[The morphogenesis of layer I of the mouse cerebral cortex in the prenatal developmental period]

Cajal-Retzius (CR) cells begin to differentiate in mice at day 10 of embryonic development. At days 11 and 12, the subpial zone becomes visible, as well as the cell population, which will comprise the plexiform layer, which appears at day 13. All cell types characteristic of layer I appear at day 14. We have described a characteristic feature of neurogenesis of layer I, i.e., found that the appearance of its cell elements proceeds in two phases: the first peak corresponds to early postimplantation development, whereas the second peak begins from day 14 of development and continues to the end of the fetal period.