Modification of Germinal Constitution of Organisms 243 



'Normal Range of Variation" 



Classes 23 22 21 20 19 18 17 16 15 14- 13 12 II 10 9 8 7654324 a. b. a d. e. f . h. 



FIG. 79. Diagrammatic representation of the results obtained in the creation 

 of albinic and melanic races by the combined influence of selection and environ- 

 mental stimuli. These experiments show a difference from the results shown in 

 some of the former diagrams, in that there are a number of extreme variations 

 produced which apparently are stable in several successive generations; however, 

 when the selective effect is removed the divergent race is seen not to be stable and 

 to revert with considerable rapidity to the mediocre or parental stock. 



