The Saturday Reviewwas much more moderate, by no means sharing the anxiety of those who regarded evolutionary theories as hostile to Christianity. The author is saidto have encountered the difficulties of his theory “with admirable skill and ability,” and thoughThe Saturdayremained unconvinced of his general argument, yet it acknowledged itself “persuaded that natural selection must henceforward be admitted as the chief mode by which the structure of organised beings is modified in a state of nature;” and thought it very possible that, through its agency, considerable groups of nearly allied species might have been derived from a single progenitor: but thereThe Saturdaystopped, believing in limits to this power.
The second edition of “The Origin of Species,” which appeared in January, 1860, only six weeks after the first, contained but few alterations; the third, in March, 1861, had received extensive additions and corrections. The most important of these discussed the so-called tendency of organisation to advance, and explained the present coexistence of high and lowly organised forms. A valuable historical sketch of the modern progress of opinion on the subject, from Lamarck’s time, was prefixed to the book. It was further enlarged in subsequent editions, as evidences accumulated that various thinkers had independently adopted the evolution theory, or the more special one of natural selection. Notable instances of anticipation were those of Dr. Wells, who, in a paper read before the Royal Society in 1813, but not published till 1818, had expressed the opinion that all animals tend to vary; that agriculturists improve breeds by selection; and that what they do by art “seems to be done with equal efficacy, though more slowly, by nature, in the formation of varieties of mankind.” He thengoes on to exemplify the survival of the fittest, though in other words. Mr. Patrick Matthew, in 1831, published a work on “Naval Timber and Arboriculture,” in which he expressed, in scattered passages, a view nearly resembling Darwin’s.
The fourth edition of “The Origin,” in 1866, was longer, by fifty pages, than its predecessor. Among the additions may be mentioned a fuller treatment of the argument from embryology, which was made stronger by later investigations. The fifth edition (1869) was comparatively little increased in bulk, though altered in many details. In particular it contained a somewhat important change relating to the extent of the influence of natural selection. This is also referred to in “The Descent of Man” (first edition, vol. i. pp. 152-3), where the author says he had not formerly considered sufficiently the existence of many structures which appeared to be neither beneficial nor injurious, and had attributed too much to natural selection. “I was not able,” he says, “to annul the influence of my former belief, then widely prevalent, that each species had been purposely created; and this led to my tacitly assuming that every detail of structure, excepting rudiments, was of some special, though unrecognised, service.... If I have erred in giving to natural selection great power, which I am far from admitting, or in having exaggerated its power, which is in itself probable, I have, at least, as I hope, done good service in aiding to overthrow the dogma of separate creations.”
The sixth edition (1872), in smaller type, was considerably revised and altered, and remains permanent. A glossary of scientific terms was added by Mr. W. S.Dallas. A new chapter was inserted after the sixth, and entitled “Miscellaneous Objections to the Theory of Natural Selection.” It was partly derived from modified portions of chapter iv. of former editions, but the latter and larger part was new, and relates chiefly to the supposed incompetency of natural selection to account for the very early stages of useful structures. Numerous cases, such as the development of the giraffe’s neck, the baleen of the whale, the mammary glands, &c., are admirably discussed. Causes preventing the acquisition, through natural selection, of useful structures in many cases are dealt with, and reasons given for disbelieving in great and sudden modifications. In the concluding chapter Darwin further admits that he had formerly underrated the frequency and importance of use and disuse of parts, of the direct action of external conditions, and of variations which seem to us, in our ignorance, to arise spontaneously. He alludes to misrepresentations of his views, and calls attention to the fact that, in the first edition, at the close of the introduction, he stated his conviction that natural selection had been the main,but not the exclusivemeans of modification. “This has been of no avail. Great is the power of steady misrepresentation; but the history of science shows that, fortunately, this power does not long endure.” This is Darwin’s almost sole allusion in his works to the persistence with which views not his had been attributed to him, or he had been calumniated for views he did hold. But in his own lifetime—nay, within fifteen years—he witnessed a sufficiently satisfying revolution. “I formerly spoke to very many naturalists on the subject of evolution, and neveronce met with any sympathetic agreement. It is probable that some did then believe in evolution, but they were either silent or expressed themselves so ambiguously, that it was not easy to understand their meaning. Now things are wholly changed, and almost every naturalist admits the great principle of evolution” (“Origin,” sixth edition, p. 424). At present the sale of the book in this country approaches forty thousand copies. Its sale in America has been very large; and numerous translations into German, French, Italian, Russian, Dutch, and Swedish, and even into Japanese and Hindustani, have been largely sold. It must always be one of the most valued of all English classics.
WE have already gathered much concerning Darwin’s mental and moral fibre in our survey of his works. Let us make some further acquaintance with his personality as known to his friends. Outwardly he appeared a man of powerful physique, standing six feet high, with prominent forehead and over-arching brow, and keen, deep-set eyes in which resolute strength and piercing insight were indicated. Apart from his persistent infirmity, he was actively disposed, as indeed is evident from the laborious journeys he undertook during his travels. Field sports, including hunting, were among the recreations of his more active years. But through all his work or recreation the imperious conditions necessitated by his infirmity of stomach had to be considered, and nothing but the most rigorous care could possibly have enabled him to achieve what he did. On many days he could not work at all, and on many others two or three hours were his limit. And what but his own system, his own orderliness and perseverance could have accomplished his task? In preparing his books he had a special set of shelves for each, standing on or near his writing-table, one shelf for each chapter. The maxim,“Early to bed, and early to rise,” was his essentially, and regularity kept all balanced. Rising at six, he took a cold plunge bath, breakfasted simply, and took a first walk, beginning work often at eight. “Later in the day,” I quote from Mr. Woodall’s pleasant pages, “he generally walked again, often in his own grounds, but sometimes further afield, and then generally by quiet footpaths rather than frequented roads. The walks at one time were varied by rides along the lanes on a favourite black cob, but some years before his death his four-footed friend fell, and died by the roadside, and from that day the habit of riding was given up. Part of the evening was devoted to his family and his friends, who delighted to gather round him to enjoy the charm of his bright intelligence, and his unrivalled stores of knowledge. To Down, occasionally, came distinguished men from many lands; and there in later years would sometimes be found the younger generation of scientific students, looking up to the great naturalist with the reverence of disciples, who had experienced his singular modesty, his patient readiness to listen to all opinions, and the winning grace with which he informed their ignorance and corrected their mistakes. In the midst of all the delights of home and the demands of study, Darwin kept an open mind for public affairs. He united the earnest politician with the patient student: a rare combination, which supplies another proof of his largeness of heart and sympathy with his fellow men. In the village of Down he was liked by everybody, old and young, and in his own household the same servants lived year after year under his roof. One of them,Margaret Evans, who assisted in nursing him in his last illness, had come to Down nearly forty years before, from Shrewsbury, where her uncle and aunt were in Dr. Darwin’s service.”
At Down the family in time numbered nine children, two, however, not surviving childhood; one died in 1842, another in 1858. His five sons have already attained distinction or positions of influence. The eldest, William Erasmus, became a banker in Southampton; the second, George, was second Wrangler and Smith’s Prizeman at Cambridge in 1868, became a Fellow of Trinity, and is now Plumian Professor of Astronomy at his university, having early gained the Fellowship of the Royal Society for his original papers bearing on the evolution of the universe and the solar system, and many other subjects of high mathematical and philosophical interest. His third son, Francis, gained first-class honours in the Cambridge Natural Science Tripos in 1870, and is likewise a Fellow of the Royal Society, in recognition of his original botanical investigations. The fourth, Leonard, an officer in the Royal Engineers, has done valuable astronomical work. The fifth, Horace, has devoted himself to mechanical science, and has largely aided in developing the Cambridge Scientific Instrument Company.
The great thinker, fulfilling his duties as head of a family with singular success, charged with the burden of new thoughts and observations, slowly perfecting his life work, had neither time nor inclination for controversy. He set himself to publish facts, which by their accumulation tended to clench his arguments. Soon after the“Origin of Species” he had in course of publication several important botanical papers, on the two forms of flower in the Primrose genus (1862), and in the genus Linum (flax), 1863, on the forms of Loosestrife, 1864, all published in the Linnean Society’s Journal.
In 1862 he brought out his first botanical book, the “Fertilisation of Orchids,” more fully entitled, “On the various Contrivances by which Orchids are Fertilised by Insects.” These most singular flowers had long attracted great attention owing to their peculiar shapes and often their great beauty, while their marked deviation from typical forms of flowers perplexed botanists extremely. The celebrated Robert Brown, in a well-known paper in the Linnean Society’s Transactions, 1833, expressed the belief that insects are necessary for the fructification of most orchids; and as far back as 1793, Christian Sprengel (in “The Newly Discovered Secret of Nature”) gave an excellent account of the action of the several parts in the genus Orchis, having discovered that insects were necessary to remove the pollen masses. But therationaleof the process was not fully known until Darwin revealed it, and illuminated it by the light of natural selection. He had, in the “Origin of Species,” given reasons for the belief that it is an almost universal law of nature that the higher organic beings require an occasional cross with another individual. He here emphasised that doctrine by a series of proofs from a peculiar and otherwise inexplicable order of plants, and showed that the arrangements by which orchids are fertilised have for their main object the fertilisation of the flowers with pollen brought by insects from a distinct plant.
In the group to which our common orchids belong, remarkable adaptations for securing that the pollen masses brought from another flower solely through the visits of insects shall reach their precise destination, were brought to light. “A poet,” says Darwin, “might imagine that whilst the pollinia were borne through the air from flower to flower, adhering to an insect’s body, they voluntarily and eagerly placed themselves in that exact position in which alone they could hope to gain their wish and perpetuate their race.” As he had examined all the British genera, Darwin’s conclusions were indubitable. He had patiently watched for hours on the grass to notice insects’ visits, had counted the fertilised flowers on many spikes, the fertilised spikes on many plants, had dissected and redissected the flowers till he saw how the fertilisation must absolutely be effected; and utilising the enthusiasm of orchid growers, had excited them to do the same, till his storehouse of facts was full.
On examining the exotic forms of orchids, which are so conspicuous in our conservatories, still more striking facts presented themselves. In the great group of the Vandeæ, relative position of parts, friction, viscidity, elastic and hygrometric movements were all found to be nicely related to one end—the aid of insects in fertilisation. Without their aid not a plant in the various species of twenty-nine genera which Darwin examined would set a seed. In the majority of cases insects withdraw the pollen masses only when retreating from the flower, and, continuing their flower visits, effect a union between two flowers, generally on distinct plants. Inmany cases the pollen masses slowly change their position while adhering to the insects, and so assume a proper direction for striking the stigma of another flower, and the insects during this interval will almost certainly have flown from one plant to another.
The family to which Catasetum belongs furnished the most remarkable examples. This plant possesses a special sensitiveness in certain parts, and when definite points of the flower are touched by an insect the pollen masses are shot forth like an arrow, the point being blunt and adhesive. The insect, disturbed by so sharp a blow, or having eaten its fill, flies sooner or later to a female plant, and whilst standing in the same position as before, the pollen-bearing end of the arrow is inserted into the stigmatic cavity, and a mass of pollen is left on its viscid surface. The strange structures of Cypripedium, or the Lady’s Slipper, were then analysed, and the mode of fertilisation by small bees was discovered. The whole structure of orchids, as modified to secure insects’ visits and cross fertilisation, was now expounded, and the benefits shown by cases where insects’ visits were prevented, and no seed was set. The number of seeds in a capsule was reckoned, and thence it was found that the progeny of a single plant of the common orchis would suffice to cover the globe in the fourth generation. A single plant of another orchid might bear seventy-four millions of seeds: surely an ample provision for a struggle for existence, and selection and survival of the fittest. But, as Darwin remarks, profuse expenditure is nothing unusual in nature, and it appears to be more profitable for a plant to yield a few cross-fertilised than many self-fertilised seeds.
Darwin impresses forcibly on his readers the endless diversity of structures, and the prodigality of resources displayed for gaining the same end, the fertilisation of one flower by pollen from another plant. “The more I study nature,” he says, “the more I become impressed with ever-increasing force that the contrivances and beautiful adaptations slowly acquired through each part occasionally varying in a slight degree ... transcend in an incomparable manner the contrivances and adaptations which the most fertile imagination of man could invent.” Finally he concludes: “It is hardly an exaggeration to say that nature tells us, in the most emphatic manner, that she abhors perpetual self-fertilisation”; and thus was announced a new doctrine in botany. A second much-improved edition of this book appeared in 1877.
In 1864, in presenting the Copley medal of the Royal Society to the author of the “Origin of Species,” Major-General Sabine, the President, entered into a full description of the merits of his works, “stamped throughout with the impress of the closest attention to minute details and accuracy of observation, combined with large powers of generalisation.” The award, while highly eulogising the “Origin,” was not however based upon it, but on the more recent botanical writings. “The Fertilisation of Orchids” was described as perhaps the most masterly treatise on any branch of vegetable physiology that had ever appeared; and the fact was justly emphasised that all Darwin’s botanical discoveries had been obtained by the study of some of the most familiar and conspicuous of our native plants, and some of the best-known and easily-procured cultivated exotics.
In 1865 appeared another work from the Darwinian treasury, but in this case it was at first restricted to the Journal of the Linnean Society (vol. ix.), and was not made generally available till the second edition was published separately in 1875. “The Movements and Habits of Climbing Plants” described in the first place the twining of the hop plant, studied by night and day continuously, in a well-warmed room, to which the author was confined by illness. Again and again were different species of plants watched, and the periods in which their shoots revolved noted. The clematises, tropæolums, solanums, gloriosa lilies among leaf-climbing plants; the bignonias, cobæas, bryonies, vines, passion flowers, and other tendril-bearing plants; the ivy, and other root and hook climbers were carefully studied; and botanists for the first time realised fully the advantages which climbing plants possess in the struggle for existence. The climbing faculty depends on a sensitiveness to contact with any firm support, and a most interesting series of modifications has probably, as Darwin suggests, led to the present development of climbing organs, by the spontaneous movement of young shoots and other organs, and by unequal growth.
In concluding, the author made some most profoundly suggestive remarks, which went far to revolutionise our conception of plants. “It has often been vaguely asserted that plants are distinguished from animals by not having the power of movement. It should rather be said that plants acquire and display this power only when it is of some advantage to them; this being of comparatively rare occurrence, as they are affixed to the ground,and food is brought to them by the air and rain. We see how high in the scale of organisation a plant may rise, when we look at one of the more perfect tendril-bearers. It first places its tendrils ready for action, as a polypus places its tentacula. If the tendril be displaced, it is acted on by the force of gravity, and rights itself. It is acted on by the light, and bends towards or from it, or disregards it, which ever may be most advantageous. During several days the tendrils, or internodes, or both, spontaneously revolve with a steady motion. The tendril strikes some object, and quickly curls round and firmly grasps it. In the course of some hours it contracts into a spire, dragging up the stem, and forming an excellent spring. All movements now cease. By growth the tissues soon become wonderfully strong and durable. The tendril has done its work, and has done it in an admirable manner.”
The labour of revising the successive editions of the “Origin of Species,” together with prolonged ill-health, delayed the fulfilment of the promise given in that work, that the facts upon which it was based should be published. It was not till 1868 that the first instalment, “The Variation of Animals and Plants under Domestication,” was given to the world, in two large volumes, with numerous illustrations. The author’s design was to discuss in a second work the variability of organic beings in a state of nature, and the conversion of varieties into species, the struggle for existence and the operation of natural selection, and the principal objections to the theory, including questions of instinct and hybridisation. In a third work it was intended to test the principle ofnatural selection by the extent to which it explains the geological succession of organic beings, their distribution in past and present times, and their mutual affinities and homologies. The two latter works were never completed, in consequence of ill-health, and the labour involved in dealing with objections to and new facts in support of the “Origin,” and of the other works which at various times it became important to complete. But many portions of these subjects were admirably dealt with by disciples. In some cases Darwin’s views led to the rapid growth of a new science, such as that of comparative embryology, and it would not have been possible for him to cope with and interpret the multitude of new and astonishing facts discovered, which changed the face of organic nature as viewed by biologists. By doing each day the work which seemed most necessary, and which he could best do, Darwin managed, in spite of his infirmity of constitution, to complete a larger body of original work, both in experiment and in thought, together with a greater quantity of bibliographical study and collation of observed facts, than any Englishman perhaps has ever done.
The valuable book on “Variation” records and systematises a vast number of facts respecting all our principal domestic animals and cultivated plants. It gives evidence of wide reading, as well as great diligence in writing letters of inquiry to all living authorities who could give accurate information. Very many visits were paid to zoological gardens, breeders’ establishments, nursery grounds, &c.; and the preparation of skulls, skins, &c., was a frequent occurrence in the Darwinian laboratory. To take the case of rabbits alone, whichoccupied but a fraction of the time devoted to pigeons: over twenty works are quoted for historical facts, skeletons of various rabbits were prepared and exhaustively compared, the effects of use and disuse of parts traced, most careful measurements are given, and a list of the modifications which domestic rabbits have undergone, with the probable causes, concludes the chapter. As to pigeons, no pigeon-fancier ought to be without the book, for never assuredly was a sporting topic treated by so great a thinker and so admirably. The numerous experiments in crossing different breeds, and the results obtained, make this one of the most instructive books for all breeders. It would seem desirable that this portion of the book should be issued in a separate form. Again, when we turn to the sections on plants we see how indefatigable Darwin was, for he tells us that he cultivated fifty-four varieties of gooseberries alone, and compared them throughout in flower and fruit.
The chapters on Inheritance, and on Reversion to ancestral characters, or atavism, are profoundly suggestive. What can be more wonderful, the author asks, than that some trifling peculiarity should be transmitted through a long course of development, and ultimately reappear in the offspring when mature or even when old? Nevertheless, the real subject of surprise is not that a character should be inherited, but that any should ever fail to be inherited. Gradually leading up to the important hypothesis with which the work closes, he observes that to adequately explain the numerous characters that reappear after intervals of one or more generations, we must believe that a vast number of characters, capableof evolution, lie hidden in every organic being. “The fertilised germ of one of the higher animals, subjected as it is to so vast a series of changes from the germinal cell to old age—incessantly agitated by what Quatrefages well calls thetourbillon vital—is perhaps the most wonderful object in nature. It is probable that hardly a change of any kind affects either parent, without some mark being left on the germ. But on the doctrine of reversion the germ becomes a far more marvellous object, for, besides the visible changes to which it is subjected, we must believe that it is crowded with invisible characters, proper to both sexes, to both the right and left side of the body, and to a long line of male and female ancestors separated by hundreds or even thousands of generations from the present time; and these characters, like those written on paper with invisible ink, all lie ready to be evolved under certain known or unknown conditions.”
Through a further discussion of many deeply interesting facts, about the intercrossing of breeds and species, and about the causes of variability, we pass to the hypothesis of pangenesis, which, briefly stated, supposes that the cells or units of the body are perpetually throwing off minute granules or gemmules, which accumulate in the reproductive system, and may, instead of developing in the next generation, be transmitted in a dormant state through more than one generation and then be developed. Combination in various degrees between these gemmules is supposed to influence their appearance or non-appearance in the offspring at various stages.
This hypothesis certainly gives a picture of a possiblemode of accounting for many peculiarities shown by living organisms. Although not generally accepted, it has certainly not been disproved. Mr. Grant Allen’s opinion that it is Darwin’s “one conspicuous failure,” and that it is “crude and essentially unphilosophic,” must be discounted by his known devotion to Mr. Herbert Spencer’s philosophy. If Darwin had been a specialist in modern physiology, he might, perhaps, have expressed his hypothesis in a more persuasive form; but Weismann’s germ plasma theory is the only alternative one hitherto suggested in place of it.
ALTHOUGH the descent of man from animal ancestors was directly implied in the “Origin of Species,” Darwin hesitated at the time of its publication to declare his views fully, believing that he would only thus augment and concentrate the prejudice with which his theory would be met. He had for many years held the views he afterwards expressed; but it was not until he had by his other works raised up a strong body of scientific opinion in favour of his great generalisation, that he fully presented his views on man to the public. The “Descent of Man” was studied as a special case of the application of his general principles, a test all the more severe because several classes of argument were necessarily cut off, such as the nature of the affinities which connect together whole groups of organisms, their geographical distribution, and their geological succession. But adopting the high antiquity of man as demonstrated, he considered in detail the evidence as to man’s descent from some pre-existing form, the manner of his development, and the value of the differences between the so-called races of man. No originality is claimed for the theory or for the facts advanced; but it may safely be affirmed thatthe master’s acuteness, his moderation, his candour, and his desire to state facts which tell against him, are as conspicuous in the “Descent of Man” as in any of his works.
The “Descent of Man,” which was published in 1871 in two volumes, with numerous illustrations, began, after a short introduction, with a suggestive series of questions, which to the evolutionist suffice to decide the question as to man’s origin. As the answers to these questions are obvious, Darwin first concentrated his inquiry upon two points on which disputes must necessarily occur, namely, the traces which man shows, in his bodily structure, of descent from some lower form, and the mental powers of man as compared with those of lower animals. The facts of our bodily structure are inexplicable on any other view than our community of descent with the quadrumana, unless structure is but a snare to delude our reason. It is only our natural prejudice, says Darwin, and that arrogance which made our fathers declare that they were descended from demigods, which leads us to demur to this conclusion.
The comparison of the mental powers of animals with those of man, proving, as Darwin contends, that they therein also show traces of community of descent, was certain to provoke much more debate, for the term “instinct” and the use made of it by naturalists and psychologists as signifying untaught, unlearnt ability, largely tended to obscure the question, and to create prejudices against believing that instincts could be built up by inherited experience, that instincts were really not absolute and fixed, but relative and variable, and that all instinctswere not perfect or perfectly useful. The working out of the evolution theory as applied to animal minds, the study of the first beginnings of nerve action, and the analysis of instinct, all due largely to Darwin’s prominent disciple, Romanes, together with the immensely fuller knowledge of molecular physics, of protoplasm, and of brain function, acquired in the years since Darwin wrote, have sufficed to place these questions on a much more secure basis. But the collection of facts made by him, and the suggestive remarks he everywhere makes, render his book of permanent value. His sympathy is obvious in such passages as this: “Every one has heard of the dog suffering under vivisection who licked the hand of the operator; this man, unless he had a heart of stone, must have felt remorse to the last hour of his life;” the “terrible” superstitions of the past, such as human sacrifices, trial by ordeal, &c., show us, he says, “what an indefinite debt of gratitude we owe to the improvement of our reason, to science, and our accumulated knowledge.” We see the fruit of Darwin’s repeated visits to the Zoological Gardens, especially in his study of the habits and mental powers of monkeys. We gain a definition from him of imagination, by which faculty man “unites, independently of the will, former images and ideas, and thus creates brilliant and novel results.... The value of the products of our imagination depends of course on the number, accuracy, and clearness of our impressions; on our judgment and taste in selecting or rejecting the involuntary combinations, and to a certain extent on our power of voluntarily combining them.” As to religion, he says, “There is no evidence that manwas aboriginally endowed with the ennobling belief in the existence of an omnipotent God.” On the contrary, evidence proves that there are and have been numerous races without gods and without words to express the idea. The question, he says, is “wholly distinct from that higher one, whether there exists a Creator and Ruler of the universe; and this has been answered in the affirmative by the highest intellects that have ever lived.” The fact of races existing without a belief in a god is shown to be compatible with the origin of religious ideas from attempts to explain external phenomena and man’s own existence, by attributing to other objects and agencies a similar spirit to that which his consciousness testifies to in himself.
Man’s social qualities, as well as those of animals, Darwin regards as having been developed for the general good of the community, which he defines as “the means by which the greatest possible number of individuals can be reared in full vigour and health, with all their faculties perfect, under the conditions to which they are exposed.” This may be regarded as a more satisfactory expression of the idea underlying the phrase, “the greatest happiness of the greatest number.” Sympathy for animals he notes as one of the later acquisitions of mankind, and remarks that he found the very idea of humanity a novelty to the Gauchos of the Pampas. “The highest stage in moral culture at which we can arrive is when we recognise that we ought to control our thoughts.... Whatever makes any bad action familiar to the mind, renders its performance so much the easier”—a significant expression for thosewho would compare the teachings of Darwinism with those of Christianity. Finally, he concludes that the difference in mind between man and the higher animals is one of degree, not of kind. “At what age does the new-born infant possess the power of abstraction, or become self-conscious and reflect on its own existence? We cannot answer; nor can we answer in regard to the ascending organic scale.” Yet that man’s mental and moral faculties may have been gradually evolved “ought not to be denied, when we daily see their development in every infant; and when we may trace a perfect gradation from the mind of an utter idiot, lower than that of the lowest animal, to the mind of a Newton.”
The action of natural selection on the variations known to occur in man, is next shown to be sufficient to account for his rise from a lowly condition. Perhaps it is in discussing the development of the intellectual and moral faculties that Darwin is least successful; more knowledge of psychology than he possessed is demanded for this discussion. He gives up the problem of the first advance of savages towards civilisation as “at present much too difficult to be solved.” He, however, vigorously contests the idea that man was at first civilised and afterwards degenerated; and expresses the opinion that the “highest form of religion—the grand idea of God hating sin and loving righteousness—was unknown during primeval times.” Finally, after discussing the steps in the genealogy of man, he comes to the conclusion that from the old-world monkeys, at a remote period, proceeded man, “the wonder and glory of the universe.” The early progenitors of man he believes tohave been covered with hair, both sexes having had beards; their ears were pointed and capable of movement; their bodies were provided with a tail, and the foot was probably prehensile. Our primitive ancestors lived chiefly in trees in some warm forest-clad land, and the males were provided with formidable weapons in the shape of great canine teeth.
“Thus,” says Darwin, “we have given to man a pedigree of prodigious length, but not, it may be said, of noble quality. The world, it has been often remarked, appears as if it had long been preparing for the advent of man; and this, in one sense, is strictly true, for he owes his birth to a long line of progenitors. If any single link in this chain had never existed, man would not have been exactly what he now is. Unless we wilfully close our eyes, we may, with our present knowledge, approximately recognize our parentage; nor need we feel ashamed of it. The most humble organism is something much higher than the inorganic dust under our feet; and no one with an unbiassed mind can study any living creature, however humble, without being struck with enthusiasm at its marvellous structure and properties.”
In considering the formation and perpetuation of the races of mankind, Darwin was again and again baffled. He could not decide that any of the physical differences between the races are of direct and special service to him, thus giving opportunity to natural selection to work. Hence he was led to study in detail the effects of sexual selection, especially as applicable to man. The greater part of “The Descent of Man” is occupied with tracing out what may be called the history of courtship in manand animals. The great variety of interesting subjects dealt with cannot be detailed here. We must only notice a few points about mankind which are of special importance.
Darwin concludes that man’s predominance over woman in size, strength, courage, pugnacity, and even energy was acquired in primeval times, and that these advantages have been subsequently augmented chiefly through the contests between men for women. Even man’s intellectual vigour and inventiveness are probably due to natural selection, combined with inherited effects of habit, for the most able men will have succeeded best in defending and providing for their wives and offspring. Beards, beardlessness, voice, beauty are all related to sexual charm, and have been selectively developed. Early man, less licentious, not practising infanticide, was in several respects better calculated to carry out sexual selection than he is now; and thus we find the various races of men fully differentiated at the earliest date of historic records.
Incidentally Darwin gives us his views on the mental differences between man and woman. Woman is more tender and less selfish than man, whose ambition “passes too easily into selfishness,” which latter qualities “seem to be his natural and unfortunate birthright.” Woman’s powers of intuition, of rapid perception, and perhaps of imitation, are more strongly marked than in man. Yet the chief pre-eminence of man he considers to consist in attaining greater success in any given line than woman, by reason of greater energy, patience, &c. “In order that woman should reach the same standard as man, sheought, when nearly adult, to be trained to energy and perseverance, and to have her reason and imagination exercised to the highest point, and then she would probably transmit these qualities chiefly to her adult daughters.” Here we have a plan of women’s higher education according to the great evolutionist, although he does not assert that it is the essential and desirable one; but given a certain object, here is the best method of securing it. “The whole body of women, however, could not be thus raised, unless during many generations the women who excelled in the above robust virtues were married, and produced offspring in larger numbers than other women.”
The doctrine that man is descended from some less highly organised form, Darwin asserts in his concluding chapter, rests on grounds which will never be shaken—namely, the similar structure and course of development of embryos of the higher animals, and vast numbers of facts of structure and constitution, rudimental structures, and abnormal reversions. The mental powers of the higher animals graduate into those of man. Language, and the use of tools, made man dominant. The brain then immensely developed, and morality sprang from the social instinct. Comparing and approving certain actions and disapproving others, remembering and looking back, he became conscientious and imaginative. Sympathy, arising in the desire to give aid to one’s fellows, was strengthened by praise and blame, and conduces to happiness. “As happiness is an essential part of the general good, the greatest happiness principle indirectly serves as a nearly safe standard of right and wrong....But with the less civilised nations reason often errs, and many bad customs and base superstitions come within the same scope, and consequently are esteemed as high virtues and their breach as heavy crimes.”
The belief in God, the author says, is not innate or intuitive in man, but only arises after long culture. As to the bearing of the evolution theory on the immortality of the soul, Darwin thinks few people will find cause for anxiety in the impossibility of determining at what period in the ascending scale man became an immortal being. “The birth, both of the species and of the individual, are equally parts of that grand sequence of events, which our minds refuse to accept as the result of blind chance. The understanding revolts at such a conclusion.”
The bearing of the Darwinian doctrine on some important practical questions for society leads to the remark that, while man scans with scrupulous care the pedigree of his animals, when he comes to his own marriage he rarely or never takes any such care. Perhaps Darwin was somewhat in error here; and, also, he seems to have underrated the unconscious tendency to act according to natural law, which has no doubt influenced mankind largely. He lays down the principle that both sexes ought to refrain from marriage if markedly inferior in body or mind, or if they cannot avoid abject poverty for their children. When the laws of inheritance are thoroughly known, he says, we shall not hear ignorant members of our legislature rejecting with scorn a plan for ascertaining, by an easy method, whether or not consanguineous marriages are injurious to man. But Darwin is by no means in favour of any restriction on man’snatural rate of increase; for it is the greatest means of preventing indolence from causing the race to become stagnant or to degenerate. Only, there should be open competition for all men; and the most able should not be prevented by laws or customs from succeeding best and rearing the largest number of offspring.
In summing up on the entire subject, Darwin expresses himself with more than his wonted vigour and point. On the one hand, he endeavours to disarm opposition by quoting heroic monkeys as contrasted with degraded barbarians; on the other hand, he welcomes the elevation of man so far above his barbarous ancestors. Finally, he takes his stand upon truth, as against likes and dislikes. “The astonishment which I felt on first seeing a party of Fuegians on a wild and broken shore will never be forgotten by me, for the reflection at once rushed into my mind—such were our ancestors. These men were absolutely naked and bedaubed with paint; their long hair was tangled, their mouths frothed with excitement, and their expression was wild, startled, and distrustful. They possessed hardly any arts, and, like wild animals, lived on what they could catch. They had no government, and were merciless to every one not of their own small tribe. He who has seen a savage in his native land will not feel much shame, if forced to acknowledge that the blood of some more humble creature flows in his veins. For my own part, I would as soon be descended from that heroic little monkey, who braved his dreaded enemy in order to save the life of his keeper; or from that old baboon, who, descending from the mountains, carried away in triumph his young comradefrom a crowd of astonished dogs—as from a savage who delights to torture his enemies, offers up bloody sacrifices, practises infanticide without remorse, treats his wives like slaves, knows no decency, and is haunted by the grossest superstitions.
“Man may be excused for feeling some pride at having risen, though not through his own exertions, to the very summit of the organic scale; and the fact of his having thus risen, instead of having been aboriginally placed there, may give him hopes for a still higher destiny in the distant future. But we are not here concerned with hopes or fears, only with the truth as far as our reason allows us to discover it. I have given the evidence to the best of my ability; and we must acknowledge, as it seems to me, that man, with all his noble qualities, with sympathy which feels for the most debased, with benevolence which extends not only to other men, but to the humblest living creature, with his god-like intellect which has penetrated into the movements and constitution of the solar system—with all these exalted powers—Man still bears in his bodily frame the indelible stamp of his lowly origin.”
The reception accorded to “The Descent of Man” was more excited than that of “The Origin of Species.” The first large edition was quickly exhausted, and discussion or ridicule of the book was the fashionable recreation.Mr. Punch, week after week, reflected passing opinion. One of his Darwinian ballads on our ancestors is worth quoting from:—
“They slept in a wood,Or wherever they could,For they didn’t know how to make beds;They hadn’t got huts,They dined upon nuts,Which they cracked upon each other’s heads.They hadn’t much scopeFor a comb, brush, or soap,Or towels, or kettle, or fire;They had no coats nor capes,For ne’er did these apesInvent what they didn’t require.
“They slept in a wood,Or wherever they could,For they didn’t know how to make beds;They hadn’t got huts,They dined upon nuts,Which they cracked upon each other’s heads.They hadn’t much scopeFor a comb, brush, or soap,Or towels, or kettle, or fire;They had no coats nor capes,For ne’er did these apesInvent what they didn’t require.
·····
From these though descended,Our manners are mended,Though still we can grin and backbite;We cut up each other,Be he friend or brother,And tails are the fashion—at night.This originationIs all speculation—We gamble in various shapes;So Mr. DarwinMay speculate inOur ancestors having been apes.”
From these though descended,Our manners are mended,Though still we can grin and backbite;We cut up each other,Be he friend or brother,And tails are the fashion—at night.This originationIs all speculation—We gamble in various shapes;So Mr. DarwinMay speculate inOur ancestors having been apes.”
The Athenæumwas unbelieving, but not denunciatory.The Edinburgh Reviewdeclared the doctrine of natural selection hopelessly inadequate to explain the phenomena of man’s body; although its truth and falsehood had no necessary connection with the general theory of evolution: some law as yet unknown being looked for. Darwin’s attempt to explain the evolution of mind and the moral sense is regarded as failing in every point. “Never, perhaps, in the history of philosophy, have such wide generalisations been derived from such a small basis of fact.”The Quarterly Reviewnow acknowledged that“the survival of the fittest” was a truth which readily presented itself to any one considering the subject, and that to Darwin was due the credit of having first brought it forward and demonstrated its truth, and asserted that the destruction of the least fit was recognised thousands of years ago. But, in regard to the descent of man, it fastens specially upon the author’s theory of mental and moral evolution, and declares that he has utterly failed.The Saturday Review, however, admitted the high antiquity of man, and the nearness of his bodily structure to the apes, and went much further. In discussing the evolution of morals, the author’s unexampled grasp of facts, with his power of correlation, is, according toThe Saturday, seen at its highest, in an exquisite chain of philosophical deduction. The mode in which, at a remote period, the races of mankind became differentiated, is declared to be the weak point in the argument.
“THE Expression of the Emotions in Man and Animals” followed “The Descent of Man” in 1872. The motive which suggested it was the desire to explain the complexities of expression on evolution principles. But the study of emotional expression had evidently engaged Darwin’s attention at least from the time when the Fuegians and the Gauchos had vividly roused his imaginative faculties; and his direct observations commenced as early as 1838; when he was already inclined to believe in evolution, and were continued at intervals ever after. The third edition of Sir Charles Bell’s “Anatomy of Expression,” published in 1844, while greatly admired by him, was unsatisfactory in being throughout based on the conviction that species came into existence in their present condition; and notwithstanding that Bain and Herbert Spencer had made considerable advances in a treatment of the subject based on physiology, an exhaustive book was wanted, which should throw on Expression the new and interesting light of Darwinism.
What was Darwin’s method? Observation, cleverlydevised appeal to nature; observation over a wide field as to the varied races of man still existing, utilising the aid of travellers and residents in many lands; observation of domestic animals in familiar and in untried circumstances; observation of infants, especially his own, from a very early age; observation of the insane, who are liable to the strongest passions, and give them uncontrolled vent. It was in 1867 that Darwin circulated his group of questions designed to ascertain the mode of expressing every emotion, and their physical concomitants in every possible race. Sculpture, paintings, and engravings, afforded little evidence, because beauty is their main object, and “strongly contracted facial muscles destroy beauty.” Information was specially sought as to natives who had had little communication with Europeans, and in whom imitation might not have destroyed ancestral and original expression.
The result was to develop three principles which appeared, in combination, to account for most of the expressions and gestures involuntarily used by man and animals. The first was that of serviceable associated habits: certain complex actions being somehow serviceable in particular states of mind, to gratify and relieve certain sensations, desires, &c., whenever the same state of feeling is repeated, there is a tendency to the same movements or actions, though they may not then be of the least use. The second principle, that of antithesis, is the converse of the last; when an opposite state of mind is induced, there is an involuntary tendency to directly opposite movements, though of no use. The third principle, that of the direct action of the nervoussystem, is independent of the will and of habit; nerve force being generated in excess by strong emotions.
In discussing all these principles we discover how every thought and every circumstance of the great naturalist seem to have been utilised in his life work. “I have noticed that persons in describing a horrid sight, often shut their eyes momentarily and firmly, or shake their heads as if not to see, or to drive away, something disagreeable; and I have caught myself, when thinking in the dark of a horrid spectacle, closing my eyes firmly.” “I noticed a young lady earnestly trying to recollect a painter’s name, and she first looked to one corner of the ceiling, and then to the opposite corner, arching the one eyebrow on that side, although of course there was nothing to be seen there.” “Many years ago I laid a small wager with a dozen young men that they would not sneeze if they took snuff, although they all declared that they invariably did so; accordingly they all took a pinch, but from wishing much to succeed, not one sneezed, though their eyes watered, and all, without exception, had to pay me the wager.” “I put my face close to the thick glass-plate in front of a puff-adder in the Zoological Gardens, with the firm determination of not starting back if the snake struck at me; but as soon as the blow was struck, my resolution went for nothing, and I jumped a yard or two backwards with astonishing rapidity. My will and reason were powerless against the imagination of a danger which had never been experienced.” “I observed that though my infants started at sudden sounds, when under a fortnight old, they certainly did not always wink their eyes, and I believe never did so.The start of an older infant apparently represents a vague catching hold of something to prevent falling. I shook a pasteboard box close before the eyes of one of my infants, when 114 days old, and it did not in the least wink; but when I put a few comfits into the box, holding it in the same position as before, and rattled them, the child blinked its eyes violently every time, and started a little.” The behaviour of dogs and horses under many circumstances was watched. Cats and monkeys were most carefully scrutinised. At all moments Darwin seized upon and recorded the passing emotion and its associated movements. “I remember once seeing a boy who had just shot his first snipe on the wing, and his hands trembled to such a degree from delight, that he could not for some time reload his gun;” an instance of an emotional movement being disadvantageous.
Some of Darwin’s descriptions of emotional outbursts are among the best portions of his writing; as when he speaks of a mother whose infant has been intentionally injured, “how she starts up with threatening aspect, how her eyes sparkle and her face reddens, how her bosom heaves, nostrils dilate, and heart beats.” In describing a mourner when quiescent, he says: “The sufferer sits motionless, or gently rocks to and fro; the circulation becomes languid; respiration is almost forgotten, and deep sighs are drawn. All this reacts on the brain, and prostration soon follows with collapsed muscles and dulled eyes.”
One of the most striking features of this book is the evidence it affords of Darwin’s acuteness and persistence in observation during his travels, and of the excellence ofhis memory. “I remember that my mules and dogs, brought from a lower and warmer country, after spending a night on the bleak Cordillera, had the hair all over their bodies as erect as under the greatest terror.” He noted that Jemmy Button, the Fuegian, blushed when he was quizzed about the care which he took in polishing his shoes, and in otherwise adorning himself; and this fact long after is fitted into the theory of blushing. Guanacoes in South America, when not intending to bite, but merely to spit their offensive saliva from a distance at an intruder, yet retract their ears as a sign of their anger; and Darwin found the hides of several which he shot in Patagonia, deeply scored by teeth marks, in consequence of their battles with each other. A party of natives in Tierra del Fuego endeavoured to explain that their friend, the captain of a sealing vessel, was out of spirits, by pulling down their cheeks with both hands, so as to make their faces as long as possible; and the fact is treasured till it comes in to illustrate the lengthening of features under depression. As if he foreknew that he should want the fact forty years later, he inquired of Jemmy Button whether kissing was practised by his people, and learnt that it was unknown to them. “I remember,” he says, “being struck whilst travelling in parts of South America, which were dangerous from the presence of Indians, how incessantly—yet as it appeared, unconsciously—the half-wild Gauchos closely scanned the whole horizon.” “In Tierra del Fuego, a native touched with his finger some cold preserved meat which I was eating at our bivouac, and plainly showed utter disgust at its softness; whilst I felt utter disgust at myfood being touched by a naked savage, though his hands did not appear dirty.” And this illustrates the primary meaning of disgust—anything offensive to the taste.
In later years his own children, and his domestic pets, were incessantly watched, and suitable experiments were devised to bring out the real nature of their expressions. The period at which tears are formed and crying begins, the shape of the mouth in crying, the contraction of the muscles in shouting, the effects of steady gazing at objects, the various stages of smiling, the effects of shyness, shame, and fear, are all set before us, as thus observed. For instance, “I asked one of my boys to shout as loudly as he possibly could, and as soon as he began he firmly contracted his orbicular muscles (surrounding the eyes). I observed this repeatedly, and on asking him why he had every time so firmly closed his eyes, I found that he was quite unaware of the fact: he had acted instinctively or unconsciously.” Some of his early observations were afterwards published by Darwin inMind, vol. ii., under the title of “A Biographical Sketch of an Infant.”
Here is a carefully-worded and very suggestive experiment on animals: “Many years ago, in the Zoological Gardens, I placed a looking-glass on the floor before two young orangs, who, as far as it was known, had never before seen one. At first they gazed at their own images with the most steady surprise, and often changed their point of view. They then approached close, and protruded their lips towards the image, as if to kiss it, in exactly the same manner as they had previously done towards each other when first placed, a few days before, in the same room. They next made all sorts of grimaces, andput themselves in various attitudes before the mirror; they pressed and rubbed the surface; they placed their hands at different distances behind it; looked behind it; and finally seemed almost frightened, started a little, became cross, and refused to look any longer.” So monkeys were tested with a dressed doll, a live turtle, and stuffed snakes, &c.
The mode and purpose of erection of the hair, feathers, and dermal appendages of animals were the subject of much careful inquiry. Chimpanzees, monkeys, baboons, and many other creatures, were tested in the Zoological Gardens. A stuffed snake taken into the monkey-house caused several species to bristle. When Darwin showed the same to a peccary, the hair rose in a wonderful manner along its back. A cassowary erected its feathers at sight of an ant-eater.
Every unexpected occurrence was pressed into service. Witness the following anecdote: “One day my horse was much frightened at a drilling machine, covered by a tarpaulin and lying on an open field. He raised his head so high that his neck became almost perpendicular; and this he did from habit, for the machine lay on a slope below, and could not have been seen with more distinctness through the raising of the head; nor if any sound had proceeded from it could the sound have been more distinctly heard. His eyes and ears were directed intently forwards; and I could feel through the saddle the palpitations of his heart. With red, dilated nostrils, he snorted violently, and whirling round, would have dashed off at full speed had I not prevented him.”
We see, too, in this book the results of Darwin’sextensive reading. The novelists are laid considerably under contribution, their power of describing expressive signs of emotion being particularly appreciated. Dickens, Walter Scott, Mrs. Oliphant, and Mrs. Gaskell are among the novelists quoted; while the author of Job, Homer, Virgil, Seneca, Shakespeare, Lessing, Sir Joshua Reynolds, and many other deceased writers, illustrate the subject. The living authorities—scientific men, travellers, doctors—referred to for facts are exceedingly numerous, including Sir James Paget, Professor Huxley, Mr. Herbert Spencer, Sir J. Crichton Browne, Sir Samuel Baker, Sir Joseph Lister, Professors Cope and Asa Gray, and many others.
One of the most interesting chapters in the book is that dealing with blushing. It is shown to depend on self-attention, excited almost exclusively by the opinion of others. “Every one feels blame more acutely than praise. Now, whenever we know, or suppose, that others are depreciating our personal appearance, our attention is strongly drawn towards ourselves, more especially to our faces.” This excites the nerve centres receiving sensory nerve for the face, and in turn relaxes the blood capillaries, and fills them with blood. “We can understand why the young are much more affected than the old, and women more than men, and why the opposite sexes especially excite each others’ blushes. It becomes obvious why personal remarks should be particularly liable to cause blushing, and why the most powerful of all the causes is shyness; for shyness relates to the presence and opinion of others, and the shy are always more or less self-conscious.”
One great result made clear by Darwin is that the muscles of expression have not been created or developed for the sake of expression only, and that every true or inherited movement of expression had some natural or independent origin. All the chief expressions are proved to be essentially the same throughout the world, which is an additional argument for man being descended from one stock. We cannot refrain from admiring the tone of the pages which close the book, describing as they do the probable expressions of our early ancestors, their utility, the value of differences of physiognomy, and the desirability or otherwise of repressing signs of emotion. The subject, says the author, “deserves still further attention, especially from any able physiologist;” and so simply ends a volume of surpassing human interest, a text-book for novelists and students of human nature, a landmark in man’s progress in obedience to the behest “Know thyself.”
To fully measure the merit of one so far elevated above ordinary men is almost impossible; rather is it desirable to recognise the undeniable greatness of a great man, and learn all that is possible from him. An undoubted authority in mental science, however, has given a judgment on Darwin’s services to that science, which it is right to quote: “To ourselves it almost seems one of the most wonderful of the many wonderful aspects of Mr. Darwin’s varied work that by the sheer force of some exalted kind of common-sense, unassisted by any special acquaintance with psychological method, he should have been able to strike, as it were, straight down upon some of the most important truths which have ever beenbrought to light in the region of mental science.”12These truths are specified as the influence of natural selection in the formation of instinct, in the “Origin of Species;” the evolution of mind and of morals, in the “Descent of Man,” considered by the late Professor Clifford as containing the simplest and clearest and most profound philosophy that was ever written on the subject; and the evolution of expression in the book described in this chapter. Thus, says Mr. Romanes, in respect both of instincts and intelligence, the science of comparative psychology may be said to owe its foundation to Darwin.
IN 1875 appeared another great work from the master’s pen, “Insectivorous Plants,” which was destined to place in a yet more striking light the many-sidedness and fertility of his mind. As usual Darwin tells us that this work dated from many years back. “During the summer of 1860,” he says, “I was surprised by finding how large a number of insects were caught by the leaves of the common sun-dew (Drosera rotundifolia) on a heath in Sussex. I had heard that insects were thus caught, but knew nothing further on the subject. I gathered by chance a dozen plants, bearing fifty-six fully expanded leaves, and on thirty-one of these dead insects or remnants of them adhered.” Here was the germ of something, the discoverer scarcely knew what. It was evident to him that the little sun-dew was excellently adapted for catching insects, and that the number of them thus slaughtered annually must be enormous. What bearing might this have upon the problem of the struggle for existence?
A masterly series of experiments was forthwith set on foot, with the result of proving that sun-dews and a number of other plants obtain the bulk of their nourishmentby catching, killing, and digesting insects. They may be called truly carnivorous plants. What an unexpected reversal this was of the order of things hitherto believed to prevail universally. Animals live on other animals or on plants. Here were plants living on animals, and keeping down their number. Moreover, without a nervous system, the action of the parts of a sun-dew leaf was proved to be as apparently purposive as the combined action of the limbs of an animal. Without a stomach, the sun-dew poured forth a digestive fluid as effective in extracting and fitting the nutritious matter of the insect for its own purposes as that of an animal. Without sensory nerve-endings, there was a percipient power in the sun-dew which recognised instinctively and at once the non-nutritious nature of various objects, and which responded to the most delicate chemical stimuli and to the minutest weights.
We cannot describe the little sun-dew better than in Darwin’s own words: “It bears from two or three to five or six leaves, generally extended more or less horizontally, but sometimes standing vertically upwards. The leaves are commonly a little broader than long. The whole upper surface is covered with gland-bearing filaments, or tentacles as I shall call them from their manner of acting. The glands were counted on thirty-one leaves, but many of these were of unusually large size, and the average number was 192; the greatest number being 260, and the least 130. The glands are each surrounded by large drops of extremely viscid secretion, which, glittering in the sun, have given rise to the plant’s poetical name of the sun-dew.”
This secretion, when excited by nutritious matter, becomes distinctly acid, and contains a digestive ferment allied to the pepsin of the human stomach. So excited, it is found capable of dissolving boiled white of egg, muscle, fibrin, cartilage, gelatine, curd of milk, and many other substances. Further, various substances that animal gastric juice is unable to digest are not acted upon by the secretion of the sun-dew. These include all horny matter, starch, fat, and oil. It is not however prejudiced in favour of animal matter. The sun-dew can absorb nutriment from living seeds of plants, injuring or killing them, of course, in the process, while pollen and fresh green leaves yield to its influence.
The action of salts of ammonia and other chemicals was even more wonderful. “It is an astonishing fact that so inconceivably minute a quantity as the one twenty-millionth of a grain of phosphate of ammonia should induce some change in a gland of Drosera sufficient to cause a motor impulse to be sent down the whole length of the tentacle; this impulse exciting movement often through an angle of above 180°. I know not whether to be most astonished at this fact, or that the pressure of a minute bit of hair, weighing only178700of a grain, and largely supported by the dense secretion, should quickly cause conspicuous movement.”
These are but specimens of a multitude of profoundly interesting facts brought out in this exhaustive investigation. If this single research were his only title to fame Darwin’s name must rank high as an experimenter of rare ingenuity and success. But he concludes his summary of results by the utterly modest remark, “We see howlittle has been made out in comparison with what remains unexplained and unknown.”
The facts relating to Venus’ fly-trap (Dionæa muscipula) and other members of the order to which the sun-dew belongs were better known, but Darwin elicited new truths by his ingenious and varied experiments. The rapidity with which the two lobes of the leaf of dionæa close together when anything touches the tiny spikes which stand up vertically from the upper surface of the lobes, is astonishing, and any insect which causes the closure is almost certain to be caught. Digestion is accomplished in the case of the dionæa by a separate agency, consisting of a large number of minute reddish glands covering the surface of the lobes. These secrete a digestive fluid when stimulated by the contact of any nitrogenous matter, and of course this takes place when any insect is caught. In fact, essentially the same process of digestion and absorption takes place as in the sun-dew. The insect is held firmly for days, until its juices have been absorbed, and then the leaf slowly reopens, not being able to close again for many subsequent days.
It is interesting to note the extreme caution with which the great naturalist speculates upon the mode by which the varied members of the sun-dew order became modified from an ordinary plant-form to such a remarkable degree. The details are too special for quotation here. He suggests, but he does not in the slightest degree dogmatise. For many years to come Darwin’s suggestions and comments must be the pregnant soil out of which fruitful research will spring, and his caution will remainthe model, to depart from which will but sow hindrances in the path of scientific progress.
The order to which the butterwort and the bladderworts belong also afforded valuable results. The leaf of the butterwort bears glandular hairs, and its margins curve inwards when excited by contact of various bodies, especially living insects, and, at the same time, these are caught in the viscid secretion of the glands, and their juices absorbed by the plant. The bladderworts are even more remarkably constructed, for they have a portion of their leaves developed into subaqueous bladders, with a narrow entrance beneath, defended by a complex valve, which facilitates the entrance of water insects or crustaceans, but prevents their exit. The whole interior of the bladder is lined with transparent four-branched protoplasmic hairs, but nevertheless the bladderwort is unlike the preceding plants in having no power of digesting its prey, however long it may remain in captivity. Yet there is no doubt that the imprisoned creatures do decay in their watery cell, and that the hairs just described absorb the products of their decay.
Such is a brief account of Darwin’s work on “Insectivorous Plants.” With his characteristic expressions he acknowledges the valuable aid given him by Professor Burdon-Sanderson, and by his son, Mr. Francis Darwin. The former was enabled to give the first brief account of the process of digestion in these plants, as observed by Darwin, in a lecture before the Royal Institution, in June, 1874, and Dr. (now Sir Joseph) Hooker called general public notice to the subject of Carnivorous Plants in his lecture before the British Association atBelfast in the same year: so that a thoroughly awakened attention was given to this new work from Darwin’s pen. The public and the scientific world learnt to appreciate yet more keenly his varied talent, his long patience, his reserve of power; and thence dated very definitely a general appreciation of the fundamental unity of the animal and plant kingdoms, seeing that the salient faculties of digestion, of purposive locomotion, of rapid communication and consentaneous action were no longer restricted to animals, but were possessed in a high degree by plants also. Eager followers soon brought forward further proofs of unity of functions in the two kingdoms, and of reciprocal combinations between them, and now no one in the slightest degree acquainted with modern biology doubts that life is at bottom one phenomenon, shared equally and manifested in essentially the same modes by the living substance of plant and animal alike.
Following “Insectivorous Plants” came “The Effects of Cross and Self-Fertilisation in the Vegetable Kingdom,” in 1876. Darwin had led the way in the study of this subject by his book on Orchids, and his lead had been excellently followed by Hildebrand, Hermann Müller, Sir John Lubbock, and others. The path having been indicated, it had appeared comparatively easy for botanists to follow it up. But there yet remained a region of experimental inquiry which it required Darwin’s patience and ingenuity to master and to expound conclusively. Although it might be practically granted that natural selection developed a process because advantage was gained by it, was it possible to demonstrate thatflowers cross-fertilised bear more and larger seeds, which produce healthier offspring than those fertilised from their own pollen? This Darwin set himself exhaustively to do. For more than a dozen years after his book on orchids appeared, unwearied experiments on plants were progressing, and nature was being questioned acutely, untiringly. Competitive germination was carried on. The two classes of seeds were placed on damp sand in a warm room. As often as a pair germinated at the same time, they were planted on opposite sides of the same pot, with a partition between. Besides these pairs of competitors, others were planted in beds, so that the descendants of the crossed and self-fertilised flowers might compete. The resulting seeds were carefully compared, and their produce again compared. Species were selected from widely distinct families, inhabiting various countries. From a large number of plants, when insects were quite excluded by a thin net covering the plant, few or no seeds were produced. The extent of transport of pollen by insects was unveiled, and the relation between the structure, odour, and conspicuousness of flowers, the visits of insects, and the advantages of cross-fertilisation was shown. “We certainly,” says Darwin, “owe the beauty and odour of our flowers, and the storage of a large supply of honey, to the existence of insects.” The multitude of facts gathered about insects could only have been discovered and rightly appreciated by one who was a true entomologist as well as a botanist.