Developmental biology took shape between 1880 and the 1920s Basic concepts like the developmental role of chromosomes and the germ plasm (today's genome), self differentiation, embryonic regulation and induction, gradients and organizers hail from that period; indeed, the discipline was defined as a whole by the programmatic writings of Wilhelm Roux as early as 1889. The present essays cover the period up to the Nobel prize-winning work of Hans Spemann and Hilde Mangold. They were originally published in Roux's Archives of Developmental Biology, from Vol. 200 onward to the journal's centennial issues in 1995/96. The essays aim at introducing current adepts of developmental biology to observations and experiments that have lead their predecessors towards basic concepts still influential today.