LIVING SUBSTANCE 25 



seems to be necessary to the cytoplasm in order for 

 it to properly carry out its functions, for we find 

 that a fragment of a cell, provided it has a bit of 

 nuclear matter included, will continue to live, whereas 

 a bit of cytoplasm without a nucleus soon disintegrates 

 and dies. The nucleus, in other words, is essential 

 for the life of the cell, and, accordingly, since the 

 presence or absence of a cell-wall is not a determin- 

 ing character, we may consider the essential features 

 of a cell to be a mass of protoplasm dominated by a 

 nucleus. The cell is thus a dynamic or functional 

 unit rather than a static or structural one. On this 

 account the term energid has been used in place 

 of the less accurate word " cell." 



