138 THE STORY OF LIFE'S MECHANISM. 



and, above all, the fact that the nucleus alone is 

 handed down from one generation to the next in 

 reproduction, all attested to its great importance 

 and to the secondary importance of the rest of 

 the cell. 



This was the most extreme position of the cell 

 doctrine. The cell was the unit of living action, 

 and the higher animal or plant simply a colony 

 of such units. An animal was simply an associa- 

 tion together for mutual advantage of indepen- 

 dent units, just as a city is an association of 

 independent individuals. The organization ot 

 the animals was simply the result of the com- 

 bination of many independent units. There 

 was no activity of the organism as a whole, 

 but only of its independent parts. Cell life 

 was superior to organized life. Just as, in a 

 city, the city government is a name given to 

 the combined action of the individuals, so are 

 the actions of organisms simply the combined 

 action of their individual cells. 



Against such an extreme position there has 

 been in recent years a decided reaction, and 

 to-day it is becoming more and more evident 

 that such a position cannot be maintained. In 

 the first place, it is becoming evident that the cell 

 substance is not to be entirely obliterated by the 

 importance of the nucleus. That the nucleus is 

 a most important vital centre is clear enough, but 

 it is equally clear that nucleus and cell substance 

 must be together to constitute the life substance. 

 The complicated structure of the cell substance, 

 the decided activity shown by its fibres in the 

 process of cell division, clearly enough indicate 



