EMBRYO OF 9 MM. STUDIED IN SECTIONS. 



255 



The similar edge on the ventral side provides for the extension of the muscle-plate 

 downward. In the median line, below the spinal cord is the small notochord, Nch, 

 and the large median dorsal aorta, Ao. In the ventral portion of the embryo 

 appears the large body-cavity into which protrude the Wolffian bodies and the intes- 



tn.pl. G. Sp.c. 



V.U.S 



''i"ft v ^ 



FIG. 186. PIG, 9.0 MM. FRONTAL SERIES 54, SECTION 194. 



Ao, Aorta, card, Cardinal vein. F, F.ctodermal fold at the border of the limb-bud. G, Ganglion, gen, Genital 

 ridge. Glo, Glomerulus. In, Small intestine (jejunum), mes, Splanchnic mesoderm (of the intestinal 

 wall), m.pl, Dorsal growing edge of the muscle-plate. My, Muscle-plate of secondary segment. Nch, 

 Notochord. P.L, Posterior limb. Reel, Large intestine. Som, Somatopleure. Sp.c, Spinal cord. V.U.D, 

 Right umbilical vein. V.U.S, Left umbilical vein. W.b, Wolffian body. W.D, Wolffian duct. X 35 

 diams. 



tine. The ccelom also has a downward prolongation into the beginning of the 

 umbilical cord, and in this prolongation lies the so-called extra-embryonic loop of 

 the intestine, In. The coelom is bounded everywhere by the layer of mesothelium 

 represented in the engraving as a continuous line. With a higher power the meso- 



