360 HEREDITY AND ENVIRONMENT 



a given heredity the characteristics of the 

 developed organism may vary enormously 

 depending upon the extrinsic factors. He- 

 reditary possibilities are not changed by acci- 

 dents of environment but development is so 

 changed. After the fertilization of the egg the 

 hereditary potencies of every organism are un- 

 alterably fixed but the extrinsic factors re- 

 main variable and may be controlled. 



All of our social and ethical institutions such 

 as government, education and religion deal 

 only with extrinsic factors of development and 

 of life. Nevertheless there is no evidence 

 that such extrinsic influences ever modify he- 

 redity, no evidence that the effects of good 

 environment or good training ever change the 

 germinal constitution. The influences of 

 environment and education affect only the de- 

 velopment of the individual and not the con- 

 stitution of the race, and consequently such in- 

 fluences are temporary in effect and must be 

 repeated generation after generation. 



But though the effects of environment and 

 training are not inherited, the environment 

 and training and experience of former gener- 



