396 Maternal hiheritaiice and Meudelism 



In this scheme, if we replace A hy R and jB by D we shall see that 

 the results actually obtained and those calculated come in the same 

 category, the whitish grey being dominant to the normal, and the 

 brown and the spindle-shaped characteristics being recessive to normals. 

 As to the yellow and white colours of newly laid eggs, the former is 

 dominant to the latter. 



Crosses between Bomhyx mori, L. and Theophila i/uindarina, M,, 

 which gave the result mentioned below : 



may come in the same category, the Theophila colour being dominant 

 towards that of the Bomhyx. 



Back-crossing. 



If females derived from the Fi D eggs were mated with the parental 

 recessive form, we should expect to have the combination $ DR x (/* RR, 

 which gives all D eggs, while in the reversed mating we should expect 

 all R eggs, in spite of the zygotic composition being a mixture of DR 

 and RR in an equal proportion in both cases, since the maternal 

 characteristic predetermines the egg-character. Of moths derived from 

 the D eggs, some will be, therefore, DR in their constitution and the 

 others RR. As we have however no means of distinguishing DR males 

 or females from RR males or females, we must expect to have random 

 matings between these two forms which will result in the following 

 combination : 



Outward appearance 

 Zygotic composition of egg-batches of egg-batches 



a. ^DR X s DR = {DD + DR + RR) D 



b. iDR X i RR = {DR + RR) D 



iRRx i DR = (DR + RR) B 



iRR X s RR=RR R 



it 



Hence in this generation, certain matings will give all D batches, 

 others will give all R batches. 



As the formulae above mentioned shew, the D and R eggs are 

 heterozygous except No. 2 b which is homozygous, and therefore the 

 moths which came out from them even when paired inter se among 

 those from the same batch would produce antagonistic eggs again. 



