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THE AMEBIC AN NATURALIST [Vol. XLVIII 



age proposed by Morgan ( '11). Here I shall use the same 

 data for a test of the reduplication theory. It may be of 

 value to contrast the two views by making a rigorous 

 application of them to the same facts. Since the data 

 concerning the sex-linked group of genes in Drosnphila 

 form the simplest and most extensive series now avail- 

 able, I shall deal more especially with them. The reader 

 is referred to my other paper for the detailed data, for 

 references to original sources, and for a full treatment of 

 the chromosome hypothesis as applied to these and other 

 data. 



It may be well to give first a brief catalogue of the 

 sex-linked genes discussed in this paper. The nomen- 

 clature is that suggested by Morgan ( '13). This may be 

 confusing to those accustomed to the "presence and ab- 

 sence" system, but this should not be a serious objection 

 here, since a clear conception of the somatic appearance 

 of the animals discussed is not essential for our present 

 purpose. The relations would be as clear if hieroglyphics 

 were used for symbols. 



Y is the gene which differentiates the wild "gray" 

 bodied fly from the yellow mutant, y. 



V differentiates the wild red-eyed fly from the ver- 

 milion-eyed mutant, v. 



M differentiates the "long" wing of the wild fly from 

 that of the miniature-winged mutant, m. 



R is another gene affecting the wings. The wild fly 

 has R, the rudimentary- winged mutant has r. 



Br* occurs in a dominant mutant form having a narrow 

 eye known as barred. The allelomorph present in the 

 wild fly is designated W. 



The other characters concerned bear such a relation to 

 one another that the genes involved are considered as 

 forming a system of quadruple allelomorphs. The alter- 

 native to this view is the assumption of complete linkage, 

 but I have given elsewhere (Sturtevant, '13) my reasons 

 for preferring the multiple allelomorph interpretation. 

 The eye of the wild Drosophila is red in color. A single 



