The theoretic interest, with which alone we need concern ourselves here, seems to me of two kinds. Professor Ripley, as a student of anthropology, declares, as the result of his inquiries, that there has been so large an admixture of round skulls with the (hypothetically assumed) original long skulls of the Hebrews that all signs of racial unity have disappeared. I, on the other hand, who have approached the subject as a student of history,[10] see no evidence of any such large admixture of alien elements in the race since its dispersion from Palestine, and have come, therefore, to the opposite conclusion--that the Jews now living are, to all intents and purposes, exclusively the direct descendants of the Diaspora. Here, then, anthropology and history--if Professor Ripley and I have respectively interpreted their verdicts aright--appear to speak in two opposite senses, and no conference at La Hague or elsewhere can appoint a court of appeal which can decide between contrary propositions by two different sciences. [Footnote 10: To prevent misunderstanding, I should perhaps add that I have not neglected the anthropological aspects of the question. My paper on The Racial Characteristics of Modern Jews, which appeared in the Journal of the Anthropological Institute for 1885, contained, I believe Professor Ripley would allow, the fullest account of Jewish anthropometry collected up to that date.] But the point in discussion seems to me to raise also a problem of exceeding interest within the anthropological sphere itself. Professor Ripley assumes that round heads beget round heads, and long heads descend from long heads for all time unchanged. That appears to carry with it the assumption that no amount of brain activity can increase the mass of brain, that skull capacity has no relation to mental capacity, and that alone among the organs of the body the brain and skull are incapable of growth, change, or development. The _crux_ of Jewish anthropology raises this problem, as I shall proceed to show, and, if I have interpreted history aright, offers valuable material toward its solution.