YET, as we look at Nature, the fact will force itself upon us that there are structures in which we cannot recognise any use; that there are contrivances which often fail of their effect; and that there are others which appear to be separated from the conditions they were intended to meet, and under which alone their usefulness could arise. Such instances occur in many branches of inquiry; and although in the great mass of natural phenomena the supremacy of Purpose is evident enough, such cases do frequently come across our path as cases of exception — cases in which Law does not seem to be subservient to Will, but to be asserting a power and an endurance of its own.

The degree of importance which may be attached to such cases as a source of real difficulty, will vary [181/182] with the character of the individual mind, and its capacity of holding by the great lines of evidence which run through the whole Order of Nature. It is with these cases as with the local currents which sometimes obscure the rising and falling of the tides. When watched from hour to hour, the greater law is clearly discernible by well — marked effects; but when watched from minute to minute, that law is not distinct, and there are waves which seem like a rebellion of the sea against the force which is dragging it from the land. The Order of Nature is very complicated, and very partially understood. It is to be expected therefore that there should be a vast variety of subordinate facts, whose relation to each other and to the whole must be a matter of perplexity to us. It is so with the relation in which different known laws of Nature stand to each other; much more must it be so with the far deeper subject of the relation which these laws bear to the Will and the intentions of the Supreme. But as cases of intention frustrated, of structure without apparent purpose, of organs dissociated from function and from the opportunities of use, are sometimes sources of [182/183] difficulty, it may be well to consider this subject a little nearer.

There is one explanation which it cannot be doubted applies to many cases, and this is the simple explanation, that we often mistake the purpose of particular structures in Nature, and connect them with intentions which are not and never were the intentions really in view. The best naturalists are liable to such mistakes. A very curious illustration is afforded by an observation of Mr Darwin, in his "Origin of Species." He says that "if green Woodpeckers alone had existed, and we did not know that there were any black and pied kinds, I daresay we should Nave thought that the green colour was a beautiful adaptation to hide this tree frequenting bird from its enemies." Now, this introduces us to a very curious subject, and one as well adapted as any other to illustrate the relation in which Law stands to Purpose in the economy of Nature.

There can be no doubt that the principle of adapted colouring with the effect and for the purpose of concealment, prevails extensively in various branches of the Animal Kingdom. It arises [183/184] probably, like all other phenomena, by way of Natural Consequence out of some combination of forces which are the instruments employed. We have no knowledge what these forces are, but we can imagine them to be worked into a law of assimilation, founded on some such principle as that which photography has revealed. It is true that Man has not yet discovered any process by which the tints of Nature can be transferred, as the most delicate shades of light can be transferred, to surfaces artificially prepared to receive them. Such a process is, however, very probably within the reach even of human chemistry, and it is one which is certainly known in the laboratory of Nature. The Chameleon is the extreme case in which the effect of such a process is proverbially known. Many fish exhibit it in a remarkable degree, — changing colour rapidly in harmony with the colour of the water in which they swim, or of the bottom on which they lie. The law on which such changes depend is very obscure, but it appears to be a natural process, as constant as all other laws are; that is, constant whenever given conditions are brought together. It is possible that [184/185] the effect may be due to a cause which is well known to be capable of producing somewhat analogous results. Even before the days of Jacob and of Laban, it seems to have been known, that through the eyes of the female parent, colour can be determined in her young; and although this is certainly not the law which commonly determines colour, operating as it does, so far as we know, seldom, and only in a small degree, it is quite conceivable that, under special conditions, it is capable of being worked as a great power in Nature. But then, these conditions are not brought together except with a view to purpose. For now let us see how this law, whatever it may be, is regulated and applied.

One thing is certain, — assimilated colouring is not applied universally; on the contrary, it is applied very partially. Is it therefore applied arbitrarily at haphazard, or without reference to conditions in which we can trace a reason and a rule? Far from it. The rule appears to be this: — adaptive colouring as a means of concealment is never applied (I) to any animal whose habits do not expose it to special danger, or (a) to any animal which is [185/186] suffciently endowed with other more effective means of escape.

This is the higher Law of Purpose which governs the lesser law, whatever it may be, by which assimilative colouring is produced. Now, no man who had observed this higher law could ever fall into the error of supposing that the colour of the Green Woodpecker was given to it as a means of concealment. Few birds are so invisible as Woodpeckers, because their structure and habits give them other methods of escaping observation which are most curious and effective. They have few natural enemies but Man, and when in danger of being seen by him, they slip and glide round the bole of the tree or bough on which they may be climbing with a swift, silent, and cunning motion, and from behind that shelter, with nothing visible but their head, they keep a close watch upon the movements of the enemy. With such sleight of feet there is no need of lazier methods of concealment.

Accordingly in this family of birds the law of assimilation is withheld from application, and the most violent and strongly contrasted colouring [186/187]

prevails. Jet black, side by side with pure white, and the most brilliant crimsons, are common in the plumage of the Woodpeckers. No birds are more conspicuous in colouring, yet none are more seldom seen. The Green Woodpecker itself, with its yellow tints and crimson hood, contrasts strongly with the bark on which it climbs. The purpose of concealment being effected by other means, gives way to the purpose of beauty or of adornment in the disposition of colours. And in general the same rule applies to all birds whose life is led among woods and forests. Comparatively inaccessible to birds of prey, they exhibit every variety of tint, and the principle of invisibility from assimilated colouring is almost unknown.

It must always be remembered, that animals of prey are as much intended to capture their food, as their victims are intended to have some chances and facilities of escape. The purpose here is a double purpose — a purpose not in all cases to preserve life, but to maintain its balance and due proportion. In order to effect this purpose, the means of aggression, and of defence, or of escape, must bear a definite relation to each [187/188] other both in kind and in degree. When arboreal birds leave their sheltering trees they are exposed to the attacks of Hawks, but they have fair opportunities of retreating to their coverts again; and the upward spring of the disappointed Falcon in the air, when his quarry reaches the shelter of trees, tells how effective such a retreat is, and how completely it ends the chase. On the other hand, there is a great variety of birds whose habitat is the open plain — the desert — the unprotected shore — the treeless moor — the stony mountain — top. These are the favourite hunting-grounds of the Eagles, and the Falcons, and the Hawks. There they have free scope for their great powers of wing, and uninterrupted range for their piercing powers of sight. And it must be remembered, that even the slowest of the Hawks can on such ground capture with ease birds which when once on the wing could distance their pursuer by superior speed, because the Hawk, sweeping over the ground, takes the prey at a disadvantage, pouncing on it before it can get fairly into the air. Birds whose habitat is thus exposed could not Maintain their existence at all without special means of [188/189] concealment or escape. Accordingly it is among such birds almost exclusively that the law of assimilative colouring prevails. And among them it is carried to a perfection which is wonderful indeed. Every ornithologist will recognise the truth of the observation, that this law prevails chiefly among the Grouse, the Partridges, the Plovers, the Snipes, Woodcocks, Sandpipers, and other kindred families, all of which inhabit open ground. There can be no better examples than the Grouse and the Ptarmigan of our Scottish mountains. The close imitation in the plumage of these birds of the general tinting and mottling of the ground on which they lie and feed is apparent at a glance, and is best known to those who have tried to see Grouse or Ptarmigan when sitting, and when their position is indicated within a few feet or a few inches by the trembling nostrils and dilated eyeballs of a steady Pointer-Dog. In the case of the common Grouse, as the ground is nearly uniform in colour throughout the year, the colouring of the bird is constant also. But in the case of the Ptarmigan, it changes with the changing seasons. The pearly grays which in summer match so [189/190] exactly with the lichens of the mountain peaks, give place in winter to the pure white Which matches not less perfectly with the wreaths of snow.

This is indeed a change which requires for its production the agency of other laws than those merely of reflected light, because the substitution of one entire set of feathers for another of a different colour, twice in every year, implies arrangements which lie deep in the organic chemistry of the bird. The various genera of Sand-Grouse and Sand-Partridges, which frequent the deserts and naked plains of the Asiatic continent, are coloured in exquisite harmony with the ground. Our common Woodcock is another excellent example, and is all the more remarkable as there is one very peculiar colour introduced into the plumage of this bird which exactly corresponds with a particular stage in the decay of fallen leaves — I mean that in which the browns and yellows of the Autumn rot away into the pale ashy skeletons which lie in thousands under every wood in winter. This colour is exactly reproduced in the feathers of the Woodcock, and so mingled with the dark browns and warm yellows of fresher leaves, that [190/191] the general imitation of effect is perfect. And so curiously is the purpose of concealment worked out in the plumage of the Woodcock, that one conspicuous ornament of the bird is covered by a special provision from the too curious gaze of those for whose admiration it was not intended. The tail-feathers of the Woodcock can be erected and spread out at pleasure like a fan, and, being tipped on their under surface with white of a brilliant and silvery lustre, set off by contrast with an adjacent patch of velvety black, they then produce a most conspicuous effect. But the same web, which on its under surface bears this beautiful but dangerous ornament, is on its upper surface dulled down to a sombre ashy-gray, and becomes as invisible as the rest of the plumage. These are all provisions of Nature, which stand in clear and intelligible relation to the habits of the bird. It rests all day upon the ground, under trees; and were it not for its ingeniously adapted colouring, it would be peculiarly exposed to destruction. Man is an enemy whose cunning inventions overcome all such methods of protection, and the Woodcock when in his most rapid flight is now [191/192] an easier prey than in older times when sitting on the ground. But before fire-arms had reached the perfection which has enabled us to shoot flying birds, the colouring of the Woodcock served it in good stead, even against the Lords of the Creation. In old times it required special skill and practice to see Woodcocks on the ground, and the large lustrous black eye, which is adapted for night-vision, was the one spot of colour which enabled the fowler of a century and a half years ago to detect the bird. Thus Hudibras has it: —

"For fools are known by looking wise,
As men find Woodcocks by their eyes."1

In Snipes, again, there is a remarkable series of straw-coloured feathers introduced along the back and shoulders, which perfectly imitate the general effect of the bleached vegetable stalks common on the ground which the bird frequents.

There are other animals in which the principle of imitation with a view to concealment is carried very much farther than the mere imitation of colour, and extends also to form and structure. [192/193] There are some examples of this in the Class of Insects, so remarkable that it is impossible to look at them without ever fresh astonishment. I refer to some families of the Orthopterous order, and especially to some genera of the Mantidaeand Phasmidae. Many species of the genus Mantis are wholly modelled in the form of vegetable growths. The legs are made to imitate leaf-stalks, the body is elongated and notched so as to simulate a twig; the segment of the shoulders is spread out and flattened in the likeness of a seed-vessel; and the large wings are exact imitations of a fullblown leaf, with all its veins and skeleton complete, and all its colour and apparent texture. There is something startling and almost horrible in the completeness of the deception — very horrible it must be to its hapless victims. For in this case the purpose of the imitation is a purpose of destruction, the Mantisbeing a predacious insect, armed with the most terrible weapons, hid under the peaceful forms of the vegetable world. It is the habit of these creatures to sit upon the leaves which they so closely resemble apparently motionless, but really advancing on their prey with a [193/194] slow and insensible approach. Their structure disarms suspicion. Wonderful as this structure is, it would be none the less, but all the more wonderful, if it should arise by way of Natural Consequence from some law of development or of growth. It must be a law of which at present we have no knowledge, and can hardly form any conception. But certain it is that here, as in all other cases, the purpose which is actually attained, is attained by a special adaptation of ordinary structure to a special and extraordinary purpose. No new members are given to the Mantis; there is no departure from the plan on which all other insects of the same order are designed. The body has the same number of segments, the legs are the same in number, and are composed of the same joints; every part of this strange creature which seems like a bit of foliage animated with insect life, can be referred to its corresponding part in the ordinary anatomy of its class. The whole effect is produced by a little elongation here, a little swelling there, a little dwarfing of one part, a little development of another. The most striking part of the whole [194/195] imitation — that of the "nervation" of the leaf — is produced by a modification, not very violent, of a structure which belongs to all flying insects. Their wings are constructed of a thin filmy material stretched upon a framework of stronger substance, as the sails of a windmill are stretched upon a trelliswork of spars. This framework is designed in a great variety of patterns — more elaborate and more beautiful than the tracery of Gothic windows. In the Mantis this tracery, instead of being drawn in a mere pattern, is drawn in imitation of the nervature of a leaf. And imitative colouring is added to imitative structure so that nothing should be wanting to its completeness and success.

It must always be remembered, however, that Contrivance in Nature can never be reduced to a single purpose, and to that alone. Almost every example of it is connected with a number of effects which fit into each other in endless ramifications of adjustment. For example, this imitative structure of the Mantido serves as well for their own protection from insectivorous birds as for the procuring of their food in the capture of other [195/196] insects. And this, which is perhaps the subordinate purpose in the case of the Mantidae , emerges as the main purpose in another family of imitative insects, the Phasmidae. These last are vegetable feeders, and their imitative structure is, if possible, even more wonderful, as it certainly is more beautiful. In some species the wings are not only made like leaves in form, in structure, and in general colour, but they are tinted at different seasons of the year with the varying colours of spring, of summer, or of autumn. The fundamental green is shaded off into browns, and reds, and yellows, with a few of those crimson touches which are so common in the "Pageant of the year." There is one specimen in the British Museum where the imitative effect is pursued, as it were, into a region of still more minute and curious observation. The general aspect of summer vegetation is much affected by the ravages of insect life. Minute larva cat into the cuticle of leaves, and mark them with various spots of bleached or faded colour. Now the specimen of Phasma I refer to has its wing covered with spots which exactly imitate this appearance of a larva-eaten [196/197] leaf. Can it be that this effect is itself produced by a really similar cause — the eating of some larval parasite into the tissue of the wing? If so, the combination of means to the production of so wonderful an effect becomes only the more bewildering in the endless vistas of adjustment which are opened out. And there is another fact connected with these insects which is as astonishing as any other. It is this — that the idea and purpose of imitation is carried into effect consistently and perseveringly through all the stages of the creature's metamorphoses. The eggs are as perfect imitations of vegetable seeds as the adult insect is of the expanded leaf. In the larval form they are like bits of stalk, or chips or cuttings of leaves.

But although the laws which determine both form and colouring are here seen to be subservient to use, we shall never understand the phenomena of Nature unless we admit that mere ornament or beauty is in itself a purpose, an object, and an end. Mr Darwin denies this; but he denies it under the strange impression, that to admit it would be absolutely fatal to his own theory on the [197/198] Origin of Species. So much the worse for his theory, if this incompatibility be true. There is indeed a difference, at least in words, between the doctrine now asserted and the doctrine which Mr Darwin denies. What he denies as a purpose in nature is beauty "in the eyes of Man." But this evades the real point at issue. The relation in which natural beauty stands to Man's appreciation of it, is quite a separate question. It is certain enough that the gift of ornament in natural things has not been lavished, as it is lavished, for the mere admiration of Mankind. Ornament was as universal — applied upon a scale at once as grand and as minute as now — during the long ages before Man was born. Some of the most beautiful forms in Nature are the shells of the marine Mollusca, and many of them are the richest, too, in surface ornament. But, prodigal of beauty as the Ocean now is in the creatures which it holds, its wealth was even greater and more abounding in times when there was no man to gather them. The shells and corals of the old Silurian Sea were as elaborate and as richly carved as those which we now admire: and the noble Ammonites of the [198/199] Secondary ages must have been glorious things indeed. Even now there is abundant evidence that although Man was intended to admire beauty, beauty was not intended only for Man's admiration. Nowhere is ornament more richly given, nowhere is it seen more separate from the use, than in those organisms of whose countless millions the microscope alone enables a few men for a few moments to see a few examples. There is no better illustration of this than a class of forms belonging to the border-land of animal and vegetable life called the Diatomacno, which, though invisible to the naked eye, play an important part in the economy of Nature. They exist almost everywhere, and of their remains whole strata, and even mountains, are in great part composed. They have shells of pure silex, and these, each after its own kind, are all covered with the most elaborate ornament — striated, or fluted, or punctured, or dotted in patterns which are mere patterns, but patterns of perfect, and sometimes of most complex beauty. No graving done with the graver's tool can equal that work in gracefulness of design, or in delicacy and strength of touch. Yet it is impossible to look [199/200] at these forms — in all the variety which is often crowded under a single lens — without recognising instinctively that the work of the graver is work strictly analogous, — addressed to the same perceptions, — founded on the same idea, — having for its object the same end and aim. And as the work of the graver varies for the mere sake of varying, so does the work on these microscopic shells. In the same drop of moisture there may be some dozen or twenty forms, each with its own distinctive pattern, all as constant as they are distinctive, yet having all apparently the same habits, and without any perceptible difference of function.

It would be to doubt the evidence of our senses and of our reason, or else to assume hypotheses of which there is no proof whatever, if we were to doubt that mere ornament, mere variety, are as much an end and aim in the workshop of Nature as they are known to be in the workshop of the goldsmith and the jeweller. Why should they not? The love and desire of these is universal in the mind of Man. It is seen not more distinctly in the highest forms of civilised art than in the [199/201] habits of the rudest savage, who covers with elaborate carving the handle of his war-club, or the prow of his canoe. Is it likely that this universal aim and purpose of the mind of Man should be wholly without relation to the aims and purposes of his Creator? He that formed the eye to see beauty, shall He not see it? He that gave the human hand its cunning to work for beauty, shall His hand never work for it? How, then, shall we account for all the beauty of the world — for the careful provision made for it where it is only the secondary object, not the first? Even in those cases, for example, where concealment is the main object in view, ornament is never forgotten, but lies as it were underneath, carried into effect under the conditions and limitations imposed by the higher law and the more special purpose. Thus the feathers of the Ptarmigan, though confined by the law of assimilative colouring to a mixture of black and white or gray, have those simple colours disposed in crescent-bars and mottlings of beautiful form, even as the lichens which they imitate spread in radiating lines and semicircular ripples over the weather-beaten [201/202] stones. It is the same with all other birds whose colour is the colour of their home. For the purpose of concealment, that colouring would be equally effective if it were laid on without order or regularity of form. But this is never done. The required tints are always disposed in patterns, each varying with the genus and the species; varying for the mere sake of variation, and for the beauty which belongs to ornament. And where this purpose is not under the restraint of any other purpose controlling it and keeping it down as it were within comparatively narrow limits, how gorgeous are the results attained ! What shall we say of flowers — those banners of the vegetable world, which march in such various and splendid triumph before the coming of its fruits? What shall we say of the Humming Birds whose feathers are made to return the light which falls upon them as if rekindled from intenser fires, and coloured with more than all the colours of all the gems?

There is one instance in Nature (and, as far as I know, only one) in which ornament takes the form of pictorial representation. The secondary feathers in the wing of the Argus Pheasant are developed [202/203] into long plumes, which. the bird can erect and spread out like a fan, as a Peacock spreads his train. These feathers are decorated with a series of conspicuous spots or "eyes," which are so coloured as to imitate the effect of balls. The shadows and the "high light" are placed exactly where an artist would place them in order to represent a sphere.2 The "eyes" of the Peacock's train are wonderful examples of ornament; but they do not represent anything except their own harmonies of colour. The "eyes" of the Argus Pheasant are like the "ball and socket" ornament, which is common in the decorations of human art. It is no answer to this argument in respect to beauty, that we are constantly discovering the use of beautiful structures in which the beauty only, and not the usefulness, had been hitherto perceived. The harmonies on which all beauty probably depends are so minutely connected in Nature that "use" and ornament may often both arise out of the same conditions. Thus, some of the most beautiful lines on the surface of shells, are simply [203/204] the lines of their annual growth, which growth has followed definite curves, and it is the"law" of these curves that is beautiful in our eyes. Again, the forms of many fish which are so beautiful, are also forms founded on the lines of least resistance. The same observation applies to the form of the bodies and of the wings of birds. Throughout Nature, ornament is perpetually the result of conditions, and arrangements fitted to use, and contrived for the discharge of function. But the same principle applies to human art, and few persons are probably aware how many of the mere ornaments of architecture are the traditional representation of parts which had their origin in essential structure. Yet Who would argue from this fact that ornament is not a special aim in the works of Man? When the savage carves the handle of his war-club, the immediate purpose of his carving is to give his own hand a firmer hold. But any shapeless scratches would be enough for this. When he carves it in an elaborate pattern, he does so for the love of ornament, and to satisfy the sense of beauty.

There is, however, another department of [204/205] natural phenomena which, much more than the one we have been now considering, does at first sight suggest to the mind the subordination of Purpose and the supremacy of Law. It is the department of Comparative Anatomy. It is a fact now well known and universally accepted, that in many animal structures, perhaps in all except one, there are parts the presence of which cannot be explained, from their serving any immediate use, or discharging any actual function. For example, the limbs of all the Mammalia, and even of all the Lizards, terminate in five jointed bones or fingers. But in many animals the whole five are not needed. but only some one, or two, or three. In such cases the remainder are indeed dwarfed, sometimes almost extinguished; but the curious fact is that rudimentally the whole number are always to be traced. Even in the Horse, where one only of the five is directly used, and where this one is enlarged and developed into a hoof, parts corresponding to the remaining four fingers can be detected in the anatomy of the limb. Other examples of the same principle might be given without number. Thus there are Monkeys which have no thumbs for [205/206] use, but only thumb-bones hid beneath the skin the wingless bird of New Zealand, the "Apteryx," has useless wing-bones similarly placed: snakes destined always to creep "upon their belly" have nevertheless rudiments of legs, and the common "Slowworm" has even the "blade bone" and "collar bone" of rudimentary or aborted limbs, the Narwhal has only one tusk, on the left side, developed for use, like the horn of an heraldic Unicorn, but the other tusk, on the right side, is present as a useless germ: the female Narwhal has both tusks reduced to the same unserviceable condition: young whalebone Whales are born with teeth which never cut the gum, and which are afterwards absorbed as entirely useless to the creature's life.

At first sight it may appear as if these were facts not to be reconciled with the supremacy of Purpose: — at first sight, but at first sight only. For as we look at them and wonder at them, and set ourselves to discover how many of alike nature can be found, our eye catches sight of an Order which had not been at first perceived. Exceptions to one narrow rule such as we might [206/207] have laid down and followed for ourselves, they are now seen to be in strict subordination to a larger rule which it would never have entered into our imagination to conceive. These useless members, these rudimentary or aborted limbs which puzzled us so much, are parts of an universal Plan. On this plan the bony skeletons of all living animals have been put together. The forces which, have been combined for the moulding of Organic Forms have been so combined as to mould them after certain types or patterns. And when Comparative Anatomy has revealed this fact as affecting all the animals of the existing world, another branch of the same science comes in to conform the generalisation, and extend it over the innumerable creatures which have existed and have passed away. This one Plan of Organic Life has never been departed from since Time began.

When we have grasped this great fact, all the lesser facts which are subordinate to it assume a new significance. In the first place a Plan of this kind is in itself a Purpose. An Order, so vast as this, including within itself such variety of detail, and maintained through such periods of Time, [207/208] implies combination and adjustment founded upon, and carrying into effect, one vast conception. It is only as an Order of Thought that the doctrine of Animal Homologies is intelligible at all. It is a Mental Order, and can only be mentally perceived. For what do we mean when we say that this bone in one kind of animal corresponds to such another bone in another kind of animal? Corresponds in what sense? Not in the method of using it for very often limbs which are homologically the same are put to the most diverse and opposite uses. To what standard, then, are we referring when we say that such and such two limbs are homologically the same? It is to the standard of an Ideal Order — a Plan — a Type — a Pattern mentally conceived. This sounds very recondite and metaphysical; and yet the habit of referring physical facts to some ideal standard and order of thought is a universal instinct in the human mind. It is one of the earliest of our efforts in endeavouring to understand the phenomena around us. The science of Homologies, as developed by Cuvier and Hunter and Owen and Huxley, is indeed an intricate, almost a transcendental science. Yet Dr [208/209] Livingstone found the natives of Africa debating a question which belongs essentially to that science, and involves the whole principle of the mental process by which it is pursued. The debate was on the question "whether the two toes of the Ostrich represent the thumb and forefinger in Man, or the little and ring-finger."3 This is purely a question of Comparative Anatomy. It is founded on the instinctive perception that even between two frames so widely separated as those of an Ostrich and a Man there is a common Plan of structure, with reference to which plan, parts wholly dissimilar in appearance and in use, can nevertheless be identified as "representative" of each other: — that is, as holding the same relative place in one Ideal Order of arrangement.

The recognition of this idea in minds so rude is not the less remarkable from the fact that both sides in this African debate were wrong in their practical application of the idea to the particular case before them. Unity of design amidst variety of form is so conspicuous and universal in the works of Nature that the perception of it could not [209/210] possibly escape recognition even by the rudest human mind, formed as that Mind is to see Order, and to work for it, and to admire it. But though instinct is enough to give us the general idea, and to trace it in a thousand instances where it can hardly be overlooked, yet it needs close and laborious study, and high powers of analysis and of thought, to trace correctly the true Order and Plan through the fine and subtle passages of Nature. It would have astonished those poor savages of Africa to be told, as is the truth, that if they wished to find in the Ostrich the parts corresponding to their own middle finger, or ring-finger, or any other finger, they must look not to the toes of the Ostrich but to her little aborted wings, which though useless for the purposes of flight are still retained as representing the wings of other Birds, and the forearms of all the Mammals.

For here we come upon the interchange and crossing as it were of two distinct ideas, which seem to stand the one as the warp and the other as the woof in the fabrics of Organic Life. There is the idea of Homology in Structure and the idea of Analogy in Use. The one represents [210/211] the Unity of Design, the other represents Variety of Function. It might have been supposed that these could not easily be reconciled — that where great differences in use and application are essential, rigid adherence to one pattern of structure would be an impediment in the way. But it is not so. The same bones in different animals are made subservient to the widest possible diversity of function. The same limbs are converted into paddles, and wings, and legs, and arms. And so it is with every other part of the skeleton and every other organ of the body. Indeed it is difficult to say whether the law of unity in design, or the law of variety in adaptation, is pushed to the greatest length. There are some cases in which the adaptation of form to special function is carried so far that all appearance of common structure is entirely lost. It is very difficult, for example, to persuade persons ignorant of the principles of anatomy that the Whale and the Porpoise are not Fish, that they breathe with lungs as Man breathes, that they would be drowned if kept long under water, and that as they suckle their young they belong to the same great Class, Mammalia. [211/212]

Living in the same element as fish, and feeding very much as fishes feed, a similar outward form has been given to them because that form is the best adapted for progression through the water. But that form has been, so to speak, pant on round the Mammalian skeleton, and covers all the organs proper to the Mammalian Class. Whales and Porpoises, notwithstanding their form, and their habitat, and their food, are as separate from Fishes as the Elephant, or the Hippopotamus, or the Giraffe.

And when we remember that the immense variety of Organic Forms in the existing world does not exhaust the adaptability of their Plan, but that the still vaster varieties of all the extinct creations have circled round the same central Types, it becomes evident that these Types have had from the first a Purpose which has been well and wonderfully fulfilled. As a matter of fact, we see that the original conception of the framework of Organic Life has included in itself provisions for applying the principle of adaptation in infinite degrees. Its last development is in Man. In His frame there is no aborted member. Every part is put to its highest use: — highest, [212/213] that is, in reference to the supremacy of Mind.4 There are stronger arms, there are swifter limbs, there are more powerful teeth, there are finer ears, there are sharper eyes. There are creatures which go where he cannot go, and can live where he would die. But all his members are co-ordinated with one power — the power of Thought. Through this he has the dominion over all other created things — whilst yet as regards the type and pattern of His frame he has not a single bone or joint or organ which he does not share with some one or other of the Beasts that perish. It is not in any of the parts of His structure, but in their combination and adjustment, that he stands alone.

All these facts must convince us that we must enlarge our ideas as to what is meant by Use in the economy of Nature. In the first place, it must be so interpreted as to include ornament; and in the second place, it must include also not merely Actual Use, but Potential Use, or the capacity of [213/214] being turned to use in new creations. In this point of view rudimentary or aborted organs need no longer puzzle us, for in respect to Purpose they may be read either in the light of History, or in the light of Prophecy. They may be regarded as indicating always either what had already been, or what was yet to be. Why new creations should never have been made wholly new; — why they should have been always moulded on some pre-existing Forms; — why one fundamental ground-plan should have been adhered to for all Vertebrate Animals, we cannot understand. But as a matter of fact it is so. For it appears that Creative Purpose has been effected through the instrumentality of Forces so combined as to arrange the particles of organic matter in definite forms: which forms include many separate parts having a constant relation to each other and to the whole, but capable of arrestment or development according as special organs are required for the discharge of special functions. Each new creation seems to have been a new application of these old materials. Each new House of Life has been built [214/215] on these old foundations. Among the many wonders of Nature there is nothing more wonderful than this — the adaptability of the one Vertebrate Type to the infinite variety of Life to which it serves as an organ and a home. Its basement has been so laid that every possible change or addition of superstructure could be built upon it. Creatures destined to live on the earth, or in the earth, on the sea, or in the sea, under every variety of condition of existence, have all been made after that one pattern; and each of them with as close an adaptation to special function as if the pattern had been designed for itself alone. It is true that there are particular parts of it which are of no use to particular animals. But there is no part of it which is not of indispensable use to some member of the group; and there is one Supreme Form in which all its elements receive their highest interpretation and fulfilment. It is indeed wonderful to think that the feeble and sprawling paddles of a Newt, the ungainly flippers of a Seal, and the long leathery wings of a Bat, have all the same elements, bone for bone, with that human hand [215/216] which is the supple instrument of Man's contrivance, and is alive, even to the finger-tips, with the power of expressing his Intellect and his Will. Here again the Laws of Nature are seen to be nothing but combinations of Force with a view to Purpose: combinations which indicate complete knowledge not only of what is, but of what is to be, and which foresees the End from the Beginning.

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Last modified 10 December 2008