NUCLEI AM) KINETIC ELEMENTS 



101 



evidence of constructive metabolic activities in the cell. For these 

 reasons I believe, with Kofoid, that the term "parabasal body" 

 expresses the relationships and functional activities of the so-called 

 "kinetonucleus" much better than does the latter term and should 

 take its place in literature dealing with the Protozoa. 



/0^ 



•I? 



0m.... 







h-- 



mM^- 





mIMW 



im.m;:;. 



n F 



Fig. 52. — NocHluca ntUiaris Sur. Origin of the spindle and division of the nucleus. 

 A, Endosomes fragmenting; B, grouping of fragments into linear chromosomes; C, 

 formation of the amphiaster and orientation of the chromosomes; D, section through 

 one pole of anaphase stage showing centrioles and mantle fibers; £", nuclear furrow 

 holding the amphiaster; F, anaphase stage. (After Calkins.) 



3. Other Ci/toplasmic Kinetic Elements.— A unique cytoplasmic 

 kinetic element, apparently homologous with the centroblepharo- 

 plast of certain flagellates, is found in some types of Heliozoa. The 

 non-committal name central granule (Centralkorn) was given to this 

 structure by Grenadier, in 1S()9, who was the first to observe it. 

 In some types it lies in the geometrical center of the cell (Acantfw- 

 cystis acideata, Sphcerastrum fockei, Raphidiophrys pallida, etc.); 

 in other types it is excentric {Dimorpha midans, WagnereUa borealis) 

 or absent altogether (Actinophrys sol, ActinosjyhcErium eichhornii, 



