218 ALBERT KUNTZ 



In the selachians the anlagen of the sympathetic trunks arise as 

 ganglionic enlargements on the spinal nerves (Balfour, Van 

 Wijhe, Hoffmann). In the amphibians fibers are present in the 

 communicating rami before the anlagen of the sympathetic trunks 

 appear. The latter arise along the sides of the dorsal surface of 

 the aorta (Hoffmann, Neumayer). In Lacerta (spec?), a rep- 

 tilian type, the sympathetic anlagen arise as short cellular out- 

 growths on the spinal nerves, which early show ganglionic 

 enlargements at their distal ends (Neumayer). In birds the pri- 

 mary sympathetic trunks arise as a pair of cell-columns lying along 

 the sides of the dorsal surface of the aorta. These early give 

 way to the secondary sympathetic trunks which arise as cell- 

 aggregates just median to the ventral roots of the spinal nerves 

 (His, Jr. , Lillie) . In mammals the sympathetic trunks arise as a pair 

 of cell-columns lying along the sides of the dorsal surface of the 

 aorta (Paterson, His, Jr., Kohn). 



With these morphogenetic differences in mind, it is apparent 

 that the view of Onodi was based primarily on the selachians, 

 while the theory of the active migration of sympathetic cells 

 finds its basis primarily in birds and mammals. 



Kohn and Neumayer have rejected both these views. They 

 admit of no active cell migration, but trace the origin of the sym- 

 pathetic system to elements which arise in situ in the spinal 

 nerves, and account for the multiplication of cells along the paths 

 of the communicating rami and in the sympathetic anlagen by 

 local cell division. Their views, however, are obviously influenced 

 by their conception of the neurone and their allegiance to the 

 theory of local differentiation and the multicellular nature of 

 nerve-fibers. 



III. METHODS OF INVESTIGATION 



The following observations are based on embryos of the pig. 

 Several embryos of the cat and a goodly number of embryos of 

 the chick were at my disposal and were used for checking results. 

 Embryos of the pig were found to be more desirable than embryos 

 of the cat, because the cells in the former are comparatively 

 larger and appear to be less crowded. 



