The transformation of degenerating young medusae of the clavid hydroid Turritopsis nutriculla into polyps is described. Under laboratory conditions the medusae settled on the aquarium bottom and produced stolonal structures from which new polyps arose. This process differs from the more common asexual production of polyps from the free swimming medusae because the transformation involves the whole medusa. The conversion of the young Turritopsis medusa into polyp is one example of how the general succession from polyp to medusa stage in the life cycle of Hydrozoa can be reversed.