Epalnts has is just about right but I would like to clarify a bit. Utrics are very diverse having evolved to be aquatic, terrestrial and epiphytic. Most people are more familiar with the aquatic species but the terrestrials far out number them.
For more explaination try checking out the Utric forum [img]http://www.**********.com/iB_html/non-cgi/emoticons/smile.gif[/img]