Of germ-plasm and zymoplasm: August Weismann, Carlo Emery and the debate about the transmission of acquired characteristics

In this essay I discuss the contents and the context of Italian zoologist and entomologist Carlo Emery's discussion of the germ-plasm theory. August Weismann considered him one of his very few creditable supporters, and encouraged him to publish his theoretical reflections. In his Gedanken zur Descendenz- und Vererbungstheorie, which appeared between 1893 and 1903 as a series of five essays in the journal Biologisches Zentralblatt, Emery developed a very personal account, applying the concept of determinants to problems like atavism, sexual dimorphism, speciation, geographical isolation, transmission of characters, and putting forward, as early as 1903, the idea of a genetic program.