This stinger is a stinging cell area made of nematocysts, sensory hair that are capable of firing a warning to animals and people. While jellyfish have tentacles under their stomach, these usually limit them to moving either up or down. They can fill their stomach with water and contract quickly, propelling themselves in a straight line. They also contain special muscles on either side of their pulpy body that contract and pulsate according to the stimuli that their nerve endings receive. Other than these movements, they are generally at the mercy of people, winds, tides and waves.
Jellies mate in an interesting manner.
The female will produce eggs around her mouth and underside, and the male fill fire sperm in her direction. The female gather the sperm with her tentacles and, in essence, uses them to fertilize herself. Her eggs then attach to her tentacles, and stay for a while until they are released into the water. They then attach to rocks, and sit for months, even years, in some cases producing replicas of themselves. They then split into several jellyfish, and swim away.