Charles Lyell, from further reflexion entertains grave doubts on this subject.  I feel how rash it is to differ from these great authorities, to whom, with others, we owe all our knowledge.  Those who think the natural geological record in any degree perfect, and who do not attach much weight to the facts and arguments of other kinds given in this volume, will undoubtedly at once reject my theory.  For my part, following out Lyell’s metaphor, I look at the natural 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, in which the history is supposed to be written, being more or less different in the interrupted succession of chapters, may represent the apparently abruptly changed forms of life, entombed in our consecutive, but widely separated formations.  On this view, the difficulties above discussed are greatly diminished, or even disappear.

CHAPTER 10.  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 areas. 
Summary of preceding and present chapters.

Let us now see whether the several facts and rules relating to the geological succession of organic beings, better accord with the common view of the immutability of species, or with that of their slow and gradual modification, through descent 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 them, and to make the percentage system of lost and new 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 lost forms, and only one or two are new forms, having here appeared for the first time, either locally, or, as far as we know, on the face of the earth.  If we may trust the observations of Philippi in Sicily, the successive changes in the marine inhabitants of that island have been many and most gradual.  The secondary formations are more broken; but, as Bronn has remarked, neither the appearance nor disappearance of their many now extinct species has been simultaneous in each separate formation.