“A jellyfish, if you watch it long enough, begins to look like a heart beating. It doesn't matter what kind: the blooded Atolla with its flashing siren lights, the frilly flower hat variety, or the near-transparent moon jelly, Aurelia aurita. It's their pulse, the way they contract swiftly, than release. Like a ghost heart-- a heart you can see right through, right into some other world where everything you ever lost as gone to hide. 
Jellyfish don't even have hearts, of course-- no heart, no brain, no bone, no blood. But watch them for a while. You will see them beating.” 

— Ali Benjamin, The Thing About Jellyfish —