The fundamental idea, which must necessarily lie at the bottom of all natural theories of development, is that of a gradual development of all (even the most perfect) organisms out of a single, or out of a very few, quite simple, and quite imperfect original beings, which came into existence, not by supernatural creation, but by spontaneous generation.[1] [1] Haeckel, _History of Creation_, 1884, vol. i., p. 75. According to the theory of evolution as elaborated by scientists, the history of man begins with small animated particles, or Monera, which appeared in the primeval sea. These marine specks were albuminous compounds of carbon, generated by the sun’s heat, which made their appearance as soon as the mists which enveloped the earth were sufficiently cleared away to permit the rays of the sun to penetrate them and reach the surface of the globe. Concerning the origin of the principle of life which these particles contained, or regarding the development of organic bodies from inorganic substances, the more timid among naturalists declare that in the present state of human knowledge it is impossible to know anything, while others of them, more bold, or more confident of the latent powers of the human intellect, after having elaborated a natural or mechanical explanation for the development of all organic forms, are not disposed to accept a supernatural theory for the beginning of life. For example, since organic structures represent the development of matter according to laws governing the chemical, molecular, and physical forces inherent in it, it is believed that the gulf separating organic and inorganic substances is not so difficult to span as has hitherto been supposed. Among those who hold this view may be ranked the celebrated naturalist, Ernst Haeckel. Regarding the phenomena of life this writer observes: “We can demonstrate the infinitely manifold and complicated physical and chemical properties of the albuminous bodies to be the real cause of organic or vital phenomena.”[2] Indeed, in whatever manner the vital force within them originated, naturalists agree that from these particles have been derived all the forms, both animal and vegetable, which have ever existed upon the earth. [2] _History of Creation_, vol. i., p. 331.