It should be noted that many marine organisms are able to accumulate metals in cytoplasmic granules (Coombs & George, 1978) and it has been suggested that such metals are associated with metallothionein (George & Pirie, 1979).These granules may be related to lysosomes (Porter, 1974)and are thought to function in metal detoxification(Coombs & George, 1978;George and Pirie, 1979, 1980),either in conjunction with metallothionein or separately.Regardless of the specific systems involved, metals which were not detoxified would be expected to spill over into the HMW pool. Our data indicates that spill over is not occurring and that the detoxification capacity of urchins is not exceeded by the ambient metal concentrations at the three stations.