THE DIVIDING CELL 



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extended by many others, and we can now give approximately 

 the whole story of cell-mitosis, 1 its antecedents and its con- 

 sequences. We prefer to take for description the cells of 

 Higher Animals — Metazoa — where the appearances are more 

 complete than in Flowering Plants, as shown in fig. 1. 



In a the cell is "at rest," i.e. performing its routine duties; 

 the nucleus is seen to have at one side of it a small rounded 

 body, the centrosome, with two central dots of denser matter, 



Fig. 1 (a). — Diagrammatic history of cell division in Echinoderm embryo (from P.Ji.S., after 



Wilson). For explanations, see text. 



the " centrioles " (c). In b this structure has divided into two 

 small spheres, the " centrosomes," each with its centriole ; and 

 we already see the likeness of the magnetic field, for the 

 ambient cytoplasm has developed a thread-structure, radiating 

 into stars at the outer sides of the centrosomes, and uniting 



1 The more usual term in English, " karyokinesis," is not so convenient, 

 since the kinesis is as much or more that of the extranuclear protoplasm 

 (" cytoplasm") as of the nucleus; " mitosis," which means resolution into threads 

 is far more apt. 



