130 



GENETICS 



progeny obtained, in the direction of the selection simply 

 by isolating out a pure line of one type. Thus beans 

 Pure Line chosen from the 



extreme 1 e f t- 

 hand test tube in 

 the population 

 cited would be- 

 long only to pure 

 line 2, while those 

 taken from the 

 extreme right- 

 hand test tube 

 could belong only 

 to pure line 3. 



Galton's "law 

 of regression," 

 namely, that 

 minus parents 

 give minus off- 

 spring and plus 

 parents plus off- 

 spring, with a 

 tendency to re- 

 version from gen- 

 eration to gener- 

 ation, depends 



FIG. 26. Diagrams showing five pure lines s i m ply upon a 

 and a population formed by their union. r t j r 



The beans of each pure line are repre- partial but not 

 sented as assorted into inverted test tubes . i 



making a curve of fluctuating variability. < 



Test tubes containing beans of the same tion of pure lines 

 weight are placed in the same vertical f , 



row. After Johannsen. out of a popula- 

 tion. 



