Tunicates, or "sea squirts" are common in all marine habitats, attaching
themselves to any fixed object on a coral reef. To feed, they constantly filter out bacteria and phytoplankton
by passing a continuous stream of water through their body. The larger of the two openings is the mouth, or incurrent
aperture, and the smaller is the excurrent aperture. The water stream is kept moving by the action of tiny cilia
(hairs) that line the inside of the tunicate body. Waste products are also expelled through the excurrent aperture.
http://home.mem.net/~zipper/tunicate.htm
For other references and photos, please consult the web sites below.
http://www.mit.edu/people/corrina/tunicates.html
http://www.eeph.com/~queue/images/yeltuni.jpg
http://www.eeph.com/~queue/images/yeltuni.jpg
For more information see