No. 573] 



REDUPLICATWX II V POT II ES I s 



511 



passage quoted above and elsewhere. If reduplication 

 occurs at all it is the same in the wild fly as in the most 

 complex linkage experiment we have yet carried out. 



If it is assumed that the intensity of coupling and re- 

 pulsion is identical, it becomes unnecessary to consider 

 them separately. I shall therefore lump together all the 

 data involving the same groups of allelomorphs, regard- 

 less of how they were put into the cross. When three 

 pairs of genes are involved there 1 are eight possible com- 

 binations of them in F 2 , but only four if we add together 

 the two halves of the reduplication diagram. There are 

 the two original combinations, which T shall designate 

 ABC. Then there are three combinations derived from 

 each of these by a shifting of one gene, which I shall 

 designate ABc, AbC and aB(\ the small letters referring 

 to those pairs which have been shifted. Thus, to take an 

 imaginary case, if we cross LMn by ImN, the gametes 

 produced by the F 1 individuals will be classified as 

 follows : 



In the following tables I shall reduce all data to this 

 form. In each case the genes will be arranged so that 

 AB and BC will be the primary reduplication series. 1 



Table II contains such a summary of all the crosses in- 

 volving three pairs of sex-linked genes. Table III shows 

 the gametic ratios derived from these data, and also the 

 values for the secondary series calculated on the basis of 

 Trow's "special" hypothesis. For the sake of brevity 

 only one term is used: a gametic ratio of 3:1 is written 3; 

 a ratio of 3: 2 becomes 1.5, etc. With the simplifications 

 introduced here Trow's formula becomes 



ABC 

 LMn 

 ImN 



ABc 

 LMN 

 Imn 



aBC 

 IMn 

 LmN 



