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ALBERT KUNTZ 



Fig. 2 Transverse section through the trunk region of a nine-day embryo of 

 Thalassochelys caretta. X 210. Ao., aorta;' M. P., muscle phxte; Nc, notochord; 

 Sp.G., spinal ganglion; Sp.N., spinal nerve; Sy., anlage of symphathetic trunk; 

 V.N.R., ventral nerve-root. 



continuous lines of cells may be traced from the mantle layer into 

 the proximal parts of the ventral nerve-roots, and occasionally 

 one of these cells may be observed half in and half out of the neu- 

 ral tube. These cells obviously advance peripherally along the 

 fibers of the ventral nerve-roots. After they have advanced 

 beyond the point of union of the dorsal and the ventral nerve- 

 roots it is no longer possible to distinguish between the cells which 

 have their origin in the ventral part of the neural tube and wander 



