Birds stand out from other egg-laying amniotes by producing relatively small numbers of large eggs with very short incubation periods (average 11-85 d). This aspect promotes high survivorship by limiting exposure to predation and environmental perturbation, allows for larger more fit young, and facilitates rapid attainment of adult size. Birds are living dinosaurs; their rapid development has b...

PURPOSE We reviewed the literature to better elucidate the history behind our understanding of the anatomy, classification and embryology of posterior urethral valves. MATERIALS AND METHODS A directed MEDLINE literature review of the anatomy, classification and embryology of posterior urethral valves was performed. An effort was made to focus on the most frequently cited historical articles a...

THE possibility of using inherited abnormalities in place of conventional experimental embryological methods has been explored by several workers in Drosophila, where there is a large range of lethal and female sterile genes readily available (reviewed Waddington, 1956). These genes are usually pleiotropic, i.e. with manifold effects, and tracing these diverse effects back as far as possible to...