Ten days after hatching the first columnar cells are almost completely filled with secretory material (Fig. 8A). Meanwhile spacing epithelial cells have emerged between the glandular cells and separate them from each other. However, so far we could not find any indication of fusiform cells, which are obligatory in each columnar cell cluster in the adults. In addition, the first granular cells arise (Fig. 8B). As for the columnar cells the secretory granules initially agglomerate at the apical cell pole.