Linktons were humanoid, though not much was known about their physiology. They were known to have three fingers on each hand, and to be made mainly of wax. They were thus highly vulnerable to fire.
When the Linktons tried to teleport their way to Earth, they were stopped by the Fourth Doctor and Leela, who smashed their teleportation equipment. This caused a fire, which melted those few Linktons who had successfully travelled to Earth. (PROSE: The Living Wax)