Day Octopus Octopus cyanea order Octopoda This marine invertebrate is a cephalopod mollusc The octopus has a large brain and well-developed eyes Eight tentacles form a ring around its mouth a horny beak, not seen It swims by jet propulsion with its b. Day Octopus Octopus cyanea order Octopoda This marine invertebrate is a cephalopod mollusc The octopus has a large brain and well-developed eyes Eight tentacles form a ring around its mouth a horny beak, not seen It swims by jet propulsio