with that concluding volume of Cuvier's great work in which he deals with the mollusca, articulata, and radiata; with, however, this difference, that the three great divisions, instead of occurring in a continnous series, are ranged, like the terrestrial herbs and trees, in parallel columns. The chain of animal being on its first appearance is, if I may so express myself, a threefold chain;—a fact nicely correspondent with the further fact, that we cannot in the present creation range serially, as either higher or lower in the scale, at least two of these divisions—the mollusca and articulata. In one of the higher beds of the Upper Silurian System—a bed which borders on the base of the Old Red Sandstone—the vertebrates make their earliest appearance in their fourth or ichthyic class; and we find ourselves in that volume of the geologic record which corresponds to Cuvier's volume on the fishes. In the many-folded pages of the Old Red Sandstone, till we reach the highest and last, there occur the remains of no other vertebrates than those of this fourth class; but in its uppermost deposits there appear traces of the third or reptilian class; and in passing upwards still, through the Carboniferous, Permian, and Triassic Systems, we find reptiles continuing the master existences of the time. The geologic volume in which these great formations are included corresponds to the Cuvierian one devoted to the Reptilia. Early in the Oolitic System, birds, Cuvier's second class of the vertebrata, make their first appearance, though their remains, like those of birds in the present time, are rare and infrequent; and, for at least the earlier periods of their existence, we know that they were—that they haunted for food the waters of the period, and waded in their shallows—only from marks similar to those by which Crusoe became first aware of the visits paid to his island by his savage neighbors—their footprints, left impressed on the sands over which they stalked of old. This early Oolitic volume corresponds in its contents to the section devoted by Cuvier, in his great work, to his second class, the birds. And in the Stonisfield slate—a deposit interposed between the "Inferior" and "Great Oolites," we detect the earliest indications of his first or mammaliferous class, apparently represented, however, by but one order—the Marsupiata, or pouched animals, to whose special place in the scale I shall afterwards have occasion to refer. Not until we reach the times of the Tertiary division do the mammals in their higher orders appear. The great Tertiary volume corresponds to those volumes of Cuvier which treat of the placental animals that suckle their young. And finally—last born of creation—man appears upon the scene, in his several races and varieties; the sublime arch of animal being at length receives its keystone; and the finished work stands up complete, from foundation to pinnacle, at once an admirably adjusted occupant of space, and a wonderful monument of Divine arrangement and classification, as it exists in time. Save at two special points, to which I shall afterwards advert, the particular arrangement unfolded by geologic history is exactly that which the greatest and most philosophic of the naturalists had, just previous to its discovery, originated and adopted as most conformable to nature: the arrangements of geologic history as exhibited in time, if, commencing at the earliest ages, we pursue it downwards, is exactly that of the "Animal Kingdom" of Cuvier read backwards.
Let us then, in grappling with the vast multiplicity of our subject, attempt reducing and simplifying it by means of the classifying principle; not simply, however—again to recur to the remark of the metaphysician—as an internal principle given us by nature, but as an external principle exemplified by nature. Let us take the organisms of the old geologic periods in the order in which they occur in time; secure, as has been shown, that if our chronology be correct, our classification will, as a consequence, be good. It will be for the natural theologians of the coming age to show the bearing of this wonderful fact on the progress of man towards the just and the solid, and on the being and character of man's Creator—to establish, on the one hand, against the undue depreciators of intellect and its results, that in certain departments of mind, such as that which deals with the arrangement and development of the scheme of organic being, human thought is not profitlessly revolving in an idle circle, but progressing Godwards, and gradually unlocking the order of creation. And, on the other hand, it will be equally his proper business to demand of the Pantheist how—seeing that only persons (such as the Cuviers and Lindleys) could have wrought out for themselves the real arrangement of this scheme—how, I say, or on what principle, it is to be held that it was a scheme originated and established at the beginning, not by a personal, but by an impersonal God. But our present business is with the fact of the parallel arrangements, Divine and human—not with the inferences legitimately deducible from it.
Fig. 5.
Fig. 6.
Beginning with the plants, let us, however, remark, that they do not precede in the order of their appearance the humbler animals. No more ancient organism than the Oldhamia of the Lowest Irish Silurians, a plant-like zoophyte somewhat resembling our modern sertularia, has yet been detected by the geologist; though only a few months ago the researches of Mr. Salter in the ancient rocks of the Longmynd, Shropshire, previously deemed unfossiliferous, have given, to it what seem to be contemporary vegetable organisms, in a few ill-preserved fucoids. So far as is yet known, plants and animals appear together. The long upward march of the animal kingdom takes its departure at its starting point from a thick forest of algæ. In Bohemia, in Norway, in Sweden, in the British Islands, in North America, wherever, in fine, what appears to be the lowest, or at least one of the lowest, zones of life has yet been detected, the rocks are found to be darkened by the remains of algæ, so abundantly developed in some cases, that they compose, as in the ancient Lower Silurians of Dumfriesshire, impure beds of anthracite several feet in thickness. Apparently, from the original looseness of their texture, the individual plants are but indifferently preserved; nor can we expect that organisms so ancient should exhibit any very close resemblance to the plants which darken the half-tide rocks and skerries of our coasts at the present time. We do detect, however, in some of these primordial fossils, at least a noticeable likeness to families familiar to the modern algæologist. The cord-like plant, Chorda filum, known to our children as "dead men's ropes," from its proving fatal at times to the too adventurous swimmer who gets entangled in its thick wreaths, had a Lower Silurian representative, known to the Palæontologist as the Palæochorda, or ancient chorda, which existed apparently in two species—a larger and smaller. The still better known Chondrus crispus, the Irish moss or carrageen of our cookery-books, has likewise its apparent though more distant representative in Chondritis, a Lower Silurian algæ, of which there seems to exist at least three species. The fucoids, or kelp weeds, appear to have had also their representatives in such plants as Fucoides gracilis of the Lower Silurians of the Malverns; in short, the Thallogens of the first ages of vegetable life seem to have resembled, in the group, and in at least their more prominent features, the algæ of the existing time. And with the first indications of land we pass direct from the Thallogens to the Acrogens—from the sea weeds to the fern allies. The Lycopodiaceæ;, or club mosses, bear in the axils of their leaves minute circular cases, which form the receptacles of their spore-like seeds. And when, high in the Upper Silurian System, and just when preparing to quit it for the Lower Old Red Sandstone, we detect our earliest terrestrial organisms, we find that they are composed exclusively of those little spore receptacles. The number of land plants gradually increases as we ascend into the overlying system. Still, however, the Flora of even the Old Red is but meagre and poor; and you will perhaps permit me to lighten this part of my subject, which threatens too palpably to partake of the poverty of that with which it deals, by a simple illustration.
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Fig. 7. |
Fig. 8. |
We stand, at low ebb, on the outer edge of one of those
