204 



THE PERPETUATION OF ADAPTATIONS 



i.l 



FIG. 88. Diagram showing the early stages of mitosis. A, Resting cell with 

 reticular nucleus and nucleolus; at c, the attraction sphere with two centrosomes; 

 B, early prophase, the chroma tin in the form of a continuous thread or spireme; 

 the centrosomes have separated forming a spindle figure between them; this is 

 the amphiaster (at a) ; C, D, two later stages in the prophase of division in which 

 the spireme is divided into segments, the chromosomes; E, formation of the 

 mitotic figure with centrosomes at the poles and with the chromosomes split longi- 

 tudinally F, the mitotic figure fully established. (From Wilson.) 



