develops from neural plate 神经板 neural keel 神经龙骨 An intermediate stage (between the neural plate and neural rod) during the early segmentation period in the morphogenesis of the central nervous system primordium; the keel is roughly triangular shaped in cross section. presumptive central nervous system 中间阶段（神经板和神经棒之间）在中枢神经系统原基形态发生的早期分割阶段；龙骨横截面大致呈三角形。 推定的中枢神经系统 future central nervous system 原中枢神经系统