Thomas Henry Huxley

Huxley and his wife had five daughters and three sons:

From 1870 onwards, Huxley was to some extent drawn away from scientific research by the claims of public duty. He served on eight Royal Commissions, from 1862 to 1884. From 1871 to 1880 he was a Secretary of the Royal Society and from 1883 to 1885 he was president. He was president of the Geological Society from 1868 to 1870. In 1870, he was president of the British Association at Liverpool and, in the same year was elected a member of the newly constituted London School Board. He was president of the Quekett Microscopical Club from 1877 to 1879. He was the leading person amongst those who reformed the Royal Society, persuaded government about science, and established scientific education in British schools and universities.[28]

He was awarded the highest honours then open to British men of science. The Royal Society, who had elected him as Fellow when he was 25 (1851), awarded him the Royal Medal the next year (1852), a year before Charles Darwin got the same award. He was the youngest biologist to receive such recognition. Then later in life he received the Copley Medal in 1888 and the Darwin Medal in 1894; the Geological Society awarded him the Wollaston Medal in 1876; the Linnean Society awarded him the Linnean Medal in 1890. There were many other elections and appointments to eminent scientific bodies; these and his many academic awards are listed in the Life and Letters. He turned down many other appointments, notably the Linacre chair in zoology at Oxford and the Mastership of University College, Oxford.[29]

Huxley
by Bassano c. 1883

In 1873 the King of Sweden made Huxley, Hooker and Tyndall Knights of the Order of the Polar Star: they could wear the insignia but not use the title in Britain.[30] Huxley collected many honorary memberships of foreign societies, academic awards and honorary doctorates from Britain and Germany. He also became foreign member of the Royal Netherlands Academy of Arts and Sciences in 1892.[31]

As recognition of his many public services he was appointed Privy Councillor in 1892.

Despite his many achievements he was given no award by the British state until late in life. In this he did better than Darwin, who got no award of any kind from the state. (Darwin's proposed knighthood was vetoed by ecclesiastical advisers, including Wilberforce)[32] Perhaps Huxley had commented too often on his dislike of honours, or perhaps his many assaults on the traditional beliefs of organised religion made enemies in the establishment—he had vigorous debates in print with Benjamin Disraeli, William Ewart Gladstone and Arthur Balfour, and his relationship with Lord Salisbury was less than tranquil.[11][33]

Huxley was for about thirty years evolution's most effective advocate, and for some Huxley was "the premier advocate of science in the nineteenth century [for] the whole English-speaking world".[34]

Though he had many admirers and disciples, his retirement and later death left British zoology somewhat bereft of leadership. He had, directly or indirectly, guided the careers and appointments of the next generation. Huxley thought he was "the only man who can carry out my work": the deaths of Balfour and W. K. Clifford were "the greatest losses to science in our time".[11]

The first half of Huxley's career as a palaeontologist is marked by a rather strange predilection for 'persistent types', in which he seemed to argue that evolutionary advancement (in the sense of major new groups of animals and plants) was rare or absent in the Phanerozoic. In the same vein, he tended to push the origin of major groups such as birds and mammals back into the Palaeozoic era, and to claim that no order of plants had ever gone extinct.

Much paper has been consumed by historians of science ruminating on this strange and somewhat unclear idea.[35] Huxley was wrong to pitch the loss of orders in the Phanerozoic as low as 7%, and he did not estimate the number of new orders which evolved. Persistent types sat rather uncomfortably next to Darwin's more fluid ideas; despite his intelligence, it took Huxley a surprisingly long time to appreciate some of the implications of evolution. However, gradually Huxley moved away from this conservative style of thinking as his understanding of palaeontology, and the discipline itself, developed.

Huxley's detailed anatomical work was, as always, first-rate and productive. His work on fossil fish shows his distinctive approach: whereas pre-Darwinian naturalists collected, identified and classified, Huxley worked mainly to reveal the evolutionary relationships between groups.

Huxley by Wirgman
a drawing in pencil, 1882

The lobed-finned fish (such as coelacanths and lung fish) have paired appendages whose internal skeleton is attached to the shoulder or pelvis by a single bone, the humerus or femur. His interest in these fish brought him close to the origin of tetrapods, one of the most important areas of vertebrate palaeontology.[36][37][38]

The study of fossil reptiles led to his demonstrating the fundamental affinity of birds and reptiles, which he united under the title of Sauropsida. His papers on Archaeopteryx and the origin of birds were of great interest then and still are.[20][39][40]

Apart from his interest in persuading the world that man was a primate, and had descended from the same stock as the apes, Huxley did little work on mammals, with one exception. On his tour of America Huxley was shown the remarkable series of fossil horses, discovered by O. C. Marsh, in Yale's Peabody Museum.[41][42] An Easterner, Marsh was America's first professor of palaeontology, but also one who had come west into hostile Indian territory in search of fossils, hunted buffalo, and met Red Cloud (in 1874).[43] Funded by his uncle George Peabody, Marsh had made some remarkable discoveries: the huge Cretaceous aquatic bird Hesperornis, and the dinosaur footprints along the Connecticut River were worth the trip by themselves, but the horse fossils were really special. After a week with Marsh and his fossils, Huxley wrote excitedly, "The collection of fossils is the most wonderful thing I ever saw."[44]

Huxley's sketch of then hypothetical five-toed Eohippus being ridden by "Eohomo"

The collection at that time went from the small four-toed forest-dwelling Orohippus from the Eocene through three-toed species such as Miohippus to species more like the modern horse. By looking at their teeth he could see that, as the size grew larger and the toes reduced, the teeth changed from those of a browser to those of a grazer. All such changes could be explained by a general alteration in habitat from forest to grassland. And, it is now known, that is what did happen over large areas of North America from the Eocene to the Pleistocene: the ultimate causative agent was global temperature reduction (see Paleocene–Eocene Thermal Maximum). The modern account of the evolution of the horse has many other members, and the overall appearance of the tree of descent is more like a bush than a straight line.

The horse series also strongly suggested that the process was gradual, and that the origin of the modern horse lay in North America, not in Eurasia. If so, then something must have happened to horses in North America, since none were there when Europeans arrived. The experience with Marsh was enough for Huxley to give credence to Darwin's gradualism, and to introduce the story of the horse into his lecture series.[45]

Marsh's and Huxley's conclusions were initially quite different. However, Marsh carefully showed Huxley his complete sequence of fossils. As Marsh put it, Huxley "then informed me that all this was new to him and that my facts demonstrated the evolution of the horse beyond question, and for the first time indicated the direct line of descent of an existing animal. With the generosity of true greatness, he gave up his own opinions in the face of new truth, and took my conclusions as the basis of his famous New York lecture on the horse."[45]

Famously, Huxley responded to Wilberforce in the debate at the British Association meeting, on Saturday 30 June 1860 at the Oxford University Museum. Huxley's presence there had been encouraged on the previous evening when he met Robert Chambers, the Scottish publisher and author of Vestiges, who was walking the streets of Oxford in a dispirited state, and begged for assistance. The debate followed the presentation of a paper by John William Draper, and was chaired by Darwin's former botany tutor John Stevens Henslow. Darwin's theory was opposed by the Bishop of Oxford, Samuel Wilberforce, and those supporting Darwin included Huxley and their mutual friends Hooker and Lubbock. The platform featured Brodie and Professor Beale, and Robert FitzRoy, who had been captain of HMS Beagle during Darwin's voyage, spoke against Darwin.[61]

Wilberforce had a track record against evolution as far back as the previous Oxford B.A. meeting in 1847 when he attacked Chambers' Vestiges. For the more challenging task of opposing the Origin, and the implication that man descended from apes, he had been assiduously coached by Richard Owen—Owen stayed with him the night before the debate.[62] On the day, Wilberforce repeated some of the arguments from his Quarterly Review article (written but not yet published), then ventured onto slippery ground. His famous jibe at Huxley (as to whether Huxley was descended from an ape on his mother's side or his father's side) was probably unplanned, and certainly unwise. Huxley's reply to the effect that he would rather be descended from an ape than a man who misused his great talents to suppress debate—the exact wording is not certain—was widely recounted in pamphlets and a spoof play.

The letters of Alfred Newton include one to his brother giving an eyewitness account of the debate, and written less than a month afterwards.[63] Other eyewitnesses, with one or two exceptions (Hooker especially thought he had made the best points), give similar accounts, at varying dates after the event.[64] The general view was and still is that Huxley got much the better of the exchange, though Wilberforce himself thought he had done quite well. In the absence of a verbatim report, differing perceptions are difficult to judge fairly; Huxley wrote a detailed account for Darwin, a letter which does not survive; however, a letter to his friend Frederick Daniel Dyster does survive with an account just three months after the event.[65][66][67][68][69][70]

One effect of the debate was to hugely increase Huxley's visibility amongst educated people, through the accounts in newspapers and periodicals. Another consequence was to alert him to the importance of public debate: a lesson he never forgot. A third effect was to serve notice that Darwinian ideas could not be easily dismissed: on the contrary, they would be vigorously defended against orthodox authority.[71][72] A fourth effect was to promote professionalism in science, with its implied need for scientific education. A fifth consequence was indirect: as Wilberforce had feared, a defence of evolution did undermine literal belief in the Old Testament, especially the Book of Genesis. Many of the liberal clergy at the meeting were quite pleased with the outcome of the debate; they were supporters, perhaps, of the controversial Essays and Reviews. Thus, both on the side of science and on that of religion, the debate was important and its outcome significant.[73] (see also below)

That Huxley and Wilberforce remained on courteous terms after the debate (and able to work together on projects such as the Metropolitan Board of Education) says something about both men, whereas Huxley and Owen were never reconciled.

For nearly a decade his work was directed mainly to the relationship of man to the apes. This led him directly into a clash with Richard Owen, a man widely disliked for his behaviour whilst also being admired for his capability. The struggle was to culminate in some severe defeats for Owen. Huxley's Croonian Lecture, delivered before the Royal Society in 1858 on The Theory of the Vertebrate Skull was the start. In this, he rejected Owen's theory that the bones of the skull and the spine were homologous, an opinion previously held by Goethe and Lorenz Oken.[74]

Huxley at 32

From 1860–63 Huxley developed his ideas, presenting them in lectures to working men, students and the general public, followed by publication. Also in 1862 a series of talks to working men was printed lecture by lecture as pamphlets, later bound up as a little green book; the first copies went on sale in December.[75] Other lectures grew into Huxley's most famous work Evidence as to Man's place in Nature (1863) where he addressed the key issues long before Charles Darwin published his Descent of Man in 1871.

Although Darwin did not publish his Descent of Man until 1871, the general debate on this topic had started years before (there was even a precursor debate in the 18th century between Monboddo and Buffon). Darwin had dropped a hint when, in the conclusion to the Origin, he wrote: "In the distant future... light will be thrown on the origin of man and his history".[76] Not so distant, as it turned out. A key event had already occurred in 1857 when Richard Owen presented (to the Linnean Society) his theory that man was marked off from all other mammals by possessing features of the brain peculiar to the genus Homo. Having reached this opinion, Owen separated man from all other mammals in a subclass of its own.[77] No other biologist held such an extreme view. Darwin reacted "Man...as distinct from a chimpanzee [as] an ape from a platypus... I cannot swallow that!"[78] Neither could Huxley, who was able to demonstrate that Owen's idea was completely wrong.

Huxley with sketch
of a gorilla skull (c1870)

The subject was raised at the 1860 BA Oxford meeting, when Huxley flatly contradicted Owen, and promised a later demonstration of the facts. In fact, a number of demonstrations were held in London and the provinces. In 1862 at the Cambridge meeting of the B.A. Huxley's friend William Flower gave a public dissection to show that the same structures (the posterior horn of the lateral ventricle and hippocampus minor) were indeed present in apes. The debate was widely publicised, and parodied as the Great Hippocampus Question. It was seen as one of Owen's greatest blunders, revealing Huxley as not only dangerous in debate, but also a better anatomist.

Owen conceded that there was something that could be called a hippocampus minor in the apes, but stated that it was much less developed and that such a presence did not detract from the overall distinction of simple brain size.[79]

Huxley's ideas on this topic were summed up in January 1861 in the first issue (new series) of his own journal, the Natural History Review: "the most violent scientific paper he had ever composed".[50] This paper was reprinted in 1863 as chapter 2 of Man's Place in Nature, with an addendum giving his account of the Owen/Huxley controversy about the ape brain.[80] In his Collected Essays this addendum was removed.

The extended argument on the ape brain, partly in debate and partly in print, backed by dissections and demonstrations, was a landmark in Huxley's career. It was highly important in asserting his dominance of comparative anatomy, and in the long run more influential in establishing evolution amongst biologists than was the debate with Wilberforce. It also marked the start of Owen's decline in the esteem of his fellow biologists.

The following was written by Huxley to Rolleston before the BA meeting in 1861:

"My dear Rolleston... The obstinate reiteration of erroneous assertions can only be nullified by as persistent an appeal to facts; and I greatly regret that my engagements do not permit me to be present at the British Association in order to assist personally at what, I believe, will be the seventh public demonstration during the past twelve months of the untruth of the three assertions, that the posterior lobe of the cerebrum, the posterior cornu of the lateral ventricle, and the hippocampus minor, are peculiar to man and do not exist in the apes. I shall be obliged if you will read this letter to the Section" Yours faithfully, Thos. H. Huxley.[81]

During those years there was also work on human fossil anatomy and anthropology. In 1862 he examined the Neanderthal skull-cap, which had been discovered in 1857. It was the first pre-sapiens discovery of a fossil man, and it was immediately clear to him that the brain case was surprisingly large.[82] Huxley also started to dabble in physical anthropology, and classified the human races into nine categories, along with placing them under four general categorisations as Australoid, Negroid, Xanthochroic and Mongoloid. Such classifications depended mainly on physical appearance and certain anatomical characteristics.[83][84]

Huxley was certainly not slavish in his dealings with Darwin. As shown in every biography, they had quite different and rather complementary characters. Important also, Darwin was a field naturalist, but Huxley was an anatomist, so there was a difference in their experience of nature. Lastly, Darwin's views on science were different from Huxley's views. For Darwin, natural selection was the best way to explain evolution because it explained a huge range of natural history facts and observations: it solved problems. Huxley, on the other hand, was an empiricist who trusted what he could see, and some things are not easily seen. With this in mind, one can appreciate the debate between them, Darwin writing his letters, Huxley never going quite so far as to say he thought Darwin was right.

Huxley's reservations on natural selection were of the type "until selection and breeding can be seen to give rise to varieties which are infertile with each other, natural selection cannot be proved".[85][86] Huxley's position on selection was agnostic; yet he gave no credence to any other theory. Despite this concern about evidence, Huxley saw that if evolution came about through variation, reproduction and selection then other things would also be subject to the same pressures. This included ideas because they are invented, imitated and selected by humans: ‘The struggle for existence holds as much in the intellectual as in the physical world. A theory is a species of thinking, and its right to exist is coextensive with its power of resisting extinction by its rivals.’[87] This is the same idea as meme theory put forward by Richard Dawkins in 1976.[88]

Darwin's part in the discussion came mostly in letters, as was his wont, along the lines: "The empirical evidence you call for is both impossible in practical terms, and in any event unnecessary. It's the same as asking to see every step in the transformation (or the splitting) of one species into another. My way so many issues are clarified and problems solved; no other theory does nearly so well".[89]

Huxley's reservation, as Helena Cronin has so aptly remarked, was contagious: "it spread itself for years among all kinds of doubters of Darwinism".[90] One reason for this doubt was that comparative anatomy could address the question of descent, but not the question of mechanism.[91]

Huxley was a pallbearer at the funeral of Charles Darwin on 26 April 1882.[92]

In the early 1870s the Royal School of Mines moved to new quarters in South Kensington; ultimately it would become one of the constituent parts of Imperial College London. The move gave Huxley the chance to give more prominence to laboratory work in biology teaching, an idea suggested by practice in German universities.[28] In the main, the method was based on the use of carefully chosen types, and depended on the dissection of anatomy, supplemented by microscopy, museum specimens and some elementary physiology at the hands of Foster.

The typical day would start with Huxley lecturing at 9am, followed by a program of laboratory work supervised by his demonstrators.[102] Huxley's demonstrators were picked men—all became leaders of biology in Britain in later life, spreading Huxley's ideas as well as their own. Michael Foster became Professor of Physiology at Cambridge; Ray Lankester became Jodrell Professor of Zoology at University College London (1875–91), Professor of Comparative Anatomy at Oxford (1891–98) and Director of the Natural History Museum (1898–1907); S.H. Vines became Professor of Botany at Cambridge; W.T. Thiselton-Dyer became Hooker's successor at Kew (he was already Hooker's son-in-law!); T. Jeffery Parker became Professor of Zoology and Comparative Anatomy at University College, Cardiff; and William Rutherford[103] became the Professor of Physiology at Edinburgh. William Flower, Conservator to the Hunterian Museum, and THH's assistant in many dissections, became Sir William Flower, Hunterian Professor of Comparative Anatomy and, later, Director of the Natural History Museum.[33] It's a remarkable list of disciples, especially when contrasted with Owen who, in a longer professional life than Huxley, left no disciples at all. "No one fact tells so strongly against Owen... as that he has never reared one pupil or follower".[104]

Photograph of Huxley (c. 1890)

Huxley's courses for students were so much narrower than the man himself that many were bewildered by the contrast: "The teaching of zoology by use of selected animal types has come in for much criticism";[105] Looking back in 1914 to his time as a student, Sir Arthur Shipley said "Darwin's later works all dealt with living organisms, yet our obsession was with the dead, with bodies preserved, and cut into the most refined slices".[106] E.W MacBride said "Huxley... would persist in looking at animals as material structures and not as living, active beings; in a word... he was a necrologist.[107] To put it simply, Huxley preferred to teach what he had actually seen with his own eyes.

This largely morphological program of comparative anatomy remained at the core of most biological education for a hundred years until the advent of cell and molecular biology and interest in evolutionary ecology forced a fundamental rethink. It is an interesting fact that the methods of the field naturalists who led the way in developing the theory of evolution (Darwin, Wallace, Fritz Müller, Henry Bates) were scarcely represented at all in Huxley's program. Ecological investigation of life in its environment was virtually non-existent, and theory, evolutionary or otherwise, was at a discount. Michael Ruse finds no mention of evolution or Darwinism in any of the exams set by Huxley, and confirms the lecture content based on two complete sets of lecture notes.[108]

Since Darwin, Wallace and Bates did not hold teaching posts at any stage of their adult careers (and Műller never returned from Brazil) the imbalance in Huxley's program went uncorrected. It is surely strange that Huxley's courses did not contain an account of the evidence collected by those naturalists of life in the tropics; evidence which they had found so convincing, and which caused their views on evolution by natural selection to be so similar. Adrian Desmond suggests that "[biology] had to be simple, synthetic and assimilable [because] it was to train teachers and had no other heuristic function".[109] That must be part of the reason; indeed it does help to explain the stultifying nature of much school biology. But zoology as taught at all levels became far too much the product of one man.

Huxley was comfortable with comparative anatomy, at which he was the greatest master of the day. He was not an all-round naturalist like Darwin, who had shown clearly enough how to weave together detailed factual information and subtle arguments across the vast web of life. Huxley chose, in his teaching (and to some extent in his research) to take a more straightforward course, concentrating on his personal strengths.

Huxley was also a major influence in the direction taken by British schools: in November 1870, he was elected to the London School Board in its first elections.[110] In primary schooling, he advocated a wide range of disciplines, similar to what is taught today: reading, writing, arithmetic, art, science, music, etc. In secondary education he recommended two years of basic liberal studies followed by two years of some upper-division work, focusing on a more specific area of study. A practical example of the latter is his famous 1868 lecture On a Piece of Chalk which was first published as an essay in Macmillan's Magazine in London later that year.[111] The piece reconstructs the geological history of Britain from a simple piece of chalk and demonstrates science as "organized common sense".

Huxley supported the reading of the Bible in schools. This may seem out of step with his agnostic convictions, but he believed that the Bible's significant moral teachings and superb use of language were relevant to English life. "I do not advocate burning your ship to get rid of the cockroaches".[112] However, what Huxley proposed was to create an edited version of the Bible, shorn of "shortcomings and errors... statements to which men of science absolutely and entirely demur... These tender children [should] not be taught that which you do not yourselves believe".[113][114] The Board voted against his idea, but it also voted against the idea that public money should be used to support students attending church schools. Vigorous debate took place on such points, and the debates were minuted in detail. Huxley said "I will never be a party to enabling the State to sweep the children of this country into denominational schools".[115][116] The Act of Parliament which founded board schools permitted the reading of the Bible, but did not permit any denominational doctrine to be taught.

It may be right to see Huxley's life and work as contributing to the secularisation of British society which gradually occurred over the following century. Ernst Mayr said "It can hardly be doubted that [biology] has helped to undermine traditional beliefs and value systems"[117]—and Huxley more than anyone else was responsible for this trend in Britain. Some modern Christian apologists consider Huxley the father of antitheism, though he himself maintained that he was an agnostic, not an atheist. He was, however, a lifelong and determined opponent of almost all organised religion throughout his life, especially the "Roman Church ... carefully calculated for the destruction of all that is highest in the moral nature, in the intellectual freedom, and in the political freedom of mankind".[116][118] In the same line of thought, in an article in Popular Science, Huxley used the expression "the so-called Christianity of Catholicism", explaining: "I say 'so-called' not by way of offence, but as a protest against the monstruous assumption that Catholic Christianity is explicitly or implicitly contained in any trust-worthy record of the teaching of Jesus of Nazareth."[119]

Originally coining the term in 1869, Huxley elaborated on "agnosticism" in 1889 to frame the nature of claims in terms of what is knowable and what is not. Huxley states

Agnosticism, in fact, is not a creed, but a method, the essence of which lies in the rigorous application of a single principle... the fundamental axiom of modern science... In matters of the intellect, follow your reason as far as it will take you, without regard to any other consideration... In matters of the intellect, do not pretend that conclusions are certain which are not demonstrated or demonstrable.[120]

Use of that term has continued to the present day (see Thomas Henry Huxley and agnosticism).[121] Much of Huxley's agnosticism is influenced by Kantian views on human perception and the ability to rely on rational evidence rather than belief systems.[122]

In 1893, during preparation for the second Romanes Lecture, Huxley expressed his disappointment at the shortcomings of 'liberal' theology, describing its doctrines as 'popular illusions', and the teachings they replaced 'faulty as they are, appear to me to be vastly nearer the truth'.[123]

Vladimir Lenin remarked that for Huxley "agnosticism serves as a fig-leaf for materialism".[124] (See also the Debate with Wilberforce above.)

Thomas Henry Huxley, c. 1885, from a carte de visite

Method and results, 1893

Huxley's interest in education went still further than school and university classrooms; he made a great effort to reach interested adults of all kinds: after all, he himself was largely self-educated. There were his lecture courses for working men, many of which were published afterwards, and there was the use he made of journalism, partly to earn money but mostly to reach out to the literate public. For most of his adult life he wrote for periodicals—the Westminster Review, the Saturday Review, the Reader, the Pall Mall Gazette, Macmillan's Magazine, the Contemporary Review. Germany was still ahead in formal science education, but interested people in Victorian Britain could use their initiative and find out what was going on by reading periodicals and using the lending libraries.[125][126]

In 1868 Huxley became Principal of the South London Working Men's College in Blackfriars Road. The moving spirit was a portmanteau worker, Wm. Rossiter, who did most of the work; the funds were put up mainly by F.D. Maurice's Christian Socialists.[127][128] At sixpence for a course and a penny for a lecture by Huxley, this was some bargain; and so was the free library organised by the college, an idea which was widely copied. Huxley thought, and said, that the men who attended were as good as any country squire.[129]

The technique of printing his more popular lectures in periodicals which were sold to the general public was extremely effective. A good example was "The Physical Basis of Life", a lecture given in Edinburgh on 8 November 1868. Its theme—that vital action is nothing more than "the result of the molecular forces of the protoplasm which displays it"—shocked the audience, though that was nothing compared to the uproar when it was published in the Fortnightly Review for February 1869. John Morley, the editor, said "No article that had appeared in any periodical for a generation had caused such a sensation".[130] The issue was reprinted seven times and protoplasm became a household word; Punch added 'Professor Protoplasm' to his other soubriquets.

The topic had been stimulated by Huxley seeing the cytoplasmic streaming in plant cells, which is indeed a sensational sight. For these audiences Huxley's claim that this activity should not be explained by words such as vitality, but by the working of its constituent chemicals, was surprising and shocking. Today we would perhaps emphasise the extraordinary structural arrangement of those chemicals as the key to understanding what cells do, but little of that was known in the nineteenth century.

When the Archbishop of York thought this 'new philosophy' was based on Auguste Comte's positivism, Huxley corrected him: "Comte's philosophy [is just] Catholicism minus Christianity" (Huxley 1893 vol 1 of Collected Essays Methods & Results 156). A later version was "[positivism is] sheer Popery with M. Comte in the chair of St Peter, and with the names of the saints changed". (lecture on The scientific aspects of positivism Huxley 1870 Lay Sermons, Addresses and Reviews p. 149). Huxley's dismissal of positivism damaged it so severely that Comte's ideas withered in Britain.

• 1862: Trawling for herrings on the coast of Scotland.
• 1863–65: Sea fisheries of the United Kingdom.
• 1870–71: The Contagious Diseases Acts.
• 1870–75: Scientific instruction and the advancement of science.
• 1876: The practice of subjugating live animals to scientific experiments (vivisection).
• 1876–78: The universities of Scotland.
• 1881–82: The Medical Acts. [i.e. the legal framework for medicine]
• 1884: Trawl, net and beam trawl fishing.

• 1866: On the Royal College of Science for Ireland.
• 1868: On science and art instruction in Ireland.

Biographers have sometimes noted the occurrence of mental illness in the Huxley family. His father became "sunk in worse than childish imbecility of mind",[145] and later died in Barming Asylum; brother George suffered from "extreme mental anxiety"[146] and died in 1863 leaving serious debts. Brother James, a well known psychiatrist and Superintendent of Kent County Asylum, was at 55 "as near mad as any sane man can be".[147] His favourite daughter, the artistically talented Mady (Marian), who became the first wife of artist John Collier, was troubled by mental illness for years. She died of pneumonia in her mid-twenties.[148][149]

About Huxley himself we have a more complete record. As a young apprentice to a medical practitioner, aged thirteen or fourteen, Huxley was taken to watch a post-mortem dissection. Afterwards he sank into a "deep lethargy" and, though Huxley ascribed this to dissection poisoning, Bibby[150] and others may be right to suspect that emotional shock precipitated the depression. Huxley recuperated on a farm, looking thin and ill.

The next episode we know of in Huxley's life when he suffered a debilitating depression was on the third voyage of HMS Rattlesnake in 1848.[151] Huxley had further periods of depression at the end of 1871,[152] and again in 1873.[153] Finally, in 1884 he sank into another depression, and this time it precipitated his decision to retire in 1885, at the age of 60.[154] This is enough to indicate the way depression (or perhaps a moderate bipolar disorder) interfered with his life, yet unlike some of the other family members, he was able to function extremely well at other times.

The problems continued sporadically into the third generation. Two of Leonard's sons suffered serious depression: Trevennen committed suicide in 1914 and Julian suffered a breakdown in 1913,[155] and five more later in life.