1 The race problem has someti:mes been described as a problem in assimilation. It is not always clear, however, what assimilation means. Historically the word has had two distinct significations. According to earlier usage it meant "to compare" or "to make like." According to later usage it signifies "to take up and incorporate." There is a process that goes on in society by which individuals spontaneously acquire one another's language, characteristic attitudes, habits, and modes of behavior. There is also a process by which individuals and groups of individuals are taken over and incorporated into larger groups. Both processes have been concerned in the formation of modern nationalities. The modern Italian, Frenchman, and German is a composite of the broken fragments of several different racial groups. Interbreeding has broken up the ancient stocks, and interaction and imitation have created new national types which exhibit definite uniformities in language, manners, and formal behavior. It has sometimes been assumed that the creation of a national type is the specific function of assimilation and that national solidarity is based upon national homogeneity and "like-mindedness." The extent and importance of the kind of homogeneity that individuals of the same nationality exhibit have been greatly exaggerated. Neither interbreeding nor interaction has created, in what the French term "nationals," a more than superficial likeness or like-mindedness. Racial differences have, to be sure, disappeared or been obscured, but individual differences remain. Individual differences, again, have been intensified by education,