Final answer:
In the Peripheral Nervous System, Schwann cells are responsible for forming the myelin sheath around axons.
Step-by-step explanation:
The cells in the Peripheral Nervous System (PNS) that form myelin are called Schwann cells. These cells are different from oligodendrocytes, which perform a similar myelinating function in the Central Nervous System (CNS). Schwann cells wrap around a single axon segment to provide myelin insulation, whereas oligodendrocytes can extend their processes to multiple axons. The myelin sheath is essential for rapid conduction of nerve impulses along the axons.