Helgoland - I collected some jellyfish from the North Sea (from a boat) and let them degrade over two days into, well...jelly. These microorganisms were having lunch.

Biology project on Cnidocytes, a type of venomous cell unique to the phylum Cnidaria (corals, sea anemones, hydrae, jellyfish etc.). It evolved as a means to catch prey and defend from predators, despite these creatures being morphologically simple, lacking a skeleton and usually being sessile. A cnidocyte fires a structure which contains the toxin, from a characteristic sub-cellular organelle called a cnidocyst (or cnida or nematocyst). This is for instance responsible for the stings delivered by jellyfish.

A study of jellyfish.

Jellyfish are marine invertebrates of the class Scyphozoa, and can be found in every ocean in the world. The body of an adult jellyfish consists of a bell shape producing jelly and enclosing its internal structure, from which tentacles are suspended. Each tentacle is covered with cells called cnidocytes, that can sting or kill other animals. Most jellyfish use these cells to secure prey or for defense. Others, such as Rhizostomae, do not have tentacles at all. Jellyfish lack basic sensory organs and a brain, but their nervous systems and rhopalia allow them to perceive stimuli, such as light and odor, and respond quickly. Canon ZR800 Camera Test

Jellyfish are marine invertebrates belonging to the Scyphozoan class. The body of an adult jellyfish is composed of a bell-shaped, jelly producing substance enclosing its internal structure, from which the creature's tentacles are suspended. Each tentacle is covered with stinging cells (cnidocytes) that can sting or kill other animals: most jellyfish use them to secure prey or as a defense mechanism. Others, such as Rhizostomae, do not have tentacles at all. To compensate for a lack of basic sensory organs and a brain, the jellyfish exploits its nervous system and rhopalia to perceive stimuli, such as light or odor, and orchestrate expedient responses. In its adult form, it is composed of 94--98% water and can be found in every ocean in the world. Some jelly fish do have these body parts such as the box jelly fish.