Part of the "The Biology Classics" series. Hydra is a genus of simple fresh-water animals possessing radial symmetry. Observes feeding behavior of hydra, shows detailed microscopy of stinging cells used in capturing prey, and reviews two digestive processes: cellular and extracellular. Also covers locomotion, reproduction by budding, the development of sex organs, and symbiotic guests, both external and internal. Accessibility options on the DVD are: (1) expanded description, (2) English subtitles in a black box, (3) subtitled description.