How is a cnidarians more complex than worms?
Cnidarians only have one unique development over any class or order of worms … nematocysts. Nematocysts are part of a cell called Cnidocytes (hence the phylums name of Cnidaria). The nematocysts are stinging cells used to stun the prey of various members of this large group of animals to consume with less issues. As for complexity, worms have cnidarians beat. They have organ development, a complex coelom structure with three layers (ectoderm, mesoderm, and endoderm). Many worms have two openings for digestion, making food travel one-way (where cnidarians have a singular gut opening). Even the annelids moved general development of organisms further with the onset of repeated segmentation. Worms are more complex than cnidarians (jellyfish, corals, hydras, sea anemones, etc.
