[AS. wyrm, a worm or snake.] Earth-worms are humble animals, yet they are valuable aids to the agriculturist. On making a section down through the earth for several feet, there will be found innumerable tunnels formed by worms. A naturalist considers that they average 100,000 to the acre, and in especially rich ground in New Zealand it was estimated that there were 348,840 in a single acre. This vast body of worms is continually at work boring this way and that, coming to the surface during the night and retreating to greater depths during the day ; and their tunnels constitute a system of irrigation and ventilation. Rain, instead of running off, enters the holes, and so penetrates the earth, thus being held for a longer time. Air also finds its way below the surface. But this is a very small part of the work accomplished. Worms are continually swallowing the earth and depositing it at the surface, and working it over and over. Darwin states that the vegetable mold thus transported in some places amounts to ten tons an acre. Worms not only carry all this material to the surface, but they drag vast quantities of leaves and other matter down that serve to enrich the soil and render it capable of producing larger crops. Some worms are a foot in length. Their bodies are formed of a large number of rings. On each ring there are a great many bristles. Grubs move forward by means of their tiny feet, snakes by means of their scales, and worms by means of their bristles. Their bodies are very elastic. The worm pushes forward its head, the bristles in the front part of its body take hold of the ground, and the rest of the body is then pulled along. In addition to the earth-worms, the name worm is applied to a large variety of elongated water animals, very many of them dwelling in the ocean, also to numerous internal parasites, some of which dwell in the human body. (See Tape.)