THE CELL AND PROTOPLASM. 



8 9 



nucleus, and as it was done little by little they 



began to find the presence of nucleii in cells in 



which they had hitherto not been seen. As micro- 



scopists now studied one after another of these 



animals and plants whose cells had been said to 



contain no nucleus, they began to find nucleii in 



them, until the conclusion was finally reached that 



a nucleus is a fundamental part of all active cells. 



Old cells which have lost their activity may not 



show nucleii, but, 



so far as we know, 



all activecells pos- 



sess these struc- 



tures, and appar- 



ently no cell can 



carry on its activ- 



ity without them. 



Some cells have 



several nucleii, 



and others have 



the nuclear matter 



scattered through 



the whole cell in- 



stead of being ag- 



gregated into a 



FIG. 24. Acellcutinto three pieces, each 

 containing a bit of the nucleus. Each 

 continues its life indefinitely, soon ac- 

 must have to quiring the form of the original as at C. 



carry on its life. 



Later the experiment was made of depriving 

 cells of their nucleii, and it still further empha- 

 sized the importance of the nucleus. Among uni- 

 cellular animals are some which are large enough 

 for direct manipulation, and it is found that if 

 these cells are cut into pieces the different pieces 

 will behave very differently in accordance with 



mass ; but nuclear 



