The subcommissural organ of the lizard Lacerta s. sicula Raf. ultrastructure during the winter.

The secretory activity of the SCO cells of Lacerta s. sicula Raf. is strongly reduced during the winter. Such reduction is documented by the decrease of the decrease of the number of secretory granules type A and B described in previous papers in the summer SCO cells. Also the sacks of RER filled with electron-dense material (type C secretion) are very few; in their place there are, in the basal region of the cells, large vacuoles. In the distal region of the cells, at the free cell surface, a pronounced increase in the number of microvilli is noticed.