by smaller satellite "balancing globes", protrudes. This layout was generally adopted and used in subsequent Dalek plans and comic strip representations. This is at variance with the few glimpses seen in early Doctor Who television episodes and films, which made little attempt to show (or hide) anything other than the actual base of the Dalek prop. As this usually took the form of a plywood board to which castors had been attached and a hole cut out for the operator's feet, these brief appearances were of little assistance in maintaining the illusion of the props being functional, armoured casings housing an alien being. This situation was finally remedied in the episode "Dalek" (2005) and subsequent appearances of the "New Series" Dalek. This variant is shown to have an underside consisting of a large, recessed central hemisphere surrounded by eight satellite hemispheres. The central hemisphere and four of the satellite hemispheres glow when the Dalek is in flight mode. Dalek mutant The creatures inside the "travel machines" are depicted as repulsive in appearance and vicious even without their mechanical armour. Rarely glimpsed until the programme's revival in 2005, they were usually shown as amorphous green blobs with strong tentacles capable of strangulation or, occasionally, as having clawed hands. Their appearance and evolution is variously attributed to radioactive fallout from a catastrophic war, artificially accelerating pre-existing genetic mutations in the Kaled species and the manipulation of genetic material forcibly obtained from other (usually human) species. From 2005 onward the Dalek creature has been seen more frequently, in its latest incarnation resembling a pale octopus-like being with a single viable eye, a vestigial nose and mouth, and an exposed brain. In the episode "The Witch's Familiar" (2015) it is revealed that the mutants are biologically immortal, yet still gradually age to eventually rot away into a liquid mass. These decayed Daleks are ultimately deposited in Skaro's sewer system, where they decompose further into a living, maddened sludge. Voice Daleks have distinctive electronic voices, the harsh, staccato sound being created by actors speaking through a microphone into a device called a ring modulator. While this produces considerable distortion and a monotone effect, inflection and pace are used to express a range of emotions including rage, triumph, disdain and, very occasionally, fear. ( ) Locomotion and manoeuvrability Dalek locomotion is usually shown as a gliding movement a few centimetres above the ground. The Dalek Book