What we do know is that this race shows as perfect an adaptation to the climate of forest-clad temperate Europe as Mediterranean man does to the dry climate of that region. Just as the border of the Mediterranean is the province of Mediterranean man, and has been his for countless ages, so north-western Europe is the almost unchallenged possession of Nordic man. Between the two, along the great wedge of uplands, is the land of Alpine man, which widens to the east, his original home. Just as Mediterranean man in the days of his prime pushed north wherever conditions permitted, so Nordic man has pushed south, across the Alpine barrier, both in the literal and anthropological sense, and has left traces of his coming even within the territory of Mediterranean man. Just as the dark-haired Welsh and the dark-haired strain of Scottish Highlanders bear witness to the old exploits of Mediterranean man, so do the fair-haired, tall-statured Lombards bear witness to the former activity of Nordic man. Nevertheless, the main territory of the two races is widely separated. The relation of these two types, at least, to their zones of distribution is relatively easy to explain. Mediterranean man is highly susceptible to diseases of the breathing-organs to which the fair-haired Nordic type is more resistant. Here is one possible explanation of their command of their respective habitats, and there are many others. The forest-dwelling Nordic type, as Prof. Penck points out, must necessarily have had the family as the unit, for only by dwelling in small family groups can primitive man war against the forest. Mediterranean man, with his early use of irrigation, had necessarily to evolve a larger unit, for irrigation means extensive co-operation, so that political organisations would arise early in the Mediterranean. We can hardly doubt that these two facts had some bearing on the survival rate of the two races. The Nordic race with their strong family life, and with their abundant pasturage, had doubtless a relatively low death-rate among the children, though, as Prof. Myres points out, the struggle in adult life must have been keen. In the Mediterranean, as he also notes, the dry summer means difficulties with the water supply, difficulties in sanitation, and the risk of pestilence, which, with the abundant supply of fruit and the absence or scarcity of milk, has probably always meant a very high death-rate among the children. But the fact that the struggle for existence among adults was much less keen than among the forest folk, perhaps prevented this high infantile death-rate from being a great handicap. Once the geographical surroundings of the two peoples were changed by migration, the qualities which aided them to survive in their native habitat might become a positive hindrance. In brief, as two types evolved in harmony with well-defined geographical conditions, the very perfectness of their respective adaptations would hinder either from appropriating the