348 HEREDITY AND ENVIRONMENT 



nificant, and this furnishes the basis of his 

 theory. Semon holds that every condition of 

 hfe, every functional activity of an organism 

 leaves a permanent record of itself in what he 

 calls an "engramme." If these conditions or 

 activities are long continued their engrammes 

 are heaped up and affect heredity. Se- 

 mon does not ask if "acquired characters" are 

 inherited, but rather "Are the hereditary po- 

 tencies of the germ cells altered by stimuli act- 

 ing on the parental body?" This is a very 

 different thing from the inheritance of a par- 

 ticular acquired character, and there is evi- 

 dence that such stimuli may in some instances 

 produce changes in the hereditary constitution 

 of the germ cells, especially at or near their 

 maturation stages. The observations and ex- 

 periments of deVries on the evening primrose, 

 of Hansen on yeast and of Fischer, Standfuss. 

 Tower and Morgan on the production of mu- 

 tations in insects favor such a belief. 



On the other hand certain changes may be 

 produced in germ cells or embryos which last 

 only for a generation or two and then disap- 

 pear. It is well known that plants grown in 



