MITOSIS 



torial region, but in many cases great indifference is shown in their 

 distribution, and it may even be that all ends reach toward the same 

 pole, leaving the other side empty 

 of chromatin. 



The change from the present 

 stage as seen in Figure 30 to Fig- 

 ure 31 is marked by one very 

 noticeable fact to which all else is 

 subsidiary. This is that every 

 chromosome as of one accord 

 moves so that the exact middle 

 of its length will lie directly in the 

 equatorial plane. As an accom- 

 paniment to this, its ends are apt 

 to straighten out in a variety of 

 directions, so that a definite though 

 irregular horseshoe-shaped loop, 

 much elongated, is usually the 



result. FIG. 31. Hyacinth root -tip cell. Chromosomes 



\Vhile this is being done doubled and with their points of first division 



in the equatorial plate. 



another very important change 



takes place. Each chromosome splits for its whole length into two 



halves, the halves remaining at- 

 tached for all their length by an 

 achromatic substance which per- 

 mits of their dual structure being 

 seen. This stage figured in Fig- 

 ure 31 is rare. It is very quickly 

 followed by the stage seen in 

 Figure 32, where it is quite evi- 

 dent that each dual loop is being 

 pulled apart by fibers attached 

 to the apices, one fiber reaching 

 from a pole to one half of each 

 loop, while another fiber from the 

 opposite pole is attached to the 

 apex of each of the other daughter 

 loops. Thus, when these fibers 

 contract, the daughter chromo- 

 somes are well apart (Fig. 33). 

 They move with ends straight 

 out and form a common and characteristic figure. 



The question naturally arises as to the motive power involved in this 



FIG. 32. Hyacinth root-tip cell, 

 the chromosomes. 



Division of 



