The nature of a starfish: ‘a disembodied head walking about on its lips’

Next time you see a starfish, any starfish, look at the centre of it, on the side that faces the sky. Now look just off centre, and – whether it is large or small or spiny or pointy or bright blue or dull orange – you will see a roughly circle-shaped spot. Every starfish has one – it is called a madreporite – and every starfish uses it to suck water into its body to inflate its hundreds, or thousands, of tube-shaped feet.