I know this sounds like a really stupid question but just bear me out.
I was just watching a TV program about jellyfish and they really puzzled me. They seem to be nothing more than a sac and a load of tentacles - no brain, or indeed any other internal organs.
Should they even count as animals at all? In many ways they seem to act more like carnivorous plants. Is this a more accurate description of them or are they something completely different?