H. Onslow 



133 



from the cross (F^) x varleyata, and they illustrate practically the same 

 points as the previous insects. This is best seen in the frequency 

 distribution diagram (Text-fig. 6) in which the (/•(/ and ? % of all four 

 families have been combined in two curves. The average black value 

 is about 80 per cent., that of the % % being 75 per cent, and that of 

 the cTc/ ^'5 per cent., that is to say, the percentage of black on the fore 

 wings is (1) greater than in the type specimens, and (2) greater in 

 the c/c/ than in the %%. 



Percentage of Black 



Text-fig. 6 (cf. Text-fig. 5). Diagram showing the frequency distribution of 

 the values for the black pattern of (J (J and 5 2 in the four families 

 in Text-fig. 5, combined together. 



As might be expected, it makes no apparent difference which parent 

 is the varleyata; for instance, family '18 R comes from a varleyata ? 

 X grossulariata (/ (88 per cent, black), and- family '18 P comes from a 

 grossulariata $ (75 per cent, black) x varleyata ^ (see Text-fig. 5). The 

 correlation between the black values of the parents and the offspring is also 

 clearly seen. The arrows on the right-hand side of Text-fig. 5 show the 

 parental values, which in the case of '18 JJ is 57 per cent. The offspring 

 of this mating are not so dark as the other two families, the parental 

 values of which are 75 and 88 per cent. Readings were made from 

 only a small number of families, owing to the great labour involved, 

 but the curves given are representative of all the families in the pre- 

 ceding tables, in which the two classes — those which inherit the localising 

 factor Z, and those which do not — can be very clearly differentiated. 



9—2 



