In 1849, Hofmeister began investigations into the life-histories of plants, since when the study of Vegetable Physiology has progressed side by side with Chemistry. To Darwin great subjects are due: the cross-fertilization of plants, their reproduction, and their relations to insects and their movements. It may be mentioned, however, that in 1693 Ray attempted to explain the movements of leaves, tendrils, and petals by physical and mechanical laws. Since the middle of the Nineteenth Century, the branches of Botany that have been particularly studied are Vegetable Physiology and Pathology, Inner Morphology, and Fossil Botany—and the discoveries made have naturally had an effect upon the classification of vegetable life. According to Agassiz: “We must come down to the last century, to Linnæus, before we find the history taken up where Aristotle had left it, and some of his suggestions carried out with new freshness and vigor. Aristotle had already distinguished between genera and species; Linnæus took hold of this idea, and gave special names to other groups, of different weight and value. Besides species and genera, he gives us orders and classes—considering classes the most comprehensive, then orders, then genera, then species. He did not, however, represent these groups as distinguished by their nature, but only by their range; they were still to him, as genera and species had been to Aristotle, only larger or smaller groups, not founded upon and limited by different categories of structure. He divided the animal kingdom into six classes: Mammalia, Birds, Reptiles, Fishes, Insects, and Worms.” Linnæus’s classification was, therefore, the first attempt to group animals; but until Cuvier there was no great principle of classification. In 1707 Buffon succeeded in making Zoology, which had been regarded as a most uninteresting study, popular and respected. He also had the idea of collecting all the known facts of scientific investigation and arranging them systematically. Buffon was ridiculed as a scientist by his contemporaries, Hevelius, Diderot, D’Alembert, and Condillac, who opposed his explanations of natural phenomena. Buffon’s _Histoire Naturelle Générale et Particulière_ is his most important work. A complete edition in thirty-six volumes appeared in Paris in 1749-1788. Although it is said to “have made an epoch in the study of the natural sciences” in Buffon’s day, it now possesses little scientific value. Cuvier’s classification has never been overthrown. His original investigations in various departments of science, and particularly that of fossil vertebrate animals, opened up new fields of study. His talents with both pen and pencil contributed largely to making that branch of science popular. Lamarck, Cuvier’s contemporary, divided the animal kingdom into Vertebrates and Invertebrates. Lamarck, like Geoffroy Saint-Hilaire, was a believer in the theory of evolution, which was opposed by Cuvier.