Image From University of Winnipeg

Jellyfish are medusae, which are free swimming. They have radial symmetry, which helps them react to enemies or food in all directions very quickly. The outer layer of a jellyfish, or the epidermis, covers the entire outer surface of the animal. The middle layer consists of a jelly like substance called mesoglea. The inner surface, or the gastrodermis, lines the digestive system of jellyfish. The bell of a jellyfish allows for movement by opening and closing the bell. Coming off of the bell of a jellyfish are the tentacles, which are covered in nematocytes, which are the stinging cells of a jellyfish. The tentacles help with defense and capturing prey.