IX] HEREDITY AND SEX 123 



and $ for female, these results may be summarised 

 thus: 



The important points about these facts are that 

 lacticolor is clearly a recessive variety when crossed 

 with grossidariata, but the distribution of the char- 

 acter among- the sexes is dilJerent in the reciprocal 

 crosses, nos. 3 and 4 above. The only explanation 

 that has been offered to account for this is that 

 females lay two kinds of eggs, one destined to become 

 males and the other to become females, and that the 

 female-bearing eggs cannot carry the grossidariata 

 factor. Thus in mating no. 4 above (using G and L 

 for gross, and lact), the heterozygous {G (L)) female 

 produces male eggs bearing G and female eggs bearing 

 L ; all the spermatozoa (germ-cells) of the male bear 

 L, and thus the offspring are GL (= gross.) males 

 and LL (= lact.) females. But in the converse cross 

 no. 3, the lact. female (LL) produces male and female 

 eggs both bearing L, the heterozygous (GL) male 

 produces equal numbers of G and L spermatozoa, 

 and thus the offspring are GL and LL males, GL and 

 LL females. We thus arrive at the conclusion that 



