FIG. 22. Mitosis in the segmenting egg of the clam, Unio. From Dahlgren 

 and Kepner. A. Prophase of the fourth cleavage. Chromatin reticulum; 

 centrosomes on opposite sides of nucleus. B. Prophase. Spireme beginning to 

 segment into chromosomes; nuclear membrane disappearing; spindle forming. 

 C. Late prophase. Chromosomes formed; spindle becoming completed; nucle- 

 olus nearly disappeared. D. Mesophase. Chromosomes in equatorial plate. 

 E. Early anaphase. Divergence of the daughter chromosome groups. F. 

 Telophase. Nuclear division completed and daughter nuclei reformed; cyto- 

 plasmic division commencing. 



