An “immortal” jellyfish? In the hydrozoan, Turritopsis nutricula (Piraino, 1996), asexual reproduction by budding of hydroid polyps (p) from a stolon (s) follows rejuvenation from the sexual medusoid (jellyfish) stage (m) in a unique mechanism of reverse metamorphosis. In theory, these animals could continue this forever, hydroid colonies producing sexual medusae that eventually return to the hydroid stage and then repeat the cycle, leading to the popular name in news accounts of “The Immortal Jellyfish.”