194. HEREDITY AND ENVIRONMENT 



characters are associated with the chrom- 

 osomes. The differentiation of the oosperm 

 into the developed organism is accomplished 

 in part by the associations and dissociations of 

 germinal units which lead to the formation of 

 new materials, and in part by the segregation 

 and localization of these in definite cells. 



Germ cells and probably all other kinds of 

 cells are almost incredibly complex. We know 

 that former students of the cell greatly under- 

 estimated this complexity and there is no 

 reason to suppose that we have fully compre- 

 hended it. What Darwin said of the entire 

 organism may now be said of every cell: "An 

 organic being is a microcosm— a little universe, 

 formed of a host of self-propagating organ- 

 isms, inconceivably minute and numerous as 

 the stars in heaven." 



