Charles Darwin

by Janet Browne

  In the summer of 1878, and again in 1879 and 1881, Francis went to Würzburg, near Frankfurt in Germany, for a few months to study with the experimental botanist Julius Sachs and learn the craftmanship that then made Sachs’s laboratory the leading centre for plant physiology in the world. To spend time in Sachs’s laboratory was a key requirement for ambitious young botanists. In fact, the dissemination of Sachs’s techniques to Cambridge marked the beginnings of plant physiology in England, and the story was repeated in every European capital where botany was intensively studied. Francis went intending to investigate the growth patterns of roots and shoots. He came back with his botanical horizons extended in every direction.

  In particular, Francis’s imagination was fired by Sachs’s lavishly equipped laboratory—an enviable procession of the latest instrumental designs, a pageant of rotating drums, dials, electrical terminals, smoked cylinders, microtomes for cutting wafer-thin slices, high-resolution microscopes, and ingenious devices for amplifying and measuring plant growth and movement. Several of these instruments were adapted by Sachs from animal physiology researches and could be encountered only in his laboratory. Francis was deeply impressed. He felt that Sachs was more inventive than even Darwin, especially in the manner that he turned plants into active participants in experiments by attaching the living organism to whatever form of machinery was required and letting it inscribe, or self-record, its own movements on a chart. In this way each plant wrote its personal autograph.44 This focus on instruments—a fundamental shift in late-nineteenth-century science—transformed the living organism, with all its individual foibles and attributes, into a standardised object of research.

  Thus inspired, Francis injected a new sense of purpose into Darwin’s researches. He wanted to have instruments like Sachs’s, urged his father to use rigorous experimental controls, and initiated wider-ranging investigations into cellular structure and chemical activity than Darwin would have been inclined to pursue on his own. It seems likely that the expensive Hartaack microscope listed in Darwin’s effects at his death was chosen and brought back to Down House by Francis. In 1881, Darwin asked Haeckel’s advice about a Zeiss instrument, again probably for Francis. In short, Francis became his father’s experimental eyes and hands, bringing him fresh ways of thinking about plant functions. He propelled Darwin into new areas, most notably the means by which plants perceive stimuli, a field that Sachs also investigated.

  One area of research was to establish that every growing shoot described tiny circles or spirals in the air. Darwin thought these “circumnutations” formed the basis of all other plant movements, with each additional twist or turn being an adaptation to the plant’s special circumstances of life, the handwriting that distinguished one moving species from another. The evolutionary aspect excited them both. Darwin and Francis made extensive use of grass seedlings (grass coleoptiles) in this research, a choice of experimental organism copied from Sachs, and as significant in its own way as the use of flowering peas to Mendel or fruit flies to Thomas Hunt Morgan. Day by day, they measured trays of seedlings stretching towards the window. These measurements confirmed, in a manner acceptable to science, that young plants always grow towards the light and could correct their orientation in a matter of hours if needed.

  They also inquired into what it was that helped plants recognise the vertical, and the rapidity with which they sensed and responded to stimuli, such as touch. A passion-flower tendril could move within twenty-five seconds of stimulation. It was this phenomenon, more than any other, that made them doubt Sachs’s opinion that movement originated in the unequal growth on either side of the tendril. Good-humouredly, Darwin regarded shoots and tendrils almost as if they were earthworms, with tiny brains in their tips.

  It is impossible not to be struck with the resemblance between … the movements of plants and many of the actions performed unconsciously by the lower animals.45

  Another area of research was to identify what it was that made roots move downwards. In Darwin’s day it was assumed that gravity acted mechanically on the entire root (radicle), pulling it downwards by its own weight. Certainly Sachs said so in his authoritative textbook Lehrbuch der Botanik (1868, English translation 1875), and this phenomenon was part of what Francis had studied in Würzburg. If the root was placed horizontally on the ground, the cells on the lower side were thought to become turgid and heavier, pulling the root down into the earth. Darwin discounted this mechanistic explanation and believed he could show that the tip of the root was the active agent. When the tip was cut off, roots lost their sensitivity and remained horizontal. Further experiments led him to suggest that the tip transmitted an unknown internal “stimulus” to the rest of the root, which then responded. Now known as tropisms, these stimuli were almost beyond the bounds of the nineteenth-century botanical imagination. For one thing, plants were not thought to be actively responsive agents like animals, and for another, Darwin’s proposals were made some years before the concept of animal and then plant hormones was fully articulated. Interpreting plant movements as responses to stimuli was unusual. Darwin probably arrived at this position by thinking of roots as somewhat like simple animals acting according to their unconscious instincts. Sachs “will swear and curse when he finds out he has missed sensitiveness of apex,” he told Francis with satisfaction.

  Yet there could be no denying that Francis felt cramped by the lack of laboratory facilities at Downe. Resourcefully, he used lamp-black to darken thin pieces of glass and paper in the fashion he had learned at Würzburg. Using a humdrum collection of thread and blobs of wax, he attached these black papers to root tips to record their movements. It was a poor imitation of Sachs’s technique, and the blackened papers that remain in the archive show only faint and incomprehensible traces of the plant roots that once wriggled across them. Darwin was grateful, no doubt about that. But he spoiled the professional effect by adding glass beads as weights or needles from Emma’s sewing box.46

  Few of these ad hoc experiments could be easily repeated. Darwin was working in the old-fashioned style of a gentleman-amateur, a tradition that had served him well in the past and was still common enough in the last third of the nineteenth century, even in the case of physics; well-financed individuals might experiment with air pumps when at home in the country or keep enormous electrical batteries in their cellars for scientific investigations. Many of these independent experimenters regarded their activities as an important feature of intellectual integrity. To be paid for scientific work still suggested the possibility of being indebted to an employer. At the very least the scientific data emerging from paid work was not the personal property of the scientist. Nor was a project necessarily of his own choosing.47 If a man could afford it, he would tend to pursue independent research and therefore “own” his own results.

  But Darwin stood on a cusp. Cultural changes within science during the 1870s were shifting the emphasis on to endeavours performed in specialised, usually metropolitan settings, where the findings could be witnessed by others, be repeated time after time, and emerge as validated facts.48 In actuality, repetition was honoured mainly in the breach, since experimental procedures involved a degree of subjectivity and more incomplete data than most practitioners liked to admit. Nevertheless, these changes created groups of individuals who shared the same criteria of judgement about experimental results, and soon developed into distinctive subcultures with their own rules, technical practices, and languages. The spaces, or places, in which properly authenticated science could be done were therefore shifting. Darwin’s study and greenhouse looked increasingly amateurish, increasingly inappropriate. Huxley’s innovative programme of laboratory training in the Science Schools at South Kensington had headed the charge, in which a cohort of late Victorian naturalists learned high standards of laboratory technique, including Edwin Ray Lankester, William Rutherford, William Thiselton Dyer, Frank Bower, and H. G. Wells. Wells regarded his time in Huxley’s top-floor domain as the most educational year i
n his life.49 Further afield, Foster pushed ahead in London and Cambridge, and Hooker and Thiselton Dyer busied themselves in creating a physiological laboratory at Kew, funded by T. J. Phillips-Jodrell and opened in 1876. Darwin wrote to Hooker recommending the purchase of “good instruments” for the advancement of science. He said that if the Jodrell Laboratory owned a centrifuge or heliostat, he would want to use it.

  Obstinately, Darwin refused to buy any of the expensive equipment for which Francis yearned. Afterwards Francis said, “I have always felt it to be a curious fact, that he who has altered the face of Biological Science, and is in this respect the chief of the moderns, should have written and worked in so essentially a non-modern spirit and manner.” At Down House they made do with a miscellaneous collection of improvised gadgets and measuring devices. None of them would have passed muster on Sachs’s laboratory benches. “If any one had looked at his tools, &c. lying on the table,” admitted Francis, “he would have been struck by an air of simpleness, make-shift, and oddness.”50 Darwin’s seven-foot wooden measuring rule was calibrated by the village carpenter. He measured very small objects with a piece of card marked up from an ancient book that turned out to be wrong. He used the battered old chemical balance from his Shrewsbury days, and he altered his Smith and Beck microscope to suit himself without hesitation, evidently treating instruments as nonchalantly as the scientific books he would tear apart for convenient reading. When he needed a black box, or a turntable, he would find something close to what he wanted and get it darkened with shoe-blacking, as John Lewis, the carpenter, recalled.

  One day Mr. Darwin told me to make him six mahogany boxes, three inch square inside, and one side perforated zinc. I brought them up, and he bid me put them on six wee Dutch clocks and take off the hands. Then they were fixed so that the boxes went round and round with the clockwork. And he sowed seeds in them. I never could make out what it was for, but one day he says to me, “I’ve gained my object.” But I never knew what that was.51

  Darwin trusted these rough and ready instruments implicitly, and Francis doubted if he even noticed that they were a probable source of error. His one virtue, said his son, was that he used his equipment consistently. Any mistakes were the same mistakes throughout.

  Nevertheless, Francis felt pride in his father’s ingenuity. This pride contributed in large degree to the admiring imagery that was to grow up around Darwin’s simple approach to investigative work, for Francis made much of it in his edition of his father’s Life and Letters, but it was further bolstered by a general undercurrent of admiration for the string-and-sealing wax approach to scientific research. The Russian botanist Kliment Timiryazev, who had done a great deal to translate and promote Darwin’s views in Russia, on visiting Down House was impressed by seeing only “a series of pots with sundew turfs; each one of them was partitioned off into two halves by a tin plate: the leaves of one received meat, the leaves of the other were left without meat products.”52

  Alphonse de Candolle, who visited Darwin from Geneva in 1882, also admired these unsophisticated tricks of the trade. De Candolle plainly thought that the essence of Darwin’s approach was to ask very direct questions, the simpler the better.

  He was not one of those who would construct a whole palace to lodge a laboratory. I sought out the greenhouse in which so many admirable experiments had been made on hybrids. It contained nothing but a vine.53

  VI

  On his seventieth birthday, in February 1879, Darwin’s attention turned again to the past. His grandfather came back to haunt him in ways he could never have imagined.

  This started innocently enough with a congratulatory number of the journal Kosmos, a Festschrift to celebrate Darwin’s seventieth birthday, published by Ernst Krause in Germany in February 1879. The special issue included an article written by Krause on the life of Dr. Erasmus Darwin, Darwin’s paternal grandfather and an early proponent of evolution, titled “A Contribution to the History of Descent-Theory.” Krause praised grandfather and grandson, although he drew too close an intellectual connection for Darwin’s complete ease of mind.

  Nevertheless Darwin was intrigued by Krause’s article and decided to have it translated into English. He proposed adding his own “preliminary notice” of Erasmus Darwin to the translation. In part he was buoyed up by completing his autobiographical sketch, in which he had touched on the first Erasmus Darwin, and in part he thought that succeeding generations of Darwins would be as interested as he was in a fuller account of their ancestor. Moreover, an essay of his own provided an opportunity to correct inaccuracies arising from Krause’s reliance on what Darwin called Anna Seward’s overblown and “sarcastic” memoir, and the “calumnies published by Mrs. Schimmelpenninck.” These female contemporaries of Dr. Erasmus Darwin had not told the tale in the manner that Darwin heard it from his own father. He resolved to go through the family papers and supplement Krause’s essay. Before long, he wrote to Francis Galton for advice. Galton shared the same grandfather and retained his own family papers. Together the two evolutionists began to explore their own ancestry.

  As it turned out, Krause’s essay was too long for Murray to contemplate publishing in its entirety, especially if Darwin’s own notice was added. Krause’s part (translated by William Dallas) was consequently cut down mercilessly by Darwin. “F. keeps quite firm about employing Murray,” Emma informed the sons early in 1879, “but he is quite willing that any of you shd undertake the ornamental part of the affair.”

  He has got materials to make a pleasant preface—one a very capital letter of Dr D to Miss Howard before they were married—which shows him to be quite a human creature. Things always grow in his hands so that I expect it will be quite a small book & not a mere pamphlet.54

  One of the sons was in his element. George Darwin had a weakness for family history that he usually suppressed, feeling that his brothers were prone to tease. This romantic urge would take flight with any theme that went back into the mists of time. He liked playing about with ancient dialects or the pedigrees of words, “adored Roman roads” and Walter Scott’s novels, and, in time, took up archery and real tennis (the original indoor form of the game), half imagining himself “a character in medieval history.”55 That summer George was inflamed anew with heraldic inscriptions and genealogical charts. Pedigree talk dominated. “All your astronomical work is a mere insignificant joke compared with your Darwin discoveries,” chuckled his father in June. “Oh good Lord that we should be descended from a Steward of the Peverel; but what in the name of heaven does this mean?”56 Leonard’s humour was broader. Making play with the lexicographical conventions of genealogists, he quipped: “[William?] Darwin had a son whom he named after himself, leaving out the bracket and the ?”

  George commissioned a formal pedigree to be made by an American acquaintance, a Colonel Chester who had an enthusiasm for such researches. The chart went back two hundred years.57 Darwin roused himself to a similar pitch, poring over the old family papers bequeathed by his father. He was amused by the ancient wills that left only one shilling to descendants.

  Henrietta and Leonard pitched in too. Relaxed about the content and still in autobiographical mode from writing his own life story, Darwin dotted his text with personal comments and memories. “Henrietta. Is this too egoistic to include?” he jotted at the top of one page.58 As a result, Henrietta went through his text with a red pencil, excising passages containing mentions of living individuals who could be identified (all the Galton sisters, for instance), any overly personal judgements, and family finances, including a sentence recording Erasmus Darwin’s avowed desire to acquire wealth. A mature woman with opinions of her own, she thought it was improper that her father should discuss money, always the most interesting yet most inviolable barrier in polite Victorian society. Moreover, she also deleted a footnote in which Darwin commented approvingly on Erasmus Darwin’s religious scepticism. She had coped well enough with editing her father’s ideas about sexual relations in biology; now she c
ensored the family story. Darwin accepted her deletion. Leonard added his own suggestions. “Humbug,” he wrote beside Darwin’s long, self-absorbed passage about the qualities of a man of science.

  Still, he had enjoyed himself. The writing of this, the only biographical study that he ever attempted, was undertaken entirely for personal reasons. Even so, he found that it clarified some of his views about the role of speculation and originality in science. In thinking about Erasmus Darwin he necessarily pondered his own contribution to biology, wondering what made a man a discoverer; and with Galton’s opinions on heredity fresh in his mind he reflected on the traits that linked the men of the Darwin family line together as thinkers and innovators. There was much in his grandfather’s personality that was mirrored in his own, and in places, Darwin seemed almost unsure about whom he was writing. He could have been speaking of himself when he praised Erasmus Darwin’s “indifference to fame.” More ambiguously, he did not know whether to criticise or admire his grandfather’s inexhautible zest for speculation—presumably the flash of self-recognition was strong. In the end he criticised Erasmus Darwin’s “overpowering tendency to theorise and generalise,” saying that the “vividness of his imagination seems to have been one of his preeminent characteristics,” while adding the backhanded tribute that “his remarks … on the value of experiments and the use of hypotheses show that he had the true spirit of the philosopher.” Darwin’s pronounced sense of his own individuality made him declare that “unfettered speculation” was worthless unless it was kept closely in check by observation.59 These internal tensions came to a head in speaking of Erasmus Darwin’s most philosophical treatise, the Zoonomia, the book in which Dr. Darwin had proposed a system of evolution, and on which Charles Darwin had drawn extensively during the early days of his own riotous speculations on evolution. Darwin dismissively wrote, “I fear that his speculations on this subject cannot be held to have much value.” For the last, decisive time, he broke away from his grandfather and from his past.