Alfred Russel Wallace, a young Welsh biologist, went out at twenty-four, in 1848, to the Amazons River, in company with Bates (the author of 'The Naturalist1 on the Amazons'), to collect birds and butterflies, and to study tropical life in the richest region of equatorial America. Like all other higher zoologists2 of their time, the two young explorers were deeply interested in the profound questions of origin and metamorphosis, and of geographical3 distribution, and in the letters that passed between them before they started they avowed4 to one another that the object of their quest was a solution of the pressing biological enigma5 of creation or evolution. Starting with fresh hopes and a few pounds in pocket, on an old, worn-out, and unseaworthy slave-trader, they often discussed these deep problems of life and nature together upon the Sargasso sea, or among the palms and lianas of the Brazilian woodlands. The air was thick with whiffs and foretastes of evolutionism, and the two budding naturalists7 of the Amazons expedition had inhaled8 them eagerly with every breath. They saw among the mimicking9 organisms of that[Pg 80] equatorial zone strange puzzles to engage their deepest attention; they recognised in the veins10 and spots that diversified11 the filmy membranes12 of insects' wings the hieroglyphs13 of nature, writing as on a tablet for them to decipher the story of the slow modification14 of species. In 1852—the year when Herbert Spencer in England published his essay on the 'Development Hypothesis,' and when Naudin in France put forth15 his bold and able paper on the 'Origin of Species'—Wallace once more returned to Europe, and gave to the world his interesting 'Travels on the Amazons and the Rio Negro.' Two years later the indefatigable16 traveller set out a second time on a voyage of tropical exploration, among the islands of the Malay archipelago, and for eight years he wandered about in Malay huts and remote islets, gathering17 in solitude18 and isolation19 the enormous store of minute facts which he afterwards lavished21 with so prodigal22 a hand upon 'Tropical Nature,' and the 'Geographical Distribution of Animals.'
While Wallace was still at Amboyna, he sent home in 1858 a striking memoir23, addressed to Darwin, with a request that he would forward it to Sir Charles Lyell, for presentation to the Linnean Society. Darwin opened and read his brother naturalist's paper, and found to his surprise that it contained his own theory of natural selection, not worked out in detail, as he himself was working it out, but still complete in spirit and essence, with no important portion of the central idea lacking to its full rotundity of conception. A jealous man would have thrown obstacles in the way of publication; but both Darwin and Wallace were born superior to the meannesses of jealousy24. The elder naturalist commended[Pg 81] his young rival's paper at once to Sir Charles Lyell, who sent it on immediately to the Linnean Society.
But Sir Charles Lyell and Sir Joseph Hooker, both of whom knew of Darwin's work, thought it advisable that he should publish, in the 'Journal' of the Society, a few extracts from his own manuscripts, side by side with Wallace's paper. Darwin, therefore, selected some essential passages for the purpose from his own long-gathered and voluminous notes, and the two contributions were read together before the Society on July the 1st, 1858. That double communication marks the date of birth of modern evolutionism. It is to the eternal credit of both thinkers that each accepted his own true position with regard to the great discovery in perfect sincerity27. The elder naturalist never strove for a moment to press his own claim to priority against the younger: the younger, with singular generosity28 and courtesy, waived29 his own claim to divide the honours of discovery in favour of the elder. Not one word save words of fraternal admiration30 and cordial appreciation31 ever passed the lips of either with regard to the other.
The distinctive32 notion of natural selection, indeed, like all true and fruitful ideas, had more than once flashed for a moment across the penetrating33 mind of more than one independent investigator34. As early as 1813, Dr. Wells, the famous author of the theory of dew, applied35 that particular conception to the single case of the production of special races among mankind.
'Of the accidental varieties of man, which would occur among the first few and scattered36 inhabitants of the middle regions of Africa,' he wrote, 'some one would be better fitted than the others to bear the diseases of[Pg 82] the country. This race would consequently multiply, while the others would decrease; not only from their inability to sustain the attacks of disease, but from their incapacity of contending with their more vigorous neighbours.... The same disposition37 to form varieties still existing, a darker and a darker race would in the course of time occur; and as the darkest would be the best fitted for the climate, this would at last become the most prevalent, if not the only race in the country.' Here we have not merely the radical39 concept of natural selection, but also the subordinate idea of its exertion40 upon what Darwin calls 'spontaneous variations.' What is wanting in the paper is the application of the faintly descried41 law to the facts and circumstances of general biology: Wells saw only a particular instance, where Darwin and Wallace more vividly42 perceived a universal principle. Again, in 1831, Mr. Patrick Matthew in that singular appendix to his book on naval43 timber actually enunciates44 the same idea, applied this time to the whole of nature, in words sometimes almost identical with Darwin's own. 'As nature in all her modifications45 of life,' says this unconscious discoverer, 'has a power of increase far beyond what is needed to supply the place of what falls by Time's decay, those individuals who possess not the requisite46 strength, swiftness, hardihood, or cunning, fall prematurely48 without reproducing—either a prey49 to their natural devourers, or sinking under disease, generally induced by want of nourishment51, their place being occupied by the more perfect of their own kind, who are pressing on the means of existence.... The self-regulating adaptive disposition of organised life may, in part, be traced to[Pg 83] the extreme fecundity52 of nature, who, as before stated, has in all the varieties of her offspring a prolific53 power much beyond (in many cases a thousandfold) what is necessary to fill up the vacancies54 caused by senile decay. As the field of existence is limited and preoccupied55, it is only the hardier56, more robust57, better-suited-to-circumstance individuals, who are able to struggle forward to maturity58, these inhabiting only the situations to which they have superior adaptation and greater power of occupancy than any other kind; the weaker and less circumstance-suited being prematurely destroyed. This principle is in constant action; it regulates the colour, the figure, the capacities, and instincts; those individuals in each species whose colour and covering are best suited to concealment59 or protection from enemies, or defence from inclemencies and vicissitudes60 of climate, whose figure is best accommodated to health, strength, defence, and support; whose capacities and instincts can best regulate the physical energies to self-advantage according to circumstances—in such immense waste of primary and youthful life those only come forward to maturity from the strict ordeal61 by which nature tests their adaptation to her standard of perfection and fitness to continue their kind by reproduction.' Of the ideas expressed in these paragraphs, and others which preceded them, Darwin himself rightly observes, 'He gives precisely62 the same view on the origin of species as that propounded63 by Mr. Wallace and myself. He clearly saw the full force of the principle of natural selection.'
In 1852, once more, so eminent64 and confirmed an evolutionist as Mr. Herbert Spencer himself had hit[Pg 84] upon a glimpse of the same great truth, strange to say without perceiving the width and scope of its implications. 'All mankind,' he wrote in that year in an essay on population in the 'Westminster Review,' 'in turn subject themselves more or less to the discipline described; they either may or may not advance under it; but, in the nature of things, only those who do advance under it eventually survive. For, necessarily, families and races whom this increasing difficulty of getting a living which excess of fertility entails65 does not stimulate66 to improvements in production.... are on the high road to extinction67; and must ultimately be supplanted68 by those whom the pressure does so stimulate.... And here, indeed, without further illustration, it will be seen that premature47 death, under all its forms, and from all its causes, cannot fail to work in the same direction. For as those prematurely carried off must, in the average of cases, be those in whom the power of self-preservation69 is the least, it unavoidably follows that those left behind to continue the race must be those in whom the power of self-preservation is the greatest, must be the select of their generation.' In this striking pre-Darwinian passage we have a partial perception of what Mr. Spencer afterwards described as the survival of the fittest; but, as our great philosopher himself remarks, it 'shows how near one may be to a great generalisation without seeing it.' For not only does Mr. Spencer, like Wells before him, limit the application of the principle to the case of humanity; but, unlike Wells, he overlooks the all-important factor of spontaneous variation, and the power of natural selection, acting70 upon such, to produce specific and[Pg 85] generic71 divergences72 of structure. In short, in his own words, the paragraph 'contains merely a passing recognition of the selective process, and indicates no suspicion of the enormous range of its effects, or of the conditions under which a large part of its effects are produced.' On the other hand, it must be noted74 that both Spencer and Matthew, like Darwin himself, based their ideas largely upon the Malthusian principle, and thus held the two true keys of the situation fairly within their unconscious hands.
Frankly75 to recognise these various foreshadowings of the distinctive Darwinian theory of natural selection is not in any way to undermine the foundations of Charles Darwin's own real and exceptional greatness. On the contrary, the mere38 fact that his views were so far anticipated by Wells, Matthew, Spencer, and others, and were simultaneously76 arrived at across half the globe by the independent intellect of Alfred Russel Wallace, is in itself the very best proof and finest criterion of Charles Darwin's genuine apostleship. No truly grand and fruitful idea was ever yet the sole property of a single originator. Great discoveries, says an acute critic, must always be concerned with some problem of the time which many of the world's foremost minds are just then cudgelling their active brains about. It was so with the discovery of the differential calculus77, and of the planet Neptune78; with the interpretation79 of the Egyptian hieroglyphics80, and of the cuneiform inscriptions81; with the undulatory theory of light, with the mechanical equivalent of heat, with the doctrine82 of the correlation83 and conservation of energies, with the invention of the steam engine, the locomotive, the[Pg 86] telegraph and the telephone; with the nebular hypothesis, and with spectrum84 analysis. It was so, too, with the evolutionary85 movement. The fertile upturning of virgin86 sod in the biological field which produced Darwin's forerunners87, as regards the idea of descent with modification, in the persons of Buffon, Lamarck, and Erasmus Darwin, necessarily produced a little later, under the fresh impetus88 of the Malthusian conception, his forerunners or coadjutors, as regards the idea of natural selection, in the persons of Wells, Matthew, and Wallace. It was Darwin's task to recognise the universal, where Wells and Spencer had seen only the particular; to build up a vast and irresistible89 inductive system, where Matthew and Wallace had but thrown out a pregnant hint of wonderful a priori interest and suggestiveness. It is one thing to draw out the idea of a campaign, another thing to carry it to a successful conclusion; one thing rudely to sketch90 a ground-plan, another thing finally to pile aloft to the sky the front of an august and imposing91 fabric92.
As soon as the papers at the Linnean had been read and printed, Darwin set to work in real earnest to bring out the first instalment of his great work. That instalment was the 'Origin of Species.' The first edition was ready for the public on November the 24th, 1859.
In his own mind Darwin regarded that immortal93 work merely in the light of an abstract of his projected volumes. So immense were his collections and so voluminous his notes that the 'Origin of Species' itself seemed to him like a mere small portion of the contemplated94 publication. And indeed he did ultimately work out several other portions of his original plan in his[Pg 87] detailed95 treatises97 on the Variation of Animals and Plants under Domestication98, on the Effects of Cross and Self-Fertilisation, and on the Descent of Man and Sexual Selection. But the immense and unexpected vogue99 of his first volume, the almost immediate25 revolution which it caused in biological and general opinion, and the all but universal adhesion to his views of all the greatest and most rising naturalists, to a great extent saved him the trouble of carrying out in full the task he had originally contemplated as necessary. Younger and less occupied labourers took part of the work off their leader's hands; the great chief was left to prosecute100 his special researches in some special lines, and was relieved from the necessity of further proving in minuter detail what he had already proved with sufficient cogency101 to convince all but the wilfully102 blind or the hopelessly stupid.
The extraordinary and unprecedented104 success of the 'Origin of Species' is the truest test of the advance it made upon all previous evolutionary theorising. Those who had never been convinced before were now convinced by sheer force of reasoning; those who believed and those who wavered had their faith confirmed into something like the reposeful105 calm of absolute certitude.
Let us consider, therefore, what exactly were the additions which Charles Darwin offered in his epoch-making work to the pre-existing conceptions of evolutionists.
In 1852, seven years before the publication of Darwin's masterpiece, Mr. Herbert Spencer wrote as follows in an essay in the 'Leader' on creation and evolution. The expressions of so profound and philosophical106[Pg 88] a biologist may be regarded as the high-water mark of evolutionary thinking up to the date of the appearance of Wallace and Darwin's theory:—
'Even could the supporters of the development hypothesis merely show that the production of species by the process of modification is conceivable, they would be in a better position than their opponents. But they can do much more than this; they can show that the process of modification has effected and is effecting great changes in all organisms, subject to modifying influences ... they can show that any existing species—animal or vegetable—when placed under conditions different from its previous ones, immediately begins to undergo certain changes of structure fitting it for the new conditions. They can show that in successive generations these changes continue until ultimately the new conditions become the natural ones. They can show that in cultivated plants and domesticated107 animals, and in the several races of men, these changes have uniformly taken place. They can show that the degrees of difference, so produced, are often, as in dogs, greater than those on which distinctions of species are in other cases founded. They can show that it is a matter of dispute whether some of these modified forms are varieties or modified species. They can show too that the changes daily taking place in ourselves; the facility that attends long practice, and the loss of aptitude108 that begins when practice ceases; the development of every faculty109, bodily, moral or intellectual, according to the use made of it, are all explicable on this same principle. And thus they can show that throughout all organic nature there is at[Pg 89] work a modifying influence of the kind they assign as the cause of these specific differences, an influence which, though slow in its action, does in time, if the circumstances demand it, produce marked changes; an influence which, to all appearance, would produce in the millions of years, and under the great varieties of condition which geological records imply, any amount of change.'
This admirable passage, written seven years before the publication of the 'Origin of Species,' contains explicitly110 almost every idea that ordinary people, not specially111 biological in their interests, now associate with the name of Darwin. That is to say, it contains, in a very philosophical and abstract form, the theory of 'descent with modification' without the distinctive Darwinian adjunct of 'natural selection' or 'survival of the fittest.' Yet it was just that particular lever, dexterously112 applied, and carefully weighted with the whole weight of his endlessly accumulated inductive instances, that finally enabled our modern Archimedes in so short a time to move the world. The public, that was deaf to the high philosophy of Herbert Spencer, listened at once to the practical wisdom of Charles Darwin. They did not care at all for the a priori proof, but they believed forthwith as soon as a cautious and careful investigator laid bare before their eyes in minute detail the modus operandi of nature herself.
The main argument of Darwin's chief work runs somewhat after the following fashion[2]:[Pg 90]—
Variation, to a greater or less degree, is a common and well-known fact in nature. More especially, animals and plants under domestication tend to vary from one another far more than do the individuals of any one species in the wild state. Rabbits in a warren are all alike in shape, size, colour, and features: rabbits in a hutch vary indefinitely in the hue113 of their fur, the length of their ears, the character of their coat, and half a dozen other minor114 particulars, well known to the observant souls of boys and fanciers. This great variability, though partly perhaps referable to excess of food, is probably due on the whole to their having been raised under conditions of life not so uniform as, and somewhat different from, those to which the parent species is commonly exposed in a state of nature. In other words, variability is one result of altered and more varied115 surrounding circumstances.
Again, this variability is usually indefinite. You cannot say what direction it will take, or to what particular results it is likely in any special instance to lead. Marked differences sometimes occur even between the young of the same litter, or between the seedlings116 sown from the same capsule. As a rule, the variations exhibit themselves in connection with sexual reproduction; but sometimes, as in the case of 'sporting plants,' a new bud suddenly produces leaves or flowers of a different character from the rest of those on the self-same stem, thus showing that the tendency to vary is inherent, as it were, in the organism itself. Upon this[Pg 91] fundamental fact of the existence in nature of numerous and indefinite variations, the whole theory of natural selection is ultimately built up. In illustrating118 by example the immense variability of domesticated creatures, Darwin lays great stress upon the case of pigeons, with which he was familiar from his long experience as a breeder and fancier in his own home at Down. Naturalists are almost universally of opinion that all the breeds of domestic pigeons, from the carrier to the tumbler, from the runt to the fantail, are alike descended119 from the wild rock pigeon of the European coasts. The immense amount of variation which this original species has undergone in domestication may be seen by comparing the numberless breeds of pigeon now exhibited at all our poultry120 shows with one another.
But variation gives us only half the elements of the ultimate problem, even in the case of domestic kinds. For the other half, we must have recourse to human selection, which, by picking out for seed or breeding purposes certain specially favoured varieties, has produced at last all the purposive or intentional121 diversity between the different existing stocks or breeds. In these artificially produced domestic races we see everywhere special adaptations to man's particular use or fancy. The dray-horse has been fashioned for purposes of strength and sure-footedness in draught122, the race-horse for purposes of fleetness in running. In the fox-hound, man has encouraged the special properties that tend to produce a good day's hunting; in the sheepdog, those that make for the better maintenance and safety of a herd123. The cauliflower is a cabbage, with specialised and somewhat abortive124 flower-heads; the[Pg 92] fuller's teasel is a sport of the wild form, with curved hooks specially adapted by a freak of nature for the teasing of wool. So in every case man, by deliberately125 picking out for breeding or seeding purposes the accidental variations which happened best to suit his own needs, has succeeded at last in producing races admirably fitted in the minutest particulars for the special functions to which they are applied. There appears indeed to be hardly any limit to the almost infinite plasticity and modifiability of domestic animals. 'It would seem,' said a great sheep-breeder, speaking of sheep, 'as if farmers had chalked out upon a wall a form perfect in itself, and then proceeded to give it existence.'
Now, what is thus true within narrow limits, and in a short space of time about the deliberate action of man, Darwin showed to be also true within wider limits and spread over longer geological epochs about the unconscious action of nature. And herein consisted his great advance upon the earlier evolutionism of Lamarck, Goethe, and Erasmus Darwin. For while these instinctive126 pioneers of the evolutionary spirit saw clearly that animals and plants betrayed signs of common descent from one or a few original ancestors, they did not see what was the mechanism127 by which such organisms had been differentiated128 into so many distinct genera and species. They caught, indeed, at the analogy of variation under domestication and in the wild state, but they missed the subtler and deeper analogy between human and natural selection. Now, variation alone would give us a world consisting not of definite kinds fairly well demarcated one from the other, but of innumerable unclassified and unorganisable individuals, all shading off[Pg 93] indefinitely one into the other, and incapable129 of being reduced by human ingenuity130 to any orderly hierarchical system. Furthermore, it would give us creatures without special adaptation of any kind to the peculiar131 circumstances of their own environment. To account for adaptation, for the almost perfect fitness of every plant and every animal to its position in life, for the existence (in other words) of definitely correlated parts and organs, we must call in the aid of survival of the fittest. Without that potent132 selective agent, our conception of the becoming of life is a mere chaos133; order and organisation134 are utterly135 inexplicable136 save by the brilliant illuminating137 ray of the Darwinian principle. That is why Darwin destroyed at one blow the specious138 arguments of the early teleologists; he showed that where Chambers139 and even Erasmus Darwin had seen the working of a final cause, we ought rather to recognise the working of an efficient cause, whose outcome necessarily but fallaciously simulates the supposed features of an a priori finality.
From art, then, Darwin harks back once more to nature. He proceeds to show that variability occurs among all wild plants and animals, though not so frequently under ordinary circumstances as in the case of domesticated species. Individual differences everywhere occur between plant and plant, between animal and animal. Sometimes these differences are so very numerous that it is impossible to divide the individuals at all into well-marked kinds; for example, among British wild-roses, brambles, hawkweeds and epilobes, with a few other very variable families, Babington makes as many as 251 distinct species, where Bentham[Pg 94] gives only 112—a margin140 of 139 doubtful forms of shadowy indefiniteness. Varieties, in fact, are always arising, and dominant141 species in particular always tend to vary most in every direction. The reason why variation is not so marked in the wild state as under domestication is of course because the conditions are there less diverse; but where the conditions of wild things are most diverse, as in the case of dominant kinds, which range over a wide space of country or of ocean, abundant individual variations habitually142 occur. Local varieties thus produced are regarded by Darwin as incipient143 species: they are the raw material on which natural selection gradually exerts itself in the struggle for existence.
Granting individual variability, then, how do species arise in nature? And how are all the exquisite144 adaptations of part to whole, and of whole to environment, gradually initiated145, improved, and perfected?
Here Malthus and the struggle for life come in to help us.
For the world is perpetually over-populated. It is not, as many good people fearfully imagine, on a half-comprehension of the Malthusian principle, shortly going to be over-populated; it is now, it has always been, and it will always be, pressed close up to the utmost possible limit of population. Reproduction is everywhere and in all species for ever outrunning means of subsistence; and starvation or competition is for ever keeping down the number of the offspring to the level of the average or normal supply of raw material. A single red campion produces in a year three thousand seeds; but there are not this year three thousand times[Pg 95] as many red campions as there were last summer, nor will there be three thousand times as many more in the succeeding season. The roe146 of a cod147 contains sometimes nearly ten million eggs; but supposing each of these produced a young fish which arrived at maturity, the whole sea would immediately become a solid mass of closely packed codfish. Linn?us reckoned that if an annual plant had two seeds, each of which produced two seedlings in the succeeding season, and so on continually, in twenty years their progeny148 would amount to a million plants. A struggle for existence necessarily results from this universal tendency of animals and plants to increase faster than the means of subsistence, whether those means be food, as in the first case, or carbonic acid, water, and sunshine as in the second. Animals are all perpetually battling with one another for the food-supply of the moment; plants are perpetually battling with one another for their share of the soil, the rainfall, and the sunshine.
The case of the plant is a very important one to understand in this connection, because it is probable that most people greatly misunderstand the biological meaning of the phrase 'struggle for existence.' They imagine that the struggle is chiefly conducted between different species, whereas in reality it is chiefly conducted between members of the same species. It is not so much the battle between the tiger and the antelope149, between the wolf and the bison, between the snake and the bird, that ultimately results in natural selection or survival of the fittest, as the struggle between tiger and tiger, between bison and bison, between snake and snake, between antelope and antelope. A human[Pg 96] analogy may help to make this difficult principle a little clearer. The baker150 does not fear the competition of the butcher in the struggle for life: it is the competition of the other bakers151 that sometimes inexorably crushes him out of existence. The lawyer does not press hard upon the doctor, nor the architect upon the journeyman painter. A war in the Soudan or in South Africa is far less fatal to the workman in our great towns than the ceaseless competition of his fellow-workmen. It is not the soldier that kills the artisan, but the number of other artisans who undersell him and crowd to fill up every vacant position. In this way the great enemies of the individual herbivore are not the carnivores, but the other herbivores. The lion eats the antelope, to be sure; but the real struggle lies between lion and lion for a fair share of meat, or between antelope and antelope for a fair share of pasturage. Homo homini lupus, says the old proverb, and so, we may add, in a wider sense, lupus lupo lupus, also. Of course, the carnivore plays a great part in the selective process; but he is the selector only; the real competition is between the selected. Now, let us take the case of the plant. A thousand seedlings occupy the space where few alone can ultimately grow; and between these seedlings the struggle is fierce, the strongest and best adapted ultimately surviving. To take Darwin's own example, the mistletoe, which is a parasite152, cannot truly be said to struggle with the apple tree on which it fastens; for if too many parasites153 cover a tree, it perishes, and so they kill themselves as well as their host, all alike dying together. But several seedling117 mistletoes growing together on the same branch may[Pg 97] fairly be said to struggle with one another for light and air; and since mistletoe seeds are disseminated154 by birds and dropped by them in the angles of branches, the mistletoe may also be said to compete with other berry-bearing bushes, like cornel and hawthorn155, for the ministrations of the fruit-eating birds. The struggle is fierce between allied156 kinds, and fiercest of all between individual members of the same species.
Owing to this constant struggle, variations, however slight, and from whatever cause arising, if in any degree profitable to the individual which presents them, will tend to the preservation of the particular organism, and, being on the average inherited by its offspring, will similarly tend to increase and multiply in the world at large. This is the principle of natural selection or survival of the fittest—the great principle which Darwin and Wallace added to the evolutionism of Lamarck and his successors.
Let us take a single concrete example. In the desert, with its monotonous157 sandy colouring, a black insect or a white insect, still more a red insect or a blue insect, would be immediately detected and promptly158 devoured159 by its natural enemies, the birds and lizards160. But any greyish or yellowish insects would be less likely to attract attention at first sight, and would be overlooked as long as there were any more conspicuous161 individuals of their own kind about for the birds and lizards to feed on at their leisure. Hence, in a very short time, the desert would be depopulated of all but the greyest and yellowest insects; and among these the birds would pick out those which differed most markedly in hue or shade from the sand around them. But those[Pg 98] which happened to vary most in the direction of a sandy or spotty colour would be most likely to survive, and to become the parents of future generations. Thus, in the course of long ages, all the insects which inhabit deserts have become sand-coloured; because the least sandy were perpetually picked out for destruction by their ever-watchful foes162, while the most sandy escaped and multiplied and replenished163 the earth with their own likes.
Conversely, the birds and the lizards again would probably begin by being black, and white, and blue, and green, like most other birds and lizards in the world generally. But the insect would have ample warning of the near approach of such conspicuous self-advertising enemies, and would avoid them accordingly whenever they appeared within range of his limited vision, either by lying close, or by shamming164 death, or by retreating precipitately165 to holes and crannies. Therefore, whatever individual birds or lizards happened to vary most in the direction of grey or sand-colour, and so to creep unobserved upon the unguarded insects, would succeed best on the average in catching166 beetles167 or desert grasshoppers168. Hence, by the slow dying out of the more highly coloured and distinctive insect-eaters, before the severe competition of the greyest and sandiest, all the birds and lizards of the desert have become at last as absolutely sand-coloured as the insects themselves. Only the greyest insect could escape the bird; only the greyest bird, en revanche, could surprise and devour50 the unwary insect.
Sir Charles Lyell and the elder De Candolle had already seen the great importance of the struggle for existence in the organic world, but neither of them had observed the magnificent corollary of natural selection,[Pg 99] which flows from it almost as a mathematical necessity when once suggested; for, given indefinite variability, and a geometrical, rate of increase, it must needs follow that some varieties will be better suited to the circumstances than others, and therefore that they will survive on the average in increased proportions. A passage from one of Lyell's early letters will show how near he too went to this great luminous26 generalisation, and yet how utterly he missed the true implications of his own vague and chaotic169 idea. He writes thus to Sir John Herschel in 1836, while Darwin was still but homeward bound on the voyage of the 'Beagle':—
'In regard to the origination of new species, I am very glad to find that you think it probable that it may be carried on through the intervention170 of intermediate causes.... An insect may be made in one of its transformations171 to resemble a dead stick, or a leaf, or a lichen172, or a stone, so as to be somewhat less easily found by its enemies; or if this would make it too strong, an occasional variety of the species may have this advantage conferred on it; or if this would be still too much, one sex of a certain variety. Probably there is scarcely a dash of colour on the wing or body of which the choice would be quite arbitrary, or which might not affect its duration for thousands of years.'
Now, this comes in some ways perilously173 near to Darwin indeed; but in the most important point of all it is wide apart from him as the pole is from the equator. For Lyell thought of all this as a matter of external teleological174 arrangement; he imagined a deliberate power from outside settling it all by design beforehand, and granting to varieties or species these[Pg 100] special peculiarities175 in a manner that was at bottom essentially176 supernatural, or in other words miraculous177; whereas Darwin thinks of it as the necessary result of the circumstances themselves, an inevitable178 outcome of indefinite variability plus the geometrical rate of increase. Where Lyell sees a final cause, Darwin sees an efficient cause; and this distinction is fundamental. It marks Darwin's position as that of a great philosophical thinker, who can dash aside at once all metaphysical cobwebs, and penetrate179 to the inmost recesses180 of things, unswerved by the vain but specious allurements181 of obvious and misleading teleological fallacies.
Darwin also laid great stress on the immense complexity182 of the relations which animals and plants bear to one another, in the struggle for existence. For example, on the heathy uplands near Farnham in Surrey, large spaces were at one time enclosed, on which, within ten years, self-grown fir-trees from the wind-borne seeds of distant clumps183 sprang up so thickly as actually to choke one another with their tiny branches. All over the heaths outside, when Darwin looked for them, he could not find a single fir, except the old clumps on the hilltops, from which the seedlings themselves had originally sprung. But, on looking closer among the stems of the heath, he descried a number of very tiny firs, which had been perpetually browsed184 down by the cattle on the commons; and one of them, with twenty-six rings of growth, had during many years endeavoured unsuccessfully to raise its head above the surrounding heather. Hence, as soon as the land was enclosed, and the cattle excluded, it became covered at once with a thick growth of vigorous[Pg 101] young fir-trees. Yet who would ever have supposed beforehand that the mere presence or absence of cattle would absolutely have determined185 the very existence of the Scotch186 fir throughout a wide range of well-adapted sandy English upland?
To take another curious instance mentioned by Darwin. In Paraguay, unlike the greater part of neighbouring South America, neither horses nor cattle have ever run wild. This is due to the presence of a parasitic187 fly, which lays its eggs in their bodies when first born, the maggots killing188 off the tender young in their first stages. But if any cause were to alter the number of the dangerous flies, then cattle and wild horses would abound189; and this would alter the vegetation, as Darwin himself observed in other parts of America; and the change in the vegetation would affect the insects; and that again the insectivorous birds; and so on in ever widening circles of incalculable complexity. Once more, to quote the most famous instance of all, the visits of humble-bees are absolutely necessary in order to place the pollen190 in the right position for setting the seeds of purple clover. Heads from which Darwin excluded the bees produced no seeds at all. Hence, if humble-bees became extinct in England, the red clover, too, would die off: and indeed, in New Zealand, where there are no humble-bees, and where the efforts to introduce them for this very purpose have been uniformly unsuccessful, the clover never sets its seed at all, and fresh stocks have to be imported at great expense every year from Europe. But the number of humble-bees in any district largely depends upon the number of field-mice, which destroy the combs and[Pg 102] nests in immense quantities. The number of mice, again, is greatly affected191 by the proportion of cats in the neighbourhood; so that Colonel Newman, who paid much attention to this subject, found humble-bees most numerous in the neighbourhood of villages and small towns, an effect which he attributed to the abundance of cats, and the consequent scarcity192 of the destructive field-mice. Yet here once more, who could suppose beforehand that the degree to which the purple clover set its seeds was in part determined by the number of cats kept in houses in the surrounding district?
One of Darwin's own favourite examples of the action of natural selection, which he afterwards expanded largely in his work on Orchids193 and in several other volumes, is that which relates to the origin of conspicuous flowers. Many plants have a sweet excretion, which is eliminated sometimes even by the leaves, as in the case of the common laurel. This juice, though small in quantity, is eagerly sought and eaten by insects. Now let us suppose that, in some variety of an inconspicuous flower, similar nectar was produced in the neighbourhood of the petals194 and stamens. Insects, in seeking the nectar, would dust their bodies over with the pollen, and would carry it away with them to the next flower visited. This would result in an act of crossing; and that act, as Darwin afterwards abundantly proved in a separate and very laborious195 treatise96, gives rise to exceptionally vigorous seedlings, which would therefore have the best chance of flourishing and surviving in the struggle for existence. The flowers which produced most honey would oftenest be visited, and oftenest crossed; so that they would finally form a new[Pg 103] species. The more brightly coloured among them, again, would be more readily discriminated196 than the less brightly coloured; and this would give them such an advantage that in the long run, as we actually see, almost all habitually insect-fertilised flowers would come to have brilliant petals. The germ of this luminous idea, once more, is to be found in Sprengel's remarkable197 work on the fertilisation of flowers—a work far in advance of its time in many ways, and to which Darwin always expressed his deep obligations; but, as in so many other instances, while Sprengel looked upon all the little modifications and adaptations of flower and insect to one another as the result of distinct creative design, Darwin looked upon them as the result of natural selection, working upon the basis of indeterminate spontaneous variations.
How do these variations arise? Not by chance, of course (for in the strict scientific sense nothing on earth can be considered as really fortuitous), but as the outcome for the most part of very minute organic causes, whose particular action it is impossible for us to predict with our present knowledge. Some physical cause in each case there must necessarily be; and indeed it is often possible to show that certain changes of condition in the parent do result in variations in the offspring, though what special direction the variation will take can never be foretold198 with any accuracy. In short, our ignorance of the laws of variation is profound, but our knowledge of the fact is clear and certain. The fact alone is essential to the principle of natural selection; the cause, though in itself an interesting subject of inquiry199, may be safely laid aside for the present as[Pg 104] comparatively unimportant. What we have actually given to us in the concrete universe is, organisms varying perpetually in minute points, and a rapid rate of increase causing every minute point of advantage to be exceptionally favoured in the struggle for existence.
But Darwin is remarkable among all broachers of new theories for the extraordinary candour and openness of his method. He acknowledged beforehand all the difficulties in the way of his theory, and though he himself confessed that some of them were serious (a statement which subsequent research has often rendered unnecessary), he met many of them with cogent200 arguments by anticipation201, and demolished202 objections before they could even be raised against him by hostile critics. Of these objections, only two need here be mentioned. The first is the question, why is not all nature even now a confused mass of transitional forms? Why do genera and species exist as we see them at present in broad distinction one from the other? To this Darwin answers rightly that, where the process of species-making is still going on, we do actually find fine gradations and transitional forms existing between genera, varieties, and species.[3] But, furthermore, as natural selection acts solely203 by the preservation of useful modifications, each better-adapted new form will always tend in a fully103 stocked country to oust204 and exterminate205 its own unimproved parent type, as well as all other competing but less perfect varieties. Thus natural selection and extinction of intermediates go for ever[Pg 105] hand in hand. The more perfect the new variety, the more absolutely will it kill off the intermediate forms. The second great difficulty lies in the question of the origin of instinct, which, as Darwin shows, by careful inductive instances, may have arisen by the slow and gradual accumulation of numerous slight yet profitable variations.
I have dwelt at some length upon those portions of the 'Origin of Species' which deal in detail with the theory of natural selection, the chief contribution which Darwin made to the evolutionary movement, because it is impossible otherwise fully to understand the great gulf206 which separates his evolutionism from the earlier evolutionism of Lamarck and his followers207. But it is impracticable here to give any idea of the immense wealth of example and illustration which Darwin brought to the elucidation208 of every part of his complex problem. In order to gain a full conception of this side of his nature, we must turn to the original treatise itself, and still more to the subsequent volumes in which the ground-work of observations and experiments on which he based his theory was more fully detailed for the specialist public.
The remainder of Darwin's epoch-making work deals, strictly209 speaking, rather with the general theory of 'descent with modification' than with the special doctrine of natural selection. It restates and reinforces, by the light of the new additional concept, and with fuller facts and later knowledge, the four great arguments already known in favour of organic evolution as a whole, the argument from Geological Succession, the argument from Geographical Distribution, the argument[Pg 106] from Embryological Development, and the argument from Classificatory Affinities211. Each of these we may briefly212 summarise213.
The geological record is confessedly imperfect. At the time when Darwin first published the 'Origin of Species,' it had disclosed to our view comparatively few intermediate or transitional forms between the chief great classes of plants or animals; since that time, in singular confirmation214 of the Darwinian hypothesis, it has disclosed an immense number of such connecting types, amongst which may be more particularly noticed the 'missing links' between the birds and reptiles216, the ancestors of the horses, the camels, and the pigs, and the common progenitor217 of the ruminants and the pachyderms, two great groups classed by Cuvier as distinct orders—all of which instances were incorporated by Darwin in later editions of his 'Origin of Species.' But, apart from these special and newly discovered cases, the whole general course of geological history 'agrees admirably with the theory of descent with modification through variation and natural selection.' The simpler animals of early times are followed by the more complex and more specialised animals of later geological periods. As each main group of animals appears upon the stage of life, it appears in a very central and 'generalised' form; as time goes on, we find its various members differing more and more widely from one another, and assuming more and more specialised adaptive forms. And in each country it is found, as a rule, that the extinct animals of the later formations bear a close general resemblance and relationship to the animals which now inhabit the same regions. For example,[Pg 107] the fossil mammals from the Australian caves are nearly allied to the modern kangaroos, phalangers, and wombats218; and the gigantic extinct sloths219 and armadillos of South America are reproduced in their smaller representatives at the present day. So, too, the moa of New Zealand was a huge apteryx; and the birds disentombed from the bone-caves of Brazil show close affinities to the toucans220 and jacanars that still scream and flit in countless221 flocks among Brazilian forests. The obvious implication is that the animals now inhabiting any given area are the modified descendants of those that formerly222 inhabited it. 'On the theory of descent with modification, the great law of the succession of the same types within the same areas is at once explained.'
This last consideration leads us up to the argument from Geographical Distribution. In considering the various local faunas223 and floras224 on the face of the globe, no point strikes one more forcibly than the fact that neither their similarities nor their dissimilarities can be accounted for by climate or physical conditions. The animals of South Africa do not in the least resemble the animals of the corresponding belt of South America; the Australian beasts and birds and trees are utterly unlike those of France and Germany; the fishes and crustaceans225 of the Pacific at Panama are widely different from those of the Caribbean at the same point, separated from them only by the narrow belt of intervening isthmus227. On the other hand, within the same continuous areas of sea or land, however great the differences of physical conditions, we find everywhere closely related types in possession of the most distinct and[Pg 108] varied situations. On the burning plains of La Plata we get the agouti and the bizcacha as the chief rodents228; we ascend229 the Cordillera, and close to the eternal snows we discover, not hares and rabbits like those of Europe, but a specialised chilly230 mountain form of the same distinctly South American type. We turn to the rivers, and we see no musk-rat or beaver231, but the coypu and capybara, slightly altered varieties of the original bizcacha ancestor. Australia has no wolf, but it has instead fierce and active carnivorous marsupials; it has no mice, but some of its tiny kangaroo-like creatures fulfil analogous232 functions in its animal economy. Everywhere the evidence points to the conclusion that local species have been locally evolved from pre-existing similar species. The oceanic isles233, of which Darwin had had so large an experience, and especially his old friends the Galapagos, come in usefully for this stage of the question. They are invariably inhabited, as Darwin pointed234 out, and as Wallace has since abundantly shown in the minutest detail, by waifs and strays from neighbouring continents, altered and specialised by natural selection in accordance with the conditions of their new habitat. As a rule, they point back to the districts whence blow the strongest and most prevalent winds; and the modifications they have undergone are largely dependent upon the nature of the other species with which they have to compete, or to whose habits they must needs accommodate themselves. In such cases it is easy to see how far Darwin's special conception of natural selection helps to explain and account for facts not easily explicable by the older evolutionism of mere descent with modification.[Pg 109]
Embryology, the study of early development in the individual animal or plant, also throws much side light upon the nature and ancestry235 of each species or family. For example, gorse, which is a member of the pea-flower tribe, has in its adult stage solid, spiny236, thorn-like leaves, none of which in the least resemble the foliage237 of the clover, to which it is closely related; but the young seedling in its earliest stages has trefoil leaves, which only slowly pass by infinitesimal gradations into flat blades and finally into the familiar defensive238 prickles. Here, natural selection under stress of herbivorous animals on open heaths and commons has spared only those particular gorse-bushes which varied in the direction of the stiffest and most inedible239 foliage; but the young plant in its first days still preserves for us the trefoil leaf which it shared originally with a vast group of clover-like congeners. The adult barnacle, once more, presents a certain fallacious external resemblance to a mollusk240, and was actually so classed even by the penetrating and systematic241 intellect of Cuvier; but a glance at the larva shows an instructed eye at once that it is really a shell-making and abnormal crustacean226. On a wider scale, the embryos242 of mammals are at first indistinguishable from those of birds or reptiles; the feet of lizards, the hoofs243 of horses, the hands of man, the wings of the bat, the pinions244 of birds, all arise from the same fundamental shapeless bud, in the same spot of an almost identical embryo210. Even the human foetus, at a certain stage of its development, is provided with gill-slits, which point dimly back to the remote ages when its ancestor was something very like a fish. The embryo is a picture, more or less[Pg 110] obscured and blurred245 in its outline, of the common progenitor of a whole great class of plants or animals.
Finally, classification points in the same way to the affiliation246 of all existing genera and species upon certain early divergent ancestors. The whole scheme of the biological system, as initiated by Linn?us and improved by Cuvier, Jussieu, De Candolle, and their successors, is essentially that of a genealogical tree. The prime central vertebrate ancestor—to take the case of the creatures most familiar to the general reader—appears to have been an animal not unlike the existing lancelet, a mud-haunting, cartilaginous, undeveloped fish, whose main lineaments are also embryologically preserved for us in the ascidian larva and the common tadpole247. From this early common centre have been developed, apparently248, in one direction the fishes, and in another the amphibian249 tribes of frogs, newts, salamanders, and axolotls. From an early amphibian, again, the common ancestor of birds, reptiles, and mammals seems to have diverged250: the intermediate links between bird and reptile215 being faintly traced among the extinct deinosaurians and the arch?opteryx, some years subsequently to the first appearance of the 'Origin of Species;' while the ornithorhyncus, which to some extent connects the mammals, and especially the marsupials, with the lower egg-laying types of vertebrate, was already well-known and thoroughly251 studied before the publication of Darwin's great work. Throughout, the indications given by all the chief tribes of animals and plants point back to slow descent and divergence73 from common ancestors; and all the subsequent course of pal6?ontological research has supplied us rapidly, one after[Pg 111] another, with the remains252 of just such undifferentiated family starting-points.
Stress has mainly been laid, in this brief and necessarily imperfect abstract, on the essentially Darwinian principle of natural selection. But Darwin did not himself attribute everything to this potent factor in the moulding of species. 'I am convinced,' he wrote pointedly253 in the introduction to his first edition, 'that natural selection has been the main but not the exclusive means of modification.' He attributed considerable importance as well to the Lamarckian principle of use and disuse, already so fully insisted upon before him by Mr. Herbert Spencer. The chief factors in his compound theory, as given in his own words at the end of his work, areas follows: 'Growth with Reproduction; Inheritance, which is almost implied by reproduction; Variability, from the indirect and direct action of the conditions of life, and from use and disuse; a Ratio of Increase, so high as to lead to a Struggle for Life, and as a consequence to Natural Selection, entailing254 Divergence of Character, and the Extinction of the less improved forms. Thus, from the war of nature, from famine and death, the most exalted255 object which we are capable of conceiving, namely, the production of the higher animals, directly follows.'
Such was the simple and inoffensive-looking bombshell which Darwin launched from his quiet home at Down into the very midst of the teleological camp in the peaceful year 1859. Subsequent generations will remember the date as a crisis and turning-point in the history of mankind.
[2] The remainder of the present chapter, which consists almost entirely256 of an exposition of the doctrine of natural selection, may safely be skipped by the reader already well acquainted with the Origin of Species. The abstract is taken for the most part from the latest and fullest enlarged edition, but attention is usually called in passing to the points which did not appear in the first issue of 1859.
[3] The researches of Seebohm and others have since proved that this is really the case to a far greater extent than Darwin was aware of in 1859, or, indeed, till many years afterward20.
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1
naturalist
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| n.博物学家(尤指直接观察动植物者) | |
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zoologists
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| 动物学家( zoologist的名词复数 ) | |
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geographical
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| adj.地理的；地区(性)的 | |
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avowed
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| adj.公开声明的，承认的v.公开声明，承认( avow的过去式和过去分词) | |
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enigma
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| n.谜，谜一样的人或事 | |
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pal
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| n.朋友，伙伴，同志；vi.结为友 | |
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naturalists
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| n.博物学家( naturalist的名词复数 )；（文学艺术的）自然主义者 | |
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inhaled
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| v.吸入( inhale的过去式和过去分词 ) | |
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mimicking
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| v.（尤指为了逗乐而）模仿( mimic的现在分词 )；酷似 | |
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veins
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| n.纹理；矿脉( vein的名词复数 )；静脉；叶脉；纹理 | |
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diversified
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| adj.多样化的，多种经营的v.使多样化，多样化( diversify的过去式和过去分词 )；进入新的商业领域 | |
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membranes
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| n.（动物或植物体内的）薄膜( membrane的名词复数 )；隔膜；（可起防水、防风等作用的）膜状物 | |
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hieroglyphs
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| n.象形字（如古埃及等所用的）( hieroglyph的名词复数 )；秘密的或另有含意的书写符号 | |
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modification
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| n.修改，改进，缓和，减轻 | |
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forth
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| adv.向前；向外，往外 | |
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indefatigable
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| adj.不知疲倦的，不屈不挠的 | |
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gathering
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| n.集会，聚会，聚集 | |
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solitude
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| n. 孤独; 独居,荒僻之地,幽静的地方 | |
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isolation
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| n.隔离，孤立，分解，分离 | |
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afterward
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| adv.后来；以后 | |
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lavished
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| v.过分给予，滥施( lavish的过去式和过去分词 ) | |
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prodigal
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| adj.浪费的，挥霍的，放荡的 | |
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memoir
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| n.[pl.]回忆录，自传；记事录 | |
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jealousy
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| n.妒忌，嫉妒，猜忌 | |
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immediate
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| adj.立即的；直接的，最接近的；紧靠的 | |
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luminous
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| adj.发光的，发亮的；光明的；明白易懂的；有启发的 | |
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sincerity
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| n.真诚，诚意；真实 | |
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generosity
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| n.大度，慷慨，慷慨的行为 | |
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waived
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| v.宣布放弃( waive的过去式和过去分词 )；搁置；推迟；放弃（权利、要求等） | |
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admiration
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| n.钦佩，赞美，羡慕 | |
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appreciation
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| n.评价；欣赏；感谢；领会，理解；价格上涨 | |
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distinctive
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| adj.特别的，有特色的，与众不同的 | |
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penetrating
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| adj.（声音）响亮的，尖锐的adj.（气味）刺激的adj.（思想）敏锐的，有洞察力的 | |
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investigator
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| n.研究者，调查者，审查者 | |
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applied
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| adj.应用的；v.应用，适用 | |
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scattered
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| adj.分散的，稀疏的；散步的；疏疏落落的 | |
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disposition
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| n.性情，性格；意向，倾向；排列，部署 | |
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mere
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| adj.纯粹的；仅仅，只不过 | |
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radical
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| n.激进份子，原子团，根号；adj.根本的，激进的，彻底的 | |
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exertion
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| n.尽力，努力 | |
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descried
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| adj.被注意到的，被发现的，被看到的 | |
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vividly
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| adv.清楚地，鲜明地，生动地 | |
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naval
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| adj.海军的，军舰的，船的 | |
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enunciates
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| n.（清晰地）发音( enunciate的名词复数 )；确切地说明v.（清晰地）发音( enunciate的第三人称单数 )；确切地说明 | |
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modifications
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| n.缓和( modification的名词复数 )；限制；更改；改变 | |
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requisite
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| adj.需要的，必不可少的；n.必需品 | |
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premature
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| adj.比预期时间早的；不成熟的，仓促的 | |
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prematurely
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| adv.过早地，贸然地 | |
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prey
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| n.被掠食者，牺牲者，掠食；v.捕食，掠夺，折磨 | |
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devour
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| v.吞没；贪婪地注视或谛听，贪读；使着迷 | |
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nourishment
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| n.食物，营养品；营养情况 | |
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fecundity
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| n.生产力；丰富 | |
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prolific
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| adj.丰富的，大量的；多产的，富有创造力的 | |
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54
vacancies
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| n.空房间( vacancy的名词复数 )；空虚；空白；空缺 | |
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preoccupied
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| adj.全神贯注的，入神的；被抢先占有的；心事重重的v.占据（某人）思想，使对…全神贯注，使专心于( preoccupy的过去式) | |
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hardier
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| 能吃苦耐劳的，坚强的( hardy的比较级 )； （植物等）耐寒的 | |
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57
robust
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| adj.强壮的，强健的，粗野的，需要体力的，浓的 | |
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58
maturity
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| n.成熟；完成；(支票、债券等)到期 | |
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59
concealment
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| n.隐藏, 掩盖，隐瞒 | |
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60
vicissitudes
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| n.变迁，世事变化；变迁兴衰( vicissitude的名词复数 )；盛衰兴废 | |
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61
ordeal
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| n.苦难经历，（尤指对品格、耐力的）严峻考验 | |
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62
precisely
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| adv.恰好，正好，精确地，细致地 | |
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63
propounded
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| v.提出（问题、计划等）供考虑[讨论]，提议( propound的过去式和过去分词 ) | |
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64
eminent
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| adj.显赫的，杰出的，有名的，优良的 | |
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65
entails
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| 使…成为必要( entail的第三人称单数 )； 需要； 限定继承； 使必需 | |
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66
stimulate
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| vt.刺激，使兴奋；激励，使…振奋 | |
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67
extinction
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| n.熄灭，消亡，消灭，灭绝，绝种 | |
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68
supplanted
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| 把…排挤掉，取代( supplant的过去式和过去分词 ) | |
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69
preservation
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| n.保护，维护，保存，保留，保持 | |
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70
acting
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| n.演戏，行为，假装；adj.代理的，临时的，演出用的 | |
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71
generic
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| adj.一般的，普通的，共有的 | |
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72
divergences
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| n.分叉( divergence的名词复数 )；分歧；背离；离题 | |
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73
divergence
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| n.分歧，岔开 | |
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74
noted
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| adj.著名的，知名的 | |
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75
frankly
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| adv.坦白地，直率地；坦率地说 | |
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76
simultaneously
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| adv.同时发生地，同时进行地 | |
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77
calculus
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| n.微积分；结石 | |
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78
Neptune
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| n.海王星 | |
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79
interpretation
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| n.解释，说明，描述；艺术处理 | |
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80
hieroglyphics
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| n.pl.象形文字 | |
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81
inscriptions
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| （作者）题词( inscription的名词复数 )； 献词； 碑文； 证劵持有人的登记 | |
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82
doctrine
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| n.教义；主义；学说 | |
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83
correlation
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| n.相互关系，相关，关连 | |
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84
spectrum
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| n.谱，光谱，频谱；范围，幅度，系列 | |
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85
evolutionary
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| adj.进化的；演化的，演变的；[生]进化论的 | |
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86
virgin
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| n.处女，未婚女子；adj.未经使用的；未经开发的 | |
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87
forerunners
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| n.先驱( forerunner的名词复数 )；开路人；先兆；前兆 | |
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88
impetus
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| n.推动，促进，刺激；推动力 | |
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89
irresistible
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| adj.非常诱人的，无法拒绝的，无法抗拒的 | |
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90
sketch
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| n.草图；梗概；素描；v.素描；概述 | |
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91
imposing
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| adj.使人难忘的，壮丽的，堂皇的，雄伟的 | |
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92
fabric
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| n.织物，织品，布；构造，结构，组织 | |
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93
immortal
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| adj.不朽的；永生的，不死的；神的 | |
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94
contemplated
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| adj. 预期的 动词contemplate的过去分词形式 | |
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95
detailed
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| adj.详细的，详尽的，极注意细节的，完全的 | |
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96
treatise
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| n.专著；(专题)论文 | |
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97
treatises
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| n.专题著作，专题论文，专著( treatise的名词复数 ) | |
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98
domestication
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| n.驯养，驯化 | |
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99
Vogue
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| n.时髦，时尚；adj.流行的 | |
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100
prosecute
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| vt.告发；进行；vi.告发，起诉，作检察官 | |
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101
cogency
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| n.说服力；adj.有说服力的 | |
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102
wilfully
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| adv.任性固执地；蓄意地 | |
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103
fully
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| adv.完全地，全部地，彻底地；充分地 | |
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104
unprecedented
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| adj.无前例的，新奇的 | |
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105
reposeful
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| adj.平稳的，沉着的 | |
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106
philosophical
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| adj.哲学家的，哲学上的，达观的 | |
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107
domesticated
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|
| adj.喜欢家庭生活的；（指动物）被驯养了的v.驯化( domesticate的过去式和过去分词 ) | |
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108
aptitude
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| n.(学习方面的)才能，资质，天资 | |
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109
faculty
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| n.才能；学院，系；(学院或系的)全体教学人员 | |
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110
explicitly
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| ad.明确地，显然地 | |
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111
specially
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| adv.特定地；特殊地；明确地 | |
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112
dexterously
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| adv.巧妙地，敏捷地 | |
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113
hue
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| n.色度；色调；样子 | |
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114
minor
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| adj.较小(少)的，较次要的；n.辅修学科；vi.辅修 | |
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115
varied
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| adj.多样的，多变化的 | |
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116
seedlings
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| n.刚出芽的幼苗( seedling的名词复数 ) | |
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117
seedling
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| n.秧苗，树苗 | |
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118
illustrating
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| 给…加插图( illustrate的现在分词 )； 说明； 表明； （用示例、图画等）说明 | |
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119
descended
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| a.为...后裔的，出身于...的 | |
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120
poultry
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| n.家禽，禽肉 | |
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121
intentional
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| adj.故意的，有意（识）的 | |
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122
draught
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| n.拉，牵引，拖；一网（饮，吸，阵)；顿服药量，通风；v.起草，设计 | |
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123
herd
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| n.兽群，牧群；vt.使集中，把…赶在一起 | |
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124
abortive
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| adj.不成功的，发育不全的 | |
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125
deliberately
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| adv.审慎地；蓄意地；故意地 | |
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126
instinctive
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| adj.(出于)本能的；直觉的；(出于)天性的 | |
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127
mechanism
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| n.机械装置；机构，结构 | |
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128
differentiated
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| 区分，区别，辨别( differentiate的过去式和过去分词 )； 区别对待； 表明…间的差别，构成…间差别的特征 | |
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129
incapable
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| adj.无能力的，不能做某事的 | |
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130
ingenuity
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| n.别出心裁；善于发明创造 | |
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131
peculiar
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| adj.古怪的，异常的；特殊的，特有的 | |
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132
potent
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| adj.强有力的，有权势的；有效力的 | |
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133
chaos
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| n.混乱，无秩序 | |
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134
organisation
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| n.组织，安排，团体，有机休 | |
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135
utterly
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| adv.完全地，绝对地 | |
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136
inexplicable
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| adj.无法解释的，难理解的 | |
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137
illuminating
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| a.富于启发性的，有助阐明的 | |
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138
specious
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| adj.似是而非的；adv.似是而非地 | |
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139
chambers
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| n.房间( chamber的名词复数 )；（议会的）议院；卧室；会议厅 | |
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140
margin
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| n.页边空白；差额；余地，余裕；边，边缘 | |
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141
dominant
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|
| adj.支配的，统治的；占优势的；显性的；n.主因，要素，主要的人(或物)；显性基因 | |
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142
habitually
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| ad.习惯地，通常地 | |
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143
incipient
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| adj.起初的，发端的，初期的 | |
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144
exquisite
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| adj.精美的；敏锐的；剧烈的，感觉强烈的 | |
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145
initiated
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| n. 创始人 adj. 新加入的 vt. 开始，创始，启蒙，介绍加入 | |
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146
roe
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| n.鱼卵；獐鹿 | |
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147
cod
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| n.鳕鱼；v.愚弄；哄骗 | |
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148
progeny
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| n.后代，子孙；结果 | |
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149
antelope
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| n.羚羊；羚羊皮 | |
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150
baker
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| n.面包师 | |
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151
bakers
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| n.面包师( baker的名词复数 )；面包店；面包店店主；十三 | |
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152
parasite
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| n.寄生虫；寄生菌；食客 | |
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153
parasites
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| 寄生物( parasite的名词复数 )； 靠他人为生的人； 诸虫 | |
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154
disseminated
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| 散布，传播( disseminate的过去式和过去分词 ) | |
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155
hawthorn
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| 山楂 | |
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156
allied
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| adj.协约国的；同盟国的 | |
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157
monotonous
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| adj.单调的，一成不变的，使人厌倦的 | |
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158
promptly
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| adv.及时地，敏捷地 | |
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159
devoured
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| 吞没( devour的过去式和过去分词 )； 耗尽； 津津有味地看； 狼吞虎咽地吃光 | |
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160
lizards
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| n.蜥蜴( lizard的名词复数 ) | |
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161
conspicuous
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| adj.明眼的，惹人注目的；炫耀的，摆阔气的 | |
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162
foes
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| 敌人，仇敌( foe的名词复数 ) | |
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163
replenished
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| 补充( replenish的过去式和过去分词 )； 重新装满 | |
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164
shamming
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| 假装，冒充( sham的现在分词 ) | |
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165
precipitately
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| adv.猛进地 | |
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166
catching
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| adj.易传染的，有魅力的，迷人的，接住 | |
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167
beetles
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| n.甲虫( beetle的名词复数 ) | |
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168
grasshoppers
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| n.蚱蜢( grasshopper的名词复数 )；蝗虫；蚂蚱；（孩子）矮小的 | |
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169
chaotic
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| adj.混沌的，一片混乱的，一团糟的 | |
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170
intervention
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| n.介入，干涉，干预 | |
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171
transformations
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| n.变化( transformation的名词复数 )；转换；转换；变换 | |
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172
lichen
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| n.地衣, 青苔 | |
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173
perilously
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| adv.充满危险地，危机四伏地 | |
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174
teleological
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| adj.目的论的 | |
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175
peculiarities
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| n. 特质, 特性, 怪癖, 古怪 | |
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176
essentially
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| adv.本质上，实质上，基本上 | |
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177
miraculous
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| adj.像奇迹一样的，不可思议的 | |
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178
inevitable
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| adj.不可避免的，必然发生的 | |
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179
penetrate
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| v.透(渗)入；刺入，刺穿；洞察，了解 | |
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180
recesses
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| n.壁凹( recess的名词复数 )；（工作或业务活动的）中止或暂停期间；学校的课间休息；某物内部的凹形空间v.把某物放在墙壁的凹处( recess的第三人称单数 )；将（墙）做成凹形，在（墙）上做壁龛；休息，休会，休庭 | |
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181
allurements
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| n.诱惑( allurement的名词复数 )；吸引；诱惑物；有诱惑力的事物 | |
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182
complexity
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| n.复杂(性)，复杂的事物 | |
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183
clumps
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| n.（树、灌木、植物等的）丛、簇( clump的名词复数 )；（土、泥等）团；块；笨重的脚步声v.（树、灌木、植物等的）丛、簇( clump的第三人称单数 )；（土、泥等）团；块；笨重的脚步声 | |
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184
browsed
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| v.吃草( browse的过去式和过去分词 )；随意翻阅；（在商店里）随便看看；（在计算机上）浏览信息 | |
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185
determined
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| adj.坚定的；有决心的 | |
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186
scotch
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| n.伤口，刻痕；苏格兰威士忌酒；v.粉碎，消灭，阻止；adj.苏格兰(人)的 | |
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187
parasitic
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| adj.寄生的 | |
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188
killing
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| n.巨额利润；突然赚大钱，发大财 | |
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189
abound
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| vi.大量存在；(in，with)充满，富于 | |
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190
pollen
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| n.[植]花粉 | |
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191
affected
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| adj.不自然的，假装的 | |
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192
scarcity
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| n.缺乏，不足，萧条 | |
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193
orchids
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| n.兰花( orchid的名词复数 ) | |
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194
petals
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| n.花瓣( petal的名词复数 ) | |
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195
laborious
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| adj.吃力的，努力的，不流畅 | |
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196
discriminated
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| 分别，辨别，区分( discriminate的过去式和过去分词 )； 歧视，有差别地对待 | |
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197
remarkable
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| adj.显著的，异常的，非凡的，值得注意的 | |
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198
foretold
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| v.预言，预示( foretell的过去式和过去分词 ) | |
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199
inquiry
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| n.打听，询问，调查，查问 | |
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200
cogent
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| adj.强有力的，有说服力的 | |
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201
anticipation
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| n.预期，预料，期望 | |
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202
demolished
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| v.摧毁( demolish的过去式和过去分词 )；推翻；拆毁（尤指大建筑物）；吃光 | |
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203
solely
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| adv.仅仅，唯一地 | |
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204
oust
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| vt.剥夺，取代，驱逐 | |
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205
exterminate
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| v.扑灭，消灭，根绝 | |
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206
gulf
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| n.海湾；深渊，鸿沟；分歧，隔阂 | |
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207
followers
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| 追随者( follower的名词复数 )； 用户； 契据的附面； 从动件 | |
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208
elucidation
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| n.说明，阐明 | |
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209
strictly
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| adv.严厉地，严格地；严密地 | |
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embryo
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| n.胚胎，萌芽的事物 | |
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211
affinities
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| n.密切关系( affinity的名词复数 )；亲近；（生性）喜爱；类同 | |
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briefly
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| adv.简单地，简短地 | |
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summarise
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| vt.概括，总结 | |
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confirmation
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| n.证实，确认，批准 | |
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reptile
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| n.爬行动物；两栖动物 | |
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reptiles
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| n.爬行动物，爬虫( reptile的名词复数 ) | |
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progenitor
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| n.祖先，先驱 | |
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wombats
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| n.袋熊( wombat的名词复数 ) | |
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219
sloths
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| 懒散( sloth的名词复数 )； 懒惰； 树獭； （经济）停滞。 | |
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220
toucans
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| n.巨嘴鸟，犀鸟( toucan的名词复数 ) | |
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countless
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| adj.无数的，多得不计其数的 | |
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formerly
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| adv.从前，以前 | |
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223
faunas
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| 动物群 | |
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224
floras
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| n.（某地区或某时期的）植物群，植物区系，植物志( flora的名词复数 ) | |
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225
crustaceans
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| n.甲壳纲动物（如蟹、龙虾）( crustacean的名词复数 ) | |
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crustacean
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| n.甲壳动物；adj.甲壳纲的 | |
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isthmus
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| n.地峡 | |
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rodents
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| n.啮齿目动物( rodent的名词复数 ) | |
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229
ascend
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| vi.渐渐上升，升高；vt.攀登，登上 | |
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chilly
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| adj.凉快的，寒冷的 | |
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231
beaver
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| n.海狸，河狸 | |
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analogous
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| adj.相似的；类似的 | |
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233
isles
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| 岛( isle的名词复数 ) | |
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234
pointed
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| adj.尖的，直截了当的 | |
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235
ancestry
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| n.祖先，家世 | |
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236
spiny
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| adj.多刺的，刺状的；n.多刺的东西 | |
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237
foliage
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| n.叶子，树叶，簇叶 | |
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238
defensive
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| adj.防御的；防卫的；防守的 | |
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239
inedible
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| adj.不能吃的，不宜食用的 | |
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240
mollusk
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| n.软体动物 | |
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241
systematic
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| adj.有系统的，有计划的，有方法的 | |
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242
embryos
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| n.晶胚；胚，胚胎( embryo的名词复数 ) | |
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243
hoofs
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| n.（兽的）蹄，马蹄( hoof的名词复数 )v.（兽的）蹄，马蹄( hoof的第三人称单数 ) | |
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pinions
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| v.抓住[捆住]（双臂）( pinion的第三人称单数 ) | |
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blurred
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| v.（使）变模糊( blur的过去式和过去分词 )；（使）难以区分；模模糊糊；迷离 | |
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246
affiliation
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| n.联系，联合 | |
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247
tadpole
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| n.[动]蝌蚪 | |
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248
apparently
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| adv.显然地；表面上，似乎 | |
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249
amphibian
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| n.两栖动物；水陆两用飞机和车辆 | |
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250
diverged
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| 分开( diverge的过去式和过去分词 )； 偏离； 分歧； 分道扬镳 | |
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251
thoroughly
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| adv.完全地，彻底地，十足地 | |
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252
remains
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| n.剩余物，残留物；遗体，遗迹 | |
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253
pointedly
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| adv.尖地，明显地 | |
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254
entailing
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| 使…成为必要( entail的现在分词 )； 需要； 限定继承； 使必需 | |
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255
exalted
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| adj.(地位等)高的，崇高的；尊贵的，高尚的 | |
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256
entirely
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| ad.全部地，完整地；完全地，彻底地 | |
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