by Grant Allen
It was in 1881 that Darwin published his last volume, ‘The Formation of Vegetable Mould through the Action of Worms.’ In this singularly fascinating and interesting monograph he took in hand one of the lowliest and humblest of living forms, the common earthworm, and by an exhaustive study of its habits and manners strove to show how the entire existence of vegetable mould — the ordinary covering of fertile soil upon the face of the earth — is due to the long but unobtrusive action of these little-noticed and ever-active architects. By the acids which they evolve, they appear to aid largely in the disintegration of the stone beneath the surface; by their constant practice of eating fallen leaves, which they drag down with them into their subterranean burrows, they produce the fine castings of soft earth, so familiar to everybody, and thus reinstate the coating of humus above the bare rock as often as it is washed away again in the course of ordinary denudation by the rain and the torrents. It is true that subsequent investigation has shown the possibility of vegetable mould existing under certain conditions without the intervention of worms to any marked extent; but, as a whole, there can be little doubt that over most parts of the world the presence of soil, and therefore of the vegetable growth rooted in it, is entirely due to the unsuspected yet ceaseless activity of these humble creatures.
The germ of the earthworm theory appears to me to have been first suggested to Darwin’s mind by a passage in a work where one would little have suspected it — White’s ‘Natural History of Selborne.’ ‘Earthworms,’ says the idyllic Hampshire naturalist, ‘though in appearance a small and despicable link in the chain of nature, yet, if lost, would make a lamentable chasm. For to say nothing of half the birds, and some quadrupeds, which are almost entirely supported by them, worms seem to be the great promoters of vegetation, which would proceed but lamely without them, by boring, perforating, and loosening the soil, and rendering it pervious to rains and the fibres of plants, by drawing straws and stalks of leaves into it; and, most of all, by throwing up such infinite numbers of lumps of earth, called worm-casts, which, being their excrement, is a fine manure for grain and grass. Worms probably provide new soils for hills and slopes where the rain washes the earth away; and they affect slopes, probably, to avoid being flooded. Gardeners and farmers express their detestation of worms; the former, because they render their walks unsightly, and make them much work; and the latter, because, as they think, worms eat their green corn. But these men would find, that the earth without worms would soon become cold, hard-bound, and void of fermentation; and, consequently, sterile.’
If Darwin ever read this interesting passage, which he almost certainly must at some time have done, it would appear that he had overlooked it in later life; for he, who was habitually so candid and careful in the acknowledgment of all his obligations, however great or however small, does not make any mention of it at all in his ‘Vegetable Mould,’ though he alludes incidentally to some other observations of Gilbert White’s on the minor habits and manners of earthworms. But whether Darwin was originally indebted to White or not for the foundation of his theory on the subject of mould, the important point to notice is really this, that what with the observant parson of Selborne was but a casual glimpse, the mere passing suggestion of a fruitful idea, became with Darwin, in his wider fashion, a carefully elaborated and powerfully buttressed theory, supported by long and patient investigation, ample experiment, and vast collections of minute facts. The difference is strikingly characteristic of the strong point of Darwin’s genius. While he had all the breadth and universality of the profoundest thinkers, he had also all the marvellous and inexhaustible patience of the most precise and special microscopical student.
For years, indeed, Darwin studied the ways and instincts of the common earthworm with the same close and accurate observation which he gave to every other abstruse subject that engaged in any way his acute intellect. The lawyer’s maxim, ‘De minimis lex non curat,’ he used to say, never truly applies to science. As early as the year 1837 he read a paper, before the Geological Society of London, ‘On the Formation of Mould,’ in which he developed with some fulness the mother idea of his complete theory on the earthworm question. He there showed that layers of cinders, marl, or ashes, which had been strewn thickly over the surface of meadows, were found a few years after at a depth of some inches beneath the turf, yet still forming in spite of their burial a regular and fairly horizontal stratum. This apparent sinking of the stones, he believed, was due to the quantity of fine earth brought up to the surface by worms in the form of castings. It was objected to his theory at the time that the work supposed to be accomplished by the worms was out of all reasonable proportion to the size and numbers of the alleged actors. Here Darwin’s foot was on his native heath; he felt himself immediately on solid ground again. The cumulative importance of separately infinitesimal elements is indeed the very keynote and special peculiarity of the great biologist’s method of thinking. He had found out in very truth that many a little makes a mickle, that the infinitely small, infinitely repeated, may become in process of infinite years infinitely important. So he set himself to work, with characteristic contempt of time, to weigh and measure worms and worm-castings.
He began by keeping tame earthworms in flower-pots in his own house, counting the number of worms and burrows in certain measured spaces of pasture or garden, and starting his long and slow experiment in his field at Down already alluded to. He tried issues on their senses, on their instincts, on their emotions, on their intelligence; he watched them darting wildly like rabbits into their holes when alarmed from without, overcoming engineering difficulties in dragging down oddly-shaped or unfamiliar leaves, and protecting the open mouths of their tunnels from intruders with a little defensive military glacis of rounded pebbles. He found that more than 53,000 worms on an average inhabit every acre of garden land, and that a single casting sometimes weighs as much as three ounces avoirdupois. Ten tons of soil per acre pass annually through their bodies, and mould is thrown up by them at an average rate of 22 inches in a century. Careful observations on the stones of Stonehenge; on the tiled floors of buried buildings; on Roman ruins at Silchester and Wroxeter, and on his own meadows and pastures at Down, finally enabled the cautious experimenter to prove conclusively the truth of his thesis, and to present to the world the despised earthworm in a new character, as the friend of man and of agriculture, the producer and maintainer of the vegetable mould on our hills or valleys, and the prime cause of the very existence of that cloak of greensward that clothes our lawns, our fields, and our pleasure-grounds.
It was his last work. Persistent ill-health and equally persistent study for seventy-three years had broken down a constitution never really strong, and consumed from within by the ceaseless fires of its own overpowering and undying energy. On Tuesday, April the 18th, 1882, he was seized at midnight by violent pains, and at four o’clock on Wednesday afternoon he died suddenly in his son’s arms, after a very short but painful illness. So retired was the family life at Down that the news of the great biologist’s death was not actually known in London itself till two days after he had breathed his last.
The universal regret and grief expressed at the loss in all civilised countries was the best measure of the immense change of front which had slowly come over the whole educated community, in the twenty-three years since the first publication of the ‘Origin of Species.’ No sooner was Darwin’s death announced than all lands and all classes vied with one another in their eagerness to honour the name and memory of the great biologist. Indeed, the spontaneous and immediate nature of the outburst of regret and affectionate regard which followed hard upon the news of Darwin’s death, astonished even those who had watched closely the extraordinary revolution the man himself had brought so well to its final consummation. In England, it was felt instinctively on every side that the great naturalist’s proper place was in the aisles of Westminster, hard by the tomb of Newton, his immortal predecessor. To this universal and deep-seated feeling Darwin�
�s family regretfully sacrificed their own natural preference for a quiet interment in the graveyard at Down. On the Wednesday morning next after his death, Charles Darwin’s remains were borne with unwonted marks, of respect and ceremony, in the assembled presence of all that was noble and good in Britain, to an honoured grave in the precincts of the great Abbey. Wallace and Huxley, Lubbock and Hooker, his nearest peers in the domain of pure science, stood among the bearers who held the pall. Lowell represented the republics of America and of letters. Statesmen, and poets, and philosophers, and theologians mingled with the throng of scientific thinkers who crowded close around the venerated bier. No incident of fitting pomp or dignity was wanting as the organ pealed out in solemn strains the special anthem composed for the occasion, to the appropriate words of the Hebrew poet, ‘Happy is the man that findeth wisdom.’ Even the narrow Philistine intelligence itself, which still knew Darwin only as the man who thought we were all descended from monkeys, was impressed with the sole standard of greatness open to its feeble and shallow comprehension by the mere solemnity and ceremony of the occasion, and began to enquire with blind wonderment what this thinker had done whom a whole people thus delighted to honour.
Of Darwin’s pure and exalted moral nature no Englishman of the present generation can trust himself to speak with becoming moderation. His love of truth, his singleness of heart, his sincerity, his earnestness, his modesty, his candour, his absolute sinking of self and selfishness — these, indeed, are all conspicuous to every reader, on the very face of every word he ever printed. Like his works themselves, they must long outlive him. But his sympathetic kindliness, his ready generosity, the staunchness of his friendship, the width and depth and breadth of his affections, the manner in which ‘he bore with those who blamed him unjustly without blaming them in return,’ these things can never so well be known to any other generation of men as to the three generations who walked the world with him. Many even of those who did not know him loved him like a father; to many who never saw his face, the hope of winning Charles Darwin’s approbation and regard was the highest incentive to thought and action. Towards younger men, especially, his unremitting kindness was always most noteworthy: he spoke and wrote to them, not like one of the masters in Israel, but like a fellow-worker and seeker after truth, interested in their interests, pleased at their successes, sympathetic with their failures, gentle to their mistakes. Not that he ever spared rightful criticism; on the contrary, the love of truth was with him so overpowering and enthralling a motive that he pointed out what seemed to him errors or misconceptions in the work of others with perfect frankness, fully expecting them to be as pleased and delighted at a suggested amendment of their faulty writing as he himself was in his own case. But his praise was as generous as his criticism was frank; and, amid all the toil of his laborious life in his study at Down, he could always find time to read and comment at full length upon whatever fresh contributions to his own subjects the merest tyro might venture to submit for his consideration. He had the sympathetic receptivity of all truly great minds, and when he died, thousands upon thousands who had never beheld his serene features and his fatherly eyes felt they had lost indeed a personal friend.
Greatness is not always joined with gentleness: in Charles Darwin’s case, by universal consent of all who knew him, ‘an intellect which had no superior’ was wedded to ‘a character even nobler than the intellect.’
CHAPTER XI.
DARWIN’S PLACE IN THE EVOLUTIONARY MOVEMENT.
To most people Darwinism and evolution mean one and the same thing. After what has here been said, however, with regard to the pre-Darwinian evolutionary movement, and the distinction between the doctrines of descent with modification and of natural selection, it need hardly be added that the two are quite separate and separable in thought, even within the limits of the purely restricted biological order. Darwinism is only a part of organic evolution; the theory, as a whole, owes much to Darwin, but it does not owe everything to him alone. There were biological evolutionists before ever he published the ‘Origin of Species;’ there are biological evolutionists even now who refuse to accept the truth of his great discovery, and who cling firmly to the primitive faith set forth in earlier and cruder shapes by Erasmus Darwin, by Lamarck, or by Robert Chambers.
Much more, then, must Darwinism and the entire theory of organic development to which it belongs be carefully discriminated, as a part or factor, from evolution at large, as a universal and all-embracing cosmical system. That system itself has gradually emerged as a slow growth of the past two centuries, a progressive development of the collective scientific and philosophical mind of humanity, not due in its totality to any one single commanding thinker, but summing itself up at last in our own time more fully in the person and teaching of Mr. Herbert Spencer than of any other solitary mouthpiece. Indeed, intimately as we all now associate the name of Darwin with the word ‘evolution,’ that term itself (whose vogue is almost entirely due to Mr. Spencer’s influence) was one but rarely found upon Darwin’s own lips, and but rarely written by his own pen. He speaks rather of development and of natural selection than of evolution: his own concern was more with its special aspect as biological modification than with its general aspect as cosmical unfolding. Let us ask, then, from this wider standpoint of a great and far-reaching mental revolution, what was Charles Darwin’s exact niche in the evolutionary movement of the two last centuries?
Evolutionism, as now commonly understood, may be fairly regarded as a mode of envisaging to ourselves the history of the universe, a tendency or frame of mind, a temperament, one might almost say, or habit of thought rather than a definite creed or body of dogmas. The evolutionist looks out upon the cosmos as a continuous process unfolding itself in regular order in obedience to definite natural laws. He sees in it all, not a warring chaos restrained by the constant interference from without of a wise and beneficent external power, but a vast aggregate of original elements, perpetually working out their own fresh redistribution, in accordance with their own inherent energies. He regards the cosmos as an almost infinite collection of material atoms, animated by an almost infinite sum-total of energy, potential or kinetic.
In the very beginning, so far as the mental vision of the astronomer can dimly pierce with hypothetical glance the abyss of ages, the matter which now composes the material universe seems to have existed in a highly diffuse and nebulous condition. The gravitative force, however, with which every atom of the whole vast mass was primarily endowed, caused it gradually to aggregate around certain fixed and definite centres, which became in time the rallying-points or nuclei of future suns. The primitive potential energy of separation in the atoms of the mass was changed into actual energy of motion as they drew closer and closer together about the common centre, and into molecular energy or heat as they clashed with one another in bodily impact around the hardening core. Thus arose stars and suns, composed of fiery atomic clouds in a constant state of progressive concentration, ever gathering-in the hem of their outer robes on the surface of the solid globe within, and ever radiating off their store of associated energy to the impalpable and hypothetical surrounding ether. This, in necessarily brief and shadowy abstract, is the nebular theory of Kant and Laplace, as amended and supplemented by the modern doctrine of the correlation and conservation of energies.
Applied to the solar system, of which our own planet forms a component member, the evolutionary doctrine (in its elder shape) teaches us to envisage that minor group as the final result of a single great diffuse nebula, which once spread its faint and cloud-like mass with inconceivable tenuity, at least as far from its centre, now occupied by the sun’s body, as the furthest point in the orbit of Neptune, the outermost of the yet known planets. From this remote and immense periphery it has gradually gathered itself in, growing denser and denser all the time, towards its common core, and has left behind, at irregular intervals, concentric rings or belts of nebulous matter, which, after rupturing at their weakest point,
have hardened and concentrated round their own centre of gravity into Jupiter, Saturn, the Earth, or Venus. The main central body of all, retreating ever within as it dropped in its course the raw material of the planetary masses, has formed, at last, the sun, the great ruler and luminary of our system. Much as this primitive evolutionary concept of the development and history of the solar system has been modified and altered of late years by recent researches into the nature of comets and meteors and of the sun’s surface, it still remains for all practical purposes of popular exposition the best and simplest mental picture of the general type of astronomical evolution. For the essential point which it impresses upon the mind is the idea of the planets in their several orbits and with their attendant satellites as due, not to external design and special creation, in the exact order in which we now see them, but to the slow and regular working out of preordained physical laws, in accordance with which they have each naturally assumed, by pure force of circumstances, their existing size, and weight, and orbit, and position.
