Having no longer any hope to prove by direct demonstrations that the distinctive characters of human races are transformations of one primitive type, the monogenists sought for indirect proofs. They believed to have found them in this fact, or rather assertion, that there is always a certain relation between the characters of human races and the media in which they exist. On close examination this assertion is found to be without any foundation. On studying one by one the principal ethnological characters and their distribution on the surface of the globe, it has been shown that there is no relation between these different characters and the climatic and hygienic conditions. The monogenists then resorted to an argumentation still more indirect. They advanced that in the whole _genus homo_ there existed a fund of common ideas, creeds, knowledge, and language, attesting the common origin of all human beings. It might be objected that this argument is without any value whatever; considering that indirect communications between peoples of different origin might have passed to each other words, usages, and ideas. But a profound study of the question has shown that there are certain peoples who have absolutely no notion of God or soul, whose languages have no relation whatever to any, who are altogether anti-social, and who differ from the Caucasians more by the intellectual and moral capacities than by their physical characters. There was even no necessity to insist upon the difficulty, or rather geographical impossibility of the dispersion of so many races proceeding from a common origin, nor to remark that before the remote and the almost recent migrations of Europeans, each natural group of human races occupied upon our planet a region characterised by a special fauna; that no American animal was found either in Australia nor in the ancient continent, and where men of a new type were discovered, there were only found animals belonging to species, even to genera, and sometimes to zoological orders, without analogues in other regions of the globe.