The Religion of Geology and Its Connected Sciences

by Edward Hitchcock

In the fourth place, the laws of zoölogy and botany have always been the same on the globe.

An examination of the animals now living, amounting to some hundred thousand species, perhaps to one or two millions, shows that they may be arranged in four great classes. The first class embraces the vertebral animals, distinguished by having a vertebral column, or back-bone, a regular skeleton, and a regular nervous system. It comprehends all the quadrupeds and bipeds, with man at their head, and is much superior to all other classes in complexity of organization and strength of the mental powers. The second class embraces the mollusks, or animals inhabiting shells. They are destitute of a spinal marrow, and for the most part their muscles are attached to the external covering, called the shell, although this shell is sometimes internal. The third class are called articulated animals, having envelopes connected by annulated plates, or rings. It includes such animals as the lobster, bloodsucker, spider, and insects generally. The fourth class have a radiated structure, and often resemble plants, or their habitation is a stony structure. Hence they are sometimes called zoöphytes, which means animal plants; or lithophytes, which means stony plants. They swarm in the ocean, and some of them build up those extensive stony structures called coral reefs.

Now, if we examine the descriptions of the organic remains in the rocks, we find that in all ages of the world these four great classes of animals have existed. But in the earliest times, the three last classes—the mollusks, the articulated, and the radiated tribes—vastly preponderated, while the vertebral class had only a few representatives; and it is not till we rise as high as the new red sandstone, that we meet with any, except fishes, save a few batrachians in the old red sandstone, and the carboniferous group, detected alone by their tracks. Then the reptiles began to appear in abundance, with tortoises and enormous birds of a low organization, but no mammiferous animal is found, until we reach the oölite; and scarcely any till we rise to the tertiary strata, when they became abundant; but not so numerous as at present, though for the most part of larger size. Thus we find that the more perfect animals have been developed gradually, becoming more and more complex as we rise on the scale of the rocks. But in the three other classes, there does not appear to have been much advance upon the original types, although in numbers and variety there has been a great increase.

The plants now growing upon the globe, amounting probably to nearly one hundred thousand species, are divided into two great classes, by a very decided character. Some of them have distinct flowers, and others are destitute of them. The former are called phenogamian, or flowering plants; and the latter cryptogamian, or flowerless plants.

At present, the flowering plants very much predominate in the flora of every country. But in the earliest periods of organic existence, the reverse was the case. We find, indeed but very few flowering plants, and these of a character somewhat intermediate between flowering and flowerless; such as the coniferæ and cycadeæ, including the pine tribe. A few palms appeared almost as early, and some other monocotyledons. But most of the dicotyledons did not appear till the tertiary period, where more than two hundred species have been found. Of the three hundred species found in and beneath the carboniferous group, two thirds are tree ferns, or gigantic equisetaceæ. More than one third of the entire flora of the secondary formation consists of cycadeæ; whereas, this family of plants forms not more than the two thousandth part of the existing flora. In short, we find the more perfect plants as well as animals to be few in the earliest periods, and to have been gradually introduced up to the present time. But as to the flowerless plants, most of them seem to have been as perfect at first as they now are.

These facts teach us conclusively that the outlines of organic life on the globe have always been the same; that the great classes of animals and plants have always had their representatives, and that the variations which have been introduced, have been merely adaptations to the varying condition of the earth’s surface. The higher and more complex natures, both of animals and plants, were not introduced at first, because the surface was not adapted to their existence; and they were brought in only as circumstances, favorable to their development, prepared the way.

There is another fact of great interest on this subject. Even a cursory examination of the animals and plants now on the globe, shows such a gradation of their characters that they form a sort of chain, extending from the most to the least perfect species. But we see at once that the links of this chain are of very unequal length; or, rather, that there are in some instances wide intervals between the nearest species, as if one or more links had dropped out. How remarkable that some of these lost links should be found among the fossil species! I will refer to a few examples.

Among existing animals no genera or tribes are more widely separated than those with thick skins, denominated pachydermata; such as the rhinoceros and the elephant. But among the fossil animals of the tertiary strata, this tribe of animals was much more common; and many of them fill up the blanks in the existing families, and thus render more perfect and uniform the great chain of being which binds together into one great system the present and past periods of organic life.

A similar case occurs among fossil plants. In tropical climates we find a few species—not much over twenty—of a singular family of plants, the cycadeæ connecting the great families of coniferæ, or dicotyledons, with the palms, which are monocotyledonous, and the ferns, which are acotyledonous. The chasm, however, between those great and dissimilar classes of plants is but imperfectly filled by the few living species of cycadeæ. But of the fossil species hitherto found above the coal formation, almost one half are cycadeæ; so that here, too, the lost links of the chain are supplied.

“Facts like these,” says Dr. Buckland, “are inestimably precious to the natural theologian, for they identify, as it were, the Artificer, by details of manipulation throughout his works. They appeal to the physiologist, in language more commanding than human eloquence; the voice of very stocks and stones, that have been buried for countless ages in the deep recesses of the earth, proclaiming the universal agency of one all-directing, all-sustaining Creator, in whose will and power these harmonious systems originated, and by whose universal providence they are, and have at all times been, maintained.”—Bridgewater Treatise, vol. i. p. 502.