This book explores early theories about the mechanisms of inheritance. Beginning with Charles Darwin's now rejected Gemmule hypothesis, the book documents the reception of Gregor Mendel's work on peas and follows the work of early 20th century scholars. The research of Francis Galton, a cousin of Darwin, and the friction it caused between these two is part of longer story of the development of genetics and an understanding of how offspring inherit the characteristics of their parents. Bateson, Garrod, de Vries, Tschermak and others are all characters in a scientific story of discovery, acrimony, cooperation and revelation.