The well-known freshwater polyp Hydra viridis.
Dr. Ralf Wagner
CC BY 3.0
<p>Transferred from <span class="plainlinks"><a class="external text" href="https://de.wikipedia.org">de.wikipedia</a></span> to Commons.<br></p>
(<span lang="en" dir="ltr">Original text: <i><bdi lang="">Dr. Ralf Wagner, von ihm unter GNU-FDL gestellt</bdi></i></span>)