Hydra vulgaris is a fresh-water hydrozoan, an animal related to the jellyfish. It can extend its flexible body to an extreme extent and reach a length of 2 centimetres. The tentacles bear tiny harpoon-like organs called nematocysts. These are used for capturing water fleas and other small crustaceans. It can turn itself inside out and has amazing capabilities of regeneration.

See another image of Hydra.

Part of the Collection of the Other Invertebrates of the Micropolitan Museum © Wim van Egmond