SYMPATHETIC SYSTEM IN TURTLES 



301 



cells wander out from them and become arranged in a broken 

 ring encircling the oesophagus. 



At the close of the seventeenth day of incubation the cell-aggre- 

 gates in the walls of the oesophagus have become more conspicu- 

 ous and the cells composing them more numerous. They are no 







e ^ ^ 





>:^i* r " ® ^ 



***^ 



«> a- 







Fig. 11 Transverse section through the region of the heart in a seventeen- 

 day embryo of Thalassoehelys caretta. X HO. B., bronchi; C.P., anlage of cardiac 

 plexus; D.PF. A., dorsal wall of atria; Mes., mesentery; M.S. P., anlagen of myen- 

 teric and submucous plexuses; Oe., oesophagus; Vag., vagus nerves. 



longer arranged in a single broken ring, but the anlagen of the 

 myenteric and the submucous plexuses are becoming more dis- 

 tinct (fig. 11, M. S. P.). Branches of the vagi may now be traced 

 along the walls of the stomach. From these branches cells may be 

 traced laterally in the walls of the stomach until the latter is 

 completely encircled by groups of sympathetic cells. 



