Some hydrozoans, like Solanderia ericopis (Carter, 1873)  (Anthomedusae, Solanderiidae) from New Zealand, form quite large colonies (here about 55 cm). Many thousands of tiny, individual polyps are scattered on the branches

Solanderia ericopsis does not produce free medusae. Its gonophores remain attached to the colony (fixed sporosacs). Their evolutionary origin from medusae is still discernible: the four conspicuous radial canals and the tentacle bulbs are clearly visible. The size of the gonophores is about 1 mm. They are surrounded by polyps.