106 



COMPARATIVE PHYSIOLOGY. 



Fig. 111. 



Fig. 112. 



Fig. no.— Transverse section through Inmbar region of an embryo at end of fourth 

 day (Poster and Balfour). ». e, neural canal; pr, posterior root of spinal nerve 

 with ganglion; ar, anterior root; A. G. 0, anterior gray column of spinal cord; 

 A. W. 0, anterior white column in course of formation; m. p , muscle-plate; c.Ti, 

 notochord ; TWJ, Wolffian ridge ; A 0, dorsal aorta ; «. c. a, posterior cardinal 

 vein; W. d, Wolfian duct; TKb, Wolffian body, consisting of tubules and Mai- 



