Two kinds of large neurones were studied in histological preparations and electron micrographs of the parenchyma of the anterior region of the body, the pharynx and the oral and ventral suckers of Fasciola hepatica. These are called the α and β neurones. The latter are larger than the α cells and vary in structure. An interstitial system composed of amorphous material of medium electron density was observed in the parenchyma, the suckers and the pharynx. Invaginations of the plasma membrane containing interstitial material extend into the β neurones and are often continuous with the nuclear envelope. It is suggested that the β cells are neuro-secretory in function and that they may be derived from the α neurones.