CHAPTER VIII 



KARYOKINESIS 



Normal cells, when full grown and mature, have a 

 marvellous method of division known as Karyokinesis or 

 indirect division. Some have a less usual method which is 

 called Amitosis or direct division. This latter may be 

 dismissed after being briefly mentioned. It is a mere split- 

 ting in halves, of a bulk or form which is mature, or has 

 become too large or too extended for its position and its 

 constitution, without particular regard for the quality of 

 the two halves. This is a crude mechanical division. In 

 nature it is found only in such places as make it probable 

 that it is a degenerate or decadent process, of cells losing 

 their ancestral force, and becoming specialized for a simple 

 function without need of successors. It is a process ignor- 

 ing heredity, and may thus belong to conditions either 

 before heredity begins, or after it is exhausted. In a skin 

 or membrane where destruction is sure, and replacement 

 must depend upon an inner supply, such a production may 

 economically occur. 



But in general, and wherever cell production occurs in 

 an environment favoring continuance, or necessitating con- 

 tinuance, the indirect division occurs which is called Karyo- 

 kinesis. This is the marvellous method, revealed by modern 

 microscopy. The centrosome, which seems to be the focus 



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