Unicellular and Multicellular Animals 



shape. It is continually 

 pushing out finger-like pro- 

 jections from various parts 

 of its surface, feeling, in a 

 dim, vague way, for its food. 

 It moves, if but slowly, by 

 withdrawing its substance in 

 one direction and pouring it 

 forth in another. It indulges 

 in such fare as bacteria or 

 particles of dead organic 

 matter and feeds by the 

 simple method of surround- 

 ing the food particle with 

 its protoplasm, and gradu- 

 ally digesting and absorbing 

 whatever it contains of nutri- 

 ment. Undigested portions 

 are simply left behind as the 

 creature moves on. The 

 waste products are drained 

 into a simple cavity in the 

 protoplasm called the con- 

 tractile vacuole, which emp- 

 ties itself periodically to the 

 outside. The Amoeba re- 

 produces by the ordinary 

 process of simple fission, 

 illustrated, with the creature 

 in its ordinary condition, in 

 Figs. 21 and 22. 



Somewhat higher than 

 the Amoeba, and apparently 

 along the main line of pro- 

 gress, stands the group 

 which includes the slipper 



