SYMPATHETIC SYSTEM IN TURTLES 311 



not from cell which migrate ventrally from the sympathetic 

 trunks, as earlier workers supposed, but from cells which have 

 their origin in the hind-brain and in the vagus ganglia and mi- 

 grate peripherally along the paths of the vagi. The results here 

 recorded agree with the writer's observations on embryos of mam- 

 mals, birds, and fishes. 



10. The phenomena presented in embryos of the turtle afford 

 evidence in favor of the view advanced by the writer in an earlier 

 paper, according to which the peripheral displacement of the cells 

 taking part in the development of the sympathetic nervous system 

 is probably determined by the influence of hormones. 



11. In turtles, as in the higher vertebrates, the cells which 

 migrate peripherally from the cerebro-spinal nervous system into 

 the sympathetic anlagen have the same genetic relationships as 

 the cells which give rise to the neurones and to the the neuroglia 

 cells in the central nervous system. The sympathetic nervous 

 system is, therefore, homologous with the other functional divi- 

 sions of the peripheral nervous system, and the sympathetic 

 neurones are homologous with their afferent and their efferent 

 components. 



