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MERE IMMORTALS

In defence of worms

In defence of worms
LONDON, ENGLAND - SEPTEMBER 04: Earthworms are preserved at The Grant Museum of Zoology on September 4, 2012 in London, England. Containing 67,000 specimens, the Grant Museum of Zoology is the only one of it's kind in London. Started as a teaching collection in 1828 the collection displays only about 5% of all the specimens it holds. (Photo by Peter Macdiarmid/Getty Images)

There was a time when the only thought people had about earthworms was how to exterminate them. Then two men, an adventurer and a stick-in-the-mud, came to their defence.

Of the great worm hunt that began in the early 1850s, history has retained only the faintest traces.

We know there was a book, Ludwig K Schmarda’s Reise um die Erde (Journeys Around the Earth) published in 1861 and a copy or two are undoubtedly in some German university library. For all but the most dogged researcher, however, details of the journey are today inaccessible.

We are left to speculate. Contemplating another long, dreary German winter, Professor Karl Schmarda, a university biologist, chose instead to take an extended sabbatical and set sail in pursuit of his strange passion: worms. Today they are still regarded as slimy, distasteful things. In his day, they suffered added associations with death and serpents. Of the few publications of that period which survive, almost all deal with their eradication.

Undeterred by the inevitable bad jokes from his colleagues, Schmarda set sail for Ceylon, where he found yet-to-be-named worms in profusion. He dug them out, dusted them off, sketched them and moved on. South Africa attracted him next, though he failed to find there the world’s biggest earthworm, Microchaeta rappi (up to 4m, found in the Eastern Cape). Then he braved the southern oceans to dig up worms in Australia, New Zealand and, finally, the Americas.

He returned triumphant, bearing the sketches and remains of 191 new species of leech and worm, wrote a two-volume monograph in which were included his illustrations, then drifted into scientific obscurity.

Illustrations from Ludwig K. Schmarda: Journeys Around the Earth

Plate 26 – Illustrations from Ludwig K. Schmarda: Journeys Around the Earth

Plate 24 – Illustrations from Ludwig K. Schmarda: Journeys Around the Earth

He was mentioned in a few biographies, but a recent book on the history of earthworm ecology doesn’t even footnote him. The illustrations you are now looking at have not seen the light of print publication for more than 140 years.

Apart from his sketches, however, the interesting question about Professor Schmarda’s travels is: who fired his interest in this obscure branch of science, now known as invertebrate ethology? The answer raised even more questions about strange biological fascinations. It was Charles Darwin, that Victorian champion of revolutionary ideas concerning natural selection and the origin of species.

Plate 35 – Illustrations from Ludwig K. Schmarda: Journeys Around the Earth

Plate 31 – Illustrations from Ludwig K. Schmarda: Journeys Around the Earth

Plate 30 – Illustrations from Ludwig K. Schmarda: Journeys Around the Earth

Between 1831 and 1836 Darwin sailed around the world in the Beagle. In those five years he gathered experiences, material and notes which were, eventually, to lead him to the notion of natural selection – the idea that chance mutations over great lengths of time lead to the evolution of species from lower to higher forms, including us.

The trip, however, exhausted him and caused his health to deteriorate. He had contracted Chagas disease, a prolonged and debilitating ailment similar to African sleeping sickness, though it was never diagnosed in his lifetime. His doctor strongly urged him to “knock off all work and go live in the country for a few weeks”.

He went to ground at the country seat of his uncle, Josiah Wedgwood (of pottery fame). While strolling the fields, Wedgwood suggested that, by bringing earth to the surface in their castings (faeces), earthworms must undermine any objects on that surface.

The young Darwin, eager of mind but with a disinclination to travel ever again further than he could walk, seized on the idea. He sat on his uncle’s wide veranda drinking tea and watching worms – for weeks. On hand was JC Loudon’s Encyclopaedia of Gardening which listed earthworms, along with snails, caterpillars and other insects as noxious animals. Poisons for eradicating them were quoted.

Darwin disagreed with him. In 1837, he wrote a paper which he read at the Geological Society of London. In essence, it stated that earthworms created essential vegetable mould, aerated the soil and, over time, raised surface levels of the earth. The paper was translated into German and piqued Schmarda’s interest. His destiny was to go on a long journey and remain obscure.

Darwin was never to leave the countryside again. Being of the wealthier classes (and marrying into the Wedgwood empire), he bought himself a small estate in Kent and, in the following decades, focused his attention on his other publications which established his fame.

He hadn’t saved earthworms from a bad press and horticultural literature continued to devise methods for their extermination. As far as worms went, that seemed to be that.

By 1877, after 40 years of battling against an often hostile church and general public over his evolutionary theories, Darwin – then famous beyond his humble imaginings – considered himself to be a spent force. In a letter to an old friend, Reverend Leonard Jenyns, he wrote:

“My dear Jenyns, You ask about my future work; I doubt whether I shall be able to do much more that is new. I suppose that I shall go on as long as I can without obviously making a fool of myself.

“I have a great mass of matter with respect to variation under nature; but so much has been published since the appearance of the Origin of Species, that I very much doubt whether I retain power of mind and strength to reduce the mass into a digested whole.”

About that he was correct – no more writing about evolution was ever again to flow from his pen. For the next six years, until his death in 1882, Darwin disappeared into profound contemplation of his lawn and the paths surrounding it. Beneath them were an unimaginable number of worms.

Earthworms, he discovered (by shouting at them) are deaf, but (by breathing on them) extremely sensitive to touch and have enough perception of light to distinguish between night and day.

History was to show, however, that they had never been far from his attention. In his letters, now housed in Cambridge University Library, are notes from academics and relations which suggest that Darwin, glued to his estate like a barnacle, had been cautiously enlisting aid in worm work.

“My worms have not turned up any earth since I enclosed them,” informed one note from his niece, Lucy Wedgwood. Another brief correspondence, from Archibald Gerkie of Edinburgh University, was headed “Some notes on the action of the earthworm.”

It turned out that three of Darwin’s sons (he sired 10 children) had been raising earthworms in pots and reporting the results to their father.

On October 1881, to the astonishment of those who thought Darwin was a spent force, he brought to press a book with the rambling title The Formation of Vegetable Mould Through the Action of Worms with Observations on their Habits. It was to be the foundation of modern soil science and much more.

To write it he had hardly moved from his lawn and adjoining field, sending his sons and friends poking round fields, woods and ancient ruins all over the world. His conclusions were, as usual, controversial.

Earthworms, he discovered (by shouting at them) are deaf, but (by breathing on them) extremely sensitive to touch and have enough perception of light to distinguish between night and day. They’re hermaphrodites, but share sperm by entwining, have five hearts and can live in air or water. Without moisture they die.

To make holes, they shove sand aside when they can and consume it when they can’t, grinding rock particles to smaller pieces in their gizzards and extracting nutrients as soil passes through their gut. They line their tunnels and any open spaces under the ground with their castings and also stack them above their holes.

At night they close their holes by dragging leaves down them or rolling small stones over them.

Though most of this is fairly basic, little of this was known. The combined effect of these actions and what they implied, however, turned Darwin’s final book into an overnight success.

By painstakingly observing (at night – earthworms are nocturnal), Darwin discovered that, in seizing leaves to close their holes, the worms always grabbed the pointed end, which permitted easy passage down the hole. This occurred even when he cleared all leaves and “strewed” small paper triangles – the earthworms always attached themselves to the sharpest point. This, wrote Darwin, implied intelligence.

By counting and averaging the number of worms in various soils, he calculated that in temperate zones there were around 133,000 worms a hectare (some recent estimates run at more than two million).

“Archaeologists,” he wrote, “are probably not aware how much they owe to worms for the preservation of many ancient objects.”

Weighing their castings brought to the surface, he discovered that earthworms were the planet’s prime earth-moving equipment, bringing an annual average of up to 30 tons of soil to the surface across each hectare. In a million years, “not very long in a geological sense,” they’d covered Britain in around 320 billion tons of earth.

The planet’s entire soil, he speculated, had passed through the alimentary canals of worms. To it they’d added useful intestinal chemicals, broken-down vegetable matter and ground-down sand. Without this process, almost nothing on earth would grow – and life as we know it wouldn’t have existed at all.

From forays by his sons to Beaulieu Abbey in Hampshire, a Roman villa in Gloucestershire, the remains of a Roman town at Silchester, Stonehenge and other similar sites, Darwin assembled information suggesting that ancient walls and pillars (such as Stonehenge) could be toppled by the action of worms beneath them. Entire ruins, he found, were quite soon covered over by the castings of earthworms.

“Archaeologists,” he wrote, “are probably not aware how much they owe to worms for the preservation of many ancient objects.”

In an attention to detail which would surely have driven a less pedantic mind crazy, Darwin measured the volume of dry castings which rolled down slopes, wet castings washed down by rain and “castings blown to leeward by wind”.

He would write: “In a day of rain, for every 100 yards in length in a valley with sides sloping six degrees, 480 cubic inches of damp earth, weighing above 23 pounds, will annually reach the bottom. On the same slope annually, nearly seven pounds of dry castings will cross a horizontal line, 100 yards in length.” These are merely statistics until you realise that Darwin was out there with ruler and scales measuring entire hillsides.

A year after the book’s publication, Darwin had joined his beloved worms beneath the ground. His study is today considered to be the first work in a then-unnamed branch of biology – ecology – and the foundation of both invertebrate ethology and soil science.

“When we behold a wide, turf-covered expanse,” he wrote in the conclusion to his book, “we should remember that its smoothness, on which so much of its beauty depends, is mainly due to all the inequalities having been slowly levelled by worms.

“It may be doubted whether there are many other animals which have played so important a part in the history of the world, as have these lowly organised creatures.”

It may be doubted, one could add, that so much important scientific speculation had ever taken place on the evidence of a small field and a single front lawn.

A year after the book’s publication, Darwin had joined his beloved worms beneath the ground. His study is today considered to be the first work in a then-unnamed branch of biology – ecology – and the foundation of both invertebrate ethology and soil science.

As the English translations were prepared, German, French, Italian and Russian editions were being translated. Professor Ludwig K Schmarda, then 61, would undoubtedly have read the German translation. If any colleagues were still around who had doubted the sanity of his great worm hunt, he would have felt well vindicated.

Darwin, it seems, never read Ludwig K Schmarda’s Reise um die Erde or he would surely have referred to the monographs in his study. It’s a pity. He would have enjoyed them. DM/ ML

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