218 ORIGIN AND NATURE OF LIFE 



anything of nutrient value for the amoeba ; 

 other inert particles, as a rule, are left alone. 



The particle after being engulfed is acted 

 upon and digested by fluid contained in the 

 amoeba, and when that process is completed, 

 any particles of debris which have accumulated 

 are got rid off by a process of flowing away 

 from them which is the exact opposite of the 

 process of uptake. These two processes of 

 taking in and giving out are called ingestion 

 and egestion. They can occur apparently 

 at any part of the microscopic mass. 



Within the mass, two structures may 

 usually be made out. The first of these is 

 not a universal structure in cells, and is called 

 the cell vacuole ; it seems to be more devoid 

 of structure and clearer than the rest as if 

 it were more fluid. It slowly varies in size 

 from time to time, and there seem to be 

 streaming movements about it as if it were 

 responsible for movements of fluid and a 

 kind of circulation of dissolved materials 

 and minute suspensory materials within the 

 cell. The second structure, on the contrary, 

 is more granular and solid-looking than the 

 remainder. It is only dimly seen when the 

 cell is alive, but it differs in chemical nature 

 from the rest of the cell contents, as is shown 

 by the fact that when the cell is killed and 



