760 THE AMERICAN NATURALIST [Vol. XLIV 



tants, and we can easily see how de Vries was misled by his ma- 

 terial. He got the idea that the organism is composed of dis- 

 tinct and independently heritable units and that when one of 

 these units is lost out or when a new one springs into existence 

 we get an organism which differs in all of its characters from 

 the parent form. He assumes that all permanent evolutionary 

 change comes about by the introduction of new pangenes. For 



