Original: Jellyfish have several different morphologies that represent several different cnidarian classes including the Scyphozoa ( over 200 species ) , Staurozoa ( about 50 species ) , Cubozoa ( about 20 species ) , and Hydrozoa ( about 1000 -- 1500 species that make jellyfish and many more that do not ) .
Simplified: In the second stage , the tiny polyps asexually produce jellyfish , each of which is also known as a medusa .