next seen to split lengthwise into equal portions, and soon 

 the two sets migrate towards the poles of the spindle. As 

 they reach the poles they gradually elongate and fuse so as 

 again to form the chromatin network of two new nuclei. 

 A wall begins to form between the two nuclei, and soon two 

 daughter-cells take the place of the original mother-cell. 

 (Fig. 23). 



Fig. 23.— DIAGRAM OP STAGES IX NUCLEAR DIVISION. 



(After Lock). 

 1 — The resting cell; 2 — The chromatin forming- a tangled thread; 

 3 — Thread forming chromosomes: 4 — The nuclear membrane 

 disappear.^, the spindle forms and the chromosomes form the 

 equatorial plate — this marks the end of the prophase stage; 

 5 — Each chromosome splits lengthways — the metaphase stage; 

 6 — Each half-chomosome moves towards the poles of the spmdle; 

 7 — The half-chromosomes come together at the poles — the end ot 

 the anophase stage; 8 — The network is formed again, a wall is 

 laid down between the two cells, and result is two cells, each 

 with its nucleus — the end of the telophase stage. 



(b)— Number of Chromosomes 



The number of chromosomes varies from 2 to 200 and 

 more in different kinds of animals and plants, but they are 

 always constant for the same organism. It is believed by 

 many that the chromosomes are really the transplanters, or 

 the bearers, of hereditary characters inasmuch as they are 

 persistent organs of the nucleus and at every division they 



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