46 Mr. W. B. Alexander. Experiments on the [Jan. 3, 



though certain males, even reared from Hyeres eggs direct, were as yellow as 

 my moths. 



The history of this race appears to be as follows : — Some light forms 

 appeared among the dark ones in generation 6 in a box which was supposed 

 to contain the pure dark strain. A number of the descendants of this brood 

 were reared and in general gave a mixture of pure light forms and forms 

 intermediate between light and dark. In some cases where two of these 

 light individuals were mated they yielded nothing but lights, in others 

 a mixture of lights and intermediates. On the other hand the darkest forms 

 continued to throw light individuals when mated together. The actual 

 parents of my Brood 2 appear not to be known, but there is no doubt that 

 they were members of the generation 4 in descent from the original aberrant 

 individuals. We thus see that it took five generations to establish a pure 

 light brood from the original light individuals whose origin was quite 

 inexplicable. 



Brood 4. — This was the brood labelled DxLMxi by Mr. Bacot. They 

 were the result of mating a pure dark male with a pure light female, both of 

 whose ancestors had been reared in captivity for 11 generations. It was 

 thus what is ordinarily known as an I\ brood, though readers of 

 Messrs. Prout and Bacot's paper will note that, though they claim to have 

 numbered their broods according to " the well-known Bateson method," they 

 have not confined I\, F 2 , etc., to the first, second, etc., generations of a hybrid 

 •strain, but have given these numbers also to broods of the pure strain, 

 -dating arbitrarily from the broods which were first reared in confinement. 



My Fi brood consisted of seven moths (5^,2?), all of them distinctly 

 speckled with black to a greater extent than in the light form, whilst 

 their ground colour was a dirty white, not nearly so yellow as in my 

 Brood 2. 



From this brood I obtained one lot of ova — Brood 8, both of whose 

 parents were of the type just described, and another lot of ova from a male 

 of this brood mated with a female of Brood 7 (one of the pure yellow 

 ■canteneraria broods descended from Brood 4). This I labelled Brood 10. 



Brood 10. — This brood, consisting of 44 moths, possessed the yellow 

 ground colour of its mother throughout, but 28 of the moths were distinctly 

 speckled like their father, whilst 16 were exactly like their mother. This 

 points to the ratio of 2 speckled : 1 unspeckled, but I think the numbers 

 in this brood must be distrusted, since for some reason there were 

 also 29 females and 15 males, which again suggests a ratio of 2 to 1, 

 though of the total number of moths I have examined 305 were males and 

 509 females. 



