Taxonomic characters from the hydranths of live thecate hydroids: European Haleciidae (Cnidaria: Leptothecatae)

The hydranths of six species of hydroids of the family Haleciidae from NW Europe are described from life and compared. Notes are given on the hydranths of three other species, and general taxonomic comments on some others. Hydranth character-states are useful in defining and distinguishing Halecium species, but the characters may not be useful in routine identification by non-specialists. Halecium undulatum is recorded for the first time from Sweden, and from three localities in Norway whence there was just one previous record. Halecium halecinum may breed year-round in British waters.