The Portuguese Man-of-war is in the order Siphonophorae. Members of this order are technically colonies of many individual animals. This prevents the Portuguese man-of-war from having the nervous system many of its cnidarian brethren enjoy. However, even though it doesn't have a nervous system it can react to stimuli. The animals that make up its tentacles, dactylzooids, have venom-filled nematocysts that sting prey. There are also contractile cells that allow the organism to drag prey in the range of the digestive polyps. These animals allow the Portuguese man-of-war to react to stimuli despite not having a central nervous system.