44 



HEREDITY AND SEX 



chromosomes produces an individual with fourteen 

 chromosomes. This individual is a female. 



In another species of insect, Lygseus bicrucis, the male 

 differs from the female, not in having a different 



^y^ 



aetts 



S 







! I; 



D^ 



Fig. 23. 



j:^ 



number of chromosomes as in protenor, but by the 

 occurrence of a pair of different-sized chromosomes. 



The body cells of the male have twelve ordinary 

 chromosomes and tw^o sex chromosomes — one larger, 

 X, than the other, Y (Fig. 23, A). 



After synapsis there are six double chromosomes and 

 the two sex chromosomes, called X and Y (Fig. 23, D). 



