Now it was time for Huxley to tackle the subject of evolution at full length, in what became the defining work of his life. His book ' was written whilst he was Secretary to the Zoological Society, and made use of his remarkable collection of reprints covering the first part of the century. It was published in 1942. Reviews of the book in learned journals were little short of ecstatic; the American Naturalist called it "The outstanding evolutionary treatise of the decade, perhaps of the century. The approach is thoroughly scientific; the command of basic information amazing".