The Mental Life of Plants and Worms, Among Others

The Formation of Vegetable Mould through the Action of Worms: with Observations on Their Habits

by Charles Darwin
London: John Murray (1881)

Jelly-Fish, Star-Fish, and Sea-Urchins: Being a Research on Primitive Nervous Systems

by George John Romanes
London: Kegan Paul, Trench and Co. (1885)

Mental Evolution in Animals

by George John Romanes
London: Kegan Paul, Trench and Co. (1883)

The Foundations of Ethology

by Konrad Lorenz
Springer (1981)

Behavior of the Lower Organisms

by Herbert Spencer Jennings
Columbia University Press (1906)

Cephalopod Behaviour

by Roger T. Hanlon and John B. Messenger
Cambridge University Press, 256 pp., $79.00 (paper)
The Large Flowering Sensitive Plant, whose ‘plant electricity,’ Oliver Sacks writes, ‘moves slowly…as one can see by watching the leaflets…closing one by one along a leaf that is touched.’ Illustration from Robert John Thornton’s The Temple of Flora (1799–1807), published in a new edition by Taschen.

Charles Darwin’s last book, published in 1881, was a study of the humble earthworm. His main theme—expressed in the title, The Formation of Vegetable Mould through the Action of Worms—was the immense power of worms, in vast numbers and over millions of years, to till the soil and change the face of the earth. But his opening chapters are devoted more simply to the “habits” of worms.

Worms can distinguish between light and dark, and they generally stay underground, safe from predators, during daylight hours. They have no ears, but if they are deaf to aerial vibration, they are exceedingly sensitive to vibrations conducted through the earth, as might be generated by the footsteps of approaching animals. All of these sensations, Darwin noted, are transmitted to collections of nerve cells (he called them “the cerebral ganglia”) in the worm’s head.

“When a worm is suddenly illuminated,” Darwin wrote, it “dashes like a rabbit into its burrow.” He noted that he was “at first led to look at the action as a reflex one,” but then observed that this behavior could be modified—for instance, when a worm was otherwise engaged, it showed no withdrawal with sudden exposure to light.

For Darwin, the ability to modulate responses indicated “the presence of a mind of some kind.” He also wrote of the “mental qualities” of worms in relation to their plugging up their burrows, noting that “if worms are able to judge…having drawn an object close to the mouths of their burrows, how best to drag it in, they must acquire some notion of its general shape.” This moved him to argue that worms “deserve to be called intelligent, for they then act in nearly the same manner as a man under similar circumstances.”

As a boy, I played with the earthworms in our garden (and later used them in research projects), but my true love was for the seashore, and especially tidal pools, for we nearly always took our summer holidays at the seaside. This early, lyrical feeling for the beauty of simple sea creatures became more scientific under the influence of a biology teacher at school and our annual visits with him to the Marine Station at Millport in southwest Scotland, where we could investigate the immense range of invertebrate animals on the seashores of Cumbrae. I was so excited by these Millport visits that I thought I would like to become a marine biologist myself.

If Darwin’s book on earthworms was a favorite of mine, so too was George John Romanes’s 1885 book Jelly-Fish, Star-Fish, and Sea-Urchins: Being a Research on Primitive Nervous…

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