| Radiata | Bilateria |
| Body radially or bi-radially symmetrical Organ systems are incipient and not well marked Diploblastic. Mesoderm is not well developed Coelomic cavity invariably absent Mouth is the principal opening of digestive cavity Tentacles with nematocysts Comb plates in some organisms Fertilisation is mostly external Example: Coelenterata, Ctenophora | Body bilaterally symmetrical Organ systems are well marked Triploblastic. Mesoderm is well developed. Coelom: Pseudocoelomate or Eucoelomate Coelom may be present or absent Mouth and anus are both principal openings Tentacles if present, are without nematocysts No comb plates present Fertilisation is mostly internal Examples: Protostomata, Deuterostomata |