HISTOLOGY 



transportation of chromatin. 



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 

 FIG. 33 . -Hyacinth root-tip cell, chromo- the division mantle fibrils, be- 



somes reaching the spindle poles. Spindle caUSC they are placed On the OUtCI 



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 were withdrawn while dragging 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. 



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

 the newly divided chromosomes. Beginning 

 of a division in the cell-plate. 



Secondly, there has 



