Six (of seven) months of Mid-Career Fellowship in Environmental Biology tenure will be spent at Dalhousie University (Canada), enabling Dr. William R. Atchley of North Carolina State University to engage in a collaborative synthesis with Dr. Brian K. Hall and his group. The effort will be to integrate approaches of developmental biology with quantitative genetics; mammalian craniomandibular growth and morphogenesis will serve as the paradigmatic focus of interest. In particular, first Dr. Atchley will strive to acquire expertise in laboratory procedures pertinent to skeletal developmental biology, such as isolation and culture of skeletal tissue condensations, in order to determine cellular architecture, relative rates of development, and temporal orchestration of events during ontogeny. Secondly, he will elaborate on a previously developed covariance matrix model by exploring in greater detail topics such as (1) the role of various developmental processes (e.g., hyperplasia and hypertrophy) in generating genetic correlations among dissimilar traits, (2) the developmental origin of evolutionary constraints, (3) quantitative genetic aspects of heterochronic events during development, and (4) how epigenetic interactions can be incorproated into quantitative genetic models. A final month of fellowship tenure will be spent at the University of Edinburgh's (Scotland) Department of Genetics in Dr. William G. Hill's laboratory.