No. 553] MEN DELI AN HEREDITY 7 



color series a new color is expected in the F 2 generation, 

 represented here by rv. This new color I called orange, 

 and since rv only meant two absences, I followed the con- 

 ventional method and added the symbol to stand for 

 orange. The completed formulae were : 



RVO red 

 rVO vermilion 

 RvO pink 

 rvO orange 



This is identical with the scheme that Bateson adopted 

 for the mouse color series, viz : 



GBCh gray 



gBCh black 



GbCh cinnamon 



gbCh chocolate 



In a later paper (1912) I used the symbol P instead of 

 R, so that the series stood : 



PVO red 



pVO vermilion 



PvO pink 



pvO orange 



Let us now examine some of the possible interpreta- 

 tions of these symbols to see in what sense the letters 

 were used for factors. 



It is undoubtedly implied, on the presence mid absence 

 scheme, that something is lost from the original germ- 

 plasm PVO when the vermilion pVO arises. The ver- 

 milion color is supposed to be the product of what is left 

 when this something (called P) is lost. It is not sup- 

 posed on this hypothesis that the vermilion factor alone 

 is responsible for the vermilion color, for it is hypothet- 

 ically only a part of what is left when something (P) is 

 lost. Yet it is the identification of the vermilion factor 

 with the vermilion eye-color that the opponents of Men- 

 delism seem anxious to impute to the Mendelians. 



