NATIONAL LIBRARY OF MEDICINE Bethesda, Maryland %-.»-*» v. %t ••! « V 0 EXPLANATIONS. <2tf 7, \Hi o 1 jJ 6 EXPLANATIONS A SEQUEL TO VESTIGES OF THE NATURAL HISTORY OF CREATION." BY THE AUTHOR OF THAT WORK. 8y Sir Richard WTam NEW YORK: WILEY & PUTNAM, 161 BROADWAY. 1846. 1 '~1 • v t ■ • CONTENTS. PAGE Design of the Vestiges explained......................... 2 Proper Position of the Nebular Hypothesis in the Argument.. 3 Imputed Failure of the Hypothesis from the Earl of Rosse's discoveries, denied.................................... 6 Experiments illustrating and confirming the Hypothesis by Professor Plateau..................................... 10 Objection from the retrogression of Uranus's Satellites consi- dered ................................................. 13 Objection respecting the convergence of atoms to a central nucleus, answered.................................... 14 The Nebular Hypothesis not a supersession of Deity, but only a description of his mode of working..................... 16 Quetelet's inquiries, establishing law in mental operations.... 17 Limits of the system being under law, the whole is probably so 18 Question of the Origin of Organic nature.................. 19 Geology proves it to have observed a progress in time....... 21 Objections respecting this progress......................... 22 Lower Silurian Fossils................................... 23 Upper Silurian Fossils................................... 33 Old Red Sandstone....................................... 34 Carboniferous System.................................... 42 Permian System......................................... 45 Outline of the Genetic Plan of the Animal Kingdom........ 49 Bearing of this Plan on the Arguments of Objectors......... 53 Reptiles of the Muschelkalk, Lias, &c.................... 58 Objections as to first Footmarks of Birds................... 60 Vi CONTENTS. PAGE Objections as to Earliest Mammalia........................ 62 Tertiary Formation...................................... 64 Opinions of Cuvier and Agassiz........................... 70 Apology of Mr. Sedgwick for Over-Ardent Generalizations... 71 Physiological Objections of Dr. Clark, of Cambridge........ 73 Views of others respecting Embryotic Development......... 75 Germs not alleged to be identical......................... 77 Transmutation of Plants................................. 78 Species a Term, not a Fact............................... 80 Instances of Transmutation............................... 81 Transmutation does not imply extinction of Elder Species.... 83 The Broomfield Experiment.............................. 84 Proof of Aboriginal Life in the present era not essential to the theory of Organic Creation by Law.................... 86 The Opposite Theory characterized........................ 88 Views of Dr. Whewell, and objections to them.............. 90 Views of the Edinburgh Reviewer—these analyzed.......... 95 Views of Professor Agassiz............................... 99 Views of Sir John Herschel.............................. 100 Support to Theory of Law from Rev. Dr. Pye Smith and Black- wood's Magazine..................................... 101 Mr. Stuart Mill on Universal Causation.................... 102 Present State of Opinion on the Origin of Organic Nature examined............................................ 105 Animals have not come immediately on the occurrence of proper conditions............................................ 107 Great number of distinct Floras........................... 107 Supposed Formation of New Species, as upheld by Professor Owen, &c, inadmissible.............................. 108 Opinions of Professor Pictet on Peculiarity of Species in each formation............................................ no Time the true key to difficulties arising from apparent per- manency of species................................... HI Vast spaces of time involved in the Geological record........ 112 Zoology of Galapagos Islands, an instance of comparatively re- cent development..................................... 114 Author's theory supported by facts connected with the distri- bution of plants...................................... H7 CONTENTS. yii PAGE Whence the lirst impulse to vitality ?....................... 119 The Vestiges—its object purely scientific—defended on this ground..............................................120 Ungenerous policy of Geological Objectors................. 120 Opposition of the Scientific Class......................... 123 Estimate of this Opposition............................... 124 Utility of Hypotheses.................................... 127 Bearing of the new doctrine on Human Interests............ 129 Its Moral Results........................................ 130 Consolations and Encouragements offered by it.............. 132 Appendix—Letters of Mr. Weekes on Aboriginal Production of [nsects.............................................. 134 EXPLANATIONS. When the work to which this may be regarded as a sup- plement was published, my design was not only to be per- sonally removed from all praise or censure which it might evoke, but to write no more upon the subject. I said to myself, Let this book go forth to be received as truth, or to provoke others to a controversy which may result in establishing or overthrowing it ; but be my task now ended. I did not then reflect that, even though written by one better informed or more skilled in argument than I can pretend to be, it might leave the subject in such a condition that the author should have to regret seeing it in a great measure misapprehended in its general scope, and also so much excepted to, justly and unjustly, on par- ticular points, that ordinary readers might be ready to suppose its whole indications disproved. Had I bethought me of such possible results, I might have announced, from the beginning, my readiness to enter upon such explana- tions of points objected to, and such reinforcements of the general argument, as might promise to be serviceable. And this would have seemed the more necessary, in as far as it may be expected that there are many points in a new and startling hypothesis which no one can be so well qualified to clear up and strengthen as its author. I might 2 2 EXPLANATIONS. have felt, at the same time, that a new adventure, for whatever purpose, in the same field, was hazardous, with regard to any favorable impression previously produced j yet such an objection would, again, have been at once overruled, seeing that public favor and disfavor were alike beyond the regard of an author who bore no bodily shape in the eyes of his fellow-countrymen, and was likely to remain for ever unknown. Such reflections now occur to me, and I am consequently induced to take up the pen for the purpose of endeavoring to make good what is deficient, and reasserting and confirming whatever has been un- justly challenged in my book. In doing so, I shall study to direct attention solely to fact and argument, or what appear as such, overlooking the uncivil expressions which the work has drawn forth in various quarters, and which, of course, can only be a discredit to their authors. I must start with a more explicit statement of the gene- ral argument of the Vestiges, for this has been extensively misunderstood. The book is not primarily designed, as many have intimated in their criticisms, and as the title might be thought partly to imply, to establish a new theory respecting the origin of animated nature; nor are the chief arguments directed to that point. The object is one to which the idea of an organic creation in the manner of natural law is only subordinate and ministrative, as like- wise are the nebular hypothesis and the doctrine of a fixed natural order in mind and morals. This purpose is to show that the whole revelation of the works of God pre- sented to our senses and reason is a system based in what we are compelled, for want of a better term, to call law ; by which, however, is not meant a system independent or exclusive of Deity, but one which only proposes a certain EXPLANATIONS. 3 mode of Ms working. The nature and bearing of this doc- trine will be afterwards adverted to; let me, meanwhile, observe, that it has long been pointed to by science, though hardly anywhere broadly and fully contemplated. And this was scarcely to be wondered at, since, while the whole physical arrangements of the universe were placed under law by the discoveries of Kepler and Newton, there was still such a mysterious conception of the origin of organic nature, and of the character of our own fitful being, that men were almost forced to make at least large exceptions from any proposed plan of universal order. What makes the case now somewhat different is, that of late years we have attained much additional knowledge of nature, point- ing in the same direction as the physical arrangements of the world. The time seems to have come when it is pro- per to enter into a re-examination of the whole subject, in order to ascertain whether, in what we actually know, there is most evidence in favor of an entire or a partial system of fixed order. When led to make this inquiry for myself, I soon became convinced that the idea of any ex- ception to the plan of law stood upon a narrow, and con- stantly narrowing foundation, depending, indeed, on a few difficulties or obscurities, rather than objections, which were certain soon to be swept away by the advancing tide of knowledge. It appeared, at the same time, that there was a want in the state of philosophy amongst us, of an impulse in the direction of the consideration of this theory, so as to bring its difficulties the sooner to a bearing in the one way or the other; and hence it was that I presumed to enter the field. My starting point was a statement of the arrangements of the bodies of space, with a hypothesis respecting the 4 EXPLANATIONS. mode in which those arrangements had been effected. It is a mistake to suppose this (nebular), hypothesis essential, as the basis of the entire system of nature developed in my book. That basis lies in the material laws found to prevail throughout the universe, which explain why the masses of space are globular; why planets revolve round suns in elliptical orbits ; how their rates of speed are high in proportion to their nearness to the centre of attraction ; and so forth. In these laws arises the first powerful pre- sumption that the formation and arrangements of the celes- tial bodies were brought about by the Divine will, acting in the manner of a fixed order or law, instead of any mode which we conceive of as more arbitrary. It is a presump- tion which an enlightened mind is altogether unable to re- sist, when it sees that precisely similar effects are every day produced by law on a small scale, as when a drop of water spherifies, when the revolving hoop bulges out in the plane of its equator, and the sling, swung round in the hand, increases in speed as the string is shortened. The philosopher, on observing these phenomena, and finding incontestable proof that they are precisely of the same nature as those attending the formation and arrangement of worlds, learns his first great lesson—that the natural laws work on the minutest and the grandest scale indiffer- ently ; that, in fact, there is no such thing as great and small in nature, but world spaces are as a hair-breadth, and a thousand years as one day. Having thus all but demonstration that the spheres were formed and arranged by natural law, the nebular hypothesis becomes important, as shadowing forth the process by which matter was so transformed from a previous condition, but it is nothing more ; and, though it were utterly disproved, the evidence NEBULAR HYPOTHESIS. 5 which we previously possessed that physical creation, so to speak, was effected by means of, or in the manner of law, would remain exactly as it was. We should only be left in the dark with regard to the previous condition of matter, and the steps of the process by which it acquired its present forms. It would nevertheless strengthen the presumption, and, indeed, place it near to ascertained truths, if we were to obtain strong evidence for what has hitherto been called the nebular hypothesis. The evidence for it is sketched in the Vestiges: it is exhibited with greater clearness, and in elegant and impressive language, in Professor Nichol's Views of the Architecture of the Heavens. The position held by this hypothesis in the philosophical world when my book was written, is shown, with tolerable distinctness, in the Edinburgh Review for 1838, where it is spoken of in the following general terms :—" These views of the origin and destiny of the various system of worlds which fill the immensity of space, break upon the mind with all the inte- rest of novelty, and all the brightness of truth. Appealing to our imagination by their grandeur, and to our reason by the severe principles on which they rest, the mind feels as if a revelation had been vouchsafed to it of the past and future history of the universe." It may also be remarked that this writer considered the hypothesis as " confirming, rather than opposing the Mosaic cosmogony, whether alle- gorically or literally interpreted." With this testimony to the mathematical expositions of MM. La Place and Comte, I rest content, as the expositions themselves would be un- suitable in a popular treatise. But the hypothesis has been favorably entertained in many authoritative quarters, dur- ing the last few years, and probably would have continued 6 EXPLANATIONS. to be so, if no attempt had been made to enforce by it a system of nature on the principle of universal order. The chief objection taken to the theory is, that the ex- istence of nebulous matter in the heavens is disproved by the discoveries made by the Earl of Rosse's telescope. By this wondrous tube, we are told, it is shown to be " an unwarrantable assumption that there are in the heavenly spaces any masses of matter different from solid bodies composing planetary systems."* The nebulse, in short, are said to be now shown as clusters of stars, rendered apparently nebulous only by the vast distance at which they are placed. There is often seen a greater vehemence and rashness in objecting to, than in presenting hypothe- ses ; and we appear to have here an instance of such hasty counter-generalization. The fact is, that the nebulse were always understood to be of two kinds : 1, nebulse which were only distant clusters, and which yielded, one after another, to the resolving powers of telescopes, as these powers were increased ; 2, nebulse comparatively near, which no increase of telescopic power affected. Two classes of objects wholly different were, from their partial resemblance, recognized by one name, and hence the con- fusion which has arisen upon the subject. The resolution of a great quantity of the first kind of nebulse by Lord Rosse's telescope was of course expected, and it is a fact, though in itself interesting, of no consequence to the ne- bular hypothesis. It will only be in the event of the second class being also resolved, and its being thus shown that there is only one class of nebulse, that the hypothesis will suffer. Such, at least, I conclude to be the sense of a * North British Review, iii.,477. NEBULAR HYPOTHESIS. 7 rvassage which I take leave to transfer, in an abridged form, from a recent edition of Professor Nichol's work. " I. By far the greater number of the milky streaks, or spots, whose places have hitherto been recorded, lie at the outermost, or nearly at the outermost boundary of the sphere previously reached by our telescopes ; and in this case there is no certain principle on the ground upon which a pure nebula can be distinguished from a cluster so remote that only the general or fused light of its myriads of constituent orbs can be seen. Sometimes,—resting on a pecu- liarity of form or other characteristic,—the astronomer may venture a guess that such an object is probably a firmament; as, indeed, I was bold enough to do in former editions of this work with regard to several which have since been resolved; but, in the main, he can tell little concerning them, or have any other belief, than that, as with similar masses near him, a great, probably the greater num- ber, are true clusters, grand arrangements of stars, incredibly re- mote, but resembling in all things our own home galaxy. Now, the application to such objects of a new and enlarged power of vision, could be attended only by one result—magnificent, but far from unexpected: and it is here that the six-feet mirror has achieved its earliest triumphs. Under its piercing glance, great numbers of the milky specks have unfolded their starry constitu- ents ; some of these, which previously were almost unresolved, shining with a lustre equivalent to that of our brightest orbs to the naked eye. How far it will go with its resolving power has not yet been ascertained; but I perceive that Sir James South has given his authority that some spots examined by it continue in- tractable. " II. The influence of the new discoveries either to impair or strengthen the foundations of the nebular hypothesis, must clearly be looked for among their bearings on less remote and ambiguous objects. Now, the new aspects of these may lead us to question our former opinions as to the existence of the supposed filmy self- luminous masses,—or they may throw doubt on the reality of those forms according to whieh we have arranged them, and which seem to indicate the steps of a stupendous progress. "1. Astronomers have never rested their belief in the reality 8 EXPLANATIONS. and wide diffusion of the nebulous matter, on the objects referred to in the first paragraph; but on others, much within the range of our previous vision. In so far as we have hitherto understood the nature of clusters, the telescopic power required to resolve them is never very much higher than that which first descries them as dim milky spots. But, there are many most remarkable objects which, in this essential feature, are wholly contrasted with clusters. For instance, the nebula in Orion, as I have fully shown in the text, is visible to the naked eye, as also is the gorgeous one in Andromeda; while the largest instrument heretofore turned to them has given no intimation that their light is stellar, but rather the contrary; although small stars are found buried amidst their mass. Now, if Lord Rosse's telescope resolves these, and others with similar attri- butes, such as some of the streaks among the following plates, we shall thereby be informed that we have generalized too hastily from the character of known firmaments,—that schemes of stellar being exist, infinitely more strange and varied than we had ventured to suppose,—and certainly we shall then hesitate in averring further, concerning the existence or at least the diffusion of the purely nebulous modification of matter. " 2. Lord Rosse's telescope may also, as I have said, disprove the reality of our arrangement of the forms of the nebula? as steps of a progression. And in regard of this question, there seem two classes of objects meriting attention. " First, I shall refer to the nebulous stars properly so called, or to that form in which the diffused matter has reached the condition of almost pure fixed stars. Now, of these objects there are two distinct sets, presenting at first to the telescope very much the same appearance, but in regard of which our knowledge is very different. It will readily be conceived that a distant cluster, with strong concentration about the centre of its figure, must, to the telescope which first descries it, look like a star with a halo around it. When a higher power is applied, that central star, however, will appear as a disc, and to a still higher power the cluster will be revealed. A very great number of what are called nebulous stars, are doubtless of this class; and we have hitherto had no means of accurately ascertaining the fact, just because our largest telescopes were required to descry them ; but there are multitudes NEBULAR HYPOTHESIS. 9 of others—the true ' photospheres'—quite of a different descrip- tion. Many of these are easily seen as fixed stars with haloes of different sizes diminishing to the mere ' bur ;' and under the great- est power as yet applied, the apparent central star never expands into a disc, or departs from the stellar character. It is by its effect on these that the new instrument will at all bear on this portion of the nebular hypothesis. " Secondly, The foregoing being our grounds of belief in the existence of nebulae—first, in a diffused or chaotic state, and again in a condition proximate to pure stars ; the only remaining point has reference to nebulae in an intermediate state,—when the round- ish masses seem to have begun a process of organization or concen- tration, and carried it onwards through several stages : a state to which we have every variety of analogon in the various forms and densities of cometic nuclei. Sir William Herschel certainly was not ignorant that round or spherical clusters abound in the skies, which, when first seen, present all the appearances of such nebula? -—nay, he grounded on the fact of their approximate sphericity and varying degrees of concentration, some of the boldest and most engrossing of his conjectures ; nor would he have doubted that multitudes which, even to his instruments, seemed only general lights, would, in after times, be resolved ; but here, as before, the gist of the question is not, can you resolve round nebula? never re- solved before ; but can you resolve such as, quite within the range of former vision, have continued intractable under the scrutiny of powers which, judging from the average of our experience, must surpass what ought to have resolved them ? " Such are my views as to the present condition of this impor- tant question; and if they are correct, it will appear that, not- withstanding the resolutions achieved by the new instruments, they are, as yet, quite as likely—by accumulating new objects belonging to the three foregoing classes, and by more surely and distinctly establishing their characteristic features—to strengthen, as to in- validate the grounds of the nebular hypothesis. Eagerly, but pa- tiently, let us watch the approaching revelations." Various minor objections have been presented to the nebular hypothesis; but, before adverting to any of them, 2* 10 EXPLANATIONS. I may give a brief abstract of certain recent experiments, by which it has been remarkably illustrated. Here it is peculiarly important to bear in mind, that the phenomena of nature are, if I may so speak, indifferent to the scale on which they act. The dew-drop is, in physics, the pic- ture of a world. Remembering this, we are prepared in some measure, to hear of a Belgian professor imitating the supposed- formation and arrangement of a solar sys- tem, in some of its most essential particulars, on the table of a lecture-room ! The experiments were first conducted by Professor Plateau of Ghent, and afterwards repeated by our own Dr. Faraday. The following abstract of Professor Plateau's experi- ments is also presented in the fifth edition of the Vestiges. Its being repeated here is, that it may meet the eyes of many who are not likely to see any edition of that work besides those from which it is absent: Placing a mixture of water and alcohol in a glass box, and therein a small quantity of olive oil, of density pre- cisely equal to the mixture, we have in the latter a liquid mass relieved from the operation of gravity, and free to take the exterior form given by the forces which may act upon it. In point of fact, the oil instantly takes a globular form by virtue of molecular attraction. A vertical axis being introduced through the box, with a small disc upon it, so arranged that its centre is coincident with the centre of the globe of oil, we turn the axis at a slow rate, and thus set the oil sphere into rotation. " We then presently see the sphere flatten at its poles and swell out at its equator, and we thus realize, on a small scale, an effect which is admitted to have taken place in the planets." The spheri- fying forces are of different natures, that of molecular NEBULAR HYPOTHESIS. 11 attraction in the case of the oil, and of universa attrac- tion in that of the planet, but the results are " analogous, if not identical." Quickening the rotation makes the figure more oblately spheroidal. When it comes to be so quick as two or three turns in a second, " the liquid sphere first takes rapidly its maximum of flattening, then becomes hollow above and below, around the axis of rota- tion, stretching out continually in a horizontal direction, and finally, abandoning the disc, is transformed into a per- fectly regular ring." At first this remains connected with the disc by a thin pellicle of oil ; but on the disc being stopped this breaks and disappears, and the ring becomes completely disengaged. The only observable difference between the latter and the ring of Saturn is, that it is rounded, instead of being flattened; but this is accounted for in a satisfactory way. A little after the stoppage of the rotatory motion of the disc, the ring of oil, losing its own motion, gathers once more into a sphere. If, however, a smaller disc be used, and its rotation continued after the separation of the ring, rotatory motion and centrifugal force will be generated in the alcoholic fluid, and the oil ring, thus prevented from returning into the globular form, divides itself into " several isolated masses, each of which immediately takes the globular form." These are " almost always seen to assume, at the instant of their formation, a movement of rotation upon them- selves—a movement which constantly takes place in the same direction as that of the ring. Moreover, as the ring, at the instant of its rupture, had still a remainder of velocity, the spheres to which it has given birth tend to fly off at a tangent; but as, on the other side, the disc, turning in the alco- holic liquor, has impressed on this a movement of rotation, the 12 EXPLANATIONS. spheres are especially carried along by this last movement, and revolve for some time round the disc. Those which revolve at the same time upon themselves, consequently, then present the curious spectacle of planets revolving at the same time on themselves and in their orbits. Finally, another very curious effect is also manifested in these cir- cumstances : besides three or four large spheres into which the ring revolves itself, there are almost always produced one or two very small ones, which may thus be compared to satellites. The experiment which we have thus des- cribed presents, as we see, an image in miniature of the formation of the planets, according to the hypothesis of Laplace, by the rupture of the cosmical rings attributable to the condensation of the solar atmosphere."* Such illustrations certainly tend to take from the nebular cosmogony the character of a " splendid vision," which one of my critics has applied to it. I may here also remind the reader that there are other grounds for this hypothesis, besides observations on the nebulae. Overlook- ing the zodiacal light, which has been thought a residuum of the nebulous fluid of our system, we find geology taking us back towards a state of our globe which cannot other- wise be explained. It was clearly at one time in a state of igneous fluidity,—the state in which its oblately sphe- roidal form was assumed under the law of centrifugal force. Since then it has cooled, at least in the exterior crust. We thus have it passing through a chemical pro- cess attended by diminishing heat. Whence the heat at first, if not from the causes indicated in the nebular * Dr. Plateau on the Phenomena presented by a free Liquid Mass withdrawn from the action of gravity. Taylor's Scientific Memoirs. November, 1844. NEBULAR HYPOTHESIS. 13 hypothesis ? But this is not all. In looking back along the steps of such a process, we have no limit imposed. There is nothing to call for our stopping till we reach one of those extreme temperatures which would vaporize the solid materials ; and this gives us exactly that condition of things which is implied by the nebular cosmogony. Of particular objections it is not necessary to say much. That there should be difficulties attending such a hypothe- sis is only to be expected ; but where general evidence is so strong, we should certainly be scrupulous about allow- ing them too much weight. It is represented, for instance, that the matter of the solar system could not, in any con- ceivable gaseous form, fill the space comprehended by the orbit of Uranus. If this be the case, let it be allowed as a difficulty. It is pointed out that the planets do not increase regularly in density from the outermost to the innermost. Their sizes are also not in a regular pro- gression, though the largest, generally speaking, are towards the exterior of the system. It was not, perhaps, to be expected, that such gradations should be observed ; but, grant there was some reason to look for them, their absence constitutes only another and a slight difficulty. Then we know no law to determine the particular " stages at which rings are formed and detached." Be it so— although something of the kind there doubtless is, as the distances of the planets, according to Bode's law, observe a geometrical series of which the ratio of increase is 2. From these objections, which cannot now be answered, let us pass to some which can. It has been said that a confluence of atoms towards a central point, as presumed by the nebular hypothesis, 14 EXPLANATIONS. would result, not in a rotation, but in a state of rest.* According to the North British Review—" . . . Supposing the uniformly distributed atoms to agglomerate round their ringleader, the space left blank by the slow advance of the atoms in radial lines converging to the nucleus, must be a ring bounded by concentric circles, the outermost circle being the limit of the nebulous matter not drawn to the centre of the nascent sun. Now, as all the forces which act upon the agglomerating particles, whether they pro- ceed from the circumference of the undisturbed nebulous matter, or from the gradually increasing nucleus, must have their resultants in the radial lines above mentioned, —there can be no cause whatever capable of giving a rotatory motion to the mass. It must remain at rest." Now, there can be no doubt that a confluence proceed- ing precisely to a centre, has this result; but this is only an abstract truth, not an exact and absolute description of any actual confluence of the kind. The explanation was afforded by Professor Nichol, long before the objection was started, and it could not be given in better language on the present occasion : " When we reflect on the solar nebula in the act of condensing, it appears that the act consists in a flow or rush of the nebulous matter from all sides towards a central region; which is virtually equivalent, in a mechanical point of view, to what we witness so frequently, both on a small and large scale—the meeting and inter- mingling of opposite gentle currents of water. Now, what do we find on occasion of such a meeting ? Herschel's keen glance lighted at once on this simple phenomenon, and drew from it the secret of one of the most fertile pro- • North British Review, No. 6. Atlas Newspaper, Aug. 30, 1845. NEBULAR HYPOTHESIS. 15 cesses of Nature ! In almost no case do streams meet and intermingle, without occasioning, where they intermingle, a dimple or whirlpool; and, in fact, it is barely possible that such a flow of matter from opposite sides could be so nicely balanced in any case, that the opposite momenta or floods would neutralize each other, and produce a condition of cen- tral rest. In this circumstance, then—in the whirlpool to be expected where the nebulous floods meet—is the obscure and simple germ of rotatory movement. The very act of the condensation of the gaseous matter as it flows towards a central district, almost necessitates the commencement of a process, which, though slow and vague at first, has, it will be found, the inherent power of reaching a perfect and definite condition . . ."* The exception presented by the satellites of Uranus to the otherwise uniform orbitual movements of the planetary bodies, is brought forward as a startling difficulty.f It is, in reality, only a trifling objection, seeing that so many other movements follow one rule, and that we may any day be able to fix upon a cause for this exception, per- fectly in harmony with all the associated facts. There was once a similar difficulty in geology—strata uppermost where they ought to have been lowermost; but it was in time cleared. Geologists found that there had been a fold- ing over of the strata, so as to reverse their proper and original positions. May we not rest in hope, that a similar exception in astronomy may find a similar solution ? I have thrown out the hint of a possible bouleversement of the whole of that planet's system : it has been scoffed at; but it is only the supposition of a greater degree of obliquity in * Views of the Architecture of the Heavens. First edition, 1837. t Edinburgh Review, No. 165, p. S4. 16 EXPLANATIONS. the inclination ot the axis of the planet to the plane of its orbit than what we find in several others. The same causes which made the inclination of the axis of Venus towards her orbit 75 degrees, may have turned that of Uranus a little further along, and so reversed the position of his poles. The admitted inclination of the axis of Uranus towards the plane of his orbit is 79 degrees, the greatest found in any of the planets. This implies only the necessity for an increase of inclination to the extent of 22 degrees, or about one-fourth of the quadrant, in order to account for the surmised reverse arrangement. Nor are causes for such a phenomenon far to seek. In the revolution of the presumed nebular mass, there would be great undulations, as I venture to say there would be found in any similar body which we might set into a similar rotatory motion. Such I esteem as the causes of the departure of the planetary axes from the vertical. A curve in the outermost portion, amounting to a fold—like the curl of a high wave—would cause the bouleversement of Uranus, and the consequent (apparent) retrogression of his satellites. It appears then, that, overlooking a few minor unex- plained difficulties, the objections to the nebular hypothesis are not formidable to it. It approaches the region of ascer- tained truths, and may reasonably be held as a strong cor- roboration of what first appears from the material laws of the universe, that the whole Uranographical arrangements were effected in the manner of natural law. It is, how- ever, altogether a mistake to regard this conclusion, as far as it is one, as equivalent to a superseding of Deity in the history of creation. It proposes nothing beyond a view of the mode in which the Divine Will has been pleased to I NEBULAR HYPOTHESIS. 17 act, in this first and most important of its works. The formation of worlds and their atrangement now appear but as steps in a Historical Progress, for matter is necessarily presumed to have existed before in a different form. By what means and under what circumstances creation, in the true sense of the word, took place,—that is, how existence was given to the matter which we suppose to have been capable of such evolutions—no one can as yet tell; we only are sure, if any trust can be placed in the laws of our minds, that it had a Cause, or an Author. Leaving such an inquiry as one, in which we have not, at present, ground for a single step, it is surely a great gratification that we can at least trace the operations of the Great First Cause, from a condition of matter anterior to its present forms, and learn with certainty that these operations were in no way arbitrary or capricious, that they were not single and de- tached phenomena, but the result of principles flowing from the Eternal and Immutable, and which prevailed over all the realms of Infinity at once. We have fixed mechanical laws at one end of the sys- tem of nature. If we turn to the mind and morals of man, we find that we have equally fixed laws at the other. The human being, a mystery considered as an individual, becomes a simple natural phenomenon when taken in the mass, for a regularity is observed in every peculiarity of our constitution and every form of thought and deed of which we are capable, when we only extend our view over a sufficiently wide range. It is to M. Quetelet, of Brussels, that we are indebted for the first satisfactory ex- plication of this great truth: it is presented in his well- known and very able treatise, Sur L'Homme, et le Deve- 18 EXPLANATIONS. loppement de ses Facultes. He first shows the regularity which presides over the births and deaths of a community, liable to be affected in some degree by accidental circum- stances, but fixed again when these are uniform. He then makes it clear that the stature, weight, strength, and other physical peculiarities of men are likewise regulated by fixed principles of nature. Afterwards, the moral quali- ties,—the impulses of all our various sentiments and pas- sions,—even the tendency to yield to those temptations which give birth to crime,—are proved to be of no less determinate character, however impossible it may be to predict the conduct of any single person. These are doc- trines not to be resisted by inconsiderate prejudices. They rest on the most powerful of all evidence, that of numbers. If they appear to take from the personal responsibility of individuals, it is merely an appearance, for the doctrine immediately steps forward to show that laws, education, and moral influences of every kind exercise an equally determinate control over men ; so that the need for their being called into use becomes even more palpable than before. We are not, however, required at this moment to argue respecting the bearing which this doctrine may have upon human interests. What we are at present concerned with is the simple fact, that Morals—that part of the sys- tem of things which seemed least under natural regulation or law—is as thoroughly ascertained to be wholly so, as the arrangements of the heavenly bodies. Now we have here two most remarkable truths. The wondrous masses which people the Mighty Void are under the control of natural law. The workings of the little world of the human mind—the opposite extreme of the system—are under law likewise. We have thus the cha- NEBULAR HYPOTHESIS. 19 racter of the limits of the system fixed. So far we proceed upon solid ground. Now it has been seen that phenomena precisely the same as the formation and arrangement of worlds take place daily before our eyes, under the influ- ence of the laws of matter, showing that the whole cosmo- gony might have been effected—proving, indeed, that it roas effected—by the Divine will acting in that manner. Having attained this point, we are called upon to remem- ber the many appearances of unity in nature ; how, when we take a sufficiently wide view, there is nothing discre- pant and exceptive in it; how a noble and affecting sim- plicity breathes from it in every part. So reflecting, we ask, " Can it be that, as the first and the last parts of the system are under law, and the first (this being also the greatest) was manifestly created in that manner, so the whole is under law, and has been produced in that man- ner ?" It is at the moment when we have arrived at this question, that the origin of the organic world becomes a point of importance. The sceptic of science steps in, and says, " No; the idea of an entire system under law, and produced by it, here breaks down, for who can pretend to penetrate the mysteries of vitality and organization ? and who can say that species have had other than a miraculous origin?" The tone in which this objection is usually made seems to me inappropriate, considering that the ob- jectors stand on a mere fragment of nature, and one which the discoveries of science are every day lessening. It is but in a nook, to which light has not yet penetrated, that the opponents of the theory of universal order take refuge. On coming to the consideration of the question, I am at the very first struck by the great d priori unlikelihood that there can have been two modes of Divine working in the 20 EXPLANATIONS. history of nature—namely, a system of fixed order or law in the formation of globes, and a system in any degree dif- ferent in the peopling of these globes with plants and animals. Laws govern both : we are left no room to doubt that laws were the immediate means of making the first; is it to be readily admitted that laws did not preside at the creation of the second also, particularly when we find that laws equally at this moment govern and sustain both ? Most undoubtedly, it would require very powerful evidence to justify such an admission. And, on the other hand, it would require very decisive counter-evidence to forbid the conclusion that the organic creation originated in law. How actually stands the evidence on either side ? Simply thus : that no actual evidence has ever yet been offered to prove that the Divine will acted otherwise than in the usual natural order in the organic creation ; while, on the other hand, geology and physiology exhibit lively vestiges or traces of that mode having actually been followed. On this narrow ground, it appears, is the great question to be de- bated. If the opponents of the hypothesis of an organic creation by law can bring, from these or any other sciences, facts which appear as powerful objections to any such con- clusion, then it must, at the very least, be held in suspense. If, again, the other party can show these sciences as pre- senting far more argument for a law creation of organisms than against it, the hypothesis must be admitted to have the advantage. I have so presented these sciences; the evidence has been disputed, and some obscure points have been largely insisted upon in objection. It is now my duty to enter into the consideration of these objections, and see if they are really of the importance which has been attri- buted to them. GEOLOGY. 21 Fifty years ago, science possessed no facts regarding the origin of organic creatures upon earth ; as far as know- ledge acquired through the ordinary means was concerned, all was a blank antecedent to the first chapters of what we usually call ancient history. Within that time, by re- searches in the crust of the earth, we have obtained a bold outline of the history of the globe, during what appears to have been a vast chronology intervening between its form- ation and the appearance of the human race upon its sur- face. It is shown, on powerful evidence, that, during this time, strata of various thickness were deposited in seas, each in succession being composed of matters worn away from the previous rocks; volcanic agency broke up the strata, and projected chains of mountains ; sea and land repeatedly changed conditions ; in short, the whole of the arrangements which we see prevailing in the earth's crust took place, and that most undoubtedly under the influ- ence of natural laws which we yet see continually operat- ing. The remains and traces of plants and animals found in the succession of strata, show that, while these opera- tions were going on, the earth gradually became the thea- tre of organic being, simple forms appearing first, and more complicated afterwards. A time when there was no life is first seen. We then see life begin, and go on; but whole ages elapsed before man came to crown the work of nature. This is a wonderful revelation to have come upon the men of our time, and one which the philosophers of the days of Newton could never have expected to be vouchsafed. The great fact established by it is, that the organic creation, as we now see it, was not-placed upon the earth at once ;—it observed a progress. Now we can imagine the Deity calling a young plant or animal into ex- 22 EXPLANATIONS. istence instantaneously ; but we see that he does not Usu- ally do so. The young plant and also the young animal go through a series of conditions, advancing them from a mere germ to the fully developed repetition of the respec- tive parental forms. So, also, we can imagine Divine power evoking a whole creation into being by one word ; but we find that such had not been his mode of working in that instance, for geology fully proves that organic cre- ation passed through a series of stages before the highest vegetable and animal forms appeared. Here we have the first hint of organic creation having arisen in the manner of natural order. The analogy does not prove identity of causes, but it surely points very broadly to natural order or law having been the mode of procedure in both instan- ces. But the question is, Does geology really show such a progress of being ? This has been denied in some quar- ters, and particularly in the elaborate criticism upon the Vestiges, which appeared in the Edinburgh Review* In reality, the whole of the geologists admit that we have first the remains of invertebrated animals ; then with these, fish, being the lowest of the vertebrated ; next, reptiles and birds, which occupy higher grades; and, finally, along with the rest, mammifers, the highest of all; and yet con- troversialists will be found gravely telling their readers, " It is not true that only the lowest forms of animal life are found in the lowest fossil bands, and that the more com- plicated structures are gradually developed among the higher bands, in what we might call a natural ascending scale ;"■]- the pretext for giving this unqualified contradic * July, 1845. t " Edinburgh Review." LOWER SILURIAN FOSSILS. 23 tion to the above grand fact being, that when we take the special groups of animals, as the invertebrata, the fishes, the reptiles, &c, there are some real or apparent grounds for denying that the low forms of these groups came before the higher. The fallacy consists in sinking the great broad palpable facts of the case, about which not the least doubt anywhere exists, and giving prominence to certain facts of far inferior magnitude, and comparatively obscure, but in whose obscurity there is a possibility of creating a kind of diversion. I trust to be able to show that, even in the special groups of fossils, there is no real obstacle to the theory of a gradual natural development of life upon our planet. The view which the Edinburgh critic gives of the ear- liest stratified rocks is much the same as my own account of them. There is a Hypozoic formation, or series, devoid of remains of plants and animals ; then a formation (Lower Silurian) called in my early editions, The Clay-slate and Grawacke system, in which we find " no animals of the higher classes, with a regular skeleton and a backbone ;" only corals, encrinil.es, crustaceans, and mollusks. "Ve- getable appearances," he says, " do not appear among the British rocks ; but there must have been a mass of vegeta- ble life in the ancient sea, as no fauna can appear without a flora to uphold it." This last inference is of little imme- diate consequence ; but I may remark, that it coincides with one which I ventured to make, prompted thereto by some of the recent papers of Mr. Murchison. We here see it sanctioned by a writer who is understood to be a distinguished investigator of the lowest fossiliferous beds. It is from no wish to amuse the reader, but merely as a pleading in behalf of several of the alleged geological mis 24 EXPLANATIONS. statements in my book, that I bring forward another dis- tinguished reviewer of the Vestiges of Creation, (North British Review, No. 6), taxing me with having been driven to make this very surmise as an escape from a difficulty ! More than this: the North British Reviewer is at odds with his Edinburgh brother, in bringing bones and teeth of fish into the first fossiliferous formation ; grounding the statement upon Sir Henry de la Beche's Manual, pub- lished about eleven years ago, and contrasting with it, in a foot-note, my remark, " Neither fishes nor any higher ver- tebrata as yet roamed through the marine wilds." The fact is, that this last critic—understood to be a very eminent philosophical writer—was not aware, that since the publi- cation of De la Beche's Manual, the lower fossiliferous rocks had been divided into several distinct formations, in the lowest of which, it is fully admitted, there are no vertebrata. More than this still: a body called the Literary and Philo- sophical Society of Liverpool had brought before them (January, 1845) a set of letters which one of their mem- bers had drawn, with reference to my book, from several of the chief geologists of the day. We there find Mr. Lyell stating upon hearsay, that I represented fish begin- ning in the coal, and Mr. Murchison speaking of me as beginning with zoophytes and polypiaria alone ; statements, I need hardly say, conveying the most erroneous impres- sions regarding the book. This, however, is not the im- mediate point. The two gentlemen here named will be allowed to stand in the very first rank as geologists. They are able men, of marvellous industry, and unimpeached zeal for science. These men, nevertheless, in the corres- pondence to which I am pointing, give entirely opposite views of the first fossiliferous formation. Mr. Murchison LOWER SILURIAN FOSSILS. 25 says, '• No trace of a vertebrated animal has been found in the lower Silurian rocks." Mr. Lyell says, " The fact that, with the earliest type of organization, we meet with vertebrated animals, true fish, so far from being explained away since I affirmed it in my book, is confirmed and ex- tended by fresh evidence." The very latest affirmation we have on this point from Mr. Murchison—an affirmation made after examining Silurian rocks in Russia, where they are presented in vast extent—contains these words : " The absence of even the lowest of the vertebrata in the inferior Silurian rocks,—an absence which is total, so far as can be inferred from the researches of geologists in all parts of the world,—gives them a true Protozoic character."* These extracts speak for themselves. The only thing calling for further remark, is the surprising circumstance of this correspondence having been brought before a learned society, as wholly and nothing else but a condemnation of the Vestiges /f A leading objection, with regard to the first fossiliferous formation (Lower Silurian) is, that it does not solely pre- sent animals of the lowest sub-kingdom, as corals and encrinites, but also examples of the two next higher sub- kingdoms, the articulata and mollusca, some of the latter being of the highest order, the cephalopods. The latter particular is what is chiefly insisted upon. At the time when I wrote, it was understood that the highest orders of mollusca were not found in the first fos- * Abstract of a paper by Mr. Murchison, Report of British As- sociation of 1844, page 54. t See Examination of the theory contained in Vestiges of the Natural History of Creation. By the Rev. A. Hume. Liverpool, Whitby, 1S45. 8 26 EXPLANATIONS. siliferous rocxs. Professor Phillips, in 1839 (Treaiise on Geology), said, expressly, with regard to what was then called the Clay-slate and Grawacke system, " No gastero- pods or cephalopods are as yet mentioned in these rocks in Britain; and we do not feel sufficiently acquainted with the geological age of the limestones of the Hartz, to intro- duce any of the fossils of that argillaceous range of mountains." So much as a justification of the view given of the Clay-slate fossils in my first edition. Since then, this formation, as it exists in England, has been found to contain gasteropods and cephalopods, though not of such high forms as afterwards appeared. I might here repeat what was remarked in the later editions of the Vestiges, " Even though the cephalopoda could be shown as per- vading all the lowest fossiliferous strata, what more would the fact denote than that, in the first seas capable of con- taining any kind of animal life, the creative energy ad- vanced it, in the space of one formation (no one can tell how long a time this might be), to the highest forms possi- ble in that element, excepting such as were of vertebrate structure." 1 might add, that this was no great advance in comparison with the whole line of the animal kingdom, if we may take, as a criterion on this point, the analogous progress of an embryo of the highest animals, as the por- tion of that progress representing the organization of the intervebrated animals is only the first month. I might here also revert to the book for some views with respect to the space required for such a development. According to the plan of animated nature, to which I have made approaches in the later editions, we have not to account for the deve- lopment of one long line, but of many comparatively short ones. And, as I have also remarked, there is a rapidity LOWER SILURIAN FOSSILS. 27 of generation amongst the lower animals which may well suggest something like that " rush of life," which, if we were to judge from British strata alone, would seem to have taken place in the early seas. But, fortunately, none of these speculative answers to the objection are required ; for the question first arises, Does the lowest band of the English Lower Silurians indicate, beyond all question, the point of time at which animal life commenced upon our planet ? Are we quite sure that cephalopoda were among the first of all earth's living creatures ? Far from it. It has only been ascertained that certain comparatively small cephalopods are found as far down as any other animals of inferior organization at certain spots in Wales and Cumberland. When we remember that, in modern seas, certain kinds of such animals haunt special places suita- ble for their subsistence—that we may have Crustacea and mollusks exclusively at one place, and radiata (as corals and zoophytes) at some other, not perhaps far distant, but different with respect to depth or some other circumstance —we can conceive that cephalopods may occur in the first fossil bands in the places which have been examined in England, and yet remains of inferior animals may be found by themselves on the same or a lower level in some as yet unexplored place not far off; so that a time-interval may there appear to allow for a progressive development. Such seems but a reasonably cautious surmise, when we are told by a high authority, that there are " detached Silurian districts in England, presenting particular changes and modifications, arising from difference of depth, and the variety of currents, and chemical combinations in the seas in which they were formed;" and that, " in conse- quence of this variety of physical condition, there is a cor- 28 EXPLANATIONS. responding diversity in the traces of organic life in each situation."* What, however, places the matter beyond doubt is, that in North America, where the early stratified rocks are even more amply developed than with us, the highest invertebrated forms do not appear at the first. In the earliest ascertained fossiliferous strata, the Potsdam Sandstone, the only fossils are lingula (a brachiopodous mollusk) and fucoids. In the next, the Calciferous Sand- rock, are fucoidal layers, encrinital beds, and the brachio- pods, orthis, lingula, and bellerophon, together with ortho- cerata, these being the first examples of the cephalopoda. And in all these cases, the fossils are few and obscure; they comprise no Crustacea. It is not till we ascend to a fourth fossiliferous series, Trenton Limestone, that fossils become abundant, or that trilobites appear. Perhaps even this is not the most decisively adverse view which could be derived from the American fossils, for lately there have been found, in the Green Mountains of Vermont, strata which, from their metamorphic character, are believed by some native geologists to be inferior and of course anterior to the Silurians, and these contain traces of fucoids and of vermiform bodies called Nereites, the last being an humble form of articulata. If this be true, it would at least add materially to the grounds for hesitation before pronouncing definitely, as the Edinburgh reviewer has done, on the commencement of fossiliferous strata and the nature of the first fossils. Here we must also remember, that in rocks of the elder continent anterior to the Silurians, there are limestones, held by many to be an indication of organic * Profesaor Phillips, British Association, 1845. Athenaeum's Report. LOWER SILURIAN FOSSILS. 29 life at the places where they are found: the chemical ex- periments of Braconnot upon masses of these earlier rocks gave ammoniacal and combustible products, likewise indi- cative of the presence of organic matter: in the same sub-silurian region, " fragments, apparently organic, and resembling cases of infusoria," have been detected,* and in Bohemia actual fossils have been announced. Even dubious traces of life in sub-silurian rocks must be admit- ted to be of importance, when we consider that they have mostly been subjected to such a degree of heat as could not fail to obliterate organic memorials, seeing that it has even changed the texture of the rocks themselves. From what Mr. Lyell saw of the Silurian rocks in America, he finds himself called upon, in the most emphatic manner, to warn geologists against " the hasty assumption, that in any of these sections we have positively arrived at the lowest stratum containing organic remains in the crust of the earth, or have discovered the first living beings which were embed- ded in sediment." "A geologist," he says, " whose observations had been confined to Switzerland, might imagine that the coal mea- sures were the most ancient of the fossiliferous series. When he extended his investigations to Scotland, he might modify his views so far as to suppose that the Old Red Sandstone marked the beginning of the rocks charged with organic remains. He might, indeed, after a search of many years, admit that here and there some few and faint traces of fossils had been found in still older slates, in Scotland ; but he might naturally conclude, that all pre-existing fossiliferous formations must be very insignifi- * Ansted's Geology, ii., 60. 30 EXPLANATIONS. cant, since no pebbles containing organic remains have yet been detected in the conglomerates of the Old Red Sandstone. Great would be the surprise of such a theo- rist, when he learnt that in other parts of Europe, and still more particularly in North America, a great succession of antecedent strata had been discovered, capable, accord- ing to some of the ablest paleontologists, of constituting no less than three independent groups, each of them as important as the ' Old Red' or Devonian system, and as distinguishable from each other by their organic remains. Yet it would be consistent with methods of generalizing not uncommon on such subjects, if he still took for granted that in the lowest of these ' Transition' or Silurian rocks, he had at length arrived at the much-wished-for termina- tion of the fossiliferous series, and that nature had begun her work precisely at the point where his retrospect hap- pened then to terminate."* It is exactly to such theorizers as the Edinburgh re- viewer that his rebuke is applicable. When he asserts the contemporaneousness of the highest mollusks with the origin of organic life, he says—" We are describing phe- nomena that we have seen. We have spent years of active life among these ancient strata—looking for (and we might say longing for) some arrangement of the ancient fossils which might fall in with our preconceived notions of a natural ascending scale. But we looked in vain, and we were w eak enough to bow to nature." The weakness consisted in looking only in one little portion of the earth, and believing it to be a criterion for all the rest. This writer seems yet to have to learn that knowledge is to be * Travels in North America, ii., 131. LOWER SILURIAN FOSSILS. 31 acquired b)r communication as well as examination. Were a philosopher (supposing there could be such a being) to limit his view of mankind to juvenile schools, he might with equal rationality deny that there is any such thing in the world as infants in arms. " We speak of what we have seen," he might say, " and, finding no specimens of humanity under three feet high, we are weak enough to bow to nature and believe that babes are a mere fancy." Even taking the English Lower Silurians as he and others would have them taken, it still appears that these rocks denote, generally, a low state of the animal kingdom. It is customary for those who take opposite views, to speak of the creatures of this period as high—" highly-organized Crustacea and mollusca " is the usual phrase. Some, in- cluding the Upper Silurians in their view, tell us that the first formation presents examples of the whole of the great divisions, the fish being held as representing the vertebrata. Of course, this is only done through ignorance, or for the purpose of deceiving. Where particulars are overlooked, it is still customary to speak of the earliest fauna as one of an elevated kind. When rigidly examined, it is not found to be so. In the first place, it contains no fish. There were seas supporting crustacean and molluscan life, but utterly devoid of a class of tenants who seem able to live in every example of that element which supports meaner creatures. This single fact, that only invertebrated ani- mals now lived, is surely, in itself, a strong proof that, in the course of nature, time was necessary for the creation of the superior creatures. And, if so, it undoubtedly is a powerful evidence of such a theory of development as that which I have presented. If not so, let me hear any equally plausible reason for the great and amazing fact that seas 32 EXPLANATIONS. were for numberless ages destitute of fish. I fix my op- ponents down to the consideration of this fact, so that no diversion respecting high mollusks shall avail them. But this is not all. The Silurian is an age, as were several subsequent ones, of only marine animals. It is now in- contestable, from a few land-plants found in the Silurians of America, and a fern leaf in our own, that there was dry land : yet no trace of a land animal appears for ages after- wards. Moreover, though we have now a pretty full de- velopment of the first sub-kingdom, Radiata, we have but an imperfect one of the two next—namely, the Articulata and Mollusca. Not to speak of the utter absence of fresh- water and land mollusks, and of such land articulata as in- sects and spiders, we do not find any decapedous Crustacea (crabs, &c), though these could have lived wherever other mollusks and Crustacea could. In fact, it is 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 an humble exhibition of the animal kingdom as we might expect, upon the development theory, to find at an early stage of the history of organ- ization.* * Objectors to the development theory have, in the eagerness of counter-theorizing, committed themselves on the subject of the Silurian fossils, in a way which they will yet feel to be extremely awkward. The North British Review we have seen placing even fishes in the first fossiliferous rocks, grounding this statement upon an authority which has been antiquated for fully eight years—avast UPPER SILURIAN FOSSILS. 33 We now come to the Upper Silurians, where new spe- cies of invertebrated animals appear, besides a few obscure fishes. There is no appearance, according to the Edin- burgh reviewer, of a transition from the former species to the present—but does he know the signs by which such a transition could be detected ? I am aware of none. He says the new species are sharply defined—that is, strongly distinct; and so they may be, without any prejudice to the transmutation theory—as far, at least, as I understand it. And here he remarks that there are the same difficulties in the way of this theory, " both in the grouping of each separate system, and in the passage from one system to another ; and that is true, whatever part of the ascending geological series we choose to take between the lowest formations and the highest." As he does not state the nature of the difficulties, I cannot undertake to say what period in the history of geology. The British Quarterly Review is equally unfortunate. " The Author's theory," says this writer, " requires that these animals should be the lowest in the scale. But no argument can convert a fish, with its back-bone, and highly- developed nervous and muscular systems, into an animal of low organization." (!) The dogmatic allegations of the Edinburgh re- viewer on this point are sufficiently exposed in the text. I have only further to express my surprise at finding Dr. Whewell par- ticipating in the mere ignorance of the first two of the above-men- tioned journals. In the preface to a volume which he has recently published, under the title of Indications of the Creator, he meets my arguments with a crude and incorrect view of the fossil history, commencing with this sentence—" Vertebrate animals do exist in the Silurian rocks, from which the asserted law [that of develop- ment] excludes them." The existence of a non-pisciferous form- ation had been unknown to him. Many of the objections made to the development theory, in obscurer quarters, rest on errors of a similar kind. 3* 34 EXPLANATIONS. argument or what reconstruction of my system may be necessary to meet them. Till we are more clear, how- ever, regarding the actual affinities of animals, I would suppose that any judgment as to difficulties in their group- ing in geological formations, or succession in different formations, might well be given somewhat less dogma- tically than they are by this writer. The few fish-remains of the Upper Silurians may be asssociated with the ample development of this class in the next (Devonian or Old Red Sandstone) system. They belong to Agassiz's two orders of placoids (these by them- selves in the Upper Silurians) and ganoids, the former of which are represented by our sharks and rays, the latter by the bony pike of America and the polypterus of the Nile. Such are the only fishes found till we come up to the chalk formation, when the now predominant orders of cycloids and ctenoids begin.* The Edinburgh reviewer makes a strong point of the placoid and ganoid orders, as unfavorable to the progressive theory. " Taking into ac- * The North British Review presents, as a strong objection that, " several new ctenoids, which had been found only in the carboni- ferous system, have been discovered among the fishes brought by Mr. Murchison from the Old Red Sandstone of Russia. Resolved to make out his position, the author asserts," &c. This is an un- lucky venture in opposition. The critic evidently meant it to have a very damaging effect, in consideration that the ctenoids are osseous fishes. The fact is, that the fishes brought home by Mr. Murchison are not of the ctenoid order, but belong to a placoidan family called Ctenodus. The mistakes made by this writer, in the geological part of his paper, are of a very grave kind, yet only such as many men of scientific eminence may be expected to make when they venture out of their own peculiar department, and rashly under- estimate the strength of the arguments to which they are opposed FOSSILS OF OLD RED SANDSTONE. 35 count," he says, " the brain, and the whole nervous, cir- culating, and generative system, the placoids stand at the highest point of a natural ascending scale, and the ganoids are also very highly organized." Of certain families of the first order, found in the Old Red Sandstone of Russia, he says, " Let the reader bear in mind that these fishes are among the very highest types of their class, and that we can reason upon them with certainty, because some of them belong to families now living in our seas." He in- stances a crestaceon—a high kind of placoid—recently found in the Wenlock limestone, a low portion of the Upper Silurians, and therefore near the beginning offish. Some of the ganoids, also, of the Old Red Sandstone make an approach to a higher class—reptilia. Besides the usual row of fish-teeth, they have an inner range, in which we see the form of those organs among the sauria. It appears, in short, according to this writer, that the farther back we go among the fishes, we find them possessed of the higher characters. Of the real character of all this hardy as- sertion I shall enable the reader to judge. The fishes of this early age, and of all other ages previous to the chalk, are for the most part cartilaginous. The cartilaginous fishes—Chondropterigii of Cuvier—are placed by that naturalist as a second series in his descending scale; be- ing, however, he says, " in some measure parallel to the first." How far this is different from their being the highest types of the fish class, need not be largely insisted on. Linnaeus, again, was so impressed by the low charac- ters of many of this order, that he actually ranked them with the worms.* Some of the cartilaginous fishes, never- * Dr. Fletcher places the Chondropterigii lowest in a scale which 36 EXPLANATIONS. theless, haye certain peculiar features of organization, chiefly connected with reproduction, in which they excel other fish; but such features are partly partaken of by families in inferior sub-kingdoms, showing that they cannot truly be regarded as marks of grade in their own class. When we look to the great fundamental characters, par- ticularly to the framework for the attachment of the mus- cles, what do we find ?—why, that of these placoids— " the highest types of their class !"—it is barely possible to establish their being vertebrata at all, the back-bone having generally been too slight for preservation, although the vertebral columns of later fossil-fishes are as entire as those of any other animals. In many of them, traces can be observed of the muscles having been attached to the external plates, strikingly indicating their low grade as vertebrate animals. The Edinburgh reviewer's " highest types of their class " are, in reality, a separate series of that class,—generally inferior, taking the leading features of organization of structure as a criterion,—but, when details of organization are regarded, stretching further both downward and upward than the other series ; so that, looking at one extremity, we are as much entitled to call them the lowest, as the reviewer, looking at another ex- tremity, is to call them the highest of iheir class. Of the general inferiority, there can be no room for doubt. Their cartilaginous structure is, in the first place, analogous to the embryotic state of vertebrated animals in general.* takes as its criterion " an increase in the number and extent of the manifestations of life, or of the relations which an organized being bears to the external world." * Cartilage, " in many animals, forms the entire structure, and in the early state of the human embryo it does the same."—Carpen- ter's General Physiology, p. 37. FOSSILS OF OLD RED SANDSTONE. 37 The maxillary and intermaxillary bones are in them rudi- mental. Their tails are finned on the under side only, an admitted feature of the salmon in an embryotic stage; and the mouth is placed on the under side of the head, also a mean and embryotic feature of structure. These charac- ters are essential and important, whatever the Edinburgh reviewer may say to the contrary ; they are the characters, which, above all, 1 am chiefly concerned in looking to, for they are features of embryotic progress, and embryotic progress is the grand key to the theory of development. I therefore throw back to my reviewer the charge that I have " clung to feeble analogies," and " kept out of view the broad and speaking facts of nature." With regard to the alleged falsity of the crustacean character of some of these fishes, and the discredit of re- peating the blunders and guesses made by the first obser- vers, before any good evidence was before them, I can only say, that at the time when my book was written, geologists and inquirers into fossil ichthyology of the high- est character were writing, publicly and privately, of the cephalaspis and coccosteus, as apparently links between the Crustacea and fish, the vertical mouth of the latter ani- mal being particularly cited, as a feature indicating the intermediate character. In what the reviewer calls " the excellent work of our meritorious self-taught countryman," Mr. Hugh Miller, published in 1841, the apparently crus- tacean character of these fishes is repeatedly referred to.* * Mr. Miller calls upon his readers to " mark the form of the cephalaspis, or buckler-head, a fish of the formation over that in which the remains of the trilobite most abound. He will find," ho says, " the fish and crustacean are wonderfully alike: the fish is more elongated, but both possess the crescent-shaped head, and 38 EXPLANATIONS. Not having access at the time to the work of Agassiz, I deemed myself safe in trusting to the report of this indus- trious inquirer and ingenious writer, whose volume was then newly published. How recent the contradiction of the once-supposed affinity may be, or what faith to place in it, I know not; but the reader will probably hold one who only pretends, in this instance, to the character of a general writer, excused, when he shows so distinguished an expositor of physiology as Dr. Carpenter, still more recently countenancing the idea :—" The bodies of fishes," says he, " are usually covered with scales or plates, which have sometimes a bony hardness, and which, in some species of fish that do not now exist alive, appear to have been of the density of enamel. Thus we have a sort of transition to the external skeletons of the invertebrated ani- mals ; and in this class, also, we not infrequently find the internal skeleton so deficient in the stony matter from which bone derives its hardness, that it seems like cartilage or gristle ; and in a few of the lowest species, we do not even find a distinct vertebral column ; so that the change of character from the vertebrated to the invertebrated series is a gradual, and not an abrupt one, and would probably be found still more gradual, if we were acquainted, not only with all the forms of animal life which now exist, but also those which have existed in ages long gone by, and are now extinct." ooth the angular and apparently jointed body. They illustrate ad- mirably how two distinct orders may meet. They exhibit the joints, if I may so speak, at which the plated fish is linked to the shelled crustacean. Now, the coccosteus is a stage further on ; it is more unequivocally a fish ; it is a cephalaspis, with a scale-covered tail attached to the angular body, and the horns of the crescent- ehaped head cut off."—Old Red Sandstone, p. 54. FOSSILS OF OLD RED SANDSTONE. 39 The above argument relates to the general fact of the first fishes being placoidean. It is necessary, also, to meet the inquiry why there should be no fossil remains indicat- ing a transition from the lower animals to fish. The re- viewer speaks of a recently discovered cestraceon below ariy other fish-beds in England. " Such," he exclaims, " are nature's first abortive efforts." " We entreat," he adds, " any good naturalist well to consider such facts as these, and tell us whether they do not utterly demolish every attempt to derive such organic structures from any inferior class of animal life found in the older strata ? " Now, I cannot tell what good naturalists may say in answer to this appeal; but I feel, for my own part, that • the facts in question—as far as they can be admitted to be so—have no such destructive effect. In the first place, the cestraceon is only one of those cartilagines, the real character of which had just been ex- plained. It is not the lowest of its order, but neither is it the highest. So far from this being the case, the respira- tion of the whole family (Selacii, Cuv.; Plagiostomi, Desm.) to which it belongs, and which also includes sharks, is performed in a manner which approximates these fishes to the worms and insects—namely, " by numerous vesicles called internal gills, the entrance to which is from their gullet, while the exit is in general by corresponding aper- tures on the side of their neck ; " * other fishes having free gills, marking a higher organization. The sub-divided form of the stomach—the absence of that concentration, which is, perhaps, the most emphatic mark of animal ad- vancement—belongs to this family alone amongst fishes, * Fletcher's Physiology. Part L, p. 20. 40 EXPLANATIONS. as it does to the lowest families of several of the higher orders of the vertebrata. Thus, the cestraceon is, on many considerations, a low fish, though certainly possessing some traits of superior character, and not the lowest of its order. In the second place, I would protest against any inference unfavorable to the hypothesis of development being drawn from a discovery so new, so isolated, and in a branch of inquiry so extremely unsettled. At no time during the last ten years, have we had, for a twelvemonth at once, stable views respecting the initiation of fishes. Lately— so lately that part of my book was written at the time—the lowest were understood to be some of a minute size, imme- diately over the Aymestry limestone, in the Upper Silu- rians.* Now, we have a cestraceon announced to us at a lower point in that formation. But how far it is likely that our information is to rest at this point the reader may judge, when he hears of M. Agassiz announcing, within the last few months, that, though acquainted with seven- teen hundred species of fossil fishes, he regards the history of the class as so far from complete, that the number of species successively entombed in the crust of the globe might be estimated at thirty thousand, without any chance of approaching the truth ! j" If such be the case, we may surely expect to hear of other fishes prior to or contempo- rary with the cestraceon, showing that, humble as that * " The minute and curious fishes in the uppermost bed of the Ludlow rock, are the earliest precursors of many singular ichthy- olites which succeed in that enormous formation, the Old Red Sandstone."—Murchison's Address to the Geological Society, February, 1842. t Review of Professor Pictet's Traite Elementaire de Palaeonto- logie, translated in Jameson's Journal from the Bibliotheque Uni- verselle de Geneve, No. 112, 184*5. FOSSILS OF OLD RED SANDSTONE. 41 animal was, it is not to be regarded as the initial of its slass.* But even although simpler fishes be not found in lower or contemporary strata, this may only be owing, like the non-discovery of vegetation in the early rocks, to the unsuitableness of these fishes for being preserved. Sup- posing the inferior tribes, petromyzonidse (lampreys) to have been then in existence, we should have no trace of them preserved, because of their osteological structure be- ing slight, and their wanting those teeth and spines which form, after all, the chief memorials of the higher families of their own order. One word more as to these fishes. The critic says (p. 33), it is shown to demonstration in the Poissons Fossiles of Agassiz, that " the sauroids, in their general osseous structure, and in the development of their nobler organs, run close upon the class of reptiles." There is no doubt that the sauroid fishes partake of reptilian characters, though, perhaps, in a more external and less important way than such writers as the Edinburgh reviewer suppose ; but, be it remembered, the sauroids are not the first fishes. There is not one of them in the Silurian formation, where placoideans appear to begin. Yet I do not, for this reason, suppose that the sauroids arose from placoideans. More probably, they are part of a distinct line of development, * Such shifts are of frequent occurrence in geology. Insects, formerly found first in the oolitic formation, are now taken back to the carboniferous. Birds are now inferred from foot-tracks in the New Red Sandstone, their first place formerly being in the oolite. We have mammifers in the oolite, which, a few years ago, were be- lieved not to occur before the tertiary. None of these shifts, how- ever, in the least interfere with the general fact of the advance from the lower to the higher classes of animals. 42 EXPLANATIONS. which had inferior forms in its first stages, also of too slight a structure to be preserved. Following this reviewer into his discussion of the Car- boniferous System, we find him commencing with a taunt, that there are now traces of land vegetation in earlier formations. This is, in reality, a point of no importance for the development theory. The question is, with what kind of plants did land vegetation begin ? The anxiety of the reviewer to force a verdict in his favor is here strongly shown. " What," he says, " are these first fruits of na- ture's vegetable germs ? Are they rude, ill-fashioned forms ? Far otherwise. We find among them palms and tree-ferns, &c." In this passage, which substantially con- veys the same information as my book, there is an evident design of inducing the belief, that the first land vegetation was of a high character. The rigid truth is, that though this was a "grand " in the sense of a luxuriant vegetation, it was composed, as far as positive evidence goes, almost wholly of plants which stand low in the scale of organiza- tion. The ascertained dicotyledons (plants having double- lobed seeds and an exterior growth) are extremely rare. On this point, I cannot do better than quote the laborious young Professor of King's College—" The plants which have hitherto been described [in the carboniferous form- ation], belong either to the acotyledonous class, as the ferns, or to the monocotyledons, and, on the whole, they constitute the simplest forms of vegetation ; but there have also been met with among coal plants, unquestionable evidences of dicotyledonous structure, and a genus has been formed under the name of Pinites, to include a number of specimens of fossil wood, &c"* To the un- * Ansted's Geology, 1844. FOSSILS OF CARBONIFEROUS FORMATION. 43 doubted evidence of Mr. Ansted, may be added that of his more eminent contemporary, Mr. Lyell, whose sense of the botanical character of this age is such that he emphatically calls it the Age of Ferns.* It is evident, then, taking the landscape of this era as the first, that it is of a nature to harmonize with the development the- ory, for its chief forms are humble, and only a few are of higher grade, most of these, too, being of an interme- diate character between the low and the high. I am re- minded, however, in other quarters, of certain experiments of Dr. Lindley, showing that the plants chiefly found in the coal are of thei*kinds which best resist decomposition in water; whence it is inferred that many trees of a high class may have existed at that time, but perished in the sea, while weaker vegetation survived. This evidence would be negative at the best; and it says as much for the non-preservation of mosses and other humble plants as for dicotyledons. It has also been remarked that, considering such facts as the disappearance of equisetum hyemale in water, a plant containing an unusual quantity of silex, " the proportion of fossil plants in each formation must de- pend on other circumstances besides their power of resist- ing decomposition."f " Too much importance has," in the opinion of the author of this observation, " been attached to Dr. Lindley's experiments." The British Quarterly Review says—" The author ad- mits there were dicotyledons among these plants, and does not see that, however few they may be, it entirely upsets * Travels in North America, ii., 52. t Mr. C. J. Bunbury, at the British Association, 1845 ; Athenae- um's Report. 44 EXPLANATIONS. the theory of progressive advance, especially in the ab- sence of any proof as to whether they were created first or last." This proceeds, as do many similar objections, upon the idea that a formation represents one point in time. A formation, in reality, represents many years, or rather ages. Such expressions as that simple and complex plants occur together in the carboniferous formation, or even (shall we say) in its first fossil bands, are vague ex- pressions, perhaps conveying an idea substantially false. There is no such precision in the ascertained relations of fossils to particular strata, as to entitle any one to say that the simple and complex plants of this*£>rmation are rigidly contemporaneous. They may have followed each other within the space of half a century in a particular region, and yet been preserved in but one stratum, or little group of strata. The actual appearances of the carboniferous form- ation thus, perhaps, allow full time for a progressive ad- vance in particular regions, from the fleshy luxuriant plants of the marsh and low sea margin, to the robust tree of the more elevated regions. We must remember, too, that the vegetation of the carbonigenous era, even if we take it back to include the confer said to have lately been found in the Old Red of Cromarty, or the fern leaf of the Silurians, was preceded by unequivocally simple plants in the fucoids. Starting with these, and finding the first great burst of land vegetation composed mainly of low cryptoga- mic and monocotyledonous plants,—finding, moreover, the exceptions chiefly of the intermediate character, and that the dicotyledons increase afterwards while the others de- cline,—we cannot well resist the conclusion, that we see the traces of a progress in the history of this kingdom of nature. It may be less clear than we could wish ; but FOSSILS OF THE PERMIAN SYSTEM. 45 such light as we have certainly favors the development theory. We now come to the Magnesian Limestone deposit, lat- terly called the Permian System. At this place, the Edin- burgh reviewer introduces some general observations, which I hope he will yet acknowledge to be unjust, as I am sure the whole of his substantive charges are. " It may be true," he says, " that sea-weeds came first, but of this we have no proof." How a good geologist can have allowed himself to speak in this manner, even in eager- ness to theorise against theory, I am quite at a loss to un- derstand, for the positive facts of the occurrence of fucoids in the Lower Silurians, and of the very first traces of land vegetation in subsequent formations, are as palpable and undoubted as he himself acknowledges the precedence of fish by invertebrata to be ; nor has any one ever pretended to expect that land vegetation would be found earlier than the marine. I have here ventured no conjecture of my own, but only spoken as all the geological books teach. " Of land plants," he continues, " we have not the shadow of proof that the simpler forms came into being before the more complex." The reader has just been told upon un- doubted authority that, in the first great show of land vege- tation, taking such positive evidence as we have, the sim- ple forms are vastly more numerous than the complex. Finding that we have first ample marine vegetation, then a land vegetation in which the plants, with only a small exception, are cellular and cryptogamic, while of the ex- ception a very small number are dicotyledonous, and a con- spicuous group (the conifers) intermediate—I feel that I am entitled to say that positive evidence speaks for a pre- cedence of high but simple forms; which is what I have 46 EXPLANATIONS. done. " It is true," thus proceeds the reviewer, " that we see polypiaria, crinoidea, articulata, and mollusca; but it is not true that we meet with them in the order stated by our author." It is humiliating to have to answer an objec- tion so mean. There is no statement that the animals came in this order. I have only put the words into this arrangement, in accordance with the custom now commonly followed of observing the ascending grades of the animal kingdom. With respect, then, to what follows—" The sentence on which we here comment contains three distinct propositions, and all three are false to nature, and no better than a dream,"—I believe I may safely leave the reader to say which party is the falsifier and the dreamer. He goes on in the same strain—" It is true that the next step gives us fishes ; but it is not true that the earliest fishes link on to the radiata: this is a grand and at the present day an unpardonable blunder." This is another dream of the reviewer, for certainly such an affinity was not sug- gested in any edition of the Vestiges hitherto published. In the first four editions, which alone were under his no- tice, no passage except from the articulata was even hinted at. So much as a proof of the reviewer's recklessness in making charges ; there is no need, however, to affirm, with him, that a connexion between certain high radiates and some of the lowest fishes does not exist. I venture to pre- dict that affinities of an equally startling nature will yet be made familiar to naturalists. Meanwhile, it is enough to show that this confident critic has raised an accusation for which he has not a shadow of ground. Taking up the special fossils of the Permian system, he says, " The earliest reptiles are not of such a structure as to link themselves, on a natural scale, to the noble sauroids EARLIEST REPTILES. 47 Df the preceding carboniferous epoch." They are not the marine saurians, or fish lizards (ichthyosauri) which occur in a higher formation, but lacertilians, or animals of lizard-like character. Now what first strikes me here is the extraordinary narrowness of a mind which sees no- thing indicative of natural procedure, no hint towards great generalizations, in the simple fact of reptiles following upon fish in this grand march of life through the morning time of the world. He knows that, in every classification of the animal kingdom, reptiles rank next above fish, that in some living families there is such a convention and intermixture of both characters, that naturalists cannot agree to which class they should be assigned. He actually sees, in a general view of the earlier reptiliferous forma- tions, animals combining the fish and reptile in the most unequivocal manner. Despising, however, the great fact which shines through these obscurities, this person, and I am sorry to add, geologists generally, can only fasten upon such particulars as may be made out to be difficulties in the way of generalization. Passing to the particulars, a few land lacertilians come first, whereas the first, according to my hypothesis, ought to be marine forms, and linked to fish. He says of this difficulty, that I have stated it feebly. Perhaps it would have been well for his own credit that he had stated it somewhat less confidently ; for before his sheets had seen the light, a prospect had arisen of his affirmations on this point being thoroughly falsified. In Sillimarts Journal, for April, 1845, is an account of sand- stone surfaces pretty far down in the Carboniferous forma- tion of Pennsylvania, marked with the vestiges of terrestrial animals. Setting aside in the meantime one class of these markings, which are said to indicate wading birds, we 48 EXPLANATIONS. have a variety of others plainly denoting reptiles. In one group, the foot consists of a ball, with five toes radiat- ing from it in front. In another, the impression resembles that made by a coarse human hand, with the rudiment of a sixth toe at the outside. The reptilian families indicated by these foot-marks have not yet been pronounced upon, as far as I am aware ; but from the extreme resemblance of some of them to the vestiges of the labyrinthidon, there can hardly be a doubt that some of the order batrachia are amongst them. If they prove wholly batrachian, as is not unlikely, for we have living families with feet resembling the first group of vestiges, or even if only a portion of them be certified as of this order, where will be the lacer- tilians, and where the confident counter-assertions of the Edinburgh reviewer ? The batrachia he has himself allowed to be a low order of reptiles (p. 51). They are so considered by all naturalists. Might 1 not here, then, take my stand upon the fact of animals, the lowest apparently of the reptile order, being now found at the earliest point of time ? I might unquestionably do so with a decided immediate advantage to my hypothesis. It would in a great measure neutralise the whole of the objections of the reviewer with regard to the chronology of the reptiles. But I am, whatever he may think of me, willing to read the book of nature aright. I receive the fact as one liable any day to receive a new aspect from fresh discoveries. In as far as it is so, it only teaches that we are not to be too confident in drawing inferences either for or against the theory of development from the particulai succession in which the orders of the reptilia occur in those early strata where their remains and vestiges are few. In as far as it may be taken as a positive fact, I only development of the animal kingdom. 49 claim a modified benefit from it, because the view which I take of the affinities and connexions of the animal king- dom (and by analogy of the vegetable kingdom also) makes it a matter of less consequence than would be generally supposed, which order of any class appears first in the stone record, though still perhaps a matter of some consequence. This view suggests that development has not proceeded, as is usually assumed, upon a single line which would require all the orders of animals to be placed one after an- other, but in a plurality of lines in which the orders, and even minuter subdivisions, of each class, are ranged side by side. It also suggests that the development of these various lines has proceeded independently in various regions of the earth, so as to lead to forms not everywhere so like as to fall within our ideas of specific character, but generally, or in some more vague degree, alike. The progress of the lines becomes clearest when we advance into the ver- tebrate sub-kingdom. We can there trace several of them with tolerable distinctness, as they singly pass through the four classes of Fishes, Reptiles, Birds, and Mammals ; the Birds, however, being a branch in some part derived equally with the reptiles from fishes, and thus leaving some of the mammal order in immediate connexion with the reptiles. The lines or stirpes have all of them pecu- liar characters which persist throughout the various grades of being passed through, one presenting carnivorous, another gentle and innocent animals, and so on. We have, therefore, in the animal kingdom, not one long range of affinities, but a number of short series, in each of which a certain general character is observable, though not always to the exclusion of the organic peculiarities of 4 50 EXPLANATIONS. families in neighboring lines, especially in the class of reptiles. According to this view, the matrix of organic life is, speaking generally, the sea. Fluid, required for all embryotic conditions, is also necessary to the origination of the various stirpes of both kingdoms. The whole of the lowest animal sub-kingdom (Radiata) is aquatic ; so are nearly the Mollusca and a very large proportion of the Articulata. In the Vertebrata, the lowest class also is wholly aquatic. The arrangement appears to be this— the basis of each line is a series of marine forms; the remainder consists of a series designed to breathe the atmosphere and live upon land, these being all of improved organization. The classification which this system implies may be said to be transverse to all ordinary classifications. The invertebrate, ichthyic, reptilian, ornithoid, and mam- malian characters are horizontal grades, through which the lines pass, and where they send off branches; not separate and independent divisions. In any of these branches where we have a clear knowledge of the various forms, it is possible to trace the affinities, in conjunction with an improved organization, through genera which are adapted to a partially marine life, to a residence in the mouths of rivers, or on shores and muddy shallows, then through genera which are, in succession, appropriate to marshes, jungles, dry elevated plains, and mountains. And it is this series of external conditions and adaptations which has caused that system of analogies between various families of animals which has of late attracted attention. But the immediate cause of the development of each line through its various general grades of being is to be sought in an internal impulse, the nature of which is unknown to DEVELOPMENT OF THE ANIMAL KINGDOM. 51 us, but which resembles the equally mysterious impulse by which an individual embryo is passed through its suc- cession of grades until ushered into mature existence. Geology shows us each line taking a long series of ages to advance from its humble invertebrate effluents to its highest mammalian forms ; and this I have ventured to call " the universal gestation of Nature." The traces of this order of the animal kingdom have been seen in all ages of science. Every zoologist ac- knowledges the gradations and affinities which appear amongst animals. Prompted by what so palpably meets observation, many have tried to range the various orders or families in one line, or (to use the favorite phrase) chain of being ; but they have always failed, which is not to be wondered at. One cause why zoologists have not up to this time thought of trying any different arrangement, is the confusion arising from prevalence amongst many families of parallelisms of structure, which have been regarded as affinities, when in reality they are only identi- cal characters demanded by common conditions, or result- ing from equality of grade in the scale. True affinities— and these are the affinities of genealogy—are not to be looked for horizontally amongst orders, but vertically, from an order in one class to the corresponding order in the class next higher. Generally, the first and lowest forms of the orders in a class are marine, and often these are of comparatively large size. We usually see in them a vestige of the essential characters of the class next below. Thus, the perennibranchiate batrachia in their order, the ichthyosauri in the series of crocodilia, and the divers among birds, all exhibit an affinity to fish. The cetacea and phocidae, which I regard as the immediate basis of the 52 EXPLANATIONS. pachydermata, carnivora, and other orders of terrestrial mammals, ought, according to this view, to show an alliance to the reptiles; and such a connection does exist between the cetacea and certain marine sauria; but from the general extinction of the marine reptiles, the linking of the mammals to that lower class is less clearly seen than might be wished. It must be kept in view that only an outline of the progress of the animal kingdom is here designed. Exceptions as to the course which development has taken appear to be by no means few ; leading to the idea that the grades of organization are not determinate in this respect, but may be reached by steps of unequal length. Thus, for example, the marsupials appear very clearly a development from certain birds ; probably the rodent and edentate orders are derived through the same channel. From the approach made by certain of the reptilia to birds, we may surmise that there also there are exceptions to the rule. In short, the progress of animality in the different stirpes has been attended by peculiarities which evidently affix peculiar characters to each, and make the idea of a difference in time not only probable, but unavoidable. Regarding the animal kingdom simply as a combination of independent stirpes, each with its distinct affinities, the theory of transmutation puts on a totally new aspect; so truly is this the case, that transmutation is hardly any longer a term appropriate to the idea. The difficulty of supposing such changes as that from the rodent to the ruminant, or the carnivorous animal to the quadrumane, vanishes, leaving only transitions from one form to another of a series generally similar—from the aquatic pachyderm, for instance, to the terrestrial, from the otary to the otter, EARLY REPTILIAN FOSSILS. 53 from certain phocse to the bear, and so on. There is a unity in all instances in the moral as well as physical characters of the various members of one stirps; we only see it advancing from low to high characters, just as we see the foetus of a high animal passing through various inferior stages before it reach its proper mature character. The lines, moreover, being independent of each other, and not quite uniform as to the stages of animality through which they pass, it follows that, unless we knew of some law governing their different gestative periods, we are not entitled to look for the first occurrence of their various ichthyic, reptilian, and mammalian sections, in any order as regards each other, even though we could be sure (which we are not) that we are surveying a geographical region where they all started fair in the race of progres- sive organization. Hence it is that, though the batrachia are usually placed by zoologists at the bottom of the list of reptilian orders, I attach little importance to their ves- tiges being now found so low. All that I think we can expect is, that, in a particular area where we have reason to believe that the lines have started abreast, they should all reach their various grades nearly about one time, or what may be considered as one time compared with the whole extent of geological chronology. And such ap- pears to be pretty much the case in those regions which geologists have explored. The Edinburgh reviewer will observe that this view of the animal kingdom leaves much of his opposition in a very awkward predicament. He has everywhere assumed that the genealogy of the orders of each class was sup- posed to be en suite, which it certainly never was in my book. In the early editions I spoke with diffidence of the 54 EXPLANATIONS. course of the supposed development,* because I had not then seen or conceived any arrangement of the animal kingdom which answered to that hypothesis, although I thought proper to attempt to show that the quinarian and circular classification, which I found in vogue at the time when I was writing, did not necessarily militate against it. In the third edition, the present view was first hinted at; and in the fourth it was sketched, though with liability to correction ; thus anticipating by some months the pub- lication of the criticism to which I am adverting. I need hardly remark, that in all criticism, the actual subject criticized must be brought forward for comment, and nothing else; otherwise the commentaries become of no imaginable use but to obscure true judgment. Now the Edinburgh reviewer has presented his subject, in this in- stance, in lineaments entirely of his own imagining, and directly in contradiction to those which belong to it. He had no title to assume any plan of development and to represent his victory over that as a triumph over the hy- pothesis of his author. In such conduct, he has thoroughly vitiated the whole fabric of his criticism, and left it, in reality, no pretension to remain for a moment in court. My immediate object, however, is not to take such excep- tions against him, but to show how the ascertained facts of a limited portion of the field of nature may be recon- ciled with that conception to which a view of what ap- pears over the whole field may lead an honest inquirer. If the hypothesis of a plurality of genetic lines be ad- * " . . it does not appear that this gradation passes along one line, on which every animal form can be, as it were, strung; there may be branching or double lines at some places," &c.— Vestiges, 1st ed.,p. 191. EARLY REPTILIAN FOSSILS. 55 mitted, we are not of course to ask which order of rep- tiles, or of any other class, first existed (such being the language of the old classification) ; but, having first set- tled the whole affinities of the animal kingdom on the new plan, we are to inquire if the geological presentment of the families was accordant with the scheme, allowing for the negative nature of much of the geological evidence of this kind. Now, in the first place, the affinitiesof the animal kingdom are only in part made out; in the second, geological evidence is only partial. We are clearly, therefore, not to expect in nature's museum a full exhibi- tion of any one entire stirps, as it may be supposed to have passed through its successive stages up to our time. All that we can expect is a succession of fossils marking out portions of what we may suppose likely yet to. be es- tablished as lines of animal descent. Blanks, and large ones too, must be allowed for ; possible errors as to the animal pedigrees must be contemplated. But, if we have any ground for generalizing in a particular direction, as I think there is in this case, we may be held as called upon not to conclude hastily and rashly on the unfavorable side, but to look and consider patiently, and to suspend judgment wherever the adverse evidence may appear to be of a nature likely to be reversed. Let us now see how all this applies to the conduct of the Edinburgh re- viewer, with regard to the early reptilian fossils. The formations where these occur have only been examined in such a degree, that they are almost every year giving forth new responses : for example, the existence of birds at this era was not dreamt of ten years ago ; the existence of tortoises in the time of the New Red Sandstone was equally unknown only two or three years earlier. It is 56 EXPLANATIONS. a still less time since the labyrinthidonts of the Keuper of Germany were discovered ; and we have just seen that the unqualified affirmations of the Edinburgh reviewer, as to the oldest reptiles, were overturned by intelligence from America, before his sheets had seen the light. When these things are considered, we must see the objections of the reviewer to be extremely rash. It might be allowed that the earliest known lacertilia are not of strictly ma- rine forms or allied to fish ; it might equally be admitted of the first batrachians, that " their near affinities are not with fishes," as this writer takes it upon him to say. Yet we should still see the absurdity of affirming that either these batrachia or lacertilia were the first created of their respective orders, seeing that their relics were so few and the discovery of these so accidental, that we might look for new and superseding facts every day.* But, as the case actually stands, is this line of defence more than hypothetically necessary ?" I doubt it very much. The lacertilia of the magnesian limestone, and these labyrinthidonts of the Trias (perhaps also of the carboniferous formation), are they so far removed from fish characters as the reviewer would make them ? Let any naturalist who has ever studied the transmutation of * It is necessary to guard against a supposition that I undervalue such isolated relics, as inferring the positive fact of the existence of particular orders of animals at particular times. For this pur- pose, the smallest fragment betraying the character of the organiza- tion is often sufficient. What is really meant is, that, when we find a few outlying relics belonging to a class which does not ap- pear in any force till afterwards, we cannot be sure that we have acquired the means of forming a distinct idea of the time of the origin of that class or the orders with which the class started, as further discoveries on these points may be looked for. EARLY REPTILIAN FOSSILS. 57 the individual batrachian, passing in a few weeks from the branchiated fish to the lunged and limbed frog or newt, its circulatory and alimentary system entirely changed, and then say if the labyrinthidon may not be the very first step from some ichthyic form. What though the propor- tions of the head remind Mr. Owen of the sauria, and re- move the animal, as he thinks, above the present batra- chian type ! Against any such inferences we have the positive fact, in the organization of this batrachian, of a biconcave form of the vertebrae, the form peculiar to fishes, —arguing, by Mr. Owen's own acknowledgement, aqua- tic if not marine habits,—also a decidedly piscine charac- ter in the arrangement and even microscopic structure of the teeth, together with that position of the breathing apertures near the end of the snout which we see in croco- diles, for the purpose of allowing them to drag their prey under water without ceasing to respire. With regard to the lacertilia, we have this same fish-like biconcave form of the vertebras, and the same fish-like arrangement of the teeth, equally arguing that alliance to the lower vertebrate class which it is the pleasure of this hardy critic to deny, —the biconcave structure of the reptiles, showing, as Mr. Owen himself owns, that these animals, which the Edin- burgh reviewer deems so utterly separated from fish, had probably " a more aquatic, if not marine theatre of life,"* than was assigned to their successors. In subsequent and present reptiles, this form is superseded by the ball and socket, or concavo-convex form; but it is remarkable that, in the embryo state, the frog and crocodile (if not * On the Reptilian Fossils of South Africa. Geological Trans- actions, Feb., 1845. 4* 58 EXPLANATIONS. others) exhibit the double hollow form still, resembling in this respect the mature animal of the secondary rocks. Such is the actual character of reptiles which our critic would set up as high : he has, after this, only to speak of the annelid as above the butterfly, or the proteus as su- perior to the land salamander, to establish his character as a naturalist. Need I say that these Permian reptiles are, in reality, by these facts degraded to a place in prox- imity with fishes ? So much for the batrachia and lacertilia. When we come to the great saurian line in the Muschelkalk, Lias, Oolite, and Wealden, we have a case which cannot be disputed, for here the marine character of the earliest of the series, and their intermediateness between fish and true crocodiles, are admitted by all. The first remove from the fish is the ichthyosaur, its name declaring the convention of class characters for which it is remarkable. With piscine body and tail, and fins advanced into a paddle form, it has a true crocodilian head. In the pliosaur, which is later in appearing, we have a stage of advance to the true sauria, which come forward in the oolite, in the forms of teleosaurus, steneosaurus, &c. Afterwards, chiefly in the Wealden, we have the dinosauria, which betray an approach to the mammalian type in the pachydermatous order. Another oolite saurian, the cetiosaur, exhibits in the form of the vertebras a verging towards the cetaceous mammalia. Here there is the most perfect and even striking harmony with the theory of a progressive deve- lopment. Below these formations, fish : then, low in these formations, fish saurians; above them, true and complete saurians; finally, higher still, saurians advancing to a more elevated grade of animality ; and where do these EARLY REPTILIAN FOSSILS. 59 more elevated types occur ? In the next formation, pass- ing over one which hardly represents any but deep-sea life. Nay, cetaceous relics have been found before we leave the strata so remarkable for the saurians. Thus, it appears that the whole of this chapter of palaeontology, when read by a light from nature, and not from man's capricious hu- mor, so far from being opposed to the natural genesis of animals, gives it support. Men, however, and of lively parts too, might go on for an age misreading such palpable facts, if they be determined against putting them into the collocation in which a sense can be made of them, just as we might puzzle for ever over a Latin or Greek sentence, if obstinately resolved against making English out of it ex- cept in its original construction. After presenting the case of the reptilian fossils of the secondary formation in this way, I feel it hardly necessary to track the Edinburgh reviewer through all his particular objections. They are a mass of confusion, resulting from erroneous assumptions on his own part respecting the de- velopment theory, as that the orders of animals are all to be affiliated to each other, and every parental form held as extinguished by the fact of transmutation (the latter being a peculiarly gratuitous supposition—see p. 50 of the Review); together with equally rash and unjustified con- clusions regarding the earliest forms of the reptilian orders, all mixed up in the way that promised to tell most effec- tually in favor of his own opinion, and with a disregard of everything that pointed in the opposite direction. The great unquestioned facts of a succession of birds and mam- mals to the fishes and reptiles, these being also the next higher classes in the scale of the naturalist, tell nothing to this writer, as the succession of the reptiles to the fishes 60 EXPLANATIONS. told nothing before. From the slight remarks with which he passes over these facts, an unlearned reader would hardly suppose that they were of the least significance, while, in reality, they are of the greatest. It is much the same as if a historian were to sink all such events as changes of dynasties, and fix attention upon the displace- ment of under-secretaries of state. And what makes this conduct the more marked is, that the minor facts upon which he fastens for the purpose of supporting his own theory, are mostly presented to us in circumstances which show their uncertainty and the likelihood of their being superseded. For example, the earliest traces of birds do not indicate marine forms, which, according to my general views, ought, he says, to be the case. Instead of natatorial birds, they are waders and runners. Let the reader judge of the character of this objection, when he learns the real circumstances of the case. The traces of birds here spoken of are merely a few foot-prints found upon certain rock surfaces in America. Not a bone of these animals has been found in this early period. It must therefore be inferred, either that the circumstances were not favorable for the entombment of the bodies of these birds, or that our researches in the strata formed at the time when they lived have been insufficient to discover them. If such be the case with birds which lived upon shores,—places where, as we learn from the nature of the strata, accumulations of sand and mud were constantly taking place,—it is of course %iot to be expected that any remains of natatorial birds should be found, animals mostly living far out at sea. To put the case in its strongest form—foot-prints on shores being the record of the birds of this era, we are not EARLY CETACEOUS FOSSILS. 61 to expect any traces of such birds as, generally speaking, are not in the way of making foot-prints on shores. I might go further than this, and point out that certain nata- torial genera have feet not to be distinguished from those of waders, so that certain of these foot-prints may be those of natatorial species after all; but I feel it to be my best duty in the case, only to deny that we are in circumstances to say that waders and runners were the first created birds. Mr. Lyell, who stands as high as this or any other writer on geology, says, with regard to those very ornithichnites, as they are called—" This sandstone is of much higher antiquity than any formation in which fossil bones or any other indications of birds have been detected in Europe. Still we have no ground for inferring from such facts, that the feathered tribe made its first appearance in the western hemisphere at this period. It is too common a fallacy to fix the era of the first creation of each tribe of plants or animals, and even of animate beings in general, at the precise point where our present retrospective knowledge happens to stop."* What now gives force to this observation is, the recent dis- covery of a new set of bird foot-prints—said to be of waders only—in the carboniferous formation of Pennsylvania. The emergence of such a fact in the midst of the review- er's speculations on the foot-prints of the New Red Sand- stone, forms a most emphatic commentary on all decisive inferences where the facts are obviously casual and isolated. Of a somewhat different character are the reviewer's remarks on the first relics of mammalia—the few bones of cetacea from the Lower Oolite and of marsupials from the * Travels in North America, i., 255. 62 EXPLANATIONS. Stonesfield Slate. Here the very first mammal family ia undoubtedly marine ; and, if it were to receive equal con- sideration with the grallatorial foot-prints, he ought cer- tainly to admit that it favors the development theory. But he escapes from this claim by a mode of his own. He has not seen these relics! The American foot-prints were good evidence, without being seen ; but a fact which makes against his theory requires personal inspection, even though it may come forward with the authority of Baron Cuvier.* He is more at ease with the marsupials, which are of course unequivocally land animals. I have only here to refer to the fourth edition of my book—published two months before the appearance of the review, and while I was unrecking of any great objection being grounded on this point—where it is suggested that the peculiar organi- zation of the marsupials points to their having been derived through a different medium from other mammals. The critic, eager to let nothing escape, tells us that there are other land mammals lower in organic type than the mar- supials. One answer to this objection might be found in an explanation of my views respecting the ornithic descent of these animals; but I am unwilling to pause upon such an inferior matter, and will therefore meet him with the question, if any other mammals show that lowly grade of organization which is marked by the absence of a placenta 1 " There are no other organic types," he says, " to which they [the marsupials] offer the shadow of a near affinity. * " There is in the Oxford Museum an ulna from the Great Oolite of Enstone, near Woodstock, Oxton, which was examined by Cuvier and pronounced to be cetaceous ; and also a portion of a very large rib, apparently of a whale, from the same locality."— Buckland's Bridgewater Treatise, i., 115, note. AFFINITIES OF MARSUPIALIA. 63 They are therefore in direct antagonism with the scheme of regular development." To this it may be replied, that the affinity of the marsupials to the oviparous vertebrata is admitted by every naturalist, being shown in the small size of the brain and consequent exposure of the cerebellum, the absence of the septum lucidum and corpus callosum in the brain, and various other traits. Professor R'ymer Jones, of King's College, whose testimony on such a point will be admitted by the reviewer, speaks of the marsupials as " connecting links between the oviparous and placental vertebrata." Striking traits of their affinity to birds are shown, he says, in the structure of the ear and of the re- productive organs.* In reality, the whole figure of the cursorial bird, the small head upon the long neck, the ex- treme length of the hinder limbs, and the imperfect deve- lopment of the fore extremities, as well as the tendency of the feathers to a hair-like character, speak irresistibly for its approach to certain marsupials. The ornithorhynchus is as clearly an advance from the natatorial bird towards the rodent form, the latter being an order whose osteologi- cal structure is allowed by every naturalist to be bird-like. New and curious illustrations of the connexion between the birds and the implacental mammalia are constantly ap- pearing. We lately heard of a bird which has a pouch for its young like the kangaroo,! and Mayer has discovered in the female emeu a purse form of certain organs, indi- cating an approach to the marsupial in that part of struc- ture which is the most distinctive in the case.:]: It would appear that the reviewer is simply ignorant of this depart- ment of natural history, and, with the self-esteem which * General View of the Structure of the Animal Kingdom. f Magazine of Natural History. f Reports of Ray Society, I. 64 EXPLANATIONS. often attends upon ignorance, he has somewhat unluckily ventured to give a positive contradiction to that which is incontestably true. The reviewer at length comes to the organic phenomena of the Tertiary system. " On the theory of development," says he, "' the stages of advance are in all cases very small—from species to species,' and the phenomena, ' as shown in the pages of geology, are always of a simple and modest character.' Let us test these assumptions by one single step, from the chalk to the London clay, or any other tertiary deposit. Among the millions of organic forms, from corals up to mammals, we find hardly so much as one single secondary species." The exceptions in reality are, the infusoria of the chalk, and " two or three secondary species," which are said to " straggle into the tertiary system." " Organic nature," he says, " is once more 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 species, nor in their affinities with the types of an older world, is there the shadow of any approach to a regular plan of organic development." Now the almost total break in the organic creation here insisted upon, occurs in the interval between the extensive deposits of the secon- dary formation, and the comparatively isolated deposits of the tertiary. It is an interval which the lithological arrangements clearly indicate to have been longer than any of those between the other formations, during which minor changes of organic creation had taken place. It is simply, then, a period not represented by strata or by fos- sils ; while it elapsed, the continual advance of the organic world proceeded to a point at which nearly all the old spe- TERTIARY FOSSILS. 65 cies had died out or been changed. There was nothing more in the "step" of our reviewer than this. Such is the geological doctrine. " Is the present creation of life," says Professor Phillips, "a continuation of the previous ones; a term of the same long series of communicated being ? I answer, yes."* " There is no break," he says, " in the vast chain of organic development till we reach the existing order of things." The reader will further be able to judge of the candor of the reviewer respecting the zoology of the tertiary, when he is reminded that it shows exactly those new portions of the animal kingdom which might have been expected, according to the theory of development. Heretofore, we have only few and faint traces of mammalia; but now they are added in abun- dance, mammalia being the crowning class of the verte- brated form. As far as class, therefore, is concerned, it is incontestably a " regular plan of organic development." But this is not all. We have seen the reptile forms of the secondary approaching the cetacean character; and now there is an abundance of the aquatic mammalia, as well as of those land pachyderms which are universally classed with some of the forms of that order, these being the only suite of creatures which my ideas of development would lead me to expect at this place. Here I must meet the reviewer on a special ground. He admits the dinosaurs to have been the nearest approach to mammals ; but " they died away," he says (" if we are to trust to geology), ages before the end of the chalk." These mammals have, therefore, " no zoological base to rest upon." That is, there is no connection between them and any such animals * He adds—" But not as the offspring is a continuation