MITOSIS OR KARYOKINESIS 



29 



plasm " or " idioplasm " of relatively great persistence, which 

 gives the cell its own racial qualities.^ 



The process we have just examined is called " mitosis/' 

 " karyomitosis," or " karyokinesis " ; and the nucleus is said to 

 undergo " indirect " division, as compared to " direct " division 

 by mere constriction. In an intermediate mode, common to 

 many Protista, the nuclear wall persists throughout the whole 



Fig. 8.— Fission with modified Icaryokiuesis in tlie Filose Ehizopod Eurjlypha. A, out- 

 growth of halt of the cytoplasm, passage of siliceous plates for young shell 

 outwards ; B, completion of shell of second cell, formation of iMfra-nuclear spindle ; 

 C, D, farther stages. (From Wilson, after SchewiakofT.) 



process, though a spindle is constituted within, and chromosomes 

 are formed and split: the division of the nucleus takes place, 

 however, by simple constriction, as seen in the Filose Ehizopod 

 Eughjpha (Fig. 8). 



In many Sarcodina and some Sporozoa the nucleus gives off 

 small fragments into the cytoplasm, or is resolved into them ; 



1 The fact that it is by mitotic division that the undiffei^ntiated germ-cells 

 produce the "differentiated" tissue-cells of the body of the highest animals, is 

 again irreconcilable with such theories, whose chief advocates have been A. Weis- 

 mann and his disciples. 



