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...