FRESH-WATER POLYPE. 6l3 
bulant ; if it be an animal, it may be propagated by 
slips and cuttings, like many plants.” 
Some of these animals are capable of extending 
their tentacula, or arms, to a considerable length ; 
we have seen them full six inches long, and so 
slender that their extremities could hardly be ob- 
served. With these arms they secure their prey, 
and no insect less than themselves can escape 
them. If a small worm happens to come in con- 
tact with one of the arms, it is immediately seized 
without a possibility of retreating. The little crea- 
ture endeavours in vain to disengage itself, often 
swimming and dragging the arm from one side of 
the glass to the other. The polype, in order to 
counteract these exertions, contracts itself as much 
as possible, and thus brings the worm within the 
reach of its other arms ; when it is presently con- 
veyed to the mouth, and gradually swallowed. 
After the worm is completely ingorged, it may be 
distinctly seen through the transparent sides of the 
polype; and if the animal be conveyed under a 
microscope, the process of digestion will become 
visible. This is effected by the motion of the 
stomach, which continually pushes the aliment 
backwards and forwards till it is sufficiently softened 
and has lost all traces of its original form. 
Sometimes several polypes will seize on a small 
worm, and each dispute the prize. When two of 
them happen to contend for the same object, they 
drag it with great force in opposite directions. It 
often happens that while one is swallowing its 
