150 MODIFICATIONS OF BEHAVIOR 
therefore no occasion for wonder if the organism responds in 
different ways to a given stimulus. The wonder would be 
if it always responded in the same way. 
INFLUENCE OF INTERNAL FACTORS ON BEHAVIOR 
That behavior of organisms in general should be greatly 
influenced by their internal condition is obvious. Hunger 
and repletion influence the activity of animals, even in the 
lowest forms. Even the white blood corpuscles when they 
have ingested a number of bacteria refuse to take in any 
more. Paramcecium, while it may not reject food swept 
into its gullet, behaves differently when well fed, and Stentor, 
as we have seen in a previous chapter, takes in objects 
when it is hungry which at other times are rejected. Hy- 
dras when hungry eagerly take in food, but they are quite 
indifferent to it when well fed. If starved for some time 
they become more active, extend and contract the tentacles 
and body, and move about in various directions as if to 
increase their chances of coming in contact with food. The 
jelly-fish Gonionemus when hungry swims about actively, 
frequently coming to the surface and settling slowly through 
the water, with its tentacles extended tocatchits food. After 
a hearty meal the jelly-fish is more frequently at rest and has 
its tentacles contracted. 
The effect of hunger on the movements of sea anemones 
is very striking. When starving, anemones will often take 
in such things as filter-paper and stones which they reject 
under ordinary conditions, as is well shown in the experiments 
of Torrey on Sagartia. Weak food stimuli produced by 
giving the anemones filter-paper soaked with dilute crab 
juice produce at first the food reaction, but in a little while 
the animal no longer responds (Nagel, Parker). If meat 
is offered the food taking activities continue for a long time. 
