The capacity for removal of amino acids from solution by marine animals was studied by following the concentration of an acid added to the ambient sea water. Thirty‐five genera representing 11 phyla were examined. The representatives of 10 of the phyla removed significant quantities of glycine from solution during an observation period of from 16 to 24 hr. This capacity for uptake of glycine was not limited to filter‐feeding animals. Observations using representatives of 3 phyla and various amino acids indicated that uptake could occur whether the acid concerned behaved as a cation or an anion at the pH of sea water. Comparison of the amino acid concentrations at the incurrent and excurrent siphons of the clam, Spisula, indicated that removal of glycine took place in the mantle cavity of this animal. Differences as great as 14% were observed. Disappearance of glycine at ambient concentrations as low as 1.5 mg/L could be demonstrated.