part of part of bounding layer of bounding layer of adjacent to adjacent to neural tube neural tube lumen germinal neuroepithelium germinal neuroepithelium original neural tube As the cells adjacent to the lumen continue to divide, the migrating cells form a second layer around the original neural tube. This layer becomes progressively thicker as more cells are added to it from the germinal neuroepithelium. This new layer is called the mantle (or intermediate) zone, and the germinal epithelium is now called the ventricular zone (and, later, the ependyma)[NCBIBook:NBK10047] UBERON:0004022 The single layer of epithelial cells that lines the early neural tube and develops into the nervous system and into the neural crest cells. germinal neuroepithelial layer embryonic tissue sensory epithelium proliferating neuroepithelium