Excretion in echinoderms is accomplished by simple diffusion of metabolic wastes across thin regions of the body wall. A variety of gas exchange structures is found in various echinoderms. There is a blood vascular system but its role in transport is still poorly understood and the primary transport system is the circulating fluid of the various coelomic compartments. It is possible that the blood vascular system is a through transport system that delivers nutrients to these local compartments. The nervous system consists of two central nerve rings from which arise radial nerves to the periphery.
Echinoderms are gonochoristic and fertilization is usually external.
The body wall of cucumbers is thick and well developed. It is similar to that of other echinoderms in consisting of a nonciliated epidermis, connective tissue dermis, circular and longitudinal muscles, and a ciliated peritoneum. It is unusual in that the longitudinal muscles are in five longitudinal bands and the ossicles are microscopic plates scattered in the dermis. Collagen fibers in the dermis can, under nervous control, be cross-linked with each other to form a rigid skeleton that can scarcely be cut with a scalpel. The gut is a simple tube extending from mouth to anus.