The earliest definable groups indeed seem confined to the shores of the enlarged post-glacial sea. During the Ice Age Scotland, covered with glaciers, had been simply uninhabitable. The whole life of Neolithic society is revealed with such an unique wealth of detail in the miraculously preserved domestic sites of Skara Brae and Rinyo that a description of stage II can begin most conveniently there, albeit at the cost of a departure from the strictly chronological order. The self-contained units just described had been linked up at least by the last phase at Skara Brae into a larger whole through the system of covered passages. It is much less easy to define the economy of the Megalith-builders; for no actual dwellings and only two domestic sites are known. In speculating on the course of social development the author have anticipated the order of events.