Embryology and developmental biology are increasingly prominent in modern evolutionary biology. Many advocates of the importance of development argue that the processes of organic growth produce constraints on adaptive evolution. This approach contrasts with "adaptationism," a feature of mainstream neo-Darwinian evolutionary biology that emphasizes natural selection and the particular adaptations-to-environment it produces. Adaptationism is said by its critics to ignore the structural processes of development which are common to large groups of organisms and which produce non-adaptational similarities. Dr. Amundson is examining the methodological basis of the adaptation- versus-constraint debates from an historical perspective. A remarkably similar debate occurred among pre-Darwinian British biologists, between natural theologians and continental style morphologists and comparative anatomists. Comparisons between the two debates suggest that the contrast between adaptational and structural biological explanation is not a special feature of evolutionary biology at all. The methodological similarities will contribute to a better understanding of the current debates and a better understanding of the diverse explanatory strategies used in biological science.