hydroidea

1 definition found

hydroidea - Collaborative International Dictionary of English v.0.48 :

  Hydroidea \Hy*droi"de*a\, n. pl. [NL. See Hydra, and -oid.]
     (Zool.)
     An extensive order of Hydrozoa or Acaleph[ae]. [Written also
     Hydroida.]
     [1913 Webster]
  
     Note: This order includes the hydras and the free-swimming
           hydromedus[ae], 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]