General Theoretical Meaning of the Idea of Species.—Distinction between the Theoretical and Practical Definition of the Idea of Species.—Cuvier’s Definition of Species.—Merits of Cuvier as the Founder of Comparative Anatomy.—Distinction of the Four Principal Forms (types or branches) of the Animal Kingdom, by Cuvier and Bär.—Cuvier’s Services to Palæontology.—His Hypothesis of the Revolutions of our Globe, and the Epochs of Creation separated by them.—Unknown Supernatural Causes of the Revolutions, and the subsequent New Creations.—Agassiz’s Teleological System of Nature.—His Conception of the Plan of Creation, and its six Categories (groups in classification).—Agassiz’s Views of the Creation of Species.—Rude Conception of the Creator as a man-like being in Agassiz’s Hypothesis of Creation.—Its internal Inconsistency and Contradictions with the important Palæontological Laws discovered by Agassiz 47 CHAPTER IV. THEORY OF DEVELOPMENT ACCORDING TO GOETHE AND OKEN. Scientific Insufficiency of all Conceptions of a Creation of Individual Species.—Necessity of the Counter Theories of Development.—Historical Survey of the most Important Theories of Development.—Aristotle.—His Doctrine of Spontaneous Generation.—The Meaning of Nature-philosophy.—Goethe.—His Merits as a Naturalist.—His Metamorphosis of Plants.—His Vertebral Theory of the Skull.—His Discovery of the Mid Jawbone in Man.—Goethe’s Interest in the Dispute between Cuvier and Geoffroy St. Hilaire.—Goethe’s Discovery of the two Organic Formative Principles, of the Conservative Principle of Specification (by Inheritance), and of the Progressive Principle of Transformation (by Adaptation).—Goethe’s Views of the Common Descent of all Vertebrate Animals, including Man.—Theory of Development according to Gottfried Reinhold Treviranus.—His Monistic Conception of Nature.—Oken.—His Nature-philosophy.—Oken’s Theory of Protoplasm.—Oken’s Theory of Infusoria (Cell Theory).—Oken’s Theory of Development 72 CHAPTER V. THEORY OF DEVELOPMENT ACCORDING TO KANT AND LAMARCK.