THE WONDER OF LIFE 603 



belief took before Weismann's scepticism. The change 

 to evergreenness was physiological rather than structural 

 a change in the rhythm of metabolisnTperhaps. More- 

 over it is quite likely that the climatic change operating 

 for many years influenced the germ-cells of the peach along 

 with the whole tree. This is a legitimate theoretical dis- 

 tinction, though it is not, perhaps, of much practical im- 

 portance. 



Let us try to state Semon's central position without 

 using his somewhat bewildering terminology. Every one 

 admits that an organism reacts to many different kinds 

 of external change. It registers within itself its novel 

 experiences. Some of these produce changes in what 

 Semon calls the ' energetic situation ' of the whole organism, 

 and these are supposed to impress themselves in a lasting 

 way on the germ-cells. The impressed effects on the germ- 

 cells are conveniently called * engrams '. Just as our mind 

 becomes rich in memories of experiences, so the germ- plasm 

 becomes stored with many ' engrams '. 



The second general idea in Semon's theory concerns de- 

 velopment. When the germ- cell which has been impressed 

 with ' engrams ' comes to develop, a partial recurrence 

 of the ' energetic situation ', which previously acted * en- 

 graphically ', will call forth the latent engrams into expres- 

 sion. Given appropriate stimuli the ' memories ' will stir, 

 and they will influence what is going on, namely the 

 development of the individual. 



Let us recapitulate. Year after year a complex influ- 

 ence plays upon the organism and modifies its constitution. 

 The internal ' energetic situation ' is changed and result- 

 ing stimuli are supposed to pass to the germ-cells. The 

 corresponding changes in the germ-cells are called en- 



