hydra is a genus of small, fresh-water animals of the phylum cnidaria and class hydrozoa.

amoeboid anatomy and animals background basal biologists biology bud budding bulbs cell class cnida cnidaria cnidocytes disc education freshwater gastrodermis genus green hermaphrodites hydra hydramacin hydroid hydrozoa hydrozoans laboratory macro magnification medusa microorganism microscope microscopic microscopy motion mount nematocysts nucleus organism ovary phylum polyp predator radially regeneration reproduction science sedentary sessile small sticky structure symmetric tentacles wildlife