Modification of Germinal Constitnlion oj Organisms 243 



"Normal Range of Variation" 



Classes 23 22 21 20 19 18 17 16 15 1+ 13 12 II 10 9 8 7 6 5 4 3 2 I a. b. c. d. e. f g h 



Fig. 79. — Diagrammatic reprcscntalion of ihc results obtained in the creation 

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

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

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

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

 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. 



