I. _Negroids._ Color yellowish brown to black, stature large or very small. Hair short, black or reddish brown, frizzly, flattened-elliptical in cross-section. Nose broad and flattened. Cheek-bones small, somewhat retreating. Examples: Negritoes, Negroes. II. _Mongoloids._ Color yellowish. Stature below average. Hair coarse, lank, round in cross-section. Nose very small. Cheek-bones prominent. Examples: Malays, Chinese, Japanese, Thibetans, Siberian "Hyperboreans." III. _Americans._ Color reddish or coppery. Stature large. Hair long, lank, coarse, black, round in cross-section. Nose large, bridged, or aquiline. Cheek-bones moderately prominent. (Probably a branch of II.) Examples: Indians of North and South America. IV. _Caucasians._ Color pale or florid. Hair long, wavy or straight, elliptical in cross-section. Nose large, straight or arched. Cheek-bones small, unmarked. Examples: Hamitic, Semitic, and European peoples. We may now imagine quite primitive human beings starting from their early home and seeking their fortunes widely apart. They came under quite different climatic and other physical conditions. Their environment, problems, stimuli, and opportunities were unlike. Thus, having become more or less unlike in the homeland, they gradually became differentiated into the present great groups or races already mentioned. Some started earlier or marched more rapidly than others. Many proved unequal to the dangers and difficulties of the journey or new place of settlement, and disappeared. Many stagnated or degenerated. Only the comparatively successful or fortunate have survived. Hence, our scheme is hardly an adequate expression of prehistoric racial groups and their characteristics, except in very general outline. We have seen that the apes, retreating before the approach of harsh and dry climatic conditions and diminished forest areas and food supply, migrated southward into India and Africa. The Orang settled in Borneo, Pithecanthropus in Java, the Chimpanzee and Gorilla went into Africa. These routes presented the fewest difficulties and demanded the least readaptation or change of habit. The climate was mild and food generally abundant and easily obtained. Their environment was neither stimulating, trying, nor exacting. Progress was hardly to be expected, but survival was far easier than in more northerly regions. The Negritos followed almost exactly the same routes. We find them purest and perhaps least modified in the "Pygmies" of the African forests; but also in the Malay Peninsula, the Andaman Islands, and the Philippines. De Morgan believes that he has found proofs of their presence on the Iranian plateau at a comparatively late date.