118 



THE PROTOZOA 



of that type of mitosis found in the cells of Metazoa ; it would be 

 more reasonable to expect that in some cases at least other distinct 

 types 'of division- mechanisms would have been evolved side- 



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FIG. 64. Division of Acanthocystis aculeata. A, Resting state of the animal. 

 N., Nucleus ; c., central grain ; a.f., axial filaments of the pseudopodia, ps. ; 

 sp., spicules. B, Pseudopodia withdrawn ; nucleus in the spireme-stage ; 

 central grain dividing. C, Division of the central grain further advanced ; 

 nucleus showing distinct chromosomes. D, Central grain completely divided 

 into centrosomes, between which the nucleus is placed ; in the nucleus the 

 membrane is becoming dissolved, the reticulum is becoming modified in 

 arrangement to form the achromaturc spindle (or a part of it), and the chromo- 

 somes are taking up their position in the equatorial plate. E, Complete 

 nuclear spindle, with centrosomes, achromatinic spindle, and equatorial plate. 



F, Later stage with daughter-plates and division of the cell-body beginning. 



G. Division of the nucleus and of the cell-body nearly complete. After 

 Schaudinn (82). 



