SEX-CHROMOSOMES AND INHERITANCE 181 



groups. Several stages in the maturation of the sperma- 

 tozoon of the bee are shown in Fig. 80. In a, the spindle 

 for the first spermatocyte division has appeared. A small 

 piece of the cytoplasm cuts off, but the chromosomes do 

 not separate, and they return again {h and c) to a resting 



a 



a e 



Pro. 80. — First spermatocyte divisions a-c, and the second spermatocyte division d-g 



in the bee. (After Meves.) 



stage. Another spindle forms {d)^ and the chromosomes 

 separate into two groups, one of which is pinched off 

 as a rudimentary cell that never becomes a spermatozoon. 

 Hence only one, and not four spermatozooa as in ordi- 

 nary cases, is formed from each spermatocyte. In the 

 hornet (Fig. 81), the spermatogenesis is similar to that of 

 the bee in that the first division is abortive. It is different 



