EXPLANATION OF PLATE IV 



Fig- 17. X i>o. Metaphase of first spermatocyte. Chromosomes grouped in 

 equatorial plate. Centrosomes on cell-membrane. Spindle fibers do not extend to 

 centrosomes, but lie free in the cytoplasm, their ends converging slightly. Nucleolar 

 remains of karyosphere drawn to extremities of spindle fibers. 



FIG. 1 8. X 1,000. Early anaphase. Chromosomes have divided, and again 

 assumed their dumb-bell shape. Nucleolar remains of karyosphere drawn farther 

 toward the centrosomes. Net-work still regular. 



Fig. 19. X 1 ,000. Late anaphase. Chromosomes at poles of the spindle. 

 Nucleolar remains of karyosphere drawn almost to cell-wall. Net-work beginning 

 to break down in equatorial plate. 



FIG. 20. X l,ooo. Early telophase. Chromosomes massed at ends of spindle 

 fibers, which have spread across equatorial region and begun to disintegrate at the 

 extremities. Centrosomes have disappeared. Region from centrosomes to equatorial 

 area considerably lighter, showing influence of centrosomes. 



FIG. 21. X l>ooo. Spindle forming into sheaf-shaped bundle. Chromosomes 

 somewhat spread, becoming granular except accessory, which is still homogeneous. 



FIG. 22. X 1 ) 000 - Telophase of first spermatocyte. The vesicles in each one of 

 which a chromosome has become enclosed are beginning to fuse. 



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