H. Onslow 



•281 



inclusion would greatly coinplicatc the record, they have been omitted, 

 the black values alone being given. From these figures a number of 

 curves have been constructed, showing the distribution and percentage 

 distribution of the colour values, on the system previously adopted, to 

 illustrate the variation of the insects in the principal families of each 

 type of mating. The colours of the parents are shown by arrows, and in 

 addition to the curves, tables have been given which include every in- 

 sect bred. For simplicity, the male insects in these tables had to be 

 classified into three groups. The black group, consisting of insects like 

 the wild type, and the white or cream coloured group of insects like 

 var. rustica, obviously represent the DD and RR classes, but the BR 

 class of insects presents a difficulty. It includes all the grey or buff 

 coloured males of the F^ generation, and as these have been called var. 

 standfussi, that name might have served to designate the whole class. The 

 name is, however, misleading, because whereas buflf or grey males are 

 always intended, the name should include every insect of the DR class, 

 some of which, it has been pointed out, are so pale as to be indistinguish- 

 able from pure rustica (see families '16 J. and '19 5 in Fig. 1). Thus 



10 20 



Number of Insects 



^ Q parents of 

 '16^, '19 7.' 

 and '16 Z> 



Fig. 1 (cf. Fig. 2). Curve showing the distribution of the black values of the ^ ^ 

 in family '16 D bred from rustica $ x rustica^; also the values of the rj r^ in 

 the two families "16 A and '19 B bred from (Fj) x rustica. 



there may be some males, which, though they appear to be pure rustica, 

 are genetically heterozygous for the black pigment, the white form being 

 completely dominant. For this reason, the DD class has been called 

 "pure rustica" to distinguish it from the DR class, called ''rustica and 

 standfussi" which includes both standfussi and the heterozygous males 

 indistinguishable from rustica. It was also necessary that the classes 



