prometaphase. The long-debated question as to whether the spindle 

 is a component of the nucleus, cytoplasm, or both is still unanswered. 

 There are many views concerning the nature of the spindle fibers 

 themselves, ranging from the opinion that they are precipitation arti- 

 facts to the idea that they represent real fibers presumably protein 

 in composition. They have also been assumed to be lines of force or 

 stress lines and channels. There is very little doubt that they represent 

 real organization (Figure 6-2 (a) and (b)) as indicated by studies with 

 polarized light (Inoue, 1953; Swann, 1951 ) and by electron micrography 

 (Figure 6-3). 



Figure 6-3. {Contin. on opposite page.) 



142 / CHAPTER 6 



