8. The inference of evolutionists that because certain forms of life succeed each other in geological time, they must have been derived from each other, has an aspect of truth and simplicity; but the idea of law or plan in creation suggests that the link of connection may be of a less direct nature than mere descent with modification. This has been referred to under a previous head. 9. In the scheme of revelation all the successions and changes of organized beings, just as much as their introduction at first, belong to the will and plan of God. Revelation opposes no obstacle to any scientific investigation of the nature and method of this plan, nor does it contemplate the idea that any discoveries of this kind in any way isolate the Creator from his works. Farther, inasmuch as God is always present in all his works, one part of his procedure can scarcely be considered an "intervention" any more than another. 10. As an illustration of the hypothetical condition of this subject, and of the views which may be taken as to its details, I quote from a memoir of my own certain conclusions with reference to the origin of the species of land plants which are found in the older geological formations. The conclusions stated are at the end of a detailed consideration of these plants and the circumstances of their occurrence: "(1.) Some of the forms reckoned as specific in the Devonian and Carboniferous formations may be really derivative races. There are indications that such races may have originated in one or more of the following ways: (_a_) By a natural tendency in synthetic types to become specialized in the direction of one or other of their constituent elements. In this way such plants as _Arthrostigma_ and _Psilophyton_ may have assumed new varietal forms. (_b_) By embryonic retardation or acceleration,[151] whereby certain species may have had their maturity advanced or postponed, thus giving them various grades of perfection in reproduction and complexity of structure. The fact that so many Erian and Carboniferous plants seem to be on the confines of the groups of Acrogens and Gymnosperms may be supposed favorable to such exchanges. (_c_) The contraction and breaking up of floras which occurred in the Middle Erian and Lower Carboniferous may have been eminently favorable to the production of such varietal forms as would result from what has been called the 'struggle for existence.' (_d_) The elevation of a great expanse of new land at the close of the Middle Erian and the beginning of the Coal period would, by permitting the extension of series over wide areas and fertile soils, and by removing the pressure previously existing, be eminently favorable to the production of new, and especially of improved, varieties.