The fishlike amphioxus has a structure called a notochord which in humans develops into this column
[DOC] [TLE] Biological Diversity 9 - Estrella Mountain Community College [PAR] Humans are coelomates, since we have an abdomenal cavity containing ... 
Deuterostomes (as exemplified by the echinoderms and chordates) develop the 
... Water passes through a stone canal to a ring canal and into the radial canals in 
each arm.