Anatomy of a coral polyp.
NOAA
Uploaded on the English Wikipedia by <a href="https://en.wikipedia.org/wiki/User:Spaully" class="extiw" title="en:User:Spaully">User:Spaully</a> 13:18, 31 January 2006
<a rel="nofollow" class="external text" href="http://oceanservice.noaa.gov/education/tutorial_corals/coral01_intro.html">NOAA website</a>