the BBC-licensed The Dalek Book (1964), and again in The Doctor Who Technical Manual (1983), these items are described as being part of a sensory array. In "Dalek" (2005) they are shown to act as components in a self-destruct mechanism. Eye Historically, a Dalek's eye has been depicted as its most vulnerable spot. In "Silence in the Library" (2008) the Doctor, speaking of how to deal with various alien menaces, says "Daleks: aim for the eye stalk". In the revived series from 2005 onwards, storylines have shown Daleks as having systems to protect their vision. In the 2008 episode "The Stolen Earth", Wilfred Mott attempts to disable a Dalek by blinding it using a paintball gun. The Dalek is seen to simply evaporate the paint from its eye. Eye lens, eye discs and dome lights While maintaining their general shape and appearance, the design of these components has varied over the years. Eye lenses were first shown as blank, white discs, sometimes featuring internal illumination. Later, lenses with a black "pupil" were introduced. "New Series" Daleks have a clear lens which glows with a blue light while New Paradigm Daleks, introduced in the episode "Victory of the Daleks" (2010), are equipped with an "organic eyeball" set behind a small transparent hemisphere. Throughout the 1960s Daleks were occasionally shown with a functioning iris, a feature also seen in the "New Series" Dalek design. The eye discs have varied in number, size, spacing, profile and configuration. Colour has generally been restricted to powder blue, white or gold, with "New Series" Dalek eye discs having a translucent, frosted appearance and those of the New Paradigm variant being black. The dome-light covers first resembled table tennis balls, before items having the appearance of plastic egg cup inserts were substituted. Later these were replaced by various types of "bee skep-shaped" vehicle side light lenses. The flattened lights fitted to the Imperial Daleks seen in Remembrance of the Daleks were formed from Perspex discs capped by commercially available saucer-shaped plastic components, while "New Series" and New Paradigm Daleks have light-covers consisting of tubular beacon lenses, the former variant's being surrounded by a metal cage. Underside The underside structure of a Dalek casing was indeterminate until the publication of The Dalek Book (1964). This included a cutaway drawing entitled "Anatomy of a Dalek" which showed it to have a base through which a large central sphere, surrounded