Scanning electron micrograph of Trypanosoma brucei brucei, the parasite that causes sleeping sickness. This appears to be a long-slender or intermediate bloodstream trypomastigote. Note the undulating membrane and the short, free flagellum that is emerging from the flagellar pocket. The morphology of intermediate forms represents a partial change from long-slender to short-stumpy forms. Supplied by Sue Vaughan, courtesy of Wellcome Images.