The present reflections originate from a retrospective view of Seventeenth-Century Leyden law professors and their influence on the development of the civil law, by R. Feenstra and C.J.D. Waal (1975), a study mainly concerning Arnold Vinnius (1588–1657) and Johannes Voet (1647–1713). They supplement that work with references to bibliographic studies since 1975 and with some rectifications. An important part of the reflections, however, concerns Hugo Grotius (1583–1645) and the origins of his ideas in the field of private law (largely followed by Vinnius and Voet). His preferred sources would seem to have been Hugo Donellus (1527–1591) and Matthaeus Wesenbecius (1531–1586). As far as Donellus is concerned, attention is paid to manuscripts of his lectures and to his pupil Gerard Tuning (1566–1610), a Leiden professor; he (and his family) had various links with Grotius.