neurula /no͝or″ələ/ pl. neurulas, neurulae [Gk, neuron, nerve] , an early embryo during the period of neurulation when the nervous system tissue begins to differentiate. The embryo at this level of growth represents a third stage in embryonic development, after the morula and blastocyst stages in humans and higher animals and the blastula and gastrula stages in lower animals. In humans the neurula stage occurs from about 19 to 26 days after fertilization.
