MITOSIS 



47 



some cases what is known as an equatorial jdate. End views at this time 

 show that the chromosomes may form a ring about the equator of the 

 spindle but that more often they are distributed through it. The asters 

 reach a maximum development, extending sometimes to the periphery 

 of the cell. At this time the mitotic figure is called the amphiaster, and 

 the stage the amphiastei- stage. The chromosomes are in pairs and the 

 two of a pair are similar. Now the two of each pair of chromosomes 



Nucleus 



Centra/ body 

 and cen- 

 t Holes 



Linin 



Spindle 

 Aster 



Spireme 



(Linin disappears) 



Spireme shor- 

 tens and thickens 



Nuclear 



membrane 



disappears 



7 



Chromosomes 



Nuclear Asters 



membranes and Spindle 



appear disappear 



Fig. 12. — Diagrams representing the steps in a typical mitosis. The steps numbered 

 1 to 4 represent the prophase, 1 being a resting cell; 5, the metaphase; 6, the anaphase; and 

 7 to 9, the telophase, 9 showing the two daughter resting cells. 



begin to separate, one moving along the rays of the spindle toward one 

 central body and the second moving toward the other central body. As 

 the two separating groups of chromosomes approach the central bodies 

 these chromosomes become scattered about the respective ends of the 

 spindle in an irregular fashion. Then a series of steps occur which in a 

 general way are the reverse of the steps occurring at the beginning of the 

 process. The separate chromosomes become irregular in shape and fuse, 



