The mutations of opinion on the subject during the last fifty years have been remarkable.
A due appreciation of the far-reaching results of " correlated variation " must, it appears, give a new and distinct explanation to the phenomena which are referred to as " large mutations," " discontinuous variation " and " saltatory evolution."
Professor Flinders Petrie, in his Huxley Lecture for 1906 on Migrations (reprinted by the Anthropological Institute), deals with the mutations and movements of races from an anthropological standpoint with profound knowledge and originality.
He proposed the term " mutations " for the minute progressive changes of single characters in definite directions as observed in successive stratigraphic levels.
More recent analysis has shown, however, that certain modifications observed within the same stratigraphic level are really grades of mutations which show divergences comparable to those found in successive levels.
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