A medusa is the free swimming form of a cnidarian, with the sessile form being a polyp. The body looks like a bell or umbrella, with the mouth located on the bottom surface and tentacles hanging down from the edges of the bell. They are commonly referred to as jellyfish due to a very thick mesoglea (an extra cellular layer between the outer (epidermis) and inner (gastrodermis) epithelium) forming a jelly-like mass.
- Medusa (biology) - Wikipedia
- (Ruppert Barnes 1994): Ruppert, E.E., Barnes, R.D., Invertebrate Zoology, Saunders College Publishing: Sydney, 1994.