230 The Inheritance of Wing Colour in Lepidoptera 



variation is small, though the slight broadening of the curve, just before 

 a colour-value of 2*0, shows that a small percentage of the offspring are 

 very perceptibly tinged with yellow. The result of mating one of these 

 rather yellow hybrids with a type insect will be seen in section (e), p. 239. 

 The broken line denotes the curve formed by the excess of yellow in 

 the colour measurements, and it runs roughly parallel to the orange 



curve. 



J? 8 



E 



a 

 t 6 



2- 



Colour-units 



[3-6: 3-4] [3-9: 3-7] 



Mean colour- values of 



lutea parents 



Fig. 3. (Cf. Fig. 16.) Curve showing frequency distribution of the orange 

 and yellow colour- values from 13 pairings of lutea x lutea. 



(h) Var. lutea x var. lutea. 



This curve (Fig. 3) is again composed of a number of small families, 

 and though asymmetrical, it is more like a normal frequency curve 

 than Fig. 2. It reaches a maximum immediately above the arrows 

 indicating the mean orange value of the respective parents. The base 

 of the curve is fairly broad showing that the range of variation is 

 considerable. Reference to Fig. 16 shows that about 10 insects have 

 an orange value below 2*5. Although some of the parents had a low 

 value, as may be seen from the pedigree, these offspring are unusually 

 pale, and there can be little doubt that some of them are due to experi- 

 .niental errors, i.e. of labelling or while feeding. The general appearance 

 of the black pattern on one or two of them is quite dissimilar to that of 

 the other members of the family, and these no doubt have strayed from 

 elsewhere. This explanation cannot account either for all the pale 

 individuals in this cross, or for the deepest yellows in the Fi generation. 



