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In fresh-water ponds, attached by its base to the under surfaces of aquatic plants, may be found a very small animal, just large enough to be seen without the aid of a lens, usually pale green, but sometimes of a brown color. This is our common hydra, technically called Hydra fusca. It is nothing more than a tube or sac, with a sucker at one end to hold on with, and a mouth at the other, surrounded with from five to eight hollow tentacles or feelers, which opens into a central cavity or stomach. Firm and muscular are the walls of the sac, so that the little creature, which is not fixed permanently to whatever it is found clinging to, may stretch itself out or draw back as its own volition dictates, or move slowly along by means of its sucker, or float easily or contentedly upon the water. But the most remarkable, as well as the most interesting thing about this odd creature is the power which it possesses of overcoming animals more powerful and active than itself.

FRESH-WATER HYDRA MOORED AND SEARCHING FOR PREY.