290 Descriptive Zoology. 



dormant for a long time, until more favorable conditions 

 return, when it ruptures the cyst, crawls out, and once 

 more renews its former active life. 



SUMMARY OF THE CHARACTERISTICS OF AMCEBA 



1. It eats ; it takes in material through its surface from 

 the surrounding water. 



2. It digests ; the material thus taken in is made soluble 

 so that it can be used in building up the body of the amoeba. 



3. It assimilates ; after suitable preparation the mate- 

 rial is taken into the actual substance of the amoeba ; it is 

 "made like," as the word "assimilate" signifies. 



4. It grows, as a result of assimilation. Growth is the 

 increase in size and substance of a living thing as a result 

 of taking material from the outside and making it over 

 into its own body. Growth should be distinguished from 

 the mere increase in size of such dead objects as an icicle 

 or a crystal by the accretion of more material on the 

 outside. 



5. It moves ; it has power, not to change its bulk, but 

 to change its shape. It is able to rearrange its particles, 

 which is what is meant by the term "contract." Contrac- 

 tility does not mean ability to occupy less space. Distinc- 

 tion must be made between "motion" and "locomotion"; 

 when an amoeba extends a pseudopod and then withdraws 

 it, this is motion; when an amoeba changes its place, or 

 moves on," this is not only motion, but also locomotion. 



6. It breathes ; the energy of motion is maintained by 

 a process of oxidation going on within the substance of 

 the amoeba. Oxygen is absorbed through the outer surface 

 and unites with the materials of the body of the amoeba. 

 Its energy is furnished by this oxidation as truly as the 



