This slide shows a portion of a branching colony of the marine bryozoan (ectoproct) Bugula.  Branching within the colony is produced by repeated asexual budding of individuals called zooids.  Note the tentacles of the lophophores (ciliated feeding devices surrounding the mouth that can also be used for gas exchange).  Like many colonial cnidarians, ectoproct colonies are polymorphic, with most of the zooids functioning as feeding individuals.  Defensive zooids called avicularia protect the colony against small organisms, including settling larvae and crawling tube-building polychaete worms and arthropods.  Each avicularium resembles the head of a bird complete with powerful musculature and a sharp beak-like structure (rostrum) that is used to seize the appendages of trespassing organisms.