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HUXLEY, THOMAS HENRY (1825–1895), man of science, was born at Ealing on 4 May 1825. His father, George Huxley, was senior assistant master in a school at Ealing, which had at that time a considerable reputation under the head-mastership of Dr. Nicholas. Huxley was the seventh child of his parents, and the youngest of those who survived infancy. His mother's maiden name was Rachel Withers. He says of himself: 'Physically and mentally I am the son of my mother so completely — even down to peculiar movements of the hands, which made their appearance in me as I reached the age she had when I noticed them — that I can hardly find a trace of my father in myself, except an inborn faculty for drawing, which unfortunately, in my case, has never been cultivated, a hot temper, and that amount of tenacity of purpose which unfriendly observers sometimes call obstinacy.'

When Huxley was eight years old he was sent to the school in which his father worked; but the death of the head-master led to a change in the character of the school, and George Huxley left it, taking his family to his native town of Coventry. From this time Huxley received little or no systematic education, and his reading does not seem to have been guided by any definite plan. He did, however, earnestly and thoroughly read books on a great variety of subjects. At fourteen he had read Sir William Hamilton's 'Logic,' and under the influence of Carlyle's writings he had begun to learn German.

In 1839 his two sisters married, and each married a doctor. This circumstance seems to have determined the choice of a profession for Huxley himself, although he tells us that his own wish at the time was to become a mechanical engineer. One brother-in-law, Dr. Cooke of Coventry, strongly excited his interest in human anatomy, and in 1841 he went to London as apprentice to the other, Dr. J. G. Scott. At the first post-mortem examination he attended he was in some way poisoned; a serious illness resulted, and after the immediate effects had passed away a form of chronic dyspepsia remained, which was a source of serious trouble throughout his after life.

In 1842 he matriculated at London University, attended Lindley's lectures on botany at Chelsea, and endeavoured, in spite of a still imperfect knowledge of German, to read the great work of Schleiden. In the autumn of the same year he and his elder brother James obtained scholarships at the Charing Cross hospital, where Huxley first felt the influence of daily intercourse with a really able teacher. He says : 'No doubt it was very largely my own fault, but the only instruction from which I ever obtained the proper effect of education was that which I received from Mr. Wharton Jones, who was the lecturer on physiology at the Charing Cross school of medicine.... I do not know that I have ever felt so much respect for anybody as a teacher before or since.' During the next three years he must have accomplished an enormous amount of work. He distinguished himself in the ordinary subjects of professional study, but in addition to this he acquired in some way or other a remarkably thorough knowledge of comparative anatomy, and a wide acquaintance with the writings of the great biologists. In 1845 he announced his discovery of that layer of cells in the root-sheath of hair which now bears his name. Any one who will try to demonstrate the existence of this layer by the methods at Huxley's command will appreciate the power of observation shown by the discovery.

He graduated M.B. in London University in 1845, winning a gold medal for anatomy and physiology. In 1846, being qualified to practise his profession, he applied for an appointment in the royal navy. An application to the director-general, suggested by a fellow-student, was successful, and he was sent to Haslar hospital on the books of Nelson's ship Victory. Sir John Richardson [q. v.], who was Huxley's chief at Haslar, quickly recognised his qualities, and resolved to find him an appointment which should enable him to prove his worth. Accordingly, when Captain Owen Stanley asked for an assistant surgeon to be appointed to H.M.S. Rattlesnake, then about to start on a surveying cruise in the seas between Australia and the Great Barrier Reef, Huxley was recommended and accepted.

The Rattlesnake left England on 3 Dec. 1846, and was paid off at Chatham, on her return, on 9 Nov. 1850. During the voyage Huxley devoted himself chiefly to the study of animals which could not be adequately preserved, for examination at home, by any methods then in use. Accordingly the first results of his work are described in a series of memoirs on those delicate hydrozoa, tunicates, and mollusca, which float near the surface of the sea, and can be caught in abundance from the deck of a sailing vessel in calm weather. The value of these memoirs is due as much to the method of morphological analysis adopted as to the very large amount of new anatomical information they contain. The conception of a morphological type, which was then supported in England by the great influence of (Sir) Richard Owen [q. v.], may be understood from his definition of homology, which he interprets 'as signifying that essential character of a part which belongs to it in its relation to a predetermined pattern, answering to the "idea" of the archetypal world in the Platonic cosmogony, which archetype or primal pattern is the basis supporting all the modifications of such part ... in all animals possessing it' (Owen, On the Nature of Limbs, 1849). The conception of morphological type as an 'archetypal idea,' which Owen had derived from Laurenz Oken (1779-1851), the German naturalist, and his followers, was clearly incapable of being tested by experiment, and Huxley from the first rejected it. For him, as for Von Baer and Johannes Müller, the only useful 'morphological type' was a general statement of those structural characters common to all members of a group of animals in the embryonic or the adult state. Such conceptions could be tested and corrected by observation ; and, until the 'Origin of Species' appeared, Huxley regarded any hypothesis concerning the nature of the bond between animals which exhibit the same structural plan as altogether premature.

When the Rattlesnake left 'England, the hydrozoa were commonly associated with starfishes, parasitic worms, and infusoria in Cuvier's group 'Radiata.' In 1847 Huxley sent two papers, dealing with the structure of a great division of the hydrozoa, to the Linnean Society ; in 1848 he sent to the Royal Society a memoir 'On the Affinities of the Family of the Medusæ' (Phil. Trans. 1849), and he wrote a letter to Edward Forbes [q. v.], published in 1850 (Ann. Mag. Nat. Hist. vi.) In these memoirs the morphological type common to all the hydrozoa is clearly explained, and in the letter to Edward Forbes it is shown that the same structural plan may be recognised in sea-anemones, corals, and their allies. It is pointed out that the plan common to these animals is not exhibited by the other 'Radiata,' and it is proposed to remove both sets of animals from the Radiata, regarding them as subdivisions of a separate class, 'Nematophora.' The views embodied in this suggestion were speedily accepted, and Huxley's statement of the morphological plan common to the class is now held to embody a firmly established anatomical truth. In the memoir on the medusæ a comparison was made between the two cellular 'foundation layers' out of which the body wall and the various organs of a polyp or a medusa are formed, and the two primary layers recognised by Pander and Von Baer in the early embryos of vertebrates. Similarities between the adult condition of lower, and the embryonic condition of higher members of the same group of animals had been recognised by Meckel, and more fully by Von Baer ; but this comparison between the early embryo of the highest vertebrates and the adult condition of the simplest multicellular animals then known went far beyond any previous suggestion of the kind. This comparison paved the way for the attempts inaugurated later by Haeckel and Dr. Ray Lankester, under the influence of Darwin, to interpret the embryonic histories of the higher animals as evidence of their common descent from a two-layered ancestor, essentially like a hydroid polyp.

On his return to England in 1850 Huxley learnt that the value of his work on Medusæ had been fully recognised. He was elected F.R.S. in 1851, was granted the society's medal in 1852, and found the leading biologists in London, especially Edward Forbes, were anxious to help him. With their help, and that of Sir John Richardson, he obtained from the admiralty an appointment as assistant surgeon to a ship then stationed at Woolwich, with leave of absence which enabled him to arrange the materials amassed during his voyage, and to prepare his notes for publication. Accordingly in 1851 he published two memoirs on the Ascidians, in which several aberrant genera (especially appendicularia and doliolum) are shown to be modifications of the same morphological type as that found in other ascidians ; the relation between salpa and other ascidians is clearly explained, while the phenomenon of budding, alternating with sexual reproduction, which had been shown to occur by Chamisso and Eschscholtz, is fully described. In the paper 'On the Morphology of the Cephalous Mollusca' (Phil. Trans. 1853) a great advance is made upon all previous efforts to recognise the structural plan common to the various modifications of the 'foot,' and the structure of the pelagic 'heteropods' is described. These expositions of the morphology of three widely different groups of animals established Huxley's reputation as a scientific anatomist of the first rank; and the success which attended his use of simple inductive generalisation as a statement of morphological type had great effect upon the methods of English biologists. While winning reputation and the warm friendship of many among the ablest men in London, he was not earning money ; and without pecuniary help of some sort it was impossible even to publish some of his results. The admiralty felt unable to use funds, entrusted to it for other purposes, in assisting to publish anatomical works ; and not only so, but in January 1854 Huxley's request for further leave of absence was met by an order to join a ship at once. Rather than obey this order he preferred to leave the service, and with it his only certain income, determined to maintain himself somehow, by writing and lecturing, until he could gain an assured income without giving up all hope of scientific work. Fortunately a chance of doing this soon appeared. In June 1854 his friend, Edward Forbes, who had just commenced his course of lectures at the Royal School of Mines in Jermyn Street, was appointed to the professorship of natural history in Edinburgh. Huxley undertook to finish the course in London ; in July he was appointed lecturer on natural history at the Royal School of Mines, and naturalist to the geological survey in the following year. The salary attached to these posts was small, but with such additions as he could make to it in other ways he felt justified in taking an important step. During the visits of the Rattlesnake to Sydney, Huxley had met and won the affection of Miss H. A. Heathorn, and he felt that his position was now so secure that he might ask her to share it. Miss Heathorn and her parents set sail for England early in 1855, reaching London in May. The marriage took place in July of the same year.

Before the end of 1855 Huxley had published more than thirty technical papers, and he had given a number of lectures to unprofessional audiences. One of these, 'On the Educational Value of the Natural History Sciences' (1854, Collected Essays, vol. iii.), contains those statements concerning the fundamental unity of method in all sciences, the value of that method in the affairs of daily life, and its importance as a moral and intellectual discipline, which form the essence of his popular teaching in later years.

From 1855 until 1859 Huxley's time was largely occupied by the duties of his new post. In his teaching he quickly adopted a system afterwards developed until it became the model which teachers of biology throughout the country endeavoured to imitate. In his lectures he described a small series of animals, carefully chosen to illustrate important types of structure ; and his aim was that every student should be enabled to test general statements concerning a group of animals by reference to one member of the group which he had been made to know thoroughly. Huxley realised from the first that the thorough knowledge of representative animals, which is the only proper foundation for a knowledge of morphology, ought to be acquired by direct observation in the laboratory ; this, however, was impossible in Jermyn Street, and his ideal was not completely realised until later. In spite of a certain distaste for public speaking, which only time and practice enabled him to overcome, he devoted much of his most strenuous effort to the work of popular exposition. In a letter dated 1855 he says, 'I want the working classes to understand that science and her ways are great facts for them — that physical virtue is the base of all other, and that they are to be clean and temperate and all the rest — not because fellows in black with white ties tell them so, but because these are plain and patent laws of nature, which they must obey under penalties.'

His scientific work during this period was influenced by his official duties in a museum of palæontology. The monograph of the oceanic hydrozoa, although published in 1859, had been completed long before. Two papers, which continue work begun on the Rattlesnake, are the memoir on Pyrosoma (Trans. Linn. Soc. 1859), and that on Aphis (1857). Each of these describes an alternation of generation, and so continues the early work on salpa : but with these exceptions the greater part of the work published between 1855 and 1859 deals either with fossil forms or with problems suggested by them. Among the more important of the descriptive memoirs (some twenty in number) published before the end of 1859, we must mention that on cephalaspis and pteraspis (1858), in which the truth of the suggestion that pteraspis is a fish is finally demonstrated ; the accounts of the eurypterina (1856-9) ; the descriptions of dicynodon, rhamphorhynchus, and other reptiles. These studies of fossils seem to have been carried on simultaneously with that of the living forms related to them; thus the work on fossil fishes (the main results of which were not published until 1862) was accompanied by a study of the development of skull and vertebral column in recent fishes (Quart. Journ. Micr. Sci. 1859), and by the histological work upon their exoskeleton published in Todd's 'Encyclopædia of Anatomy and Physiology' (article 'Tegumentary Organs'). The description of extinct crocodilia led to an investigation of the dermal skeleton in living genera (Journ. Linn. Soc. 1860). The most important problem, suggested by continual work upon vertebrates, whether recent or fossil, is that presented by the composition of the skull. The doctrine prevalent in England was that which Owen had learned from Goethe and Oken. According to Owen, the archetype skeleton of a vertebrate 'represents the idea of a series of essentially similar segments succeeding each other in the axis of the body ; such segments being composed of parts similar in number and arrangement.' Attempts were made, in accordance with this theory, to divide the skull into a series of rings, each of which was supposed to contain every element present in a post-cranial vertebra. The result was a method of description which obscured the actual anatomical relations of the parts described ; and the attempt to demonstrate an archetypal idea by anatomical methods reached its climax of absurdity. Huxley applied to the skull the same method of analysis as that he had so successfully applied to other structures. In his essay 'On the Theory of the Vertebrate Skull,' read as the Croonian lecture before the Royal Society in 1858, he endeavours to formulate a morphological type of cranial structure in an inductive statement of those characters which are common to the skulls of a number of representative vertebrates in the adult and embryonic conditions. The lecture is based partly on the embryological work of Reichert, Rathke, and Remak, supplemented by observations of his own upon fishes and amphibia ; partly on a careful study of adult skulls. The result is a statement of cranial structure which has been justified in all essential points by the work of the last forty years. The lecture on the skull is admirable not only in substance but in form. The character of the audience justified the free use of such aid to concise statement as technical terms afford ; but when this is remembered the lecture must be regarded as a masterpiece of concise and lucid exposition, worthy to rank with the most brilliantly successful efforts of Huxley's later years.

For Huxley, as for many others, the most important event of 1859 was the publication of the 'Origin of Species.' He had maintained a sceptical attitude towards all previous hypotheses which involved the transmutation of species, and, in the chapter written for Mr. Francis Darwin's 'Life and Letters of Charles Darwin,' he says : 'I took my stand upon two grounds : firstly, that up to that time the evidence in favour of transmutation was wholly insufficient ; and, secondly, that no suggestion respecting the causes of the transmutation assumed, which had been made, was in any way adequate to explain the phenomena.'

Darwin rendered a belief in the occurrence of transmutation far easier than it had been by his collection of facts illustrating the extent of variation ; while the theory of natural selection provided a working hypothesis, adequate to explain the alleged phenomena, and capable of being experimentally tested. The attempt to secure a fair trial for the new hypothesis, which Huxley felt it his duty to make, involved a great expenditure of time and strength. The account of the 'Origin of Species' written for the 'Times' in 1859, and a lecture 'On Races, Species, and their Origin,' delivered in 1860, mark the beginning of a long effort, which only ceased as the need for it became gradually less. Many were the discussions of this doctrine in which he took part, and especially important and interesting was his share in the debate on the question during the meeting of the British Association for the Advancement of Science at Oxford in 1860.

The consequence of Darwin's theory, which many persons found the greatest difficulty in accepting, was a belief in the gradual evolution of man from some lower form ; and evidence which seemed to establish a broad gap between the structure of man and that of other animals was welcomed. Great interest was therefore excited by a paper which Owen had read in 1857, and repeated with slight modification as the Kede lecture before the university of Cambridge in 1859. Owen declared that the human brain was distinguished from that of all other animals by the backward projection of the cerebral hemispheres, so as to cover the cerebellum, and by the backward prolongation of the cavity of each cerebral hemisphere into a 'posterior horn,' with an associated 'hippocampus minor.' It is difficult to understand how an anatomist of Owen's experience can have made these statements; and his subsequent explanations are equally unintelligible (e.g. Owen, Comparative Anatomy of Vertebrata, 1866, vol. i. pp. xix-xx). In 1861 Huxley published two essays, one 'On the Brain of Ateles Paniscus,' and one 'On the Zoological Relations of Man with the Lower Animals,' in which it was clearly shown that Owen's statements were inaccurate and inconsistent with well-known facts. Between 1859 and 1862 he gave a series of lectures 'On the Comparative Anatomy of Man and the Higher Apes,' published in book form under the title 'Zoological Evidences as to Man's Place in Nature' (1863, Collected Essays, vol. vii.) There is a sense in which the publication of this book marks the beginning of a new period of his work ; because from the time of its appearance his writings attracted greater attention and affected a far greater number of people than before. This book and a series of lectures 'On the Causes of the Phenomena of Organic Nature,' addressed to working men and printed in 1863, were widely read and discussed, and from henceforth Huxley devoted a continually increasing amount of energy to popular teaching and to the controversy arising in connection with it. His sense of the importance of such work, and the enjoyment he derived from it, may be gathered from words which seem, although he uses them of Priestley, to give an admirable picture of himself. He says :

'It seems to have been Priestley's feeling that he was a man and a citizen before he was a philosopher, and that the duties of the two former positions are at least as imperative as those of the latter. However, there are men (and I think Priestley was one of them) to whom the satisfaction of throwing down a triumphant fallacy is at least as great as that which attends the discovery of a new truth, who feel better satisfied with the government of the world when they have been helping Providence by knocking an imposture on the head, and who care even more for freedom of thought than for mere advancement of knowledge. These men are the Carnots who organise victory for truth, and they are at least as important as the generals who visibly fight her battles in the field ' (1874, Collected Essays, vol. iii.)

The freedom of thought for which Huxley contended was freedom to approach any problem whatever in the manner advocated by Descartes; and he wishes his more important essays to be regarded as setting forth 'the results which, in my judgment, are attained by an application of the "method" of Descartes to the investigation of problems of widely different kinds, in the right solution of which we are all deeply interested' (ib. vol. i. preface). In 1870, after describing Descartes's condition of assent to any proposition, he says : 'The enunciation of this great first commandment of science consecrated doubt. It removed doubt from the seat of penance among the grievous sins to which it had long been condemned, and enthroned it in that high place among the primary duties which is assigned to it by the scientific conscience of these latter days.' While he held doubt to be a duty, he had no tolerance for careless indifferentism ; and he was fond of quoting Goethe's description of a healthy active doubt: 'Eine thätige Skepsis ist die, welche unablässig bemüht ist, sich selbst zu überwinden.'

The fearless application of Cartesian criticism aroused great indignation between 1860 and 1870, but the essays and addresses published during this period did their work. They were certainly among the principal agents in winning a larger measure of tolerance for the critical examination of fundamental beliefs, and for the free expression of honest reverent doubt. The best evidence of the effect they have produced is the difficulty with which men of a younger generation realise the outcry caused by 'Man's Place in Nature,' or by the lecture 'On the Physical Basis of Life ' (ib. vol. i. 1868). Two passages from the last-named lecture may be quoted as giving a summary of Huxley's philosophical position in his own words :

'But if it is certain that we can have no knowledge of the nature of either matter or spirit, and that the notion of necessity is something illegitimately thrust into the perfectly legitimate conception of law, the materialistic position that there is nothing in the world but matter, force, and necessity, is as utterly devoid of justification as the most baseless of theological dogmas. The fundamental doctrines of materialism, like those of spiritualism and most other "-isms," lie outside "the limits of philosophical enquiry," and David Hume's great service to humanity is his irrefragable demonstration of what those limits are. . . . Why trouble ourselves about matters of which, however important they may be, we do know nothing and can know nothing ? We live in a world which is full of misery and ignorance, and the plain duty of each and all of us is to try to make the little corner he can influence somewhat less miserable and somewhat less ignorant than it was before he entered it. To do this effectually it is necessary to be fully possessed of only two beliefs the first, that the order of nature is ascertainable by our faculties to an extent which is practically unlimited ; the second, that our volition counts for something as a condition of the course of events. Each of these beliefs can be verified experimentally as often as we like to try. Each, therefore, stands upon the strongest foundation upon which any belief can rest, and forms one of our highest truths. If we find that the ascertainment of the order of nature is facilitated by using one terminology, or one set of symbols, rather than another, it is our clear duty to use the former ; and no harm can accrue so long as we bear in mind that we are dealing merely with terms and symbols.'

Those who 'care even more for freedom of thought than for mere advancement of knowledge' may well consider the effect produced by his lectures and essays upon the minds of English-speaking peoples to be the most important result of Huxley's work between 1860 and 1870. But they represent only a small part of the work he actually did during this period. He was an active member of four royal commissions (on the acts relating to trawling for herrings on the coast of Scotland, 1862 ; on the sea-fisheries of the United Kingdom, 1864-5; on the Royal College of Science for Ireland, 1866 ; on science and art instruction in Ireland, 1868). He was Hunterian professor at the Royal College of Surgeons from 1863 to 1869, and Fullerian professor at the Royal Institution from 1863 to 1867 ; he undertook an increasing amount of administrative work in connection with various learned societies, especially the Royal, the Zoological, and the Ethnological ; and he wrote frequently for the reviews, being himself for a short time an editor of the quarterly 'Natural History Review.' In spite of the increased demands upon his time and strength made by all these new duties, his purely scientific work rather increased than diminished in value and in amount.

The papers on fossil fishes, already referred to, were followed in 1861 by an 'Essay on the Classification of Devonian Fishes.' Apart from its great value as an addition to our knowledge of a difficult group of fishes, this essay is remarkable because in it Huxley drew attention to the type of fin which he called 'crossopterygian,' or fringed, because the fin-rays are borne on the sides of a longer or shorter central axis. The imperfect knowledge attainable from the study of fossils did not permit him at this time to describe the structure of the crossopterygium very fully ; but after the discovery of Ceratodus the conceptions foreshadowed in this essay acquired great importance in connection with attempts to find a common type of limb from which both the fin of an ordinary fish and the limb of an air-breathing vertebrate might conceivably have been derived.

In 1862 he delivered an address to the Geological Society, in which he attacked a doctrine then widely held. The order in which the various forms of life appear, as we examine the fossiliferous rocks from the oldest to the most recent, is practically the same in all parts of the world. This fact had led many geologists to infer that any step in the successional series must have occurred simultaneously all over the earth, so that two series of rocks containing the same fossils were held to be of contemporaneous origin, however distant from one another they might be. Huxley gave a forcible summary of the evidence against this view, and declared that 'neither physical geology nor palaeontology possesses any method by which the absolute synchronism of two strata can be demonstrated. All that geology can prove is local order of succession.' The justice of this statement has not been questioned ; and the limitation imposed by it is one of the many difficulties encountered when we attempt to learn the ancestral history of animals from the fossil records.

In 1863 he delivered a course of lectures at the College of Surgeons 'On the Classification of Animals,' and another 'On the Vertebrate Skull.' These lectures were published together in 1864. Other courses 'On the Comparative Anatomy of Vertebrates' followed, and a condensed summary of these was published as a 'Manual of the Comparative Anatomy of Vertebrated Animals' in 1871. The scrupulous care with which he endeavoured to verify by actual observation every statement made in his lectures rendered the labour of preparation very great. Sir William Flower [q. v. Suppl.] describes the way in which he would spend long evenings at the College of Surgeons, dissecting animals available among the stores, or making rapid notes and drawings, after a day's work in Jermyn Street. The consequences were twofold ; the vivid impression of his own recent experience was communicated to his hearers, and the work of preparation became at once an incentive to further research and a means of pursuing it.

The lectures in 1867 dealt with birds, and Professor Newton writes of them : 'It is much to be regretted that his many engagements hindered him from publishing in its entirety his elucidation of the anatomy of the class, and the results which he drew from his investigations of it ; for never, assuredly, had the subject been attacked with greater skill and power, or, since the days of Buffon, had ornithology been set forth with greater eloquence' (Newton, A Dictionary of Birds, p. 38). One great result of the work on birds, together with the study of fossil reptiles, was a recognition of the fundamental similarities between the two, which Huxley expressed by uniting birds and reptiles in one great group, the Sauropsida. Other results obtained were shortly summarised in an essay 'On the Classification of Birds' (Zool. Soc. Proc. 1867), containing an elaborate account of the modifications exhibited by the bones of the palate. This essay exhibits in an entirely new light the problems which have to be solved before we can establish a natural classification of birds. The solution offered has not been accepted as final ; but there is no question about the great value of the essay as a contribution to cranial morphology.

The lectures on birds must serve as examples of others given at the College of Surgeons; they were probably the most strikingly novel of any except the first course 'On the Classification of Animals ;' but the condensed summary, published in 1871, shows that every course of lectures must have marked important additions to our knowledge of the animals with which it dealt. One other important problem, that of the homologies of the bones which connect the tympanic membrane with the ear-capsule, must be mentioned as treated in these lectures, and more fully in a paper read before the Zoological Society (1869).

Apart from the lectures, and from the books based on them, Huxley published about fifty technical papers between 1860 and 1870. Among these are numerous descriptions of dinosauria, including that of hypsilophodon, the results being summarised in the essay on the classification of the group (Quart. Journ. Geol. Soc. 1869), and in the statements of the relation between reptiles and birds, already referred to. The account of hyperodapedon (1869) is of great importance in connection with another group of reptiles, and there are many valuable memoirs on fossil amphibia. Much of his work on systematic ethnology remains unpublished ; but in 1865 he published an essay 'On the Methods and Results of Ethnology,' containing a scheme of classification of the races of mankind, based on the characters of the hair, the colour of the skin, and the cranial index. He evidently contemplated a more complete study of physical anthropology ; for among the materials left in his laboratory are some hundreds of photographs of various races of men, which he had collected before 1870.

The 'Elementary Lessons in Physiology,' published in 1866, is probably better known than any elementary text-book of its kind. It has been reprinted no less than thirty times since its first appearance.

The years from 1870 to 1885 comprise a period of constant activity, ending in an almost complete withdrawal from public life, made necessary by increasing illness.

In 1872 the removal of the School of Mines from Jermyn Street to South Kensington gave the long-desired opportunity of completing his plan of instruction, by enabling every student to examine for himself, in the laboratory, the types described in the lectures. With the help of his four demonstrators, Thiselton Dyer, Michael Foster, Ray Lankester, and W. Rutherford, the course of laboratory work was perfected, and its main features are described in the well-known text-book of 'Elementary Biology' (1875), written in conjunction with Mr. H. N. Martin.

An important characteristic of Huxley's teaching, both in his lectures to students and in his technical memoirs, may here be noticed. Darwin had suggested an interpretation of the facts of embryology which led to the hope that a fuller knowledge of development might reveal the ancestral history of all the great groups of animals, at least in its main outlines. This hope was of service as a stimulus to research, but the attempt to interpret the phenomena observed led to speculations which were often fanciful and always incapable of verification. Huxley was keenly sensible of the danger attending the use of a hypothetical explanation, leading to conclusions which cannot be experimentally tested, and he carefully avoided it. This is well seen in the important essay on Ceratodus (1876), where a discussion of the way in which the iaws are suspended from the skull leads him to divide all fishes into three series. In one series the mode of suspension of the jaws is identical with that found in amphibia and the higher vertebrates ; and the hypothesis that these 'autostylic' fishes resemble the ancestors of air-breathing forms suggests itself at once. Although this was clearly present in Huxley's mind, he is careful to confine himself to a statement of demonstrable structural resemblance, which must remain true, whatever hypothesis of its origin may ultimately be found most useful. Again, in the preface to the 'Manual of the Comparative Anatomy of Invertebrated Animals' (1877) he says : 'I have abstained from discussing questions of ætiology, not because I underestimate their importance, or am insensible to the interest of the great problem of Evolution, but because, to my mind, the growing tendency to mix up ætiological speculations with morphological generalisations will, if unchecked, throw Biology into confusion.' The only attempts to trace the ancestry of particular forms which Huxley ever made are based on palæontological evidence, in the few cases in which the evidence seemed to him sufficiently complete. Such are the essays on the horse (Presidential Address to the Geological Society, 1870; American Addresses, 1876; Collected Essays, vols. iii. and viii.), and that on the 'Classification of the Mammalia' (Proc. Zool. Soc. 1880). The treatise on the crayfish (1879) may be taken as a statement of his mature convictions ; and the discussion of the evolution of crayfishes, given in this work, relates solely to the evidence of their modification since liassic times, which is afforded by fossils.

In 1870 the school board for London was instituted, and Huxley's interest in the problem of education led him to become one of its first members. In an essay on the first duties of the board (Contemporary Review, 1870 ; Collected Essays, vol. iii.) he lays stress on the primary importance of physical and moral culture. 'The engagement of the affections in favour of that particular line of conduct which we call good,' he says, 'seems to me to be something quite beyond mere science. And I cannot but think that it, together with the awe and reverence which have no kinship with base fear, but arise whenever one tries to pierce below the surface of things, whether they be material or spiritual, constitutes all that has any unchangeable reality in religion.' This feeling can, in his judgment, be best cultivated by a study of the Bible 'with such grammatical, geographical, and historical explanations by a lay teacher as may be needful.' He held that the elements of physical science, with drawing, modelling, and singing, afforded the best means of intellectual training in such schools. Huxley's influence upon the scheme of education finally adopted was very great, although he left the board in 1872.

In speaking of the later stages of education, he dwelt upon the great value of literary training as a means of intellectual culture, but he never tired of contending that a perfect culture, which should 'supply a complete theory of life, based upon a clear knowledge alike of its possibilities and of its limitations,' could not be acquired without a training in the methods of physical science. At the same time he was careful to emphasise his horror of the prevalent idea that a mere acquaintance with the 'useful' results of scientific work has any educational value. He well knew that educational discipline can only be obtained by the pursuit of knowledge without regard to its practical applications ; and he saw the need for sharply separating such educational discipline from the preparation for a handicraft or profession. Writing in 1893 to one of those engaged in the attempt to obtain an adequate university for London, he says : 'I would cut away medicine, law, and theology as technical specialities. . . . The university or universities should be learning and teaching bodies devoted to art (literary and other), history, philosophy, and science, where any one who wanted to learn all that is known about these matters should find people who could teach him and put him in the way of learning for himself. That is what the world will want one day or other, as a supplement to all manner of high schools and technical institutions in which young people get decently educated and learn to earn their bread — such as our present universities. It would be a place for men to get knowledge, and not for boys and adolescents to get degrees.'

Between 1870 and 1885 he published a number of essays on philosophical subjects, the most important being his sketch of Hume (1879) in Mr. John Morley's 'English Men of Letters' series. In the chapter on the object and scope of philosophy, Huxley adopts the view that the method of psychology is the same as that of the physical sciences, and he points to Descartes, Spinoza, and Kant as showing the advantage to a philosopher of a training in physical science. The chapter dealing with volition and necessity is an expansion of the passage in the lecture 'On the Physical Basis of Life' already quoted. The chapter on miracles begins by demonstrating the absurdity of a priori objections to belief in miracles because they are violations of the 'laws of nature ;' but while it is absurd to believe that that which never has happened never can happen without a violation of the laws of nature, he agrees with Hume in thinking that 'the more a statement of fact conflicts with previous experience, the more complete must be the evidence which is to justify us in believing it.' The application of this criterion to the history of the world as given in the Pentateuch and to the story of the gospels forms the subject of numerous controversial essays and addresses, reprinted in the fourth and fifth volumes of the 'Collected Essays.'

In 1871, on the retirement of William Sharpey [q. v.], Huxley was chosen as one of the two secretaries of the Royal Society. The duties of this office were even more severe than usual during the years through which he held it. The Royal Society was requested by the admiralty to plan the equipment and to nominate the scientific staff of the Challenger, in preparation for her voyage round the world. Later on, the task of distributing her collections, and arranging for the publication of the monographs in which they are described, was also entrusted to the society; and the chief burden of the organisation fell upon Huxley. Many other matters, especially the organisation of arrangements for administering the annual grant of 4,000l. made by the treasury in aid of scientific research, made the duties of the secretary a serious addition to other demands upon him. In 1881 he was elected president of the society ; but in 1885 he was forced by ill-health to retire. He received the Copley medal in 1888, and the Darwin medal in 1894. From 1870 to 1884 he served upon the following royal commissions : upon the Administration and Operation of the Contagious Diseases Acts (1870-1) ; on Scientific Instruction and the Advancement of Science (1870-5) ; on the Practice of subjecting Live Animals to Experiments for Scientific Purposes (1876) ; to inquire into the Universities of Scotland (1876-8) ; on the Medical Acts (1881-2) : on Trawl, Net, and Beam Trawl Fishing (1884). He also acted as an inspector of fisheries from 1881 to 1885.

In spite of the immense amount of work he contrived to perform, Huxley never enjoyed robust health after the accidental poisoning already mentioned. Fresh air and some daily exercise were necessary in order to ward off digestive difficulties, accompanied by lassitude and depression of a severe kind ; but fresh air and exercise are the most difficult of all things for a busy man in London to obtain. The evil effects of a sedentary life had shown themselves at the very beginning of his work in London, and they increased year by year. At the end of 1871 he was forced to take a long holiday ; but this produced only a temporary improvement, and finally symptoms of cardiac mischief became too evident to be neglected. For this reason he gave up his public work in 1885, and in 1890 he finally left London, living thenceforward at Eastbourne.

The years of comparative leisure after 1885 were occupied in writing many of the essays on philosophy and theology reprinted in the fourth and fifth volumes of his 'Collected Essays.' An attack of pleurisy in 1887 caused grave anxiety, and after its occurrence he suffered severely from influenza, so that the work of helping those teachers in London in their efforts to obtain an adequate university, which he undertook in 1892 and 1893, involved physical effort of a very severe kind, as did the delivery of his Romanes lecture on 'Evolution and Ethics' before the university of Oxford in 1893. An attack of influenza in the winter of 1894 was followed by an affection of the kidneys, and he died at Eastbourne on 29 June 1895. He was buried at Finchley on 4 July. Several portraits of Huxley are given in his 'Life and Letters.' The best is that painted in 1883 by the Hon. John Collier, now in the National Portrait Gallery, London. His widow, with two sons, Leonard and Henry, and two daughters (Mrs. Waller and the Hon. Mrs. John Collier), survived him; a son Noel died in 1860.

Huxley was rector of Aberdeen University from 1872 to 1874, was created hon. D.C.L. of Oxford on 17 June 1885, and also received honorary degrees from Edinburgh, Dublin, Breslau, Würzburg, Bologna, and Erlangen. He was elected member of countless foreign societies, and in 1892 he accepted the office of privy councillor, but he cared little for such honours. The only reward for which he cared is that freely given to him by earnest men of every kind, in every country, who gratefully reverence his labours in furthering the noble objects which he set before himself, 'to promote the increase of natural knowledge and to further the application of scientific methods of investigation to all the problems of life to the best of my ability, in the conviction which has grown with my growth and strengthened with my strength, that there is no alleviation for the sufferings of mankind except veracity of thought and action, and the resolute facing of the world as it is when the garment of make-believe, by which pious hands have hidden its uglier features, is stripped off.'

Those of Huxley's essays which he wished to collect in a final edition are published in nine volumes of Collected Essays (Macmillan, 1893-4). An edition of his scientific memoirs, edited by Sir Michael Foster and Professor Lankester, is in course of publication in four quarto volumes; three have appeared.

[The Life and Letters of T. H. Huxley, by his son, Leonard Huxley, 2 vols. 1900, is the main authority; it contains a full list of his published works. An account of his scientific work is given in Thomas Henry Huxley, a Sketch of his Life and Work, by P. Chalmers Mitchell, London and New York, 1900. See also article by Mr. Leslie Stephen in Nineteenth Century, December 1900.]

W. F. R. W.