Under the Maples by John Burroughs

It is remarkable, I think, that Professor Osborn, in his "Origin and Evolution of Life," makes no account of the micro-organisms or unicellular lives that are older than the continents, older than the Cambrian rocks, and that have survived unchanged even to our times. I saw in the Grand Canon of the Colorado where they were laid down horizontally on the old Azoic or original rocks, as if by the hand of a mason building the foundation of a superstructure. All the vast series of limestone rocks are made up from the skeletons of minute living bodies. Other strata of rocks are made up of the skeletons of diatoms. Some of our polishing powders are made from these rocks. Formed of pure silex, these rocks are made up of the skeletons of organisms of many exquisite forms, _Foraminiferae_. The Pyramids are said to be built of rocks formed by these organisms. "No single group of the animal kingdom," says Mr. W. B. Carpenter, "has contributed, or is at present contributing, so largely as has the _Foraminiferae_ to the formation of the earth's crust. " In the face of these facts, how unsatisfactory seem Professor Osborn's statements that life probably originated on the continents, either in the moist crevices of rocks or soils, in the fresh waters of continental pools, or in the slightly saline waters of the "bordering primordial seas. " This last suggestion comes nearer the mark. There is no variation during geologic time of these primordial living organisms. All conceivable changes of environment have passed over them, but they change not. Bacteria struggle together, one form devouring another form. Unicellular life long precedes multicellular. Biologists usually begin with the latter; the former are fixed; with the latter begins development or evolution, and the peopling of the world with myriads of animal forms.