Darwin and the Barnacle

by Rebecca Stott

  Like Aristotle, Grant had come to understand the inner workings of sponges by patient observation and dissection. Like Aristotle, he wanted to know whether they were animals or vegetables or both; how its body worked and how the laws that governed its digestion and reproduction. No one had looked hard enough, watched for long enough – no one, that is, since Aristotle, Grant wrote:

  But the philosophy of the sponge, the immutable foundations on which scientific discriminations of the species ought to rest, the minute investigation of the mechanism, the composition, and the uses of all the parts of the animal, and of the extraordinary phenomenon it exhibits in the living state, – its mode of growth, – its kind of food, – its habits and diseases, – the means of cultivating an animal, which has so long rendered important services to mankind, – its mode of propagating the species, and extending them over the globe, and the great purposes which it is destined to fulfil in the universe, have remained where Aristotle left them, or rather, in this branch of study, mankind have gone backward ever since his time.15

  One of the primary mysteries of the sponge – whether it was an animal or a vegetable – Grant would have to determine for himself, reaching a conclusion where scores of other naturalists had failed to do so. To establish that it was an animal, Grant had to prove three things: that it was sensitive, that it could move independently and that it had a stomach and anus for digestion. His experiments began with an attempt to discover the purpose of the holes that covered the sea sponge’s body: were these the elementary forms of a digestive system? Some experts thought that these holes were made by other parasitic creatures burrowing into the soft flesh. Other zoologists believed that sponges were vegetables and therefore argued that the holes were like the pores on the surfaces of leaves, holes through which the vegetable absorbed water. Grant knew that the only way to settle this matter once and for all was to keep watch – to watch the holes of the sponge night and day under a microscope.

  Discovering that the single, intense light of a candle enabled him to observed more effectively than the diffuse light of day, he soon developed a habit of entirely nocturnal research at Prestonpans. He made his first major breakthrough some weeks after he began this watch, alone in the middle of the night, with only the sounds of the waves and an occasional lone gull to break the silence:

  On moving the watch-glass, so as to bring one of the apertures on the side of the sponge fully into view, I beheld, for the first time, the splendid spectacle of this living fountain vomiting forth, from a circular cavity, an impetuous torrent of liquid matter, and hurling along, in rapid succession, opaque masses, which it strewed everywhere around. The beauty and novelty of such a scene in the animal kingdom, long arrested my attention, but, after twenty-five minutes of constant observation, I was obliged to withdraw my eye from fatigue, without having seen the torrent for one instance change its direction, or diminish, in the slightest degree, the rapidity of its course. I continued to watch the same orifice, at short intervals, for five hours … but still the stream rolled on with constant and equal velocity.16

  ‘Vomit’ hurt and ‘strew’ are peculiarly violent words for an animal known for its silent, stubborn stillness; however, Grant soon came to see that he was not watching vomiting but excretion. He was the first to observe the excretion of the sea sponge at close range and it was for him a splendid spectacle, because it had been so long awaited and because it showed evidence of digestion. This animal can indeed excrete for five hours continuously through a single hole and, now that he had witnessed this spectacle of excretion with his own eyes, Grant could confidently call this hole a ‘fecal orifice’. His revelation occurred in the middle of a November night with no one to share it. He had discovered the anus of the sea sponge – or rather he had discovered that sea sponges are covered with anuses; and where there is an anus there is a stomach. He was putting together incontrovertible evidence that the sponge had animal characteristics.

  The next question for Grant was about the strength of the current of the ‘fecal fountains’. For several nights he experimented with blocking the anal orifices of the sponges with a variety of domestic objects to determine the strength of the current: pieces of chalk, cork, dry paper, soft bread, unburnt black coal – almost anything to hand. He recorded all the experiments in detail in his notebooks. Only a drop of mercury was heavy enough to block the stream. So Grant concluded that, whilst some of the holes on the body of the sea sponge are ‘fecal orifices’, the others are ‘pores’ used for ingesting food, like mouths. The holes that lead into the labyrinthine passages of the sponge afford a constant passage of liquids: food passing in and opaque fecal liquids passing out. Aristotle had known this too; this was where being able to read Aristotle’s original Greek text was important for Grant, for he could show that the words Aristotle used meant ‘pore’ and ‘orifice’.17

  Grant, however, was not so sure that it was definitively an animal. He had a hunch that it was an intermediate form, a link between the animal and vegetable kingdoms. For the final proof of its animal status, Grant had to prove that the sponge was sensitive, another important area of dispute amongst zoologists. So Grant set to work; over the nights of three winters he systematically tortured the sea sponges in his collection in Prestonpans in an inventive series of ways, but failed to find any evidence of sensitivity: ‘I have plunged portions of the branched and sessile sponges alive into acids, alcohol and ammonia, in order to excite their bodies to some kind of visible contractile motions, but have not produced, by these powerful agents, any more effect upon the living specimens, than upon those which had long been dead.’18

  The third area of investigation was the question of voluntary movement: animals move independently; plants don’t. In his long nocturnal vigils in late autumn, Grant watched a sea sponge excrete eggs – or ova – through its holes, and under his microscope he saw to his amazement that the eggs seemed to be moving by themselves. Under a more powerful lens he was able to see that these eggs were covered in small hairs (cilia), which propelled them along, away from the parent sponge. The parent sponges might have been stubbornly inert then, apparently insensate, but the young ones moved like things possessed, gyrating and twisting and wriggling together, propelling themselves away from their parents. Grant was sure there was an evolutionary reason for this: the propagation of the species depended upon the spontaneous motion of the young, their ability to reach new breeding grounds and disperse the species. The enigmatic and peculiar sponge was perfectly adapted, then, to survival in the deep sea – so perfectly that it had not needed to evolve any further, given that its aquatic conditions had remained relatively stable: ‘This animal … seems eminently calculated for an extensive distribution, from the remarkable simplicity of its structure, and the few elements required for its subsistence.’19

  By 1826 Grant was claiming that his evidence proved that the sea sponge, which had changed relatively little since prehistoric times, was indeed an animal but one that was so close to the frontier between animal and vegetable kingdoms as to be virtually on it. By comparing sponge ova and those of other simple living organisms with the ova of the algae, he argued that there was a common monadic base for plants and animals. They had similar components. Somewhere in their ancestry there had been a meeting point.20 Grant had been able to reach these conclusions in part because his European tour had taken him beyond Paris and Lamarck and into Germany where, in the University of Heidelberg, he had met the young Professor of Anatomy and Physiology, Frederick Tiedemann. Lamarck, for all his transmutationism, still believed in an absolute demarcation between animal and vegetable kingdoms. Tiedemann, however, believed that in the most simple and ancient life forms the boundaries between these kingdoms were not fixed. Grant’s sea-sponge work had helped him to think through these problems; but he was a long way from establishing a working theory as yet.

  Grant’s tireless series of seasponge observations, published between 1825 and 1827, formed part of the burden of proof necessary to su
pport a theory of transmutation of species that had so far been held by most as mere speculation. But it was only a beginning. Grant had spent five years dissecting, watching and describing sea sponges, ancient, enigmatic and entirely borderline creatures. Other borderline creatures from the seabed would need to be examined by men and women with the patience, determination and philosophical drive of Grant if the secrets of the aquatic origins of life were to be fully understood. New observers and natural philosophers were needed.

  *

  It is 9 February 1826. Charles Darwin, sixteen years old, stands amongst the black rocks on the sands at Leith at the foot of Constitution Street, making notes in a small red notebook, while all around him bare-footed fisherwomen and their children collect mussels to bait their lines. He has enrolled as a medical student at the University, but, bored by the lectures, he escapes to the winter seashore every few days. His boots are salt-stained. The leather-bound notebook is a diary called The Edinburgh Ladies’ and Gentlemen’s Pocket Souvenir for 1826, a present from his elder and much-loved brother Erasmus Alvey Darwin – ‘Ras’ – also a student at the University. The diary lists tide times alongside a list of the dates of accessions of the Scottish kings. Darwin’s handwriting is small and neat despite the fact that his hands, ungloved, are cold and stiff in the biting February sea winds. The paper of his notebook flaps about. The bright scarlet leather is good quality; it has a leather fastening flap. Inside, down the seam along the spine, there is a sheath designed to hold a very small pencil, but Darwin writes in ink and has already marked it as his own, signing and dating his name confidently as ‘C. Darwin, Jan 1st, 1826’ inside the front cover.

  Behind him the bathing machines used by the summer tourists are covered in tarpaulin and stand in a line in front of the warehouses and cone-shaped brick kilns of the Leith Glassworks Company. To his left, beyond the Martello tower built to defend the town against French invasion during the Napoleonic Wars, the masts of moored boats in the harbour look like a flagged winter forest on the horizon. The whaling boats will sail for the Davies Straits or Greenland in March, but in January the men work on the boats or in the boiling houses that back on to the sands next to the glassworks, boiling the blubber to make soap and candles, or packing up the whalebone for the corset makers of Edinburgh. The air is full of the pungent oily smell of blubber.21

  4 Leith Races

  Darwin crouches to peer at a small hairy creature, marooned in one of the pools between the black rocks on the rippled grey sand. It looks like a mouse; in fact the fishermen call it a sea mouse. An incoming wave washes the body clean of the sand that covers it, revealing a green, brown and gold furry body, about three or four inches long. Darwin writes its Latin name neatly in his scarlet notebook: Aphrodita aculeata – ‘Stinging Aphrodite’. Linnaeus named this creature after the Greek goddess of love, who rose from the waves, but this creature is neither goddess nor mouse. It is a worm that lives buried in sand on the seabed and is only rarely found washed up on to the shore, usually after a storm.

  Darwin reaches for a stick to prod at it. He knows its hairs will sting him painfully. Irritated by Darwin’s stick, the mouse recoils and tries to roll itself into a ball. Almost dead, it moves very slowly. Darwin is excited. Although they are not uncommon on the Leith sands, he has probably not seen a live sea mouse before; but he has read about them. He remembers that the marine invertebrate specialists Turton and Linnaeus disagree about the number of feelers it has. He records all these experiments and descriptions in his scarlet diary: ‘Caught a sea mouse Aphrodita Aculeata of Linnaeus; length about three or four inches, when its mouth was touched it tried to coil itself in a ball, but it was very inert. Turton states that it has only two feelers, does not Linnaeus say 4? I thought I perceived them.’22

  Mating wagtails and swallows gathering in the warm winds above Edinburgh will distract his attention from the beach in early summer; but in the spring of 1826 it is sea creatures Charles Darwin wants to know about. So he has come here to the shore between Leith and Portobello to see what the night’s storms and spring tides have washed up. He has sand in his shoes. He will come back to this shoreline every few days over the following weeks throughout March and April, walking the fifteen-minute walk from his lodgings down to the seashore past the caravan shows, street singers and organ grinders of Leith Walk. It is here on the Leith seashore that he will meet Dr Grant, the philosophical sponge doctor.

  Notes

  1 The Annual Register, vol. 64 (1822), p. 10, records that the weather was exceptionally mild in January, particularly in Scotland, where summer flowers were recorded as blooming in Edinburgh gardens. For information about the execution of the pirates, see Alex Young (1998), The Encyclopaedia of Scottish Executions 1750 to 1963, Eric Dobby Publishing, Kent.

  2 See Janet Browne, Charles Darwin: Voyaging (London: Pimlico, 1995), p. 58–9.

  3 See painting of Leith Races by William Reed, City of Edinburgh Art Centre.

  4He joined the Medico-Chirurgical Society at the age of 18 and was elected President within months. At 19 he joined the Royal Medical Society and was elected their President three years later.

  5 For further information on Professor Jameson see James A. Second, ‘Edinburgh Lamarckians: Robert Jameson and Robert E. Grant’, Journal of History of Biology, vol. 24 (1991), pp. 1–18.

  6 Erasmus Darwin, Zoonomia, or the Laws of Organic Life, Dublin (printed for P. Byrne, and W. Jones, 1794–6), 2 vols, vol. 1, p. 506.

  7 Ibid., p. 509.

  8 For work on Erasmus Darwin see Desmond King-Hele, Erasmus Darwin: A Life of Unequalled Achievement (London: Giles de la Mare Publishers, 1999) and Maureen McNeil, Under the Banner of Science: Erasmus Darwin and His Age (Manchester: MUP, 1987).

  9 See Roy Porter, The Greatest Benefit to Mankind: A Medical History of Humanity From Antiquity to the Present (London: Fontana, 1997), pp. 306–14.

  10 See Phillip R. Sloan, ‘Darwin’s Invertebrate Program, 1826–1836: Preconditions for Transformism’ in D. Kuhn, ed. (1985), The Darwinian Heritage (Princeton: Princeton University Press, 1985), p. 75.

  11 The most detailed research into Grant’s life and work has been undertaken by Adrian Desmond in The Politics of Evolution: Morphology, Medicine and Reform in Radical London (Chicago: University of Chicago Press, 1989), ‘Robert E. Grant’s Later Views on Organic Development’, ANH, vol. 11 (1984), pp. 395–413 and ‘Robert E. Grant: The Social Predicament of a Pre-Darwinian Transmutationist’, Journal of the History of Biology, 17: 2 (Summer 1984), pp. 189–223. Grant, trained in Parisian medical research techniques, took notes about everything he dissected, all his ideas, particular trains of thought and critical conversations. But all of this has disappeared. He died unmarried with no close relatives and, although his library survived, these valuable journals and bundles of notes and letters did not. So tracing his intellectual and physical journeys is a matter of detective work. There is a short biographical essay written by his friend Thomas Wakley in 1850 for The Lancet and probably based on interviews with Grant, but almost nothing else, apart from the dozens of essays he published in the 1820s and 1830s. Thomas Wakley, ‘Biographical Sketch of Robert Edmund Grant, M.D.’, The Lancet, vol. 2 (1850), pp. 686–95.

  12 John Barclay, An Inquiry into the Opinions, Ancient and Modern, Concerning Life and Organisation (Edinburgh: Bell and Bradfute, 1822), p. 525.

  13 Robert Grant, ‘Observations and Experiments on the Structure and Functions of the Sponge’, Edinburgh Philosophical Journal, vol. 14 (1826), no. 27, p. 122.

  14 Robert Grant, ‘Observations and Experiments on the Structure and Functions of the Sponge’, Edinburgh Philosophical Journal, vol. 13 (1825), no. 25, p. 97.

  15 Ibid., p. 99.

  16 Ibid., p. 102.

  17 Robert Grant, ‘Observations and Experiments on the Structure and Functions of the Sponge’, Edinburgh New Philosophical Journal, vol. 2 (1826), p. 126.

  18 Robert Grant, ‘Observations and Experiments on the Structure and Functions
of the Sponge’, Edinburgh Philosophical Journal, vol. 14 (1826), no. 27, p. 123.

  19 Robert Grant, ‘Observations and Experiments on the Structure and Functions of the Sponge’, Edinburgh New Philosophical Journal, vol. 2 (1826), p. 136.

  20 I am grateful to Adrian Desmond for generous assistance and advice on this matter.

  21 For the social history of Leith see James Scott Marshall, The Life and Times of Leith (Edinburgh: John Donald, 1986); Sue Mowat, The Port of Leith: Its History and Its People (Edinburgh: John Donald in association with the Forth Ports PLC, 1994); Joyce M. Wallace, Traditions of Trinity and Leith (Edinburgh: John Donald, 1997).

  22 Darwin’s 1826 Notebook, DAR 129.

  2

  Riddles of the Rock Pools

  Before the land rose out of the ocean, and became dry land, chaos reigned; and between high and low water mark, where she is partially disrobed and rising, a sort of chaos reigns still, which only anomalous creatures can inhabit …