The Biological Problem of To-day: Preformation Or Epigenesis? / The Basis of a Theory of Organic Development

The author examines competing explanations of organic development, contrasting preformation with epigenesis and analyzing germplasm theory that posits a distinct hereditary nuclear substance organized into nested units (ids, determinants, biophores) which undergo doubling and differentiating divisions to transmit and allocate hereditary material during embryogenesis. He compares germplasm with ordinary protoplasm, outlines how reproductive nuclei remain continuous while somatic nuclear material differentiates, and considers implications for inheritance of acquired characters, regeneration, and the origin of reproductive cells. Close attention is paid to cellular and embryological observations that support or challenge these mechanisms and to the conceptual vocabulary needed to discuss heredity.