ARE RECESSIVES LOSSES OF GENES? 77 



genes are absent, by the rest of the genes. Such an inter- 

 pretation avoids the rather naive assumption that each 

 gene in itself represents a character of the individual. 



Before discussing this view it should be pointed out 

 that in certain aspects this interpretation is similar to, 

 and in fact derived from, another more familiar interpre- 

 tation of the relation between gene and character. For 

 instance, if the mutation process is interpreted to mean 

 a change in the constitution of a gene, the result that 

 follows, when two recessive mutant genes are present, 

 is not that the new character is due to the new gene alone, 

 but that the new character is the end product of the 

 activity of all the genes, including the new ones, in the 

 same sense that the original character was also due to 

 the original gene (that mutated) and to the rest of the 

 genes. 



These last two interpretations may be briefly stated 

 as follows : The first one states that in the absence of a 

 pair of genes all the rest of the genes are responsible for 

 the mutant character. The second states that when a gene 

 changes its constitution, the end-result, produced by the 

 new genes, and the rest of the genes, is the mutant 

 character. 



There is a certain amount of recently obtained evidence 

 that has some bearing on the question here at issue 

 although it cannot be said to furnish a decisive answer 

 in favor of either view. The evidence is, nevertheless, 

 worth considering on its own merits, since it brings out 

 certain possibilities relating to mutation that have not, 

 so far, been discussed. 



There are several mutant stocks called collectively 

 notch that can be identified by one or more incisions at 

 the end of the wings and by the thickening of the third 

 vein of the wing (Fig. 44). Only females having these 

 characteristics appear. Any male carrying the gene for 



