We found that some morphological properties of the pineal gland and submandibular salivary gland of mice are significantly distinct at the new and full moon. We suppose that the differences are initiated by the displacements of the electron-dense concretions in the secretory vesicles of pinealocytes. This presumably occurs under the influence of the gravitational field, which periodically changes during different phases of the moon. It seems that the pinealocyte is both an endocrine and gravisensory cell. A periodic secretion of the pineal gland probably stimulates, in a lunaphasic mode, the neuroendocrine system that, in turn, periodically exerts influence on different organs of the body. The observed effect probably serves, within the lifelong clock of a brain, to control development and aging in time.