Cnidarians (A) rank the lowest in cephalization. Cephalization is when organisms tend to group all their major organs near the front of their body. The organism attempts to form a definite head with the nervous tissue or brain and feeding mechanisms in or close to the head of the organism. This tendency is considered an advancement in evolution.
Examples of Cnidarians are jellyfish, fire corals, box jellies, sea anemones, and sea pens. A common factor between all cnidarians is that they have stingers with poisonous barbs attached