290 NATHAN FASTEN. 



K.X PLANTATION OF PLATE II. 



FIG. 16. Pre-synapsis stage, primary spermatocyte, showing the parallel, 

 side-by-side arrangement of pairs of leptotene threads. 



FIG. 17. Pachytene stage, primary spermatocyte. 



FIGS. 18 AND 19. Diplotene and post-diplotene stages, primary spermatocyte. 



FIGS. 20 AND 21. Pre-tetrad, tetrad and dumb-bell formation, primary 

 spermatocyte. 



FIGS. 22 AND 23. Metaphase stages, primary spermatocyte. 



FIG. 24. Polar view, metaphase, primary spermatocyte, showing sixty-two 

 bivalent chromosomes. 



FIGS. 25 TO 28. Stages in division of primary spermatocyte. 



FIGS. 29 TO 34. Stages in division of secondary spermatocyte that possesses 

 a chromatoid body. 



FIGS. 35 TO 38. Stages in mitosis of secondary spermatocyte which lacks tin.- 

 chromatoid body. 



