16 



HEREDITARY CHARACTERS 



being at opposite poles of the cell, and the chromosomes being 

 attached to the spindle on the equatorial plane (Figs. 5 and 6). 

 The chromosomes still retain the shape of U's and V's in the 

 majority of cases, and they lie flat upon the equatorial plane 



FIG. 4. Disappearance 

 of nuclear membrane. 



FIG. 5. Chromosomes 

 attached to spindle 

 fibres (lateral view). 



FIG. 6. Same (polar 

 view). 



at right angles to the axis of the spindle. Very soon after 

 they get into this position, it is seen that each of the chromo- 

 somes is split lengthwise. This splitting becomes more and 

 more evident, until each chromosome is completely divided 



FIG. 7- Splitting of the 

 chromosomes. 



FIG. 8. Longitudinal halves 

 of chromosomes drawn to- 

 wards opposite poles of 

 spindle. 



FIG. 9. The cytoplasm 

 dividing. 



into two longitudinal halves (Fig. 7). Each of these halves 

 is gradually drawn away from its fellow towards opposite 

 poles of the spindle, until two groups of half-chromosomes 

 are collected round each centrosome (Fig. 8). In each of 



