In the review of Mary P. Winsor, Reading the Shape of Nature: Comparative Zoology at the Agassiz Museum, published in our March 1993 issue, p. 115, Professor Winsor is quoted as having concluded that ‘By the middle of the nineteenth century the study of diversity was a natural science.’ This should have read ‘By the middle of the nineteenth century the study of diversity was a mature science.’ We apologize to Professor Winsor for this error.