Mormyrid fish have amongst the largest brain to body mass ratio of any animals, larger even than humans. This is due largely to the hypertrophy of the cerebellum which covers the entire brain. Curtis Bell referred to the mormyrid brain as a “kind of cerebellar festival” because the cerebellum was so large and because of the interesting differences in the histology of different parts of the mormyrid cerebellum (figure courtesy of Hans Meek and Curtis Bell).