The Common Octopus has an extremely complex and magnificent nervous system. It is centrally located in the brain of the the octopus. However, two-thirds of a common octopus' neurons are located in the arms of it. The arms of the octopus are so persistent, that even when they have no input from the brain, the arms are able to perform many reflexive abilities. All vertebrates except for the common octopuses have complex motor skills organized in their brain using an internal somatotopic map of its body. However, octopuses have non-somatotopic systems uniquely similar to large-brained invertebrates. Despite this delegation of control, octopus arms do not become tangled or stuck to each other because the suction cups on each arm have chemical sensors that recognize octopus skin and prevent self-attachment. Also, its eyes are similar to humans and contain an iris, pupil, lens and retina. The octopus has a great knack for spotting prey and reaching to attack them.