"Each cone-shaped shell consists of six nearly fitted plates forming an encircling ring. A covering door of four plates closes to protect the barnacle from drying when the tide has ebbed, or swings open to allow it to feed."
"The creature inside each shell is something like a small pinkish shrimp that lies head downward, firmly cemented to the base of this chamber it cannot leave. Only the appendages are ever exposed-six pairs of branched, slender wands, jointed and set with bristles."
"The eggs develop inside the parent's shell and presently hatch into the sea in milky clouds of larvae. ... Larval life lasts about three months in the rock barnacle, with several molts and transformations of form. At first the larva, a little swimming creature called a nauplius, is indistinguishable"