the idea that this protoplasm is essentially the same in all plants and ani- 

 mals. It has, in fact, been called "the living substance", although we know 

 that it is a very complex mixture of many different substances (see illus- 

 tration, p. 22). 



We continue to speak of the cell as "the unit" of living things, even 



!""■ 



© General Biological Supply House 



AN EXCEPTIONALLY LARGE AMEBA, Chaos chaos 



The protoplasm is constantly stirring around, constantly changing its shape, moving 

 sluggishly about. The slimy mass wraps itself around food particles, and it crawls 

 away from particles within that are no longer usable. Without distinct regions or 

 organs, the omeba does all it takes to keep alive 



23 



