Molluscan bodies are broadly divided into two parts: a muscular foot and a shell-secreting mantle. Like different poets improvising with the same poetry form, different mollusks have adapted the same body plan for various lifestyles. Snails ooze along on their foot and carry a coiled shell on their back; clams dig into the mud with their foot and hide in a hinged shell; squid divide their foot into arms and tentacles and repurpose the mantle for jet propulsion, shrugging off its shell-producing capabilities.
