The correspondence of Charles Darwin, volume 5: 1851-1855

Edited by Frederick Burkhardt, Sydney Smith. (Cambridge University Press 1988)

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Introduction

The correspondence in this volume reveals the main preoccupations of Darwin’s life with a new intensity. It opens with a family tragedy in the death of Darwin’s oldest and favourite daughter, Anne, and it shows how, weary and mourning his dead child, Darwin persevered with his scientific work, single-mindedly committed to the completion of his cirripede monographs. The anguish felt by Darwin is painfully expressed in letters written at Anne’s bedside at James Manby Gully’s hydropathic establishment in Malvern to Emma, who was confined to Down awaiting the birth of their ninth child. After Anne’s death, neither of them could speak of her again. Yet the family gradually recovered, Darwin’s monographs were printed, and by the time this volume closes Darwin, revitalised, was swept up in a rush of intellectual activity, able at last to renew his direct attack on the species question.

Between these two extremes were three-and-a-half more years devoted to the cirripedes. Before turning to his species work, Darwin somewhat ruefully recorded in his ‘Journal’ that he had spent nearly eight years classifying barnacles and many years later, in his autobiography, he wondered whether he had been right in spending so much time on the group. He was surely thinking of the years covered in this volume of correspondence: the exciting discoveries had already been made and, with the notable exception of Alcippe, the novel cirripedes already described. The intricacies of systematics had begun to weary him. The process of writing his volumes took longer than he had expected, and the publication of the monographs by natural history societies, though welcomed by Darwin, did not run smoothly. Nevertheless, his efforts were rewarded with the first public recognition of his scientific achievements when, in 1853, he was awarded a Royal Medal by the Royal Society of London for his contributions to geology and natural history, and in particular his Cirripedia work. Appendix II in volume four of the Correspondence describes the major achievements of Darwin’s cirripede work as a whole and assesses its significance to Darwin and to his contemporaries.

Throughout 1851, Darwin concentrated on the pedunculated cirripedes, arranging for drawings and plates and settling publication details with the Ray Society for Living Cirripedia (1851) and with the Palaeontographical Society for Fossil Cirripedia (1851). The next two years were devoted to the anatomy and classification of sessile cirripedes and culminated in Living Cirripedia (1854) and Fossil Cirripedia (1854), again published by the Ray Society and the Palaeontographical Society. One drawback to publishing with these societies, which were supported by subscriptions, was that Darwin’s volumes were not publicly available. In order to make his cirripede monographs more widely known among European naturalists, particularly those in Germany at the forefront of work in invertebrate zoology, Darwin began a correspondence with Thomas Henry Huxley. Huxley, by virtue of his current research interests and his fluency in the language, was well acquainted with the leading German naturalists in the field and with their work. His general knowledge of invertebrate anatomy and taxonomy and his commitment to developmental embryology as a basis for classification provided the foundations for a relationship with Darwin that soon developed into a valued friendship.

As letters in this volume indicate, Darwin began to rely on Huxley’s expertise in zoological matters, just as he did on Joseph Dalton Hooker’s in botany. Moreover, this circle of friendship and of shared interests was extended into the political realm of scientific life in London, as revealed in a series of letters pertaining to the Royal Society. In April 1854, when his cirripede study was drawing to a close, Darwin re-entered London scientific society, accepting membership in the Philosophical Club of the Royal Society (having declined to join in 1847). In November of the same year, he was elected to the council of the Royal Society and became active in the society’s affairs during his two years in office. He took great interest in the public awards of the society, giving thought to proposing men of scientific eminence, such as Charles Lyell and Henri Milne-Edwards, for the Copley Medal and suggesting for the Royal Medal lesser-known naturalists whom he believed deserved recognition. In 1855, he nominated John Obadiah Westwood for the Royal Medal, and his candidate subsequently became the first naturalist to receive the award for entomological pursuits.

Perhaps Darwin’s decision to take a more active interest in London scientific life was prompted by a general feeling of well-being and intellectual vigour now that the drudgery of publishing was behind him. An improvement in his health was indicated by his comment in a letter to Hooker on 29 [May 1854]: ‘Very far from disagreeing with me, my London visits have just lately taken to suit my stomach admirably;— I begin to think, that dissipation, high-living, with lots of claret is what I want, & what I had during the last visit.—’ In September 1854, as soon as the final proofs of the last barnacle volume had been returned to the printer, he threw himself into new and revived lines of inquiry bearing on the question of species. Letters are crammed with fresh ideas and plans. He talked freely of a projected book. Confidence in his theory of species origins and in his own ability to gather the evidence he felt necessary to substantiate it is manifest in the correspondence. Darwin’s friends and colleagues were unmistakably impressed. Even new correspondents, such as the prominent botanists Asa Gray and Hewett Cottrell Watson or outspoken young naturalists like Huxley, reacted eagerly to Darwin’s suggestions, although not always agreeing with his conclusions. The letters reveal the full depth of Darwin’s novel and challenging inquiries and the respect they engendered in his fellow workers.

Darwin initiated this new bout of research by rereading and sorting through the portfolios of notes on the species question he had collected previously, largely through his correspondence and reading. From the letters in this volume, it is clear that his plan was to carry out a wide range of practical investigations and experiments in order to support his theory.

One major experimental project was designed to investigate possible mechanisms for the geographical distribution of animals and plants. Darwin began a series of researches on the migration and dispersal of organisms in order to supplement views already expressed in his essay of 1844 (Foundations ; Correspondence vols. 3 and 4). In particular, he undertook to determine the ability of seeds to withstand the effects of salt-water and of plants with ripe fruit to float, also drawing the botanist Miles Joseph Berkeley, his friend Hooker, and various readers of the popular journal the Gardeners’ Chronicle into the study. He investigated other potential means of distribution, particularly the dispersal of seeds and ova by fish, birds, insects, and other animals. These investigations were part of his commitment to explain geographical distribution as a consequence of the operation of demonstrable means of dispersal combined with the effects of known changes in climate and geology. Darwin boldly rejected the popular idea of former land-bridges between continents, and between continents and oceanic islands, and proposed transport over sea as the alternative to such speculative, large-scale geological changes. As he told Hooker in a letter of 5 June [1855], ‘it shocks my philosophy to create land, without some other & independent evidence.’ With insular floras and faunas the key elements of a study of geographical distribution, he carefully analysed lists of the species on various island groups—focussing on Madeira, the Canary Islands, and the Azores—and compared them with the floras and faunas of nearby landmasses. Some of the most interesting letters in this volume set out Darwin’s practical researches and forceful arguments for the dispersal of animals and plants with Hooker who, with Charles Lyell and Edward Forbes, was one of the most public proponents of land-bridges.

The other main focus of Darwin’s research centred on determining the origin and frequency of variation in nature. The role of Darwin’s barnacle work in directing his attention to variation in nature cannot be over emphasised. The letters make it clear that Darwin’s discovery of the remarkable variation shown by certain Balanus species far exceeded what he had previously supposed when he first wrote out his species essay in full. In 1850, he had written to Hooker (Correspondence vol. 4, letter to J. D. Hooker, 13 [June 1850]), ‘You ask me what effect studying species has had on my variation theories; … I have been struck … with the variability of every part in some slight degree of every species’. His work on the Cirripedia also brought prominently into view the occurrence of aberrance through the effects of extinction. In his first letters after ‘packing up’ all his cirripedes, he began to explore this phenomenon with George Robert Waterhouse, Hooker, and others. He was subsequently led, under their guidance, into the lengthy tabulation of various catalogues of animals and plants in an attempt to ascertain whether aberrant species (and, later, variable species) tended to occur in genera that possessed many species or in those with few species. He sought statistical support for his notions that aberrant forms would generally be found where extinction had removed related species, and that variable forms should occur in successful genera with many closely related species, all partaking of common, advantageous characteristics.

An interest in variation naturally led Darwin to study the works of plant hybridisers, particularly those of Joseph Gottlieb Kölreuter and Karl Friedrich von Gärtner. In part to test Gärtner’s views concerning decreased fertility of hybrids, Darwin began in the spring of 1855 a series of hybridising experiments with more than thirty varieties of peas. A by-product of this work was the little note published, like the results of the seed-soaking experiments, in the Gardeners’ Chronicle describing his observations on the role of bees in pollination, a subject to which he returned in later years.

Darwin also undertook experiments relating to the question of the ultimate sources of variation in organisms. Advised by Robert Hunt, he planned to test the effects of coloured light on the growth of plants. This study, like another on sensitive plants, was an attempt by Darwin to ‘break the constitution of plants’ and produce heritable changes. Like most of the experiments conducted during this period, many of which can be traced to entries in his Questions & experiments notebook (Notebooks) and in his Experimental book (DAR 157a), this investigation demonstrates Darwin’s ability to grasp those consequences of his theories that might be subject to experiment and illustrates his skill in exploiting simple experiments to yield information pertinent to complex problems.

Just as he had previously utilised a world-wide network of specialists in his cirripede study, so Darwin began in 1855 to establish a comparable, yet even more elaborate, web of contacts to provide facts and specimens for his researches into the origins and variations of domesticated animals. His correspondence reveals the means by which he gained access to information and specimens from all quarters of the world, drawing upon acquaintances at home and abroad to give him an introduction to anyone who might assist him. In this regard, the naturalist and museum curator Edward Blyth figures most prominently. Blyth’s copious letters and memorandums in this volume, remarkable for their wealth of detailed and eclectic information, provided Darwin not only with facts he found useful but also with lines of research he might otherwise not have considered, such as an examination of ancient monuments for representations of the domesticated plants and animals of earlier civilisations. Blyth sent specimens from India and put Darwin in touch with others, such as Edgar Leopold Layard, whose first-hand knowledge of the plants and animals of particular regions proved extremely useful. Blyth’s importance for Darwin’s work is well shown by the number of times his information is cited in Natural selection, Origin, and Variation.

Selecting poultry, ducks, rabbits, and pigeons as particular subjects for study, Darwin moved beyond the usual circle of naturalists into closer contact with the world of breeders, dealers, and fanciers. His reading expanded to include works on domestic animals by Edmund Saul Dixon and others, as well as a variety of travelogues that described unusual domestic breeds. Early in 1855, following the advice of William Yarrell, Darwin began to keep pigeons at Down House to study the variations between breeds. His desire to acquire all the major breeds prompted him to visit pigeon shows, such as those held in Anerley, Kent, and, later, to become a member of two societies of pigeon-fanciers; it also provided an unexpected source of pleasure for him and especially for his daughter Henrietta. Through Yarrell, Darwin made the acquaintance of William Bernhard Tegetmeier, who, like so many of the others approached by Darwin, was flattered and eager to offer his services to such a distinguished naturalist. Darwin nurtured Tegetmeier’s interests in the stuctural variations shown by various breeds of fowls and, as he did with others, directed Tegetmeier’s studies along lines that he hoped would advance his own investigations.

To acquire specimens of domestic poultry and ducks, Darwin also relied upon the good nature of his friend and relative William Darwin Fox, who kept a wide assortment of animals at his ‘Noah’s ark’ in Delamere and who had long been actively interested in animal breeding. As Darwin told Fox in a letter of 27 March [1855], the object of his work was ‘to view all facts that I can master (eheu, eheu, how ignorant I find I am) in Nat. History, (as on geograph. distribution, palæontology, classification Hybridism, domestic animals & plants &c &c &c) to see how far they favour or are opposed to the notion that wild species are mutable or immutable: I mean with my utmost power to give all arguments & facts on both sides. I have a number of people helping me in every way, & giving me most valuable assistance; but I often doubt whether the subject will not quite overpower me.—’ Fox supplied him with a steady stream of material, even taking on the unpleasant task of killing newly-hatched chicks for his cousin’s comparative studies.

Throughout the correspondence of 1854 and 1855, the overwhelming impression given by Darwin’s letters is of his determination to pursue his theories through experimental means. His barnacle work had undoubtedly shown him the value of minute investigative researches and inculcated in him a firm belief that he could himself find the evidence in nature necessary to support his theories. This conviction was only occasionally shaken when his experiments failed to live up to his expectations, giving rise to his frustrated cry: ‘all nature is perverse & will not do as I wish it’ (letter to W. D. Fox, 7 May [1855]). But, whether successful or not, the impressive scope of Darwin’s practical researches, demonstrating a desire to examine fully the consequences of his theories, provided the basis for the eventual presentation of natural selection as a theory firmly founded on observation and on experiment.