quences of the observations which, he interpreted, Buffon sought rather to foresee what should be or ought to be, than to fix what he ascertained. He was thus often in advance of his time, and the elevated considerations to which he gave himself were within the grasp of only a small number. Linnæus, on the contrary, described, simply and clearly, what was. With such qualities these two men would often be far from agreeing; and we might apply to them the distinction, which had not yet been expressed, between the school of facts and the school of reasoning. While Linnæus and Buff on thus summarized in themselves all of zoölogy, although from different points of view, their labors lacked a basis the imperious need of which was universally felt. It was already beginning to be understood that the study of the habits, geographical origin, and external characteristics of animals was not enough. At that moment Cuvier appeared. The reform which he introduced in zoölogy was very important, and his work, on the "Animal Kingdom distributed according to its Organization," produced a momentous impression. His great fame, like that of Linnæus, is due to the fact that the modification he made in zoölogical studies corresponded to a certain want, and was a necessary reform that came at the time when it was most needed. Zoölogists of the classifying kind, who occupy themselves only with the externals of animals, have been compared to librarians who arrange their libraries according to the backs or covers of the books, without regard to what is within them. It was Cuvier's great merit that he saw clearly that to reach a truer knowledge of things we must not only be acquainted with the names and external features, but with the internal characteristics as well. To that end he introduced the anatomical idea into the history of animals. In doing it he rendered the greatest service to zoölogy; and to this, too, must be attributed his great success, which was equaled only by that of Linnæus, and also the great reputation in which French zoölogy shone at the beginning of the century. To-day, even those zoölogists who criticise Cuvier the most, nevertheless follow his precepts. We can not apply the same standards of criticism to his work that we would insist upon in judging a work of to-day. To make an equitable estimate, we should put ourselves back to his time, and take account of the gaps in the knowledge of that period, and of the insufficiency of the means which observers could control. It will soon have been a hundred years since Cuvier's work was performed. In that time a great many discoveries have been made, and many conquests have been achieved to cast a new light on questions which were insoluble then.
Zoölogy remained for a long time at the point to which Cuvier led it; and we have to come to the middle of our century to see new ideas brooding and bringing about great modifications in the