Hydra - Overview of this freshwater polyp with photographs of a budding specimen and several closeup views. - http://www.microscopy-uk.org.uk/mag/articles/hydra.html
Hydras - Photographic study by Jan Parmentier of these organisms, with images of various reproductive structures. - http://www.microscopy-uk.org.uk/mag/artjun98/janhydra.html
Hydra Oligactis - Rosemarie Arbur has made a series of drawings of a hydra devouring a water flea. - http://www.microscopy-uk.org.uk/mag/artsep01/rahydra.html
Image gallery: Hydra - Includes downloadable video clips of the behavior of a typical hydra extending and contracting. - http://www.microscopy-uk.org.uk/mag/artoct03/dfhydra.html
The Hydrozoa Directory - Information about the classification, anatomy, and life cycle of this class, including photographs and diagrams. Also provides biographies and photos of hydrozoan systematists and marine naturalists of the past. - http://www.ville-ge.ch/musinfo/mhng/hydrozoa/hydrozoa-directory.htm