If sponges didn't exist jellies would be the simplest of the multicellular life forms. Their bodies consist of three layers: the outer ectoderm, the inner endoderm that lines the gut. The middle layer is called the mesoglea and would appear as goo. Their mouths and tentacles hang downward for most (there is an upside down jelly that I'm not getting into here). The mouths of the jellies hang down in the center of the medusa with frilly extensions that are feeding arms that convey food to the mouth. The tentacles hang from the edge of the bell and contain the infamous stinging cells, the nematocysts. A jellyfish's tentacles may contain thousands of nematocysts. Each nematocyst contains a hollow needle attached to a coiled thread. Upon contact with prey this needle shoots out and injects venom of varying potency, depending on species. Here on the Central Coast the sting of our local jellyfish is barely perceptible to humans. In other areas around the world the toxin can be extremely potent causing paralysis and death.
Visitors to the aquarium have been known to spend their entire visit just watching the jellies swimming. The grace and seemingly effortless movements have a mesmerizing effect on many people. They provide a quiet escape from the hubbub and frenzy of everyday life.
In bocca al lupo. m & v