hydra anatomy. cnidaria.

anatomy and animal animals asexual background biological biology body budding cavity cell cnida cnidaria cnidocytes design diagram education educational for fresh freshwater gastrodermis green hydra hydramacin hydroid hydrozoa illustration laboratory macro magnification microbiology microorganism microscope motion mouth nematocysts organism ovary phylum predator protozoa regeneration reproduction scheme science sperm structure tentacles use vector vulgaris water wildlife