Darwin and the Barnacle

by Rebecca Stott

  The story of Darwin’s barnacle work is also the story of how scientific discovery sometimes proceeds through indirection, for Darwin’s eight-year voyage into barnacle darkness – the last voyage he undertook before publishing On the Origin of Species by Natural Selection in 1859 – was a voyage driven by curiosity and obsession but also by an instinct for postponement. Darwin was no doubt hesitating by taking on the barnacles before he went to print with his bold species theory, but it was a particular kind of hesitation, not driven by fear, uncertainty or ambivalence, but by his realisation that the time was not yet ripe for publication of his theory and that he would need to prove himself as a systematizer if he was to be listened to when he did publish.

  This passion to classify a commonplace sea creature was not as bizarre as it seems. In the 1830s and 40s invertebrates, particularly marine invertebrates, were at the centre of controversies in taxonomy, comparative anatomy and evolutionary speculation. If all species had evolved from common stocks as some believed, the earliest life forms would have been aquatic single-celled organisms. Thus, Jean-Baptiste Lamarck, the French evolutionist, had claimed in 1809 that invertebrates were the key to understanding how all higher forms had evolved. But the amount of variation within the invertebrate groups made them extremely difficult to classify. As the century progressed, however, and as advanced dredging techniques brought up more previously unclassified creatures from the seabed, microscopes and developing dissection equipment and techniques made it possible for naturalists to see sharper detail inside the bodies of preserved invertebrate specimens, and to record and compare their spectacular anatomies, lifecycles and modes of reproduction.

  By the 1840s many naturalists, armed with increasingly powerful microscopes, had taken on particular marine invertebrate groups as classification challenges and opportunities to speculate on a range of conceptual problems in natural philosophy. T.H. Huxley, for instance, ship’s naturalist on the Rattlesnake, was working on crayfish, squid and jellyfish. Edward Forbes, lecturer in botany at King’s College, had finished his book on starfish and had moved on to ‘naked eyed’ medusae. In the mid 1840s marine invertebrates became critical to debates about sex when a Scandinavian naturalist called Japetus Steenstrup published a controversial study of the reproductive modes of marine invertebrates, showing how extensive multiple-generational asexual reproduction was in nature, particularly under the sea. Sexual reproduction no longer appeared to be nature’s dominant method, now that sea creatures were recorded as reproducing every which way: splitting, budding and self-fertilising.

  Barnacles were especially challenging to marine naturalists at this time. In the 1830s an army surgeon called John Vaughan Thompson had showed that adult barnacles develop from fee-swimming young and consequently were most like crustacea, not molluscs which they had previously been thought to be. Barnacles were now officially misplaced and misunderstood, their place in nature undetermined. But by 1846 when Darwin took out his Chilean barnacle once again, the barnacles were still unclaimed as a classification project. No naturalist had taken on the whole group. No one knew – yet – how difficult the task would be.

  Barnacles may have driven Darwin mad, given him nightmares, wrecked his health and his patience, but they were the perfect problem. Barnacles are small. Darwin was astute enough to know this had considerable advantages for him as a systematise. Specimens would travel around the world on mail carriages and trains in small glass jars or in pill boxes. They would come to him, posted by an army of collectors, friends, missionaries, friends, naturalists, mineralogists and shell collectors, to his house in Kent. Barnacles cluster on shorelines, they are ubiquitous and easy to collect and preserve. When he had a full collection of specimens, they would be small enough to lay out on a large table in his study so that he could map their diversification from one of the ancient fossil specimens, moving the specimens around to make the continuously branching patterns of a family tree that told an evolutionary story. The perfect puzzle for a speculative man.

  The barnacle project would bring Darwin into intimate global correspondence with a community of naturalists, comparative anatomists and zoologists working on similar philosophical problems. He was not a lone genius working in isolation. Through letters and specimen exchanges delivered by an increasingly sophisticated postal system, he worked through his classification and natural philosophical problems in relentless dialogue with hundreds of correspondents, forging ever more nuanced questions and propositions to be answered. In return he was cross-questioned, consulted, challenged and congratulated. By the time he had finished the barnacles, Darwin was at the centre of an intricate web. Each of the thousands of letters he wrote in the barnacle years created another delicate skein in that web, made possible by postal and railway networks stretching out from Kent to numerous European cities and beyond that to Australia, America, and Africa. When he later came to write On the Origin of Species by Natural Selection the existence of that web helped to determine the reception of his spectacular and controversial idea. Even those who denounced his theory could not dismiss Darwin as a mere speculator. He was a man who had classified the barnacles, won his spurs, been awarded the Royal Society medal. He was a man of authority and a man with important contacts and supporters.

  This book is a reconstruction of Darwin’s barnacle voyage pieced together using the thousands of letters he wrote during those years, the books he read, the philosophical questions he formulated for himself and others, and the conversations he had with other zoologists working on similar problems.

  Between 1846 and 1854, whilst Darwin remained glued to his microscope, mapping barnacle body parts, all around him the world was changing: his own family swelled and grew from four children to eight; one child – his favourite, Annie – died from a mysterious illness; and beyond his own fine house in Kent the political map of Europe shifted and mutated through waves of revolution. Another intellectual and philosophical revolution was waiting in the wings during these years, already formulated in embryonic form as an essay in Darwin’s study drawers: the publication of the On the Origin of Species by Natural Selection. But before he turned his mind to the species book, Darwin had to finish his barnacles.

  Darwin’s encounter with the barnacle began on a Chilean beach in 1835 but his fascination with marine zoology began in Edinburgh in 1825, a fascination shaped and nurtured by conversations with a Scottish doctor and sea sponge expert, Robert Grant, who taught the sixteen-year-old Darwin to dissect sea creatures on the shoreline of the Firth of Forth. He captured Darwin’s young imagination, planting philosophical questions about sea creatures and the origins of life that would germinate much later.

  1

  The Sponge Doctor

  Were this world an endless plain, and by sailing eastward we could for ever reach new distances, and discover sights more sweet and strange than any Cyclades or Islands of King Solomon, then there were promise in the voyage. But in pursuit of those far mysteries we dream of, or in tormented chase of that demon phantom that, some time or other, swims before all human hearts; while chasing such over this round globe, they either lead us on in barren mazes or midway leave us whelmed.

  Herman Melville, Moby Dick (1851)

  January 1822. Leith, the harbour town of Edinburgh. The weather is so mild that lupins and sweet williams bloom in Edinburgh gardens. From the elegant buildings of old Edinburgh up on the hill crowds of city dwellers follow a black cart carrying two prisoners through open fields down the elegant old Roman road, Leith Walk, to the sands of the harbour town, where gallows have been erected at low tide at the foot of Constitution Street. The cart carries Peter Heaman, from Sweden, and Francois Gautiez, a Frenchman, who had killed their ship’s captain and escaped with the cargo of Spanish gold, only to be caught by excise officers in the act of sharing out their gold coins with pint pots on a remote Scottish island. They have been sentenced to death by the High Court of the Admiralty. At the back of the cart, Heaman bows and performs to the crowd, but Gautiez
sits silently, hands folded. As the cart turns on to the sands, he looks up to see for a moment the audience that has gathered on the seashore in the January sunshine to watch him die.

  Here, on the seashore, crowds from the city join workers from the soap, glass, candle and sailmaking industries of Leith itself, like three great rivers converging. From the west, along the coastal paths, stroll whalers and fishermen and women from the neighbouring fishing village of Newhaven, the women dressed in their distinctive bonnets and striped costumes. From the east stride fishermen from Portobello and those who work in the salt and mining industries of Prestonpans. Children pull mussels off the black rocks underfoot. Seagulls scream. Out in the Firth of Forth, the oyster men fill their boats with paying tourists to provide the best view of all, a ringside seat from the ocean itself.1

  Just before midday the church choir begins to sing the Fifty-First Psalm, voices struggling against the sound of wind and tide:

  Purge me with hyssop, and I shall be clean

  Wash me, and I shall be whiter than snow.

  … Then shalt thou be pleased with the sacrifices of righteousness,

  With burnt offering and whole burnt offering

  Then shall they offer bullocks upon thine altar.

  The two men shake hands and step forward on to the wooden platform. They have rehearsed this step in their dreams. Arms tied behind their backs they fix their gaze upon the horizon, beyond the grimacing, jeering faces of the crowd, whilst the executioner, Thomas Williams, places a rope around each of their necks and black cloth bags over their heads. The light on the sea is still visible through the thickly woven black cloth as they listen for the sound of the lever moving inexorably into its wooden groove to release the platform beneath their feet. The floor drops away. Bodies spin and jerk in the air like deranged puppets hoisted above their wooden stage. The crowd cheers, throwing paper balls at the twisting bodies like confetti. Startled seagulls scream in the wake of the oyster boats.

  Later that afternoon, when the crowds have dispersed and oyster catchers have returned to the winter beach, two porters from the Medical Faculty of the University will cut down the bodies and place them back on the cart. There will be no crowds this time to watch the cart carry the bodies back up the hill, nor to watch the porters carry the corpses through the doors of the Surgeons’ Hall and on to the black marble tables of the dissection rooms. Most of the bodies of criminals hanged in Scotland are brought here to the Medical Faculty housed in the elegant and leafy Surgeons’ Square. Corpses are few and far between for Dr Munro and his medical students – a double public execution a rare event. In his dissection theatre, Dr Munro, dressed in a bloodied white apron, and waving a scalpel, will make these pickled bodies last for several weeks, lecturing to a steeply tiered audience of students whilst a paid demonstrator teases out delicate nerves and sinews or saws through limbs.

  With cadavers in high demand and in short supply, Edinburgh and its medical schools have become the centre of bodysnatching. Town councils struggle to find funds to build watchtowers and high walls with railings around local graveyards to deter bodysnatchers, but market forces prevail. Bodies fetch money. In Edinburgh, Merryless, Spune and Mowatt, a well-known group of body-buyers, barter openly for the bodies of the recently deceased at the doors of tenement blocks.2

  Surgeons’ Square, Edinburgh. Midnight. Medical school porters patrol the Old Surgeons’ Hall, where the stiffening bodies of the pirates lie in an ante-room of the dissection theatre. Otherwise, the square is empty apart from a stray cat or two hunting in the bushes around the lawns; but in an upper window in Dr Barclay’s Anatomy School next door, a light flickers. Inside, a well-dressed man in his late twenties, well known to the porters, works alone late into the night, surrounded by human body parts arranged on tables and notes and drawings scattered around the room. The air is thick with the smell of alcohol preservative. Robert Grant is wiry and slight in build, but even at this time of night he is neatly dressed and cleanshaven. He has a high forehead and, despite his youth, he is already balding. He prefers to work at night and, when the anatomy rooms are empty, he often works all night. It is always the way with him. The University porters tidy the room around him before the morning’s classes begin. Tomorrow, after his sleepless night, he will join the students to watch the dissection of the pirates.

  There is no light in the dissecting room apart from a circle of candles arranged around a watch glass. The lens of Grant’s microscope is focused on the watch glass. Inside, lying inert in seawater on the bottom of the glass, there is a small brightly coloured organism, covered with holes. It is a sea sponge – Spongia compressa – retrieved today from the dredging nets of the Newhaven fishermen and passed on to Grant. The fishermen are careful to keep the brightly coloured but inedible sea sponges for the Doctor, to tease them out of their nets and throw them into a bucket of seawater. Dr Grant pays well – more than the farmers who buy barrel-loads of discarded fish parts to use as manure; but the Doctor is particular about the body parts he will buy.

  3 Robert Grant

  Now Grant peers closely into his watch glass, his body taut and still, for twenty minutes at a time, breaking only to stretch his back and blink his eyes before he returns to the watch. Long periods of time pass like this, in which nothing appears to be moving inside the glass jar or outside in the room itself, except the shadows thrown on the wall by flickering candles.

  *

  Tall, clever and cynical, with a sharp tongue and a dry sense of humour, Robert Grant was passionate about sea sponges. The seventh of fourteen children, he had grown up in Edinburgh on the shores of the Firth of Forth, one of the richest marine habitats of the world, especially in sea sponges. He had spent much of his childhood with his parents or private tutor on the beach at Leith, watching the horse races on the sands, or sketching the whaling boats moored in Leith harbour or the oyster boats at Newhaven. Leith races were a particular pleasure: horses galloping the sand racecourse of two miles, Punch and Judy shows, swing-boats, clowns and fortune-tellers.3 Robert was the child who collected seashells while his brothers wrestled on the sand. He carried them home to arrange them on his mantelpiece amongst his favourite geometry and Greek schoolbooks.

  Whilst his brothers went into the army and into the East India Company, Robert signed up for the literature classes of Edinburgh University in 1808, when he was just fifteen; but it was the medical and anatomy classes that held his attention, and soon he had determined to train as a doctor, compelled by the opportunity to study anatomy rather than by any particular desire to heal the sick. The Medical Faculty gave him training in dissection and surgery, but cadavers were scarce; so in order to develop his dissection skills further he joined the Infirmary of Edinburgh as a pupil at the age of seventeen. He signed up as a member of several student societies, where he read research papers and argued with other ambitious young men about the philosophy of human and animal anatomy, the design and structure of bodies and the age of the Earth.

  These were exciting times. Fossil and geological discoveries gathered in caves and quarries around the world, and the remains of oyster beds found at the tops of mountains were forcing geologists and comparative anatomists to speculate on the age of the Earth and how it had come to be. This was an age of speculation. There were extraordinary theories abroad that were challenging religious scholarship, and the sea seemed to hold the answer to so many questions. If the Earth had started out as a ball of water, as some argued, the first life forms would have been aquatic. If, as a few others supposed, species had evolved, mutated, over millions of years of unimaginable time, these primitive aquatic creatures were ancestors. Evolutionary riddles were to be pursued in the dark crevices of rock pools and on the seabed.

  As President of two reputable student societies,4 Grant attracted the patronage of the professors of science from his first enrolments in classes. One of these was Robert Jameson, Professor of Natural History, an expert in comparative anatomy and geology, a natural philos
opher and one of the most influential men in the University. In 1813 the famous fifty-two-year-old Jameson was formulating a new essay by the French comparative anatomist, Baron Georges Cuvier, An Essay on the Theory of the Earth. Like Cuvier and other palaeontologists, Professor Jameson was formulating a theory about the processes that had shaped the Earth since its beginnings. There were many different theories being contested in the universities of Europe, but Jameson was a Neptunist, a follower of the ideas of Abraham Gottlob Werner, a German mineralogist who argued that the earth had begun as a ball of water, a universal ocean, and that all that was now solid on the earth had gradually settled like sediment from that primal water. But Jameson was also interested in other ideas and evidence from Germany and from France in particular.

  Throughout Europe natural philosophers were using every fragment of evidence they had collected and labelled – fossils, rock samples, information about plant and animal distribution, anatomical knowledge – to speculate and hypothesize about the beginnings of time. If Jameson and others like him were right and the earth had started out as a ball of water, how had life begun? What were the first creatures on the planet? Why were there shells and the bones of enormous sea creatures to be found thousands of miles inland and at the tops of mountain ranges? Professor Jameson took Grant and his other students into his museum filled with shells, fossils and bones and to the hills around Edinburgh to speculate upon their formation. He translated the new French and German ideas, summarized them in his lectures, and his students debated them noisily in their societies.5

  By his late teens Grant’s studies were directed almost exclusively to comparative anatomy. Like other men of science in Europe he was searching for common patterns in the bodies of animals, patterns of similarity between very diverse species, because these would reveal the essential laws of nature and the origins of life. In preparing for his dissertation in 1813 on the circulation of blood in the foetus, Grant discovered a new book in the University library that opened his mind to new possibilities about the origins of living forms. It was called Zoonomia, or the Laws of Organic Life (1794–6) and its author was Erasmus Darwin, an English doctor, poet, inventor and naturalist. By the time Robert Grant read this book in 1813, Erasmus Darwin was dead but his son, Robert, had several children with burgeoning scientific interests including a four-year-old boy, Charles Darwin, already an avid collector of pebbles and plants.