The cross section of the hair of the so-called Caucasians, including the Mediterranean, Alpine and Nordic subspecies, is an oval ellipse and consequently is intermediate between the cross-sections of the Negroes and Mongoloids. Hair of this structure is wavy or curly, never either kinky or absolutely straight and is characteristic of all the European populations almost without exception. Of these three hair types the straighter forms most closely represent the earliest human form of hair. We have confined the discussion to the most important characters but there are many other valuable aids to classification to be found in the proportions of the body and the relative length of the limbs. In this latter respect, it is a matter of common knowledge that there occur two distinct types, the one long legged and short bodied, the other long bodied and short legged. Without going into further physical details, it is probable that all relative proportions in the body, the features, the skeleton and the skull which are fixed and constant and lie outside of the range of individual variation represent dim inheritances from the past. Every generation of human beings carries the blood of thousands of ancestors, stretching back through thousands of years, superimposed upon a prehuman inheritance of still greater antiquity and the face and body of every living man offer an intricate mass of hieroglyphs that science will some day learn to read and interpret. Only the foregoing main characters will be used as the basis for determining race and attention will be called later to such temperamental and spiritual traits as seem to be associated with distinct physical types. We shall discuss only European populations and, as said, shall not deal with exotic and alien races scattered among them nor with those quarters of the globe where the races of man are such that other physical characters must be called upon to provide clear definitions. A fascinating subject would open up if we were to dwell upon the effect of racial combinations and disharmonies, as, for instance, where the mixed Nordic and Alpine populations of Lombardy usually retain the skull shape, hair color and stature of the Alpine race, with the light eye color of the Nordic race, or where the mountain populations along the east coast of the Adriatic from the Tyrol to Albania have the stature of the Nordic race and an Alpine skull and coloration. III RACE AND HABITAT The laws which govern the distribution of the various races of man and their evolution through selection are substantially the same as those controlling the evolution and distribution of the larger mammals.