Darwin's Ghosts

by Rebecca Stott

  With a clear set of philosophical problems in mind, Grant set off for southern Europe to collect new species and to visit as many European marine-invertebrate specialists, libraries, and natural history collections as he could before his inheritance ran out. These questions took him to Rome, Florence, Pisa, Padua, and Pavia, not for paintings or ruins but for scientific books and articles in French, German, and Italian and for beaches and rock pools. He collected and dissected Mediterranean sea sponges on the shores of Leghorn, Genoa, and Venice. He spent eighteen months in Germany, then traveled through Prague, Munich, Switzerland, back down to the south of France, and to the University of Montpellier. In 1820 he returned to the natural history and anatomy collections and libraries in Paris and then London, making last checks and rereading manuscripts. He arrived back in Edinburgh at the end of the year with crates of notebooks, copies of papers, and dried and bottled specimens. He kept his work to himself, however, anxious to avoid being associated with any form of materialist science. Like Erasmus Darwin before him, he knew he would have to establish and maintain a practice as a doctor in a small town, where reputation was everything.

  By the time Grant returned to Edinburgh, he knew his time and his inheritance were running out. Preparing himself for earning a living as a doctor and as a part-time lecturer in comparative anatomy, he enrolled in Dr. Barclay’s private anatomy school in 1821, training in anatomy during the day and conducting his sea sponge dissections and experiments in the anatomy school dissection rooms at night. Eventually an acquaintance offered him the use of a house in Prestonpans through the winter, a village on the Firth of Forth a few miles to the east of Edinburgh. There Grant set up his own secret laboratory.

  The men and women of Prestonpans still worked mainly in the salt industry, boiling water dredged from the Firth in enormous pans. But by the early nineteenth century the village had also become a picturesque tourist attraction, offering newly fashionable bathing machines to the summer tourists who rented the large seafront houses. Grant had found Prestonpans Bay to be especially rich in sea sponges. Walford House, his new winter residence, had a high-walled garden with direct access through a gate to the beach. He could collect sponges on the shore early in the morning or after a night’s storm and transfer them to shallow seawater basins in his study within a few minutes.

  He began by trying to discover the purpose of the holes that covered the sea sponge’s body. Were these, he speculated, the elementary forms of a digestive system? Some experts claimed that the holes were made by parasitic creatures burrowing into the soft flesh, others that sponges were vegetables and that the holes were like the pores on the surface of leaves, 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 observe the holes of the sponge night and day under a microscope, just as Charles Bonnet had done with the aphid.

  Discovering that the intense light of a single candle enabled him to view his specimens more effectively than daylight, Grant soon developed a habit of entirely nocturnal research at Prestonpans. He made his first major breakthrough some weeks after he began his watch, alone in the middle of the night, his eye pressed to the microscope, with only the sound 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,” he wrote,

  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.

  Grant concluded that the hole could be described as a “fecal orifice.” If this was a primitive anus, there had to be a digestive system of some kind. Next he had to find a mouth. 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 “fecal current”; he used pieces of chalk, cork, dry paper, soft bread, unburned black coal, almost anything at hand. He recorded all the experiments in detail in his notebooks. Only a drop of mercury, he discovered, was heavy enough to block the stream. So Grant concluded that while some of the holes on the body of the sea sponge were fecal orifices, the others were “pores” used for ingesting food, like mouths. The holes that led into the labyrinthine passages of the sponge were, he observed, a constant conduit of liquids: food passing in and opaque fecal liquids passing out. And Aristotle had known this, too, he realized when he consulted the manuscript. The Greek words Aristotle used for these holes meant both “pore” and “orifice.”

  The sponge had met the first of the three criteria for animalhood: it seemed to have a form of digestion. Next Grant had to determine if it had independent movement—animals move independently, plants do not. 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 were covered in small hairs, which they used to propel themselves along, away from the parent sponge. The parent sponges were inert, but the young had independent movement. Grant was sure there was a good reason for this: the propagation of the species depended upon the spontaneous motion of the young, their ability to reach new breeding grounds. 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, as had been the case for Lamarck’s mummified ibises. “This animal,” Grant wrote, “… seems eminently calculated for an extensive distribution, from the remarkable simplicity of its structure, and the few elements required for its subsistence.”

  Next Grant had to prove that the sponge was sensitive, another important area of dispute among zoologists since Aristotle’s time. Over the nights of three winters he failed to find any evidence of sensitivity. “I have plunged portions of the branched and sessile sponges alive into acids, alcohol and ammonia,” he wrote in frustration, “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.” The sponge had failed the final criteria of animalhood, but for Grant that was a good result. The lack of sensitivity, he believed, proved it to be a transitional organism, just as he had hoped it might be. It shared both plant and animal characteristics.

  During these experiments Grant recruited several local boys to help him collect sea sponges. One of them was John Coldstream, a young naturalist and medical student. Like Grant, Coldstream had been born and raised in Leith. But unlike Grant, Coldstream was a devout Christian, a member of the Leith Juvenile Bible Society. He had been collecting sea creatures on these shores since he was child. Grant, obsessive, clever, and utterly convinced of the transmutation of species, turned Coldstream’s head. Beginning in 1823, when he came into Grant’s orbit, Coldstream’s diaries record a sudden conflict of beliefs. He was seventeen when he met the charismatic Leith doctor, and his journals from 1823 onward record a painful story of self-blame, torment, and physical self-loathing. On his eighteenth birthday, March 19, 1824, he wrote: “My praise is altogether an unclean thing; my glorifying of the Lord is filthiness before Him. From the dust do I cry unto thee, O God! Hear me, hear me. I earnestly beseech Thee to purify my heart.… I am at a time of life when the amusements of this little world lead me away into temptation; now, heavenly Father, point out to me in what measure I should best enjoy these, that all my conduct may be to Thy glory. O
h, were I prepared, how I would fly from the attractions of the flesh.”

  Yet Coldstream did not leave the Plinian Society or stop assisting Grant in his work. He continued to struggle with his religious doubts and with a certain mysterious sense of disgust about his body during these years. He became one of the Society’s presidents in 1824–25 and one of the doctor’s closest companions, collecting sea sponges for him and for the Museum of Natural History at the university and was always on the lookout for other young naturalists who might be recruited to the Society or to help Grant. In return, Grant trained his assistant in dissection techniques and encouraged him to publish natural history papers in the Edinburgh Philosophical Journal, articles on the springs of Ben Nevis, on the saltiness and transparency of the water of the ocean, on hoarfrost, on the aurora borealis, which he saw out in the Firth of Forth on his nineteenth birthday in 1825, and on the sea sponges and the zoophytes of the Firth. Though Coldstream struggled to maintain his faith, he was beginning to ask questions he did not want to ask.

  In the spring of 1825, Grant was ready to unveil the results of his five-year investigation and moved back to Edinburgh. First he decided to test some of the basic premises of his philosophy on the members of the Wernerian Natural History Society, run by Professor Jameson. He turned up to give his very first paper to the Society on April 2, 1825, carrying buckets of dead cuttlefish recently dredged from the Firth of Forth. Cuvier had argued that no invertebrate had a pancreas; Grant opened up the stomach of one of his Firth cuttlefish and revealed to his audience that what had been thought to be the creature’s ovarium was in fact a pancreas. He repeated the dissection several times until everyone agreed with his conclusions. There could be no doubt, he claimed, that the pancreas was to be found much lower in the scale of animals than had previously been believed. A cuttlefish had a pancreas just like a human; there were common structures shared by both vertebrates and invertebrates.

  A few weeks later he was back with buckets of gastropods and sea slugs. These, he showed his audience, had a pancreas too. Grant was using cuttlefish and sea slugs to bring Cuvier’s influential map of nature, fixed and divided into four absolute branches, into question. Cuvier had pronounced there to be no common structures shared between organisms belonging to the four branches; Grant, paper by paper, stage by stage, was proving Cuvier wrong.

  By 1826, in the last of the carefully sequenced and stage-managed papers, Grant was claiming that his evidence proved that the sea sponge was so close to the boundary between the 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. Somewhere in their ancestry there had been a meeting point, and the sponge represented that point.

  And it was at this moment, just as Grant was in the middle of publishing his most controversial of ideas, that the grandson of Erasmus Darwin turned up on the beach at Leith.

  Over the winter of 1826–27, Grant, Darwin, and Coldstream walked the shores of the Firth of Forth carrying microscopes and collection jars, poking about under rocks, lowering nets carefully into rock pools, collecting sponges, sea anemones, and sea squirts, and debating the philosophical implications of Grant’s recent findings. In the fishing villages, they stopped to talk with fishermen and women selling fish or sitting mending nets on the steps of the red-tiled two-story houses. The fishermen knew Grant well; they kept the discarded contents of their nets for him to look through. Every few weeks, the three naturalists joined the fishermen on the dredging boats at dawn, sailing out from the harbor at Newhaven, the center of the oyster trade in the Firth and only a mile to the west of Leith, sometimes traveling as far as the coast of Fifeshire or out to the islands of May and Inchkeith looking for new marine organisms.

  On Tuesday evenings, Grant accompanied Darwin and Coldstream to the Plinian Natural History Society meetings held in an underground room at the university. Many of the members were young medical students, some, like Darwin, still very young.* Grant was the only older man in the group. Members and invited guests gave short papers every week describing natural history expeditions or presented reports on new methods of obtaining bromine from soap boilers’ waste, or on the capture of whales on the coast of the Shetlands, or on the oceanic and atmospheric currents. Occasionally students presented philosophically controversial ideas. When the seventeen-year-old William Greg gave a paper that would prove that “the lower animals possess every faculty & propensity of the human mind,” the details of his paper were later struck from the record. Grant, accustomed to Continental freedom of debate and speculation, encouraged the younger members to read widely and to challenge orthodoxies. Enlightenment, he told Darwin and Coldstream, depended on it.

  Zoophytes illustrated in an engraved plate from the Encyclopaedia Britannica, ca. 1813.

  In 1826, Grant announced his discovery that the eggs of the sea sponge were free-swimming, that they propelled themselves along by the vibration of small hairs, or cilia, that covered their bodies. This was a crucial discovery, an important part of the process of solving the riddle of the sea sponge and determining its place in nature. The sponge may not have movement of any kind, he wrote, but its eggs could move. He ended his essay with the words: “How far this law is general with zoophytes must be determined by future observations.”

  Now that he had finished his sponge investigations, Grant turned to other zoophytes, other marine animals that looked like plants, to see if he could determine whether they also had free-swimming eggs. Grant, Coldstream, and Darwin began to work closely together, dissecting in Grant’s rooms and even on the beach itself, searching for the presence of swimming eggs in as many different apparently immobile sea creatures as they could. Darwin began to work on the Flustra, a pale brown seaweedlike organism known colloquially as a sea mat or hornwrack, which grew in colonies made up of hundreds of interdependent, connected polyps on rocks close to the shoreline.

  On March 19, 1827, Darwin made a small but important discovery. He rushed to Grant’s house in Prestonpans with the news as soon as the dredger moored in the harbor. He later described the moment:

  Having procured some specimens of the Flustra Carbocea (Lam.) from the dredge boats at Newhaven; I soon perceived without the aid of a microscope small yellow bodies studded in different directions on it.—They were of an oval shape & of the colour of the yolk of an egg, each occupying one cell. Whilst in their cells I could perceive no motion; but when left at rest in a watch glass, or shaken they glided to & fro with so rapid a motion, as at some distance to be distinctly visible to the naked eye.… That such ova had organs of motion does not appear to have been hitherto observed either by Lamarck Cuvier Lamouroux or any other author:—This fact although at first it may appear of little importance yet by adducing one more to the already numerous examples will tend to generalize the law that the ova of all Zoophytes enjoy spontaneous motion.

  Now that he knew how to look, what to look for, and how to wait and watch, Darwin quickly made a second discovery also described in his notebook:

  One frequently finds sticking to oyster and other old shells, small black globular bodies which the fishermen call great Pepper-corns. These have hitherto been always mistaken for the young Fucus Lorius … to which it bears a great resemblance.… But on examining some others I found that this fluid, acquiring by degrees a vermicular shape, when matured was the young Pontobdella Muricata (Lam.) which were in every respect perfect & in motion.

  Darwin found swimming eggs in almost all the zoophytes he dissected, but the more evidence he collected, the more Grant felt the originality of his own work to be compromised. Grant announced the discovery of the free-swimming ova of the Flustra to the prestigious Wernerian Society on March 24, 1827. He also announced that he had found cilia on the young of other zoophytes and that he had discovered the mode of reproduction of the sea leech, Pontobdella muricata. Darwin gave a paper on the ova of the Flustra t
o the Plinian Society three days later, his very first scientific paper. He was eighteen.

  The relations between Darwin and Grant cooled. This was Darwin’s first experience of scientific territorialism, and it upset him. A note written by one of Darwin’s daughters and allegedly found in a bundle of papers in 1947 (and since lost again) confirms this. Henrietta wrote:

  I then made him repeat what he had told me before, namely his first introduction to the jealousy of scientific men. When he was at Edinburgh he found out that the spermatozoa (?) / ova (?) of (things that grow on sea weed) / Flustra move. He rushed instantly to Prof. Grant who was working on the subject to tell him, thinking he wd be delighted by so curious a fact. But was confounded on being told that it was very unfair of him to work at Prof. G’s subject and in fact that he shd take it ill if my Father published it. This made a very deep impression on my Father and he has always expressed the strongest contempt for all such little feelings—unworthy of searchers after truth.

  These were also, perhaps thankfully, Darwin’s last weeks in Edinburgh. Grant, too, was destined to leave Edinburgh that summer. He had been recommended for a chair at the new London University, founded to open up a university education to some of those who were denied it by the traditional universities (Dissenters, Catholics, and Jews were all excluded from Oxford and Cambridge) and to bring about reform in the nation’s professions and institutions. Darwin, on the other hand, was destined for Cambridge. His father had decided that if he was not going to qualify as a doctor, he should try for the Church. His uncle Josiah Wedgwood (in one of the many Wedgwood-Darwin alliances, in 1796 Erasmus Darwin’s son, Robert Waring Darwin, had married the first Josiah Wedgwood’s daughter, Susannah—this Josiah was Susannah’s brother) reminded his rather dejected nephew that a clergyman might also be a naturalist.