Animals are classified as non-chordates or chordates depending on the absence and presence of notochord. Non-chordates are further divided into many phyla beginning from phylum Porifera to phylum Hemichordates. Phylum Porifera includes the simplest animals while chordates include advanced animals as many features are seen evolving. One such important feature is the presence of body coelom, as the development of organs and organ systems will largely depend on this feature. Porifera, Coelenterate, Ctenophora, Platyhelminthes are acoelomates. Aschelminthes are pseudocoelomates as the coelom is not completely formed. All animals from phylum Annelids to chordates show presence of true coelom and hence are eucoelomates. Thus hemichordates are also eucoelomates and it includes Balanoglossus, Saccoglossus etc.