308 ALBERT KUNTZ 



ence of substances, hormones, which are produced in those regions. 

 Furthermore, the form-changes of the nuclei of the migrant cells 

 indicate that these elements play more than a passive role in their 

 peripheral advancement. All along the paths of migration, both 

 in the nerve-trunks and in the cellular tracts passing through the 

 mesenchyme, many of the nuclei are distinctly elongated, while in 

 the sympathetic anlagen they resume a more rounded outline. 

 Not infrequently these migrant cells present evidence of amoeboid 

 movement. In some instances the nuclei are irregular in outline, 

 while in still others they are distinctly pyriform with the broader 

 end directed peripherally. These variations in the form of the 

 nuclei of these migrant nervous elements, doubtless, indicate 

 the presence of processes going on within the cells which play a 

 part in their peripheral advancement and which are probably 

 stimulated by the influence of the same agents which determine the 

 direction of migration. 



The phenomena observed in the development of the vagal sym- 

 pathetic plexuses indicate that the peripheral migration of the 

 cells giving rise to these plexuses is determined by the same in- 

 fluences which determine the peripheral migration of the cells 

 giving rise to the sympathetic trunks. The cells which become 

 distributed in the walls of the digestive tube to give rise to the 

 anlagen of the myenteric and the submucous plexuses wander out 

 from the vagus trunks and become aggregated into small cell- 

 groups which are more or less closely associated with each other, 

 but many of which, in the early stages, are quite free from nerve- 

 fibers. The distribution of these cells cannot be explained by the 

 purely mechanical processes involved in growth or by osmotic 

 influences. If, however, we assume that the location of these 

 cell-groups is determined by the influence of hormones which are 

 produced by the cells in the walls of the digestive tube the problem 

 becomes very simple. Likewise, the cells which wander into the 

 walls of the heart to give rise to the cardiac plexus are not com- 

 pactly aggregated in the early stages, nor are they always found in 

 contact with nerve-fibers. Here again the problem becomes simple 

 if we assume that sympathetic cells are attracted toward the heart 

 by the influence of hormones which are produced in that region. 



