QS Study

Eumetazoa is a major division of the animal kingdom comprising all multicellular forms except the sponges. It is a large group including most of the multicellular animals. Hence it is subdivided further into two groups.

  1. Diploblastic animals – having ectoderm and entoderm as two layers in the body wall. Ex : Coelenterata. Diploblastic organisms are organisms which evolve from such an ovum, and include cnidaria and ctenophores.
  2. Triploblastic animals – having ectoderm, mesoderm and endoderm as three layers in the body wall. Triploblasty is a condition of the blastula in which there are three primary germ layers: the ectoderm, mesoderm, and endoderm.


The Triploblastic animals are further divided into three groups based on the presence or absence of an embryonic body cavity called coelom.

  1. Acoelomata – no coelom Ex : Platyhelminthes
  2. Pseudocoelomata – with a false coelom Ex : Nematoda
  3. Coelomata – with a true coelom