Easily the most influential book published in the nineteenth century, Darwin's The Origin of Species is also that most unusual phenomenon, an altogether readable discussion of a scientific subject. On its appearance in 1859 it was immediately recognized by enthusiasts and detractors alike as a work of the greatest importance: its revolutionary theory of evolution by means of natural selection provoked a furious reaction that continues to this day. The Origin of Species is here published together with Darwin's earlier Voyage of the 'Beagle .' This 1839 account of the journeys to South America and the Pacific islands that first put Darwin on the track of his remarkable theories derives an added charm from his vivid description of his travels in exotic places and his eye for the piquant detail.