GENETICS AND ETHICS 469 



The truth then seems to lie somewhere be- 

 tween these two extremes. Our personalities 

 were not absolutely predetermined in the germ 

 cells from which we came, and yet they have 

 arisen from those germ cells and have been 

 conditioned by them. When it is said that any 

 characteristic is predetermined in the germ 

 cell, what does this mean? What but that the 

 development of that characteristic is made pos- 

 sible? Adult characteristics are potential and 

 not actual in the germ, and their actual ap- 

 pearance depends upon many complicated re- 

 actions of the germinal units with one another 

 and with the environment. In short, our ac- 

 tual personalities are not predetermined in the 

 germ cells, but our possible personalities are. 



2. The Determinism of Environment. — 

 This determinism of heredity is matched by a 

 corresponding determinism of environment. 

 Life is possible only within rather narrow 

 limits of physical and chemical conditions and 

 in the main these limits are fixed by the con- 

 stitution of nature. But apart from these an- 

 tecedent conditions of life in general there are 

 many minor conditions of environment which 



