364 



ELEMENTARY BIOLOGY 



409. Flight. Beginning with the ameba, that withdraws its 

 " false feet " from a point of disturbance, and reaching to man 

 himself, all animals that are not confined or attached protect 

 themselves by some form of flight or escape. With this fact is 

 associated a wonderful series of organs of locomotion, from the 

 false feet and cilia of the protozoa, the water feet of the starfish, 

 the flapping shell movements of the scallop, the wriggling of 



FIG. 182. The hermit crab 



These crabs make themselves at home in the cast-off shells of whelks and snails. (From 

 photograph by New York Zoological Society) 



worms, and the legs and wings of insects, up to the various 

 kinds of legs and wings and fins of the backboned animals. 



It is impossible to say that organs of locomotion are pri- 

 marily related to protection or that they are primarily related 

 to food-getting. At the very lowest levels of life, among the 

 protozoa, we find the same structures and activities serving 

 organisms in both relations. Thus, the paramecium, moving 

 about by means of cilia, also gets food particles into the inte- 

 .rior of the protoplasm by means of cilia. And farther up we 

 find feeding organs and locomotive organs differentiated from 

 the same structures (see Fig. 183). 



