Page:Natural History, Mollusca.djvu/135

 there are closely packed a vast multitude of clear oblong capsules, within each of which a narrow body is discerned running through its length. At the will of the animal, a number of these oblong capsules are ejected from the aperture, and at the same instant each capsule shoots forth with great force from one end a long thread or hair. These thread capsules are found in the Actiniæ and Coral animals, as also in Medusæ; and there can be little doubt that they are weapons of defence, and that the propulsion of the thread is the immediate cause of the stinging power possessed by many of these animals; probably, indeed, by all, though not appreciable by us.

PAPILLÆ OF EOLIS.

The structure of the mouth and of the tongue with its numerous teeth has been already described. A short gullet leads into a large membranous stomach, sending off on each side branches which subdivide and lead by smaller tubes into the canals, which I have already mentioned as running through the branchial papillæ.