"More Letters of Charles Darwin". A record of his work in a series of hitherto unpublished Letters. Edited by Francis Darwin and A.C. Seward, 2 Vols., London, 1903.
I. INTRODUCTORY LETTER From Sir Joseph Dalton Hooker, O.M., G.C.S.I., C.B., M.D., D.C.L., LL.D., F.R.S., ETC.
The Camp,
near Sunningdale,
January 15, 1909.
Dear Professor Seward,
The publication of a Series of Essays in Commemoration of the century of the birth of Charles Darwin and of the fiftieth anniversary of the publication of "The Origin of Species" is a.s.suredly welcome and is a subject of congratulation to all students of Science.
These Essays on the progress of Science and Philosophy as affected by Darwin"s labours have been written by men known for their ability to discuss the problems which he so successfully worked to solve. They cannot but prove to be of enduring value, whether for the information of the general reader or as guides to investigators occupied with problems similar to those which engaged the attention of Darwin.
The essayists have been fortunate in having for reference the five published volumes of Charles Darwin"s Life and Correspondence. For there is set forth in his own words the inception in his mind of the problems, geological, zoological and botanical, hypothetical and theoretical, which he set himself to solve and the steps by which he proceeded to investigate them with the view of correlating the phenomena of life with the evolution of living things. In his letters he expressed himself in language so lucid and so little burthened with technical terms that they may be regarded as models for those who were asked to address themselves primarily to the educated reader rather than to the expert.
I may add that by no one can the perusal of the Essays be more vividly appreciated than by the writer of these lines. It was my privilege for forty years to possess the intimate friendship of Charles Darwin and to be his companion during many of his working hours in Study, Laboratory, and Garden. I was the recipient of letters from him, relating mainly to the progress of his researches, the copies of which (the originals are now in the possession of his family) cover upwards of a thousand pages of foolscap, each page containing, on an average, three hundred words.
That the editorship of these Essays has been entrusted to a Cambridge Professor of Botany must be gratifying to all concerned in their production and in their perusal, recalling as it does the fact that Charles Darwin"s instructor in scientific methods was his lifelong friend the late Rev. J.S. Henslow at that time Professor of Botany in the University. It was owing to his recommendation that his pupil was appointed Naturalist to H.M.S. "Beagle", a service which Darwin himself regarded as marking the dawn of his scientific career.
Very sincerely yours,
J.D. HOOKER.
II. DARWIN"S PREDECESSORS. By J. Arthur Thomson.
Professor of Natural History in the University of Aberdeen.
In seeking to discover Darwin"s relation to his predecessors it is useful to distinguish the various services which he rendered to the theory of organic evolution.
(I) As everyone knows, the general idea of the Doctrine of Descent is that the plants and animals of the present-day are the lineal descendants of ancestors on the whole somewhat simpler, that these again are descended from yet simpler forms, and so on backwards towards the literal "Protozoa" and "Protophyta" about which we unfortunately know nothing. Now no one supposes that Darwin originated this idea, which in rudiment at least is as old as Aristotle. What Darwin did was to make it current intellectual coin. He gave it a form that commended itself to the scientific and public intelligence of the day, and he won wide-spread conviction by showing with consummate skill that it was an effective formula to work with, a key which no lock refused. In a scholarly, critical, and pre-eminently fair-minded way, admitting difficulties and removing them, foreseeing objections and forestalling them, he showed that the doctrine of descent supplied a modal interpretation of how our present-day fauna and flora have come to be.
(II) In the second place, Darwin applied the evolution-idea to particular problems, such as the descent of man, and showed what a powerful organon it is, introducing order into ma.s.ses of uncorrelated facts, interpreting enigmas both of structure and function, both bodily and mental, and, best of all, stimulating and guiding further investigation. But here again it cannot be claimed that Darwin was original. The problem of the descent or ascent of man, and other particular cases of evolution, had attracted not a few naturalists before Darwin"s day, though no one (except Herbert Spencer in the psychological domain (1855)) had come near him in precision and thoroughness of inquiry.
(III) In the third place, Darwin contributed largely to a knowledge of the factors in the evolution-process, especially by his a.n.a.lysis of what occurs in the case of domestic animals and cultivated plants, and by his elaboration of the theory of Natural Selection, which Alfred Russel Wallace independently stated at the same time, and of which there had been a few previous suggestions of a more or less vague description.
It was here that Darwin"s originality was greatest, for he revealed to naturalists the many different forms--often very subtle--which natural selection takes, and with the insight of a disciplined scientific imagination he realised what a mighty engine of progress it has been and is.
(IV) As an epoch-marking contribution, not only to Aetiology but to Natural History in the widest sense, we rank the picture which Darwin gave to the world of the web of life, that is to say, of the inter-relations and linkages in Nature. For the Biology of the individual--if that be not a contradiction in terms--no idea is more fundamental than that of the correlation of organs, but Darwin"s most characteristic contribution was not less fundamental,--it was the idea of the correlation of organisms. This, again, was not novel; we find it in the works of naturalist like Christian Conrad Sprengel, Gilbert White, and Alexander von Humboldt, but the realisation of its full import was distinctively Darwinian.
AS REGARDS THE GENERAL IDEA OF ORGANIC EVOLUTION.
While it is true, as Prof. H.F. Osborn puts it, that ""Before and after Darwin" will always be the ante et post urbem conditam of biological history," it is also true that the general idea of organic evolution is very ancient. In his admirable sketch "From the Greeks to Darwin"
("Columbia University Biological Series", Vol. I. New York and London, 1894. We must acknowledge our great indebtness to this fine piece of work.), Prof. Osborn has shown that several of the ancient philosophers looked upon Nature as a gradual development and as still in process of change. In the suggestions of Empedocles, to take the best instance, there were "four sparks of truth,--first, that the development of life was a gradual process; second, that plants were evolved before animals; third, that imperfect forms were gradually replaced (not succeeded) by perfect forms; fourth, that the natural cause of the production of perfect forms was the extinction of the imperfect." (Op. cit. page 41.) But the fundamental idea of one stage giving origin to another was absent. As the blue Aegean teemed with treasures of beauty and threw many upon its sh.o.r.es, so did Nature produce like a fertile artist what had to be rejected as well as what was able to survive, but the idea of one species emerging out of another was not yet conceived.
Aristotle"s views of Nature (See G.J. Romanes, "Aristotle as a Naturalist", "Contemporary Review", Vol. LIX. page 275, 1891; G. Pouchet "La Biologie Aristotelique", Paris, 1885; E. Zeller, "A History of Greek Philosophy", London, 1881, and "Ueber die griechischen Vorganger Darwin"s", "Abhandl. Berlin Akad." 1878, pages 111-124.) seem to have been more definitely evolutionist than those of his predecessors, in this sense, at least, that he recognised not only an ascending scale, but a genetic series from polyp to man and an age-long movement towards perfection. "It is due to the resistance of matter to form that Nature can only rise by degrees from lower to higher types." "Nature produces those things which, being continually moved by a certain principle contained in themselves, arrive at a certain end."
To discern the outcrop of evolution-doctrine in the long interval between Aristotle and Bacon seems to be very difficult, and some of the instances that have been cited strike one as forced. Epicurus and Lucretius, often called poets of evolution, both pictured animals as arising directly out of the earth, very much as Milton"s lion long afterwards pawed its way out. Even when we come to Bruno who wrote that "to the sound of the harp of the Universal Apollo (the World Spirit), the lower organisms are called by stages to higher, and the lower stages are connected by intermediate forms with the higher," there is great room, as Prof. Osborn points out (op. cit. page 81.), for difference of opinion as to how far he was an evolutionist in our sense of the term.
The awakening of natural science in the sixteenth century brought the possibility of a concrete evolution theory nearer, and in the early seventeenth century we find evidences of a new spirit--in the embryology of Harvey and the cla.s.sifications of Ray. Besides sober naturalists there were speculative dreamers in the sixteenth and seventeenth centuries who had at least got beyond static formulae, but, as Professor Osborn points out (op. cit. page 87.), "it is a very striking fact, that the basis of our modern methods of studying the Evolution problem was established not by the early naturalists nor by the speculative writers, but by the Philosophers." He refers to Bacon, Descartes, Leibnitz, Hume, Kant, Lessing, Herder, and Sch.e.l.ling. "They alone were upon the main track of modern thought. It is evident that they were groping in the dark for a working theory of the Evolution of life, and it is remarkable that they clearly perceived from the outset that the point to which observation should be directed was not the past but the present mutability of species, and further, that this mutability was simply the variation of individuals on an extended scale."
Bacon seems to have been one of the first to think definitely about the mutability of species, and he was far ahead of his age in his suggestion of what we now call a Station of Experimental Evolution. Leibnitz discusses in so many words how the species of animals may be changed and how intermediate species may once have linked those that now seem discontinuous. "All natural orders of beings present but a single chain"... "All advances by degrees in Nature, and nothing by leaps."
Similar evolutionist statements are to be found in the works of the other "philosophers," to whom Prof. Osborn refers, who were, indeed, more scientific than the naturalists of their day. It must be borne in mind that the general idea of organic evolution--that the present is the child of the past--is in great part just the idea of human history projected upon the natural world, differentiated by the qualification that the continuous "Becoming" has been wrought out by forces inherent in the organisms themselves and in their environment.
A reference to Kant (See Brock, "Die Stellung Kant"s zur Deszendenztheorie," "Biol. Centralbl." VIII. 1889, pages 641-648. Fritz Schultze, "Kant und Darwin", Jena, 1875.) should come in historical order after Buffon, with whose writings he was acquainted, but he seems, along with Herder and Sch.e.l.ling, to be best regarded as the culmination of the evolutionist philosophers--of those at least who interested themselves in scientific problems. In a famous pa.s.sage he speaks of "the agreement of so many kinds of animals in a certain common plan of structure"... an "a.n.a.logy of forms" which "strengthens the supposition that they have an actual blood-relationship, due to derivation from a common parent." He speaks of "the great Family of creatures, for as a Family we must conceive it, if the above-mentioned continuous and connected relationship has a real foundation." Prof. Osborn alludes to the scientific caution which led Kant, biology being what it was, to refuse to entertain the hope "that a Newton may one day arise even to make the production of a blade of gra.s.s comprehensible, according to natural laws ordained by no intention." As Prof. Haeckel finely observes, Darwin rose up as Kant"s Newton. (Mr Alfred Russel Wallace writes: "We claim for Darwin that he is the Newton of natural history, and that, just so surely as that the discovery and demonstration by Newton of the law of gravitation established order in place of chaos and laid a sure foundation for all future study of the starry heavens, so surely has Darwin, by his discovery of the law of natural selection and his demonstration of the great principle of the preservation of useful variations in the struggle for life, not only thrown a flood of light on the process of development of the whole organic world, but also established a firm foundation for all future study of nature."
("Darwinism", London, 1889, page 9). See also Prof. Karl Pearson"s "Grammar of Science" (2nd edition), London, 1900, page 32. See Osborn, op. cit. Page 100.))
The scientific renaissance brought a wealth of fresh impressions and some freedom from the tyranny of tradition, and the twofold stimulus stirred the speculative activity of a great variety of men from old Claude Duret of Moulins, of whose weird transformism (1609) Dr Henry de Varigny ("Experimental Evolution". London, 1892. Chap. 1. page 14.) gives us a glimpse, to Lorenz Oken (1799-1851) whose writings are such mixtures of sense and nonsense that some regard him as a far-seeing prophet and others as a fatuous follower of intellectual will-o"-the-wisps. Similarly, for De Maillet, Maupertuis, Diderot, Bonnet, and others, we must agree with Professor Osborn that they were not actually in the main Evolution movement. Some have been included in the roll of honour on very slender evidence, Robinet for instance, whose evolutionism seems to us extremely dubious. (See J. Arthur Thomson, "The Science of Life". London, 1899. Chap. XVI. "Evolution of Evolution Theory".)
The first naturalist to give a broad and concrete expression to the evolutionist doctrine of descent was Buffon (1707-1788), but it is interesting to recall the fact that his contemporary Linnaeus (1707-1778), protagonist of the counter-doctrine of the fixity of species (See Carus Sterne (Ernest Krause), "Die allgemeine Weltanschauung in ihrer historischen Entwickelung". Stuttgart, 1889.
Chapter ent.i.tled "Bestandigkeit oder Veranderlichkeit der Naturwesen".), went the length of admitting (in 1762) that new species might arise by intercrossing. Buffon"s position among the pioneers of the evolution-doctrine is weakened by his habit of vacillating between his own conclusions and the orthodoxy of the Sorbonne, but there is no doubt that he had a firm grasp of the general idea of "l"enchainement des etres."
Erasmus Darwin (1731-1802), probably influenced by Buffon, was another firm evolutionist, and the outline of his argument in the "Zoonomia"
("Zoonomia, or the Laws of Organic Life", 2 vols. London, 1794; Osborn op. cit. page 145.) might serve in part at least to-day. "When we revolve in our minds the metamorphoses of animals, as from the tadpole to the frog; secondly, the changes produced by artificial cultivation, as in the breeds of horses, dogs, and sheep; thirdly, the changes produced by conditions of climate and of season, as in the sheep of warm climates being covered with hair instead of wool, and the hares and partridges of northern climates becoming white in winter: when, further, we observe the changes of structure produced by habit, as seen especially in men of different occupations; or the changes produced by artificial mutilation and prenatal influences, as in the crossing of species and production of monsters; fourth, when we observe the essential unity of plan in all warm-blooded animals,--we are led to conclude that they have been alike produced from a similar living filament"... "From thus meditating upon the minute portion of time in which many of the above changes have been produced, would it be too bold to imagine, in the great length of time since the earth began to exist, perhaps millions of years before the commencement of the history of mankind, that all warm-blooded animals have arisen from one living filament?"... "This idea of the gradual generation of all things seems to have been as familiar to the ancient philosophers as to the modern ones, and to have given rise to the beautiful hieroglyphic figure of the proton oon, or first great egg, produced by night, that is, whose origin is involved in obscurity, and animated by Eros, that is, by Divine Love; from whence proceeded all things which exist."
Lamarck (1744-1829) seems to have become an evolutionist independently of Erasmus Darwin"s influence, though the parallelism between them is striking. He probably owed something to Buffon, but he developed his theory along a different line. Whatever view be held in regard to that theory there is no doubt that Lamarck was a thorough-going evolutionist.
Professor Haeckel speaks of the "Philosophie Zoologique" as "the first connected and thoroughly logical exposition of the theory of descent."
(See Alpheus S. Packard, "Lamarck, the Founder of Evolution, His Life and Work, with Translations of his writings on Organic Evolution".
London, 1901.)
Besides the three old masters, as we may call them, Buffon, Erasmus Darwin, and Lamarck, there were other quite convinced pre-Darwinian evolutionists. The historian of the theory of descent must take account of Trevira.n.u.s whose "Biology or Philosophy of Animate Nature" is full of evolutionary suggestions; of Etienne Geoffroy St Hilaire, who in 1830, before the French Academy of Sciences, fought with Cuvier, the fellow-worker of his youth, an intellectual duel on the question of descent; of Goethe, one of the founders of morphology and the greatest poet of Evolution--who, in his eighty-first year, heard the tidings of Geoffroy St Hilaire"s defeat with an interest which transcended the political anxieties of the time; and of many others who had gained with more or less confidence and clearness a new outlook on Nature. It will be remembered that Darwin refers to thirty-four more or less evolutionist authors in his Historical Sketch, and the list might be added to. Especially when we come near to 1858 do the numbers increase, and one of the most remarkable, as also most independent champions of the evolution-idea before that date was Herbert Spencer, who not only marshalled the arguments in a very forcible way in 1852, but applied the formula in detail in his "Principles of Psychology" in 1855. (See Edward Clodd, "Pioneers of Evolution", London, page 161, 1897.)
It is right and proper that we should shake ourselves free from all creationist appreciations of Darwin, and that we should recognise the services of pre-Darwinian evolutionists who helped to make the time ripe, yet one cannot help feeling that the citation of them is apt to suggest two fallacies. It may suggest that Darwin simply entered into the labours of his predecessors, whereas, as a matter of fact, he knew very little about them till after he had been for years at work. To write, as Samuel Butler did, "Buffon planted, Erasmus Darwin and Lamarck watered, but it was Mr Darwin who said "That fruit is ripe," and shook it into his lap"... seems to us a quite misleading version of the facts of the case. The second fallacy which the historical citation is a little apt to suggest is that the filiation of ideas is a simple problem. On the contrary, the history of an idea, like the pedigree of an organism, is often very intricate, and the evolution of the evolution-idea is bound up with the whole progress of the world. Thus in order to interpret Darwin"s clear formulation of the idea of organic evolution and his convincing presentation of it, we have to do more than go back to his immediate predecessors, such as Buffon, Erasmus Darwin, and Lamarck; we have to inquire into the acceptance of evolutionary conceptions in regard to other orders of facts, such as the earth and the solar system (See Chapter IX. "The Genetic View of Nature" in J.T.
Merz"s "History of European Thought in the Nineteenth Century", Vol. 2, Edinburgh and London, 1903.); we have to realise how the growing success of scientific interpretation along other lines gave confidence to those who refused to admit that there was any domain from which science could be excluded as a trespa.s.ser; we have to take account of the development of philosophical thought, and even of theological and religious movements; we should also, if we are wise enough, consider social changes. In short, we must abandon the idea that we can understand the history of any science as such, without reference to contemporary evolution in other departments of activity.
While there were many evolutionists before Darwin, few of them were expert naturalists and few were known outside a small circle; what was of much more importance was that the genetic view of nature was insinuating itself in regard to other than biological orders of facts, here a little and there a little, and that the scientific spirit had ripened since the days when Cuvier laughed Lamarck out of court. How was it that Darwin succeeded where others had failed? Because, in the first place, he had clear visions--"pensees de la jeunesse, executees par l"age mur"--which a University curriculum had not made impossible, which the "Beagle" voyage made vivid, which an unrivalled British doggedness made real--visions of the web of life, of the fountain of change within the organism, of the struggle for existence and its winnowing, and of the spreading genealogical tree. Because, in the second place, he put so much grit into the verification of his visions, putting them to the proof in an argument which is of its kind--direct demonstration being out of the question--quite unequalled. Because, in the third place, he broke down the opposition which the most scientific had felt to the seductive modal formula of evolution by bringing forward a more plausible theory of the process than had been previously suggested.
Nor can one forget, since questions of this magnitude are human and not merely academic, that he wrote so that all men could understand.
AS REGARDS THE FACTORS OF EVOLUTION.
It is admitted by all who are acquainted with the history of biology that the general idea of organic evolution as expressed in the Doctrine of Descent was quite familiar to Darwin"s grandfather, and to others before and after him, as we have briefly indicated. It must also be admitted that some of these pioneers of evolutionism did more than apply the evolution-idea as a modal formula of becoming, they began to inquire into the factors in the process. Thus there were pre-Darwinian theories of evolution, and to these we must now briefly refer. (See Prof. W.A.
Locy"s "Biology and its Makers". New York, 1908. Part II. "The Doctrine of Organic Evolution".)
In all biological thinking we have to work with the categories Organism--Function--Environment, and theories of evolution may be cla.s.sified in relation to these. To some it has always seemed that the fundamental fact is the living organism,--a creative agent, a striving will, a changeful Proteus, selecting its environment, adjusting itself to it, self-differentiating and self-adaptive. The necessity of recognising the importance of the organism is admitted by all Darwinians who start with inborn variations, but it is open to question whether the whole truth of what we might call the Goethian position is exhausted in the postulate of inherent variability.
To others it has always seemed that the emphasis should be laid on Function,--on use and disuse, on doing and not doing. Practice makes perfect; c"est a force de forger qu"on devient forgeron. This is one of the fundamental ideas of Lamarckism; to some extent it met with Darwin"s approval; and it finds many supporters to-day. One of the ablest of these--Mr Francis Darwin--has recently given strong reasons for combining a modernised Lamarckism with what we usually regard as sound Darwinism. (Presidential Address to the British a.s.sociation meeting at Dublin in 1908.)
To others it has always seemed that the emphasis should be laid on the Environment, which wakes the organism to action, prompts it to change, makes dints upon it, moulds it, prunes it, and finally, perhaps, kills it. It is again impossible to doubt that there is truth in this view, for even if environmentally induced "modifications" be not transmissible, environmentally induced "variations" are; and even if the direct influence of the environment be less important than many enthusiastic supporters of this view--may we call them Buffonians--think, there remains the indirect influence which Darwinians in part rely on,--the eliminative process. Even if the extreme view be held that the only form of discriminate elimination that counts is inter-organismal compet.i.tion, this might be included under the rubric of the animate environment.
In many pa.s.sages Buffon (See in particular Samuel Butler, "Evolution Old and New", London, 1879; J.L. de Lanessan, "Buffon et Darwin", "Revue Scientifique", XLIII. pages 385-391, 425-432, 1889.) definitely suggested that environmental influences--especially of climate and food--were directly productive of changes in organisms, but he did not discuss the question of the transmissibility of the modifications so induced, and it is difficult to gather from his inconsistent writings what extent of transformation he really believed in. Prof. Osborn says of Buffon: "The struggle for existence, the elimination of the least-perfected species, the contest between the fecundity of certain species and their constant destruction, are all clearly expressed in various pa.s.sages." He quotes two of these (op. cit. page 136.):