Part 20

It will scarce be urged against the degradation theory, that those races which, tried by the tests of defect or misplacement of parts, we deem degraded, are not less fitted for carrying on what in their own little spheres is the proper business of life, than the non-degraded orders and families. The objection is, however, a possible one, and one which a single remark may serve to obviate. It is certainly true that the degraded families are thoroughly fitted for the performance of all the work given them to do. They greatly increase when placed in favorable circumstances, and, when vigorous and thriving, enjoy existence. But then the same may be said of all animals, without reference to their place in the scale;—the mollusc is as thoroughly adapted to its circumstances and as fitted to accomplish the end proper to its being, as the mammiferous quadruped, and the mammiferous quadruped as man himself; but the fact of perfect adaptation in no degree invalidates the other not less certain fact of difference of rank, nor proves that the mollusc is equal to the quadruped, or the quadruped to man. And, of course, the remark equally bears on the reduced as on the unelevated,—on lowness of place when a result of degradation in races pertaining to a higher division of animals, as on lowness of place when a result of the humble standing of the division to which the races belong.

The vertebral column in the genus Diplopterus ran, as in the placoid genus Scyllium, nearly through the middle of the caudal fin.

In the following diagram a few simple lines serve to exhibit the progress of degradation. Fig. a represents the symmetrical Placoids of the Silurian period, consisting of head, neck, body, tail, fore limbs and hinder limbs; fig. b represents those heterocercal Ganoids of the Old Red Sandstone, Coal Measures, and Permian System, in which the neck is extinguished, and the fore limbs stuck on to the occiput; fig. c, those homocercal Ganoids of the Trias Lias, Oolite, and Wealden, whose tails spread out into broad terminal processes, without homologue in the higher animals; fig. d, those Acanthopterygii of the Chalk that, in addition to the non-homological processes, have both fore limbs and hinder limbs stuck round the head; while fig. e represents the asymmetrical Platessa, of the same period, with one of its eyes in the middle of its head, and the other thrust out to the side.

I would, however, respectfully suggest, that that theory of cerebral vertebræ, on which, in this question, the comparative anatomists proceed as their principle, and which finds as little support in the geologic record from the actual history of the fore limbs as from the actual history of the bones of the cranium, may be more ingenious than sound. It is a shrewd circumstance, that the rocks refuse to testify in its favor. Agassiz, I find, decides against it on other than geological grounds; and his conclusion is certainly rendered not the less worthy of careful consideration by the fact that, yielding to the force of evidence, his views on the subject underwent a thorough change. He had first held, and then rejected it. “I have shared,” he says, “with a multitude of other naturalists, the opinion which regards the cranium as composed of vertebræ; and I am consequently in some degree called upon to point out the motives which have induced me to reject it.”

“M. Oken,” he continues, “was the first to assign this signification to the bones of the cranium. The new doctrine he expounded was received in Germany with great enthusiasm by the school of the philosophers of nature. The author conceived the cranium to consist of three vertebræ, and the basal occipital, the sphenoid, and the ethmoid, were regarded as the central parts of these cranial vertebræ. On these alleged bodies of vertebræ, the arches enveloping the central parts of the nervous system were raised, while on the opposite side were attached the inferior pieces, which went to form the vegetative arch destined to embrace the intestinal canal and the large vessels. It would be too tedious to enumerate in this place the changes which each author introduced, in order to modify this matter so as to make it suit his own views. Some went the length of affirming that the vertebræ of the head were as complete as those of the trunk; and, by means of various dismemberments, separations, and combinations, all the forms of the cranium were referred to the vertebræ, by admitting that the number of pieces was invariably fixed in every head, and that all the vertebrata, whatever might be their organization in other respects, had in their heads the same number of points of ossification. At a later period, what was erroneous in this manner of regarding the subject was detected; but the idea of the vertebral composition of the head was still retained. It was admitted as a general law, that the cranium was composed of three primitive vertebræ, as the embryo is of three blastodermic leaflets; but that these vertebræ, like the leaflets, existed only ideally, and that their presence, although easily demonstrated in certain cases, could only be slightly traced, and with the greatest difficulty, in other instances. The notion thus laid down of the virtual existence of cranial vertebræ did not encounter very great opposition; it could not be denied that there was a certain general resemblance between the osseous case of the brain and the rachidian canal; the occipital, in particular, had all the characteristic features of a vertebra. But whenever an attempt was made to push the analogy further, and to determine rigorously the anterior vertebræ of the cranium, the observer found himself arrested by insurmountable obstacles, and he was obliged always to revert to the virtual existence.

“In order to explain my idea clearly, let me have recourse to an example. It is certain that organized bodies are sometimes endowed with virtual qualities, which, at a certain period of the being’s life, elude dissection, and all our means of investigation. It is thus that at the moment of their origin, the eggs of all animals have such a resemblance to each other, that it would be impossible to distinguish, even by the aid of the most powerful microscope, the ovarial egg of a craw-fish, for example, from that of true fish. And yet who would deny that beings in every respect different from each other exist in these eggs? It is precisely because the difference manifests itself at a later period, in proportion as the embryo develops itself, that we are authorized to conclude, that, even from the earliest period, the eggs were different,—that each had virtual qualities proper to itself, although they could not be discovered by our senses. If, on the contrary, any one should find two eggs perfectly alike, and should observe two beings perfectly identical issue from them, he would greatly err if he ascribed to these eggs different virtual qualities. It is therefore necessary, in order to be in a condition to suppose that virtual properties peculiar to it are concealed in an animal, that these properties should manifest themselves once, in some phase or other of its development. Now, applying this principle to the theory of cranial vertebræ, we should say, that if these vertebræ virtually exist in the adult, they must needs show themselves in reality, at a certain period of development. If, on the contrary, they are found neither in the embryo nor the adult, I am of opinion that we are entitled likewise to dispute their virtual existence.

“Here, however, an objection may be made to me, drawn from the physiological value of the vertebræ, the function of which, as is well known, is, on the one hand, to furnish a solid support to the muscular contractions which determine the movements of the trunk, and, on the other, to protect the centres of the nervous system, by forming a more or less solid case completely around them. The bodies of the vertebræ are particularly destined to the first of these offices; the neurapophyses to the second. What can be more natural than to admit, from the consideration of this, that in the head, the bodies of the vertebræ diminish in proportion as the moving function becomes lost, while the neurapophyses are considerably developed for protecting the brain, the volume of which is very considerable, when compared with that of the spinal marrow? Have we not an example of this fact in the vertebræ of the tail, where the neurapophyses become completely obliterated, and a simple cylindrical body alone remains? Now, may it not be the case, that in the head, the bodies of the vertebræ have disappeared; and that, in consequence, there is a prolongation of the cord only as far as the moving functions of the vertebræ extend? There is some truth in this argument, and it would be difficult to refute it a priori. But it loses all its force the moment that we enter upon a detailed examination of the bones of the head. Thus, what would we call, according to this hypothesis, the principal sphenoid, the great wings of the sphenoid, and the ethmoid, which form the floor of the cerebral cavity? It may be said they are apophyses. But the apophyses protect the nervous centres only on the side and above. It may be said that they are the bodies of the vertebræ. But they are formed without the concurrence of the dorsal cord; they cannot, therefore, be the bodies of the vertebræ. It must therefore be allowed, that these bones at least do not enter into the vertebral type; that they are in some measure peculiar. And if this be the case with them, why may not the other protective plates be equally independent of the vertebral type; the more so, because the relations of the frontals and parietals vary so much, that it would be almost impossible to assign to them a constant place?”

It is stated by Mr. Witham, that, “except in a few instances, he had ineffectually tried, with the aid of the microscope, to obtain some insight into the structure of coal. Owing,” he adds, “to its great opacity, which is probably due to mechanical pressure, the action of chemical affinity, and the percolation of acidulous waters, all traces of organization appear to have been obliterated.” I have heard the late Mr. Sanderson, who prepared for Mr. Witham most of the specimens figured in his well-known work on the “Internal Structure of Fossil Vegetables,” and from whom the materials of his statement on this point seem to have been derived, make a similar remark. It was rare, he said, to find a bit of coal that exhibited the organic structure. The case, however, is far otherwise; and the ingenious mechanic and his employer were misled, simply by the circumstance, that it is rare to find pieces of coal which exhibit the ligneous fibre, existing in a state of keeping solid enough to stand the grinding of the lapidary’s wheel. The lignite usually occurs in thin layers of a substance resembling soft charcoal, at which, from the loose adhesion of the fibres, the coal splits at a stroke; and as it cannot be prepared as a transparency, it is best examined by a Stanhope lens. It will be found, tried in this manner, that so far is vegetable fibre from being of rare occurrence in coal,—our Scotch coal at least,—that almost every cubic inch contains its hundreds, nay, its thousands, of cells.

On a point of such importance I find it necessary to strengthen my testimony by auxiliary evidence. The following is the judgment, on this ancient petrifaction, of Mr. Nicol of Edinburgh,—confessedly one of our highest living authorities in that division of fossil botany which takes cognizance of the internal structure of lignites, and decides, from their anatomy, their race and family:—

“Edinburgh, 19th July, 1845.

“DEAR SIR,—I have examined the structure of the fossil wood which you found in the Old Red Sandstone at Cromarty, and have no hesitation in stating, that the reticulated texture of the transverse sections, though somewhat compressed, clearly indicates a coniferous origin; but as there is not the slightest trace of a disc to be seen in the longitudinal sections parallel to the medullary rays, it is impossible to say whether it belongs to the Pine or Araucarian division. I am, &c.,

“WILLIAM NICOL.”

It will be seen that Mr. Nicol failed to detect what I now deem the discs of this conifer,—those stippled markings to which I have referred, and which the engraver has indicated in no exaggerated style, in one of the longitudinal sections (b) of the wood-cut given above. But even were this portion of the evidence wholly wanting, we would be left in doubt, in consequence, not whether the Old Red lignite formed part of a true gymnospermous tree, but whether that tree is now represented by the pines of Europe and America, or by the araucarians of Chili and New Zealand. Were I to risk an opinion in a department not particularly my province it would be in favor of an araucarian relationship.

The following digest from Professor Balfour’s very admirable “Manual of Botany,” of what is held on this curious subject, may be not unacceptable to the reader. “It is an interesting question to determine the mode in which the various species and tribes of plants were originally scattered over the globe. Various hypotheses have been advanced on the subject. Linnæus entertained the opinion that there was at first only one primitive centre of vegetation, from which plants were distributed over the globe. Some, avoiding all discussions and difficulties, suppose that plants were produced at first in the localities where they are now seen vegetating. Others think that each species of plant originated in, and was diffused from, a single primitive centre; and that there were numerous such centres situated in different parts of the world, each centre being the seat of a particular number of species. They thus admit great vegetable migrations, similar to those of the human races. Those who adopt the latter view recognize in the distribution of plants some of the last revolutions of our planet, and the action of numerous and varied forces, which impede or favor the dissemination of vegetables in the present day. They endeavor to ascertain the primitive flora of countries, and to trace the vegetable migrations which have taken place. Daubeny says, that analogy favors the supposition that each species of plant was originally formed in some particular locality, whence it spread itself gradually over a certain area, rather than that the earth was at once, by the fiat of the Almighty, covered with vegetation in the manner we at present behold it. The human race rose from a single pair; and the distribution of plants and animals over a certain definite area would seem to imply that the same was the general law. Analogy would lead us to believe that the extension of species over the earth originally took place on the same plan on which it is conducted at present, when a new island starts up in the midst of the ocean, produced either by a coral reef or a volcano. In these cases the whole surface is not at once overspread with plants, but a gradual progress of vegetation is traced from the accidental introduction of a single seed, perhaps, of each species, wafted by winds or floated by currents. The remarkable limitation of certain species to single spots on the globe seems to favor the supposition of specific centres.”

Rhodomenia palmata and Alaria esculenta.

Porphyra laciniata, Chorda filum, and Enteromorpha compressa.

“Dr. Neill mentions,” says the Rev. Mr. Landsborough, in his complete and very interesting “History of British Sea-Weeds,” “that on our shores algæ generally occupy zones in the following order, beginning from deep water:—F. Filum; F. esculentus and bulbosus, F. digitatus, saccharinus, and loreus; F. serratus and crispus; F. nodosus and vesiculosus; F. canaliculatus; and, last of all, F. pygmæus; which is satisfied if it be within reach of the spray.”

We are supplied with a curious example of that ever-returning cycle of speculation in which the human mind operates, by not only the introduction of the principle of Epicurus into the “Vestiges,” but also by the unconscious employment of even his very arguments, slightly modified by the floating semi-scientific notions of the time. The following passages, taken, the one from the modern work, the other from Fénélon’s life of the old Greek philosopher, are not unworthy of being studied, as curiously illustrative of the cycle of thought. Epicurus, I must, however, first remind the reader, in the words of his biographer, “supposed that men, and all other animals, were originally produced by the ground. According to him, the primitive earth was fat and nitrous; and the sun, gradually warming it, soon covered it with herbage and shrubs: there also began to arise on the surface of the ground a great number of small tumors like mushrooms, which having in a certain time come to maturity, the skin burst, and there came forth little animals, which, gradually retiring from the place where they were produced, began to respire.” And there can be little doubt, that had the microscope been a discovery of early Greece, the passage here would have told us, not of mushroom-like tumors, but of monads. Save that the element of microscopic fact is awanting in the one and present in the other, the following are strictly parallel lines of argument:—

“To the natural objection that the earth does not now produce men, lions, and dogs, Epicurus replies that the fecundity of the earth is now exhausted. In advanced age a woman ceases to bear children; a piece of land never before cultivated produces much more during the few first years than it does afterwards; and when a forest is once cut down, the soil never produces trees equal to those which have been rooted up. Those which are afterwards planted become dwarfish, and are perpetually degenerating. We are, however, he argues, by no means certain but there may be at present rabbits, hares, foxes, bears, and other animals, produced by the earth in their perfect state. The reason why we are backward in admitting it is, that it happens in retired places, and never falls under our view; and, never seeing rats but such as have been produced by other rats, we adopt the opinion that the earth never produced any.” (Fénélon’s Lives of the Ancient Philosophers.)

“In the first place, there is no reason to suppose that, though life had been imparted by natural means, after the first cooling of the surface to a suitable temperament, it would continue thereafter to be capable of being imparted in like manner. The great work of the peopling of this globe with living species is mainly a fact accomplished: the highest known species came as a crowning effort thousands of years ago. The work being thus to all appearance finished, we are not necessarily to expect that the origination of life and of species should be conspicuously exemplified in the present day. We are rather to expect that the vital phenomena presented to our eyes should mainly, if not entirely, be limited to a regular and unvarying succession of races by the ordinary means of generation. This, however, is no more an argument against a time when phenomena of the first kind prevailed, than it would be a proof against the fact of a mature man having once been a growing youth, that he is now seen growing no longer..... Secondly, it is far from being certain that the primitive imparting of life and form to inorganic elements is not a fact of our times.” (Vestiges of Creation.)

“Vestiges of the Natural History of Creation,” and “Explanations, being a Sequel to the Vestiges.”

The chapter in which this passage occurs originally appeared, with several of the others, in the Witness newspaper, in a series of articles, entitled “Rambles of a Geologist,” and drew forth the following letter from a correspondent of the Scottish Press, the organ of a powerful and thoroughly respectable section of the old Dissenters of Scotland. I present it to the reader merely to show, that if, according to the author of the “Vestiges,” geologists assailed the development hypothesis in the fond hope of “purchasing impunity for themselves,” they would succeed in securing only disappointment for their pains:—

“THE PRE-ADAMITE EARTH.

“To the Editor of the Scottish Press.

“SIR,—I occasionally observe articles in your neighbor and contemporary the Witness, characteristically headed ‘Rambles of a Geologist,’ wherein the writer with great zeal once more ‘slays the slain’ heresies of the ‘Vestiges of Creation.’ This writer (of the ‘Rambles,’ I mean) nevertheless, and at the same time, announces his own tenets to be much of the same sort, as applied to mere dead matter, that those of the ‘Vestiges’ are with regard to living organisms. He maintains that the world, during the last million of years, has been of itself rising or developing, without the interposition of a miracle, from chaos into its present state; and, of course, as it is still, as a world, confessedly far below the acme of physical perfection, that it must be just now on its passage, self-progressing, towards that point, which terminus it may reach in another million of years hence.[!!!] The author of the ‘Vestiges,’ as quoted by the author of the ‘Rambles,’ in the last number of the Witness, complains that the latter and his allies are not at all so liberal to him as, from their present circumstances and position, he had a right to expect. He (the author of the ‘Vestiges’) reminds his opponents that they have themselves only lately emerged from the antiquated scriptural notions that our world was the direct and almost immediate construction of its Creator,—as much so, in fact, as any of its organized tenants,—and that it was then created in a state of physical excellence, the highest possible, to render it a suitable habitation for these tenants, and all this only about six or seven thousand years ago,—to the new light of their present physico-Lamarckian views; and he asks, and certainly not without reason, why should these men, so circumstanced, be so anxious to stop him in his attempt to move one step further forward in the very direction they themselves have made the last move?—that is, in his endeavor to extend their own principles of self-development from mere matter to living creatures. Now, Sir, I confess myself to be one of those (and possibly you may have more readers similarly constituted) who not only cannot see any great difference between merely physical and organic development,[!!] but who would be inclined to allow the latter, absurd as it is, the advantage in point of likelihood.[!!!] The author of the ‘Rambles,’ however, in the face of this, assures us that his views of physical self-development and long chronology belong to the inductive sciences. Now, I could at this stage of his rambles have wished very much that, instead of merely saying so, he had given his demonstration. He refers, indeed, to several great men, who, he says, are of his opinion. Most that these men have written on the question at issue I have seen, but it appeared far from demonstrative, and some of them, I know, had not fully made up their mind on the point.[!!!] Perhaps the author of the ‘Rambles’ could favor us with the inductive process that converted himself; and, as the attainment of truth, and not victory, is my object, I promise either to acquiesce in or rationally refute it.[?] Till then I hold by my antiquated tenets, that our world, nay, the whole material universe, was created about six or seven thousand years ago, and that in a state of physical excellence of which we have in our present fallen world only the ‘vestiges of creation.’ I conclude by mentioning that this view I have held now for nearly thirty years, and, amidst all the vicissitudes of the philosophical world during that period, I have never seen cause to change it. Of course, with this view I was, during the interval referred to, a constant opponent of the once famous, though now exploded, nebular hypothesis of La Place; and I yet expect to see physical development and long chronology wither also on this earth, now that THEIR ROOT (the said hypothesis) has been eradicated from the SKY.[!!!]—I am, Sir, your most obedient servant,

“PHILALETHES.”

I am afraid there is little hope of converting a man who has held so stoutly by his notions “for nearly thirty years;” especially as, during that period, he has been acquainting himself with what writers such as Drs. Chalmers, Buckland, and Pye Smith have written on the other side. But for the demonstration which he asks, as I have conducted it, I beg leave to refer him to the seventeenth chapter of my little work, “First Impressions of England and its People.” I am, however, inclined to suspect that he is one of a class whose objections are destined to be removed rather by the operation of the laws of matter than of those of mind. For it is a comfortable consideration, that in this controversy the geologists have the laws of matter on their side;—“the stars in their courses fight against Sisera.” Their opponents now, like the opponents of the astronomer in the ages gone by, are, in most instances, men who have been studying the matter “for nearly thirty years.” When they study it for a few years longer they disappear; and the men of the same cast and calibre who succeed them are exactly the men who throw themselves most confidently into the arms of the enemy, and look down upon their poor silent predecessors with the loftiest commiseration. It is, however, not uninstructive to remark how thoroughly, in some instances, the weaker friends and the wilier enemies of Revelation are at one in their conclusions respecting natural phenomena. The correspondent of the Scottish Press merely regards the views of the author of the “Vestiges” as possessing “the advantage, in point of likelihood,” over those of the geologists his antagonists: his ally the Dean of York goes greatly further, and stands up as stoutly for the transmutation of species as Lamarck himself. Descanting, in his New System of Geology, on the various forms of trilobites, ammonites, belemnites, &c. Dean Cockburn says,—

“These creatures appear to have possessed the power of secreting from the stone beneath them a limy covering for their backs, and perhaps, fed partly on the same solid material. Supposing, now that the first trilobites were destroyed by the Llandeilo Slates, some spawn of these creatures would arise above these flags, and, after a time, would be warmed into existence. These molluscs,[!!] then, having a better material from which to extract their food and covering, would probably expand in a slightly different form, and with a more extensive mantle than what belonged to the parent species. The same would be still more the case with a new generation, fed upon a new deposit from some deeper volcano, such as the Caradoc or Wenlock Limestone, in which lime more and more predominates. Now, if any one will examine the various prints of trilobites in Sir R. Murchison’s valuable work, he will find but very trifling differences in any of them,[!!] and those differences only in the stony covering of their backs. I knew two brothers once much alike: the one became a curate with a large family; the other a London alderman. If the skins of these two pachydermata had been preserved in a fossil state, there would have been less resemblance between them than between an Asaphus tyrannus and an Asaphus caudatus.... A careful and laborious investigation has discovered, as in the trilobites, a difference in the ammonites of different strata; but such differences, as in the former case, exist only in the form of the external shell, and may be explained in the same manner.[!!] ... As to the scaphites, baculites, belemnites, and all the other ites which learned ingenuity has so named, you find them in various strata the same in all important particulars, but also differing slightly in their outward coverings, as might be expected from the different circumstances in which each variety was placed.[!!] The sheep in the warm valleys of Andalusia have a fine covering like to hair; but remove them to a northern climate, and in a few generations the back is covered with shaggy wool. The animal is the same,—the covering only is changed.... The learned have classed those shells under the names of terebratula, orthis, atrypa, pecten, &c. They are all much alike.[!!!] It requires an experienced eye to distinguish them one from another: what little differences have been pointed out may readily be ascribed, as before, to difference of situation.”[!!!]