1912.] Cross-breeding of Tivo Races of Acidalia virgularia. 



47 



Brood 8. — This was the F 2 brood of 34 individuals, and exhibited a very 

 considerable amount of variation, much more than that in Fi. I found, 

 however, that it was quite easy to distinguish 9 moths as having no more 

 speckling than pure canteneraria, whilst the remaining 25 were distinctly 

 more speckled. Of the nine unspeckled (4^,5?), three males were as 

 yellow as the individuals of Brood 4, one distinctly paler, the females were all 

 paler, two of them as white as the lightest of the pure Hyeres race. It thus 

 appeared that about one quarter (9 out of 34) of the F 2 brood were referable 

 to the pure light race, though several of the males were yellower than any 

 but extreme examples of it. The numbers suggested at once that the 



Pedigree of Broods of 

 Acidalia vireul&ria. speckled forms as in 



typical Unglish race. 



unspeckled Hyeres race was recessive to the speckled English form. I 

 reared a number of further broods from pairs of the F 2 moths, and with 

 one exception (Brood 39) this supposition would account for the composition 

 of all the succeeding broods (see Pedigree). 



I do not think it is necessary to deal with the subsequent broods in so 

 much detail, as their mutual relationships will be visible from the pedigree. 



The last generation emerged at irregular intervals in the early months of 

 1911, and only 3 females laid eggs. From one set of ova a few larvae 

 emerged, but only lived for a few days. Thus the race became extinct, 

 perhaps owing to complete inbreeding for six generations. 



The descendants of Brood 8 may be classified as follows : — 



