48 



FUNDAMENTAL PRINCIPLES 



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

 reach a maximum development, their rays extending sometimes to the 

 periphery of the cell. At this time the mitotic figure is called the amphi- 

 aster, and the stage the aniphiaster stage. The chromosomes are in pairs 

 and the two of a pair are similar. Now the two of each pair of chromo- 

 somes begin to separate, one being pulled along the rays of the spindle 



Nucleus 



Central body 

 and cen- 

 trioles 



Lin in 



Spindle 

 Aster 



Spireme 



(Linin disappears) 

 5 



Spireme shor- 

 tens and tiiickens 



Nuclear 



membrane 



disappears 



7 



Chromosomes 



Amphiaster 



Nuclear Asters 



membranes and Spjndle 



appear disappear 



Fig. 15. — 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. 



toward one central body and the second being pulled toward the other 

 central body. As the two separating groups of chromosomes approach 

 the central bodies these chromosomes become scattered about the respec- 

 tive 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, forming a mesh work, from which finally are produced 



