<P> Important characteristics: </P> <Ul> <Li> lack a vascular blood system <Ul> <Li> diffusion and osmosis circulate nutrients and waste products throughout the body . </Li> </Ul> </Li> <Li> lack a skeleton <Ul> <Li> hydrostatic pressure gives the body a supportive framework that acts as a skeleton . </Li> </Ul> </Li> <Li> no segmentation </Li> <Li> body wall <Ul> <Li> epidermis and muscle </Li> <Li> often syncytial </Li> <Li> usually covered by a secreted cuticle </Li> </Ul> </Li> <Li> most are microscopic </Li> <Li> parasites of almost every form of life (although some are free living) </Li> <Li> eutely in some </Li> <Li> loss of larval stage in some </Li> <Li> possibly pedomorphism </Li> </Ul> <Li> lack a vascular blood system <Ul> <Li> diffusion and osmosis circulate nutrients and waste products throughout the body . </Li> </Ul> </Li> <Ul> <Li> diffusion and osmosis circulate nutrients and waste products throughout the body . </Li> </Ul>

During development the coelom is divided into what cavities