<p><strong>Fig. 3.25.</strong>&nbsp;(<strong>E</strong>) <em>Porpita porpita</em>, known as a Blue Button, a colony of hydroids surrounding a float.</p>

Fig. 3.25. (E) Porpita porpita, known as a Blue Button, a colony of hydroids surrounding a float.

Image courtesy of National Oceanic and Atmospheric Administration (NOAA) Ocean Explorer