ceeded also in turning a hydra inside out, and it was able to catch food and digest it as well as before. The creature, however, insisted on turning itself back again, and this was not what the experimenter wished. He therefore passed a needle through the body, near the mouth, and kept it there.
The method of this Dutch naturalist was very ingenious. Holding the hydra in a little water in the palm of his hand, he induced it to swallow a small worm. He then took a bristle and began to push against the base, working the end of the body upward against the worm, and soon had the animal inverted. Thrusting a needle through the base of the tentacles, he had what he wanted. He says: "I have seen a polyp turned inside out, which has eaten a small worm two days after the operation. I have fed one in this state for more than two years, and it has multiplied in that condition."
Hydras have but low powers of locomotion, but still they can move from place to place. When one wishes to go upon its travels it attaches itself to the surface of its support by a tentacle, and then moves the disk up to the tentacle. In this way it can get over about eight inches in twenty-four hours. It can, however, take a longer journey by attaching itself to the shell of a water snail, and thus travel in a few minutes a greater distance than it could do in a day alone. It can also swim with the disk floating on the surface of the water as if suspended.
Although without eyes and a nervous system, the green hydra is very sensitive to the light, and indeed all seem to be instantly aware of a ray of sunlight. Would it not be curious if it was discovered that the rays which affect sightless creatures, like the hydra, are those about which so much investigation is being carried on?
Many more interesting things might be said about hydras, but these must suffice. I will only add that the more I think about them and the more I see of their habits, the more I realize the truth of the words of Charles Bennet, of Geneva, in Switzerland, about them: "We can only judge of things by comparison, and have taken our ideas of animal life from the larger animals; and an animal we can cut and turn inside out, which we can cut again and it still bears itself well, gives one a singular shock. How many facts are ignored which will come one day to derange our ideas of subjects which we think we understand! At present we just know enough to be aware that we should be surprised at nothing."
