THE CELLULAR BASIS 157 



that every oosperni and every individual which 

 develops from it is absolutely unique. 



Indeed the production of unique individuals 

 seems to be the chief purpose and result of 

 sexual reproduction. In asexual reproduc- 

 tion the individual variations which occur are 

 chiefly if not entirely due to environment, 

 but in sexual reproduction they are also due to 

 new combinations of hereditary elements. 

 The particular germinal organization trans- 

 mitted from one generation to the next de- 

 pends upon (a) the ancestral organization, 



(b) the particular character of the cell di- 

 visions by which the germ cells are formed, 



(c) the particular kinds of egg and sperm 

 cells which combine in fertilization. The an- 

 cestral organization determines all the gen- 

 eral characteristics of race, species, genus, 

 order, phylum. It determines the possibili- 

 ties and limitations of individual variations. 

 Given a certain ancestral organization, the 

 individual peculiarities of the germ cells are 

 determined by the particular character of cell 

 division by which the germ cells are formed, 

 and the peculiarities of the individuals or per- 



