Every one who has pursued embryological researches, and in a lesser4 degree every one who has merely read about them, must have been impressed by this marvel6 of marvels7: an exceedingly minute portion of living matter, so simple in aspect that a line will define it, passes by successive modifications10 into an organism so complex that a treatise11 is needed to describe it; not only do the cells in which the ovum and the spermatozoon originate, pass into a complex organism, reproducing the forms and features of the parents, and with these the constitutional peculiarities14 of the parents (their longevity15, their diseases, their mental dispositions16, nay18, their very tricks and habits), but they may reproduce the form and features, the dispositions and diseases, of a grandfather or great-grandfather, which had lain dormant19 in the father or mother. Consider for an instant what this implies. A microscopic20 cell of albuminous compounds, wholly without trace of organs, not appreciably21 distinguishable from millions of other cells, does nevertheless contain within it the “possibilities” of an organism so complex and so special as that of a Newton or a Napoleon. If ever there was a case90 when the famous Aristotelian notion of a “potential existence” seemed justified23, assuredly it is this. And although we can only by a fallacy maintain the oak to be contained in the acorn24, or the animal contained in the ovum, the fallacy is so natural, and indeed so difficult of escape, that there is no ground for surprise when physiologists26, on first learning something of development, were found maintaining that the perfect organism existed already in the ovum, having all its lineaments in miniature, and only growing into visible dimensions through the successive stages of evolution.44 The preformation of the organism seemed an inevitable27 deduction28 from the opinions once universal. It led to many strange, and some absurd conclusions; among them, to the assertion that the original germ of every species contained within it all the countless29 individuals which in process of time might issue from it; and this in no metaphysical “potential” guise30, but as actual boxed-up existences (embo?tés); so that Adam and Eve were in the most literal sense progenitors32 of the whole human race, and contained their progeny33 already shaped within them, awaiting the great accoucheur, time.
100. This was the celebrated34 “embo?tement” theory. In spite of obvious objections it gained scientific acceptance, because physiologists could not bring themselves to believe that so marvellous a structure as that of a human organism arose by a series of successive modifications, or because they could not comprehend how it was built up, part by part, into forms so closely resembling the parent-forms. That many and plausible35 reasons pleaded in favor of this opinion is evident in the fact that illustrious men like Haller, Bonnet36, Vallisneri, Swammerdamm, Réaumur, and Cuvier, were its advocates; and if there is not a sigle91 physiologist25 of our day who accepts it, or who finds any peculiar13 difficulty in following the demonstrations38 of embryologists, how from the common starting-point of a self-multiplying epithelial cell parts so diverse as hairs, nails, hoofs39, scales, feathers, crystalline lens, and secreting40 glands41 may be evolved, or how from the homogeneous germinal membrane43 the complex organism will arise, there are very few among the scorners of the dead hypothesis who seem capable of generalizing the principles which have destroyed it, or can conceive that the laws of Evolution apply as rigorously to the animal and vegetable kingdoms as to the individual organisms. The illustrious names of those who advocated the preformation hypothesis may serve to check our servile submission44 to the authorities so loudly proclaimed as advocates of the fixity of species. The more because the two doctrines46 have a common parentage. The one falls with the other, and no array of authorities can arrest the fall. That the manifold differentiations noticeable in a complex organism should have been evolved from a membrane wholly destitute47 of differences is a marvel, but a marvel which Science has made intelligible48. Yet the majority of those to whom this has been made intelligible still find an impossibility in admitting that the manifold forms of plant and animal were successively evolved from equally simple origins. They relinquish49 the hypothesis of preformation in the one case, and cling to it in the other. Evolution, demonstrable in the individual history, seems preposterous50 in the history of the class. And thus is presented the instructive spectacle of philosophers laughing at the absurdities51 of “preformation,” and yet exerting all their logic3 and rhetoric52 in defence of “creative fiats54”—which is simply the preformation hypothesis “writ large.”
101. It would not be difficult to show that the doctrine92 of Epigenesis, with which Wolff forever displaced the doctrine45 of Preformation, leads by an inevitable logic to the doctrine of universal Evolution; and that we can no more understand the appearance of a new organism which is not the modification9 of some already existing organism, than we can understand the sudden appearance of a new organ which is not the modification of some existing structure. In the one case as in the other we may disguise the process under such terms as creative fiat53 and preformation; but these terms are no explanations; they re-state the results, they do not describe the process; whereas Epigenesis describes the process as it passes under the eye of science.
102. If any reader of these pages who, from theological or zo?logical suspicion of the Development Hypothesis, clings to the hypothesis of a creative Plan which once for all arranged the organic world in Types that could not change, will ask what rational interpretation55 can be given to the succession of phases each embryo2 is forced to pass through, it may help to give him pause. He will observe that none of these phases have any adaptation to the future state of the animal, but are in positive contradiction to it, or are simply purposeless; whereas all show stamped on them the unmistakable characters of ancestral adaptations and the progressions of Organic Evolution. What does the fact imply? There is not a single known example of a complex organism which is not developed out of simpler forms. Before it can attain56 the complex structure which distinguishes it, there must be an evolution of forms similar to those which distinguish the structures of organisms lower in the series. On the hypothesis of a Plan which prearranged the organic world, nothing could be more unworthy of a supreme57 intelligence than this inability to construct an organism at once, without previously58 making several93 tentative efforts, undoing59 to-day what was so carefully done yesterday, and repeating for centuries the same tentatives, and the same corrections, in the same succession. Do not let us blink this consideration. There is a traditional phrase much in vogue61 among the anthropomorphists, which arose naturally enough from the tendency to take human methods as an explanation of the divine—a phrase which becomes a sort of argument—“The Great Architect.” But if we are to admit the human point of view, a glance at the facts of embryology must produce very uncomfortable reflections. For what should we say to an architect who was unable, or being able was obstinately62 unwilling63, to erect64 a palace except by first using his materials in the shape of a hut, then pulling it down and rebuilding them as a cottage, then adding story to story and room to room, not with any reference to the ultimate purposes of the palace, but wholly with reference to the way in which houses were constructed in ancient times? What should we say to the architect who could not form a museum out of bricks and mortar65, but was forced to begin as if going to build a mansion66: and after proceeding67 some way in this direction, altered his plan into a palace, and that again into a museum? Yet this is the sort of succession on which organisms are constructed. The fact has long been familiar; how has it been reconciled with Infinite Wisdom? Let the following passage answer for a thousand:—“The embryo is nothing like the miniature of the adult. For a long while the body in its entirety and its details presents the strangest of spectacles. Day by day and hour by hour the aspect of the scene changes, and this instability is exhibited by the most essential parts no less than by the accessory parts. One would say that Nature feels her way, and only reaches the goal after many times missing the path,—on dirait que la nature tatonne et ne conduit94 son ?uvre à bon fin8 qu’après s’être souvent trompée.”45 Writers have no compunction in speaking of Nature feeling her way and blundering; but if in lieu of Nature, which may mean anything, the Great Architect be substituted, it is probable that the repugnance68 to using such language of evasion69 may cause men to revise their conceptions altogether; they dare not attribute ignorance and incompetence70 to the Creator.
103. Obviously the architectural hypothesis is incompetent71 to explain the phenomena72 of organic development. Evolution is the universal process; not creation of a direct kind. Von Baer, who very properly corrected the exaggerations which had been put forth73 respecting the identity of the embryonic75 forms with adult forms lower in the scale, who showed that the mammalian embryo never was a bird, a reptile76, or a fish, nevertheless emphasized the fact that the mammalian embryo passes through all the lower typical forms; so much so that, except by their size, it is impossible to distinguish the embryos77 of mammal, bird, lizard78, or snake. “In my collection,” he says, “there are two little embryos which I have omitted to label, so that I am now quite incompetent to say to what class they belong. They may be lizards79, they may be small birds, or very young mammals; so complete is the similarity in the mode of formation of the head and trunk. The extremities80 have not yet made their appearance. But even if they existed in the earliest stage we should learn nothing from them, for the feet of lizards, mammals, and the wings of birds, all arise from the same common form.” He sums up with his formula: “The special type is always evolved from a more general type.”46
95 Such reminiscences of earlier forms are intelligible on the supposition that originally the later form was a modification of the earlier form, and that this modification is repeated; or on the supposition that there was a similarity in the organic conditions, which similarity ceased at the point where the new form emerged. But on no hypothesis of creative Plan are they intelligible. They are useless structures, failing even to subserve a temporary purpose. Sometimes, as Mr. Darwin remarks, a trace of the embryonic resemblance lasts till a late age: “Thus birds of the same genus, and of closely allied81 genera, often resemble each other in their first and second plumage: as we see in the spotted82 feathers in the thrush group. In the cat tribe most of the species are striped and spotted in lines; and stripes or spots can plainly be distinguished83 in the whelp of the lion and the puma84. We occasionally, though rarely, see something of this kind in plants.... The points of structure in which the embryos of widely different animals of the same class resemble each other often have no direct relation to their conditions of existence. We cannot, for instance, suppose that in the embryos of the vertebrata the peculiar loop-like courses of the arteries85 near the bronchial slits86 are related to similar conditions in the young mammal which is nourished in the womb of its mother, in the egg of a bird which is hatched in a nest, and in the spawn87 of a frog under water.”
104. It would be easy to multiply examples, but I will content myself with three. The tadpole88 of the Salamander has gills, and passes his existence in the water; but the Salamandra atra, which lives high up among the mountains, brings forth its young full-formed. This animal never lives in the water. Yet if we open a gravid female, we find tadpoles89 inside her with exquisitely91 feathered gills, and (as I have witnessed) these tadpoles “when96 from the mother’s womb untimely ripped,” if placed in water, swim about like the tadpoles of water newts. Obviously this aquatic92 organization has no reference to the future life of the animal, nor has it any adaptation to its embryonic condition; it has solely93 reference to ancestral forms, it repeats a phase in the development of its progenitors. Again, in the embryo of the naked Nudibranch, we always observe a shell, although the animal is without a shell, and there can be no purpose served by the shell in embryonic life.47 Finally, the human embryo has a tail, which is of course utterly94 purposeless, and which, although to be explained as a result of organic laws, is on the creative hypothesis only explained as an adherence95 to the general plan of structure—a specimen96 of pedantic97 trifling98 “worthy of no intellect above the pongo’s.”48
105. Humanly appreciated, not only is it difficult to justify99 the successive stages of development, the incessant100 building up of structures immediately to be taken down, but also to explain why development was necessary97 at all. Why are not plants and animals formed at once, as Eve was mythically101 affirmed to be taken from Adam’s rib12, and Minerva from Jupiter’s head? The theory of Evolution answers this question very simply; the theory of Creation can only answer it by affirming that such was the ordained102 plan. But the theory of Evolution not only gives the simpler and more intelligible answer to this question, it gives an answer to the further question which leaves the theory of Creation no loophole except a sophism—namely, why the formation of organisms is constantly being frustrated104 or perverted105? And, further, it gives an explanation of the law noticed by Milne Edwards, that Nature is as economical in her means as she is prodigal106 in her variation of them: “On dirait qu’avant de recourir à des ressources nouvelles elle a voulu épuiser, en quelque sorte, chacun des procédés qu’elle avait mis en jeu.”49 The applause bestowed107 on Nature for being economical is a curious transference to Nature of human necessities. Why, with a whole universe at her disposal, should Nature be economical? Why must she always be working in the same groove108, and using but a few out of the many substances at her command? Economy is a virtue109 only in the poor. If Nature, in organic evolutions, is restricted to a very few substances, and a very few modes of combination, always creating new forms by modification of the old, and apparently110 incapable111 of creating an organism at once, this must imply an inherent necessity which is very unlike the free choice that can render economy a merit.
106. There may indeed be raised an objection to the Development Hypothesis on the ground that if the complex forms were all developed from the simpler forms, we ought to trace the identities through all their stages. If the fish developed into the reptile, the reptile into the98 bird, and the bird into the mammal (which I, for one, think questionable), we ought to find, it is urged, evidence of this passage. And at one time it was asserted that the evidence existed; but this has been disproved, and on the disproof the opponents of Evolution take their stand. Although I cannot feel much confidence in the idea of such a passage from Type to Type, and although the passage, if ever it occurred, must have occurred at so remote a period as to leave no evidence more positive than inference, I cannot but think the teaching of Embryology far more favorable to it than to our opponents. Supposing, for the sake of argument, that the passage did take place, ought we to find the embryonic stages accurately112 reproducing the permanent forms of lower types? Von Baer thinks we ought; and lesser men may follow him without reproach. But it seems to me that he starts from an inadmissible assumption, namely, that the development must necessarily be in a straight line rather than in a multiplicity of divergent lines. “When we find the embryonic condition,” he says, “differing from the adult, we ought to find a corresponding condition somewhere in the lower animals.”50 Not necessarily. We know that the mental development of a civilized113 man passes through the stages which the race passed through in the course of its long history, and the psychology114 of the child reproduces the psychology of the savage115. But as this development takes place under conditions in many respects different, and as certain phases are hurried over, we do not expect to find a complete parallel. It is enough if we can trace general resemblances. Von Baer adds, “That certain correspondences should occur between the embryonic states of some animals and the adult states of others seems inevitable and of no significance(?). They could not fail, since the embryos lie within the animal sphere,99 and the variations of which the animal body is capable are determined116 for each type by the internal connection and mutual117 reaction of its organs, so that particular repetitions are inevitable.” A profound remark, to which I shall hereafter have occasion to return, but its bearing on the present question is inconclusive. The fact that the embryonic stages of the higher animals resemble in general characters the permanent stages of the lower animals, and very closely resemble the embryonic stages of those animals, is all that the Development Hypothesis requires. Nor is its value lessened118 by the fact that many of the details and intermediate stages seem passed over in the development of the higher forms, for the recapitulation can only be of outlines, not of details; since there are differences in the forms, there must be differences in their histories.
107. In the preceding observations the object has simply been to show that the phenomena to be explained can be rationally conceived as resulting from gradual Evolution, whereas they cannot be so rationally interpreted on any other hypothesis. And here it may be needful to say a word respecting Epigenesis.
The Preformation hypothesis, which regarded every organism as a simple educt and not the product of a germ, was called by its advocates an evolution hypothesis—meaning that the adult form was an outgrowth of the germ, the miniature magnified. Wolff, who replaced that conception by a truer one, called his, by contrast, Epigenesis, meaning that there was not simply out-growth but new growth. “The various parts,” he says, “arise one after the other, so that always one is secreted119 from (excernirt), or deposited (deponirt) on the other; and then it is either a free and independent part, or is only fixed121 to that which gave it existence, or else is contained within it. So that every part is the effect of a pre-existing part, and in100 turn the cause of a succeeding part.”51 The last sentence expresses the conception of Epigenesis which embryologists now adopt; and having said this, we may admit that Wolff, in combating the error of preformation, replacing it with the truer notion of gradual and successive formation, was occasionally open to the criticism made by Von Baer, that he missed the true sense of Evolution, since the new parts are not added on to the old parts as new formations, but evolved from them as transformations122. “The word Evolution, therefore, seems to me more descriptive of the process than Epigenesis. It is true that the organism is not preformed, but the course of its development is precisely124 the course which its parents formerly125 passed through. Thus it is the Invisible—the course of development—which is predetermined.”52 When the word Epigenesis is used, therefore, the reader will understand it to signify that necessary succession which determines the existence of new forms. Just as the formation of chalk is not the indifferent product of any combination of its elements, carbon, oxygen, and calcium126, but is the product of only one series of combinations, an evolution through necessary successions, the carbon uniting with oxygen to form carbonic acid, and this combining with the oxide127 of calcium to form chalk, so likewise the formation of a muscle, a bone, a limb, or a joint128 has its successive stages, each of which is necessary, none of which can be transposed. The formation of bone is peculiarly instructive, because the large proportion of inorganic129 matter in its substance, and seemingly deposited in the organic tissue, would lead one to suppose that it was almost an accidental formation, which might take place anywhere; yet101 although what is called connective tissue will ossify130 under certain conditions, true bone is the product of a very peculiar modification, which almost always needs to be preceded by cartilage. That the formation of bone has its special history may be seen in the fact that it is the last to appear in the animal series, many highly organized fishes being without it, and all the other systems appearing before it in the development of the embryo. Thus although the mother’s blood furnishes all the requisite131 material, the f?tus is incapable of assimilating this material and of forming bone, until its own development has reached a certain stage. Moreover, when ossification132 does begin, it generally begins in the skull133 (in man in the clavicle); and the only approach to an internal skeleton in the Invertebrates135 is the so-called skull of the Cephalopoda. Not only is bone a late development, but cartilage is also; and although it is an error to maintain that the Invertebrates are wholly destitute of cartilage, its occasional presence having been fully60 proved by Claparède and Gegenbaur, the rarity of its presence is very significant. The animals which can form shells of chalk and chitine are yet incapable of forming even an approach to bone.
108. Epigenesis depends on the laws of succession, which may be likened to the laws of crystallization, if we bear in mind the essential differences between a crystal and an organism, the latter retaining its individuality through an incessant molecular136 change, the former only by the exclusion137 of all change. When a crystalline solution takes shape, it will always take a definite shape, which represents what may be called the direction of its forces, the polarity of its constituent138 molecules139. In like manner, when an organic plasmode takes shape—crystallizes, so to speak—it always assumes a specific shape dependent on the polarity of its molecules. Crystallographers102 have determined the several forms possible to crystals; histologists have recorded the several forms of Organites, Tissues, and Organs. Owing to the greater variety in elementary composition, there is in organic substance a more various polar distribution than in crystals; nevertheless, there are sharply defined limits never overstepped, and these constitute what may be called the specific forms of Organites, Tissues, Organs, Organisms. An epithelial cell, for example, may be ciliated or columnar, a muscle-fibre striated141 or non-striated, a nerve-fibre naked or enveloped142 in a sheath, but the kind is always sharply defined. An intestinal143 tube may be a uniform canal, or a canal differentiated144 into several unlike compartments146, with several unlike glandular147 appendages148. A spinal149 column may be a uniform solid axis150, or a highly diversified151 segmented axis. A limb may be an arm, or a leg, a wing, or a paddle. In every case the anatomist recognizes a specific type. He assigns the uniformities to the uniformity of the substance thus variously shaped, under a history which has been similar; the diversities he assigns to the various conditions under which the processes of growth have been determined. He never expects a muscular tissue to develop into a skeleton, a nervous tissue into a gland42, an osseous tissue into a sensory152 organ. He never expects a tail to become a hand or a foot, though he sees it in monkeys and marsupials serving the offices of prehension and locomotion153. He never expects to find fingers growing anywhere except from metacarpal bones, or an arm developed from a skull. The well-known generalization154 of Geoffroy St. Hilaire that an organ is more easily annihilated155 than transposed, points to the fundamental law of Epigenesis. In the same direction point all the facts of growth. Out of a formless germinal membrane we see an immense variety of forms evolved; and out of a common nutritive fluid this variety103 of organs is sustained, repaired, replaced; and this not indifferently, not casually156, but according to rigorous laws of succession; that which precedes determining that which succeeds as inevitably157 as youth precedes maturity158, and maturity decay. The nourishment159 of various organs from plasmodes derived160 from a common fluid, each selecting from that fluid only those molecules that are like its own, rejecting all the rest, is very similar to the formation of various crystals in a solution of different salts, each salt separating from the solution only those molecules that are like itself. Reil long ago called attention to this analogy. He observed that if in a solution of nitre and sulphate of soda161 a crystal of nitre be dropped, all the dissolved nitre crystallizes, the sulphate remaining in solution; whereas on reversing the experiment, a crystal of sulphate of soda is found to crystallize all the dissolved sulphate, leaving the nitre undisturbed. In like manner muscle selects from the blood its own materials which are there in solution, rejecting those which the nerve will select.
109. Nay, so definite is the course of growth, that when a limb or part of a limb is cut off from a crab162 or salamander, a new limb or new part is reproduced in the old spot, exactly like the one removed. Bonnet startled the world by the announcement that the Na?s, a worm common in ponds, spontaneously divided itself into two worms; and that when he cut it into several pieces, each piece reproduced head and tail, and grew into a perfect worm. This had been accepted by all naturalists163 without demur164, until Dr. Williams, in his “Report on British Annelida, 1851,” declared it to be a fable165. In 1858, under the impulse of Dr. Williams’s very emphatic166 denial, I repeated experiments similar to those of Bonnet, with similar results. I cut two worms in half, and threw away the head-bearing segments, placing the others in two separate vessels167, with104 nothing but water and a little mud, which was first carefully inspected to see that no worm lay concealed169 therein. In a few days the heads were completely reformed, and I had the pleasure of watching them during their reconstruction170. When the worms were quite perfect, I again cut away their heads, and again saw these reformed. This was repeated, till I had seen four heads reproduced; after which the worms succumbed171.
110. The question naturally arises, Why does the nutritive fluid furnish only material which is formed into a part like the old one, instead of reproducing another part, or one having a somewhat different structure? The answer to this question is the key to the chief problem of organic life. That a limb in situ should replace its molecular waste by molecules derived from the blood, seems intelligible enough (because we are familiar with it), and may be likened to the formation of crystals in a solution; but how is it that the limb which is not in existence can assimilate materials from the blood? How is it that the blood, which elsewhere in the organism will form other parts, here will only form this particular part? There is, probably, no one who has turned his attention to these subjects who has not paused to consider this mystery. The most accredited172 answer at present before the world is one so metaphysiological that I should pass it by, were it not intimately allied with that conception of Species, which it is the object of these pages to root out. It is this:
111. The organism is determined by its Type, or, as the Germans say, its Idea. All its parts take shape according to this ruling plan; consequently, when any part is removed, it is reproduced according to the Idea of the whole of which it forms a part. Milne Edwards, in a very interesting and suggestive work, concludes his survey of organic phenomena in these words: “Dans l’organisme105 tout174 semble calculé en vue d’un résultat déterminé, et l’harmonie des parties ne résulte pas de l’influence qu’elles peuvent exercer les unes sur les autres, mais de leur co-ordination sous l’empire d’une puissance commune, d’un plan précon?u, d’une force pré-existante.”53 This is eminently175 metaphysiological. It refuses to acknowledge the operation of immanent properties, refuses to admit that the harmony of a complex structure results from the mutual relations of its parts, and seeks outside the organism for some mysterious force, some plan, not otherwise specified176, which regulates and shapes the parts. Von Baer, in his great work, has a section entitled, “The nature of the animal determines its development”; and he thus explains himself: “Although every stage in development is only made possible by the pre-existing condition [which is another mode of expressing Epigenesis], nevertheless the entire development is ruled and guided by the Nature of the animal which is about to be (von der gesammten Wesenheit des Thieres welches werden soll), and it is not the momentary177 condition which alone and absolutely determines the future, but more general and higher relations.”54 One must always be slow in rejecting the thoughts of a master, and feel sure that one sees the source of the error before regarding it as an error; but in the present case I think the positive biologist will be at no loss to assign Von Baer’s error to its metaphysical origin. Without pausing here to accumulate examples both of anomalies and slighter deviations178 which are demonstrably due to the “momentary conditions” that preceded them, let us simply note the logical inconsistency of a position which, while assuming that every separate stage in development is the necessary sequence of its predecessor179, declares the whole of the stages independent106 of such relations! Such a position is indeed reconcilable on the assumption that animal forms are moulded “like clay in the hands of the potter.” But this is a theological dogma, which leads to very preposterous and impious conclusions; and whether it leads to these conclusions or to others, positive Biology declines theological explanations altogether. Von Baer, although he held the doctrine of Epigenesis, coupled it, as many others have done, with metaphysical doctrines to which it is radically181 opposed. He believed in Types as realities; he was therefore consistent in saying, “It is not the Matter and its arrangements which determine the product, but the nature of the parent form—the Idea, according to the new school.” How are we to understand this Idea? If it mean an independent Entity74, an agency external to the organism, we refuse to acknowledge its existence. If it mean only an a posteriori abstraction expressing the totality of the conditions, then, indeed, we acknowledge that it determines the animal form; but this is only an abbreviated182 way of expressing the law of Evolution, by which each stage determines its successor. The Type does not dominate the conditions, it emerges from them; the animal organism is not cast in a mould, but the imaginary mould is the form which the polarities of the organic substance assume. It would seem very absurd to suppose that crystals assumed their definite shapes (when the liquid which held their molecules in solution is evaporated) under the determining impulse of phantom183-crystals, or Ideas; yet it has not been thought absurd to assume phantom forms of organisms.
112. The conception of Type as a determining influence arises from that fallacy of taking a resultant for a principle, which has played so conspicuous184 a part in the history of philosophy. Like many others of its class it exhibits an interesting evolution from the crude metaphysical107 to the subtle metaphysical point of view, which at last insensibly blends into the positive point of view. At first the Type or Idea was regarded as an objective reality, external to the organism it was supposed to rule. Then this notion was replaced by an approach to the more rational interpretation, the idea was made an internal not an external force, and was incorporated with the material elements of the organism, which were said to “endeavor” to arrange themselves according to the Type. Thus Treviranus declares that the seed “dreams of the future flower”; and “Henle, when he affirms that hair and nails grow in virtue of the Idea, is forced to add that the parts endeavor to arrange themselves according to this Idea.”55 Even Lotze, who has argued so victoriously186 against the vitalists, and has made it clear that an organism is a vital mechanism187, cannot relinquish this conception of legislative188 Ideas, though he significantly adds, “these have no power in themselves, but only in as far as they are grounded in mechanical conditions.” Why then superfluously189 add them to the conditions? If every part of a watch, in virtue of the properties inherent in its substance, and of the mutual reactions of these and other parts, has a mechanical value, and if the sum of all these parts is the time-indicating mechanism, do we add to our knowledge of the watch, and our means of repairing or improving it, by assuming that the parts have over and above their physical properties the metaphysical “tendency” or “desire” to arrange themselves into this specific form? When we see that an organism is constructed of various parts, each of which has its own properties inalienable from its structure, and its uses dependent on its relation to other parts, do we gain any larger insight by crediting these parts with desires or108 “dreams” of a future result which their union will effect? That which is true in this conception of legislative Ideas is that when the parts come together there is mutual reaction, and the resultant of the whole is something very unlike the mere5 addition of the items, just as water is very unlike oxygen or hydrogen; further, the connexus of the whole impresses a peculiar direction on the development of the parts, and the law of Epigenesis necessitates190 a serial191 development, which may easily be interpreted as due to a preordained plan.
113. In a word, this conception of Type only adds a new name to the old difficulty, adding mist to darkness. The law of Epigenesis, which is simply the expression of the material process determined by the polarity of molecules, explains as much of the phenomena as is explicable. A lost limb is replaced by the very processes, and through the same progressive stages as those which originally produced it. We have a demonstration37 of its not being reformed according to any Idea or Type which exists apart from the immanent properties of the organic molecules, in the fact that it is not reformed at once, but by gradual evolution; the mass of cells at the stump192 are cells of embryonic character, cells such as those which originally “crystallized” into muscles, nerves, vessels, and integument193, and each cell passes through all its ordinary stages of development. It is to be remembered that so intimately dependent is the result on the determining conditions, that any external influence which disturbs the normal course of development will either produce an anomaly, or frustrate103 the formation of a new limb altogether. One of my tritons bit off the leg of his female;56 the leg which replaced it was much malformed,109 and curled over the back so as to be useless; was this according to the Idea? I cut it off, and examined it; all the bones were present, but the humerus was twisted, and of small size. In a few weeks a new leg was developed, and this leg was normal. If the Idea, as a ruling power, determined the growth of this third leg, what determined the second, which was malformed? Are we to suppose that in normal growth the Idea prevails, in abnormal the conditions? That it is the polarity of the molecules which at each moment determines the group those molecules will assume, is well seen in the experiment of Lavalle mentioned by Bronn.57 He showed that if when an octohedral crystal is forming, an angle be cut away, so as to produce an artificial surface, a similar surface is produced spontaneously on the corresponding angle, whereas all the other angles are sharply defined. “Valentin,” says Mr. Darwin, “injured the caudal extremity194 of an embryo, and three days afterwards it produced rudiments196 of a double pelvis, and of double hind197 limbs. Hunter and others have observed lizards with their tails reproduced and doubled. When Bonnet divided longitudinally the foot of the salamander, several additional digits198 were occasionally formed.”58 Where is the evidence of the Idea in these cases?
110 114. I repeat, the reproduction of lost limbs is due to a process which is in all essential respects the same as that which originally produced them; the genesis of one group of cells is the necessary condition for the genesis of its successor, nor can this order be transposed. But—and the point is very important—it is not every part that can be reproduced, nor is it every animal that has reproductive powers. The worm, or the mollusk199, seems capable of reproducing every part; the crab will reproduce its claws, but not its head or tail; the perfect insect of the higher orders will reproduce no part (indeed the amputation200 of its antennae201 only is fatal), the salamander will reproduce its leg, the frog not. In human beings a muscle is said never to be reproduced; but this is not the case in the rare examples of supplementary202 fingers and toes, which have been known to grow again after amputation. The explanation of this difference in the reproductive powers of different animals is usually assigned to the degree in which their organisms retain the embryonic condition; and this explanation is made plausible by the fact that the animals which when adult have no power of replacing lost limbs, have the power when in the larval state. But although this may in some cases be the true explanation, there are many in which it fails, as will be acknowledged after a survey of the extremely various organisms at widely different parts of the animal series which possess the reproductive power. Even animals in the same class, and at the same stage of development, differ in this respect. I do not attach much importance to the fact that all my experiments on marine203 annelids failed to furnish evidence of their power of reproducing lost segments; because it is difficult to keep them under conditions similar to those in which they live. But it is111 significant that, among the hundreds which have passed under my observation, not one should have been found with a head-segment in the process of development, replacing one that had been destroyed; and this is all the more remarkable204 from the great tenacity205 of life which the mutilated segments manifest. Quatrefages had observed portions of a worm, after gangrene had destroyed its head and several segments, move about in the water and avoid the light!59
115. A final argument to show that the reproduction is not determined by any ruling Idea, but by the organic conditions and the necessary stages of evolution, is seen in the reappearance of a tumor206 or cancer after it has been removed. We find the new tissue appear with all the characters of the normal tissue of the gland, then rapidly assume one by one the characters of the diseased tissue which had been removed; and there as on is, that the regeneration of the tissue is accompanied by the same abnormal conditions which formerly gave rise to the tumor: the directions of “crystallization” are similar because the conditions are similar. In every case of growth or regrowth the conditions being the same, the result must be the same.
112 116. It seems a truism to insist that similarity in the results must be due to similarity in the conditions; yet it is one which many theorists disregard; and especially do we need to bear it in mind when arguing about Species. I will here only touch on the suggestive topic of the analogies observed not simply among animals at the extreme ends of the scale, but also between animals and plants where the idea of a direct kinship is out of the question.
My very imperfect zo?logical knowledge will not allow me to adduce a long array of instances, but such an array will assuredly occur to every well-stored mind. It is enough to point to the many analogies of Function, more especially in the reproductive processes—to the existence of burrowers, waders, flyers, swimmers in various classes—to the existence of predatory mammals, predatory birds, predatory reptiles208, predatory insects by the side of herbivorous congeners,—to the nest-building and incubating fishes; and in the matter of Structure the analogies are even more illustrative when we consider the widely diffused209 spicula, set?, spines210, hooks, tentacles211, beaks212, feathery forms, nettling-organs, poison-sacs, luminous214 organs, etc.; because these have the obvious impress of being due to a community of substance under similar conditions rather than to a community of kinship. The beak213 of the tadpole, the cephalopod, the male salmon216, and the bird, are no doubt in many respects unlike; but there is a significant likeness217 among them, which constitutes a true analogy. I think there is such an analogy between the air-bladder of fishes and the tracheal rudiment195 which is found in the gnat-larva (Corethra plumicornis).60 Very113 remarkable also is the resemblance of the avicularium, or “bird’s-head process,” on the polyzoon known popularly as the Corkscrew Coralline (Bugula avicularia), which presents us in miniature with a vulture’s head—two mandibles, one fixed, the other moved by muscles visible within the head. No one can watch this organ snapping incessantly218, without being reminded of a vulture, yet no one would suppose for a moment that the resemblance has anything to do with kinship.
117. Such cases are commonly robbed of their due significance by being dismissed as coincidences. But what determines the coincidence? If we assume, as we are justified in assuming, that the possible directions of Organic Combination, and the resultant forms, are limited, there must inevitably occur such coincident lines: the hooks on a Climbing Plant will resemble the hooks on a Crustacean219 or the claws of a Bird, as the one form in which under similar external forces the more solid but not massive portions of the integument tend to develop. I am too ill acquainted with the anatomy220 of plants to say how the hooks so common among them arise; but from examination of the Blackberry, and comparison of its thorns with the hooks and spines of the Crustacea, I am led to infer that in each case the mode of development is identical—namely, the secretion221 of chitine from the cellular222 matrix of the integument.
114 Another mode of evading223 the real significance of such resemblances is to call them analogies, not homologies. There is an advantage in having two such terms, but we ought to be very clear as to their meaning and their point of separation. Analogy is used to designate similarity in Function with dissimilarity in Structure. The wing of an insect, the wing of a bird, and the wing of a bat are called analogous224, but not homologous, because their anatomical structure is different: they are not constructed out of similar anatomical parts. The fore-leg of a mammal, the wing of a bird, or the paddle of a whale, are called homologous, because in spite of their diverse uses they are constructed out of corresponding anatomical parts. To the anatomist such distinctions are eminently serviceable. But they have led to some misconceptions, because they are connected with a profound misconception of the relation between Function and Organ. Embryology teaches that the wing of the bird and the paddle of the whale are developed out of corresponding parts, and that these are not like the parts from which the wing of an insect or the flying-fish will be developed; nevertheless, the most cursory225 inspection226 reveals that the wing of a bird and the paddle of a whale are very unlike in structure no less than in function, and that their diversities in function correspond with their diversities in structure; whereas the wing of the insect, of the bird, and of the bat, are in certain characters very similar, and correspondingly there are similarities in their function. It is, however, obvious that the resemblance in function is strictly227 limited to the resemblance in anatomical structure; only in loose ordinary speech can the flight of an insect, a bird, or a bat be said to be “the same”: it is different in each—the weight to be moved, the rapidity of the movement, the precision of the movements, and their endurance, all differ.
115
118. It is impossible to treat of Evolution without taking notice of that luminous hypothesis by which Mr. Darwin has revolutionized Zo?logy. There are two points needful to be clearly apprehended229 before the question is entered upon. The first point relates to the lax use of the phrase “conditions,” sometimes more instructively replaced by “conditions of existence.” Inasmuch as Life is only possible under definite relations of the organism and its medium, the “conditions of existence” will be those physical, chemical, and physiological173 changes, which in the organism, and out of it, co-operate to produce the result. There are myriads230 of changes in the external medium which have no corresponding changes in the organism, not being in any direct relation to it (see § 54). These, not being co-operant conditions, must be left out of the account; they are not conditions of existence for the organism, and therefore the organism does not vary with their variations. On the other hand, what seem very slight changes in the medium are often responded to by important changes in the vital chemistry, and consequently in the structure of the organism. Now the nature of the organism at the time being, that is to say, its structure and the physico-chemical state of its tissues and plasmodes, is the main condition of this response; the same external agent will be powerful, or powerless, over slightly different organisms, or over the same organism at different times. Usually, and for convenience, when biologists speak of conditions, they only refer to external changes. This usage has been the source of no little confusion in discussing the Development Hypothesis. Mr. Darwin, however, while following the established usage, is careful in several places to declare that of the two factors in Variation—the nature of the organism116 and the nature of the conditions—the former is by far the more important.
118a. A still greater modification of terms must now be made. Instead of confining the “struggle for existence” to the competition of rivals and the antagonism231 of foes232, we must extend it to the competition and antagonism of tissues and organs. The existence of an organism is not only dependent on the external existence of others, and is the outcome of a struggle; but also on the internal conditions which co-operate in the formation of its structure, this structure being the outcome of a struggle. The organism is this particular organism, differing from others, because of the particular conditions which have co-operated. The primary and fundamental struggle must be that of the organic forces at work in creating a structure capable of pushing its way amid external forces. The organism must find a footing in the world, before it can compete with rivals, and defend itself against foes. Owing to the power of reproduction, every organism has a potential indefiniteness of multiplication233; that potential indefiniteness is, however, in reality restricted by the supply of food, and by the competition of rivals for that supply. The multiplication of any one species is thus kept down by the presence of rivals and foes: a balance is reached, which permits of the restricted quantities of various species. This balance is the result of a struggle.
Now let me call attention to a similar process in the formation of the organism itself. Every organite, and every tissue, has a potential growth of indefinite extent, but its real growth is rigorously limited by the competition and antagonism of the others, each of which has its potential indefiniteness, and its real limits. Something, in the food assimilated, slightly alters the part which assimilates it. This change may be the origin of117 other changes in the part itself, or in neighboring parts, stimulating234 or arresting the vital processes. A modification of structure results. Or there may be no new substance assimilated, but external forces may call a part into increased activity—which means increased waste and repair; and this increase here is the cause of a corresponding decrease somewhere else. Whatever the nature of the change, it finds its place amid a complex of changes, and its results are compounded with theirs. When organites and tissues are said to have a potential indefiniteness of growth, there is assumed a potential indefiniteness in the pabulum supplied: if the pabulum were supplied, and if there were no antagonism thwarting235 its assimilation, growth would of course continue without pause, or end; but in reality this cannot be so. For, take the blood as the vehicle of the pabulum—not only is its quantity limited, and partly limited by the very action of the tissues it feeds, but even in any given quantity there is a limit to its composition—it will only take up a limited quantity of salts, iron, albumen, etc.; no matter how abundant these may be in the food. So again with the plasmodes of the various tissues—they have each their definite capacities of assimilation. What has already been stated respecting chemical affinity (§ 20) is equally applicable to organic affinity; as the presence of fused iron in the crucible236 partially237 obstructs238 the combination of sulphur and lead, so the presence of connective tissue partially obstructs the combination of muscle protoplasm with its pabulum.
118 b. Owing to the action and reaction of blood and plasmode, of tissues on tissues, and organs on organs, and their mutual limitations, the growth of each organism has a limit, and the growth of each organ has a limit. Beyond this limit, no extra supply of food will increase the size of the organism; no increase of activity will118 increase the organ. “Man cannot add a cubit to his stature239.” The blacksmith’s arm will not grow larger by twenty years of daily exercise, after it has once attained240 a certain size. Increase of activity caused it to enlarge up to this limit; but no increase of activity will cause it to pass this limit. Why? Because here a balance of the co-operating formative forces has been reached. Larger muscles, or more muscle-fibres, demand arteries of larger calibre, and these a heart of larger size; with the increase of muscle would come increase of connective tissue; and this tissue would not only compete with the muscle for pabulum, but by mechanical pressure would diminish the flow of that pabulum. And why would connective tissue increase? Because, in the first place, there is a formative association between the two, so that owing to a law, not yet understood, the one always accompanies the other; and, in the second place, there is a functional241 association between the two, a muscle-fibre being inoperative unless it be attached to a tendon, or connective tissue; it will contract out of the body although separated from its tendon or other attachment242; but in the body its contraction243 would be useless without this attachment. We must bear in mind that muscle-fibres are very much shorter than ordinary muscles; according to the measurements of W. Krause they never exceed 4 cm in length, and usually range between 2 and 3 cm; their fine points being fixed to the interstitial connective tissue, as the whole muscle is fixed to its tendon. The function of the muscle is thus dependent on a due balance of its component244 tissues; if that balance is disturbed the function is disturbed. Should, from any cause, an excess of muscle-fibre arise, the balance would be disturbed; should an encroachment245 of connective tissue, or of fat, take place, there would be also a defect of function.
Here we have the co-operation and limitation of the119 tissues illustrated246; let us extend our glance, and we shall see how the co-operation and limitation of the organs come into play, so that the resulting function depends on the balance of their forces. The contractile power of each individual muscle is always limited by the resistance of antagonists247, which prevent the muscle being contracted more than about a third of its possible extent, i. e. possible when there are no resistances to be overcome. Not only the increasing tension of antagonist248 muscles, but the resistance of tendons, bones, and softer parts must be taken into account. Thus, the increase of the blacksmith’s muscular power would involve a considerable increase in all the tissues of the arm; but such an increase would involve a reconstruction of his whole organism.
Whenever there is an encroachment of one tissue on another, there is a disturbance249 of the normal balance, which readily passes into a pathological state. If the brain is overrun with connective tissue, or the heart with fatty tissue, we know the consequences. If connective tissue is deficient250, epithelial runs to excess, no longer limited by its normal antagonist, and pus, or cancer, result.
118c. It is unnecessary here to enlarge on this point. I have adduced it to show that we must extend our conception of the struggle for existence beyond that of the competition and antagonism of organisms—the external struggle; and include under it the competition and antagonism of tissues and organs—the internal struggle. Variability is inherent in organic substances, as the result of their indefiniteness of composition (§ 45b). This variability is indefinite, and is rendered definite by the competition and antagonism, so that every particular variation is the resultant of a composition of forces. The forces in operation are the internal and external conditions of existence—i. e. the nature of the organism, and its response to the actions of its medium. A change may take place120 in the medium without a corresponding response from the organism; or the change may find a response and the organism become modified. Every modification is a selection, determined by laws of growth; it is the resultant of a struggle between what, for want of a better term, may be called the organic affinities251—which represent in organized substances what chemical affinities are in the anorganized. Just as an organism which has been modified and thereby252 gained a superiority over others, has by this modification been selected for survival—the selection being only another aspect of this modification—so one tissue, or one organ, which has surpassed another in the struggle of growth, will thereby have become selected. Natural Selection, or survival of the fittest, therefore, is simply the metaphorical253 expression of the fact that any balance of the forces which is best adapted for survival will survive. Unless we interpret it as a shorthand expression of all the internal and external conditions of existence, it is not acceptable as the origin of species.
118d. Mr. Darwin has so patiently and profoundly meditated254 on the whole subject, that we must be very slow in presuming him to have overlooked any important point. I know that he has not altogether overlooked this which we are now considering; but he is so preoccupied255 with the tracing out of his splendid discovery in all its bearings, that he has thrown the emphasis mainly on the external struggle, neglecting the internal struggle; and has thus in many passages employed language which implies a radical180 distinction where—as I conceive—no such distinction can be recognized. “Natural Selection,” he says, “depends on the survival under various and complex circumstances of the best-fitted individuals, but has no relation whatever to the primary cause of any modification of structure.”61 On this we may remark, first, that121 selection does not depend on the survival, but is that survival; secondly256, that the best-fitted individual survives because of that modification of its structure which has given it the superiority; therefore if the primary cause of this modification is not due to selection, then selection cannot be the cause of species. He separates Natural Selection from all the primary causes of variation, either internal or external—either as results of the laws of growth, of the correlations257 of variation, of use and disuse, etc., and limits it to the slow accumulations of such variations as are profitable in the struggle with competitors. And for his purpose this separation is necessary. But biological philosophy must, I think, regard the distinction as artificial, referring only to one of the great factors in the production of species. And for this reason: Selection only comes into existence in the modifications produced either by external or internal changes; and the selected change cannot be developed further by mere inheritance, unless the successive progeny have such a disposition17 of the organic affinities as will repeat the primary change. Inherited superiority will not by mere transmission become greater. The facts which are relied on in support of the idea of “fixity of species” show at any rate that a given superiority will remain stationary258 for thousands of years; and no one supposes that the progeny of an organism will vary unless some external or internal cause of variation accompanies the inheritance. Mr. Darwin agrees with Mr. Spencer in admitting the difficulty of distinguishing between the effects of some definite action of external conditions, and the accumulation through natural selection of inherited variations serviceable to the organism. But even in cases where the distinction could be clearly established, I think we should only see an historical distinction, that is to say, one between effects produced by particular causes now122 in operation, and effects produced by very complex and obscure causes in operation during ancestral development.
118e. The reader will understand that my criticism does not pretend to invalidate Mr. Darwin’s discovery, but rather to enlarge its terms, so as to make it include all the biological conditions, and thus explain many of the variations which Natural Selection—in the restricted acceptation—leaves out of account. Mr. Darwin draws a broad line of distinction between Variation and Selection, regarding only those variations that are favorable as selected. I conceive that all variations which survive are by that fact of survival, selections, whether favorable or indifferent. A variety is a species in formation; now Selection itself is not a cause, or condition, of variation, it is the expression of variation. Mr. Darwin is at times explicit259 enough on this head: “It may metaphorically260 be said that Natural Selection is daily and hourly scrutinizing261 throughout the world the slightest variations; rejecting those that are bad, preserving and adding up all that are good; silently and insensibly working, whenever and wherever opportunity offers, at the improvement of each organic being in relation to its organic and inorganic conditions of life.”62 But the metaphorical nature of the term is not always borne in mind, so that elsewhere Natural Selection is said to “act on and modify organic beings,” as if it were a positive condition and not the expression of the modifying processes. Because grouse262 are largely destroyed by birds of prey263, any change in their color which would render them less conspicuous would enable more birds to escape; but it is obvious that this change of color will be due to Organic Affinity; and only when the change is effected will there have been that selection which expresses it. Mr. Darwin’s language, however,123 is misleading. He says: “Hence Natural Selection might be most effective in giving the proper color to each kind of grouse, and in keeping that color when once acquired.” This is to make Selection an agent, a condition of the development of color; which may be accepted if we extend the term so as to include the organic changes themselves. Again: “Some writers have imagined that Natural Selection induces variability, whereas it only implies the preservation264 of such variations as are beneficial to the being under its conditions of life.” It, however, is made to imply more than this, namely, the accumulation and further modification of such variations. “The mere existence of individual variability and of some well-marked varieties, though necessary as the foundation, helps us but little in understanding how species arise in nature. How have all those exquisite90 adaptations of one part of the organization to another part, and to the conditions of life, and of one organic being to another being, been perfected?” My answer to this question would be: By Organic Affinity, and the resulting struggle of the tissues and organs, the consequences of which are that very adaptation of the organism to external conditions, which is expressed as the selection of the structures best adapted. The selections are the results of the struggle, according to my proposed extension of the term “struggle.” Mr. Darwin defines the struggle: “The dependence265 of one being on another, and including (what is more important) not only the life of the individual but success in leaving progeny.” This definition seems defective266, since it omits the primary and more important struggle which takes place between the organic affinities in operation. To succeed in the struggle with competitors, the organism must have first acquired—by selection—a superiority in one or more of its organs.
118f. A little reflection will disclose the importance124 of keeping our eyes fixed on the internal causes of variation, as well as on the external conditions of the struggle. Mr. Darwin seems to imply that the external conditions which cause a variation are to be distinguished from the conditions which accumulate and perfect such variation, that is to say, he implies a radical difference between the process of variation and the process of selection. This, I have already said, does not seem to me acceptable; the selection, I conceive, to be simply the variation which has survived.63
If it be true that a Variety is an incipient267 Species and shows us Species in formation, it is in the same sense true that a variation is an incipient organ. A species is the result of a slowly accumulating divergence268 of structure; an organ is the result of a slowly accumulating differentiation. At each stage of differentiation there has been a selection, but we cannot by any means say that this selection was determined by the fact of its giving the organism a superiority over rivals, inasmuch as during all the early stages, while the organ was still in formation, there could be no advantage accruing269 from it. One animal having teeth and claws developed will have a decided270 superiority in the struggle over another animal that has no teeth and claws; but so long as the teeth and claws are in an undeveloped state of mere preparation they confer no superiority.
118g. Natural Selection is only the expression of the125 results of obscure physiological processes; and for a satisfactory theory of such results we must understand the nature of the processes. In other words, to understand Natural Selection we must recognize not only the facts thus expressed, but the factors of these facts,—we must analyze271 the “conditions of existence.” As a preliminary analysis we find external conditions, among which are included not only the dependence of the organism on the inorganic medium, but also the dependence of one organism on another,—the competition and antagonism of the whole organic world; and internal conditions, among which are included not only the dependence of the organism on the laws of composition and decomposition272 whereby each organite and each tissue is formed, but also the dependence of one organite and one tissue on all the others—the competition and antagonism of all the elements.
The changes wrought273 in an organism by these two kinds of conditions determine Varieties and Species. Although many of the changes are due to the process of natural selection brought about in the struggle with competitors and foes, many other changes have no such relation to the external struggle, but are simply the results of the organic affinities. They may or they may not give the organism a greater stability, or a greater advantage over rivals; it is enough that they are no disadvantage to the organism, they will then survive by virtue of the forces which produced them.
119. The position thus reached will be important in our examination of the Theory of Descent by which Mr. Darwin tentatively, and his followers274 boldly, explain the observed resemblances in structure and function as due to blood-relationship. The doctrine of Evolution affirms that all complex organisms are evolved by differentiation from simpler organisms, as we see the complex organ evolved from simpler forms. But it does not necessarily affirm126 that the vast variety of organisms had one starting-point—one ancestor; on the contrary, I conceive that the principles of Evolution are adverse275 to such a view, and insist rather on the necessity of innumerable starting-points. Let us consider the question.
That the Theory of Descent explains many of the facts must be admitted; but there are many which it leaves obscure; and Mr. Darwin, with that noble calmness which distinguishes him, admits the numerous difficulties. Whether these will hereafter be cleared away by an improvement in the Geological Record, now confessedly imperfect, or by more exhaustive exploration of distant countries, none can say; but, to my mind, the probability is, that we shall have to seek our explanation by enlarging the idea of Natural Selection, subordinating it to the laws of Organic Affinity. It does not seem to me, at present, warrantable to assume Descent as the sole principle of morphological uniformities; there are other grounds of resemblance beyond those of blood-relationship; and these have been too much overlooked; yet a brief consideration will disclose that similarity in the physiological laws and the conditions of Organic Affinity must produce similarity in organisms, independently of relationship; just as similarity in the laws and conditions of inorganic affinity will produce identity in chemical species. We do not suppose the carbonates and phosphates found in various parts of the globe, or the families of alkaloids and salts, to have any nearer kinship than that which consists in the similarity of their elements and the conditions of their combination. Hence, in organisms, as in salts, morphological identity may be due to a community of conditions, rather than community of descent. Mr. Darwin justly holds it to be “incredible that individuals identically the same should have been produced through Natural Selection from parents specifically127 distinct,” but he, since he admits analogous variations, will not deny that identical forms might issue from parents having widely different origins, provided that these parent forms and the conditions of their reproduction were identical, as in the case of vegetable and animal resemblances. To deny this would be to deny the law of causation. And that which is true of identical forms under identical conditions is true of similar forms under similar conditions. When History and Ethnology reveal a striking uniformity in the progression of social phases, we do not thence conclude that the nations are directly related, or that the social forms have a common parentage; we conclude that the social phases are alike because they have had common causes. When chemists point out the uniformity of type which exists in compounds so diverse in many of their properties as water and sulphuretted or selenetted hydrogen, and when they declare phosphoretted hydrogen to be the congener of ammonia, they do not mean that the one is descended276 from the other, or that any closer link connects them than that of resemblance in their elements.
In the case of vegetal and animal organisms, we observe such a community of elementary substance as of itself to imply a community in their laws of combination; and under similar conditions the evolved forms must be similar. With this community of elementary substance, there are also diversities of substance and of co-operant conditions; corresponding with these diversities there must be differences of form. Thus, although observation reveals that the bond of kinship does really unite many widely divergent forms, and the principle of Descent with Natural Selection will account for many of the resemblances and differences, there is at present no warrant for assuming that all resemblances and differences are due to this one cause, but, on the contrary, we128 are justified in assuming a deeper principle which may be thus formulated277: All the complex organisms are evolved from organisms less complex, as these were evolved from simpler forms; the link which unites all organisms is not always the common bond of heritage, but the uniformity of organized substance acting278 under similar conditions.
It is therefore consistent with the hypothesis of Evolution to admit a variety of origins or starting-points, though not consistent to admit the sudden appearance of complex Types, such as is implied in the hypothesis of specific creations.
119 a. The analogies of organic forms and functions demand a more exhaustive scrutiny279 than has yet been given them. Why is it that vessels, nerves, and bones ramify like branches, and why do these branches take on the aspect of many crystalline forms? Why is it that cavities are constantly prolonged in ducts, e. g. the mouth succeeded by the ?sophagus, the stomach by the intestines280, the bladder by the urethra, the heart by the aorta281, the ovary by the oviduct, and so on? Why are there never more than four limbs attached to a vertebral column, and these always attached to particular vertebr?? Why is there a tendency in certain tissues to form tubes, and in these tubes commonly to assume a muscular coat?64 To some of these queries282 an answer might be suggested which would bring them under known physical laws. I merely notice them here for the sake of emphasizing the fact that such analogies lie deeply imbedded in the laws of evolution, and that what has been metaphorically called organic crystallization will account for many similarities in form, without forcing us to have recourse to kinship. To take a very simple case. No one will maintain that the crystalline forms of snow have any kinship with the plants which they often resemble.129 Mr. Spencer has noticed the development of a wing-bearing branch from a wing of the Ptilota plumosa, when its nutrition is in excess. “This form, so strikingly like that of the feathery crystallizations of many inorganic substances, proves to us that in such crystallizations the simplicity283 or complexity284 of structure at any place depends on the quantity of matter that has to be polarized at that place in a given time. How the element of time modifies the result, is shown by the familiar fact that crystals rapidly formed are small, and that they become larger when they are formed more slowly.”65
It may be objected, and justly, that in the resemblance between crystals and organisms the analogy is purely285 that of form, and usually confined to one element, whereas between organisms there is resemblance of substance no less than of form, and usually the organisms are alike in several respects. The answer to this objection is, that wherever there is a similarity in the causal conditions (substance and history) there must be a corresponding similarity in the results; if this similarity extends to only a few of the conditions, the analogy will be slight; if to several, deep. But whether slight or deep we are not justified, simply on the ground of resemblance, in assuming, short of evidence, that because they are alike, two organisms are related by descent from a common ancestor.
120. Let us glance at a few illustrations. It has been urged as a serious objection to Mr. Darwin’s hypothesis,66 that it fails to explain the existence of phosphorescent organs in a few insects; and certainly, when one considers the widely different orders in which these organs appear, and their absence in nearly related forms, it is a difficulty. In noctiluc?, earthworms, molluscs, scolopendra,130 and fireflies, we may easily suppose the presence of similar organic conditions producing the luminosity; but it requires a strong faith to assign Descent as the cause.67 We may say the same of the electric organs possessed286 by seven species of fish, belonging to five widely separated genera. Although each species appears to have a limited geographical287 range, one or the other is found in almost every part of the globe. These organs occupy different positions, being now on each side of the head, now along the body, and now along the tail; and in different species they are innervated from different sources. Their intimate structure also varies; as appears from the remarkable investigations288 of Max Schultze.68 They cannot, therefore, be homologous. How could they have arisen? Not by the slow accumulations of Natural Selection, because, until the organs were fully formed, they could be of no advantage in the struggle; hence the slow growth of the organ must have proceeded without the aid of an advantage in the struggle—in each case131 from some analogous conditions which produced a differentiation in certain muscles. The fundamental resemblance to muscles was pointed289 out by Carus long ago. It has been insisted on by Leydig:69 and Owen says, “The row of compressed cells constituting the electric prism of the Torpedo290 offers some analogy to the row of microscopic discs of which the elementary muscle fibre appears to consist.”70 We must not, however, forget that these resemblances are merely such as suggest that the electric organ is a differentiation of the substance which elsewhere becomes muscular, and that Dr. Davy was justified in denying the organ to be muscular.71 That it is substituted for muscle cannot be doubted. Now, although we are entirely291 ignorant of the conditions which cause this differentiation of substance which elsewhere becomes muscular, but here becomes electric organs, we can understand that, when once such a development had taken place, if it in any way profited the fish in its struggle for existence, Natural Selection would tend to its further increase and propagation. So far Mr. Darwin carries us with him; but we decline proceeding further. The development of these organs in fishes so widely removed, does not imply an ancestral community. It is interpretable as mere growth on a basis once laid; and therefore would occur with or without any advantage in the struggle with rivals. The similarity in concurrent292 conditions is quite enough to account for the resemblance in structure. This, with his accustomed candor293, Mr. Darwin admits. “If the electric organs,” he says, “had been inherited from one ancient progenitor31 thus provided, we might have expected that all electric fishes would be specially207 related to each other. Nor does Geology at all132 lead to the belief that formerly most fishes had electric organs which most of their modified descendants have lost.”
121. It may seem strange that he should urge a difficulty against his hypothesis when it could be avoided by the simple admission that even among nearly allied animals great differences in development are observable, and the electric organs might be ranged under such diversities. But Mr. Darwin has so thoroughly294 wrought out his scheme, that he foresees most objections, and rightly suspects that if this principle of divergent development be admitted, it will cut the ground from under a vast array of facts which his hypothesis of Descent requires.
The sudden appearance of new organs, not a trace of which is discernible in the embryo or adult form of organisms lower in the scale,—for instance, the phosphorescent and electric organs,—is like the sudden appearance of new instruments in the social organism, such as the printing-press and the railway, wholly inexplicable295 on the theory of Descent,72 but is explicable on the theory of133 Organic Affinity. For observe: if we admit that differentiations of structure, and the sudden appearance of organs, can have arisen spontaneously—i. e. not hereditarily—as the outcome of certain changed physical conditions, we can hardly refuse to extend to the whole organism what we admit of a particular organ. If, again, we admit that organs very similar in structure and function spontaneously appear in organisms of widely different kinds—e. g. the phosphorescent and electric organs—we must also admit that similar resemblances may present themselves in organisms having a widely different parentage; and thus the admission of the spontaneous evolution of closely resembling organs carries with it the admission of the spontaneous evolution of closely resembling organisms: that the protoplasm of muscular tissue should, under certain changed conditions, develop into the tissue of electric organs, is but one case of the law that organized substance will develop into organisms closely resembling each other when the conditions have been similar.
122. It is to be remarked that Mr. Darwin fixes his attention somewhat too exclusively on the adaptations which arise during the external struggle for existence, and to that extent neglects the laws of organic affinity; just as Lamarck too exclusively fixed his attention on the influence of external conditions and of wants. Not that Mr. Darwin can be said to overlook the organic laws; he simply underestimates the part they play. Occasionally he seems arrested by them, as when instancing the “trailing palm in the Malay Archipelago, which climbs the loftiest trees by the aid of exquisitely constructed hooks,134 clustered around the ends of the branches, and this contrivance no doubt is of the highest service to the plant; but as there are nearly similar hooks on many trees which are not climbers, the hooks on the palm may have arisen from unknown laws of growth, and have been subsequently taken advantage of by the plant undergoing further modification and becoming a climber.”
123. I come round to the position from which I started, that the resemblances traceable among animals are no proof of kinship; even a resemblance so close as to defy discrimination would not, in itself, be such a proof. The absolute identity of chalk in Australia and in Europe is a proof that there was absolute identity in the formative conditions and the constituent elements, but no proof whatever that the two substances were originally connected by genesis. In like manner the similarity of a plant or animal in Africa and Europe may be due to a common kinship, but it may also be due to a common history. It is indeed barely conceivable that the history, from first to last, would ever be so rigorously identical in two parts of the globe as to produce complex identical forms in both; because any diversity, either in structure or external conditions, may be the starting-point of a wide diversity in subsequent development; and the case of organic combinations is so far unlike the inorganic, that while only one form is possible to the latter (chalk is either formed or not formed), many forms are possible to organic elements owing to the complexity and indefiniteness of organic composition. But although forms so allied as those of Species are not readily assignable to an identical history in different quarters of the globe, it is not only conceivable, but is eminently probable, that Orders and Classes have no nearer link of relationship than is implied in their community of organized substance and their common history. The fact that there is not a single135 mammal common to Europe and Australia is explicable, as Mr. Darwin explains it, on the ground that migration296 has been impossible to them; but it is also explicable on the laws of Evolution—to have had mammals of the same species and genera would imply a minute coincidence in their history, which is against the probabilities. Again, in the Oceanic Islands there are no Batrachians; but there are Reptiles, and these conform to the reptilian297 type. Mr. Darwin suggests that the absence of Batrachia is due to the impossibility of migration, their ova being destroyed by salt water. But may it not be due to the divergence from the reptilian type, which was effected elsewhere, not having taken place in these regions? When we find the metal Tin in Prussia and Cornwall, and nowhere else in Europe, must we not conclude that in these two countries, and nowhere else, a peculiar conjunction of conditions caused this peculiar evolution?
124. The question at issue is, Are the resemblances observable among organic forms due to remote kinship, and their diversities to the divergences298 caused by adaptation to new conditions? or are the resemblances due to similarities, and the diversities to dissimilarities in the substance and history of organic beings? Are we to assume one starting-point and one centre of creation, or many similar starting-points at many centres? So far from believing that all plants and animals had their origin in one primordial299 cell, at one particular spot, from which descendants migrated and became diversified under the diverse conditions of their migration, it seems to me more consistent with the principle of Evolution to admit a vast variety of origins more or less resembling each other; and this initial resemblance will account for the similarities still traceable under the various forms; while the early differences, becoming intensified300 by development under different conditions, will yield the diversities. The136 evolution of organisms, like the evolution of crystals, or the evolution of islands and continents, is determined, 1st, by laws inherent in the substances evolved, and, 2d, by relations to the medium in which the evolution takes place. This being so, we may à priori affirm that the resultant forms will have a community strictly corresponding with the resemblance of the substances and their conditions of evolution, together with a diversity corresponding with their differences in substance and conditions. It is usually supposed that the admission of separate “centres of creation” is tantamount to an admission of “successive creations” as interpreted by the majority of those who invoke301 “creative fiats.” But the doctrine of Evolution, which regards Life as making its appearance consequent upon a concurrence302 of definite conditions, and regards the specific forms of Life as the necessary consequences of special circumstances, must also accept the probability of similar conditions occurring at different times and in different places. Upon what grounds, cosmical or biological, are we to assume that on only one microscopic spot of this developing planet such a group of conditions was found—on only one spot a particle of protein substance was formed out of the abundant elements, and under conditions which caused it to grow and multiply, till in time its descendants overran the globe? The hypothesis that all organic forms are the descendants of a single germ, or of even a few germs, and are therefore united by links of kinship more or less remote, is not more acceptable than the hypothesis that all the carbonates and phosphates, all the crystals, and all the strata303 found in different parts of the globe, are the descendants of a single molecule140, or a few molecules; or,—since this may seem too extravagant,—than that the various maladies which afflict304 organic beings are, in a literal sense, members of families having a nearer relationship than137 that of being the phenomena manifested by similar organs under similar conditions—a conception which might have been accepted by those metaphysical pathologists who regarded Disease as an entity. Few philosophers have any hesitation305 in supposing that other planets besides our own are peopled with organic forms, though, from the great differences in the conditions, these forms must be extremely unlike those of our own planet. If separate worlds, why not separate centres? The conclusion seems inevitable that wherever and whenever the state of things permitted that peculiar combination of elements known as organized substance, there and then a centre was established—Life had a root. From roots closely resembling each other in all essential characters, but all more or less different, there have been developed the various stems of the great tree. Myriads of roots have probably perished without issue; myriads have developed into forms so ill-adapted to sustain the fluctuations306 of the medium, so ill-fitted for the struggle of existence, that they became extinct before even our organic record begins; myriads have become extinct since then; and the descendants of those which now survive are like the shattered regiments307 and companies after some terrific battle.
125. There seems to me only one alternative logically permissible308 to the Evolution Hypothesis, namely, that all organic forms have had either a single origin, or else numerous origins; in other words, that a primordial cell was the starting-point from which all organisms have been successively developed; or that the development issued from many independent starting-points, more or less varied309. This is apparently not the aspect presented by the hypothesis to many of its advocates; they seem to consider that if all organic forms are not the lineal descendants of one progenitor, they must at any rate be the descendants of not more than four or five. The common138 belief inclines to one. Mr. Darwin, whose caution is as remarkable as his courage, and whose candor is delightful310, hesitates as to which conclusion should be adopted: “I cannot doubt,” he says, “that the theory of descent, with modifications, embraces all the members of the same class. I believe that animals have descended from, at most, only four or five progenitors, and plants from an equal or lesser number. Analogy would lead me one step further, namely, to the belief that all animals and plants have descended from some one prototype. But analogy may be a deceitful guide.”
126. I cannot see the evidence which would warrant the belief that Life originated solely in one microscopic lump of protoplasm on one single point of our earth’s surface; on the contrary, it is more probable that from innumerable and separate points of this teeming311 earth, myriads of protoplast sprang into existence, whenever and wherever the conditions of the formation of organized substance were present. It is probable that this has been incessantly going on, and that every day new protoplasts appear, struggle for existence, and serve as food for more highly organized rivals; but whether an evolution of the lower forms is, or is not, still going on, there can be no reluctance312 on the part of every believer in Evolution to admit that when organized substance was first evolved, it was evolved at many points. If this be so, the community observable in organized substance, wherever found, may as often be due to the fact of a common elementary composition as to the fact of inheritance. If this be so, we have a simple explanation both of the fundamental resemblances which link all organisms together, and of the characteristic diversities which separate them into kingdoms, classes, and orders. The resemblances are many, and close, because the forms evolved had a similar elementary composition, and their stages of evolution were139 determined by similar conditions. The diversities are many, because the forms evolved had from the first some diversities in elementary composition, and their stages of evolution were determined under conditions which, though similar in general, have varied in particulars. Indeed, there is no other ground for the resemblances and differences among organic beings than the similarities and dissimilarities in their Substance and History; and, whether the similarities are due to blood-relationship, or to other causes, the results are the same. There is something seductive in the supposition that Life radiated from a single centre in ever-increasing circles, its forms becoming more and more various as they came under more various conditions, until at last the whole earth was crowded with diversified existences. “From one cell to myriads of complex organisms, through countless ?ons of development,” is a formula of speculative313 grandeur314, but I cannot bring myself to accept it; and I think that a lingering influence of the tradition of a “creative fiat” may be traced in its conception. May we not rather assume that the earth at the dawn of Life was a vast germinal membrane, every slightly diversified point producing its own vital form; and these myriads upon myriads of forms—all alike and all unlike—urged by the indwelling tendencies of development, struggled with each other for existence, many failing, many victorious185, the victors carrying their tents into the camping ground of the vanquished315. The point raised is the immense improbability of organized substance having been evolved only in one microscopic spot; if it were evolved at more than one spot, and under slightly varying conditions, there would necessarily have arisen in these earliest formations the initial diversities which afterwards determined the essential independence and difference of organisms.
129. Let us for a moment glance at the resemblances and140 diversities observable in all organisms. All have a common basis, all being constructed out of the same fundamental elements: carbon, hydrogen, nitrogen, and oxygen; these (the organogens, as they are named), with varying additions of some other elements, make up what we know as Organic Substance, vegetal and animal. Another peculiarity316 all organisms have in common, namely, that their matter is neither solid nor liquid, but viscid. Beside this community of Substance we must now place a community of History. All organisms grow and multiply by the same process; all pass through metamorphic stages ending in death; all, except the very simplest, differentiate145 parts of their substance for special uses, and these parts (cilia, membranes317, tubes, glands, muscles, nerves) have similar characters in whatever organism they appear, and their development is always similar, so that the muscles or nerves of an intestinal worm, a lobster318, or a man, are in structure and history fundamentally alike. When, therefore, we see that there is no biological character of fundamental importance which is not universal throughout the organic world, when we see that in Structure and History all organisms have a community pervading319 every variety, it is difficult not to draw the conclusion that some hidden link connects all organisms into one; and when, further, it is seen that the most divergent forms may be so arranged by the help of intermediate forms only slightly varying one from the other, that the extreme ends—the monad and the man—may be connected, and a genealogical tree constructed, which will group all forms as modified descendants from a single form, the hypothesis that kinship is the bidden link of which we are in search becomes more and more cogent320.
130. But now let the other aspect be considered. If there is an unmistakable uniformity, there is also a diversity141 no less unmistakable. The chemical composition of organic substances is various. Unlike inorganic substances, the composition of which is rigorously definite, organic substances are, within narrow limits, variable in composition (§ 45).
I pass over the resemblances and differences observed in the earliest stages of development, marked as they are, and direct attention to the fact, that down at what must be considered the very lowest organic region, we meet with differences not less striking than those met with in the highest, we find structures (if structures they may be called), which cannot be affiliated321, so widely divergent is their composition. The structureless vibrio, for example, is not only capable of living in a medium destitute of Oxygen, but is, according to M. Pasteur, actually killed by oxygen; whereas the equally simple bacteria can no more dispense322 with Oxygen than other animals can. Consider for a moment the differences implied in the fact that one organism cannot even form an enveloping323 membrane to contain its protoplasm, whereas another contrives324 to secrete120 an exquisite shell; yet between the naked Rhizopod and the shelled Rhizopod our lenses and reagents fail to detect a difference. One Monad can assimilate food of only one kind, another Monad assimilates various kinds.73 What a revelation of chemical differences appears in the observations of M. Pasteur respecting the vibrio and bacteria, in a fermentescible liquid—the former beginning the putrid325 fermentation which the latter completes! We cannot doubt that some marked difference must exist between the single-celled organism which produces alcoholic326 fermentation, and that which produces acetic327 fermentation, and that again which produces butyric fermentation; and if we find distinctions thus established at the lowest142 region of the organic series, we need not marvel if the distinctions become wider and more numerous as the series becomes more diversified. The structure and development of an organism are dependent on the affinities of its constituent molecules, and it is a biological principle of great importance which Sir James Paget insists on, when he shows how “the existence of certain materials in the blood may determine the formation of structures in which they may be incorporated.”74 Any initial diversity may thus become the starting-point of a considerable variation in subsequent evolution.75 Thus, supposing that on a given spot there are a dozen protoplasts closely resembling each other, yet each in some one detail slightly varying; if this variation is one which, by its relations to the external medium, admits of a difference in the assimilation of materials present in the medium, it may be the origin of some new direction in development, and the ultimate consequence may be the formation of a shell, an internal skeleton, a muscle, or a nerve. Were this not so,143 it would be impossible to explain such facts as that chitine is peculiar to the Articulata, cellulose to Molluscoida, carbonates of lime to Mollusca and Crustacea, and phosphates to Vertebrata—all assimilated from the same external medium. But we see that from this medium one organism selects the materials which another rejects; and this selection is determined by the nature of the structure: which assimilates only those materials it is fitted to assimilate. We hear a great deal of Adaptation determining changes of structure and function, and are too apt to regard this process as if it were not intimately dependent on a corresponding structural328 change. By no amount of external influence which left the elementary composition of the structure unchanged, could an organism with only two tissues be developed into an organism with three or four. By no supply or stimulus329, could an animal incapable of assimilating peroxide of iron acquire red blood corpuscles, although it might have the iron without the corpuscles; nor could an oyster330 form its shell unless capable of assimilating carbonate of lime. For myriads of years, in seas and ponds, under endless varieties of external conditions, the am?b? have lived and died without forming a solid envelope, although the materials were abundant, and other organisms equally simple have formed envelopes of infinite variety. In all the seas, and from the earliest ages, zoophytes have lived, and assumed a marvellous variety of shapes and specialization of functions; but although some of them have acquired muscles, none have acquired true nerves, none bone. Ages upon ages rolled on before fishes were capable of forming bone; and thousands are still incapable of forming it, though living in the same waters as the osseous fishes.
131. “Looking to the dawn of life,” says Mr. Darwin (repeating an objection urged against his hypothesis),144 “when all organic beings, as we imagine, presented the simplest structure, how could the first steps in advancement331, or in the differentiation and specialization of parts have arisen? I can make no sufficient answer; and can only say that, as we have no facts to guide us, all speculation332 would be baseless and useless.”
Where Mr. Darwin hesitates, lesser men need extra caution; but I must risk the danger of presumption333, at least so far as to suggest that while an answer to this question is difficult on that dynamical view of Evolution which regards Function as determining Structure, it is less difficult on the statico-dynamical view propounded334 in these pages; the difficulty which besets335 the explanation when all the manifold varieties of organic forms are conceived as the successive divergences from an original starting-point, is lessened when a variety of different starting-points is assumed, in each of which some initial diversity prepared the way for subsequent differentiations; just as we know that between the ovum of a vertebrate and the ovum of an invertebrate134, similar as they are, there is a diversity which manifests itself in their subsequent evolution. If Function is determined by Structure, and Evolution is the product of the two, it is clear that the different directions in the lines of development will have their origin in structural differences, and not in the action of external circumstances, unless these previously bring about a structural change. The action of the medium on the organism is assuredly a potent22 factor which Biology cannot ignore: but the organism itself is a factor, and according to its nature the influence of the medium is defined. (§ 118.)
132. Quitting for a moment the track of this argument, let us glance at the resemblances and differences observable in Plants and Animals, because most people admit that these have separate origins. The resemblances145 are scarcely less significant than those existing among animals. Both have a similar basis of elementary composition; not only are both formed out of protoplasts with similar properties, but in both the first step from the protoplasm to definite structure is the Cell. And the life of this Cell is remarkably336 alike in both, its phases of development being in many respects identical; nay, even such variations as obtain in the cell-membranes are curiously337 linked together by a community in the formative process.76 In both Plants and Animals we find individuals constituted—1st, by single cells; 2d, by groups of cells undistinguishable among each other; and 3d, by groups of differentiated cells. In both we find colonies of individuals leading a common life. In both the processes of Nutrition and Reproduction are essentially338 similar; both propagate sexually and asexually; both exhibit the surprising phenomena of parthenogenesis and alternate generations. In both there are examples of a free-roving embryo which in maturity becomes fixed to one spot, losing its locomotive organs and developing its reproductive organs. In both the development of the reproductive organs is the climax339 which carries Death. So close is the analogy between plant-life and animal-life, that it even reaches the properties usually held to be exclusively animal; I mean that even should we hesitate to accept Cohn’s discovery of the muscles in certain plants,77 we cannot deny146 that plants exhibit Contractility; and should we refuse to interpret as Sensibility the phenomena exhibited by the Sensitive Plants, we cannot deny that they present a very striking analogy to the phenomena of Sensibility exhibited by animals.
133. It is unnecessary to continue this enumeration340, which might easily be carried into minute detail. A chapter of such resemblances would only burden the reader’s mind, without adding force to the conclusion that a surprising community in Substance and Life-history must be admitted between Plants and Animals. This granted, we turn to the differences, and find them no less fundamental and detailed341. Chemistry tells us nothing of the differences in the protoplasms from which animals and plants arise; but that initial differences must exist is proved by the divergence of the products. The vegetable cell is not the animal cell; and although both plants and animals have albumen, fibrine, and caseine, the derivatives342 of these are unlike. Horny substance, connective tissue, nerve tissue, chitine, biliverdine, creatine, urea, hippuric acid, and a variety of other products of evolution or of waste, never appear in plants; while the hydrocarbons343 so abundant in plants are, with two or three exceptions, absent from animals. Such facts imply differences in elementary composition; and this result is further enforced by the fact that where the two seem to resemble, they are still different: the plant protoplasm forms various cells, but never forms a cartilage-cell or nerve-cell; fibres, but never a fibre of elastic344 tissue; tubes, but never a nerve tube; vessels, but never a vessel168 with muscular coatings; solid “skeletons,” but always from an organic substance (cellulose), not from phosphates and carbonates. In no one character can we say that the plant and the animal are identical; we can only point throughout the two kingdoms to a great similarity accompanying a radical diversity.
147 134. Having brought together the manifold resemblances, and the no less marked diversities, we must ask what is their significance? Do the resemblances imply a community of origin, an universal kinship? If so, the diversities will be nothing more than the divergences which have been produced by variations in the Life-history of the several groups. Or—taking the alternative view—do the diversities imply radical differences of origin? If so, the resemblances will be nothing more than the inevitable analogies resulting from Organized Substance being everywhere somewhat similar in composition, and similar in certain phases of evolution. To state the former position in the simplest way, we may assume that of two masses of protoplasm having a common parentage, one, by the accident of assimilating a certain element not brought within the range of the other, thereby becomes so differentiated as to form the starting-point of a series of evolutions widely divergent from those possible to its congener; and at each stage of evolution the introduction of a new element (made possible by that stage) will form the origin of a new variation. It is thus feasible to reduce all organic forms to a primordial protoplasm, in the evolutions of which successive differentiations have been established. On the other hand, it is equally feasible to assume that the existence of radical differences must be invoked345 to account for the possibility of the successive differentiations.
135. The hunt after resemblances has led to much mistaken speculation; and with reference to the topic now before us, it may be urged, that although by attaching ourselves to the points of community, in disregard of the diversities, we may make it appear that all animals have a common parentage, and that plants and animals are merely divergent groups of the same prototype, a rigorous logic will force us onwards, and compel us to148 admit that a kinship no less real unites the organic with the inorganic world. For upon what principle are we to pause at the cell or protoplasm? If by a successive elimination346 of differences we reduce all organisms to the cell, we must go on and reduce the cell itself to the chemical elements out of which it is constructed; and inasmuch as these elements are all common to the inorganic world, the only difference being one of synthesis, we reach a result which is the stultification347 of all classification, namely, the assertion of a kinship which is universal. We must bear in mind that all things may be reduced to a common root by simply disregarding their differences. All things are alike when we set aside their unlikeness.
136. Suppose, for the sake of illustration, we regard an Orchestra in the light of the Development Hypothesis. The various instruments of which it is composed have general resemblances and particular differences, not unlike those observable in various organisms; and as we proceed in the work of classification we quickly discover that they may be arranged in groups analogous to the Sub-kingdoms, Classes, Orders, Genera, and Species of the organic world. Each group has its cardinal348 distinction, its initial point of divergence. All musical instruments resemble each other in the fundamental character of producing Tone by the vibrations349 of their substance. This may be called their organic basis. The first marked difference which determines the character of two sub-kingdoms (namely, instruments of Percussion350 and Wind instruments) arises from a difference in the method of impressing the vibrations; and the grand divisions of these sub-kingdoms arise from the nature of the vibrating substances. Each type admits of many modifications, but the primary distinction is ineffaceable. We can conceive the Pipe modified into a Flute351, a Flageolet, a Clarionet, a Hautbois, a Bassoon, or a Fife, by simple accessory149 changes; to modify the Pipe into a Trumpet353, and thus produce the peculiar timbre354 of the trumpet, would be impossible except by the substitution of a new material; by replacing the wood with metal we may adhere to the old Type, but we have created a new Class. (Attention is requested to this point, because the current views respecting the transmutation of tissues, which seem to lend a decisive support to the hypothesis of the transmutation of species are very commonly vitiated by the confusion of transformation123 with substitution. No anatomical element is transformed into another specifically different—an epithelial-cell into a nerve-cell, for instance—but one anatomical element is frequently substituted for another.) To convert the Pipe or the Trumpet into a Violin or a Drum would be impossible. We can follow the modifications of a Tambourine355 into a Drum or Kettle-drum, but no modifications of these will yield the Cymbals356. That is to say, the vibrating materials—wood, metal, parchment, and the combination of wood and strings—have peculiar properties, and the instruments formed of such materials must necessarily from the very first belong to different groups, each subdivision of the groups being dependent on some characteristic difference in methods of impressing the vibrations, or in the materials. Although all musical instruments have a common property and a common purpose, we do not regard them as transformations of one primitive357 instrument; their kindred nature is a subjective358 conception; the analogies are numerous and close, but we know their origin. It is obvious that men being pleased by musical tones, have been led by their delight to construct instruments whenever they have discovered substances capable of musical vibrations, or methods of impressing such vibrations. By substituting the bow for the plectrum or the fingers, they may have changed the Lyre into the150 Violin, Viola, Violoncello, and Bass352. (It seems historically probable that the real origin of the Violin class was an instrument with one string played on by a bow.) By grouping together Pipes of various sizes they got the Panpipes; by substituting metal and enlarging the blowing apparatus359 they got the Organ. By beating on stretched parchment with the finger, they got the Tambourine and Tom-Tom; by doubling this and using a stick they got the Drum. By beating metal with metal they got the Cymbals; by beating wood they got the Castanets.
137. The application of this illustration is plain. Just as a wind-instrument is incapable of becoming a stringed instrument, so a Mollusc, with all its muscles unstriped, and its nervous system unsymmetrical, is incapable of becoming a Crustacean, with all its muscles striped and its nervous system symmetrical. Indeed there are probably few biologists of the present day who imagine the transmutation of one kind into the other to be possible; but many biologists assume that both may have been evolved from a common root. The point is beyond proof; yet I think there is a greater probability in the assumption that both were evolved from different roots. At any rate, one thing is certain; a divergence could only have been effected by a series of substitutions; and the question when and how these substitutions took place is unanswerable: one school believes them to have been creative fiats, the other school believes them to have been transmutations.
138. When we see an annelid and a vertebrate resembling each other in some special point which is not common either to their classes or to any intermediate classes—as when we see the wood-louse (Oniscus) and the hedgehog defend themselves in the same strange way by rolling up into a ball—we cannot interpret this as a trace of distant kinship. When we see a breed of pigeons and a breed151 of canaries turning somersaults, and one of the Bear family (Ratel) given to the same singular habit, we can hardly suppose that this is in each case inherited from a common progenitor. When we see one savage race tipping arrows with iron, and another, ignorant of iron, using poison, there is a community of object effected by diversity of means; but the analogy does not necessarily imply any closer connection between the two races than the fact that men with similar faculties360 and similar wants find out similar methods of supplying their wants. Even those who admit that the human race is one family, and that the various peoples carried with them a common fund of knowledge when they separated from the parent stock, may still point to a variety of new inventions and new social developments which occurred quite independently of each other, yet are strikingly alike. Their resemblance will be due to resemblance in the conditions. The existence, for example, of a religious worship, or a social institution, in two nations widely separated both in time and space, and under great historical diversities, is no absolute proof that these two nations are from the same stock, and that the ideas have the same parentage. It may be so; it may be otherwise. It may be an analogy no more implying kinship than the fact of ants making slaves of other ants (and these the black ants!) implies a kinship with men. Given an organization which in the two nations is alike, and a history which is in certain characteristics analogous, there must inevitably result religious and social institutions having a corresponding resemblance. I do not wish to imply that the researches of philologists361 and ethnologists are misdirected, or that their conclusions respecting the kinship of mankind are to be rejected; I only urge the consideration that perhaps too much stress is laid on community of blood, and not enough on community of conditions.
152
RECAPITULATION.
139. The various lines of argument may here be recapitulated362. The organic world presents a spectacle of endless diversity, accompanied by a pervading uniformity. The general resemblances in forms and functions are more or less masked by particular differences. The resemblances, it is said, may be all due to kinship, all the living individuals having descended from a primordial cell; and at each stage of the descent the adaptations to new conditions may have issued in deviations from the ancestral form, while the process of Natural Selection giving stability to those variations which best fitted the organism in the struggle of existence, has made greater and greater gaps, and produced more marked diversities among the descendants. This is the Darwinian Theory: “On my theory unity215 of Type is explained by unity of Descent.”
140. By the general consent of biologists, this theory is held to explain many if not all the observed facts. It is a very luminous suggestion; but it requires an enlargement so as to include Organic Affinity; and when once this fundamental principle is admitted, it brings with it very serious doubts as to the theory of Descent. We are then entitled to assume that many of the most striking resemblances, instead of being due to kinship, are due simply to the general principle that similar causes must have similar effects, and that organic substances having a very close resemblance, organized substances must have similar stages of evolution under similar conditions; and thus organs will necessarily take on very similar forms in very different organisms (for example, the eye of the cephalopod and the eye of the vertebrate), and organisms having widely different parentage may closely resemble each other. If we are entitled to assume that protoplasm appeared not in one microscopic spot alone, but in many153 places and in vast quantities—and this is surely the more justifiable363 assumption—then we must also admit that these germinal starting-points were from the first, or very shortly afterwards, differentiated by variations in their elementary composition. Now we know that a very minute change in composition may lead to immense differences in evolution. Thus the descendants of two slightly different progenitors may, by continual differentiation, become very markedly unlike; yet, because of the original resemblance of their substances, they will reveal a pervading similarity.
While it is thus conceivable that all organisms may resemble each other, and all differ, owing to the similarities and diversities in the “conditions of existence” (and among those conditions that of descent is of wide range), it is not very readily conceivable how advantage in the external struggle could have determined the varieties of form and function, because many differentiations give no superiority in the struggle. As Mr. St. George Mivart urges, “Natural Selection utterly fails to account for the conservation and development of the minute and rudimentary beginnings, the slight and infinitesimal commencements of structures, however useful those structures may afterwards become.”78 And this is undeniable on the supposition that Natural Selection is an agency not identical with the variations of growth, but exclusively confined to the accumulation of favorable variations.
141. In estimating the two hypotheses—First, of Descent from one primordial germ, and the modifications due to Natural Selection, or, as I should say, expressed in Selection; and Secondly, of Descent from innumerable germs having initial differences, which differences radiated into the marked modifications, there is this superiority to be claimed for the first, that it is more easily handled as154 an aid to research, and is therefore more decidedly useful. The laws of Organic Affinity are at present too obscure for any successful application. I only wish to point out that the theory of Descent is an imaginary construction of what may have been the process of species-formation, not a transcription of the process observed. It constructs an imaginary Type as progenitor of a long line of widely different descendants. The annelid which is taken as the ancestor of the vertebrates is not any annelid known either to zo?logists or geologists364, but a generalized and imaginary type. So daringly liberal is the imagination in endowing the ancestor with whatever may be required for the descendants, that Mr. Darwin thinks it probable, from what we know of the embryos of vertebrates, that these animals “are the modified descendants of some ancient progenitor which was furnished in its adult state with branchi?, a swim-bladder, four simple limbs, and a long tail, all fitted for an organic life,” (p. 533); and Dr. Dohrn conceives the original type to have contained within itself all that has been subsequently evolved in the highest vertebrate, the other and less elaborate organisms being mere degradations365 from this type.79 This use of the imagination, although not without advantages, is also not without dangers. It may direct research, it must not be suffered to replace research.
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1
differentiation
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| n.区别，区分 | |
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embryo
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| n.胚胎，萌芽的事物 | |
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logic
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| n.逻辑(学)；逻辑性 | |
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lesser
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| adj.次要的，较小的；adv.较小地，较少地 | |
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mere
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| adj.纯粹的；仅仅，只不过 | |
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6
marvel
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| vi.(at)惊叹vt.感到惊异；n.令人惊异的事 | |
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7
marvels
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| n.奇迹( marvel的名词复数 )；令人惊奇的事物（或事例）；不平凡的成果；成就v.惊奇，对…感到惊奇( marvel的第三人称单数 ) | |
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fin
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| n.鳍；(飞机的)安定翼 | |
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modification
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| n.修改，改进，缓和，减轻 | |
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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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treatise
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| n.专著；(专题)论文 | |
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rib
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| n.肋骨，肋状物 | |
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peculiar
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| adj.古怪的，异常的；特殊的，特有的 | |
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peculiarities
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| n. 特质, 特性, 怪癖, 古怪 | |
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longevity
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| n.长命；长寿 | |
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dispositions
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| 安排( disposition的名词复数 )； 倾向； （财产、金钱的）处置； 气质 | |
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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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nay
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| adv.不；n.反对票，投反对票者 | |
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dormant
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| adj.暂停活动的；休眠的；潜伏的 | |
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microscopic
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| adj.微小的，细微的，极小的，显微的 | |
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appreciably
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| adv.相当大地 | |
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potent
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| adj.强有力的，有权势的；有效力的 | |
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justified
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| a.正当的，有理的 | |
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acorn
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| n.橡实，橡子 | |
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physiologist
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| n.生理学家 | |
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physiologists
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| n.生理学者( physiologist的名词复数 )；生理学( physiology的名词复数 )；生理机能 | |
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inevitable
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| adj.不可避免的，必然发生的 | |
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deduction
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| n.减除，扣除，减除额；推论，推理，演绎 | |
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countless
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| adj.无数的，多得不计其数的 | |
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guise
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| n.外表，伪装的姿态 | |
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progenitor
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| n.祖先，先驱 | |
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progenitors
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| n.祖先( progenitor的名词复数 )；先驱；前辈；原本 | |
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progeny
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| n.后代，子孙；结果 | |
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celebrated
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| adj.有名的，声誉卓著的 | |
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plausible
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| adj.似真实的，似乎有理的，似乎可信的 | |
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bonnet
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| n.无边女帽；童帽 | |
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demonstration
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| n.表明，示范，论证，示威 | |
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demonstrations
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| 证明( demonstration的名词复数 )； 表明； 表达； 游行示威 | |
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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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secreting
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| v.（尤指动物或植物器官）分泌( secrete的现在分词 )；隐匿，隐藏 | |
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glands
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| n.腺( gland的名词复数 ) | |
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gland
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| n.腺体，(机)密封压盖，填料盖 | |
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membrane
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| n.薄膜，膜皮，羊皮纸 | |
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submission
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| n.服从，投降；温顺，谦虚；提出 | |
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doctrine
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| n.教义；主义；学说 | |
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doctrines
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| n.教条( doctrine的名词复数 )；教义；学说；（政府政策的）正式声明 | |
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47
destitute
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| adj.缺乏的；穷困的 | |
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intelligible
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| adj.可理解的，明白易懂的，清楚的 | |
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49
relinquish
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| v.放弃，撤回，让与，放手 | |
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preposterous
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| adj.荒谬的，可笑的 | |
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absurdities
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| n.极端无理性( absurdity的名词复数 )；荒谬；谬论；荒谬的行为 | |
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rhetoric
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| n.修辞学，浮夸之言语 | |
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fiat
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| n.命令，法令，批准；vt.批准，颁布 | |
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fiats
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| n.命令，许可( fiat的名词复数 )；菲亚特汽车（意大利品牌） | |
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interpretation
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| n.解释，说明，描述；艺术处理 | |
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56
attain
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| vt.达到，获得，完成 | |
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supreme
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| adj.极度的，最重要的；至高的，最高的 | |
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previously
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| adv.以前，先前（地） | |
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undoing
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| n.毁灭的原因，祸根；破坏，毁灭 | |
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fully
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| adv.完全地，全部地，彻底地；充分地 | |
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Vogue
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| n.时髦，时尚；adj.流行的 | |
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obstinately
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| ad.固执地，顽固地 | |
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unwilling
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| adj.不情愿的 | |
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erect
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| n./v.树立，建立，使竖立；adj.直立的，垂直的 | |
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mortar
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| n.灰浆，灰泥；迫击炮；v.把…用灰浆涂接合 | |
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mansion
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| n.大厦，大楼；宅第 | |
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proceeding
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| n.行动，进行，(pl.)会议录，学报 | |
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repugnance
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| n.嫌恶 | |
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evasion
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| n.逃避，偷漏(税) | |
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incompetence
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| n.不胜任，不称职 | |
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incompetent
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| adj.无能力的，不能胜任的 | |
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phenomena
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| n.现象 | |
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forth
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| adv.向前；向外，往外 | |
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entity
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| n.实体，独立存在体，实际存在物 | |
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embryonic
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| adj.胚胎的 | |
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reptile
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| n.爬行动物；两栖动物 | |
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embryos
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| n.晶胚；胚，胚胎( embryo的名词复数 ) | |
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lizard
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| n.蜥蜴，壁虎 | |
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lizards
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| n.蜥蜴( lizard的名词复数 ) | |
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extremities
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| n.端点( extremity的名词复数 )；尽头；手和足；极窘迫的境地 | |
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allied
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| adj.协约国的；同盟国的 | |
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spotted
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| adj.有斑点的，斑纹的，弄污了的 | |
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distinguished
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| adj.卓越的，杰出的，著名的 | |
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puma
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| 美洲豹 | |
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arteries
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| n.动脉( artery的名词复数 )；干线，要道 | |
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slits
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| n.狭长的口子，裂缝( slit的名词复数 )v.切开，撕开( slit的第三人称单数 )；在…上开狭长口子 | |
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spawn
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| n.卵，产物，后代，结果；vt.产卵，种菌丝于，产生，造成；vi.产卵，大量生产 | |
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tadpole
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| n.[动]蝌蚪 | |
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tadpoles
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| n.蝌蚪( tadpole的名词复数 ) | |
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exquisite
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| adj.精美的；敏锐的；剧烈的，感觉强烈的 | |
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exquisitely
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| adv.精致地；强烈地；剧烈地；异常地 | |
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aquatic
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| adj.水生的，水栖的 | |
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solely
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| adv.仅仅，唯一地 | |
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utterly
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| adv.完全地，绝对地 | |
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adherence
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| n.信奉，依附，坚持，固着 | |
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96
specimen
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| n.样本，标本 | |
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97
pedantic
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| adj.卖弄学问的；迂腐的 | |
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98
trifling
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| adj.微不足道的；没什么价值的 | |
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99
justify
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| vt.证明…正当(或有理)，为…辩护 | |
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100
incessant
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| adj.不停的，连续的 | |
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101
mythically
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| adv.想像地，虚构地 | |
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102
ordained
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| v.任命（某人）为牧师( ordain的过去式和过去分词 )；授予（某人）圣职；（上帝、法律等）命令；判定 | |
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103
frustrate
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| v.使失望；使沮丧；使厌烦 | |
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104
frustrated
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| adj.挫败的，失意的，泄气的v.使不成功( frustrate的过去式和过去分词 )；挫败；使受挫折；令人沮丧 | |
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105
perverted
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| adj.不正当的v.滥用( pervert的过去式和过去分词 )；腐蚀；败坏；使堕落 | |
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106
prodigal
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| adj.浪费的，挥霍的，放荡的 | |
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107
bestowed
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| 赠给，授予( bestow的过去式和过去分词 ) | |
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108
groove
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| n.沟，槽；凹线，（刻出的）线条，习惯 | |
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109
virtue
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| n.德行，美德；贞操；优点；功效，效力 | |
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110
apparently
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| adv.显然地；表面上，似乎 | |
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111
incapable
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| adj.无能力的，不能做某事的 | |
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112
accurately
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| adv.准确地，精确地 | |
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113
civilized
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| a.有教养的，文雅的 | |
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114
psychology
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| n.心理，心理学，心理状态 | |
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115
savage
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| adj.野蛮的；凶恶的，残暴的；n.未开化的人 | |
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116
determined
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| adj.坚定的；有决心的 | |
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117
mutual
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| adj.相互的，彼此的；共同的，共有的 | |
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118
lessened
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| 减少的，减弱的 | |
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119
secreted
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| v.（尤指动物或植物器官）分泌( secrete的过去式和过去分词 )；隐匿，隐藏 | |
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120
secrete
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| vt.分泌；隐匿，使隐秘 | |
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121
fixed
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| adj.固定的，不变的，准备好的；(计算机)固定的 | |
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122
transformations
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| n.变化( transformation的名词复数 )；转换；转换；变换 | |
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123
transformation
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| n.变化；改造；转变 | |
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124
precisely
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| adv.恰好，正好，精确地，细致地 | |
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125
formerly
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| adv.从前，以前 | |
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126
calcium
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| n.钙(化学符号Ca) | |
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127
oxide
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| n.氧化物 | |
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128
joint
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| adj.联合的，共同的；n.关节，接合处；v.连接，贴合 | |
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129
inorganic
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| adj.无生物的；无机的 | |
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130
ossify
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| v.硬化，骨化 | |
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131
requisite
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| adj.需要的，必不可少的；n.必需品 | |
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132
ossification
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| n.骨化，（思想等的）僵化 | |
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133
skull
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| n.头骨；颅骨 | |
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134
invertebrate
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| n.无脊椎动物 | |
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135
invertebrates
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|
| n.无脊椎动物( invertebrate的名词复数 ) | |
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136
molecular
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| adj.分子的；克分子的 | |
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137
exclusion
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| n.拒绝，排除，排斥，远足，远途旅行 | |
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138
constituent
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| n.选民；成分，组分；adj.组成的，构成的 | |
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139
molecules
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| 分子( molecule的名词复数 ) | |
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140
molecule
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| n.分子，克分子 | |
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141
striated
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| adj.有纵线，条纹的 | |
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142
enveloped
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| v.包围，笼罩，包住( envelop的过去式和过去分词 ) | |
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143
intestinal
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| adj.肠的；肠壁；肠道细菌 | |
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144
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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145
differentiate
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| vi.(between)区分；vt.区别；使不同 | |
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146
compartments
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|
| n.间隔( compartment的名词复数 )；（列车车厢的）隔间；（家具或设备等的）分隔间；隔层 | |
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147
glandular
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| adj.腺体的 | |
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148
appendages
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| n.附属物( appendage的名词复数 )；依附的人；附属器官；附属肢体（如臂、腿、尾等） | |
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149
spinal
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|
| adj.针的，尖刺的，尖刺状突起的；adj.脊骨的，脊髓的 | |
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150
axis
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| n.轴，轴线，中心线；坐标轴，基准线 | |
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151
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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152
sensory
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|
| adj.知觉的，感觉的，知觉器官的 | |
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153
locomotion
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| n.运动，移动 | |
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154
generalization
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| n.普遍性，一般性，概括 | |
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155
annihilated
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|
| v.（彻底）消灭( annihilate的过去式和过去分词 )；使无效；废止；彻底击溃 | |
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156
casually
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|
| adv.漠不关心地，无动于衷地，不负责任地 | |
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157
inevitably
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| adv.不可避免地；必然发生地 | |
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158
maturity
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| n.成熟；完成；(支票、债券等)到期 | |
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159
nourishment
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|
| n.食物，营养品；营养情况 | |
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160
derived
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|
| vi.起源；由来；衍生；导出v.得到( derive的过去式和过去分词 )；（从…中）得到获得；源于；（从…中）提取 | |
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161
soda
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|
| n.苏打水；汽水 | |
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162
crab
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|
| n.螃蟹，偏航，脾气乖戾的人，酸苹果；vi.捕蟹，偏航，发牢骚；vt.使偏航，发脾气 | |
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163
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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164
demur
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| v．表示异议，反对 | |
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165
fable
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| n.寓言；童话；神话 | |
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166
emphatic
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|
| adj.强调的，着重的；无可置疑的，明显的 | |
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167
vessels
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|
| n.血管( vessel的名词复数 )；船；容器；（具有特殊品质或接受特殊品质的）人 | |
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168
vessel
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| n.船舶；容器，器皿；管，导管，血管 | |
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169
concealed
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| a.隐藏的，隐蔽的 | |
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170
reconstruction
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| n.重建，再现，复原 | |
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171
succumbed
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|
| 不再抵抗（诱惑、疾病、攻击等）( succumb的过去式和过去分词 )； 屈从； 被压垮； 死 | |
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172
accredited
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|
| adj.可接受的；可信任的；公认的；质量合格的v.相信( accredit的过去式和过去分词 )；委托；委任；把…归结于 | |
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173
physiological
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|
| adj.生理学的，生理学上的 | |
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174
tout
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| v.推销，招徕；兜售；吹捧，劝诱 | |
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175
eminently
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| adv.突出地；显著地；不寻常地 | |
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176
specified
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| adj.特定的 | |
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177
momentary
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| adj.片刻的，瞬息的；短暂的 | |
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178
deviations
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| 背离，偏离( deviation的名词复数 )； 离经叛道的行为 | |
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179
predecessor
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| n.前辈，前任 | |
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180
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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181
radically
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| ad.根本地，本质地 | |
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182
abbreviated
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| adj. 简短的，省略的 动词abbreviate的过去式和过去分词 | |
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183
phantom
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| n.幻影，虚位，幽灵；adj.错觉的，幻影的，幽灵的 | |
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184
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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185
victorious
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|
| adj.胜利的，得胜的 | |
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186
victoriously
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|
| adv.获胜地，胜利地 | |
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187
mechanism
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|
| n.机械装置；机构，结构 | |
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188
legislative
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| n.立法机构，立法权；adj.立法的，有立法权的 | |
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189
superfluously
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| 过分地； 过剩地 | |
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190
necessitates
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| 使…成为必要，需要( necessitate的第三人称单数 ) | |
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191
serial
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| n.连本影片，连本电视节目；adj.连续的 | |
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192
stump
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| n.残株，烟蒂，讲演台；v.砍断，蹒跚而走 | |
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193
integument
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| n.皮肤 | |
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194
extremity
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| n.末端，尽头；尽力；终极；极度 | |
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195
rudiment
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| n.初步；初级；基本原理 | |
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196
rudiments
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| n.基础知识，入门 | |
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197
hind
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| adj.后面的，后部的 | |
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198
digits
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| n.数字( digit的名词复数 )；手指，足趾 | |
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199
mollusk
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| n.软体动物 | |
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200
amputation
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| n.截肢 | |
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201
antennae
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| n.天线；触角 | |
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202
supplementary
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| adj.补充的，附加的 | |
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203
marine
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| adj.海的；海生的；航海的；海事的；n.水兵 | |
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204
remarkable
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| adj.显著的，异常的，非凡的，值得注意的 | |
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205
tenacity
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| n.坚韧 | |
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206
tumor
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| n.（肿）瘤，肿块(英)tumour | |
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207
specially
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| adv.特定地；特殊地；明确地 | |
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208
reptiles
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|
| n.爬行动物，爬虫( reptile的名词复数 ) | |
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209
diffused
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| 散布的，普及的，扩散的 | |
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210
spines
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| n.脊柱( spine的名词复数 )；脊椎；（动植物的）刺；书脊 | |
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211
tentacles
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| n.触手( tentacle的名词复数 )；触角；触须；触毛 | |
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212
beaks
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| n.鸟嘴( beak的名词复数 )；鹰钩嘴；尖鼻子；掌权者 | |
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213
beak
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| n.鸟嘴，茶壶嘴，钩形鼻 | |
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214
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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215
unity
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| n.团结，联合，统一；和睦，协调 | |
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216
salmon
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| n.鲑，大马哈鱼，橙红色的 | |
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217
likeness
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| n.相像，相似（之处） | |
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218
incessantly
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| ad.不停地 | |
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219
crustacean
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| n.甲壳动物；adj.甲壳纲的 | |
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220
anatomy
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| n.解剖学，解剖；功能，结构，组织 | |
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221
secretion
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| n.分泌 | |
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222
cellular
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| adj.移动的；细胞的，由细胞组成的 | |
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223
evading
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| 逃避( evade的现在分词 )； 避开； 回避； 想不出 | |
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224
analogous
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| adj.相似的；类似的 | |
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225
cursory
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| adj.粗略的；草率的；匆促的 | |
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226
inspection
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| n.检查，审查，检阅 | |
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227
strictly
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| adv.严厉地，严格地；严密地 | |
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228
affinity
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| n.亲和力，密切关系 | |
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229
apprehended
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| 逮捕，拘押( apprehend的过去式和过去分词 )； 理解 | |
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230
myriads
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| n.无数，极大数量( myriad的名词复数 ) | |
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231
antagonism
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| n.对抗，敌对，对立 | |
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232
foes
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| 敌人，仇敌( foe的名词复数 ) | |
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233
multiplication
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| n.增加，增多，倍增；增殖，繁殖；乘法 | |
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234
stimulating
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| adj.有启发性的，能激发人思考的 | |
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235
thwarting
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| 阻挠( thwart的现在分词 )； 使受挫折； 挫败； 横过 | |
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236
crucible
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| n.坩锅，严酷的考验 | |
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237
partially
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| adv.部分地，从某些方面讲 | |
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238
obstructs
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| 阻塞( obstruct的第三人称单数 )； 堵塞； 阻碍； 阻止 | |
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239
stature
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| n.（高度）水平，（高度）境界，身高，身材 | |
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240
attained
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| （通常经过努力）实现( attain的过去式和过去分词 )； 达到； 获得； 达到（某年龄、水平、状况） | |
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241
functional
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| adj.为实用而设计的，具备功能的，起作用的 | |
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242
attachment
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| n.附属物，附件；依恋；依附 | |
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243
contraction
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| n.缩略词，缩写式，害病 | |
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244
component
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| n.组成部分，成分，元件；adj.组成的，合成的 | |
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245
encroachment
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| n.侵入，蚕食 | |
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246
illustrated
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| adj. 有插图的，列举的 动词illustrate的过去式和过去分词 | |
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247
antagonists
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| 对立[对抗] 者，对手，敌手( antagonist的名词复数 )； 对抗肌； 对抗药 | |
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248
antagonist
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| n.敌人，对抗者，对手 | |
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249
disturbance
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|
| n.动乱，骚动；打扰，干扰；(身心)失调 | |
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250
deficient
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| adj.不足的，不充份的，有缺陷的 | |
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251
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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252
thereby
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| adv.因此，从而 | |
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253
metaphorical
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| a.隐喻的，比喻的 | |
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254
meditated
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|
| 深思，沉思，冥想( meditate的过去式和过去分词 )； 内心策划，考虑 | |
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255
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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256
secondly
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|
| adv.第二，其次 | |
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257
correlations
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| 相互的关系( correlation的名词复数 ) | |
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258
stationary
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| adj.固定的，静止不动的 | |
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259
explicit
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|
| adj.详述的，明确的；坦率的；显然的 | |
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260
metaphorically
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| adv. 用比喻地 | |
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261
scrutinizing
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|
| v.仔细检查，详审( scrutinize的现在分词 ) | |
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262
grouse
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| n.松鸡；v.牢骚，诉苦 | |
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263
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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264
preservation
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| n.保护，维护，保存，保留，保持 | |
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265
dependence
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| n.依靠，依赖；信任，信赖；隶属 | |
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266
defective
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|
| adj.有毛病的，有问题的，有瑕疵的 | |
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267
incipient
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|
| adj.起初的，发端的，初期的 | |
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268
divergence
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|
| n.分歧，岔开 | |
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269
accruing
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|
| v.增加( accrue的现在分词 )；（通过自然增长）产生；获得；（使钱款、债务）积累 | |
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270
decided
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|
| adj.决定了的，坚决的；明显的，明确的 | |
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271
analyze
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|
| vt.分析，解析 (=analyse) | |
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272
decomposition
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|
| n. 分解, 腐烂, 崩溃 | |
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273
wrought
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|
| v.引起；以…原料制作；运转；adj.制造的 | |
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274
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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275
adverse
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|
| adj.不利的；有害的；敌对的，不友好的 | |
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276
descended
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| a.为...后裔的，出身于...的 | |
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277
formulated
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|
| v.构想出( formulate的过去式和过去分词 )；规划；确切地阐述；用公式表示 | |
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278
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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279
scrutiny
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| n.详细检查，仔细观察 | |
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280
intestines
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|
| n.肠( intestine的名词复数 ) | |
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281
aorta
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|
| n.主动脉 | |
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282
queries
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|
| n.问题( query的名词复数 )；疑问；询问；问号v.质疑，对…表示疑问( query的第三人称单数 )；询问 | |
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283
simplicity
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|
| n.简单，简易；朴素；直率，单纯 | |
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284
complexity
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|
| n.复杂(性)，复杂的事物 | |
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285
purely
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|
| adv.纯粹地，完全地 | |
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286
possessed
|
|
| adj.疯狂的；拥有的，占有的 | |
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287
geographical
|
|
| adj.地理的；地区(性)的 | |
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288
investigations
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|
| （正式的）调查( investigation的名词复数 )； 侦查； 科学研究； 学术研究 | |
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289
pointed
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|
| adj.尖的，直截了当的 | |
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290
torpedo
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|
| n.水雷，地雷；v.用鱼雷破坏 | |
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291
entirely
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|
| ad.全部地，完整地；完全地，彻底地 | |
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292
concurrent
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|
| adj.同时发生的，一致的 | |
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293
candor
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|
| n.坦白，率真 | |
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294
thoroughly
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|
| adv.完全地，彻底地，十足地 | |
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295
inexplicable
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|
| adj.无法解释的，难理解的 | |
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296
migration
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|
| n.迁移，移居，（鸟类等的）迁徙 | |
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297
reptilian
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|
| adj.（像）爬行动物的；（像）爬虫的；卑躬屈节的；卑鄙的n.两栖动物；卑劣的人 | |
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298
divergences
|
|
| n.分叉( divergence的名词复数 )；分歧；背离；离题 | |
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299
primordial
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|
| adj.原始的；最初的 | |
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300
intensified
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|
| v.（使）增强， （使）加剧( intensify的过去式和过去分词 ) | |
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301
invoke
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|
| v.求助于(神、法律)；恳求，乞求 | |
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302
concurrence
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|
| n.同意；并发 | |
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303
strata
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|
| n.地层（复数）；社会阶层 | |
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304
afflict
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|
| vt.使身体或精神受痛苦，折磨 | |
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305
hesitation
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|
| n.犹豫，踌躇 | |
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306
fluctuations
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|
| 波动，涨落，起伏( fluctuation的名词复数 ) | |
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307
regiments
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| （军队的）团( regiment的名词复数 )； 大量的人或物 | |
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308
permissible
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|
| adj.可允许的，许可的 | |
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309
varied
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|
| adj.多样的，多变化的 | |
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310
delightful
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|
| adj.令人高兴的，使人快乐的 | |
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311
teeming
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|
| adj.丰富的v.充满( teem的现在分词 )；到处都是；（指水、雨等）暴降；倾注 | |
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312
reluctance
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|
| n.厌恶，讨厌，勉强，不情愿 | |
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313
speculative
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|
| adj.思索性的，暝想性的，推理的 | |
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314
grandeur
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|
| n.伟大，崇高，宏伟，庄严，豪华 | |
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315
vanquished
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|
| v.征服( vanquish的过去式和过去分词 )；战胜；克服；抑制 | |
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316
peculiarity
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|
| n.独特性，特色；特殊的东西；怪癖 | |
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317
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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318
lobster
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|
| n.龙虾，龙虾肉 | |
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319
pervading
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| v.遍及，弥漫( pervade的现在分词 ) | |
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320
cogent
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|
| adj.强有力的，有说服力的 | |
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321
affiliated
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|
| adj. 附属的, 有关连的 | |
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322
dispense
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| vt.分配，分发；配(药)，发(药)；实施 | |
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323
enveloping
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| v.包围，笼罩，包住( envelop的现在分词 ) | |
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324
contrives
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|
| （不顾困难地）促成某事( contrive的第三人称单数 )； 巧妙地策划，精巧地制造（如机器）； 设法做到 | |
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325
putrid
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|
| adj.腐臭的；有毒的；已腐烂的；卑劣的 | |
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326
alcoholic
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|
| adj.（含）酒精的，由酒精引起的；n.酗酒者 | |
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327
acetic
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|
| adj.酸的 | |
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328
structural
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|
| adj.构造的，组织的，建筑（用）的 | |
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329
stimulus
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| n.刺激，刺激物，促进因素，引起兴奋的事物 | |
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330
oyster
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|
| n.牡蛎；沉默寡言的人 | |
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331
advancement
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|
| n.前进，促进，提升 | |
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332
speculation
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|
| n.思索，沉思；猜测；投机 | |
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333
presumption
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| n.推测，可能性，冒昧，放肆，[法律]推定 | |
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334
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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335
besets
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|
| v.困扰( beset的第三人称单数 )；不断围攻；镶；嵌 | |
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336
remarkably
|
|
| ad.不同寻常地，相当地 | |
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337
curiously
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|
| adv.有求知欲地；好问地；奇特地 | |
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338
essentially
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|
| adv.本质上，实质上，基本上 | |
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339
climax
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|
| n.顶点；高潮；v.(使)达到顶点 | |
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340
enumeration
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|
| n.计数，列举；细目；详表；点查 | |
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341
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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342
derivatives
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|
| n.衍生性金融商品；派生物，引出物( derivative的名词复数 )；导数 | |
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343
hydrocarbons
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|
| n.碳氢化合物，烃( hydrocarbon的名词复数 ) | |
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344
elastic
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|
| n.橡皮圈，松紧带；adj.有弹性的；灵活的 | |
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345
invoked
|
|
| v.援引( invoke的过去式和过去分词 )；行使（权利等）；祈求救助；恳求 | |
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346
elimination
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|
| n.排除，消除，消灭 | |
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347
stultification
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|
| n.使显得愚笨，使变无效 | |
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348
cardinal
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|
| n.(天主教的)红衣主教；adj.首要的，基本的 | |
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349
vibrations
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|
| n.摆动( vibration的名词复数 )；震动；感受；（偏离平衡位置的）一次性往复振动 | |
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350
percussion
|
|
| n.打击乐器；冲突，撞击；震动，音响 | |
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351
flute
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|
| n.长笛；v.吹笛 | |
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352
bass
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|
| n.男低音(歌手)；低音乐器；低音大提琴 | |
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353
trumpet
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|
| n.喇叭，喇叭声；v.吹喇叭，吹嘘 | |
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354
timbre
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|
| n.音色，音质 | |
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355
tambourine
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| n.铃鼓，手鼓 | |
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356
cymbals
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| pl.铙钹 | |
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357
primitive
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| adj.原始的；简单的；n.原(始)人，原始事物 | |
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358
subjective
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| a.主观(上)的，个人的 | |
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359
apparatus
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| n.装置，器械；器具，设备 | |
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360
faculties
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| n.能力( faculty的名词复数 )；全体教职员；技巧；院 | |
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361
philologists
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| n.语文学( philology的名词复数 ) | |
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362
recapitulated
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| v.总结，扼要重述( recapitulate的过去式和过去分词 ) | |
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363
justifiable
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| adj.有理由的，无可非议的 | |
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364
geologists
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| 地质学家，地质学者( geologist的名词复数 ) | |
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365
degradations
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| 堕落( degradation的名词复数 )； 下降； 陵削； 毁坏 | |
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