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). 
