Every fact has a meaning.

itself would be without meaning or explanation. The essential argument in favour of "Darwinism" is that it brings all biological facts into unison from whatever field of investigation these facts may be derived. However much evolutionists have at times seemed to drift away from Darwin's conclusions, it is always the most accurate research and the sanest thought which come nearest the opinions set forth in the Origin of Species. The body of facts has grown enormously year by year, but the conclusions we must accept are substantially those laid down by Darwin himself.

Geographical distribution.

The facts of "geographical distribution," for example, have a meaning to us when we view them as the results of centuries of the restlessness of individuals. Each species of animal or plant has been subjected to the various influences implied in the term "natural selection," and under varying conditions its representatives have undergone many different modifications. Each species. may be conceived as making each year inroads on territory occupied by other species. If these colonies are able to hold their own in the struggle for possession they will multiply in the new conditions and the range of the species becomes widened. If the surroundings. are different, new species or varieties may be formed with time, and these new forms may again invade the territory of the parent species. Again, colony after colony of species after species may be destroyed by other species or by uncongenial surroundings.

Only in the most general way can the history of any species be traced; but, could we know it all, it would be as long and eventful a story as the history of the colonization and settlement of North America by immigrants from Europe. Each region where animals or

plants can live has been thousands of times discovered, its colonization a thousand times attempted. In these efforts there is no co-operation. Every individual is for himself, every struggle a struggle for life and death. To each species each member of every other species is an alien and a savage.

Survival of the existing.

The study of geographical distribution shows the relations of creative processes to space. The forms inhabiting one district are the children of the earlier inhabitants. The survival of these forms is due to that which I have elsewhere called the "survival of the existing," for it is certain that in any part of the world a totally different grouping of animals or plants would have been equally fitted to the environment. The laws of geographical distribution may be summed up thus: The reason why any given species of animal or plant is not found in a given district is (a) because it could not get there from its own habitat, or (b), being there, it could not maintain itself either in competition with others or from the stress of environment, or else (c) it has in maintaining itself become altered into a distinct species.

Geological distribution.

In like manner the facts of geological distribution have a meaning when we view them in the light of the theory of descent. The birth, increase, decline, and final change or disappearance of species or types in geological history are necessary parts of the Darwinian theory. They would be inexplicable on any other hypothesis. These changes represent the survival of the fittest as related to time. With the lapse of time come changes in environment, and these changes produce corresponding changes in animal or plant life. But these changes on the earth and in its life are for the most part gradual

Epoch making

ones. The evolution of the earth and its life has rarely been subject to great leaps and catastrophes. Yet epoch-making events have taken place on the earth. Such changes in life, as the acquisition of lungs, of wings, of speech, are marked by the increased rapidity of the processes of evolution.

events.

Professor Bergen says: "Until an evolutionary rise of species had been assigned as an explanation of the succession of higher and higher animals and plants throughout the geological ages, what adequate reason for this progress of life could be given? Strike out from our present conception of the organic world, class after class, all notion of actual relationship by descent, and what have we left but a mighty host of extinct creatures whose rise, progress, and disappearance are far more unaccountable than that of the genii in the Arabian Nights?"

But not all change has been progress. The idea of some of the earlier evolutionists that the advance of

Change not progress.

life has been the simple result of an innate "uniform tendency toward progression" can not be maintained. For progress, while general, is by no means uniform or universal. Progress ceases when its direct cause ceases. In every group there are some members characterized by degeneration and loss of specialization. This is involved in the theory of "natural selection." If progress comes through competition, lack of competition would imply retrogression. When animals or plants are withdrawn from the stress of life to some protected condition, the character of the type is lowered. There is less need for specialization when the range of wants is narrowed. Hence it is that all parasitic animals or plants-lice, leeches, dodders, mistletoe, Indian pipe—are

degenerate forms. So it is with cave animals, as well as with most organisms of the deep sea or the far North. All forms which are withdrawn from open competition to a solitary and secluded life lose one by one the advantages which competition has gained for them, and are known as degenerate types. What is true of the lower animals is likewise true of man. The highest type of manhood, of human powers and human virtues, will come from victory in the struggle for existence and not from withdrawal from the struggle. Easy living always brings degeneration. The sheltered life is the source of weakness. The desire to get something for nothing is the bane of human society.

Parallel with the case of general degeneration of type is that of the degeneration of individual parts of the organism. An organ well developed in Vestigial organs. one group of animals or plants may in some other be reduced to an imperfect organ or rudiment so small or incomplete as not to perform its normal function, or, indeed, to serve any purpose whatever. Such rudimentary or functionless structures may be found in the body of any of the higher animals and in most or all of the higher plants. The appendix vermiformis and the unused muscles of the ears in man are examples. Such are also the atrophied lung, pelvis, and limbs of the snake, the "thumb" of the bird, the splint bone of the horse, and the like, without mentioning less familiar internal organs. By the theory of descent we may understand how much structures may be retained by the action of the law of heredity, while their reduction may be the result of long-continued disuse, or the growth and selection of other organs at the expense of these which are no longer needed.

Among a multitude of examples I need refer especially to but one-a recent discovery in homology.

Within the brain of man, resting on the optic lobes, is a little roundish structure scarcely larger than a pea, known as the pineal "gland" or "conarium." It has no evident purpose or

It

The pineal eye. function, and a philosopher once suggested that it might be the seat of the soul. is larger in the embryo, and still larger in the brains of some of the lower vertebrates. Recent investigations have shown that it is especially developed in certain lizards, and that in them it ends in a more or less perfect eye, which is placed between the

FIG. I.-Pineal body in the lizard (Hatteria) developed as rudimentary eye; p, pineal eye. After Spencer.

others in the centre of the forehead. These lizards have in fact three eyes, and the pineal body is the optic nerve of the third. In the common horned toad the pearl - like scale above the pineal eye can be readily recognised. The shrunken rudiment found in man is therefore what is left of an ancestral third eye, probably once characteristic of vertebrates, but now displaced and de

stroyed by the increased development and greater perfection of the outer pair. By the theory of descent the presence of the pineal body in man is a simple result.