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THE NEW INDIVIDUAL 



Part IV 



XO 

 Grasshopper 



Domestic fowl 



Honeybee 



Fig. 20.6. Four types of sex determination, different ways by which the chromo- 

 somes determine the sex of an individual. Man, cells of the body (except sex cells) ; 

 male and female each has 48 chromosomes. In males the members of one pair 

 called xy are of different sizes, y being the smaller. In females, members of the 

 counterpart of this pair are the same size and called xx. 



All of the eggs contain an x chromosome. Half of the sperm cells contain an x 

 and half of them the y chromosome. Thus the sex of an individual depends upon 



