INDIVIDUAL AND ANCESTRAL DEVELOPMENT 319 



The doctrine that individual development is due to the reciprocal 

 interaction between the embryo and its internal environment is 

 inadequate, but when it is joined to the doctrine that ancestral 

 development is due to the reciprocal interaction between the living 

 being and its environment of competitors and enemies, it seems to 

 me to give an outline of an epigenetic account of both individual 

 development and ancestral development: an outline which it will 

 require generations of investigators to expand and perfect. In view 

 of this, is it not time to have done with the pre- Darwinian meta- 

 physical notion of species as something that resides in living beings 

 and is handed down by a substance of inheritance? 



