THE CELL AND CELL PROLIFERATION. 7 



with its aster (or two centrioles with asters) and one-half the achromatic 

 spindle. The resting nucleus is formed by a reverse of the series of changes 

 described as occurring in the prophase, the chromosomes uniting end to end to 

 form a skein or spireme, lateral buds appearing which anastomose, thus giving 

 rise to the reticulum of the resting nucleus. The nucleolus reappears as 

 mysteriously as it disappeared during the prophase and the nuclear membrane 

 is reformed. 



Fig. 4. — Diagrams of successive stages of mitosis. Wilson. 



E, Metaphase. Longitudinal splitting of chromosomes to form daughter chromosomes, ep; 



n, cast-off nucleolus. 



F, Anaphase. Daughter chromosomes passing along fibers of achromatic. spindle toward centro- 



somes; centrioles again divided ; */, interzonal fibers of central bpindle. 



G, Late anaphase. Chromosomes at ends of spindle; spindle fibers less distinct; thickenings of 



fibers in equatorial plane indicate beginning of cytoplasmic plate; cell body beginning to 

 divide; nucleolus has disappeared. 

 H, Telophase. Cell body divided; chromatic substance in each daughter nucleus as in resting 

 stage; nuclear membrane and nucleolus has reappeared in each daughter cell. 



It is to be noted that the numbej of chromosomes which enter into the forma- 

 tion of the chromatic reticulum of the resting nucleus is the same as the number 

 of chromosomes derived from that nuclear reticulum when the cell prepares for 

 mitotic division. It is thus possible that the chromosomes maintain their 

 individuality even during the resting stage. 



In plant mitosis the central spindle fibers show minute chromatic thicken- 



