and diplomat, in 1770 or 1771 have been published by V. A. Eyles and J. M. Eyles as "Some Geological Correspondence of James Hutton," in Annals of Science, 7 (1951), 316–339.

II. SECONDARY LITERATURE. The only complete account of Hutton's life is John Playfair, "Biographical Account of the Late Dr James Hutton, F.R.S. Edin.," in Transactions of the Royal Society of Edinburgh, 5 (1803), 39-99, facs. repr. in Contributions to the History of Geology, V (1970), 141-203, repr. in The Works of John Playfair, IV (Edinburgh, 1822), 33-118. Playfair discusses critically Hutton's published works. A few additional details about Hutton's activities as a farmer are included in "Principles of Agriculture."

W. Ramsay, Life and Letters of Joseph Black, M.D. (London, 1918); and Partners in Science: Letters of James Watt and Joseph Black, E. Robinson and D. McKie, eds. (London, 1970), contain interesting references to Hutton; especially to his illness and to his natural son. Other unpublished letters of Black in the library of Edinburgh University are also worth consulting. For brief references to Hutton in the published diaries and letters of contemporaries, see V. A. Eyles, "Introduction," in Contributions to the History of Geology, V (1970), xi-xxiii.

Playfair's Illustrations of the Huttonian Theory of the Earth (Edinburgh, 1802), repr. in The Works of John Playfair, I (Edinburgh, 1822), 1-514, facs. repr. of 1802 ed. (Urbana, 1956), with intro. by G. W. White, is widely used as a source of Hutton's views, but does not always present them with complete accuracy. Its publication stimulated John Murray of Edinburgh, lecturer in chemistry and supporter of Wernerian geology, to publish anonymously A Comparative View of the Huttonian and Neptunian Systems of Geology (Edinburgh, 1802). The Illustrations and Comparative View, translated into French and annotated by the translator, C. A. Basset, were published in one volume, Explication de Playfair sur la Théorie par Hutton, et examen comparatif des systèmes géologiques ... par M. Murray (Paris, 1815).

W. H. Fitton, “A Review of Mr Lyell's 'Elements of Geology'; With Observations on the Progress of the Huttonian Theory of the Earth," in Edinburgh Review, 69 (1839), 406-466, includes a detailed discussion of the value of Hutton's theory in relation to contemporary geological knowledge. Fitton shows that some prominent geologists of the period, particularly in France, were either unaware of Hutton's work, or, if familiar with it, failed to acknowledge Hutton's priority when putting forward their own conclusions.

The following modern commentaries on various aspects of Hutton's work, principally his geology, may be consulted: "James Hutton 1726-1797, Commemoration of the 150th Anniversary of His Death," in Proceedings of the Royal Society of Edinburgh, 63B (1950), 351-402, contains five articles on Hutton's life and work: M. Macgregor, "Life and Times of James Hutton"; E. B. Bailey, "James Hutton, Founder of Modern Geology"; G. W. Tyrrell, "Hutton on Arran"; V. A. Eyles, "Note on the Original Publication of Hutton's Theory of the Earth and the Subse

quent Forms in Which It Was Issued"; and S. I. Tomkeieff, "James Hutton and the Philosophy of Geology," repr. from Transactions of the Edinburgh Geological Society, 14 (1948), 253-276. Tomkeieff notes that G. H. Toulmin, in The Antiquity and Duration of the World (London, 1780), expressed views in some respects similar to those in Hutton's Theory of the Earth. References to Toulmin and Hutton were also made by D. B. McIntyre, "James Hutton and the Philosophy of Geology," in C. C. Albritton, ed., The Fabric of Geology (Reading, Mass., 1963), 1-11; and G. L. Davies, "George Hoggart Toulmin and the Huttonian Theory of the Earth," in Bulletin of the Geological Society of America, 78 (1967), 121-124.

A useful source book and guide to Hutton's geological thought is E. B. Bailey, James Hutton-the Founder of Modern Geology (Amsterdam-London-New York, 1967), which contains a summary of each chapter of Theory of the Earth, a well-informed commentary on Hutton's ideas, and a less detailed discussion of his other works, particularly "Principles of Agriculture."

R. H. Dott, Jr., "James Hutton and the Concept of a Dynamic Earth," in C. J. Schneer, ed., Toward a History of Geology (Cambridge, Mass.-London, 1969), 122-141, provides a short summary and commentary on Hutton's contributions to geology.

Anthologies of Hutton's more important geological observations and conclusions, with commentaries, are J. Challinor, "The Early Progress of British GeologyIII. From Hutton to Playfair, 1788-1802," in Annals of Science, 10 (1954), 107-148; and D. A. Bassett, "James Hutton, the Founder of Modern Geology: An Anthology," in Geology: The Journal of the Association of Teachers of Geology, 2 (1970), 55-76. S. I. Tomkeieff, "Unconformityan Historical Study," in Proceedings of the Geologists' Association, 73 (1962), 383-401, discusses Hutton's use of unconformities as evidence for his geological theory.

Hutton's contributions to geomorphology are discussed in E. B. Bailey, "The Interpretation of Scottish Scenery," in Scottish Geographical Magazine, 50 (1934), 301–330; R. J. Chorley, A. J. Dunn, and R. P. Beckinsale, The History of the Study of Land Forms (London-New York, 1964); G. L. Davies, "The Eighteenth Century Denudation Dilemma and the Huttonian Theory of the Earth," in Annals of Science, 22 (1966), 129–138; and "The Huttonian Earth-Machine," in The Earth in Decay, a History of British Geomorphology 1578 to 1878 (London, 1969), ch. 6. R. Hooykaas, Natural Law and Divine Miracle (Leiden, 1959; 2nd ed., 1963), discusses Hutton's geological theory in relation to the general theory of uniformitarianism. See also his paper "James Hutton und die Ewigkeit der Welt," in Gesnerus, 23 (1966), 55–66.

V. A. Eyles, "A Bibliographical Note on the Earliest Printed Version of James Hutton's Theory of the Earth, its Form and Date of Publication," in Journal of the Society for the Bibliography of Natural History, 3 (1955), 105-108, gives the evidence establishing the authorship and date of publication of the Abstract, which was issued anonymously and undated.

The following commentaries refer to Hutton's work in

subjects other than geology: J. R. Partington and D. McKie, "Historical Studies on the Phlogiston Theory-III. Light and Heat in Combustion," in Annals of Science, 3 (1938), 366-370, analyzes Hutton's views on the nature of phlogiston and concludes that his theory was almost identical with that of A. Crawford; and P. A. Gerstner, "James Hutton's Theory of the Earth and his Theory of Matter," in Isis, 59 (1968), 26-31, and "The Reaction to James Hutton's Use of Heat as a Geological Agent," in British Journal of the History of Science, 5 (1971), 353-362, discusses Hutton's ideas about heat and matter in relation to his theory of the earth.

Works on the development of science in the eighteenth and early nineteenth centuries that contain numerous references to Hutton are C. C. Gillispie, Genesis and Geology (Cambridge, Mass., 1951), particularly valuable for its very extensive bibliography; Loren Eiseley, Darwin's Century (New York, 1958-London, 1959); and F. C. Haber, The Age of the World (Baltimore, 1959).

The most frequently reproduced portrait of Hutton is the painting by the Scottish artist Sir Henry Raeburn. Two contemporary etchings are in A Series of Portrait and Caricature Etchings by the Late John Kay, 2 vols. (Edinburgh, 1837). A medallion portrait by the Scottish artist James Tassie is reproduced in the English trans. of K. A. von Zittel, History of Geology and Palaeontology (London, 1901).

V. A. EYLES

HUXLEY, THOMAS HENRY (b. Ealing, Middlesex, England, 4 May 1825; d. Hodeslea, Eastbourne, Sussex, England, 29 June 1895), zoology, evolution, paleontology, ethnology.

Thomas Henry Huxley was the seventh and youngest surviving child of George and Rachel Huxley. His father taught mathematics and was assistant headmaster at a school in Ealing which Thomas Henry attended for a brief period. The regular instruction which Huxley received was minimal and lasted no more than two years. He was not considered a precocious child but did exhibit in his youth the natural ability to draw which later, in spite of no training, served him well in his zoological work. For his general education Huxley was largely self-taught; while still in his teens he read extensively, particularly in science and metaphysics, and gained a facility in reading German and French.

Huxley had early leanings toward mechanical engineering as a career, but the combination of a family of moderate means and two medical brothers-in-law led him into medicine. He attended a postmortem when he was about fourteen and may have contracted some sort of dissection poisoning which manifested itself in an apathy remedied only by a stay in the open countryside. The "hypochondriacal dyspepsia" recurrent throughout the remainder of his life he

thought to have been brought on by this incident; whatever it was, he was usually cured by a spell in fresh air. In 1841 Huxley became apprenticed to one of his brothers-in-law, John Godwin Scott, who practiced in the north of London. During his apprenticeship, he continued his wide reading, attended some courses, and earned the silver medal in a botanical competition.

In September 1842 Huxley and his brother James were awarded free scholarships at Charing Cross Hospital. The lecturer on physiology, Thomas Wharton Jones, had a strong influence on Huxley's interest in physiology and anatomy and helped teach him methods of scientific investigation. Jones encouraged and aided Huxley with his first scientific paper, on the discovery of a layer of cells (Huxley's layer) directly within Henle's layer in the root sheath of hair. Huxley passed the M.B. examination at London University in 1845 and soon afterward that for membership in the Royal College of Surgeons. He applied to and was taken into the Royal Navy, being assigned to H.M.S. Victory for service at Haslar Hospital, where he remained until assigned to H.M.S. Rattlesnake.

Huxley was to join the Rattlesnake on a surveying voyage to the Torres Straits off Australia as ship's surgeon, not as a naturalist, a position filled by John MacGillivray. Any natural history Huxley undertook on the four-year voyage was his own affair, but it was to set the course of his career toward zoology rather than medicine. Aboard the Rattlesnake, Huxley's scientific equipment was minimal, consisting principally of a microscope and a makeshift collecting net. The limitation of his equipment was perhaps fortunate, as he focused his attention on the wealth of planktonic life for the study of which a steady supply of fresh specimens was necessary. Through extensive shipboard dissections and through library work in Sydney, Australia (where he also saw much of William Macleay), Huxley was able to bring some order to these minute organisms which had been simply lumped together in those two great zoological lumber rooms, Linnaeus' Vermes and Cuvier's Radiata.

The novelty of much of his material was evident to Huxley and prompted him to send several papers to the Linnean Society, about which he received no word. Somewhat disheartened, he directed in 1849 a major paper "On the Anatomy and the Affinities of the Family of the Medusae" to the Royal Society, which turned out to be the first of a series of wedges he drove into Cuvier's Radiata. By the time of the Rattlesnake's return the paper had been published in the Philosophical Transactions and soon earned

him election as a fellow of the Royal Society. Combined with several other papers it brought Huxley the Royal Medal in 1852. After his return to England in 1850 Huxley arranged for leave from active duty in order to remain in London to work on the materials he had brought back. During these several years he became very much a part of the London scientific scene, making many friendships and enlisting the support of leading scientific figures in his running battle with the Admiralty over payment for the publication of his results. The battle continued until the Admiralty became exasperated and ordered Huxley back to active duty. He refused, leaving himself without any means of support and no prospect of a scientific appointment in London, where he felt he must remain to do effective scientific work. During this period he wrote articles and miscellaneous pieces for several reviews, when the editors would pay.

Invertebrate Studies. Nearly all of Huxley's scientific effort in the period 1850-1854, during which he published about twenty scientific papers, was concentrated on the materials from the Rattlesnake. Working out the details and relationships of the delicate marine animals he studied set the pattern for his career and gave him a firm grasp of major zoological problems. Of his numerous publications on these invertebrates his major contributions are found in four memoirs; his 1849 paper on the Medusae, two 1851 papers on tunicates, and one in 1853 on the Cephalous Mollusca. In his paper on the Medusae (Scientific Memoirs, I, 9-32), Huxley made two notable contributions-recognition of this group as a coherent whole and of an embryological analogy. First, he described the structure common to the different groups of Medusae, recognizing that they all consist fundamentally of two layers, or "foundation membranes" which produce the inner and outer parts, that they all seem to lack blood and blood vessels, and that the existence of any nervous system was doubtful. He then allied with the Medusae the Hydroid and Sertularian polyps, whose structure is similarly based on the same two foundation. membranes. Although it was less obvious, Huxley recognized that the complicated colonies (for example, the Portuguese man-of-war) making up the Physophoridae and Diphydae were colonies of hydralike organisms each of which had the typical Medusae double-membrane structure. The group of organisms which Huxley connected on the basis of this fundamental structure was readily accepted as one of the major groups of animals, becoming the nucleus of the Coelenterata, and as such required and received the attention of zoologists. Although its importance was perhaps not fully appreciated until after Charles

Darwin's On the Origin of Species, the embryological analogy that Huxley drew was an even more fundamental contribution than the organization of the medusoid organisms. He concluded that the two foundation membranes are physiologically analogous to the serous and mucous layers in a typical embryo. At this time Huxley made only the comparison and did not speculate on its possible significance.

In 1851 Huxley presented to the Royal Society two major papers on tunicates: "Observations on the Anatomy and Physiology of Salpa and Pyrosoma" and "Remarks Upon Appendicularia and Doliolum, Two Genera of Tunicates" (Scientific Memoirs, I, 38-68, 69-79). In the Salpa paper Huxley confirmed earlier suggestions that this organism's life cycle passes through an alternation of solitary and chainlike colonial generations. Huxley observed a great abundance of specimens at various growth stages, from which he was able to come to the important conclusion that the solitary stage is the product of sexual generation and that the colony results from budding. This recognition contributed strongly to his theory of animal individuality in which he stated that both forms are parts or organs of a single individual, because they both develop from a single ovum. Huxley elaborated this thesis in a discourse "Upon Animal Individuality" at the Royal Institution in April 1852. He related, anatomically and systematically, all four genera of free-swimming forms covered in these two papers to the Ascidiacea, or sea squirts, and thus gathered the ascidians into a group based on their typical structure as he had done with the Medusae. The zoological position of Appendicularia had been most unsettled owing to its possession of a tail. Huxley demonstrated that this tail is a retained larval feature lost by most adult ascidians. The significance of this urochordal structure in relation to the vertebrate pedigree did not become evident until later.

Just as with the Medusae and the ascidians, Huxley sought and found in the Cephalous Mollusca a typical structure of which each genus and species is a modification. Briefly, Huxley started with several surface-dwelling forms with transparent shells and then dissected a wide variety of mollusks, determining their anatomical similarities on comparative grounds. Drawing heavily on the German embryologists who had studied their development, Huxley concluded that their parts are homologous and that they constitute a great group, the Cephalous Mollusca, comprising the Cephalopoda, Gasteropoda, and Lamellibranchiata all of which are modifications of a typical form, or "archetype." The paper which resulted, "On the Morphology of the Cephalous Mollusca ..." (Scientific Memoirs, I, 152-193), was

highly important to his contemporaries for the anatomical and systematic conclusions which Huxley reached. It is also of particular interest for its insights into Huxley's zoological methods, not only in his study of the invertebrates from the Rattlesnake but also in his later work on vertebrates, both fossil and recent.

Huxley opened his paper on the Cephalous Mollusca with a quotation from "the highest authority," Richard Owen, setting forth what Huxley believed to be "the true aims of anatomical investigation." In this passage Owen states that mere anatomical description is of relatively little value until the facts "have been made subservient to establishing general conclusions and laws of correlation, by which the judgment may be safely guided." Whether with invertebrates, birds, the structure of the vertebrate skull, or fossil horses, Huxley sought to establish conclusions which, no matter how general or widesweeping, were invariably firmly based on facts from his experience. Huxley's use of one of Owen's favorite words, "archetype," could lead to some confusion because of the naturphilosophisch and platonic connotations associated with it and because of his attitude toward the output of that mode of thinking, of which Owen's work was a part. Huxley explicitly denied any connection between his archetypes and any ideas after which organisms might be modeled. To him the word meant "the conception of a form embodying the most general propositions that can be affirmed" about the organisms under consideration. Within any great group, such as the Cephalous Mollusca, Huxley thought that the members varied by excess or defect of the parts of the archetype. He rejected the idea of any progression from a lower to a higher type within the group and instead thought there was "merely a more or less complete evolution of one type." Here Huxley used "evolution" in its historic sense of an unfolding, or unrolling-that is, an embryological unfolding. While the manner in which he treated the Cephalous Mollusca was fundamentally the same as that used with the Medusae and ascidians, the discussion of the archetype and its modifications as a result of embryological development was a new element. There is more than a coincidental relationship between these ideas and those in the "Fragments Relating to Philosophical Zoology" which Huxley selected and translated from the works of Karl Ernst von Baer. Huxley had a broad acquaintance with the German zoological literature and held a high regard for much of it, especially in embryology and cytology; for example, see his major review "The Cell-Theory" (Scientific Memoirs, I, 241-278).

Vertebrate Studies. In 1854, when he succeeded Edward Forbes as lecturer in natural history at the Government School of Mines, Huxley at last had a means of support within the scientific community. Soon afterward he was appointed to the additional post of naturalist with the Geological Survey. He now had not only a scientific position but also the income needed to marry Henrietta Heathorn, whom he had met in 1847 in Sydney. They became engaged in 1849 but did not see each other again until she came to England for their marriage in 1855. Their son Leonard, the well-known teacher and writer, was the father of Julian Huxley, the biologist, Aldous Huxley, the writer, and Andrew Fielding Huxley, the physiologist.

At least in part, Huxley saw these positions as being temporary, while he awaited a post in physiology; since no such position became available, he held the same appointments for over thirty years. With considerable rapidity the focus of Huxley's attention shifted from the invertebrates to the vertebrates. This shift was induced by his duties as lecturer on natural history, which required him to prepare in unfamiliar areas of biology, combined with his duties in connection with the Geological Survey, which brought him in close contact with a range of vertebrate fossils. Although beginning with a certain distaste for fossils, he soon became deeply involved in problems in paleontology and geology. His first fossil work was in cooperation with John William Salter, identifying a variety of fossils, an experience which was to prove invaluable in the aftermath of Darwin's Origin. As with the invertebrates, Huxley was not concerned with species as such, but only as they led to more general zoological problems. In addition to his paleontological work, Huxley helped to organize the Museum of Practical Geology where he began, in 1855, his series of lectures to workingmen. He further developed his own regular course at the School of Mines. In addition to this he was appointed to the triennial Fullerian lectureship at the Royal Institution for 1856-1858. This sampling of his activities is indicative of the number of projects he would undertake at one time.

In the late 1850's, Huxley began a detailed study of the embryology of the vertebrates, which provided a firm base for much later work as well as strengthening his teaching. An outcome of this study was his 1858 Croonian lecture at the Royal Society, "On the Theory of the Vertebrate Skull" (Scientific Memoirs, I, 538-606). Huxley made an important methodological contribution to morphology by his insistence that, as suggestive as they are, comparisons of adult structures are insufficient for the demon

stration of homologies. Only by studying the embryological development of the various structures from their earliest stages and determining that they follow the same path of development can we say with certainty that they are homologous. Huxley was continuing the tradition of K. E. von Baer and M. H. Rathke and, more specifically, was reviving detailed studies of the skull done by Rathke and others in 1836-1839. These neglected earlier studies had shown the inadequacies of the vertebral theory of the skull originated by Goethe, elaborated by Lorenz Oken, and developed to its fullest by Richard Owen.

Huxley's objective in his Croonian lecture was to put morphological studies on a more scientific basis, especially by the utilization of embryological criteria which could be as productive for the vertebrates as they had already been for the invertebrates. Many, and particularly Owen himself, saw this lecture as an attack on Owen, who was still considered England's preeminent anatomist. Although not intended as such, it assuredly helped to prepare the way for the disputes between Huxley and Owen after 1859. In his lecture Huxley established that the various vertebrate skulls are modifications of the same basic type and, importantly, distinguished and named the different modes by which the lower jaw is articulated to the skull, which has become an important diagnostic character. Huxley concluded that the differentiation of the skull and the vertebral column occurs at such an early stage that they could not have a common origin. He also drew an analogy between the membranous, cartilaginous, and osseous stages of the development of the skull and between the skulls of Amphioxus, sharks, and the higher vertebrates.

The Evolution Controversy. Those today who know Huxley know him primarily as the protagonist of evolution in the controversies immediately following the publication of On the Origin of Species late in 1859. Huxley was prepared for the role he was to play, since he had by then acquired a broad background in vertebrate and invertebrate zoology and in paleontology. He also had read widely in the zoological literature in English, German, and French. Inevitably, he was familiar with the various hypotheses concerning the transmutation of species, particularly those of Lamarck and Robert Chambers, both of whom he held in low opinion. Huxley's review of the 1854 edition of Chambers' Vestiges of the Natural History of Creation was the only one he later regretted for its "needless savagery." Before the Origin, Huxley was constitutionally opposed to transmutation ideas because of his critical skepticism of all theories, the same skepticism which he embodied in the term he coined, "agnosticism." Also, his belief

that the natural groups of organisms were demarcated by sharp lines seemed, if valid, to negate the possibility of evolution occurring.

When the Origin was ready for publication, Darwin sent Huxley one of three prepublication copies, the other two going to Charles Lyell and Joseph Hooker. Darwin was not confident that Huxley would react favorably to his book but wanted him as one of its judges. Darwin and Huxley had become by then close friends, and Darwin often had drawn on Huxley's wide-ranging knowledge. On 23 November 1859 Huxley wrote to Darwin that nothing had impressed him more since his reading of Baer, praised Darwin for his new views, and warned him about the abuse he was bound to receive. Already Huxley was sharpening his claws and beak in preparation for the impending battles. Entirely by chance, Huxley had an early opportunity to praise the Origin publicly, although anonymously, when he was asked to review it for the London Times (26 December 1859). Huxley followed this with a Friday evening discourse at the Royal Institution in February 1860 and an article in the April issue of the Westminster Review. His February discourse "On Species and Races, and their Origin" (Scientific Memoirs, II, 388-394) set a model for many later defenses of the Origin. After discussing the varieties and species of horses and pigeons, Huxley turned to man's relation to the apes, the topic of greatest concern to his listeners and one only hinted at in the Origin. Without going into the full details, he argued that man differs less from the highest members of the Quadrumana than the extreme members of that group differed from one another. This was an implicit rejection of Owen's classification of the Mammalia. Moreover, and most importantly, Huxley made a strong plea, often to be repeated, for judging Darwin's work on scientific grounds, as a work in science, for "the man of science is the sworn interpreter of nature in the highest court of reason."

When the British Association for the Advancement of Science met in Oxford late in June 1860, Huxley was recognized as an able younger biologist, but his name certainly was not yet a household word. During this meeting he had two encounters important for the future of Darwin's hypothesis, as well as for his own career: one with Owen on scientific details, which was settled later, and one with Samuel Wilberforce, bishop of Oxford, which was of a more general nature. The result was Huxley's being recognized as the principal defender of the Origin and he thus earned the name "Darwin's bulldog." The less prolonged, although more dramatic, of these was the second, the exchange with "Soapy Sam" Wilberforce. Wilberforce had