ABSTRACT
Excretion is the elimination of metabolic wastes, essentially nitrogenous products which originate from the utilization of dietary proteins and from the breakdown and turnover of body cell constituents. In contrast, Diehl and Lawrence were unable to detect amino acid excretion in Luidia clathrata. 1.2 Ammonia excretion predominates among echinoderms. The increase in the rate of ammonia excretion of hyposmotically stressed animals has been interpreted by these workers as catabolism of amino acids resulting in ammonia excretion during intracellular isosmotic regulation. It is unlikely that nitrogenous excretion in this echinoid should be so different from that of other echinoderms. The excretion of amino acids is a rather peculiar phenomenon which still must be investigated carefully. Excretion is the elimination of metabolic wastes, previously detoxified or not, into the external medium. Nitrogenous excretion is still poorly known in echinoderms and it is presently impossible to propose a general excretory scheme.
