creatures in whom no sign of an auditory organ exists. And if we call to mind the facts that congenitally deafi persons are acutely affected by sonorous vibrations in iJie5' bodies they touch, and can perceive such vibrations even in the air when produced by loud concussions, as the firing of ] cannon — if we infer, as we must, that even in man tlv,r whole body is in some degree sensitive to sound, and that' the extreme sensitiveness of one part is simply a specialization of this general sensitiveness; we shall have no difficulty in understanding how the humblest zoophytes and molluscoid animals feel the jar of those rapid undulations which constitute objective sound. Of lax tissue, and of like specific gravity with its medium, one of these creatures must be permeated by such undulations throughout its entire mass, almost as though it were so much water; and can scarcely fail to have the substance of its tissues so disturbed as to produce a marked change in their general state, and some consequent change in the external manifestations. Still it may be asked — How do these facts and inferences affiliate the faculty of hearing on the primary vital processes? I reply — They tend to do this by suggesting that the contraction produced by any sonorous vibration permeating a zoophyte's body, results from some modification of these vital processes. The life of one of these creatures is little else than the cumulative result of the lives of its component cells or nucleated portions of protoplasm, which severally absorb the nutrient juices percolating among them, are severally bathed by the oxygenating medium, and severally carry on the integrating and disintegrating actions by and for themselves. Now anything which causes a sudden agitation of the aerating liquid diffused through this almost homogeneous tissue, will produce a sudden increase of vital activity in all the components of the tissue.
A rapid succession of undulations propagated through it must do this. And we have but to suppose that the increased vital activity of each component is accompanied by '312 GENERAL SYNTHESIS.
some change, probably isomeric, which alters its form, to understand how a contraction of the entire creature may result.
Thus, there is not a little reason to think that all forms of sensibility to external stimuli, are, in their nascent shapes, nothing but the modifications which those stimuli produce in that duplex process of integration and disintegration winch constitutes the primordial life, physiologically considered. A zoophyte cannot be touched without the fluids diffused throughout the disturbed tissues being put hi motion, and so made to supply oxygon and nutriment with greater rapidity. Nutritive matter brought in cout.act with the surface, which is everywhere absorbent, must oxcito the vital actions still more; and so must cause the touch of nutritive matter to be specially responded to. A diffusion of such matter in the form of an odour, will tend in a slight degree to produce analogous effects. Tho tissue having the requisite chemical nature, light, also, must modify the assimilative actions. And, as just shown, sonorous vibrations probably do the like. If we make tho reasonable assumption that the protoplasm of these almost unorganized creatures is isornerically changed by changes in Iheir vital activity, we have an adequate explanation of! the effects which outer agencies produce. fcSo. far as they go, facts harmonize with the deduction from the law of organic "development — the deduction that as the primitive tissue out of which are evolved, the organs of vegetative life, possesses, to some extent, the functional powers of those organs; so must it, to some extent, possess the functional powers of the organs of animal life, and among thorn of the senses, which similarly arise out of it by a continuous differentiation, and integration.
Closing here these speculations respecting the genesis of the several faculties through which the animal organism holds communication with the external world, let us now go on to our immediate subject — that extension of the corro- 7RE CORRESPONDENCE AS EXTENDING IN SPACE. 313 spondence in Space,, which accompanies the evolution of those faculties.
§ 141. Differentiated gradually, as, in aquatic creatures, smell is from touch and taste, its nascent form is not likely to be detected without careful experiments; and I have notmet with accounts of such. " How far any sense of smell exists in the lower invertebrata, cannot be satisfactorily determined/' says Dr. Carpenter: " but it would seem not improbable that even where no special organ is apparent, some part of the general surface may be endowed with olfactive sensibility." But however the sense of smell originates, we. may conclude that only when in some degree localized, does it become a means whereby internal relations can be brought into something like definite correspondence with external relations which do not occur in contact with the body.
Supposing, for argument's sake, that along with its other diffused faculties the whole mass of the primitive animal possesses a feeble susceptibility to odours; the only correspondence which may be established through this, must be seen in some state of readiness to seize the prey, or avoid the enemy, whose proximity an odour implies. Though, by means of such endowment, an inner relation can be adjusted to an outer relation a little removed from the surface; yet, there can be no adjustment to relations either of direction in space or of distance in space. But as soon as there exists a susceptibility that is somewhat localized, the organism /• must be differently affected by an odoriferous body, according as it is situated in this or that position. And when, as an accompaniment of specialization, there is increased efficiency, a feebly-scented object near to the more highly sensitive tract, may produce a response as great as a strongly-scented object somewhere in its neighbourhood produces in an organism possessed of a diffused but inferior susceptibility.
Passing from these vague beginnings, it will be obvious that as fast as there is developed at the entrance of the respiratory passages a definite apparatus capable of being excited by floating particles, there must be an extension of the space through which co-existences and sequences in the environment can establish corresponding co-existences and sequences in the organism. When we trace up the evolution of the faculty to that perfection in which it is possessed by dogs and by deer, we see that one of the aspects under which the advance presents itself, is the increasing distance at which certain inner and outer relations can be brought into adjustment; and that, other things equal, there is a simultaneous advance in the degree of life.
§ 142. Though that ability to distinguish light from darkness which characterizes the entire body in sundry of tho humblest types, foreshadows the visual faculty, nothing like what we call sight results until this ability is concentrated in a particular spot. The rudimentary eye consisting; as in a Planar ia, of some pigment grains, may be considered as simply a part of the surface more irritable by light than the rest. Some idea of the impression it is fitted to receive raay be formed by turning our closed eyes towards the light, and passing the hand backwards and forwards before them. Bat as soon as even this slight specialization of function is reached, it becomes possible for the organism to respond to the motions of opaque bodies that pass near. While only a general sensitiveness to light exists, the intercepting of the sun's rays by something which throws the whole or a greater part of the creature into shade, is required to produce an internal change; but when there comes to be a specially sensitive spot, anything which casts a shadow on that spot alone, produces an internal change. And as that which obscures only a small part of the organism is usually a comparatively small object, this advance from diffused sensitiveness to concentrated sensitiveness enables the onranism o to respond, not only to marked general changes in luminousness which its environment undergoes, but also to marked special changes in luminousness caused by the motions of adjacent bodies.
The contrast between light and darkness., or rather "between widely different degrees of light, being all that the most rudimentary vision recognizes; and distinct obscuration being producible by an adjacent small object only when it is very close; we may infer that nascent vision extends to those objects alone which are just about to touch the organism, either in consequence of their motion or of its motion. We may infer that it amounts at first to little more than anticipatory touch; and that so there is established in the organism a general relation between visual and tactual impressions, corresponding to the general relation between opacity and solidity in the environment. Be this as it may, however, it is clear that an incipient faculty of sight, though the vaguest imaginable in the sensations it gives, and the most limited that can be conceived in range, I implies not only some extension of the correspondence in space, but a new order of correspondence.
As we ascend to creatures haying more developed eyesj we find an increase in the sphere of surrounding space! throughout which external relations can establish correspond-* ing internal relations. A slight convexity of the epidermic layer lying over the sensitive tract, first serves, by concentrating the rays, to render appreciable less marked variations in the quantity of light; and thus brings into view the same bodies at a greater distance, and smaller or less opaque bodies ^ the same distance. From this point upwards, through the various types of aquatic creatures to the higher air-breathing creatures, we trace, under various forms and modifications, a complicating visual apparatus and a widening space througfi which the correspondence extends. It is needless to go into details. Hypotheses and! illustrations aside, it is obvious that from the polype which! does not stir till touched, up to the telescopic-eyed vulture!
gi6 GENERAL SYNTHESIS.
lor the far-sighted Bushman, one aspect of progressing life ]is the greater and greater remoteness at which visible rela-:tions in the environment produce adapted relations in the § 143. Similarly with the auditory faculty. So long as the susceptibility to sonorous vibrations is slight, and possessed by the body at large, there is nothing like what we call hearing. Only when the susceptibility conies to be intensified in one place, can a sound proceeding from a particular point in the environment, be distinguished from a tremor of the environment as a whole. After there has arisen a rudimentary ear, consisting of a dermal sac containing otolithes, which multiply the vibrations striking the skin that covers them as the primitive cornea concentrates the rays passing through it; then, a moderate sound at some distance or a slight sound close to it, may produce on the creature as great an effect as the violent shock of its entire medium produces on a creature not thus endowed. And along with this new sense there comes into existence a new set of correspondences — those between certain auditory impressions and consequent motions in the organism, and certain sound-causing powers and co-existent properties in adjacent bodies.
Successive improvements of this faculty, as of those already dealt with, expand the surrounding sphere throughout which certain relations in the environment cause adapted relations in the organism. It cannot be denied that though the minor irregularities involved by their special habits are considerable, yet, viewed in the mass, animals of higher.and higher types show us greater and greater ranges in their auditory correspondences.
§ 144. The extension of the correspondence in space does not end "with the perfecting of the senses. In creatures of comparatively-advanced organization, there arise powers of adjusting inner relations to outer relations that are far too remote for direct perception. The motions by which a carrier-pigeon finds its way home though taken a hundred miles away, cannot be guided by sight, smell, or hearing, in their direct and simple forms. Chased animals that make their way across the country to places of refuge out of view, are obviously led by combinations of past and present impressions which enable them to transcend the sphere of the senses. And thus also it must be with creatures that annually migrate to other lands.
Ill jm^, this secondary process of extension is carried j still further. Though the correspondences he effects by <! immediate perception have a narrower range in space than those of some inferior creatures; and though in that species of indirect adjustment just exemplified, he is behind sundry wild and domestic animals; yet, by still more indirect means, he adjusts internal relations to external relations that are immensely beyond the appreciation of lower beings. By combining his own perceptions with the perceptions of j others as registered in maps, he can reach special places | lying thousands of miles away over the Earth's surface. A **• ship, guided by compass, and stars, and chronometer, brings* him from the antipodes information by which his purchases I here are adapted to prices there. From, the characters j of exposed strata he infers the presence of coal below; and thereupon adjusts the sequences of his actions to coexistences a thousand feet underneath. Nor is the environ-1;-ment through which his correspondences reach, limited to) the surface and the substance of the Earth. It stretches into the surrounding sphere of infinity. It was extended to the nib OIL when the Chaldeans "discovered how to predict eclipses; to the sun and nearer planets when the Copernican system was established; to the remoter planets when an improved telescope disclosed one, and calculation fixed the position of the other; to the stars when, their parallax: \ and proper motion were measured; and, in a vague way, ] even to tlie nebulae, when their composition and forms of structure were ascertained.
§ 145. Before leaving this general proposition, that tho progress of life and intelligence is, under one of its aspects, an extension of the space through which the correspondence between the organism and its environment reaches, it may be well to remark that its truth is independent of all conclusions as to the modes in which the correspondence is developed. In the earlier part of the chapter I have filled up some of the gaps in our knowledge by reasonings that are partially hypothetical; and have thus opened the door to possible criticisms, which may at first sight be supposed to tell against the doctrine at large. But a moment's consideration will show that by whatever steps the senses of smell, sight, and hearing, arise, the result remains the same. Unquestionable facts form the substance of the argument. It is a fact that where the sense of touch is the only one definitely manifested, the correspondence between tho organism and its environment extends only to that part of the environment by which the organism is bathed. It is a fact that the appearance of the higher senses, even in their most rudimentary forms, is accompanied by some extension of the space throughout which correspondences can be effected. It is a fact that the successive stages in tho development of each sense imply successive enlargements of this sphere of space. And it is a fact that the advent of rationality is, among other ways, shown in the carrying of tEese enlargements still further.
Here, indeed, let me draw attention to tho truth indicated by some of the above examples, that the extension of the correspondence in space is exhibited not in the ascending grades of animal life alone, but in the successive phases of human civilization, and is even now going on. 1'rom early races acquainted only with neighbouring localities, up to modern geographers who specify the latitude and THE COMHB&rONDENCE AS EXTENDING IN SPACE. 319 longitude of every place on tie globe — from the ancient builders and metallurgists, knowing but surface-deposits,, up to the geologists of our day whose data in some cases enable them to describe the material existing at a depth never yet reached by the miner — from the savage barely able to say in how many days a full moon will return,, up to the astronomer who ascertains the period of revolution of a double star — there has been a gradual widening of the surrounding region throughout which the adjustment of inner to outer relations extends.
It remains only to point out the additional evidence thus afforded that the degr^ of life varies as_ the degree of coin^espondence. On the one hand, each further extension of the correspondence in space adds to the number of external relations to which internal relations are adjusted — adds,, that is, to the number of internal changes — adds therefore to the amount of life. On the other hand, the greater the space throughout which the correspondence reaches, and the more numerous the adjustments which can consequently be made, the greater must be the number of cases in which food is obtained and danger shunned. Whence we may clearly see how life and ability to maintain life, are two sides of the same fact — how life is a combination of processes the^ result of whose workings is their o\vn continuance.
CHAPTER V.
THE CORRESPONDENCE AS EXTENDING- IN TIME, § 146. It was pointed out some pages back (§ 186), that • while tlie lowest Protopliytct and Protozoa display no manifest adjustments of internal changes to changes in the environment, the higher plants pass through cycles of states answering to the cycles of the seasons. Whether this should be regarded as a progress towards correspondence in Time, is doubtful. It may be said that since in a tree the budding, blossoming, ripening the fruit, and dropping the leaves, occur at the same times with fit external conditions,, the inner sequences are conformed to the outer ones. But it may be replied that this is an incidental result of the perpetual adaptation of the internal actions to external coexistences (temperature, light, moisture), which, by passing through a series of variations, involve a parallel series of variations in the plant. It may be argued that the putting forth of leaves has reference simply to the then concurring influences, and has no direct reference to the subsequent nutrition of the fruit; that the true nature of these vegetative changes is seen in the fact that a tree will flower in the autumn if the heat be great enough; and that thus plantlife exhibits no true correspondence to sequences in the environment, but only to co-existences in it. To decide between these views is not easy; though on the whole the last seems the more rational. But at any rate, this species THE CORRESPONDENCE AS EXTENDING IN TIME. 321 of correspondence in Time, if suck it be, is of a vague kind compared witli that properly so called.
Turning to those more definite cases which animal life displays-it is to be observed that in creatures possessing no other sense than that of touch, the sole external relations with which internal relations can be put in correspondence, are relations of co-existence. Only when there comes to be some amount of smell, or sight, or hearing, can sequences in the environment be met by adjusted sequences in the orgar^m. The connexion between the tangibility of an adjacent body and some co-existent property possessed by it, is the only one to which, in a zoophyte, the connexion between irritation and contraction answers. Time is no more involved than Space. But when relations among. things or attributes that are in any degree removed from the organism, become cognizable — when, for example, there exists incipient vision, and obstruction of light is often followed by a touch from the obstructing body — then, an organic response to an external sequence becomes possible: then the organism can move in anticipation of motion in an -external body. Two phenomena in the Environment, the one immediately succeeding the Bother, produce two phenomena in the organism ia like.succession.
~ Or, to present the proposition under another aspect:— -As the simplest sequences, and those first perceived, are mechanical sequences; as mechanical sequences imply change of position,• as change of position implies progress through Space; it follows that only when there is some degree of space-penetrating faculty, can there be any adaptation in the organism to changes of position in adjacent objects — any adjustment to external sequences — any correspondence* in Time. After the ability to respond to the touches of surrounding bodies, the next advance is the ability to respond to those motions of them which precede touch; and since motion involves both Time and Space, the first extensum of the correspondence in Tinio is necessarily coeval with its first extension in Space.
§ 147. Throughout Hie successive sfntfos in fin* dovlnptriont of the senses, these two orders of eonvxpMitdrnru progress together. In proportion as i.ho disf.mrn n\. which a moving object is perceivable increases, the irr^iffT brcornr-A the duration of the (external actions, or chains oi adion^, to which the internal changes may In* adjusted. Othor fining equal, the more \*einot.o any body, the IMU^T must, In* tin* interval before it can net on the organism or th«* origan i--ni on it; that is — the longer must bt^ the fini*% Ix-fwrou th«* outer antecedents and consequents with whi«*li Ihr ii»n»*r ant(K*«!detii«H and consequents ar<^ put in rorrr^prtnilonri*.
The inner and outer sequences Khown in the pursuit of a lioron by a hawk, are longer than those shown in th«* pursuit of a iish by a horou; and are HO rhiHly Invuu1^ tho vision of a heron is wider than that of a fish. Without,! giving eases, it will bo manifest that by tin* <ltnvl«»pwt»nt **f smell and hearing" also, the correspondences an* hiwultimoously extended in duration and distance. Nfof' Uwl thry maintain a constant ratio. The connexioti bi'twc««n fh«nit IH variously tuotUlitHl by circuinstanceH, The cl»irncii«r of tin* cuviroinncmfc, the particular powt*rH <?f the orpwisw in respect of locomotion, as well as othtn* condiltonn, ^rt'afly affect its. All that can be said is, that tin? two- kiittU nf extension nro connate; and that, in HO fur us w*«rlwniriil phonoinena are concerned, they display throughout a gvfti<ml inter- dependence* § 148, This limitation — "infto far HH mcrlmnintt |ih(*m»* txiona arc concerned ''—serves to introduce tlm furt IhiU, in respect to other orders of plwmoiufna, tho pmgm»»w uf tlio corresponclonco in Time has little or nothing to c!o with IIH progress in Spaco, Bid nil actuinn involve motion— wore altoratioxx of position a THE COREESPONDENCE AS EXTENDING IN TIME. 323 raent of every alteration, the two would be uniformly related. Bat as tliere are hosts of changes, chemical, thermal, electric, vital, which involve no appreciable mechanical change — as there are numberless changes of state which occur without changes of place; it results that, in the growth of internal adjustments to these, there is an extension of the correspondence in Time separate from, and additional to, that which arises from its extension in Space.
This second species of correspondence in Time is of a much higher order — is, in fact, a far more extended correspondence. For the ordinary mechanical sequences in surrounding bodies by which each organism is affected, are incalculably more rapid than the non-mechanical sequences. The motions of enemies or of prey, even when sluggish, are readily appreciable: a few seconds only, at most, are needed to bring about manifest changes. But the decay of a dead animal, or tlie ripening of fruit, or the drying up of a pool, or the hatching of an egg, occupies an immensely longer interval. One of these latter sequences has a duration a hundred, a tliousand, a million times as great as one of the former; and the ability of the organism to adjust itself to them, implies a proportionate extension of the correspondence in Time.
Hence the fact that only when we come to creatures of comparatively high inteffigeiice, do w^ meet with inner changes in adaptation to ^outer changes of anon-mechanical kind7 "" For -we must not class as coming under this head such actions of inferior animals as are adjusted to daily and annual modifications of the environment. These, like parallel actions in. plants, are most likely nothing but the cumulative results of successive adaptations of the organism to successive co-existences in the environment. It is ana- l tornically demonstrable that the^airing jndjaidifiQatiDa of birds in the spring, is preceded^by constitutional changes which are probably produced by more food and higher temperature. And it is a rational inference that the whole 324 " GENERAL SYNTHESIS.
series of processes implied in the rearing of a brood, are severally gone through, act with any recognition of remote ends, but solely under the stimulus of conditions continuously present.