A great deal of work has been done on the distribution of copper in plant and animal matter. It is not the intention of the authors to critically review all of the work of a biological nature concerning this element but only such as applies to the problem at hand. Investigations concerning the presence and role of copper in marine life are numerous. Harless found this metal in combination with protein in the blood of Eledone and Helix Pomatia and concluded that it functioned in a manner similar to that of hemoglobin of higher animals. Fredericq also said that copper plays the same role in the mollusks as iron does in the blood of higher animals. He called the copper protein compound hemocyanin. Since the work of these authors a number of experiments have conclusively demonstrated that hemocyanin functions as a respiratory pigment