210 S. W. GEISER. 



PLATE II. 



FIGS. 20-21. Tetrads. 

 FIG. 22. Diakinesis. 



FIG. 23. Tetrads grouping to form an equatorial plate. 

 FIGS. 24-25. First-spermatocyte divisions, viewed from the side. 

 FIG. 26. Metaphase plate of second-speratocyte division. 

 FIG. 27. Fusion of chromosomes after completion of the second-spermato- 

 cyte division. 



FIGS. 28-30. Stages in the reconstitution of the spermatid nucleus. 



