EXPLANATION OF PLATE IV. 



Fig. 1. The usual arrangement of the chromosomes in the eqtia- 

 torial plate of spermatocytes of Bruchus. 



Fig. 2. An equatorial plate showing but nine chromosomes. 



Fig. 3. A lateral view of the mitotic figure. (Metaphase). 



Fig. 4. An unusual arrangement of the chromosomes in the equa- 

 torial plate. 



Fig. 5. Division of the tetrads to diads. (Anaphase). 



Fig. 6. Division of the tetrads to diads. (Late anaphase). 



