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considered as a comparatively modern event Eozoon belongs to the most lowly organised classes of animals, but is highly organised for it it existed in countless numbers, and, as Dr. Daw remarked, certainly preyed on other minute beings, which must have lived in great numbers the words, which I wrote in 1859, about the e of living beings long before the Cambrian per which are almost the same with those since use W. Logan, have proved true. Nevertheless, the d of assigning any good reason for the absence piles of strata rich in fossils beneath the C system is very great. It does not seem probal the most ancient beds have been quite worn a denudation, or that their fossils have been obliterated by metamorphic action, for if this h the case we should have found only small rem the formations next succeeding them in age, an would always have existed in a partially metamo condition. But the descriptions which we po the Silurian deposits over immense territories in and in North America, do not support the vi the older a formation is, the more invariably suffered extreme denudation and metamorphism

The case at present must remain inexplicab may be truly urged as a valid argument agai views here entertained. To show that it may l receive some explanation, I will give the fo hypothesis. From the nature of the organic which do not appear to have inhabited profound

in the several formations of Europe and of the United States; and from the amount of sediment, miles in thickness, of which the formations are composed, we may infer that from first to last large islands or tracts of land, whence the sediment was derived, occurred in the neighbourhood of the now existing continents of Europe and North America. This same view has since been maintained by Agassiz and others. But we do not know what was the state of things in the intervals between the several successive formations; whether Europe and the United States during these intervals existed as dry land, or as a submarine surface near land, on which şediment was not deposited, or as the bed of an open and unfathomable sea.

Looking to the existing oceans, which are thrice as extensive as the land, we see them studded with many islands; but hardly one truly oceanic island (with the exception of New Zealand, if this can be called a truly oceanic island) is as yet known to afford even a remnant of any palæozoic or secondary formation. Hence we may perhaps infer, that during the paleozoic and secondary periods, neither continents nor continental islands existed where our oceans now extend; for had they existed, palæozoic and secondary formations would in all probability have been accumulated from sediment derived from their wear and tear; and these would have been at least partially upheaved by the oscillations of level, which must have intervened during these enormously long periods. If then we may infer anything from these facts, we may infer that, where our oceans now extend, oceans have extended from the remotest period of which we have any record; and on the other hand, that where continents now exist, large tracts of

subsidence, the great archipelagoes still areas of tions of level, and the continents areas of el But we have no reason to assume that things ha remained from the beginning of the world. Our ents seem to have been formed by a preponderance many oscillations of level, of the force of elevati may not the areas of preponderant movemer changed in the lapse of ages? At a period long an to the Cambrian epoch, continents may have exist oceans are now spread out; and clear and oper may have existed where our continents now stan should we be justified in assuming that if, for i the bed of the Pacific Ocean were now converted continent we should there find sedimentary forma a recognisable condition older than the Cambria supposing such to have been formerly deposited might well happen that strata which had subsid miles nearer to the centre of the earth, and wh been pressed on by an enormous weight of supe bent water, might have undergone far more meta action than strata which have always remained to the surface. The immense areas in some part world, for instance in South America, of naked morphic rocks, which must have been heated great pressure, have always seemed to me to some special explanation; and we may perhaps that we see in these large areas, the many for long anterior to the Cambrian epoch in a con metamorphosed and denuded condition.

The several difficulties here discussed, namely—that, though we find in our geological formations many links between the species which now exist and which formerly existed, we do not find infinitely numerous fine transitional forms closely joining them all together ;—the sudden manner in which several groups of species first appear in our European formations;-the almost entire absence, as at present known, of formations rich in fossils beneath the Cambrian strata,—are all undoubtedly of the most serious nature. We see this in the fact that the most eminent palæontologists, namely, Cuvier, Agassiz Barrande, Pictet, Falconer, E. Forbes, &c., and all our greatest geologists, as Lyell, Murchison, Sedgwick, &c., have unanimously, often vehemently, maintained the immutability of species. But Sir Charles Lyell now gives the support of his high authority to the opposite side; and most geologists and palæontologists are much shaken in their former belief. Those who believe that the geological record is in any degree perfect, will undoubtedly at once reject the theory. For my part, following out Lyell's metaphor, I look at the geological record as a history of the world imperfectly kept, and written in a changing dialect; of this history we possess the last volume alone, relating only to two or three countries. Of this volume, only here and there a short chapter has been preserved; and of each page, only here and there a few lines. Each word of the slowly-changing language, more or less different in the successive chapters, may represent the forms of life, which are entombed in our consecutive formations, and which falsely appear to have been abruptly introduced. On this view, the difficulties above discussed are greatly diminished, or even disappear.

CHAPTER XI.

ON THE GEOLOGICAL SUCCESSION OF ORGANIC BEINGS

On the slow and successive appearance of new species-On their different rates of change-Species once lost do not reappear― Groups of species follow the same general rules in their appearance and disappearance as do single species-On extinction -On simultaneous changes in the forms of life throughout the world-On the affinities of extinct species to each other and to living species-On the state of development of ancient forms— On the succession of the same types within the same areasSummary of preceding and present chapter.

LET us now see whether tho several facts and laws relating to the geological succession of organic beings accord best with the common view of the immutability of species, or with that of their slow and gradual modification, through variation and natural selection.

New species have appeared very slowly, one after another, both on the land and in the waters. Lyell has shown that it is hardly possible to resist the evidence on this head in the case of the several tertiary stages; and every year tends to fill up the blanks between the stages, and to make the proportion between the lost and existing forms more gradual. In some of the most recent beds, though undoubtedly of high antiquity if measured by years, only one or two species are extinct, and only one or two are new, having appeared there for the first time, either locally, or, as far as we know, on the face of the earth. The secondary formations are more broken;

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