252 BREEDING 



always in the heterozygous $ cJ (DR), whilst maleness 

 occurs in the homozygous (recessive) condition cJc? 

 (RR). 



Only one instance of the kind of evidence, based 

 on Mendelian investigations, by which this theory is 

 supported will be given here. 



The common currant moth (Abraxas grossulariata) 

 has a variety lacticolor, which is characterised by 

 the fact that the black spots on its wings, though 

 they resemble those of the parent species in distri- 

 bution, are very much smaller. This variety is only 

 known as a female. 



A series of crossings between the parent species 

 and its variety were made by Mr. Doncaster and 

 Mr. Raynor, and gave the following remarkable 

 results : — 



1. Ladicolor $ X grossulariata (J gave in Fl* (Js and $s 



all grossulariata. 



2. Fl grossulariata $ X Fl grossulariata $ gave grossulariata (Js 



and 5s, and lacticolor $s ; no (Js of ladicolor appeared. 



3. Lacticolor $ X Fl grossulariata (J gave all four kinds, 



grossulariata (Js and $s and lacticolor (Js and $s. 

 The lacticolor males were the first males of the variety 

 that had ever been seen. 



4. Perhaps the most curious result of all. Fl grossulariata 



5 X lacticolor ^ gave equal numbers of lacticolor ^s 

 and grossulariata $s. 



Mr. Doncaster attempted to account for this 

 remarkable series of results by adopting Professor 

 Castle's idea that both sexes were heterozygous ; and 

 he elaborated a consistent explanation of his results. 



* A symbol, introduced by Mr. Bateson, to denote the first hybrid 

 generation. 



