Hydractinia, [263], [265], [268], [270]
Hydrallmania falcata, [278]
Hydrichthys mirus, [268]
Hydroceratinidae, [279]
Hydrocladia, [276]
Hydrocoel (including left hydrocoel), [428];
of Antedon rosacea, [585];
development of, [608] f., [609];
development in Asterina gibbosa, [611];
in Auricularia, [615];