Marine invertebrates have been pivotal in solving key problems in developmental and general biology, with marine stations offering vital technical and intellectual support. Notable discoveries include the first observations of egg and sperm cell fusion, the fusion of pronuclei during fertilization, and changes in egg membrane charge and ion mobility in mussel and echinoderm eggs. The regulation of cell loss compensation was first studied in sea urchin eggs, and cyclins, which control the cell cycle, were identified during student courses with clams at a marine station. The six authors, experienced in teaching developmental biology courses, particularly at the Helgoland Marine Station, have compiled valuable methodological information and shared unpublished insights. The text includes a narrative that explores the challenges, thoughts, and solutions in developmental biology related to the "model" species discussed. The authors aim to inspire students through the observations and experiments with living marine invertebrate eggs and embryos, highlighting their relevance to understanding basic processes in embryonic development.
