HISTOGENESIS OF THE LIVER 



277 



to their lumina, the cells are more columnar and there is no 

 definite external cuticula as there seems to be in the hepatic 

 cells at this time. The cytoplasm of the cells is also more granu- 

 lar. The mesothelial tubules may extend downward and come 



Fig. 7 Transverse section through the anterior part of the anlage of the 

 liver of an Acanthias embryo 7.5 mm. long (H.E.C. 1496). X 400. B, tangential 

 section of the mesothelial wall surrounding radicle of the left omphalo-mesenteric 

 vein; M./iep. p., median hepatic pouch; M.v., mesothelial villus; F.L, left omphalo 

 mesenteric vein; V.r., right omphalo-mesenteric vein; X, proliferated mesenchyma. 



in contact with the hepatic cylinders, but generally they are 

 replaced in this region by cords of mesenchymal cells. Figure 9 

 is a cross-section of a portion of the liver of an Acanthias embryo 

 15 nmi. in length (H.E.C. 227) showing these tubules (Mes.t.) in 

 the highest state of development. 



THE AMERICAN JOURNAL OF ANATOMY, VOL. 17, NO. 3 

 MARCH, 1915 



