Wolff's _Theoria Generationis_, 1759, and his _De Formatione Intestinorum_, 1764, especially the latter, were pieces of observation marking the highest level of investigation of development prior to that of Pander and Von Baer. Cuvier, in _Le Règne Animal_, 1816, applied the principles of comparative anatomy to the entire animal kingdom. The publication in 1800 of Bichat's _Traité des Membranes_ created a new department of anatomy, called histology. Lamarck's book, _La Philosophie Zoologique_, 1809, must have a place among the great works in biology. Its influence was delayed for more than fifty years after its publication. The monumental work of Von Baer on _Development_ (_Ueber Entwicklungsgeschichte der Thiere_), 1828, is an almost ideal combination of observation and conclusion in embryology. The _Microscopische Untersuchungen_, 1839, of Schwann marks the foundation of the cell-theory. The _Handbook_ of Johannes Müller (_Handbuch der Physiologie des Menschen_), 1846, remains unsurpassed as to its plan and its execution. Max Schultze in his treatise _Ueber Muskelkörperchen und das was man eine Zelle zu nennen habe_, 1861, established one of the most important conceptions with which biology has been enriched, viz., the protoplasm doctrine. Darwin's _Origin of Species_, 1859, is, from our present outlook, the greatest classic in biology. Pasteur's _Studies on Fermentation_, 1876, is typical of the quality of his work, though his later investigations on inoculations for the prevention of hydrophobia and other maladies are of greater importance to mankind. It is somewhat puzzling to select a man to represent the study of fossil life, one is tempted to name E.D. Cope, whose researches were conceived on the highest plane. Zittel, however, covered the entire field of fossil life, and his _Handbook of Palæontology_ is designated as a mile-post in the development of that science. Before the Renaissance the works of Aristotle and Galen should be included. From the view-point suggested, the more notable figures in the development of biology are: Aristotle, Galen, Vesalius, Harvey, Malpighi, Linnæus, Wolff, Cuvier, Bichat, Lamarck, Von Baer, J. Müller, Schwann, Schultze, Darwin, Pasteur, and Cope. Such a list is, as a matter of course, arbitrary, and can serve no useful purpose except that of bringing into combination in a single group the names of the most illustrious founders of biological science. The individuals mentioned are not all of the same relative rank, and the list should be extended rather than contracted. Schwann, when the entire output of the two is considered, would rank lower as a scientific man than Koelliker, who is not mentioned, but the former must stand in the list on account of his connection with the cell-theory. Virchow, the presumptive founder of pathology, is omitted, as are also investigators like Koch, whose line of activity has been chiefly medical.