The "hydroid" family Bougainvilliidae Lutken, 1850 pertains to a group of historically and conveniently (i.e., not monophyletically) described of cnidarians in the orders Leptothecata and "Anthoathecata" (the latter, also not monophyletic, Cartwright et al., 2008) in the class Hydrozoa. As with other anthoathecates, the family Bougainvilliidae has two phases in its life cycle: fixed to a substrate as a polyp and as free swimming medusae (which may also have a reduced form that remains with the polyp, Russell, 1953).
In a recent classification scheme (Naito et al., 1993) cnidarian homeoboxes are sorted into eight mutually paralogous classes (Table I), but 18 of 20 of the cnidarian genes are from members of the class Hydrozoa. Little is known of homeobox genes in other classes, including the corals and anemones of the class Anthozoa.