Today, Hugo de Vries is chiefly remembered as the first of three botanists who, in 1900, publicly announced that they had discovered what we now call the laws of Mendel. All three maintained that they had found the laws on their own and that, at the moment they did their discovery, they had been completely unaware of the fact that the Austrian amateur botanist Gregor Mendel (1822-1884) had published similar conclusions already in 1866. Whereas his contributions to the development of evolutionary thought are generally unappreciated or simply unknown, De Vries is credited in many surveys on the history of genetics for his rediscovery of Mendel’s laws. It is generally accepted that, together with his two fellow-rediscoverers, Carl Correns from Tubingen and Erich von Tschermak-Seysenegg from Vienna, De Vries made these basic rules of genetics widely known to the scientific world. The year 1900 can be considered as the year of birth of modern genetics, and Hugo de Vries as one of the founders of the discipline. Among historians of biology the fame of De Vries as a rediscoverer is mingled with a good deal of notoriety. That he was indeed the first who published the rediscovered laws nobody can deny. But his claim that he was also an independent rediscoverer is widely doubted. Over the past 40 years many attempts have been made to reconstruct the way De Vries has arrived at his rediscovery.1 Some researchers have found evidence that supports De Vries’ claim, but they form a minority. The more recent studies, in particular, have argued that De Vries’ views on the nature of the material carriers of hereditary characters prior to his ‘rediscovery’ was so non-Mendelian in several respects that it is virtually impossible that he found the famous laws on his own. It must have been only after the incidental reading of the original paper of Mendel, presumably sent to him in early 1900 by his colleague and friend Martinus Beijerinck, that De Vries formulated them. Frustrated and irritated, it is said, De Vries first silently changed his original views quite substantially to bring them into line with those of Mendel, and subsequently completely absorbed Mendel’s findings in his much cherished theory of speciation through genetic mutation, giving them eventually only a minor position in his elaborate theoretical framework.