The history of Europe presents a long series of nations successively rising and falling in the scale of prosperity and influence. Such persistent alternations suggest a common cause underlying the phenomena. All history is the record of change. The outward change as recorded by the chronicler has probably its counterpart in unnoticed variations of the internal biological structure of the nation. Most nations are composite in character. They contain two or more racial stocks, fulfilling different functions in the national life. It is probable that the proportion in which these stocks are present is not always constant. The variation in proportion is possibly the agent effecting the internal change in structure, which becomes manifest outwardly in the rise or decline of the nation. The physical characters of the population of Europe during historic times indicate three chief races: (1) the Mediterranean, (2) the Alpine, (3) the Northern. The individuals of these races possess also distinct mental and intellectual attributes, and the history of Europe is fundamentally the story of the interaction of the three races. It is suggested that the supreme power of Greece and Rome, each in its own direction, was due to the attainment of a fortunate balance between the social and political functions of the constituents of the nation, the directing power being supplied chiefly by the invaders of northern race, who formed the dominant class among the southern indigenous Mediterranean population. In each case, the northern elements grew gradually less, through such agencies as losses in war, the selective action of a differential birth rate, and by racial merging into the more numerous southern stock. The outburst of artistic genius and intellectual pre-eminence which marked the Renaissance in North Italy may perhaps be due to a similar racial composition, the northern elements being supplied by the descendants of the barbarian invaders of the later Roman Empire. Great Britain has also similar racial elements. The Mediterranean race, spreading up the shores of the Atlantic, enters largely into the composition of the people of the south-west. The northern element, immigrant from the shores of the Baltic and North Sea, is strongest in the east and north. We know that there are now at work two influences affecting the average racial character of the English nation; (1) the increase in the urban population at the expense of the rural, (2) the voluntary restriction of the birth rate which affects certain sections of all classes more than others. It is probable that both these changes tend to favour selectively the southern racial elements at the expense of the northern. Eventually, the present structure of society may become unstable in consequence of this racial alteration, and the necessary readjustment, in its turn, will contribute a chapter to history. SOME INTER-RELATIONS BETWEEN EUGENICS AND HISTORICAL RESEARCH. (Abstract.)