Pilobolus, the hat thrower, is a minute fungus belonging to the Mucorales, which grows on the dung of herbivores. It has adapted itself to their way of life and ingestive habits: in the daily rhythm of its phototropic sporangiophore development, violent sporangium discharge, the attachment mechanism of its sporangia to herbage, and spore germination. The video-tape carefully documents the asexual development of the fungus by time lapse cinematography and lays emphasis on the phototropism of...