ORIGIN OF NEURON PATTERN 



197 







65 



64 



FIGS. 62-65. Developmental stages of neural tube and spinal 

 ganglia in salamander, Amblystoma punctatum: Fig. 62, one side of 

 neural plate, showing early stage of neural fold; Fig. 63, neural tube 

 just after closure, cells of neural crest indicated by shading; Fig. 64, 

 later stage, showing beginning migration of spinal ganglion cells; Fig. 65, 

 still later stage; cells of neural crest have migrated lateroventrally to 

 form spinal ganglion (from Johnston, 1906). 



