2 



"gene" should be preferred. This word 

 must be used commonly in the plural form, 

 but there is already a word " gens " in rather 

 common literary use and having, at least some- 

 times, a genetic meaning. 



Eegarding the definition of "phenotype," 

 few who carefully read the passage translated 

 by Dr. Cook from Johannsen's book will 

 agree with the translator that "phenotype" 

 as used by its author was ever anything but 

 an abstraction. " Centers among series of 

 variations around which the variants are 

 grouped " must always be abstractions, and 

 yet they are, as Johannsen rightly says, 

 "measurable realities." Every individual or- 

 ganism possesses an external appearance and 

 a fundamental constitution, and is therefore a 

 representative of some phenotype and of some 

 genotype. The words "phenotype" and 

 " genotype " were never intended to be limited 

 to statistically investigated organisms. Sta- 

 tistical investigation may discover, meas- 

 ure and describe phenotypes, but it does not 

 create them. Phenotypes and genotypes exist 

 among Mendelian hybrids just as among all 

 other organisms, and my use of the Men- 

 delian categories to illustrate the proper use 

 of these two words involves no "new version 

 of phenotype." 



G. H. SHULL 



COLD SPRING HARBOR, L. I., 

 April 29, 1912 



