SIMPLIFICATION OF MENDELIAN FORMULAE 



PROFESSOR W. E. CASTLE 

 Bussey Institution, Harvard University 



Professor Bessey in his recent presidential address 1 

 expresses the opinion that Mendelian terminology is need- 

 lessly complicated. This opinion most biologists will 

 heartily endorse, and not a few Mendelians will be among 

 their number. For those who work most extensively with 

 Mendelian formulae feel most keenly the need of simpli- 

 fication in these the tools of their investigations. 



Professor Morgan, in the January Naturalist, 2 makes 

 a commendable effort to introduce reforms. I desire 

 heartily to endorse his effort, but would suggest certain 

 modifications in method. 



The Mendelian may say in justification of existing us- 

 age that it has arisen naturally step by step as knowledge 

 of Mendelian phenomena has advanced, but this is of 

 course no justification of its continued use, if it has be- 

 come a hindrance rather than a help in the further ad- 

 vance of knowledge. 



Morgan clearly points out the two historical steps by 

 which present usage was reached. The first of these was 

 Mendel's original recognition of segregating dominant 

 and recessive characters existing in contrasted pairs, and 

 his convenient designation of the former by capitals and 

 of the latter by small letters. This usage answered per- 

 fectly so long as only a single modification of any char- 

 acter came under consideration, and indeed Mendel's 

 observations did not go beyond this. But this system 

 broke down when characters more complex in nature came 

 under observation, as for example when Cuenot showed 

 that more than a single differential factor exists between 

 gray mice and albino mice. (2) The ingenious and useful 



1 Science, January 3, 1913. 



2 Vol. 47, pp. 5-16. 



170 



