in the embryo, which, under Pander and von Baer, became the fundamental conception in structural embryology—he laid the foundation for the germ layer theory. Wolff foreshadowed the germ layer theory by showing that the material out of which the embryo is constructed is, in an early stage of development, arranged in the form of leaf-like layers. Locy recognizes Wolff as the foremost investigator in embryology before von Baer. Wolff contended that the organs of animals make their appearance gradually and that he could actually follow their successive stages of formation.(Dye) Eponyms Wolff's eponyms are: Wolffian ducts or mesonephric ducts Wolffian cysts Wolffian body or mesonephros Wolff's islands or blood islands References William A. Locy, Biology and its Makers, Henry Holt and Company, New York, 1908 Frank J. Dye, Dictionary of Developmental Biology and Embryology, Wiley-Liss, New York, 2002 Speert H. Obstetrical and Gynecological Milestones. The Macmillan C., New York, 1958. Medical eponyms 1733 births 1794 deaths German embryologists German physiologists German military doctors Scientists from Berlin People from the Margraviate of Brandenburg German people of the Seven Years' War University of Halle alumni Full members of the Saint Petersburg Academy of Sciences Physicians of the Charité