The aim of this article is to analyse the trajectory of Octavio Domingues (1897-1972) and Salvador de Toledo Piza Jr. (1898-1988), two geneticists in the Agricultural School of Sao Paulo State, who engaged with the main propagandist for the eugenics in Brazil, Renato Kehl (1889-1974). This approach is embodied in its association surrounding the publication of the Boletim de Eugenia, an important vehicle for the dissemination of the eugenics movement between the years 1929 and 1933. From the analysis of this journal, it was possible to detect that even sharing both Mendelian theory of heredity, Toledo Piza Jr. considered miscegenation of the Brazilian population as something against nature, while Octavio Domingues judged it healthy.