No. 555] SIMPLIFICATION OF MENDELI AN F0RMUL2E 175 



Morgan's in calculating the expected result of any ma- 

 ting, and it is equally reliable. The result of every pos- 

 sible mating within the series can be readily computed 

 without the confusing presence of the large letters. 



To those who have grown accustomed to the presence 

 and absence terminology the objection will suggest itself 

 that in naming the recessive character and ignoring its 

 allelomorph, we are naming an absence or negative and 

 disregarding what is present and positive. But this does 

 not follow. Because a character is recessive it does not 

 follow that it is negative. I quite agree with Morgan that 

 the physiological condition which produces an eosin eye 

 is as real as that which produces a vermilion, a pink or 

 a red eye, and no mere negation ; it is simply different. It 

 is quite impossible to decide, from its behavior as a domi- 

 nant or recessive in crosses, whether a character is posi- 

 tive or negative. This I have pointed out elsewhere 

 (1911) and the same view has been repeatedly expressed 

 by Shull. We have on record many instances in which 

 one and the same character may behave at one time as a 

 dominant, at another time as a recessive. 



Our terminology may well recognize the dominant or 

 recessive behavior of a variation, without implying any- 

 thing as to its positive or negative nature, which must in 

 many cases be conjectural or possibly non-existent. Dif- 

 ferent gradations of color, such as we have in the eye- 

 series of Drosophila described by Morgan, may result 

 merely from quantitative variations in cell constituents 

 and consequent activities, nothing being lost. This idea 

 concerning the possible nature of Mendelian factors in 

 general I have developed elsewhere, concluding that "it 

 is the substantial integrity of a quantitative variation 

 from cell-generation to cell-generation that constitutes 

 the basis of Mendelism. All else is imaginary.' ' 5 



Morgan applies his altered system of nomenclature also 

 to the body-color series and wing mutation series which 

 he has discovered. This nomenclature we may simplify, 



