VII.] 



THE LIMBS. 

 FIG. 68. 



199 



WM 



SECTION THROUGH THE LUMBAR KEGION OF AN EMBRYO AT 

 THE END OF THE FOURTH DAY. 



n. c. neural canal, p.r. posterior root of spinal nerve with gan- 

 glion, a.r. anterior root of spinal nerve. A.G.C. anterior 

 grey column of spinal cord. A. W.C. anterior white column 

 of spinal cord just commencing to be formed, and not very 

 distinctly marked in the figure, m.p. muscle-plate, ch. 

 notochord. W.R. Wolfnan ridge. A.O. dorsal aorta. V.c.a. 

 posterior cardinal vein. W.d. Wolffian duct. W.b. Wolffian 

 body, consisting of tubules and Malpighian corpuscles. One 

 of the latter is represented on each side. g.e. germinal 



