SO ENDS this first part on the evolutionary impact of viruses. They do not fit into the relatively tidy box that Victorian biologists constructed of the world. They defy the idea of species. They frustrate definitions of life. Their form is pure Euclidian geometry. They shimmer at the edge of our definitions of life. They mutate and reproduce at extraordinary rates. And contrary to the old picture, few are pathogenic and many have played an integral role in the evolution of life on this planet. A radical new picture.