The correspondence of Charles Darwin, volume 12: 1864

Edited by Frederick Burkhardt, Duncan M. Porter, Sheila Ann Dean, Paul S. White, Sarah Wilmot. (Cambridge University Press 2001)

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Introduction

On receiving a photograph from Charles Darwin, the American botanist Asa Gray wrote on 11 July 1864: ‘the venerable beard gives the look of your having suffered, and … of having grown older’. This portrait, the first of Darwin with his now famous beard, had been taken by his son William in April, when Darwin was beginning to feel better after the long illness that had plagued him since the spring of 1863. Because of poor health, Darwin corresponded little during the first three months of 1864, dictating nearly all his letters and having scientific papers read to him. In March, his health improved enough for him to make some observations of dimorphic plants with William’s help; he also ordered a selection of new climbing plants for his greenhouse and hothouse, and continued pursuing his investigations into their movements.

In the same month, Darwin began to consult William Jenner, professor of clinical medicine at University College, London, and physician-in-ordinary to Queen Victoria. Jenner prescribed a variety of antacids and purgatives, and limited Darwin’s fluid intake; this treatment differed considerably from that of the five physicians Darwin had consulted in 1863. In a letter of 26[–7] March [1864], Darwin exclaimed to his close friend, the botanist Joseph Dalton Hooker: ‘Hurrah! I have been 52 hours without vomiting!!’. In April he decided that Jenner had done him much good; his sickness had subsided enough for him to carry out tasks like counting seeds of Lythrum, crossing cowslips with polyanthuses, and searching for specimens of the dimorphic aquatic cut-grass Leersia.

In May, Darwin finished his paper on Lythrum (‘Three forms of Lythrum salicaria’) and sent it to the Linnean Society of London, thus completing the work he had started on the genus in 1862. His varied botanical observations and hybridising experiments continued throughout the summer. When he finished a preliminary draft of his paper on climbing plants in mid-September, he noted in his ‘Journal’ and in letters to several friends that on the very next day he resumed work on the manuscript of The variation of animals and plants under domestication (Variation), the long-awaited sequel to On the origin of species by means of natural selection (Origin) that he had set aside the previous summer. In October, Darwin let his friends know that on his good days he could work (presumably at writing) for two hours. As his health grew worse during the last two months of the year, he again complained to correspondents of feeling weak and unusually unwell, and he received more letters of advice from Jenner. In a letter of 15 December [1864] to the surgeon and naturalist Francis Trevelyan Buckland, Darwin described his symptoms in some detail: ‘I have suffered from almost incessant vomiting for nine months, & that has so weakened my brain, that any excitement brings on whizzing & fainting feelings, when I cannot speak; & much of this makes me for days afterwards very unwell’.

November and December were also marked by the award to Darwin of the Royal Society’s Copley Medal; he had been nominated for the medal in June, having been unsuccessfully nominated the two previous years. As Darwin explained to his cousin William Darwin Fox in a letter of 30 November [1864], ‘the Copley being open to all sciences & all the world is reckoned a great honour’; the gold medal was considered the greatest accolade that the Royal Society could bestow. The announcement of the award at the end of November, and the controversy that arose over the grounds on which it was conferred, brought a dramatic conclusion to the year. Darwin also wrote to Fox that he was mostly pleased to have been awarded the Copley Medal because it indicated that ‘Natural Selection [was] making some progress’ in Britain.

Darwin’s concern about the acceptance of his theory of transmutation remained paramount, and his botanical studies continued to be his favoured means of seeking further substantiation for the theory presented in Origin five years earlier. His primary botanical preoccupation in 1864 was climbing plants. He had become interested in climbers the previous year, noting the diverse powers of movement displayed by different organs, including the stem, flower-peduncle, petiole, leaf, and aerial roots. When his health deteriorated in 1863, he found that he could still continue his observations indoors (Correspondence vol. 11). In a letter of [27 January 1864], Darwin wrote to Hooker: ‘The only approach to work which I can do is to look at tendrils & climbers, this does not distress my weakened Brain—’. However, the queries that Darwin, describing himself as ‘a broken-down brother-naturalist’, sent to Daniel Oliver, keeper of the herbarium at the Royal Botanic Gardens, Kew, and professor of botany at University College, London, were of substance, testifying to his critical reading of the tendril literature, and to his developing research on the origin of climbing plants. In early February, he wrote: ‘I can show beautiful gradation by which leaves produce tendrils’ (letter to J. D. Hooker, [8 February 1864]). Darwin’s excitement about his observations and findings is palpable in his description of tying thread on Clematis peduncles to test sensitivity, and in his request to Hooker for another specimen: ‘I want it fearfully for it is a leaf climber & therefore sacred’ (letter to J. D. Hooker, 2 June [1864]).

When Darwin asked Oliver whether the tendrils of Passiflora might be modified flower peduncles rather than modified branches or leaves as most botanists thought, Oliver initially expressed reservations. However, he later apologised for his teacherly tone, explaining that he had felt that Darwin had misunderstood some accepted botanical tenets, and that his query indicated ‘doubt upon one or two matters which routinists regard in the light of axioms’ (letter from Daniel Oliver, [17 March 1864]). Though Darwin replied with his typical humility that he preferred being treated as one who was ignorant of the rudiments of botany, he continued to assemble evidence that challenged certain conventions in plant morphology. Many of his other correspondents, such as Hooker and Gray, had grown accustomed to the originality of his botanical queries, and were not surprised by the length and content of the paper ‘On the movements and habits of climbing plants’ (‘Climbing plants’), which Darwin submitted to the Linnean Society in January 1865.

Darwin’s paper divided plants into different categories: spiral-twiners, leaf-climbers, tendril-bearers, hook-climbers, and root-climbers. As was often the case, he was interested in transitional forms. Darwin came to think, for example, that a leaf, while still serving the functions of a leaf, could grasp an adjoining object if sensitised by contact with it. Over time, leaves could then acquire the function of tendrils, with the leaf blades eventually aborting to form true tendrils. After observing a variety of climbing plants, he argued that most had originated as spiral-twiners and then developed, in turn, the diverse climbing powers of leaf-climbers and tendril-bearers. At the end of his paper, Darwin used species from the genus Lathyrus as hypothetical examples of climbing plants that had developed into leaf-climbers, later graduating into tendril-bearers, to have the tendrils then revert to leaves, as in L. nissolia. Darwin wrote (‘Climbing plants’, p. 115): ‘If it be true that species become modified in the course of ages, we may conclude that L. nissolia is the result of a long series of changes . . .’ When he told Asa Gray in a letter of 29 October [1864] that he was continuing to study climbing plants after the completion of his first draft of the paper, he noted: ‘I have been pleased to find what a capital guide for observation, a full conviction of the change of species is.

In addition to his work on climbing plants, Darwin engaged in 1864 in botanical observations and crossing experiments as part of his ongoing programme to understand and explain the transformation of one species into another. He had already found, with dimorphic Primula and Linum species, that when a short-styled plant with long stamens was pollinated by a plant of the same form, rather than by a long-styled plant with short stamens, either no seeds at all, or infertile seeds, were produced. Continuing from these earlier studies, in 1864 he conducted crossing experiments between different forms of Pulmonaria species, and between Primula species and hybrids, in order to investigate further the relationship between species and varieties, and the nature of hybridity. Darwin noticed that the sterility resulting from crosses between plants of the same form was not necessarily different from the result of crosses between two different hybrids, or even between different species that had descended from common parents and differentiated over a long period of time.

Darwin remarked on the similar role of sexual structures in causing sterility both within and between species in his 1864 paper, ‘Three forms of Lythrum salicaria ’. In the two preceding years, he had made crosses between the long-styled, mid-styled, and short-styled forms of the trimorphic Lythrum, and when his health permitted in 1864 he drew up the results (see Appendix III). Darwin sought to show that the existence of long-styled and short-styled forms was not mere variability, but an adaptation to ensure cross-pollination between the two different forms. His research on L. salicaria suggested an even more intricate adaptation, whereby each form achieved the highest fertility only with pollen from the other two forms. The advantage he suggested that this gave the species was that each plant could achieve its highest fertility with around two-thirds of the neighbouring plants, rather than with half, as was likely to be the case with dimorphic forms. The risk of sterility at which the adaptation for cross-pollination was purchased was thus reduced. After the Lythrum paper was published, Darwin remarked to Hooker in a letter of 26 November [1864] that nothing had interested him so much since his discovery in 1848 of what he called ‘Complemental males’ parasitic on hermaphrodites in species of the barnacle Scalpellum.

Darwin’s interest in species, hybrids, and different forms within a species also led him to continue his experiments with the primrose (Primula vulgaris) and the cowslip (Primula veris). Their ranking as separate species had long been in question and Darwin seemed pleased to contribute to a long-running debate among botanists. He pursued experiments to determine the relationship of the two species with the common oxlip. In a letter of 22 October [1864], Darwin triumphantly wrote to Hooker: ‘I will fight you to the death, that as Primrose & Cowslip are different in appearance (not to mention odour, habitat & range) & as I can now show that when they cross, the intermediate offspring are sterile like ordinary Hybrids, they must be called as good species as a man & a Gorilla’. He had concluded that when crossed, the the primrose and cowslip produced the common oxlip which he determined was a hybrid. In following years, Darwin also established the relationship of the primrose and cowslip to the Bardfield oxlip ( P. elatior ), and published his results in an 1868 article (‘Illegitimate offspring of dimorphic and trimorphic plants’), and later in his 1877 book, The different forms of flowers on plants of the same species (Forms of flowers).

Darwin’s 1864 correspondence with family members shows the degree to which his botanical research was increasingly a household enterprise. Rarely being able to observe plants outside the confines of Down, Darwin enlisted the help of his family to collect specimens and make observations. His son George, who later studied mathematics at Cambridge University, assisted with a problem of weights and measures, and drew the figures for ‘Climbing plants’. Francis, aged 14, collected specimens of Echium vulgare. Darwin’s daughter Henrietta was often at his side in the hothouse or garden, taking notes by dictation. His niece Lucy Caroline Wedgwood sent observations of Pulmonaria officinalis from her family’s home in Surrey; Darwin incorporated these into Forms of flowers.

The greatest assistance in 1864, however, was provided by William, Darwin’s eldest son and a banker in Southampton. Their letters reveal their collaborative work in determining what differences in flower structures, in addition to stigma and stamen shape and size, indicated fertility between dimorphic forms. William participated in the detailed observations involved in the study of dimorphism by collecting and measuring flower parts, drawing pictures of pollen-grains, stigmas, and anthers, and sending them to his father. He was evidently keen to undertake such minute and painstaking observations, writing on 14 April [1864], ‘I can do as much pollen work as ever you like’. Comments on William’s findings, along with other household news, were sometimes written by Darwin’s wife, Emma, or by Henrietta. Darwin’s own replies to William disclose his delight in discovering the ‘splendid case of Dimorphism’ in Menyanthes (letter from Emma and Charles Darwin to W. E. Darwin, [20 May 1864]), or his excitement when he began to suspect that the structures of Pulmonaria angustifolia indicated that the species represented a transition to gynodioecism, a form that has hermaphrodite and female flowers on different plants.

Darwin remained convinced that the general advantage of dimorphism in plants was that it assured the participation of different individuals in reproduction, thus guaranteeing the vitality of a species by maintaining a level of variation upon which natural selection could act. In his ongoing quest to confirm the statement in his 1862 book on orchids that nature ‘abhors self-fertilisation’ (Orchids, p. 359), he continued studying the adaptations in orchids that favoured cross-pollination by insects; his correspondence with Gray, Philip Henry Gosse, George Chichester Oxenden, Friedrich Hildebrand, and others mentioned below, reflect this interest. At the start of the year, he received a letter, insect specimens, and an article on orchids from Hermann Crüger, head of the botanic garden in Trinidad. Darwin’s exhilaration is apparent in his reports to several correspondents that Crüger had confirmed the finding Darwin had published the previous year on different forms of Catasetum (‘Three sexual forms of Catasetum tridentatum ’). He was also delighted that Crüger confirmed both his observation of Catasetum pollen adhering to a humble-bee’s back, illustrating the force behind the ejection of the pollinia, and his speculation that insects chewed the labellum of some orchids to facilitate pollination. Darwin excused his boasting to Oliver, explaining that it was ‘the best medicine for my stomach’ (letter to Daniel Oliver, 17 February [1864]).

Darwin was also impressed by Crüger’s discovery of the unique bucket-like labellum, full of fluid, which facilitated a particular mode of insect pollination in Coryanthes ; he asked Oliver whether he knew the orchid, ‘with its wonderful bucket of water’. Darwin was interested enough by this case to add it to future publications, including the 1866 edition of Origin. He communicated Crüger’s paper to the Linnean Society, in addition to a paper on Bonatea speciosa that he received later in the year from Roland Trimen in South Africa. Darwin’s work with orchids continued to inspire the research of others as well; he influenced the 1864 publication of a paper by another of his orchid correspondents, John Traherne Moggridge, who in June sent him four spectacular watercolours of several orchid species (see plates facing pp. 248 and 249).

When Darwin requested orchid specimens from Hooker in November, he said that he did not intend ever to publish his new material on them. Nevertheless, his work in 1864 contributed to his 1869 paper focusing on the role of insects in orchid pollination (‘Fertilization of orchids’), and to additions in the second edition of Orchids, published in 1877. These publications were partly inspired by Crüger’s work, and by Darwin’s continuing identification of insect pollinators in 1864 and following years.

Much of Darwin’s correspondence in the spring and summer of 1864 is preoccupied with the plight of another of Darwin’s fellow orchid-experimenters, John Scott. Their correspondence had been initiated by Scott, a gardener at the Royal Botanic Garden, Edinburgh, in 1862 with a letter regarding the fertilisation of the orchid Acropera. Darwin communicated one of Scott’s papers on the orchid Oncidium to the Linnean Society in 1864 (Scott 1864b). Recognising Scott’s skills in experimental work, and an interest in dimorphism and heredity that was scarcely matched by anyone else in Britain at the time, Darwin suggested a number of topics for him to work on. Darwin encouraged Scott to publish his results independently, and Scott increasingly came to occupy the position of collaborator as well as protégé. Aided by a steady stream of suggestions and support from Darwin, Scott produced a paper on the Primulaceae that was communicated by Darwin to the Linnean Society (Scott 1864a); other papers of Scott’s followed, reporting the results of crossing experiments on different species.

In March, Darwin and Scott’s typically technical and detailed correspondence was interrupted by a short note from Scott stating that he had left the botanic garden at Edinburgh, where he had worked as foreman of the propagating department for five years. Scott felt that his superiors, James McNab and John Hutton Balfour, no longer treated him fairly, and he could see no future for himself at the garden and no hope of attaining a foreign appointment. Convinced of Scott’s talent and his ‘burning zeal for science’, and anxious about finding another person ‘fitted to investigate certain difficult & tedious points’, Darwin asked Hooker about the possibility of Scott’s conducting experiments at Kew on Darwin’s behalf for one or two years, with his stipend being paid by Darwin himself (letter to J. D. Hooker, [1 April 1864]). Hooker’s series of responses, some quite impassioned, present a picture of a distinctive professional and social hierarchy in place at Kew, and suggest Hooker’s own difficulties with the staff he supervised as assistant director of the Royal Botanic Gardens. He noted, for example, the jealousies that would be provoked by Scott’s position, suggesting that the gardeners were often at odds with one another: ‘Gardeners are the very d—l, & where two or three are gathered together I would rather not be in the midst of them: it is difficult enough to play your part over them’ (letter from J. D. Hooker, [2 April 1864]).

Hooker warned Darwin: ‘Do pray take care, of all classes of men Gardeners are the most troublesome … they do require very careful treatment’ (letter from J. D. Hooker, 8 April 1864). Nevertheless, Hooker solicited and received a confidential reference from Balfour that suggested that while Scott was a good worker and showed great promise as an experimenter, he had pursued his experiments at the cost of his regular duties as a gardener. Balfour also raised doubts about Scott’s abilities to work either in a subordinate capacity or as a manager of others. This reply only strengthened Hooker’s conviction that Scott aspired unrealistically towards science, without first carrying out the duties necessary to make his way in the world. In short, Hooker thought he was unfitted for the struggle for life: ‘I could cry like a child when appeals for charity come to me from cases to which I must apply your theory in all its force, & come to the conclusion that in giving I am hastening the fall’ (letter from J. D. Hooker, 20 April 1864). In his reply of 25 April [1864], Darwin suggested that Hooker took ‘a rather hard view of [Scott's] character’, adding, however, that he had followed Hooker’s suggestion, and had advised Scott to ‘grapple with the difficulties of life’.

Darwin persisted, however, in looking to Hooker for help in finding a suitable position for Scott, either at Kew or overseas. Fearing that his encouragement of Scott’s botanical researches might have contributed to his predicament, Darwin was determined to provide assistance. In time, Hooker concluded that India would be the best place for Scott to find a position, and he began to make enquiries with his contacts in forest departments, botanic gardens, and plantations. Darwin wrote a testimonial for Scott to carry with him in India while seeking employment; he praised his ‘remarkable powers of observation, his accuracy, his indomitable perseverance, and his knowledge’ (letter to John Scott, 10 June 1864). Hooker met Scott in August, and Scott impressed him as ‘thoroughly respectable & intelligent looking’, on which basis he recommended a first-class cabin for the journey (letter from J. D. Hooker, [15 August 1864]).

Darwin had been offering Scott financial support ‘on the grounds of science’ (letter to John Scott, 9 April 1864), but Scott declined assistance until it became clear that his own resources were inadequate to pay his passage to India. Scott then accepted Darwin’s offer, promising to repay the sum once he had settled into a position. After Scott visited Down prior to his departure for Calcutta, Darwin remarked to Hooker on the superiority of his manners and his mind. By September, Hooker learned that Thomas Anderson, the director of the botanic garden at Calcutta, had need of a gardener to work on a plantation in Darjeeling, and it seemed likely that Scott would take up this position when he arrived in India.

Although no-one had become as dependable or active a collaborator with Darwin on questions of hybridity as Scott, Darwin continued to cultivate ties with other people who lay on the margins, or sometimes outside the boundaries, of recognised scientific expertise. He maintained his contacts with a large body of gardeners, horticulturalists, and animal-breeders. As in earlier years, Darwin consulted Charles William Crocker about his crossing experiments with hollyhocks, and William Bernhard Tegetmeier about his pigeon breeding. To gather scientific information, Darwin read newspapers and journals popular among gardeners and commercial growers. While trying to collect information for Variation, he asked readers of the Gardeners’ Chronicle to consult their old gardening treatises or almanacs on the recommended date of sowing for French or runner beans over the last two centuries; he received numerous replies.

Darwin’s international network of sources of information seemed only to grow in 1864. In addition to Crüger’s and Trimen’s orchid observations, he received, for example, information on insects visiting flowers of the family Melastomataceae from Robert Thomson, a gardener at the new botanic garden in Castleton, Jamaica. Darwin and Friedrich Hildebrand in Germany compared results of crossing experiments with a Pulmonaria species. References and enclosures in letters from Gray and Hooker show how Darwin was able to extend his own network through friendships with men whose institutional positions enabled them to direct the activities of collectors and curators at a great distance. Gray forwarded a letter from Charles Wright, a plant collector in Cuba, that included information on orchids. Hooker passed on a query from Darwin to Richard Spruce on the climbing habit of a strangling fig that had been described in Henry Walter Bates’s Naturalist on the river Amazons. The response from Spruce, who had recently returned from fifteen years of collecting in South America, indicates how Darwin’s social contacts were an aid in confirming information he had acquired through reading.

International support for Darwin’s theory also expanded in 1864. A number of letters indicate that Darwin’s work was being read with particular enthusiasm in Germany. Hermann Kindt, a German living in England, claimed that Darwin’s writings had captured German students of natural philosophy, who read it ‘quasi a commentary’ to the materialist philosophy of Ludwig Buchner (letter from Hermann Kindt, 5 September 1864). Fritz Müeller sent his book, Für Darwin, and Darwin had it translated by a former governess at Down House, Camilla Ludwig. From Ernst Haeckel, Darwin learned of the support that his theory was gaining among German and Swiss scientific practitioners, including Haeckel’s colleagues at the University of Jena, August Schleicher and Carl Gegenbaur, Edouard Claparéde in Geneva, Max Schultze in Bonn, Rudolf Leuckart in Giessen, and Alexander Braun in Berlin. Darwin’s most ardent German supporter was undoubtedly Haeckel himself. Haeckel’s scientific life, he reported in a letter of 9 [July 1864], had been transformed by reading Origin : ‘Of all the books I have ever read, not a single one has come even close to making such an overpowering and lasting impression on me… . Since then your theory … has occupied my mind every day most pressingly’. Giving an account of how the theory of natural selection had been prefigured in German thought, Haeckel placed Darwin in a line of descent extending through Goethe back to Kant. He also described his own commitment to the theory as a tribute to his wife, Anne Sethe, who had died of typhoid fever in March 1864 on Haeckel’s thirtieth birthday: ‘she constantly encouraged me to work on it [Darwin's theory of descent] further and in the most loving manner often called me her German “Darwin–Mann” ’ (letter from Ernst Haeckel, 10 August 1864). Haeckel sent Darwin a number of his recent publications, noting the passages in which he had indicated his support for natural selection.

News from France was more ambiguous in 1864. Darwin’s brother Erasmus sent notice of an article by the philosopher Paul Janet, who discussed Origin, but accepted natural selection only under certain conditions. Darwin also heard of a discussion with a professor at Dijon University who despaired that ‘he could not get his pupils to listen to any thing from him except á la Darwin!’ (letter from Hugh Falconer, 3 November 186[4]). The French botanist, Charles Victor Naudin, wrote a gracious letter of congratulation for the award of the Copley Medal, and requested Darwin’s photograph, but he withheld any clear endorsement of Darwin’s theory.

While Darwin was bothered slightly by a critical review of Origin by the French physiologist, Marie Jean Pierre Flourens, he was far more upset by Rudolf Albert von Kölliker’s negative review; the distinguished Swiss anatomist and physiologist called Darwin a ‘ Teleologist in the fullest sense of the word’ (Kölliker 1864c, p. 200). Darwin was sufficiently concerned about the review to consider replying in the pages of the Reader, a weekly periodical directed at general readers while providing a forum for scientific debate. He had begun taking the journal in April 1863 and was an enthusiastic subscriber. However, when Darwin proposed using such a periodical to defend himself, Hooker and Lyell discouraged him, and he decided to avoid the direct engagement in controversy that he had chosen the previous year when he sent two letters to the Athenæum (Correspondence vol. 11). Darwin’s anxiety about the matter was eased when his cause was taken up by Huxley, whose critical notice of Flourens and Kölliker, published in the October issue of the Natural History Review, argued that teleology ‘had received its death blow’ with the publication of Origin (T. H. Huxley 1864a, p. 567).

In 1864, Darwin received his first letter from Benjamin Dann Walsh, a new advocate from North America who skilfully defended Darwin’s transmutation theory against the prominent Harvard zoologist Louis Agassiz, whose Methods of study in natural history began with a series of criticisms of Darwin’s theory. Agassiz was now at the height of his popularity in the United States, writing regularly for magazines and lecturing widely throughout the eastern and mid-western states. In his letter to Darwin of 7 November 1864, Walsh denounced Agassiz and sent a paper of his own in which he showed the ‘absurdity of Agassiz’s refutation of the “Origin of Species” ’ (Walsh 1864b). Darwin congratulated Walsh: ‘I am delighted at the manner in which you have bearded this lion in his den’ (letter to B. D. Walsh, 4 December [1864]). Walsh also supported Darwin’s theory through his own research, and sent a number of papers that showed him to be one of the first entomologists in America to find evidence for the theory of natural selection. Darwin was interested in Walsh’s work and was pleased at how ‘boldly & clearly’ he spoke out on the modification of species (letter to B. D. Walsh, 21 October [1864]).

Another letter from the United States in 1864 was from a Swiss palaeobotanist and devout Lutheran who, like Agassiz, had published criticisms of Origin based largely on religious grounds. However, Leo Lesquereux prefaced his long letter on the North American coal formations by saying that after a second reading of Darwin’s book, what had once seemed hostile to any religious faith now satisfied his reason ‘far better than any other human explanation could have done, concerning some of the most obscure points of the biblical teachings’ (letter from Leo Lesquereux, 14 December 1864). A notably rambling and long letter arrived from John Beck, a Shrewsbury schoolfellow of Darwin’s brother; Beck admitted to never having read Origin, but nevertheless felt compelled to oppose its alleged sceptical tendencies with his own inspired account of the ‘divine origin of species’. With copious citations from scripture and Byron’s Manfred, Beck unfolded his view that ‘lower’ forms of life were composed of the spirits of fallen angels, placed on earth by a merciful deity for the use of humankind (letter from John Beck, 6 October 1864).

Theological statements of a more public nature captured the attention of Darwin and some of his correspondents in 1864. Early in the year, his brother Erasmus told him of a subscription fund for John William Colenso, bishop of Natal, South Africa, who was fighting charges of heresy brought by an ecclesiastical court in Cape Town. The court was concerned about the controversial views expressed in the first parts of The Pentateuch and Book of Joshua critically examined (Colenso 1862–79). After reading extracts from Colenso’s work two years earlier, Darwin had suspected that Colenso’s views would ‘make a noise’, since the author evidently ‘smashe[d] most of the old Testament’ ( Correspondence vol. 10, letter to Asa Gray, 6 November [1862]). A declaration that Erasmus said was ‘in favor of freedom of opinion & defending the rights’ of Colenso was circulating with the 1864 subscription fund (letter from E. A. Darwin, 1 February [1864]). Darwin and Hooker both donated money to the fund. It is not known whether Darwin signed the declaration; Hooker did not, confiding to Darwin that however much he cared to defend Colenso’s religious freedom, he thought him ‘sanguine & unsafe’ (letter from J. D. Hooker, 16 February 1864). Hooker became acquainted with Colenso when Colenso was in England in 1864, socialising with Charles Lyell and other members of the London scientific circle.

Another theological dispute, resulting partly from new findings in science, was settled in 1864 when the Privy Council decided to drop the charges of heresy that had been brought against two of the authors of the controversial Essays and reviews, a volume written by six clergymen and one lay author, and expressing liberal theological views; some of the essays had touched upon the conflict between the teachings of the Church of England and recent findings of science, including Darwin’s transmutation theory (see Correspondence vol. 9, Appendix VI). Seven months after happily noting that the Council had ruled in favour of the two authors, Hooker expressed displeasure about a declaration written in response to the Council’s judgment. The declaration, drafted by a group of London chemists and signed by over 200 practitioners of science, expressed regret that some scientific research was being used to cast doubt on scriptural truth and urged investigators not to assume that their results were correct if they contradicted the Bible (see letter from J. D. Hooker, [19 September 1864]). When Hugh Falconer noted that the award of the Copley Medal to Darwin at the end of 1864 discredited these types of efforts, Darwin referred to the declaration as the latest ‘outburst of bigotry’ (letter to Hugh Falconer, 8 November [1864]).

Although Darwin was aware of disputes involving the Church of England during the early 1860s, he remained far more concerned about the support for his theory among practitioners of science, as well as philosophers. He was interested in, if somewhat sceptical of, the first instalments of Herbert Spencer’s Principles of biology (1864–7). Also unsure about Spencer’s work, Hooker was more pleased by the qualified support for Darwin’s theory and his work on hybridity that George Bentham expressed in his presidential address to the Linnean Society; Darwin, however, remained doubtful about the meaning behind some of Bentham’s language. Nevertheless, Bentham was one of the few contemporary British botanists to discuss Darwin’s studies of dimorphism and hybridity publicly, and he compared his fellow countryman’s work favourably with that of the French botanist, Naudin.

Darwin’s correspondence in 1864 reflects the strong interest he still took in geological questions. The arguments taking place about the glacial origin of lakes in Europe and New Zealand, and about the changes in climate over time, were not always immediately related to his theory; however, his early geological studies on the Beagle voyage and in Great Britain, as well as the relevance of geological findings to the geographic distribution of plants and animals, lay behind the spirited discussions he engaged in with Hooker. They paid close attention to arguments involving Falconer, Andrew Crombie Ramsay, Joseph Beete Jukes, and Roderick Impey Murchison that were first presented at the Royal Geographical Society, and later elaborated in letters and abstracts in the Reader. Darwin had been strongly influenced by Ramsay’s arguments in favour of the glacial formation of rock-basins, but like others was uncertain of the extent of the power of glaciers in shaping the landscape: ‘I have now come round again, to Ramsay’s view for third or fourth time; but Lyell says when I read his discussion in the Elements [C. Lyell 1865] I shall recant for fifth time’ (letter to J. D. Hooker, 22 October [1864]). Lyell persisted in favouring the view that rock-basins had primarily been formed by gradual movements of upheaval and subsidence. Darwin’s changes to the geological chapters in later editions of Origin, particularly the fifth and sixth editions, testify to his close attention to the geological discussions of the 1860s.

The controversies regarding human origins that seemed to dominate the first half of the previous year in scientific journals and British periodicals were less apparent in 1864. However, Darwin’s correspondence reveals that interest in the early history of humans and their predecessors had continued to grow following the 1863 publication of Huxley’s Evidence as to man’s place in nature and Lyell’s Antiquity of man, and that the hope of finding more human fossil remains had only been reinforced. Lyell urged financial support for the exploration of a Borneo cave in the hope that hominid fossils would be found. Other letters refer to cave discoveries in Gibraltar, including a fossil skull fragment believed by some to indicate that a Neanderthal race once extended across Europe. John Lubbock mentioned his forthcoming volume on prehistoric humans to Darwin, and Hooker discussed Huxley’s heated dispute with officers of the recently formed Anthropological Society of London, many of whose members sought a scientific basis justifying the slavery practised in North America.

Unlike in the preceding year, Darwin passed over most of these developments with very little commentary. However, when Alfred Russel Wallace sent him a copy of his recently published article, ‘The origin of human races and the antiquity of man deduced from the theory of “natural selection’, Darwin’s response revealed his conviction that the theory expressed in Origin encompassed human descent from the anthropoid apes. Some other readers were also aware of the significance of Wallace’s paper as the first published application of natural selection to humans, and Darwin proclaimed it as ‘ most striking & original & forcible’, displaying ‘remarkable genius’ (letter to J. D. Hooker, 22 [May 1864]). He added that he wished Wallace had written Lyell’s section on humans in Antiquity of man ; Darwin had been deeply disappointed by Lyell’s caution in his discussions of both Darwin’s transmutation theory and the question of human origins (Correspondence vol. 11). Wallace, however, traced a possible path of human divergence from the apes, proposing that natural selection then acted over a long period of time primarily on the human brain rather than on the rest of the body. This particular notion, that it was mental and moral faculties that had been most affected by natural selection in humans, was new to Darwin.

Wallace’s paper dealt not only with human descent, but also with the differentiation of the human races; he attempted to find a compromise between the polygenist views of the Anthropological Society, which for the most part consisted of those who disagreed with Darwin’s theory and advocated the separate creation of the human races, and the monogenist views of the Ethnological Society, most of whose members believed that humans had a single origin and later separated into distinct races. It appeared that Darwin, who later endorsed monogenism, supported Wallace’s attempt to mediate in the controversy on human racial origins. He told Wallace he had come to agree with him that the ‘struggle between the races of man’ and their divergence from one another ‘depended entirely on intellectual & moral qualities’ (letter to A. R. Wallace, 28 [May 1864]).

Darwin admitted to Hooker that in spite of the genius of Wallace’s paper, he was not sure that he could ‘fully agree’ with Wallace’s views on humans (letter to J. D. Hooker, 22 [May 1864]), and he pointed out some of these differences to Wallace in his letter of 28 [May 1864]. Darwin suggested a greater role for natural selection than Wallace had, endorsing a stronger influence of environmental conditions on various human racial changes. He also stressed sexual selection as the ‘most powerful means of changing the races of man’, asserting, for example, that among ‘savages the most powerful men will have the pick of the women & they will generally leave the most descendants’.

While praising the paper, both Hooker and Darwin were astonished at Wallace’s modesty in referring to the theory of natural selection as Darwin’s, without acknowledging his independent discovery of it. Darwin admonished him for this, but in his letter of 29 May [1864], Wallace replied: ‘I shall always maintain it [the theory of natural selection] to be actually yours & your’s only … All the merit I claim is the having been the means of inducing you to write & publish at once.’ Though Darwin offered Wallace his notes on humans in May 1864, supposing that he himself would never use them, most of his comments to Wallace that month were expanded on when he published The descent of man, and selection in relation to sex (Descent) in 1871. Along with other publications in the 1860s, Wallace’s 1864 paper stimulated Darwin’s thinking on human transmutation. Within a few years he began gathering new material for The expression of the emotions in man and animals (1870) and for Descent.

After the award of the Royal Society’s Copley Medal, Darwin may have felt more hopeful regarding the application of his theory to human descent than he had the previous year, particularly when Hugh Falconer suggested in his letter of 7 November [1864] that half the significance of the Royal Society’s award related to the ‘question of the antiquity of the human race in reference to the Biblical account’. Darwin had earlier revealed his awareness that a Royal Society medal could not be easily won when he suggested Wallace for the Society’s Royal Medal: ‘his Nat. Selection would, I suppose, rather go against him with Royal Soc y’ (letter to J. D. Hooker, 3 November [1864]). Darwin and Wallace’s theory of natural selection had been at least partly responsible for Darwin’s failure to win the award in the two preceding years. An 1863 letter from the president of the Royal Society, Edward Sabine, to the geologist John Phillips revealed Sabine’s fears that in 1864 he would no longer be able to prevent the award going to Darwin (see Appendix IV). With the help of supporters on the Council, including Hugh Falconer and George Busk, who had nominated him, the vote was settled by a ‘splendid majority’, despite rumours of opposition that had caused some of Darwin’s friends ‘to whet their beaks and sharpen their claws in preparation for taking a very decided course of action had there been any failure of justice’ (letter from T. H. Huxley, 4 November 1864).

Huxley anticipated another chance to sharpen his claws when Sabine’s anniversary address was delivered at the Royal Society on 30 November, when the award of the Copley Medal to Darwin was announced. Sabine’s power on the Council of the Royal Society and his opposition to Origin had already aroused Huxley’s suspicions, and when he described events at the meeting to Hooker in a letter of 3 December 1864, he wrote: ‘My distrust of Sabine is as you know, chronic—: and I went determined to keep careful watch on his address—lest some crafty phrase injurious to Darwin should be introduced’. Huxley seized on to what he thought was a harmful phrase, instigating a controversy as to whether Sabine’s address misrepresented the Council by saying that Origin had not been considered as one of the grounds of the award. The details of the ensuing debate, discussed in Appendix IV, demonstrate how Darwin’s supporters maintained their vigilance in the face of those who still held strong objections to his transmutation theory.

Darwin himself did not attend the meeting at which the award was announced, fearing that the excitement would make him seriously ill. In Darwin’s absence, the Copley Medal was received by George Busk and deposited with Darwin’s brother, Erasmus, who remarked that it was ‘rather ugly … & too light to turn into candlesticks’ (letter from E. A. Darwin, 1 December 1864). Without denying the wider implications of his award, Darwin wrote to Falconer that ‘the real cream of the enjoyment’ was the knowledge that his friends had taken so much interest on his behalf (letter to Hugh Falconer, 4 November [1864]). Darwin must have been particularly heartened when his former mentor, Lyell, congratulated him by saying that ‘an honour openly conferred by an old chartered institution acts on the outsiders and helps to increase that stock of moral courage which is so small still’ (letter from Charles Lyell, 4 November 1864); in recent years Darwin had grown unsure of the extent of Lyell’s support for his theory. In regard to the row Huxley stirred up, Darwin said it was ‘just like him to defend an absent friend’, and noted that Huxley had also done good service in blaming Sabine ‘for modifying in ever so little degree the Council’s award’ (letter to John Lubbock, 21 December [1864]). In letters to friends, Darwin concentrated on his gratitude for Sabine’s ‘splendid eulogium’; however, when he expressed his pleasure about the address to Sabine, he could not help adding that he would have liked him ‘to have said a little more on the “Origin’, and assured him that he felt ‘no shadow of doubt on the future progress of Natural Selection’ (letter to Edward Sabine, 4 December [1864]).

Darwin received news of support for natural selection largely in the form of letters during 1864; because of his fragile state of health, he saw few people outside the family and, according to Emma Darwin’s diary and his own ‘Journal’, left Down on only one occasion. Letters remained his primary means of contact with friends and scientific colleagues, and he continued writing even as his health worsened again in November and December. He was well enough, however, to continue reading some scientific journals, and to discuss botanical and geological questions with Hooker. He also noted, as he occasionally did, the ‘endless foolish novels’ that were read aloud to him by his ‘dear womenkind’ (letter to Asa Gray, 29 October [1864]).

It was Darwin’s work that truly enlivened him. Though he complained to his cousin Fox in the letter of 30 November [1864] that he felt ‘very weak & continually knocked up’, he added that he was ‘occasionally recreating’ himself with a ‘little Botanical work’, and that his work was ‘the only thing which [made] life endurable …’ With his animated exclamation to Hooker in December on finding species in three different families of climbing plants with adhesive disks at the end of the tendrils, and with queries to several correspondents asking about the feet of otter hounds compared with those of dogs that did not swim, Darwin’s questions and labours seemed likely to continue.