The central nervous system coordinates the activity of all parts of the bodies of bilaterian animals – all multi-cellular animals except sponges and radially symmetric animals such as jellyfish. It contains the majority of the nervous system and comprises the brain and spinal cord, as well as the retina. It has a fundamental role in the control of behaviour. The CNS is contained within the dorsal cavity, with the brain in the cranial cavity and the spinal cord in the spinal cavity.