272 MARY T. HARMAN. 



EXPLANATION OF PLATES. 



All figures were made at table level by means of a Zeiss compensating ocular 

 No. 6 and a 1.5 mm. objective with the aid of a camera lucida. The drawings 

 were enlarged two diameters and then reduced one third. 



PLATE I. 



FIG. i. Early prophase of spermatogonial division. A, a mass of chromatin 

 which does not become reticular but remains more or less compact. 



FIG. 2. Formation of spermatogonial chromosomes. 



FIGS. 3 TO 6. Metaphase plates of spermatogonial chromosomes. 



FIG. 7. Metaphase, lateral view, spermatogonial division showing position of 

 the chromosomes on the spindle. 



FIG. 8. Anaphase of spermatogonial division. 



FIG. 9. Beginning of the growth period. A, a mass of chromatin which does 

 not pass into a reticular condition and forms the accessory chromosome. 



FIG. 10. Formation of chromatin thread. 



FIG. ii. Synizesis. 



FIG. 12. Beginning of the formation of the primary spermatocyte chromosomes. 



