INHERITANCE OF A MACULA MUTATION. 273 



other group had two black spots on the left elytron and two red 

 ones on the right. When the two types of females were added, 

 the trait was found to be inherited as a recessive to normal 

 (Breitenbecher, 1925). Every male, for the entire list of char- 

 acters enumerated, had non-spotted tan elytra similar to the 

 wild type. 



It is improbable that such latent characters in the male are 

 caused by developmental differences, because in sex-limited, as 

 well as other Bruchid mutations, the male emerges a fraction of 

 a day before the female. Inhibitors associated with the male 

 complex may produce this peculiarity. Or, since the female has 

 two X-chromosomes, and the male only one X-chromosome, the 

 sex-limited traits may be caused by pattern, or normal, genes 

 within the X-chromosome. These may be associated with 

 factors in other chromosomes in a degree enabling the character 

 to be completely manifested in the female. The one sex- 

 chromosome of the male may not be sufficient for complete 

 manifestation of the trait. This conception is similar to that 

 of Bridges (1922) for Drosophila. 



The macula and normal patterns of Bruchus, illustrating sex 

 differences, may be considered as the result of identical pheno- 

 types for the female, since the females for each trait have dupli- 

 cate spotting patterns on the elytra. The mm genes in the wild 

 male are non-visible, while the MM factors for the normal four 

 black spots are visible in the macula male. 



It is to be hoped that some mutation may occur, in which the 

 gene concerned with the entire pattern or non-pattern trait may 

 appear. This might assure a definite solution for these sex- 

 limited differences in Bruchus. 



CONCLUSIONS. 



1. The macula mutation is dominant to the wild type. 



2. Genes, mm, represent the wild type, having spotted females 

 and non-spotted males. 



3. Factors, MM, represent the macula mutation, in which 

 both males and females are spotted. 



4. The macula character is not sex-linked. 



5. Inhibitors probably produce latent traits in the male. 



