Herbert Spencer Jennings

(1868–1947). American zoologist, born at Tonica, Illinois. His studies of the behaviour of lower organisms, such as protozoa, convinced him that their reactions are too variable to find explanation in terms of mechanistic principles. He therefore promulgated the unfashionable view that mind extends to all levels of the evolutionary scale. His best-known book is Contribution to the Study of the Lower Organisms (1904). Jennings's views were strongly contested by the German–American zoologist Jacques Loeb, who advocated a strictly mechanistic explanation of animal behaviour.

(Published 1987)

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