Final answer:
In cephalopods, the muscular foot is modified into a set of arms or tentacles and a funnel used for jet propulsion and locomotion.
Step-by-step explanation:
In the class Cephalopoda, which includes organisms such as octopuses, squids, cuttlefish, and nautiluses, the muscular foot is modified into a set of arms or tentacles and a funnel. This adaptation is used for locomotion through a method of jet propulsion, where water is expelled at high velocity from the mantle cavity through the funnel. Additionally, the tentacles assists these animals with anchorage and capturing prey.