In the worm forms, which evolve from the Gastrœada, we come across the first attempt at special sense-organ formation, in the shape of depressions on the integument of the body. The Himatega, or sack-worms, possess a rudimentary spinal cord, and were the parents of the first true vertebrates, organisms without skulls or brains, but with a true vertebral cord. These little vermiform animals, in addition to their rudimentary spinal cords, exhibited upon the surface of the body several small depressions, which answered the purpose of a set of special sense-organs, one tiny depression being set apart especially for the perception of light waves, another for the perception of sound waves, another for the perception of odours, etc.; and thus gradually came about that wonderful evolutionary process by which bodies became endowed with more or less perfect special sense-organs. As the animal kingdom developed into higher and higher forms of life, and skulls and brains became the order of the day, the special sense-organs became possessed of larger powers, at the same time that the whole nervous organisation assumed higher and more complex functions, resulting eventually in a very gradual unfolding of the most wonderful of all the latent potentialities of universal life—the marvel of consciousness. This is the present climax of Nature’s evolution, the grandest and most awful achievement of that hidden and mysterious force which baffles comprehension, and beside which all things seen, heard, or felt pale into insignificance. To point out the precise method of the evolution of mind, step by step, until the final climax of consciousness was reached, would require an abler pen than mine; therefore I shall be content to briefly notice the different products of intellectual development in the order in which they are unfolded, showing the analogy between ontogenesis, or the life-history of the individual, and phylogenesis, or that of the whole race, not now as regards bodily, but only mental, evolution. We must ever remember that the biogenetic law insists that the process of development in the race is reflected in miniature in the embryonic history of every individual. In other words, it is, beyond doubt, an accepted article of faith with biologists that the development of the individual from the embryo _in utero_ to the full-grown man is an exact counterpart of the development of the whole race from the primitive protoplasmic atom, the lowly Moneron, to _homo sapiens_, equally in regard to mental as to bodily evolution.