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 ORIGIN AND EVOLUTION OF LIFE 289

��THE ORIGIN AND EVOLUTION OF LIFE UPON THE EARTH^

By henry FAIRFIELD OSBORN

COLUMBIA UNIVEBSITY, AMEBICAM MUSEUM OF NATUBAX^ HISTOBY

Lecture I. Part III

Biochemical Evolution of Bacteria — Evolution of Protoplasm and of Chro- matin — The Fundamental Biologic Law — Chlorophyll and the Energy of Sunlight — ^Alg©.

Primary Stages of Biochemical Evolution in Bacteria

A BACTERIA-LESS earth and a bacteria-less ocean would soon be uninhabitable either for plants or animals; conversely, it is probable that bacteria-like organisms prepared both the earth and the ocean for the further evolution of plants and animals, and that life passed through a very long bacterial stage.

Owing to their minute size or actual invisibility bacteria are classi- fied less by their shape than by their chemical actions, reactions, and interactions, the analysis of which is one of the triumphs of modern research. In the origin of life they lie half way between the hypothet- ical chemical pre-cellular stages (pp. 179-189) and the chemistry and definite cell structure of the lowliest plants or algae. The size of bac- teria is in inverse ratio to their importance in the primordial and present history of the earth. The largest known are slightly above 1/20 of a millimeter in length and 1/200 of a millimeter in width.^ The smaller forms range from 1/2000 of a millimeter to organisms on the very limit of microscopic vision, 1/5000 of a millimeter in size, and to the bacteria beyond the limits of microscopic vision, the existence of which is in-

1 Fourth course of lectures on the William EUery Hale Foundation, Na- tional Academy of Sciences, delivered at the meeting of the academy at Wash- ington, on April 17 and 19^ 1916. The author desires to express his special acknowledgments to Professor E. B. Wilson, of Columbia University, Dr. I. J. Kligler, of the American Museum of Natural History, Professor T. H. Good- speed, of the University of California, and Dr. M. A. Howe, of the New York Botanical Garden, for notes and suggestions used in the preparation of this section.

2 The influenza baciUus, 5/10 X 2/10 of a micron (1/1000 mm.) in size, and the germ of infantile paralysis, measuring 2/10 of a micron, are on the limit of microscopic vision. Beyond these are the ultra- microscopic bacteria, some of which can pass through a porcelain filter. See Jordan, Edwin O., 1908, pp. 52, 53.

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