Bipedal locomotion.
In the letter "Tanker 'dumping' regulations" by T. S. Wyman (5 June, p. 1160), the years of amendations to the International Convention for the Prevention of Pollution from Ships, 1973, mentioned in the second paragraph, were incorrect. The amendations were made in 1978, 1984, and 1985 (not 1987).
D000818:Animals; D002415:Cats; D000882:Haplorhini; D006801:Humans; D008124:Locomotion; D007614:Macropodidae