THE BEHAVIOR OF PROTOZOA 71 



would have to be! Yet a simple, apparently almost struc- 

 tureless mass of jelly does all this and more. And if our 

 mechanism had the property of repairing its own injuries and 

 producing other pieces of mechanism like itself, its structural 

 arrangements would be almost if not quite beyond our power 

 to conceive. One cannot, therefore, but look with a feeling of 

 admiration and wonder at so comparatively simple a creature 

 as Amoeba, which is capable of performing so much. 



But the story does not end even here. In addition to all 

 the adaptive properties mentioned Amosba has the power 

 of modifying its behavior to suit new conditions. Toward 

 water different from that in which it is immersed Amoeba 

 reacts negatively, but after remaining in such water for 

 some time it resumes its usual activities. When first ex- 

 posed to bright light it withdraws its pseudopods and re- 

 mains quiet, but after continued exposure it adapts its be- 

 havior to the new conditions and again becomes active. 

 After a short period of starvation Amreba moves about 

 more actively than usual, whereas when it is gorged with 

 food it becomes relatively sluggish. The condition of the 

 animal determines its behavior in other ways and the changes 

 of behavior are usually advantageous to the organism. The 

 behavior of Amoeba is essentially like that of higher animals; 

 it avoids things which are injurious; it seeks things which 

 are beneficial and it adapts its behavior to new conditions. 

 Life is very much the same sort of thing whether in an 

 Amoeba or a man. 



The chief rival of Amoeba in the attentions of the com- 

 parative psychologist is Paramoecium. This is a cigar- 

 shaped infusorian rounded in front and pointed at the 

 posterior end, and covered by a uniform coating of cilia. 

 It has an oblique oral groove leading posteriorly into a gullet 

 into which are swept small particles which serve for food. 



