No. 555] SIMPLIFICATION OF MENDELIAN FORMULAE 173 



out and his paper illustrates amply how under the dual 

 system "the letters used may unintentionally come to 

 stand for different things." The obvious thing to do, if 

 we attempt reform, is to omit the superfluous symbol, 

 either the small letter or the large one. 



Morgan, however, clings to the dual nomenclature, but 

 suggests a reversal of the usual significance. Thus the 

 factor for pink-eye, he assumes, is present only in animals 

 which are not pink-eyed, and the factor for black body 

 color, he suggests, is present in all sorts of flies except 

 those which are black bodied. This is confusion worse 

 confounded. 



But, seriously, I do not see that it is possible to improve 

 the existing terminology, so long as we use two terms of 

 opposite significance with reference to a single germinal 

 variation. Certainly merely reversing the significance of 

 existing terms will not do it. What we need first of all is 

 one set of symbols, used in a single significance. 



If this reduction is allowed, then I think that another 

 aspect of Morgan's proposition might be extremely use- 

 ful, viz., that a mutation which behaves as a recessive in 

 crosses be designated by a small letter. This proposition 

 was put into effect more than three years ago in a paper 

 dealing with color inheritance in mice, though Morgan 

 does not seem to have observed it. See Castle and Little 

 (1909). 4 In the paper cited, three recessive color factors 

 of mice were designated by small letters, viz., "d, the dilu- 

 tion factor"; il s , the factor which causes spotting with 

 white;" and il p, the pink-eye (or paucity) factor." 



In that same paper all dominant color factors of mice 

 were designated by capitals. This seems to me a very 

 necessary complement to the use of small letters to ex- 

 press recessive variations, and is in entire harmony with 

 Mendel's original usage. But neither of these proposals 

 can help matters much, unless ive discard the duplicate 

 set of symbols, which is the chief cause of present con- 

 fusion. Thus if we use s for spotting, then we have no 



* Science, N. 8., Vol. 30, pp. 312-314. 



