Darwin and the Barnacle

by Rebecca Stott

  The world of zoology had changed, too, in these eight long years. It had been a period of intense zoological enquiry for scores of naturalists, and many had been working away like him on sea creatures, examining the dark world of rock pools and the seabed, creatures made visible on glass slides and the lenses of microscopes. Darwin’s barnacle volumes were only a small part of a new push into the unknown undersea world. Most of these writers were men whom Darwin either knew personally or with whom he had corresponded over the previous years – men such as Dana, Huxley, Hancock, Bate, Forbes and Bosquet, meticulous observers like himself. Almost all of them were listed in the footnotes of his barnacle volumes – the hidden labourers – now they were underground, down there in the subterranean depths of his books.

  What had been the result of their investigations into the watery unknown? Back in 1837 the Revd Jenyns had insisted that each naturalist should specialize on one area of zoology, then the combined collection of data would begin to tell its own story. Now early twenty years had passed since Jenyns had urged young naturalists not to speculate on nature’s ways without first minutely describing them. Speculations about the origin of life or the relationship between the ‘higher’ and the ‘lower’ organisms must, he argued, be built only on the bedrock of extensive empirical observation. A speculator must be – or have been – an accurate systematist. Hooker had reaffirmed this principle even in 1845 when he had written to Darwin that ‘no one has the right to examine the question of species who has not minutely described many.’ Darwin felt the truth of this observation acutely in 1846. The barnacles would win him that right.

  When he carefully pieced together the Preface to On the Origin of Species by Natural Selection in 1859, it was precisely this right that he claimed when he declared that these years of hard systematic observation and analysis proved that he had not been ‘hasty’ in coming to his decision: ‘After five years’ work I allowed myself to speculate on the subject, and drew up some short notes; these I enlarged in 1844 into a sketch of the conclusions, which then seemed to me probable: from that period to the present day I have steadily pursued the same object. I hope that I may be excused for entering on these personal details, as I give them to show that I have not been hasty in coming to a decision.’

  Eight years winning a reputation as a brilliant and dogged systematist had brought Darwin other advantages. It had bought him time. In the barnacle years, the weight of systematic work undertaken in botany, zoology and comparative anatomy had brought the question of the permanence of species to centre stage. For, during these years, like Hooker with his New Zealand plants and Darwin with his barnacles, naturalists trying to systematise nature had been confounded by decisions about where variations within a species or subspecies ended and new species or subspecies began. In the Preface to the third edition of The Origin of Species Darwin listed the thirty-four naturalists who had published on the impermanence of species since 1800. Ten of these published their claims between 1846 and 1854. The idea of the fixity of species came under considerable pressure, then, during the barnacle years. Darwin’s species theory would be read differently as a consequence of such increasing pressure.

  Darwin also made an intricate web of correspondence through the barnacle work, a web established by gentlemanly good will, specimen exchange and philosophical and theoretical debate. In the thousands of letters he wrote during the barnacle years, he had written references, requested specimens, congratulated naturalists on their recently-published work, corrected errors in manuscripts, asked questions, answered questions, enquired after family and friends, cajoled, bantered, bartered, flattered and criticised. As a man of independent means with considerable charm and humility, he had made no enemies and kept himself remarkably unentangled in the politics of academic institutions. He had been overwhelmed, he wrote in the Preface to the book on the stalked barnacles, by the generosity of his fellow naturalists: ‘if a person wants to ascertain how much true kindness exists amongst the disciples of Natural History, he should undertake, as I have done, a monograph on some tribe of animals, and let his wish for assistance be known.’ And of course Darwin, contributing a specimen here, a reference or contact there, was himself only a skein in the knowledge webs of other naturalists working on similar projects. The elaborate global epistolary web to which he was joined would help to shape the reception of the species book.

  Darwin had decided not to add an additional volume, or a long introduction, as Hooker had done, explaining what all of this weight of barnacle anatomical detail meant philosophically. He had determined to keep his barnacles publicly unframed by his species theory. He would keep his systematic barnacle work largely unspeculative, his speculation for a separate performance. Although the development hypothesis was now much more widely known and discussed, it was still inextricably linked to the brilliant and frustrating book published in 1844 as Vestiges,6 which was now in its tenth edition and had sold tens of thousands of copies. Vestiges had helped to popularize questions about the laws of nature and the origins of life, but at the same time, because it involved grotesque speculation and was implicitly materialistic, it made the development hypothesis easy to demolish and ridicule. Its author just hadn’t done the painful watching and recording and dissecting that was necessary. He hadn’t earned the authority to speculate. Thomas Henry Huxley had published a savage review of the tenth edition of Vestiges in the pages of The British and Foreign Medico-Chirurgical Review. It was a review that made Darwin shudder. He could remember the opening sentences word for word: ‘In the mind of any one at all practically acquainted with science, the appearance of a new edition of the “Vestiges” at the present day, has much the effect that the inconvenient pertinacity of Banquo had upon Macbeth. “Time was, that when the brains were out, the man would die.”’7

  Darwin, acutely aware that Huxley had promised to review his own barnacle works, had already written to him about the Vestiges review, which, he wrote, was: ‘incomparably the best review I have read on the Vestiges; but I cannot think but that you are rather hard on the poor author. I must think that such a book, if it does no other good, spreads the taste for natural science. – But I am perhaps no fair judge for I am almost as unorthodox about species as the Vestiges itself, though I hope not quite so unphilosophical’.8

  Darwin did not need to worry about Huxley’s opprobrium, however. Whatever clues the barnacle volumes might have carried about Darwin’s big idea, as yet undeclared, Huxley found them impressive and inoffensive. The books confirmed Darwin’s rank as a systematist of international standing, Huxley declared:

  Mr Darwin’s present work shows him to he as able an observer of nature on the small as on the large scale. It deals with the anatomy and metamorphoses of certain crustaceans, those well-known barnacles, in all their varieties, from those which infest the bottoms of our ships, to those which lodge in the skins of Leviathan himself. Blind, fixed, and helpless as they seem to us, these animals in their young state, are active, sharp-sighted little creatures, somewhat like our water-fleas, with long leg-like antennae, provided with cups at their extremities. A time comes, however, when they know that they have to settle down in life; they adhere to some fixed or floating body by their sucking cups; then a long hump – we can call it nothing else – somewhat like that with which Mr Punch is provided, only ten times as long, grows out of their backs. From the end of the hump a sticky cement is poured out, which glues them firmly to their support; the function of the sucking-arms thus cease, but, as Mr Darwin has made out, they remain during life the witnesses of a different state of existence.9

  Huxley, writing for the educated readers of the Westminster Review, had compared Darwin’s books to the most important zoological studies of Europe, and at the same time had exploited the comic potential of the barnacle by turning it into a Mr Punch, a theatrical zoological sideshow. He anthropomorphized the barnacle as a man settling down, gluing himself to a rock. Although he wouldn’t admit it in the review, Huxley was in the process
of metamorphosing himself, trying his utmost to shift from a free-swimming form to a cemented one; he couldn’t many his fiancée Nettie until he had secured the job that would make married life possible. In 1854 permanent employment was within his grasp and his metamorphosis would be complete.

  Sea creatures were worth watching; they were both entertaining and philosophical and, now that the aquarium had been invented, it was possible to do so. The Westminster Review, committed to progressive ideas, had been interested in the philosophy of sea creatures since the relaunch of the journal in 1852 under the editorship of John Chapman and Mary Ann Evans (later George Eliot). Evans had commissioned Professor Edward Forbes to write a splendid piece called ‘Shell-Fish: Their Ways and Works’. In the journal it sat sandwiched between an article on representative political reform and one on the relationship between employers and the employed. This was one of Forbes’s most lyrical publications yet – ‘there is a philosophy in oyster-shells undreamed of by the mere conchologist!’ he wrote; ‘a noble and wondrous philosophy revealing to us glimpses of the workings of creative power among the dim and distant abysses of the incalculable past … unfolding for us the pages of the volume in which the history of our planet, its convulsions and tranquilities, its revolutions and gradualities, are inscribed in unmistakable characters.’10

  Like the oyster, the story of the barnacle was a story of ‘convulsions and tranquilizes … revolutions and gradualities’; for Darwin, it was a tale impossible to tell or explain without recourse to the development hypothesis. This tiny creature had both a life cycle and an adaptation since prehistory that were as epic and spectacular as the story told in the pages of the Vestiges of the Natural History of Creation; it also had a life history that bizarrely shadowed patterns of human life, shaped as it was by the same natural laws of survival, development and reproduction.

  So if sea creatures had, by 1854 when Darwin finished his books, become engorged with philosophical questions, they had also begun to capture the imagination of the British public, particularly now that the spread of the railways had made seaside excursions and seaside holidays so fashionable. Gosse had followed up A Naturalist’s Sojourn in Jamaica with a much more popular book two years later called A Naturalist’s Rambles on the Devonshire Coast.11 Still committed to finding ways to study live marine creatures in conditions close to their natural habitats, he had by 1853 worked out a chemical formula for reproducing artificial seawater that supported marine life. That year the keepers of the Zoological Gardens, working closely with Gosse, had opened an aquarium, which had become one of the spectacles of London. These tanks, filled with seawater carried from the North Sea to London by the Great Eastern Railway Company, were theatres of glass in which sea creatures performed epic natural dramas, as John Timbs described in Curiosities of London:

  27 The Outside of an Acorn Barnacle

  28 ‘Common Objects at the Seaside’

  The Aquatic Vivarium, built of iron and glass, in 1853, in the south garden, consists of glass tanks, in which fish spawn, zoophytes produce young, and algae luxuriate; crustacea and mollusca live successfully, and ascidian poplypes are illustrated, together with sea anemones, jelly fishes and star fishes, rare shell-fishes &c.: a new world of animal life is here seen as in the depths of the ocean, with masses of rock, sand, gravel, corallines, seaweed and sea-water; the animals are in a state of natural restlessness, now quiescent, now eating and being eaten.12

  29 ‘Valuable Additions to the Aquarium’

  As Darwin rewrote and expanded the species theory essay into the book he would publish in 1859, called On the Origin of Species by Natural Selection, aquarium mania began to sweep the country. By this point Darwin was compelled by new questions and new experiments, and pumping Hooker and his newer correspondents – seed growers, horse, cattle and pigeon breeders and nurserymen – with endless questions about plant and animal distribution. In March 1855 he was concerned to understand the means by which botanical species spread from continent to continent: wind, seawater, rafts; in the stomachs of birds, or on the feet of birds. ‘Really these questions are like Cerberus & his heads,’ Hooker wrote in response to another set of questions posted to him by Darwin, ‘the more arguments one disposes of the more rise up in grim array.’13

  When Darwin met Gosse for the first time on 2 March at the Linnaean Society meeting in London, his mind was full of questions and problems about the distribution of species between continents. There was no way to settle some of these questions without extensive and carefully described experiments with living species. His meeting with Gosse was timely, for the naturalist told him of his own experiments with seawater tanks in his home in St Mary Church, Devon, the tanks now successfully moved to London. He’d invented a formula for artificial seawater, he said, that made these experiments much easier because now he wasn’t dependent on seawater supplies being shipped up the Thames. The recipe he had finally fixed on was a quarter-ounce of Epsom Salts to three and a quarter ounces of common table salt with 200 grains of chloride of magnesium and 40 grains of chloride of potassium, all mixed into four quarts of water. He was using water from London’s New River suppliers, he said, one of the purest of the London water supplies. If Darwin wanted to undertake experiments with seawater, he should write to Mr Bolton of Holborn, a chemist who had agreed to market the salt mixture in special packets.

  Gosse had written all these instructions out clearly for his readers in a new book he’d just published, called A Handbook to the Marine Aquarium, a sequel to his earlier book The Aquarium: an Unveiling of the Wonders of the Deep Sea. It took Darwin several days to see what Gosse’s invention had made possible for him. Several weeks later he was still excited. He wrote to Henslow: ‘I saw Mr Gosse the other night & he told me that he had now the same several sea-animals & algae living & breeding for 13 months in the same artificially made sea water! Does not this tempt you? It almost tempts me to set up a marine vivarium.’14

  After all, Darwin had only studied dead barnacles. How much more there might be to learn with live ones.

  It was Hooker who was most in Darwin’s mind as he thought through his seawater experiments, for Hooker had always said that seeds of freshwater species couldn’t travel in seawater because the water would kill them. They wouldn’t germinate after a sea voyage. With seawater now so easily available through Gosse’s artificial formula, Darwin realized that he could prove that seeds could be carried by seawater from island to island and continent to continent, by a series of experiments that no one had yet undertaken. The experiments would be extensive, he told Emma. He would need to enlist the labour of the entire household, including the children.

  At Darwin’s request, Henslow posted a parcel of waterweed from the ponds around Hitcham. First he had to establish a way of keeping the freshwater organisms, to be used in his experiments, alive. Emma put together a glass tank with gravel and water from a local pond, and when the waterweed arrived she slipped its roots into the gravel. At Gosse’s advice they waited several days for the plant to establish itself and aerate the water.15 Meanwhile, Emma, already skilled as a chemist in her role as supplier of remedies for the villagers of Down, made up Gosse’s recipe for artificial seawater when the chemicals arrived in the post from Mr Bolton, 146 Holborn Bars.16

  Darwin and Etty dropped and sprinkled cabbage, radish, spinach, oat, barley, borage, beet and canary seeds into small bottles, tanks or saucers filled with the artificial seawater. Darwin made lists of all the seeds and labelled the saucers carefully, giving George and Etty some limited responsibility for daily checking. The servants carried the saucers to the designated locations on Darwin’s list – window sills in the schoolroom, drawing room, study, kitchen – and they measured the temperature in each room, carefully recording it in the notebooks Darwin gave them, so that he could check the effect of different temperatures on germination. The children, excited about competing against Hooker, eagerly watched for the results, keeping notes, watching the saucers in the schoolroom and
in the drawing room, checking several times a day for the faint green flush which would confirm germination.17 Despite the foul smell of the water, almost all the seeds germinated after between seven and fourteen days, to the children’s triumphant delight.18

  At the same time Darwin began a series of related experiments to see if freshwater animal species and their eggs would survive in sea-water, writing to John Lubbock to request some freshwater molluscs, which he introduced into the tanks. By May he had decided to try lizard eggs and land snail eggs in seawater, but lizards’ eggs were particularly difficult to procure, so he wrote to the Gardeners’ Chronicle for assistance: ‘If any of your readers could obtain for me some eggs of the Lacerta agilis, I would be greatly obliged. Lizards are most widely distributed, and I want to ascertain whether the eggs will float in sea-water, and, if so, whether they will retain their vitality. A reward of five shillings … offered to schoolboys, would perhaps get these eggs in the proper districts collected.’19

  In June he was still watching the seeds and giving Hooker regular bulletins about the results. He wrote to tell Miles Berkeley, a clergyman and botanist, who had undertaken similar experiments with seeds, that he had one set of seeds that took fifty-six days to germinate. This was excellent news – seeds could travel a considerable distance in fifty-six days and still be washed up on a shoreline with a chance of germinating; but Hooker was still not conceding ground, Darwin complained to a friend – he wanted yet more evidence: ‘Hooker seems much interested in these experiments; but they seem to have had very little influence, or no influence, in making him think that plants thus get distributed, which I am rather surprised at: & I shd like sometime very much to hear your opinion on this head.’20