GAMETIC COUPLING AND REPULSION IN THE SILKWORM. 



125 



between stripedness (S) and normalness (N). The gametes produced by these 

 striped yellows (SnYsNy) must have been, therefore, of only four kinds 

 as follows : 



SnY, sNY, Sny, sNy. 



as observed in the experiment— striped yellow, striped white, normal yellow 

 and normal white, in the ratio of 9 : 3 : 3 : 1. This normal ratio is, 

 however, disturbed in the present case by virtue of partial coupling taking 

 place between the striped and yellow factors, the detailed statement of which 

 is given in the following pages. 



V. Gametic Coupling. 



Two cases of partial and one example of complete coupling were observed 

 ill my experiments. 



A. Partial coupling. 

 L Partial coupling between stripedness (S) and yellowness (Y). 



a ) The hereditary behaviour of the F, striped yellow SnYsNy just 

 referred to above (H. 1. '11) clearly points to the conclusion that there 

 occurs a partial coupling between striped marking and yellow colour, as 

 may be seen from the following consideration. 



" If we take for granted that a perfect repulsion occurs between striped 

 and normal character in the F t striped yellows, we should obtain four F 2 

 forms in the ratio 



9 striped yellow 

 3 striped white 

 3 normal y.llow 



