136 THE ORIGIN OF LIFE 



does actually play so important a part in vital 

 actions. 



The gaps have to be filled up ; they may never be 

 filled up ; but it is by such methods as these in filling 

 in some of those gaps that an insight into the nature 

 of the inner mechanism of the cell may be attained. 



The amount of work that has been done on cell 

 structure is amazing, and it is not improbable that in 

 that vast complexity the actual mechanism by which 

 the vitality in the cell is carried out has possibly 

 been lost sight of ; or indeed that the principles 

 upon which that mechanism depends were not within 

 the reach of investigators till quite recently. 



Now it is upon the nature of the nucleus that the 

 whole mystery, so far as it is a mystery, depends ; 

 and the phenomenon of karyokinesis, or mode of 

 subdivision of the inner portions of the nucleus, or 

 nucleosus, the centrosome as it is more commonly 

 called, can be imitated in the artificial radio-active 

 cells. The karyokinesis of the centrosome is shown 

 in the figures. It precedes the subdivision of the 

 cell itself. 



The protoplasm between the nucleus and the cell 

 wall is familiarly called the cytoplasm ; and authori- 

 ties disagree as to whether the subdivision is due to 

 stimulus in the cytoplasm, the nucleus, or the more 

 obscure part, the centrosome. But it is generally 

 admitted that it is upon the latter that the sub- 

 division really depends. Boveri postulates another 

 source of the phenomenon in the centrosome to its 

 vicinity, which he calls the archoplasm. He has 



