SCALE OF ANIMAL KINGDOM. ORDER OF ANIMALS IN ASCENDING SERIES FOETAL HUMAN BRAIN
OF ROCKS. RESEMBLES, IN
Invertebrata.
1 Infusoria Traces of Infusoria(?) 1 Gneiss and Mica\
Slate System \
2 Polypi Polypiaria \ \
5 Echinodermata Echinodermata \ \
{ 7 Brachiopoda {15-20 Brachiopoda} Crustacea } 2 Clay Slate System \ 1st month, typically,
Moll-{ 9 Pteropoda Artic-{Crustacea Pteropoda } / } that of an
usca {10 Gasteropoda ulata {12-14 Gasteropoda} Annelides / / avertebrated animal
{11 Cephalopoda {Annelides Cephalopoda} \ /
} 3 Silurian system /
Vertebrata. { Remains of Fishes / /
{ Fishes of low type; \ \
32-36 Fishes { heterocercal; allied } 4 Old Red Sandstone } 2nd month, that of a fish;
{ to crustacea / /
{ Sauroid Fishes \
37 Batrachia (frogs, &c.) Batrachia \
} 5 Carboniferous
39 Sauria (lizards, &c.) Sauria / formation
40 Chelonia (tortoises) Chelonia / 3rd month, that of a turtle;
41-46 Birds Footsteps of Birds 6 New Red Sandstone 4th month, that of a bird;
47 Cetacea (dolphins, whales, &c.) Bones of a \
Cetaceous Animal } 7 Oolite
Bones of a Marsupial /
8 Chalk
48 Pachydermata (tapirs, &c.) Pachydermata \
49 Edentata (sloths) Edentata \
50 Rodentia (squirrels, hare, &c.) Rodentia \ 5th month, that of a rodent;
51 Marsupialia (opossums, &c.) Marsupialia \
52 Ruminantia (oxen, stag, &c.) Ruminantia \ 6th month, that of a ruminant;
53 Amphibia (seals) } 9 Tertiary
54 Digitigrada (dog, cat, &c.) Digitigrada / 7th month, that of a digitigrade animal;
55 Plantigrada (bear, &c.) Plantigrada /
56 Insectivora (shrew, &c.) Insectivora /
57 Cheiroptera (bats) Cheiroptera /
58 Quadrumana (apes) Quadrumana / 8th month, that of the quadrumana;
29 Bimana (man) Bimana 10 Superficial deposits 9th month, attains full human character.
TRANSMUTATION OF SPECIES.
In the two last sections we have gone through the earth's geological history, first of the changes in its physical structure, next of the mutations in the organic forms that have, in serial order, appeared in the successive strata of its external envelope, from the period of that far distant crisis when it was a molten globe on which its primitive granitic covering was just beginning to concrete, in consequence of abating heat, until we have arrived at the first prognostic signs of approaching human existence.
The rock upon rock of vast thickness, by which the earth's crust, through countless ages, has been formed, unquestionably constitutes a most extraordinary phenomenon of physical creation, but hardly so marvellous and incomprehensible as the beginning, progress, and end of the divers orders of marine and terrestrial beings that filled each world of life. It is to geologists, to PLAYFAIR, HUTTON, LYELL, BUCKLAND, SEDGWICK, OWEN, and other great names, native and foreign, to whom we are indebted for this singular revelation of Nature's works. It is their unwearied research that has opened to us the surprising spectacle we have attempted briefly to describe of the diversified groups of species which have, in the course of the earth's history, succeeded each other at vast intervals of time; one set of animals and plants wholly or partly disappearing from the face of our planet, and others, which apparently did not before exist, becoming the only or predominant occupants of the globe.
Now the great question arises—whence, by what power, or by what law, were these reiterated transitions brought about? Were the organized species of one geological epoch, by some long-continued agency of natural causes, transmuted into other and succeeding species? or were there an extinction of species, and a replacement of them by others, through special and miraculous acts of creation? or, lastly, did species gradually degenerate and die out from the influence of the altered and unfavourable physical conditions in which they were placed, and be supplanted by immigrants of different species, and to which the new conditions were more congenial?
The last, we confess, is the view to which we are most inclined—first, because we think a transmutation of species, from a lower to a higher type, has not been satisfactorily proved; and second, because of the strong impression we entertain, that the universe, subject to certain cyclical and determinate mutations, was made complete at first, with self-subsisting provisions for its perpetual renewal and conservation. We shall advert to this matter hereafter; but at present it is the conclusions of the author of the Vestiges that claim consideration. He adopts the first interpretation of animal phenomena, namely, that there has been a transmutation of species, that the scale of creation has been gradually advancing in virtue of an inherent and organic law of development. Nature, he contends, began humbly; her first works were of simple form, which were gradually meliorated by circumstances favourable to improvement, and that everywhere animals and plants exhibit traces of a parallel advance of the physical conditions and the organic structure. The general principle, he inculcates, is, that each animal of a higher kind, in the progress of its embryo state, passes through states which are the final condition of the lower kind; that the higher kinds of animals came later, and were developed from the lower kinds, which came earlier in the series of rock formations, by new peculiar conditions operating upon the embryo, and carrying it to a higher stage. These conclusions the author maintains geology has established, and of the results thence derived he gives the subjoined recapitulation:—
"In pursuing the progress of the development of both plants and animals upon the globe, we have seen an advance in both cases, from simple to higher forms of organization. In the botanical department we have first sea, afterwards land plants; and amongst these the simpler (cellular and cryptogamic) before the more complex. In the department of zoology, we see, first, traces all but certain of infusoria [shelled animalculæ]; then polypiaria, crinoidea, and some humble forms of the articulata and mollusca; afterwards higher forms of the mollusca; and it appears that these existed for ages before there were any higher types of being. The first step forward gives fishes, the humblest class of the vertebrata; and, moreover, the earliest fishes partake of the character of the lower sub-kingdom, the articulata. Afterwards come land animals, of which the first are reptiles, universally allowed to be the type next in advance from fishes, and to be connected with these by the links of an insensible gradation. From reptiles we advance to birds, and thence to mammalia, which are commenced by marsupialia, acknowledgedly low forms in their class. That there is thus a progress of some kind, the most superficial glance at the geological history is sufficient to convince us."
Now this appears plausible and conclusive, but the correctness of the recapitulation here made, and its conformity to actual nature, have been sharply disputed. It may be true that sea plants came first, but of this there is no proof; and of land plants there is not a shadow of evidence that the simpler forms came into being before the more complex: the simple and complex forms are found together in the more ancient flora. It is true that we first see polypiaria, crinoidea, articulata, and mollusca, but not exactly in the order stated by the author. It is true that the next step gives us fishes, but it is not true that the earliest fishes link on to the lower sub-kingdom, the articulata. It is true that we afterwards find reptiles, but those which first appear belong to the highest order of the class, and show no links of an insensible gradation into fishes. In the tertiary deposit of the London clay the evidence of concatenation entirely fails. Among the millions of organic forms, from corals up to mammalia of the London and Paris basins, hardly a single secondary species is found. In the south of France it is said that two or three secondary species struggle into the tertiary strata; but they form a rare and evanescent exception to the general rule. Organic nature at this stage seems formed on a new pattern—plants as well as animals are changed. It might seem as if we had been transported to a new planet; for neither in the arrangement of the genera and the species, nor in their affinities with the types of a pre-existing world, is there any approach to a connected chain of organic development.
For some discrepancies the author endeavours to account, and it is fair to give his explanation:—
"Fossil history has no doubt still some obscure passages; and these have been partially adverted to. Fuci, the earliest vegetable fossils as yet detected, are not, it has been remarked, the lowest forms of aquatic vegetation; neither are the plants of the coal-measures the very lowest, though they are a low form, of land vegetation. There is here in reality no difficulty of the least importance. The humblest forms of marine and land vegetation are of a consistence to forbid all expectation of their being preserved in rocks. Had we possessed, contemporaneously with the fuci of the Silurians, or the ferns of the carboniferous formation, fossils of higher forms respectively, equally unsubstantial, but which had survived all contingencies, then the absence of mean forms of similar consistency might have been a stumbling-block in our course; but no such phenomena are presented. The blanks in the series are therefore no more than blanks; and when a candid mind further considers that the botanical fossils actually present are all in the order of their organic development, the whole phenomena appear exactly what might have been anticipated. It is also remarked, in objection, that the mollusca and articulata appear in the same group of rocks (the slate system) with polypiaria, crinoidea, and other specimens of the humblest sub-kingdom; some of the mollusca, moreover, being cephalopods, which are the highest of their division in point of organization. Perhaps, in strict fact, the cephalopoda do not appear till a later time, that of the Silurian rocks. But even though the cephalopoda could be shewn as pervading all the lowest fossiliferous strata, what more would the fact denote than that, in the first seas capable of sustaining any kind of animal life, the creative energy advanced it, in the space of one formation, (no one can say how long a time this might be,) to the highest forms possible in that element, excepting such as were of vertebrate structure. It may here be inquired if geologists are entitled to set so high a value as they do upon the point in the scale of organic life which is marked by the upper forms of the mollusca. It will afterwards be seen that this is a low point compared with the whole scale, if we are to take as a criterion that parity of development which has been observed in the embryo of one of the higher animals. The human embryo passes through the whole space representing the invertebrate animals in the first month, a mere fraction of its course. There is indeed a remarkably rapid change of forms in such an embryo at first: the rapidity, says Professor Owen, is 'in proportion to the proximity of the ovum to the commencement of its development;' and, conformable to this fact, we find the same zoologist stating that, in the lowest division of the animal kingdom, (the Acrita of his arrangement,) there is a much quicker advance of forms towards the next above it, than is to be seen in subsequent departments. There is, indeed, to the most ordinary observation, a rapidity and force in the productive powers of the lowest animals, which might well suggest an explanation of that rush of life which seems to be indicated in the slate and Silurian rocks. With regard to the so-called early occurrence of fishes partaking of the saurian character, I would say that their occurrence a full formation after the earliest and simplest fishes, is, considering how little we know of the space of time represented by a formation, not early: their being later in any degree is the fact mainly important. The subsequent rise of new orders of fishes, fully piscine in character, may be explained by the supposition of their having been developed, as is most likely, from a different portion of the inferior sub-kingdom. In short, all the objections which have been made to the great fact of a general progress of organic development throughout the geological ages, will be found, on close examination, to refer merely to doubtful appearances of small moment, which vanish into nothing when rightly understood."