Earthworm, or Angleworm, a well known genus of worms including many essentially similar species. A large number of cutworms, silk worms, measuring worms, and army worms are not real worms at all. They are the young, the larvae--of corresponding butterflies, millers, moths, and flies of all kinds; but the earthworm once is an earthworm always,--a genuine worm, unchanged save in size from the time it hatches from the egg. The body is cylindrical, tapering to the tip, and slightly flattened at the rear end. It is covered with a soft, somewhat slimy skin. A straight digestive tube tract or intestine runs without coil or twist through the center of the entire body. Between this inner tube and the skin, which may be called an outer tube, there is a space comparable to a hollow cylinder. This space, that is to say, the body, is divided by cross portions or braces into many rings or segments easily counted by the corresponding bands which encircle the body. As high as 120 segments have been found. The jaw of a vertebrate animal works up and down. The lips of the earthworm open, not up and down, but sidewise. The mouth slit is not horizontal; it is vertical. Under the skin a double set of muscles is found. One long set runs lengthwise; the other, a circular set, runs around the body. When the worm desires to shorten its body it shortens the long muscles. When it desires to extend its body it shortens the circular muscles literally squeezing its body out lengthwise. The under part of the body is furnished with short, stiff bristles, four pairs to a segment. These bristles are controlled by muscles and may be set to point forward or backward, or they may be drawn up into little pits where they are not noticeable. If the body be drawn up short by the long muscles, and the bristles be pointed backward, the body will be pushed out forward when the circular muscles act. If, under similar conditions, the bristles are pointed forward, the body is extended backward and retreats. On a surface so theoretically smooth that no foothold could be obtained, the body would extend equally in either direction, and no change of place could be made. The same is true of a person, however, or of any animal. Locomotion is effected by gaining a foothold and pushing the body forward. The earthworm has a nervous system. A double nerve cord, with an enlargement in each segment, runs beneath the intestine and ends in a sort of brain in the shape of a ring or collar surrounding the swallow. There is no evidence that an earthworm can hear. It has no eyes; yet it is sensitive to light and can tell the difference between day and night. Without doubt the sense of touch is well developed, as well as that of heat and cold. It seems also to have a sense of smell. The body is provided with a regular system of blood circulation. The chief organs are a tube running the length of the back and another following the lower surface, through which the blood is driven by muscular action of the tube walls. The blood is red, due to coloring matter in the liquid itself, not to floating bodies as in the case of man. The entire skin serves as lungs. Living bloodvessels lie in the surface, separated from the air by a thin membrane only. As long as this membrane is moist, air passes; but if an earthworm be kept in warm, dry air, the surface of the body dries and the animal smothers for want of air. The home of the earthworm is a burrow,--a slender hole going down, it may be several feet, always into moist earth, and in the winter time below the reach of frost. The chief food is earth, from which the worm extracts vegetable and animal matter. The spiral heap of fine earth found about the entrance to its burrow is the earth which the worm has eaten and then voided or cast away. Leaves are frequently dragged into burrows to be eaten when half decayed. The worm has mere lobes for lips or jaws, no real mouth cavity. The work of boring burrows and of seizing leaves is done by the muscular end of the swallow or pharynx. The earthworm is an animal of agricultural importance. By boring deep it forms tubes which admit air and rainwater to the soil. Burrowing mellows the soil. The castings may seem trifling, but investigations undertaken by Mr. Charles Darwin of England go to show that, in a grassplot well peopled by earthworms, their castings amount to an inch in five years, or twenty inches in a century; enough in the course of time to bury a city. Mr. Darwin is of the opinion that in many parts of England no less than ten tons of soil are eaten and brought to the surface per acre each year. The grinding that takes place in the gizzard of the earthworm produces rock flour of fineness and fertility. See TAPEWORM; SOIL.