Two types of pigment granules in esophageal muscle cells are compared in the light and the electron microscope. The dark-reddish “eyespot granules” are located only in the anteriormost radial muscle cell and are highly concentrated anterolaterally in the cell, forming the eyespots. The paler greenish “esophageal granules” are found in other radial muscle cells and in the marginal muscle cells. In addition to their color and location, the two granules are distinguishable by their fine structure. The morphology of the eyespot suggests that the eyespot of this species is not a photoreceptor, as previously supposed. Evidence is discussed which indicates that the eyespot may function to shade a possible light-sensitive structure in an adjacent enlargement of the amphidial organ.