protostome

pro to stome |ˈprōtəˌstōm ˈproʊdəˌstoʊm | ▶noun Zoology a multicellular organism whose mouth develops from a primary embryonic opening, such as an annelid, mollusk, or arthropod. ORIGIN 1950s: from proto- ‘primitive ’ + Greek stoma ‘mouth. ’

protostome

protostome |ˈprəʊtə (ʊ )stəʊm | ▶noun Zoology a multicellular organism whose mouth develops from a primary embryonic opening, such as an annelid, mollusc, or arthropod. ORIGIN 1950s: from proto- ‘primitive ’ + Greek stoma ‘mouth ’.