Chitin is the b-1, 4 linked polysaccharide of N-acetylglucosamine. It ranks as the material with the second highest biomass on earth following cellulose. Wheat Germ Agglutinin (WGA), a lectin from wheat, Triticum vulgaris , has been shown to bind specifically to chitin. Using histological techniques and Fluorescein (FITC) labeled WGA, I have identified chitin in some types of hemocytes in crustaceans, such as shrimp and lobsters. Crustacean hemocytes maybe divided into two groups: hyaline and granulocytes. Hyaline lack granules and initiate coagulation of the hemolyph. They do not stain with FITC-WGA. Granulocytes are subdivided into small and large granule hemocyte, based on the size of the cytoplasmic granules. These cells phagocytose and encapsulate foreign material. Both the small and large granules stain with FITC-WGA. I am currently testing the specificity of the labeling and developing testable questions regarding the possible function of chitin in circulating blood cells.