STEPHEN JAY GOULD, a professor of geology at Harvard, has become one of the best known American scientists. His many essays on natural history are entertaining and highly readable, and his attack on the “establishment” version of Darwinian evolution has received so much attention that his picture appeared on the cover of Newsweek. He personalizes his expository writing in a breezy, self-deprecating manner, and he comes across as warm-hearted, socially concerned, and commendably on the side of the underdog. Hence he is able to present scientific material effectively to a popular audience-a valuable contribution, and a public service, as long as his scientific message is sound.