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migrate peripherally from the cerebro-spinal nervous system the 

 anlagen of the sympathetic trunks assume more definite propor- 



Fig. 6 Diagrammatic transverse section through the trunk region of a twenty- 

 day embryo of Thalassochelys caretta. Ao., aorta; C.R., communicating ramus; 

 A'^c, notochord; S.C.R., secondary cellular tract from spinal nerve to sympathetic 

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

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



Fig. 7 Diagrammatic transverse section through the trunk region of a twenty- 

 four day embryo of Thalassochelys caretta. Ao., aorta; C.R., communicating 

 ramus; Nc, notochord; S.C.R., secondary cellular tract from spinal nerve to 

 sympathetic anlage; Sp. G., spinal ganglion; Sy., anlage of sympathetic trunk; 

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



tions, but the sympathetic ganglia do not appear as compact and 

 definitely limited cell-aggregates until development has advanced 

 for a considerable period after this stage is reached. 



