There is a certain profit in studying one's own ancestry. It has been somewhat astonishing to me to find how very slight are the social oscillations traceable in a middle-class family and the families it intermarries with through several centuries. A professional family tends to form a caste marrying within that caste. An ambitious member of the family may marry a baronet's daughter, and another, less pretentious, a village tradesman's daughter; but the general level is maintained without rising or falling. Occasionally, it happens that the ambitious and energetic son of a prosperous master-craftsman becomes a professional man, marries into the professional caste, and founds a professional family; such a family seems to flourish for some three generations, and then suddenly fails and dies out in the male line, while the vigour of the female line is not impaired.

The new social adjustment of a family, it is probable, is always difficult, and if the change is sudden or extreme, the new environment may rapidly prove fatal to the family. Lorenz (Lehrbuch der Genealogie, p. 135) has shown that when a peasant family reaches an upper social class it dies out in a few generations.