<Li> Pseudocoelomate animals have a pseudocoelom (literally "false cavity"), which is a fluid filled body cavity . Tissue derived from mesoderm partly lines the fluid filled body cavity of these animals . Thus, although organs are held in place loosely, they are not as well organized as in a coelomate . All pseudocoelomates are protostomes; however, not all protostomes are pseudocoelomates . An example of a Pseudocoelomate is the roundworm . Pseudocoelomate animals are also referred to as Hemocoel and Blastocoelomate . </Li> <Li> Acoelomate animals, like flatworms, have no body cavity at all . Semi-solid mesodermal tissues between the gut and body wall hold their organs in place . </Li> <P> Coeloms developed in triploblasts but were subsequently lost in several lineages . The lack of a coelom is correlated with a reduction in body size . Coelom is sometimes incorrectly used to refer to any developed digestive tract . Some organisms may not possess a coelom or may have a false coelom (pseudocoelom). Animals having coeloms are called coelomates, and those without are called acoelomates . There are also subtypes of coelom: </P> <Ul> <Li> schizocoelom: develops from split in mesoderm found in annelids, arthropods and molluscs </Li> <Li> haemocoelom: true coelom reduced & cavity filled with blood found from arthropoda and mollusca </Li> <Li> enterocoelom: develops from wall of embryonic gut found from echinodermata to chordata </Li> </Ul>

An animal that lacks a coelom or body cavity