As time moved forward in the nineteenth century, with more collections coming back to Europe, and with more fossils being encountered, thinking began to turn toward explanations of the origin of this diversity. Ideas of change in organisms over time had been considered by many persons, including Lamarck, but no satisfying explanation was achieved. Somehow organisms must have changed over geological time, but it took Darwin (1859) with his theory of evolution by means of natural selection to put the pieces together in a convincing way. Although Darwin’s theory provided explanation of the origin of the diversity of life, it did not change the way in which classifications were constructed. Characters were still selected, compared, and groups were formed, followed by formal ranking. What did change was the orientation of the classification following presumptive evolutionary tendencies, usually explained clearly by authors in the form of aphorisms, or dicta. Haeckel was also influential (1866), particularly in emphasizing the importance of evolutionary trees, or phylogenies.