Is it ensure, insure, or assure?
Haeckel Haeck·el (hěk'əl), Ernst. 1834-1919.
German philosopher and naturalist who supported Darwin's theory and mapped a genealogical tree relating all animal life.
German naturalist who was the first to attempt a genealogical tree of all animals. He was also one of the first scientists to publicly support Darwin's theory of evolution. His own ideas about evolution attracted popular attention, and though they were later disproved, they helped to stimulate biological research.