Anthozoa Sea anemones and corals. Have only the polyp stage. HOX genes in one or more clusters with the genes within a cluster arranged in the same order as the body parts they affect. The bilaterians contain two clades, the protostomia and the deuterostomia . Protostomia Deuterostomia Blastopore forms future mouth and anus Blastopore forms future anus only.
Mouth forms later.
They share similar sequences in their 18S rRNA genes. Planaria share with the other members of the phylum a flat, almost ribbonlike, shape bilateral symmetry. The bilateral symmetry of planarians is associated with active locomotion by secreting a layer of mucus underneath them and propelling themselves forward with the myriad of cilia on their ventral surface. Planarians feed through a mouth on their ventral surface. It leads to an elaborate gastrovascular cavity.