THEORY OF EVOLUTIOX 



99 



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Fig. 51. The two maturation divisions of tiie egg. Tlie divi- 

 sions are unequal, so that two small polar bodies are formed 

 one of these subsequently divides. The three polar bodies 

 and the egg are comparable to the four sperms. 



50) come to contain only lialf tlie total num- 

 ber of chromosomes. 



When the eggs are fertilized tlie Avhole num- 

 ber of chromosomes is restored again. 



I The Mechanism of ^Iexdeliax Heredity 

 Disco^t:rei) IX the Behavior of 

 THE Chromosomes 



If the factors in heredity are carried in the 

 chromosomes and if the chromosomes are defin- 

 ite structures, we should anticipate that there 

 I should be as many groups of characters as 

 there are kinds of chromosomes. In only one 



