6 SEX-DETERMINATION 



that in animals also sex- determination was due to segrega- 

 tion of hereditary factors. 



Bateson and Punnett (1908), basing their interpretation 

 on the assumption that the character femaleness was 

 dominant to the contrasted character maleness, and that the 

 female in Abraxas was always heterozygous in respect of 

 the character femaleness, devised a scheme, of considerable 

 historical interest, to show the relationship of the sex of the 

 individual to its colour pattern. If the hereditary factor for 

 the grossulariata colour pattern is symbolized by G, that for 

 lactocolor by g, that for the dominant femaleness character 

 by F, and that for the recessive maleness character by f, then 

 the results of Doncaster's experiments can easily be accom- 

 modated, if it is assumed that the female is always con- 

 stitutionally heterozygous (Ff) for the character femaleness, 

 and further, that the two dominant factors G and F repel 

 each other so that they can never be present together in the 

 same gamete. 



The results of the breeding experiments carried out by 

 Doncaster were as follows: 



1. lacticolor $ x gross. (^=gross. sons and daughters. Gross, was 



dominant to lacticolor. 

 In the F.2 both gross, and lact. occurred, there being on the 

 average in every 4, 3 gross, to i lact. Among the gross, indi- 

 viduals there were both males and females but the lacticolors 

 were all females. 



2. F.I gross. (^ X lact. $=gross. and lact. individuals in equal 



numbers and among both of these types males and females in 

 equal numbers. 



3. lact. S from 2 x F.i gross. $=equal numbers of gross, and lact. 



individuals but all the gross, were males and all the lact. were 

 females. 



4. lact. o from 2 x wild gross. $ = equal numbers of gross, and lact. 



individuals but all gross, were males and all lact, were females. 



Bateson and Punnett's explanation of these results was 

 as follows : 



1. lact. $ X gross. <? 



ggFf GGff P.I 



gF gf : Gf gametes 



GgFf Ggff F.I 



gross. ? gross. <S 



