The axocele (from the Greek ax = 'axis' and Greek koilos = 'hollow') designates a portion of the coelom in echinoderms . This is the part extending from the protocele, ie the uppermost portion of the coelom. It is created in larval pairs, with the left axocele developing into a channel between the hydrocele and the madreporite. The right axocele is reduced to a small dorsal blade.
References
Axocele Wikipedia(Text) CC BY-SA