CYTOLOGY 



21 



of its slight affinity for stains. Studies by micro-dissection have shown that 

 the spindle is not a mere appearance in the cytoplasm, but a definite body, 



i-^i>j^-.--- 



ACHROMATIC SPINDLE, ^-^:V?' " : ' ''^-^r.' 



~\: ■'!;// '^^V:^- SEPARATING ^i^:"':>;<-, 

 ~ ■■?}'•:■ --v: CHROMATIDS y/^Vvv 



i/^/^^: 



'PAIRED 

 CHROMATIDS 



■ ■■■■■.'• ^^. ■•'' 



:v^.^::vy. 



A B 



Fig. 7. — Vicia faba. Diagrams of two successive stages, A and B, in the 

 metaphase of mitosis. {After Eraser and Snell.) 



which can be extracted entire from the cell, with the enclosed chromosomes. 

 One end of each spindle fibre is attached to the kinetochore of a chromosome. 

 There is indeed some evidence that the kinetochores may be concerned in 

 their formation by the secretion of nuclear material. At any rate if a chromo- 

 some loses its kinetochore it has no spindle attachment and can take no part 

 in the subsequent movements. 



The next stage, or anaphase (Fig. 8) opens with the chromosomes 



■ ' i-'-^L-: 





. 'Nci-:-'.- SECONDARY 

 J^:\>^ SPINDLE FIBRES-V 



..■;.'-v.'(-Ki;- -■*-■■;,■ ■ , ■ 



V- i-T-. 



A" 



B 



Fig. 8. — Vicia faba. Diagram of two successive stages, A and B, 

 anaphase of mitosis. (After Eraser and Snell.) 



in the 



