Injection on E13, survival to E14

Figure 15 shows a sagittal-slice of an E14 embryo 24 hrs after its mother was injected with ³H‑thymidine on E13.  The slice is filled with a haze of “noise” but one can see that there are some areas where unlabeled cells are accumulating under the pia—the neurons that were generated on E12.  The largest accumulation is outside the basal ganglionic NEP; some of these cells appear to be migrating forward beneath the basal telencephlic NEP.  For the most part, cells outside the NEP are either heavily or lightly labeled, were generated on E13, and have migrated outside by E14.  There is no part of the basal forebrain NEP that can be identified as the olfactory bulb NEP, but a zone of heavily labeled cells adhering to the anteroventral brain might be specifying the future olfactory bulb NEP.  The olfactory epithelium is continuing to invaginate and most cells are labeled.  There is a large accumulation of presumptive glial precursors outside the olfactory epithelium that will probably associate with developing olfactory nerve fibers as they grow toward the brain