Under these circumstances, the symptoms of rutting are sufficiently distinctly marked to make it possible, as Thury suggests, to determine the advanced state of ripeness or its commencement in the ova. But it is scarcely possible to say when the period of ripeness commenced in this ovum or that. An ovum which had begun to ripen early may, at the beginning of the rutting time, have attained to the condition of a male-producing ovum. At the same time, others which are fertilized at the conclusion of the rutting, but had begun to ripen comparatively late, may, at the end of the rutting time, not yet have advanced far enough to be able to develop male individuals. * * * * * Thury bases his doctrine on a number of phenomena of the vegetable and animal world, and upon various experiences in the case of man. He also adduces many statistical data in explanation and support of his theory. The observations on plants make it indisputably clear that all the circumstances which favor growth and ripening are favorable conditions for the development of male organs. If all these circumstances are lacking, female organs are produced. Dark and cold, for instance, cause the male organs to perish. In recent times a great number of extended studies of the phenomena of vegetable life in this direction have appeared. I may mention more particularly the following experiments made by M. von Treskow in Gorlitz with _Arisæma_ (Verhandlungen des Botanischen Vereins der Provinz Brandenburg, 1895). This plant first produces male flowers. In the later year, when it has become larger, it produces female flowers. The transition from the male flowers of the early stage to the female flowers of the later stage can be hastened at pleasure by planting in rich garden mold and manuring with horn shavings. If, on the other hand, the plant be placed in poor, sandy soil, it reverts to the male flowers. The same author quotes in his essay a remark of Heyer’s (Halle, 1884), who declares that no sufficient observations exist respecting the influence which different situations exert over sex. I adduce this instance, for the sake of remarking respecting it, that on this subject also controversies exist, which must be settled by wider studies of the life of plants. Cornaz has tried to derive from cows evidence in support of Thury’s theory. He had twenty-nine cows impregnated with attention to the rutting time, and from twenty-nine births received twenty-two females and seven males. Cornaz attested his experiment by a declaration, and the experiment was repeated in the French state domains. But the experiment alone was striking enough to invite repetition. It also met with partial success. But the plan was afterwards entirely given up, perhaps in consequence of disappointments.