<P> The flatworms , flat worms , Platyhelminthes , Plathelminthes , or platyhelminths ( from the Greek πλατύ , platy , meaning `` flat '' and ἕλμινς ( root : ἑλμινθ - ) , helminth - , meaning `` worm '' ) are a phylum of relatively simple bilaterian , unsegmented , soft - bodied invertebrates . Unlike other bilaterians , they are acoelomates ( having no body cavity ) , and have no specialized circulatory and respiratory organs , which restricts them to having flattened shapes that allow oxygen and nutrients to pass through their bodies by diffusion . The digestive cavity has only one opening for both ingestion ( intake of nutrients ) and egestion ( removal of undigested wastes ) ; as a result , the food can not be processed continuously . </P>
<P> The flatworms , flat worms , Platyhelminthes , Plathelminthes , or platyhelminths ( from the Greek πλατύ , platy , meaning `` flat '' and ἕλμινς ( root : ἑλμινθ - ) , helminth - , meaning `` worm '' ) are a phylum of relatively simple bilaterian , unsegmented , soft - bodied invertebrates . Unlike other bilaterians , they are acoelomates ( having no body cavity ) , and have no specialized circulatory and respiratory organs , which restricts them to having flattened shapes that allow oxygen and nutrients to pass through their bodies by diffusion . The digestive cavity has only one opening for both ingestion ( intake of nutrients ) and egestion ( removal of undigested wastes ) ; as a result , the food can not be processed continuously . </P>
what is unique about the digestive system in platyhelminthes
what is unique about the digestive system in platyhelminthes
only one opening for both ingestion ( intake of nutrients ) and egestion ( removal of undigested wastes )
only one opening for both ingestion ( intake of nutrients ) and egestion ( removal of undigested wastes )