No. 553] MENDELIAN HEREDITY 13 



The only logical method that could be followed, if an 

 attempt is made to apply consistently the current scheme 

 of presence and absence 3 would be the following: 



When it becomes necessary to construct a series, let us 

 say one involving three characters (PVE), the three 

 double recessives (Pve, pVe, pvE) must be made up and 

 suitable names given to them, the initial letters of these 

 names then become the factors sought. Such a procedure 

 not only involves holding in suspense the naming of the 

 factors until all the double recessives have been obtained, 

 but involves renaming all the factors, each time a new 

 series is made up. 4 This method is not likely to recom- 

 mend itself if a simpler one can be employed. The plan 

 here advocated avoids such difficulties. 



The first letter (or the first and second or some other 

 significant letter) of the name of the new character stands, 

 as heretofore, as its symbol ; thus P stands for the pink 

 factor and small p stands for the correlative factor of the 

 pink-eyed fly. Whether small p represents the loss of the 

 P factor, or a change in that factor when the pink eye 

 appears, is immaterial. The large letter represents the 

 dominant character in conformity with the current 

 scheme. 5 The eye color series will then be : 



Bed 



PVE 



Vermilion 



PvE 



Pink 



pVE 



Vermilion-pink 



pvE 



Eosin 



PVe 



Eosin-vermilion 



Pve 



Eosin-pink 



pVe 



Eo sin-pink- vermilion 



pve 



* It is the nomenclature that is here brought into question and not, for 

 the moment, the underlying conception of presence and absence, for even in 

 my scheme this conception might still be held if it seemed desirable to do so. 



* When, as in the case of the mouse colors, all the members of the series 

 are known, there is no difficulty in finding suitable symbols, for the current 

 names of the characters give the letters for the symbols. 



B When a new dominant character appears it is represented by the capital 

 letter and its allelomorph in the original form by a small letter. 



