Chapter 16   The Law of Evolution (continued)

§128. But does this generalization express the whole truth? Does it include everything essentially characterizing Evolution and exclude everything else? Does it comprehend all the phenomena of secondary redistribution which Compound Evolution presents, without comprehending any other phenomena? A critical examination of the facts will show that it does neither.

Changes from the less heterogeneous to the more heterogeneous, which are not included in what we here call Evolution, occur in every local disease. In a morbid growth we see a new differentiation. Whether this morbid growth be, or be not, more heterogeneous than the tissues in which it is seated, is not the question. The question is whether the organism as a whole is, or is not, rendered more heterogeneous by the addition of a part unlike every pre-existing part, in form, or composition, or both. To this question there can be none but an affirmative answer. Again, the earlier stages of decomposition in a dead body involve increase of heterogeneity. Supposing the chemical changes to commence in some parts sooner than in others, as they commonly do, and to affect different tissues in different ways, as they must, it seems clear that the entire body, made up of undecomposed parts and parts decomposed in various modes and degrees, has become more heterogeneous than it was. Though grater homogeneity will be the eventual result, the immediate result is certainly not Evolution. Other instances are furnished by social disorders and disasters. A rebellion which, while leaving some provinces undisturbed, develops itself here in secret societies, there in public demonstrations, and elsewhere in actual conflicts, necessarily renders the society, as a whole, more heterogeneous. Or when a dearth causes commercial derangement with its entailed bankruptcies, closed factories, discharged operatives, food-riots, incendiarisms; it is manifest that as a large part of the community retains its ordinary organization displaying the usual phenomena, these new phenomena must be regarded as adding to the complexity previously existing. But such changes, so far from constituting further Evolution, are steps towards Dissolution.

So that the definition arrived at in the last chapter is an imperfect one. The changes above instanced as coming within the formula as it now stands, are so obviously unlike the rest, that the inclusion of them implies some distinction hitherto overlooked. Such further distinction we have now to supply.

§129. At the same time that Evolution is a change from the homogeneous to the heterogeneous, it is a change from the indefinite to the definite. Along with an advance from simplicity to complexity, there is an advance from con fusion to order -- from undetermined arrangement to determined arrangement. Development, no matter of what kind, exhibits not only a multiplication of unlike parts, but an increase in the clearness with which these parts are marked off from one another. And this is the distinction sought. For proof, it needs only to reconsider the instances given above. The changes constituting local disease, have no such definiteness, either in place, extent, or outline, as the changes constituting development. Though certain morbid growths are more common in some parts of the body than in others (as warts on the hands, cancer in the breasts, tubercle in the lungs), yet they are not confined to these parts; nor, where found, are they anything like so precise in their relative positions as are the normal parts around. Their sizes are very variable: they bear no such constant proportions to the body as organs do. Their forms, too, are far less specific than organic forms. And they are extremely confused in their internal structures. That is, they are in all respects comparatively indefinite. The like peculiarity may be traced in decomposition. That total indefiniteness to which a dead body is finally reduced, is a state towards which the putrefactive changes tend from their commencement. The advancing destruction of the organic compounds blurs the tissue-structures -- diminishes their distinctness. From the portions that have undergone most decay, there is a gradual transition to the less decayed portions, not a sharp demarcation. And step by step the lines of organization, once so precise, disappear. Similarly with social changes of an abnormal kind. The disaffection initiating a political outbreak, implies a loosening of those ties by which citizens are bound up into distinct classes and sub-classes. Agitation, growing into revolutionary meetings, fuses ranks that are usually separated. Acts of insubordination break through the ordained limits to individual conduct, and tend to obliterate the lines between those in authority and those beneath them. At the same time arrest of trade causes artizans and others to lose their occupations; and, ceasing to be functionally distinguished, they merge into an indefinite mass. When at last there comes positive insurrection, all magisterial and official powers, all class distinctions, all industrial differences, cease: organized society lapses into an unorganized aggregate of social units. Similarly, in so far as famines and pestilences cause changes from order towards disorder, they cause changes from definite arrangements to indefinite arrangements.

Thus, then, is that increase of heterogeneity which is not a trait of Evolution, distinguished from that increase of heterogeneity which is. Though in disease and after death, individual or social, the earliest modifications are additions to the pre-existing heterogeneity, they. are not additions to the pre-existing definiteness. From the outset they begin to destroy this definiteness, and gradually produce a heterogeneity that is indeterminate instead of determinate. As a city, already multiform in its variously-arranged structures of various architecture, may be made more multiform by an earthquake, which leaves part of it standing and overthrows other parts in different ways and degrees, but is at the same time reduced from orderly arrangement to disorderly arrangement; so may organized bodies be made for a time more multiform by changes which are nevertheless disorganizing changes. And in the one case as in the other, it is the absence of definiteness which distinguishes the multiformity of regression from the multiformity of progression.

If advance from the indefinite to the definite is an essential characteristic of Evolution, we shall of course find it everywhere displayed; as in the last chapter we found displayed the advance from the homogeneous to the heterogeneous. To see whether it is so, let us now consider the same several classes of facts.

§130. Beginning, as before, with a hypothetical illustration, we have to note that each step in the evolution of the Solar System, supposing it to have originated from diffused matter, was an advance towards more definite structure. As usually conceived, the initial nebula was irregular in shape and with indistinct margins, like those of nebulae now existing. Having partially-different proper motions, the parts of its attenuated substance, while being drawn together, generated, by the averaging of their motions, as well as by changes in the directions of these motions, a certain angular momentum; and the entire mass as it concentrated and acquired rotation must have assumed the form of an oblate spheroid which with every increase of density, became more specific in outline, and had its surface more distinctly marked off from the surrounding void. Simultaneously, the constituent portions of nebulous matter, instead of moving round their common centre of gravity in various planes, as they would at first do, must have had these planes more and more merged into a single plane, that became less vague as the concentration progressed -- became gradually defined.

According to the hypothesis, change from indistinct characters to distinct ones, was repeated in the evolution of planets and satellites. A gaseous spheroid is less definitely limited than a liquid spheroid, since it is subject to larger undulations of surface, and to greater distortions of general form; and, similarly, a liquid spheroid, covered as it must be with waves of various magnitudes, tidal and other, is less definite than a solid spheroid. The decrease of oblateness which goes along with increase of integration, brings relative definiteness of other elements. A concentrating planet having an axis inclined to the plane of its orbit, must, while very oblate, have its plane of rotation much disturbed by external attractions; whereas its approach to a spherical form, involves a smaller precessional motion, and less marked variations in the direction of its axis.

With progressing settlement of the space-relations, the force-relations simultaneously become more settled; and the exact calculations of physical astronomy show us how definite these force-relations now are. In short, it needs but to think of the contrast between the chaos of the primitive nebula and the ordered relations of the Solar System in the sizes, shapes, motions, and combined inter-actions of its members, to see that increase of definiteness has been a marked trait of its evolution.

§131. From that primitive molten state of the Earth inferable from geological data as well as from the nebular hypothesis (probably a liquid shell having a nucleus of gases above the "critical point" of temperature, kept by pressure at a density as great as that of the superjacent liquid) the transition to its existing state has been through stages in which the characters became more determinate. A liquid spheroid is less specific than a solid spheroid in having no fixed distribution of parts. Currents of molten matter, though kept to certain general circuits by the conditions of equilibrium, cannot, in the absence of solid boundaries, be precise in their limits and directions: all parts must be in motion with respect to other parts. But a superficial solidification, even though partial, is a step towards the establishment of definite relations of position. In a thin crust, however, often ruptured by disturbing forces, and moved by every tidal undulation, fixity of relative position can be but temporary. Only as the crust thickens can there arise distinct and settled geographical positions. Observe, too, that when, on a surface adequately cooled, there begins to precipitate the water floating above as vapour, the deposits cannot maintain definiteness either of state or place. Falling on a solid envelope not thick enough to preserve anything beyond slight variations of level, the water must form small and shallow pools over the coolest areas; which areas must pass insensibly into others that are too hot to allow condensation. With progressing refrigeration, however -- with a thickening crust, a consequent formation of larger elevations and depressions, and the precipitation of more atmospheric water, there comes an arrangement of parts which is comparatively fixed; and the definiteness of position increases, until there result continents and oceans -- a distribution that is not only topographically settled, but presents separations of land from water more definite than could have existed when all the uncovered areas were low islands with shelving beaches, over which the tide ebbed and flowed to great distances.

Respecting the characters classed as geological, we may draw kindred inferences. While the Earth's crust was thin, mountain-chains were impossibilities: there could not have been long and well-defined axes of elevation, with distinct water-sheds and areas of drainage. Moreover, the denudation of small islands by small rivers, and by tidal streams both feeble and narrow, would produce no clearly-marked sedimentary strata. Confused and varying masses of detritus, such as we now find at the mouths of brooks, must have been the prevailing formations. And these could give place to distinct strata, only as there arose continents and oceans, with their great rivers, long coast-lines, and wide-spreading marine currents.

There must simultaneously have resulted more definite meteorological conditions. Differences of climates and seasons grew relatively decided as the heat derived from the Sun became distinguishable from the proper heat of the Earth; and the production of more specific conditions in each locality was aided by increasing permanence in the distribution of lands and seas. These are conclusions sufficiently obvious.

§132. We come now to the evidence yielded by organic bodies. In place of deductive illustrations, we shall here find illustrations which have been inductively established, and are therefore less open to criticism. The course of mammalian development, for example, will supply us with numerous proofs ready-described by embryologists.

The first change which the ovum of a mammal undergoes after repeated segmentation has reduced it to a mulberry-like mass, is the appearance of a distinction between the peripheral or epiblastic cells of this mass and the internal or hypoblastic cells. While growing rapidly the cluster of cells becomes hollow, and the blastodermic vesicle so formed presents a definite contrast between the outer layer, or epiblast, and its contents. The mass of hypoblast cells, having at first an indefinite, lens-like figure attached to the inside of the epiblast, spreads out and flattens into a membrane, the boundary of which is irregular -- indefinite alike in form and constitution. And then the middle or thicker part presently becomes an opaque circular spot constituting the embryonic area: a spot which gradually acquires a pronounced outline. In the centre of this there at length comes the primitive streak or trace, which, as its name implies, is indefinite but by-and-by "becomes a more pronounced structure." Within this streak or trace the vertebrate axis first shows itself. Beginning as a shallow groove, it becomes slowly more pronounced; its sides grow higher; their summits overlap and at last unite; and so the indefinite groove passes into a definite tube, forming the vertebral canal. In this vertebral canal the leading divisions of the brain are at first discernible only as slight bulgings; while the proto-vertebrae commence as indistinct modifications of the tissue bounding the canal. Meanwhile in kindred ways the indefinite out-spread membrane through which are absorbed the materials for the unfolding structures around, is changed, into a definite alimentary canal. And in an analogous manner the entire embryo, which at first lies outspread on the yelk-sack, gradually rises up from it, and by the infolding of its ventral region becomes a separate mass, definitely outlined, connected with the yelk-sack only by a narrow duct.

These changes through which the general structure is marked out with slowly-increasing precision, are paralleled in the evolution of each organ. The liver commences by multiplication of certain cells in the wall of the intestine. The thickening produced by this multiplication, "increases so as to form a projection upon the exterior of the canal -- a hollow bud;" and at the same time that the organ grows and becomes distinct from the intestine, the channels running through it are transformed into ducts having clearly-marked walls. Similarly, certain cells of the external coat of the alimentary canal at its upper portion, accumulate into lumps or buds from which the lungs are developed; and these, in their general outlines and detailed structure, acquire distinctness step by step. But even were no examples given, it would be undeniable that since a simple cluster of similar cells grows into head, trunk, and limbs of distinct shapes, each made up of many organs containing parts severally having clear outlines and composed of specific tissues, increase of definiteness has been a leading trait of the transformation.

Changes of this order continue long after birth; and, in the human being, are some of them not completed till middle life. During youth, most of the articular surfaces of the bones remain rough and fissured -- the calcareous deposit ending irregularly in the surrounding cartilage. But between puberty and the age of thirty, these articular surfaces are finished off into smooth, hard, sharply-cut "epiphyses." Generally, indeed, we may say that increase of definiteness continues when there has ceased to be any appreciable increase of heterogeneity. And there is reason to think that those modifications which take place after maturity bringing about old age and death, are modifications of this nature; since they cause rigidity of structure, a consequent restriction of movement and of functional pliability, a gradual narrowing of the limits within which the vital processes go on, ending in an organic adjustment too precise -- too narrow in its margin of possible variation to permit the requisite adaptation to changes of external conditions.

§133. To give clear proof that the Earth's Flora and Fauna, regarded either as wholes or in their separate species, have progressed in definiteness, is no more possible than it was to prove that they have progressed in heterogeneity: the facts are not sufficient. If, however, we allow ourselves to reason from the hypothesis, now daily rendered more probable, that every species has arisen through the accumulation of modifications upon modifications, just as every individual arises. we shall see that there must have been a progress, from the indeterminate to the determinate, both in the particular forms and in the groups of forms.

We may set out with the significant fact that the lowest organisms (which are analogous in structure to the germs of all higher ones) have so little definiteness that it is difficult, if not impossible, to decide whether they are plants or animals. Respecting sundry of them there are unsettled disputes between zoologists and botanists. Note next that among the Protozoa, great indefiniteness of shape is general. Of sundry shell-less Rhizopods the form is so irregular as to admit of no description: it is neither alike in any two individuals nor in the same individual at successive moments. By aggregation of Protozoa, are produced, among other creatures, the Sponges, most of which are indefinite in size, in contour, in internal arrangement; and such more definite aggregates as the Hydra are made indefinite both by the great differences between their contracted and expanded states and by their reproductive developments. As further showing how relatively indeterminate are the simplest organisms, it may be mentioned that their structures vary greatly with surrounding conditions: so much so that, among the Protozoa and Protophyta, many forms which were once classed as distinct species, and even as distinct genera, are found to be merely varieties of one species. If, now, we call to mind how precise in their traits are the highest organisms -- how sharply cut their outlines, how invariable their proportions, and how comparatively constant their structures under changed conditions; we cannot deny that greater definiteness is one of their characteristics. If they have been evolved out of lower organisms, increase of definiteness has been an accompaniment of their evolution.

That, in course of time, species have become more sharply marked off from other species, genera from genera, and orders from orders, is a conclusion not admitting of a more positive establishment than the foregoing. If, however, species and genera and orders have arisen by evolution, then, as Mr. Darwin shows, the contrasts between groups must have become greater. Disappearance of intermediate forms, less fitted for special spheres of existence than the extreme forms they connected, must have made the differences between the extreme forms decided; and so, from indistinct varieties, must have been produced distinct species: an inference which is in harmony with what we know respecting races of men and races of domestic animals.

§134. The successive phases through which societies pass, obviously display the progress from indeterminate arrangements to determinate arrangements. A wandering tribe of savages, being fixed neither in its locality nor in its internal distribution, is far less definite in the relative positions of its parts than a nation. In such a tribe the social relations are confused and unsettled. Political authority is vague. Distinctions of rank are neither clearly marked nor impassable. And save in the different occupations of men and women, there are no decided industrial divisions. Only in tribes of considerable size, which have enslaved other tribes, is economic differentiation distinct.

But one of these primitive societies that evolves, becomes step by step more specific. Increasing in size, consequently ceasing to be so nomadic, and restricted in its range by neighbouring societies, it acquires, after prolonged border warfare, a settled territorial boundary. The distinction between the ruling race and the people, sometimes amounts, in the popular belief, to a difference of nature. The warrior-class attains a perfect separation from classes devoted to the cultivation of the soil or to other occupations regarded as servile. And there arises a priesthood which is defined in its rank, its functions, its privileges. This sharpness of definition, growing both greater and more variously exemplified as societies advance to maturity, is extremest in those which have reached their full development or are declining. Of ancient Egypt we read that its social divisions were precise and its customs rigid. Recent investigations make it more than ever clear that among the Assyrians and surrounding peoples, not only were the laws unalterable, but even the minor habits, down to those of domestic routine, Assessed a sacredness which insured their permanence. In India at the present day, the unchangeable distinctions of caste, not less than the constancy in modes of dress, industrial processes, and religious observances, show how definite are the arrangements where the antiquity is great. Nor does China, with its long-settled political organization, its elaborate and precise conventions, fail to exemplify the same truth.

The successive phases of our own and adjacent societies, furnish facts somewhat different in kind but similar in meaning. Originally monarchical authority was more baronial, and baronial authority more monarchical, than afterwards. Between modern priests and the priests of old times, who while officially teachers of religion were also warriors, judges, architects, there is a marked difference in definiteness of function. And among the people engaged in productive occupations, like contrasts hold: the regulative parts have become definitely distinct from the operative parts and the distributive parts from both. The history of our constitution, reminding us how the powers of King, Lords, and Commons have been gradually settled, describes analogous changes. Countless facts bearing the like construction meet us when we trace the development of legislation; in the successive stages of which we find statutes gradually rendered more specific in their applications to particular cases. Even now each new law beginning as a vague proposition, is, in the course of enactment, elaborated into specific clauses; and only after its interpretation has been established by judges' decisions in courts of justice, does it reach its final definiteness. From the annals of minor institutions like evidence may be gathered. Religious, charitable, literary, and all other societies, starting with ends and methods roughly sketched out and easily modifiable, show us how, by the accumulation of rules and precedents, the purposes become more precisely formulated and the modes of action more restricted; until at last decay follows a fixity which admits of no adaptation to new conditions. Should it be objected that among civilized nations there are examples of decreasing definiteness (instance the breaking down of limits between ranks), the reply is, that such apparent exceptions are the accompaniments of a social metamorphosis -- a change from the military type of social structure to the industrial type, during which old lines of structure are disappearing and new ones becoming more marked.

§135. All organized results of social action -- all super-organic structures, pass through parallel phases. Being, as they are, objective products of subjective processes, they must display corresponding changes; and that they do this, the cases of Language, of Science, of Art, clearly prove.

Strike out from our sentences everything but nouns and verbs, and there stands displayed the vagueness characterizing undeveloped tongues. Each inflection of a verb, or addition by which the case of a noun is marked, by limiting the conditions of action or of existence, enables men to express their thoughts more precisely. That the application of an adjective to a noun, or an adverb to a verb narrows the class of things or changes indicated, implies that the additional word serves to make the proposition more distinct. And similarly with other parts of speech.

The like effect results from the multiplication of words of each order. When the names for objects, and acts, and qualities, are but few, the range of each is proportionately wide, and its meaning therefore unspecific. The similes and metaphors so much used by aboriginal races, indirectly and imperfectly suggest ideas which they cannot express directly and perfectly from lack of words. Or to take a case from ordinary life, if we compare the speech of the peasant who, out of his limited vocabulary, can describe the contents of the bottle he carries, only as "doctor's stuff" which he has got for his "sick" wife, with the speech of the physician, who tells those educated like himself the particular composition of the medicine and the particular disorder for which he has prescribed it; we have vividly brought home to us the precision which language gains by the multiplication of terms.

Again, in the course of its evolution, each tongue acquires a further accuracy through processes which fix the meaning of each word. Intellectual intercourse slowly diminishes laxity of expression. By-and-by dictionaries give definitions. And eventually, among the most cultivated, indefiniteness is not tolerated, either in the terms used or in their grammatical combinations.

Once more, languages considered as wholes become more sharply marked off from one another, and from their common parent; as witness, in early times, the clear distinction that arose between the two connate languages Greek and Latin, and in later times the divergence of three Latin dialects into Italian, French, and Spanish.

§136. In his History of the Inductive Sciences, Dr. Whewell says that the Greeks failed in physical philosophy because their "ideas were not distinct, and appropriate to the facts." I do not quote this remark for its luminousness; since it would be equally proper to ascribe the indistinctness and inappropriateness of their ideas to the imperfection of their physical philosophy; but I quote it because it serves as good evidence of the indefiniteness of primitive science. The same work and its fellow, The Philosophy of the Inductive Sciences, yield other evidences equally good, because equally independent of any such hypothesis as is here to be established. Respecting mathematics, we have the fact that geometrical theorems grew out of empirical methods; and that these theorems, at first isolated, did not acquire the clearness which demonstration gives, until they were arranged by Euclid into a series of dependent propositions. At a later period, the same general truth was exemplified in the progress from the "method of exhaustions" and the "method of indivisibles" to the "method of limits;" which is the central idea of the infinitesimal calculus. in early mechanics may be traced a dim perception that action and reaction are equal and opposite; though, for ages after, this truth remained unformulated. And similarly, the property of inertia, though not distinctly comprehended until Kepler lived, was vaguely recognized long before. "The conception of statical force," "was never presented in a distinct form till the works of Archimedes appeared;" and "the conception of accelerating force was confused, in the mind of Kepler and his contemporaries, and did not become clear enough for purposes of sound scientific reasoning before the succeeding century." To which specific assertions may be added the general remark, that "terms which originally, and before the laws of motion were fully known, were used in a very vague and fluctuating sense, were afterwards limited and rendered precise." When we turn from abstract scientific conceptions to the concrete previsions of science, of which astronomy furnishes numerous examples, a like contrast is visible. The times at which celestial phenomena will occur, have been predicted with ever-increasing accuracy. Errors once amounting to days are now diminished to seconds. The correspondence between the real and supposed forms of orbits has been gradually rendered more precise. Originally thought circular, then epicyclical, then elliptical, orbits are now ascertained to be curves which always deviate from perfect ellipses, and are ever undergoing changes.

But the general advance of Science in definiteness is best shown by the contrast between its qualitative stage and its quantitative stage. At first the facts ascertained were that between such and such phenomena some connexion existed -- that the appearances a and b always occurred together or in succession; but it was known neither what was the nature of the relation between a and b, nor how much of a accompanied so much of b. The development of Science has in part been the reduction of these vague connexions to distinct ones. Most relations have been classed as mechanical, chemical, thermal, electric, magnetic, etc.; and we have learnt to infer the relative amounts of the antecedents and consequents with exactness. Of illustrations, some furnished by physics have been given, and from other sciences plenty may be added. We have ascertained the constituents of numerous compounds which our ancestors could not analyze, and of a far greater number which they never even saw; and the combining equivalents of the elements are now accurately calculated. Physiology shows advance from qualitative to quantitative prevision in ascertaining definite relations between organic products and the materials consumed; as well as in measurement of functions by spirometer and sphygmograph. By Pathology it is displayed in the use of the statistical method of determining the sources of diseases, and the effects of treatment. In Botany and Zoology, the numerical comparisons of Floras and Faunas, leading to specific conclusions respecting their sources and distributions, illustrate it. And in Sociology, questionable as are many conclusions drawn from the classified sum-totals of the census, from the Board-of-Trade tables, and from criminal returns, it must be admitted that these imply a progress towards more precise conceptions of social phenomena.

That an essential characteristic of advancing Science is increase in definiteness, appears indeed almost a truism, when we remember that Science may be described as definite knowledge, in contradistinction to that indefinite knowledge possessed by the uncultured. And if, as we cannot question, Science has, in the course of ages, been evolved out of this indefinite knowledge of the uncultured, then, the gradual acquirement of that great definiteness which now distinguishes it, must have been a leading trait in its evolution.

§137. The arts, industrial and aesthetic, supply illustrations perhaps still more striking. Palaeolithic flint implements show the extreme want of precision in men's first handiworks. Though a great advance on these is seen in the tools and weapons of existing savage tribes, yet an inexactness in forms and fittings distinguishes such tools and weapons from those of civilized races. In a smaller degree, the productions of the less-advanced nations are characterized by like defects. A Chinese junk, with all its contained furniture and appliances, nowhere presents a line that is quite straight, a uniform curve, or a true surface. Nor do the utensils and machines of our ancestors fail to exhibit a similar inferiority to our own. An antique chair, an old fireplace, a lock of the last century, or almost any article of household use that has been preserved for a few generations, proves by contrast how greatly the industrial products of our time excel those of the Past in their accuracy. Since planing machines have been invented, it has become possible to produce absolutely straight lines, and surfaces so truly level as to be air-tight when applied to each other. While in the dividing-engine of Troughton, in the micrometer of Whitworth, in microscopes that show fifty thousand divisions to the inch, and in ruled divisions up to 200,000, we have an exactness as far exceeding that reached in the works of our great-grandfathers, as theirs exceeded that of the aboriginal celt-makers.

In the Fine Arts there has been a parallel progress. From the rudely-carved and painted idols of savages, through the early sculptures characterized by limbs without muscular detail, wooden-looking drapery, and faces devoid of individuality, up to the later statues of the Greeks or some of those now produced, the increased accuracy of representation is conspicuous. Compare the mural paintings of the Egyptians with the paintings of medieval Europe, or these with modern paintings, and the more precise rendering of the appearances of objects is manifest. It is the same with fiction and the drama. In the marvellous tales current among Eastern nations, in the romantic legends of feudal Europe, as well as in the mystery-plays and those immediately succeeding them, we see great want of correspondence to the realities of life; alike in the predominance of supernatural events, in the extremely improbable occurrences, and in the vaguely-indicated personages. Along with social advance, there has been a progressive diminution of unnaturalness -- an approach to truth of representation. And now, cultivated men applaud novels and plays in proportion to the fidelity with which they exhibit characters. improbabilities, like the impossibilities which preceded them, are disallowed; and we see fewer of those elaborate plots which life rarely furnishes: realities are more definitely pictured.

§138. Space might be filled with evidences of other kinds, but the basis of induction is already wide enough. Proof that all Evolution is from the indefinite to the definite, we find not less abundant than proof that all Evolution is from the homogeneous to the heterogeneous.

It should, however, be added that this advance in definiteness is not a primary but a secondary phenomenon -- is a result incidental on other changes. The transformation of a whole that was originally diffused and uniform into a concentrated combination of multiform parts, implies progressive separation both of the whole from its environment and of the parts from one another. While this is going on there must be indistinctness. Only as the whole gains density, does it become sharply marked off from the space or matter lying outside of it; and only as each division draws into its mass those peripheral portions which are at first imperfectly disunited from the peripheral portions of neighbouring divisions, can it acquire anything like a precise outline. That is to say, the increasing definiteness is a concomitant of the increasing consolidation, general and local. While the secondary re-distributions are ever adding to the heterogeneity, the primary redistribution, while augmenting the integration, is incidentally giving distinctness to the increasingly unlike parts as well as to the aggregate of them.

But though this universal trait of Evolution is a necessary accompaniment of the traits set forth in preceding chapters, it is not expressed in the words used to describe them. It is therefore needful further to modify our formula. The more specific idea of Evolution now reached is -- a change from an indefinite, incoherent homogeneity, to a definite coherent heterogeneity, accompanying the dissipation of motion and integration of matter.

Chapter 17   The Law of Evolution (concluded)

§139. The conception of Evolution elaborated in the foregoing chapters, is still incomplete. True though it is, it is not the whole truth. The transformations which all things undergo during the ascending phases of their existence, we have contemplated under three aspects; and by uniting these three aspects as simultaneously presented, we have formed an approximate idea of the transformations. But there are concomitant changes about which nothing has yet been said, and which, though less conspicuous, are no less essential.

For thus far we have attended only to the re-distribution of Matter, neglecting the accompanying redistribution of Motion. Distinct or tacit reference has, indeed, repeatedly been made to the dissipation of Motion, that goes on along with the concentration of Matter; and were all Evolution absolutely simple, the total fact would be contained in the proposition that as Motion dissipates Matter concentrates. But while we have recognized the ultimate re-distribution of the Motion, we have passed over its proximate re-distribution. Though something has from time to time been said about the escaping motion, nothing has been said about the motion which does not escape. In proportion as Evolution becomes compound -- in proportion as an aggregate retains, for a considerable time, such quantity of motion as permits secondary re-distributions of its component matter, there necessarily arise secondary redistributions of its retained motion. As fast as the parts are transformed, there goes on a transformation of the sensible or insensible motions possessed by the parts. They cannot become more integrated, either individually or as a combination, without their motions, individual or combined, becoming more integrated. There cannot arise among them heterogeneities of size, of form, of quality, without there also arising heterogeneities in the amounts and directions of their motions, or the motions of their molecules. And increasing definiteness of the parts implies increasing definiteness of their motions. In short, the rhythmical actions going on in each aggregate, must differentiate and integrate at the same time that the structures do so.

§139a. The general theory of this re-distribution of the retained motion, must here be briefly stated. Properly to supplement our conception of Evolution under its material aspect by a conception of Evolution under its dynamical aspect, we have to recognize the source of the integrated motions that arise, and to see how their increased multiformity and definiteness are necessitated.

If Evolution is passage from a diffused state to an aggregated state, then the motions of the celestial bodies must have resulted from the uncancelled motions of their once dispersed components. Along with the molecular motions everywhere active, there were molar motions of those vast streams of nebulous matter which were generated during the process of concentration -- molar motions of which large portions were gradually dissipated as heat, leaving undissipated portions. But since the molar motions of these nebulous streams were constituted from the motions of multitudinous incoherent gaseous parts severally moving more or less independently it follows that when aggregation into a liquid and finally solid celestial mass was reached, these partially independent motions of the incoherent parts became merged into the motion of the whole: or, in other words, unintegrated motions became an integrated motion.

While we must leave in the shape of hypothesis the belief that the celestial motions have thus originated, we may see, as a matter of fact, that the integration of insensible motions originates all sensible motions on the Earth's surface. As all know, the denudation of lands and deposit of new strata, are effected by water while descending to the sea, or during the arrest of those undullations produced on it by winds; and, as before said, the elevation of water to the height whence it fell, is due to solar heat, as is also the genesis of those aerial currents which drift it about when evaporated and agitate its surface when condensed. That is to say, the molecular motion of the ethereal medium is transformed into the motion of gases, thence into the motion of liquids, and thence into the motion of solids: stages in each of which a certain amount of molecular motion is lost and an equivalent motion of masses gained. It is the same with organic movements. Certain rays issuing from the Sun, enable the plant to reduce special elements existing in gaseous combinations around it, to solid forms -- enable the plant, that is, to grow and carry on its functional changes. And since growth, equally with circulation of sap, is a mode of sensible motion, while those rays which have been expended in generating both consist of insensible motions, we have here, too a transformation of the kind alleged Animals, derived as their forces are, directly or indirectly, from plants, carry this transformation a step further. The automatic movements of the viscera, together with the voluntary movements of the limbs and body at large, arise at the expense of certain molecular movements throughout the nervous and muscular tissues; and these originally arose at the expense of certain other molecular movements propagated by the Sun to the Earth; so that both the structural and functional motions which organic Evolution displays, are motions of aggregates generated by the arrested motions of units. Even with the aggregates of these aggregates the same rule holds. For among associated men the progress is ever towards a merging of individual actions in the actions of corporate bodies. In militant life this is seen in the advance from the independent fighting of separate warriors to the combined fighting of regiments, and in industrial life in the advance from the activities of separate workers to the combined activities of factory hands. So is it, too, when instead of acting alone citizens act in bodies -- companies, unions, associations, etc. While, then, during Evolution the escaping motion becomes, by widening dispersion, more disintegrated, the motion that is for a time retained, becomes more integrated; and so, considered dynamically, Evolution is a decrease in the relative movements of parts and an increase in the relative movements of wholes -- using the words parts and wholes in their most general senses. The advance is from the motions of simple molecules to the motions of compound molecules; from molecular motions to the motions of masses; and from the motions of smaller masses to the motions of larger masses.

The accompanying change towards greater multiformity among the retained motions, takes place under the form of an increased variety of rhythms. A multiplication of rhythms must accompany a multiplication in the degrees and modes of aggregation, and in the relations of the aggregated masses to incident forces. The degree or mode of aggregation will not, indeed, affect the rate or extent of rhythm where the incident force increases as the aggregate increases, which is the case with gravitation: here the only cause of variation in rhythm is difference of relation to the incident force; as we see in a pendulum which, though unaffected in its movements by a change in the weight of the bob, alters its rate of oscillation when its length is altered or when, otherwise unchanged, it is taken to the equator. But in all cases where the incident forces do not vary as the masses, every new order of aggregation initiates a new order of rhythm: witness the conclusion drawn from the recent researches into radiant heat and light, that the molecules of different gases have different rates of undulation.*<* This was written in 1867.> So that increased multiformity in the arrangement of matter necessarily generates increased multiformity of rhythm; both through increased variety in the sizes and forms of aggregates, and through increased variety in their relations to the forces which move them. That these motions, as they become more integrated and more heterogeneous, must become more definite, is a proposition that need not detain us. In proportion as any part of an evolving whole segregates and consolidates, and in so doing loses the relative mobility of its components, its aggregate motion must obviously acquire distinctness.

Here, then, to complete our conception of Evolution, we must contemplate throughout the Cosmos, these metamorphoses of retained motion which accompany the metamorphoses of component matter. We may do this with comparative brevity: the reader having now become so familiar with the mode of looking at the facts, that less illustration will suffice. To save space, it will be convenient to deal with the several aspects of the metamorphoses at the same time.

§140. Masses of diffused matter moving towards a common centre, from many points at many distances with many degrees of indirectness, must carry into the nebulous mass eventually formed, numerous momenta unlike in their amounts and directions. As the integration progresses, such parts of these momenta as conflict are mutually neutralized, and dissipated as heat. Unless the original distribution is quite symmetrical, which is infinitely improbable, rotation will result. The mass having at first unlike angular velocities at the periphery and at various distances from the centre will have its differences of angular velocity gradually reduced; advancing towards a final state, now nearly reached by the Sun in which the angular velocity of the whole mass is the same -- in which the motion is integrated. So, too, with each planet and satellite. Progress from the motion of a nebulous ring, incoherent and admitting of much relative motion within its mass, to the motion of a dense spheroid, is progress to a motion that is completely integrated. The rotation, and the translation through space, severally become one and indivisible. Meanwhile, there has been established that further integration displayed by the motions of the Solar System as a whole. Locally in each planet and its satellites, and generally in the Sun and the planets, we have a system of simple and compound rhythms, with periodic and secular variations, forming together an integrated set of movements.

Along with advancing integration of the motions there has gone advance in the multiformity and distinctness of them. The matter which, in its original diffused state, had movements that were confused, indeterminate, or without sharply-marked distinctions, has, during the evolution of the Solar System, acquired definitely heterogeneous movements. The periods of revolution of all the planets and satellites are unlike; as are also their times of rotation. Out of these definitely heterogeneous motions of a simple kind, arise others that are complex, but still definite; -- as those produced by the revolutions of satellites compounded with the revolutions of their primaries; as those of which precession is the result; and as those which are known as perturbations. Each additional complexity of structure has caused additional complexity of movements; but still, a definite complexity, as is shown by having calculable results.

§141. While the Earth's surface was molten, the currents in the voluminous atmosphere surrounding it, mainly of ascending heated gases and of descending precipitated liquids, must have been local, numerous, indefinite, and but little distinguished from one another. But when after a vast period the surface, now solidified, had so far cooled that solar radiation began to cause appreciable differences of temperature between the equatorial and polar regions, an atmospheric circulation from poles to equator and from equator to poles, must have slowly established itself: other vast moving masses of air becoming, at last, trade-winds and other such permanent definite currents. These integrated motions, once comparatively homogeneous, were rendered heterogeneous as great islands and continents arose, to complicate them by periodic winds, caused by the varied heating of wide tracts of land at different seasons. Rhythmical motions of a constant and simple kind, were, by increasing multiformity of the Earth's surface, differentiated into an involved combination of constant and recurrent rhythmical motions, joined with smaller motions that are irregular.

Parallel changes must have taken place in the motions of water. On a thin crust, admitting of but small elevations and depressions, and therefore of but small lakes and seas, none beyond small local circulations were possible. But along with the formation of continents and oceans, came the vast movements of water from warm latitudes to cold and from cold to warm -- movements increasing in amount, in definiteness, and in variety of distribution, as the features of the Earth's surface became larger and more contrasted. The like holds with drainage waters. The tricklings of insignificant streams over small tracts of land, were once alone possible; but as fast as wide areas came into existence, the motions of many tributaries became massed into the motions of great rivers; and instead of motions very much alike, there arose motions considerably varied.

Nor can we well doubt that the changes in the Earth's crust itself, have presented an analogous progress. Small, numerous, local, and like one another, while the crust was thin, the movements of elevation and subsidence must, as the crust thickened, have extended over larger areas, must have continued for longer eras in the same directions, and must have been made more unlike in different regions by local differences of structure.

§142. In organisms the advance towards a more integrated, heterogeneous, and definite distribution of the retained motion, which accompanies the advance towards a more integrated, heterogeneous, and definite distribution of the component matter, is mainly what we understand as the development of functions. All active functions are either sensible movements, as those produced by contractile organs; or such insensible movements as those propagated through nerves; or such insensible movements as those by which, in secreting organs, molecular re-arrangements are effected, and new combinations of matter produced. And during evolution functions, like structures, become more consolidated individually, as well as more combined with one another, at the same time that they become more multiform and more distinct.

The nutritive juices in animals of low types move hither and thither through the tissues quite irregularly, as local strains and pressures determine: in the absence of a true blood and a distinct vascular system, there is no definite circulation. But along with the structural evolution which establishes a good apparatus for distributing blood, there goes on the functional evolution which establishes large and rapid movements of blood, definite in their courses and definitely distinguished as efferent and afferent, and that are heterogeneous both in their directions and in their characters: being here divided into gushes and there continuous.

Again, accompanying the structural differentiations and integrations of the alimentary canal, there arise differentiations and integrations both of its mechanical movements and its actions of a non-mechanical kind. Along an alimentary canal of a primitive type there pass, almost uniformly from end to end, waves of constriction. But in a well-organized alimentary canal, the waves of constriction are widely unlike at different parts, in their kinds, strengths, and rapidities. In the oesophagus they are propulsive in their office, and travelling with considerable speed, take place at intervals during eating, and then do not take place till the next meal. In the stomach another modification of this originally uniform action occurs: the muscular constrictions are powerful, and continue during the long periods that the stomach contains food. Throughout the upper intestines, again, a further difference shows itself -- the waves travel along without cessation but are relatively moderate. Finally, in the rectum this rhythm departs in another way from the common type: quiescence, lasting for many hours, is followed by a series of strong contractions. Meanwhile, the essential actions which these movements aid, have been growing more definitely heterogeneous. Secretion and absorption are no longer carried on in much the same way from end to end of the tube; but the general function divides into various subordinate functions. The solvents and ferments furnished by the coats of the canal and the appended glands, become widely unlike at upper, middle, and lower parts of the canal; implying different kinds of molecular changes. Here the process is mainly secretory there it is mainly absorbent, and in other places, as in the oesophagus, neither secretion nor absorption takes place to any appreciable extent. While these and other internal motions, sensible and insensible, are being rendered more various, and severally more integrated and more distinct, there is advancing the integration by which they are united into local groups of motions and a combined system of motions. While the function of alimentation subdivides, its subdivisions become co-ordinated, so that muscular and secretory actions go on in concert, and so that excitement of one part of the canal sets up excitement of the rest. Moreover, the whole alimentary function, while it supplies matter for the circulatory and respiratory functions, becomes so integrated with them that it cannot for a moment go on without them. And, as evolution advances, all three of these fundamental functions fall into greater subordination to the nervous functions -- depend more and more on the due mount of nervous discharge; while at the same time their motions become co-ordinated, or in a sense integrated, with those of the nervo-muscular system, on which they depend for the supply of materials.

When we trace up the functions of motor organs the same truth discloses itself. Microscopic creatures are moved through the water by the oscillations of cilia, here large and single or double, and here smaller and numerous; and various larger forms, as the Turbellaria, progress by ciliary action over solid surfaces. These motions of cilia are, in the first place, severally very minute; in the second place they are homogeneous; and in the third place there is but little definiteness in them individually, or in their joint product, which is mostly a random change of position not directed to any selected point. Contrasting this ciliary action with the action of developed locomotive organs, we see that instead of many small or unintegrated movements there are a few comparatively large or integrated movements; that actions all alike are replaced by actions partially or wholly unlike; and that instead of being very feebly or almost accidentally co-ordinated, their definite co-ordination renders the motions of the body as a whole, precise. A parallel contrast, less extreme but sufficiently decided, is seen when we pass from the lower types of creatures with limbs to the higher types of creatures with limbs. The legs of a Centipede have motions that are numerous, small, and homogeneous; and are so little integrated that when the creature is divided and subdivided, the legs belonging to each part propel that part independently. But in one of the higher Arthropoda: as a Crab, the relatively few limbs have motions which are comparatively large in their amounts, which are considerably unlike one another, and which are integrated into total bodily movements of much definiteness.

§143. The last illustrations introduce us to illustrations of the kind classed as mental. They are the physiological aspects of the simpler among those functions which, under a more special and complex aspect, we distinguish as psychological. The phenomena subjectively known as changes in consciousness, are objectively known as nervous excitations and discharges, which science now interprets into modes of motion. Hence, in following up organic evolution, advance of the retained motion alike in integration, in heterogeneity, and in definiteness, may be expected to show itself both in the visible nervo-muscular actions and in the correlative mental changes. We may conveniently look at the facts as exhibited during individual evolution, before looking at them as exhibited in general evolution.

The progress of a child in speech very clearly displays the transformation. Infantine noises are comparatively homogeneous; alike as being severally long-drawn and nearly uniform from end to end, and as being constantly repeated with but little variation of quality. They are quite un-co-ordinated -- there is no integration of them into compound sounds. They are inarticulate, or without those definite beginnings and endings and joinings characterizing words. Progress shows itself first in the multiplication of the inarticulate sounds: the extreme vowels are added to the medium vowels, and the compound to the simple. Presently the movements which form the simpler consonants are achieved, and some of the sounds become sharply cut; but this definiteness is partial, for only initial consonants being used, the sounds end vaguely. While an approach to distinctness thus results, there also results, by combination of different consonants with the same vowels, an increase of heterogeneity; and along with the complete distinctness which terminal consonants give, arises a further great addition to the number of unlike sounds produced. The more difficult consonants and the compound consonants, imperfectly articulated at first, are by-and-by articulated with precision; and hence arises another multitude of different and definite words -- words that imply many kinds of vocal movements, severally performed with exactness, as well as perfectly integrated into complex groups. The subsequent advance to dissyllables and polysyllables, and to involved combinations of words, shows the still higher degree of integration and heterogeneity eventually reached by these organic motions.

The acts of consciousness correlated with these nervo-muscular acts, of course go through parallel phases; and the advance from childhood to maturity yields daily proof that the changes which, on their physical side are nervous processes, and on their mental side are processes of thought, become more various, more defined, more coherent. At first the intellectual functions are much alike in kind -- recognitions and classifications of simple impressions alone go on; but in course of time these functions become multiform. Reasoning grows distinguishable, and eventually we have conscious induction and deduction; deliberate recollection and deliberate imagination are added to simple unguided association of ides; more special modes of mental action, as those which result in mathematics, music, poetry, arise; and within each of these divisions the mental movements are ever being further differentiated. In definiteness it is the same. At first the infant makes its observations so inaccurately that it fails to distinguish individuals. The child errs continually in its spelling, its grammar, its arithmetic. The youth forms incorrect judgments on the affairs of life. Only with maturity comes that precise co-ordination of data which is implied by a good adjustment of thoughts to things. Lastly, with the integration by which simple mental acts are combined into complex mental acts, we see the like. In the nursery you cannot obtain continuous attention -- there is inability to form a coherent series of impressions; and there is a parallel inability to unite many co-existent impressions, even of the same order: witness the way in which a child's remarks on a picture, show that it attends only to the individual objects represented, and never to the picture as a whole. But advancing years bring the ability to understand an involved sentence, to follow long trains of reasoning, to hold in one mental grasp numerous concurrent circumstances. A like progressive integration takes place among the mental changes we distinguish as feelings; which in a child act singly, producing impulsiveness, but in an adult act more in concert, producing a comparatively balanced conduct.

After these illustrations supplied by individual evolution, we may deal briefly with those supplied by general evolution, which are analogous to them. A creature of very low intelligence, when aware of some large object in motion near it, makes a spasmodic movement, causing, it may be, a leap or a dart. The perceptions implied are relatively simple, homogeneous, and indefinite: the moving objects are not distinguished in their kinds as injurious or otherwise, as advancing or receding. The actions of escape, too, are all of one kind, have no adjustments of direction, and may bring the creature nearer the source of peril instead of further off. At a higher stage the dart or the leap is away from danger: the nervous changes are so far specialized that there results distinction of direction; indicating a greater variety among them, a greater co-ordination or integration of them in each process, and a greater definiteness. In still higher animals, able to discriminate between enemies and not-enemies, as a bird which flies from a man but not from a cow, the acts of perception have severally become united into more complex wholes, since cognition of certain differential attributes is implied; they have also become more multiform, since each additional component impression adds to the number of possible compounds; and they have, by consequence, become more specific in their correspondences with objects -- more definite. And then in animals so intelligent that they identify by sight not species only but individuals of a species, the mental changes are yet further distinguished in the same three ways. In the course of human evolution the law is equally manifested. The thoughts of the savage are nothing like so heterogeneous in their kinds as those of the civilized man, whose complex environment presents a multiplicity of new phenomena. His mental acts, too are much less involved -- he has no words for abstract ideas, and is found to be incapable of integrating the elements of such ideas. And in all but simple matters there is none of that precision in his thinking, and that grasping of many linked conceptions, which, among civilized men, leads to the exact conclusions of science.

§144. How in societies the movements or functions produced by the confluence of individual actions, increase in their amounts, their multiformities, their precision, and their combination, scarcely needs insisting upon after what has been potted out in foregoing chapters. For the sake of symmetry of statement, however, a typical example or two may be set down.

At first the military activities, undifferentiated from the rest (all men in primitive societies being warriors) are relatively homogeneous, ill-combined, and indefinite: savages making a joint attack severally fight independently; in similar ways, and without order. But as societies evolve the movements of the thousands of soldiers which replace the tens of warriors, are divided and re-divided in their kinds of movements: here are gunners, there infantry and elsewhere cavalry. Within each of the differentiated functions of these bodies there come others: there are distinct actions of privates, sergeants, captains, colonels, generals, as also of those who constitute the commissariat and those who attend to the wounded. The clustered motions that have thus become comparatively heterogeneous in general and in detail, have simultaneously increased in precision; so that in battle, men and the regiments formed of them, are made to take definite positions and perform definite acts at definite times. Once more, there has gone on that integration by which the multiform actions of an army are directed to a single end. By a co-ordinating apparatus having the commander-in-chief for its centre, the charges, and halts, and retreats are duly concerted; and a hundred thousand individual motions are united under one will.

Again on comparing the rule of a savage chief with that of a civilized government, aided by its subordinate local governments and their officers, down to the police, we see how, as men have advanced from tribes of hundreds to nations of millions, the regulative action has grown large in amount; how, guided by written laws, it has passed from vagueness and irregularity to comparative precision; and how it has subdivided into processes increasingly multiform. Or after observing how the barter that goes on among barbarians differs from our own commercial processes, by which a million's worth of commodities is distributed daily; by which the relative values of articles immensely varied in kinds and qualities are exactly measured, and the supplies adjusted to the demands; and by which industrial activities of all orders are so combined that each depends on the rest and aids the rest; we see that the kind of movement which constitutes trade, has become progressively more vast, more varied, more definite, and more integrated.

§145. A finished conception of Evolution thus includes the re-distribution of the retained motion, as well as that of the component matter. This added element of the conception is scarcely, if at all, less important than the other. The movements of the Solar System have a significance equal to that which the sizes, forms, and relative distances of its members possess. The Earth's geographical and geological structure are not more important elements in the order of Nature than are the motions, regular and irregular, of the water and the air clothing it. And of the phenomena presented by an organism, it must be admitted that the combined sensible and insensible actions we call its life, do not yield in interest to its structural traits. Leaving out, however, all implied reference to the way in which these two orders of facts concern us, it is clear that with each redistribution of matter there necessarily goes a re-distribution of motion; and that the unified knowledge constituting Philosophy, must comprehend both aspects of the transformation.

Our formula, therefore, needs an additional clause. To combine this satisfactorily with the clauses as they stand in the last chapter, is scarcely practicable; and for convenience of expression it will be best to change their order. On doing this, and making the requisite addition, the formula finally stands thus: -- Evolution is an integration of matter and concomitant dissipation of motion; during which the matter passes from an indefinite, incoherent homogeneity to a definite, coherent heterogeneity and during which the retained motion undergoes a parallel transformation.

[Note. Only at the last moment, when this sheet is ready for press and all the rest of the volume is standing in type, so that new matter cannot be introduced without changing the "making up" throughout 150 pages, have I perceived that the above formula should be slightly modified. Hence my only practicable course is to indicate here the alteration to be made, and to set forth the reasons for it in Appendix A.

The definition of Evolution needs qualifying by introduction of the word "relatively" before each of its antithetical clauses. The statement should be that "the matter passes from a relatively indefinite, incoherent homogeneity to a relatively definite, coherent heterogeneity." Already this qualification has been indicated in a note to §116 (page 295), but, more effectually to exclude misapprehensions, it must be incorporated in the definition. In Appendix A are named the circumstances which led to inadequate recognition of it.]