rhamphotheca:

The Moon Jelly (Aurelia aurita) is a widely studied species of jellyfish found throughout most of the world&rsquo;s oceans. It is translucent, usually about 25&ndash;40&nbsp;cm (10&ndash;16 in) in diameter, and can be recognized by its four horseshoe-shaped gonads, easily seen through the bell. It is capable of only limited motion, and drifts with the current, even when swimming.
(photo: Dante Alighieri)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; (via: Wikipedia)