"Over eight hundred Reformed churches sprang into existence in France between 1555 and 1562. Their advent occurred after a thirty-five year period of buildup, during which evangelical doctrines gained adherents throughout the kingdom and local networks formed out of which those churches would coalesce. (..) why and how these conventicles grew and then suddenly metamorphosed into well-organized churches remains largely a mystery"
Thanks to Jonathan Reid, this mystery is solved now. In a Open edition full text version now available, let's read his contribution "French evangelical networks before 1555: proto-churches?", in Philip Benedict, Silvana Seidel Menchi & Alain Tallon (ed.), LA RÉFORME EN FRANCE ET EN ITALIE, Ecole Française de Rome, 2007 (p.105-124).