What question is there of the present day, respecting which we can consult the literature of the ancients, that does not take us back to the writings of Hippocrates, Aristotle, or Galen, or to those of the old authors of those oriental races whom we regard as the earliest cultivated peoples? Hippocrates held that to produce a male, the generative material must be of a stronger quality. The future destiny of the male rendered it necessary that it should be constructed on a stouter foundation. He must be capable of a stronger development, and must, therefore, be a product of stronger elements alike on the father’s and the mother’s side. A second hypothesis was soon added to this primary one, but without any foundation of facts. According to Aristotle, the woman supplied the primary material for the development of the future individual. It was the function of the man to give the impulse, in consequence of which the future individual came into being. Next followed the purely mythical theory, already mentioned, in which Anaxagoras believed. The much-sought-for origin of the future difference of sex in the various individuals was assigned to the right or left side of the organism. And Galen even concluded that the right side of the body was the warmer, and the left the colder, further claiming for the warmer side the privilege of producing male individuals. * * * * * Various notions respecting the origin of sex have been also accommodated to these primitive theories of the ancients, without resting upon any positive foundation. No evidence exists to show from whom they originated, nor how they were disseminated. Nevertheless, the historical connection of these speculations justifies a reference to them, and various hypotheses of this kind will be found in a little publication of Dr. Heinrich Janke’s (Stuttgart, 1896). The older literature on the subject of the generation of the sexes has been collected by His. (_Archiv für Anthropologie, Vol. IV. V._) In ‘_Das Weib in der Natur and Völkerkunde_’ (Leipzig), Ploss has collected ample information concerning both ancient and modern ideas on this subject amongst the different races of mankind. The procreative elements, furnished by the male and female organs, after their mixture, compete with each other, by virtue of their inherent forces, for the mastery. In this conflict, if the male molecules are the more numerous, a male results. On the contrary, if the female molecules are more numerous, the result is a female. Nicholaus Venette ascribes the difference of sex to the earliest phases of the life of the ovule. * * * * *