370 



THE WORLD OF LIFE 



chr. 



^ii 



ciftr 



J) 



Fig. 110. — Diagram of Nuclear 

 Division. 



A. Cell with nucleus (n) and centro- 

 somes {cs) preparatory to division. 

 The chromatin has become thick- 

 ened so as to form a spiral thread 

 (c/ir). 



B. The nuclear membrane has dis- 

 appeared. Delicate threads radiate 

 from the chromosomes, and form 

 the "nuclear spindle," and the 

 equator of which eight chromo- 

 somes or nuclear loops (chr=Jd) 

 are arranged; these have been 

 formed by the spiral thread of 

 chromatin in A becoming broken 

 up. 



C. The chromosomes have each be- 

 come split longitudinally into two, 

 and are about to be drawn apart 



by means of the spindle threads. (For clearness four only of the eight chromo- 

 somes are shown.) 



D. The daughter-loops pass towards the poles of the spindle. 



E. The cell has divided, each new cell containing a centrosome and eight nuclear 

 loops. 



(From Weismann's Germ-Plasm, by permission of Walter Scott, Ltd.) 



