Yet man is never at rest in his speculations as to causes; and he contrives all manner of theories to satisfy his demands for them. A favorite theory nowadays is what is called the Development theory, which proceeds on the assumption, that one germ of being was originally planted on the earth, and that from this germ, by the wondrous power of Life, all forms of vegetable and animal life have progressively been developed. Unquestionably, all living beings are organized on one grand plan, and the higher forms of living beings, in the process of their growth, successively pass through the lower organized forms. Thus, the human being is successively a monad, an a-vertebrated animal, an osseous fish, a turtle, a bird, a ruminant, a mammal, and lastly an infant Man. Through all these types of organization, Tiedemann has shown that the brain of man passes. This theory, however, does nothing to explain the causes of life, or the strikingly diversified, and yet determinate characters of living beings; why some so far transcend others in the stages of development to which they ascend, and how it is that they stop there—how it is that animals succeed each other in right lines, the offspring inheriting the physical structure and the moral disposition of their parents, and never, by any chance, stopping short at any other stage of being—man, for instance, never issuing in a lion, a fish, or a polypus. We can scarcely conceive it possible that, had merely the Germ of Being been planted on the earth, and “set a-going,” any thing like the beautiful harmony and extra ordinary adaptation which is every where observable throughout the animated kingdoms of Nature, would have been secured. That there has been a grand plan of organization, on which all living beings have been formed, seems obvious enough; but to account for the diversity of being, by the theory that plants and animals have gradually advanced from lower to higher stages of being by an inherent power of self-development, is at variance with known facts, and is only an attempt to get rid of one difficulty by creating another far greater. Chemists are equally at fault, in endeavoring to unvail the mysterious processes of Life. Before its power they stand abashed. For Life controls matter, and to a great extent overrules its combinations. An organized being is not held together by ordinary chemical affinity; nor can chemistry do any thing toward compounding organized tissues. The principles which enter into the composition of the organized being are few, the chief being charcoal and water, but into what wondrous forms does Life mould these common elements! The chemist can tell you what these elements are, and how they are combined, when dead; but when living, they resist all his power of analysis. Rudolphi confesses that chemistry is able to investigate only the lifeless remains of organized beings.