I. THE ethnological area here under consideration comprises the south-eastern corner of the Asiatic mainland, and nearly the whole of the Indian and Pacific Oceans. Of the three great divisions of the human family—the black, yellow, and fair—the two former alone are usually supposed to be represented in this region, the black by the Australians, extinct Tasmanians, Melanesians or Papûans, and Negritos, the yellow by the Indo-Chinese (Annamese, Siamese, Burmese, &c.), of the mainland, and the so-called “Malayo-Polynesians” of Oceanica. But it will be one of the main objects of these papers to show that room must here be henceforth made for the third also, and that most of the difficulties associated with the mutual classification of the other two are due to the omission or neglect of this third factor in the problem. It has long been an accepted doctrine of ethnologists that this fair or Caucasian type, using the term “Caucasian” in Blumenbach's sense, is limited by some mysterious law of nature or providential arrangement to the western portion of Asia, to the northern section of its African, and to nearly the whole of its European peninsula. But anthropology is a very young science, and as facts accumulate and knowledge expands, many of its conclusions too hastily arrived at will have to be modified or abandoned. The time seems to have already arrived for very materially modifying the views hitherto entertained regarding the geographical limits of the Caucasian species, which, instead of being confined to a western corner of the Old World, will be found to have been diffused in prehistoric times eastwards to within 2,500 miles of the American continent.