将胚胎发育主要分为4个时期：卵裂期、原肠脊索与体腔中胚层形成期、胎膜形成期和器官发生期；
And divided the embryonic development into four main stages : Cleavage , the formation of archenteron notochord and coelomic mesoderm , the formation of embryonic membranes and the organo-genesis ;
脊索中胚层