Note 15 — THE MIND OF WOMAN AND THE LOWER RACES
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Food affords the basis for metabolic changes in the parent organism, but it is probable that food is less directly related than heat and light to the determination of sex. Sachs, whose experiments must be given the greatest possible weight, has determined that the ultra-violet rays of light are necessary to the chemical changes essential to the formation of the reproductive organs. (J. Sachs, "Ueber die Wirkung der ultravioletten Strahlen auf die Blüthenbildung," Gesammelte Abhandlungen über Pflanzen-Physiologie, Vol. I, pp. 293ff.) More recently, Klebs has shown that by diminishing the intensity of light the development of female sex organs in ferns can be interrupted, so that, in spite of the presence of male organs, fertilization is impossible; at the same time, the prothallia are enabled in weak light to grow feebly and to put out small asexual processes, which in the presence of bright light become normal prothallia. Similarly, the development of sexual organs in algae is dependent on a certain intensity of light, and the plant remains sterile if the light is diminished below a certain point. (G. Klebs, Ueber einige Probleme der Physiologie der Fortpflanzung, pp. 13-16.)