This volume focuses on a group of diverse developmental processes that have resisted incisive analysis when conventional genetic and biochemical methodologies were employed. Relatively little is known at the molecular level about these processes, but the contributors have taken a firm stand by either presenting hypotheses or suggesting new ways to approach research problems in their fields.

The authors describe new models and hypotheses for such complex questions as: Embryos are biological clocks, but how do they keep time? Oncogenes cause many tumors, even though they are, or are...