Ultrastructure of intestinal cells of Heterakis gallinarum is described and compared with that of Ascaridia galli from ecomorphological point of view. The great analogy in bionomy and ecology of both worms is reflected in the great analogy of ultrastructural construction. A new organoid in the intestinal cells of H. gallinarum, hitherto unknown among nematodes, is also described. It is of a vacuole-like shape running in stripes close under the terminal bar. The paper is also meant to be a supplement to the authors' previous paper (1975) dealing with ultrastructure of muscle cells of Heterakis gallinarum.