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 ORIGIN AND EVOLUTION OF LIFE

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��acters arise definitely and continuously, and, as Osbom has subse- quently shown, adaptively.2» It is unfortunate that the same term, "mutation,** was chosen by de Vries to express his observation that

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�� ��Fig. 17. Successiyb Mutations of Bpirifer mucronatus. Specimens from the Alpena section arranged by Grabau. In the scale of strata at the right 8V4 mm. » 100 ft. depth.

��certain characters in plants arise discontinuously through changes in the chromatin and without any definite direction or adaptive trend. The essential feature of de Vries's observations, in contrast to Waagen's, is that of discontinuous saltations either in indefinite or non-adaptive directions.

{To he coniiwued)

List of Woeks Cited

Calkins, Gary K., 1916. Gkneral Biology of the Protozoan Life Cycle. Amer.

Naturalist, Vol. L,, No. 593, May, 1916, pp. 257-270. Darwin, Charles, 1859. On the Origin of Species, by Means of Natural Selec- tion; or the Preservation of Favoured Races in the Struggle for Life.

London, 1859. Heron-Allen, Edward, 1915. Contributions to the Study of the Bionomics and

Reproductive Processes of the Foraminifera. Phil, Trans., Vol. CCVI.,

B. 329, June 23, 1915, pp. 227-279. Hutchinson, Henry Brougham (with Russell, Edward John), 1909. The Effect

of Partial Sterilization of Soil on the Production of Plant Food.

Introd. and Part I. See Russell, 1909. 1913. Part II. See Russelly

1913. Jennings, H. S., 1906. Behavior of the Lower Organisms. New York, 1906.

2» Osbom, Henry Fairfield, 1912.

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