HISTOLOGY 



transportation of chromatin. 



FlG. 33. Hyacinth root-tip cell. Chromo- 

 somes reaching the spindle poles. Spindle 

 fibrils shown between. 



The chromosomes seem to possess the 

 power of independent motion, as 

 witnessed by their movements in 

 Figures 30 and 31; when pulled 

 apart as in 33. However, the very 

 probable and entirely possible mo- 

 tive power is the contracting fibril. 

 In Figure 33 the fibrils between 

 these two masses of separating 

 daughter chromosomes show us 

 that not all the fibrils of the original 

 spindle were employed to draw the 

 parent chromosomes apart. Con- 

 sequently we are able to distin- 

 guish between the two kinds, the 

 remaining fibrils being called true 

 spindle fibrils, and those used in 

 the division mantle fibrils, be- 

 cause they are placed on the outer 

 surface of the spindle. 

 The spindle, whose form and poles were so perfectly seen in Figures 



29, 30, 31, and 32, is now, for the 



first time, seen clearly at the equa- 

 tor from which the chromatin has 



moved. This leaves the equator 



free but obscures the poles, which 



will not be seen again because 



the chromatin is so thick and 



dark. The spindle as seen in this 



stage is composed of true spindle 



fibers only, as the mantle fibers 



were withdrawn while dragging 



the chromosomes to the poles. 

 Two changes mark the next 



stage which is represented in Fig- 

 ure 34. First, the chromosomes 



have shortened and thickened and 



become compacted into a denser 



mass than at any other time in the 



whole process of division. They 



have partly lost their individual- 

 ity by blending together as though 



being of wax which had been subjected to heat. Secondly, there has 



FIG. 34. Hyacinth root-tip cell. Massing of 

 the newly divided chromosomes. Beginning 

 of a division in the cell-plate. 



