The cnidarians include corals, sea anemones, jellyfish and hydras. Hydras are a genus of the Cnidaria phylum. Some species camouflage themselves with hydras, sponges, or seaweed. Hydras are simple, freshwater animals possessing radial symmetry and no post-mitotic cells. However, this does not explain how hydras are consequently able to maintain telomere lengths. Another type of regeneration is Morphallaxis, which is usually observed in Hydras. Plan for the "Hydras" is to extend their operational lifespan well into the 2030s. Only two Hydras were built, the type never entered production. "Hydras" have two significant structures on their body&colon; the "head" and the "foot".