North-west European thecate hydroids and their medusae (part 1)

Hydroids and their medusae are amongst the most exquisitely beautiful and intriguing of marine invertebrate groups. Because of the large number of groups and species involved, this Synopsis is divided into two parts.

Part One: Introduction, the minor families and Haleciidae.

Part Two: the hydroid families with larger colonies Sertulaeiidae, Plumulariidae, Aglaopheniidae and Campanulariidae