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 Amoeba 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 Amoeba 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 Amceba 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 Paramacium. 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. 
