Professor Henderson shows us how well this planet, with its oceans and continents, and its mechanical and chemical forces and elements, is suited to sustain life, but he brings us no nearer the solution of the mystery than we were before. His title, to begin with, is rather bewildering. Has the "fitness of the environment" ever been questioned? The environment is fit, of course, else living bodies would not be here. We are used to taking hold of the other end of the problem. In living nature the foot is made to fit the shoe, and not the shoe the foot. The environment is the mould in which the living organism is cast. Hence, it seems to me, that seeking to prove the fitness of the environment is very much like seeking to prove the fitness of water for fish to swim in, or the fitness of the air for birds to fly in. The implication seems to be made that the environment anticipates the organism, or meets it half way. But the environment is rather uncompromising. Man alone modifies his environment by the weapon of science; but not radically; in the end he has to fit himself to it. Life has been able to adjust itself to the universal forces and so go along with them; otherwise we should not be here. We may say, humanly speaking, that the water is friendly to the swimmer, if he knows how to use it; if not, it is his deadly enemy. The same is true of all the elements and forces of nature. Whether they be for or against us, depends upon ourselves. The wind is never tempered to the shorn lamb, the shorn lamb must clothe itself against the wind. Life is adaptive, and this faculty of adaptation to the environment, of itself takes it out of the category of the physico-chemical. The rivers and seas favor navigation, if we have gumption enough to use and master their forces. The air is good to breathe, and food to eat, for those creatures that are adapted to them. Bergson thinks, not without reason, that life on other planets may be quite different from what it is on our own, owing to a difference in chemical and physical conditions. Change the chemical constituents of sea water, and you radically change the lower organisms. With an atmosphere entirely of oxygen, the processes of life would go on more rapidly and perhaps reach a higher form of development. Life on this planet is limited to a certain rather narrow range of temperature; the span may be the same in other worlds, but farther up or farther down the scale. Had the air been differently constituted, would not our lungs have been different? The lungs of the fish are in his gills: he has to filter his air from a much heavier medium. The nose of the pig is fitted for rooting; shall we say, then, that the soil was made friable that pigs might root in it? The webbed foot is fitted to the water; shall we say, then, that water is liquid in order that geese and ducks may swim in it? One more atom of oxygen united to the two atoms that go to make