448 



Leiand Griggs. 



Fig. 2. Neural plate and neural crest just before the appearance of neuro- 

 meres, fifth stage, a, anus; agd, anterior germinal depression; ap, anterior 

 pit; bg, blastogroove; br, blastoporic rim; id, infundibular depression; li, lateral 

 infolding; n4, fourth neuromere; nc, neural crest; nee, neurenteric canal; ng, 

 neural groove; pel, procephalic lobes; pep, postcephalic plate; pgd, posterior 

 germinal depression; teg, transverse cephalic groove. 



neural crest from which the dorsal ganglia of the spinal nerves 

 arise. Almost conclusive evidence is found in the fact that the 

 crests in the open plate and in the closed tube hold the same 

 position, lying in both cases immediately adjacent to the edges 

 of the plate or to their line of fusion in the tube. Johnston ('05) 

 has recently shown by a series of sections that the rounded or 

 cubical cells of the crest in the open plate stage can be easily 

 followed into the anlage of the dorsal roots of the cerebral nerves. 

 His sections are drawn from Amblystoma embryos. My obser- 



