256 THE THEORY OF THE GENE 



By assigning numerical values to the big M's (none to 

 the m) and to PF he has built up a scheme to show how, 

 in the cross first mentioned, equal numbers of males and 

 females result when the cross is made in one direction, 

 and intersexes when it is made in the opposite direction. 



In like manner, by assigning suitable values to the 

 letters in each of the other crosses an approximately con- 

 sistent account can be given of the results. 



The unique feature of these formulas of Goldschmidt 

 is not, in my opinion, the numerical values attached to 

 the factors, for these are arbitrary, but the statements 

 that the results can be explained only by the assumption 

 that the factors for femaleness are in the cytoplasm, or 

 else in the W-chromosome. In this respect his view is dif- 

 ferent from the condition that Bridges has found in 

 Drosophila from a study of triploids, where the opposing 

 influences are in the X-chromosomes and in the auto- 

 somes. 



Goldschmidt has recently (1923) reported a few ex- 

 ceptional cases in which the evidence indicates, he be- 

 lieves, that the female-producing factors lie in the W- 

 chromosome. One such case relates to certain racial 

 crosses, where, through non-disjunction, a female re- 

 ceives a W-chromosome (Y in his formula) from the 

 father and the Z from the mother. This is the reverse of 

 the ordinary transmission of these chromosomes. The 

 results indicate that the female factors follow the W. 

 Logically, the evidence appears satisfactory, but on the 

 other hand both Doncaster and Seller have reported a 

 few exceptional female moths in which the W-chromo- 

 some is at times absent. These moths were normal females 

 in every respect and bred as such.^ They could not be 



1 There are 56 chromosomes present in the female and in the male of 

 Abraxas. That one of those in the female is a W-chromosome is very prob- 

 able, from Doncaster 's discovery of a strain in which the females have only 



