DEVELOPMENT OF THE ELASMOBRANCH LIVER 



379 



V.ompK.l 



G.bl 



Fig. 27 Frontal section of an Acanthias embryo 86 mm. long (H.E.C. 410). 

 X 40. D.chol., ductus choledochus; G.bl., gall bladder; Pane, pancreas; St., 

 stomach; V.omph.L, left omphalo-mesenteric vein. 



Along with the changes described above comes a very extensive 

 alteration in both the form and position of the cystic apparatus 

 which is apparently produced by the development of the internal 

 yolk sac. This structure begins to develop from the vitelline 

 duct just internal to the ventral body wall in embryos from 

 25 to 30 mm. in length. An early stage is seen in section in figure 

 17. It grows rapidly and its anterior end pushes forward be- 

 tween and below the stomach and left and cystic lobes of the 

 liver on one side and the right lobe of the liver on the other. The 

 frontal section shown in figure 27 illustrates its size and relations 

 in an embryo 60 mm. in length. 



