we have a striking example of a comprehensive type. They had the general form of palms, the mode of unrolling the leaf from the bud that is characteristic of ferns, but had wood and flowers (ripening into cones) very much like the conebearing evergreens, such as pines and spruces. Now, the idea may not unnaturally occur to

any one, on looking over any statement of the succession of forms of life on the earth, that perhaps the reason why ordinary flowering plants (angiosperms) are not found at an earlier date than is assigned them is because the earth's sur face was not fit for them; the soil, the climate, or both, having been unsuited to their growth.

The same kind of argument might be urged, with still greater apparent reason, in the case of animals.

But it is in the power of the geologist to transport himself back in thought, even to the scanty North-American continent and the scattered archipelago of Europe in the eozoic era. From the many thousands of analyses of minerals and rocks made by skilful chemists, from the known thickness of the various strata of rocks of all the geological ages from eozoic time till now, and from the microscopical study of these rocks, it is possible to decide approximately under what conditions they were formed. It would seem to be pretty clear that most types of plants might have flourished in some part of the earth during or at any time since the Devonian age. There may have been too much carbonic acid gas in the atmosphere to allow birds or mammals similar to those now living to occupy the earth's surface till the close of the carboniferous age.

Why each type of animal or of plant life should not have appeared on our planet as soon as it could have existed is a question to which no answer can be given, except on the basis of the doctrine of descent. But this theory readily explains all such cases; for obviously no animal or plant could occupy any part of the earth's surface, no matter how fit the conditions were for its existence, until the type in question could be developed from pre-existing species.

Many common flowering plants (angiospermous dicotyledons) now seem fully as capable as are evergreen trees of living under disadvantageous conditions; and so would it not have been quite possible for ordinary hard-wood trees to flourish side by side with the trees of the pine family that lived at least as far back as the beginning of the carboniferous age? The introduction of deciduous trees at this early period would have increased the time of their occupancy of the earth's surface to something like four times the length at which it is now estimated.

But what possible reason could be put forward by the believer in special creations to account for this great apparent waste of opportunities?

Some other classes of facts, derived from the study of geology, and confirmatory of the development theory, remain to be stated. Among the most striking of these is the well-known resemblance often noticeable between the present and the fossil inhabitants of any region. It was, among other things, the observation of this resemblance in South America, that led Mr. Darwin, after his return from a voyage round the world, to insist on this "law of the succession of types" on "this wonderful relationship in

the same continent between the dead and the living;" for in South America there are found fossil remains of the armor of gigantic extinct animals which bore a striking likeness to the existing armadillo, which occupies a large extent of the same continent, but is found nowhere else in the world.

Huge sloths also, closely allied to those now living in South America, are abundantly represented there by their fossil remains. The fossil mammals of Australia, like the living ones, are marsupials; and an equally close resemblance is found to exist between the remarkable extinct and recent birds of New Zealand. The occurrence of such likenesses is indeed worldwide.

The explanation of these facts is certainly not to be found in any incapacity of the regions to support other forms of life than those which have characterized them for so many hundreds of centuries.

The animals and plants of Europe have in many other parts of the world, as already mentioned, proved themselves easily capable of driving out the native species. From this strange fact the ready conclusion is, that the present

1 Animals which carry the young in a pouch.

fauna and flora of countries resemble the fossil ones, as offspring always resemble parents. When the native productions are as easily displaced by foreign immigrants as they are in Australia and New Zealand, it can only be because the former have long been protected by some geographical barrier from competition with more advanced forms of life.

And now, before leaving the subject of the geological evidence for the doctrine of descent, a case more striking in its confirmation of the theory than even that of the Steinheim snails must be cited. It is that of the series of transitional forms to be found among the remains of fossil horses.1 The modern horse has on each foot, as all are aware, but one toe, the third. Two other toes are represented by rudiments in the shape of two slender bones, the "splint-bones," one ou either side of the leg, reaching down nearly to the pastern-joint, and sometimes each bearing a little hoof. Rudiments of two other toes still are sometimes found to occur as bits of gristle or cartilage at the base of the splint-bones.

Going back in the history of the horse family as far as the mammalian age, we find that

1 Dana's Manual of Geology, pp. 504-507; article IIorse, by Professor O. C. Marsh, in Johnson's Cyclopædia.