116 



GENETICS 



tube of pure line 5, may be identical with the com- 

 monest size in another line, as pure line 2. The 

 PURE LINE five pure lines 



represented in 

 Figure 40 are 

 combined in a 

 population at the 

 bottom of the 

 figure, making 

 a phenotype 

 that marks the 

 five phenotypes 

 above, which are 

 also five geno- 

 types. In the 

 population, how- 

 ever, the five 

 genotypes are 

 hidden within 

 one phenotype. 

 Hence, while 

 selection within 

 a pure line has 



POPULAT.ON | ]| lUiiiiiiil II II II no hereditary in- 

 fluence, it is evi- 

 dent that selec- 

 tion within a 

 population may 

 shift or move 

 over the type 

 of the progeny 



FIG. 40. Diagrams showing five pure lines 

 and a population formed by their union. The 

 beans of each pure line are represented as as- 

 sorted into inverted test tubes making a curve 

 of fluctuating variability. Test tubes contain- 

 ing beans of the same weight are placed in the 

 same vertical row. After Johannsen. 



