INTRODUCTION 



15 



tween the centrosomes (Z>, ep) . The stage shown in 

 Fig. 3, D, is known as the amphiaster ; at this time 



FIG. 3. Mitosis. Diagrams illustrating mitotic cell division. (From 

 Wilson.) A, resting cell; B, prophase showing spireme and nucle- 

 olus within the nucleus and the formation of spindle and asters (a) ; 

 C, later prophase showing disintegration of nuclear membrane, and 

 breaking up of spireme into chromosomes; D, end of prophases, 

 showing complete spindle and asters with chromosomes in equatorial 

 plate (ep); E, metaphase each chromosome splits in two; F, ana- 

 phase the chromosomes are drawn toward the asters, if = inter- 

 zonal fibers; G, telophase, showing reconstruction of nuclei; H, later 

 telophase, showing division of the cell into two. 



all of the mechanism concerned in mitosis is present. 

 There are two asters, each consisting of a centrosome 



