INTRODUCTION 15 
tween the centrosomes (D, ep). The stage shown in 
Fig. 3, D, is known as the amphiaster ; at this time 
Fic. 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 
