Science / Biology / Coelomates: Animals that have a coelom or body cavity lined with mesoderm.
Science / Biology / Pseudocoelomates: Animals that have a body cavity that is in direct contact with the outer muscular layer of the body and does not arise by splitting of the mesoderm; e.g., roundworms. MORE
Science / Biology / Acoelomates: Animals that do not have a coelom or body cavity; e.g., sponges and flatworms. MORE