430 E. L. SHAFFER. 



EXPLANATION OF PLATE II. 



FIG. 13. Anaphase of first spermatocyte, showing relation of spindle and 

 mitochondria. 



FIG. 14. Late anaphase of first spermatocyte. Cell constriction has divided 

 mitochondria so that the daughter cells contain approximately equal amounts. 



Fie. 15. Cross-section of first spermatocyte near pole of spindle, showing 

 absence of mitochondria here. 



FIG. 16. Second spermatocytes (interkinesis). Mitochondria present in 

 daughter cells in compact masses, also showing the persistence of the spindle and 

 cell-plate. 



FIG. 17. Metaphase of second spermatocyte. Mitochondria again sur- 

 rounding the spindle peripherally. 



Fie. 1 8. Telophase of second maturation. Mitochondria again divided by 

 the cell constriction into two equal masses. Note position of the centrosome (c) 

 lying on the nuclear membrane. 



FIG. 19. Spermatid. Nebenkern (N) derived from the mitochondria, with a 

 peripheral vacuolated portion. Persistence of centrosome (c) with a precocious 

 growth of the axial filament; spindle derivative (s) enclosing a deeply-staining 

 body. 



FIG. 20. Changes in the Nebenkern during transformation of spermatid. 

 c, cross-section of the tail showing the Nebenkern lying on each side of the axial 

 filament, d, Nebenkern with lighter central portion where spindle of previous 

 division had passed through. 



FIG. 21. Stage in the transformation of the spermatid. A portion of the 

 spindle derivative (s) occupies a position at the head end and a portion passes 

 into the tail. Nebenkern elongating, and the axial filament growing out of the 

 centrosome (c) between the two halves of the Nebenkern. 



FiG. 22. Later stages in the transformation of the spermatid. b, giant 

 spermatid. 



