GENETICS AND ETHICS 463 



science recognizes everywhere the inevitable se- 

 quence of cause and effect, the universality of 

 natural processes, the reign of natural law. 

 Man also is a part of nature, a part of the 

 great mechanism of the universe, and all that 

 he is and does is limited and prescribed by laws 

 of nature. Every human being comes into ex- 

 istence by a process of development, every step 

 of which is determined by antecedent causes. 



1. The Determinism of Heredity. — There 

 can be no doubt that the main characteristics 

 of every living thing are unalterably fixed by 

 heredity. Men differ from horses or turnips 

 because of their inheritance. Our family traits 

 were determined by the hereditary constitu- 

 tions of our ancestors, our inherited personal 

 traits by the hereditary constitutions of our 

 fathers and mothers. By the shuffle and 

 deal of the hereditary factors in the forma- 

 tion of the germ cells and by the chance union 

 of two of these cells in fertilization our heredi- 

 tary natures were forever sealed. Our ana- 

 tomical, physiological, psychological possibili- 

 ties were predetermined in the germ cells from 

 which we came. All the main characteristics 



