Portrait and signature of ALFONSO L. HERRERA (1868-1942). Mexican biologist (he studied pharmacy but considered himself a biologist) who promoted the development of general biology as a unified and independent scientific field that should be based on evolution. In Mexico, where he introduced those ideas, his writings were considered the best Darwinian works of his time in México. Herrera was the author, among many other books, of Nociones de Biología (Notions of Biology, 1904), a textbook used at the School of Education (Escuela Normal para Profesores), which he directed beginning in 1902. In that book, Herrera developed his hypothesis of plasmogeny, which he had proposed several years before, and which paved the way to an understanding of the uniformity of nature and the origin of life. Herrera insisted that microbes should be seen not only as pathogens but also as the ancestors of extant plants and animals. Despite his failed attempts to produce “protoplasm” in the laboratory, he and several contemporaries remained proponents of the idea of the spontaneous generation of life, before Oparin’s 1924 theory of the chemical evolution of life.