SummaryAccording to Ernst Mayr, most geneticists were not particularly interested in or well informed about macro-evolutionary processes and thus did not make major contributions to the evolutionary synthesis of the 1930s and 1940s. Although this characterization applies to many American geneticists of the period, it does not fit their German counterparts. German geneticists' active interest in evolutionary mechanisms can be clearly seen in the German debates of the 1920s and 1930s over the significance of cytoplasmic inheritance. While morphologists celebrated the (...) evidence for cytoplasmic heredity as a basis for neo-Lamarckian mechanisms, those geneticists who actually studied cytoplasmic inheritance regarded it as a way of strengthening the case for natural selection. This German-American contrast suggests that our understanding of the evolutionary synthesis would benefit from an analysis of the institutional circumstances of the various contributing disciplines. (shrink)