The question of the numerical increase of species seems to rest on somewhat better grounds. As far as the posi tive bare evidence derived from numbers goes, it appears satisfactory; but that evidence is subject to the nbje‘ttotis already made respecting the dectrtirtion of more ancient deposits. We may here also add, that it presumes on what we have no right a priori to suppose, namely, a pro gressive and gradual creation of animals; a question, how ever, which is of too metaphysical and theological a na ture to admit of a place in such an investigation of mere evidence as this is.
Taking the bare evidence of the actual presence of ani mals in rocks, there is an increase of species when we proceed upwards in the series; but it is far from being equable or regular. Hence prohably we may fairly argue, that there has been no such increase in reality, but that the appearances are to be explained on the ground of col lateral causes, as already stated. There are more species in the argillaceous schists of the primary strata than in the first red sandstone ; there are even more in it than in some of the tipper limestones. Thus, also, there are fishes in argillaceous schist, and in some secondary strata, while they are absent from superior ones. In the same manner, there are crocodiles in the lias when they are not found in many of the strata above it ; as vegetable remains are also found in this stratum, though they are wanting in every member of the secondary series that follows it. So imperfect, in short, is the evidence respecting an increase of species, that, like the question which relates to the pro gressive amelioration, it.ljems safest to abandon it alto gether. NVith respect to the mere increase of numbers, or of the quantity of fossil remains in the relative strata, nothing need be here added to what has already been said on that subject in former parts of this essay.
It has been said that not only the species but the genera change with the strata. That would not be probable, on considering the mode in which the animals lived, and it is not true in tact. If it is true in sonic places, it is contra dicted in others; since gryphites, belemnites, cchini, and many other animals, are not only found in far distant stra ta, but many different species, and even genera, inhabit to gether the same stratum. But this question will be more
particularly examined, in considering the identification of strata by means of their imbedded organic remains.
If any argument were necessary to prove the want of a regular succession throughout the buried fossil remains, it would be found in the coal series, where plants are in terposed between marine remains of distant dates. But this apparent anomaly is readily explained by considering the nature of the revolutions whence these rocks derived their present positions; by examining, in shot t, those col lateral circumstances to which we have already so often alluded, and which render nugatory that kind of evidence on which geologists have often dwelt too much, to the ne glect of appearances that ought to have been abundantly obvious.
On the Connection between Fossil and Living Species.
The next object of inquiry is the connection between buried and existing species, or rather, whether any or all of the species now imbedded in rocks are extinct, or whether some of them are not perfectly similar to those now occupying the globe. This, merely in a practical view, is a question of great difficulty, from the limited state of our knowledge both of fossil and living animals; while it is of a nature far too voluminous to be here ex amined in detail, as must be perceived from attending to the general remarks on fossil species formerly made. As it relates to the question of a progressive or interrupted creation, it is equally important, but not less difficult. Of this wo must also content ourselves with a bare sketch, lest, in pursuing it, we should wander into regions more delightful than appropriate, and trespass on the provinces of those who have taken moral rather than physical views of the subject.
It had formerly been believed that none of the species of organic bodies found in a fossil state, and few even of the genera, were now inhabitants of the globe. Increased observation has shown that this opinion was unfounded. Yet, in general, it has since been remarked, that while, in the more ancient strata, corresponding species and even genera are rare, the resemblances increase as we advance upwards in the order of the deposits, and that the most recent of all contain numerous species no way differing from existing ones.