Thomas Henry Huxley, an English naturalist, born in Ealing, Middlesex, May 4, 1825. He spent two and a half years at Ealing school, in which his father was one of the masters, but with this exception his education was 'carried on chiefly at home. In 1842 he entered the medical school of Charing Cross hospital, and in 1845 received the degree of M. B. from the university of London, being placed second in the list of honors for anatomy and physiology. He began his literary career while yet a student by contributing to the "Medical Times and Gazette" a paper on that layer in the root sheath of hair which has since borne his name. In 1846 he joined the medical service of the royal navy, and was stationed at Haslar hospital, whence he was selected the same year to accompany Capt. Stanley, as assistant surgeon of the Rattlesnake, in his expedition to the South Pacific. After a four years' voyage of circumnavigation, during which surveys of the east coasts of Australia and Papua were made, the ship returned to England in November, 1850. While absent Mr. Huxley, who made extensive observations on the natural history of the seas traversed, sent home a number of communications, the first of which, read before the royal society in 1849, is " On the Anatomy and Affinities of the Family of the Medusa3." On his return some of these papers were elaborated by him and published in the "Philosophical Transactions" of the royal society, of which, in June, 1851, he was elected a fellow.

In 1853 he resigned his position in the navy, and in the following year he succeeded Prof. Edward Forbes as professor of natural history in the royal school of mines, an office which he still holds (1874). He has since resided in London, where he has devoted himself to constant scientific labor and research. In addition to his annual course of lectures on general natural history, he has delivered many lectures on kindred subjects to mixed audiences, and has done much to popularize science. He was Hunterian professor in the royal college of surgeons from 1863 to 1869, and was twice chosen Fullerian professor of physiology in the royal institution. In 1869 and 1870 he was president both of the geological and the ethnological society; in 1870 he was president of the British association for the advancement of science; and in 1872 he became secretary of the royal society. Since 1870 he has been a member of the royal commission on scientific instruction and the advancement of science. From 1870 to 1872 he served on the London school board, where he was chairman of the committee which drew up the scheme of education adopted in the board schools.

During this time he took an active part in its deliberations, and became conspicuous by his opposition to denominational teaching, and particularly by his denunciation of the doctrines of the Roman Catholic church. In 1872 he was elected lord rector of the university of Aberdeen. - Prof. Huxley has done as much probably as any living investigator to advance the science of zoology, and the world is indebted to him for many important discoveries in each of the larger divisions of the animal kingdom. His earlier labors were devoted chiefly to the lower marine animals, with which he formed a most thorough empirical acquaintance during his Pacific voyage, and he has described many which previously had been either unknown or very imperfectly studied. During the past ten years he has devoted himself assiduously to the comparative anatomy and the classification of the vertebrata, and has embodied the results of his more important researches in numerous monographs. In his first published work, on the medusae, he called attention to the fact that the body of these animals is formed of two cell layers, which may be compared to the two germinal layers of the higher animals; an idea which has since found its complete expression in the gastraea theory of Haeckel. To him also is due the vertebral theory of the skull, which has since been demonstrated so clearly by Gegenbaur; and he was the first to extend to man Darwin's theory of natural selection.

In his three lectures on "Man's Place in Nature," delivered in 1863, he made an elaborate exposition of the doctrine of evolution as applied to man, asserting that the anatomical differences between man and the highest apes are of less value than • those between the highest and the lowest apes. Among his many popular lectures, that " On the Physical Basis of Life," delivered in 1868, has attracted much attention. In it he advances the idea that there is some one kind of matter common to all living beings; that this matter, which he designates as protoplasm, depends on the preexistence of certain compounds, carbonic acid, water, and ammonia, which when brought together under certain conditions give rise to it; that this protoplasm is the formal basis of all life, and therefore all living powers are cognate, and all living forms, from the lowest plant or animalcule to the highest being, are fundamentally of one character. Prof. Huxley is a corresponding member of the principal foreign scientific societies, , and has received honorary degrees from the universities of Breslau and Edinburgh. His works are as follows: "The Oceanic Hydro-zoa" (1857); "Evidence as to Man's Place in Nature" (1863); "Lectures on the Elements of Comparative Anatomy" (1864); "Lessons in Elementary Physiology" (1866); "An Introduction to the Classification of Animals" (1869); "Lay Sermons, Addresses, and Reviews" (1870); and "Critiques and Addresses" (1873): He is the author also of a large number of papers published in the journals of the royal, the Linnaean, the geological, and the zoological societies, and in the memoirs of the geological survey of Great Britain.