between the organ systems of cephalopods and those of less ambitious molluscs. Octopus does, as we would predict, live close to the limits set by its own physiology. The circulation, to take one example, is barely adequate for such an active animal, mainly because of the absence of any system for pack- aging the blood pigment; haemocyanin in solution is a poor oxygen carrier. Cephalopod blood can transport less than 5 millilitres of oxygen per 100 ml of blood (compared with about 15 vol% in fish) and the whole supercharged system of triple hearts, high blood pressure and pulsating blood...