FIG. 54. CELL-DIVISION. (After Rauber-Kopsch). 



Fig. 1 shows a cell before the process of nuclear division has quite begun. 

 The chromatin in the nucleus is in the form of a network. The centrosome 

 has divided into two and is surrounded by very delicate radiating filaments. 



Fig. 2. The chromatin reticulum is being unravelled into a number of 

 chromosomes and the nuclear membrane is giving way. The centrosomes 

 are separating. 



Fig. 3. The nuclear membrane is gone, the chromosomes are more 

 distinct. 



Fig, 4. The chromosomes are arranged (in an astroid) on the equatorial 

 plane in the middle of the cell. There is a centrosome at each pole, and 

 a nuclear spindle of fine threads between. Some threads run from pole to 

 pole. Some are attached to chromosomes at the equator. The changes 

 up to this point constitute the prophases. 



Fig. 5. Each chromosome is split lengthwise. (Metdkinesis.) 



Fig. 6. The chromosomes form a diastroid figure and there is a move- 

 ment towards the pole. In each contingent there is one half of each 

 chromosome. 



Fig. 7. The chromosomes continue to move from the equator. The 

 cell-substance begins to be divided. 



Fig. 8. At each pole a daughter nucleus begins to be constituted. A 

 partition is formed across the equator of the cell. 



Fig. 9. There are now two cells, and the daughter-nuclei are passing 

 into a resting phase. The centrosome has again become paired. The 

 changes after the splitting of the chromosomes and on to reconstruction 

 constitute the anaphases. 



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