Page:Sea and River-side Rambles in Victoria.djvu/45

26 them, we learn that the tentacles of these creature are prehensile, and this power depends on the presence of tiny barbed weapons coiled in elastic cells, which are found in inconceivable multitudes in the tissues of the tentacles, of the lips, of the stomach, of the frilled ovarian bands, and especially in some species, in long threads or filiferous capsules, which are protruded from pores in the integument of the body.

The structure of these weapons is as follows: Each consists of an oval or elliptical sac of transparent membrane, within which is seen a thread coiled up, and in some instances an oblong or lozenge-shaped chamber. At the pleasure of the animal, or under the stimulus of pressure, this thread is shot forth from one end of the cell with great force, until it extends to a length from twice to fifty times that of the cell. When fully extended it is seen that the thread is but a continuation of the cell itself, that when it was dormant it was turned in, and that in the process of expulsion, every part of its length has actually been turned inside out like the finger of a glove. Sometimes the thread appears simple, but in those cases in which a chamber appears within the cell, it is furnished with an armature of barbed weapons, which, after expulsion of the threads, project from their sides in all directions. The propulsion of these small threads is sufficiently forcible to enable them to enter the tissues of animals, and the barbed structure enables the weapon to retain its hold in the flesh, which facts Mr. Gosse (from whose Work the foregoing has been sketched) thinks,