76 



CELL-DIVISION 



pheral mable-fibres ; and the chromosomes extend entirely through 

 the substance of the spnidle in its equatorial plane. If there be sup- 

 porting, as opposed to contractile, fibres, they must be intermingled 

 with the latter; and both forms must have the same origin. The 



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c 



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D 





E 



pig_ 27. — The later stages of mitosis in the egg of the sea-urchin Toxopiienstes {A-D, X 1000; 

 L-F, X 500). 



A. Metaphase; daughter-chromosomes drawing apart but still united at one end. B. Daugh- 

 ter-chromosomes separating. C. Late anaphase; daughter-chromosomes lying at the spindle- 

 poles. D. Final anaphase; daughter-chromosomes converted into vesicles. £. Immediately 

 after division, the asters undivided; the spindle has disappeared. K Resting 2-cell stage, the 

 asters divided into two in anticipation of the next division. 



In Figs. A to D, the centrosphere appears as a large reticulated mass from which the rays pro- 

 ceed. It is probable that a minute centrosome, or pair of centrosomes, lies near the centre ot the 

 centrosphere, but this is not shown. 



daughter-chromosomes appear to move towards the poles tJinnigh 

 Ihe substance of the spindle, and do not travel along its periphery as 

 described by Hermann and Drtiner in amphibia and by Strasburger 

 ('93, 2) in the plants 



No shortening or thickening of the rays can 



