The eumetazoans other than Radiata, show triploblastic, bilaterally symmetrical and organ level of organisation The grade Bilateria includes two taxonomic levels called Division.
Division: 1 Protostomia (Proto: first; stomium: mouth):
Protostomia includes the eumetazoans in which the embryonic blastopore develops into mouth.
This division includes three subdivisions namely acoelomata, pseudocoelomata and schizocoelomata.
Division: 2 Deuterostomia (deuteron: secondary):
Eumetazoans in which anus is formed from or near the blastopore and the mouth is formed away from the blastopore.
It includes only one subdivision Enterocoelomata.
They have a true coelom called enterocoel, formed from the archenteron.
