Metamorphosis in the Facetotecta and Rhizocephala. A. Y-cyprid (Facetotecta) has metamorphosed into the slug-shaped ypsigon stage, leaving behind the empty cuticle of the cyprid (adapted from ). B. A cyprid of Sacculina carcini (Rhizocephala) settled on a crab has formed an injection stylet through which it is now injecting the slug-shaped vermigon into the haemocoelic fluid of the host. The specimen was removed in vivo from the host cuticle which would have been at the dotted line. Photo by J. Høeg and H. Glenner.