Dr. Darwin’s theory of evolution differed from that of Buffon in at least one important respect. Nowhere does he stress the direct influence of environment in the production of variations; on the contrary, he maintained that modifications spring from the reactions of the organism. In this he clearly stated the theory which is generally known as Lamarck’s version of the theory of the transmission of acquired characters. In fact, he carried his ideas much farther than did Lamarck, attributing to plants the attribute of sendibility, and supposed their evolution to be due to their own efforts toward the development of certain characters. Adaptations, which Aristotle had believed to be caused by a definite plan, Dr. Darwin interpreted in a purely naturalistic manner. The Creator had, at the beginning, endowed organisms with the power to change and develop, and that power was handed down from one generation to another until it was possessed by every animal and plant. This power was the cause of all variation, adaptation, and evolution, and there was no further divine interference. Dr. Darwin did not see any great, all-encompassing plan of improvement, such as is postulated by the teleologists of today; to him everything was the logical and necessary outcome of the original powers of living things. In this, as we shall see, he believed essentially as do modern evolutionists who do not see in the laws of the universe any necessity for abandoning religion, but who at the same time do not believe in a highly personal god who, as one theologian expressed it recently, “works out His divine will through the processes of evolution.” Dr. Darwin was author of two other distinctly modern ideas, among the most important of his entire work. The first of these is that all living things are descended from a single original living mass, or “filament”--that every living thing on the earth is related to every other living thing. The second is that the process of evolution is almost inconceivably slow, and that millions upon millions of years have been necessary for it. The first idea, while quite conceivably true, can never be proved definitely, but the second has been demonstrated over and over again. Just how many millions we shall allow is, of course, undetermined; some authorities demand sixty; others say that eight hundred is a figure none too large. In this series of books the larger figure is adopted, not because we are certain that it is right, but because it seems to fit more closely with the facts of evolution than do the smaller ones. How fully Dr. Darwin was a prophet of modern scientific chronology we are just beginning to recognize.