THE 



AMERICAN NATURALIST 



Vol. XLVIII January, 19U No. 565 



A GENETIC ANALYSIS OF THE CHANGES PRO- 

 DUCED BY SELECTION IN EXPERIMENTS 

 WITH TOBACCO 1 



PROFESSOR E. M. EAST and H. K. HAYES 

 Bussey Institution of Harvard University 

 The Problem 

 In 1903 Johannsen announced that continued selection 

 of the extreme values of certain quantitative characters 

 in successive self-fertilized generations of a number of 

 strains of beans had produced no changes in the mean 

 values of the characters. He concluded that these par- 

 ticular strains were homozygous for the gametic factors 

 whose interaction resulted in the characters investigated, 

 that these homozygous characters may be properly de- 

 scribed by one or more gametic factors nonvariable in 

 transmissible qualities and properties, and that the varia- 

 tions observed in the characters of any single fraternity 

 were due entirely to the action of environmental condi- 

 tions during ontogeny and were not inherited. Funda- 

 mentally, these conclusions were a recognition of the gen- 

 eral value of Mendelian description for all forms of in- 

 heritance through sexual reproduction, combined with an 



i These investigations were conducted with funds furnished by the Con- 

 necticut Agricultural Experiment Station from their Adams' appropria- 

 tions, by the Bureau of Plant Industry of the United States Department of 

 Agriculture, and by the Bussey Institution of Harvard University, and the 

 writers desire to take this opportunity of expressing their sincere appre- 



