MITOSIS AND AMITOSIS 



23 



3. The nuclear membrane and nucleolus disappear, the nucleoplasm and 

 cytoplasm becoming continuous. 



4. During the above changes the chromatic network of the resting nucleus 

 resolves itself into a skein or spireme, the thread of which soon breaks up 

 into distinct, heavily-staining 



bodies, the chromosomes. A 

 definite number of chromo- 

 somes is always found in the 

 cells of a given species. The 

 chromosomes may be block- 

 shaped, rod-shaped, or bent 

 in the form of a U. 



5. The chromosomes ar- 

 range themselves in the equa- 

 torial plane of the central 

 spindle. If U-shaped the 

 base of each U is directed 

 toward a common center. 

 The ampluaster and the eliro- 

 mosomes together constitute a 

 mitotic figure and at the end 

 of the prophase this is called 

 a monaster. 



Metaphase. — The longi- 

 tudinal splitting of the chro- 

 mosomes into exactly similar 

 halves constitutes the meta- 

 phase (Fig. S, IV, V). The 

 aim of mitosis is thus accom- 

 plished, an accurate division 

 of the chromatin between the 

 nuclei of the daughter cells. 



Anaphase. — At this stage the two groups of daughter chromosomes separate 

 and move up along the central spindle fibers, each toward one of the two asters. 

 Hence this is called the Master stage (Fig. 8, VI). At this stage, the centrioles 

 may each divide in preparation for the next division of the daughter cells. 



Telophase (Fig. 8, VII, VIII). — 1. The daughter chromosomes resolve them- 



VI ..--" 



m 



FlG. S. — Diagram of the phases of mitosis (Schafer). 



