CHAPTER XXXIII 



ucleus 



Fig. 129. 



An ameba. 

 enlarged. 



Much 



LIFE PROCESSES IN ANIMALS 



Ameba. An ameba is one of the simplest animals in 

 existence. Since it is composed of but one very small 

 cell, its life can not be made up of many complicated 



processes. However, it 

 must perform certain 

 functions or it would 

 not be alive. By study- 

 ing the few functions 

 which an ameba does 

 perform, we will be 

 able to determine what 

 processes are essential to^the life of any animal. 



In stagnant water there is often found an irregular, 

 jelly-like mass. If this is carefully observed under 

 a microscope, it will be found to consist of one cell 

 containing protoplasm and a nucleus. Imbedded in the 

 protoplasm are particles of food. Since the ameba has 

 no mouth, food is taken into the body by a very simple 

 method. Projections are sent out from the body which 

 surround the food and envelop it. The protoplasm of 

 the cell then transforms part of this food into parts of 

 the cell. The shape of the ameba gradually changes and 



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