The embryology course at the MBL, as Trinkaus’s course notebooks depict, covered an extensive selection of topics in embryogenesis, including fertilization, cleavage, gastrulation, organogenesis, regeneration, polarity and gradients, parthenogenesis, and many more. Each day, one of the instructors presented a lecture in the morning and the students then worked on the marine embryos for the rest of the afternoon. Trinkaus’s instructors represented an impressive list of biologists who worked during the first half of the twentieth century, boasting names like Viktor Hamburger, Donald Costello, Oscar Schotté, William Ballard, and Trinkaus’s mentor, H.B. Goodrich. Trinkaus was also privy to guest lectures by Edwin G. Conklin, Frank R. Lillie, Mary E. Rawles, and Alfred H. Sturtevant. The living marine embryos on which the students experimented were collected from the ocean around Woods Hole and included vertebrates, such as a variety of teleost fish, and invertebrates, such as sponges, annelids, molluscs, echinoderms, and tunicates.