Prior to the First World War, more people learned of evolutionary theory from the voluminous writings of Charles Darwin’s foremost champion in Germany, Ernst Haeckel (1834–1919), than from any other source, including the writings of Darwin himself. But, with detractors ranging from paleontologist Stephen Jay Gould to modern-day creationists and advocates of intelligent design, Haeckel is better known as a divisive figure than as a pioneering biologist. Robert J. Richards’s intellectual biography rehabilitates Haeckel, providing the most accurate measure of his science and art yet written, as well as a moving account of Haeckel’s eventful life.