SYMPATHETIC SYSTEM IN TURTLES 299 



tral type of the ganglion of Remak which is so enormously de- 

 veloped in the avian branch of the vertebrate series. 



Genital plexuses 



In embryos of Thalassochelys caretta from the sixteenth to 

 the twentieth day of incubation or in embryos of Chelydra ser- 

 pentina about 10 mm. in length, cells may be traced ventrally 

 along the median sides of the Wolffian bodies to the lateral sur- 

 faces of the genital ridges (fig. 8, G. P.), where they become aggre- 

 gated to give rise to the genital plexuses. The conditions here 

 described agree with the conditions described by Held in embryos 

 of Emys europea. 



Vagal sympathetic plexuses 



a. Introductory . In my earlier papers I have shown that in 

 mammals and in birds the sympathetic plexuses related to the 

 vagi; viz., the cardiac plexus and the sympathetic plexuses in 

 the walls of the visceral organs, do not arise from cells which 

 migrate ventrally from the sympathetic trunks and from the pre- 

 vertebral plexuses, as the earlier investigators believed, but have 

 their origin in cells which migrate from the vagus ganglia and 

 from the walls of the hind-brain along the paths of the vagi. Be- 

 cause of the genetic relationship of these plexuses to the vagi, 

 I have designated them as the 'vagal sympathetic' plexuses.* 

 More recently 1 have traced the cells giving rise to the sympathetic 

 plexuses in the walls of the digestive tube in fishes to the same 

 sources. The present series of observations will show that in 

 the turtles also the cardiac plexus and the sympathetic plexuses 

 in the walls of the visceral organs arise from cells which have 

 their origin in the vagus ganglia and in the walls of the hind-brain 

 and migrate peripherally along the paths of the vagi. 



h. Myenteric and submucous plexuses. In transverse sections 

 through the anterior region of the oesophagus in embryos of Thal- 



^ The development of the sympathetic nervous system in mammals, p. 235. 

 Jour. Comp. Neur. Psych., vol. 20, no. 3, pp. 211-258. 



THE AMERICAN JOURNAL, OF ANATOMY, VOL. II, NO. 3 



