as·cid·i·an /əˈsɪdiən/
  海鞘類
  As·cid·i·an n.  Zool. One of the Ascidioidea, or in a more general sense, one of the Tunicata. Also as an adj.
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  ascidian
       n : minute sedentary marine invertebrate having a saclike body
           with siphons through which water enters and leaves