the world > animals > invertebrates > subkingdom Metazoa > grade Diploblastica > phylum Coelenterata > [noun] > class Hydrozoa > member of > zooid > sac into which coenosarc can be retracted (1)
hydrœcium1861
a sac into which the cœnosarc can be retracted in certain Hydrozoa, as the Calycophoridæ.