356 HEREDITY AND ENVIRONMENT 



their intimate union in a hybrid, so that pure 

 dominants and pure recessives may be obtained 

 in subsequent generations from this mixture? 

 Why does every child have to learn anew what 

 his parents learned so laboriously before him? 

 Even the strongest defenders of the inheri- 

 tance of acquired characters are constrained 

 to admit that it occurs only sporadically and 

 exceptionally. 



Many modifications of the Lamarckian hy- 

 pothesis of the inheritance of acquired char- 

 acters have been proposed in recent years. 

 Foremost among these are the "mneme" 

 theory of Semon and the "centro-epigenesis" 

 theory of Rignano. To Semon as to many 

 other biologists the apparent resemblance be- 

 tween memory and heredity has seemed sig- 

 nificant, and this furnishes the basis of his 

 theory. Semon holds that every condition of 

 life, 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 



