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SCIENCE PROGRESS 



their inner sides by a spindle formed of these threads. In c, d, 

 the figure has grown ; in c the nucleus occupies the middle of 

 the spindle ; in d it lies to one side of it, and the nuclear wall 

 has disappeared on that side. In e the figure has enlarged still 

 more and the nuclear wall has quite disappeared. The spindle 

 persists and elongates in g, h, i. It is lost in j, on the completion 

 of the process. It will be noticed that the contents of the 



Fig. i (]8). 



nucleus arrange themselves so that by the time c is reached they 

 are represented by thick threads : these take up certain dyestuffs 

 readily, and are hence termed " chromosomes." In e it will be 

 noticed that each chromosome has split along its whole length 

 into a pair of daughter chromosomes. In f these are shortened 

 and assembled at the equator of the spindle figure into what 

 is called the equatorial plate (e.p.) In g and h the two sister 

 halves of each chromosome separate and glide along the threads 

 of the spindle towards the nearer centrosome. Sometimes 



