EARTHWORM, Lumbricus, a genus of annelida (q.v.), of the order terrimks. There are many species, all of them pretty closely resembling in characters and habits the common E. or dew-worm (L. terrestris), which is everywhere plentiful in Britain and throughout Europe, and is familiar to everybody. It has no head distinct from the body, no eyes, no antenna;, nor any organs external to the rings of which its body is composed, except minute bristles pointing backwards, of which each ring bears four pair, and which are of use in its locomotion. It sometimes attains to nearly a foot in length, and more than 120 rings have been counted in its body. The end at which the mouth is situated is pointed, and the tail is flattened, whilst the general form is cylin drical. The mouth consists merely of two lips, the upper lip elongated; there are no teeth nor tentacles, and the worm subsists by swallowing fine particles of the soil, from which its digestive organs extract the digestible matter, the rest being voided often in little intestine shaped heaps, called on the surface of the ground. The loco motion of the E. is effected by means of two sets of muscles, which enable it to contract and dilate its rings; its bristles preventing motion backwards, and the whole muscular effort thus resulting in progress; whilst the expansion of the rings, as it contracts the anterior segments, and draws forward the hinder parts, widens a passage for it through earth whose particles were close together before. Earthworms are thus of very great use, their multitudes continually stirring and loosening the soil through which they work their way; and moles, pursuing to feed on them, stir and loosen it still more; whilst worm-casts gradually accumulate on the surface to form a layer of the very finest soil, to which it is supposed that the best old pastures in a great measure owe their high value.
Earthworms do not often visit the surface of the ground, except during night, and when the ground is moist. In the evening, during or after rain, or in the morning, when the dew is abundant, they may sometimes be seen traveling about in great num bers. Both drought and cold cause them to retreat more deeply into the earth.—Their respiration is effected by means of little sacs, which communicate by minute pores with the external air. They are hermaphrodite, but mutual fecundation takes place by means of the thickened knot (c/itellum) which is situated before the middle of their body. Their eggs often contain two embryos, and the young worms escape by a sort of valvular opening at the end.
Besides their usefulness in the improvement of the soil, earthworms are of impor tance as food for birds, fishes, etc. Their value as bait for fishes is well known to every angler. The instinct which prompts them to hasten to the surface, when, in quest of bait, the angler shakes the soil with a spade or fork, is probably to be referred to the similar shaking on the approach of their constant enemy, the mole.
An E. of great size is common in the East Indies, wherever the climate is moist, from the Himalaya to Ceylon and Java. It is iethyophis glutinosus, and abounds very much in that viscid secretion which in the common E. also forms a kind of protecting sheath for the animal, and smooths its way.
a contrivance for improving the hearing of the partially deaf. For this purpose many ingenious instruments have been devised. The principle in them all is the same: to collect the sonorous vibrations, and to convey them in an intensified form to the deeper parts of the ear. In this way the hand placed behind the external car constitutes the simplest form of ear-trumpet: Though, in a great number of cases of impaired hearing, there can be no doubt that much assistance and comfort are obtained from the use of one or other of the varieties of the ear-trumpet, still they must not be used indiscriminately, for in unsuitable cases they often do much mischief, both by increasing the deafness, and aggravating the noises in the head from which deaf persons often suffer so much. They are of most use, perhaps, in advanced cases of ner vous deafness, though injurious in the early stages of this complaint; they are hurtful also in all acute diseases of the organ, and of little or no use in those cases of great thickening of the contents of the middle ear, where the adapting power of the organ has been lost. There are many varieties of trumpet in common use. By far the most use ful and comfortable are those which are worn on the bead, which go by the name of ear-cornets or acoustic auricles. They can be concealed under the hair or cap, and may be adapted to one or both ears by means of a spring over the head. The apparatus most commonly in use requires to be held in the hand, and consists of a narrow portion inserted into the ear-passage, and which gradually expands into a wide mouth; or the extremity of the instrument may be turned downwards, as in that form which passes by the name of Miss 'Martineau's trumpet. Another variety, applicable to the more severe cases of deafness, consists of an elastic tube, one end of which is tipped with i rory, and is placed in the ear of the patient; the other is held in the hand of the speaker, who applies his mouth to the open extremity. With this instrument only one voice can be heard at a time. With the first-mentioned variety, general conversation can be heard often quite well. Ear-trumpets are generally made of some thin metallic substance, such as tin. Gutta-percha, vulcanite, and other substances, are also frequently used.