hydroidea

CIDE DICTIONARY

hydroidea, n. pl. [NL. See Hydra, and -oid.].

 An extensive order of Hydrozoa or Acalephæ.  [1913 Webster]
" This order includes the hydras and the free-swimming hydromedusæ, together with a great variety of marine attached hydroids, many of which grow up into large, elegantly branched forms, consisting of a vast number of zooids (hydranths, gonophores, etc.), united by hollow stems. All the zooids of a colony are produced from one primary zooid, by successive buddings. The Siphonophora have also been included in this order by some writers. See Gymnoblastea, Hydromedusa, Gonosome, Gonotheca."  [1913 Webster]