290 The Inheritance of Wing -Colour in Lepidoptera 



20 



30 



50 



(J parent 

 of '18^ 



60 70. 



Number of Insects 

 Fig. 9 (cf. Fig. 10). Curves showing the distribution of the black values of the ^ ^ 

 in two families of the cross (Fi) x type. Note the two distinct plateaux in '18 B. 



(J parent Colour Units 

 of '18 A 



Fig. 10 (cf. Fig. 9). Diagrams showing the percentage frequency of the black values 

 of the (J (J in the two families of the cross (Fj) x type shown in the last figure. 



