sentences:  The story would use the same space station setting as "Space Station", the setting being dictated by the production office as means of saving money by having it share sets with "Revenge of the Cybermen".Commissioned in June 1974, Lucarotti devised the concept of the ark, a space station that housed a huge plot of countryside the size of Kent – a sort of Home Counties in space.His six-part story concerned the invasion of the ark by a species called the Delc, a spore-like fungus with separate heads and bodies.