History of the Development of the Earth.—Kant’s Theory of the Development of the Universe, or the Cosmological Gas Theory.—Development of Suns, Planets, and Moons.—First Origin of Water.—Comparison of Organisms and Anorgana.—Organic and Inorganic Substances.—Degrees of Density, or Conditions of Aggregation.—Albuminous Combinations of Carbon.—Organic and Inorganic Forms.—Crystals and Formless Organisms without Organs.—Stereometrical Fundamental Forms of Crystals and of Organisms.—Organic and Inorganic Forces.—Vital Force.—Growth and Adaptation in Crystals and in Organisms.—Formative Tendencies of Crystals.—Unity of Organic and Inorganic Nature.—Spontaneous Generation, or Archigony.—Autogony and Plasmogony.—Origin of Monera by Spontaneous Generation.—Origin of Cells from Monera.—The Cell Theory.—The Plastid Theory.—Plastids, or Structural Units.—Cytods and Cells.—Four Different Kinds of Plastids. In our considerations hitherto we have endeavoured to answer the question, “By what causes have new species of animals and plants arisen out of existing species?” We have answered this question according to Darwin’s theory, that natural selection in the struggle for existence—that is, the interaction of the laws of Inheritance and Adaptation—is completely sufficient for producing mechanically the endless variety of the different animals and plants, which have the appearance of being organized according to a plan for a definite purpose. Meanwhile the question must have already repeatedly presented itself to the reader, how did the first organisms, or that one original and primæval organism arise, from which we derive all the others? This question Lamarck(2) answered by the hypothesis of _spontaneous generation_, or _archigony_. But Darwin passes over and avoids this subject, as he expressly remarks that he has “nothing to do with the origin of the soul, nor with that of life itself.” At the conclusion of his work he expresses himself more distinctly in the following words:—“I imagine that probably all organic beings which ever lived on this earth descended from some primitive form, which was first called into life by the Creator.” Moreover, Darwin, for the consolation of those who see in the Theory of Descent the destruction of the whole “moral order of the universe,” appeals to the celebrated author and divine who wrote to him, that “he has gradually learnt to see that it is just as noble a conception of the Deity to believe that he created a few original forms capable of self-development into other and needful forms, as to believe that he required a fresh act of creation to supply the voids caused by the action of his laws.”