SHORTER ARTICLES AND DISCUSSION 



SIMPLIFIED MENDELIAN FORMULAE 



I was somewhat surprised by Morgan's and Castle's sugges- 

 tions for a simplification of Mendelian formulae. 1 My surprise 

 was not occasioned so much by the forms these suggestions took 

 as by the fact that any pronounced changes were deemed neces- 

 sary. I had not only employed the usual formula? in my own 

 work but had found no difficulty Avorth mentioning in under- 

 standing the formula? used by most other workers in Mendelian 

 fields. My experience with students in elementary courses in 

 genetics had not prepared me for the idea that such formula? 

 were particularly difficult. Nevertheless I believe in siniMlityini: 

 the formula? if some system can be found that will be applicable 

 to all sorts of Mendelian inheritance. I believe, however, that I 

 have no right to adopt formula? for my own cases, no matter how 

 simple they might be, if the same type of formula could not read- 

 ily be applied to the materials with which other investigators 

 are working. Such procedure on my part would result in no 

 end of confusion if followed by any considerable number of work- 

 ers each using his own special type of formula. The important 

 question now is not whether I prefer a new style of formula that 

 fits my case but whether it will fit all sorts of cases so that, if it 

 is an improvement on the old style, it can be adopted by others 

 and not necessitate the use of two styles where but one sufficed 



Let us examine Morgans and Castle's suggestions in the 

 light of these remarks. Morgan's principal objection to the usual 

 type of formula — that "it is not sufficiently elastic to allow the 

 introduction of a new term in the series, unless a complete re- 

 vision of the method is made each time that a new mutation in 

 kind occurs" — seems to me to have little merit. Morgan uses eye 

 color in Drosophila to illustrate his contention. Four eye colors 

 had been designated as follows : red PVO, vermilion pVO, pink 

 PvO, and orange pvO. A fifth color, eosin, arose and was found 

 to produce red when crossed with orange, and hence was as- 

 sumed to have the formula PVo. Morgan regards this as "in- 

 consistent with the scheme already adopted because the small 

 letter o stands for a character called eosin," whereas the capital 

 letter P had been used for pink, for orange, V for vermilion, 

 'American Naturalist, 47: 5-16, and 47: 170-182, 1913. 



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