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THE AMERICAN NATURALIST [Vol. XL VII 



as we did in the case of the eye-color series, without im- 

 pairing its utility. 



Wild fly normal YBES 



Yellow y yBES 



Yellow-black yb ybES 



Ebony e YBeS 



Sable * YBEs 1 



Wild fly normal MB 



Miniature m mB 



Eudimentary r Mr 



The taste of the reader will govern his choice between 

 these two systems. Doubtless either can be used success- 

 fully, though the revised terminology seems to me prefer- 

 able on the ground of simplicity and suggestiveness. 



In the series with which Morgan has dealt, all the muta- 

 tions under consideration are recessive in character, so 

 that one can read the names of the varieties directly from 

 his formulae, if one disregards altogether his large letters 

 and pays attention only to the small ones. To insure 

 this I have suggested omitting the large ones. 



But if one were to extend Morgan's terminology to a 

 series in which dominant mutations as well as recessive 

 ones occur, hopeless confusion would result. For here 

 some of the large letters would stand for mutations, while 

 others would stand for the negation of mutations, so that 

 without a key constantly at hand the formulae would be 

 unusable. 



If, however, we use the single system of symbols as I 

 have suggested, a series which includes both dominant 

 and recessive mutations may be handled without con- 

 fusion. In this case every symbol is significant, and its 



