A and B is of the form 

 m : 1 : 1 : m, and between A and C is of the form n : \ : \ \ n, then 

 the secondary form of reduplication, derived from these two primary 

 ones and expressing the relation between B and C, is of the form 

 nm-\- 1 : m4- w : w+ n : mn + 1. The only experimental data with 



