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LEFT SKEAT 446 SKELETON SKEAT, WALTER WILLIAM, an English Anglo-Saxon scholar; born in London, Nov. 21, 1835. In 1883 he be- came Professor of Anglo-Saxon at Cam- bridge; was one of the founders of the English Dialect Society; and an author- ity on early English literature. He ed- ited "The Vision of William Concerning Piers Plowman" (1867-1885); Bar- bour's "The Bruce" (1870-1889) ; "Speci- mens of English Literature, 1298-1579" (1871 and 1872; "The Works of Chaucer" (1894) ; numerous poems, metrical ro- mances, etc.; compiled "An Etymological Dictionary of the English Language" (1879-1881; 1884); and wrote "A Stu- dent's Pastime" (1896); "Notes on Eng- lish Etymology" (1901), etc. He died in 1912. SKELETON, a general term for the more or less hard parts of animals, whether forming an internal supporting framework — an endoskeleton, or an exter- nal exoskeleton, often useful as armor. Skeleton of Invertebrates. — Many of the Protozoa have shells of lime, or of flint, or of some organic substance, such as acanthin. These are formed by the living matter of the units, in the case of the lime and flint shells from materials absorbed from the surrounding water, but in what precise way we do not know. Al- most all sponges are supported by loose or firmly fused spicules of lime or of flint, or have, as in the bath spone, an inter- woven supporting skeleton of "horny" fi- bers. The spicules or fibers are formed by cells in the middle stratum of the sponge. Among ccelenterates various forms of skeleton, both external and in- ternal, both limy and "horny," are repre- sented by the different kinds of corals. With few exceptions these skeletons are produced by cells belonging to the outer layer or ectoderm of the animal. Worms have little that can be called a skeleton. The tubes, calcareous or otherwise, in which many sedentary worms are shel- tered, have no vital connection with the animals which make and inhabit them. Echinoderms tend to be very calcareous; lime is deposited in the mesodermic tissue of the body in almost any part, though predominantly near the surface. Most arthropods have well-developed exoskele- tons, cuticles formed from the epidermis, consisting in great part of an organic basis of chitin, on which, in crustaceans and most myriopods, carbonate of lime is also deposited. As this cuticle is not al- ways restricted to the outside of the ani- mal, but sometimes extends inward, an apparent endoskeleton arises — e. g., in the lobster, the king crab, and the scor- pion. Most mollusks have shells in which carbonate of lime occurs along with an organic basis conchiolin, and in cuttlefish there is a remarkable development of car- tilage around the nerve centers in the head — an analogue of the skull in verte- brate animals. ia-j SKELETON