In the psychological and sociological life of all three divisions of the population, there are many curious points of similarity and difference, which will be stated later on in this account.

The illustrations were made by Mr. Rudolf Weber; the photographs in the field, by Mr. Alexander Axelrod of Switzerland, and by myself. The drawings for Plates V (Fig. 2), VII, XIV, were made by Mr. A. E. Döring from several photographs in my collection.