MITOSIS OR KARYOKINESIS 



29 



plasm " or " idioplasm " of relnti\ely great persistence, which 

 g'ives 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. — Fissiou witli modified karyokinesis iu the Filose Rhizopod Eufjhjpha. A, out- 

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

 oiitwards ; B, completion of shell of second cell, formation of Mi</-«-nuclear spindle ; 

 C, D, further stages. (From Wilson, after Schewiakott'.) 



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 Rhizopod 

 Eiifihjpha (Fig. 8). 



In many Sarcodina and some Sporozoa the nucleus gives off 

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



^ The fact tliat it is Iiy mitotic division that the uiiditrcrcntiated germ-cells 

 lU'oduce the "differentiated" tissue-cells of the body of the highest animals, is 

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

 niann and his disciv>les. 



