EXPLANATION OF PLATE. 



All figures were drawn with the aid of a camera lucida and are magnified 

 2073 diameters. 



Figure 1. Primary spermatocyte, resting stage. 



Figure 2. Primary spermatocyte ; tlie two centrosomes moving apart. 



Figures. Primary speruiatocyte ; the centrosomes have arrived at opposite 

 poles of cell. 



Figure 4. Proximal fiiiger-like process of the cell, terminating in the proximal 

 centrosome ; from the distal centrosome extend prominent extranuclear fibres. 



Figure 5. Nucleus of primary spermatocyte, sliowing sixteen dyads. 



Figure 6. Cross section of a primary spermatocyte in the same stage as that of 

 Figure 9. 



Figure 7. Elongation of the nucleus toward the distal centrosome. 



JiGURE 8. The nucleus exhibits a spindle-shaped elongation, and intranuclear 

 spindle fibres are established. 



• Figure 9. The interzonal body has migrated to the base of the finger-like 

 process. 



Figure 10. The interzonal body in the course of being constricted off from 

 the cell. 



Figure 11. The interzonal body is detached, and there is a typical spindle in 

 the beginning of the metaphase. 



Figure 12. Late anaphase. 



Figure 13. Finger-like process surmounted by chromatin of polar cell. 



Figure 14. Chromatin of finger-like process nearly detached from the process. 



Figure 15. Spermatid, interzonal body reduced in size, and polar cell. 



