This diagram represents the vertical section through an arm and an interradis of a starfish. a, anus; amp., ampulla; c.b., circular blood vessel; c.w., circular water canal; co., caelom; co.e., caelomic epithelium; d.b., dermal branchae; e, position of the eyespot; ect., ectoderm; ent, entoderm; f, ambulacral foot; g, ambulacral foot; g, ambulacral groove; h, hepatic caeca or liver; i, insestine; i.c., intestinal caeca; mes, mesoderm; mo., mouth; m.p., madreporic body; n.r., nerve ring; os., ossicles in mesoderm; r.n., radial nerve band; r.b., radial blood vessel; r.p., reproductive pore; r.w., radial water canal; s.c., stone canal; sp., spines; z, lacunar spaces in the mesoderm.

Starfish

This diagram represents the vertical section through an arm and an interradis of a starfish. a, anus;…