Organised nervous systems — and so complex active behaviour — first appeared in Cnidaria, the phylum that includes present day marine anemones, corals and jellyfish, and Ctenophora, the phylum that includes present-day comb jellies. For comparison, sponges (Porifora) still lack even the most primitive nervous system, though it was just recently discovered that they have most of the genetic requirements for developing synapses.