428 E. L. SHAFFER. 



EXPLANATION OF PLATE I. 



FIG. i. Primary spermatogonium. No clear indication of the presence of 

 mitochondria. Note small mass of chromatoid substance in cytoplnsm. 



FIG. 2. Anaphase of secondary spermatogonium. Note lightly-staining cyto- 

 plasm, well-defined cell-plate, and the tendency of the cell to become round. 



FIG. 3. Metaphase plate of ovarian follicle cell, showing thirteen equal pairs 

 of chromosomes. 



FIG. 4. Resting stages of secondary spermatogonia. Mitochondria granular 

 and diffusely spread. Note persistence of spindle and cell-plate. 



FIG. 5. Degenerating spermatogonium. Mitochondria larger in size; chro- 

 matin concentrated in two large karyosomes. 



FIG. 6. Pachytene stage of first spermatocyte. Mitochondria still granular, 

 with only a slight indication of threads forming; note denser perinuclear zone and 

 the persistence of the spindle remains of the last spermatogonial division. 



FIG. 7. Late prophase of first spermatocyte, Flemming fixation. Nucleus 

 uncut. Mitochondria filar, with their lengths in the direction of the chief cell axis. 



FIG. 8. Sirrrilar stage as above, showing remains of spindle still persisting, 

 two large cytoplasmic vacuoles of problematic origin, and small bodies in the cyst 

 cavity which have been budded off from the cytoplasm of the spermatocytes. 



FIG. 9. Prophase of first spermatocyte, Hermann fixation; showing agglomera- 

 tion of the mitochondria. 



FIG. 10. Formation of the first maturation spindle; mitochondria at one side. 



FIG. ii. Mitochondria beginning to envelop first maturation spindle. 



FIG. 12. Cross-section of the metaphase plate of first spermatocyte, showing 

 mitochondria completely surrounding the spindle. Thirteen bivalent chromosomes. 



