144 JAMES O. FOLEY. 



PLATE II. 



FIGS. 15, 16, AND 17. Resting spermatogonia of last multiplication division. 



FIGS. 1 8 AND 19. Leptotene stages. 



FIGS. 20, 21, AND 22. Zvgotene stages. 



FIG. 23. Late zygonema or early pachynema. 



FIG. 24. Pachytene stage. 



FIG. 25. Beginning of synizesis. The pachytene thread is massing around the 

 nuclear membrane. 



FIG. 26. Synizesis further advanced. 



FIG. 27. Synizesis showing a looped condition of the chromatin. 



FIG. 28. Synizesis completed. Complete contraction. 



FIG. 29. Initial breaking up of synizesis. Only eight of the eleven chromatin 

 masses are shown in figure. 



FIG. 30. Final breaking up of synizesis. 



FIG. 31. Continuation of unravelling process as shown in figure 30 and the 

 beginning of diakenesis. 



FIGS. 32, 33, AND 34. Various stages in diakenesis and contraction of the rings. 



FIGS. 35 AND 36. Metaphases of primary spermatocytes showing tetrad nature 

 of the chromosomes. Fig. 35 magnified 1650 diameters. 



FIG. 37. Early anaphase of primary spermatocyte. 



FIG. 38. Secondary spermatocyte in resting condition. 



FIGS. 39, 40, AND 41. Early metaphase of secondary spermatocytes. Only six 

 of the chromosomes are shown in figure 41. 



FIG. 42. Late metaphase of secondary spermatocyte. 



FIG. 43. Late metaphase spindle of secondary spermatocyte. 



FIG. 44. Anaphase of secondary spermatocyte showing eleven univalent 

 chromosomes. 



FIG. 45. Resting spermatid. 



FIGS. 46 TO 55. Various stages in nuclear behavior during the transformation 

 of the spermatid. Figs. 51, 54, and 55 are taken from smears. Condition shown in 

 figure 51 is similar to that shown in figure 52 but viewed from a different angle. 



