The cells of the hatching gland contain enzymes responsible for solubilization of the egg chorion, facilitating the hatching process[GO]. A transversely oriented set of cells located deep to the EVL on the pericardial membrane, especially prominent during pharyngula period because of the brightly refractile cytoplasmic granules (containing hatching enzymes) of the principal cells of the gland. [ http://zfin.org/curator ]