fortunately, is a man who writes his own prefaces. Readers of the fourth edition have, as a result, bis personal description of the evolution of his thinking about animal breeding. Having passed through the darkness of the pre-Mendelian era, the false hopes of the Mendelian period, and the difficulties and uncertainties of the Wright stage, he now presents the experimental justification for the New Philosophy. Beginning with the lore, so to speak, he has now arrived at the law.