384 The Spermatogenesis of Bufo Lentiginosus 
EXPLANATION OF PLATE II. 
Fics. 24-25. Post-synizesis stages in the primary spermatocytes. The 
chromatin is being evolved in the form of a continuous spireme. 
Fias. 26-27. Continuous spireme found in the primary spermatocytes at 
the end of the synizesis stage. 
Fig. 28. Beginning of the segmentation of the continuous spireme into 
the reduced number of chromosomes. 
Fig. 29. A slightly later stage than that shown in Fig. 28. The spireme 
is being constricted into chromatin segments. 
Fig. 30. The stage succeeding that shown in Fig. 29. The chromosomes 
are nearly separated and they are distinctly dumbbell shape. 
Figs. 31-33. Formation of ring-shaped chromosomes in the early prophase 
of mitosis. 
Fic. 34. Primary spermatocyte in which the chromosomes are in the form 
of bead-like segments. before they have separated. Such segments later form 
rings. 
Fic. 35. Primary spermatocyte in which the spireme has segmented into 
rectangular shaped blocks. 
Fic. 36. Formation of ring-shaped chromosomes from the spireme in the 
early prophase of mitosis. 
Fic. 37. Primary spermatocyte in the early prophase of mitosis. The 
nucleus contains dumbbell-shaped chromosomes that are connected end to 
end by linin fibers. 
Fic. 38. About the same stage as Fig. 37. The nucleus contains both dumb- 
bell and ring-shaped chromosomes. 
Fig. 39. Later prophase of mitosis. Chromosomes of different shapes are 
seattered throughout the nucleus. 
Fic. 40. Ring-shaped chromosomes in the nucleus previous to the forma- 
tion of the first maturation spindle. 
Fies. 41-42. Stages in the formation of the first maturation spindle. 
Fic. 43. Equatorial plate of the first maturation spindle showing 12 
chromosomes of different sizes. 
Fics. 44-45. Longitudinal sections of the first maturation spindle during 
metakinesis. 
Fic. 46. Same stage as the preceding. The chromosomes have formed 
typical tetrad groups. 
