GLOSSARY OF EMBRYOLOGICAL TERMS 291 



Nerve, Auditory — eighth ( VllI ) cranial nerve, purely sensory, arising from 

 acoustic ganghon and associated with geniculate ganglion of seventh 

 nerve. 



Nerve, Facial — seventh (VII) cranial nerve, both sensory and motor, re- 

 lated to taste buds and facial muscles. 



Nerve, Glossopharyngeal — ninth (IX) cranial nerve, mixed, associated 

 with superior and petrosal ganglia. 



Nerve, Oculomotor — third (III) cranial nerve which arises from neuro- 

 blasts in ventral zone of midbrain near median line just before hatch- 

 ing in frog tadpole. 



Nerve, Vagus — tenth (X) cranial nerve, mixed, arising from rhom- 

 bencephalon and associated with jugular ganglion. 



Nervous Layer — innermost of two layers found in roof of segmentation 

 cavity of amphibian blastula, from which bulk of central nervous sys- 

 tem is developed. 



Neural Arch — ossified cartilages which extend dorsally from centrum 

 around nerve cord. 



Neural Canal — See Neurocoel and Neural Tube. 



Neural Crest — continuous cord of ectodermally derived cells lying on each 

 side in angle between neural tube and body ectoderm, separated from 

 ectoderm at time of closure of neural tube and extending from ex- 

 treme anterior to posterior end of embryo; material out of which 

 spinal and possibly some cranial ganglia develop, and related to de- 

 velopment of sympathetic ganglia by cell migration. 



Neural Fold — elevation of ectoderm on either side of thickened and de- 

 pressing medullary plate; folds which close dorsally to form neural 

 tube. (Syn., medullary folds.) 



Neural Groove — depression caused by sinking in of center of medullary 

 plate to form a longitudinal groove, later to be incorporated within 

 neural tube (spinal cord). (Syn., medullary groove.) 



Neural Plate — thickened broad strip of ectoderm along future dorsal side 

 of all vertebrate embryos, later to give rise to central nervous system. 

 (Syn., medullary plate.) 



Neural Tube — tube formed by dorsal fusion of neural folds, rudiment of 

 nerve or spinal cord. 



Neurenteric Canal — posterior neurocoel where it is connected with clos- 

 ing blastopore and posterior enteron of amphibian; the large com- 



