WORM, a term used popularly to denote almost any kind of elongated, apparently limbless creature, from a lizard, like the blindworm, to the grub of an insect or an earthworm. In old usage it sometimes denoted a mythical dragon. The word "worm" is applied to many objects resembling the animals in having a spiral shape or motion, as the spiral thread of a screw, or the spiral pipe through which vapour is passed in distillation (q.v.). As a term of disparagement and contempt the word is also used of persons, from the idea of wriggling or creeping on the ground, partly, too, perhaps, with a reminiscence of Genesis iii. 14. Linnaeus applied the Latin term Vermes to the modern zoological divisions, Mol lusca, Coelenterata, Protozoa, Tunicata, Echinoderma (qq.v.), as well as to those forms which modern zoologists recognize as worms. As a matter of convenience the term Vermes is still employed, for instance, in the International Catalogue of Zoological Literature and the Zoological Record, to cover a number of worm-like ani mals. In systematic zoology, however, the use of a division Vermes has been abandoned, as it is now recognized that many of the animals that even a zoologist would describe as worms belong to different divisions of the animal kingdom. The so-called flatworm (Platyhelminthes, q.v.), including the Planarians, the Flukes (see TREMATODES), and Cestodes (see TAPEWORMS) are no doubt re lated. The marine Nemertine worms (see NEMERTINEA) are iso
lated. The thick-skinned round worms, such as the common horse worm and the threadworms (see NEMATODA), together with the Nematomorpha (q.v.), the Chaetosomatida, the Desmoscolecida and the Acanthocephala • (q.v.), form a fairly natural group. The Rotifera (q.v.), with possibly the Kinorhyncha (q.v,) and Gastrotricha (q.v.), are again isolated. The remaining worms are probably all coelomate animals. There is a definite Annelid group (see ANNELIDA), including the Archiannelida, the bristleworms of which the earthworm (q.v.) is the most familiar type, the My zostomida (q.v.) Hirudinea (see LEECH) and the armed Gephy reans (see The unarmed Gephyreans (see GEPHY REA) are now separated from their former associates and divided into two groups of little affinity, the Sipunculoidea (q.v.) and the Priapuloidea (q.v.). The Phoronidea and the Chaetognatha (q.v.) are also isolated.
Mention is made under TAPEWORM of the worms of that species inhabiting the human body as parasites. Another common human parasite is Ascaris lumbricoides or round worm, found chiefly in children and occupying the upper portion of the intestine. (See