o, 



[Reprinted from SCIENCE, N. S. t Vol. XXXV., No. 

 892, Pages 182-188, February f , 





" PHENOTYPE " AND " CLONE " 



IN calling attention to the frequent misuse 

 of the words " genotype " and " pure line," 

 Jennings says 1 that the word " phenotype " 

 " designates a group of organisms which in 

 outward appearance seem to belong to one 

 type, although in hereditary constitution they 

 may actually differ greatly. Genotype, in 

 Johannsen's usage, is not directly contrasted 

 with phenotype," etc. 



As I have also used " phenotype " with the 

 meaning indicated by Jennings, I did not 

 recognize the fundamental misconception in- 

 volved in the quotation given above, when I 

 wrote my note 2 in response to the article from 

 which this quotation is taken. My attention 

 has been called to this point by Dr. Jo- 

 hannsen, and it seems best to set the matter 

 straight at once, in connection with the at- 

 tempt made by Jennings and seconded by 

 myself, to restrict to their original meanings, 

 the other terms introduced by Johannsen. 

 " Phenotype " and " genotype," when both are 

 rightly used, are contrasted terms, both be- 

 ing abstractions referring to the type to 

 which an individual or group of individuals 

 belongs, and not to the group of individuals 

 belonging to that type. To illustrate the use 

 of " phenotype " in its correct sense, reference 

 may be made to the F* of a Mendelian hybrid. 

 When an F hybrid whose genotypic constitu- 

 tion may be represented by the formula, 

 XXAaB~b, is self -fertilized or crossed with 



1 SCIENCE, December 15, 1911. 



2 SCIENCE, January 5, 1912. 



