2io Heredity and Environment 



brought about by extremely numerous permutations in the distri- 

 bution of the chromosomes of the sex cells in maturation and ferti- 

 lization. Sex is an inherited character dependent, primarily, upon 

 an alternative distribution of certain chromosomes to the germ cells. 

 There is much evidence that the factors for all sorts of Mendelian 

 characters are associated with the chromosomes. The differen- 

 tiation of the oosperm into the developed organism is accom- 

 plished in part by the interaction of chromosomes and cytoplasm 

 which leads to the formation of new materials, and in part by the 

 segregation and localization of these materials 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 underestimated this complexity and there is no reason to 

 suppose that we have fully comprehended it. What Darwin said 

 of the entire organism may now be said of every cell : It "is a mi- 

 crocosm a little universe, formed of a host of self -propagating 

 organisms, inconceivably minute and numerous as the stars in 

 heaven." 



