50 GERM-CELL CYCLE IN ANIMALS 



As already indicated, perhaps the most essential 

 phase in the fertilization process does not occur until 

 the homologous maternal and paternal chromosomes 

 unite during synapsis, when the germ cells of the 

 new individual become mature. The immediate 

 results of fertilization are : (1) the inauguration of 

 the development of the egg, (2) the increase of the 

 chromosomes from the haploid to the diploid (so- 

 matic) number, and (3) the union of hereditary 

 substances from, as a rule, two individuals. 



This completes the last stage in the germ-cell 

 cycle of animals. Many extremely important and 

 interesting phases of the subject have had to be 

 omitted from the account. Certain of these will 

 be more fully discussed in succeeding chapters, es- 

 pecially those concerned with the early history of 

 the germ cells during embryological development, 

 but for the details of the nutrition, growth, matura- 

 tion, and fertilization of the germ cells, the reader 

 must be referred to other sources (Wilson, 1900; 

 Jenkinson, 1913; Kellicott, 1913). 



