Is this a page about the worm, its alias, or the species? Needs clarification.
Demesne Furze was the human form of the White Worm. The worm had been genetically engineered to create wormholes. The worm had been on Earth for about two millennia by the time the Fourth Doctor and Leela met her in 1979. The Master created a storm and used a lightning bolt from it to activate the worm's wormhole generating capacity. He did this because he was in league with the Kraals, and used the wormhole to bring them from their homeworld of Oseidon to Earth. The worm was killed in the process. (AUDIO: Trail of the White Worm)