After dwelling at such length on the earlier fishes, it may seem scarce necessary to advert to their lower contemporaries the mollusca,—that great division of the animal kingdom which Cuvier places second in the descending order, in his survey of the entire series, and first among the invertebrates; and which Oken regards as the division out of which the immediately preceding class of the vertebral animals have been developed. “The fish,” he says, “is to be viewed as a mussel, from between whose shells a monstrous abdomen has grown out.” There is, however, a peculiarity in the molluscan group of the Silurian system, to which I must be permitted briefly to refer, as, to employ the figure of Sterne, it presents “two handles” of an essentially different kind, and as in all such two-handled cases, the mere special pleader is sure to avail himself of only the handle which best suits his purpose for the time.

Cuvier’s first and highest class of the molluscs is formed of what are termed the Cephalopods,—a class of creatures possessed of great freedom of motion: they can walk, swim, and seize their prey; they have what even the lowest fishes such as the lancelet, want,—a brain enclosed in a cartilaginous cavity in the head, and perfectly formed organs of sight; they possess, too, what is found in no other mollusc,—organs of hearing; and in sagacity and activity they prove more than matches for the smaller fishes, many of which they overmaster and devour. With this highest class there contrasts an exceedingly low molluscous class at the bottom of the scale, or, at least, at what is now the bottom of the scale; for they constitute Cuvier’s fifth class; while his sixth and last, the Cirrhopodes, has been since withdrawn from the molluscs altogether, and placed in a different division of the animal kingdom. And this low class, the Brachiopods, are creatures that, living in bivalve shells, unfurnished with spring hinges to throw them open, and always fast anchored to the same spot, can but thrust forth, through the interstitial chinks of their prison-houses, spiral arms, covered with cilia, and winnow the water for a living. Now, it so happens that the molluscan group of the Silurian system is composed chiefly of these two extreme classes. It contains some of the other forms; but they are few in number, and give no character to the rocks in which they occur. There was nothing by which I was more impressed, in a visit to a Silurian region, than that in its ancient graveyards, as in those of the present day, though in a different sense, the high and the low should so invariably meet together. It is, however, not impossible that, in even the present state of things, a similar union of the extreme forms of the marine mollusca may be taking place in deep-sea deposits. Most of the intermediate forms provided with shells capable of preservation, such as the shelled Gasteropoda and the Conchifers, are either littoral, or restricted to comparatively small depths; whereas the Brachiopoda are deep-sea shells; and the Cephalopoda may be found voyaging far from land, in the upper strata of the sea above them. Even in the seas that surround our own island, the Brachiopodous molluscs—terebratula and crania—have been found, ever since deep-sea dredging became common, to be not very rare shells; and in the Mediterranean, where they are less rare still, fleets of Argonauts, the representatives of a highly organized family of the Cephalopods, to which it is now believed the Bellerophon of the Palæozoic rocks belonged, may be seen skimming along the surface, with sail and oar, high over the profound depths in which they lie. And, of course, when death comes, that comes to high and low, the remains of both Argonauts and Brachiopods must lie together at the bottom, in beds almost totally devoid of the intermediate forms.

Now, the author of the “Vestiges,” in maintaining his hypothesis, suspends it on the handle furnished him by the immense abundance of the Silurian Brachiopods. The Silurian period, he says, exhibits “a scanty and most defective development of life; so much so, that Mr. Lyell calls it, par excellence, the age of Brachiopods, with reference to the by no means exalted bivalve shell-fish which forms its predominant class. Such being the actual state of the case, I must persist in describing even the fauna of this age, which we now know was not the first, as, generally speaking, such a humble exhibition of the animal kingdom as we might expect, upon the development theory, to find at an early stage of the history of organization.” The reader will at once discern the fallacy here. The Silurian period was peculiarly an age of Brachiopods, for in no other period were Brachiopods so numerous, specifically or individually, or of such size or importance; whereas it was not so peculiarly an age of Cephalopods, for these we find introduced in still greater numbers during the Liasic and Oolitic periods. In 1848, when Professor Edward Forbes edited the Palæontological map of Britain and Ireland, which forms one of the very admirable series of “Johnstone’s Physical Atlas,” the Cephalopods of the Silurian rocks of England and Wales were estimated at forty-eight species, and the Brachiopods at one hundred and fifty; whereas at the same date there were two hundred and five Cephalopods of the Oolitic formations enumerated, and but fifty-four Brachiopods. It is the molluscs of the inferior, not those of the superior class, that constitute (with their contemporaries the Trilobites) the characteristic fossils of the Silurian rocks; and hence the propriety of the distinctive name suggested by Sir Charles Lyell. But in the development question, what we have specially to consider is, not the numbers of the low, but the standing of the high. A country may be distinctively a country of flocks and herds, or a country of the carnivorous mammalia, or, like New South Wales or the Galapagos, a country of marsupial animals or of reptiles. Its human inhabitants may be merely a few hunters or shepherds, too inconsiderable in numbers, and too much like their brethren elsewhere, to give it any peculiar standing as a home of men. But in estimating the highest point in the scale to which the animal kingdom has attained within its limits, it is of its few men, not of its many beasts, that we must take note. And the point to be specially decided regarding the organisms of the Silurian system, in this question, is, not the proportion in number which the lower forms bore to the higher, but the exact rank which the higher bore in the scale of existence. Did the system furnish but a single Cephalopod or a single fish, we would yet have as certainly to determine that the chain of being reached as high as the Cephalopod or the fish, as if the remains of these creatures constituted its most abundant fossils. The chain of animal life reached quite as high on the evening of the sixth day of creation, when the human family was restricted to a single pair, as it does now, when our statists reckon up by millions the inhabitants of the greater capitals of the world; and the special pleader who, in asserting the contrary, would insist on determining the point, not by the rank of the men of Eden, but by the number of minnows or sticklebacks that swarmed in its rivers, might be perhaps deemed ingenious in his expedients, but certainly not very judicious in the use of them. It is worthy of remark, however, that the Brachiopods of those Palæozoic periods in which the group occupied such large space in creation, consisted of greatly larger and more important animals than any which it contains in the present day. It has yielded to what geological history shows to be the common fate, and sunk into a state of degradation and decline.

The geological history of the vegetable, like that of the animal kingdom, has been pressed into the service of the development hypothesis; and certainly their respective courses, both in actual arrangement and in their relation to human knowledge, seem wonderfully alike. It is not much more than twenty years since it was held that no exogenous plant existed during the Carboniferous period. The frequent occurrence of Coniferæ in the Secondary deposits had been conclusively determined from numerous specimens; but, founding on what seemed a large amount of negative evidence, it was concluded that, previous to the Liasic age, nature had failed to achieve a tree, and that the rich vegetation of the Coal Measures had been exclusively composed of magnificent immaturities of the vegetable kingdom,—of gigantic ferns and club-mosses, that attained to the size of forest trees, and of thickets of the swamp-loving horsetail family of plants, that well nigh rivalled in height those forests of masts which darken the rivers of our great commercial cities. Such was the view promulgated by M. Adolphe Brongniart; and it may be well to remark that, so far as the evidence on which it was based was positive, the view was sound. It is a fact, that inferior orders of plants were developed in those ages in a style which, in their present state of degradation, they never exemplify: they took their place, not, as now, among the pigmies and abortions of creation, but among its tallest and goodliest productions. It is, however, not a fact that they were the highest vegetable forms of their time. True exogenous trees also existed in great numbers and of vast size. In various localities in the coal fields of both England and Scotland,—such as Lennel Braes and Allan Bank in Berwickshire, High-Heworth, Fellon, Gateshead, and Wideopen near Newcastle-upon-Tyne, and in quarries to the west of the city of Durham,—the most abundant fossils of the system are its true woods. In the quarry of Craigleith, near Edinburgh, three huge trunks have been laid open during the last twenty years, within the space of about a hundred and fifty yards, and two equally massy trunks, within half that space, in the neighboring quarry of Granton, all low in the Coal Measures. They lie diagonally athwart the strata,—at an angle of about thirty,—with the nether and weightier portion of their boles below, like snags in the Mississippi; and we infer, from their general direction, that the stream to which they reclined must have flowed from nearly north-east to south-west. The current was probably that of a noble river, which reflected on its broad bosom the shadow of many a stately tree. With the exception of one of the Granton specimens, which still retains its strong-kneed roots, they are all mere portions of trees, rounded at both ends as if by attrition or decay; and yet one of these portions measures about six feet in diameter by sixty-one feet in length; another four feet in diameter by seventy feet in length; and the others, of various thickness, but all bulky enough to equal the masts of large vessels, range in length from thirty-six to forty-seven feet. It seems strange to one who derives his supply of domestic fuel from the Dalkeith and Falkirk coal-fields, that the Carboniferous flora could ever have been described as devoid of trees. I can scarce take up a piece of coal from beside my study fire, without detecting in it fragments of carbonized wood, which almost always exhibit the characteristic longitudinal fibres, and not unfrequently the medullary rays. Even the trap-rocks of the district enclose, in some instances, their masses of lignite, which present in their transverse sections, when cut by the lapidary, the net-like reticulations of the coniferæ. The fossil botanist, who devoted himself chiefly to the study of microscopic structure, would have to decide, from the facts of the case, not that trees were absent during the Carboniferous period, but that, in consequence of their having been present in amazing numbers, their remains had entered more palpably and extensively into the composition of coal than those of any other vegetable.[32] So far as is yet known, they all belonged to the two great divisions of the coniferous family, araucarians and pines. The huge trees of Craigleith and Granton were of the former tribe, and approximate more nearly to Altingia excelsa, the Norfolk-Island pine,—a noble araucarian, that rears its proud head from a hundred and sixty to two hundred feet over the soil, and exhibits a green and luxuriant breadth of foliage rare among the Coniferæ,—than any other living tree.

Beyond the Coal Measures terrestrial plants become extremely rare. The fossil botanist, on taking leave of the lower Carboniferous beds, quits the land, and sets out to sea; and it seems in no way surprising, that the specimens which he there adds to his herbarium should consist mainly of Fucaceæ and Conferveæ. The development hypothesis can borrow no support from the simple fact, that while a high terrestrial vegetation grows upon dry land, only algæ grow in the sea; and even did the Old Red Sandstone and Silurian systems furnish, as their vegetable organisms, fucoids exclusively, the evidence would amount to no more than simply this, that the land of the Palæozoic periods produced plants of the land, and the sea of the Palæozoic periods produced plants of the sea.

In the Upper Old Red Sandstone,—the formation of the Holoptychius and the Stagonolepis,—the only vegetable remains which I have yet seen are of a character so exceedingly obscure and doubtful, that all I could venture to premise regarding them is, that they seem to be the fragments of sorely comminuted fucoids. In the formation of the Middle Old Red,—that of the Cephalaspis and the gigantic lobster of Carmylie,—the vegetable remains are at once more numerous and better defined. I have detected among the gray micaceous sandstones of Forfarshire a fucoid furnished with a thick, squat stem, that branches into numerous divergent leaflets or fronds, of a slim parallelogrammical, grass-like form, and which, as a whole, somewhat resembles the scourge of cords attached to a handle with which a boy whips his top. And Professor Fleming describes a still more remarkable vegetable organism of the same formation, “which, occurring in the form of circular, flat patches, composed each of numerous smaller contiguous circular pieces, is altogether not unlike what might be expected to result from a compressed berry, such as the bramble or rasp.” In the Lower Old Red,—the formation of the Coccosteus and Cheiracanthus,—the remains of fucoids are more numerous still. There are gray slaty beds among the rocks of Navity, that owe their fissile character mainly to their layers of carbonized weed; and “among the rocks of Sandy-Bay, near Thurso,” says Mr. Dick, “the dark impressions of large fucoids are so numerous, that they remind one of the interlaced boughs and less bulky pine-trunks that lie deep in our mosses.” A portion of a stem from the last locality, which I owe to Mr. Dick, measures three inches in diameter; but the ill-compacted cellular tissue of the algæ is but indifferently suited for preservation; and so it exists as a mere coaly film, scarcely half a line in thickness.

The most considerable collection of the Lower Old Red fucoids which I have yet seen is that of the Rev. Charles Clouston of Sandwick, in Orkney,—a skilful cultivator of geological science, who has specially directed his palæontological inquiries on the vegetable remains of the flagstones of his district, as the department in which most remained to be done; but his numerous specimens only serve to show what a poverty-stricken flora that of the ocean of the Lower Old Red Sandstone must have been. I could detect among them but two species of plants;—the one an imperfectly preserved vegetable, more nearly resembling a club-moss than aught else which I have seen, but which bore on its surface, instead of the well-marked scales of the Lycopodiaceæ, irregular rows of tubercles, that, when elongated in the profile, as sometimes happens, might be mistaken for minute, ill-defined leaves; the other, a smooth-stemmed fucoid, existing on the stone in most cases as a mere film, in which, however, thickly-set longitudinal fibres are occasionally traceable, and which may be always distinguished from the other by its sharp-edged outline, and from the circumstance that its stems continue to retain the same diameter for considerable distances, after throwing off at acute angles numerous branches nearly as bulky as themselves. In a Thurso specimen, about two feet in length, which I owe to the kindness of Mr. Dick, there are stems continuous throughout, that, though they ramify in that space into from six to eight branches, are nearly as thick atop as at bottom. They are the remains, in all probability, of a long, flexible weed, that may have somewhat resembled those fucoids of the intertropical seas, which, streaming slantwise in the tide, rise not unfrequently to the surface in from fifteen to twenty fathoms of water; and as, notwithstanding their obscurity, they are among the most perfect specimens of their class yet found, and contrast with the stately araucarians of the Coal Measures, in a style which cannot fail to delight the heart of every assertor of the development hypothesis, I present them to the reader from Mr. Dick’s specimen, in a figure (fig. 54) which, however slight its interest, has at least the merit of being true. The stone exhibits specimens of the two species of Mr. Clouston’s collection,—the sharp-edged, finely-striated weed, a, and that roughened by tubercles, b; which, besides the distinctive character manifested on its surface, differs from the other in rapidly losing breath with every branch which it throws off, and, in consequence, runs soon to a point. The cut on the opposite page (fig. 55) represents not inadequately the cortical peculiarities of the two species when best preserved. The surface of the tubercled one will perhaps remind the Algologist of the knobbed surface of the thong or receptacle of Himanthalia lorea, a recent fucoid, common on the western coast of Scotland, but rare on the east. An Orkney specimen lately sent me by Mr. William Watt, from a quarry at Skaill, has much the appearance of one of the smaller ferns, such as the moor-worts, sea spleen-worts, or maiden-hairs. It exists as an impression in diluted black, on a ground of dark gray, and has so little sharpness of outline, that, like minute figures in oil-paintings, it seems more distinct when viewed at arm’s length than when microscopically examined; but enough remains to show that it must have been a terrestrial, not a marine plant. The accompanying print (fig. 56) may be regarded as no unfaithful representation of this unique fossil its state of imperfect keeping. The vegetation of the Silurian system, from its upper beds down till where we reach the zero of life, is, like that of the Old Red Sandstone, almost exclusively fucoidal. In the older fossiliferous deposits of the system in Sweden, Russia, the Lake Districts of England, Canada, and the United States, fucoids occur, to the exclusion, so far as is yet known, of every other vegetable form; and such is their abundance in some localities, that they render the argillaceous rocks in which they lie diffused, capable of being fired as an alum slate, and exist in others as seams of a compact anthracite, occasionally used as fuel. They also occur in those districts of Wales in which the place and sequence of the various Silurian formations were first determined, though apparently in a state of keeping from which little can be premised regarding their original forms. Sir Roderick Murchison sums up his notice of the vegetable remains of the system in the province whence it derives its name, by stating that he had submitted his specimens to “Mr. Robert Brown and Dr. Greville, and that neither of these eminent botanists were able to say much more regarding them than that they were fucoid-like bodies.”

Such are the vegetable organisms of the Old Red Sandstone and Silurian systems: they are the remains of the ancient marine plants of ancient marine deposits and, as such, lend quite as little support to the development hypothesis as the recent algæ of our existing seas. The case, stated in its most favorable form, amounts simply to this,—that at certain early periods,—represented by the Upper and Lower Silurian and the Old Red deposits,—the seas produced sea-plants; and that, at a certain later period,—that of the Carboniferous system,—the land produced land-plants. But even this, did it stand alone, would be a too favorable statement. I have seen, on one occasion, the fisherman bring up with his nets, far in the open sea, a wild rose-bush, that, though it still bore its characteristic thorns, was encrusted with serpula, and laden with pendulous lobularia. It had been swept from its original habitat by some river in flood, that had undermined and torn down the bank on which it grew; and after floating about, mayhap for months, had become so saturated with water, that it could float no longer. And in that single rose-bush, dragged up to the light and air from its place among Sertularia, Flustra, Serpula, and the deep-sea fucoids, I had as certain an evidence of the existence of the dicotyledonous plant, as if I had all the families of the Rosaecæ before me. Now, we are furnished by the more ancient formations with evidence regarding the existence of a terrestrial vegetation, such as that which the rose-bush in this case supplied. We cannot expect that the proofs should be numerous. In the chart of the Pacific attached to the better editions of “Cook’s Voyages,” there are several notes along the tract of the great navigator, that indicate where, in mid ocean, trees or fragments of trees had been picked up. These entries, however, are but few, though they belong to all the three voyages together: if I remember aright, there are only five entries in all,—two in the Northern, and three in the Southern Pacific. The floating shrub or tree, at a great distance from land, is of rare occurrence in even the present scene of things, though the breadth of land be great, and trees numerous; and in the times of the Silurian and Old Red Sandstone systems, when the breadth of land was apparently not great, and trees and shrubs, in consequence, not numerous, it must have been of rarer occurrence still. We learn, however, from Sir Charles Lyell, that in the “Hamilton group of the United States,—a series of beds that corresponds in many of its fossils with the Ludlow rocks of England,—plants allied to the Lepidodendra of the Carboniferous type are abundant; and that in the lower Devonian strata of New York the same plants occur associated with ferns.” And I am able to demonstrate, from an interesting fossil at present before me, that there existed in the period of the Lower Old Red Sandstone vegetable forms of a class greatly higher than either Lepidodendra or ferns.

In my little work on the Old Red Sandstone, I have referred to an apparent lignite of the Lower Old Red of Cromarty, which presented, when viewed by the microscope, marks of the internal fibre. The surface, when under the glass, resembled, I said, a bundle of horse-hairs lying stretched in parallel lines: and in this specimen alone, it was added, had I found aught in the Lower Old Red Sandstone approaching to proof of the existence of dry land. About four years ago I had this lignite put stringently to the question by Mr. Sanderson, and deeply interesting was the result. I must first mention, however, that there cannot rest the shadow of a doubt regarding the place of the organism in the geologic scale. It is unequivocally a fossil of the Lower Old Red Sandstone. I found it partially embedded, with many other nodules half-disinterred by the sea, in an ichthyolitic deposit, a few hundred yards to the east of the town of Cromarty, which occurs more than four hundred feet over the Great Conglomerate base of the system. A nodule that lay immediately beside it contained a well-preserved specimen of the Coccosteus Decipiens; and in the nodule in which the lignite itself is contained, (fig. 57,) the practised eye may detect a scattered group of scales of Diplacanthus, a scarce less characteristic organism of the lower formation. And what, asks the reader, is the character of this very ancient vegetable,—the most ancient, by three whole formations, that has presented its internal structure to the microscope? Is it as low in the scale of development as in the geological scale? Does this venerable Adam of the forest appear, like the Adam of the infidel, as a squalid, ill-formed savage, with a rugged shaggy nature, which it would require the suggestive necessities of many ages painfully to lick into civilization? Or does it appear rather like the Adam of the poet and the theologian, independent, in its instantaneously-derived perfection, of all after development?

Is its tissue vascular or cellular, or, like that of some of the cryptogamia, intermediate? Or what, in fine, is the nature and bearing of its mute but emphatic testimony, on that doctrine of progressive development of late so strangely resuscitated?

In the first place, then, this ancient fossil is a true wood,—a Dicotyledonous or Polycotyledonous Gymnosperm, that, like the pines and larches of our existing forests, bore naked seeds, which, in their state of germination, developed either double lobes to shelter the embryo within, or shot out a fringe of verticillate spikes, which performed the same protective functions, and that, as it increased in bulk year after year, received its accessions of growth in outside layers. In the transverse section the cells bear the reticulated appearance which distinguish the coniferæ, (fig. 58, a;) the lignite had been exposed in its bed to a considerable degree of pressure; and so the openings somewhat resemble the meshes of a net that has been drawn a little awry; but no general obliteration of their original character has taken place, save in minute patches, where they have been injured by compression or the bituminizing process. All the tubes indicated by the openings are, as in recent coniferæ, of nearly the same size; and though, as in many of the more ancient lignites, there are no indications of annual rings, the direction of the medullary rays is distinctly traceable. The longitudinal sections are rather less distinct than the transverse one; in the section parallel to the radius of the stem or bole the circular disks of the coniferæ were at first not at all detected; and, as since shown by a very fine microscope, they appear simply as double and triple lines of undefined dots, (b,) that somewhat resemble the stippled markings of the miniature painter; nor are the openings of the medullary rays frequent in the tangental section (i. e. that parallel to the bark,) (c;) but nothing can be better defined than the peculiar arrangement of the woody fibre, and the longitudinal form of the cells. Such is the character of this, the most ancient of lignites yet found, that yields to the microscope the peculiarities of its original structure. We find in it an unfallen Adam,—not a half-developed savage.[33]

The olive leaf which the dove brought to Noah established at least three important facts, and indicated a few more. It showed most conclusively that there was dry land, that there were olive trees, and that the climate of the surrounding region, whatever change it might have undergone, was still favorable to the development of vegetable life. And, further, it might be very safely inferred from it, that if olive trees had survived, other trees and plants must have survived also; and that the dark muddy prominences round which the ebbing currents were fast sweeping to lower levels, would soon present, as in antediluvian times, their coverings of cheerful green. The olive leaf spoke not of merely a partial, but of a general vegetation. Now, the coniferous lignite of the Lower Old Red Sandstone we find charged, like the olive leaf, with a various and singularly interesting evidence. It is something to know, that in the times of the Coccosteus and Asterolepis there existed dry land, and that that land wore, as at after periods, its soft, gay mantle of green. It is something also to know, that the verdant tint was not owing to a profuse development of the mere immaturities of the vegetable kingdom,—crisp, slow-growing lichens, or watery spore-propagated fungi that shoot up to their full size in a night,—nor even to an abundance of the more highly organized families of the liverworts and the mosses. These may have abounded then, as now; though we have not a shadow of evidence that they did. But while we have no proof whatever of their existence, we have conclusive proof that there existed orders and families of a rank far above them. On the dry land of the Lower Old Red Sandstone, on which, according to the theory of Adolphe Brogniart, nothing higher than a lichen or a moss could have been expected, the ship-carpenter might have hopefully taken axe in hand, to explore the woods for some such stately pine as the one described by Milton,—

Viewed simply in its picturesque aspect, this olive leaf of the Old Red seems not at all devoid of poetry. We sail upwards into the high geologic zones, passing from ancient to still more ancient scenes of being; and, as we voyage along, find ever in the surrounding prospect, as in the existing scene from which we set out, a graceful intermixture of land and water, continent, river, and sea. We first coast along the land of the Tertiary, inhabited by the strange quadrupeds of Cuvier, and waving with the reeds and palms of the Paris Basin; the land of the Wealden, with its gigantic iguanodon rustling amid its tree ferns and its cycadeæ, comes next; then comes the green land of the Oolite, with its little pouched insectivorous quadruped, its flying reptiles, its vast jungles of the Brora equisetum, and its forests of the Helmsdale pine; and then, dimly as through a haze, we mark, as we speed on, the thinly scattered islands of the New Red Sandstone, and pick up in our course a large floating leaf, veined like that of a cabbage, which not a little puzzles the botanists of the expedition. And now we near the vast Carboniferous continent, and see along the undulating outline, between us and the sky, the strange forms of a vegetation, compared with which that of every previously seen land seems stunted and poor. We speed day after day along endless forests, in which gigantic club-mosses wave in air a hundred feet over head, and skirt interminable marshes, in which thickets of reeds overtop the mast-head. And, where mighty rivers come rolling to the sea, we mark, through the long-retiring vistas which they open into the interior, the higher grounds of the country covered with coniferous trees, and see doddered trunks of vast size, like those of Granton and Craigleith, reclining under the banks in deep muddy reaches, with their decaying tops turned adown the current. At length the furthermost promontory of this long range of coast comes full in view: we near it,—we have come up abreast of it: we see the shells of the Mountain Limestone glittering white along its further shore, and the green depths under our keel lightened by the flush of innumerable corals; and then, bidding farewell to the land forever,—for so the geologists of but five years ago would have advised,—we launch into the unmeasured ocean of the Old Red, with its three consecutive zones of animal life. Not a single patch of land more do those geologic charts exhibit which we still regard as new. The zones of the Silurian and Cambrian succeed the zones of the Old Red; and, darkly fringed by an obscure bank of cloud ranged along the last zone in the series, a night that never dissipates settles down upon the deep. Our voyage, like that of the old fabulous navigators of five centuries ago, terminates on the sea in a thick darkness, beyond which there lies no shore and there dawns no light. And it is in the middle of this vast ocean, just where the last zone of the Old Red leans against the first zone of the Silurian, that we have succeeded in discovering a solitary island unseen before,—a shrub-bearing land, much enveloped in fog, but with hills that at least look green in the distance. There are patches of floating sea-weed much comminuted by the surf all around it; and on one projecting headland we see clear through our glasses a cone-bearing tree.

This certainly is not the sort of arrangement demanded by the exigencies of the development hypothesis. A true wood at the base of the Old Red Sandstone, or a true Placoid in the Limestones of Bala, very considerably beneath the base of the Lower Silurian system, are untoward misplacements for the purposes of the Lamarckian; and who that has watched the progress of discovery for the last twenty years, and seen the place of the earliest ichthyolite transferred from the Carboniferous to the Cambrian system, and that of the earliest exogenous lignite from the Lias to the Lower Devonian, will now venture to say that fossil wood may not yet be detected as low in the scale as any vegetable organism whatever, or fossil fish as low as the remains of any animal? But though the response of the earlier geologic systems be thus unfavorable to the development hypothesis, may not men such as the author of the “Vestiges” urge, that the geologic evidence, taken as a whole, and in its bearing on groupes and periods, establishes the general fact that the lower plants and animals preceded the higher,—that the conifera, for instance, preceded our true forest trees, such as the oak and elm,—that, in like manner, the fish preceded the reptile, that the reptile preceded the bird, that the bird preceded the mammiferous quadruped and the quadrumana, and that the mammiferous quadruped and the quadrumana preceded man? Assuredly yes! They may and do urge that Geology furnishes evidence of such a succession of existences; and the arrangement seems at once a very wonderful and very beautiful one. Of that great and imposing procession of being of which this world has been the scene, the programme has been admirably marshalled. But the order of the arrangement in no degree justifies the inference based upon it by the Lamarckian. The fact that fishes and reptiles were created on an earlier day than the beasts of the field and the human family, gives no ground whatever for the belief that “the peopling of the earth was one of a natural kind, requiring time,” or that the reptiles and fishes have been not only the predecessors, but also the progenitors of the beasts and of man. The geological phenomena, even had the author of the “Vestiges” been consulted in their arrangement, and permitted to determine their sequence, would yet have failed to furnish, not merely an adequate foundation for the development hypothesis, but even the slightest presumption in its favor. In making good the assertion, may I ask the reader to follow me through the details of a simple though somewhat lengthened illustration?