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

This work tackles one of biology’s oldest puzzles—the nature of organic development—by contrasting the old notion of pre‑formation with the emerging idea of epigenesis. Written by a leading German zoologist of the late 1800s, it surveys the experimental evidence of the day and lays out a systematic argument about how hereditary material might be organized inside cells. The author engages directly with contemporary theories, especially Weismann’s germ‑plasm concept, and questions whether new individuals arise from a tiny, pre‑formed package or from a more fluid process of differentiation.

The translator adds a clear, concise introduction for listeners who are unfamiliar with nineteenth‑century terminology, and includes a handy glossary of technical words. Early chapters walk the audience through the hierarchy of “ids,” “determinants,” and “biophores,” showing how these imagined units could direct embryonic growth. For anyone curious about the intellectual roots of modern genetics and developmental biology, the book offers a vivid snapshot of a pivotal scientific debate.