man appeared on the globe. He is to be a mental, intelligent being. But he is not to be governed by appetite or mere prudential considerations. These are animal, not human motives. These are not to be disregarded any more than digestion can be safely disregarded by man. But they are not to be his chief motives. He must subordinate these to the higher motives furnished by right and duty. Man is not merely a mental but a moral being. If he sinks below this plane of life he is not following the path marked out for him in all his past development. In order to progress, the higher vertebrate had to subordinate everything to mental development. In order to become man it had to develop the rational intelligence. In order to become higher man, present man must subordinate everything to moral development. This is the great law of animal and human development clearly revealed in the sequence of physical and mental functions.

Must man be a religious being also? This question we must try to answer in a future lecture.

CHAPTER VI

NATURAL SELECTION AND ENVIRONMENT

But

I HAVE attempted to show that animal development has not been an aimless drifting. Functions developed and organs arose and were perfected in a certain order. First the purely vegetative organs appeared, and the animal lived for digestion and reproduction; then came muscle and it brought with it nerve. these were not enough; the brain had all the time been gradually improving, and now it becomes the dominant function to which all others are subordinated. The experiment was fairly tried. Mere digestion and reproduction are carried to about the highest perfection which can be expected of them in worms and mollusks. The bird tried what could be done with digestion ministering to locomotion guided by the very keenest senseorgans and controlled by no mean brain. Even this experiment was not a success. But one organ remained, the brain, and on its mental possibilities depend the future of the animal kingdom. Vegetative organs and muscle have been tried and found wanting.'

We have followed hastily the development of mind. The mind began its career as the servant of digestion, recognizing and aiding to attain food. Action is at first mainly reflex. But conscious perception plays an ever more important part. The animal is at first guided by natural selection through the survival of 1 See chart, p. 310.

the most suitable reflex actions, then by inherited tendencies, finally by its own conscious intelligence and will. The first motives are the appetites, but these are succeeded by ever higher motives as the perceptions become clearer and more subtile relations in environment are taken into account. Governed first purely by appetites, the will is ever more influenced by prudential considerations, and finally shows well-developed "natural affections." It has set its face toward unselfishness.

Digestion and muscle, as well as mind, have persisted in man. He is not, cannot be, disembodied spirit. And in his mental life reflex action and instinct, appetite and prudence, are still of great importance. But the higher and supreme development of these powers could never have resulted in man. They might alone have produced a superior animal, never man. His mammalian structure found its logical and natural goal in family and social life. And even the lowest goal of family life is incompatible with pure selfishness, and as family life advanced to an ever higher grade it became the school of unselfishness and love. And social life had a similar effect.

Moreover, man as a social being early began to learn that he could claim something from his fellows, and that he owed something to them. If he refused to help others, they would refuse to help him. This was his first, very rude lesson in rights and duties. Love, duty, and right have ever since been the watchwords of his development and progress. We have not yet considered, and must for the present disregard, the value and efficiency of religion in aiding his advance. At present we emphasize only the historical

fact that man has not become what he is by a higher development of the body, nor by giving free rein to appetite, nor yet by making the dictates of selfish prudence supreme. And if there is any such thing as continuity in history, such modes and aims of life, if now followed, would surely only brutalize him and plunge him headlong in degeneration. He must live for right, truth, love, and duty. In just so far as he makes any other aim in life supreme, or allows it to even rival these, he is sinking into brutality. This is the clear, unmistakable verdict of history, and we shall do well to heed it.

But granting all that can be claimed for this sequence, have not the lower forms whose anatomy we have sketched-worm, fish, and bird-halted at various points along this line of march? Yet they have evidently survived. And if they have found safe restingplaces, cannot higher forms turn back and join them? In other words, is not degeneration easier than advance and just as safe? What is the result if an animal tries to return to a lower plane of life or refuses to take the next upward step? Generally extermination. The very classification of worms in a number of small isolated groups, which must once have been connected by a host of intermediate forms, is indisputable proof of most terrible extermination. They did not go forward, and the survivors are but an infinitesimal fraction of those which perished. Let us take an illustration where paleontology can help us. The earth was at one time covered with marsupial mammals. Some advanced into placental forms. The great mass remained behind. And outside of Australia the opossums are the only survivors of them all. And this is

only one example where a thousand could be given. Place is not long reserved for mere cumberers of the ground. There are so few exceptions to this statement that we might almost call it a law of biology. Let us see how it fares with an animal which retreats to a lower plane of life. A worm, rather than seek its own food, becomes a parasite. It degenerates, but still is easily recognized as a worm. A crustacean tries the same experiment, though living outside of its host instead of in it. It sinks to a place even lower, if possible, than that of the parasitic worm. A locomotive form becomes sessile. It loses most of its muscles and the larger part of its nervous system; and even the digestive system, which it has made the goal of its existence, is inferior to that of its locomotive ancestors and relatives. But to the vertebrate these lowest depths of stagnation and degeneration are, as a rule, impossible. From true fish upward parasitism and sessile life are practically impossible. Here stagnation and degeneration mean, as a rule, extinction. Of all the relatives of vertebrates back to worms only the very aberrant lines of amphioxus and of the tunicata remain. Of the rest not a single survivor has yet been discovered. And yet what hosts of species must have peopled the sea. The primitive round-mouthed fishes have practically disappeared. The ganoids survive in a few species out of thousands. The amphibia of the carboniferous and the next period and the reptiles of the mesozoic have disappeared; only a few feeble degenerate remnants persist. And this was necessarily so. Each advancing form crowded hardest on those which occupied the same place and sought the same food, that is, the members of the same species. And the first to