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E14 to E15 and survival to embryonic day (E)21

Figure 12.  The new feature that is shown in this specimen is the large population (over 60%) of unlabeled neurons in the accessory bulb output layer.  Most of these cells were generated on E13, and by E21 they are permanently settled in a thick layer surrounded by the internal and external plexiform layers of the accessory bulb.  The densely-labeled granule cells in the dorsal part of the granular layer are tentatively identified as the accessory olfactory bulb granule cells; nearly all are labeled so they are still proliferating on E14.  Most of the main bulb mitral cells are labeled but an occasional superficial cell is unlabeled; thus, on E14, most mitral cell precursors are still proliferating and the older neurons are arrayed in a large outer circle that defines the superficial mitral cell border.  The heavily labeled cells in the internal plexiform layer are most likely mitral cells still migrating into the layer on E21.  The granule cells themselves are more labeled, but few to none have been generated by the morning of E14.

This slice does not show ruptured cells spilling into the lumen of the olfactory recess of the lateral ventricle; however, other slices in this specimen do have that feature.