The fine structure of the pineal gland in the pocket gopher, Geomys bursarius

The morphology of the pineal gland of the pocket gopher, Geomys bursarius, is of special interest because this species is exposed to extremes of environmental lighting in its natural habitat. The pineal gland of the gopher has been studied in specimens collected as they were about to enter their winter dormant period. The gopher pineal is similar to other mammalian pineal glands in that it possesses light and dark parenchymal cells, glia, and pigment‐containing‐cells. Vascular‐parenchymal relationships are similar to other species. Vesicles containing electron‐opaque cores are infrequently encountered in the parenchymal cells. Parenchymal cells and pigment cells occasionally abut a lumen, suggesting an acinar arrangement. Large cytoplasmic vacuoles several microns in diameter are present in the parenchymal cells.