Tortoiseshell

Taku prodded the brownish lump. The turtle retracted its head further, but did not otherwise move. "Remind you of anyone?" he asked.

"No," said the Wisest Stone.

"Don't be difficult."

"The turtle misunderstands the purpose," the Wisest Stone went on, settling deeper into his mossy bed. "He builds the hard shell, but then he lives within, letting the world break against it."

"Like a rock in a stream, yes?" Taku plucked a green leaf and placed it in front of the turtle, who remained stubbornly hidden.

"To be rock is to be the shell, not to be behind the shell."