Historecognition, broadly defined, spans the processes responsible for the regulation of the genetic integrity of self in the face of conspecific (allogeneic) and heterospecific (xenogeneic) nonself. The existence of precise historecognition systems in the invertebrates can be traced back to Bancroft's discovery in 1903 of, strain specific regulation of colony fusion in the compound ascidian Botryllus schlosseri, and Wilson's report in 1907 of species-specific sponge re-aggregation. Despite this provocative history, invertebrate historecognition remained largely unexplored for over half a...

Gastrulation is a fundamental process of early embryonic development. It involves virtually every aspect of cell and developmental biology and results in the formation of fundamental structural elements around which a developing animal's body plan is organized. As such it is not only an important process, but also one that is complicated and not easily dissected into its component parts. To understand the mechanisms of gastrulation one must acknowledge that gastrulation is fundamentally a biomechanical process (that is, a problem of cells generating forces in a three dimensional array,...