Any hydroid belonging to the suborder Tubularida. [
1913 Webster]
" These hydroids usually form tufts of delicate tubes, and both gonophores and hydranths are naked. The gonophores of many of the species become free jellyfishes; those of other species remain permanently attached as medusoid buds or sporosacs. See Illust. under Gonosome, and Cymnoblastea."
[1913 Webster]