In our era of computers and computer models, the importance of physical or graphical models for both research and education in developmental biology (embryology) is often forgotten or at least underappreciated. Still, one important aspect of embryology is the (evolutionary) developmental anatomy of both human and animal embryos. Here, we present a short history of the visualization of Ernst Haeckel's "biogenetic law" and his "gastraea theory" in biology textbooks from the German Democratic Republic (GDR) between 1951 and 1988. Our analysis of GDR textbooks showed embryology was integrated into different disciplines and remained an educational constant within the school textbooks throughout the GDR despite various educational reforms. While the majority of these textbooks failed to reference either Ernst Haeckel or his contributions to embryology, they often did mention Haeckel in sections dedicated to the theory of evolution and the promotion of Soviet ideals such as materialism.
Keywords: Biogenetic law; Biology education; Biology in the GDR; Embryonic development; Ernst Haeckel; Gastraea; Textbooks.