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Show ANATOMY OF AN EARTH-WORM. The body of a large worm consists of one or two hundred almost cylindrical rings or segments, each furnished with minute bristles, and is endowed with a well developed muscular system. The month is provided with a little projection or lip, capable of taking hold of things, and of sucking. Internally, a strong pharynx, corresponding, according to ??, with the ?? trunk or proboscis of other ??, and which is pushed forward when the animal eats, is situated beyond the mouth. The pharynx leads into the esophagus on each side of the lower part of which are three pairs of large bands, which secrete a surprising amount of carbonate of lime. They are unlike anything that is known in any other animal, and their use is largely a matter of speculation. Mr. Darwin thinks they are partly excretions of the excess of lime contained in the leaves which the animal eats, and that they otherwise and digestion by affording a neutralizing agent against the acids of its food. In most of the species the esophagus is enlarged into a cup in front of the gizzard. The latter organ is lined with a smooth, thick, chitinous membrane, and is surrounded by weak longitudinal but powerful transverse muscles. Grains of sand and small stones from one twentieth to a little more than one tenth of an inch in diameter may be found in the gizzard and intestines, and are supposed to serve like millstone, to tolerate the food. The gizzard opens into the intestine, which presents a peculiar remarkable longitudinal involution of the walls, by which an extensive absorbent surface is gained. The circulatory system is well developed, breathing is done by the skin, without special respiratory organs. The nervous systems is fairly developed, with two almost confluent cerebral ganglia situated near the anterior end. Worms have no eyes, and are measurably indifferent to light, yet they can distinguish night from day and are quickly affected by a strong light and after some that by a moderate light shining continuously them. They do not much mind a moderate radiant heat, but are sensitive to cold. They have no sense of hearing, but are extremely sensitive to vibrations in any solid object. Worms in pots, which had paid no attention to the sound of a piano, when placed on the piano instantly drew into their holes when the notes were struck. Their whole body is sensitive to contact, as of a puff of air. Their sense of smell is feeble, but responds fairly well to the odor of the cabbage and onion or whatever they like us was shown to Mr. Darwin by some very interesting experiments. They are omnivorous, and swallow enormous quantities of earth, out of which they extract any digestible matter which it may contain, consume decayed and fresh leaves and vegetable matter, raw, roasted and decayed meat, but like raw fat best.-Popular Science Monthly. |
