Thomas Henry Huxley, British biologist and science educationist, was the son of George Huxley, a mathematics teacher, and his wife Rachel, born Withers. He received only two years of schooling (during 1833-1835) and for the rest educated himself. He was apprenticed to a medical man for some time and from 1841 studied anatomy, surgery and botany at Sydenham College, and from October 1842 at Charing Cross Hospital. Though he passed Part I of the MB degree he did not complete the degree. By 1845 he had already acquired French and German, and had read widely. That year he published his first scientific paper (in the London Medical Gazette, 1845), describing a hitherto unrecognised middle layer of cells in the inner root sheath of hairs, which came to be known as Huxley's layer.
Huxley joined he navy in 1845. From December 1846 to November 1850 he was assistant surgeon on HMS Rattlesnake, which was sent to explore and survey southern New Guinea and the Barrier Reef. He kept a diary of the voyage, which was eventually published by his son in 1935. He spent most of his time studying the surface life of the seas through which they passed. The ship arrived at Simon's Bay on 8 March 1847 and stayed for a month. He studied the local marine life but did not travel inland, or even to Cape Town.
In an important paper "On the anatomy and the affinities of the family of Medusae", published in the Transactions of the Royal Society of London in 1849, he grouped these animals together with others in a class which he later named Hydrozoa. He also pointed out that all these animals consisted essentially of two membranes enclosing a central cavity or stomach, and compared these membranes to the endoderm and ectoderm of the vertebrate embryo - a profound insight which was immediately recognised as important. His observations during the voyage of HMS Rattlesnake were described more fully in The oceanic Hydrozoa, published in 1859.
On his return to England Huxley was elected a fellow of the Royal Society of London in 1851 and two years later was elected on its council. For the next few years the navy allowed him to work on the observations he had collected, which led to the publication of several important memoirs on various groups of marine invertebrates.
On being recalled to active duty Huxley resigned his post and in July 1854 was appointed professor of natural history at the Royal School of Mines, with an additional appointment as naturalist to the Geological Survey the next year. His most important contribution to zoology during these years was a lecture delivered before the Royal Society in 1858 on "The theory of the vertabrate skull". The next year Charles Darwin* published his theory of evolution and Huxley became one of its most important public defenders. He furthermore applied the theory to humans in a paper on "Zoological evidence as to man's place in nature" in 1863. He was an enormously popular lecturer and found his true vocation in the popularisation of science. Among the numerous books that he wrote, most published in many editions over a period of decades, were introductory texts on physiology (1866), practical biology (1875) and zoology (1880); A manual of the anatomy of invertebrated animals (1877), The advance of science in the last half century (1887), and Darwinian essays (1893).
During his 31 years at the School of Mines Huxley devoted much of his time to palaeontological research. He published many papers on fossil fish, and his study of fossil reptiles allowed him to demonstrate their close relationship to birds. Several of his papers dealt with fossils from South Africa, for example, "On a new species of Dicynodon (D. murrayi) from near Colesberg, South Africa" (1859), "On some amphibian and reptilian remains from South Africa and Australia" (1859), and "On some remains of large dinosaurian reptiles from the Stormberg Mountains, South Africa" (1867), all of which were published in the Quarterly Journal of the Geological Society and in several other journals, while "On Saurosternon bainii and Pristerodon mackayi, two new fossil lacertilian reptiles from South Africa (with notes by G. Mackay)" (1868) appeared in the Geological Magazine.
Public life also took up much of his time. From 1862 to 1884 he served on no less than ten Royal Commissions. In 1870 he was president of the British Association for the Advancement of Science. From 1871 to 1880 he was a secretary of the Royal Society, and from 1883 to 1885 its president. He served as inspector of fisheries from 1881 to 1885, but devoted an increasing share of his attention to lectures, public addresses, and more or less controversial writings on philosophy and theology, coining the term "agnostic" to describe his own position with regard to religion. In 1885 his health broke down, forcing him to retire from his post and from public life. In 1890 he moved to Eastbourne, where he died five years later. He was married to Henrietta Anne Heathhorn, with whom he had five daughters and three sons.